DMD Projection System Using Holographic Optics for Compact Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing spatial light modulator projection systems are limited by the use of costly and inefficient light sources, leading to large physical volumes and high weights, making them unsuitable for portable applications where minimum size, weight, and cost are critical.
Innovation Solution
A projection system utilizing a digital micromirror device (DMD) with a holographic optical element and solid-state lasers to produce collimated, colored light beams, where the holographic optical element is optically coupled to the light source and sequentially illuminated to control light intensity and redirect waste light, allowing for compact assembly on a printed-wiring board.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If traditional UHP arc lamps and complex relay optics are used to illuminate the DMD, then the projection system achieves sufficient brightness, but the physical volume and weight of the system become large and complex
Solution Approach 1:
The patent extracts and eliminates the complex relay optics, condenser lenses, and color filter wheel assembly from the traditional projection system. By using a DMD with integrated illumination and a simplified optical path, the system removes unnecessary components while maintaining projection brightness, thereby reducing physical volume and complexity.
Solution Approach 2:
The DMD serves multiple functions: it acts as both the spatial light modulator and the projection element. The illumination source is integrated directly with the DMD, eliminating the need for separate illumination and projection optical paths. This multi-functionality reduces the number of components and overall system volume.
2Power
If traditional projection optics are used to achieve high brightness output, then the projection intensity exceeds 1000 Lm, but the system weight exceeds one pound
Solution Approach 1:
The patent replaces traditional mechanical projection optics with a digitally controlled DMD system. The DMD uses microelectromechanical mirrors to modulate light directly, eliminating the need for heavy projection lenses and complex mechanical adjustment mechanisms. This substitution of mechanical optical systems with digital control reduces overall system weight while maintaining high brightness output.
3Volume of stationary object
If LED light sources with Lambertian emission pattern are used, then the system size is reduced, but the projection brightness level drops below 50 Lm
Solution Approach 1:
The patent changes the illumination parameters by using a DMD with high etendue that can efficiently couple with LED light sources. The DMD's micromirror array is designed to accept light from a wide angular range (Lambertian pattern) and redirect it into a collimated projection beam. This parameter change in light coupling efficiency allows the system to maintain small size while achieving high projection brightness.
4Device complexity
If a single DMD with sequential color frames is used, then the system complexity is reduced, but the color rendering accuracy and image quality are compromised
Solution Approach 1:
The patent uses periodic action by sequentially displaying color frames at high frequency (greater than 180 Hz) through the single DMD. The DMD rapidly switches between different color patterns corresponding to red, green, and blue channels, and the human eye integrates these sequential frames to perceive full-color images. This periodic modulation maintains simple system architecture while achieving accurate color rendering through temporal multiplexing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration achieves a bright image in a small physical volume with low weight and cost, enabling the projection system to be compactly assembled with control, power, and sensor electronics, suitable for portable applications.
Implementation Method 1
a diffractive optical element is a holographic optical element... the diffractive optical element comprises an illumination hologram that is optically coupled to the light source and is sequentially illuminated by the light beams
Implementation Method 2
An array of micromirrors with selectively controllable orientations to form a projectable image
Data Source
AI summary
A method and apparatus for a projection display system includes a spatial light modulator and a volume illumination hologram. The spatial light modulator comprises a digital micromirror device, and the projection system includes a laser light source to produce a sequence of collimated, colored, light beams for the illumination hologram. Waste light produced by the spatial light modulator is transmitted to the illumination hologram, and the illumination hologram emits waste light from at least one of its edges. Waste light emitted from an edge of the illumination hologram is absorbed by a light sensor to control the intensity of the light beams. A projection focusing element is mounted proximate a side of the illumination hologram to focus the image beam from the spatial light modulator for viewing. A projection hologram is interposed between the side of the illumination hologram and the projection focusing element to manage waste light.