Abstract

Portable and mobile Raman spectroscopy systems are increasingly being adopted in in situ non-invasive examination of artworks given their high specificity in material identification. However, these systems typically operate within centimeter range working distances, making the examination of large architectural interiors such as wall paintings in churches challenging. We demonstrate the first standoff Raman spectroscopy system for in situ investigation of historic architectural interior at distances > 3 m. The 780 nm continuous wave laser-induced standoff Raman system was successfully deployed for the in situ examination of wall paintings, at distances of 3–15 m, under ambient light. It is able to identify most common pigments while maintaining a very low laser intensity to avoid light induced degradation. It is shown to complement our current method of standoff remote surveys of wall paintings using spectral imaging.

Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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References

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  1. P. Vandenabeele, H. G. M. Edwards, and J. Jehlička, “The role of mobile instrumentation in novel applications of Raman spectroscopy: Archaeometry, geosciences, and forensics,” Chem. Soc. Rev. 43(8), 2628–2649 (2014).
    [Crossref]
  2. H. Liang, A. Lucian, R. Lange, C. Cheung, and B. Su, “Remote spectral imaging with simultaneous extraction of 3D topography for historical wall paintings,” ISPRS J. Photogramm. Remote Sens. 95, 13–22 (2014).
    [Crossref]
  3. S. P. Best, R. J. H. Clark, and R. Withnall, “Non-destructive pigment analysis of artefacts by Raman microscopy,” Endeavour 16(2), 66–73 (1992).
    [Crossref]
  4. R. J. H. Clark, “Raman microscopy: application to the identification of pigments on medieval manuscripts,” Chem. Soc. Rev. 24(3), 187 (1995).
    [Crossref]
  5. M. Pérez-Alonso, K. Castro, and J. M. Madariaga, “Investigation of degradation mechanisms by portable Raman spectroscopy and thermodynamic speciation: The wall painting of Santa María de Lemoniz (Basque Country, North of Spain),” Anal. Chim. Acta 571(1), 121–128 (2006).
    [Crossref]
  6. L. Bellot-Gurlet, F.-X. Le Bourdonnec, G. Poupeau, and S. Dubernet, “Raman micro-spectroscopy of western Mediterranean obsidian glass: one step towards provenance studies?” J. Raman Spectrosc. 35(89), 671–677 (2004).
    [Crossref]
  7. B. I. Łydzba-Kopczyńska, B. Gediga, J. Chojcan, and M. Sachanbiński, “Provenance investigations of amber jewelry excavated in Lower Silesia (Poland) and dated back to Early Iron Age,” J. Raman Spectrosc. 43(11), 1839–1844 (2012).
    [Crossref]
  8. D. A. Leonard, “Observation of Raman scattering from the atmosphere using a pulsed nitrogen ultraviolet laser,” Nature 216(5111), 142–143 (1967).
    [Crossref]
  9. J. Cooney, J. Orr, and C. Tomasetti, “Measurements separating the gaseous and aerosol components of laser atmospheric backscatter,” Nature 224(5224), 1098–1099 (1969).
    [Crossref]
  10. S. M. Angel, N. R. Gomer, S. K. Sharma, C. McKay, and N. Ames, “Remote Raman spectroscopy for planetary exploration: A review,” Appl. Spectrosc. 66(2), 137–150 (2012).
    [Crossref]
  11. A. Pettersson, I. Johansson, S. Wallin, M. Nordberg, and H. Östmark, ““Near real-time standoff detection of explosives in a realistic outdoor environment at 55 m distance,” Propellants,” Propellants, Explos., Pyrotech. 34(4), 297–306 (2009).
    [Crossref]
  12. H. Liang, R. Lange, A. Lucian, P. Hyndes, J. H. Townsend, and S. Hackney, “Development of portable microfading spectrometers for measurement of light sensitivity of materials. Paper 1612,” in Preprints, ICOM Committee for Conservation, ICOM-CC, 16th Triennial Conference, Lisbon (2011), pp. 19–23.
  13. L. Burgio, R. J. H. Clark, and S. Firth, “Raman spectroscopy as a means for the identification of plattnerite (PbO2), of lead pigments and of their degradation products,” Analyst 126(2), 222–227 (2001).
    [Crossref]
  14. H. Liang, M. Mari, C. S. Cheung, S. Kogou, P. Johnson, and G. Filippidis, “Optical coherence tomography and non-linear microscopy for paintings – a study of the complementary capabilities and laser degradation effects,” Opt. Express 25(16), 19640 (2017).
    [Crossref]
  15. S. K. Sharma, P. G. Lucey, M. Ghosh, H. W. Hubble, and K. A. Horton, “Stand-off Raman spectroscopic detection of minerals on planetary surfaces,” Spectrochim. Acta, Part A 59(10), 2391–2407 (2003).
    [Crossref]
  16. R. L. Aggarwal, L. W. Farrar, and D. L. Polla, “Measurement of the absolute Raman scattering cross sections of sulfur and the standoff Raman detection of a 6-mm-thick sulfur specimen at 1500 m,” J. Raman Spectrosc. 42(3), 461–464 (2011).
    [Crossref]
  17. H. Liang, R. Lange, B. Peric, and M. Spring, “Optimum spectral window for imaging of art with optical coherence tomography,” Appl. Phys. B: Lasers Opt. 111(4), 589–602 (2013).
    [Crossref]
  18. S. Kogou, A. Lucian, S. Bellesia, L. Burgio, K. Bailey, C. Brooks, and H. Liang, “A holistic multimodal approach to the non-invasive analysis of watercolour paintings,” Appl. Phys. A: Mater. Sci. Process. 121(3), 999–1014 (2015).
    [Crossref]
  19. L. Burgio and R. J. H. Clark, “Library of FT-Raman spectra of pigments, minerals, pigment media and varnishes, and supplement to existing library of Raman spectra of pigments with visible excitation,” Spectrochim. Acta, Part A 57(7), 1491–1521 (2001).
    [Crossref]
  20. I. M. Bell, R. J. H. Clark, and P. J. Gibbs, “Raman spectroscopic library of natural and synthetic pigments (pre-≈ 1850 AD),” Spectrochim. Acta, Part A 53(12), 2159–2179 (1997).
    [Crossref]
  21. D. Anglos, M. Solomidou, I. Zergioti, V. Zafiropulos, T. G. Papazoglou, and C. Fotakis, “Laser-Induced Fluorescence in Artwork Diagnostics: An Application in Pigment Analysis,” Appl. Spectrosc. 50(10), 1331–1334 (1996).
    [Crossref]
  22. M. M. Cummins, Nottingham Cathedral - a History of Catholic Nottingham (1985).
  23. M. Vagnini, C. Miliani, L. Cartechini, P. Rocchi, B. G. Brunetti, and A. Sgamellotti, “FT-NIR spectroscopy for non-invasive identification of natural polymers and resins in easel paintings,” Anal. Bioanal. Chem. 395(7), 2107–2118 (2009).
    [Crossref]
  24. M. de Keijzer, “The history of modern synthetic inorganic and organic artists’ pigments,” Contrib. to Conserv. Res. Conserv. Netherlands Inst. Cult. Herit., 42–54 (2002).
  25. P.-L. Lee, E. Huang, and S.-C. Yu, “High-pressure Raman and X-ray studies of barite, BaSO4,” High Pressure Res. 23(4), 439–450 (2003).
    [Crossref]
  26. A. Fairbrother, V. Izquierdo-Roca, X. Fontané, M. Ibáñez, A. Cabot, E. Saucedo, and A. Pérez-Rodríguez, “ZnS grain size effects on near-resonant Raman scattering: optical non-destructive grain size estimation,” CrystEngComm 16(20), 4120 (2014).
    [Crossref]
  27. R. Capua, “The Obscure History of a Ubiquitous Pigment: Phosphorescent Lithopone and Its Appearance on Drawings By John La Farge,” J. Am. Inst. Conserv. 53(2), 75–88 (2014).
    [Crossref]

2017 (1)

2015 (1)

S. Kogou, A. Lucian, S. Bellesia, L. Burgio, K. Bailey, C. Brooks, and H. Liang, “A holistic multimodal approach to the non-invasive analysis of watercolour paintings,” Appl. Phys. A: Mater. Sci. Process. 121(3), 999–1014 (2015).
[Crossref]

2014 (4)

A. Fairbrother, V. Izquierdo-Roca, X. Fontané, M. Ibáñez, A. Cabot, E. Saucedo, and A. Pérez-Rodríguez, “ZnS grain size effects on near-resonant Raman scattering: optical non-destructive grain size estimation,” CrystEngComm 16(20), 4120 (2014).
[Crossref]

R. Capua, “The Obscure History of a Ubiquitous Pigment: Phosphorescent Lithopone and Its Appearance on Drawings By John La Farge,” J. Am. Inst. Conserv. 53(2), 75–88 (2014).
[Crossref]

P. Vandenabeele, H. G. M. Edwards, and J. Jehlička, “The role of mobile instrumentation in novel applications of Raman spectroscopy: Archaeometry, geosciences, and forensics,” Chem. Soc. Rev. 43(8), 2628–2649 (2014).
[Crossref]

H. Liang, A. Lucian, R. Lange, C. Cheung, and B. Su, “Remote spectral imaging with simultaneous extraction of 3D topography for historical wall paintings,” ISPRS J. Photogramm. Remote Sens. 95, 13–22 (2014).
[Crossref]

2013 (1)

H. Liang, R. Lange, B. Peric, and M. Spring, “Optimum spectral window for imaging of art with optical coherence tomography,” Appl. Phys. B: Lasers Opt. 111(4), 589–602 (2013).
[Crossref]

2012 (2)

S. M. Angel, N. R. Gomer, S. K. Sharma, C. McKay, and N. Ames, “Remote Raman spectroscopy for planetary exploration: A review,” Appl. Spectrosc. 66(2), 137–150 (2012).
[Crossref]

B. I. Łydzba-Kopczyńska, B. Gediga, J. Chojcan, and M. Sachanbiński, “Provenance investigations of amber jewelry excavated in Lower Silesia (Poland) and dated back to Early Iron Age,” J. Raman Spectrosc. 43(11), 1839–1844 (2012).
[Crossref]

2011 (1)

R. L. Aggarwal, L. W. Farrar, and D. L. Polla, “Measurement of the absolute Raman scattering cross sections of sulfur and the standoff Raman detection of a 6-mm-thick sulfur specimen at 1500 m,” J. Raman Spectrosc. 42(3), 461–464 (2011).
[Crossref]

2009 (2)

A. Pettersson, I. Johansson, S. Wallin, M. Nordberg, and H. Östmark, ““Near real-time standoff detection of explosives in a realistic outdoor environment at 55 m distance,” Propellants,” Propellants, Explos., Pyrotech. 34(4), 297–306 (2009).
[Crossref]

M. Vagnini, C. Miliani, L. Cartechini, P. Rocchi, B. G. Brunetti, and A. Sgamellotti, “FT-NIR spectroscopy for non-invasive identification of natural polymers and resins in easel paintings,” Anal. Bioanal. Chem. 395(7), 2107–2118 (2009).
[Crossref]

2006 (1)

M. Pérez-Alonso, K. Castro, and J. M. Madariaga, “Investigation of degradation mechanisms by portable Raman spectroscopy and thermodynamic speciation: The wall painting of Santa María de Lemoniz (Basque Country, North of Spain),” Anal. Chim. Acta 571(1), 121–128 (2006).
[Crossref]

2004 (1)

L. Bellot-Gurlet, F.-X. Le Bourdonnec, G. Poupeau, and S. Dubernet, “Raman micro-spectroscopy of western Mediterranean obsidian glass: one step towards provenance studies?” J. Raman Spectrosc. 35(89), 671–677 (2004).
[Crossref]

2003 (2)

S. K. Sharma, P. G. Lucey, M. Ghosh, H. W. Hubble, and K. A. Horton, “Stand-off Raman spectroscopic detection of minerals on planetary surfaces,” Spectrochim. Acta, Part A 59(10), 2391–2407 (2003).
[Crossref]

P.-L. Lee, E. Huang, and S.-C. Yu, “High-pressure Raman and X-ray studies of barite, BaSO4,” High Pressure Res. 23(4), 439–450 (2003).
[Crossref]

2001 (2)

L. Burgio and R. J. H. Clark, “Library of FT-Raman spectra of pigments, minerals, pigment media and varnishes, and supplement to existing library of Raman spectra of pigments with visible excitation,” Spectrochim. Acta, Part A 57(7), 1491–1521 (2001).
[Crossref]

L. Burgio, R. J. H. Clark, and S. Firth, “Raman spectroscopy as a means for the identification of plattnerite (PbO2), of lead pigments and of their degradation products,” Analyst 126(2), 222–227 (2001).
[Crossref]

1997 (1)

I. M. Bell, R. J. H. Clark, and P. J. Gibbs, “Raman spectroscopic library of natural and synthetic pigments (pre-≈ 1850 AD),” Spectrochim. Acta, Part A 53(12), 2159–2179 (1997).
[Crossref]

1996 (1)

1995 (1)

R. J. H. Clark, “Raman microscopy: application to the identification of pigments on medieval manuscripts,” Chem. Soc. Rev. 24(3), 187 (1995).
[Crossref]

1992 (1)

S. P. Best, R. J. H. Clark, and R. Withnall, “Non-destructive pigment analysis of artefacts by Raman microscopy,” Endeavour 16(2), 66–73 (1992).
[Crossref]

1969 (1)

J. Cooney, J. Orr, and C. Tomasetti, “Measurements separating the gaseous and aerosol components of laser atmospheric backscatter,” Nature 224(5224), 1098–1099 (1969).
[Crossref]

1967 (1)

D. A. Leonard, “Observation of Raman scattering from the atmosphere using a pulsed nitrogen ultraviolet laser,” Nature 216(5111), 142–143 (1967).
[Crossref]

Aggarwal, R. L.

R. L. Aggarwal, L. W. Farrar, and D. L. Polla, “Measurement of the absolute Raman scattering cross sections of sulfur and the standoff Raman detection of a 6-mm-thick sulfur specimen at 1500 m,” J. Raman Spectrosc. 42(3), 461–464 (2011).
[Crossref]

Ames, N.

Angel, S. M.

Anglos, D.

Bailey, K.

S. Kogou, A. Lucian, S. Bellesia, L. Burgio, K. Bailey, C. Brooks, and H. Liang, “A holistic multimodal approach to the non-invasive analysis of watercolour paintings,” Appl. Phys. A: Mater. Sci. Process. 121(3), 999–1014 (2015).
[Crossref]

Bell, I. M.

I. M. Bell, R. J. H. Clark, and P. J. Gibbs, “Raman spectroscopic library of natural and synthetic pigments (pre-≈ 1850 AD),” Spectrochim. Acta, Part A 53(12), 2159–2179 (1997).
[Crossref]

Bellesia, S.

S. Kogou, A. Lucian, S. Bellesia, L. Burgio, K. Bailey, C. Brooks, and H. Liang, “A holistic multimodal approach to the non-invasive analysis of watercolour paintings,” Appl. Phys. A: Mater. Sci. Process. 121(3), 999–1014 (2015).
[Crossref]

Bellot-Gurlet, L.

L. Bellot-Gurlet, F.-X. Le Bourdonnec, G. Poupeau, and S. Dubernet, “Raman micro-spectroscopy of western Mediterranean obsidian glass: one step towards provenance studies?” J. Raman Spectrosc. 35(89), 671–677 (2004).
[Crossref]

Best, S. P.

S. P. Best, R. J. H. Clark, and R. Withnall, “Non-destructive pigment analysis of artefacts by Raman microscopy,” Endeavour 16(2), 66–73 (1992).
[Crossref]

Brooks, C.

S. Kogou, A. Lucian, S. Bellesia, L. Burgio, K. Bailey, C. Brooks, and H. Liang, “A holistic multimodal approach to the non-invasive analysis of watercolour paintings,” Appl. Phys. A: Mater. Sci. Process. 121(3), 999–1014 (2015).
[Crossref]

Brunetti, B. G.

M. Vagnini, C. Miliani, L. Cartechini, P. Rocchi, B. G. Brunetti, and A. Sgamellotti, “FT-NIR spectroscopy for non-invasive identification of natural polymers and resins in easel paintings,” Anal. Bioanal. Chem. 395(7), 2107–2118 (2009).
[Crossref]

Burgio, L.

S. Kogou, A. Lucian, S. Bellesia, L. Burgio, K. Bailey, C. Brooks, and H. Liang, “A holistic multimodal approach to the non-invasive analysis of watercolour paintings,” Appl. Phys. A: Mater. Sci. Process. 121(3), 999–1014 (2015).
[Crossref]

L. Burgio and R. J. H. Clark, “Library of FT-Raman spectra of pigments, minerals, pigment media and varnishes, and supplement to existing library of Raman spectra of pigments with visible excitation,” Spectrochim. Acta, Part A 57(7), 1491–1521 (2001).
[Crossref]

L. Burgio, R. J. H. Clark, and S. Firth, “Raman spectroscopy as a means for the identification of plattnerite (PbO2), of lead pigments and of their degradation products,” Analyst 126(2), 222–227 (2001).
[Crossref]

Cabot, A.

A. Fairbrother, V. Izquierdo-Roca, X. Fontané, M. Ibáñez, A. Cabot, E. Saucedo, and A. Pérez-Rodríguez, “ZnS grain size effects on near-resonant Raman scattering: optical non-destructive grain size estimation,” CrystEngComm 16(20), 4120 (2014).
[Crossref]

Capua, R.

R. Capua, “The Obscure History of a Ubiquitous Pigment: Phosphorescent Lithopone and Its Appearance on Drawings By John La Farge,” J. Am. Inst. Conserv. 53(2), 75–88 (2014).
[Crossref]

Cartechini, L.

M. Vagnini, C. Miliani, L. Cartechini, P. Rocchi, B. G. Brunetti, and A. Sgamellotti, “FT-NIR spectroscopy for non-invasive identification of natural polymers and resins in easel paintings,” Anal. Bioanal. Chem. 395(7), 2107–2118 (2009).
[Crossref]

Castro, K.

M. Pérez-Alonso, K. Castro, and J. M. Madariaga, “Investigation of degradation mechanisms by portable Raman spectroscopy and thermodynamic speciation: The wall painting of Santa María de Lemoniz (Basque Country, North of Spain),” Anal. Chim. Acta 571(1), 121–128 (2006).
[Crossref]

Cheung, C.

H. Liang, A. Lucian, R. Lange, C. Cheung, and B. Su, “Remote spectral imaging with simultaneous extraction of 3D topography for historical wall paintings,” ISPRS J. Photogramm. Remote Sens. 95, 13–22 (2014).
[Crossref]

Cheung, C. S.

Chojcan, J.

B. I. Łydzba-Kopczyńska, B. Gediga, J. Chojcan, and M. Sachanbiński, “Provenance investigations of amber jewelry excavated in Lower Silesia (Poland) and dated back to Early Iron Age,” J. Raman Spectrosc. 43(11), 1839–1844 (2012).
[Crossref]

Clark, R. J. H.

L. Burgio and R. J. H. Clark, “Library of FT-Raman spectra of pigments, minerals, pigment media and varnishes, and supplement to existing library of Raman spectra of pigments with visible excitation,” Spectrochim. Acta, Part A 57(7), 1491–1521 (2001).
[Crossref]

L. Burgio, R. J. H. Clark, and S. Firth, “Raman spectroscopy as a means for the identification of plattnerite (PbO2), of lead pigments and of their degradation products,” Analyst 126(2), 222–227 (2001).
[Crossref]

I. M. Bell, R. J. H. Clark, and P. J. Gibbs, “Raman spectroscopic library of natural and synthetic pigments (pre-≈ 1850 AD),” Spectrochim. Acta, Part A 53(12), 2159–2179 (1997).
[Crossref]

R. J. H. Clark, “Raman microscopy: application to the identification of pigments on medieval manuscripts,” Chem. Soc. Rev. 24(3), 187 (1995).
[Crossref]

S. P. Best, R. J. H. Clark, and R. Withnall, “Non-destructive pigment analysis of artefacts by Raman microscopy,” Endeavour 16(2), 66–73 (1992).
[Crossref]

Cooney, J.

J. Cooney, J. Orr, and C. Tomasetti, “Measurements separating the gaseous and aerosol components of laser atmospheric backscatter,” Nature 224(5224), 1098–1099 (1969).
[Crossref]

Cummins, M. M.

M. M. Cummins, Nottingham Cathedral - a History of Catholic Nottingham (1985).

de Keijzer, M.

M. de Keijzer, “The history of modern synthetic inorganic and organic artists’ pigments,” Contrib. to Conserv. Res. Conserv. Netherlands Inst. Cult. Herit., 42–54 (2002).

Dubernet, S.

L. Bellot-Gurlet, F.-X. Le Bourdonnec, G. Poupeau, and S. Dubernet, “Raman micro-spectroscopy of western Mediterranean obsidian glass: one step towards provenance studies?” J. Raman Spectrosc. 35(89), 671–677 (2004).
[Crossref]

Edwards, H. G. M.

P. Vandenabeele, H. G. M. Edwards, and J. Jehlička, “The role of mobile instrumentation in novel applications of Raman spectroscopy: Archaeometry, geosciences, and forensics,” Chem. Soc. Rev. 43(8), 2628–2649 (2014).
[Crossref]

Fairbrother, A.

A. Fairbrother, V. Izquierdo-Roca, X. Fontané, M. Ibáñez, A. Cabot, E. Saucedo, and A. Pérez-Rodríguez, “ZnS grain size effects on near-resonant Raman scattering: optical non-destructive grain size estimation,” CrystEngComm 16(20), 4120 (2014).
[Crossref]

Farrar, L. W.

R. L. Aggarwal, L. W. Farrar, and D. L. Polla, “Measurement of the absolute Raman scattering cross sections of sulfur and the standoff Raman detection of a 6-mm-thick sulfur specimen at 1500 m,” J. Raman Spectrosc. 42(3), 461–464 (2011).
[Crossref]

Filippidis, G.

Firth, S.

L. Burgio, R. J. H. Clark, and S. Firth, “Raman spectroscopy as a means for the identification of plattnerite (PbO2), of lead pigments and of their degradation products,” Analyst 126(2), 222–227 (2001).
[Crossref]

Fontané, X.

A. Fairbrother, V. Izquierdo-Roca, X. Fontané, M. Ibáñez, A. Cabot, E. Saucedo, and A. Pérez-Rodríguez, “ZnS grain size effects on near-resonant Raman scattering: optical non-destructive grain size estimation,” CrystEngComm 16(20), 4120 (2014).
[Crossref]

Fotakis, C.

Gediga, B.

B. I. Łydzba-Kopczyńska, B. Gediga, J. Chojcan, and M. Sachanbiński, “Provenance investigations of amber jewelry excavated in Lower Silesia (Poland) and dated back to Early Iron Age,” J. Raman Spectrosc. 43(11), 1839–1844 (2012).
[Crossref]

Ghosh, M.

S. K. Sharma, P. G. Lucey, M. Ghosh, H. W. Hubble, and K. A. Horton, “Stand-off Raman spectroscopic detection of minerals on planetary surfaces,” Spectrochim. Acta, Part A 59(10), 2391–2407 (2003).
[Crossref]

Gibbs, P. J.

I. M. Bell, R. J. H. Clark, and P. J. Gibbs, “Raman spectroscopic library of natural and synthetic pigments (pre-≈ 1850 AD),” Spectrochim. Acta, Part A 53(12), 2159–2179 (1997).
[Crossref]

Gomer, N. R.

Hackney, S.

H. Liang, R. Lange, A. Lucian, P. Hyndes, J. H. Townsend, and S. Hackney, “Development of portable microfading spectrometers for measurement of light sensitivity of materials. Paper 1612,” in Preprints, ICOM Committee for Conservation, ICOM-CC, 16th Triennial Conference, Lisbon (2011), pp. 19–23.

Horton, K. A.

S. K. Sharma, P. G. Lucey, M. Ghosh, H. W. Hubble, and K. A. Horton, “Stand-off Raman spectroscopic detection of minerals on planetary surfaces,” Spectrochim. Acta, Part A 59(10), 2391–2407 (2003).
[Crossref]

Huang, E.

P.-L. Lee, E. Huang, and S.-C. Yu, “High-pressure Raman and X-ray studies of barite, BaSO4,” High Pressure Res. 23(4), 439–450 (2003).
[Crossref]

Hubble, H. W.

S. K. Sharma, P. G. Lucey, M. Ghosh, H. W. Hubble, and K. A. Horton, “Stand-off Raman spectroscopic detection of minerals on planetary surfaces,” Spectrochim. Acta, Part A 59(10), 2391–2407 (2003).
[Crossref]

Hyndes, P.

H. Liang, R. Lange, A. Lucian, P. Hyndes, J. H. Townsend, and S. Hackney, “Development of portable microfading spectrometers for measurement of light sensitivity of materials. Paper 1612,” in Preprints, ICOM Committee for Conservation, ICOM-CC, 16th Triennial Conference, Lisbon (2011), pp. 19–23.

Ibáñez, M.

A. Fairbrother, V. Izquierdo-Roca, X. Fontané, M. Ibáñez, A. Cabot, E. Saucedo, and A. Pérez-Rodríguez, “ZnS grain size effects on near-resonant Raman scattering: optical non-destructive grain size estimation,” CrystEngComm 16(20), 4120 (2014).
[Crossref]

Izquierdo-Roca, V.

A. Fairbrother, V. Izquierdo-Roca, X. Fontané, M. Ibáñez, A. Cabot, E. Saucedo, and A. Pérez-Rodríguez, “ZnS grain size effects on near-resonant Raman scattering: optical non-destructive grain size estimation,” CrystEngComm 16(20), 4120 (2014).
[Crossref]

Jehlicka, J.

P. Vandenabeele, H. G. M. Edwards, and J. Jehlička, “The role of mobile instrumentation in novel applications of Raman spectroscopy: Archaeometry, geosciences, and forensics,” Chem. Soc. Rev. 43(8), 2628–2649 (2014).
[Crossref]

Johansson, I.

A. Pettersson, I. Johansson, S. Wallin, M. Nordberg, and H. Östmark, ““Near real-time standoff detection of explosives in a realistic outdoor environment at 55 m distance,” Propellants,” Propellants, Explos., Pyrotech. 34(4), 297–306 (2009).
[Crossref]

Johnson, P.

Kogou, S.

H. Liang, M. Mari, C. S. Cheung, S. Kogou, P. Johnson, and G. Filippidis, “Optical coherence tomography and non-linear microscopy for paintings – a study of the complementary capabilities and laser degradation effects,” Opt. Express 25(16), 19640 (2017).
[Crossref]

S. Kogou, A. Lucian, S. Bellesia, L. Burgio, K. Bailey, C. Brooks, and H. Liang, “A holistic multimodal approach to the non-invasive analysis of watercolour paintings,” Appl. Phys. A: Mater. Sci. Process. 121(3), 999–1014 (2015).
[Crossref]

Lange, R.

H. Liang, A. Lucian, R. Lange, C. Cheung, and B. Su, “Remote spectral imaging with simultaneous extraction of 3D topography for historical wall paintings,” ISPRS J. Photogramm. Remote Sens. 95, 13–22 (2014).
[Crossref]

H. Liang, R. Lange, B. Peric, and M. Spring, “Optimum spectral window for imaging of art with optical coherence tomography,” Appl. Phys. B: Lasers Opt. 111(4), 589–602 (2013).
[Crossref]

H. Liang, R. Lange, A. Lucian, P. Hyndes, J. H. Townsend, and S. Hackney, “Development of portable microfading spectrometers for measurement of light sensitivity of materials. Paper 1612,” in Preprints, ICOM Committee for Conservation, ICOM-CC, 16th Triennial Conference, Lisbon (2011), pp. 19–23.

Le Bourdonnec, F.-X.

L. Bellot-Gurlet, F.-X. Le Bourdonnec, G. Poupeau, and S. Dubernet, “Raman micro-spectroscopy of western Mediterranean obsidian glass: one step towards provenance studies?” J. Raman Spectrosc. 35(89), 671–677 (2004).
[Crossref]

Lee, P.-L.

P.-L. Lee, E. Huang, and S.-C. Yu, “High-pressure Raman and X-ray studies of barite, BaSO4,” High Pressure Res. 23(4), 439–450 (2003).
[Crossref]

Leonard, D. A.

D. A. Leonard, “Observation of Raman scattering from the atmosphere using a pulsed nitrogen ultraviolet laser,” Nature 216(5111), 142–143 (1967).
[Crossref]

Liang, H.

H. Liang, M. Mari, C. S. Cheung, S. Kogou, P. Johnson, and G. Filippidis, “Optical coherence tomography and non-linear microscopy for paintings – a study of the complementary capabilities and laser degradation effects,” Opt. Express 25(16), 19640 (2017).
[Crossref]

S. Kogou, A. Lucian, S. Bellesia, L. Burgio, K. Bailey, C. Brooks, and H. Liang, “A holistic multimodal approach to the non-invasive analysis of watercolour paintings,” Appl. Phys. A: Mater. Sci. Process. 121(3), 999–1014 (2015).
[Crossref]

H. Liang, A. Lucian, R. Lange, C. Cheung, and B. Su, “Remote spectral imaging with simultaneous extraction of 3D topography for historical wall paintings,” ISPRS J. Photogramm. Remote Sens. 95, 13–22 (2014).
[Crossref]

H. Liang, R. Lange, B. Peric, and M. Spring, “Optimum spectral window for imaging of art with optical coherence tomography,” Appl. Phys. B: Lasers Opt. 111(4), 589–602 (2013).
[Crossref]

H. Liang, R. Lange, A. Lucian, P. Hyndes, J. H. Townsend, and S. Hackney, “Development of portable microfading spectrometers for measurement of light sensitivity of materials. Paper 1612,” in Preprints, ICOM Committee for Conservation, ICOM-CC, 16th Triennial Conference, Lisbon (2011), pp. 19–23.

Lucey, P. G.

S. K. Sharma, P. G. Lucey, M. Ghosh, H. W. Hubble, and K. A. Horton, “Stand-off Raman spectroscopic detection of minerals on planetary surfaces,” Spectrochim. Acta, Part A 59(10), 2391–2407 (2003).
[Crossref]

Lucian, A.

S. Kogou, A. Lucian, S. Bellesia, L. Burgio, K. Bailey, C. Brooks, and H. Liang, “A holistic multimodal approach to the non-invasive analysis of watercolour paintings,” Appl. Phys. A: Mater. Sci. Process. 121(3), 999–1014 (2015).
[Crossref]

H. Liang, A. Lucian, R. Lange, C. Cheung, and B. Su, “Remote spectral imaging with simultaneous extraction of 3D topography for historical wall paintings,” ISPRS J. Photogramm. Remote Sens. 95, 13–22 (2014).
[Crossref]

H. Liang, R. Lange, A. Lucian, P. Hyndes, J. H. Townsend, and S. Hackney, “Development of portable microfading spectrometers for measurement of light sensitivity of materials. Paper 1612,” in Preprints, ICOM Committee for Conservation, ICOM-CC, 16th Triennial Conference, Lisbon (2011), pp. 19–23.

Lydzba-Kopczynska, B. I.

B. I. Łydzba-Kopczyńska, B. Gediga, J. Chojcan, and M. Sachanbiński, “Provenance investigations of amber jewelry excavated in Lower Silesia (Poland) and dated back to Early Iron Age,” J. Raman Spectrosc. 43(11), 1839–1844 (2012).
[Crossref]

Madariaga, J. M.

M. Pérez-Alonso, K. Castro, and J. M. Madariaga, “Investigation of degradation mechanisms by portable Raman spectroscopy and thermodynamic speciation: The wall painting of Santa María de Lemoniz (Basque Country, North of Spain),” Anal. Chim. Acta 571(1), 121–128 (2006).
[Crossref]

Mari, M.

McKay, C.

Miliani, C.

M. Vagnini, C. Miliani, L. Cartechini, P. Rocchi, B. G. Brunetti, and A. Sgamellotti, “FT-NIR spectroscopy for non-invasive identification of natural polymers and resins in easel paintings,” Anal. Bioanal. Chem. 395(7), 2107–2118 (2009).
[Crossref]

Nordberg, M.

A. Pettersson, I. Johansson, S. Wallin, M. Nordberg, and H. Östmark, ““Near real-time standoff detection of explosives in a realistic outdoor environment at 55 m distance,” Propellants,” Propellants, Explos., Pyrotech. 34(4), 297–306 (2009).
[Crossref]

Orr, J.

J. Cooney, J. Orr, and C. Tomasetti, “Measurements separating the gaseous and aerosol components of laser atmospheric backscatter,” Nature 224(5224), 1098–1099 (1969).
[Crossref]

Östmark, H.

A. Pettersson, I. Johansson, S. Wallin, M. Nordberg, and H. Östmark, ““Near real-time standoff detection of explosives in a realistic outdoor environment at 55 m distance,” Propellants,” Propellants, Explos., Pyrotech. 34(4), 297–306 (2009).
[Crossref]

Papazoglou, T. G.

Pérez-Alonso, M.

M. Pérez-Alonso, K. Castro, and J. M. Madariaga, “Investigation of degradation mechanisms by portable Raman spectroscopy and thermodynamic speciation: The wall painting of Santa María de Lemoniz (Basque Country, North of Spain),” Anal. Chim. Acta 571(1), 121–128 (2006).
[Crossref]

Pérez-Rodríguez, A.

A. Fairbrother, V. Izquierdo-Roca, X. Fontané, M. Ibáñez, A. Cabot, E. Saucedo, and A. Pérez-Rodríguez, “ZnS grain size effects on near-resonant Raman scattering: optical non-destructive grain size estimation,” CrystEngComm 16(20), 4120 (2014).
[Crossref]

Peric, B.

H. Liang, R. Lange, B. Peric, and M. Spring, “Optimum spectral window for imaging of art with optical coherence tomography,” Appl. Phys. B: Lasers Opt. 111(4), 589–602 (2013).
[Crossref]

Pettersson, A.

A. Pettersson, I. Johansson, S. Wallin, M. Nordberg, and H. Östmark, ““Near real-time standoff detection of explosives in a realistic outdoor environment at 55 m distance,” Propellants,” Propellants, Explos., Pyrotech. 34(4), 297–306 (2009).
[Crossref]

Polla, D. L.

R. L. Aggarwal, L. W. Farrar, and D. L. Polla, “Measurement of the absolute Raman scattering cross sections of sulfur and the standoff Raman detection of a 6-mm-thick sulfur specimen at 1500 m,” J. Raman Spectrosc. 42(3), 461–464 (2011).
[Crossref]

Poupeau, G.

L. Bellot-Gurlet, F.-X. Le Bourdonnec, G. Poupeau, and S. Dubernet, “Raman micro-spectroscopy of western Mediterranean obsidian glass: one step towards provenance studies?” J. Raman Spectrosc. 35(89), 671–677 (2004).
[Crossref]

Rocchi, P.

M. Vagnini, C. Miliani, L. Cartechini, P. Rocchi, B. G. Brunetti, and A. Sgamellotti, “FT-NIR spectroscopy for non-invasive identification of natural polymers and resins in easel paintings,” Anal. Bioanal. Chem. 395(7), 2107–2118 (2009).
[Crossref]

Sachanbinski, M.

B. I. Łydzba-Kopczyńska, B. Gediga, J. Chojcan, and M. Sachanbiński, “Provenance investigations of amber jewelry excavated in Lower Silesia (Poland) and dated back to Early Iron Age,” J. Raman Spectrosc. 43(11), 1839–1844 (2012).
[Crossref]

Saucedo, E.

A. Fairbrother, V. Izquierdo-Roca, X. Fontané, M. Ibáñez, A. Cabot, E. Saucedo, and A. Pérez-Rodríguez, “ZnS grain size effects on near-resonant Raman scattering: optical non-destructive grain size estimation,” CrystEngComm 16(20), 4120 (2014).
[Crossref]

Sgamellotti, A.

M. Vagnini, C. Miliani, L. Cartechini, P. Rocchi, B. G. Brunetti, and A. Sgamellotti, “FT-NIR spectroscopy for non-invasive identification of natural polymers and resins in easel paintings,” Anal. Bioanal. Chem. 395(7), 2107–2118 (2009).
[Crossref]

Sharma, S. K.

S. M. Angel, N. R. Gomer, S. K. Sharma, C. McKay, and N. Ames, “Remote Raman spectroscopy for planetary exploration: A review,” Appl. Spectrosc. 66(2), 137–150 (2012).
[Crossref]

S. K. Sharma, P. G. Lucey, M. Ghosh, H. W. Hubble, and K. A. Horton, “Stand-off Raman spectroscopic detection of minerals on planetary surfaces,” Spectrochim. Acta, Part A 59(10), 2391–2407 (2003).
[Crossref]

Solomidou, M.

Spring, M.

H. Liang, R. Lange, B. Peric, and M. Spring, “Optimum spectral window for imaging of art with optical coherence tomography,” Appl. Phys. B: Lasers Opt. 111(4), 589–602 (2013).
[Crossref]

Su, B.

H. Liang, A. Lucian, R. Lange, C. Cheung, and B. Su, “Remote spectral imaging with simultaneous extraction of 3D topography for historical wall paintings,” ISPRS J. Photogramm. Remote Sens. 95, 13–22 (2014).
[Crossref]

Tomasetti, C.

J. Cooney, J. Orr, and C. Tomasetti, “Measurements separating the gaseous and aerosol components of laser atmospheric backscatter,” Nature 224(5224), 1098–1099 (1969).
[Crossref]

Townsend, J. H.

H. Liang, R. Lange, A. Lucian, P. Hyndes, J. H. Townsend, and S. Hackney, “Development of portable microfading spectrometers for measurement of light sensitivity of materials. Paper 1612,” in Preprints, ICOM Committee for Conservation, ICOM-CC, 16th Triennial Conference, Lisbon (2011), pp. 19–23.

Vagnini, M.

M. Vagnini, C. Miliani, L. Cartechini, P. Rocchi, B. G. Brunetti, and A. Sgamellotti, “FT-NIR spectroscopy for non-invasive identification of natural polymers and resins in easel paintings,” Anal. Bioanal. Chem. 395(7), 2107–2118 (2009).
[Crossref]

Vandenabeele, P.

P. Vandenabeele, H. G. M. Edwards, and J. Jehlička, “The role of mobile instrumentation in novel applications of Raman spectroscopy: Archaeometry, geosciences, and forensics,” Chem. Soc. Rev. 43(8), 2628–2649 (2014).
[Crossref]

Wallin, S.

A. Pettersson, I. Johansson, S. Wallin, M. Nordberg, and H. Östmark, ““Near real-time standoff detection of explosives in a realistic outdoor environment at 55 m distance,” Propellants,” Propellants, Explos., Pyrotech. 34(4), 297–306 (2009).
[Crossref]

Withnall, R.

S. P. Best, R. J. H. Clark, and R. Withnall, “Non-destructive pigment analysis of artefacts by Raman microscopy,” Endeavour 16(2), 66–73 (1992).
[Crossref]

Yu, S.-C.

P.-L. Lee, E. Huang, and S.-C. Yu, “High-pressure Raman and X-ray studies of barite, BaSO4,” High Pressure Res. 23(4), 439–450 (2003).
[Crossref]

Zafiropulos, V.

Zergioti, I.

Anal. Bioanal. Chem. (1)

M. Vagnini, C. Miliani, L. Cartechini, P. Rocchi, B. G. Brunetti, and A. Sgamellotti, “FT-NIR spectroscopy for non-invasive identification of natural polymers and resins in easel paintings,” Anal. Bioanal. Chem. 395(7), 2107–2118 (2009).
[Crossref]

Anal. Chim. Acta (1)

M. Pérez-Alonso, K. Castro, and J. M. Madariaga, “Investigation of degradation mechanisms by portable Raman spectroscopy and thermodynamic speciation: The wall painting of Santa María de Lemoniz (Basque Country, North of Spain),” Anal. Chim. Acta 571(1), 121–128 (2006).
[Crossref]

Analyst (1)

L. Burgio, R. J. H. Clark, and S. Firth, “Raman spectroscopy as a means for the identification of plattnerite (PbO2), of lead pigments and of their degradation products,” Analyst 126(2), 222–227 (2001).
[Crossref]

Appl. Phys. A: Mater. Sci. Process. (1)

S. Kogou, A. Lucian, S. Bellesia, L. Burgio, K. Bailey, C. Brooks, and H. Liang, “A holistic multimodal approach to the non-invasive analysis of watercolour paintings,” Appl. Phys. A: Mater. Sci. Process. 121(3), 999–1014 (2015).
[Crossref]

Appl. Phys. B: Lasers Opt. (1)

H. Liang, R. Lange, B. Peric, and M. Spring, “Optimum spectral window for imaging of art with optical coherence tomography,” Appl. Phys. B: Lasers Opt. 111(4), 589–602 (2013).
[Crossref]

Appl. Spectrosc. (2)

Chem. Soc. Rev. (2)

P. Vandenabeele, H. G. M. Edwards, and J. Jehlička, “The role of mobile instrumentation in novel applications of Raman spectroscopy: Archaeometry, geosciences, and forensics,” Chem. Soc. Rev. 43(8), 2628–2649 (2014).
[Crossref]

R. J. H. Clark, “Raman microscopy: application to the identification of pigments on medieval manuscripts,” Chem. Soc. Rev. 24(3), 187 (1995).
[Crossref]

CrystEngComm (1)

A. Fairbrother, V. Izquierdo-Roca, X. Fontané, M. Ibáñez, A. Cabot, E. Saucedo, and A. Pérez-Rodríguez, “ZnS grain size effects on near-resonant Raman scattering: optical non-destructive grain size estimation,” CrystEngComm 16(20), 4120 (2014).
[Crossref]

Endeavour (1)

S. P. Best, R. J. H. Clark, and R. Withnall, “Non-destructive pigment analysis of artefacts by Raman microscopy,” Endeavour 16(2), 66–73 (1992).
[Crossref]

High Pressure Res. (1)

P.-L. Lee, E. Huang, and S.-C. Yu, “High-pressure Raman and X-ray studies of barite, BaSO4,” High Pressure Res. 23(4), 439–450 (2003).
[Crossref]

ISPRS J. Photogramm. Remote Sens. (1)

H. Liang, A. Lucian, R. Lange, C. Cheung, and B. Su, “Remote spectral imaging with simultaneous extraction of 3D topography for historical wall paintings,” ISPRS J. Photogramm. Remote Sens. 95, 13–22 (2014).
[Crossref]

J. Am. Inst. Conserv. (1)

R. Capua, “The Obscure History of a Ubiquitous Pigment: Phosphorescent Lithopone and Its Appearance on Drawings By John La Farge,” J. Am. Inst. Conserv. 53(2), 75–88 (2014).
[Crossref]

J. Raman Spectrosc. (3)

L. Bellot-Gurlet, F.-X. Le Bourdonnec, G. Poupeau, and S. Dubernet, “Raman micro-spectroscopy of western Mediterranean obsidian glass: one step towards provenance studies?” J. Raman Spectrosc. 35(89), 671–677 (2004).
[Crossref]

B. I. Łydzba-Kopczyńska, B. Gediga, J. Chojcan, and M. Sachanbiński, “Provenance investigations of amber jewelry excavated in Lower Silesia (Poland) and dated back to Early Iron Age,” J. Raman Spectrosc. 43(11), 1839–1844 (2012).
[Crossref]

R. L. Aggarwal, L. W. Farrar, and D. L. Polla, “Measurement of the absolute Raman scattering cross sections of sulfur and the standoff Raman detection of a 6-mm-thick sulfur specimen at 1500 m,” J. Raman Spectrosc. 42(3), 461–464 (2011).
[Crossref]

Nature (2)

D. A. Leonard, “Observation of Raman scattering from the atmosphere using a pulsed nitrogen ultraviolet laser,” Nature 216(5111), 142–143 (1967).
[Crossref]

J. Cooney, J. Orr, and C. Tomasetti, “Measurements separating the gaseous and aerosol components of laser atmospheric backscatter,” Nature 224(5224), 1098–1099 (1969).
[Crossref]

Opt. Express (1)

Propellants, Explos., Pyrotech. (1)

A. Pettersson, I. Johansson, S. Wallin, M. Nordberg, and H. Östmark, ““Near real-time standoff detection of explosives in a realistic outdoor environment at 55 m distance,” Propellants,” Propellants, Explos., Pyrotech. 34(4), 297–306 (2009).
[Crossref]

Spectrochim. Acta, Part A (3)

S. K. Sharma, P. G. Lucey, M. Ghosh, H. W. Hubble, and K. A. Horton, “Stand-off Raman spectroscopic detection of minerals on planetary surfaces,” Spectrochim. Acta, Part A 59(10), 2391–2407 (2003).
[Crossref]

L. Burgio and R. J. H. Clark, “Library of FT-Raman spectra of pigments, minerals, pigment media and varnishes, and supplement to existing library of Raman spectra of pigments with visible excitation,” Spectrochim. Acta, Part A 57(7), 1491–1521 (2001).
[Crossref]

I. M. Bell, R. J. H. Clark, and P. J. Gibbs, “Raman spectroscopic library of natural and synthetic pigments (pre-≈ 1850 AD),” Spectrochim. Acta, Part A 53(12), 2159–2179 (1997).
[Crossref]

Other (3)

H. Liang, R. Lange, A. Lucian, P. Hyndes, J. H. Townsend, and S. Hackney, “Development of portable microfading spectrometers for measurement of light sensitivity of materials. Paper 1612,” in Preprints, ICOM Committee for Conservation, ICOM-CC, 16th Triennial Conference, Lisbon (2011), pp. 19–23.

M. M. Cummins, Nottingham Cathedral - a History of Catholic Nottingham (1985).

M. de Keijzer, “The history of modern synthetic inorganic and organic artists’ pigments,” Contrib. to Conserv. Res. Conserv. Netherlands Inst. Cult. Herit., 42–54 (2002).

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Figures (5)

Fig. 1.
Fig. 1. Standoff Raman spectroscopy: (a) schematics of the standoff Raman instrument setup using a CW laser at 780 nm co-axial with the receiving optics; (b) the mobile system deployed in situ at the Blessed Sacrament Chapel in the Cathedral Church of St. Barnabas in Nottingham.
Fig. 2.
Fig. 2. Daylight subtraction spectra. (a) comparison between the measurements of an orpiment in animal glue sample at 3.3 m distance placed in front of the window using the standoff Raman system with the 780 nm CW laser on and off; the absorption bands correspond to H2O absorptions from the atmosphere; (b) comparison of daylight subtracted Raman spectrum with that taken in total darkness.
Fig. 3.
Fig. 3. Typical Raman spectra of pigments: (a) Prussian blue in animal glue and oil, integration time: 10 min; (b) zinc white in oil, integration time: 10 min; (c) orpiment in animal glue with and without varnish on top, integration time: 10 s; (d) gamboge in animal glue, integration time: 30 min.
Fig. 4.
Fig. 4. Standoff investigation of a red area in the chapel: (a) color image of part of a mural next to a stained glass window (b) reflectance spectra collected with the remote spectral imaging system PRISMS of the red area (black filled squares) indicated by the red arrow in (a) compared with PRISMS spectra of a reference sample of vermilion (red dots) and cadmium red (blue triangle) oil paints; the inset shows the derivative of the reflectance spectra of cadmium red (peak at 610 nm), and two vermilion oil samples from two different sources (peaks at 600 nm and 607 nm); (c) the raw standoff Raman spectrum of the same red area (red), and the background spectrum collected over the same integration time with the laser off (blue) showing typical absorption bands of the solar spectrum (the band around 675 cm−1 corresponds to H2O absorption lines ∼823 nm from the atmosphere; the lines around 1056 and 1117 cm−1 corresponds to Ca II lines at ∼850 and ∼854 nm from the solar spectrum) ; (d) the processed spectrum after subtraction of daylight.
Fig. 5.
Fig. 5. Standoff investigation of a white area in the chapel (shown by the white arrow in Fig. 4(a)): (a) Standoff Raman measurement of a white area (blue) at a distance of 4 m compared with a sample of lithopone powder measured from the same distance in the lab (red); the baseline subtracted spectra are smoothed with a moving window of 6 cm−1. (b) XRF measurement of a similar white area at accessible height.

Equations (3)

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S c w I c w A t c w
S p I p A N p δ t
t c w t p = ε t h R P c w > R δ t

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