Variable Coherence Illumination for Quantitative Phase Imaging
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Solution Overview
Problem
Quantitative phase imaging (QPI) is hindered by coherent artifacts such as speckle noise and coherent noise, which deteriorate image quality and make accurate phase shift measurements difficult due to multiple reflections and unintended diffraction in optical elements.
Innovation Solution
A variable coherence illumination device is introduced, comprising a light source generator, focusing lens, first and second diffusers, collimating lens, and a stage that adjusts the distance between the diffusers, allowing for control of spatial coherence and generation of uncorrelated speckle patterns to reduce coherent artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a coherent light source is used for quantitative phase imaging, then measurement capability of 3D structure is improved, but image quality deteriorates due to coherent artifacts such as speckle noise
Solution Approach 1:
The patent applies dynamics by making the second diffuser rotatable around its normal direction and enabling the stage to move in the first direction, allowing the system to dynamically adjust the spatial coherence of light. This dynamic adjustment generates multiple uncorrelated speckle patterns that can be averaged to reduce coherent artifacts while preserving the measurement capability of the coherent light source
Solution Approach 2:
The patent changes the spatial coherence parameter of the light source by adjusting the distance between the first and second diffusers through stage movement, and by rotating the second diffuser. These parameter changes transform the coherent light into light with reduced coherence, generating uncorrelated speckle patterns that when averaged reduce the harmful coherent artifacts while maintaining the ability to perform phase shift measurements
2Area of stationary object
If the distance between the first diffuser and the second diffuser is increased, then the area of the focusing region increases, but the system complexity increases
Solution Approach 1:
Rather than providing multiple fixed diffuser positions to achieve different focusing region areas, the patent uses a dynamic approach where the stage can move the second diffuser along the first direction. This single movable component allows continuous adjustment of the focusing region area without requiring multiple discrete components, thereby increasing functionality while minimizing system complexity
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
The device effectively reduces coherent artifacts, improving image quality by increasing the number of uncorrelated speckle patterns, which in turn enhances the accuracy of phase shift measurements in QPI.
Implementation Method 1
a focusing lens configured to focus the beam
Implementation Method 2
a first diffuser on which a beam passing through the focusing lens is incident
Implementation Method 3
a second diffuser facing the first diffuser and rotatable around a rotation axis of the second diffuser
Implementation Method 4
a collimating lens configured to convert a beam scattered passing through the second diffuser into a parallel beam
Data Source
AI summary
A variable coherence illumination device is disclosed. The variable coherence illumination device includes a light source generator configured to emit a beam and configured to control a wavelength of the beam, a focusing lens configured to focus the beam, a first diffuser on which a beam passing through the focusing lens is incident, a second diffuser facing the first diffuser and rotatable around a rotation axis of the second diffuser, in which a focusing region on which the beam passing through the first diffuser is focused by the focusing lens is formed on the second diffuser, in which the focusing region of the second diffuser is spaced apart from the rotation axis of the second diffuser.