Ratio temperature method can avoid difficulties of correction of target emissivity in temperature measurement, which enables simultaneous measurement of temperature distribution of targets having different emissivity, for example, melting and solidifying process of metal. We have studied ratio temperature method using two wavelength images captured by either a color high-speed camera or a twoimage- sensor camera. The minimum temperature limit which can be measured with a color high-speed camera is about 900 degrees centigrade, because the camera can only capture visible wavelengths. The technique for measuring temperature distribution less than 900 degrees centigrade at high-speed using single sensor camera hasn't been established. In late years, a multi-spectrum camera become commercially available, with which multiple wavelengths images can be captured simultaneously by utilizing pixel-bypixel band pass filters. If we apply this technique to sensors with high-speed capability, and with near infrared wavelength bandpass filters, temperature measurement down to 500 degrees centigrade would be possible. In this study, we report the result of temperature distribution measurements by ratio temperature method using a commercially available multi-spectrum camera which captures four wavelengths images in near infrared.
Two-color radiometry by a high-speed camera is effective to obtain the temperature distribution map of high temperature
phenomenon, which changes its figure rapidly. We have developed the two-color method by a color high-speed camera
and put it into practical use. However, in the case of phenomenon that has chemical luminescence besides the thermal
emission, it is difficult to get accurate data from the method that measures visible wavelength images. In case that
chemiluminescence is in visible wavelengths but not in near-infrared region, we can obtain high-speed NIR images and
high-speed temperature distribution map by two frame-synchronized high-speed cameras which are equipped with NIR
band-pass filters.
We would report on the result of an experiment using an optical bench and software which we have developed.
By the recent development in electronics, including new solid-state image sensors such as area CCD and C-MOS sensors
and the progress of image processing techniques, new imaging radiometers have been developed which
two-dimensionally acquire image data of objects moving at a high speed and under high temperature, and (graphically)
present the temperature distribution over the object immediately.
We successfully measured the temperature distribution and the term KL distribution, which is the absorption strength of
combustion in diesel engine cylinders or other luminous flames taking place at a high speed, using single-sensor color
high-speed cameras and applying two-color pyrometry introduced by H. C. Hottel and F. P. Btoughton.
The measurement accuracy depends on the accuracy of color reproducibility of the high-speed camera being used which
is considered a brightness pyrometer, because two-color pyrometry for measuring luminous flames is based on the
brightness temperature at two wavelength bands such as red and green.
In this paper, we present a method of maintaining the accuracy of measurement using a high-speed camera as a
brightness pyrometer and of two-color pyrometry that was developed based on it.
KEYWORDS: Temperature metrology, Radiometry, Sensors, Radio optics, Light sources and illumination, Photography, High speed cameras, Mirrors, Relays, Near infrared
In order to analyze mechanism of melting and deformation of metal while it is being rapidly heating, or a combusion process, it is important not only to measure the time displacement of a sample and its acceleration, but to measure the change in the temperature distribution of the sample over time. For this purpose, we have developed a new Multi-Spectral Optics. By mounting combining a high-speed camera with our Multi-Spectral Optics system, we have successfully acquired a temperature distribution map and its color image simultaneously. In our system, a color image is composed with three spectrum images from wavelengths, 450 nm, 550 nm and 750 nm. A temperature distribution map can be created from two images in the near infra-red wavelengths, 750 nm and 850 nm, which were obtained by applying the ratio temperature pyrometry method. However, in order to observe and analyze rapid deformation of a sample, it is important to capture vivid images in color. This task requires additional external light. Since a high intensity of emitted light will cause an error in temperature, it is very difficult correctly to measure temperature and deformation of the sample at the same time. Temperature measured with near infra-red lights is not be influenced by the external surrounding light. In particular, for taking photos of welding phenomena, it is possible to capture clear images with excessive lighting without affecting temperature measurement. Moreover, in combustion phenomenon, it is possible to avoid the influence of chemiluminescence caused by radicals such as C2 in flame.
Plasma behaviors in various magnetic fields were discussed by using the result from a 3D hybrid code. First, an instability of expanding plasma in a uniform magnetic field was discussed by comparing experimental data with numerical result. The effect of magnetic field diffusion on the plasma instability was studied. Second, the plasma behaviors in a dipole field were examined and comparison was made among the experimental data, MHD analysis and the result from the 3D hybrid code. So far, an overall good agreement among these result was found.
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