JPH0420846A - Method and apparatus for measuring gloss - Google Patents

Abstract

PURPOSE:To make it possible to determine the amount of the gloss of the surface of a body as a value which agrees with visual observation by determining the value of the gloss based on the ratio between the product of the glossinesses of a mirror surface at a plurality of light emitting angles and the diffuse reflectivity at an arbitrary angle. CONSTITUTION:When the gloss of a body to be measured 1 is measured, the glossinesses of a mirror surface caused by the light beams which are emitted from light sources 2 and 3 at light emitting angles theta1 and theta2 on a the body to be measured 1 are measured with photodetectors 5 and 6 at light receiving angles theta1' and theta2'. At this time, the angles are set at theta1 = theta1' and theta2 = theta2'. The diffuse reflectivity of the light which is emitted from a light source 4 at a light emitting angle theta3 is measured with a photodetector 7 whose light axis forms an angle theta3 + or -5 degrees or more. The light from the light source 4 is regularly reflected with a lighting optical system at a light emitting angle theta3. The amount of the value of the gloss can be determined based on the ratio between the product of the measured glossinesses of the mirror surface and the diffuse reflectivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention (Industrial Application Field) The present invention relates to a method and apparatus for measuring the surface properties of objects, particularly the gloss of printed matter, coatings, metal surfaces, plastic surfaces, etc.

(Prior Art) Gloss is an important factor that determines the properties of the surface of an object, and is an important characteristic along with hue, especially in evaluating the finished state of a paint film.

Since the degree of gloss possessed by the surface of a substance is caused by the roughness of the surface of the substance, several measuring methods have been proposed so far. for example,#! The projection and reception angles are specified depending on the type of object to be measured, such as membranes, paper, plastic, and floating surfaces. , specular gloss measurement method (JIS Z-8741), in which the luminous flux at a specified acceptance angle reflected in the specular reflection direction is measured with a light receiver to determine the glossiness, and in the specular reflection direction,
A polarization contrast gloss measurement method that measures the degree of polarization of light to obtain the ratio of total reflected luminous flux to specularly reflected luminous flux. The brightness of specular reflection or reflected light is expressed by comparing the brightness of reflected light in seven directions and the reflected light flux in other specific directions. There is an aperture angle versus gloss measurement method that compares the reflected luminous flux when the aperture angle of the light receiver is changed in the direction of specular reflection.

However, the glossiness evaluation expressed using these methods is based on one color, image clarity, surface curvature,
The current situation is that it does not match the visual gloss evaluation due to differences in people's tastes.

(Invention or Problem to be Solved) As a result of study, the present inventor found that the ratio of the product of specular gloss at multiple projection angles and the diffuse reflectance at any angle has a high correlation with visual evaluation of gloss. The present invention is directed to a method and apparatus for measuring glossiness that have excellent correlation with visual evaluation of glossiness.

(Means for Solving the Problems) The present invention provides a method for determining the gloss of coating films, printed matter, etc., in which the specular gloss at a plurality of projection angles is determined.

In the present invention, the product of specular gloss at multiple projection angles is defined as the product of specular gloss at multiple projection angles in a plane that includes a light receiver that is on the perpendicular to the surface of the object to be measured, the optical axis of the illumination light optical system, and the optical axis of the specularly reflected light. , 2 types in the range of 5 to 85 degrees for the projection angle between the perpendicular to the surface of the object to be measured and the optical axis of the illumination optical system, and the acceptance angle between the perpendicular to the surface of the object to be measured and the optical axis of the specularly reflected light. The measurement is performed at each of the above different angles, preferably at an angle of 5 degrees or more.

If the projection and reception angles are less than 5 degrees, the incident optical axis will avoid the receiver, making it impossible to measure specular gloss. Part of the light is not reflected by the surface of the object to be measured, and the amount of light is directly measured by the light receiver, making it impossible to accurately measure specular gloss.

In addition, if two or more different light projection angles or light reception angles are less than 5 degrees, no difference will appear between them, so it will not be possible to obtain a measurement value that is highly correlated with the visual gloss evaluation, which is the purpose of the present invention. .

On the other hand, the diffuse reflectance at any angle is to measure the diffuse reflectance in a space that is 5 degrees or more in front, back, left and right from the angle formed by the perpendicular to the surface of the object to be measured and the optical axis specularly reflected by the illumination optical system. .

If the diffuse reflectance is measured at an angle of 5 degrees or less in front, back, left, and right from the angle formed by the perpendicular to the surface of the object to be measured and the optical axis specularly reflected by the illumination optical system, part of the amount of reflected light is diffused. Since it is measured as reflectance, accurate values cannot be obtained.

Furthermore, the apparatus for realizing this method includes an illumination optical section having two or more light sources that illuminates the object to be measured, and a light receiving means that measures the amount of light that has been specularly or diffusely reflected by the object to be measured. A photoelectric conversion unit is installed in an area where the light is not incident, and further includes a photoelectric conversion unit that converts the specular reflection light intensity and diffuse reflection light intensity reflected from the surface of the object to be measured into electrical signals, and specular glossiness is determined by the light intensity signal from the charging conversion means. The device is equipped with an arithmetic unit for calculating the diffuse glossiness and the ratio of the product of the specular glossiness at a plurality of angles and the diffuse reflectance at an arbitrary angle.

The following will explain based on the drawings. FIG. 1 is a sectional view showing one embodiment of the present invention. In Fig. 1, the specular glossiness of the light irradiated onto the object 1 from the light sources 2 and 3 at the positions of the light projection angles θ1 and θ2 is expressed as Measure with instruments 5 and 6.

Here, θ,=θ, , θ2=θ2'.

In addition, the diffusely reflected light of the light irradiated onto the measured object 1 from the light source 4 located at the position of the projection angle θ3 is reflected by the optical axis specularly reflected by the illumination optical system at θ, at an angle of θ3±5 degrees or more. Measured using a photodetector located in

(Example) The present invention will be explained below with reference to Examples.

Example 1 Ten indigo prints with different gloss were selected and 30 evaluators
We conducted a visual test and determined the ranking value, with the one with the highest gloss being 101 and the one with the lowest gloss being 1.
The visual gloss value was determined using the following formula.

Here, R: rank value, n/total number of evaluators, M: total number of samples, i: evaluator Nα, and j: sample Nα.

Table 1 shows the visual gloss values obtained by the above method in descending order of gloss: 60 degree specular gloss, 45 degree - 0 degree contrast gloss, and specular gloss in the optical system shown in Figure 1. The projection angles θ1 and θ2 are 20 degrees and 75 degrees, respectively.
the light source and receiver for diffuse reflectance measurement.
The measurement results and rankings are shown for the cases where the temperature was set to 5 degrees and 0 degrees. According to this, the glossiness determined by this measurement method matches the ranking based on visual glossiness, and moreover, it is possible to quantitatively measure the glossiness of printed matter.

Example 2 Table-2, Table-3, and Table-4 show yellow with different gloss,
10 prints in red and ink were selected and visually tested by 30 evaluators, and the obtained visual gloss values were ranked from highest to average: 60 degree specular gloss, 45 degree - 0 degree contrast gloss, and In the optical system shown in Figure 1, the projection angle θ of specular gloss is
The angles of 1 and θ2 were set to 20 degrees and 75 degrees, respectively, and the light source and receiver for diffuse reflectance measurement were set to 45 degrees and 0 degrees, and the measurement results and rankings are shown. According to this, the glossiness determined by this measurement method matches the ranking based on visual glossiness, regardless of the difference in color, and can quantitatively measure the glossiness of printed matter.

(Effects of the Invention) As described above, according to the present invention, it is possible to quantify the surface properties of the surface of an object, particularly the gloss of a coating film, a printed surface, etc., as a value that matches visual observation.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention. l...Object to be measured, 2.3...Light source for specular gloss measurement, 4...Light source for diffuse reflectance measurement, 5.6...Light receiver for specular gloss measurement, 7... Receiver for diffuse reflectance measurement,
8-15...Lens, 16-20...Aperture.

Claims (1)

[Claims] 1. In a method for determining the gloss of paint films, printed matter, etc., the gloss value is quantified by the ratio of the product of specular gloss at a plurality of projection angles and the diffuse reflectance at an arbitrary angle. A gloss measurement method featuring: 2. In the plane including the light receiver, which is on the extension of the perpendicular to the surface of the object to be measured, the optical axis of the illumination light optical system, and the optical axis of the specularly reflected light, the perpendicular to the surface of the object to be measured and the optical axis of the illumination optical system 2. The gloss measuring method according to claim 1, wherein the light projection angle formed by the object to be measured and the light reception angle formed between the perpendicular to the surface of the object to be measured and the optical axis of the specularly reflected light are each in the range of 5 to 85 degrees. 3. In the plane including the light receiver, which is on the extension of the perpendicular to the surface of the object to be measured, the optical axis of the illumination light optical system, and the optical axis of the specularly reflected light, the perpendicular to the surface of the object to be measured and the optical axis of the illumination optical system The diffuse reflectance is measured in a space where the projection angle is in the range of 5 to 85 degrees, and the angle between the perpendicular to the surface of the object to be measured and the optical axis specularly reflected by the illumination optical system is 5 degrees or more in the front, back, left, and right directions. The gloss measuring method according to claim 1, characterized in that: 4. A method for determining the gloss of paint films, printed matter, etc., including a calculation unit that quantifies the gloss value by the product of specular reflectance at a plurality of projection angles and the ratio of diffuse reflectance at an arbitrary angle. Featured device. 5. In the plane including the light receiver, which is on the extension of the perpendicular to the surface of the object to be measured, the optical axis of the illumination light optical system, and the optical axis of the specularly reflected light, the perpendicular to the surface of the object to be measured and the optical axis of the illumination optical system 5. The apparatus according to claim 4, wherein the light projection angle formed by the object to be measured and the light reception angle formed between the perpendicular to the surface of the object to be measured and the optical axis of the specularly reflected light are each in the range of 5 to 85 degrees. 6. The line between the perpendicular to the surface of the object to be measured and the optical axis of the illumination optical system in a plane that includes the light receiver, which is on the extension of the optical axis of the illumination light optical system and the optical axis of the specularly reflected light. The diffuse reflectance is measured in a space where the projection angle is in the range of 5 to 85 degrees, and the angle between the perpendicular to the surface of the object to be measured and the optical axis specularly reflected by the illumination optical system is 5 degrees or more in front, back, left, and right. 5. The device according to claim 4, characterized in that: