Contact lens inspection method and system
Disclosed is an inspection and system method and system for determining the orientation of a contact lens on a lens support, particularly in an automated contact lens manufacturing line.
1. A method for determining the orientation of a contact lens on a lens support comprising the steps of:
providing a contact lens having a lens center and a sagittal height (h),
providing a lens support,
arranging the contact lens on the lens support,
providing a camera system having a depth of field of less than the sagittal height (h),
illuminating the contact lens arranged on the lens support with a light beam,
focusing the camera system to a set focus corresponding to the expected position of the lens center of the properly oriented contact lens arranged on the lens support with the lens center of the properly oriented contact lens on the lens support being within the depth of field of the focused camera system,
producing an image of the contact lens,
scanning the image of the contact lens in at east one image portion (S) of a predetermined size;
determining the image defocus of the at least one image portion (S),
determining the orientation of the contact lens from the image of the contact lens by comparing the determined image defocus with a predetermined threshold (T).
2. The method according to claim 1 , wherein the step of providing a camera system comprises providing a camera system having a depth of field of up to about 40% of the sagittal height (h).
3. The method according to claim 2 , wherein the step of determining the image defocus is performed by determining an image blur level and the step of determining the orientation of the contact lens is performed by comparing the determined image blur with a predetermined threshold (T).
4. The method according to claim 1 , wherein the step of determining the image defocus is performed by determining an image blur level and the step of determining the orientation of the contact lens is performed by comparing the determined image blur with a predetermined threshold (T).
5. The method according to claim 4 , wherein the step of determining the image blur is performed by determining an image noise level and determining the orientation of the contact lens is performed by comparing the determined image noise with a predetermined threshold (T).
6. The method according to claim 5 , wherein determining the image noise of the at least one image portion (S) is performed by applying a Wiener filter or a Fourier transform.
7. The method according to claim 1 , wherein the step of producing an image of the contact lens comprises producing an orthographic image of the contact lens.
8. The method according to claim 1 , wherein the step of producing an image of the contact lens comprises using a bright field imaging unit.
9. The method according to claim 1 , wherein the step of producing an image of the contact lens comprises using a dark field imaging unit.