JP2011002255A - Optical encoder and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical encoder which can obtain a linearly-fluctuating asymmetrical triangular wave from a light receiving element, while avoiding an influence of optical dispersion of an optical component, detecting highly accurately a moving direction of a moving body by one light receiving signal, and detecting an absolute position of the moving body.SOLUTION: In the optical encoder, a light receiving surface 4 of a first light receiving element 3 has a step shape having four step parts 4A-4D, and a width dimension of each step part 4A-4D is equal to a width dimension L of a light-on part 5 of the moving body 1, and each step dimension d thereof is equal to each other. Hereby, a light receiving signal A+ output from the first light receiving element 3 is linearly fluctuated corresponding to movement of the moving body 1, and has a triangular wave shape which is asymmetrical with respect to the normal/reverse state of the moving direction, and therefor the moving direction of the moving body 1 can be detected highly accurately by one signal, and the absolute position of the moving body can be detected. Further, even when incident light into the light receiving surface 4 is dispersed to the moving direction, fluctuation of the total amount of a light receiving quantity can be avoided, to thereby enable highly accurate movement detection.

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 receiving element, and as an example, lens focus adjustment particularly in a copying machine, a printing device such as a printer, an FA device, a camera, The present invention relates to an optical encoder suitable for use in detecting the amount of rotation and movement of a vehicle drive component such as a crankshaft.

  Conventionally, in Patent Document 1 (Japanese Patent Laid-Open No. 11-101614), an optical scale composed of element gratings whose light transmission intensity changes at equal intervals stepwise is used, and light that has passed through the optical scale is received as a single light. A technique for detecting the amount of movement by a light receiver that detects the surface is disclosed. The light reception signal by the light receiver has a signal waveform of an asymmetric triangle, and the signal waveform detects the moving direction and the amount of movement based on the fluctuation rate of the intensity of the light reception signal of the asymmetric triangle.

  Patent Document 2 (Japanese Patent Application Laid-Open No. 2007-248359) includes a moving scale having a triangular pattern that transmits light and a light receiving element that receives light transmitted through the moving scale, and receives light from the light receiving element. A technique for detecting movement of a moving scale by a signal is disclosed.

  Patent Document 3 (Japanese Patent Laid-Open No. 61-138111) discloses a technique for measuring a subject by using a light receiving portion of a light receiving element as a triangular shape.

  Further, in Patent Document 4 (Japanese Patent Laid-Open No. 61-292016), four light receiving signals are received so as to receive light from the light transmitting portion of the optical track of the code board and to output a light receiving signal having a phase difference of 90 °. An optical encoder is disclosed in which a light receiving element is disposed and a triangular wave signal is obtained from the four light receiving elements.

  Further, in Patent Document 5 (Japanese Patent Application Laid-Open No. 2001-153585), a low-reflectance square digital pattern and a low-reflectance triangle analog pattern are provided on the scale, and the light reflected by the scale is received by the light receiving unit. An optical encoder that performs movement detection is disclosed.

  By the way, in the technique disclosed in Patent Document 1 described above, a light reception signal having a triangular wave is obtained from a light receiver in the form of an optical scale used as a moving body, so that the resolution is higher than when the light reception signal is a pulse signal. improves. In addition, if the triangular wave is an asymmetric triangular wave, not only the absolute position of the moving body can be detected, but also the moving direction detection accuracy can be improved.

  However, with the technique disclosed in Patent Document 1 described above, even if a scale in which the light transmission intensity varies stepwise is produced, the light amount of the light emitting element varies due to the emission wavelength, aging, variation, disturbance, and the like. In addition, since the received light intensity varies depending on the scale position, there are many factors that cause the light intensity to vary in addition to the transmittance of the scale, and it is very difficult to form a triangular wave in which the received light signal varies linearly.

  Therefore, in order to obtain a linear triangular wave, the above-mentioned Patent Document 2 proposes a technique of forming a triangular pattern that transmits light on the moving scale, and the above-mentioned Patent Document 3 proposes a technique for making the light receiving portion of the light receiving element a triangular shape. Yes.

  However, in order to form a rectangular processing pattern, the processing machine can be manufactured by mechanically operating the X-axis (one-dimensional), whereas the above-described moving scale and the triangular processing pattern in the light receiving element are X It is necessary to adjust and manufacture the processing machine in two dimensions of the axis and the Y axis. For this reason, there is a limit in constructing linearity, particularly in an optical encoder that requires an accuracy of the order of several μm. Further, the mask shape when manufacturing the light receiving element is a quadrangle, and the pattern having an angle with respect to the X axis and the Y axis is likely to be displaced.

  Further, in the received light image on the light receiving element, light is refracted due to a slit or the like when the moving body moves, and the gradient in the moving direction of the amount of light incident on the light receiving surface varies. For this reason, with a triangular shape that has an inclination in the gradient direction (movement direction), the total amount of received light is likely to fluctuate when the gradient in the movement direction of the amount of light incident on the light receiving surface varies and is formed on a moving scale or light receiving element. It is difficult to obtain a triangular wave according to the triangular processing pattern.

  On the other hand, in the optical encoder disclosed in Patent Document 4 described above, a conventional rectangular light transmission part (slit) is used, and the four light receiving elements are also formed in the same shape, so that these four A triangular wave signal having an isosceles triangular waveform is obtained from the light receiving signal output from the light receiving element.

  However, although the method according to Patent Document 4 improves the resolution, since the waveform of the triangular wave signal obtained from the light reception signal is an isosceles triangle, the potential value variation rate is constant, and the absolute position of the moving body and the moving direction are changed. It cannot be detected. For this reason, the method according to Patent Document 4 requires a two-phase triangular wave signal in order to detect the direction of the moving body.

  Further, in the optical encoder disclosed in Patent Document 5 described above, it is possible to count the number of pulses by forming not only a triangular pattern but also a quadrangular digital pattern on the scale, thereby expanding the movement detection range of the scale. Can be easily done.

  However, the optical encoder of Patent Document 5 also has difficulty in maintaining optical characteristics because the scale area is increased by providing two patterns on the scale. In other words, unless the light incident on the scale is parallel light and the light emission density is not uniform, it is difficult to synchronize the triangular wave of the light reception signal obtained from the light receiving unit and the digital waveform.

JP 11-101614 A JP 2007-248359 A JP-A-61-138111 JP-A-61-292016 Japanese Patent Laid-Open No. 2001-153585

  Accordingly, an object of the present invention is to obtain an asymmetric triangular wave that fluctuates linearly from a light receiving element while avoiding the influence of optical variations of optical components, and to detect the moving direction of a moving body with a single light receiving signal with high accuracy. An optical encoder capable of detecting the absolute position of a movable body is provided.

In order to solve the above problems, an optical encoder of the present invention includes a light emitting unit,
A first light receiving element disposed in a region where light from the light emitting unit can reach;
When the light passes through a position corresponding to the first light receiving element, the light is turned on when passing through the position corresponding to the first light receiving element, and when the light passes through a position corresponding to the first light receiving element. A moving body that has a light-off portion that prevents light from entering the first light-receiving element and that alternately passes through the position corresponding to the light-receiving element when the light-on portion and the light-off portion move in one direction. And
The width dimension that is the dimension in one direction of the light-off portion of the moving body is a positive integer multiple of the width dimension in one direction of the light-on portion,
The first light receiving element is:
In the width dimension of one pitch obtained by adding the width dimension of the pair of adjacent light-on and light-off parts of the moving body, the stepped shape has a plurality of steps, and the width of each step is the light-on It has a light receiving surface that is equal to the width dimension of each part and has the same step size in each step part.

  According to the optical encoder of the present invention, each step portion of the first light receiving element has a width dimension equal to a width dimension of the light-on portion of the moving body and a step dimension equal to each other. Make up surface. As a result, the first light receiving signal output from the first light receiving element has a triangular waveform that fluctuates linearly corresponding to the movement of the moving body and is asymmetric with respect to forward and reverse of the moving direction. With the first light-receiving signal having the asymmetric triangular waveform, the moving direction of the moving body can be detected with high accuracy with one signal, and the absolute position of the moving body can be detected.

  According to the present invention, in the range corresponding to one side of the apex of the asymmetric triangular waveform of the first light receiving signal, the irradiation area on the light receiving surface is uniform according to the amount of movement per unit of the moving body. Therefore, the rate of change in the received light intensity is always constant in the above range, and there is no fear that the intensity change varies.

  In addition, since it is not necessary to make the light receiving surface of the light receiving element triangular, or to form a triangular light transmitting portion on the moving body, it is possible to ensure processing accuracy on the order of several μm required for the optical encoder. Further, according to the present invention, unlike a light receiving element having a triangular light receiving surface, the total amount of received light varies even when the gradient (light amount distribution state) of the light amount incident on the light receiving surface varies and varies. Therefore, it is possible to secure a light receiving signal having a highly accurate asymmetric triangular waveform.

  Further, in the present invention, by setting the width dimension of the light-on part to be narrower than the width dimension of the light-off part, it is possible to reduce the influence of light sneaking into the light-off part and improve the variation characteristics of the received light signal. Further, by changing the ratio of the width dimension of the light-off portion with respect to the width dimension of the light-on portion, it is possible to adjust the waveform of the asymmetric triangle of the first light reception signal output from the first light-receiving element. .

  Also, the optical encoder of one embodiment outputs the second light receiving signal, which is a signal waveform obtained by inverting the signal waveform of the first light receiving signal output from the first light receiving element at the center level. The light-receiving surface of the first light-receiving element is rotated by 180 °, and a second light-receiving element having a light-receiving surface having the same shape as the light-receiving surface of the first light-receiving element is provided.

  According to this embodiment, the first light receiving signal output from the first light receiving element and the second light receiving signal output from the second light receiving element are inverted with each other. By comparing and calculating the two received light signals, the SN ratio can be improved. Further, by combining the stepped portions of the light receiving surfaces of the first and second light receiving elements, the shape of the light receiving surface as a whole can be made a quadrangle, and the light receiving surface per unit width dimension Since a larger area can be secured, this leads to an improvement in the SN ratio.

  An optical encoder according to an embodiment includes a plurality of sets of light receiving elements each including the first light receiving element and the second light receiving element adjacent to each other in the moving direction.

  According to this embodiment, since the plurality of sets of light receiving elements are provided, when the moving body has a smaller light-on portion area than the light-off portion, a part of the light-on portion of the moving body is soiled or the like. Even when the light transmittance is deteriorated, it is possible to avoid a decrease in the SN ratio.

  In the optical encoder according to the embodiment, the first light receiving signal output from the first light receiving element and the second light receiving signal output from the second light receiving element are input and the first light receiving signal is input. A differential arithmetic circuit that differentially calculates the light reception signal and the second light reception signal is provided.

  According to this embodiment, the differential calculation of the first and second light reception signals not only doubles the SN ratio, but also averages the variation in the light reception signals.

  An optical encoder according to an embodiment includes an AD conversion circuit that performs AD conversion on a signal that has been differentially calculated by the differential arithmetic circuit.

  According to this embodiment, the first and second received light signals have two locations where the inclination changes in one cycle of the waveform of the asymmetric triangle, and the differentially calculated signal waveform has one cycle. There are two places where the slope changes. Therefore, by performing A / D conversion on the differentially calculated signal, a digital output signal of one pulse can be obtained in the one period synchronized with the asymmetric triangular waveform of the first and second light receiving signals. . Therefore, for example, the period is counted by the digital output signal, and the absolute position in the period can be read by the triangular wave output by the first and second light receiving signals. Thereby, the absolute position can be detected in a wider range.

Further, in the optical encoder of one embodiment, the differential arithmetic circuit outputs two identical current signals as differentially calculated signals,
The AD converter circuit receives a current signal from one of the two current signals.
Further, a feedback circuit is provided to which a current signal of one of the two current signals is input.

  According to this embodiment, a digital output signal of one pulse is obtained from the AD conversion circuit in one cycle synchronized with the first and second light receiving signals having the above-described asymmetric triangular waveform. In addition, a signal having an asymmetric triangular waveform that is stable with respect to the reference voltage is obtained from the feedback circuit. The AD conversion circuit and the feedback circuit output the digital output signal and the asymmetric triangular waveform signal from the same current signal from the same differential operation circuit. Therefore, not only the digital output signal and the asymmetric triangular waveform signal can be synchronized, but also the variation between the signals can be reduced.

  In addition, the electronic apparatus according to the embodiment includes the optical encoder, so that an asymmetric triangular wave that linearly varies while avoiding the influence of variation in characteristics of optical components is obtained, and not only the resolution is improved, Optical design becomes easy. Therefore, it can be used for mobile devices (electronic devices) such as lens focus of smaller cameras. Furthermore, the SN ratio can be improved by providing the differential arithmetic circuit, and a wide range of positions can be detected by the digital output signal synchronized with the non-target triangular wave by providing the AD conversion circuit. In addition, since the differential arithmetic circuit outputs two identical current signals, the variation between the signals can be reduced. The electronic device shown here is the above camera device in addition to the FA device such as an ink jet printer and a copying machine in which an optical encoder is usually used. It also shows all devices that require movement detection, such as consumer and industrial robot devices.

  According to the optical encoder of the present invention, the light receiving surface of the first light receiving element has a stepped shape having a plurality of stepped portions, and each stepped portion has a width dimension equal to the width dimension of the light-on portion of the moving body and a step. Since the dimensions are equal to each other, the first light receiving signal output from the first light receiving element varies linearly in accordance with the movement of the moving body and becomes an asymmetric triangular waveform with respect to the forward and reverse movement directions. The moving direction can be detected with high accuracy with one signal and the absolute position of the moving body can be detected. In addition, unlike the case where the light receiving surface has a triangular shape, it is easy to ensure processing accuracy, and even when the incident light on the light receiving surface varies in the moving direction, it can be avoided that the total amount of light received varies. High-precision movement detection becomes possible.

It is a figure which shows arrangement | positioning and the light-receiving signal waveform of the light receiving element of 1st Embodiment of the optical encoder of this invention. It is a figure for demonstrating the light reception operation | movement in the said 1st Embodiment. It is a figure which shows arrangement | positioning and the light reception signal waveform of the light receiving element of the comparative example of the said 1st Embodiment. It is a figure which shows arrangement | positioning and the light-receiving signal waveform of the light receiving element of 2nd Embodiment of the optical encoder of this invention. It is a figure which shows arrangement | positioning of the light receiving element of 3rd Embodiment of the optical encoder of this invention. It is a figure which shows the light receiving circuit of 4th Embodiment of the optical encoder of this invention. It is a figure which shows an example of the circuit of the differential amplifier (differential arithmetic circuit) 43 of the light-receiving circuit of the said 4th Embodiment. It is a wave form diagram which shows the simulation result of the signal waveform of each part in the light receiving circuit of the said 4th Embodiment. It is a figure which shows a mode that the light reception image Z1 is irradiated to the light-receiving surface of the said 1st Embodiment. It is a figure which shows a mode that the light reception image Z2 is irradiated to the light-receiving surface of the said 1st Embodiment. It is a figure which shows a mode that the light reception image Z1 is irradiated to the light-receiving surface of the comparative example of the said 1st Embodiment. It is a figure which shows a mode that the light reception image Z2 is irradiated to the light-receiving surface of the comparative example of the said 1st Embodiment.

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

(First embodiment)
As shown in FIG. 1, the first embodiment of the optical encoder of the present invention includes a scale 1 as a moving body, a light emitting unit 2 that irradiates light to the scale 1, and the light emitting unit 2 via the scale 1. Thus, the first light receiving element 3 that receives light is provided. The light emitting unit 2 is configured by a light emitting diode or the like as an example, and as an example, is disposed on the back side of the scale 1 (back side of the paper surface of FIG. 1) so as to face the scale 1.

  On the other hand, the first light receiving element 3 is configured by a photodiode or the like as an example, and the light receiving surface 4 faces the scale 1 so that light emitted from the light emitting unit 2 and passed through the scale 1 enters the light receiving surface 4. Are arranged to be. That is, the light receiving surface 4 is arranged so as to face the facing surface of the scale 1 depicted in FIG.

  The scale 1 includes a light-on unit 5 that transmits light from the light-emitting unit 2 and a light-off unit 6 that does not transmit light from the light-emitting unit 2. The light-on unit 5 and the light-off unit 6 Are alternately arranged in the moving direction X. In this embodiment, the width dimension that is the dimension in the movement direction X of the light-off part is three times the width dimension L that is the dimension in the movement direction X of the light-on part 6 in this embodiment ( 3L).

  The light receiving surface 4 of the first light receiving element 3 has a dimension in the movement direction X that is the sum of the width dimension of the light-on part 5 and the width dimension of the light-off part 6 (L + 3L), that is, one pitch of the scale 1. Equal to P. That is, the width dimension of the first light receiving element 3 is four times the width dimension L of the light-on portion 5. The light receiving surface 4 of the first light receiving element 3 has a stepped shape having four step portions 4A, 4B, 4C, 4D. Moreover, the width dimension of each step part 4A-4D is equal to the width dimension L of the said light ON part 5. FIG. Moreover, the step dimension d of each step part 4A-4D is equal. Note that the length of the light-on portion 5 of the scale 1 in the direction orthogonal to the moving direction X is longer than four times the step size d of the first light receiving element 3.

  In the optical encoder configured as described above, the scale 1 moves in the moving direction X, and the light emitted from the light emitting unit 2 and transmitted through the light-on unit 5 of the scale 1 is provided on the light receiving surface 4 of the light receiving element 3. It injects into part 4A, 4B, 4C, 4D in order. As a result, the light receiving element 3 outputs a light receiving signal A + according to the amount of light incident on the light receiving surface 4. The signal waveform of the light reception signal A + is a triangular wave that is asymmetric with respect to forward and reverse movement directions, as shown in the lower column of FIG. By moving the scale 1 by one pitch in the moving direction, an asymmetric triangular wave of one period T of the received light signal A + is obtained.

  Next, with reference to FIG. 2, a part of the process in which the light receiving signal A + of the asymmetric triangular wave is obtained from the light receiving element 3 will be described.

  First, the boundary C1 between the light-on part 5 and the light-off part 6 adjacent to each other in the scale 1 is located at the boundary (0) between the first step part 4A and the second step part 4B of the light receiving surface 4. When in the corresponding position, the area where light enters the light receiving surface 4 from the scale 1 is the area (3 × S1) of the first step 4A. At this time, the area where the light is incident on the light receiving surface 4 is the smallest, and corresponds to the lower limit value Q0 of the asymmetric triangular wave of the light receiving signal A + shown in the lower column of FIG.

  Next, the boundary C1 moves in the moving direction X by (1/3) L1, and the position (1 of the second step 4B of the light receiving surface 4 from the position corresponding to the position (0) of the boundary (1). ), The incident area of the first step 4A of the light receiving surface 4 decreases by the area S1, while the incident area of the second step 4B increases by the area S2 = 2 × S1. To do. Therefore, the light incident area on the light receiving surface 4 is increased by an area S1 that is one third of the area of the first step 4A. The area S1 is the width dimension L × (1/3) × the step dimension d of the stepped portion 4A. At this time, the received light signal A + shown in the lower column of FIG. 1 corresponds to the value Q1 of the asymmetric triangular wave. Note that the locations (1) and (2) shown in FIG. 2 are positions where the width dimension L of the second step 4B is equally divided into three.

  Next, the boundary C <b> 1 between the adjacent light-on part 5 and light-off part 6 of the scale 1 is moved in the moving direction X from the position corresponding to the position (1) of the second step part 4 </ b> B of the light receiving surface 4. When the boundary C1 moves by a moving distance (1/3) L and reaches the position corresponding to the position (2) of the step 4B, the incident area of the first step 4A of the light receiving surface 4 is further increased. While decreasing by S1, the incident area of the second step 4B further increases by area S2. As a result, the incident area of the light receiving surface 4 is increased by the area S1. At this time, the light reception signal A + shown in the lower column of FIG. 1 corresponds to the value Q2 of the asymmetric triangular wave.

  Next, it is assumed that the boundary C1 has moved from a position corresponding to the position (2) of the second step 4B to a position corresponding to the position (3) of the third step 4C. In addition, the said location (3) and location (4) are made into the position which divides the width dimension L of the step part 4C into 3 equal parts. Therefore, the moving distance is (1/3) L + (1/3) L = (2/3) L. This (2/3) L movement reduces the incident area by the area S1 of the first step 4A and the area S2 of the second step 4B, and at the same time, the second step 4B. The incident area increases by the area S2 and the area S3 of the third step 4C. Therefore, by the movement of (2/3) L, the light incident area of the entire light receiving surface 4 is increased by (S3−S1) = 2S1. At this time, the light reception signal A + shown in the lower column of FIG. 1 corresponds to the value Q3 of the asymmetric triangular wave.

  Next, the boundary C1 is moved from the position corresponding to the position (3) of the second step 4B to the position corresponding to the position (4) of the third step 4C by (1/3) L. Suppose you move. By the movement of (1/3) L, the incident area of the second step 4B is reduced by the area S2, and the incident area of the third step 4C is increased by the area S3. Therefore, by the movement of (1/3) L, the light incident area of the entire light receiving surface 4 increases by (S3−S2) = S1. At this time, the light reception signal A + shown in the lower column of FIG. 1 corresponds to the value Q4 of the asymmetric triangular wave.

  Next, the boundary C1 extends from a position corresponding to the position (4) of the third step 4C to a position corresponding to the end (5) of the fourth step 4D (4/3) L. Just move. By this (4/3) L movement, the incident area of the light receiving surface 4 becomes the area 3 × S4 of the fourth step 4D. Therefore, the incident area of the light receiving surface 4 increases by 4 × S1 from (S2 + 2 × S3) before the (4/3) L movement to (3 × S4). At this time, the light reception signal A + shown in the lower column of FIG. 1 corresponds to the upper limit value Q5 of the asymmetric triangular wave. Further, the inclination of the triangular wave from the lower limit value Q0 to the upper limit value Q5 is constant.

  Next, the boundary C <b> 1 further moves by L in the movement direction X, so that light is incident only on the first step 4 </ b> A of the light receiving surface 4. As a result, the light incident area on the light receiving surface 4 is reduced by (12 × S1−3 × S1) = 9 × S1, and the incident area on the light receiving surface 4 becomes the area of the stepped portion 4A, that is, 3 × S1. Become. As a result, the asymmetric triangular wave of the light reception signal A + shown in the lower column of FIG. 1 returns to the lower limit value Q0.

  Thus, one period T of the light receiving signal A + that is an asymmetric triangular wave corresponds to the scale 1 moving by one pitch P = 4 × L1. In the region corresponding to the lower limit value Q0 to the upper limit value Q5 of the light receiving signal A +, every time the scale 1 moves by (1/3) L in the moving direction X, the incident area of the light receiving surface 4 of the light receiving element 3 is It increases by the area S1. That is, every time the scale 1 moves in the movement direction X by the width dimension L of the light-on portion 5, the amount of incident light on the light receiving surface 4 increases by the light receiving area of the first step portion 4A. Accordingly, the boundary C1 of the scale 1 from the position corresponding to the boundary (0) between the first step 4A and the second step 4B of the light receiving surface 4 is the end of the fourth step 4D. Is moved by three quarters of one pitch P in the movement direction X to the position corresponding to the point (5), so that the light incident area on the light receiving surface 4 is the light receiving area (3 of the first step 4A). It increases linearly from (S1) to the light receiving area (12 × S1) of the fourth step 4D. Therefore, when the boundary C1 of the scale 1 moves from the position corresponding to the location (0) to the location corresponding to the location (5) by (3/4) P, the amount of light received on the light receiving surface 4 increases linearly. The light receiving signal A + shown in the lower column of FIG. 1 increases with a constant slope from the lower limit value Q0 to the upper limit value Q5. Further, when the boundary C1 of the scale 1 further moves from the position corresponding to the location (5) by L in the moving direction X, the amount of light received by the light receiving surface 4 decreases linearly, and the light receiving signal A + is the upper limit value. It decreases with a constant slope from Q5 to the lower limit Q0.

  Thus, when the scale 1 moves in the movement direction X, the light receiving signal A + having the asymmetric triangular waveform shown in the lower column of FIG. Further, when the scale 1 moves in the direction opposite to the moving direction X, a light receiving signal A− having an asymmetric triangular waveform indicated by a broken line in the lower column of FIG. 1 is obtained. The slope of the increase in the light reception signal A− from Q0 to Q5 corresponds to the slope of the decrease in the light reception signal A + from Q5 to Q0, and the slope of the decrease in the light reception signal A− from Q5 to Q0 is Q0 of the light reception signal A +. This corresponds to an increasing slope from 1 to Q5.

  Here, with reference to FIG. 3, a comparative example of the above embodiment (corresponding to Japanese Patent Laid-Open No. 61-292016) will be described. In this comparative example, the width dimension M in the movement direction of the light-on part 102 of the scale 101 is equal to the width dimension M in the movement direction of the light-off part 103. Further, four light receiving elements 105, 106, 107, and 108 are arranged with respect to 1 pitch P = 2M of the scale 101, and the width dimension of each of the light receiving elements 105 to 108 is (1/2) M. When the scale 101 moves in the movement direction X, the light receiving signal A + output from the light receiving element 105 becomes a trapezoidal wave. The light receiving signal B + output from the light receiving element 106 is a trapezoidal wave whose phase is delayed by 90 ° with respect to the light receiving signal A +. Further, the light receiving signals A− and B− output from the light receiving elements 107 and 108 are also trapezoidal waves whose phases are sequentially delayed by 90 °. Then, by adding the light reception signal A + and the light reception signal B +, a signal ((A +) + (B +)) that is an isosceles triangular wave is obtained. This comparative example is often used in an ink jet printer or the like. However, since the absolute position within one cycle cannot be detected with an isosceles triangular wave signal as described above, it can be used in a minute operating range such as a camera focus. Not suitable for downsizing.

  On the other hand, according to the present embodiment, since the light receiving signal A + having an asymmetric triangular waveform as shown in FIG. 1 is obtained, the absolute position within one cycle can be detected, which is optimal for micro operation and miniaturization. I can say that.

  Here, with reference to FIG. 9A and FIG. 9B, the operation when the received light image irradiated from the light-on portion 5 of the scale 1 to the light receiving surface 4 of the light receiving element 3 varies in the present embodiment will be described. First, the received light image Z2 illustrated in FIG. 9B has a high light intensity W1 in the central region U1, and the light intensity is lower in the regions U2a and U2b on both sides of the central region U1 than in the central region U1. , W2b.

  Next, the light reception image Z1 illustrated in FIG. 9A has a high light intensity W1 in the central region U1, and the light intensities W3a and W3b in the regions U2a and U2b on both sides of the central region U1. The light intensities W3a and W3b are lower than the light intensity U2 in the region U2 of the received light image Z2. Further, the received light image Z1 has regions U3a and U3b on both sides of the regions U2a and U2b. In these regions U3a and U3b, the light intensities W4a and W4b are lower than the light intensities W3a and W3b of the regions U2a and U2b. It has become. That is, the regions U2a and U2b of the light intensity W2 of the light reception image Z2 in FIG. 9B are diffused into regions U2a and U2b and U3a and U3b of the light reception image Z1 in FIG. 9A. The variation in the light amount distribution as in the light reception images Z1 and Z2 is caused by light being refracted due to the light-on portion 5 or the like when the scale 1 is moved.

  Here, according to the light receiving surface 4 of the light receiving element 3 of this embodiment, it can be seen that the total amount of light received by the received light image Z1 shown in FIG. 9A is equal to the total amount of light received by the received light image Z2 shown in FIG. 9B.

  On the other hand, in the comparative example illustrated in FIGS. 10A and 10B, the light receiving surface 204 has a triangular shape. Here, similarly to the above, the regions U2a and U2b of the light intensity W2 of the light reception image Z2 in FIG. 10B are diffused into regions U2a and U2b and U3a and U3b of the light reception image Z1 in FIG. 10A. In this case, when the triangular light receiving surface 204 diffuses from the light receiving image Z2 in FIG. 10B to the light receiving image Z1 in FIG. 10A, the total amount of light received by the regions U2a and U3a on the left side of the central region U1 in FIG. This is less than the total amount of light received by the region U2a on the left side of the central region U1. On the other hand, in FIG. 10A, the total amount of light received by the regions U2b and U3b on the right side of the central region U1 is larger than the total amount of light received by the region U2b on the right side of the central region U1 in FIG. Here, the amount of light in the right region U2b in FIG. 10B is the same as the amount of light in the left region U2a in FIG. 10B, and the diffusion in the right regions U2b and U3b and the diffusion in the left regions U2a and U3a in FIG. Except for the same case, the amount of decrease in the total amount of received light is different from the amount of increase in the total amount of received light. Therefore, according to the light receiving surface 204 of this comparative example, except for the above case, the total amount of light received by the received light image Z1 shown in FIG. 10A is different from the total amount of light received by the received light image Z2 shown in FIG. 10B.

  On the other hand, according to the light receiving surface 4 of the light receiving element 3 of the present embodiment, the total amount of light received by the region U2b on the right side of the central region U1 in FIG. 9B is based on the regions U2b and U3b on the right side of the central region U1 in FIG. The total received light amount is equal to the total received light amount, and the total received light amount by the region U2a on the left side of the central region U1 in FIG. 9B is equal to the total received light amount by the regions U2a and U3a on the left side of the central region U1 in FIG. Therefore, according to the light receiving surface 4 of the present embodiment, even if the received light image on the light receiving surface 4 is diffused from Z2 to Z1, the total amount of received light does not fluctuate. Accurate movement information can be obtained.

  In the above embodiment, the width of the light-off portion 6 of the scale 1 that is a moving body is three times the width of the light-on portion 5, but the width of the light-off portion 6 is the width of the light-on portion 5. It is good also as an integer multiple of 2 times or 4 times or more of a dimension.

(Second embodiment)
Next, a second embodiment of the optical encoder according to the present invention will be described with reference to FIG. This second embodiment differs from the first embodiment only in that a second light receiving element 23 is provided in addition to the first light receiving element 3. Therefore, in the second embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and different points from the first embodiment will be mainly described.

  The light receiving surface 24 of the second light receiving element 23 has the same shape as the light receiving surface 4 of the first light receiving element 3, and has a stepped shape having four step portions 24A, 24B, 24C, and 24D. The light receiving surface 24 of the second light receiving element 23 is in a posture in which the light receiving surface 4 of the first light receiving element 3 is rotated by 180 °. Further, the step portions 4A, 4B, 4C, 4D of the light receiving surface 4 of the first light receiving element 3 are combined with the step portions 24D, 24C, 24B, 24A of the light receiving surface 24 of the second light receiving element 23. First and second light receiving elements 3 and 23 are arranged. Thus, the light receiving surface in which the light receiving surface 4 and the light receiving surface 24 are combined has a rectangular shape as a whole.

  In the optical encoder having the above-described configuration, when the scale 1 moves in the movement direction X, the first light receiving element 3 has a period T shown in the lower column of FIG. 1 as described in the first embodiment. The first light receiving signal A + of the asymmetric triangular wave is output. On the other hand, the second light receiving element 23 outputs a second light receiving signal A− of an asymmetric triangular wave having one period T shown in the lower column of FIG. The second light receiving signal A− is a signal waveform obtained by inverting the signal waveform of the first light receiving signal A + at the center level. Since the first light receiving signal A + and the second light receiving signal A- are inverted from each other, the S / N ratio can be improved by comparing the first and second light receiving signals A + and A-. .

  Further, the combination of the light receiving surfaces 4 and 24 results in a rectangular light receiving surface as a whole. Therefore, when the scale 1 is moved, the amount of light received on the light receiving surface as a whole can be increased, and the SN ratio can be improved.

(Third embodiment)
Next, a third embodiment of the optical encoder of the present invention will be described with reference to FIG. In the third embodiment, only the point that a plurality of pairs of light receiving elements 31 that are a combination of the first light receiving element 3 and the second light receiving element 23 are provided adjacent to each other in the moving direction is the second embodiment described above. And different. Therefore, in the third embodiment, the same parts as those in the second embodiment are denoted by the same reference numerals, and differences from the second embodiment will be mainly described.

  In the third embodiment, since the plurality of light receiving element pairs 31 are provided, the first light receiving signals A + from the plurality of first light receiving elements 3 are added and the second light receiving elements 23 from the plurality of second light receiving elements 23 are added. By adding the two received light signals A−, even if some of the light-on portions 5 are in a state where the transmittance is poor due to dirt or the like, the signals are averaged, and the SN ratio is avoided by reducing the SN ratio. Can be held.

  A plurality of first light receiving elements 3 arranged adjacent to each other in the moving direction are integrally formed as one light receiving element, and a plurality of second light receiving elements 23 arranged adjacent to each other in the moving direction are integrally formed. It is good also as one formed light receiving element.

(Fourth embodiment)
Next, a fourth embodiment of the optical encoder of the present invention will be described with reference to FIG. The fourth embodiment includes the first light receiving element 3 and the second light receiving element 23 of the optical encoder of the second embodiment described above.

  In the fourth embodiment, the first light receiving signal A + output from the first light receiving element 3 is logarithmically compressed, and the second light receiving element 23 outputs the second light receiving element 23. A first stage amplifier 42 for logarithmically compressing the signal A- is provided. The fourth embodiment also includes a differential amplifier (differential arithmetic circuit) 43 to which the amplified signal from the amplifier 41 and the amplified signal from the amplifier 42 are input, and the differential amplifier (differential arithmetic circuit). An AD converter (AD converter circuit) 45 to which a current signal of one of the two systems of the same current signal output from 43 is input, and a current of one of the two systems of the same current signal A feedback circuit 46 to which a signal is input is provided. The feedback circuit 46 includes a comparator 47, a resistor 48, and a reference voltage unit 49.

  In the fourth embodiment, the first and second light receiving signals A + and A− from the first and second light receiving elements 3 and 23 are logarithmically compressed by the amplifiers 41 and 42, thereby removing the light quantity dependency. . Further, the first and second light receiving signals A + and A− logarithmically compressed are subjected to differential operation by a differential amplifier (differential operation circuit) 43, whereby the first light receiving signal A + and the second light receiving signal A are obtained. A differential output signal corresponding to the difference from − is obtained. As a result, not only the SN ratio is doubled, but also when the scale 1 and the light receiving elements 3 and 23 are inclined with respect to each other, the influence of the inclination is offset and the SN ratio can be maintained.

  Further, in the differential amplifier (differential arithmetic circuit) 43, the light reception signals A + and A− logarithmically compressed by the amplifiers 41 and 42 in the first stage are expanded, and an asymmetric triangular waveform current signal is used as the differential output signal. Is output to an AD converter (AD conversion circuit) 45. In this AD converter (AD conversion circuit) 45, the current signal having the asymmetric triangular waveform is converted into a 1/0 signal, and a digital output signal having one pulse in one period T synchronized with the current signal having the asymmetric triangular waveform. Is obtained. Therefore, for example, the period can be counted by the digital output signal, and the absolute position within one period can be read by the triangular wave output by the first and second light receiving signals A + and A−. Thereby, the absolute position can be detected in a wider range.

  In the fourth embodiment, the differential amplifier (differential arithmetic circuit) 43 outputs two systems of the same current signal, and the current signal of one of the systems is input to the feedback circuit 46. By this feedback circuit 46, an analog voltage output having an asymmetric triangular waveform which is stable with respect to the reference voltage by the reference voltage unit 49 is obtained. As a result, the digital output signal output from the AD converter (AD conversion circuit) 45 and the analog voltage output of the asymmetric triangular waveform output from the feedback circuit 46 can be synchronized, and the digital output signal and the analog voltage can be synchronized. Variations between outputs are also reduced.

  FIG. 7 shows an example of a circuit constituting the differential amplifier (differential arithmetic circuit) 43. In this circuit example, a differential amplifier circuit (differential arithmetic circuit) 81 and two current mirror circuits 82 and 83 are provided, and a current signal output from the current mirror circuit 82 is input to the feedback circuit 46, and the current mirror is output. A current signal output from the circuit 83 is input to an AD converter (AD conversion circuit) 45. The current signals output from the two current mirror circuits 82 and 83 have the same current value and are not only synchronized, but also with respect to variations in the first and second received light signals A + and A−. Since the same variation is exhibited, the variation between the digital output signal and the analog voltage output is also reduced.

  Next, the waveform diagram of FIG. 8 shows the simulation result of the signal waveform of each part in the circuit diagram of FIG. In FIG. 8, the horizontal axis represents time (μ seconds), and the vertical axis represents the signal value (amplitude) of each signal. As described above, the waveform of the first light reception signal A + is an asymmetric triangular waveform, and the waveform of the second light reception signal A− is obtained by inverting the first light reception signal A + at the center level (0.6 μA). Asymmetric triangular waveform. The differential output signal output from the differential amplifier (differential arithmetic circuit) 43 has a triangular waveform corresponding to the difference between the first light receiving signal A + and the second light receiving signal A−. The analog voltage output Aout having an asymmetric triangular waveform output from the feedback circuit 46 to which the differential output signal having the triangular waveform is input corresponds to the difference between the first light receiving signal A + and the second light receiving signal A−. Triangular wave analog voltage.

  The digital output signal Dout output from the AD converter (AD converter circuit) 45 is a pulse of one pulse in one period T synchronized with the first and second light receiving signals A + and A− having an asymmetric triangular waveform. It has a waveform.

  In the fourth embodiment, the case where the pair of the first light receiving element 3 and the second light receiving element 23 of the second embodiment described above is provided has been described. A plurality of pairs of light receiving elements 31 of the third embodiment described above may be provided. In this case, a plurality of first light reception signals A + are added and inputted to the first stage amplifier 41, and a plurality of second light reception signals A− are added and inputted to the first stage amplifier 42. Therefore, the signals are averaged and the SN ratio can be prevented from decreasing.

DESCRIPTION OF SYMBOLS 1 Scale 2 Light-emitting part 3,23 Light-receiving element 4,24 Light-receiving surface 4A-4D, 24A-24D Step part 5 Light-on part 6 Light-off part 23 2nd light-receiving element 41,42 Amplifier 43 Differential amplifier (Differential operation) circuit)
45 AD converter (AD conversion circuit)
46 feedback circuit 81 differential amplifier circuit 82,83 current mirror circuit C1 boundary Z1, Z2 received light image

Claims (7)

A light emitting unit;
A first light receiving element disposed in a region where light from the light emitting unit can reach;
When the light passes through a position corresponding to the first light receiving element, the light is turned on when passing through the position corresponding to the first light receiving element, and when the light passes through a position corresponding to the first light receiving element. It has a light-off part that prevents light from entering the first light-receiving element, and the light-on part and the light-off part alternately pass through positions corresponding to the first light-receiving element when moving in one direction. And a moving body
The width dimension that is the dimension in one direction of the light-off portion of the moving body is a positive integer multiple of the width dimension in one direction of the light-on portion,
The first light receiving element is:
In the width dimension of one pitch obtained by adding the width dimension of the pair of adjacent light-on and light-off parts of the moving body, the stepped shape has a plurality of steps, and the width of each step is the light-on An optical encoder having a light receiving surface that is equal to the width dimension of each section and has the same step dimension at each step section. The optical encoder according to claim 1,
The light receiving surface of the first light receiving element is 180 ° so as to output a second light receiving signal which is a signal waveform obtained by inverting the signal waveform of the first light receiving signal output from the first light receiving element at the center level. An optical encoder comprising a second light receiving element having a light receiving surface that is rotated and has the same shape as the light receiving surface of the first light receiving element. The optical encoder according to claim 2, wherein
An optical encoder comprising a plurality of sets of light receiving elements each including the first light receiving element and the second light receiving element adjacent to each other in the moving direction. The optical encoder according to claim 2 or 3,
The first light receiving signal output from the first light receiving element and the second light receiving signal output from the second light receiving element are input, and the difference between the first light receiving signal and the second light receiving signal is input. An optical encoder comprising a differential operation circuit for performing dynamic operation. The optical encoder according to claim 4, wherein
An optical encoder comprising an AD conversion circuit for AD converting a signal differentially calculated by the differential arithmetic circuit. The optical encoder according to claim 5, wherein
The differential arithmetic circuit is
Output two identical current signals as differentially calculated signals,
The AD converter circuit receives a current signal from one of the two current signals.
The optical encoder further comprises a feedback circuit to which a current signal of one of the two current signals is input.   The electronic device provided with the optical encoder as described in any one of Claim 1 to 6.