Floating point image sensors with different integration times

• US 9,344,649 B2
• Filed: 08/12/2014
• Issued: 05/17/2016
• Est. Priority Date: 08/23/2013
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Inventors: Bock, Nikolai
• Primary Examiner(s): Peterson, Christopher K
• Application Number:
  US14/458,108
• Publication Number:
  US 20150055000A1
• Time in Patent Office: 644 Days
• US Class Current: 1/1
• CPC Class Codes: H04N 25/583 with different integration times
• CPC Class Codes: H04N 25/771 comprising storage means other than floating diffusion

Abstract

An image sensor may include an array of image sensor pixels arranged in rows and columns. Each image pixel arranged along a given column may be coupled to analog-to-digital converter (ADC) circuitry that is capable of converting analog pixel signals into a floating point number. The ADC circuitry may be configured to obtain an illumination value during an auto exposure period. The illumination value, which serves as an exponent value, can be stored as tile data in respective shutter tile column memory circuits. A rolling shutter scheme may be implemented to read signals out from the array. Each tile may be allowed to integrate for a different period of time depending on the exponent value stored in the shutter tile column memory circuits. During readout, the signal generated from the ADC circuitry may represent a mantissa value that is combined with the exponent value to yield a floating point number.

Claims

1. An image sensor, comprising:

an array of image sensor pixels arranged in rows and columns, wherein the array is grouped into a plurality of tiles each of which includes multiple rows and columns of image sensor pixels;

a plurality of shutter tile column memory circuits, wherein each tile in the plurality of tiles receives bits from a selected one of the plurality of shutter tile column memory circuits; and

readout circuitry, wherein the readout circuitry is configured to read data out from a selected row of image sensor pixels that is part of a first tile in the plurality of tiles at a first point in time, and wherein the image sensor performs a reset on one other row of image sensor pixels that is part of a second tile in the plurality of tiles at a second point in time that is different than the first point in time.

2. The image sensor defined in claim 1, wherein a first portion of tiles in the plurality of tiles exhibits a first integration time when receiving bits from a first shutter tile column memory circuit in the plurality of shutter tile column memory circuits, and wherein a second portion of tiles in the plurality of tiles exhibits a second integration time that is different than the first integration time when receiving bits from a second shutter tile column memory circuit in the plurality of shutter tile column memory circuits.

3. The image sensor defined in claim 1, wherein each image sensor pixel in the array comprises:

a photodiode;

a floating diffusion region; and

a double gate charge transfer transistor coupled between the photodiode and the floating diffusion region.

4. The image sensor defined in claim 3, wherein the double gate charge transfer transistor comprises a first gate that receives the bits from the plurality of shutter tile column memory circuits via a column control line and a second gate that receives a row control signal via a row control line.

5. The image sensor defined in claim 1, wherein the array of image sensor pixels is read out using a rolling shutter scheme, wherein a first shutter tile column memory circuit in the plurality of shutter tile column memory circuits serves to perform a first additional shutter reset for the array at a third point in time, wherein the third point in time is different than the first and second points in time, and wherein a second shutter tile column memory circuit in the plurality of shutter tile column memory circuits serves to perform a second additional shutter reset for the array at a fourth point in time that is different than the first, second, and third points in time.

6. The image sensor pixel defined in claim 1, wherein the readout circuitry is configured to convert pixel signals received from the array of image sensor pixels into floating point numbers.

7. The image sensor pixel defined in claim 1, wherein the bits that are stored in the plurality of shutter tile column memory circuits are obtained during an auto exposure period.

8. The image sensor pixel defined in claim 1, further comprising:

a multiplexer that is coupled between the plurality shutter tile column memory circuits and the array of image sensor pixels.

9. The image sensor pixel defined in claim 8, further comprising:

a logic gate that is coupled between the multiplexer and the array of image sensor pixels.

10. The image sensor pixel defined in claim 9, wherein the logic gate has a first input that is coupled to an output of the multiplexer and a second input that receives a read enable signal.

11. A method of operating an image sensor that includes an array of image sensor pixels arranged in rows and columns, wherein the array is grouped into tiles each of which includes multiple rows and columns of image sensor pixels, the method comprising:

with a plurality of shutter tile column memory circuits, providing bits to the array of image sensor pixels, wherein each tile in the array of image sensor pixels receives bits from a selected one of the plurality of shutter tile memory circuits;

with readout circuitry, reading data out from a selected row of image sensor pixels that is part of a first tile in the array; and

after reading data out from the row of image sensor pixels and before reading data out from another row, performing shutter reset on one other row of image sensor pixels that is part of a second tile in the array that is different than the first tile.

12. The method defined in claim 11, further comprising:

after performing the shutter reset on the one other row of image sensor pixels and before reading data out from another row, performing an additional shutter reset on yet another row of image sensor pixels that is different from the selected row and the one other row.

13. The method defined in claim 11 wherein providing bits to the array of image sensor pixels determines whether each tile is allowed to integrate for a first period of time or to integrate for a second period of time that is different than the first period of time.

14. The method defined in claim 13, further comprising:

performing auto exposure operations to obtain the bits that are stored in the plurality of shutter tile column memory circuits.

15. The method defined in claim 11, wherein each image sensor pixel in the array has a double gate charge transfer transistor, the method further comprising:

providing a row control signal to a first gate terminal of the double gate charge transfer transistor;

providing a column control signal to a second gate terminal of the double gate charge transfer transistor; and

asserting a read enable signal to force the column control signal high.

16. A system, comprising:

a central processing unit;

memory;

input-output circuitry; and

an imaging device, wherein the imaging device comprises;

an array of image sensor pixels arranged in rows and columns, wherein the array is grouped into tiles each of which includes multiple rows and columns of image sensor pixels;

a first shutter tile column memory circuit that provides asserted bits to a first portion of tiles such that the first portion of tiles exhibits a first integration time;

a second shutter tile column memory circuit that provides asserted bits to a second portion of tiles that is different than the first portion such that the second portion of tiles exhibits a second integration time that is different than the first integration time; and

readout circuitry, wherein the readout circuitry is configured to read data out from a selected row of image sensor pixels that is part of a first tile in the array at a first time, and wherein the image sensor performs a first shutter reset on one other row of image sensor pixels that is part of a second tile in the array at a second time that is different than the first time.

17. The system defined in claim 16, wherein the imaging device further comprises:

a multiplexer having a first input that is coupled to the first shutter tile column memory circuit, a second input that is coupled to the second shutter tile column memory circuit, and an output.

18. The system defined in claim 17, wherein the imaging device further comprises:

a logic OR gate having a first input that is coupled to the output of the multiplexer, a second input that receives a read enable signal, and an output.

19. The system defined in claim 18, wherein each image sensor pixel in the array has a multi-gate charge transfer transistor, and wherein each multi-gate charge transfer transistor in a given column of tiles has a first gate that is coupled to the output of the logic OR gate and a second gate that receives respective different row control signals.

20. The system defined in claim 16 wherein the readout circuitry generates mantissa information during readout operations, wherein the mantissa information is combined with exponent information obtained during auto exposure operations to yield floating point numbers.