JP2006329652A - Optical displacement sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To generate an origin-detecting signal of reduced detection position fluctuation, i.e. precise origin-detecting signal, together with the position signal, while being synchronized with the position signal. <P>SOLUTION: A photodetecting part has PDs 12b1-12b4 used for detecting three or more of origins, the first set and the second set are set by selecting two specified signals out of the signals output from the PDs 12b1-12b4 to form the one set, and an origin detecting circuit 70 of a signal processing circuit part outputs the origin detecting signal PZ of a fixed signal level, when a moving body positioned between a position A and a position B, and outputs the origin detecting signal PZ of a signal level different from the fixed signal level, when the moving body is not positioned between the position A and the position B, where the position A is the position of the moving object with the signal level of the two signals becoming equal in the vicinity of the origin in the first set, and where the position B is the position of the moving object with the signal level of the two signals becoming equal in the vicinity of the origin in the second set. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical displacement sensor that performs displacement detection, and more particularly to an optical displacement sensor that stably generates an origin detection signal synchronized with a position signal.

  For example, an encoder device is known as an optical displacement sensor. A general configuration of a conventionally known encoder device is shown in FIG. A general configuration and operation of a conventionally known encoder device will be described below with reference to FIG.

  That is, the encoder apparatus includes a light source unit 6 including a light emitting unit 2 such as an LED and an optical element 4 for converting the light beam from the light emitting unit 2 into parallel light. The parallel light from the light source unit 6 is sequentially applied to the index scale 8 and the scale 10. Further, a light detection unit 12 is provided on the opposite side of the light source unit 6 with respect to the scale 10. The encoder device further includes a signal processing circuit unit 14 that processes a signal from the light detection unit 12 and outputs the processed signal as an encoder signal.

  Here, the index scale 8, the scale 10, and the light detection unit 12 have a position detection portion and an origin detection portion. Specifically, the index scale 8 is provided with a position detection pattern 8a, which is a position detection slit, and an origin detection pattern 8b, which is an origin detection slit. Similarly, the scale is provided with a position detection pattern 10a, which is a position detection slit, and an origin detection pattern 10b, which is an origin detection slit. Further, the light detection unit 12 is provided with a position detection unit 12a that is a photodetector for position detection and an origin detection unit 12b that is a light detection unit for origin detection.

  Of the encoder devices, in a linear encoder that performs linear position detection, the origin detection pattern 10b is often arranged near one end of the linear scale that the encoder has. On the other hand, in a rotary encoder that detects rotational movement, an origin detection pattern 10b is usually arranged at one place on a disk-like scale.

  A conventionally known encoder device enables position detection and origin detection with the above-described configuration. Note that, in an object for position detection, such as a stage or a motor, the light source unit 6, the index scale 8, and the light detection unit 12 are attached to any one of the moving body and the fixed body in the object. It is done. And the said scale 10 is attached to the direction in which the said light source part 6, the said index scale 8, and the said light detection part 12 are not attached among the moving bodies and fixed bodies in the said target object.

  As a general encoder output signal having the above-described configuration, sinusoidal signals or pulses (rectangular shapes) having phases different from each other by 90 ° are output in accordance with the displacement of the movable portion (movable portion of the object) in the encoder device. There are A phase signal and B phase signal which are (wave) signals, and Z phase signal (origin detection signal) which is output when the reference position of the movable part is detected.

  Also, when the absolute position of the moving body is unknown when the encoder device is turned on or when the detected position information is cleared, a new origin detection is performed so that only the relative displacement amount can be obtained. Therefore, it is possible to obtain accurate absolute position information. If necessary, an origin detection signal synchronized with the position signal can be obtained.

  In the detection of the origin detection signal in such an encoder, the moving body is moved, and the light from the light source unit 6 is transmitted through the origin detection pattern 8b on the index scale 8 and the origin detection pattern 10b on the scale 10. The signal processing circuit unit 14 processes the output from the origin detection unit 12b, which is detected by the origin detection unit 12b in the light detection unit 12.

  In the detection of the origin signal, a method is often used in which the origin detection signal is in the origin detection state when the origin detection signal having a peak in the vicinity of the origin exceeds a predetermined slice level.

  In order to improve the reliability and accuracy in detecting the origin signal, for example, the index scale 8 and the scale 10 are provided with a mechanism for generating a reference position signal that is a signal having a period longer than the period of the position signal, By providing the light detection unit 12 with a mechanism for detecting this signal, in addition to the position signal and the origin signal which is the reference position signal, the reference position auxiliary signal is used when the origin detection signal is synchronized with the position signal. The technique used as an index is also known.

  As an example of the encoder device as described above, for example, Patent Document 1 discloses an optical encoder. Hereinafter, the outline of the characteristic part of the optical encoder will be described with reference to FIG. FIG. 11 is a diagram illustrating an outline of the light detection unit 110 of the optical encoder disclosed in Patent Document 1.

  In the optical detector 110 of this optical encoder, as shown in FIG. 11A, as a photodetector array 120 for position detection and a photodetector 140 for origin detection, as shown in FIG. A partial photo detector 142 and an end photo detector 144 are arranged.

  Here, when the signals obtained from the center photodetector 142 and the end photodetector 144, which are the origin detection photodetectors 140, are A, B, and C in this order from the left in the figure, these signals A , B, and C are graphs as shown in FIG. Further, by combining these signals A, B, and C as shown in the following expression, a signal S1 and a signal S2 are obtained. These signals S1 and S2 are graphed as shown in FIG.

S1 = −A + 2B−C (1)
S2 = A-2B + C (2)
Here, the origin detection signal Z is obtained as a digital signal as follows.

When S1> S2 + O: Z = 1 (where O is an offset)
When S1 ≦ S2 + O: Z = 0 (O is offset)
That is, as can be seen from the figure, the portion between the intersections of the signal S1 graph and the signal S2 graph is used as the origin detection signal. Here, the portion where INDEX SIGNAL in FIG. 11B is high is the portion where the origin detection signal is detected. In other words, it can be said that this is a method of defining the beginning and end (rise and fall) of the origin detection signal by the above two inequalities.

As described above, the optical encoder disclosed in Patent Document 1 performs origin detection with high accuracy.
US Patent Application Publication No. 2003/0047674 A1

  However, according to the optical encoder disclosed in Patent Document 1, for example, as shown in FIG. 11C, when the intensity of the signal detected by the light detection unit 110 is increased, the detection width is expanded. Thus, the start and end (rising and falling) edge positions of the origin detection signal may also move, or a plurality of pulses may be generated as signals to be detected.

  Further, in the conventional origin detection method using the general encoder device shown in FIG. 1, a change in the light amount of the light source unit 6 or a change in the arrangement relationship between the light detection unit 12 serving as the sensor head and the scale 10 (gap shift or track). The detection edge position and detection width of the origin detection signal detected by the light detection unit 12 are likely to fluctuate due to a positional shift or a rotational shift such as a shift.

  If the detection width of the origin detection signal varies, the origin position detected as a result may also vary. In particular, when an origin detection signal is output in synchronization with a position signal that is a periodic signal, if the detection width of the origin detection signal fluctuates, the position of the origin detection is more than one period of the position signal. Such a large deviation may occur.

  The present invention has been made in view of the above circumstances, and an optical displacement sensor capable of generating an origin detection signal with a small variation in the detection position, that is, an origin detection signal with high accuracy, together with a position signal, It is an object of the present invention to provide an optical displacement sensor that can stably generate an origin detection signal synchronized with a position signal.

  In order to achieve the above object, an optical displacement sensor according to an aspect of the present invention includes a light source unit and a light receiving unit attached to any one of a fixed body and a moving body that move relative to each other, and A scale having a predetermined optical pattern attached to the fixed body and the moving body where the light source unit is not attached, and displacement or position of the moving body based on a signal detected by the light receiving unit And a signal processing circuit for outputting an origin detection signal which is a digital signal indicating that the origin has been detected when the moving body is at the origin position. The optical source in which the light source unit, the light receiving unit, and the scale are spatially arranged so that light emitted from the light source unit is detected by the light receiving unit through the scale. In the sensor, the light receiving unit includes a photodetector used for detecting at least three or more origins, and a set of two signals selected from the signals output by the photodetector in the light receiving unit is selected. By setting the first set and the second set, the position of the moving body in which the signal levels of the two signals are equal in the vicinity of the origin in the first set is the first position, and in the vicinity of the origin in the second set. When the position of the moving body in which the signal levels of the two signals are equal to each other is the second position, the signal processing circuit moves the moving body to a position between the first position and the second position. An origin detection signal having a signal level different from the constant level is output when the moving body is not at a position between the first position and the second position at a constant signal level in some cases. And

  According to the present invention, together with the position signal, an origin detection signal with a small variation in the detected position, that is, an optical displacement sensor that can generate a highly accurate origin detection signal, and an origin detection signal synchronized with the position signal are provided. An optical displacement sensor that can be generated stably can be provided.

  Hereinafter, an optical encoder will be described as an example of the optical displacement sensor according to the present embodiment.

[First Embodiment]
The optical encoder device according to the present embodiment may have the same configuration as the conventionally known general optical encoder device shown in FIG. 1 except for the generation portion of the origin detection signal. Therefore, the description thereof is omitted, and only the characteristic part of the present embodiment will be described below.

  That is, in the present embodiment, as shown in FIG. 2, four origin detection photodetectors are arranged as the origin detection unit 12 b in the light detection unit 12.

  Hereinafter, the detection signal in the optical encoder device according to the present embodiment will be described.

  Here, signals (A (+), A (−), B (+) whose phases are different from each other by 90 ° from the light receiving element of the position detecting unit 12a in the light detecting unit 12 in accordance with the movement of the scale 10. ), B (−)) are output to the signal processing circuit unit 14.

  In the signal processing circuit unit 14, the current output from each light receiving element of the position detection unit 12a is converted into a voltage by current-voltage conversion, and an A (+) signal or [A (+)-A (-) ] Signal is used for position detection as position signal (a), and B (+) signal or [B (+)-B (-)] signal is used as position signal (b).

  In addition, from the respective photodetectors of the origin detection unit 12b in the light detection unit 12, there are origin detection signals for generating a Z-phase (origin) signal that is output when the reference position of the movable unit is detected. An origin detection signal is output and input to the signal processing circuit unit 14.

  However, the origin detection signal is not necessarily synchronized with the position signal (a) and the position signal (b) which are periodic signals. Therefore, in order to synchronize the origin detection signal with the position signal (a) and the position signal (b), for example, the signal processing circuit unit 14 needs to have a synchronization circuit 60 as shown in FIG.

  Here, the synchronization circuit 60 will be described with reference to FIG. The synchronization circuit here does not indicate a circuit that detects a specific phase of the position signal, but synchronizes the origin signal with a specific timing of the position signal or is at a specific position based on the position signal. Sometimes it is a circuit for outputting an origin signal.

  In the synchronization circuit 60, the synchronization timing is switched with the binarization circuit 61 that binarizes the position signal (a) and the position signal (b) to obtain the position signal (c) and the position signal (d). A position can be obtained by using a synchronization timing changeover switch (hereinafter referred to as a synchronization changeover switch) 63, the position signal (c), the position signal (d), the output of the synchronization changeover switch 63, and the origin detection signal (e) as inputs. And a synchronization processing unit 62 that outputs an origin detection signal (f) synchronized with the signal.

  The synchronization circuit 60 configured as described above outputs an origin signal (f) synchronized with the position signal from the input of the position signal (a), the position signal (b), and the origin detection signal (e). That is, the synchronization circuit 60 detects the origin in accordance with a specific phase of the position signal (a), for example, the rising or falling timing of the position signal (c) or the position signal (d) and the moving direction of the moving body. It becomes possible to output the signal (f).

  Note that the light that has passed through the origin detection pattern 10b on the scale 10 forms an image on the light detection unit 12, but the light pattern formed on the light detection unit 12 when the scale 10 moves in the vicinity of the origin. The imaging pattern that is also moves with this.

  In many cases, the amount of movement of the scale 10 and the amount of movement of the imaging pattern at this time usually have a linear relationship. Therefore, the following relationship often holds between the moving amount x of the scale 10 and the moving amount y of the imaging pattern, where a and b are constants.

x = a · y + b (3)
Here, the absolute value of a is different depending on the configuration of the optical element 4, but often takes an integer value such as 1 or 2. This is because when the amount of movement of the scale 10 and the amount of movement of the imaging pattern are in a linear relationship as described above, this photodetector is used when designing the arrangement of the photodetectors in the photodetector 12. This means that the width and interval can be set based on (3) above.

  FIG. 4A shows the configuration of the origin detection unit 12b in the light detection unit 12 of the optical encoder according to the present embodiment.

  As shown in the figure, the origin detector 12b is composed of four photodiodes (photo diodes; hereinafter referred to as PD) 12b1 to 12b4, and the movable body and the fixed body are used for position detection. These four PDs are arranged in the direction in which the light for detecting the origin is scanned. Here, the distance between the detection center of the first photodetector PD12b1 and the detection center of the second photodetector PD12b2 is P, and similarly, the detection center of the third photodetector PD12b3 is Let P be the distance from the detection center of the PD 12b4 which is the fourth photodetector. Also, let Q be the distance between the detection center of PD12b2 and the detection center of PD12b3.

  The current output from each PD is converted into a voltage by a current-voltage conversion circuit (not shown) configured in the signal processing circuit unit 14, and FIG. 1 (c) configured in the signal processing circuit unit 14. ) To the origin detection circuit 70 as shown in FIG. Details of the origin detection circuit 70 will be described later. Further, it is assumed that each PD has the same shape and structure and has an equivalent photoelectric conversion function.

  The signals detected by each of the PDs 12b1 to 12b4 are obtained when the movable body and the fixed body are relatively displaced, that is, when the movable body and the fixed body have a specific arrangement relationship. Each value becomes the maximum value, and the value decreases as the position deviates from the position of the specific arrangement relationship.

  In other words, regarding the PD arrangement in the origin detection unit 12b of the light detection unit 12, the difference between the position where the detection signal of the PD 12b1 is the maximum (peak) value and the position where the detection signal of the PD 12b2 is the maximum value is It can be said that the linear relationship is proportional to the interval P.

  Actually, in the normal configuration, regarding the PD arrangement in the origin detection unit 12b of the light detection unit 12, the difference between the position where the detection signal of the PD 12b1 becomes the maximum value and the position where the detection signal of the PD 12b2 becomes the maximum value is In many cases, the relationship is proportional, such as being equal to the interval P or half the interval P.

  Whether or not such a linear relationship is satisfied depends on the configuration and arrangement of the optical element 4, but in the present embodiment, it is assumed that such a linear relationship is established. That is, it is assumed that the position, width, and interval of the light detection unit 12 can be converted into the position of the scale 10 or the movement amount of the scale 10.

  In general, the level of the output signal from the origin detection PD is changed by changing the light amount of the light source unit 6 or by changing the arrangement relationship of the light source unit 6, the scale 10, and the light detection unit 12. fluctuate. However, if the central position of the intensity of light irradiated from the light source unit 6 to the light receiving unit does not change or changes in a direction that does not easily affect the position detection even if it changes, two adjacent shapes / The positions at which the output signals of PDs having the same structure are equal do not change.

  Hereinafter, the position A which is the first position and the position B which is the second position used in the description of the present embodiment will be defined and described.

  First, a position where the detection signal of PD12b1 and the detection signal of PD12b2 are equal in the vicinity of the origin is defined as position A. Similarly, a position where the detection signal of PD12b3 and the detection signal of PD12b4 are equal in the vicinity of the origin is defined as position B. Further, if the displacement amount for one period of the position signal (a) and the position signal (b) is T, the distance between the position A and the position B is T / 2, or T, and further nT / 2 (n The structure of the optical element 4 and the light detection unit 12 that is a light receiving unit is designed so that ≧ 3).

  Here, when the linear relationship is established, the position A is an intermediate point between the position where the detection signal of the PD 12b1 is maximum (peak) and the position where the detection signal of the PD 12b2 is maximum. At this time, it is derived that the position B is an intermediate point between the position where the detection signal of the PD 12b3 becomes maximum and the position where the detection signal of the PD 12b4 becomes maximum.

  Further, from the linear relationship, the position on the origin detection unit 12b corresponding to the position A is the midpoint X between the detection center in the PD 12b1 and the detection center in the PD 12b2, and the origin detection corresponding to the position B is also performed. The position on the part 12b is a midpoint Y between the detection center in the PD 12b3 and the detection center in the PD 12b4. At this time, the distance d between the position (middle point X) on the origin detection unit 12b corresponding to the position A and the position (middle point Y) on the origin detection unit 12b corresponding to the position B is shown in FIG. As can be seen from a), P / 2 + Q + P / 2 = P + Q. Further, from the above equation (3), the interval P and the interval Q are set so that (P + Q) is equal to the absolute value of T / 2a, T / a, and further nT / 2a.

  Hereinafter, the origin detection circuit 70 provided in the signal processing circuit unit 14 will be described with reference to FIG.

  As shown in the figure, the origin detection circuit 70 is mainly composed of comparators 71 to 73 and a logic circuit.

  That is, the comparator 71 compares the output voltage V1 from the PD 12b1 with the output voltage V2 from the PD 12b2, and generates a signal A that logically indicates whether the output voltage V2 from the PD 12b2 is greater. The comparator 72 compares the output voltage V3 from the PD 12b3 with the output voltage V4 from the PD 12b4, and generates a signal B that logically indicates whether the output from the PD 12b3 is greater. Then, the comparator 73 generates a signal C that logically indicates whether the sum of the output voltage V2 from the PD 12b2 and the output voltage V3 from the PD 12b3 is greater than a predetermined slice level voltage S.

  Further, the output signals A to C of the comparators 71 to 73 are input to a logical product (AND) circuit 74 in which the output signal PZ is true only when all of the input signals are true. Therefore, the origin detection state is when the logical product circuit 74 performs a true output.

  The output signal PZ is an origin detection signal, which is sent as an origin detection signal (e) shown in FIG. 3 to the synchronization processing unit 62 in the synchronization circuit 60 and is synchronized with the position signal ((f) ).

  Hereinafter, the length of (interval P + interval Q) on the PD in the optical detection unit 12, that is, the optical detector, and the displacement amount based on the position signal (a) and the position signal (b) (the relative movement amount of the scale 10) Will be described.

  Since the value of a in the above equation (3) is equal when a = ± 1, the length (interval d) of (interval P + interval Q) on the light receiving unit and the position signal (a ) And the absolute value of the displacement amount based on the position signal (b) may be compared as they are.

  On the other hand, if a = ± 1 is not satisfied, the length (interval d) of (interval P + interval Q) on the light receiving unit is multiplied by a, so that it is based on the position signal (a) and the position signal (b). It can be converted into a displacement amount (a relative movement amount of the scale 10).

  As described above, in the following, the length (interval d) on the light receiving unit is multiplied by a so that the length can be applied to any case regardless of the value of a. A description will be given on the assumption that conversion is performed so as to correspond to the amount of movement.

  First, the length (interval d) of (interval P + interval Q) on the light-receiving unit corresponds to the displacement amount (relative movement amount of the scale) for ½ period of the position signal (a) or the position signal (b). In this case, the synchronization processing unit 62 includes a circuit that synchronizes with both rising and falling of the position signal (a) and a circuit that synchronizes with both rising and falling of the position signal (b). To have. Then, the synchronization switch 63 selects and decides which of the origin detection signals (f) is synchronized.

  Further, when the length (interval d) of (interval P + interval Q) on the light receiving unit is made to correspond to the displacement amount for one cycle of the position signal (a) or the position signal (b), the displacement is constant. A circuit that is synchronized with the rising edge of the position signal (a) in the case of the direction, and in synchronization with the falling edge of the position signal (a) in the opposite direction. When the falling edge of (b) is in the opposite direction, the synchronization processing unit 62 is provided with a circuit that is synchronized with the rising edge of the position signal (b). Then, the synchronization switch 63 selects and decides which of the origin detection signals (f) is synchronized.

  As described above, in the present embodiment, the length (interval d) of (interval P + interval Q) on the light receiving unit is set to 1/2 period of the position signal (a) and the position signal (b), or 1 It corresponds to the amount of displacement for the period. However, if the circuit is configured so that the synchronization position is uniquely determined, in other words, the origin can be detected at the same position every time, the length (interval P + interval Q) on the light receiving unit (interval d) ) May be set to an arbitrary value. Further, the length (interval d) of (interval P + interval Q) on the light receiving unit corresponds to the displacement amount for N / 2 periods of the position signal (a) and the position signal (b), where N is a natural number. It is also possible to make it.

  Here, although two options are provided as the synchronization position by the synchronization selector switch 63, it is of course possible to prepare three or more options, or a configuration without the synchronization selector switch 63 for the purpose of a simple configuration. Of course.

  That is, the length (interval d) of (interval P + interval Q) on the photodetector of the photodetection unit 12 that is a light receiving unit is defined as N (≧ 3) as a natural number, and the position signal (a) and the position signal ( In order to correspond to the displacement amount corresponding to N / 2 periods of b), the signal processing circuit unit 14 is provided with 0, 1, 2, N, or 2N synchronization changeover switches 63. It is also possible to do. In these cases, it is necessary to provide a circuit for limiting the position to synchronize in the synchronization circuit 60 and specify the origin position.

  For example, as a simple example, adding a counter can be considered. Here, for example, the following measurement objects can be considered.

  By using the counter, one of the rising edge, falling edge, and specific phase of the position signal (a), and the rising edge, falling edge, specific phase, and movement direction of the position signal (b) are designated. For a plurality of signals, signal changes in the origin detection state are counted.

  Here, the timing for issuing the origin detection signal is, for example, the moment when the counter reaches a specific value, or when the timing or phase of the specific signal is detected for the first time after the counter reaches a specific value. Can be mentioned.

  The operation control and operation of the optical encoder device according to this embodiment will be described below.

  FIG. 5 shows how the input signal is processed in the signal processing circuit unit 14. In the waveform diagram shown in the figure, the horizontal axis represents time, and each waveform diagram shows how the signal changes when a constant speed displacement occurs.

  The binarization circuit 61 binarizes the position signal (a) and the position signal (b), which are analog signals that periodically change according to the displacement, so that the position signal (c) and the position signal ( d) is obtained. Further, the origin detection signal (e) shown in the figure corresponds to the signal PZ obtained by the origin detection circuit 70 shown in FIG. 4 (c). A waveform diagram shown in FIG. 4B shows the state of signal processing in the origin detection circuit 70 shown in FIG. That is, in FIG. 4B, the output from the PD12b1 to PD12b4, the output signals A to C from the comparators 71 to 73, and the origin detection signal due to the relative displacement between the moving body and the fixed body. It shows how PZ (origin detection signal (e)) changes.

  In FIG. 5, the origin detection signal (e) is an origin detection signal whose detection width x is one cycle of the position signals (a) and (b), and the origin detection signal (e ′) x ′ is an origin detection signal corresponding to a half cycle of the position signals (a) and (b). The detection width of the origin detection signal is determined by the arrangement interval of the PDs 12b1 to 12b4 and the photodetector. Therefore, various detection widths can be set by design in addition to the detection widths corresponding to 1/2 or 1 period of the position signals (a) and (b) as shown in the waveform of FIG. Is possible.

  In FIG. 4B, V1 to V4 indicated by bold lines irradiate the scale 10 with the light source intensity set to a predetermined value, and the arrangement of the scale 10 and the light detection unit 12 that is the sensor head is ideal. The waveforms of the output voltages from the PDs 12b1 to 12b4 are shown. On the other hand, V1 to V4 indicated by thin lines indicate that the light intensity of the light source unit 6 decreases, the interval between the light source unit 6 and the scale 10 increases, the interval between the scale 10 and the light detection unit 12 increases, or their arrangement. The waveform when deviating from the optimum position is shown.

  As described above, the comparator 71 compares the output voltage V1 of the PD 12b1 with the output voltage V2 of the PD 12b2, and generates a signal A that logically indicates whether the output voltage V2 of the PD 12b2 is greater. Similarly, the comparator 72 compares the output voltage V3 of the PD 12b3 with the output voltage V4 of the PD 12b4, and a signal B logically indicates whether the output voltage V3 of the PD 12b3 is larger. The comparator 73 compares the output voltage V2 of the PD 12b2 A signal C is generated that logically indicates whether the sum (V2 + V3) with the output voltage V3 is greater than the constant slice level voltage S. Further, the AND circuit 74 outputs an origin detection signal PZ whose output is true only when all of the signals A, B, and C are true.

  Here, as shown in FIG. 4B, when the signals V1 to V4 output from the PD12b1 to PD12b4 are functions of the position, the V1 to V4 have a certain deviation in the horizontal axis direction and are specified. It has a shape that is maximal at the point and is almost line symmetric about the point.

  Therefore, the position where the level of the signal A changes, that is, the position where the output voltage V1 of the PD 12b1 and the output voltage V2 of the PD 12b2 are equal (V1 = V2) is the point where the output voltage V1 of the PD 12b1 is maximum (peak). Thus, the output voltage V2 of the PD 12b2 is substantially at a midpoint with respect to the maximum. Similarly, the position where the level of the signal B changes, that is, the position where the voltage levels of the PD 12b3 and the PD 12b4 are equal (V3 = V4) is the point where the output voltage V3 of the PD 12b3 is maximized and the output voltage V4 of the PD 12b4 is Almost halfway to the maximum point.

  The signal C is a mask for detecting the origin detection signal PZ only in the vicinity of the origin detection position. That is, the signal C is a signal for preventing erroneous detection near the origin position.

  Then, by taking the logical product of the signals A to C, as shown in FIG. 4B, the point where the output voltage V1 of the PD 12b1 becomes maximum (peak) and the point where the output voltage V2 of the PD 12b2 becomes maximum. Thus, the origin detection signal PZ is output between approximately the middle point and the substantially middle point between the point where the output voltage V3 of the PD 12b3 becomes maximum and the point where the output voltage V4 of the PD 12b4 becomes maximum.

  Here, variations in the shape and arrangement of the PD in the light detection unit 12 are shown in FIGS. According to the shape and arrangement of the PD shown in these drawings, the light receiving area of each PD is increased, and the center of gravity position of each PD does not change in the direction in which the movable portion and the fixed portion move relative to each other. Therefore, the position where the level of the signal to be detected becomes maximum can be prevented from changing. As described above, when the PD as shown in FIGS. 6A and 6B is used, the output voltages V1 to V4 from the PDs 12b1 to PD12b4 are increased in the light receiving area as described above, so that FIG. As shown in FIG. 4B, the level of the output signal is increased as compared with the case shown in FIG.

  Further, in this embodiment, when the origin detection signal is synchronized with the position signal, the detection width x ′ of the origin detection signal is ½ period of the position signal as shown by the origin detection signal (e ′) in FIG. In this case, the synchronization circuit 60 outputs the origin detection signal (f ′) in synchronization with the position signal (a) or the position where the signal level of the position signal (b) changes. Since there is only one point that rises and falls within a ½ cycle for one position signal except at both ends of the ½ cycle, the origin detection signal is set at a fixed point. The synchronization position can be changed by ¼ period by switching the signal to be synchronized by the synchronization switch 63. Note that (f ′) shown in FIG. 5 is a waveform diagram of the origin detection signal synchronized with the position signal, and the rising edge of the origin detection signal (f ′) is synchronized with the falling edge of the position signal (c). FIG. Here, the detection width y ′ of the origin detection signal (f ′) is ½ period of the position signal. Of course, the value of the detection width y 'is not limited to the half cycle of the position signal, and may be set to an arbitrary value. Further, as described above, in this embodiment, the length is used as a reference for switching the signal level in each signal. For example, the signal level is switched on the basis of time, for example, a high level is set for a certain time. Of course.

  Similarly, when the detection width x is one cycle of the position signal as in the origin detection signal (e) in FIG. 5, the signal level of the position signal (a) therein is displaced in a specific direction. The origin signal is output in synchronization with the position that rises or falls when Since there is only one point that rises or falls when displaced in a specific direction within one cycle, except for the case where both ends of one cycle, the origin signal can be output at a fixed point. The synchronization position can be changed by 1/2 cycle by switching the signal to be synchronized by the synchronization switch 63. Note that (f) shown in FIG. 5 is a waveform diagram of the origin detection signal synchronized with the position signal, and a waveform when the rise of the origin detection signal (f) is synchronized with the rise of the position signal (d). FIG. Here, the detection width y of the origin detection signal (f) is ¼ period of the position signal.

  That is, the length (interval d) of (interval P + interval Q) on the photodetector of the photodetection unit 12 that is a light receiving unit is defined as N (≧ 3) as a natural number, and the position signal (a) and the position signal ( In order to correspond to the displacement amount corresponding to N / 2 periods of b), the signal processing circuit unit 14 is provided with 0, 1, 2, N, or 2N synchronization changeover switches 63. It is also possible to do. In these cases, it is necessary to provide a circuit for limiting the position to synchronize in the synchronization circuit 60 and specify the origin position.

  Therefore, when a counter is added as described above, by using this counter, the rise and fall of the position signal (a) and a specific phase, and the rise and fall of the position signal (b) A signal change in the origin detection state is counted for one or a plurality of signals from among those specifying a specific phase and further a moving direction. That is, signal changes after the origin detection state is counted, and an origin detection signal synchronized with the position signal is output based on the value of this counter and other signals.

  To do so, first reset the counter when the origin detection state is reached, then, for example, the moment when the counter reaches a specific value, or the timing and phase of a specific signal first after the counter reaches a specific value. When detected, the origin detection signal (f) synchronized with the position signal is output.

  Here, as the timing of outputting the origin detection signal (f), for example, the timing or phase of a specific signal is first detected at the moment when the counter reaches a specific value or after the counter reaches a specific value. And so on.

  As described above, according to the present embodiment, an optical displacement sensor that can generate an origin detection signal with little variation in the detected position, that is, a highly accurate origin detection signal, along with the position signal, and further, a position signal It is possible to provide an optical displacement sensor that can stably generate an origin detection signal synchronized with the.

  In other words, the detection range does not change easily, and it is possible to generate an origin detection signal with a detection range corresponding to a certain amount of displacement. Further, it is possible to provide an optical displacement sensor that is a sensor and can generate an origin detection signal in synchronization with a position signal.

  Hereinafter, the effect of the optical encoder device according to the present embodiment described above will be specifically described.

  First, the positions corresponding to both ends of the detection width in which the origin detection signal is detected are positions where the signal levels of the two PDs are equal, and are not easily affected by changes in the arrangement of the optical system or changes in the amount of light. Then, in the two sets of PDs each composed of two PDs, the center intervals between the PDs in each set are equalized, so that the detection accuracy of the positions at which the output signals of the respective PDs are equal becomes substantially equal in both sets.

  In particular, by making the shape and structure of the PDs equal in each group, and also in all four PDs, the detection accuracy of the two positions where the output signals of the PDs are equal becomes more equal.

  By doing so, an error in the detection width is likely to occur, and even when an error occurs, the error in the two positions is likely to be generated in the same direction, so that the detection width is not easily changed. Become.

  Specifically, in FIG. 4B, all the signal levels are the same for the output voltages V1 to V4 from each PD even when the signal level changes from a thick line to a thin line. By doing so, the position of the intersection of V1 and V2 and the position of the intersection of V3 and V4 are substantially unchanged.

  Therefore, it is possible to generate an origin detection signal having a detection width corresponding to a certain amount of displacement. Also, the detection position is less likely to fluctuate. Therefore, an optical encoder that performs stable origin detection can be provided.

  Further, when synchronizing the origin detection signal with the position signal, when the detection width of the origin detection signal is ½ period of the position signal, the position synchronized with the rise and fall of the position signal (a), or It is possible to generate an origin detection signal that is synchronized with one of two positions, that is, a position synchronized with the rising edge and the falling edge of the position signal (b).

  In the synchronization method shown in the present embodiment, the possibility that the synchronization position is shifted by 1/2 period of the position signal due to unstable factors such as the change in the arrangement of the optical system and the change in the light amount is not zero. By selecting the more stable of the two synchronization positions shifted by ¼ period, stable origin detection is possible.

  Similarly, when synchronizing the origin detection signal with the position signal, when the detection width of the origin detection signal is one period of the position signal, the origin signal is displaced in the direction opposite to the rising edge of the position signal (a) when displaced in a specific direction. It synchronizes with one of two positions: a position that is synchronized with the falling edge when moving, or a position that is synchronized with the rising edge when moving in the opposite direction to the falling edge of the position signal (a) when moving in a specific direction. Thus, an origin detection signal can be generated.

  In such a synchronization method, there is a possibility that the synchronization position is shifted by one cycle of the position signal due to unstable factors such as a change in the arrangement of the optical system and a change in the amount of light. By selecting the more stable one of the two synchronization positions, stable origin detection is possible.

  Further, when (interval P + interval Q) on the light receiving unit is made to correspond to a displacement amount for N / 2 periods of the position signals (a) and (b), where N (≧ 3) is a natural number, N = The origin detection state is wider than when 1 or N = 2.

  For this reason, the width of the PD can be increased, the SN ratio of the PD signal can be improved, and the accuracy of the detection position can be improved. In this way, it is possible to improve the performance of the origin detection unit and improve the accuracy of the origin detection.

  In addition, as described above, when the signal processing circuit unit 14 is configured to have a counter added, the counter is required to have a count function of only a few bits, and when used for a high-speed displacement sensor. However, a signal processing capability of about 1 MHz is sufficient.

  Such addition of the counter function is light as a load on the circuit, and when a circuit is realized by programming such as FPGA, it can be said that there is substantially no load, and there is a sufficient margin in terms of speed. Accordingly, it is possible to reduce the load in terms of accuracy applied to the origin detection unit while the load on the circuit surface is substantially not or slight.

  In addition, when the shape and arrangement of the PD are as shown in FIGS. 6 (a) and 6 (b), in addition to the same effects as those obtained when shown in FIG. 4 (a), The effect of reducing the influence of noise is born. This is because the level of the detected signal that is an analog signal is increased by increasing the area of the PD without changing the substantial arrangement interval of the PD.

  In order to improve the accuracy of the origin detection position or to reduce the width of the light receiving portion of the photodetector, if the width of the PD in the origin detection unit 12b that simply performs origin detection is reduced, (interval P + The value of the interval Q) becomes small, and as a result, the output signal from the PD becomes small and the SN ratio deteriorates. However, as shown in FIG. 6A or 6B, it is possible to perform stable origin detection by expanding the width while maintaining the center of gravity in the PD.

[Second Embodiment]
The main difference between the optical encoder device according to the present embodiment and the optical encoder device according to the first embodiment is the arrangement of PDs in the light detection unit 12. Therefore, the same configuration, operation, and action as those in the first embodiment are basically omitted, and description will be made focusing on the features of the present embodiment.

  Regarding the arrangement of the PDs, in the first embodiment, as shown in FIG. 4A, the arrangement is the same as the PD numbers, but in this embodiment, as shown in FIG. 7A, the PDs 12b1 are sequentially arranged from the end. , PD12b3, PD12b2, and PD12b4. As shown in the figure, the distance between PD12b1 and PD12b2 and the distance between PD12b3 and PD12b4 are both P ', and the distance between PD12b3 and PD12b2 is Q.

  Further, as a modified example of the present embodiment, there is an arrangement of PDs shown in FIGS. In this example, the PD area is increased with no change in the center of gravity of each PD, as in the modification of the PD arrangement in the first embodiment shown in FIGS. 6A and 6B. Therefore, there is no change in the position where the detection signal level becomes maximum.

  Regarding the arrangement of PDs on the origin detection unit 12b, which is a light receiving unit for origin detection, the difference between the position at which the detection signal of the PD 12b1 is maximum and the position at which the detection signal of the PD 12b2 is maximum depends on the configuration of the optical system. Although it depends on the arrangement, in this example, it is proportional to the interval P ′. Here, in an actual normal configuration, the difference in position is often proportional to the distance P ′ or 1/2 of the distance P ′.

  Further, in the present embodiment, with respect to the interval P ′ and the interval Q, (interval P′−interval Q) on the light receiving unit is ½ of the detected position signal (a) or position signal (b). Alternatively, the arrangement of the optical system is set so as to correspond to the displacement amount for one cycle.

  Further, when (interval P′−interval Q) on the light receiving unit is made to correspond to a displacement amount corresponding to ½ period of the detected position signal (a) or position signal (b), the position signal ( The synchronization processing unit 62 includes a circuit that synchronizes both the rising and falling edges of a) and a circuit that synchronizes both the rising and falling edges of the position signal (b), and a synchronization changeover switch. 63 is operated to select and determine which one is synchronized.

  Further, when (interval P′−interval Q) on the light receiving unit corresponds to the displacement amount for one cycle of the detected position signal (a) or position signal (b), the displacement is in a constant direction. A circuit that synchronizes with the rising edge of the position signal (a) in some cases and the falling edge of the position signal (a) in the reverse direction, and the position signal (a) when the displacement is in a fixed direction. In the opposite direction to the falling edge, the synchronization processing unit 62 has a circuit that synchronizes with the rising edge of the position signal (a), and the synchronization selector switch 63 selects and determines which one to synchronize. .

  As described above, in the present embodiment, (interval P′−interval Q) on the light receiving unit is equal to ½ period of the detected position signal (a) or position signal (b), or one period. It corresponds to the amount of displacement of the minute. However, if the synchronization circuit 60 is configured so that the synchronization position is uniquely determined, that is, the origin can be detected at the same position every time, the displacement amount corresponding to (interval P′−interval Q) on the light receiving unit. May be set to any value.

  In the present embodiment, as in the first embodiment, two options are assumed as synchronization positions that can be switched by the synchronization selector switch 63, but three or more options may be prepared. For the purpose of simple configuration, it is of course possible to eliminate the synchronization changeover switch 63 and to provide only one synchronization position.

  The operation and action of the optical encoder device according to this embodiment will be described below.

  FIG. 7B is a diagram illustrating a state of signal processing in the origin detection circuit 70 as illustrated in FIG. Here, how the outputs from the PDs 12b1 to PD12b4, the output signals A to C from the comparators 71 to 73, and the origin detection signal PZ change depending on the relative displacement between the moving body and the fixed body. FIG. 7B shows the same operation as that shown in FIG. 4B in the first embodiment. As in the first embodiment, output voltages from the PDs 12b1 to PD12b4 are represented by V1 to V4, respectively.

  FIG. 8C shows the signal processing in the origin detection circuit when the light receiving area of the PD is enlarged as the arrangement and shape of the PD shown in FIG. 8A or 8B. As shown in FIG. 6, according to the arrangement and shape of the PD shown in FIGS. 8A and 8B, the PD shown in FIGS. 6A and 6B in the first embodiment. The same effect as in the case of the arrangement and the shape is produced.

  As described above, according to the present embodiment, in addition to the same effects as those of the first embodiment, an optical displacement sensor that can obtain the following effects as effects unique to the present embodiment can be provided. .

  As an effect peculiar to the second embodiment, since the arrangement of the PDs 12b1 to PD12b4 is as described above, the length of the portion corresponding to the origin detection width that is the width of the origin detection on the light receiving unit is (interval P '-Interval Q). Here, assuming that four PDs are arranged at the same interval Q, the length of the portion corresponding to the origin detection width is 2Q in the first embodiment, whereas Q in the second embodiment is Q. Thus, the origin detection width can be halved.

  Furthermore, according to the shape and arrangement of the PD shown in FIG. 8B, the origin detection width can be reduced as much as possible by bringing Q as close as possible to P ′. In addition, the interval P 'between the PDs required for comparing the signals from the PDs can be increased. Therefore, the optimum origin detection width can be specified with high accuracy while taking into consideration the distortion of the optical system, the noise of signal detection from the PD, the displacement of the detection system, and the like.

[Third Embodiment]
The main difference between the optical encoder device according to this embodiment and the optical encoder device according to the first embodiment is that three PDs are used in this embodiment, and the arrangement is shown in FIG. Accordingly, the origin detection circuit 70 is configured as shown in FIG. 9B. Therefore, the same configuration, operation, and action as those in the first embodiment are basically omitted, and description will be made focusing on the features of the present embodiment.

  Hereinafter, a configuration unique to the optical encoder device according to the present embodiment will be described.

  First, in this embodiment, three PDs to be used are arranged as shown in FIG. Here, the correspondence relationship between the PD in the first embodiment and the PD in the present embodiment is shown. PD12b1, PD12b2, PD12b3, and PD12b4 in the first embodiment shown in FIG. 4 correspond to PD12b1, PD12b2, PD12b2, and PD12b3 in the present embodiment, respectively. That is, in the present embodiment, the PD 12b2 arranged at the center of the three PDs is used as a substitute for the two PDs arranged at the center of the four PDs in the first embodiment. Each PD has the same shape and structure, and each PD has an equivalent photoelectric conversion function.

  Here, the signal detected by each PD is such that when the moving body and the fixed body are relatively displaced, a certain position, that is, when the moving body and the fixed body have a specific arrangement relationship. Each of the detected values becomes smaller and the detected value becomes smaller as it deviates from the arrangement relationship.

  Further, the current output from each PD is converted into a voltage by a current-voltage conversion circuit (not shown) configured in the signal processing circuit unit 14, and is input to the origin detection circuit 70 shown in FIG. 9B. It has a configuration. That is, the origin detection circuit 70 illustrated in FIG. 9B is a part of the signal processing circuit unit 14 illustrated in FIG. 1 and includes a comparator and a logic circuit. Specifically, in the origin detection circuit 70 in the present embodiment, the comparator 71 compares the output voltage V1 of the PD 12b1 and the output voltage V2 of the PD 12b2, and a signal A that logically indicates whether the output of the PD 12b2 is greater; The comparator 72 compares the output voltage V2 of the PD 12b2 with the output voltage V3 of the PD 12b3, and the signal B indicating in logic whether the output from the PD 12b2 is larger, and the sum of the output voltages of the PDs 12b1, 12b2, 12b3 in the comparator 73 A signal C is generated that logically indicates whether the voltage is greater than a certain slice level voltage S. Further, as shown in the figure, the AND circuit 74 makes the output true only when all of the signals A, B, C are true, and this AND circuit produces a true output (this output is the origin detection signal PZ). The time to perform is the origin detection state.

  Here, in the present embodiment, the interval P on the light receiving unit is made to correspond to a half period of the detected position signal (a) or position signal (b), or a displacement amount for one period. Sets the arrangement of the optical system.

  First, when the interval P on the light receiving unit is made to correspond to the displacement amount corresponding to a half cycle of the detected position signal (a) or the position signal (b), the rising and rising of the position signal (a). The synchronization processing unit 62 has a circuit that synchronizes with both of the falling and a circuit that synchronizes with both the rising and falling of the position signal (b). The user decides whether to synchronize.

  On the other hand, when the interval P on the light receiving portion is made to correspond to the displacement amount for one cycle of the detected position signal (a) or position signal (b), the position signal (a ) At the rising edge of the position signal (a) when it is in the reverse direction, and at the falling edge of the position signal (a) when the displacement is in a certain direction, The synchronization processing unit 62 has a circuit that synchronizes with the rising edge of the position signal (a), and the user selects and decides which to synchronize with the operation of the synchronization changeover switch 63 by the user.

  As described above, in the present embodiment, the interval P on the light receiving unit is made to correspond to a half period of the detected position signal (a) or (b) or a displacement amount for one period. I have to. However, in the circuit that synchronizes the origin detection signal with the position signal, if the synchronization position is uniquely determined, that is, the circuit is configured so that the origin can be detected at the same position every time, the interval P on the light receiving unit is made to correspond. The amount of displacement may be determined to an arbitrary value.

  In the present embodiment, as in the first embodiment, two options are assumed as synchronization positions that can be switched by the synchronization selector switch 63, but three or more options may be prepared. For the purpose of simple configuration, it is of course possible to eliminate the synchronization changeover switch 63 and to provide only one synchronization position.

  FIG. 9C is a diagram showing a state of signal processing in the origin detection circuit.

  In the graph shown in the figure, the output voltages V1 to V4 of the PDs 12b1 to 12b3, the output signals A to C from the comparator, and the origin detection signal PZ are determined depending on the relative displacement between the moving body and the fixed body. How it changes.

  Here, as shown in FIG. 9C, when the signals V1 to V3 output from the PD12b1 to PD12b3 are functions of the position, the V1 to V3 have a certain deviation in the horizontal axis direction and are specified. It has a shape that is maximal at the point and is almost line symmetric about the point.

  Therefore, the position where the level of the signal A changes, that is, the position where the output voltage V1 of the PD 12b1 and the output voltage V2 of the PD 12b2 are equal (V1 = V2) is the point where the output voltage V1 of the PD 12b1 becomes maximum, The output voltage V2 is approximately the midpoint between the maximum points. Similarly, the position where the level of the signal B changes, that is, the position where the signal levels of the output voltages of the PD 12b2 and the PD 12b3 are equal (V2 = V3) is the point where the output voltage V2 of the PD 12b2 becomes maximum and the output voltage of the PD 12b3. This is an approximately halfway point from the point at which V3 is maximized.

  The signal C is a mask for detecting the origin detection signal PZ only in the vicinity of the origin detection position. That is, the signal C is a signal for preventing erroneous detection near the origin position.

  Here, when the level of the output voltage from the origin detection PD varies due to a change in the amount of light in the light source unit 6, a change in the arrangement relationship between the light detection unit 12 serving as the sensor head and the scale 10, or the like, FIG. As can be seen from (c), with respect to the output voltages V1 to V3 from the PDs 12b1 to PD12b3, the positions of the intersections of V1 and V2 and the intersections of V2 and V3 change when the signal levels change in the same manner. Hardly changes.

  As described above, according to this embodiment, it is possible to provide an optical displacement sensor that exhibits the same effects as those of the first embodiment and also provides the following effects specific to this embodiment. .

  In this embodiment, the length of the portion corresponding to the origin detection width on the light receiving unit is the interval P by setting the number and arrangement of PDs as described above. Here, if all the PDs are arranged at the same interval Q, the length of the portion corresponding to the origin detection width is 2Q in the first embodiment, whereas the length is Q in the present embodiment. The origin detection width can be halved.

  Furthermore, by setting the number of PDs to three, one PD is reduced as compared with the case of the first embodiment, so that an optical displacement sensor capable of a simpler and more compact configuration is obtained. This means that the area irradiated with light from the light source unit 6 can be reduced, which works advantageously on the design of the optical system.

[Fourth Embodiment]
The difference between the optical encoder device according to the present embodiment and the optical encoder device according to the third embodiment is an origin detection circuit 70. Therefore, here, the difference will be mainly described, and the same configuration and operation as the third embodiment will be basically omitted.

  In the present embodiment, the current output from each PD is converted into a voltage by a current-voltage conversion circuit (not shown) configured in the signal processing circuit section 14, and is sent to the origin detection circuit 70 shown in FIG. It is configured to input. The origin detection circuit 70 is a part of the signal processing circuit unit 14 shown in FIG. 1, and is composed of a comparator and a logic circuit. In this embodiment, as can be seen from the figure, an offset S2 is added to the output from the PD 12b2.

  That is, the comparator 71 compares the output voltage V1 of the PD 12b1, the sum of the output voltage V2 of the PD 12b2 and the offset S2, and a signal A indicating in logic whether (the output voltage V2 + S2 of the PD 12b2) is larger, 72, the sum of the output voltage V2 of the PD 12b2 and the offset S2 is compared with the output voltage V3 of the PD 12b3, and a signal B indicating in logic that (the output voltage V2 + S2 of the PD 12b2) is larger, and the comparator 73 A signal C is generated that logically indicates whether the sum of the output voltages of PD12b1, PD12b2, and PD12b3 is greater than a certain slice level voltage S. The AND circuit 74 whose output is true only when all of the signals A, B, and C are true is in the origin detection state.

  The value of the offset S2 is such that the signal A and the signal B are stable and positive at a position sufficiently away from the origin detection position, that is, (the output voltage V2 + S2 from the PD 12b2) is the output voltage v1 from the PD 12b1 or The output voltage V3 from the PD 12b3 is set larger than the output voltage V3 as much as possible. In addition, the offset S2 in the signal A and the signal B is the same value here, but may be a different value if a configuration of an origin detection system that does not cause a problem even if different values are adopted.

  FIG. 10B shows the state of signal processing in the origin detection circuit 70 in the present embodiment. That is, how the outputs V1 to V3 from the PDs 12b1 to 12b3, the output signals A to C from the comparator, and the origin detection signal PZ change depending on the relative displacement between the moving body and the fixed body. Represents.

  Here, as shown in FIG. 10B, when the voltages V1 to V3 output from the PD12b1 to PD12b3 are a function of the position, the V1 to V3 have a certain deviation in the horizontal axis direction and are specified. It has a shape that is maximal at the point and is almost line symmetric about the point. The signal C is a mask for detecting the origin detection signal only near the origin detection position.

  As described above, according to the present embodiment, it is possible to provide an optical displacement sensor having effects similar to those of the third embodiment and having the following effects specific to the present embodiment. .

  In this embodiment, by adding a slight offset S2 to the output voltage V2 from the PD 12b2, the position signal A and the position signal B at a position away from the origin are stabilized. Thereby, compared with the case where offset S2 is not added to PD12b2, noises, such as a digital noise which generate | occur | produces with time in the signal processing circuit unit 14, are suppressed. An optical displacement sensor that can obtain a more stable origin detection signal can be provided by removing such noise that easily affects an analog signal or the like in the signal processing circuit unit 14.

  The present invention has been described above based on the embodiments, but the present invention is not limited to the above-described embodiments, and various modifications and applications are possible within the scope of the gist of the present invention. .

  For example, in the apparatus shown in FIG. 1, a transmissive type scale is used as the scale 10 as described above, but a reflective scale is used, or a lens or the like for condensing light on a photodetector is inserted. It doesn't matter.

  In addition to the encoder device that measures the relative movement between the sensor head and the scale 10, a device such as a length measuring device that measures the distance between the light detection unit 12 that is the sensor head and the mirror, and a relative change in position. The sensor to which the present embodiment is applied is not particularly limited as long as it is a sensor having a displacement signal based thereon and an optical origin detection unit.

  Although the optical encoder device has been described here as an example, it is needless to say that other methods such as a magnetic method may be used instead of the optical method except for the portion related to the detection of the origin detection signal.

  Further, the above-described embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the column of the effect of the invention Can be extracted as an invention.

(Appendix)
The invention having the following configuration can be extracted from the specific embodiment.

(1) a light source unit and a light receiving unit attached to any one of a fixed body and a moving body that move relative to each other;
A scale having a predetermined optical pattern attached to one of the fixed body and the moving body to which the light source unit is not attached;
Based on the signal detected by the light receiving unit, the displacement or position of the moving body is detected, the displacement amount or position is output as a position signal, and the origin is detected when the moving body is at the origin position. A signal processing circuit for outputting an origin detection signal which is a digital signal indicating;
Comprising
In the optical displacement sensor in which the light source unit, the light receiving unit, and the scale are spatially arranged so that light emitted from the light source unit is detected by the light receiving unit through the scale,
The light receiving unit has a photodetector used for detecting at least three or more origins,
The first set and the second set are set by selecting two specific signals out of the signals output from the photodetector in the light receiving unit, and the two sets near the origin in the first set. When the position of the moving body where the signal levels of the signals are equal is the first position, and the position of the moving body where the signal levels of the two signals are equal near the origin in the second set is the second position,
The signal processing circuit has a constant signal level when the moving body is located between the first position and the second position, and the moving body moves from the first position to the second position. An optical displacement sensor that outputs an origin detection signal having a signal level different from the above signal level when the position is not between the two.

(Corresponding embodiment)
The embodiment relating to the optical displacement sensor described in (1) corresponds to the first to fourth embodiments. In these embodiments, the scale corresponds to, for example, the scale 10, the light source unit corresponds to, for example, the light source unit 6, the light receiving unit corresponds to, for example, the light detection unit 12, and the light detector corresponds to, for example, the origin detection unit. The 12b PDs 12b1 to 12b3 or 12b4 correspond, and the signal processing circuit corresponds to the signal processing circuit unit 14, for example.

(Function and effect)
According to the optical displacement sensor described in (1), an optical displacement sensor that can generate an origin detection signal with little variation in the detection position, that is, an origin detection signal with high accuracy, along with the position signal, The origin detection signal synchronized with the position signal can be generated stably.

(2) The light receiving unit includes first to fourth photodetectors as photodetectors used for origin detection,
The first set includes an output signal of the first photodetector and an output signal of the second photodetector, and the second set includes an output signal of the third photodetector and the fourth light. The optical displacement sensor according to (1), comprising an output signal of a detector.

(Corresponding embodiment)
The embodiment relating to the optical displacement sensor described in (2) corresponds to the first embodiment and the second embodiment. In those embodiments, the photodetector corresponds to, for example, PDs 12b1 to 12b4 of the origin detection unit 12b.

(Function and effect)
According to the optical displacement sensor described in (2), an optical displacement sensor that can generate an origin detection signal with little variation in the detected position, that is, an origin detection signal with high accuracy, along with the position signal, The origin detection signal synchronized with the position signal can be generated stably.

(3) The light receiving unit includes first to third photodetectors as photodetectors used for origin detection,
The first set includes an output signal of the first photodetector and an output signal of the second photodetector, and the second set includes an output signal of the second photodetector and the third light. The optical displacement sensor according to (1), comprising an output signal of a detector.

(Corresponding embodiment)
The third embodiment corresponds to the optical displacement sensor described in (3). In the embodiment, for example, the PDs 12b1 to 12b3 of the origin detection unit 12b correspond to the photodetector.

(Function and effect)
According to the optical displacement sensor described in (3), it becomes an optical displacement sensor capable of a simpler and more compact configuration. This also makes it possible to reduce the area irradiated with light from the light source unit.

  (4) The detection centers of the four photodetectors are arranged in the displacement direction of the moving body in the first photodetector, the second photodetector, the third photodetector, and the fourth photodetector. The optical displacement sensor according to (2), wherein the first to fourth photodetectors are provided in the light receiving section so as to be sequentially arranged.

(Corresponding embodiment)
The embodiment relating to the optical displacement sensor described in (4) corresponds to the first embodiment.

(Function and effect)
According to the optical displacement sensor described in (4), an optical displacement sensor that can generate an origin detection signal with little variation in the detected position, that is, an origin detection signal with high accuracy, along with the position signal, The origin detection signal synchronized with the position signal can be generated stably.

  (5) The detection centers of the four photodetectors are arranged in the displacement direction of the moving body in the first photodetector, the third photodetector, the second photodetector, and the fourth photodetector. The optical displacement sensor according to (2), wherein the first to fourth photodetectors are provided in the light receiving section so as to be sequentially arranged.

(Corresponding embodiment)
The second embodiment corresponds to the embodiment relating to the optical displacement sensor described in (5).

(Function and effect)
According to the optical displacement sensor described in (5), the detection width is unlikely to change, it is possible to generate an origin detection signal having a detection width corresponding to a certain amount of displacement, and the detection position also varies. Since it is difficult, it is an optical displacement sensor that performs stable origin detection, and an origin detection signal can be generated in synchronization with a position signal.

  (6) The detection centers of the three photodetectors are arranged in the order of the first photodetector, the second photodetector, and the third photodetector in the displacement direction of the moving body. The optical displacement sensor according to (3), wherein the first to third photodetectors are provided in the light receiving section.

(Corresponding embodiment)
The third embodiment and the fourth embodiment correspond to the optical displacement sensor described in (6).

(Function and effect)
According to the optical displacement sensor described in (6), it becomes an optical displacement sensor capable of a simpler and more compact configuration. Thereby, the area which irradiates the light from a light source part can be made small.

  (7) The photodetectors that output the first set of output signals have the same shape and structure, and the photodetectors that output the second set of output signals have the same shape and structure. The optical displacement sensor according to 1).

(Corresponding embodiment)
The embodiment relating to the optical displacement sensor described in (7) corresponds to the first to third embodiments.

(Function and effect)
According to the optical displacement sensor described in (7), an optical displacement sensor that can generate an origin detection signal with little variation in the detected position, that is, an origin detection signal with high accuracy, along with the position signal, The origin detection signal synchronized with the position signal can be generated stably.

  (8) The interval between the detection centers in each photodetector that outputs the first set of output signals is made equal to the interval between the detection centers in each photodetector that outputs the second set of output signals. The optical detector according to (1), wherein the photodetector is arranged in

(Corresponding embodiment)
The embodiment relating to the optical displacement sensor described in (8) corresponds to the first to third embodiments.

(Function and effect)
According to the optical displacement sensor described in (8), an optical displacement sensor that can generate an origin detection signal with little variation in the detected position, that is, an origin detection signal with high accuracy, along with the position signal, The origin detection signal synchronized with the position signal can be generated stably.

  (9) One of the two output signals in the first set has a predetermined current value that is greater than that of the other output signal at a position more than a predetermined distance away from the position where the origin detection signal is detected. Alternatively, the optical displacement sensor according to (1), wherein the optical displacement sensor is set so that an output signal is increased by a predetermined voltage value.

(Corresponding embodiment)
The embodiment relating to the optical displacement sensor described in (9) corresponds to the fourth embodiment. In the embodiment, the predetermined voltage value corresponds to, for example, the offset S2.

(Function and effect)
According to the optical displacement sensor described in (9), noise such as digital noise generated with time in the signal processing circuit unit 14 can be suppressed as compared with the case where the offset S2 is not added. Then, by removing such noise that easily affects an analog signal or the like inside the signal processing circuit unit 14, it is possible to provide an optical displacement sensor that can obtain a more stable origin detection signal.

  (10) The distance of the difference between the first position and the second position in the moving body matches the length of (N / 2) periods in the position signal, where N is a natural number. (1) The optical displacement sensor according to (1).

(Corresponding embodiment)
The first to fourth embodiments correspond to the optical displacement sensor according to (10).

(Function and effect)
According to the optical displacement sensor described in (10), an optical displacement sensor that can generate an origin detection signal with little variation in the detection position, that is, an origin detection signal with high accuracy, along with the position signal, It is possible to stably generate an origin detection signal synchronized with the position signal.

(11) The position of the moving body when a signal detected by any of the photodetectors reaches a peak is a position x, and the position of the detection center of the photodetector in a direction corresponding to the displacement direction of the moving body Is a position y, and a and b are constants, the above x and y have a linear relationship as shown in the following equation:
x = a · y + b
Let X be the midpoint of the detection center of the two photodetectors that output the first set of output signals, and Y be the midpoint of the detection center of the two photodetectors that output the second set of output signals. The absolute value of a · d matches the length of N / 2 periods in the position signal, where d is the length component of the minute XY in the direction corresponding to the displacement direction of the moving body and N is a natural number. (1) The optical displacement sensor according to (1).

(Corresponding embodiment)
The first to fourth embodiments correspond to the embodiment relating to the optical displacement sensor described in (11).

(Function and effect)
According to the optical displacement sensor described in (11), an optical displacement sensor that can generate an origin detection signal with little variation in the detected position, that is, an origin detection signal with high accuracy, along with the position signal, The origin detection signal synchronized with the position signal can be generated stably.

  (12) The optical displacement sensor according to (1), wherein an origin detection signal synchronized with the position signal is generated based on the origin detection signal and the position signal which are digital signals.

(Corresponding embodiment)
The first to fourth embodiments correspond to the optical displacement sensor described in (12).

(Function and effect)
According to the optical displacement sensor described in (12), an optical displacement sensor that can generate an origin detection signal with little variation in the detected position, that is, an origin detection signal with high accuracy, along with the position signal, It is possible to stably generate an origin detection signal synchronized with the position signal.

The figure which shows the general structure of an encoder apparatus. The figure which shows a photon detection part in case the number of photon detectors is four. The figure which shows the structure of the synchronous circuit given to a signal processing circuit part. (A) is a figure which shows the structure of the origin detection part in the photon detection part of the optical encoder apparatus which concerns on 1st Embodiment of this invention. FIG. 6B is a waveform diagram illustrating a state of signal processing in the origin detection circuit. (C) is a figure which shows the structure of an origin detection circuit. The wave form diagram which shows a mode that the input signal is processed within the signal processing circuit part. The figure which shows the variation of shape and arrangement | positioning of PD in a photon detection part. (A) is a figure which shows arrangement | positioning of PD in 2nd Embodiment. FIG. 7B is a diagram illustrating a state of signal processing in the origin detection circuit. (A) And (b) is a figure which shows the modification of arrangement | positioning of PD in 2nd Embodiment of this invention, respectively. FIG. 6C is a diagram illustrating a state of signal processing in the origin detection circuit. (A) is a figure which shows arrangement | positioning of PD in 3rd Embodiment of this invention. FIG. 6B is a diagram illustrating a configuration of an origin detection circuit. (C) is a diagram showing the state of signal processing in the origin detection circuit. (A) is a figure which shows the origin detection circuit in 4th Embodiment of this invention. FIG. 6B is a diagram showing a state of signal processing in the origin detection circuit. (A) is a figure which shows the optical detection part of the optical encoder by a prior art. (B) And (c) is a figure which shows the signal processing of the optical encoder by a prior art, respectively.

Explanation of symbols

    DESCRIPTION OF SYMBOLS 2 ... Light emission part, 4 ... Optical element, 6 ... Light source part, 8 ... Index scale, 8a ... Position detection pattern, 8b ... Origin detection pattern, 10 ... Scale, 10a ... Position detection pattern, 10b ... Origin detection Patterns: 12: Light detection unit, 12a: Position detection unit, 12b: Origin detection unit, 12b1 to 12b4 ... PD, 14: Signal processing circuit unit, 60: Synchronization circuit, 61 ... Binarization circuit, 62 ... Synchronization processing unit 63 ... Synchronous (timing) changeover switch, 70 ... Origin detection circuit, 71, 72, 73 ... Comparator, 74 ... Logical product circuit.

Claims (12)

A light source unit and a light receiving unit attached to any one of a fixed body and a moving body that move relative to each other;
A scale having a predetermined optical pattern attached to one of the fixed body and the moving body to which the light source unit is not attached;
Based on the signal detected by the light receiving unit, the displacement or position of the moving body is detected, the displacement amount or position is output as a position signal, and the origin is detected when the moving body is at the origin position. A signal processing circuit for outputting an origin detection signal which is a digital signal indicating;
Comprising
In the optical displacement sensor in which the light source unit, the light receiving unit, and the scale are spatially arranged so that light emitted from the light source unit is detected by the light receiving unit through the scale,
The light receiving unit has a photodetector used for detecting at least three or more origins,
The first set and the second set are set by selecting two specific signals out of the signals output from the photodetector in the light receiving unit, and the two sets near the origin in the first set. When the position of the moving body where the signal levels of the signals are equal is the first position, and the position of the moving body where the signal levels of the two signals are equal in the vicinity of the origin in the second set is the second position,
The signal processing circuit has a constant signal level when the moving body is located between the first position and the second position, and the moving body moves from the first position to the second position. An optical displacement sensor which outputs an origin detection signal having a signal level different from the constant signal level when the position is not between the two. The light receiving unit includes first to fourth photodetectors as photodetectors used for origin detection,
The first set includes an output signal of the first photodetector and an output signal of the second photodetector, and the second set includes an output signal of the third photodetector and the fourth light. The optical displacement sensor according to claim 1, comprising an output signal of a detector. The light receiving unit includes first to third photodetectors as photodetectors used for origin detection,
The first set includes an output signal of the first photodetector and an output signal of the second photodetector, and the second set includes an output signal of the second photodetector and the third light. The optical displacement sensor according to claim 1, comprising an output signal of a detector.   The detection centers of the four photodetectors are arranged in the order of the first photodetector, the second photodetector, the third photodetector, and the fourth photodetector in the displacement direction of the moving body. The optical displacement sensor according to claim 2, wherein the first to fourth photodetectors are provided in the light receiving section.   The detection centers of the four photodetectors are arranged in the order of the first photodetector, the third photodetector, the second photodetector, and the fourth photodetector in the displacement direction of the moving body. The optical displacement sensor according to claim 2, wherein the first to fourth photodetectors are provided in the light receiving section.   The first photo detector, the second photo detector, and the third photo detector are arranged in the order of detection centers of the three photo detectors in the displacement direction of the moving body. 4. The optical displacement sensor according to claim 3, wherein a third photodetector is provided in the light receiving unit.   The shape and structure of the photodetectors that output the first set of output signals are equal to each other, and the shape and structure of the photodetectors that output the second set of output signals are also equal to each other. The optical displacement sensor described.   The interval between the detection centers in each photodetector that outputs the first set of output signals and the interval between the detection centers in each photodetector that outputs the second set of output signals are equalized. The optical displacement sensor according to claim 1, further comprising a photodetector.   A specific one of the two output signals constituting the first set is at a predetermined current value or more than the other output signal at a position more than a predetermined distance from the position where the origin detection signal is detected. The optical displacement sensor according to claim 1, wherein the optical displacement sensor is set so that an output signal is increased by a predetermined voltage value.   The distance of the difference between the first position and the second position in the moving body matches the length of (N / 2) periods in the position signal, where N is a natural number. The optical displacement sensor according to claim 1. The position of the moving body when the signal detected by any of the photodetectors reaches a peak is defined as a position x, and the position of the detection center of the photodetector in a direction corresponding to the displacement direction of the moving body is defined as a position y. Where a and b are constants, the above x and y have a linear relationship as shown in the following equation:
x = a · y + b
Let X be the midpoint of the detection center of the two photodetectors that output the first set of output signals, and Y be the midpoint of the detection center of the two photodetectors that output the second set of output signals. The absolute value of a · d matches the length of N / 2 periods in the position signal, where d is the length component of the minute XY in the direction corresponding to the displacement direction of the moving body and N is a natural number. The optical displacement sensor according to claim 1.   2. The optical displacement sensor according to claim 1, wherein an origin detection signal synchronized with the position signal is generated based on the origin detection signal and the position signal which are digital signals.

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