Cam Disk Coupling for Barcode Reader Scan Line Distortion
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Solution Overview
Problem
Existing barcode readers with a direct coupling of a pivoting mirror to a drive shaft suffer from irregular scan line distortions due to discrete rotational increments, resulting in suboptimal scanning patterns and increased distances between scanning lines.
Innovation Solution
A barcode reader design featuring a cam disk with a spiral groove structure to securely couple the pivoting mirror to the drive shaft, allowing for precise control of the pivoting mirror's movement, enabling a larger angular range and minimizing distortion by using a stepping motor with a large transmission ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the pivoting mirror is directly coupled to the shaft of the drive, then the structure is simple, but the scan line distortion increases due to discrete rotational increments
Solution Approach 1:
A cam disk with spiral groove is introduced as an intermediary element between the drive shaft and the pivoting mirror. The cam disk converts the discrete rotational increments of the stepping motor into continuous, smooth oscillating motion of the pivoting mirror, thereby eliminating scan line distortion while maintaining structural simplicity.
Solution Approach 2:
The cam disk changes the motion parameters by transforming discrete angular steps into continuous oscillatory motion. The spiral groove geometry is specifically designed to provide a transmission ratio that smooths out the discrete increments, converting them into a continuous scanning motion that eliminates distortion.
2Device complexity
If the pivoting mirror is directly coupled to the drive shaft, then the coupling is simple, but the distances between scanning lines are too great
Solution Approach 1:
The cam disk acts as a motion transmission intermediary that provides a precise transmission ratio. This allows the small angular range of the pivoting mirror to be achieved with a full revolution of the drive shaft, thereby reducing the distance between scanning lines while keeping the coupling mechanism simple.
Solution Approach 2:
The spiral groove of the cam disk uses a curved geometric profile to transform the rotational motion into the desired oscillating motion. The curved groove path provides a non-linear transmission ratio that optimizes the spacing between scanning lines.
3Measurement precision
If a stepping motor is used to drive the pivoting mirror, then the positioning is precise, but the discrete increments cause scan line distortion
Solution Approach 1:
The cam disk with spiral groove serves as a motion smoothing intermediary between the stepping motor and the pivoting mirror. It converts the discrete positioning steps of the stepping motor into continuous oscillating motion, preserving the precision positioning capability while eliminating the distortion caused by discrete increments.
Solution Approach 2:
The cam disk changes the motion parameters by transforming discrete angular positions into continuous oscillatory motion. The spiral groove geometry is designed to provide a transmission ratio that smooths the discrete steps into a continuous scanning pattern, maintaining positioning precision without distortion.
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 design ensures reproducible and exact scanning patterns with reduced scan line distortion and adjustable spacing between lines, enhancing the accuracy and reliability of barcode detection.
Implementation Method 1
A cam disk is provided for coupling the pivoting mirror to the drive. The cam disc seated on the shaft of the drive has a spiral groove structure. A driver is guided in this grooved structure and is connected to a carrier which forms a rotary bearing for the pivoting mirror.
Implementation Method 2
The driver has in particular a ball bearing, which is guided in the grooves of the cam disc with little play. This guidance of the ball bearing is insensitive to interference and ensures a secure coupling of the driver to the cam.
Implementation Method 3
The deflection unit of the barcode reader typically consists of a polygon mirror wheel, which has a predetermined number of identical mirror surfaces on its side walls. As a result of this rotational movement, the transmitted light beams reflected on the mirror surfaces are guided within a plane that forms the scanning area.
Implementation Method 4
The transmitted light beams are deflected out of the plane with a second deflection unit in the form of an oscillating mirror driven by a drive. The pivoting mirror is rotated periodically within a range of angles of rotation with respect to a pivot axis.
Data Source
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AI summary
The reader (1) has an emitter (3) and a receiver (5) respectively emitting and receiving transmission and reception light beams (2, 4). A motor driven polygonal reflector wheel (6) periodically diverts the emitted light beams in a level. A drive e.g. stepper motor (14), driven movable mirror (10) diverts the emitted light beams from the level. A cam disc (16) is provided for coupling the movable mirror to the drive, and an actuator connected with the moving mirror is guided in the cam disc. The movable mirror is attached to a carrier (11) that is rotatably supported around a swivel axis.