Patent ID: 9638909
Date: 2017-05-02
CPC Classifications: G02B

Claim:
1. A focusing apparatus for use with an optical system having a high numerical aperture (NA) objective lens, the apparatus including: an image forming and capturing means configured to receive light from a specimen via the high NA objective lens, wherein the image forming and capturing means includes a high NA lens that focuses the light received via the high NA objective lens to form an image in an intermediate image zone, and a reflective element at an axial position within the intermediate image zone that reflects the image formed by the high NA lens back into the same high NA lens so that the high NA lens captures an image from a selected focal plane within said intermediate image zone; and a focus adjusting means that adjusts the axial position of the reflective element to adjust a position of the selected focal plane within the intermediate image zone, whereby spherical aberration is reduced.