JP3205680B2 - Reflective optical encoder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type optical encoder for detecting a linear displacement or a rotational displacement. More specifically, the present invention relates to a structure of a reflection type optical encoder in which a light emitting element and a light receiving element are arranged on the same side of a moving plate on which a lens array is formed.

[0002]

2. Description of the Related Art An example of a conventional optical encoder is shown in FIG.
Shown in This optical encoder includes a light emitting element 101, a light receiving element 102, a moving plate 107, a fixed plate 108, and the like. The light emitting element 101 and the light receiving element 102 are movable plate 1
07 and the fixing plate 108, and are optically opposed to each other. The moving plate 107 has a transmitting portion 10 through which light passes.
9 and non-transmissive portions 111 for blocking light are formed at a constant pitch. Similarly, the transmitting portion 110 and the non-transmitting portion 112 are formed on the fixed plate 108 at a constant pitch. When the moving plate 107 moves, the transmission portion 109 and the fixed plate 10
8 overlaps with the transmission section 110. Accordingly, the amount of light emitted from the light emitting element 101 and received by the light receiving element 102 changes. The light receiving element 102 can detect a displacement amount of the moving plate 107 by converting a change in light amount into an electric signal.

In the above conventional example, slits are formed in the movable plate 107, and the transmitting portions 109 and the non-transmitting portions 111 are alternately arranged. An optical encoder using a moving plate in which a plurality of lenses are arranged at a constant pitch instead of the slit is also known, and is disclosed in, for example, Japanese Utility Model Laid-Open No. 57-26008. Further, an optical encoder employing a cylindrical lens as a lens is known, for example, disclosed in Japanese Patent Application Laid-Open No. 2-71118.

[0004]

The conventional optical encoder shown in FIG. 11 requires a fixed plate 108 in addition to the moving plate 107, and thus has a problem that the structure is complicated. In addition, the transmitting portion and the non-transmitting portion provided on the moving plate 107 and the fixed plate 108 are formed by etching or vapor deposition. For this reason, there was a problem that the productivity of these members was poor. Furthermore, since the moving plate 107 and the fixed plate 108 include a non-transmitting portion that blocks light in addition to the transmitting portion, there is a problem that the light flux emitted from the light emitting element 101 cannot be used effectively. . In addition, since the light emitting element 101 and the light receiving element 102 are arranged to face each other with the moving plate 107 and the fixed plate 108 interposed therebetween, the overall length of the optical encoder is increased in the optical axis direction, and the support mechanism for each member is separately provided. , There is a problem that the structure becomes complicated.

[0005] Japanese Utility Model Laid-Open No. 57-26008 and
In the optical encoder disclosed in Japanese Patent Application Laid-Open No. 71118/1995, a lens is formed on a moving plate instead of a slit. However, even in this structure, it is necessary to arrange the light emitting element and the light receiving element on both sides of the moving plate so that there is a problem that the overall length is large and the structure is complicated as in the conventional encoder shown in FIG.

[0006]

The following means have been taken in order to solve the above-mentioned problems of the prior art. That is, the reflection type optical encoder according to the present invention includes a moving plate, a light emitting element, and a light receiving element as a basic configuration. The moving plate is linearly or rotationally displaced along a predetermined moving direction. The light emitting element is arranged at a first fixed point facing the front side of the moving plate and in a width direction substantially orthogonal to the moving direction. The light receiving element is also arranged at a second fixed point facing the front side of the moving plate and separated from the first fixed point along the width direction. As a characteristic matter, a plurality of lenses arranged at a constant pitch along the moving direction and having a top and a valley are formed on the front side of the moving plate so as to be adjacent to each other via the valley . Each lens is arranged to pass through the first fixed point and the second fixed point, respectively. On the back side of the moving plate, a reflecting surface continuous in the moving direction so as to pass through the first fixed point and the second fixed point is provided on the lens.
Are formed integrally with each other, and reflect the light beam incident from the first fixed point side and direct it to the second fixed point side. In such a configuration, the light emitting element irradiates the light beam condensed through the top of the lens passing through the first fixed point onto the reflecting surface, and further emits the first fixed point.
The light flux diverging through the valley of the lens passing through
Irradiate the surface . In contrast, the light receiving elements receive again condensing through the top <br/> of the lens through a second fixed point a light beam said population light from the reflecting surface, is the divergent from Mata該reflecting surface
Emitted light again through the valley of the lens passing through the second fixed point
The maximum level corresponding to the collected light flux
And it outputs a detection signal representing the amount of movement of the transfer <br/> moving plate has a minimum level corresponding to the divergent light flux. Specifically, lenses formed on the front side of the moving plate is made of a cylindrical lens having a cylindrical axis along the width direction, each other
Are arranged so that they are adjacent to each other, and the top and the valley are alternately formed.
Has been established. The reflecting surface formed on the back side of the moving plate includes an incident total reflection surface for reflecting the light beam incident from the first fixed point side in the width direction, and a second reflecting point surface for reflecting the reflected light beam again. Outgoing total reflection surface.

[0007] Preferably, in addition to the light emitting element and the light receiving element arranged at the first fixed point and the second fixed point, an additional light emitting element and light receiving element are arranged at positions effectively shifted by 1/4 pitch along the moving direction. are doing. As a result, it is possible to output a detection signal indicating the moving direction in addition to the moving amount. or,
In addition to a plurality of lenses arranged at a constant pitch, a reference lens disposed at a reference position of the moving plate is included. Further, an additional set of a light emitting element and a light receiving element is provided so as to match the pass area of the reference position. As a result, a detection signal indicating the reference position is output separately from the movement amount. More preferably, the moving plate is formed with irregularities for determining a degree at a predetermined pitch in a moving direction along a side end face sandwiched between the front side and the back side so that a click feeling can be obtained.

[0008]

According to the present invention, a set of a light emitting element and a light receiving element are arranged side by side in the width direction orthogonal to the moving direction. A movable plate that is relatively movable at a position facing the set of the light emitting element and the light receiving element is disposed in the vicinity thereof. On the moving plate, a cylindrical lens extending in the width direction is formed on the front side facing the set of the light emitting element and the light receiving element, and on the back side, a pair of incident total reflection surface and emission total reflection surface are provided in parallel with the moving direction. Provide a chevron prism. The light beam emitted from the light emitting element is repeatedly focused and diffused by the cylindrical lens provided on the moving body. Thus, the intensity of the light beam emitted from the light emitting element can be modulated according to the displacement of the movable plate without providing any fixed plate. Since all of this light beam is collected / diffused by the cylindrical lens, the light beam can be effectively used. or,
A pair of incident total reflection surface and emission total reflection surface are provided on the back side, and the direction of the incident light beam is changed by 180 ° to be an output light beam.
Thus, the light emitting element and the light receiving element can be arranged in the same direction.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic perspective view showing a first embodiment of the reflective optical encoder according to the present invention.
As shown in the figure, the reflective optical encoder is a light emitting element 1
And a light receiving element 2 and a moving plate 3. The moving plate 3 is linearly displaced along a predetermined moving direction. Light emitting element 1
Is disposed at a first fixed point facing the front side of the moving plate 3 and in the width direction substantially orthogonal to the moving direction. The light receiving element 2 is also disposed at a second fixed point facing the front side of the movable plate 3 and separated from the first fixed point along the width direction. A plurality of cylindrical lenses 4 arranged at a constant pitch P along the moving direction are formed on the front side of the moving plate 3. The cylindrical axis of each cylindrical lens 4 is parallel to the width direction. Each cylindrical lens 4 has a first fixed point and a second fixed point.
Width W sufficient to pass both fixed points and cover both
have. On the other hand, on the back side of the moving plate 3, the incident total reflection surface 5S continuous in the moving direction so as to pass through the first fixed point, and continuous in the moving direction so as to pass through the second fixed point and opposed to the incident total reflection surface 5S. Outgoing total reflection surface 5T. The pair of incident total reflection surface 5S and emission total reflection surface 5T constitute a concave reflection surface 5. In such a configuration, the light emitting element 1 irradiates the incident total reflection surface 5S with a light flux whose intensity has been modulated via the cylindrical lens 4 passing through the first fixed point.
On the other hand, the light receiving element 2 is a cylindrical lens 4 that simultaneously passes the light beam emitted from the emission total reflection surface 5T through the second fixed point.
And outputs a detection signal indicating the amount of movement of the movable plate 3.

Next, the operation of the reflection type optical encoder shown in FIG. 1 will be described in detail with reference to FIG. FIG. 2B shows a cross-sectional shape of the moving plate 3 cut along the width direction. 2A is a side view as viewed from the arrow A, and FIG. 2C is a side view as viewed from the arrow C. First, as shown in (B), a pair of light emitting element 1 and light receiving element 2 are optically connected to each other along a predetermined optical axis. This optical axis starts from the light emitting element 1, passes through the lens 4, is turned back by 90 ° by the incident total reflection surface 5S, further turned back by 90 ° by the outgoing total reflection surface 5T, and then reaches the light receiving element 2 through the lens 4. I do. Next, as shown in (A),
The luminous flux emitted from the light emitting element 1 is a cylindrical lens 4
And enter the incident total reflection surface 5S. Thereafter, as shown in (B), the light beam is turned by 90 ° by the incident total reflection surface 5S.
It is turned back and enters the outgoing total reflection surface 5T. Finally (C)
As shown in (1), the light beam is turned back to the front side of the movable plate 3 by the emission total reflection surface 5T, collected again by the lens 4, and then received by the light receiving element 2. As described above, the light beam emitted from the light emitting element 1 is turned 180 ° by the concave reflecting surface 5 including the pair of total reflecting surfaces 5S and 5T, and returns to the light receiving element 2.
When the top of the cylindrical lens 4 is exactly aligned with the set of the light emitting element 1 and the light receiving element 2, the maximum amount of the light beam is received by the light receiving element 2 due to the condensing action of the cylindrical lens 4 twice. That is, the light receiving element 2 outputs the maximum value of the detection signal.

FIG. 3 shows a state where the moving body 3 is displaced by a half pitch (P / 2) from the position shown in FIG. At this time, the cylindrical lenses 4L and 4R adjacent to each other
Are aligned with the light emitting element 1 and the light receiving element 2. As shown in (A), the light beam emitted from the light emitting element 1 is diverged by the valley. As shown in (B), the divergent luminous flux is turned back by the incident total reflection surface 5S and exits the total reflection surface 5T.
To enter. As shown in (C), the divergent light flux is turned back to the front side at the emission total reflection surface 5T, and then diverged again by the cylindrical lenses 4L and 4R. As a result, the light receiving element 2 has the minimum light receiving amount. Therefore, the light receiving element 2 outputs the detection signal of the minimum level. That is, when the movable plate 3 is displaced by a half pitch, the detection signal changes from the maximum value to the minimum value. When the movable plate 3 is again displaced by a half pitch, the detection signal returns from the minimum value to the maximum value. As described above, the light beam is repeatedly converged and diverged by passing through the cylindrical lens 4, and accordingly, the detection signal outputs a detection signal which fluctuates at a cycle corresponding to one pitch. The amount of displacement of the movable plate 3 can be determined by counting the period of the detection signal.

FIG. 4 is a schematic perspective view showing a second embodiment of the reflection type optical encoder according to the present invention. In this example, the moving plate 3 has two tracks M, Z in parallel with the moving direction.
Is divided into A plurality of lenses 4 are arranged on the track M at a constant pitch P. Further, a pair of the light emitting element 1 and the light receiving element 2 are arranged in alignment with the track M. On the back side of the track M, a pair of incident total reflection surfaces 5S and emission total reflection surfaces 5T are formed. Therefore, this track M
Has the same configuration as that of the first embodiment shown in FIG. 1, and the light receiving element 2 outputs a detection signal indicating the amount of movement of the moving plate 3.
On the other hand, the additional track Z includes a reference lens 4Z disposed at a reference position of the moving plate 3. In this example, the reference lens 4Z is formed by extending one cylindrical lens 4 over both the track M and the track Z. On the back side of the track Z, a pair of incident total reflection surfaces 5SZ and emission total reflection surfaces 5TZ are formed. An additional light emitting element 1Z and light receiving element 2Z are provided on the front side of the track Z. That is, the set of the added light emitting element 1Z and light receiving element 2Z is aligned with the passage area at the reference position. With this configuration, the light receiving element 2Z can output a detection signal indicating the reference position separately from the movement amount. Further, another light-emitting element and a light-receiving element are located at positions effectively shifted by １ ／ pitch (P / 4) along the moving direction from the set of the light-emitting element 1 and the light-receiving element 2 arranged at the first fixed point and the second fixed point. If a set of elements is arranged, it is possible to detect the moving direction in addition to the moving amount.

FIG. 5 is a schematic perspective view showing a third embodiment of the reflection type optical encoder according to the present invention. As shown, the moving plate 3 is divided into a center track AB and tracks ZS and ZT on both sides in parallel with the moving direction.
On the track AB, a plurality of cylindrical lenses 4 are arranged at a constant pitch. A reference lens 4Z is arranged on the outer tracks ZS and ZT. One outer track Z
S corresponds to the light emitting element 1Z, and the other outer track ZT
Corresponds to the light receiving element 2Z. With this configuration, the reference position of the movable plate 3 can be detected. On the other hand, on the inner track AB, in addition to the light emitting element 1A and the light receiving element 2A arranged at the first fixed point and the second fixed point, an additional light emitting element is provided at a position which is effectively shifted by 1/4 pitch along the moving direction. 1B
And a light receiving element 2B. As a result, it is possible to output a detection signal indicating the moving method in addition to the moving amount.
Since the light receiving elements 2A and 2B have their spatial phases shifted by P / 4, the detection signals also have their phases shifted by π / 2 accordingly. Since the phase shift direction is reversed depending on the moving direction, the moving direction of the moving plate 3 can be known by detecting this.

FIG. 6 shows a fourth embodiment of the reflection type optical encoder according to the present invention, and shows an example applied to a rotary encoder. The moving plate 3 is processed into a disk shape, and is attached to the rotating shaft 6. Therefore, the moving plate 3 is rotationally displaced along the circumferential direction. The light emitting element 1 is disposed at a first fixed point (inner fixed point) facing the front side of the moving plate 3 and in a width direction (ie, a radial direction) orthogonal to the moving direction (circumferential direction). The light receiving element 2 is also disposed at an outer fixed point (second fixed point) facing the front side of the movable plate 3 and separated from the inner fixed point along the radial direction. On the front side of the moving plate 3, a plurality of cylindrical lenses 4 radially arranged at a constant pitch along the circumferential direction are formed. Each lens 4 has a sufficient width dimension (radial dimension) to cover the inner fixed point and the outer fixed point. On the back side of the moving plate 3, an inner incident total reflection surface 5S continuous in the circumferential direction so as to pass through the inner fixed point, and a circumferentially continuous inner surface passing through the outer fixed point and opposed to the incident total reflection surface 5S. An outer emission total reflection surface 5T is formed. The moving plate 3 including the lens 4, the incident total reflection surface 5S, and the emission total reflection surface 5T can be manufactured by integral molding (mold) using a transparent resin as a material. With the above configuration, the light emitting element 1 irradiates the light beam whose intensity has been modulated via the lens 4 passing through the inner fixed point onto the incident total reflection surface 5S, and the light receiving element 2 simultaneously emits the light beam radiated from the emission total reflection surface 5T. Light is received via the lens 4 passing through the outer fixed point,
A detection signal indicating the amount of movement of the moving plate is output. In other words, the lens 4 modulates its intensity by repeatedly condensing / diverging the light beam passing through the moving body 3.

FIG. 7 is a schematic sectional view showing a specific configuration example of the rotary encoder shown in FIG. As shown, the moving plate 3 is housed in a case 7 and a rotating shaft 6
It is attached to. The end 6 a of the rotating shaft 6 projects outside from the case 7. A circuit board 8 is incorporated facing the front side of the moving plate 3. A photoreflector unit 9 is attached to the inner surface of the circuit board 8. The photoreflector unit 9 integrally incorporates a light emitting element 1 such as an LED and a light receiving element 2 such as a phototransistor. An IC 1 for processing a detection signal output from the light receiving element 2 is provided on an outer surface of the circuit board 8.
0 etc. are mounted. The outer surface of the circuit board 8 is the cover 1
Covered by 1. A connector 12 for external connection protrudes from a side surface of the cover 11. The rotary encoder having such a configuration can be applied to, for example, an adjustment knob of a measuring instrument. When the end 6a of the rotating shaft 6 is manually rotated,
A detection signal is input to the measuring instrument main body via the connector 12 according to the amount of rotation. Electrical adjustment or calibration of the measuring instrument is performed according to the detection signal.

FIG. 8 shows a plan view of the rotary encoder shown in FIG. 7, in which the moving plate 3 appears on the surface. The moving plate 3 is housed in a cylindrical case 7 and has a rotating shaft 6.
Is rotationally displaced about. On the front side of the moving plate 3, lenses 4 are radially arranged at an equal angular pitch P. Along the side end face sandwiched between the front side and the back side of the moving plate 3, irregularities 4a for determining the degree are formed at a predetermined pitch in the moving direction (circumferential direction). The click member 13 is fixed to the inner surface of the case 7 so as to engage with the unevenness 4a. The click member 13 is urged radially inward by a spring 13a. As the moving member 3 rotates, the click member 13 rides over the unevenness 4a sequentially, so that a desired click feeling can be obtained.

FIG. 9 is a plan view of the rotary encoder also shown in FIG. 7, in which the outer surface of the circuit board 8 is shown. As shown by the dotted lines, a pair of photoreflector units 9A and 9B are attached to the inner surface of the circuit board 8. As described above, one set of light emitting element and light receiving element is incorporated in one photo reflector unit.
As shown in the drawing, one of the photoreflector units 9B is (（) larger than the other photoreflector unit 9A.
+ N) The spatial phase is shifted by P. Here, n represents an arbitrary integer. As described above, by using the pair of photoreflector units 9A and 9B which are effectively shifted by 1/4 pitch, it becomes possible to output a detection signal indicating the rotation direction in addition to the rotation amount of the movable plate 3.

Finally, according to the present invention, with reference to FIG.
Various modifications of the reflective optical encoder are shown. In addition,
Parts corresponding to those of the first embodiment shown in FIG. 1 are denoted by the same reference numerals to facilitate understanding. In the modification shown in (A), cylindrical lenses 4S and 4T separated from each other are formed on the movable plate 3. One lens 4S passes through the incident light beam, and the other lens 4T passes through the output light beam. In the modification shown in (B), each of the lenses 4S and 4T is not a cylindrical lens but a spherical lens or an aspherical lens. These lenses 4S and 4T can also focus and diverge the incident light beam and the outgoing light beam. In the modification shown in (C), the concave reflection surface 5 is made of a polyhedron. Similarly to the V-shaped reflecting surface (prism reflecting surface) shown in the first embodiment, the incident light beam is shifted by 180 °.
It can be turned back and converted into an emitted light beam. In the modification shown in (D), the concave reflecting surface 5 is formed of a cylindrical body. In this case as well, the incident light beam can be turned back by 180 ° and converted into an outgoing light beam.

[0019]

As described above, according to the present invention, the light emitting element and the light receiving element are arranged side by side along the width direction orthogonal to the moving direction, and the position opposing the light emitting element and the light receiving element is located near the light emitting element and the light receiving element. A moving body relatively movable with is disposed. The movable body has cylindrical lenses arranged at a constant pitch on a side facing the light emitting element and the light receiving element, and a pair of incident total reflection surface and emission total reflection surface are provided on the back side in parallel with the moving direction. The light beam emitted from the light emitting element is repeatedly focused and diverged by the cylindrical lens provided on the moving plate, and the intensity is modulated. Therefore, unlike the conventional case, the fixing plate is not required, and the light emitting element and the light receiving element can be arranged on the same surface side. Therefore, the structure can be simplified and the optical axis length can be reduced by using a common support member for each element. . Further, since the moving plate can be integrally formed with a mold or the like, productivity is improved. Further, since the light beam emitted from the light emitting element is condensed by the lens without being blocked by the non-transmissive portion as in the related art, the light beam can be used efficiently. Therefore, it is possible to provide a high-performance reflective optical encoder which is inexpensive and has a small optical axis length.

[Brief description of the drawings]

FIG. 1 is a first view of a reflection type optical encoder according to the present invention.
It is a perspective view showing an example.

FIGS. 2A and 2B are a cross-sectional view and a side view for explaining the operation of the first embodiment shown in FIG.

FIGS. 3A and 3B are a cross-sectional view and a side view for explaining the operation of the first embodiment.

FIG. 4 shows a second example of the reflection type optical encoder according to the present invention.
It is a perspective view showing an example.

FIG. 5 shows a third example of the reflection type optical encoder according to the present invention.
It is a perspective view showing an example.

FIG. 6 shows a fourth example of the reflection type optical encoder according to the present invention.
It is sectional drawing which shows an Example.

FIG. 7 is a longitudinal sectional view showing a specific configuration example of the fourth embodiment shown in FIG.

FIG. 8 is a plan view showing a specific configuration of the fourth embodiment.

FIG. 9 is a plan view showing a specific configuration of the fourth embodiment.

FIG. 10 is a schematic perspective view showing various modified examples of the reflective optical encoder according to the present invention.

FIG. 11 is a perspective view showing an example of a conventional optical encoder.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light emitting element 2 Light receiving element 3 Moving plate 4 Lens 5S Incident total reflection surface 5T Emission total reflection surface 6 Rotation axis

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-202714 (JP, A) JP-A-2-71118 (JP, A) JP-A-2-268227 (JP, A) 50315 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01D 5/26-5/38 G01B 11/00-11/30

Claims (6)

(57) [Claims] A moving plate displaced along a predetermined moving direction; a light emitting element facing a front side of the moving plate and arranged at a first fixed point in a width direction substantially orthogonal to the moving direction; Similarly, a first surface facing the front side of the moving plate and along the width direction.
A reflective optical encoder comprising a light receiving element disposed at a second fixed point separated from the fixed point, wherein the movable plate is arranged at a constant pitch along the moving direction on the front side of the moving plate, and has a peak and a valley. Have multiple valleys
The lenses are arranged so as to be adjacent to each other through the first fixed point and the second fixed point, and the individual lenses are arranged so as to pass through the first fixed point and the second fixed point, respectively. A reflecting surface continuous in the moving direction is formed integrally with the lens so as to reflect the light beam incident from the first fixed point side and direct it toward the second fixed point side; Irradiates the light beam condensed through the top of the lens passing through the first fixed point onto the reflecting surface, and passes through the first fixed point.
The light diverging through the valley of the lens that illuminates the reflecting surface
Shines, the light receiving elements receive again condensing through the top of the lens passing through the second fixed point a light beam said population light from the reflecting surface,
The divergent light beam from the reflecting surface passes through a second fixed point.
The light diverges again through the valley of the lens and receives light, and the maximum level corresponding to the collected light flux and the divergent light
A reflection-type optical encoder having a minimum level corresponding to the luminous flux and outputting a detection signal indicating the amount of movement of the moving plate. Wherein the lens formed on the front side of the moving plate Ri cylindrical lens der having a cylindrical axis along the width direction, is arranged so as adjacent to each other, said top and valley
2. The reflective optical encoder according to claim 1, wherein the portions are formed alternately . 3. The reflecting surface formed on the back side of the moving plate reflects an incident total reflection surface in the width direction of a light beam incident from a first fixed point side, and a second reflecting surface reflects the reflected light beam again. 2. The reflection type optical encoder according to claim 1, further comprising an emission total reflection surface directed to a fixed point. 4. In addition to the light emitting element and the light receiving element arranged at the first fixed point and the second fixed point, the light emitting element and the light receiving element are effectively moved along the moving direction.
2. The reflection device according to claim 1, wherein an additional light emitting element and a light receiving element are arranged at positions shifted by / 4 pitch, so that a detection signal indicating a moving direction in addition to a moving amount can be output.
Type optical encoder. 5. In addition to a plurality of lenses arranged at a constant pitch, a reference lens disposed at a reference position of a moving plate is provided, and an additional set of light emitting elements and light receiving elements is provided in conformity with a passage area of the reference position. And outputting a detection signal indicating a reference position separately from the movement amount.
Reflective optical encoder. 6. The moving plate, wherein irregularities for determining a degree are formed in a moving direction at a predetermined pitch along a side end face sandwiched between a front side and a back side. Anti
Injection optical encoder.