# US 10,484,628 B2 · Flexible pixel-wise exposure control and readout

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- Number: US 10,484,628 B2
- Document ID: US10484628B2
- Status: Granted
- Kind: B2
- Application number: 15/785,301
- Filed: 2017-10-16
- Published: 2018-04-26
- Granted: 2019-11-19
- Earliest claimed: 2016-10-21
- Assignees: The Johns Hopkins University
- Applicants: The Johns Hopkins University
- Inventors: Jie Zhang; Ralph Etienne-Cummings; Tao Xiong; Trac D. Tran; Sang H. Chin
- Web page: https://patentgrep.com/patent/US10484628B2

## CPC

- H04N 25/585: with pixels having different sensitivities within the sensor, e.g. fast or slow pixels or pixels having different sizes
- H04N 25/00: Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N 25/533: by using differing integration times for different sensor regions
- H04N 25/77: Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components
- H04N 25/78: Readout circuits for addressed sensors, e.g. output amplifiers or A/D converters
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

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.

## Claims

### Claim 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.

### Claim 2 (depends on 1)

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.

### Claim 3 (depends on 1)

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.

### Claim 4 (depends on 1)

The pixel of claim 1, wherein said variable exposure period of said photodiode differs between a first frame and a second frame.

### Claim 5 (depends on 1)

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.

### Claim 6 (depends on 1)

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.

### Claim 7 (depends on 1)

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.

### Claim 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.

### Claim 9 (depends on 8)

The image capture device of claim 8 further comprising a random exposure sequence generator configured to generate said random exposure sequence.

### Claim 10 (depends on 9)

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.

### Claim 11 (depends on 10)

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.

### Claim 12 (depends on 9)

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.

### Claim 13 (depends on 8)

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.

### Claim 14 (depends on 8)

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.

### Claim 15 (depends on 14)

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.

### Claim 16 (depends on 8)

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.

### Claim 17 (depends on 8)

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.

### Claim 18 (depends on 8)

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.

### Claim 19 (depends on 18)

The method of claim 18, wherein the coded image is processed using a low pass filter to extract a high dynamic range scene.

### Claim 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.

### Claim 21 (depends on 20)

The method of claim 20, wherein said dictionary is a sparsifying dictionary.

### Claim 22 (depends on 21)

The method of claim 21, wherein said sparsifying dictionary is an overcomplete dictionary.