Microscope Oblique Illumination Digital Contrast Enhancement

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Solution Overview

Problem

Oblique illumination in microscopy, particularly when used with microtiter plates, leads to issues such as geometric shadowing and shifts in the illuminated surface due to the depth of wells and liquid meniscus, resulting in reduced contrast and image quality, which conventional methods like phase contrast or differential interference contrast cannot effectively address.

Innovation Solution

The method combines oblique illumination with digital image processing using a convolution kernel to enhance contrast, where the illumination beam path is decentered and larger than conventional settings, and the convolution kernel is aligned with the direction of oblique illumination to amplify contrast-enhancing effects, minimizing artifacts and noise.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If oblique illumination is used with microtiter plates, then contrast enhancement is achieved, but geometric shadowing and image quality degradation occur due to well depth and liquid meniscus

Engineering Contradiction:

ImprovecontrastVSAvoidgeometric shadowing

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The patent applies digital image processing with convolution kernels to modify the captured image parameters, enhancing contrast while compensating for geometric shadowing effects. The convolution kernel transforms the raw image data to emphasize edges and relief features without being affected by the physical illumination geometry

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the mechanical/optical solution (adjusting illumination geometry to avoid shadowing) with a digital signal processing approach. Instead of physically modifying the illumination path to eliminate shadowing, the system captures the shadowed image and uses convolution-based digital processing to enhance contrast and compensate for artifacts

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Illumination intensity

If decentered aperture diaphragm is used for oblique illumination, then relief impression is enhanced, but lateral image shift occurs when focusing in Z direction

Engineering Contradiction:

Improverelief impressionVSAvoidimage position stability

Core Design Contradiction:

Illumination intensityVSManufacturing precision

Solution Approach 1:

The patent applies digital image processing with convolution kernels to pre-compensate for lateral image shifts that occur during Z-axis focusing. The convolution operation enhances edges and features in a way that maintains positional consistency across different focal planes, effectively predicting and correcting for the lateral shift before it degrades image quality

Inventive Principle:

Principle #10Preliminary action

3Illumination intensity

If conventional oblique illumination is used, then contrast is increased for low-contrast specimens, but artifacts and noise are amplified

Engineering Contradiction:

ImprovecontrastVSAvoidartifacts and noise

Core Design Contradiction:

Illumination intensityVSObject-generated harmful factors

Solution Approach 1:

The patent uses convolution-based digital image processing as a feedback mechanism to enhance contrast while suppressing artifacts and noise. The convolution kernel operates on the captured image to emphasize true structural features while filtering out spurious artifacts and noise that are amplified by conventional oblique illumination

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent transforms the image data through convolution operations that selectively enhance contrast parameters for genuine structural features while suppressing parameters associated with artifacts and noise. The digital processing allows independent control of contrast enhancement and artifact suppression

Inventive Principle:

Principle #35Parameter changes

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 produces a contrast-enhanced image with a relief impression that overcomes the limitations of oblique illumination alone, reducing lateral image shifts and maintaining object similarity, making it suitable for low-contrast specimens like microtiter plates.

Implementation Method 1

the wave fronts of the illuminating light pass through the preparation more or less obliquely, i.e., angled relative to the optical axis within a certain angular range. Due to the asymmetry of the illumination, the differently angled wave fronts do not average out when there is interference in the image

Methodology Applied

Scientific EffectInterference: Interference

Implementation Method 2

An examination with oblique incident light is, for example, used when examining wafers, in order to exploit the diffraction effects arising at the structures of the wafer surface

Methodology Applied

Scientific EffectDiffraction: Diffraction

Data Source

PatentUS10823951B2Method for imaging in a microscope with oblique illumination

Publication Date: 2020.11.03 LEICA MICROSYSTEMS CMS GMBH

AI summary

A method for imaging in a microscope with oblique illumination includes illuminating an object by an illumination beam path that is obliquely incident on an object plane of the microscope. A microscopic image of the object and a corresponding digital image signal are produced. The digital image signal is processed by digital image processing using a convolution kernel to increase contrast. An increased-contrast digital image is produced from the processed digital image signal.