Biometric Sensor Segmentation for Stray Light Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing biometric authentication devices face challenges in improving the signal-to-noise (S/N) ratio during imaging operations, leading to degraded detection accuracy and low-contrast images, especially when detecting temporal changes in biometric information such as pulse wave data.
Innovation Solution
The biometric authentication device employs a configuration where the sensor and illumination device are stacked, with both divided into groups of pixels. The control units synchronize to light only one light emitting element per group in the illumination device and acquire signals from corresponding pixels in the sensor, minimizing stray light and enhancing the S/N ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple light emitting elements are lit simultaneously to improve illumination coverage, then the imaging area is expanded, but the S/N ratio deteriorates due to increased stray light
Solution Approach 1:
The imaging area is divided into multiple regions, each corresponding to a group of light emitting elements. By selectively lighting only the light emitting elements corresponding to the currently imaged region, the patent expands the total imaging area while maintaining high S/N ratio in each sub-region, avoiding the stray light problem that would occur if all elements were lit simultaneously.
Solution Approach 2:
The patent employs time-division multiplexing where light emitting elements are lit sequentially in different time periods rather than simultaneously. Each group of light emitting elements is activated for a specific duration to illuminate its corresponding imaging region, allowing the sensor to capture images from different regions at different times. This periodic activation prevents stray light contamination while achieving comprehensive area coverage.
2Illumination intensity
If all light emitting elements are lit to improve illumination intensity, then the image brightness is enhanced, but the S/N ratio worsens due to increased noise from distant light sources
Solution Approach 1:
The patent applies illumination locally by activating only the light emitting elements that correspond to the current imaging region. This ensures that the illumination intensity is concentrated on the relevant area, providing sufficient brightness for high-quality imaging without introducing stray light from distant or irrelevant light sources that would degrade the S/N ratio.
3Productivity
If imaging operation is performed by all sensor pixels simultaneously to improve detection speed, then the productivity is enhanced, but the S/N ratio deteriorates due to simultaneous reception of stray light from multiple light sources
Solution Approach 1:
The patent synchronizes the periodic activation of light emitting elements with the periodic operation of sensor pixel groups. By coordinating these periodic actions, the system maintains high detection speed through continuous sequential imaging while ensuring that each pixel group only receives light from its corresponding illuminated region, thereby preserving high S/N ratio despite simultaneous operation of multiple pixel groups across different time periods.
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 approach results in improved image contrast and accurate detection of biometric information, including high-contrast images of blood vessel patterns and precise temporal changes in biometric data, by reducing stray light incidence and enhancing signal quality.
Implementation Method 1
The sensor includes a first base material, a plurality of photodiodes and a first control unit. The photodiodes are arranged in a matrix on the first base material and output a detection signal according to an amount of received light.
Implementation Method 2
The illumination device includes a second base material, a plurality of light emitting elements and a second control unit. The light emitting elements are arranged in a matrix on the second base material and apply light received by the photodiodes.
Data Source
AI summary
According to one embodiment, a biometric authentication device includes a sensor and an illumination device. The sensor includes a first base material, a plurality of photoelectric conversion elements and a first control unit. The illumination device includes a second base material, a plurality of light emitting elements and a second control unit. Upon lighting the light emitting element at a predetermined position in the groups of the light emitting elements by the second control unit, the first control unit controls the operation of the photoelectric conversion elements so as to acquire a signal from the photoelectric conversion elements at predetermined positions of the groups of the photoelectric conversion elements.