JP6066384B2 - Projection device and projection-type image display device - Google Patents

Description

  The present invention relates to a projection device having a spatial light modulator and an illumination device that illuminates the spatial light modulator with coherent light, and a projection-type image display device having the projection device, and in particular, makes speckle generation inconspicuous. The present invention relates to a projection device and a projection-type image display device that can perform the same.

  Projection-type image display devices having a screen and a projection device that projects image light on the screen are widely used. In a typical projection-type image display device, an original two-dimensional image is generated by using a spatial light modulator such as a liquid crystal micro display or a DMD (Digital Micromirror Device), and the two-dimensional image is projected into an optical system. An image is displayed on the screen by enlarging and projecting on the screen using the system.

  Various types of projectors have been proposed, including commercially available products called “optical projectors”. In general optical projectors, a spatial light modulator such as a liquid crystal display is illuminated using a lighting device consisting of a white light source such as a high-pressure mercury lamp, and the resulting modulated image is projected onto a screen using a lens. Adopted. For example, in Patent Document 1 below, white light generated by an ultra-high pressure mercury lamp is divided into three primary color components of R, G, and B by a dichroic mirror, and these lights are guided to a spatial light modulator for each primary color. A technique is disclosed in which a generated modulated image for each primary color is synthesized by a cross dichroic prism and projected onto a screen.

  However, high-intensity discharge lamps such as high-pressure mercury lamps have a relatively short life, and when used in optical projectors or the like, it is necessary to frequently replace the lamps. Further, since it is necessary to use a relatively large optical system such as a dichroic mirror in order to extract the light of each primary color component, there is a problem that the entire apparatus becomes large.

  In order to cope with such a problem, a method using a coherent light source such as a laser has been proposed. For example, a semiconductor laser widely used in the industry has a very long life compared to a high-intensity discharge lamp such as a high-pressure mercury lamp. In addition, since the light source can generate light having a single wavelength, a spectroscopic device such as a dichroic mirror is not necessary, and the entire device can be reduced in size.

  On the other hand, a method using a coherent light source such as a laser beam has a new problem such as generation of speckle. A speckle is a speckled pattern that appears when a scattering surface is irradiated with laser light or other coherent light. When it appears on a screen, it is observed as speckled brightness irregularities (brightness irregularities). It becomes a factor having a physiological adverse effect on the person. The reason why speckles occur when coherent light is used is that coherent light reflected by each part of a scattering reflection surface such as a screen interferes with each other because of its extremely high coherence. . For example, in the following Non-Patent Document 1, detailed theoretical considerations regarding the generation of speckle are made.

  As described above, in the system using the coherent light source, a problem inherent to the generation of speckles occurs, and thus a technique for suppressing the generation of speckles has been proposed. For example, in Patent Document 2 below, the speckle is reduced by irradiating a scattering plate with laser light, guiding the scattered light obtained therefrom to a spatial light modulator, and rotating the scattering plate by a motor. Technology is disclosed.

JP 2004-264512 A Japanese Patent Laid-Open No. 6-208089

Speckle Phenomena in Optics, Joseph W. Goodman, Roberts & Co., 2006

  As described above, technologies for reducing speckles have been proposed in projection devices and projection-type video display devices using a coherent light source. However, the methods proposed so far effectively and sufficiently suppress speckles. I can't do it. For example, in the method disclosed in the above-mentioned Patent Document 2, laser light is irradiated on the scattering plate and scattered, and therefore, part of the laser light is wasted without contributing to video display at all. In addition, even if the scattering plate is rotated, the position of the optical axis of the illumination light does not change, so that speckles visually recognized on the screen cannot be sufficiently suppressed.

  Nowadays, there is an increasing demand for miniaturization of projection apparatuses represented by optical projectors. On the other hand, in the method disclosed in Patent Document 2, it is necessary to rotate the scattering plate for speckle reduction. By including such a mechanical rotation mechanism, the projection apparatus becomes extremely large. There is also a possibility of end. Also in this point, the method disclosed in Patent Document 2 is not preferable.

  The present invention has been made in consideration of the above points, and is a projection device and a projection-type image display device using coherent light, and effectively prevents speckle while preventing the device from becoming extremely large. It is an object of the present invention to provide a projection device and a projection-type image display device that can be made inconspicuous.

A first projection device according to the present invention comprises:
A spatial light modulator having a rectangular modulation image forming surface;
An illumination device for illuminating the spatial light modulator,
The lighting device includes:
An optical element including a hologram recording medium;
The coherent light scans on the hologram recording medium, and the coherent light incident on each position of the hologram recording medium is diffracted by the hologram recording medium to illuminate the spatial light modulator. An irradiation device for irradiating the optical element with the coherent light,
Regions on the spatial light modulator illuminated by coherent light incident on each position of the hologram recording medium overlap at least partially;
The coherent light repeatedly scans a linear path parallel to one side of the rectangular shape forming the modulation image forming surface on the hologram recording medium, or parallel to one side of the rectangular shape forming the modulation image forming surface. Scan within an elongated region extending in a different direction.

  In the first projection device according to the present invention, the hologram recording medium may have an elongated shape extending in a direction parallel to one side of the rectangular shape forming the modulated image forming surface.

The second projection device according to the present invention is:
A spatial light modulator having a rectangular modulation image forming surface;
An illumination device for illuminating the spatial light modulator,
The lighting device includes:
An optical element including a hologram recording medium;
The coherent light scans on the hologram recording medium, and the coherent light incident on each position of the hologram recording medium is diffracted by the hologram recording medium to illuminate the spatial light modulator. An irradiation device for irradiating the optical element with the coherent light,
Regions on the spatial light modulator illuminated by coherent light incident on each position of the hologram recording medium overlap at least partially;
The hologram recording medium has an elongated shape extending in a direction parallel to one side of the rectangular shape forming the modulated image forming surface.

  In the first or second projection device according to the present invention, the one side of the rectangular shape may be the short side of the rectangular shape.

The third projection device according to the present invention is:
A spatial light modulator;
An illumination device for illuminating the spatial light modulator,
The lighting device includes:
An optical element including a hologram recording medium;
The coherent light scans on the hologram recording medium, and the coherent light incident on each position of the hologram recording medium is diffracted by the hologram recording medium to illuminate the spatial light modulator. An irradiation device for irradiating the optical element with the coherent light,
The spatial light modulator is a digital micromirror device including a plurality of reflecting surfaces that can be rotated around rotation axes that are parallel to each other.
Regions on the spatial light modulator illuminated by coherent light incident on each position of the hologram recording medium overlap at least partially;
The coherent light repeatedly scans a linear path parallel to the rotational axis of the reflection surface of the digital micromirror device on the hologram recording medium, or of the reflection surface of the digital micromirror device. The inside of the elongate area | region extended in the direction parallel to the said rotation axis is scanned.

  In the third projection apparatus according to the present invention, the hologram recording medium may have an elongated shape extending in a direction parallel to the rotation axis of the reflection surface of the digital micromirror device.

A fourth projection device according to the present invention includes:
A spatial light modulator;
An illumination device for illuminating the spatial light modulator,
The lighting device includes:
An optical element including a hologram recording medium;
The coherent light scans on the hologram recording medium, and the coherent light incident on each position of the hologram recording medium is diffracted by the hologram recording medium to illuminate the spatial light modulator. An irradiation device for irradiating the optical element with the coherent light,
The spatial light modulator is a digital micromirror device including a plurality of reflecting surfaces that can be rotated around rotation axes that are parallel to each other.
Regions on the spatial light modulator illuminated by coherent light incident on each position of the hologram recording medium overlap at least partially;
The hologram recording medium has an elongated shape extending in a direction parallel to the rotation axis of the reflection surface of the digital micromirror device.

The fifth projection device according to the present invention is:
A spatial light modulator;
An illumination device for illuminating the spatial light modulator,
The lighting device includes:
An optical element including a hologram recording medium;
The coherent light scans on the hologram recording medium, and the coherent light incident on each position of the hologram recording medium is diffracted by the hologram recording medium to illuminate the spatial light modulator. An irradiation device for irradiating the optical element with the coherent light;
It is arranged between the optical element and the spatial light modulator in the optical path of the coherent light from the irradiation device to the spatial light modulator, and reflects the coherent light from the irradiation device to the spatial light modulator. A deflecting element including a reflecting surface to be directed,
Regions on the spatial light modulator illuminated by coherent light incident on each position of the hologram recording medium overlap at least partially;
The coherent light is linear on the hologram recording medium and parallel to a direction orthogonal to both the normal direction to the incident surface of the spatial light modulator and the normal direction to the reflecting surface of the deflection element. In the elongated region extending in a direction perpendicular to both the normal direction to the incident surface of the spatial light modulator and the normal direction to the reflecting surface of the deflection element. Scan.

  In the fifth projection apparatus according to the present invention, the hologram recording medium has a direction orthogonal to both a normal direction to the incident surface of the spatial light modulator and a normal direction to the reflection surface of the deflection element. It may be an elongated shape.

A sixth projection device according to the present invention includes:
A spatial light modulator;
An illumination device for illuminating the spatial light modulator,
The lighting device includes:
An optical element including a hologram recording medium;
The coherent light scans on the hologram recording medium, and the coherent light incident on each position of the hologram recording medium is diffracted by the hologram recording medium to illuminate the spatial light modulator. An irradiation device for irradiating the optical element with the coherent light;
It is arranged between the optical element and the spatial light modulator in the optical path of the coherent light from the irradiation device to the spatial light modulator, and reflects the coherent light from the irradiation device to the spatial light modulator. A deflecting element including a reflecting surface to be directed,
Regions on the spatial light modulator illuminated by coherent light incident on each position of the hologram recording medium overlap at least partially;
The hologram recording medium has an elongated shape extending in a direction orthogonal to both the normal direction to the incident surface of the spatial light modulator and the normal direction to the reflecting surface of the deflection element.

A seventh projection device according to the present invention is:
A spatial light modulator;
An illumination device for illuminating the spatial light modulator,
The lighting device includes:
An optical element including a hologram recording medium;
The coherent light scans on the hologram recording medium, and the coherent light incident on each position of the hologram recording medium is diffracted by the hologram recording medium to illuminate the spatial light modulator. An irradiation device for irradiating the optical element with the coherent light;
Located between the optical element and the spatial light modulator in the optical path of the coherent light from the irradiation device to the spatial light modulator, reflects light of a specific polarization component and transmits light of another polarization component A polarizing beam splitter having a separating surface to be
Regions on the spatial light modulator illuminated by coherent light incident on each position of the hologram recording medium overlap at least partially;
On the hologram recording medium, the coherent light is a straight line parallel to a direction orthogonal to both the normal direction to the incident surface of the spatial light modulator and the normal direction to the separation surface of the polarization beam splitter. An elongated region extending in a direction orthogonal to both the normal direction to the incident surface of the spatial light modulator and the normal direction to the separation surface of the polarization beam splitter. Scan inside.

  In the seventh projection apparatus according to the present invention, the hologram recording medium is a direction orthogonal to both the normal direction to the incident surface of the spatial light modulator and the normal direction to the separation surface of the polarization beam splitter. It may be an elongated shape extending in the direction.

The eighth projection apparatus according to the present invention is
A spatial light modulator;
An illumination device for illuminating the spatial light modulator,
The lighting device includes:
An optical element including a hologram recording medium;
The coherent light scans on the hologram recording medium, and the coherent light incident on each position of the hologram recording medium is diffracted by the hologram recording medium to illuminate the spatial light modulator. An irradiation device for irradiating the optical element with the coherent light;
Located between the optical element and the spatial light modulator in the optical path of the coherent light from the irradiation device to the spatial light modulator, reflects light of a specific polarization component and transmits light of another polarization component A polarizing beam splitter having a separating surface to be
Regions on the spatial light modulator illuminated by coherent light incident on each position of the hologram recording medium overlap at least partially;
The hologram recording medium has an elongated shape extending in a direction orthogonal to both the normal direction to the incident surface of the spatial light modulator and the normal direction to the separation surface of the polarization beam splitter.

  In the seventh or eighth projection device according to the present invention, the irradiation device is configured so that coherent light of a polarization component that is reflected by the separation surface of the polarization beam splitter proves the spatial light modulator. You may make it irradiate the said coherent light to the said optical element.

The ninth projection apparatus according to the present invention is
A spatial light modulator having a rectangular modulation image forming surface;
An illumination device for illuminating the spatial light modulator,
The lighting device includes:
An optical element including a light diffusing element that changes a traveling direction of incident light; and
The coherent light scans the light diffusing element and the traveling direction of the coherent light incident on each position of the light diffusing element is changed by the light diffusing element to illuminate the spatial light modulator. An irradiating device for irradiating the optical element with the coherent light, and
Regions on the spatial light modulator illuminated by coherent light incident on each position of the light diffusing element overlap at least in part,
The coherent light repeatedly scans a linear path parallel to one side of the rectangular shape forming the modulation image forming surface on the light diffusing element, or parallel to one side of the rectangular shape forming the modulation image forming surface. Scan within an elongated region extending in a different direction.

  In the ninth projection apparatus according to the present invention, the light diffusing element may have an elongated shape extending in a direction parallel to one side of the rectangular shape forming the modulated image forming surface.

A tenth projection device according to the present invention is:
A spatial light modulator having a rectangular modulation image forming surface;
An illumination device for illuminating the spatial light modulator,
The lighting device includes:
An optical element including a light diffusing element that changes a traveling direction of incident light; and
The coherent light scans the light diffusing element and the traveling direction of the coherent light incident on each position of the light diffusing element is changed by the light diffusing element to illuminate the spatial light modulator. An irradiating device for irradiating the optical element with the coherent light, and
Regions on the spatial light modulator illuminated by coherent light incident on each position of the light diffusing element overlap at least in part,
The light diffusing element has an elongated shape extending in a direction parallel to one side of the rectangular shape forming the modulated image forming surface.

  In the ninth or tenth projection apparatus according to the present invention, the one side of the rectangular shape may be the short side of the rectangular shape.

The eleventh projection apparatus according to the present invention is:
A spatial light modulator;
An illumination device for illuminating the spatial light modulator,
The lighting device includes:
An optical element including a light diffusing element that changes a traveling direction of incident light; and
The coherent light scans the light diffusing element and the traveling direction of the coherent light incident on each position of the light diffusing element is changed by the light diffusing element to illuminate the spatial light modulator. An irradiating device for irradiating the optical element with the coherent light, and
The spatial light modulator is a digital micromirror device including a plurality of reflecting surfaces that can be rotated around rotation axes that are parallel to each other.
Regions on the spatial light modulator illuminated by coherent light incident on each position of the light diffusing element overlap at least in part,
The coherent light repeatedly scans a linear path parallel to the rotation axis of the reflection surface of the digital micromirror device on the light diffusing element, or of the reflection surface of the digital micromirror device. The inside of the elongate area | region extended in the direction parallel to the said rotation axis is scanned.

  In an eleventh projection apparatus according to the present invention, the light diffusing element may have an elongated shape extending in a direction parallel to the rotation axis of the reflecting surface of the digital micromirror device.

A twelfth projection apparatus according to the present invention is
A spatial light modulator;
An illumination device for illuminating the spatial light modulator,
The lighting device includes:
An optical element including a light diffusing element that changes a traveling direction of incident light; and
The coherent light scans the light diffusing element and the traveling direction of the coherent light incident on each position of the light diffusing element is changed by the light diffusing element to illuminate the spatial light modulator. An irradiating device for irradiating the optical element with the coherent light, and
The light diffusing element is a digital micromirror device including a plurality of reflecting surfaces that are rotatable about rotation axes parallel to each other.
Regions on the spatial light modulator illuminated by coherent light incident on each position of the light diffusing element overlap at least in part,
The light diffusing element has an elongated shape extending in a direction parallel to the rotation axis of the reflecting surface of the digital micromirror device.

A thirteenth projection apparatus according to the present invention is
A spatial light modulator;
An illumination device for illuminating the spatial light modulator,
The lighting device includes:
An optical element including a light diffusing element that changes a traveling direction of incident light; and
The coherent light scans the light diffusing element and the traveling direction of the coherent light incident on each position of the light diffusing element is changed by the light diffusing element to illuminate the spatial light modulator. An irradiating device for irradiating the optical element with the coherent light,
It is arranged between the optical element and the spatial light modulator in the optical path of the coherent light from the irradiation device to the spatial light modulator, and reflects the coherent light from the irradiation device to the spatial light modulator. A deflecting element including a reflecting surface to be directed,
Regions on the spatial light modulator illuminated by coherent light incident on each position of the hologram recording medium overlap at least partially;
The coherent light is linear on the light diffusing element and parallel to a direction orthogonal to both the normal direction to the incident surface of the spatial light modulator and the normal direction to the reflecting surface of the deflecting element. In the elongated region extending in a direction perpendicular to both the normal direction to the incident surface of the spatial light modulator and the normal direction to the reflecting surface of the deflection element. Scan.

    In a thirteenth projection apparatus according to the present invention, the light diffusing element is in a direction orthogonal to both the normal direction to the incident surface of the spatial light modulator and the normal direction to the reflecting surface of the deflecting element. It may be an elongated shape.

A fourteenth projection device according to the present invention is
A spatial light modulator;
An illumination device for illuminating the spatial light modulator,
The lighting device includes:
An optical element including a light diffusing element that changes a traveling direction of incident light; and
The coherent light scans the light diffusing element and the traveling direction of the coherent light incident on each position of the light diffusing element is changed by the light diffusing element to illuminate the spatial light modulator. An irradiating device for irradiating the optical element with the coherent light,
It is arranged between the optical element and the spatial light modulator in the optical path of the coherent light from the irradiation device to the spatial light modulator, and reflects the coherent light from the irradiation device to the spatial light modulator. A deflecting element including a reflecting surface to be directed,
Regions on the spatial light modulator illuminated by coherent light incident on each position of the hologram recording medium overlap at least partially;
The light diffusing element has an elongated shape extending in a direction orthogonal to both the normal direction to the incident surface of the spatial light modulator and the normal direction to the reflecting surface of the polarizing element.

The fifteenth projection apparatus according to the present invention is
A spatial light modulator;
An illumination device for illuminating the spatial light modulator,
The lighting device includes:
An optical element including a light diffusing element that changes a traveling direction of incident light; and
The coherent light scans the light diffusing element and the traveling direction of the coherent light incident on each position of the light diffusing element is changed by the light diffusing element to illuminate the spatial light modulator. An irradiating device for irradiating the optical element with the coherent light,
Located between the optical element and the spatial light modulator in the optical path of the coherent light from the irradiation device to the spatial light modulator, reflects light of a specific polarization component and transmits light of another polarization component A polarizing beam splitter having a separating surface to be
Regions on the spatial light modulator illuminated by coherent light incident on each position of the hologram recording medium overlap at least partially;
The coherent light is a straight line parallel to a direction perpendicular to both the normal direction to the incident surface of the spatial light modulator and the normal direction to the separation surface of the polarization beam splitter on the light diffusing element. An elongated region extending in a direction orthogonal to both the normal direction to the incident surface of the spatial light modulator and the normal direction to the separation surface of the polarization beam splitter. Scan inside.

  In the fifteenth projection apparatus according to the present invention, the light diffusing element is perpendicular to both a normal direction to the incident surface of the spatial light modulator and a normal direction to the separation surface of the polarization beam splitter. It may be an elongated shape extending in the direction.

The sixteenth projection apparatus according to the present invention is
A spatial light modulator;
An illumination device for illuminating the spatial light modulator,
The lighting device includes:
An optical element including a light diffusing element that changes a traveling direction of incident light; and
The coherent light scans the light diffusing element and the traveling direction of the coherent light incident on each position of the light diffusing element is changed by the light diffusing element to illuminate the spatial light modulator. An irradiating device for irradiating the optical element with the coherent light,
Located between the optical element and the spatial light modulator in the optical path of the coherent light from the irradiation device to the spatial light modulator, reflects light of a specific polarization component and transmits light of another polarization component A polarizing beam splitter having a separating surface to be
Regions on the spatial light modulator illuminated by coherent light incident on each position of the hologram recording medium overlap at least partially;
The light diffusing element has an elongated shape extending in a direction orthogonal to both the normal direction to the incident surface of the spatial light modulator and the normal direction to the separation surface of the polarizing beam splitter.

  In the fifteenth or sixteenth projection device according to the present invention, the irradiation device is configured so that coherent light of a polarization component that is reflected by the separation surface of the polarization beam splitter proves the spatial light modulator. The coherent light may be applied to the optical element.

  In any one of the ninth to sixteenth projection apparatuses according to the present invention, the light diffusing element may be a lens array.

  Any one of the first to sixteenth projection devices according to the present invention may further include a projection optical system that projects light forming a modulated image generated by the spatial light modulator.

A projection-type image display device according to the present invention includes:
Any one of the first to sixteenth projection devices according to the present invention described above;
And a screen onto which the modulated image generated by the spatial light modulator is projected.

  ADVANTAGE OF THE INVENTION According to this invention, the speckle on the surface which projects an image | video can be made effectively inconspicuous, preventing the extreme enlargement of a projection apparatus.

FIG. 1 is a diagram for explaining an embodiment according to the present invention, and shows a schematic configuration of a projection device and a projection-type image display device as an embodiment from above, in other words, a projection device. It is a top view shown from the normal line direction to the surface which comprises this optical system. FIG. 2 is a side view showing the schematic configuration of the projection apparatus of FIG. 1 from the side, in other words, from the direction parallel to the plane constituting the optical system of the projection apparatus. FIG. 3 is a diagram showing a schematic configuration of the projection display apparatus of FIG. 1 from the same direction as FIG. However, in FIG. 3, the irradiation device of the projection device is omitted. FIG. 4 is a perspective view showing a schematic configuration of the projection apparatus of FIG. FIG. 5 is a view for explaining an exposure method for producing a hologram recording medium that forms an optical element of the projection apparatus of FIG. FIG. 6 is a diagram for explaining the operation of the hologram recording medium manufactured through the exposure method of FIG. FIG. 7 is a diagram corresponding to FIG. 1, and is a plan view for explaining a modification of the illumination device of the projection device and its operation. FIG. 8 is a diagram corresponding to FIG. 1, and is a plan view for explaining another modification of the illumination device of the projection device and its operation. FIG. 9 is a diagram corresponding to FIG. 2, and is a side view for explaining a modification of the irradiation device included in the illumination device of the projection device and its operation.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIGS. 1-9 is a figure for demonstrating the projection apparatus and projection type video display apparatus which concern on one embodiment of this invention, and its modification. In the drawings attached to the present specification, for the sake of illustration and ease of understanding, the scale, the vertical / horizontal dimension ratio, and the like are appropriately changed and exaggerated from those of the actual product.

[One embodiment]
First, with reference to FIGS. 1-6, the projection apparatus and projection type video display apparatus which concern on one embodiment are demonstrated. Thereafter, an example of a modification to the projection apparatus and the projection display apparatus according to the embodiment will be described with reference to FIGS. 7 to 9 as appropriate.

  First, the configuration of a projection-type image display device that includes an illumination device that projects coherent light and a projection device and can make speckles inconspicuous will be described mainly with reference to FIGS.

  A projection video display device 10 shown in FIG. 1 includes a screen 15 and a projection device 20 that projects video light including coherent light. The projection device 20 includes an illuminating device 40 that illuminates the illuminated region LZ located on the virtual plane with coherent light, and a spatial light modulator that is disposed at a position overlapping the illuminated region LZ and that is illuminated with the coherent light by the illuminating device 40. 30 and a projection optical system 25 that projects the coherent light from the spatial light modulator 30 onto the screen 15.

  The spatial light modulator 30 is illuminated in a planar shape by the illumination device 40, and forms a modulated image using the illumination light. The modulated image (video light) formed by the spatial light modulator 30 is projected onto the screen 15 by the projection optical system 25 at the same magnification or scaled. As a result, the modulated image is displayed on the screen 15 at the same magnification or at a variable magnification, usually enlarged, and the observer can observe the image.

  As a specific example, in the accompanying drawings, the spatial light modulator 30 is configured as a digital micromirror device (DMD) as in the above-described Patent Document 2. The digital micromirror device 30 is a MEMS element having a modulated image forming surface 31 in which a large number of micromirrors 32 are arranged, and functions as a reflective spatial light modulator. The modulation image forming surface 31 has a rectangular shape, that is, a rectangular or square outer contour, as can be understood from FIG. 4. In such a reflective spatial light modulator, a surface on which the spatial light modulator 30 is irradiated with coherent light from the illumination device 40, a surface on which video light forming a modulated image from the spatial light modulator 30, and a spatial light The surface where the discarded light that does not form a modulated image from the modulator 30 is the same.

  As shown in FIG. 4, the multiple micromirrors 32 of the digital micromirror device 30 are configured to be rotatable about rotation axes RAm that are parallel to each other. Each micromirror 32 has a reflecting surface 32 a, and light from the illumination device 40 is reflected toward the projection optical system 25 by each micromirror 32. In other words, in the spatial light modulator 30 configured as a digital micromirror device, each micromirror 32 forms one pixel, and each micromirror 32 is driven to control the direction of the reflecting surface 32a, thereby providing a predetermined direction. A modulated image can be formed toward On the other hand, in many reflective spatial light modulators typified by the digital macromirror device 30, as shown in FIG. 1, the light that does not form an image, in other words, the discarded light is in a direction different from the light that forms the image. It is reflected and absorbed by appropriate elements or the like. In FIG. 1, the projection device 20 is shown from the direction along the rotation axis RAm of the micromirror 32.

  The spatial light modulator 30 that can be used here is not limited to the illustrated reflective spatial light modulator (reflective microdisplay), and is also configured by a transmissive spatial light modulator (transmissive microdisplay). Can be done. Even when any known spatial light modulator is used as the spatial light modulator 30, the speckle is made inconspicuous while preventing the size of the projection device 20 from becoming extremely large, as will be described later. Can do.

  In addition, the incident surface of the spatial light modulator 30, that is, the modulated image forming surface 31, preferably has the same shape and size as the illuminated region LZ irradiated with coherent light by the illumination device 40. In this case, it is because the coherent light from the illuminating device 40 can be used with high utilization efficiency for displaying the image on the screen 15.

  The screen 15 may be configured as a transmissive screen or may be configured as a reflective screen. In the case where the screen 15 is configured as a reflective screen, the observer observes an image displayed by coherent light reflected by the screen 15 from the same side as the projection device 20 with respect to the screen 15. On the other hand, when the screen 15 is configured as a transmissive screen, the observer observes an image displayed by coherent light transmitted through the screen 15 from the side opposite to the projection device 20 with respect to the screen 15. .

By the way, the coherent light projected on the screen 15 is diffused and recognized as an image by the observer. At this time, the coherent light projected on the screen interferes by diffusion and causes speckle. However, in the projection display apparatus 10 described here, the illumination apparatus 40 described below illuminates the illuminated area LZ on which the spatial light modulator 30 is superimposed with coherent light that changes in angle with time. It is like that.
More specifically, the illuminating device 40 described below illuminates the illuminated region LZ with diffused light composed of coherent light, and the incident angle of this diffused light changes over time. As a result, the diffusion pattern of the coherent light on the screen 15 also changes with time, and speckles generated by the diffusion of the coherent light are temporally superimposed and become inconspicuous. Hereinafter, such an illuminating device 40 will be described in more detail.

The illumination device 40 shown in FIGS. 1 to 4 includes an optical element 50 that directs the traveling direction of coherent light toward the illuminated region LZ, and an irradiation device 60 that irradiates the optical element 50 with coherent light. . The optical element 50 includes a hologram recording medium 55 that functions as a light diffusing element (light diffusing element), in particular, a hologram recording medium 55 that can reproduce the image 5 of the scattering plate 6.
In the illustrated example, the optical element 50 is formed from a hologram recording medium 55.

  As shown in FIG. 2, the hologram recording medium 55 constituting the optical element 50 can receive the coherent light irradiated from the irradiation device 60 as the reproduction illumination light La and diffract the coherent light with high efficiency. . In particular, the hologram recording medium 55 can reproduce the image 5 of the scattering plate 6 by diffracting coherent light incident on each position, in other words, each minute region that should be called each point. ing.

  On the other hand, the irradiation device 60 irradiates the optical element 50 with the coherent light so that the coherent light of the hologram recording medium 55 scans the hologram recording medium 55 of the optical element 50. Therefore, the region on the hologram recording medium 55 that is irradiated with the coherent light by the irradiation device 60 at a certain moment is a part of the surface of the hologram recording medium 55, and in particular in the illustrated example, a minute region to be called a point. It has become.

  Then, the coherent light irradiated from the irradiation device 60 and scanned on the hologram recording medium 55 is diffracted by the hologram recording medium 55 at each position (each point or each region (hereinafter the same)) on the hologram recording medium 55. Incidence is made at an incident angle that satisfies the conditions. The coherent light incident on each position of the hologram recording medium 55 from the irradiation device 60 is diffracted by the hologram recording medium 55 and illuminates areas that overlap each other at least partially. In particular, in the embodiment described here, the coherent light incident on each position of the hologram recording medium 55 from the irradiation device 60 is diffracted by the hologram recording medium 55 to illuminate the same illuminated region LZ. . More specifically, as shown in FIG. 2, the coherent light incident on each position of the hologram recording medium 55 from the irradiation device 60 is superimposed on the illuminated region LZ to reproduce the image 5 of the scattering plate 6. It has become. That is, the coherent light that has entered the hologram recording medium 55 from the irradiation device 60 is diffused and spread by the optical element 50 and enters the illuminated area LZ.

  In the illustrated example, a reflection type volume hologram using a photopolymer is used as the hologram recording medium 55 that enables the diffraction action of such coherent light. As shown in FIG. 5, the hologram recording medium 55 is manufactured using scattered light from a real scattering plate 6 as object light Lo. FIG. 5 shows a state in which the hologram photosensitive material 58 having photosensitivity that forms the hologram recording medium 55 is exposed to the reference light Lr and the object light Lo, which are coherent light beams having coherence with each other. ,It is shown.

  As the reference light Lr, for example, laser light from a laser light source that oscillates laser light in a specific wavelength region is used, and passes through the condensing element 7 formed of a lens and enters the hologram photosensitive material 58. In the example shown in FIG. 5, the laser light that forms the reference light Lr is incident on the condensing element 7 as a parallel light beam parallel to the optical axis of the condensing element 7. The reference light Lr passes through the condensing element 7, so that it is shaped (converted) into a convergent light beam from the parallel light beam so far, and is incident on the hologram photosensitive material 58. At this time, the focal position FP of the convergent light beam Lr is at a position beyond the hologram photosensitive material 58. In other words, the hologram photosensitive material 58 is disposed between the condensing element 7 and the focal position FP of the convergent light beam Lr collected by the condensing element 7.

  Next, the object light Lo is incident on the hologram photosensitive material 58 as scattered light from a scattering plate 6 made of, for example, opal glass. Here, since the hologram recording medium 55 to be manufactured is a reflection type, the object light Lo is incident on the hologram photosensitive material 58 from the surface opposite to the reference light Lr. The object light Lo needs to have coherency with the reference light Lr. Therefore, for example, laser light oscillated from the same laser light source can be divided, and one of the divided lights can be used as the reference light Lr and the other can be used as the object light Lo.

  In the example shown in FIG. 5, a parallel light beam parallel to the normal direction to the plate surface of the scattering plate 6 is incident on the scattering plate 6 and scattered, and the scattered light transmitted through the scattering plate 6 is the object light Lo. The light enters the hologram photosensitive material 58. According to this method, when an isotropic scattering plate that is usually available at a low cost is used as the scattering plate 6, the object light Lo from the scattering plate 6 is incident on the hologram photosensitive material 58 with a substantially uniform light amount distribution. Is possible. Further, according to this method, although depending on the degree of scattering by the scattering plate 6, the reference light Lr is incident on each position of the hologram photosensitive material 58 with a substantially uniform light amount from the entire area of the exit surface 6 a of the scattering plate 6. It becomes easy. In such a case, the light incident on each position of the obtained hologram recording medium 55 reproduces the image 5 of the scattering plate 6 with the same brightness, and the reproduced scattering plate 6 It can be realized that the image 5 is observed with substantially uniform brightness.

  As described above, when the hologram recording material 58 is exposed to the reference light Lr and the object light Lo, an interference fringe formed by the interference of the reference light Lr and the object light Lo is generated. In the case of a pattern and a volume hologram, for example, it is recorded on the hologram recording material 58 as a refractive index modulation pattern. Thereafter, appropriate post-processing corresponding to the type of the hologram recording material 58 is performed, and the hologram recording medium 55 is obtained.

  FIG. 6 shows the diffraction action (reproduction action) of the hologram recording medium 55 obtained through the exposure process of FIG. As shown in FIG. 6, the hologram recording medium 55 formed from the hologram photosensitive material 58 of FIG. 5 is light having the same wavelength as that of the laser beam used in the exposure process, and the optical path of the reference light Lr in the exposure process. The light traveling in the opposite direction satisfies the Bragg condition. That is, as shown in FIG. 6, the reference point SP positioned with respect to the hologram recording medium 55 so as to have the same positional relationship as the relative position of the focal point FP with respect to the hologram photosensitive material 58 during the exposure process (see FIG. 5). The divergent light beam that diverges from the light and has the same wavelength as the reference light Lr during the exposure process is diffracted as the reproduction illumination light La to the hologram recording medium 55, and the relative position of the scattering plate 6 relative to the hologram photosensitive material 58 during the exposure process A reproduced image 5 of the scattering plate 6 is generated at a specific position with respect to the hologram recording medium 50 that has the same positional relationship as (see FIG. 3).

  At this time, the reproduction light Lb for generating the reproduced image 5 of the scattering plate 6, that is, the diffracted light Lb obtained by diffracting the reproduction illumination light La by the hologram recording medium 55 is transferred from the scattering plate 6 to the hologram photosensitive material 58 during the exposure process. Each point of the image 5 of the scattering plate 6 is reproduced as light traveling in the opposite direction along the optical path of the object light Lo traveling forward. As described above and as shown in FIG. 5, the scattered light Lo emitted from each position on the exit surface 6 a of the scattering plate 6 in the exposure process is incident on almost the entire region of the hologram photosensitive material 58. Is spreading (spreading). That is, the object light Lo from the entire area of the exit surface 6 a of the scattering plate 6 is incident on each position on the hologram photosensitive material 58, and as a result, information on the entire exit surface 6 a is placed on each position of the hologram recording medium 55. Each is recorded. For this reason, each light which forms the divergent light beam from the reference point SP functioning as the reproduction illumination light La shown in FIG. 6 is incident on each position of the hologram recording medium 55 independently and has the same contour. The image 5 of the scattering plate 6 can be reproduced at the same position (illuminated area LZ).

On the other hand, the irradiation device 60 that irradiates the optical element 50 composed of the hologram recording medium 55 with the coherent light can be configured as follows. As well shown in FIG. 2, the irradiation device 60 includes a laser light source 61a that generates coherent light in a specific wavelength range, and a scanning device 65 that changes the traveling direction of the coherent light from the laser light source 61a. doing.
The scanning device 65 changes the traveling direction of the coherent light with time, and directs it in various directions so that the traveling direction of the coherent light is not constant. As a result, the coherent light whose traveling direction is changed by the scanning device 65 scans the incident surface of the hologram recording medium 55 of the optical element 50.

  As shown well in FIGS. 2 and 4, in the illustrated form, the scanning device 65 includes a reflective device 66 having a reflective surface 66a that is rotatable about one axis RA1. More specifically, the reflection device 66 is configured as a mirror device having a mirror as a reflection surface 66a that can be rotated about one axis RA1. As shown in FIGS. 2 and 4, the mirror device 66 changes the traveling direction of coherent light from the laser light source 61a by changing the orientation of the mirror 66a. At this time, as shown in FIGS. 2 and 4, the mirror device 66 generally receives coherent light from the laser light source 61 a at the reference point SP. For this reason, the coherent light whose traveling direction is finally adjusted by the mirror device 66 is reproduced illumination light La (see FIG. 6) that can form one light beam diverging from the reference point SP, and the hologram recording medium 55 of the optical element 50. Can be incident. As a result, the coherent light from the irradiation device 60 scans on the hologram recording medium 55, and the image of the scattering plate 6 in which the coherent light incident on each position on the hologram recording medium 55 has the same contour. 5 is reproduced at the same position (illuminated area LZ).

  As a practical problem, the hologram recording material 58 may shrink when the hologram recording medium 55 is produced. In such a case, it is preferable to adjust the incident / exit angle of the coherent light irradiated from the irradiation device 60 to the optical element 50 in consideration of the shrinkage of the hologram recording material 58. Therefore, the wavelength of the coherent light generated by the coherent light source 61a does not need to be exactly the same as the wavelength of the light used in the exposure process (recording process) in FIG. 3, and may be substantially the same.

  For the same reason, even if the traveling direction of the light incident on the hologram recording medium 55 of the optical element 50 does not take exactly the same path as the one light beam included in the divergent light beam from the reference point SP, it is illuminated. The image 5 can be reproduced in the region LZ. Actually, in the example shown in FIGS. 2 and 4, the mirror (reflection surface) 66a of the mirror device 66 constituting the scanning device 65 is inevitably deviated from the rotation axis RA1. Therefore, when the mirror 66a is rotated around the rotation axis RA1 that does not pass through the reference point SP, the light incident on the hologram recording medium 55 may not be a single light beam that forms a divergent light beam from the reference point SP. is there. However, in practice, the image 5 can be substantially reproduced by being superimposed on the illuminated region LZ by coherent light from the irradiation device 60 having the illustrated configuration.

  By the way, similarly to the projection apparatus 20 according to the present embodiment shown in FIGS. 1 to 4, in the conventional optical projector, the normal direction to the front surface of the spatial light modulator, in other words, the modulated image forming surface. For example, a projection lens forming a projection optical system has been arranged at a position facing the spatial light modulator along the optical axis. For this reason, the illuminating device illuminates the modulated image forming surface of the spatial light modulator from a direction inclined with respect to the front direction, as in the embodiment shown in FIG. Further, in the conventional general optical projector, the optical axis of the optical path from the light source to the spatial light modulator, that is, the central optical path is along a direction substantially orthogonal to the rotation axis of the micro mirror of the digital micro mirror device. .

  As already explained, in an optical system such as a digital micromirror device, unnecessary light that does not form a modulated image is thrown away by rotation about the rotation axis of the micromirror, and the direction is different from that of the modulated image. Is heading to. As a result, in such a conventional optical projector, the light that enters the spatial light modulator from the light source to form a modulated image and the light that enters the spatial light modulator from the light source and becomes discarded light are very small. An optical system is formed along one virtual plane orthogonal to the rotation axis of the mirror. In other words, in the conventional optical projector, the optical path center of light that enters the spatial light modulator from the light source to form a modulated image, and the optical path center of light that enters the spatial light modulator from the light source and becomes discarded light. Advances along one virtual plane orthogonal to the rotation axis of the rotation axis of the micromirror. According to such a configuration, the optical path in the optical projector is extremely simplified, and the size of the optical projector along the direction of the rotation axis of the micromirror can be reduced. The size of the projector can be reduced.

  As is well shown in FIGS. 1, 3, and 4, in the present embodiment, the normal direction to the front surface of the spatial light modulator 30, in other words, to the modulated image forming surface 31, as in the prior art. A projection optical system 25 is disposed at a position facing the spatial light modulator 30 along the line. As shown in FIG. 1, the illumination device 40 moves the modulated image forming surface 31 of the spatial light modulator 30 relative to the normal direction to the modulated image forming surface 31, that is, the front direction. Illuminated from an inclined direction. Further, the optical axis of the optical path of the coherent light from the light source 61 a included in the illumination device 40 to the spatial light modulator 30, that is, the central optical path is in a direction orthogonal to the rotation axis RAm of the micro mirror 32 of the digital micro mirror device 30. Along.

  For this reason, also in the projection device 20 according to the present embodiment, the light that enters the spatial light modulator 30 from the light source 61a of the illumination device 40 and forms the modulated image, and the light that enters the spatial light modulator 30 from the light source 61a. The light that becomes discarded light forms an optical system along one virtual plane orthogonal to the rotation axis RAm of the micromirror 32 and travels along the virtual plane. According to such a projection device 20, the optical path in the projection device 20 can be greatly simplified, and the size of the projection device 20 along the direction of the rotation axis RAm of the micromirror 32 can be reduced. Thus, the projection device 20 can be downsized.

  As described above, in the present embodiment, the illumination device 40 of the projection device 20 includes the optical element 50 formed of the hologram recording medium 55 and the irradiation device 60 that irradiates the optical element 50 with coherent light. ing. The modulated image forming surface 31 of the spatial light modulator 30 is illuminated with diffracted light from the hologram recording medium 55. The irradiation device 60 includes a scanning device 65 and irradiates the optical element 60 with the coherent light so that the coherent light scans the hologram recording medium 55. And according to this Embodiment, the enlargement of the projection apparatus 20 is prevented effectively, including the illuminating device 40 of such a structure.

  Specifically, as shown in FIGS. 2 and 4, the mirror device 66 constituting the scanning device 65 of the irradiation apparatus 60 is configured to rotate the mirror 66a along one axis RA1. In particular, as shown in FIG. 4, the rotation axis RA1 of the mirror 66a is parallel to the optical system defined by the optical path in the projection apparatus 20, that is, the micromirror 32 of the digital micromirror device 30. It extends perpendicular to the rotation axis RAm. In addition, light incident on the scanning device 65 from the light source 61 a travels linearly in parallel with the optical system defined by the optical path in the projection apparatus 20. For this reason, the incident point IP of the coherent light from the irradiation device 60 to the optical element 50 reciprocates in a direction orthogonal to the optical system defined by the optical path in the projection device 20.

  Therefore, the coherent light irradiated from the irradiation device 60 repeatedly scans on the hologram recording medium 55 along a linear path parallel to the rotation axis RAm of the reflecting surface 32a of the micromirror 32 of the digital micromirror device 30. become. In the present embodiment, the coherent light irradiated from the irradiation device 60 repeats a linear path parallel to one side of the rectangular shape forming the modulation image forming surface 31 of the spatial light modulator 30 on the hologram recording medium 55. To scan. In the form shown in FIG. 4, the modulation image forming surface 31 of the spatial light modulator 30 is a rectangle, and the scanning path of the coherent light on the hologram recording medium 55 is parallel to the short side of the rectangle. ing.

  Corresponding to the scanning path of such coherent light on the hologram recording medium 55, the hologram recording medium 55 constituting the optical element 50 is formed of the micromirror 32 of the digital micromirror device 30 as shown in FIG. The reflecting surface 32a has an elongated shape extending in a direction parallel to the rotation axis RAm. In the present embodiment, in other words, the hologram recording medium 55 forming the optical element 50 has an elongated shape extending in a direction parallel to one side of the rectangular shape forming the modulation image forming surface 31 of the spatial light modulator 30, particularly, The elongated shape extends in a direction parallel to the rectangular short side forming the modulated image forming surface 31.

  As will be described in detail later, the incident position IP of the coherent light to the optical element 50 is scanned on the hologram recording medium 55 because the incident of the coherent light incident on each position of the spatial light modulator 30 is performed. The purpose is to multiplex the angles over time and finally make the speckles that are generated when the modulated image formed by the spatial light modulator 30 is observed inconspicuous. In order to satisfy this purpose, the length of the scanning path of the coherent light on the hologram recording medium 55 needs to exceed the length of one side of the spatial light modulator 30 as in the illustrated example. Absent.

  Therefore, when the elongated optical element 50 made of the hologram recording medium 55 extends in a direction parallel to the rotation axis RAm of the reflection surface 32a of the micromirror 32 of the digital micromirror device 30, this rotation axis RAm Without changing the size of the projection device 20 along the direction perpendicular to the plane defined by the optical system in the projection device 20 to the rotation axis RAm. The dimension of the projection apparatus 20 along the orthogonal direction, in other words, the dimension of the projection apparatus 20 along the plane defined by the optical system in the projection apparatus 20 can be sufficiently reduced. That is, according to the projection device 20 according to the present embodiment, speckles can be made inconspicuous as described later while effectively suppressing an increase in size of the projection device.

  Next, the operation of the illumination device 40, the projection device 20, and the projection display device 10 having the above-described configuration will be described.

  First, the irradiation device 60 irradiates the optical element 50 with coherent light so that the coherent light scans the hologram recording medium 55 of the optical element 50. Specifically, coherent light having a specific wavelength traveling along a certain direction is generated by the laser light source 61 a, and the traveling direction of the coherent light is changed by the scanning device 65. The scanning device 65 causes coherent light having a specific wavelength to enter each position on the hologram recording medium 55 at an incident angle that satisfies the Bragg condition at the position. As a result, the coherent light incident at each position is superimposed on the illuminated region LZ by the diffraction at the hologram recording medium 55 to reproduce the image 5 of the scattering plate 6. That is, the coherent light that has entered the hologram recording medium 55 from the irradiation device 60 is diffused (expanded) by the optical element 50 and enters the entire illuminated area LZ. In this way, the irradiation device 60 illuminates the illuminated area LZ with coherent light.

  As shown in FIG. 1, in the projection device 20, the spatial light modulator 30 is arranged so that the modulated image forming surface 31 of the spatial light modulator 30 overlaps the illuminated region LZ of the illumination device 40. For this reason, the modulated image forming surface 31 of the spatial light modulator 30 is illuminated in a planar shape by the illumination device 40, and a modulated image is formed by controlling the reflection of coherent light for each pixel. The formed modulated image is projected onto the screen 15 by the projection optical system 25. The coherent light projected on the screen 15 is diffused and recognized as an image by the observer. However, at this time, the coherent light projected on the screen interferes by diffusion and causes speckle.

  However, according to the illumination device 40 in the present embodiment described here, speckles can be made extremely inconspicuous as described below.

According to the aforementioned Non-Patent Document 1, it is effective to multiplex parameters such as polarization, phase, angle, and time and increase the mode in order to make speckle inconspicuous.
The mode here refers to speckle patterns that are uncorrelated with each other. For example, when coherent light is projected from different directions onto the same screen from a plurality of laser light sources, there are as many modes as the number of laser light sources. In addition, when coherent light from the same laser light source is projected onto the screen from different directions by dividing the time, the mode is set to the number of times the incident direction of the coherent light has changed during a time that cannot be resolved by the human eye Will exist. When there are a large number of these modes, the interference patterns of light are uncorrelated and averaged, and as a result, speckles observed by the observer's eyes are considered inconspicuous.

  In the irradiation device 60 described above, the optical element 50 is irradiated with the coherent light so as to scan the hologram recording medium 55. Further, the coherent light incident on each position of the hologram recording medium 55 from the irradiation device 60 illuminates a region including at least a part overlapping with the coherent light, but the illumination direction of the coherent light illuminating the overlapping part is Different from each other. In particular, in the present embodiment, the coherent light incident on each position of the hologram recording medium 55 from the irradiation device 60 illuminates the entire illuminated area LZ with the coherent light, and illuminates the illuminated area LZ. The illumination directions of the coherent light to be different are different from each other. Since the position on the hologram recording medium 55 where the coherent light enters changes with time, the incident direction of the coherent light to the illuminated region LZ also changes with time.

  Considering the illuminated area LZ as a reference, coherent light constantly enters each position in the illuminated area LZ, and the incident direction is always as indicated by the arrow A1 in FIGS. Will continue to change. As a result, the light forming each pixel of the image formed by the light transmitted through the spatial light modulator 30 is projected to a specific position on the screen 15 while changing its optical path over time as indicated by an arrow A2 in FIG. Will come to be.

  The coherent light continuously scans on the hologram recording medium 55. Accordingly, the incident direction of the coherent light from the irradiation device 60 to the illuminated region LZ also changes continuously, and the incident direction of the coherent light from the projection device 20 to the screen 15 also changes continuously. Here, the incident direction of the coherent light from the projection device 20 to the screen 15 is slightly, for example, 0. If it changes by a few degrees, the speckle pattern generated on the screen 15 also changes greatly, and an uncorrelated speckle pattern is sufficiently superimposed. In addition, the frequency of scanning devices 65 such as MEMS mirrors and polygon mirrors that are commercially available is usually several hundred Hz or higher, and scanning devices 65 that reach tens of thousands of Hz are not uncommon.

  From the above, according to this embodiment described above, the incident direction of coherent light changes temporally at each position on the screen 15 displaying an image, and this change is As a result, a non-correlated coherent light scattering pattern is multiplexed and observed by the human eye. Therefore, speckles generated corresponding to each scattering pattern are overlapped and averaged and observed by an observer. Thereby, speckles can be made very inconspicuous for an observer who observes the image displayed on the screen 15.

  Note that conventional speckles observed by humans include not only speckles on the screen caused by scattering of coherent light on the screen 15, but also scattering of coherent light before being projected on the screen. Speckle on the projection device side can also occur. The speckle pattern generated on the projection device side is projected onto the screen 15 via the spatial light modulator 30 so that it can be recognized by the observer. However, according to the basic mode described above, the coherent light continuously scans on the hologram recording medium 55, and the coherent light incident on each position of the hologram recording medium 55 is superimposed on the spatial light modulator 30, respectively. The entire illuminated area LZ is illuminated. That is, the hologram recording medium 55 forms a new wavefront that is separate from the wavefront used to form the speckle pattern, and the illumination area LZ and further the spatial light modulator 30 are formed in a complex and uniform manner. Through this, the screen 15 is illuminated. Due to the formation of a new wavefront on the hologram recording medium 55, the speckle pattern generated on the projection apparatus side is made invisible.

  By the way, Non-Patent Document 1 described above proposes a method using a numerical value called speckle contrast (unit%) as a parameter indicating the degree of speckle generated on the screen. This speckle contrast is defined as a value obtained by dividing the standard deviation of the actual luminance variation on the screen divided by the average luminance value when displaying a test pattern image that should have a uniform luminance distribution. Amount. The larger the speckle contrast value is, the larger the speckle occurrence level on the screen is, which indicates that the spot-like luminance unevenness pattern is more prominently presented to the observer.

  The speckle contrast of the basic projection type image display apparatus 10 described with reference to FIGS. 1 to 6 was 3.0% (Condition 1). Further, as the above-described optical element 50, an uneven shape designed by using a computer so that the image 5 of the scattering plate 6 can be reproduced when receiving specific reproduction illumination light instead of the reflective volume hologram. The speckle contrast in the case of using the relief type hologram as a computer-generated hologram (CGH) having a ratio of 3.7% was (Condition 2). In HDTV (high-definition television) video display applications, a speckle contrast of 6.0% or less is a standard (for example, WO / 2001/081996) as a level at which an uneven brightness pattern is hardly recognized when an observer observes with the naked eye. The basic form described above sufficiently satisfies this standard. In addition, when actually observed with the naked eye, brightness unevenness (brightness unevenness) that could be visually recognized did not occur.

  On the other hand, when the laser light from the laser light source is shaped into a parallel light beam and incident on the spatial light modulator 30, that is, the spatial light modulator 30 of the projection display apparatus 10 shown in FIG. When the coherent light from the laser light source 61a was made incident as a parallel light beam without passing through 65 or the optical element 50, the speckle contrast was 20.7% (Condition 3). Under these conditions, a spot-like luminance unevenness pattern was observed quite noticeably by visual observation.

  Further, when the light source 61a is replaced with a green LED (non-coherent light source) and light from the LED light source is incident on the spatial light modulator 30, that is, the projection-type image display apparatus 10 shown in FIG. When the non-coherent light from the LED light source is incident as a parallel light beam on the spatial light modulator 30 without using the scanning device 65 or the optical element 50, the speckle contrast is 4.0% (condition 4). . Under these conditions, brightness unevenness (brightness unevenness) that could be visually recognized by naked eye observation did not occur.

  The results of Condition 1 and Condition 2 were much better than the results of Condition 3, and were also better than the measurement results of Condition 4. As already mentioned, the problem of speckle generation is a problem inherent in the case of using a coherent light source such as a laser beam in practice, and it is necessary to consider in an apparatus using a non-coherent light source such as an LED. There is no problem. In addition, in condition 1 and condition 2, as compared with condition 4, an optical element 50 that can cause speckles is added. From these points, it can be said that Condition 1 and Condition 2 were sufficient to cope with speckle defects.

  In addition, according to the embodiment described above, the following advantages can be obtained.

  According to the embodiment described above, coherent light incident on each position of the hologram recording medium 55 illuminates the same illuminated area LZ by generating the image 5 of the scattering plate 6 at the same position. The spatial light modulator 30 is arranged so as to overlap the illuminated area LZ. Therefore, the light diffracted by the hologram recording medium 55 can be used for image formation with high efficiency, and the use efficiency of light from the light source 61a is excellent.

  Further, according to the embodiment described above, the optical element 50 for making speckles inconspicuous also functions as an optical member for shaping and adjusting the beam form of coherent light emitted from the irradiation device 60. obtain. Therefore, the optical system can be reduced in size and simplified.

  Furthermore, according to the embodiment described above, coherent light repeatedly scans a linear path parallel to the rotational axis RAm of the reflecting surface 32a of the digital micromirror device 30 on the hologram recording medium 55, and Corresponding to this configuration, the hologram recording medium 55 has an elongated shape extending in a direction parallel to the rotation axis RAm of the reflecting surface 32a of the digital micromirror device 30. Further, according to the present embodiment, coherent light repeatedly scans a linear path parallel to one side of the rectangular shape forming the modulated image forming surface 31 on the hologram recording medium 55, and corresponds to this configuration. The hologram recording medium 55 has an elongated shape extending in a direction parallel to one side of the rectangular shape forming the modulated image forming surface 31. For this reason, in the projection apparatus in which the optical system defined by the optical path in the projection apparatus 20 is planar, speckles are conspicuous while effectively suppressing the enlargement of the projection apparatus 20. It can be eliminated.

  In addition, in the present embodiment, the projection optical system 25 is disposed on the front surface of the spatial light modulator 30, in other words, at a position facing the spatial light modulator 30 along the normal direction to the modulated image forming surface 31. Has been placed. For this reason, as shown in FIG. 1, the illuminating device 40 moves the modulated image forming surface 31 of the spatial light modulator 30 relative to the normal direction to the modulated image forming surface 31, that is, the front direction. Illuminated from an inclined direction. When the scanning path of the coherent light on the hologram recording medium 55 in combination with such a configuration is parallel to the rotation axis RAm of the reflecting surface 32a of the digital micromirror device 30, the following description will be given. As described above, the hologram recording medium 55 can stably diffract the light from the irradiation device 60 toward the spatial light modulator 30 with high diffraction efficiency.

  First, for convenience of understanding, as shown in FIG. 4, an XY coordinate system is defined on the modulated image forming surface 31 of the spatial light modulator 30. In this XY coordinate system, the Y axis is a direction parallel to the rotation axis RAm of the micromirror 32, and the X axis is parallel to the direction on the modulation image forming surface 31 orthogonal to the Y axis. If expressed using this coordinate system, the scanning path of the coherent light on the hologram recording medium 55 in the above-described embodiment is parallel to the Y axis.

  As described above, from the viewpoint of reducing the size of the projection device 20, the optical system defined by the optical path in the projection device 20 is formed on the virtual plane, and the virtual plane is the micromirror 32. Is orthogonal to the rotation axis RAm. In this case, the hologram recording medium 55 constituting the optical element 50 is disposed at a position shifted in the X-axis direction from the front of the spatial light modulator 30 because the projection optical system 25 is disposed in front of the spatial light modulator 30. Is done.

  Here, since the areas illuminated by the diffracted light from each position of the hologram recording medium 55 need to overlap each other at least in part, that is, the same illuminated area LZ needs to be illuminated. The direction of the interference fringes recorded in the hologram recording medium 55 is different at each position on the scanning path. Then, as in the present embodiment, the hologram recording medium 55 is disposed at a position shifted in the X-axis direction with respect to the spatial light modulator 30, and the scanning path of the coherent light on the hologram recording medium 55 is When parallel to the Y-axis direction, a change in the direction of interference fringes recorded at each position along the scanning path of the hologram recording medium 55 can be minimized. For this reason, the production of the hologram recording medium 55, more specifically, the recording of interference fringes can be made relatively easy. In addition, the hologram recording medium 55 can efficiently generate coherent light from the irradiation device 60. And the spatial light modulator 30 can be illuminated brightly.

  On the other hand, when the scanning path of the coherent light on the hologram recording medium 55 is inclined with respect to the Y-axis direction, the direction of interference fringes recorded at each position along the scanning path of the hologram recording medium 55 changes. growing. In particular, the hologram recording medium 55 is disposed at a position shifted in the X-axis direction with respect to the spatial light modulator 30, and the scanning path of coherent light on the hologram recording medium 55 is parallel to the X-axis direction. The direction of the interference fringes recorded on the hologram recording medium 55 is very different between one end and the other end of the linear scanning path. Furthermore, at the position farthest from the spatial light modulator 30 in the linear scanning path, the diffraction direction becomes a direction that is greatly inclined from the front direction.

  When the direction of interference fringes to be recorded on one hologram recording medium 55 changes greatly as described above, all interference fringes are not necessarily Bragg conditions if the incident / exit angles are adjusted in consideration of material shrinkage and reproduction wavelength shift. Will not be satisfied. In addition, the hologram recording medium 55 used here records interference fringes having a complex pattern that can exhibit a light diffusion function, and thus such a tendency is more likely to appear. If the planned interference fringes do not sufficiently satisfy the Bragg condition at the reproduction wavelength, the hologram recording medium can no longer exhibit high diffraction efficiency, and the spatial light modulator 30 can be illuminated brightly. Can not. In addition, the energy efficiency of the entire apparatus also decreases, which is not preferable in this respect.

  Further, when the hologram recording medium 55 is produced by actually exposing the hologram photosensitive material 58 described above, the reference light having a wavelength different from the wavelength of the coherent light generated by the light source 61a mounted on the projection device 20 is used. It is also assumed that Lr and object light Lo are used. In order to realize high diffraction efficiency, it is necessary to expose the hologram photosensitive material 58 using a high-power light source, while the wavelength of light that can be generated by a high-power light source that can be used for exposure is This is because it is limited. When the hologram photosensitive material 58 is exposed using the reference light Lr and the object light Lo having a wavelength different from the wavelength of the coherent light generated by the light source 61a of the projection device 20, recording is performed according to the wavelengths of the reference light Lr and the object light Lo. The reference light Lr and the object light Lo irradiate the hologram photosensitive material 58 along an optical path deviated from the planned optical path of the coherent light in the projection apparatus 20 so that the Bragg condition of the interference fringes that can be performed is satisfied. Is done. At this time, when the direction of the interference fringes to be recorded changes greatly between the hologram recording media 55 along the scheduled scanning path, the reference light Lr and the object light Lo that can be oscillated at high output are actually generated. The resulting light may not be able to satisfy the Bragg condition at all positions along the scheduled scan path. That is, interference fringes cannot be recorded using exposure light that can be oscillated at a high output. As a result, interference fringes whose direction at each position along the scanning path greatly changes cannot be clearly and accurately recorded, and the diffraction efficiency of the hologram recording medium 55 is lowered.

  From the above, according to the above-described embodiment in which the scanning path of the coherent light on the hologram recording medium 55 is parallel to the rotation axis RAm of the reflecting surface 32a of the digital micromirror device 30, the hologram recording is performed. Since the change in the direction of the interference fringes recorded at each position along the scanning path of the medium 55 is suppressed, the interference fringes can be clearly and accurately recorded. Therefore, the hologram recording medium 55 can stably diffract the light from the irradiation device 60 toward the spatial light modulator 30 with high diffraction efficiency. As a result, the hologram recording medium 55 can diffract the light from the irradiation device 60 with high efficiency, and the spatial light modulator 30 can be illuminated brightly.

[Modification to the above-described embodiment]
Various modifications can be made to the embodiment illustrated in FIGS.
Hereinafter, an example of modification will be described with reference to the drawings. In the drawings used in the following description, the same reference numerals as those used for the corresponding parts in the above-described embodiment are used, and redundant descriptions are omitted.

(Lighting device)
According to the embodiment described above, speckle can be effectively made inconspicuous. However, this effect is mainly due to the lighting device 40. Therefore, the lighting device 40 can be usefully used in various aspects. For example, the illumination device 40 can be used as simple illumination, and in this case, unevenness in brightness (luminance unevenness, flicker) can be made inconspicuous.

  Moreover, you may change the whole structure of the illuminating device 40. FIG. For example, a deflection element that changes the traveling direction of coherent light may be provided. FIG. 7 shows an example in which a deflecting element 70 is disposed between the spatial light modulator 30 and the projection optical system 25. The example shown in FIG. 7 differs from the above-described embodiment in that the polarizing element 70 is provided, and other points can be configured identically. Hereinafter, the modified example shown in FIG. 7 will be further described focusing on the differences from the above-described embodiment.

  In the modification shown in FIG. 7, the deflection element 70 is disposed between the optical element 50 and the spatial light modulator 30 in the optical path from the light source 61 a of the irradiation device 60 to the spatial light modulator 30 of the coherent light. ing. The deflection element 70 is formed by a first prism 71 and a second prism 72. The pair of prisms 71 and 72 are arranged at a substantially constant interval, and a gap 73 is formed between them. The first prism 71 has a first surface 71 a that faces the spatial light modulator 30, a second surface 71 b that faces the second prism 72, and a third surface 71 c that receives light from the optical element 50. ing. The second prism 72 has a symmetrical shape with the first prism 71 and is arranged symmetrically with the first prism 71. Therefore, the second prism 72 has a first surface 72a facing the projection optical system 25, a second surface 72b facing the first prism 71, and a surface on the opposite side of the third surface 71c of the first prism 71. The third surface 72c is formed.

  The deflecting element 70 directs the diffused light beam shaped by diffraction at each position of the hologram recording medium 55 to the spatial light modulator 30. Specifically, the light incident from the third surface 71c of the first prism 71 is reflected by the second surface 71b of the first prism 71, and then enters the spatial light modulator 30 via the first surface 71a. It becomes like this. The configuration and arrangement of the optical element 50 are such that the reflection on the second surface 71b of the first prism 71 is total reflection due to the refractive index difference between the first prism 71 and the gap 73. It is determined. Therefore, the light incident on the deflecting element 70 from the optical element 50 changes its traveling direction as planned without causing a light amount loss.

  The light incident on the spatial light modulator 30 then passes through the deflecting element 70 toward the projection optical system 25 as light forming a modulated image without being totally reflected by the second surface 71b of the first prism 71. The second surface 71b of the first prism 71 and the second surface 72b of the second prism 72 are parallel, and the first surface 71a of the first prism 71 and the first surface 72a of the second prism 72 are parallel. When parallel, the traveling direction of light when entering the projection optical system 25 from the deflecting element 70 is maintained parallel to the traveling direction when reentering the deflecting element 70 from the spatial light modulator 30. become.

  In the modification shown in FIG. 7, unnecessary light that does not form a modulated image reenters the deflecting element 70 and then exits from the deflecting element 70 via the third surface 72 c of the second prism 72. It is absorbed by a simple element.

  By the way, in the example shown in FIG. 7, the deflecting element 70 that reflects the coherent light from the optical element 50 is on the surface parallel to the normal direction to the second surface 71 b of the first prism 71. To an optical system (center optical path) of the optical path from to the spatial light modulator 30. As described above, the digital micromirror display 30 defines the optical system (center optical path) of the optical path before and after being reflected by the digital micromirror display 30 on a plane orthogonal to the rotation axis RAm of the reflecting surface 32a. obtain. In the example shown in FIG. 7, the normal direction to the second surface 71 b of the first prism 71 is located on a plane orthogonal to the rotation axis RAm of the reflecting surface 32 a of the digital micromirror display 30. As described above, the deflection element 70 and the digital micromirror display 30 are positioned. As a result, the optical system (optical path center) formed by the optical path in the projection device 20 can be formed on one virtual plane.

  According to the modification shown in FIG. 7, the same operational effects as those of the above-described embodiment can be obtained. That is, the hologram recording medium 55 of the optical element 50 diffracts the coherent light incident on each position of the hologram recording medium 55 so as to scan the hologram recording medium 55, and illuminates the spatial light modulator 30. . At this time, each position of the spatial light modulator 30 is continuously irradiated with coherent light from different directions as the coherent light is scanned on the hologram recording medium 55, and as a result, the screen 15 The incident angle of the image light at each position also changes continuously. For this reason, speckles can be made inconspicuous while displaying an image with coherent light.

  Further, in the modification shown in FIG. 7, the coherent light is a linear path parallel to the rotation axis RAm of the reflecting surface 32 a of the digital micromirror device that forms the spatial light modulator 30 on the hologram recording medium 55. And the hologram recording medium 55 has an elongated shape extending in a direction parallel to the rotation axis RAm of the reflecting surface 32a of the digital micromirror device 30 corresponding to this configuration, or The coherent light repeatedly scans a linear path parallel to one side of the rectangular shape forming the modulated image forming surface 31 on the hologram recording medium 55, and the hologram recording medium 55 is modulated in accordance with this configuration. In the case of an elongated shape extending in a direction parallel to one side of the rectangular shape forming the image forming surface 31, the image is formed by the optical path in the projection device 20. In the projection device 20 that the optical system has a planar shape that is, while it effectively suppressed that would by size of the projection apparatus 20, it is possible to obscure the speckles.

  Further, in the modification shown in FIG. 7, the scanning path of the coherent light on the hologram recording medium 55 is parallel to the rotation axis RAm of the reflecting surface 32 a of the digital micromirror device forming the spatial light modulator 30. In this case, the hologram recording medium 55 can stably diffract the light from the irradiation device 60 toward the spatial light modulator 30 with high diffraction efficiency. As a result, the hologram recording medium 55 can diffract the light from the irradiation device 60 with high efficiency, and the spatial light modulator 30 can be illuminated brightly.

  In the modification shown in FIG. 7, as described above, the optical system (optical path center) formed by the optical path in the projection device 20 is directed to the second surface 71 b of the first prism 71 of the deflection element 70. In other words, the normal direction to the reflecting surface 71b of the first prism 71 of the deflecting element 70, and the normal direction to the modulated image forming surface 31 of the spatial light modulator 30, in other words, spatial light modulation. It is located on one virtual plane defined by the normal direction to the incident surface of the container 30. The rotation axis RAm of the reflecting surface 32 a of the digital micromirror device 30 is normal to the second surface 71 b of the first prism 71 of the deflecting element 70 and the normal to the incident surface of the spatial light modulator 30. And one direction perpendicular to one virtual plane defined by the direction.

Therefore, in other words, the coherent light is reflected on the hologram recording medium 55 in the direction normal to the incident surface (modulated image forming surface) 31 of the spatial light modulator 30 and the reflecting surface (first prism 71 of the deflection element 70). (Second surface) A linear path parallel to the direction perpendicular to both the normal direction to 71b is repeatedly scanned, and the hologram recording medium 55 corresponds to this configuration. Elongate in a direction perpendicular to both the normal direction to the incident surface (modulated image forming surface) 31 and the normal direction to the reflecting surface (second surface) 71b of the first prism 71 of the deflection element 70. In the projection device 20 in which the optical system defined by the optical path in the projection device 20 is planar, the enlargement of the projection device 20 is effectively suppressed. Speckle It is possible to inconspicuous. Further, the scanning path of the coherent light on the hologram recording medium 55 includes the normal direction to the incident surface (modulated image forming surface) 31 of the spatial light modulator 30 and the reflecting surface of the first prism 71 of the deflecting element 70 ( If it is parallel to the direction perpendicular to both the normal direction to the second surface 71b, the hologram recording medium 55 directs the light from the irradiation device 60 toward the spatial light modulator 35 and performs high diffraction. It becomes possible to diffract stably and efficiently. As a result, the hologram recording medium 55 can diffract the light from the irradiation device 60 with high efficiency, and the spatial light modulator 30 can be illuminated brightly.
Such effects can be achieved even when the spatial light modulator 30 is composed of a device other than the digital micromirror device, such as a liquid crystal display device.

(Spatial light modulator, projection optical system, screen)
According to the embodiment described above, speckle can be effectively made inconspicuous. However, this effect is mainly due to the lighting device 40. Even if this lighting device 40 is combined with various known spatial light modulators, projection optical systems, screens, etc., speckles can be effectively made inconspicuous. From this point, the spatial light modulator, the projection optical system, and the screen are not limited to those illustrated, and various known members, components, devices, and the like can be used. For example, as described above, the spatial light modulator 30 may be configured as a transmissive spatial light modulator including a transmissive liquid crystal display or the like.

  Further, as shown in FIG. 8, a reflective spatial light modulator made of LCOS (Liquid Crystal on Silicon) may be used as the spatial light modulator 35. The example shown in FIG. 8 is different from the above-described embodiment in that the spatial light modulator 35 is changed to LCOS and a polarizing element 75 is provided, and the other points are the same. obtain. Hereinafter, the modified example shown in FIG. 8 will be further described focusing on the differences from the above-described embodiment.

  In the modification shown in FIG. 8, the spatial light modulator 35 is configured as a reflective spatial light modulator made of LCOS (Liquid Crystal on Silicon). The LCOS 35 is a reflective liquid crystal element, and forms a modulated image using light of one linearly polarized light component that vibrates in one direction among incident light. More specifically, the LCOS 35 converts the incident light of one linearly polarized light component into the light of the other linearly polarized light component that vibrates in the other direction orthogonal to the one direction, in other words, the one of the linearly polarized light components. Is converted into the light of the other linearly polarized light component whose phase is shifted by 180 °. The light converted from one linear polarization component to the other linear polarization component in the LCOS 35 is reflected toward the projection optical system 25. On the other hand, the light of the other linearly polarized component incident on the LCOS 35 and the light incident on the LCOS 35 as one linearly polarized component but not converted to the other polarized component are absorbed by the LCOS 35 and used to form a modulated image. Not.

  In the modification shown in FIG. 8, a deflection element 75 made of a polarization beam splitter is used in combination with the spatial light modulator 35 made of LCOS. The polarization beam splitter 75 is an optical element that reflects one linearly polarized component and transmits the other linearly polarized component. As a specific configuration, in the example shown in FIG. 8, the polarization beam splitter 75 is bonded with two right-angle prisms so that their slopes face each other with a dielectric multilayer film expressing a polarization separation function in between. It is configured as a rectangular parallelepiped or cubic element. In the polarization beam splitter 75, the dielectric multilayer film disposed between the right-angle prisms functions as a separation surface (reflection surface) 76 that reflects the linearly polarized light component oscillating in one direction.

  In the modification shown in FIG. 8, a deflection element 75 made up of a polarization beam splitter is disposed between the spatial light modulator 35 and the projection optical system 25. In the modification shown in FIG. 8, the polarization beam splitter 75 that reflects the coherent light from the optical element 50 has a spatial light modulator from the optical element 50 on a plane parallel to the normal direction to the separation surface 76. Define an optical system (central optical path) with up to 35 optical paths. On the other hand, since the LCOS 35 functions as a reflection surface that regularly reflects (specular reflection) the light forming the modulated image, the LCOS 35 is reflected by the LCOS 35 on a plane parallel to the normal direction to the incident surface. Define the optical system (center optical path) of the front and rear optical paths. In the example shown in FIG. 8, the normal direction nda to the incident surface 36 of the LCOS 35 and the normal direction ndb to the separation surface 76 of the polarization beam splitter 75 are located on the same virtual plane. Thus, the polarization beam splitter 75 and the LCOS 35 are positioned. As a result, the optical system (optical path center) formed by the optical path in the projection device 20 can be formed on one virtual plane.

  According to the modification shown in FIG. 8, the same operational effects as those of the above-described embodiment can be obtained. That is, the hologram recording medium 55 of the optical element 50 diffracts the coherent light incident on each position of the hologram recording medium 55 so as to scan the hologram recording medium 55, and illuminates the spatial light modulator 35. . At this time, each position of the spatial light modulator 35 is continuously irradiated with the coherent light from different directions as the coherent light is scanned on the hologram recording medium 55, and as a result, the screen 15 The incident angle of the image light at each position also changes continuously. For this reason, speckles can be made inconspicuous while displaying an image with coherent light.

  Further, in the modification shown in FIG. 8, the coherent light is deflected on the hologram recording medium 55 in the normal direction nda to the incident surface (modulated image forming surface) 36 of the LCOS forming the spatial light modulator 35. A linear path parallel to the direction perpendicular to both the normal direction ndb to the separation surface (reflection surface) 76 of the polarization beam splitter forming the element 75 is repeatedly scanned, and in correspondence with this configuration, The hologram recording medium 55 has an elongated shape extending in a direction orthogonal to both the normal direction nda to the incident surface 36 of the LCOS 35 and the normal direction ndb to the separation surface (reflection surface) 76 of the polarization beam splitter 75. Or coherent light repeatedly scans a linear path parallel to one side of the rectangular surface forming the incident surface 36 on the hologram recording medium 55 and Corresponding to the configuration, when the hologram recording medium 55 has an elongated shape extending in a direction parallel to one side of the rectangular shape forming the incident surface 36, the optical system defined by the optical path in the projection device 20 is In the projection device 20 having a planar shape, speckles can be made inconspicuous while effectively preventing the projection device 20 from becoming large.

  Further, in the modification shown in FIG. 8, the scanning path of the coherent light on the hologram recording medium 55 includes a normal direction nda to the incident surface 36 of the LCOS forming the spatial light modulator 35 and a deflection element 75. The hologram recording medium 55 spatially modulates the light from the irradiation device 60 if it is parallel to the direction perpendicular to the normal direction ndb to the separation surface (reflection surface) 76 of the polarization beam splitter formed. It becomes possible to diffract stably toward the device 35 with high diffraction efficiency. As a result, the hologram recording medium 55 can diffract the light from the irradiation device 60 with high efficiency, and the spatial light modulator 35 can be illuminated brightly.

(Irradiation device)
In the above-described embodiment, the example in which the coherent light scans on the hologram recording medium 55 along the linear path is shown, but the present invention is not limited to this. For example, in the above-described embodiment and the modification shown in FIG. 7, the coherent light is elongated on the hologram recording medium 55 and extends in a direction parallel to one side of the rectangular shape forming the modulation image forming surface 31. The area may be scanned. Such a modification also makes it possible to make speckles inconspicuous while effectively suppressing an increase in the size of the projection device 20. Alternatively, in the embodiment described above and the modification shown in FIG. 7, the coherent light extends on the hologram recording medium 55 in a direction parallel to the rotation axis RAm of the reflection surface 32 a of the digital micromirror device 30. You may make it scan in the elongate area | region. Even with such a modification, it is possible to make the speckle inconspicuous while effectively suppressing an increase in the size of the projection device 20, and the hologram recording medium 55 is provided from the irradiation device 60. Light can be diffracted stably toward the spatial light modulator 30 with high diffraction efficiency. Furthermore, in the modification shown in FIG. 8, the coherent light is polarized on the hologram recording medium 55 by a polarization beam splitter that forms a deflection element 75 with a normal direction nda to the incident surface 36 of the LCOS that forms the spatial light modulator 35. You may make it scan the inside of the elongate area | region extended in the direction orthogonal to both directions with respect to the normal line direction ndb to the separation surface 76 of this. Even with such a modification, it is possible to make the speckle inconspicuous while effectively suppressing an increase in the size of the projection device 20, and the hologram recording medium 55 is provided from the irradiation device 60. Light can be diffracted stably toward the spatial light modulator 30 with high diffraction efficiency.

  In order to be able to scan the area on the hologram recording medium 55, two or more intersecting each other instead of the mirror device 66 that can be rotated only about one axial direction in the embodiment described above. A mirror device that can rotate about the axis RA1 may be used. Further, the scanning device 65 may include two or more mirror devices 66. In this case, even if the mirror 66a of the mirror device 66 can be rotated only about a single axis, the incident point IP of the coherent light from the irradiation device 60 to the optical element 50 is expressed by the hologram recording medium 55. It can be moved in a two-dimensional direction on the plate surface.

  Specific examples of the mirror device 66a included in the scanning device 65 include a MEMS mirror and a polygon mirror.

  The scanning device 65 may be configured to include a reflection device that changes the traveling direction of coherent light by reflection, for example, a device other than the mirror device 66 described above. For example, the scanning device 65 may include a refractive prism, a lens, and the like.

  In the first place, the scanning device 65 is not essential, and the light source 61a of the irradiation device 60 can be displaced with respect to the optical element 50. For example, the light source 61a is configured to move, swing, and rotate. The coherent light irradiated from the above may be scanned on the hologram recording medium 55.

  Furthermore, although the light source 61a of the irradiation device 60 has been described on the assumption that the laser light shaped as a linear light beam is oscillated, the present invention is not limited to this. In particular, in the above-described form, the coherent light irradiated to each position of the optical element 50 is shaped by the optical element 50 into a light beam that enters the entire illuminated area LZ. Therefore, there is no inconvenience even if the coherent light irradiated to the optical element 50 from the light source 61a of the irradiation device 60 is not accurately shaped. For this reason, the coherent light generated from the light source 61a may be diverging light. Further, the cross-sectional shape of the coherent light generated from the light source 61a may be an ellipse or the like instead of a circle. Furthermore, the transverse mode of the coherent light generated from the light source 61a may be a multimode.

  When the light source 61a generates a divergent light beam, the coherent light is incident not on a point but in a region having a certain area when entering the hologram recording medium 55 of the optical element 50. In this case, the light diffracted by the hologram recording medium 55 and incident on each position of the illuminated area LZ is multiplexed in angle. In other words, at each moment, coherent light is incident on each position of the illuminated area LZ from a certain angle range. Speckle can be made more inconspicuous by such multiplexing of angles.

  Furthermore, although the irradiation apparatus 60 showed the example which injects coherent light into the optical element 50 so that the optical path of one light ray contained in a divergent light beam may be followed in the form mentioned above, it is not restricted to this. For example, as shown in FIG. 9, the scanning device 65 may further include a condensing lens 67 disposed on the downstream side of the mirror device 66 along the optical path of the coherent light. In this case, as shown in FIG. 9, the light from the mirror device 66 that travels along the optical path of the light beam constituting the divergent light beam becomes light that travels in a certain direction by the condenser lens 67. That is, the irradiation device 60 causes the coherent light to be incident on the optical element 50 so as to follow the optical path of the light beam constituting the parallel light flux. In such an example, a parallel light beam is used as the reference light Lr instead of the above-described convergent light beam in the exposure process when the hologram recording medium 55 is manufactured. Such a hologram recording medium 55 can be produced and duplicated more easily.

  In the above-described embodiment, an example in which the irradiation device 60 includes only a single laser light source 61a has been described. For example, the irradiation device 60 may include a plurality of light sources that oscillate light in the same wavelength region. In this case, the illumination device 40 can illuminate the illuminated area LZ more brightly. Further, coherent lights from different solid laser light sources do not have coherence with each other. Therefore, the multiplexing of the scattering pattern further proceeds and the speckle can be made less noticeable.

  Further, the irradiation device 60 may include a plurality of light sources that generate coherent light in different wavelength regions, or may include a single light source that generates a plurality of coherent lights in different wavelength regions. . According to this example, a color that is difficult to display with a single laser beam can be generated by additive color mixing, and the illuminated area LZ can be illuminated with that color. Further, in this case, in the projection device 20 or the transmissive image display device 10, the spatial light modulator 30 includes, for example, a color filter, and a modulated image can be formed for each coherent light in each wavelength region. Makes it possible to display images in a plurality of colors. Alternatively, even if the spatial light modulator 30 does not include a color filter, the irradiation device 60 irradiates the coherent light of each wavelength region in a time-sharing manner, and the spatial light modulator 30 is irradiated with the wavelength region. Even when operating in a time-sharing manner so as to form a modulated image corresponding to the coherent light, it is possible to display an image in a plurality of colors. In particular, in the projection device 20 or the transmissive image display device 10, the irradiation device 60 includes a coherent light in a wavelength region corresponding to red light, a coherent light in a wavelength region corresponding to green light, and a wavelength region corresponding to blue light. When it is possible to irradiate white light including the coherent light, it is possible to display an image in full color.

Note that the hologram recording medium 55 included in the optical element 50 has wavelength selectivity.
Therefore, when the irradiation device 60 irradiates coherent light in different wavelength regions, the hologram recording medium 55 includes hologram elements corresponding to the wavelength regions of the coherent light generated by the respective light sources in a stacked state. You may make it. The hologram element for coherent light in each wavelength region is obtained by using, for example, the coherent light in the corresponding wavelength region as exposure light (reference light Lr and object light Lo) in the method already described with reference to FIGS. It can be made by using light. Further, instead of stacking hologram elements in each wavelength region to produce the hologram recording medium 55, the object light Lo and the reference light Lr made of coherent light in each wavelength region are simultaneously exposed to the hologram photosensitive material 58, respectively. A single hologram recording medium 55 may diffract light in a plurality of wavelength ranges.

(Optical element)
In the embodiment described above, an example in which the optical element 50 includes the reflective volume hologram 55 using a photopolymer has been described, but the present invention is not limited thereto. As already described, the optical element 50 may include a plurality of hologram recording media 55. Further, the optical element 50 may include a volume hologram that is recorded using a photosensitive medium including a silver salt material. Further, the optical element 50 may include a transmission type volume hologram recording medium or a relief type (emboss type) hologram recording medium.

  However, in the relief (embossed) hologram, hologram interference fringes are recorded by the concavo-convex structure on the surface. However, in the case of this relief type hologram, the scattering due to the concavo-convex structure on the surface may cause a loss of light amount or a new unintended speckle generation factor. In this respect, the volume type hologram is preferable. In the volume hologram, since the hologram interference fringe is recorded as a refractive index modulation pattern (refractive index distribution) inside the medium, it is not affected by scattering due to the uneven structure on the surface.

  However, in a volume hologram that is recorded using a photosensitive medium containing a silver salt material, scattering by the silver salt particles may cause a loss of light amount or an unintended new speckle generation factor. In this respect, the hologram recording medium 55 is preferably a volume hologram using a photopolymer.

  In addition, in the exposure process shown in FIG. 3, a so-called Fresnel type hologram recording medium is produced. However, a Fourier transform type hologram recording medium obtained by performing recording using a lens may be produced. Absent. However, when a Fourier transform type hologram recording medium is used, a lens may also be used during image reproduction.

  Further, the striped pattern to be formed on the hologram recording medium 55, for example, the refractive index modulation pattern or the uneven pattern, does not use the actual object light Lo and the reference light Lr, but the planned wavelength and incident direction of the reproduction illumination light La. In addition, it may be designed using a computer based on the shape and position of the image to be reproduced. The hologram recording medium 55 obtained in this way is also called a computer-generated hologram. When a plurality of coherent lights having different wavelength ranges are irradiated from the irradiation device 60 as in the above-described modification, the hologram recording medium 55 as a computer-generated hologram corresponds to each coherent light in each wavelength range. The coherent light in each wavelength region may be diffracted in the corresponding region to reproduce an image.

  Furthermore, in the embodiment described above, the optical element 50 expands the coherent light irradiated to each position, and uses the expanded coherent light as a light diffusing element or light diffusing element that illuminates the entire illuminated area LZ. Although the example which has the hologram recording medium 55 was shown, it is not restricted to this. The optical element 50 changes or diffuses the traveling direction of the coherent light irradiated to each position instead of the hologram recording medium 55 or in addition to the hologram recording medium 55, and diffuses the entire illuminated area LZ with coherent light. You may make it have a lens array as a light-diffusion element to illuminate. Specific examples of the lens array that functions as a light diffusing element include a total reflection type or a refractive type Fresnel lens or a fly-eye lens provided with a diffusion function. Note that “diffusion” in the light diffusing element in the present invention means that incident light is angularly expanded in a predetermined direction and emitted, and a diffusion angle by a diffractive optical element such as a hologram recording medium or a lens array is sufficient. In addition to the case where the emission angle is controlled, the case where the emission angle is expanded by scattering particles such as opal glass is also included. Also in such an illuminating device 40, the irradiating device 60 scans the light diffusing element formed of the lens array so that the coherent light scans the optical element 50, and the irradiating device 60 emits the coherent light. The irradiation device 60 and the optical element 50 are configured so that the coherent light incident on each position of the optical element 50 is changed in the traveling direction by the lens array that forms the light diffusing element and illuminates the illuminated area LZ. Thus, speckle can be effectively inconspicuous.

(Lighting method)
In the above-described embodiment, the light diffusing device 60 is configured so that the irradiation device 60 can scan the coherent light on the optical element 50 in a one-dimensional direction, and includes the hologram recording medium 55 of the optical element 50, a lens array, and the like. The element is configured to diffuse the coherent light irradiated to each position in a two-dimensional direction, that is, to spread or diverge, so that the illumination device 40 illuminates the two-dimensional illuminated region LZ. An example is shown. However, as described above, the present invention is not limited to such an example. For example, the irradiation device 60 is configured to be able to scan the coherent light on the optical element 50 in a two-dimensional direction, and A light diffusing element composed of a hologram recording medium 55 or a lens array of the optical element 50 is configured to diffuse, that is, spread or diverge, coherent light irradiated to each position in a two-dimensional direction, Thereby, the illuminating device 40 may illuminate the two-dimensional illuminated area LZ.

  In addition, each of the light diffusing elements configured such that the irradiation device 60 can scan the coherent light on the optical element 50 in a one-dimensional direction, and includes the hologram recording medium 55 and the lens array of the optical element 50 is provided. The coherent light irradiated to the position is configured to diffuse in one dimension, that is, to spread or diverge, so that the illumination device 40 illuminates the one-dimensional illuminated area LZ. Also good. In this aspect, the scanning direction of the coherent light by the irradiation device 60 and the diffusion direction by the light diffusing element composed of the hologram recording medium 55 or the lens array of the optical element, that is, the direction expanded by the light diffusing element are parallel to each other. It may be made to become.

Further, the irradiation device 60 is configured to be able to scan the coherent light on the optical element 50 in a one-dimensional direction or a two-dimensional direction, and is configured from the hologram recording medium 55 of the optical element 50, a lens array, or the like. The diffusing element may be configured to diffuse, that is, spread or diverge the coherent light irradiated to each position in a one-dimensional direction.
In this aspect, as already described, the optical element 50 has a plurality of light diffusing elements composed of the hologram recording medium 55 or a lens array, and sequentially illuminates the illuminated areas LZ corresponding to the light diffusing elements. By doing so, the illumination device 40 may illuminate a two-dimensional area. At this time, each illuminated area LZ may be sequentially illuminated at a speed as if it were illuminated simultaneously by the human eye, or it can be recognized that the illuminated area LZ is also illuminated sequentially by the human eye. It may be illuminated sequentially at such a slow speed.

(Combination of modified examples)
In addition, although the some modification with respect to the basic form mentioned above has been demonstrated above, naturally, it is also possible to apply combining several modifications suitably.

5 Image 6 Scattering plate 10 Projection-type image display device 15 Screen 20 Projection device 25 Projection optical system 30 Spatial light modulator, digital micromirror device 31 Modulated image forming surface, incident surface 32 Micro mirror 32a Reflecting surface 35 Spatial light modulator, LCOS
36 Entrance surface, modulated image forming surface 40 Illumination device 50 Optical element 55 Hologram recording medium 58 Holographic photosensitive material 60 Irradiation device 61 Light source mechanism 61a Light source, laser light source 65 Scan device 66 Mirror device (reflection device)
66a Mirror (reflective surface)
67 condensing lens 70 deflection element 71 first prism 71a first surface 71b second surface 71c third surface 72 second prism 72a first surface 72b second surface 72c third surface 73 gap 75 deflection element, polarization beam splitter 76 separation Surface, reflective surface LZ Illuminated area RAm Rotation axis

Claims (6)

A spatial light modulator having a rectangular modulation image forming surface;
An illumination device for illuminating the spatial light modulator,
The lighting device includes:
An optical element including a light diffusing element that changes a traveling direction of incident light; and
The coherent light scans the light diffusing element and the traveling direction of the coherent light incident on each position of the light diffusing element is changed by the light diffusing element to illuminate the spatial light modulator. An irradiating device for irradiating the optical element with the coherent light, and
Regions on the spatial light modulator illuminated by coherent light incident on each position of the light diffusing element overlap at least in part,
The spatial light modulator is a digital micromirror device including a plurality of reflecting surfaces that can be rotated around rotation axes that are parallel to each other.
The rotation axis of the reflecting surface of the digital micromirror device is parallel to the rectangular short side forming the modulated image forming surface,
The coherent light repeatedly scans a linear path parallel to the rectangular short side forming the modulated image forming surface on the light diffusing element, or the rectangular short forming the modulated image forming surface. A projection device that scans an elongated region extending in a direction parallel to a side. The irradiation apparatus includes a light source, and a scanning device including a reflective surface that reflects coherent light from the light source,
The projection apparatus according to claim 1 , wherein the reflection surface is rotatable about an axis orthogonal to a rectangular short side forming the modulation image forming surface. The light diffuser, the modulated image forming plane wherein the rectangular said forming the a elongated shape extending in the short side direction parallel projection apparatus of claim 1 or 2. The projection device according to claim 1, wherein the light diffusing element is a lens array. The projection apparatus as described in any one of Claims 1-4 further equipped with the projection optical system which projects the light which makes the modulation | alteration image produced | generated by the said spatial light modulator. A projection device according to any one of claims 1 to 5 ;
A projection type image display device comprising: a screen onto which the modulated image generated by the spatial light modulator is projected.

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