Flexible pixel-wise exposure control and readout
A pixel having a variable exposure for a scene capture device, the pixel comprising a photodiode, a buffer and a memory element and a switching mechanism. The memory element is configured to store an exposure control bit and the switching mechanism configured to control a variable exposure period of the photodiode based on the exposure control bit and to reset a voltage on said photodiode to a reference voltage.
1. A pixel for a scene capture device, said pixel comprising:
a photodiode;
a buffer;
a memory element configured to store an exposure control bit; and
a switching mechanism configured to control a variable exposure period of said photodiode based on said exposure control bit and to reset a voltage on said photodiode to a reference voltage;
wherein:
said switching mechanism is configured to disconnect said photodiode from said buffer and said reference voltage during said variable exposure period; or
said switching mechanism comprises a first switch selectively coupling said photodiode to said buffer to control said variable exposure of said photodiode and a second switch configured to reset said photodiode to a reference voltage.
2. The pixel of claim 1 , wherein said buffer is configured to isolate said photodiode from one or more circuit elements of said image capture device.
3. The pixel of claim 1 , wherein said switching mechanism is configured to disconnect said photodiode from said buffer and said reference voltage during said variable exposure period.
4. The pixel of claim 1 , wherein said variable exposure period of said photodiode differs between a first frame and a second frame.
5. The pixel of claim 1 , wherein said variable exposure period of said photodiode during a first frame and a second variable exposure period of a second photodiode of said image capture device during said first frame differ.
6. The pixel of claim 1 , wherein said memory element is coupled to a driver configured to provide said exposure control bit to said memory element.
7. The pixel of claim 1 , wherein said switching mechanism comprises a first switch selectively coupling said photodiode to said buffer to control said variable exposure of said photodiode and a second switch configured to reset said photodiode to a reference voltage.
8. An image capture device comprising:
a plurality of pixels comprising:
a photodiode;
a buffer;
a memory element configured to store an exposure control bit; and
a switching mechanism configured to control a variable exposure period of said photodiode based on said exposure control bit and to reset a voltage on said photodiode to a reference voltage;
a plurality of drivers coupled to said plurality of pixels, wherein said plurality of drivers is configured to:
receive a random exposure sequence; and
provide an exposure control bit to a memory element of each pixel of said plurality of pixels based on said random exposure sequence; and
a plurality of analog-to-digital converters (ADCs) coupled to said plurality of pixels.
9. The image capture device of claim 8 further comprising a random exposure sequence generator configured to generate said random exposure sequence.
10. The image capture device of claim 9 , wherein said random exposure sequence generator, said plurality of pixels, said plurality of drivers and said plurality of ADCs are part of a common integrated controller.
11. The image capture device of claim 10 , wherein an exposure control bit of said first pixel of said plurality of pixels differs between said first frame and said second frame.
12. The image capture device of claim 9 , wherein said random exposure sequence generator are part of a first integrated controller and at least one of said plurality of pixels, plurality of drivers, plurality of ADCs are part of a second integrated controller.
13. The image capture device of claim 8 , wherein a variable exposure period of a first pixel of said plurality of pixels differs between a first frame and a second frame.
14. The image capture device of claim 8 , wherein a variable exposure period of a first and second pixel of said plurality of pixels differ during a first frame.
15. The image capture device of claim 14 , wherein a sampling time for each of the plurality of ADCs is based on said exposure control bit for each said corresponding pixel.
16. The image capture device of claim 8 , wherein said random exposure sequence comprises a length equal to a number of pixels in a row of said image capture device.
17. The image capture device of claim 8 , wherein each of said plurality of ADCs are configured to receive a sampling control bit corresponding to each pixel of said plurality of pixels.
18. A method for capturing a high dynamic range (HDR) image using a single capture, said method comprising:
programming said plurality of pixels of claim 8 to have different exposure lengths; and
acquiring pixel values from the plurality of pixels using the said plurality of ADCs of claim 8 to form a coded image.
19. The method of claim 18 , wherein the coded image is processed using a low pass filter to extract a high dynamic range scene.
20. A method for reconstructing a video from a coded image, said method comprising:
receiving pixel values and one or more corresponding exposure patterns corresponding to said coded image;
determining an optimal video corresponding to the coded image based on a dictionary by solving an inverse problem with said dictionary for said pixel values; and
outputting said optimal video to an storage device.
21. The method of claim 20 , wherein said dictionary is a sparsifying dictionary.
22. The method of claim 21 , wherein said sparsifying dictionary is an overcomplete dictionary.