Variable-Focus Document Imaging for IR and White Light Sharpness
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Solution Overview
Problem
Document capture devices struggle to achieve ideal focus for both infrared and white light illumination due to chromatic aberrations, resulting in reduced image sharpness for authentication features.
Innovation Solution
A document capture device with adjustable optics and lighting for multiple wavelength ranges, controlled by an electronic unit to capture images with high sharpness under different lighting conditions, and a system for compensating for temperature drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the optics are corrected for chromatic aberrations to focus multiple wavelength ranges at a single focus, then image quality in the visible spectrum is improved, but the infrared range is not sharply imaged because the ideal focus lies in different planes for different wavelength ranges
Solution Approach 1:
The patent implements a dynamically adjustable focus mechanism that allows the optics to change focus position based on the illumination wavelength range being used. The control unit detects the current wavelength range and automatically adjusts the focus to the optimal position for that specific range, enabling sharp imaging across IR, visible, and UV spectrums without compromising any single wavelength range
2Adaptability or versatility
If a compromise focus position is chosen between IR and white light illumination, then both wavelength ranges can be captured, but neither is captured at ideal focus, reducing maximum achievable sharpness
Solution Approach 1:
Rather than using a static compromise focus position, the system dynamically adjusts the focus to the ideal position for each wavelength range. The control unit switches between different focus positions depending on whether IR, white light, or other wavelength ranges are being used, ensuring maximum sharpness is achieved for each specific illumination condition
3Manufacturing precision
If the focus is adjusted for optimal white light imaging, then visible spectrum authentication features are sharply captured, but infrared authentication features lose sharpness
Solution Approach 1:
The system dynamically compensates for chromatic aberration effects by adjusting the focus position according to the wavelength range being used. When switching between white light and infrared illumination, the control unit automatically shifts the focus to the optimal position for each range, eliminating the need to choose between visible and IR sharpness
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 high-sharpness imaging of authentication features under both infrared and white light, facilitating reliable and automated document verification.
Implementation Method 1
a lighting device (120) configured for illumination with at least two different wavelength ranges
Implementation Method 2
the camera having an image sensor (112) and optics (114), the optics having adjustable focus
Implementation Method 3
a camera (110), the camera having an image sensor (112)
Data Source
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AI summary
A document capture device (100) for optically capturing a document (102) is disclosed, comprising: - a camera, wherein the camera (110) has an image sensor (112) and optics (114), wherein the optics (114) has an adjustable focus, - a lighting means (120), wherein the lighting means (120) is configured for illumination with at least two different wavelength ranges, - a document holder (130), - an electronic control, wherein the electronic control is configured to control the camera (110) and the lighting means (120) at least for a first capture with illumination in a first wavelength range and a first focus, and for a second capture with illumination in a second wavelength range and a second focus.Also disclosed is a document verification system (200) comprising a document recording device (100) and an electronic evaluation device (210), wherein the electronic evaluation device (210) is configured to receive and evaluate the recordings.