Handheld Scanner Tilted PCB Fold Mirrors Parallax
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Solution Overview
Problem
Existing handheld area readers have limited working distance range due to pixel resolution and depth of focus constraints, and are hindered by parallax issues and high costs associated with complex electro-mechanical structures, which restrict market growth.
Innovation Solution
A compact scan engine with a rear-facing image sensor and a single tilted printed circuit board (PCB) that uses fold mirrors to create a folded optical path, allowing the imaging lens assembly to be positioned parallel to the PCB, thereby increasing the internal optical path length and reducing field of view divergence, while minimizing parallax and maintaining image sharpness across a wider range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a front-facing image sensor is used in conventional handheld readers, then the internal optical path length is limited, but the field of view divergence increases and working distance range is restricted
Solution Approach 1:
The patent applies dimensionality change by reorienting the image sensor from a conventional front-facing position to a rear-facing position on the PCB. This spatial reconfiguration allows the optical path to extend in a different dimension, effectively increasing the internal optical path length without increasing the physical footprint of the device. The rear-facing sensor enables the light to travel a longer distance through the imaging lens assembly, thereby extending the working distance range while maintaining compact dimensions.
Solution Approach 2:
The patent employs inversion by placing the image sensor at the opposite end of the conventional arrangement. Instead of positioning the sensor at the front of the device where light enters, the sensor is positioned at the rear of the PCB, facing backward. This inverted configuration allows the optical path to traverse the entire length of the PCB, maximizing the internal optical path length and enabling extended working distances that were previously unachievable in compact handheld readers.
2Volume of moving object
If the imaging lens assembly is positioned closer to the image sensor, then the device is more compact, but the field of view divergence increases
Solution Approach 1:
The patent resolves this contradiction by changing the spatial arrangement from a linear front-to-back configuration to a rear-facing configuration. The imaging lens assembly remains positioned close to the PCB for compactness, but the rear-facing sensor orientation creates an extended optical path that reduces field of view divergence. This dimensional reconfiguration allows the system to maintain compact form factor while achieving better field of view control through the extended light path.
3Adaptability or versatility
If a complex electro-mechanical structure is used to achieve extended working distance, then the working distance range increases, but the device complexity and cost increase
Solution Approach 1:
The patent replaces complex electro-mechanical structures with a simplified optical configuration. Instead of using movable lenses, adjustable focus mechanisms, or complex mechanical assemblies to extend working distance, the invention achieves the same effect through a rear-facing image sensor arrangement on a tilted PCB. This substitution of mechanical complexity with a straightforward optical geometry reduction simplifies the device structure while maintaining extended working distance capability.
Solution Approach 2:
The patent changes the geometric parameters of the optical system by tilting the PCB at an acute angle and repositioning the image sensor to face the rear. This parameter change in the optical configuration naturally extends the working distance range without requiring additional mechanical components. The altered geometry of the optical path achieves the desired functionality through design parameters rather than mechanical complexity.
4Length of stationary object
If the image sensor is positioned far from the front window, then the internal optical path length increases, but parallax issues increase
Solution Approach 1:
The patent uses inversion to resolve the parallax issue. By positioning the image sensor at the rear of the PCB facing backward, the optical path is configured such that the aiming light assembly and image sensor are more closely aligned in the optical path. This inverted arrangement reduces the angular separation between the aiming light axis and the imaging axis, thereby minimizing parallax error while maintaining a long internal optical path length for extended working distance.
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 configuration extends the working distance range, improves pixel resolution, and reduces parallax issues, resulting in a more durable and cost-effective handheld imaging reader with enhanced performance and market potential.
Implementation Method 1
An optical assembly, including a pair of fold mirrors, is mounted on the tilted rear surface. The fold mirrors are arranged relative to each other and relative to the image sensor, 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 optical path.
Implementation Method 2
An imaging lens assembly is mounted in the folded optical path between the fold mirrors and has an imaging axis that is generally parallel to the PCB, and is operative for capturing return light returning from the target and for projecting the return light onto the image sensor to enable the image sensor to detect the return light over the field of view.
Data Source
AI summary
An apparatus 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 an internal folded optical path. An imaging lens assembly is mounted between the fold mirrors and has an imaging axis that extends generally parallel to the PCB. The 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.