Digital pulse circuit for processing successive pulses

Details Digital pulse circuit for processing successive pulses Digital pulse circuit for processing successive pulses

1988-05-04

1990-11-27

Shoop, Jr., William M.

Coded data generation or conversion

Digital pattern reading type converter

Optical

375 26, H03M 124, G01D 5245

Patent

active

049739590

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Technical Field
The present invention relates to a digital pulse circuit for maintaining required intervals between succession pulses and for suppressing noise in the pulses.
The present invention is particularly advantageously used for processing output pulses of high-resolution pulse encoder circuit.
2. Background Art
Pulse encoders are used for precise position detection in numerical control (NC) apparatuses or the like.
In general, two types of pulse encoders are known; an incremental type and an absolute type. Recently, incremental type pulse encoders having a simple constitution and functioning substantially as an absolute type, have been proposed. (Cf. JPA No.60-218027, and No.218029)
As shown in FIG. 1, the pulse encoder, as mentioned above has an rotating code disc 111 a pair of light-emitting devices 112a, 112b, a pair of light-detecting devices 113a, 113b, light-detecting device output amplifiers 114a and 114b, and a rectangular pulse generating circuit 120. The rotating code disc 111 is fixed to a rotation axle which rotates in correspondence with a motion of an object, and accordingly rotates with the rotation axle. The pulse encoder is provided with a pair of light-emitting devices 112a, 112b and the pair of light-detecting devices 113a, 113b are provided on opposite sides of the rotating code disc 111. And each of the light-emitting devices 112a, 112b and a corresponding one of the light-detecting devices 113a, 113b confronting each other with the rotating code disc 111 intervening therebetween. The circumference of the rotating code disc 111 is provided with alternative patterns of a translucent part and nontranslucent part. When the rotating code disc 111 rotates, a part of light emitted from each of the light-emitting devices 112a, 112b passes through the translucent parts of the rotating code disc 111 and is transformed to an A-phase signal and a B-phase signal respectively, where the phase of the B-phase signal differs by 90.degree. from the phase of the A-phase signal. These signals then transformed into sine wave signals D.sub.A and D.sub.E (as shown in FIG. 2A and FIG. 2B) at light-detecting device output amplifiers 114a and 114b, respectively. The A-phase signal leads the B-phase signal by 90.degree. in phase when the rotating code disc 111 rotates in the positive direction (as shown in FIG. 2A), and the B-phase signal leads the A-phase signal by 90.degree. in phase when the rotating code disc 111 rotates in the negative direction (as shown in FIG. 2B). The above sine wave signals D.sub.A and D.sub.E enter the rectangular pulse generating circuit 120. The rectangular pulse generating circuit 120, for example, is provided with a comparator for comparing the levels of input signals with a predetermined threshold level, and thus, rectangular pulses P.sub.A and P.sub.E, as shown in FIG. 2A and FIG. 2B, are obtained. Although not shown, in general, NC apparatuses are produced with a counter for counting the above rectangular pulses P.sub.A and P.sub.B, and thus are able to determine the direction of the rotation of the rotating code disc 111, as explained later. The counter in the NC apparatus detects the direction of the rotating code disc 111, namely, the counter determines the direction of motion of the object from the sign of the phase-difference between the above pulses P.sub.A and P.sub.B. At every timing of a leading (rising) edge and a trailing (falling) edge of the pulses P.sub.A and P.sub.E, the count at the counter in the NC apparatus is incremented if the positive direction is determined, and the count is decremented if the negative direction is determined.
FIGS. 3A-3H show the manner of counting at the counter in the NC apparatus as mentioned above. The counting (.+-.1) is made according to the level of one of the pulses P.sub.A and P.sub.B and the direction of the transition of the level (leading edge or trailing edge of the pulses) in the other of the pulses P.sub.A and P.sub.B.
To obtain information on the position of the above object from outputs of the p

REFERENCES:
patent: 4064504 (1977-12-01), Lepetit et al.
patent: 4443738 (1984-04-01), Breslow
patent: 4631520 (1986-12-01), Wingate
patent: 4700063 (1987-10-01), Hara

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