JP2012008301A - Volume-scanning type 3d image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a 3D image display device whose scanning optical system can be compactly configured and that can alleviate the problem of increased vibration and noise when driven, be more easily increased in size than conventional optical systems and display larger 3D pictures.SOLUTION: A volume-scanning type 3D image display device comprises a display unit that displays images as objects of projection, a scanning element that varies the angle of emission relative to the angle of incidence by curving incident light from the display unit and whose face can rotate in a state of being orthogonal to or inclined relative to the direction of incidence of the incident light from the display unit, and an image forming element that causes the light emitted from the scanning element to form an image.

Description

The present invention relates to a three-dimensional video display device capable of displaying a stereoscopic aerial video by a volume scanning method.

In recent years, techniques for enabling viewing of stereoscopic images have been developed. Many of the stereoscopic display devices in practical use currently use only binocular parallax among the stereoscopic viewing factors, but cannot meet the conditions such as focus adjustment and convergence when viewing stereoscopic images. Therefore, there is a problem that eyes are fatigued by watching for a long time, and a technique that is easier to use is desired.

For example, the following non-patent document 1 discloses a three-dimensional image display device based on a volume scanning method. FIG. 11 shows a schematic configuration diagram of the 3D video display apparatus. A confocal convex lens is used as the imaging optical system, and a two-dimensional display capable of high-speed display is arranged inclined with respect to the optical axis of the optical system, and is inclined with respect to the optical axis by a mirror scanner, a galvanometer mirror, or the like. A three-dimensional image is formed by moving the two-dimensional image and displaying a cross-sectional image of the display object on the two-dimensional display accordingly. According to this, since a three-dimensional real image is formed, a wearing object such as eyeglasses is unnecessary, and it is expected to satisfy all the factors of human perception of stereoscopic vision.

FIG. 12 is a schematic configuration diagram showing another three-dimensional video display device. In this apparatus, a transmissive surface-symmetric imaging optical element is used as the imaging element. The transmission-type plane-symmetric imaging optical element forms a projection object without distortion as a real image at an equal magnification in a plane-symmetric position with respect to a symmetry plane set in the optical system, as disclosed in Patent Document 1 below. Is. When this element is used for imaging, an image can be formed at a free position that is not limited by the focal length, and there is no distortion of the image generated by the convex lens.

“Volumetric display systembased on three-dimensional scanning of inclined optical image”, Daisuke Miyazaki et al, Optic Express, Vol. 14 Issue 26, pp12760-12769

JP 2009-75483 A

However, since the above-described 3D video display apparatus uses a mirror as a scanning element, the angle at which the display image can be observed is limited by the mirror size. When the size of the mirror is expanded, a large driving force is required, and further, vibration and noise increase. Further, since it is necessary to use a reflection optical system, the configuration of the optical system is complicated, and it is difficult to reduce the size of the system.

On the other hand, even in the technique using the transmissive surface-symmetric imaging optical element as shown in FIG. 12, when the image is enlarged due to the presence of the mirror scanner, the scanning volume is remarkably increased. There was a problem that it was difficult to solve problems such as vibration.

The present invention has been proposed for the purpose of solving the above-described problems, and enables downsizing of the apparatus and simplification of the structure, as well as shortening the distance between the optical element and the imaging position, thereby enabling diffraction. A main object is to provide a three-dimensional video display device capable of suppressing blur.

The three-dimensional image display apparatus of the present invention includes a display that displays an image as a projection object, and changes the exit angle with respect to the incident angle by bending the incident light from the display, and the element surface has an incident direction of incident light from the display. And a scanning element that can be rotated while maintaining the orthogonal or inclined angle, and an imaging element that forms an image of light emitted from the scanning element.

Here, the bending of the incident light by the scanning element includes not only refraction but also reflection and diffraction. Specifically, a prism to be refracted, a mirror to be reflected, a diffraction element to be diffracted, and the like are included in the scanning element of the present invention. Applicable. In the case of using a prism, a prism sheet having a long and narrow prism plate arranged in a saw blade shape may be used. In the case of using a mirror, a prism sheet having a mirror coating applied may be used. good.

When the scanning element is rotated, the image forming position is moved in a circle. When the scanning element is rotated faster than the afterimage threshold of the eye and the cross-sectional image of the three-dimensional object is displayed on the two-dimensional spatial light modulation device according to the position of the image, all cross-sectional images can be observed by the afterimage. A three-dimensional image can be formed.

A compact optical system can be constructed by using a rotatable scanning element. In addition, since the scanning element is provided in a state where the element surface is orthogonal or inclined with respect to the incident direction of incident light and is rotated in the in-plane direction while maintaining the orthogonal or inclined angle, the mirror scanner can be used even when the area increases. Compared to the above, the problem of increased vibration and noise during driving is reduced.

Further, as the imaging element, a transmissive surface-symmetric imaging optical element that forms the light emitted from the scanning element as a real image at an equal magnification in a plane symmetry position with respect to the element surface of the imaging element can be used. Here, the element surface of the imaging element refers to a plane on which light from the scanning element is incident, and is a symmetry plane when an object to be projected is formed as a real image at a plane symmetry position. By using a transmissive surface-symmetric imaging optical element, an image can be formed at a free position that is not limited by the focal length, and there is no image distortion generated by a normal lens.

As the plane-symmetric imaging element, it is possible to use a two-surface corner reflector array in which a plurality of two-surface corner reflectors composed of two mirror surfaces perpendicular to each other perpendicular to the element surface are arranged on the element surface.

In another aspect, the plane-symmetric imaging element may include a retroreflector array that retroreflects light rays and a half mirror that has a half mirror surface that reflects and transmits light rays. The element surface of the imaging element in this case refers to a half mirror surface. Furthermore, as the plane-symmetric imaging element of another aspect, an afocal lens array in which a plurality of afocal lenses having an optical axis perpendicular to the element surface are arranged on the element surface can be used.

The three-dimensional image display apparatus of the present invention can be made more compact than a conventional reflective optical system by using a rotatable scanning element such as a prism sheet. In addition, since a transmissive surface-symmetric imaging optical element is used, the display position can be freely changed and the image distortion can be suppressed by changing the optical distance between the screen and the transmissive surface-symmetric imaging optical element. be able to.

1 is a schematic configuration diagram of a 3D video display device according to a first embodiment. The conceptual diagram which looked at the prism sheet in 1st Embodiment from diagonally upward The figure which shows the basic composition of the 2 surface corner reflector array in 1st Embodiment. The figure which shows the operation | movement principle of the 2 surface corner reflector array in 1st Embodiment. The figure which shows the image formation of the three-dimensional video display apparatus in 2nd Embodiment. Schematic configuration diagram of a retroreflector array in the second embodiment The figure which shows the operation | movement principle of the retroreflector array in 2nd Embodiment. Schematic configuration diagram of a 3D image display apparatus according to a third embodiment The figure which shows the basic composition of the image formation element in 3rd Embodiment. Schematic configuration diagram of a 3D image display apparatus according to a fourth embodiment Schematic configuration diagram of a conventional 3D video display device Schematic configuration diagram of a conventional 3D video display device

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a 3D video display apparatus according to the first embodiment.

A three-dimensional image display device 100 according to the first embodiment includes a display device 101 that displays an image as a projection object, a prism sheet 104 that is formed by arranging micro prisms as scanning elements in a plane, and a transmissive surface. A two-surface corner reflector array 105 as a symmetric imaging optical element is provided.

The display apparatus 101 includes a two-dimensional display 102 that projects a two-dimensional cut surface image of a projection object that is an object to be displayed, and a spherical achromaticity that expands the two-dimensional cut surface image from the two-dimensional display 102 to an appropriate image size. It is composed of a cleanse 103 and a diffusion plate 106 that can be observed from the opposite side to which light is applied.

The two-dimensional display 102 of the present embodiment creates a cut surface image of an object to be displayed by irradiating light from a light source and using the reflected light. A display that has already been put into practical use may be used. For example, a “DMD Discover1100 ControllerBoard” manufactured by Texas Instruments that can switch images at high speed can be used.

Light emitted from the two-dimensional display 102 (that is, a cut surface image of an object to be displayed) passes through the spherical achromatic lens 103. The spherical achromatic lens 103 of this embodiment enlarges the two-dimensional cut surface image from the two-dimensional display 102 to an image size suitable for the size of the optical system by the prism sheet 104 and the two-surface corner reflector array 105.

The spherical achromatic lens 103 is made so that chromatic aberration can be removed with respect to light beams of three types of wavelengths of blue, green, and red by combining two types of lenses, a low dispersion material and a high material lens. Yes. In addition, spherical aberration is much improved over spherical single lenses. In place of this spherical achromatic lens, an aspherical lens capable of minimizing aberration can be used.

In this way, the image whose size is adjusted by the spherical achromatic lens 103 is projected onto the diffusion plate 106. The diffusion plate 106 is formed of a lenticular screen, and is disposed at an angle of 35 degrees with respect to the imaging optical system formed by the prism sheet 104 and the two-surface corner reflector array 105. When the light projected from the diffusion plate 106 passes through the prism sheet 104, the direction of the light changes due to the effect of refraction.

The display device 101 may be any means as long as it can display an image as a projection object. For example, a display device such as a liquid crystal display, a plasma display, or an organic EL display that displays an image on a screen may be used. Further, it may be capable of displaying an image such as a screen for projecting an image projected by a projector, and the display surface may be a curved surface as well as a flat surface.

FIG. 2 is a conceptual diagram of the prism sheet 104 according to the present embodiment as viewed obliquely from above. The prism sheet 104 is a scanning element in which slit-like long and narrow prisms 201 are arranged in a sawtooth cross section. As shown in FIG. 2, the prism sheet 104 of the present embodiment has a saw-toothed cross section with respect to only one surface of the prism sheet 104 (that is, the surface opposite to the surface on which incident light is incident (the exit surface)). Although it is formed to have a blade shape, the opposite surface (that is, the surface on which incident light is incident (element surface)) also has a saw-tooth cross section for the purpose of improving the focusing state of the light beam. You may form as follows. The shape, size, and material are not particularly limited, but in this embodiment, the size is 80 mm × 110 mm, the thickness is 2 mm, the prism angle is 15 °, and the pitch is 0.9 mm. The material is polymethyl methacrylate resin.

The prism sheet 104 refracts and emits light incident from the element surface in another direction. Therefore, by performing in-plane rotation around the rotation axis perpendicular to the element surface (that is, rotating in the in-plane direction of the element surface), the prism angle with respect to incident light changes, and light beam scanning can be performed. The lower flat portion in FIG. 2 is an element surface, and light is incident on the element surface and emitted from the upper sawtooth-shaped portion. In this embodiment, the element surface is rotated in a state orthogonal to the incident direction of incident light from the display. However, the element surface is disposed in an inclined state with respect to the incident direction, and the inclined angle is set. You may make it rotate, maintaining.

As a driving means for rotating the prism sheet, an encoder-integrated servo motor (smart motor) is used. The shaft of the motor is extended with an acrylic pipe, and the prism sheet is attached to the end of the motor shaft.

The smart motor is provided with an encoder and a memory inside, and by writing a user program in the memory, the smart motor can be rotated at a desired speed or the current rotational position can be acquired. In addition, this motor can communicate with a PC using an EIA-232-D / E standard (RS232-C) cable. This function is used to synchronize the rotation of the prism sheet and the image update command of the control board. A specific method is shown below.

First, a program with the content of “accelerate to 1200 rpm, send a signal to the PC side as soon as it reaches 1200 rpm and the rotational position is a multiple of 360 °, and continues to rotate at a constant speed” on the motor side. Write it down. The motor is operated with the PC, smart motor, and control board connected. When the rotation speed of the motor reaches 1200 rpm and a signal is sent to the PC, a command to start image display is sent to the control board. However, since there is a time lag when sending and receiving to / from the PC, it is programmed on the PC so that the first image is displayed when the rotational position of the motor is a multiple of 360 degrees taking this time lag into account. Keep it.

Thus, by using the rotatable prism sheet 104 in the scanning portion, a compact optical system can be configured, and the problem of increased vibration and noise during driving even when the area is increased is reduced. Further, in the present embodiment, the imaging position can be made shorter than that of the conventional optical system, and the influence of blur due to diffraction that occurs in the dihedral corner reflector array 105 described later can be reduced.

As the scanning element, other optical elements can be used as long as the incident light from the display is bent to change the emission angle with respect to the incident angle. For example, instead of the prism sheet 104, a diffraction element that diffracts incident light from a two-dimensional display may be used. In this case, the grating pattern of the diffraction element is not particularly limited, and for example, a diffraction grating having a one-dimensional pattern in which a large number of slits are arranged in parallel can be used. The diffractive element can rotate around a rotation axis perpendicular to the element surface. Therefore, the light diffraction direction changes according to the rotation, and optical scanning can be performed by the change in the reflection direction.

Further, instead of the prism sheet 104, a mirror having a sawtooth cross section with an element surface formed as a mirror surface may be used. For example, the prism sheet having a mirror coat on the surface may be used. The mirror having a sawtooth cross section can rotate around a rotation axis perpendicular to the element surface. Accordingly, the light reflection direction changes according to the rotation, and optical scanning can be performed by the change in the reflection direction.

The light whose direction has been changed by the effect of refraction by the prism sheet 104 then passes through the two-surface corner reflector array 105 and forms an image at a plane-symmetrical position.

FIG. 3 is a diagram showing a basic configuration of the two-surface corner reflector array 105. In the two-surface corner reflector array 105 of the present embodiment, a plurality of two-surface corner reflectors 301 composed of two mirror surfaces 301A and 301B perpendicular to a predetermined element surface and perpendicular to each other are arranged on the element surface S1. For example, a transmissive surface-symmetric imaging optical element disclosed in Japanese Patent Application Laid-Open No. 2009-75483 can be used.

In the present embodiment, a large number of square through holes (hereinafter referred to as mirror holes 302) are opened perpendicular to the element surface S1, and the inner wall of the mirror hole 302 is used as a mirror surface to form a two-surface corner reflector 301. is doing. The size of the mirror hole 302 is not particularly limited, but in this embodiment, the width is 150 μm, the length is 150 μm, and the depth is 150 μm, and the interval between the mirror holes 302 is 60 μm.

In the present embodiment, a master mold is formed by forming pillars on a copper substrate by nano-processing, and after reverse transfer to nickel by electroforming, the master mold is melted by etching.

FIG. 4 shows the operating principle of the two-sided corner reflector array 105. First, the irradiated light enters the mirror hole 302, is reflected twice by the adjacent mirrors 301 </ b> A and 301 </ b> B in the mirror hole 302, and then passes through the two-surface corner reflector array 105. That is, the light component reflected once by the two mirror surfaces of each of the two-surface corner reflectors 301 and retroreflected by the light component parallel to the element surface S1 forms a real image in the air at the plane-symmetric position of the element surface. Thereby, the observer can observe the real image of the image formed by reflection by the two-surface corner reflector 301 in which the inner angles of the two mirror surfaces face the line-of-sight direction as a stereoscopic aerial image.

In this way, with the element surface of the two-sided corner reflector array 105 as the symmetry plane, a real mirror image of the image as the projection object is formed at the plane symmetry position, and a stereoscopic aerial image is observed. With this two-sided corner reflector array 105, an image can be formed at a free position that is not limited by the focal length, and there is no image distortion generated by a normal lens. However, since this image is formed at a plane-symmetrical position, when the projection object is a three-dimensional object, an image with an inverted depth is seen from the observation direction.

In the image formation by the two-surface corner reflector array 105, the light beam passes through a minute through hole, and therefore is affected by diffraction, so that the resolution deteriorates as the image formation distance increases.

Here, since direct light, one-time reflected light, and multiple reflected light that pass through the mirror hole 301 of the two-sided corner reflector array 105 become stray light, the usable range is limited. For this reason, it is preferable that the optimal observation direction of the twice reflected light is 30 to 50 degrees in the vertical direction and plus or minus 20 degrees in the horizontal direction. The multiple reflection is suppressed by giving an inclination of 18 degrees to the surfaces other than the two surfaces that form the two-surface corner reflector 301. In addition, since there is a problem that the resolution is lowered when the imaging distance is increased due to the influence of diffraction or processing accuracy, it is preferable to dispose the projection object within a predetermined distance from the two-surface corner reflector array 105.

As described above, the cut surface image of the display object is sequentially displayed on the two-dimensional display 101, and the cut surface image is moved by synchronizing with the rotation of the prism sheet 104. The three-dimensional space can be scanned by moving the cut surface image, and the video O is formed in the air.

As described above, according to the 3D image display apparatus of the present embodiment, a compact optical system can be configured by using the rotatable prism sheet 104 in the scanning portion, and vibration and noise during driving can be generated even when the area increases. The problem of becoming larger is alleviated. Further, in the present embodiment, the imaging position can be made shorter than in the conventional optical system, and the influence of blur caused by diffraction that occurs in the two-surface corner reflector array 105 can be reduced.

Next, a 3D image display apparatus 500 according to the second embodiment will be described. Description of points common to the first embodiment will be omitted, and different points will be mainly described. FIG. 5 is a diagram showing image formation of the 3D image display apparatus according to the present embodiment. The difference between this embodiment and the first embodiment is an imaging optical system, and the display device and the scanning element have the same configuration as that of the first embodiment.

FIG. 6 is a schematic configuration diagram of the retroreflector array 502 in the present embodiment. FIG. 7 is a diagram illustrating an operation principle of the retroreflector array 502 in the present embodiment. The imaging optical system of this embodiment includes a retroreflector array 502 that retroreflects light rays and a half mirror 503 having a half mirror surface that reflects and transmits light rays. For example, Japanese Patent Application Laid-Open No. 2009-75483 discloses What is disclosed can be used. The half mirror surface S2 is a symmetric surface in the imaging optical system, and the retroreflector array 502 is arranged in the same space as the projection object with respect to the half mirror 503. Here, “retroreflection”, which is the action of the retroreflector 502, refers to a phenomenon in which reflected light is reflected (reversely reflected) in the direction in which the incident light is incident. The incident light and the reflected light are parallel and opposite to each other. It becomes.

The retro-reflector array 502 is a corner cube array that is a set of corner cubes that use one of the corners of the cube. Each retroreflector 701 forms a regular triangle when the mirror surfaces 701a, 701b, and 701c forming three isosceles right-angled isosceles triangles are gathered at one point and viewed from the front. The mirror surfaces 701a, 701b, and 701c are orthogonal to each other to form a corner cube.

The retroreflector array 502 shown in FIG. 7 will be described as an example. Light incident on one of the mirror surfaces (for example, 701a) is sequentially reflected on the other mirror surfaces (701b and 701c), so that the light is transmitted to the retroreflector 701. Is reflected in the original direction from which it was incident. The paths of incident light and outgoing light with respect to the retroreflector array 701 are not strictly overlapping but are parallel, but when the retroreflector 61 is sufficiently smaller than the retroreflector array 6, the paths of incident light and outgoing light. May be considered as overlapping.

In the case of such a multi-viewpoint aerial image display optical system using the retroreflector array 502 and the half mirror 503, the light emitted from the projection object is reflected by the half mirror surface S2, and further retroreflected by the retroreflector array. Since it returns to the original direction and forms an image through the half mirror surface S2, the shape and position of the retroreflector array are not limited as long as the reflected light from the half mirror is received.

Next, a 3D video display apparatus according to the third embodiment will be described. Description of points common to the first embodiment will be omitted, and different points will be mainly described. FIG. 8 is a schematic configuration diagram of a 3D image display apparatus 800 in the present embodiment. The difference between this embodiment and the first embodiment is a scanning element and an imaging element. The two-dimensional display 801, the spherical achromatic lens 802, and the diffusion plate 803 have the same configuration as that of the first embodiment. .

The scanning element of this embodiment is a mirror 804 that reflects incident light from a two-dimensional display. This scanning element can rotate around a rotation axis 804A having an angle that is not perpendicular to the reflecting surface. Accordingly, the light reflection direction changes according to the rotation of the mirror 804. Optical scanning can be performed by this change in the reflection direction. The light reflected by the mirror 804 enters an afocal lens array 805 shown below.

The imaging element of the present embodiment is an afocal lens array in which a plurality of afocal lenses having an optical axis perpendicular to a predetermined element surface are arranged on the element surface, and is disclosed in, for example, Japanese Patent Application Laid-Open No. 2009-75483. Can be used. The element surface S3 is a plane of symmetry.

FIG. 9 is a diagram showing a basic configuration of the afocal lens array 805 in the present embodiment. The afocal lens 901 has an infinite focal length, and includes, for example, two lenses 901A and 901B having an optical axis perpendicular to the element surface S3 and spaced apart from each other. . An afocal lens array 805 can be configured by arranging a large number of such afocal lenses 901 side by side on the element surface S3. As the configuration of the afocal lens 901, a convex lens, an optical fiber lens, or the like can be employed.

As shown in FIG. 9, the afocal lens array 805 includes a large number of afocal lenses 901 arranged on one element surface. Specifically, the afocal lens 901 includes two lenses 901A and 901B that share an optical axis g perpendicular to the element surface and are spaced from each other by focal lengths fs and fe. In this example, convex lenses are applied as the lenses 901A and 901B. As a result, light incident on the lenses 901A from one side of the element surface is emitted from the other pair of lenses 901B, and condensed at a position that is plane-symmetric with respect to the element surface. . That is, the image displayed on the display serving as the light source forms an image at a plane symmetrical position with respect to the element surface.

Next, a 3D image display apparatus according to the fourth embodiment will be described. Description of points common to the first embodiment will be omitted, and different points will be mainly described. In the first embodiment, a three-dimensional image display apparatus using a plane-symmetric imaging element has been described. In this embodiment, a convex lens 501 is used as the imaging element.

FIG. 10 is a schematic configuration diagram of a 3D video display apparatus according to the present embodiment. The convex lens 10 is a refractive and transmissive element, and the basic optical principle is the same as in the above-described embodiment. A concave mirror, a Fresnel lens, or the like can be used instead of the convex lens. The Fresnel lens is a refractive transmission element and the concave mirror is a reflection element, but the basic optical principle is the same. These have a specific focal length and form an object that is further away than this distance as a real image.

DESCRIPTION OF SYMBOLS 100 3D image display apparatus 101 Display apparatus 102 Two-dimensional display 103 Spherical achromatic lens 104 Prism sheet 105 Two-surface corner reflector array 106 Diffuser

Claims (9)

A display for displaying an image as a projection object;
The incident light from the display is bent to change the emission angle with respect to the incident angle, and the element surface is provided in a state orthogonal or inclined with respect to the incident direction of the incident light from the display, and the orthogonal or inclined angle is maintained. A rotatable scanning element;
An imaging element for imaging light emitted from the scanning element;
A three-dimensional image display device. The three-dimensional image display apparatus according to claim 1, wherein the scanning element is a prism that refracts incident light from the display. 3. The three-dimensional image display device according to claim 2, wherein the prism is a prism sheet in which elongated prism plates are arranged in a saw blade cross section. The three-dimensional image display apparatus according to claim 1, wherein the scanning element is a diffraction element that diffracts incident light from the display. The three-dimensional image display apparatus according to claim 1, wherein the scanning element is a mirror that reflects the incident light while rotating in a state inclined with respect to the incident direction of the incident light from the display. The imaging element is
6. The three-dimensional image display device according to claim 1, wherein the three-dimensional image display device is a plane-symmetric imaging element capable of imaging a real image of a projection object at a plane-symmetric position with respect to a certain geometric plane serving as a symmetry plane. The plane-symmetric imaging element is
A two-surface corner reflector array in which a plurality of two-surface corner reflectors composed of two mirror surfaces perpendicular to each other perpendicular to the element surface are arranged on the element surface, and the element surface is the symmetric surface. Item 7. The three-dimensional image display device according to item 6. The plane-symmetric imaging element is
A retroreflector array for retroreflecting light rays and a half mirror having a half mirror surface for reflecting and transmitting light rays, the half mirror surface being the symmetric surface, and the retroreflector array with respect to the half mirror The three-dimensional video display apparatus according to claim 6, wherein the three-dimensional video display apparatus is disposed in a space on the same side as the projection object. The plane-symmetric imaging element is
The three-dimensional image according to claim 6, wherein the afocal lens array includes a plurality of afocal lenses having an optical axis perpendicular to a predetermined element surface arranged on the element surface, and the element surface is the symmetry plane. Display device.