JP6241051B2 - Light source device and projector - Google Patents

Description

  The present invention relates to a light source device, and more particularly to a light source device using an optical fiber as a light guide. The present invention also relates to a projector that projects and displays an image using light emitted from such a light source device.

In recent years, a light irradiation device using a laser as a light source has been developed, and an image display device using the light irradiation device has also been developed.
An advantage of using a laser as a light source is that the light emitted from the light source can be injected into a small etendue because the light source has a very high directivity. Therefore, there is an advantage that a highly efficient light source can be provided by using a laser as the light source of the image display device.

  However, since a laser is a coherent light source with very high coherence, an interference phenomenon called so-called speckle, in which a granular or speckled pattern inevitably appears especially when projected light passing through an optical fiber is projected. There is a problem that occurs. That is, when a laser and an optical fiber are used as the light source of the image display apparatus, the image quality of the projected image is significantly deteriorated.

A method for reducing such speckle is disclosed in, for example, Patent Documents 1 and 2 below.
Patent Document 1 discloses a configuration in which coherent light emitted from each light source is incident on an optical fiber through a magnifying optical system and a condensing optical system at the maximum incident angle of the optical fiber.
With this configuration, the number of reflections of light incident on the optical fiber increases while propagating through the optical fiber. This disturbs the equiphase surface of each coherent light and further mixes the light inside the optical fiber, thereby matching the spatial intensity distribution, propagation angle, and divergence angle of the light from each light source, thereby reducing the coherence of the entire light source. It is supposed to be possible.

  Patent Document 2 discloses a configuration in which coherent light emitted from each light source arranged one-dimensionally is incident on an optical fiber via a beam shaping unit and a condensing optical system for the purpose of reducing the degree of coherence of the light. Is disclosed.

JP 2008-242371 A JP 2009-54325 A

  However, in these conventional techniques, the speckle reduction effect by mixing light from a plurality of light sources that are incoherent to each other cannot be fully utilized.

  In both methods of Patent Documents 1 and 2, when light emitted from each light source is incident on the light incident end face of the optical fiber, the inclination of the principal ray of the light is different for each light source. (See FIG. 15). Here, the “principal ray” refers to a ray corresponding to the center of the angular distribution of the luminous flux emitted from one point light source. That is, a group of light beams having a spread at an angle with the principal light beam as the center corresponds to the light flux.

FIG. 15 is a diagram schematically illustrating a state in which radiated light from different light source elements 200, 210, and 220 is emitted from the optical fiber 10 after being incident on the optical fiber 10. In FIG. 15, the optical fiber 10 shows only the core, and the cladding is omitted.
In FIG. 15, in order to avoid complication of the drawing, the radiated light from each light source element (200, 210, 220) is expressed only by the principal ray (201, 211, 221). Furthermore, description of the coupling optical system for injecting the radiated light from each light source element (200, 210, 220) into the optical fiber 10 is omitted. Actually, from the light source element 200, a light beam having a certain angle spread around the principal ray 201 is incident on the light incident end face 10 a of the optical fiber 10. Similarly, from the light source element 210, a light beam having a certain angle spread centered on the principal ray 211, and from the light source element 220, a light flux having a certain angle spread centered on the principal ray 221 is emitted. The light is incident on the light incident end face 10 a of the fiber 10.

  Here, it is assumed that the principal ray 201 is incident perpendicular to the light incident end face 10a of the optical fiber 10, that is, parallel to the fiber axis 10c. On the other hand, both the principal ray 211 and the principal ray 221 are incident on the fiber axis 10c of the optical fiber 10 at an angle θ1. Here, the angle of the principal ray (211, 221) with respect to the normal line of the light incident end face 10a is θ1.

  In the optical fiber 10, the light flux is stretched and mixed around the fiber axis 10 c for each reflection at the core-cladding boundary, but the length of the optical fiber 10 is not so long (for example, a diameter of 1 mm). In the case of a fiber having a core diameter of about 10 m or less), the angle of light incident on the optical fiber 10 is preserved in the optical fiber 10. In other words, the principal ray 201 incident in parallel to the fiber axis 10c on the light incident end face 10a of the optical fiber 10 is a group of rays substantially parallel to the fiber axis 10c also on the light exit end face 10b of the optical fiber 10. Is emitted (ray group 202). Similarly, the principal rays 211 and 221 incident at the angle θ1 with respect to the fiber axis 10c at the light incident end face 10a of the optical fiber 10 are light rays having an angle θ1 with respect to the fiber axis 10c at the light exit end face 10b. It is emitted (ray groups 212 and 222).

Here, since the light beam group 212 and the light beam group 222 are emitted at the same emission angle θ1 with respect to the fiber axis 10c, these lights are mixed. On the other hand, the light beam group 202 does not mix with the light beam groups 212 and 222 because they have different exit angles.
For example, in the techniques of Patent Document 1 and Patent Document 2, chief rays emitted from the respective light emitting points are directed to the incident end face of the optical fiber with an angle after passing through the condensing optical system. The chief rays located on the opposite sides of the fiber axis are mixed, but the chief rays that are not are not mixed.

  As an example, when the light source element 200 and the light source element 210 are compared, the light emitted from the light source element 200 spreads at a certain angle around the light beam group 202 when emitted from the light emitting end face 10b of the optical fiber 10. The luminous flux 202s is formed. Similarly, when the light emitted from the light source element 210 is emitted from the light emitting end face 10b, a light beam 212s having a spread at a certain angle with respect to the light ray group 212 is formed.

  However, since the emission angle with respect to the fiber axis 10c differs between the principal ray 202 and the principal ray 212, the light flux 202s and the light flux 212s are not mixed as shown in FIG. That is, in this configuration, the light source elements (for example, the light source element 210 and the light source element) are arranged so that the principal rays of the emitted light from each light source element are axially symmetrical with respect to the fiber axis 10c of the optical fiber 10. 220) is mixed only (light flux 212s and light flux 222s).

  When a light source is configured by arranging a plurality of light source elements that emit coherent light, in order to effectively reduce speckle, the light emitted from as many different light sources as possible is irradiated to the same place. It is effective to flow interference fringes by mixing light with each other. However, in the above method, since the number of radiation sources capable of mixing light with each other is extremely small, the speckle reduction effect cannot be expected so much.

  Incidentally, on the light emitting end face 10b of the optical fiber 10, since the coherent light from each light source element passes through any point in the plane, it can be said that the light from each light source element is mixed at this point. Therefore, if this surface can be projected and used as an image, illumination with reduced speckles becomes possible. However, this surface is surrounded by a clear core-cladding boundary of the optical fiber 10, and this boundary cannot be erased using an integrator (described later). Therefore, uniform illumination cannot be obtained unless only a necessary (rectangular) region is cut out from the inside of the core image and used, and the use efficiency of light is significantly reduced, which is not practical.

  On the other hand, since the core-cladding boundary disappears blurryly on the distant projection surface 250 that is a sufficient distance d from the light emitting end surface 10b, if an image of this surface is projected, it is uniform using an integrator. Lighting can be obtained. However, as described above, the light from each light source element (200, 210, 220) is emitted from the light emitting end face 10b at an emission angle depending on the incident angle with respect to the light incident end face 10a of the optical fiber 10, resulting in a result. As a result, the speckle reduction effect is reduced.

  In view of the above problems, an object of the present invention is to provide a light source device in which speckles are sufficiently reduced in a light source device including a plurality of light source elements that emit coherent light. Another object of the present invention is to provide a projector that projects and displays an image using light emitted from such a light source device.

The light source device of the present invention comprises:
A plurality of light source elements that emit coherent light;
Optical fiber,
A coupling optical system for guiding emitted light from the plurality of light source elements to the light incident end face of the optical fiber;
The coupling optical system has a condensing optical system that receives radiated light from each of the plurality of light source elements and collects light collectively on a light incident end face of the optical fiber,
Light emitted from each of the plurality of light source elements is incident on the optical fiber through the condensing optical system as a chief ray corresponding to the center of the angular distribution of the light beam when the light is input to the condensing optical system. The chief ray just after is substantially parallel to the central axis of the optical fiber.

According to the light source device of the present invention, each coherent light emitted from a plurality of light source elements is a light beam around a principal ray substantially parallel to the central axis of the optical fiber immediately after entering the light incident end face of the optical fiber. Propagating.
The angle of light incident on the optical fiber is stored in the optical fiber. For this reason, in the case of the above configuration, the principal rays of the radiated light from the plurality of light source elements are maintained substantially parallel to the central axis of the optical fiber even at the light exit end face of the optical fiber. As a result, the radiated light from the plurality of light source elements all forms a principal ray substantially parallel to the central axis of the optical fiber and a light beam having a spread at an angle with the principal ray as a center. That is, radiated light from a plurality of light source elements is mixed in the light flux having a spread at a certain angle with respect to the central axis of the optical fiber.

Therefore, when the projection surface is installed at a position away from the light emission end face of the optical fiber, light in a state in which radiated light from more light source elements than in the conventional configuration is mixed is irradiated at any position on the projection surface. Is done. Therefore, an extremely high speckle reduction effect can be obtained compared to the conventional configuration.
In particular, with the above configuration, even if the configuration of the optical fiber has a relatively large end face area and a relatively short length, the speckle reduction effect can hardly be expected with the conventional configuration. The effect of reducing the level can be obtained.

  Here, the phrase “substantially parallel” to the central axis of the optical fiber immediately after the principal ray is incident on the light incident end face of the optical fiber means that the principal ray is completely parallel to the central axis of the optical fiber, and at most It is a concept including a state having only an angle of about degrees.

  As a specific method for realizing the above configuration, a method in which the light incident end face of the optical fiber is configured by a plane perpendicular to the central axis of the optical fiber and the condensing optical system is telecentric on the output side is used. it can.

  Here, when the condensing optical system includes a plurality of lenses, a lens arranged at a position closest to the output side among the plurality of lenses is substantially disposed on a light incident end surface of the optical fiber. It is preferable to adhere closely.

Radiated light from the plurality of light source elements is incident on a condensing optical system and is emitted from a lens (hereinafter referred to as “final lens”) disposed at a position closest to the output side of the condensing optical system. Then, it is incident as a light beam having a spread angle on the light incident end face of the optical fiber.
Here, if there is a large separation between the final lens and the light incident end face of the optical fiber, a part of the light beam included in the light flux is caused by the spread angle of the light flux. It is conceivable that the utilization efficiency of the radiated light from the plurality of light source elements decreases.
Therefore, the speckle reduction effect can be remarkably enhanced without lowering the light utilization efficiency by substantially bringing the final lens into close contact with the light incident end face of the optical fiber as described above.

  Here, the final lens is “substantially in close contact with” the light incident end face of the optical fiber, in addition to the state in which the final lens is completely in close contact with the light incident end face of the optical fiber. It is a concept that includes a state that is only a fraction of a few.

In addition to the above-described configuration, the light source device of the present invention is characterized in that light incident on the light incident end face of the condensing optical system exhibits a substantially axially symmetric angular distribution.
Thereby, the light incident on the light incident end face of the optical fiber becomes substantially axially symmetric. As a result, when the emitted light from the plurality of light source elements is emitted from the light exit end face of the optical fiber, all of the principal rays are substantially parallel and the divergence angles are all equal. Thereby, the speckle reduction effect can be further enhanced.

  Here, light indicates “substantially axisymmetric angular distribution” as well as a state showing a completely axisymmetric angular distribution, as well as a half-width half-width angle of the distribution (from the central axis up to an angle that is half the center) This is a concept including a state in which the ratio between the maximum and the minimum of the angle is about 10 percent or less.

More specifically, in the case where the emitted light from the plurality of light source elements shows an angular distribution in which the angular distribution of light emission is non- axisymmetric and substantially symmetric with respect to a plane including the central axis of light emission. ,
The coupling optical system has a plurality of angle distribution conversion elements corresponding to the plurality of light source elements,
The plurality of angle distribution conversion elements are configured to convert the emitted light from the plurality of light source elements into light having a substantially axially symmetric angle distribution and to emit the light to the light incident end face of the condensing optical system. Thus, it is possible to realize a state in which light incident on the light incident end face of the condensing optical system exhibits a substantially axially symmetric angular distribution.

  At this time, there is an advantage that the optical system can be easily designed by making the principal rays of the light emitted from the plurality of angle distribution conversion elements substantially parallel to each other.

  Here, the principal rays of the light emitted from the plurality of angle distribution conversion elements are “substantially parallel to each other”, in addition to the case where they are in a completely parallel relationship with each other, in addition to an angle of about several degrees at most. It is a concept including a state that only has.

Various forms can be assumed as the plurality of angle distribution conversion elements.
As one method, the plurality of angle distribution conversion elements can be realized by including an optical element having a non- axisymmetric refracting surface. More specifically, it can be realized by a cylindrical lens, a toric lens, or a spheroid lens.

  Further, as another method, the plurality of angle distribution conversion elements can be realized by including a light diverging element that converts parallel light into divergent light. More specifically, it can be realized by a diffuser plate, a two-dimensional lens array, or a cylindrical lens array.

  As another method, the plurality of angle distribution conversion elements can be realized by including a light guide bar.

  In addition, a projector according to the present invention is characterized in that an image is projected using light emitted from a light source device having the above-described characteristics. Thereby, even when a light source device including a plurality of light source elements that emit coherent light is used, a projector in which speckle noise is not visually recognized in a projected image can be realized.

  According to the light source device of the present invention, speckle can be sufficiently reduced even when a plurality of light source elements that emit coherent light are provided.

It is a figure which shows typically the structure of 1st Embodiment of a light source device. It is a figure which shows typically the structure of 2nd Embodiment of a light source device. It is a figure which shows typically the other structure of 2nd Embodiment of a light source device. It is a figure which shows typically an example of the detailed structure of 2nd Embodiment of a light source device. It is a figure which shows typically the structure of 3rd Embodiment of a light source device. It is a figure which shows typically the radiated light from a light source element. It is a figure which shows typically angle distribution in case the radiated light from a light source element is non- axisymmetric . It is a schematic diagram at the time of using a light guide rod as an angle distribution conversion element. It is a schematic diagram at the time of using the optical element which has a non- axisymmetric refractive surface as an angle distribution conversion element. It is a schematic diagram when a cylindrical lens is used as an optical element having a non- axisymmetric refracting surface, and a schematic diagram of an angular distribution of emitted light at that time. It is a schematic diagram at the time of using a light divergent element as an angle distribution conversion element. It is a schematic diagram at the time of using a diffusing plate as a light divergent element, and a schematic diagram of the angle distribution of the emitted light at that time. It is a figure which shows typically an example of the detailed structure of 3rd Embodiment of a light source device. It is a figure which shows typically another example of the detailed structure of 3rd Embodiment of a light source device. It is a figure which shows typically the structure of the projector using the light source device of this invention. It is a figure which shows typically another structure of the projector using the light source device of this invention. It is a figure which shows typically another structure of the projector using the light source device of this invention. In the conventional light source device, it is a figure which shows typically the state in which the emitted light from a different light source element injects into an optical fiber, and is inject | emitted from an optical fiber.

  The light source device and projector of the present invention will be described with reference to the drawings. In each drawing, the dimensional ratio of the drawings does not necessarily match the actual dimensional ratio. In addition, the same code | symbol is attached | subjected about the component same as FIG.

[First Embodiment]
FIG. 1 is a diagram schematically illustrating the configuration of the first embodiment of the light source device. The light source device 1 includes a light source unit 20, a coupling optical system 30, and an optical fiber 10.
The light source unit 20 includes a plurality of light source elements (100, 110, 120,...). Each light source element (100, 110, 120,...) Is configured to emit coherent light, and corresponds to each emitter (light emitting unit) of the semiconductor laser as an example.
The coupling optical system 30 is an optical system that guides radiated light from a plurality of light source elements (100, 110, 120,...) To the light incident end face 10a of the optical fiber 10, and has a condensing optical system 31. The condensing optical system 31 condenses the emitted light from the plurality of light source elements (100, 110, 120,...) On the light incident end face 10a of the optical fiber 10. In FIG. 1, only the core of the optical fiber 10 is shown, and the cladding is omitted.

Hereinafter, the light source element 100, the light source element 110, and the light source element 120 will be representatively discussed as the light source elements included in the light source unit 20.
In FIG. 1, the principal ray 101 of the emitted light from the light source element 100, the principal ray 111 of the emitted light from the light source element 110, and the principal ray 121 of the emitted light from the light source element 120 are the light of the condensing optical system 31. The state in which it injects into the incident end surface is shown typically. Here, as described above with reference to FIG. 15, the principal ray refers to a ray located at the center of the angular distribution among the emitted light from each light source element. In other words, actually, a light beam having a certain angle spread around the principal ray 101 is incident on the light incident end face of the condensing optical system 31 from the light source element 100. The same applies to the light emitted from the light source element 110 and the light source element 120.
In addition, the condensing optical system 31 can be comprised including a some lens (41, 42, ...).

  In the configuration of the present embodiment, the principal ray of the radiated light from each light source element (100, 110, 120) is incident on the light incident end face 10a of the optical fiber 10 and immediately after entering the fiber axis 10c ("" (Corresponding to “the central axis of the optical fiber”) and substantially parallel (chief rays 102, 112, 122). In addition, the design guideline of the condensing optical system 31 for the principal ray to be substantially parallel to the fiber axis after being incident on the optical fiber 10 will be described later.

  The angle of each light beam incident on the light incident end surface 10a of the optical fiber 10 propagates through the optical fiber 10 while being stored in the optical fiber 10, and is emitted from the light emitting end surface 10b. That is, according to the configuration of the light source device 1, the chief rays (102, 112, 122) of the radiated light from the plurality of light source elements (100, 110, 120) are also reflected on the light exit end face 10 b of the optical fiber 10. A state substantially parallel to the shaft 10c is maintained.

  Therefore, even after the emitted light from the plurality of light source elements (100, 110, 120) is emitted from the light emitting end face 10b, all the principal rays (103, 113, 123) substantially parallel to the fiber axis 10c are emitted. A light beam having a spread at a certain angle as a center is formed, and these reach the same position at a distance (103s, 113s, 123s). Therefore, the radiated light from the plurality of light source elements (100, 110, 120) is mixed in the light flux having a spread at a certain angle with respect to the fiber axis 10c.

  That is, a light beam exiting from the light exit end face 10b in parallel to the fiber axis 10c, a light beam exiting at a certain angle with respect to the fiber axis 10c, and a light beam exiting so as to form the outermost periphery of the light beam are all a plurality of Radiant light from the light source elements (100, 110, 120) is mixed. That is, the light emitted from the light emitting end face 10b at any angle is mixed with the emitted light from the plurality of light source elements (100, 110, 120).

  As a result, when the projection surface 250 is installed at a distant position away from the light emitting end surface 10b by a sufficient distance d, a plurality of light source elements (100 that constitute the light source unit 20 at any position on the projection surface 250). , 110, 120,...) Is irradiated with light in a mixed state, so that a very high speckle reduction effect can be obtained.

  In FIG. 1, chief rays (101, 111, 121) at the time of incidence of light emitted from the light source elements (100, 110, 120) on the light incident end face of the condensing optical system 31 are mutually connected. The condensing optical system 31 is not limited to the parallel case, and even under general conditions where the light incident end face 10a of the optical fiber 10 is not limited to a flat surface, the condensing optical system 31 has principal rays (101, 111, 121) incident from the preceding stage. ) Is converted to a principal ray (102, 112, 122) substantially parallel to the fiber axis 10c at the subsequent stage of the light incident end face 10a of the optical fiber 10, and the condensing optics As long as the system 31 has this function, the extremely high speckle reduction effect described above is exhibited.

  Also in the configuration of FIG. 1, as described above, the speckle is reduced because the light from the light source elements is mixed on the light emitting end face 10b of the optical fiber 10. Accordingly, in the light source device 1 of the present invention, illumination with reduced speckles is performed using projection surfaces that are continuous from the surface of the light emitting end surface 10b of the optical fiber 10 to the projection surface 250 that is sufficiently far away. Can be realized.

  The light source unit 20 shown in FIG. 1 is more preferable as long as it has a configuration that emits light whose angle distribution is axisymmetric, but in the present embodiment, such light may not necessarily be emitted. The content that “the angular distribution is axially symmetric” will be described later in the third embodiment.

[Second Embodiment]
FIG. 2 is a diagram schematically illustrating the configuration of the second embodiment of the light source device.
In the light source device 1 shown in FIG. 2, the light incident end face 10a of the optical fiber 10 is constituted by a plane perpendicular to the fiber axis 10c. The condensing optical system 31 is telecentric on the output side.
With the configuration shown in FIG. 2, the principal rays (104, 114, 124) of the light emitted from the light exit end face of the condensing optical system 31 of the radiated light from each light source element (100, 110, 120). Are substantially parallel to the optical axis, that is, the fiber axis 10 c of the optical fiber 10.
In FIG. 2, the light exit end face of the condensing optical system 31 is illustrated as corresponding to the light exit end face of the lens 42, but this illustrated mode is an example. The condensing optical system 31 may include an optical member (such as a lens) other than the lenses 41 and 42.

  In addition, as shown in FIG. 3, in the present embodiment, the lens 42 disposed at the position closest to the output side of the condensing optical system 31 is substantially in close contact with the light incident end face 10 a of the optical fiber 10. It doesn't matter.

The radiated light from each light source element (100, 110, 120) exits the lens (final lens) 42 disposed at the position closest to the output side of the condensing optical system 31, and then enters the optical fiber 10. The light is incident on the end surface 10a as a light beam having a certain spread angle.
Here, if there is a large separation between the lens 42 and the light incident end face 10 a of the optical fiber 10, a part of the light beam contained in the light beam is caused by the spread angle of the light beam. The case where it cannot take in into the light-incidence end surface 10a is assumed. When such a situation occurs, among the plurality of light source elements (100, 110, 120,...) Provided in the light source unit 20, there are light source elements that cannot effectively use the emitted light, and the light use efficiency is increased. descend.
Therefore, as shown in FIG. 3, the speckle reduction effect can be remarkably enhanced without substantially reducing the light utilization efficiency by closely contacting the lens 42 to the light incident end face 10a of the optical fiber 10.

In addition, since the light source device 1 of the present embodiment is telecentric on the output side, the entrance pupil of the final lens of the condensing optical system 31 coincides with the input-side focal point. FIG. 4 depicts an embodiment in which the final lens 42 of the condensing optical system 31 is a lens (convex lens) having a positive focal length. From the light source elements (100,...) Of the light source unit 20, FIG. It can be seen that the principal rays of the light beam may be arranged so as to intersect at the input side focal point existing on the input side (left side in the drawing) from the final lens 42.
The final lens 42 may be a lens (concave lens) having a negative focal length. In this case, the input-side focal point of the final lens 42 is positioned on the output side (right side in the drawing) from the final lens 42. To do. Accordingly, the principal ray from each light source element (100,...) Of the light source unit 20 may be arranged so as to be directed to the input side focal point existing on the output side (right side in the drawing) from the final lens 42.

  In other words, in order to make the condensing optical system 31 telecentric on the output side, regardless of whether the focal length of the final lens 42 is positive or negative, the final lens 42 of the condensing optical system 31 is input to the input side ( It can be seen that the exit pupil of the partial optical system existing on the left side in the drawing may be designed so as to coincide with the input side focal point of the final lens 42.

  Here, looking back on the configuration of FIG. 1 described above, for example, when the light incident end surface 10a of the optical fiber 10 is a convex surface or a concave surface, the light incident end surface 10a portion of the optical fiber 10 is assumed to be a virtual plano-convex or flat surface. Since it can be regarded as a concave lens, it is understood that the condensing optical system 31 of FIG. 1 may be designed so that the input side focal point of this virtual lens and the exit pupil of the condensing optical system 31 coincide.

Incidentally, FIG. 4 depicts a state in which the chief rays from the light source elements (100,...) Of the light source unit 20 are all parallel. In such a case, the condensing optical system 31 is also telecentric on the input side. The design should be such that
4 is merely an example, and in the light source device 1 of the present embodiment, it is not necessary to make all the principal rays from the light source elements (100,...) Of the light source unit 20 parallel. In FIG. 4, the mirror 81 is illustrated for the purpose of changing the light beam direction, but the mirror 81 is not an essential element for the light source device 1.

[Third Embodiment]
FIG. 5 is a diagram schematically showing the configuration of the third embodiment of the light source device.
In the light source device 1 illustrated in FIG. 5, the coupling optical system 30 includes a plurality of angle distribution conversion elements 60 corresponding to the plurality of light source elements (100, 110, 120,...). The angle distribution conversion element 60 converts the emitted light from the plurality of light source elements (100, 110, 120,...) Into light having a substantially axially symmetric angle distribution, and the light incident end face of the condensing optical system 31. To ejaculate. In FIG. 5, an angle distribution conversion element 61 corresponding to the light source element 100 is shown as an example.

With reference to FIG. 6A and FIG. 6B, the light which shows an axially symmetrical angle distribution is demonstrated.
FIG. 6A is a diagram schematically showing emitted light from one light source element 100 constituting the light source unit 20. Here, the optical axis direction, that is, the axial direction of the fiber axis 10c of the optical fiber 10 is defined as a z-axis, and two axes perpendicular to the z-axis are defined as an x-axis and a y-axis, respectively.
In FIG. 6A, as the emitted light from the light source element 100, a light ray 106x traveling at an angle θx along a plane α parallel to the xz plane and a light ray 106y traveling at an angle θy along a plane β parallel to the yz plane. Is illustrated.
FIG. 6B schematically shows the relationship between the angle and the light intensity (corresponding to “angle distribution”) when θx and θy are changed for the light ray 106x and the light ray 106y.

The emitted light from each light source element (100, 110, 120,...) Constituting the light source unit 20 diverges at a certain angle. Here, there is symmetry in the angular distribution for light rays that diverge along a certain plane. That is, light rays that diverge along a certain plane have the highest intensity of light that diverges at a specific angle (hereinafter referred to as “maximum intensity angle”), and diverge at an angle away from the maximum intensity angle. The intensity of the light beam decreases with increasing angle. According to FIG. 6B, regarding the light emitted from the light source element 100, both the light ray 106x traveling along the xz plane (plane α) and the light beam 106y traveling along the yz plane (plane β) have the above-described properties. Appears.
On the other hand, according to FIG. 6B, the light beam 106x traveling along the xz plane (plane α) and the light beam 106y traveling along the yz plane (plane β) are the same as the light beam traveling at the same angle as the z axis. The strength is different. Such light is referred to as light having a non- axisymmetric angular distribution.

That is, when the emitted light from the light source element 100 shows an angle distribution as shown in FIG. 6B, the light emitted from the light source element 100 has an xz plane (plane α) even if the angle formed with the z axis is the same. ) And the intensity of the light beam traveling along the yz plane (plane β) are different in intensity, or the distribution width is different in the x direction and the y direction.
However, even light having such an angular distribution is symmetric with respect to the xz plane (plane α) or the yz plane (plane β). This is because the distribution described in FIG. 6B is symmetric with respect to the angles θx and θy.

When the light having the non- axisymmetric property of the angle distribution is incident on the angle distribution conversion element 60 as described above, the angle distribution conversion element 60 converts the light into the light having the angle distribution axisymmetric and converts it into the light incident end face of the condensing optical system 31. Has the function to inject.
According to the configuration of the present embodiment, all of the light emitted from the condensing optical system 31 and condensed on the light incident end face 10a of the optical fiber 10 is light having an angular distribution of axial symmetry. As a result, no matter where the light is incident on the light incident end face 10a, the light propagates through the optical fiber 10 with the same propagation angle. Therefore, the light exit end face 10b of the optical fiber 10 has an optical axis of all the light. And the divergence angle becomes equal.
As a result, since the emitted light from the light source elements (100, 110, 120,...) Is mixed in every place even at a position away from the light emitting end face 10b of the optical fiber 10 by a distance d, speckle is reduced. The effect is maximized.
In addition, there is an advantage that the optical system can be easily designed by configuring the principal rays of the light emitted from the angle distribution conversion element 60 to be substantially parallel to each other.

  Hereinafter, a specific example of the angle distribution conversion element 60 of the present embodiment will be described. Hereinafter, the angle distribution conversion element 61 corresponding to the light source element 100 will be described as an example.

(Specific example 1)
As shown in FIG. 7, a light guide rod 71 can be employed as the angle distribution conversion element 61. The light guide rod 71 has a function of making the angle distribution uniform by propagating light incident at various incident angles while causing the light to be reflected a plurality of times inside. For example, the optical fiber 10 has the same configuration and the length is shorter than that of the optical fiber 10, the columnar one made of a light-transmitting material such as glass or resin, or the cylindrical shape in which the reflecting mirror is formed on the inner surface. Things can be used.
For the purpose of suppressing the divergence angle of the radiated light from the light source element 100, the light incident end surface and / or the light exit end surface of the light guide rod 71 may be configured with a curved surface. As an example, the light incident end face of the light guide rod 71 can be a cylindrical shape, and the light exit end face can be a spherical shape.

(Specific example 2)
As another specific example, as shown in FIG. 8A, an optical element 72 having a non- axisymmetric refracting surface can be adopted as the angle distribution conversion element 61. FIG. 8A (a) is a schematic diagram in the case where an optical element 72 having a non- axisymmetric refracting surface is employed as the angle distribution conversion element 61, and FIG. 8A (b) is a view of the optical element 72 viewed from the y direction and the x direction. FIG.
Since the optical element 72 has a non- axisymmetric refracting surface, the optical element 72 has a characteristic that the focal length differs in the x direction and the y direction. Therefore, as shown in FIG. 6B, the angular distribution of light rays that diverge along the xz plane (plane α) and the angle of light rays that diverge along the yz plane (plane β), as shown in FIG. 6B. When the distribution is different, an optical element 72 having a non- axisymmetric refracting surface in which the focal length in each direction is set so that one angular distribution matches the other angular distribution can be used as the angular distribution conversion element 61.

As a specific example of the optical element 72 having a non- axisymmetric refracting surface used as the angle distribution conversion element 61, as shown in FIG. 8B, a cylindrical lens 73 having different curvatures in the xz plane and the yz plane can be used. FIG. 8B illustrates a case where two sets of cylindrical lenses 73 having different curvatures are used as the angle distribution conversion element 61.

  As shown in FIG. 8B (a), since the cylindrical lens 73 has different curvatures in the xy plane and the yz plane, the light beams having different angular distributions (106x, 106y) in both planes as shown in FIG. By passing through the lens 73, both planes are converted to those having the same angular distribution (107x, 107y) as shown in FIG. 8B (b).

When the optical element 72 having a non- axisymmetric refracting surface is used as the angle distribution conversion element 61, a toric lens and a spheroid surface lens can be used in the same manner as the optical element 72 in addition to the cylindrical lens.

(Specific example 3)
As another specific example, as shown in FIG. 9A, a light divergent element 74 that converts parallel light into divergent light can be employed as the angle distribution conversion element 61.
The light divergence element 74 is an element capable of setting the divergence angle θx ′ of the light beam traveling along the xz plane and the divergence angle θy ′ of the light beam traveling along the yz plane to different angles. Therefore, as shown in FIG. 6B, the angle distribution of light rays that diverge along the xz plane (plane α) and the angle of light rays that diverge along the yz plane (plane β), as shown in FIG. When the distribution is different, the light divergence element 74 in which the divergence angle of the light beam traveling along each plane is set so as to match one angle distribution with the other angle distribution can be used as the angle distribution conversion element 61.

As a specific example of the light diffusing element 74 used as the angle distribution conversion element 61, as shown in FIG. 9B, a diffusing plate 75 having different light diffusion angles in the xz plane and the yz plane can be used. As shown in FIG. 9B (a), since the diffusion plate 75 has different diffusion angles between the xy plane and the yz plane, the light rays having different angular distributions (106x, 106y) in both planes as shown in FIG. By passing through the diffuser plate 75, both planes are converted to those having the same angular distribution (107x, 107y) as shown in FIG. 9B (b).
When the light divergence element 74 is used as the angle distribution conversion element 61, a hologram, a two-dimensional lens array, or a cylindrical lens array can be similarly used as the light divergence element 74 in addition to the diffusion plate.

FIG. 10 is a diagram schematically illustrating an example of a detailed configuration of the present embodiment. The light source unit 20 assumes a plurality of single emitter laser elements as a plurality of light source elements. These light source elements emit coherent light whose angular distribution is non- axisymmetric .
The radiated light from each light source element is converted into light whose axis distribution is axisymmetric via an angle distribution conversion element 60 formed by a cylindrical lens, and then the traveling direction of the light is changed via each mirror 82. The light is condensed by the condensing optical system 31 and guided to the light incident end face 10 a of the optical fiber 10. The principal ray of light incident on the light incident end face 10a is substantially parallel to the fiber axis 10c.

FIG. 11 is a diagram schematically illustrating another example of the detailed configuration of the present embodiment. The light source unit 20 includes a multi-emitter laser as a plurality of light source elements. These light source elements emit coherent light whose angular distribution is non- axisymmetric .
The radiated light from each light source element is converted into light whose axis distribution is axisymmetric via an angle distribution conversion element 60 constituted by a light guide rod, and then the traveling direction of the light is changed via a mirror 81. The light is condensed by the condensing optical system 31 and guided to the light incident end face 10 a of the optical fiber 10. The principal ray of light incident on the light incident end face 10a is substantially parallel to the fiber axis 10c.
Similar to FIG. 4, in the configurations of FIGS. 10 and 11, the mirror 81 and the mirror 82 are installed only for the purpose of changing the light beam direction, and are not essential elements of the light source device 1.

[Fourth Embodiment]
Next, with reference to FIGS. 12 to 14, an example of the case where the light guided using the light source device 1 described in the first to third embodiments is used for a projector, in particular, the optical fiber 10. The portion after the injection end will be described.
As shown in FIG. 12, the light propagated by the optical fiber 10 of the light source device 1 is obtained with the help of a light collecting means (not shown) such as a concave reflecting mirror or a lens. FmA) is input to the incident end (PmiA) and output from the exit end (PmoA).

Here, as the light uniformizing means (FmA), for example, a light guide can be used. This is also called a name such as a rod integrator or a light tunnel, and is constituted by a prism made of a light-transmitting material such as glass or resin. The light input to the incident end (PmiA) propagates through the light uniformizing means (FmA) while repeating total reflection on the side surface of the light uniformizing means (FmA) according to the same principle as the optical fiber. Even if the distribution of light input to the incident end (PmiA) is uneven, it functions so that the illuminance on the exit end (PmoA) is sufficiently uniform.
In addition to the light guide made of a light-transmitting material such as glass or resin, this light guide is a hollow square tube whose inner surface is a reflecting mirror, and similarly, it repeatedly reflects on the inner surface. However, it is also possible to use a device that performs the same function by propagating light.

The light output from the emission end (PmoA) is arranged by arranging the illumination lens (Ej1A) so that a square image of the emission end (PmoA) is formed on the two-dimensional light amplitude modulation element (DmjA). Illuminates the two-dimensional light amplitude modulation element (DmjA).
FIG. 12 shows a configuration in which a mirror (MjA) is disposed between the illumination lens (Ej1A) and the two-dimensional light amplitude modulation element (DmjA).
The two-dimensional light amplitude modulation element (DmjA) modulates light on a screen (Tj) by modulating light so that light is incident on the projection lens (Ej2A) or not on the screen according to the video signal. Display an image.

  This two-dimensional light amplitude modulation element is sometimes called a light valve. In the optical system shown in FIG. 12, for example, DMD (registered trademark) (digital micromirror device) can be used as the two-dimensional light amplitude modulation element (DmjA).

  Regarding the light uniformizing means, in addition to the light guide, a so-called fly eye integrator can be used. As an example, a projector using this light uniformizing means will be described with reference to FIG.

Similar to the configuration of FIG. 12, the light propagated by the optical fiber 10 of the light source device 1 is converted into a substantially parallel light beam with the help of collimator means (not shown) such as a concave reflecting mirror or lens. The light is input to the incident end (PmiB) of the light uniformizing means (FmB) by the eye integrator and output from the exit end (PmoB).
Here, the light uniformizing means (FmB) is composed of a combination of an incident side front stage fly-eye lens (F1B), an exit side rear stage fly-eye lens (F2B), and an illumination lens (Ej1B).
Both the front fly-eye lens (F1B) and the rear fly-eye lens (F2B) are formed by arranging a large number of rectangular lenses having the same focal length and the same shape in the vertical and horizontal directions.

Each lens of the front-stage fly-eye lens (F1B) and the corresponding lens of the rear-stage fly-eye lens (F2B) in each subsequent stage constitute an optical system called Koehler illumination. That is, in the light uniformizing means (FmB) using the fly eye integrator, a number of Koehler illumination optical systems are arranged vertically and horizontally.
In general, the Kohler illumination optical system is composed of two lenses. When the front lens collects light and illuminates the target surface, the front lens does not form a light source image on the target surface, but the center of the rear lens. A light source image is formed on this surface, and the rear lens is arranged so as to form an image of the quadrangle of the outer shape of the front lens on the target surface (surface to be illuminated), thereby uniformly illuminating the target surface.
If there is no rear stage lens, when the light source is not a perfect point light source but has a finite size, a phenomenon may occur in which the illuminance at the periphery of the square of the target surface is lowered depending on the size. The rear lens is provided in order to prevent such a phenomenon, and the rear lens can make the illuminance uniform to the periphery of the square of the target surface without depending on the size of the light source.

In the case of the optical system shown in FIG. 13, it is basically based on the input of a substantially parallel light beam to the light uniformizing means (FmB), so the distance between the front fly-eye lens (F1B) and the rear fly-eye lens (F2B). Are arranged to be equal to their focal lengths. Therefore, the image of the target surface of uniform illumination as the Kohler illumination optical system is generated at infinity.
However, since the illumination lens (Ej1B) is disposed at the subsequent stage of the rear stage fly-eye lens (F2B), the target surface is attracted from the infinity to the focal plane of the illumination lens (Ej1B).
A number of Kohler illumination optical systems arranged in the vertical and horizontal directions are parallel to the incident optical axis (ZiB), and light beams are input substantially axially symmetrically with respect to the respective central axes, so that the output light beams are also substantially axially symmetric. For this reason, due to the nature of the lens, that is, the Fourier transform action of the lens, light rays that are incident on the lens surface at the same angle are refracted toward the same point on the focal plane, regardless of the incident position on the lens surface. The outputs of all the Koehler illumination optical systems are imaged on the same object plane on the focal plane of the illumination lens (Ej1B).

As a result, since the illuminance distributions on the respective lens surfaces of the front fly-eye lens (F1B) are all overlapped, one synthetic quadrangle in which the illuminance distribution is more uniform than in the case of one Koehler illumination optical system. Are formed on the incident optical axis (ZiB).
Then, by arranging the two-dimensional light amplitude modulation element (DmjB) at the position of the composite square image, the two-dimensional light amplitude modulation element (DmjB) to be illuminated is illuminated by the light output from the emission end (PmoB). Illuminated.
In the optical system shown in FIG. 13, a polarization beam splitter (MjB) is arranged between the illumination lens (Ej1B) and the two-dimensional light amplitude modulation element (DmjB), and thereby the light is two-dimensional light amplitude modulated. It is configured to be reflected toward the element (DmjB).
The two-dimensional light amplitude modulation element (DmjB) modulates the polarization direction of light by 90 degrees for each pixel according to the video signal, or modulates and reflects the light so that only the rotated light is polarized. The light passes through the beam splitter (MjB) and is incident on the projection lens (Ej3B), and an image is displayed on the screen (Tj).

In the optical system shown in FIG. 13, for example, LCOS (registered trademark) (silicon liquid crystal device) can be used as the two-dimensional light amplitude modulation element (DmjB).
In the case of such a liquid crystal device, since only the light component in the specified polarization direction can be effectively modulated, in general, the component parallel to the specified polarization direction is transmitted as it is, and only the component perpendicular to the specified polarization direction is transmitted. The polarization direction is rotated by 90 degrees. Therefore, a polarization alignment functional element (PcB) for enabling effective use of all the light is inserted, for example, in the rear stage of the rear fly-eye lens (F2B).
For example, a field lens (Ej2B) is inserted immediately before the two-dimensional light amplitude modulation element (DmjB) so that substantially parallel light is incident thereon.

  As for the two-dimensional light amplitude modulation element, in addition to the reflective type as shown in FIG. 13, a transmissive liquid crystal device (LCD) can be used with an optical arrangement adapted thereto.

Although not shown in FIGS. 12 and 13, in order to display an image in color, for example, a dynamic color filter such as a color wheel is disposed after the light uniformizing means (FmA, FmB). , R (red), G (green), and B (blue) can be configured to illuminate the two-dimensional light amplitude modulation element as a color sequential light beam and realize color display by time division.
Similarly, as another method for realizing color display, a dichroic mirror or a dichroic prism is arranged after the light uniformizing means (FmA, FmB), and R (red), G (green), and B (blue). A two-dimensional light amplitude modulation element provided independently for each color is illuminated with light separated into the three primary colors, and a dichroic mirror or dichroic prism is provided for color synthesis of the modulated light beams of the three primary colors. it can.

  FIG. 14 is a diagram schematically illustrating another configuration of a projector using the light source device 1. In FIG. 14, R (red), G (green), and B (blue) light is emitted from the light source device 1, and light of each color is propagated by the optical fiber 10 corresponding to each color. Assume the case.

  More specifically, as the optical fiber 10, a plurality of optical fibers corresponding to R, G, and B3 primary colors, that is, optical fibers for R color light sources (EfR1, EfR2,...), Optical fibers for G color light sources (EfG1,. EfG2,...) And B-color light source optical fibers (EfB1, EfB2,...), Each of which is configured as a fiber bundle in which the exit ends are aligned.

The light beams emitted from the exit ends of these three fiber bundles are converted into infinite images by collimator lenses (EsR, EsG, EsB), respectively, and then mirror (HuR) and dichroic mirror (HuG, HuB). Is used to generate an output light beam (Fo).
The output light beam (Fo) is input to the condensing lens (Eu), and the incident end (Fm) of the light uniformizing means (Fm) is passed through a diffusion element (Edm) for further removing speckles as necessary. Pmi).
The light uniformizing means (Fm) and the optical system after the exit end (Pmo) are the same as those shown in FIGS.

  As described above in the first to third embodiments, the light emitted from the light emitting end face of the optical fiber 10 is light in which radiated light from a plurality of light source elements is mixed. Therefore, according to the projector of the present embodiment that projects an image on the projection surface (Tj) using this light, an image on which speckle noise is superimposed is not visually recognized, and a clear image can be realized.

  In the above, a semiconductor laser is used as an example of a coherent light source. However, in addition to this, other laser light sources, for example, a radiated light from a semiconductor laser or the like, is used for nonlinear generation such as harmonic generation or optical parametric effect. Even in the case of using a light source for wavelength conversion utilizing an optical phenomenon, the present invention exhibits a good effect.

DESCRIPTION OF SYMBOLS 1: Light source device 10: Optical fiber 10a: Light incident end surface 10b of optical fiber 10: Light emission end surface 10c of optical fiber 10: Fiber axis of optical fiber 10 20: Light source part 30: Coupling optical system 31: Condensing optical system 41 : Lens 42: Lens 60: Wavelength distribution conversion element 61: Wavelength distribution conversion element corresponding to the light source element 100 71: Light guide rod 72: Optical element having a non- axisymmetric refracting surface 73: Cylindrical lens 74: Light diverging element 75: Diffuser plate 81: Mirror 82: Mirror 100: Light source element 101: Principal ray of emitted light from the light source element 100 102: Principal ray of emitted light from the light source element 100 103: Principal ray of emitted light from the light source element 100 104: chief ray of emitted light from the light source element 100 103s: emission of light emitted from the light source element 100 Bundle 106x: Light ray traveling from the light source element 100 along the xz plane 106y: Light ray traveling from the light source element 100 along the yz plane 110: Light source element 111: Main light beam emitted from the light source element 110 112: Light source element 110 113: principal ray of emitted light from the light source element 110 113: luminous flux of emitted light from the light source element 110 114: principal ray of emitted light from the light source element 120: light source element 121: light source element The principal ray of the emitted light from 120: The principal ray of the emitted light from the light source element 123: The principal ray of the emitted light from the light source element 120 123s: The luminous flux of the emitted light from the light source element 124 The 124: From the light source element 120 Principal ray of emitted light 200: Light source element 201: Principal ray of emitted light from light source element 200 202: Light beam group of radiated light from light source element 200 202s: Light beam of radiated light from light source element 200 210: Light source element 211: Main light beam of radiated light from light source element 210 212: Light beam group of radiated light from light source element 210 : Light beam emitted from the light source element 210 220: Light source element 221: Main light beam emitted from the light source element 220 222: Light beam group emitted from the light source element 220 222s: Light beam emitted from the light source element 220 250 : Projection surface DmjA: Two-dimensional light amplitude modulation element DmjB: Two-dimensional light amplitude modulation element Edm: Diffusing element EfB1: Optical fiber for B color light source EfB2: Optical fiber for B color light source EfG1: Optical fiber for G color light source EfG2: G Optical fiber for color light source EfR1: Optical fiber for R color light source EfR2: Optical fiber for R color light source Ej1A: Illumination lens Ej1B: Illumination lens Ej2A: Projection lens Ej2B: Field lens Ej3B: Projection lens EsB: Collimator lens EsG: Collimator lens EsR: Collimator lens Eu: Condenser lens F1B: Fly-eye lens F1B : Light uniformizing means FmA: Light uniformizing means FmB: Light uniformizing means Fo: Output light flux HuB: Dichroic mirror HuG: Dichroic mirror HuR: Mirror LCD: Liquid crystal device MjA: Mirror MjB: Polarizing beam splitter PcB: Polarizing alignment element Pmi: incident end PmiA: incident end PmiB: incident end Pmo: exit end PmoA: exit end PmoB: exit end SjA: light source SjB: light source Tj: scan Lean ZIB: incident optical axis alpha: a plane parallel to the xz plane beta: yz plane plane parallel to the [theta] x: diffusion angle of the light beam diffused along the plane alpha [theta] y: diffusion angle of the light beam diffused along the plane beta

Claims (12)

A plurality of light source elements that emit coherent light of the same color ;
Optical fiber,
A coupling optical system for guiding emitted light from the plurality of light source elements to the light incident end face of the optical fiber;
The coupling optical system has a condensing optical system that receives radiated light from each of the plurality of light source elements and collects light collectively on a light incident end face of the optical fiber,
Light emitted from each of the plurality of light source elements is incident on the optical fiber through the condensing optical system as a chief ray corresponding to the center of the angular distribution of the light beam when the light is input to the condensing optical system. The light source device characterized in that the chief ray immediately after is substantially parallel to the central axis of the optical fiber. The light incident end face of the optical fiber is constituted by a plane perpendicular to the central axis of the optical fiber,
The light source device according to claim 1, wherein the condensing optical system is telecentric on an output side. The condensing optical system has a plurality of lenses,
The light source device according to claim 2, wherein a lens disposed at a position closest to the output side among the plurality of lenses is substantially in close contact with a light incident end face of the optical fiber.   The light source device according to claim 1, wherein the light incident on the light incident end face of the condensing optical system exhibits a substantially axially symmetric angular distribution. The emitted light from the plurality of light source elements exhibits an angular distribution in which the angular distribution of the optical emission is non-axisymmetric and substantially symmetric with respect to a plane including the central axis of the optical emission,
The coupling optical system has a plurality of angle distribution conversion elements corresponding to the plurality of light source elements,
The plurality of angle distribution conversion elements convert radiated light from the plurality of light source elements into light having a substantially axially symmetric angle distribution and emit the light to a light incident end face of the condensing optical system. The light source device according to claim 4.   6. The light source device according to claim 5, wherein the chief rays of light emitted from the plurality of angle distribution conversion elements are substantially parallel to each other.   The light source device according to claim 5, wherein the plurality of angle distribution conversion elements include an optical element having a non-axisymmetric refracting surface.   The light source device according to claim 7, wherein the optical element including the non-axisymmetric refracting surface is configured by a cylindrical lens, a toric lens, or a spheroidal surface lens.   The light source device according to claim 5, wherein the plurality of angle distribution conversion elements include a light diverging element that converts parallel light into divergent light.   The light source device according to claim 9, wherein the light diverging element includes a diffusing plate, a two-dimensional lens array, or a cylindrical lens array.   The light source device according to claim 5, wherein the plurality of angle distribution conversion elements include a light guide bar. The projector which projects and displays an image using the emitted light from the light source device of any one of Claims 1-11.