Wedge Cylindrical Lens for Astigmatism Correction in Spectrometers
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Solution Overview
Problem
Current spectrometers face challenges in correcting astigmatism across the entire spectrum, leading to reduced sensitivity due to wasted light and limited demagnification, as conventional cylindrical lenses focus only at specific wavelengths, failing to effectively address astigmatism beyond the center of the detector array.
Innovation Solution
A spectrometer design incorporating a cylindrical lens with a wedge shape, positioned between the reflective concave element and the detector, which corrects astigmatism and provides demagnification across the entire detector length by adjusting the angle of its cylindrical and flat faces, ensuring optimal focus and sensitivity across the spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional cylindrical lens is used to correct astigmatism, then astigmatism is corrected at one specific wavelength, but the focus is not maintained across the entire spectrum
Solution Approach 1:
The cylindrical lens is designed with a wedge shape where different portions of the lens have different optical powers. The lens thickness varies across its surface, creating local variations in refractive properties that enable astigmatism correction across multiple wavelengths simultaneously, rather than at a single wavelength as in conventional lenses.
Solution Approach 2:
The invention changes the geometric parameters of the cylindrical lens by introducing a wedge angle between the cylindrical face and the base. This parameter modification alters the optical path length across the lens surface, enabling the lens to correct astigmatism across the entire spectral range while maintaining focus at all wavelengths.
2Volume of moving object
If the reflective elements are set off-axis to reflect light within the housing, then the spectrometer fits within compact housing, but astigmatism is introduced causing light to focus to a line rather than a spot
Solution Approach 1:
The cylindrical lens acts as an intermediary optical element placed in the light path between the off-axis reflective elements and the detector. It compensates for the astigmatism introduced by the off-axis mirrors by providing opposing astigmatic power, thereby restoring spot focus while allowing the compact off-axis geometry to be maintained.
3Measurement precision
If a cylindrical lens is used to correct astigmatism, then focus is improved, but demagnification is limited and light intensity is reduced
Solution Approach 1:
The wedge-shaped cylindrical lens modifies the optical parameters to provide both astigmatism correction and demagnification simultaneously. By adjusting the wedge angle and lens curvature, the system achieves demagnification of the spectral image onto the detector, concentrating more light onto each detector element and increasing detected intensity while maintaining focus quality.
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 effectively corrects astigmatism and achieves substantial demagnification across the entire detector length, enhancing the sensitivity and spectral resolution of the spectrometer by focusing light into narrower spots, thereby reducing light wastage and improving overall performance.
Implementation Method 1
a cylindrical lens located between the reflective concave element and the detector and in the path of the light, the cylindrical lens extending along at least a portion of the detector, the cylindrical lens having a substantially cylindrical face and a substantially flat face
Implementation Method 2
the longitudinal axis of the cylindrical face is at an angle with respect to the flat face such that at least a portion of the cylindrical lens has a wedge shape
Data Source
Figure 1
Figure 1A~2
Figure 2A~3
AI summary
A spectrometer which in one embodiment including a dispersive element and a concave element. The dispersive element may be a flat or concave grating which receives light and reflects the light in different collimated wavelengths. The concave element being located downstream from the dispersive element and arranged to reflect and focus the light toward a detector. The reflected light from the concave element including astigmatism. A cylindrical lens positioned between the concave element and the detector and configured to simultaneously correct the astigmatism and demagnify the light across the detector. In one embodiment the cylindrical lens varies in thickness progressively along its length.