JPH10332432A - Optical encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical encoder wherein a square photo-detecting element can be used, and characteristics of photo-detecting elements are matched with each other. SOLUTION: The encoder comprises a light-emitting part 11 allocated on a fixed side, an annular rotation side slit disc 5 which, provided with a slit which allows transmission or shields the light transmitted from the light-emitting part 11 through optical guides 3 and 4, is allocated on a spindle, an annular fixing-side slit disc 6 which, allocated near the disc 5, comprises slits in plural stages in circumferential direction which correspond to the slit of disc 5, a condensing part 15 where the light transmitting the slit of disc 6 is sent through optical guides 7 and 8 while corresponded to the plural stages, and a photo- detecting part 10 which detects the light from the condensing part 15. Here, the condensing part 15 comprises plural concentric lenses, with foci of the lenses not on the same optical axis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical encoder for detecting a plurality of signals using an annular fixed slit, and in particular, condensing a plurality of detected optical signals on each square light receiving element having the same area. The present invention relates to an optical encoder having a condensing lens that can be used.

[0002]

2. Description of the Related Art As a conventional optical encoder, FIG.
As shown in FIG. That is, the rotating disk 51
A slit 51a is formed on the outer periphery of the rotating disk 51, a fixed slit 52 for forming a slit having the same shape is arranged below the slit 51a of the rotating disk 51, and a light receiving element 53 is arranged below the fixed slit 52. Rotating disk 51
The light of the lamp 54 is irradiated from the upper part of the slit 51a of
The change in illuminance of the light receiving element 53 is converted into an electric signal.

In such an optical encoder, since the detection area is a part of the rotating disk 51, there is a disadvantage that a high precision is required for forming the fixed slit 52. In addition, since the detection area is a part of the rotating disk 51, a sufficient amount of light cannot be obtained. Therefore, a lamp 54 having a large amount of light is required to obtain a sufficient amount of light.

An optical encoder using the entire circumference of a rotating disk as a detection area as shown in FIG. 10 has been considered next. FIG. 10A is an exploded perspective view of the optical encoder, and FIG. 10B is a longitudinal sectional view of the optical encoder. In FIG. 10, the light emitted from the point light source lamp 40 is
After passing through 1 and becoming a parallel ray, it is made to enter the central portion of the diffusion guide 42, is radially reflected by the 45 ° taper surface at the central portion, and is reflected again downward by the 45 ° taper surface at the outer peripheral portion. . This diffusion guide 4
The light guided from the light source 2 is directed to the light-collecting guide 45 by the slit of the rotating-side slit disk 43 and the light-collecting guide 45, which are formed by cutting out n slits at equal intervals on the outer periphery. The incidence is intercepted periodically. The intermittent light that passes through the slit and enters the condensing guide 45 is reflected to the inner periphery by the 45 ° tapered surface below the slit, and is reflected again downward by the 45 ° tapered surface at the center. The light guided from the light collecting guide 45 is
6 is intermittently irradiated, and the impedance of the light receiving element 46 is changed at a period of 1 / n times the rotation speed of the rotating shaft 44.

As described above, according to the conventional optical encoder shown in FIG. 10, since the rotation detection area is extended to the entire outer periphery of the disk, the slit formation errors are averaged, and the rotation detection caused by the slit formation errors is detected. The error is reduced, and the light from the light source is also collected from all the slits on the outer periphery of the disk.
The conventional optical encoder has a disadvantage that two or more signals cannot be detected.

Therefore, an optical encoder which solves such a problem that two or more signals can be detected is conventionally known.
Proposed. FIG. 8 shows such an optical encoder. According to FIG. 8, the rotary slit disk 5 fixed to the rotary shaft 1 by the hub 2 is provided with a radial rotary slit 51 (FIG. 3) having a pitch P whose entire circumference is equally divided by a predetermined number N, and is provided in an annular shape. The rotating-side entire-circumferential light reflecting portion 3 is opposed to one surface of the rotating-side slit disk 5 and has a rotating-side slit disk 5.
It is provided to be concentric with. The hub 2 has a rotation-side light reflection portion 4 formed of a conical surface having an angle of 45 degrees with respect to the rotation axis 1, and an angle of 45 degrees with respect to the rotation axis 1 facing the rotation-side light reflection portion 4. And a rotating-side full-circumferential light reflecting portion 3 which is a part of the conical surface. The rotation-side light reflection portion 4 and the rotation-side full-circumference light reflection portion 3 function as a light guide that guides light incident in the rotation-side central axis direction to the fixed-side full-circle direction. The constituent material of the hub 2 is made of a transparent resin, and the reflecting portion having an angle of 45 degrees is finished with mirror accuracy, so that light transmitted through the inside is totally reflected by the reflecting portion. . Further, the material of the fixed portion is made of the same transparent resin as the material of the hub 2, and the light transmitted through the fixed-side reflecting portion is reflected at this portion. Therefore, light emitted from the light emitting element 13 disposed in the light emitting unit 11 passes through the convex lens 14 and becomes parallel light L1.
Light enters the rotation-side light reflection unit 4. In the rotation side light reflection part 4,
As described above, the light is totally reflected, is reflected in a direction perpendicular to the rotation center axis and radially, and enters the rotation-side full-circular light reflection unit 3 as L2. Similarly, the rotation-side full-circumference light reflecting portion 3 is totally reflected in the right-angle direction to become L3. Rotation side all-around light reflection part 3
Has a 45 degree angle with respect to the rotation center axis,
The light beam L3 becomes parallel to the rotation center axis, and becomes an annular parallel light beam having the same diameter as the rotation side slit disk.

[0007] A disk-shaped fixed-side slit disk 6 is provided on the other surface of the rotary-side slit disk 5. The fixed slit disk 6 is provided with fixed slits having the same pitch P as the slits 51 of the rotary slit disk 5 shown in FIG. FIG. 4 shows the fixed-side slit disk 6.
The fixed slit 61B is provided at a position which is concentric with the fixed slit 61A and is shifted by P / 4 pitch and forms a fixed slit 61 having two tracks. The light passing through the A channel 61A and the B channel 61B of the fixed slit becomes two light beams, a light beam LA and a light beam LB, and is totally reflected at right angles by the fixed-side entire-circumference light reflecting portion 7, and is condensed at the center of the rotation axis. become.

The totally reflected light beams are totally reflected at right angles by the fixed-side light reflecting portion 8 arranged near the center of the rotation axis, and are converted into annular parallel light beams parallel to the rotation center axis to the light receiving portion 10 '. Light comes in. In this case, the light beam LA is applied to the photodiode 10A ', and the light beam LB is applied to the photodiode 10A'.
Light enters each of B ′. FIG. 9 shows an arrangement state of photodiodes 10A 'and 10B' which are light receiving elements 10 '. Since the light beam LA converges on the outer peripheral side, the photodiode 10A 'is also disposed on the outer peripheral side, and the light beam LB converges on the inner peripheral side, so that the photodiode 10B' is disposed on the inner peripheral side. Thus, in this optical encoder, the photodiode 10 on the outer peripheral side is used.
A plurality of signals can be detected by A 'and the inner side photodiode 10B'.

[0009]

However, in the case of an optical encoder having such a structure, it is necessary to arrange the light receiving elements concentrically as shown in FIG. In the case of a concentric arrangement in which the light receiving elements are constituted by photodiodes or the like, the light receiving area of each element of the photodiode is different, and the capacitance between the electrodes of the photodiode is different for each element. There has been a problem that accuracy varies and performance deteriorates. Therefore, it has been a problem to obtain a high-precision optical encoder by making the light receiving areas of a plurality of annular detection elements the same and making the inter-electrode capacitance of the photodiode the same so that the frequency characteristics are uniformed. .

[0010]

According to the present invention, there is provided a light emitting unit which is disposed on a fixed side and emits light toward a rotation axis of a rotating body to be measured. An annular rotating slit disk disposed on the rotating shaft with a slit for passing and blocking light sent to the annular region via the light guide from the rotary guide; An annular fixed-side slit disk having a plurality of slits corresponding to the slits of the side slit disk in the circumferential direction,
A light-collecting unit that transmits light passing through the slit of the fixed-side slit disk via a light guide in association with the plurality of stages,
A light receiving unit having a light receiving element for receiving light collected by the light collecting unit and converting a change in light amount into an electric signal, wherein the light collecting unit has a plurality of concentric lenses. The focus of each lens is not on the same optical axis.

With this configuration, it is not necessary to arrange the light receiving elements concentrically, so that the light receiving area of each light receiving element can be made the same, and the frequency characteristics of each element become uniform. Thus, the encoder performance is improved.

[0012]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of the optical encoder of the present invention. The rotary slit disk 5 fixed to the rotary shaft 1 by the hub 2 is provided with a radial rotary slit 51 shown in FIG. The disk-shaped rotating-side full-circumferential light reflecting portion 3 is provided so as to face one surface of the rotating-side slit disk 5 so as to be concentric with the rotating-side slit disk 5.

The hub 2 has a rotating-side light reflecting portion 4 formed of a conical surface having an angle of 45 degrees with respect to the rotating shaft 1, and a 45-degree angle with respect to the rotating shaft 1 facing the rotating-side light reflecting portion 4. A rotating-side full-circumferential light reflecting portion 3 formed of a part of a conical surface having an angle of
Is provided. The rotation-side light reflection portion 4 and the rotation-side full-circumference light reflection portion 3 function as a light guide that guides light incident in the rotation-side central axis direction to the fixed-side full-circle direction. Hub 2
Is made of a transparent resin, and the reflecting portion having an angle of 45 degrees is finished with mirror accuracy, so that light transmitted through the inside is totally reflected by the reflecting portion. Further, the material of the fixing portion is the same transparent resin as the material of the hub 2, and the light transmitted through the light reflecting portion on the fixed side is reflected at this portion. The light emitting section 11 is configured by mounting a light emitting element 13 such as a light emitting diode on a light emitting element substrate 12 and arranging a convex lens 14 for changing light emitted from the light emitting element 13 into parallel rays in front of the light emitting element 13. Therefore, the light emitted from the light emitting element 13 disposed on the light emitting element substrate 12 passes through the convex lens 14 and enters the rotation side light reflecting section 4 as parallel light L1.

In the rotation-side light reflection section 4, as described above, the light is totally reflected, reflected in a direction perpendicular to the rotation center axis and radially, and enters the rotation-side entire circumference light reflection section 3 as L2.
Similarly, the rotation-side full-circumference light reflecting portion 3 is totally reflected in the right-angle direction to become L3. Since the rotation-side entire-circumference light reflecting portion 3 has an angle of 45 degrees with respect to the rotation center axis, the light beam L3 is parallel to the rotation center axis, and has a circular parallel light beam having the same diameter as the rotation-side slit disk. Become. A disk-side fixed slit disk 6 is provided on the other surface of the rotating slit disk 5. The fixed slit disk 6 is provided with fixed slits having the same pitch P as the slits 51 of the rotary slit disk 5 shown in FIG. FIG. 4 shows the arrangement of the fixed slits 61 in the fixed-side slit disk 6. The B-channel fixed slits 61 are concentric with the A-channel fixed slits 61 </ b> A and offset by P / 4 pitch.
B is provided to form a fixed slit 61 having two tracks. The fixed-side entire-circumference light reflecting portion 7 and the fixed-side light reflecting portion 8 function as a light guide for guiding the light incident on the entire fixed-side periphery to the fixed-side central axis. Therefore,
The light that has passed through the A-channel fixed slit 61A and the B-channel fixed slit 61B is converted into two light beams, a light beam LA and a light beam LB, and is totally reflected at right angles by the fixed-side entire-circumferential light reflecting portion 7 with the V-groove portion 71. A two-channel light beam L4 condensed at the center. Each of the totally reflected light beams is totally reflected at right angles by the fixed-side light reflecting portion 8 having the V-shaped groove portion 81 arranged at the center of the rotation axis, thereby forming a two-channel light beam parallel to the rotation center axis and annularly parallel. Condensing part 1
Light 5 enters.

FIG. 2 is an enlarged view of the condensing section 15. The condenser section 30 is a condenser lens composed of a concentric lens 15A and a concentric lens 15B. The focal point of each concentric condenser lens is designed to have a fixed angle and to focus on the photodiode. Each of the concentric lenses is a plane having a certain inclination angle with respect to the incident light, and the outgoing light portion has a convex lens structure. In addition, the inclination angles of the planes are configured to be opposite to each other. That is, it is easy to understand if it is considered that the prism and the lens are united and have a concentric shape. The incident light has a structure in which the light is bent at a certain angle in the prism part and is condensed in the lens part. The light beam LA transmitted through the respective condenser lenses is condensed on the photodiode 10A, and the light beam LB is condensed on the photodiode 10B to enter the light.

Note that the annular incident light due to the prism is condensed into an elliptical shape when condensed. If this is a problem, however, if an aspherical lens is used as the lens, the circular incident light becomes circular. Can be corrected. Each detection signal is converted into a pulse signal or the like by a conversion device (not shown).

As described above, the detection light is condensed by the concentric lens which is designed so as not to be focused on the same optical axis and is incident on the photodiode. The capacity is reduced, so that the frequency characteristics are improved and the cost is reduced. Further, since the shape of the photodiode can be made the same, two signals having uniform characteristics can be obtained, and the performance of the encoder is improved. Furthermore, since there is no restriction that the shape of each photodiode must be annular, the photodiode can be arranged at a place suitable for the purpose of design.

FIG. 5 shows a detailed layout of photodiodes for detecting this light beam. The light receiving unit 10 includes a square photodiode 10A and a photodiode 10A.
B are arranged on the same photodiode so that two different electric signals can be obtained. In the present invention, two signals have been described. However, when detecting a large number of signals, the fixed slit and the condenser lens are arranged on the same optical axis, and each condenser lens is not arranged on the same optical axis. It is clear that the lens should be designed as follows. Further, since the entire configuration of the optical encoder is suitable for being formed by a transparent resin mold, it is characterized in that it can be formed by an integrally molded part.

FIG. 6 is a sectional view showing an application example of FIG. In the present embodiment, the outer diameter extension 15
C is provided with a function of attaching the light receiving element substrate 9 and a positioning portion 16 for positioning, so that the number of components is reduced. By adopting this structure, there is no mechanical error when attaching the concentric lens and the photodiode, and there is an effect that the performance of the encoder is improved because the condensed light accurately enters the photodiode. Further, there is an effect that the cost can be reduced by reducing the number of parts.

FIG. An application example in which a Fresnel lens is used as a concentric lens will be described. The use of the Fresnel lens has the effect of reducing the thickness of the lens and making the encoder compact. Although only the photodiode has been described in the present invention, it goes without saying that the same effect can be obtained even if a phototransistor or an optical IC in which a light receiving element and an integrated circuit for waveform shaping are integrated is adopted as the light receiving element. No.

[0021]

As can be seen from the above embodiment, as shown in the present invention, light is condensed by a concentric lens that is not focused on the same optical axis and is incident on the photodiode. Since a photodiode having a small area is sufficient, the capacitance between the electrodes of the photodiode is reduced, and the frequency characteristics are improved. 2. Since the shape of the photodiode can be the same,
Two signals having the same characteristics are obtained, and the characteristics of the encoder are improved. 3. The restriction that each photodiode has to be annular is eliminated, and the photodiode can be arranged at a place suitable for the design purpose. 4. As a result, the area of the photodiode is reduced, which leads to cost reduction. The effects such as come out. 5. Also, by providing the function of attaching the concentric condensing part and the light receiving element substrate and the positioning part on the outer diameter part of the condensing lens to reduce the number of components, there is no mechanical error when attaching the concentric lens and the photodiode, The effect that the performance of the encoder is improved because the condensed light accurately enters the photodiode, and the effect that the cost can be reduced by reducing the number of components occurs. 6. By employing the Fresnel lens, the thickness of the concentric condenser lens can be reduced, and the effect that the encoder can be downsized occurs.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is an enlarged view of details of a condenser lens of the present invention.

FIG. 3 is a detailed partial view of a rotating slit disk.

FIG. 4 is a detailed partial view of a fixed slit.

FIG. 5 is a layout diagram of a photodiode according to the present invention.

FIG. 6 is a partial sectional view showing a first application example of the present invention.

FIG. 7 is a partial sectional view showing an application example using the Fresnel lens of the present invention.

FIG. 8 is a sectional view showing a third conventional example.

FIG. 9 is a layout diagram of a photodiode of Conventional Example 3.

FIG. 10 is a sectional view showing Conventional Example 2, FIG. 10A is an exploded perspective view of an optical encoder, and FIG. 10B is a longitudinal sectional view of the optical encoder.

FIG. 11 is a sectional view showing Conventional Example 1.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Rotation axis 2 Hub 3 Rotation side whole circumference light reflection part 4 Rotation side light reflection part 5 Rotation side slit disk 51 Rotation slit 6 Fixed side slit disk 61A A channel fixing slit 61B B channel fixing slit 7 Fixed side whole circumference light Reflecting portions 71, 81 V-groove portions 8 Fixed-side light reflecting portions 9, 9 ', 9A Light receiving element substrate 10, 10' Light receiving portions 10A, 10B, 10A ', 10B' Photodiode 11 Light emitting portion 12 Light emitting element substrate 13 Light emitting element ( Light emitting diode) 14 Convex lens 15 Condenser 15A, 15B Concentric lens 15C Outer diameter extension 16 Positioning part 17 Fresnel lens

Claims (6)

[Claims] 1. A light emitting unit which emits light toward a rotation axis side of a rotating body to be measured, and a slit which passes and shields light transmitted from the light emitting unit to an annular region via a light guide is provided on the rotation shaft. An annular rotating slit disk that is disposed, and an annular fixed slit disk that is disposed adjacent to the rotating slit disk and has a plurality of circumferentially arranged slits corresponding to the slits of the rotating slit disk in the circumferential direction. A light-collecting unit that transmits the light passing through the slit of the fixed-side slit disk to the plurality of stages via a light guide, and receives the light collected by the light-collecting unit to change the amount of light. An optical encoder comprising: a light receiving unit having a light receiving element that converts the light into an electric signal; wherein the light condensing unit has a plurality of concentric lenses, and the focal points of the concentric lenses are not on the same optical axis. Optical encoder characterized by having Da. 2. The optical encoder according to claim 1, wherein said concentric lens is a plano-convex lens. 3. The optical encoder according to claim 1, wherein in the optical encoder, the concentric lens includes a flat surface and an aspherical convex lens. 4. The optical encoder according to claim 1, wherein said concentric lens has a Fresnel lens structure. 5. The optical encoder according to claim 1, wherein the light condensing portion has a function of fixing and positioning the light receiving element. 6. The optical encoder according to claim 1, wherein in the optical encoder, the light receiving section includes a rectangular light receiving element.