Phase Plate Aperture Zoning for Extended Imaging Working Range
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Solution Overview
Problem
Conventional symbol readers with fixed-focus lenses have a limited working range, which is inadequate for objects with varying symbol locations, especially when objects are moving quickly, leading to challenges in decoding symbols due to depth-of-field limitations and reduced image intensity.
Innovation Solution
Incorporating a phase plate with specific phase delays in the aperture stop of the imaging system, including central, inner annular, and outer annular regions, to extend the working range by adjusting focal lengths for different radial zones, thereby enhancing the depth of field without reducing image intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the aperture size is reduced to increase depth-of-field and extend working range, then the working range is improved, but image intensity is lost
Solution Approach 1:
The aperture stop is segmented into multiple radial zones (central region, inner annular region, outer annular region), each with different phase delays. This segmentation allows different parts of the aperture to contribute to different focal planes, extending the working range while maintaining sufficient light intensity by utilizing the full aperture area rather than reducing the overall aperture size.
Solution Approach 2:
Different radial zones of the aperture stop are assigned different phase delay characteristics (first, second, and third phase delays as functions of radial distance). This local differentiation enables each zone to focus light from objects at different distances, achieving extended working range while preserving image intensity through optimized local phase control.
2Productivity
If objects are tracked at higher speeds with shorter exposure times to limit blur, then productivity is improved, but image intensity is reduced
Solution Approach 1:
By segmenting the aperture into zones with different phase delays, the system achieves extended depth-of-field that allows shorter exposure times for high-speed tracking without sacrificing image intensity. Each zone contributes to focusing light from different depth planes, maintaining sufficient intensity even with reduced exposure duration.
3Adaptability or versatility
If the distance between the imaging device and tracked objects is increased to increase depth-of-field, then the working range is improved, but image intensity decreases due to longer distances and potential obstructions
Solution Approach 1:
The phase delays applied to different radial zones of the aperture stop are adjusted to create an extended depth-of-field effect. By changing the phase parameter distribution across the aperture, the system achieves increased depth-of-field without increasing the physical distance between the imaging device and objects, thereby maintaining image intensity.
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 provides extended working range and improved image quality for decoding symbols over a broader distance, maintaining high contrast for spatial frequencies of interest, without the need for specialized software or post-processing, and is compatible with existing imaging devices.
Implementation Method 1
adding a first phase delay to a central region of the aperture stop; adding a second phase delay to an inner annular region, of the aperture stop, that surrounds the central region; adding a third phase delay to an outer annular region
Data Source
AI summary
A working-range-extending phase plate includes a central region, an inner annular region surrounding the central region, and an outer annular region surrounding the central region and the inner annular region. The central region has a central phase-transmission function. The inner annular region has an inner phase-transmission function. The outer annular region has an outer phase-transmission function. Respective magnitudes of the central, the inner, and the outer phase-transmission functions are, as a function of radial distance from an optical axis of the phase plate, one of: (i) constant, increasing, and increasing, (ii) decreasing, constant, and increasing, or (iii) decreasing, decreasing, and constant.