Head-mounted light field display with integral imaging and waveguide prism
Freeform waveguide prism and use with head-mounted light field display with integral imaging and relay group.
1. A head-mounted display integral imaging (InI) system, comprising:
a microscopic InI unit (micro-InI) configured to create light fields of a selected 3D scene at a selected position along an optical axis of the system;
a relay unit having a vari-focal element (VFE) disposed therein, the relay unit disposed on the optical axis at a location so the selected position is an optical conjugate of the relay unit, the relay unit configured to receive the light fields created by the microscopic InI unit; and
the freeform waveguide prism according to any of the preceding claims for receiving light from the relay unit to provide an image of the 3D scene at an exit pupil of the system for viewing by a user of the head-mounted display system,
wherein the VFE is configured to tune the location of the intermediate image within the body of the prism, the freeform waveguide prism comprising:
a first freeform optical surface disposed to receive light from the lightfield and refract the received light into the body of the prism;
a second freeform optical surface disposed to receive the refracted light from the first freeform optical surface and reflect the light into the body of the prism to provide an intermediate image of the lightfield at a selected location within the body of the prism;
a third freeform optical surface disposed to receive the light from the intermediate image and total internally reflect the light into the body of the prism; and
a fourth freeform optical surface disposed to receive the reflected light from the third freeform optical surface and reflect the light back to the third freeform optical surface at an angle that allows the light to exit the prism, the first through fourth freeform optical surfaces cooperating so that the light exiting the prism through the third freeform optical surface produces an image of the light field at a selected location external to the prism.
2. The head-mounted display integral imaging (InI) system according to claim 1 , wherein the second freeform optical surface is configured to total internally reflect the light into the body of the prism.
3. The head-mounted display integral imaging (InI) system according to claim 1 , wherein the second freeform optical surface is mirrored to reflect the light into the body of the prism.
4. The head-mounted display integral imaging (InI) system according to claim 1 , wherein the third freeform optical surface is configured to total internally reflect the light from the second freeform optical surface into the body of the prism.
5. The head-mounted display integral imaging (InI) system according to claim 1 , wherein the fourth freeform optical surface is mirrored.
6. The head-mounted display integral imaging (InI) system according to claim 1 , wherein the fourth freeform optical surface includes a beamsplitting coating.
7. The head-mounted display integral imaging (InI) system according to claim 1 , wherein for an orthogonal X-Y-Z coordinate system, the Z-axis is along the viewing direction, the Y-axis is parallel to the horizontal direction aligned with interpupilary direction of a user, and the X-axis is in the vertical direction aligning with the head orientation of the user.
8. The head-mounted display integral imaging (InI) system according to claim 7 , wherein the freeform waveguide prism is symmetric about the horizontal (Y-Z) plane.
9. The head-mounted display integral imaging (InI) system according to claim 7 , wherein the first through fourth freeform optical surfaces are decentered along the horizontal Y-axis and rotated about the vertical X-axis.
10. The head-mounted display integral imaging (InI) system according to claim 1 , wherein the shape of any one of the first through fourth freeform optical surfaces is given by
z
=
c
r
2
1
+
1
-
(
1
+
k
)
c
2
r
2
+
∑
j
=
2
6
6
C
j
x
m
y
n
j
=
(
m
+
n
)
2
+
m
+
3
n
2
+
1
,
where z is the sag of the free-form surface measured along the z-axis of a local x, y, z coordinate system, c is the vertex curvature (CUY), r is the radial distance, k is the conic constant, and C j is the coefficient for x m y n .
11. The head-mounted display integral imaging (InI) system of claim 1 , wherein the microscopic InI unit (micro-InI) is configured to reproduce full-parallax light fields of a 3D scene having a constrained viewing zone.
12. The freeform waveguide prism or head-mounted display integral imaging (InI) system of claim 1 , comprising a see-through unit in optical communication with the freeform waveguide prism to transmit a view of a real world to the freeform waveguide prism.
13. The head-mounted display integral imaging (InI) system of claim 1 , wherein the relay unit comprises a first lens group and wherein the VFE is located at a back focal length of the first lens group.
14. The head-mounted display integral imaging (InI) system of claim 1 , wherein the field of view of the system is independent of the optical power of the VFE.
15. The head-mounted display integral imaging (InI) system of claim 1 , wherein the VFE is disposed on the optical axis at a location such that the compound optical power of the relay unit is maintained constant, independent of the optical power of the VFE.
16. The head-mounted display integral imaging (InI) system of claim 1 , wherein the microscopic InI unit includes a microdisplay and the subtended field angle of the microdisplay through the freeform waveguide prism is maintained constant, independent of the optical power of the VFE.
17. The head-mounted display integral imaging (InI) system of claim 1 , wherein the relay unit is configured to tune the position along the optical axis of the position of a reconstructed 3D virtual scene through the eyepiece by up to 5 diopters.
18. The head-mounted display integral imaging (InI) system of claim 1 , wherein the focal range of the VFE is 75-100 mm.
19. The head-mounted display integral imaging (InI) system of claim 1 , wherein the focal length of the freeform waveguide prism is 27.5 mm.
20. The head-mounted display integral imaging (InI) system of claim 1 , wherein the diagonal field of view of the system is 35°.
21. The head-mounted display integral imaging (InI) system of claim 1 , wherein the system has an optical resolution as high as 2 arc minutes per pixel.
22. The head-mounted display integral imaging (InI) system of claim 1 , wherein the microscopic InI unit comprises a micro-lens array of which at least one lens surface is represented by the equation
z
=
c
r
2
1
+
1
-
(
1
+
k
)
c
2
r
2
+
A
r
4
+
B
r
6
+
C
r
8
+
D
r
1
0
+
E
r
1
2
,
where z is the sag of the surface measured along the z-axis of a local x, y, z coordinate system, c is the vertex curvature, r is the radial distance, k is the conic constant, A through E are the 4th, 6th, 8th, 10th and 12th order deformation coefficients, respectively.
23. The head-mounted display integral imaging (InI) system of claim 1 , wherein the microscopic InI unit comprises a microdisplay image source that renders set of 2D elemental images, each image representing a different perspective of a 3D scene, and an aperture array disposed between the microdisplay image source and the relay unit.