Miloslav Frumar: In the footsteps of the chalcogenide semiconductors

The year 2021 is the year of the 85th anniversary of the birth of Professor Miloslav Frumar the enthusiastic chemist who dedicated his whole professional life to the study of amorphous and glassy chalcogenides which are used in numerous applications like copying machines, laser printers, DVDs or memories.

Using Quantitative Characteristics of Document Images for Identification of Laser Printers

The article provides a brief overview of the current state of the theory and practice of identifying laser printers and the results of research work aimed at discovering individual features of the printing mechanism of a laser printer.The author analyses the scheme of a laser printer, describes the printing cycle, presents the main results of the analysis of a printer’s mechanism and the influence of its individual parts on the optical density of printing. The method of assessment of the optical density of the print by the digital image of the printed document is proposed, the complex of the necessary technical and program tools is described.A hypothesis on the correlation between fluctuations in the optical density of printing of solid fills and fluctuations in the area of printed elements was put forward and confirmed; a visual representation of the study results in graphical form is presented, the relationship between the shape of the obtained graphs and defects of the printer’s components and parts is substantiated. The author proposes ways to detect the inhomogeneity of printing density on text arrays based on changes in the area of printed elements and processing of the results, which allows comparing distributions for texts printed in fonts of different sizes and styles. Based on experimental material, the individuality of the form of the obtained distributions and the possibility of their use as identifying features of the printing device are substantiated.

NUMBER OF FINE PARTICLES’ AND THEIR MASS CONCENTRATION: COMPARISON OF EMISSION OF NEW PRINTING TECHNOLOGY VERSUS TRADITIONAL LASER TECHNOLOGY

For many years the printers have been essential part of our offices and exposures from various printing technologies have been widely researched. The main objective of this study was to compare emitted number and mass of fine particles from laser printers and new Micro Piezo technology ink jet printers during the printing process and one hour afterwards as these emissions have potential for negative health effects.Air samples were taken with the particle size spectrometer for real-time ELPI+, Dekati (air flow rate 10 l/min). Measurements were taken ~0.5 m from the printers: one hour before the test, during printing and one hour afterwards. Similar class blackwhite (b/w) and colour printer of each technology were tested. Each printer performed a 10-page and a 100-page test according to ECMA 328-1 Standard [1].During laser printer tests from 8324 to 19943 pt/cm3 fine particles were determined on printing phase from b/w and colour printers. Ink jet (Micro Piezo) printers produced less: from 3239 to 5247 pt/cm3. One hour after the printing phase for both types of laser printers’ there were 54722 to 152351 pt/cm3 particles in air and 4270 to 9579 pt/cm3 particles for ink jet printers. Detected particle mass differences was insignificant: in range of 0.002 to 0.012 mg/m³ for laser printers and 0.002 to 0.019 mg/m³ for ink jet printers. Micro Piezo technology printers emitted mass particles were with bigger median size μm.The highest number of particles was observed one hour after the printing for both tested printer technologies. Laser printers’ emitted 2.5 to 3.8 times more particles in printing phase and 12.8 to 15.9 times more after printing phase. Particle mass in mg/m³ was detected in the size range 6nm - 2.5 μm with no significant mass differences.