Document Inspection Sensor Microlens Array Illumination
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Solution Overview
Problem
Existing document value sensors face inefficiencies in illuminating a spatially limited area of documents with multiple light sources, leading to uneven illumination and reduced intensity due to the use of beam splitters and light guides.
Innovation Solution
A sensor system with a microlens array and imaging optics that collects and images the emission light from multiple light sources onto a defined, spatially limited area of the document, ensuring efficient and uniform illumination using a microlens array and imaging optics to focus light from multiple sources onto a single area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If beam splitters are used to combine light paths from multiple light sources, then a common beam path is achieved, but a large proportion of emission light remains unused due to partial transparency
Solution Approach 1:
Multiple light paths are merged into a single common beam path using beam splitters arranged in a specific configuration. The patent combines light from multiple light sources through sequential beam splitting and recombination, achieving a unified illumination path while minimizing light loss through optimized optical geometry.
Solution Approach 2:
Beam splitters serve as intermediary optical elements that redirect and combine light paths. The patent uses these intermediary components to merge multiple light sources into a common path, with the beam splitters acting as mediators that manage light distribution and combination efficiently.
2Ease of operation
If a light guide is used to direct light from multiple light sources onto the document, then illumination is achieved, but the illuminated area is relatively large and illumination intensity is correspondingly low due to light divergence
Solution Approach 1:
The illumination system is segmented into multiple discrete light sources rather than using a single extended light guide. Each light source is positioned and oriented to contribute to a focused illumination area, avoiding the divergence problems inherent in extended light guides while maintaining ease of illumination delivery.
Solution Approach 2:
The patent transitions from a one-dimensional light guide approach to a multi-dimensional arrangement of discrete light sources. By positioning multiple point sources in specific three-dimensional configurations and using reflective surfaces, the system achieves focused illumination without the area expansion problem of light guides.
3Adaptability or versatility
If multiple differently colored light sources are used to illuminate the same area, then comprehensive spectral coverage is achieved, but the illumination is uneven and intensity is reduced without proper optical concentration
Solution Approach 1:
Multiple light sources with different emission spectra are merged into a common beam path using beam splitters. The patent combines these diverse light sources spatially and spectrally, maintaining comprehensive spectral coverage while achieving uniform illumination intensity through the shared optical path and focused geometry.
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 solution allows for effective, uniform illumination of a small area on documents, enhancing the detection of optical properties and improving the spatial resolution of document authentication and condition assessment.
Implementation Method 1
The light emitted by the illumination device is collected by a microlens array, which is part of the illumination device and which is arranged between the light sources and the imaging optics. The microlens array of the illumination device contains a multiplicity of microlenses that direct the collected light onto the imaging optics.
Implementation Method 2
The imaging optics are arranged on the side of the microlens array that faces the document of value. The imaging optics are designed to collect the emission light of each of the light sources after it has passed through the respective microlens and to image it onto a document of value to be checked by the sensor.
Data Source
AI summary
The invention relates to a sensor for inspecting value documents, said sensor having an illumination device for illuminating a value document, imaging optics and a detection device. The illumination device of said sensor contains a plurality of light sources arranged next to one another with emission spectra that differ from one another and a microlens array comprising a plurality of microlenses. The microlens array and the light-source holder are located in such a way that each of the light sources that are positioned on the holder is associated uniquely with one of the microlenses. The measuring plane of the sensors lies in such close proximity to the focal point of the imaging optics that the light from the different light sources emitted by the illumination device is imaged largely onto the same illuminated region of the measuring plane.