Different Types of Optical Comparators
The easiest optical design used in optical comparators is named the simple optics design. This optical comparator incorporates a light source, a magnification lens, the main reflecting mirror and a screen. Optical Comparator machines with this design display images that are both upside down and reversed.
Another Optical Comparator is named the corrected optics design. This Optical Comparator system uses two internal mirrors to flip the image so that it’s displayed right side up, but it is reversed on the horizontal axis.
On systems with simple optics and corrected-optics designs, the working distance decreases as the magnification increases. More sophisticated Optical Comparator machines incorporate a relay lens system that provides a constant working distance at all magnifications.
Another type of Optical Comparator design is the fully corrected system, which displays images that are both erect and unreversed. The convenience of seeing parts on the screen in the same orientation as they are seen on the worktable makes the machine easier to use, particularly by inspectors new to optical comparators.
Another useful addition to the Optical Comparator design that is found in many modern comparators is telecentric optics. A small opening, similar to a camera’s shutter opening and named telecentric stop, is placed in the optical path to block light rays that aren’t parallel to the optical path. This Optical Comparator design increases the depth of field, which in turn ensures magnification consistency across a range of focal settings. The size of the image does not change even when it is slightly out of focus. This reduces measurement variability from one inspector to another. Optical Comparator Telecentric systems provide a flat field and a more accurate representation of 3-D parts in relation to their 2-D drawings.
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