JP4425112B2 - Encoder - Google Patents

Description

  The present invention relates to an optical encoder.

As a conventional optical encoder, Patent Document 1 describes the following. That is, light is irradiated onto an optical scale in which a plurality of grating windows made of different types of diffraction gratings are formed at predetermined distances, and a pattern of diffracted light diffracted by the grating windows is imaged by a two-dimensional image sensor. Then, the grating window is specified based on the imaged pattern of diffracted light, and the position of the grating window in the operating direction of the optical scale is specified based on the position of the diffracted light pattern in the image. Is detected.
Japanese Patent Publication No.8-10145

  However, in the encoder as described above, although the resolution of the optical scale operating distance detection is high, the use of a two-dimensional image sensor requires a frame memory. is there.

  Therefore, the present invention has been made in view of such circumstances, and an object of the present invention is to provide an encoder that can accurately detect an absolute value such as an operating angle or an operating distance of a scale plate with a simple configuration. And

  In order to achieve the above object, an encoder according to the present invention includes a scale plate movable in a predetermined operation direction, and a plurality of scale plates formed on a line along the operation direction in the scale plate, and transmits light in a direction perpendicular to the operation direction. And a light non-propagating unit arranged one-dimensionally, an optical repeater configured to project light toward the optical repeater, and light projected by the light source device via the optical repeater It has a light receiving area that is arranged to receive light and is configured by two-dimensionally arranging a plurality of pixels in an operation direction and a direction perpendicular to the operation direction, and each of the operation direction and the direction perpendicular to the operation direction And a light detection device that outputs light intensity profile data indicating a one-dimensional distribution of incident light intensity, and each of the optical repeaters has a different pattern of the one-dimensional arrangement of the light propagation part and the light non-propagation part, Adjacent light The interval between sets, characterized in that the pattern of the one-dimensional array of light propagation portion and a light non-transmissible portion is different locations 1.

  In this encoder, each of the plurality of optical repeaters formed on the line along the operation direction on the scale plate has a different one-dimensional array pattern of the light propagation part and the light non-propagation part. Accordingly, if the information of absolute values (operation absolute values) such as the operation angle and the operation distance of the scale plate is given to each optical repeater using the one-dimensional array pattern as a code, for example, the direction perpendicular to the operation direction Based on the light intensity profile data for, the light relay unit that relays the light projected by the light source device to the light detection device is identified, and the basic operation absolute value is obtained from the identified light relay unit Can do. Furthermore, based on the light intensity profile data for the operation direction, the position of the identified optical repeater relative to the reference position in the light receiving area is calculated, the basic operation absolute value is corrected from the calculated position, and more Detailed operation absolute values can be obtained. As described above, by using the light detection device that outputs the light intensity profile data indicating the one-dimensional distribution of the incident light intensity in each of the operation direction and the direction perpendicular to the operation direction, the operation angle and the operation distance of the scale plate, etc. The absolute value of can be detected with a simple configuration with high accuracy. In addition, even when there are a plurality of optical repeaters that simultaneously relay the light projected by the light source device to the light detection device, a one-dimensional array of light propagation portions and light non-propagation portions is provided between adjacent light repeaters. Therefore, the identification of the plurality of optical repeaters based on the light intensity profile data in the direction perpendicular to the operation direction is not hindered.

  In addition, based on the light intensity profile data in the direction perpendicular to the operation direction, after identifying the light relay unit that relays the light projected by the light source device to the light detection device, the light intensity profile in the operation direction It is preferable to include a processing unit that calculates the position of the optical repeater relative to the reference position in the light receiving area based on the data, and obtains the operation absolute value of the scale plate from the position of the optical repeater. By providing such a processing unit, as described above, it is possible to easily detect absolute values such as the operating angle and operating distance of the scale plate.

  Moreover, it is preferable that the light detection device is disposed so as to receive the light projected by the light source device via one or two light repeaters. Thereby, when detecting absolute values such as the operating angle and the operating distance of the scale plate, the processing can be simplified.

  According to the encoder of the present invention, absolute values such as the operating angle and operating distance of the scale plate can be accurately detected with a simple configuration.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of an encoder according to the invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 1, the encoder 1 is a so-called absolute rotary encoder, and includes a rotating shaft 2 connected to a measurement object (not shown). A disc-shaped scale plate 3 is fixed to the rotary shaft 2, and the scale plate 3 rotates as the rotary shaft 2 rotates. This rotation direction is defined as an operation direction α of the scale plate 3. As shown in FIG. 2, a plurality of light repeaters 4 are formed on the scale plate 3 on the line L <b> 1 along the operation direction α at equal angles around the rotation axis 2.

  As shown in FIG. 3, the optical repeater 4 includes a light transmission part (light propagation part) 5 and a light blocking part (light non-propagation part) 6 formed as light transmission holes in a direction perpendicular to the operation direction α. A one-dimensional array is used. The light transmitting unit 5 propagates light by transmitting light, and the light blocking unit 6 does not propagate light by reflecting or absorbing light. Each of the optical repeaters 4 has a different one-dimensional pattern of the light transmitting portion 5 and the light blocking portion 6, and the light transmitting portion 5 and the light blocking portion between the adjacent light repeating portions 4 and 4. The one-dimensional array pattern 6 is different in one place.

  Here, it is assumed that eight optical repeaters 4 are arranged on the line L1 at equal angles around the rotation axis 2. At this time, in order to make the patterns of the one-dimensional array of the light transmitting unit 5 and the light blocking unit 6 different from each other for each of the optical repeating units 4, a 3-bit code may be used. In order to make the pattern of the one-dimensional array of the light transmitting portion 5 and the light blocking portion 6 different between the four positions, a so-called gray code may be used. That is, when the light transmission unit 5 is “1”, the light blocking unit 6 is “0”, and the optical repeater unit 4 is represented by a code, “000”, “001”, “011”, “010” are sequentially shown from the right in FIG. ”,“ 110 ”,“ 111 ”,“ 101 ”,“ 100 ”.

  Further, on the scale plate 3, a line 1 between the optical repeater 4 and the line L <b> 2 passing through the optical repeater 4 along the direction perpendicular to the operation direction α and the line L <b> 3 along the operation direction α is 1 to the scale plate 3. A reference light transmission part (reference light propagation part) 7 is formed as a light transmission hole across the light blocking parts 6.

  As shown in FIG. 1, the encoder 1 includes a light source device 8 composed of an LED or the like that projects parallel light toward the optical repeater 4 disposed on the line L <b> 1, and a scale plate 3. A profile sensor (light detection device) 9 is provided so as to face the device 8. The profile sensor 9 receives light transmitted through the light transmission unit 5 of the optical relay unit 4 among the light projected by the light source device 8 (in other words, optically relays the light projected by the light source device 8). The light intensity profile data is output to the processing unit 11 by receiving light via the unit 4.

Here, the configuration of the profile sensor 9 will be described. As shown in FIG. 4, the profile sensor 9 includes a light receiving region 100, a first signal processing unit 110, and a second signal processing unit 120. The light receiving region 100 is configured by M × N pixels two-dimensionally arranged in the operation direction α (tangential direction of the line L1) and in a direction perpendicular to the operation direction α, and the position of the m-th row and the n-th column. Two photodiodes PD _{X, m, n} and PD _{Y, m, n} are formed in the pixel in FIG. Each of M and N is an integer of 2 or more, m is an arbitrary integer of 1 to M, and n is an arbitrary integer of 1 to N. The anode terminals of the photodiodes PD _{X, m, n} and PD _{Y, m, n} are grounded. The cathode terminals of the _M photodiodes PD _{X, 1, n to} PD _{X, M, n} in the n-th column are connected to the first signal processing unit 110 by a common wiring L _{X, n} . The cathode terminal of the m in the row N photodiodes PD _{Y, m,} 1 -PD _{Y, m, N} are connected common line L _Y, and the second signal processing unit 120 by _m.

As illustrated in FIG. 5, the first signal processing unit 110 includes a shift register 111, an integration circuit 112, and N switches SW _{1 to} SW _N. One end of each switch SW _n is connected to the wiring L _{X, n} , and the other end of each switch SW _n is connected to the input end of the integrating circuit 112 via a common wiring. Each switch SW _n is sequentially closed based on a control signal output from the shift register 111. The integrating circuit 112 includes an amplifier A, a capacitive element C, and a switch SW. The capacitive element C and the switch SW are connected in parallel to each other and are provided between the input terminal and the output terminal of the amplifier A. When the switch SW is closed, the capacitive element C is discharged, and the voltage value output from the integrating circuit 112 is initialized. Switch SW is opened, the switch SW _n is closed, the wiring L _X, M-number of photodiodes of the n columns being connected to _{n PD X, 1, n ~PD} X, M, n on each of the light incident The sum total of the generated charges is input to the integration circuit 112, the charge is stored in the capacitive element C, and the voltage value V _X (n) corresponding to the stored charge amount is output from the integration circuit 112. The second signal processing unit 120 also has the same configuration as the first signal processing unit 110 and performs the same operation.

The profile sensor 9 configured as described above receives first light intensity profile data V _X (n) indicating a one-dimensional distribution of incident light intensity with respect to the operation direction α (the tangential direction of the line L1) in the light receiving region 100 as the first. The second light intensity profile data V _Y (m) indicating the one-dimensional distribution of the incident light intensity in the direction perpendicular to the operation direction α can be output from the second signal processor 120 while being output from the signal processor 110. . The first light intensity profile data V _X (n) and the second light intensity profile data V _Y (m) are input to the processing unit 11.

  The profile sensor 9 is disposed so as to receive the light projected by the light source device 8 via one or two light repeaters 4. That is, as shown in FIG. 6, if the width along the operation direction α of the light receiving region 100 is W and the distance along the operation direction α of the adjacent optical repeaters 4 and 4 is D, W / 2 < The relational expression D <W is satisfied. As a result, one or two optical repeaters 4 are always located on the light receiving region 100.

  Next, a processing procedure in the processing unit 11 will be described with reference to FIG.

First, the number of areas exceeding a predetermined threshold th1 is calculated based on the first light intensity profile data V _X (n) for the operating direction α, and the number of optical repeaters 4 located on the light receiving area 100 is determined. Is done.

Subsequently, the center of gravity position of the reference light transmitting unit 7 is calculated based on the second light intensity profile data V _Y (m) in the direction perpendicular to the operation direction α, and the center of gravity position is set as the reference position y ₀ . When calculating the position of the center of gravity of the reference light transmitting portion 7, the second light intensity profile is formed because the reference light transmitting portion 7 is formed with one light blocking portion 6 interposed between the light repeating portion 4. Based on the data V _Y (m), the position of the center of gravity of the reference light transmitting portion 7 can be accurately calculated.

Then, with reference to the reference position y ₀ , the code of the light transmitting part 5 or the light blocking part 6 appearing at _{every other} center-of-gravity distance p ₁ in the optical repeater 4 is j bits (j = 1, 2, 3) Read.
(1) When the number of the optical repeaters 4 located on the light receiving area 100 is one
code (j) = f (V _Y (y _j )) = f (V _Y (y ₀ + (j + 1) × p ₁ ))
if (V _Y (y _j )> th2) then f (V _Y (y _j )) = 1;
else f (V _Y (y _j )) = 0;
(2) When the number of optical repeaters 4 located on the light receiving area 100 is two
code (j) = f (V _Y (y _j )) = f (V _Y (y ₀ + (j + 1) × p ₁ ))
_{if (V Y (y j)} > th3) then f (V Y (y j)) = 2;
if (V _Y (y _j )> th2) and (V _Y (y _j ) <th3) then f (V _Y (y _j )) = 1;
if (V _Y (y _j ) <th2) then f (V _Y (y _j )) = 0;
Here, f (V _Y (y _j )) is a threshold function. Further, th2 and th3 are thresholds determined in advance from the light receiving sensitivity of the light source device 8 and the profile sensor 9, and the threshold th2 is the brightness when one light transmission part 5 exists along the operation direction α. The threshold th3 is determined as a criterion for determining brightness when there are two light transmission parts 5 along the operation direction α.

  With the above calculation, for example, the output value obtained in the case shown in FIG. 6 is “120”. Thus, only one set in the encoder 1 has the output value of the adjacent optical repeaters 4 and 4 being “120”. That is, the codes of the optical repeater 4 located on the light receiving area 100 are “010” and “110”. Since the processing unit 11 stores the code arrangement (“000”, “001”, “011”,..., “100” in order from the right in FIG. 3) of the optical repeater 4, the right side in FIG. The code of the optical repeater 4 is uniquely identified as “010”, and the code of the left optical repeater 4 is uniquely identified as “110”.

Subsequently, the operation angle of the scale plate 3 is calculated as follows. First, based on the first light intensity profile data V _X (n) for the movement direction α, the center-of-gravity position pos of the region exceeding the threshold th1 is calculated by the following calculation. The center position of the light receiving region 100 in the operation direction α is set as the origin (reference position) of the center of gravity position pos.
pos = first moment / 0-order moment first moment _{= Σ (V X (n)} × n) (V X (n)> for successive regions of th1)
0th-order moment = Σ (V _X (n)) (for a continuous region where V _X (n)> th1)

Then, from the center of gravity position pos calculated by this calculation, the operating angle θ of the scale plate 3 is calculated by the following calculation. A state where the center of gravity of the optical repeater 4 with the code “000” coincides with the center position of the light receiving region 100 in the operation direction α is defined as 0 degree.
theta = (code order _{+ pos / p 2) × (} 360 / number of codes)
Here, p ₂ is the distance between the centers of gravity of adjacent optical repeater unit 4,4. Further, in the code order, “000” is “0”, “001” is “1”, “011” is “2”,..., “100” is “7” in order from the right in FIG.

As a specific example, in the case shown in FIG. 6, the barycentric position of the optical repeater 4 with the code “010” is pos = + 150 (pixels), and the barycentric position of the optical repeater 4 with the code “110” is pos = −250 ( Pixel), when the distance between the centroids of the adjacent optical repeaters 4 and 4 is p ₂ = 400 (pixel), based on the centroid position pos of the optical repeater 4 of the code “010”, the operating angle of the scale plate 3 θ is as follows.
θ = (3 + 150/400) × (360/8) = 152 degrees

On the other hand, based on the barycentric position pos of the optical repeater 4 of the code “110”, the operating angle θ of the scale plate 3 is as follows.
θ = (4 + (− 250) / 400) × (360/8) = 152 degrees

  As described above, when the two optical repeaters 4 are located on the light receiving region 100, the operating angle θ of the scale plate 3 can be calculated based on the center of gravity position pos of any of the optical repeaters 4. .

As described above, in the encoder 1, each of the plurality of optical repeaters 4 formed on the line L <b> 1 along the operation direction α in the scale plate 3 is a one-dimensional array of the light transmitting unit 5 and the light blocking unit 6. The patterns are different from each other. Thus, the optical repeater 4 located on the light receiving region 100 is processed based on the second light intensity profile data V _Y (m) in the direction perpendicular to the operation direction α using the one-dimensional array pattern as a code. 11 for identification. Further, based on the first light intensity profile data V _X (n) for the operation direction α, the center position of the identified optical repeater 4 with respect to the reference position in the light receiving region 100 is calculated, and the scale plate 3 is calculated from the center position. The detailed operation angle can be calculated. As described above, by using the profile sensor 9, a frame memory or the like required when using the two-dimensional image sensor is not required, and the operating angle of the scale plate 3 can be accurately detected with a simple configuration. . In addition, by using the profile sensor 9, if the number of pixels is the same, the processing time can be significantly shortened compared to the case of using a two-dimensional image sensor.

As shown in FIG. 6, even when two optical repeaters 4 are simultaneously located on the light receiving region 100, between the adjacent optical repeaters 4 and 4, the light transmitting portion 5 and the light blocking portion 6 are not connected. Since the one-dimensional array pattern is different at one place, the identification of the two optical repeaters 4 based on the second light intensity profile data V _Y (m) in the direction perpendicular to the operation direction α is hindered. There is no.

  In the encoder 1, a profile sensor 9 is disposed so as to receive the light projected by the light source device 8 via one or two light repeaters 4. Thereby, when calculating the operating angle of the scale plate 3, the process can be simplified.

  The present invention is not limited to the embodiment described above.

  For example, the encoder 1 according to the embodiment described above is a rotary encoder in which the scale plate 3 rotates and the rotation direction is the operation direction α of the scale plate 3 and a plurality of optical repeaters 4 are formed on the scale plate 3. However, the encoder according to the present invention may be a linear encoder in which the scale plate performs a linear operation, and a plurality of optical repeaters are formed on the scale plate with the linear direction as the operation direction of the scale plate. Good.

  In addition, the encoder 1 according to the above-described embodiment is configured by the profile sensor 9 being arranged so as to receive light transmitted through the light transmission unit 5 of the optical relay unit 4 among the light projected by the light source device 8. Although the encoder according to the present invention is a transmission type encoder, the profile sensor is arranged so as to receive light diffracted or scattered by the light propagation unit of the optical relay unit among the light projected by the light source device. A reflection type encoder configured as described above may be used. In other words, the encoder according to the present invention only needs to be configured so that the profile sensor is arranged so as to receive the light projected by the light source device via the optical repeater.

In addition, when the number of the optical repeaters 4 located on the light receiving region 100 is two, the two optical repeaters 4 can be identified as follows. First, as in the above embodiment, the code output values of the two optical repeaters 4 are obtained based on the second light intensity profile data V _Y (m) in the direction perpendicular to the operation direction α. Subsequently, a plurality of threshold values (th1 × 1, th1 × 2, th1 × 3, th1 × 4) are set for the first light intensity profile data V _X (n) for the operation direction α, and the plurality of threshold values are set. By performing the threshold processing in step S4, the numbers of the light transmission units 5 and the reference light transmission units 7 included in each optical relay unit 4 are determined. As described above, with respect to the two optical repeaters 4 simultaneously located on the light receiving region 100, the output values of the codes of the two optical repeaters 4, and the light transmitting portions 5 and the reference light that each optical repeater 4 has. If the number of transmission parts 7 is known, the two optical repeaters 4 can be identified.

As a specific example, in the case illustrated in FIG. 6, the code output values of the two optical repeaters 4 based on the second light intensity profile data V _Y (m) are “120”. In FIG. 6, the number of the light transmission parts 5 and the reference light transmission parts 7 included in the right light relay part 4 is two, and the number of the light transmission parts 5 and the reference light transmission parts 7 included in the left light relay part 4 is as follows. There will be three. In this way, the output value of the adjacent optical repeaters 4 and 4 is “120”, and the right optical repeater 4 has two light transmitting units 5 and reference light transmitting units 7, and the left optical repeater. The encoder 1 has only one set in which the number of the light transmission parts 5 and the reference light transmission parts 7 included in the part 4 is three. Therefore, in FIG. 6, the code of the right optical repeater 4 can be uniquely identified as “010”, and the code of the left optical repeater 4 can be uniquely identified as “110”.

Further, when the number of the optical repeaters 4 located on the light receiving region 100 is two, the two optical repeaters 4 can be identified as follows. First, as in the above embodiment, the code output values of the two optical repeaters 4 are obtained based on the second light intensity profile data V _Y (m) in the direction perpendicular to the operation direction α. Subsequently, a comparison is made between the second light intensity profile data V _Y (m) and the threshold value th2, and it can be seen that there is an opening if V _Y (m)> th2. Here, since the difference from the adjacent code is always one place, among the blocks satisfying the condition of V _Y (m)> th2, the position of the code (1) having the smallest V _Y (m) is different. That can be decided.

It is a block diagram of one Embodiment of the encoder which concerns on this invention. It is a front view of the scale board of the encoder shown in FIG. FIG. 2 is a diagram illustrating an optical repeater and a reference light transmission unit of the encoder illustrated in FIG. 1. It is a block diagram of the profile sensor of the encoder shown by FIG. It is a circuit diagram of the 1st signal processing part contained in the profile sensor of the encoder shown by FIG. It is a figure which shows the relationship between the light reception area | region and optical repeater in the encoder shown by FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Encoder, 3 ... Scale board, 4 ... Light relay part, 5 ... Light transmission part (light propagation part), 6 ... Light shielding part (light non-propagation part), 8 ... Light source device, 9 ... Profile sensor (light detection) Apparatus), 11... Processing unit, L1... Line, .alpha.

Claims (3)

A scale plate movable in a predetermined operating direction;
A plurality of optical repeaters formed on the scale plate on the line along the operation direction, the light propagation unit and the light non-propagation unit being arranged one-dimensionally in a direction perpendicular to the operation direction,
A light source device that projects light toward the optical relay unit;
A light receiving device that is arranged so as to receive light projected by the light source device via the optical relay unit, and is configured by two-dimensionally arranging a plurality of pixels in the operation direction and in a direction perpendicular to the operation direction. A light detection device that has a region and outputs light intensity profile data indicating a one-dimensional distribution of incident light intensity for each of the operation direction and the direction perpendicular to the operation direction;
Each of the optical repeaters is different from each other in the one-dimensional array pattern of the light propagation part and the light non-propagation part,
An encoder characterized in that a pattern of the one-dimensional array of the light propagation part and the light non-propagation part is different at one place between the adjacent optical relay parts.   Based on the light intensity profile data in a direction perpendicular to the operation direction, after identifying the light relay unit that relays the light projected by the light source device to the light detection device, the operation direction A processing unit that calculates a position of the optical repeater with respect to a reference position in the light receiving region based on the light intensity profile data of the light, and obtains an operation absolute value of the scale plate from the position of the optical repeater. The encoder according to claim 1, wherein:   The encoder according to claim 1, wherein the light detection device is disposed so as to receive light projected by the light source device via one or two light repeaters. .

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