points, conjugatemedical dictionary

<microscopy> The pair of points on the principal axis of a mirror or lens so located that light emitted from either point will be focused at the other. Related points in the object and image are located optically so that one is the image of the other.

See: polarizing element

(05 Aug 1998)

points of convergencemedical dictionary

Preferred term: convergence

point sourcemedical dictionary

In photometry, a very small source of light which is regarded as a geometrical point from which light emanates in straight lines in all directions.

(05 Mar 2000)

point-spread functionmedical dictionary

<microscopy> The mathematical representation of the image of a point source. For a diffraction-limited optical system operating in the absence of aberrations, the point-spread function is the Airy disk.

See: three-dimensional diffraction pattern.

(05 Aug 1998)

point system test typesmedical dictionary

A near-vision test chart in which the various test types are multiples of a point (1/72 inch), lower-case letters being one-half the designated point size; reading 4-point at 16 inches is normal, and is designated N-4.

(05 Mar 2000)