collimation


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collimation

(kol-ă-may -shŏn) The alignment of the optical elements in a telescope. For a simple refractor the only adjustment required is to position the object lens at right angles to the optical axis by adjusting the screws on its supporting cell. In a simple Newtonian reflector the orientation of both the primary and diagonal mirrors must be adjusted, and the latter positioned correctly opposite the draw tube. Final small adjustments are then made to obtain bright star images as free as possible from coma.
References in periodicals archive ?
Real world superposition cannot be performed without the use of collimation.
Parks et al reported that film placement errors were not affected regardless of collimation technique used or operator skill.
Although SCTs require collimation, they need it less frequently than Newtonians do.
The setup of S1-S2 includes a collimation lens with focal length [f.sub.C] = 700 mm and diameter [d.sub.C] = 90 mm.
Five of the eight cases that scored 0 were acquired at 5 mm or 2.5 mm collimation. Two cases (patients 14 and 20) were scored 0 because they involved perineural spread of tumor along the second and third divisions of the trigeminal nerve, so that complete extent of tumor was not well demonstrated.
The evaluation was based on x-ray beam collimation observed on radiographs stored in the film library of the hospitals, questionnaires administered to radiographers and light beam misalignment test conducted on the x-ray machines.
Pitch is the distance the table travels per rotation divided by the beam collimation. Dose varies inversely with pitch.
High-resolution optics provide beam collimation. The sample fixture (z-stage) holds the sample in place and excludes ambient light.
Here is another view regarding the lack of a lead glove and collimation in the radiograph of a toddler's hand originally published in the Technical Query column and discussed in the May/June Open Forum (see Figure): While tight collimation and lead gloves are both important for radiation safety and protection, anyone who has taken many hand radiographs of toddlers knows it can be a very difficult procedure!
Mechanical or optical x-ray beam collimation in conjunction with video camera alignment allows confirmation of specific analysis areas/ features.
Other problems have included improper collimation, no purging and incorrect zero diopter settings and infinity focus.