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5.7
Scheimpflug adjustment
What has to be done ?
The lens holder has to be adjusted so that the "sharp focus plane" of the projected image falls together with the plane of the screen
(Fp1→Fp2). This is achieved by changing the distance between the DMD plane and the lens plane (Lp1→Lp2). The closer the lens
plane comes to the DMD plane the further the sharp focus plane will be. It can happen that you won't be able to get a complete
focused image on the screen due to a tilt (or swing) of the lens plane with respect to the DMD plane. This is also know as Sheimpflug's
law. To solve this the lens plane must be placed parallel with the DMD plane. This can be achieved by turning the lens holder to
remove the tilt (or swing) between lens plane and DMD plane (Lp3→Lp4).
Lp1
Lp2
DMD
Image 5-16
The lens holder has three adjustment mechanisms. The first mechanism allows to shift the lens back and forward, the second
mechanism allows to tilt the lens and the third mechanism allows to swing the lens. Note that all three adjustment mechanisms
stand in relation with each other. So, a change to one of them will also effect the adjustment result of the two others. Therefore,
all three adjustment points have to be alternately and repeatedly adjusted until the projected image is completely focused on the
screen.
Scheimpflug principle
The "plane of sharp focus" can be changed so that any plane can be brought into sharp focus. When the DMD plane
and lens plane are parallel, the plane of sharp focus will also be parallel to these two planes. If, however, the lens
plane is tilted with respect to the DMD plane, the plane of sharp focus will also be tilted according to geometrical and
optical properties. The DMD plane, the principal lens plane and the sharp focus plane will intersect in a line below the
projector for downward lens tilt.
Necessary tools
•
3 mm Allen wrench.
•
5,5 mm nut driver or flat screw driver.
•
White paper sheet.
How to set up the projector for lens holder adjustment?
1. Place the projector upon a stable pedestal in its final location.
2. Remove the front cover, side cover and top cover of the projector.
3. Switch on the projector and project the internal green focus pattern.
4. Focus the projected image as sharp as possible upon the screen.
How to adjust the lens holder?
1. Loosen (not remove) the following lock screws of the lens holder adjustment mechanism using a 3 mm Allen wrench:
a) The three screws of the lens holder front plate. Note that the three retaining springs of the lens holder plate are not strong
enough to keep some heavy lenses into position while adjusting the lens holder. If this is the case you have to fasten these
screws immediately after adjusting the focus shift plate.
b) The two screws of the lens holder tilt mechanism.
c) The two screws of the lens holder swing mechanism.
R59770242 DP-1200 06/01/2009
Fp1
Fp2
DMD
Lp3
Lp4
5. Lenses & lens holder
Fp4
Fp3
(Scheimpflug)
53
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