Projection Lens Astigmatism Correction via Moving Group
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Solution Overview
Problem
Projection systems in image display apparatuses face challenges in correcting astigmatism and other optical aberrations that worsen due to temperature changes, particularly when high luminance levels increase lens temperature, leading to image quality degradation.
Innovation Solution
A projection system with a correction lens group that moves along the optical axis to correct astigmatism, where the focal length of the correction lens group and the entire lens system satisfy specific conditional expressions to minimize back focus position movement, reducing the need for additional correction lens groups and maintaining image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the temperature of the lens increases due to high luminance projection, then the optical characteristics change and astigmatism worsens, but adding more lens groups to correct the aberration increases device complexity
Solution Approach 1:
The first lens group is segmented into a correction lens group and a fixed lens group. The correction lens group specifically addresses astigmatism caused by temperature changes, while the fixed lens group maintains other optical functions. This segmentation allows targeted correction without adding complete additional lens groups.
Solution Approach 2:
The correction lens group serves multiple functions: it corrects astigmatism caused by temperature changes, maintains focus across temperature variations, and works within the existing zoom mechanism. By making this single group multi-functional, the patent avoids needing separate correction mechanisms for each issue.
2Reliability
If a correction lens group is moved to correct astigmatism, then optical characteristics improve, but the back focus position changes affecting image quality
Solution Approach 1:
The patent carefully selects the focal length of the correction lens group relative to the entire lens system according to specific conditional expressions. By controlling this parameter relationship, the movement of the back focus position is limited to within the depth of focus range, preventing noticeable image quality degradation while still achieving astigmatism correction.
3Reliability
If multiple lens groups are moved to correct both field curvature and back focus position, then comprehensive aberration correction is achieved, but the mechanism complexity and number of moving parts increase
Solution Approach 1:
The patent combines the correction of astigmatism, field curvature, and back focus position changes into a single correction lens group. By strategically positioning this group and controlling its movement, multiple aberration types are corrected simultaneously, avoiding the need for separate lens groups for each correction function.
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 solution effectively corrects astigmatism and other aberrations caused by temperature changes without affecting image quality, even at high luminance levels, by moving the correction lens group within the projection system, thus ensuring consistent image projection.
Implementation Method 1
a correction lens group that is moved in the direction of an optical axis to correct a change in an aberration produced due to a temperature change
Data Source
AI summary
A projection system includes a first lens group that does not move when the projection magnification is changed with the aid of the zoom function, and the first lens group includes a correction lens group that is moved in the direction of the optical axis to correct worsened astigmatism. The projection system satisfies the following conditional expressions (1) and (2):|ΔBF20|<P×FNO×√2 (1)1.5<|f1/f| (2)where P represents the pixel pitch in an image displayed by liquid crystal panels, FNO represents the F number of the entire lens system, ΔBF represents the amount of movement of the back focus position in a case where the correction lens group is moved by the amount of movement for correction of the aberration that changes when the temperature changes by 20° C., f represents the focal length of the entire lens system, and f1 represents the focal length of the correction lens group.