Kallol Bhattacharya | University of Calcutta (original) (raw)

Papers by Kallol Bhattacharya

International Conference on Optics and Photonics 2015, 2015

Physica Scripta

This work describes a full-field and near-common-path in-line laser interferometer and interferom... more This work describes a full-field and near-common-path in-line laser interferometer and interferometric microscope utilizing a wire-grid polarizer (WGP) placed normally on the laser beam illuminating the sample. The WGP serves the dual purpose of a beam splitter and a polarization separator where the reference and sample beams reflected and transmitted from it respectively are orthogonally polarized so that, unlike other conventional interferometers, polarization phase shifting is inherent in its architecture. This arrangement presents experimental results showing quantitative phase analysis of transparent and reflecting phase samples.

2018 Emerging Trends in Electronic Devices and Computational Techniques (EDCT), 2018

Development of computer networking generates many benefits in cyber world. Due to this great adva... more Development of computer networking generates many benefits in cyber world. Due to this great advancement, nowadays networking facilities are available at very low cost. But unfortunately this easy access becomes a threat to information security. Watermarking is a technique that is very often used in image processing to trace copyrighted products. It can also be used to trace products which are illegally distributed without permission. In our research work, a new technique for invisible watermarking of images using alpha blending has been proposed. Alpha blending is used to display an alpha bitmap and an alpha bitmap is that one which has transparent and semi-transparent pixels. We have worked on color image and gray scale image. Gray scale image is used as watermark image which is kept hidden in the main scale image by different values of alpha in alpha blending method. This technique is actually done on each plane of the color image. The resulting image contains the information of color image and gray scale images but the main image is unseen to others. PSNR values are also calculated to check the robustness of the reconstructed image. Applying some post-processing work, this can be used in image steganography also.

Satellite Systems - Design, Modeling, Simulation and Analysis, 2021

This chapter presents a novel method for compressing satellite imagery using phase grating to fac... more This chapter presents a novel method for compressing satellite imagery using phase grating to facilitate the optimization of storage space and bandwidth in satellite communication. In this research work, each Satellite image is first modulated with high grating frequency in a fixed orientation. Due to this modulation, three spots (spectrum) have been generated. From these three spots, by applying Inverse Fourier Transform in any one band, we can recover the image. Out of these three spots, one is center spectrum spot and other spots represent two sidebands. Care should be taken during the spot selection is to avoid aliasing effect. At the receiving end, to recover image we use only one spectrum. We have proved that size of the extracted image is less than the original image. In this way, compression of satellite image has been performed. To measure quality of the output images, PSNR value has been calculated and compared this value with previous techniques. As high-resolution satell...

Journal of Optical Technology, 2020

Achromatic retarders are key components used in optical system design. Various researchers have p... more Achromatic retarders are key components used in optical system design. Various researchers have proposed different combinations of quarter-wave plates that exhibit good achromatic behavior over a broad wavelength range. One of the pioneering works in this area was that of Pancharatnam, who proposed a combination of three wave plates where the fast axis of the first and the last wave plates were parallel, and both quarter-wave and half-wave achromatic retarders were obtained by proper orientation of the central wave plate. In this paper the superachromatic behavior of a quarter-wave retardation system, consisting of three wave plates, is studied in the spectral range from 500–700 nm (i.e., the visible range), centered around the design wavelength of 575 nm. It will be shown that, if the second and third wave plates of the proposed configuration are oriented at 67.5° and 90°, respectively, a retardation variation of as low as ±0.13∘ is observed over the said visible range, indicating the superachromatic nature of the proposed system.

Optik, 2017

This work aims to characterize the retardation of birefringent samples such as wave-plates and bi... more This work aims to characterize the retardation of birefringent samples such as wave-plates and birefringent wedges where the principal axis is uniform over the sample zone. The in-line procedure described and implemented for the purpose uses four frames of intensity data that are digitally recorded and combined to characterize the sample in terms of its retardance from 0 to 2 as also to uniquely identify the direction of its fast axis. Simulated and experimental results presented are in good agreement with the proposed theory.

International Conference on Optics and Photonics 2015, 2015

A mathematical model which has been developed for interferometric analysis of birefringent sample... more A mathematical model which has been developed for interferometric analysis of birefringent sample is experimentally verified using a modified Mach – Zehnder arrangement. It is shown that full field analysis of samples with varying birefringence in magnitude and orientation is possible.

In this exploration, we present a compact and easy-to-set imaging system to analyze quantitativel... more In this exploration, we present a compact and easy-to-set imaging system to analyze quantitatively macroscopic and microscopic transparent phase samples (TPS) using interferograms created by a radial shearing interferometer (RSI). The proposed set-up employs a wire grid polarizer (WGP) as a beam-splitting optical element in a triangular cyclic interferometer (TCI) configuration to render the two counter-propagating beams linearly polarized in orthogonal directions as they emerge from the interferometer. These beams are made to pass through the TPS in a counter direction. The focusing lens to image the sample is aligned in such a way that either a p-polarized beam illuminates the phase sample in such a way that the sample is in focus with respect to the focusing lens and the other polarization fixed in focus of the lens and for s-polarized beam illumination it is far apart from its focal length. So due to this polarization phase shifting (PPS) is implemented so as to generate a three...

Arabian Journal for Science and Engineering

Medical images are treated as sensitive as it carries patients' confidential information and henc... more Medical images are treated as sensitive as it carries patients' confidential information and hence must be protected from unauthorized access. So, a strong encryption mechanism is a primary criterion to transmit these images over the internet to protect them from intruders. In many existing algorithms, noise affection in the extracted images is high, hence not suitable for medical data encryption. Here, we present a new method using phase grating to multiplex as well as encrypting 32 cross-sectional CT scan images (slices) in a single canvas for optimization of storage space and improvement of security. The entire process is divided into a few steps. Before transmission, the main canvas is encrypted with the help of a random phase matrix. The main canvas is further encrypted by the transposition method to enhance security. After decryption, inverse Fourier transform is applied at the proper location of the decrypted canvas to extract the images from the spectra. Quality is measured with peak-signal-to-noise ratio and correlation coefficient methods. Here, it is greater than 38 and the correlation coefficient is close to 1 for all images, thereby indicating of good quality of extracted images. The effect of three common cyber-attacks (viz. known-plaintext attack, chosen-plaintext attack, and chosen-ciphertext attack) is also presented here. The correlation coefficient during cyber-attacks is found to be close to zero, which implies the robustness of the algorithm against cyber-attacks. Finally, a comparison with existing techniques shows the effectiveness of the proposed method.

Computational Intelligence and Its Applications in Healthcare

Abstract Developments in optical image processing have guided a new era in teleconferencing for m... more Abstract Developments in optical image processing have guided a new era in teleconferencing for medical research work. As medical images carry a great deal of information, image storage using minimal space, as well as image recovery, are important research areas for telemedicine services. In this chapter, a new scheme for storing and recovering multiple medical images using a sinusoidal amplitude grating has been proposed. In this scheme, all medical images are modulated separately using a high value of spatial grating frequency; in addition, the orientation angle of the grating is varied during this process. As a result of modulation, three spectra for each image are generated. All spectrum planes are added together to form a single spectrum plane. The entire spectrum plane is Gaussian filtered to eliminate speckle noise. For proper optimization of limited storage space and bandwidth requirements, we transmit only a part of the entire spectrum plane. An intensity graph was plotted to find the location of maximum image information. In the intensity graph, an inverse Fourier transform is applied around the peaks to retrieve the transmitted images. To maintain the quality of the output, information loss of images should be kept to the minimum possible during processing. To measure the quality of the output images, a conventional PSNR checking method was applied. The frequency of the grating should be high to avoid any aliasing problem. The main objective of this work is to provide efficient storage and quick transmission of medical images.

Pramana, 2021

In this communication, the construction and transmission characteristics of a narrow band-pass bi... more In this communication, the construction and transmission characteristics of a narrow band-pass birefringent filter have been investigated. The filter is formed by a combination of two sets of retarders with a polariser in between, and two linear polarisers placed at the two extreme ends. The sets of retarders are chosen to be a cascaded fan-type Solc filter having two different kinds of retardations, resulting in filtering characteristics better than those birefringent filters proposed for the visible range. The performance of this proposed filter is better in terms of effective suppression of side peak amplitudes as well as reduction of bandwidth with less number of waveplates. This birefringent filter can be used inside a linear resonator.

Compression of images is an important application in the field of image processing as it is suita... more Compression of images is an important application in the field of image processing as it is suitable for optimization of storage space and sharing over internet with optimum bandwidth utilization. This study presentsa novel method for compressing image using amplitude grating. The selected image is first modulated with high frequency amplitude grating in a fixed orientation. Therefore, the image is converted into optical frequency domain from spatial domain. Due to this modulation, three spots (spectrum bands) have been generated. From these three spots, by applying Inverse Fourier Transform in any one band, we can recover the image.Out of these three spots, one is center spectrum spot and other spots are two sidebands. However, to a get a reasonably good output, we have to selectspotcarefully to avoid aliasing effect. Information of the selected image is basically distributed among three spots of the spectrum. Therefore by selecting any one spot from the spectrum, we can retrieve t...

International Journal of Innovative Knowledge Concepts, 2019

Optical Engineering, 2020

Abstract. Recent developments in the areas of image processing have guided a new paradigm for res... more Abstract. Recent developments in the areas of image processing have guided a new paradigm for research work in communication of images over the internet. Hence, secure storage and retrieval of digital images is a demanding task for future communication services. A scheme to securely store and encrypt multiple images using sinusoidal phase grating is highlighted. In the proposed scheme, images are modulated using different spatial frequencies and orientation angles. In addition, images have been encrypted using random phase mask after filtering. In order to avoid any human intervention in the system, an intensity graph is plotted to retrieve the images by applying inverse Fourier transform. Using this method, it is possible to independently store, encrypt, and retrieve multiple images due to absence of aliasing problem.

Applied Optics, 2017

A full-field polarization-based technique is presented for quantitative evaluation of the spatial... more A full-field polarization-based technique is presented for quantitative evaluation of the spatial distribution of the refractive index in macro and micro samples. The sample is mounted on a glass-air interface of a prism, illuminated by a linearly polarized collimated light beam, and two intensity frames are digitally recorded with specific orientations of an analyzer. The pair of intensity data frames captured with this simple setup is combined through an algorithm specially developed for the purpose, to yield the phase difference between the transverse electric and transverse magnetic components of the total internally reflected light field. The phase difference is then related to the refractive index of the sample. Experimental results for refractive index variations in a laser-etched glass plate and red blood corpuscles are presented. One of the salient features of the proposed technique is that the depth of measurement is dependent on the penetration depth of the sample's evanescent field, which is typically of the order of a few hundred nanometers, thereby facilitating refractive index measurements along a thin section of the sample.

Optical Engineering, 2016

Abstract. It is well known that the phase change in total internal reflection (TIR) is a function... more Abstract. It is well known that the phase change in total internal reflection (TIR) is a function of the refractive indices of the pair of media involved. The spatial phase variations in a totally internally reflected beam are accurately measured using a Mach Zehnder interferometer employing polarization phase shifting technique. The evaluated phase change is then related to the refractive index variations of the rarer medium. One of the salient features of the proposed technique is that, unlike most interferometric methods where the measured phase is a function of the sample thickness, TIR phase is independent of the sample thickness as long as the evanescent wave field is fully confined within the sample. The theory of the technique is discussed and experimental results showing the three-dimensional profiles of the measured refractive indices and its spatial variations are presented.

Optik, 2021

Abstract The present work proposes an optical polarization based reflection technique for determi... more Abstract The present work proposes an optical polarization based reflection technique for determining surface roughness of metal surfaces. A linearly polarized light beam is used to illuminate the sample surface and two intensity data frames are recorded with specific orientations of an analyzer. An algorithm is developed to combine the pair of intensity data frames captured with this simple setup. Assuming that the refractive index of the sample is known and constant throughout the sample, the phase difference between the transverse electric and transverse magnetic components of the light reflected from the surface preserve the information about surface roughness in terms of local angular tilts, which is subsequently converted to axial deviations about the nominal surface.

International Conference on Optics and Photonics 2015, 2015

Physica Scripta

This work describes a full-field and near-common-path in-line laser interferometer and interferom... more This work describes a full-field and near-common-path in-line laser interferometer and interferometric microscope utilizing a wire-grid polarizer (WGP) placed normally on the laser beam illuminating the sample. The WGP serves the dual purpose of a beam splitter and a polarization separator where the reference and sample beams reflected and transmitted from it respectively are orthogonally polarized so that, unlike other conventional interferometers, polarization phase shifting is inherent in its architecture. This arrangement presents experimental results showing quantitative phase analysis of transparent and reflecting phase samples.

2018 Emerging Trends in Electronic Devices and Computational Techniques (EDCT), 2018

Development of computer networking generates many benefits in cyber world. Due to this great adva... more Development of computer networking generates many benefits in cyber world. Due to this great advancement, nowadays networking facilities are available at very low cost. But unfortunately this easy access becomes a threat to information security. Watermarking is a technique that is very often used in image processing to trace copyrighted products. It can also be used to trace products which are illegally distributed without permission. In our research work, a new technique for invisible watermarking of images using alpha blending has been proposed. Alpha blending is used to display an alpha bitmap and an alpha bitmap is that one which has transparent and semi-transparent pixels. We have worked on color image and gray scale image. Gray scale image is used as watermark image which is kept hidden in the main scale image by different values of alpha in alpha blending method. This technique is actually done on each plane of the color image. The resulting image contains the information of color image and gray scale images but the main image is unseen to others. PSNR values are also calculated to check the robustness of the reconstructed image. Applying some post-processing work, this can be used in image steganography also.

Satellite Systems - Design, Modeling, Simulation and Analysis, 2021

This chapter presents a novel method for compressing satellite imagery using phase grating to fac... more This chapter presents a novel method for compressing satellite imagery using phase grating to facilitate the optimization of storage space and bandwidth in satellite communication. In this research work, each Satellite image is first modulated with high grating frequency in a fixed orientation. Due to this modulation, three spots (spectrum) have been generated. From these three spots, by applying Inverse Fourier Transform in any one band, we can recover the image. Out of these three spots, one is center spectrum spot and other spots represent two sidebands. Care should be taken during the spot selection is to avoid aliasing effect. At the receiving end, to recover image we use only one spectrum. We have proved that size of the extracted image is less than the original image. In this way, compression of satellite image has been performed. To measure quality of the output images, PSNR value has been calculated and compared this value with previous techniques. As high-resolution satell...

Journal of Optical Technology, 2020

Achromatic retarders are key components used in optical system design. Various researchers have p... more Achromatic retarders are key components used in optical system design. Various researchers have proposed different combinations of quarter-wave plates that exhibit good achromatic behavior over a broad wavelength range. One of the pioneering works in this area was that of Pancharatnam, who proposed a combination of three wave plates where the fast axis of the first and the last wave plates were parallel, and both quarter-wave and half-wave achromatic retarders were obtained by proper orientation of the central wave plate. In this paper the superachromatic behavior of a quarter-wave retardation system, consisting of three wave plates, is studied in the spectral range from 500–700 nm (i.e., the visible range), centered around the design wavelength of 575 nm. It will be shown that, if the second and third wave plates of the proposed configuration are oriented at 67.5° and 90°, respectively, a retardation variation of as low as ±0.13∘ is observed over the said visible range, indicating the superachromatic nature of the proposed system.

Optik, 2017

This work aims to characterize the retardation of birefringent samples such as wave-plates and bi... more This work aims to characterize the retardation of birefringent samples such as wave-plates and birefringent wedges where the principal axis is uniform over the sample zone. The in-line procedure described and implemented for the purpose uses four frames of intensity data that are digitally recorded and combined to characterize the sample in terms of its retardance from 0 to 2 as also to uniquely identify the direction of its fast axis. Simulated and experimental results presented are in good agreement with the proposed theory.

International Conference on Optics and Photonics 2015, 2015

A mathematical model which has been developed for interferometric analysis of birefringent sample... more A mathematical model which has been developed for interferometric analysis of birefringent sample is experimentally verified using a modified Mach – Zehnder arrangement. It is shown that full field analysis of samples with varying birefringence in magnitude and orientation is possible.

In this exploration, we present a compact and easy-to-set imaging system to analyze quantitativel... more In this exploration, we present a compact and easy-to-set imaging system to analyze quantitatively macroscopic and microscopic transparent phase samples (TPS) using interferograms created by a radial shearing interferometer (RSI). The proposed set-up employs a wire grid polarizer (WGP) as a beam-splitting optical element in a triangular cyclic interferometer (TCI) configuration to render the two counter-propagating beams linearly polarized in orthogonal directions as they emerge from the interferometer. These beams are made to pass through the TPS in a counter direction. The focusing lens to image the sample is aligned in such a way that either a p-polarized beam illuminates the phase sample in such a way that the sample is in focus with respect to the focusing lens and the other polarization fixed in focus of the lens and for s-polarized beam illumination it is far apart from its focal length. So due to this polarization phase shifting (PPS) is implemented so as to generate a three...

Arabian Journal for Science and Engineering

Medical images are treated as sensitive as it carries patients' confidential information and henc... more Medical images are treated as sensitive as it carries patients' confidential information and hence must be protected from unauthorized access. So, a strong encryption mechanism is a primary criterion to transmit these images over the internet to protect them from intruders. In many existing algorithms, noise affection in the extracted images is high, hence not suitable for medical data encryption. Here, we present a new method using phase grating to multiplex as well as encrypting 32 cross-sectional CT scan images (slices) in a single canvas for optimization of storage space and improvement of security. The entire process is divided into a few steps. Before transmission, the main canvas is encrypted with the help of a random phase matrix. The main canvas is further encrypted by the transposition method to enhance security. After decryption, inverse Fourier transform is applied at the proper location of the decrypted canvas to extract the images from the spectra. Quality is measured with peak-signal-to-noise ratio and correlation coefficient methods. Here, it is greater than 38 and the correlation coefficient is close to 1 for all images, thereby indicating of good quality of extracted images. The effect of three common cyber-attacks (viz. known-plaintext attack, chosen-plaintext attack, and chosen-ciphertext attack) is also presented here. The correlation coefficient during cyber-attacks is found to be close to zero, which implies the robustness of the algorithm against cyber-attacks. Finally, a comparison with existing techniques shows the effectiveness of the proposed method.

Computational Intelligence and Its Applications in Healthcare

Abstract Developments in optical image processing have guided a new era in teleconferencing for m... more Abstract Developments in optical image processing have guided a new era in teleconferencing for medical research work. As medical images carry a great deal of information, image storage using minimal space, as well as image recovery, are important research areas for telemedicine services. In this chapter, a new scheme for storing and recovering multiple medical images using a sinusoidal amplitude grating has been proposed. In this scheme, all medical images are modulated separately using a high value of spatial grating frequency; in addition, the orientation angle of the grating is varied during this process. As a result of modulation, three spectra for each image are generated. All spectrum planes are added together to form a single spectrum plane. The entire spectrum plane is Gaussian filtered to eliminate speckle noise. For proper optimization of limited storage space and bandwidth requirements, we transmit only a part of the entire spectrum plane. An intensity graph was plotted to find the location of maximum image information. In the intensity graph, an inverse Fourier transform is applied around the peaks to retrieve the transmitted images. To maintain the quality of the output, information loss of images should be kept to the minimum possible during processing. To measure the quality of the output images, a conventional PSNR checking method was applied. The frequency of the grating should be high to avoid any aliasing problem. The main objective of this work is to provide efficient storage and quick transmission of medical images.

Pramana, 2021

In this communication, the construction and transmission characteristics of a narrow band-pass bi... more In this communication, the construction and transmission characteristics of a narrow band-pass birefringent filter have been investigated. The filter is formed by a combination of two sets of retarders with a polariser in between, and two linear polarisers placed at the two extreme ends. The sets of retarders are chosen to be a cascaded fan-type Solc filter having two different kinds of retardations, resulting in filtering characteristics better than those birefringent filters proposed for the visible range. The performance of this proposed filter is better in terms of effective suppression of side peak amplitudes as well as reduction of bandwidth with less number of waveplates. This birefringent filter can be used inside a linear resonator.

Compression of images is an important application in the field of image processing as it is suita... more Compression of images is an important application in the field of image processing as it is suitable for optimization of storage space and sharing over internet with optimum bandwidth utilization. This study presentsa novel method for compressing image using amplitude grating. The selected image is first modulated with high frequency amplitude grating in a fixed orientation. Therefore, the image is converted into optical frequency domain from spatial domain. Due to this modulation, three spots (spectrum bands) have been generated. From these three spots, by applying Inverse Fourier Transform in any one band, we can recover the image.Out of these three spots, one is center spectrum spot and other spots are two sidebands. However, to a get a reasonably good output, we have to selectspotcarefully to avoid aliasing effect. Information of the selected image is basically distributed among three spots of the spectrum. Therefore by selecting any one spot from the spectrum, we can retrieve t...

International Journal of Innovative Knowledge Concepts, 2019

Optical Engineering, 2020

Abstract. Recent developments in the areas of image processing have guided a new paradigm for res... more Abstract. Recent developments in the areas of image processing have guided a new paradigm for research work in communication of images over the internet. Hence, secure storage and retrieval of digital images is a demanding task for future communication services. A scheme to securely store and encrypt multiple images using sinusoidal phase grating is highlighted. In the proposed scheme, images are modulated using different spatial frequencies and orientation angles. In addition, images have been encrypted using random phase mask after filtering. In order to avoid any human intervention in the system, an intensity graph is plotted to retrieve the images by applying inverse Fourier transform. Using this method, it is possible to independently store, encrypt, and retrieve multiple images due to absence of aliasing problem.

Applied Optics, 2017

A full-field polarization-based technique is presented for quantitative evaluation of the spatial... more A full-field polarization-based technique is presented for quantitative evaluation of the spatial distribution of the refractive index in macro and micro samples. The sample is mounted on a glass-air interface of a prism, illuminated by a linearly polarized collimated light beam, and two intensity frames are digitally recorded with specific orientations of an analyzer. The pair of intensity data frames captured with this simple setup is combined through an algorithm specially developed for the purpose, to yield the phase difference between the transverse electric and transverse magnetic components of the total internally reflected light field. The phase difference is then related to the refractive index of the sample. Experimental results for refractive index variations in a laser-etched glass plate and red blood corpuscles are presented. One of the salient features of the proposed technique is that the depth of measurement is dependent on the penetration depth of the sample's evanescent field, which is typically of the order of a few hundred nanometers, thereby facilitating refractive index measurements along a thin section of the sample.

Optical Engineering, 2016

Abstract. It is well known that the phase change in total internal reflection (TIR) is a function... more Abstract. It is well known that the phase change in total internal reflection (TIR) is a function of the refractive indices of the pair of media involved. The spatial phase variations in a totally internally reflected beam are accurately measured using a Mach Zehnder interferometer employing polarization phase shifting technique. The evaluated phase change is then related to the refractive index variations of the rarer medium. One of the salient features of the proposed technique is that, unlike most interferometric methods where the measured phase is a function of the sample thickness, TIR phase is independent of the sample thickness as long as the evanescent wave field is fully confined within the sample. The theory of the technique is discussed and experimental results showing the three-dimensional profiles of the measured refractive indices and its spatial variations are presented.

Optik, 2021

Abstract The present work proposes an optical polarization based reflection technique for determi... more Abstract The present work proposes an optical polarization based reflection technique for determining surface roughness of metal surfaces. A linearly polarized light beam is used to illuminate the sample surface and two intensity data frames are recorded with specific orientations of an analyzer. An algorithm is developed to combine the pair of intensity data frames captured with this simple setup. Assuming that the refractive index of the sample is known and constant throughout the sample, the phase difference between the transverse electric and transverse magnetic components of the light reflected from the surface preserve the information about surface roughness in terms of local angular tilts, which is subsequently converted to axial deviations about the nominal surface.