# US 2018/0321383 A1 · Triangulation scanner having flat geometry and projecting uncoded spots

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- Number: US 2018/0321383 A1
- Document ID: US20180321383A1
- Status: Published application
- Kind: A1
- Application number: 15/784,437
- Filed: 2017-10-16
- Published: 2018-11-08
- Earliest claimed: 2017-05-05
- Assignees: Faro Technologies, Inc.
- Applicants: FARO Technologies, Inc.
- Inventors: Rolf Heidemann; Mark Brenner; Simon Raab
- Web page: https://patentgrep.com/patent/US20180321383A1

## CPC

- G01S 17/66: Tracking systems using electromagnetic waves other than radio waves
- G01B 11/002: {for measuring two or more coordinates}
- G01B 11/2513: {with several lines being projected in more than one direction, e.g. grids, patterns}
- G01B 11/2545: {with one projection direction and several detection directions, e.g. stereo}
- G01S 17/87: Combinations of systems using electromagnetic waves other than radio waves
- G01S 17/89: for mapping or imaging
- G06T 7/521: from laser ranging, e.g. using interferometry; from the projection of structured light
- G06T 7/593: from stereo images
- H04N 13/254: in combination with electromagnetic radiation sources for illuminating objects
- H04N 13/271: wherein the generated image signals comprise depth maps or disparity maps
- H04N 13/296: Synchronisation thereof; Control thereof
- G06T 2207/10028: Range image; Depth image; 3D point clouds
- G06T 2207/30244: Camera pose
- 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
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

A projector projects an uncoded pattern of uncoded spots onto an object, which is imaged by a first camera and a second camera, 3D coordinates of the spots on the object being determined by a processor based on triangulation, the processor further determining correspondence among the projected and imaged spots based at least in part on a nearness of intersection of lines drawn from the projector and image spots through their respective perspective centers.

## Claims

### Claim 1

A method comprising:
in a first instance:
with a projector having a perspective center, projecting a first uncoded pattern of uncoded spots from a projector reference plane to form illuminated object spots on an object;
with a first camera having a first-camera perspective center, capturing the illuminated object spots as first-image spots in a first image;
with a second camera having a second-camera perspective center, capturing the illuminated object spots as second-image spots in a second image;
with a processor, determining three-dimensional (3D) coordinates of a first collection of points on the object, the 3D coordinates of the first collection of points based at least in part on the first uncoded pattern of uncoded spots, the first image, the second image, relative positions of the projector, the first camera, and the second camera, and on a selected plurality of intersection sets, each intersection set including a first spot, a second spot, and a third spot, the first spot being one of the first uncoded pattern of uncoded spots in the projector reference plane, the second spot being one of the first-image spots, the third spot being one of the second-image spots, the selecting of each intersection set based at least in part on a nearness of intersection of a first line, a second line, and a third line, the first line being a line drawn from the first spot through the projector perspective center, the second line being a line drawn from the second spot through the first-camera perspective center, the third line being a line drawn from the third spot through the second-camera perspective center; and
storing the determined 3D coordinates of the first collection of points.

### Claim 2 (depends on 1)

The method of claim 1 further comprising:
in a second instance:
with a scanner system having the projector, the first camera, the second camera, and the processor, determining 3D coordinates of a second collection of points.

### Claim 3 (depends on 2)

The method of claim 2 further comprising:
with the processor, registering the first collection of points and the second collection of points in a common frame of reference based at least in part on the determined 3D coordinates of the first collection of points and the determined 3D coordinates of the second collection of points.

### Claim 4 (depends on 3)

The method of claim 3 further comprising:
coupling a retroreflector to the scanner system;
in the first instance, measuring first 3D coordinates of the retroreflector with a laser tracker;
in the second instance, measuring second 3D coordinates of the retroreflector with the laser tracker; and
with the processor, registering the first collection of points and the second collection of points in the common frame of reference further based at least in part on the measured first 3D coordinates of the retroreflector and the measured second 3D coordinates of the retroreflector.

### Claim 5 (depends on 2)

The method of claim 2 further comprising:
with the processor, determining a change in pose of the scanner system from a first pose in the first instance to a second pose in the second instance based at least in part on the determined 3D coordinates of the first collection of points and the determined 3D coordinates of the second collection of points.

### Claim 6 (depends on 5)

The method of claim 5 further comprising:
coupling a retroreflector to the scanner system;
in the first instance, measuring first 3D coordinates of the retroreflector with a laser tracker;
in the second instance, measuring second 3D coordinates of the retroreflector with the laser tracker; and
with the processor, determining the change in pose of the scanner system from the first pose to the second pose further based on the measured first 3D coordinates of the retroreflector and the measured second 3D coordinates of the retroreflector.

### Claim 7 (depends on 6)

The method of claim 6, further comprising:
measuring 3D coordinates of a reference artifact with the scanner system; and
with the processor, determining the change in pose of the scanner system from the first pose to the second pose further based on the measured 3D coordinates of the reference artifact.

### Claim 8 (depends on 5)

The method of claim 5 further comprising:
coupling a robotic mechanism to the scanner system; and
with the processor, calculating a desired change in pose of the robotic mechanism based at least in part on the determined change in pose of the scanner system from the first pose to the second pose; and
adjusting the robotic mechanism to obtain the desired change in pose.

### Claim 9 (depends on 8)

The method of claim 8 further comprising:
altering at least one of a direction and a velocity of the robotic mechanism in response to a probability of an interaction that includes an operator being equal to or above a predetermined probability threshold.

### Claim 10 (depends on 8)

The method of claim 8 further comprising:
coupling a retroreflector to the scanner system;
in the first instance, measuring first 3D coordinates of the retroreflector with a laser tracker;
in the second instance, measuring second 3D coordinates of the retroreflector with the laser tracker; and
with the processor, calculating the desired change in pose of the robotic mechanism further based on the measured first 3D coordinates of the retroreflector and the measured second 3D coordinates of the retroreflector.

### Claim 11 (depends on 8)

The method of claim 8 further comprising:
measuring 3D coordinates of a reference artifact with the scanner system; and
with the processor, calculating the desired change in pose of the robotic mechanism further based on the measured 3D coordinates of the reference artifact.

### Claim 12 (depends on 3)

The method of claim 3 further comprising:
coupling a third camera to the scanner system;
in the first instance, with the third camera, capturing a first third-camera image of a first mark;
in the second instance, with the third camera, capturing a second third-camera image of the first mark; and
with the processor, registering the first collection of points and the second collection of points in the common frame of reference further based on the first third-camera image of the first mark and on the second third-camera image of the first mark.

### Claim 13 (depends on 12)

The method of claim 12 wherein:
in capturing the first third-camera image and the second third-camera image, the first mark is selected from the group consisting of: an aspect of a natural feature and an artificial target.

### Claim 14 (depends on 2)

The method of claim 2 further comprising:
coupling a line scanner device to the scanner system, the line scanner device having a line projector and a two-dimensional (2D) camera;
in the first instance, projecting a first line of light from the line projector onto the object and capturing with the camera a first line-scanner image of the first line of light on the object;
in the second instance, projecting a second line of light from the line projector onto the object and capturing with the camera a second line-scanner image of the second line of light on the object;
with the processor, registering the first line of light on the object to the second line of light on the object based at least in part on the first collection of points, the second collection of points, the projected first line of light, the captured first line-scanner image, the projected second line of light, and the captured second line-scanner image.

### Claim 15 (depends on 1)

The method of claim 1 wherein:
in projecting with the projector an uncoded pattern of uncoded spots, the projector includes an optical axis that shares a common plane with an optical axis of the first camera and an optical axis of the second camera.

### Claim 16 (depends on 1)

The method of claim 1 wherein:
in projecting with the projector an uncoded pattern of uncoded spots, the projector, the first camera, and the second camera are coupled to a top structural element and a bottom structural element, the top structural element and the bottom structural element are rigid plates held apart by spacers.

### Claim 17 (depends on 1)

The method of claim 1 further comprising:
with the projector, projecting light from a light source to a pattern generator, the pattern generator selected from the group consisting of: a diffractive optical element (DOE), a transparent or reflective slide having a pattern, a digital micromirror device (DMD), a lenslet array.

### Claim 18 (depends on 1)

The method of claim 1, further comprising:
with a beam-steering mechanism, steering an uncoded pattern of uncoded spots, the beam-steering mechanism including a solid-state deflector or a reflective element actuated by a mechanism selected from a group consisting of: a piezo actuator, a microelectromechanical system (MEMS) device, and a magnetic coil.

### Claim 19 (depends on 3)

The method of claim 3 wherein:
the first collection of points is obtained in the first instance for the object when arranged on a moving conveyor belt; and
the second collection of points is obtained in the second instance for the object on the moving conveyor belt.

### Claim 20 (depends on 3)

The method of claim 3 wherein:
the first collection of points is obtained in the first instance for the object when arranged on a moving end effector of a robot; and
the second collection of points is obtained in the second instance for the object on the object on the moving end effector of the robot.

### Claim 21

A system comprising:
a projector having a perspective center, the projector operable to project a first uncoded pattern of uncoded spots from a projector reference plane to form illuminated object spots on an object;
a first camera having a first-camera perspective center, the first camera operable to capture the illuminated object spots as first-image spots in a first image;
a second camera having a second-camera perspective center, the second camera operable to capture the illuminated object spots as second-image spots in a second image; and
a processor operable to execute computer instructions that, when executed on the processor, determine three-dimensional (3D) coordinates of a first collection of points on the object, the 3D coordinates of the first collection of points based at least in part, in a first instance, on the first uncoded pattern of uncoded spots, the first image, the second image, relative positions of the projector, the first camera, and the second camera, and on a selected plurality of intersection sets, each intersection set including a first spot, a second spot, and a third spot, the first spot being one of the first uncoded pattern of uncoded spots in the projector reference plane, the second spot being one of the first-image spots, the third spot being one of the second-image spots, the selecting of each intersection set based at least in part on a nearness of intersection of a first line, a second line, and a third line, the first line being a line drawn from the first spot through the projector perspective center, the second line being a line drawn from the second spot through the first-camera perspective center, the third line being a line drawn from the third spot through the second-camera perspective center.

### Claim 22 (depends on 21)

The system of claim 21 wherein:
a scanner system includes the projector, the first camera, the second camera, and the processor, the processor being operable, in a second instance, to execute computer instructions that, when executed on the processor, determine 3D coordinates of a second collection of points.

### Claim 23 (depends on 22)

The system of claim 22 wherein:
the processor is operable to execute computer instructions that, when executed on the processor, register the first collection of points and the second collection of points in a common frame of reference based at least in part the measured 3D coordinates of the first collection of points and the measured 3D coordinates of the second collection of points.

### Claim 24

A system comprising:
a projector having a projector optical axis and a projector perspective center, the projector operable to project onto an object a collection of uncoded spots of light in a first uncoded pattern;
a first camera having a first-camera optical axis and a first-camera perspective center, the first camera operable to capture a first image of the collection of uncoded spots of light on the object;
a second camera having a second-camera optical axis and a second-camera perspective center, the second camera operable to capture a second image of the collection of uncoded spots of light on the object;
an enclosure having a front side, the front side intersected by the projector optical axis, the first-camera optical axis, and the second-camera optical axis, the front side further intersected by a first plane that includes the projector perspective center, the first-camera optical axis, and the second-camera optical axis; and
a processor operable to execute computer instructions that, when executed on the processor, determine three-dimensional (3D) coordinates of a point on the object based at least in part on the first uncoded pattern of uncoded spots, the first image, and the second image.

### Claim 25 (depends on 24)

The system of claim 24 wherein:
the projector optical axis, the first-camera optical axis, and the second camera optical axis lie on a common plane.

### Claim 26 (depends on 24)

The system of claim 24 wherein:
the projector further includes a laser source and a diffractive optical element, the collection of uncoded spots of light being produced by a light from the laser source passing through the diffractive optical element.