JP2009103607A - Optical encoder and electronic equipment provided therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical encoder having a simple signal processing circuit, capable of preventing positioning precision from getting worse when rotated at a low speed, and capable of reducing a mounting area to be constituted compactly. <P>SOLUTION: This optical encoder is provided with a light emitting element and a light-receiving element 10. The light-receiving element 10 is brought into a light incident or nonincident state, when a moving body passes at a prescribed moving frequency with respect to the light-receiving element 10. A prescribed multiplication frequency generating part 12 outputs a multiplication signal D1 having a prescribed multiplication of frequency with respect to the moving frequency. Frequency detecting parts 13, 14 obtain a theoretical value expressing which frequency area the moving frequency is located in out of a high or low frequency area with respect to a blocking frequency, using an output D3 of a filter 14 having the prescribed blocking frequency. A frequency switching part 15 outputs the multiplication signal D1 as an output signal D4, when the moving frequency is located in the low frequency area, and outputs a signal having 1/n (n is 2 or more of natural number) of frequency with respect to the frequency of the multiplication signal D1, when the moving frequency is located in the high frequency area. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical encoder that detects a position, a moving speed, a moving direction, and the like of a moving body using a light emitting element and a light receiving element.

  The present invention also relates to an electronic apparatus provided with such an optical encoder. Examples of such electronic devices include printing devices such as copying machines and printers, and FA (factory automation) devices.

  An optical encoder that uses a light emitting element and a light receiving element to detect the position of a moving body, such as that used in printing equipment, outputs at a frequency that follows the operating speed of a motor that drives the moving body. In general, the characteristics of the motor and its control system are unstable during low-frequency operation, but are stable during high-frequency operation.

  Therefore, conventionally, as this type of optical encoder, for example, one described in Patent Document 1 (Japanese Utility Model Publication No. 4-96018) has been proposed. In the optical encoder (referred to as “incremental encoder”) of the same document, a plurality of concentric light transmission slits are formed on the circumference of the rotating plate, and a light emitting element and a light receiving element are received for each track. A pair of elements is arranged. During operation, the counted pulse is compared with a reference value based on the set number of pulses, and a track in which a rotation pulse to be processed is detected is selected based on the result. When the rotating shaft is rotated at a high speed, a low-resolution output is supplied when it is unnecessary, and at a low-speed rotation or when necessary, a high-resolution output is supplied. This simplifies the processing of the output signal and the configuration of the counting circuit (the requirement becomes severe during high-speed rotation), and the positioning accuracy can be maintained during low-speed rotation.

  Patent Document 2 (Japanese Utility Model Laid-Open No. 1-57817) discloses an exclusive OR circuit in which a frequency signal of a natural frequency and a frequency signal including a frequency variation due to a physical quantity are input to the input, and this exclusive logic. There is described a frequency subtracting circuit including a low-pass filter that removes a high-frequency component from the output of the sum circuit and allows a frequency fluctuation to pass, and means for shaping a waveform of the frequency signal that has passed through the low-pass filter and outputting the waveform. According to this frequency subtraction circuit, the frequency can be accurately subtracted in a short measurement time, and a minute frequency fluctuation can be detected with high accuracy.

In Patent Document 3 (Japanese Patent Laid-Open No. 2002-81963), sinusoidal A-phase signals and B-phase signals obtained from an output signal of a photodetector through an amplifier or the like are further passed through a low-pass filter and output. A measurement signal generation circuit is described. In this measurement signal generation circuit, when a signal having a cutoff frequency of the low-pass filter is mixed in this circuit, it is removed as a noise signal.
Japanese Utility Model Publication No. 4-96018 Japanese Utility Model Publication No. 1-57817 JP 2002-81963 A

  However, in the optical encoder of Patent Document 1, a plurality of light transmission slits are formed on the periphery of the rotating plate, and a pair of light emitting element and light receiving element is arranged for each track, so that the mounting area becomes large, There is a problem of increasing the size. Further, the output signal is adversely affected by misalignment between the pair of the light emitting element and the light receiving element.

  Note that the techniques in Patent Documents 2 and 3 for removing high-frequency components of signals as noise using a low-pass filter cannot be applied as they are to the output signal of an optical encoder. This is because the original signal is removed as noise by the low-pass filter during high-speed operation.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical encoder that has a simple signal processing circuit, that does not lose positioning accuracy during low-speed rotation, and that can be configured compactly with a small mounting area.

  Moreover, the subject of this invention is providing the electronic device provided with such an optical encoder.

In order to solve the above problems, an optical encoder of the present invention is
A light emitting element;
A light receiving element disposed in a region where light from the light emitting element can reach,
A moving body that alternately has a light-on portion and a light-off portion that create a state in which the light is incident on the light receiving element and a state in which the light is not incident in one direction has a predetermined position corresponding to the light receiving element along the one direction. When the light passes through at a predetermined moving frequency, the output of the light receiving element takes a value corresponding to whether light from the light emitting element is incident or not incident on the light receiving element,
A frequency multiplication unit that receives the output of the light receiving element and outputs a multiplied signal having a frequency multiplied by the frequency of the moving body;
A filter that receives the output of the frequency multiplication unit or the light receiving element and attenuates and passes the other frequency component with respect to either one of the outputs higher or lower than a predetermined cutoff frequency, A frequency range detector that obtains a logical value indicating whether the moving frequency is higher or lower than the cut-off frequency using the output of the filter;
A signal having the same frequency as the frequency of the multiplied signal output from the multiplied frequency generation unit when the moving frequency is in a frequency range lower than the cut-off frequency according to the logical value obtained by the frequency range detection unit. On the other hand, when the moving frequency is higher than the cut-off frequency, a signal having a frequency of 1 / n (n is a natural number of 2 or more) with respect to the frequency of the multiplied signal is output. And a frequency switching unit.

  Here, the “one direction” in which the light-on part and the light-off part of the moving body are provided is not limited to one linear direction. For example, when the moving body has a disk shape, the circumferential direction along the outer periphery thereof may be used.

  In the optical encoder according to the present invention, the frequency range detection unit receives the output of the multiplied frequency generation unit or the light receiving element, and outputs a frequency component that is higher or lower than a predetermined cutoff frequency among the outputs. A filter that attenuates and passes the other frequency component is included, and a logical value indicating whether the moving frequency is in a high or low frequency range with respect to the cut-off frequency is obtained using the output of the filter. For example, when the filter is a low-pass filter, the magnitude (amplitude) of the signal passing through the low-pass filter becomes high when the moving frequency is in a frequency range lower than the cutoff frequency. To obtain a logical value of 1. On the other hand, when the moving frequency is in a frequency range higher than the cut-off frequency, a logical value 0 is obtained corresponding to the magnitude (amplitude) of the signal passing through the low-pass filter being low. When the moving frequency is in a frequency range lower than the cut-off frequency according to the logical value obtained by the frequency range detection unit (when the logical value is 1 in the above example), the frequency switching unit A signal having the same frequency as the frequency of the multiplied signal output from the multiplied frequency generation unit is output. On the other hand, when the moving frequency is in a frequency range higher than the cut-off frequency (in the above example, when the logical value is 0), the frequency switching unit 1 / n (n is the frequency of the multiplied signal). A signal having a frequency of 2 or a natural number) is output.

  As a result, this optical encoder has a high resolution when the moving frequency is in a frequency range lower than the cutoff frequency, and has a low resolution when the moving frequency is in a frequency range higher than the cutoff frequency. Accordingly, the positioning accuracy can be maintained at a low speed of the moving body, and the configuration of the signal processing circuit including the above-described multiplied frequency generation section, the frequency range detection section, and the frequency switching section (the demand is severe at the high speed of the moving body). Become simple). In addition, the light receiving element does not need to be provided in a plurality of tracks, and may be provided in one track along one direction through which the light-on part and the light-off part of the moving body pass. Therefore, this optical encoder can be made compact by reducing the mounting area.

In one embodiment of the optical encoder,
The frequency range detection unit includes a plurality of filters having different cutoff frequencies, and obtains a logical value indicating which frequency range the moving frequency is divided by the plurality of cutoff frequencies,
The frequency switching unit has the same frequency as the frequency of the multiplied signal output from the multiplied frequency generation unit when the moving frequency is in the lowest frequency range according to the logical value obtained by the frequency range detection unit. While outputting a signal, the value of n is sequentially increased to output a signal having the frequency of 1 / n as the frequency range including the moving frequency increases from the lowest frequency range. To do.

  In the optical encoder of this embodiment, the resolution can be set for each frequency region divided by a plurality of cutoff frequencies. That is, the highest resolution is obtained when the moving frequency is in the lowest frequency range. As the frequency range including the moving frequency increases from the lowest frequency range, the resolution gradually decreases. Therefore, it becomes possible to operate with accuracy according to the requirements of various motors and control systems, and reliability is improved.

In one embodiment of the optical encoder,
A plurality of the light receiving elements are arranged side by side along the one direction in a region where the light from the light emitting element can reach, and each of the light receiving elements outputs a signal having a phase different from each other as the moving body moves in the one direction. Output,
The frequency multiplication unit, the frequency band detection unit, and the frequency switching unit are provided for each light receiving element.

  In the optical encoder of this embodiment, the light receiving elements output signals having different phases. As a result, each frequency switching unit provided for each light receiving element outputs signals having different phases. Therefore, the movement direction of the moving body can be detected by the signals having different phases from each other, which is useful.

  The plurality of light receiving elements may be a plurality of light receiving regions formed by partitioning the surface of one light receiving chip.

In one embodiment of the optical encoder,
The frequency range detector is
A phase inversion unit that receives the output of the frequency multiplication frequency generation unit and changes the phase of the output by 180 °;
It has the same characteristics as the filter, receives the output of the phase inverting unit, attenuates the other frequency component of the output with respect to one of the frequency components higher or lower than the cut-off frequency, and passes it. Including another filter,
The logical sum of the logical values represented by the outputs of the two filters is the logical value representing whether the moving frequency is in a high or low frequency range with respect to a predetermined cutoff frequency.

  In the optical encoder of this embodiment, the two filters have the same characteristics. Therefore, for example, when the two filters are low-pass filters, the logical sum of the logical values represented by the outputs of the two filters is calculated when the moving frequency is in a frequency range lower than the cutoff frequency. Corresponding to the fact that the magnitude (amplitude) of the output of the filter alternately and complementarily becomes a high level, the logical value becomes 1. On the other hand, the logical sum of the logical values represented by the outputs of the two filters is such that the magnitude (amplitude) of the outputs of the two filters is low when the moving frequency is in a frequency range higher than the cutoff frequency. Corresponding to the level, the logical value becomes zero. Thus, a logical value indicating whether the moving frequency is higher or lower than the cut-off frequency is obtained.

In one embodiment of the optical encoder,
The frequency band detection unit includes a differential amplification unit that differentially amplifies the output of the light receiving element and the output of the filter that receives the output of the light receiving element, and uses the output of the differential amplification unit Thus, the logical value indicating whether the moving frequency is in a high or low frequency range with respect to a predetermined cut-off frequency is obtained.

  In the optical encoder according to this embodiment, the differential amplification unit of the frequency band detection unit receives the output of the light receiving element and the output of the filter that has received the output of the light receiving element to perform differential amplification. . For example, when the filter is a low-pass filter, when the moving frequency is in a frequency range lower than the cut-off frequency, two inputs to the differential amplifying unit are signals having substantially the same waveform. The magnitude of the output of the dynamic amplification unit becomes a low level and becomes a logical value 0. On the other hand, when the moving frequency is higher than the cut-off frequency, the output of the low-pass filter is reduced with respect to the output of the light receiving element, and the difference between the two inputs to the differential amplifier is Therefore, the magnitude of the output of the differential amplification unit becomes a high level and becomes a logical value 1. In this way, a logical value indicating whether the moving frequency is higher or lower than the cut-off frequency is obtained (in this example, the logical value is opposite to the above-described example). However, on the premise of this, the frequency switching unit may perform a switching operation opposite to the above. In this optical encoder, since the output of the light receiving element and the output of the filter receiving the output of the light receiving element are used, control by analog signals is performed. As a result, the CR constant of the filter circuit can be reduced. Therefore, when this optical encoder is composed of one chip, the chip size can be reduced, which is beneficial.

  In the optical encoder according to an embodiment, the differential amplifier has a hysteresis characteristic in which an input difference when the output level falls is smaller than an input difference when the output level rises.

  In the optical encoder of this embodiment, the differential amplifier has a hysteresis characteristic in which the input difference when the output level falls is smaller than the input difference when the output level rises. Therefore, problems such as chattering do not occur when the moving frequency changes and the frequency switching unit switches the output frequency.

  An optical encoder according to an embodiment is characterized in that the cutoff frequency of the filter is variable.

  In the optical encoder of this embodiment, since the cutoff frequency of the filter is variable, the frequency range for the moving frequency can be arbitrarily set. As a result, the frequency switching unit can switch the frequency at a frequency that meets the requirements of various motors and control systems. Therefore, the usability of the optical encoder is improved, which is beneficial.

  An electronic apparatus according to the present invention is an electronic apparatus including the optical encoder.

  In the electronic apparatus according to the present invention, since the optical encoder does not deteriorate the positioning accuracy when the moving body is at a low speed, the accuracy of the control when the moving body starts or stops is increased. Further, since the optical encoder is configured in a small size, the electronic apparatus is also configured in a small size.

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

  FIG. 12 shows a cross section of a light transmission type photoelectric encoder according to an embodiment. In this photoelectric encoder, the light emitting portion 142 is accommodated on one side (upper side in FIG. 12) of the case 145 having the groove 147 at the substantially center, and the light receiving portion 144 is accommodated on the other side (lower side in FIG. 12). Has been. Thereby, the light emission part 142 and the light-receiving part 144 have opposed. The light emitting part 142 is configured by mounting a semiconductor light emitting chip 141 as a light emitting element on a header part 148 a of a lead frame 148 and sealing it with a transparent resin 152. The light receiving portion 144 is configured by mounting the semiconductor light receiving chip 110 on the header portion 149 a of the lead frame 149 and sealing it with a transparent resin 154. The semiconductor light receiving chip 110 includes a light receiving element (a region that receives and photoelectrically converts incident light) and a signal processing circuit that processes an output of the light receiving element (details will be described later). In front of the light emitting unit 142 on the optical axis 150 connecting the semiconductor light emitting chip 141 and the light receiving element included in the semiconductor light receiving chip 110, a collimating lens 146 for collimating the light emitted from the light emitting unit 142 is disposed. Has been. In the groove 147, a disc-shaped moving body 40 provided with a plurality of slits (collectively represented by the symbol X) as light-on portions is inserted.

  In operation, the moving body 40 is rotated at a constant speed around a central axis (not shown) parallel to the optical axis 150. The light emitting chip 141 is energized through the lead frame 148, the light emitting chip 141 emits light, and light is emitted along the optical axis 150 through the collimating lens 146.

  The upper part of FIG. 1B schematically shows a portion of the moving body 40 provided with the slits X1, X2,... Perpendicular to the plate surface. The portion where the plate material between the slits X1, X2,... Exists is light to the light receiving element 10 (schematically shown in the lower part of FIG. 1B, which is composed of the photodiode PD in this example) included in the light receiving chip 110. Light off portions Y1, Y2,... That are not incident are configured. In FIG. 1B, the rotation direction K of the moving body 40 is approximately represented as a straight line. The moving body 40 has slits X1, X2,... And light-off portions Y1, Y2,. The slits X1, X2,... And the light-off portions Y1, Y2,... Have the same ½ pitch (that is, P / 2) dimension in the rotation direction K.

  The light receiving element 10 photoelectrically converts light incident through the slits X1, X2,... Of the moving body 40 and outputs a signal corresponding to the amount of incident light. A frequency at which the slits X1, X2,... Of the moving body 40 pass through a position corresponding to the light receiving element 10 is defined as a moving frequency f. The output of the light receiving element 10 is processed by a signal processing circuit described below.

  FIG. 1A illustrates the configuration of the signal processing circuit 1 that processes the output of the light receiving element 10.

  The signal processing circuit 1 includes an AD conversion unit 11 that converts an analog output of the light receiving element 10 into a digital signal, a multiplied frequency generation unit 12, a distribution unit 13, and a low-pass filter as a filter ("LPF" in the figure). 14), a logic circuit unit 15 as a frequency switching unit, and an output unit 16 that amplifies and outputs the output D4 of the logic circuit unit 15.

  The multiplied frequency generator 12 receives the output of the light receiving element 10 through the AD converter 11 and outputs a multiplied signal D1 having a frequency multiplied by the moving frequency f. In this example, as shown in FIGS. 2A1 and 2B1, the multiplied signal D1 output from the multiplied frequency generator 12 has a frequency 2f that is twice the moving frequency f. The output D2 of the AD conversion unit 11 has the same frequency f as the moving frequency f. 2 (FIG. 2 (A1) to (A3)) shows signal waveforms when the moving body 40 is operating at high speed (at high speed), and the lower stage in FIG. 2 (FIG. 2 (B1)). (B3)) shows signal waveforms when the moving body 40 is operating at low speed (at low speed). The horizontal axis in FIG. 2 represents time, and the vertical axis represents the level of signal magnitude (amplitude) (the same applies to FIGS. 7 and 9 described later). T corresponds to the time of one cycle of the moving body 40.

  In this example, the distribution unit 13 and the low-pass filter 14 shown in FIG. 1A constitute a frequency band detection unit.

  The distribution unit 13 branches the output D1 of the multiplied frequency generation unit 12 into two.

  The low-pass filter 14 has a predetermined cutoff frequency (denoted as fc) determined by the time constant of the CR circuit constituting the filter. The low-pass filter 14 receives one output D1 branched by the distribution unit 13, and attenuates and passes a high frequency component with respect to a frequency component lower than the cutoff frequency fc in the output D1. The output that has passed through the low-pass filter 14 is referred to as D3. As shown in FIGS. 2A2 and 2B2, the output D3 of the low-pass filter 14 shows a waveform that rises logarithmically according to the time constant described above. Therefore, depending on whether the output D3 exceeds or does not exceed a predetermined threshold value (shown by a broken line in FIGS. 2A2 and 2B2), the frequency range of the moving frequency f is higher or lower than the cutoff frequency fc. A logical value indicating whether or not That is, when the filter 14 is a low-pass filter 14 as in this example, when the moving frequency f is in a frequency range lower than the cut-off frequency fc (at low speed), as shown in FIG. 2 (B2), the low-pass filter In response to the magnitude (amplitude) of the signal passing through 14 becoming a high level, a logical value 1 is obtained. On the other hand, when the moving frequency f is higher than the cut-off frequency fc (at high speed), the magnitude (amplitude) of the signal passing through the low-pass filter 14 is low as shown in FIG. 2 (A2). Correspondingly, a logical value of 0 is obtained.

  The logic circuit unit 15 shown in FIG. 1A has a frequency that is lower than the cut-off frequency fc according to the obtained logic value (when the logic value is 1 in the above example), FIG. As shown in (B3), a signal D4 having the same frequency 2f as the frequency 2f of the multiplied signal D1 output by the multiplied frequency generator 12 is output. On the other hand, when the moving frequency f is in a frequency range higher than the cutoff frequency fc (when the logical value is 0 in the above example), the logic circuit unit 15 generates the multiplication signal D1 as shown in FIG. 2 (A3). A signal D4 having a frequency f that is ½ of the frequency 2f is output. That is, when the moving frequency f is in a frequency range lower than the cut-off frequency fc, the signal D4 = D1. On the other hand, when the moving frequency f is higher than the cutoff frequency fc, the signal D4 = D2.

  The signal D4 output from the logic circuit unit 15 is amplified and output by the output unit 16 while maintaining the frequency.

  As a result, in this optical encoder, the resolution is high when the moving frequency f is in a frequency range lower than the cutoff frequency fc, and the resolution is low when the moving frequency f is in a frequency range higher than the cutoff frequency fc. Therefore, the positioning accuracy can be kept low when the moving body 40 is low speed, and the configuration of the signal processing circuit including the multiplied frequency generation section 12, the frequency band detection section, and the logic circuit section 15 (required when the moving body 40 is high speed). It becomes simpler. In addition, the light receiving element 10 does not have to be provided on a plurality of tracks, and may be provided on one track along one direction K through which the slits X1, X2,. Therefore, this optical encoder can be made compact by reducing the mounting area.

  FIG. 3 shows a modification (denoted by reference numeral 1A) of the signal processing circuit that processes the output of the light receiving element 10.

  This signal processing circuit 1A is provided with a first multiplied frequency generating unit 12A and a second multiplied frequency generating unit 12B as two types of multiplied frequency generating units, compared to the one shown in FIG. 1A. In addition, the signal processing circuit 1A includes a distribution unit 13A, 13B that branches the outputs D11, D12 of the multiplied frequency generation units 12A, 12B in two as a frequency range detection unit, and a low-pass filter as two types of filters. 14A, 14B. Unless otherwise specified, elements denoted by the same reference numerals in FIG. 3 as those in FIG. 1A indicate the same elements (the same applies to other drawings).

  The multiplied signal D11 output from the first multiplied frequency generator 12A has a frequency 4f that is four times the moving frequency f. The multiplied signal D12 output from the second multiplied frequency generator 12B has a frequency 2f that is twice the moving frequency f. The output D2 of the AD conversion unit 11 has the same frequency f as the moving frequency f.

  The low-pass filters 14A and 14B have cutoff frequencies fc1 and fc2 (fc1 <fc2) different from each other. The low-pass filters 14A and 14B receive one of the outputs D11 and D12 branched by the distributing units 13A and 13B, respectively, and the frequency components lower than the cutoff frequencies fc1 and fc2 among the outputs D11 and D12. A high frequency component is attenuated and passed. The outputs that have passed through the low-pass filters 14A and 14B are called D14 and D15. These outputs D14 and D15 indicate whether the moving frequency f is higher or lower than the cutoff frequencies fc1 and fc2, respectively, similarly to the output D3 example of FIG. 1A. As a result, as shown in FIG. 4, a logical value indicating which frequency range (“low speed”, “medium speed”, and “high speed”) in which the moving frequency f is divided by a plurality of cutoff frequencies fc1 and fc2 is obtained. can get. Here, “low speed” represents a frequency range in which the moving frequency f is lower than the cutoff frequency fc1, “medium speed” represents a frequency range in which the moving frequency f is between the cutoff frequencies fc1 and fc2, and “high speed”. Represents a frequency range in which the moving frequency f is higher than the cutoff frequency fc2. The logical value represented by the output D14 is 1 at “low speed” and 0 at “medium speed” and “high speed”. The logical value represented by the output D15 is 1 at “low speed” and “medium speed”, and 0 at “high speed”.

  The logic circuit unit 15A shown in FIG. 3 outputs a signal D16 having the same frequency 4f as the frequency 4f of the multiplied signal D11 output from the first multiplied frequency generation unit 12A at the “low speed” according to the obtained logical value. Output. At "medium speed", a signal D16 having the same frequency 2f as the frequency 2f of the multiplied signal D12 output from the second multiplied frequency generator 12B (this corresponds to 1/2 of the frequency 4f at "low speed") is output. To do. Further, at the time of “high speed”, a signal D16 having the same frequency f as the frequency f of the output D13 of the AD converter 11 (this corresponds to ¼ of the frequency 4f at the time of “low speed”) is output. That is, at the time of “low speed”, the signal D16 = D11. At “medium speed”, D16 = D12. At “high speed”, D16 = D13. In this way, as the frequency range including the moving frequency f increases from the lowest frequency range, the value of n is sequentially increased and a signal having a frequency of 1 / n is output.

  The signal D16 output from the logic circuit unit 15A is amplified and output by the output unit 16 while maintaining the frequency.

  In this optical encoder, the resolution can be set for each frequency region divided by a plurality of cutoff frequencies fc1 and fc2. That is, the highest resolution is obtained when the moving frequency f is in the lowest frequency range. As the frequency range including the moving frequency f increases from the lowest frequency range, the resolution gradually decreases. Therefore, it becomes possible to operate with accuracy according to the requirements of various motors and control systems, and reliability is improved.

  In the example shown in FIG. 5, the optical encoder has a plurality of light receiving elements arranged side by side along the rotation direction K of the moving body in an area where light from the light emitting element can reach (in this example, the surface area of the light receiving chip). Elements PD1 and PD2 are provided. Each of the light receiving elements PD1 and PD2 outputs signals having phases different from each other as the moving body 40 moves in the rotation direction K. In this optical encoder, the same signal processing circuits 1-1 and 1-2 as the signal processing circuit 1 shown in FIG. 1A are provided for the respective light receiving elements PD1 and PD2.

  In this optical encoder, the signal processing circuits 1-1 and 1-2 provided for the respective light receiving elements PD1 and PD2 output signals having different phases. Therefore, the moving direction of the moving body 40 can be detected by these signals having different phases, which is beneficial.

  In the example of FIG. 5, two sets of the light receiving element and the signal processing circuit shown in FIG. 1A are provided, but of course, three or more sets may be provided. For example, four sets of light receiving elements and signal processing circuits may be provided to output four systems of signals having different phases.

  The phase difference between the plurality of output signals can also be formed by performing multiplication and addition operations such as sin θ → sin 2θ using a sine function in the signal processing circuit.

  FIG. 6 shows another modification (denoted by reference numeral 1C) of the signal processing circuit that processes the output of the light receiving element 10.

  This signal processing circuit 1C is different from that shown in FIG. 1A in that it serves as a frequency region detection unit, a distribution unit 13C that branches the output D21 of the multiplied frequency generation unit 12 in three, and a 180 ° inversion phase as a phase inversion unit. The generator 17 and a low-pass filter 14C having two parallel input / output paths having the same characteristics are provided.

  As shown in FIGS. 7A1 and 7B1, the output D21 of the multiplied frequency generator 12 and the output D22 of the AD converter 11 are the outputs D1 and D1 shown in FIGS. 2A1 and 2B1, respectively. Same as D2.

  The 180 ° inversion phase generation unit 17 shown in FIG. 6 receives one output D21 branched by the distribution unit 13C, and outputs the output D21 with a phase difference of 180 °.

  One input / output path (lower input / output path in FIG. 6) of the low-pass filter 14C receives one output D21 branched by the distributing unit 13C in the same manner as the low-pass filter 14 in FIG. 1A. A high frequency component is attenuated and passed through a frequency component lower than the cutoff frequency fc in the output D21. This output is called D24. Another input / output path (upper input / output path in FIG. 6) of the low-pass filter 14C receives the output of the 180 ° inversion phase generation unit 17 and outputs a frequency component lower than the cutoff frequency fc in the output. On the other hand, a high frequency component is attenuated and passed. This output is called D23.

  In this example, a logical sum of the logical values represented by the two outputs D23 and D24 of the low-pass filter 14C (referred to as D25) is set so that the moving frequency f is higher or lower than the predetermined cutoff frequency fc. A logical value indicating whether or not there is.

  When the moving frequency f is in a frequency range lower than the cut-off frequency fc (at low speed), as shown in FIG. 7B2, the magnitudes (amplitudes) of the two outputs D23 and D24 are alternately complementary to a high level. In response to this, as shown in FIG. 7B3, a logical value 1 is obtained as the logical sum D25. On the other hand, when the moving frequency f is higher than the cut-off frequency fc (at high speed), the magnitudes (amplitudes) of the two outputs D23 and D24 are both low as shown in FIG. Corresponding to this, as shown in FIG. 7A3, a logical value 0 is obtained as the logical sum D25.

  In this example, the operation of taking the logical sum D25 is performed by the logic circuit unit 15C shown in FIG. When the moving frequency f is in a frequency range lower than the cutoff frequency fc according to the obtained logical value (when the logical value is 1 in the above example), the logic circuit unit 15C is shown in FIG. 7 (B4). As described above, the signal D26 having the same frequency 2f as the frequency 2f of the multiplied signal D21 output by the multiplied frequency generator 12 is output. On the other hand, when the moving frequency f is in a frequency range higher than the cut-off frequency fc (when the logical value is 0 in the above example), the logic circuit unit 15C has the multiplication signal D21 as shown in FIG. 7 (A4). A signal D26 having a frequency f that is ½ of the frequency 2f is output. That is, the signal D26 = D21 when the moving frequency f is in a frequency range lower than the cut-off frequency fc. On the other hand, when the moving frequency f is in a higher frequency range than the cutoff frequency fc, the signal D26 = D22.

  The signal D26 output from the logic circuit unit 15C is amplified and output by the output unit 16 while maintaining the frequency.

  According to the example of FIG. 6, the same effect as that of FIG. 1A can be obtained. In addition, the configuration of the frequency range detection unit is simplified, which is beneficial.

  FIG. 8 shows still another modified example (denoted by reference numeral 1D) of the signal processing circuit that processes the output of the light receiving element 10.

  The signal processing circuit 1D includes a low-pass filter 14D that receives an analog output D33 of the light receiving element 10, and an output D33 of the light receiving element 10 and an output D34 of the low-pass filter 14D as a frequency range detection unit with respect to that of FIG. 1A. And a differential amplifying unit 18 that differentially amplifies the received signal. The output of this differential amplifier 18 is referred to as D35.

  As shown in FIGS. 9A1 and 9B1, the output D31 of the multiplied frequency generator 12 and the output D32 of the AD converter 11 are the outputs D1 and D1 shown in FIGS. 2A1 and 2B1, respectively. Same as D2.

  The low-pass filter 14D attenuates the high frequency component of the analog output D33 of the light receiving element 10 with respect to the frequency component lower than the cut-off frequency fc and passes the attenuated component as an output D34. When the moving frequency f is in a frequency range lower than the cut-off frequency fc (at low speed), the output D34 of the low-pass filter 14D is approximately the same size as the analog output D33 of the light receiving element 10 (as shown in FIG. 9B2). Amplitude). Therefore, as shown in FIG. 9 (B3), a logical value 0 is obtained as the output D35 (= D33-D34) of the differential amplifier 18. On the other hand, when the moving frequency f is higher than the cutoff frequency fc (at high speed), the output D34 of the low-pass filter 14D is compared with the analog output D33 of the light receiving element 10 as shown in FIG. Get smaller. Therefore, as shown in FIG. 9A3, a logical value 1 is obtained as the output D35 (= D33−D34) of the differential amplifier 18.

  In this example, the logical values obtained for the example of FIG. 1A are reversed, but the logic circuit unit 15D shown in FIG. When the moving frequency f is in a frequency range lower than the cutoff frequency fc according to the obtained logical value (when the logical value is 0 in the above example), the logic circuit unit 15D is shown in FIG. 9 (B4). Thus, the signal D36 having the same frequency 2f as the frequency 2f of the multiplied signal D31 output from the multiplied frequency generator 12 is output. On the other hand, when the moving frequency f is higher than the cut-off frequency fc (when the logical value is 1 in the above example), the logic circuit unit 15D has the multiplication signal D31 as shown in FIG. 9 (A4). A signal D36 having a frequency f that is ½ of the frequency 2f is output. That is, the signal D36 = D31 when the moving frequency f is in a frequency range lower than the cutoff frequency fc. On the other hand, when the moving frequency f is higher than the cutoff frequency fc, the signal D36 = D32.

  The signal D36 output from the logic circuit unit 15D is amplified and output by the output unit 16 while maintaining the frequency.

  According to the example of FIG. 8, the same effect as that of FIG. 1A can be obtained. In addition, since this optical encoder uses the output of the light receiving element 10 and the output of the low-pass filter 14D that has received the output of the light receiving element 10, control by analog signals is performed. As a result, the CR constant of the low-pass filter 14D can be reduced. Therefore, when the light receiving element 10 of this optical encoder and the signal processing circuit 1D are configured by one chip, it is beneficial to reduce the chip size.

  A signal processing circuit 1E shown in FIG. 10 differs from the signal processing circuit 1D shown in FIG. 8 only in that a differential amplifier (indicated by reference numeral 18A) has hysteresis characteristics. This hysteresis characteristic is such that the input difference when the output level falls is smaller than the input difference when the output level rises. Therefore, when the moving frequency f changes and the logic circuit unit 15D switches the output frequency, problems such as chattering do not occur.

  The signal processing circuit 1F shown in FIG. 11 differs from the signal processing circuit 1 shown in FIG. 1A only in that the cutoff frequency fc of the low-pass filter (represented by reference numeral 14A) is variable. The low-pass filter 14A includes a variable resistor 14e and a variable capacitor 14f, and the cutoff frequency fc is variable according to the CR constant created by these elements 14e and 14f. Thus, if the cut-off frequency fc of the low-pass filter 14A is variable, the frequency range for the moving frequency f can be set arbitrarily. As a result, the logic circuit unit 15 can switch the frequency at a frequency that meets the requirements of various motors and control systems. Therefore, the usability of the optical encoder is improved, which is beneficial.

  In each of the above-described examples, the case where the frequency range detection unit has a low-pass filter as a filter has been described, but the present invention is not limited to this. A high pass filter may be used instead of the low pass filter. When the high pass filter is used, the logical value obtained as the frequency range detection unit is reversed as compared with the case where the low pass filter is used. Therefore, when the high pass filter is used, the logic circuit unit may perform the reverse switching operation as compared with the case where the low pass filter is used.

  In the electronic apparatus provided with the above-described photoelectric encoder, the photoelectric encoder accurately detects the passage of the slits X1, X2,... And the light off portions Y1, Y2,. Therefore, an appropriate operation can be performed using the detection result.

  In this embodiment, the light transmission type photoelectric encoder has been described. However, the present invention is not limited to this. The present invention is similarly applied to a light reflection type photoelectric encoder. However, in the light reflection type, contrary to the light transmission type, the slit of the moving body corresponds to a light-off portion where light does not enter the light receiving element, and a portion made of a plate material between the slits (a portion that reflects light) Corresponds to a light-on portion where light is incident on the light receiving element.

  In each of the above examples, the resolution is high when the moving body is operating at a low frequency, and the resolution is low when the moving body is operating at a high frequency. However, the present invention is not limited to this. Anyway.

It is a figure which shows the light receiving element and signal processing circuit which comprise the photoelectric encoder of one Embodiment of this invention. It is a figure which shows arrangement | positioning of the moving body and light receiving element of the said photoelectric encoder. It is a figure which shows the signal waveform of each part in the signal processing circuit of the photoelectric encoder of FIG. 1A. It is a figure which shows the modification of the signal processing circuit which comprises the photoelectric encoder of FIG. 1A. It is a figure which shows the correspondence of the logical value which the control signal of the signal processing circuit of FIG. 3 represents, and an output signal. It is a figure which shows the example of the photoelectric encoder provided with two sets of the light receiving element and signal processing circuit which were shown to FIG. 1A. It is a figure which shows another modification of the signal processing circuit which comprises the photoelectric encoder of FIG. 1A. It is a figure which shows the signal waveform of each part in the signal processing circuit of the photoelectric encoder of FIG. It is a figure which shows another modification of the signal processing circuit which comprises the photoelectric encoder of FIG. 1A. It is a figure which shows the signal waveform of each part in the signal processing circuit of the photoelectric encoder of FIG. It is a figure which shows the modification of the signal processing circuit which comprises the photoelectric encoder of FIG. It is a figure which shows another modification of the signal processing circuit which comprises the photoelectric encoder of FIG. 1A. It is a figure which shows the cross section of the light transmission type photoelectric encoder of one Embodiment of this invention.

Explanation of symbols

1, 1A, 1-1, 1-2, 1C, 1D, 1E, 1F Signal processing circuit 10 Light receiving element

Claims (8)

A light emitting element;
A light receiving element disposed in a region where light from the light emitting element can reach,
A moving body that alternately has a light-on portion and a light-off portion that create a state in which the light is incident on the light receiving element and a state in which the light is not incident in one direction has a predetermined position corresponding to the light receiving element along the one direction When the light passes through at a predetermined moving frequency, the output of the light receiving element takes a value corresponding to whether light from the light emitting element is incident or not incident on the light receiving element,
A frequency multiplication unit that receives the output of the light receiving element and outputs a multiplied signal having a frequency multiplied by the frequency of the moving body;
A filter that receives the output of the frequency multiplication unit or the light receiving element and attenuates and passes the other frequency component with respect to either one of the outputs higher or lower than a predetermined cutoff frequency, A frequency range detector that obtains a logical value indicating whether the moving frequency is higher or lower than the cut-off frequency using the output of the filter;
A signal having the same frequency as the frequency of the multiplied signal output from the multiplied frequency generation unit when the moving frequency is in a frequency range lower than the cut-off frequency according to the logical value obtained by the frequency range detection unit. On the other hand, when the moving frequency is higher than the cut-off frequency, a signal having a frequency of 1 / n (n is a natural number of 2 or more) with respect to the frequency of the multiplied signal is output. An optical encoder comprising: a frequency switching unit that performs the same. The optical encoder according to claim 1,
The frequency range detection unit includes a plurality of filters having different cutoff frequencies, and obtains a logical value indicating which frequency range the moving frequency is divided by the plurality of cutoff frequencies,
The frequency switching unit has the same frequency as the frequency of the multiplied signal output from the multiplied frequency generation unit when the moving frequency is in the lowest frequency range according to the logical value obtained by the frequency range detection unit. While outputting a signal, the value of n is sequentially increased to output a signal having the frequency of 1 / n as the frequency range including the moving frequency increases from the lowest frequency range. An optical encoder. The optical encoder according to claim 1 or 2,
A plurality of the light receiving elements are arranged side by side along the one direction in a region where the light from the light emitting element can reach, and each of the light receiving elements outputs a signal having a phase different from each other as the moving body moves in the one direction. Output,
The optical encoder, wherein the multiplied frequency generation unit, the frequency range detection unit, and the frequency switching unit are provided for each of the light receiving elements. The optical encoder according to claim 1,
The frequency range detector is
A phase inversion unit that receives the output of the frequency multiplication frequency generation unit and changes the phase of the output by 180 °;
It has the same characteristics as the filter, receives the output of the phase inverting unit, attenuates the other frequency component of the output with respect to one of the frequency components higher or lower than the cut-off frequency, and passes it. Including another filter,
An optical encoder characterized in that a logical sum of logical values represented by outputs of the two filters is the logical value indicating whether the moving frequency is in a high or low frequency range with respect to a predetermined cutoff frequency. . The optical encoder according to claim 1,
The frequency band detection unit includes a differential amplification unit that differentially amplifies the output of the light receiving element and the output of the filter that receives the output of the light receiving element, and uses the output of the differential amplification unit An optical encoder characterized in that the logical value indicating whether the moving frequency is in a high or low frequency range with respect to a predetermined cutoff frequency is obtained. The optical encoder according to claim 5, wherein
The differential amplifier has an hysteresis characteristic in which an input difference when the output level falls is smaller than an input difference when the output level rises. The optical encoder according to claim 1,
An optical encoder characterized in that the cutoff frequency of the filter is variable.   The electronic device provided with the optical encoder as described in any one of Claim 1-7.

Images