Abstract

A Photonic-based multi-wavelength sensor capable of discriminating objects is proposed and demonstrated for intruder detection and identification. The sensor uses a laser combination module for input wavelength signal multiplexing and beam overlapping, a custom-made curved optical cavity for multi-beam spot generation through internal beam reflection and transmission and a high-speed imager for scattered reflectance spectral measurements. Experimental results show that five different wavelengths, namely 473nm, 532nm, 635nm, 670nm and 785nm, are necessary for discriminating various intruding objects of interest through spectral reflectance and slope measurements. Objects selected for experiments were brick, cement sheet, cotton, leather and roof tile.

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References

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    [CrossRef] [PubMed]
  4. K. Sahba, S. Askraba, and K. E. Alameh, “Non-contact laser spectroscopy for plant discrimination in terrestrial crop spraying,” Opt. Express 14(25), 12485–12493 (2006).
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    [CrossRef]
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2008

2007

2006

2004

P. Hosmer, “Use of laser scanning technology for perimeter protection,” IEEE Aerosp. Electron. Syst. Mag. 19(8), 13–17 (2004).
[CrossRef]

1995

B. R. Myneni, F. G. Hall, J. P. Sellers, and A. L. Marshak, “The interpretation of spectral vegetation indexes,” IEEE Trans. Geosci. Rem. Sens. 33(2), 481–486 (1995).
[CrossRef]

Alameh, K. E.

Askraba, S.

Hall, F. G.

B. R. Myneni, F. G. Hall, J. P. Sellers, and A. L. Marshak, “The interpretation of spectral vegetation indexes,” IEEE Trans. Geosci. Rem. Sens. 33(2), 481–486 (1995).
[CrossRef]

Hosmer, P.

P. Hosmer, “Use of laser scanning technology for perimeter protection,” IEEE Aerosp. Electron. Syst. Mag. 19(8), 13–17 (2004).
[CrossRef]

Marshak, A. L.

B. R. Myneni, F. G. Hall, J. P. Sellers, and A. L. Marshak, “The interpretation of spectral vegetation indexes,” IEEE Trans. Geosci. Rem. Sens. 33(2), 481–486 (1995).
[CrossRef]

Myneni, B. R.

B. R. Myneni, F. G. Hall, J. P. Sellers, and A. L. Marshak, “The interpretation of spectral vegetation indexes,” IEEE Trans. Geosci. Rem. Sens. 33(2), 481–486 (1995).
[CrossRef]

Paap, A.

Rowe, J.

Sahba, K.

Sellers, J. P.

B. R. Myneni, F. G. Hall, J. P. Sellers, and A. L. Marshak, “The interpretation of spectral vegetation indexes,” IEEE Trans. Geosci. Rem. Sens. 33(2), 481–486 (1995).
[CrossRef]

Smith, C. L.

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Figures (12)

Fig. 1
Fig. 1

Typical measured reflectance spectrum of cotton soil, vegetation and clear water. The reflectance spectrum of a material is a unique signature that can be used for material identification.

Fig. 2
Fig. 2

Schematic diagram for the experimental set up.

Fig. 3
Fig. 3

Experimental set up for object discrimination. Objects are illuminated with laser beams at varying wavelengths along one optical path, striking the same spot on the object. By measuring and processing the reflected light intensities for each wavelength, a large variety of objects can be identified.

Fig. 4
Fig. 4

Laser beam combination module with five wavelengths and four beam combiners. This arrangement generates five collimated and overlapped laser beams with the same polarization orientation.

Fig. 5
Fig. 5

Measured output optical power for each laser beam after passing through the optical cavity.

Fig. 6
Fig. 6

The multi-spot beam generator: (a) schematic diagram showing 90° curvature; (b) photograph of the fabricated product showing 45° curvature. The front and rear surface are coated with semitransparent and highly reflective thin films, respectively.

Fig. 7
Fig. 7

Spectral response of the image sensor used for the experiments (as per manufacturers specifications).

Fig. 8
Fig. 8

Fitted Gaussian function for Leather@635nm

Fig. 9
Fig. 9

Experimental setup for measuring the reflectance spectra of the different sample objects.

Fig. 10
Fig. 10

Typical measured spectral response of sample objects used for experimentation.

Fig. 11
Fig. 11

Calculated average slope values for five different objects.

Fig. 12
Fig. 12

Average values with standard deviation for slopes S1, S2, S3 and S4 for five different objects.

Equations (1)

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S 1 = R 473 R 532 λ 532 λ 473                 , S 2 = R 635 R 532 λ 635 λ 532 S 3 = R 670 R 635 λ 670 λ 635               a n d     S 4 = R 785 R 670 λ 785 λ 670

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