JP5700212B2 - Illumination device and projection-type image display device - Google Patents

Description

  The present invention relates to an illumination device that uses coherent light such as laser light, and a projection-type image display device that illuminates a micro display using coherent light and projects an image on a screen.

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

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

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

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

Japanese Patent Laid-Open No. 6-208089

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

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

  By the way, the laser used for the light source may not be aligned with the polarization component of a specific vibration direction depending on the type and situation, or the vibration direction may not be constant even if they are aligned. For example, a gas laser without a Brewster window (polarized components are not aligned), a surface emitting laser (random polarized light: polarized light is aligned but the vibration direction is changed), and the like can be mentioned. When such a laser is used as a light source, light use efficiency is required in applications such as liquid crystal panels and LCOS such as LCOS that require uniform incident polarization, and 3D displays that display parallax images for each polarization component. Various problems such as a decrease in image quality or a decrease in image quality due to crosstalk of polarization components may occur.

  The present invention suppresses speckles generated when coherent light is used as a light source and emits illumination light having a uniform polarization direction, and projection using such illumination light for display image formation It aims at providing a type image display device.

The lighting device according to the present invention includes:
A light source that emits coherent light;
A polarization separator that separates coherent light emitted from the light source in different directions;
An optical scanning unit that scans coherent light separated by the polarization separation unit;
A wave plate disposed in the optical path of any one of the coherent lights separated by the polarization separation unit, and aligning the polarization direction of the coherent light separated by the polarization separation unit;
E Bei and a light diffusing element diffuses the scanned scanning light, diffusing light emitted from each point to illuminate overlapping the illuminated area by the light scanning unit,
The polarization separation unit is a device having birefringence that separates incident light according to a vibration direction of polarized light.

  Further, in the illumination device according to the present invention, the device having birefringence is a birefringent crystal element in which at least one of light incident / exiting surfaces is inclined from a plane perpendicular to the optical axis of the coherent light. It is characterized by being.

Furthermore, in the illumination device according to the present invention, the device having birefringence encloses a birefringent material between two transparent substrates,
It is a device in which prisms having an inclined surface inclined from a surface perpendicular to the optical axis of coherent light are arranged in an array on the surface of the transparent substrate on which light is incident on the birefringent material side. And

Furthermore, in the illumination device according to the present invention, the device having birefringence encloses a birefringent material between two transparent substrates,
It is a device in which prisms having an inclined surface inclined from a surface perpendicular to the optical axis of coherent light are arranged in an array on the surface of the transparent substrate on which light is incident on the birefringent material side. And

  Furthermore, in the illumination device according to the present invention, the light diffusing element is a hologram.

  Furthermore, the illumination device according to the present invention is characterized in that the hologram records an image of a second light diffusing element.

  Furthermore, in the illumination device according to the present invention, the hologram is any one of a transmission hologram and a reflection hologram.

  Furthermore, in the illumination device according to the present invention, the light diffusion element is a diffusion plate.

  Furthermore, in the illumination device according to the present invention, the light diffusing element is a lens array.

A projection display apparatus according to the present invention is also provided:
A light source that emits coherent light;
A polarization separator that separates coherent light emitted from the light source in different directions;
An optical scanning unit that scans coherent light separated by the polarization separation unit;
A wave plate disposed in the optical path of any one of the coherent lights separated by the polarization separation unit, and aligning the polarization direction of the coherent light separated by the polarization separation unit;
A light modulation element having an image forming region on which an image is formed;
A light diffusing element that diffuses the scanning light scanned by the light scanning unit, and diffused light emitted from each point illuminates the image forming region;
A projection optical system that projects an image of the light modulation element onto a screen ,
The polarization separation unit is a device having birefringence that separates incident light according to a vibration direction of polarized light.

  According to the illumination device of the present invention, by scanning the coherent light with the optical scanning unit, the diffused light from each point of the light diffusing element irradiates the illuminated region at different angles in time, It is possible to change speckles generated in the region with time to make the viewer invisible. Furthermore, in the projection type image display apparatus of the present invention, speckles generated on the screen can be effectively suppressed by irradiating the screen at different angles in time.

  Furthermore, by aligning the polarization components using the polarization separation unit and the wave plate, it is possible to improve the light utilization efficiency in optical elements having polarization selectivity, such as light modulation elements and holograms, and to reduce image quality such as crosstalk. It becomes possible to suppress. Since the polarization conversion can be performed in the state of a laser beam, the optical system can be miniaturized.

The figure which shows the structure of the projection type video display apparatus provided with the illuminating device which concerns on embodiment of this invention. The figure which shows the structure of the illuminating device which concerns on embodiment of this invention. The figure which shows the mode of the hologram creation used with the illuminating device which concerns on embodiment of this invention. The figure which shows the mode of the optical scanning which concerns on embodiment of this invention. The figure which shows the mode of the optical scanning which concerns on other embodiment of this invention. The figure which shows an example of the polarization separation part which concerns on embodiment of this invention The figure which shows an example of the polarization separation part which concerns on embodiment of this invention The figure which shows an example of the polarization separation part which concerns on embodiment of this invention The figure which shows the structure of the projection type video display apparatus provided with the illuminating device (no condensing optical system) which concerns on other embodiment. The figure which shows the illumination area | region in other embodiment (no condensing optical system) The figure which shows the structure of the projection type video display apparatus provided with the illuminating device which concerns on other embodiment. The figure which shows the structure of the illuminating device which concerns on other embodiment. The figure which shows the mode of the hologram creation used with the illuminating device which concerns on other embodiment.

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

  The projection-type image display device 10 of this embodiment includes a lighting device 20, a light modulation element 31 for forming an image, and a projection optical system 32 that projects an image formed by the light modulation element 31 onto a screen 41. Yes. In the figure, the screen 41 on which an image is projected is an XY plane, and an axis perpendicular to the XY plane is a Z axis. As the screen 41, either a reflective screen for observing an image reflected by the screen 41 or a transmissive screen for observing an image transmitted through the screen 41 can be used.

  The illumination device 20 of the present embodiment includes a light source 11, a polarization separation unit 12, a λ / 2 wavelength plate 13 (wavelength plate), a condensing optical system 14, an optical scanning unit 15, and a hologram 21 (light diffusing element). It is configured.

  As the light source 11, various laser devices such as a semiconductor laser device that emits laser light as coherent light are used. The polarization separation unit 12 is an optical device having birefringence, and separates incident light according to the polarization vibration direction. In the present embodiment, the coherent light L0 emitted from the light source 11 and having no uniform polarization component is separated into coherent light of s-polarization component and p-polarization component of coherent light whose vibration direction is shifted by 90 ° from the s-polarization component. And emit in different directions. Various types of forms can be used for the polarization separation unit 12, and details will be described later.

  The λ / 2 wavelength plate 13 (wavelength plate) is arranged to align the polarization directions of the two coherent lights emitted from the polarization separation unit 12, and is one of the two coherent lights separated from each other. It arrange | positions in one optical path. In the present embodiment, the light is disposed in the optical path of one coherent light emitted from the polarization separation unit 12. The half-wave plate 13 may be attached to the exit surface of the polarization separation unit 12. By integrating the λ / 2 wavelength plate 13 and the polarization separation unit 12, the number of parts is reduced and the layout is simplified.

  The coherent light L1 transmitted through the λ / 2 wavelength plate 13 is aligned in polarization direction with the other coherent light L1 ′ emitted from the polarization separation unit 12. At this time, the polarization direction is preferably matched with the polarization direction of the light modulation element 31 disposed in the later optical path. Furthermore, when a hologram having polarization selection characteristics is used as the light diffusing element 21, it is preferable to set the polarization direction in consideration of the polarization direction. The two coherent lights L1 and L1 ′ having the same polarization direction are arranged in the optical path of the two coherent lights L1 and L1 ′, and are configured to be condensed at one point of the optical scanning unit 15. .

  The optical scanning unit 15 is a mirror device that can rotate the reflection surface around the rotation center Ra, and mechanically rotates a movable mirror such as a polygon mirror, a galvano scanner, or a MEMS scanner. Is used. In addition, various forms such as an acousto-optic effect scanner that modulates the refractive index can be employed.

One coherent light L1 and the other coherent light L1 ′ transmitted through the λ / 2 wavelength plate 13 are condensed by the condensing optical system 14 and incident on the reflection surface of the optical scanning unit 15. At this time, it is preferable that both the coherent lights L1 and L1 ′ are condensed on one point (hereinafter also referred to as “reference point”) on the reflecting surface with little positional fluctuation when the optical scanning unit 15 rotates. By making both coherent lights L1 and L1 ′ incident on such a reference point, the scanning range of the light diffusing element 21 by each of the coherent lights L1 and L1 ′ becomes different. In this way, a common reference point is provided. This facilitates the design of the light diffusing element 21. Specifically, when a hologram is used for the light diffusing element 21, it is possible to set the condensing position of the reference light used when creating the hologram as a reference point of the optical scanning unit 15, and to reproduce the recorded hologram It is also possible to reliably obtain an image.

  The two coherent lights L 1 and L 1 ′ reflected by the light scanning unit 15 in this way become the scanning light La, and scan the incident surface of the light diffusing element 21 while changing its position temporally. FIG. 2 is a diagram illustrating a configuration of the illumination device 20 according to the embodiment of the present invention, and is a diagram illustrating a state of illumination by the light diffusing element 21. Actually, the optical scanning unit 15 reflects the two coherent lights L1 and L1 ′ having different incident angles. However, in order to facilitate the explanation in each figure, the time of either one of the coherent lights is determined. Only the rays at t1 and t2 are shown. In the present embodiment, the coherent lights L1 and L1 ′ separated by the polarization separation unit 12 take different optical paths, but are reflected at the reference point of the optical scanning unit 15, and the same incident angle at each point on the light diffusing element 21. Because there is no incident, there is no problem.

  Here, the light diffusing element 21 scanned with the scanning light by the optical scanning unit 15 will be described. The light diffusing element 21 is an optical element that illuminates the illuminated area, in the case of this embodiment, the entire image forming area of the light modulation element 31 when the scanning light La is incident thereon. In this embodiment, the light diffusing element 21 is transmissive. Type holograms are used. Employing a hologram as the light diffusing element 21 makes it possible to always obtain the same reproduced image regardless of the incident position of the scanning light La, and illuminates the entire light modulation element 31 serving as an illuminated area without unevenness. be able to. Further, the beam cross-sectional shape of the scanning light La incident on the hologram or the incident angle thereof can be given freedom, and the layout of the apparatus can be made flexible.

  The light diffusing element 21 is not limited to such a hologram, but may be any optical element that allows the diffused light emitted from each point to illuminate the illuminated area. It is preferable to illuminate the entire illumination area. For example, a lens array in which fine lenses are arranged in an array, or a so-called normal diffusion plate such as opal glass, ground glass, or a resin diffusion plate may be used. 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 the diffusion angle is sufficiently controlled like a diffractive optical element or a lens array. Not only the case but also the case where the emission angle is expanded by scattering particles such as opal glass is included.

  The transmission hologram as the light diffusing element 21 used in the present embodiment reproduces the diffusion plate image 22i as a recorded reproduction image. As shown in FIG. 2, the coherent light L <b> 1 scanned by the optical scanning unit 15 is reflected by the rotating optical scanning unit 15 and becomes a scanning light La to scan back and forth on the incident surface of the light diffusing element 21. . The figure shows the state of the scanning lights La (t1) and La (t2) at certain times t1 and t2. The light diffusing element 21 of the present embodiment uses a transmission hologram that forms a reproduced image with respect to light (reproduced illumination light) having a predetermined incident angle. The scanning light La scanned by the optical scanning unit 15 is set to be reproduction illumination light for the transmission hologram at any scanning position. The creation of a transmission hologram used in this embodiment will be described later.

As shown in FIG. 2, the scanning light La (t1) at time t1 emits illumination light Lb (t1) as reproduction light at the light diffusing element 21 to form a diffusion plate image 22i. Further, the scanning light La (t2) at time t2 emits the illumination light Lb (t2) by the light diffusing element 21 to form the same diffusing plate image 22i. By scanning the scanning light La in this way, a diffusion plate image 22i is formed when any incident position of the light diffusing element 21 is irradiated. By positioning the diffusion plate image 22i so as to include the entire illuminated area, the entire illuminated area can be illuminated uniformly at any scanning position.

  FIG. 3 is a diagram showing a configuration (interference exposure) when recording (creating) a transmission hologram used in the illumination device according to the embodiment of the present invention. Laser light is irradiated from the back side of the diffusion plate 2, and the object light Ob diffused forward is incident from one surface of the hologram recording material 24. At that time, diffused light (object light Ob) from each point of the diffusion plate 22 is diffused so as to illuminate at least the entire use region of the hologram recording material 24.

  Then, the reference light R condensed by the condensing optical system 23 is irradiated from the same surface of the hologram recording material 24. The focal position A of the condensing optical system 23 is arranged so as to coincide with a reference point by the optical scanning unit 15 in use. The object light Ob and the reference light R are simultaneously incident and interfered in the hologram recording material 24. The object beam Ob and the reference beam need to have coherency. Therefore, it is conceivable to divide laser light oscillated from the same light source and use one as object light Ob and the other as reference light R.

  The hologram recording material 24 is subjected to post-processing such as heating and ultraviolet irradiation to produce a transmission hologram 21 that reproduces a diffusion plate image at the same position at each point on the surface. Further, for irradiation of the object light Ob used at the time of recording, not only the diffuser plate 22 such as an opal glass file, but also an optical element (light diffusing element 21) such as a lens array, which can illuminate the entire use area with diffused light from each point. (Referred to as “second light diffusing element”). In the present embodiment, interference fringes are recorded (interference exposure) by causing the object beam Ob and the reference light R to interfere with each other. However, the interference fringes calculated by the computer are directly recorded on the hologram recording material 21. A so-called computer-generated hologram may be used.

  The diffuser plate image 22i reproduced by the light diffusing element 21 in FIG. 2 is positioned so as to illuminate the entire image forming region of the light modulating element 31 in FIG. In FIG. 1, the image forming area of the light modulation element 31 is two-dimensionally positioned on the XY plane. In the present embodiment, two coherent lights L1 and L1 ′ having different incident angles are incident on the optical scanning unit 15, but the reference points of the two coherent lights L1 and L1 ′ in the optical scanning unit 15 are used as the reference points. By making it coincide with the focal position A at the time of hologram creation, it is possible to form the same diffuser plate image 22i with either coherent light L1, L1 ′.

  The light modulation element 31 such as a micro display is illuminated with the illumination light Lb from the light diffusion element 21 and transmits the illumination light for each pixel to form an image. At this time, the polarization direction of the illumination light Lb is aligned by the polarization separation unit 12 and the λ / 2 wavelength plate 13, and this polarization direction is made to coincide with the polarization direction used in the light modulation element 31. Thus, it is possible to improve the light use efficiency in the light modulation element 31 and improve the image quality.

  The modulated light Lc modulated by the light modulation element 31 is magnified by the projection optical system 32 and projected onto the screen 41 as the image reproduction light Ld, and allows the observer to observe the reflected or transmitted image. At this time, the coherent light projected on the surface of the screen 41 interferes with each other to cause speckle. However, in the present embodiment, since the coherent light is scanned by the optical scanning unit 15, as a result, the video reproduction light Ld projected on the screen 41 is changed with time, and this speckle is made inconspicuous very effectively. .

For example, at the point P1 on the screen shown in FIG. 1, the video reproduction light Ld (t1) at time t1 and the video reproduction light Ld (t2) at time t2 are irradiated at different incident angles. The same applies to other points P2 shown in the figure and other points not shown, and the image reproduction light Ld projects an image on the screen 41 while changing the incident angle with time. Therefore, speckles formed on the screen in a very short time are averaged by the image reproduction light Ld being irradiated at different incident angles depending on the time, and an observer who observes the image projected on the screen 41 is used. It becomes inconspicuous enough.

  The speckles observed by the observer are not only speckles generated due to the scattering of coherent light on the screen 41 as described above, but also those generated on various optical elements of the projection display apparatus 10. is there. This speckle is projected on the screen 41 via the light modulation element 31 and is observed by the observer. In the present embodiment, the scanning light La scans the light diffusing element 21 to illuminate the image forming area of the light modulation element 31 as the illuminated area. That is, by illuminating the illuminated area so that diffused light from each point of the light diffusing element 21 is temporally separated, the phase information before the light diffusing element 21 is canceled and each of the light diffusing elements 21 is It is also possible to prevent the diffused light from the points from interfering with each other, and it is possible to make the speckles generated in the various optical elements of the projection display apparatus 10 inconspicuous.

  As described above, the lighting device and the projection type image display device according to the embodiment of the present invention have been described. Embodiments of various configurations used in the lighting device will be described. Although the details of the scanning mode of the optical scanning unit 15 have not been described in the above-described embodiment, the scanning of the optical scanning unit 15 may use either one-dimensional or two-dimensional scanning. In any case, it is required that the diffused light from each point on the light diffusing element 21 can sufficiently illuminate the entire illuminated area.

  FIG. 4 shows an embodiment of the optical scanning unit 15 that performs one-dimensional scanning. In this embodiment, the coherent light emitted from the light source unit 11 is reflected on the reflection surface of the optical scanning unit 15 that resonates and vibrates in one axial direction, and scans the light diffusion element 21 back and forth on the line. When a hologram is used as the light diffusing element 21, a diffusing plate image 22i is formed at any scanning position. In such an embodiment, the light diffusion element 21 can be reduced in size because the scanning region only needs to be a line. In order to obtain a sufficiently illuminated area by line-shaped scanning, it is preferable to use a hologram.

  FIG. 5 shows an embodiment of the optical scanning unit 15 that performs two-dimensional scanning. In this embodiment, the coherent light from the light source unit 11 is reflected on the reflection surface of the optical scanning unit 15 that resonates and oscillates in two axial directions, and scans the light diffusion element 21 two-dimensionally. Also in this embodiment, the diffused light from the light diffusing element 21 sufficiently illuminates the entire illuminated area, and in particular when a hologram is used, a diffuser plate image shaped to match the illuminated area. 22i can be formed, and the light use efficiency is increased. Such an embodiment is effective when a normal diffusion plate such as opal glass is used. Even if the illuminance distribution of diffused light from each point is not constant, the illuminance can be averaged and the entire illuminated area can be illuminated uniformly.

  Now, various forms of the polarization separation unit 12 according to the embodiment of the present invention will be described. Each of the polarization separation units 12 described below is a device having birefringence that separates incident light according to the oscillation direction of polarized light. Such a device having birefringence has advantages in terms of processing and arrangement as compared with a conventional polarizing beam splitter (cube type), and can be expected in a small optical system.

FIG. 6 is a diagram illustrating an example of the polarization separation unit 12 according to the embodiment of the present invention. In this example, a birefringent crystal element 161 is used. The birefringent crystal element 161 has a wedge shape in which at least one of the entrance surface and the exit surface, in the case shown in FIG. 6, the exit surface is inclined from a plane perpendicular to the optical axis of the incident light. By making the coherent light L0 emitted from the light source 11 incident on an incident surface perpendicular to the optical axis, coherent light of s-polarized component and coherent light of p-polarized component are emitted from the inclined emission surface. In the present embodiment, by arranging the λ / 2 wavelength plate 13 on the s-polarized component side, two coherent lights L1 and L1 ′ having the same polarization direction are obtained.

  FIG. 7 is a diagram illustrating an example of the polarization separation unit 12 according to the embodiment of the present invention. In this example, the polarization separation unit 12 includes a device in which liquid crystal is sealed between two transparent substrates 162a and 162b. The two transparent substrates 162 are made of transparent glass, plastic, or the like. A sealing material 163 for enclosing liquid crystal is provided between the two transparent substrates 162. This sealing material 163 also functions as a means for defining the distance between the transparent substrates 162.

  On the liquid crystal side surface of the incident-side transparent substrate 162b, prisms having an inclined surface inclined from a surface perpendicular to the optical axis of incident light are formed in an array. The prism array 164 is formed of a UV curable resin created by imprint or the like, or glass created by etching. Liquid crystal is sealed between the prism array 164 and the transparent substrate 162a on the emission side. The liquid crystal to be sealed is aligned parallel to the wall surface of the transparent substrate 162 by an alignment film formed on the transparent substrate 162 or the like, or an electric field applied from an electrode (not shown).

  The liquid crystal aligned in this way has birefringence (refractive index anisotropy) having a refractive index that varies depending on the polarization direction. The normal light refractive index no is substantially the same as the refractive index np, and the extraordinary light refractive index ne is different from the refractive index np of the prism array 164 for the polarization component of p-polarized light. Therefore, for the coherent light L0 emitted from the light source 11, the s-polarized component travels straight through the interface between the prism array 164 and the liquid crystal, and the p-polarized component is refracted at the interface and emitted in different directions. Similar to the above-described embodiment, by arranging the λ / 2 wavelength plate 13 on the s-polarization component side, two coherent lights L1 and L1 'having the same polarization direction can be obtained.

  In this embodiment, the liquid crystal oriented in the position direction is used as the birefringent material. However, the liquid crystal is not limited to this form. For example, an amorphous polymer, a low-molecular glassy compound, an amphiphilic compound, and the like. Various materials can be used.

  FIG. 8 is a diagram illustrating an example of the polarization separation unit 12 according to the embodiment of the present invention. The polarization separation unit 12 of the present embodiment also uses the birefringence effect as in the embodiment of FIG. It has become a thing. As in the previous embodiment, a space through the sealing material 163 is formed between the two transparent substrates 162a and 162b. In this space, a liquid crystal rich layer 166A containing a large amount of liquid crystal molecules and a polymer rich layer 166B containing a large amount of polymer material are formed inclined with respect to the optical axis of the coherent light.

  The liquid crystal rich layer 166A has birefringence having a different refractive index depending on the polarization direction, and has an ordinary light refractive index no substantially equal to the refractive index np of the polymer rich layer 166B for the polarization component of s-polarized light. The p-polarized light component is set to have an extraordinary refractive index ne different from the refractive index np of the polymer rich layer 166B. Therefore, for the coherent light L0 emitted from the light source 11, the s-polarized component passes straight through the interface between the liquid crystal rich layer 166A and the polymer rich layer 166B, and the p-polarized component is diffracted at the interface in different directions. Emitted. Also in this case, by arranging the λ / 2 wavelength plate 13 on the s-polarization component side, two coherent lights L1 and L1 ′ having the same polarization direction can be obtained.

Various materials other than liquid crystal can be used for the birefringent material of the present embodiment. In addition, the method for creating the polarization separation unit 12 of the present embodiment is performed by first sealing a mixture of a birefringent material and a monomer between the transparent substrates 162a and 162b and exposing the interference fringes. . At this time, the photopolymerization reaction of the monomer starts in the bright part of the interference fringes, and the liquid crystal molecules are deposited in the dark part (polymerization-induced phase separation) while aligning the major axis direction in the movement direction, and the liquid crystal rich layer 166A. As a result, the polymer rich layer 166B is formed.

  Although the three forms of the polarization separation unit 12 have been described above, various forms can be adopted as long as the form can be separated into different linearly polarized light components.

  In the illuminating device 20 described with reference to FIG. 1, the coherent lights L1 and L1 ′ separated in different directions by the polarization separation unit 12 are condensed on the reference point of the optical scanning unit 15 using the condensing optical system 14. However, instead of using the condensing optical system 14, the separated coherent lights L 1 and L 1 ′ may be reflected at different points on the optical scanning unit 15.

  FIG. 9 is a view showing the illumination device of such an embodiment, and is an embodiment in which the condensing optical system 14 is excluded from the illumination device described in FIG. In this embodiment, the description of the same points as in FIG. 2 will be omitted.

  In this embodiment, the two coherent lights L1 and L1 'separated by the polarization separation unit 12 are incident on the optical scanning unit 15 as they are. In such a form, the coherent lights L1 and L1 'are reflected at two locations on the reflection surface of the optical scanning unit 15. Therefore, at each incident position of the light diffusing element 21, the two scanning lights La and La ′ are incident at different incident angles. Therefore, when a hologram with angle selectivity is used, the light use efficiency may be reduced. Therefore, in such an embodiment, it is preferable to make the separation angle of the coherent light separated by the polarization separation unit 12 as small as possible, or shorten the optical path length from the polarization separation unit 12 to the optical scanning unit 15.

  Further, in such a case, when a lens array, a normal diffusing plate such as opal glass, or the like is used as the light diffusing element 21, a deviation occurs in the illumination area due to a difference in incident angle at each point of the light diffusing element 21. There is a case. Therefore, as shown in FIG. 10, both the illumination region 22i by the light diffusing element 21 when the coherent light La is incident and the illumination region 22i ′ by the light diffusing element 21 when the coherent light La ′ is incident are both illuminated regions. It is preferable to illuminate the entire image forming area of the light modulation element 31 as a uniform illumination.

  In the embodiment of FIG. 1, the transmissive light diffusing element 21 is used. However, as the light diffusing element 21, a reflective type may be used. FIGS. 11 to 13 show an embodiment in which a reflection hologram is used as the light diffusing element 21, and each drawing corresponds to the transmission type shown in FIGS.

  FIG. 11 is a diagram illustrating a configuration of the projection type video display device, and FIG. 12 is a diagram illustrating an illumination device portion in the projection type video display device. In the present embodiment, a reflection hologram is used as the light diffusing element 21. Similar to the above-described embodiment, the scanning light La from the optical scanning unit 15 performs scanning while changing the position of the incident surface of the light diffusing element 21 in terms of time. In the reflection hologram, this incident surface also functions as a reflection surface, and the reflected reproduced image illuminates the entire image forming region of the light modulation element 31 as the illuminated region, as in the previous embodiment. Even when any point of the light diffusing element 21 is scanned, the diffused light emitted from each point can illuminate the illuminated area, thereby making it possible to vary the incident angle with respect to the illuminated area in terms of time. Become. Therefore, as in the previous embodiment, speckles generated on the screen 41 and speckles generated by various optical elements of the projection display apparatus 10 can be made sufficiently inconspicuous.

FIG. 13 is a diagram showing a configuration (interference exposure) when creating a reflection hologram used in the present embodiment. Laser light is irradiated from the back side of the diffusion plate 2, and the object light Ob diffused forward is incident from one surface of the hologram recording material 24. At that time, diffused light (object light Ob) from each point from the diffusion plate 22 is diffused so as to illuminate at least the entire use region of the hologram recording material 24.

  Then, the reference light R condensed by the condensing optical system 23 is irradiated from the other surface of the hologram recording material 24. The focal position A of the condensing optical system 23 is arranged so as to coincide with the irradiation light divergence point (reference point) by the light scanning unit 15 in use. The object light Ob and the reference light R are simultaneously incident and interfered in the hologram recording material 24.

  The hologram recording material 24 is subjected to post-processing such as heating and ultraviolet irradiation to produce a reflection hologram 21 that reproduces a diffuser plate image at the same position at each point on the surface. As in the previous embodiment, the object light Ob is irradiated not only with the diffuser plate 22 such as an opal glass file, but also with an optical element (second lens) such as a lens array that can illuminate the entire use area. Light diffusing element). Moreover, it is good also as using a computer-generated hologram also about this reflection type hologram.

  As described above, according to the present embodiment, speckle noise is not noticeable, and the speckle noise is noticeable by illuminating the light modulation element with the illumination device that emits illumination light having a uniform polarization direction. It is possible to provide a projection-type image display device that can provide a non-image.

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

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

DESCRIPTION OF SYMBOLS 10 ... Projection type image display apparatus 11 ... Light source 12 ... Polarization separation part 13 ... (lambda) / 2 wavelength plate 14 ... Condensing optical system 15 ... Optical scanning part

161 ... birefringent crystal element 162 ... transparent substrate 163 ... sealing material 164 ... prism array 165 ... liquid crystal molecule 166A ... polymer rich layer 166B ... liquid crystal rich layer 17 ... [lambda] / 2 wavelength plate 20 ... illumination device 21 ... light diffusing element (hologram) )
22i ... Diffuser plate image 23 ... Condensing optical system 24 ... Hologram recording material 31 ... Light modulation element (micro display)
31a ... Image forming area 32 ... Projection optical system 41 ... Screen

Claims (10)

A light source that emits coherent light;
A polarization separator that separates coherent light emitted from the light source in different directions;
An optical scanning unit that scans coherent light separated by the polarization separation unit;
A wave plate disposed in the optical path of any one of the coherent lights separated by the polarization separation unit, and aligning the polarization direction of the coherent light separated by the polarization separation unit;
E Bei and a light diffusing element diffuses the scanned scanning light, diffusing light emitted from each point to illuminate overlapping the illuminated area by the light scanning unit,
The illumination apparatus, wherein the polarization separation unit is a device having birefringence that separates incident light according to a vibration direction of polarized light . The device having birefringence is a birefringent crystal element in which at least one of light incident / exiting surfaces is inclined from a plane perpendicular to the optical axis of coherent light.
The lighting device according to claim 1 . The birefringent device encapsulates a birefringent material between two transparent substrates,
It is a device in which prisms having an inclined surface inclined from a surface perpendicular to the optical axis of coherent light are arranged in an array on the surface of the transparent substrate on which light is incident on the birefringent material side. Be
The lighting device according to claim 1 . In the birefringent device, a layer containing a birefringent material and a layer containing a monomer material or a polymer material are alternately inclined with respect to a plane perpendicular to the optical axis of coherent light between two transparent substrates. It is a stacked device
The lighting device according to claim 1 . The illumination device according to any one of claims 1 to 4 , wherein the light diffusion element is a hologram. The hologram is a recording of an image of a second light diffusing element.
The lighting device according to claim 5 . The hologram is any one of a transmission hologram and a reflection hologram
The illumination device according to claim 5 or 6 . The lighting device according to any one of claims 1 to 4 , wherein the light diffusing element is a diffusion plate. The lighting device according to claim 1, wherein the light diffusing element is a lens array. A light source that emits coherent light;
A polarization separator that separates coherent light emitted from the light source in different directions;
An optical scanning unit that scans coherent light separated by the polarization separation unit;
A wave plate disposed in the optical path of any one of the coherent lights separated by the polarization separation unit, and aligning the polarization direction of the coherent light separated by the polarization separation unit;
A light modulation element having an image forming region on which an image is formed;
A light diffusing element that diffuses the scanning light scanned by the light scanning unit, and diffused light emitted from each point illuminates the image forming region;
A projection optical system that projects an image of the light modulation element onto a screen ,
The projection-type image display device, wherein the polarization separation unit is a device having birefringence that separates incident light in accordance with a polarization vibration direction .

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