JP2017026425A - Optical sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To downsize an optical sensor.SOLUTION: An optical sensor 1 of the present invention is an optical sensor 1 detecting a matter in a fluid and comprising: a sensitive part 5 having a convex surface 53 on a front surface thereof, reacting with the matter in the fluid, and changing an index of refraction; a light-emitting element 3 disposed around the sensitive part 5, and irradiating the convex surface 53 of the sensitive part 5 with light; and a light-receiving element 4 disposed around the sensitive part 5 and receiving reflection light reflected by the convex surface 53 of the sensitive part 5, the matter being detected by a change in a light intensity of the reflection light in response to a change of the index of refraction of the sensitive part 5. As a result, the optical sensor 1 can be downsized.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical sensor.

  In recent years, a sensor device that easily and accurately measures a very small amount of sample has been demanded. As this sensor device, for example, an optical sensor device using surface plasmons generated on a metal surface has been developed. Here, the optical sensor device using the surface plasmon detects or detects a specific substance by utilizing the light-surface plasmon wave interaction generated on the surface of the metal thin film (sensitive portion) provided on the light transmissive medium. It is a sensor to measure. An optical sensor device using surface plasmon has been studied as a method for detecting low concentrations of gas, ions, antigens, DNA, and the like because of its high detection sensitivity (see, for example, Patent Document 1).

JP-A-11-344437

  In such an optical sensor device, light reflected by a metal thin film is received by a sensor array. At this time, in order to improve the resolution in the sensor array, it is necessary to increase the spot diameter of light incident on the sensor array. Therefore, it is necessary to increase the distance between the metal thin film and the sensor array, and the optical sensor device is likely to be enlarged. Therefore, there is a demand for downsizing the optical sensor device.

  The present invention has been devised in view of such circumstances, and an object thereof is to provide an optical sensor that can be miniaturized.

  The optical sensor of the present invention is an optical sensor that detects a substance in a fluid, and has a convex curved surface on the surface, and a sensitive part that changes a refractive index in response to the substance in the fluid; A light emitting element arranged around the sensitive part to irradiate the convex curved surface of the sensitive part, and a light receiving element arranged around the sensitive part to receive the reflected light from the convex curved surface of the sensitive part The substance is detected by a change in the light intensity of the reflected light according to a change in the refractive index of the sensitive part.

  According to the present invention, the sensitive part has a convex curved surface, and the spot diameter of the reflected light can be easily increased by reflecting light on the convex curved surface of the sensitive part. Therefore, the optical sensor can be reduced in size.

It is sectional drawing which showed the cross section along the up-down direction of the optical sensor concerning one Embodiment of this invention. It is sectional drawing which expanded and showed a part of cross section of the optical sensor shown in FIG. It is a figure explaining how to reflect light. FIG. 2 is a perspective view showing some constituent members of the optical sensor shown in FIG. 1. It is sectional drawing which showed the cross section along the plane direction of the optical sensor shown in FIG.

  Hereinafter, an optical sensor 1 according to an embodiment of the present invention will be described with reference to the drawings. In the optical sensor according to the embodiment of the present invention, any direction may be upward or downward, but in the following description, an orthogonal coordinate system (X, Y, Z) is defined for convenience. The positive side in the Z-axis direction is the upper side.

  FIG. 1 shows a cross section cut in the vertical direction (Z-axis direction) of an optical sensor 1 according to an embodiment of the present invention. In addition, the arrow of the broken line in FIG. 1 illustrates an optical path.

  As shown in FIG. 1, the optical sensor 1 according to the present embodiment is arranged on a translucent substrate 2, a light emitting element 3, a light receiving element 4, and a translucent substrate 2 and responds to a specific substance. Part 5. Then, the light emitted from the light emitting element 3 is incident on the sensitive part 5 through the translucent substrate 2, and the light reflected at the boundary between the sensitive part 5 and the translucent substrate 2 is received by the light receiving element 4. . By having such a configuration, the optical sensor 1 exposes the sensitive part 5 in a fluid such as air or liquid, and changes the intensity of light reflected by the sensitive part 5 by the light receiving element 4. By detecting, a specific substance in the fluid can be detected.

  The translucent substrate 2 supports the sensitive part 5. The translucent substrate 2 guides light emitted from the light emitting element 3 to the sensitive part 5 and guides light reflected by the sensitive part 5 to the light receiving element 4. The translucent substrate 2 is formed of a material such as glass, sapphire, acrylic resin, polycarbonate resin, cycloolefin polymer resin, or cycloolefin copolymer resin. The refractive index of the translucent substrate 2 is set to 1.4 or more and 1.6 or less, for example. The refractive index can be measured, for example, with an ellipsometer.

  The translucent substrate 2 according to the present embodiment has a rectangular parallelepiped outer shape. And the translucent board | substrate 2 concerning this embodiment has an upper surface, a lower surface, and a side surface. In the optical sensor 1 according to the present invention, the outer shape of the translucent substrate 2 is not limited to a rectangular parallelepiped shape, and may be a shape other than a rectangular parallelepiped.

  As shown in FIG. 1, the translucent substrate 2 has a concave curved surface that is recessed inside the translucent substrate 2 on the surface of the translucent substrate 2. Specifically, in the translucent substrate 2 according to the present embodiment, a cutout portion 21 is formed over the upper surface and side surfaces of the translucent substrate 2. And the shape of the notch surface (inner surface) of the notch part 21 is a concave curved surface.

  The translucent substrate 2 can be formed by, for example, molding or cutting glass or a resin material. Moreover, the notch 21 of the translucent substrate 2 can also be formed by, for example, mold molding or excavation.

The light emitting element 3 emits light incident on the sensitive part 5 through the translucent substrate 2. As the light emitting element 3, for example, a laser diode (LD), a light emitting diode (
An LED (Light Emitting Diode) or a surface emitting laser (VCSEL) can be used.

The light receiving element 4 receives light reflected at the interface between the sensitive portion 5 and the translucent substrate 2 and converts it into current. The optical sensor 1 detects a change in the intensity of reflected light from the sensitive portion 5 based on the current value generated by the light receiving element 4. The light emitting / receiving element 4 is an array element in which a plurality of light receiving portions are arranged. As the light receiving element 4, for example, a photodiode (PD: Photo Diode)
Etc. can be used.

In the present embodiment, the light emitting element 3 and the light receiving element 4 are installed on the lower surface of the translucent substrate 2. The light emitting element 3 and the light receiving element 4 are optically connected to the sensitive part 5.

  The sensitive part 5 is exposed in the fluid, and changes the refractive index of light by reacting to a specific substance in the fluid, thereby changing the intensity of the reflected light reflected by the sensitive part 5. is there. The sensitive part 5 is exposed to the atmosphere and has a function of changing the refractive index in response to a specific substance in the atmosphere.

  In FIG. 2, the translucent board | substrate 2 and the sensitive part 5 of the optical sensor 1 are expanded and shown.

  The optical sensor 1 according to the present invention uses the surface plasmon resonance phenomenon to change the intensity of reflected light at the sensitive portion 5. Therefore, the sensitive unit 5 according to the present invention includes a first thin film 51 disposed on the translucent substrate 2 and a second thin film 52 disposed on the upper surface of the first thin film 51, as shown in FIG. doing.

  The first thin film 51 is formed of a metal material so that surface plasmon waves can be easily excited on the surface. Specifically, for example, a metal material such as silver, gold, copper, zinc, aluminum, or potassium can be used for the first thin film 51. Note that the material of the first thin film 51 may be selected in consideration of the material of the second thin film 52 disposed on the first thin film 51 or the wavelength of light of the light emitting element 3.

  Moreover, the 1st thin film 51 may use the single layer of a metal material, and may be the laminated body which laminated | stacked the several layer which consists of metal materials. The thickness of the first thin film 51 is set to a thickness at which light incident on the first thin film 51 oozes by the tunnel effect so that the surface plasmon wave is excited on the upper surface of the first thin film 51. Specifically, the thickness of the first thin film 51 can be set to be, for example, not less than 0.5 nm and not more than 1 μm.

  The second thin film 52 has a function of changing the refractive index (dielectric constant) in response to a specific substance in the atmosphere. Specifically, when the second thin film 52 detects hydrogen gas or the like, for example, a film of magnesium, palladium, or the like can be used as the sensitive film. When ammonia gas or the like is detected, a film made of acrylic acid polymer or copper phthalocyanine can be used as the sensitive film. In addition, the antigen can be detected by using a membrane such as a monoclonal antibody, biotin or gale lectin.

  Since the sensitive portion 5 has the above-described configuration, when the light that has traveled through the translucent substrate 2 is reflected at the interface of the first thin film 51, surface plasmon waves are generated on the upper surface of the first thin film 51. Excited. Here, since the surface plasmon resonates with the light incident on the first thin film 51 at a specific incident angle, a part of the light energy is lost due to excitation of the surface plasmon wave, and the light incident at the specific incident angle. The reflectance at the first thin film 51 becomes extremely small. Since the incident angle of light when the surface plasmon wave is excited differs depending on the refractive index of the second thin film 52 located on the upper surface of the first thin film 51, the refractive index of the second thin film 52 changes, The reflectance of light at the first thin film 51 changes, and as a result, the intensity of the reflected light at the sensitive portion 5 changes. Therefore, the substance with which the second thin film 52 has reacted can be specified by detecting the change in the intensity of the reflected light.

  Note that the first thin film 51 and the second thin film 52 can be formed by, for example, a vapor deposition method or a sputtering method.

  The sensitive part 5 is arranged on the translucent substrate 2 as described above. Specifically, the sensitive portion 5 is disposed so as to cover the inner surface of the cutout portion 21 of the translucent substrate 2 as shown in FIG. That is, the sensitive part 5 has a convex curved surface 53 corresponding to the concave curved surface of the translucent substrate 2. Then, the light of the light emitting element 3 enters the convex curved surface 53 of the sensitive portion 5.

  Here, conventionally, when the light receiving element 4 receives the reflected light from the sensitive portion 5, it is necessary to increase the spot diameter of the reflected light when entering the light receiving element 4 in order to improve the resolution of the reflected light. It was. Therefore, it is necessary to ensure a large distance between the light receiving element 4 and the sensitive portion 5 in order to spread the reflected light. As a result, the optical sensor 1 may be increased in size.

  On the other hand, in the optical sensor 1 according to the present invention, the sensitive portion 5 has a convex curved surface 53, and the light of the light emitting element 3 is reflected by the convex curved surface 53. Therefore, as shown in FIG. 3, since the distribution of the incident angle of the light to the sensitive part 5 can be increased compared to the case where the light of the light emitting element 3 reflects the plane, the light reflected by the sensitive part 5 is reflected. The spot diameter of the reflected light can be increased. Therefore, since the distance between the sensitive portion 5 and the light receiving element 4 can be reduced, the optical sensor 1 can be reduced in size.

  FIG. 3 illustrates the influence of the shape of the reflecting surface when light is reflected. FIG. 3A shows a state when light is reflected by a flat surface, and FIG. 3B shows a state when light is reflected by a convex curved surface. Further, the solid line arrow in FIG. 3 indicates incident light, and the broken line arrow indicates reflected light.

  As shown in FIG. 4, the convex curved surface 53 of the sensitive portion 5 is curved in a convex shape when the convex curved surface 53 is viewed along the first direction A1, and the convex curved surface 53 is orthogonal to the first direction A1. When viewed along the second direction A2, it may be curved in a concave shape. As a result, with respect to the reflected light reflected by the convex curved surface 53 of the sensitive part 5, the component along the first direction A1 can be increased and the component along the second direction A2 can be increased among the spot diameter of the reflected light. Can be reduced. Therefore, since the spot diameter can be increased only in the necessary part of the reflected light, the increase in the spot diameter of the unnecessary part can be reduced, and the optical sensor 1 can be miniaturized.

  FIG. 4 shows a perspective view of the sensitive part 5. In FIG. 4, the description of the first thin film 51 and the second thin film 52 is omitted.

  The shape of the convex curved surface 53 will be described in detail below.

  As shown in FIGS. 1 and 2, the convex curved surface 53 moves the optical sensor 1 in the vertical direction (Z-axis direction) along one direction (X-axis direction in this description) from the upper surface of the translucent substrate 2. When the cross section when cut is viewed, it is curved in a convex shape. On the other hand, as shown in FIG. 5, a cross section when the optical sensor 1 is cut in a plane direction (XY axis direction) along one direction (X-axis direction in this description) from the side surface of the translucent substrate 2. When viewed, the convex curved surface 53 is curved in a concave shape.

  FIG. 5 shows a cross-sectional view of the optical sensor 1 taken along the plane direction (XY plane direction) along the X axis from the side surface of the translucent substrate 2.

  Further, the shape of the convex curved surface 53 will be described in detail below.

  As shown in FIG. 4, the convex curved surface 53 has a second direction when, for example, a first direction A1, a second direction A2, and a third direction A3 orthogonal to the first direction A1 and the second direction A2 are defined. A curved surface formed when a plurality of arcuate line segments having components in the first direction A1 and the third direction A3 are continuously arranged on one arcuate line segment having components in the A2 and third directions A3. It is the shape.

  In the optical sensor 1 according to the present embodiment, the shape of the convex curved surface 53 can be controlled by controlling the shape of the concave curved surface when the translucent substrate 2 is formed.

  Note that the present invention is not limited to the present embodiment, and various changes or improvements can be made without departing from the gist of the present invention.

  In the above-described embodiment, the example in which the optical sensor 1 has one light receiving element 4 has been described. However, the optical sensor 1 may have a plurality of light receiving elements 4. In this case, for example, the optical sensor 1 has a first light receiving element and a second light receiving element arranged next to the first light receiving element, and the convex curved surface is formed by the first light receiving element and the second light receiving element. The shape may be curved in a convex shape with respect to the arrangement direction. That is, it is sufficient that the convex curved surface is curved in a convex shape when viewed along the arrangement direction. As a result, the reflected light from the sensitive part can be incident on the first light receiving element and the second light receiving element, and the second light receiving element can be used for monitoring.

  In the above-described embodiment, the example in which the optical sensor 1 has the light-transmitting substrate 2 has been described. However, the optical sensor 1 may not have the light-transmitting substrate 2. The optical sensor has a housing, for example, and the sensitive part, the light emitting element, and the light receiving element may be accommodated in the housing.

  In this case, the sensitive part may be supported not by the translucent substrate but by being fixed to the inner wall surface of the housing.

  In the above-described embodiment, the example in which the light of the light emitting element 3 is emitted toward the sensitive unit 5 has been described. However, the light of the light emitting element 3 may not be emitted toward the sensitive unit 5. In this case, the optical line sensor may have a mirror, for example. As a result, the light from the light emitting element may be emitted toward the mirror and reflected by the mirror toward the sensitive portion. The mirror can be formed by attaching a metal material such as silver or copper, for example, by gold, for example, vapor deposition or sputtering.

  Moreover, although the above-mentioned embodiment demonstrated the example in which the whole surface of the sensitive part 5 into which light injects is a convex curved surface, the whole surface of the sensitive part into which light injects may not be a convex curved surface. In this case, it is only necessary that a part of the surface of the sensitive part on which light is incident has a convex curved surface.

  Moreover, although the above-mentioned embodiment demonstrated the example which used the notch surface of the notch part 21 of the translucent board | substrate 2 as the concave curved surface, the bottom face of the recessed part opened on the upper surface of the translucent board | substrate may be used as a concave curved surface. Good.

  The light emitting element 3 may be an array element having a plurality of light emitting portions.

DESCRIPTION OF SYMBOLS 1 ... Optical sensor 2 ... Translucent substrate 21 ... Notch part 3 ... Light emitting element 4 ... Light receiving element 5 ... Sensitive part 51 ... 1st thin film 52 ... Second thin film 53 ... convex curved surface A1 ... first direction A2 ... second direction A3 ... third direction

Claims (4)

An optical sensor for detecting a substance in a fluid,
A sensitive part that has a convex curved surface and changes the refractive index in response to a substance in the fluid;
A light emitting element disposed around the sensitive portion and irradiating the convex curved surface of the sensitive portion;
A light receiving element disposed around the sensitive part and receiving the reflected light from the convex curved surface of the sensitive part;
An optical sensor that detects the substance by a change in light intensity of reflected light according to a change in refractive index of the sensitive part. It further comprises a translucent substrate having a concave curved surface corresponding to the convex curved surface,
The optical sensor according to claim 1, wherein the sensitive portion is arranged on the light transmitting substrate such that the convex curved surface is aligned with the concave curved surface of the light transmitting substrate.   The convex curved surface is curved in a convex shape when the convex curved surface is viewed along the first direction, and is concave when the convex curved surface is viewed in a second direction orthogonal to the first direction. The optical sensor according to claim 1, wherein the optical sensor is curved. When the light receiving element is a first light receiving element,
A second light receiving element arranged next to the first light receiving element;
The optical sensor according to claim 1, wherein the convex curved surface has a shape curved in a convex shape with respect to an arrangement direction of the first light receiving element and the second light receiving element.

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