# US 2021/0080554 A1 · Time-of-flight sensor and method of calibrating errors in the same

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- Number: US 2021/0080554 A1
- Document ID: US20210080554A1
- Status: Published application
- Kind: A1
- Application number: 16/829,467
- Filed: 2020-03-25
- Published: 2021-03-18
- Earliest claimed: 2019-09-17
- Assignees: Samsung Electronics Co., Ltd.
- Applicants: Samsung Electronics Co., Ltd.
- Inventors: Muncheon KANG; Kwanghyuk BAE; Hayoung KO; Duckchan SEO; Chulwoong LEE
- Web page: https://patentgrep.com/patent/US20210080554A1

## CPC

- G01S 7/497: Means for monitoring or calibrating
- G01S 7/4808: {Evaluating distance, position or velocity data}
- G01S 7/4915: Time delay measurement, e.g. operational details for pixel components (signal extraction and conditioning G01S7/493); Phase measurement
- G01S 17/08: for measuring distance only (indirect measurement G01S17/46; active triangulation systems G01S17/48)
- G01S 17/36: with phase comparison between the received signal and the contemporaneously transmitted signal
- 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

## Abstract

A method of calibrating errors in a time-of-flight (ToF) sensor includes illuminating a test object with a transmission light that is modulated based on a modulation signal; generating, using a buffer chain circuit, a plurality of demodulation signals having different local delay phases; providing a plurality of measured phase differences by providing the plurality of demodulation signals to a plurality of pixel groups included in a ToF sensor to sample a reception light reflected from the test object based on the plurality of demodulation signals; determining a wiggling error based on the plurality of measured phase differences, the wiggling error depending on a phase difference between the transmission light and the reception light; and calibrating a measured distance from the ToF sensor to a target object based on the wiggling error.

## Claims

### Claim 1

A method of calibrating errors in a time-of-flight (ToF) sensor, the method comprising:
illuminating a test object with a transmission light that is modulated based on a modulation signal;
generating, using a buffer chain circuit, a plurality of demodulation signals having different local delay phases among a plurality of local delay phases;
providing a plurality of measured phase differences by providing the plurality of demodulation signals to a plurality of pixel groups included in a ToF sensor to sample a reception light reflected from the test object based on the plurality of demodulation signals;
determining a wiggling error based on the plurality of measured phase differences, the wiggling error depending on a phase difference between the transmission light and the reception light; and
calibrating a measured distance from the ToF sensor to a target object based on the wiggling error.

### Claim 2 (depends on 1)

The method of claim 1, further comprising:
generating the modulation signal such that the modulation signal has different global delay phases respectively in a plurality of measurement cycles.

### Claim 3 (depends on 2)

The method of claim 2, wherein the test object is fixed at a same position during the plurality of measurement cycles.

### Claim 4 (depends on 2)

The method of claim 2, wherein the plurality of local delay phases are fixed during the plurality of measurement cycles.

### Claim 5 (depends on 2)

The method of claim 2,
wherein the wiggling error is determined based on the plurality of measured phase differences that are measured with respect to all pixels included in the ToF sensor, and
wherein the plurality of measured phase differences are provided during each of the plurality of measurement cycles.

### Claim 6 (depends on 2)

The method of claim 2, wherein the generating the modulation signal comprises:
generating, using a variable delay circuit, the modulation signal such that the modulation signal has a variable delay depending on a control code; and
changing the control code sequentially in the plurality of measurement cycles such that the modulation signal has the different global delay phases respectively in the plurality of measurement cycles.

### Claim 7 (depends on 6)

The method of claim 6, wherein the variable delay circuit is disposed outside the ToF sensor.

### Claim 8 (depends on 2)

The method of claim 2,
wherein the determining the wiggling error comprises:
with respect to each pixel of a plurality of pixels included in the ToF sensor, fitting the measured phase differences corresponding to the each pixel and measured during the plurality of measurement cycles into each linear function;
obtaining a plurality of offset values, each offset value corresponding to a difference between each measured phase difference corresponding to the each pixel and a value of the each linear function;
obtaining, for each measured phase difference among the plurality of measured phase differences, a representative offset value based on the offset values corresponding to the each measured phase difference having the same value; and
obtaining a mapping function representing the wiggling error based on the obtained representative offset values respectively corresponding to the measured phase differences having different values.

### Claim 9 (depends on 8)

The method of claim 8, wherein the obtaining the mapping function includes generating a mapping table that maps the measured phase differences having the different values to the representative offset values.

### Claim 10 (depends on 1)

The method of claim 1, wherein the buffer chain circuit is integrated in the ToF sensor.

### Claim 11

A test system comprising:
a time-of-flight (ToF) sensor; and
a test device configured to measure a wiggling error of the ToF sensor,
the ToF sensor comprising:
a light source configured to illuminate a test object with a transmission light that is modulated based on a modulation signal;
a buffer chain circuit configured to generate a plurality of demodulation signals having different local delay phases; and
a pixel array including a plurality of pixels configured to sample a reception light reflected from the test object based on the plurality of demodulation signals, the plurality of pixels being grouped into a plurality of pixel groups, each pixel group receiving the plurality of demodulation signals having each local delay phase.

### Claim 12 (depends on 11)

The test system of claim 11, wherein the modulation signal has different global delay phases respectively in a plurality of measurement cycles.

### Claim 13 (depends on 12)

The test system of claim 12, wherein the test device includes a variable delay circuit having a variable delay, the variable delay circuit configured to generate the modulation signal based on a control code such that the modulation signal has the variable delay corresponding to the control code, and
wherein the test device changes the control code sequentially in the plurality of measurement cycles such that the modulation signal has the different global delay phases respectively in the plurality of measurement cycles.

### Claim 14 (depends on 13)

The test system of claim 13, wherein the variable delay circuit includes a plurality of delay units that are connected serially, and each of the plurality delay units includes:
a delay circuit configured to delay an output signal of a previous delay unit to output a delayed signal; and
a selector configured to select and output one of the output signal of the previous delay unit and the delayed signal in response to each bit of the control code.

### Claim 15 (depends on 12)

The test system of claim 12, wherein the ToF sensor includes a variable delay circuit having a variable delay, the variable delay circuit configured to generate the modulation signal based on a control code such that the modulation signal has the variable delay corresponding to the control code, and
wherein the test device changes the control code sequentially in the plurality of measurement cycles such that the modulation signal has the different global delay phases respectively in the plurality of measurement cycles.

### Claim 16 (depends on 12)

The test system of claim 12, wherein the test device is configured to:
with respect to each pixel of a plurality of pixels included in the ToF sensor, fit the measured phase differences corresponding to the each pixel and measured during the plurality of measurement cycles into each linear function;
obtain a plurality of offset values, each offset value corresponding to a difference between each measured phase difference and a value of the each linear function;
obtain each representative offset value of a plurality of representative offset values based on the offset values corresponding to each measured phase difference value, the each representative offset value corresponding to the each measured phase difference; and
obtain a mapping function representing the wiggling error based on the plurality of representative offset values and the plurality of measured phase differences.

### Claim 17 (depends on 16)

The test system of claim 16, wherein the test device provides the mapping function as a mapping table representing mapping relations between the plurality of measured phase differences and the plurality of representative offset values, and
wherein the ToF sensor calibrates a measured distance from the ToF sensor to a target object based on the mapping table.

### Claim 18

A time-of-flight (ToF) sensor comprising:
a light source configured to illuminate a test object with a transmission light that is modulated based on a modulation signal;
a buffer chain circuit configured to generate a plurality of demodulation signals having different local delay phases; and
a pixel array including a plurality of pixels configured to sample a reception light reflected from the test object based on the plurality of demodulation signals, the plurality of pixels being grouped into a plurality of pixel groups, each pixel group receiving the plurality of demodulation signals having each local delay phase.

### Claim 19 (depends on 18)

The ToF sensor of claim 18, wherein the variable delay circuit includes a plurality of delay units that are connected serially and configured to generate the plurality of demodulation signals.

### Claim 20 (depends on 19)

The ToF sensor of claim 19, further comprising:
a variable delay circuit configured to generate the modulation signal based on a control code such that the modulation signal has a variable delay depending corresponding to the control code, and
wherein the ToF sensor receives from an external test device, the test device changing the control code sequentially in the plurality of measurement cycles such that the modulation signal has the different global delay phases respectively in the plurality of measurement cycles.