DIFFRACTION LIGHT GUIDE PLATE

Abstract

A diffraction light guide plate capable of increasing the area of an output image without increasing the total size thereof and having an advantage that the pupil position of a user is not limited. The diffraction light guide plate comprises first and second diffraction optical elements, wherein the first diffraction optical element is an element capable of receiving light incident onto the first diffraction optical element and outputting the received light toward the second diffraction optical element, and the second diffraction optical element is an element capable of emitting light therefrom out of the incident light from the first diffraction optical element.

Claims

1. A diffraction light guide plate comprising first and second diffraction optical elements, wherein the first diffraction optical element is an element capable of receiving light incident onto the first diffraction optical element and outputting the received light toward the second diffraction optical element, and the second diffraction optical element is an element capable of emitting light therefrom out of the incident light from the first diffraction optical element, and wherein the first diffraction optical element comprises a linear diffraction grating extending in a first direction, the second diffraction optical element comprises first and second regions, and a third region existing between the first and second regions, the first region comprises a linear diffraction grating extending in a second direction different from the first direction, the second region comprises a linear diffraction grating extending in a third direction different from the first and second directions, the third region comprises a diffraction grating in the form that the linear diffraction gratings of the first and second regions overlap, and the first to third regions are disposed such that light incident from the first diffraction optical element is incident onto the first region without passing through the second and third regions, that light incident from the first diffraction optical element is incident onto the second region without passing through the first and third regions, and that light incident from the first diffraction optical element is incident onto the third region without passing through the first and second regions.

2. The diffraction light guide plate according to claim 1, wherein the first to third directions form a triangle.

3. The diffraction light guide plate according to claim 2, wherein the angle formed by the second direction and the third direction is in a range of 50 degrees to 70 degrees.

4. The diffraction light guide plate according to claim 3, wherein the angle formed by the first direction and the second direction or the angle formed by the first direction and the third direction is in a range of 50 degrees to 70 degrees.

5. The diffraction light guide plate according to claim 1, wherein the average pitch of the diffraction grating in the first or second region is in a range of 200 nm to 600 nm.

6. The diffraction light guide plate according to claim 1, wherein the average height of the diffraction grating in the first or second region is in a range of 1 nm to 1 μm.

7. The diffraction light guide plate according to claim 5, wherein the average width of the diffraction grating in the first or second region is in a range of 0.1 times to 0.9 times the average pitch of the diffraction grating.

8. The diffraction light guide plate according to claim 1, wherein the refractive index of the first or second region is in a range of more than 1.0 to 2.0 or less for light having a wavelength of 525 nm.

9. The diffraction light guide plate according to claim 1, wherein the diffraction grating of the third region consists of a plurality of pillars, and the angle formed by the direction of any one side of the hexagon and the first direction is in a range of −10 degrees to 10 degrees, the angle formed by the direction of another side of the hexagon and the second direction is in a range of −10 degrees to 10 degrees, and the angle formed by the direction of another side of the hexagon and the third direction is in a range of −10 degrees to 10 degrees with the proviso that when six pillars among the plurality of pillars have been selected such that a virtual line connecting the six pillars forms a hexagon.

10. The diffraction light guide plate according to claim 9, wherein the angle formed by the first side among the hexagonal sides forming the angle in the range of −10 degrees to 10 degrees with the first direction and the side among the hexagonal sides facing the first side is in a range of −10 degrees to 10 degrees, the angle formed by the second side among the hexagonal sides forming the angle in the range of −10 degrees to 10 degrees with the second direction and the side among the hexagonal sides facing the second side is in a range of −10 degrees to 10 degrees, and the angle formed by the third side among the hexagonal sides forming the angle in the range of −10 degrees to 10 degrees with the third direction and the side among the hexagonal sides facing the third side is in a range of −10 degrees to 10 degrees.

11. The diffraction light guide plate according to claim 9, wherein the average pitch of the pillars in the diffraction grating of the third region is in a range of 200 nm to 600 nm.

12. The diffraction light guide plate according to claim 9, wherein the average height of the pillars in the diffraction grating of the third region is in a range of 1 nm to 1 μm.

13. The diffraction light guide plate according to claim 11, wherein the average width of the pillars in the diffraction grating of the third region is in a range of 0.1 times to 1.3 times the average pitch of the pillars.

14. The diffraction light guide plate according to claim 9, wherein the refractive index of the third region is in a range of more than 1.0 to 2.0 or less for light having a wavelength of 525 nm.

15. The diffraction light guide plate according to claim 1, wherein the ratio (Z3/(Z1+Z2+Z3)) of the length (Z3) of the third region in the z-axis direction to the total length (Z1+Z2+Z3) of the first to third regions in the z-axis direction is in a range of 0.3 to 0.9, with the proviso that when three axes perpendicular to each other formed by the diffraction light guide plate are set to the x-axis, the y-axis and the z-axis, and the z-axis is set to be in a direction parallel to the direction of gravity.

16. The diffraction light guide plate according to claim 15, wherein the ratio (Z1/Z2) of the length (Z1) of the first region in the z-axis direction to the length (Z2) of the second region in the z-axis direction is in a range of 0.9 to 1.1.

17. The diffraction light guide plate according to claim 15, wherein the length (Z3) of the third region in the z-axis direction is in a range of 15 mm to 25 mm.

18. The diffraction light guide plate according to claim 16, wherein the length (Z1) of the first region in the z-axis direction or the length (Z2) of the second region in the z-axis direction is in a range of 1 mm to 15 mm.

19. The diffraction light guide plate according to claim 1, wherein the light incident onto the first diffraction optical element is an image signal, and the second diffraction optical element forms an image output surface.

20. The diffraction light guide plate according to claim 1, wherein the area of the second diffraction optical element is in a range of 1 cm.sup.2 to 50 cm.sup.2.

21.-22. (canceled)

Description

BRIEF DESCRIPTION OF DRAWINGS

[0106] FIG. 1 schematically illustrates a conventional diffraction light guide plate structure.

[0107] FIG. 2 schematically illustrates the structure of a diffraction light guide plate introduced to solve the problem of the diffraction light guide plate according to FIG. 1.

[0108] FIG. 3 is a diagram for indicating a positional range of user's pupil to recognize an image emitted from the diffraction light guide plate according to FIG. 2.

[0109] FIG. 4 schematically illustrates a diffraction light guide plate structure of the present application.

[0110] FIG. 5 is a diagram for explaining a pupil range of a user who can recognize an image emitted from the diffraction light guide plate according to FIG. 4. FIG. 6 schematically illustrates the structure of a second diffractive optical element that can be considered to design.

[0111] FIGS. 7a to 7c are plan views illustratively showing light paths in the diffraction light guide plate of the present application.

[0112] FIG. 8 illustrates a combination of grating vectors of the first diffraction optical element, and the first region and the second region in the diffraction light guide plate of the present application.

[0113] FIGS. 9a to 9c illustrate diffraction gratings formed on the first diffraction optical element, the first region and the second region in the diffraction light guide plate of the present application.

[0114] FIG. 10 illustrates the light emission efficiency for the height of the diffraction grating in the diffraction optical element, according to Experimental Example 1.

[0115] FIG. 11 is a schematic view of a diffraction optical element of Experimental Example 2.

[0116] FIG. 12 illustrates the light emission efficiency for the height of the diffraction grating in the diffraction optical element, according to Experimental Example 2.

[0117] FIG. 13 is a SEM photograph of the second diffraction optical element of Comparative Example.

[0118] FIG. 14 is simulation results of images output by the diffraction light guide plate of Comparative Example.

[0119] FIG. 15 is a photograph of an image output by the diffraction light guide plate of Comparative Example.

[0120] FIG. 16 is simulation results of images output by the diffraction light guide plate of Example.

DETAILED DESCRIPTION

[0121] Hereinafter, the present application will be described in detail with reference to examples, but the scope of the present application is not limited by the following examples.

Experimental Examples

[0122] In the following experimental examples, the relevant diffraction optical element was designed using the RCWA (rigorous coupled wave analysis) function of LIGHTTRANS' Virtual Lab software, and the light emission efficiency of the element was calculated.

Experimental Example 1

[0123] A diffraction optical element was designed, in which a linear diffraction grating in the form of grooves spaced at an average pitch of about 388 nm in a single direction as in FIG. 9a and having an average width of about 0.55 times the average pitch was formed on a surface of a glass substrate having a refractive index of about 1.8 for light with a wavelength of 525 nm. The efficiency that light having a wavelength of about 525 nm totally reflected inside the diffraction optical element was emitted toward the atmosphere from the surface of the diffraction optical element by diffraction was measured according to Equation 1 below. The results of calculating the light emission efficiency of the diffraction optical element for the height of the diffraction pattern (shown as depth in the drawing) were shown in FIG. 10:

[00003]$\begin{array}{cc}\mathrm{Light}\mathrm{emission}\mathrm{efficiency}\left(\%\right)=\left(A\text{/}B\right)\times 100& \left[\mathrm{Equation}3\right]\end{array}$

[0124] In Equation 3 above, A is the light quantity of light output from the diffraction optical element, and B is the total light quantity of light totally reflected inside the diffraction optical element.

Experimental Example 2

[0125] A diffraction optical element in the form that cylindrical grooves having a diameter of about 200 nm were arranged on a surface of a glass substrate having a refractive index of about 1.8 for light with a wavelength of 525 nm in an approximately hexagonal shape as in FIG. 11 was designed. Specifically, a linear diffraction grating having an average pitch of about 388 nm was formed in the diffraction optical element.

[0126] The efficiency that light having a wavelength of about 525 nm totally reflected inside the diffraction optical element was emitted toward the atmosphere from the surface of the diffraction optical element by diffraction was measured according to Equation 3 above. The results of calculating the light emission efficiency of the diffraction optical element for the height of the diffraction grating (shown as depth in the drawing) were shown in FIG. 12:

[0127] According to FIGS. 10 and 12, it can be confirmed that in the case of having a linear diffraction grating as the first diffraction optical element and the first region or the second region of the second diffraction optical element of the present application, the light emission efficiency varies depending on to the height (or depth) of the grating. In addition, in the case of an element having diffraction gratings in the form that linear diffraction gratings overlap as the third region, it can be confirmed that the light emission efficiency is mostly low (5% or less) regardless of the depth (or height).

Comparative Example

[0128] A diffraction light guide plate was designed, in which a first diffraction optical element having a linear diffraction grating and a second diffraction optical element having first and second regions having linear diffraction gratings in different traveling directions were disposed as in FIG. 2. It was designed such that the traveling direction of the linear diffraction grating in the first diffraction optical element had the same direction as the z-axis direction of FIG. 2 and the traveling directions of the linear diffraction gratings in the first and second regions were in directions of about 30 degrees and about −30 degrees with the x-axis of FIG. 2, respectively. Here, the pitch of each diffraction grating was about 388 nm, the width was about 0.55 times the pitch, and the height was about 100 nm.

[0129] The second output diffraction optical element of Comparative Example was photographed by SEM (scanning electron microscope, HITACHI S 4800), and the photograph was shown in FIG. 13. Then, the simulation results of the images that the images incident at the incident angles of about 0 degrees ((a) in FIG. 14) and about 5 degrees ((b) in FIG. 14) based on the normal of the first diffraction optical element in the diffraction light guide plate were output from the normal of the second optical element were shown in FIG. 14. A photograph obtained by inputting an image to the first diffraction optical element of the diffraction light guide plate using a projector (Miniray, Sekonix) at an incident angle of about 5 degrees and photographing the image, in which the relevant image was output from the second diffraction optical element of the light guide plate, using a CMOS (complementary metal-oxide semiconductor) camera (DCC1645C, Thorlabs, Inc.) was shown in FIG. 15.

[0130] According to FIGS. 14 and 15, it can be confirmed that in the diffraction light guide plate according to Comparative Example, the input image is divided and output from the respective output diffraction optical elements, and thus if the incident angle of the image is only slightly changed (about 5 degrees), a part of the image is not output, whereby the image corresponding to the sites adjacent to the plurality of regions in the output diffraction optical element is not clearly recognized, as shown in FIG. 15.

Example

[0131] A diffraction light guide plate was produced in the same manner as in Experimental Example 2, but in the same manner as in Comparative Example, except that a diffraction optical element having a depth of about 50 nm as a third region of the second diffraction optical element is disposed between the first region and the second region. At this time, the ratio (Z3/(Z1+Z2+Z3)) of the second diffraction optical element occupied by the length (length in the direction parallel to the z-axis in FIG. 4, Z3) of the third region in the second optical element was approximately 0.33 or so.

[0132] Then, the simulation results of the images that the images incident at the incident angles of about 0 degrees ((a) in FIG. 16) and about 5 degrees ((b) in FIG. 16) based on the normal of the first diffraction optical element in the diffraction light guide plate were output from the normal of the second optical element were shown in FIG. 16.

[0133] According to FIG. 16, it can be seen that all the images incident on the diffraction light guide plate are output from the respective regions in the second diffraction optical element. Specifically, according to FIG. 16, it can be confirmed that the diffraction light guide plate, in which the diffraction optical element formed by diffraction gratings in the form that linear diffraction gratings having traveling directions different from each other overlap is disposed between diffraction optical elements formed by the linear diffraction gratings as in the present application, can output all the images corresponding to the respective regions regardless of the incident angles of the input images.