JPH01100609A - Optical position controller - Google Patents

Abstract

PURPOSE:To make the position control of the titled controller more accurate and to simplify its constitution by differentiating the slit widths of a first plate and a second plate, leveling the maximum level of a light receiving output, and obtaining the reference maximum level in sampling signals with different phases. CONSTITUTION:A plate 60 and a plate 90 have different split widths, for a light receiving outputs phi0 and phi90, whose phases are mutually dislocated at 90 deg., the maximum and minimum level parts are shaped in a flat waveform, a maximum tilting point P0 or P90 of one light receiving output corresponds to the position of a maximum level part k90 or k0 of the other light receiving output. There, when the one light receiving point is sampled at the maximum tilting point of the other light receiving output, and controlled by a second control system so that the value may be at the prescribed level, the effect due to the temperature drift of the light receiving outputs phi0 and phi90 is eliminated, the maximum level of the output phi0 and phi90 is made into a prescribed level VREF, and the aimed position of the position control by a first control system is always made correct.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical position control device suitable for use, for example, in tracking control of a head of a disk device.

[Summary of the invention]

In this invention, two flat plates with slits formed at a predetermined pitch are provided facing each other, one of which is moved together with a moving object, and light transmitted through these two plates is received to generate signals with a 90° phase difference. is obtained from a light-receiving element, and the position of the point at a predetermined level of the slope portion of one output signal of this light-receiving element is controlled as a target point, and the maximum level of the output signal of this light-receiving element is controlled to be constant. In order to compensate for the temperature by making use of the phase relationship between the signals from the light receiving element and by making the widths of the slits of the two flat plates different, it is possible to provide an optical sensor section for level reference. It is designed so that it is not necessary.

[Conventional technology]

For example, it has been known to use an optical sensor as a positional sensor for tracking control of a magnetic disk (see, for example, Japanese Patent Application No. 55533/1982).

FIG. 4 shows an example of the head movement control section of this magnetic disk device.
It is designed to rotate in the direction of.

A plurality of concentric recording tracks are formed on this magnetic disk (1).

(2) is a magnetic head, which is attached to the arm member (3). The arm member (3) is driven by, for example, a stepping motor (4) and is rotated in the direction shown by arrow R, thereby causing the head (2) to move towards the magnetic disk +1).
is moved in a direction across the upper recording track.

The magnetic head (2) is stopped on a track on the magnetic disk (1) and the disk +11 rotates to write and read information.

Further, the arm member (3) is provided with a photo encoder (5) as a speed and position detection sensor for detecting the moving speed and position of the magnetic head (2) on the disk (1). This photo encoder (5) includes, for example, an optical scale (6) attached to an arm member (3), and a reticle (9) arranged to face and overlap this optical scale (6) and provided at a fixed position. ), and a light emitting section (7) and a light receiving section (8) arranged at fixed positions so as to sandwich the optical scale (6) and reticle (9).

As shown in FIG. 5A, the optical scale (6) has slits S having a width of d and successively formed with a pinch of 2d so that the width of the light-shielding part and the light-transmitting part is 1:1.

On the other hand, Fig. 5B shows a reticle (9), and on this reticle (9) side, the pinch is 2d1, the slit width is d, and it is the same as the scale (6), but the phase is sequentially shifted by 90°.
Seed slit groups S^, SB, S^, SB are formed. And this slit group S^, SR, SA
, The light receiving section (8) has four light receiving elements L corresponding to the SR.
A, LB, LA.

LB is provided as shown by the broken line in FIG. 5B.

In this case, the pitch of tracks on the magnetic disk (11) is d/2.

Therefore, the head (2) is rotated by the rotation of the arm member (3).
) moves, the optical scale (6) moves accordingly, and the light receiving section (8) outputs a signal A with a frequency corresponding to the moving speed of the head (2), as shown in FIG.
, a signal B having a phase difference of 90° from this signal A, and further signals A and B having opposite phases to the signals A and B, respectively, are obtained.

The moving speed of the head (2) can be detected from the frequency of any one of the signals A, B, A, and B, and the moving direction of the head (2) can be detected from the phase leading and lagging relationship between the signals A and B. can. In this case, signals A and B.

Since the linearity of A and B is good, for example, these signals A and B
, A, H level 1/2 of the maximum level Ve point Tl
, T2, T3, and T4 correspond to four track positions on the disk (1), respectively. Therefore, signal A,
These points T1.B, A, B. T2, T3.

Tracking control of the magnetic head (2) is performed using T4 as the target point.

By the way, the point T1. of the above-mentioned level Ve. T2゜T3. T
Phase 4 will always be the correct target tracking phase if the maximum levels of signals A, B, A, and B do not change. However, the output level of the light-receiving element of the optical sensor fluctuates due to temperature changes, and for example, even though the solid line in Figure 7 is the correct output level, it becomes like the broken line in the figure. The target position of tracking control changes from the correct position Po to the incorrect position P1, making it impossible to perform correct tracking servo.

Therefore, in order to receive all the light transmitted from the light source through the optical scale (6), the reticle (9) is provided with a window S.
RI! F is provided, and a light receiving part LREF corresponding to the window part 5REF is provided in the light receiving part (8), and the light receiving part LA,
LB.

A reference sensor that obtains a light receiving output corresponding to the maximum level of the light receiving output of LA and LB is formed, and the light emitting brightness of the light source is controlled so that the light receiving output of this reference sensor becomes a constant value, and the light receiving parts LA, LB, LA.

The maximum value of the light receiving output of the LB is controlled to always be a predetermined constant value.

[Problem that the invention seeks to solve]

However, this method has the disadvantage that a reference sensor for detecting the temperature drift of the optical sensor must be provided separately.

In view of this point, it is an object of the present invention to provide an optical sensor capable of temperature compensation without providing a reference sensor.

[Means for solving problems]

In this invention, the first flat plate (60) has the light shielding part and the light transmitting part formed at a predetermined pitch and the width ratio thereof is 1:1; The width ratio of the widths of the two plates formed at the above pitch is 1ax (x ``q 1 ), and the light shielding part and the light transmitting part are opposite to the first flat plate (60), and as the movable body moves, the light shielding part and the light transmitting part a second flat plate (90) that is movable relative to the first flat plate (60) in the direction of forming the part; and a light emitting source (IIA), (IIB).
The light from this light source is transmitted to the first and second flat plates (60).
and (90), and two light receiving elements (12^) (12B) that obtain light receiving outputs with a phase shift of 90" from each other.
and a first control system that controls the position of the moving body with the target being the reference level point T1 or T2 of the light receiving output of one of the two light receiving elements (12^) (12B), and the two light receiving elements. (12^) A second control system that controls the level of the other light reception output of (12B) at a phase point substantially the same as the reference level point of the output of the above-mentioned negative light receiving element to a predetermined level VREF.

[Effect]

Since the slit width of the first flat plate, such as an optical scale, and the slit width of the second flat plate, such as a reticle, are different, the received light outputs φ0 and ψ9°, which have different phases, have the maximum and minimum level portions as shown in FIG. It becomes a flat waveform. Even if there is a temperature drift, the phase difference of 90° between the received light outputs ψ0 and ψ9o does not change. Therefore, the maximum slope point Pa or Pso of one light reception output corresponds to the position 9o or ko at the maximum level of the other light reception output. Therefore, when the received light output of one side is sampled at the maximum slope point of the other received light output and the second control system controls the sampled value to be at a predetermined level, the received light output φ0. The influence of temperature drift on ψ9o is removed, and the output ψ0. The maximum level of ψ9o is the predetermined level V
It becomes RE r.

Therefore, the target position of position control in the first control system is always the correct position.

〔Example〕

FIG. 1 shows an example in which the present invention is applied to the above-mentioned tracking control of a magnetic disk.For the sake of simplicity, this example assumes that the received light output has two phases having a phase difference of 90'' from each other.

Figure 2 shows the structure of the photoencoder in this example, in which the optical scale (60) that moves with the rotation of the arm (3) has a slit S with a width d and a pitch of 2d (
d is twice the track pitch of the magnetic disk), as described above.

On the other hand, in this case, the reticle (90) is provided with a slit group So(!:390) to obtain two-phase output.
Although the formation pitch remains unchanged at 2d, the width of the slit is set to a width d1 narrower than the width d of the conventional slit shown by the broken line. The scale (60) and the reticle (90) are arranged so that their slit positions overlap in the vertical direction, but in this example, the longitudinal direction of the slit on the reticle (90) side is aligned with the scale ( It is made longer than the longitudinal direction of the slit 60), so that there is an adjustment margin for the positional deviation of the slit in the longitudinal direction.

In addition, in FIG. 2, (IIA) and (12A) are light emitting diodes and phototransistors for light reception to obtain zero-phase light reception output, and (IIB) and (12B) are 90°
These are a light emitting diode and a phototransistor for obtaining phase light reception output.

As mentioned above, since the width of the slit S is different between the scale (60) and the reticle (90), the scale (60) and the reticle (90) have different widths.
0), the received light outputs ψ0 and ψ9o obtained from the phototransistors (12A) and (12B) are the third
As shown in the figure, the maximum and minimum level portions are flat waveforms.

This flat maximum level portion corresponds to the phase point portion of the target position that is the reference voltage Vθ of the other light reception output having a phase difference of 90°.

The light emitting diodes (IIA) and (IIB) are connected in series as shown in FIG. Supplied to the series circuit. In this case, as will be described later, the control signal EC from the controller (10) is converted into an analog voltage by the D/A converter (15) and supplied to the operational amplifier (13), and the control signal EC from the operational amplifier (13) is An output voltage corresponding to the voltage is obtained and applied to the base of the transistor (14). As a result, a current corresponding to the signal EC flows from the power supply Vcc through this transistor (14) to the light emitting diode (IIA).
<118). Therefore, the current flowing through the light emitting diodes (IIA) (IIB) is controlled by the control signal EC from the controller (10). In other words, light emitting diodes (IIA) (IIB
) is controlled.

The light from the light emitting diode (11^) and CIIB) is
The light is received by the phototransistors (12A) and (12B)C through the slit groups So and Sso of the optical scale (60) and reticle (90), respectively.

And phototransistors (12A) and (12B)
The received light outputs ψ0 and ψ9o are supplied to a switch circuit (16). This switch circuit (16) has outputs ψ0 and ψ9
This is used to switch which of the signals o is to be subjected to tracking position control, and is controlled by a switching signal from the switching signal generating means (105) of the controller (10). The light receiving output obtained from one output end of this switch circuit (16) is then output from the operational amplifier (
17). On the other hand, the reference level ordering means (101) of the controller (10)
The reference signal from is converted by the D/A converter (18) into a voltage Ve that is 1/2 of the maximum level of the received light output, and this voltage Ve is supplied to the other input terminal of the operational amplifier (17). And this operational amplifier (17)
, the light receiving output from the switch circuit (16) and the voltage Va
You can obtain the voltage difference between This difference voltage is the amplifier (19
) through the arm drive motor (4) shown in l.
) and is controlled so that the output of the operational amplifier (17) becomes zero, that is, the head (2) is brought to the tracking target value WT1 or T2 shown in FIG. .

At this time, from the other output end of the switch circuit (16), a received light output is obtained which has a phase difference of 90 degrees from the received light output obtained from the one output end, and in this example, this is used for temperature drift compensation. Ru. In other words, this switch circuit (
The other output of 16) is an operational amplifier (
20). In addition, the voltage Va from the D/A converter (18) is applied to the level shift circuit (
21) to double the voltage, that is, the maximum level of the set standard of the light reception output V RE F, and this voltage V RE r is supplied to the other input terminal of the operational amplifier (20). The operational amplifier (20) obtains the voltage difference between this voltage V RE F and the output held at the other output terminal of the switch circuit (16), which is converted into a digital signal by the A/D converter (22). , is supplied to the sampling means (102) of the controller (10).

On the other hand, the light reception output from one output end of the switch circuit (16) is converted into a digital signal in the A/D converter (23), and the digital signal is sent to the controller (10).
is supplied to the sampling signal generating means (10). This sampling signal generating means (104) generates a sampling signal when the received light output becomes the voltage ve as shown in FIG.

Then, this sampling signal is transmitted to the sampling means (1
02) and the digital signal from the A/D converter (22) is sampled.

As is clear from Fig. 3, the voltage Vθ of one light receiving output
, the other received light output has a flat maximum level portion.

Therefore, the difference between the maximum level of the received light output and the reference maximum level V RE F is obtained from the sampling means (102), and the output of this difference is sent to the light emission brightness control means (103).
is supplied to This light emission brightness control means (103
), the emission brightness control signal EC is obtained, and this is the D/A
converted into an analog voltage by a converter (15);
As described above, the current supplied to the operational amplifier (13) and flowing to the light emitting diodes (IIA) (IIB) is controlled. This control loop then controls the light emitting diode (
The light emission brightness of IIA) (IIB) is controlled so that the maximum level of the light reception outputs ψ0 and ψ9o becomes V RE F.

Therefore, the target position by tracking control is correctly the desired point T1 or T2.

In addition, in the initial stage of control, the maximum level of the light receiving output is not V RE F due to temperature drift, and the light receiving output level ■θ is at point Po or Pso in FIG.
It is considered that the sampling means (102
) is a problem. However, in the case of the present invention, the received light output reaches its maximum level not at one point like a triangular wave, but at a flat portion of a predetermined width. Therefore, even if the sampling position changes within the width of this flat portion, the control that makes the maximum level equal to the reference value V RE F functions correctly.

Incidentally, since track seeking from the current trunk position to the target track position is actually performed using the received light output, the above-mentioned temperature drift of the photo encoder is compensated for during this seek as well.

Note that the controller (10) in the example of FIG. 1 can be easily realized using a microcomputer.

In addition, in the example shown in Fig. 1, the maximum level of the light receiving output that is 90 degrees out of phase with the light receiving output used for the tracking servo is set as the reference value V RE F, but the maximum level of the light receiving output used for the trunking servo is The reference value V RE
It may also be controlled to be F.

〔Effect of the invention〕

According to this invention, by making the widths of the slits of the optical scale and the reticle different, the part where the received light output is at its maximum level is made into a flat part of a predetermined width, and the signal number obtained from the received light output with a phase difference of 90 degrees from this is made into a flat part of a predetermined width. This flat part is sampled using the signal so that the maximum level of the received light output becomes the reference maximum level, so even if there is a temperature change, the slope part of the received light output and the target phase position obtained by comparing it with the reference level will be maintained. There is no change and accurate position control is possible.

Further, in order to control the maximum level of the received light output to the reference maximum level, there is no need to use a conventional reference sensor, and the configuration of the photo encoder can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a diagram showing an example of its essential parts, FIG. 3 is a diagram showing a received light output waveform, and FIG. 4 is an example of a head position control mechanism. 5 is a diagram showing a prior example of a photo encoder, FIG. 6 is a diagram showing its light reception output, and FIG. 7 is a diagram for explaining temperature drift of the light reception output. (IIA) (IIB) is a light emitting diode, (12^
) (12B) is a phototransistor, (17) and (2
0) is an operational amplifier constituting a comparison circuit, and (103) is a light emission brightness control means.

Claims (1)

[Claims] a) a first flat plate in which a light shielding part and a light transmitting part are formed at a predetermined pitch and a width ratio of both is 1:1; b) a light shielding part and a light transmitting part are formed at the above-mentioned pitch, and the ratio of the widths thereof is 1:x (x≠1), and the light-shielding portion is opposed to the first flat plate, and as the movable body moves, the light-shielding portion,
a second flat plate that is movable relative to the first flat plate in the direction of forming the transparent portion; c) a light emitting source; and d) transmitting light from the light emitting source to the first and second flat plates. two light-receiving elements that receive light through the light-receiving element and obtain light-receiving outputs that are out of phase with each other by 90 degrees; f) a second control system that controls the level of the light reception output of the other of the two light receiving elements at a phase point that is substantially the same as the reference level point of the output of the one light receiving element to a predetermined level; An optical position control device equipped with a control system.