POS Image Reader Lighting and Stray Light Control
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Solution Overview
Problem
Conventional image readers experience issues with stray light interference due to the reflection of lighting device emissions from the transparent plate, leading to uneven illumination and reduced reading performance, particularly in POS systems where accurate image capture of code symbols is crucial.
Innovation Solution
The lighting device is strategically placed both within an inner area and an outer area of the imaging region, with an optical-path modifying element, such as a light shield or optical-path modifying element, to redirect potential stray light away from the image detector, ensuring uniform illumination and minimizing stray light interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the lighting device is disposed adjacent to an edge of the transparent plate, then stray light is prevented from arriving at the image detector, but illumination uniformity deteriorates
Solution Approach 1:
The lighting device is positioned not only in the horizontal direction (adjacent to the edge) but also in the vertical direction (below the transparent plate), creating a three-dimensional lighting arrangement. This multi-dimensional positioning allows the lighting device to illuminate the object uniformly while the transparent plate blocks stray light from reaching the image detector.
Solution Approach 2:
The transparent plate serves as an intermediary element between the lighting device and the image detector. It transmits useful light from the object to the image detector while blocking stray light from the lighting device, enabling simultaneous achievement of uniform illumination and stray light prevention.
2Illumination intensity
If the lighting device is placed within the imaging area, then illumination uniformity is improved, but stray light generation increases
Solution Approach 1:
The lighting device is positioned below the transparent plate in the vertical dimension, separate from the imaging area in the horizontal dimension. This spatial separation in multiple dimensions allows the lighting device to illuminate the object uniformly without generating stray light that would interfere with the imaging area.
Solution Approach 2:
The transparent plate acts as a mediator that separates the lighting function from the imaging function spatially. It allows light from the lighting device to reach the object for illumination while blocking stray light from reaching the image detector, enabling both uniform illumination and stray light prevention.
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 arrangement achieves uniform illumination across the image reading area, enhances image resolution, and prevents stray light from affecting the image detector, thereby improving the accuracy and reliability of code symbol capture in POS systems.
Implementation Method 1
an optical lens which forms an image of the object on the image detector through the transparent plate
Implementation Method 2
The lighting device includes an LED (Light Emitting Diode). A part of Light, emitted by the lighting device, which is reflected by the transparent plate
Implementation Method 3
an optical-path modifying element which modifies an optical path of a potential stray light resulting from the light which is emitted by the lighting device and is reflected by at least one of the first and second surfaces
Data Source
AI summary
An image pick-up device, which photographs an object to generate an image signal, including: an opening formed to pass light therethrough; a transparent plate which covers the opening; an image detector arranged to generate the image signal; an optical lens forming an image of the object on the image detector through the transparent plate when the object is positioned in an imaging area; a lighting device arranged to illuminate the object and is placed both in an inner area in which the imaging area outside the housing is folded into the housing with reference to the transparent plate, and in an outer area of the imaging area in the housing; and an optical-path modifying element which modifies an optical path of a potential stray light.