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.
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.
Other simple dose-reduction strategies include decreasing the tube current or tube voltage, increasing pitch, and choosing wider collimation.
2 [micro]Gy per image for group A; the protocol included collimation.
We performed thoracic high-resolution computed axial tomography (HRCT), using 7 mm helical technique after intravenous contrast administration followed by high-resolution imaging, using 1 mm collimation every 1 cm from lung apex to base (Figure 1B-D).
It can be attained by the magnetic collimation method, which is independent of the position of neutron [beta]-decay.
They include better collimation for cleaner signal and better cooling for extended life.
PolyLED lamps are solid-state light sources that provide the high reliability and light collimation associated with leaded discrete LEDs.
Coronal noncontrast computed tomography (CT) performed with 3-mm collimation and interval revealed a left ICB, minimal and scattered mucosal thickening, and partial bilateral ostiomeatal unit obstruction (figure).
These include improving the tracking speed to 10 degrees/second, the automatic collimation area to +/- 5 degrees, the distance measuring range to 7,200 feet to a single prism and the tilt compensating range to +/-4 feet.
Features include mechanical or optical x-ray beam collimation, gas proportional counter or semiconductor x-ray detector, and dual-encoded stage driver options.