JP2001141522A - Optical encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To preclude an angle error in an electrical angle of a subordinate signal from being generated affected by an assembling error, sensitivity dispersion in a photo-receiving element, illumination unevenness of an LED and the like, so as to realize detection of highly precise and high resolution. SOLUTION: The photo-receiving element 700 has four groups of photo- receiving cell arrays comprising an A-group 18, B-group 28, C-group 38 and D-group 48 divided into four groups by dead zones substantially orthogonally, and the four groups of the photo-receiving cell arrays are arranged to bring photocurrent signals output therefrom into periodic signals having phases different each other, in this optical encoder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical encoder for measuring a displacement in a rotation direction or a linear direction.

[0002]

2. Description of the Related Art First, an optical rotary encoder will be briefly described as an example of the prior art. FIG. 4 is a configuration diagram of the optical rotary encoder. FIG. 4A is a cross-sectional configuration diagram thereof, and FIG. 4B is a plan view of a slit disk. This optical rotary encoder includes an encoder case 1, bearings 2, 3, a hollow shaft 4, a slit disk 5,
An LED (Light Emitting Diode) 6, a light receiving element 7, and a printed circuit board 8 are provided.

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. The slit disk 5 is provided with a detection track 5a in which rows of a plurality of slits are arranged in a track shape, and transmits and blocks light depending on the presence or absence of the slit. In this specification, the term “slit” refers to a through-hole shown in FIG. 4A or a transparent portion of a pattern printed on a transparent slit disk (not shown) in a light and dark grid pattern.

The detection track 5a of 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. Further, the light receiving element 7 is arranged and fixed on a printed circuit board 8 attached to the encoder case 1.

FIG. 5 shows a configuration diagram of a conventional light receiving element 7.
Arrows 2 common to FIGS. 4 and 5 to clarify the positional relationship
This will be described using 01, 202, 203, and 204. The downward direction in FIGS. 4 and 5 is the center direction 20 of the rotary encoder.
1 and the upward direction is the outer peripheral direction 202. The left-right direction is the circumferential direction 203,204.

Next, the configuration of the light receiving element 7 will be described. The hatched area in FIG. 5 indicates a light receiving cell that senses light, and the other area indicates a dead zone where light is not detected. The light receiving element 7 includes six light receiving cells 11 to 11 on the left side of FIG.
A light receiving cell array A group 18 composed of
A light receiving cell array B group 28 including six light receiving cells 21 to 26 on the right side of FIG. 5 is provided. Each of the light receiving cells 11 to 16 of the group A 18 and each of the light receiving cells 21 of the group B 28
To 26 are electrically connected in parallel.

The light receiving cells are periodically arranged. adjacent
Pitch 51, which is the distance between two light receiving cells
Below, when P is used, it indicates a periodic pitch. )
Is a value determined by the number of slits of the slit disk 5
is there. For example, if the number of slits is 2 ⁸(= 256)
The mechanical angle becomes (360/256) ゜, and the pitch 51
The length is approximately 2πR · (256/360).
Here, R is the radius of the detection track which is a circle. Ma
In addition, one cycle pitch 51 of the two light receiving cells is set to an electrical angle of 36.
If the angle is set to 0 degree, the light receiving cells 16 of the group A 18 and the receiving cells of the group B 28
By setting the distance 52 of the optical cell 21 to 0.25P,
The phase difference between group A 18 and group B 28 is 90 ° or 27 °.
The phase difference is set to 0 ° electrical angle.

FIG. 6 shows A group 1 of a conventional light receiving cell array.
A circuit configuration diagram of the 8, B group 28 and its peripheral components is shown.
In FIG. 6, a power supply is provided on the cathode side of the group A 18 and the group B 28.
(V _cc ) is connected, which is a reverse bias connection. On the other hand, the anode side of the A group 18 is connected to a current-voltage conversion resistor 19 and an A / D converter (Analog / Digital converter) (not shown) built in the CPU (Central Processing Unit) 100, and is used for current-voltage conversion. The other end of the resistor 19 is grounded. Note that the group B 28 is also connected to the current-voltage conversion resistor 29.
8 has the same circuit configuration.

Next, the operation of the optical rotary encoder will be described. As shown in FIGS. 4A and 4B, L
It is assumed that the irradiation light emitted from the ED 6 passes through the slit of the detection track 5a of the slit disk 5 and reaches the light receiving element 7. The light receiving element 7 outputs a photocurrent signal in proportion to the amount of the irradiating light that has arrived. The photocurrent signal from the light receiving element 7 is converted into current-voltage conversion resistors 19 and 29 as shown in FIG.
Is converted into a voltage signal, and is converted from an analog signal to a digital signal by an A / D converter (not shown) built in the CPU 100 and is taken into the CPU 100.

FIG. 7 shows an analog voltage signal before being taken in by the CPU 100. The vertical axis indicates a voltage signal obtained by converting the photocurrent signal from the light receiving element 7 by the current / voltage conversion resistors 19 and 29, and the horizontal axis indicates the rotation direction of the optical rotary encoder. The A-phase signal 181 is the A-phase signal of the light receiving cell array.
The photocurrent signal from the group 18 is converted into a voltage signal. Similarly, the B-phase signal 281 is the B group 2 of the light receiving cell array.
8 is obtained by converting the photocurrent signal from No. 8 into a voltage signal.

The A-phase signal 181 and the B-phase signal 28
1 is a periodic signal, one cycle of which is a detection track 5a.
Corresponds to the case where the slit moves by one period pitch. A
The phase signal 181 and the B phase signal 281 are 90 ° or 27 degrees.
It has a phase difference of 0 ° and can be expressed as the following equation.

[0012]

(Equation 3)

[0013] I _A is A-phase signal, I _B is B-phase signal, X is the offset voltage of the A-phase and B-phase signals, Y represents respectively a signal amplitude of the A-phase and B-phase signals. Also,
θ indicates the rotation angle θ of the optical rotary encoder at a certain timing as an electrical angle, and the electrical angle θ
Is changed by 360 °, it corresponds to the case where the slit disk 5 moves by one pitch of the slit.

Next, the principle of angle detection when the slit disk 5 of the optical rotary encoder makes one rotation (mechanical angle of 360 °) will be described. This optical rotary encoder is used for the A-phase signal I _A or B shown in FIG.
Via an A / D converter (not shown) of a phase I _B CPU 1
A pulse signal is generated as a higher-order signal by inputting the signal to 00 and shaping the waveform into a square wave by digital signal processing.
This pulse signal is a signal in which the H level and the L level alternately appear according to the presence or absence of the slit.

Further, a more high-resolution low-order signal from the previous-level signal is generated by processing the A-phase signal I _A and the B phase signal I _B. Specifically, as shown in Figure 7 A-phase signal I _A
And the B-phase signal I signal I to remove the offset voltage amount X94 from _{B 'A,} I' make _B, and calculating the arctangent of the signal ratio. That is, the lower signal is represented by the following equation.

[0016]

(Equation 4)

In this way, an upper signal and a lower signal can be obtained. By combining these upper signals and lower signals, a high-resolution optical rotary encoder can be realized.

[0018]

[SUMMARY OF THE INVENTION] However, the actual optical A-phase signal I _A and the B phase signal I _B obtained from the rotary encoder assembly error of the optical rotary encoder, variations in sensitivity of the light receiving element, LED of Affected by uneven lighting. Due to this effect, the offset voltage has offset voltage errors ΔX _A and ΔX _B , the signal amplitude has signal amplitude errors ΔY _A and ΔY _B , and the phase has phase error Δ
theta _A, [Delta] [theta] _B is generated, the waveform of the A-phase signal I _A and the B phase signal I _B is distorted as in the following equation by the influence of these errors.

[0019]

(Equation 5)

When the waveform is distorted like these I _Areal and I _Breal , an angle error Δθ is generated in the rotation angle as a lower signal as shown in the following equation.

[0021]

(Equation 6)

When the angle error Δθ increases, there is a problem that the angle detection accuracy of the optical rotary encoder deteriorates and it becomes difficult to obtain a predetermined accuracy.

In order to solve the above-mentioned problems, the present invention avoids a situation where an angle error occurs in the electrical angle of a lower signal due to an assembling error, variation in sensitivity of a light receiving element, unevenness in LED lighting, and the like. It is another object of the present invention to provide an optical encoder that realizes high-precision and high-resolution detection.

[0024]

According to an aspect of the present invention, there is provided an optical encoder, comprising: a light emitting element; a light emitting element disposed at a position facing the light emitting element; A light receiving element that receives irradiation light, and a slit plate having a detection track formed of a slit array for transmitting and blocking irradiation light from the light emitting element, an optical encoder including: There are light receiving cell arrays A, B, C, and D which are obtained by dividing light receiving cells arranged on a two-dimensional plane into four groups by a substantially orthogonal dead zone, and output from these four groups of light receiving cell arrays. The four groups of light receiving cell arrays are arranged such that the photocurrent signals are periodic signals having different phases.

According to the optical encoder of the second aspect, in the optical encoder of the first aspect,
The one group of light receiving cell arrays has a plurality of light receiving cells arranged periodically, and a cycle pitch of the plurality of light receiving cells is set to be the same length as a cycle pitch of a slit row of a detection track of the slit plate. Features.

According to the optical encoder of the third aspect, in the optical encoder of the first or second aspect, the photocurrent signals respectively output from the light receiving cell arrays of the groups A to D are: One periodic pitch of the slit row of the detection track is a periodic signal corresponding to the electrical angle of 360 °, and the four groups of the light receiving cell arrays A and B
The four groups of light receiving cell arrays are arranged so that the phase difference between each of the groups, the groups B and C, the groups C and D, and the groups D and A is 90 ° in electrical angle.

According to the optical encoder of the fourth aspect, in the optical encoder of the third aspect,
The fourth group periodic signals I _A output from the light receiving cell array, I _B, comprises a central processing unit for calculating the I _C, the electrical angle in one cycle pitch of slit rows of the detection track using I _D theta an optical encoder, the central processing unit, periodic signals _{I a, I B, I C} , the I _D, and calculates the electrical angle θ is substituted into equation 1.

According to the optical encoder of the fifth aspect, in the optical encoder of the third aspect,
The fourth group periodic signals I _A output from the light receiving cell array, I _B, comprises a central processing unit for calculating the I _C, the electrical angle in one cycle pitch of slit rows of the detection track using I _D theta an optical encoder, the central processing unit, periodic signals _{I a, I B, I C} , the I _D, equation 2
(M, n, p are constants) to calculate the electrical angle θ.

According to the optical encoder of the sixth aspect, in the optical encoder of the fifth aspect,
It is characterized in that the constant satisfies the condition of (mn) / 2 = P.

According to a seventh aspect of the present invention, in the optical encoder according to any one of the first to sixth aspects, the slit plate has a detection track formed in a substantially linear shape. A substantially rectangular slit plate to be disposed, wherein the light-emitting element and the light-receiving element move along the fixed slit plate in a linear direction while facing each other, and the linear encoder detects a displacement in the linear direction. It is characterized by.

According to the optical encoder described in claim 8, in the optical encoder according to any one of claims 1 to 6, the slit plate has a substantially circular detection track. A disc-shaped slit plate to be disposed, wherein the light emitting element and the light receiving element disposed to face each other with the slit plate interposed therebetween are used as a rotary encoder for detecting a displacement amount of a rotating slit plate in a rotation direction. It is characterized by the following.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the optical encoder of the present invention, particularly, an optical rotary encoder will be described. The configuration of the optical rotary encoder of this embodiment is different from the conventional light receiving element 7 in that the light receiving element 70
This is the same as the conventional optical rotary encoder except that 0 is attached to the printed circuit board 8. Less than,
The description of the same components as those in the related art will be omitted, and only different points will be described.

The configuration of the light receiving element 700 of this embodiment will be described. FIG. 1 shows a configuration diagram of a light receiving element 700 of the present embodiment. The hatched area in FIG. 1 indicates a light receiving cell, and the other areas indicate dead zones in which no light is detected. This dead zone has at least a substantially cross-shaped dead zone, and divides the light receiving cell array group into four regions A, B, C, and D. Specifically, the lower left six light receiving cells 11 in FIG.
1, a light receiving cell array A group 18 composed of six light receiving cells 21 to 26 in FIG. 1, and a light receiving cell array B group 28 composed of six light receiving cells 21 to 26 in FIG. Light receiving cell array C group 3 composed of 36
8 and a light receiving cell array D group 48 composed of six light receiving cells 41 to 46 on the upper right side of FIG.
The light receiving cells of the A group 18, the B group 28, the C group 38 and the D group 48 are electrically connected in parallel.

One period pitch 5 between two adjacent light receiving cells
1 (= P) is a value determined by the number of slits provided on the detection track 5 a of the slit disk 5. Further, assuming that one period pitch P is between two adjacent light receiving cells, 51 is P, 52 is 0.25P, 53 is 0.5P, 5
4 is a distance of 1.25P.

By arranging in this manner, one period pitch of the slit row of the detection track is a periodic signal corresponding to the electrical angle of 360 °, and the phase difference between the groups A and B is (90)
+ Α × 360) ゜, the phase difference between the groups A and C is (18)
0 + β × 360) ゜, the phase difference between group A and group D is (2
70 + γ × 360) ゜. Where α,
β and γ are arbitrary arbitrary integers. In this embodiment, the phase difference between the groups A and B is 90 °, the phase difference between the groups A and C is 180 °, and the phase difference between the groups A and D is 270 °.

FIG. 2 shows A of the light receiving cell array of the present embodiment.
A circuit configuration diagram of the group 18, the B group 28, the C group 38, the D group 48 and its peripheral parts is shown. In FIG. 2, group A, B
Power supply (V _cc ) is applied to the cathode side of group 28, group C 38 and group D 48.
Are connected to form a reverse bias connection. On the other hand, the anode side of the A group 18 is connected to an A / D converter (not shown) in the current / voltage conversion resistor 19 and the CPU 100, and the other end of the current / voltage conversion resistor 19 is grounded. ing. Similarly, the B group 28 is connected to the current / voltage conversion resistor 29, and the C group 38 is connected to the current / voltage conversion resistor 3
9 and the D group 48 is connected to the current-voltage conversion resistor 49. These have the same circuit configuration as the group A 18.

Next, the operation of the optical rotary encoder will be described. As shown in FIGS. 4A and 4B, L
It is assumed that the irradiation light emitted from the ED 6 passes through the slit of the detection track 5 a of the slit disk 5 and reaches the light receiving element 700. The light receiving element 700 outputs a photocurrent signal in proportion to the amount of the irradiation light that has reached. The photocurrent signal from the light receiving element 7 is, as shown in FIG.
At 9, 29, 39 and 49, it is converted into a voltage signal,
00 is converted from an analog signal to a digital signal by an A / D converter (not shown) built in
It is taken in.

FIG. 3 shows an analog voltage signal before being taken into the CPU 100. The vertical axis indicates the voltage signal obtained by converting the photocurrent signal from the light receiving element 7 by the current-voltage conversion resistors 19, 29, 39, and 49, and the horizontal axis indicates the rotation direction of the optical rotary encoder. The A-phase signal 181 is a signal obtained by converting the photocurrent signal from the A-group 18 of the light receiving cell array into a voltage signal.
8, a C-phase signal 381 is added to the voltage signal corresponding to the photocurrent signal.
Is a voltage signal corresponding to the photocurrent signal of the C group 38, and the D-phase signal 481 is a voltage signal corresponding to the photocurrent signal of the D group 48.

These A-phase signal 181, B-phase signal 281,
One cycle of C-phase signal 381 and D-phase signal 481 (electrical angle = 3
60 °) corresponds to the movement amount of one period pitch of two adjacent slits in the detection track of the slit disk. The A-phase signal 181, the B-phase signal 281, the C-phase signal 381, and the D-phase signal 481 have a phase difference as described above, and can be expressed by the following equation.

[0040]

(Equation 7)

[0041] Here I _A is A-phase signal, I _B is B-phase signals, I
_C is the C-phase signal, _ID is the D-phase signal, X is the offset voltage of the A-phase signal, B-phase signal, C-phase signal, and D-phase signal, and Y is the A-phase signal, B-phase signal, C-phase signal, D Signal amplitude of phase signal, ΔX
_A , ΔX _B , ΔX _C , ΔX _D are offset voltage amount errors, ΔY
_A , ΔY _B , ΔY _C , ΔY _D are signal amplitude errors, Δθ _A , Δ
θ _B , Δθ _C , and Δθ _D are phase errors. is the electrical angle of the rotation angle θ of the optical rotary encoder at a certain timing, and when θ changes by 360 °, it corresponds to the case where the slit disk moves by one pitch of the slit. Is a lower signal of a division unit smaller than one cycle pitch.

Next, the principle of angle detection when the slit disk of the optical rotary encoder makes one rotation (mechanical angle of 360 °) will be described. This optical rotary encoder generates an upper-level signal by the signal processing of the CPU 100 described above. Specifically, A-phase signal I _A shown in FIG. 3, B-phase signal I _B, C-phase signal I _C, or,, D-phase signal I _D
Is input to the CPU 100 via an A / D converter (not shown), and is shaped into a square wave by digital signal processing to be a pulse signal. This pulse signal is a signal in which the H level and the L level alternately appear according to the presence or absence of the slit.

The CPU 100 performs arithmetic processing on the A-phase signal I _A , the B-phase signal I _B , the C-phase signal I _C , or the D-phase signal _ID, and generates a lower signal having a higher resolution than the previous upper signal. Generate. More specifically, the principle of derivation of Equation 1 will be described. First, A
Phase signal I _A and the B phase signal I _B signals signal to remove the offset voltage amount X94 from I _'A, I' make _B, and calculating the arctangent of the signal ratio. The lower signal is represented by the following equation.

[0044]

(Equation 8)

Equation 8 can be modified as follows.

[0046]

(Equation 9)

The signals I ' _A and I' _B are represented by the following equations.

[0048]

(Equation 10)

By substituting the signals I ' _A and I' _B of the equation (10) into the equation (9), the following equations are obtained.

[0050]

[Equation 11]

Subsequently, the equation (11) is operated as follows.

[0052]

(Equation 12)

Here, the formula of the trigonometric function is shown.

[0054]

(Equation 13)

By manipulating equation 12 using equation 13,
It is converted as follows:

[0056]

[Equation 14]

Here, the denominator and the numerator are converted into variables M and N as shown in the following equations.

[0058]

(Equation 15)

Then, Equation 14 is expressed as the following equation.

[0060]

(Equation 16)

On the other hand, the photocurrent signals obtained from the light receiving cell arrays of the groups A, B, C, and D are expressed by the following equations, respectively, obtained by modifying the equation (7).

[0062]

[Equation 17]

Subsequently, error components included in the photocurrent signals output from the light receiving cell arrays of the groups A, B, C and D are averaged. Using Equation 17, the following equation is used.

[0064]

(Equation 18)

Using M1 and M2 thus obtained, a sum is obtained as in the following equation.

[0066]

[Equation 19]

Here, the errors of ΔX _A , ΔX _B , ΔX _C and ΔX _D cancel each other to reduce the offset voltage error. Further, ΔX and X, ΔY and Y, and Δθ and θ have sufficiently small errors, and thus have the relationship shown in the following equation.

[0068]

(Equation 20)

Therefore, it can be expressed as M1ＭM2, and can be expressed as the following equation.

[0070]

(Equation 21)

Subsequently, similarly to the equations (18) and (19), the equation (1)
7, the following equation is used.

[0072]

(Equation 22)

Using N1 and N2 obtained in this manner, a sum is obtained as in the following equation.

[0074]

(Equation 23)

Here, the errors of ΔX _A , ΔX _B , ΔX _C and ΔX _D cancel each other to reduce the offset voltage error. Further, ΔX and X, ΔY and Y, Δθ and θ are N1 ≒ − (− N2) because the error is sufficiently small, so that they can be expressed by the following equation.

[0076]

(Equation 24)

By substituting equations (21) and (24) into equation (16), the following equation can be obtained.

[0078]

(Equation 25)

Therefore, the electrical angle θ serving as the lower signal is expressed by the following equation.

[0080]

(Equation 26)

The CPU 100 substitutes the A-phase signal I _A , the B-phase signal I _B , the C-phase signal I _C , or the D-phase signal I _D input via an A / D converter (not shown) into Equation 26. , An electrical angle θ, which is a lower signal having a higher resolution than the previous upper signal. In this embodiment, the upper signal and the lower signal can be obtained in this way. By combining these upper signal and lower signal, it becomes possible to realize an optical rotary encoder capable of detecting a displacement amount with high resolution.

Next, a second embodiment of the present invention will be described. In the present embodiment, the averaging of the error component is performed by changing the content of the arithmetic processing. First, Expression 16 described in the first embodiment is modified as follows.

[0083]

[Equation 27]

Further, the right and left sides of the numerator of the equation (27) are modified as follows.

[0085]

[Equation 28]

Equations (28) to (27) are transformed as follows.

[0087]

(Equation 29)

By substituting M1 and M2 obtained by Expression 18 and N obtained by Expression 24 into Expression 29, the following modification is made.

[0089]

[Equation 30]

Therefore, the electrical angle θ is expressed by the following equation.

[0091]

(Equation 31)

When such a division method in Expressions 27 and 28 is changed to a general expression, the following expression is obtained.

[0093]

(Equation 32)

Here, m, n, and p satisfy the following relationship.

[0095]

[Equation 33]

Here, in the second embodiment, m = 3, n =
1, p = 1. These m, n, and p are determined by the designer according to the required accuracy of the optical rotary encoder and the CPU 1.
It can be arbitrarily set in consideration of the processing capacity of 00 and the like. As described above, the CPU 100 controls the A / D (not shown).
A-phase signal I _A , B-phase signal I _B ,
By substituting the C-phase signal I _C or the D-phase signal _ID into Equation 32, an electrical angle θ which is a lower signal having a higher resolution than the previous upper signal is generated. In the present embodiment, it is possible to realize an optical rotary encoder that can detect a high-resolution displacement amount by combining the upper signal and the lower signal.

As described above, in the optical rotary encoders of the first and second embodiments, the CPU 100 calculates the upper signal and the lower signal, and by using these, the position can be determined with high resolution and the corresponding signal can be output. . Also, C
The PU 100 may output the upper signal or the lower signal independently. These outputs can be appropriately selected according to requirements.

Although not shown, even if the CPU 100 does not have a built-in A / D converter,
Comparators A, B, C, D
It can also be arranged and used for groups. The presence or absence of the comparator is appropriately designed according to the CPU 100.

In the first and second embodiments, 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.

[0100]

As described above, according to the present invention, it is possible to avoid a situation in which an angle error occurs in the electrical angle of the lower signal due to an assembly error, a variation in the sensitivity of the light receiving element, unevenness in the illumination of the LED, etc. An optical encoder realizing high-resolution detection can be provided.

[Brief description of the drawings]

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

FIG. 2 is a circuit configuration diagram of groups A, B, C, and D of a light receiving cell array of an optical rotary encoder according to an embodiment of the present invention and peripheral components thereof.

FIG. 3 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. 4 is a configuration diagram of an optical rotary encoder.

FIG. 5 is a configuration diagram of a light receiving element of a conventional optical rotary encoder.

FIG. 6 is a circuit configuration diagram of groups A and B of a light receiving cell array of a conventional optical rotary encoder and peripheral components thereof.

FIG. 7 is 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 5 Slit disk 5a Detection track 6 LED 700 Light receiving element 8 Printed circuit board 18 Light receiving cell array A 28 Light receiving cell array B 38 Light receiving cell array C 48 Light receiving cell array D 11-16 Light receiving cells 21-26 Light receiving cells 31 to 36 Light receiving cells 41 to 46 Light receiving cells 51 Pitch between cells P 52 0.25P 53 0.5P 54 1.25P 19, 29, 39, 49 Current / voltage conversion resistor 90 A phase and B phase Phase difference 91 A phase amplitude 92 B phase amplitude 93 Offset voltage error amount 94 Offset voltage amount 95 One cycle length of B phase 181 A phase signal 281 B phase signal 381 C phase signal 481 D phase signal

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasumitsu Nagasaka 1-1-1, Tanabe-Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fuji Electric Co., Ltd. (72) Inventor Tohru Yoshizawa 2-24-16 Nakamachi, Koganei-shi, Tokyo University of Agriculture and Technology (72) Inventor Yukitoshi Otani 2-24-16 Nakamachi, Koganei-shi, Tokyo F-term (reference) 2F103 BA00 BA07 CA01 CA02 DA12 DA13 EA12 EA15 EB06 EB12 EB16 ED01 ED27 FA00 FA16 FA17

Claims (8)

[Claims] A light-emitting element; a light-receiving element disposed at a position facing the light-emitting element to receive light emitted from the light-emitting element; and a slit array for transmitting and blocking light emitted from the light-emitting element. An optical encoder comprising: a slit plate having a detection track comprising: a light-receiving element, wherein the light-receiving element is formed by dividing light-receiving cells arranged on a two-dimensional plane into four groups by a substantially orthogonal dead zone; , B
Group, C group and D group, and four groups of light receiving cell arrays are arranged such that photocurrent signals output from the four groups of light receiving cell arrays become periodic signals having different phases. Characteristic optical encoder. 2. The optical encoder according to claim 1, wherein said one group of light receiving cell arrays has a plurality of light receiving cells arranged periodically, and a period pitch of said plurality of light receiving cells is equal to that of said slit plate. An optical encoder characterized in that it has the same length as the periodic pitch of a slit row of a detection track. 3. The optical encoder according to claim 1, wherein a photocurrent signal output from each of the light receiving cell arrays of the groups A to D has an electric pitch of one period of a slit row of a detection track. A periodic signal corresponding to an angle of 360 °, and the four groups of light receiving cell arrays A and B, B and C
An optical encoder, wherein the four groups of light receiving cell arrays are arranged such that the phase differences between the groups, the C and D groups, and the D and A groups each have an electrical angle of 90 °. 4. The optical encoder according to claim 3, of the output from the four groups of light receiving cell array periodic signals _{I A, I B, I C} , slit rows of the detection track using I _D 1 an optical encoder comprising a central processing unit for calculating the electrical angle θ in the cycle pitch, the central processing unit, periodic signals _{I a, I B, I C} , ## EQU1 ## the I _D An optical encoder characterized in that the electrical angle θ is calculated by substituting the electric angle into the electric angle θ. 5. The optical encoder according to claim 3, of the output from the four groups of light receiving cell array periodic signals _{I A, I B, I C} , slit rows of the detection track using I _D 1 an optical encoder comprising a central processing unit for calculating the electrical angle θ in the cycle pitch, the central processing unit, periodic signals _{I a, I B, I C} , equation 2] the I _D (M, n, p are constants) to calculate the electrical angle θ. 6. The optical encoder according to claim 5, wherein the constant satisfies a condition of (mn) / 2 = P. 7. The optical encoder according to claim 1, wherein the slit plate is a substantially rectangular slit plate on which detection tracks are arranged substantially linearly. An optical encoder, wherein a light-emitting element and a light-receiving element move in a linear direction while being opposed to each other along a fixed slit plate to detect a displacement in the linear direction. 8. The optical encoder according to claim 1, wherein the slit plate is a disk-shaped slit plate on which detection tracks are arranged in a substantially circular shape. An optical encoder, characterized in that the optical encoder is a rotary encoder that detects the amount of displacement of the rotating slit plate in the rotation direction by the light emitting element and the light receiving element arranged to face each other with the slit plate interposed therebetween.