JP6010077B2 - Surface plasmon detection device and surface plasmon detection method - Google Patents

Description

The present invention relates to a surface plasmon detecting device and the surface plasmon detecting method for detecting a target substance of the conductive material surface by utilizing generation of surface plasmons in the conductive material surface.

  Surface plasmon is a wave of surface charge density on the surface of a conductive material, and a substance detector and a detection method using this phenomenon are known. In general, a surface plasmon detection device using surface plasmons passes a prism, a metal thin film formed directly on one surface of the prism or at a predetermined interval with respect to one surface of the prism, and the light beam through the prism. An optical system that allows the incident angle to be obtained with respect to the interface between the prism and the metal thin film, and light detection that can detect the intensity of the light beam totally reflected at the interface at each incident angle. Means.

  In the surface plasmon detection device, the surface plasmon on the surface of the metal thin film has an inherent dispersion relationship determined by the dielectric conditions of the metal thin film and the prism and the surface state of the metal thin film.

  When the light beam is incident on the metal thin film at an incident angle θ that is equal to or greater than the total reflection angle, a part of the incident light becomes light called evanescent light that transmits the inside of the metal thin film along the surface of the metal thin film. The wave vector of the evanescent light is equal to the traveling direction component of the evanescent light of the wave vector of the incident light. That is, the wave number of the evanescent light has a different value according to sin θ for each of various incident θs.

  When the condition that the wave number of the surface plasma and the wave number of the evanescent light are equal, a phenomenon called surface plasmon resonance occurs, and a significant decrease in intensity is observed in the total reflected light corresponding to the incident angle that satisfies this condition. The

  Since surface plasmons are very sensitive to the state of the surface of the metal thin film, when a substance adheres to the surface of the metal thin film, the incident angle of light at which a decrease in the intensity of the total reflected light is observed is shifted. Therefore, the substance adhering to the metal thin film can be detected by observing the deviation of the incident angle of the light where the decrease in the intensity of the total reflected light is observed.

  As a document disclosing such a surface plasmon detection device for detecting a substance adhering to a metal thin film by observing a shift in the incident angle of light in which a decrease in the intensity of the total reflected light is observed, for example, Japanese Patent Laid-Open No. 10-101609 No. 19768 (Patent Document 1), JP-A-10-239233 (Patent Document 2) and JP-A 2006-47000 (Patent Document 3).

  In the surface plasmon detection device disclosed in Patent Document 1, a light beam composed of light components having various incident angles is made incident on the interface between the metal thin film and the dielectric member in a convergent light state or a divergent light state. Each ray component reflected at various reflection angles at the interface is detected by a multi-cell type line sensor or a two-dimensional array sensor extending in a direction in which all of the rays can be received, and the ray component corresponding to the detection position of the dark line is incident. The angle is specified as the total reflection attenuation angle.

  In the surface plasmon detection device disclosed in Patent Document 2, parallel light beams are sequentially incident on the interface between the metal thin film and the dielectric member while changing the incident angle, and the light beam whose reflection angle changes according to the change of the incident angle. Is detected by a small one-cell type light receiving part that moves in synchronization with the change in the reflection angle, or a one-cell type or multi-cell type light receiving part that extends along the change direction of the reflection angle. In this case, the incident angle when the dark line is detected is specified as the total reflection attenuation angle.

  In the surface plasmon detection device disclosed in Patent Document 3, a Gaussian distribution according to an incident angle in a plane of incidence of a central ray of the light bundle as a light beam incident on an interface between a metal thin film and a dielectric member, Alternatively, one having a beam cross-sectional intensity that monotonously increases or monotonously decreases is used. In this case, the reflection attenuation angle is obtained by specifying the incident angle of the ray component subjected to the reflection attenuation.

Japanese Patent Laid-Open No. 10-19768 Japanese Patent Laid-Open No. 10-239233 JP 2006-47000 A

  However, the surface plasmon detection device disclosed in Patent Document 1 is expensive because each light component reflected at the interface at various reflection angles is detected by a multi-cell line sensor or a two-dimensional array sensor. A detector (light receiving unit) is required. In addition, calculation processing using a complicated algorithm is required to detect the dark line position. Furthermore, the detection accuracy of the dark line position is limited by the influence of the unevenness of the interface and the spread width of the dark line (especially when a light source other than a laser is used).

  In the surface plasmon detection device disclosed in Patent Document 2, since parallel light beams are sequentially incident while changing the incident angle, the mechanism for changing the incident angle is complicated and high-speed processing is difficult. There was a problem. Furthermore, when the incident angle is changed by a mechanical moving mechanism, the detection accuracy is limited by the angle setting accuracy of the moving mechanism.

  In the surface plasmon detection device disclosed in Patent Document 3, a light beam having a Gaussian beam cross-sectional intensity is generated by a laser light source, and once expanded, the light beam is converged toward the interface. Incident on the interface. As a result, it is possible to generate a light flux including a large number of light rays having various incident angles θ and intensities having a correlation (Gaussian distribution) with the incident angles θ. In such a configuration, a light beam having a Gaussian beam intensity distribution emitted from a laser light source needs to be incident on the interface while maintaining the intensity distribution.

  However, in general, the shape of the beam intensity distribution is greatly deformed in the process of the optical path of the beam due to natural diffusion of the beam accompanying the progress of the beam light and disturbance by the diverging / condensing optical system. Considering these influences, an incident optical system having a very sophisticated and complicated structure is required to enter the interface with the shape of the intensity distribution controlled with high accuracy.

  For this reason, when the configuration of the surface plasmon detection device disclosed in Patent Document 3 is adopted, for example, the number of members for controlling the light flux increases, and the position and angle adjustment operations become complicated. It can be considered that the cost of the members of the system rises and that a space for accommodating them is required.

  In order to obtain a monotonically increasing or monotonically decreasing intensity distribution from a light beam having a Gaussian beam intensity distribution emitted by a laser light source, an inverse Gaussian filter for converting the Gaussian distribution into a uniform intensity distribution, and a uniform Since a wedge filter for converting a simple intensity distribution into a monotonically increasing or monotonically decreasing intensity distribution is required and it is necessary to provide them before the detection substrate, the structure of the incident optical system is further complicated.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a surface plasmon detection device and a surface plasmon detection method capable of obtaining sufficient detection accuracy with a simple configuration. It is in.

  A surface plasmon detection device according to the present invention includes a dielectric member having a main surface and a metal thin film formed on the main surface, and an incident angle is generated by a surface plasmon phenomenon at an interface between the dielectric member and the metal thin film. A surface plasmon element that reflects incident light composed of a luminous flux having a distribution as a reflected light composed of a luminous flux having an angle dependence on the amount of light, and a light projecting unit that projects the incident light toward the surface plasmon element, A light receiving unit that receives the reflected light reflected by the surface plasmon element. The light receiving unit includes a light receiving region configured to detect a different light amount according to a difference in light amount distribution caused by the angle dependency of the reflected light.

  In the surface plasmon detection device according to the present invention, the light projecting section gradually has an incident angle as the incident light with respect to a uniaxial direction in an incident light beam cross section perpendicular to the optical axis of the incident light. It is preferable to project light having a changing angular distribution. Moreover, it is preferable that the said light-receiving part receives the light which has the said light quantity distribution in the direction corresponding to the said 1 axial direction in the reflected light beam cross section perpendicular | vertical to the optical axis of the said reflected light as said reflected light. In this case, in the first plane including the light receiving region and on which the reflected light is projected, the light receiving region has a length in a direction perpendicular to the direction corresponding to the one axis direction and a direction corresponding to the one axis direction. It is preferable that it is formed so as to gradually change along a direction parallel to.

  In the surface plasmon detection device according to the present invention, the reflected light beam cross section has a direction corresponding to the uniaxial direction because the reflected light has the light amount distribution and the amount of light is less than other portions. It is preferable to include a dark line formed so as to extend in the vertical direction. In this case, it is preferable that the outline of the light receiving region has a portion that intersects non-parallel to the dark line projected on the first plane.

  In the surface plasmon detection device according to the present invention, it is preferable that the length of the light receiving region extending in a direction perpendicular to the direction corresponding to the one axis direction gradually changes at a constant change rate. .

  In the surface plasmon detection device according to the present invention, the light receiving unit may include a shielding member having an opening and a light receiving element that detects the amount of the reflected light transmitted through the opening. . In this case, it is preferable that the light receiving region is defined by the opening.

  In the surface plasmon detection device according to the present invention, the shielding member may be constituted by a single or a plurality of shielding members. When the shielding member is constituted by the single shielding member, The single shielding member preferably has a plurality of openings having different shapes, and the light receiving portion is provided so that one opening defining the light receiving region can be selected from the plurality of openings. preferable. In the case where the shielding member is constituted by the plurality of shielding members, the plurality of shielding members preferably have the openings having different shapes, and the light receiving unit is formed of the plurality of shielding members. It is preferable that one of the shielding members is provided so as to be selectable.

  In the surface plasmon detection device according to the present invention, it is preferable to detect the measurement object based on the relationship between the received light amount detected by the light receiving unit and the reference amount detected in advance by the light receiving unit. .

  In the surface plasmon detection device according to the present invention, the surface plasmon element preferably includes a staying layer that causes gas to stay on the surface of the metal thin film.

  The surface plasmon detection method according to the present invention projects incident light comprising a light beam having a distribution in incident angle onto a surface plasmon element including a dielectric member having a main surface and a metal thin film formed on the main surface. The incident light incident on the surface plasmon element is reflected as reflected light composed of a light flux having an angle dependency on the amount of light due to the surface plasmon phenomenon at the interface between the dielectric member and the metal thin film, A surface plasmon detection method in which the reflected light reflected by the surface plasmon element is received by a light receiving unit, wherein the light receiving unit is configured to respond to a difference in light amount distribution caused by the angle dependency of the reflected light. Those having a light receiving area configured to detect different amounts of light are used.

  According to the present invention, it is possible to provide a surface plasmon detection device and a surface plasmon detection method capable of obtaining sufficient detection accuracy with a simple configuration.

It is the schematic which shows the structure of the surface plasmon detection apparatus which concerns on Embodiment 1. FIG. It is a schematic sectional drawing which shows the structure of the surface plasmon element of the surface plasmon detection apparatus shown in FIG. It is a figure which shows the relationship between the incident angle contained in the incident light which has incident angle distribution in the surface plasmon detection apparatus shown in FIG. 1, and a reflectance. It is a figure which shows the cross section of the light beam of the reflected light reflected in the interface of the dielectric material member shown in FIG. 1, and a metal thin film. It is a top view which shows an example of the change of the position of a dark line at the time of detecting using the shielding member shown in FIG. It is a schematic diagram for demonstrating the surface plasmon detection method in a comparative example. It is a top view which shows an example of the dark line at the time of detecting using the shielding member which concerns on the modification 1. FIG. It is a top view which shows an example of the dark line at the time of detecting using the shielding member with which the surface plasmon detection apparatus which concerns on Embodiment 2 is equipped. It is a figure which shows an example of the change of the position of a dark line at the time of detecting using the shielding member shown in FIG. It is a figure which shows the other example of the change of the position of a dark line at the time of detecting using the shielding member shown in FIG. It is a top view which shows an example of the dark line at the time of detecting using the shielding member which concerns on the modification 2. It is a top view which shows an example of the dark line at the time of detecting using the shielding member which concerns on the modification 3. It is a top view which shows an example of the dark line at the time of using the surface plasmon detection apparatus which concerns on Embodiment 3. FIG. It is a top view which shows an example of the dark line at the time of using the surface plasmon detection apparatus which concerns on Embodiment 4, when the 1st opening provided in the shielding member is selected, and the 2nd opening provided in the shielding member It is a top view which shows an example of the dark line at the time of selecting. It is a top view which shows an example of the dark line at the time of using the surface plasmon detection apparatus which concerns on the modification 4, and is a top view which shows an example of the dark line when the 1st shielding member is selected and the 2nd shielding member is selected. is there. It is a figure which shows an example of the dark line at the time of using the surface plasmon detection apparatus which concerns on Embodiment 5. FIG. It is a figure which shows the relationship between the density | concentration of a measuring object, and the detection value by a detection part in the case of measuring the density | concentration of a measuring object in order to verify the effect of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, the same or common parts are denoted by the same reference numerals in the drawings, and description thereof will not be repeated.

(Embodiment 1)
FIG. 1 is a schematic diagram showing the configuration of the surface plasmon detection device according to the present embodiment. With reference to FIG. 1, the surface plasmon detection apparatus 1 which concerns on this Embodiment is demonstrated.

  The surface plasmon detection device 1 includes a light projecting unit 2, a light receiving unit 3, a surface plasmon element 60, and an arithmetic processing unit 90. The light projecting unit 2 projects incident light L1 toward the surface plasmon element 60. The light receiving unit 3 receives the reflected light L <b> 2 reflected from the surface plasmon element 60.

  The light projecting unit 2 includes a light source 10, a collimator lens 20, a polarizer 30, a reflection mirror 40, and a condenser lens 50. As the light source 10, for example, a semiconductor laser can be employed. The outgoing light emitted from the light source 10 is converted into a parallel light beam by the collimating lens 20.

  The polarizer 30 is for extracting p-polarized light that causes surface plasmons from the emitted light emitted from the light source 10. The outgoing light converted into the parallel light flux is converted into p-polarized light by the polarizer 30 and reflected toward the condenser lens 50 by the reflection mirror 40.

  The outgoing light reflected by the reflection mirror 40 is collected by the condenser lens 50 and enters the surface plasmon element 60. As a result, incident light L <b> 1 composed of a light beam having a distribution in incident angles enters the surface plasmon element 60. Specifically, the incident light L1 is incident on an interface between a dielectric member 67 and a metal thin film 64 described later. At this time, the incident light L1 enters the interface with a uniform intensity distribution.

  In the surface plasmon element 60, the incident light L1 composed of a light flux having a distribution in the incident angle is reflected by the surface plasmon phenomenon at the interface between the dielectric member 67 and the metal thin film 64. As reflective.

  The light receiving unit 3 includes a collimating lens 70, a shielding member 81, and a light receiving element 82. The reflected light L <b> 2 reflected by the surface plasmon element 60 is converted into a parallel light beam by the collimating lens 70. The reflected light L <b> 2 converted into the parallel light flux passes through an opening 83 (see FIG. 5) provided in the shielding member 81 and is received by the light receiving element 82. The opening 83 defines a light receiving region of the light receiving unit 3. As the light receiving element 82, for example, a photodiode can be employed. The amount of reflected light L2 received can be detected by the photodiode. The light receiving unit 82 is connected to the arithmetic processing unit 90.

  The arithmetic processing unit 90 calculates the concentration or the like of a measurement object such as a volatile organic substance based on the light amount of the reflected light L2 detected by the light receiving element 82. The arithmetic processing unit 90 includes a processing unit 91, a storage unit 92, a table storage unit 93, and a thermohygrometer 94 which will be described later.

  FIG. 2 is a schematic cross-sectional view showing the configuration of the surface plasmon element of the surface plasmon detection device shown in FIG. The surface plasmon element 60 will be described with reference to FIG.

  The surface plasmon element 60 includes a prism 61, a transparent substrate 62, a first adhesion layer 63, a metal thin film 64, a second adhesion layer 65, and a staying layer 66. The prism 61 and the transparent substrate 62 constitute a dielectric member 67.

  The material of the prism 61 is preferably a material that has high light transmittance and a large difference in dielectric constant from vacuum. As the prism 61, for example, a translucent resin, glass, or the like can be employed. In the present embodiment, glass is adopted as the prism 61.

  The material of the transparent substrate 62 is preferably a material having substantially the same refractive index as that of the prism 61 in order to suppress light loss due to a difference in refractive index. As the transparent substrate 62, similarly to the prism 61, a light-transmitting resin, glass, or the like can be used. In the present embodiment, glass is used.

  The transparent substrate 62 is bonded to the prism 61 using an adhesive without a gap. In order to suppress the optical loss due to the difference in refractive index, it is preferable to use a member having substantially the same refractive index as that of the prism 61 and the transparent substrate 62 as the adhesive. A first adhesion layer 63, a metal thin film 64, a second adhesion layer 65, and a staying layer 66 are laminated in this order on the main surface 62b located on the side opposite to the prism 61 side. After these layers are laminated on the main surface 62b, the main surface 62a of the transparent substrate 62 located on the opposite side of the main surface 62b is bonded to the bottom surface 61a of the prism 61 using the adhesive.

  The first adhesion layer 63 is formed when the adhesion between the metal thin film 64 and the transparent substrate 62 is poor. For this reason, when the metal thin film 64 can be directly formed on the main surface 62b of the transparent substrate 62 while ensuring adhesion, the first adhesion layer 63 can be omitted.

  As the first adhesion layer 63, a material having good adhesion to the transparent substrate 62 and the metal thin film 64 is used. For example, when the metal thin film 64 is made of a noble metal such as gold or silver, a material such as titanium, nickel, chromium, or molybdenum can be used for the first adhesion layer 63. In the present embodiment, titanium is employed.

  In addition, the first adhesion layer 63 is preferably formed as thin as possible as long as adhesion is obtained so that the arrival of the incident light L1 to the metal thin film 64 is not hindered. Specifically, the thickness of the first adhesion layer is preferably about 1 nm. Even when the first adhesion layer 63 is formed, since the thickness of the first adhesion layer 63 is very thin as described above, the interface between the dielectric member 67 and the thin metal thin film 64 is the prism 61. The main surface 64a of the metal thin film 64 located in the side is pointed out.

  As the metal thin film 64, gold, silver, copper, platinum, aluminum, or the like can be employed. In this embodiment, gold is adopted. When gold is employed as the metal thin film 64, the thickness of the metal thin film 64 is preferably within a range in which the reflection intensity attenuation effect due to surface plasmon resonance is most obtained, and is preferably 40 to 55 nm, for example.

  The second adhesion layer 65 is formed when the adhesion between the metal thin film 64 and the staying layer 66 is poor. For this reason, when the staying layer 66 can be directly formed on the main surface 64b of the metal thin film 64 while ensuring adhesion, the second adhesion layer 65 can be omitted.

  As the second adhesion layer 65, a material having good adhesion to the metal thin film 64 and the staying layer 66 is used. When the staying layer 66 is made of silicon dioxide, a material such as titanium, nickel, chromium, or molybdenum can be used. In the present embodiment, titanium is employed.

  The stagnant layer 66 is formed on the metal thin film 64 or the second adhesion layer 65 when the object to be measured is a substance having poor adsorptivity to the metal thin film 64, such as a volatile organic substance (VOC) in a gas. Is done. The retention layer 66 temporarily retains the gas containing the measurement object on the metal thin film 64. For this reason, the staying layer 66 preferably has a porous shape in which a plurality of through-holes penetrating in the thickness direction are provided. Thereby, the gas can be retained in the through hole.

  As a material of the staying layer 66, silicon dioxide can be adopted. In this case, in order to form a silicon dioxide film having a porous shape, first, a solution in which TEOS (Tetraethyl orthosilicate) is mixed is prepared after the pH is adjusted by mixing water and a surfactant. The solution can be formed by applying the solution on the metal thin film 64 or the second adhesion layer 65 using a spin coating method, followed by drying and baking.

  The staying layer 66 is for increasing the gas detection sensitivity by retaining the gas on the metal thin film 64 for a long time when the detection target is a gas, and is not a configuration essential for the implementation of the present invention. . For example, when the detection target is a liquid, it is possible to detect the component contained in the liquid by omitting the staying layer 66 and directly attaching the detection target liquid to the surface of the metal thin film 64 (for example, the main surface 64b). It is. If it is such a form, for example, the present invention can be used also for the use which attaches the antibody ingredient in a liquid to metal thin film 64, and detects the antibody reaction.

  In addition, when the second adhesion layer 65 is formed, the second adhesion layer 65 has adhesion so that a measurement object such as a volatile organic substance can adhere to the metal thin film 64. It is preferable to form as thin as possible at the limit. Specifically, the thickness of the second adhesion layer 65 is preferably 1 nm.

  In the present embodiment, the case where the dielectric member 67 is configured by the prism 61 and the transparent substrate 62 has been described as an example. However, the present invention is not limited to this and may be configured by the prism 61. In this case, the metal thin film may be directly formed on the bottom surface 61a of the prism 61, or the first adhesion layer and the metal thin film may be formed in this order. Further, in this case, the staying layer may be directly formed on the metal thin film according to the measurement object, or the second adhesion layer and the staying layer may be formed in this order.

  FIG. 3 is a diagram showing the relationship between the incident angle and the reflectance included in the incident light having the incident angle distribution in the surface plasmon detector shown in FIG. With reference to FIG. 3, the relationship between the incident angle and the reflectance included in the incident light L1 having the incident angle distribution in the surface plasmon detector 1 will be described.

  As shown in FIG. 3, the incident light L1 having a distribution in the incident angle has an angular distribution in which the incident angle gradually changes with respect to one axial direction in the incident light beam cross section perpendicular to the optical axis of the incident light L1. Light is incident on the interface between the metal thin film 64 and the dielectric member 67. In this case, at the portion where the incident angle is approximately 38 degrees, the wave number of the surface plasma and the wave number of the evanescent light transmitted along the main surface 64a of the metal thin film 64 through the inside of the metal thin film 64 become equal. Resonance occurs. As a result, the reflection intensity (reflectance) of light incident at an incident angle near 38 degrees is attenuated. Here, the uniaxial direction refers to a predetermined one direction on the incident light beam cross section.

  The resonance angle (incident angle) at which surface plasmon resonance occurs varies depending on the surface state of the metal thin film 64. When a measurement object (volatile organic substance) adheres (contacts) to the main surface 64b of the metal thin film 64, the reflection intensity of light incident at an incident angle different from the above example is attenuated. Further, the portion where the reflection intensity is attenuated (resonance angle) varies depending on the concentration of the volatile organic substance. As described above, when the position where the reflection intensity is attenuated varies depending on the incident angle, the reflected light L2 reflected at the interface has an angle dependency on the light amount.

  FIG. 4 is a view showing a cross section of the reflected light beam reflected at the interface between the dielectric member and the metal thin film shown in FIG. 4 shows a cross section of reflected light (reflected light beam cross section) after incident light having an incident angle range of 32 ° to 46 ° (angle distribution) shown in FIG. 3 is reflected at the interface. Yes. The reflected light reflected at the interface between the dielectric member and the metal thin film will be described with reference to FIG.

  As shown in FIG. 4, the reflected light L2 has a light amount distribution by being reflected in a state where the reflection intensity is attenuated in a part of the angle range. Specifically, the reflected light L2 has a light amount distribution in which the amount of light changes in a direction corresponding to the one axis direction in the cross section of the reflected light beam perpendicular to the optical axis of the reflected light L2. In the reflected light beam cross section, a dark line BL is formed in a portion where the amount of light is smaller than in other portions. The dark line BL is formed to extend in a direction perpendicular to the direction corresponding to the one axis direction (AR1 direction).

  FIG. 5 is a plan view showing an example of a change in the position of the dark line when detected using the shielding member shown in FIG. With reference to FIG. 5, the surface plasmon detection method using the surface plasmon detection apparatus 1 is demonstrated. In this case, a method for measuring the concentration of volatile organic substances will be described.

  As shown in FIG. 5, a shielding member 81 having a circular opening 83 is used as the shielding member. The position of the dark line BL formed by the surface plasmon phenomenon changes not only with the concentration of the measurement object (volatile organic substance) but also with temperature and humidity. For this reason, the light quantity of the reflected light L2 at each temperature and humidity is detected in advance by the light receiving unit 3 in a state where there is no measurement object in the apparatus. Each light amount detected in advance is stored in the storage unit 92 (see FIG. 1) as a reference amount at each temperature and humidity. Further, a conversion table for calculating the gas concentration based on the fluctuation amount from the reference amount is also stored in the table storage unit 93 (see FIG. 1).

  In order to determine the reference amount, first, the temperature and humidity in the apparatus at the time of measurement are measured using a temperature and humidity meter 94 (see FIG. 1) in the absence of a measurement object. Based on the information about the measured temperature and humidity, the processing unit 91 determines a reference amount necessary at the time of measurement from the information stored in the storage unit 92.

  In the figure, the position of the dark line (the initial position of the dark line) when the amount of light corresponding to the determined reference amount is detected is indicated by a two-dot chain line. The center line of the dark line coincides with the center line C1 of the opening 83.

  Subsequently, the light receiving unit 3 detects the amount of the reflected light L <b> 2 reflected at the interface in a state where the gas containing the measurement object is in contact with the main surface 64 b of the metal thin film 64. As described above, the position of the dark line BL varies depending on the surface state of the metal thin film 64 and moves in a direction parallel to the direction facing the one axial direction. In the present embodiment, the dark line BL moves to a position away from the center line C1 of the opening 83 in the AR1 direction in the drawing.

  In the plane (first plane) on which the reflected light L2 including the opening 83 is projected, the opening 83 has a direction in which a length d1 in a direction perpendicular to the direction corresponding to the one-axis direction corresponds to the one-axis direction. It is formed so as to gradually change along a direction parallel to. For this reason, when the position of the dark line BL changes, the ratio of the area of the dark line BL occupying the light receiving region changes. Thereby, the light quantity of the reflected light which the light-receiving part 3 detects changes according to the position of the dark line BL.

  The processing unit 91 calculates the difference (variation amount) between the amount of the reflected light L2 detected at the time of measurement and the reference amount, and calculates the concentration of the measurement object using the conversion table.

  In the present embodiment, the rate of change of the area of the opening is not constant with respect to the moving direction of the dark line BL. That is, the rate of change of the length d1 of the opening perpendicular to the direction corresponding to the one axis direction is not constant. As a result, when a shift occurs in the initial position of the dark line BL, the amount of change in the area of the dark line BL differs even if the amount of movement of the dark line BL is the same. For this reason, the density | concentration of a measurement object is reliably computable by using the above conversion tables.

  For example, when the concentration of the measurement object is low and the dark line BL moves only slightly, it is preferable that the initial position of the dark line BL is set so as to be located in a portion away from the center line C1. The rate of change of the length d1 of the opening increases as the distance from the center line C1 increases. For this reason, when the initial position is set at a position away from the center line C1, the dark line BL is slightly moved compared to the case where the initial position is set near the center line. However, the amount of change in the area of the dark line BL increases. For this reason, the difference between the detected light amount and the reference amount is increased, and the detection sensitivity can be increased.

  As described above, in the present embodiment, by appropriately setting the position of the dark line when detecting the reference amount (initial position of the dark line), it is possible to cope with a case where particularly high sensitivity is required. For this reason, the surface plasmon detection device 1 according to the present embodiment can optimize the sensitivity depending on the use environment.

  FIG. 6 is a schematic diagram for explaining a surface plasmon detection method in a comparative example. With reference to FIG. 6, the surface plasmon detection method in a comparative example is demonstrated. In the comparative example, a multi-cell line sensor is used as the light receiving unit.

  As shown in FIG. 6, when a multi-cell line sensor is used, for example, the measurement object is within a measurement range R having n × m pixels (n and m are arbitrary positive integers) g. The initial position of the dark line BL1 in the absence state and the position of the dark line BL2 in the state where the measurement object is present are detected. It detects how many pixels the dark line has moved, and calculates the concentration of the measurement object based on the amount of movement. In order to detect the position of the dark line, a calculation process using a complicated algorithm is required. Therefore, the configuration of the detection unit is complicated and the detection unit itself is expensive.

  As described above, in the surface plasmon detection device 1 and the surface plasmon detection method according to the present embodiment, the light receiving unit 3 detects different amounts of light according to the difference in the light amount distribution caused by the angle dependency of the reflected light L2. By detecting the amount of the reflected light L2 using a light receiving region configured as described above, sufficient detection accuracy can be obtained with a simple configuration.

  In the present embodiment, the case where the shape of the opening 83 is circular has been described as an example. However, the present invention is not limited to this, and the opening 83 is short in a direction parallel to the direction perpendicular to the direction corresponding to the one axis direction. An elliptical shape or an elliptical shape having an axis or a major axis may be used.

(Modification 1)
FIG. 7 is a plan view illustrating an example of a dark line when detected using the shielding member according to the present modification. With reference to FIG. 7, the shielding member 81A according to the present modification will be described.

  As shown in FIG. 7, the opening 83 </ b> A of the shielding member 81 </ b> A according to the present modification has a curved shape so that the hypotenuse of the right triangle approaches the other two sides. Of the other two sides excluding the curved side 83c of the outline of the opening 83A, one side 83b extends in a direction parallel to the direction corresponding to the one axis direction (AR1 direction), and the other side 83a extends in a direction orthogonal to a direction corresponding to the one-axis direction.

  Also in such a shielding member 81A, the opening 83A is gradually formed along a direction (AR1 direction in the drawing) in which the length d1 in the vertical direction is parallel to the direction corresponding to the uniaxial direction in the direction corresponding to the uniaxial direction. It is formed so as to change. Even in this case, since the rate of change of the length d1 of the opening is not constant along the AR1 direction, the environment of use can be determined by appropriately setting the position of the dark line (the initial position of the dark line) when detecting the reference amount. The sensitivity can also be optimized.

  As described above, even when the shielding member 81A according to the present modification is used in the surface plasmon detection device according to the first embodiment, it is substantially the same as the surface plasmon detection device and the surface plasmon detection method according to the first embodiment. An effect is obtained.

(Embodiment 2)
FIG. 8 is a plan view showing an example of a dark line when detected using a shielding member provided in the surface plasmon detection device according to the present embodiment. With reference to FIG. 8, the surface plasmon detection device according to the present embodiment will be described.

  As shown in FIG. 8, the surface plasmon device according to the present embodiment is different from the surface plasmon device according to the first embodiment in the shape of the opening 83B of the shielding member 81B. Other configurations are almost the same.

  The opening 83B has a right triangle shape. One of the two sides excluding the hypotenuse 83c in the outline of the opening 83B extends in a direction parallel to the direction corresponding to the one axial direction (AR1 direction), and the other side 83a It extends in a direction orthogonal to a direction corresponding to one axial direction. Of the outline of the opening 83B, the hypotenuse 83c intersects the dark line projected on the plane including the opening 83C.

  In this case, the length d1 of the opening 83B extending in the direction perpendicular to the direction corresponding to the one axis direction gradually changes along the AR1 direction at a constant change rate. For this reason, if the moving amount of the dark line BL is the same regardless of the initial position of the dark line BL, the amount of change in the area of the dark line BL is constant. Thereby, the amount of change in the amount of reflected light detected by the light receiving unit 3 is also constant.

  9 and 10 are diagrams illustrating an example of a change in the position of the dark line when the detection is performed using the shielding member illustrated in FIG. 8 and other examples. The amount of change in the area of the dark line BL when the initial position of the dark line is different and the amount of movement of the dark line BL is the same will be described with reference to FIGS.

  9 and 10, in order to make the movement amount easy to understand, a predetermined region R on the plane including the opening 83 </ b> B is divided into n × m unit regions g. Further, the hypotenuse of the opening 83B coincides with the diagonal line of the unit region g through which it passes. Note that the region R in FIG. 9 and the region R in FIG. 10 are in the same range, and the opening 83B in FIG. 9 and the opening 83B in FIG. 10 have the same shape.

  FIG. 9 shows a case where the initial position of the dark line is P1 and the position of the dark line BL after movement is P2. FIG. 10 shows the case where the initial position of the dark line is P3, the position of the dark line BL after movement is P4, and the initial position of the dark line is P5, and the position of the dark line BL after movement is P6. Yes. In any case, the moving amount of the dark line BL is 4 squares in the AR1 direction.

  At this time, in each case, the area of the dark line BL after the movement is reduced by an area of 4 unit regions with respect to the area of the dark line at the initial position. Thus, in this embodiment, if the amount of movement of the dark line is the same regardless of the initial position, the amount of change in the area of the dark line BL is also constant.

Therefore, it is possible to easily determine the conditions simply by adjusting the incident angle incident on the light receiving unit 3 so that the initial position of the dark line enters the opening 83B. Parts For this reason, the does not require the assembling work involving fine adjustment of the light projecting section 2 and the light receiving unit 3 of the order to you the initial position of the dark line in place, and does not require any member for fine adjustment The number of points can be reduced and the cost can be reduced.

  In the present embodiment as well, the concentration of the measurement object can be measured from the difference between the reference amount and the detected value, as in the first embodiment.

  As described above, also in the surface plasmon detection device and the surface plasmon detection method according to the present embodiment, different light amounts are detected as the light receiving unit 3 according to the difference in the light amount distribution caused by the angle dependency of the reflected light L2. By detecting the amount of the reflected light L2 using a light receiving region configured as described above, sufficient detection accuracy can be obtained with a simple configuration.

(Modification 2)
FIG. 11 is a plan view showing an example of a dark line when detected using the shielding member according to the present modification. With reference to FIG. 11, the shielding member 81C according to the present modification will be described.

  As shown in FIG. 11, the opening 83C of the shielding member 81C according to the present modification has a trapezoidal shape. Of the outline of the opening 83C, one set of parallel opposite sides is parallel to the direction corresponding to the one axis direction (AR1 direction) and the vertical direction. Of the outline of the opening 83C, another set of opposite sides excluding one set of parallel opposite sides intersects the dark line projected on the plane including the opening 83C.

  Even when the opening 83C has such a shape, the length d1 of the opening 83C extending in the direction perpendicular to the direction corresponding to the one axis direction (AR1 direction) is constant along the AR1 direction. It gradually changes at the rate of change. As a result, also in this modification, it is possible to obtain substantially the same effect as in the second embodiment.

(Modification 3)
FIG. 12 is a plan view illustrating an example of a dark line when detected using the shielding member according to the present modification. With reference to FIG. 12, shielding member 81D which concerns on this modification is demonstrated.

  As shown in FIG. 12, the opening 83D of the shielding member 81D according to the present modification has a triangular shape. One side (bottom side) 83a of the outline of the opening 83D is parallel to a direction (AR1 direction) corresponding to the one-axis direction and a vertical direction. The other two sides 83b and 83c of the outline of the opening 83D are inclined so as to approach each other in the direction of the AR1. The other two sides 83b and 83c of the outline of the opening 83D intersect with the dark line projected on the plane including the opening 83C. One side 83c of the other two sides is connected to one end of the one side 83a, and the other side 83b of the other two sides is connected to the other end of the one side. Yes.

  Even when the opening 83D has such a shape, the length d1 of the opening 83D extending in the direction perpendicular to the direction corresponding to the one-axis direction (AR1 direction) is constant along the AR1 direction. It gradually changes at the rate of change. As a result, also in this modification, it is possible to obtain substantially the same effect as in the second embodiment.

(Embodiment 3)
FIG. 13 is a diagram illustrating an example of a dark line when the surface plasmon detection device according to the present embodiment is used. With reference to FIG. 13, the surface plasmon detection device according to the present embodiment will be described.

  As shown in FIG. 13, the surface plasmon device according to the present embodiment is different from the surface plasmon device according to the second embodiment in that the shielding member 81 is not used in the light receiving unit 3 and the light receiving element. The difference is that 82 is arranged to rotate in the circumferential direction with respect to the central axis C2. Other configurations are almost the same.

  The light receiving element 82 has a substantially rectangular light receiving region. The light receiving element 82 is arranged so that the diagonal line D1 of the light receiving area of the light receiving element 82 is parallel to a direction perpendicular to the direction corresponding to the one axis direction (AR1 direction).

  Also in this case, in the light receiving region, the length d1 in the direction perpendicular to the direction corresponding to the uniaxial direction gradually changes at a constant change rate along the direction parallel to the direction corresponding to the uniaxial direction. It is formed as follows.

  However, for example, when the initial position of the dark line is at a position indicated by a two-dot chain line, and the position of the dark line BL after measuring the concentration of the measurement object is at a position symmetrical to the initial position across the diagonal line D1, the dark line It is possible that the area of the dark line BL does not change before and after the movement of BL.

  For this reason, in the present embodiment, it is necessary to pay attention to the initial position of the dark line, and it is preferable to use only the half surface of the light receiving region located on the left or right side of the diagonal line D1. When only the half surface of the light receiving region is used, if the moving amount of the dark line BL is the same regardless of the initial position of the dark line BL, the amount of change in the area of the dark line BL is constant. Thereby, the amount of change in the amount of reflected light detected by the light receiving unit 3 is also constant. As a result, also in the present embodiment, it is possible to obtain substantially the same effect as in the second embodiment.

  In the present embodiment, since the shielding member is unnecessary, the surface plasmon detection device can be further simplified.

(Embodiment 4)
FIG. 14 is a plan view showing an example of a dark line when the surface plasmon detection device according to the present embodiment is used, in the case where the first opening provided in the shielding member is selected and provided in the shielding member. It is a top view which shows an example of the dark line at the time of selecting a 2nd opening part. FIG. 14A is a plan view illustrating an example of a dark line when the first opening provided in the shielding member is selected. FIG. 14B is a plan view illustrating an example of a dark line when the second opening provided in the shielding member is selected. With reference to FIG. 14 (A) and FIG. 14 (B), the surface plasmon detection apparatus which concerns on this Embodiment is demonstrated.

  As shown in FIGS. 14 (A) and 14 (B), the surface plasmon detection device according to the present embodiment is compared with the surface plasmon detection device 1 according to the first embodiment. A point provided with (not shown) and the structure of a shielding member differ. Other configurations are almost the same.

  The shielding member 81E according to the present embodiment has a plurality of openings 83E1 and 83E2. The plurality of openings 83E1 and 83E2 are arranged, for example, so as to be aligned in a direction perpendicular to the direction corresponding to the one axial direction (AR1 direction). The shielding member 81E is slidably provided.

  In the surface plasmon detection device according to the present embodiment, the opening corresponding to the light receiving unit 3 is moved by sliding the shielding member 81E in the DR direction (direction perpendicular to the direction corresponding to the one axis direction) by the opening selection unit. 83E1 and 83E2 can be selectively arranged. The direction in which the openings 83E1 and 83E2 are arranged and the direction in which the shielding member 81E is moved can be set as appropriate. In the present embodiment, it is sufficient that at least one of the plurality of openings is selectable, and the shielding member is manually used by using a slide mechanism or the like without using the opening selection means. The opening may be selected by moving the.

  Each of the openings 83E1 and 83E2 has a triangular shape. The sides 83b1 and 83c1 of the outline of the opening 83E1 and the sides 83b2 and 83c2 of the outline of the opening 83E2 are directed toward the apex from the base 83a1 and the base 83a2 toward the apex in the AR1 direction. Tilt to approach. As a result, the length d11 of the opening 83E1 and the length d12 of the opening 83E2 extending in the direction perpendicular to the direction corresponding to the one axis direction (AR1 direction) are respectively constant change rates along the AR1 direction. Gradually changes.

  Here, the openings 83E1 and 83E2 have different distances La and Lb from the bases 83a1 and 83a2 that are part of the contour line to the apex. As a result, the openings 83E1 and 83E2 have different inclinations of the sides 83b1 and 83c1, and the sides 83b2 and 83c1. For this reason, the rate of change of the length d11 of the opening 83E1 and the length d12 of the opening 83E2 are different.

  When detecting a detection target, the range in which the dark line shifts (the amount of movement by which the dark line moves in the AR1 direction) varies greatly depending on the use environment. If the shift range of the dark line exceeds the size of the opening (the distance from the base to the apex), the shift amount of the dark line can no longer be measured. For this reason, it is desirable to select the shape of the opening so that the dark line shift range is within the size of the opening. On the other hand, in an environment where the dark line shift range is small, the ratio of the dark line region in the opening changes rapidly according to the dark line shift so that the shift amount can be determined with high accuracy within the dark line shift range. Thus, it is desirable to select the shape of the opening.

  In the surface plasmon detection device according to the present embodiment, the single shielding member 81E is slid according to the shift amount of the dark line that differs based on the use environment, and a plurality of openings 83E1 having different shapes as appropriate. , 83E2 can be selectively arranged to improve detection accuracy in each use environment.

  For example, in a work site such as a painting process or a cleaning process in which a large amount of VOC gas is generated, the concentration of the generated gas is high, so that a measurable concentration range is required to be wider than the detection sensitivity (measurement resolution). The In this case, the opening 83E1 is selected to detect the amount of reflected light. On the other hand, detection sensitivity is required for measurement in an environment where a small amount of gas is generated from wall materials or furniture. In this case, the opening 83E2 is selected to detect the amount of reflected light.

(Modification 4)
FIG. 15 is a plan view showing an example of the dark line when the surface plasmon detection device according to the present modification is used, and shows an example of the dark line when the first shielding member is selected and when the second shielding member is selected. FIG. FIG. 15A is a plan view illustrating an example of a dark line when the first shielding member is selected. FIG. 15B is a plan view showing an example of a dark line when the second shielding member is selected. With reference to FIG. 15 (A) and FIG. 15 (B), the surface plasmon detection apparatus which concerns on this modification is demonstrated.

  As shown in FIGS. 15A and 15B, the surface plasmon detection device according to the present modification has a plurality of shields having different opening shapes when compared with the surface plasmon detection device according to the fourth embodiment. The difference is that the openings 83F1 and 83F2 corresponding to the light receiving unit 3 can be selectively arranged by exchanging the members 81F1 and 81F2. Other configurations are substantially the same.

  On the left side in FIGS. 15A and 15B, a plurality of shielding members 81F1 and 81F2 that can be arranged in the light receiving unit 3 are shown. Of these, the shielding members arranged in the light receiving unit 3 are indicated by two-dot chain lines. Show. On the right side in FIG. 15A and FIG. 15B, the shielding member selected and disposed in the light receiving unit 3 is shown.

  When the shielding member is selectively disposed in the light receiving unit 3, the shielding member selected in advance from the shielding member storage unit that stores the plurality of shielding members 81F1 and 81F2 in the apparatus is provided to the light receiving unit 3 by the shielding member selection unit. Deploy. In the present embodiment, it is sufficient that at least one of the plurality of shielding members is selectable, and the light shielding member is manually selected without using the light shielding member selection unit. Also good.

  In this modification, as a plurality of shielding members, the shielding member 81F1 whose rate of change of the length d11 of the opening 83F1 is not constant along the AR1 direction, and the length of the opening 83F2 at a constant rate of change along the AR1 direction. A shielding member 81F2 whose length d12 gradually changes is used.

  Specifically, the opening 83F1 includes a side 83a1, a side 83b1, and a side 83c1. The side 83a1 extends in a direction orthogonal to the direction corresponding to the one axis direction (AR1 direction), and the side 83b1 extends in a direction opposite to the one axis direction. The side 83c1 connects the end of the side 83a1 and the end of the side 83b1 that are located opposite to the connection point of the side 83a1 and the side 83b1. The side 83c1 includes a plurality of side parts 83c11, 83c12, and 83c13 having different degrees of inclination. Thereby, in the shielding member 81F1, the rate of change of the length d11 of the opening 83F1 changes stepwise along the AR1 direction. For this reason, the sensitivity of the shielding member 83F1 changes from the initial position of the dark line.

  The opening 83F2 has a triangular shape in which the base 83a2 is parallel to the direction corresponding to the one axis direction and the vertical direction. For this reason, the length d12 of the opening 83F2 gradually changes at a constant change rate along the AR1 direction.

  In this modification, the change rate of the length d11 of the opening 83F1 is not constant along the AR1 direction, and the length d12 of the opening 83F2 is gradually changed at a constant change rate along the AR1 direction. Although the case where the shielding member 81F2 that changes to is used has been described as an example, the present invention is not limited to this. Although the length d12 of the opening changes at a constant rate of change in the AR1 direction, a plurality of shielding members having different rates of change of the length d12 of the opening may be used.

  By having such a configuration, in the surface plasmon detection device according to the present modification, even when the position of the dark line and the amount of movement change depending on the concentration and type of the gas to be detected, the shape of the opening is By preparing a plurality of different shielding members and selecting them appropriately, the sensitivity can be optimized according to the use environment.

(Embodiment 5)
FIG. 16 is a diagram illustrating an example of a dark line when the surface plasmon detection device according to the present embodiment is used. With reference to FIG. 16, the surface plasmon detection device according to the present embodiment will be described.

  As shown in FIG. 16, the surface plasmon detection device according to the present embodiment is different from the surface plasmon detection device according to the third embodiment in that a shielding member 81 is provided. Other configurations are almost the same.

  In the present embodiment, the light receiving region located on the left side of the diagonal line D1 is covered with the shielding member 81 in order to reliably use only the half surface of the light receiving region located on the left or right side of the diagonal line D1. With this configuration, the present embodiment can provide substantially the same effect as that of the third embodiment.

(Verification experiment)
FIG. 17 is a diagram showing the relationship between the concentration of the measurement object and the value detected by the detection unit when the concentration of the measurement object is measured in order to verify the effect of the present invention. With reference to FIG. 17, the relationship between the density | concentration of a measuring object and the detected value by a detection part is demonstrated.

  In this verification experiment, toluene was used as a measurement object. Using the surface plasmon detector 1 according to Embodiment 1, a value based on the amount of light detected when toluene having each concentration was measured was detected as a detection value. In FIG. 17, the detection value when measuring toluene having a concentration of 1 ppm is standardized as 1.

  When the surface plasmon detection device 1 according to Embodiment 1 is used, the greater the amount of dark line movement, the smaller the proportion of the dark line that occupies the light receiving area, and the greater the detected light amount. In this verification experiment, the same result was obtained, and the detected value increased as the concentration of toluene increased.

  From the above results, it can be said that it has been experimentally proved that the surface plasmon detection device according to the present embodiment is used to accurately measure the concentration and the like of the measurement object.

  Although the embodiments of the present invention have been described above, the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, and includes meanings equivalent to the terms of the claims and all modifications within the scope.

  DESCRIPTION OF SYMBOLS 1 Surface plasmon detection apparatus, 2 light projection part, 3 light-receiving part, 10 light source, 20 collimating lens, 30 polarizer, 40 reflection mirror, 50 condensing lens, 60 surface plasmon element, 61 prism, 61a bottom face, 62 transparent substrate, 62a, 62b principal surface, 63 first adhesion layer, 64 metal thin film, 64a, 64b principal surface, 65 second adhesion layer, 66 staying layer, 67 dielectric member, 70 collimating lens, 81, 81A, 81B, 81C, 81D , 81E, 81F1, 81F2 shielding member, 82 light receiving element, 83, 83A, 83B, 83C, 83D, 83E1, 83E2, 83F1, 83F2 opening.

Claims (9)

Incident light comprising a light beam having a distribution in incident angle due to a surface plasmon phenomenon at the interface between the dielectric member and the metal thin film, including a dielectric member having a main surface and a metal thin film formed on the main surface. A surface plasmon element that reflects as reflected light composed of a light beam having an angular dependence on the amount of light;
A light projecting unit that projects the incident light toward the surface plasmon element;
A light receiving portion that receives the reflected light reflected by the surface plasmon element,
The surface plasmon detection device, wherein the light receiving unit has a non-divided light receiving region configured to detect a different light amount according to a difference in light amount distribution caused by the angle dependency of the reflected light. The light projecting unit projects, as the incident light, light having an angular distribution in which an incident angle gradually changes with respect to one axial direction in an incident light beam cross section perpendicular to the optical axis of the incident light,
The light receiving unit receives, as the reflected light, light having the light amount distribution in a direction corresponding to the one axial direction in a reflected light beam cross section perpendicular to the optical axis of the reflected light,
In the first plane including the light receiving region and on which the reflected light is projected, the light receiving region has a length in a direction perpendicular to the direction corresponding to the one axis direction and a direction parallel to the direction corresponding to the one axis direction. The surface plasmon detection device according to claim 1, wherein the surface plasmon detection device is formed so as to gradually change along the surface. The reflected light beam cross section is a dark line formed so as to extend in a direction perpendicular to the direction corresponding to the one-axis direction when the reflected light has the light amount distribution so that the amount of light is smaller than other portions. Including
The surface plasmon detection device according to claim 2, wherein a contour line of the light receiving region has a portion that intersects non-parallel to the dark line projected on the first plane.   4. The surface plasmon detection device according to claim 2, wherein a length of the light receiving region extending in a direction perpendicular to the direction corresponding to the one axis direction gradually changes at a constant change rate. The light receiving unit includes a shielding member having an opening, and a light receiving element that detects the amount of the reflected light transmitted through the opening,
The surface plasmon detection device according to claim 1, wherein the light receiving region is defined by the opening. The shielding member is constituted by one or a plurality of shielding members,
When the shielding member is constituted by the single shielding member,
The single shielding member has a plurality of openings each having a different shape,
The light receiving portion is provided so that one opening defining the light receiving region can be selected from the plurality of openings.
When the shielding member is constituted by the plurality of shielding members,
The plurality of shielding members have the openings having different shapes,
The surface plasmon detection device according to claim 5, wherein the light receiving unit is provided so that one of the plurality of shielding members can be selected.   The surface plasmon detection according to any one of claims 1 to 6, wherein a measurement object is detected based on a relationship between a received light amount detected by the light receiving unit and a reference amount detected in advance by the light receiving unit. apparatus.   The surface plasmon detection device according to any one of claims 1 to 7, wherein the surface plasmon element includes a staying layer that causes gas to stay on the surface of the metal thin film. A surface plasmon element including a dielectric member having a main surface and a metal thin film formed on the main surface is irradiated with incident light composed of a light flux having a distribution in an incident angle from a light projecting unit, and the surface plasmon element The incident light that has entered is reflected as reflected light composed of a light flux having an angle dependence on the amount of light due to a surface plasmon phenomenon at the interface between the dielectric member and the metal thin film, and reflected by the surface plasmon element. A surface plasmon detection method for receiving reflected light at a light receiving unit,
A surface plasmon detection method using a non-divided light receiving region configured to detect a different light amount according to a difference in light amount distribution caused by the angle dependency of the reflected light as the light receiving unit.

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