Optical Speckle Positioning for Sub-Micron Precision
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Solution Overview
Problem
Current two-dimensional precise positioning systems, such as CCD and magnetic induction systems, face limitations in achieving high precision due to reliance on invariant imaging and signal intensity changes, which are inadequate for advanced mechanical processing requirements, and existing optical speckle-based methods lack effective two-dimensional positioning capabilities.
Innovation Solution
A method utilizing optical speckles involves selecting a reference point on a surface with unique textures, partitioning it into zones, irradiating with coherent light to capture speckle images, establishing a look-up table, and comparing images to determine the relative location of a detection point, allowing for precise two-dimensional positioning with improved precision and repeatability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If CCD automatic positioning system uses telecentric lenses to get invariant images, then imaging quality is improved, but positioning precision is limited to around ±20μm due to insufficient judging features
Solution Approach 1:
The patent uses optical speckle pattern changes (intensity distribution changes) instead of traditional color or grayscale changes. When the measured object moves, the speckle pattern undergoes characteristic intensity variations that provide rich judging features for sub-micron positioning precision, resolving the limitation of insufficient features in traditional invariant imaging systems
Solution Approach 2:
The patent changes the measurement parameter from traditional image intensity or edge position to optical speckle pattern intensity distribution. By monitoring changes in speckle pattern parameters (intensity at different positions), the system achieves positioning precision beyond the diffraction limit, transforming the limitation of invariant imaging into an advantage for high-precision measurement
2Productivity
If magnetic induction positioning system uses Hall Effect to scan periodic magnetic template, then positioning function is achieved, but positioning precision cannot be improved for fast movement and is limited to around 20μm
Solution Approach 1:
The patent replaces the magnetic induction measurement mechanism with optical speckle measurement. Instead of using Hall Effect sensors to detect magnetic field changes during movement, the system uses optical beams to create speckle patterns on the object surface. This substitution allows high-speed movement measurement because optical measurement is non-contact and insensitive to movement speed, achieving both high productivity and high precision
3Measurement precision
If optical displacement sensor scans object with light beams to receive scattered light beams, then displacement measurement is achieved, but two-dimensional positioning capability is lacking or precision is insufficient
Solution Approach 1:
The patent extends one-dimensional displacement measurement to two-dimensional positioning by analyzing the speckle pattern across multiple positions. The speckle pattern intensity distribution contains information about both x and y coordinates, allowing the system to determine two-dimensional position by comparing the observed speckle pattern with reference patterns, thus adding dimensional capability without sacrificing precision
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 enables higher precision positioning, suitable for advanced mechanical applications, by maintaining constructive interference and minimizing noise, achieving positioning accuracy beyond the limitations of existing systems.
Implementation Method 1
irradiating the surface with a highly coherent parallel light at an incident angle θ to produce scattered light beams
Implementation Method 2
maintaining constructive interference
Data Source
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AI summary
A method and system for positioning by using optical speckle are disclosed in this invention. A highly coherent laser light irradiates a positioning template in advance to record optical speckles caused by interference by scattered light beams from the positioning template for establishing a speckle database. Furthermore, a reference point is defined to position each recorded speckle. Therefore, a coordinate with respect to the reference point corresponding to a specified speckle can be used to position a target or applied to distance measurement by the speckle database. The precision of the speckles according to the present invention is within several micrometers. Hence, it can provide high precision positioning.