Coded Aperture for Scanning System Signal Noise
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Solution Overview
Problem
Scanning systems face challenges in maintaining a consistent signal-to-noise ratio due to intensity differences caused by distance and angular variations in reflected light, leading to reduced dynamic range and increased costs in resolving these issues.
Innovation Solution
A coded aperture is placed between the rotating wheel and the conveyor structure, with varying non-transmissive areas to block or diffuse light, ensuring consistent light intensity across the scan, thereby maintaining a high signal-to-noise ratio and extending the operational range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a rotating wheel with laser light source is used to scan objects on a conveyor, then the scanning system can detect objects across a wide area, but intensity differences occur due to distance and angular variations causing inconsistent signal-to-noise ratio
Solution Approach 1:
The patent applies local quality by varying the aperture width at different transverse positions to compensate for local intensity variations. The aperture is narrower where light intensity is higher (center positions) and wider where intensity is lower (edge positions), creating a non-uniform aperture structure that equalizes the signal-to-noise ratio across the entire scan area.
Solution Approach 2:
The patent changes the aperture parameter (width) as a function of transverse position to compensate for intensity variations. By making the aperture width a variable parameter rather than a constant, the system adapts the light collection area to maintain consistent signal-to-noise ratio across different scan positions.
2Measurement precision
If gain is increased to improve signal-to-noise ratio, then detection sensitivity improves, but the system becomes more complex and costly
Solution Approach 1:
The patent introduces an aperture as an intermediary optical element that passively equalizes light intensity before detection. This optical intermediary provides signal normalization without requiring active electronic gain adjustment or complex signal processing, thereby improving signal-to-noise ratio consistency while avoiding increased system complexity.
3Illumination intensity
If the aperture width is increased to capture more light, then signal intensity improves, but light from certain angles is not properly blocked causing noise
Solution Approach 1:
The patent applies local quality by making the aperture width a function of transverse position. At center positions where on-axis light is strongest, the aperture is narrower to block off-axis noise. At edge positions where reflected light is weaker, the aperture is wider to capture sufficient signal. This spatially varying aperture design simultaneously optimizes both signal capture and noise rejection at different locations.
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
The coded aperture system effectively addresses intensity differential issues, allowing for increased gain application and improved signal-to-noise ratio, enhancing the scanning system's ability to operate across a greater range without increasing sensor costs.
Implementation Method 1
when the wheel rotates, and a facet receives light from the laser light source, the facet reflects the light to the conveyor structure in a scan across the conveyor structure... receives light reflected from the conveyor structure and objects carried by the conveyor structure
Implementation Method 2
The aperture has a second area that receives and blocks or diffuses light from the laser light source that is reflected from the conveyor structure and the objects
Data Source
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AI summary
A scanning system has a collimated light source and a movable reflective surface. The surface receives light from the light source, reflects the received light to a target surface, receives light reflected from the target surface, and reflects this light to a detector. An aperture disposed between the reflective surface and the target surface has a non-transmissive portion with a width in a direction perpendicular to the laser scan direction that varies over the scan direction.