Spatial Light Modulator Phase Retrieval for Optical Imaging
Solution Overview
Problem
Current methods for spatially resolved determination of the phase and amplitude of electromagnetic fields in the image plane of an object irradiated with coherent light are inefficient, often requiring iterative and time-consuming processes, and are limited by defocusing techniques which can lead to blurred images and reduced accuracy.
Innovation Solution
The method involves spatial frequency filtering in a pupil plane between the object and image plane, allowing for precise modification of phase and amplitude, enabling the capture of images under various conditions and improving accuracy through the use of iterative algorithms like Gerchberg-Saxton, with options for further image manipulation such as defocusing and polarization variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If defocusing is used to capture multiple images for phase determination, then more images can be acquired, but image quality deteriorates due to blurring
Solution Approach 1:
A spatial light modulator is introduced as an intermediary device in the optical path to modulate the light field. This modulator can impose phase or amplitude patterns on the light without physically defocusing the imaging system, thereby avoiding image blurring while still providing the varied intensity measurements needed for phase retrieval algorithms
Solution Approach 2:
The patent replaces the mechanical defocusing method with an optical field modulation approach using a spatial light modulator. Instead of mechanically moving the lens or detector to change focus, the system uses programmable optical elements to modify the light field, eliminating mechanical wear and maintaining constant focus for sharp images
2Measurement precision
If iterative phase retrieval algorithms are used, then phase can be determined from intensity measurements, but computing time increases significantly
Solution Approach 1:
The spatial light modulator is programmed in advance with specific phase or amplitude patterns before each measurement. This preliminary configuration allows the system to capture multiple varied intensity images quickly without requiring iterative adjustments during the measurement process, reducing total acquisition and computation time
Solution Approach 2:
The system uses periodic modulation of the light field through the spatial light modulator, cycling through different known phase or amplitude patterns. This periodic action provides structured variations in the intensity measurements that accelerate convergence of phase retrieval algorithms compared to random or mechanical defocusing approaches
3Measurement precision
If multiple images are captured with different phase/amplitude modifications, then phase determination accuracy improves, but device complexity increases
Solution Approach 1:
The spatial light modulator serves multiple functions: it can impose phase patterns, amplitude patterns, or combinations thereof, and can be reprogrammed for different measurement configurations. This single multi-functional device replaces what would otherwise require multiple separate optical components or mechanical adjustment mechanisms
Solution Approach 2:
The spatial light modulator provides dynamic, programmable control over the light field characteristics. Rather than requiring fixed optical components or mechanical adjustments, the system can electronically reconfigure the modulation patterns adaptively, reducing mechanical complexity while maintaining measurement flexibility
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 allows for more accurate and flexible phase reconstructions with reduced computing effort, overcoming the limitations of defocusing and enabling the determination of phase and amplitude with higher precision and flexibility.
Implementation Method 1
illuminating the object with coherent light from a lighting device and imaging it in an image plane
Implementation Method 2
imaging optics
Implementation Method 3
spatial frequency filtering in a pupil plane between the object and image plane, allowing for precise modification of phase and amplitude
Implementation Method 4
detecting light in the image plane in a spatially resolved manner in pixels
Data Source
Figure 1
Figure 2A~2C
AI summary
The invention relates to a method for the spatially resolved determination of the phase and amplitude of the electromagnetic field in the image plane of an image of an object. Here, images are produced by virtue of the fact that the object is illuminated using coherent light and is imaged into an image plane, light is detected in the image plane in a spatially resolved manner in pixels, wherein for each pixel the intensity of the light is determined, stored in image points and the image points are assigned to an image. First, a first then at least one further image are produced, wherein the phase and/or the amplitude of the light is modified in a predefined manner and the modification for each image differs from those for the other images. The phase in the image of the object in the image plane is determined in a spatially resolved manner from the images produced. The invention also relates to an apparatus for implementing the method. In such a method, the phase and/or the amplitude of the light is/are modified by a spatial frequency filtering in a pupil plane between object and image plane.