Jarkko Mutanen, Jarno J. Kaakkunen, Hemmo Tuovinen, Jouni Hiltunen, Sini Kivi, Maunu Toiviainen, Juha Väyrynen, Janne Laukkanen, Victor Prokofiev, Pertti Pääkkönen, Mikko Juuti, Markku Kuittinen, Kari Mönkkönen
In this study we tested ns-laser and an atomic layer deposition (ALD) for polishing and coating CNC-machined aluminum freeform mirrors that are used in a compact multipoint fiber optical probe. Two types of ALD coatings, aluminum oxide and silicon dioxide were tested. The surface roughness of mirrors was analyzed prior to and after nanosecond-laser polishing and coating them on a Beneq TFS 200 ALD device. The freeform aluminum mirrors with and without coatings were then measured with optical profiler. The results show that improvement in the surface roughness can be seen with ns-laser polished and ALD coated aluminum surfaces.
Black liquor is the fuel of Kraft recovery boilers. It is sprayed into the furnace of a recovery boiler through splashplate
nozzles. The operation of a recovery boiler is largely influenced by the particle size and particle size distribution of black
liquor. When entrained by upwards-flowing flue gas flow, small droplet particles may form carry-over and cause the
fouling of heat transfer surfaces. Large droplet particles hit the char bed and the walls of the furnace without being dried.
In this study, particles of black liquor sprays were imaged using a high-speed infrared camera. Measurements were done
in a functional recovery boiler in a pulp mill. Objective was to find a suitable wavelength range and settings such as
integration time, frame rate and averaging for the camera.
The low energy efficiency of conventional light sources is mainly caused by generation of waste heat. We used infrared
(IR) imaging in order to monitor the heating of both LED tube luminaires and ordinary T8 fluorescent tubes. The IR
images showed clearly how the surface temperatures of the fluorescent tube ends quickly rose up to about +50...+70°C,
whereas the highest surface temperatures seen on the LED tubes were only about +30...+40°C. The IR images
demonstrated how the heat produced by the individual LED chips can be efficiently guided to the supporting structure in
order to keep the LED emitters cool and hence maintain efficient operation. The consumed electrical power and
produced illuminance were also recorded during 24 hour measurements. In order to assess the total luminous efficacy of
the luminaires, separate luminous flux measurements were made in a large integrating sphere. The currently available
LED tubes showed efficacies of up to 88 lm/W, whereas a standard "cool white" T8 fluorescent tube produced ca. 75
lm/W. Both lamp types gave ca. 110 - 130 lx right below the ceiling-mounted luminaire, but the LED tubes consume
only 40 - 55% of the electric power compared to fluorescent tubes.
Gloss of a product, such as print gloss, is mainly inspected with conventional white light glossmeters both at laboratory or production facilities. However, problems occur in conventional gloss measurement when the inspected surface is vertically moved in the plane of incidence and reflection or when the measurement area is small or curved. For a partial solution to these problems, we have previously introduced diffractive optical element-based glossmeters (DOGs) for the gloss inspection in laboratories and off-line use. We present a new construction of DOG, termed μDOG 1D, for the one-dimensional on-line print gloss measurement, in the form of the reflectance determination normal to the surface. The function of the glossmeter is demonstrated by laboratory tests and on-line measurements at a heat-set web offset printing machine. It is shown that gloss (i.e., normal reflectance) and minute gloss variation of papers and prints can be measured at the printing line using the glossmeter. This glossmeter is expected to be useful in real-time monitoring of the gloss and surface-specific absorption not only in the printing industry but also in inspection of products in other industrial sectors, such as metal finishing, laminating, paper, and construction materials manufacturing.
Commercial glossmeters are usually provided with a gloss reference. In some cases the reference is derived from black glass. Light reflection from the reference depends both on the complex refractive index and on the surface quality, such as the roughness and the cleanness of the reflecting surface, of the black glass. If we want to obtain accurate data on gloss or the minute gloss mottling of an object, we must be certain of the optical properties and surface quality of the reference in regard to reliable gloss analysis. In this study the complex refractive index of a gloss reference, as a function of wavelength, was measured with an ellipsometer, and the reflectance at standardized gloss measurement angles was calculated for the case of nonpolarized light. We show that the gloss reference has a substantial extinction coefficient, which must be considered in accurately describing the reflectance of the reference. Furthermore, the gloss variation of the reference was detected with a diffractive-optical-element-based glossmeter by scanning the reference surface at normal light incidence. We observed that the reference had rather high gloss mottling and consider the reasons for it.
The surface microroughness of paper has an important role on its gloss. Unfortunately, commercial glossmeters do not provide information on the local gloss of paper. In this study a low-coherence interferometer was employed for the assessment of the average surface roughness of fine, supercalendered, and Xerox papers by means of recorded topography maps. Furthermore, the local and average gloss were measured by a diffractive-optical-element-based glossmeter. This is the first time that the measurement of the local gloss of paper has been accomplished. The information on both surface roughness and gloss, obtained by the two devices in this study, should help papermakers in their research and development of optimal paper surface quality, which is crucial to optimal ink absorption in printing.
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