# Patent

## Title
Image sensor with flexible interconnect capabilities

## Abstract

Electronic devices may include image sensors having configurable image sensor pixel interconnections. Image sensors may include image sensor pixels coupled to analog circuitry via configurable interconnect circuitry. The analog circuitry may include many analog circuit blocks. The analog circuit blocks may control and read out signals from associated image sensor pixels. The configurable interconnect circuitry may be controlled to reroute the connections between the analog circuit blocks and specific groups of image sensor pixels. Digital circuitry may be coupled to the analog circuitry via configurable interconnect circuitry. The digital circuitry may include digital circuit blocks. There may be significantly more image pixels controlled by a small number of analog circuit blocks, which are in turn controlled by a smaller number of digital circuit blocks. The image sensor pixel array, the configurable interconnect circuitry, the analog circuitry, and the digital circuitry may be vertically stacked.

## Background
This application claims the benefit of provisional patent application No. 61/537,537, filed Sep. 21, 2011, which is hereby incorporated by reference herein in its entirety.


BACKGROUND
This invention relates generally to imaging devices, and more particularly, to imaging devices with configurable interconnect fabric.
Modern electronic devices such as cellular telephones, cameras, and computers often use digital image sensors to capture images. In a typical arrangement, an electronic device with an image sensor is provided with an array of image sensor pixels (sometimes referred to as image pixels) that are arranged in pixel rows and columns. Row control circuitry is coupled to each pixel row to provide row control signals to the image pixels such as reset and transfer control signals. Column circuitry is typically coupled to each column for reading out image signals from the image pixels.
Conventional image sensors typically feature row circuitry that implements raster scan techniques to sequentially read out the image signals from an image pixel array. When performing a raster scan, column circuitry processes the read out image signals on a row-by-row basis for the entire image pixel array. Accessing image pixels on a row-by-row basis using the row and column circuitry requires scanning the entire image pixel array before adjustments are made to individual image pixel signals. Processing image data in this way greatly limits the performance of the image sensor.
It would therefore be desirable to be able to provide imaging devices with more flexible pixel access capabilities.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram of a conventional image sensor with image sensor pixels that are connected to row and column lines.
FIG. 2 is a diagram of an illustrative image sensor with circuitry for processing image data in a hierarchical fashion in accordance with an embodiment of the present invention.
FIG. 3 is a diagram of an illustrative image sensor having multiple layers of circuitry coupled to one another via configurable interconnect fabric in accordance with an embodiment of the present invention.
FIG. 4 is a diagram of an illustrative image sensor with vertically and horizontally stacked circuits in accordance with an embodiment of the present invention.
FIG. 5 is a diagram of an illustrative image sensor with configurable pixel interconnects in accordance with an embodiment of the present invention.
FIG. 6 is a circuit diagram of a configurable pixel access path in accordance with an embodiment of the present invention.
FIG. 7 is a table summarizing image pixel interconnections as a function of user-specified control signals in accordance with an embodiment of the present invention.
FIG. 8 is a diagram of an illustrative image sensor with circuitry and various levels of interconnect in accordance with an embodiment of the present invention.
FIG. 9 is a block diagram of a processor system employing the image sensor of FIGS. 2-8 in accordance with an embodiment of the present invention.



DETAILED DESCRIPTION
Electronic devices such as digital cameras, computers, cellular telephones, and other electronic devices include image sensors that gather incoming light to capture an image. The image sensors may include large arrays of image sensor pixels (sometimes referred to as image pixels). The image pixels may include photosensitive elements such as photodiodes that convert the incoming light into charge. Image sensors may have any number of image pixels (e.g., hundreds or thousands or more). A typical image sensor may, for example, have hundreds or millions of image pixels (e.g., megapixels). Image sensors may include control circuitry, such as circuitry for operating the image pixels, and readout circuitry for reading out image signals corresponding to the electric charge collected using the photosensitive elements.
FIG. 1 is a diagram of conventional image sensor circuitry for image pixel control and readout. Image sensor 316 includes image sensor pixel array 300 containing image sensor pixels 390 arranged in rows and columns. Processing circuitry 18 is coupled to row control circuitry 394 and column readout circuitry 304. Row control circuitry 394 receives row addresses from processing circuitry 18 and supplies corresponding row control signals to image pixels 390 via control paths 306. Image pixels 390 in each column of image pixel array 300 are connected to a corresponding column line 40. During image pixel readout operations, a pixel row in image pixel array 300 is selected by row control circuitry 394 and image data associated with image pixels 390 in that pixel row is read out via column lines 40.
Image sensor 316 typically performs raster scans to control and read out image pixels 390. During a raster scan, row control circuitry 394 selects one row of image pixels 390 for readout. Row control circuitry 394 then selects the next row of image pixels 390 in image pixel array 300 for readout. The different rows in array 300 are sequentially accessed until the entire image pixel array 300 has been read out. Each pixel 390 arranged along the same row is connected to a common row control line 306, whereas each pixel 390 arranged along the same column is connected to a common column line 40. Connected using this arrangement, the flexibility with which image pixels 390 can be read out is limited. Implementing a raster scan requires reading out the entire image pixel array before gain adjustments can be made to image signals from any individual pixel. It may therefore be desirable to be able to access desired subsets of image pixels via configurable interconnections.
FIG. 2 is a block diagram of an illustrative image sensor having circuitry that allows for control and readout of an image pixel array via configurable interconnections in accordance with an embodiment of the present invention. Image sensor 16 may include image pixel array 100 coupled to analog processing and control circuitry 120 via configurable paths 112. Analog processing and control circuitry 120 may send control signals to image pixel array 100 and may receive image signals from image pixel array 100 via respective paths 112. Depending on the current configuration of paths 112, each image sensor pixel in array 100 may be coupled to a selected analog block in circuitry 120.
Analog processing and control circuitry 120 may be coupled to digital processing and control circuitry 140 via configurable paths 114. Analog processing and control circuitry 120 may process image signals (e.g., perform analog-to-digital conversion) before conveying the image signals to digital processing and control circuitry 140. Digital processing and control circuitry 140 may send control signals to analog processing and control circuitry 120 as well as to image pixel array 100.
Circuitry 140 may be coupled to memory circuitry 150. Digital processing and control circuitry 140 may further process image signals that are received from analog processing and control circuitry 120 before forwarding the image signals to memory circuitry 150.
Memory circuitry 150 may be coupled to processing circuitry 160. Memory circuitry 150 may temporarily store image signals that are received from digital processing and control circuitry 140 before sending the image signals to processing circuitry 160. Processing circuitry 160 may further process the image signals that are received from memory circuitry 150.
The circuitry of FIG. 2 may be arranged in a stacked layer configuration as shown in FIG. 3 in accordance with an embodiment of the present invention. Image sensor 16 may include image pixel array 100 coupled to analog processing and control circuitry 120 via first configurable interconnect fabric 110 that is interposed between image pixel array 100 and analog processing and control circuitry 120. Analog processing and control circuitry 120 may be coupled to digital processing and control circuitry 140 via second configurable interconnect fabric 130 that is interposed between analog processing and control circuitry 120 and digital processing and control circuitry 140. Memory 150 may serve as a buffer between digital processing and control circuitry 140 and processing circuitry 160.
Image pixel array 100 may include hundreds or thousands of image pixels 190 arranged in rows and columns. Image pixels 190 may gather light to generate image signals. The image signals that are generated by image pixels 190 may be read out, stored in memory, or further processed. Analog processing and control circuitry 120 and digital processing and control circuitry 140 may supply control signals (e.g., pixel reset signals, charge transfer gate control signals, pixel select signals, etc.) to at least some of image pixels 190.
First interconnect fabric 110 may be formed as an integral part of image pixel array 100, as an integral part of analog processing and control circuitry 120, or separately in its own integrated circuit. For example, consider an example in which array 100 is formed on a first integrated circuit and circuitry 120 is formed on a second integrated circuit. In one suitable arrangement, fabric 110 may be formed on the first integrated circuit. In another suitable arrangement, fabric 110 may be formed on the second integrated circuit. In yet another suitable arrangement, fabric 110 may be formed on a third integrated circuit that is interposed between the first and second integrated circuits when all three devices are stacked together.
Analog processing and control circuitry 120 may include a number of analog circuit blocks 122 that are coupled to image pixels 190 via first interconnect fabric 110. Analog circuit blocks 122 may include control circuitry, data sampling circuitry (e.g., sample-and-hold circuits), readout circuitry, data conversion circuitry, or other circuitry for interfacing with pixel array 100 via first interconnect fabric 110. First interconnect fabric 110 may include configurable paths 112 (see FIG. 2) that couple image pixels 190 to analog circuit blocks 122. Paths 112 may be configured to change the electrical connections between analog circuit blocks 122 and image pixels 190.
For example, paths 112 may be placed in a first configuration to couple a first analog circuit block 122 to a first subset of image pixels 190 in image pixel array 100 or may be placed in a second configuration to couple the first analog circuit block 122 to a second subset of image pixels 190 in image pixel array 100. Paths 112 may be supplied with control signals for placing paths 112 in the desired configuration.
Image sensor array 100 may be divided into respective groups of image pixels, where each group of image pixels may be referred to as an image pixel group 196. In an example, image pixel group 196 may be formed from image pixels 190 arranged along at least two adjacent rows and at least two adjacent columns in image sensor array 100. In another example, image pixel group 196 may be formed from image pixels 190 arranged along non-adjacent rows and non-adjacent columns in image sensor array 100. Similarly, circuitry 120 may contain multiple analog circuit blocks 122 that are divided into respective groups of analog circuit blocks, where each group of analog circuit blocks 122 may be referred to as an analog circuit block group 126. Each image pixel 190 may be coupled to at least one analog circuit block 122 in a corresponding group 126 via configurable paths 112 in first interconnect fabric 110. Paths 112 may be configured to selectively allow at least one analog circuit block 122 in analog circuit block group 126 to provide control signals to each image pixel 190 and to receive image signals from each image pixel in image pixel group 196.
In the example of FIG. 3, image pixel group 196 includes 64 image pixels 190 and analog circuit block group 126 includes four analog circuit blocks 122. A first configuration of paths 112 may allow a portion of image pixels 190 in image pixel group 196 to be coupled to each analog circuit block 122 in analog circuit block group 126 (e.g., a first portion of image pixels 190 in image pixel group 196 may be coupled to a first analog circuit block 122 in analog circuit block group 126, a second portion of image pixels 190 may be coupled to a second analog circuit block 122, etc). A second configuration of paths 112 may allow each group of image pixels 190 in image pixel group 196 to be coupled to a different one of each of the four analog circuit blocks 122 (e.g., the first group of image pixels 190 may be coupled to the second analog circuit block 122, the second group of image pixels 190 may be coupled to the first analog circuit block, etc). In this way, more than one image pixel 190 may be controlled and read out using each analog circuit block 122, and the connections between each analog circuit block 122 and image pixels 190 may rerouted as the configuration of paths 112 is changed.
Second interconnect fabric 130 may be formed as a part of analog processing and control circuitry 120, as a part of digital processing and control circuitry 140, or separately in its own integrated circuit. For example, consider an example in which circuitry 120 is formed on integrated circuit X and circuitry 140 is formed on integrated circuit Y. In one suitable arrangement, fabric 130 may be formed on integrated circuit X. In another suitable arrangement, fabric 130 may be formed on integrated circuit Y. In yet another suitable arrangement, fabric 130 may be formed on a separate integrated circuit Z that is interposed between integrated circuits X and Y when all three devices are stacked together.
Digital processing and control circuitry 140 may include digital circuit blocks 142 that are coupled to analog circuit blocks 122 via configurable paths 114 in second interconnect fabric 130 (see FIG. 2). Paths 114 may serve as configurable interconnection paths between analog circuit blocks 122 and digital circuit blocks 142. Digital circuit blocks 142 may include control circuitry, readout circuitry, conversion circuitry, or other circuitry related to the control of image pixels 190 and the processing of image signals from image pixels 190.
Digital circuit blocks 142 may be coupled to a number of analog circuit blocks 122. In the example of FIG. 3, four analog circuit blocks 122 in analog circuit block group 126 may be coupled to one digital circuit block 142 via corresponding paths 114. Coupled in this way, multiple analog circuit blocks 122 may be controlled and read out using only one digital circuit block 122.
The wiring complexity of device 16 may drastically decrease when progressing from layer 100 to layer 160 (e.g., the number of interconnections at the pixel level may be substantially greater than the number of interconnections at the digital block level). For example, a small number of digital circuit blocks 142 may be coupled to a large number of analog circuit blocks 122. The large number of analog circuit blocks 122 may also be coupled to an even larger number of image pixels 190. This type of interconnect arrangement allows for a small number of digital and analog control and processing circuit blocks to directly control a large number of image pixels 190. The connections between analog processing and control circuitry 120 and image pixels 190 can be adjusted by reconfiguring paths 112, and the connections between digital circuitry 140 and analog circuitry 120 can be adjusted by reconfiguring paths 114, allowing for a flexible image pixel control and readout process in image sensor 16.
Image sensor 16 of FIG. 3 is merely illustrative. If desired, image pixels 190 may be formed in any suitable arrangement in image pixel array 100. Image pixel group 196 may include any number of image pixels 190. Analog circuit block group 126 may include any number of analog circuit blocks 122. Any number of image pixels 190 may be coupled to any number of analog circuit blocks 122 via programmable interconnect fabric 110, whereas any number of analog circuit blocks 122 may be coupled to any number of digital circuit blocks 142 via programmable interconnect fabric 130.
Image pixel array 100, interconnect fabrics 110 and 130, analog processing and control circuitry 120, digital processing and control circuitry 140, memory circuitry 150, and processing circuitry 160 may be formed using any suitable number of integrated circuits. For example, digital processing and control circuitry 140 may be formed on the same integrated circuit layer as memory circuitry 150, as shown in FIG. 4 in another embodiment of the invention. Additional layers of interconnect fabric may be used, such as a third interconnect fabric 134 interposed between the processing circuitry 160 and the integrated circuit layer that includes digital processing and control circuitry 140 and memory circuitry 150. Interconnect fabric 134 may be formed as a part of memory circuitry 150 and digital processing and control circuitry 140, or as a part of processing circuitry 160, or on its own separate integrated circuit.
One suitable arrangement of the interconnect fabric coupling the analog processing and control circuitry 120 to image pixels 190 in image sensor 16 is shown in FIG. 5. Analog circuit blocks 122 may be coupled to first interconnect fabric 110 via interconnect input lines 50 and interconnect output lines 52. First interconnect fabric 110 may include configurable interconnect circuitry 212 that is coupled to interconnect input lines 50 and interconnect output lines 52. Pixels 190 may be selectively routed to one analog circuit block 122 in analog circuit block group 126 by rerouting paths 112 using configurable interconnect circuitry 212.
Analog circuit block group 126 may supply pixel control signals Vc to configurable routing circuitry 212 via interconnect input lines 50. For example, a first analog block 122-0 may supply a first pixel control signal Vc<0>; second analog block 122-1 may supply a second pixel control signal Vc<1>; third analog block 122-2 may supply a third pixel control signal Vc<2>; and a fourth analog block 122-3 may supply a fourth pixel control signal Vc<3> to interconnect circuitry 212. Pixel control signals Vc may include pixel reset signals, charge transfer gate control signals, and other suitable signals for controlling image pixels 190. Interconnect circuitry 212 may convey pixel output signals Vout to analog circuit blocks 122 via interconnect output paths 52. Pixel output signals Vout may include reset level or image level signals.
Device 16 may also include addressing circuitry 116 that is used to supply first selector bits f1_sel and first inversion bit f1_inv to configurable interconnect circuitry 212 via lines 72 and 74, respectively. In addition, addressing circuitry 116 may supply second selector bits f0_sel and second bit inversion signal f0_inv to configurable interconnect circuitry 212 via lines 76 and 78, respectively. Addressing circuitry 116 may be formed as a part of analog processing and control circuitry 120, digital processing and control circuitry 140, processing circuitry 160, or as its own independent integrated circuit. Interconnect circuitry 212 may route configurable paths 112 to a plurality of image pixels 190 via pixel control lines 54 and pixel output lines 56.
In the example of FIG. 5, analog circuit block group 126 may include four analog circuit blocks 122 (e.g., a first analog circuit block 122-0, a second analog circuit block 122-1, etc.) and a corresponding image pixel group 196 may include 64 image pixels 190 that are coupled to analog circuit block group 126 via routing paths 112. Analog circuit blocks 122 may send pixel control signals Vc to configurable interconnect circuitry 212 via interconnect input lines 50. Addressing circuitry 116 may provide first selector bits f1_sel, first inversion bit f1_inv, second selector bits f0_sel, and second inversion bit f0_inv to configurable interconnect circuitry 212 to selectively route pixel control signals Vc from interconnect input lines 50 to selected image pixels 190 via pixel control lines 54. First selector bits f1_sel, first inversion bit f1_inv, second selector bits f0_sel, and second inversion bit f0_inv may serve to program paths 112 so that each image pixel 190 receives control signal Vc from a selected one of blocks 122.
Configurable interconnect circuitry 212 may receive pixel output signals Vout from image pixels 190 via pixel output lines 56. Addressing circuitry 116 may provide first selector bits f1_sel, first inversion bit f1_inv, second selector bits f0_sel, and second inversion bit f0_inv to interconnect circuitry 212 to selectively route pixel output signals Vout from pixel output lines 56 to selected analog circuit blocks 122 via interconnect output lines 52 (e.g., programmable paths 112 may route pixel output signal Vout to analog circuit block 122-0, may route pixel output signal Vout to analog circuit block 122-1, etc.). Configurable interconnect circuitry 212 may program paths 112 to route pixel control signals Vc to a particular image pixel 190 and to route pixel output signals from the particular image pixel 190 to an associated analog circuit block 122. In this way, image sensor 16 may flexibly select which image pixels 190 in image pixel group 196 are controlled and read out by analog circuit blocks 122.
FIG. 6 shows a circuit diagram showing one possible implementation of a set of configurable routing circuits 210 interposed in path 112 in accordance with an embodiment of the invention. Each image pixel 190 may have its own associated set of configurable routing circuit 210 formed in configurable interconnect circuitry 212. Configurable interconnecting routing circuit 210 may include a first multiplexer 80, a second multiplexer 82, a first logic XOR gate 84, a second logic XOR gate 86, a pixel control signal routing multiplexer 88, and a pixel output signal routing multiplexer 90 (sometimes referred to as a demultiplexer). In the example of FIG. 6, first multiplexer 80 and second multiplexer 82 may have a data input terminal 0, a data input terminal 7, data inputs <6:1>, an output, and a control input that receives control signals to route one of the data inputs to the output. Pixel control signal routing multiplexer 88 may have data inputs <3:0>, an output, and first and second control inputs that receive control signals to route one of the data inputs to the output. Pixel output signal routing multiplexer 90 may have data outputs <3:0>, an input, and first and second control inputs that receive control signals to route one of the data outputs to the input.
The control inputs of first multiplexer 80 may be coupled to addressing circuitry 116 via paths 72, as shown in FIG. 5. The control inputs of first multiplexer 80 may receive first selector bits f1_sel from addressing circuitry 116. Data input terminal 0 of first multiplexer 80 may receive a constant ground signal. Data input terminal 7 of first multiplexer 80 may receive a constant high signal. The data inputs <6:1> of first multiplexer 80 may receive pixel address bits pix<5:0> (assuming each pixel group 196 includes 64 image pixels). Pixel address bits pix<5:0> may be hardwired in each interconnect circuit 210 to provide a specific address for each corresponding image pixel 190 in image pixel group 196. For example, a 0th pixel in array 100 may be designated a predetermined pixel address of “000000.” As another example, a 3rd pixel in array 100 may be given a predetermined pixel address of “000011.” As another example, a 34th pixel in array 100 may be given a fixed pixel address of “100010.” Based on first selector bits f1_sel, signals at a selected one of the inputs of first multiplexer 80 may be routed to the output of first multiplexer 80.
The output of first multiplexer 80 may be coupled to an input of first XOR gate 84. The input of first XOR gate 84 may also be coupled to addressing circuitry 116. The input of first XOR gate 84 may receive first inversion bit f1_inv from addressing circuitry 116. An output of first XOR gate 84 may be coupled to the first control inputs of pixel control signal routing multiplexer 88 and pixel output demultiplexer 90.
The control inputs of second multiplexer 82 may be coupled to addressing circuitry 116 via paths 72. The control inputs of second multiplexer 82 may receive second selector bits f0_sel from addressing circuitry 116. Data input terminal 0 of second multiplexer 82 may receive a constant ground signal. Data input terminal 7 of second multiplexer 82 may receive a constant high signal. The data inputs <6:1> of second multiplexer 82 may receive pixel address bits pix<5:0> (assuming each pixel group 196 includes 64 image pixels). Pixel address bits pix<5:0> may be hardwired in each interconnect circuit 210 to provide a specific address for each corresponding image pixel 190 in image pixel group 196. For example, a 0th pixel in array 100 may be designated a predetermined pixel address of “000000.” As another example, a 3rd pixel in array 100 may be given a predetermined pixel address of “000011.” As another example, a 34th pixel in array 100 may be given a fixed pixel address of “100010.” Based on second selector bits f0_sel, signals at a selected one of the inputs of second multiplexer 82 may be routed to the output of second multiplexer 82.
The output of second multiplexer 82 may be coupled to an input of second XOR gate 86. The input of second XOR gate 86 may also be coupled to addressing circuitry 116. The input of second XOR gate 86 may receive second inversion bit f0_inv from addressing circuitry 116. An output of second XOR gate 86 may be coupled to the second control inputs of pixel control signal routing multiplexer 88 and pixel output demultiplexer 90. Data inputs <3:0> of pixel control signal routing multiplexer 88 may be coupled to analog circuit block group 126 via interconnect input lines 50. The output of pixel control signal routing multiplexer 88 may be coupled to an image pixel 190 in image pixel group 196 via pixel control line 54. The data input of pixel output demultiplexer 90 may be coupled to an image pixel 190 via pixel output line 56. Outputs <3:0> of pixel output demultiplexer 90 may be coupled to analog circuit block group 126 via interconnect output lines 52.
Four analog circuit blocks 122 in analog circuit block group 126 may be coupled to data inputs <3:0> of pixel control signal routing multiplexer 88 and outputs <3:0> of pixel output demultiplexer 90, as shown in FIG. 5. The output of pixel control multiplexer 88 and the input of pixel output demultiplexer 90 may each be coupled to one of the 64 image pixels 190 in image pixel group 196. Pixel address bits pix<5:0> that are supplied to data inputs <6:0> of first multiplexer 80 and second multiplexer 82 may correspond to each image pixel 190 in image pixel group 196. First selector bits f1_sel may be supplied by addressing circuitry 116 to route the signal from one of data inputs <6:0> of first multiplexer 80 to the input of first XOR gate 84. Second selector bits f0_sel may be supplied by addressing circuitry 116 to route the signal from one of data inputs <6:0> of second multiplexer 82 to the input of second XOR gate 86. First inversion bit f1_inv may be used to selectively invert the bit supplied to first XOR gate 84 from first multiplexer 80. Second inversion bit f0_inv may be used to selectively invert the bit supplied to second XOR gate 86 from second multiplexer 82.
The output bits from first XOR gate 84 and second XOR gate 86 may form the control inputs for multiplexer 88. The output bits may control multiplexer 88 to route the control signal Vc that is supplied by a particular analog circuit block 122 to the associated image pixel 190. The output bits from first XOR gate 84 and second XOR gate 86 may also form the control inputs for pixel output demultiplexer 90. The output bits may control demultiplexer 90 to route the pixel output signal Vout from the associated image pixel 190 to a particular analog circuit block 122. In this way, first selector bits f1_sel, second selector bits f0_sel, first inversion bit f1_inv, and second inversion bit f0_inv, may be used to selectively route the image pixel associated with each configurable interconnect circuit 210 to the individual analog circuit blocks 122 in analog circuit block group 126 by rerouting paths 112. The routing of Vc and Vout between analog circuit blocks 122 and image pixels 190 may be controlled based on pixel address bits pix<5:0>, f1_sel, f0_sel, f1_inv, and f0_inv.
Programmable paths 112 of FIGS. 5 and 6 are merely illustrative. If desired, analog circuit block group 126 may include any number of analog circuit blocks 122, and image pixel group 196 may include any number of image pixels 190. First multiplexer 80 and second multiplexer 82 in configurable interconnect circuit 210 may include however many data inputs, pixel addressing bits pix, first selector bits f1_sel, and second selector bits f0_sel, as are needed to provide a unique address to each pixel in image pixel group 196. Pixel control signal routing multiplexer 88 may be formed with a data input corresponding to each analog circuit block 122 in analog circuit block group 126. Pixel output demultiplexer 90 may be formed with data outputs corresponding to each data input used in pixel control multiplexer 88. Additional multiplexers and XOR gates may be formed to ensure that a suitable number of control inputs are supplied to pixel control multiplexer 88 and pixel output demultiplexer 90. Each analog circuit block 122 that is coupled to interconnect circuit 210 may thereby be connected to the corresponding image pixel 190. Configurable paths 112 of the type shown in FIGS. 5 and 6 may also be formed on paths 114 of second interconnect fabric 130, as shown in FIG. 2, to provide similar interconnects between analog processing and control circuitry 120 and digital processing and control circuitry 140.
FIG. 7 shows a table that illustrates the interconnection between analog circuit blocks 122 and image pixels 190 when first selector bits f1_sel and second selector bits f2_sel are supplied, in accordance with an embodiment of the invention. In the example of FIG. 7, image pixel group 196 includes 16 image pixels 190 and analog circuit block group 126 includes four analog circuit blocks 122. First multiplexer 80 and second multiplexer 82 include a data input terminal 0 that receives a constant ground signal, a data input terminal 5 that receives a constant high signal, and data inputs <1:4:> that receive pixel address bits pix<3:0>.
As shown in column 500, when first selector bits f1_sel has a numerical value of 5 and second selector bits f0_sel has a numerical value of 4, image pixels 0-15 are connected to analog circuit block 122-0 (e.g., each and every pixel in that group 196 is coupled to first block 122-0). As shown in column 502, when first selector bits f1_sel has a numerical value of to 4 and second selector bits f0_sel has a numerical value of 3, image pixels 0-7 are connected to analog circuit block 122-0 and image pixels 8-15 are connected to analog circuit block 122-1. As shown in column 504, when first selector bits f1_sel has a numerical value of 3 and second selector bits f0_sel has a numerical value of 2, image pixels 0-3 are connected to analog circuit block 122-0, image pixels 4-7 are connected to analog circuit block 122-1, image pixels 8-11 are connected to analog circuit block 122-2, and image pixels 12-15 are connected to analog circuit block 122-3. As shown in column 506, when first selector bits f1_sel has a numerical value of 1 and second selector bits f0_sel has a numerical value of 0, image pixel 0 is connected to analog circuit block 122-0, image pixel 1 is connected to analog circuit block 122-1, image pixel 2 is connected to analog circuit block 122-2, and image pixel 3 is connected to analog circuit block 122-3. Each four consecutive image pixels are connected in this way.
As shown in column 508, when first selector bits f1_sel has a numerical value of 1, second selector bits f0_sel has a numerical value of 0, and second pixel inversion bit f0_inv is applied to invert the output from second multiplexer 82, image pixel 0 is connected to analog circuit block 122-0, image pixel 1 is connected to analog circuit block 122-1, image pixel 2 is connected to analog circuit block 122-2, and image pixel 3 is connected to analog circuit block 122-3. Each four consecutive image pixels are connected in this way. First inversion bit f1_inv and second inversion bit f0_inv are applied to change the interconnections between image pixels 190 in image pixel group 196 and analog circuit blocks 122 in analog circuit block group 126. The table of FIG. 7 only illustrates some of the possible configurations of selector bits f1_sel and f0_sel applied to interconnect circuit 210. Any suitable combination of selector bits f1_sel and f0_sel as well as inversion bits f1_inv and f0_inv may be implemented by configurable interconnect 210.
FIG. 8 shows a diagram of the layers of interconnection in image sensor 16 in accordance with an embodiment of the invention. Image sensor 16 may include image pixel array 100 that includes a first number of image pixels 190. Image pixels 190 may be coupled to configurable paths 112 formed in first interconnect fabric 110. Analog processing and control circuitry 120 may include a second number of analog circuit blocks 122 that is less than the first number. Each analog circuit block 122 may be selectively coupled to each image pixel 190 via paths 112. Analog circuit blocks 122 may include analog to digital converters 128 for converting image signals into digital signals. Analog circuit blocks 122 may be coupled to paths 114 formed in second interconnect fabric 130. Digital processing and control circuitry 140 may include a third number of digital circuit blocks 142 that is less than the second number. Each digital circuit block 142 may be selectively coupled to each analog circuit block 122 via programmable paths 112. Digital circuit blocks 142 may be coupled to memory circuitry 150. Memory circuitry 150 may be coupled to processing circuitry 160.
By forming configurable paths 112 between image pixels 190 and analog circuit blocks 122, a large number of image pixels 190 may be controlled and read out by a small number of analog circuit blocks 122 and an even smaller number of digital circuit blocks 142. In addition, the specific interconnections between image pixels 190 and analog circuit blocks 122 can change while operating image sensor 16. In this way, image pixels 190 may be controlled and read out in any suitable manner based upon the configuration of paths 112. Paths 112 may be configured to allow image sensors 16 to flexibly control and read out image pixels 190 for use in, for example, HDR imaging, light field cameras, and micro-saccade imaging. Image sensors 16 may also allow for local error correction to correct errors in image pixel subsets 196 without having to read out all image pixels 190 in image pixel array 100, thereby introducing fewer loading and timing problems.
FIG. 9 shows in simplified form a typical processor system 300, such as a digital camera, which includes an imaging device 2000 (e.g., an imaging device 2000 such as imaging sensor 16 of FIGS. 2-8 employing a flexible and highly interconnected image pixel array as described above). The processor system 300 is exemplary of a system having digital circuits that could include imaging device 2000. Without being limiting, such a system could include a computer system, still or video camera system, scanner, machine vision, vehicle navigation, video phone, surveillance system, auto focus system, star tracker system, motion detection system, image stabilization system, and other systems employing an imaging device.
The processor system 300, for example a digital still or video camera system, generally includes a lens 396 for focusing an image on pixel array 100 when a shutter release button 397 is pressed, central processing unit (CPU) 395, such as a microprocessor which controls camera and one or more image flow functions, which communicates with one or more input/output (I/O) devices 391 over a bus 393. Imaging device 2000 also communicates with the CPU 395 over bus 393. The system 300 also includes random access memory (RAM) 392 and can include removable memory 394, such as flash memory, which also communicates with CPU 395 over the bus 393. Imaging device 2000 may be combined with the CPU, with or without memory storage on a single integrated circuit or on a different chip. Although bus 393 is illustrated as a single bus, it may be one or more busses or bridges or other communication paths used to interconnect the system components.
Various embodiments have been described illustrating an image sensor with configurable image sensor pixel interconnections. An image sensor may include an image sensor array formed from rows and columns of image sensor pixels. Analog control circuitry may control and read out the image sensor pixels in the image sensor pixel array. The analog control circuitry may be vertically stacked with respect to the image sensor pixel array. Configurable interconnect circuitry may be interposed between the analog control circuitry and the image sensor pixel array. The analog control circuitry may include a number of analog circuit blocks that are arranged into analog circuit block groups. The configurable interconnect circuitry may include configurable paths that couple each image sensor pixel in the image sensor pixel array to at least one analog circuit block in a corresponding analog circuit block group. The configurable interconnect circuitry may be controlled to reroute the connections between the image sensor pixels and the particular analog circuit blocks in each analog circuit block group.
In one suitable arrangement, the analog circuit blocks may be coupled to a group of image sensor pixels arranged in the image sensor array via the configurable interconnect circuitry. The group of image sensor pixels may be formed from a portion of the image sensor array. Addressing circuitry may supply control signals to the configurable interconnect circuitry to selectively route an analog circuit block to a corresponding image sensor pixel by rerouting the configurable paths in the first configurable interconnect fabric. Signals to and from a portion of the image sensor pixels in the image sensor pixel group may be routed to a first analog circuit block in the analog circuit block group and signals to and from a different portion of the image sensor pixels in the image sensor pixel group may be routed to a second analog circuitry block in the analog circuit block group. The configurable interconnect fabric may include a configurable interconnect circuit corresponding to each image pixel in the image pixel group.
Each image pixel in the image pixel group may be accessed simultaneously by the analog circuitry block group via the corresponding configurable interconnect circuits. Each group of image sensor pixels that is accessed may be formed, for example, from image pixels arranged in at least two adjacent rows, at least two adjacent columns, at least two non-adjacent rows, or at least two non-adjacent columns in the image sensor array. The image sensor array may include a first group of image sensor pixels and a second group of image sensor pixels. The image sensor pixels in the first group may be simultaneously accessed during a first time period and the image sensor pixels in the second group be simultaneously accessed during a second time period that is different than the first time period. A selected group of image sensor pixels in the image sensor array may be accessed simultaneously without accessing at least some image sensor pixels in the at least two rows that are part of another group of image sensor pixels that is different than the selected group.
The image sensor may be placed in a first configuration in which the configurable interconnect circuitry routes first control signals from a first analog control circuit block to a first image sensor pixel in the image sensor array and the configurable interconnect circuitry routes the first control signals to a second image sensor pixel in the image sensor array. When the image sensor is placed in the first configuration, the configurable interconnect circuitry may, for example, route the first control signals to the first image sensor pixel without routing the second control signals to the first image sensor pixel. When the image sensor is placed in the first configuration, the configurable interconnect circuitry may also route pixel output signals generated from the first image sensor pixel to the first analog circuit block.
The image sensor may also be placed in a second configuration in which the configurable interconnect circuitry routes second control signals from a second analog control circuit block to the first image sensor pixel and the configurable interconnect circuitry routes pixel output signals generated from the first image sensor pixel to the second control circuit.
A configurable interconnect circuit may include a pixel control signal routing multiplexer which serves to route control signals from the analog circuit blocks in the analog circuit block group to the corresponding image pixel. The configurable interconnect circuit may also include a pixel output signal routing multiplexer which serves to route pixel output signals from the corresponding image pixel to the analog circuit block group.
The configurable interconnect circuit may also include multiplexers hardwired with the address of the corresponding pixel to its data inputs and logic XOR gates that are coupled to the multiplexers. The addressing circuitry may provide selector and inversion control signals to the multiplexers and XOR gates to control the pixel output signal routing multiplexer and the pixel control signal routing multiplexer. The addressing circuitry may control the routing of pixel output signals and pixel control signals by adjusting control signals provided to the multiplexers and XOR gates.
As an example, four analog control blocks may be coupled to 64 image pixels in an image pixel group via configurable paths. Two multiplexers with six data inputs and two XOR gates may be provided with control signals for routing each of the 64 image pixels to one of the four analog circuit blocks.
As another example, four analog control blocks may be coupled to 16 image pixels in an image pixel group via configurable paths. Two multiplexers with four data inputs and two XOR gates may be provided with control signals for routing each of the 16 image pixels to one of the four analog circuit blocks.
Image sensor digital processing and control circuitry may control the image sensor pixels in the image sensor pixel array and receive image signals from the analog control circuitry. The image sensor digital processing and control circuitry may be vertically stacked with respect to the analog control circuitry. A second configurable interconnect circuitry may be interposed between the analog control circuitry and the digital circuitry. The digital circuitry may include a number of digital circuit blocks that are arranged into digital circuit block groups. The second configurable interconnect fabric may include many configurable paths that couple each analog circuit block in the analog circuit block group to at least one digital circuit block in a corresponding digital circuit block group. The digital circuitry may be coupled to processing circuitry via memory circuit blocks.
The digital processing and control circuitry, analog control circuitry, first configurable interconnect circuitry, and second configurable interconnect circuitry may be formed on shared or separate integrated circuits. The integrated circuits may be vertically stacked. There may be a large number of image sensor pixels in the image sensor pixel array coupled to a small number of analog circuit blocks in the analog control circuitry which are coupled to an even smaller number of digital circuit blocks in the digital control circuitry. The wiring complexity of and the number of interconnections at the pixel level may be substantially greater than the number of interconnections at the digital block level.
The image sensor with configurable pixel interconnections may be implemented in a system that also includes a central processing unit, memory, input-output circuitry, and an imaging device that further includes a pixel array, a lens for focusing light onto the pixel array, and a data converting circuit.
The foregoing is merely illustrative of the principles of this invention which can be practiced in other embodiments.

## Claims

1. An image sensor, comprising:
a plurality of groups of image sensor pixels;
a plurality of control circuits operable to receive pixel output signals, wherein the control circuits are vertically stacked with respect to the image sensor pixels; and
configurable interconnect circuitry interposed between the image sensor pixels and the control circuits, wherein the configurable interconnect circuitry is operable to selectively route the pixel output signals from a selected group of image sensor pixels to at least one of the control circuits, selectively route first control signals from a first one of the control circuits to at least a first portion of image sensor pixels in the selected group, and selectively route the pixel output signals from the first portion of image sensor pixels to the first control circuit.

2. The image sensor defined in claim 1, wherein the control circuits comprise analog control circuitry, and wherein the image sensor further comprises:
image sensor digital processing circuitry that is vertically stacked with respect to the analog control circuitry.

3. The image sensor defined in claim 2, further comprising:
additional configurable interconnect circuitry interposed between the analog control circuitry and the image sensor digital processing circuitry.

4. The image sensor defined in claim 1, further comprising:
addressing circuitry that is coupled to the configurable interconnect circuitry and that generates control signals for programming the configurable interconnect circuitry.

5. The image sensor defined in claim 4, wherein the plurality of groups of image sensor pixels, the analog control circuitry, the digital processing circuitry, and the addressing circuitry are each formed on different respective integrated circuits that are each vertically stacked with respect to each other.

6. The image sensor defined in claim 1, wherein the image sensor pixels are arranged in an array of rows and columns, wherein each group of the plurality of groups of image sensor pixels includes image sensor pixels from at least two rows and at least two columns in the array.

7. The image sensor defined in claim 6, wherein the selected group of image sensor pixels comprises image sensor pixels from at least two adjacent rows of the array.

8. The image sensor defined in claim 7, wherein the selected group of image sensor pixels comprises image sensor pixels from at least two adjacent columns of the array.

9. The image sensor defined in claim 6, wherein the control circuits are configured to access each image sensor pixel in the selected group of image sensor pixels simultaneously through the configurable interconnect circuitry.

10. The image sensor defined in claim 1, wherein the configurable interconnect circuitry is configured to selectively route second control signals from a second one of the control circuits to at least a second portion of image sensor pixels in the selected group that is different than the first portion, and wherein the configurable interconnect circuitry is configured to selectively route the pixel output signals from the second portion of image sensor pixels to the second control circuit.

11. The image sensor defined in claim 1, wherein the plurality of groups of image sensor pixels are formed on a first integrated circuit, wherein the plurality of control circuits are formed on a second integrated circuit that is different from the first integrated circuit, wherein the second integrated circuit is vertically stacked with respect to the first integrated circuit, and wherein the configurable interconnect circuitry is formed on the first integrated circuit.

12. The image sensor defined in claim 1, wherein the plurality of groups of image sensor pixels are formed on a first integrated circuit, wherein the plurality of control circuits are formed on a second integrated circuit that is different from the first integrated circuit, wherein the second integrated circuit is vertically stacked with respect to the first integrated circuit, and wherein the configurable interconnect circuitry is formed on the second integrated circuit.

13. The image sensor defined in claim 1, wherein the plurality of groups of image sensor pixels are formed on a first integrated circuit, wherein the plurality of control circuits are formed on a second integrated circuit that is different from the first integrated circuit, wherein the configurable interconnect circuitry is formed on a third integrated circuit that is different from the first and second integrated circuits, wherein the second integrated circuit is vertically stacked with respect to the first integrated circuit, and wherein the third integrated circuit is vertically stacked with respect to the first integrated circuit and interposed between the first and second integrated circuits.

14. An image sensor, comprising:
a plurality of groups of image sensor pixels;
a plurality of control circuits operable to receive pixel output signals, wherein the control circuits are vertically stacked with respect to the image sensor pixels;
configurable interconnect circuitry interposed between the image sensor pixels and the control circuits, wherein the configurable interconnect circuitry is operable to selectively route the pixel output signals from a selected group of image sensor pixels to at least one of the control circuits; and
addressing circuitry that is coupled to the configurable interconnect circuitry and that generates control signals for programming the configurable interconnect circuitry, wherein the configurable interconnect circuitry comprises:
first multiplexers operable to selectively route the pixel output signals from the selected group of image sensor pixels to at least one of the control circuits; and
second multiplexers operable to selectively route pixel control signals from the at least one of the control circuits to the selected group of image sensor pixels.

15. The image sensor defined in claim 14, wherein the configurable interconnect circuitry further comprises:
third multiplexers that receive the control signals from the addressing circuitry and that generate control bits for controlling the first and second multiplexers.

16. The image sensor defined in claim 15, wherein the configurable interconnect circuitry further comprises:
exclusive OR gates coupled to outputs of the third multiplexers, wherein first and second multiplexers receive the control bits generated using the third multiplexers via the exclusive OR gates.