JP2003185571A - Sensor using attenuated total reflection - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a total reflection cancellation angle with high accuracy when a sample is temperature-adjusted to two or more mutually different specific temperatures so as to detect an attenuated total reflection state in a sensor using attenuated total reflection. <P>SOLUTION: When the sample 11 is temperature-adjusted to the two or more mutually different specific temperatures so as to detect the attenuated total reflection state, a light detection means 17 composed of a plurality of light receiving elements is kept at a predetermined definite temperature by a temperature adjusting means 50, a light beam 13 is made incident on a dielectric block 10 at various angles through an incident optical system 15 in such a way that a total reflection condition is obtained at an interface 10b between the dielectric block 10 and a metal film 12, and the light beam 13 reflected at the various angles on the interface 10b is received by the means 17. <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 using attenuation of total reflection, such as a surface plasmon sensor for quantitatively analyzing a substance in a sample by utilizing the generation of surface plasmon. The present invention relates to a sensor that utilizes the attenuation of total internal reflection that adjusts the temperature to a specific temperature.

[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 for quantitatively analyzing a substance in a sample by utilizing the phenomenon that the surface plasmon is excited by a light wave.
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. With respect to the light source to be generated and the above-mentioned light beam with respect to the dielectric block, the total reflection condition can be obtained at the interface between the dielectric block and the metal film, and the total reflection attenuation due to the surface plasmon resonance can occur at various angles. And an optical system for measuring the intensity of the light beam totally reflected at the interface to detect the state of surface plasmon resonance, that is, the state of attenuated total reflection.

In order to obtain various incident angles as described above, an optical system for making a relatively thick light beam incident on the above interface in a convergent light state or in a divergent light state is used. To measure the intensity of the totally reflected light beam,
A photodiode array is used in which a large number of light receiving elements are arranged in a direction capable of receiving a light beam reflected at various reflection angles.

In the surface plasmon sensor having the above structure, when a light beam is incident on the metal film at an angle of incidence of a total reflection angle or more, an evanescent wave having an electric field distribution is generated in the sample in contact with the metal film, This evanescent wave excites surface plasmons at the interface between the metal film and the sample. When the wave vector of the evanescent light 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 energy of light incident at a specific incident angle above the total reflection angle is transferred to the surface plasmon. As a result, the intensity of light incident on the interface between the dielectric block and the metal film at the above-mentioned specific incident angle and reflected at this interface sharply decreases. This decrease in the intensity of reflected light (that is, attenuation of total reflection) is generally detected as a dark line by the photodetection means. That is, the specific incident angle indicating attenuation of total reflection is the total reflection elimination angle, and the reflected light intensity shows a minimum value at this angle.

The above-described attenuation of total reflection occurs only when the incident beam is p-polarized. Therefore, it is necessary to set the polarization direction of the light beam to a predetermined direction in advance so that the light beam is incident as p-polarized light.

When the wave number of the surface plasmon is known from the specific incident angle θ _{SP at which the} attenuated total reflection (ATR) occurs, the permittivity of the sample can be obtained. That is, assuming that the wave number of the surface plasmon is K _{S P} , the angular frequency of the surface plasmon is ω, c is the speed of light in vacuum, and ε _m and ε _S are the metal and the permittivity of the sample, respectively, 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 specific incident angle θ _{SP at} which the intensity of the reflected light decreases eventually can be obtained. It is possible to determine the properties related to the permittivity of, that is, the refractive index.

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 with respect to the dielectric block, a total reflection condition is obtained at the interface between the dielectric block and the cladding layer, and the light guide layer is used. The optical system that is incident at various angles so that the attenuation of the total reflection due to the excitation of the wave mode may occur, and the intensity of the light beam totally reflected at the interface is measured to determine the excited state of the guided mode, that is, the attenuated total reflection state. And a light detecting means for detecting.

In the leak 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 greater than the total reflection angle, the light beam is propagated through the cladding layer into the optical waveguide layer formed on the cladding layer, and the optical waveguide layer In, only light having a specific incident angle and having a specific wave number is propagated in the guided mode. When the guided mode is excited in this way, most of the light incident at the specific incident angle is taken into the optical waveguide layer, so that the light is incident on the interface at the specific incident angle,
The intensity of light reflected at this interface sharply decreases. That is, total reflection attenuation occurs. 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 or
The properties of the sample associated with it can be analyzed.

From among the light beams incident on the photodiode array at the various angles described above, the light beams incident on the interface at a specific incident angle at which attenuation of total reflection occurs and reflected by the interface are specified. Is a region where the light intensity of the profile showing the intensity distribution of the light beam detected by this photodiode array is locally reduced (hereinafter,
It is only necessary to specify the position showing the minimum value in the (light intensity minimum region).

[0013]

By the way, in the sensor utilizing the attenuated total reflection as described above, the sample is temperature-controlled to two or more specific temperatures different from each other to detect the attenuated total reflection state, and The reflection angle may be measured. For example, a surface plasmon sensor is installed in a thermostat, and the total reflection angle is measured by keeping the temperature of the sample at about 37 ° C. when analyzing the enzyme reaction and at about 80 ° C. when analyzing the DNA. .

However, a change in the light receiving characteristic of each light receiving element forming the above photodiode array due to temperature,
That is, the temperature characteristics may differ among the light receiving elements. The light receiving characteristic represents the relationship between the intensity of light received by the light receiving element and the output value of the signal output from the light receiving element by receiving this light. That is, even if the light receiving characteristics of the respective light receiving elements are uniform at a specific temperature, the light receiving characteristics of the respective light receiving elements may not be uniform at a temperature different from the specific temperature. In the light intensity distribution indicated by the output value when each light receiving element receives a fixed amount of light in, and at a temperature different from this specific temperature, when each light receiving element receives the same amount of light as above. The light intensity distribution indicated by the output value may be different. Therefore, there is a problem that it is difficult to measure the total internal reflection elimination angle with high accuracy by the surface plasmon sensor arranged in a constant temperature bath or the like whose temperature is adjusted to various set temperatures.

The present invention has been made in view of the above circumstances, and when the temperature of a sample is adjusted to two or more specific temperatures different from each other to detect the attenuated total reflection angle, the total reflection elimination angle is set to a greater value. It is an object of the present invention to provide a sensor utilizing attenuated total reflection that can be detected with high accuracy.

[0016]

A first sensor utilizing attenuation of total reflection according to the present invention comprises a dielectric block, a thin film layer formed on one surface of the dielectric block and brought into contact with a sample, and an optical layer. A light source that generates a beam, 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 thin film layer, and total light at the interface. The intensity of the reflected light beam is measured, the state of attenuation of total reflection is detected, and a photodetector comprising a plurality of light receiving elements for individually receiving the light beams reflected at various reflection angles, Is a sensor for detecting the state of attenuated total internal reflection by controlling the temperature of the light to two or more specific temperatures different from each other, and is provided with temperature control means for maintaining the light detection means at a predetermined constant temperature. To do.

A second sensor utilizing attenuation of total reflection according to the present invention comprises a dielectric block, a metal film formed on one surface of the dielectric block and brought into contact with a sample, and a light source for generating a light beam. , This optical beam is incident on 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 the intensity of the light beam totally reflected at the interface. And detecting the state of attenuation of total internal reflection due to surface plasmon resonance, and a light detecting means comprising a plurality of light receiving elements for individually receiving light beams reflected at various reflection angles, and the above sample, A sensor for detecting the state of attenuation of total reflection by controlling the temperature to two or more specific temperatures different from each other, characterized by comprising temperature control means for maintaining the light detection means at a predetermined constant temperature. Is a thing

A third sensor utilizing attenuation of total reflection of the present invention is a dielectric block, a clad layer formed on one surface of the dielectric block, and a clad layer formed on the clad layer and brought into contact with a sample. Optical waveguide layer, a light source that generates a light beam, and an optical system that causes the light beam to enter the dielectric block at various angles so that total reflection conditions are obtained at the interface between the dielectric block and the cladding layer. The light beam reflected at various reflection angles is detected by measuring the intensity of the light beam totally reflected at the system and the above interface and detecting the state of attenuation of total reflection due to the excitation of the guided mode in the optical waveguide layer. A sensor for detecting the state of attenuated total reflection by controlling the temperature of the sample to two or more specific temperatures different from each other, the sensor comprising a plurality of light receiving elements that individually receive light. One predetermined And it is characterized in that it comprises a temperature control means for maintaining the temperature.

It is preferable that the plurality of light receiving elements have substantially the same light receiving characteristics at the constant temperature.

The sensor may be provided with a correction means for correcting the difference in the light receiving characteristic between the plurality of light receiving elements at the constant temperature.

The "predetermined constant temperature" may be any temperature as long as it can normally drive the light detecting means.

[0022]

As described above, according to the first, second and third sensors utilizing the attenuated total reflection of the present invention, the temperature detecting means for keeping the light detecting means at a predetermined constant temperature is provided. The light receiving characteristics of the respective light receiving elements forming the light detecting means are kept substantially constant, that is, the change in the light receiving characteristics due to the temperature of each light receiving element is suppressed, and thus even if the temperature around the light detecting means changes. The profile of the intensity distribution of the light beam indicated by the output from the photodetector can be approximated by the profile of the intensity distribution of the light beam received by the photodetector, and the sample can have two or more specific temperatures different from each other. It is possible to detect the total internal reflection elimination angle with higher accuracy when the temperature is adjusted to and the attenuated total internal reflection state is detected.

Further, the plurality of light receiving elements may have light receiving characteristics substantially equal to each other at a constant temperature, or a correction means for correcting a difference in light receiving characteristic between the plurality of light receiving elements at a constant temperature may be provided. By doing so, it is possible to output a value that more accurately indicates the light intensity distribution of the light beam reflected by the dielectric block, from each of the light receiving elements.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. The sensor using the attenuated total reflection according to the embodiment of the present invention is installed in a thermostatic chamber capable of controlling the temperature at various different temperatures, and controls the sample to two or more specific temperatures different from each other to attenuate the attenuated total reflection. Is a surface plasmon sensor that uses surface plasmon resonance to detect the state of
FIG. 1 shows a side surface shape of this surface plasmon sensor.

In the surface plasmon sensor of the above-mentioned embodiment, a part including the apex angle at which the four ridges of the quadrangular pyramid are gathered is cut out, and the concave portion 10c is formed on the bottom surface of the quadrangular pyramid. Formed on the bottom surface of the recess 10c which is one surface of the dielectric block 10,
For example, it has a metal film 12 which is a thin film layer made of gold, silver, copper, aluminum or the like, and the boundary between the metal film 12 and the dielectric block 10 is an interface 10b.

The dielectric block 10 is made of, for example, a transparent resin, and by forming the recess 10c, the periphery of the portion where the metal film 12 is formed has a raised shape. The separated portion 10a functions as a sample holder that stores the liquid sample 11. In this example, the sensing medium 30, which is a part of the sample, is fixed on the metal film 12, and the sensing medium 30 will be described later.

The dielectric block 10 together with the metal film 12
It constitutes a disposable measuring chip, and is fitted and fixed one by one in a plurality of chip holding holes 31a provided in the turntable 31, for example. After the dielectric block 10 is fixed to the turntable 31 in this manner, the turntable 3
1 is intermittently rotated around the rotation axis Z of the turntable 31 by a constant angle, and the liquid sample 11 dropped on the dielectric block 10 stopped at a predetermined position is held in the sample holding portion 10a. It Thereafter, when the turntable 31 is further rotated by a certain angle, the dielectric block 10 is sent to the measurement position shown in FIG.
Rotation stops. By repeating such an operation, the liquid sample 11 dropped on the dielectric block 10 is sequentially measured.

In addition to the dielectric block 10, the surface plasmon sensor further includes a light source 14 (hereinafter referred to as a laser light source 14) including a semiconductor laser or the like for generating one light beam 13 and the light beam 13 as a dielectric. An incident optical system 15 that is an optical system that allows light to enter the body block 10 at various incident angles so that total reflection conditions can be obtained at the interface 10b between the dielectric block 10 and the metal film 12, and the interface 1 described above.
0b, a detection optical system 16 for injecting the light beam 13 totally reflected and emitting the light beam 13 toward a light detecting means 17 described later, and a light beam 13 reflected at various reflection angles.
Light detecting means 17 including a plurality of light receiving elements for individually receiving light through the detection optical system 16, temperature controlling means 50 for keeping the light detecting means 17 at a predetermined constant temperature, and light detecting means 1
Differential amplifier array 18 connected to 7 and driver 19
And a signal processing unit 20 including a computer system, etc.
And a display means 21 connected to the signal processing section 20.

The incident optical system 15 has a collimator lens 15a for collimating the light beam 13 emitted from the laser light source 14, and a condenser for converging the collimated light beam 13 toward the interface 10b. It is composed of a lens 15b.

Since the light beam 13 is condensed by the condensing lens 15b as described above, it contains 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 totally reflected at the interface 10b contains the components of the light beam 13 totally reflected at various reflection angles. The optical system 15 may be configured so that the light beam 13 is incident on the interface 10b in a defocused state instead of being condensed in a point shape. By doing so, since the light beam 13 is totally reflected in a wider area on the interface 10b, the detection error of the attenuated total reflection state is averaged, and the measurement accuracy of the total reflection elimination angle can be improved.

The light beam 13 is incident on the interface 10b as p-polarized light. In order to do so, the laser light source 14 may be arranged in advance so that the polarization direction thereof is the above predetermined direction. In addition, the light beam 13 is applied to the interface 10
To make p-polarized light incident on b, use a wave plate 1
The direction of the polarized light of No. 3 may be controlled.

The detection optical system 16 is provided with a collimator lens 16a for collimating the light beam 13 which is totally reflected and diverged at the interface 10b.

As the temperature adjusting means 50, a Peltier element, a heat pipe or a heat exchanger using circulating cooling water can be used.

The sample analysis by the surface plasmon sensor having the above-mentioned structure will be described below.

As shown in FIG. 1, the light beam 13 emitted from the laser light source 14 is converged on the interface 10b between the dielectric block 10 and the metal film 12 through the optical system 15.

It converges on the interface 10b, and this interface 10b
The light beam 13 that is totally reflected by is detected by the photodetection means 17 through the detection optical system 16. Light detection means 17
Are photodiodes 17a, 1 which are a plurality of light receiving elements.
Has a photodiode array in which 7b, 17c, ... Are arranged side by side in one row, and the arrangement direction of the photodiodes is
It is arranged so as to be substantially parallel to the paper surface of FIG. 1 and to be substantially orthogonal to the propagation direction of the light beam 13 that is collimated and incident. Therefore, the components of the light beam 13 totally reflected at various reflection angles at the interface 10b are converted into different photodiodes 17a and 17a.
b, 17c ... Receive light. It should be noted that each photodiode forming this photodiode array has two
Elements that have substantially the same light receiving characteristics at 0 ° C. are used, and the temperature adjusting means 50 adjusts the temperature of the light detecting means 17 so as to keep it at 20 ° C. which is a predetermined constant temperature.

As the light detecting means, a thermal type element such as a thermopile or a pyroelectron can be used instead of the photodiode.

The components of the light beam 13 incident on the interface 10b at the specific incident angle θ _SP are the metal film 12 and the liquid sample 11.
Since the surface plasmon is excited at the interface with and, the reflected light intensity sharply decreases for this light. That is, the specific incident angle θ _SP is a total reflection elimination angle, and the reflected light intensity shows a minimum value at this angle θ _SP . The area where the reflected light intensity decreases is observed as a dark line in the reflected light, as indicated by D in FIG.

Here, a case will be described in which the light beam 13 totally reflected by the dielectric block 10 is received and the total reflection elimination angle is measured. The light intensity distribution of the light beam 13 described below means the distribution of the light intensity of the light beam 13 in the radial direction within the plane of the paper shown in FIG. 2 and 3 are views showing the radial intensity distribution of the light beam in the optical path of the light beam,
The horizontal axis represents the radial position R of the light beam, and the vertical axis represents the light intensity P. FIG. 4 is a diagram showing the light receiving characteristic of each photodiode at 20 ° C., the horizontal axis shows the light intensity P received by the photodiode, and the vertical axis shows the output I of the photodiode. FIG. 5 is a diagram showing the light intensity distribution of the light beam received and output by each photodiode at 20 ° C., the horizontal axis shows the position J of the photodiode, and the vertical axis shows the output I of the photodiode. Figure 6 shows 80 ° C
3 is a diagram showing the light receiving characteristic of each photodiode in FIG. 3, where the horizontal axis represents the light intensity P received by the photodiode and the vertical axis represents the output I of the photodiode. FIG. 7 is a diagram showing the light intensity distribution of the light beam received and output by each photodiode at 80 ° C., the horizontal axis represents the position J of the photodiode, and the vertical axis represents the output I of the photodiode.

First, the light intensity distribution of the light beam 13 emitted from the laser light source 14 and collimated by the collimator lens 15a (at the position of arrow V1 in FIG. 1) has a Gaussian distribution as shown in FIG. It is shown. A light beam 13 having an intensity distribution showing this Gaussian distribution passes through the dielectric block 10 and the dielectric block 1
0 is totally reflected at the interface 10b between the metal film 12 and collimated by the collimator lens 16a, the light intensity distribution of the light beam 13 (position indicated by arrow V2 in FIG. 2) is as shown in FIG. In addition, the influence of the total reflection attenuation at the interface 10b is superimposed on the Gaussian distribution, and the light intensity minimum region M exists in the profile of the light beam 13.

The light beam 13 having such an intensity distribution
When the light is received by the light detecting means 17, the light receiving characteristics of the respective photodiodes constituting the light detecting means 17 are substantially the same as described above, and therefore the light distribution from the light detecting means 17 is equivalent to the intensity distribution of the light beam. A signal indicating the intensity distribution is output, and the total reflection elimination angle can be obtained by specifying the position N indicating the minimum value in the minimum light intensity region M based on the intensity distribution of the light beam indicated by this output. it can.

Even when the setting of the temperature of the thermostatic chamber in which the surface plasmon sensor is installed is changed and the temperature of the sample 11 is adjusted to a temperature different from the above, the attenuated total reflection state is detected. Since the light detecting means 17 is kept at a predetermined temperature of 20 ° C. by the temperature adjusting means 50, the light receiving characteristics of the respective photodiodes can be made uniform, and the light beam received in the same manner as described above can be obtained. A signal having an intensity distribution equivalent to that of is output.

As described above, when the light detecting means 17 is kept at 20 ° C., the light receiving characteristics of the respective photodiodes 17a, 17b, 17c ... Are substantially uniform as shown in FIG. The light intensity distribution (see FIG. 3) of the generated light beam and the light intensity distribution (see FIG. 5) indicated by the output value from the light detecting means 17 by receiving this light beam can be matched, and The position N indicating the minimum value in the minimum light intensity region M can be specified. However, when the light detecting means 17 is not kept at a predetermined constant temperature, for example, the light detecting means 17 has a temperature of 20 ° C.
When the temperature reaches 80 ° C, which is different from
As shown in, each photodiode 17a, 17b, 17
Due to the difference in temperature characteristics of c ...
Since the light intensity distribution of the received light beam (see FIG. 3) and the light intensity distribution indicated by the output value from the light detecting means 17 (see FIG. 7) do not match, the local minimum in the minimum light intensity region M is obtained. It may be difficult to specify the position N indicating the value, and it may be difficult to detect the total reflection elimination angle with high accuracy.

Next, the signal processing after the light detecting means 17 will be described in detail.

FIG. 8 is a block diagram showing the electrical construction of this surface plasmon sensor. As shown in the figure, the driver 19 is provided for each differential amplifier 18 of the differential amplifier array 18.
The sample-hold circuits 22a, 22b, 22c, which sample and hold the outputs of a, 18b, 18c ..., the multiplexer 23 to which the outputs of these sample-hold circuits 22a, 22b, 22c. A / D converter 24 which is converted to be input to the signal processing unit 20, a driving circuit 25 which drives the multiplexer 23 and the sample and hold circuits 22a, 22b, 22c ..., And a driving circuit 25 based on an instruction from the signal processing unit 20. It is composed of a controller 26 for controlling the operation of.

The photodiodes 17a, 17b, 1
.. of the differential amplifier array 18 are input to the differential amplifiers 18a, 18b, 18c. At this time, the outputs of two photodiodes adjacent to each other are input to a common differential amplifier. Therefore, each differential amplifier 18
The outputs of a, 18b, 18c ... Are the photodetection signals output by the plurality of photodiodes 17a, 17b, 17c.
It can be considered that they are differentiated with respect to their juxtaposition direction.

The outputs of the differential amplifiers 18a, 18b, 18c ... Are sample and hold circuits 22a, 22 respectively.
.. are sample-held at a predetermined timing by b, 22c, ... And inputted to the multiplexer 23. The multiplexer 23 uses the sample-and-hold differential amplifiers 18
Outputs a, 18b, 18c, ...
Input to the / D converter 24. The A / D converter 24 digitizes these outputs and inputs them to the signal processing unit 20.

FIG. 9 shows the light intensity for each incident angle θ of the light beam 13 totally reflected at the interface 10b, and the differential amplifiers 18a and 18a.
The relationship with the outputs of b, 18c ... Here, it is assumed that the relationship between the incident angle θ of the light beam 13 on the interface 10b and the light intensity I is as shown in the graph of FIG.

That is, the specific incident angle θ _{SP at the} interface 10b
Since the light incident on the light excites surface plasmons at the interface between the metal film 12 and the liquid sample 11, the reflected light intensity I of this light sharply decreases. That is, θ _SP is the total reflection elimination angle.

Further, FIG. 9B shows the photodiode 1
7a, 17b, 17c, ... Are shown in parallel, and as described above, these photodiodes 17a, 17b are provided.
The positions of b, 17c, ... Arranged in parallel are uniquely corresponding to the incident angle θ.

Then, the photodiodes 17a, 17b,
The relation between the positions of the 17c in parallel, that is, the incident angle θ, and the output I ′ (differential value of the reflected light intensity I) of the differential amplifiers 18a, 18b, 18c, ... Is as shown in FIG. It will be

The signal processing section 20 uses the differential amplifier 18 based on the value of the differential value I ′ input from the A / D converter 24.
Among a, 18b, 18c, ..., an output that is closest to the differential value I ′ = 0 corresponding to the specific incident angle θ _SP is obtained (in the example of FIG. 9 (3), it is the differential amplifier 18d). Is selected, and the differential value I ′ output from it is subjected to predetermined correction processing, and then the value is displayed on the display means 21. In addition,
In some cases, there may be a differential amplifier that outputs a differential value I ′ = 0, and in that case, that differential amplifier is naturally selected.

After that, every time a predetermined time elapses, the differential value I'output from the selected differential amplifier 18d is displayed on the display means 21 after undergoing a predetermined correction process. This differential value I'changes the dielectric constant of the substance in contact with the metal film 12 of the measurement chip, that is, the refractive index, and the light intensity minimum region indicated by the curved portion in FIG. Then, it goes up and down accordingly. Therefore, by continuing to measure this differential value I ′ over time,
A change in the refractive index of the substance in contact with the metal film 12, that is, a change in the characteristic can be examined.

In particular, in this embodiment, the sensing medium 30 that binds to the specific substance in the liquid sample 11 is fixed to the metal film 12, and the refractive index of the sensing medium 30 changes according to the binding state. By continuously measuring the differential value I ′, it is possible to check the state of change in the binding state. That is, in this case, both the liquid sample 11 and the sensing medium 30 are samples to be analyzed. Examples of such a combination of the specific substance and the sensing medium 30 include an antigen and an antibody.

As is apparent from the above description, in the present embodiment, a plurality of photodiodes 17 are used as the light detecting means 17.
Since a photodiode array in which a, 17b, 17c, ... Are arranged side by side in one row is used, the light intensity minimum region shown in FIG. Even if the incident angle fluctuates in the θ direction, the specific incident angle can be detected. That is, it is possible to secure a wide measurement range by using such an array-shaped light detecting means 17.

Further, a plurality of differential amplifiers 18a, 18b,
One differential amplifier is provided instead of using the differential amplifier array 18 composed of 18c ...
It is also possible to switch each output of 17b, 17c ... By a multiplexer and to input two adjacent outputs of them sequentially to this one differential amplifier.

In order to investigate the change of the binding state between the specific substance in the liquid sample 11 and the sensing medium 30 with the passage of time, the differential value I'is obtained and displayed every time a predetermined period of time elapses. In addition, the differential value I'measured first
The difference ΔI ′ between (0) and the differential value I ′ (t) measured after the elapse of a predetermined time may be obtained and displayed.

Even when the light receiving characteristics of the photodiodes constituting the light detecting means 17 are not uniform,
By keeping the light detecting means 17 at a predetermined constant temperature by the temperature adjusting means 50, it is possible to obtain the effect of suppressing the change of the light receiving characteristic due to the temperature of each photodiode.

Further, even if the light detecting means 17 is kept at 20 ° C. which is a constant temperature predetermined by the temperature adjusting means 50, if the light receiving characteristics of the respective photodiodes are not uniform at this temperature, As shown in the block diagram of FIG. 10 in which an operational amplifier array, which is a correcting means, is added to the surface plasmon sensor, the difference in the light receiving characteristics between the photodiodes at the above-mentioned constant temperature is corrected between the light detecting means 17 and the differential amplifier 18. The operational amplifier array 60, which is a correction means for controlling the photodiodes 17, is provided.
operational amplifiers 60a, 60 for adjusting the light receiving characteristics of the photodiodes arranged in correspondence with a, 17b, 17c ...
An operational amplifier array 60 including b, 60c ...
The light receiving characteristics of each photodiode are set to the respective operational amplifier 60a,
After being corrected by adjusting 60b, 60c, ..., The signal from each photodiode is output through the operational amplifier array 60, and by this, the photodetection means 17 receives light by adjusting the difference in the light receiving characteristics of each photodiode. A signal indicating the intensity distribution of the light beam more accurately can be output through the correction means 60.

In the surface plasmon sensor described above, a leak mode sensor can be obtained by changing a part of the configuration. Hereinafter, description will be given with reference to the drawings.

FIG. 11 is a diagram showing an example of the leak mode sensor. In FIG. 11, elements that are the same as the elements in FIG. 1 are given the same numbers, and descriptions thereof are omitted unless necessary.

This leaky mode sensor is obtained by changing the surface plasmon sensor described in the above embodiment into a leaky mode sensor, and in this example as well, the dielectric block 10 formed into a measuring chip is used. .
A clad layer 40 is formed on the bottom surface of the concave portion 10c, which is one surface of the dielectric block 10, and an optical waveguide layer 41 is formed on the clad layer 40. The clad layer 40 and the optical waveguide layer 41 form a thin film layer.

The dielectric block 10 is formed of, for example, synthetic resin or optical glass such as BK7. On the other hand, the clad layer 40 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 41 is also formed in a thin film using a dielectric material having a higher refractive index than the cladding layer 40, for example, PMMA. The film thickness of the clad layer 40 is, for example, 36.5 nm when it is formed of a gold thin film, and the film thickness of the optical waveguide layer 41 is approximately 700 nm when it is formed of PMMA.

In the leak mode sensor having the above structure,
When the light beam 13 emitted from the laser light source 14 is incident on the cladding layer 40 through the dielectric block 10 at an angle of incidence equal to or more than the total reflection angle, many components of the light beam 13 are included in the dielectric block 10 and the cladding layer. Interface 10 with 40
Light having a specific wave number, which is totally reflected by b but is transmitted through the cladding layer 40 and is incident on the optical waveguide layer 41 at a specific incident angle, is propagated in the optical waveguide layer 41 in a waveguide mode. When the guided mode is excited in this way, most of the incident light that has entered at the specific incident angle is taken into the optical waveguide layer 41, so that the intensity of the light that is incident on the interface 10b at the specific incident angle and totally reflected is sharp. Decreasing total internal reflection attenuation occurs.

Since the wave number of guided light in the optical waveguide layer 41 depends on the refractive index of the liquid sample 11 on the optical waveguide layer 41, it is necessary to know the total reflection elimination angle which is the above-mentioned specific incident angle at which attenuation of total reflection occurs. Thus, the refractive index of the liquid sample 11 and the characteristics of the liquid sample 11 related thereto can be analyzed. Further, the characteristics of the liquid sample 11 can be analyzed based on the detection of the reflected light intensity I in the vicinity of the specific incident angle and the differential value I ′ output by each differential amplifier of the differential amplifier array 18.

Further, in order to obtain the above various incident angles, a relatively thin light beam is incident on the interface while changing the incident angle, and the reflection angle changes according to the change of the incident angle of these incident light beams. The total reflection angle may be measured by detecting the light beam with a small photodetector that moves in synchronization with the change in the reflection angle.

[Brief description of drawings]

FIG. 1 is a diagram showing a side surface shape of a surface plasmon sensor according to an embodiment of the present invention.

FIG. 2 is a diagram showing an intensity distribution of a light beam.

FIG. 3 is a diagram showing a diagram showing an intensity distribution of a light beam.

FIG. 4 is a diagram showing a light receiving characteristic of each photodiode at 20 ° C.

FIG. 5 is a diagram showing a light intensity distribution output from each photodiode at 20 ° C.

FIG. 6 is a diagram showing a light receiving characteristic of each photodiode at 80 ° C.

FIG. 7 is a diagram showing a light intensity distribution output from each photodiode at 80 ° C.

FIG. 8 is a block diagram showing an electrical configuration of a surface plasmon sensor.

FIG. 9 is a diagram illustrating a relationship between an incident angle of a light beam and an output of a differential amplifier.

FIG. 10 is a block diagram in which correction means is added to the surface plasmon sensor.

FIG. 11 is a diagram showing an example of a leak mode sensor.

[Explanation of symbols]

10 Dielectric block 10b Interface between dielectric block and metal film 11 samples 12 metal film 13 light beam 14 Laser light source 15 Incident optical system 17 Light detection means 50 Temperature control means

Claims (5)

[Claims] 1. A dielectric block, a thin film layer formed on one surface of the dielectric block and brought into contact with a sample, a light source for generating a light beam, and the light beam to the dielectric block. An optical system that makes incidence at various 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 is measured to determine the state of attenuation of total reflection. And a photodetector including a plurality of light-receiving elements that individually receive the light beams reflected at various reflection angles, and adjust the temperature of the sample to two or more specific temperatures different from each other. A sensor for detecting the state of reflection attenuation, comprising a temperature adjusting means for maintaining the light detection means at a predetermined constant temperature, wherein the sensor uses attenuation of total reflection. 2. A dielectric block, a metal film formed on one surface of the dielectric block and brought into contact with a sample, a light source for generating a light beam, the light beam with respect to the dielectric block, An optical system that makes incidence at various angles so that total reflection conditions are obtained at the interface between the dielectric block and the metal film, and the intensity of the light beam totally reflected at the interface is measured, and the result is associated with surface plasmon resonance. And a photodetector that detects a state of attenuation of total reflection and that individually receives the light beams reflected at various reflection angles, and the sample is exposed to two or more specific temperatures different from each other. A sensor for detecting the state of attenuation of total internal reflection by controlling temperature, comprising a temperature adjusting means for maintaining the light detecting means at a predetermined constant temperature, wherein the sensor utilizing attenuation of total internal reflection is provided. 3. A dielectric block, a clad layer formed on one surface of the dielectric block, an optical waveguide layer formed on the clad layer and brought into contact with a sample, and a light source for generating a light beam. 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 cladding layer; and total reflection at the interface A plurality of light receptions for individually receiving the light beams reflected at various reflection angles by measuring the intensity of the light beam and detecting the state of attenuation of total reflection associated with excitation of a guided mode in the optical waveguide layer. A sensor for detecting the state of attenuated total reflection by controlling the temperature of the sample to two or more specific temperatures different from each other, the sensor comprising: Temperature control means to keep Sensor utilizing attenuated total reflection, characterized in that it comprises. 4. The attenuated total reflection according to claim 1, wherein the plurality of light receiving elements have substantially the same light receiving characteristics at the constant temperature. Sensor. 5. The attenuated total reflection according to claim 1, further comprising a correction unit that corrects a difference in light receiving characteristic between the plurality of light receiving elements at the constant temperature. The sensor used.