Tunable Laser Scanning Apparatus for Mid-Infrared Surface Imaging
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Solution Overview
Problem
Quantum cascade lasers face challenges in imaging non-flat and non-parallel samples due to out-of-focus areas, which limit image resolution, as existing technologies struggle to efficiently adjust the focal distance in real-time for mid-infrared spectroscopic measurements.
Innovation Solution
A scanning apparatus with a tunable light source, a displacement sensor, and a controller that adjusts the focal length or distance between the focusing lens and the specimen to maintain focus, allowing for raster scanning and rapid imaging by separating the displacement sensor from the scanning assembly and using piezoelectric drives for focal adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the focusing lens maintains a fixed distance from the stage, then the device structure is simple, but the image resolution deteriorates in areas that are not in focus
Solution Approach 1:
The patent applies dynamics by making the focusing lens movable along the optical axis through a piezoelectric actuator, allowing the in-focus distance to be dynamically adjusted based on the measured surface topology of the specimen. This enables the system to maintain focus across varying surface heights while keeping the overall device structure relatively simple.
Solution Approach 2:
The patent implements feedback by using a displacement sensor to measure the surface topology of the specimen and feeding this information back to the controller, which then adjusts the in-focus distance of the focusing lens accordingly. This closed-loop feedback mechanism ensures that the system adapts to surface variations and maintains optimal focus for high-resolution imaging.
2Manufacturing precision
If the in-focus distance is adjusted for each measurement point, then the image resolution is improved, but the scanning speed decreases
Solution Approach 1:
The patent applies preliminary action by using a displacement sensor to measure and map the surface topology of the specimen before the infrared imaging process. This pre-measurement allows the controller to pre-calculate and prepare the appropriate in-focus distance adjustments, enabling rapid focal adjustments during scanning without compromising imaging speed or resolution.
3Measurement precision
If the displacement sensor moves with the scanning assembly, then the measurement accuracy is improved, but the device complexity and mass increase
Solution Approach 1:
The patent uses an intermediary approach by introducing a separate stationary displacement sensor that measures surface topology independently of the scanning assembly. The sensor measures the surface at a displaced location, and the controller uses this information to adjust the focusing lens for the actual measurement point, eliminating the need for the displacement sensor to move with the scanning assembly.
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 solution enables high-resolution imaging of non-flat samples by maintaining focus across varying surface topologies, improving scanning speed and accuracy by using a displacement sensor to map specimen surfaces and adjust the focal point dynamically, thereby enhancing the quality of mid-infrared images.
Implementation Method 1
Quantum cascade lasers provide a tunable mid-infrared (MIR) light source that can be used for spectroscopic measurements and images
Implementation Method 2
a focusing lens that focuses the light beam to a measurement point on the specimen
Implementation Method 3
a displacement sensor that measures a distance between the scanning assembly at a mapping point on the specimen
Implementation Method 4
using piezoelectric drives for focal adjustments
Data Source
AI summary
A scanning apparatus having a stage adapted to hold a specimen to be imaged and to move the specimen in a first direction, and a light source that includes a tunable laser that generates a light beam having an illumination wavelength that varies as a function of an input signal is disclosed. The apparatus includes an imaging system having a scanning assembly that includes a focusing lens that focuses the light beam to a measurement point on the specimen, a first mirror that moves in a second direction relative to the stage such that the focusing lens maintains a fixed distance between the focusing lens and the stage, and a displacement sensor that measures a distance between the scanning assembly at a mapping point on the specimen, and a light detector that measures an intensity of light leaving the measurement point on the specimen.