Spherical Lens Projection Optical System Thermal Stability
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Solution Overview
Problem
Miniaturized projection optical systems face performance deterioration due to variations in manufacturing errors and temperature changes, particularly when using aspherical or cemented lenses, which are sensitive to these factors.
Innovation Solution
A projection optical system comprising a series of spherical single lenses with specific refractive power distributions and configurations, including a magnification side lens group with negative refractive power and a reduction side lens group with positive refractive power, optimized to minimize aberrations and maintain performance across temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If aspherical lenses or cemented lenses are used to achieve miniaturization and improve optical performance, then the optical system size is reduced and aberration is corrected, but the system becomes sensitive to manufacturing errors and temperature variations
Solution Approach 1:
The patent changes the fundamental parameter of lens surface geometry from aspherical to spherical, and changes the lens construction from cemented to single lenses. This parameter change reduces sensitivity to manufacturing errors while maintaining miniaturization through optimized spherical lens arrangements with specific refractive powers and focal lengths
Solution Approach 2:
The patent uses simple spherical single lenses that are easier and cheaper to manufacture with high precision compared to aspherical or cemented lenses. These standard spherical lenses can be mass-produced with consistent quality, reducing the impact of manufacturing variations on system performance
2Volume of moving object
If aspherical lenses or cemented lenses are used to achieve miniaturization, then the optical system size is reduced, but the optical performance deteriorates due to temperature changes
Solution Approach 1:
The patent changes the lens construction parameter from cemented multi-element lenses to single spherical lenses, eliminating cement interfaces that are sensitive to temperature-induced expansion and contraction. This parameter change improves thermal stability while maintaining compact size through optimized lens arrangements
Solution Approach 2:
The patent uses homogeneous spherical single lenses throughout the optical system, avoiding the heterogeneous cemented interfaces between different lens materials. This homogeneity reduces differential thermal expansion effects and improves overall system reliability under temperature variations
3Volume of moving object
If miniaturization is pursued with conventional lens designs, then the optical system size is reduced, but light quantity is locally condensed causing high light resistance
Solution Approach 1:
The patent changes the lens design parameters including using spherical surfaces instead of aspherical, single lenses instead of cemented lenses, and optimizes the arrangement of lenses with specific refractive powers. These parameter changes reduce light resistance while maintaining miniaturization by improving light transmission efficiency through the compact optical path
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 reduces performance deterioration caused by manufacturing errors and temperature variations, achieving high optical performance and light resistance while enabling miniaturization.
Implementation Method 1
A projection optical system according to the embodiment includes, in order from a magnification side: a first lens group having negative refractive power; and a second lens group having positive refractive power
Data Source
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AI summary
According to an embodiment, a projection optical system for an image projection device, that includes a plurality of lenses. The projection optical system satisfies conditional expression (1): where fw is a focal length of a lens having the weakest refractive power in the lenses and f is a focal length of the whole projection optical system.