Depolarizer in Optical Imaging Systems for Polarization Fading

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Solution Overview

Problem

Optical imaging systems, particularly those using Michelson and Mach-Zehnder interferometers, face polarization fading issues due to differential polarization evolution in interfering paths, which reduces interferometric efficiency and requires frequent adjustments of polarization controllers to maintain optimal performance.

Innovation Solution

Incorporating a depolarizer and birefringence controller in the optical imaging system to modify polarization-dependent optical path lengths and ensure that light is substantially unpolarized, reducing polarization fading and making the system less sensitive to thermal and mechanical disturbances.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If polarization controllers are used to maintain optimal interferometric efficiency, then signal strength is improved, but system complexity and maintenance requirements increase due to frequent adjustments needed

Engineering Contradiction:

Improveinterferometric signal strengthVSAvoidpolarization controller adjustment frequency

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

The patent extracts the polarization control function from the main interferometric path by introducing a separate depolarizer component. This removes the need for complex polarization controllers that require frequent manual adjustment, as the depolarizer passively handles polarization state management without requiring active control mechanisms.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The depolarizer is designed to automatically maintain optimal polarization conditions through its inherent optical properties. The birefringent elements within the depolarizer self-adjust to compensate for polarization fading without requiring external control systems or manual intervention, making the system self-regulating.

Inventive Principle:

Principle #25Self-service

2Power

If polarization controllers are frequently adjusted to compensate for polarization fading, then interferometric efficiency is maintained, but loss of time and operational productivity decrease

Engineering Contradiction:

Improveinterferometric efficiencyVSAvoidsystem operational continuity

Core Design Contradiction:

PowerVSProductivity

Solution Approach 1:

The depolarizer is pre-configured with birefringent elements that anticipate and prevent polarization fading before it occurs. By establishing the correct polarization state distribution in advance through the depolarizer's fixed optical path differences, the system eliminates the need for reactive adjustments during operation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The depolarizer maintains continuous optimal interferometric efficiency without interruption. The fixed birefringent structure ensures uninterrupted polarization management, allowing the interferometer to operate continuously at peak efficiency without pauses for controller adjustments.

Inventive Principle:

Principle #20Continuity of useful action

3Power

If polarization-dependent optical paths are used in interferometers, then interferometric signal can be generated, but sensitivity to thermal and mechanical disturbances increases

Engineering Contradiction:

Improveinterferometric signal generationVSAvoidenvironmental stability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent transforms the polarization state parameter from a controlled variable requiring active management to a passively managed parameter through the depolarizer. By changing the polarization parameters through fixed birefringent path differences rather than active control, the system becomes insensitive to thermal and mechanical fluctuations that would otherwise require frequent recalibration.

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

The solution significantly reduces polarization fading, stabilizes system performance, and minimizes the need for frequent adjustments of polarization controllers, enhancing the interferometric signal strength and robustness against environmental changes.

Implementation Method 1

A depolarizer is coupled to the light source in the source arm of the optical imaging system and is configured to substantially depolarize the light from the light source

Methodology Applied

Scientific EffectDepolarization: Polarisation

Implementation Method 2

birefringence controller...configured to modify a polarization-dependent optical path length

Methodology Applied

Scientific EffectBirefringence: Birefringence

Implementation Method 3

Low coherence interferometry is a specific class of the more general concept of optical interferometry...An interferometric signal whose modulation amplitude is proportional to the product of the two mixed signals is generated when the difference between optical path lengths is within the coherence length of the signal

Methodology Applied

Scientific EffectInterference: Interference

Data Source

PatentUS7545504B2Imaging systems using unpolarized light and related methods and controllers

Publication Date: 2009.06.09 LEICA MICROSYSTEMS NC INC

AI summary

Optical imaging systems are provided including a light source and a depolarizer. The light source is provided in a source arm of the optical imaging system. A depolarizer is coupled to the light source in the source arm of the optical imaging system and is configured to substantially depolarize the light from the light source. Related methods and controllers are also provided.