Spectral Camera Filter Positioning to Prevent Vignetting
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Solution Overview
Problem
In existing spectral cameras, the spectral filter often functions as an unintended diaphragm due to its small optical region, leading to vignetting and a decrease in the effective size of the spectral image.
Innovation Solution
The spectral camera design includes a spectral filter with an optical region that transmits light of a predetermined wavelength, an imaging device with an effective imaging region larger than the optical region, and an imaging optical system that guides the light to be focused at the imaging device. The spectral filter is positioned within a predetermined range along the optical axis, centered around the intersection of the chief ray and the optical axis, to prevent vignetting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the spectral filter uses small reflective films to maintain stable wavelength extraction, then the spectral wavelength stability is improved, but the optical region size is reduced causing vignetting
Solution Approach 1:
The patent resolves the contradiction by moving the spectral filter from a position where it limits the optical region to a position along the optical axis where it does not obstruct light paths. By changing the positional dimension (depth along optical axis), the filter can maintain its small size for wavelength stability while no longer causing vignetting in the image plane.
Solution Approach 2:
The patent introduces an imaging optical system as an intermediary between the spectral filter and the imaging device. This intermediary component properly directs and focuses the light that passes through the filter's limited optical region, ensuring that the full effective imaging region of the imaging device is utilized without vignetting.
2Reliability
If the spectral filter optical region is made small for stability, then the wavelength extraction stability is improved, but the effective imaging region size is reduced
Solution Approach 1:
The patent resolves this contradiction by positioning the spectral filter at a specific depth along the optical axis where its small optical region does not project to limit the effective imaging region. By changing the dimensional position from the image plane to a location in front of the imaging optical system, the filter maintains wavelength stability while the full imaging region remains effective.
3Measurement precision
If the spectral filter is positioned to maintain stability, then the wavelength precision is improved, but vignetting occurs reducing image quality
Solution Approach 1:
The imaging optical system serves as an intermediary that takes the light passing through the spectral filter's small optical region and properly directs it to cover the entire effective imaging region of the imaging device. This intermediary function eliminates vignetting while preserving the wavelength precision provided by the stable filter positioning.
Solution Approach 2:
By repositioning the spectral filter along the optical axis to a location where it does not obstruct the light paths to the image periphery, the patent eliminates vignetting. The filter maintains its precision-oriented small size while the dimensional repositioning prevents the harmful vignetting effect.
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
This configuration prevents vignetting, maintaining the original imaging angle of view and resolution, and allows a wider range of light to be focused on the effective imaging region, reducing the impact of foreign matter and wavelength unevenness.
Implementation Method 1
a spectral filter having an optical region that transmits light having a predetermined wavelength out of incident light
Implementation Method 2
an imaging optical system configured to guide the light having the predetermined wavelength passing through the optical region in such a way that the light having the predetermined wavelength is brought into focus at the imaging device
Data Source
AI summary
A spectral camera includes a spectral filter having an optical region that transmits light having a predetermined wavelength out of incident light; an imaging device having an effective imaging region larger than the optical region; and an imaging optical system configured to guide the light having the predetermined wavelength passing through the optical region in such a way that the light having the predetermined wavelength is brought into focus at the imaging device. The spectral filter is disposed within a predetermined range extending along an optical axis of the imaging optical system and centered around a position where a chief ray of a luminous flux brought into focus at a peripheral section of the effective imaging region intersects with the optical axis.