JP2003227792A - Sensor for utilizing total reflection attenuation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately measure the state of total reflection attenuation regardless of the refractive index of a sample in a sensor utilizing total reflection attenuation. <P>SOLUTION: In the sensor, light beams 13 are applied so that various incident angles can be obtained to an interface 10b between a dielectric block 10 and a metal film 12, the light beams 13 that are totally reflected from the interface 10b are detected by a photodiode array 17, and the characteristics of a sample liquid 11 are analyzed. In the sensor, the following dark line position adjustment operation is made before measurement. First, an incident angle control section 34 detects the profile of the light beams 13, thus obtaining the relative position of a dark line D for indicating the state of total reflection attenuation in the profile. A light source 14 and a condensing lens 15 are moved so that the dark line D is at the center of the profile, and an incident angle where the beams 13 enter the interface 10b is adjusted. Measurement can be made in a state where the dark line D is at the center of the profile regardless of the refractive index of the sample liquid 11. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor that utilizes attenuation of total reflection, such as a surface plasmon sensor that analyzes the characteristics of a substance in a sample by utilizing the generation of surface plasmons. The present invention relates to a sensor that uses attenuated total reflection to detect a dark line generated in measurement light by attenuation using a light detection means.

[0002]

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

Conventionally, various surface plasmon sensors have been proposed which analyze the characteristics of substances in a sample by utilizing the phenomenon that the surface plasmons are excited by light waves. Among them, one that is particularly well known is one that uses a system called Kretschmann arrangement (see, for example, JP-A-6-167443).

A surface plasmon sensor using the above system basically emits a light beam and a dielectric block formed in a prism shape, a metal film formed on one surface of the dielectric block and brought into contact with a sample. A light source to be generated, an optical system that causes the light beam to enter the dielectric block at various angles so that total reflection conditions can be obtained at the interface between the dielectric block and the metal film, and total reflection at the interface. The light detecting means for detecting the intensity of the light beam and the measuring means for measuring the state of surface plasmon resonance, that is, the state of attenuated total reflection based on the detection result of the light detecting means.

In order to obtain various incident angles as described above, a relatively thin light beam may be incident on the interface by changing the incident angle, or may be incident on the light beam at various angles. A relatively thick light beam may be incident on the interface in a convergent light state or a divergent light state so as to include the component. In the former case, the light beam whose reflection angle changes according to the change of the incident angle of the incident light beam is detected by a small photodetector that moves in synchronization with the change of the reflection angle, or the direction of change of the reflection angle. It can be detected by an area sensor extending along. On the other hand, in the latter case, each light beam reflected at various reflection angles can be detected by an area sensor extending in a direction in which all the light beams can be received.

In the surface plasmon sensor having the above structure, when a light beam is incident on the metal film at a specific incident angle θ _SP which is equal to or greater than the total reflection angle, an evanescent wave having an electric field distribution in the sample in contact with the metal film. Is generated, and surface plasmons are excited at the interface between the metal film and the sample by this evanescent wave. When the wave number vector of the evanescent wave is equal to the wave number of the surface plasmon and the wave number matching is established, the two are in a resonance state and the light energy is transferred to the surface plasmon, so that at the interface between the dielectric block and the metal film. The intensity of the reflected light sharply decreases. This decrease in light intensity is generally detected as a dark line by the light detecting means.

The above resonance occurs only when the incident beam is p-polarized. Therefore, it is necessary to set in advance that the light beam is incident as p-polarized light.

When the wave number of the surface plasmon is known from the incident angle θ _{SP at} which this attenuated total reflection (ATR) occurs, the dielectric constant of the sample can be obtained. That is, the wave number of the surface plasmon is K
_{Let SP be} the angular frequency of the surface plasmons be ω, c be the speed of light in a vacuum, ε _m and ε _s be the metal, and the permittivity of the sample respectively, and the following relationships are established.

[0009]

[Equation 1] If the permittivity ε _s of the sample is known, the concentration of the specific substance in the sample can be known based on a predetermined calibration curve, etc., so that the total reflection attenuation angle θ, which is the incident angle at which the reflected light intensity decreases, is eventually obtained.
By knowing _SP , it is possible to determine the characteristics related to the dielectric constant of the sample, that is, the refractive index.

In this type of surface plasmon sensor, the above-mentioned total reflection attenuation angle θ _SP is measured with high accuracy and a large dynamic range.
As disclosed in Japanese Patent Laid-Open No. 11-326194, it is considered to use an array of light detecting means. The light detecting means comprises a plurality of light receiving elements arranged side by side in a predetermined direction, and is arranged so that the components of the light beam totally reflected at various reflection angles at the interface are received by different light receiving elements. It is a thing.

In that case, there is provided a differentiating means for differentiating and outputting the photodetection signals output from the respective light receiving elements of the array of light detecting means with respect to the juxtaposed direction of the light receiving elements. In many cases, the characteristic related to the refractive index of the sample is obtained based on the output differential value, particularly the differential value corresponding to the dark line portion.

Further, as a similar sensor utilizing the attenuated total reflection (ATR), for example, "Spectroscopic Research" Vol. 47, No. 1 (1998), pages 21 to 23 and 26 to 27.
Leakage mode sensors described on the page are also known. This leaky mode sensor is basically formed by, for example, a dielectric block formed in a prism shape, a clad layer formed on one surface of the dielectric block, and formed on the clad layer and brought into contact with a sample. An optical waveguide layer, a light source for generating a light beam, and the light beam are incident on the dielectric block at various angles so that total reflection conditions are obtained at the interface between the dielectric block and the cladding layer. An optical system, a light detecting means for detecting the intensity of the light beam totally reflected at the interface, and a measuring means for measuring the excited state of the guided mode, that is, the attenuated total reflection state based on the detection result of the light detecting means. It is equipped with and.

In the leaky mode sensor having the above structure,
When a light beam is incident on the cladding layer through the dielectric block at an angle of incidence equal to or more than the total reflection angle, only light with a specific incident angle having a specific wave number is transmitted in the optical waveguide layer after passing through the cladding layer. It propagates in the guided mode. When the guided mode is excited in this manner, most of the incident light is taken into the optical waveguide layer, so that the total reflection attenuation occurs in which the intensity of the light totally reflected at the interface sharply decreases.
This decrease in light intensity is generally detected as a dark line by the light detecting means. Since the wave number of the guided light depends on the refractive index of the sample on the optical waveguide layer, the refractive index of the sample and the related characteristics of the sample are analyzed by knowing the above-mentioned specific incident angle at which attenuation of total reflection occurs. be able to.

The surface plasmon sensor and leak mode sensor described above are sometimes used in random screening to find a specific substance that binds to a desired sensing substance in the field of drug discovery research, and in this case, the thin film layer ( In the case of the surface plasmon sensor, it is a metal film, and in the case of the leaky mode sensor, the sensing substance is fixed on the cladding layer and the optical waveguide layer, and a solution of various substances (sample solution) is added onto the sensing substance, The above-mentioned differential value is measured every time a predetermined time elapses. If the added substance binds to the sensing substance, the binding causes the refractive index of the sensing substance to change over time. Therefore, by measuring the differential value for each elapse of a predetermined time, and by measuring whether or not there is a change in the differential value, whether the added substance and the sensing substance are bound, that is, the added substance It can be determined whether or not is a specific substance that binds to the sensing substance. In this case, both the sensing substance and the sample solution serve as the sample to be analyzed. Examples of such a combination of the specific substance and the sensing substance include an antigen and an antibody. As a specific measurement relating to such a substance, for example, the sensing substance is a rabbit anti-human Ig.
As the G antibody, there may be mentioned a measurement in which presence / absence of binding with a human IgG antibody in a subject is detected and a quantitative analysis thereof is performed.

In order to measure the binding state between the analyte and the sensing substance, it is not always necessary to detect the angle of the total reflection attenuation angle θ _SP itself. For example, it is also possible to add a sample solution to the sensing substance, measure the angle change amount of the total reflection attenuation angle θ _SP after that, and measure the binding state based on the magnitude of the angle change amount.

[0016]

FIG. 9 (a) is a simplified block diagram of a conventional surface plasmon sensor, and FIG. 9 (b) shows the incident angle θ of the light beam 13 on the interface 10b, The reflected light intensity I of the light beam 13 totally reflected at the interface 10b between the dielectric block and the metal film, detected by the photodiode array 17
It is a figure which shows the relationship with. Interface 10b of the dielectric block 10
In addition, since the light incident at the attenuated total reflection angle θ _SP excites surface plasmons at the interface between the metal film 12 and the sample 9, the reflected light intensity I of this light sharply decreases. This decrease in the reflected light intensity I is observed as a dark line D in the reflected light in FIG. Further, as shown in FIG. 9B, in the profile of the light beam 13, the reflected light intensity I is detected as a dark line in which the intensity I is greatly reduced. The attenuated total reflection state can be measured based on the reflection angle θ at which the reflected light intensity I is minimum at this dark line, that is, the attenuated total reflection angle θ _SP .

On the other hand, since various samples are used, their refractive indexes are different. For example, when a sample 9'having a refractive index greatly different from that of the sample 9 used in FIG. 9 is used, the position of the dark line D is largely deviated from the center of the light beam 13 as shown in (a) of FIG. It may happen. In such a case, the incident angle θ of the light beam 13 and
The relationship with the reflected light intensity I of the light beam 13 is as shown in FIG. 10 (b), and the dark line deviates from the central portion of the profile of the light beam 13, and the total reflection attenuation angle θ _SP is accurately determined. It may not be detected well, and the measurement accuracy may decrease.

The present invention has been made in view of the above circumstances, and provides a sensor utilizing attenuated total reflection capable of accurately measuring the state of attenuated total reflection regardless of the refractive index of a sample. That is the purpose.

[0019]

A first sensor utilizing attenuation of total reflection according to the present invention is a light source for generating a light beam, a dielectric block transparent to the light beam, and a dielectric block of the dielectric block. A thin film layer formed on one surface and brought into contact with a sample, and various incidents of the light beam to the dielectric block so that total reflection conditions can be obtained at the interface between the dielectric block and the thin film layer. An optical system that makes the light incident at an angle, a photodetection unit that detects the intensity of the light beam that is totally reflected at the interface, and a measurement unit that measures the state of attenuation of total reflection based on the detection result of the photodetection unit. In the sensor utilizing attenuation of total internal reflection, the profile of the light beam totally reflected at the interface is detected, the relative position of the dark line indicating the attenuation of total internal reflection in the profile is determined, and based on the relative position , The incident angle of the light beam is incident on the interface, and is characterized in that the position of the dark line further comprising an incident angle adjusting means for adjusting to come to substantially the center of the profile.

As such a sensor, the above-mentioned surface plasmon sensor using a metal film as the thin film layer, a clad layer formed on one surface of the dielectric block,
There is the above-mentioned leaky mode sensor which uses a layer formed of an optical waveguide layer formed on the clad layer as the thin film layer.

Further, "to detect the profile of the light beam totally reflected at the interface" means, for example, that a relatively thick light beam is made incident on the interface in a convergent light state or a divergent light state and at various reflection angles. An area sensor that extends in the direction in which the reflected angle changes can be detected by an area sensor that extends in the direction in which all reflected light beams are received, or a relatively thin light beam that changes the incident angle and is incident on the interface and that extends in the direction in which the reflection angle changes. Or a light beam whose reflection angle changes according to the change of the incident angle of the incident light beam is detected by a small photodetector which moves in synchronization with the change of the reflection angle.

As the incident angle adjusting means, one that adjusts the incident angle by moving the light source or the optical system can be used. Further, as the incident angle adjusting means, it is possible to use one that adjusts the incident angle by rotating the dielectric block with an axis perpendicular to the plane where the light beam is present as a rotation axis.

[0023]

The sensor utilizing attenuation of total reflection of the present invention obtains the relative position of the dark line in the profile of the light beam totally reflected at the interface, and based on this relative position,
By providing an incident angle adjusting means for adjusting the incident angle at which the light beam is incident on the interface so that the position of the dark line is approximately in the center of the profile, according to the refractive index of each sample,
Since the relative position of the dark line in the profile of the light beam can be adjusted, it is possible to accurately measure the attenuated total reflection state regardless of the refractive index of the sample.

When the incident angle adjusting means for adjusting the incident angle by moving the light source or the optical system is used, the incident angle can be adjusted with a simple structure.

When the incident angle adjusting means is one that adjusts the incident angle by rotating the dielectric block with the axis perpendicular to the plane in which the light beam is present as the axis of rotation, Since the incident optical path of the light beam does not change, adjustment can be easily performed.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The sensor utilizing attenuation of total internal reflection according to the first embodiment of the present invention is a surface plasmon sensor utilizing surface plasmon resonance, and FIG. 1 shows a side surface shape of the surface plasmon sensor.

This surface plasmon sensor has, for example, a dielectric block 10 having a shape in which a part of a roughly square pyramid is cut out, and one surface of the dielectric block 10 (upper surface in the drawing).
And a metal film 12 made of, for example, gold, silver, copper, aluminum or the like.

The dielectric block 10 is made of, for example, a transparent resin and has a shape in which the periphery of the portion where the metal film 12 is formed is raised, and this raised portion functions as a sample holding portion 10a for storing the sample liquid 11. To do. In this example, the metal film 12
The sensing substance 40 is fixed on the above, and the sensing substance 40 will be described later.

The dielectric block 10 constitutes a one-time-use measuring chip together with the metal film 12, for example, a table 41.
It is fitted and fixed in the chip holding hole 42 provided in the. After the dielectric block 10 is thus fixed to the table 41, the sample liquid 11 is dropped onto the dielectric block 10,
11 is held in the sample holder 10a.

The surface plasmon sensor of this embodiment is
In addition to the above dielectric block 10, one light beam
A light source 14 including a semiconductor laser for generating 13 and the light beam 13 are passed through the dielectric block 10 so that various incident angles can be obtained with respect to the interface 10b between the dielectric block 10 and the metal film 12. Condensing lens 15 as an optical system
And a photodiode array 17 for detecting the light beam 13 totally reflected at the interface 10b, and a photodiode array 17
To the differential amplifier array 18, the amplifier array 19 also connected to the photodiode array 17, the driver 20, and the signal processing unit 30 including a computer system and the like.
A display unit 31 connected to the signal processing unit 30 and a light source 14
And the condenser lens 15 is moved so that the light beam 13 moves to the interface 10b.
And an actuator 32 for changing the incident angle of the incident light.

The signal processing unit 30 is a measuring unit for performing actual measurement.
33, and an incident angle control unit 34 that performs control processing for adjusting the incident angle of the light beam 13 before actual measurement. Also, the light source 14, driver 20 and actuator
32 is connected to the signal processing unit 30.

The light beam 13 is directed to the interface 10 by the condenser lens 15.
Since it is focused on b, various incident angles θ with respect to the interface 10b
Will include the component that is incident at. This incident angle θ
Is an angle equal to or greater than the total reflection angle. So the light beam 13
Is totally reflected at the interface 10b, and the reflected light beam 13 has
Components that reflect at various reflection angles will be included.

The light beam 13 is incident on the interface 10b as p-polarized light. To do so, the light source 14
May be arranged so that the polarization direction thereof is a predetermined direction. Alternatively, the polarization direction of the light beam 13 may be controlled by the wave plate.

FIG. 2 is a block diagram showing the electrical construction of this surface plasmon sensor. As shown in the figure, the driver 20 includes the differential amplifiers 18 a, 18 a of the differential amplifier array 18.
Sample hold circuits 21a, 21b, 21c, ... for sampling and holding the outputs of b, 18c ..., Multiplexer 22, multiplexer 22 and sample hold circuit to which the outputs of these sample hold circuits 21a, 21b, 21c. Drive circuit 23 for driving 21a, 21b, 21c ...
Sample-hold circuits 24a, 24 for sample-holding the outputs of the amplifiers 19a, 19b, 19c ... Of the amplifier array 19.
b, 24c ..., these sample hold circuits 24a, 24
multiplexer 25 to which each output of b, 24c ...
Multiplexer 25 and sample and hold circuits 24a, 24b,
24c ... Driving circuit 26 for driving, A / D converter 27 for digitizing the output of multiplexer 22 or multiplexer 25 and inputting it to signal processing section 30, and driving circuit 23 based on an instruction from signal processing section 30. Or a controller 28 for operating 26.

The photodiode array 17, the amplifier array 19, the sample and hold circuits 24a, 24b, 24c ...
..., multiplexer 25, drive circuit 26, A / D converter 27,
The incident angle controller 34 and the actuator 32 function as the incident angle adjusting means of the present invention.

A sample analysis method using the surface plasmon sensor having the above structure will be described below. Sensing substance
After the sample liquid 11 is dropped on 40, a dark line position adjusting operation for adjusting the dark line position is performed before the measurement so that the dark line D generated by the attenuation of total reflection is located at the center of the profile of the light beam 13. First, the profile of the light beam 13 is detected, the relative position of the dark line D in this profile is determined, and the dark line D
The light source 14 and the condenser lens 15 are moved so that is positioned at the center of the profile, and the incident angle of the light beam 13 incident on the interface 10b is adjusted. The details of the dark line position adjusting operation will be described below.

First, as shown in FIG. 1, the light source 14 is driven so that the light beam 13 is emitted from the light source 14. The light beam 13 emitted from the light source 14 in a divergent state is converged on the interface 10b between the dielectric block 10 and the metal film 12 by the action of the condenser lens 15. Therefore, the light beam 13 includes components that are incident on the interface 10b at various incident angles θ. The incident angle θ is set to an angle equal to or larger than the total reflection angle. Therefore, the light beam 13 is totally reflected at the interface 10b, and the reflected light beam
13 includes components that reflect at various reflection angles.

After total reflection at the interface 10b, the light beam 13
It is detected by the photodiode array 17. The photodiode array 17 in this example comprises a plurality of photodiodes 17a, 17b, 17c, ... Arranged side by side in a row, and in the plane of the drawing of FIG. It is arranged so that the installation direction is substantially a right angle. Therefore, the different photodiodes 17a, 17b, 17c ... Receive the respective components of the light beam 13 totally reflected at various reflection angles at the interface 10b.

When performing the dark line position adjusting operation, the signal processing section 30 operates the drive circuit 26 via the controller 28. The outputs of the photodiodes 17a, 17b, 17c ... Are input to and amplified by the amplifiers 19a, 19b, 19c. The outputs of the amplifiers 19a, 19b, 19c ... Are sample and hold circuits 24a, 24b, 24, respectively.
The signal is sampled and held at a predetermined timing by c ... And is input to the multiplexer 25. Multiplexer 25
Are sample-and-holded amplifiers 19a, 19b, 19c
.. is input to the A / D converter 27 in a predetermined order. These outputs are digitized by the A / D converter 27 and input to the incident angle control unit 34 of the signal processing unit 30.

In the incident angle control section 34, the incident angle θ of the light beam 13 totally reflected at the interface 10b and the photodiode array 17 are determined.
The relationship with the reflected light intensity I detected in step 1 is obtained, and the pattern of the dark line D included in the profile of the reflected light intensity I of the light beam 13 is analyzed. The profile patterns are roughly classified into four patterns shown in (a) to (d) of FIG.

FIG. 3A shows the pattern A in which the dark line D is located at the center of the profile of the reflected light intensity I. Figure 3
(B) is a pattern B in which the dark line D deviates from the center of the profile to the left. FIG. 3C is a pattern C in which the dark line D deviates from the center of the profile to the right. FIG. 3D is a pattern D that occurs when the dark line D is not included in the profile, that is, when the dark line D cannot be observed because the position of the dark line D is largely displaced.

If the analyzed profile pattern is pattern A, it is not necessary to adjust the incident angle of the light beam 13 again, and the measurement is immediately started.

When the profile pattern is pattern B, the light source 14 and the condenser lens 15 are moved by the actuator 32 to change the incident angle at which the light beam 13 is incident on the interface 10b. That is, in the case of the pattern B, the light source 14 is placed at the position occupied by the dotted line in FIG.
And the condenser lens 15 is located. When the light source 14 and the condenser lens 15 are moved to the positions shown by the solid lines, the angle at which the light beam 13 is incident on the interface 10b changes, and the angle of the reflected light of the light beam 13 also changes. On the other hand, the total reflection attenuation angle θ _SP generated by the dark line D does not change, so the position of the dark line D does not change. That is, the profile of the light beam 13 changes in the direction shown by the arrow in FIG. Incident angle adjustment unit 34
Then, until the position of the dark line D is substantially in the center of the profile of the reflected light intensity I, as shown by the solid line in FIG.
The light source 14 and the condenser lens 15 are moved by the actuator 32. The measurement is started in a state where the profile pattern of the reflected light intensity I is the pattern A. The actuator 32 does not change the position where the light beam 13 is incident on the interface 10b but changes only the incident angle.
And the condenser lens 15 is moved.

When the profile pattern is pattern C, the actuator 32 moves the light source 14 and the condenser lens 15 in the opposite direction to the pattern B, and the incident angle at which the light beam 13 is incident on the interface 10b. Is changed, and the measurement is started with the profile changed to the pattern A.

When the profile pattern is pattern D, the display section 31 indicates that measurement is impossible. Alternatively, the light source 14 and the condenser lens 15 are moved within the maximum movable range to change the incident angle of the light beam 13 from the minimum angle to the maximum angle, and if the dark line D falls within the profile, the measurement is started, and the dark line D It may be displayed that the measurement is impossible unless is included in the profile.

When performing the actual measurement, the signal processing unit 30
Operates the drive circuit 23 via the controller 28. The outputs of the photodiodes 17a, 17b, 17c ... Are supplied to the differential amplifiers 18a, 18b, 18 of the differential amplifier array 18, respectively.
It is input to c ……. In the differential amplifier array 18,
The outputs of two photodiodes adjacent to each other are input to a common differential amplifier. Therefore each differential amplifier 18
The output of a, 18b, 18c ...
It can be considered that the photodetection signals output by 17a, 17b, 17c ... Are differentiated with respect to their parallel arrangement direction.

The outputs of the differential amplifiers 18a, 18b, 18c ... Are respectively held by the sample hold circuits 21a, 21b, 21c.
Are sampled and held at a predetermined timing by the ... And input to the multiplexer 22. The multiplexer 22 includes the sample-and-hold differential amplifiers 18a, 18b, 18c ...
The outputs of ... Are input to the A / D converter 27 in a predetermined order. The A / D converter 27 digitizes these outputs and inputs them to the measuring section 33 of the signal processing section 30.

FIG. 5 shows the light beam 13 totally reflected at the interface 10b.
Intensity of each incident angle θ and differential amplifiers 18a, 18b, 18c
FIG. 6 is a schematic diagram for explaining the relationship with the output of. Here, the relationship between the incident angle θ of the light beam 13 on the interface 10b and the light intensity I is assumed to be as shown in the graph of FIG.

As described above, the light incident on the interface 10b at the specific incident angle θ _SP is the metal film 12 and the sensing substance.
Since the surface plasmon is excited at the interface with 40, the reflected light intensity I of this light sharply decreases. That is, θ _SP
Is the attenuated total reflection angle, and the reflected light intensity I turns from decrease to increase at this angle θ _SP .

FIG. 5B shows the photodiode 17
a, 17b, 17c ... are shown in a line, and as described above, these photodiodes 17a, 17b, 17c are shown.
The position in the parallel direction of ...... uniquely corresponds to the incident angle θ.

Then, the photodiodes 17a, 17b, 17c
……, the parallel installation position, that is, the incident angle θ and the differential amplifier
The relationship between the outputs 18 ', 18b, 18c ... And the output I' (differential value of the reflected light intensity I) is as shown in FIG.

In the measuring section 33 of the signal processing section 30, based on the value of the differential value I'input from the A / D converter 27, the total reflection attenuation from the differential amplifiers 18a, 18b, 18c. Angle θ
_The differential value I ′ corresponding to _SP , which has the output closest to 0 (the differential amplifier 18d in the example of FIG. 5) is selected, and the differential value I ′ output by the selected one is displayed on the display unit. Display on 31. In some cases, there is a differential amplifier that outputs a differential value I ′ = 0, and in that case, that differential amplifier is naturally selected.

Thereafter, every time a predetermined time elapses, the differential value I'output from the selected differential amplifier 18d is displayed on the display unit 31.
Is displayed in. This differential value I ′ is the metal film of the measuring chip.
When the dielectric constant of the substance in contact with 12, that is, the refractive index changes, and the curve shown in FIG. 5A changes in the form of moving to the left and right, it rises and falls accordingly. Therefore, by continuously measuring the differential value I ′ with the passage of time, it is possible to investigate the change in the refractive index of the substance in contact with the metal film 12, that is, the change in the characteristic.

Particularly in this embodiment, the sample solution 11 is applied to the metal film 12.
The sensing substance 40 that binds to the specific substance in is fixed, and the refractive index of the sensing substance 40 changes according to the binding state thereof, so by continuously measuring the differential value I ′, the binding state You can check the state of change. That is, in this case, both the sample liquid 11 and the sensing substance 40 are the samples to be analyzed.

In order to investigate the change in the binding state between the specific substance in the sample liquid 11 and the sensing substance 40 with the passage of time, the differential value I'is obtained and displayed every time a predetermined period of time elapses. In addition, the difference ΔI 'between the differential value I' (0) measured first and the differential value I '(t) measured after the elapse of a predetermined time.
May be displayed in search of.

As is apparent from the above description, according to the sensor using attenuation of total reflection according to the present embodiment, the relative position of the dark line D in the profile of the light beam 13 totally reflected at the interface 10b is measured before the measurement. If the dark line is out of the center of the profile, the light source 14 and the condenser lens 15 are moved to adjust so that the position of the dark line is substantially in the center of the profile, regardless of the refractive index of the sample. Since the measurement can be started from the state where the dark line D always exists in the center of the profile of the light beam 13, the change in the refractive index of the substance in contact with the metal film 12, that is, the change in the characteristic can be accurately measured. You can Further, as in the present embodiment, when observing the change with time of the refractive index of the sensing substance 40, even if the refractive index changes with the passage of time, the dark line is completely removed from the profile of the light beam 13. There is almost no deviation, and accurate measurement can be performed until the end of measurement. In addition, using the actuator 32, the light source
Since the configuration is such that 14 and the condenser lens 15 are moved, the incident angle can be adjusted with a simple configuration. In addition,
In the present embodiment, the light source 14 and the condenser lens 15 are moved together, but when the adjustment angle is small,
The adjustment may be performed by moving either the light source 14 or the condenser lens 15, and the incident angle can be adjusted with a simpler configuration. Further, in the present embodiment, the incident angle of the light beam 13 is adjusted so that the position of the dark line D is at the center of the profile of the light beam 13, but the present invention is not limited to this, and the position of the dark line D is not limited to this. Is
Even if the profile is slightly deviated from the center, it may be close to the center so that the attenuated total reflection angle θ _SP can be accurately detected. In addition, for example, in consideration of the movement of the dark line D due to a change with time, the position of the dark line D is changed to the light beam at the start of measurement.
The incident angle may be adjusted so that it is located slightly off the center of the 13th profile.

Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 6, elements that are the same as the elements in FIG. 1 are given the same numbers, and descriptions thereof are omitted unless necessary.

FIG. 6 shows the side surface shape of the surface plasmon sensor according to the second embodiment of the present invention. In this surface plasmon sensor, instead of the actuator used in the first embodiment, a rotation axis is an axis that is perpendicular to a plane where the light beam 13 exists and that passes through a position where the light beam 13 enters the interface 10b. A rotating unit 35 for rotating the dielectric block 10 is provided.

Similar to the first embodiment, prior to the measurement, the profile of the reflected light intensity I of the light beam 13 is acquired, and the incident angle control unit 34 analyzes this profile.

If the analyzed profile pattern is pattern A shown in FIG. 3, it is not necessary to adjust the incident angle of the light beam 13 again, and the measurement is immediately started.

When the profile pattern is pattern B, the rotating unit 35 rotates the dielectric block 10 to change the incident angle at which the light beam 13 is incident on the interface 10b. That is, in the case of pattern B, (a) of FIG.
The dielectric block 10 is located at such a position as to be occupied by the dotted line. When this dielectric block 10 is rotated by an angle θ1 to the position shown by the solid line, the angle at which the light beam 13 is incident on the interface 10b changes, and the angle of the reflected light of the light beam 13 is 2 · θ1.
Change. On the other hand, the total reflection attenuation angle θ at which the dark line D occurs
_{Since SP} does not change, the reflection angle of the dark line D changes by the angle θ1. Therefore, the dark line D generated by the light beam transmitted through the lower end of the condenser lens 15 before the rotation causes the condenser lens 15 to rotate when the dielectric block 10 rotates in the direction shown by the arrow in FIG. It is caused by the light beam 13 that has transmitted through the central portion of 15. In this way, the dielectric block 10
By rotating, the profile pattern can be converted to the pattern A as shown by the solid line in FIG. The horizontal axis of FIG. 7B is the light beam.
Since 13 is the incident angle θ incident on the interface 10b, it does not coincide with the detection position of the light beam 13 on the photodiode array 17.

The rotating part 35 rotates the dielectric block 10 and the measurement is started in a state where the profile pattern of the reflected light intensity I becomes the pattern A.

When the profile pattern is the pattern C, the rotating unit 35 rotates the dielectric block 10 in the opposite direction to the case of the pattern B, and the light beam 13 causes the interface 10 to rotate.
The angle of incidence on b is changed, and measurement is started with the profile pattern changed to pattern A.

When the profile pattern is pattern D, the display section 31 indicates that measurement is impossible. Alternatively, the dielectric block 10 is rotated to the maximum rotatable range, the incident angle of the light beam 13 is changed from the minimum angle to the maximum angle, the measurement is started when the dark line D falls within the profile, and the dark line D falls within the profile. If it does not enter, it may be displayed that the measurement is impossible.

As is apparent from the above description, according to the sensor using attenuation of total reflection according to the present embodiment, the relative position of the dark line in the profile of the light beam 13 totally reflected at the interface 10b is obtained before the measurement. , If the dark line is off the center of the profile, the dielectric block 10 is rotated to adjust the position of the dark line to approximately the center of the profile. Therefore, as in the first embodiment, Regardless of the refractive index of, the measurement can be started from the state where the dark line D always exists in the substantially central portion of the profile of the light beam 13, so that the refractive index change of the substance in contact with the metal film 12 can be accurately performed, In other words, it is possible to investigate the change in characteristics. Since the incident angle is adjusted by rotating the dielectric block 10 using the rotating unit 35, the incident optical path of the light beam 13 does not change, so that the adjustment can be easily performed.

Next, a third embodiment of the present invention will be described with reference to FIG. In addition, in FIG.
Elements that are the same as the elements inside are given the same numbers, and descriptions thereof are omitted unless otherwise necessary.

The sensor utilizing the attenuated total reflection of the third embodiment is a sensor in which the surface plasmon sensor described in the first embodiment is replaced with a leaky mode sensor, which is also a measurement chip in this example. It is configured to use the dielectric block 10. A clad layer 50 is formed on one surface (upper surface in the figure) of the dielectric block 10, and an optical waveguide layer 51 is further formed on the clad layer 50.

The dielectric block 10 is made of synthetic resin or B, for example.
It is formed using an optical glass such as K7. On the other hand, the clad layer 50 is formed into a thin film using a dielectric material having a lower refractive index than the dielectric block 10 or a metal such as gold. The optical waveguide layer 51 is a dielectric material having a higher refractive index than the cladding layer 50,
For example, PMMA is also used to form a thin film. The clad layer 50 has a film thickness of, for example, 36.5 nm when formed from a gold thin film, and the optical waveguide layer 51 has a film thickness of, for example, PMMA.
When formed from, the thickness is about 700 nm.

In the leaky mode sensor having the above structure,
When the light beam 13 emitted from the light source 14 is incident on the cladding layer 50 through the dielectric block 10 at an angle of incidence equal to or more than the total reflection angle, the light beam 13 is generated at the interface 10b between the dielectric block 10 and the cladding layer 50. The light having a specific wave number that is totally reflected but is transmitted through the clad layer 50 and incident on the optical waveguide layer 51 at a specific incident angle propagates through the optical waveguide layer 51 in a waveguide mode.
When the guided mode is excited in this way, most of the incident light is taken into the optical waveguide layer 51, so that total reflection attenuation occurs in which the intensity of the light totally reflected at the interface 10b sharply decreases.

Since the wave number of the guided light in the optical waveguide layer 51 depends on the refractive index of the sensing substance 40 on the optical waveguide layer 51, the sensing substance 40 can be obtained by knowing the specific incident angle at which attenuation of total reflection occurs. You can know the refractive index of.
Further, it is possible to check the change in the binding state between the sensing substance 40 and the specific substance in the sample liquid 11 based on the differential value I ′ output from each differential amplifier of the differential amplifier array 18. Further, also in the third embodiment, the dark line position adjusting operation is performed prior to the measurement, and the same effect as that of the first embodiment can be obtained. Further, as a modified example, it is conceivable that the rotating portion 35 used in the second embodiment is provided and the dark line position adjusting operation is performed by rotating the dielectric block 10.

In each of the embodiments, a plurality of outputs of the photodiodes 17a, 17b, 17c ... Are input to the differential amplifiers 18a, 18b, 18c. Photodiodes 17a, 17b, 17c
The state of attenuation of total reflection was measured based on a differential value I ′ obtained by differentiating the photodetection signals output by …… with respect to the juxtaposed directions thereof, but the present invention is not limited to this, and the reflected light intensity I It is also possible to measure the state of attenuated total reflection based on the above. In this case, the differential amplifier array 18, the sample and hold circuits 21a, 21b, 21c ..., The multiplexer 22 and the like are unnecessary, and the measurement can be performed with a simple configuration.

[Brief description of 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 block diagram showing an electrical configuration of the surface plasmon sensor.

FIG. 3 is an explanatory diagram of a relationship between a light beam incident angle and a reflected light intensity in the surface plasmon sensor.

FIG. 4 is an explanatory diagram of a relationship between a light beam incident angle and a reflected light intensity in the surface plasmon sensor.

FIG. 5 is a schematic diagram showing a relationship between a light beam incident angle and a detected light intensity in the surface plasmon sensor, and a relationship between a light beam incident angle and a differential value of a light intensity detection signal.

FIG. 6 is a side view of a surface plasmon sensor according to a second embodiment of the present invention.

FIG. 7 is an explanatory diagram of a relationship between a light beam incident angle and a reflected light intensity in the surface plasmon sensor.

FIG. 8 is a side view of a leaky mode sensor according to a third embodiment of the present invention.

FIG. 9 is an explanatory diagram of a relationship between a light beam incident angle and a reflected light intensity in a conventional surface plasmon sensor.

FIG. 10 is an explanatory diagram of a relationship between a light beam incident angle and a reflected light intensity in a conventional surface plasmon sensor.

[Explanation of symbols]

9, 9 ', 11, 11' Sample liquid 10 Dielectric block 10a Sample holder 10b Interface 12 Metal film 13 Light beam 14 Light source 15 Condenser lens 17 Photodiode array 17a, 17b, 17c ... Photodiode 18 Differential amplifier Array 18a, 18b, 18c ...... Differential amplifier 19 Amplifier array 19a, 19b, 19c ...... Amplifier 20 Driver 21a, 21b, 21c ...... 24a, 24b, 24c …… Sample hold circuit 22, 25 Multiplexer 23, 26 Drive circuit 27 A / D converter 28 Controller 30 Signal processing unit 31 Display unit 32 Actuator 33 Measuring unit 34 Incident angle control unit 35 Rotating unit 40 Sensing substance 41 Table 50 Clad layer 51 Optical waveguide layer

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2G057 AA02 AB04 AB07 AC01 BA01                       BB06 BC07 HA04                 2G059 AA01 AA05 BB04 BB12 CC16                       DD12 EE02 EE05 GG01 GG04                       JJ11 JJ19 JJ20 KK04 MM01                       MM09 MM11 PP04

Claims (3)

[Claims] 1. A light source for generating a light beam, a dielectric block transparent to the light beam, a thin film layer formed on one surface of the dielectric block and brought into contact with a sample, and the light beam An optical system that allows the dielectric block to be incident at various incident angles so that total reflection conditions are obtained at the interface between the dielectric block and the thin film layer, and the intensity of the light beam totally reflected at the interface In a sensor utilizing attenuated total internal reflection, which comprises a light detecting means for detecting and a measuring means for measuring the state of attenuation of total internal reflection based on the detection result of the optical detecting means, The profile is detected, the relative position of the dark line indicating the attenuated total reflection in the profile is determined, and the incident angle at which the light beam is incident on the interface is determined based on the relative position. Sensor There utilizing attenuated total reflection, characterized by further comprising an incident angle adjusting means for adjusting to come to substantially the center of the profile. 2. The sensor utilizing attenuation of total internal reflection according to claim 1, wherein the incident angle adjusting means adjusts the incident angle by moving the light source or the optical system. . 3. The incident angle adjusting means adjusts the incident angle by rotating the dielectric block with an axis perpendicular to a plane where the light beam is present as an axis of rotation. A sensor utilizing attenuated total internal reflection according to claim 1.