JPH10239233A - Surface plasmon sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow change in incident angle of the light beam on a sensor surface with ease. SOLUTION: Relating to the sensor, a hologram optical element comprising lens function and aberration correction function is used as an input part 13 and an output part 14 of a coupler means 10. A light source optical means 20 and a photo-detecting means 30 are placed on stages 26 and 35, respectively, allowing them to move in X direction on the stages 25 and 35, respectively. Here, an light beam L projected from the light source optical means 20 is incident on the input part 13 and converged on a specified point of an interface 4 between a sensor substrate 2 and a metal film 3, thus incident at a specified incidence angle. By interlocking the light source optical means 20 with the photo-detection means 30 to move them in approaching direction or receding direction, the incident angle of the light beam L at the specified point is changed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface plasmon sensor for quantitatively analyzing a substance in a sample by utilizing the generation of surface plasmons, and more particularly, to a surface plasmon sensor having improved light beam coupling means. It is about.

[0002]

2. Description of the Related Art In a metal, free electrons vibrate collectively to generate a compression wave called a plasma wave. And, the quantization of this compression wave generated on the metal surface is
It is called surface plasmon.

Conventionally, various surface plasmon sensors for quantitatively analyzing a substance in a sample by utilizing the phenomenon that surface plasmons are excited by light waves have been proposed.
Among them, a particularly well-known one uses a system called a Kretschmann configuration (see, for example, JP-A-6-167443).

A surface plasmon sensor using the above system basically includes a prism, a metal film formed on one surface of the prism and brought into contact with a sample, a light source for generating a light beam, and a light source for applying the light beam to the prism. An optical system which passes through the interface between the prism and the metal film so as to obtain various angles of incidence, and a light which can detect the intensity of the light beam totally reflected at the interface at various angles of incidence. And a detecting means.

In order to obtain various angles of incidence as described above, a so-called goniometer (see, for example, JP-A-6-50882) for rotating a light beam irradiation system is used, or various types of light beams are used. An optical system is used in which a relatively thick light beam is incident so as to be focused at the interface so that a component incident at an angle is included. In the former case, the light beam whose reflection angle changes with the deflection of the light beam is detected by a small photodetector that moves synchronously with the deflection of the light beam, or by an area sensor that extends along the direction of change in the reflection angle. Can be detected. On the other hand, the latter case can be detected by an area sensor extending in a direction in which all light beams reflected at various reflection angles can be received.

When a light beam is incident on a metal film at an incident angle θ equal to or larger than the total reflection angle, a “smear wave” called an evanescent wave is generated in the metal film on the reflection surface. The evanescent wave has an electric field distribution in the sample in contact with the metal film, and surface plasmons are generated at the interface between the metal film and the sample. When the wave vector of the evanescent wave generated by the incidence of the p-polarized light beam on the metal film is equal to the wave vector of the above-described surface plasmon and the wave number matching is established, both are in a resonance state, and the light energy is changed to the surface plasmon. The plasmon is excited by the migration. At this time, the intensity of the totally reflected light is significantly reduced due to the transfer of light energy.

Therefore, in the above-mentioned surface plasmon sensor, the intensity of the light beam totally reflected by the metal film is measured for the light beam incident on the metal film at various incident angles θ, so that the reflection is performed. An incident angle θ _sp (total reflection elimination angle) at which a phenomenon in which the intensity significantly decreases occurs, and the total reflection elimination angle θ _sp and the wave number vector K _{1 of the} incident light are obtained.
, The resonance wave number K _sp is derived from the relationship K _sp = K ₁ sin θ _sp . When the wave number K _{sp of the} surface plasmon is known, the dielectric constant of the sample is obtained. That is, assuming that the angular frequency of the surface plasmon is ω, the speed of light in vacuum is c, and the dielectric constants of the metal and the sample are ε _m and ε _s , respectively, the following relationship is obtained.

[0008]

(Equation 1)

[0009] Knowing the dielectric constant epsilon _s of the sample, since it is found the concentration of a specific substance in the sample based on a predetermined calibration curve or the like, after all, the total reflection overcome angle the reflected light intensity decreases theta _sp
, A specific substance in the sample can be quantitatively analyzed.

[0010]

In the conventional surface plasmon sensor of the type described above, since a prism is used for coupling a light beam to an interface, multiple reflection interference inside the prism causes noise. There is a problem that the analysis accuracy is low. Further, under the condition that the incident angle of the beam is large, there is a disadvantage that the size of the optical system becomes large.

In addition, when a rectangular prism or a right-angle prism is used, when the incident angle of the light beam to the prism is changed in order to make the light beam enter the interface at various incident angles, aberration occurs and the light beam There is a problem that the focusing position is shifted, and a complicated optical axis adjusting mechanism is required to solve this problem. In addition, the rotation of the irradiation optical system for changing the angle of incidence of the light beam on the prism involves a complicated structure.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and can reduce the size of an optical system without causing multiple reflection interference of light. It is an object of the present invention to provide a surface plasmon sensor capable of obtaining various angles of incidence with respect to.

Further, in view of the fact that it is desired to measure a plurality of samples under the same conditions, or to obtain two-dimensional physical property information of a substance in a sample, a light beam of a light beam is similarly generated by a simple optical system. It is an object of the present invention to provide a surface plasmon sensor that can obtain various incident angles with respect to an interface and can perform one-dimensional or two-dimensional scanning.

[0014]

The surface plasmon sensor of the present invention comprises a transparent substrate having a predetermined refractive index, and
A sensor unit including a metal film disposed on one surface side of the transparent substrate and being brought into contact with a sample, and the other surface side of the transparent substrate opposite to the one surface is substantially equal to the predetermined refractive index. Coupling means arranged with a matching liquid having the same refractive index interposed therebetween, transmitting a light beam incident from an input portion formed in a part thereof and entering an interface between the transparent substrate and the metal film. In other words, a coupler that transmits a light beam totally reflected at the interface and emits the light beam from an output portion formed in another portion, wherein the light beam transmitting portion has a refractive index substantially equal to the predetermined refractive index Means, and a light source for generating a light beam, the light beam generated from the light source is incident as parallel light from the input unit, the intensity of the light beam totally reflected at the interface and emitted from the output unit Detect In the surface plasmon sensor, the inputs and outputs is characterized in that comprising a holographic optical element.

In the above-mentioned surface plasmon sensor, the hologram optical element focuses the incident parallel light beam at a predetermined position, and the light source approaches the predetermined position within a plane parallel to the interface. A light source moving means for moving the light source in a direction or in a direction away from the interface, by moving the light source so that the light beam is incident on different positions of the input unit, and the light beam is transmitted to the interface at the predetermined position. The light may be incident at various angles of incidence.

The hologram optical element may have a lens function and an aberration correction function, and may focus the light beam at the predetermined position by using both functions. Alternatively, the hologram optical element may have a cylindrical lens function and an aberration correction function. And the two functions may be used to focus the light beam at the predetermined position. In the case of the former,
The "predetermined position" is a dot, and in the latter case, the "predetermined position" is a line.

That is, the "lens function" means a function of converging an incident light beam to one point, and the "cylindrical lens function" has a refractive index only in one direction and only has a light in that direction. It is a function to converge the beam.

Further, there are provided: positioning means for positioning the sensor unit so that the distance between the transparent substrate and the coupler means is always constant; and sensor moving means for moving the sensor unit in a predetermined direction. The interval may be filled with the matching liquid.

An incident position moving means for moving an incident position of the light beam at an input portion so that the light beam is sequentially incident on the interface at different positions in the same direction as the axial direction of the cylindrical lens function. May be provided.

The “axial direction of the cylindrical lens function” refers to an axis perpendicular to a plane having a refractive power.
The "different portions in the same direction as the axial direction" is not necessarily limited to the portions along the axial direction, but it is sufficient if there is a positional change in the axial direction.

In a surface plasmon sensor having both the sensor moving means and the incident position moving means, a predetermined direction in the sensor unit and an axial direction of the cylindrical lens may intersect each other. desirable.

The "incident position moving means" may be means for moving the incident position by deflecting a light beam by an optical system having a galvanometer mirror or the like, or mechanically moving the light source itself. The incident position may be moved.

Here, "coupler means" is a general term for means for coupling a light beam incident on the interface to conditions for generating surface plasmon resonance.

[0024]

According to the surface plasmon sensor of the present invention, since a hologram optical element is used for coupling a light beam to the sensor portion, it is possible to prevent multiple reflection interference generated when a prism is used for coupling. . Further, as compared with the case where a prism is used, the size of the apparatus can be reduced, and the adjustment of the optical axis becomes easy.

The hologram optical element focuses the incident parallel light beam at a predetermined position, and moves the light source in a plane parallel to the interface in a direction approaching or away from the predetermined position. Since the light source moving means is provided, various incident angles can be obtained at predetermined positions simply by moving the light source.

By using a lens or a hologram optical element having a cylindrical lens function and an aberration correcting function, a light beam can be focused to a predetermined position at an interface without aberration.

Further, by providing at least one or both of the sensor unit moving means and the incident position moving means, a sample extending in one-dimensional or two-dimensional direction;
Analysis of a plurality of samples arranged in one-dimensional or two-dimensional directions can be efficiently performed.

[0028]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows one side shape of a surface plasmon sensor according to a first embodiment of the present invention.

As shown in the figure, the basic configuration of the surface plasmon sensor is as follows. A sensor unit 1 having a metal film made of gold, silver, etc., which is brought into contact with a sample S to be measured, and a sensor supporting the sensor unit 1 A coupler means provided with a support means for disposing a refractive index matching oil (matching liquid) with respect to the sensor unit; a light beam is generated; and the light beam is made incident on the coupler means. It comprises a light source optical means 20 and a light detecting means 30 for measuring the intensity of a light beam emitted from the coupler means 10.

Next, a detailed configuration of each unit in the first embodiment of the present invention will be described.

The sensor unit 1 is formed by forming a metal film 3 of gold, silver or the like on a sensor substrate 2 which is a transparent substrate made of glass or the like having a uniform thickness. In addition, the glass substrate 2
When a metal film 3 such as gold is formed thereon, the glass substrate 2
This is performed after chromium is arranged on the upper side by about 1 nm in advance. This facilitates the formation of the metal film 3 and suppresses peeling. In the analysis using a surface plasmon sensor, generally, a binding reaction film (antigen (or antibody)) is formed on the metal film 3 and an antigen-antibody reaction that selectively responds to a specific substance is used, and the specific reaction is performed. The amount of antibody (or antigen) that is specifically adsorbed is measured as a change in incident angle. Here, the metal film 3 and a bonding reaction film (not shown) formed on the metal film 3 are integrally referred to as a sensor film.

The coupler means 10 comprises a cell 12 made of glass having a recess 11 formed on the side facing the sensor unit 1, an input section 13 made of a hologram optical element formed on the other surface of the cell 12, and And an output unit 14. Further, the coupler means 10 is provided with a sensor support means (sensor attachment) 15 for supporting the sensor unit 1 at a part thereof, and the distance between the sensor substrate 2 and the cell 12 is always constant by the sensor attachment 15. So that the sensor unit 1 is supported. The space between the sensor substrate 2 and the coupler means 10 is filled with a refractive index matching oil 9. Coupler means 10 including sensor substrate 2 and input / output units 13 and 14 composed of hologram optical elements
In addition, the refractive index matching oil 9 having substantially the same refractive index is used to prevent reflection of the light beam at each interface.

The light source optical means 20 comprises a light source 21 composed of a semiconductor laser or the like for generating a light beam L, and a lens 22 for emitting the light beam L as parallel light. The light source optical unit stage 25 is movable on the stage 25 in the X direction. The light beam L emitted from the light source 21 is p-polarized by a polarizer (not shown), is incident from the input unit 13, and is incident on the interface 4 between the sensor substrate 2 and the metal film 3 at a predetermined incident angle θ. At this time, it is possible to change the incident angle θ to various angles by moving the light source optical means 20 in the X direction on the light source optical means stage 25. Here, the movement in the X direction is equivalent to the movement in the direction parallel to or away from the focal position of the light beam at the interface 4 in a plane parallel to the interface 4. The incident angle θ of the light beam L to the interface 4 is set so as to be changed in an angle range equal to or larger than the critical angle for total reflection, so that the light beam L is totally reflected at the interface 4.

The hologram optical element used as the input unit 13 and the output unit 14 has a lens function for converging the light beam and an aberration correction function, and is designed to narrow the incident parallel light beam to one point. It was done.
For example, as shown in FIG. 2, an optical path indicated by a dotted line 23 is set so that parallel light incident at a predetermined angle is focused on a predetermined point P on the interface. As described above, since the parallel light beams incident from the different incident positions on the input unit 13 are all focused on a predetermined point, the incident position of the parallel light beam L is shifted from the position X1 to the position X2 in the X direction. By moving, the incident angle of the light beam at the predetermined point P can be changed from θ ₁ to θ ₂ . Therefore, a light beam can be incident at various incident angles at a predetermined point on the interface simply by moving the light source optical means in parallel.

As the light detecting means 30, for example, a photodiode, a two-segmented photodiode described in Japanese Patent Application No. 8-109366, a photodiode array, a CCD line sensor or the like is used. Since the position of the light beam L emitted from the emission HOE also changes in accordance with the change in the incident position of the light beam L, the light detection means 30 is installed on the light detection means stage 35, The movable stage 35 is movable in the X direction. Light source optical means 20 and light detection means 30
Means that the light beam L emitted from the light source optical means 20 and reflected at the interface 4 is constantly emitted by being moved in a direction approaching or apart from each other on the respective stages 25 and 35 in conjunction with each other. Detecting means 30 can detect.

Hereinafter, the sample analysis by the surface plasmon sensor having the above-described configuration will be described. The sample S to be analyzed is placed in a state of contacting the metal film 3. Light beam L generated by light source optical means 20 and set to p-polarized light
Is incident on the coupler means 10 from the input unit 13, passes through the coupler means 10 and the matching oil 9, and is incident on the interface 4 between the metal film 3 and the sensor substrate 2. As described above, the light beam L is moved to the interface 4 by moving the light source optical means 20 in the X direction on the light source optical means stage 25.
At various angles of incidence θ. The light beam L is totally reflected at the interface 4 and is emitted from the output unit 14, and the emitted light beam L is detected by the light detection means 30.

The light detection signal output by the light detecting means 30 indicates the intensity I of the totally reflected light beam L for each incident angle θ to the interface 4, and the difference between the reflected light intensity I and the incident angle θ The relationship is generally as shown in FIG.

Here, light incident at a specific incident angle (total reflection elimination angle) θ _sp excites surface plasmons at the interface between the metal film 3 and the sample S, and the reflected light intensity I of this light is Declines sharply. Therefore, the total reflection elimination angle θ _sp can be determined by using the light detection signal S output from the light detection means 30, and the specific substance in the sample S can be quantitatively analyzed based on the value of the total reflection elimination angle θ _sp. Can be. The reason is as described in detail above.

Next, an embodiment of the two-dimensional scanning type surface plasmon sensor of the present invention will be described. FIG. 4 shows one side shape of the surface plasmon sensor according to the first embodiment of the present invention. FIGS. 5 and 6 show the shape of the plasmon sensor shown in FIG. And the shape viewed from the direction of arrow B. However, FIG.
In FIG. 4, the light source optical means is omitted, and FIG. 4 is a partial sectional view. Hereinafter, only the configuration and operation different from the first embodiment will be described,
A detailed description of the same configuration and operation portion will be omitted.

In the sensor unit 1, a metal film 3 of gold, silver or the like is formed on a sensor substrate 2 which is a transparent substrate made of glass or the like having a uniform thickness, and a waterproof wall 5 is provided so as to surround the metal film 3. The lower part of the sensor unit 1 is immersed in the matching oil 9 during measurement.

As shown in FIG. 5, in the surface plasmon sensor according to the present embodiment, the coupler means 10 is formed so as to extend in one direction.
15 is formed along the concave portion 11 of the coupler means 10. The sensor attachment 15 includes a transport rail (not shown), and the sensor unit 1 is moved along the transport rail, that is, along the sensor attachment 15.
Is movable. A transport shaft 6 is fixed to the sensor unit 1, and the transport shaft 6 is sandwiched between rollers 7. The sensor unit 1 is configured to be moved in the direction of the arrow X with the rotation of the rollers 7. That is, in the present embodiment, the sensor unit moving means is configured by the transport rail, the transport shaft 6 and the rollers 7 provided in the sensor attachment 15.

The light source optical means 20 comprises a light source 21 composed of a semiconductor laser or the like for generating a light beam L, a cylindrical lens 22, and a telecentric scanner 23 which is a light deflecting means using a telecentric optical system (FIG. 6).
reference). The telecentric scanner 23 includes a galvanomirror 24 disposed at a focal position of the cylindrical lens 22.
, And a cylindrical lens 25. The light beam L emitted from the light source 21 is focused on a galvanometer mirror 24 by a cylindrical lens 22, is reflected by the galvanometer mirror 24, and is incident on a cylindrical lens 25 of a telecentric scanner 23. In the cylindrical lens 25, the light beam L is converted into a parallel light, and is incident from the input unit 13. In the present embodiment, the hologram optical element constituting the input unit 13 and the output unit 14,
It has a cylindrical lens function and an aberration correction function, and the light beam incident from the input unit 13 is focused in one direction at the interface between the metal film 3 and the sensor substrate 2.
In the present embodiment, it has a cylindrical lens function having a refractive power only in a plane parallel to the paper surface in FIG.
The direction perpendicular to the paper is the axial direction of the cylindrical lens function. Note that this axial direction is the same as the Y direction in FIG. 6, and the incident position of the light beam L on the input unit 13 is translated in the Y direction as the galvanomirror 24 swings.

Instead of using a telecentric scanner, which is a light deflecting means, as the means for moving the light beam incident position, for example, the light source optical means stage 25 is arranged on a stage movable in the Y direction, and is moved in the Y direction. By moving the stage 25, the incident position of the light beam can be changed to Y.
It may be configured to move in parallel in the direction.

The arrangement of the light detecting means 30 is controlled so as to always receive the light beam reflected by the interface 4 and emitted from the output section 14.

Hereinafter, a sample analysis by the surface plasmon sensor having the above configuration will be described. First, a plurality of sample cells 8 containing different samples S ₁ , S ₂ , S ₃ ,... Are arranged on the sensor film, and each sample Sn (n = 1, 2,. The state is brought into contact with the film (see FIG. 7). FIG. 7B shows a cross section of FIG.

In this apparatus, the sensor unit 1 is intermittently transported in the X direction along the transport rail of the sensor attachment 15, and the light beam L is moved in parallel in the Y direction by the telecentric scanner 20, and the light beam is sequentially transmitted to each sample. L
And make each sample analyzed. The analysis of each sample is performed in the same manner as in the above-described first embodiment.
The light beam is incident on the sample at various angles of incidence while moving in the direction, and the intensity of the light beam totally reflected at the interface 4 is measured. As described above, by performing two-dimensional scanning so that a light beam is incident on each sample under the same conditions, analysis of a plurality of samples can be performed efficiently in a short time.

Since the light beam can be scanned two-dimensionally as described above, the present apparatus mounts a sample such as a gel sheet used for electrophoresis on the metal film 3 and The two-dimensional scanning can also be used to obtain two-dimensional physical property information of a substance to be analyzed distributed in a sample.

Further, as shown in FIG.
By setting a plurality of regions 3a and using a sensor film in which a different binding reaction film is formed in each region 3a and performing two-dimensional light beam scanning, different immune reactions etc. generated in each region are performed. Analysis can also be performed for each region.

The surface plasmon sensor according to another embodiment includes only one of the sensor unit moving means and the incident position moving means, and analyzes a plurality of samples arranged in a one-dimensional direction. Surface plasmon sensor.

[Brief description of the drawings]

FIG. 1 is a side view of a surface plasmon sensor according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining focusing of a light beam by a hologram optical element;

FIG. 3 is a graph showing a schematic relationship between an incident angle of a light beam in a surface plasmon sensor and a light intensity detected by a light detecting unit.

FIG. 4 is a side view of a surface plasmon sensor according to a second embodiment of the present invention.

FIG. 5 is a view of the surface plasmon sensor shown in FIG.

FIG. 6 is a view of the surface plasmon sensor shown in FIG.

FIG. 7 is a diagram showing a multi-channel sensor.

FIG. 8 is a view showing a sensor film divided into a plurality of regions.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sensor unit 2 Sensor board 3 Metal film 4 Interface 9 Refractive index matching oil 10 Coupler means 12 Cell 13 Input part 14 Output part 15 Sensor attachment 20 Light source optical means 23 Telecentric scanner 25 Light source optical means stage 30 Light detection means 35 Light detection Stage for means L Light beam

Claims (6)

[Claims] 1. A sensor unit comprising: a transparent substrate having a predetermined refractive index; a metal film disposed on one surface side of the transparent substrate and brought into contact with a sample; Is a coupler means disposed on the other surface side on the opposite side with a matching liquid having a refractive index substantially the same as the predetermined refractive index interposed therebetween, and a light beam incident from an input portion formed partially. Is transmitted to the interface between the transparent substrate and the metal film, the light beam totally reflected at the interface is transmitted, and the light beam is emitted from an output part formed in another part. A coupler having a refractive index substantially the same as the predetermined refractive index; and a light source for generating a light beam. The light beam generated from the light source is incident as parallel light from the input unit, and the interface is formed. With total reflection A surface plasmon sensor for detecting an intensity of a light beam emitted from the output unit, wherein the input unit and the output unit include a hologram optical element. 2. The hologram optical element focuses an incident parallel light beam at a predetermined position, and moves the light source in a direction parallel to the interface in a direction approaching the predetermined position or at a distance from the predetermined position. Light source moving means for moving the light beam in different directions of the input unit by moving the light source, and causing the light beam to enter the interface at different positions with respect to the interface at various positions. 2. The surface plasmon sensor according to claim 1, wherein the light is incident at an incident angle. 3. The hologram optical element according to claim 2, wherein the hologram optical element has a lens function and an aberration correction function, and focuses the light beam to the predetermined position by the two functions. Surface plasmon sensor. 4. The hologram optical element according to claim 2, wherein the hologram optical element has a cylindrical lens function and an aberration correction function, and focuses the light beam to the predetermined position by the two functions. Surface plasmon sensor. 5. A positioning unit for positioning the sensor unit so that a distance between the transparent substrate and the coupler unit is always constant, and a sensor unit moving unit for moving the sensor unit in a predetermined direction. 5. The surface plasmon sensor according to claim 4, wherein the gap is filled with the matching liquid. 6. An incident position moving means for moving an incident position at an input portion of the light beam such that the light beam is sequentially incident on a different portion of the interface in the same direction as the axial direction of the cylindrical lens function. The surface plasmon sensor according to claim 4, further comprising: