Optics: measuring and testing – By shade or color – Fluid color transmission examination
Patent
1984-02-09
1987-04-14
Evans, F. L.
Optics: measuring and testing
By shade or color
Fluid color transmission examination
250343, 250353, 350630, 356 51, 356432, 356436, G01N 2131
Patent
active
046573976
DESCRIPTION:
BRIEF SUMMARY
The present invention is in the fields of geometrical optics and optical spectroscopy. It relates to a device for collecting radiation emanating from a light source within a concave reflector to give a narrow, quasi-parallel beam and the use of said device for optical spectroscopic purposes, particularly for the detection of gases. The invention is based on Swiss Patent Application No. 1,266/81-0 of Feb. 25, 1981, PCT Application No. PCT/CH82/00026 of Feb. 23, 1982 (now U.S. Pat. No. 4,557,603), Swiss Patent Application No. 3939/82-9 of June 25, 1982 and Swiss Patent Application No. 2654/83 of May 14, 1983.
Concave mirrors are known for the purpose of collecting radiation from light sources. In particular, spherical, elliptical and parabolic reflectors are frequently used, particular significance being attached to the two latter devices.
A more detailed description will firstly be given of elliptical concave mirrors. Such reflection devices are very frequently used if the radiation of a small light source is to be focused on a target with a high efficiency level. For this purpose, the light sources and target are arranged in two opposite focal points. A particular use is, for example, the excitation of the ruby laser. One focal point is located in the excitation light source and the other in the ruby rod forming the laser cavity. Reference is made in this connection to the book by B. A. Lengyet, entitled "Lasers", Wiley Publications, 1971. In this application use is made of the fact that any beam emanating from one focal point, occurs in the other focal point following reflection. Thus, a very considerable efficiency of the radiation intensity transmission can be achieved. However, the light bundle is very divergent, if radiation is collected from a large solid angle. It is often not possible to accept this divergence, e.g. if the light is to be dispersed in a monochromator.
The efficient formation of a quasi-parallel beam by means of an ellipsoidal reflector is described in Swiss Patent application No. 1,266/81-0. Not only a single reflection on the ellipsoidal concave mirror is observed and instead it is assumed that, after a second reflection on the reflector surface, the light is again returned into the source and partially penetrates the latter. Thus, the ellipsoidal surface has the double function, on the one hand as a reflector which conducts the light of the source located in one focal point into the other focal point and on the other hand as a retroreflector which again returns the radiation to the source. The light collection is based on the fact that all the light beams emanating from a focal point with increasing numbers of reflections on the ellipsoidal mirror surface and light source penetrations asymptotically approach the large major axis. Thus, there is a light collection along this axis. The beam is coupled out through a small opening of diameter D, provided in the extension of this large major axis A. Tests were carried out on a prolate ellipsoid of revolution, i.e. for the case where A is simultaneously the rotation axis and consequently the two other major axes have the same length B. For A/B=1.2 and D/B=0.1, it was found that 30% of the light of a filament arranged in a focal point could be coupled out, the emitted light being within a cone of 15.degree..
A disadvantage of this construction is that the light beam must in each case after 2, 4, 6 . . . reflections penetrate the light source provided in a focal point. Due to the incomplete transparency of the light source, which in the case of a filament is approximately 70%, the efficiency of the light collector is reduced.
Moreover, the geometrical dimensions of the device must be made very large, because a good luminous efficiency is only ensured if the dimensions of the reflector are large compared with those of the radiation source.
It is often desired to concentrate the light radiation on a small circular or square surface, for example onto the light-sensitive surface of a photo-detector. The problem occasionally arises of illumina
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patent: 3179898 (1965-04-01), Meltzer
patent: 3745325 (1973-07-01), Harvey
patent: 3763348 (1973-10-01), Costello
patent: 4188542 (1980-02-01), Hogg et al.
patent: 4188543 (1980-02-01), Brunsting et al.
patent: 4557603 (1985-12-01), Oehler et al.
Fries Alexis
Oehler Oskar
Sourlier David
Evans F. L.
Oehler Oskar
Sourlier David
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