Prismless Projector Lens Set Design for Compact DMD Illumination
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Solution Overview
Problem
Conventional prismless projectors face challenges in size reduction due to the requirement of a TIR prism, which increases the projector's size and can cause interference between the lens set and imaging lens, making them less competitive and inconvenient.
Innovation Solution
A prismless, non-telecentric projector design featuring a biaxially-tilted digital micro mirror device (DMD) with a lens set composed of a first and second lens group, where the effective focal length ratio of the second lens group to the first is between 1.4 and 1.8, and the first lens group consists of spherical or aspheric lenses, reducing component costs and preventing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a TIR prism is used in the projector, then the light can be properly directed to the DMD, but the projector size increases and component interference occurs
Solution Approach 1:
The patent removes the TIR prism from the optical system and replaces it with a combination of lens groups that can directly direct light to the DMD without requiring the prism's total internal reflection function. This extraction of the unnecessary component reduces projector size while maintaining light direction capability through alternative optical means.
Solution Approach 2:
The patent changes the optical parameters by using lens groups with specific focal length ratios (1.4-1.8) to achieve the same light direction function that previously required a TIR prism. This parameter change allows direct illumination of the DMD at appropriate angles without the prism, reducing overall system volume.
2Reliability
If a TIR prism is used in the projector, then the light path can be controlled, but interference between the lens set and imaging lens occurs
Solution Approach 1:
By removing the TIR prism from the optical path, the patent eliminates the source of interference between optical components. The lens groups are positioned and configured to direct light to the DMD without interfering with the imaging lens, thus removing the harmful interference effect while maintaining light path control.
Solution Approach 2:
The patent introduces lens groups as intermediary optical elements that perform the light direction function previously handled by the TIR prism. These lens groups act as mediators between the light source and DMD, controlling the light path without causing interference with other components through proper positioning and focal length selection.
3Volume of moving object
If the lens set is positioned close to the DMD, then the projector size is reduced, but interference with the imaging lens occurs
Solution Approach 1:
The patent specifies particular focal length ratios (1.4-1.8) for the lens groups that allow them to be positioned closer to the DMD without causing interference with the imaging lens. This parameter optimization enables compact positioning while avoiding harmful optical interference through mathematically determined focal length relationships.
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
The design enables a more compact projector with reduced component costs, improved image quality, and prevention of interference between lens groups, enhancing efficiency and competitiveness by eliminating the need for a TIR prism.
Implementation Method 1
a lens set for transmitting an incident light to the biaxially-tilted DMD and comprising a first lens group and a second lens group
Implementation Method 2
a biaxially-tilted digital micro mirror device (DMD) receiving the incident light and converting the incident light into an imaging light
Data Source
AI summary
The invention provides a projector with a biaxially-tilted (with a 17-degree tilting angle) digital micro mirror device (DMD) whose light source module and lens set deployment is improved so that the incident light provided by the light source module travels along a first light route and is enlarged by the lens set before traveling along a second light route and provided to the biaxially-tilted DMD. The projector features in that the first lens group is composed of two specific spherical lenses or one specific aspheric lens and the second lens group is composed of one aspheric lens. Therefore, the prismless, non-telecentric projector, without using any TIR prism, can be made with fewer components, lower cost, and enhanced efficiency.