Autofocus Microscopy via Refractive Index Detection
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Solution Overview
Problem
Existing autofocus techniques in microscopy fail to accurately maintain focus when samples are on substrates with inconsistent thickness, leading to off-focus images due to refractive index changes between plastic and liquid media.
Innovation Solution
An autofocus microscope apparatus using a light source, fiber optic circulator, optical collimator, and microprocessor to process analog voltage signals from reflected light, allowing for precise adjustment of the microscopy stage to achieve optimal focus by analyzing voltage peaks and position feedbacks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If autofocus techniques measure distance from the front lens to the bottom of the container using light reflection, then automatic focus adjustment is achieved, but focus accuracy deteriorates when the container has inconsistent thickness
Solution Approach 1:
The patent introduces an intermediary measurement approach by detecting the refractive index change at the plastic-liquid interface rather than directly measuring physical distance. The light reflection technique is used as an intermediary to detect the optical property change, which then serves as a proxy for determining the actual sample focus position, resolving the contradiction between automation and precision.
Solution Approach 2:
The patent changes the measurement parameter from physical distance (which varies with substrate thickness) to refractive index (which is consistent regardless of substrate thickness). By measuring the optical property change at the interface between plastic substrate and liquid medium, the system achieves focus accuracy that is independent of substrate thickness variations.
2Adaptability or versatility
If the substrate thickness varies, then adaptability to different samples is improved, but image focus quality deteriorates
Solution Approach 1:
The patent changes the measurement parameter from physical distance to refractive index, which allows the system to adapt to varying substrate thickness while maintaining consistent focus quality. The refractive index measurement is inherently independent of the physical path length through the substrate.
Solution Approach 2:
The patent replaces the mechanical distance measurement approach with an optical measurement approach based on refractive index detection. This substitution allows the system to handle mechanical variations in substrate thickness without compromising optical focus quality.
3Ease of manufacture
If light reflection off the first surface is used for focus measurement, then simple implementation is achieved, but measurement accuracy worsens due to substrate thickness deviation
Solution Approach 1:
The patent uses light reflection as an intermediary technique to detect refractive index changes rather than directly measuring distance. The reflection provides information about the optical property change at the plastic-liquid interface, which then serves as the basis for focus determination, maintaining simplicity while improving accuracy.
Solution Approach 2:
The patent changes what parameter is being measured using the light reflection technique - instead of measuring physical distance, the system measures the optical path change caused by refractive index variation. This parameter change allows the simple reflection-based method to provide accurate focus information.
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 system effectively maintains focus on samples with varying substrate thickness, enhancing image clarity and suitability for high-content screening and biological imaging applications by reducing background noise and improving focus accuracy.
Implementation Method 1
an optical collimator for directing a light output from the second port of the fiber optic circulator onto a sample through a Dichroic mirror and a microscope objective
Implementation Method 2
a balance detector for converting a light signal, reflected off of a substrate that the sample is placed on, into an analog voltage signal
Data Source
AI summary
An autofocus apparatus includes, in one embodiment, a light source; a splitter; a fiber optic circulator; an optical collimator; a balance detector; and a microprocessor. The fiber optic circulator couples one of the split light signals at a first port, to the optical collimator at a second port, and to the balance detector at the third port. The optical collimator directs the light beam from the fiber optic circulator onto a sample through a Dichroic mirror and a microscope objective. The balance detector uses another one of the split light signals as an input, and converts a light signal, reflected off of a substrate the sample is placed on, into an analog voltage signal. The microprocessor processes the output of the balance detector and position feedbacks from an adjustable microscopy stage to generate a command for moving the position of the adjustable microscopy stage to achieve a desired focus.