Row and column jumping for pixel readout using burst switching mode

• US 8,446,505 B2
• Filed: 10/27/2010
• Issued: 05/21/2013
• Est. Priority Date: 10/27/2010
• Status: Active Grant

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Inventors: Wong, Mark Ging Yeon, Tan, Zi Hao, Tan, Shan Chong, Song, Willie
• Primary Examiner(s): LAM, HUNG H
• Application Number:
  US12/913,262
• Publication Number:
  US 20120105661A1
• Time in Patent Office: 937 Days
• Field of Search: 348/207, 348/231, 348/294, 348/302, 348/303, 348/304, 348/307, 348/308, 348/309, 348/231.3, 348/240.2
• US Class Current: 348/302
• CPC Class Codes: H04N 25/44 by partially reading an SSIS array
• CPC Class Codes: H04N 25/74 Circuitry for scanning or addressing the pixel array
• CPC Class Codes: H04N 25/779 Circuitry for scanning or addressing the pixel array

Abstract

An imaging apparatus is described for obtaining images. The imaging apparatus includes a pixel array, a row decoder, a column decoder, and a trigger circuit. The pixel array integrates electrical signals corresponding to incident light from a scene. The row decoder enables a selected row of pixels within the pixel array. The column decoder enables readout of a pixel in a selected column of the selected row within the pixel array. The trigger circuit generates one or more burst pulses to traverse through a corresponding number of decoder stages that correspond to pixels which are identified for discarding. Each burst pulse has a duration that is less than a stipulated minimum pulse duration of a typical decoder pulse of the decoders. By using shorter burst pulses, the trigger circuit can quickly jump to a desired row and/or column of pixels for readout, while conserving power.

Claims

1. An imaging apparatus for obtaining images, the imaging apparatus comprising:

a pixel array to integrate electrical signals corresponding to incident light from a scene;

a row decoder coupled to the pixel array, the row decoder to enable a selected row of pixels within the pixel array;

a column decoder coupled to the pixel array, the column decoder to enable readout of a pixel in a selected column of the selected row within the pixel array; and

a trigger circuit coupled to at least one of the decoders, wherein the trigger circuit is configured to generate one or more burst pulses to traverse through a corresponding number of decoder stages that correspond to pixels which are identified for discarding, wherein each burst pulse has a duration that is less than a stipulated minimum pulse duration of a typical decoder pulse of the decoders;

wherein the trigger circuit comprises a row burst generator to generate the one or more burst pulses to traverse through the corresponding number of row decoder stages; and

wherein the row burst generator is further configured to generate the one or more burst pulses to traverse through the corresponding number of row decoder stages prior to assertion of a first column select signal and a first column clock signal.

2. The imaging apparatus of claim 1, wherein the trigger circuit further comprises a row counter to store a count, wherein a value of the count is associated with a corresponding row within the pixel array.

3. The imaging apparatus of claim 2, wherein the trigger circuit is further configured to use the count of the row counter to track a number of discarded rows within the pixel array and to identify the selected row within the pixel array.

4. The imaging apparatus of claim 1, wherein the trigger circuit is further configured to enable readout of a plurality of pixels in multiple rows within the pixel array and to stop traversal of the decoder stages prior to readout of pixels in a last row within the pixel array in response to a determination that readout is finished for a predetermined number of rows within the pixel array.

5. The imaging apparatus of claim 1, wherein the trigger circuit comprises a column burst generator to generate the one or more burst pulses to traverse through the corresponding number of column decoder stages within the selected row of pixels.

6. The imaging apparatus of claim 5, wherein the trigger circuit further comprises a column counter to store a count, wherein a value of the count is associated with a corresponding column within the pixel array.

7. The imaging apparatus of claim 6, wherein the trigger circuit is further configured to use the count of the column counter to track a number of discarded columns within the pixel array and to identify the selected column within the pixel array.

8. The imaging apparatus of claim 7, wherein the trigger circuit is further configured to purge pixel data associated with the discarded columns.

9. The imaging apparatus of claim 1, wherein the trigger circuit is further configured to enable readout of a plurality of pixels in multiple columns within the selected row of the pixel array and to stop traversal of the decoder stages prior to readout of pixels in a last column within the selected row of the pixel array in response to a determination that readout is finished for a predetermined number of columns within the selected row of the pixel array.

10. The imaging apparatus of claim 1, wherein the duration of each burst pulse is approximately one sixth (⅙

) of the stipulated minimum pulse duration of the typical decoder pulse.

11. The imaging apparatus of claim 1, wherein the duration of each burst pulse is less than approximately twenty-five percent (25%) of the stipulated minimum pulse duration of the typical decoder pulse.

12. The imaging apparatus of claim 1, wherein the duration of each burst pulse is less than approximately ten percent (10%) of the stipulated minimum pulse duration of the typical decoder pulse.

13. A trigger circuit for an optical imaging device, the trigger circuit comprising:

a row decoder output channel coupled to a row decoder of a pixel array, wherein the row decoder is configured to enable a selected row of pixels within the pixel array;

a column decoder output channel coupled to a column decoder of the pixel array, wherein the column decoder is configured to enable readout of a pixel in a selected column of the selected row of pixels within the pixel array;

a burst pulse generator coupled to at least one of the decoder output channels, wherein the burst pulse generator is configured to generate one or more burst pulses to traverse through a corresponding number of decoder stages that correspond to pixels which are identified for discarding, wherein each burst pulse has a duration that is less than a stipulated minimum pulse duration of a typical decoder pulse of the decoders;

further comprising an electronic memory device coupled to the burst pulse generator, wherein the electronic memory device is configured to store;

a value of a counter, wherein the value is associated with a corresponding decoder stage of at least one of the decoders;

a start stage indicator, wherein the start stage indicator is associated with an initial decoder stage of at least one of the decoders, where the initial decoder stage is a decoder stage at which the readout of an initial pixel of a subset of selected pixels occurs; and

an end stage indicator, wherein the end stage indicator is associated with a final decoder stage of at least one of the decoders, wherein the final decoder stage is a decoder stage at which readout of a final pixel of the subset of selected pixels occurs.

14. The trigger circuit of claim 13, further comprising a row clock signal generator coupled to the row decoder output channel, wherein the row clock signal generator is configured to generate a typical row decoder pulse having a duration of at least the stipulated minimum pulse duration of the decoders.

15. The trigger circuit of claim 13, further comprising a column clock signal generator coupled to the column decoder output channel, wherein the column clock signal generator is configured to generate a typical column decoder pulse having a duration of at least the stipulated minimum pulse duration of the decoders.

16. A method for operating decoders of an optical imaging device, the method comprising:

obtaining an indication of a subset of selected pixels of a pixel array, wherein remaining pixels outside of the subset of selected pixels are identified as pixels to be discarded;

identifying at least one decoder stage of a row or column decoder corresponding to a unit of pixels to be discarded, wherein the row or column decoder has a stipulated minimum pulse duration for a typical decoder pulse;

generating one or more burst pulses, wherein each burst pulse has a duration that is less than the stipulated minimum pulse duration of the typical decoder pulse of the row or column decoder;

transmitting the one or more burst pulses to the row or column decoder to traverse through the at least one identified decoder stage corresponding to the unit of pixels to be discarded;

further comprising;

storing a value of a counter in an electronic memory device, wherein the value of the counter is associated with a corresponding decoder stage of the row or column decoder;

storing a start stage indicator in the electronic memory device, wherein the start stage indicator is associated with an initial decoder stage of the row or column decoder, where the initial decoder stage is a decoder stage at which the readout of an initial pixel occurs for the subset of selected pixels; and

storing an end stage indicator in the electronic memory device, wherein the end stage indicator is associated with a final decoder stage of the row or column decoder, wherein the final decoder stage is a decoder stage at which the readout of a final pixel occurs for the subset of selected pixels.