Methods and devices for standoff differential Raman spectroscopy with increased eye safety and decreased risk of explosion
Inventors
Vakhshoori, Daryoosh • Blanchard, Romain • Chen, Peili • Azimi, Masud • Mansuripur, Tobias • Krishnamurthy, Kalyani • Bibby, Arran M. • Huettig, III, Fred R. • Ulu, Gokhan • Vander Rhodes, Greg
Assignees
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Publication Number
US-12339165-B2
Publication Date
2025-06-24
Expiration Date
Abstract
A compact, portable Raman spectrometer makes fast, sensitive standoff measurements at little to no risk of eye injury or igniting the materials being probed. This spectrometer uses differential Raman spectroscopy and ambient light measurements to measure point-and-shoot Raman signatures of dark or highly fluorescent materials at distances of 1 cm to 10 m or more. It scans the Raman pump beam(s) across the sample to reduce the risk of unduly heating or igniting the sample. Beam scanning also transforms the spectrometer into an instrument with a lower effective safety classification, reducing the risk of eye injury. The spectrometer's long standoff range automatic focusing make it easier to identify chemicals through clear and translucent obstacles, such as flow tubes, windows, and containers. And the spectrometer's components are light and small enough to be packaged in a handheld housing or housing suitable for a small robot to carry.
Core Innovation
The invention provides standoff differential Raman spectroscopy that improves eye safety and reduces explosion and ignition risk associated with Raman pump beams. A Raman pump laser illuminates a sample with Raman pump beam(s), while a beam-steering element scans the Raman pump beam across the sample to reduce a risk of igniting the sample. This scanning lowers accessible exposure by increasing an apparent spot size and by reducing sample radiance and heating.
The system performs differential Raman spectroscopy using ambient-light/background subtraction. It acquires interleaved background frames and applies ambient-light/background subtraction to obtain a post-processed signature from the scattered Raman signal. Raman pump beams can include Raman pump lasers at different wavelengths to support measurement of Raman signals and signatures.
The invention also includes automatic standoff focusing and fail-safe monitoring. A telescope with a laser ranging beam and a camera acquires an image of a spot formed by the ranging beam on the sample, and a controller determines a focus of the telescope based on the position of the spot, with an actuator adjusting the focus in response. The system monitors scan position, including shutdown if malfunction, and monitors sample temperature with laser shutoff, and can use temperature measurement via infrared thermometry or Raman Stokes/anti-Stokes methods with Raman temperature markers.
System architectures are provided for handheld and robot-mounted use, including two-part system with probe and core modules, telescopic ranging, and long standoff range from centimeters to meters. The system can measure through obstacles and windows, using camera-based imaging and aim tracking with beam-steering elements to scan the Raman pump beam.
Claims Coverage
The document contains one independent claim. It requires a Raman spectroscopy system that combines telescope/camera ranging-based focus adjustment with Raman pump scanning using a beam-steering element to reduce ignition risk, and includes user display and input via a touchscreen. The dependent claims further refine optical geometry relationships, add multi-wavelength Raman pumping, and define robot-mounted implementations.
Ranging-beam telescope focus determination and adjustment
A system with a laser to emit a ranging beam, a telescope to illuminate a sample with the ranging beam, a camera to acquire an image of a spot formed by the ranging beam on the sample, a controller to determine a focus of the telescope based on a position of the spot in the image, and an actuator to adjust the focus of the telescope in response to a command from the controller.
Raman pump scanning for ignition-risk reduction
A Raman pump laser to illuminate the sample with a Raman pump beam, a spectrometer to measure a spectrum of a Raman signal scattered by the sample in response to the Raman pump beam, and a beam-steering element to scan the Raman pump beam across the sample so as to reduce a risk of igniting the sample with the Raman pump beam.
User imaging display and input via touchscreen
A touchscreen coupled to the camera to display the image of the sample to a user and to receive an input from a user.
Geometric alignment of ranging beam with telescope optical axis at Raman pump focal plane
The system configured so the ranging beam intersects the telescope optical axis at a focal plane of the Raman pump beam.
Lateral offset between camera and telescope optical axes
The system characterized by a camera whose optical axis is laterally offset from the telescope optical axis.
Multi-wavelength Raman pumping with second Raman pump laser
The system configured with a second Raman pump laser at a different wavelength so that a spectrometer measures a spectrum of a second Raman signal scattered by the sample in response to the second Raman pump beam.
Robot-supported Raman spectroscopy system
A robot that supports the system described in the Raman spectroscopy system.
Robot arm supporting and moving the system
The robot further includes an arm to support and move the system.
Overall, the claim set focuses on a Raman spectroscopy system that uses ranging-beam telescope focus determination and scanning of the Raman pump beam via a beam-steering element to reduce ignition risk, while measuring Raman spectra with a spectrometer. Dependent claims refine optical alignment geometry, add a second Raman pump laser at a different wavelength, and cover robot-supported and arm-supported system implementations.
Stated Advantages
Reduces a risk of igniting the sample with the Raman pump beam.
Improves eye safety.
Lowers accessible exposure via increased apparent spot size.
Reduces sample radiance and heating.
Provides a way to measure differential Raman using ambient-light/background subtraction with interleaved background frames.
Enables automatic standoff focusing based on ranging-beam spot position.
Provides fail-safe monitoring including scan position monitoring with shutdown if malfunction and temperature monitoring with laser shutoff.
Documented Applications
Standoff differential Raman spectroscopy measurement through obstacles and windows at long standoff ranges from centimeters to meters.
Use in handheld standoff instruments.
Use in robot-mounted systems, including a two-part system with probe and core modules.
Temperature measurement using infrared thermometry and/or Raman Stokes/anti-Stokes temperature measurement with Raman temperature markers.
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