Method for contamination detection in a TOF range camera

• US 9,025,071 B2
• Filed: 06/12/2008
• Issued: 05/05/2015
• Est. Priority Date: 06/15/2007
• 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: Mirbach, Bruno, Ginhoux, Romuald
• Primary Examiner(s): Haskins, Twyler
• Assistant Examiner(s): BHUIYAN, FAYEZ A
• Application Number:
  US12/664,025
• Publication Number:
  US 20100283888A1
• Time in Patent Office: 2,518 Days
• Field of Search: 348/348, 356/5.01
• US Class Current: 348/348
• 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 2007/4975 of sensor obstruction by, e.g. dirt- or ice-coating, e.g. by reflection measurement on front-screen
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating
• CPC Class Codes: H04N 23/60 Control of cameras or camera modules
• CPC Class Codes: H04N 5/2226 Determination of depth image, e.g. for foreground/background separation determining depth by image analysis in general G06T7/50; segmentation by image analysis in general G06T7/10

Abstract

A method for contamination detection in a time-of-flight (TOF) range imaging system is described, wherein the TOF range imaging system receives light reflected from a scene, through an optical interface, on an imager sensor having an array of pixels, and wherein distance information and amplitude information are determined for the sensor pixels. The presence of contamination on the optical interface is determined on the basis of amplitude information determined for the sensor pixels.

Claims

1. A method for contamination detection in a time-of-flight (TOF) range imaging system, said TOF range imaging system receiving light reflected from a scene, through an optical interface, on an imager sensor having an array of pixels, wherein distance information and amplitude information are determined for said sensor pixels, and wherein the presence of contamination disposed on said optical interface is determined on the basis of said amplitude information determined for said sensor pixels, wherein the contamination deposited onto the optical interface includes at least one contaminant, further including the step of evaluating the statistics of the amplitude information over the entire image by

determining a number of pixels having an amplitude lower than a given amplitude threshold, and concluding the presence of contamination if said number of pixels having an amplitude lower than said amplitude threshold is less than a predetermined number of pixels, or

determining the amplitude value for which the sum of pixels of lower amplitude equals a predetermined number of pixels;

and concluding the presence of contamination if the amplitude value equals or exceeds a predetermined amplitude threshold.

2. The method according to claim 1, wherein said amplitude threshold is dependent on the mean of the amplitude values in the image.

3. The method according to claim 1, wherein said scene is illuminated by means of an active illumination module emitting modulated light waves and said distance information is determined based on the phase delay between emitted and received light signal.

4. The method according to claim 1, comprising generating a signal indicative of the presence or absence of contamination, respectively indicative of the level of contamination, depending on the analysis of said amplitude information.

5. A time-of-flight imager system comprising an imager sensor having an array of pixels receiving light reflected from a scene, through an optical interface, said time-of-flight imager system further including means for implementing the method according to claim 4 and for generating a signal indicative of the level of contamination.

6. The method according to claim 1, wherein said amplitude threshold is dependent on the mean of the amplitude values in the image.