JPH11325968A - Fixed slit structure for optical encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove high order components of analog encoder signal obtained from a light receiving element by dividing a fixed slit part and arranging the divided slit parts along the rotational angle of a rotary disc while shifting from each other. SOLUTION: Each slit part 1A, 1B of a fixed slit 1 comprises four divided slit parts S1-S4 continuous along the radial direction A of a rotary disc. The slit parts S1-S4 are arranged along the rotational direction B of the rotary disc such that they are located at different rotational angle positions. More specifically, the slit parts S1-S4 are arranged along the rotational angle of the rotary disc while being shifted from each other such that high order components of analog encoder signal are removed. Consequently, an analog encoder signal approximate to sine wave from which undesired high order components are removed can be obtained using a smaller number of slit parts 1 resulting in a highly accurate small encoder having high resolution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixed slit structure of an optical encoder, and more particularly to a method for removing a high-order component of an analog encoder signal obtained from a light receiving element even in a small-sized structure having a small number of slit portions. To a new improvement to be able to.

[0002]

2. Description of the Related Art As a fixed slit structure of an optical encoder of this type which has been conventionally used, for example, a method for removing distortion of an encoder signal disclosed in Japanese Patent Laid-Open No. 6-26885 shown in FIG. be able to. That is, as shown in FIG. 4, the respective slits S _{1 to} S ₄ of the fixed slit 1 are provided at unequal intervals (P / 6, P / 4, 5 / 12P in the rotation direction of the rotary disk, and S
_The phase of S ₂ (S ₄ ) is shifted by π / 3 with respect to ₁ (S ₃ ),
S ₃ (S ₄ ) is provided at a position shifted in phase by π / 2 from S ₁ (S ₂ ). The encoder signal generated from the unequally-spaced fixed slit 1 shown in FIG.

[0003]

(Equation 1)

Next, a description will be given of a method of removing the distortion of the nth-order component (n> 2) from the signal shifted in position by π / n. First, the first signal A having a distortion obtained by the slit 1 of FIG. 3 is a _{A = a 1 sinθ + a n} sin (nθ),
Next, a second signal A ′ whose phase is shifted by π / n is prepared. This second signal A ′ = a ₁ sin (θ + π / n) + a
_n sin {n (θ + n / n)} = a ₁ sin (θ + π /
n) it is -a _n sin (nθ). Next, when the sum of the above-mentioned signals A and A ′ is calculated, A + A ′ = a ₁ sin θ + a
₁ sin (θ + π / n) = 2 a ₁ cos (π / 2n) s
in (θ + π / 2n), and the sum of the signals A and A ′ removes the nth-order component (n> 2) to obtain an encoder signal composed of an analog signal having only the first-order component and having no distortion. The feature of the fixed slit 1 in FIG. 4 described above, [pi / 2, create a second signal shifted by π / 3 ··· π / n, the amplitude (a _n) of the second signal is equal for all,
The above calculation of the sum (A + A ′) is performed on a light receiving element of an optical encoder (not shown). As a result, the encoder signal obtained can approach an ideal sine wave signal with extremely little distortion. By electrically dividing the sine wave signal, a high resolution encoder signal can be obtained.

When only the secondary component is removed, the first signal A, which is an encoder signal having a secondary component, is A = a ₁
to sinθ + a _n sin2θ, providing a second signal A 'whose phase is shifted by [pi / 2. A ′ = a ₁ sin (θ + π / 2) + a ₂ sin2 (θ + π / 2) = a ₁
sin (θ + π / 2) -a n sin2θ. Here, when the sum of the signals A and A ′ is obtained, A + A ′ = a ₁ sin θ + a ₁ sin (θ + π / 2) = a ₁ sin (θ + π / 4−π / 4) + a ₁ sin (θ + π / 4−) π / 4) = a ₁ {sin (θ + π / 4) cos (-π / 4) + cos (θ + π / 4) sin (-π / 4) + sin (θ + π / 4) cosπ / 4 + cos (θ + π / 4) sinπ / 4} = 2a ₁ sin (θ + π / 4) sin π / 4 = a ₁ 2 ^2/1 sin (θ + π / 4) Accordingly, 2 × odd-order components can be removed.

Further, when only the third order component is removed,
The first signal A, which is an encoder signal having the next component, is A = a
A second signal A ′ whose phase is shifted by π / _{3 with} respect to ₁ sin θ + a ₃ sin 3θ is prepared. A ′ = a ₁ sin (θ + π / 3) + a ₃ sin3 (θ + π / 3) = a ₁ si
n (θ + π / 3) −a ₃ sin3θ. Here, when the sum of the signals A and A ′ is obtained, A + A ′ = a ₁ sin θ + a ₁ sin (θ + π / 3) = a ₁ {sin (θ + π / 6) cos (−π / 6) + cos (θ + π / 6 ) sin (−π / 6) + sin (θ + π / 6) cos (π / 6) + cos (θ + π / 6) sin (π / 6)} = 2a ₁ cos (π / 6) sin (θ + π / 6) = a ₁ 3 ^2/1 sin (θ + π / 6) Therefore, 3 × odd-order components can be removed. That is, by taking the sum of the first signal including the distortion and the second signal having a phase shift of π / n, the n-order component can be completely removed, and the encoder signal consisting of the obtained almost perfect sine wave can be obtained. Is electrically divided to achieve high resolution.

[0007]

The method for removing distortion of an encoder signal in a conventional optical encoder has the following problems because it has been configured as described above. That is, in the conventional configuration shown in FIG. 4, it is advantageous that the number of slits is large, provided that each slit is uniformly irradiated with light. However, when the light receiving element is downsized due to the downsizing of the encoder as in recent years, the number of the slits of the fixed slits has to be reduced, and the influence of the unevenness of the light intensity of each slit becomes large, There has been a problem that the effect of removing higher-order components of the analog encoder signal obtained from the light receiving element is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. In particular, even in a configuration in which the number of slit portions is small and the size is reduced, a high-order component of an analog encoder signal obtained from a light receiving element is reduced. An object of the present invention is to provide a fixed slit structure of an optical encoder which can be removed.

[0009]

SUMMARY OF THE INVENTION A fixed slit structure of an optical encoder according to the present invention converts an analog encoder signal by guiding light passing through a pattern of a rotating disk to a light receiving element through a slit portion of the fixed slit. In the fixed slit structure of the optical encoder, the slit portion is divided into a plurality of portions along the radial direction of the rotating disk to form divided slit portions, and each of the divided slit portions has a height of the analog encoder signal. The slits are arranged so as to be shifted from each other along the rotation angle of the rotating disk so that the next component is removed, and the slits are arranged at equal intervals from each other.
, P / 6, P / 4, 5 / 12P (P is the pitch of each slit), and the slits are divided into two in the radial direction. Each slit piece is composed of four of the divided slit portions.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a fixed slit structure of an optical encoder according to the present invention will be described below with reference to the drawings. Note that the same or equivalent parts as those in the related art will be described using the same reference numerals. In FIG.
Is a fixed slit, and this fixed slit 1 comprises first and second slit portions 1A and 1B (arbitrary number), and each slit portion 1A and 1B is formed in a radial direction of a well-known rotating disk (not shown). A is composed of four divided slit portions S _{1 to} S ₄ which are continuous with each other and divided along A.
Each of the split slits S _{1 to} S ₄ is disposed at a different rotation angle position along the rotation direction B of the rotating disk,
S ₁ and S ₂ are P / 16, S ₂ and S ₃ are P / 4, S ₃ and S ₄ are 5
/ 12P (P is a pitch between the slits 1A and 1B).

That is, each of the divided slit portions S _{1 to} S ₄
Has the same configuration in principle as the slits S _{1 to} S ₄ of the conventional configuration shown in FIG. 4, and according to the well-known principle described in the conventional example,
Higher order components of the analog encoder signal can be removed.

In another embodiment shown in FIG. 2, the slit portion 1A of FIG. 1 is composed of first and second slit pieces 30, 31 divided into two in the radial direction of the rotating disk. , 31 together are composed of divided slits S ₁ to S ₄ which are the same division as in FIG. 1, similarly formed each interval the Figure 1 in the rotational direction B of the divided slit sections S ₁ to S ₄ Have been. Further, in another embodiment shown in FIG. 3, is composed of first, second slit pieces 30 and 31 Metropolitan which likewise slit portion 1A and FIG. 2 is made of each division slit portions S ₁ to S _4, and each The slit pieces 30 and 31 are formed in a V shape. The output principle of the analog encoder signal is the same as in FIG.

[0013]

Since the fixed slit structure of the optical encoder according to the present invention is configured as described above, the following effects can be obtained. In other words, since the slit portion of the fixed slit is formed by a plurality of divided slit portions, an analog encoder signal closer to a sine wave is obtained by removing unnecessary high-order components even with a smaller number of slit portions than in the related art. And a small, high-resolution, high-precision encoder using a small fixed slit can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a fixed slit structure of an optical encoder according to the present invention.

FIG. 2 is a configuration diagram showing another embodiment of FIG. 1;

FIG. 3 is a configuration diagram showing another embodiment of FIG. 2;

FIG. 4 is a configuration diagram showing a conventional configuration.

[Explanation of symbols]

1 fixed slit 1A · · · slit portions S ₁ to S ₄ division slits 30 and 31 first, second slit piece

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Yasushi Ono 1879 Okyu, Iida City, Nagano Prefecture Inside Tamagawa Seiki Co., Ltd.

Claims (3)

[Claims] An optical encoder for obtaining an analog encoder signal by guiding light passing through a pattern of a rotating disk to a light receiving element through a slit portion (1A ...) of a fixed slit (1). in the stationary slit structure, the slit portion (1A · · ·) in the radial direction of the rotary disk to form a dividing slit portion is divided into a plurality (S ₁ to S _4), wherein each of the divided slit portions ( S _{1 to} S ₄ ) are arranged so as to be shifted from each other along the rotation angle of the rotating disk so that higher-order components of the analog encoder signal are removed, and the slit portions (1
A ...) are fixed slit structures of the optical encoder, wherein the fixed slit structures are arranged at equal intervals to each other. 2. The method according to claim 1, wherein each of the divided slit portions (S _{1 to} S ₄ ) is composed of four, and is shifted from each other by P / 6, P / 4, 5 / 12P (P is an interval between the slit portions). Claim 1
The fixed slit structure of the optical encoder described in the above. 3. The slit portion (1A...) Comprises first and second slit pieces (30, 31) divided into two in the radial direction, and each slit piece (30, 31) has four pieces. The split slit part
Fixed slit structure of an optical encoder according to claim 1, wherein (S ₁ to S ₄₎ made it more.