Long-Pass Filtered Light Sensor for Stable Narrow-Band Imaging
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Solution Overview
Problem
Existing narrow-band imaging technologies face challenges with band-pass filters that attenuate unnecessary wavelengths, leading to reduced light intensity at the periphery of imaging regions and temperature-dependent sensitivity issues due to broad absorption properties of materials like InGaAs and InGaAsP, making them unsuitable for robust narrow-band imaging.
Innovation Solution
A light sensor configuration featuring a photoelectric conversion layer with a long-pass filter that selectively transmits wavelengths longer than the cut-on wavelength, allowing for specific wavelength imaging without the need for narrow-band-pass filters, utilizing materials like carbon nanotubes or quantum dots for sharp spectral sensitivity peaks and reduced temperature dependency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a band-pass filter is used to limit wavelength for narrow-band imaging, then the imaging contrast is improved, but the light intensity is reduced and temperature-dependent sensitivity issues occur
Solution Approach 1:
The patent changes the material parameter of the photoelectric conversion layer from conventional InGaAsP to InGaAs, which has a longer cutoff wavelength (1.7 μm vs 1.35 μm). This material parameter change allows the use of a long-pass filter with a lower cutoff wavelength (e.g., 1.0 μm), thereby transmitting more light intensity while maintaining narrow-band imaging capability through the combination of filter and material spectral characteristics.
2Reliability
If a long-pass filter is used to transmit specific wavelengths, then the temperature sensitivity is reduced, but the spectral selectivity may be insufficient without a narrow-band-pass filter
Solution Approach 1:
The patent merges two wavelength-selection mechanisms into a unified system: (1) the long-pass optical filter that blocks short wavelengths and transmits long wavelengths, and (2) the InGaAs photoelectric conversion layer that has inherent spectral sensitivity peaking at longer wavelengths (1.5-1.7 μm). This combination achieves narrow-band imaging effect without requiring a complex narrow-band-pass filter, reducing device complexity while maintaining spectral selectivity.
3Ease of manufacture
If materials with broad absorption properties like InGaAsP are used, then the manufacturing is easier, but the temperature-dependent sensitivity increases
Solution Approach 1:
The patent changes the material composition parameter from InGaAsP to InGaAs, which has a longer cutoff wavelength and different temperature coefficient. This material substitution maintains manufacturability through established semiconductor fabrication processes while providing reduced temperature-dependent sensitivity, as InGaAs exhibits more stable spectral characteristics over temperature variations compared to InGaAsP.
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 enables efficient narrow-band imaging with improved light intensity distribution and reduced temperature sensitivity, providing a cost-effective solution for imaging specific wavelengths while minimizing unwanted sensitivity outside the target range.
Implementation Method 1
a long-pass filter that is disposed above the photoelectric conversion layer and that selectively transmits a component of incident light, the component having a wavelength longer than or equal to a cut-on wavelength of the long-pass filter
Implementation Method 2
a photoelectric conversion layer; and a long-pass filter that is disposed above the photoelectric conversion layer
Data Source
AI summary
A light sensor includes a photoelectric conversion layer and a long-pass filter that is disposed above the photoelectric conversion layer. The photoelectric conversion layer has a spectral sensitivity characteristic having a first peak at a first wavelength that is longer than a cut-on wavelength of the long-pass filter, and a spectral sensitivity of the photoelectric conversion layer at the cut-on wavelength is greater than or equal to 0% and less than or equal to 50% of a spectral sensitivity of the photoelectric conversion layer at the first wavelength.