Photonics Dictionary: R

A type of internal focusing in which only the lens elements closest to the rear of the lens barrel are moved.

Also known as reversed telephoto lens. A lens consisting of an ordinary objective with a negative component near its front focal point. Thus, the back focus is large, relative to its focal length....

In gradient index optics, a gradient profile in which the index varies in a direction perpendicular to the optical axis. Radial gradient lenses can focus light even when the lens surfaces are flat,...

Also known as radiation thermometer. A pyrometer in which the radiant intensity from the source to be measured is used to calculate its temperature. The usual detector is a thermocouple, thermopile...

In the region of a Gaussian beam focus by a diffraction-limited lens, it is the axial distance from the point of minimum beam waist (Wo) to the point where the beam diameter has increased to .

The restricting opening at the rear of a lens or prism that is commonly defined as the maximum diameter of the emergent cone for the specified field of view, at infinity focus.

Reflectance confocal microscopy (RCM) is a non-invasive imaging technique that allows for high-resolution, in vivo imaging of biological tissues at the cellular level. It is particularly useful in...

A solar spectrograph that uses long focus concave mirrors as its collimator and camera element.

A telescope that uses a reflecting objective to focus an image of a distant object at a focal point.

A means of high resolution study through the application of soft and hard x-rays onto a sample surface in order to obtain image information from 1-10 nm layers and surfaces. The x-ray source emission...

A sequential scanning device, utilizing a revolving lens, in which the cathode-ray tube image is transformed into a circle of fibers. The rotating lens focuses each fiber successively on a multiplier...

The circle that contains the slit, grating and primary astigmatic focus of a concave diffraction grating.