Frequency compensated multiple sampling method for a video digital camera

• US 6,542,189 B1
• Filed: 11/08/2001
• Issued: 04/01/2003
• Est. Priority Date: 11/08/2001
• Status: Expired due to Term

• Current Assignee: Pixim, Inc. (Sony Group Corp.)
• Original Assignee: Pixim, Inc. (Sony Group Corp.)
• Inventors: Tian, Hui
• Primary Examiner(s): Garber, Wendy R.
• Assistant Examiner(s): TOPPIN, CATHERINE J
• Application Number:
  US10/005,834
• Time in Patent Office: 509 Days
• Field of Search: 348/362, 348/364, 348/296, 348/297
• US Class Current: 348/297
• CPC Class Codes: H04N 23/70 Circuitry for compensating brightness variation in the scene
• CPC Class Codes: H04N 23/76 by influencing the image signals
• CPC Class Codes: H04N 25/53 Control of the integration time
• CPC Class Codes: H04N 25/583 with different integration times
• CPC Class Codes: H04N 25/772 comprising A/D, V/T, V/F, I/T or I/F converters
• CPC Class Codes: H04N 3/155 Control of the image-sensor operation, e.g. image processing within the image-sensor

Abstract

A system and method for performing frequency compensation in a video digital cameral utilizing a time-indexed multiple sampling technique is presented. The frequency compensation removes distortion from the digital image signal captured by the video digital camera as compared with a human-perceived image signal.

Claims

1. A method of frequency compensation for a digital image sensor configured to select from a set of exposure times, comprising:

forming a plurality of digital image signals using the digital image sensor, each digital image signal corresponding to a frame,

dividing the plurality of digital image signals into a plurality of subsets, wherein a first subset corresponds to a first exposure time, a second subset corresponds to a second exposure time, and so on, and at least one subset is missing a digital image signal for a given frame; and

performing a discrete Fourier transform of each of the subsets of digital image signals to form a completed subset of digital image signals.

2. The method of claim 1, wherein the plurality of exposure times comprises an integer multiple of a given time period T.

3. The method of claim 2, wherein the integer multiples comprise T, 2T, 4T, and 8T.

4. The method of claim 3, wherein the plurality of subsets of digital image signals comprises a first subset formed using the exposure time T, a second subset formed using the exposure time 2T, a third subset formed using the exposure time 4T, and a fourth subset formed using the exposure time 8T.

5. The method of claim 4, wherein the completed subset is formed using the exposure time T.

6. The method of claim 4, wherein the completed subset is formed using the exposure time 2T.

7. The method of claim 4, wherein the completed subset is formed using the exposure time 4T.

8. The method of claim 4, wherein the completed subset is formed using the exposure time 8T.

9. An image processor, comprising:

a digital image sensor configured to produce a plurality of digital signals respectively confined with a plurality of exposure times to form a digital image signal during a given frame;

a memory configured to store a plurality of frames of digital image signals resulting from a light signal exciting the digital image sensor, the memory also storing the exposure times for each of the frames of digital image signals; and

a processor configured to perform a discrete transform on the stored plurality of frames of digital image signals with reference to the corresponding stored exposure times to derive a complete set of digital image signals.

10. The image processor of claim 9, wherein the processor is a single instruction multiple data processor.

11. The image processor of claim 9, wherein the processor is further configured to store the complete set of digital image signals corresponding to the given exposure time for each frame for the plurality of frames within the memory.