# US 2014/0152974 A1 · Method for time of flight modulation frequency detection and illumination modulation frequency adjustment

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- Number: US 2014/0152974 A1
- Document ID: US20140152974A1
- Status: Published application
- Kind: A1
- Application number: 13/693,390
- Filed: 2012-12-04
- Published: 2014-06-05
- Earliest claimed: 2012-12-04
- Assignees: Texas Instruments Incorporated
- Applicants: Texas Instruments Incorporated
- Inventors: Dong-Ik KO
- Web page: https://patentgrep.com/patent/US20140152974A1

## CPC

- G01S 7/493: Extracting wanted echo signals
- 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
- G01C 15/002: {Active optical surveying means (optical plumbing G01C15/105)}
- 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
- G01C: MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY (measuring liquid level G01F; radio navigation, determining distance or velocity by use of propagation effects, e.g. Doppler effects, propagation time, of radio waves, analogous arrangements using other waves G01S)

## Abstract

A method removing adjecent frequency interference from a Time Of Flight sensor system by adaptively adjusting the infrared illumination frequency of the TOF sensor by measuring the interfering infrared illuminating frequencies and dynamicaly adjusting the illuminating infrared frequency of the TOF sensor to eliminate the interference.

## Claims

### Claim 1

A method of interference rejection in a Time of Flight (TOF) measurement system comprising the steps of:
receiving all ambient infrared illumination;
measuring the modulation frequencies of said received infrared illumination;
comparing duration of said measured modulation frequencies to a preset threshold;
adjusting the infrared illumination modulating frequency of the Time of Flight measurement system if the preset threshold is exceeded.

### Claim 2 (depends on 1)

The method of claim 1 wherein:
the TOF measurement system's infrared illumination modulation frequency is dynamically adjusted to a value that is offset from the strongest detected ambient infrared modulation frequency.

### Claim 3 (depends on 1)

The method of claim 1 wherein:
the TOF measurement system's infrared illumination modulation frequency is dynamically adjusted to a value that is offset from a plurality of the detected ambient infrared modulation frequencies.