Object-Space Telecentric Varifocal Microscope Objective
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Solution Overview
Problem
Conventional 3D microscopy techniques face limitations due to shallow depth of field, requiring multiple measurements at different depths for samples with large height variations, leading to time-consuming processes and potential focusing errors, and variable magnification in extended depth-of-field (EDOF) microscopes complicates image combination and introduces parallax errors.
Innovation Solution
An EDOF microscope with an object-space telecentric varifocal microscope objective and structured illumination, allowing focal length tuning while maintaining constant magnification, enables the generation of extended depth-of-field images by scanning focal lengths across depth ranges and combining images with phase-shifted modulation patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional microscopy with standard depth of field is used, then imaging speed is fast, but the depth of field is too shallow to capture thick samples or surfaces with large height variations
Solution Approach 1:
The patent employs a tunable lens that can dynamically adjust its focal length to scan through different depth ranges. This dynamic focusing capability allows the system to capture images at multiple depths without mechanical movement, thereby extending the effective depth of field while maintaining fast acquisition speed. The tunable lens responds to electrical signals to change focus, enabling rapid depth scanning.
Solution Approach 2:
The patent replaces mechanical z-axis translation stages with an electrically tunable lens for depth scanning. This substitution eliminates inertial vibrations and mechanical complexity associated with moving the microscope objective or sample, while achieving the same goal of capturing images at different depths. The electrical tuning mechanism provides faster and more stable depth scanning compared to mechanical systems.
2Length of stationary object
If EDOF microscopy with mechanical z-axis translation is used, then depth of field is extended, but inertial vibration causes focusing errors and reduces measurement stability
Solution Approach 1:
The patent replaces mechanical z-axis translation with an electrically tunable lens that adjusts focal length through electrical signals. This eliminates mechanical inertial vibrations entirely, as the lens elements are repositioned using electro-optical mechanisms rather than physical motors or stages. The result is vibration-free depth scanning with superior focusing accuracy and measurement stability.
Solution Approach 2:
The tunable lens acts as an intermediary between the light path and the sample, enabling depth scanning without direct mechanical movement of the objective or sample stage. By placing the tunable lens in the optical path, the system achieves depth variation through optical focusing changes rather than physical displacement, thereby avoiding mechanical vibration issues.
3Length of stationary object
If varifocal microscopy without object-space telecentric design is used, then depth of field is extended, but magnification varies with focal length causing parallax errors in image combination
Solution Approach 1:
The patent implements object-space telecentricity specifically in the illumination path while allowing the imaging path to maintain standard characteristics. This localized telecentric design ensures that the illumination angle remains constant regardless of focal length changes, eliminating parallax errors in surface height measurement. The telecentric condition is applied only where needed for measurement accuracy rather than throughout the entire system.
Solution Approach 2:
The patent creates an asymmetric optical design where the illumination path is made object-space telecentric while the imaging path follows conventional microscopy principles. This asymmetric configuration allows the system to achieve both extended depth of field through focal length tuning and accurate surface profiling through telecentric illumination, without the complexity of making the entire system telecentric.
4Length of stationary object
If multiple images at different depths are captured and combined, then extended depth of field is achieved, but image combination becomes complex and time-consuming
Solution Approach 1:
The patent uses electrical tuning of the lens focal length instead of mechanical z-axis scanning, which enables faster and more precise control over the depth scanning process. This electrical control allows for systematic capture of images at predetermined depth intervals, simplifying the subsequent image combination process. The tunable lens can be programmed to scan through specific depth ranges, making the image acquisition more organized and easier to process.
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 simplifies image interpretation and combination, reduces reconstruction errors, and achieves a significantly extended depth of field, allowing for accurate surface profiling and defect detection across large height variations without the need for mechanical scanning or deconvolution.
Implementation Method 1
The acoustic tunable lens (from, e.g., TAG Optics) provides a highest speed at 140 kHz
Implementation Method 2
The electrically tunable lens (from, e.g., Optotune) provides only up to 400 Hz scanning rate
Data Source
AI summary
An extended depth-of field microscope includes (a) a microdisplay having an array of emitters capable of illuminating a sample with structured illumination, (b) an image sensor for capturing an image of the sample, and a microscope objective configured to direct the structured illumination toward the sample and direct light from the sample toward the image sensor, wherein the microscope objective has tunable focal length and is object-space telecentric such that tuning of the focal length does not substantially affect magnification of either one of the image formed on the image sensor and the structured illumination projected into object space.