Autofocus Mechanism for Phase Contrast Observation Device

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Solution Overview

Problem

Existing phase contrast image observation devices face challenges in accurately determining the focus position due to multiple contrast peaks, making it difficult to identify the true focus position using conventional autofocus methods.

Innovation Solution

The observation device employs an autofocus mechanism that utilizes a combination of phase contrast and oblique illumination, where the illumination light is selectively output from different regions to modulate the phase and block light, allowing for accurate focus detection by analyzing contrast peaks, specifically using oblique illumination to ensure a single peak at the focus position.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If phase contrast observation method is used for autofocus, then the contrast measurement can be performed, but multiple contrast peaks appear making it difficult to determine the true focus position

Engineering Contradiction:

Improvefocus position detection accuracyVSAvoidcomplexity of focus determination process

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The illumination light is segmented into two distinct paths: one passing through the phase modulation region and another blocked by the light blocking region. This segmentation creates two separate illumination modes (phase contrast and oblique illumination) that can be selectively applied. The oblique illumination path specifically generates a single contrast peak at the true focus position, resolving the ambiguity of multiple peaks in conventional phase contrast

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The light blocking region acts as an intermediary element that prevents direct light from reaching the image plane through the central region. By blocking this direct light path and allowing only oblique light to pass, the system creates a specific illumination geometry that produces a unique single-peak contrast characteristic at the true focus position, enabling unambiguous focus detection

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If conventional autofocus method with phase contrast is used, then focus detection can be performed, but the position of maximum contrast is not necessarily the true focus position

Engineering Contradiction:

Improvespeed of focus detectionVSAvoidaccuracy of focus position

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The system changes the illumination parameters by switching between two distinct illumination geometries: phase contrast illumination (along the optical axis) and oblique illumination (at an angle to the optical axis). The oblique illumination mode specifically produces a contrast maximum that coincides with the true focus position, thereby improving both the speed and accuracy of focus detection compared to conventional phase contrast alone

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If mask with multiple output regions is used, then selective illumination can be achieved, but the device structure becomes more complex

Engineering Contradiction:

Improveflexibility of illumination controlVSAvoidstructure of illumination optical system

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The mask integrates two distinct output regions (phase contrast region and oblique illumination region) into a single component, along with the light blocking region, all positioned at the same plane. This merging of multiple functional regions into one mask structure allows selective illumination control while avoiding the complexity of separate optical components for each illumination mode

Inventive Principle:

Principle #5Merging (Combining)

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 enables quick and accurate focus detection without complex processes, as the contrast peak at the focus position is distinct, simplifying the autofocus process and improving focus positioning accuracy.

Implementation Method 1

a phase modulation region that is provided in a part of a pupil of the objective optical system and that modulates a phase of the illumination light

Methodology Applied

Scientific EffectPhase modulation: Phase Modulation

Implementation Method 2

a light blocking region that surrounds the pupil and that blocks the illumination light

Methodology Applied

Scientific EffectLight blocking: Absorption (EM radiation)

Data Source

PatentUS11016279B2Observation device

Publication Date: 2021.05.25 EVIDENT CORP

AI summary

An observation device includes: an illumination optical system that irradiates illumination light onto a sample, an objective optical system that has a phase modulation region and a light blocking region and that acquires an image of the illumination light transmitted through the sample, and an autofocus mechanism. The objective optical system selectively outputs the illumination light from a first output region disposed at a position where the illumination light is to be projected onto the phase modulation region and a second output region disposed at a position where a portion of the illumination light is to be projected onto the light blocking region. The autofocus mechanism causes the objective optical system to acquire an image of the illumination light while causing the illumination light to be output from the second output region, and detects the focus position of the objective optical system based on the contrast of the acquired image.