JPH08193946A - Biosensor - Google Patents

Abstract

PURPOSE: To reduce the size of a biosensor while enhancing the sensitivity of measurement. CONSTITUTION: The biosensor 10 comprises a prism 12 having upper surface mounted with a sample plate 16 through a matching oil 14. Upper surface of the sample plate 16 is deposited with Au thin film 18 to provide a light reflection surface 20 and an evanescent wave coupling is formed. The biosensor 10 condenses the light emitted from a light source, e.g. an LED, through a condenser lens 24 and irradiates the light reflection surface 20 with a light condensed linearly. A CCD image pickup element 26 is disposed through a concave lens 28 on the side where the total reflection light from the light reflection surface 20 leaves the prism 12. Since the advancing path of light is altered by the concave lens 28, the reflection light is introduced to the CCD image pickup element 26 over a wide range.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a biosensor for measuring a substrate to be measured in a solution to be measured by using an optical system,
More specifically, a light-reflecting surface provided with a metal thin film has a light-transmitting light-transmitting medium that reflects light under geometric total reflection conditions, and the light-transmitting medium and the metal thin film form an evanescent wave coupling. The present invention relates to one using an optical system.

[0002]

2. Description of the Related Art Generally, in a biosensor, a substrate to be measured, which is a blood component such as a specific protein or antigen in blood, or a urine component such as glucose or ascorbic acid in urine, has a function of discriminating these substrates. A biological substance that has a biochemical reaction with the substrate is used. Then, various physicochemical displacements associated with the progress of this biochemical reaction are detected by the physicochemical device, and the specification of the measurement target substrate, its concentration, etc. are detected. For example, one that detects the substrate concentration through the electrode reaction of an electrode active substance that is consumed or produced by a biochemical reaction, or one that detects the enthalpy change that occurs with the progress of the biochemical reaction with a thermistor to detect the substrate concentration. These biosensors have been put to practical use since early on.

On the other hand, in recent years, attention has been paid to changes in the dielectric constant with the progress of biochemical reactions, and biosensors have been proposed for measuring a substrate to be measured in a solution to be measured using an optical device. (Japanese Patent Application Laid-Open No. 1-138443, Japanese Patent Application Publication No. 4-501462). In this biosensor, as an optical system, a light-transmitting light-transmitting medium that reflects light under a geometrical total reflection condition is provided on a light-reflecting surface provided with a metal thin film. An optical system that forms an evanescent wave coupling is used. The measuring principle is as follows.

When a light-transmitting medium of an optical system for forming an evanescent wave coupling, for example, a prism, is irradiated with a p-polarized light on a light-reflecting surface at various incident angles satisfying the condition of total reflection, it is peculiar when the incident angle has a certain value. The phenomenon occurs. That is, when the p-polarized light is applied to the light reflecting surface, an evanescent wave having a wave number with the incident angle θ as a variable is generated on the prism-side film surface of the metal thin film. Since metal can be regarded as a solid plasma, a surface plasmon wave as a quantum charge density wave is generated on the anti-prism side film surface of the metal thin film (hereinafter referred to as the thin film outer surface) by the tunnel effect of light. Caused by. This surface plasmon wave is generated as a wave between the medium contacting the metal thin film with the outer surface of the thin film as a boundary surface.

When the incident angle θ has a certain value, a surface plasmon resonance phenomenon occurs in which the wave numbers of the evanescent wave and the surface plasmon wave coincide with each other, and the light energy is used as the excitation energy of the surface plasmon wave. Be seen. At this time, in terms of energy, there is a relation that the energy of the light incident on the light reflecting surface is equal to the sum of the energy used to excite the surface plasmon wave and the energy of the reflected light from the reflecting surface. For this reason, the state of changes in the reflection angle and the energy (light amount) is measured by using, for example, a multi-channel light receiving device, and the presence or absence of the surface plasmon resonance phenomenon, and consequently the incident angle when the phenomenon occurs, are obtained. be able to.

On the other hand, there is a correlation between the incident angle when the surface plasmon resonance phenomenon occurs and the refractive index of the medium, and this refractive index can be defined by the dielectric constant of the medium from Maxwell's equation, and the biochemistry by biological substances. There is a correlation between the progress of the static reaction and the dielectric constant. Therefore, the angle of incidence at that time is determined from the angle of reflection when the amount of reflected light suddenly decreases, and the degree of progress of the biochemical reaction by the biological substance, that is, the substrate concentration is calculated from the above correlations.

By the way, in such a biosensor, the metal thin film is very close to the outer surface of the thin film, specifically, the evanescent region (about 100 nm) that causes the tunnel effect.
In, it is necessary for the biochemical reaction between the substrate and the biological substance to occur. For this reason, the patent application publication No. 4-501605
As has been proposed in US Pat. No. 5,968,967, it is generally practiced to immobilize a layer on which a biological substance is immobilized, a so-called ligand layer, on the above-mentioned membrane surface of a metal thin film.

As described above, the biosensor for measuring the substrate to be measured in the solution to be measured using the optical system that forms the evanescent wave bond is not affected by the degree of coloring or opacity of the solution to be measured, or Since it has the advantage that it is sufficient to fix a biological substance that causes a biochemical reaction with the substrate on the outer surface of the thin metal film, it is rapidly spreading.

[0009]

In the above biosensor, the measurement principle is to detect the change in the dielectric constant of the metal thin film near the outer surface of the thin film. Therefore, when the adsorption of the substrate of the low molecular weight molecule to the ligand layer or the adsorption of the substrate to the layer is small, the change in the dielectric constant is small and the measurement sensitivity is lowered.

As one measure for improving the measurement sensitivity, it is considered that the angular resolution of the reflected light intensity (amount of received light) -reflection angle curve is increased. This angular resolution is defined by the distance from the prism to the light receiving device, provided that the size of each light receiving element forming the multi-channel light receiving device and the distance between the light receiving elements are constant. When the light receiving device is separated from the prism, its light receiving region is widened and the distribution of the amount of received light along the line of the light receiving element can be diffused, so that the angular resolution of the reflection angle can be improved. For example, in a multi-channel light receiving device in which light receiving elements having a size of about 20 μm are arranged as close to each other as possible, the resolution of each light receiving element at a distance of 20 cm from the prism corresponds to 0.1 m degrees. However, when the light receiving device is separated from the prism by 40 cm, the resolution is 0.05 m, which is about twice the resolution.

By thus separating the light receiving device from the prism, the angular resolution can be easily increased and the measurement sensitivity can be improved. However, the size of the sensor becomes large because the light receiving device is separated. On the other hand, if the sensor is downsized, the light receiving device approaches the prism, so that the measurement sensitivity cannot be improved. It should be noted that if the light receiving element is made small, the angular resolution can be improved without separating the light receiving device and the sensor can be downsized, but there is a physical limit to miniaturization of the light receiving element, Miniaturization and improved resolution are limited.

The present invention has been made to solve the above problems, and an object thereof is to achieve both miniaturization of a sensor and improvement of measurement sensitivity.

[0013]

In order to achieve the above object, the means adopted by the biosensor according to claim 1 is to reflect light under a geometric total internal reflection condition on a light reflecting surface provided with a metal thin film. An optical system having a light-transmitting light-transmitting medium for forming an evanescent wave bond between the light-transmitting medium and the metal thin film is used to measure a measurement target substrate in a solution to be measured in contact with the metal thin film. The biosensor is a biosensor, wherein the optical system transmits light from a light source through the light transmitting medium and collects and irradiates the light on the light reflecting surface, and the light transmitting means reflects the light on the light reflecting surface. Light receiving means for receiving the reflected light emitted from the medium to the outside and detecting the amount of the reflected light,
Interposing between the light receiving means and the light transmitting medium, the traveling path of the reflected light emitted from the light transmitting medium to the outside is changed to a side where the light receiving area of the light receiving means is expanded, and the light receiving means reflects the reflected light. The gist of the present invention is to provide a reflected light guide means for guiding light.

According to another aspect of the biosensor, the reflected light guiding means has a concave lens.

According to a third aspect of the biosensor, the reflected light guiding means has a reflecting mirror.

In the biosensor according to claim 4, the reflecting mirror is a convex mirror.

In the biosensor of the fifth aspect, the reflecting mirror is a concave mirror.

In the biosensor according to the sixth aspect, the reflected light guiding means has a convex lens, the convex lens is focused on the lens side of the light receiving means, and an enlarged image is formed on the light receiving means. It was arranged to do.

[0019]

In the biosensor according to claim 1 having the above structure, the behavior of the light from the light source entering the light transmissive medium to being totally reflected by the light reflective surface and being emitted from the light transmissive medium is The same as before. That is, the light condensed and emitted from the light source by the irradiation means to the light reflecting surface reaches the light reflecting surface of the light transmitting medium and is totally reflected by the light reflecting surface. Then, for incident light incident at a specific incident angle, a surface plasmon resonance phenomenon in which the evanescent wave on the light-transmitting medium-side film surface of the metal thin film and the surface plasmon wave on the exposed surface of the metal thin film resonate with their wave numbers matching each other. cause. When this surface plasmon resonance phenomenon occurs, the energy of light is used as the excitation energy of the surface plasmon wave, so the energy of light reflected from the light reflecting surface decreases. In this case, when the exposed surface of the metal thin film comes into contact with the solution to be measured of the substrate to be measured via the ligand layer, the biochemical reaction between this substrate and the biological substance proceeds, and the dielectric constant of the solution to be measured, Since the refractive index changes, the incident angle θ reflects the substrate concentration in the solution to be measured.

Light of various incident angles is incident on the light reflecting surface at one time by condensing and is reflected. Therefore, reflected light totally reflected at various reflecting angles corresponding to each incident angle is reflected from the light reflecting surface. Emit from the light transmission medium at once. At this time, only the reflected light having the reflection angle corresponding to the incident angle θ is emitted from the light transmissive medium as light with a small amount of energy lost, and the reflected light having the reflection angle corresponding to the incident angle other than θ is generated. , And emits as a high-intensity light without energy loss.

Further, in the biosensor according to claim 1, the reflected light emitted from the light transmitting medium is received by the light receiving means along its traveling path by the reflected light guiding means interposed between the light receiving means and the light transmitting medium. The area is changed to the expanding side and guided to the light receiving means. Therefore, in the light receiving means, the light receiving area thereof is expanded even if the light receiving means is not separated from the light transmitting medium, so that the distribution of the amount of received light is diffused and the angular resolution is improved. Then, the light receiving means having a high angular resolution receives the reflected light from the light reflecting surface for each incident angle and detects the light amount. Therefore,
The correlation between the incident angle and the light amount thereof can be obtained with high sensitivity, and the incident angle θ when the light amount of the reflected light is at the lowest level can be obtained with high accuracy. As a result, the correlation between this incident angle θ and the refractive index of the medium, the correlation between the refractive index of the medium and the dielectric constant, the correlation between the progress of the biochemical reaction by the biological substance and the dielectric constant, etc. From this, the substrate concentration can be calculated.

In the biosensor according to the second aspect, the concave lens is used to change the traveling path of the reflected light emitted from the light transmission medium and guide the light to the light receiving means, thereby expanding the light receiving area in the light receiving means and distributing the received light amount. Promote diffusion.

In the biosensor according to the third aspect, the reflected light emitted from the light transmitting medium is reflected by the reflecting mirror to change its traveling path, and the optical path length is ensured through the reflection by the reflecting mirror.
Therefore, it is not necessary to lengthen the linear distance between the light receiving means and the light transmitting medium by the amount of reflecting the reflected light. Then, by securing the optical path length, the light receiving area of the light receiving means is expanded and the received light amount is distributed and diffused.

In the biosensor according to claim 4, the reflected light is reflected by the convex mirror to secure the optical path length through the change of the traveling path, and the traveling path of the reflected light to the side where the light receiving area of the light receiving means is expanded. And change. As a result, the light receiving area of the light receiving unit is expanded and the distribution of the received light amount is diffused.

In the biosensor according to the fifth aspect, the reflected light is reflected by the concave mirror to secure the optical path length through the change of the traveling path and the traveling path of the reflected light to the side where the light receiving area of the light receiving means is expanded. And change. As a result, the light receiving area of the light receiving unit is expanded and the distribution of the received light amount is diffused.

In the biosensor according to the sixth aspect, the reflected light emitted from the light transmitting medium passes through the convex lens, changes its traveling path, passes through the focal point of the lens, and is guided to the light receiving means. Since this convex lens focuses on the lens side of the light receiving means and forms an enlarged image on the light receiving means,
When the reflected light is guided to the light receiving means via the focal point, it diffuses to the side where the light receiving region of the light receiving means expands and reaches the light receiving means. Therefore, in the light receiving means, the distribution of the amount of received light is diffused.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the biosensor according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic side view of the biosensor 10 of the first embodiment.

As shown in the figure, the biosensor 10 is provided with a prism 12, and a sample plate 16 is placed on the upper surface of the prism 12 with a matching oil 14 interposed. The sample plate 16 is the prism 1
It is made of the same light-transmitting material as that of No. 2 and its refractive index is the same as that of the prism 12. The matching oil 14 is an oil whose refractive index is similar to that of the prism 12 and the sample plate 16, and functions to match the refractive index between the prism 12 and the matching oil 14. Therefore, gel, hydrophobic polymer, or the like can be used instead of the matching oil 14 as long as it can fulfill the function.

A gold thin film (Au thin film) 18 having a film thickness of 50 nm is formed on the upper surface of the sample plate 16 by vapor deposition. The Au thin film 18 is formed on the upper surface of the sample plate 16.
The light reflection surface 20 is a total reflection surface that reflects light under the geometrical total reflection condition over the vapor deposition range. The sample plate 16 and the Au thin film 18 form evanescent wave coupling on the light reflecting surface 20. Further, on the exposed film surface of the Au thin film 18 (hereinafter, simply referred to as a surface), a ligand layer 2 on which a biological substance having a function of discriminating against a measurement target substrate and causing a biochemical reaction with the substrate is immobilized.
2 is formed. The ligand layer 22 is divided into two parts on the front side and the back side of the paper surface, and the ligand layer 22 on the front side is a ligand layer on which an active biological substance is immobilized, and the other ligand layer on the back side. Reference numeral 22 is a ligand layer on which an inactivated biomaterial is immobilized. That is, the front side ligand layer 22 is used as the substrate measurement sensor section, and the back side ligand layer 22 is used as the correction sensor section. In this case, the biological material is inactivated by a strong acid or a strong alkali, or by electron beam irradiation such as ultraviolet rays, ultrasonic treatment, or heat treatment at about 70 ° C.

In addition, the biosensor 10 includes a light source (not shown) that linearly emits light of a single wavelength such as an LED (light emitting diode), and irradiates the prism 12 with light from this light source. A condenser lens 24 is arranged between the light source and the prism 12 in front of the prism 12, and a p polarizing plate (not shown) is arranged between the light source and the condenser lens 24. The position of the condenser lens 24 is adjusted so that the light passing through the condenser lens 24 is condensed in a line on the light reflection surface 20. Therefore, the light emitted from the light source reaches the condenser lens 24 after being p-polarized, and thereafter passes through the prism 12 as p-polarized light and is linearly condensed on the light reflection surface 20. Therefore, the p-polarized light is incident on the light reflection surface 20 at an incident angle (θ1 to θ2) within a predetermined range determined by the focal length F of the condenser lens 24, the aperture length D, the angle of the optical axis of the condenser lens 24, and the like. To reach.

On the side where the reflected light totally reflected by the light reflecting surface 20 is emitted from the prism 12, a CCD image pickup device 26 for detecting the amount of received light and converting it into an electric signal is arranged with a concave lens 28 interposed. Has been done. CCD image sensor 2
Reference numeral 6 is a linear image sensor in which 2048-bit light receiving elements are arranged in a line. Therefore, the light reflecting surface 2
The light (p-polarized light) totally reflected at 0 passes through the prism 12 and is emitted to the outside and reaches the concave lens 28.
As a result, the traveling path of light is changed as shown in FIG.
It is guided to the image sensor 26. Then, the CCD image pickup device 26 detects the amount of light. The reflected light reflected by the light reflecting surface 20 is the same as the incident light on the light reflecting surface 20.
It is a wave of amplitude within the incident plane, and in the CCD image pickup device 26, the amount of light for each reflection angle, that is, the incident angle (θ1
The amount of light for each θ 2) is detected by the light receiving element in the light receiving range of the CCD image pickup element 26.

In this case, on the surface of the Au thin film 18 on the sample plate 16, the dielectric constant of the solution to be measured changes as described below depending on the presence or absence of the activity of the biological substance and stabilizes at the value after the change. It is detected from each CCD image pickup device 26.

On the side of the ligand layer 22 to which the active biological substance is fixed, the biochemical reaction between the biological substance and the substrate to be measured proceeds to the extent defined by the substrate concentration. The index, and thus its refractive index, changes as the biochemical reaction progresses and stabilizes at a value defined by the substrate concentration. At this time, the change in the dielectric constant of the solution to be measured, and thus in the refractive index, is different from that of the sample plate 16 and Au.
By the evanescent wave coupling formed with the thin film 18,
It is observed as a phenomenon of energy of reflected light when the surface plasmon resonance phenomenon occurs.

That is, the p-polarized light emitted from the light source is condensed by the condenser lens 24 and is in the above range (θ1 to θ).
At the incident angle of 2), the light reaches the light reflecting surface 20 where the evanescent wave coupling is formed. At this time, the p-polarized light that is incident at an incident angle of a certain angle (θS1) within the above range is an evanescent wave on the film surface of the light reflecting surface 20 of the Au thin film 18 and a surface plasmon of the Au thin film 18 on the measured solution side. The waves are caused to resonate with their wave numbers matched to cause a surface plasmon resonance phenomenon. When this surface plasmon resonance phenomenon occurs, the energy of light with an incident angle of θS1 is used as the excitation energy of the surface plasmon wave, and the energy of reflected light with a reflection angle of θS1 from the light reflecting surface 20 decreases.

Therefore, the state of the amount of light received by the CCD image pickup device 26 which receives the reflected light from the light reflecting surface for each incident angle (θ1 to θ2) at the reflection angle of θ1 to θ2 is shown in FIG.
As schematically shown in FIG. 2, the energy (light amount) of the reflected light at θS1 is the lowest (FIG. 2 (A)).

On the other hand, on the side of the ligand layer 22 to which the inactivated biological substance is fixed, the biochemical reaction with the substrate to be measured does not proceed, so that the dielectric constant of the solution to be measured, and hence its refractive index, is initially set. The value of is constant. However, the surface plasmon resonance phenomenon occurs due to p-polarized light incident at an incident angle of a certain angle (θS0), and in this case, the amount of received light in the CCD image pickup device 26 is such that the energy of reflected light at θS0 becomes the minimum (FIG. 2). (B)).

By the way, the incident angle on the horizontal axis in the schematic view of FIG. 2 corresponds to the arrangement of the 2048-bit light receiving elements in the CCD image pickup element 26, and such a light amount distribution is CC.
The state changes as the light receiving area received by the D image pickup device 26 changes. More specifically, in the conventional biosensor in which the concave lens 28 does not exist, the light receiving area of the CCD image pickup device 26 is indicated by SOLD in the figure as shown by the chain double-dashed line in FIG. In the case of the example, the light receiving area is SNEW. That is, in the biosensor 10,
The concave lens 28 changes the traveling path of light to guide the light to the CCD image pickup device 26, and the light receiving area of the CCD image pickup device 26 is expanded.

Then, the detection result of each light receiving element of the CCD image pickup element 26 in this light receiving area forms the above light amount distribution. Therefore, when the light receiving area is narrow, the light amount distribution can be obtained only by a small number of light receiving elements, whereas when the light receiving area is extended, a light amount distribution can be obtained by a large number of light receiving elements. For this reason, the biosensor 1 of the present embodiment having an expanded light receiving region.
According to 0, the angular resolution of the CCD image pickup device 26 can be improved. On the other hand, in order to obtain the same light receiving area as the biosensor 10 of the present embodiment with the conventional biosensor in which the concave lens 28 does not exist, the CCD image pickup device 26 must be separated from the prism 12 as shown in FIG. On the other hand, the biosensor 10 does not require this. As a result, according to the biosensor 10 of the first embodiment, it is possible to reduce the size of the sensor and improve the measurement sensitivity.

A comparison test between the biosensor 10 of this embodiment and a conventional biosensor having no concave lens 28 will be described below. The CCD image pickup device 26 in each of these sensors is a linear image sensor (model number: μPD35H73) manufactured by NEC Corporation having a 2048-bit light receiving element. Further, in subjecting both sensors to a comparison test, human serum albumin was used as the measurement target substrate, and human serum albumin antibody was immobilized on the ligand layer 22 of both sensors as an active biological substance (antibody).

First, the ligand layer 22 of the biosensor 10
The intensity (light quantity) of reflected light when pure water was introduced into was measured. Next, the ligand layer 22 has a concentration of 50 μg / m 2.
The reflected light intensity (light amount) was measured when 1 human aqueous solution of human serum albumin was introduced and the human serum albumin was brought into contact with the biological material of the ligand layer 22 for 5 minutes. Then, the correlation between the reflected light intensity and the reflection angle was obtained for each.
The result is shown in FIG. The horizontal axis in the figure is a number indicating the position of each light receiving element corresponding to the reflection angle.

Next, with a conventional biosensor having no concave lens 28, the reflected light intensity (light amount) of pure water and human serum albumin aqueous solution (50 μg / ml) was measured in the same manner as above, and The correlation of the reflection angle was obtained. The result is shown in FIG.

As can be seen from FIG. 3, in the biosensor 10 of the embodiment, the number of the light receiving element that gives the lowest reflected light intensity is 15 for pure water and an aqueous solution of human serum albumin having a predetermined concentration.
5 move, whereas 4 in conventional biosensor
It was 6. Therefore, according to the biosensor 10 of the example, the reflected light intensity change can be greatly expressed by changing the traveling path of light by the concave lens 28 and expanding the light receiving region. As a result, the biosensor 10 of the example
According to the above, it can be said that a slight change in the concentration of the substrate to be measured can be captured as a large change in the intensity of reflected light, and the sensitivity can be improved.

Next, another embodiment will be described. In the biosensor of each of the following examples, the first sensor
The biosensor 10 of the embodiment, the prism 12, the sample plate 16, the CCD image pickup device 26, and the like have the same main configuration, but the configurations are different in the following points. In the following description of each embodiment, the same members as those in the first embodiment will be designated by the same reference numerals to avoid duplication of description, and the description thereof will be omitted.

In the biosensor 30 of the second embodiment, as shown in FIG.
As shown in FIG.
Instead, it has a convex lens 32. This convex lens 32
As shown in the figure, the focal point f is located closer to the lens than the CCD image pickup device 26, and is arranged so as to form an enlarged image on the CCD image pickup device 26. Therefore, the second
Also with the biosensor 30 of the embodiment, the sensor can be downsized and the measurement sensitivity can be improved by changing the traveling path of the light passing through the focus f by the convex lens 32 and expanding the light receiving region.

As shown in FIG. 5, the biosensor 40 of the third embodiment is provided with an Au thin film 18 formed directly on the upper surface of the prism 12, and the upper surface of this prism 12 is used as a light reflecting surface 20. Further, the light source 3 is provided on the light reflecting surface 20 on the upper surface of the prism 12.
In collecting and irradiating the light from the light source 4, a combination lens including convex lenses 44 and 46 is used between the light source 34 and the prism 12. Note that, similarly to the biosensor 10, the sample plate 16 may be placed on the upper surface of the prism 12 with the matching oil 14 interposed.

In this biosensor 40, instead of the concave lens 28 in the biosensor 10, the concave mirror 4 is used.
8 As shown in the figure, the concave mirror 48 reflects the reflected light emitted from the prism 12 on the concave mirror surface, changes the traveling path of the reflected light, and expands the light receiving area of the CCD image pickup device 26. Therefore, also with the biosensor 40 of the third embodiment, it is possible to reduce the size of the sensor and improve the measurement sensitivity by changing the traveling path of light by the concave mirror 48 and expanding the light receiving region.

The biosensor 50 of the fourth embodiment, as shown in FIG. 6, has the concave mirror 4 in the biosensor 40 described above.
Instead of 8, it has a convex mirror 52. This convex mirror 52
As shown, the reflected light emitted from the prism 12 is reflected by the convex mirror surface to change the traveling path of the reflected light, and C
The light receiving area of the CD image pickup device 26 is expanded. Therefore, also by the biosensor 50 of the fourth embodiment, it is possible to reduce the size of the sensor and improve the measurement sensitivity by changing the traveling path of light by the concave mirror 48 and expanding the light receiving region.

Although some embodiments of the present invention have been described above, the present invention is not limited to such embodiments and can be implemented in various modes without departing from the scope of the present invention. Of course.

For example, instead of the concave mirror 48 and the convex mirror 52 in the biosensor in the above-mentioned third and fourth embodiments, a plane reflecting mirror can be used. With the plane reflecting mirror, the reflected light emitted from the prism 12 can be reflected by the plane reflecting mirror to change its traveling path, and the optical path length in the sensor can be secured. Therefore, that much CC
It is not necessary to increase the linear distance between the D image pickup device 26 and the prism 12. Further, by securing the optical path length, the light receiving region in the sample plate 16 can be expanded without separating the CCD image pickup device 26 and the prism 12 so much. In this case, if the optical path length is secured by combining two or more plane reflecting mirrors, the CCD image pickup device 26 need not be separated from the prism 12.

[0050]

As described in detail above, in the biosensor of the present invention described in claims 1 to 6, the reflected light reflected by the light reflecting surface and emitted from the light transmitting medium is received in the traveling direction thereof. The light receiving area of the means is changed to the side where the light receiving area expands, and the light receiving area is guided to the light receiving means. Therefore, the improvement of the angular resolution through the expansion of the light receiving area of the emitted reflected light is realized without separating the light receiving means from the light transmitting medium. As a result, according to the biosensor of the present invention described in claims 1 to 6, both miniaturization of the sensor and improvement in measurement sensitivity can be achieved.

[Brief description of drawings]

FIG. 1 is a schematic side view of a biosensor 10 according to a first embodiment.

FIG. 2 is a CCD image pickup device 26 in the biosensor 10.
The graph which shows the correlation of the incident angle and its light quantity obtained from.

FIG. 3 is a graph for explaining the results of a comparison test between the biosensor 10 of the example and a conventional biosensor.

FIG. 4 is a schematic side view of a biosensor 30 according to a second embodiment.

FIG. 5 is a schematic side view of a biosensor 40 according to a third embodiment.

FIG. 6 is a schematic side view of a biosensor 50 according to a fourth embodiment.

[Explanation of symbols]

 10, 30, 40, 50 ... Biosensor 12 ... Prism 14 ... Matching oil 16 ... Sample plate 18 ... Au thin film 20 ... Light reflecting surface 22 ... Ligand layer 24 ... Condensing lens 26 ... CCD image sensor 28 ... Concave lens 32 ... Convex lens 34 ... Light source 44, 46 ... Convex lens 48 ... Concave mirror 52 ... Convex mirror

Claims (6)

[Claims] 1. A light-reflecting surface provided with a metal thin film, comprising a light-transmitting light-transmitting medium that reflects light under geometric total reflection conditions, and the light-transmitting medium and the metal thin film couple evanescent waves. A biosensor for measuring a substrate to be measured in a solution to be measured, which is in contact with the metal thin film, by using an optical system for forming the optical system, wherein the optical system transmits light from a light source through the light transmission medium. A light irradiating unit that collects and irradiates the light reflecting surface, and a light receiving unit that receives the reflected light that is reflected by the light reflecting surface and is emitted to the outside from the light transmitting medium, and that detects the light amount of the reflected light, Interposing between the light receiving means and the light transmitting medium, the traveling path of the reflected light emitted from the light transmitting medium to the outside is changed to a side where the light receiving area of the light receiving means is expanded, and the light receiving means reflects the reflected light. And a reflected light guide means for guiding light. Biosensor. 2. The biosensor according to claim 1, wherein the reflected light guiding unit has a concave lens. 3. The biosensor according to claim 1, wherein the reflected light guiding unit has a reflecting mirror. 4. The biosensor according to claim 3, wherein the reflecting mirror is a convex mirror. 5. The biosensor according to claim 3, wherein the reflecting mirror is a concave mirror. 6. The biosensor according to claim 1, wherein the reflected light guiding unit has a convex lens, and the convex lens is focused on the lens side of the light receiving unit and is an image enlarged on the light receiving unit. A biosensor arranged to image the.