A projector color wheel is a key component in DLP (digital light processing) projectors. It is a rotating wheel with color filters that works together with the DLP chip to produce full color images on the projection screen. In this article, we will explore what a color wheel is, how it works, the different types of color wheels, and some common issues related to projector color wheels.
What is a Projector Color Wheel?
A projector color wheel is a small disc made of glass or metal that is mounted on the projector engine. It is situated between the projection lamp and the DLP chip. The color wheel is divided into segments, with each segment filtering out a primary color – red, green, and blue.
As the color wheel spins rapidly, each color segment filters the white light from the lamp into the respective color. This illuminated colored light then shines on the DLP chip which processes and reflects that single color. The reflection is done at high speeds to create full color images we see on screen.
So in summary, a projector color wheel takes the white light and splits it into the three primary colors sequentially. It acts like a filter that passes only one color at a time to the DLP chip. This process combined with the fast mirror flipping of the DLP chip produces the full color image.
How Does a Projector Color Wheel Work?
Here are the step-by-step workings of a projector color wheel:
- White light is emitted from the projection lamp/bulb and directed onto the color wheel.
- As the color wheel spins at high speed (up to 10,000 rpm), the white light passes through each color segment in sequence – red, green, blue.
- With each spin, the filter allows only one primary color to pass through at any instant.
- This illuminated single-color light is then transmitted onto the DLP chip.
- The DLP chip processes each color separately by quickly flipping its microscopic mirrors to reflect that color’s information.
- The mirrors modulate the colored light to produce the pixels needed for that particular color.
- The rotating color segments combined with the DLP mirrors’ flipping creates full color images by merging the red, green and blue color frames.
- The projected image we see on screen is the combined result of the color wheel rotation and the DLP chip reflections.
So in essence, the color wheel produces a sequential colored light stream synchronized with the DLP chip’s image processing to generate vibrant and rich colors for the projection display.
Types of Projector Color Wheels
There are two main types of color wheels used in DLP projectors:
1. Single-Chip Color Wheel
This is the most common type of color wheel. In single-chip DLP projectors, there is only one DLP chip. The color wheel has the three basic color segments – red, green and blue (RGB). This wheel allows single-chip projectors to produce full color images.
2. Three-Chip Color Wheel
In three-chip DLP projectors, there are separate red, green and blue DLP chips. This allows parallel color processing. The color wheel in these projectors is divided into more segments for enhanced colors. Common configurations include:
- RGBRGB – Two sets of red, green, blue segments
- RGBCMY – Red, green, blue with complementary cyan, magenta, yellow
- RGBCYW – Red, green, blue, cyan, yellow, white
These multi-chip color wheels produce richer colors with reduced rainbow effects compared to single-chip wheels.
Projector Color Wheel Speeds
Color wheels are designed to spin at very high revolution rates to produce seamless full color projection. Standard speed for color wheels is 6x rotation per video frame (at 60 Hz refresh rate). This equals 360 spins per second or 21,600 rpm.
Faster color wheel speeds help minimize color separation issues like rainbow effect. High-end projectors use 8x to 10x color wheels spinning at 28,800 – 36,000 rpm. Slower color wheels can cause visible color breakup.
| Color Wheel Speed | Spins per Second | Rotations per Minute (rpm) |
|---|---|---|
| 2x | 120 | 7200 |
| 4x | 240 | 14400 |
| 6x (standard) | 360 | 21600 |
| 8x | 480 | 28800 |
| 10x | 600 | 36000 |
Common Projector Color Wheel Problems
Here are some common issues related to faulty color wheels:
- No image: If the color wheel stops spinning, it blocks the light source causing a blank projection screen.
- Solid yellow/blue/red tint: If a color wheel segment gets stuck, it filters only that color.
- Rainbow effect: When color wheel speed is too slow, rainbow banding appears in image.
- Color flashes: If wheel is unbalanced, colors may flash or flicker on screen.
- grinding noises: Any odd noises when wheel spins could indicate impending issues.
- Color convergence: Misaligned or wobbly wheel leads to color fringing or convergence issue.
Repairing or replacing the color wheel is needed when such problems are noticed for proper color projection.
Projector Color Wheel Replacement
Projector color wheels are precision optical components. The wheel has to be perfectly balanced and aligned for smooth operation at high speeds. Thus replacing just the glass wheel is not recommended.
It is better to install a new OEM (original equipment manufacturer) color wheel for optimal performance and color quality. Generic or used color wheels often result in recurrence of problems.
Replacement color wheels can be sourced from the projector manufacturer or third party suppliers. Prices range from $100 for basic models to over $300 for high-end projectors.
Here are some tips for projector color wheel replacement:
- Buy the exact same OEM part number for proper fit and compatibility.
- Ensure the new wheel is balanced and wobble-free.
- Align and seat the wheel correctly in the motor hub.
- Calibrate projector colors after installing new wheel.
- Reset the color wheel sensor if required.
With some care and precaution, projector owners can replace color wheels on their own and revive projectors at a fraction of repair shop costs.
Conclusion
The color wheel is a crucial optical component in DLP projection systems. It filters white light into color segments to work together with the DLP chip and produce the projected images we see. Color wheels spin at blazing fast speeds to avoid visible color breakup. Issues with color wheels can severely impact image quality and need prompt servicing. Overall, understanding the working and maintenance of the color wheel allows users to get the best performance from their DLP projectors.
