Measurement of surface topography of a work-piece

1. An apparatus for measuring surface topography comprising:

a light emitting assembly configured to emit an emitted beam of light, the emitted beam being emitted at a plurality of wavelengths and being modulated with a modulating frequency, the emitted beam being directed onto a surface of a work-piece;

a detector configured to:

receive a reflected beam of light that includes at least a portion of the emitted beam as reflected from the surface of the work-piece; and

generate a signal indicative of a position of the reflected beam on the detector; and

a signal processing unit configured to remove noise from the signal thus generated based on the modulating frequency to obtain a processed signal; and

a control unit configured to:

determine a topography of the surface based on the processed signal.

2. The apparatus as claimed in claim 1 , wherein the light emitting assembly comprises:

at least three light sources, each of the at least three light sources emitting electromagnetic radiation at a wavelength selected from the plurality of wavelengths; and

a beam combiner configured to combine the electromagnetic radiation from each of the at least three light sources into the emitted beam.

3. The apparatus as claimed in claim 2 , wherein the light emitting assembly is further configured to:

modulate each of electromagnetic radiations with the modulating frequency; and

generate the emitted beam by combining the electromagnetic radiations thus modulated prior to the emitted beam being directed onto the surface of the work-piece.

4. The apparatus as claimed in claim 1 , wherein the detector is selected from a group comprising of a one-dimensional position sensitive detector and two-dimensional position sensitive detector.

5. The apparatus as claimed in claim 1 , wherein the signal processing unit coupled to the light emitting assembly, the detector, and the control unit.

6. The apparatus as claimed in claim 5 , wherein the signal processing unit is selected from a group comprising of a phase sensitive detector, a low-noise amplifier, analog lock-in amplifier and a digital lock-in amplifier.

7. The apparatus as claimed in claim 1 , wherein the apparatus further comprises:

a first beam directing unit coupled to the light emitting assembly via a single mode optical fiber and configured to direct the emitted beam onto the surface of the work-piece; and

a second beam directing unit configured to direct the reflected beam from the surface of the work-piece to the detector.

8. The apparatus as claimed in claim 1 , wherein the apparatus further comprises a holder configured to receive the work-piece.

9. The apparatus as claimed in claim 8 , wherein the control unit is further configured to impart a linear motion to the holder such that the emitted beam is caused to scan across the surface of the work-piece in a scanning direction.

10. The apparatus as claimed in claim 9 , wherein:

the detector is further configured to generate a series of signals indicative of positions of the reflected beam on the detector as the emitted beam is scanned across the surface of the work-piece in the scanning direction; and

the control unit is further configured to determine the topography of the surface based on the series of signals.

11. The apparatus as claimed in claim 1 , wherein the surface of the work-piece is provided with a film.

12. The apparatus as claimed in claim 11 , wherein the control unit is further configured to determine stress imparted on the film formed on the surface of the work-piece based on the determined topography.

13. The apparatus as claimed in claim 12 , wherein the control unit is further configured to:

obtain a blank topography of the work-piece prior to application of the film on the surface of the work-piece; and

process the blank topography and the determined topography to determine the stress imparted on the film.

14. A method for measuring surface topography comprising:

emitting an emitted beam of light, the emitted beam being emitted at a plurality of wavelengths and modulated with a modulating frequency;

directing the emitted beam onto a surface of a work-piece;

receiving a reflected beam of light that includes at least a portion of the emitted beam as reflected from the surface of the work-piece;

generating a signal indicative of a position of the reflected beam on a detector;

removing noise from the signal thus generated on the modulating frequency to obtain a processed signal; and

determining a topography of the surface based on the processed signal.

15. The method as claimed in claim 14 , the method further comprising:

emitting at least three electromagnetic radiations at a wavelength selected from the plurality of wavelengths; and

combining the electromagnetic radiations into the emitted beam.

16. The method as claimed in claim 15 , the method further comprising:

modulating each of electromagnetic radiations with the modulating frequency; and

combining the electromagnetic radiations thus modulated to generate the emitted beam.

17. The method as claimed in claim 14 , the method further comprising determining stress imparted on a film formed on the surface of the work-piece based on the determined topography.

18. The method as claimed in claim 17 , the method further comprising:

obtaining a blank topography of the work-piece prior to application of the film on the surface of the work-piece; and

processing the blank topography and the determined topography to determine the stress imparted on the film.

19. An apparatus for measuring surface topography comprising:

a first light emitting assembly configured to emit a first emitted beam of light, the first emitted beam being emitted at a plurality of wavelengths and modulated at a first modulating frequency, the first emitted beam being directed onto a surface of a work-piece;

a second light emitting assembly configured to emit a second emitted beam of light, the second emitted beam being emitted at a plurality of wavelengths and modulated at a second modulating frequency, the second emitted beam being directed onto the surface of the work-piece, the second modulating frequency being substantially different from the first modulating frequency;

a detector configured to:

receive a first reflected beam of light and a second reflected beam of light, the first reflected beam includes at least a portion of the first emitted beam as reflected from the surface of the work-piece and the second reflected beam includes at least a portion of the second emitted beam as reflected from the surface of the work-piece;

generate a first signal indicative of a position of the first reflected beam on the detector based on the first modulating frequency; and

generate a second signal indicative of a position of the second reflected beam on the detector based on the second modulating frequency; and

a control unit configured to:

determine a topography of the surface based on the first signal and the second signal.

20. The apparatus as claimed in claim 19 , wherein the detector is disposed at a fixed position in a plane containing the first reflected beam and the second reflected beam and wherein the detector is operating in a linear region.

21. The apparatus as claimed in claim 20 , wherein the apparatus further comprises:

a first signal processing unit coupled to the first light emitting assembly, the detector, and the control unit, the first signal processing unit configured to:

remove noise from the first signal based on the first modulating frequency.

22. The apparatus as claimed in claim 20 , wherein the apparatus further comprises:

a second signal processing unit coupled to the second light emitting assembly, the detector, and the control unit, the second signal processing unit configured to:

remove noise from the second signal based on the second modulating frequency.

23. A method for measuring surface topography comprising:

emitting a first emitted beam of light, the first emitted beam being emitted at a plurality of wavelengths and modulated at a first modulating frequency;

emitting a second emitted beam of light, the second emitted beam being emitted at a plurality of wavelengths and modulated at a second modulating frequency, the second modulating frequency being substantially different from the first modulating frequency;

directing the first emitted beam and the second emitted beam onto a surface of a work-piece,

receiving a first reflected beam of light and a second reflected beam of light, the first reflected beam includes at least a portion of the first emitted beam as reflected from the surface of the work-piece and the second reflected beam includes at least a portion of the second emitted beam as reflected from the surface of the work-piece;

generating a first signal indicative of a position of the first reflected beam on a detector based on the first modulating frequency;

generating a second signal indicative of a position of the second reflected beam on the detector based on the second modulating frequency; and

determining a topography of the surface based on the first signal and the second signal.

24. The method as claimed in claim 23 , wherein the method further comprises:

removing noise from the first signal based on the first modulating frequency.

25. The method as claimed in claim 23 , wherein the method further comprises:

removing noise from the second signal based on the second modulating frequency.