Multiple-Band Liquid Crystal Filter for High-Transmission Imaging
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Solution Overview
Problem
Existing optical filters, including those based on birefringent materials, suffer from low peak transmission values, requiring high sensitivity cameras and illumination intensities, limiting their application in multi-spectral imaging systems.
Innovation Solution
A multi-stage optical filter design comprising entrance polarizing and constant retarding elements with periodic transmission characteristics that overlap to form spectrally separated passbands, allowing for tunable and simultaneous imaging of multiple spectral bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional fixed-wavelength optical filters are used, then high transmission values are achieved, but the system cannot capture multiple spectral bands simultaneously
Solution Approach 1:
The optical filter is divided into multiple filter stages (at least two), each stage contributing to the formation of specific spectral passbands. This segmentation allows the filter to transmit multiple discrete spectral bands simultaneously while maintaining high transmission values in each band, resolving the contradiction between multi-spectral capability and transmission efficiency.
Solution Approach 2:
Each filter stage is designed with specific local optical properties (different retardation values) that create periodic transmission characteristics with peaks at specific wavelengths. This local quality differentiation across stages enables selective transmission of multiple spectral bands with high efficiency, addressing both the versatility and energy loss concerns.
2Adaptability or versatility
If multi-stage birefringent filters are used to achieve multiple passbands, then spectral versatility is improved, but peak transmission values decrease
Solution Approach 1:
The invention carefully controls and optimizes the retardation parameters of each birefringent filter stage. By selecting specific retardation values and configuring the overlap of periodic transmission characteristics, the system achieves multiple spectral passbands while maintaining high peak transmission values, thus resolving the contradiction between spectral versatility and transmission intensity.
3Measurement precision
If sequential spectral scanning is used, then spectral resolution is achieved, but imaging speed is reduced
Solution Approach 1:
The optical filter simultaneously transmits multiple spectral passbands through all filter stages at the same time, enabling parallel capture of multiple spectral bands in a single exposure. This continuous simultaneous action eliminates the need for sequential scanning, thereby maintaining high spectral resolution while dramatically improving imaging speed.
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 real-time multi-spectral imaging with improved transmission values, faster scanning speed, lower losses, and reduced costs by allowing simultaneous capture of multiple spectral bands, enhancing the efficiency of multi-spectral imaging systems.
Implementation Method 1
each of the at least two optical filter stages may comprise at least one entrance polarizing element
Implementation Method 2
each of the at least two optical filter stages may comprise at least one constant retarding element
Data Source
Figure 1~2c
Figure 3~4
Figure 5
AI summary
The invention relates to an optical filter (1) for transmitting light (13) of a pass wavelength (17), comprising at least two optical filter stages (3) arranged along a transmission direction (11), along which the light (13) of the pass wavelength (17) is transmitted through the optical filter (1), wherein each of the at least two optical filter stages (3) comprises at least one entrance polarizing element (5) and at least one constant retarding element (7). The invention further relates to a camera (53) for simultaneously capturing at least two images, wherein each image is limited to light (13) in a limited spectral band (44) and to a multi-spectral imaging system (87) and an illumination system (73) applying the inventive optical filter (1). Solutions of the art have low peak transmission values and may furthermore only provide monochrome images in real time. The present invention improves optical filters (1) of the art by each of the at least two optical filter stages (3) comprising a periodic transmission characteristic (35) that extends over a working wavelength range (41), wherein each transmission characteristic (35) comprises at least two peaks (43c - 43e), which each overlap at least one peak (43c - 43d) of each of the other transmission characteristics (35) and wherein an overall transmission characteristic (29) of the optical filter (1) comprises at least two spectral passbands (45) that are spectrally separated from each other. The inventive camera (53), multi-spectral imaging system (87) and inventive illumination system (73) apply an optical filter (1) according to the invention.