JVC 250 Service Manual

Contents

Chapter 4---OpticalModel 250 Service Manual 4-9The Dichroic Beamsplitter Assembly separates the white light into its red, green,and blue components. Each component light beam goes into the Prism Assemblywhere it is polarized.Light can be viewed as having two electromagnetic components: a Horizontal-electric field and a Vertical-electric field. These fields are perpendicular to eachother. When unpolarized light travels through a polarizing beamsplitter, one ofthese fields is reflected and one is transmitted or passes through the beamsplitter.Upon striking the Prepolarizer, the Vertical field is reflected and is wasted, the P-electric field is passed through the Prepolarizing Beamsplitter and continues on tothe Main Polarizer. The Main Polarizing Beamsplitter (PBS) is rotated 90° fromthe Pre-Polarizing Beamsplitter so the Horizontal field that was transmittedthrough the Prepolarizer is reflected by the Main Polarizer. The reflectedpolarized light, either red, green or blue, leaves the PBS and goes directly into theILA ® (see Figure 4-6 and Figure 4-7).Each color exits the Prism Assembly and enters an ILA ® where the Liquid Crystalin the ILA ® rotates the polarized light. The image light striking the input side ofthe ILA® modulates the polarized light. The image on the input of the ILA ®originates as a image signal and is transformed into an image by the CRT. Theimage from the CRT passes through the Relay Lens and is focused onto the inputside of the ILA ®. The modulated image light leaves the output side of the ILA ®and re-enters the Prism Assembly where all three colors combine in the 4Pcombining optic. The image light exits the Prism Assembly, passes through theProjection Lens, and is projected out on the screen (see Figure 4-7).WARNING!!! Wear safety goggles (rated X5) whenworking anywhere near the light path from the arc lamp or the projectionlens.DO NOT open any of the Optical Support Assembly covers while theprojector is ON. The bright light can cause severe eye damage.