JP4776285B2 - Illumination optical device and virtual image display device using the same - Google Patents

Description

  The present invention relates to an illumination optical apparatus suitable for use in illumination of a spatial light modulation unit in an image display apparatus, and particularly suitable for use in a virtual image display apparatus such as a viewfinder of a video camera or a head-mounted display. The present invention relates to a device and a virtual image display device using the same.

In an image display device such as a projection display device, a configuration using a tapered light pipe is proposed as an illumination optical device for a spatial light modulation unit that modulates an image (see, for example, Patent Documents 1 to 3).
With reference to FIG. 15, an example of an illumination optical apparatus using a conventional tapered light pipe described in Patent Document 1 will be described. As shown in the schematic configuration diagram of FIG. 15, this illumination optical apparatus includes a light source 1506, a reflecting mirror 1508, and a tapered light pipe 1502, a reflector 1512 that reflects light 1501 emitted from the light source 1506 forward, and light For example, a concave reflecting mirror 1508 that reflects 1501 and tapered light pipes 1502 and 1516 are formed.
In such a configuration, the light 1501 emitted from the light source 1506 is reflected by the reflecting mirror 1508, and an image of the light source 1506 is formed near the input end 1507 of the tapered light pipe 1502 by the reflecting mirror 1508. ing. The light beam incident on the tapered light pipe 1502 exits from the exit surface 1503 formed in a lens shape with a reduced numerical aperture (Numerical Aperture: NA), and then enters another light pipe 1516 that is arranged.
With this illumination optical device, the light beam emitted from the light source is converted into a desired divergence angle and area to improve efficiency and uniformity of illuminance.
Other conventional examples of illumination optical devices using a tapered light pipe are disclosed in the above-mentioned Patent Documents 2 and 3, etc., but in any case, an optical fiber is provided between the tapered light pipe and the spatial light modulator. And a polarization converter are arranged to further improve uniformity and illumination efficiency.

  The illumination optical devices according to these conventional examples are mainly used for projection type image display devices, and are configured to re-image the image of the spatial light modulator illuminated by the illumination optical device on the screen. Yes. Alternatively, after the light pipe is emitted, it is used as a configuration in which the spatial light modulator is not directly illuminated but is incident on the optical fiber or another light pipe again to further improve the uniformity.

US Patent Application Publication No. 2005/0047723 U.S. Pat.No. 6,739,726 US Patent Application Publication No. 2003/0021530

The conventional illumination optical device described above is suitable when used in a projection-type image device as described above, but has the following drawbacks as an illumination optical device for a virtual image display device.
(1) In particular, when applied to an image display device that is required to be reduced in size and weight, such as a head mounted display (HMD), after the tapered light pipe, it is further necessary to improve the uniformity. If the light pipe or the optical fiber is used, the entire lighting device becomes large, which is not preferable.
(2) The illumination light emitted from the exit surface of the tapered light pipe has a relatively large luminance non-uniformity in the exit NA as it is. This non-uniformity is not a problem in the case of a projection-type image display device that re-images light emitted from an arbitrary pixel of the spatial light modulator on the screen, but in the case of a virtual image display device, This is not preferable because it causes a luminance change when the pupil position of the person moves.

  The reason for the above (2) will be described with reference to FIG. 16 and FIGS. First, as shown in FIG. 16, an optical system of a projection display device in which a tapered light pipe 20, a spatial light modulator 60, and a projection lens 170 are arranged on the optical axis of light emitted from the light source 10 will be described. To do. In this case, the light emitted from the light source 10 is emitted by adjusting the numerical aperture NA by the tapered light pipe 20 and is incident on the spatial light modulation unit 60 such as a transmissive liquid crystal panel. Modulated. The light emitted from the spatial light modulator 60 is projected onto the screen 180 by the projection lens 170. In this case, the variation in the luminous flux (or light energy) within the radiation angle of the image display light emitted from one point of the spatial light modulator 60 is re-imaged on the screen 180, and thus is not recognized by the observer. It doesn't matter.

On the other hand, when the light pipe is applied to the virtual image coupling optical system as described above, the following problems occur. That is, in this case, as shown in FIGS. 17A to 17C, the light source 10, the light pipe 20, the spatial light modulator 60, and the eyepiece lens 270 are arranged on the optical axis, and the image display light modulated by the spatial light modulator 60 is obtained. Let us consider an optical system that observes the image with the pupil 80 through the eyepiece 270.
At this time, as shown in FIG. 17A, the variation in the luminous flux (or light energy) within the radiation angle of the image display light emitted from one point of the spatial light modulation unit 60 is as follows. If it moves as shown by arrow a in FIG. 17 or rotates as shown by arrow b in FIG. 17C, it will be recognized as a fluctuation in brightness.

  For such a problem, for example, if the total length of the tapered light pipe is increased, this non-uniformity tends to be improved. In this case, however, the apparatus becomes larger and the above-mentioned head-mounted display or the like is used. If used, it is not desirable.

  In view of the above problems, the present invention provides an illumination optical device that modulates light by a spatial light modulation unit, and can maintain high uniformity and efficiency of illumination while suppressing an increase in size of the device. And it aims at providing the virtual image display apparatus using the same.

To solve the above problems, an illumination optical device according to the invention chromatic light source, a light pipe, an optical lens, a diffusion plate, a spatial light modulator. The light beam emitted from the light source is incident on the inside from the incident surface of the light pipe, and after at least a part of the light beam is totally internally reflected on the side surface of the light pipe, is emitted from the emission surface having a larger area than the incident surface, Subsequently, after passing through the optical lens and being diffused by the diffusion plate, the spatial light modulator is illuminated. At least one of the optical lenses is formed by arranging two cylindrical lenses so that their optical powers are orthogonal to each other, and the optical power is different from one direction in the display surface of the spatial light modulation unit and the other. Different from each other.
Further, at least one of the optical lenses is formed by arranging two Fresnel lenses having optical power only in one direction so that their optical powers are orthogonal to each other, and the optical power is displayed on the display of the spatial light modulator. The one direction and the other direction in the plane may be different from each other.

Further, the present invention is a virtual image display device having an illumination optical device and a virtual image imaging optical system that guides a display image modulated by the spatial light modulation unit to an observer's pupil, the illumination optical device comprising: a light source; and organic and light pipe, an optical lens, a diffusion plate, a spatial light modulator. The light beam emitted from the light source is incident on the inside from the incident surface of the light pipe. After at least a part of the light beam is totally internally reflected on the side surface, the light beam is emitted from the emission surface having a larger area than the incident surface, and then After passing through the optical lens and being diffused by the diffusion plate, the spatial light modulator is illuminated. At least one of the optical lenses is formed by arranging two cylindrical lenses so that their optical powers are orthogonal to each other, and the optical power is different from one direction in the display surface of the spatial light modulation unit and the other. Different from each other.
Further, at least one of the optical lenses is formed by arranging two Fresnel lenses having optical power only in one direction so that their optical powers are orthogonal to each other, and the optical power is displayed on the display of the spatial light modulator. The one direction and the other direction in the plane may be different from each other.

As described above, the illumination optical device of the present invention has a light source, a light pipe, and a diffuser plate. First, the illumination light having a large numerical aperture NA emitted from the light source is first converted into a tapered light pipe or the like. By converting to illumination light having a smaller numerical aperture NA, readjustment including anamorphic diffusion angle and reduction of luminance unevenness within the radiation angle can be performed in the diffusion plate.
In addition, when an optical lens is arranged between the light pipe exit surface or between the light pipe and the diffuser plate, the chief ray angle of the illumination light from the light source can be controlled by the optical lens. The diffusion plate can be used to readjust the diffusion angle and reduce luminance unevenness.

  That is, according to the present invention, it becomes possible to control the chief ray angle and the numerical aperture NA according to the position of the spatial light modulation unit or the like on the illuminated object, and the illumination luminance uniformity is high with small size and light weight. A high illumination optical device can be realized.

As described above, according to the illumination optical device of the present invention, by controlling the diffusion angle, it is possible to illuminate with high efficiency and uniform illumination brightness while suppressing an increase in size of the device.
Further, according to the virtual image display device of the present invention, it is possible to provide a virtual image display device using an illumination optical device capable of suppressing the enlargement of the entire device and capable of illumination uniformity and highly efficient illumination.

Examples of the best mode for carrying out the present invention will be described below, but the present invention is not limited to the following examples.
(1) First Embodiment A first embodiment of a virtual image display device using an illumination optical device according to the present invention will be described with reference to the schematic configuration diagram of FIG. The illumination optical device 100 of this example includes a light source 10 made of an LED (light emitting diode), for example, a tapered light pipe 20, a diffuser plate 40, a spatial light modulator 60, a collimating optical system 70, for example, a finder lens. .
In this case, the illumination light emitted from the light source 10 is incident from the incident surface 21 with the smaller area of the tapered light pipe 20, and a part of the light beams are emitted from the emission surface 22 after repeating total internal reflection. In the present embodiment, the emission surface 22 is a cylindrical surface.

The illumination light emitted from the emission surface 22 is diffused by the diffusion plate 40 that is subsequently arranged, and then illuminates the object to be irradiated, in this case, the transmissive spatial light modulator 60 such as a liquid crystal panel.
The illumination light L that has passed through the spatial light modulator 60 is then made into substantially parallel light via the collimating optical system 70 and is incident on the pupil 80 of the observer.

  In the present embodiment, the light source 10 such as an LED and the light pipe 20 are in optical contact with each other. Thereby, the light use efficiency can be increased.

Further, in the example of FIG. 1, the exit surface 22 of the light pipe 20 is a cylindrical surface, that is, the direction indicated by the arrow X along the paper surface of FIG. The direction indicated by the arrow Y (perpendicular to the plane of FIG. 1) is a plane.
By adopting such a curved surface shape, as shown in FIG. 2A, with respect to the direction indicated by the arrow Y orthogonal to the curved surface of the cylindrical surface, the central light beam of the divergence angles of the illumination light beams LY1, LY2,. The angle formed by the broken line) and the normal of the display surface of the spatial light modulator 60 increases toward the periphery of the spatial light modulator 60 and deviates from telecentricity.
On the other hand, as shown in FIG. 2B, with respect to the direction indicated by the arrow X along the curved surface of the cylindrical surface, the central ray (indicated by a broken line) of the divergence angle of the illumination rays LX1, LX2,. The angle formed with the normal of the display surface of 60 is small, that is, close to telecentric.
That is, in this case, the principal ray angle of light emitted from each part of the exit surface is controlled in the X direction and the Y direction according to the shape of the curved surface of the exit surface of the light pipe 20.

Further, in the embodiment shown in FIG. 1, the diffusion plate 40 may have a configuration in which the diffusivity is different in a direction along the curved surface of the cylindrical surface and in a direction orthogonal thereto.
In this case, as shown in FIG. 3A, in the direction orthogonal to the curved surface of the cylindrical surface indicated by the arrow Y, the illumination rays LY1 ′, LY2 ′,. As shown in FIG. 3B, in the direction indicated by the arrow X along the curved surface of the cylindrical surface, the illuminating rays LX1 ′, LX2 ′,. That is, by adjusting the diffusion angle of the diffusion plate 40, it is possible to illuminate with a desired numerical aperture NA.
In this way, in the illumination optical device of the present invention, the chief ray angle of the emitted light with respect to one direction and the other direction in the display surface of the spatial light modulator 60, for example, the direction corresponding to the vertical direction and the horizontal direction. The numerical aperture NA may be illuminated under different conditions.

An example in which the difference in illuminance uniformity with and without the diffuser plate 40 is observed is shown in FIGS. FIG. 4 shows a case where a diffusion plate is not provided, and FIG. 5 shows a case where a diffusion plate configured to diffuse under different conditions, for example, in the vertical direction and the horizontal direction in the display surface of the spatial light modulator as described above. FIG. 4 shows the radiance distribution of image display light from the spatial light modulator.
From FIG. 4, when there is no diffusion plate, the required numerical aperture NA, in this case, the uniformity is insufficient in the range of ± 10 degrees in the vertical direction and ± 5 degrees in the horizontal direction, as described above. When observing a virtual image, it turns out that brightness changes with pupil movement and rotation.
On the other hand, as is apparent from FIG. 5, according to the configuration of the present invention in which the diffusion plate is arranged, it can be seen that uniform brightness can be obtained within the necessary numerical aperture NA.
Therefore, in the illumination optical device 100 shown in FIG. 1 described above, even when the observer's pupil 80 is shifted or rotated in the horizontal direction, the luminance is uniform and thus is not recognized as a variation in brightness. It is possible to display a good image without uneven brightness.

(2) Second Embodiment Next, a second embodiment of the illumination optical apparatus according to the present invention will be described with reference to FIG. In FIG. 6, parts corresponding to those in FIG.
In this example, the optical lens 30 is disposed between the tapered light pipe 20 and the diffusion plate 40, and the other configuration is the same as the configuration described in FIG.

In this case, the illumination light emitted from the light source 10 is incident from the smaller incident surface 21 of the tapered light pipe 20 that is optically in close contact with the light source 10, and some of the light rays undergo total internal reflection. After repeating, the light exits from the exit surface 22.
The illumination light emitted from the exit surface 22 enters the optical lens 30 that is subsequently arranged. The optical lens 30 is an optical lens having at least one optical surface whose optical power is different in one direction and another direction, for example, the vertical direction and the horizontal direction in the display surface of the spatial light modulator 60. . In other words, the optical lens 30 is not rotationally symmetric with respect to the optical axis, for example, but has different directions in a plane orthogonal to the optical axis, for example, two directions orthogonal to each other (X direction and Y direction) as symmetry axes. The configuration is a toric surface. In this case, the optical power differs in the X direction and the Y direction, and the incident angle of the illumination light to the diffuser plate 40 also differs in these two directions.

  The illumination light diffused by the diffusion plate 40 illuminates the transmissive spatial light modulator 60. Then, the illumination light L that has passed through the spatial light modulator 60 is made into substantially parallel light and then enters the observer's pupil 80 via a collimating optical system 70 such as a finder optical system.

In this embodiment, as described above, the optical lens 30 is a toric surface, and the central light beam of the divergence angle of the illumination light beam and the spatial light modulator 60 in the direction along the curved surface of the surface with a larger curvature (X direction). The angle formed by the normal line is small, that is, close to telecentric, and in the direction perpendicular to this (Y direction), the angle formed by the central ray of the divergence angle of the illumination light beam and the normal line of the spatial light modulator 60 is The configuration is such that it increases toward the periphery of the spatial light modulator 60, that is, deviates from telecentricity.
Also in this case, the diffusing plate 40 may have a configuration in which the diffusivity is different between a direction along the curved surface of the surface of the optical lens 30 having a larger curvature and a direction orthogonal thereto. Here, it is assumed that the diffusivity in the direction (X direction) along the curved surface having a large curvature of the optical lens 30 is larger than the diffusivity in the direction orthogonal to the optical lens 30 (Y direction). With such a configuration, the spatial light modulator 60 can be illuminated, for example, under different conditions in the vertical and horizontal directions.
Therefore, even in this case, the area displayed by the spatial light modulation unit 60 can be illuminated uniformly, and a change in brightness is not observed even when the observer's pupil 80 is displaced or rotated. Display can be made.

(3) Third Embodiment Next, a third embodiment of the illumination optical apparatus according to the present invention will be described with reference to FIG. In FIG. 7, parts corresponding to those in FIG. In this example, an example in which a uniaxial Fresnel lens 31 is disposed as an optical lens between the light pipe 20 and the diffusion plate 40 is shown. When the Fresnel lens 31 is used, the device can be thinned.

  In this case, the illumination light emitted from the light source 10 such as an LED is incident from the incident surface 21 having the smaller area of the tapered light pipe 20 optically adhered to the light source 10, and some of the light rays are totally reflected internally. After repeating the above, the light is emitted from the emission surface 22. In this embodiment, the emission surface 22 is a cylindrical surface.

  The illumination light emitted from the emission surface 22 is incident on the subsequently arranged uniaxial Fresnel lens 31. The uniaxial Fresnel lens 31 is arranged such that the cylindrical surface-shaped exit surface 22 has optical power in a direction orthogonal to the direction having optical power. For this reason, the angle of the illumination light incident on the diffusion plate 40 is also different in two orthogonal directions.

  The illumination light diffused by the diffusion plate 40 illuminates the transmissive spatial light modulator 60. The illumination light L that has passed through the spatial light modulator 60 is then converted into substantially parallel light through the collimating optical system 70 and enters the observer's pupil 80.

  Here, as described above, the emission surface 22 of the light pipe 20 is a cylinder surface, and the optical power is smaller than that of the uniaxial Fresnel lens 31 that is subsequently arranged. With respect to the direction in which the uniaxial Fresnel lens 31 has optical power (X direction), the angle formed by the central ray of the divergence angle of the illumination ray and the normal of the spatial light modulator 60 is small, that is, close to telecentric. With respect to the orthogonal direction (Y direction), the angle formed by the central ray of the divergence angle of the illumination light beam and the normal of the spatial light modulator 60 increases toward the periphery of the spatial light modulator 60, that is, deviates from telecentricity. It becomes composition to go.

Furthermore, the diffuser plate 40 used in this embodiment has a diffusivity in a direction along the curved surface of the surface of the Fresnel lens 31 having a higher optical power (X direction) and a direction perpendicular to the curved surface (Y direction). It is good also as a different structure. For example, the diffusivity in the direction in which the optical power is high is configured to be larger than the diffusivity in the direction in which the optical power is low.
In this manner, the illumination optical apparatus according to the present embodiment is configured to illuminate the spatial light modulator 60 under different conditions in two directions within the display surface, for example, the vertical direction and the horizontal direction. Can do.
Therefore, even in this case, the area displayed by the spatial light modulation unit 60 can be illuminated uniformly, and a change in brightness is not observed even when the observer's pupil 80 is displaced or rotated. Display can be made.

(4) Fourth Embodiment Next, another embodiment of the illumination optical apparatus according to the present invention will be described with reference to FIG. In FIG. 8, parts corresponding to those in FIG. In this example, in the illumination optical apparatus described in the third embodiment, not only the exit surface 22 but also the side surface 23 is curved as a light pipe. That is, in this case, the side surface 23 of the light pipe 20 has a curved surface that protrudes outward in a cross section along the optical axis of the light pipe 20.
In this way, when the side surface 23 of the light pipe 20 is curved, the probability that a light beam emitted from the light source 10 with a relatively large radiation angle will be totally reflected inside the light pipe 20 increases. Use efficiency can be increased.
In this case, the uniformity can be improved by increasing the total number of reflections of light propagating from the entrance surface to the exit surface. Alternatively, when equal uniformity is sufficient, the entire length of the light pipe 20 can be shortened, and the apparatus can be reduced in size.

Also in this case, similarly to the third embodiment described above, for example, when the uniaxial Fresnel lens 31 is used, the direction having the optical power and the optical power of the exit surface 22 of the light pipe 20 are set. The same effect can be obtained by selecting the direction relative to the direction in which the light pipe 20 is held, the shape of the exit surface 22 of the light pipe 20 and the direction having the optical power, and the setting of the diffusivity of the diffusion plate 40. That is, the spatial light modulator 60 may be configured to illuminate under two different conditions in the display surface, for example, the vertical direction and the horizontal direction.
Therefore, even in this case, the area displayed by the spatial light modulation unit 60 can be illuminated uniformly, and a change in brightness is not observed even when the observer's pupil 80 is displaced or rotated. Display can be made.

In each of the exemplary embodiments described above, a spatial light modulation unit is used as an object to be illuminated of the illumination optical apparatus, and illumination is performed under different conditions in, for example, two vertical and horizontal directions within the display surface. For example, the spatial light modulator can be illuminated with a desired incident angle and numerical aperture in the long side direction and the short side direction in the display surface.
For this reason, as described in detail in the following embodiments of the virtual image display device, when the image display light is guided to the pupil from the optical system including the spatial light modulator via the light guide plate, as described above, By illuminating under different conditions in the two directions, image display light is emitted with a desired numerical aperture and emission angle from the spatial light modulator toward the light guide plate, thereby efficiently displaying a good image on the pupil. Can be performed.

Hereinafter, an embodiment in which a virtual image display device is configured using such an illumination optical device having the configuration of the present invention will be described.
(5) Fifth Embodiment An embodiment of a virtual image display device using the illumination optical device according to the present invention will be described with reference to FIGS. 9A and 9B. FIG. 9A is a schematic top configuration diagram in a state where the observer's pupil 80 observes the virtual image display device 200 according to the present invention, and FIG. 9B is a schematic side configuration diagram. 9A and 9B show a common XYZ coordinate system, with respect to the observer's pupil 80, the left / right (horizontal) direction is the X direction, the up / down (vertical) direction is the Y direction, and the depth direction is the Z direction.

  9A and 9B, the virtual image display device 200 includes a light source 10 such as an LED, for example, a tapered light pipe 20, an optical lens composed of first and second uniaxial Fresnel lenses 31 and 32, and a diffusion plate. 40, a beam splitter 50, a reflective spatial light modulator 61, a collimating optical system 70 such as a finder optical system, and a light guide plate 90 having a hologram structure to be described later.

  As shown in FIG. 9B, the illumination light emitted from the light source 10 made of LED or the like is incident from an incident surface 21 having a smaller area of, for example, a tapered light pipe 20 optically in close contact with the light source 10, Some light beams are emitted from the emission surface 22 after repeating total internal reflection.

The illumination light emitted from the exit surface 22 is incident on the optical lens 30 that is subsequently arranged, in this case, the first and second uniaxial Fresnel lenses 31 and 32. These uniaxial Fresnel lenses 31 and 32 are arranged so that directions having optical powers are orthogonal to each other, and optical powers (that is, focal lengths) are different from each other.
In some cases, the Fresnel lens is an anamorphic lens, and the light utilization efficiency can be increased. In that case, it is desirable to arrange two Fresnel lenses in one direction with different pitches (that is, functionally cylindrical lenses) orthogonally.

  And the illumination light which passed these uniaxial Fresnel lenses 31 and 32 injects into the diffuser plate 40 arrange | positioned succeedingly. The diffuser plate 40 has different diffusibility along the direction in which the optical lens 30 including the uniaxial Fresnel lenses 31 and 32 has optical power. In the case of this embodiment, the diffuser 40 diffuses along the direction in which the optical power is large. Sex is getting bigger. Thus, the light emitted from the diffusion plate 40 is incident on the polarization beam splitter (PBS) 50 with the emission angle and numerical aperture adjusted by the optical characteristics of the Fresnel lenses 31 and 32 and the diffusibility of the diffusion plate 30. The

The illumination light emitted from the diffusion plate 40 in this way is incident from the incident surface 51 of the polarization beam splitter 50, and only the S-polarized component is reflected by the polarization separation film 52 and is emitted from the emission surface 53.
This illumination light illuminates a reflective spatial light modulator 61 such as a reflective liquid crystal panel or DMD (Digital Micro-mirror Device). The image display light modulated by the reflective spatial light modulation unit 61 corresponding to the image to be displayed, for example, is emitted with the above-described emission angle reversed by reflection and the numerical aperture maintained, and again the polarized beam. For example, only the P-polarized light component is transmitted through the polarization separation film 52 and exits from the exit surface 54.

  In the XZ plane shown in FIG. 9A, the image display light emitted from the exit surface 54 of the polarization beam splitter 50 is angled by the collimating optical system 70 (that is, light emitted from each pixel of the reflective spatial light modulator 61). Of the light beams are different from each other. In the YZ plane orthogonal to the parallel light beam group, as shown in FIG. 9B, the parallel light beam groups are made into light beam groups having different angles of view and enter the light guide plate 90. 9A shows typical parallel light beams La, Lb and Lc in the XZ plane, and FIG. 9B shows typical parallel light beams LA, LB and LC in the YZ plane.

As shown in FIG. 9A, the light guide plate 90 has a thin flat plate configuration, and one end of the optical surface 91 out of the collimating optical system 70 out of the optical surfaces 91 and 92 facing the pupil 80 in the depth direction. An incident portion 91A where the emitted light is incident is used, and the other end of the optical surface 91 is an emission portion 91B where the light emitted toward the pupil 80 is emitted.
As described above, in this example, the left / right (horizontal) direction is the X direction, and the up / down (vertical) direction is the Y direction. Image display light for displaying information and the like is guided and incident on the pupil 80.
In addition, when this virtual image display device is applied to a head-mounted display (HMD), the illumination optical device, the spatial light modulation unit, and the virtual image display optical system are not arranged above the pupil, and thus in the lateral direction. In the case of arrangement, as compared with the case of arrangement in the upper direction close to the pupil 80, for example, an optical system is not provided in the upper and lower visual fields, so that it is possible to observe the external environment better. On the other hand, in this case, since the distance for guiding the inside of the light guide plate 90 becomes relatively long, the following device is required.

  In the above configuration, the image display light incident on the light guide plate 90 from the incident portion 91A is incident on the first reflective volume hologram grating 93 provided on the optical surface 92 at a position facing the incident portion 91A. In this example, the first reflective volume hologram grating 93 has a uniform hologram surface interference fringe pitch regardless of position.

Then, the light diffracted and reflected by the first reflective volume hologram grating 93 is formed in the light guide plate 90 in the Z direction of the XZ plane shown in FIG. The light is guided while repeating total reflection between 92 and proceeds in the X direction toward the second reflective volume hologram grating 94 provided at the other end. In FIG. 9A, the luminous flux La is indicated by a broken line, Lb is indicated by a solid line, and Lc is indicated by a two-dot chain line.
In this embodiment, since the light guide plate 90 is thin and the optical path traveling through the light guide plate 90 is relatively long as described above, as shown in FIG. The total number of reflections up to 94 is different.

More specifically, the number of reflections of the parallel light La incident on the light guide plate 90 while being inclined toward the second reflective volume hologram grating 94 out of the parallel lights La, Lb, and Lc is opposite to that. It is less than the number of reflections of the parallel light Lc incident on the light guide plate 90 at the angle of the direction. That is, since the interference fringe pitches on the hologram surface of the first reflective volume hologram grating 93 are equally spaced, the exit angle diffracted and reflected by the first reflective volume hologram grating 93 is the second reflective volume hologram grating. The parallel light incident while tilting toward 94 is larger than the exit angle of the parallel light incident at an angle opposite to that.
The parallel light of each angle of view that has entered the second reflective volume hologram grating 94 deviates from the total reflection condition due to diffraction reflection, and exits from the light guide plate 90 and enters the observer's pupil 80.

In the light guide plate 90, the Y direction which is the vertical direction with respect to the pupil 80 is not reflected. That is, each parallel light beam group does not reflect in the Y direction substantially orthogonal to the plane along the reflection direction in the light guide plate 90 and the propagation direction.
As shown in FIG. 9B, the incident lights LA, LB, and LC having different angles of view on the YZ plane repeatedly reflect in the Z direction within the light guide plate 90, but do not reflect in the Y direction and reach the exit portion 91B.
This is shown in the schematic side view of FIG. 10, parts corresponding to those in FIG. 9B are denoted by the same reference numerals, and redundant description is omitted. As shown in FIG. 10, the light emitted from the collimating optical system 70 is converged on the YZ plane and is incident from the incident portion 91 </ b> A to the inside of the light guide plate 90 in the X direction (direction perpendicular to the paper surface of FIG. 10). proceed. Arrows Ai, Bi, and Ci indicate the traveling directions of typical incident light having different angles of view emitted from the collimating optical system 70 in the YZ plane. These lights converge in the Y direction and travel while reflecting the optical surfaces 91 and 92 of the light guide plate 90 as indicated by arrows Ai1, Ai2,..., Ci1, Ci2,. The light is reflected and diffracted by the reflection type volume hologram grating 94, is emitted from the exit portion 91B, and enters the observer's pupil 80 as indicated by arrows Ao, Bo, and Co.
In this case, as described above, since these lights are converged in the Y direction, the reflection of the second reflection type volume hologram grating 94 with respect to the length of the first reflection type volume hologram grating 93 in the Y direction. The diffractive surface may have a relatively short configuration.

Differences in the emission angle and numerical aperture of the light beams in the X direction and Y direction described above from the spatial light modulator will be described with reference to FIGS.
In this embodiment of the virtual image display device, since the light guide plate 90 provided with the hologram is used, when the observer's pupil 80 is considered as the exit pupil, the image light is emitted from the reflective spatial light modulator 61. The corners and the numerical aperture NA differ depending on, for example, the long side (X) direction and the short side (Y) direction of the image display area of the spatial light modulation unit such as a reflection type, and also depending on the distance from the center of the image display area. .
That is, as shown in FIG. 11, in the X direction corresponding to the long-side direction of the spatial light modulator 60, the light emitted from each pixel has its chief ray as indicated by the alternate long and short dash line. The display surface is substantially perpendicular to the 60 display surface and close to a telecentric state, and the numerical aperture NA is set to be relatively large by the use described later.
On the other hand, as shown in FIG. 12, in the Y direction corresponding to the short side direction, the light emitted from each pixel is in a state where the emission angle becomes telecentric as the distance from the center of the display surface of the spatial light modulator 60 increases, that is, in the space. The angle formed by the display surface of the light modulator 60 and the principal ray indicated by the one-dot chain line of the image display light moves away from the vertical state, and the numerical aperture NA is made relatively small.

  The differences in the exit angles in the directions shown in FIGS. 11 and 12 are shown in Tables 1 and 2 below. In each Table 1 and Table 2, at the image height position from the optical axis, the principal ray angle that is the angle from the optical axis of the light passing through the center of each angle of view, and the upper ray angle that is the spread angle of the emitted light, and Each lower ray angle is shown.

From Table 1, the spread angle is about ± 20 degrees in the X direction, whereas the spread angle is about ± 5 degrees in the Y direction. That is, the numerical aperture NA is large in the X direction, and the numerical aperture NA is small in the Y direction.
That is, in this case, it can be seen that the numerical aperture of the emitted light and the emission angle of the principal ray are different from each other in one direction and the other direction, that is, the X direction and the Y direction.

As described above, the reason why the numerical aperture NA and the emission angle have anisotropy in the X direction and the Y direction in the above-described virtual image display device will be described with reference to FIGS. 13A and 13B and FIG. To do.
As described in FIG. 9A, in the traveling direction corresponding to the long side direction (X direction) of the spatial light modulator, the number of times of reflection in the light guide plate 90 is different depending on each angle of view, that is, the optical path length is different. As shown in FIG. 13A, since the propagating light beams are all parallel light beams, the angle of view emitted from the light guide plate is changed even if the light beam group advances and the optical path length of the light beams of each angle of view changes so as to be folded. The image is not disturbed because it is unchanged. In this case, the aperture in the X direction in the collimating optical system 70 can be made relatively small.

  On the other hand, in the short side direction (Y direction) of the spatial light modulation unit, as shown in FIG. 13B, the vertical field angle is far apart as is apparent when reverse ray tracing is performed from the exit pupil. As described above, when applied to a head-mounted display, if the optical system is disposed laterally with respect to the pupil, the length Lg of the light guide plate needs to be about 60 mm from the average size of a human face, for example. It becomes. If the light is reflected in the Y direction, that is, the vertical direction inside the light guide plate 90, the image is inverted up and down. Therefore, if the light is advanced without being reflected in the Y direction as described above, the light reaches the collimating optical system 70. And the diameter in the Y direction increases. In other words, in this case, the upper and lower (Y-direction) angle-of-view rays are configured to deviate from the telecentric state with respect to the spatial light modulator 60.

On the other hand, numerical apertures NAx and NAy in the X direction and Y direction are as follows, respectively.
First, the numerical aperture NAy in the Y direction is such that the pupil diameter of the observer is D and the focal length of the collimating optical system 70 is f.
NAy = D / (2f)
It becomes.

On the other hand, the numerical aperture NAx in the X direction is not uniquely determined from the pupil diameter as in the Y direction because the light beam is reflected back in the light guide plate as described above.
That is, as apparent from the back ray tracing in the configuration diagram shown in FIG. 14, there is a light beam that is reflected back and reflected at a position straddling the edge of the first reflective volume hologram grating 93 and the optical surface 92. When reverse ray tracing is performed, a part of this light beam (that is, a part reflected by the optical surface 92) is repeatedly reflected and diffracted at different positions of the first reflective volume hologram grating 93 to reach the collimating optical system 70. . On the other hand, the remaining light flux is diffracted at the end of the first reflective volume hologram grating 93 and reaches the collimating optical system 70 as it is. That is, this light beam is a parallel light beam having the same angle of view emitted from the same pixel, but is diffracted and reflected by different parts of the first reflection type volume hologram grating 93 and combined and propagated in the light guide plate 90. There will be a luminous flux that
In order to allow light to reach the entire area of the pupil 80, it is desirable to illuminate including a so-called branched light beam. However, it is difficult to illuminate the light emitted from one pixel into two divergent lights. . Therefore, as shown in FIG. 14, it is necessary to increase the apparent NAx of the illumination light. In FIG. 14, parts corresponding to those in FIG.
Therefore, it can be seen that in this optical system, the apparent numerical aperture NAx in the X direction is relatively large, and the numerical aperture NAy in the Y direction is relatively small.

As described above, in the virtual image display device according to the above-described embodiment, the spatial light modulation unit changes from the spatial light modulation unit to the collimating optical system due to the configuration conditions such as the shape of the light guide plate and the traveling form of the light beam in the light guide plate. Optical characteristics having anisotropy in which the emission angle and numerical aperture of the principal ray corresponding to each emitted pixel are different in the X direction and the Y direction are required.
On the other hand, in the present invention, as described above, the diffusing plate 40 is provided in the illumination optical system for the spatial light modulator, and the optical characteristics of the optical lens 30 and the diffusing plate 40, and the light pipe 20 and the diffusing plate 40 are provided. 1 to 3 and FIGS. 6 to 8, respectively, for example, the X direction is close to telecentric, the diffusion angle is relatively large, and the Y direction is deviated from telecentric and the diffusion angle. By making the optical anisotropy such as relatively small, it is possible to provide an illumination optical device that appropriately illuminates the spatial light modulator in the virtual image display device described above.
As a result, the emitted light that displays the image modulated by the spatial light modulator propagates through the light guide plate with a desired numerical aperture and emission angle, and reaches the pupil without waste and without causing image distortion. Therefore, according to the illumination optical device and the virtual image display device of the present invention, as described above, the light is efficiently used with uniform luminance, so that the brightness does not change even if the pupil 80 is displaced or rotated. And a good image can be displayed.

  The present invention is not limited to each of the above-described embodiments. The configuration of the present invention is not limited to the type and arrangement of the light source and the spatial light modulator, the optical characteristics of the light pipe, the optical lens, and the diffusion plate. It goes without saying that various modifications and changes can be made without departing from the scope, and in particular, it can be applied to various virtual image display devices other than the head-mounted display described in the above embodiment.

1 is a schematic configuration diagram of an embodiment of an illumination optical apparatus according to the present invention. 1A is a schematic configuration diagram of a main part of an embodiment of an illumination optical apparatus according to the present invention. FIG. B is a schematic configuration diagram of a main part of an embodiment of an illumination optical apparatus according to the present invention. 1A is a schematic configuration diagram of a main part of an embodiment of an illumination optical apparatus according to the present invention. FIG. B is a schematic configuration diagram of a main part of an embodiment of an illumination optical apparatus according to the present invention. It is an observation figure which shows the luminance distribution in an example of the illumination optical apparatus by a comparative example. It is an observation figure which shows the luminance distribution in an example of the illumination optical apparatus by this invention. It is a schematic block diagram of the principal part of one Embodiment of the illumination optical apparatus by this invention. It is a schematic block diagram of the principal part of one Embodiment of the illumination optical apparatus by this invention. It is a schematic block diagram of the principal part of one Embodiment of the illumination optical apparatus by this invention. A is a schematic top view of an embodiment of a virtual image display device according to the present invention. B is a schematic side view of an embodiment of a virtual image display device according to the present invention. It is a schematic side block diagram of the principal part of one Example of the virtual image display apparatus by this invention. It is explanatory drawing of the emission angle and numerical aperture of the X direction of the light inject | emitted from the spatial light modulation part. It is explanatory drawing of the emission angle and numerical aperture of the Y direction of the light inject | emitted from the spatial light modulation part. A is an explanatory diagram in which reverse ray tracing in the X direction is performed from the exit pupil. B is an explanatory diagram in which reverse ray tracing in the Y direction is performed from the exit pupil. It is explanatory drawing of the numerical aperture of the X direction of one Example of the virtual image display apparatus by this invention. It is a schematic block diagram of an example of the image projection apparatus using the conventional light pipe. It is a schematic block diagram of an example of the image projection apparatus using the conventional light pipe. A is a schematic block diagram of an example of a virtual image display device using a light pipe. B is a schematic configuration diagram of an example of a virtual image display device using a light pipe. C is a schematic configuration diagram of an example of a virtual image display device using a light pipe.

Explanation of symbols

  10. Light source, 20. Light pipe, 21. Incident surface, 22. Emission surface, 30. Optical lens, 31. Fresnel lens, 40. Diffusion plate, 50. Polarizing beam splitter, 60. Spatial light modulator 70. Collimating optical system, 80. Pupil, 90. Light guide plate, 91. Optical surface, 91A. Incident part, 91B. Injection part, 92. Optical surface, 93. First reflective volume hologram grating, 94. Second reflective volume hologram grating, 100. Illumination optical apparatus, 200. Virtual image display device

Claims (14)

A light source;
An incident surface on which light beams emitted from the light source is incident, a light pipe having a side surface for total internal reflection of a portion of said light beam at least incident, and a large exit surface area than the incident surface,
At least one optical lens on which a light beam emitted from the light pipe is incident;
A diffusion plate for diffusing a light beam emitted from the optical lens;
A spatial light modulator illuminated with light diffused by the diffuser , and
At least one of the optical lenses is formed by arranging two cylindrical lenses so that their optical powers are orthogonal to each other, and the optical power is different from one direction in the display surface of the spatial light modulator and the other. Different illumination optical devices depending on the direction . A light source;
A light pipe having an incident surface on which a light beam emitted from the light source is incident, a side surface that totally internally reflects at least a part of the incident light beam, and an emission surface having a larger area than the incident surface;
At least one optical lens on which a light beam emitted from the light pipe is incident;
A diffusion plate for diffusing a light beam emitted from the optical lens;
A spatial light modulator illuminated with light diffused by the diffuser, and
At least one of the optical lenses is formed by arranging two Fresnel lenses having optical power only in one direction so that their optical powers are orthogonal to each other, and the optical power is the display surface of the spatial light modulator. Illumination optical devices that are different from each other in one direction and the other. Incident surface of the light pipe, at least one side of the exit surface or the side surface, the illumination optical apparatus according to claim 1 or 2, wherein the curved surface. The illumination optical apparatus according to claim 3 , wherein the curvature of the curved surface of at least one of the incident surface and the exit surface of the light pipe is different in one direction and the other direction in the display surface of the spatial light modulator. . The illumination optical device according to claim 4 , wherein the diffusing plate has a diffusivity that increases along a direction in which the curvature of the curved surface of the light pipe exit surface is large. It said light pipe and the light source, the illumination optical apparatus according to claim 1 or 2, characterized in that formed by optically adhesion. The diffusion plate, the illumination optical apparatus according to claim 1 or 2, wherein having different diffusivity in one direction and the other direction in the spatial light modulator of the display surface. The diffusion plate, the illumination optical apparatus according to claim 1 or 2, wherein the diffusion resistance along the direction of larger optical power is large in the optical lens. An illumination optical device and a virtual image forming optical system which guides the observer's pupil modulated displayed image by the spatial light modulator possess,
The illumination optical device comprises:
A light source;
An incident surface on which light beams emitted from the light source is incident, a light pipe having a side surface for total internal reflection of a portion of said light beam at least incident, and a large exit surface area than the incident surface,
At least one optical lens on which a light beam emitted from the light pipe is incident;
A diffusion plate for diffusing a light beam emitted from the optical lens;
A spatial light modulator illuminated with light diffused by the diffuser , and
At least one of the optical lenses is formed by arranging two cylindrical lenses so that their optical powers are orthogonal to each other, and the optical power is different from one direction in the display surface of the spatial light modulator and the other. Different virtual image display devices depending on the direction . An illumination optical device, and a virtual image imaging optical system that guides the display image modulated by the spatial light modulator to the observer's pupil,
The illumination optical device comprises:
A light source;
A light pipe having an incident surface on which a light beam emitted from the light source is incident, a side surface that totally internally reflects at least a part of the incident light beam, and an emission surface having a larger area than the incident surface;
At least one optical lens on which a light beam emitted from the light pipe is incident;
A diffusion plate for diffusing a light beam emitted from the optical lens;
A spatial light modulator illuminated with light diffused by the diffuser, and
At least one of the optical lenses is formed by arranging two Fresnel lenses having optical power only in one direction so that their optical powers are orthogonal to each other, and the optical power is the display surface of the spatial light modulator. Virtual image display devices that are different from each other in one direction and the other. In the virtual image forming optical system, the numerical aperture of the light emitted from the spatial light modulator and / or the emission angle of the principal ray along the one direction and the other direction in the display surface of the spatial light modulator are mutually different. The virtual image display device according to claim 9 or 10 . The virtual image forming optical system includes a collimating optical system that converts light beams emitted from each pixel of the spatial light modulation unit into parallel light beam groups having different traveling directions, and the parallel light beam groups are incident and propagated by total internal reflection. It is composed of a light guide plate configured to emit toward the pupil of the rear observer,
The light guide plate includes a first reflective volume hologram grating that diffracts and reflects the parallel light beam group so as to satisfy an internal total reflection condition in the light guide plate while maintaining the parallel light beam group in the incident region of the parallel light beam group; The virtual image display apparatus according to claim 11 , further comprising: a second reflective volume hologram grating that diffracts and reflects the parallel light beam group so that the parallel light beam group is emitted from the light guide plate as the parallel light beam group in an emission region of the parallel light beam group. The virtual image display according to claim 12 , wherein the parallel light beam group is propagated without being reflected in a direction substantially orthogonal to a plane along a direction reflecting in the light guide plate and a direction propagating in the light guide plate. apparatus. The virtual image display device according to claim 12 , wherein the parallel light beam group includes parallel light beams that are diffracted and reflected by different portions of the first reflective volume hologram grating and combined.