Projector Thermal Focus Compensation via Resin Expansion
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Solution Overview
Problem
Existing projector technologies face challenges in correcting focus position changes due to temperature variations, often requiring complex structures or special control circuits, and fail to provide effective temperature compensation for projection lenses.
Innovation Solution
A projector design incorporating an expanding and contracting member with a specific temperature coefficient that adjusts the focal distance of the projection lens, using a holder member and frame member configuration to maintain image formation conditions across temperature changes, without complicating the lens barrel structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bimetal correcting mechanism is incorporated in the lens barrel to correct focus position changes, then the focus position can be corrected, but the lens barrel structure becomes complicated and optical design is limited
Solution Approach 1:
The correcting mechanism is extracted from the lens barrel and placed in the holder member that supports the display device. The expanding and contracting member is disposed between the frame member and the holder member, separating the correction function from the lens barrel structure while maintaining focus position correction capability.
Solution Approach 2:
An expanding and contracting member made of resin is introduced as an intermediary between the frame member and the holder member. This member has a temperature coefficient of linear expansion that corresponds to the temperature coefficient for change in focal distance, enabling it to mediate the correction of focus position changes caused by temperature variations.
2Stability of the object's composition
If a heat conductive lens barrel is used to prevent shift or separation of laminated lens, then lens stability is improved, but the focus position change caused by temperature cannot be positively corrected
Solution Approach 1:
Different parts of the system have different thermal properties. The frame member and holder member are made of materials with appropriate thermal expansion characteristics, while the expanding and contracting member made of resin has a specific temperature coefficient of linear expansion that enables focus correction. This local differentiation of material properties allows both lens stability and focus correction to be achieved.
3Reliability
If a cam ring with different temperature coefficient is used to cancel focus shift, then focus correction is achieved, but the lens barrel structure becomes complicated
Solution Approach 1:
The correction function is extracted from the lens barrel and implemented in the holder member assembly. The expanding and contracting member is disposed between the frame member and the holder member, removing the need for complex cam ring mechanisms within the lens barrel while achieving the same focus correction effect.
4Ease of operation
If a piezoelectric element is used to shift the refraction optical lens, then focus control is achieved, but a special control circuit is required
Solution Approach 1:
The piezoelectric actuation system is replaced with a passive thermal expansion mechanism. The expanding and contracting member utilizes the temperature coefficient of linear expansion of resin materials to automatically adjust focus position in response to temperature changes, eliminating the need for piezoelectric elements and their associated control circuits.
Solution Approach 2:
The system utilizes changes in the physical parameter of thermal expansion of the resin material to achieve focus adjustment. By selecting a resin with an appropriate temperature coefficient of linear expansion, the system automatically compensates for temperature-induced focus drift without requiring external control signals or complex electronics.
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 solution allows for simple and effective temperature compensation, maintaining image projection quality by canceling focal distance changes caused by temperature variations, without the need for complex auto-focus mechanisms or special control circuits.
Implementation Method 1
an expanding and contracting member disposed between the frame member and the display device... The temperature coefficient for the expansion and contraction of the expanding and contracting member in the direction of the optical axis of the projection lens corresponds to a temperature coefficient for the increase and decrease of the focal distance of the projection lens
Data Source
AI summary
A projector includes: a display device which modulates illumination light; a projection lens which projects modulation light produced by the display device; and a holding device which has a holder member supporting the display device, a frame member supporting the projection lens and functions as a base capable of supporting the holder member, and an expanding and contracting member disposed between the frame member and the display device, wherein a temperature coefficient for the expansion and contraction of the expanding and contracting member in the direction of the optical axis of the projection lens corresponds to a temperature coefficient for the increase and decrease of the focal distance of the projection lens.