Range image generating apparatus

• US 7,697,119 B2
• Filed: 11/11/2008
• Issued: 04/13/2010
• Est. Priority Date: 11/14/2007
• Status: Active Grant

• Current Assignee: Stanley Electric Company Limited
• Original Assignee: Stanley Electric Company Limited
• Inventors: Ikeno, Ryohei, Urabe, Hideki, Kawata, Tadashi
• Primary Examiner(s): ALSOMIRI, ISAM A
• Application Number:
  US12/268,487
• Publication Number:
  US 20090122297A1
• Time in Patent Office: 518 Days
• Field of Search: 356/4.01, 356/4.07, 356/5.01, 356/5.15, 382/106, 382/107
• US Class Current: 356/4.07
• 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
• CPC Class Codes: G01S 17/931 of land vehicles
• CPC Class Codes: G01S 7/4808 Evaluating distance, position or velocity data
• CPC Class Codes: G01S 7/493 Extracting wanted echo signals

Abstract

A range image generating apparatus capable of preventing or reducing generation of range images with interference, which contain e.g., pixels with erroneous distance values is provided. The range image generating apparatus includes: a light source radiating a light; an image pickup element; a range image generating unit; a frequency changing unit that changes a modulation frequency for each frame rate or charge storage time; and a control unit that controls the light source and the image pickup element in synchronization with the modulation frequency changed by the frequency changing unit.

Claims

1. A range image generating apparatus comprising:

a light source that radiates modulated light to a target space;

an image pickup element including;

(i) a plurality of photoelectric conversion elements that receive reflected light radiated from the light source and reflected by an object in the target space and that convert the reflected light into charges, (ii) a plurality of charge storage units provided for the respective photoelectric conversion elements, and (iii) a distribution unit that distributes the charges converted by the photoelectric conversion elements into the plurality of charge storage units in synchronization with modulation of the light source;

a range image generating unit that performs a predetermined arithmetic operation based on the charges stored in the plurality of charge storage units and that generates a range image whose pixel values are distance values;

a frequency changing unit that changes a modulation frequency for each frame rate or charge storage time;

a control unit that controls the light source and the image pickup element in synchronization with the modulation frequency changed by the frequency changing unit; and

a determination unit that compares a plurality of range images generated by the range image generating unit at successive times with each other, and when at least one range image from among the plurality of range images includes a pixel indicating a finite value and when a pixel in another one of the range images, which is at a same position as the pixel indicating the finite value, indicates infinity or non-measurability, the determination unit determines the pixel indicating the finite value to be a pixel indicating a value for a light source of another range image generating apparatus.

2. The range image generating apparatus according to claim 1, wherein the frequency changing unit changes the modulation frequency to a frequency obtained by one of adding a frequency that is an integral multiple of a frame rate or light storage time to a predetermined reference modulation frequency, and subtracting the frequency from the predetermined reference modulation frequency.

3. The range image generating apparatus according to claim 1, wherein when at least one range image from among the plurality of range images includes a pixel with a distance value considerably different from an actual distance or a non-measurable pixel, and when a pixel in another one of the range images, which is at a same position as the pixel with the distance value considerably different from the actual distance or the non-measurable pixel, indicates a proper distance value, the determination unit determines the pixel with the distance value considerably different from the actual distance or the non-measurable pixel to have been interfered with.

4. The range image generating apparatus according to claim 3, further comprising a replacing unit that replaces the distance value of the pixel determined to have been interfered with by the determination unit, with a distance value of a pixel temporally adjacent to said pixel.

5. The range image generating apparatus according to claim 1, wherein the frequency changing unit changes the modulation frequency randomly or according to a certain rule.

6. The range image generating apparatus according to claim 5, wherein when at least one range image from among the plurality of range images includes a pixel with a distance value considerably different from an actual distance or a non-measurable pixel, and when a pixel in another one of the range images, which is at a same position as the pixel with the distance value considerably different from the actual distance or the non-measurable pixel, indicates a proper distance value, the determination unit determines the pixel with the distance value considerably different from the actual distance or the non-measurable pixel to have been interfered with.

7. The range image generating apparatus according to claim 5, wherein the frequency changing unit changes the modulation frequency to a frequency obtained by one of adding a frequency that is an integral multiple of a frame rate or light storage time to a predetermined reference modulation frequency, and subtracting the frequency from the predetermined reference modulation frequency.

8. The range image generating apparatus according to claim 7, further comprising a replacing unit that replaces the distance value of the pixel determined by the determination unit to be the pixel indicating the value for the light source of the other range image generating apparatus, with a distance value of a pixel spatially adjacent to said pixel.

9. The range image generating apparatus according to claim 7, wherein when at least one range image from among the plurality of range images includes a pixel with a distance value considerably different from an actual distance or a non-measurable pixel, and when a pixel in another one of the range images, which is at a same position as the pixel with the distance value considerably different from the actual distance or the non-measurable pixel, indicates a proper distance value, the determination unit determines the pixel with the distance value considerably different from the actual distance or the non-measurable pixel to have been interfered with.

10. The range image generating apparatus according to claim 9, further comprising a replacing unit that replaces the distance value of the pixel determined to have been interfered with by the determination unit, with a distance value of a pixel temporally adjacent to said pixel.

11. The range image generating apparatus according to claim 1, further comprising a replacing unit that replaces the distance value of the pixel determined by the determination unit to be the pixel indicating the value for the light source of the other range image generating apparatus, with a distance value of a pixel spatially adjacent to said pixel.