JP2014164175A - Illumination device and projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illumination device capable of effectively reducing a speckle.SOLUTION: An illumination device (2b) includes: a light source device (7); a superposition optical system (10) to which light is made incident from the light source device; and an optical path shift device (9) for temporally changing the incident position of the light emitted from the light source device to the superimposition optical system.

Description

  The present invention relates to a lighting device and a projector.

  Conventionally, a projector is known as one of display devices (see, for example, Patent Document 1). For example, the projector forms an image by modulating light from the illumination device with a light modulation device, and projects the image onto a screen using a projection lens or the like.

  Various light sources are used as the light source of the illumination device, and a coherent light source that emits coherent light (coherent light) may be used. The coherent light source is a solid light source using a laser diode (LD), a super luminescence diode (SLD) or the like, a short arc lamp light source, or the like. For example, since a projector using a laser light source has a narrow wavelength range of the laser light source, the color reproduction range can be sufficiently widened, and the size and the number of components can be reduced.

  By the way, when display is performed by a projector using a coherent light source, a so-called speckle may be recognized by an observer who observes an image. Speckle is a pattern in which bright spots and dark spots are distributed in a striped pattern or a spotted pattern due to light interference, which gives an observer a glare and may cause discomfort when viewing an image. Therefore, it is expected to devise a technique that makes it difficult to recognize speckle (hereinafter referred to as “reducing speckle”).

  As one of the techniques for reducing speckles, Patent Document 1 proposes a technique for rotating a spot formed on the pupil plane of a projection lens around the optical axis on the pupil plane. According to the technique of Patent Document 1, the angular distribution of rays incident on each point on the screen changes with time, and the spec pattern changes with time. As a result, speckles are observed and superimposed on the observer in terms of time (integration), and speckles are reduced.

JP 2009-216843 A

  The above-described technology has room for improvement in reducing speckle effectively. For example, in the method of moving the pupil image on the pupil surface, the speckle cannot be sufficiently reduced because the pattern of the pupil image itself does not change. In addition, since the effective pupil (effective diameter) of the projection lens must be increased, the projection lens is increased in size and cost. It is an object of the present invention to provide an illumination device and a projector that can effectively reduce speckle.

  The illumination device according to the first aspect of the present invention temporally changes a light source device, a superimposing optical system into which light from the light source device is incident, and an incident position of the light emitted from the light source device into the superimposing optical system. An optical path shift device.

  In this illuminating device, the angular distribution of light incident on each point on the illuminated region changes with time. Therefore, the speckle pattern changes with time, and the speckle pattern becomes difficult to be visually recognized.

  In the illumination device of the first aspect, the optical path shift device may include a first prism that transmits light from the light source device and rotates around a rotation axis that intersects the direction of the optical axis of the superposition optical system. .

  In this illuminating device, the optical path between the light source device and the uniformizing optical system changes with the rotation of the first prism, so that the speckle pattern is less visible.

  In the illumination device of the first aspect, the first prism may have a first surface on which light from the light source device is incident and a second surface parallel to the first surface.

  In this illumination device, the optical path of light when entering the first surface and the optical path of light when exiting from the second surface are substantially parallel.

  In the illumination device of the first aspect, the first prism may have a square cross-sectional shape orthogonal to the rotation axis.

  In this illumination device, the optical path of light when entering the surfaces of the first prism and the optical path of light when exiting from each surface are substantially parallel. Further, in this illumination device, since the first prism has a square cross-sectional shape, rotation of the prism around an axis passing through the center of the square can suppress the occurrence of vibration associated with the rotation.

  In the illumination device according to the first aspect, the first prism may have a rectangular cross-sectional shape orthogonal to the rotation axis.

  In this illumination device, the optical path of light when entering the surfaces of the first prism and the optical path of light when exiting from each surface are substantially parallel. Further, in this illumination device, the change in the optical path differs between a state in which light is incident on the surface including the long side of the rectangular shape of the first prism and a state in which light is incident on the surface including the short side. Therefore, this illuminating device can increase variations in the angular distribution of light when entering each point of the illuminated area, and can significantly reduce speckle.

  In the illumination device of the first aspect, the rotation speed of the first prism may be 6 rotations or more per second.

  When the cross-sectional shape of the first prism is square or rectangular, the light from the light source device enters one of the four surfaces while the first prism rotates once. For this reason, in this illumination device, the angular distribution of light incident on the illuminated area is switched to a period of 1/24 seconds or less, and speckle can be significantly reduced.

  In the illumination device according to the first aspect, the optical path shift device may include a second prism that transmits light from the first prism and rotates around a rotation axis that intersects the direction of the optical axis of the superposition optical system. Good.

  In this illumination device, the amount of shift of the optical path by the optical path shift device changes according to the rotation angle of the first prism and the rotation angle of the second prism. Therefore, this illumination device can increase variations in the optical path, and can increase variations in the angular distribution of light when entering each point of the illuminated area, so that speckle can be significantly reduced.

  In the illumination device of the first aspect, the rotation axis of the second prism may intersect the direction of the rotation axis of the first prism.

  In this illumination device, the shift direction of the optical path due to the rotation of the first prism is different from the shift direction of the optical path due to the rotation of the second prism, so that the variation of the angular distribution of the light when entering each point of the illuminated area is increased. And speckle can be greatly reduced.

  In the illumination device according to the first aspect, the light source device may include a plurality of light sources arranged in a direction crossing a direction in which the incident position changes.

  In this lighting device, light emitted from the light source device is distributed in the arrangement direction of the plurality of light sources. Since this illumination device changes the optical path in the direction intersecting with the direction in which the light emitted from the light source device is distributed, the amount of change in the angular distribution of light when entering each point of the illuminated area can be increased. , Speckle can be greatly reduced.

  In the lighting device of the first aspect, the light emission amount of the first light source among the plurality of light sources is different from the light emission amount of the other light sources among the plurality of light sources in the first period, and the plurality of light sources in the second period You may provide the light source control apparatus which controls a light source device so that the light emission amount of the 2nd light source among light sources may differ from the light emission amount of the 2nd light source in a 1st period.

  In this illumination device, since the pattern of light emitted from the light source device changes between the first period and the second period, variations in the angular distribution of light when entering each point of the illuminated area are increased. And speckle can be greatly reduced.

  In the illumination device of the first aspect, the light source control device may reduce or increase each of the light emission amounts of the light sources adjacent to each other among the plurality of light sources.

  This illuminating device can increase the amount of change in the angular distribution of light when entering each point of the illuminated region, and can significantly reduce speckle.

  In the illumination device of the first aspect, the light source control device increases the light emission amount of the other light source adjacent to each other when reducing the light emission amount of one of the light sources adjacent to each other among the plurality of light sources. You may let them.

  This lighting device can reduce speckles, and can compensate for the decrease in the amount of light emitted from one light source with the increase in the amount of light emitted from the other light source, suppressing changes in the amount of light emitted from the light source device. it can.

  In the illumination device of the first aspect, the superimposing optical system superimposes the lens array including a plurality of lens elements on which light from the optical path shift device is incident and the light from each of the plurality of lens elements on the illuminated area. And a superimposing lens to be included.

  This illuminating device spatially distributes the light from the optical path shift device to a plurality of lens elements of the lens array and superimposes the light from the lens elements in the illuminated area, so that the illuminance distribution in the illuminated area is made uniform it can.

  In the illumination device according to the first aspect, the superimposing optical system includes: an incident end face on which light is incident; an optical rod having an exit end face from which light incident from the incident end face is emitted; an exit end face of the optical rod; And a relay system that optically conjugates.

  In this illuminating device, the illuminance distribution on the exit end face of the optical rod is made uniform, and the exit end face and the illuminated area are optically conjugate, so the illuminance distribution in the illuminated area is made uniform.

  A projector according to a second aspect of the present invention includes an illumination device of the illumination device according to the first aspect, an image forming system that forms an image with light from the illumination device, and a projection system that projects an image formed by the image forming system. And comprising.

  In this projector, speckles are not easily seen by the observer of the image, so that the image can be expressed with high quality.

  In the projector according to the second aspect of the present invention, the image forming system includes a first microlens provided in each of the plurality of pixels arranged in the illuminated region, and an afocal optical system together with the first microlens. A second microlens to be configured may be included.

  Since this projector suppresses the change in the angle distribution of the light indicating the image in the image forming system, the angle distribution of the light incident on each point on the projection surface on which the image is projected can be controlled with high accuracy. Speckle can be effectively reduced.

It is a figure which shows the projector of 1st Embodiment. It is a figure which shows an illuminating device, an image forming apparatus, a color composition system, and a projection system. It is a figure for demonstrating the definition of the parameter in a Fresnel diffraction type. It is a figure for demonstrating the principle which changes an aperture function in time. It is a figure for demonstrating the change of the optical path by an optical path shift apparatus. It is a figure which shows the 1st prism of the optical path shift apparatus of a 1st modification. It is a figure which shows the change of the optical path accompanying rotation of a 1st prism. It is a figure which shows the illuminating device by a 2nd modification. It is a figure which shows the illuminating device by a 3rd modification. It is a figure which shows the illuminating device by a 4th modification. It is a figure which shows the light source device of the illuminating device by a 5th modification. It is a timing chart which shows an example of control of a laser light source. It is a figure for demonstrating the temporal change of a lighting pattern and a light emission pattern. It is a figure which shows the change of the pupil image when a part of several laser light source is light-extinguished. 1 is a diagram illustrating an example of an image forming apparatus. It is a figure which shows the other example of an image forming apparatus. It is a figure which shows the other example of an image forming apparatus. It is a figure which shows the other example of an image forming apparatus. It is a figure which shows the illuminating device and image forming system of 2nd Embodiment. It is a figure which shows an optical rod. It is a figure which shows an optical rod and a relay optical system. It is a figure which shows an example of the pattern of the light source image formed in the incident end surface of an optical rod. It is a figure which shows the pupil image formed corresponding to the pattern of a light source image.

[First Embodiment]
A first embodiment will be described. Here, the outline of the projector of this embodiment will be described first, and then the details of each part of the projector such as the illumination device will be described.

  FIG. 1 is a diagram illustrating a projector 1 according to the first embodiment. The projector 1 forms an image according to image data supplied from a signal source such as a DVD player or a PC, and projects the formed image onto a projection surface SC (display screen) such as a screen or a wall.

  The projector 1 controls an illumination system 2, an image forming system 3 that forms an image with illumination light from the illumination system 2, a projection system 4 that projects an image formed by the image forming system 3, and each part of the projector 1. And a control system 5. The projector 1 according to the present embodiment is a so-called three-plate projector, and forms a full-color image by individually forming images of each color of red, green, and blue, and combining the formed three-color images by the color composition system 6. Is possible.

  The illumination system 2 includes an illumination device 2a that emits red illumination light, an illumination device 2b that emits green illumination light, and an illumination device 2c that emits blue illumination light. Each of these illumination devices has the same configuration, and includes a light source device 7 and an illumination optical system 8, respectively.

  The image forming system 3 includes an image forming apparatus 3a that forms a red image, an image forming apparatus 3b that forms a green image, and an image forming apparatus 3c that forms a blue image. There is a one-to-one correspondence between the illumination device for each color of the illumination system 2 and the image forming apparatus.

  Each image forming apparatus forms an image of each color with illumination light from each corresponding illumination device, and emits image light corresponding to the image of each color. For example, the red image forming apparatus 3a forms a red image with illumination light (red light) from the red illumination apparatus 2a. The image forming apparatus 3a emits light (image light) corresponding to the image. Similarly to the image forming apparatus 3a for red, the image forming apparatus for colors other than red emits image light of each color corresponding to the formed image of each color.

  The image light of each color emitted from the image forming system 3 enters the color synthesis system 6. The color composition system 6 is, for example, a dichroic prism, and includes two wavelength separation films that reflect or transmit incident light according to the wavelength of incident light. One wavelength separation film transmits red light and green light and reflects blue light. Another wavelength separation film has a characteristic of transmitting green light and blue light and reflecting red light.

  Each color light incident on the color synthesis system 6 from the image forming system 3 is emitted from the color synthesis system 6 with the traveling direction aligned by reflection or transmission at the wavelength separation film. Image light emitted from the color synthesis system 6 enters the projection system 4. The projection system 4 is a so-called projection lens, and enlarges and projects the image formed by the image forming system 3 on the projection surface SC.

  Next, each part of the projector 1 will be described in more detail. In the present embodiment, the illumination devices for each color have the same configuration, and the image forming apparatuses for each color have the same configuration. Therefore, the configuration of the system corresponding to the green image is typically described, and the description of the system corresponding to the other color image may be simplified or omitted.

  FIG. 2 is a diagram showing the illumination device 2 b, the image forming device 3 b, the color composition system 6, and the projection system 4. The illuminating device 2b illuminates a region in which a plurality of pixels in the image forming device 3b are arranged with substantially uniform brightness by a Kohler illumination method or the like. The illumination device 2b can suppress the speckle from being visually recognized by temporally changing the angular distribution of the light incident on each point of the illuminated area IR.

  The illumination device 2 b includes a light source device 7 and an illumination optical system 8. The illumination optical system 8 temporally changes the angular distribution of light incident on each point on the illuminated area IR while uniformizing the illuminance distribution of the light from the light source device 7 in the illuminated area IR (image forming apparatus 3b). Change.

  The light source device 7 includes, for example, a laser light source, and emits green laser light as coherent light.

  The illumination optical system 8 includes an optical path shift device 9 and a superimposing optical system 10. In the present embodiment, the superimposing optical system 10 includes a fly eye lens 13, a fly eye lens 14, and a superimposing lens 15. The light emitted from the light source device 7 enters the fly-eye lens 13 included in the superimposing optical system 10 via the optical path shift device 9. The optical path shift device 9 temporally changes the incident position of the light emitted from the light source device 7 on the fly-eye lens 13. Details of the optical path shift device 9 will be described later. The superimposing optical system 10 is disposed at a position where light passing through the optical path shift device 9 is incident, and uniformizes the illuminance distribution in the illuminated region IR. Further, the superimposing optical system 10 superimposes light incident on different positions of the superimposing optical system 10 at each point on the illuminated region IR.

  The fly-eye lens 13 includes a plurality of lens elements 13a arranged two-dimensionally on a predetermined surface. The predetermined surface on which the plurality of lens elements 13 a are arranged is substantially parallel to the surface including the light emission region 7 a where light is emitted from the light source device 7. The normal direction of the predetermined surface on which the plurality of lens elements 13 a are arranged is defined as the optical axis 15 a of the superposition optical system 10.

  Each of the plurality of lens elements 13a forms a surface optically conjugate with the surface including the light emission region 7a of the light source device 7 (hereinafter referred to as the first conjugate surface 16). In other words, each of the lens elements 13 a forms a light source image (secondary light source) on the first conjugate surface 16.

  The fly-eye lens 14 includes a plurality of lens elements 14a arranged two-dimensionally. The surface on which the lens elements 14a are arranged is disposed at or near the position of the first conjugate surface 16 formed by the fly-eye lens 13. A light source image is formed on each lens element 14a of the fly-eye lens 14, and a light emission pattern including a plurality of light source images is formed on the fly-eye lens 14 (first conjugate surface 16).

  The superimposing lens 15 superimposes the light emitted from each of the lens elements 14a of the fly-eye lens 14 on substantially the same region (illuminated region IR). The superimposing lens 15 includes, for example, one or more lenses that are rotationally symmetric about a predetermined axis, such as a spherical lens or an aspherical lens. The predetermined axis corresponds to the optical axis of the superimposing lens 15 (the optical axis of the illumination optical system 8), and is substantially perpendicular to the first conjugate surface 16 formed by the light emission region 7a of the light source device 7 and the fly-eye lens 13. It is.

  In the present embodiment, the polarization conversion element 11 is provided in the optical path between the fly-eye lens 14 and the superimposing lens 15. The polarization conversion element 11 converts the polarization state of the light incident from the fly-eye lens 14 so that the polarization state of the light incident on the image forming apparatus 3b is substantially linearly polarized light. In the present embodiment, a field lens 19 is provided in the optical path between the superimposing lens 15 and the illuminated area IR.

  The illumination optical system 8 configured as described above divides the light emitted from the light source device 7 and passed through the optical path shift device 9 into a plurality of partial light beams for each lens element 13 a of the fly-eye lens 13. The illumination optical system 8 superimposes a plurality of partial light beams divided by the fly-eye lens 13 on the illuminated area IR by the superimposing lens 15. Therefore, the illuminance distribution on the illuminated area IR is made uniform.

  An image forming apparatus 3b in FIG. 2 is, for example, a transmissive liquid crystal light valve, and includes a liquid crystal panel 17 having a plurality of pixels, a polarizing plate 18a disposed on the incident side (light source device 7 side) of the liquid crystal panel 17, And a polarizing plate 18b disposed on the exit side (projection system 4 side) of the liquid crystal panel 17. A field lens 19 is disposed in the vicinity of the illuminated region IR on the incident side of the polarizing plate 18a.

  The incident-side polarizing plate 18a transmits linearly polarized light in a first direction parallel to a surface on which a plurality of pixels are arranged in the liquid crystal panel 17 (hereinafter referred to as a pixel arrangement surface), and extends in a second direction orthogonal to the first direction. Blocks (absorbs) linearly polarized light. The liquid crystal panel 17 is controlled by the image control device 20, and changes (modulates) the polarization state of light incident on each pixel for each pixel. The image control device 20 is a part of the control system 5 shown in FIG. 1, for example.

  The exit-side polarizing plate 18b is disposed, for example, so that its transmission axis is orthogonal to the transmission axis of the incident-side polarizing plate 18a. The image control device 20 controls the liquid crystal panel 17 based on the image data, and controls the polarization state of the light passing through each pixel, thereby changing the transmittance of the polarizing plate 18a, the liquid crystal panel 17 and the polarizing plate 18b to the pixel. Control every. In this way, the image forming apparatus 3b forms an image defined in the image data.

  As described with reference to FIG. 1, the image light emitted from the image forming apparatus 3 b enters the projection system 4 via the color synthesis system 6. The projection system 4 forms an image plane optically conjugate with the image forming apparatus 3b (object plane), and the image formed by the image forming apparatus 3b is projected onto the projection plane SC arranged on this image plane. The

  In the projection system 4, a second conjugate surface 21 optically conjugate with the light source image (fly eye lens 14) that becomes the source of illumination light is formed. The second conjugate plane 21 is a so-called pupil plane, and the second conjugate plane 21 has a spot (also called a pupil image, an angle image, etc.) of a pattern corresponding to the angular distribution of light emitted from the image forming apparatus 3b. It is formed.

  By the way, when an image is formed by using coherent light for illumination, for example, a pattern in which bright spots and dark spots are distributed in a striped pattern or a spotted pattern due to interference of image light via the projection plane SC ( Speckle) may be visible. When the speckle is visually recognized by an observer of the image, it may give the viewer a glare, and the quality of the image display may be deteriorated.

  One of the methods for making the speckles less visible is a time multiplexing method in which the speckle pattern on the screen is temporally changed. In this method, the speckle pattern is changed at a frequency that cannot be visually recognized by the observer (for example, 24 Hz or more), so that the time-integrated speckle contrast decreases, and the observer has a specific light-dark pattern. Is difficult to see. For example, if the uncorrelated pattern is switched N times within 1/24 seconds or less, the speckle contrast is reduced to 1 / √N.

  Here, the speckle pattern will be described with reference to FIG. 3 and the following equation (1). FIG. 3 is a diagram for explaining the definition of parameters in the Fresnel diffraction equation (the following equation (1)).

  In FIG. 3, symbols x and y indicate coordinates on the second conjugate plane 21 (the pupil plane of the projection system 4), and symbols x 'and y' indicate coordinates on the projection plane SC (screen). Here, for convenience of explanation, it is assumed that the second conjugate plane 21 and the projection plane SC are parallel to the XY plane (see FIG. 2). The XY plane is a plane orthogonal to the optical axis 15a. A symbol R in FIG. 3 indicates a distance from the second conjugate plane 21 to the projection plane SC.

  The following equation (1) is a so-called Fresnel diffraction equation, u (x ′, y ′) on the left side is the amplitude distribution on the projection surface SC, A on the right side is the amplitude, i is the imaginary unit, and k is the wave number (propagation). Constant), λ is the wavelength of the image light, and f (x, y) is the aperture function. Since the speckle pattern has a corresponding relationship with the amplitude distribution u (x ′, y ′) on the projection surface SC, it is assumed that the speckle pattern changes according to the aperture function f (x, y). The illumination device according to the present embodiment changes the speckle pattern by temporally changing the aperture function f (x, y) indicating the bright and dark pattern on the second conjugate plane 21, thereby reducing speckle. it can.

  FIG. 4 is a diagram for explaining the principle of changing the aperture function f (x, y) with time. In FIG. 4, reference numerals 13 a 1 and 13 a 2 indicate one lens element arbitrarily selected from the plurality of lens elements 13 a of the fly-eye lens 13. Similarly, reference numerals 14a1 and 14a2 denote one lens element arbitrarily selected from the plurality of lens elements 14a of the fly-eye lens 14, respectively.

  Light emitted from the lens element 13a1 (hereinafter referred to as a partial light beam La) passes through the lens element 14a1 and is irradiated on the entire illuminated area IR. Light emitted from the lens element 13a2 (hereinafter referred to as a partial light beam Lb) passes through the lens element 14a2 and is irradiated to the entire illuminated area IR.

  Here, in a state where the sum of the light amount of the partial light beam La and the light amount of the partial light beam Lb is constant, even if the light amount of the partial light beam La and the light amount of the partial light beam Lb are changed, The brightness does not change. On the other hand, the angular distribution of the light incident on each point on the illuminated area IR is different from the relative position of the lens element 14a1 with respect to the illuminated area IR and the relative position of the lens element 14a2 with respect to the illuminated area IR. It changes according to the change of the light quantity of the light beam La and the partial light beam Lb.

  That is, the light pattern (spatial distribution of light intensity) when entering the fly-eye lens 13 changes with time, so that the pattern of the light source image formed on the fly-eye lens 14 changes with time. The pattern of the pupil image on the second conjugate plane 21 (the pupil plane of the projection system 4) optically conjugate with the light source image, that is, the aperture function f (x, y) changes with time.

  The illumination system 2 (illumination device 2b) of this embodiment includes an optical path shift device 9 on the optical path between the light source device 7 and the fly-eye lens 13 (superimposing optical system 10). The optical path shift device 9 temporally changes the incident position of the light emitted from the light source device 7 to the fly-eye lens 13 (superimposing optical system 10). Thereby, the pattern of the light incident on the fly-eye lens 13 changes with time, and as a result, the aperture function f (x, y) changes with time.

  Next, the optical path shift device 9 will be described in detail. As shown in FIG. 2, the optical path shift device 9 includes a first prism 51 that rotates around a rotation axis 50 that intersects the direction of the optical axis 15 a of the superimposing optical system 10. The first prism 51 is provided so as to be rotatable around a rotation axis 50 perpendicular to the optical axis 15a, and is rotated by torque supplied from a drive unit 52 such as an electric motor.

  The first prism 51 is disposed at a position where the light from the light source device 7 is incident, and transmits the light from the light source device 7. The 1st prism 51 has the 1st surface 51a in which the light from a light source device injects, and the 2nd surface 51b parallel to a 1st surface. In the present embodiment, the first prism 51 has a square cross section perpendicular to the rotation axis 50, and has a third surface 51c and a fourth surface 51d perpendicular to the first surface 51a. The third surface 51c and the fourth surface 51d are parallel to each other. The rotation axis 50 is an axis that passes through the center (center of gravity) of a cross section (square) orthogonal to the rotation axis 50 of the first prism 51, for example.

  FIG. 5 is a diagram for explaining the change of the optical path by the optical path shift device 9. In FIG. 5, the rotation angle of the first prism 51 is obtained when the rotation position where the light from the light source device 7 is incident on the first surface 51a from the normal direction of the first surface 51a is the reference position (0 °). The rotational position of the first prism 51 from the reference position is shown.

  In FIG. 5, the light incident on the first surface 51 a in a state where the rotation angle is 0 ° is emitted from the second surface 51 b through the inside of the first prism 51. In the state where the rotation angle is 0 degree, the light incident on the first surface 51a is not refracted by the first surface 51a and the second surface 51b, so that the light path on the incident side to the first surface 51a (hereinafter referred to as the incident-side optical path Lx1). And the exit-side optical path from the second surface 51b (hereinafter referred to as the exit-side optical path Lx2) are coaxial.

  Most of the light from the light source device 7 is incident on the first surface 51a when the rotation angle is not more than a predetermined angle (for example, 15 °). The light incident on the first surface 51a is refracted by the first surface 51a and the second surface 51b and is emitted from the second surface 51b. In the present embodiment, since the first surface 51a and the second surface 51b are parallel to each other, the incident side optical path Lx1 and the emission side optical path Lx2 are parallel to each other. The positions in the direction (here, the X-axis direction) intersecting the direction of the optical axis 15a (Z-axis direction) are shifted from each other. That is, the emission side optical path Lx2 is shifted from the incident side optical path Lx1 in the X-axis direction.

  The shift amount between the incident side optical path Lx1 and the exit side optical path Lx2 (hereinafter referred to as the optical path shift amount d) includes the refractive index of the first prism 51, the distance between the first surface 51a and the second surface 51b, and the first prism. It is determined by the rotation angle of 51. In other words, the optical path shift amount changes according to the rotation angle of the first prism 51, and the optical path shift amount d also changes with time as the rotation angle of the first prism 51 changes with time.

  When the rotation angle is equal to or greater than a predetermined angle (for example, 30 °), the light from the light source device 7 enters the first surface 51a and the third surface 51c. Of the light from the light source device 7, the light incident on the first surface 51 a (hereinafter referred to as the first partial light Ba) is refracted by the first surface 51 a and the second surface 51 b, and its emission side optical path is the first portion. Shift in the X-axis direction with respect to the incident-side optical path of the light Ba. Of the light from the light source device 7, the light incident on the third surface 51c (hereinafter referred to as the second partial light Bb) is refracted by the third surface 51c and the fourth surface 51d, and the emission side optical path is the second portion. Shift in the X-axis direction with respect to the incident side optical path of the light Bb. The exit-side optical path of the first partial light Ba and the exit-side optical path of the second partial light Bb are offset from each other in the X-axis direction, and here are optical paths that do not overlap each other.

  As the rotation angle becomes larger than a predetermined angle, the amount of light incident on the first surface 51a (ratio of the first partial light Ba to the light from the light source device 7) decreases and enters the third surface 51c. The amount of light (the ratio of the second partial light Bb to the light from the light source device 7) increases. Here, when the rotation angle is 45 °, about half of the light from the light source device 7 is incident on the first surface 51a, and the remaining half is incident on the third surface 51c. In a state where the rotation angle is about 45 °, the exit side optical path of the first partial light Ba and the exit side optical path of the second partial light Bb are related to the rotation axis 50 of the first prism 51 and the plane including the light traveling direction. Become symmetrical.

  In addition, the emission side optical path of the first partial light Ba and the emission side optical path of the second partial light Bb are between the rotation angles changing from 0 ° to 45 ° while the rotation angles change from 45 ° to 90 °. It changes symmetrically with respect to the change of the optical path and the YZ plane. For example, the emission side optical path of the first partial light Ba in a state where the rotation angle is 60 ° (45 ° + 15 °) is the emission side optical path of the first partial light Ba in a state of 30 ° (45 ° −15 °). On the other hand, it becomes symmetrical with respect to the YZ plane. When the rotation angle reaches 90 °, the light from the light source device 7 enters the third surface 51c from the normal direction, which is the same as the state where the rotation angle is 0 °. In this way, the optical path shift device 9 temporally changes the incident position of the light emitted from the light source device 7 to the fly-eye lens 13 (superimposing optical system 10).

  The optical path shift device 9 has a fly-eye lens 13 (superimposing optical system 10) for light emitted from the light source device 7 in the same manner as when the rotation angle changes from 0 ° to 90 ° while the rotation angle changes by 90 °. Change the incident position to. While the first prism 51 makes one rotation, the incident position is changed for four periods. Therefore, when the rotation speed of the first prism 51 is set to 6 rotations per second or more, the incident position changes 24 times or more per second (one cycle is 1/24 seconds or less), and the light incident on each point of the illuminated region IR. The angular distribution changes with a period of 1/24 seconds or less. As a result, the speckle pattern changes at a speed higher than a human-identifiable speed (period is 1/24 seconds or less), and is less likely to be visually recognized by a viewer as a fixed pattern.

  In the illuminating device 2b of the present embodiment configured as described above, the position of the light incident on the superimposing optical system 10, that is, the irradiation pattern, is temporally changed by the optical path shift device 9, so that the pupil image pattern (aperture function f (X, y)) can be changed with time, and speckle can be effectively reduced. Moreover, since the projector 1 provided with this illumination device 2b is difficult for the viewer of the image to see the speckles, it is possible to suppress the deterioration of the display quality of the image.

  In addition, since the projector 1 temporally changes the pattern of the pupil image by a device outside the projection system 4 (illumination device 2b), a device for adjusting the angle distribution of the projected light is provided in the projection system 4. In comparison, an increase in the size and cost of the projection system 4 can be avoided. Further, the projector 1 is less required to increase the effective diameter of the pupil plane of the projection system 4 than the method of moving a fixed pattern pupil image on the pupil plane of the projection plane SC. Larger and higher cost can be avoided.

  Next, a modified example of the lighting device 2b will be described.

[First Modification]
FIG. 6 is a diagram illustrating the first prism 51 of the optical path shift device 9 of the first modification. In the present modification, the first prism 51 has a rectangular cross-sectional shape orthogonal to the rotation axis, and the long side length of the cross-sectional shape is different from the short side length. The first prism 51 includes a first surface 51a and a second surface 51b including long sides of a cross-sectional rectangle, and a third surface 51c and a fourth surface 51d including short sides of the cross-sectional rectangle. Have. The distance between the first surface 51a and the second surface 51b corresponds to the length of the short side of the cross-sectional shape, and the distance between the third surface 51c and the fourth surface 51d corresponds to the length of the long side of the cross-sectional shape. To do.

  The optical path shift amount between the incident-side optical path and the exit-side optical path of the first prism 51 is based on the surface on which light is incident on the first prism 51 and the surface on which light incident on this surface is emitted from the first prism 51. It is an amount according to the interval. Therefore, the optical path shift amount d1 of the light incident on the first surface 51a including the long side is different from the optical path shift amount d2 of the light incident on the third surface 51c including the short side.

  FIG. 7 is a diagram showing a change in the optical path accompanying the rotation of the first prism 51. 7A shows an optical path change when the cross-sectional shape orthogonal to the rotation axis of the first prism 51 is a square, and FIG. 7B shows a cross-section orthogonal to the rotation axis of the first prism 51. The optical path change when the shape is rectangular is shown.

  As shown in FIG. 7A, the optical path change when the cross-sectional shape of the first prism 51 is square includes a mode (first mode) during which the rotation angle changes from 0 ° to 45 °, and a rotation angle. Includes a mode (second mode) during which the angle changes from 45 ° to 90 °, and the first mode and the second mode are symmetrical with respect to a plane parallel to the YZ plane as described above.

  As shown in FIG. 7B, the optical path change when the cross-sectional shape of the first prism 51 is rectangular includes a mode in which the rotation angle changes from 0 ° to 45 °, and a rotation angle from 45 ° to 90 °. The aspect while changing to is asymmetric with respect to a plane parallel to the YZ plane. Therefore, the variation of the optical path change is more diversified than the case where the cross-sectional shape is a square, and the variation of the change of the angular distribution of the light incident on each point of the illuminated region IR is diversified. As a result, the variation of the change of the speckle pattern is diversified, and the speckle can be effectively reduced.

  Note that the cross-sectional shape of the first prism 51 on the surface orthogonal to the rotation axis 50 (see FIG. 2) of the first prism 51 may not be rectangular. When the first prism 51 having parallel surfaces is used, in addition to a prism having a rectangular cross-sectional shape, a polygonal prism such as a parallelogram, rhombus, trapezoid, hexagon, octagon, etc. A prism having a rounded corner shape or the like can be used. Further, the first prism 51 may not have surfaces parallel to each other, and the shape of the first prism 51 can be changed as appropriate so that the superimposing optical system 10 can swallow light from the first prism 51.

[Second Modification]
FIG. 8 is a diagram illustrating an illumination device 2b according to a second modification. In the illumination device 2b, the optical path shift device 9 includes a second prism 53 disposed at a position where light from the first prism 51 enters.

  The second prism 53 is provided so as to be rotatable around a rotation axis 54 that intersects the direction of the optical axis 15a. The second prism 53 rotates around the rotation shaft 54 by torque supplied from a drive unit such as an electric motor. In this modification, the rotation axis 54 of the second prism 53 is substantially parallel to the rotation axis 50 of the first prism 51. The rotating shaft 54 is set so as to pass through the center (center of gravity) of the shape of the second prism 53 in a cross section orthogonal to the rotating shaft 54, for example. The cross-sectional shape of the second prism 53 on the plane orthogonal to the rotation axis 54 is a square in the present modification, but may be a rectangle as described in the first modification, or a shape other than a rectangle.

  The second prism 53 transmits the light from the first prism 51. The second prism 53 temporally changes the optical path between the first prism 51 and the superimposing optical system 10 based on the same principle as the first prism 51. In this modification, the direction in which the incident position of light incident on the superposition optical system 10 changes (shifts) is perpendicular to the optical axis 15a (Z-axis direction) and the rotation axis 50 (Y-axis direction) of the first prism 51. Is a direction perpendicular to (X-axis direction).

  In this modification, the optical path of light when entering the superimposing optical system 10 via the second prism 53 changes according to the rotation angle of the first prism 51 and the rotation angle of the second prism 53. For this reason, the illumination device 2b of the present modification has various variations in optical path changes, and various variations in the angular distribution of light incident on each point of the illuminated region IR. As a result, the variation of the change in the speckle pattern is diversified, and the speckle can be effectively reduced.

  The rotation angle of the second prism 53 is appropriately set so that the incident position of the light incident on the superimposing optical system 10 changes with time. For example, the rotation angle of the second prism 53 may always be the same as the rotation angle of the first prism 51. For example, when the second prism 53 rotates at the same rotational speed as that of the first prism 51 from a state in which the rotational angle defined in the same manner as in FIG. It will always be the same.

  Further, the rotation angle of the second prism 53 may be different from the rotation angle of the first prism 51 in a part during rotation. For example, when the rotation angle of the second prism 53 is the same as the rotation angle of the first prism 51 and rotates at a rotation speed different from that of the first prism 51, the rotation angle of the second prism 53 is different from that of the first prism 51. It will be.

  Further, the rotation angle of the second prism 53 may always be different from the rotation angle of the first prism 51 during the rotation. For example, when the second prism 53 rotates at the same rotational speed as the first prism 51 from a state in which the rotation angle is different from the rotation angle of the first prism 51, the rotation angle is always different from that of the first prism 51 during the rotation. Become.

[Third Modification]
FIG. 9 is a diagram showing an illumination device 2b according to a third modification. In this illumination device 2 b, the rotation axis 54 of the second prism 53 of the optical path shift device 9 intersects the direction of the optical axis 15 a of the superposition optical system 10 and the direction of the rotation axis 50 of the first prism 51.

  In this modification, the direction in which the optical path is shifted by the rotation of the first prism 51 is the X-axis direction, and the direction in which the optical path is shifted by the rotation of the second prism 53 is the Y-axis direction. That is, the illumination device 2b of the present modification can change the incident position of the light incident on the superposition optical system 10 in two directions. For this reason, the illumination device 2b of the present modification has various variations in optical path changes, and various variations in the angular distribution of light incident on each point of the illuminated region IR. As a result, the variation of the change in the speckle pattern is diversified, and the speckle can be effectively reduced.

  In the above-described embodiment and modification, the example in which the prism of the optical path shift device 9 rotates in one of the forward direction and the reverse direction around the rotation axis has been described. A mode of rotating in both the forward direction and the reverse direction is also possible.

[Fourth Modification]
FIG. 10 is a diagram showing an illumination device 2b according to a fourth modification. In the illumination device 2b, the optical path shift device 9 includes a mirror 55 on which light from the light source device 7 is incident, a mirror 56 that guides the light reflected by the mirror 55 to the superimposing optical system 10, and a moving unit 57 that moves the mirror 55. With.

  The mirror 55 is inclined non-perpendicular with respect to the light emission direction 15 b of the light source device 7. The mirror 56 is tilted non-perpendicular with respect to the optical axis 15a. For example, the mirror 55 and the mirror 56 are disposed so as to be substantially parallel to each other. The moving unit 57 moves the mirror 55 along a direction in a plane perpendicular to the mirror 55. For example, the moving direction of the mirror 55 by the moving unit 57 is a direction perpendicular to the light emission direction of the light source device 7.

  In the present modification, the incident position on the mirror 55 of the light from the light source device 7 changes in time with the movement of the mirror 55 by the moving unit 57, and the incident position on the mirror 56 changes in time. . Therefore, also with such an optical path shift device 9, the incident position of the light incident on the superimposing optical system 10 can be temporally changed in a direction intersecting the direction of the optical axis 15a.

  The moving direction of the mirror 55 may be parallel to or intersecting with the light emission direction of the light source device 7. The optical path shift device 9 may be configured to move the mirror 56 instead of moving the mirror 55, or may be configured to move the mirror 55 and the mirror 56. When both the mirror 55 and the mirror 56 are moved, the moving speed of each mirror and the relative position of both mirrors can be appropriately set so that the incident position of the light incident on the superimposing optical system 10 changes. Further, the mirror 55 and the mirror 56 may not be parallel to each other. The optical path shift device 9 may be configured to shift the optical path by rotating one or both of the mirror 55 and the mirror 56, or may be configured to shift the optical path by both rotation and translation of the mirror.

[Fifth Modification]
FIG. 11 is a diagram showing the light source device 7 of the illumination device 2b according to the fifth modification. The light source device 7 has a plurality of light emission regions that emit coherent light, and can adjust the light amount (hereinafter referred to as cell light amount) of light emitted from each of the light emission regions. The light source device 7 is a so-called laser light source array, and includes a plurality of laser light sources 60. In the light source device 7, each of the plurality of light emission regions corresponds to a light emission port of each laser light source 60.

  In the light source device 7, the plurality of laser light sources 60 are two-dimensionally arranged. However, the plurality of laser light sources 60 may be arranged so that the plurality of lights are arranged at least in the direction (Y-axis direction) intersecting the direction in which the optical path changes (X-axis direction). In the present modification, the plurality of laser light sources 60 are arranged at least in the Y-axis direction, and light beams from the plurality of laser light sources 60 arranged in the Y-axis direction are emitted from the optical path shift device 9 in the Y-axis direction. It is lined up in the direction.

  The laser light source 60 is a solid light source that emits a laser beam having a light amount corresponding to the supplied power. Therefore, the light source device 7 can adjust the light amount (cell light amount) emitted from each light emission region by adjusting the power supplied to each laser light source 60.

  Note that the cell light amount is a concept including 0. For example, when the laser light source is turned off without power being supplied to the laser light source 60, the cell light amount is 0. That is, the cell light amount can be adjusted by switching the laser light source 60 on and off, and can also be adjusted by reducing the light emission amount while the laser light source 60 is turned on.

  The power supplied to each laser light source 60 of the light source device 7 is controlled by the light source control device 61. The light source control device 61 is a part of the illumination device 2 b in the present modification, for example, a part of the light source device 7. The light source controller 61 controls the amount of light emitted from each laser light source 60 (light emission region) (that is, the amount of cell light) by controlling the power supplied to each laser light source 60. For example, the light source control device 61 switches the laser light source 60 from off to on by starting power supply to the laser light source 60. Further, the light source control device 61 switches the laser light source 60 from turning on to turning off by stopping the power supply to the laser light source 60.

  Further, the light source control device 61 increases or decreases the light emission amount of the laser light source 60 by increasing or decreasing the power supplied to the laser light source 60 when the laser light source 60 is turned on. When the laser light source 60 is pulse-driven, as a method for increasing / decreasing the supply power, a method for increasing / decreasing the current value (pulse amplitude) supplied to the laser light source 60 (for example, amplitude modulation), and a current to the laser light source 60 are used. One or both of methods (pulse width modulation) for increasing or decreasing the supplied time (pulse width) may be used.

  FIG. 12 is a timing chart showing an example of control of the laser light source 60 by the light source control device 61. In FIG. 12, the first to third laser light sources are each arbitrarily selected from a plurality of laser light sources 60, and are, for example, three laser light sources arranged in the Y-axis direction. In FIG. 12, the horizontal axis indicates the time during which the laser light source is being driven, and the vertical axis indicates the level of power (current value) supplied to the laser light source. Reference sign PH indicates a high level of supply power, and reference sign PL indicates a low level of supply power. For example, the level PH is supply power at which the laser light source emits a predetermined amount of light, and the level PL is supply power at which the laser light source does not emit light (in short, 0). The level PL may be power supplied by the laser light source that emits less light than the level PH.

  The light source control device 61 maintains the first laser light source in the extinguished state by maintaining the power supplied to the first laser light source at the level PL during a period T1 (first period) from time t0 to t1. To do. Further, the light source control device 61 maintains the supply power to the second laser light source and the third laser light source at the level PH in the period T1, thereby turning on the second laser light source and the third laser light source. To maintain.

  At time t1, the light source control device 61 switches on the power supplied to the first laser light source to the level PH to turn on the first laser light source and switches the power supplied to the second laser light source to the level PL. This turns off the second laser light source. The light source control device 61 maintains the first laser light source and the third laser light source in the on state and maintains the second laser light source in the off state during the period T2 (second period) from time t1 to t2. To do. Similarly, the light source control device 61 maintains the first laser light source and the second laser light source in a lighting state during a period T3 (third period) from time t2 to time t3, and turns on the third laser light source. Keep it off.

  As described above, the light source control device 61 changes the laser light source 60 so that the combination of the laser light sources 60 that are lit among the plurality of laser light sources 60 (hereinafter referred to as lighting patterns) changes between the period T1 and the period T2. Control. In other words, the light source control device 61 controls the laser light source 60 so that the spatial distribution (light emission pattern) of the light emitted from the light source device 7 changes between the period T1 and the period T2. The lengths of the period T1 and the period T2, for example, are set to be equal to or shorter than the time during which a human can perceive a change in the image, and may be 1/24 seconds or less, or 1/30 seconds or less. .

  FIG. 13 is a diagram for explaining temporal changes in the lighting pattern and the light emission pattern of the light source device 7. FIG. 13B is a diagram schematically showing a light emission pattern of the laser light source array. In the lighting pattern shown in FIG. 13A, the plurality of laser light sources 60 are all lit, and the light emission pattern LP1 of FIG. 13B corresponding to this state is occupied by the bright portion LP2. In the lighting pattern shown in FIG. 13C, some laser light sources (indicated by reference numeral 60a) are turned off and the remaining laser light sources (indicated by reference numeral 60b) are turned on. The light emission pattern LP3 of 13 (d) is a pattern including a dark portion LP4 that is darker than the light portion LP2 as compared with the light emission pattern LP1 at the time of full lighting. Thus, the light source control device 61 changes the lighting pattern of the light source device 7 with time.

  When the light emission pattern changes with time, the incident position of the light emitted from the light source device 7 on the superimposing optical system 10 changes with time, and the second conjugate surface 21 (projection) optically conjugate with the fly-eye lens 14. The light intensity distribution (pupil image) on the pupil plane of the system 4 changes with time.

  FIG. 14 is a diagram illustrating an example of a change in brightness distribution (pupil image) on the second conjugate plane 21 when some of the plurality of laser light sources 60 are turned off. 14A corresponds to a state in which all of the plurality of laser light sources 60 are turned on, and FIG. 14B corresponds to a state in which some of the plurality of laser light sources 60 are turned off. Since the second conjugate plane 21 (the pupil plane of the projection system 4) is optically conjugate with the light source image (fly eye lens 14), the brightness distribution (spot distribution) on the second conjugate plane 21 is fly-eye. There is a correspondence relationship with the brightness distribution in the lens 14.

  In a state where all of the plurality of laser light sources 60 are turned on, a light source image is formed on each of the lens elements 14 a of the fly-eye lens 14. In a state where a part of the plurality of laser light sources 60 is turned off, a light source image derived from the turned off laser light sources 60 is not formed, and a dark portion LP4 is formed on the second conjugate surface 21. As described above, the illumination device 2b effectively selects a pupil image by selecting at least one of the plurality of laser light sources 60, switching between turning on and off, and changing the laser light source 60 to be selected over time. Can be changed over time.

  The illumination device 2b of this modification not only changes the incident position of the light incident on the superimposing optical system 10 by the optical path shift device 9, but also temporally changes the light emission pattern of the light source device 7 by the light source control device 61. The incident position of the light incident on the superimposing optical system 10 is also temporally changed by changing the position. Therefore, the illuminating device 2b can increase the variation of the pupil image change, and can effectively reduce speckle.

  For example, the optical path shift device 9 temporally changes the incident position of light incident on the superimposing optical system 10 in the X-axis direction, and the light source control device turns on a laser that is lit among the laser light sources 60 aligned in the Y-axis direction. The combination of the light sources 60 is changed with time. Thereby, the pattern of the pupil image changes in each of the X-axis direction and the Y-axis direction, so that the illumination device 2b can effectively reduce speckle.

  Note that the light source control device 61 controls the light source device 7 so that the number of laser light sources 60 that are turned on among the plurality of laser light sources 60 is the same in the period T1 and the period T2. As a result, the amount of light emitted from the light source device 7 becomes substantially the same in the period T1 and the period T2, and the illumination device 2b has the same brightness in the illuminated region IR (image forming system 3) in the period T1 and the period T2. Now illuminate.

  Note that the number of the laser light sources 60 that are kept off at each time during which light is emitted from the light source device 7 may be one or two or more. Further, instead of making the number of the laser light sources 60 in the lit state the same in the period T1 and the period T2, the amount of light emitted from the light source device 7 is substantially the same in the period T1 and the period T2. The light emission amount of the laser light source 60 to be turned on may be adjusted. Moreover, the illuminating device 2b may vary the amount of light emitted from the light source device 7 between the period T1 and the period T2, for example, in order to widen the dynamic range.

  In addition, the combination (lighting pattern) of the laser light sources 60 maintained in the lighting state in each period among the plurality of laser light sources 60 can be appropriately changed. For example, the light source control device 61 may reduce or increase the power supplied to each of at least two laser light sources adjacent to each other. That is, the light source control device 61 may turn off two or more laser light sources 60 arranged in the row direction out of the plurality of laser light sources 60 arranged two-dimensionally, or may be arranged in the column direction 2. The above laser light sources 60 may be turned off collectively. Thereby, since the variation | change_quantity of the pattern of a pupil image can be increased, the illuminating device 2b can reduce a speckle effectively.

  Note that the light source control device 61 makes the power supplied to at least one part of the plurality of laser light sources 60 relatively small among the plurality of laser light sources 60 and is adjacent to the laser light source 60 having relatively small power supply. The power supplied to the laser light source 60 may be relatively increased among the plurality of laser light sources 60. Such an illuminating device 2b can make up for the decrease in the light emission amount of the laser light source 60 whose supply power has been reduced by the increase in the light emission amount of the laser light source 60 whose supply power has been increased. In addition, the laser light source 60 with the reduced power supply reduces the amount of heat generation, and the power supply of the laser light source 60 adjacent to the laser light source 60 is increased. Therefore, the heat dissipation of the laser light source 60 that increases the power supply is ensured. be able to.

  In the example of FIG. 12, the first period (period T1) and the second period (period T2) do not overlap, but the first period and the second period partially overlap, And the other part does not need to overlap. In this case, the first period does not overlap with the second period, the first period overlaps with the second period, and the second period does not overlap with the first period. The lighting pattern differs depending on the period, and the lighting pattern can be changed into three types from the start of the first period to the end of the second period.

[Sixth Modification]
In the above embodiment, a transmissive liquid crystal light valve is used as the image forming apparatus 3b. In the transmissive liquid crystal light valve, a light shielding layer (black matrix) that covers the periphery of the pixel P is provided. The opening of the light shielding layer corresponds to the pixel P. Since the light shielding layer shields part of the illumination light, the use efficiency of the illumination light is reduced. Therefore, in a transmissive liquid crystal light valve, a microlens may be provided for each pixel. However, when the refractive power of the microlens is large, the speckle reduction effect according to the present invention may be reduced. Therefore, in this modification, the image forming apparatus 3b includes an afocal optical system, thereby suppressing a reduction in speckle reduction effect.

  The configuration of the image forming apparatus 3b according to this modification will be described. FIG. 15 is a diagram illustrating an example of the image forming apparatus 3b. The image forming apparatus 3b includes an afocal optical system 30, and the afocal optical system 30 includes a first micro lens 31a and a second micro lens 31b. In this example, the first microlens 31 a and the second microlens 31 b are lens arrays provided on the same optical member, and this optical member is disposed on the incident side of the liquid crystal layer 32.

  The afocal optical system 30 of this example is a so-called Kepler type, and the first microlens 31a and the second microlens 31b are convex lenses each having a positive power (refractive power). The first microlens 31 a is provided for each pixel P on the incident light incident side with respect to the liquid crystal layer 32. The second micro lens 31 b is disposed between the focal position of the first micro lens 31 a and the liquid crystal layer 32.

  The image forming apparatus 3 b includes a light shielding layer 33 (black matrix) that covers the periphery of the pixel P, and the afocal optical system 30 is configured so that the light beam incident on each pixel P is accommodated in the opening of the light shielding layer 33. Reduce the beam diameter. Therefore, in the image forming apparatus 3b, the light loss in the light shielding layer 33 is reduced, and the light use efficiency is increased.

  In addition, since the afocal optical system 30 converts the light beam incident on each pixel P into a parallel light beam, the influence of the image forming device 3b on the angular distribution of light passing through the image forming device 3b can be reduced. Therefore, it becomes easy to reflect the angle distribution of the light which the illuminating device 2b changes temporally in the pupil image on the 2nd conjugate plane 21, and the effect which makes it difficult to visually recognize a speckle can be heightened.

  16 to 18 are diagrams showing other examples of the image forming apparatus 3b. In the image forming apparatus 3b shown in FIG. 16, the afocal optical system 30 is a so-called Galileo type, the first microlens 31a is a convex lens having a positive power, and the second microlens 31b has a negative power. It is a concave lens. The Galileo afocal optical system 30 can make the optical path length shorter than the Kepler type.

  In the image forming apparatus 3b shown in FIG. 17, the afocal optical system 30 is a Kepler type, and the first microlens 31a and the second microlens 31b are both convex lenses having positive power. In this example, the first microlens 31a and the second microlens 31b are lens arrays provided on separate optical members, respectively. The first microlens 31 a is disposed on the incident side with respect to the liquid crystal layer 32, and the focal position thereof is disposed, for example, inside the liquid crystal layer 32. The second microlens 31 b is disposed on the light emission side with respect to the liquid crystal layer 32.

  When the Kepler type afocal optical system 30 is used, by using the optical path between the first microlens 31a and the second microlens 31b as the arrangement space of the liquid crystal layer 32 as in this example, For example, the image forming apparatus 3b can be thinned. In addition, the Kepler afocal optical system 30 can easily reduce the beam diameter of light when passing through the opening of the light shielding layer 33 as compared with the Galileo system, so that loss of light in the light shielding layer 33 can be easily reduced.

  In the image forming apparatus 3b shown in FIG. 18, the afocal optical system 30 is of the Galileo type, the first micro lens 31a is a convex lens having a positive power, and the second micro lens 31b is a concave lens having a negative power. is there. The first microlens 31 a is disposed on the incident side of the liquid crystal layer 32, and the second microlens 31 b is disposed on the exit side of the liquid crystal layer 32. Such an image forming apparatus 3b can be made much thinner than, for example, a Kepler type.

  In the illumination device 2b of this modification, the incident position of the light incident on the superimposing optical system 10 is temporally changed by the optical path shift device 9, so that the pattern of the pupil image can be temporally changed, and the speckle can be changed. It can be effectively reduced. Moreover, since the projector 1 provided with this illumination device 2b is difficult for the viewer of the image to see the speckles, it is possible to suppress the deterioration of the display quality of the image.

  Further, in the projector 1 of this modification, the pupil image pattern is temporally changed by a device (illumination device 2b) outside the projection system 4, so that the projection system 4 can be prevented from becoming large and expensive. it can. Further, the projector 1 is less required to increase the effective diameter of the pupil plane of the projection system 4 than the method of moving a fixed pattern pupil image on the pupil plane of the projection plane SC. Larger and higher cost can be avoided.

  In addition, since the image forming apparatus 3b of the present modification includes the afocal optical system 30, it is possible to reduce the influence of the image forming apparatus 3b on the angular distribution of light passing through the image forming apparatus 3b. Therefore, it becomes easy to reflect the angle distribution of the light which the illuminating device 2b changes temporally in the pupil image on the 2nd conjugate plane 21, and the effect which makes a speckle difficult to visually recognize can be heightened further.

[Second Embodiment]
A second embodiment will be described. FIG. 19 is a diagram illustrating the illumination device 2b and the image forming system 3 (image forming device 3b) according to the second embodiment. The optical path shift device 9 has the same configuration as the optical path shift device described in the first embodiment. This illumination device 2b is different from the first embodiment in the configuration of the superimposing optical system 10b. In the present embodiment, the superimposing optical system 10 includes an input lens 35, an optical rod 36, and a relay optical system 37.

  The light from the optical path shift device 9 enters the input lens 35. The input lens 35 condenses the light from the optical path shift device 9 so as to be within the incident end face 36 a of the optical rod 36. The input lens 35 includes, for example, a lens that is axisymmetric with respect to a predetermined axis.

  FIG. 20 is a view showing the optical rod 36. The optical rod 36 is a so-called rod integrator (rod lens) or the like. The central axis of the optical rod 36 is the optical axis 8a of the superposition optical system 10. The optical rod 36 is a quadrangular prism-shaped optical member extending in a direction parallel to the optical axis 8a. The optical rod 36 has an incident end face 36a, an inner face 36b, and an exit end face 36c. The incident end face 36a and the exit end face 36c are substantially parallel to each other and are substantially orthogonal to the optical axis 8a. The inner surface 36b is an inner surface of four side surfaces connecting the incident end surface 36a and the exit end surface 36c, and is substantially parallel to the optical axis 8a.

  For example, the incident end surface 36a is disposed at or near the position where the light source image is formed by the input lens 35. The light emitted from the light source device 7 enters the incident end surface 36a via the input lens 35 (see FIG. 19). The angular distribution of light when entering the incident end face 36a is a distribution according to the optical path that changes with time by the optical path shift device 9.

  For example, a component having a relatively large divergence angle (wide angle component) in the light incident on the incident end surface 36a of the optical rod 36 corresponds to light passing through an optical path relatively far from the optical axis 8a. In addition, a component having a relatively small divergence angle (telephoto component) in the light incident on the incident end surface 36a of the optical rod 36 corresponds to light passing through an optical path relatively close to the optical axis 8a.

  The light incident on the incident end surface 36a of the optical rod 36 is guided to the exit end surface 36c by multiple reflection at the inner surface 36b. The number of reflections of light on the inner surface 36b is different for each angle component, and the number of reflections of the wide-angle component is larger than the number of reflections of the telephoto component. On the exit end surface 36c of the optical rod 36, the number of reflections such as a light beam with zero reflection on the inner surface 36b, a light beam Lb with one reflection as shown in FIG. 20, and a light beam Lc with two reflections as shown in FIG. Are superimposed on each other, and the illuminance distribution on the exit end face 36c is made uniform.

  FIG. 21 is a diagram showing the optical rod 36 and the relay optical system 37. The relay optical system 37 forms a surface (illuminated region IR) optically conjugate with the emission end surface 36c of the optical rod 36. Since the illuminance distribution of the light from the light source device 7 is made uniform at the exit end face 36c of the optical rod 36, it is also made uniform in the illuminated region IR conjugate with the exit end face 36c. As described above, the superimposing optical system 10 makes the illuminance distribution in the illuminated region IR uniform by superimposing the light beams from the plurality of light emission regions (laser light sources 60) of the light source device 7 on the illuminated region IR. .

  Incidentally, the relay optical system 37 is formed with a third conjugate plane 38 (so-called pupil plane) conjugate with the light source image formed by the input lens 35. This third conjugate plane 38 is also optically conjugate with the second conjugate plane 21 of the projection system 4 shown in FIG. The illuminating device 2b changes the spot pattern on the third conjugate plane 38 with time by changing the optical path at the time of entering the superimposing optical system 10 with the optical path shift device 9, thereby changing the first pattern of the projection system 4. 2 The pupil image pattern on the conjugate plane 21 is changed with time.

  FIG. 22 is a diagram showing an example of a light source image pattern LP5 formed on the incident end face 36a of the optical rod 36. As shown in FIG. FIG. 23 is a diagram showing a spot pattern LP5 (pupil image) formed on the third conjugate plane 38 corresponding to the light source image pattern of FIG. In FIG. 22, reference numerals 40 a to 40 d indicate light spots that pass through different optical paths through the optical path shift device 9.

  As shown in FIG. 20, a plurality of light beams having different numbers of reflections on the inner surface 36b are incident on each point of the emission end surface 36c of the optical rod 36. Therefore, when observed from the exit side of the optical rod 36, it appears that the real image Im1 and the plurality of virtual images Im2 of the light source image are arranged on the surface including the incident end surface 36a. In this example, since the third conjugate plane 38 has a substantially conjugate relationship with the incident end face 36a, the third conjugate plane 38 corresponds to the pattern 41a corresponding to the real image Im1 and the virtual image Im2 as shown in FIG. A plurality of patterns 41b are arranged. The pattern 41 a and the pattern 41 b are patterns (mirror image, inverted image) that are line symmetric with respect to the boundary line 42 corresponding to the inner surface 36 b of the optical rod 36.

  Here, it is assumed that the region 43a conjugate with the spot 40a on the third conjugate plane 38 is arranged in the vicinity of the boundary line 42a and the boundary line 42b that intersect each other. A region 43b symmetric with the region 43a with respect to the boundary line 42a, a region 43c symmetric with the region 43b with respect to the boundary line 42b, and a region 43d symmetric with the region 43c with respect to the boundary line 42a are regions conjugated with the spot 40a. The region 43e symmetric with the region 43a with respect to the boundary line 42c, the region 43f symmetric with the region 43e with respect to the boundary line 42d, and the region 43g symmetric with the region 43f with respect to the boundary line 42c are also conjugate regions with the light emitting region 40a. . Therefore, when the brightness of the spot 40a changes, the brightness of a large number of areas (9 areas in the example of FIG. 23) collectively changes. Accordingly, the change in the pattern of the light source image on the third conjugate plane 38 becomes large.

  In the illuminating device 2b of the present embodiment, the optical path is temporally changed by the optical path shift device 9, so that the incident position of light on the input lens 35 (superimposing optical system 10) changes temporally. This makes it difficult for the observer to see the speckles. Further, since the light source image (for example, the spot 40a) corresponding to one of the optical paths which the optical path shift device 9 changes with time is in correspondence with a plurality of regions on the third conjugate plane 38, the optical path shift device 9 Compared with the change in the optical path, the change in the pattern of the pupil image on the third conjugate plane 38 can be increased, and the speckle can be effectively reduced.

  The technical scope of the present invention is not limited to the above embodiment. The requirements described in the above embodiments can be combined as appropriate. In addition, at least one of the requirements described in the above embodiment may be omitted.

  In the above-described embodiment, an illuminating device is provided for each image forming apparatus, but one illuminating device may be provided for a plurality of image forming apparatuses. For example, the illumination device may be configured to separate each color light from light including a plurality of color lights (in short, white light) and guide each color light to the image forming apparatus for each color. The light source device that generates white light includes, for example, a laser light source that emits red laser light, a laser light source that emits green laser light, and a laser light source that emits blue laser light, and each color laser light is dichroic. The composition may be made by a prism or a dichroic mirror. The light source device that generates white light may include a solid light source such as a light emitting diode, a short arc lamp light source such as a metal halide lamp, and the like.

  Note that at least a part of the superimposing optical system 10 may be provided as a part of the light source device 7. For example, in the illuminating device 2b shown in FIG. 2, the light source device 7 may be an optical unit including the fly-eye lens 13 and the fly-eye lens 14. In this case, the light source device 7 can adjust the amount of light emitted from each of the lens elements 14 a of the fly-eye lens 14 by adjusting the light emission amount of the laser light source 60. Therefore, in the light source device 7, each of the lens elements 14a of the fly-eye lens 14 corresponds to a light emission region.

  In the above embodiment, the projector 1 is a projector including a three-plate transmissive liquid crystal, but images of each color are projected sequentially in time, and the images of each color are integrated and observed over time. In this case, a full color image may be expressed. The number of colors of the image displayed by the projector 1 is not limited, and a single color image may be displayed. Instead of expressing a full color image with three colors (three channels) of color light, an image is displayed with two or more color lights. It may be displayed.

  The light modulator used in the image forming apparatus may be a reflective liquid crystal device, a digital mirror device, or the like in addition to the transmissive liquid crystal device. The light modulator may be a light valve based on HTPS (High Temperature Poly-Silicon) technology, LCOS (Liquid Crystal on Silicon) technology, or the like, and includes a light shielding film 33 (black matrix) as shown in FIGS. It does not have to be. When an optical modulator other than the liquid crystal device is used as the optical modulator, the field lens 19 may be omitted.

DESCRIPTION OF SYMBOLS 1 Projector, 2a-2c Illuminating device, 3a-3c Image forming apparatus, 4 Projection system, 7 Light source device, 9 Optical path shift device, 10 Superimposing optical system, 13-14 Fly eye lens, 15 Superimposing lens, 36 Optical rod, 37 Relay optical system, 50 rotation axis, 51 first prism, 53 second prism, 54 rotation axis, IR illuminated area, SC projection plane

Claims (16)

A light source device;
A superimposing optical system into which light from the light source device is incident;
An illumination device comprising: an optical path shift device that temporally changes an incident position of light emitted from the light source device to the superimposing optical system. The optical path shift device is
The illuminating device according to claim 1, further comprising a first prism that transmits light from the light source device and rotates around a rotation axis that intersects an optical axis direction of the superimposing optical system. The lighting device according to claim 2, wherein the first prism has a first surface on which light from the light source device is incident and a second surface parallel to the first surface. The lighting device according to claim 3, wherein the first prism has a square cross-sectional shape perpendicular to the rotation axis. The lighting device according to claim 3, wherein the first prism has a rectangular cross-sectional shape orthogonal to a rotation axis thereof. The lighting device according to claim 4, wherein a rotation speed of the first prism is 6 rotations or more per second. The optical path shift device is
The illumination device according to any one of claims 2 to 6, further comprising a second prism that transmits light from the first prism and rotates around a rotation axis that intersects an optical axis direction of the superimposing optical system. The illuminating device according to claim 7, wherein the rotation axis of the second prism intersects the direction of the rotation axis of the first prism. The illuminating device according to claim 1, wherein the light source device includes a plurality of light sources arranged in a direction intersecting a direction in which the incident position changes. In the first period, the amount of light emitted from the first light source among the plurality of light sources is different from the amount of light emitted from other light sources in the plurality of light sources, and the second amount out of the plurality of light sources in the second period. The lighting device according to claim 9, further comprising: a light source control device that controls the light source device so that a light emission amount of the light source is different from a light emission amount of the second light source in the first period. The illuminating device according to claim 10, wherein the light source control device decreases or increases each of light emission amounts of light sources adjacent to each other among the plurality of light sources. The said light source control apparatus increases the emitted light amount of the other light source of the said adjacent light source, when reducing the emitted light amount of one light source of the light sources adjacent to each other among these light sources. Lighting device. The superimposing optical system includes:
A lens array including a plurality of lens elements on which light from the optical path shifting device is incident;
The illuminating device according to claim 1, further comprising: a superimposing lens that superimposes light from each of the plurality of lens elements on the illuminated area. The superimposing optical system includes:
An optical rod having an incident end face to which light is incident and an exit end face from which light incident from the incident end face is emitted;
The illuminating device according to claim 1, further comprising: a relay system that optically conjugates the emission end face of the optical rod and the illuminated region. The lighting device according to any one of claims 1 to 14,
An image forming system for forming an image with light from the illumination device;
And a projection system that projects an image formed by the image forming system. The image forming system includes:
A first microlens provided in each of a plurality of pixels arranged in the illuminated region;
The projector according to claim 15, further comprising: a second microlens that forms an afocal optical system together with the first microlens.

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