JPS63111418A - Rotary encoder - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rotary encoder that uses a semiconductor laser to detect rotational displacement.

(Summary of the Invention) The present invention supplies a plurality of irradiation beams from a laser light source to a plurality of photodetectors via a disc-shaped encoder plate on which a detection pattern is continuously formed in the circumferential direction. In a rotary encoder that detects the amount of rotational displacement by obtaining a plurality of signals with phase differences from a plurality of photodetectors, by providing a means for sending a laser light source and a plurality of photodetectors in the tangential direction of the encoder plate. , the phase difference between signals from a plurality of photodetectors can be easily adjusted to an arbitrary phase difference.

[Conventional technology]

In a rotary encoder that detects the amount of rotational displacement using a semiconductor laser, it has been considered to improve the discrimination of rotational direction and the resolution by using a plurality of irradiations and HM. FIG. 3 shows an example.

In the figure, (1) is a disk constituting an encoder plate. A striped detection pattern extending in the radial direction is formed continuously in the circumferential direction on the front surface of the disk +11. First, striped pit portions (2A) and mirror surface portions (2B) are alternately formed at a ratio of, for example, 1:1.

Further, (4) is a semiconductor laser constituting the optical big amplifier (3), and the laser beam LB from this semiconductor laser (4) is transmitted to a grating plate (diffraction grating) (5).
) and is supplied to the collimating lens (6) to be made into parallel light beams. The laser beam LB from this collimating lens (6) is supplied to an objective lens (9) through a polarizing beam splitter (7) and a quarter-wave plate (8). Then, the laser beam LB is focused by this objective lens (9) so that it is focused on the surface of the disk (1).

In reality, since the grating plate (5) is arranged, the laser beam LB is divided into three, and the disk! In addition to the main beam LBn+, two sub-beams L B sl 1 L B s2 strike the surface 1). FIG. 4 shows this state, in which the laser beams LBst and LB+w+LBS2 are lined up in this order. In FIG. 4, AA' indicates the center line.

Here, the laser beam LB (LBm, LI3S1
When the ゜LBS2) hits the pit part (2A), it diffuses around and does not return to the objective lens (9), but the mirror part (2B
), it is specularly reflected and most of it returns to the objective lens (9).

The laser beam LB reflected by the mirror surface (2B) is 1/4
It passes through a wave plate (8) and is supplied to a polarizing beam splitter (7). The laser beam LB reflected by the polarizing beam splitter (7) is focused by a condenser lens (10) and a cylindrical lens (11), and is supplied to a photodetector (12).

FIG. 5 shows the light receiving part pattern of this photodetector (12). (12a) to (12d) are four-divided detectors, and the main beam LBm reflected by the disk (1) is supplied to these four-divided detectors. Furthermore, sub-beams LBsx and LBs2 reflected by the disk +1) are supplied to (12e) and (12f).

Here, when the laser beam LB is not focused on the surface of the disk (1), a four-part detector (12a
) ~ (12d) The beam spot of the main beam LBrs on (12d) becomes an ellipse. Therefore, the signal difference between the diagonals of the four-divided detectors (12a) to (12d) becomes the focus error signal 81F. Therefore, the output signals of the four-divided detectors (12a) to (12d) % S a ”
S d is supplied to the arithmetic circuit (14) via amplifiers (13a) to (13d), respectively, and is expressed as (Sa+5c)−(
Sb + Sd) is calculated and the focus error signal e
F is obtained. This error signal ep is supplied to the phase compensation circuit (15
) to the driver (16) of the focus coil (17).
). This controls the position of the objective lens (9) so that the laser beam LB is focused on the surface of the disk (1).

In addition, four detectors (12a) to (12d)
The output signals Sa"Sd of
13d.

is supplied to the arithmetic circuit (1 day) via (Sa + Sd
-(Sb +Sc) is calculated. The output signal is then supplied to the waveform shaping circuit (19), and the output terminal (
20), a detection signal SA (square wave) of a pattern on the disk (11) is obtained by the main beam LBm.

Further, the output signal Se or Sf of the detector (12e) or (12f) is supplied to the waveform shaping circuit (21) via the amplifier (13e), and the output terminal (22) is connected to the disk (1) by the sub-beam LI3S1 or LBS2.
The detection signal SB (square wave) of the above pattern is obtained.

Although not mentioned above, the orientation of the rows of laser beams LBSL, LBm, and LI3j2 on the surface of the disk (1) is radial direction (direction of center line AA') so that the detection signals SA and SB have a predetermined phase. [Problem to be solved by the invention]) In the example of FIG. 3, the detection signal SA and
Laser beams LBSII LBm, LBS2 on the surface of the disk (1) so that SB has a predetermined phase.
The orientation of the rows is adjusted by tilting the grating plate (5) or by tilting the entire pickup (3).

Therefore, mounting the pickup (3) requires extremely high precision technology. That is, the detection signal SA
It was not easy to adjust the phase difference between SB and SB.

In view of this point, the present invention enables the phase difference between a plurality of detection signals to be easily adjusted to an arbitrary phase difference.

[Means for solving problems]

The present invention provides a plurality of irradiation beams L B m + L B
Laser light source (41, (51
, a disc-shaped encoder plate (1) on which a detection pattern extending in the radial direction is continuously formed in the circumferential direction, and a plurality of irradiation beams L B ts via the encoder plate (1).
+L B ss * A plurality of photodetectors (12a) to (12f) that receive LBS2 and a laser light source (4
), (51 and a plurality of photodetectors (12a) to (12f)
) in the tangential direction DT of the encoder plate (1).

Then, the laser light source (4) is sent to the laser light source (4) by the sending means (31) to (34) so that the detection signals SA and SB from the plurality of photodetectors (12a) to (12f) have a predetermined phase difference.

(5) and a plurality of photodetectors (12a) to (12f) are sent by a predetermined amount.

[Effect]

In the above configuration, the laser light source (41, (5) and the plurality of photodetectors (12a) to (12f) are connected to the encoder plate (1
) in the tangential direction DT, the laser beams LBst, LB at the surface of the encoder 'M11t+ are
The direction of the row m +L B s2 changes by a predetermined angle with respect to the radial direction of the encoder plate (1). Thereby, the detection signals qsA and SB from the plurality of photodetectors (12a) to (12f) are adjusted to have a predetermined phase difference.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, parts corresponding to those in FIG. 3 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

In the figure, (3) is a pink-up including a semiconductor laser (4), a photodetector (12), etc., and a base (31).
). Further, a guide shaft (32) is attached to one end of the base (31), and a guide shaft (32) is attached to one end of the base (31).
is slidable along the guide shaft (32) in the tangential direction DT of the disk (11).A feed screw (33) is attached to the other end of the base (31), and the feed screw (33) is attached to the other end of the base (31). 33) is rotated by the motor (34), thereby moving the base (31) in the tangential direction DT.

The rest of the structure is the same as the example shown in FIG.

In this example, when the base (31) is moved in the tangential direction DT as shown by the two-dot chain line in FIG. 1, the pink-up (3) also moves in the tangential direction DT, and the laser beam LBs1. The column LBm + LBS2 is the second
For example, it moves from the position shown in FIG. L1 to the position shown in L2. At this time, laser beam LBs1. LBm+L B The direction of the S20 row changes by a predetermined angle with respect to the radial direction of the disk (1). And the value of this change angle is the pick amplifier (3)
The amount of movement of Uchi laser beam LBSI.

113m, which can be arbitrarily changed depending on the amount of movement of the LBs2 column.

Therefore, in this example, by moving the base (31) and therefore the pickup (3) in the tangential direction DT of the disk (11), the phase difference between the detection signals SA and SB (see Fig. 3) is arbitrarily adjusted. be able to.

For example, main beam LI3m and sub beam L B s
z rLBS2 distance is 20 μm 1 disk + 1) is 1
For a disc with a circumference of 250,000 pulses, and the main beam LBm is located 5On+m from the center of the disc (11), the laser beams LBs1.LB11 are required to have a 90° phase difference between the detection signals SA and SB. .It is sufficient to shift the row of LBS2 by about 0.6 mm from the position of Ll.

In reality, an arbitrary phase difference can be set by adjusting the amount of movement of the base (31) and thus the pickup (3) while observing the detection signals SA and SB with a measuring instrument.

As described above, according to this example, there is no need for sophisticated techniques such as those required in the past to adjust the mounting angle of the grating plate (5) or the pickup (3), and it is possible to easily set an arbitrary phase difference. can.

The feeding means of the big amplifier (3) in the above-mentioned embodiment is just an example, and any means that can move the pickup (3) in the tangential direction DT of the disk (11) may be used.

In addition, multiple irradiation beams LBsz, LBm, LBS2
Although the grating plate (5) is used to obtain this, other methods such as "ζ" using a plurality of semiconductor lasers may also be used.

〔Effect of the invention〕

According to the present invention described above, by sending a laser light source and a plurality of photodetectors in the tangential direction of the encoder plate, the phase difference of the detection signals from the plurality of photodetectors can be adjusted to an arbitrary phase difference. No technique is required and any phase difference can be easily set.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a diagram for explaining the same, Fig. 3 is a block diagram of an example of a rotary encoder, and Figs. 4 and 5 are for explaining the same. This is a diagram. (11 is a disk, (3) is a pickup, (4) is a semiconductor laser, (5) is a grating plate, (12
) is a photodetector, (31) is a base, (32) is a guide shaft, (33) is a feed screw, and (34) is a morph.

Claims (1)

[Scope of Claims] (a) a laser light source that generates a plurality of irradiation beams; (b)
) a disc-shaped encoder plate on which a detection pattern extending in the radial direction is continuously formed in the circumferential direction; and (c) a plurality of photodetectors that receive the plurality of irradiation beams via the encoder plate. (e) a sending means for sending the laser light source and the plurality of photodetectors in a tangential direction of the encoder plate, and (f) detection signals from the plurality of photodetectors have a predetermined phase difference. A rotary encoder characterized in that the laser light source and the plurality of photodetectors are fed by a predetermined amount by the feeding means.