AGFA CR 30-X Service Manual page 70

Functional Description
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Chapter 2 / 10
Agfa Company Confidential
STEP 2: Determination of translucence of the system
An IP with 20µG is scanned by the system. The exact dose is measured by
production people and entered in the system. The analog output signal at the
PMT is measured by the system, put into a relation to the entered dose and
stored in the PMT EEPROM as REF CAL value.
Parameters of REF CAL: Overall translucence of light collector incl. PMT
sensitivity
STEP 3: Shading calibration
An IP with 20µG is scanned. A reference value for each pixel of each line and
each polygon facet is stored in the PMT Flash ROM.
Parameters: Translucence of Lightcollector - PMT system per pixel on the
scan line.
⇒ Signal corrections before scan: AUTOZERO
With laser and blue LED switched off, the system measures the output of the
PMT. This value is the AUTOZERO value.
Parameters: Noise of the PMT electronics; Remaining light
→ Error message if AUTOZERO value exceeds certain limit (e.g. covers
opened)
⇒ Signal corrections during scan: AUTOCAL and Shading Correction
AUTOCAL Correction:
During laser blank time, till the next facet scans a line, the blue LED is
switched on to measure the sensitivity of the PMT. By combining the
measured values of several lines the sensitivity is automatically adjusted (HT
at PMT)
Shading correction:
The digital value of each pixel is corrected with a correction factor determined
during shading calibration.
DOCUMENT CONTROL NOTE:
Type 5175/100
CR30-X
DD+DIS150.06E
Edition 1, Revision 0