Optical measurement refers to noncontact measurement utilizing numerous light sources. It often requires a minimum of one lens, a light supply and a detector. It differs from different forms of inspection in that instead of using a tactile measurement technique like a contact probe, it uses either a point of reference (e.g. a crosshair) or a pc to calculate edge detection. Two of its greatest benefits are its capability to measure features too small or fragile to measure by touch, and the truth that it is faster in comparison to different forms of measurement.
The medical, plastics, aerospace and automotive industries are where optical measurement has, and will continue to have, significant impact. But, in reality, this form of noncontact detection applies to applications throughout most verticals and sectors. Adopters of modern optical measurement devices are looking for easy-to-use technology that helps the acquisition of more accurate data in less time. As a result, there’s a rising demand for in-line measurement and faster processing of acquired images as well as image stitching capability and bigger fields of view. There’s additionally a growing demand for revolutionary elements like liquid lenses. However when deciding which—if any—optical measurement units are best for you, all factors have to be considered.
Profile Projectors/Optical Comparators
You possibly can think of this optical measuring system as a high-accuracy overhead projector just like what schools used within the 1970s, ‘80s and ‘90s. It will probably accommodate goal lenses up to 100x magnification, use either contour or surface illumination, and has either a microscope-type stage or metal stage with T-slots that may hold as much as 100 lbs. The stage is married to high-accuracy linear scales, which provide positional feedback, and a crosshair is typically etched onscreen as a measurement reference point. Measurement throughput could be elevated by adding edge detection, often in the form of an onscreen fiber optic detector.
Operation is fairly straightforward, with a person inserting a workpiece on the stage with the required fixturing, then bringing the workpiece into focus by adjusting the Z-axis position. As soon as there’s a focused image on screen, the person moves the stage so the onscreen reference reticle is aligned with the function of interest. The person then can zero the scales on either the X- or Y-axis and move the stage to the subsequent position on the feature. The size readout will decide the gap traveled with increased measurement repeatability made potential with the usage of edge detection software. Final data is stored and analyzed by an optional 2D processor.
Advantages: The design of the target lens, coupled with a screen dimension that can measure 14 inches or larger, means profile projectors typically have a larger subject of view. Having been a familiar staple for decades, they’re one of many best measurement devices to use. Unlike a measuring microscope, profile projectors tend to inflict a low level of eye strain. And, total, they are usually the least expensive option while remaining one of many fastest.
Disadvantages: Profile projectors/optical comparators have a lower optical decision in comparison to measuring microscopes as well as a lack of digital processing capability and low throughput. Lighting options are also limited, typically only including contour illumination.
Measuring Microscopes
It’s vital to level out that measuring microscopes are completely different from traditional microscopes. Unlike a traditional microscope, in a measuring microscope the stage is linked to linear scales that provide positional feedback, and a reticle is either constructed into the eyepiece itself or located in the light path as a reference point for measurement. In addition, a measuring microscope accommodates both in-line illumination for applications that require mirrored light and transmitted illumination that enables for contour or profile measurements.
When it comes to operation, measuring microscopes perform in an analogous method to profile projectors. A workpiece is placed on the stage, and an image of the function of curiosity is then brought into focus by adjusting the coarse and fine focus knob. Once a transparent image is viewable, the consumer aligns the built-in reticle and then moves the stage to the following edge of the feature. The ensuing scale readout shows the distance traveled. As with profile projectors, edge detection software will be added to achieve greater accuracy and repeatability towards determining the exact edge of a part.
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