Goniophotometer Research Articles

Goniophotometric study of reflectance of non-circular cross-section polyester monofilament and its yarn under various applied tensions

The relative intensity-angular distribution of surface reflectance of one kind of non-circular cross-section (NCCS), herein referred to as octagonal cross-section, polyester monofilament and its yarn was investigated. Using a goniophotometer (GP), both the horizontally and vertically mounted substrate geometries were used, with the fiber or yarn at various, but known, tensions. An angle of incidence of 45° with respect to the fiber axis was used for the horizontally mounted fiber. The results indicate that the (specular) maximum appears at the expected surface reflectance angle around 40°, with the fiber held straight under applied load. The maximum in the reflection profile for the vertically mounted fiber or yarn, under the same conditions, was around 85°. It was also found, as is to be expected, that the calculated luster of the octagonal cross-section fiber and its yarn, using a Gaussian fitting model, was affected significantly by the load applied for both the horizontal and vertical geometries of the substrate. Further, it was observed that the relative reflection intensity of vertically mounted single octagonal fiber/monofilament was higher than that of horizontally mounted one under the same value of applied tension, while it was the reverse for the yarn from these filaments. With increased tension, the shine values of both horizontally and vertically mounted single fiber increased while those of its corresponding yarn decreased. Further, for both the horizontally and vertically mounted fiber, the difference in shine values for the two cases of tension and no tension was large, whereas such differences were much smaller for the yarn.

Effect of hair color on luster

The effect of color on instrumentally evaluated luster of hair dyed to different colors and depths of shades is studied. For natural hair colors, such as blond, brown, and black, the increase in luster with increasing color is associated with a decrease in diffusely scattered light as a result of light absorption by melanin granules. On dyed hair the interpretation of data from a goniophotometer (GP) is more complicated. Using the colors covering the extremes and middle of the visible spectrum, our results demonstrate how dye composition (single or multicomponent), concentration, and penetration depth into the fiber affect the absorptive and scattering processes within the hair fiber to impact luster. Finally, we make an attempt to study the effect of hair color on subjective evaluation of luster. An equation for perceived luster, taking into account the spectral sensitivity of the human eye is derived. Theoretical considerations show that the luster of hair of different colors is perceived differently by the human eye.

Effects of Fabric Parameters on Specular Reflection of Single-Jersey Knitted Fabrics

This paper is concerned with the prediction of goniophotometric curves (distribution curves of specularly reflected light) based on our mathematical model developed earlier for single-jersey knitted fabrics made from monofilament yarns. The theory is extended to include fabrics from multifilament yarns. Four physical and optical parameters related to the fabric and the light source are investigated: fiber refractive index, yarn cross section, incident light angle, and fiber ellipticity. Their effects on the goniophotometric curves and luster index of knitted fabrics are determined. In addition, the great difference is high lighted between light reflected from knitted fabrics and light received by the goniopho tometer.

面の明るさの変角光度計による検討

面の明るさの変角光度計による検討

Gloss Measurements on Fabrics

The gloss or luster of a surface is essentially a subjectively evaluated property which is re lated to the manner in which the surface reflects light falling on it. Although the impression or sensation of glossiness is a matter of common experience, measurement of this property in physical terms and correlation of the measurements with its psychological aspects are extremely difficult. The most satisfactory physical measurement involves the use of a goniophotometer, an instrument which measures the amount of light reflected from a surface at various angles. Curves showing intensity of reflected light vs. the scanning angle exhibit a peak at the so- called specular angle for surfaces rated as being of high gloss. Surfaces of more complex struc ture, such as those of fabrics, show a displacement of maximum reflectance from the specular angle; the displacement is related to the angle of the incident light. The curve shape is char acteristic for different fabrics. This article describes the experimental measurement of reflectance by means of a goniopho tometer for a group of fabrics. The results are presented in the form of curves, computed "gloss indexes" or "gloss numbers," and visual ratings by different observers.

Construction and Test of a Goniophotometer

Construction and Test of a Goniophotometer

A Recording Goniophotometer

A Recording Goniophotometer