JP4631308B2 - Image display device - Google Patents

Description

  The present invention relates to an image display apparatus suitable for use as, for example, a viewfinder of a video camera, a head-mounted display, or the like. Specifically, in the present invention, the light emitted from the image display element is incident on the prism as incident light, reflected a predetermined number of times and emitted as emitted light, and the emitted light is diffracted by a transmission type diffractive optical element. The present invention relates to an image display apparatus in which light utilization efficiency can be increased and the angle of view can be increased to increase magnification by emitting light toward a user's pupil.

  Conventionally, for example, an image display device used as a viewfinder of a video camera, a head-mounted display, or the like has been proposed. Some image display apparatuses of this type include a virtual image observation optical system that observes a display image of an image display element as a virtual image.

  For example, Patent Document 1 describes an image display device 200 as shown in FIG. The image display device 200 includes an image display element 201 including a liquid crystal display (LCD), a half mirror 202, and a concave mirror 203. Light emitted from the image display element 201 is incident on the half mirror 202. The reflected light reflected by the half mirror 202 enters the concave mirror 203. The reflected light reflected by the concave mirror 203 is incident on the half mirror 202 again. The transmitted light that has passed through the half mirror 202 is incident on the pupil 204.

  Further, for example, Patent Document 2 describes an image display device 300 as shown in FIG. The image display apparatus 300 includes a light emitting diode (LED) 301, a lens 302, a transmissive liquid crystal display 303, a prism 304, and a reflective holographic optical element 305.

  The light emitted from the light emitting diode 301 is uniformly irradiated on the entire surface of the LCD 303 by the lens 302. The LCD 303 modulates the light irradiated on the entire surface for each pixel and displays an image. The emitted light emitted from the LCD 303 is incident on the prism 304, reflected by the inner surface of the prism 304 a predetermined number of times, and then incident on the reflective holographic optical element 305 and diffracted. The diffracted light from the optical element 305 passes through the prism 304 and enters the pupil 306.

JP 2000-221899 A (see page 2, FIG. 7) JP 2001-305476 A (refer to pages 4 to 5 and FIG. 2)

  In the image display device 200 shown in FIG. 11, the light emitted from the image display element 201 is incident on the pupil 204 after passing through the half mirror 202 twice. Is about 20%. In addition, when the concave mirror 203 is a half mirror, a see-through structure is obtained, and the other side of the optical component can be seen through. However, in this case, the light utilization efficiency on the other side is 25% at the maximum. In this case, the light use efficiency of the emitted light emitted from the image display element 201 is 12.5% at the maximum.

  In the image display device 300 shown in FIG. 12, the reflected light reflected by the inner surface of the prism 304 a predetermined number of times is finally incident on the reflective holographic optical element 305 and diffracted, and the diffracted light enters the pupil 306. Is done. Therefore, when the angle of view θ is increased, a large diffraction capability by the reflective holographic optical element 305 is required, which causes a decrease in diffraction efficiency. Therefore, there is a problem that the angle of view θ cannot be increased too much. It was.

  An object of the present invention is to increase the magnification by increasing the angle of view by increasing the light utilization efficiency.

An image display device according to the present invention includes an image display element and a prism that emits light emitted from the image display element as incident light, reflects the incident light on a plurality of surfaces a predetermined number of times, and then emits the light as emitted light. And a first transmissive diffractive optical element that diffracts the light emitted from the prism, and a second transmissive diffractive optical element that diffracts the light emitted from the image display element. The second transmissive diffractive optical element and the first transmissive diffractive optical element described above have diffraction efficiency with respect to the same wavelength band. The first transmissive diffractive optical element and the second transmissive diffractive optical element include a first layer having diffraction efficiency with respect to a red wavelength band in the visible light region, and a visible light region, respectively. A second layer having diffraction efficiency for the green wavelength band and a third layer having diffraction efficiency for the blue wavelength band in the visible light region, and at least the second transmission type diffractive optics. The first layer, the second layer, and the third layer of the element are arranged in the order of the third layer, the first layer, and the second layer from the prism side, or the first layer. Are arranged in the order of the first layer, the third layer, and the second layer, or the first transmissive diffractive optical element and the second transmissive diffractive optical element are respectively red in the visible light region. A first layer having diffraction efficiency for a wavelength band; A second layer having diffraction efficiency with respect to a green to blue wavelength band in the visible light region, and at least the first layer and the second layer of the second transmission type diffractive optical element are: From the prism side, the first layer and the second layer are arranged in this order. In this case, when it is configured by an optical system that forms an image on the display surface of the image display element when a ray at the pupil position, for example, a parallel ray is traced backward, the diffraction by the first transmissive diffractive optical element A wavelength dispersion opposite to the generated wavelength dispersion is generated by the second transmission type diffractive optical element, so that the chromatically dispersed light beam is condensed at the imaging position. Thereby, chromatic aberration generated by diffraction is canceled out.

  The human eye is most sensitive to green light, red next to blue and lowest. As described above, in the second transmissive diffractive optical element, the layer having the diffraction efficiency with respect to the green wavelength band is disposed on the side opposite to the prism side, so that the second transmissive diffractive optical element is concerned. Since the light emitted from the image display element to be diffracted by the element is first incident on a layer having diffraction efficiency for the green wavelength band, the green light flux is not affected by the other layers, It is diffracted by the layer having diffraction efficiency for the green wavelength band. Therefore, a green light beam with high visibility can be diffracted with high accuracy, and the user can perceive an image with good resolution.

  According to the present invention, the light emitted from the image display element is incident on the prism as incident light, reflected a predetermined number of times and emitted as the emitted light, and the emitted light is diffracted by the transmission type diffractive optical element. Is emitted toward the user's pupil, so that the light use efficiency can be increased, and the angle of view can be increased to increase the magnification.

  A first embodiment of the present invention will be described. FIG. 1 shows a configuration of an image display apparatus 100 as the first embodiment. The image display device 100 includes, for example, an image display element 101 including a liquid crystal display (LCD), an imaging optical element 102, a prism 103, and polarization selective transmission holographic optical elements 104 and 105. It consists of and. When the image display element 101 is a liquid crystal display, for example, a light emitting diode (LED: Liquid Crystal Display) is used as a light source.

  The prism 103 has a triangular cross section and has three surfaces 103a to 103c. The imaging optical element 102 is disposed between the image display element 101 and the surface 103 a of the prism 103. A holographic optical element 104 is attached to a portion of the surface 103a of the prism 103 where light emitted from the image display element 101 is incident. The holographic optical element 104 constitutes a second transmissive diffractive optical element. A holographic optical element 105 is attached to a portion of the surface 103a of the prism 103 where light emitted from the prism 103 is emitted. The holographic optical element 105 constitutes a first transmission type diffractive optical element.

  The surface 103b of the prism 103 constitutes a reflecting surface that reflects the emitted light from the image display element 101 that is incident as incident light from the surface 103a of the prism 103. The inclination angle of the surface 103b with respect to the surface 103a is such that the incident angle of the incident light on the surface 103b satisfies the condition of total reflection, and the incident angle of the reflected light from the surface 103b on the surface 103a is totally reflected. It is set to satisfy the conditions. Further, the inclination angle of the surface 103c of the prism 103 with respect to the surface 103a is set so that the incident angle of the reflected light from the surface 103a to the surface 103c satisfies the condition of total reflection.

  At least one of the surface 103b and the surface 103c of the prism 103 is a curved surface so as to have a lens effect. The image display apparatus 100 is configured by an optical system that forms an image on the display surface of the image display element 101 when a ray at the position of the user's pupil 106, for example, a parallel ray is traced back. As described above, by providing at least one of the surface 103b and the surface 103c of the prism 103 as a curved surface and having a lens effect, the spread of the light beam can be suppressed, the prism 103 can be made thinner and smaller, and the burden on the imaging optical element 102 is increased. Can be reduced.

  In the present embodiment, light emitted from the image display element 101 is p-polarized light that is linearly polarized light, and the holographic optical elements 104 and 105 have diffraction efficiency with respect to the p-polarized light. . The light emitted from the image display element 101 may be s-polarized light that is linearly polarized light having a polarization plane orthogonal to p-polarized light, and the holographic optical elements 104 and 105 may have diffraction efficiency with respect to s-polarized light. .

  Further, when considering the above-described reverse ray tracing, the chromatic dispersion opposite to the chromatic dispersion caused by the diffraction in the holographic optical element 105 is generated by the diffraction in the holographic optical element 104, and the chromatically dispersed light rays are collected at the imaging position. The diffraction power and the like of the holographic optical element 104 are set so that the light is emitted.

  Further, when considering the above-described back ray tracing, the curved surface shapes of the surfaces 103b and 103c of the prism 103 are set so that the emitted light emitted from the prism 103 and incident on the holographic optical element 104 is substantially parallel at all angles of view. Etc. have been optimized. Thereby, the diffraction efficiency of the holographic optical element 104 is improved.

  In addition, the holographic optical elements 104 and 105 each have diffraction efficiency with respect to a red wavelength band, a green wavelength band, and a blue wavelength band in the visible region. In addition, the holographic optical elements 104 and 105 have different effects.

  In the present embodiment, these holographic optical elements 104 and 105 are formed by stacking a red light diffraction holographic optical element 110R, a green light diffraction holographic optical element 110G, and a blue light diffraction holographic optical element 110B. A three-layer structure is adopted. The holographic optical elements 110R, 110G, and 110B are respectively in a red wavelength band (for example, 620 nm to 640 nm), a green wavelength band (for example, 520 nm to 540 nm), and a blue wavelength band (for example, 450 nm to 500 nm) in the visible region. On the other hand, it has diffraction efficiency.

  In this case, as shown in FIG. 2, the holographic optical elements 104 and 105 are arranged in the order of the holographic optical element 110R, the holographic optical element 110B, and the holographic optical element 110G from the prism 103 side. Note that the holographic optical element 110B, the holographic optical element 110R, and the holographic optical element 110G may be arranged in this order from the prism 103 side.

  The human eye is most sensitive to green light, red next to blue and lowest. As described above, in the holographic optical element 104, the holographic optical element 110G having diffraction efficiency with respect to the green wavelength band is disposed on the side opposite to the prism 103 side. Therefore, the light emitted from the image display element 101 to be diffracted by the holographic optical element 104 is first incident on the holographic optical element 110G, and the green light beam is affected by the other holographic optical elements 110B and 110R. Without being diffracted by the holographic optical element 110G. Therefore, the holographic optical element 104 can accurately diffract a green light beam having high visibility, and the user can perceive an image with good resolution.

  In the present embodiment, the holographic optical elements 110G, 110B, and 110R that constitute the holographic optical elements 104 and 105 are configured to be physically continuous, and are changed by changing exposure conditions in a manufacturing process that will be described later. The different parts have different powers. Therefore, also in the holographic optical element 105, the holographic optical element 110R, the holographic optical element 110B, and the holographic optical element 110G are arranged in this order from the prism 103 side.

  However, in the holographic optical element 105, originally, from the prism 103 side, the holographic optical element 110G, the holographic optical element 110B, and the holographic optical element 110R are arranged in this order, or the holographic optical element 110G and the holographic optical element 110R. And the holographic optical element 110B are preferably arranged in this order. In this way, by arranging the holographic optical element 110G on the prism 103 side, the emitted light emitted from the prism 103 is first incident on the holographic optical element 110G. It is diffracted by the holographic optical element 110G without being influenced by the other holographic optical elements 110B and 110R. Therefore, the holographic optical element 105 can accurately diffract a high-visibility green light beam, and the user can perceive an image with good resolution.

  Here, with reference to FIG. 3 and FIG. 4, the structure and manufacturing process of the polarization selective transmission type holographic optical element 110 constituting the holographic optical elements 110R, 110G, and 110B described above will be described. The holographic optical element 110 is described in, for example, Japanese Patent Application Laid-Open No. 2002-221710.

  The holographic optical element 110 is formed by exposing a liquid crystal panel made of polymer dispersed liquid crystal (hereinafter referred to as “PDLC”) with interference fringes by a laser beam to form a hologram.

  That is, first, a pair of glass substrates 3 each having a transparent electrode 2 formed on PDLC 1 mixed with a polymer (hereinafter referred to as “prepolymer”), a nematic liquid crystal, an initiator, and a dye before photopolymerization is mixed. , 3 to form a PDLC panel. At this time, the weight ratio of the nematic liquid crystal is about 30% of the whole. The layer thickness of the PDLC 1 (hereinafter referred to as “cell gap”) is in the range of about 2 μm to 15 μm, and is adapted to the specifications of the polarization selective transmission holographic optical element, for example, the wavelength band that gives diffraction efficiency. The optimum value is chosen.

  Next, in order to record interference fringes on the PDLC panel, object light 4 and reference light 5 from a laser light source (not shown) are irradiated to the PDLC panel, and light intensity (A) due to these interferences is generated. At this time, in a place where the interference fringes are bright, that is, a place where the energy of photons is large, the prepolymer in the PDLC undergoes photopolymerization and polymerizes due to the energy. For this reason, the prepolymer is supplied one after another from the peripheral portion, and as a result, the polymerized prepolymer is divided into a dense region and a sparse region. In regions where the prepolymer is sparse, the concentration of nematic liquid crystal is high. As a result, two regions of the polymer region 6 and the liquid crystal region 7 are formed.

  By the way, the polymer region 6 of the above-mentioned PDLC panel is isotropic with respect to the refractive index, and its value is, for example, 1.5. On the other hand, in the liquid crystal region 7 of the PDLC panel, nematic liquid crystal molecules 8 are arranged with their optical axes substantially perpendicular to the interface with the polymer region 6. Therefore, in this liquid crystal region 7, the refractive index has an incident polarization azimuth dependency. In this case, the ordinary ray is s when the incident light incident on the light incident surface 9 of the PDLC panel is considered. It is a polarization component.

  If the ordinary refractive index nlo of the liquid crystal region 7 is substantially equal to the refractive index np of the polymer region 6, for example, the refractive index difference is less than 0.01, the refractive index for the incident s-polarized component. The modulation of is very small and has little diffraction efficiency. In general, the difference Δn between the ordinary ray refractive index nlo and the extraordinary ray refractive index nle of the nematic liquid crystal is about 0.1 to 0.2, so that the p-polarized component having the same incident direction as the s-polarized component is high. A difference in refractive index is generated between the molecular region 6 and the liquid crystal region 7, functions as a phase modulation hologram, and has diffraction efficiency. This is an operation principle when no voltage is applied between the transparent electrodes 2 and 2 of the polarization selective transmission holographic optical element (H-PDLC panel) 110 using a PDLC panel (see FIG. 3).

  Next, as shown in FIG. 4, an operation when a voltage is applied between the transparent electrodes 2 and 2 of the H-PDLC panel 110 will be described. A power supply 11 is connected between the transparent electrodes 2 and 2 via a switch 10. By closing the switch 10, a voltage from the power source 11 is applied between the transparent electrodes 2 and 2. Thus, when an electric field is applied to the material inside the H-PDLC panel 110, the liquid crystal molecules 8 having dielectric anisotropy change the direction so that the optical axis is aligned with the electric field direction by an angle corresponding to the voltage. It is done. It is possible to control so as not to cause diffraction regardless of the polarization direction of incident light.

  Based on the above-described principle, the holographic optical element (H-PDLC panel) 110 has two states of diffracting only the p-polarized component of incident light and not diffracting the polarized component in all directions of incident light. The operation to switch to the state becomes possible.

  The image display element 101 sequentially displays, for example, a red image, a green image, and a blue image with a predetermined period, for example, a period of 1/180 seconds. The image display element 101 emits red light, green light, and blue light, respectively, when a red image, a green image, and a blue image are displayed. A control unit (not shown) includes optical elements 110R, 110G, and 110B constituting the holographic optical elements 104 and 105, and only the p-polarized light component when a red image, a green image, and a blue image are displayed on the image display element 101, respectively. Is in a state of diffracting, and in other cases, the polarization component in all directions is not diffracted.

  In this image display device 100, the emitted light (p-polarized light) emitted from the image display element 101 passes through the imaging optical element 102 and enters the transmissive holographic optical element 104 and is diffracted. The diffracted light from the transmissive holographic optical element 104 enters the prism 103 as incident light from the surface 103a.

  Incident light incident on the prism 103 is totally reflected by the surface 103 b, totally reflected by the surface 103 a, further totally reflected by the surface 103 c, and emitted from the surface 103 a of the prism 103. Light emitted from the prism 103 is incident on the transmissive holographic optical element 105 and diffracted. The diffracted light from the transmissive holographic optical element 105 enters the user's pupil 106. Thereby, the user can recognize the image displayed on the image display element 101 as a virtual image.

Here, consider ray tracing in the direction opposite to the actual traveling direction of rays.
It is assumed that a light beam having a predetermined angle of view is emitted from the pupil 106 as emitted light. This emitted light is incident on the holographic optical element 105. In the holographic optical element 105, the p-polarized component in the visible wavelength region in the red wavelength band, the green wavelength band, and the blue wavelength band is diffracted with an arbitrary power.

  The diffracted light from the holographic optical element 105 enters the prism 103 as incident light from its surface 103a. The incident light is totally reflected by the surface 103c, and then enters the surface 103a and is totally reflected. Here, the holographic optical elements 104 and 105 are attached to the surface 103 a on which the reflected light reflected by the surface 103 c is incident, and the reflected light is incident on the holographic optical elements 104 and 105.

  In this case, however, the reflected light reflected by the surface 103c is incident on the holographic optical elements 104 and 105 with a large incident angle as shown in FIG. Does not occur, and the reflected light reflected by the surface 103c is totally reflected. FIG. 5 shows only the portion of the holographic optical element 105.

  The reflected light reflected by the surface 103a enters the surface 103b and is totally reflected. The reflected light reflected by the surface 103b is emitted from the surface 103a. Light emitted from the prism 103 is incident on the holographic optical element 104. In the holographic optical element 104, the p-polarized components in the visible wavelength region in the red wavelength band, the green wavelength band, and the blue wavelength band are diffracted with an arbitrary power. The diffracted light from the holographic optical element 104 is condensed on the display surface of the image display element 101 by the imaging optical element 102. In this case, a light beam at the position of the pupil 106, for example, a parallel light beam, forms an image on the display surface of the image display element 101.

  In the image display apparatus 100 shown in FIG. 1, the light emitted from the image display element 101 is incident on the user's pupil 106 via the prism 103 and the transmission type holographic optical element 105. Light use efficiency can be made higher than that using a mirror, and the user can see a bright image. In other words, since the light use efficiency can be increased, the power consumption for making the user perceive a bright image can be kept low.

  That is, in the image display device 100 shown in FIG. 1, the surfaces 103b, 103a, and 103c on which incident light incident on the prism 103 is reflected are configured to satisfy the total reflection condition. Therefore, the deterioration or attenuation of the amount of light emitted from the image display element 101 is caused by the diffraction efficiency of the polarization selective transmission type holographic optical elements 104 and 105, the inside of the prism 103, the inside of the imaging optical element 102, and the transmission type holo. It occurs only due to absorption inside the graphic optical elements 104 and 105 and surface reflection in each optical component. Moreover, the diffraction efficiency of the polarization selective transmission holographic optical elements 104 and 105 is as high as 90% or more. Therefore, there is little deterioration or attenuation of the light quantity of the emitted light from the image display element 101, and the light quantity observed by the user's pupil 106 is increased.

  Further, in the image display device 100 shown in FIG. 1, by providing a counter prism on the surface 103c, light from the other side of the prism 103 existing in front of the user's pupil 106 is transmitted to the prism 103 and the transmissive holographic optical element. The light enters the user's pupil 106 through 105. That is, in the image display apparatus 100 shown in FIG. 1, the light from the far side is not incident on the user's pupil 106 through the half mirror as in the conventional case, and a see-through structure of an image that is bright and has no distortion is provided. it can.

  Further, in the image display device 100 shown in FIG. 1, the emitted light finally reflected and emitted by the surface 103c of the prism 103 is further diffracted by the transmissive holographic optical element 105, and the diffracted light is the user's pupil. 106 is incident. The surface 103c of the prism 103 and the transmission type holographic optical element 105 share the effect for satisfying the total reflection condition on the surface 103a of the prism 103, and the transmission type holographic optical element 105 is not required to have a large diffraction capability. . Therefore, according to the image display apparatus 100 shown in FIG. 1, the angle of view θ can be increased and the magnification can be increased as compared with the case using the conventional reflective holographic optical element.

  Further, in the image display device 100 shown in FIG. 1, in addition to the transmission type holographic optical element 105 that diffracts the light emitted from the prism 103, the transmission type holographic optical element that diffracts the light emitted from the image display element 101. 104, and a transmission type holographic optical element when it is constituted by an optical system that forms an image on the display surface of the image display element 101 when a ray at the position of the pupil 106, for example, a parallel ray is traced in the reverse ray The chromatic dispersion opposite to the chromatic dispersion caused by the diffraction in 105 is generated by the diffraction in the transmissive holographic optical element 104, and the chromatically dispersed light beam is condensed at the imaging position. Therefore, according to the image display apparatus 100 shown in FIG. 1, it is possible to cancel chromatic aberration caused by diffraction and improve image quality. This effect is particularly effective when a light emitting diode having a broad wavelength band for each of the three primary colors is used as the light source of the image display element 101.

  In the image display apparatus 100 shown in FIG. 1, the holographic optical elements 104 and 105 have a three-layer structure of holographic optical elements 110R, 110G, and 110B. Alternatively, a two-layer structure in which the holographic optical element 110R for red light diffraction and the holographic optical element 110GB for green / blue light diffraction are stacked may be used. In this case, the holographic optical element 110R has a diffraction efficiency for the red wavelength band in the visible region, whereas the holographic optical element 110GB diffracts for the green to blue wavelength band in the visible region. It is supposed to have efficiency.

  In this case, as shown in FIG. 6, the holographic optical elements 104 and 105 are arranged in order of the holographic optical element 110R and the holographic optical element 110GB from the prism 103 side. Thus, in the holographic optical element 104, the holographic optical element 110GB having diffraction efficiency with respect to the wavelength band from green to blue is disposed on the side opposite to the prism 103 side.

  Therefore, light emitted from the image display element 101 to be diffracted by the holographic optical element 104 is first incident on the holographic optical element 110GB, and the green light beam is not affected by the other holographic optical element 110R. Diffracted by the holographic optical element 110GB. Therefore, the holographic optical element 104 can accurately diffract a green light beam having high visibility, and the user can perceive an image with good resolution.

  In this case, the holographic optical elements 110GB and 110R constituting the holographic optical elements 104 and 105 are configured to be physically continuous, and the exposure conditions in the manufacturing process to be described later are changed to give different powers to the respective parts. To be prepared. Therefore, also in the holographic optical element 105, the holographic optical element 110R and the holographic optical element 110GB are arranged in this order from the prism 103 side.

  However, in the holographic optical element 105, it is originally preferable to dispose the holographic optical element 110GB and the holographic optical element 110R in this order from the prism 103 side. Thus, by arranging the holographic optical element 110GB on the prism 103 side, the emitted light emitted from the prism 103 is first incident on the holographic optical element 110GB. It is diffracted by the holographic optical element 110GB without being affected by the other holographic optical element 110R. Therefore, the holographic optical element 105 can accurately diffract a high-visibility green light beam, and the user can perceive an image with good resolution.

  In addition, the holographic optical elements 104 and 105 may have a single-layer structure of holographic optical elements 110RGB for red / green / blue light diffraction, not shown. In this case, the holographic optical element 110RGB has diffraction efficiency for the red to blue wavelength band in the visible region.

  Next explained is the second embodiment of the invention. FIG. 7 shows a configuration of an image display apparatus 100A as the second embodiment. In FIG. 7, parts corresponding to those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted as appropriate.

  The image display device 100A includes an image display element 101 formed of, for example, a liquid crystal display, an imaging optical element 102, a prism 103A, and polarization selective transmission holographic optical elements 104 and 105.

  The prism 103A has a parallelogram shape in cross section and has four surfaces 103Aa to 103Ad. The imaging optical element 102 is disposed between the image display element 101 and the surface 103Aa of the prism 103A. The holographic optical element 104 is attached to the surface 103Aa of the prism 103A. The holographic optical element 105 is attached to the surface 103Ac of the prism 103A.

  The surface 103Ab of the prism 103A constitutes a reflection surface that reflects the light emitted from the image display element 101 that is incident as incident light from the surface 103Aa of the prism 103A. The inclination angle of the surface 103Ab with respect to the surface 103Aa is such that the incident angle of the incident light on the surface 103Ab satisfies the condition of total reflection, and the incident angle of the reflected light from the surface 103Ab on the surface 103Ac is totally reflected. Is set so as to satisfy the following conditions. The inclination angle of the surface 103Ad of the prism 103A with respect to the surface 103Ac is set so that the incident angle of the reflected light from the surface 103Ac to the surface 103Ad satisfies the condition of total reflection.

  The surface 103Ad of the prism 103A is a curved surface and has a lens effect. The image display device 100 </ b> A includes an optical system that forms an image on the display surface of the image display element 101 when a ray at the position of the user's pupil 106, for example, a parallel ray is traced back. As described above, the surface 103Ad of the prism 103A is made a curved surface to give a lens effect, so that the spread of the light beam can be suppressed, the prism 103A can be made thin and small, and the burden on the imaging optical element 102 can be reduced. The surface 103Ab and the surface 103Ac of the prism 103A are parallel to each other. As described above, the prism 103A can be easily manufactured by configuring the prism 103A to have the parallel surfaces 103Ab and 103Ac.

  Further, when considering the above-described reverse ray tracing, the chromatic dispersion opposite to the chromatic dispersion caused by the diffraction in the holographic optical element 105 is generated by the diffraction in the holographic optical element 104, and the chromatically dispersed light rays are collected at the imaging position. The diffraction power and the like of the holographic optical element 104 are set so that the light is emitted.

  Further, when considering the above-described reverse ray tracing, the curved surface shape of the surface 103Ad of the prism 103A is set so that the emitted light emitted from the prism 103A and incident on the holographic optical element 104 is substantially parallel at all angles of view. Optimized. Thereby, the diffraction efficiency of the holographic optical element 104 is improved.

  In the image display device 100A, the light emitted from the image display element 101 is p-polarized light that is linearly polarized light. The holographic optical elements 104 and 105 have diffraction efficiency with respect to the p-polarized light. In addition, the holographic optical elements 104 and 105 each have diffraction efficiency with respect to a red wavelength band, a green wavelength band, and a blue wavelength band in the visible region.

  These holographic optical elements 104 and 105 have, for example, a three-layer structure in which a red light diffraction holographic optical element 110R, a green light diffraction holographic optical element 110G, and a blue light diffraction holographic optical element 110B are stacked. The In this case, the holographic optical element 104 is arranged from the prism 103A side in the order of the optical element 110R, the optical element 110B, and the optical element 110G, or in the order of the optical element 110B, the optical element 110R, and the optical element 110G. The holographic optical element 105 is arranged from the prism 103A side in the order of the optical element 110G, the optical element 110B, and the optical element 110R, or in the order of the optical element 110G, the optical element 110R, and the optical element 110B.

  As a result, in the holographic optical elements 104 and 105, the incident light bundle is first input to the holographic optical element 110G, so that the green light bundle is affected by the other holographic optical elements 110B and 110R. And diffracted by the holographic optical element 110G. Therefore, the holographic optical elements 104 and 105 can accurately diffract a green light beam having high visibility, and the user can perceive an image with good resolution.

  Emitted light (p-polarized light) emitted from the image display element 101 passes through the imaging optical element 102 and enters the transmissive holographic optical element 104 to be diffracted. The diffracted light from the transmissive holographic optical element 104 enters the prism 103A as incident light from the surface 103Aa.

  The incident light that has entered the prism 103A is totally reflected by the surface 103Ab, is totally reflected by the surface 103Ac, is further totally reflected by the surface 103Ad, and is emitted from the surface 103Ac of the prism 103A. Light emitted from the prism 103A is incident on the transmissive holographic optical element 105 and is diffracted. The diffracted light from the transmissive holographic optical element 105 enters the user's pupil 106. Thereby, the user can recognize the image displayed on the image display element 101 as a virtual image.

Here, consider ray tracing in the direction opposite to the actual traveling direction of rays.
It is assumed that a light beam having a predetermined angle of view is emitted from the pupil 106 as emitted light. This emitted light is incident on the holographic optical element 105. In the holographic optical element 105, the p-polarized component in the visible wavelength region in the red wavelength band, the green wavelength band, and the blue wavelength band is diffracted with an arbitrary power.

  The diffracted light from the holographic optical element 105 enters the prism 103A as incident light from its surface 103Ac. The incident light is totally reflected by the surface 103Ad, and then enters the surface 103Ac and is totally reflected. The reflected light reflected by the surface 103Ac enters the surface 103Ab and is totally reflected. The reflected light reflected by the surface 103Ab is emitted from the surface 103Aa.

  Light emitted from the prism 103A is incident on the holographic optical element 104. In the holographic optical element 104, the p-polarized components in the visible wavelength region in the red wavelength band, the green wavelength band, and the blue wavelength band are diffracted with an arbitrary power. The diffracted light from the holographic optical element 104 is condensed on the display surface of the image display element 101 by the imaging optical element 102. In this case, a light beam at the position of the pupil 106, for example, a parallel light beam, forms an image on the display surface of the image display element 101.

  In the image display device 100A shown in FIG. 7, similarly to the image display device 100 shown in FIG. 1, the light emitted from the image display element 101 passes through the prism 103A and the transmissive holographic optical element 105 to the user's pupil 106. The incident light is incident, and the light utilization efficiency can be increased as compared with the conventional one using a half mirror, and the user can see a bright image. In other words, since the light use efficiency can be increased, the power consumption for making the user perceive a bright image can be kept low.

  In addition, in the image display device 100A shown in FIG. 7, by providing a counter prism on the surface 103Ad, similarly to the image display device 100 shown in FIG. 1, from the other side of the prism 103A existing in front of the user's pupil 106. Is incident on the user's pupil 106 through the prism 103A and the transmissive holographic optical element 105, and the light from the other side is incident on the user's pupil 106 through the half mirror as in the prior art. Rather, it can provide a bright and distortion-free see-through structure.

  Further, in the image display device 100A shown in FIG. 7, similarly to the image display device 100 shown in FIG. 1, the outgoing light finally reflected and emitted by the surface 103Ad of the prism 103A is transmitted through the transmissive holographic optical element 105. And the diffracted light is incident on the user's pupil 106. The surface 103Ad of the prism 103A and the transmissive holographic optical element 105 share the effect of satisfying the total reflection condition on the surface 103Ac of the prism 103A, and the transmissive holographic optical element 105 is not required to have a large diffraction capability. . Therefore, according to the image display device 100A shown in FIG. 7, the angle of view θ (see FIG. 1) can be increased and the magnification can be increased as compared with the conventional one using the reflective holographic optical element.

  Further, in the image display device 100A shown in FIG. 7, in addition to the transmissive holographic optical element 105 that diffracts the light emitted from the prism 103A, similarly to the image display device 100 shown in FIG. The transmissive holographic optical element 104 that diffracts the emitted light can be offset, and the chromatic aberration caused by the diffraction can be canceled out, and the image quality can be improved.

  In the image display device 100A shown in FIG. 7, the holographic optical elements 104 and 105 have a three-layer structure of holographic optical elements 110R, 110G, and 110B. Similarly, a two-layer structure or a one-layer structure may be used.

  Further, in the image display apparatus 100A shown in FIG. 7, a reflective holographic optical element as a reflective diffractive optical element is provided on at least one of the surface 103Ab and the surface 103Ac that reflects incident light incident on the prism 103A. Also good. This reflective holographic optical element uses a photopolymer as a hologram photosensitive agent.

  As described above, by providing reflective holographic optical elements on the surfaces 103Ab and 103Ac of the prism 103A, a lens effect can be imparted to these surfaces 103Ab and 103Ac without making them curved, thereby spreading the beam bundle. The prism 103A can be made thin and small, and the burden on the imaging optical element 102 can be reduced.

  Next explained is the third embodiment of the invention. FIG. 8 shows a configuration of an image display device 100B as the third embodiment. 8, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted as appropriate.

  The image display device 100B includes an image display element 101 made of, for example, a liquid crystal display, an imaging optical element 102, a prism 103B, and polarization selective transmission holographic optical elements 104 and 105.

  The prism 103B is trapezoidal in cross section and has four surfaces 103Ba to 103Bd. The imaging optical element 102 is disposed between the image display element 101 and the surface 103Ba of the prism 103B. The holographic optical element 104 is attached to the surface 103Ba of the prism 103B. The holographic optical element 105 is attached to the surface 103Bb of the prism 103B.

  The surface 103Bb of the prism 103B constitutes a reflecting surface that reflects the light emitted from the image display element 101 that is incident as incident light from the surface 103Ba of the prism 103B. The inclination angle of the surface 103Bb with respect to the surface 103Ba is such that the incident angle of the incident light on the surface 103Bb satisfies the condition of total reflection, and the incident angle of the reflected light from the surface 103Bb on the surface 103Bc is totally reflected. Is set so as to satisfy the following conditions.

  The surface 103Bc of the prism 103B is a curved surface and has a lens effect. The image display device 100 </ b> B includes an optical system that forms an image on the display surface of the image display element 101 when a ray at the position of the user's pupil 106, for example, a parallel ray is traced back. As described above, by making the surface 103Bc of the prism 103B a curved surface and having a lens effect, the spread of the light beam can be suppressed, the prism 103B can be made thin and small, and the burden on the imaging optical element 102 can be reduced. The surface 103Bb and the surface 103Bd of the prism 103B are parallel to each other. As described above, the prism 103B can be easily manufactured by configuring the prism 103B to have the parallel surfaces 103Bb and 103Bd.

  Further, when considering the above-described reverse ray tracing, the chromatic dispersion opposite to the chromatic dispersion caused by the diffraction in the holographic optical element 105 is generated by the diffraction in the holographic optical element 104, and the chromatically dispersed light rays are collected at the imaging position. The diffraction power and the like of the holographic optical element 104 are set so that the light is emitted.

  Further, when considering the above-described reverse ray tracing, the curved surface shape of the surface 103Bc of the prism 103B is set so that the emitted light emitted from the prism 103B and incident on the holographic optical element 104 is substantially parallel at all angles of view. Optimized. Thereby, the diffraction efficiency of the holographic optical element 104 is improved.

  In the image display device 100B, the light emitted from the image display element 101 is p-polarized light that is linearly polarized light. The holographic optical elements 104 and 105 have diffraction efficiency with respect to the p-polarized light. In addition, the holographic optical elements 104 and 105 each have diffraction efficiency with respect to a red wavelength band, a green wavelength band, and a blue wavelength band in the visible region.

  These holographic optical elements 104 and 105 have, for example, a three-layer structure in which a red light diffraction holographic optical element 110R, a green light diffraction holographic optical element 110G, and a blue light diffraction holographic optical element 110B are stacked. The In this case, the holographic optical element 104 is arranged from the prism 103B side in the order of the optical element 110R, the optical element 110B, and the optical element 110G, or in the order of the optical element 110B, the optical element 110R, and the optical element 110G. In addition, the holographic optical element 105 is arranged from the prism 103B side in the order of the optical element 110G, the optical element 110B, and the optical element 110R, or in the order of the optical element 110G, the optical element 110R, and the optical element 110B.

  As a result, in the holographic optical elements 104 and 105, the incident light bundle is first input to the holographic optical element 110G, so that the green light bundle is affected by the other holographic optical elements 110B and 110R. And diffracted by the holographic optical element 110G. Therefore, the holographic optical elements 104 and 105 can accurately diffract a green light beam having high visibility, and the user can perceive an image with good resolution.

  Emitted light (p-polarized light) emitted from the image display element 101 passes through the imaging optical element 102 and enters the transmissive holographic optical element 104 to be diffracted. The diffracted light from the transmissive holographic optical element 104 enters the prism 103B as incident light from the surface 103Ba.

  The incident light that has entered the prism 103B is totally reflected by the surface 103Bb, is totally reflected by the surface 103Bc, and is emitted from the surface 103Bb of the prism 103B. The light emitted from the prism 103B is incident on the transmissive holographic optical element 105 and is diffracted. The diffracted light from the transmissive holographic optical element 105 enters the user's pupil 106. Thereby, the user can recognize the image displayed on the image display element 101 as a virtual image.

Here, consider ray tracing in the direction opposite to the actual traveling direction of rays.
It is assumed that a light beam having a predetermined angle of view is emitted from the pupil 106 as emitted light. This emitted light is incident on the holographic optical element 105. In the holographic optical element 105, the p-polarized component in the visible wavelength region in the red wavelength band, the green wavelength band, and the blue wavelength band is diffracted with an arbitrary power.

  The diffracted light from the holographic optical element 105 enters the prism 103B as incident light from its surface 103Bb. The incident light is totally reflected by the surface 103Bc, and then incident on the surface 103Bb and totally reflected. The reflected light reflected by the surface 103Bb is emitted from the surface 103Ba.

  Light emitted from the prism 103B enters the holographic optical element 104. In the holographic optical element 104, the p-polarized components in the visible wavelength region in the red wavelength band, the green wavelength band, and the blue wavelength band are diffracted with an arbitrary power. The diffracted light from the holographic optical element 104 is condensed on the display surface of the image display element 101 by the imaging optical element 102. In this case, a light beam at the position of the pupil 106, for example, a parallel light beam, forms an image on the display surface of the image display element 101.

  In the image display device 100B shown in FIG. 8, similarly to the image display device 100 shown in FIG. 1, the light emitted from the image display element 101 passes through the prism 103B and the transmissive holographic optical element 105 to the user's pupil 106. The incident light is incident, and the light utilization efficiency can be increased as compared with the conventional one using a half mirror, and the user can see a bright image. In other words, since the light use efficiency can be increased, the power consumption for making the user perceive a bright image can be kept low.

  In addition, in the image display device 100B shown in FIG. 8, by providing a counter prism on the surface 103Bc, similarly to the image display device 100 shown in FIG. Is incident on the user's pupil 106 via the prism 103B and the transmissive holographic optical element 105, and the light from the other side is incident on the user's pupil 106 via the half mirror as in the prior art. Instead, it can provide a bright and distortion-free image see-through structure.

  Further, in the image display device 100B shown in FIG. 8, similarly to the image display device 100 shown in FIG. 1, the outgoing light finally reflected and emitted by the surface 103Bc of the prism 103B is transmitted through the transmissive holographic optical element 105. And the diffracted light is incident on the user's pupil 106. The surface 103Bc of the prism 103B and the transmission type holographic optical element 105 share the effect for satisfying the total reflection condition on the surface 103Bb of the prism 103B, and the transmission type holographic optical element 105 is not required to have a large diffraction capability. . Therefore, according to the image display device 100B shown in FIG. 8, the angle of view θ (see FIG. 1) can be increased and the magnification can be increased as compared with a conventional reflective holographic optical element.

  Further, in the image display device 100B shown in FIG. 8, in addition to the transmissive holographic optical element 105 that diffracts the light emitted from the prism 103B, similarly to the image display device 100 shown in FIG. The transmissive holographic optical element 104 that diffracts the emitted light can be offset, and the chromatic aberration caused by the diffraction can be canceled out, and the image quality can be improved.

  In the image display device 100B shown in FIG. 8, the holographic optical elements 104 and 105 have a three-layer structure of holographic optical elements 110R, 110G, and 110B. However, the image display device 100B shown in FIG. Similarly, a two-layer structure or a one-layer structure may be used.

  In the image display device 100B shown in FIG. 8, a reflective holographic optical element as a reflective diffractive optical element may be provided on the surface 103Bb that reflects incident light incident on the prism 103B. Thereby, a lens effect can be imparted to the surface 103Bb without making it a curved surface, the spread of the light beam can be suppressed, the prism 103B can be made thin and small, and the burden on the imaging optical element 102 can be reduced.

  Next explained is the fourth embodiment of the invention. FIG. 9 shows a configuration of an image display device 100C as the fourth embodiment. 9, parts corresponding to those in FIG. 7 are denoted by the same reference numerals, and the description thereof is omitted as appropriate.

  The image display device 100C includes an image display element 101, an imaging optical element 102, a prism 103A, polarization selective transmission holographic optical elements 104 and 105, a quarter-wave plate 107, and a reflective surface 108a. And a prism 108 constituting the reflecting means.

  The prism 103A has a parallelogram shape in cross section and has four surfaces 103Aa to 103Ad. The imaging optical element 102 is disposed between the image display element 101 and the surface 103Ab of the prism 103A. The holographic optical element 104 is attached to the surface 103Aa of the prism 103A. Further, a quarter wave plate 107 and a prism 108 are attached to the holographic optical element 104 in this order. The holographic optical element 105 is attached to the surface 103Ac of the prism 103A.

  The light emitted from the image display element 101 is s-polarized light that is linearly polarized light having a first polarization plane. The holographic optical elements 104 and 105 have diffraction efficiency with respect to p-polarized light that is linearly polarized light having a second polarization plane orthogonal to the first polarization plane.

  Other configurations of the image display device 100C are the same as those of the image display device 100A shown in FIG.

  In the image display device 100C, the emitted light (s-polarized light) emitted from the image display element 101 passes through the imaging optical element 102 and the prism 103A and enters the transmissive holographic optical element 104. Since this transmissive holographic optical element 104 has diffraction efficiency with respect to p-polarized light, incident outgoing light (s-polarized light) is transmitted without being diffracted and is transmitted to the quarter-wave plate 107. Incident.

  From this quarter-wave plate 107, incident light (s-polarized light) is emitted as circularly polarized light. The emitted light (circularly polarized light) from the quarter wavelength plate 107 is incident on the prism 108, reflected by the reflecting surface 108 a, and then emitted from the prism 108. The outgoing light (circularly polarized light) from the prism 108 is incident on the quarter-wave plate 107 again.

  From this quarter-wave plate 107, incident light (circularly polarized light) is emitted as p-polarized light. The emitted light (p-polarized light) from the quarter-wave plate 107 is incident on the transmissive holographic optical element 104 and diffracted. The diffracted light from the transmissive holographic optical element 104 enters the prism 103A as incident light from the surface 103Aa.

  The incident light that has entered the prism 103A is totally reflected by the surface 103Ab, is totally reflected by the surface 103Ac, is further totally reflected by the surface 103Ad, and is emitted from the surface 103Ac of the prism 103A. Light emitted from the prism 103A is incident on the transmissive holographic optical element 105 and is diffracted. The diffracted light from the transmissive holographic optical element 105 enters the user's pupil 106. Thereby, the user can recognize the image displayed on the image display element 101 as a virtual image.

Here, consider ray tracing in the direction opposite to the actual traveling direction of rays.
It is assumed that a light beam having a predetermined angle of view is emitted from the pupil 106 as emitted light. This emitted light is incident on the holographic optical element 105. In the holographic optical element 105, the p-polarized component in the visible wavelength region in the red wavelength band, the green wavelength band, and the blue wavelength band is diffracted with an arbitrary power.

  The diffracted light from the holographic optical element 105 enters the prism 103A as incident light from its surface 103Ac. The incident light is totally reflected by the surface 103Ad, and then enters the surface 103Ac and is totally reflected. The reflected light reflected by the surface 103Ac enters the surface 103Ab and is totally reflected. The reflected light reflected by the surface 103Ab is emitted from the surface 103Aa.

  Light emitted from the prism 103A is incident on the holographic optical element 104. In the holographic optical element 104, the p-polarized components in the visible wavelength region in the red wavelength band, the green wavelength band, and the blue wavelength band are diffracted with an arbitrary power. The diffracted light from the holographic optical element 104 is incident on the quarter wavelength plate 107.

  From this quarter-wave plate 107, incident light (p-polarized light) is emitted as circularly polarized light. The emitted light (circularly polarized light) from the quarter wavelength plate 107 is incident on the prism 108, reflected by the reflecting surface 108 a, and then emitted from the prism 108. The outgoing light (circularly polarized light) from the prism 108 is incident on the quarter-wave plate 107 again.

  From this quarter-wave plate 107, incident light (circularly polarized light) is emitted as s-polarized light. The emitted light (s-polarized light) from the quarter-wave plate 107 passes through the holographic optical element 104 without being diffracted as it is, and further passes through the prism 103A. It is condensed on the display surface. In this case, a light beam at the position of the pupil 106, for example, a parallel light beam is imaged on the display surface of the image display element 101.

  In the image display device 100C shown in FIG. 9, the same effect as that of the image display device 100A shown in FIG. 7 can be obtained by providing a counter prism on the surface 103Ad. In the image display device 100C shown in FIG. 9, the light emitted from the image display element 101 passes through the prism 103A, is reflected by the reflecting surface 108a of the prism 108, and is diffracted by the transmissive holographic optical element 104. Since the light is incident on the prism 103A, the image display element 101 can be disposed close to the prism 103A, and the apparatus can be downsized.

  Next explained is the fifth embodiment of the invention. FIG. 10 shows a configuration of an image display device 100D as the fifth embodiment. 10, portions corresponding to those in FIG. 8 are denoted by the same reference numerals, and description thereof is omitted as appropriate.

  This image display device 100D includes an image display element 101, an imaging optical element 102, a prism 103B, polarization selective transmission holographic optical elements 104 and 105, a quarter-wave plate 107, and a reflecting surface 108a. And a prism 108 constituting the reflecting means.

  The prism 103B is trapezoidal in cross section and has four surfaces 103Ba to 103Bd. The imaging optical element 102 is disposed between the image display element 101 and the surface 103Bb of the prism 103B. The holographic optical element 104 is attached to the surface 103Ba of the prism 103B. Further, a quarter wave plate 107 and a prism 108 are attached to the holographic optical element 104 in this order. The holographic optical element 105 is attached to the surface 103Bb of the prism 103B.

  The light emitted from the image display element 101 is s-polarized light that is linearly polarized light having a first polarization plane. The holographic optical elements 104 and 105 have diffraction efficiency with respect to p-polarized light that is linearly polarized light having a second polarization plane orthogonal to the first polarization plane.

  Other configurations of the image display device 100D are the same as those of the image display device 100B shown in FIG.

  In the image display device 100D, the emitted light (s-polarized light) emitted from the image display element 101 is transmitted through the imaging optical element 102 and the prism 103B and is incident on the transmissive holographic optical element 104. Since this transmissive holographic optical element 104 has diffraction efficiency with respect to p-polarized light, incident light (s-polarized light) is transmitted without being diffracted and is incident on the quarter-wave plate 107. .

  From this quarter-wave plate 107, incident light (s-polarized light) is emitted as circularly polarized light. The emitted light (circularly polarized light) from the quarter wavelength plate 107 is incident on the prism 108, reflected by the reflecting surface 108 a, and then emitted from the prism 108. The outgoing light (circularly polarized light) from the prism 108 is incident on the quarter-wave plate 107 again.

  From this quarter-wave plate 107. Incident light (circularly polarized light) is emitted as p-polarized light. The emitted light (p-polarized light) from the quarter-wave plate 107 passes through the imaging optical element 102 and enters the transmissive holographic optical element 104 to be diffracted. The diffracted light from the transmissive holographic optical element 104 enters the prism 103B as incident light from the surface 103Ba.

  The incident light that has entered the prism 103B is totally reflected by the surface 103Bb, is totally reflected by the surface 103Bc, and is emitted from the surface 103Bb of the prism 103B. The light emitted from the prism 103B is incident on the transmissive holographic optical element 105 and is diffracted. The diffracted light from the transmissive holographic optical element 105 enters the user's pupil 106. Thereby, the user can recognize the image displayed on the image display element 101 as a virtual image.

Here, consider ray tracing in the direction opposite to the actual traveling direction of rays.
It is assumed that a light beam having a predetermined angle of view is emitted from the pupil 106 as emitted light. This emitted light is incident on the holographic optical element 105. In the holographic optical element 105, the p-polarized component in the visible wavelength region in the red wavelength band, the green wavelength band, and the blue wavelength band is diffracted with an arbitrary power.

  The diffracted light from the holographic optical element 105 enters the prism 103B as incident light from its surface 103Bb. The incident light is totally reflected by the surface 103Bc, and then incident on the surface 103Bb and totally reflected. The reflected light reflected by the surface 103Bb is emitted from the surface 103Ba.

  Light emitted from the prism 103B enters the holographic optical element 104. In the holographic optical element 104, the p-polarized components in the visible wavelength region in the red wavelength band, the green wavelength band, and the blue wavelength band are diffracted with an arbitrary power. The diffracted light from the holographic optical element 104 is incident on the quarter wavelength plate 107.

  From this quarter-wave plate 107, incident light (p-polarized light) is emitted as circularly polarized light. The emitted light (circularly polarized light) from the quarter wavelength plate 107 is incident on the prism 108, reflected by the reflecting surface 108 a, and then emitted from the prism 108. The outgoing light (circularly polarized light) from the prism 108 is incident on the quarter-wave plate 107 again.

  From this quarter-wave plate 107, incident light (circularly polarized light) is emitted as s-polarized light. The emitted light (s-polarized light) from the quarter-wave plate 107 passes through the holographic optical element 104 without being diffracted as it is, and further passes through the prism 103B. The imaging optical element 102 causes the image display element 101 to emit light. It is condensed on the display surface. In this case, a light beam at the position of the pupil 106, for example, a parallel light beam, forms an image on the display surface of the image display element 101.

  In the image display device 100D shown in FIG. 10, the same effect as the image display device 100B shown in FIG. 8 can be obtained by providing the counter prism on the surface 103Bc. In the image display device 100D shown in FIG. 10, the light emitted from the image display element 101 passes through the prism 103B, is reflected by the reflecting surface 108a of the prism 108, and is diffracted by the transmissive holographic optical element 104. Since the light is incident on the prism 103B, the image display element 101 can be disposed close to the prism 103B, and the apparatus can be downsized.

  In the above-described embodiment, in addition to the transmissive holographic optical element 105 that diffracts the light emitted from the prisms 103, 103A, and 103B, the light emitted from the image display element 101 is diffracted to obtain the prisms 103, 103A, and 103B. A transmissive holographic optical element 104 incident on 103B is provided so that chromatic aberration due to diffraction can be canceled. However, when the wavelength band of the light emitted from the image display element 101 (red light, green light, and blue light) is relatively narrow, the chromatic aberration does not become a problem, and therefore the transmission holographic optical element 104 is not provided. Can also think.

  In the above-described embodiment, the incident light incident on the prisms 103, 103A, and 103B is reflected three times or twice on the inner surface and emitted to the outside, but reflected on the inner surface of the prism. However, the number of times to be played is not limited to this. In short, the present invention is not limited as long as the outgoing light finally reflected and emitted by the prism is diffracted by the transmission type diffractive optical element and incident on the user's pupil.

  The present invention can increase the light utilization efficiency, increase the angle of view and increase the magnification, and is suitable for use as a viewfinder of a video camera, a head-mounted display, or the like.

It is a side view which shows the structure of the image display apparatus as 1st Embodiment. It is a figure for demonstrating the structural example (3 layer structure) of the transmissive | pervious holographic optical element with respect to the color light of red, green, and blue. It is a longitudinal cross-sectional view which shows the structure (voltage non-application state) of a polarization selective transmission type holographic optical element. It is a longitudinal cross-sectional view which shows the structure (voltage application state) of a polarization selective transmission type holographic optical element. It is a figure which shows the principal part of a polarization selective holographic optical element. It is a figure for demonstrating the structural example (2 layer structure) of the transmissive | pervious holographic optical element with respect to the color light of red, green, and blue. It is a side view which shows the structure of the image display apparatus as 2nd Embodiment. It is a side view which shows the structure of the image display apparatus as 3rd Embodiment. It is a side view which shows the structure of the image display apparatus as 4th Embodiment. It is a side view which shows the structure of the image display apparatus as 5th Embodiment. It is a side view which shows the structure of an example of the conventional image display apparatus. It is a side view which shows the structure of the other example of the conventional image display apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100,100A-100D ... Image display apparatus, 101 ... Image display element, 102 ... Imaging optical element, 103, 103A, 103B ... Prism, 104, 105 ... Polarization selective transmission type Holographic optical element 106 ... User's pupil, 107 ... 1/4 wavelength plate, 108 ... Prism, 110 ... Polarization selective transmission holographic optical element

Claims (2)

An image display element;
The exit light from the image display element is incident as incident light, and the incident light is reflected by a plurality of surfaces a predetermined number of times and then emitted as exit light, and
A first transmissive diffractive optical element that diffracts the light emitted from the prism;
A second transmissive diffractive optical element that diffracts the light emitted from the image display element,
Consists of an optical system that forms an image on the display surface of the image display element when the light ray at the pupil position is traced back.
The first transmissive diffractive optical element and the second transmissive diffractive optical element have diffraction efficiency for the same wavelength band,
The first transmissive diffractive optical element and the second transmissive diffractive optical element include a first layer having diffraction efficiency with respect to a red wavelength band in the visible light region, and a green layer in the visible light region, respectively. A second layer having diffraction efficiency with respect to the wavelength band, and a third layer having diffraction efficiency with respect to the blue wavelength band in the visible light region,
At least the first layer, the second layer, and the third layer of the second transmission type diffractive optical element are arranged from the prism side to the third layer, the first layer, and the first layer. Arranged in the order of two layers, or in the order of the first layer, the third layer, and the second layer,
The chromatic dispersion opposite to the chromatic dispersion caused by the diffraction in the first transmissive diffractive optical element is generated by the diffraction in the second transmissive diffractive optical element, thereby condensing the chromatically dispersed light beam at the imaging position. An image display device characterized in that An image display element;
The exit light from the image display element is incident as incident light, and the incident light is reflected by a plurality of surfaces a predetermined number of times and then emitted as exit light, and
A first transmissive diffractive optical element that diffracts the light emitted from the prism;
A second transmissive diffractive optical element that diffracts the light emitted from the image display element;
With
Consists of an optical system that forms an image on the display surface of the image display element when the light ray at the pupil position is traced back.
The first transmissive diffractive optical element and the second transmissive diffractive optical element have diffraction efficiency for the same wavelength band,
The first transmissive diffractive optical element and the second transmissive diffractive optical element are each formed of a first layer having diffraction efficiency with respect to a red wavelength band in the visible light region and green in the visible light region. A second layer having diffraction efficiency for the blue wavelength band,
At least the first layer and the second layer of the second transmission type diffractive optical element are arranged in order of the first layer and the second layer from the prism side,
The chromatic dispersion opposite to the chromatic dispersion caused by the diffraction in the first transmissive diffractive optical element is generated by the diffraction in the second transmissive diffractive optical element, thereby condensing the chromatically dispersed light beam at the imaging position. the image display apparatus characterized by causing.

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