Optical instrument for identifying and locating micro-etching on an ophthalmic lens

1. An optical instrument for identifying and localizing micro-engravings ( 16 ) present on an ophthalmic lens ( 14 ), including:

a point light source;

a collimating member ( 30 ), said point light source being placed at a first focal point of said collimating member ( 30 ) so that light issued from said point light source becomes, after having passed through said collimating member, a beam ( 20 ) of collimated light;

a member for sending back light;

a holder ( 13 ) configured to hold said ophthalmic lens ( 14 ) between said collimating member ( 30 ) and said member for sending back light; said collimating member ( 30 ), said holder ( 13 ) and said member for sending back light are placed so that the beam ( 20 ) of collimated light issued from said collimating member ( 30 ) encounters the location ( 15 ) on the ophthalmic lens ( 14 ) where micro-engravings ( 16 ) are present, passes through said ophthalmic lens ( 14 ), encounters said member for sending back light, returns toward said ophthalmic lens ( 14 ) and once again passes through said ophthalmic lens ( 14 ) then said collimating member ( 30 );

an image-exploiting unit ( 32 ); and

an image-capturing unit ( 31 ) connected to said image-exploiting unit ( 32 ), which image-capturing unit ( 31 ) includes an objective ( 35 ) placed at a second focal point of said collimating member, which objective is focused so that the images delivered to the image-exploiting unit ( 32 ), which is connected to said image-capturing unit ( 31 ), contain a representation of said micro-engravings ( 16 ) allowing said micro-engravings ( 16 ) to be identified and localized;

wherein:

said member for sending back light is a backscatterer ( 12 );

said objective ( 35 ) of said image-capturing unit ( 31 ) is focused in order to deliver to the image-exploiting unit ( 32 ) images of the backscatterer ( 12 );

said point light source ( 25 - 27 ) has a wavelength (A) comprised between 700 and 1000 nm; and

said collimating member has a focal length (F) and said point light source ( 25 - 27 ) has a diameter (D) smaller than or equal to one fiftieth of the focal length (F) of said collimating member.

2. The instrument as claimed in claim 1 , wherein the instrument is configured for micro-engravings ( 16 ) having a width (a) comprised between 10 μm and 80 μm, the diameter (D) of said point light source ( 25 - 27 ) and said focal length (F) of said collimating member ( 30 ) respecting the relationship:

D≦Fλ/ 5 a

where

D is the diameter of said point light source,

F is the focal length of the collimating member,

λ is the wavelength of said point light source ( 25 - 27 ), and

a is the width of the micro-engravings.

3. The instrument as claimed in claim 2 , wherein the instrument is configured for micro-engravings ( 16 ) having a width a comprised between 30 μm and 60 μm, the wavelength of said point light source ( 25 - 27 ) (λ) being comprised between 800 and 900 nm while the focal length of the collimating member (F) is comprised between 150 and 300 mm.

4. The instrument as claimed in claim 1 , wherein the instrument is configured for micro-engravings ( 16 ) having a width a comprised between 30 μm and 60 μm, the wavelength of said point light source ( 25 - 27 ) (λ) being comprised between 800 and 900 nm while the focal length of the collimating member (F) is comprised between 150 and 300 mm.

5. The instrument as claimed in claim 1 , wherein said point light source is formed by an extended light source ( 25 ) and by a diaphragm ( 26 ) containing a pinhole ( 27 ) placed facing said extended light source ( 25 ), the diameter of said pinhole ( 27 ) thus forming the diameter (D) of said point light source.

6. The instrument as claimed in claim 1 , wherein the instrument includes a half-silvered mirror ( 28 ) on either side of which said point light source ( 25 - 27 ) and said objective ( 35 ) of said image-capturing unit ( 31 ) are placed.

7. The instrument as claimed in claim 1 , wherein said backscatterer ( 12 ) is rotatable.

8. The instrument as claimed in claim 1 , wherein the instrument includes an image-analyzing device ( 37 ) configured to identify and localize said micro-engravings ( 16 ), and a pin centering device ( 38 ) arranged for automatically positioning a centering pin on a face ( 15 ) of said ophthalmic lens ( 14 ), the pin centering device ( 38 ) device being connected to said image-analyzing device ( 37 ).

9. The instrument as claimed in claim 1 , further comprising:

a rotation-driving device ( 50 ) for driving the backscatterer ( 112 ) to rotate being connected to a predetermined center of rotation ( 40 ) of the backscatterer ( 112 ) so that the rotation-driving device ( 50 ) turns the backscatterer ( 112 ) about the predetermined center of rotation ( 40 );

an aperture ( 41 ; 141 ; 241 ) in said backscatterer ( 112 ), said aperture ( 41 ; 141 ; 241 ) being configured so that the center of rotation ( 40 ) of the backscatterer ( 112 ) is elsewhere than in the aperture ( 41 ; 141 ; 241 ); and

an assembly ( 42 ) for receiving and analyzing light, which assembly is located on that side of the backscatterer ( 112 ) which is opposite said holder ( 13 ), said holder ( 13 ), said backscatterer ( 112 ) and said aperture ( 41 ; 141 ; 241 ) being configured so that said assembly ( 42 ) for receiving and analyzing light receives light from said beam ( 20 ) of collimated light after it has passed through said ophthalmic lens and through said aperture ( 41 ; 141 ; 241 ), said assembly ( 42 ) for receiving and analyzing light being configured to determine at least one optical characteristic of said ophthalmic lens ( 14 ).

10. The instrument as claimed in claim 9 , wherein the rotation-driving device ( 50 ) for driving the backscatterer ( 112 ) to rotate and the image-capturing unit ( 31 ) are connected to a controlling device ( 51 ) configured so that each time interval during which the image-capturing unit ( 31 ) takes an image has a duration during which the backscatterer ( 112 ) makes an integer number of turns.

11. The instrument as claimed in claim 10 , wherein said assembly ( 42 ) for receiving and analyzing light includes a Hartmann matrix ( 45 ) illuminated by said light of said beam ( 20 ) of collimated light after it has passed through said ophthalmic lens ( 14 ) and through said aperture ( 41 ; 141 ; 241 ); an additional image-capturing unit ( 46 ) illuminated by the light after it has passed through the Hartmann matrix ( 45 ); and an analyzing device ( 47 ) for analyzing the images captured by the additional image-capturing unit ( 46 ) in order to determine said at least one optical characteristic of the ophthalmic lens ( 14 ).

12. The instrument as claimed in claim 10 , wherein said analyzing device ( 47 ) for analyzing the images captured by the additional image-capturing unit ( 46 ) is connected to a displaying unit ( 32 ) in order to allow it to display said at least one optical characteristic of the ophthalmic lens ( 14 ).

13. The instrument as claimed in claim 10 , wherein said analyzing device ( 47 ) for analyzing the images captured by the additional image-capturing unit ( 46 ) is connected to a pin centering device ( 38 ) for automatically positioning a centering pin on a face ( 15 ) of said ophthalmic lens ( 14 ).

14. The instrument as claimed in claim 9 , wherein the rotation-driving device ( 50 ) for driving the backscatterer ( 112 ) to rotate and the point light source ( 25 - 27 ) are connected to a controlling device ( 55 ) configured so as to make said point light source ( 25 - 27 ) emit flashes each having a duration during which the backscatterer ( 112 ) makes an integer number of turns.

15. The instrument as claimed in claim 14 , wherein said assembly ( 42 ) for receiving and analyzing light includes a Hartmann matrix ( 45 ) illuminated by said light of said beam ( 20 ) of collimated light after it has passed through said ophthalmic lens ( 14 ) and through said aperture ( 41 ; 141 ; 241 ); an additional image-capturing unit ( 46 ) illuminated by the light after it has passed through the Hartmann matrix ( 45 ); and an analyzing device ( 47 ) for analyzing the images captured by the additional image-capturing unit ( 46 ) in order to determine said at least one optical characteristic of the ophthalmic lens ( 14 ).

16. The instrument as claimed in claim 9 , wherein said assembly ( 42 ) for receiving and analyzing light includes a Hartmann matrix ( 45 ) illuminated by said light of said beam ( 20 ) of collimated light after it has passed through said ophthalmic lens ( 14 ) and through said aperture ( 41 ; 141 ; 241 ); an additional image-capturing unit ( 46 ) illuminated by the light after it has passed through the Hartmann matrix ( 45 ); and an analyzing device ( 47 ) for analyzing the images captured by the additional image-capturing unit ( 46 ) in order to determine said at least one optical characteristic of the ophthalmic lens ( 14 ).

17. The instrument as claimed in claim 9 , wherein said analyzing device ( 47 ) for analyzing the images captured by the additional image-capturing unit ( 46 ) is connected to a displaying unit ( 32 ) in order to allow it to display said at least one optical characteristic of the ophthalmic lens ( 14 ).

18. The instrument as claimed in claim 9 , wherein said analyzing device ( 47 ) for analyzing the images captured by the additional image-capturing unit ( 46 ) is connected to a pin centering device ( 38 ) for automatically positioning a centering pin on a face ( 15 ) of said ophthalmic lens ( 14 ).

19. The instrument as claimed in claim 9 , wherein said backscatterer ( 112 ) has a circular outline and said aperture ( 41 ; 141 ) takes the form of an angular sector.

20. The instrument as claimed in claim 9 , wherein said backscatterer ( 112 ) has a circular outline and said aperture ( 241 ) is spiral shaped.