High Speed, Real-Time Machine Vision

Perry West Automated Vision Systems, Inc.

Table of ContentsIntroduction ...............................................................................................................................................1Latency ........................................................................................................................................................3Imaging........................................................................................................................................................5

Triggering The Stimulus ..........................................................................................................................5External Sensor .......................................................................................................................................5Part Detection Through Imaging .............................................................................................................6

Image Acquisition .......................................................................................................................................6The Role of the Camera ..........................................................................................................................6The Role of the Frame Grabber.............................................................................................................14

Image Processing .................................................................................................................................20Processing Architecture.............................................................................................................................20

Processor Speed ....................................................................................................................................20Instruction Set .......................................................................................................................................21Software Development ..........................................................................................................................21Single Processor ....................................................................................................................................21Multi-Processor .....................................................................................................................................22

Operating System ......................................................................................................................................23Application Software.................................................................................................................................23Resynchronization.....................................................................................................................................24

Latency Calculation .............................................................................................................................26Part Detector..............................................................................................................................................26Capture Command.....................................................................................................................................26Strobe/Shutter Trigger...............................................................................................................................26Exposure Time ..........................................................................................................................................26Video Transfer ..........................................................................................................................................27Transfer to CPU ........................................................................................................................................27Image Processing.......................................................................................................................................27Resynchronization.....................................................................................................................................27Time Base..................................................................................................................................................28Output Activation......................................................................................................................................28

Example 1 .................................................................................................................................................29The Requirements .....................................................................................................................................29Design .......................................................................................................................................................29Latency Evaluation....................................................................................................................................30

Example 2 .................................................................................................................................................31The Requirements .....................................................................................................................................31Initial Design.............................................................................................................................................31Solving the Uncertainty in Part Position ...................................................................................................33Solving the Image Blur and Motion Tear Problems..................................................................................33Number of Cameras ..................................................................................................................................34Frame Grabber ..........................................................................................................................................36Computer...................................................................................................................................................36Operating System ......................................................................................................................................36Application Software.................................................................................................................................36Ejector Operation ......................................................................................................................................36Summary ...................................................................................................................................................37

List of FiguresFigure 1 Value Functions for Soft and Hard Real-Time ..............................................................................1Figure 2 Event A ..........................................................................................................................................4Figure 3 Event B ..........................................................................................................................................4Figure 4 Events A & B Combined ...............................................................................................................4Figure 5 Event C ..........................................................................................................................................4Figure 6 Events A, B, & C Combined..........................................................................................................4Figure 7 Simplistic CCTV Timing ...............................................................................................................7Figure 8 Basic CCTV Image Acquisition Latency.......................................................................................7Figure 9 Interlace Scanning..........................................................................................................................8Figure 10 Interlace Timing...........................................................................................................................8Figure 11 Motion Tear .................................................................................................................................9Figure 12 Progressive Scan Camera Timing ................................................................................................9Figure 13 Asynchronous Camera Timing ..................................................................................................11Figure 14 Asynchronously Resettable Camera Timing..............................................................................11Figure 15 Camera Timing with Strobe Illumination ..................................................................................13Figure 16 Camera Timing with Electronic Shutter ....................................................................................14Figure 17 Basic Frame Grabber .................................................................................................................15Figure 18 Simple Frame Grabber System Timing......................................................................................15Figure 19 Frame Grabber with Ping-Pong Memory...................................................................................16Figure 20 Ping-Pong Frame Grabber System Timing ...................................