Zoom Lens M2E Extender Group for Chromatic Aberration Control
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Solution Overview
Problem
Zoom lenses with variable magnification face issues of chromatic aberration and focal position misalignment due to temperature changes when an extender lens is replaced, as existing technologies do not effectively address these problems.
Innovation Solution
A zoom lens configuration that includes a focusing unit, a variable magnification unit, and an image forming unit, where the M2N lens group is replaceable with an M2E lens group, with specific refractive index and Abbe number conditions for the M2E lenses to minimize chromatic aberration and correct focal position misalignment, including at least one positive lens with an Abbe number νd1 and average temperature change coefficients dn/dt, and partial dispersion ratios θgF, ensuring optimal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an extender lens is replaced in a zoom lens, then the image forming magnification is enlarged, but chromatic aberration is deteriorated and focal position misalignment occurs with temperature change
Solution Approach 1:
The patent applies parameter changes by carefully selecting the refractive index (nd) and Abbe number (νd) parameters of the lenses in the M2E extender lens group. Specific conditional expressions define the required ranges for these parameters to achieve both high magnification and good optical performance. By changing the material parameters of the lenses, the system achieves enlarged image forming magnification while suppressing chromatic aberration and maintaining focal position stability across temperature changes.
Solution Approach 2:
The patent employs composite materials by combining lenses with different refractive indices and Abbe numbers in the M2E lens group. The use of multiple lens elements made from different optical materials allows the system to correct chromatic aberration through dispersion compensation while maintaining the desired magnification and temperature stability characteristics.
2Adaptability or versatility
If lens groups are replaced with an extender lens, then variable magnification capability is enhanced, but temperature characteristic changes causing focal position misalignment
Solution Approach 1:
The patent addresses temperature characteristic changes by selecting lens materials with specific temperature coefficients of refractive index (dn/dt). The conditional expressions in the patent define the required ranges for dn/dt values of lenses in the M2E group, ensuring that the overall temperature characteristic of the zoom lens system is corrected and focal position remains stable across temperature variations while maintaining enhanced variable magnification capability.
Data Source
AI summary
A zoom lens has, in order from an object side, a focusing unit including a focusing lens group moving for focusing, a variable magnification unit including at least two variable magnification lens groups moving while changing a mutual interval for variable magnification, an aperture stop, and an image forming unit including an image forming lens group. The image forming unit consists of, in order from the object side, an M1 lens group, an M2N lens group, and an M3 lens group. The M2N lens group is replaceable with an M2E lens group that enlarges an image forming magnification. The M2E lens group satisfies predetermined conditional expressions (1) to (4).