Handheld Optical Scanner Polarizing Filter Brewster Angle Glare Reduction
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Solution Overview
Problem
Optical scanning devices face challenges in minimizing specular reflection, which affects image quality due to light being reflected off the scan window, and in efficiently capturing and processing images with varying field of views and resolutions.
Innovation Solution
Incorporating features such as internal light shields, sequential lighting, diffuse light sources, polarizing filters, and contoured scan windows to reduce specular reflection and enhance imaging characteristics, including the use of multiple image sensors for capturing different portions of text or images in a single pass.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If light sources are used to illuminate the scan region, then image capture is enabled, but specular reflection causes glare and degrades image quality
Solution Approach 1:
A polarizing filter is introduced as an intermediary component between the light source and the scan window. The filter polarizes the light in a specific direction, and when combined with the Brewster angle positioning of the scan window, the polarized light reflects at an angle that directs glare away from the image sensor, thereby maintaining illumination while eliminating harmful specular reflection
Solution Approach 2:
The scan window is positioned at the Brewster angle (a specific parameter value of approximately 56 degrees for typical glass-air interfaces) relative to the light source. This parameter change in the angle of incidence transforms the reflection characteristics, causing p-polarized light to be completely transmitted and s-polarized light to be reflected at a specific angle that directs glare away from the sensor
2Device complexity
If a single image sensor is used, then device simplicity is maintained, but field of view and resolution are limited
Solution Approach 1:
The imaging system is segmented into multiple image sensors (first image sensor and second image sensor) positioned at different locations and orientations. Each sensor captures a specific portion of the overall scene, with the first sensor capturing text in a first field of view and the second sensor capturing text in a second field of view, thereby expanding the total field of view through segmentation of the sensing function
Solution Approach 2:
The second image sensor is positioned at a different spatial location and oriented at a different angle relative to the scan window compared to the first sensor. This dimensional change in sensor placement allows capture of text portions that fall outside the first sensor's field of view, effectively expanding the scanning coverage area through spatial diversification
3Manufacturing precision
If contoured scan windows are used to enhance imaging characteristics, then image quality improves, but manufacturing complexity increases
Solution Approach 1:
The scan window is designed with a contoured (curved) surface instead of a flat surface. This curvature is optimized to focus light from specific regions of the document onto the image sensor, enhancing the field of view and image quality. The contoured shape allows a single scan window to effectively capture text across varying distances and angles, improving imaging characteristics despite the increased manufacturing 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
These features significantly reduce glare, improve image quality, and allow for efficient scanning and processing of images with enhanced resolution and field of view, resulting in clearer and more detailed scanned images.
Implementation Method 1
polarizing filters to reduce specular reflection
Implementation Method 2
Positioning the scan window at the Brewster angle
Data Source
AI summary
A hand-held optical scanner is described. The hand-held optical scanner has an image sensor, as well as a scan window through which image light is directed toward the image sensor.