JP2006284277A - Encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an encoder capable of detecting a fine moving quantity, and preventing decline of a detection capacity. <P>SOLUTION: This encoder 1 comprises a light source 2; a light receiving element 3 for receiving light from the light source 2, and detecting the intensity of received light; a fixed scale 5 fixed between the light source 2 and the light receiving element 3, and provided with a row of slits 4 having a fixed pitch T respectively; and a moving scale 7 moving together with a specimen between the light source 2 and the light receiving element 3, and having a row of slits 6 having the same pitch T as the fixed scale 5. The encoder 1 has opening plates 9, 11 provided respectively with transmission openings 8, 10 for transmitting light between the light source 2 and the fixed scale 5 or the moving scale 7, or otherwise between the light receiving element 2 and the fixed scale 5 or the moving scale 7. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an encoder that optically detects a movement amount.

In Patent Document 1, a light source that emits parallel light rays by a lens, a light detector (light receiving element) that receives light from the light source and detects the intensity of the received light, and a fixed between the light source and the light receiving element are disclosed. An encoder comprising a fixed scale provided with a row of slits having a constant pitch and a moving scale having a row of slits having the same pitch as the fixed scale is described.
Japanese Patent Application Laid-Open No. 08-54258

  If a point light source and a lens are used, parallel light rays can be obtained as in Patent Document 1. However, in an encoder that detects an actual minute amount, a light source composed of a light emitting diode (LED) or the like is a planar light source that emits diffused light from a non-negligible area, and it is difficult to obtain a parallel light beam by a lens. is there.

  FIG. 17 shows a conventional encoder 31 using a planar light source. The conventional encoder 31 includes a light emitting diode 32, a photodiode (PD) 33 that outputs a current proportional to the intensity of light received directly facing the light emitting diode 32, and a 1/2 pitch (1 / 2T) A grid-like fixed scale 35 provided with a row of slits 34 having a width, and a moving object provided with a row of slits 36 having the same pitch T and the same width as the fixed scale 35 are moved together with the test object to be measured. And a moving scale 37.

  Assuming that the light emitting diode 32 generates ideal parallel light, all the light emitted from the light emitting diode 32 is blocked when the moving scale 37 is shifted from the fixed scale 35 by 1/2 pitch, and the photodiode 33 emits light. Since no light is received, the output becomes zero. When the moving scale 37 is moved, the amount of light reaching the photodiode 33 increases in proportion to the amount of movement until the phase of the moving scale 37 coincides with the fixed scale 35, and further moving, the amount of light reaching the photodiode moves. Decreases inversely with quantity. In other words, ideally, the output of the encoder 31 is a triangular wave having a minimum value of 0 and a period matching the pitch T of the slits 34 and 36, as indicated by a broken line in the graph of FIG.

  However, the actual light emitting diode 32 also emits light in an oblique direction, and as shown by an arrow in FIG. 17, even if the moving scale 37 is shifted from the fixed scale 35 by 1 / 2T, the oblique light is emitted. It reaches the photodiode 33. The light emitting diode 32 has a width of 2.5T, and one end faces the center of the slit 34 of the fixed scale 35, but the other end faces the center of the portion where the slit 34 is not provided. The encoder 31 is practically the same as a slit having a width of 1 / 4T. The 1 / 4T width slit transmits light having a light amount mainly composed of a trapezoidal waveform whose peak position is shifted by 1 / 8T from the light transmitted through the 1 / 2T width slit 34. Therefore, the output of the entire photodiode 33 is distorted. give. For this reason, as shown in FIG. 18, since the output waveform is an asymmetrically distorted waveform, the position of the moving scale 37 cannot be easily calculated.

  Further, the amount of light that reaches the photodiode 33 in an oblique direction increases as the distance between the fixed scale 35 and the moving scale 37 increases, but the fixed scale 35 and the moving scale 37 move relative to each other, so that the distance is set to zero. This is impossible, and the variation due to the individual difference in the gap between the fixed scale 35 and the moving scale 37 becomes insignificant compared to the width of the light emitting diode 32 and the photodiode 33, and the waveform is corrected by calculation. Impossible.

  In such an encoder 31, the output is compared with a threshold value, and each time the output exceeds the threshold value, the value representing the position of the moving scale 37 is increased or decreased by a certain amount. That is, there is a problem that the length T of one pitch of the slit 34 is a minimum unit that can be detected, and the resolution cannot be sufficiently increased due to processing restrictions. Furthermore, the output with respect to the amount of light emitted from the light emitting diode 32 and the amount of light received by the photodiode 33 fluctuates or changes over time depending on the environmental temperature. For this reason, as shown in FIG. 18, when the output of the photodiode 33 decreases, the threshold value set does not exceed even at the peak time, and the movement of the moving scale 37 cannot be detected.

  In view of the above problems, an object of the present invention is to provide an encoder that can detect a minute amount of movement and does not have a reduced detection capability.

  In order to solve the above problems, a first aspect of an encoder according to the present invention includes a light source, a light receiving element that receives light from the light source and detects the intensity of the received light, the light source, and the light receiving element. A fixed scale provided with a row of slits with a constant pitch, and a movement having a row of slits with the same pitch as that of the fixed scale. An encoder comprising a scale, wherein light is transmitted between at least one of the light source and the fixed scale or the moving scale, and between the light receiving element and the fixed scale or the moving scale. It shall have the aperture plate which provided the opening.

  According to this configuration, the aperture plate restricts the light path that can reach the light receiving element from the light source, and blocks light that tries to reach the light receiving element in an oblique direction, so that the output of the light receiving element is ideal. The waveform is close to a triangular wave.

  Further, in the encoder according to the first aspect of the present invention, both between the light source and the fixed scale or the moving scale, and between the light receiving element and the fixed scale or the moving scale, You may have an aperture plate.

  According to this configuration, since the light path is limited on both the light source side and the light receiving element side, the ability to block light in an oblique direction is high, and an output with higher linearity can be obtained.

  Further, in the encoder according to the first aspect of the present invention, any one of the light source and the fixed scale or the moving scale, and the light receiving element and the fixed scale or the moving scale, You may have two or more aperture plates.

  According to this configuration, by providing an aperture plate that is attached together with the light source and the light receiving element and an aperture plate that is attached to the fixed scale with high accuracy, light in an oblique direction is effectively blocked and a high linearity output is obtained. can get.

  In the encoder according to the first aspect of the present invention, the transmission aperture having the narrowest width in the moving direction of the test object may have a width that is an integral multiple of the pitch of the slits.

  According to this configuration, even if slits having a substantially narrow width are formed at both ends of the effective light path, a triangular wave that matches the regular slit pitch can be obtained by adding the amount of light that has passed through the slits at both ends. For this reason, since distortion does not arise in the output waveform, the linearity of the output is not impaired depending on the mounting position of the aperture plate.

  Moreover, the encoder of the 1st aspect of this invention WHEREIN: The said transmission opening with the narrowest width | variety of the said to-be-tested object's moving direction may oppose both ends to the edge part of the said slit of the said fixed scale.

  According to this configuration, the effective light path is symmetrical before and after the moving direction of the test object, and the output waveform is not distorted.

  In the encoder according to the first aspect of the present invention, the aperture plate provided with the transmission aperture having the narrowest width in the moving direction of the test object may be fixed to the fixed scale.

  According to this configuration, since the position of the transmission aperture is accurately determined, the output of the encoder has high linearity as designed.

  The encoder according to the second aspect of the present invention includes a light source, a fixed scale having a row of slits having a constant pitch, and a reflecting unit that moves with the test object and reflects light having the same pitch as the rows of slits. An encoder comprising: a moving scale provided with a row; and a light receiving element that is emitted from the light source, passes through the slit and is reflected by the reflecting portion, and detects the intensity of the received light, An aperture plate that is partially opened is provided between at least one of the light source and the fixed scale and between the movable scale and the light receiving element.

  According to this configuration, since the reflection type moving scale has no component on one side of the moving scale, the moving scale can be directly fixed to the test object. Further, since the path other than the light reflected at the center between the light source and the light receiving element is blocked by the aperture plate, an output with high linearity can be obtained.

  In the encoder according to the first and second aspects of the present invention, the width of the transmission opening in the moving direction of the test object may be narrower than at least one of the light source and the light receiving element.

  According to this configuration, since the light path between the light source and the light receiving element is limited to the moving direction of the test object, light in an oblique direction that is not perpendicular to the moving direction of the test object is blocked, and linearity is High output can be obtained.

  In the encoder according to the first and second aspects of the present invention, the fixed scale is provided with two rows of the slits shifted by a quarter pitch in the moving direction of the test object, or the moving scale is , Two rows of the slits or the reflecting portions shifted by ¼ pitch in the moving direction of the test object are provided, each passing through one of the slit rows, or one of the reflecting portion rows There may be provided two light receiving elements for detecting the light reflected by.

  According to this configuration, the outputs of the two light receiving elements are 90 ° out of phase, and the direction of the movement scale is derived from the two outputs by drawing a Lissajous figure or the like. can do.

  In the encoders of the first and second aspects of the present invention, the output of the light receiving element is binarized by threshold processing, and a numerical value representing the position of the test object every time the binarized output changes. An operation of increasing or decreasing by a value corresponding to the length of the 1/2 pitch of the slit may be performed.

  According to this configuration, a minimum detection capability of 1/2 pitch (1 / 2T) of the slit can be obtained even by simple binarization.

  Further, a third aspect of the encoder according to the present invention is a light source, a light receiving element that receives light from the light source and detects the intensity of the received light, and is fixed between the light source and the light receiving element. An encoder comprising a fixed scale provided with a row of slits having a constant pitch, and a moving scale having a row of slits having the same pitch as that of the fixed scale, moving with the test object between the light source and the light receiving element. The moving scale has a transmission part that is opened larger than a light path that can reach the light receiving element from the light source, and an output signal of the light receiving element when the light path is in the transmission part And a value representing the position of the test object is reset.

  According to this configuration, when the transmission part does not block the light path from the light source to the light receiving element, an output that can be easily distinguished from when the light path has a slit is obtained. The position of the test object can be correctly detected by correcting the reference value so that the position where this output is obtained is the origin and the increase and decrease of the output gain of the light source and the light receiving element are offset.

  Further, a fourth aspect of the encoder according to the present invention is a light source, a light receiving element that receives light from the light source and detects the intensity of the received light, and is fixed between the light source and the light receiving element. An encoder comprising a fixed scale provided with a row of slits having a constant pitch, and a moving scale having a row of slits having the same pitch as that of the fixed scale, moving with the test object between the light source and the light receiving element. The moving scale has a shielding part having no transparent part in a range larger than a light path that can reach the light receiving element from the light source, and the light path is in the shielding part. An output signal of the light receiving element is detected, and a value representing the position of the test object is reset.

  According to this configuration, since the light path from the light source to the light receiving element is completely blocked by the moving scale by the shielding unit, a continuous output can be obtained. Based on this output, the output of the light source and the light receiving element is obtained. The position of the test object can be correctly detected by correcting the reference value so as to cancel the increase and decrease of the gain.

  Further, a fifth aspect of the encoder according to the present invention is a light source, a light receiving element that receives light from the light source and detects the intensity of the received light, and is fixed between the light source and the light receiving element. An encoder comprising a fixed scale provided with a row of slits having a constant pitch, and a moving scale having a row of slits having the same pitch as that of the fixed scale, moving with the test object between the light source and the light receiving element. Then, the output of the light receiving element is binarized by comparison with a threshold value, and the threshold value is changed so that the binary output time becomes equal when the moving scale moves at a constant speed. .

  According to this configuration, when the driving means for moving the test object is driven in a steady state, the threshold value is set so that the time during which the output of the encoder is equal to or greater than the threshold is equal to the time during which the encoder output is equal to or less than the threshold. Therefore, even when the encoder gain decreases, the position of the moving scale at which the output is equal to the threshold value is every 1/2 of the slit pitch T. For this reason, the detection position does not change due to a change in gain of the light source or the light receiving element.

  Further, a sixth aspect of the encoder according to the present invention is a light source, a light receiving element that receives light from the light source and detects the intensity of the received light, and is fixed between the light source and the light receiving element. An encoder comprising a fixed scale provided with a row of slits having a constant pitch, and a moving scale having a row of slits having the same pitch as that of the fixed scale, moving with the test object between the light source and the light receiving element. Storing the minimum value and the maximum value of the output of the light receiving element, setting one or more intermediate values between the minimum value and the maximum value, and setting the output value of the light receiving element to the minimum value and the maximum value Compared with the value and the intermediate value, a value corresponding to a length smaller than the pitch of the slit is calculated.

  According to this configuration, by storing the maximum value and the minimum value of the output of the light receiving element, setting an intermediate value such as an equivalence point between them, and calculating the position of the moving scale in comparison with the intermediate value The amount of movement smaller than the slit pitch can be detected.

  Further, a sixth aspect of the encoder according to the present invention is a light source, a light receiving element that receives light from the light source and detects the intensity of the received light, and is fixed between the light source and the light receiving element. An encoder comprising a fixed scale provided with a row of slits having a constant pitch, and a moving scale having a row of slits having the same pitch as that of the fixed scale, moving with the test object between the light source and the light receiving element. And storing a minimum value and a maximum value of the output of the light receiving element, dividing a value obtained by subtracting the minimum value from an output value of the light receiving element by a difference between the maximum value and the minimum value, A value corresponding to a length less than the pitch is calculated.

  According to this configuration, the moving amount of the moving scale can be continuously calculated by linearly approximating the position of the moving scale and the maximum value and the minimum value of the light receiving element output.

  In addition, an eighth aspect of the encoder according to the present invention is a light source, a light receiving element that receives light from the light source and detects the intensity of the received light, and is fixed between the light source and the light receiving element. A fixed scale provided with a row of slits having a constant pitch, and a movement having a row of slits having the same pitch as that of the fixed scale, moving with the test object driven by the driving device between the light source and the light receiving element. An encoder comprising a scale, which calculates a value representing the position of the test object based on an input or output of a driving device, and calculates the output when the output of the light receiving element reaches a minimum value or a maximum value. It is assumed that the position is corrected to a value corresponding to an integer position that is 1/2 of the slit pitch.

  According to this configuration, when the output of the light receiving element becomes maximum or minimum while calculating the position of the moving scale from the input or output of the driving device that drives the moving scale, the calculated position of the moving scale is set to the slit pitch. Therefore, in detecting the position below the slit pitch, the linear position can be calculated regardless of the distortion of the amount of light received by the light receiving element, and in detecting the position above the slit pitch, an error is detected for each slit pitch. Correct position can be calculated by correction.

  In the encoders according to the first to eighth aspects of the present invention, if the fixed scale and the moving scale are made of a flexible material, the adaptability to a test object for detecting a position is high, and the fixed scale and the moving The scale can be easily formed by etching stainless steel or stamping with a press, or by forming a light-shielding layer with a transparent opening by exposing the photosensitive material applied to a transparent plastic film. it can.

  The encoder of the present invention can obtain a linear output with respect to the amount of movement of the test object by the aperture plate that restricts the light path from the light source, and corrects the reference value for processing the output signal or corrects the calculation Therefore, there is no change in detection capability due to environmental changes or changes over time, and a small amount of movement can be calculated.

Embodiments of the present invention will now be described with reference to the drawings.
FIG. 1 is an exploded perspective view of an encoder 1 according to a first embodiment of the present invention. The encoder 1 is provided with a row of slits 4 between a light-emitting diode 2 that is a light source and a photodiode 3 that is a light-receiving element that outputs a current proportional to the intensity of light received in front of the light-emitting diode 2. A fixed scale 5 is fixed, a moving scale 7 is provided with a row of slits 6 that move in the direction of the arrow together with the test object, and a transmission aperture 8 is provided between the light emitting diode 2 and the fixed scale 5. The first aperture plate 9 is fixed, and the second aperture plate 11 provided with the transmission aperture 10 is fixed between the moving scale 7 and the photodiode 3. The fixed scale 5 and the moving scale 7 are formed, for example, by forming a row of slits 4 and 6 by punching a stainless steel plate by etching or pressing. Here, the positions of the fixed scale 5 and the moving scale 7 may be reversed.

  FIG. 2 shows a cross section of the encoder 1. The slits 4 of the fixed scale 5 and the slits 6 of the moving scale 7 are through holes having a width of 1 / 2T provided side by side at the same pitch T. The transmission openings 8 and 10 of the first opening plate 9 and the second opening plate 11 have a width T in the moving direction of the moving scale 7, and the center coincides with the center of one slit 4 of the fixed scale 5. ing.

Next, the output characteristic and position calculation method of the encoder 1 having the above configuration will be described.
As shown by arrows in FIG. 2, the path of light that can reach the photodiode 3 from the light emitting diode 2 by the first aperture plate 9 and the second aperture plate 11 is a path that penetrates both the transmission aperture 8 and the transmission aperture 10. Limited. For this reason, many of the paths through which the photodiode 3 can be seen through the slits 4 and 6 of the fixed scale 5 and the moving scale 7 in an oblique direction are blocked by the first opening plate 9 and the second opening plate 11. Only light in a direction substantially perpendicular to the moving direction of the moving scale 7 can reach the photodiode 3. The area in which the fixed scale 5 and the moving scale 7 can be seen in the direction perpendicular to the moving direction of the moving scale 7, that is, the overlapping area of the slit 4 and the slit 6 is the same as the phase of the moving scale 7. It is sometimes the maximum, and becomes 0 when the moving scale 7 is shifted from the fixed scale 5 by 1 / 2T.

  The output of the photodiode 3 draws a curve close to a triangular wave with respect to the position of the moving scale 7, as shown in FIG. Although it is proportional to the amount of light emitted from the light emitting diode 2 and reaches the photodiode 3, it does not form a complete triangular wave because it reaches the photodiode 3 in a slightly oblique direction, but the first opening indicated by a broken line Compared to the output waveform without the plate 9 and the second aperture plate 11, the waveform has no distortion before and after the maximum value, and the increase and decrease with high linearity are periodically repeated. Therefore, the encoder 1 stores the minimum value and the maximum value of the output of the photodiode 3, divides the value obtained by subtracting the minimum value from the output value of the photodiode 3 by the difference between the maximum value and the minimum value of the output, and the pitch The position of the moving scale 7 can be accurately calculated by performing linear approximation for calculating a value corresponding to a length less than T.

  Further, as shown in FIG. 4, when calculating the position of the moving scale 7, the maximum value Pmax and the minimum value Pmin of the output of the photodiode 3 are stored, and the output that divides the maximum value Pmax and the minimum value Pmin into four equal parts. The values are set as intermediate values Pq1, Pq2, and Pq3, the output is compared with the maximum value Pmax, the minimum value Pmin, and the intermediate values Pq1, Pq2, and Pq3, and one cycle of the output is divided into eight. The movement distance may be equivalent to 1 / 8T. Further, the intermediate value may not be an equal dividing point, and if the waveform is known in advance, it may be set to a value that divides the maximum value Pmax and the minimum value Pmin by a ratio that matches the actual moving distance.

  Next, FIG. 5 shows a cross section of the encoder 1a according to the second embodiment of the present invention. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted. The encoder 1 a has a moving scale 13 made of a permeable flexible plastic film 12. The moving scale 13 has a light shielding layer 14 that is exposed and fixed with a photosensitive material applied to the surface of the plastic film 12, and the light shielding layer 14 is opened by masking with a pitch T and a width of 1 / 2T. A slit 15 is formed. In the light shielding layer 14, the first aperture plate 9 of the encoder 1a and the transmission apertures 8 and 10 of the second aperture plate 11 have a width in the moving direction of the moving scale 13 of 2.5T. Further, the encoder 1a has a third aperture plate 17 having a transparent aperture 16 having a width 2T in the moving direction attached to the surface of the fixed scale 5 on the light emitting diode 2 side. The third aperture plate 17 is fixed so that the end of the transmission aperture 16 coincides with the end of the slit 4 of the fixed scale 5.

  An output characteristic of the encoder 1a having the above configuration and a method for calculating the position of the moving scale 13 will be described. Since both ends of the transmission aperture 16 of the third aperture plate 17 coincide with the slit 4 of the fixed scale 5, the effective widths of the slits 4 of the fixed scale 5 are all 1 / 2T. The overlapping area repeatedly increases and decreases at a constant rate with respect to the position of the moving scale 13. For this reason, as shown in FIG. 6, the output of the photodiode 3 shows a symmetric periodic waveform on both sides of the peak. In the encoder 1a, since the 3rd opening board 17 is stuck on the fixed scale 5, it can assemble so that both positional relationship may not shift | deviate. For this reason, if the width of the transmissive aperture 16 is (n + 1/2) T, the slit 4 having an effective width narrower than 1 / 2T is not formed due to an assembly error, and a target output waveform is obtained before and after the peak.

  FIG. 7 shows the relationship between the output of the photodiode 3 and the threshold value. The encoder 1a compares the output of the photodiode 3 with a threshold value and binarizes the output. Each time the binarized output value changes, the numerical value indicating the position of the moving scale 13 is increased or decreased by a value corresponding to 1 / 2T. In addition, the encoder 1a steadily keeps the distance of one or more cycles from the output of the driving device (not shown) or the input to the driving device that drives the testing object (not shown) to which the moving scale 13 is fixed. It is detected that the state is driven, and the threshold value is corrected so that the time TH when the output at that time is equal to or greater than the threshold value and the time TL when the output is equal to or less than the threshold value are the same time. Therefore, as shown in the figure, when the output decreases, the threshold is also set low. In this way, by binarizing the output with the corrected threshold, regardless of the gain of the light emitting diode 2 or the photodiode 3, a 1 / 2T movement of the moving scale 13 can be accurately detected.

  Also, if there is a large difference between the width of the convex portion and the concave portion of the output waveform, if TH and TL are made the same, the threshold value will be crossed when the slope of the output waveform is small, so the detection accuracy will be low. The threshold value may be corrected so as to maintain the ratio between TL and TL at an appropriate value. Also, TH can be measured by measuring the time from when the output crosses the threshold until it reaches the maximum or from when the output reaches the maximum until it crosses the threshold. You may correct | amend a threshold value so that ratio with 1 / 2TL which measured the time between threshold values may become an appropriate value.

  Further, when the peak of the output waveform of the photodiode 3 is sharp, it is detected that the output is the maximum value or the minimum value, and the phase of the moving scale 13 coincides with the fixed scale 5 or is deviated by 1 / 2T. It can be detected accurately. In such a case, the encoder 1a calculates the position of the moving scale 13 from the input to the driving device that drives the test object, the output pulse, and the like, and the sharp peak (maximum value or minimum value) of the output of the photodiode 3 is obtained. ) Is detected, the calculated value representing the position of the moving scale 13 is corrected to a value that matches the fixed scale 5 or a value that is shifted by 1 / 2T, so that a small amount of movement can be calculated and a large amount of movement can be calculated. The detection accuracy can be maintained even when it is done.

  FIG. 8 shows an encoder 1b according to a third embodiment of the present invention. Also in this embodiment, only components different from the first embodiment will be described. The encoder 1b has a shield 18 having an area sufficiently larger than the transmissive aperture 8 and the transmissive aperture 10 at the end of the moving scale 7 and having no slit 4 or other transmissive portions, and the transmissive aperture 8 and A transmission portion 19 that is sufficiently larger than the transmission opening 10 is provided.

  The output waveform of the photodiode 3 of the encoder 1b is shown in FIG. 9, and the functions of the shielding unit 18 and the transmission unit 19 will be described. When all the light that has passed through the transmission aperture 8 of the first aperture plate 9 and the slit 4 of the fixed scale 5 passes through the transmission part 19 without being blocked by the moving scale 7, the output of the photodiode 3 is (usually an output circuit). When it is blocked by the shielding part 18, the output of the photodiode 3 shows the maximum value Pc.

  Since light in an oblique direction cannot reach the photodiode 3 when the optical path is blocked by the shielding portion 18, the maximum value Pc is larger than the peak value when the slit 6 is on the optical path. Similarly, the minimum value Po is also smaller than the minimum value when the slit 6 is on the optical path. For this reason, the position of the moving scale 13 can be calculated by setting the position where the maximum value Pc or the minimum value Po is taken as the origin of the encoder 1b. In FIG. 9, when the maximum value Pc is detected, the value representing the position of the moving scale 13 is reset to zero. Since the moving distance from when the maximum value Pc is detected until the output first falls below the threshold is constant, a predetermined value is set as a value representing the position of the moving scale 13 when the output first falls below the threshold. to add. Alternatively, the encoder 1b may detect the minimum value Po and reset the value representing the position of the moving scale 13.

  FIG. 10 shows an encoder 1c according to a fourth embodiment of the present invention. In this embodiment, the shielding part 18 and the transmission part 19 of the encoder 1b in FIG. 8 are interchanged. The output of the encoder 1c draws the waveform shown in FIG. The encoder 1c detects the minimum value Po and resets the value representing the position of the moving scale 13.

  FIG. 12 shows an encoder 1d according to the fifth embodiment of the present invention. Also in this embodiment, only components different from the first embodiment will be described. The encoder 1d has a moving scale 7 'provided with two rows of slits 6a and 6b. Both rows of the slits 6a and 6b are moved in the moving direction of the moving scale 7' by a quarter pitch (1 / 4T). They are offset. In the first aperture plate 9 ', two transmission apertures 8a and 8b are provided side by side perpendicular to the moving direction of the moving scale 7' corresponding to both rows of the slits 6a and 6b. Similarly, the second aperture plate 11 'is also provided with two transmission apertures 10a and 10b. A photodiode 3a that receives the light that has passed through the transmission opening 8a and the transmission opening 10a, and a photodiode 3b that receives the light that has passed through the transmission opening 8b and the transmission opening 10b are provided side by side.

  FIG. 13 shows waveforms of the output Pa of the photodiode 3a and the output Pb of the photodiode 3b of the encoder 1d. As shown in the figure, since the slit 6a and the slit 6b are shifted by ¼T, the output Pa and the output Pb depict waveforms whose phases are shifted by ¼ period. The change in the values of both outputs Pa and Pb is shown in the Lissajous figure as shown in FIG. 14, and it is possible to determine in which direction the moving scale 7 'is moving from the rotation direction.

  Further, as in the encoder 1e of the sixth embodiment shown in FIG. 15, instead of the fixed scale 5 and the moving scale 7 of the encoder 1d of FIG. 12, a row of slits 4a and a row of slits 4b shifted by ¼ pitch are provided. 13 and the moving scale 7 provided with one row of slits 6 can also provide outputs Pa and Pb similar to those in FIG. 13, and the moving direction of the moving scale 7 can be detected. Moreover, even if only one transmission opening 10 is provided as in the second opening plate 11 of the present embodiment, the function of limiting the light path in the moving direction of the moving scale 7 can be achieved. Similarly, the transmission openings 8a and 8b of the first opening plate 9 'may be integrated.

  FIG. 16 shows a reflective encoder 21 according to a seventh embodiment of the present invention. The reflective encoder 21 includes a light-emitting diode 22 and a photodiode 23 arranged on the same plane, a fixed scale 25 provided with a row of slits 24 having a constant pitch, and, for example, the same as the slit 24 on the surface of a plastic substrate 26. A row of reflecting portions 27 in which metal is deposited at a pitch to form a mirror surface is provided, and is fixed between a moving scale 28 that moves together with the test object, the light emitting diode 22, the photodiode 23, and the fixed scale 25. The aperture plate 30 is provided with two transmission apertures 29. The plastic substrate 26 may transmit light or absorb most of it. Moreover, the moving scale 28 should just reflect light with a fixed pitch, and can also be comprised by providing the slit of a fixed pitch in the base material which has a mirror surface.

  The reflective encoder 21 limits the light path from the light emitting diode 22 to the photodiode 23 to a path reflected by the moving scale 28 at a position facing the center of the light emitting diode 22 and the photodiode 23 by the aperture plate 30. The output of the photodiode 23 having high linearity with respect to the position of the moving scale 28 is obtained. Since the reflective encoder 21 has no components on one side of the moving scale 28, the moving scale 28 can be directly attached to the surface of the test object.

The disassembled perspective view of the encoder of 1st Embodiment of this invention. Sectional drawing of the encoder of FIG. The graph which shows the output waveform of the photodiode of the encoder of FIG. The graph which shows the intermediate value set with respect to the output of FIG. Sectional drawing of the encoder of 2nd Embodiment of this invention. The graph which shows the output waveform of the photodiode of the encoder of FIG. The graph which shows the change of the output of FIG. 6, and correction | amendment of a threshold value. The disassembled perspective view of the encoder of 3rd Embodiment of this invention. The graph which shows the output waveform of the photodiode of the encoder of FIG. The disassembled perspective view of the encoder of 4th Embodiment of this invention. The graph which shows the output waveform of the photodiode of the encoder of FIG. The disassembled perspective view of the encoder of 5th Embodiment of this invention. The graph which shows the output waveform of the photodiode of the encoder of FIG. The Lissajous figure of the output of the encoder of FIG. The disassembled perspective view of the encoder of 6th Embodiment of this invention. Sectional drawing of the encoder of 7th Embodiment of this invention. Sectional drawing of the conventional encoder. The graph which shows the output waveform of the encoder of FIG.

Explanation of symbols

1 Encoder 2 Light emitting diode (light source)
3 Photodiode (light receiving element)
4 slit 5 fixed scale 6 slit 7 moving scale 8 transmission aperture 9 first aperture plate 10 transmission aperture 11 second aperture plate 12 plastic film 13 moving scale 14 light shielding layer 16 transmission aperture 17 third aperture plate 18 shielding portion 19 transmission portion T pitch

Claims (25)

A light source, a light receiving element that receives light from the light source and detects the intensity of the received light, and
A fixed scale provided between the light source and the light receiving element, and provided with a row of slits having a constant pitch;
It moves with the test object between the light source and the light receiving element, and is an encoder comprising a moving scale having a row of slits having the same pitch as the fixed scale,
It has an aperture plate provided with a transmission aperture through which light is transmitted at least between the light source and the fixed scale or the moving scale and between the light receiving element and the fixed scale or the moving scale. An encoder characterized by.   2. The aperture plate is provided between the light source and the fixed scale or the moving scale, and between the light receiving element and the fixed scale or the moving scale, respectively. The described encoder.   Two or more of the aperture plates are provided between one of the light source and the fixed scale or the moving scale and between the light receiving element and the fixed scale or the moving scale. Item 3. The encoder according to item 2.   The encoder according to any one of claims 1 to 3, wherein the transmission aperture having the narrowest width in the moving direction of the test object has a width that is an integral multiple of the pitch of the slit.   The encoder according to any one of claims 1 to 4, wherein both ends of the transmission opening with the narrowest width in the moving direction of the test object face the end of the slit of the fixed scale.   The encoder according to any one of claims 1 to 5, wherein the aperture plate provided with the transmission aperture having the smallest width in the moving direction of the test object is fixed to the fixed scale. A light source;
A fixed scale having rows of slits of constant pitch;
A moving scale provided with a row of reflecting portions that move with the test object and reflect light having the same pitch as the row of slits;
An encoder that includes a light receiving element that emits light from the light source, passes through the slit and is reflected by the reflection unit, and detects the intensity of the received light.
An encoder having an aperture plate partially opened between at least one of the light source and the fixed scale and between the movable scale and the light receiving element.   The encoder according to any one of claims 1 to 7, wherein a width of the transmission opening in a moving direction of the test object is narrower than a width of at least one of the light source and the light receiving element. The fixed scale is provided with two rows of the slits shifted by 1/4 pitch in the moving direction of the test object, or the moving scale is 2 shifted by 1/4 pitch in the moving direction of the test object. The slits or the reflectors in a row are provided;
9. The light receiving device according to claim 1, further comprising two light receiving elements that detect light that has passed through any one of the slit rows or reflected by any one of the reflecting portion rows. The encoder described.   The output of the light receiving element is binarized by threshold processing, and the numerical value indicating the position of the test object is increased or decreased by a value corresponding to the length of the 1/2 pitch of the slit each time the binarized output changes. The encoder according to any one of claims 1 to 9, wherein the calculation is performed. The moving scale has a transmission part that is larger than the narrowest transmission opening,
11. The value representing the position of the test object is reset by detecting an output signal of the light receiving element when the light path is in the transmissive part. 11. Encoder. The moving scale has a shielding part having no transparent part in a range larger than the narrowest transmission opening,
12. The value representing the position of the test object is reset by detecting an output signal of the light receiving element when the light path is in the shielding part. Encoder. The output of the light receiving element is compared with a threshold value and binarized,
The threshold value is changed so that a ratio of the two output times becomes a predetermined value when the moving scale moves at a constant speed. Encoder.   The minimum value and the maximum value of the output of the light receiving element are stored, one or more intermediate values between the minimum value and the maximum value are set, and the output value of the light receiving element is set to the minimum value, the maximum value, and the The encoder according to any one of claims 1 to 9, wherein a value corresponding to a length smaller than the pitch of the slit is calculated as compared with an intermediate value.   The minimum value and the maximum value of the output of the light receiving element are stored, and the value obtained by subtracting the minimum value from the output value of the light receiving element is divided by the difference between the maximum value and the minimum value to be less than the pitch of the slit. The encoder according to claim 1, wherein a value corresponding to the length is calculated.   A value representing the position of the test object is calculated based on an input or output of a driving device for moving the test object, and the position is expressed when the output of the light receiving element reaches a minimum value or a maximum value. The encoder according to claim 1, wherein the encoder is corrected to a value corresponding to a position that is an integral multiple of ½ of the pitch of the slit. A light source, a light receiving element that receives light from the light source and detects the intensity of the received light, and
A fixed scale provided between the light source and the light receiving element, and provided with a row of slits having a constant pitch;
It moves with the test object between the light source and the light receiving element, and is an encoder comprising a moving scale having a row of slits having the same pitch as the fixed scale,
The moving scale has a transmission part that is opened larger than a path of light that can reach the light receiving element from the light source,
An encoder characterized by detecting an output signal of the light receiving element when the light path is in the transmission section and resetting a value representing the position of the test object. A light source, a light receiving element that receives light from the light source and detects the intensity of the received light, and
A fixed scale provided between the light source and the light receiving element, and provided with a row of slits having a constant pitch;
It moves with the test object between the light source and the light receiving element, and is an encoder comprising a moving scale having a row of slits having the same pitch as the fixed scale,
The moving scale has a shielding part having no transmissive part in a range larger than a path of light that can reach the light receiving element from the light source,
An encoder that detects an output signal of the light receiving element when the light path is in the shielding portion, and resets a value representing a position of the test object. A light source, a light receiving element that receives light from the light source and detects the intensity of the received light, and
A fixed scale provided between the light source and the light receiving element, and provided with a row of slits having a constant pitch;
It moves with the test object between the light source and the light receiving element, and is an encoder comprising a moving scale having a row of slits having the same pitch as the fixed scale,
The output of the light receiving element is compared with a threshold value and binarized,
An encoder, wherein the threshold value is changed so that a ratio of the two output times becomes a predetermined value when the moving scale moves at a constant speed. A light source, a light receiving element that receives light from the light source and detects the intensity of the received light, and
A fixed scale provided between the light source and the light receiving element, and provided with a row of slits having a constant pitch;
It moves with the test object between the light source and the light receiving element, and is an encoder comprising a moving scale having a row of slits having the same pitch as the fixed scale,
The minimum value and the maximum value of the output of the light receiving element are stored, one or more intermediate values between the minimum value and the maximum value are set, and the output value of the light receiving element is set to the minimum value, the maximum value, and the An encoder that calculates a value corresponding to a length smaller than the pitch of the slits as compared with an intermediate value. A light source, a light receiving element that receives light from the light source and detects the intensity of the received light, and
A fixed scale provided between the light source and the light receiving element, and provided with a row of slits having a constant pitch;
It moves with the test object between the light source and the light receiving element, and is an encoder comprising a moving scale having a row of slits having the same pitch as the fixed scale,
The minimum value and the maximum value of the output of the light receiving element are stored, and the value obtained by subtracting the minimum value from the output value of the light receiving element is divided by the difference between the maximum value and the minimum value to be less than the pitch of the slit. An encoder that calculates a value corresponding to a length. A light source, a light receiving element that receives light from the light source and detects the intensity of the received light, and
A fixed scale provided between the light source and the light receiving element, and provided with a row of slits having a constant pitch;
An encoder that moves with a test object driven by a driving device between the light source and the light receiving element, and includes a moving scale having a row of slits having the same pitch as the fixed scale;
A value representing the position of the test object is calculated based on the input or output of the driving device, and when the output of the light receiving element reaches the minimum value or the maximum value, the calculated position is set to 1 / (1) of the pitch of the slit. An encoder that corrects a value corresponding to a position that is an integral multiple of 2.   The encoder according to any one of claims 1 to 22, wherein the fixed scale and the moving scale are made of a flexible material.   The encoder according to any one of claims 1 to 22, wherein at least one of the fixed scale and the moving scale is formed by punching a stainless material by etching or pressing. At least one of the fixed scale and the moving scale is made of a permeable plastic film,
The encoder according to any one of claims 1 to 22, wherein the slit is a transmission opening of a light shielding layer provided by exposing a photosensitive material applied to the plastic film.

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