Rear-Facing Image Sensor Scan Engine with Folded Optical Path
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Solution Overview
Problem
Existing handheld area imaging readers have limited working distance range due to pixel resolution and depth of focus constraints, and are costly due to complex electro-mechanical structures with multiple printed circuit boards and ribbon cable interconnects, which also cause parallax issues.
Innovation Solution
A compact handheld area reader design featuring a single tilted printed circuit board with a rear-facing image sensor and a double-folded optical path using fold mirrors, increasing the optical path length and reducing the field of view angle, combined with a narrower illuminating light beam to enhance pixel resolution and depth of focus, and minimize parallax.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional front-facing image sensor design is used, then the structure is simple, but the working distance range is limited due to pixel resolution and depth of focus constraints
Solution Approach 1:
The patent inverts the conventional front-facing image sensor design by using a rear-facing image sensor. This inversion allows the optical path to be folded back through the PCB, effectively increasing the optical path length and improving both working distance range and depth of focus while maintaining a compact handheld form factor.
Solution Approach 2:
The patent introduces fold mirrors to create a double-folded optical path, transforming the linear optical path into a multi-dimensional folded structure. This allows the optical path to traverse through the PCB and extend the effective imaging distance without increasing the external dimensions of the device.
2Adaptability or versatility
If multiple printed circuit boards and ribbon cable interconnects are used, then component placement is flexible, but the device complexity and cost increase
Solution Approach 1:
The patent consolidates multiple PCBs and ribbon cable interconnects into a single rigid PCB structure. The optical components, image sensor, and electronic circuits are all mounted on this single PCB, eliminating the need for multiple separate boards and interconnecting cables, thereby reducing structural complexity and potential failure points.
3Area of stationary object
If a wide field of view angle is used, then the coverage area is large, but the pixel resolution decreases
Solution Approach 1:
The patent optimizes the field of view angle parameter by using the double-folded optical path design. This allows the system to achieve an optimized balance between coverage area and pixel resolution, improving resolution without sacrificing excessive coverage by precisely controlling the optical path geometry.
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 solution significantly increases the working distance range and depth of focus while reducing costs by simplifying the internal structure and improving illumination intensity and accuracy, making the reader more durable and efficient.
Implementation Method 1
an optical assembly, including a pair of fold mirrors, mounted on the tilted rear surface and operative for receiving return light returning from the target and passing through the aperture along the horizontal, and for directing the return light along a folded path
Implementation Method 2
an imaging lens assembly mounted in the folded path and operative for projecting the return light onto the image sensor to enable the image sensor to detect the return light over the field of view
Implementation Method 3
A light-transmissive window is supported at a front end of a housing
Data Source
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AI summary
An arrangement for, and a method of, electro-optically reading a target by image capture, employ a scan engine in a handheld housing having a tilted handle. A single tilted printed circuit board (PCB) in the handle has front and rear surfaces that respectively face toward and away from the target during reading. An optical assembly having a pair of fold mirrors is mounted on the rear surface, for receiving return light from the target through an aperture in the PCB along the horizontal, and for directing the return light along a folded path. An imaging lens assembly projects the return light onto a solid-state, two-dimensional, image sensor to enable the return light to be detected over a field of view, and to generate an electrical signal indicative of the detected return light.