US-20260129313-A1 - Methods and Devices to Dynamically Tune an Exposure Time of an Imager for Three-Dimensional Profiling of an Object

US20260129313A1US 20260129313 A1US20260129313 A1US 20260129313A1US-20260129313-A1

Abstract

Methods and devices for dynamically tuning an exposure time of an imager are disclosed herein. The method captures, via an imaging assembly of a device, a first image of an object. The imaging assembly comprises a light source and at least one imager having a first exposure time during capture of the first image. The method determines an average number of a first class of pixels per column of pixels present in the first image and determines whether the average number of the first class of pixels per column of pixels is within a range. If the average number of the first class of pixels per column of pixels is not within the range, the method modifies the first exposure time of the at least one imager by one of decreasing or increasing the first exposure time of the at least one imager based on a classification of the first image.

Inventors

Christopher Hirst

Assignees

ZEBRA TECHNOLOGIES CORPORATION

Dates

Publication Date: 20260507
Application Date: 20241106

Claims (20)

1 . A method, comprising: capturing, via an imaging assembly of a device, a first image of an object, the imaging assembly having a light source and at least one imager having a first exposure time during capture of the first image, and the first image having a first region and a second region; determining an average number of a first class of pixels per column of pixels present in the first image based on a number of the first class of pixels present in the first image and a number of columns of pixels of the first image; determining whether the average number of the first class of pixels per column of pixels is within a predetermined range; responsive to determining the average number of the first class of pixels per column of pixels is not within the predetermined range, modifying the first exposure time of the at least one imager by one of decreasing the first exposure time of the at least one imager or increasing the first exposure time of the at least one imager based on a classification of the first image, wherein the first region is a line indicative of light present in the first image, the second region is indicative of a background of the first image, and the first class of pixels is indicative of pixels satisfying a brightness threshold present in the first image.
2 . The method of claim 1 , further comprising projecting, by the imaging assembly, light onto the object during capture of the first image.
3 . The method of claim 1 , further comprising capturing, via the imaging assembly of the device, a second image of the object based on a modified first exposure time of the at least one imager, the second image having a third region and a fourth region, wherein the third region is a line indicative of light present in the second image, and the fourth region is indicative of a background of the second image.
4 . The method of claim 1 , wherein the device is a three-dimensional profiler; the light source is a laser and the light present in the first image is laser light; and the first image is a laser profile image.
5 . The method of claim 1 , wherein the average number of the first class of pixels per column of pixels is one of a floating point or a fixed point value; and the predetermined range is indicative of a target range of the average number of the first class of pixels per column of pixels comprising a thickness of the line.
6 . The method of claim 1 , wherein modifying the first exposure time of the at least one imager comprises: determining whether the average number of the first class of pixels per column of pixels exceeds the predetermined range; responsive to determining the average number of the first class of pixels per column of pixels exceeds the predetermined range, classifying the first image as over exposed, and decreasing the first exposure time of the at least one imager; and responsive to determining the average number of the first class of pixels per column of pixels does not exceed the predetermined range, determining the average number of the first class of pixels per column of pixels is below the predetermined range, classifying the first image as under exposed, and increasing the first exposure time of the at least one imager.
7 . The method of claim 1 , wherein modifying the first exposure time of the at least one imager comprises: determining whether the average number of the first class of pixels per column of pixels is below the predetermined range; responsive to determining the average number of the first class of pixels per column of pixels is below the predetermined range, classifying the first image as under exposed, and increasing the first exposure time of the at least one imager; and responsive to determining the average number of the first class of pixels per column of pixels is not below the predetermined range, determining the average number of the first class of pixels per column of pixels exceeds the predetermined range, classifying the first image as over exposed, and decreasing the first exposure time of the at least one imager.
8 . The method of claim 1 , wherein decreasing the first exposure time of the at least one imager comprises: determining a second exposure time of the imager to generate a second image with an average number of first class of pixels per column of pixels within the predetermined range based on the average number of first class of pixels per column of pixels of the first region and the first exposure time of the at least one imager; and decreasing the first exposure time of the at least one imager, based on the second exposure time of the at least one imager, to be within the predetermined range.
9 . The method of claim 8 , wherein the second exposure time of the at least one imager is indicative of the first exposure time of the at least one imager modified by an adjustment factor of Exp(t)/Exp(m) where Exp(t) is indicative of an exposure time for an average number of a first class of pixels per column in a center of the predetermined range based on a brightness of the laser and Exp(m) is indicative of the first exposure time of the average number of first class of pixels per column of pixels of the first region based on the same brightness of the laser.
10 . The method of claim 1 , increasing the first exposure time of the at least one imager comprises: determining whether the average number of the first class of pixels per column of pixels exceeds a minimum threshold; responsive to determining the average number of the first class of pixels exceeds the minimum threshold, determining a second exposure time of the at least one imager to generate a second target range of another average number of first class of pixels per column of pixels of the first region based on the average number of first class of pixels per column of pixels of the first region and the first exposure time of the at least one imager, and increasing the first exposure time of the at least one imager, based on the second exposure time of the imager, to be within the second target range of the another average number of the first class of pixels per column of pixels of the first region; and responsive to determining the average number of the first class of pixels per column of pixels does not exceed the minimum threshold, determining an average number of a second class of pixels per column of pixels present in the first image based on a number of the second class of pixels present in the first image and the number of columns of pixels of the first image, determining an average number of a third class of pixels per column of pixels present in the first image based on a number of the third class of pixels present in the first image and the number of columns of pixels of the first image, and increasing the first exposure time of the imager by a predetermined factor based on a highest class of pixels among the second and third classes of pixels having a minimum average number of pixels per column.
11 . A device, comprising: an imaging assembly having a light source and at least one imager; one or more processors; and a non-transitory computer-readable memory coupled to the one or more processors, the memory storing instructions thereon that, when executed by the one or more processors, cause the one or more processors to: receive a first image of an object, the first image being captured by the at least one imager utilizing a first exposure time, and the first image having a first region and a second region; determine an average number of a first class of pixels per column of pixels present in the first image based on a number of the first class of pixels present in the first image and a number of columns of pixels of the first image; determine whether the average number of the first class of pixels per column of pixels is within a predetermined range; responsive to determining the average number of the first class of pixels per column of pixels is not within the predetermined range, modifying the first exposure time of the at least one imager by one of decreasing the first exposure time of the at least one imager or increasing the first exposure time of the at least one imager based on a classification of the first image, wherein the first region is a line indicative of light present in the first image, the second region is indicative of a background of the first image, and the first class of pixels is indicative of pixels satisfying a brightness threshold present in the first image.
12 . The device of claim 11 , wherein the instructions, when executed, further cause the one or more processors to project, by the imaging assembly, light onto the object during capture of the first image.
13 . The device of claim 11 , wherein the instructions, when executed, further cause the one or more processors to receive a second image having a third region and a fourth region, the second image being captured by the at least one imager utilizing a modified first exposure time of the at least one imager, wherein the third region is a line indicative of laser light present in the second image, and the fourth region is indicative of a background of the second image.
14 . The device of claim 11 , wherein the device is a three-dimensional profiler; the light source is a laser and the light present in the first image is laser light; and the first image is a laser profile image.
15 . The device of claim 11 , wherein the average number of the first class of pixels per column of pixels is one of a floating point or a fixed point value; and the predetermined range is indicative of a target range of the average number of the first class of pixels per column of pixels comprising a thickness of the line.
16 . The device of claim 11 , wherein the instructions, when executed, cause the one or more processors to modify the first exposure time of the at least one imager by: determining whether the average number of the first class of pixels per column of pixels exceeds the predetermined range; responsive to determining the average number of the first class of pixels per column of pixels exceeds the predetermined range, classifying the first image as over exposed, and decreasing the first exposure time of the at least one imager; and responsive to determining the average number of the first class of pixels per column of pixels does not exceed the predetermined range, determining the average number of the first class of pixels per column of pixels is below the predetermined range, classifying the first image as under exposed, and increasing the first exposure time of the at least one imager.
17 . The device of claim 11 , wherein the instructions, when executed, cause the one or more processors to modify the first exposure time of the at least one imager by: determining whether the average number of the first class of pixels per column of pixels is below the predetermined range; responsive to determining the average number of the first class of pixels per column of pixels is below the predetermined range, classifying the first image as under exposed, and increasing the first exposure time of the at least one imager; and responsive to determining the average number of the first class of pixels per column of pixels is not below the predetermined range, determining the average number of the first class of pixels per column of pixels exceeds the predetermined range, classifying the first image as over exposed, and decreasing the first exposure time of the at least one imager.
18 . The device of claim 11 , wherein the instructions, when executed, further cause the one or more processors to decrease the first exposure time of the at least one imager by: determining a second exposure time of the at least one imager to generate a second image with an average number of first class of pixels per column within the predetermined range based on the average number of first class of pixels per column of pixels of the first region and the first exposure time of the at least one imager; and decreasing the first exposure time of the at least one imager, based on the second exposure time of the at least one imager, to be within the predetermined range.
19 . The device of claim 18 , wherein the second exposure time of the at least one imager is indicative of the first exposure time of the at least one imager modified by an adjustment factor of Exp(t)/Exp(m) where Exp(t) is indicative of an exposure time for an average number of a first class of pixels per column in a center of the predetermined range based on a brightness of the laser and Exp(m) is indicative of the first exposure time of the average number of first class of pixels per column of pixels of the first region based on the same brightness of the laser.
20 . The device of claim 11 , wherein the instructions, when executed, further cause the one or more processors to increase the first exposure time of the at least one imager by: determining whether the average number of the first class of pixels per column of pixels exceeds a minimum threshold; responsive to determining the average number of the first class of pixels exceeds the minimum threshold, determining a second exposure time of the at least one imager to generate a second target range of another average number of first class of pixels per column of pixels of the first region based on the average number of first class of pixels per column of pixels of the first region and the first exposure time of the at least one imager, and increasing the first exposure time of the at least one imager, based on the second exposure time of the at least one imager, to be within the second target range of the another average number of the first class of pixels per column of pixels of the first region; and responsive to determining the average number of the first class of pixels per column of pixels does not exceed the minimum threshold, determining an average number of a second class of pixels per column of pixels present in the first image based on a number of the second class of pixels present in the first image and the number of columns of pixels of the first image, determining an average number of a third class of pixels per column of pixels present in the first image based on a number of the third class of pixels present in the first image and the number of columns of pixels of the first image, and increasing the first exposure time of the at least one imager by a predetermined factor based on a highest class of pixels among the second and third classes of pixels having a minimum average number of pixels per column.

Description

BACKGROUND Machine vision technologies provide a means for image-based inspection and analysis for applications ranging from automatic part inspection, process control, robotic guidance, part identification, barcode reading, and many others. Machine vision technologies rely on capturing and processing images for performing specific analysis or tasks which often require both the integrated use of imaging systems as well as processing systems. For example, machine vision technologies may capture and process images to perform three-dimensional (3D) profiling of an object (e.g., 3D measurement and/or reconstruction of the object). BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views, together with the detailed description below, are incorporated in and form part of the specification, and serve to further illustrate embodiments of concepts that include the claimed invention, and explain various principles and advantages of those embodiments. FIG. 1 is a diagram illustrating an example embodiment of a system of the present disclosure. FIGS. 2A-B are diagrams illustrating an embodiment of a device of the present disclosure. FIG. 3 is a diagram illustrating an example environment for implementing the device of FIGS. 2A-B. FIG. 4 is a flowchart illustrating processing steps carried out by an embodiment of the present disclosure. FIG. 5 is a diagram illustrating an example image captured by the device of FIGS. 2A-B. FIG. 6A is a diagram illustrating an example image captured by the device of FIGS. 2A-B. FIG. 6B is a diagram illustrating a graph of the example image of FIG. 6A. FIG. 7A is a flowchart illustrating an example embodiment of step 308 of FIG. 4 in greater detail. FIG. 7B is a flowchart illustrating another example embodiment of step 308 of FIG. 4 in greater detail. FIG. 8 is a flowchart illustrating step 404 of FIG. 7A and step 430 of FIG. 7B in greater detail. FIG. 9A is a diagram illustrating an example image captured by the device of FIGS. 2A-B. FIG. 9B is a diagram illustrating a graph of the example image of FIG. 9A. FIG. 10 is a flowchart illustrating step 410 of FIG. 7A and step 424 of FIG. 7B in greater detail. FIG. 11A is a diagram illustrating an example image captured by the device of FIGS. 2A-B. FIG. 11B is a diagram illustrating a graph of the example image of FIG. 11A. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention. The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. DETAILED DESCRIPTION As mentioned above, machine vision technologies may capture and process images to perform three-dimensional (3D) profiling of an object (e.g., 3D measurement and/or reconstruction of the object). A 3D measurement and/or reconstruction device or system utilizes a light source to project one or more sheets of light (e.g., a laser beam, a structured light, or the like) onto an object and utilizes an imaging device (e.g., a camera, imager, or the like) to capture an image of the object illuminated by the light source. For example, the image may be a laser profile image generally comprising a bright line on a dark and nearly featureless background. The device or system detects and utilizes a position of the bright line in the captured image to determine 3D measurements of and/or reconstruct the object. An accuracy of the 3D measurements and/or reconstruction of the object depends on an exposure time of the imaging device. For example, when utilizing an appropriate exposure time of an imaging device, a position of a center of a bright line in each column of a captured image can be transformed into a 3D point in a world coordinate system. The 3D points lie on a plane defined by the sheet of light, thus creating a slice or profile of the object. Multiple profiles can be combined into a 3D point cloud of the object. Conventional auto-exposure algorithms are incompatible with a laser profile image. For example, generally a center of the line present in a laser profile image is saturated when an exposure time of an imaging device is within a predetermined (e.g., a suitable) range and, as such, increasing an exposure time of the imaging device provides for widening the line rather than increasing a brightness of the line. Proposed techniques to mitigate deficienci