Method and apparatus for error detection and correction in image sensor

• US 6,707,493 B1
• Filed: 06/29/1999
• Issued: 03/16/2004
• Est. Priority Date: 06/30/1998
• Status: Expired due to Term

• Current Assignee: Hanger Solutions, LLC (IP Investments Group LLC)
• Original Assignee: Hyundai Electronics Industries Co. Ltd. (SK Hynix Inc.)
• Inventors: Lee, Suk Joong, Hwang, Gyu Tae
• Primary Examiner(s): Christensen, Andrew
• Assistant Examiner(s): WISDAHL, ERIC D
• Application Number:
  US09/343,097
• Time in Patent Office: 1,722 Days
• Field of Search: 348/246, 348/247
• US Class Current: 348/246
• CPC Class Codes: H04N 25/68 applied to defects
• CPC Class Codes: H04N 25/78 Readout circuits for addressed sensors, e.g. output amplifiers or A/D converters

Abstract

An image sensor according to the present invention can detect and correct an error value of a defective pixel. The image sensor includes an error detection circuit for detecting an error by comparing difference between a current pixel value and a previous pixel value with a predetermined reference value and an error correction circuit for correcting an error value from a pixel, by substituting the previous pixel value for the current pixel value.

Claims

1. An image sensor comprising:

a selector configured to receive a first pixel value and a second pixel value;

a first register to receive a first output from the first selector;

an error detection circuit configured to receive a second output from the first register and the second pixel value to detect an error by comparing difference between the first output of the first register and the second pixel value with a predetermined reference value; and

an error correction circuit configured to receive a third output of the error;

detection circuit and output a corrected pixel value if the third output indicates a pixel error;

wherein the error detection circuit comprises a subtractor providing the difference between the first output aid the second pixel value; and

a comparator for comparing a fourth output the subtractor with the predetermined reference value;

wherein the predetermined reference value is stored in a programmable register;

wherein the predetermined reference value is determined based on characteristics of a light sensing area and an analogue to digital converter.

2. The image sensor as recited in claim 1, wherein the image sensor is based on a correlated double sampling method.

3. The image sensor as recited in claim 2, wherein the image sensor further comprises a storing component for storing digital pixel values derived from an analogue to digital converter.

4. The image sensor as recited in claim 3, wherein the third output of the error detection circuit indicates the pixel error if a data voltage level from a pixel is higher than a reset voltage level, wherein the error correction circuit outputs the first pixel value as the corrected pixel value if the third output of the error detection circuit indicates the pixel error, the first pixel value being a previous pixel value and the second pixel value being a current pixel value.

5. An image sensor comprising:

a control and interface means for controlling the image sensor using a state machine and for interfacing the image sensor with an external system;

a pixel array including a plurality of pixels sensing images from an object and generating analogue signals according to an amount of incident light;

a conversion component for converting the analogue signals into digital signals to be processed in a digital logic circuit;

a first selector configured to receive a first pixel value and a second pixel value, the first pixel value being associated with a first given time and the second pixel value being associated with a second given time that is subsequent to the first given time;

a first register to receive a first output of the first selector, the first register being synchronized with a clock signal;

an error detection component configured to receive a second output of the first register and the second pixel value to detect an occurrence of pixel error by comparing difference between the first output of the first register and the second pixel value wit a predetermined reference value; and

an error correction component configured to receive a third output of the error detection component and output a corrected pixel value if the third output indicates a pixel error;

wherein the predetermined reference value is determined based on characteristics of a light sensing area and an analogue to digital converter.

6. The image sensor as recited in claim 5, wherein the error correcting component comprises:

a storage component for storing a reference value;

a correction signal component for providing a first control signal; and

a first logic for outputting an error signal.

7. The image sensor as recited in claim 5, wherein the error correcting component comprises:

a reference value storing component for storing a reference value used in determining whether or not a pixel error has occurred;

a correction control component for storing a first control signal;

a first logic for determining whether or not a pixel error has occurred using second, third and fourth control signals;

a second logic for outputting an error signal using an output signal of the first logic and the first control signal of the correction control component;

a defect detection component for outputting the fourth control signal upon examining the first pixel value, the second pixel value and the reference value; and

a second selector configured to receive the first pixel value and the second pixel value and output either the first pixel value or the second pixel value as a correct value in response to the error signal.

8. The image sensor as recited in claim 7, wherein the defect detection component comprises:

a subtracting means for subtracting the first pixel value and the second pixel value; and

a comparing means for comparing an output value from the subtracting means with the reference value and outputting a result of comparison as the fourth control signal.

9. The image sensor as recited in claim 7, wherein the second control signal is a signal for indicating a pixel error if a reset voltage level is lower than a data voltage level according to a correlated double sampling method.

10. The image sensor as recited in claim 7, wherein the third control signal is a signal for indicating a pixel error if the reset voltage level is lower than the data voltage level after N clock cycles.

11. The image sensor as recited in claim 7, wherein the first logic is an OR gate.

12. The image sensor as recited in claim 7, wherein the second logic is an AND gate.

13. A image sensor, comprising:

a first selector configured to receive a first pixel value and a second pixel value, the first pixel value being associated with a first given time, the second pixel value being associated with a second given time;

a second selector configured to receive the first and second pixel values;

an error detector configured to receive the first and second pixel values and determine if a pixel error exists by comparing difference between the first and second pixel values with a predetermined reference value; and

an error corrector configured to output an output signal, the output signal being an error signal if the error detector outputs a pixel error signal,

wherein the first selector is configured to output the first or second pixel value according to the output signal of the error corrector,

wherein the second selector is configured to output the fist or second pixel value according to the output signal of the error corrector, the second selector outputting the first pixel value if the output signal is the error signal;

wherein the predetermined reference value is determined based on characteristics of a light sensing area and an analogue to digital converter.

14. The sensor of claim 13, further comprising:

a register configured to receive an output from the first selector and provide an output to the error detector.

15. The sensor of claim 14, wherein the first given time precedes the second given time.

16. The sensor of claim 13, wherein the first pixel value is a previous pixel value and the second pixel value is a current pixel value.