Optics: measuring and testing – By shade or color
Reexamination Certificate
1999-06-15
2001-03-20
Evans, F L (Department: 2877)
Optics: measuring and testing
By shade or color
C356S425000
Reexamination Certificate
active
06204923
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention concerns an apparatus for the color matching or colorimetry of colored samples according to the introductory part of the main claim.
2. Description of the Prior Art
Apparatuses for colorimetry and apparatuses for color matching are known in which these apparatuses are basically each constructed differently, so that often no correspondence is achieved between the colorimetry and the visual color impression, owing to the different geometries.
With ordinary colorimetry the starting point is a sample which is fixed in place relative to the measuring device and which is illuminated from various given angles and usually observed perpendicularly to the surface. With these apparatuses the devices are arranged in the immediate vicinity of the surface, and only very small surface fractions are observed.
For the color matching of smaller samples, e.g. in DIN A4 format, small lighting cubicles are usual, e.g. cubicles arranged on tables, in which is mounted a stationary lighting system for irradiating the samples. To detect the different color effects, the sample surfaces are presented to an observer from different angles and so each lit from different angles. From EP 0 379 168 A2 is known a matching chamber of this kind. With this known matching chamber there is the drawback of poor reproducibility, because both then angles of illumination and the angles of observation change in different observation situations, and in particular color effects are difficult to detect.
SUMMARY OF THE INVENTION
It is therefore the object of the invention to provide an apparatus for color matching or colorimetry which allows color matching or colorimetry with good reproducibility and clearly defined different conditions of illumination and observation, and with which color effects can be detected easily as well.
This object is achieved according to the invention by the characteristics of the main claim.
According to the invention the sample to be inspected or measured and the lighting device which illuminates the sample are arranged in fixed geometrical relation to each other, the fixed geometrical relation also being maintained when the sample surface is pivoted to set different angles of observation. This can be achieved by a lighting device which is rigidly connected to the sample or samples or to the sample holder and which follows every pivoting and movement of the sample on account of the rigid connection and hence always causes constant lighting conditions even when the angles of observation are changed.
Preferably the lighting device is dimensioned and positioned in such a way that the sample is illuminated from angles equal to or greater than 45° to its normal. This can be done with point light sources, i.e. ones which are compact in practice, but it turned out that particularly high correlations or correspondence to the matchings which are carried out outdoors, i.e. in daylight, were produced when using linear or tubular light sources.
A particularly big advantage lies in that the apparatus can be used both for color matching and for colorimetry, the construction remaining the same and only the visual observer being replaced by a colorimetric device or by suitable receivers of the colorimetric device which spectrally evaluate the beam density of the sample.
The bulbs or lights if necessary with suitable filtering are selected in particular for visual matching in such a way that their spectral distribution corresponds to the predetermined matching conditions, e.g. a color temperature of 6500 Kelvin and a high enough index of metamerism for daylight. Suitably selected fluorescent lamps are suitable for this.
Angles of observation which can be defined by the angular distance from the main beam direction of illumination, for example 25°, 45° and 75°, proved to be particularly efficient.
Advantageously lamps with different spectral light distribution which are connected to each other by a rotating or pivoting device can be provided for testing samples for metamerism, the respective selected bulb being moved by rotation or pivoting into the respective nominal position.
REFERENCES:
patent: 2406166 (1946-08-01), Scott
patent: 3519360 (1970-07-01), Kudlek
patent: 4344709 (1982-08-01), Provder et al.
patent: 0 379 168 A2 (1990-07-01), None
Dr. Ing. Willing GmbH
Evans F L
Marshall & Melhorn
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