J. of IEIJ Vol.88, No.11

The Abstracts of the Papers
J.Illum. Engng. Inst. Jpn. Vol. 88, 2004

No. 2 February
No. 5 May
No. 8A August
No. 11 November

Position Index for a Glare Source in the Whole Visual Field
Wonwoo KIM, Yasuko KOGA and Odalea B. C. MELO

The objective of this research work is to propose a Position Index of glare sources in the whole visual field. The Guth Position Index has an issue that it does not define glare sources below the line of sight.

Our first experiment to investigate the visual field was conducted using the Goldmann Perimeter. Twenty-five observers aged from 20 to 47 participated in the experiment. Their average visual field is presented by five isopters (lines joining points of equal sensitivity on a visual field chart). These isopters show that visual sensitivity has a higher value at positions below the line of sight than above. The second experiment to assess the subjects’ sensitivity to glare was conducted using a Glare Testing Instrument made for this research. Equal glare sensitivity curves were obtained from the tests. The shapes of the equal glare sensitivity curves and those of the isopters are interrelated at positions above the line of sight. However, at positions below the line of sight, the shapes of the equal glare sensitivity curves are wider than those of the isopters. Therefore, extending the Guth Position Index to positions below the line of sight according to the isopters is inadequate. A new position index chart was derived from the equal glare sensitivity curves. In the whole visual field, the position index could be determined from the new chart.

KEYWORDS : discomfort glare, position index, isopter, sensitivity to glare, visual field

Influence of Plural Loads on Rupture of the Sealed Parts in Super High Pressure Mercury Discharge Lamps
Masahiko KASE and Toshiyuki SAWA

Super high-pressure mercury discharge lamps have been used as the light source for photolithography exposure process. In general, they are used in manufacturing  Liquid crystal displays (LCDs), Printed circuit boards (PCBs), semiconductors and other devices. Their working internal pressure is well known to be normally more than 1.0 MPa, and their temperature at the bulb outer is more than 500°C. Therefore, they are required to be secured for rupture, because they are subjected to internal pressure, thermal loadings, and so on in their services. Furthermore, rupture may occur from the sealed parts in the lamps under the loadings mentioned above. Thus, the mechanical characteristics of the sealed parts need to be examined. The objectives of the paper were to examine the safety for rupture from their sealed parts of the working lamps under internal pressure and thermal loadings by the experiments and FEM stress calculations. Rupture tests of lamps were carried out under repeated static water pressure. In addition, experiments were done under thermal loadings. The following results were obtained. 1) It was found that the effect of repeated loadings such as internal pressure and thermal loadings were substantial on the strength of the sealed parts in the lamps. 2) Fractures of the sealed parts were observed to be initiated from the interfaces where silica glass and molybdenum foil were joined. 3) From the FEM stress calculations, it was found that the strength of sealed parts was greater in operation than at room temperature. 4) Finally, the authors proposed the limited desirable pressure and temperature for safety design of lamps.

KEYWORDS : super high pressure mercury discharge lamps, sealed parts, fracture in operations, static water pressure test, heating test, current electrifying test, calculating stress distribution, FEM caluculations

Influence of Lightness, Chroma and Hue of Chromatic Letters on Readability and Equivalent Luminance Contrast under the Achromatic Background
Naoya HARA and Tarow NOGUCHI

The main purpose of coloring an object is to add information and to draw attention to it. However, the visibility of the visual object must not be spoiled by taking these effects too seriously. Explaining the influence of color on the visibility of an object is thought to be useful in showing the effect of coloring except for the visibility after securing the visibility. Our final goal is to establish a visual environment design based on the visibility of a chromatic object. We explain the influence on the visibility of the color quantitatively. The result of a subjective evaluation experiment are shown. The experiment has various conditions systematized by color difference (lightness, chroma, and hue under the CIELAB color system). The readability of chromatic documents was understood by focusing on the color difference as an index that quantitatively shows the degree of influence of the color on visibility. The relationship between the color difference and the equivalent luminance contrast described to discus the influence of the color is shown.

KEYWORDS : readability, chromatic documents, luminance, contrast, color difference, equivalent luminance contrast

Visibility Index Functions for Positive Contrast Text
Wataru IWAI and Katsunori OKAJIMA

In this paper, we propose Visibility Index Functions (VIFs), that enable evaluating and predicting the legibility of sentences quantitatively and conveniently. In light of nonlinearity attached to suprathreshold phenomena, we analyzed the data of the series of legibility evaluation experiments of Sato and Hara(1999), and constructed two formulations :

VIF_VL(VL, A) and VIF_ΔL(ΔL,L_b,A), as functions of Visibility Level VL, luminance difference ΔL [cd/m²] between a visual target and its background, background luminance L_b[cd/m²] and character size A [min]. We showed that both the VIF s can well describe both the experimental results of Sato and Hara and the legibility data derived by Inoue and Akizuki (1997) with no parameter change except low luminance conditions for background.

KEYWORDS : visibility, legibility, visibility index function, visibility level, suprathreshold, non-linear processing

Optimizing Halogen Volume in Tungsten Halogen Lamps
Kotaro SHIMOGAKI and Hisao YOSHIIKE

Halide is sealed up inside a tungsten halogen lamp.  The action of the halogen allows the lamp to maintain its initial luminous flux without being blackened until the end of its service life.  The quantity of halogen, if insufficient, blackens the lamp and shortens its life.  If excessive, however, the halogen may affect the lamp's efficacy and service life.  Although an appropriate value of quantity is consequently required, this can only be calculated by means of a great number of trial production and life tests,   due to  the theoretical complexity and associated factors.   These tests are time consuming and expensive. The aid value is therefore often determined on the excessive side to simplify  experiments, thereby avoiding any risk of blackening.  We used theoretical calculation for some success to determine an optimum value.   We  therefore aim to improve the production technology by applying our theoretical calculations to trial production and life tests.

KEYWORDS : tungsten halogen lamp, evaporation of tungsten, theoretical calculation, proper halogen volume, chemical reaction in tungsten halogen lamps, blacking on tungsten halogen lamps

A Basic Study on the Estimation of Reflectance Characteristic of Glossy Curved Object
Tetsuji YAMADA, Naotaka IKEMOTO and Minoru ISOMURA

KEYWORDS : curved object, estimation, reflectance characterstic, photometric stereo