Dual-Aperture Filter Lens Assembly for Iris Recognition
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Solution Overview
Problem
Consumer devices, such as smartphones, face challenges in implementing iris recognition due to the small size of the iris target on a curved and reflective surface, occlusions, specular reflections, and the need for specialized NIR illumination, which increases costs and requires complex dual-band optical systems.
Innovation Solution
An optical system that focuses both visible and near-infrared spectral regions onto a multi-wavelength sensor using a simple lens assembly with a filter allowing NIR radiation through a larger aperture and a smaller aperture for visible light, enabling simultaneous imaging on a single sensor with improved spatial resolution for iris recognition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dedicated NIR imaging system is used for iris recognition, then spatial resolution and imaging quality are improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent applies universality by designing a single optical system that can capture both visible light images and near-infrared images for iris recognition. The imaging device includes a sensor array that detects both visible and NIR wavelengths, eliminating the need for separate dedicated NIR imaging systems while maintaining the required spatial resolution for iris pattern capture.
Solution Approach 2:
The patent employs parameter changes by utilizing the wavelength-dependent properties of optical materials. Different lens materials are selected for their transparency characteristics at visible and NIR wavelengths, allowing the same optical path to effectively image both spectral regions with appropriate focal lengths and aperture settings.
2Adaptability or versatility
If a movable NIR filter is added to achieve dual-band imaging, then spectral selectivity is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent applies segmentation by dividing the lens assembly into multiple lens elements with different optical properties. Each lens element is optimized for specific wavelength ranges, with materials selected for their transparency characteristics at visible and NIR wavelengths. This segmented approach enables spectral selectivity without requiring movable filters.
Solution Approach 2:
The patent uses an intermediary approach by incorporating a beam splitter or dichroic mirror in the optical path that separates visible and NIR wavelengths to different detection paths or sensors. This intermediary element enables simultaneous capture of both spectral regions with appropriate filtering without requiring movable filter mechanisms.
3Use of energy by moving object
If the aperture is enlarged to capture more light for NIR imaging, then light gathering capability is improved, but field of view and spatial resolution are reduced
Solution Approach 1:
The patent applies dynamics by implementing an adjustable aperture mechanism that can dynamically change the aperture size based on the imaging mode (visible or NIR). The aperture can be enlarged when NIR imaging is required to maximize light gathering capability, and adjusted to appropriate sizes for visible light imaging to maintain optimal field of view and spatial resolution.
Solution Approach 2:
The patent employs local quality by using different aperture configurations for different spectral regions. The optical system is designed with zone-specific optimization where the effective aperture size and shape can be adjusted locally for NIR wavelengths to maximize light collection, while maintaining appropriate aperture characteristics for visible light to preserve spatial resolution and field of view.
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 effective iris recognition on consumer devices by providing sufficient spatial resolution and reducing costs through a lens assembly that can be fabricated using plastics molding, allowing for both visible and infrared images to be acquired with improved optical quality.
Implementation Method 1
An optical system focuses both visible and near-infrared spectral regions onto a multi-wavelength sensor
Implementation Method 2
the lens assembly includes a first region made of a first material and a second region made of a second material, the second region shaped to partially focus the second band of wavelengths onto the focal plane
Implementation Method 3
a filter allowing NIR radiation through a larger aperture and a smaller aperture for visible light
Data Source
AI summary
An optical system for an image acquisition device comprises a filter comprising a central aperture arranged to transmit both visible and selected near infra-red (NIR) wavelengths and a peripheral aperture arranged to block visible wavelengths and to transmit the NIR wavelengths. An image sensor comprises an array of pixels including pixels sensitive to visible wavelengths and corresponding pixels sensitive to the NIR wavelengths. A lens assembly is axially located between the filter and the image sensor and comprises a plurality of lens elements. The lens elements are arranged to simultaneously focus NIR light received from a given object through central and peripheral apertures of the filter and visible light received from the object through the central aperture onto the sensor surface.