Self-Differential Confocal Tilt Sensing for Rough Sample Surfaces
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current tilt sensors in charged particle beam systems face challenges in accurately measuring sample tilt, especially for samples with rough surfaces, due to sensitivity limitations and interference from surface irregularities, which can lead to decreased imaging quality and increased costs with the need for cooperative targets.
Innovation Solution
A self-differential confocal tilt sensor system that uses a common mode reference beam and a confocal aperture to enhance sensitivity and accuracy, canceling source power variations and ambient light interference, allowing for precise tilt measurement without a cooperative target.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional tilt sensor is used to measure sample tilt, then the measurement can be performed, but the sensitivity is insufficient and accuracy decreases for samples with rough surfaces
Solution Approach 1:
The optical beam is divided into multiple segments by introducing lateral displacement through a wedge prism or tilting the sample. Instead of measuring the entire beam position, the system segments the beam and measures the displacement of individual segments, which enhances the sensitivity to tilt angles while reducing the impact of surface irregularities on the overall measurement
Solution Approach 2:
A wedge prism is introduced as an intermediary element between the light source and the sample. This prism creates a known lateral displacement of the beam that serves as a reference, allowing the system to differentiate between displacement caused by tilt and displacement caused by surface irregularities, thereby improving measurement accuracy
2Measurement precision
If a cooperative target is used to improve tilt measurement accuracy, then measurement precision improves, but device complexity and setup steps increase
Solution Approach 1:
The system uses the sample itself or its holder as the measurement target without requiring external cooperative targets. The tilt measurement is performed by directly analyzing the position of the optical beam reflected from or transmitted through the sample/holder, eliminating the need for additional target preparation and reducing device complexity
Solution Approach 2:
The optical sensor system is designed to perform multiple functions: it can measure tilt angles, detect sample position, and characterize surface properties using the same basic configuration without requiring different targets or sensors for each measurement type, thereby reducing overall system complexity
3Device complexity
If the sensor operates without compensation for source power variations, then the system is simpler, but measurement accuracy decreases due to power fluctuations
Solution Approach 1:
The system incorporates a feedback mechanism where the position detector continuously monitors the beam position and this information is fed back to adjust measurements in real-time. This feedback loop compensates for power variations by normalizing measurements based on the actual beam intensity and position, maintaining accuracy without requiring complex additional hardware
Solution Approach 2:
The system changes the measurement parameter from absolute intensity-based detection to position-based detection. By measuring the lateral position of the beam rather than its absolute intensity, the system becomes inherently insensitive to power fluctuations, as position measurement remains accurate regardless of beam brightness variations
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 system provides improved sensitivity and accuracy in detecting sample tilt, reducing errors in imaging and increasing the useful lifetime of the sensor by compensating for laser source degradation, while also minimizing the need for additional setup steps and equipment.
Implementation Method 1
a lens configured to focus light from the light source, and the lens may be arranged between the second optical element and an aperture
Implementation Method 2
the aperture may be arranged between the third optical element and the second sensing element, and the aperture may be arranged at a focal plane of the lens
Implementation Method 3
a first beam splitter configured to transmit light toward a sample, and to reflect light toward a second beam splitter
Data Source
AI summary
A sensor may be used to measure a degree of tilt of a sample. The sensor may include an apparatus having a light source, first, second, and third optical elements, a lens, and an aperture. The first optical element may supply light from the light source toward the sample, and may supply light input into the first optical element from the sample toward the second optical element. The second optical element may supply light toward first and second sensing elements. An aperture may be arranged on a focal plane of the lens. A light beam incident on the first sensing element may be a reference beam.