Millimeter waves are able to penetrate materials that are usually opaque to both visible and infrared radiation. We used this advantage to design a free-space active millimeter-wave imaging set up for security applications. Because all existing mm-wave sources are coherent - speckle is one of the ultimate limiting factors of the imaging techniques. This problem is of special importance for mm-wave imaging, because surface roughness is closer to the object dimension as in optical imaging. The reduction of speckle is highly desirable and we propose here a Hadamard matrix solution, which is one of the most efficient ways to reduce speckle noise. By illuminating the object with a series of orthogonal phase patterns corresponding to permutations of Hadamard matrices, one can convert the sum of electrical fields (coherent) in the image pixel into a sum of intensities (non-coherent). We report a 50% speckle reduction. The effect of speckle reduction was measured using both a vector network analyzer and a W-band free-space scalar calibrated measurement setup. We processed 2 different Hadamard diffusers and present here measurement data discussing speckle contrast as a function of frequency.
Md.saiful, I, Jager, I, Koers, G & Vounckx, R 2006, W-band quasi-optical speckle contrast measurements with a Hadamard diffuser”, Society of Photo-optical Instruments (SPIE), Vol. 6341, pp-U19-U24 , 2006. in S P (ed.), PROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE). vol. 6341, PROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE), SPIE, pp. 19-24.
Md.saiful, I., Jager, I., Koers, G., & Vounckx, R. (2006). W-band quasi-optical speckle contrast measurements with a Hadamard diffuser”, Society of Photo-optical Instruments (SPIE), Vol. 6341, pp-U19-U24 , 2006. In S. P (Ed.), PROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE) (Vol. 6341, pp. 19-24). (PROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE)). SPIE.
@inbook{55a8434d8de74e18aa784d61be415511,
title = "W-band quasi-optical speckle contrast measurements with a Hadamard diffuser”, Society of Photo-optical Instruments (SPIE), Vol. 6341, pp-U19-U24 , 2006",
abstract = "Millimeter waves are able to penetrate materials that are usually opaque to both visible and infrared radiation. We used this advantage to design a free-space active millimeter-wave imaging set up for security applications. Because all existing mm-wave sources are coherent - speckle is one of the ultimate limiting factors of the imaging techniques. This problem is of special importance for mm-wave imaging, because surface roughness is closer to the object dimension as in optical imaging. The reduction of speckle is highly desirable and we propose here a Hadamard matrix solution, which is one of the most efficient ways to reduce speckle noise. By illuminating the object with a series of orthogonal phase patterns corresponding to permutations of Hadamard matrices, one can convert the sum of electrical fields (coherent) in the image pixel into a sum of intensities (non-coherent). We report a 50% speckle reduction. The effect of speckle reduction was measured using both a vector network analyzer and a W-band free-space scalar calibrated measurement setup. We processed 2 different Hadamard diffusers and present here measurement data discussing speckle contrast as a function of frequency.",
keywords = "THz; imaging; Hadamard diffuser; speckle",
author = "Islam Md.saiful and Irina Jager and Gaetan Koers and Roger Vounckx",
note = "Slangen P",
year = "2006",
month = sep,
day = "13",
language = "English",
isbn = "0-8194-6426-0",
volume = "6341",
series = "PROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE)",
publisher = "SPIE",
pages = "19--24",
editor = "Slangen P",
booktitle = "PROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE)",
address = "United States",
}