Auto collimator angle dekkor
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The document discusses the principles and applications of autocollimators and angle dekkors in mechanical measurement and metrology. It details how autocollimators use light reflection for precise angle measurements, with applications such as checking surface flatness, while angle dekkors provide a simpler means to measure angles in workshop settings. Both instruments have specific requirements for optimal performance, including the need for highly polished surfaces and effects of air currents on accuracy.
Auto collimator angle dekkor
- 1. AutoCollimator Angle Dekkor Presentation Prepared by Prof. Naman M. Dave Assistant Prof. (Mechanical Dept.) Gandhinagar Institute of Technology Mechanical measurement and metrology Prof. Naman M. Dave
- 2. Mechanical measurement and metrology Prof. Naman M. Dave Please refer this file just as reference material. More concentration should on class room work and text book methodology.
- 3. INTRODUCTION Collimation Mechanical measurement and metrology Prof. Naman M. Dave
- 4. Principle of AutoCollimator 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 change in angle of incidence.
- 5. AutoCollimator Mechanical measurement and metrology Prof. Naman M. Dave
- 7. Mechanical measurement and metrology Prof. Naman M. Dave
- 8. Mechanical measurement and metrology Prof. Naman M. Dave • These can be adjusted with the micrometer until they straddle the reflected image of the cross wires. A scale is provided in the eye piece which directly gives the tilt of the reflector. • The micrometer has 60 divisions and the micrometer moves the setting wires through 1/2 minute per revolution. Thus each division on the microscope drum corresponds to 0.5 sec. of arc. • The micrometer microscope system provided measures the deflection of the image and hence the angle of the work piece. • Autocollimators are capable of reading upto 0.1 seconds and may be used over distances upto 30 meters. But their range of measurements is small and hence they are used more as comparators than as absolute measuring devices. • They are particularly useful for checking surface flatness and alignment over large distances. For efficient working of autocollimators the work piece surface must be highly polished and should be optically flat. • Slip gauges are sometimes wrung on the surface of the work piece to help reflection. • Readings of the autocollimeter are sometimes subject to fluctuations due to air currents between the autocollimeter and the target mirror. • The fluctuations are more pronounced for larger distances between the instrument and mirror. • Flatness and reflectivity of the target mirror also affect the accuracy of the readings.
- 9. Mechanical measurement and metrology Prof. Naman M. Dave • An illuminated Cross Line Target reticule placed at the focus of the Objective collimating lens is projected after reflection from a beam splitter. • A Plane reflector placed normal to the optical axis of parallel beam in front of the objective Lens returns the beam along their original paths. • A portion of the returned light passes straight through the beam splitter and the return image of the target cross line is viewed through an Eyepiece. • The Eyepiece is provided with a measuring Graticule. The reflected Image of the Target cross line is brought to focus in the plane of the Eyepiece graticule and exactly coincident with its intersection. • If the reflector is tilted through a small angle the reflected light beam will be brought to focus in the plane of the Eyepiece Reticule but linearly displaced by an amount 2Tan θ x f. • Linear displacement of the reticule image in the plane of the eyepiece is therefore directly proportional to reflector tilt and can be measured by an eyepiece reticule or an optical micrometer system. • The focal length determines basic sensitivity and angular measuring range. The longer the focal length the larger is the linear displacement for a given reflector tilt. • The maximum working distance is the separation between reflector and autocollimator and is governed by the effective diameter of the objective lens. At long working distances the angular measuring range of the instrument reduces. Large size reflectors are required atleast equal to the diameter of the Objective lens to have better image contrast. Description from 2nd reference material
- 10. AutoCollimator
- 11. AutoCollimator
- 12. AutoCollimator Applications: 1. Checking of an internal right angle. 2. Comparative measurement using master angles. 3. Measuring straightness and flatness of the surfaces. 4. Assessment of squareness and parallelism of component. 5. For machine tool adjustment setting.
- 13. Mechanical measurement and metrology Prof. Naman M. Dave
- 14. Mechanical measurement and metrology Prof. Naman M. Dave
- 15. Mechanical measurement and metrology Prof. Naman M. Dave
- 16. Mechanical measurement and metrology Prof. Naman M. Dave
- 17. Mechanical measurement and metrology Prof. Naman M. Dave
- 18. Mechanical measurement and metrology Prof. Naman M. Dave
- 19. Angle Dekkor
- 20. Angle Dekkor
- 21. Angle Dekkor
- 22. Mechanical measurement and metrology Prof. Naman M. Dave • The reflected image of the illuminated scale shown in Fig. and the fixed datum line intersect each other at right angles • The reading on the illuminated image represents the deviation from one axis at 90" to the optical axis. The change in the angular position of the surface is shown by the variation in the position of the point of intersection of the two scale on the fixed datum scale. • Readings from scale can be read directly upto I minute without the use of a micrometer. • The optical system of the dekkor shown in Fig. is enclosed in a tube mounted on an • adjustable bracket and the whole system is mounted on a flat reflective base. • Angle dekkor can be used in conjunction with angle gauges for measuring angles, setting of jobs for machining and measuring angles of cones. The principle of measurement consists of comparing the reading obtained with a polished reflector or slip gauges in contact with the work piece and a zero reading obtained from an angle gauge block set up.
- 23. Mechanical measurement and metrology Prof. Naman M. Dave • Fig. shows schematically the method for finding the angle of a work piece using the dekkor. • First a set of angle gauge blocks with an angle close to the angle to be measured is placed on the surface plate and the reflected image for the angle set is observed in the eyepiece. The dekkor can then be set such that zero reading is obtained on the illuminated scale. • The angle gauge set is then replaced by the workpiece on which a slip gauge is attached to serve as a reflector. • The difference between the angle of the workpiece and the angle of the gauge block set, if any, appears as the difference between the position of the reflected scale on the datum line as error as shown in Fig. • Angle dekkor is not a precision measuring instrument compared to an auto collimator but serves as a simple general purpose instrument in the shop. It has the advantage of giving readings directly without the use of a vernier. The angle difference between the reference position and test position can be read to an accuracy of 10 minute which is good enough for general workshop use.
- 24. Angle Dekkor Applications: 1.Measuring the angle of a component. 2.Checking the sloping angle of a vee- block. 3.Measuring the angle of a cone or taper gauges. 4.Precise angular settings for machining operations.