Viewing optics test subsystem for head mounted displays

1. An optical evaluation workstation comprising:

an enclosure that encloses the workstation and is configured to block light from entering the workstation;

a contrast test target;

a light source configured to backlight the contrast test target with diffuse light, the light source comprising a light panel and a light diffuser, the light panel configured to generate light and positioned to illuminate at least a portion of the light diffuser, the light diffuser configured to substantially and evenly diffuse light received from the light source;

an optical element feed assembly configured to:

receive an optical element of a head mounted display (HMD), and

position the optical element at a first distance from the contrast test target, the first distance corresponding to a distance between an optics block in the HMD and an electronic display in the HMD;

a camera configured to capture one or more images of the contrast test target through the optical element, the camera at a second distance from the contrast test target, the second distance corresponding to a distance between an exit pupil of the HMD and the electronic display in the HMD, wherein the contrast test target is positioned between the light source and the camera such that the contrast test target is illuminated with diffuse light from the light diffuser; and

a control module configured to evaluate optical contrast of the optical element using the one or more images of the contrast test target.

2. The workstation of claim 1 , wherein the control module is further configured to:

determine high luminance values for high luminance areas on the contrast test pattern;

average the high luminance values to get an average high luminance value;

determine low luminance values for low luminance areas on the contrast test pattern;

average the low luminance values to get an average low luminance value;

determine a contrast ratio of the average high luminance value to the average low luminance value; and

compare the contrast ratio to a threshold value indicative of a minimum contrast for optical elements of the HMD.

3. The workstation of claim 1 , wherein the optical element feed assembly includes an optics holder which is configured to receive and hold the optical element.

4. The workstation of claim 1 , wherein the control module is further configured to:

generate a test report based in part on the evaluation of the optical element; and

present the test report to a user of the optical evaluation workstation.

5. The workstation of claim 1 , further comprising an adjustment mechanism to adjust the first distance.

6. The workstation of claim 1 , further comprising an adjustment mechanism to adjust the second distance.

7. An optical evaluation workstation comprising:

an enclosure that encloses the workstation and is configured to block light from entering the workstation;

a test pattern for evaluating one or more quality metrics;

a light source configured to backlight the test pattern with diffuse light, the light source comprising a light panel and a light diffuser, the light panel configured to generate light and positioned to illuminate at least a portion of the light diffuser, the light diffuser configured to substantially and evenly diffuse light received from the light source;

an optical element feed assembly configured to:

receive an optical element of a head mounted display (HMD), and

position the optical element at a first distance from the test pattern, the first distance corresponding to a distance between an optics block in the HMD and an electronic display of the HMD; and

a camera configured to capture one or more images of the test pattern through the optical element, the camera at a second distance from the test pattern, wherein the second distance corresponds to a distance between an exit pupil of the HMD and the electronic display in the HMD, wherein the test pattern is positioned between the light source and the camera such that the test pattern is illuminated with diffuse light from the light diffuser; and

a control module configured to evaluate the optical element using a quality metric of the one or more quality metrics and the one or more images of the test pattern.

8. The workstation of claim 7 , wherein the optical element feed assembly includes an optics holder which is configured to receive and hold the optical element.

9. The workstation of claim 7 , wherein the control module is further configured to:

generate a test report based in part on the evaluation of the optical element; and

present the test report to a user of the optical evaluation workstation.

10. The workstation of claim 7 , further comprising an adjustment mechanism to adjust the first distance.

11. The workstation of claim 7 , further comprising an adjustment mechanism to adjust the second distance.

12. The workstation of claim 7 , wherein the quality metric is selected from a group consisting of: optical contrast, spatial resolution, distortion, astigmatism, and some other optical characteristic.

13. A method comprising:

positioning an optical element of a head mounted display (HMD) at a first distance from a camera in an optical evaluation workstation, the workstation comprising an enclosure that is configured to block light from entering the workstation, the first distance corresponding to a distance between an optics block in the HMD and an exit pupil of the HMD;

capturing one or more images, via the camera, of a test pattern, the test pattern positioned between a light source and the camera, such that the test pattern is illuminated by the light source as viewed through the optical element, the light source comprising a light panel and a light diffuser, wherein the light panel is configured to generate light and is positioned to illuminate at least a portion of the light diffuser and the light diffuser is configured to substantially and evenly diffuse light received from the light source, the test pattern at a second distance from the camera, wherein the second distance corresponds to a distance between an exit pupil of the HMD and the electronic display in the HMD; and

evaluating the optical element based in part on a quality metric and the one or more images of the test pattern.

14. The method of claim 13 , further comprising:

generating a test report based in part on the evaluation of the optical element; and

presenting the test report to a user.

15. The method of claim 13 , further comprising:

capturing a dark frame of the test pattern with no illumination from the light source of the test pattern as viewed through the optical element by the camera.

16. The method of claim 15 , wherein evaluating the optical element based in part on the quality metric and the one or more images of the test pattern comprises:

subtracting the dark frame from the one or more images to create one or more intermediate images;

stacking the one or more intermediate images to create a test image; and

evaluating the test image with the quality metric.

17. The method of claim 13 , wherein the quality metric is selected from a group consisting of: optical contrast, spatial resolution, distortion, astigmatism, and some other optical characteristic.

18. The method of claim 13 , wherein the quality metric is optical contrast.