Fluorometer

Optics: measuring and testing – By shade or color

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Details

356344, 436501, G01J 346, G01N 33566

Patent

active

061444553

DESCRIPTION:

BRIEF SUMMARY
FIELD OF TECHNOLOGY

The invention relates to instrument technology and concerns fluorometers used in laboratories, which fluorometers can be used, for example, in assays of clinical chemistry and food technology. The invention is particularly suited for use in fluorometers having simultaneously a plurality of samples.


BACKGROUND

In a fluorometric assay there is directed to the sample a short-wave excitation light, which makes the substance being assayed to emit longer-wave light. The quantity of the emitted light is measured, and thereby the quantity of the substance being assayed is detected. In general, a fluorometer has one measuring channel and the assays are performed on plates having multiple wells. In this case the plate is moved relative to the measuring channel in such a way that each well in turn arrives at the measuring position.
The background fluorescence caused by excitation light incident outside the sample being assayed constitutes one problem with fluorometers. This can be reduced by using non-transparent shields. In practice, however, it is difficult to obtain sufficient light-tightness in this manner.
Fluorometric measuring through a vessel is not especially recommendable, since in such a case there passes through the vessel also a large amount of excitation light, which complicates the measuring of emitted light. Background fluorescence possibly caused by the material of the vessel constitutes a further problem. In most fluorometers currently used for routine assays, excitation light is directed to the vessel from above, and also emitted light is collected from above. In certain assays it is, nevertheless, best to carry out the measuring through the bottom of the sample-holding vessel.
From publication EP-A-108524 there is known a fluorometer measuring from above. Therein the excitation light is delimited by means of an aperture, a diverging beam of light is converged by means of a lens, and the converging beam of light is directed via a filter and a mirror as a spot to the sample-holding vessel. The emitted light, respectively, is directed from the vessel via another mirror, filter, converging lens and delimiting aperture to a detector.
From publication EP-A-640828 there is known a fluorometer measuring from above, wherein excitation light is directed simultaneously to a plurality of samples through a dichroic mirror, and emitted light from the sample vessels is reflected via the same mirror to a camera.


DESCRIPTION OF THE INVENTION



General Description

A fluorometer according to claim 1 has now been invented. Preferred embodiments of the invention are stated in the other claims.
According to the first characteristic of the invention, the fluorometer has a partly transparent mirror. In this case the axis of the excitation channel and the axis of the emission channel coincide between the mirror and the sample, and the solid angle of the entire aperture of the sample-holding vessel can be exploited. Thus there is achieved a high sensitivity, as well as inside the vessel a maximally homogenous measuring sensitivity distribution. The measuring can be carried out from either above or below.
No particularly large lenses or filters are required for implementing the system according to the invention.
The partly reflective mirror may have a dichroic dielectric film. Such films, however, in general perform only within a very narrow wavelength range (e.g. 400 . . . 600 nm), which is not sufficient in nearly all fluorometric assays. The mirror should perform within a range of, for example, 260 . . . 800 nm. A wide-band dichroic mirror can be made by vaporizing onto a glass surface a thin film partly transparent to light. However, such a film causes a great deal of losses. Preferably, a mirror is used which is made up of completely reflective and completely transparent areas. Such a mirror is easy to manufacture by vaporizing, for example, aluminum onto the surface of suitable glass. A very wide wavelength range can be achieved by using such a mirror, and the reflection capacity or transpa

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