JP2007304227A - Video display device and video photographing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a luminance difference of the video to be displayed or photographed at both ends of a viewing angle of a user when the user observes or shoots video, so that the user can observe or shoot excellent video. <P>SOLUTION: An optical path for connecting the center of a display area of a video display element to the center of a pupil observing design is defined as an optical axis in a video display device. When the video is observed, a light beam made incident on the optical axis to an intersection point M of a holographic optical element and the optical axis and a light beam outgoing on the optical axis from the intersection point M are defined as observation light beams R1, R2. When a hologram photosensitive material is exposed, two light beams made incident on an intersection point N of the hologram photosensitive material 3a and the optical axis are defined as exposure light beams S1, S2. The holographic optical element is manufactured by irradiating the hologram photosensitive material 3a with at least one of two exposure light beams S1, S2 while being parted from the observation light beams R1, R2. As a result, interference fringes can be recorded on the holographic optical element so that a difference of diffraction efficiencies becomes smaller in the directions corresponding to both ends of the viewing angle when the user observes the video. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image display device provided with a holographic optical element and an image photographing device provided with a holographic optical element.

  The holographic optical element is manufactured by performing interference exposure on a hologram photosensitive material with two coherent light beams (see, for example, Non-Patent Document 1). Since such a holographic optical element can diffract and reflect an incident light beam in an arbitrary direction, it has been conventionally studied to be used for an image display device and an image photographing device.

  The holographic optical element has a characteristic that when light having the same incident angle as one of the two exposure light beams used at the time of manufacture is incident, the other light is reproduced. Therefore, in order to obtain a light beam required at the time of use (reproduction), it is common to perform exposure with two light beams having the same incident angle as at the time of use at the time of production.

Junpei Takiuchi, “Holography”, Kasuga Hanafusa Co., Ltd., November 5, 1997, 1st edition, Chapter 11, Holographic optical elements, p295-p298, ISBN 4-7853-3233-X

  By the way, in a video display device or a video shooting device, it is necessary to handle light corresponding to a specific angle of view called a display field angle (observation field angle) or a shooting field angle. For this reason, when a holographic optical element is manufactured by the above-described conventional general exposure method and this holographic optical element is applied to a video display device or a video photographing device, both ends of the field angle are observed during observation or photographing. There is a problem in that the brightness of the observation image or the photographed image in the video is different, and good image observation or image photographing becomes impossible. This problem will be described as follows by taking a video display device as an example.

  FIG. 10 is an explanatory diagram schematically showing a configuration of a conventional video display device. In this video display device, video light (hereinafter referred to as video light) displayed on the video display element 101 enters the light guide member 102 and is guided through the light guide member 102. It is diffracted and reflected and guided to the observer's pupil. Therefore, the observer can observe an enlarged virtual image of the video displayed on the video display element 101.

  Here, an optical path connecting the center P of the display area of the video display element 101 and the center Q of the design observation pupil is defined as an optical axis. In addition, as shown in FIG. 11, when observing an image, a light beam on the optical axis incident on an intersection M (a point where the optical axis is bent on the holographic optical element 103) M is observed. Let the ray R1 be the ray on the optical axis emitted from the intersection M, and let it be the observation ray R2.

  Further, as shown in FIG. 12, during exposure of the hologram photosensitive material 103a which is a constituent material of the holographic optical element 103, two light beams incident on the intersection N between the hologram photosensitive material 103a and the optical axis are respectively exposed to the exposure light beam S1. -Let S2. Note that the intersection N may be considered to be substantially the same as the intersection M. Further, when the hologram photosensitive material 103a is subjected to interference exposure with two light beams having the exposure light beams S1 and S2 to produce the holographic optical element 103, the direction of the interference fringes recorded therein is the angle formed by the exposure light beams S1 and S2. Is perpendicular to the bisector T.

Conventionally, when the holographic optical element 103 is manufactured by interference exposure of two light beams, the exposure light beams S1 and S2 are set in the same direction as the observation light beams R1 and R2, respectively. In this case, in FIG. 10, the observer sees image light having a wavelength λ that maximizes diffraction efficiency in the A ₁ direction, which is the direction on the optical axis, and observes the image seen in the A ₁ direction brightest. be able to.

However, when an image is observed from the A ₁ direction up and down at the same angle of view θ, the directions at both ends of the angle of view (B ₁ direction and C ₁ direction) are equal to B ₁ even though the angle of view θ is the same from the center. towards the direction of observation images brighter than C ₁ direction of observation images, it can not be satisfactory image observation. Hereinafter, this reason will be described.

FIG. 13A is a cross-sectional view of a volume phase type reflective holographic optical element 201. The holographic optical element 201 is parallel to the recorded interference pattern relative to the device surface (fringe spacing; dnm) against, when light of wavelength λ is incident at an incident angle of 0 degrees (incident from A ₂ direction) In addition, the diffraction efficiency is maximized. Accordingly, the holographic optical element 201 has a function of a regular reflection mirror that reflects light in a direction opposite to the A ₂ direction by 180 degrees when light is incident from a direction perpendicular to the interference fringes (A ₂ direction). Functions as a hologram.

Here, a case is considered in which incident light is incident on the holographic optical element 201 at the same angle θ on the left and right with reference to the B ₂ direction, the C ₂ direction, and the A ₂ direction. FIG. 13B is a graph showing the diffraction characteristics in the holographic optical element 201, that is, the relationship between the incident angle and the diffraction efficiency. Note that A ₂ , B ₂ , and C ₂ in FIG. 13B indicate incident angles in the A ₂ direction, the B ₂ direction, and the C ₂ direction, respectively. Figure 13 (a), the absolute value of the incident angle to the interference fringes are the same in B ₂ direction and C ₂ direction, as shown in FIG. 13 (b), the angle of incidence B ₂ direction and C ₂ directions And the diffraction efficiency is the same. That is, the relationship between the incident angle and the diffraction efficiency, with respect to A ₂ direction of the incident angle of 0 degree indicating the maximum diffraction efficiency and symmetrical graph.

On the other hand, FIG. 14A is a cross-sectional view of a reflection type holographic optical element 301 of volume phase type. The holographic optical element 301, the interference fringes are parallel to the recording surface of the device (fringe spacing; dnm) against, when the incident (A ₃ incident direction) at an angle of incidence of light of wavelength λ is not 0 degrees The diffraction efficiency is maximized. The holographic optical element 301 is a hologram having a function of a regular reflection mirror that reflects light in a direction reverse to the B ₃ direction by 180 degrees when light is incident from a direction perpendicular to the interference fringe (B ₃ direction). Function as.

Here, in the same manner as described above, a case is considered where incident light is incident on the holographic optical element 301 with the same angle θ on the left and right with respect to the B ₃ direction, the C ₃ direction, and the A ₃ direction. . FIG. 14B is a graph showing the diffraction characteristics in the holographic optical element 301, that is, the relationship between the incident angle and the diffraction efficiency. Note that A ₃ , B ₃ , and C ₃ in FIG. 14B indicate incident angles in the A ₃ direction, the B ₃ direction, and the C ₃ direction, respectively. In FIG. 14 (a), the angle of incidence on the interference fringe, is 0 degrees B ₃ direction, since it is 2θ at C ₃ directions, differs between B ₃ direction and the C ₃ directions.

At this time, the maximum diffraction wavelength of the incident light is 2nd cos θ when incident from the A ₃ direction and 2 nd and C ₃ directions when incident from the B ₃ direction, where n is the refractive index of the medium and d is the distance between the interference fringes. 2nd cos 2θ in the case of incidence from. Therefore, the larger the incident angle of the holographic optical element 301 to the interference fringes, the larger the shift amount of the maximum diffraction wavelength due to the influence of the cos function. In other words, when light of a certain wavelength λ is incident on the interference fringe, the direction in which the incident angle on the interference fringe increases is the same as the incident angle shift compared to the direction in which the incident angle on the interference fringe decreases. This means that the amount of decrease in diffraction efficiency is large.

Therefore, as shown in FIG. 14B, the relationship between the incident angle and the diffraction efficiency is not a graph symmetrical with respect to the incident angle in the A ₃ direction indicating the maximum diffraction efficiency, and is based on the A ₃ direction. and the angular deviation be (absolute value) is the same for the B ₃ direction and the C ₃ direction, the angle of incidence is greater than C ₃ direction to the interference fringes, the angle of incidence is less than B ₃ direction to the interference fringe The diffraction efficiency is lower than that. Since the reflection-type holographic optical element has high wavelength selectivity and angle selectivity, the above phenomenon occurs particularly remarkably in the reflection-type holographic optical element.

As described above, the diffraction efficiency is lower in the direction in which the incident angle with respect to the interference fringes of the holographic optical element is larger than in the direction in which the incident angle with respect to the interference fringes is smaller. , When an observer observes an image at the same angle of view θ up and down from the A ₁ direction, the angle corresponding to the incident angle among the B ₁ direction and the C ₁ direction at both ends of the angle of view, that is, the method of interference fringes luminance of the image is the angle between the line direction and the observation direction is observed with greater becomes C ₁ direction is lower than the luminance of an image in which the angle is observed at the smaller B ₁ direction (darker).

  The present invention has been made to solve the above-described problems, and its purpose is to reduce the luminance difference between the display image and the captured image at both ends of the observation field angle and the shooting field angle. It is possible to provide a video display device and a video shooting device that can perform favorable video observation and video shooting.

  The video display device of the present invention is a video display device that causes image light from the video display element to be diffracted and reflected in the pupil direction by a holographic optical element, and allows an observer to observe the video. The hologram photosensitive material is manufactured by interference exposure with two light beams. The optical path connecting the center of the display area of the image display element and the center of the design observation pupil is used as the optical axis. The light beam on the optical axis incident on the intersection point with the light beam and the light beam on the optical axis emitted from the intersection point are respectively used as observation light beams, and two light beams incident on the intersection point between the hologram photosensitive material and the optical axis at the time of exposure. Assuming that each is an exposure light beam, the holographic optical element is produced by irradiating the hologram photosensitive material with at least one of the two exposure light beams deviating from the observation light beam. It is characterized in that it is.

  According to the above configuration, the image light from the image display element is diffracted and reflected in the pupil direction by the holographic optical element, so that the observer can image the image at a certain observation angle of view at the position of the design observation pupil. Can be observed.

  At this time, the holographic optical element is manufactured by irradiating the hologram photosensitive material with at least one of the two exposure light beams deviating from the observation light beam. Since the holographic optical element is manufactured by such an exposure method, the viewing angle of view is larger than that in the case where the holographic optical element is manufactured by aligning the two exposure light beams with the observation light beam. It is possible to record interference fringes on the holographic optical element so that the difference in diffraction efficiency in the direction corresponding to both corners is reduced. As a result, the luminance difference between the observation images at both ends of the observation angle of view can be reduced, and good image observation can be performed.

  In the present invention, the angle formed by the two observation light beams is the first angle, the angle formed by the two exposure light beams, and one exposure light beam incident on the intersection of the hologram photosensitive material and the optical axis; If the angle formed by the other exposure light beam emitted from the intersection is a second angle, the holographic optical element has two exposure light beams such that the second angle is larger than the first angle. It may be produced by exposing the hologram photosensitive material with two light beams.

  When the hologram photosensitive material is exposed by exposing the hologram photosensitive material with the second angle larger than the first angle, the exposure of the hologram photosensitive material with both of the two exposure light rays coincided with the observation light beam is recorded interference. The inclination of the stripe can be surely changed. As a result, interference fringes can be recorded on the holographic optical element with such an inclination that the difference in diffraction efficiency between the directions corresponding to both ends of the viewing angle of view becomes small. Therefore, the difference in luminance of the observation image at both ends of the observation angle of view can be surely reduced, and good image observation can be reliably performed.

  In the present invention, the two light beams for exposing the hologram photosensitive material are preferably parallel lights.

  The two light beams may be, for example, parallel light and divergent light. In this case, the light condensing position of the light diffracted by the manufactured holographic optical element has a design area (brightness). In some cases, the resolution of the image observed at the design observation pupil may be reduced by deviating from the region in which distortion, aberration, etc. are improved. When both of the two light beams are parallel light, such a shift of the condensing position does not occur, so that the observation image at both ends of the observation angle of view is avoided while avoiding the reduction in the resolution of the observation image. The brightness difference can be reduced.

  In addition, the video display device of the present invention includes light guide members having planes parallel to each other, and the holographic optical element is held on the plane of the light guide member, and is guided while being totally reflected in the light guide member. The image light from the image display element that has been illuminated may be diffracted and reflected in the pupil direction.

  In this configuration, the image light from the image display element is guided while being totally reflected in the light guide member, is diffracted and reflected by the holographic optical element, and is guided to the observer's pupil. Therefore, it is possible to use a thin light guide member, whereby the video display device can be configured to be thin and compact.

  In the present invention, the holographic optical element has an exposure light beam that enters through the incident prism, passes through the unnecessary light extraction prism after being exposed to the hologram photosensitive material, and another exposure light beam. It is produced by exposing the hologram photosensitive material with a light beam. At the time of exposure, the incident prism is formed on the surface of the hologram photosensitive material or on the surface opposite to the holding side of the hologram photosensitive material in the light guide member. The unnecessary light extraction prism is closely arranged on the surface of the light guide member opposite to the hologram photosensitive material holding side or on the hologram photosensitive material surface without an air layer. It is desirable that

  According to the above configuration, at the time of exposure of the hologram photosensitive material, one exposure light beam passes through the incident prism, the hologram photosensitive material, the light guide member, and the unnecessary light extraction prism in this order, or the incident prism, the light guide The member, the hologram photosensitive material, and the unnecessary light extraction prism are transmitted in this order.

  As described above, in either case, by exposing one exposure light beam into the light guide member via the incident prism, the exposure light beam can be incident into the light guide member at an angle that totally reflects the light guide member. it can.

  Further, since the exposure light beam is exposed to the outside through the unnecessary light extraction prism after the hologram photosensitive material is exposed, the exposure light beam is generated at the interface between the light guide member and air, or at the interface between the hologram photosensitive material and air. There is no possibility that the hologram photosensitive material is irradiated again after being totally reflected. Therefore, a holographic optical element can be produced with high efficiency. Moreover, there is little ghost of the observation image by unnecessary light, and a bright observation image can be obtained.

  The video display device of the present invention further includes another holographic optical element held on the plane of the light guide member, and the other holographic optical element is an image incident on the light guide member from the video display element. The light may be diffracted and reflected so as to be totally reflected in the light guide member.

  According to this configuration, regardless of the incident direction (incident angle) of the image light from the image display element with respect to the light guide member, the image light is diffracted and reflected by the other hologram photosensitive material and totally reflected in the light guide member. Can be guided. Accordingly, it is possible to increase the degree of freedom in arranging the video display elements.

  In the present invention, the holographic optical element may have a diffraction characteristic in which a plurality of diffraction peak wavelengths at which the diffraction efficiency reaches a peak exist. In this case, the observer can observe a color image.

  A video imaging apparatus according to the present invention is a video imaging apparatus that shoots a subject image with an imaging device by diffracting and reflecting light of the subject image with a holographic optical element and guiding the light to the imaging device. Is produced by interference exposure of a hologram photosensitive material with two light beams, and the optical path connecting the center of the imaging area of the imaging device and the center of the subject image is used as the optical axis, and the holographic optical element and the optical axis are used during shooting. The light beam on the optical axis incident on the intersection point with the light beam and the light beam on the optical axis emitted from the intersection point are respectively taken as photographic light rays, and at the time of exposure, the two light beams incident on the intersection point between the hologram photosensitive material and the optical axis are Assuming that each is an exposure light beam, the holographic optical element is formed by irradiating the hologram photosensitive material with at least one of the two exposure light beams deviating from the photographing light beam. It is characterized by being manufactured.

  According to the above configuration, the light of the subject image is diffracted and reflected by the holographic optical element and guided to the imaging element. As a result, a subject image with a certain angle of view can be captured by the image sensor.

  At this time, the holographic optical element is manufactured by irradiating the hologram photosensitive material with at least one of the two exposure light beams being deviated from the photographing light beam. Since the holographic optical element is manufactured by such an exposure method, the image of the field of view is larger than that in the case where the holographic optical element is manufactured by matching both exposure light rays with the photographic light ray. It is possible to record interference fringes on the holographic optical element so that the difference in diffraction efficiency in the direction corresponding to both corners is reduced. As a result, the brightness difference between the captured images at both ends of the captured angle of view can be reduced, and favorable image capturing can be performed.

  Further, in the present invention, the angle formed by the two photographing light beams is the first angle, the angle formed by the two exposure light beams, and one exposure light beam incident on the intersection of the hologram photosensitive material and the optical axis; If the angle formed by the other exposure light beam emitted from the intersection is a second angle, the holographic optical element has two exposure light beams such that the second angle is larger than the first angle. It may be produced by exposing the hologram photosensitive material with two light beams.

  When the hologram photosensitive material is exposed by exposing the hologram photosensitive material with the second angle larger than the first angle, the exposure of the hologram photosensitive material with both of the two exposure light rays coincided with the photographing light beam is recorded interference. The inclination of the stripe can be surely changed. Thereby, it is possible to record interference fringes on the holographic optical element with such an inclination that the difference in diffraction efficiency in the direction corresponding to both ends of the field angle of the photographic field angle becomes small. Therefore, it is possible to reliably reduce the luminance difference between the captured images at both ends of the captured angle of view, and it is possible to reliably capture a good image.

  In the present invention, the two light beams for exposing the hologram photosensitive material are preferably parallel lights.

  The two light beams may be, for example, parallel light and divergent light. In this case, the light condensing position of the light diffracted by the manufactured holographic optical element has a design area (brightness). In other cases, the resolution of the captured image may be reduced by deviating from the region in which distortion, aberration, etc. are improved. When both of the two light beams are parallel lights, such a condensing position shift does not occur, so that a reduction in the resolution of the shot image is avoided and the shot image at both ends of the shot angle of view is reduced. The brightness difference can be reduced.

  In addition, the video imaging apparatus of the present invention includes a light guide member having planes parallel to each other, and the holographic optical element is held on the plane of the light guide member, and is guided while being totally reflected in the light guide member. A configuration may be adopted in which the light of the illuminated subject image is diffracted and reflected and guided to the image sensor.

  In this configuration, the light of the subject image is guided while being totally reflected in the light guide member, is diffracted and reflected by the holographic optical element, and is guided to the imaging element. Therefore, it is possible to use a thin light guide member, whereby the video photographing apparatus can be configured to be thin and compact.

  In the present invention, the holographic optical element has an exposure light beam that enters through the incident prism, passes through the unnecessary light extraction prism after being exposed to the hologram photosensitive material, and another exposure light beam. It is produced by exposing the hologram photosensitive material with a light beam. At the time of exposure, the incident prism is formed on the surface of the hologram photosensitive material or on the surface opposite to the holding side of the hologram photosensitive material in the light guide member. The unnecessary light extraction prism is closely arranged on the surface of the light guide member opposite to the hologram photosensitive material holding side or on the hologram photosensitive material surface without an air layer. It is desirable that

  According to the above configuration, at the time of exposure of the hologram photosensitive material, one exposure light beam passes through the incident prism, the hologram photosensitive material, the light guide member, and the unnecessary light extraction prism in this order, or the incident prism, the light guide The member, the hologram photosensitive material, and the unnecessary light extraction prism are transmitted in this order.

  As described above, in either case, by exposing one exposure light beam into the light guide member via the incident prism, the exposure light beam can be incident into the light guide member at an angle that totally reflects the light guide member. it can.

  Further, since the exposure light beam is exposed to the outside through the unnecessary light extraction prism after the hologram photosensitive material is exposed, the exposure light beam is generated at the interface between the light guide member and air, or at the interface between the hologram photosensitive material and air. There is no possibility that the hologram photosensitive material is irradiated again after being totally reflected. Therefore, a holographic optical element can be produced with high efficiency. In addition, there is little ghost in the captured image due to unnecessary light, and a bright captured image can be obtained.

  In addition, the video imaging apparatus of the present invention includes another holographic optical element that is held on the plane of the light guide member, and the other holographic optical element is light of the subject image incident on the light guide member from the outside. May be diffracted and reflected so as to be totally reflected in the light guide member.

  According to this configuration, regardless of the incident direction (incident angle) of the light of the subject image with respect to the light guide member, the light of the subject image is diffracted and reflected by the other hologram photosensitive material and totally reflected within the light guide member. Can be guided. Therefore, it is possible to increase the degree of freedom of arrangement of the image sensor.

  In the present invention, the holographic optical element may have a diffraction characteristic in which a plurality of diffraction peak wavelengths at which the diffraction efficiency reaches a peak exist. In this case, a color image can be taken with the image sensor.

  According to the present invention, the holographic optical element is manufactured by irradiating the hologram photosensitive material with at least one of the two exposure light beams deviating from the observation light beam (or photographing light beam). Accordingly, it is possible to record interference fringes on the holographic optical element so that the difference in diffraction efficiency in the direction corresponding to both ends of the viewing angle of view (or the shooting angle of view) is reduced. Accordingly, it is possible to reduce the luminance difference between the observation images (or the captured images) at both ends of the observation angle of view (or the shooting angle of view), and it is possible to perform favorable image observation (or image capturing).

[Embodiment 1]
An embodiment of the present invention will be described below with reference to the drawings.
FIG. 2 is an explanatory diagram schematically showing the configuration of the video display device of the present invention. This video display device includes a video display element 1, a light guide member 2, and a holographic optical element 3.

  The video display element 1 displays video by modulating light according to image data, and is composed of, for example, a liquid crystal display element (LCD) having a light source. The light guide member 2 guides the image light from the image display element 1 inside and guides it to the holographic optical element 3. The holographic optical element 3 is a volume phase type reflection type diffractive optical element that diffracts and reflects incident light. The holographic optical element 3 is produced by subjecting a hologram photosensitive material 3a (see FIG. 1), which is a constituent material thereof, to interference exposure with two light beams, and is held on the lower end surface (inclined surface) of the light guide member 2. Yes.

  In this configuration, image light from the image display element 1 enters the light guide member 2 from its upper end surface, is guided through the light guide member 2, and is diffracted and reflected in the pupil direction by the holographic optical element 3. The Thereby, the observer can observe an image (a virtual image of a display image of the image display element 1) at a certain observation angle of view at the position of the design observation pupil.

  By the way, in this embodiment, the direction of the interference fringes recorded on the holographic optical element 3 in FIG. 2 is different from the direction of the interference fringes recorded on the holographic optical element 103 in FIG. The video display device of the present invention is different from the conventional one in that the holographic optical element 3 on which interference fringes are recorded is used. Hereinafter, this point will be described in detail.

  For convenience of explanation below, an optical path connecting the center P of the display area of the video display element 1 and the center Q of the design observation pupil is defined as an optical axis. In addition, as shown in FIG. 3, when observing an image, a light beam on the optical axis incident on an intersection M (a point at which the optical axis is bent on the holographic optical element 3) M between the holographic optical element 3 and the optical axis. An observation light beam R1 is used, and a light beam on the optical axis emitted from the intersection M is an observation light beam R2. In other words, the observation light beam R2 can be said to be a light beam on the optical axis that is emitted from the intersection M after the observation light beam R1 from the image display device 1 is diffracted and reflected by the holographic optical device 3.

  Further, as shown in FIG. 1, two light beams incident on the intersection N between the hologram photosensitive material 3a and the optical axis at the time of exposure of the hologram photosensitive material 3a are referred to as exposure light beams S1 and S2, respectively. Note that the intersection N may be considered to be substantially the same as the intersection M. Further, when the holographic optical element 3 is manufactured by interference exposure of the hologram photosensitive material 3a with the two light beams having the exposure light beams S1 and S2, the direction of the interference fringes recorded therein is the angle formed by the exposure light beams S1 and S2. Is perpendicular to the bisector T.

  In FIG. 1, the observation light beams R1 and R2 are also shown for easy understanding of the explanation to be described later. Further, although the observation light beam R1 is illustrated apart from the exposure light beam S1, it is assumed that it actually overlaps.

  In the present embodiment, as shown in FIG. 1, the exposure light beam S1 is irradiated onto the hologram photosensitive material 3a through the same optical path as the observation light beam R1, while the exposure light beam S2 deviates from the observation light beam R2 while passing through the intersection N (observation). The holographic optical element 3 is produced by irradiating the hologram photosensitive material 3a (in a direction different from the light ray R2). In particular, in the present embodiment, the angle formed by the two observation light beams R1 and R2 is the first angle θ1 (see FIG. 3), and the angle formed by the two exposure light beams S1 and S2, and the hologram photosensitive material 3a and the light. When the angle formed by one exposure light beam S1 incident on the intersection N with the axis and the other exposure light beam S2 emitted from the intersection N is a second angle θ2 (see FIG. 1), the holographic optical element 3 Is produced by exposing the hologram photosensitive material 3a with two light beams having two exposure light beams S1 and S2 such that the second angle θ2 is larger than the first angle θ1.

  Since the holographic optical element 3 is produced in such a manner of exposure, compared to the case where exposure is performed with both the directions of the two exposure light beams S1 and S2 aligned with the directions of the observation light beams R1 and R2, It is possible to record interference fringes on the holographic optical element 3 so that the difference in diffraction efficiency between the B direction and the C direction corresponding to both ends of the viewing angle of view shown in FIG. Hereinafter, this point will be described in detail.

  FIG. 4 is a graph showing the relationship between the observation angle of view and the video luminance. In particular, the broken line a1 in the figure shows the relationship between the observation angle of view and the image luminance in a holographic optical element produced by a conventional exposure method in which the exposure light rays S1 and S2 are in the same direction as the observation light rays R1 and R2. A solid line a2 indicates the relationship between the viewing angle of view and the image brightness in the holographic optical element 3 produced by the exposure method of this embodiment in which the exposure light beam S2 is shifted from the observation light beam R2.

  Note that the viewing angles A, B, and C on the horizontal axis are based on the A direction, which is the direction of the optical axis in FIG. The angle of view is 0 degrees, −θ degrees, and + θ degrees, respectively. The absolute value of the incident angle of the holographic optical element with respect to the interference fringes (here, the angle between the normal direction of the interference fringes and the observation direction) increases in the order of B direction, A direction, and C direction. And Further, the video luminance on the vertical axis is shown as a relative value when the maximum luminance is 1. Since this image luminance is determined by the diffraction efficiency of the holographic optical element in a certain observation direction, the image luminance on the vertical axis can be read as the diffraction efficiency of the holographic optical element.

  As described above, the diffraction efficiency of the holographic optical element is such that the larger the incident angle with respect to the interference fringes, the greater the reduction in diffraction efficiency with respect to the same angular deviation. In the element, of the B direction and the C direction corresponding to both ends of the field angle of the observation field angle, the diffraction angle is larger in the C direction where the incident angle to the interference fringe is larger and the incident angle to the interference fringe is smaller than the B direction. The amount of decrease in efficiency increases. Therefore, the diffraction efficiency of the holographic optical element is smaller in the C direction than in the B direction, and the image luminance at both ends of the viewing angle of the observation field angle is lower in the C direction than in the B direction. That is, in the conventional video display device, the video image observed in the B direction becomes bright and the video image observed in the C direction becomes dark (see the broken line a1).

  However, by producing the holographic optical element 3 by the exposure method of the present embodiment, as shown in FIG. 1, the normal direction of the interference fringes of the holographic optical element 3 is closer to the direction of the design observation pupil. The holographic optical element 3 recorded with tilted interference fringes can be obtained. Thereby, since the incident angle to the interference fringe at both ends of the viewing angle of view changes, the holographic optical element 3 having the characteristic that the broken line a1 is shifted to the solid line a2 can be obtained. That is, it is possible to obtain the holographic optical element 3 having such characteristics that almost no difference in image luminance (difference in diffraction efficiency) occurs between the B direction and the C direction at both ends of the viewing angle. In this way, the difference in brightness of the observation image at both ends of the observation angle of view becomes small, and thus the observer can perform good image observation.

  In particular, in this embodiment, the holographic optical element 3 exposes the hologram photosensitive material 3a with two light beams having two exposure light beams S1 and S2 such that the second angle θ2 is larger than the first angle θ1. It is produced by. As a result, the interference fringes can be reliably recorded on the holographic optical element 3 with such an inclination that the difference in diffraction efficiency between the B direction and the C direction becomes small. The effect of can be obtained reliably.

  In the present embodiment, the exposure light beam S1 is made equal to the observation light beam R1, and the exposure light beam S2 is shifted from the observation light beam R2. However, if the second angle θ2 is larger than the first angle θ1, The exposure light beam S2 may be made equal to the observation light beam R2, the exposure light beam S1 may be shifted from the observation light beam R1, or both the exposure light beams S1 and S2 may be shifted from the observation light beam R1 and R2.

Further, when at least one of the two exposure light beams S1 and S2 is shifted from the observation light beam R1 and R2, if the wavelength of light used for exposure is similar to the wavelength of video light for observation, θ2−θ1 is It is desirable to satisfy the following conditional expression.
0 ° <θ2-θ1 ≦ 20 °
This is because if at least one of the exposure light beams S1 and S2 is shifted too much from the observation light beams R1 and R2, the exposure wavelength and the wavelength of the diffracted image light are greatly shifted, and the observed image becomes dark. .

  Note that the range of θ2−θ1 is largely determined by two points of the use angle of view (which angle is desired to be used for observation) and the material used as the hologram photosensitive material 3a. Just do it. For example, when the use angle of view is wide, it is necessary to increase θ2−θ1.

  Further, in the holographic optical element 3, the wider the half-value wavelength width of the diffraction efficiency peak is, the more tolerance for wavelength shift is. , Diffraction efficiency tends to decrease). At this time, if the difference between the high refractive index portion and the low refractive index portion in the interference fringes is Δnd, the greater the Δnd, the easier the diffraction efficiency, and the half-value wavelength width becomes narrower. Moreover, even if the film thickness of the hologram photosensitive material 3a is increased, the half-value wavelength width is reduced.

  From the above, the hologram photosensitive material 3a has the characteristics that the half-value wavelength width of the diffraction efficiency peak is narrow (thick film thickness, Δnd is large), and the correction is most effective when it is desired to use at a wide angle of view. This is the case where it is necessary (when θ2−θ1 needs to be maximized), and vice versa (when Δnd is small, the film thickness is thin, and the angle of view is narrow), it can be said that it is not necessary to make much correction. .

  Even if the holographic optical element 3 manufactured by the exposure method described in the present embodiment is used, the image brightness in both directions at an angle of view (an angle of view larger than the B direction and the C direction) greatly deviated from the optical axis. The difference is improved, but remains to some extent. However, in practice, the angle of view used during observation (the angle of view at which the image is actually observed) is limited to a certain range (for example, ± 10 degrees from the optical axis) by design. What is necessary is just to make the brightness | luminance difference by a corner small. In other words, even when a large difference in brightness at both ends of the angle of view is conspicuous, the method described in this embodiment can reduce the difference in video luminance between the brightest and the darkest angles of view as a whole. Therefore, the image can be observed satisfactorily.

  In this way, by exposing at least one of the two exposure light beams S1 and S2 to the observation light beams R1 and R2 to expose the hologram photosensitive material 3a, the method of reducing the luminance difference at both ends of the viewing angle of view is as follows. Actually, when the holographic optical element 3 has a characteristic of reflecting parallel light with parallel light (a characteristic having no optical power) like a mirror that reflects incident light at a mere arbitrary angle, the above-described case is described. The effect of the present invention is exerted strongly. This is effective to some extent even when the holographic optical element 3 has a little weak optical power, but when the optical power (lens action) is strong, the incident angle is changed and exposure is performed. This is because a deviation from the design value of the image forming position itself of the light beam is increased, which causes adverse effects such as a reduction in video resolution.

  That is, the two light beams for exposing the hologram photosensitive material 3a may be, for example, parallel light and divergent light. In this case, the light condensing position of the light diffracted by the produced holographic optical element 3 is There may be a case where the resolution of the image observed on the design observation pupil is lowered from the design area where resolution is taken (area where brightness, distortion, aberration, etc. are improved). Therefore, since the two light beams for exposing the hologram photosensitive material 3a are made parallel light, and the holographic optical element 3 having almost no optical power is produced, there is no occurrence of such a condensing position shift. While avoiding a decrease in the resolution of the observation video, it is possible to reduce the luminance difference of the observation video at both ends of the observation angle of view.

[Embodiment 2]
The following will describe another embodiment of the present invention with reference to the drawings. For convenience of explanation, the same components as those in the first embodiment are denoted by the same member numbers, and the description thereof is omitted.

  FIG. 5 is an explanatory diagram showing a schematic configuration of the video display apparatus according to the present embodiment. The video display device includes a video display element 1, a light guide member 2, and holographic optical elements 3 and 4.

  The video display element 1 includes a light source 11, a light modulation element 12, and an eyepiece optical system 13. The light source 11 is composed of an LED that emits light of each wavelength of R (red), G (green), and B (blue), for example. The light modulation element 12 displays an image by modulating light from the light source 11 according to image data, and is configured by an LCD, for example. The eyepiece optical system 13 converts the image light from the light modulation element 12 into parallel light and guides it to the light guide member 2.

  The light guide member 2 is a transparent substrate that guides video light from the video display element 1 inside, and has parallel surfaces 2a and 2b facing each other.

  The holographic optical element 3 is a volume phase type reflection type diffractive optical element, and is manufactured by subjecting a hologram photosensitive material 3a, which is a constituent material thereof, to interference exposure with two light beams. The holographic optical element 3 is held on a surface 2 a opposite to the surface 2 b on the image display element 1 side of the light guide member 2, and receives image light incident from the image display element 1 into the light guide member 2. The light is diffracted and reflected so as to be totally reflected in the light guide member 2.

  The holographic optical element 4 is a volume phase type reflection type diffractive optical element, and is produced by performing interference exposure of a hologram photosensitive material 4a, which is a constituent material thereof, with two light beams. The holographic optical element 4 is held on the surface 2b of the light guide member 2 on the video display element 1 side, and is guided by being diffracted and reflected by the holographic optical element 3 while being totally reflected in the light guide member 2. The image light from the image display element 1 thus made is diffracted and reflected in the pupil direction.

  According to the above configuration, the light from the light source 11 of the video display element 1 is modulated by the light modulation element 12 and enters the eyepiece optical system 13 as video light, where it is enlarged and guided in the parallel light state. 2 enters from the surface 2b side. The image light is diffracted and reflected by the holographic optical element 3 and guided to the holographic optical element 4 while being totally reflected in the light guide member 2. In the holographic optical element 4, the incident video light is diffracted and reflected and guided to the observer's pupil. The holographic optical elements 3 and 4 may be on the same surface (for example, the surface 2a) of the light guide member 2. In this case, the number of times the light is totally reflected in the light guide member 2 is an odd number.

  In the present embodiment, the holographic optical elements 3 and 4 held on the surfaces 2a and 2b of the light guide member 2 are both produced by the exposure method as described in the first embodiment. In other words, the holographic optical elements 3 and 4 are manufactured by irradiating the hologram photosensitive materials 3a and 4a with at least one of the two exposure light beams being removed from the observation light beam.

  For example, FIG. 6 is an explanatory view schematically showing an exposure method when producing the holographic optical element 4. As shown in the figure, in the holographic optical element 4, among the two exposure light beams S1 and S2, for example, the exposure light beam S1 is irradiated to the hologram photosensitive material 4a along the same optical path as the observation light beam R1, while the exposure light beam S2 is emitted. It is produced by irradiating the hologram photosensitive material 4a off the observation light beam R2. At this time, the hologram photosensitive material 4a is exposed so that the second angle θ2> the first angle θ1. The exposure light beam S2 may be equal to the observation light beam R2, the exposure light beam S1 may be shifted from the observation light beam R1, and both the exposure light beams S1 and S2 may be shifted from the observation light beam R1 and R2. . The same applies to the production of the holographic optical element 3.

  As described above, the holographic optical elements 3 and 4 are manufactured by irradiating the hologram photosensitive materials 3a and 4a with at least one of the two exposure light beams being deviated from the observation light beam. In addition, interference fringes can be recorded on the holographic optical elements 3 and 4 so that the difference in diffraction efficiency in the direction corresponding to both ends of the viewing angle of view becomes small. As a result, even when an image observation apparatus is configured using a plurality of holographic optical elements 3 and 4 as in the present embodiment, the difference in luminance of the observation image at both ends of the angle of view can be reduced, and a good image can be obtained. Observation becomes possible.

  Further, since the holographic optical element 4 diffracts and reflects the image light from the image display element 1 guided while totally reflecting inside the light guide member 2 in the pupil direction, the light guide member 2 is configured to be thin. The video display device can be thin and compact.

  Further, the holographic optical element 3 diffracts and reflects the image light incident from the image display element 1 into the light guide member 2 so as to be totally reflected in the light guide member 2. Regardless of the incident direction (incident angle), the image light can be diffracted and reflected by the hologram photosensitive material 3 and guided so as to be totally reflected in the light guide member 2. Therefore, the degree of freedom of arrangement of each component of the video display element 1 can be increased.

  By the way, in the case where the image light is guided by total reflection in the light guide member 2 as in the present embodiment, the exposure light beam S1 needs to be incident at an angle that totally reflects in the light guide member 2. In the air, it cannot be incident at the above angle as it is. For this reason, as shown in FIG. 6, the incident prism 21 having the same refractive index as that of the light guide member 2 is disposed in close contact with the surface 2a of the light guide member 2 without using an air layer (via matching oil or the like). Then, the total reflection at the interface is prevented, and the exposure light beam S1 is incident on the light guide member 2.

  As it is, the exposure light beam S1 passes through the hologram photosensitive material 4a, is totally reflected at the interface between the hologram photosensitive material 4a and air, and is reflected again into the hologram photosensitive material 4a. In order to remove this unnecessary light, an unnecessary light extraction prism 22 having a refractive index equivalent to that of the light guide member 2 is closely arranged on the hologram photosensitive material 4a without using an air layer (via matching oil or the like), Remove to the outside. As a result, the holographic optical element 4 having the characteristic of diffracting and reflecting the image light guided by total reflection in the pupil direction can be reliably produced, and the holographic optical element 4 having good diffraction efficiency can be produced.

  Here, the incident prism 21 is disposed on the surface 2a side of the light guide member 2 and the unnecessary light extraction prism 22 is disposed on the surface side of the hologram photosensitive material 4a. However, the directions of the two exposure light beams S1 and S2 are 180 degrees. The holographic optical element 4 may be manufactured by arranging the incident prism 21 on the hologram photosensitive material 4 a side and the unnecessary light extraction prism 22 on the surface 2 a side of the light guide member 2.

  Therefore, one of the two exposure light beams S1 and S2 (for example, S1) is incident through the incident prism 21, and is exposed to the outside through the unnecessary light extraction prism 22 after exposing the hologram photosensitive material 4a. When the holographic optical element 4 is produced by exposing the hologram photosensitive material 4a with two light beams having this exposure light beam and another exposure light beam (for example, S2), the incident prism 21 and the unnecessary light extraction prism 22 are produced. Can be said to be arranged as follows.

  That is, at the time of exposure, the incident prism 21 is disposed in close contact with the surface 2a of the light guide member 2 opposite to the holding side of the hologram photosensitive material 4a without an air layer, and the unnecessary light extraction prism 22 is It is sufficient that the hologram photosensitive material 4a is disposed in close contact with the surface of the hologram photosensitive material 4a without using an air layer. Further, at the time of exposure, the incident prism 21 is disposed in close contact with the surface of the hologram photosensitive material 4a without an air layer, and the unnecessary light extraction prism 22 is provided on the light guide member 2 holding side of the hologram photosensitive material 4a. On the surface 2a on the opposite side, the air may be disposed in close contact with the air layer.

  FIG. 7 is a graph showing the diffraction characteristics of the holographic optical elements 3 and 4, that is, the relationship between the wavelength of incident light and the diffraction efficiency. As shown in the figure, the holographic optical elements 3 and 4 have diffraction characteristics in which there are a plurality of diffraction peak wavelengths at which diffraction efficiency peaks. More specifically, the holographic optical elements 3 and 4 have a characteristic that a diffraction peak wavelength exists in each wavelength region of RGB corresponding to RGB light emitted from the light source 11. Since the holographic optical elements 3 and 4 have such characteristics, RGB image lights can be guided from the image display element 1 to the pupils of the observer, so that the observer observes a color image. It becomes possible.

  In order to produce the holographic optical elements 3 and 4 having the characteristics shown in FIG. 7, it is necessary to expose the hologram photosensitive materials 3a and 4a with light of three colors of RGB. In this case, from the laser light source The emitted RGB light beams are bundled into one light beam, and these light beams are branched to form two light beams including exposure light beams S1 and S2, and three colors of light for each of the two light beams are simultaneously or sequentially holograms. The light-sensitive materials 3a and 4a may be irradiated.

  In order to manufacture the holographic optical elements 3 and 4 with high efficiency, the polarization direction of the light beams S1 and S2 is a plane including the light beams S1 and S2 (light is guided within the light guide member 2). It is desirable that the direction be perpendicular to the traveling cross section (for example, S-polarized light).

[Embodiment 3]
The following will describe still another embodiment of the present invention with reference to the drawings. For convenience of explanation, the same members as those in the first or second embodiment are denoted by the same member numbers, and the explanation thereof is omitted.

  FIG. 8 is an explanatory diagram showing a schematic configuration of the video imaging apparatus of the present embodiment. This video photographing apparatus has an image pickup element 31 (for example, CCD or CMOS), a photographing optical system 32, a light guide member 2, and holographic optical elements 3 and 4. That is, in the video imaging apparatus of the present embodiment, the light source 11 and the light modulation element 12 of the video observation apparatus of the second embodiment are replaced with the imaging element 31, the eyepiece optical system 13 is replaced with the imaging optical system 32, and the design observation pupil is replaced. The configuration is exactly the same as that of the second embodiment except that the holographic optical elements 3 and 4 are reversed in position by being replaced with a subject image. That is, the production method of the holographic optical elements 3 and 4 (the exposure method of the hologram photosensitive materials 3a and 4a), characteristics, and the like are all the same as those of the video display device of the second embodiment.

  In this configuration, the light of the subject image is diffracted and reflected by the holographic optical element 3, guided through the light guide member 2 by total reflection, and guided to the holographic optical element 4. In the holographic optical element 4, incident light is diffracted and reflected, and is emitted from the surface 2 b of the light guide member 2 in parallel with the light incident on the holographic optical element 3 from the outside. Led to. As a result, it is possible to shoot a subject image having a certain shooting angle of view with the imaging element 31.

  Note that, as shown in FIG. 9, the shooting angle of view in the video imaging apparatus corresponds to, for example, a broken line light L1, a solid line light L2, and a one-dot chain line light L3. In the video photographing apparatus, the light L1, L2, and L3 of each photographing angle of view are condensed by the photographing optical system 32 at positions X1, X2, and X3 on the imaging surface of the imaging element 31, respectively. That is, the condensing position on the image pickup surface of the image pickup element 31 is different for each light L1, L2, and L3 of each shooting field angle. Therefore, the luminance difference between both ends of the shooting angle of view corresponds to the difference in luminance of the shot image obtained based on the light condensed at the condensing positions X1 and X3.

  In addition, the observation light beam in the first and second embodiments corresponds to the photographing light beam in this embodiment. Here, the photographing light beam refers to a light beam on the optical axis that is incident on the intersection of the holographic optical element and the optical axis and a light beam on the optical axis that is emitted from the intersection at the time of photographing. In addition, the optical axis in the present embodiment refers to an optical path that connects the center of the imaging region of the image sensor 31 and the center of the subject image.

  As described above, also in the video imaging apparatus of the present embodiment, the method for manufacturing the holographic optical elements 3 and 4 is the same as that in the first and second embodiments. In other words, the holographic optical elements 3 and 4 are manufactured by irradiating the hologram photosensitive materials 3a and 4a with at least one of the two exposure light beams being separated from the photographing light beam. As a result, the difference in diffraction efficiency in the direction corresponding to both ends of the field angle of the photographic field angle is reduced as compared with the case where the holographic optical element is manufactured by making both of the two exposure light rays coincide with the photographic light beam. Thus, interference fringes can be recorded on the holographic optical elements 3 and 4. Therefore, also in the video shooting device, the difference in luminance of the shot video at both ends of the shooting angle of view can be reduced, and good video shooting can be performed.

  Note that all the configurations and techniques described in the first and second embodiments relating to the video display device can be applied to the video imaging device of the present embodiment. Therefore, in this case, an effect corresponding to the effect described in Embodiments 1 and 2 can be obtained by the video imaging apparatus.

  Needless to say, the video display device and the video observation device can be configured by appropriately combining the configurations and methods described in the embodiments.

  The video display device of the present invention can be used for, for example, a head-up display or a head-mounted display, and the video shooting device of the present invention can be used for, for example, a digital camera.

It is explanatory drawing which shows typically the exposure method when producing the holographic optical element used for the video display apparatus concerning one Embodiment of this invention. It is explanatory drawing which shows the structure of the said video display apparatus typically. In the said video display apparatus, it is explanatory drawing which shows the observation light beam at the time of video observation. It is a graph which shows the relationship between an observation angle of view and video brightness. It is explanatory drawing which shows the structure of the outline of the video display apparatus which concerns on other embodiment of this invention. It is explanatory drawing which shows typically the exposure method when producing the holographic optical element used for the said video display apparatus. It is a graph which shows the diffraction characteristic of the said holographic optical element. It is explanatory drawing which shows the structure of the outline of the video imaging device which concerns on other embodiment of this invention. It is explanatory drawing which shows typically the optical path of the light corresponding to the imaging | photography angle of view in the said video imaging device. It is explanatory drawing which shows the structure of the conventional video display apparatus typically. In the said video display apparatus, it is explanatory drawing which shows the observation light beam at the time of video observation. In the said video display apparatus, it is explanatory drawing which shows the exposure light at the time of exposure of a hologram photosensitive material. (A) is sectional drawing of the holographic optical element produced so that diffraction efficiency might become the maximum when light injects with an incident angle of 0 degree | times with respect to the interference fringe. (B) is a graph which shows the diffraction characteristic of the said holographic optical element. (A) is sectional drawing of the holographic optical element produced so that diffraction efficiency might become the maximum when light injects with the incident angle which is not 0 degree with respect to an interference fringe. (B) is a graph which shows the diffraction characteristic of the said holographic optical element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image display element 2 Light guide member 2a Surface 2b Surface 3 Holographic optical element 3a Holographic photosensitive material 4 Holographic optical element 4a Holographic photosensitive material 21 Incident prism 22 Unnecessary light extraction prism 31 Imaging element R1 Observation light R2 Observation light S1 Exposure light S2 Exposure beam θ1 First angle θ2 Second angle

Claims (14)

An image display device for diffracting and reflecting image light from an image display element in a pupil direction with a holographic optical element, and allowing an observer to observe an image,
The holographic optical element is produced by performing interference exposure of a hologram photosensitive material with two light beams,
The optical path connecting the center of the display area of the image display element and the center of the design observation pupil is the optical axis,
At the time of observation, the light beam on the optical axis that is incident on the intersection of the holographic optical element and the optical axis, and the light beam on the optical axis that is emitted from the intersection point are respectively observed light beams,
At the time of exposure, when two light beams incident on the intersection between the hologram photosensitive material and the optical axis are respectively exposed light beams,
The holographic optical element is produced by irradiating a hologram photosensitive material with at least one of two exposure light beams being separated from an observation light beam. The angle formed by the two observation beams is the first angle,
An angle formed by two exposure light beams, and an angle formed by one exposure light beam incident on the intersection between the hologram photosensitive material and the optical axis and the other exposure light beam emitted from the intersection point is defined as a second angle. ,
The holographic optical element is produced by exposing a hologram photosensitive material with two light beams having two exposure light beams such that the second angle is larger than the first angle. 2. The video display device according to 1.   3. The image display device according to claim 1, wherein the two light beams for exposing the hologram photosensitive material are parallel lights. Comprising light guide members having planes parallel to each other;
The holographic optical element is held on the plane of the light guide member, and diffracts and reflects the image light from the image display element guided while being totally reflected in the light guide member in the pupil direction. The video display device according to claim 1. The holographic optical element exposes the holographic photosensitive material with two light fluxes that enter through the incident prism, and expose the holographic photosensitive material to the outside through the unnecessary light extraction prism and other exposure light beams. Is made by
At the time of exposure, the incident prism is closely contacted on the surface of the hologram photosensitive material or on the surface of the light guide member opposite to the hologram photosensitive material holding side without an air layer, and the unnecessary light extraction prism is 5. The image according to claim 4, wherein the light guide member is closely arranged on the surface opposite to the holding side of the hologram photosensitive material, or on the surface of the hologram photosensitive material, without an air layer. Display device. Further comprising another holographic optical element held on the plane of the light guide member;
6. The image according to claim 4, wherein the other holographic optical element diffracts and reflects the image light incident from the image display element into the light guide member so as to be totally reflected in the light guide member. Display device.   7. The video display device according to claim 1, wherein the holographic optical element has a diffraction characteristic in which a plurality of diffraction peak wavelengths at which diffraction efficiency reaches a peak exist. A video imaging apparatus that shoots a subject image with an imaging element by diffracting and reflecting light of the subject image with a holographic optical element and guiding the light to the imaging element,
The holographic optical element is produced by performing interference exposure of a hologram photosensitive material with two light beams,
The optical path connecting the center of the imaging area of the image sensor and the center of the subject image is the optical axis,
At the time of shooting, a light beam on the optical axis incident on the intersection of the holographic optical element and the optical axis, and a light beam on the optical axis emitted from the intersection, respectively, are taken as shooting light beams,
At the time of exposure, when two light beams incident on the intersection between the hologram photosensitive material and the optical axis are respectively exposed light beams,
The holographic optical element is produced by irradiating a hologram photosensitive material with at least one of two exposure light rays being deviated from a photographing light beam. The angle formed by the two shooting rays is the first angle,
An angle formed by two exposure light beams, and an angle formed by one exposure light beam incident on the intersection between the hologram photosensitive material and the optical axis and the other exposure light beam emitted from the intersection point is defined as a second angle. ,
The holographic optical element is produced by exposing a hologram photosensitive material with two light beams having two exposure light beams such that the second angle is larger than the first angle. 8. The video photographing apparatus according to 8.   10. The image photographing apparatus according to claim 8, wherein the two light beams for exposing the hologram photosensitive material are parallel lights. Comprising light guide members having planes parallel to each other;
The holographic optical element is held on the plane of the light guide member, and diffracted and reflects the light of the subject image guided while totally reflecting inside the light guide member, and is guided to the imaging element. The video imaging device according to claim 8. The holographic optical element exposes the holographic photosensitive material with two light fluxes that enter through the incident prism, and expose the holographic photosensitive material to the outside through the unnecessary light extraction prism and other exposure light beams. Is made by
At the time of exposure, the incident prism is closely contacted on the surface of the hologram photosensitive material or on the surface of the light guide member opposite to the hologram photosensitive material holding side without an air layer, and the unnecessary light extraction prism is 12. The image according to claim 11, wherein the light guide member is closely disposed on the surface opposite to the holding side of the hologram photosensitive material or on the surface of the hologram photosensitive material without interposing an air layer. Shooting device. Comprising other holographic optical elements held on the plane of the light guide member;
13. The image according to claim 11, wherein the other holographic optical element diffracts and reflects the light of the subject image incident on the light guide member from the outside so as to be totally reflected in the light guide member. Shooting device.   14. The video photographing apparatus according to claim 8, wherein the holographic optical element has a diffraction characteristic in which a plurality of diffraction peak wavelengths at which diffraction efficiency reaches a peak exist.

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