4-54
P/N 9-500-0255
Service Manual
Chapter 4: Calibrations and Performance Checks
X-ray and Light Field Check and Alignment Procedures
2. Place the light detector in area
“A” on the IRSD (see Figure 4-15).
Orient the center of the probe 3.0
mm from the edge of the defined
light field toward the center of
the field (l1). Collimate the light
probe so that only a 1 square
centimeter area (near the center)
is visible.
3. Press the light field button and
record the inside lux value (I1).
Move the probe 3.0 mm from the
edge of the defined light field
away from the center of the field.
Reposition the aluminum filter,
press the light field switch, then
record the outside lux reading
(I2).
4. Subtract both edge readings from
the ambient reading and record
each of the differences:
( IA - I1 = D1 and IA - I2 = D2).
5. Divide the inside difference by
the outside difference and record
the ratio: (D1 / D2 = R).
6. Repeat the procedure for the
remaining light field edges. Place
the light meter probe at positions
B, C, and D for these checks. A
contrast ratio less than 4 at any
edge is cause for rejection.
Figure 4-15: Light Field Edge Contrast Check
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