Offset Observation Plane for Diffraction Pattern Dynamic Range Reduction
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Solution Overview
Problem
Conventional imaging systems face challenges in accurately recording diffraction patterns with high dynamic ranges due to large differences in light intensities, leading to saturation or noise issues in detectors, especially when the diffracting structure has a minimal effect on the incident wave, causing loss of detail at pattern edges.
Innovation Solution
A method and apparatus that detect the intensity of radiation scattered by a target object at an observation plane offset from the back focal plane of a focusing element, reducing the dynamic range and using an iterative phase retrieval scheme to adjust for the offset, allowing for accurate recording of diffraction patterns with reduced maximum intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a lens is used to focus scattered wave components at an observation plane coincident with the back focal plane, then the diffraction pattern is accurately recorded, but the dynamic range becomes too large causing saturation at the center and loss of detail at edges
Solution Approach 1:
The patent introduces a new dimension by offsetting the observation plane from the back focal plane along the optical axis. This spatial displacement in the third dimension (depth/focal distance) transforms the diffraction pattern distribution, spreading the intensity values more evenly across the detector array and eliminating the extreme dynamic range problem while maintaining measurement accuracy.
2Measurement precision
If the observation plane is offset from the back focal plane, then the dynamic range is reduced and recording accuracy improves, but the standard Fourier transform relationship no longer directly applies
Solution Approach 1:
The patent modifies the mathematical model by introducing a propagation distance parameter (offset distance) into the Fourier transform relationship. This parameter change adapts the standard transform to account for the displaced observation plane, allowing accurate reconstruction of the object's transmission function while maintaining computational feasibility through established optical processing techniques.
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 effectively reduces the dynamic range required for capturing diffraction patterns, improving the accuracy and detail in recorded images by spreading high and low scattering angle data across the observation plane, thereby enhancing the quality of the recorded diffraction patterns.
Implementation Method 1
Diffraction occurs when light, or any wave phenomenon, interacts with a boundary between two different mediums. Examples could be the wave patterns formed by water around harbour walls, or the fuzzy edge of a shadow, which would be very sharply defined were it not for diffraction.
Implementation Method 2
The effect of a lens is to cause focusing each wave component to a point on the observation plane. The location of this point is determined by the scattering angle of the particular wave component
Implementation Method 3
an iterative scheme to drive an initial random guess at the diffracting object toward a good estimate of its transmission function
Data Source
AI summary
A method and apparatus are disclosed for providing image data for generating an image of a region of a target object. The method includes the steps of providing incident radiation, focusing the radiation downstream or upstream of a target object and via at least one detector located downstream of a focusing element, detecting an intensity of radiation scattered by the target object at an observation plane offset from a back focal plane associated with the focusing element.