Spectral Sensor Microlens Defocusing for Sensitivity and Selectivity
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Solution Overview
Problem
Conventional spectral sensors face a trade-off between spectral selectivity and sensitivity due to the inherent light reduction caused by integrated filters, which reduces the amount of light reaching the light detecting elements.
Innovation Solution
The configuration of the microlens is adjusted such that the smallest light spot size is positioned behind the light detecting element, and the microlens is defocused to minimize the variation in angles of light incidence on the interference filter, enhancing both sensitivity and spectral selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If integrated filters are used to achieve spectral selectivity, then spectral selectivity is improved, but sensitivity deteriorates due to reduced light reaching the light detecting elements
Solution Approach 1:
The filter system is segmented into multiple independent interference filters, each tuned to transmit a specific spectral band. This allows selective transmission of different wavelength ranges to different light detecting elements while maintaining high spectral selectivity without requiring a single complex filter that would block excessive light
Solution Approach 2:
Different spectral bands are directed to different spatial locations (rows or groups of light detecting elements) through the mosaic configuration of interference filters. Each filter location is optimized for its specific spectral band, allowing high spectral selectivity locally while the overall system maintains high sensitivity by capturing light across multiple spectral channels in parallel
2Productivity
If a mosaic configuration of filters is used to acquire spectral information in a single exposure, then productivity is improved, but device complexity increases
Solution Approach 1:
Multiple interference filters with different spectral transmission characteristics are merged into a single mosaic array structure that is integrated with the light detecting element array. This combining of multiple filter functions into one unified device enables simultaneous spectral imaging across multiple bands in a single exposure, improving productivity while the integrated design manages the complexity through standardized fabrication processes
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 increases the fraction of light within the spectral bands transmitted through the interference filter, thereby improving the sensitivity and spectral selectivity of the spectral sensor.
Implementation Method 1
a microlens (120) configured to direct light towards the light detecting element (110) through the interference filter (130)
Implementation Method 2
interference filter (130) arranged between the light detecting element (110) and the microlens (120). The interference filter (130) is configured to transmit light in one or more spectral bands
Data Source
Figure 1
Figure 2~3
AI summary
The present invention relates to a spectral sensor. The spectral sensor (10) comprising: a light detecting element (110); a microlens (120); and an interference filter (130) arranged between the light detecting element (110) and the microlens (120), and configured to transmit light in one or more spectral bands; wherein the microlens (120) has an effective focal length (F) exceeding a distance (D) between the microlens (120) and the light detecting element (110). The microlens (120) may be configured such that light refracted by the microlens (120), to be transmitted through the interference filter (130), converges towards a position (P) behind the light detecting element (110). The present invention further relates to an image sensor (20) comprising a plurality of spectral sensors (10).