Microscope Focus Assist via Light Intensity Control
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Solution Overview
Problem
Existing methods for finding the best focus position in imaging optical systems, such as interferometric objectives, often result in erroneous measurements due to high irradiance saturation at the detector, making it difficult to determine the correct focal position, especially when the depth of focus exceeds the depth of fringes and when tilt occurs, leading to energy loss in the optical path.
Innovation Solution
Varying the power input to the light source to maintain a constant degree of detector saturation as the objective is moved towards the best-focus position, allowing for immediate indication of the correct direction of motion and preventing detector saturation, which enables precise focus determination and tilt correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the light source intensity is increased to achieve maximum irradiance at the detector for focus determination, then the focus position can be identified, but the detector becomes saturated and prevents accurate determination of the maximum irradiance position
Solution Approach 1:
The light source intensity is made dynamically adjustable during the focus search process. The system automatically varies the intensity level based on the current irradiance measurement, reducing intensity when approaching maximum to prevent detector saturation while maintaining the ability to detect focus position through the minimum intensity required for saturation
Solution Approach 2:
The system changes the operational parameter (light source intensity) from a fixed high level to a variable level that adapts during the measurement process. By monitoring the intensity required to maintain detector saturation, the system can determine focus position without causing harmful saturation effects
2Reliability
If the depth of focus is greater than the depth of fringes, then the sample can be in focus with high irradiance at the detector, but interference fringes become invisible resulting in erroneous measurements
Solution Approach 1:
The system uses feedback from the detector saturation level to control the light source intensity. By monitoring whether the detector is saturated and adjusting the intensity accordingly, the system maintains optimal conditions for observing interference fringes while keeping the sample in focus, thus resolving the contradiction between focus stability and fringe visibility
3Measurement precision
If trial and error method is used to find the best focus position, then the correct direction of motion can be determined, but time delays occur due to repeated assessment of scanner position
Solution Approach 1:
The system provides self-service by automatically determining the correct direction of motion through the initial saturation test and then autonomously adjusting the light source intensity and scanner position without requiring repeated manual trial and error assessments, significantly reducing the time lost in iterative focus searching
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 allows for rapid and accurate determination of the best focus position and no-tilt orientation, reducing the need for extensive searches and preventing detector saturation, thereby enhancing the efficiency and accuracy of imaging processes.
Implementation Method 1
the irradiance received at the detector will be maximum when the sample is in a no-tilt position, i.e., perpendicular to the optical path
Implementation Method 2
finding the position corresponding to maximum irradiance at the detector
Data Source
AI summary
The power input to the light source of a microscope is varied as necessary to maintain a constant degree of detector saturation as the objective is moved toward a best-focus position. Focus is found by tracking the source's intensity necessary to maintain the detector irradiance at a constant level. The in-focus position is reached when the power input (and correspondingly the intensity of the light emitted by the source) reaches a minimum. The concept can be applied in a similar manner to minimize or eliminate tilt in a sample.