Microscope Autofocus Slope Stabilization via Correction Lens
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Solution Overview
Problem
Conventional microscopes with autofocus (AF) functions face challenges in maintaining focus stability due to variations in chromatic aberration and beam diameter differences between infrared AF light and visible observation light, especially when using multiple objective lenses, leading to steep slopes in evaluation function values and narrow in-focus thresholds, which are further affected by ambient temperature and vibration.
Innovation Solution
A microscope apparatus with a switchable objective lens system, a photoreceiver unit for infrared light, an evaluation function calculation unit, and an adjustment unit that sets a constant slope for the evaluation function using a correction lens group, along with a memory unit for storing slope correction factors associated with each objective lens, ensuring stable focus tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an offset lens for chromatic aberration is arranged in the in-focus detection optical system to compensate chromatic aberration between observation light and AF light, then chromatic aberration is corrected, but the beam diameter of AF light at the pupil position becomes different, causing NA to vary and generating variations in the slope of the EF value
Solution Approach 1:
The patent changes the position parameter of the focusing offset lens on the optical path to adjust and control the beam diameter of AF light, thereby controlling the NA and stabilizing the slope of the EF value while maintaining focus measurement precision
Solution Approach 2:
The patent replaces mechanical adjustment methods with an automated control system that calculates the appropriate position of the focusing offset lens based on the relationship between lens position, beam diameter, and EF value slope, enabling automatic optimization without manual mechanical adjustment
2Measurement precision
If the position of the offset lens for chromatic aberration or focusing offset lens is adjusted to correct optical path differences, then focus accuracy is improved, but the slope of the EF value becomes steep, narrowing the in-focus threshold range and making tracking difficult to settle due to temperature or vibration influences
Solution Approach 1:
The patent implements a feedback control mechanism where the control unit continuously monitors the EF value slope and adjusts the focusing offset lens position accordingly to maintain the slope within an optimal range, ensuring stable focus tracking despite environmental disturbances
Solution Approach 2:
The patent makes the optical system dynamic by enabling real-time adjustment of the focusing offset lens position based on operating conditions, allowing the system to adapt and maintain optimal performance across varying temperatures and vibration levels
3Adaptability or versatility
If multiple objective lenses are used with different chromatic aberration characteristics, then observation versatility is improved, but variations in chromatic aberration between lenses cause variations in AF detection position and EF value slope
Solution Approach 1:
The patent creates a universal control system that can automatically adapt to multiple different objective lenses by calculating and adjusting the focusing offset lens position based on each lens's specific chromatic aberration characteristics, enabling consistent focus measurement across all lenses
Solution Approach 2:
The patent applies localized correction by adjusting the focusing offset lens position specifically for each objective lens type, compensating for the unique chromatic aberration characteristics of each lens rather than using a fixed correction for all lenses
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 solution maintains a constant slope of the evaluation function near the in-focus position, stabilizing the in-focus threshold range and reducing the impact of environmental disturbances like temperature and vibration, enabling continuous and accurate focus adjustment.
Implementation Method 1
a photoreceiver unit to receive the reflected infrared light at each of two regions
Implementation Method 2
an adjustment unit for adjusting a slope of the evaluation function calculated by the evaluation function calculation unit so as to be constant on the basis of a position of a correction lens group arranged on the optical path of the focusing optical system
Implementation Method 3
there may be variations in autofocus detection position due to the difference in wavelength of these two types of light and due to chromatic aberration for each of the objective lenses
Data Source
AI summary
The present invention can realize stable focus tracking in the AF control of a microscope by calculating an evaluation function based on a light intensity signal received in two regions and adjusting the slope of the evaluation function to be constant.