Determining surface and thickness

1. A measuring device for determining the surface of an object being measured using optical radiation, the measuring device comprising

an optical source;

an optical radiation processing unit arranged to direct different wavelengths of the optical radiation of the optical source to the object being measured from a direction differing from the normal of the surface being measured in such a manner that the different wavelengths focus on different heights in the direction of the normal of the surface being measured;

a detector to which the optical radiation processing unit is arranged to direct the optical radiation that the optical radiation processing unit is arranged to receive from the object being measured at least from the direction of specular reflection that differs from the direction of the normal of the surface being measured;

a signal processing unit arranged to determine from the detected optical radiation on the basis of the signal provided by the detector the wavelength on which the intensity of the optical radiation is the highest and to determine the location of the surface being measured using the determined wavelength.

2. A measuring device as claimed in claim 1 , wherein the measuring device comprises at least one polarizer, and at least one polarizer is arranged to polarize optical radiation reflected from the object being measured in a direction perpendicular to the normal of the surface being measured.

3. A measuring device as claimed in claim 2 , wherein the beam splitter is arranged to act as a polarizer.

4. A measuring device as claimed in claim 1 , wherein the optical radiation processing unit comprises a first optical radiation processing part for directing optical radiation to the object being measured and a second optical radiation processing part for directing optical radiation reflected from the object being measured to the detector.

5. A measuring device as claimed in claim 4 , wherein the first optical radiation processing part comprises a dispersive component that is arranged to disperse optical radiation directed to the object being measured chromatically in a non-axial direction;

the first optical radiation processing part comprises a first focusing component that is arranged to focus the different wavelengths of the non-axially dispersed optical radiation on different heights in the direction of the normal of the surface of the object being measured; and

the second optical radiation processing part comprises a second dispersive component that is arranged to remove dispersion from the optical radiation reflected from the object being measured; and

the second optical radiation processing part comprises a second focusing component that is arranged to focus optical radiation in an undispersed form to the detector.

6. A measuring device as claimed in claim 4 , wherein the first optical radiation processing part comprises a dispersive component that is arranged to disperse optical radiation directed to the object being measured chromatically in a non-axial direction;

the first optical radiation processing part comprises a first focusing component that is arranged to focus the different wavelengths of the non-axially dispersed optical radiation on different heights in the direction of the normal of the surface of the object being measured; and

the second optical radiation processing part comprises a second focusing component that is arranged to focus optical radiation in a dispersed form to the detector.

7. A measuring device as claimed in claim 1 , wherein the optical radiation processing unit comprises a first optical radiation processing part, a second optical radiation processing part, a reflector and a directional beam splitter;

the first optical radiation processing part being arranged to direct optical radiation to the object being measured;

the second optical radiation processing part being arranged to direct optical radiation reflected from the object being measured to the reflector that is arranged to reflect optical radiation reflected from the object being measured back to the object being measured through the second optical radiation processing part that is arranged to direct different wavelengths of optical radiation to the object being measured from a direction differing from the normal of the surface being measured in such a manner that the different wavelengths focus on different heights in the direction of the normal of the surface being measured, while one wavelength focuses on the surface being measured;

the first optical radiation processing part being arranged to direct optical radiation reflected from the object being measured towards the optical source; and

the directional beam splitter being arranged to direct at least part of the optical radiation directed towards the optical source to the detector.

8. A measuring device as claimed in claim 7 , wherein the first optical radiation processing part comprises a dispersive component that is arranged to disperse optical radiation directed to the object being measured chromatically in a non-axial direction;

the first optical radiation processing part comprises a first focusing component that is arranged to focus the wavelengths of the non-axially dispersed optical radiation on different heights in the direction of the normal of the surface of the object being measured; and

the second optical radiation processing part comprises a second dispersive component that is arranged to remove dispersion from the optical radiation reflected from the object being measured and to disperse the radiation reflected from the reflector chromatically in a non-axial direction;

the second optical radiation processing part comprises a second focusing component that is arranged to focus the non-axially dispersed optical radiation reflected from the reflector on different heights in the direction of the normal of the surface being measured;

the first optical radiation processing part is arranged to remove dispersion from the optical radiation reflected from the object being measured; and

the directional beam splitter is arranged to direct undispersed optical radiation to the detector.

9. A measuring device as claimed in claim 7 , wherein the detector is a line detector with a different wavelength of undispersed optical radiation directed to each of its elements.

10. A measuring device as claimed in claim 1 , wherein the measuring device comprises a reference beam splitter and reference detector;

the reference beam splitter is arranged to direct part of the optical radiation emitted by the optical source to the object being measured to the reference detector that is arranged to feed an electrical signal corresponding to the received optical radiation to the signal processing unit 124 ; and

the signal processing unit is arranged to normalize the intensities of the wavelengths detected by the detector with wavelength intensities detected by the reference detector.

11. A measuring device as claimed in claim 10 , wherein the directional beam splitter is arranged to act as a reference beam splitter.

12. A measuring device as claimed in claim 1 , wherein the signal processing unit is arranged to modulate the optical source and demodulate the signal coming from the detector, which corresponds to the detected optical radiation.

13. A measuring device as claimed in claim 1 , wherein the detector comprises a first detector part, second detector part, detector beam splitter, first filter, and second filter;

the response of the first filter is arranged to be different from that of the second filter on the measuring band;

the detector beam splitter is arranged to distribute the optical radiation reflected from the object being measured in such a manner that part of the optical radiation is directed to the first detector part through the first filter and part of it is directed to the second detector part through the second filter; and

the signal processing unit is arranged to determine from the ratio of the optical radiations detected by the first and second detector parts the wavelength with the highest intensity.

14. A measuring device for measuring the thickness of an object being measured, the measuring device comprising for the purpose of measuring a first surface:

an optical source;

an optical radiation processing unit arranged to direct different wavelengths of the optical radiation of the optical source to the object being measured from a direction differing from the normal of the surface being measured in such a manner that the different wavelengths focus on different heights in the direction of the normal of the surface being measured;

a detector to which the optical radiation processing unit is arranged to direct the optical radiation that the optical radiation processing unit is arranged to receive from the object being measured at least from the direction of specular reflection that differs from the direction of the normal of the surface being measured; and

a signal processing unit arranged to determine from the detected optical radiation on the basis of the signal provided by the detector the wavelength on which the intensity of the optical radiation is the highest and to determine the location of the surface being measured using the determined wavelength; and

the measuring device comprising for the purpose of measuring a second side of the object being measured:

a second-side optical source;

a second-side optical radiation processing unit arranged to direct different wavelengths of the optical radiation of the optical source to the object being measured from a direction differing from the normal of a second surface being measured in such a manner that the different wavelengths focus on different heights in the direction of the normal of the second surface being measured;

a second-side detector to which the optical radiation processing unit is arranged to direct the optical radiation that the radiation processing unit is arranged to receive from the object being measured at least from the direction of specular reflection that differs from the normal of the surface being measured; and

the signal processing unit is arranged to determine from the detected optical radiation on the basis of the signal provided by the second-side detector the wavelength on which the intensity of the optical radiation is the highest and to determine the location of the second surface being measured using the determined wavelength; and

the signal-processing is arranged to measure the thickness of the object being measured by means of the determined locations of the surfaces.

15. A measuring device as claimed in claim 14 , wherein the measuring device comprises at least one polarizer, and at least one polarizer is arranged to polarize optical radiation reflected from the object being measured in a direction perpendicular to the normal of the surface being measured, and the measuring device comprises at least one second-side polarizer, and at least one second-side polarizer is arranged to polarize optical radiation reflected from the object being measured in a direction perpendicular to the normal of second the surface being measured.

16. A method for determining the surface of an object being measured by means of optical radiation, the method comprising

directing different wavelengths of optical radiation to the object being measured from a direction differing from the normal of the surface being measured in such a manner that the different wavelengths focus on different heights in the direction of the normal of the surface being measured;

receiving optical radiation at least from the direction of specular reflection that differs from the normal of the surface being measured;

determining from the received optical radiation the wavelength on which the intensity of the received optical radiation is the highest; and

determining the location of the surface of the object being measured by means of the determined wavelength.

17. A method as claimed in claim 16 , the method further comprising polarizing the optical radiation reflected from the object being measured in a direction perpendicular to the normal of the surface being measured.

18. A method as claimed in claim 17 , the method further comprising removing dispersion from the received optical radiation;

determining from the undispersed optical radiation the wavelength on which the intensity of the received optical radiation is the highest.

19. A method as claimed in claim 17 , the method further comprising determining from the received dispersed optical radiation the wavelength on which the intensity of the received optical radiation is the highest.

20. A method as claimed in claim 16 , the method further comprising dispersing the optical radiation directed to the object being measured chromatically in a non-axial direction;

focusing different wavelengths of the non-axially dispersed optical radiation on different heights in the direction of the normal of the surface of the object being measured while one wavelength focuses on the surface being measured.

21. A method as claimed in claim 16 , the method further comprising reflecting the optical radiation reflected from the object being measured back to the object being measured in such a manner that the optical radiation is reflected from the object being measured in the direction differing from the normal of the surface being measured and used in directing; and

directing the optical radiation reflected from the object being measured for reception.

22. A method as claimed in claim 16 , the method further comprising directing part of the optical radiation emitted by the optical source to the object being measured to the reference detector;

feeding an electric signal corresponding to the optical radiation received by the reference detector to the signal processing unit 124 ; and

normalizing in the signal processing unit the intensities of the wavelengths detected by the detector with the wavelength intensities detected by the reference detector.

23. A method as claimed in claim 16 , the method further comprising modulating the optical radiation emitted by the optical source and correspondingly demodulating the detected signal.

24. A method for measuring the thickness of an object being measured by means of optical radiation, the method comprising

directing different wavelengths of optical radiation to the object being measured from a direction differing from the normal of the surface being measured in such a manner that the different wavelengths are directed to different heights in the direction of the normal of the first surface being measured;

receiving optical radiation at least from the direction of specular reflection that differs from the normal of the first surface being measured;

determining from the received optical radiation the wavelength on which the intensity of the received optical radiation is the highest; and

determining the location of the first surface being measured by means of the determined wavelength;

directing different wavelengths of optical radiation to the object being measured from a direction differing from the normal of a second surface being measured in such a manner that the different wavelengths are directed to different heights in the direction of the normal of the second surface being measured;

receiving optical radiation at least from the direction of specular reflection that differs from the normal of the second surface being measured;

determining from the received optical radiation the wavelength on which the intensity of the received optical radiation is the highest; and

determining the location of the second surface being measured by means of the determined wavelength; and

determining the thickness of the object being measured using the determined locations of the surfaces.

25. A method as claimed in claim 24 , the method further comprising polarizing the optical radiation reflected from the object being measured in a direction perpendicular to the normal of the second surface being measured; and

polarizing the optical radiation reflected from the object being measured in a direction perpendicular to the normal of the first surface being measured.