JP2002195943A - Sensor utilizing attenuated total reflection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light detection signal of high S/N even with an array-like light detecting means, related to a sensor utilizing attenuated total reflection. SOLUTION: The sensor utilizing attenuated total reflection comprises a dielectrics block 10, a thin film layer 12 which is formed on its one surface and allowed to contact a sample, a light source 14 emitting a light beam 13, an optical system 15 which allows the light beam 13 to enter at various angles so that a total reflection condition is provided at an interface 10b contacting the thin film layer 12, and an array-like light detecting means 17 which detects the light beam 13 which is totally reflected on the interface 10b. Here, a signal line H which conveys the output of each light-receiving element of the array-like light detecting means 17 to a post stage is grounded, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor using attenuated total reflection, such as a surface plasmon sensor for quantitatively analyzing a substance in a sample using the generation of surface plasmon, and more particularly, to an attenuated total reflection. The present invention relates to a sensor using attenuated total reflection, of a type that detects dark lines generated in measurement light by using an array of light detecting means in which a plurality of light receiving elements are arranged in a predetermined direction.

[0002]

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

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

A surface plasmon sensor using the above-described system basically includes, for example, 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, and a light beam. The light source to be generated and the light beam are set at various angles with respect to the dielectric block so that total reflection conditions can be obtained at the interface between the dielectric block and the metal film, and that total reflection attenuation due to surface plasmon resonance can occur. And an optical system for measuring the intensity of the light beam totally reflected at the interface and detecting the state of surface plasmon resonance, that is, the state of attenuated total reflection.

In order to obtain various angles of incidence as described above, a relatively narrow light beam may be deflected and incident on the interface, or a component which is incident on the light beam at various angles may be included. As described above, a relatively thick light beam may be incident on the interface in a convergent light state or a divergent light state. In the former case, the light beam whose reflection angle changes with the deflection of the light beam is detected by a small photodetector that moves synchronously with the deflection of the light beam, or by an area sensor extending along the direction of the change in the reflection angle. Can be detected. On the other hand, the latter case can be detected by an area sensor extending in a direction in which all light beams reflected at various reflection angles can be received.

In the surface plasmon sensor having the above structure, when a light beam is made incident on a metal film at a specific incident angle θ _SP equal to or larger than the total reflection angle, an evanescent wave having an electric field distribution is formed in a 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 the evanescent wave. When the wave number vector of the evanescent light is equal to the wave number of the surface plasmon and the wave number matching is established, both are in a resonance state, and the energy of light is transferred to the surface plasmon. The intensity of the reflected light drops sharply. This decrease in light intensity is generally detected as a dark line by the light detection means.

[0007] The above resonance occurs only when the incident beam is p-polarized. Therefore, it is necessary to set 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 incident angle θ _{SP at} which the attenuated total reflection (ATR) occurs, the dielectric constant of the sample is obtained. That is, the wave number of the surface plasmon is K
_{When SP} and the angular frequency of the surface plasmon are ω, c is the speed of light in vacuum, ε _m and ε _s are the metal and the dielectric constant of the sample, respectively, there is the following relationship.

[0009]

(Equation 1) If the dielectric constant ε _s of the sample is known, the concentration of the specific substance in the sample can be determined based on a predetermined calibration curve or the like. Therefore, by knowing the incident angle θ _{SP at} which the reflected light intensity decreases, the dielectric constant of the sample can be determined. Properties related to the index, or refractive index, can be determined.

In this type of surface plasmon sensor, as disclosed in Japanese Patent Application Laid-Open No. H11-326194, an array-like surface plasmon sensor has been disclosed for the purpose of accurately measuring the total reflection elimination angle θ _SP with a large dynamic range. It has been considered to use light detection means. The light detecting means includes a plurality of light receiving elements arranged in a predetermined direction,
The components of the light beam totally reflected at the interface at various reflection angles are arranged so as to be received by different light receiving elements.

In this case, there is provided a differentiating means for differentiating a light detection signal output from each light receiving element of the array-shaped light detecting means with respect to a direction in which the light receiving elements are arranged. Often, properties related to the refractive index of the sample are determined based on the values. As the differentiating means, for example, means for calculating a difference between outputs of two adjacent light receiving elements can be used. When calculating this difference, one differential amplifier may be connected to each of two adjacent light receiving elements, or all light receiving elements may be connected to one differential amplifier via a multiplexer.
The output of two light receiving elements that are sequentially adjacent to each other may be selected by the multiplexer and input to the differential amplifier.

On the other hand, as similar sensors utilizing attenuated total reflection (ATR), for example, "Spectroscopy", Vol. 47, No. 1 (1998), pp. 21-23 and 26-27.
A leak mode sensor described on the page is also known. This leak mode sensor is basically formed of, 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 condition of total reflection is obtained at an interface between the dielectric block and the cladding layer, and the light is guided by the optical waveguide layer. An optical system that enters at various angles so that total reflection attenuation can occur due to wave mode excitation, and the intensity of the light beam totally reflected at the interface is measured to determine the excited state of the waveguide mode, that is, the total reflection attenuation state. And a light detecting means for detecting.

In the leakage mode sensor having the above configuration,
When the light beam is incident on the cladding layer through the dielectric block at an incident angle equal to or greater than the total reflection angle, only light having a specific wave number at a specific incident angle is transmitted through the cladding layer. The light propagates in a guided mode. When the waveguide mode is excited in this way, most of the incident light is taken into the optical waveguide layer, so that total reflection attenuation occurs in which the intensity of light totally reflected at the interface sharply decreases.
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 characteristics of the sample related thereto are analyzed by knowing the specific incident angle at which the total reflection attenuation occurs. be able to.

In this leakage mode sensor,
In order to detect the position of the dark line generated in the reflected light due to the attenuated total reflection, the above-described array-like light detecting means can be used, and in addition to this, the above-described differentiating means is often applied.

[0015]

By the way, in sensors using total reflection attenuation, such as the above-mentioned surface plasmon sensor and leaky mode sensor, if the above-mentioned array type is applied as the light detection means, the light detection signal S
/ N tends to decrease. If the S / N of the light detection signal is reduced, the accuracy of the sample analysis will be impaired.

The present invention has been made in view of the above circumstances, and provides a sensor utilizing attenuated total reflection which can obtain a high S / N light detection signal even using an array of light detection means. The purpose is to provide.

[0017]

According to one aspect of the present invention, there is provided a sensor utilizing attenuated total reflection according to the present invention, which is formed on a dielectric block and one surface of the dielectric block, as described above.
A thin film layer that is brought into contact with the sample, a light source that generates a light beam, and various types of light beams that are applied to a dielectric block so that total reflection conditions can be obtained at an interface between the dielectric block and the thin film layer. An optical system for incidence at an angle and a plurality of light receiving elements are juxtaposed in a predetermined direction, and are arranged in such a direction that components of light beams totally reflected at various angles at the interface are received by different light receiving elements. And a light detecting means for detecting the state of attenuated total reflection, wherein a signal line transmitting an output of each light receiving element of the light detecting means to a subsequent stage is grounded. It is characterized by the following.

Another sensor utilizing attenuated total reflection according to the present invention is particularly configured as the above-described surface plasmon sensor, and is formed on a dielectric block and formed on one surface of the dielectric block to contact a sample. A metal film to be emitted, a light source for generating a light beam, and the light beam incident on the dielectric block at various angles so as to obtain a total reflection condition at an interface between the dielectric block and the metal film. An optical system, a plurality of light receiving elements are juxtaposed in a predetermined direction, and the surface is arranged in such a manner that components of light beams totally reflected at various angles at the interface are received by different light receiving elements. In a sensor using attenuated total reflection, comprising: a photodetector for detecting a state of attenuated total reflection by plasmon resonance, an output of each light receiving element of the photodetector is provided in a subsequent stage. Signal line for transmitting is characterized in that each is grounded.

Still another sensor utilizing attenuated total reflection according to the present invention is particularly configured as the above-mentioned leaky mode sensor, and includes a dielectric block and a clad formed on one surface of the dielectric block. A layer, an optical waveguide layer formed on the cladding layer and brought into contact with the sample, a light source for generating a light beam, and applying the light beam to the dielectric block with respect to the dielectric block and the cladding layer. And an optical system for incidence at various angles so as to obtain the condition of total reflection at the interface, and a plurality of light receiving elements are arranged side by side in a predetermined direction. Light detecting means for detecting a state of attenuated total reflection due to excitation of a waveguide mode in the optical waveguide layer, the components being arranged so that different light receiving elements receive the components. In sensor using a reflection attenuation, the signal line for transmitting downstream the output of the light receiving elements of the light detecting means is characterized in that each is grounded.

The present invention is preferably applied to a case where a multiplexer for sequentially selecting and outputting the outputs from a predetermined number of the plurality of light receiving elements of the light detecting means is provided. The signal line between the multiplexer and each of the light receiving elements is grounded.

On the other hand, as the light detecting means, for example, a photodiode array or the like can be suitably used.

[0022]

According to the research conducted by the present inventors, in a conventional sensor using attenuated total reflection, when an array-type light detecting means is applied, the problem that the S / N of the light detection signal is apt to be reduced tends to occur. In the detection of the total reflected light, the light accumulated in the light detecting means, for example, the photodiode array described above, rides on the light detection signal at the time of the subsequent total reflected light detection,
It has been found that this is caused by so-called charge noise.

Based on this new finding, in the sensor utilizing the attenuated total reflection according to the present invention, the signal lines for transmitting the outputs of the respective light receiving elements of the light detecting means to the subsequent stage are grounded, so that charge noise is generated. The accumulation of the charge is prevented, and a high S / N photodetection signal can be obtained.

[0024]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a side surface shape of a surface plasmon sensor according to a first embodiment of the present invention. The surface plasmon sensor includes, for example, a dielectric block 10 having a shape in which a part of a quadrangular pyramid is cut out, and one surface of the dielectric block 10 (the upper surface in the figure).
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 raised portion around a portion where the metal film 12 is formed. The raised portion 10 a serves as a sample holding portion for storing the liquid sample 11. Function. In this example, the sensing medium 30 is fixed on the metal film 12, but the sensing medium 30 will be described later.

The dielectric block 10 and the metal film 12 constitute a disposable measuring chip. For example, the dielectric block 10 is fitted and fixed one by one in a plurality of chip holding holes 31a provided in the turntable 31. After the dielectric block 10 is fixed to the turntable 31 in this way, the turntable 31 is intermittently rotated by a certain angle, and the liquid sample 11 is dropped on the dielectric block 10 stopped at a predetermined position, The liquid sample 11 is held in the sample holding section 10a. 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. 1 and stops there.

The surface plasmon sensor of this embodiment is
One light beam in addition to the dielectric block 10
Laser light source 14 composed of a semiconductor laser or the like that generates 13
And an optical system 15 for passing the light beam 13 through the dielectric block 10 and entering the interface 10b between the dielectric block 10 and the metal film 12 so as to obtain various angles of incidence. A collimator lens 16 for converting the light beam 13 totally reflected by the light into a parallel light, a light detecting means 17 for detecting the parallelized light beam 13, a driver 19 connected to the light detecting means 17, and a computer. The signal processing unit 20 includes a system and the like, and a display unit 21 connected to the signal processing unit 20.

FIG. 2 is a block diagram showing an electrical configuration of the surface plasmon sensor. The light detecting means 17 is a photodiode array in which a plurality of photodiodes 17a, 17b, 17c... Are arranged in a line. Each of these photodiodes 17a, 17b, 17c... Is connected to a multiplexer 18 of a driver 19 via a signal line H.

Here, the signal line H is grounded via a resistor R. Although FIGS. 1 and 2 show only the ground state of one signal line H, all the signal lines H are similarly grounded.

The driver 19 includes a multiplexer 18
, An amplifier 23 for amplifying the output of the differential amplifier 22, and an A / D converter for digitizing the output of the amplifier 23 and inputting it to the signal processing unit 20 24, a driving circuit 25 that inputs the clock CLK and the address signal SA to the multiplexer 18 to drive the multiplexer 18, and a controller 26 that controls the operation of the driving circuit 25 based on an instruction from the signal processing unit 20. are doing.

As shown in FIG. 1, a light beam 13 emitted in a divergent light state from a laser light source 14 is
Focusing is performed on the interface 10b between the dielectric block 10 and the metal film 12. Therefore, the light beam 13 includes components incident on the interface 10b at various incident angles θ. The incident angle θ is 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
Contains components that are reflected at various reflection angles.

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 disposed in advance so that the polarization direction thereof becomes a predetermined direction. Alternatively, the polarization direction of the light beam 13 may be controlled by a wavelength plate or a polarizing plate.

After total reflection at the interface 10b, the light beam 13 collimated by the collimator lens 16 is detected by the light detecting means 17. The light detecting means 17 which is a photodiode array is provided in the plane shown in FIG. 1 with respect to the direction of travel of the collimated light beam 13.
.., 17b, 17c,... Therefore, the different components of the light beam 13 totally reflected at the interface 10b at various reflection angles are received by the different photodiodes 17a, 17b, 17c,....

The photodiodes 17a, 17b, 17c...
Are input to the multiplexer 18. The multiplexer 18 controlled by the drive circuit 25 sequentially selects the outputs of two photodiodes adjacent to each other and inputs them to the differential amplifier 22. Differential amplifier 22
Calculates the difference between the outputs of the two photodiodes sequentially input in this manner. Therefore, the differential signal Sd sequentially output from the differential amplifier 22 is divided into a plurality of photodiodes 17a,
It can be considered that the light detection signals output from 17b, 17c... Are differentiated with respect to their juxtaposition directions.

The differential signal Sd sequentially output from the differential amplifier 22
Is amplified by the amplifier 23 and then input to the A / D converter 24. The A / D converter 24 digitizes the difference signal Sd and inputs it to the signal processing unit 20.

FIG. 3 shows a light beam 13 totally reflected at the interface 10b.
The relationship between the light intensity at each incident angle θ and the output of the differential amplifier 22 will be described. Here, the interface 10b of the light beam 13
It is assumed that the relationship between the incident angle θ and the light intensity I is as shown in the graph of FIG.

Light incident on the interface 10b at a specific incident angle θ _SP excites surface plasmons at the interface between the metal film 12 and the sample 11, and the reflected light intensity I of this light sharply decreases. That is, θ _SP is the angle for eliminating total reflection, and the reflected light intensity I takes a minimum value at this angle θ _SP . This decrease in the reflected light intensity I is observed as a dark line in the reflected light, as indicated by D in FIG.

FIG. 3B shows a photodiode 17.
a, 17b, 17c... are shown in parallel, and as described above, these photodiodes 17a, 17b, 17c
.. Correspond to the incident angle θ uniquely.

The photodiodes 17a, 17b, 17c
…… in the juxtaposition direction, that is, the incident angle θ and the differential amplifier
The relationship with the differential value I ′ of the reflected light intensity I indicated by the output Sd of 22 is as shown in FIG. In FIG. 1, for the sake of simplicity, it is shown that the differential amplifier 22 is connected to each of two photodiodes adjacent to each other. Connected to two differential amplifiers 22
One photodiode is selected.

Based on the value of the differential value I ′ indicated by the output of the A / D converter 24, the signal processing unit 20 calculates the differential value I ′ that is closest to the differential value I ′ = 0 corresponding to the total reflection elimination angle θ _SP. The combination of the photodiodes (in the example of FIG. 3, the photodiodes 17 d and 17 e) for which ′ is obtained is selected, and the differential value I ′ thereof is displayed on the display means 21. In some cases, there may be a combination of photodiodes in which the differential value I ′ = 0 has been obtained.
= 0 is displayed.

Thereafter, every time a predetermined time elapses, a differential value I 'for the output of the selected photodiodes 17d and 17e is obtained, and the value is displayed on the display means 21. This differential value I 'is obtained by changing the dielectric constant, that is, the refractive index of the substance in contact with the metal film 12 (see FIG. 1) of the measurement chip, and moving the curve shown in FIG. Changes up and down accordingly. Therefore, by continuously measuring the differential value I ′ with the passage of time, it is possible to examine the change in the refractive index of the substance in contact with the metal film 12, that is, the change in the characteristics.

In particular, in this embodiment, the liquid sample is formed on the metal film 12.
11 is fixed, and the refractive index of the sensing medium 30 changes in accordance with the state of their binding. Therefore, by continuously measuring the differential value I ′, this binding is performed. You can check how the state changes. 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 clear from the above description, in this embodiment, a plurality of photodiodes 17a,
Since a photodiode array in which 17b, 17c... Are arranged in a line is used, FIG.
Even if the curve shown in (1) changes to some extent in the form of moving in the left-right direction, dark lines can be detected. That is, by using such an array of light detecting means 17, a large dynamic range of measurement can be secured.

In this embodiment, since the signal lines H connected to the photodiodes 17a, 17b, 17c... Of the light detecting means 17 are grounded, electric charges are stored in the multiplexer 18 when the reflected light intensity I is measured. The accumulated charge is prevented from riding on the outputs of the photodiodes 17a, 17b, 17c... In the next measurement. Therefore, the occurrence of so-called charge noise due to the accumulated charges can be prevented, a high S / N photodetection signal can be obtained, and the accuracy of sample analysis can be improved.

It is to be noted that, in order to examine the state of change in 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 ′ every time a predetermined time elapses
And the difference ΔI ′ between the differential value I ′ (0) measured first and the differential value I ′ (t) measured after a predetermined time has elapsed.
May be displayed.

In the embodiment described above,
Although the dielectric block 10 and the metal film 12 constitute a disposable measurement chip, even when the dielectric block 10 is incorporated into the surface plasmon sensor main body without being formed into a chip, the same is applied by applying the present invention. The effect can be achieved.

Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 4, the same elements as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted unless otherwise required.

The sensor using the attenuated total reflection according to the second embodiment is the leak mode sensor described above.
Also in this example, the dielectric block 10 formed as a measurement chip is used. A cladding layer 40 is formed on one surface (the upper surface in the figure) of the dielectric block 10, and an optical waveguide layer 41 is further formed thereon.

The dielectric block 10 is made of, for example, synthetic resin or B
It is formed using an optical glass such as K7. On the other hand, the cladding layer 40 is formed in a thin film shape using a dielectric material having a lower refractive index than the dielectric block 10 or a metal such as gold. Further, the optical waveguide layer 41 is a dielectric having a higher refractive index than the cladding layer 40,
For example, this is also formed into a thin film using PMMA. The thickness of the cladding layer 40 is, for example, 36.5 nm when formed from a gold thin film, and the thickness of the optical waveguide layer 41 is, for example, PMMA.
Is formed to about 700 nm.

In the leakage mode sensor having the above configuration,
The light beam 13 emitted from the laser light source 14 is converted into a dielectric block.
When the light beam 13 is incident on the cladding layer 40 at an incident angle equal to or larger than the total reflection angle through the interface 10, the light beam 13 is totally reflected at the interface 10 b between the dielectric block 10 and the cladding layer 40.
The light of a specific wave number that has passed through the optical waveguide layer 41 and entered the optical waveguide layer 41 at a specific incident angle propagates through the optical waveguide layer 41 in a guided mode. When the waveguide mode is excited in this manner, most of the incident light is taken into the optical waveguide layer 41, and thus the 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 41 depends on the refractive index of the sample 11 on the optical waveguide layer 41, the specific incident angle at which the attenuated total reflection occurs is known.
The refractive index of 11 and the characteristics of the sample 11 related thereto can be analyzed. Then, the characteristics of the sample 11 can be analyzed based on the reflected light intensity I near the specific incident angle and the differential value I ′.

Also in the present embodiment, the signal lines H connected to the plurality of photodiodes (not shown) of the light detecting means 17 are also used.
Are grounded, so that the same effect as in the first embodiment can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing an electrical configuration of the surface plasmon sensor.

FIG. 3 is a schematic diagram showing a relationship between a light beam incident angle and detected light intensity and a relationship between a light beam incident angle and a differential value of a light intensity detection signal in the surface plasmon sensor.

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

[Explanation of symbols]

 10 Dielectric block 10a Sample holder of dielectric block 10b Interface between dielectric block and metal film 11 Sample 12 Metal film 13 Light beam 14 Laser light source 15 Optical system 16 Collimator lens 17 Photodetector (photodiode array) 17a , 17b, 17c... Photodiode 18 Multiplexer 19 Driver 20 Signal processing unit 21 Display means 22 Differential amplifier 23 Amplifier 24 A / D converter 25 Drive circuit 26 Controller 30 Sensing medium 31 Turntable 40 Cladding layer 41 Optical waveguide layer H Signal line

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; An optical system for incidence at various angles so as to obtain a total reflection condition at an interface between the dielectric block and the thin film layer, and a plurality of light receiving elements are arranged in a predetermined direction, and various reflections at the interface. A sensor using attenuated total reflection, comprising: a light detection unit for detecting a state of attenuated total reflection, which is disposed in a direction in which components of the light beam totally reflected at the angles are respectively received by different light receiving elements. A sensor using attenuated total reflection, wherein signal lines transmitting outputs of respective light receiving elements of the light detecting means to a subsequent stage are grounded. 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; An optical system for incidence at various angles so that total reflection conditions are obtained at the interface between the dielectric block and the metal film; and a plurality of light receiving elements arranged side by side in a predetermined direction, and various reflection angles at the interface. And a light detecting means for detecting a state of attenuated total reflection due to surface plasmon resonance, which is disposed in a direction in which the light receiving elements respectively receive the components of the light beam totally reflected by the light source. A sensor using attenuated total reflection, wherein a signal line for transmitting an output of each light receiving element of the light detecting means to a subsequent stage is grounded. 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 for causing the light beam to enter the dielectric block at various angles so as to obtain a total reflection condition at an interface between the dielectric block and the clad layer; Are arranged in parallel with each other, and are arranged in such a manner that components of the light beam totally reflected at various reflection angles at the interface are received by different light receiving elements, respectively, by excitation of a waveguide mode in the optical waveguide layer. In a sensor using attenuated total reflection, comprising: a photodetector for detecting a state of attenuated total reflection, a signal line transmitting an output of each light receiving element of the photodetector to a subsequent stage is grounded. Sensor using total reflection attenuation. 4. A multiplexer for sequentially selecting and outputting an output from a predetermined number of the plurality of light receiving elements, and a signal line between the multiplexer and each of the light receiving elements is grounded. 4. A sensor using attenuated total reflection according to claim 1, wherein: 5. The sensor using attenuated total reflection according to claim 1, wherein said light detecting means is a photodiode array.