Optical detector device

Details Optical detector device Optical detector device

2000-01-31

2001-05-29

Font, Frank G. (Department: 2877)

Optics: measuring and testing

By light interference

Spectroscopy

C385S012000

Reexamination Certificate

active

06239876

ABSTRACT:

The present invention relates to an optical detector device according to the preamble of claim
1
for determining or influencing the phase velocity of light guided in a waveguide or propagating freely in space.
For the detection of chemical reactions or for the analysis of substances or mixtures of substances and for the determination of the refractive index of a medium or the difference in the refractive indices of two liquids or gases, a high-quality detector system which is not prone to failure and composed of a few components in a relatively simple manner is needed by the users.
Interferometric or differential-refractory measuring cells and measuring means are known for such a purpose from the prior art (U.S. Pat. No. 4,229,105, U.S. Pat. No. 5,168,325, U.S. Pat. No.
5,426,505).
A direct detection of chemical or biochemical reactions, i.e. a detection without the use of labels (e.g. by fluorescence or radioactivity) can inter alia be carried out by sensing the propagation velocity of a light wave in dependence upon its being influenced or affected by the substance (detection medium) to be detected. The influencing medium (detection medium) is then inferred from the change in propagation velocity. The change in the propagation velocity of light waves can be detected by means of various optical assemblies. Frequently, the velocity measurement is based on an angular measurement. In such a case both the light rays freely propagating in space and light guided in the waveguides are used. As is known, the guidance of light in an optical waveguide is accompanied by an evanescent field part which is guided outside the optical waveguide. Therefore, it is possible with optical waveguides to detect mass deposits on the surface of the optical waveguide (strictly speaking, on the surface of the light-conducting layer of the optical waveguide).
In the instant field, the interest has specifically been directed to two measuring principles, namely surface plasmon resonance (B. Liedberg, C. Nylander, I. Lundström: Surface plasmon resonance for gas detection and biosensing; Sensors and Actuators 4 (1983), 299) and the principle of the grating coupler (Ph. Nellen, K. Tiefenthaler, W. Lukosz: Integrated optical input grating couplers as biochemical sensors; Sensors and Actuators 15 (1988) 285). In both cases the propagation constant of a guided light wave is determined on the basis of an angular measurement. In this process the fact is exploited that the excitation of the surface plasmon and of the waveguide mode, respectively (in the case of the grating coupler), during radiation onto the thin-film element is only possible within a very small angular range. This angular range is shifted in dependence upon the absorption of molecules on the surface of the structural element or component. The sensitivity of the two measuring methods as to a surface deposition with antibodies and antigens, respectively, is about the same. However, it is limited by the fact that the center of the angular range in which coupling is possible can be determined at an accuracy of about 1×10
−3
of said angular range.
Another method, the so-called “resonant mirror” principle, also ascribes the change in propagation velocity to an angular measurement (R. Cush, J. Cronin, W. Steward; C. Maule, J. Molloy; N. Goddard: The resonant mirror: a novel optical biosensor for direct sensing of biomolecular interactions, Part I: Principle of operation and associated instrumentation, Biosensors & Bioelectronics 8 (1993) 347).
Recently, integrated optical components have increasingly been used for interferometric purposes, e.g. the Mach-Zehnder interferometer or the Young interferometer (e.g. as a layer waveguide for detecting magnetic field strengths, voltages or temperatures, for refractrometry or chemical substance detections). Said integrated optical systems are very compact and mechanically stable. In the technical field of such planar optical waveguides special attention must be paid to the problems regarding fiber and light coupling into said integrated optical systems, and also to the achievement of definite measurement results because of the periodic structure of interferometrically obtained intensity distributions.
The improvement of said existing systems in the sense of a high-resolution optical detector device which for reasons of costs and for decreasing the proneness to failure should be composed of a few optical components and in a simple manner is desired by the users. Moreover, the device should permit the design as a multichannel system so that many analyses (preferably more than 100 analyses) can be carried out in parallel in one operation. Analytical assemblies which evaluate chemical or biochemical reactions on the surface of an optical waveguide require inexpensive and easily replaceable waveguide components because the immobilization of specific substances for detecting the analyte (detection medium) can only be maintained to a limited degree. In particular, only a limited number of analyses can normally be carried out with one immobilization.
It is therefore the object of the present invention to provide an optical detector device which meets the aforementioned requirements and permits a desired, substance-specific detection in an uncomplicated and inexpensive manner.
Said object is achieved according to the invention by the features of claim
1
.
The beam formation intended according to the invention and regarding the light received from a light source to obtain two radiation sources radiating divergent light permits—upon actuation of the one beam with a reference medium (reference path) and upon actuation of the other beam with a detection medium (measurement path)—a simple superimposition of the divergent beams in the detection plane in which a local resolution detector (preferably a CCD line) is positioned for detecting the characteristic intensity distribution.
The resulting line pattern corresponds to the signature as is known from the double slit experiment. Said signature (intensity distribution) changes whenever the phase velocity of the light is changing in one of the action paths (measurement path or reference path). The analysis of the diffraction pattern which is carried out by the local resolution detector permits the quantitative determination of the phase difference at the end of measurement path and reference path (action paths) and thus the analysis of a specific substance, of mixtures of substances or chemical reactions, and also the determination of the refractive indices of two liquids or gases by irradiation of the media, which are preferably positioned in a double cell or cuvette, by the beams.
In a particularly preferred embodiment, an analysis by way of fluorescence measurement can additionally be made by exploiting the fluorescence of the detection medium (or the reference medium).
Preferred embodiments of the subject matter of the invention are shown in the subclaims.


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Bo Liedberg et al., “Surface Plasmon Resonance For Gas Detection And Biosensing”, Elsevier Sequoia/Printed in The Netherlands, Sensors and Actuators, 4 , pp. 299-304, (1983).
Ph. M. Nellen et al. “Integrated Optical Input Grating Couplers As Biochemical Sensors” Elsevier Sequoia/Printed in The Netherlands, Sensors and Actuators, 15, pp. 285-295, (1988).
R. Cush et al. “The resonant mirror: a novel optical biosensor for direct sensing of biomolecular interactions Part I: Principle of operation and associated instrumentation”, Elsevier Science Publishers Ltd., Biosensors & Bioelectron

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