Asymmetrical Magnification Optical Assembly for Barcode Reader Resolution
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Solution Overview
Problem
The existing bi-optical workstations face limitations in reading bar code symbols at far working distances and tilted angles due to rapid field of view divergence, leading to reduced pixels per module (PPM) and decreased resolution.
Innovation Solution
The use of non-rotationally symmetrical optics within the workstation for asymmetric magnification of the image and field of view along orthogonal directions, combined with rotationally symmetrical optics, increases the resolution of the imager, particularly in cases where symbols are imaged at steep angles, by configuring lenses such as a Cooke triplet and asymmetrical lenses like cylindrical and toroidal lenses with aspherical profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the field of view diverges rapidly at far working distances, then the imager can cover larger areas, but the pixels per module decreases rapidly reducing reading capability
Solution Approach 1:
The patent applies asymmetrical magnification through non-rotationally symmetrical optics that magnify differently along orthogonal directions. Specifically, the system uses a cylindrical lens or toroidal lens with aspherical profiles to create asymmetric magnification in the direction of symbol tilt, compensating for the cosine projection effect and maintaining pixels per module at tilted angles.
Solution Approach 2:
The patent implements local quality by applying different magnification characteristics to different directions. The optical system provides symmetrical magnification in one direction and asymmetrical magnification in the perpendicular direction, optimizing the field of view coverage in the direction where symbols are most commonly tilted while maintaining resolution in the other direction.
2Measurement precision
If non-rotationally symmetrical optics are used for asymmetrical magnification, then resolution at tilted angles improves, but device complexity increases
Solution Approach 1:
The patent incorporates non-rotationally symmetrical optics including cylindrical lenses or toroidal lenses with aspherical profiles to achieve asymmetrical magnification. These lenses are integrated into the optical assembly with rotationally symmetrical optics (Cooke triplet), creating a hybrid system that provides direction-dependent magnification to compensate for projection effects at tilted angles.
Solution Approach 2:
The patent changes optical parameters by using lenses with specific aspherical coefficients and different curvatures in different directions. The cylindrical lens has a specific curvature in one direction and is flat in the perpendicular direction, while toroidal lenses have varying curvatures that create the desired asymmetrical magnification effect to maintain resolution at oblique imaging angles.
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 approach enhances the imager's resolution and ability to decode symbols at various angles and distances, improving the reading capability of bar code symbols by increasing pixels per module and compensating for the loss in resolution caused by tilted symbols.
Implementation Method 1
a solid-state imager that has a one- or two-dimensional sensor array of pixels, cells or photosensors that capture light returning from the symbol through the window
Implementation Method 2
an electro-optical reader, e.g., a laser scan pattern generator that projects a scan pattern of scan lines through the window and detects light returning from the symbol through the window
Implementation Method 3
an optical assembly, including non-rotationally symmetrical optics, for optically modifying and asymmetrically magnifying an image of the indicia and the field of view
Data Source
AI summary
A solid-state imager is mounted in a reader, such as a bi-optical, dual window, point-of-transaction workstation, for capturing light along an optical axis over a field of view from coded indicia. An optical assembly including non-rotationally symmetrical optics is operative for optically modifying and asymmetrically magnifying an image of the indicia and the field of view of the imager along mutually orthogonal directions generally perpendicular to the optical axis, and for increasing resolution of the imager along one of the directions. Preferably, the non-rotationally symmetrical optics includes a cylindrical lens having an aspherical profile along the one direction, and a planar profile along the other of the directions.