JP2005207822A - Photodetector for optical encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photodetector for an encoder which can satisfactorily remove noise-like carriers and which can be miniaturized. <P>SOLUTION: The photodetector 3 is constituted of a one-dimensional photodetector array 4, consisting of a plurality of photodetector elements for detecting a plurality of phase parts in a light and dark pattern, and is constituted so that the phase part, detected by the photodetector elements 4a disposed at one end of the photodetector array 4 and the phase part, detected by the photodetector elements 4d disposed at the other end of the photodetector array, are mutually out of phase by 180 degrees. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a photodetector used in an optical encoder.

  At present, optical and magnetic methods are used to detect linear displacement in machine tool stages and 3D measuring instruments, and to detect rotation angles in servo motors. So-called encoders are used. In particular, the optical encoder has features such as high accuracy, high resolution, non-contact type, and excellent resistance to electromagnetic interference. For this reason, optical encoders are used in various fields, and optical encoders are mainly used particularly when high accuracy and high resolution are required.

  In general, an optical encoder is composed of a scale fixed to a member for detecting displacement such as a stage and a sensor head for detecting displacement of the scale. The sensor head has a light emitting unit that irradiates light to the scale and a light receiving unit for detecting detection light modulated by the scale, and detects movement of the scale based on a change in intensity of the received detection light. doing.

  A typical conventional optical encoder will be described. FIG. 7 is a block diagram showing an optical encoder using a light emitting diode and a code board (scale). An optical encoder having such a configuration is proposed in Patent Document 1, for example.

  As shown in FIG. 7, the encoder includes a code board 103 and a sensor head 101. In FIG. 7, the sensor head 101 is disposed so that the light emitting diode 109 and the photodetector 107 face each other, and the code board 103 is attached so as to be movable so as to cross the optical path from the light emitting diode 109 to the photodetector 107. ing. Here, the code board 103 is periodically formed with openings 113 and light shields 115 as shown in FIG. That is, the detection light emitted from the light emitting diode 109 passes through the code board 103 only when the opening 113 comes on the optical path as the code board 103 moves. Therefore, a light / dark pattern corresponding to the period of the opening 113 and the light shielding portion 115 of the code board 103 is projected onto the photodetector 107. Here, since the light / dark pattern moves on the photodetector 107 in accordance with the movement of the code board 103, the movement of the code board 103 can be detected by detecting the movement of the light / dark pattern. .

  Further, as shown in FIG. 8, the photodetector 107 has four photodetector elements 107a, 107b, 107c, and 107d so as to be able to detect regions of the light and dark pattern that are 90 degrees out of phase with each other. Among these four photodetector elements, the difference between the output of the photodetector element 107a and the output of the photodetector element 107c, which are 180 degrees out of phase with each other, and the difference between the output of the photodetector element 107b and the output of the photodetector element 107d, By calculating and outputting, the influence of external light or the like is canceled, and an encoder signal corresponding to the light / dark pattern formed by the code board 103 is output.

  FIG. 9 shows a cross-sectional view of the photodetector 107. The photodetector elements 107a, 107b, 107c, and 107d of the photodetector 107 are generally photodetector arrays formed on a semiconductor substrate. Here, as shown in FIG. 9, when the detection light is irradiated in the vicinity of the photodetector element formed on the semiconductor substrate, the carrier 120 is generated also outside the photodetector region. Thus, the carrier 120 generated outside the photodetector region moves in various directions in the semiconductor substrate, and a part of the moved carrier 120 is detected by a nearby photodetector element, for example, the photodetector element 107d shown in FIG. May be. In this case, whether the detection signal output from the photodetector element 107d is an output based on the detection light applied to the photodetector element or a noisy carrier due to the detection light applied to a semiconductor substrate other than the photodetector element. It cannot be distinguished whether it is.

  As shown in FIGS. 8 and 9, when the photodetector elements 107 a, 107 b, 107 c, and 107 d are arranged one-dimensionally, the photodetector elements 107 b and 107 c are separated from each other in the rotation direction of the code board 103. Therefore, the noisy carrier 120 does not flow in from both ends of the photodetector element. On the other hand, the photodetector elements 107a and 107d have one end in contact with the photodetector elements 107b and 107c, respectively, while the other end faces the semiconductor substrate. For this reason, there is a possibility that the noisy carrier 120 generated when the detection light is irradiated onto the semiconductor substrate flows into the photodetector elements 107a and 107d. In this case, the signals output from the photodetector elements 107a and 107d are larger by the amount attributable to the noisy carrier 120 than the signals output from the photodetector elements 107b and 107c. Therefore, when the difference between the photodetector element 107a and the photodetector element 107c having a phase difference of 180 degrees and the difference between the photodetector element 107b and the photodetector element 107d are respectively calculated, the center of the amplitude of the encoder signal output from the photodetector is calculated. Will change by the amount caused by the noisy carrier, which will adversely affect subsequent signal processing and the like.

  Therefore, in Patent Document 1, as shown in FIG. 8, for example, dummy photodetectors 110 and 112 are provided outside the photodetector elements 107a and 107d, and a noisy carrier is absorbed by these dummy photodetectors 110 and 112. Is used. With this configuration, noisy carriers do not flow into the photodetector elements 107a, 107b, 107c, and 107d on the photodetector 107. For this reason, all the photodetector elements have the same level of light receiving capability, and stable light detection is possible.

In the method disclosed in Patent Document 1, an example in which each phase region is detected by one photodetector element 107a, 107b, 107c, and 107d is shown. However, as shown in FIG. An example in which four phase parts are detected by one group is also known. With this configuration, it is possible to detect the light / dark pattern formed by the code board 103 over a plurality of periods, increase the amount of light received by the photodetector, and shape variation of the opening 113 of the code board 103. It is possible to reduce the influence such as.
Japanese Patent Publication No. 8-3427

  However, in the method of Patent Document 1, a relatively large dummy photo detector is required in order to sufficiently remove noisy carriers. This is one of the causes that hinders downsizing of the photodetector.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an encoder photodetector that can sufficiently remove noisy carriers and can be miniaturized.

  In order to achieve the above object, a photodetector for an optical encoder according to a first aspect of the present invention includes a light source, a scale having an optical periodic structure movable relative to the light source, A photodetector for use in an optical encoder having a photodetector for detecting a periodic light-dark pattern generated by detection light emitted from a light source and passing through the scale, the light detector in the light-dark pattern A one-dimensional photodetector array comprising a plurality of photodetector elements for detecting at least three or more phase portions having different phases from each other, and a phase portion detected by a photodetector element disposed at one end of the one-dimensional photodetector array; The phase portions detected by the photodetector elements arranged at the other end of the one-dimensional photodetector array are Degree phase is different.

  According to the first aspect, since the phase portions detected by the photodetector elements arranged at one end and the other end of the photodetector array are different from each other by 180 degrees, one end of the photodetector is arranged. It is possible to cancel out the noisy carrier flowing in from the other end and the noisy carrier flowing in from the other end, and remove the influence of the noisy carrier from the signal component.

  ADVANTAGE OF THE INVENTION According to this invention, the photodetector for encoders which can fully remove a noise-like carrier and can be reduced in size can be provided.

Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
A first embodiment of the present invention will be described. FIG. 1 is a configuration diagram of an optical encoder according to the first embodiment of the present invention. In other words, the optical encoder includes a light source 1 such as a surface emitting laser, a scale 2 having an optical periodic structure, and a photodetector 3. Here, the scale 2 is attached to be movable relative to the light source 1 and the photodetector 3.

  In such a configuration, when light is irradiated from the light source 1 to the scale 2, a light / dark pattern corresponding to the optical periodic structure of the scale 2 is formed on the photodetector 3 by the light transmitted through the scale 2. The Here, a one-dimensional photo detector array (hereinafter referred to as a photo detector array) 4 is formed on the photodetector 3, and the photo detector array 4 can detect a predetermined phase portion of the light-dark pattern. Here, the predetermined phase portion is a pattern in a predetermined phase region of a periodic bright and dark pattern formed by the optical periodic structure of the scale 2.

  That is, since the light / dark pattern formed on the light detector 3 moves on the light detector 3 as the scale 2 moves, the movement of the scale 2 is detected by detecting the movement of the light / dark pattern. Things are possible. Here, if a certain positional relationship is maintained between the light source 1 and the light detector 3, the light / dark pattern formed on the light detector 3, that is, the intensity distribution of the detection light emitted from the light source 1. Does not change. Therefore, the light / dark pattern by the scale 2 moves on the photodetector 3 as the scale 2 moves while maintaining this intensity distribution.

  FIG. 2 is a view of the photodetector array 4 formed on the photodetector 3 when viewed from the surface facing the scale 2. As shown in FIG. 2, the photodetector array 4 formed on the photodetector 3 has a period equal to the period of the light / dark pattern so that four phase portions of the light / dark pattern that are 90 degrees out of phase with each other can be detected. Is composed of four photo detector groups. These four photo detector groups are each composed of a photo detector element 4a for detecting a phase portion (+ A), and a photo detector element 4b for detecting a phase portion (+ B) that is 90 degrees out of phase with the phase portion (+ A). A group consisting of a photodetector element 4c that detects a phase portion (-A) that is 90 degrees out of phase with the group, phase portion (+ B), and a phase portion (-B) that is 90 degrees out of phase with the phase portion (-A) This is a group of detected photodetector elements 4d.

  In the first embodiment, the photo detector array is configured by four photo detector groups so that the four phase portions can be detected. However, the present invention is not limited to this. For example, three phase portions may be detected by three photodetector groups.

  Here, the phase portion (+ A) detected by the group of the photodetector elements 4a and the phase portion (−A) detected by the group of the photodetector elements 4c are different from each other by 180 degrees (90 degrees + 90 degrees). Based on the outputs of these photodetector groups, the signal processing circuit 10 in the subsequent stage calculates the difference (−A) − (+ A) between both phase portions and outputs it as an encoder A phase signal. By performing such an operation, it is possible to cancel the influence of external light or the like and output only the signal component of the light / dark pattern. Similarly, an encoder B phase signal = (− B) − (+ B) is output from the group of the photodetector elements 4b and the group of the photodetector elements 4d.

  Here, in the prior art, as shown in FIG. 8, the number of photo detector elements belonging to each photo detector group is equal. On the other hand, in the first embodiment, as shown in FIG. 2, the right end of the photodetector array 4 is a photodetector element that detects the (+ A) phase, and the left end is a photo that detects the (−A) phase. It is a detector element. That is, the group of the photodetector element 4a, the photodetector element 4b, and the photodetector element 4c each have three photodetector elements, but the group of the photodetector elements 4d has two photodetector elements. The number of photo detector elements is one less than the other groups. In FIG. 2, for convenience, the number of photodetector elements in each group is three or two. However, when actually used in an encoder, each group is constituted by a larger number of photodetector elements. It is normal. However, even in such a case, the number of the photodetector elements 4d arranged at the end is larger than the number of the photodetector elements belonging to the group of the photodetector elements 4a, the photodetector elements 4b, and the photodetector elements 4c. By arranging so that the number of detector elements is reduced by one, it is possible to arrange the photodetector elements while maintaining the positional relationship according to FIG.

  Next, the operation of the photodetector having the configuration of FIG. 2 will be described. In the conventional example, signals detected in each group are calculated and output as A phase signal = (− A) − (+ A), B phase signal = (− B) − (+ B). On the other hand, in the case of the configuration as in the first embodiment, the right end and the left end of the photo detector array 4 are the photo detector element 4a and the photo detector element 4c, respectively, so that noise at both ends of the photo detector array 4 is detected. The target carrier does not affect the B phase signal. In the A-phase signal, the noisy carrier 21 incident on the right photodetector element 4d of the photodetector array 4 and the noisy carrier 22 incident on the left photodetector element 4a of the photodetector array 4 in FIG. Are substantially equal in size, the noisy carrier component is canceled when the difference is taken. Therefore, the A-phase signal is not affected by noise carriers.

  In the first embodiment, since the number of the photodetector elements belonging to the group of the photodetector elements 4d is reduced by one, when calculating the B phase signal = (− B) − (+ B), Compared with the signal components output from the group of the photodetector elements 4b, the signal components output from the group of the photodetector elements 4d are always smaller by one photodetector element. However, if the number of the photodetector elements constituting the photodetector array 4 is made sufficiently large, this deviation can be ignored. For example, in the case of a photodetector array capable of detecting a light-dark pattern for 15 cycles, the deviation of the signal component between the A-phase signal and the B-phase signal is 10% or less and can be ignored in practice. .

  Further, since it is known that the signal component is always reduced by one photodetector element, it is possible to compensate for the deviation of the signal component by the signal processing circuit 10 in the subsequent stage. For example, when the number of the photodetector elements belonging to the group of the photodetector elements 4b is 10 and the number of the photodetector elements belonging to the group of the photodetector elements 4d is 9, the B phase signal = (− B) × 1.11- ( + B). In other words, if the calculation is performed after multiplying the (−B) phase by the ratio of the number of photodetector elements, it is possible to compensate for the difference in the output of the B phase signal and the A phase signal due to the difference in the number of photodetector elements.

  As described above, according to the first embodiment, it is possible to remove the influence of noise carriers flowing into the end portion of the photodetector array.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. The basic configuration of the second embodiment as an optical encoder is the same as that of the first embodiment described in FIG. However, in the second embodiment, the number of the photodetector elements in the group of the photodetector elements 4a for calculating the A-phase signal among the groups of the four photodetector elements included in the photodetector array 4 of the photodetector 3 is as follows. The number of photo-detector elements in the group of the photo-detector elements 4c is equal, and the number of photo-detector elements in the group of the photo-detector elements 4b and the number of photo-detector elements in the group of the photo-detector elements 4d for calculating the B-phase signal are The point which is comprised so that it may become equal differs from 1st Embodiment.

  That is, in the second embodiment, the photodetector array 4 formed in the photodetector 3 is configured as shown in FIG. In other words, as compared with the first embodiment shown in FIG. 2, one photodetector element 4b at an arbitrary position is further removed. With this configuration, the number of the photodetector elements in the group of the photodetector elements 4a is equal to the number of the photodetector elements in the group of the photodetector elements 4c, and the number of the photodetector elements in the group of the photodetector elements 4b and the photodetector elements. The number of photodetector elements in the 4d group becomes equal. At this time, compared with the number of photodetector elements in the group of the photodetector elements 4a and the group of the photodetector elements 4c, the number of the photodetector elements in the group of the photodetector elements 4b and the group of the photodetector elements 4d is one each. It is running low.

  Next, the operation of the second embodiment of the present invention having such a configuration will be described. In FIG. 3, the noisy carrier 21 flowing from the right end of the photodetector array 4 and the noisy carrier 22 flowing from the left end are considered to be substantially equal to each other. That is, these noisy carriers flow into the group of the photodetector elements 4a and the group of the photodetector elements 4c by the same amount. Further, the noisy carrier 23 flowing into the area of the photodetector element 4b from which the photodetector element is removed is equally distributed to the adjacent photodetector elements, and each of these distributed elements is divided into a group of photodetector elements 4a and a photodetector. Flows into the group of elements 4c. At this time, when the A-phase signal and the B-phase signal are respectively obtained, the A-phase signal is obtained as follows: A-phase signal = ((− A) + (noise carrier 21 + noise carrier 23)) − ((+ A) + (noise Carrier 22 + noise carrier 23)) = (− A) − (+ A), and is not affected by the noise carrier. Further, since the B phase signal does not change with B phase signal = (− B) − (+ B), it is not affected by the noisy carrier as well.

  As described above, according to the second embodiment, since the number of photodetector elements is the same for both the A-phase signal and the B-phase signal, the amplitude centers of the signal components after calculating the difference are equal and more stable. It is possible to output a signal. In the second embodiment, the output of the B-phase signal is smaller than that of the A-phase signal, but the B-phase signal may be amplified by the signal processing circuit 10 in the subsequent stage.

  Further, in the second embodiment, the position of the extracted photodetector element 4b is set to an arbitrary position. However, the intensity of the detection light incident on the extracted region is closer to the end of the extracted photodetector element 4b. Therefore, a more stable detection signal can be obtained.

  In the first and second embodiments, a so-called transmissive encoder has been described as an example. However, for example, a similar configuration is used even for a reflective optical encoder as shown in FIG. It is possible to obtain the same effect.

  In the first embodiment and the second embodiment, the light source is a surface emitting laser, but a similar encoder can be configured by using an LED and a slit in combination as the light source. In this case, the slit may have a single opening, or may have a plurality of openings with a predetermined period calculated from the scale pitch, the positional relationship between the light source and the scale and the photodetector, the wavelength of the light source, and the like. I do not care.

  FIG. 4 shows a so-called triple slit type reflective optical encoder in which the light source 1 is provided with a slit 5. Even with such a configuration, the same effect can be obtained by configuring the photodetector array 4 formed on the photodetector 3 as in the first embodiment or the second embodiment. is there.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. In the third embodiment, the basic configuration as an optical encoder is the same as that described in the second embodiment, and the operation thereof is also the same.

  The third embodiment is different from the second embodiment in that a dummy photodetector is provided at the end of the photodetector array 4 of the photodetector 3.

That is, in the third embodiment, the photodetector array 4 is configured as shown in FIG. That is, the dummy photo detectors 4e to 4g for absorbing the noisy carriers D _{1 to} D ₃ in the configuration of the second embodiment shown in FIG. 3 are provided at both ends of the photo detector array and the photo detector elements inside the photo detector array. 4b is removed from the region. In FIG. 5, the dummy photodetectors 4 a to 4 d are electrically connected to a terminal fixed to the ground potential or a predetermined potential D. As a result, noisy carriers generated in the dummy photodetectors 4e to 4g or flowing into the dummy photodetectors 4e to 4g flow out from the terminal of the ground potential or the predetermined potential D and are detected by the photodetector elements 4a to 4d. The noisy carrier does not affect the generated signal. Further, in this case, noise-carrier D ₂ that has flowed into the region obtained by removing the photodetector element 4b does not flow into the photodetector elements of the neighboring, it is absorbed in the dummy photodetector 4f.

  Here, it is preferable that the dummy photodetectors 4e to 4g have substantially the same shape as the photodetector elements 4a to 4d, and the light receiving ability as the photodetector is substantially the same as that of the photodetector elements 4a to 4d. This makes it possible to reliably absorb noisy carriers and to minimize the size of the photodetector.

  By adopting such a configuration, most of the noisy carriers are absorbed by the dummy photodetectors 4e to 4g, so even if there is a slight difference in the noisy carriers flowing from the left and right of the photodetector array 4, The impact can be minimized. At this time, it is sufficient to arrange the dummy photodetectors one by one in a place where there is a high possibility that a noisy carrier flows. In this way, an increase in the device area due to the placement of the dummy photodetector can be minimized. Therefore, it is possible to obtain a desired signal from the photodetector array while suppressing the influence of noisy carriers while realizing downsizing of the entire photodetector.

  Further, as shown in FIG. 6, a predetermined number of photodetector elements in the photodetector array 4 are replaced with dummy photodetectors so that the number of photodetector elements of each photodetector group included in the photodetector array 4 becomes equal. May be. In this case, the level of the signal output from each photodetector group can be made equal, and a more stable signal output can be obtained. In this case, since the overall output becomes small, the output signal may be amplified as necessary.

  Further, in the third embodiment, the dummy photodetectors 4e to 4i are provided at both ends and inside the photodetector array 4 as shown in FIGS. 5 and 6. However, the present invention is not limited to this. . For example, the dummy photodetectors 4e and 4g may be removed from the configuration shown in FIGS. Further, only the dummy photo detectors 4e and 4f may be provided without providing the dummy photo detector inside the photo detector array 4. Further, any one of the dummy photodetectors 4f, 4h, 4i in the photodetector array 4 shown in FIG. 6 (for example, the dummy photodetector 4f) may be removed. However, it is necessary to provide a pair of dummy photodetectors at a portion where the inflow amount of noisy carriers is considered to be substantially equal, such as both ends of the photodetector array 4.

  The same effect can be obtained even if the configuration of the third embodiment is applied to the reflective optical encoder of FIG.

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

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

  Here, if the summary of this invention is summarized, in addition to what was described in the claim, the following things are included.

  (1) A light source, a scale having an optical periodic structure, movable relative to the light source, and a periodic light-dark pattern generated by detection light emitted from the light source and passing through the scale. A photodetector for an optical encoder having a photodetector for detecting, wherein the photodetector comprises a plurality of photodetector elements for detecting at least three phase portions having different phases from each other in the light-dark pattern. A phase portion detected by a photodetector element disposed at one end of the one-dimensional photodetector array, and a phase portion detected by a photodetector element disposed at the other end of the one-dimensional photodetector array. Is a photodetector for an optical encoder characterized in that the phases are different from each other by 180 degrees.

  According to the aspect of (1), the phase portions detected by the photodetector elements arranged at one end and the other end of the photodetector array are different from each other by 180 degrees. It is possible to cancel the noisy carrier flowing in from the end and the noisy carrier flowing in from the other end, and to remove the influence of the noisy carrier from the signal component.

  (2) Each of the plurality of photodetector elements constituting the one-dimensional photodetector array belongs to any one of at least three or more photodetector groups that detect the at least three or more phase portions; Among the at least three or more photo detector groups, there is at least one combination in which the number of photo detector elements belonging to a photo detector group is different from the number of photo detector elements belonging to another photo detector group. The optical detector for an optical encoder according to (1).

  (3) The number of the photo detector groups is four, the four photo detector groups detect four phase portions having a phase difference of 90 degrees from each other in the light and dark pattern, and the photo detector groups have a phase difference of 180 degrees from each other. The optical detector for an optical encoder according to (2), wherein outputs of two different groups are connected to an arithmetic circuit that calculates a difference between the two outputs.

  According to these aspects (2) and (3), each photo detector group is configured to calculate and output a difference between signals from the photo detector elements arranged at one end and the other end of the photo detector array. By adjusting the number of photodetector elements belonging to, the noisy carrier flowing in from one end of the photodetector array and the noisy carrier flowing in from the other end are canceled out, and the noise carrier is The influence can be removed.

  (4) The photodetector for an optical encoder according to (3), wherein the photodetector array is configured to detect the light / dark pattern over at least 15 periods.

  If the photodetector array is sufficiently long, the deviation in signal output due to the difference in the number of photodetector elements belonging to each photodetector group becomes relatively small. That is, according to the aspect of (4), since the photodetector array is sufficiently long as 15 cycles or more, the deviation of the signal output can be almost ignored.

  (5) The optical system according to (3) or (4), wherein the number of photodetector elements belonging to the four photodetector groups is equal for each photodetector group that detects phase portions that are 180 degrees different from each other. Photo detector for encoder.

  According to the aspect of (5), when calculating the difference of the signals from the photodetector group that detects the phase portions that are 180 degrees out of phase with each other, the number of the photodetector elements that belong to the photodetector group that calculates the difference is Since they are equal to each other, the center of amplitude when the difference is calculated does not depend on the number of photodetector elements belonging to each group.

  (6) Among the four photo detector groups, the number of photo detector elements of the photo detector group to which the photo detector element arranged at the end of the photo detector array belongs is the number of photo detector elements arranged at the end. The optical detector for an optical encoder according to any one of (3) to (5), wherein the number is one more than the number of photodetector elements of a non-belonging photodetector group.

  The smaller the difference in the number of photodetector elements that belong to each photodetector group, the smaller the difference in signal level. Therefore, the difference between the number of photo-detector elements belonging to the photo-detector group to which the photo-detector element arranged at the end of the photo-detector array and the number of photo-detector elements belonging to other photo-detector groups is as shown in (6). 1 is the smallest.

  (7) It further has a signal processing circuit that compensates for a difference in output due to a difference in the number of photodetector elements belonging to each of the photodetector groups when calculating and outputting the output from the photodetector group. The optical detector for an optical encoder according to any one of (3) to (6).

  The difference in the number of photo detector elements belonging to each photo detector group is a parameter set at the design stage, and the influence of the number of photo detector elements on the output from each photo detector group can be predicted. Therefore, by configuring the signal processing circuit as in the aspect (7), the signal level is more stable, and it is possible to achieve both miniaturization and high performance.

  (8) One dummy photodetector that absorbs a noisy carrier and is substantially the same shape as the photodetector elements constituting the photodetector array, between both ends and / or between the respective photodetector elements of the one-dimensional photodetector array. The photodetector for an optical encoder according to any one of (1) to (7), wherein the photodetector is arranged.

  (9) The number of photodetector elements belonging to a photodetector group that detects the same phase portion of the one-dimensional photodetector array is configured to be equal, and at both ends and / or gaps of the one-dimensional photodetector array, The photodetector for an optical encoder according to (1), further comprising a dummy photodetector that absorbs a noisy carrier and is substantially the same in shape as a photodetector element constituting the photodetector array.

  According to these aspects (8) and (9), the inflow of noise carriers to the respective photodetector elements of the one-dimensional photodetector can be more reliably suppressed by the effect of the dummy photodetector.

It is a block diagram of an optical encoder. It is a block diagram of the photodetector for optical encoders concerning the 1st Embodiment of this invention. It is a block diagram of the photodetector for optical encoders concerning the 2nd Embodiment of this invention. It is a block diagram of the reflection type optical encoder as a modification of this invention. It is a figure which shows an example of a structure of the photodetector for optical encoders concerning the 3rd Embodiment of this invention. It is a figure which shows another example of a structure of the photodetector for optical encoders concerning the 3rd Embodiment of this invention. It is a block diagram of the optical encoder of a prior art example. It is an enlarged view of a code | symbol plate. It is a figure for demonstrating the noisy carrier which flows into a photodetector element. It is a block diagram of the photodetector for optical encoders of a prior art example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Light source, 2 ... Scale, 3 ... Photo detector, 4 ... One-dimensional photo detector array, 4a-4d ... Photo detector element, 4e-4 i ... Dummy photo detector, 10 ... Signal processing circuit

Claims (9)

A light source, a scale having an optical periodic structure movable relative to the light source, and a photodetector for detecting a periodic light-dark pattern generated by detection light emitted from the light source and passing through the scale In a photodetector used in an optical encoder having:
The photodetector includes a one-dimensional photodetector array including a plurality of photodetector elements that detect at least three or more phase portions having different phases from each other in the light-dark pattern,
A phase portion detected by a photodetector element arranged at one end of the one-dimensional photodetector array and a phase portion detected by a photodetector element arranged at the other end of the one-dimensional photodetector array are 180 degrees out of phase with each other. Optical detectors for optical encoders, characterized in that are different.   Each of the plurality of photodetector elements constituting the one-dimensional photodetector array belongs to any one group of at least three or more photodetector groups that detect the at least three or more phase portions. Among the two or more photo detector groups, there is at least one combination in which the number of photo detector elements belonging to one photo detector group is different from the number of photo detector elements belonging to another photo detector group. Item 2. The optical detector for an optical encoder according to Item 1.   The number of the photodetector groups is four, and the four photodetector groups detect four phase portions that are 90 degrees different from each other in the light and dark pattern, and two that are 180 degrees different from each other in the photodetector group. The optical detector for an optical encoder according to claim 2, wherein the output of the group is connected to an arithmetic circuit for calculating a difference between the two outputs.   The photodetector for an optical encoder according to claim 3, wherein the photodetector array is configured to detect the light and dark pattern over at least 15 periods.   5. The photodetector for an optical encoder according to claim 3, wherein the number of photodetector elements belonging to the four photodetector groups is equal for each photodetector group that detects phase portions that are 180 degrees different from each other. .   Of the four photo detector groups, the number of photo detector elements of the photo detector group to which the photo detector element arranged at the end of the photo detector array belongs is the number of photo detector elements to which the photo detector element arranged at the end does not belong. 6. The photodetector for an optical encoder according to claim 3, wherein the number of photodetector elements is one more than the number of photodetector elements in the detector group.   The signal processing circuit further comprising: a signal processing circuit that compensates for a difference in output due to a difference in the number of photodetector elements belonging to each of the photodetector groups when calculating and outputting an output from the photodetector group. Item 7. The optical encoder photodetector according to any one of Items 3 to 6.   Further, one dummy photodetector that absorbs a noisy carrier and has the same shape as that of the photodetector elements constituting the photodetector array is arranged one by one between both ends of the one-dimensional photodetector array and / or between the respective photodetector elements. The photodetector for an optical encoder according to any one of claims 1 to 7, wherein:   The number of photodetector elements belonging to a photodetector group that detects the same phase portion of the one-dimensional photodetector array is configured to be equal, and the photodetector array is disposed at both ends and / or gaps of the one-dimensional photodetector array. The photodetector for an optical encoder according to claim 1, further comprising a dummy photodetector that absorbs a noisy carrier and has substantially the same shape as the photodetector element that constitutes the detector.

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