Laser Focusing via Acoustic Wavefront Curvature Feedback
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Solution Overview
Problem
Conventional auto-focus devices for laser light beams are limited by sensitivity to positioning errors and unwanted movements, requiring complex and costly construction, and struggle with accurate and continuous focusing adjustments, especially at close distances where high resolution is needed.
Innovation Solution
A device that adjusts the focusing distance of a laser light beam by detecting the wavefront radius of curvature of the focused beam, using a glass sheet and photodetector to generate a signal for feedback control, allowing for accurate and continuous real-time adjustment of the focusing point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If conventional auto-focus devices use mechanical movement of light source or optical focusing system to adjust focusing distance, then automatic focusing capability is achieved, but the devices become very sensitive to positioning errors and unwanted movements from thermal expansion, mechanical clearance or vibrations
Solution Approach 1:
The patent replaces the conventional mechanical auto-focus system with an acoustic wave-based system. Surface acoustic waves are generated on the substrate and interact with the optical path to achieve focusing adjustment without mechanical movement of optical components. This substitution eliminates sensitivity to mechanical positioning errors, thermal expansion, and vibrations while maintaining automatic focusing capability.
Solution Approach 2:
The patent changes the physical parameter used for focusing control from mechanical position to acoustic wave properties. By generating surface acoustic waves with specific frequencies and amplitudes, the optical path is modulated to achieve focusing at different distances. This parameter change from mechanical displacement to acoustic wave modulation reduces sensitivity to mechanical errors and enables more reliable automatic focusing.
2Extent of automation
If conventional devices use lateral interferometer to detect distance for focus adjustment, then automatic focusing is achieved, but the construction becomes complex and costly
Solution Approach 1:
The patent extracts the distance detection function from the complex lateral interferometer system and integrates it directly into the substrate where surface acoustic waves are generated. The detection means are positioned to directly measure the distance between the substrate and the object, eliminating the need for separate, complex interferometric measurement systems while maintaining automatic focusing capability.
Solution Approach 2:
The substrate serves multiple functions: it generates surface acoustic waves for optical modulation and simultaneously supports the distance detection means. This multi-functionality reduces the number of separate components needed, simplifying the overall construction while achieving automatic focusing without complex lateral interferometers.
3Extent of automation
If conventional auto-focus devices adjust focus position through measurement of reciprocal position between surface and focus, then focusing adjustment is achieved, but the devices are usable only for reflecting supports, limiting application range
Solution Approach 1:
The patent replaces mechanical/optical measurement methods that require reflecting surfaces with surface acoustic wave interaction that works with both reflecting and non-reflecting supports. The acoustic waves interact with the optical path regardless of the substrate's reflective properties, enabling the device to function with transmitted light through non-reflecting materials, thus expanding application range.
Solution Approach 2:
The patent changes the interaction mechanism from optical reflection-based measurement to acoustic wave-based optical path modulation. This parameter change allows the system to work with both reflecting and non-reflecting supports, as the surface acoustic waves modulate the optical path through the substrate itself rather than relying on light reflection from the support surface.
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 accurate, reliable, and cost-effective automatic focusing with reduced sensitivity to mechanical and optical errors, achieving high resolution and compact design, suitable for various applications including coded information readers.
Implementation Method 1
a glass sheet and photodetector to generate a signal for feedback control
Data Source
AI summary
A device for focusing a laser light beam includes an emission source of a laser light beam along an optical emission path, first focusing means of the laser light beam in a focusing point (F) located at a focusing distance (D), means for adjusting the position of the focusing point (F) relative to the device, and means for detecting the focusing distance (D) active in feedback on the adjustment means, wherein the detection means detects a parameter characteristic of the light beam leaving the first focusing means and representative of the focusing distance (D). The characteristic parameter is the wavefront radius of curvature of the light beam leaving the first focusing means.