Infrared Lens Layout for Small F-Number Aberration Correction
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Solution Overview
Problem
Distance measurement devices using infrared light face challenges in achieving a sufficiently small f-number while effectively correcting spherical aberration and field curvature, as existing optical systems do not adequately address these issues.
Innovation Solution
An optical system comprising a first chalcogenide lens with positive refractive power, a second glass lens with negative refractive power, and a third chalcogenide lens, where the refractive index difference between the chalcogenide and glass lenses is optimized to reduce the Petzval sum, thereby correcting aberrations and allowing for a small f-number.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the f-number is reduced to increase brightness for infrared sensors, then the brightness is improved, but spherical aberration and field curvature cannot be effectively corrected
Solution Approach 1:
The patent uses composite lens materials with different refractive indices - specifically combining lenses with higher refractive index (n=2.0 or more) with lenses having lower refractive index (n<2.0). This composite material approach allows the optical system to achieve both small f-number (high brightness) and effective aberration correction by optimizing the refractive index distribution throughout the lens system.
Solution Approach 2:
The patent systematically varies key optical parameters including refractive index, focal length ratios, and lens configuration to resolve the contradiction. By establishing specific parameter ranges (e.g., focal length ratios, refractive index differences) the system achieves optimal balance between brightness and aberration correction performance.
2Illumination intensity
If a chalcogenide lens with high transmittance is used, then the infrared light transmittance is improved, but the f-number cannot be sufficiently reduced and aberrations remain uncorrected
Solution Approach 1:
The patent incorporates chalcogenide glass lenses (with refractive index n≥2.0) into a composite optical system that also includes lenses with lower refractive indices. This composite structure allows the chalcogenide lens to provide high infrared transmittance while the overall system configuration corrects aberrations and achieves small f-number, thereby maintaining reliable distance measurement performance.
Solution Approach 2:
The patent applies local quality by using chalcogenide material specifically in lens positions where high infrared transmittance is most beneficial, while using other materials in positions where aberration correction is prioritized. This localized material selection optimizes both transmittance and overall system performance.
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 optical system achieves effective correction of spherical aberration and field curvature, enabling high-performance image formation with a small f-number, even in infrared light applications, thereby enhancing the accuracy of distance measurement devices.
Implementation Method 1
an optical system includes a first lens with positive refractive power, a second lens with negative refractive power, and a third lens with positive refractive power, placed in this order from an object side to an image side
Data Source
AI summary
An optical system includes a first lens L1 with positive refractive power, a second lens L2 with negative refractive power, and a third lens L3 with positive refractive power, placed in this order from an object side to an image side. At least one of the first lens L1 and the third lens L3 is made of chalcogenide material, and the second lens L2 is made of glass material. The following inequality is satisfied: 0.75<Np−Nn, where Np is a refractive index of the lens made of the chalcogenide material at a wavelength of 0.9 μm, and Nn is a refractive index of the second lens at a wavelength of 0.9 μm.