Image detecting system

• US 20020135703A1
• Filed: 12/15/2000
• Published: 09/26/2002
• Est. Priority Date: 12/17/1999
• Status: Active Grant

• Current Assignee: Robot Visual Systems GmbH (Jenoptik AG)
• Original Assignee: Robot FOTO & Electronic GmbH & Company KG (Jenoptik AG)
• Inventors: Schmitz, Thomas, Guse, Wolfgang
• Granted Patent: US 6,965,402 B2
• Time in Patent Office: Days
• US Class Current: 348/671
• CPC Class Codes: H04N 1/407 Control or modification of tonal gradation or of extreme levels, e.g. background level
• CPC Class Codes: H04N 1/4074 using histograms
• CPC Class Codes: H04N 23/70 Circuitry for compensating brightness variation in the scene
• CPC Class Codes: H04N 23/741 by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors

Abstract

Digital pictures are taken by a digital camera. The digital camera provides picture data with a large dynamic range of, for example, 10 bit. Data processing and display devices operate with 8 bit only, i.e do not take advantage of the high dynamic range of the camera This is important in traffic monitoring installations, where, on one hand, the driver in a relatively dark passenger compartment of a vehicle and, on the other hand, the bright license plate have to be recognized to provide evidence in court. For this reason, a dark picture and a bright picture are derived from the picture data provided by the camera. This is done by reading, on one hand, the eight least significant digits and, on the other hand, the eight most significant digits of the camera output to provide the dark and bright pictures, respectively. The dark and bright pictures thus obtained are balanced against color, gray, contrast or brightness values of histograms derived from previous pictures. Then the picture data of the dark and bright pictures are mixed to provide a composed picture, in which the dark and bright pictures arc superimposed. This picture permits recognition of both the driver and the license plate.

Claims

1. A device for detecting and storing digital pictures comprising

(a) image detector means for the generation of first digital picture data,

(b) a picture data memory,

(c) signal processing means including means for generating, from said first digital picture data second digital picture data representing a relatively dark picture and third digital picture data representing a relatively bright picture, and

(d) means for storing said second and third digital picture data in said picture data memory.

2. A device as claimed in claim 1, wherein said image detector means have a first dynamic range extending over a first number of digits, and said second and third picture data generating means comprising means for reading, from said image detector means, a second number of relatively low significance digits as said second digital picture data, and a third number of relatively high significance digits as said third digital picture data, said second and third numbers being smaller than said first number.

3. A device as claimed in claim 1, wherein said signal processing means further comprise picture balancing means for optimizing the picture data of said dark and bright pictures.

4. A device as claimed in claim 3, wherein said picture balancing means comprise means for providing a digital histogram of data from a previously taken picture and means for balancing said picture data relative to said histogram.

5. A device as claimed in claim 4, wherein said histogram contains color value data.

6. A device as claimed in claim 4, wherein said histogram contains gray value data.

7. A device as claimed in claim 4, wherein said histogram contains brightness value data.

8. A device as claimed in claim 1, and further comprising mixing means for superimposing said dark and bright pictures.

9. A method for detecting and storing digital pictures by means of a digital camera, wherein at least two digital pictures having different degrees of brightness are generated.

10. A method as claimed in claim 9, comprising the step of balancing the gray values of picture data of said pictures with a gray value histogram of a previously taken picture.

11. A method as claimed in claim 9, comprising the step of balancing the color values of picture data of said pictures with a color value histogram of a previously taken picture.

12. A method as claimed in claim 9, comprising the step of balancing the brightness values of picture data of said pictures with a brightness value histogram of a previously taken picture.

13. A method as claimed in claim 9, comprising the step of balancing the contrast values of picture data of said pictures with a contrast value histogram of a previously taken picture.

14. A method as claimed in claim 9, wherein digital picture data of said two digital pictures having different degrees of brightness are mixed to provide superimposed digital pictures.