JP2019211312A - Reflection type optical sensor and reflection type encoder using the same - Google Patents

Abstract

To provide a reflection type optical sensor with which it is possible to reduce the distortion of reflected light and improve the accuracy of sensing reflected light by a light receiving element.SOLUTION: Provided is a reflection type optical sensor comprising a light source for emitting light to the sensing target face of an object present at a prescribed position; a light receiving element for sensing reflected light having been reflected by the sensing target face, and an incidence lens located between the sensing target face and the light receiving element, for guiding the reflected light entering from the surface to the light receiving element, the surface of the incidence lens being formed so that reflected light having been reflected at a plurality of positions on the sensing target face which are the same position when seen from a direction x and different positions when seen from a direction separate from the direction x, with the direction x defined as a direction that links the light source and the light receiving element, is guided to positions on the light receiving face of the light receiving element that are the same position when seen from the direction x and different positions when seen from a direction separate from the direction x. Also provided is a reflection type encoder using the reflection type optical sensor.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a reflective optical sensor and a reflective encoder using the same.

  2. Description of the Related Art Conventionally, a reflection type optical sensor used in, for example, an optical encoder or the like is known as disclosed in Patent Document 1. The reflection type optical sensor emits light from a light source to an object at a predetermined position, and the reflected light reflected by the object can be sensed by a light receiving element. A light reflection pattern is formed on the object. The light reflection pattern includes a reflective part that easily reflects light and a non-reflective part that hardly reflects light. In the reflection type optical sensor, the light receiving element senses the reflected light from the reflection portion, thereby reading the light reflection pattern and obtaining various information.

  By the way, in the reflection type optical sensor as described above, a spherical incident lens may be provided between the light receiving element and the object so that the reflected light from the object such as a scale can be efficiently guided to the light receiving element. Many. However, in the reflection type optical sensor provided with such a spherical incident lens, the reflected light from the object is refracted at various angles depending on the incident position when entering the incident lens. As the light source moves from the light source to the light receiving element, the optical path of the reflected light may shift laterally when viewing the light receiving element from the light source. For this reason, there is a problem that the reflected light from the reflecting portion reaches the light receiving element in a distorted manner, and the sensing accuracy of the reflected light by the light receiving element is lowered.

JP 2006-038572 A

  The present invention has been made in view of the above problems, and a reflective optical sensor that can reduce the distortion of reflected light and improve the sensing accuracy of reflected light by a light receiving element, and a reflective encoder using the same. The purpose is to provide.

  That is, the reflective optical sensor according to the present invention includes a light source that emits light to a sensing target surface of an object at a predetermined position, a light receiving element that senses reflected light reflected by the sensing target surface, and the sensing A reflective optical sensor, which is located between a target surface and the light receiving element, and includes an incident lens that guides the reflected light incident from the surface to the light receiving element, and has a direction connecting the light source and the light receiving element. As the x direction, reflected light reflected at a plurality of different positions when viewed from the x direction and different from the x direction on the sensing target surface is received by the light receiving element. The surface of the incident lens is formed so as to be guided to a different position when viewed from a direction different from the x direction, in the same position when viewed from the x direction. To.

  If the surface of the incident lens is formed in this way, for example, when a reflection region that easily reflects light extends straight along the x direction on the sensing target surface, the reflected light from the reflection region is changed in the lateral direction. Since it can be guided straight to the light receiving element along the x direction without being distorted, the accuracy of sensing reflected light by the light receiving element can be improved.

  As an aspect of the incident lens, the direction parallel to the optical path of the principal ray of the light emitted from the light source is defined as the z direction, and the radius of curvature of the surface of the incident lens viewed from the z direction is the x direction and the z direction. And those having a radius of curvature larger than the radius of curvature of the surface of the incident lens viewed from the y direction perpendicular to.

  As a more specific aspect of the incident lens, a surface shape of the incident lens in a cross section perpendicular to the x direction is formed so as to become flat from the light source side toward the light receiving element side. Can do.

  As an aspect of the reflection type photosensor, the substrate further includes a substrate on which the light source and the light receiving element are mounted, and a translucent member that is provided on the surface of the substrate and seals the light source and the light receiving element. The surface of the translucent member is formed with an exit surface that emits light emitted from the light source and an incident surface on which reflected light reflected by the sensing target surface is incident. The thing in which the lens is formed can be mentioned.

Further, the reflective encoder of the present invention has a light reflective pattern in which the above-described reflective optical sensor, the object, and a reflective region that easily reflects light and a non-reflective region that hardly reflects light are alternately arranged. An encoder scale formed on the sensing target surface, and the encoder scale alternately passes the reflective region and the non-reflective region through the surface including the optical path of the principal ray of the light emitted from the light source. The light source emits light to the encoder scale, and the light receiving element senses the reflected light reflected by the reflection region.
With such a reflective encoder, it is possible to obtain the same effects as the above-described reflective optical sensor.

In the reflection encoder, the light receiving element has a plurality of light receiving surfaces, and the plurality of light receiving surfaces are perpendicular to the optical path of the principal ray when viewed from the x direction. Or when the reflection type encoder includes a plurality of light receiving elements, and the plurality of light receiving elements are provided along a direction perpendicular to the optical path of the principal ray as viewed from the x direction. Appears prominently.
If it is such, even if it is a case where a light receiving element has a plurality of light receiving surfaces, or a case provided with a plurality of light receiving elements, each light receiving surface or each light receiving element does not distort the reflected light from the sensing target surface Therefore, the sensing accuracy is improved in any of the plurality of light receiving surfaces or the plurality of light receiving elements.

  According to the present invention thus configured, it is possible to provide a reflection type optical sensor and a reflection type encoder that can reduce the distortion of reflected light and improve the accuracy of sensing the reflected light by the light receiving element.

The side view which shows typically the structure of the reflection type encoder using the reflection type optical sensor of this embodiment. The perspective view which shows typically the structure of the reflection type encoder using the reflection type optical sensor of the embodiment. A-A 'line sectional view showing typically the composition of the reflection type photosensor of the embodiment. The top view which shows typically the structure of the reflection type optical sensor of the embodiment. The figure explaining the optical path of the light radiate | emitted from the light source in the reflection type optical sensor of the embodiment. The figure explaining the optical path of the light radiate | emitted from the light source in the reflection type optical sensor of the embodiment. B-B 'line sectional drawing, C-C' line sectional drawing, and D-D 'line sectional drawing which show typically the composition of the reflection type photosensor of the embodiment.

A reflective encoder according to an embodiment of the present invention will be described below with reference to the drawings.
Note that the size, positional relationship, optical path of light, and the like shown in each drawing may be exaggerated for clarity of explanation.

  The reflective encoder 100 according to this embodiment is an incremental rotary encoder that is attached to a motor and detects the rotation speed, rotation angle, rotation direction, and the like of the motor. As shown in FIG. 1, the reflective encoder 100 includes a disk-shaped scale 2 (corresponding to the “object” of the present invention) connected to a rotation shaft M of a motor (not shown) so as to be coaxially rotatable. A reflection type optical sensor 1 that emits light to the back surface 21 and senses reflected light from the back surface 21 is provided.

As shown in FIG. 2, a predetermined light reflection pattern is formed on the back surface 21 of the scale 2 that is a sensing target surface. This light reflection pattern is formed by alternately arranging reflective regions 211 that easily reflect light and non-reflective regions (specifically, slits) 212 that hardly reflect light along the circumferential direction. is there. The reflection type optical sensor 1 emits light to the light reflection pattern of the scale 2 that rotates together with the rotation axis M of the motor, and senses the reflected light reflected by the reflection region 211, so that the motor rotation speed, rotation angle, and rotation are detected. The direction and the like can be detected.
Hereinafter, the configuration of the reflective optical sensor 1 will be described in detail.

As shown in FIG. 3, the reflective optical sensor 1 includes a substrate 11, a light source 12 that emits light to the sensing target surface 21, a light receiving element 13 that senses reflected light reflected by the reflective region 211, and a light source. 12 and a translucent member 14 that seals the light receiving element 13. Here, both the light source 12 and the light receiving element 13 are mounted at different positions on the surface 111 of the substrate 11.
In the following, the direction parallel to the surface 111 and connecting the light source 12 and the light receiving element 13 is the x direction, the direction parallel to the surface 111 and perpendicular to the x direction is the y direction, The vertical direction is described as the z direction.

  The substrate 11 has a substantially rectangular plate shape when viewed from the z direction, and is made of a material such as paper phenol, glass composite, or glass epoxy. Here, the front surface 111 is configured to be parallel to the back surface 21 of the scale 2.

  Specifically, the light source 12 is a light emitting diode. One light source 12 is mounted on the surface 111 so that the optical path of the principal ray of the emitted light is parallel to the z direction. The principal ray of light emitted from the light source 12 here means a principal ray in light passing through the inside of the translucent member 14 among the light emitted from the light source 12.

  The light receiving element 13 utilizes the photovoltaic effect, and is specifically a photodiode. The light receiving element 13 has a light receiving surface that receives reflected light, and is configured to output a signal proportional to the amount of light received by the light receiving surface. The light receiving element 13 is mounted on the surface 111 so that the light receiving surface thereof is orthogonal to the z direction, and is configured to receive reflected light from the z direction.

The reflective optical sensor 1 of the present embodiment includes a plurality (specifically, two) of light receiving elements 13a and 13b, which are sequentially provided from the light source 12 side along the x direction. The light receiving element 13a located near the light source 12 in the x direction has a plurality of divided light receiving surfaces, and each of the plurality of light receiving surfaces outputs different signals (A phase and B). phase). The plurality of light receiving surfaces are provided side by side along the y direction.
The light receiving element 13b at a position far from the light source 12 in the x direction has a plurality of (specifically three) light receiving surfaces divided from each other, and outputs a signal every time the scale 2 rotates once. (Z phase).

  The translucent member 14 is provided on the surface 111 of the substrate 11 so as to cover the light source 12 and the light receiving element 13. The translucent member 14 is a resin molding made of a translucent resin material such as an epoxy resin so that light emitted from the light source 12 and reflected light reflected by the reflective region 211 can pass through the inside. It has become.

  As shown in FIGS. 3 and 4, the translucent member 14 is provided on the surface 111 of the substrate 11, and on the surface facing the sensing target surface 21, an emission surface that emits light emitted from the light source 12. 141 and an incident surface 143 on which the reflected light reflected by the reflection region 211 is incident. The exit surface 141 and the entrance surface 143 are both formed to be parallel to the x direction and the y direction, and are parallel to each other.

  One exit lens 142 is formed on the exit surface 141 so as to efficiently guide the light emitted from the light source 12 to the sensing target surface 21. The exit lens 142 is an axially symmetric lens formed so as to bulge toward the sensing target surface 21, and more specifically a spherical lens. The exit lens 142 is formed on the exit surface 141 so as to intersect the principal ray of the light emitted from the light source 12.

  On the incident surface 143, an incident lens 144 that guides the reflected light reflected by the reflection region 211 to the light receiving element 13 is formed. The incident lens 144 is formed so as to be positioned between the light receiving element 13 and the sensing target surface 21 so that the reflected light can be efficiently guided to the light receiving element 13. On the surface of the incident lens 144, a reflected light transmitting surface 145 that transmits the reflected light is formed. The reflected light transmitting surface 145 faces the sensing target surface 21 and is formed to bulge into a curved surface so as to face the light source 12 side.

  Note that a plurality (specifically, two) of incident lenses 144a and 144b are formed along the x direction on the incident surface 143 of the photosensor 1 of the present embodiment. The incident lenses 144a and 144b correspond to the plurality of light receiving elements 13a and 13b, respectively. The incident lens 144a guides reflected light to the light receiving element 13a, and the incident lens 144b guides reflected light to the light receiving element 13b. Yes. Here, the plurality of incident lenses 144a and 144b are formed to have the same shape.

Therefore, the incident lens 144 of the reflective optical sensor 1 of the present embodiment is the same position on the sensing target surface 21 when viewed from the x direction and different positions when viewed from a direction different from the x direction. The surface of the light receiving surface of the light receiving element 13 is formed so that the reflected light reflected by the light is guided to the same position when viewed from the x direction and to a different position when viewed from a direction different from the x direction. ing.
Hereinafter, the configuration of the incident lens 144 will be described with the incident lens 144a as a representative, but the description can be applied to the incident lens 144b.

With reference to FIG.5 and FIG.6, the optical path of the light radiate | emitted from the light source 12 is demonstrated. 5 and 6 show three light rays L ₁ that are reflected at the same position on the sensing target surface 21 when viewed from the x direction and at different positions when viewed from a direction different from the x direction (here, the y direction). The optical paths of L ₂ and L ₃ are schematically shown. Here, for ease of explanation, the light receiving element 13a is omitted. Even when the reflected light is different in the surface 111 of the substrate 11 when viewed from the y direction, the reflected light is also reflected from the y direction on the light receiving surface of the light receiving element 13 when guided to the same position as viewed from the x direction. Although they are different positions as viewed, it can be considered that they are guided to the same position as viewed from the x direction.

FIG. 5 is a view showing a cross section passing through the light source 12 and perpendicular to the y direction. As shown in FIG. 5, the light beams L ₁ , L ₂ , and L ₃ are reflected on the sensing target surface 21 by the reflection points H ₁ , H ₂ , and H ₃ , respectively, and on the surface of the incident lens 144 a, respectively. ₁ , P ₂ and P _{3 are} incident. The reflection points H ₁ , H ₂ , and H ₃ are arranged in this order from the light source 12 side to the light receiving element 13a side along the x direction.

FIG. 6 is a view showing a cross section perpendicular to the x direction, and is a view of the light receiving element 13a side from the light source 12 side. Here, a cross section through a cross-section through the surface _{S 1} of the input lens 144a that includes an incident point _{P 1,} the surface _{S 2} of the incident lens 144a that includes an incident point _{P 2,} the surface of the entrance lens 144a that includes an incident point _{P 3} It is shown superimposed a section through the S _3. Here, the exit lens 142 is omitted for ease of explanation.

As shown in FIG. 6, the reflection points H ₁ , H ₂ , and H ₃ are at the same position when viewed from the x direction. In the optical sensor 1 of the present embodiment, the light beams L ₁ , L ₂ , and L ₃ reflected at the reflection points H ₁ , H ₂ , and H ₃ are incident at different incident points from the incident points P ₁ , P ₂ , and P _3. The light is incident at an angle and is guided to the same position on the surface 111 of the substrate 11 as viewed from the x direction, although the position is different from the y direction.

Next, the structure of such an incident lens 144a will be described.
The incident lens 144a is an aspheric lens, and specifically, a toroidal lens in which the reflected light transmitting surface 145 forms a toroidal surface. To describe its shape more specifically, the reflected light transmitting surface 145a of the input lens 144a, as shown in FIGS. 3 and 4, forms a curved shape having a first radius of curvature R ₁ of a predetermined viewed from the z direction In addition, when viewed from the y direction, a curved shape having a predetermined second curvature radius R ₂ different from the first curvature radius R ₁ is formed. Here, the first curvature radius R ₁ is formed to be larger than the second curvature radius R ₂ .

  FIG. 7 is a diagram illustrating a cross section perpendicular to the x direction in the incident lens 144a, and is a diagram illustrating three cross sections having different positions in the x direction. As shown in FIG. 7, the incident lens 144a of the present embodiment is formed such that the surface shape in a cross section perpendicular to the x direction is accelerated and flattened from the light source 12 side toward the light receiving element 13a side. Yes. Here, “accelerically flattening” means that the degree to which the surface shape of the cross section becomes flat (or the rate of change) is larger than that in the case of a spherical lens. Further, the curvature of the surface of the incident lens 144a in the one cross section is not uniform. Specifically, it is formed so that the curvature decreases as it approaches the light receiving element 13a along the y direction. That is, it is formed so as to become flatter as it approaches the light receiving element 13a.

  The surface shape of the incident lens 144a in the cross section perpendicular to the x direction is formed so as to be flattened in an accelerated manner from the light source 12 side toward the light receiving element 13a side, and thus the light source in the incident lens 144a. The refraction angle of the reflected light incident from the side far from the light source 12 can be made smaller than the refraction angle of the reflected light incident from the side close to 12. Accordingly, the reflected light reflected at the sensing target surface 21 at the same position as viewed from the x direction and at a plurality of different positions when viewed from the different direction is reflected from the sensing target surface 21 on the light receiving element 13a side. The arrival position of the light on the substrate 11 can be brought closer to the arrival position on the substrate 11 of the reflected light reflected on the light source 12 side of the sensing target surface 21. Thereby, distortion of reflected light can be reduced.

  Further, as shown in FIGS. 3 and 4, the reflective optical sensor 1 of the present embodiment has a step 146 formed between the exit surface 141 and the entrance surface 143 on the surface of the translucent member 14. The exit surface 141 is lower than the entrance surface 143. That is, the distance along the z direction between the substrate 11 and the exit surface 141 is configured to be shorter than the distance along the z direction between the substrate 11 and the incident surface 143. The step portion 146 is formed to extend along the y direction. The length along the y direction of the stepped portion 146 is formed to be the same as the length along the y direction of the exit surface 141 and the entrance surface 143. That is, the exit surface 141 and the entrance surface 143 are separated from each other by the step portion 146.

The step portion 146 includes a surface formed between the emission surface 141 and the incident surface 143. More specifically, it is composed of an inclined surface in which the distance from the substrate 11 along the z direction increases from the light source 12 side toward the light receiving element 13 side along the x direction. Stepped portion 146 is formed so as to be positioned on the light-receiving element 13 than the boundary imaginary plane S _v of the exit surface 141. This imaginary plane S _v (more specifically, the light receiving element 13a located closer to the light source) and a light source 12 light-receiving element 13 is a virtual plane in which the equidistant. Here, the stepped portion 146, the boundary between the entrance surface 143 is formed so as to be positioned in the light receiving element 13a side of the imaginary plane S _v. That is, formed on the light receiving element 113 side from the incident surface 143 is a virtual plane S _v.

  According to the reflection type optical sensor 1 of the present embodiment configured as described above, the sensing target surface 21 has a plurality of positions that are the same as viewed from the x direction and that are different from the direction different from the x direction. The surface of the incident lens 144 so that the reflected light reflected at the position is guided to the same position as viewed from the x direction on the light receiving surface of the light receiving element 13 and different from the direction different from the x direction. Thus, the reflected light from the reflection region 211 of the sensing target surface 21 can be guided to the light receiving element 13 without being distorted in the y direction. Therefore, the accuracy of sensing reflected light by the light receiving element 13 can be improved.

  The present invention is not limited to the above embodiment.

  In the embodiment, the incident lens 144 has a toroidal surface, but is not limited to this. On the sensing target surface 21, reflected light reflected at a plurality of different positions when viewed from the x direction and different from the x direction is reflected on the light receiving surface of the light receiving element 13 from the x direction. As long as the surface is formed so as to be guided to a different position when viewed from a different direction from the x direction, it may be of any other shape. .

  In the said embodiment, although the step part 146 formed in the translucent member 14 was an inclined surface, it is not limited to this. In another embodiment, for example, it may be formed in a wall shape perpendicular to the surface of the substrate 11.

In the above embodiment, the stepped portion 146 had been formed on the light-receiving element 13 than the imaginary plane S _v, may be formed on the light source 12 side of the imaginary plane S _v is not limited to this, also it may be formed across a virtual plane S _v.

  In the above embodiment, the length of the step portion 146 is the same as the length of the exit surface 141 and the entrance surface 143 in the y direction, but is not limited thereto. In other embodiments, the length of the stepped portion 146 may be shorter than the length of the exit surface 141 and the entrance surface 143 in the y direction. Thereby, the exit surface 141 and the entrance surface 143 may be partially separated from each other. In this case, the stepped portion 146 is preferably formed on a virtual line connecting the light source 12 and the light receiving element 13a.

  In the embodiment, the reflective optical sensor 1 is provided with the scale 2 such that the radial direction thereof is along the x direction, but the present invention is not limited to this. In another embodiment, the scale 2 may be provided such that its circumferential direction is along the x direction.

  The reflection type optical sensor 1 of the above embodiment is applied to the rotary encoder 100, but is not limited thereto, and may be applied to a linear encoder in which the scale 2 is formed in a linear plate shape. Further, the present invention is not limited to the incremental type, and may be applied to an absolute type encoder. Further, the present invention is not limited to the one applied to the optical encoder, and may be applied to, for example, an optical sensor for a barcode reader, an original sensor for a copying machine, a proximity sensor, a human sensor, or the like.

  Although the reflective optical sensor 1 of the said embodiment has two incident lenses 144 and two light receiving elements 13, it is not limited to this. In another embodiment, one incident lens 144 and one light receiving element 13 may be provided. Further, the number of the incident lenses 144 and the number of the light receiving elements 13 are not the same and may be different.

  In the embodiment, the step portion 146 is formed so that the incident surface 143 is higher than the exit surface 141, but the present invention is not limited to this. In other embodiments, the step portion 146 may be formed such that the incident surface 143 is lower than the exit surface 141. Further, the step portion 146 may not be formed between the exit surface 141 and the entrance surface 143, and the exit surface 141 and the entrance surface 143 may be formed at the same height.

  The reflective optical sensor 1 of the embodiment has the exit lens 142, but is not limited thereto. In other embodiments, the exit lens 142 may not be provided, and only the entrance lens 144 may be provided.

  In addition, it goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 100 ... Reflective type encoder 1 ... Reflective type optical sensor 12 ... Light source 13 ... Light receiving element 144 ... Incident lens 2 ... Scale (object)
21 ・ ・ ・ Sensing target surface

Claims (7)

A light source that emits light to a sensing target surface of an object at a predetermined position;
A light receiving element for sensing reflected light reflected by the sensing target surface;
A reflection-type optical sensor that is located between the sensing target surface and the light-receiving element and includes an incident lens that guides the reflected light incident from the surface to the light-receiving element;
Assuming that the direction connecting the light source and the light receiving element is the x direction, the sensing target surface is at the same position when viewed from the x direction and at a plurality of different positions when viewed from a direction different from the x direction. The surface of the incident lens is such that the reflected light reflected is guided to the same position on the light receiving surface of the light receiving element as viewed from the x direction and different from the direction different from the x direction. A reflection type optical sensor in which is formed.   When the direction parallel to the optical path of the principal ray of the light emitted from the light source is the z direction, the radius of curvature of the surface of the incident lens viewed from the z direction is from the x direction and the y direction perpendicular to the z direction. The reflective optical sensor according to claim 1, wherein the reflective optical sensor is larger than a radius of curvature of the surface of the incident lens as viewed.   The reflective optical sensor according to claim 2, wherein a surface shape of the incident lens in a cross section perpendicular to the x direction is formed so as to be flattened from the light source side toward the light receiving element side. A substrate on which the light source and the light receiving element are mounted;
A light transmissive member provided on the surface of the substrate and sealing the light source and the light receiving element;
On the surface of the translucent member, an exit surface that emits light emitted from the light source and an incident surface on which reflected light reflected by the sensing target surface is incident are formed, and the incident lens is formed on the incident surface. The reflection type optical sensor according to claim 1, wherein: The reflection type optical sensor according to any one of claims 1 to 4,
A light reflection pattern in which the object is an object and a light reflection pattern in which light is easily reflected and a non-reflection region in which light is difficult to be reflected are alternately arranged on the sensing target surface; and
The encoder scale is linearly or rotationally moved so that the reflective region and the non-reflective region alternately pass through the surface including the optical path of the principal ray of the light emitted from the light source,
A reflective encoder, wherein the light source emits light to the encoder scale, and the light receiving element senses reflected light reflected by the reflective region. The light receiving element has a plurality of divided light receiving surfaces;
The reflective encoder according to claim 5, wherein the plurality of light receiving surfaces are provided along a direction perpendicular to the optical path of the principal ray as viewed from the x direction. A plurality of light receiving elements;
The reflective encoder according to claim 5, wherein the plurality of light receiving elements are provided along a direction perpendicular to the optical path of the principal ray as viewed from the x direction.