Glossmeter

Details Glossmeter Glossmeter

1998-02-05

2000-01-25

Kim, Robert H.

Optics: measuring and testing

Of light reflection

With diffusion

35 34, 35445, G01N 2148

Patent

active

060183969

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The invention relates to a novel gloss-meter which provides detailed information on the gloss of a given object. It allows measurements which provide detailed Information as regards the entire surface of the object. Amongst others, the novel gloss meter can be used for determining the gloss of irregular objects and also of curved ones.


BACKGROUND OF THE INVENTION

Gloss is a surface attribute causing a shiny or lustrous appearance. It is generally associated with specular reflection by the object. However, specular reflection can vary from one surface to another as follows:
1. The fraction of light reflected in the specular direction.
2. The manner and extent to which light is spread to either side of this specular direction.
3. The change of fractional reflectance as specular angle changes.
There are at least six different visual criteria by which glossiness is ranked (Table 1).


ESTABLISHED METHODS OF MEASURING GLOSS

There exist a variety of methods to measure gloss since different aspects of reflection, need to be measured to duplicate, as closely as possible, the different visual gloss-grading parameters.
The first established method for gloss measurement (Ingersoll, 193.4) was based on the principle that light is polarized in specular reflection, whereas diffusely reflected light, is nonpolarized. The Ingersoll glarimeter had a specular geometry, with incident and viewing angles at 57.5. Gloss was evaluated by a contrast method that, with the use of a polarizing element, "substracted" the specular component from total reflection.
In around 1930, Pfund pointed out that although specular shininess is the basic (objective) evidence of gloss, actual surface glossy appearance (subjective) relates to the contrast between specular shininess and the diffuse light of the surrounding surface area (now called "contrast gloss" or "luster"). If black and white surfaces of the same shininess are visually compared, the black will appear glossier because of the greater contrast between the specular highlight and the black surroundings as compared to that with than white surroundings. Pfund was the first to suggest that more than one method is needed to analyze gloss (Pfund, 1930).
In his investigation of gloss in the early 1930s Hunter used a specular angle of 45.degree., as did the first photoelectric gloss methods.
But visual evaluation of a large number of samples (primarily paint) eventually demonstrated that the 60.degree. angle provided the best overall estimates (Hunter and Judd, 1939). The 60.degree. method suggested in 1939 was subsequently adopted by the American Society for Testing and Materials (ASTM Method D523). It is widely used for paints, plastics, waxes and floor coverings, and is more widely used than any other gloss test procedure. The old 45.degree. method is now used primarily for glazed ceramics and polyethylene and other plastic films.
Incorporated into ASTM Method D523 in 1951 as alternative procedures were a 20 specular test for evaluating high-gloss finishes, developed earlier at the duPont Company (Horning and Morse, 1947) and an 85.degree. method for evaluating low-gloss, matte surfaces. The latter sheen method was developed in 1938 by J. W. Ayers of the C. K. Williams Company (Ayers, 1938; Hunter, 1952) and was subsequently used to test matte camouflage finishes used by the Ordinance Department. It is now used for measuring flat Interior wall paints, and low-gloss exterior painted aluminum siding.
A two-parameter method for 60.degree. specular gloss designed to distinguish the image-forming gloss surface of nonmetals from nonimage-forming gloss surfaces was adopted as ASTM Method D1471 in 1969 (Nimeroff, 1957). It was designed to cover those cases in which measurements made by the ASTM Method D523 60 gloss method did not correlate with gloss appearance. Method D1471 specifies a second, two-receiver aperture, to be used in conjunction with the aperture of Method D523. An evaluation is then made of the amount of light received by each of the apertures.
In 1937,

REFERENCES:
patent: 3349665 (1967-10-01), Grosheim et al.
patent: 4218144 (1980-08-01), Whitehouse et al.
patent: 4918321 (1990-04-01), Klenk et al.
patent: 5313542 (1994-05-01), Castonguay
patent: 5550632 (1996-08-01), Harata

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