An autocollimator is an optical instrument used for measuring small angular measurements. It works by projecting a light source through a collimating lens, which is reflected off a target mirror. The angle of the reflected light is doubled, and can be measured based on the displacement seen through an eyepiece. Autocollimators are used to measure small angles and displacements, check for straightness and parallelism, and inspect flatness and squareness in machine tools. They offer high accuracy but require regular maintenance and can be time consuming.

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Prepared by,
Mr. S. B. Kamble
Department of Mechanical Engineering
Sharad Institute of Technology, College of Engineering, Yadrav
Autocollimator
Subject – Metrology and Quality Control

2. Autocollimator
Working Principle
Working Process
Merits and
Demerits
Applications
Image Source- Internet

3. Working Principle of Autocollimator
Focal Plane Collimating lens Reflector
Point
Source
An optical Instrument
Used for Small Angular Measurements

4. Working Principle of Autocollimator
Focal Plane Collimating lens Reflector
Point
Source
Ɵ
A
B
2Ɵ

5. Working Principle of Autocollimator
A
B
f
2Ɵ
AB = x
x = 2Ɵ f
x
O

6. Equipments used in Autocollimator
Lamp
Diffuser
Crossline Graticule
Beam Splitter
Eyepiece
View
Point
Objective
Reflector
Focal
Plane
Collimating lens

7. Working Process of Autocollimator
Lamp
Diffuser
Crossline Graticule
Beam Splitter
Eyepiece
View
Point
Objective
Reflector
Focal
Plane
Collimating lens
Reflector is perpendicular to ray of light

8. Working Process of Autocollimator
Lamp
Diffuser
Crossline Graticule
Beam Splitter
Eyepiece
View
Point
Objective
Reflector
Focal
Plane
Collimating lens
Reflector is tilted at some angle
Ɵ
2Ɵ

9.  Checking small linear displacements.
Applications of Autocollimator
 Checking straightness of machine tool slideways.
 Measuring very small angles.
 Checking parallelism.
 Checking squareness of column to base.
 Checking flatness of bed plates and surface tables.
 Measuring very small displacements.

10.  Wide range of accessories and levels available.
Merits of Autocollimator
 It has very high accuracy.
 It can measure wide range angle.
 It is very easy to set up and operate.
 Calibration traceable to international standards.
 It Can be used to see the result visually or electronically i.e in a computer screen.

11.  It requires sample cutting and processing for tracing by the detector.
Demerits of Autocollimator
 Maintenance is required regularly.
 It is time consuming.

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