Kodak DryView 8150, Service Manual, Page: 227 / 470

Section 6 -- Theory of Operation
6-25
2005 July Rev. B 7F3318
6-4-4-2. Reading the Dpatch
The Dpatch is an option for use only on 14 x 17 inch film. The Dpatch is an area on the sheet of film that
is exposed and processed to provide a reference for quality control of optical density. It is a patch of
density 1.0 on the top border of the film (see Figure 6-14). The density of the Dpatch is measured to
provide feedback to the AIQC system. AIQC then adjusts the optics attenuator as necessary to control the
intensity of the laser beam to achieve the target density.
Dpatch = density of 1.0
Dpatch border (fiducial)
= density of 3.1
Film Notch -- On 11 x 14 film, the notch
is at the bottom of the right edge of the film.
Figure 6-14. The Dpatch
6-4-4-3. Using Test Calibration Data to Create the Film Model
Once a successful calibration is achieved, the AIQC system and GSM use the data to create a Film Model
and Media Lookup Table, which tell the optics module how much laser attenuation is required to achieve
the desired exposure intensity. The data used is a DLogE curve generated by the density values
measured over the 19 steps of the gray scale step wedge. A sample DLogE curve is shown in
Figure 6-15.
Figure 6-15. Sample Calibration DLogE Curve