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Volume 78, Issue 2
Displaying 1-12 of 12 articles from this issue
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Takashi Irikura, Tetsuo Taniguchi, Yoshiro Aoki1994 Volume 78 Issue 2 Pages 45-50
Published: February 01, 1994
Released on J-STAGE: July 19, 2011
JOURNAL FREE ACCESSA reduction of visibility caused by a glare-source can be expressed by an “equivalent veiling luminance”. The relationship between the reduction in visibility and the size of the glare-source is not clearly understood when the glare-source size is less than 1 degree. The equivalent veiling luminance has also been studied insufficiently for small values of angle θ which the glare-source makes with the line of vision. A visual experiment was carried out to clarify these properties. In this experiment, a circular glare-source of diameter 3 to 27 minutes was presented near the line of vision of an observer. Landolt rings were employed as test objects on a screen panel.
The results show that not only the luminous intensity of the glare-source but also its area S has an effect on the reduction of visibility for a relatively small glare-source. The equivalent veiling luminance varies approximately with θ-2.4 and S-0.23. However, beyond a certain value, area does not affect the reduction very much in the case of high backgroud luminance. The apparent luminance contrast of the Landolt ring, when the visual acuity is reduced to half, is constant regardless of the background luminance of 1 to 100 cd/m2.View full abstractDownload PDF (1589K) -
In Comparison to Hot-plate Conduction HeatingMahito Ichikawa, Hisanori Nakao1994 Volume 78 Issue 2 Pages 51-57
Published: February 01, 1994
Released on J-STAGE: July 19, 2011
JOURNAL FREE ACCESSThe partial differential equation of heat conduction is transformed into a non-dimensional one to obtain generalized solutions for the two heating systems mentioned in the title. Boundary conditions are assumed to be: constant heat-flow input for infrared heating, or constant temperature input for hot-plate case.
In quife the same way for both systems, only the surface of the heated substance with a given thickness is heated by the heat sources, and heat penetrates into the inside only by thermal conduction. Moreover, no water evaporation and no convection etc. within the substance are assumed. Cases with actual water evaporation, however, are approximately analyzed in the text in detail by ordinary differential equations.
The analyses show that temperature rise charactaristics and the state of heat flow, as well, are quite different between the two heating systems. Most comparative features of the systems are generally conserved whether water evaporation takes place or not, though each thermal state is affected to a large extent by evaporation. Also some interesting features due to evaporation are fully discussed.View full abstractDownload PDF (3139K) -
Retroreflective Materials under Daytime and Nighttime Geometric ConditionsToshio Yamanaka1994 Volume 78 Issue 2 Pages 58-65
Published: February 01, 1994
Released on J-STAGE: July 19, 2011
JOURNAL FREE ACCESSAn apparatus is desined to measure spectral radiance factor of retroreflective materials used for traffic signs under nighttime and daytime geometric conditions. The paper describes a configuration and function of the appratus, the method of chromaticity measurements of enclosed lens type retroreflecting sheet. The method be examined, so that it give fairly good accuracy.
In the chromaticity measurement by a tristimulus colorimeter, to improve the accuracy have established its color calibration reference by the use of this appratus and the effectiveness be confirmed by the performances of a round-robin test.View full abstractDownload PDF (2696K) -
Koichi Ikeda, Kiyoshige Obara1994 Volume 78 Issue 2 Pages 66-75
Published: February 01, 1994
Released on J-STAGE: July 19, 2011
JOURNAL FREE ACCESSA new linear uniform colour space has been developed by systematic combinations of tristimulus values X, Y and Z.
For colours with constant value of 6 in Munsell space, numerical computer analyses have been made to minimize the deformations of hue circles from uniform circles in the new space by optimizing the coefficients in the formulae of linear transformations.
By appropriate transformations, the shapes of hue circles which are distorted in the L*a*b*, L*u*v* and Cube-Root spaces approach uniform cilcles, and the warps of hur circles with moderate chroma are reduced to 1/4-1/5 as compared with those in the traditional colour spaces.
In this new space hue and chroma can be approximated by metric hue angle and metric chroma, respectively, with considerable accuracy for colours of moderate chroma.View full abstractDownload PDF (3685K) -
Hiroyuki Shinoda, Mitsuo Ikeda1994 Volume 78 Issue 2 Pages 76-82
Published: February 01, 1994
Released on J-STAGE: July 19, 2011
JOURNAL FREE ACCESSIn everyday life, we are often required to shift our gaze by a large angle by rotating our head to compare colors of objects which are considerably separated from each other. To assess the ability to discriminate colors under such conditions, the repeatability of color matching was studied as a function of stimuli separation. Color matching ellipsoids were obtained in xyY color space with a Burnham type colorimeter at various angular separations from 6 to 120 degrees. The results showed that the ellipsoids enlarged slightly with separation but the change of the ellipsoids was not monotonic. This non-linear change did not suggest that the decrease in performance for color matching was caused primarily by the time interval between successive fixations.View full abstractDownload PDF (2476K) -
Keiji Uchikawa, Ichiro Kuriki, Hiroyuki Shinoda1994 Volume 78 Issue 2 Pages 83-93
Published: February 01, 1994
Released on J-STAGE: July 19, 2011
JOURNAL FREE ACCESSIt has been shown that the color space is consistently divided into 11 basic color categories (white, black, red, green, yellow, blue, brown, orange, purple, pink and gray). Uchikawa et al.(1993) reported that categorical regions of a colorspace, measured with the categorical color naming method, did not vary with luminance levels in the aperture mode, but varied in the surface color modes. In this investigation, we conceived a new method, called a category rating estimationmethod, that could estimate continuous color-appearance changes using basic color categories, in order to compare categorical regions and continuous color-appearance changes. In this method, color appearance of a test color was measured by ratings of three basic color categories, according to which category appeared more similar to the test color. The results show that categorical regions found in the previous experiments correspond well to highly rated category regions in the present experiments, except for white in the aperture color mode, white, gray, black and yellow in the surface color mode.
Furthermore, surface colors made by a color CRT were not found to be much different from those made by color chips.View full abstractDownload PDF (4204K) -
Mitsuo Ikeda, Shoko Ashizawa1994 Volume 78 Issue 2 Pages 94-100
Published: February 01, 1994
Released on J-STAGE: July 19, 2011
JOURNAL FREE ACCESSAlthough lightness is an important attribute of a colored object, it fails to express the brightness of the object and the object normally appears brighter than a gray scale even though the two are equated in lightness.The notion of the equivalent lightness was introduced to deal with the problem.Experiments have been carried out to measure the equivalent lightness of various colors under variours illuminance levels that covered photopic mesopic and scotopic vision.The next step would be to introduce a photometric system that can determine the equivalent lightness for any colored objects under any illuminance levels, but the work will take some more time. The present report will propose, as a tentative solution, an empirical formula that accounts for the effects of Munsell Hue, Chroma, and Value of colors and the Purkinje shift on the equivalent lightness.The equivalent lightness in the formula is composed of the achromatic and chromatic lightness. The former is further divided into photopic and scotopic lightness, which are combined with a mesopic coefficient.For the latter the effect of Munsell Hue was expressed by a square root of sinusoid of the hue angle and that of Chroma by a linear function of the chroma. The effect of illuminance was approximated by a cubic function. The empirical formula expressed fairly well the experimental data as far as our previous results are concerned on which the derivation of the formula was based.View full abstractDownload PDF (2582K) -
Masaki Shinomiya1994 Volume 78 Issue 2 Pages 101-106
Published: February 01, 1994
Released on J-STAGE: July 19, 2011
JOURNAL FREE ACCESSInductively coupled electrode-less discharge lamps have been developed as new light sources. To operate these lamps, matching networks are used for stabilizing plasma. However, the design theory of the matching networks for these lamps has not been clearly known. The difficulty comes from the non-linearity of the plasma impedance.
In this paper, the matching networks for the inductively coupled electrode-less discharge lamps are theoretically analysed by means of an equivalent circuit model consisting of a resistance and two inductors.
First, the author took measurement of the input impedance of the electrode-less fluorescent lamp circuit, and confirmed the validity of the equivalent circuit model. Using this model, he analysed the matching network, and found that an impedance-inverter circuit consisting of the matching network and the coil is most suitable for starting and stabilizing the plasma. In this circuit, plasma current Ip is limited by the formula, |Ip|<n|e| |B|, where n is constant defined by the coil structure, e is electromotive force of the power source and B is parameter defined by the circuit. The author also calculated the circuit parameters in the case of a five-ladder circuit.View full abstractDownload PDF (1588K) -
Masafumi Suzuki, Noboru Yoshimura, Osamu Kimura, Masanobu Awata1994 Volume 78 Issue 2 Pages 107-113
Published: February 01, 1994
Released on J-STAGE: July 19, 2011
JOURNAL FREE ACCESSComputer graphics is a useful simulation method for estimation or evaluation of lighting environments. Ray tracing is a common computer graphics method and this method has often been used for various lighting systems. However, in a conventional ray tracing method, it has been difficult to deal with diffusely reflected light. Therefore, synthesized images have been more or less unnatunal. On the other hand, radiosity method can treat diffusely reflected light, but it is difficult to deal with specularly reflected light and transmitted/refracted light by this method.
If we trace a beam of light from a source, it is easy to deal with both diffusely reflected and transmitted/refracted light. In a Monte Carlo simulation method, a radiation or a reflection angle is determined statistically by random number. Therefore, we can trace a beam of light from the source.
In the previouse paper, we studied the color change caused by inter-reflected light in the interior of a model room with infinite length, with attention to the spectral radiant exitance. In the present paper, luminous exitance was calculated in a model three dimensional space. In addition, calculated results are shown graphically. It was found that the color change caused by inter-reflection light can be handled accurately by using a Monte Carlo method.View full abstractDownload PDF (4185K) -
Noboru Ichinose1994 Volume 78 Issue 2 Pages 114-116
Published: February 01, 1994
Released on J-STAGE: July 19, 2011
JOURNAL FREE ACCESSDownload PDF (2236K) -
Tamaki Yaji1994 Volume 78 Issue 2 Pages 116-118
Published: February 01, 1994
Released on J-STAGE: July 19, 2011
JOURNAL FREE ACCESSDownload PDF (2193K) -
[in Japanese]1994 Volume 78 Issue 2 Pages 119-122
Published: February 01, 1994
Released on J-STAGE: July 19, 2011
JOURNAL FREE ACCESSDownload PDF (718K)
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