Segmented Diaphragm for Linear Optical Code Depth of Field
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Solution Overview
Problem
Existing optical code readers face challenges in achieving an optimal depth of field for reading linear optical codes at various distances and resolutions, as diaphragms with narrower apertures improve close-range reading but reduce long-distance performance, while wider apertures enhance distance reading but increase sensitivity to tilt angles, making correct code reading difficult.
Innovation Solution
The method involves forming two or more equally focused but differently apertured in-phase images of a linear optical code onto a sensor, using diaphragms with non-constant smaller dimensions and multiple aperture zones, such as rectangular or trapezoidal shapes, to simultaneously improve both the minimum and maximum limits of the depth of field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a diaphragm with a narrower aperture is used, then the depth of field for close-range reading is improved, but the light intensity reaching the sensor is reduced
Solution Approach 1:
The diaphragm is divided into multiple aperture zones with different smaller dimensions (first aperture zone with dimension d1, second aperture zone with dimension d2 where d1 < d2). Each zone contributes to forming an image with different depth of field characteristics, allowing the system to simultaneously achieve good depth of field for close-range reading while maintaining sufficient light intensity through the larger second aperture zone.
2Measurement precision
If a diaphragm with a wider aperture is used, then the depth of field for long-distance reading is improved, but the sensitivity to tilt angles increases
Solution Approach 1:
The diaphragm is segmented into multiple aperture zones with different smaller dimensions. The first aperture zone with smaller dimension d1 provides images less sensitive to tilt angles, while the second aperture zone with larger dimension d2 extends the depth of field for long-distance reading. By combining these zones, the system achieves both improved depth of field and reduced tilt angle sensitivity.
3Device complexity
If a single aperture diaphragm is used, then the device complexity is reduced, but the reading performance across different distances deteriorates
Solution Approach 1:
The diaphragm is divided into multiple aperture zones with different smaller dimensions to improve reading performance across different distances and resolutions. The zones are arranged within a single diaphragm structure, maintaining relatively simple device complexity while significantly enhancing adaptability and versatility for reading optical codes at various distances and resolutions.
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 allows for improved reading performance across different distances and resolutions, balancing light intensity and resolution without significant sacrifice, enabling effective reading of optical codes from closer and farther distances with enhanced signal dynamics and depth of field.
Implementation Method 1
The optical receiving device typically comprises an objective comprising one or more lenses, for collecting and forming the image of the optical code onto the sensor
Implementation Method 2
The optical receiving device typically comprises, upstream or downstream of the objective, a diaphragm meant as an opaque screen stopping the light
Implementation Method 3
The sensor therefore generates an alternating electrical signal whose waveform is modulated by the sequence of light/dark elements of the optical code
Data Source
AI summary
A method for improving the depth of field in the detection of a linear optical code includes simultaneously forming two or more overlapped equally focused but differently diaphragmed in phase images of an optical code onto a linear sensor. Diaphragms and optical receiving devices suitable to implement the method are described.