Patent Publication Number: US-11040452-B2

Title: Depth sensing robotic hand-eye camera using structured light

Description:
TECHNICAL FIELD 
     The present application generally relates to a robotic hand-eye camera having a field of vision, a control system operable for determining a region of interest within the field of vision and a light system for projecting structured light onto an object located within the region of interest. 
     BACKGROUND 
     Robots can be used with a camera system to determine a location of a work object relative to the robot. Typically, an entire field of view or “scene” is illuminated with one or more light sources to aid depth sensing of the camera. Some existing systems have various shortcomings relative to certain applications. Accordingly, there remains a need for further contributions in this area of technology. 
     SUMMARY 
     One embodiment of the present application is a unique system for sensing a location of an object in a robot work area or industrial scene. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for sensing a location of an object relative to the robot using a camera system with structured light projected only on a portion of the field of view. Further embodiments, forms, features, aspects, benefits, and advantages of the present application shall become apparent from the description and figures provided herewith. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a schematic illustration of a robot system according to one exemplary embodiment of the present disclosure; 
         FIG. 2  is a prior art schematic illustration of structured light being projected onto an entire work area or field of vision of a camera; 
         FIG. 3  a schematic illustration of a region of interest located in portion of the field of vision of the camera as determined by a control system; 
         FIG. 4  is a schematic illustration of structured light being projected onto the region of interest for facilitating robot interaction with an object in the region of interest; and 
         FIG. 5  is a flow chart illustrating a method of operation. 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS 
     For the purposes of promoting an understanding of the principles of the application, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the application is thereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the application as described herein are contemplated as would normally occur to one skilled in the art to which the application relates. 
     Structured light systems can be used to enable a computerized control system to measure shape and position of three-dimensional (3D) objects. A structured light system includes a light source and a pattern generator. A camera can measure the appearance of the light patterns and light pattern variation projected onto the objects. The observed phase of a periodic light pattern is related to the topography or depth of the object that is being illuminated. The variation in light patterns can include variation in shapes, shades, intensities, colors, wavelengths and/or frequencies of the projected light. 
     As the field of robotics continues to advance, an increasing amount of focus is placed on the development of technologies that permit the robot to perform tasks quicker and with less computation requirements. Typically, structured light is projected onto or across the entire field of view of a vision system to aid a robot system in determining position and depth of one or more objects within the field of view. Structured light interference can be problematic if the field of view from multiple stereo cameras happen to overlap. Moreover, calculating depth based on image analysis of the entire field of view is computationally intensive. For these reasons, real-time 3D camera applications typically rely on fast, less accurate algorithms that require higher power and more expensive computer systems. The present disclosure provides a method to reduce computation time, reduce the chance for light reflection interference within the vision system, and reduce the potential of eye injuries due to wide reaching array of light projection. 
     Referring now to  FIG. 1 , an illustrative robot system  10  is shown in an exemplary working environment or industrial scene. It should be understood that the robot system shown herein is exemplary in nature and that variations in the robot and/or industrial scene is contemplated herein. The robot system  10  can include a robot  12  with a vision system  36  having one or more cameras  38 . In one form, one or more of the cameras  38  can be mounted on one of the moveable arms  16   a ,  16   b  of the robot  12 . In other forms, one or more cameras  38  may be positioned apart from the robot  12 . A control system  14  including an electronic controller with a CPU, a memory, and input/output systems is operably coupled to the robot  12  and to the vision system  36 . The control system  14  is operable for receiving and analyzing images captured by the vision system  36  and other sensor data used for operation of the robot  12 . In some forms, the control system  14  is defined within a portion of the robot  12 . 
     The robot  12  may include a movable base  20  and a plurality of movable portions connected thereto. The movable portions may translate or rotate in any desired direction. By way of example and not limitation, movable portions illustrated by arrows  18 ,  26 ,  28 ,  30 ,  32  and  34  may be employed by the exemplary robot  12 . A bin  40  for holding workpieces or other objects  42  to be retrieved and/or worked on by the robot  12  may constitute at least a part of the exemplary industrial scene. An end effector  24  such as a gripping or grasping mechanism can be attached to the moveable arm  16   a  and used to grasp an object  42  and/or perform other work tasks on the object  42  as desired. It should be understood that the term “bin” is exemplary in nature and as used herein means, without limitation, any container, carton, box, tray or other structure that can receive and/or hold workpieces, parts or other objects. Additional components  44  can be associated with the vision system  36 . These components  44  can include lighting systems, reflector(s), refractor(s), diffractive element(s) and beam expander(s) or the like. 
     Referring now to  FIG. 2 , a robot scene  48 , according to a prior art embodiment, is illustrated wherein the work bin  40  can be a portion of the industrial robot scene  48  or the entirety of the industrial robot scene  48 . A light source  50 , such as a laser or other known lighting source, can project structured light into the industrial robot scene  48  so that an entire or complete field of view  54  of a camera  38  is filled with structured light  52  illustrated in the exemplary embodiment as dashed parallel lines. The field of view  54  of the camera  38  can include a portion of the entire industrial robot scene  48  or the entire industrial robot scene  48 , however the computational time delay of analyzing all objects  42  within the field of view  54  is time consuming and can be challenging in a real-time robot work process. 
     Referring now to  FIG. 3 , a system for reducing a computational time of the control system  14  required to analyze the objects  42  within the field of view  54  is illustrated. The control system  14  is operable to determine a region of interest  56  illustrated by a box shaped pattern covering only a portion of the objects  42  positioned within the entire field of view  54 . Once the region of interest  56  is determined by the control system  14 , structured light  58  can be projected from a light source  50  into the region of interest  56 , as shown in  FIG. 4 . The control system  14  need only analyze one or more objects  42  in the region of interest  56  defined by a portion of the field of view  54 . The region of interest  56  illuminated by structured light  58  illustrated by linear line segments can be captured by a camera  38  of the vision system  36 . The control system  14  then analyzes the captured image(s) and determines location and depth of one or more objects  42  within the region of interest  56 . In this manner, computational analysis requirements for the control system  14  is reduced and therefore the speed in which the robot system  10  can perform a work task on an object  42  within a region of interest  56  will increase. 
     In one form, the structured light system can project a pattern of light onto the region of interest  56  and the control system  14  can compare certain features of the pattern in a captured image with locations of the features in a reference image to determine disparities that can be used to determine depth at each location. The region of interest  56  can be illuminated by a time-multiplexed sequence of patterns. Typically, two or more patterns are used to reconstruct a 3D image with sufficiently high resolution. For example, in order to acquire  20  depth frames per second (fps), a light projector  50  must be able to project patterns at a sufficiently rapid rate—typically greater than sixty (60) fps. Various light projectors may be used such as for example, laser generators, computer controlled projectors based on LCD (liquid crystal diode), DMD (digital micro mirror device) or LED (light emitting display) and the like. In one form, the structured light  58  may be a light pattern of parallel bars having various codes and the image may comprise a plurality of pixels that corresponds to the plurality of parallel bars of light. Other forms are contemplated herein. 
     Referring now to  FIG. 5 , a method  100  is disclosed for performing a work task on an object  42  using structured light  58  to aid in determining a position and depth of an object  42 . At step  102 , the structured light  58  is turned off. At step  104  the control system  14 , including the vision system  36 , identifies an object  42  and calculates a region of interest  56  within a field of view  54 . The light source  50  then projects structured light  58  onto the region of interest  56  at step  106 . At step  108 , the control system  14  will calculate a location and depth of an object  42  within a region of interest  56  using only the pixels circumscribed by the bounding box defining the region of interest  56 . At step  110 , the robot  12  performs a robot task on an object  42  within a region of interest  56 . Robot tasks can include, but are not limited to, grasping, moving, assembling or performing other work operations on the object  42 . It should be understood that when the term robot, robot task, robot system or the like is used herein, the system is not limited to a single robot, but on the contrary may include multiple robots operating in the industrial scene. 
     In one aspect, the present disclosure includes a system comprising a robot configured to perform a robot task; a vision system including a camera operably connected to the robot, the camera operable to capture an image within a field of view; a controller operable for analyzing the image and determining a region of interest within the field of view; a light system configured to project structured light onto the region of interest; and wherein the control system is configured to determine a depth of a workpiece within the region of interest. 
     In refining aspects, wherein the region of interest has a smaller area than the field of view of the camera, wherein the control system determines a depth of a plurality of workpieces within the region of interest, wherein the structured light is defined by at least one of a plurality of patterns, shapes, shades, intensities, colors, wavelengths and/or frequencies, wherein the vision system includes one or more 3D cameras, wherein light system includes one or more laser beams projected onto the region of interest, further comprising a reflector positioned in a path of at least one of the laser beams, further comprising a refractor positioned in a path of at least one of the laser beams, further comprising an diffractive element positioned in a path of at least one of the laser beams, wherein the control system guides movement of the robot based on scanned images of workpieces within the region of interest and wherein at least a portion of the structured light projects from the robot. 
     Another aspect of the present disclosure includes a method comprising: scanning an industrial robot scene with at least one image sensor having a field of view; storing image data from the image sensor in a memory; analyzing the image data; determining a region of interest within the image data, wherein the region of interest has a smaller area than an area of the field of view; projecting structured light onto the region of interest; determining a depth of an object located within the region of interest based on analysis of the object illuminated by the structured light; transmitting the depth information to a controller operably coupled to a robot; and performing a task on the object with the robot. 
     In refining aspects, the method includes wherein the at least one image sensor is a camera, wherein the camera is a 3D video camera, wherein the projecting of structured light includes a laser beam projection, wherein the structured light is projected in different patterns, shapes, shades, intensities, colors, wavelengths and/or frequencies onto the region of interest and wherein the task includes gripping the object with a robot gripper. 
     Another aspect of the present disclosure includes a system comprising: an industrial scene that defines a work area for a robot; a vision system having a field of view in the industrial scene; a control system operably coupled to the robot, the control system configured to receive and analyze data transmitted from the vision system; means, with the control system, for determining a region of interest within a portion of the field of view; a light system configured to direct a structured light onto the region of interest; and means, with the control system, for determining a position and depth of an object within the region of interest relative to the robot. 
     In refining aspects, wherein the control system provides operational commands to the robot, wherein the light system includes a laser, wherein the structured light includes a variable output including one of a light pattern variation, light shape variation, light shade variation, light intensity variation, light color variation, light wavelength variation and/or light frequency variation, wherein the vision system includes a 3D camera, wherein portions of the vision system and the light system are mounted on the robot and wherein the robot performs a work task on the object based on controller analysis of the object having structured light projected thereon. 
     While the application has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the applications are desired to be protected. It should be understood that while the use of words such as preferable, preferably, preferred or more preferred utilized in the description above indicate that the feature so described may be more desirable, it nonetheless may not be necessary and embodiments lacking the same may be contemplated as within the scope of the application, the scope being defined by the claims that follow. In reading the claims, it is intended that when words such as “a,” “an,” “at least one,” or “at least one portion” are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. When the language “at least a portion” and/or “a portion” is used the item can include a portion and/or the entire item unless specifically stated to the contrary. 
     Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.