Barco DP2K-E series User Manual

11. Scheimpflug
11.4 Back Focal Length ad justment
When to adjust the Back Focal Length?
If a lens is used with a t hrow ratio suited for the application, (lens selection depends on projection distance a nd screen size) typically
one would NEVER need to adjust the Back Foc al Length of the projector.
A Back Focal Length adjus tment is only required in case the Focus range of th e installed lens does not c apture the projection screen
either for FLAT and/or for SCO P E. In other words, when it is impos sible t o focus the image on the screen for FLAT and/or for SCOP E.
Note that the lens es for the DP2K -E series projector are varifocal. So, switching between F LAT and S CO PE (zoom action) requires
a readjustment of the focus.
What is Back Focal Length a djustment?
Back Focal Length a djustment means moving the lens plane (Lp), thus the Lens Holder front plate, closer to o r further from the DM D
plane. The closer the lens plane to the D M D plane the further the focus range (Fr) of the lens will b
e.
SCREEN
DMD
Lp1
Lp2
Fr1
Fr
2
Image 11-13
Do not abuse the Back Focal Length adjustment of the Lens Holder. Neglecting this will result in loss of image
quality because of the len s design. Cas es requiring Back F ocal Length adjustment normally indicate incorrect
lens choice (throw ratio).
Necessary tools
• 10mm nut driver.
• 3mm Allen wre nch.
• 13mm nut driver.
How to check the Back Focal Length?
1. Ensure that the throw ratio of the ins talled lens matches with the requirements of th e application ( projection distance and screen
size).
2. Ensure that the correct lens parameters are activated. (See user guide o f the Communicator chapter Installation > Advanced >
Lens parameters)
Caution: Not using the c orrect lens parameters could result in lens damage.
3. Perform a lens HOME & RETURN operation. (S ee user guide of the Comm unicator chapter Installation > Advan ced > Lens
parameters)
4. Project the green focus test pattern. (screen fi
le “ no m asking” or “no “crop”)
Image 11-14
5. Zoom the lens for max imum image on the screen (WIDE).
6. Is it possible to focus the c enter of the projected image?
If yes, the Back Focal Length is OK .
If no, th e Back Focal Length needs realignment. Proceed with the next procedure.
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R5906693 DP2K-E SERIES 19/06/2015

Barco DP2K-E series Specifications

General

Brand	Barco
Model	DP2K-E series
Category	Projector
Language	English