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Uses of Autocollimators

8/24/2012 12:51:15 PM | by Anonymous


Autocollimators are high precision optical instrument used to measure angles without making any contact with the subject. These devices make use of internal optics to make these measurements. The purpose of these devices is to align components and measure any deflections in the systems. These instruments have an identical structure to that of telescopes; however they are positioned horizontally for measurements to be taken. The task of these devices is to take measurements of alignment of external mechanical devices and then aid the correct positioning of these objects according to the required application of the users preference. There are two variations of these devices, the visual or digital versions. A visual autocollimators have the accuracy to measure angles as small as 0.5 arcsecond whereas the digital autocollimator can provide results that are up to 100 times more accurate.


These devices work by emitting a horizontal light or image that is parallel to the device out on a reflective surface, which can be a mirror. The image or light then reflects and returns to the device’s internal optics, which then measures any aberration of the returning light against a predetermined scale. The results can be either read of visually or digitally from the device. The scale for taking these measurements is arcseconds, which can also be referred to as angular distance, to determine the amount of error in the mirror.


The application of visual autocollimators is usually checking the parallelism of optical windows and wedges. As for electronic and digital autocollimators, they are used for monitoring angular movements in mechanical systems over prolonged periods of time and ensuring that the results match the required standards, otherwise necessary replacements or adjustments would have to be made to that mechanical system. Manufacturers of fiber optics use these devices to ensure that the optical lengths meet the required standards. Laser systems that are used for leveling such as those required in the construction of a smooth roadway also make use of autocollimators for the purpose of calibrating the laser’s beam plane. Industries that require high levels of precision such as the aerospace industry make use of autocollimators to adjust machinery and final production models according to required standards.


As for the visual autocollimators, the angular error that the autocollimators measure is determined when the user looks at the results and compares them to predetermined figures. The reflective surface is set up across from the autocollimator and the user uses an eyepiece to view the reflected light beam that goes across to the reflector and comes back to the autocollimator. The user can then access the reflected beam and any angular error is identified and adjusted.


As for the digital autocollimators, the basic functions of the device are similar to that of the visual autocollimator, with the difference being that there is no eye piece on these devices as they have an internal photodetector that can sense the angular error by comparing it to predetermined results that are fed into the device. This eliminated the need for a human eye accessing the situation. The error is converted value and displayed on a screen on the autocollimator. These devices are able to provide highly accurate readings of the errors and therefore more accurate adjustments can be made to gain proper alignment. Digital autocollimators also have data storage capabilities that allow traceability. Also, as for visual autocollimators, the interpretation of the error can be based on the user’s eyesight and angle of vision. Therefore it is not as credible as the reading taken with a digital autocollimator. The readings taken rely on the precision of electronics and there are no discrepancies involved. This is why many industries that make use of autocollimators prefer to use digital autocollimators as they can provide more accurate results

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