English: Internal components of an old 1998 InFocus LP425z single-chip DLP projector, with a 4-segment color wheel.

This older 4-segment RGB+gray wheel design has a tendency to produce really poor yellows that are dark and greenish. Newer color wheels contain more segments with other colors to help improve the color gamut.

The glass segment shape is rather odd.. the exterior edge is circular, but the interior edge doesn't match the hub curvature at all. As the non-expert uploading this image I cannot explain the reason for that design. (COMMENT: The reason for this may be because of the way the glass may have been cut from a larger sheet. Two tight curves would make it quite likely to split.)

To the right is the cone-shaped light input from the lamp with a domed fisheye lens in the center. This lens works like a doorway spyhole except in reverse. Light enters as a narrowing cone, and the fisheye straightens the light into a tight beam about 5mm in diameter traveling in a parallel beam, under the main lens towards a front-surfaced mirror.

The fat pins around the edge of the cone are used to correctly align the lamp assembly that is inserted by the projector user.