Allen Cius 2013-02-24 02:20:03
Vision metrology systems’ high measurement speeds, throughput, accuracy, and suitability for in-line application are characteristics accounting for their everincreasing use in small part inspection. By leveraging advances in image capture and processing, now almost anything that can be correctly seen by a camera can be measured. Some of the most important imaging technologies include 256-level gray scale imaging, sub-pixel enhanced edge detection, measurement along multiple points of an image, streaming vision measurement, and of course the processing/software advancements associated with these technologies. 256-level gray scale images A PC stores an image after internally converting it to numeric values. A numeric value is assigned to each pixel of an image. Image quality varies depending on how many levels of gray scale are defined by the numeric values. The PC provides two types of gray scale: two-level and multi-level. The pixels in a high-fidelity image display are often displayed as the 256-level gray scale. Each pixel is displayed as one of 256 levels between black and white. See figure 1 above. Sub-pixel enhanced edge detection To increase the accuracy in edge detection, sub-pixel image processing is used. An edge is detected by determining an interpolation curve from adjacent pixel data. As a result, it allows measurement with a resolution higher than 1 pixel. See figure 2 above. Measurement along multiple points of an image Large features that cannot be contained on one screen have to be measured by precisely controlling the position of the CCD sensor and stage so as to locate each reference point within individual images. By this means the system can measure even a large circle, by detecting the edge while moving the stage across various parts of the periphery. See figure 3 above. Streaming vision measurement Conventional vision measuring systems endlessly repeat the cycle of stage displacement, stage stop, measurement, stage start and stage displacement again. This mode of operation is a fundamental limitation on improving measurement throughput. In contrast, the QuickVision® Stream system from Mitutoyo America Corporation uses an innovative image capture technique that avoids the need to repeatedly stop the stage so measurement can be continuous, but measuring accuracy is retained. Eliminating the time needed to accelerate, decelerate and then hold the stage motionless while a measurement is made achieves great improvements in productivity. mitutoyo america corporation 965 corporate blvd., aurora, il 60502 phone: (630) 820-9666 fax: (630) 820-2614 www.mitutoyo.com
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