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Yang, Li
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Publications (10 of 18) Show all publications
Gooran, S. & Yang, L. (2015). Basics of tone reproduction. In: Michael Kriss (Ed.), Handbook of Digital Imaging: . Wiley
Open this publication in new window or tab >>Basics of tone reproduction
2015 (English)In: Handbook of Digital Imaging / [ed] Michael Kriss, Wiley , 2015Chapter in book (Refereed)
Abstract [en]

 There is no doubt that printing has been one of the most important technological inventions for

human civilization. Books, magazines, news papers, and so on have been printed for different

purposes such as distributing knowledge, thoughts, and news and commercializing products.

Tone reproduction for images has been one of the challenging parts of the printing technology

because the printing devices are restricted to a few color inks, whereas the original image

may consist of millions of color tones. In this chapter, the basics of the tone reproduction

are introduced. We begin with a brief history of halftoning and a short introduction of digitalization.

It is followed by the description on visual acuity of human visual system and its

relationship with the screen resolution. Then the basic and general concepts of tone reproduction,

such as screen frequency, print resolution, screen angle and Moiré pattern, and dot gain

are described and illustrated. Dot gain is only briefl y described and illustrated in this chapter as

it is thoroughly discussed in Physical Evaluation of the Quality of Color Halftone . Finally,

technologies for color reproduction and color halftoning are discussed.

Place, publisher, year, edition, pages
Wiley, 2015
National Category
Media Engineering
Identifiers
urn:nbn:se:liu:diva-114943 (URN)978-0-470-51059-9 (ISBN)
Available from: 2015-03-06 Created: 2015-03-06 Last updated: 2015-03-24
Yang, L. L. (2010). Synthesis and Characterization of ZnO Nanostructures. (Doctoral dissertation). Linköping: Linköping University Electronic Press
Open this publication in new window or tab >>Synthesis and Characterization of ZnO Nanostructures
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

One-dimensional ZnO nanostructures have great potential applications in the fields of optoelectronic and sensor devices.  Therefore, it is very important to realize the controllable growth of one-dimensional ZnO nanostructures and investigate their properties. The main points for this thesis are not only to successfully realize the controllable growth of ZnO nanorods (ZNRs), ZnO nanotubes (ZNTs) and ZnMgO/ZnO heterostructures, but also investigate the structure and optical properties in detail by means of scanning electron microscope (SEM), transmission electron microscope (TEM), resonant Raman spectroscopy (RRS), photoluminescence (PL), time resolved PL (TRPL), X-ray photoelectron spectroscopy (XPS) and Secondary ion mass spectrometry (SIMS).

For ZNRs, on one hand, ZNRs have been successfully synthesized by a two-step chemical bath deposition method on Si substrates. The diameter of ZNRs can be well controlled from 150 nm to 40 nm through adjusting the diameter and density of the ZnO nanoparticles pretreated on the Si substrates. The experimental results indicated that both diameter and density of ZnO nanoparticles on the substrates determined the diameter of ZNRs. But when the density is higher than the critical value of 2.3×108cm-2, the density will become the dominant factor to determine the diameter of ZNRs.

One the other hand, the surface recombination of ZNRs has been investigated in detail. Raman, RRS and PL results help us reveal that the surface defects play a significant role in the as-grown sample. It is the first time to the best of our knowledge that the Raman measurements can be used to monitor the change of surface defects and deep level defects in the CBD grown ZNRs. Then we utilized TRPL technique, for the first time, to investigate the CBD grown ZNRs with different diameters. The results show that the decay time of the excitons in ZNRs strongly depends on the diameter. The altered decay time is mainly due to the surface recombination process. A thermal treatment under 500°C can strongly suppress the surface recombination channel. A simple carrier and exciton diffusion equation is also used to determine the surface recombination velocity, which results in a value between 1.5 and 4.5 nm/ps. Subsequently, we utilized XPS technique to investigate the surface composition of as-grown and annealed ZNRs so that we can identify the surface recombination centers. The experimental results indicated that the OH and H bonds play the dominant role in facilitating surface recombination but specific chemisorbed oxygen also likely affect the surface recombination. Finally, on the basis of results above, we explored an effective way, i.e. sealing the beaker during the growth process, to effectively suppress the surface recombination of ZNRs and the suppression effect is even better than a 500oC post-thermal treatment.

For ZNTs, the structural and optical properties have been studied in detail. ZNTs have been successfully evolved from ZNRs by a simple chemical etching process. Both temperature-dependent PL and TRPL results not only further testify the coexistence of spatially indirect and direct transitions due to the surface band bending, but also reveal that less nonradiative contribution to the emission process in ZNTs finally causes their strong enhancement of luminescence intensity.

For ZnMgO/ZnO heterostructures, the Zn0.94Mg0.06O/ZnO heterostructures have been deposited on 2 inch sapphire wafer by metal organic chemical vapor deposition (MOCVD) equipment. PL mapping demonstrates that Mg distribution in the entire wafer is quite uniform with average concentration of ~6%. The annealing effects on the Mg diffusion behaviors in Zn0.94Mg0.06O/ZnO heterostructures have been investigated by SIMS in detail. All the SIMS depth profiles of Mg element have been fitted by three Gaussian distribution functions. The Mg diffusion coefficient in the as-grown Zn0.94Mg0.06O layer deposited at 700 oC is two orders of magnitude lower than that of annealing samples, which clearly testifies that the deposited temperature of 700 oC is much more beneficial to grow ZnMgO/ZnO heterostructures or quantum wells.

This thesis not only provides the effective way to fabricate ZNRs, ZNTs and ZnMgO/ZnO heterostructures, but also obtains some beneficial results in aspects of their optical properties, which builds theoretical and experimental foundation for much better understanding fundamental physics and broader applications of low-dimensional ZnO and related structures.

Abstract [sv]

Endimensionella nanostrukturer av ZnO har stora potentiella tillämpningar för optoelektroniska komponenter och sensorer. Huvudresultaten för denna avhandling är inte bara att vi framgångsrikt har realiserat med en kontrollerbar metod ZnO nanotrådar (ZNRs), ZnO nanotuber (ZNTs) och ZnMgO/ZnO heterostrukturer, utan vi har också undersökt deras struktur och optiska egenskaper i detalj.

För ZNRs har diametern blivit välkontrollerad från 150 nm  ner till 40 nm. Den storlekskontrollerande mekanismen är i huvudsak relaterad till tätheten av ZnO partiklarna som är fördeponerade på substratet. De optiska mätningarna ger upplysning om att ytrekombinationsprocessen spelar en betydande roll för tillväxten av ZNR. En värmebehandling i efterhand  vid 500 grader Celsius eller användande av en förseglad glasbägare under tillväxtprocessen kan starkt hålla nere kanalerna för ytrekombinationen.För ZNT, dokumenterar vi inte bara samexistensen av rumsliga indirekta och direkta  övergångar på grund av bandböjning, men vi konstaterar också att vi har mindre icke-strålande bidrag till den optiska emissionsprocessen i ZNT.

För ZnMgO/ZnO heterostrukturer konstaterar vi med hjälp av analys av Mg diffusionen i den växta och den i efterhand uppvärmda Zn(0.94)Mg(0.06)O filmen, att en tillväxt vid 700 grader Celsius är den mest lämpliga för att växa ZnMgO/ZnO heterostrukturer eller kvantbrunnar.

 

Denna avhandling ger en teoretisk och experimentell grund för bättre förståelse av grundläggande fysik och för tillämpningar av lågdimensionella strukturer.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2010. p. 107
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1327
Keywords
Zinc oxide; nanostructures; heterostructures; controllable growth; optical properties; postannealing; diffusion coefficient
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-60815 (URN)978-91-7393-357-5 (ISBN)
Public defence
2010-09-30, K3, Kåkenhus, Campus Norrköping, Linköpings universitet, Norrköping, 10:15 (English)
Opponent
Supervisors
Projects
SSF, VR
Available from: 2010-10-28 Created: 2010-10-27 Last updated: 2014-01-15Bibliographically approved
Yang, L. & Lundström, N. (2007). Physical dot gain of offset: Understanding and determination. Nordic Pulp & Paper Research Journal, 22(3), 388-393
Open this publication in new window or tab >>Physical dot gain of offset: Understanding and determination
2007 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 22, no 3, p. 388-393Article in journal (Refereed) Published
Abstract [en]

This report consists of two parts. In the first, a methodology for estimating physical dot gain from scanned images of test patches is proposed. Mathematical relationships bridging the image intensities with the physical dot coverage have been worked out, taking into consideration of light scattering inside the paper substrate and the light reflection at air-paper and air-ink interfaces. In the second part, the possible causes for the physical dot gain in the light of ink-transfer and ink-setting are discussed. The physical dot gain obtained reveals significant differences in the light tones compared to the middle and dark tones. This indicates differences in ink-transfer and ink-setting between the prints consisting of well isolated dots in the light tones and those of overlapping dots in the middle and dark tones. A tentative explanation based on process-competition between press, ink spreading, and free ink-splitting, is given.

Keywords
physical dot gain, ink-tack, ink-paper interaction, offset
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-47996 (URN)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13
Yang, L. (2007). Qualifying the arguments used in the derivation of the revised Kubelka-Munk theory: reply. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION, 24(2)
Open this publication in new window or tab >>Qualifying the arguments used in the derivation of the revised Kubelka-Munk theory: reply
2007 (English)In: JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION, ISSN 1084-7529, Vol. 24, no 2, p. 557-560Other (Other academic)
Abstract [en]

The fundamental assumptions made in the revised Kubelka-Munk (KM) model of light propagation in scattering and absorptive media, recently proposed [J. Opt. Soc. Am. A 21, 1942 (2004), 22, 866 (2005)], are critically reviewed and analyzed. The authors argue that the model, now questioned by Edstrom [J. Opt. Soc. Am. A 24, 548 (2007)] is well founded on physical grounds and consistent with the original KM model, which has been the cornerstone of light propagation studies and utilized for more than half a century. (c) 2007 Optical Society of America

Publisher
p. 557-560
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-48037 (URN)
Available from: 2009-10-11 Created: 2009-10-11
Yang, L., Gooran, S., Eriksen, M. & Johansson, T. (2006). Color Based Maximal GCR for Electrophotography. In: IS&T Int. Conf. on Digital Printing Technologies (NIP22). Paper presented at IS&T Int. Conf. on Digital Printing Technologies (NIP22), Sept. 2006, Denver, Colorado, USA (pp. 394-397). The Society for Imaging Science and Technology
Open this publication in new window or tab >>Color Based Maximal GCR for Electrophotography
2006 (English)In: IS&T Int. Conf. on Digital Printing Technologies (NIP22), The Society for Imaging Science and Technology , 2006, p. 394-397Conference paper, Published paper (Other academic)
Abstract [en]

The underline idea of grey component replacement (GCR) is to replace a mixture of primary colors (cyan, magenta, and yellow) by a black. Current algorithms of GCR are mainly based on the concept of equal-tone-value-reduction or mixing equal amount (tone value) of primary colors generating gray, which in turn can be represented by the same amount of black. As the colors used are usually non-ideal, such a replacement can result in remarkable color deviation.    

We proposed an algorithm of maximal GCR based on color matching, i.e. the black is introduced in a way that preserves the color (before and after GCR). In the algorithm, the primary with smallest tonal value is set to be zero (tone value) while the other two are reduced according to the color matching calculations. To achieve a real color matching of print, dot gain effects have been considered in the calculation. The proposed algorithm has been tested successfully for FM halftoning using an electrophotographic printer.   

Place, publisher, year, edition, pages
The Society for Imaging Science and Technology, 2006
National Category
Media Engineering
Identifiers
urn:nbn:se:liu:diva-76842 (URN)0-89208-263-1 (ISBN)
Conference
IS&T Int. Conf. on Digital Printing Technologies (NIP22), Sept. 2006, Denver, Colorado, USA
Available from: 2012-04-20 Created: 2012-04-20 Last updated: 2012-04-27
Yang, L., Fogden, A., Pauler, N., Saevborg, O. & Kruse, B. (2006). Studying ink penetration with microscopic and spectroscopic techniques. Journal of Imaging Science and Technology, 50(4), 327-332
Open this publication in new window or tab >>Studying ink penetration with microscopic and spectroscopic techniques
Show others...
2006 (English)In: Journal of Imaging Science and Technology, ISSN 1062-3701, E-ISSN 1943-3522, Vol. 50, no 4, p. 327-332Article in journal (Refereed) Published
Abstract [en]

Distribution of ink jet ink in paper substrates and the consequences of ink penetration for printing color reproduction have been studied by combining microscopic image processing with spectroscopic analysis. The study focused on the effects of the composition of uncoated paper, for five laboratory papers plus two commercial products, all consisting of similar pulps but with different combinations of additives. In particular, it was observed that hydrophobizing internal size agents significantly reduced ink penetration, while their effect on paper optical properties was negligible. This observation thus made it possible to study experimentally the pure effects of ink penetration. Pairwise comparisons of prints on such laboratory papers with identical optical properties revealed remarkable impacts of ink penetration on optical density, causing color saturation reduction and color shift. These experimental observations confirmed the theoretical predictions.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-53490 (URN)10.2352/J.ImagingSci.Technol.(2006)50:4(327) (DOI)
Available from: 2010-01-25 Created: 2010-01-25 Last updated: 2017-12-12
Yang, L., Fogden, A., Pauler, N., Sävborg, Ö. & Kruse, B. (2005). A novel method for studying ink penetration of a print. Nordic Pulp & Paper Research Journal, 20(4), 423-429
Open this publication in new window or tab >>A novel method for studying ink penetration of a print
Show others...
2005 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 20, no 4, p. 423-429Article in journal (Refereed) Published
Abstract [en]

A method combining microscopy with image analysis for studying ink penetration of ink-jet prints has been proposed. Prints on paper substrates of various material compositions have been microtomed, imaged with optical microscopy, and analyzed with image processing. The penetration depth and distribution of the ink-jet dye in the paper, which depend on the material compositions of the substrates and printed ink volumes, are then obtained by means of statistical analysis. The study focuses on uncoated fine papers, including five types of hand-sheets and two commercial papers. It is observed that ink penetration can be significantly reduced by adding internal sizing (hydrophobizing) chemicals in the hand-sheet making, while it is relatively less affected by addition of filler and fluorescent whitening agent (FWA). Ink volume obviously influences the depth of its penetration, with depth increasing linearly for higher ink volumes but displaying a disproportionately shallow penetration for smaller applied volumes.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-32272 (URN)18160 (Local ID)18160 (Archive number)18160 (OAI)
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13
Yang, L. (2005). Spectral model of halftone on a fluorescent substrate. Journal of Imaging Science And Technology, 49(2), 179-184
Open this publication in new window or tab >>Spectral model of halftone on a fluorescent substrate
2005 (English)In: Journal of Imaging Science And Technology, ISSN 8750-9237, Vol. 49, no 2, p. 179-184Article in journal (Refereed) Published
Abstract [en]

The color rendition of a halftone image depends on, among other things, physical and optical dot gains and fluorescence of substrates. A unified model describing spectral reflectance of a print is proposed with consideration of these effects. In this model the effects of either physical or optical dot gain are characterized by a single parameter, while those of fluorescence by two sets of spectral parameters, one for fluorescence of bare paper and one for fluorescence of a print solid. This model is tested and further illustrated with applications to images generated by a laser color printer on ordinary office papers. © 2005, IS&T - The Society for Imaging Science and Technology.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-32250 (URN)18130 (Local ID)18130 (Archive number)18130 (OAI)
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13
Yang, L. & Miklavcic, S. (2005). Theory of light propagation incorporating scattering and absorption in turbid media. Optics Letters, 30(7), 792-794
Open this publication in new window or tab >>Theory of light propagation incorporating scattering and absorption in turbid media
2005 (English)In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 30, no 7, p. 792-794Article in journal (Refereed) Published
Abstract [en]

A general theoretical approach to the description of light propagating through turbid media is proposed. The theory is a modification of the two-flux model of Kubelka-Munk (KM), extending its applicability to media systems containing an absorptive component. The modified KM model takes into account the influence of internal scattering on the total path length and accommodates a wide range of absorption influences. Experimental results obtained for dyed-paper systems illuminated by diffuse light are demonstrated to be qualitatively and quantitatively reproduced by the theory. © 2005 Optical Society of America.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-24716 (URN)10.1364/OL.30.000792 (DOI)6962 (Local ID)6962 (Archive number)6962 (OAI)
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-12-13
Yang, L. (2004). A unified model of optical and physical dot gain in print color reproduction. Journal of Imaging Science And Technology, 48(4), 347-353
Open this publication in new window or tab >>A unified model of optical and physical dot gain in print color reproduction
2004 (English)In: Journal of Imaging Science And Technology, ISSN 8750-9237, Vol. 48, no 4, p. 347-353Article in journal (Refereed) Published
Abstract [en]

A unified model coping with both physical and optical dot gains on print color tone reproduction is proposed. The physical dot gain, is approximated by a quadratic function of nominal dot percentages. The function, for each color, is characterized by a single parameter depending on printing technologies as well as ink-paper interactions, and has a symmetric form around where the nominal dot percentage is 50%. The parameter can be derived from the best fit for the model to measured data, such as spectral reflectance values or CIEXYZ tristimulus values. Applications to a color laser printer (on office copy paper) reproduces the experimental dot gain curves fairly well. Dependence on physical dot percentage, a summation of the nominal dot percentage and the corresponding physical dot gain, results in the optical dot gain and in turn the overall dot gain asymmetric forms, plotted against the nominal dot percentages. Furthermore, theoretical analysis reveals fundamental differences between physical and optical dot gains. Therefore, effects of optical dot gain can not be accurately represented by any physical extension in printing practices.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-22497 (URN)1746 (Local ID)1746 (Archive number)1746 (OAI)
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-12-13
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