Optics: measuring and testing – By polarized light examination
Patent
1995-03-02
1998-08-11
Pham, Hoa Q.
Optics: measuring and testing
By polarized light examination
356436, 356442, G01J 400, G01N 2159
Patent
active
057934908
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to the field of concentration detection and more particularly to the detection of toner concentration in color liquid developer compositions especially in the presence of contaminants.
BACKGROUND OF THE INVENTION
In liquid developer systems the liquid developer is generally comprised of a carrier liquid and toner particles in a generally constant ratio. During imaging operations the concentration of toner particles is reduced and concentrated toner is added to return the concentration to its desired value.
It is important that the concentration of particles should be kept within a given range in order to realize consistent copy quality. This requirement is especially important in color printers or copiers, where the quality of the images is especially dependent on the color balance and on its stability.
In general, concentration of toner particles in liquid developers is determined by measuring the attenuation of light passing through a given path filled with the liquid developer. Since the particles absorb and scatter light, the attenuation of the light is related to the concentration of the particles.
U.S. Pat. No. 4,579,253 describes a system in which the beam of light is split into two components only one of which is attenuated by the liquid developer. The concentration is determined from the ratio of the attenuated and unattenuated beams.
Such systems work fairly well in single color systems or in multicolor systems in which there is no cross contamination between the colors. In general, the most troublesome cross-contamination is black toner particles in a relatively low attenuation color such as yellow. Since black has an attenuation several times that of yellow, visually negligible black contamination can effect the determination of the color concentration in a way which seriously disturbs the color balance of the system.
Japanese Patent Publication Kokai 1-148943 describes a system in which the attenuation of beams of light having two different colors are sequentially measured. Using these attenuation values, the publication describes a method for determining the concentration of both the black and the color particles.
SUMMARY OF THE INVENTION
The present invention is based on an analysis of the different factors which are operative in the attenuation of light by toner particles.
The two main factors are the absorption of light and the scatter of light by the particles. In general, for black toner particles, the effect of scatter is very small compared to the effect of absorption. On the other hand, for colored toner particles, especially for yellow, the effect of scatter is much greater than that of absorption.
One preferred embodiment of the present invention utilizes measurements which are selectively more sensitive to one of these effects thereby reducing the influence of the contaminant on the measurement of the color toner.
In a second, particularly preferred, embodiment of the invention, two measurements are made, one of which is relatively more sensitive to absorption and the other of which is relatively more sensitive to scatter. From these measurements and a knowledge of the scatter and absorption characteristics of the different particles, the concentration of both types of particles can be determined. Alternatively, a prioi knowledge of the attenuation of different concentration combinations to the two measurements can be used and direct knowledge of the scatter and absorption characteristics of the particles is not necessary.
In this second embodiment, a first measurement is made using polarized light to illuminate a cell containing liquid developer. A cross-polarizer (analyzer) is placed before a light detector on the other side of the cell. In the absence of scatter, no light would be detected at the detector. On the other hand, scatter also depolarizes the light and in the presence of scatter, light will be detected at the detector. In a second measurement, initially unpolarized light is used to illuminate the cell. In thi
REFERENCES:
patent: 3283644 (1966-11-01), Saltzman
patent: 3518003 (1970-06-01), Meyn
patent: 3724957 (1973-04-01), Tamate et al.
patent: 4166702 (1979-09-01), Okamoto et al.
patent: 4171916 (1979-10-01), Simms et al.
patent: 4579253 (1986-04-01), Shenier
patent: 4660152 (1987-04-01), Downing et al.
patent: 5570193 (1996-10-01), Landa et al.
International Search Report and Annex.
Forgacs Peter
Landa Benzion
Indigo N.V.
Pham Hoa Q.
LandOfFree
Method and an apparatus for detecting concentrations of first an does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and an apparatus for detecting concentrations of first an, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and an apparatus for detecting concentrations of first an will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-394501