# US 12,218,172 B2 · High-sensitivity depth sensor with non-avalanche photodetector

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- Number: US 12,218,172 B2
- Document ID: US12218172B2
- Status: Granted
- Kind: B2
- Application number: 18/542,477
- Filed: 2023-12-15
- Published: 2024-04-18
- Granted: 2025-02-04
- Earliest claimed: 2018-07-16
- Assignees: Gigajot Technology, Inc.
- Applicants: Gigajot Technology, Inc.
- Inventors: Saleh Masoodian; Jiaju Ma
- Web page: https://patentgrep.com/patent/US12218172B2

## CPC

- G01S 7/4861: Circuits for detection, sampling, integration or read-out
- H10F 39/18: Complementary metal-oxide-semiconductor [CMOS] image sensors; Photodiode array image sensors
- G01S 17/08: for measuring distance only (indirect measurement G01S17/46; active triangulation systems G01S17/48)
- H03K 17/941: {using an optical detector (H03K17/968 takes precedence)}
- H10F 39/199: {Back-illuminated image sensors}
- H10F 39/8033: {Photosensitive area}
- H10F 39/8037: {the integrated elements comprising a transistor}
- H10F 39/80373: {characterised by the gate of the transistor}
- H10F 39/80377: {characterised by the channel of the transistor, e.g. channel having a doping gradient}
- G01S 17/894: Three-dimensional [3D] imaging with simultaneous measurement of time-of-flight at a two-dimensional [2D] array of receiver pixels, e.g. time-of-flight cameras or flash lidar
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M)

## Abstract

A sensing device includes a light source to emit light, a light sensor to detect reflection of the emitted light and distance determination circuitry responsive to reflected-light detection within the light sensor. The light sensor includes a photodetector having a photocharge storage capacity in excess of one electron and an output circuit that generates an output signal responsive to light detection within the photodetector with sub-hundred nanosecond latency. The distance determination circuitry measures an elapsed time based on transition of the output signal in response to photonic detection within the photodetector and determines, based on the elapsed time, a distance between the sensing device and a surface that yielded the reflection of the emitted light.

## Claims

### Claim 1

A sensing device, comprising:
a light source to emit light;
a light sensor to detect reflection of the light emitted by the light source, the light sensor having a photodetector with a photocharge storage capacity in excess of one electron and an output circuit to generate an output signal in response to detection of the reflection, wherein the photodetector includes a pinned floating diffusion region that reduces a delay time between the detection of the reflection and the generation of the output signal; and
circuitry to measure an elapsed time based on the output signal to determine, based on the elapsed time, a distance between the sensing device and a surface that yielded the reflection of the light emitted by the light source.

### Claim 2 (depends on 1)

The sensing device of claim 1, wherein:
the photodetector includes a pinned photodiode (PPD) interconnected with a pinned floating diffusion node (PFD) via a transfer gate;
the pinned floating diffusion region is in the PFD; and
the transfer gate is configured to form a charge transfer channel between the PPD and PFD in response to a readout control signal.

### Claim 3 (depends on 2)

The sensing device of claim 2, wherein:
the pinned floating diffusion region counteracts a feedthrough of a transfer gate pulse to the PFD to reduce a settling time of the output signal after the transfer gate pulse.

### Claim 4 (depends on 1)

The sensing device of claim 1, wherein the photodetector is a multi-well photodetector.

### Claim 5 (depends on 1)

The sensing device of claim 1, wherein the delay time is less than 100 nanoseconds.

### Claim 6 (depends on 1)

The sensing device of claim 1, wherein the delay time is less than 10 nanoseconds.

### Claim 7 (depends on 1)

The sensing device of claim 1, wherein the delay time is less than 5 nanoseconds.

### Claim 8 (depends on 1)

The sensing device of claim 1, wherein the delay time is less than 1 nanosecond.

### Claim 9 (depends on 1)

The sensing device of claim 1, wherein the sensor device is configured to measure distances within 5 millimeters of accuracy.

### Claim 10 (depends on 1)

The sensing device of claim 1, wherein the sensor device is a pulse-based distance measurement device.

### Claim 11 (depends on 1)

The sensing device of claim 1, wherein the sensor device is a phase-based distance measurement device.

### Claim 12

A method comprising:
performing, by a sensing device:
emitting light via a light source;
detecting a reflection of the light via a light sensor, wherein the light sensor includes a photodetector with a photocharge storage capacity in excess of one electron and a pinned floating diffusion region;
generating, via an output circuit of the light sensor, an output signal in response to the detection of the reflection, wherein a delay time between the detection of the reflection and the generation of the output signal is reduced by the pinned floating diffusion region;
measuring an elapsed time based on the output signal; and
determining, based on the elapsed time, a distance between the sensing device and a surface that yielded the reflection of the light emitted by the light source.

### Claim 13 (depends on 12)

The method of claim 12, wherein:
the photodetector includes a pinned photodiode (PPD) interconnected with a pinned floating diffusion node (PFD) via a transfer gate,
the pinned floating diffusion region is in the PFD; and
the method further comprises forming a charge transfer channel between the PPD and PFD in response to the transfer gate receiving a readout control signal.

### Claim 14 (depends on 13)

The method device of claim 13, wherein:
the pinned floating diffusion region counteracts a transfer gate pulse feedthrough to the PFD to reduce a settling time of the output signal after assertion of the readout control signal.

### Claim 15 (depends on 13)

The method of claim 13, wherein:
the output signal is generated at a terminal of a junction field-effect-transistor (JFET) coupled to a change transfer channel; and
the output signal has a voltage level that corresponds to an amount of photocharge accumulated in the photodiode.

### Claim 16 (depends on 12)

The method of claim 12, wherein the delay time is less than 100 nanoseconds.

### Claim 17 (depends on 12)

The method of claim 12, wherein the delay time is less than 10 nanoseconds.

### Claim 18 (depends on 12)

The method of claim 12, wherein the delay time is less than 5 nanoseconds.

### Claim 19 (depends on 12)

The method of claim 12, wherein the delay time is less than 1 nanosecond.

### Claim 20 (depends on 12)

The method of claim 12, wherein the measuring of the elapsed time comprises:
using a counter to increment or decrement a count output over time in response to transitions of a clock signal; and
using latching circuitry to latch the counter output in response to the transition between voltage levels in the output signal.