Brightness control on video cameras

• US 6,362,848 B1
• Filed: 10/20/1999
• Issued: 03/26/2002
• Est. Priority Date: 01/17/1997
• Status: Expired due to Term

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Lohscheller, Herbert, Binder, Bernd
• Primary Examiner(s): Le, Vu
• Application Number:
  US09/341,777
• Time in Patent Office: 888 Days
• Field of Search: 348/149, 348/221, 348/227, 382/104-105
• US Class Current: 348/149
• CPC Class Codes: H04N 23/72 Combination of two or more compensation controls

Abstract

A method for controlling the exposure of a stationary mounted video camera is proposed, which makes it possible to attain an optimal exposure even in difficult light circumstances. For this purpose, measuring zones in the image are evaluated and, using the evaluation, a correction factor is calculated which influences the exposure parameters of the camera.

Claims

1. A method for controlling a plurality of exposure parameters of a stationary mounted video camera, comprising the steps of:

causing the stationary mounted camera to record a plurality of images;

processing the plurality of images according to a plurality of electronic pixels;

determining a correction factor by comparing gray-scale values of coherent sequences of the electronic pixels of a preceding image and the electronic pixels of a current image;

setting the plurality of exposure parameters by using the correction factor;

determining a size, a position, and a type of at least one measuring zone in an image area;

setting an optimal exposure;

extracting and storing reference values of the at least one measuring zone and reference values of current ones of the plurality of exposure parameters of the stationary mounted video camera; and

performing a continuous operation,the continuous operation having adjustable time intervals.

2. The method according to claim 1, further comprising the steps of:

generating gray-scale histograms from gray-scale values of the at least one measuring zone;

evaluating the gray-scale histograms using a cross correlation; and

calculating the correction factor from the cross correlation.

3. The method according to claim 2, wherein the step of calculating the correction factor includes the step of:

calculating the correction factor as an average value over all of the at least one measuring zone.

4. The method according to claim 1, wherein the step of performing the continuous operation in order to provide the control includes the steps of:

determining a current image by performing one of the steps of;

selecting a last one of the recorded images, and recording a new image and extracting measuring data therefrom,

comparing data of the current image with the stored reference values;

determining a correction value, monitoring for an overload condition, and

changing camera parameters if the correction value exceeds an adjustable value.

5. The method according to claim 1, further comprising:

checking a histogram of at least one of the measuring zones against criteria associated with a presence of an overload condition.

6. The method according to claim 1, wherein the step of determining the size, the position, and the type of measuring zone in the image area includes:

selecting the type of at least one of the at least one measuring zone as a measuring zone for determining the correction factor.

7. The method according to claim 1, wherein the step of determining the size, the position, and the type of measuring zone in the image area includes:

selecting the type of at least one of the at least one measuring zone as a measuring zone or overload monitoring.

8. The method according to claim 1, further comprising:

checking the correction factor for plausibility.

9. The method according to claim 1, wherein the step of determining the size includes setting the size of the at least one measuring zone, the size being variable.

10. A method for controlling a plurality of exposure parameters of a stationary mounted video camera, comprising the steps of:

causing the stationary mounted camera to record a plurality of images;

processing the plurality of images according to a plurality of electronic pixels;

determining a correction factor by comparing gray-scale values of coherent sequences of the electronic pixels of a preceding image and the electronic pixels of a current image;

setting the plurality of exposure parameters by using the correction factor;

determining a size, a position, and a type of a plurality of measuring zones in an image area;

setting an optimal exposure;

extracting and storing reference values of each one of the plurality of measuring zones and reference values of current ones of the plurality of exposure parameters of the stationary mounted video camera;

performing a continuous operation in order to provide a control at adjustable time intervals;

checking the correction factor with respect to an exploitability thereof; and

providing criteria for a plausibility of the correction factor.

11. A method for controlling a plurality of exposure parameters of a stationary mounted video camera, comprising the steps of:

causing the stationary mounted camera to record a plurality of images;

processing the plurality of images according to a plurality of electronic pixels;

determining a correction factor by comparing gray-scale values of coherent sequences of the electronic pixels of a preceding image and the electronic pixels of a current image;

setting the plurality of exposure parameters by using the correction factor;

determining a size, a position, and a type of a plurality of measuring zones in an image area;

setting an optimal exposure;

extracting and storing reference values of each one of the measuring zones and reference values of current ones of the plurality of exposure parameters of the stationary mounted video camera;

performing a continuous operation in order to provide a control at adjustable time intervals;

generating gray-scale histograms from gray-scale values of the measuring zones;

evaluating the gray-scale histograms using a cross-correlation;

calculating the correction factor from the cross correlation;

evaluating the measuring zones for overload monitoring; and

checking the gray-scale histograms of the measuring zones against criteria associated with a presence of an overload.

12. A method for controlling a plurality of exposure parameters of a stationary mounted video camera, comprising:

causing the stationary mounted camera to record a plurality of images;

establishing at least one measuring zone in an image area, the establishing step including determining a position, and a type of the at least one measuring zone;

determining a correction factor by comparing gray-scale values of electronic pixels corresponding to the selected at least one measuring zone of a preceding image and the current image; and

setting the plurality of exposure parameters by using the correction factor.

13. The method according to claim 12, further comprising:

changing at least one of the position and type of at least one of the at least one measuring zone.

14. The method according to claim 12, wherein the determining the position and the type of the at least one measuring zone includes:

determining a first one of the at least one measuring zone to be first type, the first type being a zone for determining the correction factor, and determining a second one of the at least one measuring zone to be a second type, the second type being a zone for overload monitoring of the camera.

15. The method according to claim 12, wherein the first one of the at least one measuring zone is in a position that is different than a position of the second one of the at least one measuring zone.