Camera with light valve over sensor array

• US 10,412,280 B2
• Filed: 02/10/2016
• Issued: 09/10/2019
• Est. Priority Date: 02/10/2016
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Inventors: Akkaya, Onur Can, Bamji, Cyrus, Benedetti, Arrigo, Fenton, Michael S., Gullapalli, Jayachandra
• Primary Examiner(s): Tran, Sinh
• Assistant Examiner(s): Wu, Zhenzhen
• Application Number:
  US15/040,862
• Publication Number:
  US 20170230551A1
• Time in Patent Office: 1,308 Days
• Field of Search: 348335, 348340
• CPC Class Codes: G02B 5/201 in the form of arrays
• CPC Class Codes: G02F 1/0136 for the control of polarisation, e.g. state of polarisation [SOP] control, polarisation scrambling, TE-TM mode conversion or separation G02F1/0353 takes precedence
• CPC Class Codes: G02F 1/133528 Polarisers
• CPC Class Codes: G02F 1/133531 characterised by the arrangement of polariser or analyser axes
• CPC Class Codes: G02F 1/19 based on variable-reflection or variable-refraction elements not provided for in groups G02F1/015 - G02F1/169
• CPC Class Codes: G02F 2201/346 distributed (Bragg) reflector
• CPC Class Codes: G02F 2203/055 wavelength filtering
• CPC Class Codes: H04N 2209/043 using an alternating colour separation filter, e.g. colour wheel or colour LCD
• CPC Class Codes: H04N 23/10 for generating image signals from different wavelengths
• CPC Class Codes: H04N 23/11 for generating image signals from visible and infrared light wavelengths
• CPC Class Codes: H04N 23/12 with one sensor only
• CPC Class Codes: H04N 23/55 Optical parts specially adapted for electronic image sensors; Mounting thereof

Abstract

A camera includes a sensor array including a plurality of individually addressable sensor elements, each of the plurality of sensor elements responsive to incident light over a broad wavelength band. Covering the sensor array is a light valve switchable electronically between closed and open states. The light valve is configured to, in the closed state, block light of a stopband and transmit light outside the stopband, and, in the open state, transmit the light of the stopband. An electronic controller of the camera is configured to switch the light valve from the closed to the open state and, synchronously with switching the light valve, address the sensor elements of the sensor array.

Claims

1. A camera comprising:

an illumination sensor;

a sensor array including a plurality of individually addressable sensor elements, each of the plurality of sensor elements responsive to incident light over a broad wavelength band;

arranged in parallel over the plurality of sensor elements of the sensor array, two or more light valves having two or more polarizable liquid-crystal layers arranged between fixed polarizers, wherein each light valve is switchable electronically between a closed state and an open state and configured to, in the closed state, block light of a visible stopband and transmit light outside the visible stopband, and, in the open state, transmit the light of the visible stopband, wherein the visible stopband differs for each of the two or more light valves; and

coupled operatively to the illumination sensor and to each of the two or more light valves, an electronic controller configured to individually and sequentially switch the light valve from the closed state to the open state and synchronously address the sensor elements of the sensor array, such that each sensor element responds, in sequence, to the light of the visible stopband of each of the two or more light valves,

wherein the controller is configured to maintain each of the two or more light valves in the closed state for a repeatable closed duration and in the open state for a repeatable open duration, and to vary the closed and open durations responsive to output of the illumination sensor.

2. The camera of claim 1 wherein the stopband of each of the two or more light valves is a visible band.

3. The camera of claim 1 wherein, for each of the two or more light valves, the light outside the stopband includes infrared light.

4. The camera of claim 1 further comprising an infrared emitter, wherein the electronic controller is further configured to, synchronously with switching the light valve and addressing the sensor elements, energize the infrared emitter.

5. The camera of claim 4 wherein addressing the sensor elements includes, in the closed state of the two or more light valves, resolving a phase offset from each of the plurality of sensor elements relative to infrared-emitter modulation.

6. The camera of claim 1 further comprising one or more passive filters configured to limit response of the sensor array.

7. The camera of claim 1 wherein at least one of the liquid-crystal layer and at least one of the fixed polarizers of each of the two or more light valves exhibit wavelength-dependent transmissivity.

8. The camera of claim 7 wherein at least one of the fixed polarizers provide a higher contrast ratio in the stopband than outside the stopband.

9. The camera of claim 7 wherein the fixed polarizers of each of the two or more light valves include upstream and downstream polarizers with mutually perpendicular transmission planes.

10. The camera of claim 1 wherein the two or more light valves include an optically downstream light valve coupled directly to the sensor array or to a microlens array portion of the sensor array.

11. A combination depth and flat-image camera comprising:

a sensor array including a plurality of individually addressable sensor elements, each of the plurality of sensor elements responsive to incident light over visible and infrared bands;

arranged in parallel over the plurality of sensor elements of the sensor array, two or more light valves having two or more polarizable liquid-crystal layers arranged between fixed polarizers, wherein each light valve is switchable electronically between a closed state and an open state and configured to, in the closed state, block light of a visible stopband and transmit light outside the visible stopband, and, in the open state, transmit the light of the visible stopband, wherein the visible stopband differs for each of the two or more light valves;

an infrared emitter; and

coupled operatively to the infrared emitter and to each of the two or more light valves, an electronic controller configured to individually and sequentially switch each light valve from the closed state to the open state and synchronously address the sensor elements of the sensor array, such that each sensor element responds, in sequence, to the light of the visible stopband of each of the two or more light valves,

wherein the controller is further configured to maintain each of the two or more light valves concurrently in the closed state, synchronously energize the infrared emitter and address the sensor elements of the sensor array to resolve subject depth at each sensor element based on a time-of-flight measurement.

12. The camera of claim of claim 11 wherein resolving depth to an image locus includes resolving a phase offset from each sensor element relative to infrared-emitter modulation.

13. The camera of claim 11 wherein wherein addressing the sensor elements of the sensor array includes integrating light intensity in three or more color channels.

14. The camera of claim 11 wherein the controller is further configured to:

deactivate the infrared emitter;

switch the two or more light valves to the closed state;

integrate light intensity received at each element of the sensor array to assemble a reference image while the two or more light valves are in the closed state; and

subtractively correct, based on the reference image, subsequent light intensities integrated when one of the two or more light valves is in the open state.

16. The camera of claim 11 wherein the time-of-flight measurement is a phase-discriminating time-of-flight measurement.

15. A camera comprising:

a sensor array including a plurality of individually addressable sensor elements, each of the plurality of sensor elements responsive to incident light over a broad wavelength band;

arranged in parallel over the plurality of sensor elements of the sensor array, two or more light valves having two or more polarizable liquid-crystal layers arranged between fixed polarizers, wherein each light valve is switchable electronically between a closed state and an open state and configured to, in the closed state, block light of a visible stopband and transmit light outside the visible stopband, and, in the open state, transmit the light of the visible stopband, wherein the visible stopband differs for each of the two or more light valves; and

coupled operatively to each of the two or more light valves, an electronic controller configured to individually and sequentially switch each light valve from the closed state to the open state and synchronously address the sensor elements of the sensor array, such that each sensor element responds, in sequence, to the light of the visible stopband of each of the two or more light valves.

17. The camera of claim 15 wherein the two or more light valves include an upstream light valve and a downstream light valve downstream of the upstream light valve, wherein the fixed polarizers of each of the upstream and downstream light valves include an entry polarizer and an exit polarizer, and wherein the exit polarizer of the upstream light valve and the entry polarizer of the downstream light valve are oriented in parallel.

18. The camera of claim 15 wherein the two or more light valves include a first light valve having a stopband in a red spectral region, a second light valve having a stopband in a green spectral region, and a third light valve having a stopband in a blue spectral region.