Stimulating The Phosphor - Kodak DirectView CR 800 System Theory Manual

Stimulating the Phosphor

Illustration showing the movement of the beam across the
plate and how the read out differs from the center to the edges of
the plate. This concept can be shown with the beam of a flashlight
straight on and at an angle.
also if possible the optics that can correct that. Remember this
is CR theory in general, not EK CR.
Image capture - readout ppt 8-4, 5
1234563 – 12/12/94
Stimulating Light Source
Acquiring the latent image off the phosphor screen is accomplished by exposing
the screen with high intensity light that stimulate the electrons, causing them to
luminesce. Efficient read-out of the screen requires a high stimulating light
intensity, such as that offered by a laser beam. The laser beam is scanned back
and forth across the plate.
Deflector
The entire surface of the screen is scanned by the moving beam as the screen
travels perpendicular to the scanning direction. Since the laser is stationary, a
device is necessary to move the beam across the plate (trace) and bring it back
to the starting point (retrace). This function is accomplished by a galvonometer-
driven mirror. The position of the beam is monitored and adjusted constantly to
ensure the speed and accuracy of the scanning operation.
Scanning Optics
Depending on the angle of the laser beam as it moves across the plate, the size,
shape, and speed of the beam change. Imagine the shape of a flashlight beam
as you move it across a flat surface, from one edge, to the center, and to the other
edge. Scanning optics focus and shape the beam, keeping the profile and speed
of the beam constant. The "beam-shaping" component of the CR 800 system is
a beam expander lens.
Computed Radiography (CR) Theory
2–13