Image sensors with improved signal to noise ratio

• US 6,822,213 B2
• Filed: 05/19/2003
• Issued: 11/23/2004
• Est. Priority Date: 11/27/2000
• Status: Expired due to Fees

• Current Assignee: Vision - Science, Inc.
• Original Assignee: Vision-Sciences Incorporated (2941881 Canada, Inc.)
• Inventors: Stark, Moshe
• Primary Examiner(s): Allen, Stephone B.
• Application Number:
  US10/440,331
• Publication Number:
  US 20030201379A1
• Time in Patent Office: 554 Days
• Field of Search: 250/208.1, 250/208.6, 250/214.A, 348/294, 348/297, 348/300, 348/308, 348/310, 348/313, 348/314, 257/443
• US Class Current: 250/208.1
• CPC Class Codes: H01L 27/14609 Pixel-elements with integrated switching, control, storage or amplification elements scanning details of imagers (circuitry of solid-state image sensors H04N25/00); circuitry of imagers H04N25/70
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers
• CPC Class Codes: H04N 25/41 Extracting pixel data from a plurality of image sensors simultaneously picking up an image, e.g. for increasing the field of view by combining the outputs of a plurality of sensors
• CPC Class Codes: H04N 25/443 by reading pixels from selected 2D regions of the array, e.g. for windowing or digital zooming
• CPC Class Codes: H04N 25/677 for reducing the column or line fixed pattern noise

Abstract

An image sensor array including a first plurality of unit cells coupled to a first sense amplifier, and a second plurality of unit cells coupled to a second sense amplifier, where the first plurality and the second plurality are substantially electrically isolated from each other.

Claims

1. A split column in an imaging sensor array, said split column comprises:

a first plurality of unit cells arranged in a first half-column, each unit cell of said first plurality of unit cells is controllably electrically couplable through a first half-column line to a first sense amplifier; and

a second plurality of unit cells arranged in a second half-column, each unit cells of said second plurality of unit cells is controllably electrically couplable through a second half-column line to a second sense amplifier,

wherein the number of unit cells in said first half-column is equal to the number of unit cells in said second half-column, and wherein said first half-column line is substantially electrically isolated from said second half-column line,

wherein the column capacitance of each half-column of said first half-column and said second half-column is significantly reduced as compared to the column capacitance of a non-split column.

2. The split column according to claim 1 wherein said imaging sensor array comprises a plurality of rows of unit cells and wherein each unit cell of said first plurality of unit cells and of said second plurality of unit cells belongs to a different row of said plurality of rows.

3. The split column according to claim 1 wherein said unit cells are direct injection unit cells.

4. The split column according to claim 1 wherein unit cells within the split column are arranged in a plurality of 2K unit cell clusters, wherein each half-column of said first half-column and said second half-column includes K clusters,

each cluster of the K clusters of said first half-column comprises N unit cells and a cluster selecting device operatively connected to each of said N unit cells, wherein for each cluster in said first half-column each of the unit cells of the cluster are controllably electrically connectable to said first half-column line through the cluster selecting device, and

each cluster of the K clusters of said second half-column comprises N unit cells and a cluster selecting device operatively connected to each of said N unit cells, wherein for each cluster in said second half-column each of the unit cells of the cluster are controllably electrically connectable to said second half-column line through the cluster selecting device, wherein N is an integer number equal to or larger than two.

5. The split column according to claim 4 wherein for said first half-column, only one cluster out of the K clusters included in said first half-column is actively electrically connected to said first half-column line at any given time, and wherein for said second half-column, only one cluster out of the K clusters included in said second half-column is actively electrically connected to said second half-column line at any given time.

6. The split column according to claim 4 wherein the cluster selecting device of each of said 2K clusters comprises a cluster selecting transistor, and wherein for each half-column of said first half-column and said second half-column only one cluster selecting transistor is switched on at any given time, while the remaining K-1 cluster selecting transistors of the half-column are switched off, effectively reducing the capacitance of the half-column.

7. The split column according to claim 1 wherein said first half-column line and said second half-column line are substantially electrically isolated from each other by at least 10 Mohms.

8. An image sensor array comprising a plurality of split columns and a plurality of rows, each split column of said plurality of split columns comprises:

a first plurality of unit cells arranged in a first half-column, each unit cell of said first plurality of unit cells is controllably electrically couplable through a first half-column line to a first sense amplifier; and

a second plurality of unit cells arranged in a second half-column, each unit cells of said second plurality of unit cells is controllably electrically couplable through a second half-column line to a second sense amplifier,

wherein the number of unit cells in said first half-column is equal to the number of unit cells in said second half-column, and wherein said first half-column line is substantially electrically isolated from said second half-column line,

wherein the column capacitance of each half-column of said first half-column and said second half-column is significantly reduced as compared to the column capacitance of a non-split column.

9. The image sensor array according to claim 8 wherein said first half-column line and said second half-column line are substantially electrically isolated from each other by at least 10 Mohms.

10. The image sensor array according to claim 8 wherein each unit cell of said first plurality of unit cells and of said second plurality of unit cells belongs to a different row of said plurality of rows.

11. The image sensor array according to claim 8 wherein said unit cells are direct injection unit cells.

12. The image sensor array according to claim 8 wherein said unit cells within each split column of said plurality of split columns are arranged in a plurality of 2K unit cell clusters, wherein each half-column of said first half-column and said second half-column comprises K clusters,

each cluster of the K clusters of said first half-column comprises N unit cells and a cluster selecting device operatively connected to each of said N unit cells, wherein for each cluster in said first half-column each of the N unit cells of the cluster are controllably electrically connectable to said first half-column line through the cluster selecting device, and

each cluster of the K clusters of said second half-column comprises N unit cells and a cluster selecting device operatively connected to each of said N unit cells, wherein for each cluster in said second half-column each of the unit cells of the cluster are controllably electrically connectable to said second half-column line through the cluster selecting device, wherein N is an integer number equal to or larger than two.

13. The image sensor array according to claim 12 wherein for said first half-column, only one cluster out of the K clusters included in said first half-column is actively electrically connected to said first half-column line at any given time, and wherein for said second half-column, only one cluster out of the K clusters included in said second half-column is actively electrically connected to said second half-column line at any given time.

14. The image sensor array according to claim 13 wherein the cluster selecting device of each of said 2K clusters comprises a cluster selecting transistor, and wherein for each half-column of said first half-column and said second half-column only one cluster selecting transistor is switched on at any given time, while the remaining K-1 cluster selecting transistors of the half-column are switched off, effectively reducing the capacitance of the half-column.

15. An image sensor array comprising a plurality of unit cells arranged in a plurality of columns and a plurality of rows, each column of said plurality of columns comprises:

a column line for operatively coupling unit cells of the column to a sense amplifier;

a plurality of K clusters of said unit cells, each cluster of said clusters includes N unit cells, wherein N is an integer number equal to or greater than two, each unit cell of said N unit cells belongs to a different row of said plurality of rows;

a plurality of K cluster selecting devices, each cluster selecting device is coupled to said column line through a cluster line and is operatively connected to all N unit cells of a different single cluster of said K clusters, wherein each unit cell of the N unit cells within a cluster is configured to be electrically connected to said column line by activating the cluster selecting device associated with the cluster and by selecting the row to which the unit cell belongs, and wherein said array is configured to activate only one cluster selecting device of said plurality of K cluster selecting devices of a column at any given time, substantially reducing the column capacitance.

16. The image sensor array according to claim 15 wherein each cluster selecting device of said plurality of K cluster selecting devices comprises a cluster selecting transistor connected to all the N unit cells of a cluster and to said cluster line, each cluster selecting transistor may be switched on and off, and wherein for each column of said array only one cluster selecting transistor is switched on at any given time, while the remaining K-1 cluster selecting transistors of the column are switched off, substantially reducing the column capacitance.

17. The image sensor array according to claim 15 wherein said unit cells are direct injection unit cells, each unit cell includes a readout transistor, wherein said readout transistor is configured for actively electrically connecting the unit cell to said column line through said cluster selecting transistor.

18. A method for improving the signal to noise ratio in an imaging array comprising a plurality of unit cells arranged in columns and rows, without reducing image resolution, the method comprising:

configuring each of said columns into a first half-column comprising a first plurality of unit cells and a second half-column comprising a second plurality of unit cells, wherein the number of unit cells in said first half-column is equal to the number of unit cells in said second half-column;

providing for each column of said unit cells a first half-column line and a second half-column line, said first half-column line is substantially electrically isolated from said second half-column line, wherein each unit cell of said first plurality of unit cells is controllably electrically couplable through said first half-column line to a first sense amplifier, and wherein each unit cell of said second plurality of unit cells is controllably electrically couplable through said second half-column line to a second sense amplifier, wherein the capacitance of each of said first half-column and said second half-column is substantially reduced as compared to the column capacitance of a column including all the unit cells of said first and said second pluralities of cells coupled to a column line extending along the entire length of the column to improve the signal to noise ratio;

sensing the unit cells of said first half-column with said first sense amplifier; and

sensing the unit cells of said second half-column with said second sense amplifier.

19. A method for improving the signal to noise ratio without reducing image resolution in an imaging array comprising a plurality of unit cells arranged in columns and rows, each column of said columns comprises a column line, the method comprising:

configuring the unit cells in each of said columns into K clusters of unit cells each cluster comprising N unit cells, each cluster comprises a cluster selecting device operatively connected to all N unit cells of the cluster, said cluster selecting device is controllably electrically connectable to a column line common to all the K clusters included in a column;

operating each column of said columns to sense the units cells of each column such that only one cluster of unit cells out of the K clusters included in the column is actively electrically connected to said column line at any given time, substantially reducing the column capacitance to improve the signal to noise ratio.

20. The method according to claim 19 wherein each cluster selecting device of a cluster of said K clusters comprises a cluster selecting transistor connected to all the N unit cells of the cluster and to said column line, each cluster selecting transistor is configured to be switched on and off, and wherein for each column of said array only one cluster selecting transistor is switched on at any given time to electrically connect the N unit cells of the cluster to said column line, while the remaining K-1 cluster selecting transistors of the column are switched off, substantially reducing the column capacitance.

21. The method according to claim 20 wherein the N unit cells of a cluster are separately and sequentially sensed within the time period in which the cluster selecting transistor of the cluster is switched on.

22. A method for operating an imaging array comprising a plurality of unit cells arranged in columns and rows, each column of said columns comprises a column line, the method comprising:

configuring the unit cells in each of said columns into K clusters of unit cells each cluster comprising N unit cells, each cluster comprises a cluster selecting device operatively connected to all N unit cells of the cluster, said cluster selecting device is controllably electrically connectable to a column line common to all the K clusters included in a column;

operating each column of said columns to sense the units cells of each column such that only one cluster of unit cells out of the K clusters included in the column is actively electrically connected to said column line at any given time, substantially reducing the column capacitance.

23. The method according to claim 22 wherein each cluster selecting device of a cluster of said K clusters comprises a cluster selecting transistor connected to all the N unit cells of the cluster and to said column line, each cluster selecting transistor is configured to be switched on and off, and wherein for each column of said array only one cluster selecting transistor is switched on at any given time to electrically connect the N unit cells of the cluster to said column line, while the remaining K-1 cluster selecting transistors of the column are switched off, substantially reducing the column capacitance.

24. The method according to claim 23 wherein the N unit cells of a cluster are separately and sequentially sensed within the time period in which the cluster selecting transistor of the cluster is switched on.