Optics: measuring and testing – By shade or color
Reexamination Certificate
2000-08-08
2004-03-16
Adams, Russell (Department: 2851)
Optics: measuring and testing
By shade or color
C356S425000
Reexamination Certificate
active
06707553
ABSTRACT:
This application is based on patent application No. 11-226174 filed in Japan, the contents of which are hereby incorporated by references.
BACKGROUND OF THE INVENTION
This invention relates to a measuring apparatus for measuring a characteristic of an object, and particularly to an apparatus for measuring a color of a metallic coating and a pearl-color coating.
In a metallic coating and a pearl-color coating used as a coating of an automotive vehicle, bright materials
101
comprised of thin pieces of aluminum or mica is contained in a film
102
as shown in FIG.
13
. Since the orientation of the bright materials
101
varies as shown in
FIG. 13
, the intensity of light reflected by the bright materials
101
differs depending upon a viewing direction, which provides a metallic effect and a pearl effect. Multi-angle calorimeters of the type in which illumination light is projected in one direction and detected in a multitude of directions or illumination light is projected in a multitude of directions and detected in one direction are used as calorimeters for measuring the color of the metallic coating and the pearl-color coating having such a characteristic.
Conventionally, multi-angle calorimeters whose light detecting direction is mechanically changed include those of the type in which an illumination light is projected in one direction and detected in a multitude of directions, but those of the type in which illumination lights are projected in a multitude of directions and detected in one direction are widely used as portable multi-angle calorimeters used on the spot since they have a high reliability because not having a movable portion and have a shorter measurement time.
A known multi-angle calorimeter of the type in which illumination light is projected in a multitude of directions and detected in one direction is provided with a light detector
104
for detecting reflected right in a direction at 45° to a normal to a surface of a measurement object
103
and three illuminator
106
,
107
for illuminating the measurement object
103
in three directions as shown in FIG.
14
. In such a multi-angle calorimeter, illuminating directions by the respective illuminators are generally based on a regular reflection direction of the light detecting direction, i.e., a direction (S in
FIG. 14
) symmetrical with the light detecting direction with respect to the normal to the object surface and expressed by angles with a side where the normal to the object surface is located being positive. One illuminating direction is set, for example, at 45°, i.e., the normal direction (center axis of a calorimeter main body) to the object surface (illuminator
106
), the second illuminating direction is set, for example, at 15° closer to the regular reflection direction of the light detecting direction (illuminator
105
), and the last illuminating direction is set, for example, at 110° closer to the light detecting direction (illuminator
107
). Lights reflected by the measurement object
103
when the measurement object
103
is illuminated in the respective illuminating directions are detected by the light detector
104
, and a reflection characteristic and a color value are obtained based on an amount of the detected light, and characteristics of the measurement object are expressed by the reflection characteristic and the color value in the respective illuminating directions. Generally, illuminating directions closer to the regular reflection direction of the light detecting direction are referred to as highlight directions, whereas those closer to the light detecting direction are referred to as shade directions.
The bright materials
101
shown in
FIG. 13
are so arranged as to be substantially parallel to an outer surface of the film
102
(a normal
101
in
to the bright materials
101
and a normal
102
n
to the outer surface of the film
102
are substantially parallel to each other). If an angle between the normal
101
n
and the normal
102
n
is assumed to be t as shown in
FIG. 13
, an angle distribution P(t) displays a characteristic approximate to a normal distribution having a peak at t=0 as shown in FIG.
15
. Accordingly, an angle distribution of the reflected light from the bright materials when a metallic coating or a pearl-color coating is illuminated in a certain direction also approximates to a normal distribution having a peak in a regular reflection direction (i.e., direction symmetrical with the illuminating direction with respect to a normal to the film surface) by the film surface.
When a reflection characteristic R(x) is measured by illuminating the measurement object in various directions, it contains components by diffused reflected light L
d
having no angle dependency and those by regularly reflected light from the surface of the measurement object in addition to those by the reflected light from the bright materials. In the illumination in the shade direction distant from the regular reflection direction of the light detecting direction, there is almost no contribution of the reflected light from the bright materials, and the reflection characteristic moderately changes upon a change in the angle of the illuminating direction. On the other hand, in the illumination in the highlight direction close to the regular reflection direction of the light detecting direction, there is a significantly large contribution of the reflected light from the bright materials since the reflection surfaces of the bright materials are mostly substantially parallel to the object surface as shown in
FIG. 15
, and the reflection characteristic steeply changes upon a change in the angle of the illuminating direction. In the illumination in the direction at 45° to the light detecting direction, the reflection characteristic displays an intermediate characteristic between the above two cases.
Since the reflection characteristic by the illumination in the highlight direction is particularly essential in understanding the property of the bright materials representing the features of the metallic coating and the pearl-color coating, it is desired to obtain this reflection characteristic with high precision. However, the value of the reflection characteristic largely changes even upon a slight change in the angle of the illuminating direction. For a high-precision measurement, it is necessary to precisely set the orientation of the multi-angle calorimeter with respect to the surface of the measurement object, i.e., to precisely coincide the center axis of the main body and the normal to the surface of the measurement object.
For example, in the case that a coating surface on a body of an automotive vehicle is measured by a portable colorimeter, a contact surface of the calorimeter is formed by rubber or like material so as not to damage the coating surface. Accordingly, it has not been easy to precisely coincide the center axis of the main body and the normal to the object surface. Particularly, it has been even more difficult when the surface of the measurement object is curved as the body of the automotive vehicle is.
In order to overcome the above problem, calorimeters having a function of adjusting an angle of the main body with respect to the object surface have been put into practice. However, there are still problems of an increased number of parts and a complicated construction because a sensor for detecting an angle is necessary, and also a problem of a long measurement time since time is required for angle adjustment in each measurement.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a measurement apparatus which is free from the problems residing in the prior art.
It is another object of the present invention to provide a color measurement apparatus which enables a high precision color measurement by correcting a measurement result according to an angle of inclination of a main boy of the apparatus with respect to a surface of an object.
It is another object of the present invention to provide a color measurement apparatus which can
Adams Russell
McDermott & Will & Emery
Minolta Co. , Ltd.
Nguyen Michelle
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