Liquid Crystal Auto-Focus for Imaging Scanners
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Solution Overview
Problem
Imaging-based barcode readers often require actuators or moving parts to achieve focused images over a range of working distances, which can be cumbersome and prone to mechanical errors.
Innovation Solution
An auto-focus system is constructed using a liquid crystal device in combination with a lens system, where the refractive index of the liquid crystal material is adjusted by applying voltage between parallel plate structures, allowing for focus adjustment without moving parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If actuators or moving parts are used to achieve focused images over a range of working distances, then the imaging scanner can focus on barcodes at different distances, but the device complexity increases and mechanical errors may occur
Solution Approach 1:
The patent replaces the mechanical actuator-based focusing system with an electro-optical liquid crystal device. The liquid crystal device changes its refractive index in response to applied voltage, thereby adjusting the focal length of the imaging lens without any moving parts. This substitution eliminates mechanical complexity while maintaining focus adjustment capability across different working distances.
Solution Approach 2:
The patent changes the optical parameters of the imaging system by using a liquid crystal device whose refractive index can be dynamically adjusted via voltage control. By varying the voltage applied to the liquid crystal, the refractive index changes, which in turn adjusts the focal length of the lens system, enabling focus adjustment without mechanical movement.
2Adaptability or versatility
If actuators are used for focus adjustment, then focused images can be achieved over extended range of working distances, but the reliability decreases due to mechanical errors
Solution Approach 1:
The patent eliminates mechanical actuators and replacing them with an electrically controlled liquid crystal device. This substitution removes moving parts that are prone to mechanical errors, wear, and failure, thereby significantly improving system reliability while maintaining the ability to focus on barcodes at various working distances through electrical control of the liquid crystal's refractive index.
Solution Approach 2:
The liquid crystal device automatically adjusts the focal length in response to voltage changes without requiring mechanical actuation. The system achieves focus adjustment through direct electrical control of the optical properties of the liquid crystal material, eliminating the need for mechanical components that could fail.
3Device complexity
If a liquid crystal device is used for focus adjustment, then the device complexity is reduced by eliminating actuators, but the manufacturing precision requirements may increase
Solution Approach 1:
The patent replaces complex mechanical actuator systems with a compact liquid crystal device that can be integrated directly into the imaging lens assembly. While this reduces mechanical complexity, it requires precise integration of the liquid crystal device with the existing optical elements to ensure proper optical alignment and performance.
Solution Approach 2:
The patent utilizes the tunable refractive index property of liquid crystal materials to achieve focus adjustment. The liquid crystal device is designed with specific optical parameters (refractive index range, response time, voltage requirements) that must be precisely matched to the imaging system's requirements, requiring careful selection and integration of the liquid crystal material.
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
Enables clear imaging of barcodes over a range of distances without mechanical shifts, improving image quality and simplifying assembly by eliminating the need for actuators, while allowing for easy removal of the auto-focus function if not needed.
Implementation Method 1
the refractive index of the liquid crystal material is adjusted by applying voltage between parallel plate structures
Data Source
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AI summary
A method and apparatus for using in an imaging scanner (50). The apparatus includes an illumination source (72), a solid-state imager (62), a liquid crystal device (100), a lens system (64), and a decoding circuitry (90). The liquid crystal device (100) has a liquid crystal material (110) sandwiched between two parallel plate structures (120, 130). The lens system (64) is operative to focus light reflected from the target object onto the array of photosensitive elements in the solid-state imager (62) through the liquid crystal device (100). The decoding circuitry (90) is operative to decode a barcode (40) on the target object from the image captured by the solid-state imager.