JPS63201523A - Optical encoder - Google Patents

Abstract

PURPOSE:To store the angular displacement of a body even at the time of a power failure by detecting a magnetic part to be detected which rotates integrally with the body whose angle displacement is to be detected and powering on a counter which counts the detection output by a battery all the time. CONSTITUTION:Plural pits 8 are provided at equal intervals on a track T1 of the optical disk 3 which rotates integrally with the rotary body, and one it 9 and one magnetic part 10 to be detected are provided on tracks T2 and T3 respectively. Photosensors 21 and 22 detect reflected light obtained by irradiating the pits 8 on the track T1 with laser light from a light source 12 to find the direction and speed of the rotation, and a photosensor 23 detects reflected light from the pit 9 on the track T2 to set an initial value. If a power failure occurs, magnetic detecting elements 5 and 6 which are powered on by the battery all the time detect the magnetic part 10 to be detected to decides the rotating direction, thereby holding the initial value of the optical disk in a counter. Consequently, the absolute position of the optical disk is detected with high accuracy at the time of the recovery from the power failure.

Description

TECHNICAL FIELD The present invention relates to optical encoders for detecting angular displacements of objects.

BACKGROUND ART Prior art for detecting the angular displacement of an object with high precision using an optical disk is disclosed in, for example, Japanese Patent Application Laid-Open No. 100013/1983.
It is known as such. In such prior art,
The optical disc is irradiated with laser light, the reflected light is detected by a light receiving element, and the pulses corresponding to the pits formed on the optical disc from the light receiving element are counted by a counter.

Problems to be Solved by the Invention In such prior art, the contents of the counter are not retained when a power outage occurs, and therefore, when the power is turned on after the power outage is restored, the operator has to take a lot of effort to read the counted value of the counter. must be set corresponding to the angular displacement position of the object.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical encoder that can store the angular displacement of an optical disk, and thus an object, even in the event of a power outage.

Means for solving the gap The present invention provides an optical disc having a plurality of pits formed at intervals in the circumferential direction, a laser light source that irradiates laser light onto the pits, and a light source that receives reflected light from the pits. A light-receiving element, a first counter that counts the output of the light-receiving element, and a magnetic field that rotates integrally with the object whose angular displacement is to be detected and is arranged in a circumferential direction in a smaller number than the number of pits in the circumferential direction. a magnetic detection element that detects the magnetic detection element, a second counter that counts the output of the magnetic detection element, a battery that constantly energizes the second counter, and an output of the second counter. and a circuit that initializes the contents of the first counter in response.

According to the present invention, the magnetically detected portion is provided to rotate integrally with the object whose angular displacement is to be detected, and this magnetically detected portion is detected by the magnetic detection element, and its angular displacement is detected by the magnetic detecting element. The output of the magnetic detection element is counted by a second counter. The Pt52 counter is constantly powered by a battery. Therefore, even if the contents of the first counter are no longer held when the power is turned off, such as during a power outage, the contents of the second counter are held. Therefore, when the power is turned on, such as when the power is restored, it is possible to detect the angular displacement of the optical disc, and therefore of the object, based on the contents of the second counter. Also, when an object moves when the power is turned off, such as when the working end of an industrial robot is displaced during a power outage, the magnetically detected part is detected by the magnetic detection element, and the count value of the Pt52 counter changes. Then, the position of the object can be detected.

Since the number of magnetically detected portions is smaller than the number of pits in the circumferential direction of the optical disk, the count value of the second counter may be relatively small. Therefore, the power consumption of the ttS2 counter is very small.

The burden on Tsuteri becomes lighter.

Normally, when a power outage has not occurred, the pits of the optical disk are irradiated with a laser light source, the reflected light is detected by a light receiving element, and the output of the light receiving element is counted by the first counter, thereby achieving high accuracy. It is possible to detect the angular displacement of an optical disc.

Example FIG. 1 is a sectional view of one embodiment of the present invention.

An optical disk 3 is fixed to an output shaft 2 of a motor 1 that drives a working end of an industrial robot. This disc 3 is optically detected by the detection means 4 and magnetically detected by the magnetic detection element 5.6.

FIG. 2 is a plan view of the optical disc 3. optical disc 3
is fixed to the output shaft 2, and the axis 7 of the optical disc 3 coincides with the axis of the output shaft 2. On the outermost track T1 of this disc 3, a large number of pits 8 are formed at equal intervals in the circumferential direction.

One pit 9 is formed in the circumferential direction on the track T2 that is inner than the track T1. Innermost track T3
A magnetically detected portion 10 is fixed to the magnetically detected portion 10 . Only one magnetically detected portion 10 is provided in the circumferential direction, and therefore the number is smaller than the number of pits 8 of the track T1. The magnetically detected portion 10 is realized by, for example, a magnetized ferromagnetic powder layer. The optical disc 3 is formed by forming pits 8 and 9 in an aluminum layer formed on a base material such as polycarbonate, and providing a transparent protective layer thereon. Tracks TI, Tj, and T3 are concentric virtual circles centered on the axis 7 of the optical disc 3.

Referring again to FIG.
15, and is irradiated onto the pit 8 of the track T1. Laser light [Laser light from the second
The light passes through the reflecting mirror 16, the semi-transparent reflecting mirror 17 and the lens 18, and is irradiated onto the pit 9 of the track T2. lens 1
5.18, the tracking servo mechanism 19 controls the position of the optical disc 3 in the radial direction. The reflected light of the laser beam on the track T1 passes from the lens 15 to the semi-transparent reflecting mirror 14, and from the lens 20 to the light receiving system 21.
The light is received by 22. The reflected light of the laser light from the track T2 passes through the lens 18, the semi-transparent reflecting mirror 17, and is received by the light receiving element 23 through the lens 52. Light receiving elements 21 and 22 that detect reflected light from pit 8 of track T1
receives reflected light at a position shifted in the circumferential direction of the optical disc 3 along the track T1. As a result, the light receiving element 2
The output of 1.22 has a phase difference corresponding to the rotation direction of the optical disc 3.

FIG. 3 is a perspective view showing a simplified structure of the optical disc 3 and its vicinity. Magnetic detected portion 10 of track T3
The magnetic detection elements 5 and 6 for detecting are arranged circumferentially offset along the track T3. This magnetic detection element 5.6 can be realized, for example, by a so-called magnetoresistive conversion element that detects the strength of a magnetic field as a change in resistance value. Since the magnetic detection elements 5 and 6 are arranged circumferentially offset along the track T3, the outputs of the magnetic detection elements 5 and 6 have a phase difference corresponding to the angular displacement direction of the optical disc 3. have

FIG. Pt54 is a block diagram showing the electrical configuration of the embodiment shown in FIGS. 1 to 3. Outputs from the light receiving elements 21 and 22 are given to an angular displacement direction determining circuit 27 via amplifier circuits 25 and 26. The angular displacement direction determination circuit 27 is
When the optical disc 3 is angularly displaced in one direction, the output of the light receiving element 21 is derived from the line 28, and the up/down counter 29 is caused to count up. optical disc 3
When rotating in the opposite direction, the angular displacement direction tII separate circuit 27 derives the output of the light receiving element 21 from the line 30, and supplies it to the counter 29 for down-counting. Thereby, the count value of the counter 29 can detect the angular displacement position of the optical disc 3 with high precision.

The output of the magnetic detection element 5.6 is sent to an angular displacement direction determining circuit 33 via amplifier circuits 31 and 32. This angular displacement direction determining circuit 33 determines whether the optical disc 3 is angularly displaced in the one direction. At this time, the output from the magnetic detection element 5 is given to the up/down counter 35 via the line 34, and the up/down counter 35 is caused to count up. When the optical disc 3 is angularly displaced in the opposite direction, the angular displacement direction determination circuit 33
The output from the magnetic detection element 5 is derived through the 2-in 36, and the count is down-counted by the counter 35. The battery 37 constantly energizes the magnetic detection elements 5 and 6, the amplifier circuits 31 and 32, the angular displacement direction determination circuit 33, and the counter 35. The magnetic detection elements 5 and 6 have a low power consumption: #tjt, and the count value of the counter 35, which has a small power consumption, is smaller than that of the counter 29 described above, and therefore has a small power consumption, which reduces the capacity of the battery 37. Can be made smaller. The output of the counter 35 is given to an initialization circuit 38. The output of the light receiving circuit 23 is also sent to the initialization circuit 38. The initialization circuit 38 converts the count value of the counter 29 into the optical disc 3.
Initialize it by setting it to a value corresponding to the angular displacement position of .

During normal operation, that is, when the power is turned on without a power outage, the second semiconductor laser light source, the counter 29, etc. are operating, and the counter 29 controls the optical disc 3.
The absolute position of the angular displacement is counted.

When the power is turned off due to a power outage, etc., the second semiconductor laser light source does not operate (and the contents of the counter 29 are held and become 1). It is constantly energized by the battery 37, and therefore the count value of the counter 35 is maintained even during a power outage.During this power outage, the optical disk 3 is angularly displaced, and the magnetically detected portion 10 is connected to the magnetic detection element. 5.6, the count value of the counter 35 changes, and thus the angular displacement of the optical disc 3 can be detected at all times.

When the power is turned on after a power outage is restored, first,
An optical disc 3 is angularly displaced in one predetermined direction by a motor 1. When the pit 9 of the track T2 is detected by the light receiving element 23, the initialization circuit 38 stores in the counter 29 the absolute position of the optical disc 3 in the circumferential direction, which is the absolute position of the robot arm corresponding to the count value of the counter 35. Set. Thereafter, the motor 1 stops, and thus when the optical disc 3 undergoes an angular displacement, the counter 29
The counted value represents the absolute position of the optical disc 3.

In this embodiment, the counter 29 is set to an absolute position by detecting the pit 9 of the track T2.
Therefore, the settings can be made with high precision.

As an embodiment of the present invention, the track T2 and therefore the pit 9 are omitted, and when the magnetic detecting element 5.6 detects the magnetically detected portion 10, the initialization circuit 38 causes the counter 29 to indicate that the optical disc 3 is To set the absolute position (1 may do 111).

FIG. 5 is a front view of the disc 40 of the embodiment of the present invention. Tracks T 4 , T 5 , and T 6 correspond to tracks T 1 , T 2 , and T 3 in the above-described embodiment, respectively, Jt. In this embodiment, a plurality of pits 41 are arranged at equal intervals on the track T5. Truck T
6, a plurality of magnetically detected parts 42 are provided at equal intervals in the circumferential direction. Track T4 has many pit 4
3 is formed.

fjS6 diagram (1) shows the pit 43 of truck T4,
FIG. 6(2) shows the pit 41 of truck T5,
FIG. (3) shows the magnetically detected portion 42, which shows the tracks T 4 , T 5 , and TG developed in the circumferential direction of the optical disk 40, and the left and right positions of FIG. 6. corresponds to the angular displacement position of the optical disc 40. The distance FFAW1 between the pits 41 and the distance W2 between the magnetically detected portions 42 are equal with respect to the angle in the circumferential direction of the optical disk 40. The rest of the configuration is similar to the configuration shown in FIGS. 1 to 14 described above.9 According to such a configuration, when the power is turned on after recovering from a power failure, the motor 1 moves the optical disk 40 at a distance of at most W1. It is only necessary to make an angular displacement by an angle corresponding to W2, and therefore the position of the working end of the industrial robot that is linked to the optical disk 40 can be slightly displaced.

FIG. 7 shows an optical disc 45 according to still another embodiment of the present invention.
FIG. In this example, the aforementioned track T1
．． In the area 46 corresponding to T4, T! number track 47
8. is provided in each track, and the pins of the above-mentioned embodiment are provided.
A pit 48 is provided corresponding to the hole 43. This pit 4
8 extend in the circumferential direction over a range of angle θ1 centered on the axis 7, and are aligned with a deviation of 1 in the radial direction. As a result, even if the position of the spot of the laser beam passing through the lens 15 on the optical disk 45 shifts in the radial direction,
The position of the optical disk 45 in the circumferential direction can now be detected, and the tracking servo groove 19 can be omitted. No pit 48 is formed in the range of angle θ2. θ1 may be 02. Similarly,
Track T2 of the above embodiment. i area 4 corresponding to T5
Pits 51 are formed in the plurality of tracks 50 corresponding to the above-mentioned pits 9 and 42. According to this embodiment, the tracking servo is surpassed and the cost of $19 is saved.
3, the configuration can be simplified.

Effects As described above, according to the present invention, it is possible to easily detect the absolute position of an optical disk with high precision after power is turned on, such as when recovering from a power outage.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of one embodiment of the present invention, FIG. 2 is a plan view of the optical disk 3, FIG. 3 is a simplified perspective view showing the optical disk 3 and its surrounding area, and FIG. 4 is! ¥) Block diagram showing the electrical configuration of the embodiment shown in Figures 1 to 3, No. 5
6 is a plan view of an optical disk 40 according to an embodiment of the present invention, and FIG. 6 shows tracks T 4 and T of the embodiment shown in FIG.
FIG. 7 is a plan view of a portion of an optical disc 45 according to still another embodiment of the present invention. 2... Output shaft, 3, 40.45... Yu disk, 4
. . . detection means, 5, 6 . . . magnetic detection element, 8, 9.
41, 43.48.51...Pit, 10.42...
・Representative of the magnetically detected part Patent attorney Keiichi Shisan Figure 1 Figure 2 Figure 3 Figure 5 Figure 6m Figure 7

Claims (1)

[Claims] An optical disk having a plurality of pits formed at intervals in the circumferential direction, a laser light source that irradiates the pits with laser light, a light receiving element that receives reflected light from the pits, and a light receiving element that receives reflected light from the pits. a counter that counts output; a magnetic detection target part that rotates integrally with the object whose angular displacement is to be detected and is arranged in a circumferential direction in a smaller number than the number of pits in the circumferential direction; a magnetic detection element for detecting the detection section; a second counter for counting the output of the magnetic detection element; a battery for constantly energizing the second counter; An optical encoder comprising: an initializing circuit.