Image processing apparatus having means for controlling exposure using an orthogonal transformation coefficient

• US 6,512,791 B1
• Filed: 05/12/1992
• Issued: 01/28/2003
• Est. Priority Date: 05/15/1991
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Takayama, Makoto
• Primary Examiner(s): LEE, RICHARD J
• Application Number:
  US07/881,866
• Time in Patent Office: 3,913 Days
• Field of Search: H04/N.7133, H04/N.712, 358/174, 358/228, 358/426, 358/906, 358/909, 358/227, 358/136, 354/400-409, 382/56, 382/232, 382/248, 382/250, 348/255, 348/257, 348/345, 348/347, 348/349, 348/354, 348/355, 348/363-365, 348/403, 348/220.1, 348/221.1, 348/229.1, 348/362, 375/240.01, 375/240.18, 375/240.2, 375/240.24
• US Class Current: 375/240.01
• CPC Class Codes: H04N 23/72 Combination of two or more compensation controls
• CPC Class Codes: H04N 5/20 Circuitry for controlling amplitude response
• CPC Class Codes: H04N 5/21 Circuitry for suppressing or minimising disturbance, e.g. moiré or halo
• CPC Class Codes: H04N 7/24 Systems for the transmission of television signals using pulse code modulation H04N21/00 takes precedence

Abstract

An image processing apparatus, which performs an orthogonal transformation on an image signal and which compresses the image signal, includes a control unit for controlling a range of the image signal based on a coefficient of a DC component of an output of the orthogonal transformation before the orthogonal transformation.

Claims

1. An image processing apparatus comprising:

an image pickup unit arranged to photograph an image and convert the image into an image signal in units of pixels;

a transformation unit arranged to segment the image signal to form blocks each including a plurality of pixels, perform an orthogonal transformation on the image signal in the units of blocks, and obtain transformation coefficients;

an encoding unit arranged to encode the transformation coefficients obtained by said transformation unit in units of the blocks and output encoded image data;

an extracting unit arranged to extract, as specific blocks, a part of the blocks formed by said transformation unit; and

a controlling unit arranged to control an exposure of said image pickup unit based upon DC components of the transformation coefficients of the specific blocks extracted by said extracting unit,

wherein said controlling unit integrates DC components from the specific blocks and controls the exposure in a first control width when an integrated result of the DC components is not within a range of a first level, controls the exposure in a second control width narrower than the first control width when an integrated result of the DC components is within the range of the first level but not within a range of a second level narrower than the range of the first level, and completes control of the exposure when an integrated result of the DC components is within the range of the second level.

2. An apparatus according to claim 1, wherein said image pickup unit comprises a shutter that controls an amount of light from the image, and wherein said controlling unit controls a speed of said shutter.

3. Apparatus according to claim 1, wherein said image pickup unit comprises an iris that controls an amount of light from the image, and wherein said controlling unit controls said iris.

4. An apparatus according to claim 1, further comprising a recording unit that records, onto a recording medium, the image signal encoded by said encoding unit.

5. An apparatus according to claim 1, further comprising a signal unit that signals completion of control by said controlling unit.

6. An apparatus according to claim 1, wherein said controlling unit controls the exposure by a feed-back control.

7. An apparatus according to claim 6, wherein said controlling unit controls the exposure of said image pick up unit by changing a number of steps for one control based upon the integrated result.

8. An apparatus according to claim 6, wherein said controlling unit further comprises a designating unit arranged to designate the specific blocks.

9. An apparatus according to claim 8, wherein said designating unit designates the specific blocks manually.

10. An image processing method comprising the steps of:

photographing an image and converting the image into an image signal in units of pixels using image pickup means;

segmenting the image signal to form blocks each including a plurality of pixels;

performing an orthogonal transformation on the image signal in units of each block and obtaining transformation coefficients;

encoding the transformation coefficients obtained in said transformation step in units of the block and outputting encoded image data;

extracting, as specific blocks, a part of the blocks formed in said transformation step; and

controlling an exposure of the image pickup means based upon DC components of the transformation coefficients of the specific blocks extracted in said extracting step,

wherein said controlling step integrates DC components obtained from the specific blocks and controls the exposure in a first control width when an integrated result of the DC components is not within a range of a first level, controls the exposure in a second control width narrower than the first control width when an integrated result of the DC components is within the range of the first level but not within a range of a second level narrower than the range of the first level, and completes control of the exposure when an integrated result of the DC components is within the range of the second level.