Light field display metrology

• US 10,378,882 B2
• Filed: 11/02/2016
• Issued: 08/13/2019
• Est. Priority Date: 11/04/2015
• Status: Active Grant

• Current Assignee: Magic Leap, Inc.
• Original Assignee: Magic Leap, Inc.
• Inventors: Yeoh, Ivan L., Edwin, Lionel E., Miller, Samuel A.
• Primary Examiner(s): Williams, Jeffery A
• Application Number:
  US15/341,760
• Publication Number:
  US 20170122725A1
• Time in Patent Office: 1,014 Days
• Field of Search: 348153
• CPC Class Codes: G01B 11/14 for measuring distance or clearance between spaced objects or spaced apertures G01B11/26 takes precedence; rangefinders G01C3/00
• CPC Class Codes: G01B 11/22 for measuring depth
• CPC Class Codes: G02B 2027/011 comprising device for correcting geometrical aberrations, distortion
• CPC Class Codes: G02B 2027/0178 Eyeglass type eyeglass details G02C
• CPC Class Codes: G02B 27/01 Head-up displays
• CPC Class Codes: G02B 27/017 Head mounted
• CPC Class Codes: G06F 2203/011 Emotion or mood input determined on the basis of sensed human body parameters such as pulse, heart rate or beat, temperature of skin, facial expressions, iris, voice pitch, brain activity patterns
• CPC Class Codes: G06F 3/013 Eye tracking input arrangements G06F3/015 takes precedence
• CPC Class Codes: G06T 15/20 Perspective computation
• CPC Class Codes: G06T 19/006 Mixed reality object pose determination, tracking or camera calibration for mixed reality G06T7/00
• CPC Class Codes: G06T 2207/10012 Stereo images
• CPC Class Codes: G06T 2207/10052 Images from lightfield camera
• CPC Class Codes: G06T 3/20 Linear translation of whole images or parts thereof, e.g. panning
• CPC Class Codes: G06T 3/40 Scaling of whole images or parts thereof, e.g. expanding or contracting
• CPC Class Codes: G06T 3/60 Rotation of whole images or parts thereof
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 2320/028 by changing the viewing angle properties, e.g. widening the viewing angle, adapting the viewing angle to the view direction
• CPC Class Codes: G09G 2320/029 by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
• CPC Class Codes: G09G 2320/0626 : for control of overall brightness
• CPC Class Codes: G09G 2320/0666 : for control of colour parameters, e.g. colour temperature
• CPC Class Codes: G09G 2320/0673 : for control of gamma adjustment, e.g. selecting another gamma curve
• CPC Class Codes: G09G 2320/0693 : Calibration of display systems
• CPC Class Codes: G09G 2340/0464 : Positioning
• CPC Class Codes: G09G 2360/16 : Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/003 : to produce spatial visual effects
• CPC Class Codes: G09G 3/006 : Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309
• CPC Class Codes: G09G 3/2092 : Details of a display terminals using a flat panel, the details relating to the control arrangement of the display terminal and to the interfaces thereto suitable for both CRT and flat panel G09G5/003; specific for a CRT G09G1/165
• CPC Class Codes: G09G 3/3406 : Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 5/02 : characterised by the way in which colour is displayed details of colour display specific for CRTs G09G1/28; specific for flat matrix panels other than liquid crystal displays G09G3/2003; specific for liquid crystal displays G09G3/3607
• CPC Class Codes: H04N 13/144 : for flicker reduction
• CPC Class Codes: H04N 13/327 : Calibration thereof
• CPC Class Codes: H04N 13/344 : with head-mounted left-right displays
• CPC Class Codes: H04N 13/383 : for tracking with gaze detection, i.e. detecting the lines of sight of the viewer's eyes
• CPC Class Codes: H04N 13/395 : with depth sampling, i.e. the volume being constructed from a stack or sequence of 2D image planes
• CPC Class Codes: H04N 13/398 : Synchronisation thereof; Control thereof

Abstract

Examples of a light field metrology system for use with a display are disclosed. The light field metrology may capture images of a projected light field, and determine focus depths (or lateral focus positions) for various regions of the light field using the captured images. The determined focus depths (or lateral positions) may then be compared with intended focus depths (or lateral positions), to quantify the imperfections of the display. Based on the measured imperfections, an appropriate error correction may be performed on the light field to correct for the measured imperfections. The display can be an optical display element in a head mounted display, for example, an optical display element capable of generating multiple depth planes or a light field display.

Claims

1. An optical metrology system for measuring imperfections in a light field generated by a display, the optical metrology system comprising:

a display configured to project a target light field comprising a virtual object having an intended focus position;

a camera configured to obtain images of the target light field;

a hardware processor programmed with executable instructions to;

access one or more images corresponding to a portion of the light field;

apply a display-to-camera pixel mapping to transfer pixel values of the display to pixel values of the camera, wherein the display-to-camera pixel mapping comprises;

a first gamma correction that maps color levels of the display to a first intermediate color representation;

a pixel-dependent coupling function that maps the first intermediate color representation to a second intermediate color representation; and

a second gamma correction that maps the second intermediate color representation to color levels registered by the camera;

analyze the one or more images to identify a measured focus position corresponding to a position at which the virtual object is in focus; and

determine imperfections in the light field based at least in part on a comparison of the measured focus position and the intended focus position.

2. The optical metrology system of claim 1, wherein the display comprises a stack of waveguides configured to output light to project the virtual object to at least one depth plane.

3. The optical metrology system of claim 1, wherein the camera comprises a digital camera having a small depth of focus.

4. The optical metrology system of claim 3, wherein the camera has a focus, and the system is configured to sweep the focus of the camera over a range of focuses to obtain the one or more images.

5. The optical metrology system of claim 1, wherein the camera comprises a light field camera.

6. The optical metrology system of claim 1, wherein the virtual object comprises a checkerboard pattern, a geometric pattern, or a stochastic pattern.

7. The optical metrology system of claim 1, wherein the display comprises a plurality of pixels, and the target light field corresponds to a subset of less than all of the plurality of pixels being illuminated.

8. The optical metrology system of claim 1, wherein the measured focus position includes a depth of focus.

9. The optical metrology system of claim 8, wherein the measured focus position further includes a lateral focus position.

10. The optical metrology system of claim 1, wherein the determined imperfections are based at least in part on an error vector between the intended focus position and the measured focus position.

11. The optical metrology system of claim 1, wherein the hardware processor is further programmed to determine an error correction for the display based at least in part on the determined imperfections.

12. The optical metrology system of claim 1, wherein the determined imperfections comprise a spatial imperfection.

13. The optical metrology system of claim 12, wherein the spatial imperfection comprises one or more of an in-plane translation, rotation, scaling, or warping error or an out-of-plane or focal depth error.

14. The optical metrology system of claim 1, wherein the determined imperfections comprise a chromatic imperfection.

15. The optical metrology system of claim 14, wherein the chromatic imperfection comprises one or more of a luminance flatness or a chromatic uniformity error associated with a color displayable by the display.