Freeform Mirror Projection Layout for External Light Heat Blocking
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Solution Overview
Problem
Existing image projection devices using freeform curved mirrors are susceptible to temperature increase due to external light, and existing solutions like light blocking parts or infrared cut filters either fail to effectively block external light or degrade image quality.
Innovation Solution
An image projection device with an intermediate mirror arranged at an intermediate imaging position, reflecting external light away from the image projecting unit, using a planar or cold mirror to reduce external light exposure while maintaining image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a light blocking part is disposed to block external light, then external light reaching the image projecting unit is reduced, but external light reaching through the optical path space cannot be blocked
Solution Approach 1:
An intermediate mirror is introduced as a mediator in the optical path between the first and second freeform curved mirrors. This intermediate mirror reflects external light that would otherwise reach the image projecting unit, effectively blocking harmful external light without requiring a light blocking part that would obstruct the optical path. The intermediate mirror serves as an intermediary element that redirects both projection light and external light appropriately.
2Object-affected harmful factors
If an infrared cut filter is disposed in the vicinity of the intermediate imaging position, then external light is reduced, but projection light passes through the filter causing aberration and image quality degradation
Solution Approach 1:
The intermediate mirror acts as an intermediary reflective element that redirects external light before it can reach the image projecting unit. By using reflection instead of filtration, the system avoids introducing aberrations to the projection light. The intermediate mirror selectively reflects external light paths while maintaining the integrity of the projection light path, thus improving external light rejection without compromising image quality.
Solution Approach 2:
The harmful function of external light is extracted and redirected by the intermediate mirror before it can affect the image projecting unit. The intermediate mirror separates the external light path from the projection light path, extracting only the harmful external light components and redirecting them away from the optical system, while allowing the projection light to pass through unaffected.
3Ease of operation
If freeform curved mirrors are used to reflect projection light, then the image is formed in space at the viewpoint, but external light is focused on the image projecting unit surface causing temperature increase
Solution Approach 1:
The intermediate mirror serves as a protective intermediary element positioned in the optical path to intercept external light before it reaches the image projecting unit. This intermediate mirror redirects external light away from the image projecting unit while allowing the projection light to pass through and form the virtual image in space. By introducing this intermediary element, the system maintains its image formation capability while protecting against temperature increase caused by focused external light.
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
Effectively reduces the temperature increase of the image projecting unit by blocking external light, preserving the quality of the projected image.
Implementation Method 1
a first freeform curved mirror reflecting the projection light incident from the image projecting unit
Implementation Method 2
an intermediate mirror reflecting the projection light incident from the first freeform curved mirror
Implementation Method 3
a second freeform curved mirror reflecting the projection light incident from the intermediate mirror and causing the projection light to reach a viewpoint
Implementation Method 4
intermediate mirror arranged at an intermediate imaging position, reflecting external light away from the image projecting unit
Data Source
AI summary
An image projection device that can effectively curb an increase in temperature of an image projecting unit due to external light while maintaining quality of a projected image is provided. The image projection device includes an image projecting unit configured to emit projection light including an image, a first freeform curved mirror reflecting the projection light incident from the image projecting unit, an intermediate mirror reflecting the projection light incident from the first freeform curved mirror, and a second freeform curved mirror reflecting the projection light incident from the intermediate mirror and causing the projection light to reach a viewpoint. A component in at least one imaging axis direction of the projection light reflected by the first freeform curved mirror forms an image at an intermediate imaging position before the projection light reaches the second freeform curved mirror, and the intermediate mirror is arranged at the intermediate imaging position.