JP2021103198A - Optical member, display device, head-mounted display device, and manufacturing method of optical member - Google Patents

Abstract

To uniformize brightness of image light emitted from an optical member as much as possible.SOLUTION: An optical member 10 comprises: a first diffraction optical member 20 including a first diffraction optical element 21; a second diffraction optical member 30 including, in a position displaced in a first direction d1 from the first diffraction optical member 20, a second diffraction optical element 31; and a third diffraction optical member 40 including, in a position displaced from the second diffraction optical member 30 in a second direction d2 that is non-parallel to the first direction d1, a third diffraction optical element 41. A desired relation is provided among diffraction efficiencies for the respective diffraction optical elements.SELECTED DRAWING: Figure 2

Description

The present invention relates to an optical member, a display device having an optical member, a head-mounted display device having a display device, and a method for manufacturing the optical member.

As a display device that displays the image light from the display unit in front of the observer's eyes by an optical member, a head-mounted display device (head-mounted display) that is used by being worn on the head is known. In such a display device, for example, as shown in Patent Document 1 and Patent Document 2, the optical member guides the substrate and the inside of the substrate to guide the image light and the inside of the substrate. It has a diffractive optical element provided in an incident portion, an expanding portion, and an emitting portion of the image light in order to appropriately emit the image light.

The image light incident on the incident portion of the optical member is diffracted for each wavelength by the diffractive optical element provided in the incident portion corresponding to each wavelength. The image light diffracted by the diffractive optical element provided in the incident portion is guided through the base material and incident on the extended portion. The image light incident on the expansion portion is diffracted for each wavelength so as to be expanded over a wide range of the expansion portion by another diffraction optical element provided in the expansion portion corresponding to each wavelength. The image light diffracted by the diffractive optical element provided in the expansion portion is further guided in the base material and incident on the exit portion. The image light incident on the emitting portion is expanded so as to be emitted from the entire emitting portion by another diffractive optical element provided in the emitting portion corresponding to each wavelength, and is diffracted for each wavelength. In this way, the image light of each wavelength is emitted from the optical member, and the image can be displayed in front of the observer's eyes.

Special Table 2009-186794 Japanese Unexamined Patent Publication No. 2015-102613

By the way, the amount of image light diffracted in the expansion portion increases near the incident portion, but decreases as the distance from the incident portion increases. Similarly, the amount of image light diffracted at the exit portion increases near the expansion portion, but decreases as the distance from the expansion portion increases. Therefore, the intensity of the image light emitted from the emitting portion becomes non-uniform depending on the position of the emitting portion. The intensity of the image light is the brightness of the image light. That is, the brightness of the image emitted from the emitting portion of the optical member and observed by the observer becomes non-uniform. Non-uniform brightness will reduce the quality of the image.

The present invention has been made in consideration of such a point, and an object of the present invention is to make the brightness of the image light emitted from the optical member uniform.

The optical member of the present invention
With the base material
A first diffractive optical member laminated on the base material and including a first diffractive optical element,
A second diffractive optical member laminated on the base material at a position deviated from the first diffractive optical member in the first direction and including a second diffractive optical element.
An optical member including a third diffractive optical member, which is laminated on the base material at a position deviated from the second diffractive optical member in the second direction, which is non-parallel to the first direction, and includes a third diffractive optical element. hand,
The first diffracting optical element diffracts light in the first wavelength region incident on the optical member so as to go in the first direction.
The second diffracting optical element diffracts the light in the first wavelength region incident from the first direction so as to go in the second direction.
The third diffracting optical element diffracts the light in the first wavelength region incident from the second direction so as to be emitted from the optical member.
The diffraction efficiency in a certain region having a unit area of the second diffractive optical element has a unit area of the second diffractive optical element separated from the first diffractive optical member along the first direction from the region. Less than diffraction efficiency in one other region,
The diffraction efficiency in a certain region having the unit area of the third diffractive optical element had the unit area of the third diffractive optical element separated from the second diffractive optical member along the second direction from the region. It is lower than the diffraction efficiency in one other region.

In the optical member of the present invention
The diffraction efficiency in an arbitrary region having a unit area of the second diffraction optical element has a unit area of the second diffraction optical element separated from the first diffraction optical member along the first direction from the region. Less than the diffraction efficiency in any other region
The diffraction efficiency in an arbitrary region having a unit area of the third diffractive optical element has a unit area of the third diffractive optical element separated from the second diffractive optical member along the second direction from the region. It may be lower than the diffraction efficiency in any other region.

In the optical member of the present invention, the second diffraction optical element and the third diffraction optical element may be volume holograms.

In the optical member of the present invention
The second diffracting optical element includes a second diffracting portion in which a second diffraction grating for diffracting light in the first wavelength region is formed, and a second flat portion which is a non-forming portion of the second diffraction grating. Including
The ratio of the second diffractive portion in a certain region having a unit area of the second diffractive optical element is the ratio of the second diffractive optical element separated from the first diffractive optical member along the first direction from the region. It may be lower than the proportion of the second diffracting portion in another region having a unit area.

In the optical member of the present invention
The third diffracting optical element includes a third diffractive portion in which a third diffraction grating for diffracting light in the first wavelength region is formed, and a third flat portion which is a non-forming portion of the third diffraction grating. Including
The ratio of the third diffractive portion in a certain region having a unit area of the third diffractive optical element is the ratio of the third diffractive optical element separated from the second diffractive optical member along the second direction from the region. It may be lower than the proportion of the third diffracting portion in another region having a unit area.

In the optical member of the present invention
In the second diffracting optical element, there is a difference in refractive index so as to form a second diffraction grating that diffracts light in the first wavelength region.
The difference in refractive index forming the second diffraction grating in a region having a unit area of the second diffraction optical element is the second distance from the region along the first direction from the first diffraction optical member. It may be lower than the difference in refractive index forming the second diffraction grating in a certain other region having a unit area of the diffractive optical element.

In the optical member of the present invention
In the third diffracting optical element, there is a difference in refractive index so as to form a third diffraction grating that diffracts light in the first wavelength region.
The difference in refractive index forming the third diffraction grating in a certain region having a unit area of the third diffractive optical element is the third, which is separated from the second diffractive optical member along the second direction from the region. It may be lower than the difference in refractive index forming the third diffraction grating in a certain other region having a unit area of the diffractive optical element.

In the optical member of the present invention, the length of at least a part of the second diffractive optical member along the second direction may increase as the distance from the first diffractive optical member increases.

The optical member of the present invention
A fourth diffractive optical member, which is laminated on the base material at a position deviated from the first diffractive optical member in the second direction and includes a fourth diffractive optical element, is further provided.
The first diffractive optical member further includes a fifth diffractive optical element.
The third diffractive optical member further includes a sixth diffractive optical element.
The fifth diffracting optical element diffracts light in a second wavelength region different from the first wavelength region incident on the optical member so as to go in the second direction.
The fourth diffracting optical element diffracts the light in the second wavelength region incident from the second direction so as to go toward the first direction.
The sixth diffracting optical element diffracts the light in the second wavelength region incident from the first direction so as to be emitted from the optical member.
The diffraction efficiency in a certain region having the unit area of the fourth diffractive optical element had the unit area of the fourth diffractive optical element separated from the first diffractive optical member along the second direction from the region. Less than diffraction efficiency in one other region,
The diffraction efficiency in a certain region having the unit area of the sixth diffractive optical element had the unit area of the sixth diffractive optical element separated from the second diffractive optical member along the first direction from the region. It may be lower than the diffraction efficiency in one other region.

The display device of the present invention
With any of the optics mentioned above
The optical member includes a display unit that is arranged so as to face the first diffraction optical member and emits image light.

The head-mounted display device of the present invention includes the above-mentioned display device.

The method for manufacturing the first optical member of the present invention is
The process of providing the hologram sensitive material on the base material and
The process of arranging the mask facing the hologram sensitive material and
A step of irradiating light to expose the hologram sensitive material through the mask to desensitize the hologram sensitive material, and a step of desensitizing the hologram sensitive material.
The step of removing the mask and
A step of exposing the hologram sensitive material to form a hologram on the base material is provided.
The mask has a first portion, a second portion displaced from the first portion in the first direction, and a third portion displaced from the second portion in a second direction non-parallel to the first direction. Including parts,
The mask has openings in the second part and the third part.
The proportion of the opening in a region having a unit area of the second portion is another having a unit area of the second portion separated from the first portion along the first direction from the region. Higher than the proportion of said openings in the area,
The proportion of the opening in a region having a unit area of the third portion is another having a unit area of the third portion separated from the second portion along the second direction from the region. Higher than the proportion of said openings in the area.

The method for manufacturing the second optical member of the present invention is
The process of providing the hologram sensitive material on the base material and
The step of arranging the dimming filter facing the hologram sensitive material and
A step of irradiating light to expose the hologram sensitive material through the dimming filter to desensitize the hologram sensitive material.
The step of removing the dimming filter and
A step of exposing the hologram sensitive material to form a hologram is provided.
The dimming filter is located with a first portion, a second portion displaced from the first portion in the first direction, and a second portion displaced from the second portion in a second direction non-parallel to the first direction. Including the third part,
The light transmittance in a certain region having a unit area of the second part is a certain other region having a unit area of the second part separated from the first part along the first direction from the region. Higher than the light transmittance in
The light transmittance in a certain region having a unit area of the third part is a certain other region having a unit area of the third part separated from the second part along the second direction from the region. Higher than the light transmittance in.

According to the present invention, the brightness of the image light emitted from the optical member can be made uniform.

FIG. 1 is a perspective view showing a part of a head-mounted display device, which is mounted on the head and arranged in front of the eyes. FIG. 2 is a front view of an optical member included in the display device of FIG. FIG. 3 is a cross-sectional view of the optical member of FIG. 2 along lines III-III. FIG. 4 is a cross-sectional view taken along line IV-IV of the optical member of FIG. FIG. 5 is a plan view for explaining an example of a method for manufacturing an optical member. FIG. 6 is a plan view for explaining an example of a method for manufacturing an optical member. FIG. 7 is a part of a cross section taken along the line VII-VII of FIG. 6 and is a cross-sectional view for explaining an example of a method for manufacturing an optical member. FIG. 8 is a cross-sectional view for explaining an example of a method for manufacturing an optical member. FIG. 9 is a cross-sectional view for explaining an example of a method for manufacturing an optical member. FIG. 10 is a diagram for explaining the operation of the optical member in the cross-sectional view of the optical member shown in FIG. FIG. 11 is a diagram for explaining the incident of light on the diffractive optical element in the optical member. FIG. 12 is a table showing the ratio of the guided light in the relationship between the number of incidents on the diffraction optical element and the diffraction efficiency. FIG. 13 is a front view of the optical member for explaining a modification of the diffractive optical element of the optical member corresponding to FIG. 2. FIG. 14 is a front view for explaining another modification of the diffractive optical element of the optical member corresponding to FIG. 2. FIG. 15 is a plan view for explaining an example of a manufacturing method of another modification of the diffractive optical element of the optical member. FIG. 16 is a part of a cross section taken along the line XVI-XVI of FIG. 15 and is a cross-sectional view for explaining an example of a manufacturing method of another modification of the diffractive optical element of the optical member. FIG. 17 is a cross-sectional view for explaining an example of a manufacturing method of another modification of the diffractive optical element of the optical member. FIG. 18 is a cross-sectional view for explaining an example of a manufacturing method of another modification of the diffractive optical element of the optical member. FIG. 19 is an enlarged photograph of a part of the diffractive optical element for explaining an example of the method of comparing the refractive index difference in another modified example of the diffractive optical element of the optical member. FIG. 20 is an enlarged photograph of a part of the diffractive optical element for explaining an example of the method of comparing the refractive index difference in another modified example of the diffractive optical element of the optical member. FIG. 21 is an enlarged photograph of another part of the diffractive optical element for explaining an example of the method of comparing the refractive index difference in another modified example of the diffractive optical element of the optical member. FIG. 22 is an enlarged photograph of another part of the diffractive optical element for explaining an example of the method of comparing the refractive index difference in another modified example of the diffractive optical element of the optical member. FIG. 23 is a diagram for explaining still another modification of the diffraction optical member of the optical member. FIG. 24 is a diagram for explaining still another modification of the diffraction optical member of the optical member. FIG. 25 is a cross-sectional view of the optical member for explaining a modification of the optical member.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings attached to the present specification, the scale, aspect ratio, etc. are appropriately changed from those of the actual product and exaggerated for the convenience of illustration and comprehension.

The "sheet surface (plate surface, film surface)" is a target sheet-like member (plate-like) when the target sheet-like (plate-like, film-like) member is viewed as a whole and from a broad perspective. A surface that coincides with the plane direction of a member or film-like member).

In addition, as used in the present specification, the terms such as "parallel", "orthogonal", and "identical" and the values of length and angle that specify the shape and geometric conditions and their degrees are strictly used. Without being bound by meaning, we will interpret it including the range in which similar functions can be expected.

FIG. 1 shows a head-mounted display device 1 (head-mounted display) as an example of the present embodiment. The head-mounted display device 1 is used by being worn on a human head and displays an image in front of the eyes. The head-mounted display device 1 has a display device 3 that displays an image in front of the eyes while being worn on the head. The display device 3 includes a display unit 5 that emits image light, a lens 7 that refracts the image light emitted from the display unit 5, and after the image light from the display unit 5 is incident and guided inside the display unit 5. It has an optical member 10 that emits light from the front of the observer's eyes.

The display unit 5 is a device that emits image light. As the display unit 5, any display unit such as a liquid crystal display, a plasma display, an organic EL display, LCOS, or DLP can be used. The display unit 5 is arranged at a position facing the first diffraction optical member 20 described later of the optical member 10, and emits image light toward the first diffraction optical member 20.

The lens 7 refracts the image light emitted from each position of the display unit 5 for each emission position to make light traveling in a substantially parallel direction, and causes the light to enter the first diffraction optical member 20 of the optical member 10. The lens 7 is arranged between the display unit 5 and the optical member 10 at a position facing the surface of the display unit 5 that emits image light. The lens 7 is, for example, a convex lens, and the display unit 5 is arranged at the position of the focal length thereof.

The optical member 10 guides the image light incident from one side inside the optical member 10 and emits it in front of the observer's eyes. When the image light incident on the optical member 10 travels in a substantially parallel direction, the image light emitted from the optical member 10 can be light that travels in a substantially parallel direction. The light incident on the optical member 10 and the light emitted from the optical member 10 are indicated by solid arrows in FIG. 1, and the light guiding the inside of the optical member 10 is indicated by a dotted arrow in FIG. .. As shown in FIG. 1, the light incident on the position facing the display unit 5 of the optical member 10 is guided to the position where the image of the optical member 10 is displayed while changing the traveling direction, and the observer's light is guided. It is emitted from the position where the image in front of the eye is displayed.

The optical member 10 includes a base material 11, a first diffraction optical member 20, a second diffraction optical member 30, a third diffraction optical member 40, and a fourth diffraction optical member 50. The first diffraction optical member 20, the second diffraction optical member 30, the third diffraction optical member 40, and the fourth diffraction optical member 50 are laminated at different positions on the base material 11. More specifically, the second diffractive optical member 30 is laminated on the base material 11 at a position deviated from the first diffractive optical member 20 in the first direction d1. The third diffractive optical member 40 is laminated on the base material 11 at a position deviated from the second diffractive optical member 30 in the second direction d2. The fourth diffractive optical member 50 is laminated on the base material 11 at a position deviated from the first diffractive optical member 20 in the second direction d2 and at a position deviated from the third diffractive optical member 40 in the first direction d1. .. The second direction d2 is a direction non-parallel to the first direction d1. In the illustrated example, the first direction d1 and the second direction d2 are orthogonal to each other.

Hereinafter, each component of the optical member 10 will be described with reference to FIGS. 2 to 4. FIG. 2 is a front view of the optical member 10. FIG. 3 is a cross-sectional view of the optical member 10 along the line III-III in FIG. 2, and FIG. 4 is a cross-sectional view of the optical member 10 along the line IV-IV in FIG.

The base material 11 functions as a light guide body that guides light inside the optical member 10. The base material 11 is transparent in order to guide visible light. Further, the base material 11 is a plate-shaped member. Light is reflected, especially totally reflected, by a pair of main surfaces of the plate-shaped base material 11 and each diffraction optical member provided on the base material 11, so that the inside of the base material 11 is guided. It is preferable that the refractive index of the base material 11 is sufficiently larger than the refractive index of air or the like outside the optical member 10 so that total reflection is likely to occur on the main surface of the base material 11. Specifically, the refractive index of the base material 11 is preferably 1.50 or more, more preferably 1.55 or more, still more preferably 1.6 or more, and 1.7 or more. Is even more preferable, and 1.8 or more is most preferable.

In the present specification, the refractive index means the refractive index for light having a wavelength of 587.6 nm.

In addition, transparency means the transmittance at each wavelength when measured within the measurement wavelength range of 380 nm to 780 nm using a spectrophotometer (“UV-3100PC” manufactured by Shimadzu Corporation, JIS K 0115 compliant product). It means that the visible light transmittance specified as the average value of is 60% or more.

The base material 11 is made of a material that is not easily deformed, that is, a material having high rigidity, in order to maintain a shape for guiding light inside the base material 11. Further, the base material 11 appropriately supports the first diffraction optical member 20, the second diffraction optical member 30, the third diffraction optical member 40, and the fourth diffraction optical member 50 laminated on the base material 11. Considering, for example, the visible light transmittance, rigidity, supportability of the first diffraction optical member 20, the second diffraction optical member 30, the third diffraction optical member 40, and the fourth diffraction optical member 50 as the base material 11, for example. Resin materials such as polycarbonate, cycloolefin polymer, and acrylic, and glass are preferable. In particular, the resin material is suitable from the viewpoint of weight and brittleness. Further, the base material 11 is considered to have visible light transmission and rigidity, supportability of the first diffraction optical member 20, the second diffraction optical member 30, the third diffraction optical member 40, the fourth diffraction optical member 50, and the like. The thickness is 0.1 mm or more and 2.0 mm or less, preferably 0.2 mm or more and 1.0 mm or less, and more preferably 0.3 mm or more and 0.7 mm or less. Further, in order to guide light on the main surface of the base material 11 by total reflection, it is preferable that the main surface of the base material 11 has high flatness. Specifically, in an arbitrary 1 mm square region of the base material 11 in a plan view, the difference between the thickness of the thickest portion and the thickness of the thinnest portion is preferably 5 μm or less, and preferably 2 μm or less. It is more preferably 1 μm or less, and even more preferably 0.5 μm or less.

The first diffraction optical member 20 diffracts the light incident on the optical member 10. The first diffraction optical member 20 is provided at an incident portion of the optical member 10 that incidents the image light from the display unit 5. The first diffraction optical member 20 faces the display unit 5. As is well shown in FIGS. 3 and 4, the first diffractive optical member 20 includes a first diffractive optical element 21 and a fifth diffractive optical element 22.

The first diffracting optical element 21 diffracts the light in the first wavelength region of the light incident on the incident portion of the optical member 10. In other words, the first diffraction optical element 21 has a diffraction characteristic of diffracting light in the first wavelength region incident from the normal direction of the sheet surface of the base material 11. The first diffraction optical element 21 includes a first diffraction grating that diffracts light in the first wavelength region. The first diffraction grating is formed by the difference in the refractive index of the material in the first diffraction optical element 21. That is, in the first diffraction optical element 21, there is a difference in refractive index so as to form the first diffraction grating. The first diffracting optical element 21 diffracts the light in the first wavelength region incident on the first diffracting optical member 20 toward the first direction d1 by the first diffraction grating. The light in the first wavelength region toward the first direction d1 is guided in the base material 11. The direction in which the light is guided in the base material 11 means the traveling direction of light in the base material 11 in the plan view of the optical member 10. Therefore, the movement in the thickness direction in the base material 11 is ignored.

The fact that the light in a certain wavelength range is diffracted means that the diffraction efficiency with respect to the light of an arbitrary wavelength included in the wavelength range is 10% or more. Diffraction efficiency can be measured from the difference in transmittance using, for example, a spectrophotometer (“UV-2450” manufactured by Shimadzu Corporation).

The thickness of the first diffraction optical element 21 is preferably thick. By increasing the thickness of the first diffraction optical element 21, the diffraction efficiency of the first diffraction optical element 21 can be improved. That is, it is possible to increase the rate at which the light in the first wavelength region incident on the first diffracting optical element 21 is diffracted by the first diffracting optical element 21. Specifically, the thickness of the first diffraction optical element 21 is, for example, 3 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and further preferably 15 μm or more.

On the other hand, the diffraction efficiency of the first diffraction optical element 21 is preferably in an appropriate range. Specifically, the diffraction efficiency of the first diffraction optical element 21 is preferably 50% or less, more preferably 10% or more and 40% or less, and further preferably 10% or more and 30% or less. , 15% or more and 25% or less is most preferable. By appropriately setting the diffraction efficiency of the first diffraction optical element 21, more light in the first wavelength region can be guided from the first diffraction optical member 20 to the second diffraction optical member 30.

The fifth diffraction optical element 22 diffracts the light in the second wavelength region of the light incident on the incident portion of the optical member 10. In other words, the fifth diffraction optical element 22 has a diffraction characteristic of diffracting light in the second wavelength region incident from the normal direction of the sheet surface of the base material 11. The fifth diffraction optical element 22 includes a fifth diffraction grating that diffracts light in the second wavelength region. The fifth diffraction grating is formed by the difference in the refractive index of the material in the fifth diffraction optical element 22. That is, in the fifth diffraction optical element 22, there is a difference in refractive index so as to form the fifth diffraction grating. The fifth diffraction optical element 22 diffracts the light in the second wavelength region incident on the first diffraction optical member 20 so as to go in the second direction d2 by the fifth diffraction grating. The light in the second wavelength region toward the second direction d2 is guided in the base material 11.

The thickness of the fifth diffraction optical element 22 is preferably thick. By increasing the thickness of the fifth diffraction optical element 22, the diffraction efficiency of the fifth diffraction optical element 22 can be improved. That is, the ratio of the light in the second wavelength region incident on the fifth diffracting optical element 22 to be diffracted by the fifth diffracting optical element 22 can be increased. Specifically, the thickness of the fifth diffraction optical element 22 is, for example, 3 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and further preferably 15 μm or more.

On the other hand, the diffraction efficiency of the fifth diffraction optical element 22 is preferably in an appropriate range. Specifically, the diffraction efficiency of the fifth diffraction optical element 22 is preferably 50% or less, more preferably 10% or more and 40% or less, and further preferably 10% or more and 30% or less. , 15% or more and 25% or less is most preferable. By appropriately setting the diffraction efficiency of the fifth diffraction optical element 22, more light in the second wavelength region can be guided from the first diffraction optical member 20 to the fourth diffraction optical member 50.

Here, the first wavelength region includes the wavelength regions of two colors of light, red, green, and blue. For example, the first wavelength region is 600 nm or more and 700 nm or less and 400 nm or more and 490 nm or less. That is, the first wavelength region includes a wavelength region of red light and a wavelength region of blue light. In this case, the second wavelength region is 500 nm or more and 580 nm or less. That is, the second wavelength region includes the wavelength region of green light. Alternatively, as another example, the first wavelength region is 400 nm or more and 550 nm or less. That is, the first wavelength region includes a wavelength region of green light and a wavelength region of blue light. In this case, the second wavelength region is 550 nm or more and 700 nm or less. That is, the second wavelength region includes the wavelength region of red light.

The angle formed by the first direction d1 which is the light guide direction of the light in the first wavelength region and the second direction d2 which is the light guide direction of the light in the second wavelength region in the first diffraction optical member 20 is close to a right angle. Is preferable. Specifically, the angle formed by the first direction d1 and the second direction d2 is preferably 70 ° or more and 110 ° or less, more preferably 80 ° or more and 100 ° or less, and 85 ° or more and 95 ° or less. It is more preferably 89 ° or more and 91 ° or less, and most preferably 90 ° or less.

The first diffraction optical element 21 can transmit light in the second wavelength region. Specifically, the transmittance of light in the second wavelength region of the first diffraction optical element 21 is preferably 30% or more, more preferably 50% or more, and further preferably 70% or more. It is preferably 90% or more, and even more preferably 90% or more. Similarly, the fifth diffraction optical element 22 can transmit light in the first wavelength region. Specifically, the transmittance of light in the first wavelength region of the fifth diffraction optical element 22 is preferably 30% or more, more preferably 50% or more, and further preferably 70% or more. It is preferably 90% or more, and even more preferably 90% or more.

The second diffracting optical member 30 diffracts the light in the first wavelength region diffracted by the first diffracting optical element 21 among the light diffracted by the first diffracting optical member 20. The second diffraction optical member 30 is provided in the expansion portion of the optical member 10 that expands the image light in the first direction d1. The second diffraction optical member 30 has a longitudinal direction in the first direction d1. The second diffractive optical member 30 includes a second diffractive optical element 31.

The second diffracting optical element 31 diffracts the light in the first wavelength region diffracted by the first diffracting optical element 21. In other words, the second diffraction optical element 31 has a diffraction characteristic of diffracting light in the first wavelength region traveling in the first direction d1 in the base material 11. The second diffraction optical element 31 includes a second diffraction grating that diffracts light in the first wavelength region. The second diffraction grating is formed by the difference in the refractive index of the material in the second diffraction optical element 31. That is, in the second diffraction optical element 31, there is a difference in refractive index so as to form the second diffraction grating. The second diffractive optical element 31 diffracts the light in the first wavelength region incident on the second diffracting optical member 30 from the first direction d1 by the second diffraction grating so as to go toward the second direction d2. The light in the first wavelength region toward the second direction d2 is guided in the base material 11.

The diffraction efficiency of the second diffraction optical element 31 is lower than the diffraction efficiency of the first diffraction optical element 21. Therefore, for example, only a part of the light in the first wavelength region incident on the position of the second diffraction optical element 31 is diffracted, and the inside of the base material 11 is guided in the second direction d2. However, the second diffraction optical member 30 has a longitudinal direction in the first direction d1. Therefore, the light in the first wavelength region that was not diffracted at a certain position of the second diffracting optical element 31 is then reflected (preferably total reflection) on the surfaces of the second diffracting optical element 31 and the base material 11 and again. It is incident on another position of the second diffraction optical element 31.

The thickness of the second diffractive optical element 31 is preferably thinner than the thickness of the first diffractive optical element 21. In this case, the diffraction efficiency of the second diffraction optical element 31 can be made lower than the diffraction efficiency of the first diffraction optical element 21. Specifically, the thickness of the second diffraction optical element 31 is preferably 14 μm or less, more preferably 8 μm or less, further preferably 4 μm or less, and most preferably 2 μm or less. ..

The diffraction efficiency of the second diffraction optical element 31 is diffracted by the second diffraction optical element 31 before the light in the first wavelength region traveling in the first direction d1 passes through the position where the second diffraction optical member 30 is provided. Is set to. Specifically, the diffraction efficiency of the second diffraction optical element 31 is determined in consideration of the thickness of the base material 11, the length of the second diffraction optical member 30 along the first direction d1, and the like. Further, the diffraction efficiency in a certain region having a unit area of the second diffraction optical element 31 is the unit area of the second diffraction optical element 31 separated from the first diffraction optical member 20 along the first direction d1 from the region. It is lower than the diffraction efficiency in one other region. That is, the diffraction efficiency in one region having a unit area of the second diffraction optical element 31 is a distance longer than the distance between the first diffraction optical member 20 and the one region along the first direction d1. It is lower than the diffraction efficiency in one other region having a unit area of the second diffraction optical element 31 separated from the first diffraction optical member 20 in the first direction d1. More preferably, the diffraction efficiency in an arbitrary region having a unit area of the second diffraction optical element 31 of the second diffraction optical element 31 separated from the first diffraction optical member 20 along the first direction d1 from the region. It is lower than the diffraction efficiency in any other region having a unit area. That is, the diffraction efficiency in an arbitrary region having a unit area of the second diffraction optical element 31 is a distance longer than the distance between the first diffraction optical member 20 and the region along the first direction d1. It is lower than the diffraction efficiency in any other region having a unit area of the second diffraction optical element 31 separated from the member 20 in the first direction d1. In other words, the diffraction efficiency per unit area of the second diffractive optical element 31 increases as it is separated from the first diffractive optical member 20 along the first direction d1.

The size of the unit area is such that the characteristics such as diffraction efficiency and the tendency of the configuration of the diffraction optical member can be understood, and for example, the size includes a plurality of flat portions of the diffraction optical element described later. Is. Specifically, the size of the unit area, for example, 0.0001 mm ² or more 25 mm ² or less, preferably 0.001 mm ² or more 9 mm ² or less, more preferably 0.01 mm ² or more 4 mm ² or less, more preferably 0. It may be 1 mm ² or more 1 mm ² or less. Further, the region having a unit area is preferably circular or square.

For example, as shown in FIG. 2, the second diffraction optical element 31 has a second diffraction grating 31a on which the second diffraction grating is formed and a second flat portion 31b which is a non-formation portion of the second diffraction grating. Includes. That is, the second diffracting portion 31a can diffract the light in the first wavelength region incident from the first direction d1, but the second flat portion 31b reflects the light on the surface without diffracting the light (preferably). Total reflection). Then, the ratio of the second diffraction unit 31a in a certain region having a unit area of the second diffraction optical element 31, preferably an arbitrary region, is separated from the first diffraction optical member 20 along the first direction d1 from the region. It is lower than the ratio of the second diffraction unit 31a in a certain other region having a unit area of the second diffraction optical element 31, preferably any other region. Conversely, the ratio of the second flat portion 31b in a certain region having a unit area of the second diffractive optical element 31, preferably an arbitrary region, is the ratio of the first diffractive optical member along the first direction d1 from the region. It is higher than the proportion of the second flat portion 31b in one other region, preferably any other region, having a unit area of the second diffractive optical element 31 separated from 20. For example, in this way, the above-mentioned diffraction efficiency of the second diffraction optical element 31 can be realized.

More specifically, for example, as shown in FIG. 2, in the second diffraction optical member 30, the second diffraction portion 31a and the second flat portion 31b of the second diffraction optical element 31 alternately alternate in the first direction d1. Have been placed. The width of the second flat portion 31b along the first direction d1 is, for example, 1 μm or more and 2 mm or less. The width of the second flat portion 31b along the first direction d1 is constant, but the width of the second diffraction portion 31a along the first direction d1 is separated from the first diffraction optical member 20 along the first direction d1. It gets bigger as you do. In this way, the ratio of the second diffraction unit 31a in a certain region having the unit area of the second diffraction optical element 31 is separated from the first diffraction optical member 20 along the first direction d1 from the region. It can be lower than the ratio of the second diffractive portion 31a in a certain other region having the unit area of the diffractive optical element 31.

The fourth diffracting optical member 50 diffracts the light in the second wavelength region diffracted by the fifth diffracting optical element 22 among the light diffracted by the first diffracting optical member 20. The fourth diffractive optical member 50 is an expansion portion different from the second diffraction optical member 30 and is provided in the expansion portion of the optical member 10 that expands the image light in the second direction d2. The fourth diffraction optical member 50 has a longitudinal direction in the second direction d2. The fourth diffractive optical member 50 includes a fourth diffractive optical element 51.

The fourth diffracting optical element 51 diffracts the light in the second wavelength region diffracted by the fifth diffracting optical element 22. In other words, the fourth diffraction optical element 51 has a diffraction characteristic of diffracting light in the second wavelength region traveling in the second direction d2 in the base material 11. The fourth diffraction optical element 51 includes a fourth diffraction grating that diffracts light in the second wavelength region. The fourth diffraction grating is formed by the difference in the refractive index of the material in the fourth diffraction optical element 51. That is, in the fourth diffraction optical element 51, there is a difference in refractive index so as to form the fourth diffraction grating. The fourth diffractive optical element 51 diffracts the light in the second wavelength region incident on the fourth diffractive optical member 50 from the second direction d2 by the fourth diffraction grating so as to go toward the first direction d1. The light in the second wavelength region toward the first direction d1 is guided in the base material 11.

The diffraction efficiency of the fourth diffraction optical element 51 is lower than the diffraction efficiency of the fifth diffraction optical element 22. Therefore, for example, only a part of the light in the second wavelength region incident on the position of the fourth diffraction optical element 51 is diffracted, and the inside of the base material 11 is guided in the first direction d1. However, the second diffraction optical member 30 has a longitudinal direction in the first direction d1. Therefore, the light in the second wavelength region that was not diffracted at a certain position of the fourth diffracting optical element 51 is then reflected (preferably total reflection) on the surfaces of the fourth diffracting optical element 51 and the base material 11 and again. It is incident on another position of the fourth diffraction optical element 51.

The thickness of the fourth diffractive optical element 51 is preferably thinner than the thickness of the fifth diffractive optical element 22. In this case, the diffraction efficiency of the fourth diffraction optical element 51 can be made lower than the diffraction efficiency of the fifth diffraction optical element 22. Specifically, the thickness of the fourth diffraction optical element 51 is preferably 14 μm or less, more preferably 8 μm or less, further preferably 4 μm or less, and most preferably 2 μm or less. ..

The diffraction efficiency of the fourth diffraction optical element 51 is diffracted by the fourth diffraction optical element 51 before the light in the second wavelength region traveling in the second direction d2 passes through the position where the fourth diffraction optical member 50 is provided. Is set to. Specifically, the diffraction efficiency of the fourth diffraction optical element 51 is determined in consideration of the thickness of the base material 11, the length of the fourth diffraction optical member 50 along the second direction d2, and the like. Further, the diffraction efficiency in a certain region having a unit area of the fourth diffraction optical element 51 is the unit area of the fourth diffraction optical element 51 separated from the first diffraction optical member 20 along the second direction d2 from the region. It is lower than the diffraction efficiency in one other region. That is, the diffraction efficiency in a certain region having a unit area of the fourth diffractive optical element 51 is a distance longer than the distance between the first diffractive optical member 20 and the one region along the second direction d2. It is lower than the diffraction efficiency in one other region having a unit area of the fourth diffraction optical element 51 separated from the first diffraction optical member 20 in the second direction d2. More preferably, the diffraction efficiency in an arbitrary region having a unit area of the fourth diffractive optical element 51 of the fourth diffractive optical element 51 separated from the first diffractive optical member 20 along the second direction d2 from the region. It is lower than the diffraction efficiency in any other region having a unit area. That is, the diffraction efficiency in an arbitrary region having a unit area of the fourth diffractive optical element 51 is a distance longer than the distance between the first diffractive optical member 20 and the region along the second direction d2. It is lower than the diffraction efficiency in any other region having a unit area of the fourth diffraction optical element 51 separated from the member 20 in the second direction d2. In other words, the diffraction efficiency per unit area of the fourth diffractive optical element 51 increases as it is separated from the first diffractive optical member 20 along the second direction d2.

For example, as shown in FIG. 2, the fourth diffraction optical element 51 has a fourth diffraction grating 51a on which the fourth diffraction grating is formed and a fourth flat portion 51b which is a non-formation portion of the fourth diffraction grating. Includes. That is, the fourth diffracting portion 51a can diffract the light in the second wavelength region incident from the second direction d2, but the fourth flat portion 51b reflects the light on the surface without diffracting the light (preferably). Total reflection). Then, the ratio of the fourth diffraction unit 51a in a certain region having a unit area of the fourth diffraction optical element 51, preferably an arbitrary region, is separated from the first diffraction optical member 20 along the second direction d2 from the region. It is lower than the ratio of the fourth diffraction unit 51a in a certain other region having a unit area of the fourth diffraction optical element 51, preferably any other region. Conversely, the ratio of the fourth flat portion 51b in a certain region having a unit area of the fourth diffractive optical element 51, preferably an arbitrary region, is the ratio of the first diffractive optical member along the second direction d2 from the region. It is higher than the proportion of the fourth flat portion 51b in one other region, preferably any other region, having a unit area of the fourth diffractive optical element 51 separated from 20. For example, in this way, the above-mentioned diffraction efficiency of the fourth diffraction optical element 51 can be realized.

More specifically, for example, as shown in FIG. 2, in the fourth diffraction optical member 50, the fourth diffraction portion 51a and the fourth flat portion 51b of the fourth diffraction optical element 51 alternately alternate in the second direction d2. Have been placed. The width of the fourth flat portion 51b along the second direction d2 is, for example, 1 μm or more and 2 mm or less. The sum of the width of the fourth diffraction section 51a along the second direction d2 and the width of the fourth flat portion 51b is constant, but the width of the fourth diffraction section 51a along the second direction d2 is the second direction d2. It becomes larger as it is separated from the first diffraction optical member 20 along the line. In this way, the ratio of the fourth diffraction unit 51a in a certain region having the unit area of the fourth diffraction optical element 51 is separated from the first diffraction optical member 20 along the second direction d2 from the region. It can be lower than the ratio of the fourth diffractive portion 51a in a certain other region having the unit area of the diffractive optical element 51.

The third diffracting optical member 40 diffracts the light in the first wavelength region diffracted by the second diffracting optical member 30 and the light in the second wavelength region diffracted by the fourth diffracting optical member 50 from the optical member 10. Make it emit. The third diffraction optical member 40 is provided at the exit portion of the optical member 10 that emits image light. The third diffraction optical member 40 is located in front of the observer of the optical member 10. The third diffraction optical member 40 extends in the first direction d1 and the second direction d2. As is well shown in FIGS. 3 and 4, the third diffractive optical member 40 includes a third diffractive optical element 41 and a sixth diffractive optical element 42.

The third diffracting optical element 41 diffracts the light in the first wavelength region diffracted by the second diffracting optical element 31. In other words, the third diffraction optical element 41 has a diffraction characteristic of diffracting light in the first wavelength region traveling in the second direction d2 in the base material 11. The third diffraction optical element 41 includes a third diffraction grating that diffracts light in the first wavelength region. The third diffraction grating is formed by the difference in the refractive index of the material in the third diffraction optical element 41. That is, in the third diffraction optical element 41, there is a difference in refractive index so as to form the third diffraction grating. The third diffractive optical element 41 diffracts the light in the first wavelength region incident on the third diffractive optical member 40 from the second direction d2 by the third diffraction grating so as to be emitted from the optical member 10.

The diffraction efficiency of the third diffraction optical element 41 is lower than the diffraction efficiency of the first diffraction optical element 21. Therefore, for example, only a part of the light in the first wavelength region incident on the position of the third diffracting optical element 41 is diffracted and emitted from the optical member 10. However, the third diffraction optical member 40 extends in the second direction d2. Therefore, the light in the first wavelength region that was not diffracted at a certain position of the third diffracting optical element 41 is then reflected (preferably total reflection) on the surfaces of the third diffracting optical element 41 and the base material 11 and again. It is incident on another position of the third diffraction optical element 41.

The thickness of the third diffractive optical element 41 is preferably thinner than the thickness of the first diffractive optical element 21. In this case, the diffraction efficiency of the third diffraction optical element 41 can be made lower than the diffraction efficiency of the first diffraction optical element 21. Specifically, the thickness of the third diffraction optical element 41 is preferably 14 μm or less, more preferably 8 μm or less, further preferably 4 μm or less, and most preferably 2 μm or less. ..

The diffraction efficiency of the third diffraction optical element 41 is diffracted by the third diffraction optical element 41 before the light in the first wavelength region traveling in the second direction d2 passes through the position where the third diffraction optical member 40 is provided. Is set to. Specifically, the diffraction efficiency of the third diffraction optical element 41 is determined in consideration of the thickness of the base material 11, the length of the third diffraction optical member 40 along the second direction d2, and the like. Further, the diffraction efficiency in a certain region having a unit area of the third diffraction optical element 41 is the unit area of the third diffraction optical element 41 separated from the second diffraction optical member 30 along the second direction d2 from the region. It is lower than the diffraction efficiency in one other region. That is, the diffraction efficiency in one region having a unit area of the third diffraction optical element 41 is a distance longer than the distance between the second diffraction optical member 30 and the one region along the second direction d2. It is lower than the diffraction efficiency in one other region having a unit area of the third diffraction optical element 41 separated from the second diffraction optical member 30 in the second direction d2. More preferably, the diffraction efficiency in an arbitrary region having a unit area of the third diffractive optical element 41 of the third diffractive optical element 41 separated from the second diffractive optical member 30 along the second direction d2 from the region. It is lower than the diffraction efficiency in any other region having a unit area. That is, the diffraction efficiency in an arbitrary region having a unit area of the third diffractive optical element 41 is longer than the distance between the second diffractive optical member 30 and the region along the second direction d2. It is lower than the diffraction efficiency in any one other region having a unit area of the third diffraction optical element 41 separated from the member 30 in the second direction d2. In other words, the diffraction efficiency per unit area of the third diffractive optical element 41 increases as it is separated from the second diffractive optical member 30 along the second direction d2.

For example, as shown in FIG. 2, the third diffraction optical element 41 has a third diffraction grating 41a on which the third diffraction grating is formed and a third flat portion 41b which is a non-formation portion of the third diffraction grating. Includes. That is, the third diffracting portion 41a can diffract the light in the first wavelength region incident from the second direction d2, but the third flat portion 41b reflects the light on the surface without diffracting the light (preferably). Total reflection). Then, the ratio of the third diffraction unit 41a in a certain region having a unit area of the third diffraction optical element 41, preferably an arbitrary region, is separated from the second diffraction optical member 30 along the second direction d2 from the region. It is lower than the ratio of the third diffraction unit 41a in a certain other region having a unit area of the third diffraction optical element 41, preferably any other region. Conversely, the ratio of the third flat portion 41b in a certain region having a unit area of the third diffractive optical element 41, preferably an arbitrary region, is the ratio of the second diffractive optical member along the second direction d2 from the region. It is higher than the proportion of the third flat portion 41b in one other region, preferably any other region, having a unit area of the third diffractive optical element 41 separated from 30. For example, in this way, the above-mentioned diffraction efficiency of the third diffraction optical element 41 can be realized.

More specifically, for example, as shown in FIG. 2, in the third diffraction optical member 40, the third diffraction portion 41a and the third flat portion 41b of the third diffraction optical element 41 alternately alternate in the second direction d2. Have been placed. The width of the third flat portion 41b along the second direction d2 is, for example, 1 μm or more and 2 mm or less. The sum of the width of the third diffracting portion 41a along the second direction d2 and the width of the third flat portion 41b is constant, but the width of the third diffracting portion 41a along the second direction d2 is the second direction d2. It becomes larger as it is separated from the second diffraction optical member 30 along the line. In this way, the ratio of the third diffraction unit 41a in a certain region having the unit area of the third diffraction optical element 41 is separated from the second diffraction optical member 30 along the second direction d2 from the region. It can be lower than the ratio of the third diffractive portion 41a in a certain other region having the unit area of the diffractive optical element 41.

The sixth diffracting optical element 42 diffracts the light in the second wavelength region diffracted by the fourth diffracting optical element 51. In other words, the sixth diffractive optical element 42 has a diffraction characteristic of diffracting light in the second wavelength region traveling in the first direction d1 in the base material 11. The sixth diffraction optical element 42 includes a sixth diffraction grating that diffracts light in the second wavelength region. The sixth diffraction grating is formed by the difference in the refractive index of the material in the sixth diffraction optical element 42. That is, in the sixth diffraction optical element 42, there is a difference in refractive index so as to form the sixth diffraction grating. The sixth diffraction optical element 42 diffracts the light in the second wavelength region incident on the third diffraction optical member 40 from the first direction d1 by the sixth diffraction grating so as to be emitted from the optical member 10.

The diffraction efficiency of the sixth diffraction optical element 42 is lower than the diffraction efficiency of the fifth diffraction optical element 22. Therefore, for example, only a part of the light in the second wavelength region incident on the position of the sixth diffracting optical element 42 is diffracted and emitted from the optical member 10. However, the third diffraction optical member 40 extends in the first direction d1. Therefore, the light in the second wavelength region that was not diffracted at a certain position of the sixth diffracting optical element 42 is then reflected (preferably total reflection) on the surfaces of the sixth diffracting optical element 42 and the base material 11 and again. It is incident on another position of the sixth diffraction optical element 42.

The thickness of the sixth diffractive optical element 42 is preferably thinner than the thickness of the fifth diffractive optical element 22. In this case, the diffraction efficiency of the sixth diffraction optical element 42 can be made lower than the diffraction efficiency of the fifth diffraction optical element 22. Specifically, the thickness of the sixth diffraction optical element 42 is preferably 14 μm or less, more preferably 8 μm or less, further preferably 4 μm or less, and most preferably 2 μm or less. ..

The diffraction efficiency of the sixth diffraction optical element 42 is diffracted by the sixth diffraction optical element 42 before the light in the second wavelength region traveling in the first direction d1 passes through the position where the third diffraction optical member 40 is provided. Is set to. Specifically, the diffraction efficiency of the sixth diffraction optical element 42 is determined in consideration of the thickness of the base material 11, the length of the third diffraction optical member 40 along the first direction d1, and the like. Further, the diffraction efficiency in a certain region having a unit area of the sixth diffractive optical element 42 is the unit area of the sixth diffractive optical element 42 separated from the fourth diffractive optical member 50 along the first direction d1 from the region. It is lower than the diffraction efficiency in one other region. That is, the diffraction efficiency in one region having a unit area of the sixth diffraction optical element 42 is a distance longer than the distance between the fourth diffraction optical member 50 and the one region along the first direction d1. It is lower than the diffraction efficiency in one other region having a unit area of the sixth diffraction optical element 42 separated from the fourth diffraction optical member 50 in the first direction d1. More preferably, the diffraction efficiency in an arbitrary region having a unit area of the sixth diffractive optical element 42 of the sixth diffractive optical element 42 separated from the fourth diffractive optical member 50 along the first direction d1 from the region. It is lower than the diffraction efficiency in any other region having a unit area. That is, the diffraction efficiency in an arbitrary region having a unit area of the sixth diffractive optical element 42 is longer than the distance between the fourth diffractive optical member 50 and the region along the first direction d1. It is lower than the diffraction efficiency in any one other region having a unit area of the sixth diffraction optical element 42 separated from the member 50 in the first direction d1. In other words, the diffraction efficiency per unit area of the sixth diffractive optical element 42 increases as it is separated from the fourth diffractive optical member 50 along the first direction d1.

For example, as shown in FIG. 2, the sixth diffraction optical element 42 has a sixth diffraction grating 42a on which the sixth diffraction grating is formed and a sixth flat portion 42b which is a non-formation portion of the sixth diffraction grating. Includes. That is, the sixth diffracting portion 42a can diffract the light in the second wavelength region incident from the first direction d1, but the sixth flat portion 42b reflects the light on the surface without diffracting the light (preferably). Total reflection). Then, the ratio of the sixth diffractive portion 42a in a certain region having a unit area of the sixth diffractive optical element 42, preferably an arbitrary region, is separated from the fourth diffractive optical member 50 along the first direction d1 from the region. It is lower than the ratio of the sixth diffracting portion 42a in a certain other region having a unit area of the sixth diffracting optical element 42, preferably any other region. Conversely, the ratio of the sixth flat portion 42b in a certain region having a unit area of the sixth diffractive optical element 42, preferably an arbitrary region, is the fourth diffractive optical member along the first direction d1 from the region. It is higher than the proportion of the sixth flat portion 42b in one other region, preferably any other region, having a unit area of the sixth diffractive optical element 42 separated from 50. For example, in this way, the above-mentioned diffraction efficiency of the sixth diffraction optical element 42 can be realized.

More specifically, for example, as shown in FIG. 2, in the third diffraction optical member 40, the sixth diffraction portion 42a and the sixth flat portion 42b of the sixth diffraction optical element 42 alternately alternate in the first direction d1. Have been placed. The width of the sixth flat portion 42b along the first direction d1 is, for example, 1 μm or more and 2 mm or less. The width of the sixth flat portion 42b along the first direction d1 is constant, but the width of the sixth diffraction portion 42a along the first direction d1 is separated from the fourth diffraction optical member 50 along the first direction d1. It gets bigger as you do. In this way, the ratio of the sixth diffractive portion 42a in a certain region having the unit area of the sixth diffractive optical element 42 is separated from the fourth diffractive optical member 50 along the first direction d1 from the region. It can be lower than the ratio of the sixth diffractive portion 42a in a certain other region having the unit area of the diffractive optical element 42.

Not limited to the illustrated example, in the second diffraction optical member 30, the total of the width of the second diffraction section 31a and the width of the second flat portion 31b is constant, but the first of the second diffraction section 31a. The width along the direction d1 may increase as the distance from the first diffraction optical member 20 along the first direction d1. Further, in the third diffraction optical member 40, the total of the width of the sixth diffraction portion 42a and the width of the sixth flat portion 42b is constant, but the width of the sixth diffraction portion 42a along the first direction d1 is the first. It may become larger as it is separated from the fourth diffraction optical member 50 along the one direction d1. Similarly, in the fourth diffraction optical member 50, the width of the fourth flat portion 51b along the second direction d2 is constant, but the width of the fourth diffraction portion 51a along the second direction d2 is the second direction d2. It may become larger as it is separated from the first diffraction optical member 20 along the line. Further, in the third diffraction optical member 40, the width of the third flat portion 41b along the second direction d2 is constant, but the width of the third diffraction portion 41a along the second direction d2 becomes the second direction d2. It may become larger as it is separated from the second diffraction optical member 30 along the line. Alternatively, the proportion of the diffractive portion in the region having the unit area of each diffractive optical element may be changed depending on other aspects.

The first diffraction optical element 21, the second diffraction optical element 31, the third diffraction optical element 41, the fourth diffraction optical element 51, the fifth diffraction optical element 22, and the sixth diffraction optical element 42 are typically holograms. can do. The first to sixth diffraction optical elements may be a phase type hologram or an amplitude type hologram. Further, the first to sixth diffraction optical elements may be a reflection type hologram or a transmission type hologram. Further, the first to sixth diffraction optical elements may be volumetric holograms or computer-generated holograms (CGH). In particular, the second diffraction optical element 31, the third diffraction optical element 41, the fourth diffraction optical element 51, and the sixth diffraction optical element 42 are preferably volume holograms. In the examples shown in FIGS. 3 and 4, the first diffraction optical element 21, the second diffraction optical element 31, the third diffraction optical element 41, the fourth diffraction optical element 51, the fifth diffraction optical element 22, and the sixth diffraction element. The optical element 42 is a reflective volume hologram.

In the examples shown in FIGS. 3 and 4, the first diffraction optical member 20, the second diffraction optical member 30, the third diffraction optical member 40, and the fourth diffraction optical member 50 are provided on the same side of the base material 11. ing. However, these may be provided on one side of the base material 11 and on any side of the other side, respectively. Alternatively, for example, the first diffraction optical member 20 may be provided on both one side and the other side of the base material 11. The diffractive optical element provided on one side of the base material 11 on which the image light is incident becomes a reflective hologram, and the diffractive optical element provided on the other side of the base material 11 becomes a transmissive hologram. ..

Further, as in the illustrated example, when the first diffraction optical member 20, the second diffraction optical member 30, the third diffraction optical member 40, and the fourth diffraction optical member 50 are formed on the surface of the optical member 10. The first to fourth diffraction optical members guide light together with the base material 11. In order to completely reflect light on the surface of the first to fourth diffractive optical members, the refractive indexes of the first diffracted optical member 20, the second diffracted optical member 30, the third diffracted optical member 40 and the fourth diffracted optical member 50 are set. , It is preferable that the refractive index is sufficiently larger than the refractive index of air or the like outside the optical member 10. Specifically, the refractive index of the first diffraction optical member 20, the second diffraction optical member 30, the third diffraction optical member 40, and the fourth diffraction optical member 50 is preferably 1.50 or more, preferably 1.55. The above is more preferable, 1.6 or more is more preferable, 1.7 or more is even more preferable, and 1.8 or more is most preferable.

Next, an example of a method for manufacturing the optical member 10 will be described with reference to FIGS. 5 to 9.

First, as shown in FIG. 5, a hologram sensitive material 80 for forming a diffractive optical element as a hologram is provided on the base material 11. In the illustrated example, a hologram sensitive material is provided on one side of the base material 11. As the hologram sensitive material 80, various known replica hologram sensitive materials such as silver salt emulsion and gelatin dichromate can be used. When the hologram sensitive material 80 is exposed, interference fringes due to the exposure light can be recorded.

Next, as shown in FIG. 6, the mask 60 is arranged so as to face the hologram sensitive material 80 on the base material 11. The mask 60 has a portion corresponding to each diffraction optical member of the manufactured optical member 10. That is, the mask 60 has a first portion 62, a second portion 63 displaced from the first portion 62 in the first direction d1, and a third portion 64 displaced from the second portion 63 in the second direction d2. And a fourth portion 65, which is located offset from the first portion 62 in the second direction d2. The mask 60 has openings 61 in the second portion 63, the third portion 64, and the fourth portion 65. The mask 60 blocks light in a portion where the opening 61 is not provided, but transmits light in the opening 61.

The opening 61 is provided corresponding to a flat portion in each diffractive optical element of the manufactured optical member 10. That is, the proportion of the opening 61 in a region having a unit area of the second portion 63, preferably an arbitrary region, is that of the second portion 63 separated from the first portion 62 along the first direction d1 from the region. It is higher than the proportion of openings 61 in one other region, preferably any other region, having a unit area. The proportion of the opening 61 in a region, preferably an arbitrary region, having a unit area of the third portion 64 is the unit area of the third portion 64 separated from the second portion 63 along the second direction d2 from the region. Another region having a unit area of a third portion 64 that is higher than the proportion of the opening 61 in another region and has a unit area of the third portion 64 that is separated from the fourth portion 65 along the first direction d1 from the region. It is higher than the proportion of openings 61 in the area. The proportion of the opening 61 in a region, preferably an arbitrary region, having a unit area of the fourth portion 65 is the unit area of the fourth portion 65 separated from the first portion 62 along the second direction d2 from the region. It is higher than the proportion of the opening 61 in one other area having. The width of the opening 61 in the second portion 63 along the first direction d1, the width of the openings 61 arranged along the first direction d1 in the third portion 64, along the first direction d1, the third portion 64. The width of the openings 61 arranged along the second direction d2 along the second direction d2 and the width of the openings 61 along the second direction d2 in the fourth portion 65 are, for example, 1 μm or more and 2 mm or less. is there.

Next, as shown in FIG. 7, light L7 is irradiated through the mask 60 to expose the hologram sensitive material 80. FIG. 7 is a part of a cross section taken along the line VII-VII of FIG. That is, the hologram sensitive material 80 is exposed at a position facing the portion of the mask 60 where the opening 61 is not provided. Here, the hologram sensitive material 80 irradiated with the light L7 does not form a hologram even if it is later irradiated with light for forming a hologram. That is, the hologram sensitive material 80 is desensitized. The light L7 that irradiates the hologram sensitive material 80 is preferably ultraviolet rays in order to reliably desensitize the hologram sensitive material 80 in a short time. As shown in FIG. 8, the desensitized hologram sensitive material 80 becomes a flat portion of each diffractive optical element.

After that, the mask 60 is removed, and then, as shown in FIG. 9, the hologram original plate 85 is arranged on the side opposite to the side where the hologram sensitive material 80 of the base material 11 is provided, and is irradiated with light, particularly parallel light flux. The hologram sensitive material 80 is exposed. The irradiated light L91 is incident on the hologram sensitive material 80 as reference light, and the diffracted light L92 once transmitted through the hologram sensitive material 80 and diffracted by the hologram original plate 85 is used as object light. When the light L91 and the diffracted light L92 interfere with each other, interference fringes, which are light and dark patterns, are generated in the hologram sensitive material 80. Then, the interference fringes are recorded on the hologram sensitive material 80 having photosensitivity. By recording the interference fringes on the hologram sensitive material 80 in this way, a diffraction grating is formed. The portion where the diffraction grating is formed becomes the diffraction portion of each diffraction optical element. In this way, a diffractive optical element as a hologram is formed on the base material 11, and the optical member 10 is manufactured.

Next, the operations of the head-mounted display device 1 and the optical member 10 will be described with reference to FIG. FIG. 10 shows a cross-sectional view of the optical member 10 shown in FIG. 3 in which light in the first wavelength region incident from the display unit 5 is displayed in front of the observer's eyes.

First, the display unit 5 emits image light which is diffused light. The emitted image light includes light in the first wavelength region and light in the second wavelength region. Typically, the image light includes light in the red wavelength region, light in the green wavelength region, and light in the blue wavelength region. The first wavelength region includes a blue light wavelength region and a red wavelength region or a green wavelength region. The second wavelength region includes a wavelength region that is not included in the first wavelength region among the red wavelength region and the green wavelength region.

The image light emitted from the display unit 5 is incident on the lens 7. As shown in FIG. 10, the image light emitted from each position of the display unit 5 by the lens 7 becomes light traveling in a direction substantially parallel to the diffused light at each emission position. In the example shown in FIG. 10, the image light emitted from the vicinity of the center of the display unit 5 and the image light emitted from the vicinity of the peripheral edge of the display unit 5 are formed on the optical member 10 at different angles depending on the lens 7. The light travels in a direction that is approximately parallel to the incident. The substantially parallel image light is incident on the first diffraction optical member 20 of the optical member 10.

Of the image light incident on the first diffracting optical member 20, as shown in FIG. 10, the light in the first wavelength region is diffracted by the first diffracting optical element 21. On the other hand, the light in the second wavelength region (not shown) is diffracted by the fifth diffracting optical element 22. The light in the first wavelength region diffracted by the first diffracting optical element 21 travels in the base material 11 in the first direction d1 and heads toward the second diffracting optical member 30. The light in the second wavelength region diffracted by the fifth diffracting optical element 22 travels in the base material 11 in the second direction d2 and heads toward the fourth diffracting optical member 50. The light traveling in the base material 11 is totally reflected by a pair of main surfaces of the base material 11 or a diffractive optical member provided on the base material 11, so that the light is guided in the base material 11.

As shown in FIG. 10, the light in the first wavelength region diffracted by the first diffracting optical element 21 of the first diffracting optical member 20 is incident on the second diffracting optical member 30. The light in the first wavelength region incident on the second diffracting optical member 30 is diffracted by the second diffracting optical element 31. The light diffracted by the second diffractive optical element 31 is guided through the base material 11 in the second direction d2 and directed toward the third diffractive optical member 40. Since the diffraction efficiency of the second diffraction optical element 31 is lower than the diffraction efficiency of the first diffraction optical element 21, only a part of the light in the first wavelength region incident on the position of the second diffraction optical element 31 is used. Is diffracted and guided in the base material 11 in the second direction d2. The light that is not diffracted at a certain position of the second diffracting optical element 31 is then reflected by the surfaces of the second diffracting optical element 31 and the base material 11 and is incident on another position of the second diffracting optical element 31 again.

The light in the second wavelength region diffracted by the fifth diffracting optical element 22 of the first diffracting optical member 20 (not shown) is incident on the fourth diffracting optical member 50. The light in the second wavelength region incident on the fourth diffracting optical member 50 is diffracted by the fourth diffracting optical element 51. The light diffracted by the fourth diffractive optical element 51 is directed to the third diffractive optical member 40 guided in the first direction d1 in the base material 11. Since the diffraction efficiency of the 4th diffraction optical element 51 is lower than the diffraction efficiency of the 5th diffraction optical element 22, only a part of the light in the second wavelength region incident on the position of the 4th diffraction optical element 51 is used. Is diffracted and guided in the base material 11 in the first direction d1. The light that is not diffracted at a certain position of the fourth diffractive optical element 51 is then reflected by the surfaces of the fourth diffracted optical element 51 and the base material 11 and is incident on another position of the fourth diffracted optical element 51 again.

As shown in FIG. 10, the light in the first wavelength region incident on the third diffracting optical member 40 is diffracted by the third diffracting optical element 41. The light diffracted by the third diffracting optical element 41 is emitted from the optical member 10. On the other hand, the light in the second wavelength region (not shown) incident on the third diffracting optical member 40 is diffracted by the sixth diffracting optical element 42. The light diffracted by the sixth diffracting optical element 42 is emitted from the optical member 10. The diffraction efficiency of the third diffraction optical element 41 is lower than the diffraction efficiency of the first diffraction optical element 21, and the diffraction efficiency of the sixth diffraction optical element 42 is lower than the diffraction efficiency of the fifth diffraction optical element 22. It has become. Therefore, only a part of the light incident on the position of the third diffraction optical element 41 and the sixth diffraction optical element 42 is diffracted and emitted from the optical member 10. The light that was not diffracted at a certain position of the third diffracting optical element 41 and the sixth diffracting optical element 42 is then reflected on the surfaces of the third diffracting optical element 41 and the sixth diffracting optical element 42, and is again reflected in the third diffracting optical It is incident on the element 41 and the sixth diffraction optical element 42.

The light emitted from the optical member 10 can be observed by the observer. That is, the observer can visually recognize the image displayed on the display device 3. In particular, in the head-mounted display device 1, the optical member 10 of the display device 3 is arranged in front of the observer's eyes. Therefore, the observer can visually recognize the displayed image in front of the eyes.

By the way, in the conventional optical member, the diffraction efficiency of each diffractive optical element in the expanding portion and the emitting portion is substantially constant as in the incident portion. When a part of the image light is diffracted in the extension portion, the image light is reduced by the amount of diffraction at the position separated from the incident portion from the position where the image light is diffracted. That is, the intensity of the image light decreases as the distance from the incident portion increases in the expansion portion. Similarly, when a part of the image light is diffracted in the emitting portion, the image light is reduced by the amount of diffraction at the position separated from the expansion portion from the position where the image light is diffracted. That is, the intensity of the image light decreases as the distance from the expansion portion increases at the emission portion. In this way, the intensity of the emitted image light becomes non-uniform depending on the position of the emitting portion. The stronger the intensity of the image light, the brighter the image is visually recognized. That is, the brightness of the image emitted from the emitting portion of the optical member and observed by the observer becomes non-uniform. If the brightness becomes non-uniform, the quality of the image due to the image light emitted from the optical member is deteriorated.

On the other hand, in the optical member 10 of the present embodiment, the second diffraction optical element 31 is included in the second diffraction optical member 30 provided in the expansion portion, and has a unit area of the second diffraction optical element 31. The diffraction efficiency in a certain region is lower than the diffraction efficiency in another region having a unit area of the second diffraction optical element 31 separated from the first diffraction optical member 20 along the first direction d1 from the region. .. Therefore, another part of the second diffractive optical element 31 in which the intensity of the image light diffracted in a certain region of the second diffractive optical element 31 is separated from the first diffractive optical member 20 along the first direction d1 from the region. The intensity of the image light diffracted in the region can be approached. Further, the third diffraction optical element 41 is included in the third diffraction optical member 40 provided in the exit portion, and the diffraction efficiency in a certain region having a unit area of the third diffraction optical element 41 is higher than that of the region. It is lower than the diffraction efficiency in a certain region having a unit area of the third diffractive optical element 41 separated from the second diffractive optical member 30 along the second direction d2. Therefore, another part of the third diffractive optical element 41 in which the intensity of the image light diffracted in a certain region of the third diffractive optical element 41 is separated from the second diffractive optical member 30 along the second direction d2 from the region. The intensity of the image light diffracted in the region can be approached. That is, the intensity of the image light emitted from the third diffractive optical element 41 can be made uniform. Therefore, the brightness of the image light emitted from the optical member 10 can be made uniform.

Similarly, the fourth diffraction optical element 51 is included in the fourth diffraction optical member 50 provided in the expansion portion, and the diffraction efficiency in a certain region having a unit area of the fourth diffraction optical element 51 is the region. It is lower than the diffraction efficiency in a certain region having a unit area of the fourth diffractive optical element 51 separated from the first diffractive optical member 20 along the second direction d2. Therefore, there is another fourth diffractive optical element 51 in which the intensity of the image light diffracted in a certain region of the fourth diffractive optical element 51 is separated from the first diffractive optical member 20 along the second direction d2 from the region. The intensity of the image light diffracted in the region can be approached. Further, the sixth diffraction optical element 42 is included in the third diffraction optical member 40 provided at the exit portion, and the diffraction efficiency in a certain region having a unit area of the sixth diffraction optical element 42 is higher than that of the region. It is lower than the diffraction efficiency in a certain region having a unit area of the sixth diffractive optical element 42 separated from the fourth diffractive optical member 50 along the first direction d1. Therefore, the intensity of the image light diffracted in a certain region of the sixth diffractive optical element 42 is separated from the fourth diffractive optical member 50 along the first direction d1 from the region, another of the sixth diffractive optical element 42. The intensity of the image light diffracted in the region can be approached. That is, the intensity of the image light emitted from the sixth diffraction optical element 42 can be made uniform. Therefore, the brightness of the image light emitted from the optical member 10 can be made uniform.

Further, the diffraction efficiency in an arbitrary region having a unit area of the second diffraction optical element 31 is the unit area of the second diffraction optical element 31 separated from the first diffraction optical member 20 along the first direction d1 from the region. It is lower than the diffraction efficiency in any other region having. Therefore, the intensity of the image light diffracted in an arbitrary region of the second diffracting optical element 31 is separated from the first diffracting optical member 20 along the first direction d1 from the region, and is arbitrarily separated from the second diffracting optical element 31. It is possible to approach the intensity of the image light diffracted in another region. Further, the diffraction efficiency in an arbitrary region having a unit area of the third diffraction optical element 41 is the unit area of the third diffraction optical element 41 separated from the second diffraction optical member 30 along the second direction d2 from the region. It is lower than the diffraction efficiency in any other region having. Therefore, the intensity of the image light diffracted in an arbitrary region of the third diffractive optical element 41 is separated from the second diffractive optical member 30 along the second direction d2 from the region, and is arbitrary in the third diffractive optical element 41. It is possible to approach the intensity of the image light diffracted in another region. That is, the intensity of the image light emitted from an arbitrary region of the third diffraction optical element 41 can be made uniform. Therefore, the brightness of the image light emitted from the entire emitting portion of the optical member 10 can be made uniform.

The diffraction efficiency of the first diffraction optical element 21 and the diffraction efficiency of the fifth diffraction optical element 22 are preferably in an appropriate range. For example, as shown in FIG. 11, the light diffracted by the first diffracting optical element 21 may be totally reflected by the main surface of the base material 11 and then incident on the first diffracting optical element 21 again. The light incident on the first diffracting optical element 21 again can be diffracted by the first diffracting optical element 21 again. The light diffracted by the first diffracting optical element 21 again does not go into the base material 11 and is emitted from the first diffracting optical member 20. Therefore, if the diffraction efficiency of the first diffraction optical element 21 is too high, it is likely to be diffracted by the first diffraction optical element 21 multiple times, and finally the first diffraction optical member 20 leads to the second diffraction optical member 30. Less light is shined. As confirmed by the inventors of the present invention, the light incident from the display unit 5 and diffracted by the first diffracting optical element 21 is totally reflected by the main surface of the base material 11 and then about 1 to 5 times, particularly. It was found that the light was incident on the first diffraction optical element 21 again four times.

FIG. 12 shows the relationship between the diffraction efficiency of the diffractive optical element and the number of times it is diffracted by the diffractive optical element and then incident on the diffractive optical element again. It is a table which shows the ratio of the light to be guided. That is, the ratio of the light guided from the first diffraction optical member 20 to the second diffraction optical member 30 when the light incident from the display unit 5 is 100% is shown. As can be seen from FIG. 12, when the number of times the diffraction optical element is diffracted once and then the diffraction optical element is incident again once or more, the diffraction efficiency of the diffraction optical element is preferably 50% or less. Further, when the number of times of being diffracted by the diffractive optical element and then incident on the diffractive optical element again is 3 times or more, the diffraction efficiency of the diffractive optical element is preferably 10% or more and 40% or less, and 10% or more and 30%. % Or less is more preferable. Further, when the number of times of being diffracted by the diffractive optical element and then incident on the diffractive optical element again is 4 times or more, the diffraction efficiency of the diffractive optical element is preferably 15% or more and 25% or less.

As described above, the optical member 10 of the present embodiment is laminated on the base material 11 and the base material 11, from the first diffractive optical member 20 including the first diffractive optical element 21 and the first diffractive optical member 20. The second diffractive optical member 30 which is laminated on the base material 11 at a position deviated from the first direction d1 and includes the second diffractive optical element 31, and the second diffractive optical member 30 which is non-parallel to the first direction d1. An optical member that is laminated on the base material 11 at a position deviated from d2 and includes a third diffractive optical member 40 including a third diffractive optical element 41, and the first diffractive optical element 21 is incident on the optical member. The light in the first wavelength region is diffracted toward the first direction d1, and the second diffraction optical element 31 diffracts the light in the first wavelength region incident from the first direction d1 toward the second direction d2. Then, the third diffractive optical element 41 diffracts the light in the first wavelength region incident from the second direction d2 so as to be emitted from the optical member, and in a certain region having a unit area of the second diffractive optical element 31. The diffraction efficiency is lower than the diffraction efficiency in a certain region having a unit area of the second diffractive optical element 31 separated from the first diffractive optical member 20 along the first direction d1 from the region, and the third diffractive optical element. The diffraction efficiency in one region having a unit area of 41 is in another region having a unit area of the third diffractive optical element 41 separated from the second diffractive optical member 30 along the second direction d2 from the region. It is lower than the diffraction efficiency. According to such an optical member 10, the intensity of the image light diffracted in a certain region of the second diffracting optical element 31 is separated from the first diffracting optical member 20 along the first direction d1 from the region. The intensity of the image light diffracted in a certain region of the diffractive optical element 31 can be approached, and the intensity of the image light diffracted in a certain region of the third diffracting optical element 41 is set in the second direction d2 from the region. It is possible to approach the intensity of the image light diffracted in another region of the third diffracting optical element 41 which is separated from the second diffracting optical member 30 along the line. That is, the intensity of the image light emitted from the third diffractive optical element 41 can be made uniform. Therefore, the brightness of the image light emitted from the optical member 10 can be made uniform.

It is possible to make various changes to the above-described embodiment.

In the above-described embodiment, the display device 3 is applied to the head-mounted display device 1, but the display device 3 is not limited to this, and may be applied to another member.

Further, in the above-described embodiment, as shown in FIG. 2, in the second diffraction optical member 30, the second diffraction portion 31a and the second flat portion 31b are the entire second diffraction optical element 31 in the second direction d2. Extends to. However, for example, as shown in FIG. 13, the second diffractive portion 31a and the second flat portion 31b may partially extend to the second diffractive optical element 31 in the second direction d2. Further, in the second diffraction optical member 30, the second diffraction optical element 31 is another second diffraction portion 31a and a second flat portion alternately arranged in the first direction d1 at deviated positions in the second direction d2. 31b may be included.

Similarly, in the above-described embodiment, as shown in FIG. 2, in the fourth diffraction optical member 50, the fourth diffraction portion 51a and the fourth flat portion 51b are the fourth diffraction optical element 51 in the first direction d1. It extends to the whole. However, for example, as shown in FIG. 13, the fourth diffractive portion 51a and the fourth flat portion 51b may partially extend to the fourth diffractive optical element 51 in the first direction d1. Further, in the fourth diffractive optical member 50, the fourth diffractive optical element 51 has another fourth diffractive portion 51a and a fourth flat portion alternately arranged in the second direction d2 at deviated positions in the first direction d1. 51b may be included.

Further, in the above-described embodiment, the diffraction efficiency of the second diffraction optical element 31, the diffraction efficiency of the third diffraction optical element 41, and the diffraction efficiency of the fourth diffraction optical element 51 are changed by changing the ratio of the diffraction portion and the flat portion. The diffraction efficiency and the diffraction efficiency of the sixth diffraction optical element 42 are changed. However, the diffraction efficiency of the diffractive optical element may be changed by another method. In the example shown in FIG. 14, the difference in refractive index forming the second diffraction grating in a certain region having a unit area of the second diffractive optical element 31, preferably an arbitrary region, is along the first direction d1 from the region. It is lower than the difference in refractive index forming the second diffraction grating in a certain other region having a unit area of the second diffractive optical element 31 separated from the first diffractive optical member 20, preferably any other region. In FIG. 14, a portion having a large difference in refractive index is shown dark, and a portion having a small difference in refractive index is shown lightly. The larger the difference in refractive index that forms the diffraction grating, the easier it is for light to be diffracted by the diffraction grating. Therefore, even in such a case, as in the above-described embodiment, the diffraction efficiency in a certain region, preferably an arbitrary region, having a unit area of the second diffraction optical element 31 is set to d1 in the first direction from the region. It can be made lower than the diffraction efficiency in a certain other region, preferably any other region, having a unit area of the second diffractive optical element 31 separated from the first diffractive optical member 20 along the line.

Similarly, the difference in refractive index forming the third diffraction grating in a certain region having a unit area of the third diffractive optical element 41, preferably an arbitrary region, is the second diffractive optical along the second direction d2 from the region. It is lower than the difference in refractive index forming the third diffraction grating in a certain other region having a unit area of the third diffractive optical element 41 separated from the member 30, preferably any other region. Even in such a case, as in the above-described embodiment, the diffraction efficiency in a certain region, preferably an arbitrary region, having a unit area of the third diffraction optical element 41 is set along the second direction d2 from the region. The diffraction efficiency can be lower than the diffraction efficiency in a certain other region having a unit area of the third diffractive optical element 41 separated from the second diffractive optical member 30, preferably any other region.

Further, the difference in refractive index forming the fourth diffraction grating in a certain region having a unit area of the fourth diffractive optical element 51, preferably an arbitrary region, is the first diffractive optical member along the second direction d2 from the region. It is lower than the difference in refractive index forming the fourth diffraction grating in one other region having a unit area of the fourth diffraction optical element 51 separated from 20 and preferably in any other region. Even in such a case, as in the above-described embodiment, the diffraction efficiency in a certain region, preferably an arbitrary region, having a unit area of the fourth diffraction optical element 51 is set along the second direction d2 from the region. The diffraction efficiency can be lower than the diffraction efficiency in a certain other region having a unit area of the fourth diffractive optical element 51 separated from the first diffractive optical member 20, preferably any other region.

Further, the difference in refractive index forming the sixth diffraction grating in a certain region having a unit area of the sixth diffractive optical element 42, preferably an arbitrary region, is the fourth diffractive optical member along the first direction d1 from the region. It is lower than the difference in refractive index forming the sixth diffraction grating in one other region having a unit area of the sixth diffraction optical element 42 separated from 50, preferably in any other region. Even in such a case, as in the above-described embodiment, the diffraction efficiency in a certain region, preferably an arbitrary region, having a unit area of the sixth diffraction optical element 42 is set along the first direction d1 from the region. The diffraction efficiency can be lower than the diffraction efficiency in a certain other region, preferably any other region, having a unit area of the sixth diffractive optical element 42 separated from the fourth diffractive optical member 50.

The optical member 10 having such diffractive optical elements can be manufactured, for example, as follows. First, a hologram sensitive material 80 for forming a diffractive optical element as a hologram is provided on the base material 11 in the same manner as in the manufacturing process of the optical member 10 of the above-described embodiment. Next, as shown in FIG. 15, the dimming filter 70 is arranged so as to face the hologram sensitive material 80 on the base material 11. The dimming filter 70 has a portion corresponding to each diffraction optical member of the manufactured optical member 10. That is, the dimming filter 70 has a first portion 72, a second portion 73 displaced from the first portion 72 in the first direction d1, and a third portion 73 displaced from the second portion 73 in the second direction d2. It includes a portion 74 and a fourth portion 75 located offset from the first portion 72 in the second direction d2.

The dimming filter 70 transmits a part of the incident light and absorbs or reflects the other part. That is, the dimming filter 70 attenuates the intensity of the light to be transmitted. The light transmittance of the dimming filter 70 can be appropriately set. In the dimming filter 70 shown in FIG. 15, the light transmittance is set so as to fabricate each diffractive optical element of the optical member 10 shown in FIG. In FIG. 15, a portion having a low transmittance is shown dark, and a portion having a high transmittance is shown lightly. That is, the light transmittance in a certain region having a unit area of the second portion 73, preferably an arbitrary region, is the unit of the second portion 73 separated from the first portion 72 along the first direction d1 from the region. It is higher than the light transmittance in one other region having an area, preferably any other region. The light transmittance in a certain region having a unit area of the third portion 74, preferably an arbitrary region, is the unit area of the third portion 74 separated from the second portion 73 along the second direction d2 from the region. The unit area of the third portion 74, which is higher than the light transmittance in one other region, preferably any other region, and is separated from the fourth portion 75 along the first direction d1 from the region. Is higher than the light transmittance in one other area, preferably any other area. The light transmittance in a certain region having a unit area of the fourth portion 75, preferably an arbitrary region, is the unit area of the fourth portion 75 separated from the first portion 72 along the second direction d2 from the region. It is higher than the light transmittance in one other region, preferably any other region.

Next, as shown in FIG. 16, the light L16 is irradiated through the dimming filter 70 to expose the hologram sensitive material 80. FIG. 16 is a part of a cross section taken along the line XVI-XVI of FIG. That is, the hologram sensitive material 80 is exposed according to the transmittance of the dimming filter 70. The higher the transmittance of the dimming filter 70, the stronger the hologram sensitive material 80 is exposed by the light L16. Here, the hologram sensitive material 80 is desensitized according to the intensity of the light irradiated by the light L16. The light L16 that irradiates the hologram sensitive material 80 is preferably ultraviolet rays in order to reliably desensitize the hologram sensitive material 80 in a short time. In FIG. 17, the strongly desensitized hologram sensitizer 80 is shown dark, and the weakly desensitized hologram sensitizer 80 is shown lightly. As shown in FIG. 17, the hologram sensitive material 80 is strongly desensitized by reacting with the material (monomer) that forms the difference in refractive index contained in the hologram sensitive material 80 as the transmittance of the dimming filter 70 increases. The lower the transmittance, the weaker the material (monomer) that forms the difference in refractive index contained in the hologram sensitive material 80 is, and the weaker the desensitization treatment is performed.

After that, the dimming filter 70 is removed, and then, as shown in FIG. 18, the hologram original plate 85 is arranged on the side opposite to the side where the hologram sensitive material 80 of the base material 11 is provided, and light, particularly parallel light flux is irradiated. Then, the hologram sensitive material 80 is exposed. The irradiated light L181 is incident on the hologram sensitive material 80 as reference light, and the diffracted light L182 once transmitted through the hologram sensitive material 80 and diffracted by the hologram original plate 85 is incident on the hologram sensitive material 80 as object light. When the light L181 and the diffracted light L182 interfere with each other, interference fringes, which are light and dark patterns, are generated in the hologram sensitive material 80. Then, the interference fringes are recorded on the hologram sensitive material 80 having photosensitivity. By recording the interference fringes on the hologram sensitive material 80 in this way, a diffraction grating is formed. In this way, the diffractive optical element as a hologram is formed on the base material 11, and the optical member 10 of the above-mentioned modified example is manufactured.

Here, the more strongly the hologram sensitive material 80 is desensitized, the more the material (monomer) that forms the difference in refractive index contained in the hologram sensitive material 80 at the position reacts and is desensitized. In other words, the amount of unreacted material (monomer) that forms a refractive index difference as a diffraction grating when irradiated with light L181 is reduced. When the light L181 is irradiated to form a diffraction grating, the larger the amount of unreacted material that forms a refractive index difference as the diffraction grating, the larger the diffraction grating is formed. Therefore, the stronger the desensitized hologram sensitive material 80, the smaller the difference in refractive index of the formed diffraction grating.

The magnitude of the difference in the refractive index of the diffraction grating at each portion of the diffractive optical element can be evaluated by, for example, the following method. First, as shown in FIGS. 19 to 22, a magnified image of a portion where the refractive index difference of each diffractive optical element is small and the diffraction efficiency is low and a portion where the refractive index difference is large and the diffraction efficiency is high is captured. To do. The enlarged image of each diffractive optical element can be captured by, for example, a transmission electron microscope (TEM) or a scanning electron microscope (SEM). 19 and 20 are images taken by TEM of the same portion where the diffraction efficiency is low due to the small difference in refractive index in the diffractive optical element, and FIGS. 21 and 22 show the difference in refractive index in the diffractive optical element. This is an image obtained by TEM of the same portion where the diffraction efficiency increases as the diffraction efficiency increases. The diffraction efficiency in the portions shown in FIGS. 19 and 20 was 32%, and the diffraction efficiency in the portions shown in FIGS. 21 and 22 was 16%.

In the captured image, one of the high refractive index portion and the low refractive index portion as the diffraction grating becomes a bright portion, and as a result of uneven distribution of the material when forming the bright portion, the high refractive index portion and the low refractive index portion and the low refractive index portion. The other part of the rate part is a dark part. That is, the larger the brightness ratio between the dark part and the bright part, the larger the difference in the refractive index of the diffraction grating.

Next, in order to obtain the brightness ratio between the dark part and the bright part, three dark parts extending in one direction and three bright parts extending in one direction adjacent to the dark part are defined in the captured image. As a representative, in FIGS. 19 and 21, one dark portion extending in one direction is shown along the dotted line, and in FIGS. 20 and 22, one dark portion extending in one direction extends adjacent to the dark portion defined in FIGS. 19 and 21. One bright area is shown along the dotted line. The brightness of the three dark and bright areas is read from the image, and the average of the brightness of each of the dark and bright areas is calculated.

The brightness ratio between the dark part and the bright part is calculated from the ratio of the average brightness of the bright part to the average brightness of the dark part. The larger the difference in refractive index between the dark part and the bright part, the larger the value of this luminance ratio. That is, by comparing the values of the luminance ratio, it is possible to compare the difference in the refractive index of the diffraction grating in each portion. As a specific example, the luminance ratio in the portion where the refractive index difference is small in the diffractive optical elements shown in FIGS. 19 and 20 is 1.31, and the refractive index in the diffractive optical elements shown in FIGS. 21 and 22 is 1.31. The brightness ratio in the portion where the difference is large is 1.92.

The configuration of each diffractive optical element of this modification may be combined with the configuration of each diffractive optical element of the above-described embodiment. That is, for example, the ratio of the second diffraction unit 31a in a certain region having the unit area of the second diffraction optical element 31 is the second diffraction separated from the first diffraction optical member 20 along the first direction d1 from the region. The ratio of the second diffraction unit 31a in a certain region having a unit area of the optical element 31 is lower than the ratio of the second diffraction unit 31a, and a second diffraction lattice is formed in a certain region having a unit area of the second diffraction optical element 31. Refraction to form a second diffractive lattice in another region having a unit area of the second diffractive optical element 31 separated from the first diffractive optical member 20 along the first direction d1 from the region. It may be lower than the rate difference.

Further, as shown in FIG. 23, when the second diffracting optical member 30 is rectangular in a plan view, the light in the first wavelength region diffracted by the second diffracting optical element 31 is further reduced by the second diffracting optical element 31. May be diffracted. When the second diffracting optical element 31 is diffracted a plurality of times, the intensity of the image light diffracted in a certain region having a unit area of the second diffracting optical element 31 is first determined along the first direction d1 from the region. It becomes difficult to approach the intensity of the image light diffracted in a certain region having a unit area of the second diffracting optical element 31 separated from the diffractive optical member 20. That is, it becomes difficult to uniformly approach the intensity of the image light emitted from the third diffractive optical element 41.

Therefore, in the modified example shown in FIG. 24, the length of at least a part of the second diffractive optical member along the second direction d2 becomes longer as it is separated from the first diffractive optical member 20 along the first direction d1. ing. In other words, the side of at least a part of the second diffractive optical member 30 near the first diffractive optical member 20 is thinner than the side farther from the first diffractive optical member 20. In this case, since the second diffracting optical element 31 is thin particularly on the side close to the first diffracting optical member 20, it is easy for the light in the first wavelength region to be diffracted a plurality of times by the second diffracting optical element 31. It can be avoided. Further, in this case, the area where the second diffractive optical element 31 is arranged increases as the distance from the first diffractive optical member 20 increases along the first direction d1. Therefore, the second diffractive optical element in which the intensity of the image light diffracted in a certain region having a unit area of the second diffractive optical element 31 is separated from the first diffractive optical member 20 along the first direction d1 from the region. It is possible to approach the intensity of the image light diffracted in one other region having a unit area of 31. That is, the intensity of the image light emitted from the third diffractive optical element 41 can be made uniform.

It should be noted that "the length increases as the distance from the first diffractive optical member 20 increases" does not mean that the value continuously changes according to the distance from the first diffractive optical member 20. It means that it includes a portion that becomes longer as it is separated from the first diffractive optical member 20 and does not include a portion that becomes shorter as it is separated from the first diffractive optical member 20. However, it is preferable that the length is continuously increased according to the distance from the first diffraction optical member 20.

Similar to the second diffractive optical member 30 shown in FIG. 24, the length of at least a part of the fourth diffractive optical member 50 along the second direction d2 is the first diffractive optical member 20 along the second direction d2. By increasing the distance from the first diffraction optical member 20, it is possible to easily prevent the light in the second wavelength region from being diffracted multiple times by the fourth diffraction optical element 51, particularly on the side closer to the first diffraction optical member 20. it can. Further, in this case, the area where the fourth diffractive optical element 51 is arranged increases as the distance from the first diffractive optical member 20 increases along the second direction d2. Therefore, the fourth diffractive optical element in which the intensity of the image light diffracted in a certain region having the unit area of the fourth diffractive optical element 51 is separated from the first diffractive optical member 20 along the second direction d2 from the region. It is possible to approach the intensity of the image light diffracted in one other region having a unit area of 51. That is, the intensity of the image light emitted from the third diffractive optical element 41 can be made uniform.

Further, the optical member 10 may have a protective layer 17 that covers the first diffraction optical member 20 from the side opposite to the base material 11. As in the example shown in FIG. 25, in the protective layer 17, not only the first diffraction optical member 20, but also the second diffraction optical member 30, the third diffraction optical member 40, and the fourth diffraction optical member 50 are the base materials 11. It is preferable to cover from the opposite side. Such a protective layer 17 can protect the diffractive optical element of each diffractive optical member that covers the diffractive optical member and prevent the diffractive optical element from being damaged. The protective layer 17 has sufficient strength to protect the diffractive optical element. The protective layer 17 is made of, for example, polycarbonate, an acrylic resin, a cycloolefin polymer, polyethylene terephthalate (PET) or the like, and is particularly preferably made of a material having a small birefringence such as polycarbonate, an acrylic resin or a cycloolefin polymer. Further, if the protective layer 17 is too thin, the rigidity of the protective layer 17 becomes low, so that the protective layer 17 may be deformed when an external force is applied to the optical member 10. On the other hand, if the protective layer 17 is too thick, when heat is applied to the optical member 10, the protective layer 17 is deformed so as to be greatly warped. In order to suppress such deformation of the protective layer 17, the thickness of the protective layer 17 is preferably in an appropriate range. Specifically, the thickness of the protective layer 17 is preferably, for example, 0.2 mm or more and 3 mm or less, and more preferably 0.4 mm or more and 1.5 mm or less. Further, in order to improve the surface strength of the optical member 10, the protective layer 17 is preferably hard-coated.

When such a protective layer 17 is in contact with the diffractive optical member, the light guiding the inside of the base material may be incident on the protective layer 17 from the diffractive optical member. In order to properly guide the light incident on the protective layer 17, it is required to flatten the protective layer 17. However, a protective layer having sufficient flatness is difficult to manufacture, and even if it is manufactured, it is costly. When the light guiding the inside of the base material is incident on the protective layer 17 having low flatness, the light is not properly guided in the protective layer 17, and the image displayed on the display device is deteriorated. Therefore, it has been considered that the protective layer is provided at a position separated from the diffractive optical member and an air layer is provided between the diffractive optical member and the protective layer. However, if an air layer is provided between the diffractive optical member and the protective layer, the entire optical member becomes thick. It is also difficult to properly provide an air layer.

Therefore, in the example shown in FIG. 25, the low refractive index layer 18 is provided between the base material 11 and the protective layer 17. That is, the optical member 10 further has a low refractive index layer 18 in addition to the protective layer 17. The low refractive index layer 18 is made of a material having a lower refractive index than the base material 11. The difference in refractive index between the low refractive index layer 18 and the base material 11 is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.3 or more. The refractive index of the low refractive index layer 18 is, for example, 1.4 or less, preferably 1.3 or less, and more preferably 1.2 or less. The thickness of the low refractive index layer 18 is, for example, 0.01 μm or more and 10 μm or less, preferably 0.1 μm or more and 5 μm or less. Such a low refractive index layer 18 can be easily formed by coating, for example, any of a fluororesin, an epoxy resin, a urethane resin, an acrylic resin, a hollow silica, and a mixture thereof on the base material 11 and the diffractive optical member. Can be made. In particular, the material of the low refractive index layer 18 is preferably made of a fluororesin or hollow silica having a particularly low refractive index. Further, by producing the low refractive index layer 18 in this way, it is difficult to apply pressure to the diffractive optical member, and therefore it is possible to prevent the diffractive optical member from being distorted by the low refractive index layer 18.

1 Head-mounted display device 3 Display device 5 Display unit 7 Lens 10 Optical member 11 Base material 17 Protective layer 18 Low refractive index layer 20 First diffraction optical member 21 First diffraction optical element 22 First diffraction optical element 22 Fifth diffraction optical element 30 Second Diffractive optical member 31 2nd diffractive optical element 31a 2nd diffractive part 31b 2nd flat part 40 3rd diffractive optical member 41 3rd diffractive optical element 41a 3rd diffractive part 41b 3rd flat part 42 6th diffractive optical element 42a 6th Diffraction part 42b 6th flat part 50 4th diffractive optical member 51 4th diffractive optical element 51a 4th diffractive part 51b 4th flat part 60 Mask 61 Opening 62 1st part 63 2nd part 64 3rd part 65 4th part 70 Dimming filter 72 1st part 73 2nd part 74 3rd part 75 4th part 80 Hologram sensitive material

Claims (13)

With the base material
A first diffractive optical member laminated on the base material and including a first diffractive optical element,
A second diffractive optical member laminated on the base material at a position deviated from the first diffractive optical member in the first direction and including a second diffractive optical element, and a second diffractive optical member.
An optical member including a third diffractive optical member, which is laminated on the base material at a position deviated from the second diffractive optical member in the second direction, which is non-parallel to the first direction, and includes a third diffractive optical element. hand,
The first diffracting optical element diffracts light in the first wavelength region incident on the optical member so as to go in the first direction.
The second diffracting optical element diffracts the light in the first wavelength region incident from the first direction so as to go in the second direction.
The third diffracting optical element diffracts the light in the first wavelength region incident from the second direction so as to be emitted from the optical member.
The diffraction efficiency in a certain region having a unit area of the second diffractive optical element has a unit area of the second diffractive optical element separated from the first diffractive optical member along the first direction from the region. Less than diffraction efficiency in one other region,
The diffraction efficiency in a certain region having the unit area of the third diffractive optical element had the unit area of the third diffractive optical element separated from the second diffractive optical member along the second direction from the region. An optical member whose diffraction efficiency is lower than that in one other region. The diffraction efficiency in an arbitrary region having a unit area of the second diffraction optical element has a unit area of the second diffraction optical element separated from the first diffraction optical member along the first direction from the region. Less than the diffraction efficiency in one other region
The diffraction efficiency in an arbitrary region having a unit area of the third diffractive optical element has a unit area of the third diffractive optical element separated from the second diffractive optical member along the second direction from the region. The optical member according to claim 1, which is lower than the diffraction efficiency in a certain other region. The optical member according to claim 1 or 2, wherein the second diffraction optical element and the third diffraction optical element are volume holograms. The second diffracting optical element includes a second diffracting portion in which a second diffraction grating for diffracting light in the first wavelength region is formed, and a second flat portion which is a non-forming portion of the second diffraction grating. Including
The ratio of the second diffractive portion in a certain region having a unit area of the second diffractive optical element is the ratio of the second diffractive optical element separated from the first diffractive optical member along the first direction from the region. The optical member according to any one of claims 1 to 3, which is lower than the ratio of the second diffraction unit in a certain region having a unit area. The third diffracting optical element includes a third diffractive portion in which a third diffraction grating for diffracting light in the first wavelength region is formed, and a third flat portion which is a non-forming portion of the third diffraction grating. Including
The ratio of the third diffractive portion in a certain region having a unit area of the third diffractive optical element is the ratio of the third diffractive optical element separated from the second diffractive optical member along the second direction from the region. The optical member according to any one of claims 1 to 4, which is lower than the ratio of the third diffraction unit in a certain region having a unit area. In the second diffracting optical element, there is a difference in refractive index so as to form a second diffraction grating that diffracts light in the first wavelength region.
The difference in refractive index forming the second diffraction grating in a region having a unit area of the second diffraction optical element is the second distance from the region along the first direction from the first diffraction optical member. The optical member according to any one of claims 1 to 5, which is lower than the difference in refractive index forming the second diffraction grating in a certain region having a unit area of the diffractive optical element. In the third diffracting optical element, there is a difference in refractive index so as to form a third diffraction grating that diffracts light in the first wavelength region.
The difference in refractive index forming the third diffraction grating in a certain region having a unit area of the third diffractive optical element is the third, which is separated from the second diffractive optical member along the second direction from the region. The optical member according to any one of claims 1 to 6, which is lower than the difference in refractive index forming the third diffraction grating in a certain region having a unit area of the diffractive optical element. The method according to any one of claims 1 to 7, wherein the length of at least a part of the second diffractive optical member along the second direction becomes longer as the distance from the first diffractive optical member increases. Optical member. A fourth diffractive optical member, which is laminated on the base material at a position deviated from the first diffractive optical member in the second direction and includes a fourth diffractive optical element, is further provided.
The first diffractive optical member further includes a fifth diffractive optical element.
The third diffractive optical member further includes a sixth diffractive optical element.
The fifth diffracting optical element diffracts light in a second wavelength region different from the first wavelength region incident on the optical member so as to go in the second direction.
The fourth diffracting optical element diffracts the light in the second wavelength region incident from the second direction so as to go toward the first direction.
The sixth diffracting optical element diffracts the light in the second wavelength region incident from the first direction so as to be emitted from the optical member.
The diffraction efficiency in a certain region having the unit area of the fourth diffractive optical element had the unit area of the fourth diffractive optical element separated from the first diffractive optical member along the second direction from the region. Less than diffraction efficiency in one other region,
The diffraction efficiency in a certain region having the unit area of the sixth diffractive optical element had the unit area of the sixth diffractive optical element separated from the second diffractive optical member along the first direction from the region. The optical member according to any one of claims 1 to 8, which is lower than the diffraction efficiency in a certain other region. The optical member according to any one of claims 1 to 9,
A display device including a display unit that is arranged to face the first diffraction optical member of the optical member and emits image light. A head-mounted display device including the display device according to claim 10. The process of providing the hologram sensitive material on the base material and
The process of arranging the mask facing the hologram sensitive material and
A step of irradiating light to expose the hologram sensitive material through the mask to desensitize the hologram sensitive material, and a step of desensitizing the hologram sensitive material.
The step of removing the mask and
A step of exposing the hologram sensitive material to form a hologram on the base material is provided.
The mask has a first portion, a second portion displaced from the first portion in the first direction, and a third portion displaced from the second portion in a second direction non-parallel to the first direction. Including parts,
The mask has openings in the second part and the third part.
The proportion of the opening in a region having a unit area of the second portion is another having a unit area of the second portion separated from the first portion along the first direction from the region. Higher than the proportion of said openings in the area,
The proportion of the opening in a region having a unit area of the third portion is another having a unit area of the third portion separated from the second portion along the second direction from the region. A method of manufacturing an optical member that is higher than the proportion of the openings in the region. The process of providing the hologram sensitive material on the base material and
The step of arranging the dimming filter facing the hologram sensitive material and
A step of irradiating light to expose the hologram sensitive material through the dimming filter to desensitize the hologram sensitive material.
The step of removing the dimming filter and
A step of exposing the hologram sensitive material to form a hologram is provided.
The dimming filter is located with a first portion, a second portion displaced from the first portion in the first direction, and a second portion displaced from the second portion in a second direction non-parallel to the first direction. Including the third part,
The light transmittance in a certain region having a unit area of the second part is a certain other region having a unit area of the second part separated from the first part along the first direction from the region. Higher than the light transmittance in
The light transmittance in a certain region having a unit area of the third part is a certain other region having a unit area of the third part separated from the second part along the second direction from the region. A method for manufacturing an optical member, which has a higher transmittance than the light in the above.

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