JP2016206512A - Head-mounted display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively avoid deterioration of image quality to reduce a rough feeling due to pixels regarding head-mounted displays.SOLUTION: A head-mounted display 1 has a phase type diffraction lattice 5 arranged on a panel face side of an image display panel 2A, and the phase type diffraction lattice 5 comprises a phase difference layer that is a two-dimensional phase type diffraction lattice of which a surface shape is flat, and is a phase difference layer made up of a liquid crystal material, in which first and second areas where an angle formed by a slow phase axis direction falls within 90 ± 10 degrees are repeatedly created, and a phase difference to be given to transmitting light is 1/2 wavelength. With respect to an array direction of pixels in a horizontal direction of the image display panel 2A or a vertical direction thereof, the phase difference layer is arranged so that a repeating direction forms an angle within 45 ± 10 degrees, and is arranged at a position satisfying a relation expression of (2/2)(pd/2λ)>L>0.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a head mounted display using an image display panel such as a liquid crystal display panel.

  Conventionally, various uses of head mounted displays have been proposed. Here, the head mounted display is a display device that directly provides a user with a display image of a small image display panel by an optical system arranged in front of the user's eyes. A head-mounted display is provided with a configuration in which an image is displayed by a dedicated image display panel integrated with an optical system, a configuration in which an information portable terminal such as a smartphone is detachably held, and an image is displayed on the information portable terminal. .

  With respect to an image display device using such an image display panel, Patent Document 1 proposes a device for improving the image quality by using a diffraction grating as an optical low-pass filter. Patent Document 2 proposes a device for improving the image quality by arranging a microlens array on the panel surface of the image display panel.

  By the way, after all, the head mounted display has a problem that a rough feeling due to pixels is perceived because the display image of the image display panel is enlarged and viewed from an optical system arranged in front of the eyes.

  As one method for solving this problem, although the method disclosed in Patent Document 1 can be applied, if this method is simply applied, scattered light is generated due to the uneven shape of the diffraction grating, and the image quality deteriorates instead. There is a problem to do.

Japanese Patent Laid-Open No. 5-289028 JP-A-8-248207

  The present invention has been made in view of such a situation, and an object of the present invention is to effectively avoid deterioration in image quality and reduce the feeling of roughness due to pixels in a head mounted display.

  In order to solve the above-mentioned problems, the present inventor has made intensive research and constructed a phase-type diffraction grating with a flat surface shape by alternately repeating regions where the slow axis directions are orthogonal to each other. This led to the idea of properly arranging and thus completing the present invention.

  Specifically, the present invention provides the following.

(1) A head mounted display in which a phase type diffraction grating is arranged on the panel surface side of an image display panel,
The phase-type diffraction grating is
A two-dimensional phase-type diffraction grating with a flat surface shape,
The first and second regions having an angle formed by the slow axis direction within 90 ° ± 10 ° are retardation layers made of a liquid crystal material, and the retardation given to transmitted light is ½ wavelength. With a retardation layer,
With respect to the horizontal or vertical pixel arrangement direction of the image display panel, the repeating direction of the first and second regions is arranged to form an angle within 45 ° ± 10 °,
With respect to the pixel pitch p of the image display panel and the optical distance L from the side surface of the phase type diffraction grating of the color filter provided in the image display panel to the phase type diffraction grating, (2 ^1/2 / 2) · (pd / 2λ )>L> 0
Head mounted display placed at a position that satisfies

According to (1), the first and second regions are two-dimensional phase-type diffraction gratings having a flat surface shape, and the angle formed by the slow axis direction is within 90 ° ± 10 °. A retardation layer made of a liquid crystal material that has a retardation layer with a half-wave retardation applied to transmitted light, thereby reducing zero-order light and reducing the generation of scattered light and functioning as a low-pass filter Can be made. Further, the moire pattern is arranged such that the repeating direction of the first and second regions forms an angle within 45 ° ± 10 ° with respect to the pixel arrangement direction in the horizontal direction or the vertical direction of the image display panel. Can be effectively avoided. Further, the arrangement is such that the relational expression (2 ^1/2 / 2) · (pd / 2λ)>L> 0 is satisfied, so that it is possible to efficiently reduce the feeling of roughness due to the pixels.

(2) In (1),
The phase-type diffraction grating is
The first and second regions are rectangular regions;
A head mounted display in which the retardation layer is produced by repeating the first and second regions.

(3) In (1),
The phase-type diffraction grating is
A head-mounted display manufactured by stacking one-dimensional phase-type diffraction gratings.

  According to (2) or (3), with a more specific configuration, it is possible to effectively avoid deterioration in image quality and reduce the feeling of roughness due to pixels with respect to the head mounted display.

  ADVANTAGE OF THE INVENTION According to this invention, regarding a head mounted display, deterioration of an image quality can be avoided effectively and the rough feeling by a pixel can be reduced.

It is a figure which shows the head mounted display which concerns on embodiment of this invention. It is a figure where it uses for description of arrangement | positioning of a phase type diffraction grating. It is a figure where it uses for description of the detailed structure of a phase type diffraction grating. It is a figure where it uses for description of the detailed structure of the phase type | mold diffraction grating by another example.

[First Embodiment]
FIG. 1 is a diagram showing a configuration of a head mounted display according to the first embodiment of the present invention. The head mounted display 1 holds an information portable terminal 2 using a smartphone in a detachable manner, and is used by being placed in front of the user 3. The head-mounted display 1 is provided with an optical system 4 such as a convex lens, and is configured so that the display screen of the image display panel 2A provided in the information portable terminal 2 can be enlarged and viewed through the optical system 4. Is done. Accordingly, the head mounted display 1 is configured to provide a large screen image in front of the user 3.

  Here, various configurations such as a liquid crystal display panel and an organic EL panel can be widely applied to the image display panel 2A. Further, the head mounted display 1 is not limited to the case where the image display panel by the portable information terminal 2 is used, and the image may be displayed by a dedicated image display panel that is integrally held. Further, an image composition means such as a half mirror may be used to superimpose the scenery in front of the eyes and the image on the image display panel and provide them to the user.

  Here, when the image displayed on the image display panel 2A is magnified through the optical system 4 in this way, a rough feeling due to the pixels is perceived. Therefore, in the head mounted display 1, a two-dimensional phase type diffraction grating 5 is provided between the optical system 4 and the image display panel 2A, and functions as an optical low-pass filter of the phase type diffraction grating 5 depending on the pixel. Reduce the feeling of roughness.

[Arrangement of phase diffraction grating]
Here, when the separation angle (angle formed by the + 1st order light and the 0th order light) by diffraction of the phase type diffraction grating 5 is θ and the wavelength of the emitted light is λ, the following relational expression is established. Here, d is a repetitive pitch d related to the periodic structure of the phase type diffraction grating 5.
d = λ / tan θ (1)

Let L be the optical distance from the side surface of the phase type diffraction grating 5 of the color filter 7 provided in the image display panel 2A to the phase type diffraction grating 5. Since the distance between images (separation width) of the color filter formed by the + 1st order light and the −1st order light in the phase type diffraction grating 5 by the separation angle θ is 2 tanθ = h / L, (1 The following formula can be obtained from the formula:
d = 2λ · L / h (2)
When this equation (2) is modified, the following relational expression is obtained.
h = 2λ · L / d (3)

Here, when the repetitive pitch of the black matrix 7A which is a light-shielding portion between pixels provided in the color filter 7 is p (which is the pitch in the repetitive direction of the phase type diffraction grating 5), if p = h, it is adjacent. The diffracted light related to the black matrix 7A is provided to the user 3 in an overlapping manner, thereby increasing the feeling of glare by the pixels. On the other hand, if p> h, the diffracted light related to the adjacent black matrix 7A is provided to the user without overlapping, thereby reducing the feeling of roughness due to the pixels. In particular, when p = h / 2, the diffracted light related to the adjacent black matrix 7A is arranged at the center of the pixels between the black matrices 7A, and the feeling of roughness due to the pixels can be reduced most. According to such a principle, in this embodiment, the feeling of roughness due to pixels is reduced. Even when the separation angle θ is 0, the diffracted light related to the adjacent black matrix 7A is provided to the user 3 in an overlapping manner, thereby increasing the feeling of glare by the pixels. Accordingly, it is possible to reduce glare caused by pixels by setting so as to satisfy the following relational expression.
p>h> 0 (4)

However, simply setting the repetition direction of the phase-type diffraction grating 5 in the pixel arrangement direction may cause moire. Therefore, in this embodiment, as shown in FIG. 2, a direction at an angle of 45 degrees with respect to the horizontal or vertical arrangement direction of the pixels is set as the repeating direction of the phase type diffraction grating 5. In the example of FIG. 2, the inter-image distance h is 2/3 of the pitch in the diagonal direction of the pixels. Thus, when the image display panel 2A is arranged at an angle of 45 degrees, the inter-image distance h by the separation angle θ is ^2½ times the pitch p in the horizontal direction and the vertical direction of the image display panel 2A. As a result, from equation (4), p> 2 ^1/2 · h> 0 (5)
If the above relational expression is satisfied, the feeling of roughness due to the pixels can be reduced. Here, if the equation (4) is modified, the following relational expression can be obtained.
(2 ^1/2 / 2) · (pd / 2λ)>L> 0 (6)
Note that the inclination in the oblique direction can be set within 45 ° ± 10 °, more preferably within 45 ° ± 5 °, so that moire can be sufficiently prevented practically. In addition, by setting this angle range, a visual difference (degree of thinness) between the black matrix related to the boundary between the pixels in the vertical direction and the black matrix related to the boundary between the pixels in the horizontal direction is not felt. Can be.

Thereby, in this embodiment, the interval L is set so as to satisfy the relational expression (6), and preferably, the interval L is set so as to satisfy the relational expression (7). Sets the interval L so as to satisfy the relational expression (8) to reduce the feeling of roughness due to pixels. The equation (8) is a relational expression that satisfies the condition of p = 2 ^1/2 · h / 2.
(3/4) · (2 ^1/2 / 2) · (pd / 2λ)> L
> (1/4) · (2 ^1/2 / 2) · (pd / 2λ) (7)
(2 ^1/2 / 4) (pd / 2λ) = L (8)

(Phase diffraction grating)
By the way, in the configuration in which the phase-type diffraction grating 5 reduces the feeling of roughness due to the pixels in this way, if the oblique incident light is scattered by the surface irregularities related to the periodic structure of the phase-type diffraction grating 5, the scattered light causes There is a problem that image quality deteriorates. Therefore, in this embodiment, a phase diffraction grating is formed using a retardation layer made of a liquid crystal material, and the surface shape is changed by alternately repeating regions where the slow axis directions are orthogonal to the retardation layer. The phase type diffraction grating 5 is formed flat. Thereby, in this embodiment, generation of scattered light due to the uneven shape on the surface of the phase type diffraction grating 5 is effectively avoided, and image quality deterioration due to the scattered light is prevented. The angle formed by the slow axis direction is most preferably 90 degrees which is an orthogonal angle, but it is fabricated within 90 degrees ± 10 degrees, more preferably within 90 degrees ± 5 degrees. Therefore, practically sufficient characteristics can be ensured.

  Further, the phase differences in the regions orthogonal to the slow axis direction are set to be λ / 2, respectively, so that the zero-order lights emitted from the regions orthogonal to each other are canceled out, and the image quality by the zero-order light is reduced. Effectively avoid degradation. That is, as described with reference to FIG. 1, when the feeling of roughness due to the pixels is reduced by the inter-image distance h, the zero-order light from the phase-type diffraction grating 5 is displayed although the image is displayed by the + 1st order light and the −1st order light. Creates an image between the images of the + 1st order light and the −1st order light. As a result, in the head mounted display 1, there is a possibility that a sudden luminance change due to the 0th-order light may occur, which adversely affects image display by the + 1st order light and the −1st order light. However, if the phase difference between the orthogonal regions is set to λ / 2, the 0th order light can be sufficiently suppressed, and as a result, the influence of the image display by the 0th order light can be effectively avoided. Since the center wavelength in the visible light region is 550 nm, the phase difference is created to be 200 nm or more and 300 nm or less, and the light quantity of the 0th order light is sufficiently suppressed, and the image quality is deteriorated due to the influence of the 0th order light. Can be prevented.

[Detailed configuration of phase diffraction grating]
FIG. 3 is a diagram showing the phase type diffraction grating 5. In the phase-type diffraction grating 5, for example, an orientation layer 5C and a retardation layer 5B are sequentially formed on a base 5A made of a transparent film material such as triacetyl cellulose. In the phase type diffraction grating 5, the phase difference layer 5B is formed of ultraviolet curable liquid crystal, and the alignment of the ultraviolet curable liquid crystal is patterned by the alignment regulating force of the alignment layer 5C. With this patterning, the phase-type diffraction grating 5 has a phase difference in which the first and second regions A and B having a rectangular shape with the slow axis directions orthogonal to each other are sequentially and two-dimensionally arranged at the repetition pitch d described above. The layer 5B is formed, and thereby the transmitted light is diffracted by the periodic structure in the repeating direction of the first and second regions A and B. In FIG. 3, the slow axis direction is indicated by an arrow. As a result, the first and second regions A and B are created with a region width of d / 2. Instead of forming the phase type diffraction grating by patterning the retardation layer 5B with the first and second regions A and B having a rectangular shape as described above, as shown in FIG. A one-dimensional phase-type diffraction grating 15A and 15B is formed by forming a region where the slow axis directions are orthogonal to each other, and a two-dimensional phase-type diffraction grating is formed by stacking the one-dimensional phase-type diffraction gratings 15A and 15B. 15 may be configured.

  In the phase-type diffraction grating 5, after a photo-alignment material film made of a photo-alignment material is produced, the photo-alignment material film is irradiated with ultraviolet rays based on linearly polarized light by a so-called photo-alignment technique to form an alignment layer 5C. Here, the ultraviolet rays applied to the photo-alignment material film are set so that the direction of polarization differs by 90 degrees between the region A and the region B. In place of the photo-alignment layer, the alignment layer may be created by rubbing the base material 5A, and the alignment layer is created by creating a line-shaped fine irregular shape by rubbing treatment on the surface of the base material 5A. May be. The retardation layer 5B is formed by solidifying (curing) the ultraviolet curable liquid crystal in an aligned state by the alignment regulating force of the alignment layer 5C.

〔Experimental result〕
[Example 1]
A head mounted display (Google Cardboard) that displays images using a portable information terminal using a commercially available smartphone is equipped with Apple's iPhone (pixel pitch 326 ppi (pixel size 0.078 mm x 0.078 mm)) for the left eye A phase type diffraction grating having a pitch of d = 200 μm and a phase difference value of 275 nm (= λ / 2) is arranged at an angle of 45 degrees on the lens side. Here, the arrangement position is 5 mm from the panel surface (viewer side surface) of the image display panel (liquid crystal display panel), and is a position that generally satisfies the relationship of (2 ^1/2 / 4) (pd / 2λ) = L. is there.

  In this head mounted display, when the display screen was observed with each of the right eye and the left eye, the pixel shape due to the black matrix was observed with the right eye, and a rough feeling due to the pixels was perceived. However, in the left eye, the black matrix was observed to be thin, and the feeling of roughness due to the pixels could be sufficiently suppressed.

[Example 2]
The iPAD2 (pixel pitch 132 ppi (pixel size 0.192 mm × 0.192 mm)) of Apple is mounted on the head-mounted display used in Example 1, and the pitch d = 200 μm and the phase difference value 275 nm on the left eye lens side ( = Λ / 2) phase type diffraction gratings were arranged at an angle of 45 degrees. Here, the arrangement position is 12 mm from the panel surface of the image display panel, and is a position that generally satisfies the relationship of (2 ^1/2 / 4) (pd / 2λ) = L.

  In this head mounted display, when the display screen was observed with each of the right eye and the left eye, the pixel shape due to the black matrix was observed with the right eye, and a rough feeling due to the pixels was perceived. However, in the left eye, the black matrix was observed to be thin, and the feeling of roughness due to the pixels could be sufficiently suppressed.

[Comparative Example 1]
In the configuration of Example 1, the arrangement position of the phase type diffraction grating was changed. Here, the arrangement position is 10 mm from the panel surface of the image display panel, and is a position that generally satisfies the relationship of (2 ^1/2 / 2) (pd / 2λ) = L.

  In this head-mounted display, when the display screens were observed with the right eye and the left eye, the pixel shape based on the black matrix was observed almost equally with the right eye and the left eye, and the rough feeling due to the pixels was perceived.

[Comparative Example 2]
In the configuration of Example 2, the arrangement position of the phase type diffraction grating was changed. Here, the arrangement position is 24 mm from the panel surface of the image display panel, and is a position that generally satisfies the relationship of (2 ^1/2 / 2) (pd / 2λ) = L.

  In this head-mounted display, when the display screens were observed with the right eye and the left eye, the pixel shape based on the black matrix was observed almost equally with the right eye and the left eye, and the rough feeling due to the pixels was perceived.

[Comparative Example 3]
In the configuration of Example 1, instead of the phase type diffraction grating according to the present application, a phase type diffraction grating type produced by periodically changing the thickness of a uniform transparent material is arranged, and the head mounted display of Comparative Example 3 is arranged. Configured. This phase type diffraction grating is a phase type diffraction grating having a so-called concave and convex relief surface in which concave portions having a rectangular cross section are arranged two-dimensionally with a pitch of 200 μm.

  In this head-mounted display, the edge surface connecting the concave and convex portions on the surface of the phase-type diffraction grating is brightened by total reflection, and the stray light generated on this edge surface illuminates the inside of the head-mounted display, resulting in the display screen. It was perceived that contrast was lowered and image quality deteriorated.

[Other Embodiments]
As mentioned above, although the specific structure suitable for implementation of this invention was explained in full detail, this invention can change the structure of the above-mentioned embodiment variously in the range which does not deviate from the meaning of this invention.

  That is, in the above-described embodiment, the case where the liquid crystal material is solidified by the alignment regulating force of the alignment layer to produce the retardation layer has been described. By applying a polymer, the liquid crystal material may be directly solidified in an aligned state and an unaligned state to produce a retardation layer, and the alignment layer may be omitted.

DESCRIPTION OF SYMBOLS 1 Head mounted display 2 Information portable terminal 2A Image display panel 3 User 4 Optical system 5, 15, 15A, 15B Phase type diffraction grating 5A Base material 5B Phase difference layer 5C Orientation layer 7A Color filter 7B Black matrix

Claims (3)

A head mounted display in which a phase type diffraction grating is arranged on the panel surface side of an image display panel,
The phase-type diffraction grating is
A two-dimensional phase-type diffraction grating with a flat surface shape,
The first and second regions having an angle formed by the slow axis direction within 90 ° ± 10 ° are retardation layers made of a liquid crystal material, and the retardation given to transmitted light is ½ wavelength. With a retardation layer,
With respect to the horizontal or vertical pixel arrangement direction of the image display panel, the repeating direction of the first and second regions is arranged to form an angle within 45 ° ± 10 °,
Regarding the pixel pitch p of the image display panel and the optical distance L from the side surface of the phase type diffraction grating of the color filter provided in the image display panel to the phase type diffraction grating (2 ^1/2 / 2) · (pd / 2λ) >L> 0
Head mounted display placed at a position that satisfies the relational expression. The phase-type diffraction grating is
The first and second regions are rectangular regions;
The head mounted display according to claim 1, wherein the retardation layer is manufactured by repeating the first and second regions. The phase-type diffraction grating is
The head mounted display according to claim 1, wherein the head mounted display is manufactured by stacking one-dimensional phase type diffraction gratings.

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