Method and apparatus for determining the presence of an electrical charge on the surface of a lens mold

Patent metadata

Field	Value
Publication number	US-9851385-B2
Application number	US-201615351917-A
Country	US
Kind code	B2
Filing date	Nov 15, 2016
Priority date	Dec 11, 2015
Publication date	Dec 26, 2017
Grant date	Dec 26, 2017

Abstract

A method for determining the presence of an electrical charge on a surface of an ophthalmic lens mold including the steps of exposing a sensor crystal of a sensor element to a surface of an ophthalmic lens mold on which an electrical charge generating an electrical field may be present, converting a light beam emitted from a laser light source into a linearly polarized measurement light beam by passing the light beam through the sensor element, processing the linearly polarized measurement light beam exiting the sensor element in a measurement unit, wherein the sensor crystal is selected from a non-centrosymmetrical crystallographic point group 4 3 m.

First claim

The invention claimed is:

1. A method for determining the presence of an electrical charge on a surface of an ophthalmic lens mold ( 1 , 10 ), the method comprising the steps of
exposing a sensor crystal ( 22 ) of a sensor element ( 2 ) to a surface of an ophthalmic lens mold ( 1 ) on which an electrical charge generating an electrical field may be present,
converting a light beam ( 31 ) emitted from a laser light source ( 3 ) into a linearly polarized measurement light beam ( 34 ) by passing the light beam ( 31 ) through the sensor element ( 2 ),
processing the linearly polarized measurement light beam ( 34 ) exiting the sensor element ( 2 ) in a measurement unit ( 4 ),
wherein the step of converting the light beam ( 31 ) into a linearly polarized measurement light beam ( 34 ) by passing the light beam ( 31 ) through the sensor element ( 2 ) comprises:
converting the light beam ( 31 ) emitted from the laser light source ( 3 ) into a linearly polarized light beam ( 32 ) having a first polarization direction by passing the light beam ( 31 ) through a linear polarizer ( 21 ),
converting the linearly polarized light beam ( 32 ) exiting the linear polarizer ( 21 ) into an elliptically polarized light beam ( 33 ) by passing the linearly polarized light beam ( 32 ) through the sensor crystal ( 22 ), the sensor crystal being selected from a non-centrosymmetrical crystallographic point group 4 3 m,
converting the elliptically polarized light beam ( 33 ) exiting the sensor crystal ( 22 ) into the linearly polarized measurement light beam ( 34 ) by passing the elliptically polarized light beam ( 33 ) through a quarter-wave polarizer ( 23 ), wherein the linearly polarized measurement light beam ( 34 ) has a second polarization direction forming a polarization angle (φ) with the first polarization direction of the linearly polarized light beam ( 32 ) exiting the linear polarizer ( 21 ) and entering the sensor crystal ( 22 ), the polarization angle (φ) of the linearly polarized measurement light beam ( 34 ) being representative of the presence of the electrical field generated by the electrical charge on the surface of the lens mold ( 1 ) which the sensor crystal ( 22 ) is exposed to, and

wherein the step of processing the linearly polarized measurement light beam ( 34 ) in the measurement unit ( 4 ) comprises:
rotating the second polarization direction of the linearly polarized measurement light beam ( 34 ) by passing the polarized measurement light beam through a Faraday rotator ( 41 , 42 ) thereby forming a rotated linearly polarized measurement light beam ( 35 , 36 ),
converting the rotated linearly polarized measurement light beam ( 35 , 36 ) into an analyzer light beam ( 37 ) by passing the rotated linearly polarized measurement light beam ( 35 , 36 ) through an analyzer ( 43 ),
converting the analyzer light beam ( 37 ) into an electrical detection signal ( 441 ) with the aid of a photodetector ( 44 ) and evaluating the electrical detection signal ( 441 ) generated by the photodetector ( 44 ) with the aid of an evaluator ( 45 ) thereby determining the presence of the electrical charge on the surface of the ophthalmic lens mold ( 1 ).

2. The method according to claim 1 , wherein the propagation direction of the light beam ( 31 ) passing through the sensor element ( 2 ) is perpendicular to the surface of the ophthalmic lens mold ( 1 ) the sensor crystal ( 22 ) is exposed to.

3. The method according to claim 1 , wherein the sensor crystal ( 22 ) is selected from the non-centrosymmetrical crystallographic point group 4 3 m and has crystallographic faces along the crystallographic planes [1 1 0]×[110]×[001], wherein the electrical field ( 11 ) is parallel to the direction of the crystallographic plane [110], and wherein the propagation direction of the linearly polarized light beam ( 32 ) exiting the linear polarizer ( 21 ) and entering the sensor crystal ( 22 ) has a propagation direction parallel to the crystallographic plane [1 1 0].

4. The method according to claim 2 , wherein the sensor crystal ( 22 ) is selected from the non-centrosymmetrical crystallographic point group 4 3 m and has crystallographic faces along the crystallographic planes [1 1 0]×[110]×[001], wherein the electrical field ( 11 ) is parallel to the direction of the crystallographic plane [110], and wherein the propagation direction of the linearly polarized light beam ( 32 ) exiting the linear polarizer ( 21 ) and entering the sensor crystal ( 22 ) has a propagation direction parallel to the crystallographic plane [1 1 0].

5. The method according to claim 1 , wherein the analyzer ( 43 ) is a linear polarizer allowing light having a third polarization direction perpendicular to the first polarization direction of the linearly polarized light beam ( 32 ) exiting the linear polarizer ( 21 ) and entering the sensor crystal ( 22 ) to pass through the analyzer ( 43 ).

6. The method according to claim 2 , wherein the analyzer ( 43 ) is a linear polarizer allowing light having a third polarization direction perpendicular to the first polarization direction of the linearly polarized light beam ( 32 ) exiting the linear polarizer ( 21 ) and entering the sensor crystal ( 22 ) to pass through the analyzer ( 43 ).

7. The method according to claim 1 , wherein evaluating the electrical detection signal ( 441 ) generated by the photodetector ( 44 ) is performed in the evaluator ( 45 ) using a phase-locked loop, the evaluator ( 45 ) controlling a direct current driving the Faraday rotator ( 41 ) to rotate the second polarization direction of the linearly polarized measurement light beam ( 34 ) by an angle (α) determined by the electrical detection signal ( 441 ) generated by the photodetector ( 44 ) and evaluated in the evaluator ( 45 ).

8. The method according to claim 1 , wherein the second polarization direction of the linearly polarized measurement light beam ( 34 ) is rotated by passing the linearly polarized measurement light beam ( 34 ) through a first Faraday rotator ( 41 ) thereby forming a non-modulated rotated linearly polarized measurement light beam ( 35 ), and by thereafter passing the non-modulated rotated linearly polarized measurement light beam ( 35 ) through a second Faraday rotator ( 42 ) thereby forming a modulated rotated linearly polarized measurement light beam ( 36 ), with the first Faraday rotator ( 41 ) being driven by a direct current supplied by a direct current driver ( 411 ) controlled by the evaluator ( 45 ), and with the second Faraday rotator ( 42 ) being driven by an alternating current supplied by an alternating current driver ( 421 ) connected to an oscillator ( 47 ).

9. The method according to claim 7 , wherein the modulated rotated linearly polarized measurement light beam ( 36 ) is converted into the electrical detection signal ( 441 ), and wherein the direct current supplied by the direct current driver ( 411 ) controlled by the evaluator ( 45 ) and driving the first Faraday rotator ( 41 ) is varied by the phase-locked loop of the evaluator ( 45 ) until the modulated electrical detection signal ( 441 ) is symmetrical around a minimum value.

10. The method according to claim 8 , wherein the modulated rotated linearly polarized measurement light beam ( 36 ) is converted into the electrical detection signal ( 441 ), and wherein the direct current supplied by the direct current driver ( 411 ) controlled by the evaluator ( 45 ) and driving the first Faraday rotator ( 41 ) is varied by the phase-locked loop of the evaluator ( 45 ) until the modulated electrical detection signal ( 441 ) is symmetrical around a minimum value.

11. The method according to claim 1 , wherein the sensor crystal ( 22 ) is a single crystal sel

Assignees

• Novartis Ag

Inventors

• Ochrombel Rene

Classifications

• G01R1/071

  containing electro-optic elements · CPC title

• G01N21/21

  Polarisation-affecting properties (G01N21/19 takes precedence) · CPC title

• G01R29/24 Primary

  Arrangements for measuring quantities of charge · CPC title

• B29D11/00125 Primary

  Auxiliary operations, e.g. removing oxygen from the mould, conveying moulds from a storage to the production line in an inert atmosphere · CPC title

• G01R15/24

  using light-modulating devices · CPC title