Optical Phase Object Positioning by Defocus-Induced Contrast

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Solution Overview

Problem

Phase objects in ophthalmic surgery, such as lens fragments and capsular bag tear edges, are difficult to observe due to low contrast in surgical microscopes, making it challenging to accurately position medical instruments for complete removal during procedures like cataract operations.

Innovation Solution

A method and optical observation apparatus that records digital images of an observation region at varying conjugate planes along the optical axis, analyzes image contrasts to identify phase objects, and provides indicators to guide medical instrument positioning relative to these objects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If conventional coaxial illumination is used in surgical microscopes, then the illumination of the observation region is achieved, but phase objects such as lens fragments exhibit low contrast and are difficult to recognize

Engineering Contradiction:

Improveillumination of observation regionVSAvoidvisibility of phase objects

Core Design Contradiction:

Illumination intensityVSDifficulty of detecting and measuring

Solution Approach 1:

The patent applies defocus-induced phase contrast by intentionally introducing a defocus parameter change in the optical path. The conjugate plane is displaced along the optical axis by a predetermined amount, transforming the imaging conditions to convert phase differences into amplitude differences, thereby enhancing the visibility of phase objects without requiring additional illumination equipment.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If the position of phase objects cannot be determined, then the surgical procedure can be performed, but accurate positioning of medical instruments relative to lens fragments is difficult, increasing operation time and risk of complications

Engineering Contradiction:

Improveoperation efficiencyVSAvoidposition determination of phase objects

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent replaces manual positioning and visual estimation with an automated optical measurement system. By recording image stacks at different conjugate plane positions and analyzing contrast variations, the system automatically determines the precise axial positions of phase objects, enabling accurate instrument positioning without relying on surgeon visual judgment alone.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If multiple images at different conjugate plane positions are recorded and analyzed, then the position of phase objects can be determined accurately, but the complexity of the observation apparatus increases

Engineering Contradiction:

Improveposition determination accuracyVSAvoidcomplexity of image recording and analysis system

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The system uses the existing surgical microscope optical path and image sensor to perform both surgical observation and phase object positioning measurements. The same imaging components serve dual purposes: providing surgical visualization and capturing image stacks for automated position determination, thereby minimizing additional hardware complexity while achieving precise measurement capabilities.

Inventive Principle:

Principle #25Self-service

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

Enhances the visibility and accurate positioning of phase objects, allowing for efficient removal of lens fragments and tear edges by guiding medical instruments to them, thereby reducing operation time and minimizing complications.

Implementation Method 1

images each imaging a plane in the observation region that is conjugate to the image plane of the at least one image sensor

Methodology Applied

Scientific EffectOptical focusing: Focusing

Implementation Method 2

phase objects have a different refractive index to the surrounding medium, and so the optical path length of a light beam passing through the transparent object is modified

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 3

phase objects can be highlighted if they are situated at a small distance from a plane that is conjugate to the image sensor. This is based on the defocus-induced phase contrast method

Methodology Applied

Scientific EffectDefocus-induced phase contrast:

Data Source

PatentUS20250377525A1Method for determining the position of at least one phase object in an observation region, and optical observation apparatus

Publication Date: 2025.12.11 CARL ZEISS MEDITEC AG

AI summary

Disclosed is a method and apparatus for ascertaining the position of a phase object in an imaged observation region, at least along the optical axis of an imaging beam path for imaging the observation region. The method includes recording digital images of the observation region by at least one image sensor, wherein the images each image a plane in the observation region that is conjugate to the image plane of the at least one image sensor. The method further includes varying the position of the conjugate plane in the observation region along the optical axis. The method further includes recording a stack of digital images of the observation region with different positions of the conjugate plane in the observation region. The method further includes ascertaining the position of the phase object along the optical axis from the stack of digital images by a digital image evaluation.