Zoom Lens with Right-Angle Prism for Compact Optical Path
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Solution Overview
Problem
Existing zoom lenses for small-sized imaging devices face challenges in achieving a balance between slimming down and durability, with previous configurations either compromising on durability or optical performance due to the use of high-refractive index and high-dispersion materials in right-angle prisms, which are not practical or cost-effective.
Innovation Solution
A zoom lens configuration with a first lens group containing a right-angle prism for optical path bending, a second lens group moving along the optical axis for zooming, and a fourth lens group moving for focusing, optimized with specific refractive index and Abbe number conditions for the right-angle prism and lens groups to maintain good optical performance and reduce cost, while ensuring strong durability and minimal transmittance loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a right-angle prism with high refractive index and high dispersion material is used to bend the optical path, then the optical path can be bent effectively, but the transmittance on the short wavelength side of visible light beam lowers
Solution Approach 1:
The patent changes the material parameters of the right-angle prism by specifying a refractive index range of 1.70-2.10 and Abbe number range of 25-35, optimizing the balance between optical path bending efficiency and transmittance. This parameter optimization allows effective total internal reflection while maintaining good transmittance characteristics across the visible spectrum.
Solution Approach 2:
The patent employs composite lens designs in the first lens group, combining multiple lens elements with different refractive indices and dispersion characteristics. This includes using a negative lens and positive lens with specific refractive index relationships to correct chromatic aberrations introduced by the prism while maintaining overall system performance.
2Reliability
If the first lens group is made large to accommodate the right-angle prism and maintain optical performance, then the optical system can function properly, but the overall length of the zoom lens increases
Solution Approach 1:
The patent uses a right-angle prism to bend the optical path by approximately 90 degrees, changing the spatial dimension of the optical system. This allows the optical axis to be folded, effectively reducing the overall length of the zoom lens while maintaining the necessary optical path length and performance characteristics.
Solution Approach 2:
The patent optimizes the refractive index and Abbe number parameters of the right-angle prism material to achieve effective optical path bending with compact dimensions. By selecting materials within specific parameter ranges, the prism can bend light efficiently while occupying minimal space, thus reducing the overall lens length.
3Length of moving object
If a zoom lens configuration with multiple lens groups is used to achieve slimming down, then the entire length can be shortened, but the durability against shock of drop is reduced
Solution Approach 1:
The patent divides the zoom lens into four distinct lens groups with different functions: the first lens group containing the right-angle prism for optical path bending, the second lens group for zooming, the third lens group for additional zooming, and the fourth lens group for focusing. This segmentation allows each group to be optimized independently, with the first group providing structural stability for durability while the other groups enable compact design.
Solution Approach 2:
The patent replaces a pop-up lens barrel mechanical system with a fixed first lens group containing the right-angle prism. This substitution eliminates the need for a protruding lens barrel, allowing the entire lens assembly to be housed within the imaging apparatus main body, thereby improving durability against shock while maintaining a slim profile.
4Reliability
If the number of lenses in the first lens group is increased to maintain optical performance, then the optical quality can be improved, but the manufacturing cost and complexity increase
Solution Approach 1:
The patent specifies precise parameter ranges for the right-angle prism (refractive index 1.70-2.10, Abbe number 25-35) and for the lens elements in the first lens group. By optimizing these parameters, the patent achieves good optical quality with a controlled number of lens elements, avoiding excessive complexity while maintaining performance.
Solution Approach 2:
The patent uses composite lens designs combining negative and positive lens elements with specific refractive index relationships. This allows correction of chromatic and spherical aberrations introduced by the right-angle prism using a manageable number of elements, balancing optical quality with manufacturing feasibility.
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 provides a zoom lens that is both slim and durable, maintaining good optical performance without compromising transmittance and reducing costs, by optimizing the refractive index and Abbe number of the right-angle prism and lens groups, and incorporating plastic aspheric surfaces for improved performance.
Implementation Method 1
a right-angle prism having an internal reflection face for bending an optical path approximately 90°
Implementation Method 2
a first lens having a negative refractive power; a second lens having a positive refractive power; and a third lens having positive refractive power
Data Source
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AI summary
Teleobjective-type of zoom, having four lens groups and rear focusing and comprising a first lens group which is positive and fixed during zooming and focusing, a second lens group which is negative and moves for zooming, an aperture stop, a third lens group which is positive and fixed during zooming and focusing and a fourth lens group which is positive and moving for zooming and focusing. The first lens group is formed of a negative lens, a right-angle prism and two positive lenses and fulfils a set of inequalities.