Apparatus and technique for automatic centering and focusing a corneal topographer
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United States of America Patent
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Jun 11, 1996
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N/A
app pub date -
Apr 14, 1993
filing date -
Apr 14, 1993
priority date (Note) -
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Abstract
A corneal topographer including a directional light source, a CCD and a positioning stage all controlled by a computer for automatically centering and focusing the corneal image onto the CCD. The computer receives video signals from the CCD representing the corneal image, which is digitized and displayed on a real-time basis on a monitor screen. A reflection of the directional light source is positioned to align in the center of the corneal image. An operator moves an optics head to place the corneal image on the monitor screen, roughly focuses the image, and then commands the computer to take over. The computer calculates the distance between the image of the directional light source and the center of the CCD, and activates the positioning stage to move the directional light source image to the center. The positioning stage is moved within a focusing range, where several positions and corresponding intensity characteristics of the directional light source image are tabulated. A best fit algorithm calculates the maximum intensity characteristic corresponding to the maximum focus, and the computer moves the optics head to a position corresponding to maximum focus.
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