JP2012237812A - Illumination device, projection video display device, and light deflecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illumination device that illuminates an illumination object area (image forming area) without causing a conspicuous speckle noise, and to provide a projection video display device thereof.SOLUTION: The illumination device includes a light source 11 for emitting coherent light, and a light deflecting spatial modulation element 15 for deflecting the coherent light emitted by the light source 11. The deflected coherent light emitted by the light deflecting spatial modulation element 15 illuminates the illumination object area by temporally superposing the illumination while temporally changing an incident angle to each point in the illumination object area.

Description

  The present invention relates to an illumination device that uses coherent light such as laser light, a projection-type image display device that illuminates a light modulation element using the coherent light as a light source, and projects an image on a screen, and the present invention. The present invention relates to an optical deflection apparatus.

  2. Description of the Related Art A projector (projection-type image display device) is known in which illumination light from a light source is imaged using a light modulation element (micro display) such as liquid crystal or MEMS and projected onto a screen. Among such projectors, a projector using a white light source such as a high-pressure mercury lamp as the light source is known, and an image obtained by illuminating a two-dimensional light modulation element such as a liquid crystal is magnified by a projection optical system. The image is projected above.

  However, high-intensity discharge lamps such as high-pressure mercury lamps have a relatively short life and need to be frequently replaced when used in projectors. In addition, there is a drawback that the apparatus itself is increased in size. Furthermore, the specification of a high-pressure mercury lamp that uses mercury is not preferable from the viewpoint of environmental load. In order to eliminate such drawbacks, a projector using laser light as a light source has been proposed. The semiconductor laser has a longer life than a high-pressure mercury lamp or the like, and the entire apparatus can be reduced in size.

  Thus, since the laser beam expected as the next-generation light source of the projector is excellent in straightness, it is considered that the light incident efficiency can be improved as compared with the LED or the like. However, when laser light is used as a light source, there is a drawback that speckle noise is generated due to high coherence and it is difficult to view an image.

  Speckle noise is speckled noise caused by interference of light scattered from minute irregularities on the surface of the irradiation object when coherent laser light is used as the light source. As well as causing physiological discomfort to the observer. In order to reduce this speckle noise, various attempts have been made, such as vibrating the diffusion plate through which the laser beam passes, expanding the wavelength spectrum of the laser spectrum, and vibrating the screen itself that is the target of the laser beam irradiation. . As an attempt to reduce such speckle noise, Patent Document 1 discloses a non-speckle display device that reduces speckle noise by rotating a diffusion element through which coherent light passes.

Japanese Patent Laid-Open No. 6-208089

  However, in the speckle noise reduction method disclosed in Patent Document 1, speckle noise (interference pattern) generated before reaching the diffusing element can be averaged, but the incident ray angle from the diffusion center to the screen is on the screen. Since it is invariant at any point, the light scattering characteristic of each point on the screen becomes constant, and as a result, there is a problem that the effect of removing speckle noise generated on the screen is hardly obtained.

Such speckle caused by coherent light is a problem not only in a projection-type image display device (projector) that uses coherent light as a light source but also in various illumination devices that use coherent light.

  An object of the present invention is to provide an illuminating device that suppresses speckles generated when coherent light is used as a light source, and a projection-type image display device using such an illuminating device.

The lighting device according to the present invention includes:
A light source that emits coherent light;
Comprising a deflection spatial modulation element for deflecting the coherent light emitted from the light source;
The deflected coherent light emitted from the deflecting spatial modulation element illuminates the illumination area by overlapping the illumination area with time and changes the incident angle to each point of the illumination area with time. It is characterized by that.

Furthermore, the lighting device according to the present invention includes:
Regardless of the deflection direction of the deflection spatial modulation element, the coherent light emitted from the deflection spatial modulation element illuminates the entire illuminated area.

Furthermore, in the lighting device according to the present invention,
The deflection spatial modulation element includes a variable diffraction element.

Furthermore, in the lighting device according to the present invention,
The deflection spatial modulation element includes a phase modulation element.

Furthermore, in the lighting device according to the present invention,
A beam shaping means is disposed between the light source and the deflection spatial modulation element.

In addition, the projection type video display device according to the present invention includes:
A light source that emits coherent light;
A deflection spatial modulation element for deflecting coherent light emitted from the light source;
A light modulation element having an image forming region on which an image is formed;
A projection optical system that projects an image of the light modulation element onto a screen, and the deflected coherent light emitted from the deflection spatial modulation element illuminates the image forming region over time, and Illumination is performed by changing the incident angle to each point of the image forming region with time.

Furthermore, in the projection display apparatus according to the present invention,
The coherent light emitted from the deflection spatial modulation element changes in angle symmetrically about the optical axis with respect to the projection optical system.

Moreover, an optical deflecting device according to the present invention includes:
A coherent light is incident, and a deflecting spatial modulation element that deflects and emits the incident coherent light is provided.
The deflected coherent light emitted from the deflecting spatial modulation element illuminates the illumination area by overlapping the illumination area with time and changes the incident angle to each point of the illumination area with time. It is characterized by that.

  According to the illuminating device of the present invention, the coherent light is deflected by the deflecting spatial modulation element so that the illumination light emitted from the deflecting spatial modulation element illuminates the illuminated area over time and Illumination is performed by changing the incident angle to each point in the illumination region with time, and speckles generated in the illuminated region can be changed with time to make the viewer invisible. Furthermore, in the projection type image display apparatus of the present invention, speckles generated on the screen can be effectively suppressed by irradiating the screen at different angles in time.

The figure which shows the structure of the projection type video display apparatus provided with the illuminating device which concerns on embodiment of this invention. The figure which shows the structure of the illuminating device which concerns on embodiment of this invention. The figure which shows the structure of the spatial modulation element for deflection | deviation (variable diffraction type element) which concerns on embodiment of this invention. The figure which shows the mode of a structure and phase change of the spatial modulation element (phase modulation element) for deflection | deviation which concerns on other embodiment of this invention. The figure which shows the mode of the phase change in the spatial modulation element (phase modulation element) for deflection | deviation which concerns on other embodiment of this invention.

  Now, an illumination device and a projection display apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of a projection-type image display device including an illumination device according to an embodiment of the present invention. Note that the drawings described below are schematic views and may differ from actual shapes, dimensions, and arrangements.

  The projection-type image display device 10 of this embodiment includes an illumination device, a light modulation element 31 for forming an image, a projection optical system 32 that projects an image formed by the light modulation element 31 onto a screen 41, and the like. Yes. In the figure, the screen 41 on which an image is projected is an XY plane, and an axis perpendicular to the XY plane is a Z axis. As the screen 41, either a reflective screen for observing an image reflected by the screen 41 or a transmissive screen for observing an image transmitted through the screen 41 can be used.

  The illuminating device of this embodiment includes a light source 11 and a deflection spatial modulation element 15.

  As the light source 11, a light emitting element 111 such as a semiconductor laser that emits laser light as coherent light is used. The light source 11 of the present embodiment is configured to include a beam expander 112 disposed at the subsequent stage of the light emitting element 111. The beam expander 112 is composed of a set of convex lenses 112a and 112b, and is enlarged to a diameter sufficient to illuminate the image forming region of the light modulation element 31. In addition to such a configuration, an appropriate form such as a combination of a concave lens and a convex lens can be adopted. The coherent light emitted from the light source 11 to the deflection spatial modulation element 15 is preferably emitted as parallel or substantially parallel coherent light. It is possible to illuminate each point of the deflection spatial modulation element 15 arranged in the subsequent stage under the same conditions.

The coherent light emitted from the light source 11 illuminates the deflection spatial modulation element 15. In addition, it is preferable to provide beam shaping means for uniforming the intensity distribution in the cross-sectional direction of the coherent light emitted from the light source 11. As a design example, by providing beam shaping means at the subsequent stage of the beam expander 112, the deflection spatial modulation element 15 can be illuminated with uniform intensity. The beam shaping means is an element that changes the cross-sectional intensity distribution of the beam by an effect such as refraction or diffraction, and a hologram or a refractive element is used.

  The deflection spatial modulation element 15 is an optical element that temporally changes the direction of coherent light emitted from the light source 11. As the deflection spatial modulation element 15 of the present embodiment, a variable diffraction element that changes the emission direction by electrically changing a diffraction condition, a phase modulation element, or the like is used. Since the deflection spatial modulation element 15 does not have a movable part, it is possible to reduce the size of the apparatus and improve the maintenance performance. In the present embodiment, the deflection spatial modulation element 15 is arranged close to the light modulation element 31 having the illuminated area. However, the deflection spatial modulation element 15 and the light modulation element 31 are arranged in close contact with each other. It is good to do.

  The coherent light incident from the light source 11 becomes deflected light La whose direction changes in time by the deflection spatial modulation element 15 and illuminates the image forming area of the light modulation element 31 as the illuminated area. In the figure, the states of the deflected light La (t1) and La (t2) near the outermost end are shown. In practice, however, the deflected light La passes between La (t1) and La (t2). It will move continuously or intermittently over time.

  The light modulation element 31 is a display having an image forming area in which an image is formed based on a video signal. In this embodiment, a transmissive liquid crystal display element is used. As the light modulation element 31, in addition to such a transmission type, a reflection type such as MEMS can be used. The deflected light La from the deflecting spatial modulation element 15 enters the light modulation element 31 while changing the incident angle with time, and is converted into the modulated light Lb based on the image displayed in the image forming area. .

  The projection optical system 32 enlarges and converts the modulated light Lb from the light modulation element 31 into the video reproduction light Lc and projects it onto the screen 41. In the present embodiment, a diaphragm 33 is provided downstream of the projection optical system 32.

  Now, the principle and the like of the illumination apparatus, which is a main configuration for suppressing speckles, in the projection display apparatus 10 will be described in detail. FIG. 2 is a diagram illustrating a configuration of the illumination device according to the embodiment of the present invention, and is a diagram illustrating a state of illumination by the deflection spatial modulation element 15. The deflection spatial modulation element arranged with respect to the illuminated area as described above constitutes an optical deflection apparatus in the present invention.

  As shown in FIG. 2, the deflected light La (t1) at time t1 illuminates at least a part of the image forming area in the light modulation element 31. Similarly, the deflected light La (t2) at time t2 also illuminates at least a part of the image forming area. As shown in this figure, the illuminating device illuminates the entire image forming area as the illuminated area while temporally changing the incident angle. It is preferable that the illuminated area is always set to an illuminated area regardless of the deflection direction of the deflection spatial modulation element 15 in order to achieve uniform luminance.

  The coherent light from the light source 11 incident on the deflection spatial modulation element 15 is preferably parallel light or substantially parallel light. By making the coherent light from the light source 11 parallel light or substantially parallel light, it is possible to illuminate the coherent light incident on each point of the deflection spatial modulation element 15 under the same conditions. It becomes easy to design the deflection condition at each point. Further, by making the deflected light La emitted from the deflecting spatial modulation element 15 parallel or substantially parallel, each point of the image forming region of the light modulation element 31 is illuminated under the same conditions, for example, the entire light modulation element 31 Improvements such as uniform illumination are achieved.

Further, it is preferable that the modulated light Lb emitted from the deflection spatial modulation element 15 changes its angle so as to be symmetric with respect to the optical axis of the projection optical system 32, that is, the direction orthogonal to the light modulation element 31. As shown in the figure, the imaging performance is isotropic in the plane by making the angles formed by the modulated light Lb (t1) and Lb (t2) near the outermost end with respect to the optical axis the same as the optical axis. Can be.

  Returning to FIG. 1, the modulated light Lb modulated by the light modulation element 31 is magnified by the projection optical system 32 and projected onto the screen 41 as the image reproduction light Lc, and the reflected or transmitted image is observed by the observer. Let At this time, the coherent light diffused on the surface of the screen 41 interferes with each other to cause speckle. However, in this embodiment, since the coherent light is deflected by the deflection spatial modulation element 15, the incident angle of the image reproduction light Lc projected onto the screen 41 is changed with time, and this speckle is extremely effective. Is inconspicuous.

  At the point P1 on the screen shown in FIG. 1, for example, the video reproduction light Lc (t1) at time t1 and the video reproduction light Lc (t2) at time t2 are irradiated at different incident angles. The same applies to other points P2 shown in the figure and other points not shown, and the image reproduction light Lc projects an image on the screen 41 while temporally changing the incident angle. Therefore, speckles formed on the screen in a very short time are also averaged in time within the visual response time and projected onto the screen 41 by the image reproduction light Lc being irradiated at different incident angles depending on the time. This is not sufficiently conspicuous for an observer who observes an image.

  The projection type image display device and the illumination device used therefor have been described using the present embodiment in FIGS. 1 and 2. The deflection spatial modulation element 15 that deflects incident light in these devices will be described. . The deflection spatial modulation element 15 used in this embodiment is an optical element that varies the deflection direction of incident light by electrical drive, and a variable diffraction element, a phase modulation element, or the like can be used.

  FIG. 3 is a diagram showing a configuration of a deflection spatial modulation element (variable diffraction element) according to an embodiment of the present invention, and FIG. 4 shows a deflection spatial modulation element (phase) according to another embodiment of the present invention. FIG. 5 is a diagram illustrating a phase change in a deflection spatial modulation element (phase modulation element) according to another embodiment of the present invention.

  The deflection spatial modulation element 15 in FIG. 3 is an embodiment using a variable diffractive element, and in this embodiment, an amplitude modulation type liquid crystal element is used as the variable diffractive element. The liquid crystal element constituting the deflection spatial modulation element 15 forms a diffraction grating by the liquid crystal 151. By changing the diffraction angle by changing the pitch of the diffraction grating formed by the liquid crystal 151 with time, the emission direction of the coherent light incident from the light source 11 can be changed with time. In the present embodiment, coherent light is incident obliquely with respect to the incident surface of the deflecting spatial modulation element 15 so that zero-order light can be released and diffracted light can be emitted in the normal direction of the element. .

  In addition to the liquid crystal element, an optical element that modulates the phase of light passing therethrough may be used as the variable diffraction element. Alternatively, a micromirror device that modulates the phase of the reflected light can be used.

  The deflection spatial modulation element 15 in FIG. 4 is an embodiment using a phase modulation element, and in this embodiment, a liquid crystal element that modulates only the phase is used. FIG. 4A is a diagram illustrating this configuration example, and the deflection spatial modulation element 15 includes a liquid crystal layer 152 sealed between transparent base materials 153 and 154. The liquid crystal layer 152 is provided with a pixel electrode 152a and a common electrode 152b provided for each part, and the phase of transmitted light can be changed by changing the refractive index over time for each part. It has become.

  FIG. 4B is a diagram showing a basic type of phase change, and the phase distribution is shown in a form corresponding to the configuration diagram of FIG. By changing the bias applied to the pixel electrode 152a with time, for example, a phase distribution as shown at times t1 and t2 can be formed. In such a phase distribution, as shown in FIG. 4A, the scanning light La (t1) can be deflected to the state of the scanning light La (t2) at the time t1, and at the time t2. In practice, the direction of the scanning light La can be changed in multiple steps or continuously by changing the phase state of t1 and the phase state of t2 in multiple steps or continuously.

  FIG. 5 is a diagram showing another form of phase change, in which the deflection condition is changed over time by changing the phase distribution into a kinoform type, that is, by changing a pattern that repeats from 0 to 2π over time. As in the case of FIG. 4B, the deflection direction is changed. This figure shows the phase distribution corresponding to the configuration diagram of FIG. 4A, as in FIG. 4B, and FIG. 5A shows the phase state at time t1, and FIG. 5 (e) shows the phase state at time t2. Coherent light incident from the light source 11 is deflected by temporally changing the phase shape between FIGS. 5A to 5E and 5E to 5A. The phase distribution may be a Fresnel lens type set in a range other than 0 to 2π.

  In this way, when the phase modulation element is used as the deflection spatial modulation element 15, unlike the case of using the variable diffraction element described above, zero-order light is not generated, so that the light use efficiency can be improved. Further, as shown in the drawing, it is possible to allow coherent light to enter perpendicularly to the incident surface of the deflection spatial modulation element 15.

  As described above, according to the present embodiment, an illumination device in which speckle noise is not noticeable, and a projection-type image that can provide an image in which speckle noise is not noticeable by illuminating the light modulation element 31 with the illumination device. A display device can be provided. In particular, in this embodiment, the coherent light from the light source 11 is electrically deflected by the deflecting spatial modulation element 15, so that there is no movable part, and the apparatus is downsized and the maintenance performance is improved. ing.

  Note that the present invention is not limited to these embodiments, and embodiments configured by appropriately combining the configurations of the respective embodiments also fall within the scope of the present invention.

DESCRIPTION OF SYMBOLS 10 ... Projection type image display apparatus 11 ... Light source 111 ... Light emitting element 112 ... Beam expander 112a, 112b ... Convex lens 15 ... Deflection spatial modulation element 151 ... Liquid crystal 152 ... Liquid crystal layer 152a ... Pixel electrode 152b ... Common electrode 153, 154 ... Transparent Base material 31 ... Light modulation element 32 ... Projection optical system 33 ... Aperture 41 ... Screen

Claims (8)

A light source that emits coherent light;
Comprising a deflection spatial modulation element for deflecting the coherent light emitted from the light source;
The deflected coherent light emitted from the deflecting spatial modulation element illuminates the illumination area by overlapping the illumination area with time and changes the incident angle to each point of the illumination area with time. A lighting device. The illuminating device according to claim 1, wherein the coherent light emitted from the deflection spatial modulation element illuminates the entire illuminated area regardless of the deflection direction of the deflection spatial modulation element. The lighting device according to claim 1, wherein the deflection spatial modulation element includes a variable diffraction element. The lighting device according to any one of claims 1 to 3, wherein the deflection spatial modulation element includes a phase modulation element. The illumination device according to any one of claims 1 to 4, wherein a beam shaping unit is disposed between the light source and the deflection spatial modulation element. A light source that emits coherent light;
A deflection spatial modulation element for deflecting coherent light emitted from the light source;
A light modulation element having an image forming region on which an image is formed;
A projection optical system that projects an image of the light modulation element onto a screen, and the deflected coherent light emitted from the deflection spatial modulation element illuminates the image forming region over time, and A projection-type image display apparatus, wherein illumination is performed by changing an incident angle to each point of an image forming region with time. The projection type image display apparatus according to claim 6, wherein the coherent light emitted from the deflection spatial modulation element changes in angle symmetrically about an optical axis with respect to the projection optical system. A coherent light is incident, and a deflecting spatial modulation element that deflects and emits the incident coherent light is provided.
The deflected coherent light emitted from the deflecting spatial modulation element illuminates the illumination area by overlapping the illumination area with time and changes the incident angle to each point of the illumination area with time. An optical deflecting device.

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