Value Document Sensor With Microlens Array Illumination
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Solution Overview
Problem
Existing optical sensors for checking documents of value face challenges in adapting to different spectral requirements due to limited space and inefficiencies in illumination, leading to suboptimal spectral resolution and intensity when trying to detect optical properties in a spatially limited area.
Innovation Solution
A sensor platform with a light source receptacle and microlens array, where multiple chip-shaped light sources with different emission spectra are arranged to ensure efficient light collection and imaging optics to focus light onto a defined area, allowing for easy reconfiguration of light sources and detection of various spectral ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional detectors with different color filters are integrated to increase spectral resolution, then spectral resolution is improved, but device complexity and space requirements increase making it hardly possible due to limited space inside the sensor housing
Solution Approach 1:
The patent combines multiple light sources with different emission spectra into a single illumination device, replacing the need for multiple detectors with different color filters. The microlens array focuses light from multiple sources onto a single detector, merging multiple spectral measurement functions into one detection element, thereby improving spectral resolution without increasing device complexity
Solution Approach 2:
Instead of using multiple detectors to capture different spectral ranges simultaneously, the patent inverts the approach by using multiple light sources to illuminate the document at different wavelengths and detecting all reflected light with a single detector. This inversion of the detection strategy resolves the space constraint while achieving spectral analysis
2Reliability
If a minimum distance is maintained between the light guide and sensor due to relative movement, then reliability of detection is improved, but illumination intensity decreases due to light divergence over the larger illuminated area
Solution Approach 1:
The patent introduces a microlens array as an intermediary optical element between the light sources and the document. This microlens array focuses the diverging light from multiple sources onto a concentrated spot on the document surface, maintaining high illumination intensity even at the minimum distance required for reliable detection with relative movement
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 the production of sensors that can efficiently detect optical properties in a spatially limited area with high light-gathering efficiency and adaptability to different spectral requirements, improving the accuracy and intensity of document inspection.
Implementation Method 1
a microlens array which has a plurality of microlenses, wherein the microlens array and the light source receptacle can be arranged relative to each other such that each of the light source positions is assigned to exactly one of the microlenses
Implementation Method 2
The imaging optics focus the light emitted by the lighting device onto the valuable document being inspected
Implementation Method 3
optical sensors that detect the light reflected from the documents
Data Source
Figure 1a~1c
Figure 2a~2b
Figure 3a~3c
AI summary
The invention relates to a sensor for checking value documents, comprising an illumination unit for illuminating a value document, an imaging optics and a detecting unit. The illumination unit of the sensor comprises a light source receptacle having at least two light sources that have different emission spectra. Furthermore, the illumination unit comprises a microlens array containing a plurality of microlenses. The microlens array and the light source receptacle are arranged such that each of the light sources arranged on the light source receptacle is associated with exactly one of the microlenses. The sensor can be produced from a sensor platform from which different sensors for detecting the optical properties of a value document in a spatially delimited region can be produced in a simple manner for different spectral requirements.