R5905752 /16 DP2K C64
Image 5–16
► If no, use the focus barrel on the lens to focus the image on the screen.
Take into account that the lens focus may slightly drift while the lens is warming up from cold to
operation temperature. This is a typical phenomenon for projection lenses used with high brightness
projectors. The operation temperature of the lens is reached after approximately 30 minutes
projection of average video.
5.6 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 sometimes 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 known 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).
SCREEN
DMD
Lp1
Lp2
Fp1
Fp2
SCREEN
DMD
Lp3
Lp4
Fp3
Fp4
(Scheimpflug)
Image 5–17 Scheimpflug principle
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.
Lenses & lens holder
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