Image display apparatus
An image display apparatus includes an image forming device, a collimating optical system, and an optical device. The optical device includes a light guide plate, a first deflecting member that deflects light incident on the light guide plate, and a second deflecting member that deflects the light, which propagates in the light guide plate by total reflection, a plurality of times. The first and second deflecting members are provided in the light guide plate. Light having one wavelength emitted from at least one pixel satisfies the following condition: 2 t ·sin θ−2≦ W Y ≦2 t ·sin θ+2 where an axial direction of the light guide plate is the Y-direction, W Y prepresents the width in the Y-direction of the light incident on the light guide plate, t represents the thickness of the light guide plate, and θ represents the total reflection angle.
1. An image display apparatus comprising:
an image forming device;
an optical system; and
an optical device on which a light is incident from the optical system, in which the light is guided, and from which the light is emitted,
wherein the optical device includes a light guide plate, first deflecting means, and second deflecting means,
wherein the light guide plate has the first deflecting means and the second deflecting means,
wherein the following condition is satisfied:
2 t ·tan θ−2 ≦Lh− 1≦2 t ·tan θ+2
where an axial direction of the light guide plate is the Y-direction, a normal direction of the light guide plate is the X-direction, LH−1 (unit: mm) represents an effective length of the first deflecting means in the Y-direction, t represents the thickness of the light guide plate, and θ represents the incident angle of the light, which is totally reflected in the light guide plate, on an inner surface of the light guide plate.
2. The image display apparatus according to claim 1 , wherein the second deflecting means includes a layered structure including a plurality of dielectric films.
3. The image display apparatus according to claim 2 , wherein the dielectric films include a first dielectric film including a high dielectric constant material and a second dielectric film including a low dielectric constant material.
4. The image display apparatus according to claim 2 , wherein the layered structure further includes thin film layers including a material that is the same as the light guide plate, and wherein each thin film layer is positioned between two of the plurality of the dielectric films.
5. The image display apparatus according to claim 1 , wherein the first deflecting means includes a reflecting mirror.
6. The image display apparatus according to claim 1 , further comprising:
a scanning means configured to scan light emitted from the optical system; and
a relay optical system configured to relay the light scanned by the scanning means to the optical device.
7. The image display apparatus according to claim 6 , wherein the scanning means scans the light by:
rotating a micro-mirror in a two-dimensional direction to scan incident light;
converting the scanned incident light into a two-dimensional image; and
transmitting the two-dimensional image via virtual pixels.
8. The image display apparatus according to claim 1 , wherein the following condition is satisfied:
2 t ·tan θ−2 ≦W Y ≦2 t ·tan θ+2
where WY represents the width in the Y-direction of the light incident on the light guide plate.
9. The image display apparatus according to claim 1 , wherein the first deflecting means diffracts the light incident on the light guide plate, and the second deflecting means diffracts the light, which propagates in the light guide plate by total reflection, a plurality of times.
10. The image display apparatus according to claim 9 , wherein the first deflecting means and the second deflecting means include diffraction grating elements.
11. The image display apparatus according to claim 10 , wherein the diffraction grating elements are reflective diffraction grating elements.
12. The image display apparatus according to claim 10 , wherein the diffraction grating elements are transmissive diffraction grating elements.
13. The image display apparatus according to claim 10 , wherein the diffraction grating elements include a reflective diffraction grating element and a transmissive diffraction grating element.
14. The image display apparatus according to claim 1 , wherein the first deflecting means and the second deflecting means include a reflective volume hologram diffraction grating.
15. The image display apparatus according to claim 14 , wherein the first deflecting means and the second deflecting means each include a P-number of diffraction grating layers corresponding to a P-number of types of light beams having a P-number of different wavelength bands, the light means being transmitted by the image forming device.
16. The image display apparatus according to claim 15 , wherein the P-number is equal to three when the P-number of types of light beams have wavelength bands corresponding to the colors of red, green, and blue.
17. The image display apparatus according to claim 15 , wherein the reflective volume hologram diffraction grating is configured to provide interference fringes on the diffraction grating layers that linearly extend at a fixed pitch in a Z-direction.
18. The image display apparatus according to claim 1 , wherein length of the second deflecting means is longer than length of the first deflecting means in the Y-direction.