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The above figure shows the representative structure of Liquid crystal projector. We would like to introduce how the optical filters and mirrors are used in the Liquid crystal projector.
[ 1 ] UV-IR Cut filter
As Liquid crystal is vulnerable to heat source and UV, this filter cuts off the unnecessary region of light the lamp emits.
[ 2 ] Polarization switching element
The light inserting Liquid crystal panel should be only one polarizing component (either P or S), and the other polarizing component should not be used. This element improves this function. This element consists of PBS (Polarizing Beam Splitter) and 1/2 wave plate. PBS divides the light into P and S components, and 1/2 wave plate delays phase so that all the light will be P or S. This element enables us to use the light source with high efficiency.
[ 3 ] Mirror
Due to the structure of Liquid crystal projector, the light path has to be turned 90 degrees in several places. This is used for such turning of the light path. Nowadays, some mirrors are required to have high reflectivity, which is achieved by putting several layers of dielectrics onto the Aluminum coating. Increased reflection mirror is needed especially when P component is used.
[ 4 ] Color filter (Dichroic Mirror)
This filter used at an angle divides the visible light reflecting a certain region of light and passing the other visible light. In Figure 1, you can see color filter A passes blue and green light while red is rejected, and color filter B passes blue light and reflects green light. This way, three primary colors are separated.
[ 5 ] Cross prism (Color composing prism)
his prism is made of 4 pieces triangle prism, where right angles are in contact with each other. Those contacting faces have dichroic mirrors corresponding to each of the primary colors (blue, green and red) of the liquid crystal panel, and the three kinds of light are combined into normal visible light and such light is the output towards the projection lens.
As for the item 4 and 5, please refer to the Dichroic Mirror of our product information.
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