Standoff Raman spectroscopy for architectural interiors from 3-15 m distances

Liu, Yu; Cheung, Chi Shing; Kogou, Sotiria; Liggins, Florence; Liang, Haida

doi:10.1364/oe.27.031338

Cited by 15 publications

(10 citation statements)

References 24 publications

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“…The original configuration of this system operational at 3–15 m has been described in detail in our previous publications [ 6 , 7 ]. The system employed a 780 nm continuous-wave (CW) laser as excitation source.…”

Section: The Upgraded Remote Standoff Raman Systemmentioning

confidence: 99%

“…Discussions in our earlier publication [ 6 ] show that the efficiency advantage of CW versus pulsed lasers for Raman detection depends on the damage threshold. Efficiency of Raman detection here is defined to be Raman signal detected for a given measurement time, or by proxy, the incident laser energy on the material for a given measurement time.…”

Section: Laser-induced Degradation Testsmentioning

confidence: 99%

“…As discussed in our previous paper [ 6 ], there is a balance between safe and efficient Raman measurements, which determines whether it is optimal to use a pulsed or CW laser for safe and efficient remote standoff Raman measurements. Here the relative efficiency of Raman measurement is defined by the total laser energy incident on a material, which is proportional to the Raman signal generated for a given material, in the same measurement time.…”

Section: Laser-induced Degradation Testsmentioning

confidence: 99%

“…However, drawbacks in their practical use, in particular for wall paintings and large monuments, such as difficulty in positioning the probe, instability (vibrations) of the scaffold in supporting sensitive measurements that needs integration times greater than a few milliseconds, and the inefficiency in re-positioning the system to access different parts of a large monument have been noted [ 5 ]. Recently, we reported the development and application of a remote standoff Raman system at working distance of 3–15 m dedicated to research of historical sites and large paintings and monuments [ 6 , 7 ]. The system can be placed at one position on the ground and take measurements of any part of an architectural interior from difficult to access recesses in sculptures to ceiling paintings at lofty heights.…”

Section: Introductionmentioning

confidence: 99%

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A study of potential laser-induced degradation in remote standoff Raman spectroscopy for wall paintings

et al. 2022

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A mobile remote standoff Raman spectroscopy system operational at typical distances of 10 m was developed specifically for research of historical sites and wall paintings recently. Here we present an upgrade to that system informed by a thorough experimental investigation of the relevant laser-induced degradation issues. Reflectance spectroscopy as a more sensitive technique than Raman spectroscopy was used for monitoring and a new phenomenon of reversible alterations was detected in many paint samples at very low laser intensities of less than 1 W/cm2 when Raman measurements detected no changes. Contrary to conventional wisdom, the intensity threshold for safe operation was found to decrease significantly for larger incident irradiation area in the case of a vermilion oil paint sample. Damage threshold in intensity for each material needs to be determined for different spot sizes, which can be orders of magnitude lower for 1 mm spot size compared with micro-Raman. Results from this study is also relevant to portable Raman systems which use similarly large spot sizes. However, the larger spot size still generates more Raman photons overall under safe operation than micro-Raman systems. Continuous-wave (CW) lasers are found to be best suited to efficient, that is more Raman signal detected over a given measurement time, and safe Raman operation than ns-pulse lasers at the same wavelength. While the damage threshold in intensity for ns-pulse lasers is much higher than that of CW lasers, the pulse energy allowed in one pulse for safe operation is still too low to allow detection of Raman signal, and the need for multiple pulses makes pulse laser inefficient owing to the low repetition rate necessary to ensure adequate heat dissipation between pulses. The safety of the upgraded system was evaluated and found that no permanent laser-induced degradation was detected within 60 s of laser irradiation for any of the paint samples.

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Section: The Upgraded Remote Standoff Raman Systemmentioning

confidence: 99%

Section: Laser-induced Degradation Testsmentioning

confidence: 99%

Section: Laser-induced Degradation Testsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A study of potential laser-induced degradation in remote standoff Raman spectroscopy for wall paintings

et al. 2022

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“…However, in a nuclear facility, pulsed instruments cannot be used due to the large power densities at the target. When using continuous wave (CW) lasers, stand-off Raman observations [13,14] have been demonstrated for measurement of nitrates and explosives from tens of metres up to 250 m using large 200-mm diameter telescopes. [15] Additionally, in this instance, the requirement for a low power density at the target poses significant challenges.…”

Section: The Raman Spectrometermentioning

confidence: 99%

Remote sensing of chemical agents within nuclear facilities using Raman spectroscopy

Foster

Wharton

Brooks

et al. 2020

J Raman Spectroscopy

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Stand‐off Raman spectroscopy is a promising approach for the detection and identification of bloodstains for forensic purposes

Almehmadi,

Lednev

2023

J Raman Spectroscopy

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Stand‐off Raman spectroscopy combined with chemometrics was demonstrated to have great potential for detecting and identifying biological stains from a distance for forensic purposes. Bloodstain spectra were collected using a handheld Raman spectrometer equipped with a stand‐off attachment and compared with spectra acquired with a benchtop Raman microscope. The two sets of spectra were visually similar, supporting the potential use of a handheld Raman spectrometer with stand‐off attachment for blood detection at the scene of crime. In addition, the stand‐off Raman spectra of bloodstains were correctly identified using a previously built SVM‐DA model for the identification of all main body fluids (Muro et al., Forensic Chemistry, 2016). Stand‐off Raman spectroscopy opens a new potential opportunity for further development of Raman spectroscopy as a universal tool for detecting and identifying body fluid traces for forensic purposes.

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Standoff Raman spectroscopy for architectural interiors from 3-15 m distances

Cited by 15 publications

References 24 publications

A study of potential laser-induced degradation in remote standoff Raman spectroscopy for wall paintings

A study of potential laser-induced degradation in remote standoff Raman spectroscopy for wall paintings

Remote sensing of chemical agents within nuclear facilities using Raman spectroscopy

Stand‐off Raman spectroscopy is a promising approach for the detection and identification of bloodstains for forensic purposes

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