Document Reader Polarization Lighting Homogeneity
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Solution Overview
Problem
Conventional document readers face challenges in achieving homogeneous illumination and correcting color distortions in identification documents due to inhomogeneous lighting and optical effects from security features, leading to suboptimal image quality.
Innovation Solution
A document reader design incorporating a light source with a first and second polarization filter, along with a transparent or semi-transparent lighting element, ensures only desired light components are scattered and detected, improving the optical capture of identification documents by controlling polarization and providing compact, homogeneous illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional document readers illuminate identification documents diffusely or from the side, then the device structure is simple, but the illumination homogeneity is poor and color distortions occur
Solution Approach 1:
The patent introduces a light guide element as an intermediary component between the light source and the identification document. This light guide element receives light from the light source and redistributes it across the document surface, achieving homogeneous illumination without requiring complex multi-source arrangements. The light guide element acts as a mediator that transforms direct light into diffuse, uniform illumination.
Solution Approach 2:
The patent changes the optical parameters of the illumination system by introducing polarization filters and a light guide element with specific optical properties. The polarization filters control the polarization state of light, while the light guide element modifies the spatial distribution of light intensity, transforming the illumination characteristics to achieve homogeneity.
2Measurement precision
If conventional document readers accept color distortions in digital image capture, then the device complexity is low, but the image quality is poor
Solution Approach 1:
The patent introduces polarization filters as intermediary optical components between the light source and the identification document, and between the document and the image sensor. These filters selectively transmit or block light based on polarization state, enabling precise control over which light components reach the sensor, thereby improving image quality by reducing unwanted reflections and enhancing contrast.
Solution Approach 2:
The patent changes the polarization parameter of light throughout the optical path. By controlling the polarization state of illumination light and the polarization sensitivity of the detection system, the patent enhances the ability to distinguish document features and reduces optical artifacts, thereby improving measurement precision.
3Illumination intensity
If document readers use side illumination, then the device structure is simple, but lighting inhomogeneity increases
Solution Approach 1:
The light guide element serves as a mediator that receives light from a compact light source and redistributes it uniformly across the document surface. This intermediary component transforms the spatial distribution of light, converting point-source or localized illumination into area-wide homogeneous illumination.
Solution Approach 2:
The patent transitions from one-dimensional side illumination to a more distributed illumination pattern by introducing the light guide element. This element spreads light in multiple directions and across a larger area, effectively adding spatial dimensions to the illumination distribution and achieving uniform coverage.
4Reliability
If document readers activate security features like holograms, then security verification is enabled, but optical artifacts are generated
Solution Approach 1:
The polarization filters act as intermediary components that selectively interact with light reflected from security features like holograms. By controlling the polarization state, the system can enhance the visibility of genuine security features while suppressing spurious optical artifacts, thereby improving the reliability of security verification.
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 enhances the quality of optical document detection by isolating desired light components and reducing optical artifacts, resulting in improved image homogeneity and reduced need for software corrections.
Implementation Method 1
a first polarizing filter... wherein the light source is configured to generate light and couple the generated light into the lighting element via the first polarizing filter
Implementation Method 2
a lighting element with a luminous surface... the lighting element being configured to emit the coupled light via the luminous surface in the direction of the identification document
Implementation Method 3
a detection device comprising a second polarizing filter and an image sensor, wherein the image sensor is configured to detect light emanating from the identification document via the second polarizing filter
Implementation Method 4
an image sensor, wherein the image sensor is configured to detect light emanating from the identification document
Data Source
Figure 1
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AI summary
The invention relates to a document reader (100) for optically detecting an identification document (107). The document reader (100) comprises a lighting device (101) which includes a light source (101a), a first polarizing filter (101b) and a lighting element (101c) with a luminous surface, wherein the light source (101a) is configured to generate light and couple the generated light into the lighting element (101c) via the first polarizing filter (101b), wherein the lighting element (101c) is configured to emit the coupled light via the luminous surface in the direction of the identification document (107).The document reader (100) further comprises a detection device (103) which includes a second polarizing filter (103a) and an image sensor (103b), wherein the image sensor (103b) is configured to detect light emanating from the identification document (107) via the second polarizing filter (103a) in order to optically detect the identification document (107). The invention further relates to a corresponding method.