Method for determining the refractive-index profile of a cylindrical optical object

Patent metadata

Field	Value
Publication number	US-12085506-B2
Application number	US-202117907215-A
Country	US
Kind code	B2
Filing date	Mar 18, 2021
Priority date	Mar 30, 2020
Publication date	Sep 10, 2024
Grant date	Sep 10, 2024

Abstract

A method for determining an index-of-refraction profile of an optical object, which has a cylindrical surface and a cylinder longitudinal axis, said method comprising the following method steps: (a) scanning the cylindrical surface of the object at a plurality of scanning locations by means of optical beams; (b) capturing, by means of an optical detector, a location-dependent intensity distribution of the optical beams deflected in the optical object; (c) determining the angles of deflection of the zero-order beams for each scanning location from the captured intensity distribution, comprising eliminating beam intensities, and (d) calculating the index-of-refraction profile of the object on the basis of the angle-of-deflection distribution, wherein method steps (a) and (b) are carried out with light beams having at least two different wavelengths.

First claim

The invention claimed is:

1. A method for determining an index-of-refraction profile of an optical object, which has a cylindrical surface and a cylinder longitudinal axis, comprising the following method steps:
(a) scanning the cylindrical surface of the object at a plurality of scanning locations by means of optical beams which are incident perpendicularly to the cylinder longitudinal axis;
(b) capturing, by means of an optical detector, a location-dependent beam intensity distribution of the optical beams deflected in the optical object;
(c) determining the angles of deflection of the zero-order beams for each scanning location from the intensity distribution, comprising eliminating beam intensities of higher-order beams from the intensity distribution so that an angle-of-deflection distribution is obtained for the zero-order beams and;
(d) calculating the index-of-refraction profile of the object on the basis of the angle-of-deflection distribution,
wherein method steps (a) and (b) are each carried out with light beams of different wavelengths, wherein a first location-dependent intensity distribution of a first light beam having a first wavelength and at least one further, second location-dependent intensity distribution of a second light beam having a second wavelength are obtained, and wherein the elimination of beam intensities of higher-order beams comprises a comparison of beam intensities of the first intensity distribution and of the second intensity distribution at the same scanning locations characterized in that for scanning the cylindrical surface according to method step (a), laser diodes with different emission wavelengths are combined via Y-fiber bundles to an optical beam, and wherein the optical beam is focused by means of a parabolic mirror.

2. The method according to claim 1 , wherein, in order to eliminate beam intensities of higher-order beams same-location intensities of the first and second intensity distributions are mathematically processed with each other.

3. The method according to claim 2 , wherein the mathematical processing comprises processing of the intersection sets of same-location intensities, and at least one multiplication or at least one addition of the same-location intensities of the first and second intensity distributions.

4. The method according to claim 2 , wherein the elimination of beam intensities of higher-order beams comprises a measure in which intensities of the first and/or of the second intensity distribution which fall below an intensity threshold are completely or partially eliminated.

5. The method according to claim 4 , wherein the intensity threshold is set to a value that is less than 20% of a maximum intensity value of the intensity distribution.

6. The method according to claim 2 , wherein the elimination of beam intensities of higher-order beams comprises computer-aided image processing.

7. The method according to claim 1 , wherein a line scan camera with only one light-sensitive line sensor is used as an optical detector for capturing the intensity distribution according to method step (b).

8. The method according to claim 7 , wherein a monochromatic line sensor that has a length of at least 40mm is operated at a bit depth of 8 bits is used as the light-sensitive line sensor.

9. The method according to claim 1 , wherein method steps (a) and (b) are carried out with radiation of a first wavelength and of at least one second wavelength, wherein the first wavelength and the second wavelength differ from one another by at least 50 nm and by at most 400 nm.

10. The method according to claim 9 , wherein method steps (a) and (b) are carried out with radiation of the first wavelength and subsequently with radiation of the second wavelength.

11. The method according to claim 9 , wherein method steps (a) and (b) are carried out with radiation of the first wavelength, of the second wavelength, and of a third wavelength, wherein the third wavelength is longer than the first wavelength and shorter than the second wavelength, and the third wavelength differs from the first wavelength and from the second wavelength by at least 50 nm and by at most 400 nm.

12. The method according to claim 1 , wherein the different wavelengths are in the wavelength range of 400 to 1600 nm.

13. The method according to claim 1 , wherein the different wavelengths are selected from the wavelength ranges: 635±50 nm, 840±50 nm, 970+50 nm, 1040+50 nm.

Assignees

• Heraeus Quarzglas

Inventors

• Schmitt Maximilian

Classifications

• G01N2021/4153

  Measuring the deflection of light in refractometers · CPC title

• G01N21/4133

  Refractometers, e.g. differential · CPC title

• G01M11/0207

  Details of measuring devices · CPC title

• G01M11/0285

  by measuring material or chromatic transmission properties (G01M11/0292 takes precedence) · CPC title

• G01M11/37

  in which light is projected perpendicularly to the axis of the fibre or waveguide for monitoring a section thereof · CPC title