Biometric Authentication Luminance Correction for Vignetting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional biometric authentication systems using Shape From Shading (SFS) techniques face challenges in accurately detecting hand position and shape due to vignetting effects and limitations in arranging multiple distance sensors, leading to reduced accuracy in personal identification and authentication.
Innovation Solution
An image processing apparatus and method that includes a light source, imaging device, luminance computing unit, and coefficient computing unit to correct luminance values based on distance from the light source, improving the accuracy of hand position detection and shape recognition by accounting for vignetting and distance dependencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple distance sensors are used to improve distance measurement accuracy, then measurement precision is improved, but device complexity and size increase
Solution Approach 1:
The patent replaces multiple mechanical distance sensors with an optical-based Shape From Shading (SFS) technique using a single imaging device. The SFS algorithm calculates three-dimensional shape information by analyzing luminance distribution in captured images, eliminating the need for multiple physical distance sensors while maintaining measurement capability.
Solution Approach 2:
The patent introduces luminance correction as an intermediary processing step between image capture and shape calculation. By correcting luminance values to account for vignetting effects and distance dependencies, the system enables accurate SFS-based distance measurement using only a single imaging device, rather than requiring multiple sensors.
2Illumination intensity
If the distance from light source to capturing target is made sufficiently long to reduce vignetting effects, then luminance distribution becomes more uniform, but the apparatus size increases and physical restrictions are violated
Solution Approach 1:
The patent converts the harmful vignetting effect into a useful measurement tool. Instead of trying to eliminate vignetting by increasing distance, the system deliberately maintains a short distance where vignetting is present, then uses luminance correction algorithms to compensate for the effect. This allows accurate shape and distance measurement while keeping the apparatus compact.
Solution Approach 2:
The patent changes the processing approach by introducing luminance correction coefficients that account for distance and vignetting effects. Rather than changing the physical distance parameter, the system changes the luminance parameter through computational correction, enabling accurate measurement at short distances.
3Measurement precision
If a guide member is provided to guide hand position during registration, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent enables the imaging system to self-guide the capturing target through software-based detection. The system automatically detects the position and orientation of the hand in the captured image using SFS technology, eliminating the need for physical guide members. The hand is guided to the correct position through computational analysis rather than mechanical guidance.
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
Enhances the accuracy of biometric authentication by correcting luminance values and improving distance measurement, thereby improving the matching accuracy between registered and captured biometric data, even in near-field optical systems where traditional SFS techniques fail.
Implementation Method 1
an imaging device configured to capture the object
Implementation Method 2
the so-called vignetting occurs at the lens. In a case in which the distance from the light source to the capturing target is sufficiently long, the distances from the light source to each of the points on the capturing target may be regarded as being the same, and effects of the vignetting are relatively small.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6B
AI summary
An image processing apparatus includes a light source to irradiate light on an object, an imaging device to capture the object, a luminance computing unit to compute a luminance at a plurality of positions on the object, and a coefficient computing unit. The coefficient computing unit computes a correction coefficient for each of the plurality of positions, according to a distance from the light source to each of the plurality of positions and the luminance at each of the plurality of positions.