Biometric Imaging System Using Pulsed Illumination to Reduce Ambient Light

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Solution Overview

Problem

Existing biometric imaging systems struggle to capture clear images of biometric features in high ambient light environments without requiring mechanical shielding or direct contact with the subject.

Innovation Solution

A system comprising a 2D sensor array, an optical imaging system with autofocus, and an illumination system that uses pulsed or flashed light sources to minimize ambient light exposure, allowing for effective imaging in bright conditions without mechanical shielding.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If mechanical shielding is used to block ambient light, then ambient light interference is reduced, but device complexity increases and contact with the subject is required

Engineering Contradiction:

Improveambient light interferenceVSAvoidmechanical shielding structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent replaces mechanical shielding structures with an electronic shutter system that controls light exposure electronically. The shutter mechanism opens and closes at precise moments to allow only illumination light to reach the sensor while blocking ambient light, eliminating the need for physical mechanical shields and their associated complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system uses periodic pulsing of the illumination source combined with synchronized shutter opening and closing. The illumination is flashed in brief periods, and the shutter opens only during these flash periods to capture images, while remaining closed during ambient light periods. This periodic action effectively separates illumination capture from ambient light interference.

Inventive Principle:

Principle #19Periodic action

2Illumination intensity

If exposure time is increased to improve image brightness, then image quality improves, but ambient light exposure increases

Engineering Contradiction:

Improveimage brightnessVSAvoidambient light exposure

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The system employs periodic pulsing of the illumination source and synchronized shutter opening. The illumination is delivered in brief flash periods, and the shutter opens only during these flash periods. This timing coordination ensures that the sensor receives illumination light during the flash while blocking ambient light during the same brief period, achieving high image brightness without ambient light contamination.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The system rapidly opens and closes the shutter in sync with the illumination flash, capturing the image during the brief illumination period and excluding ambient light. This rapid timing action effectively 'skips' over the ambient light exposure period, allowing the sensor to capture only the illumination light without being exposed to ambient light during the capture moment.

Inventive Principle:

Principle #21Skipping (Rushing through)

3Object-affected harmful factors

If illumination intensity is increased to overcome ambient light, then image contrast improves, but energy consumption increases

Engineering Contradiction:

Improveambient light interferenceVSAvoidillumination energy consumption

Core Design Contradiction:

Object-affected harmful factorsVSUse of energy by moving object

Solution Approach 1:

Instead of continuous high-intensity illumination, the system uses periodic pulsed flashes of illumination. The illumination source is activated only in brief periods synchronized with shutter opening, delivering sufficient light intensity to overcome ambient light during the capture moment while remaining off during the rest of the time. This periodic action significantly reduces overall energy consumption compared to continuous illumination.

Inventive Principle:

Principle #19Periodic action

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 effectively captures high-quality biometric images by reducing ambient light exposure to less than 30% of the overall exposure, ensuring sufficient brightness and contrast for accurate biometric measurements in high ambient light conditions.

Implementation Method 1

a 2D sensor array, an optical imaging system with autofocus, and an illumination system that uses pulsed or flashed light sources

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Implementation Method 2

an illumination system that uses pulsed or flashed light sources to minimize ambient light exposure

Methodology Applied

Scientific EffectLight: Light

Data Source

PatentUS9773169B1System for capturing a biometric image in high ambient light environments

Publication Date: 2017.09.26 HID GLOBAL CORP

AI summary

The invention provides an image capture system, apparatus and method for capturing a biometric image in high ambient light environments. Reflections from ambient light can introduce unwanted environmental pattern noise that can interfere with extracting information from a captured biometric image. The invention performs attenuation of ambient light without requiring employment of shielding to prevent ambient light from reflecting off of a surface being imaged. As a result, the invention can be deployed into environments with varied indoor or outdoor lighting characteristics.