Zoom Lens Segmentation for Near-Infrared Chromatic Aberration
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Solution Overview
Problem
Existing zoom lenses for image pickup apparatuses face challenges in achieving high optical performance with a wide angle of field, small size, and effective correction of chromatic aberration across a wide wavelength range from visible light to near-infrared, while maintaining low defocus and high resolving power.
Innovation Solution
A negative lead type two-unit zoom lens configuration with specific lens unit movements and refractive power distributions, including a first lens unit with two negative lenses and a second lens unit with positive refractive power, optimized by conditional expressions to control focal lengths and f-numbers across different wavelengths, ensuring reduced defocus and chromatic aberration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the zoom lens is designed with a wide angle of field and small f-number to capture clear images in low illuminance, then the ability to photograph in twilight and night conditions is improved, but chromatic aberration and defocus increase in the near-infrared wavelength range
Solution Approach 1:
The first lens unit is divided into two lens sub-units (1a and 1b) with different refractive powers. The first lens sub-unit (1a) has negative refractive power and consists of two negative lenses, while the second lens sub-unit (1b) has positive refractive power. This segmentation allows independent optimization of each sub-unit's contribution to chromatic aberration correction across different wavelength ranges, enabling effective control of both visible light and near-infrared chromatic aberrations while maintaining wide angle of field and small f-number characteristics
Solution Approach 2:
Different lens sub-units are assigned specific refractive power characteristics tailored to their functional requirements. The first lens sub-unit (1a) with negative refractive power is optimized for controlling chromatic aberration in the near-infrared range, while the second lens sub-unit (1b) with positive refractive power contributes to overall focal length and visible light performance. This local quality differentiation enables simultaneous optimization for low illuminance photography and near-infrared chromatic aberration correction
2Manufacturing precision
If the lens configuration is optimized to reduce defocus and correct chromatic aberration in the near-infrared range, then the optical performance for near-infrared photography is improved, but the lens size increases
Solution Approach 1:
The zoom lens employs dynamic movement of lens units along different loci during zooming operations. The first lens unit and second lens unit move along different trajectories, allowing the optical system to maintain optimized chromatic aberration correction and defocus control across the entire zoom range from wide angle to telephoto. This dynamic configuration enables the lens to achieve small size at all focal lengths while maintaining high optical performance in the near-infrared range
Solution Approach 2:
The lens configuration utilizes specific conditional expressions involving focal lengths (f1a, f1b, f2, fw, ft) and movement amounts (M1, M2) to optimize the balance between lens size and optical performance. By carefully controlling the ratio of focal lengths and the movement amounts of different lens units during zooming, the system achieves compact size while maintaining effective chromatic aberration correction and defocus control in the near-infrared wavelength range
3Manufacturing precision
If the first lens unit and second lens unit are moved along different loci during zooming to maintain optical performance, then the chromatic aberration correction is improved, but the device complexity increases
Solution Approach 1:
The zoom lens system is segmented into two independently controllable lens units (first lens unit and second lens unit) that move along different loci. This segmentation allows each unit to be optimized for specific functions: the first lens unit with its two sub-units focuses on chromatic aberration correction, while the second lens unit contributes to focal length adjustment. The independent movement paths enable simplified control mechanisms compared to moving all lens elements uniformly, as each unit's movement can be independently optimized for its specific 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 enables high optical performance over the entire zoom range with a small lens size, reducing defocus and maintaining high resolving power across the visible and near-infrared spectrum, while allowing for a wide angle of field and low f-number, facilitating clear imaging in various lighting conditions.
Implementation Method 1
a first lens unit having a negative refractive power; an aperture stop; and a second lens unit having a positive refractive power
Data Source
AI summary
Provided is an image pickup apparatus including a zoos lens and a solid-state image pickup element. The zoom lens includes a first lens unit having a negative refractive power, an aperture stop, and a second lens unit having a positive refractive power. The first lens unit consists of a first lens sub-unit having a negative refractive power, which consists of two negative lenses, and a second lens sub-unit having a positive refractive power. The first lens unit and the second lens unit are configured to move in different loci for zooming. Each of a full-open f-number (Fnow) of the zoom lens, a focal length of the zoom lens, a focal length of the first lens sub-unit, and a pixel pitch (P) of the solid-state image pickup element is appropriately set.