Backside-Illuminated Imager for Near-Infrared Biometric Capture
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Solution Overview
Problem
Biometric imaging systems face challenges in collecting robust data due to skin and iris pigmentation, which can mask or hide unique structural elements, especially when using traditional CMOS imagers with low sensitivity to near-infrared light.
Innovation Solution
A biometric imaging system utilizing a light source emitting electromagnetic radiation in the range of 700 nm to 1200 nm, combined with an imager device having a semiconductor layer less than 10 microns thick with doped regions and a textured region, achieving high external quantum efficiency and fast response times, allowing for effective capture of iris patterns even through pigmentation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional CMOS imagers with front side illumination are used, then the device structure is simple and manufacturing is easier, but the sensitivity to near-infrared light is low and quantum efficiency is poor
Solution Approach 1:
The patent inverts the traditional illumination direction by using backside illumination instead of front side illumination. The light source is positioned behind the semiconductor substrate, allowing near-infrared light to pass through the substrate and reach the photodiodes from the backside. This inversion enables the imager to achieve high quantum efficiency for near-infrared wavelengths while maintaining a relatively simple device structure.
2Measurement precision
If skin and iris pigmentation is present, then the individual has unique biometric characteristics, but the pigmentation masks or hides unique structural elements reducing detection accuracy
Solution Approach 1:
The patent changes the wavelength parameter of the incident light from visible light to near-infrared light (700-1200 nm). Near-infrared light has different interaction properties with biological tissues compared to visible light. The longer wavelength near-infrared light can penetrate through pigmented tissues more effectively and is less absorbed by melanin, allowing the unique structural elements of the iris and skin to be detected despite the presence of pigmentation.
3Reliability
If a thicker semiconductor layer is used, then the absorption of infrared light is improved, but the response time increases and manufacturing precision becomes more difficult to achieve
Solution Approach 1:
The patent introduces an intermediary layer or structure that facilitates the absorption of near-infrared light without requiring a thick semiconductor layer. This could include anti-reflective coatings, optical cavities, or resonant structures positioned between the light source and the photodiodes that enhance light absorption efficiency. This intermediary approach allows effective infrared light absorption while maintaining fast response times and manufacturing precision.
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 system provides efficient biometric data capture with high signal-to-noise ratio and improved quantum efficiency in both visible and infrared spectra, reducing pattern interference and enabling precise iris identification.
Implementation Method 1
an imager device positioned to receive the electromagnetic radiation upon reflection from an individual to generate an electronic representation of the individual
Implementation Method 2
a textured region positioned to interact with the electromagnetic radiation. The imaging device has an external quantum efficiency of at least about 33% for electromagnetic radiation having at least one wavelength of greater than 800 nm
Data Source
AI summary
Systems, devices, and methods for identifying an individual in both cooperative and non-cooperative situations are provided. In one aspect, for example, a system for identifying an individual can include an active light source capable of emitting electromagnetic radiation having at least one wavelength of from about 700 nm to about 1200 nm, and an imager device positioned to receive the electromagnetic radiation upon reflection from an individual to generate an electronic representation of the individual. The system can also include an image processing module functionally coupled to the imager device to receive the electronic representation. The image processing module processes the electronic representation into an individual representation having at least one substantially unique identification trait. The imager device can include a semiconductor device layer having a thickness of less than about 10 microns, at least two doped regions forming a junction, and a textured region positioned to interact with the electromagnetic radiation, and can have an external quantum efficiency of at least about 33% for at least one wavelength of greater than 800 nm.