Dynamic range of a line scanner having a photosensitive array that provides variable exposure

• US 9,531,967 B2
• Filed: 12/29/2014
• Issued: 12/27/2016
• Est. Priority Date: 12/31/2013
• Status: Active Grant

• Current Assignee: Faro Technologies Incorporated
• Original Assignee: Faro Technologies Incorporated
• Inventors: Bridges, Robert E.
• Primary Examiner(s): Kassa, Yosef
• Application Number:
  US14/583,920
• Publication Number:
  US 20150189201A1
• Time in Patent Office: 729 Days
• Field of Search: 382/154, 382/282, 382/284, 382/286, 382/291, 345/419, 345/653, 345/664
• US Class Current: 1/1
• CPC Class Codes: G01B 11/005 coordinate measuring machines
• CPC Class Codes: G01B 11/022 by means of tv-camera scanning
• CPC Class Codes: G01B 11/25 by projecting a pattern, e.g. one or more lines, moiré fringes on the object G01B11/255 takes precedence ; image analysis for depth or shape recovery G06T7/50
• CPC Class Codes: H04N 25/531 by controlling rolling shutters in CMOS SSIS
• CPC Class Codes: H04N 25/583 with different integration times

Abstract

A line scanner measures 3D coordinates of an object surface and includes a projector with a light source that projects a line of light at the object surface. The line scanner also has a camera with a 2D array of light sensors and electronics that controls the exposure and readout times of each light sensor, the exposure time being controlled in either rows or columns of the array in a non-sequential manner, the readout time being controlled in either rows or columns that are the same as the rows or columns whose exposure time is being controlled, each of the light sensors converts an amount of captured optical energy into a digital signal value, the captured optical energy being from a reflected line of light from the object surface. Further includes a processor that receives the digital signal values and calculates the 3D coordinates of the object surface.

Claims

1. A line scanner for measuring three-dimensional coordinates of a surface of an object, comprising:

a projector including a light source and a projector lens, the projector configured to project light from the light source through the lens as a line of light at the surface of the object;

a camera including a photosensitive array and a camera lens, the photosensitive array including a two-dimensional array of light sensors, the array of light sensors having M rows and N columns, where M and N are integers, the camera further including control electronics configured to control exposure time of each light sensor in the array of light sensors and to control readout time of each light sensor in the array of light sensors, the exposure time of each light sensor in the array of light sensors being controlled in one of the rows and the columns of the light sensors, the readout time of each light sensor in the array of light sensors being controlled in the one of the rows and the columns, the exposure time of each light sensor in the array of light sensors being controlled such that the array of light sensors is controlled in a non-sequential manner, each of the light sensors in the array of light sensors configured to convert an amount of optical energy captured by each of the light sensors into a digital signal value, the optical energy captured by the light sensors being from a reflected line of light from the surface of the object, the reflected line of light being the projected line of light reflected from the surface of the object, the exposure time of each of the light sensors in a first row starts with a first row reset signal and ends with a first row select signal, the first exposure time is a first time period between the first row reset signal and the first row select signal, and the readout time of the first row starts with the first row select signal; and

a processor configured to receive the digital signal values and to calculate two of the three-dimensional coordinates of the surface of the object therefrom.

2. The line scanner of claim 1, wherein the projector is fixed with respect to the camera and both are enclosed in a housing.

3. The line scanner of claim 1, wherein the exposure time of each of the light sensors in a second row starts with a second row reset signal and ends with a second row select signal, wherein the second exposure time is a second time period between the second row reset signal and the second row select signal, and wherein the readout time of the second row starts with the second row select signal.

4. The line scanner of claim 3, wherein the exposure time of each of the light sensors in a third row starts with a third row reset signal and ends with a third row select signal, wherein the third exposure time is a third time period between the third row reset signal and the third row select signal, and wherein the readout time of the third row starts with the third row select signal.

5. The line scanner of claim 4, wherein the second row is between the first row and the third row in the two-dimensional array of light sensors, wherein the second exposure time is different than the first exposure time, and wherein the readout times are in a sequential order of the first readout time, the third readout time, and the second readout time.