Optical interface means

The present invention relates to a novel use of a means for coupling light between two light transmission media, in particular the use of a reusable solid-like means for non-permanent light coupling.

The conventional way of producing a non-permanent passive (i.e., neither refractive nor diffractive) light coupling between two translucent elements consists of sealingly connecting the two elements by an immersion oil or, in some applications, by an uncured silicone rubber compound, each with a suitable refractive index. This requires application of an exact amount of the coupling medium, which requires either mechanical treatment or mechanical equipment. The immersion oil must also be removed from one or both elements with each new coupling operation in order to obtain a good light coupling free from annoying air bubbles. Such removal of the immersion oil by wiping or other means of removing it is also an annoying and time-consuming procedure which, in addition to the risk of scratching the optical surfaces, is difficult to automate, for example in a commercial measuring instrument. Furthermore, the oil can easily contaminate or smear instrument parts, optical individual parts and detection surfaces, which of course brings considerable inconveniences, especially with commercial devices.

An object of the present invention is to provide an improved passive light coupling means which avoids the aforementioned and other disadvantages and shortcomings of prior art non-permanent light coupling means in an optical imaging system.

Another object of the invention is to provide for the use of a reusable passive light coupling agent with a matched refractive index with respect to at least one of the media between which it is intended to couple light to ensure low refractive index losses, essentially no light refraction or diffraction and little light scattering and maintain the polarization directions of light.

Yet another object of the invention is to provide for the use of a passive light coupling means which is reusable, i.e. which can be repeatedly connected or coupled to the same or another solid light transmission medium, but in the event of contamination or if it is on others Way is no longer usable, can be replaced.

The above-mentioned and other objectives are achieved by the use according to claim 1 of a reusable optical solid-type transmission medium for non-permanent passive coupling of light between two fixed optically transparent light transmission media, such as between, for example, a glass prism and another optical medium, for example made of glass.

In its broadest aspect, the optical transmission means (hereinafter simply called "opto-interface" a few times) of the invention comprises a holding part and one or more (shaped) parts made of an optically transparent elastic or resilient material which is held and designed by the holding part to touch at least one of the light transmission media and to have one with respect to this matching refractive index.

The body or bodies made of elastic material can be attached to one or both surfaces of a transparent holding means, such as a portable plate or disk or a lens or a prism. In the latter case, the transparent, elastic material should of course have a refractive index that is also suitable with respect to the support means. In the latter case in particular, the holding means can preferably be provided with a holder or the like in order to facilitate handling of the unit.

The contact surface or surfaces of the body or the body made of elastic material should preferably be shaped in such a way that they extremely well prevent or prevent the inclusion of air bubbles. The optimal contact surface shape or design naturally depends on the respective application and can be dome-shaped or stepped, for example.

The optically transparent elastic material can be any material that, for any particular application, meets the specific requirements relating to elasticity, strength, refractive index, etc., and finding suitable materials for a particular application is within the scope of the disclosure given herein within the skill of a professional. As examples of wide groups of materials, transparent rubber or (cross-linked) elastomers such as silicone rubber or polybutadiene and transparent epoxy resins can be mentioned.

The present inventive concept can be used in all conceivable areas of use in which a non-permanent passive light coupling is to be produced. Examples are light couplings for all measurement methods which are based on "internal reflection", in which the reflecting surface is to be kept separable from a stationary light coupling glass body, such as when measuring ATR (attenuated total reflection), for example SPR technology (Surface Plasmon Resonance = surface plasmon resonance); Brewster angle reflectometry and ellipsometry of volatile waves; and IRS (Internal Reflection Spectroscopy), for example internal reflection infrared spectroscopy, internal reflection fluorescence or internal total reflection fluorescence. Other considerations for the coupling or optical transmission means of the present invention include:

as a prism coupler for refractive index measurements on planar substrates;

- For light coupling to / from light wave guide units for communication and / or detection;

- for light coupling with / from light guide units for transmission, reflection, light scattering and absorbance measurements;

for imaging light coupling to / from the microscope slide at the microscope;

- for coupling illuminating light to / from the substrate glass and cover glass during microscopy processes;

- For coupling light within the infrared range for effective heating of certain detail areas, for example skin sections.

The use of an optical interface according to the invention can also be used for refractometry at critical angles. Here, light rays that lie over an angle of incidence range and are reflected within a prism or an optical fiber are coupled through the optical interface between the prism and the process tube or the flow cell containing the exchangeable transparent liquid.

Another use of an opto interface is in optic grating couplers. Therefore, the opto-interface can be used to couple light between a planar waveguide and an interchangeable planar waveguide or a transparent plate provided with a grating area.

Yet another use of the optical interface is in a reflection type refractive index detector. This technique is based on coupling a light beam from a prism into a flow cell, the prism surface forming one side of the flow surface. Furthermore, the refractive index increase due to the presence of the analyte is a measurement of the light intensity, which is reflected back into the prism by a reflection surface forming the opposite side of a flow cell. By using the optical interface, the light beam can be coupled between the prism and an exchangeable, flat, transparent plate which forms a stationary or an exchangeable side of the flow cell.

The invention will now be described in more detail with reference to non-limiting embodiments of the invention, reference being made to the accompanying drawings, in which

1 is a partial schematic view of an arrangement for microscopy which includes an embodiment of the optical transmission device or "opto-interface" for use in the present invention;

2 is a schematic exploded view of an optical biosensor system based on surface plasmon resonance (SPR) with an embodiment of an optical interface for use in the present invention;

3 is a top view of the opto interface of FIG. 2; and

4 is a sectional view of the opto-interface of FIG. 2 coupled to the sensor unit and the liquid treatment block of the biosensor system from FIG. 1.

In FIG. 1, the objective lens 1 of a microscope is set for examining a sample 2, which is enclosed between a cover glass 3 and a substrate glass 4. The sample could, for example, be illuminated by an optical fiber 5a, which is coupled to the sample 2 and the cover glass and substrate glass 3 or 4 by a second optical interface 5. The objective lens 1 is light-coupled to the cover glass 3 by a transparent elastic material layer or a flat body 6, which is attached to the cover glass 3 and brought into close air-exclusion contact with the lens 1. The cover glass plate 3 and the transparent body 6 made of elastic material held thereby thereby form a reusable light coupling means or an optical interface. In this case, since the incident light is perpendicular to the contact surface between the lens 1 and the light coupler 6, a moderate deviation between the refractive index of the lens 1 and that of the transparent elastic material 6 is not detrimental to the coupling of light. The optical interface arrangement 3, 6 can be easily removed and repeatedly placed on the lens 1 without the need to wipe the lens, such as when using an immersion oil for light coupling.

In an alternative embodiment, the optical interface can consist, for example, of a separate transparent plate with elastic layers of transparent material lying opposite one another on both surfaces. In this case, the optical interface is thus a separate unit that can be inserted between the lens and the cover glass plate and can be designed, for example, by means provided for this purpose for attachment to the microscope.

2 shows a schematic exploded view of an optical biosensor system which is based on surface plasmon resonance (SPR). The system comprises a light source 7, a first lens system 8, for directing a transversely extending convergent beam 9 onto a prism 10, whereby the beam is focused in the bottom surface of the prism so as to form a light strip 11. Light rays reflected from the detection areas of a sensor unit 12 are imaged on an anamorphic lens system 13 on a two-dimensional photodetector device 14. The electrical signals created by the photodetectors are processed in an evaluation device 15 in the form of a computer. With the aid of the prism 10 and an optical interface 16 according to the present invention, light is directed into the strips 11 on the sensor unit 12, each of which is in contact with a number of parallel upwardly open sections 17A-D of flow channels 18A-D comes; only one of the flow channels, 18A, is shown. The flow channels form part of a block unit 19 for liquid treatment, and this unit is provided with schematically indicated inlet connection means 20 and outlet connection means 21 for each of the (flow channels).

FIG. 3 shows a top view of the more detailed layout of the optical interface plate 16 from FIG. 2, and FIG. 4 shows the optical interface used between the prism 10 and the sensor unit 12 in FIG. 2; wherein the sensor unit 12 contacts the liquid treatment block unit 22 which contains the flow channels 17A-D. The optical interface 16 comprises a metal (or plastic) frame or holder 23 which has two protruding tongues 24, 25, the tongues each being provided with a bore, these bores 26, 27 each extending through the entire thickness of the tongues extend and serve to receive two guide pins of a housing (not shown) in which the light source 7, the lens system 8, the prism 10, the optical imaging unit 13 and the photodetector 14 are housed in fixed positions. The guide pins serve to retain the frame 23 in the correct position. The frame 23 has two flanges 28, 29 against which a transparent plate 30 made of glass or plastic has been placed. On one of its surfaces, the plate 30 is provided with a number of ribs 31, which extend in the longitudinal direction and lie next to one another in parallel. On its opposite surface, the plate has a corresponding number of parallel longitudinal ribs 32, which lie opposite the ribs of the former plate surface. The ribs are made of a transparent elastic material and have a distance from one another which corresponds to the distance between the upwardly open sections 17A-D of the flow channels. As is clear from Fig. 4 It can be seen that the ribs 31, 32 have longitudinally extending stepped portions 33 on each side so as to form a structure with a cross-sectional configuration in a step series, the top step or the top platform of each of these step structures being elastic against the sensor unit 12 or the prism 10 can be pressed. This stepped design prevents the formation of air pockets between the separating surfaces that abut the prism or the sensor unit. FIG. 4 shows the prism, the optical interface plate 16 and the sensor unit 12 in the analysis position of the biosensor device in FIG. 2. The ribs 31, 32 are spaced apart from one another in such a way that the spacings between the spacings between the upwardly open sections 17A-D correspond to the flow channels 18A-D.

This arrangement of the ribs 31, 32 on the opto-interface plate, the bores 26, 27 for the guide pins, corresponding bores on a holding plate (not shown) of the sensor unit 12 and the stationary fastening of the upwardly open sections 17A-D of the block unit for the treatment of the Liquid ensure that the lower ribs 32 serve as light sources which lie directly over each of the corresponding channel sections 17A-D, No scattered light from adjacent ribs 32 disturbs the resonance angle determination for the individual detection surfaces. In this way it is possible to pack a large number of these channel sections in close proximity to one another. As an example, it can be mentioned that up to 20 such upwardly open channel sections can be packed over a width of about 10 mm without the measurement operation being disturbed by stray light.

The frame or holder 23 of the opto-interface 16 facilitates the handling thereof and, as previously mentioned, ensures the correct positioning thereof on the prism 10.

The transparent plate 30 can be made of borosilicate glass, for example, and can be attached to the frame 23, for example, by gluing. A suitable thickness for the application described above can be about 100 µm. The plate 30 should have at least substantially the same refractive index as the prism 10 (obliquely incident light).

The transparent elastic material forming the ribs 31, 32 should of course have essentially the same refractive index as the plate 30 and the prism 10. The elastic material can be, for example, a silicone rubber, a polybutadiene or an epoxy resin. A silicone rubber with almost the same refractive index as borosilicate glass (ne = 1.52) is available under the trade name Dow Corning Optigard X3-6663 as an optical fiber coating (ne = 1.51). For the described application, the ribs 31, 32 can have, for example, a length of approximately 7 mm, a width of approximately 700 µm and a height (or thickness) of approximately 50 µm. Instead of the stepped design shown, the ribs can also be dome-shaped or similar, which in the same way prevents the formation of air pockets.

An opto-interface as described above can be, for example, by adhering a piece of glass having an appropriate refractive index, thickness and size to a metal frame and then attaching the ribs of transparent elastic material such as silicone rubber to the glass by molding with molding devices made of a suitable material , such as metal, plastic, ceramic or silicone materials.

By providing additional ribs 31, 32, in addition to those used for light coupling, uniform compression can be ensured in the opto-interface described above and homogeneous environments can also be ensured for all light coupling ribs. Thus, for example, in the case of a single light coupling rib, two flanking ribs should preferably be provided.

An optical interface of the type described above can alternatively be provided with the transparent elastic material only on the side of the glass plate facing the sensor unit, while the other side of the glass plate is attached to the prism by means of an immersion oil.

The invention is of course not limited to the particular embodiments described above and shown in the drawings, but many modifications and modifications are within the scope of the inventive concept as set out in the appended claims.