CMOS image sensor having block scanning capability

• US 6,933,973 B1
• Filed: 02/29/2000
• Issued: 08/23/2005
• Est. Priority Date: 03/01/1999
• Status: Expired due to Fees

• Current Assignee: Kawasaki MicroElectronics (Megachips Corporation)
• Original Assignee: Kawasaki MicroElectronics (Megachips Corporation)
• Inventors: Sako, Norimitsu
• Primary Examiner(s): Ho, Tuan
• Assistant Examiner(s): Ye, Lin
• Application Number:
  US09/515,504
• Time in Patent Office: 2,002 Days
• Field of Search: 348/308, 348/214, 348/302, 348/222.1, 348/307, 348/294, 348/318, 348/241, 250/208.1, 250/367
• US Class Current: 348/308
• CPC Class Codes: H04N 25/40 Extracting pixel data from image sensors by controlling scanning circuits, e.g. by modifying the number of pixels sampled or to be sampled
• CPC Class Codes: H04N 25/51 Control of the gain
• CPC Class Codes: H04N 25/745 Circuitry for generating timing or clock signals
• CPC Class Codes: H04N 25/76 Addressed sensors, e.g. MOS or CMOS sensors
• CPC Class Codes: H04N 3/155 Control of the image-sensor operation, e.g. image processing within the image-sensor

Abstract

A CMOS image sensor includes a plurality of pixel sensors arranged in a two-dimensional array. In each pixel sensor, a signal corresponding to the absolute value of the amount of incident light with reduced reset noise is obtained. The signals of the respective pixel sensors are then output in a block scanning fashion. The CMOS image sensor does not need to include a preprocessing circuit for discrete cosine transform or a high-capacity frame memory for raster scanning.

Claims

1. A CMOS image sensor, comprising:

pixel sensors arranged in the form of a two-dimensional array, each pixel sensor comprising a photodiode at a signal detection node and a pair of pass transistors, which passes a photodiode reset signal to a gate of a transistor that resets said photodiode, only when said pixel sensor is selected;

means, disposed in each pixel sensor, for obtaining a signal whose reset noise is reduced and that corresponds to the absolute value of the amount of incident light; and

means for outputting said signal in a block-scanning fashion

wherein said photodiode reset signal is given as the logical AND of a column block selection signal and a pixel reset signal.

3. A CMOS image sensor comprising:

a pixel sensor according to claim 1; and

means for selectively connecting the output of the pixel sensor to a circuit for reading one row of block.

5. A camera that automatically controls brightness, comprising:

a CMOS image sensor according to claim 1;

means for estimating the average brightness over an entire screen of said CMOS image sensor from brightness detected for a several blocks in a central area and in a peripheral area of the screen; and

a programmable gain amplifier having a gain that is automatically controlled in accordance with the estimated brightness.

7. A camera that automatically controls brightness, comprising:

a CMOS image sensor according to claim 3;

means for estimating the average brightness over an entire screen of said CMOS image sensor from brightness detected for a several blocks in a central area and in a peripheral area of the screen; and

a programmable gain amplifier having a gain that is automatically controlled in accordance with the estimated brightness.

8. A monitor camera, comprising:

a CMOS image sensor according to claim 1;

means for detecting whether there is a substantial change in an image by reading several blocks in a central area and in a peripheral area of an image screen of said CMOS image sensor; and

means for continuously taking an image over the entire screen when a substantial change is detected.

10. An autofocus camera, comprising:

a CMOS image sensor according to claim 1;

means for adjusting focus by reading several blocks in a central area of an image screen of said CMOS image sensor; and

means for taking an image over the entire screen after completion of the focus adjustment.

12. An autofocus camera, comprising:

a CMOS image sensor according to claim 3;

means for adjusting focus by reading several blocks in a central area of an image screen of said CMOS image sensor; and

means for taking an image over the entire screen after completion of the focus adjustment.

2. A CMOS image sensor, comprising:

pixel sensors arranged in a two-dimensional array, each pixel sensor comprising floating diffusion at a signal detection mode and a pair of pass transistors, which passes a transfer signal to a gate of a transistor that transfers a signal charge of a photodiode, only when said pixel sensor is selected;

means, disposed in each pixel sensor, for obtaining a signal whose rest noise is reduces and that corresponds to the absolute value of the amount of incident light; and

means for outputting said signal in a block-scanning fashion;

wherein said transfer signal is given as the logical AND of a column block selection signal and a pixel transfer signal.

4. A CMOS image sensor comprising:

a pixel sensor according to claim 2; and

means for selectively connecting the output of the pixel sensor to a circuit for reading one row of block.

6. A camera that automatically controls brightness, comprising:

a CMOS image sensor according to claim 2;

means for estimating the average brightness over an entire screen of said CMOS image sensor from brightness detected for a several blocks in a central area and in a peripheral area of the screen; and

a programmable gain amplifier having a gain that is automatically controlled in accordance with the estimated brightness.

9. A monitor camera, comprising:

a CMOS image sensor according to claim 2;

means for detecting whether there is a substantial change in an image by reading several blocks in a central area and in a peripheral area of an image screen of said CMOS image sensor; and

means for continuously taking an image over the entire screen when a substantial change is detected.

11. An autofocus camera, comprising:

a CMOS image sensor according to claim 2;

means for adjusting focus by reading several blocks in a central area of an image screen of said CMOS image sensor; and

means for taking an image over the entire screen after completion of the focus adjustment.