Chapter 2---System Description
primary light source. The light output to the screen is the function of the Arc Lamp. The purpose of the CRTs is to generate an image and to control the amount of modulation the ILA® assemblies introduce on the light coming from the Arc Lamp. The Red, Green, and Blue image signals are routed to the CRTs from the Video Amplifier Board through the CRT socket connectors.
Relay Lens: The relay lens picks up the image from the face of the CRT and focuses the image to the ILA® assembly.
Image Light Amplifier (ILA®) Assembly: The CRT image is received from the relay lens onto the input side of the ILA® assembly. The input and output sides of the ILA® assembly are isolated from each other electrically and optically but are coupled electrostatically.
At the same time as the image is received at the input side of the ILA® assembly, the output side of the ILA® assembly is receiving high intensity light from the arc lamp through the prism. This high intensity light is modulated (changing its polarization) by the signal on the input side of the ILA® assembly. The light is then reflected back from the output side of the ILA® assembly, then travels through the prism to be picked up by the projection lens.
NOTE: The prism reflects horizontally polarized light and passes vertically polarized light. Light from the arc lamp is polarized horizontally and reflects from the prism into the ILA® assembly then back out again, after being modulated by the image signal into vertically polarized light. The vertically polarized light then passes through the prism to the projector lens. In this manner the ILA® assembly combines the image from the CRT with the high intensity light from the arc lamp. Thus, the maximum brightness of the screen image is not dependent on the brightness of the CRT, but on the light from the arc lamp.
For a more detailed description of how the ILA® assembly works, refer to Section 2.7 below.
Polarizing Prism: The polarizing prism receives the high intensity light from the xenon arc lamp and polarizes the light horizontally. The prism reflects virtually all of this light toward the ILA® assembly. This light is then modulated (altered) into a vertical plane by the image on the input side of the ILA® assembly and then reflected back into the same prism. Since the prism reflects only horizontal light and passes vertical light, this high intensity, vertically polarized image goes straight through the prism toward the Combining Prism. Light that is not completely polarized horizontally or vertically passes through the prism in varying degrees of brightness, according to how polarized it is (fully polarized light resulting in maximum brightness on the screen).
Image Mirror: The Image Mirrors direct the blue and red images toward the Combining Prism.
Model 200 Service Manual |
