JP4779887B2 - Image display device - Google Patents

Description

  The present invention relates to an image display device incorporating an optical device used for allowing an observer to observe a two-dimensional image formed by an image forming device.

  An image display device using a reflective volume hologram diffraction grating is known from, for example, WO 2005/094933 A1 in order to allow an observer to observe a two-dimensional image formed by an image forming apparatus as an enlarged virtual image by a virtual image optical system. is there.

An image display apparatus 310 disclosed in WO 2005/094933 A1 whose basic conceptual diagram is shown in FIG. 13 includes an image forming apparatus 11, a collimating optical system 12 that converts a light beam emitted from the image forming apparatus 11 into a parallel light beam, and The collimating optical system 12 is made up of an optical device 320 that receives light that is made into a parallel light beam, is guided, and is emitted. The optical device 320 is
(A) A parallel light beam group composed of a plurality of parallel light beams having different traveling directions is incident, propagated through the interior by total reflection, and then emitted from the light guide plate 21;
(B) A reflective volume hologram diffraction grating that diffracts and reflects the parallel light beam group incident on the light guide plate 21 so that the parallel light beam group incident on the light guide plate 21 is totally reflected inside the light guide plate 21. First diffraction grating member 330, and
(C) a second diffraction grating member 340 made of a reflective volume hologram diffraction grating that diffracts and reflects a parallel light beam group propagated by total reflection inside the light guide plate 21 and emits the parallel light beam group from the light guide plate 21;
It has. Note that reference numeral 50 in the drawing is an observer's pupil position where light emitted from the light guide plate 21 enters.

  The reflection type volume hologram diffraction grating in which interference fringes 331 and 341 are formed has a planar shape, but changes the traveling direction of the incident light beam and the outgoing light beam due to the diffraction phenomenon, or only for a specific wavelength band. A diffraction phenomenon can be generated. By utilizing such characteristics, it is possible to achieve thinning of the image display device and high efficiency of see-through.

WO 2005/093493 A1

  By the way, although not described in WO 2005/094933 A1, depending on the structure of the first diffraction grating member 330 and the second diffraction grating member 340, the observer's pupil is at the position a and at the position b. Depending on the case, the light path in the light guide plate 21 at each angle of view changes as shown in FIG. In the reflection type volume hologram diffraction grating, the wavelength at which it is diffracted most strongly changes in accordance with the inclination angle φ of the interference fringes, so that not only the color distribution changes at the pupil position a and the pupil position b (specifically Specifically, not only the shift to the short wavelength side), but also the luminance changes according to the wavelength spectrum emitted from the light guide plate 21. In the drawings, the light is diffracted and reflected at the interface between the light guide plate 21 and the first diffraction grating member, or at the interface between the light guide plate 21 and the second diffraction grating member. The light is diffracted and reflected inside the first diffraction grating member and inside the second diffraction grating member.

Here, the designed pupil position is a, and the position where the pupil moves from the pupil position a in the horizontal angle of view direction to the collimating optical system 12 side is the pupil position b. Also shows the position of the second diffraction grating member 340 through which the horizontal angle 0 ° of the light beam (indicated by a dashed line) a _0, a horizontal angle -8 degrees beam (thin solid line in the pupil position a at the pupil position a ) and a _-8 a position of the second diffraction grating member 340 through which the. Similarly, the position of the second diffraction grating member 340 through which a light beam having a horizontal angle of view of 0 degrees at the pupil position b (indicated by a one-dot chain line) passes is b ₀ , and a light beam having a horizontal field angle of −8 degrees at the pupil position b (in a thin solid line). The position of the second diffraction grating member 340 through which (shown) passes is b- ₈ .

14 and 15 show the incident wavelength dependence of the diffraction efficiency at these positions a ₀ , a _-8 , b ₀ , and b _-8 (shown by dotted lines in FIGS. 14 and 15). A spectrum P (shown by a solid line in FIGS. 14 and 15) of a wavelength that is diffracted and reflected by the first diffraction grating member 330, propagates through the light guide plate 21, and is incident on the second diffraction grating member 340 is represented by these positions a ₀ , A state that changes depending on a _-8 , b ₀ , and b _-8 is shown. Here, spectrum P (a ₀ ) is a spectrum at position a ₀ , spectrum P (a ₋₈ ) is a spectrum at position a ₋₈ , and spectrum P (b ₀ ) is a spectrum at position b ₀ . And the spectrum P (b _-8 ) is the spectrum at position b _-8 . The light intensity incident on the pupil is determined by the product of the light intensity incident on the second diffraction grating member 340 and the diffraction efficiency of the second diffraction grating member 340. Table 1 shows the result of calculating the relative luminance at the horizontal field angle of 0 degrees and the horizontal field angle of -8 degrees at the pupil position a and the pupil position b. From Table 1, it can be seen that the relative luminance changes as the pupil position moves along the horizontal field angle direction. In addition, when a diffraction grating member having interference fringes corresponding to light of three types of wavelength bands of red, green, and blue is formed in order to correspond to a color image, red light can be obtained by taking different optical paths in the respective wavelength bands. , Green and blue light in three wavelength bands vary in luminance, and the luminance change is observed as color unevenness.

[Table 1]
Horizontal angle of view 0 degrees Horizontal angle of view -8 degrees Pupil position a 0.9 0.9
Pupil position b 0.3 0.5

  Therefore, the object of the present invention is that even if the position of the pupil of the observer who uses the image display device has moved from the designed pupil position in the horizontal field angle direction (or even if it has shifted in the horizontal field angle direction), An object of the present invention is to provide an image display device having a configuration and a structure in which luminance change or color unevenness hardly occurs.

In order to achieve the above object, an image display device of the present invention comprises:
(A) an image forming apparatus composed of a total of M × N pixels, M along the Y direction and N along the Z direction;
(B) a collimating optical system that converts the light emitted from each pixel of the image forming apparatus into a parallel light beam;
(C) an optical device in which light that is collimated by a collimating optical system is incident, guided, and emitted;
(D) an image forming apparatus driving device including a correcting unit;
An image display device comprising:
The optical device
(A) A light guide plate extending along the Y direction that is emitted after light is incident and propagated through the interior by total reflection;
(B) A first diffraction grating composed of a reflective volume hologram diffraction grating that diffracts and reflects light incident on the light guide plate so that the light incident on the light guide plate is totally reflected along the Y direction inside the light guide plate. Members and
(C) Second diffraction composed of a reflective volume hologram diffraction grating that diffracts and reflects light propagating through the interior of the light guide plate so as to emit light from the light guide plate and enter the pupil position of the observer. Lattice members,
With
The correction means corrects the value of the image signal input to each pixel of the image forming apparatus based on a correction coefficient for each pixel along the Y direction obtained from the luminance distribution at a plurality of different pupil positions. And

  In the image display device of the present invention, the correction coefficient is a luminance distribution at a predetermined gradation display at a plurality of different pupil positions [that is, in m-th (where m = 1, 2,..., M) pixels. Measured values of luminance values at a plurality of different pupil positions corresponding to the luminance values at the time of predetermined gradation display, and a desired luminance distribution [that is, a plurality of different pupils corresponding to the mth pixel. It is possible to adopt a configuration that minimizes the difference from the luminance value (target) that will be obtained by correction at the position.

In the image display device of the present invention including the above-described preferable configuration, each pixel includes a red light emitting subpixel that emits red, a green light emitting subpixel that emits green, and a blue light emitting subpixel that emits blue. The correcting means may include a correction coefficient for each of the red light emitting subpixel, the green light emitting subpixel, and the blue light emitting subpixel, and the red light emitting subpixel, the green light emitting subpixel, and the blue light emitting subpixel. This is desirable from the viewpoint of realizing appropriate correction of the value of the input image signal in each pixel. In this case,
(1) A correction coefficient (green correction coefficient) for correcting the value of the input image signal in the green light emitting sub-pixel is a luminance distribution related to green at the time of predetermined gradation display at a plurality of different pupil positions [that is, the mth The measured value of the green luminance value at a plurality of different pupil positions corresponding to the luminance value at the time of predetermined gradation display in the th green light emitting sub-pixel], and the desired luminance distribution related to green [that is, the mth The difference between the green luminance value corresponding to the green emission sub-pixel and the green luminance value that would be obtained by correction at a plurality of different pupil positions],
(2) A correction coefficient (red correction coefficient) for correcting the value of the input image signal in the red light emitting subpixel is a luminance distribution related to red at the time of predetermined gradation display at a plurality of different pupil positions [that is, the mth Measured value of red luminance value at a plurality of different pupil positions corresponding to the luminance value at the time of predetermined gradation display in the second red light emitting sub-pixel] and green (note that it is not red) Minimizing the difference from the desired luminance distribution [ie, the green luminance value that would be obtained by correction at a plurality of different pupil positions corresponding to the mth green emitting subpixel];
(3) The correction coefficient (blue correction coefficient) for correcting the value of the input image signal in the blue light-emitting subpixel is a luminance distribution related to blue at the time of predetermined gradation display at a plurality of different pupil positions [that is, the mth Measured values of blue luminance values at a plurality of different pupil positions corresponding to luminance values at the time of predetermined gradation display in the th blue light emitting sub-pixel] and green (note that it is not blue) Configuration that minimizes a difference from a desired luminance distribution [that is, green luminance values that may be obtained by correction at a plurality of different pupil positions corresponding to the mth green light emitting subpixel] It can be.

  In the image display device of the present invention including the above-described preferable configuration, the value of the image signal input to each pixel along the Z direction (that is, N pixels along the Z direction) is the same correction. It can be set as the structure correct | amended based on a coefficient.

  Furthermore, in the image display device of the present invention including the above-described preferable configuration, the correction unit includes a plurality of correction coefficients, and the correction unit is configured based on the average value of the image signals input to all pixels. One correction coefficient can be selected from the correction coefficients, or the correction means includes one correction coefficient and an intensity coefficient corresponding to the value of the input image signal. Selects an intensity coefficient based on an average value of image signals input to all pixels, and corrects the value of the image signal input to each pixel of the image forming apparatus based on the selected intensity coefficient and correction coefficient. It can be configured. The average value of image signals input to all pixels may be a value obtained by simply averaging the values of image signals input to all pixels, or may be weighted with respect to the intensity of image signals input to all pixels. It may be a value obtained by averaging the values of the image signals obtained in this way.

  In the following description, the angle of view θ is more strictly defined as a viewing angle when the object range of the optical system is viewed from the image space of the optical system. The term total reflection means total internal reflection or total reflection inside the light guide plate. Furthermore, the inclination angle of the interference fringes means an angle formed between the surface of the diffraction grating member (or the diffraction grating layer) and the interference fringes.

  In the image display device of the present invention including the preferable configuration described above (hereinafter, may be simply referred to as the present invention), as the material constituting the first diffraction grating member and the second diffraction grating member, Mention may be made of photopolymer materials. In the diffraction grating member, interference fringes are formed from the inside to the surface. The method of forming the interference fringes itself may be the same as the conventional forming method. Specifically, for example, a member constituting the diffraction grating member is irradiated with object light from a first predetermined direction on one side to a member constituting the diffraction grating member (for example, photopolymer material), and at the same time Is irradiated with reference light from a second predetermined direction on the other side, and interference fringes formed by the object light and the reference light may be recorded inside the member constituting the diffraction grating member. By appropriately selecting the wavelength of the first predetermined direction, the second predetermined direction, the object light and the reference light, the desired pitch of the interference fringes on the surface of the diffraction grating member and the desired inclination angle of the interference fringes can be obtained. Obtainable.

  Further, in the present invention, a group of parallel light beams composed of a plurality of parallel light beams having different traveling directions is incident on the light guide plate. However, such a request that the light beams are parallel light beams is incident on the light guide plate. The light wavefront information at that time needs to be preserved even after being emitted from the light guide plate via the first diffraction grating member and the second diffraction grating member. Specifically, in order to generate a parallel light beam group composed of a plurality of parallel light beams having different traveling directions, the image forming apparatus may be positioned at the focal point (position) in the collimating optical system. Here, the collimating optical system has a function of converting pixel position information of the light beam emitted from the image forming apparatus in the image forming apparatus into angle information in the optical system of the optical apparatus.

  In the present invention, the light guide plate has two parallel surfaces (referred to as a first surface and a second surface for convenience) extending in parallel with the axis (Y direction) of the light guide plate. Here, when the surface of the light guide plate on which the parallel light flux group is incident is the light guide plate entrance surface, and the surface of the light guide plate on which the parallel light flux group is emitted is the light guide plate exit surface, the light guide plate entrance surface and the light guide plate exit are formed by the first surface. The surface may be configured, the light guide plate entrance surface may be configured by the first surface, and the light guide plate exit surface may be configured by the second surface. In the former case, the first diffraction grating member and the second diffraction grating member are arranged on the second surface. On the other hand, in the latter case, the first diffraction grating member is disposed on the second surface, and the second diffraction grating member is disposed on the first surface.

  As a material constituting the light guide plate, glass containing optical glass such as quartz glass or BK7, or plastic material (for example, PMMA, polycarbonate resin, acrylic resin, amorphous polypropylene resin, styrene resin containing AS resin) ).

  The constituent materials and basic structure of the first diffraction grating member and the second diffraction grating member made of the reflective volume hologram diffraction grating may be the same as those of the conventional reflective volume hologram diffraction grating. Here, the reflection type volume hologram diffraction grating means a hologram diffraction grating that diffracts and reflects only the + 1st order diffracted light.

  As an image forming apparatus constituting the image display apparatus of the present invention, for example, an image forming apparatus composed of light emitting elements such as organic EL (Electro Luminescence), inorganic EL, and light emitting diode (LED); light source [for example, LED] and light An image forming apparatus comprising a combination of a bulb [for example, a transmissive or reflective liquid crystal display device such as LCOS (Liquid Crystal On Silicon) or a digital micromirror device (DMD)]; a light source and a parallel light beam emitted from the light source An image forming apparatus composed of a combination with a scanning optical system [for example, MEMS (Micro Electro Mechanical Systems), galvanometer mirror] that performs horizontal scanning and vertical scanning. The number of pixels constituting the image forming apparatus may be determined based on specifications required for the image forming apparatus. As specific values of the number of pixels M × N, 320 × 240, 432 × 240, 640 × 480 are used. 1024 × 768, 1920 × 1080 can be exemplified.

  The image forming apparatus driving apparatus itself is a well-known image forming apparatus driving apparatus, specifically, a well-known driving for controlling the above-described various light emitting elements, light valves, a light passage control apparatus (to be described later), a scanning optical system, and the like. It can consist of devices. For example, the correction unit includes a storage unit that stores a correction coefficient, a control circuit that controls the operation of the entire correction unit, and a correction circuit that corrects the value of an image signal input to each pixel of the image forming apparatus. Can do.

  A configuration example of a color display image forming apparatus will be described below.

[Image forming apparatus-A]
Image forming apparatus-A
(Α) a first image forming apparatus comprising a first light emitting element panel in which first light emitting elements emitting blue light are arranged in a two-dimensional matrix;
(Β) a second image forming apparatus comprising a second light emitting element panel in which second light emitting elements emitting green light are arranged in a two-dimensional matrix; and
(Γ) a third image forming apparatus comprising a third light emitting element panel in which third light emitting elements emitting red light are arranged in a two-dimensional matrix; and
(Δ) Means for collecting light emitted from the first image forming apparatus, the second image forming apparatus, and the third image forming apparatus into one optical path (for example, a dichroic prism; the same applies to the following description) ),
With
The light emitting / non-light emitting states of the first light emitting element, the second light emitting element, and the third light emitting element are controlled.

[Image forming apparatus-B]
Image forming apparatus-B
(Α) a first light-emitting element that emits blue light, and a first light passage control device for controlling the passage / non-passage of the emitted light emitted from the first light-emitting element that emits blue light [a kind of light valve A first image forming apparatus comprising, for example, a liquid crystal display device, a digital micromirror device (DMD), and LCOS (Liquid Crystal On Silicon), and the same in the following description.
(Β) a second light-emitting control device (light valve) for controlling passage / non-passage of the emitted light emitted from the second light-emitting element emitting green light and the second light-emitting element emitting green light A second image forming apparatus comprising:
(Γ) a third light emitting device that emits red light and a third light passage control device (light valve) for controlling passage / non-passage of the emitted light emitted from the third light emitting device that emits red light A third image forming apparatus comprising:
(Δ) means for collecting the light that has passed through the first light passage control device, the second light passage control device, and the third light passage control device into one optical path;
With
An image is displayed by controlling the passage / non-passage of the emitted light emitted from these light emitting elements by the light passage control device. As a means (light guide member) for guiding the emitted light emitted from the first light emitting element, the second light emitting element, and the third light emitting element to the light passage control device, a light guide member, a microlens array, a mirror, and a reflection A plate and a condensing lens can be exemplified.

[Image forming apparatus-C]
Image forming apparatus-C
(Α) To control the first light emitting element panel in which the first light emitting elements emitting blue light are arranged in a two-dimensional matrix and the passage / non-passage of the light emitted from the first light emitting element panel. A first image forming apparatus comprising a blue light passage control device (light valve),
(Β) To control passage / non-passage of the second light emitting element panel in which the second light emitting elements emitting green light are arranged in a two-dimensional matrix and the light emitted from the second light emitting element panel. A second image forming apparatus comprising a green light passage control device (light valve),
(Γ) To control passage / non-passage of the third light emitting element panel in which the third light emitting elements emitting red light are arranged in a two-dimensional matrix and the light emitted from the third light emitting element panel. A third image forming apparatus comprising a red light passage control device (light valve), and
(Δ) comprising means for collecting light that has passed through the blue light passage control device, the green light passage control device, and the red light passage control device into one optical path;
An image is displayed by controlling passage / non-passage of the emitted light emitted from the first light emitting element panel, the second light emitting element panel, and the third light emitting element panel by a light passage control device (light valve).

[Image forming apparatus-D]
The image forming apparatus-D is a field sequential color display image forming apparatus,
(Α) a first image forming apparatus including a first light emitting element that emits blue light;
(Β) a second image forming apparatus including a second light emitting element that emits green light, and
(Γ) a third image forming apparatus including a third light emitting element that emits red light, and
(Δ) means for collecting light emitted from the first image forming apparatus, the second image forming apparatus, and the third image forming apparatus into one optical path;
(Ε) a light passage control device (light valve) for controlling the passage / non-passage of the light emitted from the means for collecting in one light path;
With
An image is displayed by controlling the passage / non-passage of the emitted light emitted from these light emitting elements by the light passage control device.

[Image forming apparatus-E]
The image forming apparatus-E is also a field sequential color display image forming apparatus,
(Α) a first image forming apparatus comprising a first light emitting element panel in which first light emitting elements emitting blue light are arranged in a two-dimensional matrix;
(Β) a second image forming apparatus comprising a second light emitting element panel in which second light emitting elements emitting green light are arranged in a two-dimensional matrix; and
(Γ) a third image forming apparatus comprising a third light emitting element panel in which third light emitting elements emitting red light are arranged in a two-dimensional matrix; and
(Δ) means for collecting light emitted from each of the first image forming apparatus, the second image forming apparatus, and the third image forming apparatus into one optical path;
(Ε) a light passage control device (light valve) for controlling the passage / non-passage of the light emitted from the means for collecting in one light path;
With
An image is displayed by controlling the passage / non-passage of the emitted light emitted from these light emitting element panels by the light passage control device.

[Image forming apparatus-F]
The image forming apparatus-F is a passive matrix type or active matrix type color display that displays an image by controlling the light emitting / non-light emitting states of the first light emitting element, the second light emitting element, and the third light emitting element. An image forming apparatus.

[Image forming apparatus-G]
The image forming apparatus-G includes a light passage control device (light valve) for controlling passage / non-passage of light emitted from the light emitting element units arranged in a two-dimensional matrix. The respective light emitting / non-light emitting states of the first light emitting element, the second light emitting element, and the third light emitting element are controlled in a time-sharing manner. This is a field sequential color display image forming apparatus that displays an image by controlling passage / non-passage of emitted light.

  Further, as a collimating optical system constituting the image display device of the present invention, an optical system having a positive optical power as a whole, which is a single lens or a combination of a convex lens, a concave lens, a free-form surface prism, and a hologram lens, is exemplified. Can do.

  With the image display device of the present invention, for example, a head-mounted HMD (Head Mounted Display) can be configured, the device can be reduced in weight and size, and discomfort at the time of device mounting is greatly increased. It is possible to reduce this, and it is also possible to reduce the manufacturing cost.

In the image display device of the present invention including the various preferable configurations and forms described above, the first diffraction grating member has interference fringes formed from the inside to the surface thereof, and the first diffraction grating member The pitch of interference fringes on the surface is equal,
In the first diffraction grating member, when the angle formed by the interference fringes in the first diffraction grating member with the surface of the first diffraction grating member is an inclination angle:
(B-1) The inclination angle of the interference fringes formed in the outer region located farther from the second diffraction grating member than the minimum inclination angle region where the inclination angle is the minimum inclination angle is so far from the minimum inclination angle region. big,
(B-2) The inclination angle of the interference fringes formed in the inner area located closer to the second diffraction grating member than the minimum inclination angle area is the maximum inclination angle in the inner area adjacent to the minimum inclination angle area. , Smaller the further away from the minimum tilt angle region,
It can be set as the 1st diffraction grating member which satisfies this. In addition, such a 1st diffraction grating member may be called the 1st diffraction grating member of a 1st structure for convenience.

  In the first diffraction grating member having the first configuration, the region of the first diffraction grating member may not exist at a position farther from the second diffraction grating member than the minimum inclination angle region where the inclination angle is the minimum inclination angle. In this case, the above item (B-1) is ignored. In some cases, the region of the first diffraction grating member does not exist closer to the second diffraction grating member than the minimum inclination angle region. In such a case, the above item (B-2) is ignored.

  In the first diffraction grating member having the first configuration, the diffraction diffraction angles of P types of light beams having different wavelength bands (or wavelengths) constituting each parallel light beam are made substantially equal to each other in the first diffraction grating member. In addition, it is preferable to adopt a configuration in which P types of interference fringes are formed. By adopting such a configuration, a parallel light beam having each wavelength band (or wavelength) is diffracted and reflected by the first diffraction grating member. The diffraction efficiency can be increased, the diffraction acceptance angle can be increased, and the diffraction angle can be optimized. Note that the inclination angles of the P types of interference fringes that diffract and reflect a parallel light beam having a certain incident angle are the same regardless of the wavelength band (or wavelength) constituting the parallel light beam. The fact that P types of interference fringes are formed may be referred to as multiple interference fringes (P overlap).

In the first diffraction grating member having the first configuration,
The center of the second diffraction grating member is the origin, the normal line of the second diffraction grating member passing through the origin is the X axis, the axis of the light guide plate passing through the origin is the Y axis, and is diffracted and reflected by the second diffraction grating member. A point on the X-axis for observing an image based on the group of parallel light beams emitted from the light beam, and the parallel light beam diffracted and reflected by the second diffraction grating member and located in the XY plane. The angle formed by the parallel light beam close to one diffraction grating member is the angle of view θ = θ ₀ (> 0), and the angle formed by the parallel light beam farthest from the first diffraction grating member is the angle of view θ = −θ ₀ (<0). When
A region of the first diffraction grating member where a parallel light beam corresponding to a parallel light beam having an angle of view θ = θ ₀ is diffracted and reflected has the maximum inclination angle,
A region of the first diffraction grating member in which a parallel light beam corresponding to a parallel light beam having an angle of view θ = −θ ₀ is diffracted and reflected can have the minimum inclination angle.

Alternatively, in the first diffraction grating member having the first configuration,
The first diffraction grating member is formed by laminating Q diffraction grating layers made of a reflective volume hologram diffraction grating,
In each diffraction grating layer constituting the first diffraction grating member, an interference fringe is formed from the inside to the surface,
The pitch of the interference fringes on the surface of each diffraction grating layer constituting the first diffraction grating member may be equal, and the pitch of the interference fringes between the diffraction grating layers may be equal. By adopting such a laminated structure, the length of the first diffraction grating member along the axial direction of the light guide plate is shortened, the light guide plate is thinned, and the first diffraction grating member is diffracted and reflected. The incident angle of the generated parallel light beam can be increased.

  In this case, the minimum inclination angle is different in all of the diffraction grating layers constituting the first diffraction grating member, and the maximum inclination angle is different in all of the diffraction grating layers constituting the first diffraction grating member. Or, in the diffraction grating layer of the Q layer constituting the first diffraction grating member, the minimum inclination angle of at least one diffraction grating layer is greater than or equal to the minimum inclination angle of the other diffraction grating layer. The maximum inclination angle of the one diffraction grating layer may be not less than the inclination angle and not less than the minimum inclination angle and not more than the maximum inclination angle of the other diffraction grating layer.

Alternatively, in this case, the center of the second diffraction grating member is the origin, the normal line of the second diffraction grating member passing through the origin is the X axis, the axis of the light guide plate passing through the origin is the Y axis, and the second diffraction grating member Diffracted and reflected by a point on the X-axis for observing an image based on a group of parallel light beams that are diffracted and emitted from the light guide plate, and a q-th diffraction grating layer (where q = 1, 2,..., Q) The angle formed by the parallel light flux diffracted and reflected by the second diffraction grating member and located closest to the first diffraction grating member among the parallel light fluxes located in the XY plane is defined as an angle of view θ _q = θ q — ₀ (> 0), where the angle formed by the parallel light beam farthest from the first diffraction grating member is the angle of view θ _q = −θ _q — ₀ (<0),
The region of the q-th diffraction grating layer where the parallel luminous flux corresponding to the parallel luminous flux _{satisfying the} angle of view θ _q = θ _q — ₀ is diffracted and reflected has the maximum inclination angle,
The region of the qth diffraction grating layer in which the parallel light beam corresponding to the parallel light beam _{satisfying the} angle of view θ _q = −θ _q — ₀ is diffracted and reflected may have the minimum inclination angle.

Alternatively, in the image display device of the present invention including the various preferable configurations and forms described above, the first diffraction grating member is formed by laminating a virtual diffraction grating layer of Q layers made of a reflective volume hologram diffraction grating. Assuming that, the pitch of interference fringes on the surface of each virtual diffraction grating layer constituting the first diffraction grating member is equal, and the pitch of interference fringes between virtual diffraction grating layers is also equal,
For each virtual grating layer, where the angle formed by the interference fringes in the virtual grating layer and the surface of the virtual grating layer is the tilt angle:
(B-1) The inclination angle of the interference fringes formed in the outer region located farther from the second diffraction grating member than the minimum inclination angle region where the inclination angle is the minimum inclination angle is so far from the minimum inclination angle region. big,
(B-2) The inclination angle of the interference fringes formed in the inner area located closer to the second diffraction grating member than the minimum inclination angle area is the maximum inclination angle in the inner area adjacent to the minimum inclination angle area. , The smaller the distance from the minimum tilt angle area,
When the first diffraction grating member is divided into R sections from a portion closest to the second diffraction grating member to a portion farthest from the second diffraction grating member, r-th (where r = 1, 2,... R) The first diffraction grating member section RG _{1_r} of R) _divides the virtual diffraction grating layer of the Q layer into R sections from a portion closest to the second diffraction grating member to a portion farthest from the second diffraction grating member. The virtual diffraction grating layer section VG _{(r, q)} (where q is an arbitrary integer selected within the range of 1 to Q and having no overlap) is obtained. One diffraction grating member can be used. In addition, such a 1st diffraction grating member may be called the 1st diffraction grating member of a 2nd structure for convenience.

  In the first diffraction grating member having the second configuration, the virtual diffraction grating layer region may not exist at a position farther from the second diffraction grating member than the minimum inclination angle region where the inclination angle is the minimum inclination angle. In this case, the above item (B-1) is ignored. In some cases, the region of the virtual diffraction grating layer does not exist closer to the second diffraction grating member than the minimum inclination angle region. In such a case, the above item (B-2) is ignored.

  In the first diffraction grating member having the second configuration, in the first diffraction grating member, the region and the section may correspond to one to one or may not correspond to one to one. . Further, in the first diffraction grating member having the second configuration, the first diffraction grating member is substantially formed by laminating Q diffraction grating layers made of a reflective volume hologram diffraction grating.

  In the first diffraction grating member having the second configuration, each virtual diffraction grating layer has substantially the same angle of diffraction reflection of P types of light beams having different wavelength bands (or wavelengths) constituting each parallel light beam. Therefore, it is preferable to adopt a configuration in which P types of interference fringes are formed. By adopting such a configuration, a parallel light flux having each wavelength band (or wavelength) can be converted into the first diffraction grating member. The diffraction efficiency can be increased, the diffraction acceptance angle can be increased, and the diffraction angle can be optimized. Note that the inclination angles of the P types of interference fringes that diffract and reflect a parallel light beam having a certain incident angle are the same regardless of the wavelength band (or wavelength) constituting the parallel light beam.

In the first diffraction grating member having the second configuration including the preferred configuration described above, the center of the second diffraction grating member is the origin, the normal line of the second diffraction grating member passing through the origin is the X axis, and the first diffraction grating member is guided through the origin. A point on the X-axis for observing an image based on the parallel light flux group that is diffracted and reflected by the second diffraction grating member and emitted from the light guide plate with the axis of the optical plate as the Y axis, and a virtual diffraction grating layer of the qth layer ( However, among the assumed parallel light fluxes that are assumed to be diffracted and reflected by q = 1, 2... Q) and to be diffracted and reflected by the second diffraction grating member, and located in the XY plane, The angle formed with the assumed parallel beam closest to the first diffraction grating member is the angle of view θ _q = θ _q — ₀ (> 0), and the angle formed with the assumed parallel beam farthest from the first diffraction grating member is the view angle θ _q = −. When θ _{q_0} (<0),
The region of the virtual diffraction grating layer of the qth layer where the assumed parallel light beam corresponding to the assumed parallel light beam _{satisfying the} angle of view θ _q = θ _q — ₀ is diffracted and reflected has the maximum inclination angle,
The region of the qth virtual diffraction grating layer where the assumed parallel light beam corresponding to the assumed parallel light beam _{satisfying the} angle of view θ _q = −θ _q — ₀ is diffracted and reflected may have the minimum inclination angle.

  Furthermore, in the first diffraction grating member having the first configuration or the first diffraction grating member having the second configuration including the various preferable configurations and forms described above, total reflection of the parallel light flux group inside the light guide plate is performed. The number of times can be different depending on the angle at which the parallel light flux group is incident on the light guide plate, thereby shortening the length of the first diffraction grating member along the axial direction of the light guide plate, The light guide plate can be made thinner, and the incident angle of the parallel light beam that can be diffracted and reflected by the first diffraction grating member to the first diffraction grating member can be increased.

  Even in the first diffraction grating member of the first configuration or the first diffraction grating member of the second configuration, interference fringes are formed from the inside to the surface, but the method of forming such interference fringes themselves is also fundamental. Specifically, it may be the same as the conventional forming method. Specifically, for example, object light is irradiated from a first predetermined direction on one side to a member constituting the first diffraction grating member, and at the same time, to a member constituting the first diffraction grating member The reference light is irradiated from the second predetermined direction on the other side, and the interference fringes formed by the object light and the reference light may be recorded inside the member constituting the first diffraction grating member. By appropriately selecting the first predetermined direction, the second predetermined direction, the wavelength of the object light and the reference light, a desired pitch of the interference fringes on the surface of the first diffraction grating member, and a desired inclination of the interference fringes You can get a corner. However, in the first diffraction grating member, as described above, the inclination angle of the interference fringe is changed depending on the region of the first diffraction grating member provided with the interference fringe.

  In the first diffraction grating member of the first configuration, the first diffraction grating member is formed by stacking Q diffraction grating layers made of a reflective volume hologram diffraction grating, and also in the first diffraction grating member of the second configuration. The first diffraction grating member is formed by laminating Q diffraction grating layers made of a reflection type volume hologram diffraction grating. In the lamination of such diffraction grating layers, each of the Q diffraction grating layers was produced separately. Thereafter, the diffraction grating layer of the Q layer may be laminated (adhered) using, for example, an ultraviolet curable adhesive. In addition, after producing a single diffraction grating layer using a photopolymer material having adhesiveness, a diffraction grating layer is produced by sequentially sticking a photopolymer material having adhesiveness thereon, thereby producing diffraction of the Q layer. A lattice layer may be produced.

In the first diffraction grating member of the first configuration or the first diffraction grating member of the second configuration, the inclination angle of the interference fringes in the first diffraction grating member changes, but the change in the inclination angle is gradual. Alternatively, it may be continuous. That is, in the former case, when the first diffraction grating member is divided into S parts from the part closest to the second diffraction grating member to the part farthest from the second diffraction grating member, the sth (where s = 1, 2 · · · S) the inclination angle in the portion RG _{1_S} of the first diffraction grating member is constant, and moreover, by a form tiltable in part RG _{1_S} of the first diffraction grating member when the value of s is different That's fine. On the other hand, in the latter case, it is sufficient that the inclination angle of the interference fringes is gradually changed. As a method for continuously changing the inclination angle, object light and / or reference light using a prism or a lens is used. And a method of exposing the reflective volume hologram diffraction grating by providing an appropriate wavefront.

The inclination angle of the interference fringes in the first diffraction grating member of the first configuration or the second diffraction grating member corresponding to the first diffraction grating member of the second configuration may be constant or may vary. In the latter case, it is desirable that the inclination angle increases as it approaches the first diffraction grating member. With such a configuration, it is possible to further reduce color unevenness and luminance unevenness. The increase in the tilt angle may be gradual or continuous. That is, in the former case, when the second diffraction grating member is divided into T parts from the part farthest from the first diffraction grating member to the part closest to the first diffraction grating member, the t th (where t = 1,2 and constant angle of inclination in the portion RG _{2_T} of the second diffraction grating member · · · T), moreover, as the value of t increases, increasing the inclination angle in the portion RG _{2_T} of the second diffraction grating member The form may be used. On the other hand, in the latter case, it may be configured to gradually change the inclination angle of the interference fringes.

  In the image display apparatus of the present invention, the correction means provided in the image forming apparatus driving apparatus is based on the correction coefficient for each pixel along the Y direction obtained from the luminance distribution at a plurality of different pupil positions. Therefore, even if the position of the pupil of the observer who uses the image display device moves from the designed pupil position in the horizontal angle of view direction (or the horizontal angle of view). Even if it is shifted in the direction), it is difficult to cause a change in luminance, and an image with little color unevenness can be observed.

  The plurality of parallel light beams emitted from the image forming apparatus and having passed through the collimating optical system have different incident angles on the first diffraction grating member depending on the emission positions from the image forming apparatus. Therefore, in the first diffraction grating member in which the inclination angle of the interference fringes is constant, the diffraction wavelength satisfying the Bragg condition varies from region to region. However, when the first diffraction grating member of the first configuration or the first diffraction grating member of the second configuration is adopted, the inclination angle of the interference fringes is changed without being constant in the first diffraction grating member, so that it is parallel. Even if the incident angle of the light beam on the first diffraction grating member is different, the Bragg condition can be satisfied for each region of the first diffraction grating member. As a result, the diffraction efficiency in a certain wavelength band in each region of the first diffraction grating member can be made as constant as possible, and the hue and brightness in the pixel image guided to the pupil by the pixel position of the image forming apparatus are reduced. It is possible to suppress the occurrence of problems such as differences (occurrence of color unevenness and brightness unevenness). In addition, by setting the inclination angle of the interference fringes to a predetermined value in a predetermined region of the first diffraction grating member, a parallel light beam incident on the first diffraction grating member and diffracted and reflected is converted into a predetermined value of the second diffraction grating member. It is possible to reliably enter the region. Further, if the first diffraction grating member has a structure in which the Q diffraction grating layers are laminated, the length of the first diffraction grating member along the axial direction of the light guide plate is shortened and the angle of view is increased. can do.

  Hereinafter, the present invention will be described based on examples with reference to the drawings.

  Example 1 relates to an image display device of the present invention. FIG. 1 shows a conceptual diagram of the image display apparatus according to the first embodiment.

  The image display apparatus 10 according to the first exemplary embodiment includes an image forming apparatus 11 including a total of M × N pixels, which is M along the Y direction and N along the Z direction. A collimating optical system 12 that converts the light emitted from the pixel into a parallel light beam, the optical device 20 that receives the light that has been converted into a parallel light beam by the collimating optical system 12, is guided, and is output. And an image forming apparatus driving device 60. Here, the image forming apparatus 11 is composed of, for example, a liquid crystal display device (LCD), and the collimating optical system 12 is composed of, for example, a convex lens, and generates a parallel light flux group composed of a plurality of parallel light fluxes having different traveling directions. Therefore, the image forming apparatus 11 is disposed at the focal length in the collimating optical system 12. One pixel is composed of a red light emitting subpixel that emits red, a green light emitting subpixel that emits green, and a blue light emitting subpixel that emits blue.

The optical device 20 of Example 1 is
(A) A light guide plate that extends along the Y direction after light (more specifically, a parallel light flux group composed of a plurality of parallel light fluxes having different traveling directions) enters, propagates through the interior by total reflection, and then exits. 21,
(B) The light (parallel light flux group) incident on the light guide plate 21 is diffracted and reflected so that the light (parallel light flux group) incident on the light guide plate 21 is totally reflected along the Y direction inside the light guide plate 21. A first diffraction grating member 30 comprising a reflective volume hologram diffraction grating, and
(C) Light is emitted from the light guide plate 21 (more specifically, emitted as a parallel light flux group) and is incident on the position (pupil position) of the pupil 50 of the observer. A second diffraction grating member 40 composed of a reflective volume hologram diffraction grating, which diffracts and reflects light (parallel light flux group) propagated by total reflection inside;
It has.

  The first diffraction grating member 30 and the second diffraction grating member 40 will be described in detail in Example 4 and Example 5 described later.

  Then, the correction unit 70 is configured to output an image signal (tone control signal) input to each pixel of the image forming apparatus based on the correction coefficient for each pixel along the Y direction obtained from the luminance distribution at a plurality of different pupil positions. Brightness signal) is corrected. The correction unit 70 includes correction coefficients (red correction coefficient, green correction coefficient, and blue correction coefficient) for each of the red light emission subpixel, the green light emission subpixel, and the blue light emission subpixel.

  Generally, it is known that a color having a high influence on luminance among the three primary colors of red, green, and blue is green. Therefore, first, each green light emission constituting the image forming apparatus is based on a correction coefficient (green correction coefficient) for each green light emission sub-pixel along the Y direction, which is obtained from luminance distributions at a plurality of different pupil positions regarding green. A method for correcting the value of the image signal input to the sub-pixel (including how to obtain the green correction coefficient) will be described. It is assumed that the value of the image signal input to each green light emitting subpixel along the Z direction (N green light emitting subpixels along the Z direction) is corrected based on the same correction coefficient.

The position of the virtual image incident on the pupil 50 corresponding to M pixels (red light emitting subpixel, green light emitting subpixel, and blue light emitting subpixel) along the horizontal angle of view direction (Y direction) is m (however, , M = 1, 2,..., M), and the pupil position (observation pupil position) is k (where k = 1, 2,..., K). In addition, the luminance distribution at the time of predetermined gradation display at a plurality of different observation pupil positions k (in the first embodiment, at the time of maximum gradation display) [that is, at the time of predetermined gradation display in the mth green light emitting subpixel. The measured value of the brightness value at a plurality of different observation pupil positions k corresponding to the brightness value] is defined as f _{k_G} (m). Here, the values of M, N, and K are not limited. For example, M = 432, N = 240, and K = 5 can be exemplified. Furthermore, a desired luminance distribution [that is, a green luminance value (target) that will be obtained by correction at a plurality of different observation pupil positions k corresponding to the mth green light emitting subpixel] is obtained. , F _{k — G} (m).

Color unevenness is luminance non-uniformity that is finally recognized by an observer. By the way, it is generally known that a luminance difference between adjacent pixels is recognized as unevenness, but is not recognized as unevenness when a change in luminance is gentle over the entire screen. Therefore, F _{k — G} (m) may be obtained by a least square method as an approximate function (for example, a third order polynomial) of low order with respect to f _{k — G} (m).

That is, based on one correction coefficient, correction is performed so that the luminance distribution at a predetermined (maximum in the first embodiment) gradation display at a different observation pupil position k is a gradual luminance change. In other words, if the green color correction coefficient is η _G (m), ideally, the green color correction coefficient η _G (m) in the mth green light emitting sub-pixel is satisfied so that the relationship of Expression (1) is established. Can be determined.

η _G (m) · f _k — _G (m) −F _k — _G (m) = 0 (1)

However, since the measured value f _{k — G} (m) of the green luminance distribution generally changes in luminance with a small period and has a different luminance distribution profile at the observation pupil position k, in reality, the green correction coefficient η _G ( m) between a predetermined luminance distribution f _{k_G} (m) and a desired luminance distribution F _{k_G} (m) at a predetermined (maximum in Example 1) gradation display at a plurality of different observation pupil positions k. Determine to minimize the difference. That is, the green correction coefficient η _G (m) for correcting the value of the input image signal in the green light-emitting subpixel is set to a luminance distribution related to green at a predetermined gradation display at a plurality of different observation pupil positions k [ie, Actual values f _{k — G} (m)] of green luminance values at a plurality of different observation pupil positions k corresponding to luminance values at the time of predetermined gradation display in the m-th green light emitting subpixel, and green The difference from the desired luminance distribution [ie, the green luminance value F _{k — G} (m) that would be obtained by correction at a plurality of different observation pupil positions k corresponding to the mth green light emitting sub-pixel] Decide to be the smallest. More specifically, the value of the green correction coefficient η _G (m) is determined so that the sum regarding k on the left side of Equation (1) is minimized.

In the following description, the symbol “Σ _k ” means obtaining a sum up to k = 1, 2,.

When displaying the maximum gradation in green (wavelength: 522 nm) when the position of the pupil of the observer who uses the image display device is in the horizontal field angle direction (Y direction) -1.0 mm from the designed observation pupil position Brightness distribution [actual measured value f _{k_G} (m)] of FIG. 2 is shown by the curve having the unevenness in FIG. 2A, and the brightness distribution at the time of maximum gradation display at the design observation pupil position [ The measured value f _{k — G} (m)] of the luminance value is indicated by the curved line having the unevenness in FIG. 2B, and is in the horizontal field angle direction (Y direction) +1.0 mm from the designed observation pupil position. The luminance distribution [measured value f _{k_G} (m) of luminance value] at the time of maximum gradation display is shown by the curve having the unevenness in FIG. Further, the desired luminance distribution [F _{k — G} (m) when the position of the pupil of the observer who uses the image display device is in the horizontal field angle direction (Y direction) −1.0 mm from the designed observation pupil position. ] _Is indicated by the smooth curve in FIG. 2A, and the desired luminance distribution [F _{k — G} (m)] at the designed observation pupil position is indicated by the smooth curve in FIG. A desired luminance distribution [F _{k — G} (m)] in the horizontal field angle direction (Y direction) +1.0 mm from the designed observation pupil position is indicated by a smooth curve in FIG. 2 (A), (B), and (C), the vertical axis is a luminance value (unit is arbitrary), and the horizontal axis is a value obtained by converting the value of m into an angle of view θ. θ = −8.0 degrees represents m = 1, and θ = + 8.0 degrees represents m = M.

More specifically, the relationship of the following formula (2) is established between the actually measured value f _{k_G} (m) of the green luminance distribution at the observation pupil position k and the average value f _{ave_G} (m).

Σ _k f _{k_G} (m) = K · f _{ave_G} (m) (2)

Next, the low-order approximation functions for _f ave_G (m) (e.g., third-order polynomial) and _F ave_G (m), is calculated based on the least squares method. Since this approximate function F _{ave_G} (m) is an approximate value from f _{ave_G} (m) that is proportional to the sum of f _{k_G} (m) at k in the observation pupil position k, F _{ave_G} (m) The approximate relationship of the following formula (3) holds between the sum of F _{k_G} (m) at k at the observation pupil position k. However, F _{k_G} (m) is a low-order approximation function for f _{k_G} (m) as described above.

Σ _k F _{k_G} (m) ≒ K · F _{ave_G} (m) (3)

  Therefore, the following formula (4) is established from the formula (2) and the formula (3).

Σ _k F _{k_G} (m) / Σ _k f _{k_G} (m) _{≈F ave_G} (m) / f _{ave_G} (m) (4)

Furthermore, from the request that the value of the green correction coefficient η _G (m) is determined so that the sum of k on the left side of Expression (1) is minimized in addition to Expressions (1) and (4), Equation (5) is established.

η _G (m) _{≈F ave_G} (m) / f _{ave_G} (m) (5)

Therefore, the green correction coefficient approximate to the ideal green correction coefficient η _G (m) shown in the expression (1) can be obtained from the expression (5).

The calculation of the green correction coefficient described above is an example in the case where the weighting of the luminance distribution at the observation pupil position k is treated equally. As an application, the luminance distribution at the observation pupil position k may be calculated by weighting the luminance distribution from the design observation pupil position. In this case, the merit function for obtaining the green correction coefficient is as shown in the following equation (6). Here, w _k is a weighting factor based on the observation pupil position k.

_{w k {η G (m)} · f k_G (m) -F k_G (m)} = 0 (6)

  Next, correction coefficients (red correction coefficient, blue correction coefficient) for each red light emission subpixel and blue light emission subpixel along the Y direction obtained from the luminance distribution at a plurality of different observation pupil positions k regarding red and blue are used. Based on this, a method for correcting the value of the image signal input to each red light emitting subpixel and blue light emitting subpixel constituting the image forming apparatus (including how to obtain the red correction coefficient and the blue correction coefficient) will be described.

Here, the luminance distribution at the time of desired gradation display at a plurality of different observation pupil positions k (in the first embodiment, at the time of maximum gradation display) [that is, in the mth red light emission subpixel and blue light emission subpixel. The measured values of the brightness values at a plurality of different observation pupil positions k corresponding to the brightness values at the time of predetermined gradation display are defined as f _{k_R} (m) and f _{k_B} (m). Further, a desired luminance distribution [that is, red and blue luminance values (that are obtained by correction at a plurality of different observation pupil positions k corresponding to the mth red light emitting subpixel and blue light emitting subpixel) ( _Is a target)] is _defined as F _{k — R} (m), F _{k — B} (m). Further, the red correction coefficient and the blue correction coefficient are η _R (m) and η _B (m).

Here, in order to align the luminance balance of red, green, and blue, f _{k_R} (m) and f _{k_B} (m) at the observation pupil position k are ideally the same value as F _{k_G} (m). Thus, the correction coefficients η _R (m) and η _B (m) may be determined. That is, ideally, equations (11-1) and (11-2) may be established.

η _R (m) · f _k — _R (m) −F _k — _G (m) = 0 (11-1)
η _B (m) · f _k — _B (m) −F _k — _G (m) = 0 (11-2)

However, as described above, the actually measured values f _{k — R} (m) and f _{k — B} (m) of the red and blue luminance distributions generally change in luminance with a small period and differ in luminance distribution profile at the observation pupil position k. In reality, the red correction coefficient η _R (m) and the blue correction coefficient η _B (m are set so that the sum of k on the left side of the expressions (11-1) and (11-2) is minimized. ) Value.

That is, the red correction coefficient η _R (m) for correcting the value of the input image signal in the red light-emitting sub-pixel, luminance distributions about the red at a predetermined gradation display at a plurality of different viewing pupil position k f _{K_R} ( m) and a desired luminance distribution F _{k — R} (m) for green are determined so as to be minimized. Further, the blue correction coefficient η _B (m) for correcting the value of the input image signal in the blue light emitting subpixel is set to a luminance distribution f _{k_B} (blue) at a predetermined gradation display at a plurality of different observation pupil positions k. m) and the desired luminance distribution F _{k — R} (m) for green are determined to be the smallest.

Here, between the measured values f _{k_R} (m) and f _{k_B} (m) of the red and blue luminance distributions at the observation pupil position k and the average values f _{ave_R} (m) and f _{ave_B} (m), The following expressions (12-1) and (12-2) are satisfied.

Σ _k f _{k — R} (m) = K · f _{ave — R} (m) (12-1)
Σ _k f _{k — B} (m) = K · f _{ave — B} (m) (12-2)

Next, low-order approximation functions (for example, third-order polynomials) F _{ave_R} (m) and F _{ave_B} (m) for f _{ave_R} (m) and f _{ave_B} (m) are calculated based on the least square method. These approximation functions _{F ave_R (m), F ave_B} (m) is, f _{K_R} the observation pupil position _k (m), f k_B f of the sum and where a proportional relationship for k in (m) _{ave_R} (m), Since it is an approximate value from f _{ave_B} (m), it is between F _{ave_R} (m) and F _{ave_B} (m) and the sum of F _{k_R} (m) and F _{k_B} (m) at k in the observation pupil position k. Is the approximate relationship of the following formulas (13-1) and (13-2). However, F _{k — R} (m) and F _{k — B} (m) are low-order approximation functions for f _{k — R} (m) and f _{k — B} (m), as described above.

Σ _k F _{k — R} (m) _≈K · F _{ave — R} (m) (13-1)
Σ _k F _{k — B} (m) ≈ K · F _{ave — B} (m) (13-2)

  Therefore, the following formulas (14-1) and (14-2) hold from the formulas (12-1), (12-2), (13-1), and (13-2).

Σ _k F _{k_R} (m) / Σ _k f _{k_R} (m) _{≈F ave_R} (m) / f _{ave_R} (m) (14-1)
Σ _k F _{k_B} (m) / Σ _k f _{k_B} (m) _{≈F ave_B} (m) / f _{ave_B} (m) (14-2)

Furthermore, in the formula (11-1), the formula (11-2), the formula (14-1), the formula (14-2), in addition to the formula (11-1) and the formula (11-2) In order to determine the values of the red correction coefficient η _R (m) and the blue correction coefficient η _B (m) so that the sum of k on the left side is minimized, the following expressions (15-1) and (15− 2) holds.

η _R (m) _{≈F ave_G} (m) / f _{ave_R} (m)
≒ η _G (m) · f _{ave_G} (m) / f _{ave_R} (m) (15-1)
η _B (m) _{≈F ave_G} (m) / f _{ave_B} (m)
≒ η _G (m) · f _{ave_G} (m) / f _{ave_B} (m) (15-2)

Therefore, from the formulas (15-1) and (15-2), the ideal green correction coefficients η _R (m) and η _B (m) represented by the formulas (11-1) and (11-2) The green correction coefficient approximated to can be obtained.

The calculation of the red and blue correction coefficients described above is an example when the weighting of the luminance distribution at the observation pupil position k is treated equally. As an application, as described above, the luminance distribution at the observation pupil position k may be calculated by weighting the luminance distribution from the design observation pupil position. In this case, the merit function for obtaining the red and blue correction coefficients is as shown in the following equations (16-1) and (16-2). Here, w _k is a weighting factor based on the observation pupil position k.

_{w k {η R (m)} · f k_R (m) -F k_G (m)} = 0 (16-1)
w _k {η _B (m) · f _k — _B (m) −F _k — _G (m)} = 0 (16-1)

  FIG. 3 shows a circuit diagram of a part of the image forming apparatus driving device 60 provided with the correcting means 70. The correction unit 70 includes, for example, a storage unit 71 that stores correction coefficients, a control circuit 72 that controls the operation of the entire correction unit, and a correction circuit 73 that corrects the value of an image signal input to each pixel of the image forming apparatus. Has been. The correction circuit 73 controlled by the control circuit 72 includes a timing generation circuit 74, a correction data generation circuit 75, and a multiplier 76. On the other hand, the image forming apparatus driving device 60 includes an image signal processing circuit 61. The image forming apparatus driving device 60 itself may be a known image forming apparatus driving device.

  In the following description, this state will be referred to as “row” and “line” for M pixels arranged in the Y direction and N pixels in the Z direction, for a total of M × N pixels. In terms of “columns”, it can be said that there are N rows × M columns of pixels. It is arranged in a two-dimensional matrix and is located at the nth row and mth column [where n = 1, 2,..., N and m = 1, 2,. In some cases, the pixel to be written is represented as (n, m). In addition, “-(n, m)” may be added to subscripts of elements and the like related to the pixel (n, m).

The red, green, and blue correction coefficients η _R (m), η _G (m), and η _B (m) for each subpixel obtained as described above are stored in the storage unit 71 that constitutes the correction unit 70. . As the storage means 71, for example, a ROM in which these correction coefficients are written can be exemplified.

During operation of the image display device, an image signal in one frame (red luminance control signal x _{R- (n, m)} for gradation control, green luminance control signal x _{G- (n, m)} , blue luminance control signal x _{B- (n, m)} ) is input to the image signal processing circuit 61 from the outside. In addition, a horizontal synchronization signal H _Sync , a vertical synchronization signal V _Sync , and a clock signal (Clock) are input to the image signal processing circuit 61 and the timing generation circuit 74 from the outside. Then, on the basis of the horizontal synchronization signal H _Sync , the vertical synchronization signal V _Sync , and the clock signal (Clock), the image signal processing circuit 61 configures each pixel [red light emitting subpixel (n, m), green color] constituting the image forming apparatus 11. Red luminance display signal X _{R- (n, m)} , green luminance display signal X _{G- (n, m)} , for controlling the light emitting subpixel (n, m), blue light emitting subpixel (n, m)], A blue luminance display signal X _{B- (n, m)} is generated and output toward each sub-pixel (n, m).

On the other hand, based on the horizontal synchronization signal H _Sync , the vertical synchronization signal V _Sync , and the clock signal (Clock) input to the timing generation circuit 74, the timing generation circuit 74 uses an address signal (Address) (specifically, an address). , M to determine a correction coefficient corresponding to m) is generated and sent to the correction data generation circuit 75 together with the read clock signal (Read_Clock).

The control circuit 72 reads the red, green and blue correction coefficients η _R (m), η _G (m), and η _B (m) from the storage unit 71 when the power is turned on. The control circuit 72 reads the correction coefficient, the address signal (Address) (the signal having the same position information as the address signal (Address) sent from the timing generation circuit 74 to the correction data generation circuit 75), and the write clock (Write_Clock). Are sent to the correction data generation circuit 75.

Then, the correction data generation circuit 75 is based on the read clock signal (Read_Clock) and the address signal (Address) from the timing generation circuit 74, and the multiplier 76 _R− for the red luminance display signal X _{R− (n, m). A} signal based on the red correction coefficient η _R (m) is sent to _{(n, m),} and the green correction coefficient is _supplied to the multiplier 76 _{G- (n, m)} for the green luminance display signal X _{G- (n, m)} A signal based on η _G (m) is transmitted, and a signal based on the blue correction coefficient η _B (m) is sent to the multiplier 76 _{B- (n, m)} for the blue luminance display signal X _{B- (n, m).} Send it out. As a result, in each of the multipliers 76 _{R- (n, m)} , 76 _{G- (n, m)} , 76 _{B- (n, m)} , the value of the image signal [red luminance display signal X _{R- ( n, m)} value, green luminance display signal X _{G- (n, m)} value, and blue luminance display signal X _{B- (n, m)} value] are red, green and blue correction coefficients η _R It is corrected (multiplied) by a signal based on (m), η _G (m), η _B (m). Then, the corrected red luminance display signal X ′ _{R− (n, m)} value, green luminance display signal X ′ _{G− (n, m)} value, and blue luminance display signal X ′ _{B− (n, m,} the value of _m) of the red light-emitting sub-pixel (n, m), green light-emitting sub-pixel (n, m), sent to the blue light-emitting sub-pixel (n, m), red light-emitting sub-pixel (n, m), green The light emission state of the light emitting subpixel (n, m) and the blue light emitting subpixel (n, m) is controlled.

Here, when the image forming apparatus is, for example, [Image forming apparatus-B] described above, the value of the corrected red luminance display signal X ′ _{R− (n, m)} , the green luminance display signal X ′ _{G− In} the third light passage control device, the second light passage control device, and the first light passage control device, depending on the value of _{(n, m) and} the value of the blue luminance display signal X ′ _{B− (n, m)} The light transmission rate (aperture ratio) is controlled.

  The second embodiment relates to a modification of the correction unit in the first embodiment. FIG. 4 shows a circuit diagram of a part of the image forming apparatus driving device 60 provided with the correcting unit 170 in the second embodiment.

  In the first place, in the image display apparatus of the present invention, the values of the image signals input to the plurality of pixels constituting the image forming apparatus are corrected. Therefore, as described in the first embodiment, when the image signal is multiplied by the signal based on the correction coefficient η, the original value of the image signal (data regarding gradation or brightness) is lost. In general, it is known that the human eye has a low sensitivity to changes in bright gradations and a high sensitivity to changes in dark gradations. That is, the sensitivity to color unevenness is low for an image signal having a large value, but the sensitivity to color unevenness is high for an image signal having a small value.

Therefore, in the second embodiment, the correction unit 170 includes a plurality of correction coefficients, and the correction unit 170 calculates 1 from the plurality of correction coefficients based on the average value x _ave of the image signals input to all pixels. Select the correction factor. That is, when the average value x _{ave of the} image signal input to all pixels is low, a correction coefficient having a large value is selected, and when the average value x _{ave of the} image signal input to all pixels is high, the correction value has a small value. Select a correction factor. It should be noted that the correction coefficient is the same as in the first embodiment except that, instead of minimizing the difference between the luminance distribution at the time of maximum gradation display at a plurality of different observation pupil positions and the desired luminance distribution, a plurality of correction coefficients are used. What is necessary is to make the difference (a plurality of correction coefficients) the difference between the luminance distribution at the time of displaying various gradations at different observation pupil positions and the desired various luminance distributions.

  Here, as in the correction unit 70 of the first embodiment, the correction unit 170 includes, for example, a storage unit 171 that stores a plurality of correction coefficients, a control circuit 172 that controls the operation of the entire correction unit, and each pixel of the image forming apparatus. The correction circuit 173 corrects the value of the image signal input to the. The correction circuit 173 controlled by the control circuit 172 includes a timing generation circuit 174, a correction data generation circuit 175, and a multiplier 176.

During operation of the image display device, an image signal in one frame (red luminance control signal x _{R- (n, m)} for gradation control, green luminance control signal x _{G- (n, m)} , blue luminance control signal x _{B- (n, m)} ) is input to the image signal processing circuit 161 from the outside. In addition, a horizontal synchronization signal H _Sync , a vertical synchronization signal V _Sync , and a clock signal (Clock) are input to the image signal processing circuit 161 and the timing generation circuit 174 from the outside. Then, on the basis of the horizontal synchronization signal H _Sync , the vertical synchronization signal V _Sync , and the clock signal (Clock), the image signal processing circuit 161 includes each pixel (red light emission subpixel, green light emission subpixel, blue color) constituting the image forming apparatus 11. A red luminance display signal X _{R- (n, m)} , a green luminance display signal X _{G- (n, m)} , and a blue luminance display signal X _{B- (n, m)} are generated to control the light emitting sub-pixel). , Output toward each sub-pixel (n, m). Further, the average value x _ave of image signals input to all pixels in one frame is obtained by the image signal processing circuit 161, and the obtained average value x _ave is sent to the timing generation circuit 174.

On the other hand, based on the horizontal synchronization signal H _Sync , the vertical synchronization signal V _Sync , the clock signal (Clock), and the average value x _ave input to the timing generation circuit 174, the timing generation circuit 174 generates an address signal (Address) for each pixel. (Specifically, a signal for determining a correction coefficient corresponding to m at the time of gradation display) is generated and sent to the correction data generation circuit 175 together with a read clock signal (Read_Clock).

The control circuit 172 reads a plurality of red, green, and blue correction coefficients η _R (m), η _G (m), and η _B (m) from the storage unit 171 when the power is turned on. The control circuit 172 includes a plurality of read correction coefficients, an address signal (Address) (a signal having the same position information as the address signal (Address) sent from the timing generation circuit 174 to the correction data generation circuit 175), and a write clock ( Write_Clock) is sent to the correction data generation circuit 175.

The correction data generation circuit 175 then generates a multiplier 176 _R− for the red luminance display signal X _{R− (n, m)} based on the read clock signal (Read_Clock) and the address signal (Address) from the timing generation circuit 174. _A signal based on the red correction coefficient η _R (m) is sent to _{(n, m),} and the green correction coefficient is supplied to the multiplier 176 _{G- (n, m)} for the green luminance display signal X _{G- (n, m)} A signal based on η _G (m) is transmitted, and a signal based on the blue correction coefficient η _B (m) is sent to the multiplier 176 _{B- (n, m)} for the blue luminance display signal X _{B- (n, m).} Send it out. Thus, in each of the multipliers 176 _{R- (n, m)} , 176 _{G- (n, m)} , 176 _{B- (n, m)} , the value of the image signal [red luminance display signal X _{R- ( n, m)} value, green luminance display signal X _{G- (n, m)} value, and blue luminance display signal X _{B- (n, m)} value] are red, green and blue correction coefficients η _R It is corrected (multiplied) by a signal based on (m), η _G (m), η _B (m). Then, the corrected red luminance display signal X ′ _{R− (n, m)} value, green luminance display signal X ′ _{G− (n, m)} value, and blue luminance display signal X ′ _{B− (n, m,} the value of _m) of the red light-emitting sub-pixel (n, m), green light-emitting sub-pixel (n, m), sent to the blue light-emitting sub-pixel (n, m), red light-emitting sub-pixel (n, m), green The light emission state of the light emitting subpixel (n, m) and the blue light emitting subpixel (n, m) is controlled.

  Except for the correcting means 170 described above, the configuration and structure of the image display apparatus according to the second embodiment can be the same as the configuration and structure of the image display apparatus described in the first embodiment. To do.

  Such correction means 170 according to the second embodiment makes it possible to perform correction with higher accuracy according to the value (gradation) of the image signal, loss of luminance due to excessive correction in a bright scene, or in a dark scene. It is possible to solve the problem of occurrence of residual “unevenness” due to insufficient correction.

  The third embodiment also relates to a modification of the correction unit in the first embodiment. FIG. 5 shows a circuit diagram of a part of the image forming apparatus driving device 60 provided with the correcting means 270 in the third embodiment.

In the third embodiment, the correction unit 270 includes one correction coefficient and an intensity coefficient corresponding to the value of the input image signal. The correction unit 270 calculates the average of the image signals input to all pixels. An intensity coefficient is selected based on the value x _ave , and the value of the image signal input to each pixel of the image forming apparatus is corrected based on the selected intensity coefficient and correction coefficient. That is, when the average value x _{ave of the} image signal input to all pixels is low, an intensity coefficient having a large value is selected, and when the average value x _{ave of the} image signal input to all pixels is high, the intensity value has a small value. Select an intensity factor (eg, 1.0). The correction coefficient may be the same as in the first embodiment.

  Here, the correction unit 270 is similar to the correction unit 70 of the first embodiment, for example, a storage unit 271 that stores a plurality of correction coefficients, a control circuit 272 that controls the operation of the entire correction unit, and each pixel of the image forming apparatus. The correction circuit 273 corrects the value of the image signal input to the. The correction circuit 273 controlled by the control circuit 272 includes a timing generation circuit 274, a correction data generation circuit 275, and a multiplier 276.

During operation of the image display device, an image signal in one frame (red luminance control signal x _{R- (n, m)} for gradation control, green luminance control signal x _{G- (n, m)} , blue luminance control signal x _{B- (n, m)} ) is input to the image signal processing circuit 261 from the outside. In addition, a horizontal synchronization signal H _Sync , a vertical synchronization signal V _Sync , and a clock signal (Clock) are input to the image signal processing circuit 261 and the timing generation circuit 274 from the outside. Then, on the basis of the horizontal synchronization signal H _Sync , the vertical synchronization signal V _Sync , and the clock signal (Clock), the image signal processing circuit 261 makes each pixel (red light emission subpixel, green light emission subpixel, blue) constituting the image forming apparatus 11. A red luminance display signal X _{R- (n, m)} , a green luminance display signal X _{G- (n, m)} , and a blue luminance display signal X _{B- (n, m)} are generated to control the light emitting sub-pixel). , Output toward each sub-pixel (n, m). The average value x _ave of the image signals input to all the pixels in one frame is obtained by the image signal processing circuit 261, and the obtained average value x _ave is sent to the correction data generation circuit 275.

On the other hand, based on the horizontal synchronization signal H _Sync , the vertical synchronization signal V _Sync , and the clock signal (Clock) input to the timing generation circuit 274, the timing generation circuit 274 generates an address signal (address) (specifically, an address). , M to determine a correction coefficient corresponding to m) is generated and sent to the correction data generation circuit 275 together with the read clock signal (Read_Clock).

The control circuit 272 reads a plurality of red, green and blue correction coefficients η _R (m), η _G (m), η _B (m) and an intensity coefficient from the storage unit 271 when the power is turned on. The control circuit 272 includes a plurality of read correction coefficients and intensity coefficients, an address signal (Address) (a signal having the same position information as the address signal (Address) sent from the timing generation circuit 274 to the correction data generation circuit 275), Both the write clock (Write_Clock) are sent to the correction data generation circuit 275.

Then, the correction data generation circuit 275 selects the red correction coefficient η _R (m) based on the read clock signal (Read_Clock) and the address signal (Address) from the timing generation circuit 274, and the selected red correction coefficient η _R A signal obtained by multiplying (m) by the intensity coefficient selected based on the average value x _ave from the image signal processing circuit 261 is a multiplier 276 _{R- (n, m)} for the red luminance display signal X _{R- (n, m) . m)} , the green correction coefficient η _G (m) is selected, and the selected green correction coefficient η _G (m) is multiplied by the intensity coefficient selected based on the average value x _ave from the image signal processing circuit 261. _Is sent to the multiplier 276 _{G- (n, m)} for the green luminance display signal X _{G- (n, m)} , the blue correction coefficient η _B (m) is selected, and the selected blue correction coefficient η _B (m) is multiplied by the intensity coefficient selected based on the average value x _ave from the image signal processing circuit 261. Is sent to the multiplier 276 _{B- (n, m)} for the blue luminance display signal X _{B- (n, m)} . Thus, in each of the multipliers 276 _{R- (n, m)} , 276 _{G- (n, m)} , 276 _{B- (n, m)} , the value of the image signal [red luminance display signal X _{R- ( n, m)} value, green luminance display signal X _{G- (n, m)} value, and blue luminance display signal X _{B- (n, m)} value] are red, green and blue correction coefficients η _R Corrected (multiplied) by signals based on (m), η _G (m), η _B (m) and the intensity factor. Then, the corrected red luminance display signal X ′ _{R− (n, m)} value, green luminance display signal X ′ _{G− (n, m)} value, and blue luminance display signal X ′ _{B− (n, m,} the value of _m) of the red light-emitting sub-pixel (n, m), green light-emitting sub-pixel (n, m), sent to the blue light-emitting sub-pixel (n, m), red light-emitting sub-pixel (n, m), green The light emission state of the light emitting subpixel (n, m) and the blue light emitting subpixel (n, m) is controlled.

  Except for the correcting means 270 described above, the configuration and structure of the image display apparatus according to the third embodiment can be the same as the configuration and structure of the image display apparatus described in the first embodiment. To do.

  Such correction means 270 of the third embodiment also enables more accurate correction according to the value (gradation) of the image signal, resulting in loss of luminance due to excessive correction in a bright scene or in a dark scene. It is possible to solve the problem of occurrence of residual “unevenness” due to insufficient correction.

  In Example 4 or Example 5 described later, the diffraction grating members 30 and 40 will be described in detail.

The inclination angle φ ₁ of the interference fringe 31 formed inside the first diffraction grating member 30 may be constant or may vary. The patent applicant applied for the latter technique in Japanese Patent Application No. 2005-258397. By changing the inclination angle φ ₁ of the interference fringe inside the first diffraction grating member 30, the diffraction efficiency in a certain wavelength band for each region of the first diffraction grating member can be made as constant as possible. It is possible to more effectively suppress the occurrence of a problem that the color and brightness of a pixel image guided to the pupil differ depending on the position of the pixel of the forming device (color unevenness and brightness unevenness occur). In addition, by setting the interference fringe inclination angle φ ₁ to a predetermined value in a predetermined region of the first diffraction grating member, the parallel light flux incident on the first diffraction grating member and diffracted and reflected is converted into the second diffraction grating member. It is possible to reliably enter the predetermined region. Further, if the diffraction grating layer constituting the first diffraction grating member has a structure in which Q diffraction grating layers are laminated, the length of the first diffraction grating member along the axial direction of the light guide plate 21 is shortened. , The angle of view θ can be increased.

  Hereinafter, the first diffraction grating member 30 having the first configuration according to the fourth embodiment will be described.

In the first diffraction grating member 30, for example, as shown in a schematic cross-sectional view of FIG. 7A or FIG. The pitch P ₁ of the interference fringes 31 on the surface of the one diffraction grating member 30 is equal.

Then, when the angle formed by the interference fringes 31 in the first diffraction grating member 30 with the surface of the first diffraction grating member 30 is the inclination angle φ ₁ , the first diffraction grating member 30 has the structure shown in FIG. As shown in the schematic cross-sectional view of (B),
(B-1) Inclination of the interference fringes 31 formed in the outer region RG _OUT located farther from the second diffraction grating member 40 than the minimum inclination angle region RG _MIN where the inclination angle φ ₁ is the minimum inclination angle φ _MIN The angle φ ₁ is larger as it is away from the minimum inclination angle region RG _MIN ,
(B-2) minimum inclination angle region inclination angle phi ₁ of the interference fringe 31 formed in the inner area RG _IN than RG _MIN is located closer to the second diffraction grating member 40, the minimum inclination angle region RG _MIN In the adjacent inner region RG _IN-NEAR , the maximum inclination angle φ _MAX is set, and becomes smaller as the _distance from the minimum inclination angle region RG _MIN increases.

FIG. 6 shows a conceptual diagram of an image display device according to the fourth embodiment (note that the configuration and structure of the image display device according to the fourth embodiment are the same as the configuration and structure of the image display device described in the first embodiment). Thus, the center of the second diffraction grating member 40 is the origin O, the normal line of the second diffraction grating member 40 passing through the origin O is the X axis, and the axis line of the light guide plate 21 passing through the origin O is the Y axis. Further, it is assumed that the pupil 50 exists at a point on the X axis where the image based on the parallel light flux group that is diffracted and reflected by the second diffraction grating member 40 and emitted from the light guide plate 21 is observed. The value of the X coordinate of the pupil 50 corresponds to the eye relief D. In the following description, a description will be given with respect to a parallel light beam positioned in the XY plane for simplification of description. Further, the distance from the end of the first diffraction grating member 30 near the second diffraction grating member 40 to the origin O is L ₁ , and the end of the first diffraction grating member 30 far from the second diffraction grating member 40 to the origin O the distance between the L _2.

Light beams r ₁ (indicated by a solid line), r ₂ (indicated by a dashed line), and r ₃ (indicated by a dotted line) emitted from the image forming apparatus 11 pass through the collimating optical system 12 and then have an angle + Θ ′ _IN. (> 0), 0 (degrees), −Θ ′ _IN (<0) as a parallel light flux and incident on the light guide plate 21, and then incident on (collides with) the first diffraction grating member 30. Diffracted and reflected by the member 30, totally reflected in the light guide plate 21, propagated toward the second diffraction grating member 40, enters (collides) with the second diffraction grating member 40, and is centered on the pupil 50, respectively. Incident light is incident at an angle of view θ = −θ ₀ (<0), 0 (degrees), + θ ₀ (> 0). The parallel light beam incident on the light guide plate 21 at an angle Θ ′ is emitted from the light guide plate 21 at an angle of view θ (= incident angle [−Θ ′]). In this case, each of the parallel light beams r ₁ , r ₂ , r ₃ travels in the light guide plate 21 at different total reflection positions and total reflection times based on the different total reflection angles α ₁ , α ₂ , α ₃ respectively. It will be. Here, the parallel light flux undergoes total reflection on the first surface 21A (surface facing the second surface 21B) of the light guide plate 21, and the second surface 21B (the first diffraction grating member 30 and the second diffraction grating member 40 is disposed). When the light is totally reflected by the second light guide plate 21), the relationship between the position of total reflection at the second surface 21B (distance L from the origin O) and the total number of reflections _NTR is as follows. When the position incident on 30 (distance from the origin O) is L _f , the thickness of the light guide plate 21 is t, and the total reflection angle of the parallel light flux is α, it is expressed by the following equation (21).

L = L _f −2 · N _TR · t · tan (α) (21)

Therefore, the above relational expression (21) at the total reflection angles α ₁ , α ₂ , α ₃ of the parallel light beams r ₁ , r ₂ , r ₃ is the incident position (first time) of each parallel light beam on the first diffraction grating member 30. , L _{f_1} , L _{f_2} , L _{f_3} , and the incident position on the second diffraction grating member 40 (the last internal reflection position, the distance from the origin O). If L _{e_1} , L _{e_2} , L _{e_3} , and the total number of reflections are N _{TR_1} , N _{TR_2} , and N _{TR_3} , the following expressions (22-1), (22-2), and (22-3) can be expressed. it can.

_{L e_1 = L f_1 -2 · N} TR_1 · t · tan (α 1) (22-1)
_{L e_2 = L f_2 -2 · N} TR_2 · t · tan (α 2) (22-1)
L _e — ₃ = L _f — ₃ −2 · N _TR — ₃ · t · tan (α ₃ ) (22-1)

_{Here, L e_1, L e_2, L} e_3 , as is apparent from FIG. 6, based on the relationship of the angle of view θ and the eye relief D, as parallel light flux is incident on the central portion of the pupil 50, uniquely To be determined. N _{TR_1} , N _{TR_2} , and N _{TR_3} must be positive integers. Such a relational expression indicates that the thickness t of the light guide plate 21, the range L _{1 to} L ₂ of the first diffraction grating member 30 where the parallel light beam enters, and the pitch P of the interference fringes 31 in the first diffraction grating member 30. These variables need to be determined with a more practical configuration in order to satisfy various conditions of α ₁ , α ₂ , and α ₃ derived from ₁ and the angle of view θ.

Under the conditions shown in Table 2 below, the second diffraction grating satisfying the Bragg condition at the same wavelength at each angle of view θ _{2_t} with the distance L 2 — _t from the origin O set to 0.5 mm from −3.0 mm to 3.0 mm The results of calculating the distribution of the inclination of the interference fringes (interference fringes that diffracted and reflect red and interference fringes that diffracted and reflected green) in the member 40 are shown in Table 3 below. The results of calculating the distribution of are shown in Table 4 below. In general, the inclination angle φ _MAX of the interference fringes that maximizes the diffraction efficiency when the parallel light beam enters the diffraction grating member at the incident angle Ψ _IN and is diffracted and reflected at the output diffraction angle Ψ _OUT is as follows: Expression (23) can be expressed, and this expression (23) can be derived based on the Bragg condition.

φ _MAX = (Ψ _OUT + Ψ _IN ) / 2 (23)

The interference fringes of the second diffraction grating member 40 in Example 4 or Example 5 described later are formed according to the values of the inclination angles in Tables 3 and 4. Specifically, the inclination angle of the interference fringes in the second diffraction grating member 40 increases as it approaches the first diffraction grating member 30. With such a configuration, it is possible to further reduce color unevenness and luminance unevenness. Note that the inclination angle may be increased stepwise or continuously. That is, in the former case, when the second diffraction grating member 40 is divided into T parts from the part farthest from the first diffraction grating member 30 to the part closest to the first diffraction grating member 30, the t-th (however, the inclination angle is constant in the portion RG _{2_T} of t = 1, 2 · · · T) of the second diffraction grating member, moreover, as the value of t increases, the inclination angle in the portion RG _{2_T} of the second diffraction grating member It may be a form that increases the value. On the other hand, in the latter case, it may be configured to gradually change the inclination angle of the interference fringes.

[Table 2]
Light guide plate thickness: 2.7 mm (refractive index of 1.526 at a wavelength of 522 nm)
Eye relief: 20mm
Angle of view θ ₀ : 8.0 ° Angle of view −θ ₀ : −8.0 ° Interference fringe pitch in diffraction grating layer 240R: 488.1 nm
Interference fringe pitch in the diffraction grating layer 240G: 399.9 nm
Interference fringe pitch in the diffraction grating layer 240B: 399.9 nm

[Table 3] Interference fringes constituting the second diffraction grating member 40 (interference fringes for diffracting and reflecting red and interference fringes for diffracting and reflecting green)
Distance L _{2_t} (mm) Angle of view θ _{2_t} (degree) Inclination angle φ _{2_t} (degree)
−3.0 to −2.5 −7.20 27.68
-2.5 to -2.0 -5.90 27.93
-2.0 to -1.5 -4.60 28.21
-1.5 to -1.0 -3.29 28.51
-1.0 to -0.5 -1.97 28.84
-0.5 to 0.0 -0.66 29.02
0.0 to 0.5 0.66 29.60
0.5-1.0 1.97 30.05
1.0-1.5 3.29 30.55
1.5-2.0 4.60 31.10.
2.0-2.5 5.90 31.73
2.5-3.0 7.20 32.46

[Table 4] Interference fringes constituting the second diffraction grating member 40 (interference fringes for diffracting and reflecting blue)
Distance L _{2_t} (mm) Angle of view θ _{2_t} (degree) Inclination angle φ _{2_t} (degree)
−3.0 to −2.5 −7.20 24.14
-2.5 to -2.0 -5.90 24.30
-2.0 to -1.5 -4.60 24.48
-1.5 to -1.0 -3.29 24.67
-1.0 to -0.5 -1.97 24.88
-0.5 to 0.0 -0.66 25.11
0.0 to 0.5 0.66 25.36
0.5-1.0 1.97 25.62
1.0-1.5 3.29 25.91
1.5-2.0 4.60 26.22
2.0-2.5 5.90 26.55
2.5-3.0 7.20 26.93

As is apparent from Tables 3 and 4, when the value of the angle of view θ increases, the inclination angle in the second diffraction grating member 40 increases. Stated words, if the value of the field angle θ is small, the value of total reflection angle α becomes smaller, the total number of reflections N _TR in the light guide plate 21 inside the parallel light beam corresponding to such angle θ increases. On the other hand, when the value of the field angle θ is large, the value of total reflection angle α increases, the total number of reflections N _TR in the light guide plate 21 inside the parallel light beam corresponding to such angle θ is reduced.

The parallel light flux of λ ₁ = 635 nm and wavelength λ ₂ = 522 nm incident on the center of the pupil 50 forms interference fringes (interference fringes for diffracting and reflecting red and interference for diffracting and reflecting green). The position of the stripe) is diffracted and reflected, and the number of times this parallel light beam is totally reflected by the second surface 21B of the light guide plate 21 to reach the pupil 50 is shown in the graph of FIG. In addition, all this graph is calculated based on Formula (21). The vertical axis in the graph represents the distance L, and the horizontal axis represents the angle of view θ. In FIGS. 8A and 8B, the portion RG _{(q, s) is represented} by (q, s) for the sake of simplicity.

In the fourth embodiment, the first diffraction grating member 30 is a diffraction grating layer 30 ₁ , 30 ₂ , 30 of a Q layer (Q = 4 in the fourth embodiment) made of a reflective volume hologram diffraction grating. ₃ and 30 ₄ are laminated, and each diffraction grating layer is formed with interference fringes extending from the inside to the surface thereof, and the pitch of the interference fringes on the surface of each diffraction grating layer is equal, and the diffraction gratings The pitch of interference fringes between layers is also equal.

Note that the minimum inclination angle φ _MIN is different in all of the diffraction grating layers, and the maximum inclination angle φ _MAX is different in all of the diffraction grating layers.

In FIG. 8A, the solid curve [1] that rises to the right represents the case of the total reflection number N _TR = 4, and the dotted line curve [2] that rises to the right represents the case of the total reflection number N _TR = 5. The solid line curve [3] rising to the right represents the case of the total reflection number N _TR = 6, and the dotted line curve [4] rising to the right represents the case of the total reflection number N _TR = 7.

The negative direction of the horizontal axis of the graph (which is the angle of view θ but also corresponds to the incident angle [−Θ ′]) is the inclination of the interference fringe 31 in the first diffraction grating member 30 that satisfies the Bragg condition at the same wavelength. The angle φ ₁ is a relatively small direction, and the positive direction of the horizontal axis of the graph (which is the angle of view θ but also corresponds to the incident angle [−Θ ′]) satisfies the Bragg condition at the same wavelength. This is the direction in which the inclination angle φ ₁ of the interference fringe 31 in the first diffraction grating member 30 is relatively large. Therefore, the curve of the graph is rising from the left to the right. As the angle of view θ changes in the plus direction, the inclination of the interference fringes 31 in the first diffraction grating member 30 that diffracts and reflects the parallel light flux of the same wavelength. This means that the angle φ ₁ changes from small to large, and further, the distance from the origin O of the region of the first diffraction grating member 30 provided with such an inclination angle gradually increases.

The parallel light flux corresponding to the angle of view θ = 4.3 degrees to 7.1 degrees (= incident angle [−Θ ′]) is the first layer constituting the first diffraction grating member 30 at L≈35 mm to 47 mm. incident on the diffraction grating layer 30 ₁ eye, is diffracted and reflected in the region of the diffraction grating layer 30 ₁ of the first layer, 4 times the second surface 21B of the light guide plate 21, after the total reflection, the second diffraction grating The light enters the member 40, is diffracted and reflected, is emitted from the light guide plate 21, and is guided to the pupil 50. In this case, as the angle of view θ changes in the plus direction, the inclination angle φ ₁ of the interference fringes of the _first diffraction grating layer 301 that diffracts and reflects the parallel light beam having the same wavelength increases from small to large. Furthermore, the distance from the origin O of the region of the _first diffraction grating layer 301 having the tilt angle φ ₁ is gradually increased.

Further, the parallel light flux corresponding to the angle of view θ = 0.2 degrees to 3.9 degrees (= incident angle [−Θ ′]) is the first diffraction grating member 30 that forms the first diffraction grating member 30 at L≈35 mm to 47 mm. second layer incident on the diffraction grating layer 30 ₂ is diffracted and reflected in the region of the diffraction grating layer 30 ₂ of the second layer, 5 times the second surface 21B of the light guide plate 21, after the total reflection, the second The light enters the diffraction grating member 40, is diffracted and reflected, is emitted from the light guide plate 21, and is guided to the pupil 50. Also in this case, as the angle of view θ changes in the plus direction, the inclination angle φ ₁ of the interference fringes of the _second diffraction grating layer 30 ₂ that diffracts and reflects the parallel light flux of the same wavelength increases from small to large. Furthermore, the distance from the origin O of the region of the _second diffraction grating layer 30 ₂ provided with such an inclination angle φ ₁ gradually increases.

Further, the parallel light flux corresponding to the angle of view θ = −3.9 ° to −0.2 ° (= incident angle [−Θ ′]) is applied to the first diffraction grating member 30 at L≈35 mm to 45 mm. enters the third layer of the diffraction grating layer 30 ₃ forming, is diffracted and reflected in the region of the diffraction grating layer 30 ₃ of the third layer, 6 times in the second surface 21B of the light guide plate 21, after the total reflection , Enters the second diffraction grating member 40, is diffracted and reflected, is emitted from the light guide plate 21, and is guided to the pupil 50. Also in this case, as the angle of view θ changes in the plus direction, the inclination angle φ ₁ of the interference fringe of the _third diffraction grating layer 30 ₃ that diffracts and reflects the parallel light beam of the same wavelength increases from small to large. Furthermore, the distance from the origin O of the region of the _third diffraction grating layer 30 ₃ provided with such an inclination angle φ ₁ gradually increases.

Further, the parallel light flux corresponding to the angle of view θ = −7.6 degrees to −4.5 degrees (= incident angle [−Θ ′]) constitutes the first diffraction grating member 30 at L≈35 mm to 43 mm. to fourth layer is incident on the diffraction grating layer 30 _4, is diffracted and reflected in the region of the diffraction grating layer 30 ₄ of the fourth layer, seven times in the second surface 21B of the light guide plate 21, after the total reflection, The light enters the second diffraction grating member 40, is diffracted and reflected, is emitted from the light guide plate 21, and is guided to the pupil 50. Also in this case, as the angle of view θ changes in the plus direction, the inclination angle φ ₁ of the interference fringes of the _fourth diffraction grating layer 304 that diffracts and reflects the parallel light flux of the same wavelength increases from small to large. In addition, the distance from the origin O of the region of the _fourth diffraction grating layer 304 having such an inclination angle φ ₁ gradually increases.

  A parallel light beam incident on a certain diffraction grating layer may be incident on at least one of the other three layers. However, in the other diffraction grating layer, the parallel light beam Since the diffraction efficiency is low, the parallel light beam is not diffracted and reflected by other diffraction grating layers.

In the diffraction grating layer 30 ₁ of the first layer, the angle of view θ ₁ = -θ _{1_0} = 4.3 ° diffraction grating layer 30 _first region of the first layer a parallel beam corresponding is diffracted and reflected in The inclination angle φ ₁ of the interference fringes in the region where L = 35 mm to 37 mm is the minimum inclination angle φ _MIN . Then, the outer region RG _OUT (L = L =) which is located farther from the second diffraction grating member 40 than the minimum tilt angle region RG _MIN (corresponding to L = 35 mm to 37 mm) where the tilt angle φ ₁ is the minimum tilt angle φ _MIN. The inclination angle φ ₁ of the interference fringes formed in the region up to 47 mm is larger as the distance from the minimum inclination angle region RG _MIN (corresponding to L = 35 mm to 37 mm) increases. Then, the region of the _first diffraction grating layer 30 ₁ (corresponding to the region of L = 45 mm to 47 mm) where the parallel light beam corresponding to the parallel light beam satisfying the angle of view θ ₁ = θ ₁ — ₀ is diffracted and reflected is the maximum inclination angle. Has φ _MAX .

On the other hand, in the diffraction grating layer 30 ₂ of the second layer, the angle of view θ ₂ = -θ _{2_0} = 0.2 second layer diffraction grating layer parallel light beam corresponding to degrees is diffracted and reflected 30 ₂ The inclination angle φ ₁ of the interference fringes in the region of L = 35 mm to 37 mm, which is the region of, is the minimum inclination angle φ _MIN . Then, the outer region RG _OUT (L = L =) which is located farther from the second diffraction grating member 40 than the minimum tilt angle region RG _MIN (corresponding to L = 35 mm to 37 mm) where the tilt angle φ ₁ is the minimum tilt angle φ _MIN. The inclination angle φ ₁ of the interference fringes formed in the region up to 47 mm is larger as the distance from the minimum inclination angle region RG _MIN (corresponding to L = 35 mm to 37 mm) increases. The region of the _second diffraction grating layer 30 ₂ (corresponding to the region of L = 45 mm to 47 mm) where the parallel light beam corresponding to the parallel light beam _{satisfying the} angle of view θ ₂ = θ ₂ — ₀ is diffracted and reflected is the maximum inclination angle. Has φ _MAX .

Further, in the third diffraction grating layer 30 ₃ , the third diffraction grating layer in which the parallel light flux corresponding to the angle of view θ ₃ = −θ _{3 —0} = −3.9 degrees is diffracted and reflected. The inclination angle φ ₁ of the interference fringes in the region of L = 35 mm to 37 mm, which is the region of 30 ₃ , is the minimum inclination angle φ _MIN . Then, the outer region RG _OUT (L = L =) which is located farther from the second diffraction grating member 40 than the minimum tilt angle region RG _MIN (corresponding to L = 35 mm to 37 mm) where the tilt angle φ ₁ is the minimum tilt angle φ _MIN. The inclination angle φ ₁ of the interference fringes formed in the region up to 45 mm is larger as the distance from the minimum inclination angle region RG _MIN (corresponding to L = 35 mm to 37 mm) increases. The region of the _third diffraction grating layer 30 ₃ (corresponding to the region of L = 43 mm to 45 mm) where the parallel beam corresponding to the parallel beam corresponding to the angle of view θ ₃ = θ ₃ — ₀ is diffracted and reflected is the maximum inclination angle. Has φ _MAX .

Further, in the fourth diffraction grating layer 30 ₄ , the fourth diffraction grating layer 30 in which the parallel light flux corresponding to the angle of view θ ₄ = −θ ₄ — ₀ = −7.6 degrees is diffracted and reflected. The inclination angle φ ₁ of the interference fringes in the region of L = 35 mm to 37 mm which is the region ₄ is the minimum inclination angle φ _MIN . Then, the outer region RG _OUT (L = L =) which is located farther from the second diffraction grating member 40 than the minimum tilt angle region RG _MIN (corresponding to L = 35 mm to 37 mm) where the tilt angle φ ₁ is the minimum tilt angle φ _MIN. The inclination angle φ ₁ of the interference fringes formed in the region up to 43 mm is larger as the distance from the minimum inclination angle region RG _MIN (corresponding to L = 35 mm to 37 mm) increases. The region of the _fourth diffraction grating layer 30 ₄ (corresponding to the region of L = 41 mm to 43 mm) where the parallel light beam corresponding to the parallel light beam _{satisfying the} angle of view θ ₄ = θ ₄ — ₀ is diffracted and reflected is the maximum inclination angle. Has φ _MAX .

Here, since the region of the diffraction grating layer does not exist closer to the second diffraction grating member 40 than the minimum inclination angle region RG _MIN , the above-described item (B-2) is ignored.

In the outer region RG _OUT, as a schematic cross-sectional view of the first diffraction grating member 30 shown in FIG. 7 (A) or FIG. 7 (B), the inclination angle phi ₁ is continuously Moreover, L In the outer region RG _OUT , the inclination angle φ ₁ may be increased stepwise and monotonously as L increases. That is, the first diffraction grating member 30 along the axial direction of the light guide plate 21, for example, a diffraction grating layer 30 ₁ of the first layer S number (specifically, S = 6) in portions of the If the inclination angle in the s-th (where s = 1, 2,..., 6) portion of the _first diffraction grating layer 301 is constant and the value of s is different, the first diffraction grating is different. it may be changed inclination angle in the portion of the layer 30 _1. The same applies to the diffraction grating layers 30 ₂ , 30 ₃ , and 30 _{4 of} the second layer, the third layer, and the fourth layer. The order of stacking the first layer of the diffraction grating layer 30 ₁ and the second layer diffraction grating layer 30 ₂ and the third layer of the diffraction grating layer 30 ₃ and the fourth layer of the diffraction grating layer 30 _4, essentially Is optional.

The _relationship between the range of the distance L _{1 — s of the} portion RG _{(q, s)} , the angle of view θ _{1 — s} (= incident angle [−Θ ′] _{1 — s} ), and the inclination angle φ _{1 — s} (φ ₂ ) is shown in Table 5 below. Table 6 shows. The wavelengths λ ₁ , λ ₂ , and λ ₃ are 635 nm, 522 nm, and 470 nm, respectively.

[Table 5] Interference fringes constituting the first diffraction grating member 30 (interference fringes for diffracting and reflecting red and interference fringes for diffracting and reflecting green)
4 times total reflection (q, s) Distance L _{1_s} (mm) Angle of view θ _{1_s} (degree) Tilt angle φ _{1_s} (degree)
(1,1) 35-37 4.30 30.97
(1,2) 37-39 4.99 31.28
(1,3) 39-41 5.61 31.58
(1,4) 41-43 6.16 31.87
(1,5) 43-45 6.66 32.14
(1,6) 45-47 7.12 32.41
5 times total reflection (q, s) Distance L _{1_s} (mm) Angle of view θ _{1_s} (degree) Inclination angle φ _{1_s} (degree)
(2,1) 35-37 0.15 29.45
(2,2) 37-39 1.03 29.73
(2,3) 39-41 1.84 30.00
(2,4) 41-43 2.58 30.27
(2,5) 43-45 3.26 30.53
(2,6) 45-47 3.88 30.79
6 times total reflection (q, s) Distance L _{1_s} (mm) Angle of view θ _{1_s} (degree) Tilt angle φ _{1_s} (degree)
(3,1) 35-37 -3.86 28.37
(3,2) 37-39 -2.85 28.62
(3,3) 39-41 -1.91 28.86
(3,4) 41-43 -1.04 29.09
(3,5) 43-45 -0.23 29.33
7 times total reflection (q, s) Distance L _{1_s} (mm) Angle of view θ _{1_s} (degree) Inclination angle φ _{1_s} (degree)
(4,1) 35-37-7.62 27.6
(4,2) 37-39 -6.53 27.81
(4,3) 39-41 -5.51 28.01
(4,4) 41-43 -4.54 28.22

[Table 6] Interference fringes constituting the first diffraction grating member 30 (interference fringes diffracting and reflecting blue)
(Q, s) Distance L _{1_s} (mm) Angle of view θ _{1_s} (degrees) Inclination angle φ _{1_s} (degrees)
(1,1) 35-37 6.20 26.62
(1,2) 37-39 7.19 26.91
(1,3) 39-41 8.11 27.18
6 times total reflection (q, s) Distance L _{1_s} (mm) Angle of view θ _{1_s} (degree) Tilt angle φ _{1_s} (degree)
(2,1) 35-37 2.01 25.61
(2,2) 37-39 3.12 25.85
(2,3) 39-41 4.15 26.09
(2,4) 41-43 5.12 26.34
(2,5) 43-45 6.02 26.57
7 times total reflection (q, s) Distance L _{1_s} (mm) Angle of view θ _{1_s} (degree) Inclination angle φ _{1_s} (degree)
(3,1) 35-37-1.85 24.89
(3,2) 37-39 -0.68 25.09
(3, 3) 39-41 0.43 25.30
(3,4) 43-45 1.48 25.50
8 times total reflection (q, s) Distance L _{1_s} (mm) Angle of view θ _{1_s} (degree) Inclination angle φ _{1_s} (degree)
(4,1) 35-37-5.39 24.36
(4,2) 37-39 -4.18 24.53
(4,3) 39-41 -3.02 24.70
(4,4) 43-45 -1.92 24.88
10 times total reflection (q, s) Distance L _{1_s} (mm) Angle of view θ _{1_s} (degree) Inclination angle φ _{1_s} (degree)
(1,1) 41-43 -8.00 24.03
(1,2) 43-45-6.9 24.16
(1,3) 45-47-5.84 24.30

  In Example 4, the diffraction grating layer constituting the first diffraction grating member has a structure in which multiple diffraction grating layers are laminated, so that the length of the first diffraction grating member along the axial direction of the light guide plate is increased. In addition, the angle of view can be further increased while the thickness of the light guide plate can be reduced, and the optical device and the image display device can be further miniaturized.

  Example 5 relates to a first diffraction grating member having a second configuration. The conceptual diagrams of the optical device and the image display device of Example 5 are basically the same as those shown in FIG. In the following description, interference fringes that diffract and reflect green light will be described. However, interference fringes that diffract and reflect red light and interference fringes that diffract and reflect blue light also differ in numerical values. Except for these, the structure and configuration have the same structure and configuration as interference fringes that diffract and reflect green light.

  In Example 5, the various parameters shown in Table 4 of Example 4 were changed to the parameters shown in Table 7 below.

[Table 7]
Light guide plate 21 thickness t: 5 mm
Eye relief d: 20 mm
Pitch of interference fringes for diffracting and reflecting green in first diffraction grating member 130
: 402.2 nm
Angle of view θ ₀ : 6.0 degrees Angle of view −θ ₀ : −6.0 degrees

  Before the specific description of the first diffraction grating member 130 of the fifth embodiment, the first diffraction grating member 130 is a Q layer made of a reflective volume hologram diffraction grating (Q = 2 in the fifth embodiment). ), The assumed diffraction grating layers 130a and 130b will be described first. FIG. 9B shows a schematic cross-sectional view of an example of the first diffraction grating member 130 that is assumed to be composed of the diffraction grating layers 130a and 130b.

Here, in each of the assumed diffraction grating layers 130a and 130b, interference fringes are formed from the inside to the surface, and the pitch of the interference fringes on the surfaces of the diffraction grating layers 130a and 130b is equal, and It is assumed that the pitch of interference fringes between the diffraction grating layers 130a and 130b is also equal. It is assumed that the minimum inclination angle φ _MIN is different in all the diffraction grating layers 130a and 130b, and the maximum inclination angle φ _MAX is different in all of the diffraction grating layers 130a and 130b.

  A parallel light beam having a wavelength λ = 522 nm incident on the center of the pupil 50 is diffracted and reflected at any position of the first diffraction grating member 130 that is assumed to be composed of the diffraction grating layers 130a and 130b. The graph of FIG. 9A shows how many times the second surface 21B of the optical plate 21 is totally reflected to reach the pupil 50.

In FIG. 9A, a solid curve [1] that rises to the right represents the case of the total reflection number N _TR = 3, and a dotted line curve [2] that rises to the right represents the case of the total reflection number N _TR = 4. To express. Here, as the curve of the graph rises from the left to the right, as described in the fourth embodiment, the parallel light flux having the same wavelength is diffracted and reflected as the angle of view θ changes in the plus direction. The tilt angle φ ₁ of the interference fringes of the first diffraction grating member 130 changes from small to large, and the distance from the origin O of the region of the first diffraction grating member 130 provided with such a tilt angle gradually increases. It means to be long.

For example, a parallel light beam corresponding to an angle of view θ = 1.3 degrees to 6.0 degrees (= incident angle [−Θ]) is incident on the second diffraction grating layer 130b at L≈36 mm to 51 mm. The second diffraction grating layer 130b is diffracted and reflected by the second surface 21B of the light guide plate 21 and then totally reflected three times. Then, the light enters the second diffraction grating member 40 and is diffracted and reflected. The light is emitted from the light guide plate 21 and guided to the pupil 50. In this case, as the angle of view θ changes in the positive direction, the inclination angle φ ₁ of the interference fringes of the second diffraction grating layer 130b that diffracts and reflects the parallel light beam having the same wavelength changes from small to large. Furthermore, the distance from the origin O of the region of the second diffraction grating layer 130b provided with such an inclination angle gradually increases.

On the other hand, when the angle of view θ is 1.3 degrees or less, that is, the parallel luminous flux corresponding to the angle of view θ = −6.0 degrees to 1.3 degrees (= incident angle [−Θ]) In the first diffraction grating layer 130a, the light enters the first diffraction grating layer 130a at L≈36 mm to 52 mm, and is diffracted and reflected in the region of the first diffraction grating layer 130a. After being totally reflected four times by the second surface 21 </ b> B of 21, it enters the second diffraction grating member 40, is diffracted and reflected, is emitted from the light guide plate 21, and is guided to the pupil 50. Also in this case, as the angle of view θ changes in the plus direction, the inclination angle φ ₁ of the interference fringe of the first diffraction grating layer 130a that diffracts and reflects the parallel light beam having the same wavelength changes from small to large. Further, the distance from the origin O of the first diffraction grating layer 130a provided with such an inclination angle gradually increases.

  The parallel light flux corresponding to the angle of view θ = −6.0 degrees to 1.3 degrees (= incident angle [−Θ]) may be incident on the second diffraction grating layer 130b. Since the diffraction efficiency in the second diffraction grating layer 130b of the parallel light beam is low, the parallel light beam is not diffracted and reflected by the second diffraction grating layer 130b. Similarly, a parallel light flux corresponding to an angle of view θ = 1.3 degrees to 6.0 degrees (= incident angle [−Θ]) is also incident on the first diffraction grating layer 130a. Since the diffraction efficiency of the first diffraction grating layer 130a is low, the parallel light beam is not diffracted and reflected by the first diffraction grating layer 130a.

In the first diffraction grating layer 130a, in the region of the first diffraction grating layer 130a where the parallel light flux corresponding to the angle of view θ ₁ = −θ _{1 —0} = −6.0 degrees is diffracted and reflected. The inclination angle φ ₁ of the interference fringes in a certain L≈36 mm region is the minimum inclination angle φ _MIN . Then, the outer region RG _OUT (up to L = 52 mm) located farther from the second diffraction grating member 40 than the minimum tilt angle region RG _MIN (corresponding to L≈36 mm) where the tilt angle φ ₁ is the minimum tilt angle φ _MIN. The inclination angle φ ₁ of the interference fringes formed in the region is equivalent to the minimum inclination angle region RG _MIN (L≈36 mm is equivalent). Then, the region of the first diffraction grating layer 130a (corresponding to the region of L = 52 mm) where the parallel light beam corresponding to the parallel light beam having the angle of view θ ₁ = θ ₁ — ₀ is diffracted and reflected has the maximum inclination angle φ _MAX . Have.

On the other hand, in the second diffraction grating layer 130b, the region of the second diffraction grating layer 130b in which the parallel light flux corresponding to the angle of view θ ₂ = −θ _{2 —0} = 1.3 degrees is diffracted and reflected. The inclination angle φ ₁ of the interference fringes in the region where L≈36 mm is the minimum inclination angle φ _MIN . Then, the outer region RG _OUT (up to L = 51 mm) located farther from the second diffraction grating member 40 than the minimum tilt angle region RG _MIN (corresponding to L≈36 mm) where the tilt angle φ ₁ is the minimum tilt angle φ _MIN. The inclination angle φ ₁ of the interference fringes formed in the region (corresponding to the above-mentioned region) is larger the further away from the minimum inclination angle region RG _MIN (corresponding to L≈36 mm). The region of the second diffraction grating layer 130b (corresponding to the region of L = 51 mm) where the parallel light beam corresponding to the parallel light beam _{satisfying the} angle of view θ ₂ = θ ₂ — ₀ is diffracted and reflected has the maximum inclination angle φ _MAX . Have.

Here, since there is no region of the diffraction grating layer closer to the second diffraction grating member 40 than the minimum inclination angle region RG _MIN , the item (B-2) is ignored as described in the fourth embodiment. .

In the outer region RG _OUT , the inclination angle φ ₁ may be configured to increase continuously and monotonously as L increases. Alternatively, as shown in FIG. 9B, the first diffraction grating member 130 is divided into S pieces (specifically, S = 6) along the axial direction of the light guide plate 21, and the sth ( However, the portion RG _{(q, s)} [RG _(1,1) , RG _(1,2) , RG _{(1, s)} of the first diffraction grating layer 130a of s = 1, 2,. ₃₎ , RG _(1,4) , RG _(1,5) , RG _(1,6) ], a portion RG _{(q, s)} [RG _{(2, 1)} , RG _(2,2) , RG _(2,3) , RG _(2,4) , RG _(2,5) , RG _(2,6) ] with a constant tilt angle, and the value of s If they are different, the inclination angle φ ₁ in the diffraction grating layers 130a and 130b may be changed.

Partial RG _{(q, s)} and range of the distance L _{1_S} of angle θ _{1_s} (= incident angle [-Θ] _{1_s)} and the relationship between the inclination angle phi _{1_S,} shown in Table 8 below.

[Table 8]
3 times total reflection (q, s) Distance L _{1_s} (mm) Angle of view θ _{1_s} (degree) Inclination angle φ _{1_s} (degree)
(2,1) 36.0 to 38.25 1.74 29.97
(2,2) 38.25-40.75 2.8 30.36
(2,3) 40.75 to 43.25 3.7 30.72
(2,4) 43.25 to 45.75 4.5 31.07
(2,5) 45.75-48.5 5.2 31.40
(2,6) 48.5 to 52.0 5.8 31.70
4 times total reflection (q, s) Distance L _{1_s} (mm) Angle of view θ _{1_s} (degree) Tilt angle φ _{1_s} (degree)
(1,1) 36.0 to 38.25 -5.4 28.03
(1,2) 38.25 to 40.75 -4.0 28.34
(1,3) 40.75-43.25-2.9 28.60
(1,4) 43.25 to 45.75 -1.75 28.90
(1,5) 45.75-48.5 -0.76 29.17
(1,6) 48.5-52.0 0.08 29.42

  Consider virtual diffraction grating layers 230a and 230b that are equivalent to such assumed diffraction grating layers 130a and 130b. Here, in Example 5, the first diffraction grating member 130 has a Q layer (Example 5) composed of a reflective volume hologram diffraction grating, as shown in a conceptual diagram (cross section) in FIG. In this case, when it is assumed that the virtual diffraction grating layer of Q = 2 is laminated, the pitch of the interference fringes on the surfaces of the virtual diffraction grating layers 230a and 230b constituting the first diffraction grating member 130 And the pitches of the interference fringes between the virtual diffraction grating layers 230a and 230b are also equal.

When the angle formed by the interference fringes in the virtual diffraction grating layers 230a and 230b and the surfaces of the virtual diffraction grating layers 230a and 230b is an inclination angle, in each virtual diffraction grating layer 230a and 230b:
(B-1) The inclination angle of the interference fringes formed in the outer region located farther from the second diffraction grating member than the minimum inclination angle region where the inclination angle is the minimum inclination angle is so far from the minimum inclination angle region. big,
(B-2) The inclination angle of the interference fringes formed in the inner area located closer to the second diffraction grating member than the minimum inclination angle area is the maximum inclination angle in the inner area adjacent to the minimum inclination angle area. The smaller the distance from the minimum inclination angle region, the smaller.

The first diffraction grating member 130 is divided into R sections (R = 6 in the fifth embodiment) from the portion closest to the second diffraction grating member to the portion farthest from the second diffraction grating member. when in, r-th (where, r = 1,2 ··· R) partition RG _{1_R} of the first diffraction grating member is, the virtual diffraction grating layer of Q layer, from the most part closest to the second diffraction grating member Section VG _{(r, q) of the} virtual diffraction grating layer obtained when dividing into R sections from the second diffraction grating member to a portion far from the second diffraction grating member (where q is an overlap selected in the range of 1 to Q ₎ It is composed of a laminated structure of any integer).

  Specifically, as shown in FIG. 10A, the first diffraction grating layer 230A and the second diffraction grating layer 230B are as shown in Table 9 below from the second diffraction grating member side. Arranged in order. In Table 9, the diffraction grating layer described in the upper part is located closer to the second diffraction grating member 40.

[Table 9]
First diffraction grating layer 230A Second diffraction grating layer 230B
Section VG _(1,2) Section VG _(1,1)
Section VG _(2,1) Section VG _(2,2)
Section VG _(3,2) Section VG _(3,1)
Section VG _(4,2) Section VG _(4,1)
Section VG _(5,1) Section VG _(5,2)
Section VG _(6,2) Section VG _(6,1)

Here, the characteristics of the partitions VG _(1,1) , VG _(2,1) , VG _(3,1) , VG _(4,1) , VG _(5,1) , VG _(6,1) are as follows: RG _{(q, s)} [RG _(1,1) , RG _(1,2) , RG _(1,3) , RG _(1,4) , RG _{(1, 5)} , RG _(1,6) ], and can have the same characteristics as the partitions VG _(1,2) , VG _(2,2) , VG _(3,2) , VG _(4,2) , VG _(5,2) , VG _(6,2) have the following characteristics: RG _{(q, s)} [RG _(2,1) , RG _(2,2) of the assumed diffraction grating layer 130b , RG _(2,3) , RG _(2,4) , RG _(2,5) , RG _(2,6) ].

FIG. 11 schematically shows the incident state of the parallel light beam on the first diffraction grating member 130 stacked as shown in FIG. The light guide plate 21 is omitted for simplification. A light beam group emitted from each pixel position of the image forming apparatus 11 is collimated by the collimating optical system 12 and converted into a light beam group composed of parallel light beams having different traveling directions. Thereafter, these parallel light beams pass through a light guide plate 21 (not shown) and enter the first diffraction grating member 130 shown in FIG. At this time, the parallel light beam r ₁ incident on the section VG _(1,2) enters the section VG _(1,1) without being diffracted and reflected by the section VG _{(1,2), and} is diffracted and reflected here. The

That is, since the parallel light beam r ₁ has the most positive incident angle (the most negative field angle −θ ₀ ), it is diffracted and reflected on the section VG _(1,1) based on a predetermined Bragg condition, It propagates while repeating total reflection. On the other hand, the parallel light beam r ₁ is hardly diffracted and reflected in the section VG ₍₁ , ₂₎ . This is because, as shown in FIG. 12, the angular characteristics of the diffraction efficiency in the other sections VG _{(r, q ′)} stacked in the same position in the respective sections VG _{(r, q)} . This is because it is not large enough to cover.

In addition, since the thickness of the laminated diffraction grating layers 230A and 230B is very thin, for example, 20 μm, the positions of the total reflection of the parallel light beam r ₁ and the parallel light beam r ₇ do not deviate. It has almost the same characteristics as described. The stacking order of the first diffraction grating layer 230A and the second diffraction grating layer 230B may be reversed.

The center of the second diffraction grating member 40 is the origin O, the normal line of the second diffraction grating member 40 passing through the origin O is the X axis, and the axis of the light guide plate passing through the origin O is the Y axis. A point (pupil 50) on the X-axis for observing an image based on the parallel light flux group that is diffracted and emitted from the light guide plate 21, and a virtual diffraction grating layer of the qth layer (where q = 1, 2,... Q is assumed to be diffracted and reflected by the second diffraction grating member 40 and is assumed to be diffracted and reflected by the second diffraction grating member 40, and is assumed to be the first diffraction grating member 130 among the assumed parallel light beams located in the XY plane. The angle formed by the near assumed parallel light beam is the angle of view θ _q = θ _q — ₀ (> 0), and the angle formed by the assumed parallel light beam farthest from the first diffraction grating member 130 is the angle of view θ _q = −θ _q — ₀ (<0). When
The region of the virtual diffraction grating layer of the q-th layer where the assumed parallel light beam corresponding to the assumed parallel light beam _{satisfying the} angle of view θ _q = θ _q — ₀ is diffracted and reflected has a maximum inclination angle,
The region of the qth virtual diffraction grating layer where the assumed parallel light beam corresponding to the assumed parallel light beam _{satisfying the} angle of view θ _q = −θ _q — ₀ has a minimum inclination angle.

  The portion (region) of the diffraction grating layer constituting the first diffraction grating member and the section of the virtual diffraction grating layer do not have to correspond one-to-one, and (C) in FIG. 10 and (D) in FIG. The conceptual diagram (cross section) of the modification of a 1st diffraction grating member and the conceptual diagram (cross section) of the laminated structure of the modification of a virtual diffraction grating layer are respectively shown.

  As mentioned above, although this invention was demonstrated based on the preferable Example, this invention is not limited to these Examples. The configuration and structure of the image display device described in the embodiments are examples and can be changed as appropriate. For example, in the fourth embodiment, the first diffraction grating member 30 has P types (for example, red with a wavelength of 635 nm, green with a wavelength of 522 nm, and green with a wavelength of 470 nm) that form different parallel light beams. In order to make the diffraction reflection angles of the three types of blue light beams substantially the same, it is possible to adopt a configuration in which P types (for example, three types) of interference fringes are formed. In the diffraction grating layer, diffraction reflections of P types of light beams having different wavelength bands (or wavelengths) constituting each parallel light beam (for example, three types of red light having a wavelength of 635 nm, green light having a wavelength of 522 nm, and blue light having a wavelength of 470 nm). In order to make the angles substantially the same, P types (for example, three types) of interference fringes can be formed.

FIG. 1 is a conceptual diagram of an image display apparatus according to the first embodiment. (A), (B), and (C) of FIG. 2 are respectively in green (wavelength: 522 nm) where the position of the pupil of the observer who uses the image display device is higher than the designed pupil position. Direction (Y direction) -1.0 mm, maximum gray scale display when in the design pupil position and in the horizontal field angle direction (Y direction) +1.0 mm from the design pupil position It is a graph which shows luminance distribution [measured value _{fk_G} (m) of luminance value] and luminance distribution [ _{Fk_G} (m)] at the time. FIG. 3 is a circuit diagram of a part of the image forming apparatus driving apparatus including the correcting unit according to the first exemplary embodiment. FIG. 4 is a circuit diagram of a part of an image forming apparatus driving apparatus including a correcting unit according to the second embodiment. FIG. 5 is a circuit diagram of a part of an image forming apparatus driving apparatus including a correcting unit according to the third embodiment. FIG. 6 is a conceptual diagram of the image display apparatus according to the fourth embodiment. 7A and 7B are schematic cross-sectional views of the diffraction grating layer constituting the first diffraction grating member in Example 4. FIG. FIG. 8A is a graph showing the relationship between the number of total reflections of the parallel light beam inside the light guide plate, the angle of view θ, and the incident position of the parallel light beam on the first diffraction grating member in Example 4. 8B is a schematic cross-sectional view of the diffraction grating layer constituting the first diffraction grating member of Example 4. FIG. FIG. 9A shows the parallelism inside the light guide plate when it is assumed in Example 5 that the first diffraction grating member has two diffraction grating layers made of a reflective volume hologram diffraction grating. FIG. 9B is a graph showing the relationship between the total number of reflections of the light beam, the angle of view θ, and the incident position of the parallel light beam on the first diffraction grating member. FIG. 9B is a schematic diagram of the assumed first diffraction grating member. FIG. FIG. 10A is a conceptual diagram (cross section) of the first diffraction grating member in the optical device of Example 5, and FIG. 10B is when it is assumed that virtual diffraction grating layers are stacked. FIG. 10 is a conceptual diagram (cross section) of each virtual diffraction grating layer constituting the first diffraction grating member, and FIG. 10C is a conceptual diagram of a modification of the first diffraction grating member in the optical device of Example 5 ( (D) of FIG. 10 is a conceptual diagram (cross section) of each virtual diffraction grating layer constituting a modification of the first diffraction grating member, assuming that the virtual diffraction grating layer is laminated. is there. FIG. 11 is a diagram schematically showing the incident state of the parallel light beam on the first diffraction grating members stacked as shown in FIG. FIG. 12 is a diagram for explaining whether or not a light beam incident on a multilayered diffraction grating layer is diffracted and reflected. FIG. 13 is a conceptual diagram of a conventional image display device. FIG. 14 is a graph showing the incident wavelength dependence of the diffraction efficiency when the pupil position moves, and the state in which the spectrum P of the wavelength incident on the second diffraction grating member changes. FIG. 15 is a graph showing the incident wavelength dependence of the diffraction efficiency when the pupil position moves, and the state in which the spectrum P of the wavelength incident on the second diffraction grating member changes.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Image display apparatus, 11 ... Image forming apparatus, 12 ... Collimating optical system, 20 ... Optical apparatus, 21 ... Light guide plate, 21A ... 1st surface of a light guide plate, 21B ... 2nd surface of light guide plate, 30, 130 ... 1st diffraction grating member, 40 ... 2nd diffraction grating member, 31, 41 ... Interference fringe, 50 ... Pupil, 60 ... Image forming apparatus driving device 61... Image signal processing circuit 70, 170, 270... Correction means 71 171 271 Storage means 72 172 272 Control circuit 73 , 173, 273 ... correction circuit, 74 ... timing generation circuit, 75, 175, 275 ... correction data generation circuit, 76 ... multiplier

Claims (6)

(A) an image forming apparatus composed of a total of M × N pixels, M along the Y direction and N along the Z direction;
(B) a collimating optical system that converts the light emitted from each pixel of the image forming apparatus into a parallel light beam;
(C) an optical device in which light that is collimated by a collimating optical system is incident, guided, and emitted;
(D) an image forming apparatus driving device including a correcting unit;
An image display device comprising:
The optical device
(A) A light guide plate extending along the Y direction that is emitted after light is incident and propagated through the interior by total reflection;
(B) A first diffraction grating composed of a reflective volume hologram diffraction grating that diffracts and reflects light incident on the light guide plate so that the light incident on the light guide plate is totally reflected along the Y direction inside the light guide plate. Members and
(C) Second diffraction composed of a reflective volume hologram diffraction grating that diffracts and reflects light propagating through the interior of the light guide plate so as to emit light from the light guide plate and enter the pupil position of the observer. Lattice members,
With
The correction unit corrects the value of the image signal input to each pixel of the image forming apparatus based on a correction coefficient for each pixel along the Y direction obtained from the luminance distribution at a plurality of different pupil positions. An image display device.   2. The image display apparatus according to claim 1, wherein the correction coefficient minimizes a difference between a luminance distribution at a predetermined gradation display at a plurality of different pupil positions and a desired luminance distribution. Each pixel is composed of a red light emitting subpixel that emits red, a green light emitting subpixel that emits green, and a blue light emitting subpixel that emits blue.
The image display apparatus according to claim 1, wherein the correction unit includes correction coefficients for each of the red light emission subpixel, the green light emission subpixel, and the blue light emission subpixel.   The image display device according to claim 1, wherein the value of the image signal input to each pixel along the Z direction is corrected based on the same correction coefficient. The correction means has a plurality of correction coefficients,
The image display apparatus according to claim 1, wherein the correction unit selects one correction coefficient from the plurality of correction coefficients based on an average value of image signals input to all pixels. The correction means includes one correction coefficient and an intensity coefficient corresponding to the value of the input image signal,
The correction unit selects an intensity coefficient based on the average value of the image signals input to all pixels, and calculates the value of the image signal input to each pixel of the image forming apparatus based on the selected intensity coefficient and correction coefficient. The image display device according to claim 1, wherein correction is performed.