Continuous Scanning Height Map Generation Using Spatial Periodic Pattern
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Solution Overview
Problem
Existing methods for determining the height of spatial positions on a sample surface require multiple images at each scanning position, interrupting the scanning motion and increasing processing time, while also compromising on depth of focus and resolution.
Innovation Solution
A method that irradiates the sample with a spatial periodic pattern, allowing continuous scanning by taking only a single image per position, with synchronized phase movement and scanning speed, and using coherence peak detection to determine amplitude and location, ensuring the light path is partially common and more than two images are taken during a pattern cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple images are taken at each scanning position to reconstruct the intensity signal, then the amplitude calculation accuracy is improved, but the scanning motion is interrupted and the measurement time increases
Solution Approach 1:
The patent applies periodic action by moving the spatial periodic pattern (grating) at a constant velocity during continuous scanning, capturing multiple images at different phase positions. This periodic movement of the pattern allows reconstruction of the intensity signal over the full width of the pattern without stopping the scanner, thereby maintaining measurement speed while achieving accurate amplitude calculation through phase-shifted image sequences.
Solution Approach 2:
The patent implements preliminary action by pre-establishing a fixed relationship between the scanning velocity and the pattern movement velocity. This predetermined relationship ensures that during continuous scanning, the phase positions of the pattern are systematically varied, allowing the system to capture sufficient phase information without interrupting the scan, thus preparing the conditions for accurate amplitude reconstruction in advance.
2Loss of information
If multiple images are taken at each scanning position, then the intensity signal reconstruction is improved, but the scanning process takes considerable time
Solution Approach 1:
The patent applies continuity of useful action by maintaining uninterrupted scanning motion while the spatial periodic pattern moves continuously at a synchronized velocity. Multiple images are captured during this continuous process at different phase positions, ensuring complete intensity signal information is obtained without any stopping or pausing of the scanning operation, thereby eliminating time loss.
3Productivity
If different projection and imaging paths are used, then continuous scanning is enabled, but the depth of focus is reduced and height resolution deteriorates
Solution Approach 1:
The patent applies merging by combining the projection path and imaging path into a single common optical path. The spatial periodic pattern is projected onto the sample and the reflected light is collected through the same optical system, ensuring that the entire light trajectory lies within the depth of focus. This unified path maintains continuous scanning capability while preserving optimal depth of focus and height resolution.
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 enhances measurement speed and resolution by enabling continuous scanning without interruptions, while improving depth of focus and accuracy of the height map generation.
Implementation Method 1
detecting the light reflected by the sample by a detector during the scanning
Implementation Method 2
an optical detector adapted to convert the received light into electrical signals
Data Source
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AI summary
The invention relates to a method for determining the height of a number of spatial positions on a sample, defining a height map of a surface of said sample comprising irradiating the surface of the sample with light comprising a spatial periodic pattern in a direction perpendicular to the optical axis and moving parallel to the pattern, scanning the surface in the direction of the optical axis for each position of the surface and detecting the light reflected by the sample by a detector during the scanning, wherein in any scanning position only a single image is taken, the scanning speed bears a predetermined relation to the phase of the periodic pattern and analysing the output signal of the detector including for each spatial position of the detector the determination of the amplitude of the signal detected during the scanning and determining the scanning location where the amplitude is maximal.