JPH06300589A - Photoelectric encoder - Google Patents

Abstract

PURPOSE:To provide an output signal of duty ratio by adjusting the phase of received signals of respective light receiving elements using adjustment signals obtained from the four light receiving elements. CONSTITUTION:A signal processing circuit is provided with first differential amplifiers 1-4 connected to respective light receiving elements 21-24 impressed by reverse bias voltage, the amplifiers 1-4 convert current generated by the elements 21-24 to voltage through respective feedback resistances, and converted signals 50-53 containing direct current components and alternating current components are output. A second differential amplifier 5 input by the signals 50, 51 lets the variation center levels of the signals 50, 51 coincide with each other, and adjusts them into sine wave signals 54 of 180 deg. phase difference. A second differential amplifier 6 input by the signals 52, 53 lets the variation center level of the signals 52, 53 coincide with each other, and adjusts them into sine wave signals 55 of 180 deg. phase difference. The signals 54, 55 are output to differential amplifiers 10, 11 for output and converted to output signals 10a, 11a from which direct current components are perfectly removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric encoder, and more particularly to a photoelectric encoder which detects a straight movement or a rotation movement by using a light emitting element and a light receiving element.

[0002]

2. Description of the Related Art FIG. 4 shows the relationship between a light receiving element group of a photoelectric encoder and a code plate having a slit. This photoelectric encoder is disclosed in Japanese Patent Publication No. 3-76428. As shown in FIG. 4, a code plate 20 in which slits 20a and 20b having a slit width ½ pitch P are formed at intervals of 1 pitch P, and a light emitting element 40 as a light source is provided on one side so as to sandwich the code plate 20. (See FIG. 5), and at the other side at least four electrically independent light receiving elements 21, 22, 23, 2 for detecting the light emitted from the light emitting element 40.
4 are provided.

Each of the light receiving elements 21, 22, 23, 24 has a width of about 1/4 pitch P, and is arranged at an interval of 1/4 pitch P in the arrangement direction of the slits 20a, 20b on the same circumference. Has been done. That is, each of the light receiving elements 21, 22, 2
Since 3 and 24 are in a positional relationship of being shifted by ¼ pitch P from each other, the light receiving element 21 and the light receiving element 22 are 90 °, the light receiving element 21 and the light receiving element 23 are 180 °, and the light receiving element 21 is
And the light receiving element 24 have a 270 ° phase difference.

The light receiving signals output from the respective light receiving elements 21, 22, 23, 24 are processed by the signal processing circuit shown in FIG. As shown in FIG. 5, the light receiving elements 21, 22,
The received light signals output from 23 and 24 are applied to each feedback resistor 3
Amplifiers 30, 31, 3 via 4, 35, 36, 37
It is amplified by 2, 33 and output to the comparators 38, 39.

As shown in FIG. 6A, the comparator 38
Is a sine wave signal 21a that is 180 ° out of phase with each other,
23a is output, and becomes a rectangular wave signal 38a that is signal-converted at the position where the sine wave signals 21a and 23a intersect. Further, the sine wave signals 22a and 24a, which are 180 ° out of phase with each other, are output to the comparator 39.
The rectangular wave signal 39a is converted at the position where 2a and 24a intersect.

The relationship between the rectangular wave signal 38a and the rectangular wave signal 39a is a signal whose phase is shifted by 90 ° from each other as shown in FIG. 6 (b). The circuit that outputs the output signal 38a is the first circuit 45, and the circuit that outputs the output signal 39a is the second circuit 46. The photoelectric encoder with the above configuration can compensate for temperature characteristics and element deterioration without arranging the reference (monitor) light receiving element, so that it is possible to reduce the size of the electric circuit components such as the light receiving element. Has the effect of increasing.

However, in general, the light emitting element and the light receiving element have variations in element characteristics such as variations in output light from the light emitting element and variations in sensitivity of the light receiving element. Therefore, due to the above variation, the light amount received by each light receiving element is unbalanced, so that the sine wave signals input to the respective comparators 38 and 39 are as shown in FIG. First circuit 4
Regarding No. 5, an example in which variation occurs will be described.

That is, as shown in FIG. 7, in the sine wave signal 21b obtained from the light receiving element 21 and the sine wave signal 23b obtained from the light receiving element 23, the amplitude and the fluctuation center level (peak of the sine wave signal) Since the average of the value and the variable value is different, the rectangular wave signal 38b converted by the comparator 38
Has a problem that the signal has a duty ratio of not 50%.

A method for solving such a problem is P of Opto Device Application Know-how (edited by Hiroshi Ito) [CQ Publisher].
110. That is, the first circuit 45 and the second circuit
It is disclosed that the feedback resistor 34 and the feedback resistor 36 of the circuit 46 are made variable resistors and the resistance values thereof are changed to adjust the variation of the light amount to output a rectangular wave signal having a duty ratio of 50%.

[0010]

In the prior art as described above, the feedback resistor 3 of the first circuit 45 and the second circuit 46 is used.
4 and the resistance value of the feedback resistor 36 are changed to adjust the light amount, so that the rectangular wave signals of the first circuit 45 and the second circuit 46 have a duty ratio of 50% and remove the DC component. Will be able to.

However, since the resistance values of the feedback resistors 34 and 36 are changed, the frequency characteristics of the first circuit 45 and the second circuit 46 are different. That is, the first circuit 4
When the rectangular wave signal output from 5 and the rectangular wave signal output from the second circuit 46 are compared, if the frequencies processed by the first circuit 45 and the second circuit 46 become higher,
There is a problem in that the output signals are out of phase with each other by 90 °.

The present invention has been made in view of the above-mentioned conventional problems, and an output signal having a duty ratio of 50% is obtained, and the output signals output signals having mutually different 90 ° phases. The purpose is to obtain a photoelectric encoder that can be used.

[0013]

The present invention according to claim 1 is a code plate (20) in which slits (20a, 20b) having a 1/2 pitch P width are formed at a constant pitch P, and a code plate. A light emitting portion arranged on one side so as to sandwich (20),
The code plate (20) is arranged on the other side so as to sandwich the code plate (20) and receives the light emitted from the light emitting unit through the slits (20a, 20b) and the light reception signal from the light receiving unit. And a signal processing means for obtaining a relative movement amount between the light receiving portion and the light receiving portion, and the light receiving portion has a width of approximately 1/4 pitch P and has a width of 1/4 pitch P in the arrangement direction of the slits (20a, 20b). In a photoelectric encoder composed of at least four light receiving elements (21, 22, 23, 24) arranged at intervals, the signal processing means includes four light receiving elements (2
1, 22, 23, 24) detected light receiving signals (50, 5)
1, 52, 53) are all added to output the adjustment signal (56), and the adjustment signal (56) is input.
Four light receiving signals (50, 51,
52, 53) and the adjusting means (5, 6, 7, 8a, 8b, 9) for adjusting the fluctuation center level.

[0014]

In the present invention, the output signals detected by the respective light receiving elements are added together to form an adjustment signal for adjusting the variation in the light quantity, so that the DC component can be completely generated without changing the frequency characteristic of each circuit. Can be removed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The photoelectric encoder according to this embodiment has the same structure as that of the conventional photoelectric encoder shown in FIG. Figure 1
It is a block diagram of a signal processing circuit in the present invention. As shown in FIG. 1, the signal processing circuit includes first differential amplifiers 1, 2, 3, 4 to which the respective light receiving elements 21, 22, 23, 24 to which a reverse bias voltage is applied are connected.

The first differential amplifiers 1, 2, 3, 4 convert the current generated by the light receiving elements 21, 22, 23, 24 into a voltage via each feedback resistor to generate a DC component and an AC component. The converted signals 50, 51, 52 and 53 including the output signals are output. The output terminal of the first differential amplifier 1 is connected to the resistor 7a of the adder 7 and the negative input terminal of the second differential amplifier 5, and the output terminal of the first differential amplifier 2 is the adder. The resistor 7b is connected to the positive input terminal of the second differential amplifier 5.

The output terminal of the first differential amplifier 3 is connected to the resistor 7c of the adder 7 and the negative input terminal of the second differential amplifier 6, and the output of the first differential amplifier 4 is connected. The terminal is connected to the resistor 7d of the adder 7, and
It is connected to the positive input terminal of the second differential amplifier 6.
The adder 7 has four resistors 7a, 7b, 7 as described above.
c and 7d, and a differential amplifier 8a for addition,
Each of the resistors 7a, 7b, 7c, 7d is a summing differential amplifier 8
It is connected to the minus input terminal of a.

Therefore, the exchange signals 50, 51, 52, 53
Becomes one addition signal 56 via the resistors 7a, 7b, 7c, 7d, and is output to the addition differential amplifier 8a.
The addition differential amplifier 8a amplifies the addition signal 56 via a feedback resistor to remove the noise component from the first adjustment signal 57.
Is output. That is, as shown in FIG. 3, the adder 7 outputs the first adjustment signal 57 by canceling out the AC components of the converted signals 50, 51, 52, 53 and adding only the DC components.

The first adjustment signal 57 is the converted signal 50,
It is four times the DC component of each of 51, 52, and 53.
The inverting circuit is composed of an amplifier 8b in which the output terminal of the adding differential amplifier 8a is connected to the negative terminal. Two variable resistors 9a and 9b forming the adjuster 9 are connected in parallel to the output terminal of the amplifier 8b of the inverting circuit.

The inverting circuit outputs the second adjustment signal 58 from which the noise component is removed in order to change the first adjustment signal 57 at a predetermined level. Then, the first adjustment signal 5
7 and the second adjustment signal 58 are applied to each variable resistor 9 of the adjuster 9.
It is output to a and 9b. The second differential amplifier 5 amplifies the converted signal 50 of the first differential amplifier 1 and the converted signal 51 of the first differential amplifier 2 via a feedback resistor and outputs it as a sine wave signal 54. The positive terminal of the second differential amplifier 5 is
It is connected to the variable resistor 9 a of the adjuster 9.

The second differential amplifier 6 amplifies the converted signal 52 of the first differential amplifier 3 and the converted signal 53 of the first differential amplifier 4 via a feedback resistor and outputs it as a sine wave signal 55. Further, the plus terminal of the second differential amplifier 6 is connected to the adjuster 9
Of the variable resistor 9b. The output terminal of the second differential amplifier 5 is connected to the plus terminal of the output differential amplifier 10, and the output terminal of the second differential amplifier 6 is connected to the plus terminal of the output differential amplifier 11.

The output differential amplifiers 10 and 11 are circuits for amplifying the sine wave signals 54 and 55 via the respective feedback resistors and outputting the output signals 10a and 10b from which the direct current component is completely removed. A case will be described in which the light receiving elements 21, 22, 23, and 24 receive light of varying amounts of light in the signal processing circuit configured as described above.

Each of the light receiving elements 21, 22, 2 which receives the light
Reference numerals 3 and 24 generate a current containing a direct current component and an alternating current component, and the currents are current-voltage converted by the first differential amplifiers 1, 2, 3 and 4, and are 90 ° in phase with each other (the light quantity does not vary). Case) the converted signals 50, 51, 52, 53 are deviated
Is obtained. Since the converted signals 50 and 51 have variations in the amount of light, the fluctuation center level is shifted as shown in FIG. 2A, and when the converted signals 50 and 51 are differentially amplified by the second differential amplifier 5, DC component could not be removed,
The sine wave signal 54 has a fluctuation center level shifted.

Similarly, converted signals 52 and 53 (not shown)
Since there is a variation in the amount of light, the fluctuation center level deviates, and when the converted signals 52 and 53 are differentially amplified by the second differential amplifier 6, the DC component cannot be removed,
The sine wave signal 55 is obtained with the fluctuation center level shifted. Therefore, by changing the resistance values of the variable resistors 9a and 9b of the adjuster 9,
The light amounts of the converted signals 51 and 53 input to the plus terminals of the second differential amplifiers 5 and 6 are adjusted, and the converted signals 50 and 5 are adjusted.
Adjust the fluctuation center level of 1, 52, 53.

That is, the second inputting the converted signals 50 and 51
The differential amplifier 5 changes the resistance value of the variable resistor 9a of the adjuster 9 to match the fluctuation center levels of the converted signals 50 and 51, and adjusts the sinusoidal signal 54 which is 180 ° out of phase with each other. In addition, the second differential amplifier 6 that receives the converted signals 52 and 53 changes the resistance value of the variable resistor 9b of the adjuster 9 to match the fluctuation center levels of the converted signals 52 and 53, and to make them 180 ° from each other. The sine wave signal 55 is adjusted in phase.

In this embodiment, the sine wave signal has been described. However, when the sine wave signal is a rectangular wave signal, the fluctuation center level is represented by a duty ratio, as shown in FIG. 1 again.
The adjusted sine wave signals 54, 55 are output to the output differential amplifiers 10, 11 and converted into output signals 10a, 10b from which the direct current component is completely removed.

In the signal processing circuit according to the present embodiment, the DC components not removed by the first differential amplifiers 1, 2, 3, 4 are the second differential amplifiers 5, 6 and the output differential amplifier 10,
It is possible to completely eliminate it by 11, and it is possible to adjust the positional deviation of the fluctuation center level by changing the resistance values of the variable resistors 9a and 9b. That is, the output signals 10a and 11a output from the output differential amplifiers 10 and 11
Is the center of fluctuation of the sine wave (the average of the peak value and the variable value), in other words, the duty ratio is 50%, and even when the output signal 10a and the output signal 11a are compared with each other, they are 90 ° out of phase with each other. The resulting digital signal is out of sync.

In the present invention, the adder 7 is provided in the signal processing circuit, and the outputs of the respective light receiving elements are added to generate the adjustment signal, so that the same effect as that of arranging the reference light receiving element can be obtained. Become. Also, the amplifier 1 and the amplifier 2
Since the frequency characteristics of the amplifier 3 and the amplifier 4 are not changed, the phase relationship between the output signals 10a and 10b becomes constant.

The respective light receiving elements 21, 22, 23 and 24 are
In the present embodiment, the number of light receiving elements is set to add four outputs, but all outputs of the light receiving elements arranged with respect to the code plate may be added.

[0030]

As described above, according to the present invention, since the adjustment signals obtained from the four light receiving elements can be used to adjust the phase of the light receiving signal of each light receiving element, the signal processing can be performed. The frequency characteristics of the circuit can be kept constant, an output signal with a duty ratio of 50% can be obtained, and output signals whose output signals are 90 ° out of phase with each other can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a signal processing circuit showing an embodiment of the present invention.

FIG. 2 is a signal diagram showing an operation of the present embodiment when there is a variation in light amount.

FIG. 3 is a signal diagram showing an adjustment signal of the present embodiment.

FIG. 4 is a diagram showing a main part of a conventional photoelectric encoder and a photoelectric encoder of the present invention.

FIG. 5 is a diagram showing a conventional signal processing circuit.

FIG. 6 is a signal diagram for explaining a conventional operation.

FIG. 7 is a signal diagram showing an operation when there is a variation in the conventional light amount.

[Explanation of symbols]

 1, 2, 3, 4 First differential amplifier 5, 6 Second differential amplifier 7, 8a Adder 8b Inversion circuit 9 Adjuster 10, 11 Output differential amplifier

Claims (1)

[Claims] 1. A code plate in which slits having a 1/2 pitch P width are formed at a constant pitch P interval, a light emitting portion arranged on one side so as to sandwich the code plate, and so as to sandwich the code plate. A light receiving unit which is arranged on the other side and receives light emitted from the light emitting unit through the slit, and signal processing of a light receiving signal from the light receiving unit to obtain a relative movement amount between the code plate and the light receiving unit. The light-receiving unit has a width of about 1/4 pitch P, and is composed of at least four light-receiving elements arranged at intervals of 1/4 pitch P in the arrangement direction of the slits. In the photoelectric encoder, the signal processing unit adds all four light-receiving signals detected by the four light-receiving elements and outputs an adjustment signal, and the adjustment signal is input, and the signal processing unit outputs the adjustment signal by the adjustment signal. Of the four received light signals An optoelectronic encoder comprising: an adjusting unit that adjusts a fluctuation center level.