JP2001194185A - Optical absolute value encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical absolute value encoder avoiding the increase in size and cost and realizing the detection of high accuracy and high resolution. SOLUTION: A light receiving element 700 detects irradiation light emitted from a LED 6 through a truck 500a for detection consisting of an M-series slit array, a first interpolation multiplication slit array, and a second interpolation multiplication slit array. Detection signals are outputted from light receiving cell array groups A and B for the M-series of the light receiving element 700, light receiving cell array groups A' and B' for the first interpolation multiplication, and light receiving cell array groups A" and B" for the second interpolation multiplication. A CPU 100 on a printed board 8 obtains absolute position information by combining these detection signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical absolute value encoder for measuring an absolute displacement amount in a rotation direction or a linear direction, and more particularly, to a slit array arranged in accordance with a so-called M-sequence rule. Optical absolute encoder having the same.

[0002]

2. Description of the Related Art First, an optical rotary encoder will be schematically described as an example of a conventional optical absolute value encoder. FIG. 7 is a configuration diagram of an optical rotary encoder, and FIG. 7A is a cross-sectional configuration diagram thereof, and FIG.
FIG. 3 is a plan view of a slit disk. This optical rotary encoder comprises an encoder case 1, bearings 2,
3, hollow shaft 4, slit disk 5, LED (Light Emittin
g Diode) 6, a light receiving element 7, and a printed circuit board 8.

In the encoder case 1, bearings 2,
A hollow shaft 4 is attached so as to be rotatable via 3. A slit disk 5 is attached to the hollow shaft 4. As shown in FIG. 7 (b), the slit disk 5 is provided with a detection track 5a in which a plurality of slit rows are arranged so that a plurality of slits are arranged on the same row, and two concentric circles are arranged. It transmits and blocks light depending on the presence or absence of a slit.

In this specification, the term “slit” refers to FIG.
In the through hole shown in (a) or a pattern (not shown) printed on a transparent slit disk in a light and dark grid pattern (bright is a transparent transmitting part, dark is a light shielding part) And so on. This detection track 5a
One of the slit rows is a slit row arranged in accordance with the rules of the M series (hereinafter, referred to as an M series slit row), and the other slit row is a slit row that alternately transmits and blocks light at a specific cycle ( Hereinafter, it is referred to as an interpolation double slit row.).

Here, the M-sequence means that N is a natural number and 1
A deterministic sequence composed of 2 ^N combinations of 1s or 0s per cycle and made by simple rules,
It resembles an irregular series in appearance. The N pieces of 1 or 0 information (pattern) continuous from the specific position of the M series have 2 ^N pieces of non-overlapping information because there is only one piece in the M series. This M-sequence slit array is a slit array having 2 ^N light-dark gratings, with 1 in the M-sequence being a transmission part and 0 being a light-shielding part.

The track 5a for detecting the slit disk 5
The LED 6 and the light receiving element 7 are arranged at positions facing each other with the. The LED 6 is disposed inside the encoder case 1 and is always supplied with power from a printed circuit board 8 via a power supply line (not shown) to constantly emit irradiation light. The light receiving element 7 is
It is arranged and fixed on a printed circuit board 8 attached to the encoder case 1.

Next, the configuration of the light receiving element 7 will be described. FIG. 8 shows a configuration diagram of a conventional light receiving element 7. In order to clarify the positional relationship, arrows 201 and common to FIG. 7 and FIG.
This will be described with reference to FIGS. The downward direction in FIGS. 7 and 8 is the central direction 201 of the optical rotary encoder, and the upward direction is the outer peripheral direction 202. The left-right direction is the circumferential direction 203,204.

The shaded areas in FIG. 8 indicate light-receiving cells that are electrically independent and each sense light, and the other areas indicate dead zones where light is not detected. Light receiving element 7
Has a plurality of groups of light receiving cell arrays and a plurality of groups of light receiving cell arrays. The light receiving cell array composed of the eight light receiving cells 21 to 28 located at the top of FIG. Cell array A group 200, FIG.
The light receiving cell array composed of the eight light receiving cells 31 to 38 located at the second stage from the top is
0, the light receiving cell array composed of six light receiving cells 61 to 66 located at the lower left of FIG.
01 and six light receiving cells 6 located at the lower right of FIG.
The light receiving cell array composed of 7 to 72 is referred to as a light receiving cell array B ′ group 402.

The light receiving cell arrays A 200 and B 300 are arranged so as to face the M-sequence slit array, detect irradiation light emitted from the transmitting portion of the M-sequence slit array, and output an M-sequence detection signal. , Light receiving cell array A 'group 401,
The B ′ group 402 is arranged to face the interpolation double slit row, detects irradiation light emitted from the transmission portion of the interpolation double slit row, and outputs an interpolation double detection signal.

Light receiving cell array A group 200, B for M series
In the group 300, since there are eight light receiving cells in one group of light receiving cell arrays, an M series of 8 bits can be detected in one group. The light receiving cells of the light receiving cell arrays A 200 and B 300 are arranged periodically, and a periodic pitch (hereinafter referred to as an M-sequence periodic pitch = P which is a distance between two adjacent light receiving cells).
That. ) 51 is a value determined by the number of slits of the slit disk 5.

For example, if the number of slits is 2 ⁸ (= 256), the mechanical angle becomes (360/256) ゜, and the length of the M-sequence period pitch 51 is approximately 2πR · (256
/ 360). Here, R is the radius of the detection track (M-sequence slit row) which is a circle. This M-sequence periodic pitch 51 is 360 electrical degrees. In order to set the phase difference between the light receiving cell arrays A 200 and B 300 to an electrical angle of 180 °, the distance of the phase difference 56 in FIG. 8 is set to half of the M-sequence period pitch P, that is, P / 2.

On the other hand, the light receiving cell array A 'group 4 for interpolation
The 01 and B 'groups 402 are arranged on the inner peripheral side of the M-sequence light receiving cell arrays A group 200 and B group 300. The six light receiving cells 61 to 6 of the light receiving cell array A 'group 401
6 and the six light receiving cells 67 of the light receiving cell array B ′ group 402
72 are electrically connected in parallel. The period pitches (hereinafter, referred to as interpolation period pitches) 52 and 54 of the light receiving cell array A ′ group 401 and B ′ group 402 are M.
The same pitch as the series detection cycle pitch 51, that is, the interpolation multiplication cycle pitch is provided to be P.

If the interpolation pitches 52 and 54 (= P) are 360 ° in electrical angle, the phase difference between the light receiving cell arrays A ′ 401 and B ′ 402 is 90 ° or 270 °.
In order to set the phase difference to the electrical angle of °, the distance 55 corresponding to the phase difference in FIG. 8 is achieved by setting P / 4 or 3P / 4. In this prior art, the description will be made assuming that the distance 55 is P / 4.

Further, a light receiving cell array B group 3 for M series
00 and the light receiving cell array A 'group 401 for detecting the interpolation magnification are arranged with an appropriate phase difference. In this prior art, the light receiving cell array B group 300 and the light receiving cell array A' group 401 are arranged.
Are arranged so that their mechanical angles are the same.

Next, a circuit for processing a detection signal output from the light receiving element will be described. FIG. 9 shows a conventional light receiving cell array A group 200, B group 300, A ′ group 401, B ′.
FIG. 3 shows a circuit configuration diagram of a group 402 and peripheral components thereof. The circuit configuration is different between the light receiving cell array groups A and B 300 for M series and the light receiving cell array groups A '401 and B' group 402 for interpolation.

The light receiving cell arrays A group 200, B group 300,
A power supply (V _cc ) is connected to the cathode side of each of the light receiving cells of the A ′ group 401 and the B ′ group 402, and is connected in reverse bias. Light receiving cell array A group 200, B for M series
Current-voltage conversion resistors 81 to 88 and 91 to 98 are connected to the anode sides of all the light receiving cells of the group 300, respectively, so that a CPU (Central Processing Unit) 100 can take in an M-sequence detection signal as a voltage signal. ing. In this case, as shown in FIG.
Waveforms are shaped through 108, 111 to 118 and input to the CPU 100 as digital signals.

Next, the light receiving cell array A 'group 4 for interpolation
The peripheral circuit configuration of the group 01 'and the group B' 402 is, for example, such that the anode sides of the light receiving cell arrays A 'group 401 and the group B' 402 for interpolation are all connected and the current-voltage conversion resistors 120 and 12 are connected.
1 and these current-voltage conversion resistors 12
The other ends of 0 and 121 are grounded. The I / V-converted interpolated signal is converted into a voltage signal by the CPU.
The data is fetched via an A / D converter (not shown) in 100. Light receiving cell arrays A group 200 and B group 300 for M series
, The detection signals output from the individual light receiving cells are respectively input to the CPU 100. On the other hand, in the light receiving cell arrays A 'group 401 and B' group 402 for interpolation, the sum of the output signals from the individual light receiving cells is obtained. Is output.

Next, the operation of the optical rotary encoder will be described. As shown in FIGS. 7A and 7B, L
It is assumed that the irradiation light emitted from the ED 6 reaches the light receiving element 7 after passing through the transmission sections of the M-sequence slit row and the interpolated double slit row of the detection track 5a of the slit disk 5.

FIG. 10 shows the slit disk 5 from the LED 6 side.
FIG. 2 shows a top view of the light receiving element 7 viewed from above. The upper row of black and white columns is the M-sequence slit row 550, and the lower row of black and white rows is the interpolation double slit row 60.
0. The region shown in black in the M-sequence slit row 550 in FIG. 10 is a light-shielding region, and the irradiation light is blocked by the light-shielding region, and the irradiation light that reaches this region cannot reach the light receiving cells. The region other than the light-shielding region is a transmission region. In the transmission region, the light receiving cell array A group 20 for M series is used.
The irradiation light reaches each light receiving cell of the 0 and B groups 300.

Similarly, the interpolated double slit array 600 shown in FIG.
The black area is a light-shielding area, the irradiation light is blocked by the light-shielding area, and the area other than the light-shielding area is a transmission area. In the transmission area, the light receiving cell array A ′ group 4 for interpolation is used.
The irradiation light reaches each of the light receiving cells of the 01 and B ′ groups 402.
As shown in FIG. 10, the interpolating double slit row 600 has regions that alternately transmit and block light at the interpolating double pitch P.

The light receiving element 7 outputs a photocurrent signal in proportion to the amount of the illuminating light that has arrived. M series slit row 550
The M-sequence detection signal of the current output from the light receiving cell arrays A 200 and B 300 of the light receiving element 7 after receiving the irradiating light transmitted through the transmission region of FIG. To 88, 91 to 98, and is converted into an M-sequence detection signal of a voltage.
After waveform shaping via 08, 111-118,
It is taken in by the CPU 100.

Similarly, the irradiation light transmitted through the transmission region of the interpolation slit array 600 is received, and the interpolation detection signal of the current output from the light receiving cell arrays A 'group 401 and B' group 402 of the light receiving element 7 is output. Is converted into a voltage interpolation detection signal by the current / voltage conversion resistors 120 and 121 as shown in FIG.
After being converted from an analog signal to a digital signal by the D converter, it is taken into the CPU 100.

FIG. 11 shows an analog voltage signal before being taken into the CPU 100. The M-sequence detection signals 130 and 131 shown in FIG.
This is a detection signal output from the light receiving cell 21 of No. 0 and the light receiving cells 31 of the light receiving cell array B group 300. FIG.
The interpolation multiplication detection signals 132 and 133 shown in FIG. 1 are detection signals obtained by summing the outputs from the light receiving cells of the light receiving cell arrays A 'group 401 and B' group 402 for interpolation.

The vertical axis in FIG. 11 shows a signal obtained by converting a current signal from each light receiving cell into a voltage signal, and the horizontal axis shows an absolute angle of the slit disk 5. Note that the interpolation double detection signal 1 from the light reception cell arrays A ′ group 401 and B ′ group 402 for interpolation
32 and 133 have an offset voltage added thereto.

Subsequently, using the captured detection signal, the CP
The detection principle of the absolute angle when the U100 detects the absolute angle will be described. For example, as shown in FIG. 10, a light receiving cell array B group 300 for the M series, light receiving / receiving for each light receiving cell is performed.
When the shading is clear, the detection for each light receiving cell can be clarified, but the light receiving cell array A group 200 for M series shown in FIG.
As shown in the light receiving cell of FIG. 10, a partial region of the light receiving cell (for example, light receiving cells 21, 22, 23, 25, 26, 27, 28, etc. in FIG. In this case, the signals from the light receiving cells 21 to 28 of the light receiving cell array A group 200 are
Alternatively, it is difficult to determine whether the light is in the transmission state, and it is difficult to obtain accurate angle information.

Therefore, paying attention to the fact that the light receiving cell array B group 300 is completely transmitted or shielded, the output signal from the light receiving cell array B group 300 is used instead of the output signal from the light receiving cell array A group 200. Thus, a correct M-sequence signal is obtained. For example, the M-sequence detection signal and the interpolation detection signal in the state shown in FIG.
804, the detection signal 130 of the light receiving cell 21 of the light receiving cell array A group 200 is M
It can be seen that the sequence signal is in the process of rising and is in an unstable state in order to determine the High or Low signal. However, since the detection signal 131 of the light receiving cells 31 of the light receiving cell array B group is completely on the High side, the M-sequence signal can be correctly detected.

In summary, when the angle is included in the angle interval 801, the CPU 100 sets the light receiving cell array A group 20
An M-sequence signal of 0 is selected. As a determination method for making this selection, for example, when the output signal of the light receiving cell array A ′ group 401 for interpolation at the angle 803 is on the minus side, that is, on the lower side than the offset component, the light receiving cell array A The M-sequence detection signals of the group 200 are selected.

Similarly, when the angle is included in the angle interval 802, the CPU 100 sets the M of the light receiving cell array B group 300 to M.
Select a sequence signal. As a determination method for making this selection, for example, the output signal of the light receiving cell array A ′ group 401 for interpolation multiplication in the case of the angle 804 is positive,
That is, when the offset component is on the High side, the M-sequence detection signal of the light receiving cell array B group 300 is selected.

The correct M-sequence detection signals of the light receiving cell arrays A 200 and B 300 obtained as described above are converted into angle information by the CPU 100, for example. Is converted to Here, the resolution of 8 bits obtained by the M-sequence detection signal is called upper 8 bits.

Further, by electrically interpolating and multiplying the interpolated double detection signal obtained in synchronization with the M-sequence detection signal, a resolution exceeding the 8-bit resolution obtained in the M-sequence can be realized. It becomes possible. Here, the resolution of X bits obtained by interpolation is referred to as lower X bits. Top 8
The resolution obtained by combining the resolution of the bits and the resolution of the lower X bits, that is, the resolution of (8 + X) bits is called the resolution of the optical rotary encoder. The prior art is such.

[0031]

In order to realize higher resolution and higher accuracy without changing the shape of the optical rotary encoder, (1) the number of bits of the M sequence is further increased, and Techniques such as improving the bit resolution and (2) improving the resolution of the lower bits by increasing the number of waveform divisions by interpolation are conceivable.

However, (1) when the resolution of the M-sequence is improved by the upper bits without changing the shape of the optical rotary encoder, the interval P of the M-sequence slit row M-cycle pitch 51 is narrowed, Accordingly, the size of the light receiving cell must be reduced. However, M
In general, the number of light receiving cells of the M-sequence light receiving cell array arranged at a position facing the series slit row cannot be increased as much as the number of light receiving cells of the interpolated double light receiving cell array that detects the interpolated double detection signal. Can not.

The reason is that the light receiving cells of the interpolated doubled light receiving cell array are connected in parallel to obtain an added signal, and the interpolated doubled detection signal has a large amplitude, whereas This is because the M series detection signal is detected by one independent light receiving cell in the series light receiving cell array, and the amplitude of the M series detection signal is smaller than that of the light receiving cells of the interpolation doubled light receiving cell array.

As the light receiving cell is made smaller by narrowing the period pitch, the amount of light detected decreases, and the resulting photocurrent also decreases. To compensate for this, the current-voltage conversion resistors 81 to 88 and 91 to 98 are generally set to have large resistance values, the amplitude is increased, and the CPU 100 receives the M-sequence detection signal. However, as a result, the response characteristic of the M-sequence detection signal deteriorates, and it becomes difficult to detect the M-sequence detection signal during high-speed rotation.

(2) In order to improve the resolution by increasing the number of lower bits, it is necessary to increase the performance of an A / D converter built in the CPU 100, which causes a problem such as an increase in manufacturing cost. Newly occurs.

[0036] In order to solve the above-mentioned problems, an object of the present invention is to provide an optical absolute encoder capable of avoiding an increase in size and cost and realizing high-accuracy and high-resolution detection. I do.

[0037]

According to an aspect of the present invention, there is provided an optical absolute value encoder, comprising: a light emitting element; and a light emitting element disposed at a position facing the light emitting element. A light-receiving element for receiving irradiation light from
A slit plate having a detection track having a plurality of slit rows arranged to transmit and block light by arranging a plurality of slits transmitting the irradiation light from the light emitting element, and an optical absolute value encoder comprising: The slit array of the detection track includes an M-sequence slit array that transmits or blocks irradiation light based on an M-sequence rule, and a first interpolation that alternately transmits or blocks light at a predetermined cycle pitch. The number of slits in the double slit row, the period pitch of 1 / N (N is a natural number of 2 or more) with respect to the periodic pitch of the first interpolation double slit row, and the number of slits in the first interpolation double slit row A second interpolating double slit row that has N times the number of slits and transmits or blocks light alternately, and the light receiving element is disposed at a position facing the M series slit row. ,Previous A light receiving cell array for M series of A group and B group having a plurality of light receiving cells arranged at the same periodic pitch as the M series slit row, and a light receiving cell array arranged at a position facing the first interpolation double slit row; A light receiving cell array for the first interpolation of the A 'group and the B' group having a plurality of light receiving cells arranged at the same periodic pitch as the first interpolation double slit row; and the second interpolation double slit row. A second group A "and a second group B" having a plurality of light receiving cells arranged at opposing positions and arranged at the same periodic pitch as the second interpolation double slit row.
A light-receiving cell array for interpolation,
It is characterized in that absolute position information is obtained by combining detection signals output from the light receiving cell arrays of the groups A ', B', A "and B".

According to the optical absolute value encoder of the second aspect, in the optical absolute value encoder of the first aspect, the light receiving cell array for the M series of the A group and the B group of the light receiving elements is: The A and B groups are divided into two upper and lower stages so that the irradiation light transmitted through one slit of the M-sequence slit row of the detection track is detected by both the A and B groups. A is set so that the photocurrent signals output from the light receiving cell array for the M series have different phases.
A group and a group B are arranged.

According to the optical absolute value encoder of the third aspect, in the optical absolute value encoder of the first or second aspect, a predetermined period of the first interpolation double slit row is provided. The pitch is the same value as the periodic pitch of the M-sequence slit row.

According to a fourth aspect of the present invention, in the optical absolute value encoder according to any one of the first to third aspects, the slit plate has a detection track. A substantially rectangular slit plate arranged substantially linearly, and the light emitting element and the light receiving element move along the fixed slit plate in the linear direction while facing each other, and the displacement of the absolute value in the linear direction is determined. A linear encoder for detection is provided.

According to the optical absolute value encoder of the fifth aspect, in the optical absolute value encoder of any one of the first to third aspects, the slit plate has a detection track. A disk-shaped slit plate arranged in a substantially circular shape, wherein the light emitting element and the light receiving element arranged opposite to each other with the slit plate interposed therebetween change the absolute value of the rotating direction of the rotating slit plate. A rotary encoder for detecting the amount is provided.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an optical rotary encoder among optical absolute value encoders of the present invention will be described. FIG. 1 is a configuration diagram of an optical rotary encoder according to the present embodiment. FIG. 1A is a cross-sectional configuration diagram thereof, and FIG. 1B is a plan view of a slit disk. The configuration of the optical rotary encoder of the present embodiment is as follows.
A conventional optical disk except that a slit disk 500 is mounted on the hollow shaft 2 instead of the conventional slit disk 5 and a light receiving element 700 is mounted on the printed circuit board 8 instead of the light receiving element 7. Same as rotary encoder. In the following, description of the same components as those in the related art is omitted,
Only the differences will be described.

The configuration of the light receiving element 700 of this embodiment will be described. FIG. 2 shows a configuration diagram of the light receiving element 700 of the present embodiment. Arrows 201, 202, 203, and 204 common to FIGS. 1 and 2 are used to clarify the positional relationship. The downward direction in FIGS. 1 and 2 is the central direction 201 of the optical rotary encoder, and the upward direction is the outer peripheral direction 202. The left-right direction is the circumferential direction 203,204.

The shaded area in FIG. 2 indicates a light receiving cell, and the other areas indicate dead zones in which no light is detected. The light receiving element 700 has a light receiving cell array in which a plurality of cells are collected as one group, and further has a plurality of light receiving cell arrays. A group, B group, A ′ group, B ′ group, A ″ group,
It has six groups of light receiving cell arrays of group B ".

More specifically, a light receiving cell array A group 200 composed of eight light receiving cells 21 to 28 at the top of FIG.
A light receiving cell array B group 300 including eight light receiving cells 31 to 38 at the second stage from the top in FIG. 2, and a light receiving cell array A including six light receiving cells 61 to 66 at the bottom left of FIG. 'Group 401, light receiving cell array B composed of six light receiving cells 67 to 72 on the lower right of FIG. 2' group 402, light receiving composed of a large number of light receiving cells on the third left from the top in FIG. The array is divided into a cell array A "group 403 and a light receiving cell array B" group 404 composed of a large number of light receiving cells on the third right side from the top in FIG.

Next, the light receiving cell arrays of each group will be described in detail. First, the light receiving cell array A group 20 for the M series
The 0, B group 300 will be described. The M-sequence period pitch 51 (= P) of two adjacent light receiving cells is a value determined by the number of slits provided on the detection track 500a of the slit disk 500.

In the present embodiment, the light receiving cell array A group 200,
The B group 300 outputs an 8-bit M-sequence detection signal. The periodic pitch 51 for the M series of adjacent light receiving cells is 2
^{If 8} = 256, the mechanical angle becomes (360/256) °, and the length of the M-sequence periodic pitch 51 is approximately 2πR · (256/360). Here, R is the radius of the detection track (M-sequence slit row) which is a circle. The M-sequence periodic pitch 51 is an electrical angle of 360 °, and the distance 56 for determining the phase difference is set to the M-sequence in order to make the phase difference between the light receiving cell arrays A 200 and B 300 300 180 electrical degrees. It is set to half of the use cycle pitch 51, that is, P / 2.

Next, the first interpolating light receiving cell arrays A 'group 401 and B' group 402 will be described. The light receiving cell array A ′ group 401 and B ′ group 402 shown in FIG.
The light receiving cell arrays A and B are arranged on the inner peripheral side of the group A and the periodic pitch between the light receiving cells (hereinafter, referred to as a first interpolation double pitch) 52 and 54 are M.
This is the same as the sequence period pitch 51. The first interpolation double period pitch is 360 ° in electrical angle, and the light receiving cell array A ′
In order to make the phase difference between the group 401 and the B ′ group 402 90 ° or 270 ° in electrical angle, the distance 55 that determines the phase difference is P / 4.

Next, the light receiving cell arrays A "403 and B" 404 for the second interpolation will be described. The light receiving cell arrays A "group 403 and B" group 404 shown in FIG.
Light receiving cell arrays A group 200 and B group 300
Light receiving cell arrays A ′ group 401 and B ′ group 402 for interpolation magnification
It is located between.

FIG. 3 shows an enlarged view of the light receiving element array of FIG. In FIG. 3, the light receiving cell array A ″ group 403
The light receiving cells 701, 719 to 724 are illustrated, and the light receiving cell array B ″ group 404
25 to 730 and 748 are respectively shown.

As is apparent from FIG. 3, the period pitch between the two light receiving cells of the light receiving cell array A "group 403 and B" group 404 (hereinafter, referred to as the second interpolation period pitch) 57.
Are the light receiving cell arrays A group 200 and B group 300 for the M series.
Is smaller than the M series cycle pitch 51 and the first interpolation cycle pitches 52 and 54 of the first interpolation light receiving cell arrays A 'group 401 and B' group 402.

In this case, the second interpolation cycle pitch is set based on a predetermined rule, and the second interpolation cycle pitch is set to the first of the light receiving cell arrays A ′ group 401 and B ′ group 402. The periodic pitch has a length of 1 / N (N is a natural number of 2 or more) with respect to the interpolating double pitch, and has N times the number of slits in the light receiving cell array A ′ group 401. Are arranged as follows.

In this embodiment, it is assumed that N = 4. That is, the light receiving cell array A "group 403,
The number of slits in the B ″ group 404 is 24, and the period pitch is １ ／ of the first interpolation period pitches 52 and 54 (= M-sequence period pitch 51 = P). The second interpolation cycle pitch 57 indicated by 3 is P / 4, and four second interpolation light receiving cells are included in the first interpolation cycle pitch.

The light receiving cell array A "group 403, B"
The second interpolation cycle pitch of the group 404 is 360 ° in electrical angle.
The phase difference between the light receiving cell array A "group 403 and the B" group 404 is set to be 90 degrees or 270 degrees in electrical angle. In the present embodiment, since the angle is 90 °, the distance 58 in FIG. 3 is set to P / 16.

In the following, this embodiment will be described on the assumption that N = 4. However, this N is not limited to 4, and N may be a value such as 2, 3, 5,. They are,
This is a value appropriately selected at the time of design according to the required resolution. As a result, as shown in FIG. 6, in the light receiving cell array A "group 403, B" group 404, the light receiving cell array A 'is formed.
1 of the period pitch for the first interpolation of the groups 401 and B ′ group 402
A detection signal of the second interpolation cycle pitch of / 4 is obtained.

Incidentally, the light receiving cell arrays A group 200, B group 3
00 and the light receiving cell array A ′ group 401 and B ′ group 402 are arranged so as to have an appropriate phase difference. In the present embodiment, as is apparent from FIGS. 2 and 3, the light receiving cell array A ′ group 401 and the light receiving cell array B group 300 are arranged so as to have the same phase.

From this, assuming that one cycle pitch of the M-sequence slit row and the first interpolation double slit row of the detection track is a periodic signal corresponding to an electrical angle of 360 °, the phase difference between the groups B and A ′ is determined. Is (0 + α × 360) ゜, and the phase difference between group B (group A ′) and group B ′ is (90 + β × 36)
0) ゜, the phase difference between group B (group A ′) and group A is (18)
0 + γ × 360) ゜. Where α,
β and γ are arbitrary arbitrary integers.

Next, a circuit for processing a detection signal output from the light receiving element 700 will be described. FIG. 4 shows a light receiving cell array A group 200, a B group 300,
A ′ group 401, B ′ group 402, A ″ group 403, B ″ group 4
FIG. 4 shows a circuit configuration diagram of the device 04 and its peripheral components. In FIG. 4, a power source (V _cc ) is connected to the cathode side of the A group 200, the B group 300, the A ′ group 401, the B ′ group 402, the A ″ group 403, and the B ″ group 404. Has become.

Light receiving cell array A group 200, B for M series
To the anode side of the group 300, designated current-voltage signal conversion resistors 81-88, 91-98 are connected, and the other ends of the current-voltage signal conversion resistors 81-88, 91-98 are grounded. Have been. Further, between the anode side of each light receiving cell and the current-voltage signal conversion resistors 81-98, C
In order to take in the M-sequence detection signal into the PU 100, comparators 101 to 108 and 111 to 118 are inserted. The M-sequence detection signal is output from comparators 101 to 108, 1
After the waveform is shaped by 11 to 118, the CPU 100
Is taken in.

Further, the light receiving cell array A 'for the first interpolation magnification is used.
The anode sides of the groups 401 and B ′ groups 402 are connected to the current / voltage conversion resistors 120 and 121 and the A / D converter (not shown) in the CPU 100. The other ends of the current-voltage conversion resistors 120 and 121 are grounded. Similarly, the second interpolating light receiving cell array A ″ group 403,
The anode side of the B ″ group 404 is connected to the current-voltage conversion resistor 12.
2, 123 and an A / D converter (not shown) in the CPU 100. Current-voltage conversion resistors 122, 1
The other end of 23 is grounded.

The detection signals from the light receiving cells of the light receiving cell arrays A 200 and B 300 are electrically independent of each other, and these detection signals are output to the CPU 100.
Further, the light receiving cell arrays A 'group 401, B' group 402,
The light receiving cells of the A ″ group 403 and the B ″ group 404 are electrically connected in parallel, respectively, and the sum of the detection signals is
Output to 0.

Light receiving cell array A group 200, B for M series
In the group 300, the detection signals output from the individual light receiving cells are input to the CPU 100, respectively. The light receiving cell array A ″ group 403 and the B ″ group 404 are different in that the sum of output signals from the individual light receiving cells is output.

Next, the operation of the optical rotary encoder will be described. As shown in FIG. 1, the irradiation light from the LED 6 is transmitted through the M-sequence slit array of the slit disk 500 and the first and second interpolation double slit arrays for transmitting and blocking light alternately. The device 700 is reached. FIG.
Is a top view when the light receiving element 700 side is viewed from the LED 6 side via the slit disk 500. FIG. The black area of the M-sequence slit row 550 in FIG. 5 is a light-blocking area, and irradiation light is blocked by the light-blocking area, and light that reaches this area cannot reach the light receiving cells. The area other than the light-shielding area is a transmission area. In the transmission area, irradiation light reaches each light receiving cell of the M-sequence light receiving cell array. As shown in FIG. 5, the M-sequence slit array 550 has regions that alternately transmit and block light at the same pitch as the M-sequence periodic pitch P of the light receiving cells.

Similarly, the first interpolated double slit row 90 shown in FIG.
The black areas of the 0 and second interpolation double slit rows 1000 are light-blocking areas, and the irradiation light is blocked by the light-blocking areas.
The area other than the light-shielding area is a transmission area. In the transmission area, irradiation light reaches each light receiving cell of the first and second interpolated light receiving cell arrays. As shown in FIG. 5, the first interpolating double slit row 900 has regions that alternately transmit and block light at the same periodic pitch P as the first interpolating periodic pitch of the light receiving cells. The two-interpolation double slit row 1000 has regions that alternately transmit and block light at the same cycle pitch P / 4 as the second interpolating cycle pitch of the light receiving cells.

In this embodiment, the width of the slit in the slit row and the width of the light receiving cell are shown as being the same, but the width of the slit and the width of the light receiving cell do not need to be the same. Even if the light receiving cell width is larger than the width,
Also, it may be small. These can be appropriately designed. In short, it is only necessary that the periodic pitches have the same value.

The light receiving element 700 outputs a photocurrent signal in proportion to the amount of the illuminating light that has arrived. M series slit row 5
The photocurrent signal output from the light receiving cell arrays A 200 and B 300 of the light receiving element 700 after receiving the irradiation light transmitted through the transmission region 50 is a current-voltage conversion resistor 81 shown in FIG.
８８88, 91９８98, and I / V converted to be converted into a voltage M-sequence detection signal.
After the waveforms are shaped through 1-118, the CPU 10
It is taken into 0.

The photocurrent signals output from the light receiving cell arrays A ′ group 401 and B ′ group 402 of the light receiving element 700 after receiving the irradiation light transmitted through the transmission area of the first interpolation slit row 900 are shown in FIG. As shown in FIG.
At 0, 121, the signal is converted into a first interpolation multiplication detection signal of a voltage, and the A / not-shown A /
After being converted from an analog signal to a digital signal by the D converter, it is taken into the CPU 100.

Similarly, the photocurrent signal output from the light receiving cell arrays A "403 and B" 404 of the light receiving element 7 after receiving the irradiation light transmitted through the transmission area of the second interpolation double slit row 1000 is As shown in FIG.
3, 124, the signal is converted into a second interpolated double detection signal of the voltage, and an A /
After being converted from an analog signal to a digital signal by the D converter, it is taken into the CPU 100.

FIG. 6 shows an analog voltage signal before being taken into the CPU of the optical rotary encoder according to the embodiment of the present invention. For example, as shown in FIG. 6, an M-sequence detection signal 130 from the light-receiving cell 21 of the M-sequence light-receiving cell array A group 200 and an M-sequence detection signal 131 from the light-receiving cell 31 of the M-sequence light receiving cell array B group 300. , The first interpolation detection signals 132 and 133 from the light-receiving cell arrays A 'group 401 and B' group 402 for the first interpolation, and the light-receiving cell array A "group 403 and B" group 404 for the second interpolation. Second from
Interpolation double detection signals 134 and 135 are generated, respectively.

The vertical axis in FIG. 6 shows a signal obtained by converting a photocurrent signal from each light receiving cell into a voltage signal, and the horizontal axis shows an absolute angle of the slit disk 500. It should be noted that the first interpolation double detection signals 132 and 133 and the second interpolation double detection signal 134,
At 135, the offset voltage is added.

Subsequently, the CPU 1
The principle of detecting the absolute angle when 00 detects the absolute angle will be described. For example, when the light receiving / shielding of each light receiving cell is clear as in the light receiving cell array B group 300 for M series shown in FIG. 5, the detection of each light receiving cell is clearly performed.
Like the light receiving cells of the light receiving cell array A group 200 for M series shown in FIG. 5, a partial area of the light receiving cells (for example, the light receiving cells 24 and 25 in FIG. ) Is light-shielded, the signals from the light-receiving cells 21 to 28 of the light-receiving cell array A group 200 are difficult to determine whether the light-shielded state or the light-transmitted state is present. It is difficult to obtain.

Therefore, the light receiving cell array B group 300 completely transmits (light receiving cell 34 and the like) or shields light (light receiving cell 3
(3, 35, etc.), a correct M-sequence signal is obtained using not the output signal from the light receiving cell array A group 200 but the output signal from the light receiving cell array B group 300. .

For example, in the detection signal at the angle 812 in FIG. 6, the detection signal 130 of the light-receiving cell 21 (not shown) of the light-receiving cell array A group 200 is in the middle of the rising of the M-sequence signal, and is high or low. Is determined to be unstable. However, even at the same angle 812, the detection signal 131 of the light receiving cells 31 (not shown) of the light receiving cell array B group is completely H.
Since it is on the high side, the M-sequence detection signal can be correctly detected.

In summary, when the angle is included in the interval 809, the CPU 100 selects the M-sequence signal of the light receiving cell array A group 200. As a determination method for making this selection, for example, when the output signal of the first interpolation light receiving cell array A ′ group 401 at the angle 811 is on the minus side, that is, on the lower side than the offset component, The M-sequence detection signal of the cell array A group 200 is selected.

Similarly, when the angle is included in the interval 810, the CPU 100 selects the M-sequence signal of the light receiving cell array B group 300. As a determination method for making this selection, for example, the output signal of the first interpolation light receiving cell array A ′ group 401 at the angle 812 is set to the plus side,
That is, when the offset component is on the High side, the M-sequence detection signal of the light receiving cell array B group 300 is selected.

Then, the CPU 100 converts the correct M-sequence detection signals of the light receiving cell arrays A 200 and B 300 obtained as described above into angle information, for example. Thereby, the M-sequence signal is converted into absolute value angle information. Here, the resolution of 8 bits obtained by the M-sequence detection signal is called upper 8 bits.

Further, in order to obtain a high resolution, the second interpolated multiplication signal obtained in synchronization with the first interpolated multiplication signal is further electrically interpolated and multiplied to obtain the M series. It is possible to realize a resolution exceeding the bit resolution. Here, the resolution of X bits obtained by the second interpolation is referred to as lower X bits. The resolution obtained by combining the resolution of the upper 8 bits and the resolution of the lower X bits, that is, 8 + X
The resolution of bits is called the resolution of the optical rotary encoder.

However, the lower second interpolation signal is
Since one cycle pitch of the M-sequence signal has interpolation multiplication information for four cycle pitches, it is difficult to determine the number of the interpolation multiplication signal. For example, when the angle information is to be obtained at the timing 812, the third second interpolated signal 8
07 is interpolated and multiplied by the first second interpolated double signal 8
It is not possible to determine which of the 05-fourth second interpolated signals 808 has been interpolated and multiplied. Thus, the first to fourth second interpolated signals 805, 806, 8 are multiplied by electrically interpolating the first interpolated multiplied signal.
07,808 can be selected.

For example, in the case of this embodiment, if the first interpolation detection signal 132 is Low and 133 is High, the first interpolation detection signal 13
2 and 133 are both Low, the second interpolation signal 806 becomes the second interpolation signal 806, and the first interpolation detection signal 132 becomes High, 13
If 3 is Low, the third second interpolation double detection signal 807 becomes:
Since the case where both the first interpolation multiplication signals 132 and 133 are High corresponds to the fourth second interpolation multiplication detection signal 808, it is determined which of the second interpolation multiplication detection signals has been interpolated. be able to.

In order to enable selection of the first to fourth second interpolated signals, the first interpolated signal may be interpolated by at least 2 bits. Here, for example, the first
The 2-bit resolution obtained by the interpolated signal is
Called bits. Thereby, the resolution 8 obtained in the M sequence
By connecting the middle 2 bits and the lower X bits to the bits, an optical rotary encoder having a resolution of (8 + 2 + X) bits can be realized.

In the optical rotary encoder according to this embodiment, it is not necessary to change the shape, and high resolution can be realized. In addition, since a high-performance A / D converter is not required, the cost is reduced.

In this embodiment, the optical rotary encoder has been described. However, the present invention is not limited to the optical rotary encoder, but can be applied to an optical linear encoder that detects an electrical angle. While the optical rotary encoder rotates the slit disk, the optical linear encoder is different in that it moves the detection unit with the light emitting element and light receiving element integrated, but the lower signal uses the electrical angle θ. The principle is the same. Higher resolution can be realized even with an optical linear encoder to which the present invention is applied.

[0083]

According to the present invention, it is possible to provide an optical absolute value encoder that realizes high-precision and high-resolution detection while avoiding an increase in size and cost.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical rotary encoder according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a light receiving element of the optical rotary encoder according to the embodiment of the present invention.

FIG. 3 is an enlarged configuration diagram of a light receiving element of the optical rotary encoder according to the embodiment of the present invention.

FIG. 4 is a diagram illustrating a light receiving cell array A, B, A ′, B ′, and A ″ of the optical rotary encoder according to the embodiment of the present invention.
FIG. 5 is a circuit configuration diagram of a group, a B ″ group and peripheral components thereof.

FIG. 5 is a top view when the light receiving element side is viewed from the LED side of the optical rotary encoder according to the embodiment of the present invention via a slit disk.

FIG. 6 is an analog voltage signal before being taken into the CPU of the optical rotary encoder according to the embodiment of the present invention.

FIG. 7 is a configuration diagram of a conventional optical rotary encoder.

FIG. 8 is a configuration diagram of a light receiving element of a conventional optical rotary encoder.

FIG. 9 is a circuit configuration diagram of a light receiving cell array A group, a B group, an A ′ group, a B ′ group of a conventional optical rotary encoder and peripheral components thereof.

FIG. 10 is a top view when a light receiving element side is viewed from a LED side of a conventional optical rotary encoder via a slit disk.

FIG. 11 shows an analog voltage signal before being taken into a CPU of a conventional optical rotary encoder.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Encoder case 2 Bearing 3 Bearing 4 Hollow shaft 500 Slit disk 500a Detection track 6 LED 700 Light receiving element 8 Printed circuit board 200 Light receiving cell array A group 300 Light receiving cell array B group 401 Light receiving cell array A '
Group 402 light receiving cell array B '
Group 403 light receiving cell array A "
Group 404 Photocell array B "
Groups 21 to 28 light receiving cells 31 to 38 light receiving cells 61 to 66 light receiving cells 67 to 72 light receiving cells 701, 719 to 724 light receiving cells 725 to 730, 748 light receiving cells 51 M cycle pitch P 52, 54 1st interpolation Period pitch P 55 Distance P / 4 56 Distance P / 2 57 Distance P / 4 58 Distance P / 16 81-88, 91-98 Current-voltage conversion resistors 120, 121, 122, 123 Current-voltage conversion resistors 101- 108 Comparator 111-118 Comparator 100 CPU 550 M-sequence slit array 900 First interpolated double slit array 1000 Second interpolated double slit array 130 M-sequence detection signal 131 M-sequence detection signal 132 First interpolated multiplication detection signal 133 First Interpolation double detection signal 134 Second interpolation double detection signal 135 Second interpolation double detection signal 805-810 square Interval 811 and 812 angle

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yasumitsu Nagasaka 1-1-1, Tanabe-Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa F-term in Fuji Electric Co., Ltd. (Reference) 2F077 AA25 NN02 NN23 NN30 PP19 QQ10 QQ15 RR03 RR07 RR17 RR23 RR27 RR29 TT32 TT35 TT43 2F103 BA37 CA02 DA06 EA12 EB06 EB15 EB16 EB33 ED07 FA07

Claims (5)

[Claims] A light-emitting element, a light-receiving element disposed at a position facing the light-emitting element to receive irradiation light from the light-emitting element, and a plurality of slits transmitting the irradiation light from the light-emitting element. And a slit plate having a detection track provided with a plurality of slit rows configured to perform transmission and light blocking by using an optical absolute value encoder, wherein the slit row of the detection track is defined by an M sequence. M that transmits or blocks irradiation light based on
A series slit row, a first interpolating double slit row that transmits or blocks light alternately at a predetermined periodic pitch, and 1 / N with respect to the periodic pitch of the first interpolating double slit row.
(N is a natural number of 2 or more) having a periodic pitch of length and N times the number of slits of the first interpolated double slit row, and alternately transmitting or blocking light.
And an interpolating double slit row, and the light receiving element is arranged at a position facing the M series slit row, and has a plurality of light receiving cells arranged at the same periodic pitch as the M series slit row. A light receiving cell array for the M series of the A group and the B group, which is arranged at a position facing the first interpolation double slit row;
A light receiving cell array for the first interpolation of A 'group and B' group having a plurality of light receiving cells arranged at the same periodic pitch as the first interpolation double slit row; and the second interpolation double slit row Is arranged at a position facing the
A light receiving cell array for a second interpolation of a group “A” and a group B ”having a plurality of light receiving cells arranged at the same periodic pitch as the second interpolation slit row; , A ′ group, B ′ group, A ″ group, and B group ″ by combining the detection signals output from the light receiving cell arrays to obtain absolute position information. 2. The optical absolute value encoder according to claim 1, wherein the light receiving cell array for M series of the A group and the B group of the light receiving elements includes one slit of the M series slit row of the detection track. The A and B groups are divided into two upper and lower stages so that the transmitted irradiation light is detected by both the A and B groups, and the photocurrent signal output from the light receiving cell array for the M series of the A and B groups is An optical absolute value encoder, wherein a group A and a group B are arranged so as to have different phases. 3. The optical absolute value encoder according to claim 1, wherein a predetermined cycle pitch of the first interpolation double slit row is the same as a cycle pitch of the M series slit row. An optical absolute encoder. 4. The optical absolute value encoder according to claim 1, wherein said slit plate is a substantially rectangular slit plate on which detection tracks are arranged substantially linearly. A light-emitting element and a light-receiving element are opposed to each other along a fixed slit plate, and move in a linear direction while detecting a displacement of an absolute value in the linear direction. Value encoder. 5. The optical absolute value encoder according to claim 1, wherein said slit plate is a disk-shaped slit plate on which detection tracks are arranged in a substantially circular shape. Wherein the light emitting element and the light receiving element arranged opposite to each other with the slit plate interposed therebetween are used as a rotary encoder for detecting a shift amount of an absolute value in a rotation direction of the rotating slit plate. Expression absolute value encoder.