JP3974157B2 - Surface plasmon sensor - Google Patents

Description

  The present invention relates to a surface plasmon sensor that detects a sample or a substance in the sample using surface plasmon resonance.

  Conventionally, surface plasmon resonance is known. The surface plasmon resonance means that when a laser beam is incident on a metal film on a dielectric substrate with an appropriate polarization direction and incident angle, a weak energy wave (evanescent wave) is generated on the metal film side by the laser beam. In addition, a dense wave (surface plasmon) in which free electrons vibrate in a direction parallel to the metal surface is excited on the metal surface, and when the wave number of the evanescent wave and the wave number of the surface plasmon coincide, It is a phenomenon that causes At this time, since the laser beam uses energy for the surface plasmon, the reflectance becomes small.

  The appropriate polarization direction refers to a polarization parallel to the incident plane, with the plane including the normal line of the dielectric substrate-metal interface and the optical axis of incident light (laser light) as the incident plane. Direction (p-polarized light). The surface plasmon resonance does not occur in the polarization direction (s-polarized light) perpendicular to the incident surface. Further, the appropriate film thickness and incident angle of the metal film are determined by the refractive index of the medium in contact with the metal film (see Non-Patent Document 1).

  Therefore, in recent years, many surface plasmon sensors using the surface plasmon resonance have been developed. The surface plasmon sensor obtains the refractive index of the medium from the incident angle that varies depending on the medium that causes the surface plasmon resonance, and when the constituent material of the medium or the constituent material of the medium is known from the result, The density can be detected. In addition, by applying this, a layer that adsorbs only specific molecules can be provided on the surface of the metal film, and the presence of specific molecules can be detected on the molecular order from the change in refractive index caused by the adsorption. . Furthermore, by tracking the time change, the adsorption process of the molecule and the time change of the reaction can be understood. In addition, since the width of the incident angle is very narrow, the resolution is high, and the change in refractive index can be measured with high accuracy. Therefore, in recent years, applications such as detection of proteins and polymers are spreading.

  By the way, in order to further improve the accuracy of the surface plasmon sensor, it is important to accurately measure the incident angle dependency of the reflectance, such as the width of the incident angle and the minimum value of the reflected light. . However, the higher the accuracy, the greater the influence of environmental changes. In particular, the intensity of the laser light changes due to the temperature change, humidity change, and time-dependent change of the light source itself that emits the laser light, resulting in measurement errors and S / N. The problem of worsening.

Therefore, as a means for solving the above problem, in Patent Document 1, attention is paid to the temperature change and humidity change of the light source, and a temperature sensor and a humidity sensor are installed in the light source, the sample part, the detector part, etc. Means for correcting the intensity of the light source by a look-up table storing the intensity variation of the light source due to change and humidity change is described. Also in Patent Document 2, correction for environmental change is made by the same means as in Patent Document 1.
JP 2003-90793 A (published March 28, 2003) JP 2004-37425 A (published February 5, 2003) JP 2002-90291 A (published March 27, 2002) JP 2003-14623 A (released on January 15, 2003) Surface Plasmons on smooth and rough surfaces and on gratings, Heinz Raether, Springer-Verlag, 1988 p.118-p.123

  However, in the solution means disclosed in Patent Document 1 and Patent Document 2, since the correction means such as the temperature sensor is provided, there is a problem that the number of parts increases and the cost increases. Further, the correction using the lookup table is complicated and further increases the cost.

  The change in the intensity of the light source is not only a problem of the light source itself but also a temperature change of a light source driving circuit for driving the light source. However, since the detection target of the temperature sensor and the humidity sensor is limited to only the light source, it cannot cope with a temperature change of the light source driving circuit or a change in intensity due to other factors. That is, a complete problem has not been solved. The other factors include the influence on the optical path.

  The present invention has been made in view of the above problems, and an object of the present invention is to realize a surface plasmon sensor that corrects the intensity change of the light source caused by any of the above factors at a low cost.

  The first polarized light described later is a polarization direction perpendicular to the incident surface, that is, s-polarized light when a normal line at the substrate-metal film interface and a surface including the optical axis of the light beam are used as the incident surface. The second polarized light is a polarization direction parallel to the incident surface, that is, p-polarized light.

In order to solve the above problems, a surface plasmon sensor according to the present invention is formed on a substrate, a light source that emits a light beam, a light source driving circuit that drives the light source by controlling the intensity of the light source, and a substrate. a metal film, a surface plasmon sensor provided with detecting means for detecting reflected light from the metal film for the incidence angle of the light beam, the cross-sectional area of the light beam, the monitor area and the measurement area comprising a dividing means for spatially dividing the bets, and adjacent to the light path of the light beam in the optical path and the measurement area of the light beam in the monitor area, the light beam of the monitor area, the polarization direction is located at a first polarization The light beam of the measurement region has a polarization direction of the second polarization, and the detection means detects the light intensity of the monitor region reflected by the metal film as a first detection result. In addition, the light intensity of the measurement region reflected by the metal film is detected as a second detection result, and the light source driving circuit controls the intensity of the light source based on the first detection result. It is said.

  According to said structure, the said surface plasmon sensor is provided with the division means divided | segmented into the said monitor area | region which is said 1st polarization | polarized-light, and the said measurement area | region which is said 2nd polarization | polarized-light, The light intensity of the said monitor area | region Is detected as the first detection result, and the intensity of the light source is controlled based on the first detection result, so that not only the temperature change and the time change due to the light source itself but also the temperature change of the light source driving circuit, etc. The intensity change of the light source due to the factor can be corrected.

  Further, since the monitor area and the measurement area pass through the same optical path, in addition to the above factors, it is possible to cope with the intensity change of the light source due to the influence on the optical path. Further, the number of parts can be reduced as compared with the case where a conventional temperature sensor and humidity sensor are provided. As described above, there is an effect that it is possible to realize a surface plasmon sensor that corrects the intensity change of the light source caused by all factors at low cost.

  In the surface plasmon sensor according to the present invention, in addition to the above configuration, the metal film is preferably replaceable with another metal film.

  With the above-described configuration, various types of detection can be performed with one apparatus. That is, the sensitivity and measurement range can be changed by replacing the metal film with a different material and film thickness. Further, by providing a layer that adsorbs only specific molecules on the surface of the metal film and replacing this layer, the specific molecules to be detected can be changed.

  In the surface plasmon sensor according to the present invention, in addition to the above-described configuration, the splitting by the splitting unit allows the light beam of the first polarization to partially pass through the splitting unit and does not pass through the splitting unit. It is preferable that the portion of the light beam is the monitoring region, and the portion of the light beam passing through the dividing means is changed from the first polarization to the second polarization to be the measurement region.

  With the above configuration, the light beam can be easily and inexpensively divided into the monitor region and the measurement region.

  In the surface plasmon sensor according to the present invention, in addition to the above configuration, the splitting by the splitting means allows the first polarized light beam to pass through the splitting means and pass through the first region in the splitting means. It is preferable to change the portion of the light beam to be the monitoring region and change the portion of the light beam passing through the second region in the dividing means from the first polarization to the second polarization to be the measurement region.

  With the above configuration, the light beam can be easily and inexpensively divided into the monitor region and the measurement region.

  In the surface plasmon sensor according to the present invention, in addition to the above configuration, the splitting by the splitting means allows the second polarized light beam to pass through the splitting means and pass through the first region in the splitting means. Preferably, the portion of the light beam to be changed from the second polarized light to the first polarized light is used as the monitor region, and the portion of the light beam passing through the second region in the dividing means is used as the measurement region.

  With the above configuration, the light beam can be easily and inexpensively divided into the monitor region and the measurement region.

  In the surface plasmon sensor according to the present invention, in addition to the above configuration, the splitting by the splitting means allows the light beam including the first polarized light and the second polarized light to pass through the splitting means, The portion of the light beam that passes through the first region is polarized to the first polarized light as the monitor region, and the portion of the light beam that passes through the second region in the dividing means is converted into the second polarized light. The measurement region is preferably polarized.

  With the above configuration, the light beam can be easily and inexpensively divided into the monitor region and the measurement region.

  In the surface plasmon sensor according to the present invention, in addition to the above-described configuration, it is preferable that the dividing means is installed in the parallel light of the light beam.

  According to said structure, since the said dividing means is installed in parallel light, it can divide | segment an area | region substantially uniformly with respect to the whole surface of the said light beam. Further, the aberration of the light beam focused on the metal film can be reduced.

  In the surface plasmon sensor according to the present invention, in addition to the above-described configuration, it is preferable that the dividing unit is installed in an optical path on the incident side with respect to the metal film.

  According to said structure, since the said dividing means is installed in the said incident side, the case where the said light beam injects only with the said 1st polarization | polarized-light can be created. As a result, the proportion of the light beam that is incident on the first polarized light whose surface plasmon is not excited increases, so that the amount of heat applied to the sample decreases and the sample is hardly damaged.

  In the surface plasmon sensor according to the present invention, in addition to the above configuration, the measurement region preferably includes a diameter in a direction parallel to the direction of the second polarization of the light beam.

  According to the above configuration, the measurement region includes a diameter in a direction parallel to the direction of the second polarization of the light beam with respect to the interface between the substrate and the metal film. When the light is condensed and incident with various incident angles, the range of incident angles can be utilized to the maximum.

  By the way, in the conventional surface plasmon sensor, in addition to the above-mentioned problems, there has been a problem that the reflectance cannot be measured accurately. More specifically, the incident angle of the light beam on the metal film is made incident with various angles by a lens in order to find an appropriate angle. At this time, the amount of incident light at each incident angle varies depending on the dust of the optical element in the optical path and the intensity distribution of the light source itself. As a result, there is a problem that the reflectance cannot be measured accurately.

  In Patent Document 3 and Patent Document 4, in order to eliminate such a non-uniform distribution of light intensity, the reflectance is obtained from the reflected light intensity of the second polarized light and the reflected light intensity of the first polarized light. However, in Patent Document 3 and Patent Document 4, since the change in the intensity of the light source is not taken into consideration, the reflectance is changed by the intensity change between the measurement with the second polarization and the measurement with the first polarization. There is a problem that an error occurs.

Therefore, in order to solve the above problems, a surface plasmon sensor according to the present invention includes a light source that emits a light beam, a light source driving circuit that drives the light source by controlling the intensity of the light source, and a substrate. a film metal layer, a surface plasmon sensor provided with detecting means for detecting reflected light from the metal film for the incidence angle of the light beam, the cross-sectional area of the light beam, a first polarization A polarization direction selecting unit that spatially divides the light beam into a monitor region and a measurement region in which the polarization direction can be selected, and the polarization direction of the light beam in the measurement region is the first polarization or the second polarization, and the measurement Calculating means for calculating the true reflectance of the second polarized light from the reflected light intensity of the second polarized light in the region and the reflected light intensity of the first polarized light, and an optical path of the light beam in the monitor region And above Adjacent to each other and the optical path of the light beam in the constant region, said detection means detects the light intensity of the monitor region reflected by the metal film as the first detection result, the measurement region reflected by the metal film Is detected as a second detection result, and the light source driving circuit controls the intensity of the light source based on the first detection result.

  According to the above configuration, the surface plasmon sensor divides the light beam into a first polarized monitor region and a measurement region in which the polarization direction can be selected, and the polarization direction of the light beam in the measurement region. Is a first polarization direction or a second polarization direction, and the light intensity of the monitor region is detected as a first detection result, and the intensity of the light source is determined based on the first detection result. In order to control, not only the temperature change and the temporal change due to the light source itself but also the intensity change of the light source due to factors such as the temperature change of the light source driving circuit can be corrected.

  Further, since the monitor area and the measurement area pass through the same optical path, in addition to the above factors, it is possible to cope with the intensity change of the light source due to the influence on the optical path. Further, the number of parts can be reduced as compared with the case where a conventional temperature sensor and humidity sensor are provided. As described above, there is an effect that it is possible to realize a surface plasmon sensor that corrects the intensity change of the light source caused by all factors at low cost.

  Further, as described above, since the intensity of the light source is corrected, the calculation means calculates the true reflectance of the second polarized light excluding the nonuniformity of the intensity distribution of the light beam. Can do. In addition, since the polarization direction selection unit is configured to divide the light beam and select the polarization direction, the surface plasmon sensor can be downsized.

  In the surface plasmon sensor according to the present invention, in addition to the above configuration, the calculation unit compares the reflected light intensity of the second polarized light in the measurement region with the reflected light intensity of the first polarized light, It is preferable to calculate the reflectance.

  According to the above configuration, the true reflectance of the second polarized light can be calculated.

  In the surface plasmon sensor according to the present invention, in addition to the above configuration, the calculation means takes a ratio or difference between the reflected light intensity of the second polarized light and the reflected light intensity of the first polarized light in the measurement region. Thus, it is preferable to calculate the reflectance.

  According to the above configuration, the true reflectance of the second polarized light can be calculated.

  In the surface plasmon sensor according to the present invention, in addition to the above configuration, the light beam incident on the polarization direction selection unit is linearly polarized light, and a λ / 2 plate is used as the polarization direction selection unit, and the λ / It is preferable to select the polarization direction by rotating two plates or by inserting / removing the λ / 2 plate.

  According to the above configuration, the light incident on the polarization direction selection unit is linearly polarized light, and the polarization direction can be selected at low cost by using the λ / 2 plate as the polarization direction selection unit. it can. When the polarization direction is selected by rotating the λ / 2 plate, the polarization direction can be selected without changing the transmittance of the light beam. On the other hand, when the polarization direction is selected by moving the λ / 2 plate, not only the same effect as the case of rotating the λ / 2 plate but also the assembly is easy.

  In the surface plasmon sensor according to the present invention, in addition to the above-described configuration, the light beam incident on the polarization direction selection unit is linearly polarized light, and a liquid crystal element is used as the polarization direction selection unit and applied to the liquid crystal element. It is preferable to select the polarization direction by adjusting the voltage.

  According to the above configuration, the use of the liquid crystal element as the polarization direction selection means does not cause a change in transmittance or a deviation of the optical path in the selected polarization direction. It is possible to reduce the size. Further, the light beam incident on the liquid crystal element can cope with any polarization state.

  In the surface plasmon sensor according to the present invention, in addition to the above configuration, the light beam incident on the polarization direction selection unit includes the first and second polarizations, and the polarization direction selection unit includes a polarizing plate or a polarizer. It is preferable to select the polarization direction by rotating the polarizing plate or the polarizer.

  According to said structure, when the said light beam has a multi-directional polarization direction, the said polarization direction can be selected cheaply by using the said polarizing plate or the said polarizer as said polarization direction selection means. If the intensity of the first polarized light and the second polarized light incident on the polarizing plate or the polarizer is the same, the polarization direction can be selected without changing the transmittance of the light beam. .

  In the surface plasmon sensor according to the present invention, in addition to the above configuration, the light beam is the first polarized light, and the polarization direction selecting means is installed only in the measurement region on the incident side, thereby allowing polarization. It is preferable to select the direction.

  With the above configuration, it is not necessary to adjust the polarization direction of the monitor region by setting the light beam from the light source to only the first polarization, and the polarization direction selection unit for the monitor region is not necessary. Is not necessary, and the cost can be reduced. Further, since the surface plasmon is not excited while the light beam is incident only with the first polarized light, the amount of heat applied to the sample is small, and the sample is hardly damaged.

  In order to solve the above problems, a surface plasmon sensor according to the present invention is formed on a substrate, a light source that emits a light beam, a light source driving circuit that drives the light source by controlling the intensity of the light source, and a substrate. A surface plasmon sensor comprising: a metal film; and a detecting means for detecting reflected light from the metal film for each incident angle of the light beam. The surface plasmon sensor comprises: a first polarized light; Polarization direction selection means capable of selectively extracting polarized light in terms of time, wherein the detection means detects the intensity of the first polarization component reflected by the metal film as a first detection result, and the metal The intensity of the second polarization component reflected by the film is detected as a second detection result, and the light source driving circuit controls the intensity of the light source based on the first detection result. .

  According to the above configuration, the surface plasmon sensor includes the polarization direction selection unit that can selectively extract the first polarization and the second polarization from the light beam in time, and the first polarization component. Is detected as a first detection result, and the intensity of the light source is controlled based on the first detection result. Therefore, not only the temperature change and the time change due to the light source itself, but also the temperature change of the light source driving circuit. It is possible to correct the intensity change of the light source due to factors such as the above.

  In addition to the above factors, the intensity of the light source is corrected based on the first detection result that is the intensity of the first polarization component reflected by the metal film, and thus the light source due to the influence on the optical path. Can respond to changes in strength. Further, the number of parts can be reduced as compared with the case where a conventional temperature sensor and humidity sensor are provided. As described above, there is an effect that it is possible to realize a surface plasmon sensor that corrects the intensity change of the light source caused by all factors at low cost. Further, since the light beam is not divided into the monitor region and the measurement region, the dividing step can be omitted, and the entire light beam can be used as the measurement region.

  In order to solve the above problems, a surface plasmon sensor according to the present invention is formed on a substrate, a light source that emits a light beam, a light source driving circuit that drives the light source by controlling the intensity of the light source, and a substrate. A metal film, a polarization direction selection means for selecting a polarization direction of the light beam as a first polarization and a second polarization, and the metal for each incident angle of the light beam that has passed through the polarization direction selection means. A surface plasmon sensor provided with a detecting means for detecting light reflected from the film, wherein the detecting means detects the intensity of the first polarized component reflected by the metal film as a first detection result. Detecting the intensity of the second polarization component reflected by the metal film as a second detection result, and determining whether the polarization direction of the light beam is the first polarization or the second polarization. Determine the above light beam When the light direction is the first polarized light, control means for controlling the light source driving circuit to provide a first detection result of the detection means in the light beam of the first polarized light to the light source The drive circuit controls the intensity of the light source based on the first detection result given by the control means.

  According to the above configuration, the surface plasmon sensor determines whether the polarization direction of the light beam is the first polarization or the second polarization, and when it is the first polarization, Comprises control means for controlling the light source driving circuit so as to give the first detection result of the detection means in the light beam of the first polarized light to the light source driving circuit, and the intensity of the light source is controlled based on the first detection result. In order to control, not only the temperature change and the temporal change due to the light source itself but also the intensity change of the light source due to factors such as the temperature change of the light source driving circuit can be corrected.

  In addition to the above factors, the intensity of the light source is corrected based on the first detection result that is the intensity of the first polarization component reflected by the metal film, and thus the light source due to the influence on the optical path. Can respond to changes in strength. Further, the number of parts can be reduced as compared with the case where a conventional temperature sensor and humidity sensor are provided. As described above, there is an effect that it is possible to realize a surface plasmon sensor that corrects the intensity change of the light source caused by all factors at low cost. Further, since the light beam is not divided into the monitor region and the measurement region, the dividing step can be omitted, and the entire light beam can be used as the measurement region.

  By the way, in the surface plasmon sensor that does not divide the light beam into the monitor region and the measurement region, the light beam cannot be produced simultaneously with the first polarized light and the second polarized light. While the beam is in the second polarization, the light source cannot be controlled.

  Therefore, in addition to the above control, the control means of the surface plasmon sensor according to the present invention has at least the above detection result in the detection means when the polarization direction of the light beam is the second polarization. It is preferable to control the storage means for storing the first detection result so that the first detection result is given to the light source driving circuit.

  According to the above configuration, when the polarization direction of the light beam is the second polarization, the control unit of the surface plasmon sensor has at least the first detection in the detection result by the detection unit. In order to control the first detection result of the storage means for storing the result to be given to the light source driving circuit, the intensity of the light source is controlled even while the polarization direction of the light beam is the second polarization. Can do.

  In the surface plasmon sensor according to the present invention, in addition to the above-described configuration, it is preferable that the polarization direction selection unit is installed in the parallel light of the light beam.

  According to said structure, since the said polarization direction selection means is installed in parallel light, the selection of a polarization direction can be performed substantially uniformly with respect to the whole surface of the said light beam. Further, the aberration of the light beam focused on the metal film can be reduced.

  In the surface plasmon sensor according to the present invention, in addition to the above configuration, it is preferable that the polarization direction selection unit is installed in an optical path on the incident side with respect to the metal film.

  According to said structure, since the said polarization direction selection means is installed in the incident side, the case where the said light beam injects only with the said 1st polarization | polarized-light can be created. As a result, since the surface plasmon is not excited during incidence with only the first polarized light, the amount of heat applied to the sample is reduced, and the sample is hardly damaged.

  In the surface plasmon sensor according to the present invention, in addition to the above configuration, the light beam incident on the polarization direction selection unit is linearly polarized light, and a λ / 2 plate is used as the polarization direction selection unit. It is preferable to select the polarization direction by rotating the plate or inserting / removing the λ / 2 plate.

  According to the above configuration, the polarization direction selection means can be provided at low cost by using the λ / 2 plate as the polarization direction selection means. When the polarization direction is selected by rotating the λ / 2 plate, the polarization direction can be selected without changing the transmittance of the light beam. On the other hand, when the polarization direction is selected by moving the λ / 2 plate, in addition to the same effect as in the case of rotating, the assembly is easy.

  In the surface plasmon sensor according to the present invention, in addition to the above configuration, the light beam incident on the polarization direction selection unit is linearly polarized light, and a liquid crystal element is used as the polarization direction selection unit, and the voltage applied to the liquid crystal element It is preferable to select the polarization direction by adjusting.

  According to the above configuration, the use of the liquid crystal element as the polarization direction selection means does not cause a change in transmittance or a deviation of the optical path depending on the selected polarization direction. It is possible to reduce the size. Further, the light beam incident on the liquid crystal element can cope with any polarization state.

  In the surface plasmon sensor according to the present invention, in addition to the above configuration, the light beam incident on the polarization direction selection unit includes first and second polarizations, and a polarizing plate or a polarizer is used as the polarization direction selection unit. Preferably, the polarization direction is selected by rotating the polarizing plate or the polarizer.

  According to said structure, when the said light beam has a multi-directional polarization direction, the said polarization direction can be selected cheaply by using the said polarizing plate or the said polarizer as the said polarization direction selection means. If the intensity of the first polarized light and the second polarized light incident on the polarizing plate or the polarizer is the same, the polarization direction can be selected without changing the transmittance of the light beam.

  In addition to the above configuration, the surface plasmon sensor according to the present invention has a true reflectance of the second polarized light from the reflected light intensity of the second polarized light and the reflected light intensity of the first polarized light. It is preferable to provide a calculation means for calculating.

  According to the above configuration, since the intensity of the light source is corrected in the surface plasmon sensor, the reflection means performs the true reflection of the second polarized light excluding the nonuniformity of the intensity distribution of the light beam. The rate can be calculated.

  In the surface plasmon sensor according to the present invention, in addition to the above configuration, the calculation means compares the reflected light intensity of the second polarized light of the light beam with the reflected light intensity of the first polarized light. It is preferable to calculate the reflectance.

  According to the above configuration, the true reflectance of the second polarized light can be calculated.

  In the surface plasmon sensor according to the present invention, in addition to the above configuration, the calculation means may calculate a ratio or difference between the reflected light intensity of the second polarized light and the reflected light intensity of the first polarized light. It is preferable to calculate the reflectance by taking it.

  According to the above configuration, the true reflectance of the second polarized light can be calculated.

  The surface plasmon sensor according to the present invention includes a light source that emits a light beam, a light source driving circuit that controls the intensity of the light source to drive the light source, a metal film formed on a substrate, and the light beam. A surface plasmon sensor provided with a detecting means for detecting reflected light from the metal film with respect to each incident angle, and comprising a dividing means for dividing the light beam into a monitor area and a measurement area, and the monitor area The light beam in the measurement region has the first polarization, the light beam in the measurement region has the polarization direction in the second polarization, and the detection means has the light intensity of the monitor region reflected by the metal film. Is detected as a first detection result, and the light intensity of the measurement region reflected by the metal film is detected as a second detection result. The light source driving circuit is configured to detect the light intensity based on the first detection result. light It is characterized by controlling the strength of the.

  According to said structure, the said surface plasmon sensor has an effect that the surface plasmon sensor which correct | amends the intensity | strength change of the said light source which arises by all the factors at low cost can be implement | achieved.

  In each of the embodiments described below, the first polarized light is incident on the incident surface when the normal of the prism 7 (substrate) -metal film 8 interface and the surface including the optical axis of the light beam 3 are used as the incident surface. The polarization direction perpendicular to the incident surface, that is, s-polarized light, and the second polarized light is a polarization direction parallel to the incident surface, that is, p-polarized light.

[Embodiment 1]
An embodiment of the present invention will be described below with reference to FIGS.

  FIG. 1 shows an outline of a surface plasmon sensor 1 according to the present embodiment.

  The surface plasmon sensor 1 includes a light source 2, a collimating lens 4, a polarization direction selection element 5 (dividing means, polarization direction selection means), a condenser lens 6, a prism 7, a metal film 8, a lens 9, a lens 10, and an APC (Automatic power). control) A monitor 11, a photodetector 12, an APC circuit unit 13 (not shown), a light source drive circuit 14, a calculation circuit 15, and a monitor 16 are provided. The APC circuit unit 13 is provided in the light source driving circuit 14.

  The light source 2 is for making the light beam 3 incident on the metal film 8 to excite surface plasmons, and a semiconductor laser or a light emitting diode is used and is driven by the light source driving circuit 14. If the light beam 3 emitted from the light source 2 includes many wavelengths, the excitation conditions of the surface plasmon are different at each wavelength, so the incident angle dependence of the reflected light of the light beam 3 on the metal film 8 is different, and the analysis is complicated. become. Therefore, it is desirable that the light source 2 has a narrow wavelength range. Note that the polarization direction of the light beam 3 emitted from the light source 2 may include only the first polarization, only the second polarization, or may include the first polarization and the second polarization.

  The collimating lens 4 is for making the light beam 3 emitted from the light source 2 into parallel light. By making the light beam 3 enter the polarization direction selection element 5 as parallel light, the polarization direction selection of the light beam 3 by the polarization direction selection element 5 is performed in the same manner for any ray (line) of the light beam 3. It can be made to be. Furthermore, by making the light beam 3 parallel light, the light beam 3 can be condensed with high performance in the condenser lens 6. The use efficiency of the light beam 3 emitted from the light source 2 increases as the focal length of the collimating lens 4 is shorter.

  The polarization direction selection element 5 is for splitting the light beam 3 into a monitor region 3A and a measurement region 3B and for selecting a polarization direction. A liquid crystal element such as a λ / 2 plate or a nematic liquid crystal used in a liquid crystal display, a polarizing plate, or a polarizer is used alone or in combination. Thereby, the light beam 3 can be divided into the monitor region 3A and the measurement region 3B, the polarization direction of the light beam 3 in the monitor region 3A is the first polarization, and the polarization direction of the light beam 3 in the measurement region 3B is the second. Either polarized light or first polarized light can be selected. Each λ of the λ / 2 plate and the λ / 4 plate is the wavelength of the incident light.

  The condensing lens 6 condenses the light beam 3 so that the light beam 3 enters the metal film 8 at various incident angles. A lens that collects light in all directions, such as a plano-convex lens, or a lens that collects light in only one direction, such as a cylindrical lens, may be used. In the case of the lens that collects all directions, the incident angle to the metal film 8 is complicated, but the irradiation area can be reduced and local information can be obtained. On the other hand, in the case of the lens that collects light in only one direction, since the direction in which light is not collected remains the original beam size, the angle of incidence on the metal film 8 depends only on the light collected direction. It becomes easy. Further, the irradiation area can be increased, and overall information can be obtained. The angle range of the incident angle is determined by the numerical aperture of the lens. However, when the sample is in contact with the metal film 8, it is necessary to determine the surface plasmon to be excited. Furthermore, the range of the incident angle is preferably set to a range in which all the light beams 3 are totally reflected.

  The prism 7 is a dielectric substrate for exciting surface plasmons on the surface of the metal film 8. An appropriate incident angle for exciting the surface plasmon is in the vicinity of 45 degrees in many cases. Normally, even if the light beam 3 is directly incident on the parallel substrate, it cannot be incident at the incident angle. Is used. The prism 7 is a triangular prism in FIG. 1, but a semi-cylindrical prism is also typically used. In the case of a semi-cylindrical prism, when the light beam 3 is incident toward the center, the incident angle to the incident surface of the prism is equal to the incident angle to the metal film 8, so that it is not necessary to convert the incident angle. On the other hand, in the case of the triangular prism 7, although the incident angle to the prism 7 and the incident angle to the metal film 8 are different due to refraction at the incident surface, it is less expensive than the semi-cylindrical prism. However, other shapes may be used as long as they can be incident on the metal film 8 at an appropriate angle. Glass or resin is typically used as the material, but is not limited to this as long as it can transmit the wavelength of the light source 2 and excite surface plasmons.

  The metal film 8 is for generating surface plasmons, and gold is most preferable because of its durability that it is difficult to oxidize and good excitation efficiency of the surface plasmons. However, any metal or alloy that excites surface plasmons, such as silver, copper, aluminum, or platinum, may be used. The film thickness is determined by the wavelength of the light source 2 and the material of the prism 7 according to Non-Patent Document 1, and is usually about several tens of nm. The prism 7 is formed by sputtering or vapor deposition. Alternatively, sputtering or vapor deposition may be performed on a substrate having the same refractive index as that of the prism 7, and the substrate may be placed on the prism 7 with an index matching agent interposed therebetween. The index matching agent may be a commercially available liquid or gel, or a UV curable resin. However, if the substrate is tilted, an error in the incident angle occurs, so it is necessary to fix the substrate. Further, another layer may be provided on the surface of the metal film 8 to detect specific molecules. In order to improve the adhesion to the substrate or the prism 7 and to improve the surface accuracy of the metal film 8, a base layer may be provided between the substrate or the prism 7 and the metal film 8. Furthermore, the metal film 8 can be replaced with another metal film. Thereby, various types of detection can be performed by one apparatus. That is, the sensitivity and measurement range can be changed by replacing the metal film with a different material and film thickness. In addition, if a layer for adsorbing only specific molecules is provided on the surface of the metal film 8, the specific molecules to be detected can be changed by replacing the entire metal layer.

  The lenses 9 and 10 focus the measurement area 3B of the light beam 3 reflected at the prism 7-metal film 8 interface onto the photodetector 12 and the monitor area 3A of the reflected light beam 3 onto the APC monitor 11, respectively. It is for making it enter. Note that this is not necessary when the measurement region 3B and the monitor region 3A of the reflected light beam 3 are all incident on the photodetector 12.

  The APC monitor 11 is for detecting the reflected light intensity of the monitor region 3A of the light beam 3 reflected at the prism 7-metal film 8 interface.

  The photodetector 12 is for detecting the reflected light intensity when the measurement region 3B of the light beam 3 reflected at the interface of the prism 7 and the metal film 8 is the first polarized light and the second polarized light. is there. The reflected light should be taken in at once with a CCD, CMOS, or array detector. In particular, if a CCD or CMOS is used, the user can recognize the monitor region 3A and the measurement region 3B of the light beam 3, and can determine which light beam of the light beam 3 in the measurement region 3B is used for measurement. .

  The APC circuit unit 13 is based on the difference between the reflected light intensity of the monitor region 3A of the light beam 3 detected by the APC monitor 11 and the target value determined from the setting of the emitted light intensity of the user to the light source driving circuit 14. This is to stabilize the intensity of the light beam 3 by detecting a change in the amount of light emitted from the light source 2 and feeding back this difference to the light source drive circuit 14.

  The light source drive circuit 14 is for driving the light source 2 and receives a voltage supply from the power source, causes a current to flow through the light source 2, and drives the light source 2 with an emitted light intensity corresponding to the setting of the user. The target value of the APC circuit unit 13 is determined from the user setting. In order to prevent destruction of the light source 2, it is preferable to provide an upper limit value for the current value flowing through the light source 2.

  The calculation circuit 15 calculates the true reflectance from the measurement result of the photodetector 12. The calculation circuit 15 may be a semiconductor chip such as an LSI or IC, or a computer that combines these.

  The monitor 16 is a device that visualizes the measurement results stored in the calculation circuit 15, the true reflectance calculated from the measurement results, or the result of the sample concentration determined from the true reflectance. A CRT or a liquid crystal display may be used.

  Next, the operation flow of the surface plasmon sensor 1 will be described.

  First, the light beam 3 emitted from the light source 2 is converted into parallel light by the collimator lens 4 and enters the polarization direction selection element 5. The polarization direction selection element 5 divides the first polarized light monitoring region 3A and the second polarized light or the measurement region 3B for selecting the first polarized light, and the condenser lens 6 has various incident angles. Then, the light enters the metal film 8 through the prism 7.

  The reflected light is condensed through the lenses 9 and 10 to the monitor area 3A to the APC monitor 11 and the measurement area 3B to the photodetector 12, respectively. The APC monitor 11 detects the reflected light intensity of the monitor region 3A, and the APC circuit unit 13 stabilizes the intensity of the light beam 3 emitted from the light source 2 based on the detection result. The photodetector 12 measures the incident angle dependence of the reflected light intensity when the measurement region 3B is selected as the second polarization and when the measurement region 3B is selected as the first polarization by the polarization direction selection element 5. The calculation circuit 15 compares the measurement results to calculate the true reflectance and displays it on the monitor 16.

  If the sample is, for example, a droplet or solid like the sample 17 shown in FIG. 8, it is placed on the metal film 8, and if it is a liquid like 17 ′ in FIG. Good, but not limited to this.

  Further, as described above, the APC monitor 11 and the light detector 12 may be provided separately, and the monitor area 3A may be detected by the APC monitor 11 and the measurement area 3B may be detected by the light detector 12. The detector 12 may also serve as the APC monitor 11 to detect the entire area, and a signal indicating the detection intensity of the monitor area 3A may be provided to the APC circuit unit 13.

  Next, the above operation will be described in detail.

  First, regarding the splitting method in which the light beam 3 is split into the monitor region 3A and the measurement region 3B by the polarization direction selection element 5, the measurement region 3B is set to the second region in order to obtain the true reflectance by the calculation circuit 15. The selection method for selecting the first polarized light or the first polarized light will be described for each of the case where the light beam 3 is only the first polarized light, the second polarized light only, and the first polarized light and the second polarized light are included. To do.

  First, a case where a λ / 2 plate or a liquid crystal element is used as the polarization direction selection element 5 when the light beam 3 incident on the polarization direction selection element 5 is only the first polarization will be described.

  First, the dividing method and the measuring method when the λ / 2 plate is used as the polarization direction selecting element 5 will be described with reference to FIGS. 2 and 3 are cases where the polarization direction selection element 5 is circular, and FIGS. 4 and 5 are cases where the polarization direction selection element 5 is rectangular. Moreover, the arrow in a figure shows the polarization direction in case the light beam 3 is 2nd polarization | polarized-light.

FIG. 2 shows that the polarization direction selection element 5 is installed so as to include the diameter D (dashed line) of the light beam 3 in a direction parallel to the polarization direction, and the center of the polarization direction selection element 5 and the center of the light beam 3. Shows a case in which does not match. In this case, the diameter of the polarization direction selection element 5 is larger than the diameter of the light beam 3.
FIG. 3 shows a case where the center of the light beam 3 and the center of the polarization direction selection element 5 are installed so as to coincide with each other. In this case, the diameter of the polarization direction selection element 5 is smaller than the diameter of the light beam 3.

  FIG. 4 shows a case where the polarization direction selection element 5 is installed so as to include the diameter D of the light beam 3 and the center of the polarization direction selection element 5 does not coincide with the center of the light beam 3. . In this case, as in FIG. 2, the size of the polarization direction selection element 5 is larger than the diameter of the light beam 3.

  FIG. 5 shows a case where the center of the light beam 3 and the center of the polarization direction selection element 5 are installed so as to coincide with each other. In this case, the polarization direction selection element 5 is rectangular, and the length of the short side of the rectangle is smaller than the diameter of the light beam 3. In FIG. 5, the polarization direction selection element 5 is rectangular, but is not limited thereto, and may be square.

  In the dividing method, the λ / 2 plate is placed on the incident side with respect to the prism 7-metal film 8 interface, and the light beam 3 that does not pass through the λ / 2 plate passes through the monitor region 3A and the λ / 2 plate. The light beam 3 to be used may be the measurement region 3B. Then, the light beam 3 can be divided into the monitor area 3A and the measurement area 3B.

  Here, the installation of the polarization direction selection element 5 when the light beam 3 is split with the above-described configuration will be described. That is, as shown in FIGS. 2 and 4, it is preferable that the polarization direction selection element 5 is installed in the polarization direction selection element 5 so as to include the diameter D of the light beam 3. By installing the polarization direction selecting element 5 as described above, it is not necessary to narrow the range of various incident angles of the light beam 3 generated by the condenser lens 6. In this case, the size of the polarization direction selection element 5 may be any size as long as it can include the diameter D of the light beam 3, and is preferably smaller in order to prevent an increase in the size of the optical system.

  Further, as shown in FIGS. 3 and 5, the center of the light beam 3 and the center of the polarization direction selection element 5 may be installed so as to coincide with each other. If the polarization direction selection element 5 is installed in this way, it is possible to prevent an increase in the size of the optical system.

  Next, in the selection method, the measurement region 3B may be selected as the first polarized light or the second polarized light by rotating or inserting / removing the λ / 2 plate in the measurement region 3B.

  More specifically, when the λ / 2 plate is rotated, for example, when the light beam 3 passes through a certain region of the λ / 2 plate, the light beam 3 is changed from the first polarized light to the second polarized light. What is necessary is just to set so that it may change into polarized light. In this case, for example, the first polarization before rotation and the second polarization after rotation, and the measurement region 3B can be selected as the first polarization or the second polarization.

  Further, when the λ / 2 plate is inserted and removed, for example, when the λ / 2 plate is inserted, the light beam 3 may be set to change from the first polarized light to the second polarized light. Then, as in the case of rotating the λ / 2 plate, the first polarized light before insertion and the second polarized light after insertion, and the measurement region 3B is changed to the first polarized light or the second polarized light. You can choose.

  When the λ / 2 plate is rotated, if the rotation axis of the λ / 2 plate and the optical axis of the optical system are not parallel, the optical path is shifted between the second polarized light and the first polarized light. When the true reflectance is obtained by the calculation circuit 15, an error occurs. Therefore, when the λ / 2 plate is rotated, the rotation axis of the λ / 2 plate and the optical axis of the optical system are parallel to each other, that is, the λ / 2 plate through which the light beam 3 passes. It is important to install so that the area does not change.

  Similarly, when inserting / removing the λ / 2 plate, it is important that the optical axis of the λ / 2 plate is parallel to the optical axis of the optical system. Since the amount of incident light of the light beam 3 incident on the metal film 8 changes by the transmittance of the λ / 2 plate, the calculation circuit 15 preferably corrects the incident light.

  Next, the division method and the measurement method when the liquid crystal element is used as the polarization direction selection element 5 will be described.

  The dividing method may be performed in the same manner as in the case of using the λ / 2 plate.

  When the liquid crystal element is used, the liquid crystal element is not only divided in the same manner as when the λ / 2 plate is used, but the liquid crystal element is disposed on the incident side with respect to the prism 7-metal film 8 interface. The entire beam 3 is passed through the liquid crystal element, the light beam 3 passing through the first region in the liquid crystal element is the monitor region 3A, and the light beam 3 passing through the second region in the liquid crystal device is the measurement region 3B. Thus, the light beam 3 can also be split.

  Here, the setting of the first area and the second area will be described.

  The first region and the second region are set by transmitting the first polarized light to the second polarized light when a voltage is applied to the liquid crystal element (hereinafter referred to as ON) or not applied (hereinafter referred to as OFF). What should I do? Hereinafter, an example will be described in which the first polarized light is changed to the second polarized light at the time of OFF, and the first polarized light is transmitted as it is at the time of ON.

  First, the voltage may be always turned on in the first region. As a result, the incident light beam 3 can be the first polarized light, that is, the monitor region 3A. Similarly, the voltage may be turned off in the second region. As a result, the incident light beam 3 can be the second polarized light, that is, the measurement region 3B. The second region is set so that the voltage can be turned ON / OFF in order to select the measurement region 3B as the second polarized light and the first polarized light (described later). Thus, by setting the first area and the second area, the light beam 3 can be divided into the monitor area 3A and the measurement area 3B.

  Next, in the selection method, the measurement region 3B may be selected as the first polarized light or the second polarized light by turning on and off the voltage in the second region. That is, when the voltage of the second region is turned on, the measurement region 3B remains as the first polarized light. On the other hand, when the voltage of the second region is turned off, the measurement region 3B changes from the first polarized light to the second polarized light. In this way, the measurement region 3B can be selected as the first polarized light or the second polarized light.

  As is clear from the above, when the light beam 3 is selected (divided) using the liquid crystal element, the second polarized light and the first polarized light in the measurement region 3B are compared with the case where the λ / 2 plate is used. The optical path is not shifted by selecting. As a result, since various corrections performed when the λ / 2 plate is used are not necessary, an adjustment jig or the like is not necessary, and the polarization direction selection element 5 can be downsized.

  Next, in the case where the light beam 3 incident on the polarization direction selection element 5 is only the second polarization, similarly to the case where the light beam 3 incident on the polarization direction selection element 5 is only the first polarization, the polarization is performed. The case where the λ / 2 plate or the liquid crystal element is used as the direction selection element 5 will be described.

  First, the dividing method and the measuring method when the λ / 2 plate is used as the polarization direction selecting element 5 will be described.

  In the dividing method, the two λ / 2 plates are placed on the incident side with respect to the prism 7-metal film 8 interface, the entire light beam 3 is passed through the two λ / 2 plates, The light beam 3 passing through the λ / 2 plate (first region) is used as the monitor region 3A, and the light beam 3 passing through the other λ / 2 plate (second region) is used as the measurement region 3B. Can be divided. In the selection method, the measurement region 3B can be selected as the first polarized light or the second polarized light by rotating or removing the other λ / 2 plate.

  Further, when the liquid crystal element is used, the light beam 3 incident on the polarization direction selection element 5 may be performed in the same manner as when only the s-polarized light is applied, and the second voltage is applied when the voltage applied to the liquid crystal element is ON or OFF. The polarized light may be changed to the first polarized light and transmitted.

  As described above, when the light beam 3 incident on the polarization direction selection element 5 is only the second polarization, it is easier to divide and select the light beam 3 by using the liquid crystal element as the polarization direction selection element 5. It can be carried out. In addition, before the light beam 3 is incident on the polarization direction selection element 5, the light beam 3 may be set to only the first polarized light in advance.

  Finally, the case where the light beam 3 incident on the polarization direction selection element 5 includes the first polarized light and the second polarized light will be described. In this case, since the λ / 2 plate and the liquid crystal element cannot be used as the polarization direction selection element 5, a polarizing plate or a polarizer is used.

  The splitting method and the selection method may be performed in the same manner as in the case where the light beam 3 incident on the polarization direction selection element 5 is only the second polarization and the λ / 2 plate is used as the polarization direction selection element 5. .

  In this case, the light source 2 is a non-polarized light source such as an LED. Conversely, when a linearly polarized light source such as an LD is used, it is not necessary to adjust the polarization direction. However, it is preferable to correct by the calculation circuit 15 when measuring the ratio of the first polarized light and the second polarized light in advance and calculating the true reflectance. In this case, the polarization direction selection element 5 can be installed in the light beam 3 on the incident side or the emission side with respect to the prism 7 -metal film 8 interface.

  As described above, with respect to the dividing method of dividing the light beam 3 into the monitor region 3A and the measurement region 3B by the polarization direction selection element 5, the measurement region 3B is set to the second region in order to obtain the true reflectance by the calculation circuit 15. The selection method for selecting the polarized light or the first polarized light has been described, but the present invention is not limited to the above configuration.

  Further, by selecting the measurement region 3B as in the above-described various selection methods, the light beam 3 is incident on the metal film 8 with the first polarized light except when measuring the sample. Therefore, the surface plasmon is not excited and the amount of heat applied to the sample is reduced, so that the sample is hardly damaged.

  Further, with respect to the above-described various division methods, the measurement region 3B is preferably divided so as to include the center of the intensity distribution of the light beam 3. Further, regarding the installation of the polarization direction selection element 5, a light shielding portion may be formed between the monitor area 3A and the measurement area 3B depending on the installation method of the polarization direction selection element 5.

  Next, a method for stabilizing the intensity of the light beam 3 emitted from the light source 2 using the APC monitor 11 and the APC circuit unit 13 will be described with reference to FIG. FIG. 6 is a circuit diagram of the light source driving circuit 14 incorporating the APC circuit unit 13, and the dotted line portion is the APC circuit unit 13.

  Here, a case will be described in which the intensity of the light beam 3 emitted from the light source 2 is reduced due to a temperature change or the like, although the driving current of the light source 2 is constant. The APC circuit unit 13 is configured such that when the driving current of the light source 2 is set by the user, the resistance value of the variable resistor R1 is determined and the target value of the APC circuit unit 13 is determined.

  First, the light beam 3 emitted from the light source 2 is converted into parallel light by the collimator lens 4, and is divided into the monitor region 3 </ b> A and the measurement region 3 </ b> B by the polarization direction selection element 5, and passes through the condenser lens 6 and the prism 7. Incident on the metal film 8. Then, the intensity of the monitor region 3A of the light beam 3 reflected by the metal film 8 is detected by the APC monitor 11. Since the intensity of the monitor region 3A is reduced due to the temperature change, the intensity detected by the APC monitor 11 is also lower than the target value.

  Then, the detected value of the intensity of the monitor area 3A of the APC monitor 11 is compared with the target value by the differential amplifier of the APC circuit unit 13, and the difference between the target value is obtained via the transistor of the light source driving circuit 14. Feedback is performed, the drive current of the light source 2 is increased until the target value is reached, and the intensity of the light beam 3 is corrected. It is sufficient that the difference between the intensity of the monitor region 3A and the target value is suppressed to within 1/100. Further, the change with time of the light source driving circuit 14 can be corrected by the same method.

  As described above, the light source 2 can be corrected with a small number of components and corresponding to all factors such as a change with time of the light source driving circuit 14 and an influence of the optical path as well as a change in temperature and humidity. The light beam 3 having the same intensity can always enter the metal film 8. When the APC circuit unit 13 operates before the light source driving circuit 14, the light beam 3 from the light source 2 is not incident on the APC monitor 11. A command to drive with voltage is sent, and the maximum voltage is suddenly applied to the light source 2 and is damaged. Therefore, it is preferable that the APC circuit unit 13 operates simultaneously with or after the light source driving circuit 14.

  Next, a calculation method for calculating the true reflectance by the photodetector 12 and the calculation circuit 15 will be described with reference to FIG.

  FIG. 7 is a graph showing the incident angle dependency of one line extracted from the reflected light intensity of the measurement region 3B of the light beam 3 detected by the photodetector 12. In FIG. FIG. 7 also shows the calculation result of the calculation circuit 15. Here, the polarization direction selection element 5 is provided on the incident side with respect to the prism 7 -metal film 8 interface.

  First, as the first step, the reflected light of the light beam 3 detected by the photodetector 12 by the polarization direction selection element 5 is set as the first polarization. That is, the measurement region 3B is set as the first polarized light. The intensity distribution is a Gaussian distribution as shown in FIG. 5A, but the intensity distribution is non-uniform due to dust adhering to optical components such as the lens and the prism 7. Since the first polarized light does not excite surface plasmons, the reflected light intensity distribution of the first polarized light is considered to be the intensity distribution itself of the light beam 3. Therefore, based on this, the amount of incident light at each incident angle can be normalized. In addition, it is possible to confirm that the intensity variation of the light beam 3 has not occurred by the APC monitor 11 as compared with another measurement.

  Next, as a second step, a sample is placed on the surface of the metal film 8, and the light beam 3 detected by the photodetector 12 by the polarization direction selection element 5 is set as the second polarized light. That is, the measurement region 3B is set as the second polarized light. Since the second polarized light excites surface plasmon on the surface of the metal film 8 at a certain incident angle, an intensity distribution in which sharp absorption occurs at the angle where the surface plasmon is excited as shown in FIG. Detected. Note that either the first stroke or the second stroke may be performed first.

  Finally, as the third step, the calculation circuit 15 obtains the incident angle and the width of the light beam 3 that minimizes the reflectance from the result of the first step and the result of the second step. Since the intensity of the light beam 3 emitted from the light source 2 is corrected by the APC monitor 11 and the APC circuit unit 13 described above, the incident intensity during measurement of the second polarized light and the first polarized light does not change. Therefore, the calculation by the calculation circuit 15 may simply take the ratio or difference between the result of the first stroke and the second stroke. The calculation result is “c” in the figure, and the Gaussian distribution in FIG. However, when the intensity ratio between the second polarized light and the first polarized light is different, it is preferable to correct this. Further, when the number of transmitting elements is different between the second polarized light and the first polarized light, correction may be made with the transmittance.

  As described above, the true reflectance of the sample can be obtained using the incident angle obtained by the calculation circuit 15. As a result, the refractive index can be obtained and the substance can be detected. Further, when measuring the concentration of the prescribed substance, the concentration can be easily obtained by measuring the relationship of the incident angle to each concentration in advance. Further, the incident angle may be automatically calculated from the true reflectance.

  Separately, the light beam 3 is measured as the second polarized light without placing the sample on the surface of the metal film 8, and the reflectance intensity distribution when there is no sample is obtained from the calculation result and the result of the first step. It is good also as a structure compared with the case where there is a sample.

  Further, the polarization direction selection element 5 may be installed in the optical path on the reflection side with respect to the prism 7-metal film 8 interface. In this case, the light beam 3 is only in the case of including the second polarized light and the first polarized light. The first process to the third process may be performed in the same manner as the case where the polarization direction selection element 5 is installed in the optical path on the incident side with respect to the prism 7-metal film 8 interface.

  The surface plasmon sensor 1 having the above-described configuration is not only a change in temperature of the light source 2 and a change with time, but also an intensity fluctuation of the light source 2 due to factors that cannot be dealt with by a conventional surface plasmon sensor such as a temperature change of the light source driving circuit 14. Can also respond. Further, since the monitor area 3A and the measurement area 3B pass through the same optical path, in addition to the above-described factors, it is possible to cope with the influence on the optical path. In addition, the number of parts can be reduced and the cost can be reduced as compared with the prior art.

[Embodiment 2]
Another embodiment of the present invention is described below with reference to FIG.

  FIG. 10 shows an outline of the operation of the surface plasmon sensor 2 according to the second embodiment. Since the surface plasmon sensor 2 has the same configuration as the surface plasmon sensor 1 shown in the first embodiment, only the parts different from the surface plasmon sensor 1 will be described below.

  The surface plasmon sensor 2 is installed such that the polarization direction selection element 5 (polarization direction selection means) selects the entire polarization direction of the light beam 3 (hereinafter, different from the polarization direction selection element 5 of the surface plasmon sensor 1). And described as a polarization direction selection element 5A). Then, the surface plasmon sensor 2 selects the light beam 3 as the second polarized light at the time of measuring the sample, turns off the APC circuit unit 13, measures the sample, and measures the measurement at the time of correcting the intensity of the light source 2. Or at an appropriate timing (time interval) during the measurement, the light beam 3 is set to the first polarization, the APC circuit unit 13 is turned on, and the intensity of the light source 2 is corrected.

  Control of the polarization direction selection element 5A may be provided with an operation circuit or may be moved by a measurer. The method for correcting the intensity of the light source 2, the method for calculating the true reflectance, and the selection of the polarization direction of the light beam 3 are the same as in the first embodiment.

  Note that if the number of times of making the light beam 3 the first polarization is large and the time interval is long, the intensity of the light source 2 can be corrected more accurately, but missing measurement data increases. Therefore, it is preferable not to measure the time change of the reaction of the sample but to measure the result of reaching the equilibrium state. If it is in an equilibrium state, the light beam 3 is set to the first polarization, and when the intensity of the light source 2 becomes constant, the polarization direction selection element 5A is controlled and the light beam 3 is measured as the second polarization. Good. Alternatively, the intensity of the first polarized light may be detected before and after the measurement, and the intensity at the time of measurement may be approximated and corrected.

  The APC monitor 11 can be replaced by the photodetector 12, and the polarization direction selection element 5A may be installed on the incident side with respect to the prism 7-metal film 8 interface, and a λ / 2 plate or a liquid crystal element may be used.

  By having the configuration as described above, the surface plasmon sensor 2 has the intensity of the light source 2 caused by all factors such as temperature change and temporal change of the light source 2, temperature change of the light source driving circuit 14, and influence on the optical path. It is possible to correct changes and non-uniform distribution of light intensity at low cost. Further, unlike the surface plasmon sensor 1, it is not necessary to divide the light beam 3 into the monitor region 3A and the measurement region 3B, so that the process can be omitted.

[Embodiment 3]
Another embodiment of the present invention is described below with reference to FIGS. 11 and 12.

  FIG. 11 shows the configuration of the surface plasmon sensor 3 according to the third embodiment. The surface plasmon sensor 3 is a specific configuration example of the surface plasmon sensor 2 according to the second embodiment. Note that members denoted by the same reference numerals as those of the surface plasmon sensor 1 shown in FIG. 1 have the same functions unless otherwise described, and the description thereof is omitted. The method for correcting the intensity of the light source 2, the method for calculating the true reflectance, and the selection of the polarization direction of the light beam 3 are the same as those for the surface plasmon sensor 1.

  Incidentally, the surface plasmon sensor 2 has the following problems. More specifically, since the surface plasmon sensor 2 does not split the light beam 3 into the monitor region 3A and the measurement region 3B, the surface plasmon sensor 2 simultaneously generates a case where the light beam 3 is the first polarization and a case where the light beam 3 is the second polarization. I can't. For this reason, there is a problem that the light source 2 cannot be controlled while the light beam 3 is set to the second polarized light. The surface plasmon sensor 3 solves this problem, that is, the intensity of the light source 2 can be corrected even while the light beam 3 is in the second polarization (when measuring the sample). . Details will be described below.

  As shown in the figure, the surface plasmon sensor 3 includes a memory 20 (storage unit), a control circuit 21 (control unit), and an operation circuit 22 in addition to the configuration of the surface plasmon sensor 1.

  The polarization direction selection element 5A is installed so as to select the entire polarization direction of the light beam 3, and unlike the surface plasmon sensor 1, it does not divide the light beam 3 into a monitor region 3A and a measurement region 3B. The photodetector 12 detects the light intensity distribution when the light beam 3 reflected at the prism 7-metal film 8 interface is the first polarized light and when the light beam 3 is the second polarized light.

  The memory 20 stores the detection results of the photodetector 12, and may store all the detection results of the photodetector 12, or the case where the light beam 3 is the first polarized light. Only the detection result (first detection result) may be stored.

  The control circuit 21 determines which polarization direction the light beam 3 is selected by the polarization direction selection element 5A, and in the case of the first polarization, the first detection result of the photodetector 12 at that time is In the case of the second polarized light, the first detection result of the photodetector 12 stored in the memory 20 is input to the APC circuit unit 13. In the case of the second polarization, the first detection result that the light beam 3 inputs to the APC circuit unit 13 may use the detection result stored immediately before or the detection result stored so far. The average may be used, or a trend may be obtained from the detection results stored so far.

  The control circuit 21 may issue an instruction to the operation circuit 22 or the measurer so as to select another polarization direction from the current polarization direction after a predetermined time has elapsed after determining the polarization direction of the light beam 3. . More specifically, after determining that the polarization direction of the light beam 3 is the first polarization, when a predetermined time elapses, the operation circuit 22 or the measurer is instructed to select the second polarization. Also good.

  The operation circuit 22 controls the polarization direction selection element 5 </ b> A based on an instruction from the control circuit 21. The operation circuit 22 is not necessarily provided, and if not provided, the measurement person may control the polarization direction selection element 5A. In this case, for example, the control circuit 21 instructs the measurer to display on the monitor 16 an instruction for controlling the polarization direction selection element 5A, and this measure causes the measurer to control the polarization direction selection element 5A. What is necessary is just composition.

  Further, the operation circuit 22 may control the polarization direction selection element 5 </ b> A without receiving an instruction from the control circuit 21. For example, the polarization direction selection element 5A may be controlled again after a predetermined time elapses after the polarization direction selection element 5A is controlled. The same applies to the measurer.

  Next, the operation of the surface plasmon sensor 3 will be described. Here, it is assumed that the polarization direction selection element 5A is controlled so that the light beam 3 is set to the first polarization as an initial state.

  The light beam 3 emitted from the light source 2 is collimated by the collimating lens 4 and enters the polarization direction selection element 5A. The light beam 3 is selected as the first polarized light by the polarization direction selection element 5A, and enters the metal film 8 through the prism 7 with various incident angles by the condenser lens 6.

  The reflected light is condensed on the photodetector 12 via the lenses 9 and 10. The control circuit 21 determines that the light beam 3 is the first polarized light, inputs the first detection result detected by the photodetector 12 to the APC circuit unit 13, and thereby the light beam emitted from the light source 2. The strength of 3 is stabilized. Then, the first detection result of the photodetector 12 is stored in the memory 20.

  Thereafter, the control circuit 21 controls the operation circuit 22 to select the light beam 3 as the second polarized light. Thereby, the sample is measured. Then, the control circuit 21 determines that the light beam 3 is the second polarization, inputs the first detection result stored in the memory 20 to the APC circuit unit 13, and outputs the light beam 3 emitted from the light source 2. Stabilize the strength.

  Next, the configuration and operation of the surface plasmon sensor 3 will be described more specifically.

  FIG. 12 shows a configuration of the APC circuit unit 13 (hereinafter referred to as APC circuit unit 13A) in the present embodiment.

  The APC circuit unit 13A includes a switch SW in the configuration of the APC circuit unit 13 as illustrated. The terminal SW1 of the switch SW is connected to the memory 20, the terminal switch SW2 is connected to the photodetector 12, and the terminal switch SW3 is connected to the differential amplifier of the APC circuit unit 13A. The switch SW is controlled by the control circuit 21.

  That is, in the above description of the operation, when the control circuit 21 determines that the light beam 3 is the first polarization, the control circuit 21 controls the switch SW to connect the terminal SW2 and the terminal SW3, and the APC circuit unit 13A. To work. When the control circuit 21 determines that the light beam 3 is the second polarized light, the control circuit 21 controls the switch SW to connect the terminal SW1 and the terminal SW3, and also controls the memory 20 to store the light. The first detection result is input to the APC circuit unit 13A, and the APC circuit unit 13A is operated.

  By having the configuration as described above, the surface plasmon sensor 3 has the intensity of the light source 2 caused by all factors such as temperature change and temporal change of the light source 2, temperature change of the light source driving circuit 14, and influence on the optical path. It is possible to correct changes and non-uniform distribution of light intensity at low cost. Further, unlike the surface plasmon sensor 1, it is not necessary to divide the light beam 3 into the monitor region 3A and the measurement region 3B, so that the division process can be omitted, and the entire light beam 3 can be used as the measurement region. Furthermore, unlike the surface plasmon sensor 2, the intensity of the light source 2 can be corrected even during measurement of the sample, and more accurate sample measurement is possible.

  If the time during which the light beam 3 is the second polarization is long, the light source 2 cannot be accurately controlled, and the control circuit 21 switches between the first polarization and the second polarization at certain time intervals. It is good also as a structure. Further, in the case of the second polarized light, the light source driving circuit 14 may be driven by the immediately preceding current / voltage value without operating the APC circuit unit 13A. The memory 20 is not necessarily provided in the surface plasmon sensor 3, and can be replaced by a recording medium as described later. The surface plasmon sensor 2 has a configuration in which the memory 20 is excluded from the configuration of the surface plasmon sensor 3.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Needless to say, these are also included in the technical scope of the present invention.

[Reference example]
Next, as reference examples, surface plasmon sensors 41, 51, and 61 other than the above embodiment are shown. In addition, the member which attached | subjected the code | symbol same as the member shown with the said surface plasmon sensor 1 shall have the same function unless it demonstrates especially, The description is abbreviate | omitted.

  FIG. 13 shows an outline of the surface plasmon sensor 41. The surface plasmon sensor 41 includes a light source 2, a collimator lens 4, an optical path branching element 31, a beam expander 33, a prism 7, a metal film 8, a lens 10, a lens 32, an APC monitor 11, a photodetector 12, an APC circuit unit 13, and a light source. A drive circuit 14, a calculation circuit 15, a monitor 16, and rotary stages 34 and 35 are provided. The APC circuit unit 13 is provided in the light source driving circuit 14.

  The optical path branching element 31 transmits the second polarized light of the light beam 3 emitted from the light source 2 and reflects the first polarized light to branch to the monitor area 3A. A polarizing beam splitter (hereinafter simply referred to as “PBS”) or a half mirror may be used. Note that when the polarization direction of the light beam 3 is the second polarization, a half mirror may be used, and when the second polarization and the first polarization are included, PBS may be used. The second polarized light or the first polarized light of the light beam 3 is the second polarized light or the first polarized light with respect to the prism 7-metal film 8 interface.

  The beam expander 33 is for allowing the light beam 3 to enter the metal film 8 at a substantially single incident angle by reducing the beam diameter r of the light beam 3 and making it parallel light. If the optical path surface of the prism 7 is only a flat surface, the beam expander 33 may not be provided. However, when the prism 7 has a curved surface in the optical path, such as an anti-cylindrical type as illustrated, the beam expander 33 causes the beam diameter to be increased. It is preferable that r is sufficiently smaller than the radius R of the prism 7. The reason is that if the beam diameter r is too large, the width of the refraction angle at the incident surface of the prism 7 becomes wide. As a result, the incident angle to the metal film 8 has a width, and the resolution of the surface plasmon sensor 41 is deteriorated.

  In addition, the beam expander 33 is usually composed of a lens set of two lenses, a concave lens and a convex lens, as shown in FIG. These lenses may be lenses that collect light in all directions, such as plano-convex lenses, or may be lenses that collect light only in one direction, such as cylindrical lenses. In the case of a lens that collects light in all directions, the irradiation area can be reduced and local information can be obtained. In the case of a lens that collects light in only one direction, the direction in which light is not collected remains the original beam size, so that the irradiation area can be increased and overall information can be obtained.

  The lens 32 is for condensing the monitor area 3 </ b> A of the light beam 3 on the APC monitor 11.

  The rotary stage 34 is for making the light beam 3 incident on the metal film 8 at various incident angles.

  The rotating stage 35 is for rotating the detector 12 to a position where the reflected light can be detected in order to detect the reflected light of the light beam 3 incident at various incident angles in the rotating stage 34.

  Next, the operation flow of the surface plasmon sensor 41 will be described.

  First, the light beam 3 emitted from the light source 2 is collimated by the collimator lens 4 and enters the optical path branching element 31. The optical path branching element 31 branches the measurement region 3B with only the second polarization and the monitoring region 3A with only the first polarization. In the measurement region 3B, the beam diameter is reduced as parallel light by the beam expander 33, enters the metal film 8 through the prism 7, and the reflected light is condensed on the photodetector 12 by the lens 10. The intensity of the measurement region 3B is detected. On the other hand, the monitor area 3A is focused on the APC monitor 11 by the lens 32. The APC monitor 11 detects the intensity distribution of the monitor area 3A, and the APC circuit unit 13 emits from the light source 2 based on the detection result. The intensity of the light beam 3 is stabilized. The rotation stage 34 rotates the entire optical system from the light source 2 to the beam expander 33 around the irradiation position of the light beam 3 on the metal film 8, so that the light beam 3 can be metallized at various incident angles. The light is incident on the film 8. Accordingly, in order to detect the light beam 3 incident at the various incident angles, the lens 10 and the photodetector 12 are rotated symmetrically to the rotary stage 34 by the rotary stage 35. The range of the incident angle needs to be determined so that the surface plasmon is excited at least when the sample is in contact with the metal film 8. Furthermore, it is preferable that the light beam 3 is in a range where it is totally reflected. Note that the sample is the same as that described in the first embodiment. The case where the optical path branching element 5, the APC monitor 11, and the APC circuit unit 13 are provided on the incident side with respect to the prism 7-metal film 8 interface has been described. You may install in the reflection side. Further, the method of correcting the intensity of the light source 2 and the method of calculating the true reflectance are the same as those of the surface plasmon sensor 1 and are omitted here.

  Next, the surface plasmon sensors 51 and 61 will be described.

  FIG. 14 shows an outline of the surface plasmon sensor 51, and FIG. 15 shows an outline of the surface plasmon sensor 61.

  The surface plasmon sensor 51 includes a light source 2, a collimator lens 4, a polarization direction adjustment element 36, an optical path branching element 31, a polarization direction selection element 5, a condenser lens 6, a prism 7, a metal film 8, a lens 10, a lens 9, and a lens 10. APC monitor 11, photodetector 12, APC circuit unit 13, light source drive circuit 14, calculation circuit 15, and monitor 16. The APC circuit unit 13 is provided in the light source driving circuit 14. Further, the surface plasmon sensor 61 is configured such that the polarization direction adjusting element 36 is not used because of the configuration of the surface plasmon sensor 51.

  The polarization direction adjusting element 36 is for adjusting the polarization direction of the light beam 3 emitted from the light source 2 with respect to the prism 7-metal 8 interface, and is a λ / 2 plate, λ / 4 plate, polarizing plate, polarizer. Etc. may be used.

  The surface plasmon sensor 61 adjusts the polarization direction according to the rotation angle of the light source 2 without using the polarization direction adjusting element 36. That is, by rotating the light source 2 around the optical axis in a plane whose normal is the optical axis of the light beam 3 emitted from the light source 2, the polarization direction of the light beam 3 is rotated, and the prism-7 The polarization direction with respect to the interface of the metal film 8 is adjusted.

  Next, the flow of operation of the surface plasmon sensor 51 is shown.

  First, the light beam 3 emitted from the light source 2 is converted into parallel light by the collimator lens 4, the polarization direction is adjusted by the polarization direction adjustment element 36, and is incident on the optical path branching element 31. The optical path branching element 31 branches the measurement region 3B with only the second polarization and the monitoring region 3A with only the first polarization. The measurement region 3B is selected as the first polarized light or the second polarized light by the polarization direction selection element 5, has various incident angles by the condenser lens 6, and enters the metal film 8 through the prism 7. To do. The reflected light is condensed on the photodetector 12 by the lenses 9 and 10, and the intensity of the measurement region 3B is detected. On the other hand, the monitor area 3A is focused on the APC monitor 11 by the lens 32. The APC monitor 11 detects the intensity distribution of the monitor area 3A, and the APC circuit unit 13 emits from the light source 2 based on the detection result. The intensity of the light beam 3 is stabilized. The operation of the surface plasmon sensor 61 is the same as the operation of the surface plasmon sensor 51 except that the polarization direction adjusting element 36 is not used, and is omitted here.

  The case where the optical path branch element 31, the APC monitor 11, and the APC circuit unit 13 are on the incident side with respect to the prism 7-metal film 8 interface has been described above. You may install in the reflection side.

  Next, the operation of the combination of the light source 2, the polarization direction adjusting element 36, the optical path branching element 31, and the polarization direction selecting element 5 will be described in detail for each of five cases.

  First, the case where the light source 2 of the surface plasmon sensor 51 uses a light source whose polarization direction is one direction such as a semiconductor laser will be described.

  The polarization direction adjusting element 36 uses a λ / 2 plate or a λ / 4 plate, and adjusts the polarization direction so as to include both the second polarized light and the first polarized light. Since the ratio between the second polarized light and the first polarized light can be adjusted by rotating the polarization direction adjusting element 36, if an adjusting mechanism is provided, it can be adjusted even after assembly.

  The optical path branching element 31 uses PBS and is installed so that either the second polarization or the first polarization corresponds to either the second polarization or the first polarization with respect to the branch plane, It is preferable that the light incident on the polarization direction selection element 5 has a polarization direction of either the second polarization or the first polarization. Note that the selection of the second polarized light and the first polarized light by the polarization direction selection element 5 is the same as that described in the first embodiment, and is therefore omitted.

  In addition, when there is an oscillation threshold as in the above semiconductor laser, when it is desired to reduce the emission intensity of the light source 2 to a level that does not cause laser oscillation, for example, because the sample is damaged by the heat of incident light and excited surface plasmon, The amount of the second polarized light can be reduced by adjusting the polarization direction adjusting element 36. At this time, it is necessary to adjust the feedback gain of the APC circuit unit 13. Specifically, the gain of the variable resistor section or differential amplifier of the APC circuit section 13 shown in FIG. 6 may be adjusted.

  In such a configuration, the polarization direction adjusting element 36, the optical path branching element 31, and the polarization direction selecting element 5 may be disposed on the reflection side with respect to the prism 7-metal film 8 interface. Moreover, you may install only the optical path branching element 31 and the polarization direction selection element 5, or the polarization direction selection element 5 in the said reflection side. When installed on the incident side with respect to the prism 7-metal film 8 interface, a case where the light beam 3 is incident only with the first polarized light can be provided as compared with the case where the prism 7 is installed on the reflecting side. Therefore, the surface plasmon is not excited, the amount of heat given to the sample is small, and the sample is hardly damaged. In addition, when installing in the said reflection side, the light quantity irradiated to the metal film 8 is the same, and the measurement result of the state which added the same calorie | heat amount is obtained, regardless of which polarization direction it measures. There is also.

  Next, a case where the light source 1 of the surface plasmon sensor 51 uses a multi-directional polarization direction such as a light emitting diode will be described. The polarization direction adjusting element 36 uses, for example, a polarizing plate or a polarizer, and the polarization direction is one direction. At this time, both the second polarized light and the first polarized light are included. The ratio between the second polarized light and the first polarized light can be adjusted by rotating the polarizing plate / polarizer as the polarization direction adjusting element 36. Other configurations and operations are the same as those in the case where the light source 1 of the surface plasmon sensor 51 is a semiconductor laser.

  Next, the case where the light source 2 of the surface plasmon sensor 61 uses a light source whose polarization direction is one direction such as a semiconductor laser will be described. The difference from the surface plasmon sensor 51 is that the polarization direction adjusting element 36 is not used, and the optical path branching element 31 includes both the second polarized light and the first polarized light by the installation method of the light source 2. Is a point. That is, by rotating the light source 2 around the optical axis in a plane having the optical axis of the light beam 3 emitted from the light source 2 as a normal line, the polarization direction of the light beam 3 is rotated. Both the polarized light and the first polarized light are included. Since the polarization direction adjusting element 36 is not used, the cost of the element and the adjustment process of the element can be omitted. Other operations are the same as those of the surface plasmon sensor 51. In this configuration, only the optical path branch element 31 and the polarization direction selection element 5 or the polarization direction selection element 5 may be provided on the reflection side. In the case where the light beam 3 is installed on the incident side, the case where the light beam 3 is incident only with the first polarized light can be provided as compared with the case where the light beam 3 is installed on the reflective side. Therefore, the surface plasmon is not excited, the amount of heat given to the sample is small, and the sample is hardly damaged. In addition, when installing in the said reflection side, the light quantity irradiated to the metal film 8 is the same, and the measurement result of the state which added the same calorie | heat amount is obtained, regardless of which polarization direction it measures. There is also.

  The case where the light source 2 of the surface plasmon sensor 61 is a semiconductor laser having a polarization direction of one direction and the optical path branching element 31 is a half mirror will be described. In this case, the polarization direction of the light source 2 may be any case. Therefore, since the polarization direction adjustment element 36 is not used and the polarization direction of the light source 2 does not need to be adjusted, the cost of the polarization direction adjustment element 36 can be reduced and the adjustment process of the light source 2 and the polarization direction adjustment element 36 can be omitted. Can do. The division of the monitor area 3A and the measurement area 3B is the same as when the PBS is used as the optical path branching element 31, and the light beam 3 reflected by the half mirror is used as the monitor area 3A, and the light beam 3 transmitted through the half mirror is used. The measurement area is 3B. In this configuration, the polarization direction selection element 5 can be installed on the reflection side. In the case where the light beam 3 is installed on the incident side, the case where the light beam 3 is incident only with the first polarized light can be provided as compared with the case where the light beam 3 is installed on the reflective side. Therefore, the surface plasmon is not excited, the amount of heat given to the sample is small, and the sample is hardly damaged. In addition, when installing in the said reflection side, the light quantity irradiated to the metal film 8 is the same, and the measurement result of the state which added the same calorie | heat amount is obtained, regardless of which polarization direction it measures. There is also.

  Finally, the same applies to the case where the light source 2 of the surface plasmon sensor 61 uses a multi-directional polarization direction such as a light emitting diode.

  Note that the above configuration is a representative of some of the configuration examples, and is not limited to the above configuration.

  As described above, the surface plasmon sensors 41, 51, 61 have a problem that the monitor region 3A and the measurement region 3B do not pass through the same optical path, and thus cannot cope with the influence on the optical path. Moreover, since there are many parts compared with the surface plasmon sensor 1, the problem that cost started also had arisen.

  The surface plasmon sensor 1 according to the present embodiment has a configuration that solves the above-described problems of the surface plasmon sensors 41, 51, and 61 and is superior in performance as compared with the surface plasmon sensors 41, 51, and 61. Needless to say.

  Finally, the calculation circuit 15 and the control circuit 21 of the surface plasmon sensor may be configured by hardware logic, or may be realized by software using a CPU as follows.

That is, the surface plasmon sensor includes a CPU (central processing unit) that executes instructions of a control program that realizes each function, a ROM (read only memory) that stores the program, and a RAM (random access memory) that expands the program. And a storage device (recording medium) such as a memory for storing the program and various data. Then, an object of the present invention is to provide program codes (execution format program, intermediate code program, source program) of the control program for the calculation circuit 15 and the control circuit 21 for the surface plasmon sensor, which is software for realizing the functions described above, on a computer. This can also be achieved by supplying a recording medium recorded so as to be readable to the surface plasmon sensor, and reading and executing the program code recorded on the recording medium by the computer (or CPU or MPU).

  Examples of the recording medium include a tape system such as a magnetic tape and a cassette tape, a magnetic disk such as a floppy (registered trademark) disk / hard disk, and an optical disk such as a CD-ROM / MO / MD / DVD / CD-R. Card system such as IC card, IC card (including memory card) / optical card, or semiconductor memory system such as mask ROM / EPROM / EEPROM / flash ROM. As described above, the memory 20 in the third embodiment can be configured by the recording medium as described above.

  The surface plasmon sensor may be configured to be connectable to a communication network, and the program code may be supplied via the communication network. The communication network is not particularly limited. For example, the Internet, intranet, extranet, LAN, ISDN, VAN, CATV communication network, virtual private network, telephone line network, mobile communication network, satellite communication. A net or the like is available. Also, the transmission medium constituting the communication network is not particularly limited. For example, even in the case of wired such as IEEE 1394, USB, power line carrier, cable TV line, telephone line, ADSL line, etc., infrared rays such as IrDA and remote control, Bluetooth ( (Registered trademark), 802.11 wireless, HDR, mobile phone network, satellite line, terrestrial digital network, and the like can also be used. The present invention can also be realized in the form of a computer data signal embedded in a carrier wave in which the program code is embodied by electronic transmission.

  The surface plasmon sensor of the present invention can be suitably used for sensing substances such as biosensors currently used. It can also be used for gap sensors.

It is a figure which shows schematic structure of the surface plasmon sensor which concerns on one Embodiment. It is a figure which shows the example of installation of the said polarization direction selection element in the case of rotating a polarization direction selection element and selecting a polarization direction. It is a figure which shows the example of installation of the said polarization direction selection element in the case of rotating a polarization direction selection element and selecting a polarization direction. It is a figure which shows the example of installation of the said polarization direction selection element in the case of selecting a polarization direction by extracting and inserting a polarization direction selection element. It is a figure which shows the example of installation of the said polarization direction selection element in the case of selecting a polarization direction by extracting and inserting a polarization direction selection element. It is a figure which shows the outline of the APC circuit part contained in a light source drive circuit. It is a graph which shows the measurement result of the sample by the surface plasmon sensor which concerns on the said embodiment. It is a figure which shows the case where the said sample is solid or a droplet. It is a figure which shows the case where the said sample is a liquid. It is a figure which shows the outline | summary of operation | movement of the surface plasmon sensor which concerns on other embodiment. It is a figure which shows schematic structure of the surface plasmon sensor which concerns on other embodiment. It is a figure which shows the outline of the APC circuit part with which the surface plasmon sensor shown in FIG. 11 is provided. It is a figure which shows schematic structure of the surface plasmon sensor as a reference example. It is a figure which shows schematic structure of the surface plasmon sensor as a reference example. It is a figure which shows schematic structure of the surface plasmon sensor as a reference example.

Explanation of symbols

1, 2, 3 Surface plasmon sensor 2 Light source 3 Light beam 3A Monitor area 3B Measurement area 5, 5A Polarization direction selection element (dividing means, polarization direction selection means)
7 Prism (substrate)
8 Metal film 11 APC monitor (detection means)
12 Photodetector (detection means)
14 Light source drive circuit 15 Calculation circuit (calculation means)
20 memory (storage means)
21 Control circuit (control means)

Claims (16)

A light source that emits a light beam;
A light source driving circuit for controlling the intensity of the light source to drive the light source;
A metal film formed on a substrate;
A surface plasmon sensor comprising detection means for detecting reflected light from the metal film for each incident angle of the light beam,
The cross-sectional area of the light beam, comprising a dividing means for spatially divided into a monitor area and the measurement area,
The optical path of the light beam in the monitor area and the optical path of the light beam in the measurement area are adjacent to each other,
The light beam in the monitor region has a first polarization direction, the light beam in the measurement region has a second polarization direction,
The detection means detects the light intensity of the monitor region reflected by the metal film as a first detection result, and detects the light intensity of the measurement region reflected by the metal film as a second detection result,
The surface light plasmon sensor, wherein the light source driving circuit controls the intensity of the light source based on the first detection result.   The surface plasmon sensor according to claim 1, wherein the metal film can be replaced with another metal film.   In the division by the dividing means, the light beam of the first polarization is partially passed through the dividing means, and the portion of the light beam that does not pass through the dividing means is passed through the monitor region and the dividing means. 3. The surface plasmon sensor according to claim 1, wherein a portion of the light beam is changed from the first polarized light to the second polarized light to form the measurement region.   The splitting by the splitting means allows the light beam of the first polarization to pass through the splitting means, and the portion of the light beam that passes through the first area in the splitting means to be in the monitor area and in the splitting means. 3. The surface plasmon sensor according to claim 1, wherein a portion of the light beam passing through the second region is changed from the first polarized light to the second polarized light to be the measurement region.   In the splitting by the splitting unit, the light beam of the second polarization is passed through the splitting unit, and the portion of the light beam that passes through the first region in the splitting unit is changed from the second polarization to the first polarization. 3. The surface plasmon sensor according to claim 1, wherein the surface plasmon sensor is defined as the monitor region, and the portion of the light beam passing through the second region in the dividing unit is defined as the measurement region.   The splitting by the splitting means allows the light beam including the first polarized light and the second polarized light to pass through the splitting means, and the portion of the light beam passing through the first region in the splitting means is changed to the first. 2. The measurement region is formed by polarizing the light beam that passes through the second region in the splitting unit into the second polarized light to be used as the measurement region. Or the surface plasmon sensor of 2.   The surface plasmon sensor according to any one of claims 1 to 6, wherein the dividing means is installed in parallel light of the light beam.   The surface plasmon sensor according to claim 1, wherein the dividing unit is installed in an optical path on an incident side with respect to the metal film.   The surface plasmon sensor according to any one of claims 1 to 8, wherein the measurement region includes a diameter in a direction parallel to a direction of the second polarization of the light beam. A light source that emits a light beam;
A light source driving circuit for controlling the intensity of the light source to drive the light source;
A metal film formed on a substrate;
A surface plasmon sensor comprising detection means for detecting reflected light from the metal film for each incident angle of the light beam,
The cross-sectional area of the light beam, as well as space divided into a first monitor area and the polarization direction-selectable measuring area of the polarization, the polarization direction of the light beam in the measurement region, the first polarized light or the second Polarization direction selection means for making the polarization of
Calculating means for calculating the true reflectance of the second polarized light from the reflected light intensity of the second polarized light and the reflected light intensity of the first polarized light in the measurement region;
Are adjacent to each other with the optical path of the light beam in the optical path and the measurement area of the light beam in the upper Symbol monitor area,
The detection means detects the light intensity of the monitor region reflected by the metal film as a first detection result, and detects the light intensity of the measurement region reflected by the metal film as a second detection result,
The surface light plasmon sensor, wherein the light source driving circuit controls the intensity of the light source based on the first detection result.   The said calculation means calculates the said reflectance by comparing the reflected light intensity of the 2nd polarized light of the said measurement area | region, and the reflected light intensity of the 1st polarized light. The surface plasmon sensor described.   The said calculating means calculates the said reflectance by taking the ratio or difference of the reflected light intensity of the 2nd polarized light of the said measurement area | region, and the reflected light intensity of the 1st polarized light. Item 12. The surface plasmon sensor according to Item 10 or 11.   The light beam incident on the polarization direction selection means is linearly polarized light, and a λ / 2 plate is used as the polarization direction selection means, and the λ / 2 plate is rotated or the λ / 2 plate is inserted and removed. The surface plasmon sensor according to any one of claims 10 to 12, wherein the polarization direction is selected.   The light beam incident on the polarization direction selection means is linearly polarized light, a liquid crystal element is used as the polarization direction selection means, and the polarization direction is selected by adjusting a voltage applied to the liquid crystal element. The surface plasmon sensor according to any one of claims 10 to 12.   The light beam incident on the polarization direction selection unit includes the first and second polarizations, and a polarizing plate or a polarizer is used as the polarization direction selection unit, and the polarizing plate or the polarizer is rotated. The surface plasmon sensor according to any one of claims 10 to 12, wherein the polarization direction is selected.   The light beam is the first polarized light, and the polarization direction is selected by installing the polarization direction selection means only in the measurement region on the incident side. The surface plasmon sensor described.

Images