DE102015116386A1 - Optical system for analyzing a medium - Google Patents

Abstract

The invention relates to an optical system (1) for analyzing a medium (2) comprising a light source (3) for emitting light beams (4) through the medium (2), a receiver (5) for receiving the light beams (4), at least one first diaphragm (6) for limiting the light beams (4) of the light source (3), at least one lens (7) for imaging the at least first diaphragm (6) on the receiver (5), at least one second diaphragm (8) between the at least one lens (7) and the medium (2).

Description

The invention relates to an optical system for analyzing a medium.

Automatic analyzers are often used for analyzing media, in particular liquids in process measurement technology. The determination of the measured variable is often carried out in these devices by an optical, z. B. photometric or spectrometric measurement.

Light-emitting diodes are widely used light sources for optical measurements. If the measuring path is relatively long, a defined beam of light rays is necessary. The simplest solution is a beam of parallel rays of light. However, there are various problems. On the one hand, with small diameters of the beam, as they usually occur in automatic analyzers, it is annoyingly noticeable that the light source is not a perfect point light source. Light-emitting diodes z. B. include a LED chip with finite extent. Therefore, the light emitting diode can not be easily placed in the focal point of a lens to produce a parallel beam. On the other hand, small lenses with small focal lengths are necessary for small beam diameters. Such lenses are difficult to adjust. Furthermore, for proper optical alignment, the LED chip must be placed in the middle of the optical axis. This can not be guaranteed due to component tolerances and tolerances in the assembly process and makes a subsequent adjustment necessary.

The invention has for its object to provide an optical system for analyzing a medium whose light source can be mounted without adjustment.

The object is achieved by the subject invention. The invention relates to an optical system for analyzing a medium comprising a light source for emitting light rays through the medium, a receiver for receiving the light beams, at least a first aperture for limiting the light beams of the light source, at least one lens for imaging the at least first aperture on the receiver, at least one second aperture between the at least one lens and the medium.

The light source is mountable in this system without adjustment because the beam geometry is defined by the positions of the first aperture and the lens, regardless of the position of the light source subject to tolerances.

According to an advantageous development, the optical system is dimensioned such that a diameter of the at least second diaphragm corresponds to an image size of the first diaphragm on the detector.

According to an advantageous variant, the at least first diaphragm is embodied on a surface facing the light source at least partially reflecting for the light beams of the light source, wherein a detector is provided in order to monitor the light beams reflected by the at least first diaphragm.

The object of the invention is also achieved by a spectrometer comprising an optical system according to the invention.

• – eine Messzelle,
• – mindestens einen Flüssigkeitsbehälter enthaltend eine Behandlungsflüssigkeit, insbesondere ein oder mehrere Reagenzien, zur Behandlung der flüssigen Probe,
• – eine Verfahrenstechnik-Einrichtung umfassend eine Förder- und Dosiervorrichtung zur Förderung und Dosierung der flüssigen Probe aus der Probensammeleinheit und der Behandlungsflüssigkeit aus dem Flüssigkeitsbehälter in die Messzelle;
• – einen, insbesondere fotometrischen Messaufnehmer, umfassend das erfindungsgemäße optische System, zur Bereitstellung mindestens eines mit der Messgröße der in der Messzelle enthaltenen, mit der Behandlungsflüssigkeit behandelten flüssigen Probe korrelierten Messsignals, gelöst.

The object of the invention is also achieved by an analytical device for determining a measured variable of a liquid sample, comprising:

• - a measuring cell,
• At least one liquid container containing a treatment liquid, in particular one or more reagents, for the treatment of the liquid sample,
• A process engineering device comprising a conveying and metering device for conveying and metering the liquid sample from the sample collecting unit and the treatment liquid from the liquid container into the measuring cell;
• A, in particular photometric, sensor, comprising the optical system according to the invention, for providing at least one measurement signal correlated with the measured variable of the liquid sample contained in the measuring cell and treated with the treatment liquid.

The liquid sample in this embodiment of the invention corresponds to the aforementioned medium through which the light rays are transmitted after passing through the aperture before they strike the receiver.

The analyzer may comprise an electrical data processing system which determines measured values of the measured variable on the basis of measurement signals provided by the receiver of the optical system. The data processing device may also be configured to control the analysis device, in particular the process engineering device for acquiring measured values.

The invention will be explained in more detail with reference to the following drawing. It shows:

1 : a sketched view of an optical system.

1 shows a sketched view of an optical system 1 , The optical system 1 includes a designed as an LED light source 3 for emitting light beams 4 and a first aperture 6 for limiting the light rays 4 the light source 3 , A lens 7 creates an image of the first aperture 6 , wherein a second aperture 8th the rays of light 4 limited to the lens. The light rays pass through a medium 2 and fall on a receiver 5 ,

The optical system generates by means of the lens 7 a picture of the first panel 6 on the receiver 5 ,

The optical system 1 is dimensioned so that a diameter of the second aperture 8th an image size of the first aperture 6 on the receiver 5 equivalent. By the diameter of the first panel 6 and the selected magnification can be the diameter of the beam set at the end of the measurement path. The rays of light 4 are thus on the larger of the two diameters of the image of the first aperture 6 on the detector 9 and the diameter of the second aperture 8th limited. Preferably, the diameters of the image are the first aperture 6 and the diameter of the second aperture 8th the same.

The first aperture 6 is at one of the light source 3 facing surface diffusely reflecting the light rays 4 the light source 3 designed so that the hidden light rays are reflected diffused. The diffuse reflection provides a kind of averaging, so that slight shifts of the components (eg due to temperature changes) have less effect. A detector 9 is intended to be that of the at least first panel 6 reflected light rays 4 to monitor. At the detector 9 it is a photodiode.

Spacer elements between the optical components ensure the correct distances. The components (First panel 6 - Spacer - Lens 7 - Second aperture 8th ) are very easy to install by design with the necessary low tolerances, without any adjustment is necessary.

If the magnification chosen is slightly larger, lenses with a larger focal length can also be used. With the larger mechanical dimensions and larger focal length, such lenses are less sensitive to installation tolerances.

From the measurement signal is a Analysemessgröße, z. B. determines an ion concentration. The liquid 2 is then usually contained in a measuring cell (cuvette) of the analyzer sample liquid.

LIST OF REFERENCE NUMBERS

1

 Optical system

2

 medium

3

 light source

4

 light rays

5

 receiver

6

 First aperture

7

 lens

8th

 Second aperture

9

 detector

Claims (5)

Optical system ( 1 ) for analyzing a medium ( 2 ) comprising a light source ( 3 ) for emitting light beams ( 4 ) through the medium ( 2 ), a receiver ( 5 ) for receiving the light beams ( 4 ), at least one first aperture ( 6 ) for limiting the light rays ( 4 ) of the light source ( 3 ), at least one lens ( 7 ) for imaging the at least first diaphragm ( 6 ) to the recipient ( 5 ), at least one second aperture ( 8th ) between the at least one lens ( 7 ) and the medium ( 2 ). An optical system according to claim 1, wherein the optical system is dimensioned such that a diameter of the at least second aperture ( 8th ) of an image size of the first aperture ( 6 ) on the detector ( 5 ) corresponds. An optical system according to claim 1 or 2, wherein the at least first aperture ( 6 ) at one of the light source ( 3 ) facing surface at least partially reflective to the light rays ( 4 ) of the light source ( 3 ), and wherein a detector ( 9 ) is provided to the of the at least first aperture ( 6 ) reflected light rays ( 4 ). Spectrometer comprising an optical system ( 1 ) according to at least one of the preceding claims. Analysis device for determining a measured variable of a liquid sample, comprising an optical system according to one of claims 1 to 3, further comprising: - a measuring cell, - at least one liquid container containing a treatment liquid, in particular one or more reagents, for the treatment of the liquid sample, - a Process engineering device comprising a conveying and metering device for conveying and metering the liquid sample from the sample collecting unit and the treatment liquid from the liquid container into the measuring cell; A measuring sensor, in particular a photometric sensor, for providing at least one measuring signal correlated with the measured variable of the liquid sample contained in the measuring cell and treated with the treatment liquid.

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