Surface-Emitting Laser Diode Illumination for Document Examination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional devices for optically examining documents of value face challenges with inhomogeneous illumination and high power consumption due to the use of halogen lamps, which also have limited service life and large space requirements, and edge-emitting laser diodes provide unsatisfactory intensity distribution and coherence.
Innovation Solution
A device utilizing surface-emitting laser diodes with a control system to generate a homogeneous illumination pattern, allowing for efficient and coherent illumination of documents, with the option to use multiple diodes arranged in a matrix or hexagonal lattice for improved beam shaping and reduced diffraction, enabling reliable feature detection without the need for homogenization elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If halogen lamps are used for illumination, then adequate cooling and large space are required, but illumination intensity and spectral range are sufficient
Solution Approach 1:
The patent transitions from broadband thermal radiation sources (halogen lamps) to narrowband coherent radiation sources (laser diodes), fundamentally changing the spectral parameters and illumination mechanism. This allows achieving sufficient illumination intensity with much lower power consumption and without requiring complex cooling systems.
Solution Approach 2:
The patent replaces the mechanical/thermal illumination system (halogen lamp with reflector and cooling apparatus) with an optical/electronic system (laser diode array). This substitution eliminates the need for mechanical cooling components while maintaining or improving illumination performance.
2Use of energy by stationary object
If edge-emitting laser diodes are used, then power consumption is reduced, but intensity distribution is inhomogeneous and coherence is high causing speckle patterns
Solution Approach 1:
The patent divides the illumination task across multiple surface-emitting laser diodes arranged in an array, where each diode contributes to the overall homogeneous illumination pattern. This segmentation allows combining the low power consumption of laser diodes with uniform intensity distribution, avoiding the speckle patterns caused by high coherence of single edge-emitting diodes.
Solution Approach 2:
The patent specifically selects surface-emitting laser diodes that provide homogeneous intensity distribution across the illumination area, directly addressing the inhomogeneity problem of edge-emitting diodes while maintaining low power consumption and reducing coherence-induced speckle patterns.
3Illumination intensity
If conventional lighting devices are used, then illumination is provided, but device size and cooling requirements increase complexity
Solution Approach 1:
The patent replaces complex mechanical illumination systems with compact semiconductor laser diodes, eliminating the need for reflectors, filters, and cooling mechanisms. This substitution dramatically reduces device complexity while maintaining effective illumination for document examination.
Solution Approach 2:
The laser diode array serves multiple functions simultaneously: illumination, spectral filtering (through wavelength selection), and compact integration. This multi-functionality eliminates the need for separate optical components, reducing overall device complexity.
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 solution provides a compact, energy-efficient, and thermally stable illumination system with reduced speckle patterns and improved coherence, enabling reliable detection of document features with increased sensitivity and reduced data processing complexity.
Implementation Method 1
which has at least one surface-emitting laser diode
Implementation Method 2
This can, in particular, be luminescence radiation excited within the valuable document
Implementation Method 3
optical radiation reflected from the valuable document
Implementation Method 4
optical radiation passing through it
Data Source
Figure 1~2
Figure 3~13
Figure 8~9
AI summary
The device has an illumination unit for illuminating a value document (12) in a part of a detection area, which contains a surface emitting laser diode. A control device is provided for controlling the laser diode, and a detection device is provided for detecting optical radiation out of a part of the detection area. The illumination unit contains another surface emitting laser diode for generating a predetermined light pattern in the detection area, and the control device is formed for controlling the other laser diode. An independent claim is also included for a method for optical examination of a value document in a detection area, involves illuminating the value document by an illumination unit.