JP2003177036A - Photoelectric encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an photoelectric encoder which makes the transmission factor of a scale have a desired property easily. <P>SOLUTION: This encoder is provided with a light emitting portion 13 for receiving light from a light generation means 6 via a transmission portion 10c of a code disk 11. A reduced value W of the width of each nontransmission part 9a into an angle is made constant. A first reduced value which is a reduced value into an angle of the distance from an n-th nontransmission part 9a up to an (n+1)-th nontransmission part 9a, is represented as P<SB>n</SB>, an angle based on the position of the nontransmission part 9a formed for the n-th time is represented as θ<SB>n</SB>, and the transmission factor of the code disk 11 is represented by a function T(θ<SB>n</SB>) of the angle θ<SB>n</SB>. The nontransmission part 9a is formed at a position of the first reduced value P<SB>n</SB>, and the angle θ<SB>n</SB>determined by the following recurrence formula T(θ<SB>n</SB>)=(P<SB>n</SB>-W)/P<SB>n</SB>θ<SB>n+1</SB>=θ<SB>n</SB>+P<SB>n</SB>. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric encoder (hereinafter appropriately referred to as an encoder) which is attached to a rotating shaft of a motor and used for detecting the position of the rotating shaft.

[Prior art]

A conventional encoder is disclosed in Japanese Patent Application Laid-Open No. 60-1401.
This will be described with reference to Japanese Patent Publication No. The encoder described in the publication uses the fact that the light quantity of the light receiving section changes in accordance with the relative movement amount of the fixed section having the pattern (optical grating) and the scale having the pattern (code disc). It is configured to detect the rotation angle of the scale. Here, the pattern is formed by providing a large number of V-shaped protrusions on the fixed portion and the scale, the protrusions acting as non-transmissive portions of light, and the flat portions acting as transmissive portions of light. Therefore, the encoder can be manufactured with a simple structure.

[0003]

However, the encoder has a complicated structure because the encoder and the scale must be provided with patterns. Here, if the fixed part is omitted and the encoder is configured only with the scale, the pattern has the transmissive part and the non-transmissive part formed by repeating the constant width and the constant interval. Regardless, it becomes constant, the output of the light receiving unit becomes constant, and the problem that the rotation angle cannot be detected occurs.
Therefore, it is conceivable to detect the rotation angle of the scale by forming the transmittance of the scale into a sine wave or the like corresponding to the rotation angle. However, there is a problem in that it is not easy to determine the width of the non-transmissive part and the transmissive part where the pattern of the scale is to be formed, and how to repeat the non-transmissive part and the transmissive part.

On the other hand, the encoders described in JP-A-64-88313 and JP-A-64-88314 are provided with grating tracks having different light non-transmission and transmission ratios or the same pitch. A scale that diffracts parallel light emitted by a photoelectric device, and a photoelectric conversion unit that receives a plurality of diffracted lights of different orders among the diffracted lights diffracted by the scale and converts the diffracted light into an electric signal corresponding to the intensity of each diffracted light. And consists of. The encoder obtains a large number of diffracted lights of different orders through a scale for parallel light generated from a laser having coherence, receives the diffracted light, and converts the diffracted light of each order by a photoelectric conversion unit. Since the electric signal is converted into an electric signal according to the intensity, an electric signal such as a sine wave can be obtained as the scale moves.

However, since the encoder uses diffraction, it is indispensable to generate coherent light such as a laser. Therefore, there is a problem that it cannot be applied to an encoder that uses incoherent light generated from a light emitting diode or the like.

The present invention has been made in order to solve the above problems, and uses a non-coherent light generating means, has a plurality of transmitting portions of a constant length, and has a constant length that does not transmit the light. It is an object of the present invention to provide a simple optical encoder that easily generates scale position information by giving a scale having a plurality of non-transmissive portions having a desired transmittance characteristic.

[0007]

Means for Solving the Problems, Action and Effect of the Invention The optical encoder according to the first invention comprises a light generating means for generating incoherent light and a fixed length for transmitting the light. A plurality of transmissive portions, and a plurality of non-transmissive portions having a fixed length that does not transmit the light, and a scale in which position information is generated by the transmissive portions and the non-transmissive portions, and the light, A first conversion in which a width of the non-transmissive portion is converted into an angle, which includes a light receiving unit that receives light through a scale, a light generation unit, and a relative movement mechanism that relatively moves the light receiving unit and the scale. A value W is constant, a second conversion value obtained by converting the distance from the nth to the n + 1th of the non-transmissive portion into an angle is P _n, and the second value based on the position of the non-transmissive portion provided at the nth position is set. The angle of 1 is θ _n , _Let T (θ _n ) = (P _n −W) / P _n θ _{n + 1} = θ _{n, where} T is the function of the first angle θ _n , T (θ _n ) [T (θ _n ) is not constant). + P _n, the first angle θ _n determined by the recurrence formula, and the second angle
The non-transmissive portion is provided at the position of the converted value P _n . The function T (θ _n ) is excluded from being constant because the relative movement position between the scale and the light receiving means cannot be detected if the transmittance (θ _n ) of the scale is constant. According to such an optical encoder, the transmittance of the scale is defined as a function T (θ _n ) of the first angle θ _n , and the first conversion value W obtained by converting the width of the non-transmission part into an angle is set to a constant value. Based on the formula, the first angle θ _n and the second conversion value P _n
Since the non-transmissive portion is provided at the position obtained by, the scale having a desired transmittance can be easily manufactured. Therefore, since the light receiving means receives the light generated from the light generating means via the scale having a desired transmittance, it is possible to generate the desired output characteristic of the light receiving means based on the position information of the scale. Moreover, since the non-coherent light generating means is used and the positional information including the transmitting portion and the non-transmitting portion is provided only in the scale, there is an effect that a simple optical encoder can be obtained.

An optical encoder according to a second aspect of the invention has a plurality of light generating means for generating incoherent light and a plurality of transmitting portions having a certain length for transmitting the light, and transmitting the light. Not having a plurality of non-transmissive portions having a constant length, a scale for which positional information is generated by the transmissive portions and the non-transmissive portions, a light receiving means for receiving the light through the scale, and the light A third conversion value P obtained by converting the distance between the adjacent non-transmissive parts into an angle is set to be constant, and the nth position is provided. The first angle based on the position of the non-transmissive portion provided is θ _n, and the transmittance of the scale is a function T (θ _n ) [T of the first angle θ _n.
(θ _n ) is not constant], and is determined by the following equation as a fourth conversion value W _{n obtained} by converting the width of the non-transmissive portion provided at the n-th position into an angle, T (θ _n ) = ( P−W _n ) / P The non-transmissive portion having the width of the fourth converted value W _n is provided at the position of the first angle θ _n . The reason why the function T (θ _n ) is not constant is for the same reason as in the first invention. According to such an optical encoder, the transmittance of the scale is determined as the function T (θ _n ) of the first angle θ _n , the third conversion value P is constant, and
The fourth conversion value W is set at the position of the first angle θ _n based on the above equation.
_{Since the} non-transmissive portion having a width of _n is provided, a scale having a desired transmittance can be easily manufactured. Therefore, since the light receiving means receives the light generated from the light generating means via the scale having a desired transmittance, it is possible to generate the desired output characteristic of the light receiving means based on the position information of the scale. Moreover, since the non-coherent light generating means is used and only the scale is provided with the pattern including the transmissive portion and the non-transmissive portion, there is an effect that a simple optical encoder can be obtained.

An optical encoder according to a third aspect of the present invention is the optical encoder according to the first or second aspect of the invention, wherein T (θ _n ) is the following equation, where T _{max and} T _min are the maximum and minimum values of transmittance, respectively. It is characterized in that T (θ _n ) = (T _max + T _min ) / 2 + {(T _max −T _min ) sin
θ _n} / 2 wherein T (theta _n) the T in the first aspect of the present invention _{(θ n) = (P n} -W)
If the second conversion value _Pn is obtained by substituting it into / _Pn , the following equation is obtained: _Pn = W / [1- ( _Tmax + _Tmin )] / 2-{( _Tmax- T
_min ) sin θn} / 2] second converted value P _n and θ _{n + 1} = θ _n in the first invention
The first angle θ _n and the second angle obtained by the recurrence formula of + P _n
By producing a scale in which a non-transmissive portion is provided at a position corresponding to the converted value P _n, the transmittance of the scale can be made a sine wave with respect to the position information of the scale.

The T (θ _n ) is the T (θ _n in the second invention.
Substituting _n ) = (P−W _n ) / P and the total number of non-transmissive portions is N, the fourth conversion value W _n is given by the following equation. _{W n = P [1- (T} max + T min) / 2 - {(T max -T min) sin
θ _n } / 2] By providing the scale with a non-transmissive portion having a width based on the fourth converted value W _n at the position of the n-th angle θ _n defined by this equation, the scale transmission with respect to the position information of the scale is performed. The rate can be sinusoidal. Therefore, the transmittance of the scale is set to a sine wave with respect to the position information of the scale, so that the optical encoder according to the third invention having the output characteristic of the sine wave in the light receiving means can be easily manufactured.

The scale of the optical encoder according to the fourth aspect of the present invention is a disk shape, has a ring shape with a transmitting portion and a non-transmitting portion, and the end angle of the first angle θ _n is θ _end. When the end angle θ _end is not 360 °, the corrected second angle θ _n ′ is obtained by the following formula. [theta] _n '= [theta] _n * 360 [deg.] / [theta] _end According to the optical encoder, in the rotary system, the corrected second angle [theta] _n ' is used to match the terminal angle [theta] _end with the angle origin [theta] ₀ . be able to. Therefore, there is an effect that it is possible to easily manufacture an optical encoder that smoothes the transmittance between the start end and the end of the disk-shaped scale.

In the light receiving means of the optical encoder according to the fifth aspect of the present invention, the length in the direction of relative movement with the scale faces the plurality of non-transmissive portions, and is formed from the end portions of the non-transmissive portions. A semi-light-shielding region having a transmittance lower than that of the transmissive portion is also provided, and the semi-light-shielding region is provided between the non-transmissive portions where the second conversion value P _n or the third conversion value P has the maximum value. It is characterized in that the regions are formed so as to overlap each other. Here, that the third conversion value P is the maximum value means the third conversion value P because the third conversion value P is constant. According to such an optical encoder, the semi-shielded regions are overlapped between the non-transmissive portions where the second converted value P _n or the third converted value P is maximum, that is, in the transmissive portions where the width is maximum. Since it is formed, the light generated from the light generating means is received by the light receiving means via the non-transmissive portion and the semi-shielded area. Therefore, the difference between the minimum light intensity of the non-transmissive portion and the maximum light intensity of the quasi-light-shielding region is reduced, so that the output variation of the light receiving means can be suppressed.

The light receiving means of the optical encoder according to the sixth invention is larger than the maximum value of the second converted value P _n or the third converted value P, and the width on the side of the scale relative to the scale is at the center. It is characterized in that it is formed thinner than the portion and receives the light transmitted through the plurality of transmission portions. Here, the maximum value of the third conversion value P is the same as the above in the fifth invention. According to such an optical encoder,
When the light receiving means and the scale move relative to each other, the light receiving area of the light receiving means gradually increases, so that the output variation of the light receiving means can be suppressed and the resolution can be improved.

The non-transmissive portion of the optical encoder according to the seventh invention is V-shaped and has an inclined surface in which the incident angle from the light generating means is set to be equal to or greater than the critical angle. Is. According to such an optical encoder, there is an effect that the non-transmissive part and the transmissive part of the scale can be easily manufactured.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. An embodiment of the present invention will be described with reference to FIGS. 1 is a perspective view of an encoder according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of each part of the code disc shown in FIG. 1, and FIG. 3 is a non-transparent portion of the code disc shown in FIG. FIG. 4 is a side sectional view for modulating the pitch distance of the non-transmissive portion. 1 to 3, the photoelectric encoder is an LED (light emitting diode) 3 as a light generating means for generating light having incoherence.
And a lens 5 for converting the light emitted from the LED 3 into substantially parallel light and a rotary shaft 7 as a moving body, and
Code disc 11 having pattern 9 as position information
(Scale) and the LED 3 and the code disk 11, and a substantially rectangular light-receiving portion which is provided at a position facing the LED 3 and the code disc 11 and has an area sufficiently larger than the spread of diffraction and has a diffraction angle of at least the third-order light. 13 and 13. Here, the LED 3, the lens 5, and the light receiving part 13 are fixed, and the LED 3, the lens 5, the light receiving part 13 and the code disk 11 are relatively moved by rotating the code disk 11 by the rotation shaft 7. A relative movement mechanism is formed. The LED 3 and the lens 5 may form the light generating means 6.

The code disk 11 is made of, for example, a polycarbonate resin, and the pattern 9 is ring-shaped and comprises a non-transmissive portion 9a that does not transmit light and a transmissive portion 10c that transmits light. Is a projection having a V-shaped cross section and is formed in a substantially rectangular shape (A in FIG. 3), and the transmissive portion 10c is a substantially rectangular shape formed by flat portions provided between the V-shaped projections (see FIG. 3). In, the non-transmissive portion 9a and the transmissive portion 10c are formed to have the same radial length Lr. The inclination angle of the V-shape of the non-transmissive portion 9a is set so that the incident angle θ _{in of the} light ray that is perpendicularly incident on the surface of the code disk 11 becomes larger than the critical angle as shown in FIG. 2 (c). The critical angle is a specific value determined by the material forming the code disk 11, and since the material is polycarbonate resin, the refractive index is about 1.58 and about 40 °. Therefore, if the inclination angle of the V-shape is set to 45 °, it is possible to obtain the non-transmissive portion 9a that does not transmit (reflects in this example) the light of the light beam that is incident perpendicularly to the surface of the code disk 11.

The transmittance of the code disk 11 is determined by the transmission part 10
c, the projected area of the non-transmissive portion 9a (the above-mentioned approximately rectangular area), but since the radial lengths Lr of the transmissive portion 10c and the non-transmissive portion 9a are equal, the transmissive portion 10c and the non-transmissive portion 9a Determined by width. In the code disc 11, the distance between the center of the non-transmissive portion 9a (the tip of the V-shaped protrusion) and the center of the non-transmissive portion 9a, that is, the pitch as shown in FIGS. 2 (a) to 2 (c). A pattern 9 having a high transmittance portion having a long distance and a low transmittance portion having a short pitch distance is provided.

Now, in FIG. 3, the width of the non-transmissive portion 9a is
The first conversion value W (°) converted to an angle is fixed and the transmission part
The width of 10c is modulated, that is, the non-transmissive portion 9a and the non-transmissive portion
By modulating (changing) the pitch distance from 9a
Rotation angle of the code disk 11 by modulating the transmittance of the disk 11
I try to get the degree of position. At the angle of the non-transmissive part 9a
The position based on the center of the V-shaped protrusion, that is, the tip of the protrusion
Angle origin θ that is the end and serves as a predetermined reference (origin)₀
Is 0 °, for example, and the position where the n-th non-transmissive portion 9a is provided
Based on the angle, that is, the first converted position into an angle
Angle θ_n(°) and the transmittance of the cord disc 11 is
Angle θ_nFunction of T (θ_n) And the n-th non-transmissive portion 9a
To the n + 1th non-transmissive portion 9a from the angle
Second conversion value P converted to_n(°) gives the following formula
It T (θ_n) = (P_n-W) / P_n  ... (1) θ_{n + 1}= Θ_n+ P_n        ... (2) Where θ_{n + 1}: Angle of the (n + 1) th non-transmissive part (°) By solving the recurrence formulas of (1) and (2) above, the first angle
θ_n,Second conversion value P _nIs obtained, so the first obtained
Angle θ_n,Second conversion value P_nThe non-transmissive part 9a at the position
It may be provided on the code disk 11. The code disk 11
Since light is received by the light receiving unit 13 via the
The amount of received light is proportional to the transmittance of the code disk 11.

Next, the structure of the pattern 9 for obtaining the code disk 11 having a desired transmittance will be described with reference to FIG. FIG. 4 is a curve diagram showing the transmittance-angle characteristics of the code disc. Since it is generally used to make the transmittance T (θ) of the angle θ at each position of the pattern 9 as the position information of the code disk 11 into a sine wave, the desired transmittance T (θ)
Is a sine wave having a DC component shown in FIG. T (θ) = (T _max + T _min ) / 2 + {(T _max −T _min ) sin θ} / 2 (3) where T _max : maximum transmittance T _min : minimum transmittance If the angle θ in the equation (3) is replaced with the first angle θ _n of the non-transmissive portion 9a to express the transmittance T (θ _n ) of the code disk 11, the following equation is established. T (θ _n ) = (T _max + T _min ) / 2 + {(T _max −T _min ) sin θ _n } / 2 (4) Substituting this equation (4) into the above equation (1), The second converted value P _{n at} the angle θ _n of 1 is given by the following equation. _Pn = W / [1- ( _Tmax + _Tmin ) / 2-{( _Tmax - _Tmin ) sin (theta) _n } / 2] ... (5) Here, the angle origin (theta) _{0 is set} to 0 degree, and non- Transmission part 9a
The first conversion value W (°) to the angle of the width of
The non-transmissive portion 9a is provided on the code disk 11 at the position of the first angle θ _n and the second conversion value P _n obtained by the expressions (2) and (5). The maximum transmittance T _max and the minimum transmittance T _min
Can be set physically from 0 to 1, but if the maximum transmittance T _max = 1 and the angle θ _n = π / 2, then
Since the denominator of the equation (5) becomes zero and the second conversion value P _n , that is, the pitch distance becomes infinite, the maximum transmittance T _max.
Must be limited to an appropriate value.

Here, in the rotary encoder,
The pattern 9 is formed on the circumference of the hard disk 11.
A non-transmissive portion 9 having a V-shaped beginning and end of the circumferential pattern 9.
Angle origin of a θ₀Must match. According to
Then, by the recurrence formula of the above equations (1) and (2) [(2) and (5)]
First angle θ that is the obtained fraction_nEnd angle θ_{e nd}
Then, the terminal angle θ_endAngle is not 360 °,
Degree origin θ₀Does not match, so to match this
Correction angle θ as the newly corrected second angle _nDown
Calculate by formula. θ_n´ ＝ θ_n× 360 ° / θ_end            ... (6) This correction angle θ_nThe non-transmissive portion 9a is provided at the position of '
11 is formed.

Next, an embodiment (numerical example) in which the transmittance T (θ _n ) of the code disk 11 is a sine wave shown in FIG. 4 will be described. Now, the maximum transmittance T _max of the code disk 11 is set to 0.
8, the minimum transmittance T _min is 0.2, the width W of the non-transmissive portion 9a is 6 (°), the number n of the non-transmissive portions 9a is 0 to 30, and the non-transmissivity is calculated by the equations (2) and (4). FIG. 5 shows the calculation results of the first angle θ _{n at} which the portion 9a is provided, the second conversion value P _n , and the correction angle θ _n ′. In the first part of this calculation process, assuming that the initial angle θ ₀ of the non-transmissive portion 9a is 0 °, the second conversion value P ₀ based on the pitch distance from the above equation (5) is as follows. P ₀ = 6 / [1− (0.8 + 0.2) / 2 − {(0.8−0.2) sin 0 °} / 2] =
12 ° Further, when the angle θ ₁ when n is 1 is obtained from the above equation (2), the following is obtained. θ ₁ = θ ₀ + P ₀ = 12 ° The angle based on the initial position of the non-transmissive portion 9a is 0 °, and n
Is zero, the second conversion value P ₁ based on the pitch distance from the above equation (5) is as follows. P ₁ = 6 / [1− (0.8 + 0.2) / 2-{(0.8−0.2) sin12 °} / 2] = 1
3.71 ° Further, when the angle θ ₂ when n is 2 is obtained from the above equation (2), it becomes the following. θ ₂ = θ ₁ + P ₁ = 12 ° + 13.71 ° = 25.71 ° In this way, the values are sequentially obtained, and the first non-transmissive portion 9a
The angle theta _n are those described in FIG. 5 that calculates a correction angle theta _{n 'by} the equation (6).

In the above embodiment, the width W of the non-transmissive portion 9a is
Is constant, that is, the width of the transparent portion 10c, that is, the non-transparent portion 9a.
The transmittance of the code disk 11 was modulated by modulating the pitch distance of. Next, an embodiment in which the transmittance of the code disk 11 is modulated by modulating the width of the non-transmissive portion 9a while keeping the third conversion value P obtained by converting the pitch distance into an angle will be described with reference to FIG. In FIG. 6, how to determine the width W _n of the non-transmissive portion 9a is as follows. First, the first angle θ _{n at} the position where the n-th non-transmissive portion 9a is provided is the third conversion value P based on the pitch distance. Since it is constant, when the total number of the non-transmissive portions 9a forming the pattern 9 is N, the following equation is obtained. θ _n = 360 ° × n / N (7) Fourth conversion value W converted into the angle of the width of the non-transmissive portion 9a
_n (°) is given by the following equation, _where T (θ _n ) is the transmittance of the code disk 11 as a function of the first angle θ _n of the non-transmissive portion 9a. T (θ _n ) = (P−W _n ) / P (8) Similarly to the above, it is generally used to make the output of the light receiving unit 13 of the code disk 11 a sine wave. Angle θ
_The transmittance T (θ _n ) as a function of _n also becomes a sine wave, and the above (4)
It will be the same as the formula, and will be listed below. T (θ _n ) = (T _max + T _min ) / 2 + {(T _max −T _min ) sin θ
_n } / 2 From the above equations (4) and (8), the fourth conversion value W _n (°) becomes the following equation. _{W n = P [1- (T} max + T min) / 2 - {(T max -T min) sin (2πn / N)} / 2] ·· (9) third based on pitch distance as described above The conversion value P is constant, the total number of the non-transmissive portions 9a forming the pattern 9 is N, and, for example, the reference angle origin θ ₀ is 0 °.
The non-transmissive portion 9a is provided on the code disc at the position of the first angle θ _n obtained by the equation (9) and the width of the fourth converted value W _n .

Next, the relationship between the light receiving portion 13 and the code disk 11 for reducing the output fluctuation δ ₁ of the light receiving portion 13 will be described with reference to FIG.
And FIG. 8. Output fluctuation δ ₁ of light receiving unit 13
Is generated every time the light receiving part 13 passes through the transmissive part 10c and the non-transmissive part 9a as the code disc 11 rotates, as shown in FIGS. Regardless, it becomes a constant value δ ₁ . Output fluctuation δ ₁ of light receiving unit 13
Can be expressed by a variation ΔR in the amount of light received by the light receiving unit 13. If the light intensity I ₀ (W / m ² ) when the light receiving unit 13 receives light only through the transmissive unit 9a and the light receiving area S (m ² ) of the light receiving unit 13 are satisfied, the following formula is established. Further, since the received light amount I ₀ · S is approximately equal to the maximum transmittance T _max , the following formula is obtained. δ ₁ = ΔR = I ₀ · S (W / L) ≈T _max (W / L) (10) Where, L: angle conversion value of light receiving section (°) In the equation (10), the length L of the light receiving portion 13 is a conversion value P _max (°) of the maximum pitch distance defined by the maximum transmittance T _max into an angle, and the length L of the light receiving portion 13 does not exist within the width L of the light receiving portion 13. When the minimum number of the transmissive portions 9a is m, the following equation is obtained. L = m · P _max ··········································································································· (10) (10) δ ₁ = ΔR≈T _max (W / m · P _max ) = T _max (W / L) (12) From this equation (12), there are m non-transmissive portions 9a in the light receiving portion 13. In this case, the length L of the light receiving unit 13 and the pitch distance P _max
Are equal to each other, that is, the non-transmissive portion 9 is included in the light receiving portion 13.
Output fluctuation δ ₁ is 1 / m compared to the case where there is one a
It is reduced to. On the other hand, the maximum transmittance T _max when m non-transmissive portions 9a exist within the length L of the light receiving portion 13 is as follows. T _max = (L-mW) / L (13)

Next, the LED 3
Assuming that there is no non-parallel component from
It However, in reality, as shown in FIG.
The width W of the non-transmissive portion 9a due to the component and diffraction_m(M)
Becomes equivalently wider and reaches the light receiving section 13,
Light from the LED 3 in the
The area that receives light due to low transmittance is defined as the semi-shielded area, and
The width D (m) of the semi-light-shielded region is given by the following formula. D = 2G tanφ + W_m          ······(14) Where φ: spread angle (°) G: Gap between code disc and light receiving part (m) The angle conversion value P of the non-transmissive portion 9a_maxAt
That is, in the transmissive portion 10c having the maximum width, the semi-shielded region
The width D of the area should overlap with the adjacent semi-shielded area.
To obtain, the following equation is obtained. D = 2G tanφ + W_m> P_max    ・ ・ ・ ・ ・ ・ (15) By satisfying this equation (13),
Due to the overlapping, the light received by the light receiving unit 13 is
At the boundary between 9a and the transmissive part 10c, there is no sudden change.
Therefore, the light receiving portion 1 that receives light through the code disk 11
The fluctuation of the light quantity of No. 3 becomes small, and as a result, the output of the light receiving unit 13
Force fluctuations can be suppressed. If this is expressed by a formula, output fluctuation
δ_TwoLet L (m) be the length of the light receiving unit 13
The maximum light intensity of the transmissive portion 10c received by 13 is I_max(W
/ M^Two), The minimum light of the non-transmissive portion 9a received by the light receiving portion 13
Strength I_min(W / m^Two) And K is a constant
Becomes   δ_Two= K (I_max-I_min) ・ S ・ (W / L) ・ ・ ・ ・ ・ ・ (16) Here, S: area of the light receiving portion (m^Two) W: Width of non-transmissive portion 9a (m) Even in the non-transmissive portion 9a, the minimum light intensity I_minRaw
It is only parallel light that is emitted from the light generating means 6
This is because a slight amount of oblique light is also generated. Equation (14) above
In, by overlapping the above semi-shielded areas,
The transmittance of the transmissive portion 10c decreases and the maximum light intensity I_maxIs low
The maximum light intensity I_maxAnd the minimum light intensity I _minThe difference with
Output fluctuation δ of the light receiving unit 13_TwoIs less.

Next, in the above embodiment, the light receiving section 13 is
Although it has a rectangular shape, as shown in FIG.
In the form, the scale is larger than the maximum value of the pitch distance.
Hit the relative movement direction of the cord plate 111 as
The width (on the side of the relative movement direction) becomes narrower toward the end
By forming it, the output of the light receiving unit 113 is smoothed.
Explain that. The light receiving portion 113 formed in this way
Each non-transmissive part 9a, 9b, 9c, 9d, 9e is a code
The light receiving unit 113 (light receiving unit
13) The light receiving part 113 (light receiving part 13) when moving
Each output from_a, O_b, O_c, O _d, O_eOpposite angle θ
The output characteristic curve is shown in Fig. 11 (a).
The synthesis of each output of 113 is the synthesis output O_tAs shown in FIG.
The output characteristics are as shown in (b). Against this
12 (a) and 12 (b) show the output characteristics of the rectangular light receiving unit 13.
As shown. As a result, the diamond-shaped light receiving unit 113 has a long
A smooth output can be obtained as compared with the rectangular light receiving unit 13.
Therefore, high resolution detection is possible. This is the light receiving unit 113
The light receiving area of the light receiving region 113 gradually increases with the width of the light receiving portion 113.
Therefore, it is possible to reduce the rate of change in the amount of received light.
is there. The shape of the light receiving unit 113 is not limited to the rhombus,
The width corresponding to the relative movement direction side of the code plate 111 is directed toward the end.
It should be formed narrower as it goes, and it has a sinusoidal and exponential relationship.
The shape may be numerical or the like. In the above embodiment, the phase
LED3, lens 5, and light receiving portion 13 are fixed to the pair moving mechanism.
And the cord disc 11 is rotated by the rotating shaft 7.
However, on the contrary, the code disc 11
Is fixed, and the LED3 and LED are attached to a moving body (not shown).
LED 5 and lens by connecting lens 5 and light receiving unit 13
5, the light receiving part 13 is simultaneously formed on the pattern 9 of the code disk 11.
You may comprise so that a front surface and a back surface may move. Also on
In the embodiment, a rotary optical encoder is used.
However, linear optical encoders are also suitable.
Can be used.

[Brief description of drawings]

FIG. 1 is a perspective view showing an overall configuration of an encoder according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the non-transmissive portions of the cord disc shown in FIG.

FIG. 3 is a cross-sectional view in which the width of the non-transmissive portion of the code disk shown in FIG. 1 is constant and the pitch distance of the non-transmissive portion is modulated (changed).

4 is a curve diagram in which the relationship between the transmittance and the angle of the code disk shown in FIG. 1 is a sine wave.

5 is a chart showing a numerical example in which the relationship between the transmittance and the angle of the code disc shown in FIG. 4 is a sine wave.

6 is a side view in which the pitch distance of the non-transmissive portion of the code disk shown in FIG. 1 is constant and the width of the non-transmissive portion is modulated (changed).

FIG. 7 is a curve diagram of transmittance versus angle of a code disc conceptually showing the output fluctuation of the light receiving unit shown in FIG.

8 is a plan view showing the relationship between the code disc shown in FIG. 1 and a light receiving portion.

FIG. 9 is a cross-sectional view of a code disc showing the overlap between adjacent semi-light-shielding regions in the width D of the semi-light-shielding regions at the maximum pitch P _max .

FIG. 10 is a plan view showing a relationship between a code plate and a light receiving unit according to another embodiment of the present invention.

FIG. 11 is a diagram illustrating the output versus angle (a) and the combined output versus angle (b) of the rhombus-shaped light receiving unit according to another embodiment of the present invention.
Is a characteristic curve of.

FIG. 12: Each output versus angle of the light receiving portion formed in a rectangular shape
(a) is a characteristic curve of combined output vs. angle (b).

[Explanation of symbols]

3 LED (light generating means), 6 light generating means, 7 rotation axis
(Moving body), 9 patterns, 9a non-transmissive part, 10c transmissive part, 11 code disc (scale), 13,113
Light receiving part (light receiving means).

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yukio Aoki             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Takashi Omuro             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Toru Oka             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Yoichi Omura             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Masahiko Sakamoto             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Koichi Sugimoto             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Toshikazu Satone             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. F-term (reference) 2F103 BA43 CA02 DA01 DA12 DA13                       EA02 EA05 EA12 EA15 EA19                       EB06 EB11 EB33

Claims (7)

[Claims] 1. A light generating means for generating non-coherent light, and a plurality of transmissive portions having a fixed length for transmitting the light, and a non-transmissive material having a fixed length for not transmitting the light. A scale having a plurality of parts, position information is generated by the transmissive part and the non-transmissive part, a light receiving means for receiving the light via the scale, the light generating means, the light receiving means and the scale. And a relative movement mechanism for relatively moving the non-transmissive portion, the first conversion value W obtained by converting the width of the non-transmissive portion into an angle is constant, and the distance from the n-th to the n + 1-th of the non-transmissive portion is set to the angle. The second conversion value converted to P _n is P _n , the first angle based on the position of the non-transmissive portion provided at the n-th position is θ _n, and the transmittance of the scale is the first angle θ.
_{Assuming that} the function of _n is T (θ _n ) [T (θ _n ) is not constant], T (θ _n ) = (P _n −W) / P _n θ _{n + 1} = θ _n + P _n The photoelectric encoder, wherein the non-transmissive portion is provided at the position of the first angle θ _n and the second conversion value P _n defined by 2. A light generating means for generating non-coherent light, and a plurality of transmissive portions having a constant length for transmitting the light, and non-transmissive having a constant length for not transmitting the light. A scale having a plurality of parts, position information is generated by the transmissive part and the non-transmissive part, a light receiving means for receiving the light via the scale, the light generating means, the light receiving means and the scale. And a relative movement mechanism that moves relative to each other, and the third conversion value P obtained by converting the distance between the adjacent non-transmissive portions into an angle is constant, and the position of the non-transmissive portion provided in the nth position. the first angle based on the theta _n, the first angle transmittance of the scale theta _n function _{T (θ n) [T (} θ n)
Is defined as the fourth converted value W _{n obtained} by converting the width of the non-transmissive portion provided at the n-th position into an angle, T (θ _n ) = (P−W _n ) / P The photoelectric encoder, wherein the non-transmissive portion having the width of the fourth converted value W _n is provided at the position of the first angle θ _n . 3. T (θ _n ) = (T _max + T _min ) / 2 + {where T (θ _n ) is the following equation, where the maximum and minimum values of the transmittance are T _{max and} T _{min ,} respectively. (T _max −T _min ) sin
θ _n } / 2 The photoelectric encoder according to claim 1 or 2, wherein 4. The scale has a disk shape, and the transmission part and the non-transmission part form a ring-shaped pattern, and a terminal angle of the first angle θ _n is θ _end , If the end angle θ _end is not 360 °, the corrected second angle θ
'Request by the following formula, theta _{n' n} photoelectric encoder according to any one of claims 1 to 3, characterized in that _{= θ n × 360 ° / θ} end. 5. The light-receiving means has a length in a relative movement direction with respect to the scale that faces the plurality of non-transmissive portions, is formed from an end portion of the non-transmissive portion, and has the transmissive portion. A semi-light-shielding area having a transmittance lower than that of the semi-light-shielding area, and between the non-light-transmitting areas where the second conversion value P _n or the third conversion value P is maximum. The photoelectric encoder according to any one of claims 1 to 4, wherein the photoelectric encoders are formed so as to overlap each other. 6. The light receiving means is configured to provide the second converted value P _n.
Alternatively, the light having a larger value than the maximum value of the third conversion value P and a width on the relative movement direction side with respect to the scale is formed to be narrower than the central portion, and receives the light transmitted through the plurality of transmission portions. The photoelectric encoder according to any one of claims 1 to 5, which is characterized. 7. The non-transmissive portion is V-shaped, and has an inclined surface in which an incident angle of the light is set to be a critical angle or more. Photoelectric encoder.