Method and apparatus for determining a need for a change in a pixel density requirement due to changing light conditions

• US 9,615,029 B2
• Filed: 04/27/2015
• Issued: 04/04/2017
• Est. Priority Date: 05/08/2014
• Status: Active Grant

• Current Assignee: Axis AB (Canon Inc.)
• Original Assignee: Axis AB (Canon Inc.)
• Inventors: Stahl, Per
• Primary Examiner(s): Velez, Roberto
• Assistant Examiner(s): Segura, Cynthia
• Application Number:
  US14/696,810
• Publication Number:
  US 20150326791A1
• Time in Patent Office: 708 Days
• Field of Search: 3482221
• CPC Class Codes: G03B 7/00 Control of exposure by setting shutters, diaphragms or filters, separately or conjointly control of exposure in television cameras by means of circuitry influencing the optical part of the camera H04N23/75
• CPC Class Codes: G08B 29/18 Prevention or correction of operating errors G08B29/02, G08B29/12 take precedence
• CPC Class Codes: H04N 23/667 Camera operation mode switching, e.g. between still and video, sport and normal or high- and low-resolution modes
• CPC Class Codes: H04N 23/69 Control of means for changing angle of the field of view, e.g. optical zoom objectives or electronic zooming
• CPC Class Codes: H04N 23/71 Circuitry for evaluating the brightness variation
• CPC Class Codes: H04N 23/72 Combination of two or more compensation controls
• CPC Class Codes: H04N 5/2628 Alteration of picture size, shape, position or orientation, e.g. zooming, rotation, rolling, perspective, translation
• CPC Class Codes: H04N 7/181 for receiving images from a plurality of remote sources

Abstract

There is provided a method for determining a need for a change in a pixel density requirement due to changing light conditions. The pixel density requirement specifies a pixel density which enables identification of an object in images captured by a camera. The method comprises receiving and monitoring (S02) a camera setting which is indicative of a light condition to which the camera is subjected and which affects the quality of images captured by the camera, and determining (S06) that there is a need for a change in the pixel density requirement upon detection (S04) of a change in the camera setting. The camera setting includes at least one of a gain and an exposure time used by the camera when capturing images.

Claims

1. A method for determining a change in a pixel density requirement due to a change in image quality, the method comprising:

receiving information corresponding to a camera setting which is automatically modified by the camera to compensate for changes in a light condition to which the camera is subjected, wherein the camera setting affects the quality of images captured by the camera and includes at least one of a gain and an exposure time used by the camera when capturing images;

detecting a change in the camera setting;

determining to change the pixel density requirement in response to detecting a change in the camera setting, the pixel density requirement corresponding to a minimum number of pixels per unit length or unit area of an object in images captured by a camera;

identifying an adjusted level of zoom for the camera in response to determining to change the pixel density requirement; and

generating a control signal to adjust a field of view of the camera based on the adjusted level of zoom for the camera.

2. The method of claim 1, wherein the camera setting includes a gain used by the camera when capturing images.

3. The method of claim 1, wherein the camera setting affects at least one of a level of noise and a level of motion blur in images captured by the camera.

4. The method of claim 1, wherein a change in the camera setting is detected by comparing the change in the camera setting to one or more thresholds.

5. The method of claim 1, wherein the level of zoom is to be adjusted such that the camera captures an object located at a given distance from the camera according to the changed pixel density requirement.

6. The method of claim 1, wherein the level of zoom is to be adjusted according to a function which associates different values of the camera setting with different levels of zoom.

7. A non-transitory computer-readable storage medium comprising computer code instructions which, when executed on a device having processing capability, carry out the method according to claim 1.

8. The method of claim 1, wherein the level of zoom is to be adjusted according to a table stored in memory that associates different values of the camera setting with different levels of zoom.

9. An apparatus comprising:

a receiver configured to receive a camera setting which is automatically modified by the camera to compensate for changes in a light condition to which the camera is subjected, wherein the camera setting affects the quality of images captured by the camera and includes at least one of a gain and an exposure time used by the camera when capturing images; and

a processor configured to

detect a change in the camera setting;

determine to change the pixel density requirement in response to detecting a change in the camera setting, the pixel density requirement corresponding to a minimum number of pixels per unit length or unit area of an object in images captured by a camera;

identify an adjusted level of zoom for the camera in response to determining to change the pixel density requirement; and

generate a control signal to adjust a field of view of the camera based on the adjusted level of zoom for the camera.

10. The apparatus of claim 9, wherein the camera setting includes a gain used by the camera when capturing images.

11. The apparatus of claim 9, wherein the camera setting affects at least one of a level of noise and a level of motion blur in images captured by the camera.

12. The apparatus of claim 9, wherein a change in the camera setting is detected by comparing the change in the camera setting to one or more thresholds.

13. The apparatus of claim 9, wherein the level of zoom is to be adjusted such that the camera captures an object located at a given distance from the camera according to the changed pixel density requirement.

14. The apparatus of claim 9, wherein the level of zoom is to be adjusted according to a function which associates different values of the camera setting with different levels of zoom.

15. The apparatus of claim 9, further comprising:

a memory configured to store a table associating different values of the camera setting with different levels of zoom.

16. The apparatus of claim 15, wherein the processor is configured to adjust the level of zoom by accessing the memory including the table associating the different values of the camera setting with different levels of zoom.

17. A system comprising:

a camera configured to capture images from which an object is to be identified, and

an apparatus comprising;

a receiver configured to receive a camera setting which is automatically modified by the camera to compensate for changes in a light condition to which the camera is subjected, wherein the camera setting affects the quality of images captured by the camera and includes at least one of a gain and an exposure time used by the camera when capturing images; and

a processor configured to

detect a change in the camera setting;

determine to change the pixel density requirement in response to detecting a change in the camera setting, the pixel density requirement corresponding to a minimum number of pixels per unit length or unit area of the object in the images captured by the camera;

identify an adjusted level of zoom for the camera in response to determining to change the pixel density requirement; and

generate a control signal to adjust a field of view of the camera based on the adjusted level of zoom for the camera.