Autofocus Control Using Focal Point Deviation Detection
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Solution Overview
Problem
Existing autofocus control methods face challenges in achieving both accuracy and speed, particularly when dealing with thin transparent samples, where the positive autofocus method lacks accuracy due to focal point ambiguity and the passive method requires extensive time for focal point determination.
Innovation Solution
An autofocus control apparatus utilizing a condenser lens with varying focal distances and a light receiving plane configuration that allows for the detection of focal point deviation based on the intersection of a focal line with the light receiving plane, enabling rapid and accurate focal point estimation through single image capture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the positive autofocus control method is used, then the response time is fast, but the measurement precision deteriorates due to focal point ambiguity
Solution Approach 1:
The detector is divided into multiple detection regions (first detection region and second detection region) positioned at different locations. By segmenting the detection function across multiple regions and comparing signals from these regions, the system resolves focal point ambiguity while maintaining fast response time, eliminating the need for slow scanning methods.
2Measurement precision
If the passive autofocus control method is used, then the measurement precision is high, but the loss of time increases due to extensive lens movement and image analysis
Solution Approach 1:
The system performs preliminary arrangement of multiple detection regions at predetermined positions before the focusing operation begins. This preliminary configuration allows the system to detect focal point deviation immediately without requiring time-consuming lens movement and image analysis, thus achieving high precision while minimizing time loss.
Solution Approach 2:
The invention replaces the mechanical scanning system (moving the objective lens to capture multiple images) with an optical detection system using multiple detection regions and signal comparison. This substitution eliminates the need for mechanical lens movement and extensive image analysis, achieving fast focal point detection with high precision.
3Measurement precision
If the objective lens is moved to find the focal point, then accurate focal point determination is achieved, but the productivity decreases due to extended operation time
Solution Approach 1:
The system uses the reflected light from the sample itself to generate detection signals at multiple regions. The sample's own reflected light serves the dual purpose of both imaging and focal point detection, eliminating the need for separate scanning operations and thereby maintaining high productivity while achieving accurate focal point determination.
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 solution enables faster and more accurate focal point detection by recognizing the focal point via single image capture, improving upon conventional methods by providing both high-speed operation and precise focal point determination.
Implementation Method 1
a beam splitter configured to direct light beams from the light source toward a sample and to pass light beams reflected from the sample
Implementation Method 2
a condenser lens configured to condense the light beams reflected from the sample and passing through the beam splitter
Data Source
AI summary
An autofocus control apparatus includes a beam splitter, a condenser lens and a detector. The beam splitter directs light beams from a light source toward a sample and passes light beams reflected from the sample to the condenser lens. The condenser lens condenses the light beams, and the detector detects a focal point deviation of the sample relative to a focal point of the condenser lens. The focal point deviation is detected based on an intersection of a focal line passing through different focal points of the condenser lens and a light receiving plane configured to receive the light beams passing through the condenser lens.