Barco F90 series, Service Manual

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4. DLP System General Description
4. DLP SYSTEM GENERAL DESCRIPTION
4.1 F90 optical principle
Optical Principle
The F90 illumination consists of two identical light paths combined using a dual rod system. Each path includes the following:
48 blue 455 nm Laser Diodes (LD) grouped into 3 banks consisting of 8 (2x4 array) LDs. The individual laser beams are combined
using mirrors and a focusing lens.
The light is focused on a static diffuser placed just before the entrance of a glass integrating rod.
The scattered light is then re fl ected multiple times in the integrating rod, creating uniform luminance at the rod exit.
The rod exit surface is then imaged onto the rotating Phosphor Wheel (PW) by the use of collimating lenses and a dichroic mirror
which only re
fl ects blue and IR light.
Image 4-1
The phosphor absorbs the blue laser light, and emits a broad band yellow light which is re fl ected back towards the dichroic mirror,
where it is transmitted, and focused onto the dual rod system.
A small portion of the blue light is transmitted through a clear segment of the PW, and is relayed around to the back of the dichroic
mirror. There it is re
fl ected a second time and combined with the yellow light from the PW before it is focused on the dual rod system.
The dual rod system consists of two solid integrating rods (one for each illumination path) and a hollow integrating rod combining
the two seamlessly. This exit surface is imaged onto the DMD using traditional relay optics and TIR prism.
To create Red and Green color, a color wheel is placed after the hollow rod exit surface, which is synchronized with the PWs in
each illumination path. This is again synchronized with the DMD producing time sequential Red, Green and Blue colors on the wall
perceived by the human eye as white light.
By using the internal illumination iris the contrast ratio can be increased, and by sliding in the motorized color fi lter (located next to
the iris) a broader color gamut can be achieved.
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