Vision measurement developing trend

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Vision Measurement Developing Trend

With feature-based measurement the vision measurement software uses the feature type information to createthe geometry and evaluate it. A range of features now are supported, including 2-D profile, which is shown here.Source: Liangyongguang www.liangyongguang.com

Multisensor measurement systems are capable of collecting geometric data from 3-D parts using variouscombinations of measurement technologies. For the most part, such systems are based on vision systems mademore versatile by the addition of tactile probes as well as lasers, white light and other devices. This allowsconfident measurement of parts using the most appropriate combination of probes for the job at hand, withoutcompromising accuracy.

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There has been a tremendous improvement in the multisensor system’s primary sensor: the camera. Some of thisowes to the enhancement of mechanical equipment and optics, but the bulk is the result of advancement incomputer-aided design (CAD)-based measurement software.

CAD Integration

Vision became a mainstream measurement technology when equipment and software vendors made thetransition from text-based programming and operating environments to CAD-based systems. Parts are designed inCAD, and computer numerical controlled (CNC) tool paths are generated in computer-aided manufacturing (CAM).It only made sense to complete the manufacturing cycle using CAD as well.

Now that many vendors have made the initial transition, they are quickly implementing improvements to theirsystems. For example, they are adding intelligence to their software that automatically adjusts parameters such aslighting, focus and magnification based on settings in the software and real-time feedback from the camera.

With CAD, vision systems are moving away from conventional approaches to defining geometries. Older softwarerequired operators to take measurements by first designating the feature type to be measured and then collectingthe associated data according to pre-defined rules. New software is eliminating those restrictions. Now, instead ofhaving to tell the software the type of feature to measure beforehand, the operator simply collects vector pointson the geometry of interest. The software automatically recognizes the feature type and then constructs and






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evaluates it. This works for an ever-growing list of feature types, including points, lines, ellipses, circles, squaresnotches and slots. Because of these improvements, programming and operating a vision system has becomesignificantly easier and more comparable to using a coordinate measuring machine (CMM).

Rather than making the operator manually apply filters to an image to detect weak edges, some vision softwarehave algorithms that automatically detect the appropriate edge based on operator-selectable criteria. Here amatching edge algorithm detects a weak circle. Source: Liangyongguang www.liangyongguang.com

Lighting, Focus and Magnification

Vision measurement has a reputation for being fussy. Magnification, focus and lighting requirements vary not onlyin relation to each other but also as changes occur in types of geometries and materials measured, not to mentionvariations in the measurement equipment itself. Until recently, operators had to take these into account whenmeasuring and adjust for them. By automating the vision measurement process, some vendors have nearlyeliminated the need for manual adjustments.

For example, software now lets operators calibrate the illumination of vision machines so that extremely linearand accurate measurements are provided for a range of illumination intensities and material reflectivity.Additional functions automatically adjust lighting intensity on-the-fly to improve contrast. This works by havingalgorithms that evaluate contrast in the area of interest and then make adjustments if needed. Somemeasurement software can even adjust lux values to compensate for the gradual loss of illumination intensity overtime. This is a particularly useful feature with LED type systems.








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Controlling focus is another area of improvement. Again, algorithms evaluate edge strength and decide if it isnecessary to refocus to improve accuracy. This functionality improves measurement cycles by selectivelyeliminating the need to refocus every time the camera pauses over a new area of interest. In addition, somesoftware allows for calibration of focus on individual machines for optimal measurement speed and accuracy. Thiscan be particularly useful when the same parts may be measured on more than one vision system, includingdifferent models.

Edge Strength. Hard probes know an edge when they meet one. Traditional vision systems have numerous filtersthat operators have to adjust to boost edge strength. These require specialized knowledge in determining whenand where to apply which type of filter.

A newer and much easier approach is to let the software decide which filters to use at the time of measurement.The software evaluates the condition and lighting of the feature it is about to measure. Then, based on anoperator-defined measurement objective, it uses built-in intelligence to decide which edge-strength algorithm willprovide the best results for the task. There is no operator intervention, and the result is faster and more accuratemeasurement.

Measurement Efficiency. Some of latest vision software releases take advantage of dual and quad core centralprocessing units (CPUs) so that imaging and image processing can take place simultaneously.

Accuracy. Conventional wisdom might deem accuracy to be solely dependent on optics and equipmentcharacteristics. In truth, well conceived and well executed measurement software makes a significant contributionto accurate, repeatable vision results. And as the mathematics gets better so will the measurement results.

CAD-based software has moved vision measurement into the manufacturing mainstream. Whether in the qualitylab or on the shop floor, manufacturers are finding it to be at least as useful and flexible as any othermeasurement tool. Because of both the integration of CAD into vision measurement and ongoing software






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improvements, vision is no longer an esoteric measurement technology best left to highly trained and experiencedspecialists.

Tech Tips

Advancements in computer-aided design (CAD)-based measurement software are driving improvement intoday’s vision measurement systems.

Such software simplifies the interface between operator and vision system, providing ease of measurement.

Because of a high level of system automation, such software has nearly eliminated the need for operators tomake adjustments in magnification, focus and lighting.

Sonny LeungYIHUI OPTOELECTRONICSVision Measurement Solution Supplierwww.liangyongguang.com




Technology

Vision measurement developing trend