Collimator

The English physicist Henry Kater was the inventor of the floating collimator, which rendered a great service to practical astronomy.

In optics, a collimator may consist of a curved mirror or lens with some type of light source and/or an image at its focus.

[4] A surveying camera may be collimated by setting its fiduciary markers so that they define the principal point, as in photogrammetry.

[5][clarification needed] Adding a beam splitter allows the viewer to see the reticle and the field of view, making a reflector sight.

Proper collimation of a laser source with long enough coherence length can be verified with a shearing interferometer.

Collimators are also used in radiation detectors in nuclear power stations to make them directionally sensitive.

This ensures that rays are recorded in their proper place on the plate, producing a clear image.

For industrial radiography using gamma radiation sources such as iridium-192 or cobalt-60, a collimator (beam limiting device) allows the radiographer to control the exposure of radiation to expose a film and create a radiograph, to inspect materials for defects.

For instance, the thinnest walls on the sides of a 4 HVL tungsten collimator 13 mm (0.52 in) thick will reduce the intensity of radiation passing through them by 88.5%.

Although collimators improve resolution, they also reduce intensity by blocking incoming radiation, which is undesirable for remote sensing instruments that require high sensitivity.

[citation needed] Collimators (beam limiting devices) are used in linear accelerators used for radiotherapy treatments.

The secondary collimator consists of two jaws which can be moved to either enlarge or minimize the size of the treatment field.

New systems involving multileaf collimators (MLCs) are used to further shape a beam to localise treatment fields in radiotherapy.

MLCs consist of approximately 50–120 leaves of heavy, metal collimator plates which slide into place to form the desired field shape.