What is an Autocollimator? An autocollimator is an optical instrument that is used to measure small angles with very high sensitivity. As such, the autocollimator has a wide variety of applications including precision alignment, detection of angular movement, verification of angle standards, and angular monitoring over long periods. Principles of Operation The autocollimator projects a beam of collimated light. An external reflector reflects all or part of the beam back into the instrument where the beam is focused and detected by a photodetector. The autocollimator measures the deviation between the emitted beam and the reflected beam.
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Disadvantages of Autocollimators : Autocollimator -Principle, Types, Application, Advantages, Disadvantages Autocollimators are optical instruments that measure angular displacements with high sensitivity. They are used to align optical components and measure optical and mechanical deflections.
Autocollimation Principle : The two main principles used in an autocollimator are a the projection and the refraction of a parallel beam of light by a lens, and b the change in direction of a reflected angle on a plane reflecting surface with the change in angle of incidence.
Autocollimator — working Principle and Application To understand this, let us imagine a converging lens with a point source of light O at its principle focus, as shown in Figure a.
When a beam of light strikes a flat reflecting surface, a part of the beam is absorbed and the other part is reflected back. If the angle of incidence is zero, i. When the reflecting plane is tilted at a certain angle, the total angle through which the light is deflected is twice the angle through which the mirror is tilted.
Thus, alternately, if the incident rays are not at the right angle to the reflecting surface they can be brought to the focal plane of the light sources by tilting the reflecting plane at an angle half the angle of reflection as shown in Figure b.
The position of the final image does not depend upon the distance of the reflector from the lens. If, however, the reflector is moved too long, the reflected ray will then completely miss the lens and no image will be formed. The optical system of an autocollimator is shown in Figure The target wires are illuminated by the electric bulb and act as a source of light since it is not convenient to visualize the reflected image of a point and then to measure the displacement x precisely.
The image of the illuminated wire after being reflected from the surface being measured is formed in the same plane as the wire itself. The eyepiece system containing the micrometer microscope mechanism has a pair of setting lines that may be used to measure the displacement of the image by setting to the original cross lines and then moving over to those of the image. Thus, the angle of inclination of the reflecting surface per division of the micrometer scale can be directly read.
Autocollimators are quite accurate and can read up to 0. The longer the focal length of the visual autocollimator, the greater the angular resolution and the smaller the field of view 2 Digital Autocollimators — Autocollimators are PC-based instruments that are designed to operate in the lab as well as in a machine shop environment.
Use an electronic photodetector to detect the reflected beam. No external controller is required. Advantages: 1 High precision. Application Of Autocollimator : Autocollimators are used by the optical industry and mechanical engineers in a variety of applications.
Their specific functions include precision alignment, the detection of angular movement, the verification of angle standards, and angular monitoring over long periods. Testing Application Autocollimators can be used in the testing of parallelism with a collimator and telescope opaque wedges and plane-parallel plates transparent wedges the accuracy of rotary tables and index tables camera objectives These optical instruments are also used in the flatness testing of reflecting surfaces, the control of wedges and plane-parallel plates, and parallel measurement of cylindrical bores.
Measurement Applications In addition to testing applications, autocollimators can be used to measure the radius of concave and convex spherical surfaces back focal of lenses and optical systems centration error of spherical surfaces centration error of lenses in transmission parallelism or perpendicularity of two surfaces Additional applications include the radius measurement of concave and convex spherical surfaces relative measurement of the angular error of prisms pitch and yaw measurement of slides parallel setting of rolls Finally, autocollimators can be used to measure straightness, flatness, roll angle, and the squareness between a vertical angle and a machine bed.
Advantages of Autocollimators : Measure the Straightness and Flatness Used for higher accuracy measurement. To check squareness and parallelism. Easy to set up and operate. Used to align components.
Autocollimator -Principle, Types, Application, Advantages, Disadvantages
Electronic Autocollimator[ edit ] The electronic autocollimator is a high precision angle measurement instrument capable of measuring angular deviations with accuracy down to fractions of an arc-second, by electronic means only, with no optical eye-piece. EAC Measuring with an electronic autocollimator is fast, easy, accurate, and will frequently be the most cost effective procedure. Used extensively in workshops, tool rooms, inspection departments and quality control laboratories worldwide, these highly sensitive instruments will measure extremely small angular displacements, squareness, twist and parallelism. Laser Analyzing Autocollimator[ edit ] Today, a new technology allows to improve the Autocollimation instrument to allow direct measurements of incoming laser beams.
Shatilar The longer the focal length, the larger the linear displacement for a given tilt of the plane reflector. Applications are roughly divided into two fields — optical and mechanical engineering. The bore autocolkimator procedure is performed in two stages. Because the human eye acts as the photodetector, resolution will vary among operators. The plane reflector is one of the vital parts of an autocollimator, because a mirror that is not flat will defocus the return image, resulting in poor definition of the image.