Reference Pixel Array with Varying Sensitivities for TOF Sensor

• US 20090020687A1
• Filed: 07/17/2008
• Published: 01/22/2009
• Est. Priority Date: 07/18/2007
• Status: Active Grant

• Current Assignee: Ams Sensors Singapore Pte. Ltd. (Ams-Osram AG)
• Original Assignee: MESA IMAGING AG (Ams-Osram AG)
• Inventors: Oggier, Thierry, Buettgen, Bernhard, Lehmann, Michael
• Granted Patent: US 7,586,077 B2
• Time in Patent Office: Days
• US Class Current: 250/208.100
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/894 3D imaging with simultaneous measurement of time-of-flight at a 2D array of receiver pixels, e.g. time-of-flight cameras or flash lidar
• CPC Class Codes: G01S 7/4816 of receivers alone
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating

Abstract

The sensitivity of a reference pixel array RPA to the reference modulated light MLR is varied for different reference pixels RP of the reference pixel array RPA. In one embodiment the different sensitivities of the reference pixels RP in the RPA is achieved by designing the pixels to have different light sensitivities with respect to each other. In another embodiment, the different sensitivities are achieved by changing optical coupling between the separate reference pixels RP of the reference pixel array RPA to the reference modulated light MLR such as by changing how the different reference pixels RP couple to the aperture LGA of the light guide LG.

Claims

1. A demodulation sensor, comprising:

an illumination module for generated modulated light for illuminating a scene;

one or more imaging pixels for detecting the modulated light returning from the scene;

an array of reference pixels in a reference pixel array for receiving reference modulated light from the illumination module, wherein the reference pixels in the reference pixel array have different sensitivities to the reference modulated light from the illumination module; and

a controller for determining a phase relationship between the modulated light generated by the illumination module with reference to the reference pixel array and the modulated light detected by the one or more imaging pixels.

2. A sensor as claimed in claim 1, wherein the one or more imaging pixels comprises a single pixel for point ranging.

3. A sensor as claimed in claim 1, wherein the one or more imaging pixels comprises a one or two dimensional array of imaging pixels for generating an image of the scene.

4. A sensor as claimed in claim 1, wherein the array of reference pixels comprises a one or two dimensional array of reference pixels on a same chip as the one or more imaging pixels and adjacent to the imaging pixels.

5. A sensor as claimed in claim 4, further comprising a light shield projecting from the chip between the reference pixels and the one or more imaging pixels to prevent the reference light from reaching the one or more imaging pixels.

6. A sensor as claimed in claim 1, wherein the reference light is transmitted from the illumination module to the reference pixel array in a light guide.

7. A sensor as claimed in claim 6, wherein reference pixels of the reference pixel array have different sensitivities to the reference modulated light from the illumination module due to different coupling to the light guide.

8. A sensor as claimed in claim 1, wherein reference pixels of the reference pixel array have different sensitivities to the reference modulated light from the illumination module due to different optical sensitivities.

9. A sensor as claimed in claim 1, wherein reference pixels of the reference pixel array have different sensitivities to the reference modulated light from the illumination module due to different proportions of light sensitive and light insensitive regions in the pixels.

10. A sensor as claimed in claim 1, further comprising a reference pixel evaluator for generating a synchronizing signal to the controller in response to selected pixels in the reference pixel array.

11. A sensor as claimed in claim 1, further comprising a reference pixel evaluator that generates a synchronizing signal to the controller in response pixels selected from the reference pixel array based on 1) which of the pixels are saturated or not and 2) which of the pixels have a good S/N or not.

12. A sensor as claimed in claim 1, further comprising a reference pixel evaluator that generates a synchronizing signal to the controller in response pixels selected from the reference pixel array based on averaging and/or weighting a phase reference based on one or more of the reference pixels in the reference pixel array.

13. A demodulation method, comprising:

generating modulated light for illuminating a scene;

detecting the modulated light returning from the scene to produce a three dimensional image of the scene;

receiving and detecting reference modulated light with a reference pixel array of reference pixels having different sensitivities to the reference modulated light; and

determining a phase relationship between the modulated light and the detected modulated light returning from the scene with reference to the reference pixel array.

14. A method as claimed in claim 13, further comprising preventing the reference modulated light from reaching imaging pixels.

15. A method as claimed in claim 13, wherein reference pixels of the reference pixel array have different sensitivities to the reference modulated light due to different coupling to a light guide.

16. A method as claimed in claim 13, wherein reference pixels of the reference pixel array have different sensitivities to the reference modulated light due to different optical sensitivities.

17. A method as claimed in claim 13, wherein reference pixels of the reference pixel array have different sensitivities to the reference modulated light due to different proportions of light sensitive and light insensitive regions in the pixels.

18. A method as claimed in claim 13, wherein the step of determining the phase relationship comprises selecting pixels from the reference pixel array and generating a synchronizing signal from the selected pixels.

19. A method as claimed in claim 13, wherein the step of determining the phase relationship comprises selecting pixels from the reference pixel array and generating a synchronizing signal from the selected pixels by averaging or weighting the pixels.

20. A demodulation sensor, comprising:

an illumination module for generated modulated light for illuminating a scene;

one or more imaging pixels for detecting the modulated light returning from the scene;

an array of reference pixels in a reference pixel array for receiving reference modulated light from the illumination module;

a controller for determining a phase relationship between the modulated light generated by the illumination module with reference to the reference pixel array and the modulated light detected by the one or more imaging pixels

a reference pixel evaluator that generates a synchronizing signal to the controller in response pixels selected from the reference pixel array based on averaging and/or weighting a phase reference based on one or more of the reference pixels in the reference pixel array.