Synchronous imaging using segmented illumination

• US 7,745,771 B2
• Filed: 04/03/2007
• Issued: 06/29/2010
• Est. Priority Date: 04/03/2007
• Status: Active Grant

• Current Assignee: Aptiv Technologies AG
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Troxell, John R., Taylor, Ronald M., Rege, Siddharth S.
• Primary Examiner(s): Epps; Georgia Y
• Assistant Examiner(s): BENNETT, JENNIFER D
• Application Number:
  US11/732,296
• Publication Number:
  US 20080245952A1
• Time in Patent Office: 1,183 Days
• Field of Search: 250/208.1, 250/221, 250/214.R, 382/173, 356/5.05, 356/5.06, 356/5.07, 356/5.08, 356/5.03, 356 301- 315, 356 401- 41, 359/227, 359/229, 359/601
• US Class Current: 250/208.1
• CPC Class Codes: G03B 15/05 Combinations of cameras with electronic flash apparatus; Electronic flash units
• CPC Class Codes: G03B 2215/0567 Solid-state light source, e.g. LED, laser
• CPC Class Codes: G03B 2215/0592 installed in front of light emitter
• CPC Class Codes: H04N 23/56 provided with illuminating means
• CPC Class Codes: H04N 23/74 by influencing the scene brightness using illuminating means
• CPC Class Codes: H04N 25/531 by controlling rolling shutters in CMOS SSIS

Abstract

In an actively illuminated imaging system, illumination of a segmented scene is synchronized with an image sensing period. A scene is segmented into a plurality of scene portions utilizing a segmented lens. In an aspect, a first scene portion is illuminated when an imager is actively collecting photogenerated charge from the first scene portion, and a second scene portion is illuminated when an imager is actively collecting photogenerated charge from the second scene portion. The sensitivity of an image sensor is maximized, while simultaneously minimizing the amount of light that must be supplied to illuminate a scene. An irradiance pattern is varied allowing a more uniform distribution of light. Bands of varying wavelength, polarization, and light intensity may be variously applied to illuminate individual scene segments, as needed to enhance an identification of an object in the scene. The present invention is particularly useful with high frame rate imaging systems.

Claims

1. A method of synchronizing an actively illuminated imaging system comprising:

employing one of a global shutter imager and a rolling shutter imager;

segmenting an image scene into a plurality of image scene portions comprising a first image scene portion and a second image scene portion;

sequentially illuminating the first image scene portion and the second image scene portion, wherein the first image scene portion is illuminated when an imager is actively collecting photogenerated charge as a function of light reflected from the first image scene portion, and the second image scene portion is illuminated when the imager is actively collecting photogenerated charge as a function of light reflected from the second image scene portion, wherein a time period of illuminating the first image scene portion is substantially equal to a time period of illuminating the second image scene portion; and

sequentially reading out pixels of the imager to produce an image, such that the segmented image scene portions form the image.

2. The method as in claim 1, wherein sequentially illuminating comprises employing a first light source to transmit to a first segment of a segmented lens to illuminate the first image scene portion, and employing a second light source to transmit to a second segment of the segmented lens to illuminate the second image scene portion.

3. The method as in claim 2, wherein the first light source transmits a first light, and the second light source transmits a second light, wherein the first light and the second light vary in at least one of band of wavelength and polarization.

4. The method as in claim 2, wherein the first light source transmits a first light intensity and the second light source transmits a second light intensity, to enhance an identification of an object in the image scene.

5. The method as in claim 1, wherein segmenting the image scene comprises dividing the plurality of image scene portions one of vertically and horizontally.

6. The method as in claim 1, wherein segmenting the image scene comprises segmenting the image scene by imager pixel row.

7. The method as in claim 1, further comprising at least one of extending an integration time of the first image scene portion pixel rows, reducing a readout time of the first image scene portion pixel rows, and reducing a quantity of the first image scene portion pixel rows, to allow for a time period during which the first image scene portion pixel rows can be illuminated when the imager is actively collecting photogenerated charge from the first image scene portion pixel rows.

8. The method as in claim 1, wherein the imaging system maintains a frame rate of at least about 30 frames per second.

9. The method as in claim 1, wherein imaging system is utilized in an automotive imaging application including a monitoring driver gaze system, vehicle night vision systems, vehicle backup aid systems, varying illumination of an object surrounding a vehicle, a security application, and augmenting illumination for a conventional imager.

10. The method of claim 1, wherein the step of sequential illuminating further comprises synchronizing the imager and a plurality of light sources that illuminate the plurality of image scene portions of the image, such that at least one of the plurality of image scene portions that is illuminated by at least one of the plurality of light sources is the portion that the imager is actively collecting photogenerated charge from.

11. The method of claim 10, wherein an irradiance pattern is spatially varied that allows for a substantially uniform distribution of light by redistributing intensity away from a center of a field to a periphery of the field.

12. An actively illuminated imaging system comprising:

a plurality of light sources for individually transmitting light; and

a segmented lens for receiving the individually transmitted light, and directing the individually transmitted light to an image scene that is segmented into a plurality of image scene portions comprising;

a first image scene portion, wherein a first light source of the plurality of light sources transmits to a first segment of segmented lens to illuminate the first image scene portion; and

a second image scene portion, wherein the first image scene portion and the second scene portion are sequentially illuminated, such that a second light source of the plurality of light sources transmits to a second segmented lens to illuminate the second image scene portion; and

an imager configured to actively collect photogenerated charge as a function of light reflected from the first image scene portion when the first image scene portion is illuminated, and actively collect photogenerated charge as a function of light reflected from the second image scene portion when the second image scene portion is illuminated, such that the imager and the plurality of light sources are synchronized so that at least one of the plurality of image scene portions illuminated by at least one of the plurality of light sources is the portion that the imager is actively collecting photogenerated charge from, wherein a time period of illuminating the first image scene portion is substantially equal to a time period of illuminating the second image scene portion, and the imager is a rolling shutter imager, wherein pixels of the imager are sequentially read out to produce an image, such that the segmented image scene portions form the image.

13. The system as in claim 12, wherein the first light source transmits a first light, and the second light source transmits a second light, wherein the first light and the second light vary in at least one of band of wavelength and polarization.

14. The system as in claim 12, wherein the first light source transmits a first light intensity and the second light source transmits a second light intensity, to enhance an identification of an object in the scene.

15. The system as in claim 12, wherein the plurality of image scene portions are divided one of vertically and horizontally.

16. The system as in claim 12, wherein the image scene is segmented by imager pixel row.

17. The system as in claim 12, wherein an integration time of the first image scene portion pixel rows is extended, a readout time of the first image scene portion pixel rows is reduced, and a quantity of the first image scene portion pixel rows is reduced, to allow for a time period during which the first image scene portion pixel rows can be illuminated when the imager is actively collecting photogenerated charge from the first image scene portion pixel rows.

18. The system as in claim 12, wherein the imaging system maintains a frame rate of at least about 30 frames per second.

19. The system as in claim 12, wherein imaging system is utilized in an automotive imaging application including a monitoring driver gaze system, vehicle night vision systems, vehicle backup aid systems, varying illumination of an object surrounding a vehicle, a security application, and augmenting illumination for a conventional imager.