Biometric Composite Imaging System Using Patterned Optical Filters
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Solution Overview
Problem
Current iris recognition systems on mobile devices require separate near infrared and visible light cameras, leading to increased size, cost, and complexity, as well as compromised user experience due to the inability to multiplex both imaging functions with a single camera.
Innovation Solution
A biological feature composite imaging system using patterned bandpass optical filters to split incident light into visible and infrared wavebands, allowing simultaneous imaging without the need for mechanical filter switching, and incorporating an image sensor with distinct regions for each band to prevent interference and enhance image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a separate near infrared camera module is added for iris recognition, then iris recognition function is achieved, but device complexity and appearance design become complicated
Solution Approach 1:
The front-facing camera module is designed to perform both visible light imaging (selfie) and near infrared imaging (iris recognition) functions. The image sensor can detect both visible light wavelengths (380-760 nm) and near infrared wavelengths (760-880 nm), allowing a single camera to serve multiple purposes and eliminate the need for separate camera modules.
Solution Approach 2:
The patent combines the visible light camera and near infrared camera into a single integrated camera module. The optical filter assembly includes both a visible light passband filter and a near infrared passband filter, allowing both types of light to pass through to the same image sensor, thereby merging two separate imaging systems into one.
2Adaptability or versatility
If a dual-bandpass optical filter is used to allow both visible and infrared light passage, then both imaging functions are enabled, but visible light images become reddish and infrared recognition precision is affected
Solution Approach 1:
The optical filter assembly is divided into distinct regions: a first region with a visible light passband filter and a second region with a near infrared passband filter. The image sensor is similarly divided into a first region for visible light imaging and a second region for near infrared imaging. This segmentation prevents cross-contamination of light wavelengths and eliminates the reddish effect in visible light images while maintaining precise infrared recognition.
Solution Approach 2:
Different regions of the optical filter assembly have different optical properties optimized for specific wavelength ranges. The visible light passband filter region allows visible light through while blocking infrared, and the near infrared passband filter region does the opposite. This local differentiation ensures that each imaging function receives only the appropriate wavelength range, preventing interference and maintaining high precision.
3Device complexity
If the existing front-facing camera is used for infrared imaging, then device integration is improved, but the camera cannot receive infrared light due to coating filtration
Solution Approach 1:
The harmful infrared-blocking coating is removed or modified in the regions of the optical filter assembly designated for near infrared imaging. By extracting or eliminating the filtration property in specific areas, the camera module becomes capable of receiving near infrared light while maintaining its visible light imaging capability in other regions.
Solution Approach 2:
The optical filter assembly acts as an intermediary component that selectively manages light wavelengths. By introducing this intermediate filtering layer with specific regional properties, the system enables the existing camera to receive both visible and near infrared light without requiring complete removal of coatings, thus facilitating integration while maintaining wavelength selectivity.
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
Enables efficient multiplexing of visible light and infrared imaging, improving user experience by maintaining selfie quality and enhancing iris recognition accuracy while reducing system complexity and power consumption.
Implementation Method 1
an optical filter assembly for filtering received light so as to image light of a waveband allowed to pass through the optical filter assembly
Implementation Method 2
an image sensor to image the filtered light on a corresponding region of the image sensor
Data Source
AI summary
An object of the present invention is to provide a biological feature composite imaging technology that multiplexing of the imaging functions and a mobile terminal comprising said composite imaging system. The composite imaging system comprises: a lens assembly (130); an optical filter assembly (120) including at least a visible light bandpass region and an infrared light bandpass region; an image sensor (110) that includes a visible light imaging region, an infrared light imaging region, and a transition region between said two regions, said image sensor (110) operating under one of the visible light imaging mode and the infrared light imaging mode. Under the infrared light imaging mode, specific physical properties of the biological features are used as the image quality information to realize auto-focus of the biological features in the region of interest.