Optical sensor including a hard resin and a soft resin and proximity sensor including the same

An optical sensor includes a light emitter to emit light, a light receiver to receive the light emitted from the light emitter, a first resin body that covers the light emitter and the light receiver to transmit the light emitted from the light emitter to emit the light outside, and a second resin body that seals the light emitter and the light receiver, in which the second resin body is included inside the first resin body, and the second resin body is harder than the first resin body.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical sensor and a proximity sensor including the optical sensor.

2. Description of the Related Art

In recent years, various sensors have been proposed which are mounted on a robot hand or the like and enable various types of sensing including tactile sense. Such sensors include, for example, a proximity sensor having a function of a tactile sensor as described in Japanese Unexamined Patent Application Publication No. 60-62496.

Japanese Unexamined Patent Application Publication No. 60-62496 discloses a composite sensor to be attached to a fingertip surface of a robot hand that performs an operation of gripping an object or the like. The composite sensor disclosed in Japanese Unexamined Patent Application Publication No. 60-62496 includes a light-transmissive flexible plate-shaped portion, a light receiving portion arranged on the flexible plate-shaped portion, a light emitting portion that irradiates the flexible plate-shaped portion from behind the light receiving portion, and an electric circuit that controls the light receiving portion and the light emitting portion. An elastic body covers the light receiving portion, and a light-shielding layer that transmits light from the light emitting portion in a limited manner is provided on the back surface side of the flexible plate-shaped portion on which the light receiving portion is arranged.

A function as a proximity sensor and a function as a contact sensor can be obtained by detecting an amount of reflected light, which is emitted from the light emitting portion, passes through a slit and the elastic body, hits an object, and returns, with the light receiving portion arranged on the front surface of the plate-shaped portion in which the slit is formed on the back surface.

However, in the related art, since an elastic body which is easily deformed is provided on the light receiving portion, when an external force is applied to the sensor, distortion directly influenced the light receiving portion, and there is a problem in that durability is reduced.

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention provide optical sensors and proximity sensors each with improved durability.

An optical sensor according to a preferred embodiment of the present invention includes a light emitter to emit light, a light receiver to receive the light emitted from the light emitter, a first resin body that covers the light emitter and the light receiver to transmit the light emitted from the light emitter and emit the light outside, and a second resin body that seals the light emitter and the light receiver, wherein the second resin body is included inside the first resin body, and the second resin body is harder than the first resin body.

A proximity sensor according to a preferred embodiment of the present invention includes an optical sensor including a light emitter to emit light, a light receiver to receive the light emitted from the light emitter, a first resin body that covers the light emitter and the light receiver to transmit the light emitted from the light emitter and emit the light outside, and a second resin body that seals the light emitter and the light receiver, wherein the second resin body is included inside the first resin body, and the second resin body is harder than the first resin body, and a controller to detect proximity and contact of an object based on a signal of the light receiver.

According to preferred embodiments of the present invention, optical sensors and proximity sensors with improved durability are able to be provided.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, optical sensors and proximity sensors according to preferred embodiments of the present invention will be described with reference to the accompanying drawings.

Each of the preferred embodiments is an example, and partial replacement or combination of configurations illustrated in different preferred embodiments is possible. In a modification, description of matters common to Preferred Embodiment 1 will be omitted, and only different points will be described. In particular, the same operation and advantageous effects of the same or corresponding configuration will not be described in each preferred embodiment.

In Preferred Embodiment 1 of the present invention, detection of proximity of an object by a simple optical mechanism including an optical sensor will be described as an example of a proximity sensor according to a preferred embodiment of the present invention.

A configuration of the proximity sensor according to Preferred Embodiment 1 will be described with reference toFIGS.1to2B.FIG.1is a diagram for illustrating an overview of a proximity sensor1according to Preferred Embodiment 1.FIG.2Ais a top view illustrating an optical sensor3.FIG.2Bis a longitudinal sectional view of the optical sensor3.

As illustrated inFIG.1, the proximity sensor1according to Preferred Embodiment 1 includes the optical sensor3, a driver15, an amplifier circuit17, and a controller19. The proximity sensor1can be applied to, for example, a robot hand in which various objects to be gripped are objects to be sensed.

The optical sensor3includes a light emitter5, a light receiver7, a substrate9, a first resin body11, and a second resin body13. The first resin body11is an example of a cover to cover the light emitter5and the light receiver7. Hereinafter, in the optical sensor3, a direction in which the first resin body11protrudes is referred to as a “Z direction”, and two directions that are orthogonal or substantially orthogonal to the Z direction and are orthogonal or substantially orthogonal to each other are referred to as an “X direction” and a “Y direction”. Note that a positive direction of Z is an upward direction, and a negative direction of Z is a downward direction.

The optical sensor3according to Preferred Embodiment 1 causes the light emitter5to emit light inside the second resin body13, detects, by the light receiver7, the light that passes through the second resin body13and the first resin body11and is reflected by an object, and outputs a light receiving signal P1corresponding to an amount of the received light from the light receiver7.

The light emitter5is, for example, a solid-state light emitter such as a Vertical Cavity surface emitting laser (VCSEL) or an LED. When a surface emitting laser is used as the light emitter5, a laser with a narrow emission angle can be emitted. As a result, it is possible to reduce direct incidence of light emitted from the light emitter5on the light receiver7without being reflected by an object. As a result, the offset of the light receiver7can be reduced, and the S/N can be improved. Note that in a case where an LED is used as the light emitter5, light irradiated from the LED may have directivity by providing the LED with a reflector. The light emitter5may be, for example, a solid-state light emitter other than a surface emitting laser and an LED. In addition, the optical sensor3may include a collimating lens that collimates the light from the light emitter5.

The light emitter5emits, for example, light having a wavelength in a near-infrared region. In Preferred Embodiment 1, a peak wavelength of the light emitted from the light emitter5is in a range, for example, between about 700 nm and about 1000 nm, and is about 850 nm, for example, in Preferred Embodiment 1. Light having the peak wavelength within this range can be received by a light receiver made of, for example, an Si-based material.

The light receiver7detects an amount of reflected light obtained by reflecting the light emitted from the light emitter5on an object Bt (seeFIG.4). The light receiver7that detects the reflected light includes, for example, a light receiver including a photodiode (PD). The light receiver7includes at least one light receiver. InFIG.1, the light receiver7includes four light receivers7ato7d. The light receiver7receives light and generates the light receiving signal P1indicating a light receiving result. The generated light receiving signal P1is transmitted to the amplifier circuit17. The light receiver7may include various light receivers, not limited to a photodiode, for example, a position detection element (PSD) or a CMOS image sensor (CIS).

The substrate9is, for example, a resin substrate. The substrate9supports the light emitter5and the light receivers7ato7dof the light receiver7, which are disposed on the same or substantially the same plane. For example, the light emitter5is disposed at the center or approximate center of the disk-shaped substrate9. The four light receivers7ato7dof the light receiver7surround the light emitter5with the light emitter5as a center, and the light receivers7aand7dand the light receivers7band7care arranged diagonally with two of the four light receivers as a pair. Further, the substrate9supports the second resin body13that seals the light emitter5and the light receiver7, and the first resin body11that covers a side portion and an upper portion of the second resin body13. Since the light emitter5and the light receivers7ato7dare located on the same or substantially the same plane, the optical sensor3can be reduced in size and height.

The first resin body11seals the second resin body13including the light emitter5and the light receiver7. The first resin body11has, for example, a rotating body shape and, for example, a truncated cone shape. The first resin body11having the truncated cone shape is arranged such that a central axis thereof coincides with a central axis of the second resin body13having a cylindrical shape, and is provided on the substrate9while including the second resin body13inside the first resin body11. The first resin body11is an elastic body that deforms in response to an external force, such as external stress. The first resin body11is made of, for example, a silicone-based or epoxy-based resin. A diameter of a lower surface of the first resin body11is, for example, about 0.5 mm to about 50 mm. A diameter of an upper surface of the first resin body11is equal to or smaller than the diameter of the lower surface. A thickness Th1of the first resin body11is a thickness from an upper surface of the substrate9to an outer surface of the first resin body11in a central axis direction of the light emitted from the light emitter5. The thickness Th1of the first resin body11is, for example, about 5 mm.

The second resin body13seals the light emitter5and the light receiver7on the substrate9. A side surface and an upper surface of the second resin body13are covered with the first resin body11. The second resin body13has, for example, a rotating body shape and, for example, a cylindrical shape. The light emitter5is positioned at the center or approximate center of the second resin body13having a cylindrical shape. The second resin body13includes the light receivers7ato7dsurrounding the light emitter5and is provided on the substrate9. The second resin body13is made of, for example, a silicone-based resin including a wavelength filter that cuts light emitted from the light emitter5in a wavelength region on a lower wavelength side than the peak wavelength. Examples of such silicone-based resins include, for example, modified silicones having organic substituents other than methyl groups and phenyl groups as a substituent, and more specifically, include AIR-7051A/B manufactured by Shin-Etsu Silicone Co., Ltd. A diameter of the second resin body13is smaller than the diameter of the lower surface of the first resin body11. A thickness Th2of the second resin body13is thicker than thicknesses of the light emitter5and the light receivers7ato7d. In addition to the shape described above, the shape of the second resin body13may be a rectangular or substantially rectangular parallelepiped, a truncated cone, or a hemispherical shape, for example.

FIG.3is a graph showing an example of the light transmittance of the second resin body13. With the second resin body13, the transmittance of light in the wavelength region of, for example, about 680 nm from the near ultraviolet region is substantially 0, and it is possible to significantly reduce incidence of ambient light mainly in the visible wavelength region from about 380 nm to about 780 nm on the light receiver7. In such a wavelength filter, for example, the transmittance of light on the short wavelength side from the peak wavelength is equal to or less than about 10% with respect to the transmittance in the peak wavelength of light emitted from the light emitter5.

As shown inFIG.3, the second resin body13also attenuates the transmittance in the peak wavelength of the light emitted from the light emitter5by about ten and several percent. When the thickness Th2of the second resin body13is small, in an optical path in which light emitted from the light emitter5is reflected by the object Bt and enters the light receiver7, it is possible to reduce or prevent attenuation of light in the second resin body13and to increase light receiving sensitivity. For example, the thickness Th2of the second resin body13is smaller than a thickness Th3that is the difference between the thickness Th1of the first resin body11and the thickness Th2of the second resin body13. Note that in a case where the thickness Th3is small, since absorption of light emitted from the light emitter5and reflected by the object Bt is reduced, it is useful for improving accuracy of the proximity sensor. In addition, in a case where the thickness Th3is large, since the range in which the first resin body11can be deformed due to pushing after the object Bt comes into contact with the first resin body11is large, the detection range of an amount of pushing of the object Bt can be widened. Therefore, it is useful for improving the function as a contact sensor. Here, the thickness Th2is a thickness from the upper surface of the substrate9to an outer surface of the second resin body13in the central axis direction of the light emitted from the light emitter5. In other words, the thickness Th2can be regarded as the shortest distance of light emitted by the light emitter5from the upper surface of the substrate9to an interface between the first resin body11and the second resin body13. In a case where the second resin body13has, for example, a cylindrical shape or a truncated cone shape, the thickness TH2is a length of a rotation center axis of the second resin body13. In a case where the second resin body13has a hemispherical shape, for example, the thickness Th2is a length of radius.

The second resin body13is harder than the first resin body11. A hardness of the first resin body11is, for example, from about Shore A20 to about Shore A80, and for example, from about Shore A30 to about Shore A50. A hardness of the second resin body13is, for example, from about Shore D40 to about Shore D90, and for example, from about Shore D60 to about Shore D80. As described above, the light emitter5and the light receiver7are sealed with the second resin body13having a high hardness, and the periphery thereof is sealed with the first resin body11that is softer than the second resin body13. Accordingly, even when external forces are applied to the optical sensor3and the first resin body11is deformed, the second resin body13is not easily deformed, therefore, it is possible to reduce direct strain applied to the light emitter5and the light receivers7ato7d, and to improve durability and reliability.

A glass-transition temperature Tg2of the second resin body13may be higher than a glass-transition temperature Tg1of the first resin body11. For example, the glass-transition temperature Tg2of the second resin body13is equal to or higher than about 50° C. In this case, even when the optical sensor3is used in a high-temperature environment, deformation of the second resin body13can be prevented and the load of the object Bt can be detected.

When the first resin body11and the second resin body13are made of the same base material, the close contact property between the first resin body11and the second resin body can be improved. Accordingly, even when an environmental load, a repeated load from the object Bt over a long period of time, or an excessive load is applied, it is possible to reduce or prevent the occurrence of peeling at the resin interface between the first resin body11and the second resin body13and to provide a sensor having excellent durability and reliability.

Both the first resin body11and the second resin body can be made of, for example, a silicone-based material. Furthermore, the first resin body11is made of, for example, methylsilicone in which all substituents are made of methyl groups, or phenylsilicone in which substituents are made of methyl groups and phenyl groups. The second resin body13is made of, for example, modified silicone including an organic substituent other than a methyl group or a phenyl group as a substituent. As such, with the first resin body11and the second resin body13, it is possible to provide the second resin body13that is harder than the first resin body11using the same base material. Note that, for example, an epoxy resin having a different hardness may be used in addition to the silicone resin.

The driver15drives the light emitter5by supplying power to the light emitter5in accordance with a timing signal from the controller19. Thus, the light emitter5can emit light at a predetermined cycle.

The amplifier circuit17amplifies the light receiving signal P1detected by the light receivers7ato7dof the light receiver7and transmits the amplified signals to the controller19.

The controller19analyzes the light receiving signal P1from the light receiver7and detects the proximity and load of the object Bt. Further, the controller19controls a light emission cycle of the light emitter5and a light detection cycle of the light receiver7. The controller19includes, for example, a CPU, a microprocessor, or an FPGA. Note that the optical sensor3may be provided as a module separate from the driver15, the amplifier circuit17, and the controller19.

Next, the operation of the proximity sensor1will be described below.FIG.4illustrates a state in which the object Bt is close to the optical sensor3. The optical sensor3according to Preferred Embodiment 1 performs proximity sensing in which a state of the object Bt spaced apart in the vicinity of the first resin body11is sensed from the light receiving signal P1.

In the optical sensor3, as illustrated inFIG.4, the light emitter5emits light L1inside the second resin body13. The light L1emitted from the light emitter5passes through the second resin body13and the first resin body11and is reflected by the object Bt, so that reflected light L2is generated. The reflected light L2passes again through the first resin body11and the second resin body13and enters the light receiver7.

In a case where the object Bt and the optical sensor3are not yet in contact with each other and there is a distance between the object Bt and the optical sensor3, the reflected light L2is diffused toward the light receiver7. The light receivers7ato7dare designed so that a diameter Ls of a spot size of the reflected light L2is larger than an arrangement diameter Ld between the light receivers7band7cor between the light receivers7aand7dfacing each other of the light receiver7. Accordingly, in a case where the object Bt is not in contact with the first resin body11of the optical sensor3, the light receiving signal P1indicating the light receiving result corresponding to the state in which the first resin body11is not deformed is generated.

FIG.5illustrates a state in which the object Bt comes into contact with the optical sensor3and further presses the optical sensor3downward. In the example ofFIG.5, the first resin body11of the optical sensor3is deformed so as to expand laterally (in an XY plane direction) in accordance with the contact force applied by contact with the object Bt. The optical sensor3performs tactile sensing for sensing various contact forces in addition to the above-described proximity sensing by outputting, as the light receiving signal P1, light receiving results that change in accordance with such deformation.

FIG.6is a graph showing the amount of light received by the light receiver7in the process of proximity and contact of the object Bt. The graph shows a change in the output value of the optical sensor3in a case where the object Bt is brought close to the optical sensor3from a position spaced apart from the upper surface of the optical sensor3by about 13 mm and is further pushed in even after coming into contact with the upper surface of the first resin body11of the optical sensor3. InFIG.6, a circle indicates a change in the amount of light received by the light receiver7under a condition in which illuminance of disturbance light applied to the optical sensor3is about 150 lux. In addition, a cross mark indicates a change in the amount of light received by the light receiver7under a condition in which the illuminance of the disturbance light is about 3000 lux. As an example of increasing the influence of disturbance light, about 3000 lux is obtained as a result of actively irradiating the optical sensor3with indoor illumination, such as fluorescent light, for example.

InFIG.6, a section La indicates a section until the object Bt comes into contact with the upper surface of the first resin body11of the optical sensor3from above the optical sensor3in the process of approaching the optical sensor3. The diameter Ls of the spot size of the reflected light L2in the section La is larger than the arrangement diameter Ld of the light receivers7ato7d. In the section La, the closer the object Bt is to the optical sensor3, the smaller the diameter Ls is, so that the amount of light received by the light receivers7ato7dincreases. The controller19can estimate a distance from the optical sensor3to the object Bt from such a change in the amount of light.

In Preferred Embodiment 1, as indicated by a position Lb, the light receivers7ato7dare designed such that the arrangement diameter Ld of the light receivers7ato7dis equal or substantially equal to the diameter Ls of the spot size of the reflected light L2when the object Bt just contacts the upper surface of the first resin body11. Thus, when the object Bt just contacts the optical sensor3, the amount of received light detected by the light receiver7is maximized. Therefore, contact between the object Bt and the optical sensor3can be detected by detecting an inflection point of the change in the amount of light.

Section Lc indicates a section from when the object Bt comes into contact with the upper surface of the first resin body11to when the object Bt further presses the first resin body11downward. After the object Bt comes into contact with the upper surface of the first resin body11, as the object Bt presses down the first resin body11, the diameter Ls of the spot size of the reflected light L2becomes smaller than the arrangement diameter Ld of the light receivers7ato7d, so that the amount of light to be detected decreases.

As described above, the light receiving result of the reflected light L2changes according to the state in which the first resin body11is deformed by the contact force of the object Bt. Therefore, it is possible to perform tactile sensing by the light receiving signal P1from the light receiver7. For example, various contact forces can be detected by analyzing the light receiving signal P1. A known technique can be appropriately applied as an analysis method, for example. In addition, since the results of the case where the illuminance of the disturbance light is about 150 lux and the case where the illuminance of the disturbance light is about 3000 lux are the same or substantially the same, it is indicated that the optical sensor3according to Preferred Embodiment 1 is a sensor that is hardly affected by the disturbance light.

FIG.7is a graph showing the sum of outputs of the light receiver7in the process of proximity and contact of the object Bt in a case where the reflecting surface of the object Bt is a mirror surface. The absolute value of the amount of reflected light can be increased by providing, for example, a mirror surface portion on the reflecting surface of the object Bt. A graph Ps1indicating the sum of outputs of the four light receivers7ato7dgradually increases in the section La in which the object Bt approaches the upper surface of the first resin body11, has an inflection point at the position Lb at which the object Bt just contacts the upper surface of the first resin body11, and gradually decreases in the section Lc in which the object Bt presses down the upper surface of the first resin body11.

In addition, a graph Fs1indicating the load applied to the first resin body11is calculated by the controller19by analyzing the decrease in the amount of light in the section Lc. The graph Fs1indicating the load increases in the section Lc.

FIG.8is a graph showing the sum of outputs of the light receiver7in the process of proximity and contact of the object Bt in a case where the reflecting surface of the object Bt is a scattering body. In the case where the reflecting surface of the object Bt is a scattering body, the absolute value of the amount of reflected light is small as compared with the case where the reflecting surface is a mirror surface.

In the section La in which the object Bt approaches the optical sensor3, the reflected light L2passes through respective media of the object Bt→the air→the first resin body11. As at the position Lb and in the section Lc, when the object Bt comes into contact with the optical sensor3, the reflection light L2passes through the object Bt→the first resin body11. In this way, since there is no air layer in the optical path at the position Lb and in the section Lc, the reflection condition changes greatly, and in the case where the reflecting surface of the object Bt is a scattering body, the influence is particularly large.

In addition, in the section Lc in which the object Bt pushes the first resin body11, in the case where the reflecting surface of the object Bt is a scattering body, the spot size of the reflected light is less likely to decrease even when the object Bt approaches the light receiver7, and thus the amount of reflected light increases as the object Bt approaches the light receiver7.

As described above, the optical sensor3according to Preferred Embodiment 1 includes the light emitter5that emits light, the light receivers7ato7dthat receive the light emitted from the light emitter5, the first resin body11that covers the light emitter5and the light receivers7ato7dand transmits the light emitted from the light emitter5to emit the light outside, and the second resin body13that seals the light emitter5and the light receivers7ato7d. The second resin body13is included inside the first resin body11, and the second resin body13is harder than the first resin body11. According to this configuration, the second resin body13that directly seals the light emitter5and the light receivers7ato7dhas a high hardness, and the first resin body11that is flexible covers the periphery of the second resin body13. As a result, it is possible to reduce the direct influence of distortion caused by external forces on the light emitter5and the light receivers7ato7d, to improve the overload resistance, and to improve the durability.

In addition, the main materials of first resin body11and the second resin body13are the same-based resin. Since the first resin body11and the second resin body13are made of the same-based resin, the close contact property between the resins is strong, and the resins are hardly peeled off by, for example, strong external force, repeated external force, and environmental load, so that reliability during long-term operation can be improved.

Further, the glass-transition temperature Tg2of the second resin body13is higher than the glass-transition temperature Tg1of the first resin body11. Thus, since the glass-transition temperature Tg2of the second resin body13that directly seals the light emitter5and the light receivers7ato7dis high and the periphery thereof is covered with the flexible first resin body11, the load can be detected in a wide temperature range.

Other Preferred Embodiments

The present invention is not limited to the above-described preferred embodiments and can be modified as follows.

(1) In the above-described preferred embodiments, the optical sensor3includes the second resin body13having a wavelength filtering function, but is not limited thereto. As illustrated inFIG.9, for example, an optical sensor3A may be provided with a band pass filter23having a wavelength filtering function on the light receiving surfaces of the light receivers7ato7dof the light receiver7. The band pass filter23is, for example, a thin film formed by vapor deposition. The thin film is, for example, SiO2or SiN. In the case where the band pass filter23is a thin film, since the band pass filter23can be formed with an accuracy of about ±60 nm with respect to the peak wavelength of the light emitters5, noise resistance to ambient light can be further improved.

(2) In the above-described preferred embodiments, the second resin body13has the wavelength filter performance, but is not limited thereto. Instead of the second resin body13, the first resin body11may have wavelength filter performance.

(3) Although an example in which one light emitter5is used as a light emitter has been described in the above-described preferred embodiments, the number of light emitters is not particularly limited to one, and a plurality of light emitters may be provided. Further, the position of the light emitter5is not limited to the center or approximate center, and can be appropriately set to various positions.

(4) In the example ofFIG.1, the light receivers7band7care positioned on both sides of the light emitter5in the X direction. In this manner, the position of the light receiver7is not limited to a position on a straight line on which the light emitter5is centered, and can be appropriately set to various positions. The light receiver7may be configured by arranging a plurality of light receivers around the light emitter5. In addition, instead of the plurality of light receivers, a plurality of the light emitters5defining and functioning as a light emitter may be caused to emit light from a plurality of positions in a time division manner, and sensing by the optical sensor3may be performed.

(5) In the above-described preferred embodiments, the shape of the first resin body11of the optical sensor3is not limited to a rotating body, and may be configured using various curved surfaces, such as a spherical surface, for example.

(6) In the above-described preferred embodiments, the side portion of the second resin body13is also covered with the first resin body11, but is not limited thereto. The side portion of the second resin body13may be exposed to the outside.