Contactless Optical Distance Measurement Using Chromatic Aberration
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Solution Overview
Problem
Existing contactless optical distance measurement devices require complex lens systems with multiple lenses, leading to large dimensions, high weight, and reduced measurement accuracy due to chromatic aberration and other imaging errors.
Innovation Solution
A device with a polychromatic light source and a measurement head featuring a chromatic longitudinal aberration optical lens system consisting of two refractive lenses, one with an aspherically curved surface, allowing for a compact design with high resolution and accuracy by using materials with a small Abbe number and optimizing the numerical aperture and beam parameter product.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a lens system with multiple lenses (at least three or four) is used to generate a measurement region with chromatic aberration, then the measurement region can be predetermined, but the device becomes complex, large in dimensions, and heavy
Solution Approach 1:
The patent divides the optical system into two functional segments: a light source unit (polychromatic source) and a measurement head unit (lens system with chromatic aberration). This segmentation allows the complex chromatic aberration generation to be isolated in a compact measurement head, separating the functions and reducing overall device complexity while maintaining measurement precision
Solution Approach 2:
The patent employs aspherically curved lens surfaces in the measurement head's optical system. These aspherical surfaces are specifically designed to generate and control chromatic longitudinal aberration, enabling the formation of a precise measurement region with axial extent corresponding to the spectral range, while minimizing the number of lenses required
2Measurement precision
If a lens system with multiple lenses is used to generate a measurement region, then chromatic aberration can be utilized for distance measurement, but the device dimensions and weight increase
Solution Approach 1:
The patent extracts the essential function of chromatic aberration generation from a complex multi-lens system and implements it in a simplified measurement head containing only one or two lenses with aspherical surfaces. This extraction maintains the distance measurement capability while significantly reducing device weight
Solution Approach 2:
The patent changes the optical parameters of the lenses by introducing aspherical surfaces with specific curvature profiles. These parameter changes enable the lenses to generate controlled chromatic longitudinal aberration, achieving the same measurement function with fewer lenses and reduced weight
3Measurement precision
If a lens system with multiple lenses is used, then a measurement region can be formed, but imaging errors increase and measurement accuracy decreases
Solution Approach 1:
The patent uses aspherically curved lens surfaces specifically designed to correct imaging errors such as spherical aberration and coma. These aspherical surfaces provide precise control over light ray paths, reducing imaging errors and improving measurement accuracy while maintaining the chromatic aberration necessary for distance measurement
Solution Approach 2:
The patent converts the typically harmful chromatic aberration into a useful measurement signal. By designing the aspherical surfaces to generate controlled chromatic longitudinal aberration, the system transforms what is normally an imaging error into the basis for accurate distance measurement through spectral analysis
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 achieves a large measurement region with high resolution and accuracy, minimizing chromatic aberration-related errors and reducing the device's size and weight, while maintaining a high signal-to-noise ratio.
Implementation Method 1
The optical lens system (12) has a chromatic longitudinal aberration. In other words, the position of the focus on the optical axis of the lens system is dependent on the wavelength.
Implementation Method 2
The optical lens system consists of a first refractive lens (1) and of a second refractive lens (2), wherein at least one of the refractive lenses has at least one aspherically curved lens surface.
Data Source
AI summary
A device for contactless optical distance measurement includes a polychromatic light source, a light analysis unit and a measurement head. The measurement head has an aperture opening and an optical lens system, which has a chromatic longitudinal aberration. The optical lens system includes a first refractive lens element and a second refractive lens element. At least one of the refractive lens elements has at least one aspherical lens surface, and the first refractive lens element and/or the second refractive lens element has an optical material with an Abbe number 20<=Vd<=41. The optical lens system has such a chromatic longitudinal aberration that a measurement region, which equals an axial focal shift of the optical lens system between the wavelengths of 450 nm and 700 nm, is between 0.2 mm inclusive and 10 mm inclusive.