Laser Confocal Scanning Microscope Throughput and Striping Reduction
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Solution Overview
Problem
2-D array laser confocal scanners face inefficiencies due to 'dead' time in scanning, random 'striping' from microlens and aperture array imperfections, and limitations in maintaining constant confocality and illumination intensity, especially at faster image capture rates.
Innovation Solution
Incorporating additional scan patterns in the microlens array, using a second galvanometer mirror to descan Gaussian illumination, inserting a small angle diffuser to reduce coherency, and employing air gaps instead of optical fluid between aperture plates to enhance throughput and reduce 'striping', while maintaining constant integrated intensities and adjustable confocality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single scan pattern is used in the microlens array, then the scanning system is simpler, but dead time occurs during scanning and throughput efficiency is reduced
Solution Approach 1:
The scan pattern is segmented into multiple repeat patterns arranged in a grid format within the microlens array. Each microlens scans across the field of view multiple times, with the scan returning to the starting position after each pass. This segmentation eliminates dead time by ensuring continuous illumination while maintaining a relatively simple microlens array structure.
2Reliability
If a single microlens pattern is scanned, then the system is easier to control, but random striping artifacts appear due to microlens and aperture array imperfections
Solution Approach 1:
Different regions of the field of view are scanned by different microlenses multiple times, with each microlens covering the entire field of view across multiple scan passes. This ensures that imperfections in any single microlens or aperture are distributed and averaged out, reducing random striping artifacts. The system maintains consistent image quality by ensuring every point in the field is scanned by multiple microlenses.
3Reliability
If optical fluid is used between aperture plates, then lubrication is provided, but the system becomes more complex and potential failure points increase
Solution Approach 1:
The optical fluid lubrication system is extracted and replaced with a dry air gap between the aperture plates. The aperture plates are positioned with precise spacing to maintain a stable air gap without requiring lubrication. This eliminates the complexity and potential failure points associated with optical fluid while maintaining reliable operation of the selectable confocal aperture mechanism.
4Adaptability or versatility
If confocal aperture size is fixed in the spinning disc, then the disc structure is simpler, but aperture size cannot be changed to maintain confocality at various magnifications
Solution Approach 1:
The confocal aperture size is made dynamic and selectable rather than fixed. Multiple arrays of confocal apertures with different sizes are provided, and the desired aperture array can be selected and positioned into the optical path as needed. This allows the system to adapt to different magnifications and imaging conditions while maintaining a relatively simple aperture plate structure without moving parts during operation.
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 design improves throughput efficiency, reduces 'striping' artifacts, and allows continuous illumination, eliminating image-to-image fluctuations and maintaining consistent image quality across varying scan speeds and magnifications.
Implementation Method 1
an array of microlenses positioned between said laser beam expander and said first galvanometer mirror, constructed and orientated such that a single scan of the first galvanometer mirror causes each microlens of the array to trace a separate scan line across the sample plane
Implementation Method 2
Light that originates above and below the focal plane of the sample is out of focus at the apertures and hence is rejected by them. The light that does pass through the apertures is used to form an image of the focal plane, hence a confocal image.
Implementation Method 3
a first galvanometer mirror for scanning and directing the laser light beam into a scanned sample plane via a microscope
Implementation Method 4
a dichromatic mirror or a beam splitter, positioned between said first galvanometer mirror and said array of microlenses for separating the return light from the incident light path
Data Source
Figure 1~2
Figure 3a~3b
Figure 4~5a
AI summary
According to a first embodiment the invention provides for increasing the throughput and reducing the striping due to imperfections in the microlens and/or confocal aperture arrays of a Laser Confocal Scanning Microscope by increasing the number of repeat patterns in the microlens and confocal aperture arrays to more than one, and incorporating an intensity modulation function that ensures constant integrated image intensities at the image detector independent of the instantaneous speed of scanning. According to a second embodiment the invention provides for reducing the striping in a Laser Confocal Scanning Microscope by introducing a second galvanometer mirror such that the emitted laser light beam is descanned at the image (sample) plane. According to embodiments three to five, striping in a Laser Confocal Scanning Microscope is also reduced by destroying coherency in the emitted light beam by insertion of a small angle diffuser, by flattening the Gaussian intensity distribution of the emitted laser light beam and changing the characteristics of the beam expander. According to embodiment six the invention provides for changing the degree of confocality of a Laser Confocal Scanning Microscope by inserting a mechanism that offers a range of selectable confocal aperture sizes.