Semi-Automation of Autocollimator

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Autocollimators are devices which are based on the optical technique of projecting an illuminated reticule to infinity and receiving the reticule image after reflected upon by a flat mirror. The flat mirror is positioned along the specimen to be tested and is moved in increments along the entire length of the specimen .If the reflected reticule is tilted by an angle a, the reflected beam is deflected by twice that angle i.e. 2a. Thus detection of errors in straightness is possible.


1. Visual autocollimators use detection of the image cross line with reference to the reticule eyepiece cross line. They have micrometers to measure deviations.

2. Electronic Autocollimator use a CCD camera to detect the position of the image and eyepiece cross lines. These are for highly precise angular deviation measurements or for calibration.


The device that we have created aims to semi-automate a visual autocollimator. By using this device a visual autocollimator is converted into a electronic type of autocollimator with a very minimum cost (5000 Rs.). The Straightness measurement is made easier and faster with this device.


1. The important feature of our device is that it is compatible with most of the visual autocollimators. The adjustment screws provided at the base of the device allows it to be fitted with any visual autocollimator. The visual autocollimators need not be modified to get fixed with the device.

2.The hardships faced while measuring the deviation in straightness are eradicated. A camera attached to the device makes it possible to view the intersection of cross-wires on to a computer screen through our software-PRECICOLL.

3. The time required to measure straightness of specimens is greatly reduced.

4. The graph pertaining to the deviation in straightness is automatically graphed by the software and deviation at a particular point can be found with ease.

5. The deviation is automatically logged on the computer and thus can be retrieved when needed.


The device has a stepper motor which transfers its steps of rotation to the micrometer of the visual autocollimator through the fixture with gear assembly. The step-angle of the stepper motor matches the least count of the micrometer of the autocollimator. This is achieved by half stepping the stepper motor. A micro-controller module bridges the serial connection between a computer and the stepper motor through USB interface. The software we have designed named PRECICOLL is used to control the stepper motor and which in turn corrects the deviation of straightness that is shown on the computer screen by the cross-wire intersection. For every position of the reflecting mirror the deviation is automatically calculated by the software. Finally after all the deviations across the sampled length are measured the software provides the straightness deviation graph.


1. The camera can be replaced with a higher resolution one.

2. The stepper motor fixture to link the motor to the micrometer can be modified with a higher precision clamping system.



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  • Name:
    Thasshwin Mathanlal
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    Innovation affordable to all.
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