JPH0472517A - Optical type rotary encoder - Google Patents

Abstract

PURPOSE:To apply a plurality of spots to a recording medium by a single optical system and adjust the phase difference of sensing signals easily as desired, by furnishing a position adjusting mechanism which transports an optical sensing means by a set amount in the radial direction of the recording medium. CONSTITUTION:A photo-pickup 6 is supported in such a way as movable in the radial direction of a disk 1 and put in contact with the tip of an adjusting screw 29 which is screw fitted to a supporting member 25. By this adjusting screw 29, a guide plate 27 of the photo-pickup 6 is moved to any position in the radial direction B. Thus each spot is moved in the radial direction B of the disk 1 by the screw 29 as coarse adjustment. As fine adjustment, thereafter, each laser spot is rotated in the direction of arrow R by a worm gear 31 installed on one end face of the photo-pickup 6. This permits adjusting the locational relation (phase) of each spot easily as desired, which requires only a minor moving distance.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an optical rotary encoder that detects the amount of rotational displacement of a disc-shaped recording medium using a semiconductor laser.

"Prior Art" Conventionally, as an optical rotary enhancer that detects the amount of rotational displacement using a semiconductor laser, a structure shown in FIG. 8 has been proposed (Japanese Patent Laid-Open No. 59195118).
. In FIG. 8, a disk 32 is attached to one end of a rotating shaft 31 supported by a hall bearing 30.30, and this disk 32 has slits 32a, 32a, is formed. Then, the laser beam LB emitted from the semiconductor laser 33 is made into parallel light by the collimating lens 34, and then condensed into a minute spot by the condensing lens 35 and irradiated onto the disk 32, and the slit formed in the disk 32 is The laser beam LB that has passed through 32a is sent to the light receiving element 3.
By providing an optical detection system 37 for detection at 6, the amount of rotational displacement of the disk 32 is detected.

In such a configuration, the number of rotating shafts per unit time is 3.
Although the rotation amount of 1 can be detected, the absolute rotation angle cannot be detected. To obtain a signal that detects this absolute rotation angle, for example, the 9th
As shown in the figure, the disk 32 has two rows of slits 32A, 32A, and 32B, 32B with mutually different phases.
, .
Three sets of optical detection systems 37, each for detecting 2B32C, must be provided. This is called an incremental type, but in such a method, at least three sets of optical detection systems 37 must be provided, which inevitably increases the number of parts and makes it difficult to downsize the entire device. .

Therefore, as shown in FIG. 10, a plurality of reflecting portions 42a are provided on the recording surface of the disk 42 and extend radially in the radial direction thereof.
and non-reflective portions 42b are recorded at predetermined intervals in the circumferential direction, and furthermore, a laser beam emitted from a semiconductor laser is focused on three minute spots LSaLSb and LSc and irradiated onto the recording surface of the disk 42, An optical detection system is provided that receives each of the reflected lights and outputs a multiphase detection signal corresponding to each amount of reflected light, and detects the amount of rotational displacement of the disk 42 based on these multiphase detection signals. A rotary encoder has been proposed.

In this case, a technique is essential for adjusting the positional relationship among the spots L Sa, L Sb, and L Sc, and for adjusting the phase difference of the multiphase detection signals obtained from the optical detection system.

Conventionally, as a technique for adjusting such a phase difference, as described in Japanese Patent Application Laid-Open No. 111418/1983,
It has been proposed to send the optical detection system in the tangential direction of the disk 42 (in the direction of the arrow shown in FIG. 1O).

"Problems to be Solved by the Invention" By the way, in the method of sending the optical detection system in the tangential direction of the disk 42 in order to adjust the phase difference of the multiphase detection signals obtained from the optical detection system as described above, As shown in FIG. 1O, the plurality of radially extending reflective portions 42a and non-reflective portions 42b recorded on the disk 42 are moved in a direction substantially orthogonal to each other (in the direction of arrow A).
Since b and f-Sc only move the same distance, for example, if you try to set the phase difference between the spots LSa and LSc at both ends to a predetermined value, the phase difference will change only slightly, and it will not necessarily be the desired value. There is a problem that it cannot be adjusted to the phase difference. This problem is caused by the spot LSa at both ends.
The narrower the distance between LSc and LSc, the more conspicuous it becomes.

This invention was made in view of the above-mentioned circumstances, and it irradiates a recording medium with a plurality of spots using a single optical detection system.
It is an object of the present invention to provide an optical rotary encoder that can arbitrarily and easily adjust the phase difference of each detection signal in a configuration that obtains multiphase detection signals.

"Means for Solving the Problems" The present invention provides a disc-shaped recording medium that is rotatably supported and on which position information extending radially in the radial direction is recorded at predetermined intervals in the circumferential direction of the recording surface, and a semiconductor. A laser beam emitted from a laser is focused on a plurality of minute spots along a substantially tangential direction and irradiated onto the recording surface of the recording medium, and each of the reflected lights is received, and a plurality of spots corresponding to the amount of each reflected light are collected. In an optical rotary encoder, the optical rotary encoder is equipped with optical detection means that outputs phase detection signals, and detects the amount of rotational displacement of the recording medium based on the detection signals, wherein the optical detection means is configured to detect rotational displacement of the recording medium in a radial direction of the recording medium. It is characterized by providing a position adjustment mechanism for transferring a set amount to.

"Operation" According to the above configuration, the optical detection means is moved by a set amount in the radial direction of the recording medium, so even if the moving distance is small, multiple minute spots along the approximately tangential direction are radially detected. The extended position information is traversed, so that the phase difference of the multiphase detection signals is arbitrarily adjusted.

"Embodiments" Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 and 2 are a plan view and a side view showing the mechanical structure of a first embodiment of the present invention. In these figures, reference numeral 25 denotes a support member fixedly provided on the main body of the apparatus, and two mutually parallel guide shafts 26a and 26b are attached to this support member 25 in parallel to the radial direction B of the disk 1. ing. A guide plate 27 is movably supported by these two guide shafts 26a and 26b, and further, an optical pickup 6, which will be described later, is rotatably supported by the guide plate 27 around its main laser beam optical axis J. Supported. As a result, the optical pickup 6 moves in the radial direction B of the disk 1.
It is supported so as to be movable to and rotatable in the direction of arrow R about the main laser beam optical axis J.

Further, a support member 25 is provided on one end surface of the guide plate 27.
The tip of an adjustment screw 29 screwed into the guide shaft 26 is in contact with the tip, and the other end surface is biased by a spring 28 provided at the end of the guide shafts 26a, 26b. As a result, the guide plate 27 can be moved to an arbitrary position along the radial direction by rotating the adjustment screw 29 in the forward direction to tighten it, or by rotating it in the reverse direction. Furthermore, one end surface of the optical pickup 6 has a main laser beam optical axis J.
A gear 30 having teeth formed along an imaginary circumference centered at is attached, and both ends of a worm gear 31 that is screwed into this gear 30 are connected to bearings 27a, 27a provided on one end surface of the guide plate 27. They are each supported rotatably and with axial movement restricted. A hole 27c is formed in the side of this bearing 27a.
A groove 31a carved in the end face of the worm gear 31 is exposed from this hole 27c. By rotating this groove 31a with a screwdriver or the like, the optical pickup 6 can be adjusted to any rotational position around the main laser beam optical axis J.

As a result, as shown in FIG. 3, the laser beam irradiated from the optical pickup 6 creates sub-laser spots S L S , main laser spots on the disk l in a row along the substantially tangential direction of the disk l. When MLS and sub-laser spot SLI are irradiated, first,
Adjust each spot to disk 1 by turning the adjustment screw 29.
After performing rough adjustment by moving in the radial direction B of With such a simple mechanism, the positional relationship (phase difference) of each spot can be adjusted arbitrarily.

Here, when compared with the conventional technology in which each spot is transferred only in the tangential direction of the disk l, each spot is moved only in the tangential direction of the disk l.
Since the lands 2a and pits 2b recorded on the disk 1 are radial, that is, fan-shaped, the positional relationship between the sub-laser spots SLS and SLS (
The phase difference) can be adjusted quickly and easily, and furthermore, by rotating around the main laser spot MLS, the adjustment can be performed with even higher precision.

Next, land 2a and pit 2b recorded on disk l
And each laser spot MLS, SLS.

In order to clarify the function and positional relationship of the SLS, the electrical and optical configuration of the above-mentioned embodiment will be explained.

In FIG. 4, l is a disk, and its moving direction M
at equal intervals along, i.e. 1. By forming a transparent plastic substrate 2 in which convex land portions 2a and concave pit portions 2b are alternately formed at a ratio of I, and by vapor-depositing a thin aluminum film on the surface of this substrate 2 on which the bit portions 2b are formed. It consists of a reflective film 3 formed and a transparent plastic protective film 4 formed to cover the reflective film 113. As shown in FIG. 5, this disk l is attached to a rotating shaft 5 that is rotatably supported by a hall bearing (not shown), and lands are placed at equal and minute intervals along the rotational direction M. The portion 2a and the bit portion 2b are formed radially.

At the reference position, which is the origin of the disk l, the reflection 113 on the land portion 2a is removed to form a reflective film removed portion 3a, as shown in FIG. In this reflective film removed portion 3a, the reflectance is approximately 0%, and the reflectance is significantly different from other portions.

6 is an optical pickup, which includes a semiconductor laser 7, a collimating lens 8, a grating plate (diffraction grating) 9,
Half mirror IO1 objective lens 11° condensing lens 12,
It is composed of a nolindrical lens 13 and a photodetector 14.

When the semiconductor laser 7 is driven by the laser drive circuit 15 and emits a laser beam LB, this laser beam LB is collimated by the collimator lens 8 and then passed through the grating plate 9 to the half mirror.
10, the optical path is bent at right angles by this half mirror 10 and guided to the objective lens 11, and further,
The objective lens 11 condenses the light into a minute spot and irradiates it onto the disk l.

In reality, the laser beam LB is divided into three laser beams by the action of the grating plate 9, and as shown in FIG. SLS and SLS occur. In this case, the laser spots SLS, , MLS, SLS,
are arranged in a line in this order.

Here, the laser beam LB is directed to the bit portion 2b of the disk l.
When the light is irradiated to the objective lens 11, the amount of reflected light incident on the objective lens 11 is reduced due to the interference effect of the reflected light from the bit portion 2b and the land portion 2a. On the other hand, the bit part 2b and the bit part 2b
In the land portion 2a between the two, all the reflected light enters the objective lens 11, so the amount of reflected light increases.

The laser beam B reflected by the disk 1 is again guided to the half mirror 10 via the objective lens 11, but this time it travels straight through this half mirror 10 and is guided to the condenser lens 12. The light is focused by the cylindrical lens 13 and reaches the photodetector 14.

As shown in FIG. 6, this photodetector 14 is roughly divided into three detection parts 14a, 14b, and I4c, and the central detection part 14b is further divided into four parts. Each of these detection ff114a-14c is constituted by, for example, a photodiode, and outputs detection signals Sa to Sc at a level corresponding to the amount of received light, respectively.

Then, the main laser beam M reflected by the disk 1
LB reaches the central detection section +4b, and the sub laser beams SLB and SLB reach the detection K I 4 a and 14c, respectively, so the detection signal 5a is output from each detection f = I 4 a to 14c, respectively. =Sc is a level corresponding to the amount of reflected light of each laser beam. These servo systems are originally intended to obtain a servo error signal that is necessary for performing focusing servo and tracking servo of the objective lens 11, but a description of these servo systems will be omitted.

Returning to FIG. 4 again, the detection signal Sa output from the detection section 14a of the photodetector 14 is supplied to comparators 16 and 17, respectively. The humpator 16 compares the detection signal Sa with a preset threshold level SL, and detects that the detection signal S8 is the threshold level SL,
When the above is reached, the judgment signal C1 of the °H" level is output. The conoperator 17 also compares the detection signal Sa with a preset threshold level SL, and determines whether the detection signal Sa is the threshold level. When the hold level SL is lower than or equal to the hold level SL, an "H" level determination signal CA is output.These determination signals C2 and C! are outputted as a relative position pulse Pr via the OR gate 18, and a determination signal C4 is output.
is output as an absolute position pulse Pa.

On the other hand, the detection of the photodetector 14! ! The detection signals sb and Sc outputted from 14b and 14c, respectively, are waveform-shaped by predetermined threshold levels in waveform shaping circuits 20 and 21, and are supplied to the direction determination circuit 23 as pulse signals P and P. Ru.

The direction determination circuit 23 determines the rotational direction of the disk 1 based on the phase relationship between the pulse signals Pl and P, and outputs a direction determination signal Pc.

In the above configuration, as the disk 1 rotates, the portion irradiated with each laser spot changes, and when the bit portion 2b of the disk 1 is irradiated, the reflected light from the bit portion 2b and the land portion 2a changes. Objective lens 11 due to interference effect
In the land portion 2a between the pit portions 2b, all of the reflected light enters the objective lens 11, so the amount of reflected light increases. As a result, substantially sinusoidal detection signals 5a to 9c having mutually different phases are output from each detection unit 14a=14c of the photodetector 14, as shown in FIGS. 7(a) to 7(c). .

Among these signals, the detection signals Sb and Sc are waveform-shaped by waveform shaping circuits 20 and 21, respectively, and are converted into pulse signals P1.
．． After being made into Pt, it is supplied to the direction determination circuit 23. Then, this direction determination circuit 23 outputs pulse signals P and P!
The rotation direction of the disk 1 is determined based on the phase relationship. For example, if the pulse signal P is ahead of the pulse signal P, it is assumed that the disk l is rotating in the normal direction, and a direction determination signal Pc of "H" level is output, and conversely, the pulse signal P, If the phase is advanced, the disk l
Assuming that the direction is reversed, the “L” level direction determination signal P
Output c.

On the other hand, at the reference position that is the origin of the disk l, the reflective film 3 on the land portion 2a is removed to form a reflective film removed portion 3a, as shown in FIG. In this case, the laser beam LB is transmitted without being reflected. Therefore, each time the reflective film removal section 3a passes over the laser spot, each detection signal 5a-3
c is originally a land [
In response to an increase in the amount of reflected light from 2a, what should have changed from level to mountain range changes to a deep valley shape as shown by the solid line in FIG. 2(d).

Therefore, as shown in FIG. 7(d), the comparator 16
Detection signal Sa and threshold hold level SL
, and when the detection signal Sa exceeds the threshold level SL, as shown in FIG.
1 is output. As a result, the land portion 2 of the disk l
A determination signal C1 is output, which is a repetitive pulse corresponding to a change in the amount of reflected light that occurs based on the interference effect of light between a and pit [2b. Further, as shown in FIG. 7(d), the detection signal Sa and the threshold level SL are compared by the comparator 17, and when the detection signal Sa is below the threshold level SL, the seventh
As shown in the figure (f), the comparator 17 outputs an "H" level determination signal C2.

As a result, the reflective film removed portion 3a at the reference position of the disc l
A determination signal C7 is obtained corresponding to a change in the amount of reflected light that occurs based on the difference in reflectance from other parts of the disc l, and this determination signal C3 is output as an absolute position pulse Pa indicating the reference position of the disc l.

Further, the OR gate 18 outputs the logical sum of the determination signals CI and C1 as a relative position pulse Pr.

Here, by providing a counter that sequentially counts the relative position pulses Pr, switches between up-counting and down-counting according to the direction determination signal Pc, and is reset by the absolute position pulse Pa, the count value of this counter is It is obtained as an absolute rotation angle with the reference position as the origin.

In addition, in the above-mentioned first embodiment, the case where the disk 1 is recorded with positional information using an uneven shape consisting of land portions 2a and pit portions 2b is explained as an example. A similar effect can be obtained by using a disk on which position information is recorded by printing different radial patterns.

"Effects of the Invention" As explained above, according to the present invention, the optical detection means is transported in the radial direction of the recording medium, so even if the transport distance is small, the optical detection means can be transported along the substantially tangential direction. A plurality of minute spots cross the radially extending position information, and as a result, the effect that the phase difference of the multiphase detection signals can be arbitrarily and easily adjusted is obtained.

[Brief explanation of the drawing]

1 and 2 are a plan view and a side view showing the mechanical configuration of an embodiment of the present invention, FIG. 3 is a plan view showing an enlarged part of the disk of the embodiment, and FIG. 4 5 is a block diagram showing the electrical and optical configuration of the embodiment; FIG. 5 is a plan view showing the configuration of the disk of the embodiment; FIG. 6 is a plan view showing the configuration of the photodetector of the embodiment; Figures 7 (a) to (g) are waveform diagrams of various parts to explain the operation of the same embodiment, Figure 8 is a perspective view showing the configuration of a conventional optical rotary encoder, and Figure 9 is a conventional incremental encoder. FIG. 10 is a plan view showing the structure of another conventional disk.・Disk (recording medium), ・Land portion (position information), pit portion (position information), ・・Optical pickup (optical detection means), 6a, 26b・
...Guide shaft, 7..Guide plate, 8. Spring, 9..Adjustment lever, 0..Gear, l.Worm gear (position adjustment mechanism). Figure 4-211 Figure 6 Figure 7

Claims (1)

[Claims] A disc-shaped recording medium is rotatably supported and has positional information recorded radially extending in a radial direction at predetermined intervals in the circumferential direction of the recording surface, and a laser beam emitted from a semiconductor laser is directed along a substantially tangential direction. an optical detection means that focuses light onto a plurality of minute spots and irradiates the recording surface of the recording medium, receives each of the reflected lights, and outputs a multiphase detection signal corresponding to each amount of reflected light; The optical rotary encoder detects the amount of rotational displacement of the recording medium based on each of the detection signals, further comprising a position adjustment mechanism that moves the optical detection means by a set amount in a radial direction of the recording medium. An optical rotary encoder featuring: