JPH04213021A - Optical absolute encoder - Google Patents

Abstract

PURPOSE:To decrease the power consumption of a reading light source by providing a constitution wherein the reliability of the pattern reading of an optical absolute encoder, in which a one-track-type absolute pattern and an incremental pattern are juxtaposed on a code plate, is secured. CONSTITUTION:A common reading light source is arranged for a one-track-type absolute pattern and an incremental pattern. When the reading of the one-track- type absolute pattern is required, the light is intensively emitted from the light source for a short time, and the pattern is read. In the other time, the light is weakly emitted from the light source, and only the incremental pattern is especially read.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an optical absolute encoder that optically reads a one-track absolute pattern using a photo sensor or the like. - Concerning power saving technology for encoders.

0002

[Prior Art] Absolute encoders, which are widely used in the mechatronics field of robots, machine tools, etc., are measuring instruments for obtaining the coordinates (absolute position information) of a detection part on a code plate. , a scale containing absolute position information (
It is constructed by combining a code plate with an absolute pattern (absolute pattern) and a detection unit equipped with a reading function (sensor) for the scale in a relatively movable manner. There are two main types: linear type, in which the detection part moves linearly, and rotary type, in which the detection part moves angularly relative to the disc-shaped code plate. At the phase position, the detection unit reads absolute position information directly from the code plate.

Conventionally, in an absolute encoder, a detection section reads a plurality of digital patterns arranged in parallel on a code plate in parallel, that is, one digital pattern is detected from each pattern.
A multi-track type that obtains absolute position information bit by bit was common, but in recent years, a detection unit reads multiple phase positions on one special pattern, that is, a single pattern
One-track type absolute encoders that obtain multiple bits of absolute position information from signals are being actively researched. This special pattern is called a one-track absolute pattern, and is a special pattern in which a special binary number sequence such as a full cycle sequence or an M sequence is arranged into two types of minimum read unit arrays with different physical properties. It has been replaced. 1 track type absolute
Since the encoder requires fewer patterns than a multi-track type encoder, it is advantageous in reducing the size of the code plate, and it is easy to attach and adjust the sensor in the detection section.

On the other hand, a single repeating pattern of equal pitch (
Incremental encoders have been commonly used in the past, in which a code plate is provided with an incremental pattern, and a detection section reads inverted pulses from the pattern. Here, the accumulated pulse counts represent the amount of relative movement of the detector with respect to the code plate, and usually the absolute position information of the detector is obtained from the pulse counts from the origin position provided on the code plate. That's what I do. In this type of incremental encoder, in order to store the initial value of absolute position information, it is necessary to return the detection unit to the home position at least when the power is turned on. It has the following advantages: the mechanical structure is simple, the response speed is fast because the pulses are transmitted to the counter in real time, and the highly reliable reading method that takes advantage of the regularity of the pattern can be used. are doing.

[0004] In order to actively utilize the advantages of such an incremental encoder, the applicant of the present application previously proposed a composite proposed a type of absolute encoder. Here, an incremental pattern and a one-track absolute pattern are arranged in parallel on the code plate, and when necessary (when a request signal is input), one
The track type absolute pattern is read to store the initial value of the absolute position, but usually the number of pulses read from the incremental pattern is added to and subtracted from the initial value to obtain the momentary absolute position. .

[0005] By the way, the applicant of this application previously filed Japanese Patent Application No. 1-2.
77122 "absolute encoder", etc., uses an incremental pattern detection signal to
We have proposed various absolute encoders that control the timing of track-type absolute pattern reading. Again, there is an incremental
The pattern and the 1-track absolute pattern are arranged in parallel, but in order to avoid detecting the boundary of the 1-track absolute pattern, the pattern obtained from the incremental pattern is The one-track absolute pattern is read only at a certain phase position of the pulse signal.

FIGS. 4 to 7 are for explaining a conventional example of an optical absolute encoder that reads the optical properties of a pattern, and uses a photosensor to detect the minimum reading range. An absolute encoder that detects transparency and opacity is shown. FIG. 4 is a plan view of the entire encoder, FIG. 5 is a side view of a portion related to detection of a one-track absolute pattern, and FIG. The figure is a side view of a portion related to incremental pattern detection, and FIG. 7 is a diagram of the amount of light received by the sensor.

[0007] In Figs. 4 to 6, the code plate A has:
An absolute pattern P in which transparent or opaque minimum reading units of length λ are arranged according to a special sequence, and 1
Incremental pattern I with pitch length λ
The detection section B has light receiving elements q, q1 to q8 for detecting the respective patterns.
It is attached so that it can be moved relative to each other along the lines P and I.

In FIG. 5, the part of the detection unit B that is related to reading the pattern P has a reading light source (light emitting diode r1) corresponding to the pattern P, and a light source for obtaining parallel light. An aspherical collimating lens l and eight photosensors q1 to q8 arranged at a pitch λ are arranged.

In FIG. 6, a reading light source (light emitting diode) is installed in a portion of the detection unit B that is related to reading the pattern I.
(r2), an aspherical collimating lens l1 to obtain parallel light, and a mask m formed with a pattern with the same pitch as pattern I to a length of 6 pitches to converge the parallel light. An aspherical collimating lens l2 and one photosensor q are disposed for the purpose of adjusting the angle. Here, pattern I
A reading method is adopted that utilizes the regularity of Despite being minute, it is possible to detect pulses with a high signal-to-noise ratio.

In the detection unit B configured as described above, eight adjacent minimum reading units on the pattern P are detected by the photosensors q1 to q8, and 8-bit absolute position information is assembled. From pattern I, one triangular wave pulse is detected for each relative movement of λ. Therefore, after storing the initial absolute position value from pattern P when the power is turned on,
The instantaneous absolute position is determined by integrating the pulses detected by the sensor q with the initial value.

FIG. 7 shows a hypothetical case where a light source (light emitting diode r
The amount of light received by sensor q and sensor q3 is compared when the light emission intensities of 1 and r2) are equal.

In FIG. 7, the amount of light received by sensor q for detecting incremental pattern I is determined by the maximum peak of the pattern by adopting a reading method that utilizes the regularity of pattern I. The amount of light received is equivalent to approximately three white areas in P.

[0013] Therefore, the ``1-track type absolute pattern'' and the ``incremental pattern'' are used to read the incremental pattern by making use of its regularity.
In the case of "combined pattern optical absolute encoders," the S/N ratio for detecting a one-track absolute pattern is relatively low, so misreading can be prevented and detected. In order to ensure the reliability of the 1-track type absolute pattern reading,
The amount of light received by the sensor is ensured by, for example, increasing the width of the pattern and the sensor for detecting the pattern by three times. For example, the above-mentioned patent application No. 2-201313
In the ``Optical Absolute Encoder'' of this issue, as method ①, a semiconductor laser that can obtain strong light emission is used as the light source for one-track absolute pattern reading. .

[0014]

[Problems to be Solved by the Invention] In an optical absolute encoder that uses a combination of a one-track absolute pattern and an incremental pattern, a light source is used for each pattern. are placed separately, but
The total load of the light source accounts for a large part of the power consumption of an absolute encoder. The power had reached more than half.

When such an absolute encoder is applied to portable devices such as triangulation equipment, it is necessary to keep the overall power consumption low from the viewpoint of battery weight and lifespan. There was a strong need to reduce the load on the light source, which accounts for half of the load.

[0016]

[Means for Solving the Problems] The present invention provides an optical absolute encoder that uses a combination of a one-track absolute pattern and an incremental pattern, which reduces the load on the light source. is intended to provide.

The optical absolute encoder according to claim 1 of the present invention has a code plate (A) in which a one-track type absolute pattern and an incremental pattern are arranged in parallel. and a detection unit (B) that is movable relative to the code plate (A).
In the absolute encoder, a light source for reading the pattern is provided in common for both patterns, and the output of the light source is turned off only for the time required to read the absolute pattern when the request signal is input. and a control circuit for increasing the number.

The optical absolute encoder according to claim 2 of the present invention is the optical absolute encoder according to claim 1, which increases the output of the light source when a request signal is input. The device is equipped with a control circuit that maintains the light source emitting light with an output that allows reading of the incremental pattern after reading the incremental pattern. Read.

[0019]

[Operation] The optical absolute encoder according to claim 1 of the present invention attempts to light up the light source provided in common for both patterns only when necessary with a minimum load. It is something. In other words, the light emitted from a single light source is distributed into each pattern using a lens optical system or a fiber optical path, and the absolute pattern is read only when a request signal is input to the control circuit. Increase the output of the light source by the amount of time required.

The optical absolute encoder according to claim 2 of the present invention is applied to an optical absolute encoder of a type that continuously reads an incremental pattern, After increasing the output of the light source upon input, the control circuit continues to emit light from the light source with an output that is readable in an incremental pattern. Here, if a reading method that takes advantage of the regularity of the incremental pattern is adopted, relatively weak light emission will naturally continue.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of an optical absolute encoder according to a first embodiment of the present invention. In this example, we use Fig. 4 (
The code plate A of the conventional example shown in a) to (c) and the portion of the detection section B excluding the light source section are used as they are.

In FIG. 1, a code plate A has a one-track absolute pattern P and an incremental pattern.
The detection section B, which is provided in parallel with the pattern I and can move (rotate) relative to the code plate A, has both patterns P,
A common light source (light emitting diode R) for I, an aspherical collimating lens L for obtaining parallel light, and light receiving elements S1 to S8 for absolute pattern detection (not shown in the paper). ), a light receiving element S for detecting the incremental pattern, a mask M for 6 pitches of the incremental pattern, and an aspherical collimator for condensing light.
and a lens L2. Furthermore, when a signal is input to terminal e, control circuit E causes light emitting diode R to emit light strongly for a predetermined period of time necessary for reading pattern P, and after that, the light emitting diode R emits light strongly for a predetermined period of time necessary for reading pattern P, and after that, the light emitting diode R emits light strongly for a predetermined period of time necessary for reading pattern P. Continue to emit minimal light.

In the detection unit B configured as described above, eight adjacent minimum reading units on the pattern P are detected by the photo-receiving elements q1 to q8, and 8-bit absolute position information is assembled. , one triangular wave pulse is detected from pattern I for every relative movement of λ. Therefore, when a signal is input to terminal e, the light emitting diode R emits light strongly, and after reading and storing the initial value of the absolute position from the pattern P, the pulses detected by the light receiving element q are integrated. We are looking for the absolute position at every moment.

FIG. 2 is a chart of the optical absolute encoder of the first embodiment. Here, the first
The operation of the optical absolute encoder of the embodiment is shown in chronological order. That is, when the power is turned on, a reset signal is output from the power-on reset circuit 11, and the JK flip-flop 18 and counter 17 are cleared. When receiving the absolute position request signal 12 from a controller such as an NC device, the J-K flip-flop 1
The output signal of 8 becomes H level and is input to the terminal e of the control circuit E, and a relatively high current is passed through the light emitting diode L for several seconds, causing it to emit strong light. At this time, the outputs of the light receiving elements S1 to S8 in FIG. 1 are converted into serial signals by the serial transfer circuit 6 and transferred to the shift register 13.
is stored and returned to the original parallel signal. When this transfer is completed, a termination signal is output, the output signal of the JK flip-flop 18 is inverted, and the control circuit E continues to flow a relatively low current to the light emitting diode L.
The light emitting diode L maintains sufficient illuminance to read the pattern I.

Furthermore, the serial transfer circuit 6 includes a light receiving element S1.
After the output of S8 is read, transferred, and stored in the shift register 13, the optical absolute encoder of this embodiment starts an incremental encoder operation. That is, the data in the shift register 13 is converted into a position pattern in the ROM 14 and then loaded into the up/down counter 15. Thereafter, when a relative movement occurs, an incremental pulse is generated, and the data previously loaded into the counter 15 is added or subtracted by one for each pulse depending on the direction of the relative movement.

On the other hand, from the output terminal 24, the number of pulses generated by the oscillator 20 and counted by the counter 17 matches the data loaded into the counter 15.
The oscillator 2
Pulses from 0 continue to be output as they are. That is,
At the moment when the comparison circuit 16 outputs the coincidence signal, the output terminal 24
The number of pulses output from the pattern I matches the absolute position of the detection unit with respect to the code plate at that time, and the tri-state buffers 22 and 23 are switched, and the light receiving element S is now shifted from the pattern I. The read pulse is output terminal 2
It will be connected to 4.

Therefore, the receiving device connected to the output terminal 24 uses an up/down counter to count the pulses from the oscillator 20 to set an initial value, and then performs normal incremental encoder operation. All you have to do is That is, up or down is determined depending on the direction of relative movement between the code plate A and the detection unit B, and the momentary absolute position is determined by performing pulse counting.

If the absolute position becomes necessary for some reason, the above operation is repeated by inputting an L level signal to the REQ terminal 12 each time.

FIG. 3 is a plan view showing a partial structure of an optical absolute encoder according to a second embodiment of the present invention. This is for explaining the more practical structure of the detection section and its operation.

In FIG. 3, the code plate A2 is provided with a one-track absolute pattern P2 and an incremental pattern I2 in parallel, and a detection sensor movable relative to the code plate A2. In part B2, both patterns P
2. A light source (not shown) provided in common to I2 (in a direction perpendicular to the plane of the paper), an aspherical collimating lens L3 that distributes the emitted light from the light source to the light receiving element, and an absolute collimating lens L3.
It includes light receiving elements Q1 to Q8 for pattern detection and masks W1 to W4 respectively provided for the four light receiving elements for incremental pattern detection.

Here, the masks W1 and W2, and the masks W3 and W4 have inverted patterns shifted by 1/2 pitch, and the masks W1 and W3, and the masks W2 and W4, are This is for detecting so-called A phase and B phase shifted by 1/4 pitch.

In the detection section B configured in this way, the first
The operation is similar to that of the embodiment, that is, after reading and storing the initial value of the absolute position from the pattern P2, the pulses detected from the incremental pattern I2 are integrated to obtain the absolute position at each moment. In addition, ■ an operation of "inverting one side and adding each" to the outputs of the light receiving elements corresponding to masks W1 and W2 or masks W3 and W4 is performed to create an incremental pattern that cancels sudden noise.
■ Compare the A and B phases of the two pulses obtained in this way to distinguish the direction of relative movement between the code plate A2 and the detection part B2, and An operation is performed to determine whether to add or subtract the pulses detected from the incremental pattern I2.

[0033]

Effects of the Invention: The optical absolute encoder according to claim 1 of the present invention provides a common light source for both patterns, so the number of parts is reduced and electrical wiring is reduced. The overall structure is simplified. Also, each pattern
Since the light source is operated with minimal load only when needed during the operation, the power consumption of the light source is reduced and the life of the light source is extended.

The optical absolute encoder according to claim 2 of the present invention is an optical absolute encoder of a type that reads and integrates an incremental pattern.
The power consumption of the light source can be suppressed without sacrificing the advantages of light source.

[Brief explanation of the drawing]

FIG. 1: Optical absolute according to the first embodiment of the present invention.
FIG. 2 is a schematic diagram of an encoder.

FIG. 2: Optical absolute according to the first embodiment of the present invention.
FIG. 3 is a chart diagram of an encoder.

FIG. 3: Optical absolute according to the second embodiment of the present invention.
FIG. 2 is a plan view showing a partial structure of an encoder.

FIG. 4 is a plan view of a code plate of a conventional optical absolute encoder.

FIG. 5 is a sectional view of a portion of a conventional optical absolute encoder that detects an absolute pattern.

FIG. 6 is a sectional view of a portion of a conventional optical absolute encoder that detects an incremental pattern.

FIG. 7 is a diagram of detection signals of a conventional optical absolute encoder.

[Explanation of symbols]

A Code board B Detection section R Light emitting diode E Control circuit M Mask P Absolute pattern I Incremental pattern L lens L2 lens S Photo receiving element S1 Photo receiving element S2 Photo receiving element S3 Light receiving element S4 Photo receiving element S5 Photo receiving element S6 Photo receiving element S7 Photo receiving element S8 Photo receiving element 12 Input terminal 24 Output terminal

Claims (2)

[Claims] [Claim 1] One-track absolute putter
An optical absolute encoder consisting of a code plate (A) in which a pattern and an incremental pattern are arranged in parallel, and a detection part (B) that is movable relative to the code plate (A). A pattern reading light source is provided in common for both patterns, and the output of the light source is increased by the time required to read the absolute pattern when a request signal is input. 1. An optical absolute encoder comprising: a control circuit for controlling the encoder; 2. The optical absolute encoder according to claim 1, wherein after increasing the output of the light source when a request signal is input, the optical absolute encoder increases the output of the light source so that the incremental pattern can be read. An optical absolute encoder comprising a control circuit for maintaining light emission from a light source, and reading the incremental pattern except for reading the absolute pattern when a request signal is input. .