Spectral Image Sensor Using Telecentric Interference Filters
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Solution Overview
Problem
Conventional hyper-spectral cameras are limited to one-dimensional spectral imaging due to the use of expensive diffraction gratings and require high costs, making them inefficient for acquiring spectral images in multiple wavelength ranges.
Innovation Solution
A spectral image sensor device with a first optical system, a luminous flux selecting member, and an interference filter that allows selective wavelength selection, eliminating the need for diffraction gratings by using a tele-centric optical system and interference filters with different wavelength characteristics, enabling two-dimensional spectral imaging across a predetermined wavelength range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a diffraction grating is used to separate light into spectral components, then spectral image acquisition is enabled, but the device complexity and cost increase significantly
Solution Approach 1:
The optical system is segmented into multiple independent interference filters, each responsible for selecting a specific wavelength range. This replaces the monolithic diffraction grating with modular filter units that can be independently controlled and optimized, reducing overall system complexity while maintaining spectral imaging capability
Solution Approach 2:
The interference filters are made dynamically controllable through position adjustment mechanisms, allowing the system to switch between different wavelength ranges by moving specific filters into the optical path. This dynamic configuration replaces the static spectral separation of diffraction gratings with an adaptable filter selection system
2Adaptability or versatility
If a diffraction grating is used for spectral separation, then wavelength range coverage is achieved, but the manufacturing cost increases
Solution Approach 1:
The wavelength range is divided into multiple bands, each handled by a separate interference filter. This segmentation allows each filter to be manufactured for a specific wavelength range, reducing the overall cost compared to manufacturing a single expensive diffraction grating that covers the entire spectrum
Solution Approach 2:
Interference filters are replaced as cheaper alternatives to diffraction gratings. Multiple low-cost filters can be manufactured and replaced individually if needed, whereas a diffraction grating represents a high-cost, single-component solution that is difficult to replace or upgrade
3Measurement precision
If the luminous flux selecting member is positioned at the focal point, then wavelength selection precision is improved, but the optical system becomes more sensitive to positioning errors
Solution Approach 1:
The optical system employs asymmetric telecentric design where the aperture stop is positioned at the focal point of the objective lens, creating a telecentric image space. This asymmetric configuration provides angular insensitivity that compensates for positioning errors, allowing the system to maintain wavelength selection precision while reducing sensitivity to exact filter positioning
Solution Approach 2:
The system changes the optical parameters by implementing telecentric design, which modifies the chief ray angles to be perpendicular to the image plane. This parameter change makes the system less sensitive to positioning variations, as the angular relationships remain consistent even when filter positions vary slightly
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 device simplifies the design, reduces costs, and allows for easy wavelength selection and change, achieving two-dimensional spectral imaging without the need for expensive diffraction gratings, while maintaining efficient wavelength selection and image acquisition.
Implementation Method 1
an optical member where the luminous fluxes selecting member is disposed so as to be at focal position on an object side or approximately at focal position on an object side, and an interference membrane is formed
Data Source
AI summary
A spectral image sensor device comprises a first optical system 47 and 48 including an objective lens, a luminous fluxes selecting member 55 for allowing a part of the luminous fluxes to pass via the first optical system selectively, an optical member 58 where the luminous fluxes selecting member is disposed so as to be at focal position on an object side or approximately at focal position on an object side, and an interference membrane is formed, and wavelength range of the luminous fluxes for passing through the luminous fluxes selecting member is selected, depending on position of the luminous fluxes selecting member, a second optical system 49 for guiding the luminous fluxes toward the optical member, and an image sensor 52 for receiving a light in wavelength range as selected by the optical member.