# US 12,111,397 B2 · Pixel domain field calibration of triangulation sensors

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- Number: US 12,111,397 B2
- Document ID: US12111397B2
- Status: Granted
- Kind: B2
- Application number: 17/303,061
- Filed: 2021-05-19
- Published: 2022-09-15
- Granted: 2024-10-08
- Earliest claimed: 2021-03-09
- Assignees: Banner Engineering Corp.
- Applicants: Banner Engineering Corp.
- Inventors: Wade Oberpriller
- Web page: https://patentgrep.com/patent/US12111397B2

## CPC

- G01S 17/58: Velocity or trajectory determination systems; Sense-of-movement determination systems
- G01S 7/4802: {using analysis of echo signal for target characterisation; Target signature; Target cross-section}
- G01S 7/4814: {of transmitters alone}
- G01S 7/4816: {of receivers alone}
- G01S 7/4972: {Alignment of sensor}
- G01S 17/06: Systems determining position data of a target
- G01S 17/42: Simultaneous measurement of distance and other co-ordinates (indirect measurement G01S17/46)
- G01S 17/48: Active triangulation systems, i.e. using the transmission and reflection of electromagnetic waves other than radio waves
- G01S 17/50: Systems of measurement based on relative movement of target
- G01S 17/88: Lidar systems specially adapted for specific applications
- G01S 17/89: for mapping or imaging
- G06T 7/0004: {Industrial image inspection}
- B65G 13/00: Roller-ways (storage devices comprising roller-ways B65G1/02; endless-chain conveyors comprising load-supporting rollers B65G17/00; rollers or arrangements thereof B65G39/00)
- B65G 43/08: Control devices operated by article or material being fed, conveyed or discharged {(and controlling the discharging devices B65G47/42)}
- B65G 2203/0233: Position of the article
- B65G 2203/0241: Quantity of articles
- B65G 2203/043: Magnetic
- B65G 2203/044: Optical
- 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
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- B65G: TRANSPORT OR STORAGE DEVICES, e.g. CONVEYORS FOR LOADING OR TIPPING, SHOP CONVEYOR SYSTEMS OR PNEUMATIC TUBE CONVEYORS (packaging B65B; handling thin or filamentary materials, e.g. paper sheets or thread, B65H; cranes B66C; portable mobile or lifting or hauling appliances, e.g. hoists, B66D; devices for lifting or lowering goods for loading or unloading purposes, e.g. fork-lift trucks, B66F9/00; emptying bottles, jars, casks, barrels or similar containers, not otherwise provided for, B67C9/00; delivering or transferring liquids B67D; filling or discharging vessels for liquefied, solidified or compressed gases F17C; pipe-line systems for fluids F17D)

## Abstract

Apparatus and associated methods relate to a field-adjustable distance sensor configured to translate a transfer function of the sensor by a substantially constant value in a position domain by calibration at one or more known distances. In an illustrative example, the transfer function may correlate multiple distances to corresponding position vectors describing a position of a light signal on a receiver. The receiver may, for example, generate a detection signal corresponding to a position on the receiver of a light signal reflected off a target. A control circuit may, for example, generate a position vector in response to the detection signal. A calibration constant (C) may be generated, for example, as a function of a known distance of the target and position vector. C may be applied, for example, to translate the transfer function in the position domain. Various embodiments may advantageously reduce non-linear error in a distance sensor.

## Claims

### Claim 1

A field-adjustable distance sensor comprising:
an emitter configured to launch an electromagnetic signal;
at least one sensing element configured to generate a detection signal in response to a reflection of the electromagnetic signal, the detection signal being a function of a position of the electromagnetic signal on the at least one sensing element;
at least one memory module comprising at least one datastore correlating each of a plurality of measured distances to a corresponding position vector, the correlation being defined by a transfer function; and,
a control circuit configured to, in a teach mode, perform calibration operations comprising:
operate the emitter to launch a first electromagnetic signal at a target located at a known distance from the at least one sensing element;
receive from the at least one sensing element a first detection signal corresponding to a reflection of the first electromagnetic signal;
determine a first position vector as a function of the first detection signal;
receive a calibration distance signal corresponding to the known distance; and,
if a difference between the known distance and a distance in the datastore correlated to the first position vector is greater than a calibration threshold, then generate, as a function of the calibration distance signal and the first position vector, a calibration constant configured to translate the transfer function by a substantially constant position value.

### Claim 2 (depends on 1)

The distance sensor of claim 1, the calibration operations further comprising:
determine a second position vector as a function of the calibration distance signal; and,
compare the first position vector and the second position vector;
wherein:
the difference between the known distance and the distance in the datastore is greater than the calibration threshold if the comparison of the first position vector and the second position vector is greater than the calibration threshold, and,
if the comparison is not zero, then the calibration constant is generated as a function of the comparison.

### Claim 3 (depends on 2)

The distance sensor of claim 2, wherein the calibration constant is a third position vector.

### Claim 4 (depends on 3)

The distance sensor of claim 3, wherein the third position vector is substantially equal to a difference between the first position vector and the second position vector.

### Claim 5 (depends on 3)

The distance sensor of claim 3, wherein:
the calibration operations further comprise storing the calibration constant, and,
the control circuit is further configured to, in a run mode, perform distance measurement operations comprising:
operate the emitter to launch a second electromagnetic signal;
receive from the at least one sensing element a second detection signal corresponding to a reflection of the second electromagnetic signal;
determine a measured position vector as a function of the second detection signal;
apply the third position vector to the measured position vector to generate a calibrated position vector; and,
generate a calibrated distance measurement signal by retrieving a distance from a lookup table corresponding to the calibrated position vector.

### Claim 6 (depends on 3)

The distance sensor of claim 3, wherein the calibration operations further comprise apply the third position vector to a plurality of the position vectors in a lookup table to generate a calibrated datastore.

### Claim 7 (depends on 1)

The distance sensor of claim 1, the at least one memory module further comprising a predetermined sensor characteristic profile, and the calibration operations further comprising:
determine an expected position vector as a function of the calibration distance signal;
generate a first distance signal by determining a distance in the datastore corresponding to the expected position vector;
generate a second distance signal by determining a distance in the datastore corresponding to the expected position vector; and,
compare the first distance signal and the second distance signal, wherein:
the difference between the known distance and the distance in the datastore is greater than the calibration threshold if the comparison of the first distance signal and the second position signal is greater than the calibration threshold, and,
if the comparison is not zero, then the calibration constant is generated as a function of the comparison and the predetermined sensor characteristic profile.

### Claim 8 (depends on 7)

The distance sensor of claim 7, wherein the predetermined sensor characteristic comprises at least one parameter of a curve-fit relationship correlating distance and sensor error.

### Claim 9 (depends on 8)

The distance sensor of claim 8, wherein the curve-fit relationship is a polynomial function of at least a second order.

### Claim 10 (depends on 7)

The distance sensor of claim 7, wherein the calibration operations further comprise store the calibration constant, and,
the control circuit is further configured to, in a run mode, perform distance measurement operations comprising:
operate the emitter to launch a second electromagnetic signal;
receive from the at least one sensing element a second detection signal corresponding to a reflection of the second electromagnetic signal;
determine a measured position vector as a function of the second detection signal;
generate a measured distance signal by determining a distance in the datastore corresponding to the measured position vector; and,
apply the calibration constant and the predetermined sensor characteristic profile to the measured position vector to generate a calibrated distance signal.

### Claim 11 (depends on 7)

The distance sensor of claim 7, wherein:
the calibration operations further comprise generate a correction datastore as a function of the datastore, the predetermined characteristic profile, and the calibration constant, wherein the correction datastore correlates each of a plurality of measured distances to a corresponding correction distance, and
the control circuit is further configured to, in a run mode, perform distance measurement operations comprising:
operate the emitter to launch a second electromagnetic signal;
receive from the at least one sensing element a second detection signal corresponding to a reflection of the second electromagnetic signal;
determine a measured position vector as a function of the second detection signal;
generate a measured distance signal by determining a distance in the datastore corresponding to the measured position vector;
retrieve a first correction distance from the datastore; and,
generate a calibrated distance signal by applying the first correction distance to the measured distance signal.

### Claim 12 (depends on 7)

The distance sensor of claim 7, wherein the calibration operations further comprise generate a calibrated datastore as a function of the datastore, the predetermined characteristic profile, and the calibration constant, wherein the calibrated datastore correlates each of a plurality of position vectors to a corresponding calibrated distance.

### Claim 13 (depends on 1)

The distance sensor of claim 1, wherein the electromagnetic signal comprises a light signal.

### Claim 14

A method of field-calibrating a distance sensor comprising providing:
an emitter configured to launch an electromagnetic signal;
at least one sensing element configured to generate a detection signal in response to a reflection of the electromagnetic signal, the detection signal being a function of a position of the electromagnetic signal on the at least one sensing element;
at least one memory module comprising at least one datastore correlating each of a plurality of measured distances to a corresponding position vector, the correlation being defined by a transfer function; and,
operating a control circuit in a teach mode, to perform calibration operations comprising:
operate the emitter to launch a first electromagnetic signal at a target located at a known distance from the at least one sensing element;
receive from the at least one sensing element a first detection signal corresponding to a reflection of the first electromagnetic signal;
determine a first position vector as a function of the first detection signal;
receive a calibration distance signal corresponding to the known distance; and,
if a difference between the known distance and a distance in the datastore correlated to the first position vector is greater than a calibration threshold, then generate, as a function of the calibration distance signal and the first position vector, a calibration constant configured to translate the transfer function by a substantially constant position value.

### Claim 15 (depends on 14)

The method of claim 14, the calibration operations further comprising:
determine a second position vector as a function of the calibration distance signal; and,
compare the first position vector and the second position vector;
wherein:
the difference between the known distance and the distance in the datastore is greater than the calibration threshold if the comparison of the first position vector and the second position vector is greater than the calibration threshold, and,
if the comparison is not zero, then the calibration constant is generated as a function of the comparison.

### Claim 16 (depends on 15)

The method of claim 15, wherein:
the calibration constant comprises a third position vector,
the calibration operations further comprise storing the calibration constant, and,
the control circuit is further configured to, in a run mode, perform distance measurement operations comprising:
operate the emitter to launch a second electromagnetic signal;
receive from the at least one sensing element a second detection signal corresponding to a reflection of the second electromagnetic signal;
determine a measured position vector as a function of the second detection signal;
apply the third position vector to the measured position vector to generate a calibrated position vector; and,
generate a calibrated distance measurement signal by retrieving a distance from a lookup table corresponding to the calibrated position vector.

### Claim 17 (depends on 15)

The method of claim 15, wherein the calibration constant comprises a third position vector, and the calibration operations further comprise apply the third position vector to a plurality of the position vectors in a lookup table to generate a calibrated datastore.

### Claim 18 (depends on 14)

The method of claim 14, the at least one memory module further comprising a predetermined sensor characteristic profile, and the calibration operations further comprising:
determine an expected position vector as a function of the calibration distance signal;
generate a first distance signal by determining a distance in the datastore corresponding to the expected position vector;
generate a second distance signal by determining a distance in the datastore corresponding to the expected position vector; and,
compare the first distance signal and the second distance signal,
wherein:
the difference between the known distance and the distance in the datastore is greater than the calibration threshold if the comparison of the first distance signal and the second position signal is greater than the calibration threshold, and,
if the comparison is not zero, then the calibration constant is generated as a function of the comparison and the predetermined sensor characteristic profile.

### Claim 19 (depends on 18)

The method of claim 18, wherein the calibration operations further comprise storing the calibration constant, and,
the control circuit is further configured to, in a run mode, perform distance measurement operations comprising:
operate the emitter to launch a second electromagnetic signal;
receive from the at least one sensing element a second detection signal corresponding to a reflection of the second electromagnetic signal;
determine a measured position vector as a function of the second detection signal;
generate a measured distance signal by determining a distance in the datastore corresponding to the measured position vector; and,
apply the calibration constant and the predetermined sensor characteristic profile to the measured position vector to generate a calibrated distance signal.

### Claim 20 (depends on 18)

The method of claim 18, wherein:
the calibration operations further comprise generate a correction datastore as a function of the datastore, the predetermined characteristic profile, and the calibration constant, wherein the correction datastore correlates each of a plurality of measured distances to a corresponding correction distance, and
the control circuit is further operated to, in a run mode, perform distance measurement operations comprising:
operate the emitter to launch a second electromagnetic signal;
receive from the at least one sensing element a second detection signal corresponding to a reflection of the second electromagnetic signal;
determine a measured position vector as a function of the second detection signal;
generate a measured distance signal by determining a distance in the datastore corresponding to the measured position vector;
retrieve a first correction distance from the datastore; and,
generate a calibrated distance signal by applying the first correction distance to the measured distance signal.

### Claim 21 (depends on 18)

The method of claim 18, wherein the calibration operations further comprise generate a calibrated datastore as a function of the datastore, the predetermined characteristic profile, and the calibration constant, wherein the calibrated datastore correlates each of a plurality of position vectors to a corresponding calibrated distance.

### Claim 22 (depends on 14)

The method of claim 14, wherein the electromagnetic signal comprises a light signal.