JP2013195501A - Laser emitting device and video display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser emitting device and video display device capable of reducing speckle noise, having less vibration sound, and suitable for downsizing.SOLUTION: A laser emitting device 1 includes a laser source 2 emitting a laser beam, a uniformizing element 5 which uniformizes intensity distribution of the laser beam, and a coupling optical system 10 which couples the laser beam emitted from the laser source 2 to the uniformizing element 5. The coupling optical system 10 includes a diffusion element 3 which transmits and diffuses the laser beam.

Description

  The present invention relates to a laser illumination device using a laser light source and an image display device using the laser illumination device.

  In recent years, video display devices such as projectors and rear projection displays have been developed that include an illumination device using a laser light source. Since the laser light source has good monochromaticity, the color reproduction range can be widened and a colorful image can be obtained. Further, since the area of the light source is small, high luminance can be realized by stacking (laser stack). In addition, the reliability is remarkably higher than that of a lamp light source, and a large projection system has an advantage of good maintainability.

  However, the laser has a high coherence, and there is a problem that an image quality deteriorates due to an interference pattern called speckle noise. Speckle noise is generated by superimposing interference patterns generated by minute irregularities in the optical system on the image and light scattered by the rough surface of the screen in the viewer's eyes. Some interference patterns are superimposed on the retina. In particular, the latter is difficult to reduce and is a problem in using a laser light source.

  In order to solve the problem of speckle noise, a technique has been proposed in which a diffusion plate is arranged at an appropriate position in an optical path in an image display device and the diffusion plate is vibrated.

  For example, in the technique disclosed in Patent Document 1, a conical prism is provided at the entrance of the light tunnel, and the conical prism is guided to the light tunnel while condensing laser light, and the conical prism is arranged in the optical axis direction of the light tunnel. By oscillating in parallel and changing the optical path of the light flux, different interference patterns are generated to reduce speckle noise.

JP 2008-216923 A (paragraphs 0049 to 0051, FIG. 1) JP 2008-96777 (paragraph 0016, FIG. 1)

  However, the conventional technique disclosed in Patent Document 1 has a problem in that vibration sound is generated because the conical prism disposed in the optical path is vibrated. In addition, since it is necessary to provide a mechanism for vibrating the conical prism, there is a problem in that the size of the apparatus is hindered.

  Also, since the laser light source has a small etendue, it is desirable to use a homogenizing element for high brightness, but in order to provide a movable part (conical prism) inside, a hollow light tunnel is used as the homogenizing element. It is necessary to use it. However, the hollow light tunnel has a problem that the reliability when the energy of the incident light is high is lower than that of the integrator rod. This is because a hollow light tunnel is often formed by bonding four glass plates or the like with an adhesive, and the adhesive force changes due to heat.

  Further, Patent Document 2 discloses a diffusion device that expands the divergence angle of laser light immediately before an integrator rod in an illuminating device including a light source having a plurality of emission points (surface emitting laser, etc.), a condenser lens, and an integrator rod. Although a technique for reducing speckle noise by disposing an element has been disclosed, it is assumed that a surface emitting laser or the like is used. When other laser light sources are used, the incident surface of the integrator rod Therefore, it is difficult to make laser light incident on a predetermined angle without waste, and there is room for improvement in terms of light utilization efficiency.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a laser illumination device and an image display device that can reduce speckle noise.

  A laser illumination apparatus according to the present invention includes a laser light source that emits laser light, a homogenizing element that equalizes the intensity distribution of the laser light, and a coupling optical system that couples the laser light emitted from the laser light source to the homogenizing element. The coupling optical system includes a diffusion element that transmits and diffuses laser light.

  An image display apparatus according to the present invention includes the above laser illumination apparatus, an image display device illuminated by the laser illumination apparatus, and a projection optical system that projects image light generated by the image display device. And

  According to the present invention, speckle noise can be reduced by diffusing laser light with a diffusion element. Further, since the laser beam can be incident on a wide area on the incident surface of the homogenizing element, the light intensity can be made more uniform. Moreover, since it is not necessary to vibrate a movable part like patent document 1, a noise does not arise and it can contribute to size reduction of an apparatus.

  Further, unlike Patent Document 2, the coupling optical system has a diffusing element that transmits and diffuses the laser light, so that the laser light can be incident on the incident surface of the homogenizing element within a predetermined angle without waste. And the light utilization efficiency can be improved.

It is a figure which shows the structure of the video display apparatus containing the laser illumination apparatus in Embodiment 1 of this invention. It is the schematic for demonstrating the effect | action of the lens as a coupling optical element. 1 is a perspective view showing a configuration of a laser illuminating device in Embodiment 1. FIG. It is the figure which illustrated the optical path of the laser beam radiate | emitted from the laser light source and injected into one cell of a diffusion element. It is the figure which showed the optical path of the whole laser beam radiate | emitted from the laser light source. It is a schematic diagram which shows in-plane intensity distribution of the laser beam in the incident surface of an integrator rod, when a diffusion element is not provided (A) and when a diffusion element is provided (B). It is a schematic diagram which shows the angular intensity distribution of the laser beam on the incident surface of the integrator rod for each of the case where no diffusion element is provided (A) and the case where a diffusion element is provided (B). It is a schematic diagram which shows angular intensity distribution of the laser beam in the output surface of an integrator rod, when a diffusion element is not provided (A) and when a diffusion element is provided (B). It is a figure which shows the structure of the video display apparatus containing the laser illumination apparatus in Embodiment 2 of this invention. It is a figure which shows the structure of the laser illuminating device in Embodiment 3 of this invention.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration of a video display device provided with a laser illumination device 1 using a laser light source 2 in Embodiment 1 of the present invention. The image display device is emitted from a laser light source 2 that emits laser light, a diffusion element 3, an integrator rod 5 that is a uniformizing element that uniformizes the intensity distribution in the beam cross section of the laser light, and the laser light source 2. And a lens 4 as a coupling optical element for coupling the laser beam to the integrator rod 5.

  The video display device also includes a relay lens 6 as an illumination optical system that irradiates the non-illuminated body (video display device 7) with the laser light whose intensity distribution is made uniform by the integrator rod 5, and the incident laser light spatially. A reflection type image display device 7 that modulates and outputs the light, a projection lens 8 as a projection optical system that projects laser light (image light) modulated by the image display device 7, and image light is projected by the projection lens 8. The screen 9 is provided.

  Among these optical elements, the laser light source 2, the diffusing element 3, the lens (coupled optical element) 4, and the integrator rod (homogenizing element) 5 constitute the laser illumination device 1.

  The laser light source 2 is, for example, a laser diode, and emits divergent laser light from the light emitting unit 2a. In order to obtain high energy, it is preferable to use a laser diode having a large light emitting region, and laser light coupled to a large-diameter optical fiber may be used.

  A diffusing element 3 and a lens 4 are arranged on the emission side of the laser light source 2. The diffusion element 3 will be described later.

  The lens 4 has a function of condensing the laser light emitted from the laser light source 2 onto the incident surface 5a of the integrator rod 5, as schematically shown in FIG. Here, the optical axis 4 c of the lens 4 is defined as the entire optical axis of the laser illumination device 1. The lens 4 may be composed of a single lens or a plurality of lenses.

  Returning to FIG. 1, the integrator rod 5 is a solid prismatic optical element. The shapes of the entrance surface 5a and the exit surface 5b of the integrator rod 5 and the cross-sectional shape orthogonal to the axial direction are both rectangular shapes that are substantially similar to the display surface 7a of the video display device 7, and have a long side and a short side. Have.

  The integrator rod 5 totally reflects the laser beam incident from the incident surface 5a a finite number of times inside, and emits the laser beam having a uniform intensity distribution in the cross section from the emission surface 5b. Here, the central axis 5c of the integrator rod 5 is coaxial with the optical axis 4c of the lens 4 (FIG. 2). Further, an antireflection film (AR coating) may be formed on the incident surface 5a.

  The relay lens 6 irradiates the display surface 7 a of the video display device 7 with the laser light emitted from the integrator rod 5. At this time, the relay lens 6 uniformly illuminates the display surface 7 a of the video display device 7 by forming an image of the exit surface 5 b of the integrator rod 5 on the display surface 7 a of the video display device 7.

  The video display device 7 (also referred to as a light modulation element or a light valve) is configured by, for example, a reflective liquid crystal panel or a digital micromirror device. The digital micromirror device has a large number of micromirrors arranged in a plane and modulates incident light by changing the tilt angle of each micromirror according to image information.

  The projection lens 8 enlarges and projects the laser light (image light) modulated by the image display device 7 onto the screen 9. In the case of a front projection type (front projector), the screen 9 has a rough surface having a minute structure, and the image light projected by the projection lens 8 is diffusely reflected by the rough surface, so that the viewer can view the image. Appreciate. On the other hand, in the case of a rear projection type (rear projector), the screen 9 is constituted by a transmission type screen in which a diffusing agent is dispersed in a material such as a resin, and a viewer views an image by transmitted light.

  The surface of the screen 9 and the display surface 7a of the video display device 7 are arranged at conjugate positions. Further, the display surface 7a of the video display device 7 and the exit surface 5b of the integrator rod 5 are arranged at conjugate positions.

  FIG. 3 is a perspective view showing the laser illumination device 1 according to the present embodiment. As shown in FIG. 3, the diffusing element 3 (light beam splitting element) is disposed in the optical path of the lens 4 that is a coupling optical element. Here, although the diffusing element 3 is disposed on the front side of the lens 4 (laser light source 2 side), it may be disposed on the integrator rod 5 side of the lens 4.

  The diffusing element 3 is a lens array in which a large number of minute cells (lens cells) 3a are arranged in a plane. The shape (opening shape) of each lens cell 3 a is a rectangular shape that is substantially similar to the rectangular incident surface 5 a of the integrator rod 5.

  Each lens cell 3 a of the diffusing element 3 is optically parallel to the incident surface 5 a of the integrator rod 5. That is, if the long side direction of each lens cell 3a of the diffusing element 3 is the X direction and the short side direction is the Y direction, the X direction and the Y direction are the long side direction (X ′ of the incident surface 5a of the integrator rod 5). Direction) and the short side direction (Y ′ direction) are optically parallel to each other. Note that “optically parallel” means that, for example, when the optical path is bent by a reflective element, the optical path is substantially parallel in consideration of the bending of the optical path.

  Each lens cell 3a of the diffusing element 3 is a lens having positive power, and here is a spherical lens convex on the incident surface side (light source 2 side). The laser light is condensed by the positive power of the lens cell 3 a and the action of the lens 4. That is, the lens cell 3a and the lens 4 of the diffusing element 3 constitute a coupling optical system 10 that makes laser light incident on the incident surface 5a of the integrator rod 5 (so that a desired focused spot is obtained).

  The size (cell size) of the lens cell 3a in the X direction and the Y direction is several tens of μm. Further, the diffusing element 3 has, for example, 100 lens cells 3a arranged in the X direction and 100 lens cells 3a in the Y direction. That is, the diffusing element 3 is configured to divide incident laser light into light beams of about 100 × 100 and emit them.

  Next, the effect of using the diffusion element 3 will be described. FIG. 4 is a schematic diagram showing an optical path of laser light emitted from the laser light source 2 and incident on one lens cell 3a of the diffusing element 3. FIG. 4A is a view seen from the Y direction, and FIG. B) is a view from the X direction.

  As shown in FIGS. 4A and 4B, the laser light emitted from the laser light source 2 in a divergent state is incident on one lens cell 3a of the diffusing element 3 and is substantially the same as the incident surface 5a of the integrator rod 5. It is emitted as a light beam having a similar rectangular cross section.

  Then, the laser light transmitted through one lens cell 3 a of the diffusing element 3 is condensed before the incident surface 5 a of the integrator rod 5 by the positive power of the lens cell 3 a and the action of the lens 4. The condensing NA (numerical aperture) is defined by the aperture of the lens cell 3a, and on the incident surface 5a of the integrator rod 5, a condensing distribution of the laser light spreading in a rectangular shape substantially similar to the aperture shape of the lens cell 3a is obtained. It is done.

  When the number of divisions of the lens cell 3a of the diffusing element 3 is increased, the intensity distribution of the laser beam incident on one lens cell 3a becomes almost constant, and therefore the intensity distribution on the incident surface 5a of the integrator rod 5 is also almost equal. It becomes constant. Further, by appropriately setting the lens curvature of the lens cell 3a and the size in the XY direction, a substantially similar condensing spot (incident area) that can be accommodated in the incident surface 5a of the integrator rod 5 can be formed. As a result, it is possible to couple the laser light to the integrator rod 5 while suppressing the light amount loss.

  FIG. 5 is a schematic diagram showing the optical path of the entire laser beam output from the laser light source 2. The laser light emitted from the laser light source 2 passes through the diffusing element 3 and the lens 4 to form a focused spot on the incident surface 5 a of the integrator rod 5. This condensing spot is a superposition of light beams that have passed through each lens cell 3 a of the diffusing element 3 and spread on the incident surface 5 a of the integrator rod 5. As a result of such superposition, on the incident surface 5a of the integrator rod 5, a rectangular uniform intensity distribution (condensation distribution) is obtained as a whole of the laser beam.

  FIG. 6 is a diagram showing the in-plane intensity distribution of the laser light on the incident surface 5a of the integrator rod 5 for each of the case where the diffusion element 3 is not provided (A) and the case where the diffusion element 3 is provided (B). is there. As shown in FIG. 6 (A), when the diffusing element 3 is not provided, a small rectangular condensing spot to which the light emitting region of the laser light source 2 is transferred is formed on the incident surface 5 a of the integrator rod 5. On the other hand, as shown in FIG. 6B, when the diffusing element 3 is provided, the entire incident surface 5a of the integrator rod 5 is rectangular regardless of the shape and size of the light emitting region of the laser light source 2. A uniform intensity distribution spreading in shape can be obtained.

  In addition, since the laser light that has passed through each lens cell 3a of the diffusing element 3 is superimposed on the incident surface 5a of the integrator rod 5, an arbitrary point on the incident surface 5a of the integrator rod 5 includes a diffusing element. The light transmitted through almost all the lens cells 3a of 3 is collected.

  FIG. 7 is a graph showing the angular intensity distribution of incident light at an arbitrary point on the incident surface 5 a of the integrator rod 5. FIG. 7A shows the angular intensity distribution when the diffusing element 3 is not provided, and FIG. 7B shows the angular intensity distribution when the diffusing element 3 is provided. The horizontal axis of FIG. 7 indicates the incident angle of incident light, and the vertical axis indicates the intensity.

  In FIG. 7B, compared to FIG. 7A, the angular intensity distribution of incident light at one point on the incident surface 5a of the integrator rod 5 is discrete. This is because the laser beam is subdivided by each lens cell 3 a of the diffusing element 3. However, since the size of the lens cell 3a of the diffusing element 3 is as small as several tens of μm, and the incident laser light is divided into about 100 × 100 luminous fluxes, the shape of the entire distribution is emitted from the laser light source 2. It is close to the distribution of light.

  As described above, by providing the diffusing element 3 in the coupling optical system 10, a rectangular condensing spot widely distributed on the incident surface 5a of the integrator rod 5 is formed, and each point on the condensing spot is a laser light source. 2 has a distribution close to the angular distribution of the laser light when emitted from 2.

  The angular intensity distribution of the laser light is steeply high in the center such as a Gaussian distribution, so that it is difficult to make it uniform with a finite number of reflections of the integrator rod 5. This can be improved by increasing the number of reflections of the laser light propagating through the integrator rod 5, but the length of the integrator rod 5 is usually limited to about 100 mm or less based on the size of the video display device.

  Therefore, in the present embodiment, by providing the diffusing element 3 in the coupling optical system 10, the intensity distribution on the incident surface 5a of the integrator rod 5 is made uniform. Thereby, even when the integrator rod 5 having a short length is used, the intensity distribution of the laser beam can be made uniform.

  In the video display device, speckle noise is generated on the exit surface 5b of the integrator rod 5, the display surface 7a of the video display device 7, or the rough surface of the screen 9 due to the high coherence of the laser beam. There is a case. This is caused by interference when the laser light partially has a small phase difference due to minute unevenness or diffusion particles on the surface of the optical element on the optical path, and the laser light overlaps.

  On the other hand, in the present embodiment, since the diffusing element 3 has a large number of minute lens cells 3a, the laser light transmitted through the diffusing element 3 is divided into luminous fluxes corresponding to the number of cells, and each has a different phase difference. Is granted. Since the light beams to which different phase differences are given in this way have different interference patterns (speckle patterns), speckle noise is reduced by superimposing these light beams.

  Further, when a phase difference is given to the laser light due to the minute unevenness of the rough surface of the screen 9 as described above, an interference pattern generated by the interference of the laser light in the viewer's eyes is generated. By forming an image on the retina, speckle noise is formed, which is recognized as an unpleasant video flicker or glare. As described below, speckle noise generated on the rough surface of the screen is reduced by angle multiplexing of the projected laser beam.

  That is, when attention is paid to a certain point on the rough surface of the screen 9, since different phase differences are given to laser beams incident on the rough surface at different angles, the generated interference patterns are also different from each other. Therefore, speckle noise can be reduced by superimposing these laser beams.

  As described above, the rough surface of the screen 9 and the display surface 7a of the video display device 7 are conjugated with each other, and the display surface 7a of the video display device 7 and the exit surface 5b of the integrator rod 5 are conjugated with each other. Therefore, the angular intensity distribution of one point on the exit surface 5b of the integrator rod 5 corresponding to one point on the screen 9 may be controlled as follows.

  FIG. 8 is a diagram showing the angular intensity distribution of laser light emitted from a certain point on the emission surface 5b of the integrator rod 5 for each of the cases where the diffusion element 3 is not provided (A) and the case where it is provided (B). It is. In the case where the diffusing element 3 is not provided, the laser light is folded back within the integrator rod 5 having a finite length, so that the intensity distribution as shown in FIG.

  Due to restrictions on the manufacturing of the integrator rod 5 and restrictions on arrangement in the video display device, the number of reflections of the laser light at the integrator rod 5 is about 10 times or less, and the number of folding in the longitudinal direction of the integrator rod 5 is further increased. Few. Therefore, the intensity distribution of the laser light emitted from a certain point of the integrator rod 5 is a discrete distribution having a number of peaks corresponding to the number of reflections. Therefore, the distribution of the incident angles of the laser light incident on one point on the rough surface of the screen 9 is also discrete, and as a result, different interference patterns are not sufficiently overlapped and speckle noise is visually recognized.

  In contrast, in the present embodiment, by providing the coupling optical system 10 with the diffusing element 3 having the minute lens cells 3a, a large number of light beams divided by the diffusing element 3 have substantially the same angular intensity distribution. Then, the light is incident on the incident surface 5a of the integrator rod 5 while changing its position. When each light beam is emitted from a minute region of the emission surface 5b, it has a discrete angular distribution (due to the reflection inside the integrator rod 5 described above), but the incident surface of the integrator rod 5 for each light beam. Since the incident positions on 5a are different, many light beams having different angular distributions are added on the exit surface 5b. As a result, the intensity distribution of the laser beam emitted from one point on the emission surface 5b of the integrator rod 5 becomes a distribution that is continuously close as shown in FIG.

  Therefore, light beams having various incident angles emitted from the exit surface 5b of the integrator rod 5 are incident on an arbitrary point on the rough surface of the screen 9 (that is, the incident angles are multiplexed). . As a result, different interference patterns are sufficiently overlapped, and speckle noise is sufficiently reduced.

  As described above, according to the first embodiment of the present invention, the coupling optical system 10 includes the diffusion element 3 that transmits and diffuses the laser light emitted from the laser light source 2, so that the phase difference is reduced. Speckle noise can be reduced by superimposing a plurality of added light beams. Further, a laser light condensing spot can be widely formed on the incident surface 5a of the homogenizing element 5, whereby the light intensity can be made uniform and the light utilization efficiency can be improved.

  Further, since there is no need to vibrate the movable part as in the prior art, no noise is generated, and no vibration mechanism is required, which can contribute to downsizing of the video display device.

  Further, in the first embodiment, the diffusing element 3 is configured by an element (specifically, a lens array in which a plurality of lens cells 3a are arranged) that divides incident laser light into a plurality of light beams. Further, it is possible to facilitate the control (diffusivity control) of dividing the laser light into a plurality of light beams to form a rectangular condensing spot on the incident surface 5a of the uniformizing element 5.

  Further, the shape of each lens cell 3a of the lens array 3 is substantially similar to the rectangular incident surface 5a of the homogenizing element 5, and the long sides are arranged so as to be optically parallel to each other. The light diffusivity can be made different in the long side and short side directions of the homogenizing element 5, and a uniform focused spot can be widely formed on the incident surface 5 a of the homogenizing element 5.

  Further, since each lens cell 3a of the lens array 3 has a positive power, each lens cell 3a condenses the light beam at a predetermined condensing position (for example, before the incident surface 5a of the uniformizing element 5). Function can be demonstrated. Thereby, the lens array 3 can be configured as a part of the coupling optical system 10.

  Further, since the diffusing element 3 is disposed in the vicinity of the optical element (lens 4) through which the widest light beam passes in the coupling optical system 10, the laser light is divided into a number of light beams and incident on the uniformizing element 5 It is possible to suppress a light amount loss when the light is incident on the surface 5a.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described.
FIG. 9 is a diagram illustrating a configuration of the video display device according to the second embodiment. The same components as those described in Embodiment 1 are denoted by the same reference numerals. In the second embodiment, an optical fiber 11 is provided between the laser light source 2 and the coupling optical system 10. Further, a fiber coupling optical system 12 (light shaping means) is provided between the laser light source 2 and the optical fiber 11.

  The optical fiber 11 has an incident end face 11a on the laser light source 2 side, and an output end face 11b on the coupling optical system 10 side. The emission end face 11b is at a position corresponding to the entrance of the coupling optical system 10, that is, a position corresponding to the light emitting portion 2a of the laser light source 2 in the first embodiment (FIG. 1).

  The fiber coupling optical system 12 couples laser light emitted from the laser light source 2 to the optical fiber 11. The fiber coupling optical system 12 converts the intensity distribution of the laser light emitted from the laser light source 2 from a Gaussian distribution to a substantially top-hat distribution. As such a fiber coupling optical system 12, a known beam shaping element (for example, one disclosed in Japanese Patent No. 4670876) can be used.

  The diffusing element 3 may be disposed anywhere between the laser light source 2 and the integrator rod 5, but is disposed in the vicinity of the optical element (here, the lens 4) through which the widest luminous flux passes in the coupling optical system 10. It is desirable to do. The reason is as follows.

  That is, when the diffusing element 3 is arranged in a portion where a narrow light beam passes in the coupling optical system 10, in order to ensure a wide condensing spot on the incident surface 5a of the integrator rod 5, the lens of the lens cell 3a The curvature must be tight (the radius of curvature is small). In this case, the light flux that has passed through the lens cell 3a of the diffusing element 3 spreads greatly, resulting in a light loss.

  On the other hand, if the diffusing element 3 is arranged in the vicinity of the optical element (lens 4) through which the widest luminous flux passes in the coupling optical system 10, the intensity of the laser beam emitted from the optical fiber 11 is approximately the top hat intensity. The laser beam can be subdivided while maintaining the distribution. Thereby, many interference patterns can be superimposed and speckle noise can be reduced effectively.

  Here, the configuration using the optical fiber 11 has been described. However, the optical fiber 11 is not necessarily used, and an optical system that controls the intensity distribution of the laser light incident on the coupling optical system 10 in a substantially top-hat shape ( For example, a fiber coupling optical system 12) may be provided and the diffusing element 3 may be configured to maintain the intensity distribution.

  As described above, according to the second embodiment of the present invention, a large number of light beams can be obtained while maintaining the intensity distribution of the laser light controlled in a substantially top hat shape by the fiber coupling optical system 12 by the diffusing element 3. Can be divided into Therefore, a wide condensing spot can be formed on the incident surface 5a of the homogenizing element 5 while suppressing light loss. As a result, speckle noise can be effectively reduced and the light intensity can be made uniform.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described.
FIG. 10 is a diagram showing the laser illumination device 1 of the video display device in the third embodiment. The same components as those described in Embodiment 1 are denoted by the same reference numerals. The laser light source 2 in the third embodiment is configured as a one-dimensional array light source in which a plurality of light emitting units 2a are arranged in one direction (here, the X direction). FIG. 10A is a diagram of the laser illumination device 1 viewed from the Y direction, and FIG. 10B is a diagram of the laser illumination device 1 viewed from the X direction.

  In general, the one-dimensional laser array light source has a small etendue in the thickness direction of the active layer, and an etendue calculated from the width in the arrangement direction (array direction) of the light emitting portions 2a and the divergence angle is very large. Therefore, the condensing spot formed on the incident surface 5a of the integrator rod 5 by the condensing action of the lens 4 without providing the diffusing element 3 is not the point shown in FIG. 2, but on the incident surface 5a. On the other hand, it may have a significant size in the array direction.

  In such a case, as described in the first and second embodiments, the shape (opening shape) of the lens cell of the diffusing element 3 is not substantially similar to the shape of the incident surface 5a of the integrator rod 5; What is necessary is just to determine the opening shape of the diffusing element 3 so that the size of the light source image formed on the incident surface 5a of the rod 5 approaches the size of the incident surface (opening) 5a of the integrator rod 5.

  Therefore, as shown in FIGS. 10A and 10B, the diffusing element 3 of the present embodiment is configured by a cylindrical lens array having a plurality of cylindrical lens cells 3b. The cylindrical lens cell 3b is a semi-cylindrical lens whose axial direction is the X direction, and a plurality of cylindrical lens cells 3b are arranged in the Y direction.

  That is, the diffusing element 3 of this embodiment does not divide the laser beam in the array direction (X direction), but divides the laser beam only in the direction orthogonal to the array direction (Y direction) to give a phase difference. In other words, the diffusing element 3 divides the laser beam and adds a phase difference only in the direction (Y direction) where the incident surface 5a of the integrator rod 5 has a margin. By comprising in this way, speckle noise can be reduced and light intensity | strength can be equalized, suppressing light quantity loss.

  In addition, although the structure which used the laser light source 2 as the one-dimensional array light source was demonstrated here, it is applicable not only to such a structure but to the structure bundled by arranging a plurality of optical fibers in a line. .

  As described above, in the third embodiment of the present invention, since the diffusing element 3 is composed of a cylindrical lens array in which a plurality of cylindrical lens cells 3b are arranged, the case where a one-dimensional array light source is used. Even if it exists, speckle noise can be reduced and the light intensity can be made uniform.

  In Embodiments 1 to 3 described above, the effects of reducing speckle noise and reducing the size of the video display device have been described. However, in addition to these, the condensing spot on the incident surface 5a of the integrator rod 5 can be increased. In addition, the energy density at the incident surface 5a can be kept low, whereby the reliability of the antireflection film (AR coating) on the incident surface 5a is also improved.

Needless to say, the above-described embodiments can be variously modified.
For example, in the first to third embodiments, a lens array having a plurality of lens cells 3a is used as the diffusing element 3, but in addition, a diffusing element having a fine structure such as a hologram element having anisotropic scattering characteristics, for example. May be used. Also in this case, by making the diffusivity of the laser light different between the long side direction and the short side direction of the incident surface 5a of the uniformizing element 5, a wide and uniform condensing spot is formed on the incident surface 5a, and speckle noise Can be reduced.

  In the first to third embodiments, the integrator rod 5 is used as a uniformizing element, but a light tunnel can also be used. However, the integrator rod 5 has an advantage of high reliability when the energy of incident light is high.

  In the first to third embodiments, the video display device 7 is described as a reflective liquid crystal panel or a digital micromirror device, but may be a projection liquid crystal panel or the like.

  The laser illumination device according to the present invention can be used as an illumination device for a video display device such as a projector or a rear projection display.

DESCRIPTION OF SYMBOLS 1 Laser illuminating device, 2 Laser light source, 3 Diffusing element, 3a Lens cell, 3b Cylindrical lens cell, 4 Lens (combining optical element), 5 Integrator rod (homogenizing element), 5a Incident surface, 5b Emission surface, 6 Relay lens (Illumination optical system), 7 image display device, 8 projection lens (projection optical system), 9 screen, 10 coupling optical system, 11 optical fiber, 11a incident end face, 11b emitting end face, 12 fiber coupling optical system (light shaping means) .

Claims (13)

A laser light source for emitting laser light;
A uniformizing element for uniformizing the intensity distribution of the laser beam;
A coupling optical system that couples the laser light emitted from the laser light source to the homogenizing element;
The laser illumination apparatus, wherein the coupling optical system includes a diffusion element that transmits and diffuses laser light.   The laser illuminating apparatus according to claim 1, wherein the diffusing element is a lens array in which a plurality of lens cells are arranged. The entrance surface of the uniformizing element is rectangular,
3. The laser illumination device according to claim 2, wherein each lens cell of the lens array has a rectangular shape having a long side optically parallel to a long side of the incident surface of the uniformizing element.   The laser illumination apparatus according to claim 3, wherein an incident surface of the uniformizing element and each lens cell of the lens array have a substantially similar shape.   5. The laser illumination device according to claim 2, wherein each lens cell of the lens array has a positive power.   The laser illuminating apparatus according to claim 1, wherein the diffusing element is disposed in the vicinity of an optical element through which the widest luminous flux passes in the coupling optical system.   The laser illumination device according to any one of claims 1 to 6, further comprising an optical fiber between the laser light source and the coupling optical system.   The optical system for controlling the intensity distribution of the laser light emitted from the laser light source is provided between the laser light source and the coupling optical system. The laser illumination device described.   The laser illuminating apparatus according to claim 1, wherein the diffusing element is a cylindrical lens array in which a plurality of cylindrical lens cells are arranged. The laser light source is a plurality of light emitting units arranged in one direction,
The laser illuminating apparatus according to claim 9, wherein an axial direction of each cylindrical lens cell of the cylindrical lens array is parallel to an arrangement direction of light emitting points of the laser light source.   The laser illuminating apparatus according to any one of claims 1 to 10, wherein the uniformizing element is configured by an integrator rod.   12. The laser illumination device according to claim 1, wherein the coupling optical system condenses laser light toward a front side of an incident surface of the homogenizing element. The laser illumination device according to any one of claims 1 to 12,
An image display device illuminated by the laser illumination device;
An image display apparatus comprising: a projection optical system that projects image light generated by the image display device.

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