3D Polarization Confocal Microscopy for Surface Profilometry
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Solution Overview
Problem
Conventional measurement techniques for microstructures are inadequate in precision and speed, and automatic optical inspection equipment faces challenges with low surface reflectivity and high-slope surfaces, leading to signal ambiguity and reduced accuracy in 3D surface profilometry.
Innovation Solution
A three-dimensional confocal microscopy method using linear-polarizing structured light with a pattern, projected onto an object, and captured through a linear-polarizing imaging module during vertical scanning, combined with phase-shifting to enhance resolution and reduce noise, employing two linear polarizers to minimize signal ambiguity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical microscopy is used for measuring microstructures, then the measurement process is simple, but the measurement precision and speed are insufficient
Solution Approach 1:
The patent segments the optical detection process by using multiple pinholes arranged in specific patterns (e.g., checkerboard, grid) that correspond to different depth planes. Each pinhole captures light from a specific focal plane, enabling simultaneous multi-plane detection. This segmentation of the detection function allows precise 3D measurement while maintaining a relatively simple optical setup compared to traditional confocal systems.
Solution Approach 2:
The patent transitions from 2D optical sectioning to 3D simultaneous detection by introducing the spatial dimension through pinhole array patterns. The pinholes are arranged in two-dimensional patterns that map to different depth planes, allowing the system to capture optical sections from multiple depths simultaneously rather than scanning through depths sequentially, thus adding a spatial dimension to the detection capability.
2Productivity
If conventional confocal microscopy with single pinhole is used, then depth of field control is achieved, but measurement speed is slow due to sequential scanning
Solution Approach 1:
The patent merges multiple single-pinhole confocal detection channels into a single imaging plane by arranging multiple pinholes in a two-dimensional pattern on the detector. This allows simultaneous detection of optical sections from multiple depth planes through a single camera exposure, eliminating the need for sequential scanning while maintaining confocal depth resolution through the spatial separation of pinhole positions.
Solution Approach 2:
The patent creates multiple virtual confocal detection channels by placing multiple pinholes in the detector plane, each corresponding to a different depth plane. These pinhole copies enable parallel detection of multiple optical sections simultaneously, effectively copying the confocal detection function across multiple spatial locations to achieve high-speed 3D imaging.
3Measurement precision
If structured light projection is used for 3D profilometry, then surface information is enhanced, but signal ambiguity occurs on low reflectivity and high-slope surfaces
Solution Approach 1:
The patent applies local quality enhancement by using polarizing filters at specific orientations in front of different pinhole groups. Each pinhole or group of pinholes can have optimally oriented polarizers tailored to the expected surface orientation at corresponding depth planes. This local optimization of polarization direction improves signal reliability for surfaces with varying slopes and reflectivity characteristics at different depths.
Solution Approach 2:
The patent uses composite optical filtering by combining multiple polarizing filters with different orientations in the detection path. This composite polarization filtering approach allows the system to handle diverse surface properties (different slopes and reflectivities) by providing multiple polarization channels, similar to how composite materials combine different properties to handle diverse conditions.
4Productivity
If multiple imaging paths with multiple image sensors are used for simultaneous multi-plane imaging, then measurement speed is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent makes a single image sensor multi-functional by placing a pinhole array pattern directly on the detector surface. Each pinhole in the array acts as an independent detection channel for a different depth plane, allowing one camera to perform the function of multiple cameras. This universalization of the detector reduces system complexity while maintaining simultaneous multi-plane imaging capability.
Solution Approach 2:
The patent nests the pinhole array structure within the image sensor plane, effectively placing multiple virtual detection channels inside a single physical detector. The pinholes are positioned at corresponding locations on the sensor surface, creating a nested configuration where multiple detection functions are embedded within one imaging device, reducing overall system complexity.
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
The method achieves high-accuracy 3D surface profilometry by reducing noise and enhancing resolution, effectively addressing the challenges of low surface reflectivity and high-slope surfaces, resulting in improved measurement precision and accuracy.
Implementation Method 1
providing a linear-polarizing structured light with a pattern
Implementation Method 2
projecting the linear-polarizing structured light onto an object so as to form a plurality of beams containing focus information
Implementation Method 3
capturing the plurality of beams containing focus information during the vertical scanning process so as to form a series of images by a linear-polarizing imaging module
Data Source
AI summary
A method and system for three-dimensional polarization-based confocal microscopy are provided in the present disclosure for analyzing the surface profile of an object. In the present disclosure, a linear-polarizing structured light formed by an optical grating is projected on the object underlying profile measurement. By means of a set of polarizers and steps of shifting the structured light, a series of images with respect to the different image-acquired location associated with the object are obtained using confocal principle. Following this, a plurality of focus indexes respectively corresponding to a plurality of inspected pixels of each image are obtained for forming a focus curve with respect to the measuring depth and obtaining a peak value associated with each depth response curve. Finally, a depth location with respect to the peak value for each depth response curve is obtained for reconstructing the surface profile of the object.