# US 11,906,353 B2 · Digital pixel with extended dynamic range

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 11,906,353 B2
- Document ID: US11906353B2
- Status: Granted
- Kind: B2
- Application number: 16/435,451
- Filed: 2019-06-07
- Published: 2019-12-12
- Granted: 2024-02-20
- Earliest claimed: 2018-06-11
- Assignees: Meta Platforms Technologies, LLC
- Applicants: Meta Platforms Technologies, LLC
- Inventors: Xinqiao Liu; Song Chen; Andrew Samuel Berkovich; Wei Gao
- Web page: https://patentgrep.com/patent/US11906353B2

## CPC

- G01J 1/44: Electric circuits {(for command of an exposure part G03B7/02)}
- G01J 1/46: using a capacitor
- G02B 27/017: {Head mounted}
- H04N 25/581: acquired simultaneously
- H04N 25/583: with different integration times
- H04N 25/621: for the control of blooming
- H04N 25/77: Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components
- H04N 25/772: comprising A/D, V/T, V/F, I/T or I/F converters
- H04N 25/78: Readout circuits for addressed sensors, e.g. output amplifiers or A/D converters
- G01J 2001/446: {Photodiode}
- H04N 25/59: by controlling the amount of charge storable in the pixel, e.g. modification of the charge conversion ratio of the floating node capacitance
- G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

In one example, an apparatus comprises a photodiode, a charge storage unit, and a processing circuits configured to: transfer overflow charge from the photodiode to the charge storage unit to develop a first voltage; compare the first voltage against a first ramping threshold voltage to generate a first decision; generate, based on the first decision, a first digital value; transfer residual charge from the photodiode to the charge storage unit to develop a second voltage; compare the second voltage against a static threshold voltage to determine whether the photodiode saturates to generate a second decision; compare the second voltage against a second ramping threshold voltage to generate a third decision; generate, based on the third decision, a second digital value; and output, based on the second decision, one of the first digital value or the second digital value to represent an intensity of light received by the photodiode.

## Claims

### Claim 1

An apparatus comprising:
a photodiode;
a charge storage unit; and
a processing circuits configured to:
transfer overflow charge from the photodiode to the charge storage unit to develop a first voltage;
compare the first voltage against a first ramping threshold voltage to generate a first decision;
generate, based on the first decision, a first digital value;
transfer residual charge from the photodiode to the charge storage unit to develop a second voltage;
compare the second voltage against a static threshold voltage to determine whether the photodiode saturates to generate a second decision, wherein the static threshold voltage is based on a quantity of the residual charge equal to a saturation capacity of the photodiode;
compare the second voltage against a second ramping threshold voltage to generate a third decision;
generate, based on the third decision, a second digital value; and
output, based on the second decision, one of the first digital value or the second digital value to represent an intensity of light received by the photodiode.

### Claim 2 (depends on 1)

The apparatus of claim 1, wherein the static threshold voltage is further based on a voltage offset representing a dark charge deposited by dark current.

### Claim 3 (depends on 2)

The apparatus of claim 2, wherein the second ramping threshold voltage starts or ends from the static threshold voltage.

### Claim 4 (depends on 1)

The apparatus of claim 1, further comprising:
a counter; and
a memory;
wherein the processing circuits are configured to:
store, based on the first decision and the third decision, at least one of a first count value from the counter as the first digital value or a second count value from the counter as the second digital value in the memory; and
output the stored digital value in the memory to represent the intensity of light received by the photodiode.

### Claim 5 (depends on 4)

The apparatus of claim 4, wherein the processing circuits are configured to overwrite the first count value with the second count value in the memory based on the second decision.

### Claim 6 (depends on 4)

The apparatus of claim 4, further comprising a register;
wherein the processing circuits are configured to:
store a first flag value indicating the second decision in the register; and
output, from the memory, one of the first digital value or the second digital value based on the first flag value from the register.

### Claim 7 (depends on 6)

The apparatus of claim 6, wherein the processing circuits are configured to:
determine a status of the first decision when the first ramping threshold voltage reaches a first breakpoint voltage;
store a second flag value indicating the status of the first decision in the register; and
output, from the memory, the one of the first digital value or the second digital value based on the first flag value and the second flag value from the register.

### Claim 8 (depends on 7)

The apparatus of claim 7, wherein the processing circuits are configured to reset the counter when the first ramping threshold voltage reaches the first breakpoint voltage.

### Claim 9 (depends on 6)

The apparatus of claim 6, wherein the processing circuits are configured to:
determine a status of the third decision when the second ramping threshold voltage reaches a second breakpoint voltage;
store a second flag value indicating the status of the third decision in the register; and
output, from the memory, the one of the first digital value or the second digital value based on the first flag value and the second flag value from the register.

### Claim 10 (depends on 9)

The apparatus of claim 9, wherein the processing circuits are configured to reset the counter when the second ramping threshold voltage reaches the second breakpoint voltage.

### Claim 11 (depends on 6)

The apparatus of claim 6, wherein the static threshold voltage is a first static threshold voltage; and
wherein the processing circuits are configured to:
compare the first voltage against a second static threshold voltage representing a saturation capacity of the charge storage unit to generate a fourth decision;
store a second flag value indicating the fourth decision in the register;
store, based on the fourth decision, a third count value from the counter as a third digital value, the first digital value, or the second digital value in the memory; and
output, based on the first flag value and the second flag value, one of the first digital value, the second digital value or the third digital value from the memory to represent the intensity of light received by the photodiode.

### Claim 12 (depends on 11)

The apparatus of claim 11, wherein the processing circuits are configured to:
compare the first voltage against the second static threshold voltage within a pre-determined time period;
determine a first status of the fourth decision when a pre-determined portion of the time period has elapsed;
store the first flag value indicating the first status of the fourth decision in the register;
determine a second status of the fourth decision when the time period has elapsed;
store the second flag value indicating the second status of the fourth decision in the register; and
output, based on the first flag value and the second flag value, one of the first digital value, the second digital value or the third digital value from the memory to represent the intensity of light received by the photodiode.

### Claim 13 (depends on 12)

The apparatus of claim 12, wherein the processing circuits are configured to reset the counter when the pre-determined portion of the time period has elapsed.

### Claim 14 (depends on 1)

The apparatus of claim 1, wherein a charge storage capacity of the charge storage unit is configurable by the processing circuit;
wherein the processing circuits are configured to:
configure the charge storage unit to have a first capacity to develop the first voltage; and
configure the charge storage unit to have a second capacity smaller than the first capacity to develop the second voltage.

### Claim 15 (depends on 14)

The apparatus of claim 14, wherein the charge storage unit comprises a floating drain node and a capacitor.

### Claim 16 (depends on 1)

The apparatus of claim 1, wherein the first digital value and the second digital value are generated from a counter; and
wherein the counter is reset based on at least one of: the first ramping threshold voltage reaching a first voltage break point, or the second ramping threshold voltage reaching a second voltage break point.

### Claim 17

A method comprising:
transferring overflow charge from a photodiode to a charge storage unit to develop a first voltage;
comparing the first voltage against a first ramping threshold voltage to generate a first decision;
generating, based on the first decision, a first digital value;
transferring residual charge from the photodiode to the charge storage unit to develop a second voltage;
comparing the second voltage against a static threshold voltage to determine whether the photodiode saturates to generate a second decision, wherein the static threshold voltage is based on a quantity of the residual charge equal to a saturation capacity of the photodiode;
comparing the second voltage against a second ramping threshold voltage to generate a third decision;
generating, based on the third decision, a second digital value; and
outputting, based on the second decision, one of the first digital value or the second digital value to represent an intensity of light received by the photodiode.

### Claim 18 (depends on 17)

The method of claim 17, wherein the static threshold voltage is a voltage offset representing a dark charge deposited by dark current.

### Claim 19 (depends on 17)

The method of claim 17, wherein the second ramping threshold voltage starts or ends from the static threshold voltage.

### Claim 20 (depends on 17)

The method of claim 17, further comprising:
storing, based on the first decision, a first count value from a counter in a memory as the first digital value;
storing, based on the third decision, a second count value from the counter in the memory as the second digital value; and
outputting, from the memory, one of the first digital value or the second digital value based on the second decision.

### Claim 21

An apparatus, comprising:
a photodiode;
a charge storage unit; and
a processing circuit configured to:
transfer overflow charge from the photodiode to the charge storage unit to develop a first voltage;
perform a first quantization operation to generate a first digital value;
perform a second quantization operation to generate a second digital value; and
output one of the first digital value or the second digital value to represent an intensity of light received by the photodiode,
wherein the first quantization operation comprises:
comparing the first voltage against a first ramping threshold voltage to generate a first decision; and
generating, based on the first decision, a first digital value from a counter;
wherein the second quantization operation comprises:
transferring residual charge from the photodiode to the charge storage unit to develop a second voltage;
comparing the second voltage against a second ramping threshold voltage to generate a second decision; and
generating, based on the second decision, a second digital value from the counter;
and
wherein the counter is reset based on at least one of: the first ramping threshold voltage reaching a first voltage break point during the first quantization operation, or the second ramping threshold voltage reaching a second voltage break point during the second quantization operation.

### Claim 22 (depends on 21)

The apparatus of claim 21, wherein the processing circuit is configured to output one of the first digital value or the second digital value based on at least one of the first decision or the second decision.

### Claim 23 (depends on 21)

The apparatus of claim 21, wherein the process circuit is configured to compare the second voltage against a second static threshold voltage to generate a third decision indicating whether the photodiode is saturated by the residual charge; and
output, based on the third decision, one of the first digital value or the second digital value to represent an intensity of light received by the photodiode.

### Claim 24 (depends on 21)

The apparatus of claim 21, wherein the processing circuit is configured to:
perform a third quantization operation comprising:
comparing the first voltage against a first static threshold voltage to generate a fourth decision; and
generating, based on the fourth decision, a third digital value from the counter; and
output one of the first digital value, the second digital value, or the third digital value to represent the intensity of light received by the photodiode; and
wherein the counter is reset based on at least one of: the first ramping threshold voltage reaching a first voltage break point during the first quantization operation, the second ramping threshold voltage reaching a second voltage break point during the second quantization operation, or a time break point is reached during the third quantization operation.