Original Publication Date: 1986-Oct-01
Included in the Prior Art Database: 2005-Mar-09
A reticle is provided which permits the viewing of an object while the light originating from a selected region of the object is measured. The reticle, which is placed in the real image plane, has a phase grating having a sufficiently high spatial frequency such that the first diffraction order is internally reflected to at least one light detector. Because some light (zeroth order) is not diffracted by the grating and passes through to the viewer, the viewer sees a diminution of light in the region of grating. This is in marked contrast to what has happened in the past when a mirror of fiber bundle was used with a microscope or telescope where the selected region was totally obscured.