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  • 1.
    Aghamiri, Seyed Mohammadreza
    et al.
    Shahid Beheshti University, Department of Radiation Medicine, Tehran, Iran.
    Namedanian, Mahziar
    Shahid Beheshti University, Department of Radiation Medicine, Tehran, Iran.
    Sanjabi, Zahora
    Shahid Beheshti University, Department of Radiation Medicine, Tehran, Iran.
    Effect of gamma irradiation on the light polarization variation of PMMA polymer2008In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 281, no 3, p. 356-359Article in journal (Refereed)
    Abstract [en]

    Analyzing the effect of ionized gamma irradiation on the optical parameters of materials is a solution for finding newer techniques in the field of detector and dosimeter systems. A PMMA (polymethylmethacrylate) polymer was radiated from a 60Co source with a power of 1800 C and a constant dose rate of 1.44 kGy/h in three steps of 5, 25 and 61.2 kGy. The ionized gamma irradiation affected the refractive index of polymer and therefore it changes the polarization of the incident light. The difference in the polarization phase shift of the polymer depended on the dose it had been irradiated with.

  • 2.
    Gooran, Sasan
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Nyström, Daniel
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Namedanian, Mahziar
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Hauck, Shahram
    manroland, Germany.
    Measuring Register Shift and Investgating its Effect on Color Appearance for Different Halftoning2011In: Proc. TAGA (Technical Association of the Graphic Arts), Sewickley, PA, USA: Technical Association of the Graphic Arts , 2011Conference paper (Other academic)
    Abstract [en]

    In commercial prints the halftone dots are seldom placed exactly at their corresponding positions in the digital bitmap, mostly due to the imprecise transportation of the printing substrate. In this study, we firstly present an image processing model to measure the displacement of the dots in different color separations by using a high resolution camera. By using a filter wheel equipped with a set of interference filters and sending light in different wavelength bands, it is possible to separate the different color inks. For example, for the combination of cyan and magenta inks, only cyan will be visible in the captured image if the wavelength band of the incoming light is concentrated around 700 nm. On the other hand, for the wavelength band concentrated around 500 nm only magenta will be visible. By comparing the positions of the dots in the captured images with those in the original bitmap we can measure register shift. Secondly in this study, we investigate how miss-registration affects the color appearance of the final print for different halftoning techniques. We use AM, FM first generation and FM 2nd generation halftoning methods and investigate and compare their sensitivity to register shift.

    In the present work we measure the register shift for color patches printed in offset by the proposed image processing model. In order to study the effect of miss-registration on the resulting color appearance we first simulate the miss-registration in the digital bitmap. Then we print the simulated bitmap using an office laser printer. Since the miss-registration is usually negligible for digital prints, especially in lower resolution, we can examine the accuracy of our model for measuring dot displacement by comparing the simulated displacement with the measured one. Finally, by using a spectrophotometer to measure color coordinates, we can study the effect of miss-registration on the resulting color appearance for different halftoning methods by calculating the ΔElab color difference.

  • 3.
    Namedanian, Mahziar
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Characterization of Halftone Prints based on Microscale Image Analysis2013Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Ink spreading and lateral light scattering in the substrate affect the color of a halftone print. One of the most important phenomena which affects the print result is dot gain, meaning that printed dots appear larger than the dots in the digital bitmap. This is partly due to the ink spreading and ink penetration into the substrate, resulting in an enhancement of the physical dot size, referred to as the physical dot gain. Lateral propagation of light in paper causes printed dots to appear larger than their physical size, which is called optical dot gain. Characterization of total dot gain, i.e. the combination of physical and optical dot gain, is an important issue in the study of paper properties and print characteristics. Many models based on macroscopic measurements are reported in the  literature to separately characterize both physical and optical dot gains. The aim of this study is to go beyond the macroscopic models, and to study the halftone prints on a microscopic scale, by using microscale images captured by a high-resolution camera.

    In this dissertation, three approaches based on the Murray-Davies model are proposed to obtain the total dot gain. In the first approach, by minimizing the root-mean-square difference between the calculated spectrum and the reflected spectrum measured by the  spectrophotometer, the total dot gain is approximated. The other two approaches are based on microscale images captured by a highresolution camera. These two approaches differ in their schemes on how to obtain the gray tone of the full tone ink. By the use of microscale images, it is also possible to illustrate the shape of the effective dot area for the investigated paper substrate.

    A novel approach based on the histogram of microscale images is also proposed to separate physical from optical dot gain. Attaining the physical dot gain characteristic makes it possible to determine the actual physical dot shape, by which the Modulation Transfer Function (MTF) of the paper substrate is estimated. The proposed approach is validated by comparing the estimated MTF of eleven offset printed coated papers to the MTF obtained from the unprinted papers using measured and Monte-Carlo simulated edge response.

    Another potential usage based on the separation of physical from optical dot gain, is to study the characterization of different color inks. In this dissertation, the dependency of dot gain and wavelength in color print is investigated. It has been illustrated that the light scattering effect, which is the reason for optical dot gain creation, must be less sensitive to different wavelength bands. It has also been shown that it is possible to separate two printed color inks by illuminating the halftone print with having light in the reflective wavelength band of one of the two colors.

    Comparison of the optical dot gain for different dot shapes and perimeters, but with the same area, shows the dependency of optical dot gain on the dot shape perimeter. The dependency of optical dot gain on the dot shape perimeter verifies the fact that the amount of optical dot gain is different for different types of halftoning.

  • 4.
    Namedanian, Mahziar
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Coppel, Ludovic
    Neuman, Magnus
    Gooran, Sasan
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Edström, Per
    Kolseth, Petter
    Analysis of Optical and Physical Dot Gain by Microscale Image Histogram and Modulation Transfer Functions2013In: Journal of Imaging Science and Technology, ISSN 1062-3701, E-ISSN 1943-3522, Vol. 57, no 2, p. 20504-1-20504-5Article in journal (Refereed)
    Abstract [en]

    The color of a print is affected by ink spreading and lateral light scattering in the substrate, making printed dots appear larger. Characterization of physical and optical dot gain is crucial for the graphic arts and paper industries. We propose a novel approach to separate physical from optical dot gain by use of a high-resolution camera. This approach is based on the histogram of microscale images captured by the camera. Having determined the actual physical dot shape, we estimate the modulation transfer function (MTF) of the paper substrate. The proposed method is validated by comparing the estimated MTF of 11 offset printed coated papers to the MTF obtained from the unprinted papers using measured and Monte Carlo simulated edge responses.

  • 5.
    Namedanian, Mahziar
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Gooran, Sasan
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Characteristic Analysis of the Primary Color Inks in Color Print2011Conference paper (Other academic)
  • 6.
    Namedanian, Mahziar
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Gooran, Sasan
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Characterization of Total Dot Gain by Microscopic Image Analysis2011In: Journal of Imaging Science and Technology, ISSN 1062-3701, E-ISSN 1943-3522, Vol. 55, no 4, p. 40501-1-40501-7Article in journal (Refereed)
    Abstract [en]

    Characterization of total dot gain gives a good insight to the study of paper and print. In this article, we propose three approaches based on the Murray-Davies model to obtain total dot gain. In the first approach, the total gain is approximated by minimizing the root-mean-square between the calculated spectrum and the reflected spectrum measured by the spectrophotometer. The other two approaches are based on microscale images captured by a high resolution camera. These two approaches differ in their schemes on how to obtain the gray tone of the full-tone ink. By the use of microscale images, the authors also illustrate the shape of the effective dot area for the investigated paper substrate. They also study the histograms of the reflected and transmitted microscale images. This comparison shows that although the transmitted image has less optical dot gain compared to the reflected image, the transmittance also incorporates some small amount of optical dot gain. (C) 2011 Society for Imaging Science and Technology [DOI: 10.2352/J.ImagingSci.Technol.2011.55.4.040501]

  • 7.
    Namedanian, Mahziar
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Gooran, Sasan
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    High-Resolution Analysis of Optical and Physical Dot Gain2010In: Proc. TAGA (Technical Association of the Graphic Arts), Sewickley, PA, USA: Technical Association of the Graphic Arts , 2010, p. 399-408Conference paper (Other academic)
    Abstract [en]

    The printed dots appear bigger than the dots in the original digital bitmap. This is partly because of the spreading and penetrating of the ink on and in the paper, called physical dot gain, and partly because of the diffusion of the light in paper, which is referred to as optical dot gain. Dot gain is often approximated by measurements obtained by densitometer or spectrophotometer. In this study we use a very high-resolution scanner with a resolution of 2 μm/pixel and with a field of view of 2.7×2 mm, which makes it possible to clearly see the small halftone dots and their surroundings. In this camera it is also possible to illuminate the paper surface both from above and below, which means that the camera can capture both the reflected and transmitted lights. Since the transmitted light does not scatter in paper the optical dot gain has no effect on the transmitted image. In this paper we investigate the behavior of physical and optical dot gain for print on coated paperin offset, by using the micro scale images. We also present a method to separate optical and physical dot gain by using the reflected and the transmitted images. By comparing the reflectance and transmittance histograms it is possible to understand that, there is no optical dot gain in transmitted image. We also compare our results with the result obtained by a spectrophotometer, which also measures both reflected and transmitted light. Previously the physical and optical dot gains were mostly analyzed numerically, however in this paper we will also graphically illustrate and compare these two concepts by using microscale images.

  • 8.
    Namedanian, Mahziar
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Gooran, Sasan
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Optical Dot Gain Study on Different Halftone Dot Shapes2013Conference paper (Refereed)
  • 9.
    Namedanian, Mahziar
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Gooran, Sasan
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Nyström, Daniel
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Investigating the Wavelength Dependency of Dot Gain in Color Print2011In: Color Imaging XVI: Displaying, Processing, Hardcopy, and Applications / [ed] Reiner Eschbach, Gabriel G. Marcu, Alessandro Rizzi, Bellingham, WA, United States: SPIE - International Society for Optical Engineering, 2011, p. 786617-1-786617-8Conference paper (Refereed)
    Abstract [en]

    By separating the optical dot gain from the physical dot gain, it is possible to study different behaviors of color inks on different papers. In this study we are investigating the dependency of dot gain and wavelength in color print. Microscopic images have been used to separate optical and physical dot gain from each other. The optical behavior of primary color inks in different absorbing wavelength bands has been studied. It has been illustrated that the light scattering in the paper is wavelength independent, and therefore the Point Spread Function which indicates the probability of light scattering of the paper does not change in visible wavelengths (380 nm -700 nm). We have shown that it is possible to separate two printed color inks on one specific wavelength, due to the filtering behavior of the color inks. By considering the fact that light scattering in the paper is wavelength independent, it was possible to separately analyze the dot gain of each color.

  • 10.
    Namedanian, Mahziar
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Mozafari, Morteza
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Modarres Razavi, Sara
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Analysis of a Three Part 230 kV Optical Voltage Transducer with Multiple Electric Field Sensors2008In: Proceedings from The 8. IASTED European conference on power and energy systems (EuroPES 2008) / [ed] P.D Bourkas, Calgary: ACTA Press , 2008Conference paper (Refereed)
    Abstract [en]

    Optical Voltage Transducer (OVT) is considered as a proper candidate for replacing the conventional inductive and capacitive transformers. The exact positioning of the electric field sensors are one of the important issues while designing an OVT. The three sensors of the OVT have been positioned according to quadrature method to satisfy the IEC 0.2% class specification. A three part OVT is designed and numerically analyzed by FLUX software and the results for different external perturbations are maintaining the 0.2% class accuracies for the given system. The advantages of using a three part OVT have been considered in this paper.

  • 11.
    Namedanian, Mahziar
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Nyström, Daniel
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Zitinski Elias, Paula
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Gooran, Sasan
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Physical and optical dot gain: characterization and relation to dot shape and paper properties2014In: COLOR IMAGING XIX: DISPLAYING, PROCESSING, HARDCOPY, AND APPLICATIONS / [ed] Reiner Eschbach, Gabriel G. Marcu and Alessandro Rizzi, International Society for Optical Engineering; 1999 , 2014, Vol. 9015, p. 9015-09-Conference paper (Refereed)
    Abstract [en]

    The tone value increase in halftone printing commonly referred to as dot gain actually encompasses two fundamentally different phenomena. Physical dot gain refers to the fact that the size of the printed halftone dots differs from their nominal size, and is related to the printing process. Optical dot gain originates from light scattering inside the substrate, causing light exchanges between different chromatic areas. Due to their different intrinsic nature, physical and optical dot gains need to be treated separately. In this study, we characterize and compare the dot gain properties for offset prints on coated and uncoated paper, using AM and first and second generation FM halftoning. Spectral measurements are used to compute the total dot gain. Microscopic images are used to separate the physical and optical dot gain, to study ink spreading and ink penetration, and to compute the Modulation Transfer Function (MTF) for the different substrates. The experimental results show that the physical dot gain depends on ink penetration and ink spreading properties. Microscopic images of the prints reveal that the ink penetrates into the pores and cavities of the uncoated paper, resulting in inhomogeneous dot shapes. For the coated paper, the ink spread on top of the surface, giving a more homogenous dot shape, but also covering a larger area, and hence larger physical dot gain. The experimental results further show that the total dot gain is larger for the uncoated paper, because of larger optical dot gain. The effect of optical dot gain depends on the lateral light scattering within the substrate, the size of the halftone dots, and on the halftone dot shape, especially the dot perimeter.

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