METHOD AND SYSTEM FOR ACQUIRING A 3-D IMAGE OF A SCENE

• US 20100045966A1
• Filed: 09/11/2007
• Published: 02/25/2010
• Est. Priority Date: 09/20/2006
• Status: Active Grant

• Current Assignee: IEE International Electronics & Engineering SA (Aerospace Hi-Tech Holding Group Company Limited)
• Original Assignee: IEE International Electronics & Engineering SA (Aerospace Hi-Tech Holding Group Company Limited)
• Inventors: Cauquy, Marie-Astrid, Lamesch, Laurent
• Granted Patent: US 7,952,690 B2
• Time in Patent Office: Days
• US Class Current: 356/5.110
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures
• CPC Class Codes: G01S 17/36 with phase comparison between the received signal and the contemporaneously transmitted signal
• 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

Abstract

For acquiring a 3-D image of a scene, the scene is illuminated with modulated light emitted by an illumination unit and imaged onto an array of lock-in pixel sensor cells, which detect the previously emitted light after it has been scattered or reflected by an object or a living being in the scene. One determines the modulation phase of the light detected at the lock-in pixel sensor cells and provides a reference modulation phase that stands in a known relationship with the modulation phase of the light at the time of the emission. Based upon the reference modulation phase and the modulation phase of the light detected at the lock-in pixel sensor cells one then calculates depth information on the scene. The modulated light is emitted by a plurality of individual light emitting devices of the illumination unit, each of the light emitting devices emitting a part of the modulated light, and the reference modulation phase is provided as an average of the modulation phases of the parts of modulated light emitted by the light emitting devices.

Claims

1. A method of acquiring a 3-D image of a scene, comprising:

illuminating said scene with modulated light emitted at an illumination unit;

imaging said scene onto an array of lock-in pixel sensor cells and detecting at said lock-in pixel sensor cells light scattered in said scene;

determining a modulation phase of the light detected at said lock-in pixel sensor cells;

providing a reference modulation phase;

calculating depth information on said scene based upon said reference modulation phase and said modulation phase of the light detected at said lock-in pixel sensor cells;

wherein said modulated light is emitted by a plurality of individual light emitting devices of said illumination unit, each of said light emitting devices emitting a part of said modulated light, and wherein said reference modulation phase is provided as an average of the modulation phases of the parts of modulated light emitted by said light emitting devices.

2. The method according to claim 1, wherein providing said reference modulation phase comprises gathering, at said illumination unit, modulated light from said light emitting devices, detecting a modulation phase of the gathered modulated light and using the modulation phase of the gathered modulated light as reference modulation phase.

3. The method according to claim 1, wherein providing said reference modulation phase comprises individually detecting the modulation phases of the parts of modulated light emitted by said light emitting devices, calculating an average of the modulation phases of the parts of modulated light and using said calculated average as reference modulation phase.

4. The method according to claim 1, wherein the individual light emitting devices contribute approximately equally to illuminating said scene and wherein the modulation phases of the different parts of modulated light contribute approximately equally to said average.

5. The method according to claim 1, wherein the individual light emitting devices contribute by different extents to illuminating said scene and wherein the modulation phases of the different parts of modulated light contribute by corresponding extents to said average.

6. A 3-D imaging system for acquiring a 3-D image of a scene comprising

an illumination unit to emit modulated light into said scene;

at least one reference light sensor to detecting a reference modulation phase;

a camera including an array of lock-in pixel sensor cells and an optical arrangement to image said scene onto said array of lock-in pixel sensor cells, said camera being configured and arranged to determine a modulation phase of light detected at said lock-in pixel sensor cells;

an evaluation unit operationally connected to said at least one reference light sensor and said lock-in pixel sensor cell array to calculate depth information on said scene based upon said reference modulation phase and said modulation phase of the light detected at said lock-in pixel sensor cells;

wherein said illumination unit comprises a plurality of individual light emitting devices, each of said light emitting devices being configured to emit a part of said modulated light, and wherein said reference light sensor is configured and arranged to provide said reference modulation phase as an average of the modulation phases of the parts of modulated light emitted by said light emitting devices.

7. The 3-D imaging system according to claim 6, wherein said reference light sensor is arranged in said illumination unit in vicinity of said individual light emitting devices so as to be able to gather light from said individual light emitting devices.

8. The 3-D imaging system according to claim 6, comprising a light guide arranged to gather light from said individual light emitting devices and guide the gathered light from said individual light emitting devices to said reference light sensor.

9. The 3-D imaging system according to claim 6, comprising a plurality of light guides arranged each to guide light from an individual light emitting device to said reference light sensor.

10. The 3-D imaging system according to of claim 6, wherein said reference light sensor comprises a lock-in pixel sensor cell.

11. The 3-D imaging system according to claim 10, wherein said reference light sensor comprises one or more lock-in pixel sensor cells of said camera.

12. The 3-D imaging system according to claim 6, wherein said reference light sensor comprises a plurality of individual lock-in pixel sensor cells, wherein said 3-D imaging system comprises a plurality of individual light guides, each individual light guide being arranged to guide light from an individual light emitting device to an individual lock-in pixel sensor cell of said reference light sensor, and wherein said evaluation unit is configured to calculate said reference modulation phase as an average of modulation phases of light detected at said individual lock-in pixel sensor cells of said reference light sensor.