NL2005902C2 - Method and apparatus for surface plasmon resonance angle scanning. - Google Patents

Method and apparatus for surface plasmon resonance angle scanning. Download PDF

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Publication number
NL2005902C2
NL2005902C2 NL2005902A NL2005902A NL2005902C2 NL 2005902 C2 NL2005902 C2 NL 2005902C2 NL 2005902 A NL2005902 A NL 2005902A NL 2005902 A NL2005902 A NL 2005902A NL 2005902 C2 NL2005902 C2 NL 2005902C2
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element
optical element
light
optical
sensor surface
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NL2005902A
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Dutch (nl)
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Richardus Bernardus Maria Schasfoort
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Ibis Technologies B V
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00Investigating or analysing materials by the use of optical means, i.e. using infra-red, visible or ultra-violet light
    • G01N21/17Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/55Specular reflectivity
    • G01N21/552Attenuated total reflection
    • G01N21/553Attenuated total reflection and using surface plasmons

Abstract

The invention relates to an apparatus for surface plasmon resonance (SPR) scanning, the apparatus comprising: - a sensor assembly comprising a first optical hemispherical element and an SPR sensor element comprising a thin layer of conductive material, at least partially provided at the sensor surface of the first optical hemispherical element; - an illumination assembly comprising a light source and a second optical element; - a detector assembly comprising a sensing element for sensing the image of the illuminated sensor surface and a third optical element; wherein the detector assembly is configured to adapt the position of at least one of the sensing element and third element during scanning to focus the reflected light in a focal point located at both the first focal plane of the first element of the sensor assembly and the third focal plane of the third element of the detector assembly.

Description

METHOD AND APPARATUS FOR SURFACE PLASMON RESONANCE ANGLE SCANNING

The invention relates to an apparatus for surface plasmon 5 resonance scanning, the apparatus comprising a sensor assembly, an illumination assembly and a detector assembly. The invention also relates to a method of surface plasmon resonance scanning.

Surface plasmon resonance (SPR) scanning is a well known optical technique for determining the adsorption of material onto 10 a planar conductive (metal) surfaces or onto the surface of conductive nanoparticles by measuring changes in refractive index near a sensor surface exposed to the material. The technique involves illuminating the conductive surface or the conductive nanoparticles of a sensor element with p-polarized light. Photons 15 of the p-polarized light reflected against a thin conductive layer interact with free electrons in the conductive layer, inducing a wave-like oscillation of the free electrons, thereby reducing the reflected light intensity. This phenomenon yields a maximum effect at a typical angle, the so-called SPR angle.

20 Changes in the refractive index near the sensor surface result in a shift of the SPR angle. Classical SPR imaging instruments use reflectivity as parameter for measuring refractive index changes. Surface plasmon resonance angle scanning relies on measuring changes in refractive index by 25 determining changes in the SPR angle. The majority of the SPR systems are of the convergent beam type. In other types of SPR systems use is made of a more or less parallel beam to image the sensor surface on a sensor.

Some of the systems used for SPR imaging in the prior art 30 represent fixed-angle instruments. These instruments are based on an almost linear relationship between the change in reflected * light intensity and the mass of bound analyte. This means that a fixed incident light angle is employed and mass changes are I : 2 estimated from the intensity of the reflected light.

Drawback of these fixed-angle instruments is that the range where the linear relationship between the reflected light intensity and the mass of bound analyte applies, is limited.

5 Furthermore, the optimal angles differ considerably when ligand or analyte panels that have different molecular weights are to be monitored. Immobilized ligands of different size and or different density will induce an initial shift. Monitoring multiple biomolecular interactions in parallel on a micro-array 10 may lead to monitoring at non-optimal angles.

A more reliable parameter that reflects mass changes on an SPR sensor surface is the SPR angle shift. The SPR angle shift may be determined by a technique called incident angle scanning.

A range of angles is scanned by stepping through the range and 15 measuring the reflected light intensity at each of the angles.

The measured reflected light intensity is plotted against the angle of incident. From these reflectivity versus angle plots, an SPR curve is constructed by curve fitting. The SPR angle can be determined from the SPR curve.

20 It is to be noted that the word scanning can apply to two different notions in this document. In its primary meaning, scanning relates to angle scanning, this means lighting a surface sequentially under a number of different angles of incident.

Secondary, scanning can mean using a narrow beam to light 25 different portions of the surface sequentially, irrespective of the angle of incident. Furthermore, if in the present document reference is made to a change, variation or adaption of the position of an optical element then this reference is not to be construed as being limited to a change, variation or adaption of 30 the location of the optical element. It also may involve a change, variation or adaption of the orientation of the optical element. 1

Scanning the sensor surface involves imaging the surface on a sensing element, such as a camera. In the current measurement 3 setup the light distribution of the image provided on the sensing element is not uniform. Sometimes a relatively high intensity spot is formed at a position corresponding to the centre of the sensor surface while in other parts of the image the sensed light 5 intensity is relatively low. A non-uniform illumination of the sensing element may be detrimental to the scanning results.

In situations in which the sensor surface has multiple spots or regions of interest (ROI's), for instance when the sensor surface is provided with a 100 spots microarray, the results of 10 the measurements obtained from individual ROI's may give a baseline variation between different ROI's. ROI's closer to the centre of the image surface display the highest and the lowest signals, with a variation of up to about 50% between the different ROI's. This baseline variation has a negative impact on the 15 performance of the scanning method.

A further drawback of the known scanning methods and apparatus is that the position of the image of the ROI's on the sensing element may vary depending on the angle of incidence of the light impinging on the sensor surface. The position 20 variation is sometimes referred to as the walking spot effect.

It is clear that this effect may impede the correct and efficient scanning operation by the apparatus.

The object of the present invention is to provide an SPR scanning apparatus and method wherein at least some of the 25 drawbacks of the prior art have been removed or at least reduced.

A further object of the present invention is to provide an SPR scanning apparatus and method that are more efficient and/or more accurate with respect to existing apparatus and method.

A further object of the present invention is to provide an 30 SPR scanning apparatus and method wherein the effect of walking spots during scanning, especially during imaging small objects s e.g. living cells, is at least partly reduced.

4

According to a first aspect of the invention at least one of the objects is achieved in an apparatus for surface plasmon resonance (SPR) scanning, the apparatus comprising: - a sensor assembly comprising: 5 ~a first optical element, substantially transparent to light and defining a first optical element focal plane and a sensor surface; - a SPR sensor element comprising a thin layer of conductive material, at least partially provided at the sensor 10 surface of the first optical element; an illumination assembly arranged to direct light diverging from an illumination assembly focal point to the sensor surface of the first optical element, the light arriving at the sensor surface at varying angles of incidence as a substantially 15 collimated light beam; - a detector assembly for the spatially resolved acquisition of a light property, for instance the intensity, of light reflected at the sensor surface of the first optical element at varying angles of incidence, the detector assembly comprising 20 a sensing element for sensing the image of the illuminated sensor surface and a third optical element having a third optical element focal plane; wherein the detector assembly is configured to adapt the position of at least one of the sensing element and third element during 25 scanning to focus the reflected light in a focal point located at both the first focus plane of the first element of the sensor assembly and the third focal plane of the third element of the detector assembly.

In embodiments of the invention the illumination assembly 30 comprises a light source and a second optical element defining an illumination assembly focal plane. The second optical element * may be a spherical lens and the illumination assembly focal plane then is the focal plane of this lens. In other embodiments the 5 illumination assembly may comprise one or more pinholes and/or one or more optical fibre light sources to generate the divergent light beam directed towards the first optical element.

It is to be noted that angle scanning of the sensor surface 5 may include an angle off-setting phase wherein the sensor surface is scanned with a relatively large angle step size (for instance providing a resolution of about 100 millidegrees) and the actual scanning phase wherein the sensor surface is scanned with a relatively small angle step size (for instance providing a 10 resolution of about 0,1 millidegrees). The adaption of the position of the focal points of the illumination assembly and the detector assembly as described herein can be employed during the angle off-setting phase, the scanning phase or during both the angle off-setting and scanning phase. The first optical element 15 may be a generally hemispheric prism or similar element, such as a prism in combination with two spherical lenses. The third optical element may be formed by one or more spherical lenses as well, but other types of optical elements may be used instead.

The sensing element may be an electronic camera, for instance a 20 CCD camera, a CMOS camera or a similar device. The light source may be a p-polarized narrow-band light source. Other types of light sources are possible as well. The light source may also be a halogen white light source with bandpass filter, a light emitting diodes (LED) or superluminescent light emitting diodes 25 (SLED). A laser source can also be used, preferably with an incoherent processed light beam.

At the side of the detector assembly, the point in which the light reflected from the sensor surface is focussed generally changes position during the scanning operation, i.e. during the 30 illumination of the first optical element at varying angles of incidence. As a result of the movement of this so-called focal * point, the optimal conditions for projecting the reflected light onto the sensing element cannot always be met in stationary 6 detection assemblies. According to embodiments of the present invention, however, the position of the sensing element, the third optical element or both the sensing element and the third optical element may be adapted depending on the position change 5 of the focal point. For instance, the elements may be moved in such a way that the focal point is at the intersection of the focal planes of the first and third optical elements. The collimation of the light reaching the sensing element may thus be better maintained during the scanning process.

10 In an embodiment of the present invention the apparatus comprises a frame having a tiltable frame element at which the sensing element and/or the third optical element are attached.

The sensing element and third optical element may be attached to the same tiltable frame element so that tilting the frame element 15 results in a tilting movement of both the sensing element and the optical element. The sensing element and third optical element may also be attached to separate tiltable frame elements. This makes it possible to move the sensing element and third optical element independently.

20 The tiltable element may be configured to tilt the sensing element and/or third optical element in the plane of incidence so that the sensing element and/or the third optical element may be tilted to an optimal position for imaging the sensor surface on the sensing element. For instance, the sensing element may be 25 positioned on a pivot arm construction to allow optical axis scanning.

In embodiments of the invention the second and third elements are selected to have the same focal distance. This creates an essentially equal radiation and reflection path and 30 will reduce the walking spot effect mentioned above, when alignment of the optical elements is correct. s

At the side of the illumination assembly a similar configuration may be applied. In an embodiment of the present invention the illumination assembly is configured to move the position of the illumination assembly focal point during scanning of the sensor surface at varying angles of incidence. The movement of the illumination assembly focal point, for instance by moving 5 the position of the second optical element (and/or other elements of the illumination assembly), may be accomplished by any suitable means. For instance, the second optical element may be attached to a pivot arm. When the movement of the focal point is such that this position of the focal point is essentially aligned 10 with the first optical element focal plane, then the light entering the first optical element remains parallel (during a stepwise change of the angle of incidence).

It is to be noted that movement of the position of the illumination assembly focal point generally results in a movement 15 of the image on the sensing element. This movement may be at least partly compensated for by a suitable movement of the sensing element, the third optical element or both the sensing element and third optical element. In specific embodiments of the present invention the position of the third optical element and/or the 20 sensing element is changed so as to minimize the movement (walking spot effect) of the image on the sensing element.

In order to correct for perspective distortion the third optical element, the sensing element and the first optical element are essentially maintained in Scheimpflug condition 25 during a sensor surface scan. In a similar way one or more parts of the illumination assembly can be moved to maintain its optical elements in Scheimpflug condition. For instance, if the light source of the illumination assembly comprises a tiltable mirror for controlling the angle of incidence, the tiltable mirror, the 30 second optical element and the first optical element may be arranged to essentially maintain the Scheimpflug condition ) during the scanning process, i.e. during varying the angle of incidence by variation of the tilt angle of the mirror.

8

In an embodiment of the present invention the apparatus comprises a frame having a tiltable pair of scissors/frame elements at which the illumination element and sensing element and/or the first and third optical element are attached. The 5 illumination and first optical element and the sensing element and third optical element on the other hand may be attached to the pair of scissors tiltable frame elements so that tilting the frame element results in a tilting movement of both the illumination and sensing elements and the optical elements. The !0 illumination / sensing element and optical elements may also be attached to separate tiltable frame elements. This makes it possible to move the sensing element and third optical element independently in Scheimpflug condition at both optical paths.

According to another aspect of the present invention an 15 apparatus for surface plasmon resonance (SPR) scanning is provided (preferably in accordance with the apparatus described above), the apparatus comprising: - a sensor assembly comprising: - a first optical element, substantially transparent 20 to light; - a SPR sensor element comprising a thin layer of conductive material, at least partially provided at the sensor surface of the first optical element; an illumination assembly for the illumination of the 25 sensor surface of the first optical element at varying angles of incidence with a substantially collimated light beam, - a detector assembly for the spatially resolved acquisition of a light property, for instance the intensity, of light reflected at the sensor surface of the first optical element at 30 varying angles of incidence, the detector assembly comprising a sensing element for sensing the image of the illuminated sensor 1 surface and a third optical element; wherein the third optical element, the sensing element and the first optical element are 9 positioned in Scheimpflug position.

For instance, the detector assembly and/or illumination assembly may be arranged so that an imaginary axis extended from the image plane at the sensor surface, an imaginary axis extended 5 from the optical element, orthogonal to its optical axis, and an imaginary axis extended from the sensing element, orthogonal to the optical axis of the sensing element, intersect in essentially one common point {herein also referred to as the (virtual) Scheimpflug point).

10 More generally, the Scheimpflug point is the position wherein the imaginary axis extending from the image plane at the sensor surface, the imaginary axis extended from the optical element, orthogonal to its optical axis, and the imaginary axis extending from the sensing element, orthogonal to the optical 15 axis of the sensing element, intersect.

In an embodiment of the invention the light source of the illumination assembly comprises a mirror to illuminate the sensor surface, wherein the mirror, the second optical element and the first optical element are positioned in Scheimpflug position. The 20 positioning of one or more of the elements may be accomplished in many ways. In one particularly useful embodiment the apparatus further comprises: - a support element arranged so as to be movable along a guide extending along an imaginary axis extended from the image plane 25 at the sensor surface, - a first support arm connected to the sensing element, - a second support arm connected to the third optical element; wherein the first and second support arms are pivotably connected 30 to the support element.

The Scheimpflug point is always on the line extended from the image plane of the sensor surface. Accordingly, the support element is movable along the axis extended from the image plane 10 and it should bo possible to find a position along the guide wherein the support elements may bring the sensing element and both optical elements in the Scheimpflug state.

A similar construction may be provided at the illumination 5 side of the apparatus. For instance, the apparatus may comprise: - a support element arranged so as to be movable along a guide generally extending along an imaginary axis extended from the image plane at the sensor surface, - a first support arm connected to the mirror, 10 -a second support arm connected to the second optical element; wherein the first and second support arms are pivotably connected to the support element.

The arms enable the mirror and the second optical element 15 to be tilted easily. In an embodiment wherein the support arms are pivotable with respect to a common pivot point (and the support element is movable in line with the sensor element), the individual movements of the mirror and second optical element and/or the individual movements of the sensing element and the 20 third optical element may be made to correspond to the displacements needed to keep the illumination assembly and/or the detector assembly in Scheimpflug configuration. For instance, the apparatus may comprise a drive construction for driving the support element to and forth across the guide. The apparatus may 25 further comprise a controller for controlling the drive means, for instance controlling the movement of the support element so that the position of the pivot of the support arms is automatically caused to coincide with the actual position of the Scheimpflug point.

30 The illumination assembly may further comprise an angle controller for controlling the tilt angle of mirror and or thereby ! indirectly controlling the angle of incidence of the light beam striking the sensor surface. When the Scheimpflug point moves 11 towards or away from the first optical element, for instance when the angle controller causes the angle of incidence to change, the controller may cause the support element to follow this movement in an attempt to keep the Scheimpflug condition.

5 In some of the embodiments the second and/or third optical element is a lens. In other embodiments the second and/or third optical elements comprise one or more pinholes,optical fibres or similar optics. In an embodiment of the present invention the second optical element is comprised of an essentially 10 non-transparent component provided with a plurality of pinholes.

The pinholes may be displaced to their respective positions so as to set the position of the second element focal point. More specifically, to set the focal point from which the light is directed (in a divergent manner) to the first optical element.

15 In other embodiments the pinholes may be selectively made transparent or non-transparent to displace the position of the second element focal point. This can be accomplished by arranging light sources, for instance LED's, behind the pinholes and by selectively turning on and off the light sources. In case the 20 first optical element is a hemispherical prism the pinholes may be situated at a virtual hemispherical focus plane relative to the optical centre of the prism. In this way a substantially parallel light beam may be present in the first optical element, for different angles of incidence.

25 Alternatively or additionally use can be made of optical fibres which are configured to provide for a divergent light beam.

In embodiments of the present invention the light source and second optical element are combined into essentially a component comprising a plurality of optical fibres. The optical fibres may 30 be selectively and subsequently switched on and off, for instance using a suitable controller for controlling the fibre, in order ! to displace the position of the second element focal point.

An advantage of the above-referenced embodiments may be that 12 no moving parts and/or drive means are needed to displace the focal point from which the light propagates in a divergent manner towards the first optical element. Furthermore, the speed of angle scanning may be increased relative to the embodiments using 5 mechanical positioning means (for example means for tilting the tiltable mirror).

In an embodiment of the invention the SPR sensor element comprises an array of regions of interest (ROI's) to be scanned with an angle of incidence from a range of angles of incidence 10 and to be imaged on the sensing element. For instance, the sensor element may be spotted with one or more different ligands, the spots forming the regions of interest to be scanned.

In an embodiment the apparatus comprises a fluidic system for delivering and exposing a sample medium to at least the sensor 15 element. The fluidic system may comprise one or more flow cells are cuvettes in which the medium to be tested can be accumulated.

In embodiments of the invention the conductive material comprises a metal, for instance silver, gold, copper, titanium or chromium.

20 In a further embodiment the first optical element and, preferably, the second and third optical elements, are made of glass. In a preferred embodiment the apparatus has the so-called Kretschmann configuration wherein the metal film is evaporated or sputtered onto the glass block. The light is illuminating from 25 the glass and an evanescent wave penetrates through the metal film.

The light source may be a light emitting diode (LED) mounted on an optical fibre acting as a pinhole. Preferably, the inner core of such optical fibre has a diameter of less than 1 mm, even 30 more preferably less than 200 micrometer. In another embodiment the light source comprises a mirror reflecting light from an array 1 of light emitting diodes (LED's).

In an embodiment the first optical element is optically 13 matched to a disposable sensor element, preferably the hemispherical lens itself, using an optogel, refractive index matching oil or other means for optical connection to the disposable sensor element.

5 In operation, the first optical element may be horizontally oriented and the sensor element may be arranged at the top side of the first optical element. This allows the measurement of gravitational processes of particles in the liquid and to get rid of air bubbles more easily.

10 According to another aspect of the invention a method for surface plasmon resonance (SPR) scanning is provided, the method comprising: - angle scanning a surface of an SPR sensor element provided at the sensor surface of a first optical element by illuminating 15 the sensor surface at varying angles of incidence with a substantially collimated light beam; - measuring a light property, for instance the intensity, of light reflected at the sensor surface by sensing the image of the illuminated sensor surface, received from a third optical 20 element, by a sensing element; the method further comprising: - adapting the position of at least one of the sensing element and third element during scanning so as to focus the reflected light in a focal point located at both the first focus 25 plane of the first element of the sensor assembly and the third focal plane of the third element of the detector assembly.

According to another aspect of the invention a method of surface plasmon resonance (SPR) scanning, is provided, the method comprising: 30 - angle scanning a surface of an SPR sensor element provided at the sensor surface of a first optical element by illuminating ! the sensor surface at varying angles of incidence with a substantially collimated light beam 14 - measuring a light property, for instance the intensity, of light reflected at the sensor surface by sensing the image of the illuminated sensor surface, received from a third optical element, by a sensing element; 5 the method further comprising: - adapting the position of the illumination assembly focal point during scanning of the sensor surface at varying angles of incidence so as to essentially align this position with the first optical element focal plane.

10 Further characteristics, advantages and details of the present invention will become apparent from the following description of several embodiments thereof. Reference is made to the annexed drawings, wherein:

Figure 1A is a schematic view of a part of an embodiment of 15 the SPR angle scanning apparatus wherein the present invention is applied;

Figure IB is enlargement of a part of figure 1A showing the conical and cylindrical light beams directed towards the sensor surface; 20 Figure 2 is a side view of the embodiment of figure 1;

Figure 3 is a top view of the embodiment of figures 1 and 2;

Figure 4 shows a SPR curves associated with a plurality of regions of interest (ROI's) resulting from a scan in accordance 25 with the present invention;

Figure 5 is a side view of the embodiment of figure 1, wherein the camera and lens are tilted to restore the Scheimpflug condition;

Figure 6 is a schematic view of a further embodiment of the 30 invention, wherein the illumination assembly focus point is displaced by movement of the combined optical element and light 4 source in order to maintain a parallel light beam inside the first optical element during at least a part of the scanning procedure; 15

Figure 7 is a schematic view of a further embodiment, wherein the illumination assembly focus point is moved by movement of an aperture;

Figure 8 is a schematic view of a further embodiment of the 5 invention, wherein the displacement of the illumination assembly focus point is realised by controlling a plurality of light sources arranged behind a plurality of apertures; and

Figure 9 is a schematic view of a further embodiment of the present invention, wherein the displacement of the illumination 10 assembly focus point is realized by selectively turning on and off a plurality of optical fibres;

Figure 10 is a schematic view of an example of a mechanical construction that is used to keep the sensing element, preferably also the third optical element, in Scheimpflug arrangement; and 15 Figure 11 is a schematic side view of a scissor-like construction carrying the optical elements in accordance with a further embodiment of the present invention.

An SPR scanning device 1 (figures 1-3), for instance a biosensor for determining information about the kinetics of 20 biomolecular interactions, in the above-mentioned Kretschmann configuration may comprise a sensor assembly 3 interacting with the medium to be scanned, an illumination assembly 9 for illuminating the sensor assembly 3 and a detector assembly 20 for detecting the influence of the biomolecular interactions on the 25 light illuminated on the sensor assembly 3.

The sensor assembly 3 comprises a generally hemispherical prism 4, for instance made of glass or any other suitable optically transparent material. The generally flat upper surface 5 of the glass hemisphere 4 is coated with a thin layer 6 of 30 conductive material, for instance gold. The thickness of the conductive layer typically is approximately 30-60 nm. The thin ' layer 6 is located between two media with different refractive indices. At the one side, the glass hemisphere 4, and at the other 16 side another media, for example a carrier liquid or a gas. The thin layer 6 forms a sensor element for sensing the interactions of the liquid or gas with one or more regions (spots) on the sensor surface.

5 The carrier liquid or gas is contained in a fluidics system for back and forth flow of the medium. A fluidics system may comprise one or more flow cells to enable interactions to occur at the surface of the sensor element. Numerous different types of fluidics systems are known, for instance serial flow cell 10 systems, independent flow cell systems and hydrodynamic addressing flow cell system. However, since fluidics systems as such are known in the art, a detailed description thereof is not needed for understanding the present invention.

The refractive index of the hemisphere 4 is required to be 15 higher than the refractive index at the other side (sensor surface side) of the conductive layer 6 e.g. water. At the other side of the layer 6 specimens (8) are present that are to be monitored by the SPR process. These specimens (8) may influence the refractive index at this side of the conductive layer 6. The 20 influence on the refractive index can be determined and may characterize the interactions occurring at the sensor surface.

The illumination assembly 9 comprises a narrow band light source, for instance halogen light with a bandpass (BP) filter, an LED with or without BP, a superluminescent LED, a laser made 25 non-coherent by fast rotating transparent medium or any other suitable means that couples light into a light guide 15. The light leaving the light guide 15 is collected by a collimator 11 that collimates the incoming light and projects the collimated light onto a p-polarizer 12. Optionally the light is subjected to a band 30 pass filtering process in a band pass filter (not shown in the drawings). The narrow band p-polarized (possibly band limited) 1 light is projected on a mirror element 13. The mirror element 13 is pivotably attached to a frame (cf. figure 11) may be tilted 17 between different positions (orientations) to vary the angle at which the reflected light is directed to a second optical element 14. Figure 1 shows the mirror in a first orientation (I), in a second orientation (II) and a third orientation (III).

5 In the embodiment shown in figures 1 and 2 the second optical element 14 is a lens 14, for instance an achromatic lens. In this configuration the scanning focal point of figure 1 is created by the illumination path consisting of focusing a collimating beam in such a way that the focal point of the second optical element 10 intersects the focal plane of the hemisphere. More specifically, lens 14 refracts the incoming collimated light beam and the resulting converging light beam is focussed in a focal point 30.

The light ??reflected off the mirror 13 and refracted by the lens 14 is then refracted into a parallel beam 35 by the hemisphere 15 4. The parallel beam 35 strikes the surface 40 (figure 2) at an angle of incident (og) large enough (more than 40 degrees (gas phase) or even more than 60 degrees (liquid phase)to cause total reflection off the surface 40. The reflected parallel light beam 36 is refracted at the water/air-hemisphere interface and 20 focussed into a focal point 50. A third optical element 21 of the detector assembly 20 converges the incoming light into a collimated beam 53 again. The collimated beam 53 is projected onto the sensing surface of a sensing element comprising a light sensitive array, such as a CCD/CMOS camera 22.

25 Before the SPR scanning is started the optical elements are arranged so that expected SPR dips are within a predefined scan range (angle offsetting phase). The optical elements need to be kept in Scheimpflug during the angle offsetting phase, for instance by using the scissor construction as described herein.

30 Then the SPR scanning device 1 is calibrated. The pivotable mirror 13 is first tilted away from lens 14 and surface 40, such that light from light source 10 does not strike the surface 40. With camera 22 the amount of remnant light in the SPR scanning device 18 1 is determined and the "null"-level of the output of camera 22 is set.

In a second step the mirror 13 is tilted such that light from the light source 10 is reflected of the mirror 13 through lens 5 14 and the hemisphere 4 to strike the surface 40 of the sensor element 39. As mentioned earlier, the angle of incidence (oti) of the light 35 striking the surface 40 is such that total reflection (TIR) occurs at the surface 40. By means of lens 21 the light reflected off the surface 40 is imaged at the surface of camera 10 22. A physical property, for instance the intensity, of the light reaching the camera 22 can be determined from the output of camera 22.

At a specific angle of incidence of the incident light 35 an interaction occurs between the incident photons and the free 15 electrons in the thin conductive layer 6 forming the sensor element 39. This interaction results in the creation of an evanescent wave in the layer of gold 114. In other words, incident photons are absorbed creating plasmons in the thin layer 6. The absorption of photons results in a reduced amount of light 20 reflecting off the surface 40, which reduction is detected by the sensor 22.

Any material present in the band of approximately half the wavelength of the applied light above the thin layer 6 (for instance, 300 nm in this particular embodiment), for example 25 specimens (8), may influence the refractive index at that side of the thin layer 6. If, for example, the binding of antigens (6) to antibodies (8) is to be monitored, antibodies (8) are applied to the thin layer 6. Antigens (6) are exposed to the antibodies (8) and will bind to the antibodies ¢8) over time. This process 30 influences the refractive index at this side of the thin conductive layer 6. Changes in refractive index cause the angle ' at which maximum plasmon generation occurs to change. By monitoring this change in angle over time, a measurement of the 19 binding rate is acquired. This change in angle is monitored by repeatedly measuring the amount of reflected light at different angles from a range of angles of incidence and determining the angle at which a minimum of reflected light is measured.

5 Figure 4 shows a plurality of typical SPR curves generated during scans of a scanner operating in accordance with the present invention. The mirror 13 in the scanner 1 is adjusted repeatedly in order to realize the angles of incidence one by one. At each angle the reflected light intensity of every region of interest 10 is measured and recorded. The horizontal axis 100 represents the angle of incidence. The scale in the example of figure 4 runs from -2000 millidegree till +2000 millidegree, but is alterable by the user. The zero at the axis corresponds to the middle of the scan range that was set for the scan using the optical assembly 15 construction. This means the angles on the axis 100 are offset and the zero does not correspond to an angle of incidence of 0 degrees. The vertical axis 101 represents the reflected light intensity. The data points 102 in the graph consist of recorded reflected light intensities at the angle of incidence the 20 measurements were taken. A smooth curve 103 has been plotted to fit the data points 102. In this particular example the data points 102 actually fit very well to the curve 103 and the minimum 104 can be calculated. In a similar way other data points 104 of the scan, associated with different regions of interest on the 25 sensor surface, fit to further curves 105.In general different position on the sensor surface provide different reflection curves. Since the light beam impinging on the sensor surface is parallel to a great extent, the dips in the SPR curves 103-104 almost perfectly align.

30 In other examples the data points 102 might be scattered alongside the curve 103 to some extent. In these examples use can ‘ be made of curve-fitting techniques, such techniques as such being well known in the art.

20

Scanning can be performed continuous with instant grabbing images at certain angles or discontinuous, eg. when an optical fibre assembly blink subsequently at fixed angles, or scanner position is stopped at fixed angles before grabbing the 5 reflectivity image.

Referring to figures 1 and 2, the light beam 35 projected onto the sensor surface 40 is a collimated light beam if the focal point 30 of the light 34 refracted by the lens 14 is caused to coincide with the plane of focus 37 of the hemisphere 4. The plane 10 of focus 37 (cf. Figure 2) describes a virtual hemisphere relative to the central midpoint of the hemisphere 4, the virtual hemisphere having a radius equal to the focal distance associated with this optical element. Furthermore, since use is made of P-polarised light, only the intersection of the virtual 15 hemispheric focal plane 37 and a polarization plane perpendicular to the hemisphere is relevant. This intersection provides a focus line (i.e. a p-focus circle) extending on the virtual plane of focus 37 of the hemisphere, on which the light from the second optical element (i.e. the lens 14) is to focus to ensure that the 20 light striking the sensor surface 40 is fully collimated.

As is indicated in more detail in figure IB, the cone-shaped light beam 34 of the light originating from the focal point 30 in its original position (shown in continuous lines) is refracted into a cylinder-shaped light beam 35, The beam 35 is a beam of 25 parallel light. At different angles of incidence the cone-shaped light beam is caused to originate from a different focal point, for instance a focal point 30' moved upward along the focal plane of the hemisphere 4 (shown in dotted lines) or a focal point 30'' moved downward along the same focal plane. The movement of the 30 focal point causes a similar movement of the image of the cone light beam on the surface of the hemisphere 4 (denoted in figure · IB by a small double arrow). When during scanning of the sensor surface, i.e. during illumination of the sensor with different 21 angles of incidence, the focal point 30 is shifted in this manner, the illuminated part or area of the sensor surface 40 remains essentially stationary. If during scanning the focal point 50 of the detector assembly is moved in a corresponding manner, the 5 illuminated part or area of the camera 22 remains essentially stationary as well.

Referring to figure IB, the cylindrical light beam 35 "pivots" as it were around an imaginary pivot axis 38 at the sensor surface. This may result in a reduction or even prevention of the 10 movement of the image on the sensor surface during the scanning operation.

The above movement of the focal point 30 may create complete blackening of the image (SPR condition over the whole surface area, as can be observed from figure 4 showing multiple SPR curves 15 obtained from various regions of interest. The SPR dip positions are almost equal).

Similarly, at the detector assembly 20 side, the light beam 36 reflected by the sensor element 39 and refracted by the hemisphere 4 (i.e. light beam 46 leaving the hemisphere 4) is 20 focussed at a focal point 50. The reflected parallel cylindrical beam will refract to a cone into the focal point. In order to ensure that the light reaching the camera 22 is fully collimated, the focal point 50 is to be exactly aligned with the virtual hemispherical focus plane 37 of the hemisphere 4 (or, more 25 precisely, with the above-identified p-focus-circle).

Accordingly, if the spherical lens 21 of the detector assembly 20 is arranged relative to the hemisphere 4 such that the focal point 50 is exactly at the focal point of the lens 21, then the light beam 46 is refracted in such a way by the lens 21 that the 30 resulting light beam 47 received by the camera 22 is a parallel light beam.

If, for instance due to the tilting of the mirror 13 during the scanning operation from tilt position I to tilt position II

22 (figure 2) the point of focus 30 moves away from the hemispherical plane of focus 37 of the hemisphere 4, a corresponding move of the focal point 50 at the detector side of the apparatus will occur. The result may be that the beam 47 reaching the camera 22 5 is not exactly collimated (parallel) anymore and that the image of the sensor surface 40 projected onto the camera 22 is somewhat shifted relative to the earlier image (i.e. the image acquired when the mirror was in its original tilt position I). Therefore the locations of the spots 6 imaged on the camera 22 in the new 10 situation (tilt position II) do not exactly correspond to the original position (tilt position I).

In embodiments of the invention the position (location and orientation) of the illumination side optics (i.e. the lens 14 and the mirror 14) is changed so that de focal point 30 is caused 15 to remain somewhere at the plane of focus 37 of the hemisphere 4 , In an embodiment the position change is only performed in the angle offsetting phase. When in the actual scanning phase the optics remain stationary. In other embodiments the position change may be performed both in the angle offsetting phase and 20 the scanning phase.

According to an embodiment of the present invention, means are provided to effect the above mentioned position change. For instance, the lens 14 may be moved mechanically to a new position wherein it is able to focus the light beam 34 on the plane of focus 25 37. For instance, the lens 14 may be mounted to a scissor construction (cf. figure 11).

Similarly, at the side of the detector assembly 20, the light beam 4 6 leaving the hemisphere 4 is focussed at a focal point 50 which should be exactly aligned with the hemispherical focus 30 plane 37 of the hemisphere 4. When the lens 21 is arranged at the focal distance relative to the hemisphere 4 such that the focal point of the lens 21 exactly coincides with the focal point 50, then the light beam 46 may be refracted in such a way by the lens 23 21 that the resulting light beam 47 is perfectly collimated.

However, if, for instance, due to the tilting of the mirror 13, the point of focus 50 has first moved away from the hemispherical plane of focus 37 and has subsequently been moved 5 back onto the plane of focus 37 by a movement of the illumination side optics, the position of focal point 50 has been shifted along the plane of focus 37 . The position of the focal point may be moved and set by changing the optical configuration in the angle offsetting phase. The result of this shift may be that the light 10 beam 47 reaching the camera 22 is not exactly collimated (parallel) anymore. The effect may be that the image of the sensor surface 40 projected onto the camera 22 is somewhat shifted relative to the earlier image (i.e. the image acquired when the mirror was in its original orientation I) . Therefore the position 15 of the spots 8 imaged on the camera 22 (spots 19 in figure 3) in the new situation (II) would not exactly correspond to the original position (in situation I).

In order to keep a perfectly collimated beam of light, in accordance with embodiments of the invention, the positions of 20 the one or more elements of the detector assembly 20 should be altered so that the focal point of the spherical lens 21 and the focal point of the hemisphere 4 coincide again. This could be accomplished by mechanical means (not shown in the drawings.

To further improve the quality of the image on the 25 camera 22, the optical elements at the detector assembly side should be arranged (oriented) to comply with the so-called Scheimpflug principle. In the situation shown in figure 2, the spherical lens 21, camera 22 and sensor element 39 are in the Scheimpflug condition (i.e. in a condition wherein the 30 Scheimpflug principle is complied with). In other words, the imaginary tangent line 60 extended from the lens plane 31 of the lens 21, the imaginary tangent line 62 of the camera plane 63 of the camera 22 and the imaginary tangent line 68 extended from the 24 sensor element 39 (as is shown in figure 2) intersects in one common point, the Scheimpflug intersection point 65. In this condition the image of the planar surface 40 of the sensor element 39 on the camera 22 is in focus.

5 A similar configuration can be accomplished at the illumination side of the apparatus. Figure 2 shows that the imaginary tangent line 68 of the lens plane 69 of the lens 14, the imaginary tangent line of the mirror 13 (in the tilt position I) and the imaginary tangent line 68 extended from the sensor 10 element 39, intersect in one common point of intersection or Scheimpflug intersection point 66. In this condition the image of the mirror surface of the mirror 13 on the sensor surface 40 can be made completely in focus.

When the mirror 13 is tilted from the tilt position I to tilt 15 position II, the Scheimpflug intersection point 66 is shifted in direction R (figure 2} to a new Scheimpflug point 66' . Therefore, in order to keep the illumination assembly in Scheimpflug condition, the lens 14 should be tilted somewhat, as is indicated with dotted line 68'.

20 Similarly at the detector assembly side, the

Scheimpflug point 65 is shifted (R2) to a new Scheimpflug point 65'. This means that the camera 22 and the spherical lens 21 should be rotated in order to bring the intersection point of lines 60' and 62' into correspondence with the new Scheimpflug 25 point 65', as is shown in figure 5. The situation wherein the Scheimpflug condition is restored is shown in figure 5.

Generally the lens 21 is positioned closer to the line 68 than the camera 22. Accordingly, the rotation angle βχ between lines 60 and 60' generally is smaller than the rotation angle β2 30 between lines 62 and 62' (β2 = 0,5 times βχ, for instance). This means that the camera needs to be rotated less than the spherical lens, at least during the actual mirror scanning process. In other situations, for instance during the angle offsetting procedure, 25 the camera may need to be rotated more than the spherical lens.

The rotation of the camera and spherical lens during the angle offsetting procedure is described more detailed in connection with figure 11.

5 In other embodiments of the invention only one of the camera/mirror and the spherical lens is rotated. Other embodiments only tilt the camera position during angle off-set and not during mirror scanning. All other embodiments of combinations of with or without tilting the illumination path and 10 /or detection path can be considered and can be assumed according to the invention. Although the Scheimpflug condition is not reached to its full extent in these embodiments, the quality of the image on the camera 20 may improve considerably.

In further embodiments of the present invention the 15 Scheimpflug orientation of the camera and/or the lens 21 is accomplished by a mechanical construction. Referring to figure 10 the mechanical construction may comprise a support element 150 that may be forced to move along a guide 151 (for instance a rail) extending along the earlier mentioned tangent line 68 of the 20 sensor element 39. A first support 152 arm may be connected to camera 22. The spherical lens 21 may be connected to the same support arm 152. In the embodiment of figure 10 a separate support art 153 is provided to connect the spherical lens 21 to the support element 150. If the support arms are both hingedly attached to 25 the support element at one common point, the optical elements 22, 21 can easily be held in a correct Scheimpflug condition by simply moving the support element along the guide. Using this mechanical construction along a guide a change in the off-set position will result also in an automatic change of camera and lens in a correct 30 tilted position according to the Scheimpflug condition.

In further embodiments the illumination assembly and/or the ’ detection assembly comprises an element provided with at least one aperture which is a hole or an opening through which light 26 travels. More specifically, the aperture is the opening or pinhole that determines the cone angle of the bundle of light rays that come to a focus in the image plane. The aperture determines how collimated the rays admitted to the first optical element are.

5 This has a positive influence on the appearance at the image plane. By changing the aperture position in the focal plane, a cone of light is generated. The light travels along the optical axis to the optical element and once arrived inside the optical element remains highly parallel. Additionally a parallel 10 (cylindrical) beam may be ref lected from the sensor surface . This may create a reflected parallel cylindrical beam which is transformed to a cone of light which travels to the second focal point. From the second focal point a reversed cone of light travels to the lens. Scanning of the coned light will occur over 15 the lens and an image is formed at a distinct position from this lens. The changed distance of travelled light from each point of the surface of the sensor surface forces the sensing element (camera) and lens both in a suitable relative angle (in accordance with the Scheimpflug condition). The tilted sensing element and 20 lens position may equalize the distance to get for each point on the sensor surface a sharp image on the sensing element (camera) .

Figure 6 illustrates a further embodiment of the present invention. The diverging light beam for illumination of the hemisphere 4 is generated in this embodiment by an optical fibre 25 115. The fibre acts as a waveguide to transmit light between the two ends of the fiber. At the proximal end of the fibre 115 a light source 10 is connected. At the distal end 116 of the optical fibre a diverging light beam 117 is generated. The diverging light beam is directed towards the hemisphere 4. In this configuration the 30 illumination assembly focal point 118 is situated at or close to the end 116 of the optical fibre. During scanning the focal point ‘ 118 may be displaced (P6 - P7) by a displacement unit (not explicitly shown, for instance a frame driven by one or more 27 electric motors or a similar construction) to coincide with the above-references P-focus circle in order to maintain a parallel beam inside the hemisphere 4.

In another embodiment shown in figure 7 the second optical 5 element is a non-transparent plate 120 provided with an aperture 121. The plate 120 may be illuminated by a remote light source 122, for instance one or more LED lights. The light source in combination with the plate generates a diverging light beam 123 having a focal point 124 at or close to the aperture 121. By moving 10 the aperture of the place the position of the illumination assembly focal point 124 move be suitable placed on the p-focus circle 125.

Referring to figure 8 an embodiment in shown wherein the second optical element comprises a plate 130 shaped so as to 15 coincide with the focus plane 37 (more specifically, the p-focus line 125) of the hemisphere 4. The plate 130 is provided with a plurality of apertures 131-133, arranged so as to coincide with the p-focus circle 125. Behind the apertures 131-133 a number of light elements, for instance LED's 134-136, are arranged that can 20 be selectively switched on and off by a controller 137. By controlling the light elements the apertures may be lighted consecutively so that a diverging light beam 137 may be generated from different positions (and corresponding different angles of incidence on the sensor surface) relative to the hemisphere. 25 Accordingly, the light beam 137 may be used to scan the sensor surface of the hemisphere 4 at different angles of incidence without any actual movement of the optical element.

Referring to figure 9 a further embodiment is shown. In this embodiment use is made of a plurality of light fibres 140, 141, 30 142. The distal ends of the fibres arranged at the p-focus circle 125. A controller 139 is connected to fibres 140-142 which acts as a light source to selectively generate a light beam 143 from one of the fibres 140-142. In this embodiment displacement of the 28 illumination assembly focal point 144 can be accomplished easily by switching the fibres 140-142 consecutively on and off.

In the embodiments described above the optical elements are arranged to correspond to the Scheimpflug condition during the 5 scanning operation (i. e. during the angle of fsetting phase and/or actual scanning phase). The Scheimpflug condition should also be maintained when the entire optical constructions has been displaced, for instance when the apparatus is rotated in order to enable different kind of measurements to take place. For 10 instance, in a gas measurement set-up the measurements are to be performed at an angle of about 40 degrees, while in the liquid measurement set-up the measurements should be performed at an angle of about (at least) 65 degrees. Furthermore, if different types of prism material is used, for instance SF10 instead of BK7, 15 other starting angles should be set.

Figure 11 shows another embodiment of the present invention.

In this embodiment the apparatus comprises a frame having a tiltable pair of scissors/frame elements at which the illumination element and sensing element and/or the first and 20 third optical element are attached. The optical components 4,13,14,21,22 are mounted on a generally rhomboidal pivotable arm construction or scissor construction 155.

Construction 155 comprises two pivotable arms 160, 161 for attaching the tiltable mirror 13 and the camera 22, respectively.

25 Arms 160, 162 may be rotated along a pivot 170. In order to force both arms 160,162 to pivot simultaneously, further arms 164,166 are provided. At one end arms 164,166 are pivotably mounted to arms 160,162 respectively, while at the opposite end arm 164,166 are pivotable attached to one another.

30 Assuming the position of the hemisphere 4 is stationary, then rotation (Rn) of a spindle 156 results in the upward (Pu) 1 or downward (PD) movement of the pivot 158 and therefore in a corresponding movement of the optical arms 160,162. If the length 29 of the arms 160,162 are suitably chosen, the operation of the spindle causes the focal points of the illumination assembly and the detector assembly to move substantially along the focal plane of the hemisphere 4.

5 Tilting the frame elements (arms) results in a tilting movement of both the illumination and sensing elements and the optical elements. More specifically, the arm construction 155 enables the set of optical components to be aligned and arranged in focus as a whole, without the need to align each of the optical 10 elements individually. The alignment can be performed in the angle offsetting phase and/or in the actual scanning phase.

Especially in the angle offsetting procedure (involving relatively large angles) the arm construction 155 may enable the illumination assembly and detector assembly to be positioned 15 easily while keeping the optical elements at the right distance from the hemisphere.

The illumination and first optical element on the one hand and the sensing element and third optical element on the other hand may be attached to the pair of scissor like tiltable frame 20 elements so that tilting the frame element, for instance in the angle offsetting phase, results in a tilting movement of both the illumination and sensing elements and the optical elements. In other embodiments the illumination element and first optical element and/or the sensing element and third optical element may 25 each be attached to a separate tiltable frame element. This makes it for instance possible to move the sensing element and third optical element independently in Scheimpflug condition at both optical paths.

If the optical elements were to be attached fixedly to the 30 arms 160,162, then the operation of the spindle 156 might cause the elements to lose their optimal Scheimpflug condition. In i: order to restore the Scheimpflug condition, use can therefore be made of the detector side construction 150 of figure 10 (and a 30 corresponding construction for the illumination side of the system).

The present invention is not limited to the specific embodiments described herein; the rights sought are defined by 5 the following claims, within the scope of which many modifications can be envisaged.

Claims (41)

    5
  1. An apparatus for surface plasmon resonance (SPR) scanning, the apparatus comprising: - a sensor assembly comprising: - a first optical element, which is substantially transparent to light and defines a first optical element focal plane and a sensor surface; - an SPR sensor element comprising a thin layer of conductive material, at least partially provided on a sensor surface of the first optical element; - an exposure assembly arranged to direct light diverging from a focal point of the exposure assembly to the sensor surface of the first optical element, the light arriving on the sensor surface at varying angles of incidence as a substantially collimated light beam; a detector assembly for the spatially determined acquisition of a light property, for example the intensity of light reflected on the central surface of the first optical element at varying angles of incidence, the detector assembly comprising a detection element for observing an image of the exposed sensor surface and a third optical element with a third optical element focal surface; wherein the detector assembly is adapted to adjust the position of at least one of the sensing element and third element during the angle scanning to focus the reflected light at a focal point located on both the first focal plane of the first element of the detector assembly as well as on the third focal plane of the third element of the detector assembly.
  2. 2. Device as claimed in claim 1, comprising a frame with a pivotable frame element to which the viewing element and / or the third optical element are attached, wherein the pivoting element is designed around the viewing element and / or third optical element in the plane of incidence to swing.
  3. Apparatus as claimed in claim 1, wherein the sensing element is pivotally mounted on the third optical element. 20
  4. 4. Device as claimed in any of the foregoing claims, wherein the exposure assembly comprises a light source and a second optical element, wherein the second optical element defines an exposure assembly 25 focal plane.
  5. The device of claim 4, wherein the focal distance of the second element corresponds to the focal distance of the third element. 30
  6. Device for surface plasmon resonance (SPR) scanning, preferably a device according to one of the preceding claims, the device comprising: - a sensor assembly comprising: - a first optical element, which is substantially transparent to light and which has a first optical element element defines a focal plane and a sensor surface 5; - an SPR sensor element comprising a thin layer of conductive material, at least partially provided on the sensor surface of the first optical element; 10. an illumination assembly arranged to direct divergent light from an illumination assembly to the sensor surface of the first optical element, the light arriving on the sensor surface at varying angles of incidence as a substantially collimated light beam; - a detector assembly for the spatially determined acquisition of a light property, for example the intensity of light reflected on the sensor surface of the first optical element at varying angles of incidence, wherein the detector assembly comprises an observation element for observing an image of the exposed sensor surface and a third optical element comprises focal plane; wherein the exposure assembly is configured to move the position of the exposure assembly focal point during scanning of the sensor surface at varying angles of incidence such that this position is substantially aligned with the first optical element focal plane.
  7. 7. Device as claimed in claim 6, wherein the exposure assembly is designed to move the exposure assembly focal point along the first optical element focal plane in such a way that displacement of the exposed area of the sensor surface is reduced or even prevented.
  8. 8. Device as claimed in claim 6 or 7, wherein the detector assembly is adapted to change the position of the third optical element and / or of the detecting element in order to at least partially control the displacement of the image on the detecting element as a result of displacement of the position focal point of the exposure assembly.
  9. 9. Device as claimed in claim 8, wherein the position of the third optical element and / or the detecting element is changed to minimize the displacement of the image on the detecting element.
  10. 10. Device as claimed in any of the foregoing claims, wherein the third optical element, the observation element and the first optical element 25 are kept substantially in Scheimpflug condition during a sensor surface scan.
  11. 11. Device as claimed in any of the foregoing claims, wherein the light source of the exposure assembly comprises a pivotable mirror for controlling the incident angle.
  12. The device of claim 11, wherein the mirror, the second optical element, and the first optical element are held substantially in Scheimpflug condition during a sensor surface scan. 5
  13. 13. Device for surface plasmon resonance (SPR) scanning, preferably a device according to any one of the preceding claims, wherein the device comprises: - a sensor assembly comprising: a first optical element, substantially transparent to light; - an SPR sensor element comprising a thin layer of conductive material, provided at least partially on the sensor surface of the first optical element; - an exposure assembly for illuminating the sensor surface of the first optical element at varying angles of incidence with a substantially collimated light beam; 20. a detector assembly for the spatially determined acquisition of a light property, for example the intensity of light reflected on the sensor surface of the first element at varying angles of incidence, the detector assembly comprising a sensing element for observing the image of the exposed light sensor surface and a third optical element; wherein the third optical element, the viewing element and the first optical element are positioned in a Scheimpflug position.
  14. Device as claimed in any of the foregoing claims, wherein the detector assembly and / or exposure assembly are arranged such that an imaginary axis extending from the image plane on the sensor surface, an imaginary axis extending from the optical element perpendicular to the optical axis thereof, and an imaginary axis extending from the viewing element, orthogonal to the optical axis of the viewing element, intersect in substantially a common point 10
  15. 15. Device as claimed in any of the foregoing claims, wherein the light source of the exposure assembly comprises a mirror for illuminating the sensor surface and wherein the mirror, the second optical element and the first optical element are positioned in Scheimpflug position.
  16. An apparatus according to any preceding claim, comprising: 20. a support element arranged to be movable along a guide extending along an imaginary axis in line with the image surface of the sensor surface; - a first supporting arm connected to the sensing element; - a second support arm connected to the third optical element; wherein the first and second support arms are rotatably connected to the support element. 30
  17. Device as claimed in any of the foregoing claims, comprising: - a support element that is arranged to be movable along a guide which extends along an imaginary axis in line with the image surface of the sensor surface; 5. a first support arm connected to the mirror; - a second support arm connected to the second optical element; wherein the first and second support arms 10 are rotatably connected to the support element.
  18. 18. Device as claimed in any of the foregoing claims, comprising a frame with a pivotable pair of scissor frame elements on which the exposure and detecting element, preferably also the first and third optical element, are mounted.
  19. 19. Device as claimed in claim 18, wherein the scissor frame elements are designed to keep the second and / or third optical element in Scheimpflug condition during a pivoting movement.
  20. 20. Device as claimed in any of the claims 15-19, wherein the support arms are pivotable relative to a common pivot axis.
  21. 21. Device as claimed in any of the claims 15-20, comprising a drive construction for driving the support element along the guide and a control unit for controlling the drive construction to arrange the support element at the Scheimpflug point.
  22. Device as claimed in any of the foregoing claims, wherein the exposure assembly comprises an angle control means for controlling the angle of incidence of the light beam incident on the sensor surface.
  23. 23. Device as claimed in any of the foregoing claims, wherein the second and third optical elements are formed by one or more spherical lenses and / or pinholes (pin holes).
  24. Device as claimed in any of the foregoing claims, wherein the second optical element is a substantially non-transparent component which is provided with a number of pinholes, which pinholes can be made selectively transparent or non-transparent around the position of the second element move focal point.
  25. 25. Device as claimed in any of the foregoing claims, wherein the light source and the second optical element are combined to substantially form a component comprising a number of optical fibers, in which optical fibers can be selectively and successively switched on and off for a position move focal point of the second element.
  26. 26. Device as claimed in any of the foregoing claims, wherein the second optical element is a light-transparent pinhole or an optical fiber and wherein the second optical element is arranged to be moved along an optical plane in order to focus the position of the second element move point.
  27. Device as claimed in any of the foregoing claims, wherein the first optical element is a substantially hemispherical prism.
  28. 28. Device as claimed in claim 25 or 26, wherein the pinholes and / or optical fibers are placed on a virtual hemispherical focal plane with respect to the optical center of the first optical element.
  29. An apparatus according to any one of the preceding claims, wherein the SPR sensor element comprises a row of regions of interest (ROIs) of interest to be scanned in a range of incidence angles and to be imaged on the sensing element.
  30. The device of any one of the preceding claims, comprising a fluid system for supplying and exposing a sample medium to at least the sensor element.
  31. The device of any one of the preceding claims, wherein the sensor element is speckled with one or more different ligands, the speckles forming areas of interest to be scanned. 30
  32. The device of any preceding claim, wherein the light source is a light emitting diode (LED) mounted on an optical fiber that serves as a pinhole.
  33. Device as claimed in any of the foregoing claims, wherein the sensor element is removably attached to the first optical element.
  34. An apparatus according to any one of the preceding claims, wherein the first optical element is optically matched with a disposable sensor element, preferably using an optogel or an oil with a matching refractive index.
  35. The device of any one of the preceding claims, wherein the first optical element is disposable.
  36. An apparatus according to any one of the preceding claims, wherein the light source comprises a mirror that reflects light from a light emitting diode (LEDs).
  37. Apparatus as claimed in any of the foregoing claims, wherein in use the first element is horizontally oriented and the sensor element is arranged on the top side of the first optical element.
  38. 38. Method for surface plasmon resonance (SPR) scanning, the method comprising: - scanning a surface of an SPR sensor element provided on the sensor surface of the first optical element by illuminating the sensor surface at varying angles of incidence with a substantially collimated light beam; - measuring a light characteristic, for example the intensity, of light reflected on the sensor surface by observing the image of the exposed sensor surface received from a third optical element by the detecting element; the method further comprising: - adjusting the position of at least one of the sensing element and a third element during scanning to focus the reflected light at a focal point located on both the first focal plane of the first element of the first element of the sensor assembly and the third focal plane of the third element of the detector assembly.
  39. A method for surface plasmon resonance (SPR) scanning, preferably a method according to claim 38, the method comprising: 20. the angle scanning of a surface of the SPR sensor element provided on a sensor surface of the first optical elements by directing the sensor surface at varying angles of incidence with a substantially collimated light beam; 25. measuring a light property, for example the intensity, of light reflected on the sensor surface by observing the image of the exposed sensor surface received from a third optical element, by a sensing element; The method further comprising: - adjusting the position of the focal point of the exposure assembly during scanning of the sensor surface at varying angles of incidence to substantially train this position with the first optical element focal plane.
  40. 40. A method according to claim 38 and / or 39, wherein an apparatus according to any one of the preceding claims 1-37 is used.
  41. Use of an apparatus according to any of the claims 1-37.
NL2005902A 2010-11-25 2010-12-22 Method and apparatus for surface plasmon resonance angle scanning. NL2005902C2 (en)

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US20040235177A1 (en) * 2000-12-13 2004-11-25 Philippe Guedon Method for characterising a surface, and device therefor
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NL1022916C2 (en) * 2003-03-13 2004-09-14 Ssens B V Device is for investigating a thin layer structure on a surface by making use of superficial plasmon resonance
US20090213382A1 (en) * 2003-08-01 2009-08-27 Ge Healthcare Bio-Sciences Ab Optical resonance analysis unit
US20100128269A1 (en) * 2006-06-16 2010-05-27 University Of Washington Miniaturized surface plasmon resonance imaging system
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