# US 12,181,611 B2 · Time-of-flight to distance calculator

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- Number: US 12,181,611 B2
- Document ID: US12181611B2
- Status: Granted
- Kind: B2
- Application number: 17/441,132
- Filed: 2020-03-18
- Published: 2022-05-26
- Granted: 2024-12-31
- Earliest claimed: 2019-03-22
- Assignees: ams International AG
- Applicants: ams International AG
- Inventors: Thomas Jessenig; Robert Kappel; Manfred Lueger; Christian Mautner
- Web page: https://patentgrep.com/patent/US12181611B2

## CPC

- G01S 7/4873: {by deriving and controlling a threshold value}
- G01S 7/4865: Time delay measurement, e.g. time-of-flight measurement, time of arrival measurement or determining the exact position of a peak (peak detection in noise, signal conditioning G01S7/487)
- G01S 7/487: Extracting wanted echo signals {, e.g. pulse detection}
- G01S 17/10: using transmission of interrupted, pulse-modulated waves (determination of distance by phase measurements G01S17/32)
- 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

Methods for detecting a time-of-flight include: emitting a light pulse toward a target; detecting a presence of light received at a light detector; obtaining a delay time between emitting the light pulse and detecting the presence of the light at the light detector; responsive to obtaining the delay time, (a) updating an overall intensity counter that counts a total number of delay times that have been obtained and (b) updating a delay time counter out of a plurality of different delay time counters, wherein each delay time counter counts a total number of delay times obtained that have a corresponding delay time value; and monitoring a threshold of each delay time counter to determine whether a threshold value is exceeded.

## Claims

### Claim 1

A method comprising:
emitting a light pulse toward a target;
detecting a presence of light received at a light detector;
obtaining a delay time between emitting the light pulse and detecting the presence of the light at the light detector;
responsive to obtaining the delay time,
(a) updating an overall intensity counter that counts a total number of delay times that have been obtained and
(b) updating a delay time counter out of a plurality of different delay time counters, wherein each delay time counter counts a total number of delay times obtained that have a corresponding delay time value;
monitoring a threshold of each delay time counter to determine whether a threshold value is exceeded;
determining that a first delay time counter exceeds the threshold value based on the monitoring;
responsive to determining that the first delay time counter exceeds the threshold value, identifying a signal-to-noise (SNR) threshold value for the first delay time counter;
determining that the SNR threshold value does not exceed the baseline intensity value; and
determining whether the threshold value corresponds to a maximum value of the first delay time counter.

### Claim 2 (depends on 1)

The method of claim 1, further comprising:
determining that a first delay time counter exceeds the threshold value based on the monitoring; and
calculating, based on the delay time value associated with the first delay time counter that exceeded the threshold value, a distance to a target.

### Claim 3 (depends on 1)

The method of claim 1 comprising:
determining the threshold value of the first delay time counter is not the maximum value of the first delay time counter; and
selecting a different value as a new threshold value.

### Claim 4 (depends on 3)

The method of claim 3 comprising continuing updates to the overall intensity counter and to the plurality of delay time counters until the new threshold value is exceeded.

### Claim 5 (depends on 1)

The method of claim 1 comprising:
determining the threshold value of the first delay time counter is the maximum value of the first delay time counter;
compressing a dynamic range of the plurality of delay time counters to obtain a new threshold value; and
continuing updates to the overall intensity counter and to the plurality of delay time counters until the new threshold value is exceeded.

### Claim 6 (depends on 1)

The method of claim 1 comprising:
determining that a maximum time period has elapsed without any of the plurality of delay time counters exceeding the threshold value;
determining a difference between a current value of each of the delay time counters and the threshold value; and
for at least the delay time counter having the smallest difference, calculating a distance to a target.

### Claim 7 (depends on 6)

The method of claim 6, further comprising, prior to calculating the distance to the target:
identifying a minimum required signal-to-noise (SNR) value for the threshold value; and
determining that the minimum required SNR value exceeds a baseline intensity value.

### Claim 8

A method comprising:
emitting a light pulse toward a target; detecting a presence of light received at a light detector;
obtaining a delay time between emitting the light pulse and detecting the presence of the light at the light detector;
responsive to obtaining the delay time,
(a) updating an overall intensity counter that counts a total number of delay times that have been obtained and
(b) updating a delay time counter out of a plurality of different delay time counters, wherein each delay time counter counts a total number of delay times obtained that have a corresponding delay time value;
determining that a first delay time counter exceeds the threshold value based on the monitoring;
responsive to determining that the first delay time counter exceeds the threshold value, identifying a signal-to-noise (SNR) threshold value for the first delay time counter;
determining that the SNR threshold value does not exceed the baseline intensity value; and
determining whether the threshold value corresponds to a maximum value of the first delay time counter
determining that a maximum time period has elapsed;
responsive to determining that the maximum time period has elapsed, determining a difference between a current value of each of the delay time counters and a threshold value; and
for at least the delay time counter having the smallest difference, calculating a distance to a target.

### Claim 9 (depends on 8)

The method of claim 8, prior to calculating a distance to the target:
identifying a minimum required signal-to-noise (SNR) value for the threshold value; and
determining that the minimum required SNR value exceeds a baseline intensity value.

### Claim 10

A time-of-flight monitoring circuit comprising: a delay time calculator configured to obtain a light pulse emission time and a light pulse detection time and to calculate a delay time as a difference between the light pulse emission time and the light pulse detection time; an overall counter coupled to the delay time calculator and configured to count a total number of delay times that have been calculated by the delay time calculator; a plurality of delay time counters coupled to the delay time calculator, wherein each delay time counter counts a total number of delay times having a corresponding delay time value that have been calculated by the delay time calculator; an threshold check circuit coupled to the plurality of delay time counters, wherein the threshold check circuit is configured to monitor an threshold of each delay time counter to determine whether any of the plurality of delay time counters exceeds a threshold value; memory comprising a signal-to-noise (SNR) lookup table and an intensity threshold value lookup table coupled to the threshold check circuit; an SNR and intensity evaluation circuit configured to derive a SNR value from the recorded delay time counts and determine whether the derived SNR value meets a specified minimum SNR determined from the SNR lookup table.