Photonics Dictionary

A unit of optical measurement that expresses the refractive power of a lens or prism. In a lens or lens system, it is the reciprocal of the focal length in meters. For example, if a lens has a focal...

The adjustment of the eyepiece of an instrument to provide accommodation for the eyesight differences of individual observers. The axial distance through which the eyepiece must be moved, to provide...

A scale located on the eyepiece focusing screw and used to measure the amount of defocusing of the eyepiece in diopters. The reciprocal of the image distance in meters is a measure of the amount of...

A unit of metric measure equivalent to 1 thousandth (or 10-3 ) of the standard unit of optical power which is the diopter (1 millidiopter is 0.001 D). The power of a lens in millidiopters is the...

A telescopic system having an eyepiece, a reticle and an objective. The instrument measures wavefront power in diopters.

A scale on an optical instrument that indicates the condition of focus. May indicate the distance to the object or diopter output, or from infinity focus.

A dial depth gauge graduated in diopters; a lens measure.

The power, expressed in prism diopters, that is the linear displacement, in centimeters, produced by the prism one meter away.

Sets of lenses (positive, negative and cylindrical) usually mounted in circular rims suitable for slipping into trial spectacle frames. The individual lenses bear codes that state their power in...