This document discusses various topics in mechanical measurement and metrology. It describes basics of optical interference and interferometry, including how optical flats can be used for flatness checking, surface contour testing, and checking parallelism. It also discusses two types of interferometers - the N.P.L. flatness interferometer and the Pitter N.P.L. gauge interferometer. The Pitter N.P.L. gauge interferometer is used for determining actual dimensions or absolute length of gauges. Finally, it provides an overview of opto-electronic measurements, describing how a simple opto-electronic inspection system works using a light source, lens assembly, and photodiode arrays.

1. Mechanical Measurement and
Metrology
1.Akash Parmar(140210125075)
2.Mit Shah(140210125112)
3.Ashish Soni(140210125117)
4.Harshil Sutariya(140210125118)

2.  Basics of optical interference and
interferometry
Optical flat
1) Flatness checking by optical flat
2) Surface contour test
3) Checking of parallelism by optical flat
Interferometers
1) The N.P.L. flatness interferometers
2) The pitter N.P.L gauge interferometer
Opto-electronic measurements

3. Basics of optical interference and
interferometry
Interference :-
Interaction of light wave.
Interferometers :-
The instruments designed to
measure with interference.

4. Optical flat
 The Essential equipment for measurement by light wave
interference is a monochromatic light source and set of
optical flat.
 Circular optical glass.
 Quartz having two plates.
 Cylindrical pieces have 25 to 300 mm diameter.
 Thickness is (1/6) of dia.
 Optical flats used in area where temp. is constant.

5. The N.P.L. flatness interferometer
Light sources lens mirror
collimating lens reflectors
optical flat surface to be tested
eye piece glass plate reflector
working
Checking flatness of objects

6. The Pitter N.P.L. gauge interferometer

7. The pitter N.P.L. gauge interferometer
 This instrument is also known as the NPL type ‘length interferometer’.
 It is used for determining actual dimensions or absolute length of the gauges .
 Fig. shows the schematic arrangement of this interferometer . The light from the sources falls
on slit through condensing lens .
 After collimation by lens , it goes through constant deviation prism whose rotation
determines wavelength passed through reference optical flat to upper surface of gauge block
and base plate with it is wrung .
 Light is reflected back in mirror and is patterns are observed through a telescope .
 The optical flat is adjustable for inclination in two planes . So that pitch and direction of the
interference fringes may be set to the best position .
 The gauge on this instrument will be absolutely flat and parallel and hence the bands on the
gauge top and the base will be of the same pitch and dire, but relatively displaced from other
.
 This dis. Is recorded for each colour as a fraction of the pitch o the fringes and is used for
calculation of the length of the gauge .

8. Opto-electronic measurement

9.  Opto-electronic measurement tech is a contactless method . It utilises photodiode
arrays having resolution.
 Fig shows the arrangement of simple opto-electronic inspection system.
 The object to be inspected is back-illuminated by collimated light source
 A lens assembly is incorporated to provide either magnification for dimensional
inspections or reductions for flaw detection .
 Here we use 45 degree prisms in order to reduce the space requirements and all
components are mounted on a precision slide to form an integral station of and
inspection machine .
Opto-electronic measurement

10. THANK YOU