Microscope Height Positioning via Partially Confocal Imaging
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Solution Overview
Problem
Existing methods for determining the height position of an object using optical microscopes are time-consuming due to the need for multiple measurements along the z-direction to achieve accurate intensity maxima, especially when determining topography over an area.
Innovation Solution
A method that involves imaging the object in wide field and partially confocal modes, calculating the expected maximum intensity using a scaling factor, and determining the z-coordinate of the point spread function's maximum intensity to quickly determine the height position, reducing the number of required measurements by utilizing a larger pinhole for partially confocal imaging, which increases the depth of field range and allows for a single partially confocal image per location.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple measurements along the z-direction are performed to determine the maximum intensity accurately, then the measurement precision is improved, but the time required for determination increases
Solution Approach 1:
A z-stack of partially confocal images is acquired in advance, covering a depth range that includes the expected object height. This preliminary acquisition allows subsequent height measurements to be performed rapidly by analyzing pre-captured images rather than performing multiple focused measurements during the actual measurement process.
Solution Approach 2:
The pinhole diameter is increased beyond the conventional confocal size to create a partially confocal imaging mode. This parameter change increases the depth of field and allows a single image to contain intensity information from a broader z-range, enabling accurate height determination without multiple measurements.
2Speed
If a larger pinhole is used for partially confocal imaging, then the depth of field range increases and measurement time decreases, but the confocal resolution is reduced
Solution Approach 1:
The evaluation function applies different weighting to different z-positions within the z-stack. Positions corresponding to the expected object height are evaluated with higher weight, allowing accurate height determination even with reduced confocal resolution from the larger pinhole.
Solution Approach 2:
The imaging approach combines wide-field and confocal imaging characteristics by using a pinhole size that is larger than conventional confocal but smaller than wide-field. This creates a composite imaging mode that balances depth of field, signal intensity, and resolution to optimize both speed and accuracy.
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 significantly reduces the time required to determine the height position at a location by up to 10% compared to traditional methods, enabling faster topography determination and allowing for the production of both two- and three-dimensional images with reduced measurement duration.
Implementation Method 1
a point spread function along a z-direction that coincides with the height direction
Implementation Method 2
a focusing device which is adapted for setting a z-position of a focus of the partially confocal image
Implementation Method 3
a pinhole device for partially confocal imaging and for imaging in wide field
Data Source
AI summary
A method for determining a height position of an object at of using a microscope which images using a point-spread function along a z-direction (height direction), comprising the steps of imaging the object in the far field and determining a far-field intensity, calculating a maximum intensity expected by multiplying the far-field intensity by a scaling factor, partially confocally imaging the object with the focus in the z-direction within the depth-of-field range, and determining a partially-confocal intensity of the imaging, calculating the intensity of the point-spread function (at the first location) by forming a difference between the partially-confocal intensity and a product of the far-field intensity and a predefined combination factor, calculating the z-coordinate of the focus at a point-spread function maximum, using a previously-known form of the point spread function, its calculated intensity, and the calculated expected maximum intensity, and using the z-coordinate as the height position of the object.