Simultaneous Multi-Focus Image Detection via Beam Segmentation
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Solution Overview
Problem
Current metrology apparatuses require sequential acquisition of multiple images at different focus settings, leading to increased acquisition time and reduced throughput, as well as the need for additional calibration due to mechanical changes and potential drift.
Innovation Solution
A detection apparatus that simultaneously acquires multiple images of an object at various focus levels using a modulator to generate multiple beam copies and a phase plate to impose different defocus levels, allowing for simultaneous capture without moving optical elements, thereby reducing computational effort and hardware costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple images are acquired sequentially at different focus settings, then focus diversity is obtained for phase retrieval, but acquisition time increases and throughput decreases
Solution Approach 1:
The incoming beam is segmented into multiple beam copies using a modulator (e.g., beam splitter, diffraction grating). Each beam copy is then directed to a different focus level by optical elements such as phase plates or deflectors, allowing simultaneous capture of multiple focus planes in a single shot without sequential scanning
Solution Approach 2:
The system transitions from temporal multiplexing (sequential acquisition over time) to spatial multiplexing (simultaneous acquisition across different spatial paths). By introducing spatial separation through beam copying and angular deflection, multiple focus levels are captured concurrently in different spatial regions of the detector
2Measurement precision
If mechanical adjustments are made to change focus settings, then different focus levels are achieved, but calibration complexity increases due to mechanical changes and drift
Solution Approach 1:
The patent replaces mechanical focus adjustment mechanisms with optical field manipulation. Phase plates or spatial light modulators impose controlled phase delays on beam copies to create different focus levels without any moving mechanical parts, thereby eliminating mechanical drift and simplifying calibration
Solution Approach 2:
The system changes the optical parameters (phase, wavelength, angle) of the beam copies to achieve different focus levels. By modulating the phase of each beam copy independently through phase plates or SLMs, the system achieves focus diversity through parameter variation rather than mechanical repositioning
3Measurement precision
If multiple diverse images are obtained sequentially, then computational phase retrieval is improved, but productivity decreases
Solution Approach 1:
The system maintains continuous beam utilization by splitting the incoming beam into multiple copies that are processed simultaneously. All beam copies traverse the optical path and are detected at the same time, ensuring continuous measurement action without interruption or sequential waiting, thereby maximizing throughput while maintaining measurement precision
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 enables faster measurements with reduced calibration needs and increased throughput by capturing focus diversity in a single image capture, improving the efficiency and accuracy of phase retrieval in metrology devices.
Implementation Method 1
a modulator for obtaining multiple beam copies of an incoming beam
Implementation Method 2
a phase plate to impose different defocus levels
Implementation Method 3
a detector operable to capture said multiple beam copies
Data Source
AI summary
Disclosed is a detection apparatus for simultaneous acquisition of multiple images of an object at a plurality of different focus levels; comprising: a modulator for obtaining multiple beam copies of an incoming beam; and a detector operable to capture said multiple beam copies, such that at two of said multiple beam copies are captured at different focus levels. Also disclosed is an inspection apparatus comprising such a detection system.