JP4022530B2 - Photoelectric encoder - Google Patents

Description

  The present invention relates to a photoelectric encoder, for example, a photoelectric encoder having a light receiving portion that is electrically divided into multiple parts.

  FIG. 9 partially shows a conventional photoelectric encoder. This photoelectric encoder includes a moving body 101, signal forming photodiodes 103a to 103d as light receiving elements arranged on the other side of the moving body 101 in FIG. 9, and a front side of the moving body 101 in FIG. A light emitting element (not shown). The moving body 101 has a plurality of slits 102a, 102b,..., And the plurality of slits 102a, 102b,... Are formed at a predetermined pitch P in the moving direction of the moving body 101. It has a half width.

  In this photoelectric encoder, light from the light emitting element passes through slits 102a and 102b and is detected by the photodiodes 103a to 103d. The photoelectric encoder has a signal processing circuit 100 as shown in FIG.

  As the light emitting element, one light source is usually used by using one element. On the other hand, the light receiving element is composed of four photodiodes 103a to 103d having a width that is a quarter of the pitch P so that the moving direction and moving speed of the moving body 101 can be detected. ing. The four photodiodes 103a to 103d are arranged adjacent to each other in the arrangement direction of the slits 102a and 102b at an arrangement pitch 1 / 4P that is a quarter of the pitch P.

  When the moving body 101 moves in any direction in the moving direction, it is shown in FIG. 10 according to the time change of the light receiving area of the light that passes through the slits 102a and 102b and is irradiated to the photodiodes 103a to 103d. Thus, the photocurrents Is1 to Is4 are formed in the photodiodes 103a to 103d. The photocurrents Is1 to Is4 are amplified by operational amplifiers 106a to 106d.

  FIG. 11A shows the waveforms of the output voltages VA + and VA− output from the operational amplifiers 106a and 106b, and FIG. 11B shows the waveforms of the output voltages VB + and VB− output from the operational amplifiers 106c and 106d. Show. In FIGS. 11A and 11B, the vertical axis represents amplitude and the horizontal axis represents time. On the horizontal axis, P represents the time required for the moving body 101 to move by the pitch P. The output voltage VA + and the output voltage VA− in FIG. 11A are in a phase-inverted relationship, and are input to the comparator 107a for comparison. Also, the output voltages VB + and VB− in FIG. 11B are in a phase-inverted relationship, and are input to the comparator 107b for comparison.

  In the comparator 107a, for example, the output voltage VA + is compared with the output voltage VA− using the output voltage VA + as a reference signal. A low level comparator output is derived in a state lower than the voltage VA−. Eventually, the comparator 107a outputs an output signal VOA shown by a rectangular wave in FIG. 11C based on the output voltages VA + and VA−, and the comparator 107b generates a signal based on the output voltages VB + and VB−. The output voltage VOB indicated by a rectangular wave is output to 11 (d). The output signals VOA and VOB have the same period as the time, that is, the period required for the slit 102a of the moving body 101 to move by one pitch, and have a phase difference of 90 °.

  However, the conventional photoelectric encoder has the following problems. That is, in the arrangement direction of the slits 102a and 102b, four photodiodes 103a to 103d having a width of (1/4) P are arranged at a pitch of a quarter of the arrangement pitch P of the slits 102a and 102b. . Therefore, when forming the light receiving element for the conventional photoelectric encoder constituted by a photodiode in which one semiconductor chip is electrically divided into four, a value that is four times the arrangement pitch of the photodiodes is obtained. It is necessary to prepare a semiconductor chip that matches the desired slit pitch (resolution).

  In this case, since the photodiodes 103a to 103d constituting the light receiving element are arranged in a line, theoretically, the finally obtained slit pitch (resolution) is 4 of the photodiode arrangement pitch. This is the pitch.

From the above, in the conventional photoelectric encoder, in order to reduce the slit pitch (increase the resolution), the photodiode array pitch must be reduced, and as a result, the output value of the detection signal is reduced. Therefore, there is a problem in that it is easily affected by crosstalk between signals of adjacent channels and the S / N ratio of the detection signal is lowered.
Japanese Examined Patent Publication No. 3-76428 Japanese Patent No. 3375578

  Accordingly, an object of the present invention is to provide a photoelectric encoder that can improve the resolution without reducing the arrangement pitch of the photodiodes and can improve the resolution while suppressing a decrease in the S / N ratio of the detection signal. It is to provide.

In order to solve the above problems, a photoelectric encoder according to the present invention includes a moving body in which a plurality of slits having a predetermined width in the moving direction are arranged in the moving direction at an arrangement pitch that is approximately twice the predetermined width, and the moving A light emitting part arranged on one side of the body and emitting light toward the moving body, and receiving light emitted from the light emitting part and passing through the slit and arranged on the other side of the moving body And a signal processing unit that processes an output signal output from the light receiving unit,
The light receiving part is
A first photodiode group having four photodiodes arranged in the arrangement direction of the slits;
Having four photodiodes arranged in the arrangement direction of the slits, and having a second photodiode group adjacent to the first photodiode group in the arrangement direction of the slits,
The second photodiode group has a size that is M times (M is a positive integer) the arrangement pitch of the slits in the slit arrangement direction with respect to the first photodiode group. The position is shifted by the dimension that is the sum of the one-minute dimension.
The signal processor is
Based on the four output signals output from the four photodiodes of the first photodiode group, the time required for the moving body to move a distance corresponding to one-half of the arrangement pitch of the slits is approximately one cycle. The moving body corresponds to one-half of the arrangement pitch of the slits based on the four output signals output from the four photodiodes of the second photodiode group that output the first rectangular wave signal. The time for moving the distance is approximately one cycle, and a second rectangular wave signal having a phase difference of approximately 90 ° with respect to the first rectangular wave signal is output.

  In the photoelectric encoder according to the present invention, the signal processing unit outputs a first rectangular wave signal and a second rectangular wave signal having a phase difference of about 90 ° with respect to the first rectangular wave signal. In the first and second rectangular wave signals, the time required for the moving body to move a distance corresponding to one half of the pitch of the slit array is approximately one cycle. The first rectangular wave signal is based on the four output signals output from the first photodiode group, and the second rectangular wave signal is based on the four output signals output from the second photodiode group.

  As described above, according to the present invention, the output signals from the first and second photodiode groups adjacent to each other in the arrangement direction of the slits have a half cycle compared to the conventional example. The first and second rectangular wave signals are obtained, and the resolution can be improved without reducing the arrangement pitch of the photodiodes. Therefore, the resolution can be improved while suppressing a decrease in the S / N ratio of the detection signal.

  In the photoelectric encoder according to one embodiment, each photodiode included in the first and second photodiode groups has a width that is approximately a quarter of the arrangement pitch of the slits.

  In the photoelectric encoder of this embodiment, since the width of each photodiode is approximately one quarter of the arrangement pitch of the slits, four photodiodes can be arranged at one arrangement pitch of the slits. Therefore, the light receiving part can be made compact.

  In the photoelectric encoder according to one embodiment, the width of each photodiode included in the first and second photodiode groups is approximately one half of the arrangement pitch of the slits. The pitch is a value obtained by multiplying the arrangement pitch of the slits by a value obtained by adding a quarter to a half value of N (N is a positive integer).

  In this embodiment, the width of each photodiode is approximately one half of the arrangement pitch of the slits, and the arrangement pitch of each photodiode is the arrangement pitch P × (1/4 + N / 2) of the slits. The light receiving area of the part can be increased.

In the photoelectric encoder according to an embodiment, the light receiving unit includes a plurality of at least one of the first photodiode group or the second photodiode group arranged in the arrangement direction of the slits.
Provided with a connection portion for connecting the outputs of the photodiodes having substantially the same amount of displacement with respect to the slit in the arrangement direction of the slits, between the plurality of first or second photodiode groups. .

  In this embodiment, a plurality of first or second photodiode groups are provided, and the connection portion is configured so that the outputs of the photodiodes whose deviation amounts (phase deviations) with respect to the slits are always substantially the same are connected to each other. Connect between. Therefore, the output values of the first and second rectangular wave signals serving as detection signals can be increased, and the S / N ratio can be improved.

Further, in the photoelectric encoder of one embodiment, the signal processing unit is
A first signal processing circuit connected to the first photodiode group;
A second signal processing circuit connected to the second photodiode group;
Third signal processing for inputting the output signal of the first signal processing circuit and the output signal of the second signal processing circuit and outputting the first rectangular wave signal and the second rectangular wave signal Circuit.

  According to this embodiment, the four output signals output by the first photodiode group are processed by the first signal processing circuit, and the four output signals output by the second photodiode group are processed by the first signal processing circuit. 2 signal processing circuit. The third signal processing circuit processes the output signal from the first signal processing circuit and the output signal from the second signal processing circuit to perform the first rectangular wave signal and the second rectangular wave. Output a signal. Therefore, the signal processing system is simple.

In one embodiment, the first signal processing circuit includes two rectangular wave outputs having a phase difference of about 90 ° based on four output signals output from the first photodiode group. Output signal,
The second signal processing circuit outputs two rectangular wave output signals having a phase difference of approximately 90 ° based on the four output signals output from the second photodiode group.

  According to this embodiment, the third signal processing circuit performs predetermined signal processing on two rectangular wave output signals having a phase difference of approximately 90 ° from the first signal processing circuit, The first rectangular wave signal is output. The third signal processing circuit performs predetermined signal processing on the two rectangular wave output signals having a phase difference of approximately 90 ° from the second signal processing circuit to obtain a second rectangular wave signal. Is output.

  The first and second rectangular wave output signals have a phase difference of approximately 90 ° with respect to each other, with a period of time required to move a distance corresponding to one-half of the pitch of the slit array as one period.

In the photoelectric encoder of one embodiment, each of the first and second signal processing circuits outputs two output signals having a predetermined phase difference to the third signal processing circuit,
The third signal processing circuit includes:
While the two output signals from the first signal processing circuit are both at a high level and when the two output signals are both at a low level, the first rectangular wave signal is set to a high level, When one of the two output signals is at a low level and the other is at a high level, the first rectangular wave signal is set to a low level,
In addition, when the two output signals from the second signal processing circuit are both at the high level and when both the two output signals are at the low level, the second rectangular wave signal is set to the high level. When one of the two output signals is at a low level and the other is at a high level, the second rectangular wave signal is set to a low level.

  According to this embodiment, the third signal processing circuit is connected to the exclusive logic circuit depending on whether the two output signals from the first and second signal processing circuits are at a low level or a high level. The logical negation of the sum can be realized by a logical operation circuit that performs a logical operation.

In the photoelectric encoder of one embodiment, each of the first and second signal processing circuits outputs two output signals having a predetermined phase difference to the third signal processing circuit,
The third signal processing circuit includes:
When one of the two output signals from the first signal processing circuit is at a high level and the other is at a low level, the first rectangular wave signal is set to a high level, while the two output signals are both When the high level or both are low level, the first rectangular wave signal is set to low level,
And when one of the two output signals from the second signal processing circuit is at a high level and the other is at a low level, the second rectangular wave signal is set to a high level, while the two output signals are The second rectangular wave signal is set to a low level when both are at a high level or both are at a low level.

  According to this embodiment, the third signal processing circuit is connected to the exclusive logic circuit depending on whether the two output signals from the first and second signal processing circuits are at a low level or a high level. This can be realized by a logical operation circuit that performs a logical operation of the sum.

  According to the photoelectric encoder of the present invention, the first and second photodiode groups are arranged so as to be adjacent to each other in the slit arrangement direction, and the signal processing unit outputs the first photodiode group 4 A first rectangular wave signal based on the two output signals and a second rectangular wave signal based on the four output signals output from the second photodiode group are output. The first and second rectangular wave signals have a phase difference of about 90 °, with the time taken for the moving body to travel a distance corresponding to one-half of the pitch of the slit array as substantially one cycle.

  Therefore, according to the present invention, the first and second rectangular wave signals having a half period can be obtained as compared with the conventional example, and the resolution can be improved without reducing the arrangement pitch of the photodiodes. Therefore, the resolution can be improved while suppressing a decrease in the S / N ratio of the detection signal.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

(First embodiment)
FIG. 1 shows the structure of the main part of the first embodiment of the photoelectric encoder of the present invention. The first embodiment includes a moving body 1, and the moving body 1 has a plurality of slits 2a, 2b, 2c,... Arranged in the width direction (movement direction) at a predetermined arrangement pitch P. The slits 2a, 2b, 2c... Have a width of approximately (1/2) P.

  A light emitting unit (not shown) is disposed on one side of the moving body 1 (the front side in FIG. 1). Moreover, this 1st Embodiment is provided with the light-receiving part 3 arrange | positioned at the other side (FIG. 1 back side of FIG. 1) of the said mobile body 1 so as to oppose the said light emission part.

  The light receiving unit 3 includes a first photodiode group G1 and a second photodiode group G2. This first photodiode group G1 has four photodiodes 3a, 3b, 3c, 3d arranged in the arrangement direction of the slits 2a, 2b, 2c. The second photodiode group G2 includes four photodiodes 3a ', 3b', 3'c, 3'd arranged in the arrangement direction of the slits 2a, 2b, 2c. Each of the photodiodes 3a to 3d and 3a 'to 3d' has a width that is approximately a quarter of the arrangement pitch P. The photodiodes 3a to 3d of the first photodiode group G1 are arranged at an arrangement pitch of approximately (1/4) P, and the photodiodes 3a ′ to 3d ′ of the second photodiode group G2 are also They are arranged at an arrangement pitch of approximately (1/4) P.

  The first photodiode group G1 and the second photodiode group G2 are arranged in a substantially single row adjacent along the arrangement direction of the slits 2a, 2b, 2c. The first photodiode group G1 and the second photodiode group G2 add approximately one-eighth of the arrangement pitch P to the arrangement pitch P in the arrangement direction of the slits 2a, 2b, 2c. The position is displaced by the measured dimension (P + (1/8) P). In the first embodiment, the positional displacement dimension between the first photodiode group G1 and the second photodiode group G2 is the dimension (P + (1/8) P). , (M × P) + (1/8) P (M is a positive integer).

  Further, as shown in FIG. 2, the first embodiment includes a first signal processing circuit 8, a second signal processing circuit 9, and a third signal processing circuit 10 that constitute a signal processing unit. The first signal processing circuit 8 includes operational amplifiers 6a to 6d. The operational amplifiers 6a, 6b, 6c, and 6d are respectively connected to both ends of the photodiodes 3a, 3b, 3c, and 3d included in the first photodiode group G1. The operational amplifiers 6a and 6c are connected to the comparator 7a and output signal voltages VA + and VA− shown in FIG. 3A (a), respectively. The operational amplifiers 6b and 6d are connected to the comparator 7b and output signal voltages VB + and VB− shown in FIG. 3A (b), respectively. The comparators 7a and 7b are connected to the third signal processing circuit 10, and output rectangular wave output signals VOA and VOB shown in FIGS. 3A (e) and 3 (f), respectively, as output signals.

  On the other hand, the second signal processing circuit 9 includes operational amplifiers 6a 'to 6d'. The operational amplifiers 6a ', 6b', 6c ', 6d' are respectively connected to both ends of the photodiodes 3a ', 3b', 3c ', 3d' of the second photodiode group G2. The operational amplifiers 6a 'and 6c' are connected to the comparator 7a 'and output signal voltages VA +' and VA- 'shown in FIG. 3B (c), respectively. The operational amplifiers 6b 'and 6d' are connected to the comparator 7b 'and output signal voltages VB +' and VB- 'shown in FIG. 3B (d), respectively. The comparators 7a 'and 7b' are connected to the third signal processing circuit 10, and output as rectangular wave output signals VOA 'and VOB' shown in FIGS. 3B (g) and (h), respectively. Is output. 3A and 3B, the vertical axis represents the amplitude of the signal, the horizontal axis represents time, and each scale on the horizontal axis is required for the moving body 1 to move the moving distance represented by the arrangement pitch P. Show time.

  In the photoelectric encoder having the above configuration, when the moving body 1 shown in FIG. 1 moves in any one of the moving directions, the photodiodes 3a to 3d and 3a ′ to 3d ′ are slit from the light emitting unit. The light receiving area of the light that passes through 2a, 2b, 2c,... As shown in FIG. 2, the photodiodes 3a to 3d and the photodiodes 3a ′ to 3d ′ generate photocurrents Is1 to Is4 and photocurrents Is1 ′ to Is4 ′ in accordance with the temporal change in the light receiving area. . The photocurrents Is1 to Is4 and the photocurrents Is1 'to Is4' are amplified by the operational amplifiers 6a to 6d and the operational amplifiers 6a 'to 6d', respectively.

  That is, the operational amplifier 6a outputs the output voltage VA + shown in FIG. 3A (a) to the comparator 7a, and the operational amplifier 6c outputs the output voltage VA− shown in FIG. 3A (a) to the comparator 7a. Then, the comparator 7a outputs a rectangular wave output signal VOA shown in FIG. 3A (e) to the third signal processing circuit 10.

  The operational amplifier 6b outputs the output voltage VB− shown in FIG. 3A (b) to the comparator 7b, and the operational amplifier 6d outputs the output voltage VB + shown in FIG. 3A (b) to the comparator 7b. Then, the comparator 7b outputs a rectangular wave output signal VOB shown in FIG. 3A (f) to the third signal processing circuit 10.

  As shown in FIG. 3A (a), the phases of the output voltage VA + and the output voltage VA− are inverted. As shown in FIG. 3A (b), the phases of the output voltage VB− and the output voltage VB + are different. Inverted. Also, the rectangular wave output signal VOA shown in FIG. 3A (e) and the rectangular wave output signal VOB shown in FIG. 3A (f) have a phase difference of about 90 °.

  On the other hand, the operational amplifier 6a ′ outputs the output voltage VA ′ + shown in FIG. 3B (c) to the comparator 7a ′, and the operational amplifier 6c ′ outputs the output voltage VA′− shown in FIG. 3B (c) to the comparator. 7a '. Then, the comparator 7 a ′ outputs a rectangular wave output signal VOA ′ shown in FIG. 3B (g) to the third signal processing circuit 10.

  The operational amplifier 6b ′ outputs the output voltage VB′− shown in FIG. 3B (d) to the comparator 7b ′, and the operational amplifier 6d ′ outputs the output voltage VB ′ + shown in FIG. 3B (d) to the comparator. 7b '. The comparator 7 b ′ outputs a rectangular wave output signal VOB ′ shown in FIG. 3B (h) to the third signal processing circuit 10.

  As shown in FIG. 3B (c), the phases of the output voltage VA ′ + and the output voltage VA′− are inverted. As shown in FIG. 3B (d), the output voltage VB′− and the output voltage VB The phase is reversed from '+'. Further, the rectangular wave output signal VOA 'shown in FIG. 3B (g) and the rectangular wave output signal VOB' shown in FIG. 3B (h) have a phase difference of about 90 °.

  As shown in FIG. 1, the photodiodes 3a, 3b, 3c, 3d of the first photodiode group G1 are respectively replaced with the photodiodes 3a ′, 3b ′, 3c ′, 3d ′ of the second photodiode group G2. On the other hand, it is displaced in the arrangement direction by a dimension (P + (1/8) · P) obtained by adding approximately one eighth of the arrangement pitch P to the arrangement pitch P. Therefore, the photodiodes 3a and 3a ′ show the same change with a time difference corresponding to the above-mentioned approximately (1/8) P, and the output voltages VA + and VA ′ + are approximately 45 °. A phase difference occurs.

  Similarly, the photodiodes 3b and 3b ′, the photodiodes 3c and 3c ′, and the photodiodes 3d and 3d ′ each show the same change with a time difference corresponding to the above (1/8) P. . Therefore, a phase difference of approximately 45 ° is generated between the output voltages VB− and VB′−, the output voltages VA− and VA′−, and the output voltages VB + and VB ′ +.

  Further, the rectangular wave output signal VOA shown in FIG. 3A (e) and the rectangular wave output signal VOA ′ shown in FIG. 3B (g) have a phase difference of about 45 °, and the rectangular wave output shown in FIG. 3A (f). The signal VOB and the rectangular wave output signal VOB ′ shown in FIG. 3B (h) have a phase difference of about 45 °.

  Next, the third signal processing circuit 10 will be described. As shown in FIG. 6, the third signal processing circuit 10 includes two XNOR (inverted exclusive OR) elements 11 and 12. The input side of the XNOR element 11 is connected to the output side of the two comparators 7 a and 7 b of the first signal processing circuit 8, and the input side of the XNOR element 12 is 2 of the second signal processing circuit 9. The comparators 7a 'and 7b' are connected to the output side. Therefore, the rectangular wave output signals VOA and VOB are input to the XNOR element 11, and the rectangular wave output signals VOA 'and VOB' are input to the XNOR element 12.

  The truth table of FIG. 7A shows the relationship between the rectangular wave output signals VOA and VOB input to the XNOR element 11 and the first rectangular wave signal VO1 output by the XNOR element 11, and FIG. ) Shows a relationship between the rectangular wave output signals VOA ′ and VOB ′ input to the XNOR element 12 and the second rectangular wave signal VO2 output from the XNOR element 12. 7A and 7B, L represents that the signal is at a low level, and H represents that the signal is at a high level.

  3A (i) shows the first rectangular wave signal VO1 output from the XNOR element 11, and FIG. 3B (j) shows the second rectangular wave signal VO2 output from the XNOR element 12. The first rectangular wave signal VO <b> 1 and the second rectangular wave signal VO <b> 2 correspond to a time period during which the moving body 1 moves a distance of half the pitch P. In addition, there is a phase difference of approximately 90 ° between the first rectangular wave signal VO1 and the second rectangular wave signal VO2.

  Therefore, according to the photoelectric encoder of the first embodiment, the resolution twice that of the prior art can be obtained, and the widths of the photodiodes 3a to 3d and 3a 'to 3d' remain the same as those of the prior art. . Therefore, according to the first embodiment, it is possible to realize a photoelectric encoder that outputs the output signals VO1 and VO2 twice the resolution of the slit without subdividing the photodiode pitch. Therefore, according to the photoelectric encoder of the first embodiment, it is possible to improve the resolution while suppressing a decrease in the S / N ratio of the output signals VO1 and VO2, which are detection signals.

(Second embodiment)
Next, FIG. 4 shows the structure of the main part of a second embodiment of the photoelectric encoder of the present invention. The second embodiment includes a moving body 1, which has a plurality of slits 2a, 2b, 2c,... Arranged in the width direction at a predetermined arrangement pitch P. The slits 2a, 2b, 2c... Have a width of approximately (1/2) P. In FIG. 4, the same parts as those in the first embodiment are denoted by the same reference numerals.

  A light emitting unit (not shown) is arranged on one side of the moving body 1 (the front side in FIG. 4). Moreover, this 2nd Embodiment is provided with the light-receiving part 33 arrange | positioned at the other side (FIG. 4 back side of FIG. 4) of the said mobile body 1 so that the said light emission part may be opposed.

  The light receiving unit 33 includes a first photodiode group G31 and a second photodiode group G32. The first first photodiode group G31 includes four photodiodes 13a, 13b, 13c, 13d arranged in the arrangement direction of the slits 2a, 2b, 2c, 2d, 2e, 2f. The second photodiode group G32 includes four photodiodes 13a ′, 13b ′, 13′c, 13′d arranged in the arrangement direction of the slits 2a, 2b, 2c, 2d, 2e, 2f. Have Each of the photodiodes 13a to 13d and 13a 'to 13d' has a width approximately half of the arrangement pitch P. The photodiodes 13a to 13d of the first photodiode group G31 are arranged at an arrangement pitch of approximately (3/4) P, and the photodiodes 13a 'to 13d' of the second photodiode group G32 are also They are arranged at an arrangement pitch of approximately (3/4) P. In the second embodiment, the arrangement pitch of the photodiodes is set to approximately three-fourths of the arrangement pitch P of the slits. However, the arrangement pitch of the photodiodes is set to (1/4 + N) of the arrangement pitch P of the slits. It may be a value obtained by multiplying (N is a positive integer) / 2).

  The first photodiode group G31 and the second photodiode group G32 are adjacent to each other in a substantially line in the arrangement direction of the slits 2a, 2b. Further, the first photodiode group G31 and the second photodiode group G32 are arranged in the arrangement direction of the slits 2a, 2b... And the arrangement pitch P is three times the arrangement pitch P of the slits 2a, 2b. The position is shifted by a dimension (3P + (1/8) P) obtained by adding approximately one-eighth of. In the second embodiment, the positional deviation dimension between the photodiode group G31 and the second photodiode group G32 is (3P + (1/8) P). However, the positional deviation dimension is (M × P + (1/8) P) (M is a positive integer of 3 or more).

  Further, as shown in FIG. 5, in the second embodiment, as in the first embodiment, the first signal processing circuit 8, the second signal processing circuit 9, and the third signal constituting the signal processing unit. A processing circuit 10 is included. The first signal processing circuit 8 includes operational amplifiers 6a to 6d. The operational amplifiers 6a, 6b, 6c, and 6d are respectively connected to both ends of the photodiodes 13a, 13b, 13c, and 13d included in the first photodiode group G31. The operational amplifiers 6a and 6c are connected to the comparator 7a and output signal voltages VA + and VA− shown in FIG. 8A (a), respectively. The operational amplifiers 6b and 6d are connected to the comparator 7b and output signal voltages VB + and VB− shown in FIG. 8A (b), respectively. The comparators 7a and 7b are connected to the third signal processing circuit 10, and output rectangular wave output signals VOA and VOB shown in FIGS. 8A (e) and 8 (f), respectively, as output signals.

  On the other hand, the second signal processing circuit 9 includes operational amplifiers 6a 'to 6d'. The operational amplifiers 6a ', 6b', 6c ', 6d' are respectively connected to both ends of the photodiodes 13a ', 13b', 13c ', 13d' of the second photodiode group G32. The operational amplifiers 6a 'and 6c' are connected to the comparator 7a 'and output signal voltages VA +' and VA- 'shown in FIG. 8B (c), respectively. The operational amplifiers 6b 'and 6d' are connected to the comparator 7b 'and output signal voltages VB + and VB- shown in FIG. 8B (d), respectively. The comparators 7a ′ and 7b ′ are connected to the third signal processing circuit 10 and output as rectangular wave output signals VOA ′ and VOB ′ shown in FIGS. 8B (g) and (h), respectively. Is output. 8A and 8B, the vertical axis represents the amplitude of the signal, the horizontal axis represents time, and each scale on the horizontal axis is required for the moving body 1 to move the moving distance represented by the arrangement pitch P. Show time.

  In the photoelectric encoder having the above configuration, when the moving body 1 shown in FIG. 4 moves in any one of the moving directions, the photodiodes 13a to 13d and 13a ′ to 13d ′ are slit from the light emitting unit. The light receiving area of the light that passes through 2a, 2b,... As shown in FIG. 5, the photodiodes 13a to 13d and the photodiodes 13a ′ to 13d ′ generate photocurrents Is1 to Is4 and photocurrents Is1 ′ to Is4 ′ in accordance with the temporal change in the light receiving area. . The photocurrents Is1 to Is4 and the photocurrents Is1 'to Is4' are amplified by the operational amplifiers 6a to 6d and the operational amplifiers 6a 'to 6d', respectively.

  That is, the operational amplifier 6a outputs the output voltage VA + shown in FIG. 8A (a) to the comparator 7a, and the operational amplifier 6c outputs the output voltage VA− shown in FIG. 8A (a) to the comparator 7a. Then, the comparator 7a outputs a rectangular wave output signal VOA shown in FIG. 8A (e) to the third signal processing circuit 10.

  The operational amplifier 6b outputs the output voltage VB− shown in FIG. 8A (b) to the comparator 7b, and the operational amplifier 6d outputs the output voltage VB + shown in FIG. 8A (b) to the comparator 7b. The comparator 7b outputs the rectangular wave output signal VOB shown in FIG. 8A (f) to the third signal processing circuit 10.

  As shown in FIG. 8A (a), the phases of the output voltage VA + and the output voltage VA− are inverted. As shown in FIG. 8A (b), the phases of the output voltage VB− and the output voltage VB + are different. Inverted. Further, the rectangular wave output signal VOA shown in FIG. 8A (e) and the rectangular wave output signal VOB shown in FIG. 8A (f) have a phase difference of about 90 °.

  On the other hand, the operational amplifier 6a ′ outputs the output voltage VA ′ + shown in FIG. 8B (c) to the comparator 7a ′, and the operational amplifier 6c ′ outputs the output voltage VA′− shown in FIG. 8B (c) to the comparator. 7a '. Then, the comparator 7 a ′ outputs a rectangular wave output signal VOA ′ shown in FIG. 8B (g) to the third signal processing circuit 10.

  The operational amplifier 6b ′ outputs the output voltage VB′− shown in FIG. 8B (d) to the comparator 7b ′, and the operational amplifier 6d ′ outputs the output voltage VB ′ + shown in FIG. 8B (d) to the comparator. 7b '. The comparator 7 b ′ outputs the rectangular wave output signal VOB ′ shown in FIG. 8B (h) to the third signal processing circuit 10.

  As shown in FIG. 8B (c), the phases of the output voltage VA ′ + and the output voltage VA′− are inverted. As shown in FIG. 8B (d), the output voltage VB′− and the output voltage VB The phase is reversed from '+'. Further, the rectangular wave output signal VOA 'shown in FIG. 8B (g) and the rectangular wave output signal VOB' shown in FIG. 8B (h) have a phase difference of about 90 °.

  As shown in FIG. 4, the photodiodes 13a, 13b, 13c, 13d of the first photodiode group G31 are respectively replaced with the photodiodes 13a ′, 13b ′, 13c ′, 13d ′ of the second photodiode group G32. On the other hand, the position is shifted by a dimension of approximately (3P + (1/8) P). Therefore, the photodiodes 13a and 13a ′ exhibit the same change with a time difference corresponding to the above (1/8) P, and the output voltage VA + and VA ′ + have a phase difference of about 45 °. Occurs.

  Similarly, the photodiodes 13b and 13b ′, the photodiodes 13c and 13c ′, and the photodiodes 13d and 13d ′ each show the same change with a time difference corresponding to (1/8) P. . Therefore, a phase difference of approximately 45 ° is generated between the output voltages VB− and VB′−, the output voltages VA− and VA′−, and the output voltages VB + and VB ′ +.

  Further, the rectangular wave output signal VOA shown in FIG. 8A (e) and the rectangular wave output signal VOA ′ shown in FIG. 8B (g) have a phase difference of about 45 °, and the rectangular wave output shown in FIG. 8A (f). The signal VOB and the rectangular wave output signal VOB ′ shown in FIG. 8B (h) have a phase difference of about 45 °.

  The third signal processing circuit 10 has the same configuration as that of the first embodiment described above, and as shown in FIG. 6, has a circuit configuration including an XNOR element 11 and an XNOR element 12, and the truth value shown in FIG. Behave according to

  8A (i) shows the first rectangular wave signal VO1 output from the XNOR element 11, and FIG. 8B (j) shows the second rectangular wave signal VO2 output from the XNOR element 12. The period of the signals of the first rectangular wave signal VO1 and the second rectangular wave signal VO2 corresponds to the time during which the moving body 1 moves a distance of half the pitch P. In addition, there is a phase difference of approximately 90 ° between the first rectangular wave signal VO1 and the second rectangular wave signal VO2.

  Therefore, according to the photoelectric encoder of the second embodiment, the resolution twice that of the conventional one can be obtained, and the widths of the photodiodes 13a to 13d and 13a 'to 13d' remain the same as the conventional one. . Therefore, according to the second embodiment, it is possible to realize a photoelectric encoder that outputs the output signals VO1 and VO2 twice the resolution of the slit without subdividing the photodiode pitch. Therefore, according to the photoelectric encoder of the second embodiment, the resolution can be improved while suppressing a decrease in the S / N ratio of the output signals VO1 and VO2, which are detection signals.

  In the first and second embodiments, the third signal processing circuit 10 is composed of the two XNOR elements 11 and 12 that perform a logical operation of the logical negation of the exclusive logical sum. You may comprise with two EX-OR elements to calculate.

  In the first and second embodiments, the light receiving units 3 and 33 are configured such that at least one of the first photodiode group G1 and G31 or the second photodiode group G2 and G32 is the slit 2a, A plurality of the elements may be arranged in the arrangement direction 2b. In this case, the outputs of the photodiodes having the same displacement amount in the arrangement direction of the slits 2a, 2b,... With respect to the slits 2a, 2b. The connection part connected with is provided. As a result, the output values of the first and second rectangular wave signals VO1, VO2 serving as detection signals can be increased, and the S / N ratio can be improved. Further, in the first and second embodiments, the first photodiode group G1, G31 and the second photodiode group G2, G32 have the slit 2a in the direction intersecting the moving direction of the slits 2a, 2b. , 2b... May be displaced in a direction that intersects with the arrangement direction of the slits 2a, 2b.

It is a structural diagram showing the positional relationship between the photodiode and the slit of the moving body in the first embodiment of the photoelectric encoder of the present invention. It is a block diagram of the signal processing circuit in the photoelectric encoder of the first embodiment. It is a signal waveform diagram for demonstrating operation | movement of the signal processing circuit in the photoelectric encoder of the said 1st Embodiment. It is another signal waveform diagram for demonstrating operation | movement of the signal processing circuit in the photoelectric encoder of the said 1st Embodiment. It is a structural diagram showing the positional relationship between the photodiode and the slit of the moving body in the second embodiment of the photoelectric encoder of the present invention. It is a block diagram of a signal processing circuit in the photoelectric encoder of the second embodiment. FIG. 4 is a circuit diagram of a third signal processing circuit 10 in the first and second embodiments. FIG. 5 is a diagram showing a truth table showing the operation of the third signal processing circuit 10. It is a signal waveform diagram for demonstrating operation | movement of the signal processing circuit in the photoelectric encoder of the said 2nd Embodiment. It is another signal waveform diagram for demonstrating operation | movement of the signal processing circuit in the photoelectric encoder of the said 2nd Embodiment. It is a structural diagram showing the positional relationship between a photodiode and a slit of a moving body in a conventional photoelectric encoder. It is a block diagram of the signal processing circuit in the conventional photoelectric encoder. It is a signal waveform diagram for demonstrating operation | movement of the signal processing circuit in the conventional photoelectric encoder.

Explanation of symbols

1 Mobile 2a, 2b, 2c, 2d, 2e, 2f Slit 3a, 3b, 3c, 3d Photodiode 3a ', 3b', 3c ', 3d' Photodiode 13a, 13b, 13c, 13d Photodiode 13a ', 13b ', 13c', 13d 'photodiode 6a, 6b, 6c, 6d operational amplifier 6a', 6b ', 6c', 6d 'operational amplifier 7a, 7b, 7a', 7b 'comparator 8 first signal processing circuit 9 Second signal processing circuit 10 Third signal processing circuit 11, 12 XNOR element G1, G31 First photodiode group G2, G32 Second photodiode group

Claims (8)

A plurality of slits having a predetermined width in the moving direction are arranged in the moving direction at an arrangement pitch that is approximately twice the predetermined width, and are arranged on one side of the moving body and directed toward the moving body. A light-emitting unit that emits light, a light-receiving unit that receives light emitted from the light-emitting unit and passed through the slit, and disposed on the other side of the moving body, and an output signal output by the light-receiving unit. A signal processing unit for processing,
The light receiving part is
A first photodiode group having four photodiodes arranged in the arrangement direction of the slits;
Having four photodiodes arranged in the arrangement direction of the slits, and having a second photodiode group adjacent to the first photodiode group in the arrangement direction of the slits,
The second photodiode group has a size that is M times (M is a positive integer) the arrangement pitch of the slits in the slit arrangement direction with respect to the first photodiode group. The position is shifted by the dimension that is the sum of the one-minute dimension.
The signal processor is
Based on the four output signals output from the four photodiodes of the first photodiode group, the time required for the moving body to move a distance corresponding to one-half of the arrangement pitch of the slits is approximately one cycle. The moving body corresponds to one-half of the arrangement pitch of the slits based on the four output signals output from the four photodiodes of the second photodiode group that output the first rectangular wave signal. And a second rectangular wave signal having a phase difference of about 90 ° with respect to the first rectangular wave signal. The photoelectric encoder according to claim 1,
Each of the photodiodes included in the first and second photodiode groups has a width that is approximately a quarter of the arrangement pitch of the slits. The photoelectric encoder according to claim 1,
The width of each photodiode of the first and second photodiode groups is approximately one half of the arrangement pitch of the slits.
The arrangement pitch of the photodiodes is a value obtained by multiplying the arrangement pitch of the slits by a value obtained by adding one-fourth to a half value of N (N is a positive integer). Photoelectric encoder. The photoelectric encoder according to claim 1,
The light receiving part is
At least one of the first photodiode group or the second photodiode group is arranged in a plurality in the arrangement direction of the slits,
A connecting portion for connecting outputs of photodiodes having substantially the same amount of displacement with respect to the slit in the arrangement direction of the slits between the plurality of first or second photodiode groups; Characteristic photoelectric encoder. The photoelectric encoder according to claim 1,
The signal processor is
A first signal processing circuit connected to the first photodiode group;
A second signal processing circuit connected to the second photodiode group;
Third signal processing for inputting the output signal of the first signal processing circuit and the output signal of the second signal processing circuit and outputting the first rectangular wave signal and the second rectangular wave signal A photoelectric encoder comprising a circuit. The photoelectric encoder according to claim 5,
The first signal processing circuit includes:
Based on the four output signals output from the first photodiode group, two rectangular wave output signals having a phase difference of approximately 90 ° are output,
The second signal processing circuit includes:
A photoelectric encoder that outputs two rectangular wave output signals having a phase difference of about 90 ° based on the four output signals output from the second photodiode group. The photoelectric encoder according to claim 5,
The first and second signal processing circuits each output two output signals having a predetermined phase difference to the third signal processing circuit,
The third signal processing circuit includes:
While the two output signals from the first signal processing circuit are both at a high level and when the two output signals are both at a low level, the first rectangular wave signal is set to a high level, When one of the two output signals is at a low level and the other is at a high level, the first rectangular wave signal is set to a low level,
In addition, when the two output signals from the second signal processing circuit are both at the high level and when both the two output signals are at the low level, the second rectangular wave signal is set to the high level. A photoelectric encoder wherein the second rectangular wave signal is set to a low level when one of the two output signals is at a low level and the other is at a high level. The photoelectric encoder according to claim 5,
The first and second signal processing circuits each output two output signals having a predetermined phase difference to the third signal processing circuit,
The third signal processing circuit includes:
When one of the two output signals from the first signal processing circuit is at a high level and the other is at a low level, the first rectangular wave signal is set to a high level, while the two output signals are both When the high level or both are low level, the first rectangular wave signal is set to low level,
And when one of the two output signals from the second signal processing circuit is at a high level and the other is at a low level, the second rectangular wave signal is set to a high level, while the two output signals are A photoelectric encoder characterized in that the second rectangular wave signal is set to a low level when both are at a high level or both are at a low level.

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