Varifocal Lens Autofocus for Barcode Scanners
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Solution Overview
Problem
Existing optical-information-reading apparatuses for code symbols, such as barcode and two-dimensional code scanners, face challenges in downsizing, achieving fast and precise autofocus, and reducing production costs due to complex optics and mechanical adjustments required for high precision focusing, especially when dealing with micro two-dimensional codes.
Innovation Solution
The use of a varifocal lens, either liquid or liquid crystal, which adjusts focus without mechanical movement by changing the curvature of its boundary surface through electric voltage, combined with a parallax method for distance measurement and temperature compensation, allows for precise and rapid autofocus without the need for mechanical adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a lens is arranged to move along an optical axis for autofocus, then focusing precision is improved, but device size increases due to required movement space
Solution Approach 1:
The patent replaces the mechanical lens movement system with a liquid lens that changes focal length through electrical control. The liquid lens uses voltage application to alter the curvature of its boundary surface, enabling focus adjustment without any mechanical movement components, thus eliminating the space required for lens travel while maintaining focusing precision.
Solution Approach 2:
The liquid lens changes its optical parameters (focal length) by altering the electrical voltage applied to it. This parameter change approach allows the lens to adjust focus dynamically without physical displacement, solving the contradiction between achieving precise focus and minimizing device volume.
2Manufacturing precision
If multiple lenses are combined for optical wavefront modulation, then focusing function is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent merges multiple lens functions into a single liquid lens component. Instead of using separate lenses for different optical functions, the liquid lens integrates these functions through its ability to dynamically adjust its optical properties via electrical control, thereby reducing the number of components and simplifying the overall optical system.
Solution Approach 2:
The liquid lens serves multiple optical functions simultaneously - it can adjust focal length, correct optical aberrations, and adapt to different imaging conditions - all through electrical parameter adjustment. This multi-functionality eliminates the need for multiple specialized lenses, reducing device complexity while maintaining or improving focusing performance.
3Manufacturing precision
If fine adjustment of lens location is performed after assembly, then imaging precision is improved, but production time and cost increase
Solution Approach 1:
The patent replaces mechanical fine-adjustment mechanisms with electrical control of the liquid lens. Instead of requiring manual or automated mechanical positioning adjustments after assembly, the liquid lens achieves precise imaging through voltage control, eliminating time-consuming adjustment procedures and enabling faster production while maintaining high imaging precision.
Solution Approach 2:
The liquid lens system incorporates self-adjustment capabilities through its electrical control mechanism. The system can automatically achieve optimal focus and imaging conditions through programmed voltage adjustments, eliminating the need for manual fine-tuning during production and thereby increasing productivity while maintaining precision.
4Volume of moving object
If a small aperture lens is used for downsizing, then device size is reduced, but focus and image formation become difficult
Solution Approach 1:
The liquid lens overcomes the limitations of small aperture by dynamically changing its optical parameters through electrical control. Even with a compact form factor, the liquid lens can adjust its focal length and optical power to achieve proper focus and image formation, eliminating the trade-off between size and focusing capability.
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 solution enables fast and precise imaging of code symbols, reduces production time and costs, and maintains focus even under long-term deterioration or temperature variations, allowing for efficient decoding of code symbols without manual adjustments.
Implementation Method 1
a varifocal lens (3), positioned posterior to the main lens (2), having a function to focus light that transmits through the main lens (2) on the imaging surface (E)
Implementation Method 2
a ranging laser (13) that measures a distance to the code symbol (100)
Data Source
Figure 1~2A
Figure 2B~3
Figure 4~5A
AI summary
To provide an optical-information-reading apparatus which realizes the imaging of a code symbol with high precision. The optical-information-reading apparatus 1A is provided with an imaging optical system 11 having a varifocal lens 3 which adjusts a focal position, a solid-state image sensing device 12 that images a code symbol 100, ranging laser 13 that measures a distance to the code symbol 100 and a decoder 200 that calculates the distance up to the code symbol 100 using the ranging laser 13, controls the varifocal lens 3 based on calculated distance information to perform the image formation of the code symbol 100 on the solid-state image sensing device 12, and controls the solid-state image sensing device 12 to image the code symbol 100. In the optical-information-reading apparatus 1A, distance measurement parameter to be used for the calculation of the distance to the code symbol 100 is previously measured, the measured distance measurement parameter which is proper to the apparatus is stored and the distance to the code symbol 100 is calculated using the measured distance measurement parameter which is proper to the apparatus.