Optical: systems and elements – Light interference – Produced by coating or lamina
Patent
1991-07-30
1993-08-10
Lerner, Martin
Optical: systems and elements
Light interference
Produced by coating or lamina
215 995, 359582, 359586, G02B 528, G02B 110
Patent
active
052354628
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to articles, the shape of which and the surface of which are designed in a specific manner to achieve an aesthetic effect.
The invention relates especially to a decorated article which exhibits a transparent body which has a specific shape and on the surface of which a layer system is provided to generate interference effects.
Technical applications for optical components are known and conventional. Examples are high-efficiency mirrors, filters and beam splitters. A survey is included in H.A.M. Macloed, Thin Film Optical Devices, in "Active and passive thin film devices", Academic Press 1978 (hereafter, reference D1)
A number of components may be produced only with the aid of interference layers. It is possible to cultivate virtually all physically non-forbidden optical properties with the aid of interference layer systems. The possibilities extend from complete dereflection to a mirror which reflects more strongly than a silver surface; from a narrow-band transmission filter to a band pass with steep edges. The dependence of the optical properties transmission T and reflection R upon the wavelength results in the fact that the layer system appears to be coloured. In particular, it is easy to achieve powerful, coloured reflection using interference layer systems; this is not possible or is possible only with difficulty when using other means.
Conventional dyeing takes place by addition of substances which absorb a specific wavelength range. The article then appears in the colour of the non-absorbed wavelengths. This mechanism takes place mainly upon the transmission of the light, scarcely at all in reflection. Absorbing coloration is characterised in that a part of the light is destroyed. An article coloured in this manner has a dark effect. The greater the purity and depth of the colour, the more light must be absorbed and the darker is the effect of the article. This effect makes itself disadvantageously noticeable especially in circumstances in which the colour is to be employed as a decorative element to achieve an aesthetic effect. The absorption is a property of the substances employed, so that the available colours are limited by the number of appropriate substances. Since what is involved is absorbing coloration, as a rule the mixing of various substances gives an impure mixed colour.
The application of absorption-free interference layer systems brings the following advantages:
Nevertheless, the absorption-free interference layer systems have not to date been used for decoration. It is to be assumed that the decisive factor concerning the non-use is the following: The colour effect of absorption-free interference layer systems shows a marked dependence upon the illumination conditions. In particular, it is harmful for an application that the colour effects almost disappear under usual, partly uniform illumination.
For explanatory purposes, the term "depth of colour" K will be used. Light of intensity I impinges upon the eye of the observer. The change in the intensity with the wavelength is of decisive importance to the colour perception. Maximum intensity Imax, and minimum intensity, Imin, occur within the visible range of the spectrum. The function K=(Imax-Imin)/Imin can be taken as a measure of the depth of colour, provided that the extreme values are not so close that the eye integrates with respect to the wavelength. In the event that the intensity does not fluctuate, Imax-Imin=0, the value 0 emerges for K. In fact, in this case the light appears white (colourless). The eye "measures" relatively, so that the ratio of intensities is computed in K. A large value of Imin reduces the value of K, so that it is taken into consideration that a basic intensity existing at all wavelengths "whitens" the colour.
of the coloration of an article, the decoration of which consists in the coloration, it is to be required that the colours become effective under many illumination conditions.
1st case: pure reflection
In the case of pure reflection, layer system
REFERENCES:
patent: 3188513 (1965-06-01), Hansler
patent: 3338730 (1967-08-01), Slade et al.
patent: 3490250 (1970-01-01), Jones
patent: 3645600 (1971-02-01), Doctoroff et al.
patent: 4793669 (1988-12-01), Perilloux
patent: 4826267 (1989-05-01), Hall et al.
patent: 4934788 (1990-06-01), Southwell
patent: 4952025 (1990-08-01), Gunning, III
H. A. M. Macleod "Thin Film Optical Devices", Academic Press, 1978y.
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