JP2004144936A - Lighting system and image display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the occurrence of speckle noise without scaling up a device configuration and without lowering a light utilization efficiency by using a coherent light source as a light source. <P>SOLUTION: A diffusion element 2 diffusing the coherent light is provided between the coherent light source 1 and an illuminated object 5 illuminated with the coherent light source 1 to vibrate the diffusion element 2. Furthermore, a diffusion means 4 is provided between the diffusion element 2 and the illuminated body. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an illumination device for illuminating a spatial light modulator in an image display device, and an image display device configured using the illumination device.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there has been proposed an image display device configured to illuminate a spatial light modulation element such as a liquid crystal panel or a so-called “DMD element” with an illumination device and form a virtual image of the spatial light modulation element with an imaging lens. .
[0003]
At present, light-emitting diodes (LEDs) are mainly used as light sources of lighting devices in such image display devices. However, when an image is displayed using a light emitting diode as a light source, it is difficult to realize a large color reproduction area because the emitted light is not monochromatic light.
[0004]
On the other hand, it has been attempted to use a semiconductor laser as a light source of a lighting device. The semiconductor laser has a practically sufficient light emission amount and lifetime and has good monochromaticity of emitted light, so that a large color reproduction region can be realized.
[0005]
[Patent Document 1]
JP 06-208089 A
[Problems to be solved by the invention]
By the way, in the lighting device using a semiconductor laser as a light source as described above, a problem of speckle noise occurs. Generally, when an observer views a virtual image formed by an image display device, an image is formed on the retina of the observer by overlapping light from each region of the spatial light modulator. At this time, light passing through different regions on the spatial light modulator is superimposed on each other in a complicated phase relationship, and the emitted light from the semiconductor laser has high coherency (coherence). Will fit. Such interference causes a random change in intensity, that is, speckle noise. The formation of such speckle noise causes deterioration in the image quality of the displayed image.
[0007]
Speckle noise is a common problem when laser light having coherency is used as illumination, and various attempts have been made to reduce speckle noise. For example, a configuration using a fiber bundle has been proposed. This fiber bundle is composed of a plurality of optical fibers, and the optical path length difference between the respective optical fibers is longer than or approximately equal to the coherent length of the laser light used as the illumination light. When coherent light is made incident from one end of such a fiber bundle, light emitted from the other end is non-interfering. By using light emitted from the other end of such a fiber bundle as illumination light, coherency of the entire illumination system can be reduced, and speckle noise on the spatial light modulator can be reduced. .
[0008]
However, in such a configuration, the following problems occur. In other words, in such a fiber bundle, the light beams passing through different optical fibers become non-interfering. Therefore, as the number of optical fibers increases, that is, as the number of divided light beams increases, the illumination light Can be reduced. Here, it is assumed that a fiber bundle including n optical fibers is used. In general, in a semiconductor laser having a single-mode power spectrum, a typical spectrum width of emitted light is about 100 MHz, and a coherent length c is on the order of several meters. Then, in order to obtain non-interfering illumination light using this fiber handle, the difference in length between the shortest optical fiber and the longest optical fiber is nxc [m]. For example, when the number n of optical fibers is 50 and the coherent length c is 1 m, the length of the longest optical fiber is 50 m or more.
[0009]
An optical system having a fiber bundle composed of a large number of optical fibers having such a difference in optical path length has a considerably large volume and weight, which leads to an increase in the size of the entire image projection apparatus. Would.
[0010]
On the other hand, as another configuration for reducing speckle noise, a configuration using a rotating diffusion plate or the like has been proposed. In this configuration, a diffusion plate that is rotated at a high speed and transmits the illumination light is disposed on the optical path of the illumination light emitted from the semiconductor laser. This diffusion plate is rotated at a high speed to split an interference pattern generated by illumination light that is coherent light, and causes this interference pattern, that is, speckle noise to move around at high speed on the spatial light modulator. .
[0011]
That is, in this configuration, the speckle noise does not actually disappear, but it looks as if the speckle noise has disappeared.
[0012]
However, in this configuration, since frosted glass or the like is used as the diffusion plate, the light use efficiency is reduced. In addition, when such a configuration is specifically incorporated into an illumination optical system, there are no specific proposals as to where to incorporate the diffuser and what properties and size of the diffusion plate should be used. Almost not done. In particular, in a portable image display device configured to be small, the distance between the diffusion plate and the spatial light modulator is extremely short. Almost no noise reduction effect was obtained, and as a result, the displayed image was a noisy and unclear image.
[0013]
Therefore, the present invention has been proposed in view of the above-described circumstances, and uses coherent light as illumination light, without increasing the size of the device configuration, and without reducing the light use efficiency. An object of the present invention is to provide a lighting device in which generation of speckle noise is suppressed, and to provide an image display device provided with such a lighting device.
[0014]
[Means for Solving the Problems]
In order to solve the above-described problems, an illumination device according to the present invention includes a coherent light source unit that emits coherent light and illuminates an object to be illuminated with the coherent light, and coherent light between the coherent light source unit and the object to be illuminated. A diffusing element disposed on the optical path of the coherent light source means for changing the intensity distribution of the coherent light incident from the coherent light source means, distributing the light to a predetermined intensity distribution, and diffusing the light; a vibration means for vibrating the diffusing element; The light emitting device further comprises a diffusing means disposed between the element and the illuminated body.
[0015]
In this lighting device, the coherent light emitted from the coherent light source means is diffused by the diffusion element vibrated by the vibrating means, and further reaches the illuminated body via the diffusing means. Can be sufficiently reduced.
[0016]
The image display device according to the present invention includes a coherent light source for emitting coherent light, a spatial light modulator illuminated by the coherent light, and light of coherent light between the coherent light source and the spatial light modulator. A diffusing element arranged on a road to distribute and diffuse the intensity distribution of the coherent light incident from the coherent light source means to a predetermined intensity distribution, a vibrating means for vibrating the diffusing element, and a diffusing element. It is characterized by comprising diffusion means provided between the spatial light modulation element and imaging means for forming a virtual image of the spatial light modulation element.
[0017]
In this image display device, the coherent light emitted from the coherent light source means is diffused by the diffusion element vibrated by the vibration means, and further reaches the spatial light modulation element via the diffusion means, whereby Speckle noise in the light modulation element can be sufficiently reduced.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0019]
In each of the following embodiments, a lighting device according to the present invention is configured to illuminate a spatial light modulator in an image display device to be illuminated, and an image display device including the lighting device is configured. is there.
[0020]
Note that the image display device is configured to be held by a holder (a hair band or a vine-like eyeglass) so that the pair of image display devices are installed corresponding to the left and right pupils of the observer. It can be configured as a so-called head mounted image display device, or can be configured as a so-called “view finder” in a video camera device or the like.
[0021]
[Embodiment (1)]
As shown in FIG. 1, the illumination device includes a semiconductor laser 1 serving as a coherent light source for emitting coherent light and illuminating the spatial light modulator 5. The coherent light beam emitted from the semiconductor laser 1 is a diffuse light beam in a linearly polarized state, and enters the diffusion element 2 while diffusing.
[0022]
The diffusing element 2 is formed so as to change the intensity distribution of the coherent light incident from the semiconductor laser 1 and to distribute and emit the light at a predetermined angle and a predetermined intensity distribution. The diffusion element 2 is, for example, formed in a flat plate shape using a transparent synthetic resin material, and has a predetermined shape of unevenness on a surface portion. By appropriately setting the size, shape, depth, and the like of the irregularities formed on the surface portion, the angle and intensity distribution of the emitted light can be set to desired states.
[0023]
In the diffusion element 2, the cross-sectional shape of the light beam transmitted through the diffusion element 2 is circular and the intensity distribution is Gaussian distribution, or the intensity distribution of the light beam transmitted through the diffusion element 2 is a rectangular distribution. be able to. The diffusion element 2 having such a characteristic that the intensity distribution of the transmitted light flux is made a rectangular distribution can be realized, for example, by forming it as a hologram element.
[0024]
Note that the intensity distribution of the light beam transmitted through the diffusion element 2 may depend on the incident angle of the light beam incident on the beam forming element 3.
[0025]
The diffusing element 2 is movably supported in a plane perpendicular to the optical axis. In order to reduce speckle noise, which will be described later, the vibrating means 3 causes the diffusing element 2 to move in a plane perpendicular to the optical axis. That is, the diffusion element 2 is vibrated at a predetermined frequency in a plane parallel to the main surface. A piezoelectric element, a voice coil, an ultrasonic motor, or the like can be used as a driving force source of the vibration unit 3.
[0026]
The coherent light beam having passed through the diffusion element 2 enters a light guide 4 serving as a diffusion unit. The light guide 4 is made of a transparent synthetic resin material, a glass material or the like, and is formed in a substantially flat wedge shape. A light beam enters the light guide 4 from an incident surface 4a which is a wide side surface of the side surfaces, and an emission surface 4b which is a main surface substantially orthogonal to the incident surface 4a. A light beam is emitted from the. The light guide 4 is not a completely transparent body, but is formed so as to include a large number of light reflection dots (diffusing material) therein so as to appropriately diffuse an incident light beam in the light guide 4. . That is, the light beam incident from the incident surface 4a of the light guide 4 is diffused by traveling inside the light guide 4, and is emitted from the emission surface 4b of the light guide 4.
[0027]
The light flux transmitted through the diffusion element 2 and the light guide 4 and emitted from the light guide 4 substantially uniformly illuminates the spatial light modulation element 5 serving as an illuminated body. As the spatial light modulator 5, for example, a liquid crystal display device or a so-called "DMD device" is used.
[0028]
Then, a virtual image of the spatial light modulator 5 is formed by an imaging lens 6 serving as imaging means, and is observed by a pupil 7 of an observer. The imaging lens 6 is a convex lens.
[0029]
Here, the relationship between the amplitude of the vibration of the diffusion element 2 in the direction orthogonal to the optical axis and the speckle contrast is examined. As shown in FIG. 2, the amplitude of the vibration of the diffusion element 2 in the direction orthogonal to the optical axis is obtained. Is larger, the speckle contrast is reduced. However, if the amplitude is larger than a certain amplitude (about 400 μm), the effect of lowering the speckle contrast becomes a saturated state even if it is larger than that, so that there is little change. I understand. FIG. 2 shows a case in which a light beam emitted from a laser light source is transmitted through a diffusion element having a specific diffusion angle and projected on a screen, and the image is obtained by photographing with a CCD (solid-state image sensor) and analyzing the image. It is a thing. In FIG. 2, the horizontal axis represents the vibration amplitude of the diffusion element, and the vertical axis represents speckle contrast.
[0030]
The speckle contrast referred to here is a value obtained by standardizing a standard deviation of a spatial intensity distribution of light on the spatial light modulator 5 as an object to be illuminated by an average value of the intensity distribution. When the number is large, the value becomes large, and when the speckle noise is reduced, the value becomes small.
[0031]
The experimental results shown in FIG. 2 were obtained by using a krypton (Kr) laser, a single-mode red semiconductor laser (output 50 mW), and a multi-mode red semiconductor laser (output 500 mW) as laser light sources. Although the value of the speckle contrast is different, a similar tendency has been confirmed for the reduction of the speckle contrast.
[0032]
The vibration frequency of the diffusion element 2 is desirably 30 Hz or more. If the vibration frequency is less than this value, it is recognized that speckle noise moves around on the illuminated object, and the effect of reducing speckle noise is reduced.
[0033]
On the other hand, if the vibration amplitude of the diffusion element 2 is too small, the effect of reducing speckle noise is reduced. Conversely, if the vibration amplitude is too large, a cause of noise generation and a decrease in mechanical reliability are caused. In this regard, according to the experimental results by the present inventor, it is desirable that the thickness be 100 μm or more and 400 μm or less.
[0034]
When the diffusion element 2 is vibrated by using a vibration element such as a piezoelectric element, a voice coil, or an ultrasonic motor, the resonance frequency (natural frequency) of the diffusion element 2 is set to about 30 Hz, thereby reducing the consumption. It can be vibrated with electric power. In this case, when the diffusion element 2 made of glass or the like having a relatively large specific gravity is used, when the vibration system is designed so as to satisfy the above-described resonance condition, the spring constant of the vibration system depends on the magnitude of the mass. If the resonance frequency is not increased, the resonance frequency cannot be set to about 30 Hz, which increases the possibility of an increase in driving noise and a decrease in mechanical reliability.
[0035]
Therefore, it is preferable to use a material having a relatively small specific gravity, for example, a synthetic resin material such as polycarbonate or polyester as a material forming the diffusion element 2.
[0036]
Further, a semiconductor laser serving as a light source is preferably a multimode oscillation having low coherency. However, this is not always the case when an illuminating device that requires a light source of a single wavelength, for example, when an optical system having an extremely small chromatic aberration tolerance is used.
[0037]
In the configuration shown in FIG. 1, a single semiconductor laser is used. However, when a plurality of semiconductor lasers are used in parallel, the effect of reducing speckle noise in the entire lighting device can be increased. .
[0038]
By using an optical system that satisfies the above conditions, it is possible to realize an illumination device and an image display device that do not have speckle noise, that is, fine illuminance unevenness, or have very little speckle noise. That is, in the image observed by the observer in this image display device, speckle noise is generated in a very short time, but the speckle noise is generated by vibrating the diffusion element 2 by the vibration means 3. Are spatially averaged, resulting in a clear image.
[0039]
As shown in FIG. 3, the diffusing element 2 realizes both beam shaping of light emitted from the semiconductor laser 1 having anisotropic radiation light intensity distribution and removal of speckle noise. Is also good.
[0040]
That is, as shown in FIG. 4, the light beam emitted from the semiconductor laser 1 has a beam diameter in the θ⊥ direction (direction orthogonal to each layer of the laminated structure forming the semiconductor laser chip) (x direction in FIG. 4). It has an elliptical shape that is longer than the beam diameter in the direction (direction parallel to each layer of the laminated structure forming the semiconductor laser chip) (the direction y in FIG. 4). The shape of the incident area 2a of the light beam emitted from the semiconductor laser 1 with respect to the diffusion element 2 is such an elliptical shape. The aspect ratio of the elliptical shape does not correspond to the aspect ratio of the incident surface 4a of the light guide 4.
[0041]
Therefore, it is difficult to efficiently use the light flux as it is, and it is also difficult to uniformly illuminate a predetermined area in an image display device or the like.
[0042]
Therefore, in this illuminating device, a diffusing element 2 having such a property that an incident light beam having an elliptical cross section is emitted while changing the aspect ratio of the elliptical shape is used. The light flux transmitted through the diffusion element 2 is incident on the incident surface 4a of the light guide 4 in an elliptical incident region 4c having an aspect ratio corresponding to the aspect ratio of the incident surface 4a of the light guide 4.
[0043]
Then, as described above, the diffusion element 2 is vibrated by the vibrating means in a plane orthogonal to the optical axis. By vibrating the diffusion element 2 in this manner, the interference pattern formed in the spatial light modulation element moves around so that it is difficult for the human eye to recognize it, and as a result, speckle noise is reduced.
[0044]
Furthermore, it is conceivable that the beam shape after transmitting the diffusion element 2 becomes the same shape as the incident surface 4 a of the light guide 4. In this case, when a light beam having an elliptical cross-sectional shape is incident, a diffusing element 2 having a characteristic of making the light beam have a rectangular cross-sectional shape is emitted. By vibrating such a diffusion element 2 in a direction perpendicular to the optical axis, the interference pattern formed in the spatial light modulation element 5 can be moved around so that it is difficult for the human eye to recognize it. As a result, speckle noise can be reduced.
[0045]
In the lighting device according to the present invention, by using the optical system described in this embodiment, it is possible to sufficiently reduce speckle noise while maintaining high light use efficiency.
[0046]
Also in this case, the vibration frequency of the diffusion element 2 is desirably 30 Hz or more. If the vibration frequency is equal to or less than this value, it is recognized that speckle noise moves around on the spatial light modulation element 5, and the effect of reducing speckle noise is reduced.
[0047]
On the other hand, if the vibration amplitude of the diffusion element 2 is too small, the effect of reducing speckle noise is reduced. Conversely, if the vibration amplitude is too large, a cause of noise generation and a decrease in mechanical reliability are caused. In this regard, according to the experimental results by the present inventor, it is desirable that the thickness be 100 μm or more and 400 μm or less as described above.
[0048]
By using an optical system satisfying the above conditions, it is possible to realize an illumination device and an image display device having no speckle noise or having very little speckle noise.
[0049]
[Embodiment (2)]
Next, as another embodiment of the lighting device and the image display device according to the present invention, as shown in FIG. 5, a second diffusing element 8 is used as a diffusing means instead of the light guide 4 described above. The following shows the configuration.
[0050]
As shown in FIG. 5, the illumination device includes a semiconductor laser 1 serving as coherent light source means for emitting coherent light and illuminating the spatial light modulator 5. The coherent light beam emitted from the semiconductor laser 1 enters the diffusion element 2 while diffusing.
[0051]
This diffusing element 2 is formed so as to change the intensity distribution of the coherent light incident from the semiconductor laser 1 and distribute and emit the light at a predetermined angle and a predetermined intensity distribution, as in the above embodiments. Have been.
[0052]
Then, in order to reduce speckle noise, the diffusing element 2 is provided by a vibrating means 3 in a plane perpendicular to the optical axis, that is, in a plane parallel to the main surface of the diffusing element 2. Vibrated at frequency. A piezoelectric element, a voice coil, an ultrasonic motor, or the like can be used as a driving force source of the vibration unit 3.
[0053]
The coherent light beam having passed through the diffusion element 2 enters a second diffusion element 8 serving as a diffusion unit. The second diffusing element 8 is formed in the same manner as the diffusing element 2 vibrated by the vibrating means 3, but is fixed to the optical axis.
[0054]
The light beam transmitted through each of the diffusion elements 2 and 8 and emitted from the second diffusion element 8 illuminates the spatial light modulation element 5 to be illuminated substantially uniformly. As the spatial light modulator 5, for example, a liquid crystal display device or a so-called "DMD device" is used.
[0055]
Then, a virtual image of the spatial light modulator 5 is formed by an imaging lens 6 serving as imaging means, and is observed by a pupil 7 of an observer.
[0056]
Also in this case, the vibration frequency of the diffusion element 2 is desirably 30 Hz or more. If the vibration frequency is less than this value, it is recognized that speckle noise moves around on the illuminated object, and the effect of reducing speckle noise is reduced. According to the experimental results by the present inventor, the vibration amplitude of the diffusion element 2 is desirably 100 μm or more and 400 μm or less.
[0057]
Further, by setting the resonance frequency (natural frequency) of the diffusion element 2 to about 30 Hz, it is possible to vibrate with low power consumption. As the material forming the diffusion element 2, it is preferable to use a material having a relatively small specific gravity, for example, a synthetic resin material such as polycarbonate and polyester.
[0058]
Further, a semiconductor laser serving as a light source is preferably a multimode oscillation having low coherency. However, this is not always the case when an illuminating device that requires a light source of a single wavelength, for example, when an optical system having an extremely small chromatic aberration tolerance is used.
[0059]
In the configuration shown in FIG. 5, a single semiconductor laser is used. However, when a plurality of semiconductor lasers are used in parallel, the effect of reducing speckle noise in the entire lighting device can be increased. .
[0060]
By using an optical system that satisfies the above conditions, it is possible to realize an illumination device and an image display device that do not have speckle noise, that is, fine illuminance unevenness, or have very little speckle noise. That is, in the image observed by the observer in this image display device, speckle noise is generated in a very short time, but the speckle noise is generated by vibrating the diffusion element 2 by the vibration means 3. Are spatially averaged, resulting in a clear image.
[0061]
[Embodiment (3)]
In the image display device according to each of the above-described embodiments, red (hereinafter, referred to as “R”), green (hereinafter, referred to as “G”), and blue (hereinafter, referred to as “B”) light sources. An image display device that displays a color image can be configured using three laser light sources that emit light of one different color among the three colors.
[0062]
In this case, the configuration is not limited to using one laser light source for each color, and a plurality of laser light sources may be used for each color. By using a plurality of laser light sources in parallel for each color, the speckle noise reduction effect can be increased for the entire illumination optical system.
[0063]
The R, G, and B coherent lights emitted from the respective laser light sources pass through the respective diffusing elements, are combined by an optical element such as a dichroic mirror, and enter the light guide or the second diffusing element. The light flux transmitted through each diffusion element and the light guide or the second diffusion element and emitted from the light guide or the second diffusion element is substantially uniform in the spatial light modulation element to be illuminated. To illuminate. Then, a virtual image of the spatial light modulation element is formed by an imaging lens serving as an imaging unit, and is observed by an observer's pupil.
[0064]
Also in this case, as described above, each diffusing element is vibrated by the vibrating means in a plane orthogonal to the optical axis. By vibrating the diffusion element in this manner, the interference pattern formed in the spatial light modulation element moves around so that it is difficult for the human eye to recognize it, and as a result, speckle noise is reduced. The vibration frequency of the diffusion element is desirably 30 Hz or more. If the vibration frequency is lower than this value, it is recognized that speckle noise moves around on the spatial light modulator, and the effect of reducing speckle noise is reduced.
[0065]
On the other hand, if the vibration amplitude of the diffusion element is too small, the effect of reducing speckle noise is reduced. Conversely, if the vibration amplitude is too large, a cause of noise generation and a decrease in mechanical reliability are caused. In this regard, according to the experimental results by the present inventor, it is desirable that the thickness be 100 μm or more and 400 μm or less, as described above.
[0066]
By using an optical system satisfying the above conditions, it is possible to realize an illumination device and an image display device having no speckle noise or having very little speckle noise.
[0067]
【The invention's effect】
As described above, in the lighting device according to the present invention, while using the coherent light source means for illuminating the object to be illuminated with the coherent light, the diffusing element disposed on the optical path of the coherent light is vibrated, and As a means, for example, by arranging a light guide or a second diffusion element, speckle noise, that is, uneven illuminance can be reduced.
[0068]
In this illumination device, a laser light source having high quantum efficiency can be used as the coherent light source means, so that power consumption can be reduced.
[0069]
In addition, by using this illumination device, a laser light source having high monochromaticity can be used as the coherent light source means, so that an image display device capable of displaying a high-resolution image with little aberration can be configured.
[0070]
In the image display device according to the present invention, by providing the above-described illumination device, for example, the holder ( Hairband or eyeglasses), when configured as a so-called head-mounted image display device, or when configured as a so-called "viewfinder" in a video camera device. Thus, it is possible to provide an image display device capable of providing an image with reduced speckle noise to an observer and displaying an image with high color purity and high contrast.
[0071]
Further, the image display device according to the present invention can be configured as an image display device having a wide color reproduction region by using a plurality of laser light sources having different oscillation wavelengths.
[0072]
That is, the present invention provides a lighting device that uses coherent light as the lighting light and suppresses the occurrence of speckle noise without increasing the size of the device configuration and without reducing the light use efficiency. Further, it is possible to provide an image display device including such a lighting device.
[Brief description of the drawings]
FIG. 1 is a side view illustrating a configuration of an illumination device according to the present invention and an image display device according to the present invention configured using the illumination device.
FIG. 2 is a graph showing a relationship between a vibration amplitude of a diffusion element and a reduction in speckle noise in the lighting device.
FIG. 3 is a perspective view showing a shape of a light guide in the lighting device.
FIG. 4 is a front view showing a cross-sectional shape of a light beam incident on the light guide.
FIG. 5 is a side view illustrating another example of the configuration of the illumination device according to the present invention and the image display device according to the present invention configured using the illumination device.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 semiconductor laser, 2 diffuser, 3 vibrator, 4 light guide, 5 spatial light modulator, 6 imaging lens, 7 pupil, 8 second diffuser

Claims (28)

Coherent light source means for emitting coherent light and illuminating an object to be illuminated with the coherent light,
The coherent light source is disposed on the optical path of the coherent light between the coherent light source and the illuminated body, and the intensity distribution of the coherent light incident from the coherent light source is changed to distribute the light to a predetermined intensity distribution and to diffuse the light. A diffusing element,
Vibrating means for vibrating the diffusion element,
An illumination device comprising: a diffusion unit disposed between the diffusion element and the illuminated body. The lighting device according to claim 1, wherein the diffusion unit is a light guide. The lighting device according to claim 1, wherein the diffusion means is a second diffusion element. The lighting device according to claim 1, wherein the illuminated body illuminates a spatial light modulation element. 2. The lighting device according to claim 1, wherein the frequency of vibration of the diffusion element by the vibrating means is 30 Hz or more. 2. The lighting device according to claim 1, wherein an amplitude of the vibration of the diffusion element by the vibrating means in a direction orthogonal to an optical axis is 100 μm to 400 μm. The lighting device according to claim 1, wherein the diffusion element is formed using a synthetic resin material as a main material. 2. The lighting device according to claim 1, wherein the vibrating means has a piezoelectric element, and the piezoelectric element vibrates the diffusion element. The lighting device according to claim 1, wherein the vibration unit has a voice coil, and the voice coil vibrates the diffusion element. The lighting device according to claim 1, wherein the vibration unit has an ultrasonic motor, and the ultrasonic motor causes the diffusion element to vibrate. The lighting device according to claim 1, wherein a plurality of the coherent light source means are provided. The lighting device according to claim 11, wherein each of the coherent light source units emits coherent light beams having different wavelengths. The lighting device according to claim 1, wherein the diffusion element has an anisotropic divergence angle. 14. The lighting device according to claim 13, wherein the diffusion element emits incident light having an elliptical cross section as a light beam having a circular cross section. 14. The lighting device according to claim 13, wherein the diffusion element emits incident light having an elliptical cross section as a light beam having a rectangular cross section. Coherent light source means for emitting coherent light,
A spatial light modulator illuminated by the coherent light,
Arranged on the optical path of the coherent light between the coherent light source and the spatial light modulator, changing the intensity distribution of the coherent light incident from the coherent light source to distribute the light to a predetermined intensity distribution. A diffusing element for diffusing,
Vibrating means for vibrating the diffusion element,
Diffusion means disposed between the diffusion element and the spatial light modulation element,
An image display device comprising: an image forming unit that forms a virtual image of the spatial light modulation element. 17. The image display device according to claim 16, wherein said diffusion means is a light guide. 17. The image display device according to claim 16, wherein said diffusion means is a second diffusion element. 17. The image display device according to claim 16, wherein the frequency of vibration of the diffusion element by the vibrating means is 30 Hz or more. 17. The image display device according to claim 16, wherein the amplitude of the vibration of the diffusion element by the vibrating means in the direction orthogonal to the optical axis is 100 μm to 400 μm. 17. The image display device according to claim 16, wherein the diffusion element is formed using a synthetic resin material as a main raw material. 17. The image display device according to claim 16, wherein a plurality of said coherent light source means are provided. 17. The image display device according to claim 16, wherein the vibrating means has a piezoelectric element, and the piezoelectric element vibrates the diffusion element. 17. The image display device according to claim 16, wherein the vibration unit has a voice coil, and the voice coil vibrates the diffusion element. 17. The image display device according to claim 16, wherein the vibration means has an ultrasonic motor, and the ultrasonic motor causes the diffusion element to vibrate. 17. The image display device according to claim 16, wherein the diffusion element has anisotropic light distribution angle. 27. The image display device according to claim 26, wherein the diffusion element emits incident light having an elliptical cross section as a light beam having a circular cross section. 27. The image display device according to claim 26, wherein the diffusion element emits incident light having an elliptical cross section as a light beam having a quadrangular cross section.

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