Zoom Lens First Unit Size Reduction via Third Lens Inversion
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Solution Overview
Problem
Existing zoom lenses do not achieve optimal movement loci of movable lens units for zooming, resulting in larger size and increased aberration variation, particularly with the first lens unit becoming larger and aberration variation worsening during zooming.
Innovation Solution
A zoom lens configuration with one or two first lens units not moving, one or two second lens units moving towards the image side, one or two third lens units moving convexly towards the object side, and a fourth lens unit moving between the second and third lens units, with specific conditional expressions to optimize lens movement and reduce aberration variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the movement locus of the third lens unit is made convex toward the image side, then the zoom lens can achieve zooming function, but the size of the first lens unit becomes larger
Solution Approach 1:
The patent inverts the conventional convex direction by making the third lens unit's movement locus convex toward the object side instead of the image side. This reversal allows the first lens unit to be downsized while maintaining the zooming function, directly resolving the technical contradiction between achieving zooming and reducing lens unit size.
2Device complexity
If the movement locus of the third lens unit is not optimized, then the zoom lens structure is simpler, but aberration variation during zooming becomes larger
Solution Approach 1:
The patent optimizes specific parameters including the convex curvature of the third lens unit's movement locus toward the object side, the conditional expression 0.05 < M4m/M2 < 0.5 for movement ratios, and the interval changes between lens units. These parameter optimizations enable effective aberration control during zooming without requiring complex lens unit configurations, resolving the contradiction between simplicity and aberration control.
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 configuration results in a smaller zoom lens with improved optical performance by reducing the size of the first lens unit and minimizing aberration variation during zooming, while maintaining a high zoom ratio.
Implementation Method 1
a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a negative refractive power, a fourth lens unit having a positive refractive power, and a fifth lens unit having a positive refractive power
Data Source
AI summary
Provided is a zoom lens including, from object side: one/two first positive units including a lens unit arranged at closest to object side not movable for zooming ; one/two second negative units movable toward image side for zooming from wide end to telephoto end; one/two third units including a negative unit arranged closest to object side and movable along a locus convex toward object side for zooming; a fourth positive unit movable for zooming; and a fifth unit, and including an aperture stop in image side of the fourth unit. A distance between object side surface of the first unit and the aperture stop, a length of the first unit, and movement amounts of the second unit from wide end to telephoto end and of the fourth unit from wide end to an intermediate zoom state where the second and third units are closest to each other are set appropriately.