JPH0313816A - Rotary encoder - Google Patents

Abstract

PURPOSE:To obtain high resolution by projecting optical beams having the phase difference of 1/4 with respect to the phase difference of an optical disk in the neighboring circumferential direction, and detecting the reflected beams respectively. CONSTITUTION:A bit 21 has the width of about 0.6mum and the length of about 100mum in the direction of the radius. The bits 21 are formed in the circumferential direction on an optical disk at the interval of about 0.6mum in the neighboring pattern. Thus, a bit pattern 20 is formed. Laser light beams having three beam spots A, B and C are projected in an optical pickup from laser units with an LD driving circuit. The phases of the beam spots A, B and C are shifted by 90 deg. with the period of the bit 21 as 360 deg.. The two reflected light beams of A and B are detected and processed with optical sensors 35 and 36. Namely, the reflected light beams from the beam spots A and B are used as the pulse reflected light beams in two phases. The reflected light from the beam spot B can be used for focus control.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rotary encoder, and more particularly, to a rotary encoder that measures a rotation angle.

High-precision rotation angle measurement has been required in a wide range of fields such as precision machine tools and telescopes.

(Prior art) A conventional rotary encoder uses photographic technology to form a fixed slit pattern and a rotating slit pattern on a glass disk, and eliminates moire fringes that occur when light that has passed through the rotating slit pattern passes through the fixed slit pattern. is detected by a light receiving element to obtain a rotation detection signal.

[Problem to be solved by the invention]

In conventional rotary encoders, the slit pattern is formed using photographic technology, so in order to increase the number of slits in the rotary slit pattern for high-precision rotation angle measurement, the diameter of the glass disk must be increased. There was a problem that the encoder became larger and became a hexavalent encoder.

The present invention has been made in view of the above points, and an object of the present invention is to provide a rotary encoder that is small and that detects a rotation angle with high precision.

(Means for Solving the Problems) In the rotary encoder of the present invention, the optical disc has a plurality of pits extending in the radial direction recorded on the same circumference at equiangular intervals.

The playback device irradiates at least two light beams having a phase difference of 1/4 with respect to the phase difference in the circumferential direction of adjacent pits of the optical disc, detects each of the two reflected beams by the optical disc, and separates each other by 90 degrees. First and second with different phases
outputs a detection signal.

[Effect]

In the present invention, since an optical disk is used, a large number of pits, numbering several hundred thousand, can be formed on the circumference of a small optical disk with a diameter of about 100M, and these pits are detected with two light beams and the 90 degree phase is detected. By obtaining two detection signals with different numbers, one revolution of the optical disc can be detected with high precision at a viscosity four times as large as the number of pits. In addition, the rotating body, which was a constraint on miniaturization, can be made smaller as an optical disk! Therefore, the rotary encoder as a whole can be made smaller.

[Embodiment] FIG. 1 is a block diagram of an embodiment of a rotary encoder of the present invention, and FIG. 2 is a block diagram of an embodiment of an optical disk manufacturing equipment used in this rotary encoder.

First, to explain the manufacturing of optical discs, in Fig. 2, 10 is a diameter 100a++ of glass or acrylic resin, etc.
This is a write-once optical disc in which a tellurium-based medium is deposited on a transparent substrate of about 100 mL, and pits are formed by irradiating a laser beam to melt part of the medium. The rotation @11 is fixed on the optical disc 10.

The motor 12 is driven by the motor drive circuit 13 and rotates at a constant speed, for example, making one revolution every 250 seconds, and the optical disc 1
Rotate 0. The rotation shaft of this motor 12 has a reference FG.
A generator 14 is installed, for example 25 per revolution.
A rotation detection pulse of 10,000 pulses, that is, 1000 pulses per second, as shown in FIG. The signal is supplied to the IAvJ circuit 16 and the LD drive circuit 17, respectively.

The lens drive circuit 16 receives the rotation detection pulse from the rotation detection pulse as shown in FIG. 3(B).
A sawtooth wave tracking signal as shown in FIG. 1 is generated and supplied to the tracking circuit of the optical pickup 18. Also LD
The AI8117 circuit 17 outputs the rotation detection pulse from the rotation detection pulse in Figure 3 (C
) is generated to drive the laser diode of the optical pickup 18. This laser diode drive signal is a signal that sets the output of the laser diode as recording power when it is at H level, and as playback power when the output is at H level.

The optical pickup 18 emits a laser beam from a laser diode with a power corresponding to the level of the laser diode drive signal, and also sets a spot of the laser beam 10 in the radial direction of the optical disk 10 according to the level of the tracking signal.
Shift the intestine by approximately 0μ.

The optical pickup 18 is fixed at a position, for example, 41.6 mm from the center of rotation of the optical disc 10.

Further, the optical pickup 18 receives a reflected beam from the optical disk 10 with an optical sensor, and the received light signal is supplied to a focus servo circuit 19, which performs focus adjustment using, for example, an astigmatism method. This focus servo operates during both the H level period and the L level period of the laser diode drive signal.

As a result, a pit pattern 20 with a radius of approximately 41.degree. 6 ml+ is recorded on the optical disk 10 as shown in FIG. 4(A). As shown in Figure (B), this pit pattern has a width of approximately 0.6 μm in the circumferential direction and a length of approximately 100 μm in the radial direction.
250,000 pits 21 are formed on the circumference of the optical disk 10, in which the pits 21 are adjacent to each other at approximately 0.6 μm intervals.

The formation of pit patterns on the optical disc 10 is relatively easy as it uses conventional write-once type optical disc recording and reproducing device technology, and the pit pattern 20 is formed much more easily than when using conventional photographic technology. ^ It becomes density.

In FIG. 1, a rotating shaft 11 of an optical disc 10 on which a pit pattern has been recorded is fixed to a measuring rotating shaft 30 for measuring a rotation angle, and the optical disc 10 rotates together with this measuring rotating shaft 30.

The optical pickup 31 is approximately 47 mm from the rotation center of the optical disk.
．． It is fixed at a pit pattern position of 6 m, and the laser diode in the optical pickup 31 is supplied with a laser diode drive signal from the D drive drive circuit 32 and constantly emits a laser beam with reproduction power. This laser beam is divided into three beams by a diffraction grating in the optical pickup 31 and irradiated onto the optical disk 10.

At this time, as shown in FIG. 5A, the three beam spots A, B, and C are set so that the adjacent pits 21 of the pit pattern have a phase difference of 360 degrees, and the three beam spots A, B, and C have a phase difference of 90 degrees from each other. Optical disc 10 of these three beams
The reflected beams A'B' and C' are reflected by the optical sensors 35, 36, and 37 in the optical pickup 31 shown in FIG. 5(B).
Each receives light and converts it into an electrical signal, which is then sent to the focus servo circuit 3.
3 and the reproduction circuit 34, respectively. The detection signal of the optical sensor 35 is amplified by the non-inverting amplifier 38 in the reproducing circuit 34 to become a first detection signal as shown in FIG.
It is output from 9. The optical sensor 36 is divided into four parts, and the summed outputs of a and d, which are in a diagonal relationship with each other, and the summed output of c are differentially amplified by a differential amplifier 40 in the focus servo circuit 33. An error signal is generated. This focus error signal is output from the terminal 41 and supplied to the focus servo system of the optical pickup 31. Further, the addition outputs of a, b and addition outputs of s, c of the optical sensor 36 are added and amplified by an addition amplifier 42 as shown in FIG.
) is output from the terminal 43 as a second detection signal.

1st. Each of the second detection signals is a pulse signal having a phase difference of 90 degrees as the optical disk 10 rotates, and one signal leads the other signal by 90 degrees depending on the rotation direction of the optical disk 10.

Since 250,000 pits 21 are formed on the optical disk 10, the first. One revolution of the optical disc 10 can be divided into one million parts by the phase difference of the second detection signal.

By the way, if there are two beam spots A and B among the three divided laser beams and optical sensors 35 and 36, the first.
The second detection signal can be obtained, but the laser beam
The reason for the division and the use of three optical sensors +J36 to 37 is because the optical pickup 31, which is currently commercially available, is used.

As described above, by using the optical disc 10 and conventional optical disc playback technology, one rotation can be divided into one million parts by one rotary encoder with a diameter of about 100 m. Assuming that the second detection signal has a sine wave waveform, its voltage can be calculated by several tens of digits.
By dividing, it is possible to measure the rotation angle with even higher accuracy.

Furthermore, since the pits 21 are recorded in the radial direction of the optical disc 10 as snow with a length of approximately 100 μm, the optical pickup 31
There is no need for tracking ribo.

(Effects of the Invention) As described above, according to the rotary encoder of the present invention,
The rotation angle can be detected with high precision, and the entire device can be small, making it extremely useful in practice.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the rotary encoder of the present invention, FIG. 2 is a block diagram of an embodiment of the optical disc manufacturing apparatus used in the rotary encoder of the present invention, and FIG. 3 is a block diagram of an embodiment of the rotary encoder of the present invention. (FF1 waveform diagram of each part, FIG. 4 is a diagram showing a pit pattern, FIG. 5 is a diagram for explaining the rotary encoder of the present invention, and FIG. 6 is a waveform diagram of a detection signal. 10... Optical disc, 11... Rotating shaft, 14...
Reference FG generator, 16... Lens drive circuit, 17.3
2... [-D drive circuit, 18.31... Optical pickup, 19.33... Focus servo circuit, 2o...
- Pit pattern, 21...pit, 34...reproduction circuit.

Claims (1)

[Claims] An optical disc in which a plurality of pits extending in the radial direction are recorded at equal angular intervals on the same circumference, and a phase difference of 1/4 in the circumferential direction between adjacent pits of the optical disc. a reproducing device that irradiates at least two light beams having a phase difference, detects each of the two reflected beams from the optical disk, and outputs first and second detection signals having a phase difference of 90 degrees from each other; A rotary encoder characterized in that the rotation angle of the optical disc is measured using first and second detection signals.