Lens measuring method and apparatus

DETAILED DESCRIPTION These and other disadvantages of the prior art are overcome with the present invention which utilizes the electrically conductive properties of certain lens to indicate when the contacts engage the surface of the lens.
The apparatus in accordance with the present invention comprises first and second electrical conducting contacts adapted to contact respective portions of the surface of the lens, the relative positioning of the first and second contacts being indicative of the desired measurement of the lens.
Moving means are provided for moving the first electrical conducting contact relative to the second electrically conducting contact to vary the relative positioning of the first and second contacts.
The apparatus also includes potential means for applying a potential across the first and second contacts to cause a current to be conducted between the first and second contacts through the lens when both the first and second contacts contact the surface of the lens, and sensing means for sensing such current to indicate that the contacts are in contact with the lens.
The method of the present invention is practiced by providing first and second electrically conducting contacts, the relative position of which is indicative of a desired measurement and applying a potential across such contacts so that when the two contacts contact the surface of the electrically conducting lens, a current is conducted between the first and second contacts through the lens.
Upon sensing this current, the movement of the first contact relative to the second contact is stopped so that the relative position of the first and second contacts can be determined.
This use of the electrical conducting characteristic of certain types of lenses provides a means by which accurate and repeatable measurement of lenses can be obtained.
This is extremely useful and overcomes the problem of subjectivity in lens measuring apparatus and methods of the prior art which rely on visual observation of contact between the contacts of the lens measuring apparatus and the lens