JPH074992A - Encoder apparatus - Google Patents

Abstract

PURPOSE:To provide an encoder apparatus wherein at least one of two diffraction gratings is movable so as to reduce influence in a change in wavelength of light. CONSTITUTION:An encoder apparatus comprises a light source 1, a lens 2 for collimating light from the light source 1, two diffraction gratings 3,4 on which collimated light from the lens 2 is made incident, a condenser lens 5 and a light receiving element 7. The two diffraction gratings 3, 4 are equal in pitch, their grating faces are parallel to each other, and the first diffraction grating 3 is fixed while the second diffraction grating 4 is movable in a direction indicated by an arrow R. In addition, light J which is diffraction light generated by the fixed diffraction grating 3 and also diffracted by the movable diffraction grating 4 (double diffraction light) and light K which is transmitted light of the fixed diffraction grating 3 which also transmits through the movable diffraction grating 4 (double transmission light) are used for measuring quantity of movement of the movable diffraction grating 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encoder device used in a precision measuring device, drum rotation control of a copying machine, a scanner, an ink jet printer or the like.

[0002]

2. Description of the Related Art FIG. 49 shows West German Patent Publication No. 2,31.
It is a block diagram of the encoder apparatus disclosed by 6,248. Referring to FIG. 49, this encoder device is
Light source 101, lens 102 for collimating light from light source 101, two diffraction gratings 103 and 104 on which collimated light from lens 102 is incident, and condenser lens 10
5 and light receiving elements 106, 107, 107 '.

Here, the two diffraction gratings 103 and 104
Has one diffraction grating 103 fixed and the other diffraction grating 1
04 is movable in the direction of arrow R (hereinafter, the diffraction grating 103 and the diffraction grating 104 are referred to as a fixed diffraction grating and a moving diffraction grating, respectively). Further, the diene - In da apparatus, the pitch lambda ₁ of the diffraction grating 103 and the pitch lambda ₂ of the diffraction grating 104 is mutually identical (lambda ₁ =
Λ ₂ ).

In the encoder device having such a configuration, the light from the light source 101 is collimated by the lens 102,
The collimated light is first incident on the fixed diffraction grating 103 and then on the movable diffraction grating 104. When the collimated light is incident on the fixed diffraction grating 103 and the movable diffraction grating 104, at least ± first-order diffracted light is generated in each of the fixed diffraction grating 103 and the movable diffraction grating 104. If the pitches Λ ₁ and Λ _{2 of the} diffraction gratings 103 and 104 are sufficiently larger than the wavelength of the collimated light, higher order diffracted light is also generated.

FIG. 50 is a diagram for explaining diffracted light generated from the diffraction gratings 103 and 104. In FIG. 50, taking the ± 1st-order diffracted light as an example, the fixing diffraction grating 10
The + 1st order light generated in 3 and the 0th order light (that is, the transmitted light) A of the moving diffraction grating 104 is condensed by the lens 105 and is incident on the light receiving element 107. Further, the 0th-order light (that is, transmitted light) generated by the fixed diffraction grating 103 and the + 1st-order light B of the moving diffraction grating 104 are also reflected by the lens 105.
The light is collected by and is incident on the light receiving element 107. On this occasion,
As the moving diffraction grating 104 moves in the direction of arrow R, the 0th order light (transmitted light) generated in the moving diffraction grating 104.
, The phase of diffracted light other than the 0th order changes. That is, the phase of the light A does not change, but the phase of the light B changes, and the phase of the interference light between the light A and the light B changes on the light receiving element 107.

By the way, in this encoder apparatus, since the pitches Λ ₁ and Λ ₂ of the two diffraction gratings 103 and 104 are the same, the diffraction angles of the diffracted lights of the respective orders are the same,
Therefore, the light A and the light B are completely parallel immediately after being emitted from the moving diffraction grating 104. When the light A and the light B are made incident on the light receiving element 107 in a state of being completely parallel and interfere with each other, the interference fringe spacing is too large, and the light is moved onto the light receiving element 107 having a light receiving surface of a predetermined size. Diffraction grating 104
The interference fringes necessary to detect the amount of movement of the do not appear.

For this reason, in this encoder apparatus, the condenser lens 105 is provided, and the light A and the light B which are parallel to each other immediately after being emitted from the moving diffraction grating 104 are condensed by the condenser lens 105.
The light A formed on the light receiving element 107 by being condensed (de-collimated) by the
The interval of the interference fringes of the interference light between the light and the light B is narrowed. Thereby, the movement amount of the moving diffraction grating 104 can be detected by using the light receiving element 107 having a light receiving surface whose size is smaller than the interval of the interference fringes. That is, when the interference fringes move on the light receiving element 107 as the moving diffraction grating 104 moves, the amount of light received by the light receiving element 107 changes in a sine wave shape, and the light receiving element 10 based on this changes.
From the output from 7, it is possible to detect the amount of movement of the moving diffraction grating 104. Specifically, the moving diffraction grating 10
When 4 moves by 1 pitch, the output from the light receiving element 107 changes by one cycle in a sinusoidal manner, and the amount of movement of the moving diffraction grating 104 can be detected from this change in output.

In the above example, the combination of the + 1st-order light and the 0th-order light is used, but the combination of the -1st-order light and the 0th-order light (the -1st-order light generated by the fixing diffraction grating 103 is used). Therefore, the 0th order light (transmitted light) D of the moving diffraction grating 104 and the 0th order light (transmitted light) generated by the fixed diffraction grating 103 which is the −1st order light C of the moving diffraction grating 104 are used. Also in this case, the movement amount of the moving diffraction grating 104 can be detected in the light receiving element 107 'in the same manner as described above.

[0009]

The light source 101 used in this type of encoder device is less susceptible to noise of the light receiving element 107 and incidence of external light.
The larger the output, the better, but due to the demand for smaller devices,
It is not possible to use a large size. A semiconductor laser (LD) is suitable as a light source satisfying such requirements.

However, the semiconductor laser has a problem that the wavelength has a high temperature dependency and the wavelength changes due to the temperature change. Therefore, the light source 10 of the conventional encoder device described above is present.
If a semiconductor laser is used for 1, due to the wavelength change,
In some cases, the optical path of the diffracted light changes, and the light receiving element 107 cannot detect the amount of movement of the moving diffraction grating 104. That is, when the same order diffracted light (for example, + 1st order light) generated by the two diffraction gratings 103 and 104 is used in the above-mentioned encoder device, the wavelength of the light from the light source 101 changes as shown in FIG. Then, since the diffraction angles of the two diffracted lights A and B change, A ′ and B ′
The optical path changes like. As a result, the diffracted light A ', B'
May go out of the light receiving element 107, the output from the light receiving element 7 may change, and even the light may not enter the condenser lens 105. Further, it is possible to reduce the diffraction angle in order to reduce the influence of the wavelength change, but in this case, it is necessary to increase the pitches Λ ₁ and Λ ₂ of the diffraction gratings 103 and 104, and the encoder device is used. However, there is a problem in that the sensitivity of is reduced.

According to the present invention, in a structure in which at least one of the two diffraction gratings is movable, even when the wavelength of light changes, the influence of the wavelength change can be reduced without lowering the sensitivity. It is an object of the present invention to provide an encoder device capable of accurately measuring information regarding the movement of a diffraction grating.

[0012]

In order to achieve the above-mentioned object, the invention according to claims 1 to 12 provides:
Information on the movement of the diffraction grating is detected based on the twice-diffracted light and the twice-transmitted light. This allows
Even when the wavelength of the light from the light source changes, the influence of the wavelength change can be reduced without lowering the sensitivity, and the information regarding the movement of the diffraction grating can be accurately measured.

In particular, according to the second aspect of the present invention, the semiconductor laser is used as the light source, which makes it possible to obtain a large output without increasing the size of the device, and as a result of using the semiconductor laser as the light source, Even when the wavelength of the light changes due to the temperature change, the influence of the wavelength change can be reduced, and the information regarding the movement of the diffraction grating can be accurately measured.

The invention according to claims 5 to 7 is the first aspect.
If the second diffraction grating and the second diffraction grating have the same pitch and the grating surfaces are arranged in parallel with each other, the twice-diffracted light and the twice-transmitted light are detected as the movement information. Decollimating means are further provided for decollimating them prior to their incidence on the means. Thus, the twice-diffracted light and the twice-transmitted light can be angled to form interference fringes with a predetermined pitch.

Further, in the invention described in claims 8 to 10, the information about the movement of the diffraction grating is detected by utilizing the rotation of the polarized light. As a result, a perfect sinusoidal signal can be obtained, and highly accurate measurement can be performed.

Further, in the invention described in claims 11 and 12, the first diffraction grating and the second diffraction grating are arranged such that the grating directions thereof are slightly different from each other, or the pitch is different. Are slightly different. This makes it possible to form interference fringes at a predetermined interval without providing a condenser lens or the like.

According to a thirteenth aspect of the present invention, the first diffracted light of the ± nth order light from the first diffraction grating is generated by the second diffraction grating having a pitch slightly different from that of the first diffraction grating. The second diffracted light of ± m-order light is generated by diffraction. As a result, it is possible to reduce the influence of the change in the wavelength of light, and it is possible to generate interference fringes at predetermined intervals without using a condenser lens, and to accurately measure the amount of movement of the diffraction grating. it can.

In the fourteenth aspect of the invention, the pitch and the number of the interference fringes can be selected with a high degree of freedom by appropriately selecting the ± nth order light and the ± mth order light, and the occurrence of the interference fringes can be prevented. It can be flexibly controlled. In particular, when the ± 1st order light is used as the ± nth order light and the ± 1st order light is used as the ± mth order light, the diffraction efficiency is high, so that it is not necessary to amplify the output of the light receiving element that receives the interference fringes. A wide band amplifier can be used to achieve high speed, and in this case, since the efficiency of light of the secondary light or higher is low, noise is small and the amount of movement can be measured with high accuracy. Furthermore, + 1st order light and -1
By using the next light, as the diffraction grating moves by one pitch, a phase difference occurs in the opposite direction between the + 1st order light as the + mth order light and the −1st order light as the −mth order light. From the light receiving element, it is possible to obtain output signals for two cycles per pitch of the diffraction grating. On the other hand, ± n-order light, ± m
When high-order light is used as the next light, the sensitivity can be improved, the pitch difference between the two diffraction gratings can be increased, and the tolerance of the grating manufacturing error between the two diffraction gratings can be increased. it can.

According to the invention described in claim 15, the light source and the light from the light source are diffracted to produce the n ₁ -order light and the n ₂ -order light (n ₁ ,
(n ₂ is an integer) The first diffraction grating for generating the first diffraction light and the first diffraction light of the n ₁ -order light and the n ₂ -order light from the first diffraction grating are respectively diffracted to m. _A second diffraction grating that generates a second diffracted light of the _first- order light and m ₂ -order light (m ₁ and m ₂ are integers), and m ₁ -order light and m ₂ -order from the second diffraction grating Interference fringes are generated by interference with light, and movement of the diffraction grating is performed based on the interference fringes that move with the movement of at least one of the first diffraction grating and the second diffraction grating. And a movement information detecting means for detecting information regarding the information. This makes it possible to make the orders and diffraction angles of the two light beams to be interfered different from each other. For example, even when the first diffraction grating is a very high-density diffraction grating, the second diffraction Compared with the first diffraction grating, the diffraction grating can be manufactured as a low-density diffraction grating, and the accuracy problem can be avoided.

According to the sixteenth and eighteenth inventions,
Light source and first of n _1st order light and n _2nd order light (n ₁ and n ₂ are integers)
A first diffraction grating for generating diffracted light, m ₁ -order light,
a second diffraction grating for generating a second diffracted light of the m ₂ -order light (m ₁ and m ₂ are integers), and (moreover, l ₁ -order light and l ₂ -order light (l ₁ and l ₂ are integers) ) The third diffraction grating for generating the third diffracted light, and) The light from the light source is transmitted twice to the first diffraction grating, the second diffraction grating and the third diffraction grating, respectively. And the light from the light source undergoes the first, second, and (third) diffraction gratings, and then is reflected by the reflecting means (third,) second , When the first diffraction grating is re-experienced and when the first diffraction grating is emitted, interference fringes are generated by the emitted diffracted light, and the first diffraction grating, the second diffraction grating, ( The movement of the diffraction grating based on the interference fringes that move with the movement of at least one diffraction grating of the third diffraction grating. Moving information detecting means for detecting information to be stored. This enhances the detection sensitivity of the movement amount,
In addition, interference fringes can be generated even when a light source such as a light emitting diode is used.

According to the invention of claims 17 and 19,
Light source and first of n _1st order light and n _2nd order light (n ₁ and n ₂ are integers)
A first diffraction grating for generating diffracted light, m ₁ -order light,
The second diffraction grating for generating the second diffracted light of the m ₂ -order light (m ₁ and m ₂ are integers) and the 3rd of the l ₁ -order light and the l ₂ -order light (l ₁ and l ₂ are integers) The third diffraction grating that generates the diffracted light and the light from the light source are made to experience the first diffraction grating and the second diffraction grating twice, respectively, and the third diffraction grating once experiences the light. The reflecting means for causing and the light from the light source experience the first, second and third diffraction gratings,
When the second diffraction grating and the first diffraction grating are reflected again by the reflecting means and are emitted from the first diffraction grating, the first diffraction grating, the second diffraction grating, and the third diffraction grating And a movement information detecting means for detecting information regarding the movement of the diffraction grating based on the interference fringes that move with the movement of at least one of the diffraction gratings.
Thereby, interference fringes can be generated even when a light source such as a light emitting diode is used.

According to a twentieth aspect of the present invention, the two optical receivers arranged at intervals of half the pitch of the interference fringes receive the interference fringes, and the two optical receivers differ in phase by 180 °. The output signal is obtained, and information on the movement of the diffraction grating is detected based on the difference between the two signals. Thus, by taking the difference between the two output signals, the bias component can be removed, and a sinusoidal signal of high quality with a high aspect ratio can be obtained. Using this signal, the amount of movement of the diffraction grating can be increased. Can be measured more accurately.

According to the twenty-first aspect of the present invention, the two optical receivers arranged at intervals of ¼ of the pitch of the interference fringes receive the interference fringes, and the phase of the two optical receivers is 90 °. Two different output signals are obtained, and information on the movement of the diffraction grating is detected based on the two output signals. Thus, the moving direction of the diffraction grating can be detected by using the above two output signals as the direction discrimination signal, and by taking the difference between the two output signals, a sinusoidal signal of high quality with a high aspect ratio can be obtained. Can be obtained, and the amount of movement of the diffraction grating can be measured more accurately using this signal.

According to a twenty-second aspect of the present invention, the three fringes are received by three photoreceivers arranged at intervals of ¼ of the pitch of the fringes, and the fringes are received by 90 ° from the three photoreceivers. It is designed to obtain two more complete two sinusoidal signals having a phase difference. This makes it possible to detect the moving direction of the diffraction grating with higher accuracy by using these two signals whose phases are different by 90 ° as the direction discrimination signal, and to accurately detect the moving amount of the diffraction grating based on the individual signals themselves. It can be measured well.

Further, in the invention described in claim 23, in the encoder device according to claim 1, at least one diffraction grating has diffraction grating regions having different phases, and the A phase and the B phase are detected from respective outputs. It is supposed to do. As a result, stable interference fringes are obtained, and stable A-phase and B-phase are obtained.
Phases can be obtained.

Further, the invention of claim 24 can provide a high-precision linear encoder device, and the inventions of claim 25 to claim 26 have a simpler structure and higher accuracy than the conventional one. A rotary encoder device can be provided.

[0027]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a first embodiment of an encoder device according to the present invention. Referring to FIG. 1, the encoder device includes a light source 1, a lens 2 for collimating the light from the light source 1, two diffraction gratings 3 and 4 on which the collimated light from the lens 2 is incident, And an information detecting means 90.

The light source 1 is a semiconductor laser or LE.
D or the like is used. The two diffraction gratings 3 and 4 are shown in FIG.
Diffraction gratings 103, 1 of the conventional encoder device shown in FIG.
Similar to 04, the pitches Λ ₁ and Λ ₂ are the same, and the grating planes are parallel to each other. For example, the first diffraction grating 3 is fixed (fixation diffraction grating), the second diffraction grating 4 is movable in the direction of arrow R (moving diffraction grating).

However, in the encoder device of the first embodiment, as shown in FIG. 2, the diffracted light generated by the fixed diffraction grating 3 and also diffracted by the moving diffraction grating 4 (double diffraction) (Light) J and light (twice transmitted light) K that is transmitted through the stationary diffraction grating 3 and that is also transmitted through the movable diffraction grating are used to measure the amount of movement of the movable diffraction grating 4 and the like. It is like this. That is, the movement information detecting means detects the diffracted light from the first diffraction grating and the light diffracted by the second diffraction grating (twice diffracted light) and the first diffraction grating. Light transmitted through the second diffraction grating (2
The information regarding the movement of the diffraction grating is detected based on the (transmission light). In addition, in the example of FIG. 1, the movement information detecting unit 90 includes the condenser lens 5 and one light receiving element 7.

Next, the operation principle of the encoder device having such a configuration will be described. The incident angle, the diffraction angle, the pitch, and the diffraction order on the fixed diffraction grating 3 are θ ₁ , θ ₂ , Λ ₁ , and n, respectively.
And the diffraction angle, pitch, and diffraction order of the moving diffraction grating 4 are θ ₃ , Λ ₂ , and m, respectively, and the wavelength of the light source 1 is λ.
Then, the diffraction conditions in the fixed diffraction grating 3 and the movable diffraction grating 4 are given by the following equations, respectively.

[0031]

## EQU1 ## sin θ ₁ + sin θ ₂ = nλ / Λ ₁ sin θ ₂ + sin θ ₃ = mλ / Λ ₂

When θ ₂ is eliminated in the above equation, the following equation is obtained.

[0033]

[Number 2] _{sinθ 1 -sinθ 3 = λ (n} / Λ 1 -m / Λ 2)

From Equation _2, it can be seen that the diffraction angle θ ₃ changes in proportion to the magnitude of (n / Λ ₁ −m / Λ ₂ ) when the wavelength λ changes. That is, (n / Λ ₁ −m / Λ ₂ )
Indicates the degree of change in the diffraction angle θ _{3 with} respect to the change in wavelength. Therefore, even if the wavelength λ changes, the diffraction angle θ ₃
In order to make the above stable, the diffraction orders n and m and the pitches Λ ₁ and Λ ₂ may satisfy the following equation.

[0035]

N / Λ ₁ −m / Λ ₂ = 0

Here, if the pitches Λ ₁ and Λ ₂ are the same, it suffices if the diffraction orders are the same through two times of diffraction.
That is, it is sufficient if n and m are the same. For example, the first-order diffracted light from the fixed diffraction grating 3 and the first-order diffracted light from the moving diffraction grating 4 may be used as J.

In any case, for pitches Λ ₁ and Λ ₂ ,
By using the diffraction orders n and m that satisfy Equation 3, (s
in θ ₁ −sin θ ₃ ) can be made independent of the wavelength change of light. That is, this can be set to "0". In other words, even if the wavelength of the light of the light source 1 changes, the diffraction angle θ ₃ at the moving diffraction grating 4 can be made equal to the incident angle θ ₁ of the light at the fixed diffraction grating 3, and The bending angle θ ₃ can be made independent of the wavelength change of light. Further, since the diffraction angle θ ₃ and the incident angle θ ₁ are the same, the light diffracted twice (double diffracted light) J is always parallel to the light K transmitted twice (double transmitted light) K. Next, light J,
K becomes extremely stable light with respect to the wavelength change. This holds even when the pitches Λ ₁ and Λ ₂ of the two diffraction gratings 3 and 4 are reduced. Therefore, it is possible to reduce the influence of the wavelength change and reduce the pitches Λ ₁ and Λ ₂ of the diffraction gratings 3 and 4 to increase the diffraction efficiency and improve the sensitivity.

As described above, the encoder of the first embodiment is used.
By satisfying the condition of Equation 3, the D-device can measure the amount of movement of the moving diffraction grating 4 and the like by using the light J and K that are extremely stable with respect to the wavelength change.

More specifically, the light from the light source 1 is collimated by the collimating lens 2 and, for example, 2 of the same pitch is used.
The two diffracted light beams J and the two transmitted light beams K from the moving diffraction grating 4 are condensed by the condensing lens 5 to be non-parallelized, and the light J on the light receiving element 7 is made incident. Even when the wavelength of the light from the light source 1 changes when the interference fringes of the light J and the light K are formed, the optical paths of the lights J and K are always stable and do not change as shown in FIG. Therefore, on the light receiving element 7,
Stable interference fringes can be formed.

As the light-receiving element 7, a light-receiving surface whose size is smaller than the interval of the interference fringes is used, or a pinhole having a hole having a diameter smaller than the interval of the interference fringes is provided on the front surface of the light-receiving element 7. If 8 is provided, in the light receiving element 7,
As shown in FIG. 3, it is possible to detect a change in the amount of light based on the interference fringes that move with the movement of the moving diffraction grating 4 in the R direction. It can be measured without being affected by changes. Further, by reducing the pitches Λ ₁ and Λ ₂ of the diffraction gratings 3 and 4,
Highly sensitive measurement becomes possible.

The sensitivity can be improved even when high-order diffracted light is used instead of reducing the pitch of the diffraction grating. In the above description, as a specific example, the first-order diffracted light from the fixed diffraction grating 3 is first-order diffracted by the moving diffraction grating 4 is used as J, but instead of this, 2
The second-order diffracted light second-order diffracted by the moving diffraction grating 4 can also be used as J. Further, the fixed diffraction grating 3 may be as large as the diameter of light, whereas the movable diffraction grating 4 needs a size corresponding to the amount of movement, that is, a length, so that the movable diffraction grating It is difficult to make the pitch of the diffraction grating 4 smaller than that of the fixed diffraction grating 3. Therefore, the moving diffraction grating 4 can be configured to have a large pitch so that it can be easily created, and high-order diffracted light can be used, and the fixing diffraction grating 3 can be configured to have a small pitch. . Specifically, the pitch Λ ₂ of the diffraction gratings 3 and 4 is set to be twice the pitch Λ ₁ of the diffraction grating 3, and in this case, the diffraction order m of the diffraction grating 4 is set to satisfy the condition of Expression 3. It is possible to use one having twice the order of three.

FIG. 4 is a diagram showing a modification of the encoder device shown in FIG. In the encoder apparatus of FIG. 1, the diffraction grating 4 and the light receiving element 7 are arranged in order to unparallelize the twice-diffracted light and the twice-transmitted light which are parallel to each other and generate interference fringes with a narrow interval. Although the condenser lens 5 is provided between the light source 1 and the diffraction grating 3, the encoder device of FIG. 4 does not include a lens corresponding to the condenser lens 5. In between, collimate the light from the light source 1.
A lens 9 having a function of focusing and a function of focusing required to generate interference fringes is provided. That is, this lens (condensing lens) 9 also serves as a non-parallelizing means for unparallelizing the twice-diffracted light and the twice-transmitted light before they enter the movement information detecting means 90. It is supposed to work. In this case, the lens 5 is unnecessary for the movement information detecting means 90.

In the encoder device having the configuration shown in FIG. 4, the light source 1
The light from is collimated by the lens 9, receives a predetermined focus, and enters the diffraction gratings 3 and 4.
In the diffraction gratings 3 and 4, by using the diffraction orders that satisfy the equation 3 for the pitches Λ ₁ and Λ ₂ , similarly to the above, stable two-time diffracted light with little influence on the wavelength change of the light is obtained. J ′ and the transmitted light K ′ can be emitted twice. At this time, the lights J ′ and K ′ are not completely parallel and are focused by the lens 9, so that the condensing lens 5 is not provided as in the encoder device of FIG.
By forming interference fringes at predetermined intervals on the light receiving element 7, it is possible to stably measure the amount of movement of the moving diffraction grating 4 and the like without being affected by the wavelength change. As described above, in the encoder apparatus of FIG. 4, the two lenses required in the encoder apparatus of FIG. 1 can be replaced with one lens, and the apparatus can be further downsized.

In each of the above-mentioned configuration examples, interference fringes are spatially generated and the amount of movement of the diffraction grating 4 is measured based on the interference fringes. It is also possible to measure the amount of movement of the diffraction grating 4 and the like by utilizing the rotation of polarized light as used in the encoder apparatus.

FIG. 5 is a diagram showing an example of the configuration of an encoder device using the rotation of polarized light. In FIG. 5, the same parts as those in FIG. 1 are designated by the same reference numerals. Referring to FIG. 5, this encoder apparatus includes a polarizing plate 11 for linearly polarizing (for example, S-polarizing) the diffracted light (twice diffracted light) J emitted from the moving diffraction grating 4, and a moving diffraction grating. Polarizing plate 12 that linearly polarizes (for example, P-polarizes) the transmitted light (twice transmitted light) K emitted from 4 in a direction orthogonal to the polarization direction in polarizing plate 11, and is linearly polarized by polarizing plate 12. The beam splitter (or polarization beam splitter) 13 that reflects the transmitted light (P-polarized light) K and the transmitted light (P-polarized light) K that is reflected by the beam splitter (or polarization beam splitter) 13 are Further, the diffracted light (S-polarized light) J that has been incident and linearly polarized by the polarizing plate 11 is incident,
A polarization beam splitter 14 for superimposing the polarized light J on the transmitted light (P polarized light) K and emitting the same, and a polarization beam splitter 14
The axes of the transmitted light (P-polarized light) K and the diffracted light (S-polarized light) J superimposed on each other are tilted by 45 ° with respect to the polarization directions of the respective linearly polarized lights. Λ / 4 plate 15 for converting into two circularly polarized light,
A polarization beam splitter 16 for separating the light from the λ / 4 plate 15 into P-polarized light and S-polarized light, and a light-receiving element 17a for receiving the S-polarized light separated by the polarization beam splitter 16.
And a light receiving element 17b that receives the P-polarized light separated by the polarization beam splitter 16.

In the example of FIG. 5, the polarizing plate 11 and the polarizing plate 12 function as linear polarization means, the polarization beam splitter 14 functions as superposition means, and the λ / 4 plate 15 is used.
Function as circular polarization conversion means, and the polarization beam splitter 16 functions as separation means. In this case, the linear polarization conversion means, superposition means, circular polarization conversion means, separation means, and light receiving element are used. 17a and 17b function as movement information detecting means.

In this encoder apparatus, generally, diffraction gratings 3 and 4 having a large pitch with respect to the wavelength of light are used, and the polarization states of the twice diffracted light J and the twice transmitted light K are
It is particularly useful when it is the same as the incident polarized light or slightly elliptically polarized.

That is, in the encoder apparatus of FIG. 5, the twice-diffracted lights J and 2 whose polarization state is the same as the incident polarization or slightly elliptically polarized are obtained from the moving diffraction grating 4.
When the once transmitted light K and the second diffracted light J are emitted,
The light is linearly polarized (S-polarized) by 1 and enters the polarization beam splitter 14. The twice transmitted light K is linearly polarized (P-polarized) by the polarizing plate 12 and is incident on the polarization beam splitter 14 via the beam splitter (or polarization beam splitter) 13.

From the polarization beam splitter 14, the S-polarized twice-diffracted light J and the P-polarized twice-transmitted light K are emitted in an overlapping manner, and these are emitted at the λ / 4 plate 15. It is converted into two circularly polarized lights having mutually different rotation directions and is incident on the polarization beam splitter 16. Here, at the time of incidence on the polarization beam splitter 16, the twice-diffracted light J and the twice-transmitted light K have the same phase (that is, from the incident point on the diffraction grating 3 to the polarization beam splitter). Adjusting each optical component so that the optical path lengths of the two lights J and K up to 16 become the same)
The light obtained by superimposing the circularly polarized light and the circularly polarized light of the twice-transmitted light K on the surface becomes apparently linearly polarized light and enters the polarization beam splitter 16. More specifically, when the moving diffraction grating 4 moves, the circularly polarized light of the diffracted light J rotates twice as a result of the movement, and as a result, the apparent linearly polarized light rotates. As a result, when the light incident on the polarization beam splitter 16, that is, the apparent linearly polarized light is separated into S-polarized light and P-polarized light, the ratio between the separated S-polarized light amount and P-polarized light amount is The apparent rotation amount of the linearly polarized light, that is, the movement amount of the moving diffraction grating 4 is reflected.
Therefore, the amount of movement of the moving diffraction grating 4 and the like can be measured by measuring the amount of light with each of the light receiving elements 17a and 17b and obtaining the ratio. By utilizing the rotation of the polarized light in this way, a perfect sinusoidal signal (a light quantity ratio is a sinusoidal wave) can be obtained, and highly accurate measurement can be performed.

In this configuration example, transmitted light (P polarized light)
In order to convert the respective linearly polarized light of K and the diffracted light (S polarized light) J into two circularly polarized light having different rotation directions, λ /
4 plate 15 is used, but instead of this, λ / 4 plate 1
Similarly to 5, a polarizing plate having an axis inclined at 45 ° with respect to the polarization direction of each linearly polarized light can be used. When the polarizing plate is used, the cost can be reduced as compared with the case where the λ / 4 plate is used.

FIGS. 6 and 7 are diagrams showing another example of the structure of the encoder device using the rotation of polarized light. 6 and 7
The encoder device of the above is the pitches Λ ₁ and Λ ₂ of the diffraction gratings 3 and 4.
Is intended to be used when is less than the wavelength of light. That is, when the pitches Λ ₁ and Λ _{2 of} the diffraction gratings 3 and 4 are smaller than the wavelength of light, there is a polarization dependence that S-polarized light is diffracted but P-polarized light is transmitted. When Λ ₁ and Λ ₂ are smaller than the wavelength of light, due to this polarization dependency, the twice-diffracted light J is S-polarized and the twice-transmitted light K is linearly polarized at the time of emission from the diffraction grating 4. Be converted. That is,
The diffraction grating functions as a polarizing plate. This eliminates the need for the polarizing plates 11 and 12, the beam splitter 13 and the polarizing beam splitter 14 in the encoder apparatus of FIG. Further, since the optical path of the twice-diffracted light J and the optical path of the twice-transmitted light K can be overlapped with each other, in the example of FIG. 6, the twice-diffracted light (S-polarized light) J from the diffraction grating 4 and the twice-transmitted light (P-polarized light) K is directly incident on the λ / 4 plate 15, and in the example of FIG. 7, these are directly incident on the polarizing plate 18. Also at this time, in the λ / 4 plate 15 or the polarizing plate 18, 2
In the case of the polarizing plate 18, the S-polarized light J which is the diffracted light and the K which is the twice-transmitted light are converted into circularly polarized lights having different rotation directions and separated into S-polarized light and P-polarized light by the polarization beam splitter 16. In this case, by aligning J and K to the same linearly polarized light and making them incident on the light receiving elements 17a and 17b, and obtaining the ratio of the respective amounts of light, the amount of movement of the moving diffraction grating 4 can be measured. As described above, in the encoder device of FIGS. 6 and 7, the number of parts can be reduced and the miniaturization can be realized as compared with the encoder device of FIG.

FIG. 8 is a diagram showing still another configuration example of the encoder apparatus according to the first embodiment of the present invention. Similarly to the encoder device shown in FIG. 1, the encoder device of FIG. 8 is provided with two diffraction gratings 23 and 24 whose grating planes are arranged in parallel with each other, but in the encoder device of FIG. , The fixing diffraction grating 2 without providing the condenser lens 5.
3 pitches lambda ₁ and the pitch lambda ₂ moving diffraction grating 24 and is slightly different.

[0053] The pitch lambda ₁ of the fixed diffraction grating 3 and the pitch lambda ₂ moving diffraction grating 4 can be slightly different, moving diffraction a n-order diffracted light generated by the fixed diffraction grating 23 The m-th order diffracted light (twice diffracted light) J in the grating 24 and the light transmitted through the fixed diffraction grating 23 and also transmitted through the moving diffraction grating 24 (twice transmitted light) K are made non-parallel. , They are designed to have a predetermined angle.

Next, the operating principle will be described. Figure 8
Also in the above configuration, the diffraction conditions in the fixed diffraction grating 23 and the movable diffraction grating 24 are given by the equation 1, and therefore the equation 2 is established. Now, assuming that the angle formed by the twice-diffracted light J and the twice-transmitted light K is dθ, dθ is given by the following equation.

[0055]

(4) dθ = θ ₁ −θ ₃

If dθ is extremely small, d
Using θ, Equation 2 can be transformed into the following equation.

[0057]

[Number 5] _{sinθ 1 -sinθ 3 = sinθ 1 -sin} (θ 1 -dθ) = sinθ 1 -sinθ 1 · cosdθ + sindθ · cosθ 1 ≒ sindθ · cosθ 1 ≒ dθ · cosθ 1 = λ (n / Λ 1 -m / Λ ₂ )

As described above, when the diffraction orders n and m are the same, for example, the pitches Λ ₁ and Λ ₂ are slightly different from each other to form an angle dθ between the twice-diffracted light J and the twice-transmitted light K.
Can have Further, when the pitch of the interference fringes formed by the twice-diffracted light J and the twice-transmitted light K is Λ ₀ , the following equation is obtained.

[0059]

(6) sin (dθ / 2) ≈dθ / 2 = λ / 2Λ ₀

Further, by substituting dθ of equation 6 into equation 5,
The following equation is obtained.

[0061]

## EQU7 ## 1 / Λ ₀ = (n / Λ ₁ −m / Λ ₂ ) / cos θ ₁

As a result, the pitch Λ ₀ of the interference fringes has nothing to do with the wavelength of the incident light. In addition, the diameter of light is W ₀ ,
The following equation is obtained by multiplying the right side and the left side of Equation 7 by W ₀ cos θ ₁ .

[0063]

[Equation 8] _{(W 0 / Λ 0) ·} cosθ 1 = nW 0 / Λ 1 -mW 0 / Λ 2

Here, W ₀ / Λ ₀ is the number of interference fringes generated within the light diameter, and nW ₀ / Λ ₁ and mW ₀ / Λ ₂ are the light diameters in the fixed diffraction grating 23 and the moving diffraction grating 24. It is the number of diffraction gratings in each multiplied by each order. That is,
The following equation is derived from Equation 8.

[0065]

(Equation 9) (Number of interference fringes) × cos θ ₁ = Order × (Number of fixed diffraction gratings) −Order × (Number of moving diffraction gratings)

Thus, by setting the pitches Λ ₁ and Λ ₂ appropriately, it is possible to generate interference fringes (that is, it is possible to obtain an arbitrary number of interference fringes).
The function of the DA can be realized. For example, λ = 0.78 μm, θ ₁ = 45 °, and Λ ₁ is a Bragg condition, and Λ ₁ = Λ / 2 sin θ ₁ = 0.5515
If Λ ₀ is increased to 1 mm for 4 μm,
Is as follows:

[0067]

[Equation 10] 1/1000 · cos 45 ° = 1 / 0.55154-1 / Λ ₂

As a result, Λ ₂ is 0.55176 μm.
Which is only 0.04% different from Λ ₁ . If the diameter of the incident light is set to about 2 mm, one or two interference fringes will be observed. The interference fringes are the moving diffraction grating 2
Since it moves in accordance with the movement of 4, if one light receiving element 27 smaller than the pitch of the interference fringes receives light, it is output as shown in FIG.
It is possible to obtain a sinusoidal signal as shown in.

[0069] Thus, in the configuration example of FIG. 8, by slightly different and pitch lambda ₂ pitches lambda ₁ and the mobile diffraction grating 24 of the fixed diffraction grating 23, similar to the configuration example of FIG. 4 , The double-diffracted light J and the double-transmitted light K can be made non-parallel without collecting the light by the condenser lens.
Double-diffracted light J and double-transmitted light K from the moving diffraction grating 24.
The interference fringes can be directly generated from and the movement of the interference fringes accompanying the movement of the moving diffraction grating 24 in the direction of the arrow R, that is, the interference between the twice-diffracted light J and the twice-transmitted light K. One light receiving element 27 can detect a change in the amount of light. With this, with a simple configuration without a condenser lens,
Information on the movement of the moving diffraction grating 24 can be obtained, and the amount of movement of the diffraction grating 24 can be measured. Also, since large interference fringes can be generated in the collimated light,
The light receiving element 27 may be arranged at a predetermined position within this collimated light. Therefore, as compared with the case where the condenser lens is used and the condenser lens is strictly arranged at the condenser position, the arrangement and the assembly adjustment of the light receiving element 27, which are necessary for accurately measuring the movement amount, are facilitated. .

In the configuration example of FIG. 8, the pitches Λ ₁ and Λ ₂ of the two diffraction gratings are slightly different, but as shown in FIG.
By setting the pitches Λ ₁ and Λ ₂ of the two diffraction gratings 3 and 4 to be the same,
Even if the diffraction directions of the two diffraction gratings 3 and 4 are slightly different so as to have an angle (tilt) θ, the twice diffracted light J and the twice transmitted light K are not parallel to each other without providing a condenser lens. Can be converted.

In each of the above examples, the moving diffraction grating 4 is used.
Alternatively, 24 is configured to move linearly in the direction of the arrow R, and thus is configured as a linear encoder device. However, not only such a linear encoder device but also a rotary encoder device may be configured. It is possible.

FIG. 11 and FIG. 12 are diagrams showing a configuration example of the rotary encoder device. First, the rotary encoder device of FIG. 11 has a light source 1, a lens 2 for collimating the light from the light source 1, a fixing diffraction grating 33, and a movable diffraction grating 33 formed on a cylindrical surface and rotatable about an axis X. Diffraction grating 3
4 and a light receiving element 37.

The rotary encoder device of FIG. 12 is formed on the light source 1, the lens 2 for collimating the light from the light source 1, the fixing diffraction grating 43, and the disk, and the axis X.
A moving diffraction grating 44 rotatable around the
7 and 7.

Also in the rotary encoder device of FIGS. 11 and 12, by using the twice-diffracted light J and the twice-transmitted light K, similar to the above-described linear encoder device,
The influence of the wavelength change can be reduced, and the lens 2 has a collimating function and a focusing function, or the pitch of the fixed diffraction gratings 33 and 43 and the pitch of the movable diffraction gratings 34 and 44 can be changed. By making them slightly different, or by making the grating directions of the diffraction gratings 33 and 43 slightly different from the grating directions of the diffraction gratings 34 and 44, a condenser lens is required as in the linear encoder device described above. It is possible to measure the movement amount (rotation amount, rotation speed, etc.) of the moving diffraction grating with high accuracy with a simple configuration.

FIG. 13 is a block diagram of the second embodiment of the encoder apparatus according to the present invention. Referring to FIG. 13, this encoder device includes a light source 1, a lens 2 that collimates the light from the light source 1, two diffraction gratings 53 and 54 on which the collimated light from the lens 2 is incident, and 1 One light receiving element 5
7 and 7.

Also in the second embodiment, as in the encoder device shown in FIG. 8, two diffraction gratings 53 and 54 are used.
Are arranged so that the lattice planes are parallel to each other, and the pitches Λ ₁ and Λ ₂ are slightly different. In the second embodiment, the light from the light source 1 is 1 The diffracted light (first diffracted light) of ± n-order light (n is positive) is caused to enter the th diffraction grating (fixed diffraction grating) 53, and this first diffracted light is used as the fixed diffraction grating 53. It is incident on the second diffraction grating (moving diffraction grating) 54 with a slightly different pitch,
The ± m-order light (m is positive) diffracted light (second diffracted light) is generated, and the ± m-order light from the moving diffraction grating 54 is used to generate an interference fringe.

FIG. 14 shows an example of the configuration of the encoder apparatus of FIG. 13 in which ± 1st order light of ± nth order light is used and ± 1st order light of ± mth order light is used. FIG. That is, in FIG. 14, the + 1st-order light E generated by the stationary diffraction grating 53 and the −1st-order light E generated by the movable diffraction grating 54 and the −1st-order light generated by the stationary diffraction grating 53 that is the movable The case where the + 1st order light F at the diffraction grating 54 for use is used is shown.

Next, the operation of the encoder device configured as shown in FIG. 14 will be described. First, the light from the light source 1 is collimated by the lens 2 and is incident on the fixed diffraction grating 3 as collimated light. From the fixed diffraction grating 53, the first diffracted light is + 1st order light and -1. The next light is generated.
+ 1st order light, -1 as the first diffracted light generated in this way
The second light is incident on the moving diffraction grating 54 and is generated by the moving diffraction grating 54 based on the + 1st order light which is the first diffracted light.
The −first-order light E of the diffracted light and the + 1st-order light F of the second diffracted light generated from the moving diffraction grating 54 based on the −first-order light which is the first diffracted light enter the light receiving element 57. Light up.

By the way, also in the second embodiment,
The pitch Λ ₁ of the fixed diffraction grating 53 and the movable diffraction grating 54
Since the pitch lambda ₂ of is slightly different, not parallel to the optical E and the light F generated as above from the moving grating 54 has a predetermined angle, therefore, the condenser lens By disposing the light receiving element 57 at a predetermined position without providing the above, an interference fringe due to the interference light of the light E and the light F can be generated on the light receiving element 57.

The operating principle of this embodiment will be described in more detail with reference to FIG. For the sake of simplicity, assuming that the collimated light is vertically incident on the fixed diffraction grating 53, the diffraction condition in the fixed diffraction grating 53 is expressed by the following equation.

[0081]

(11) sin θ ₁ = λ / Λ ₁

Here, θ ₁ and Λ ₁ are the diffraction angle and pitch of the fixed diffraction grating 53, and λ is the wavelength of the light (collimated light) from the light source 1. Further, the diffraction condition in the moving diffraction grating 54 is expressed by the following equation.

[0083]

## EQU12 ## −sin θ ₂ + sin θ ₁ = λ / Λ ₂

Here, θ ₂ and Λ ₂ are the diffraction angle and pitch of the moving diffraction grating 54. From the equations 11 and 12, the following equation is derived for the diffraction angle θ ₂ of the moving diffraction grating 54.

[0085]

(13) sin θ ₂ = λ (1 / Λ ₁ −1 / Λ ₂ )

[0086] Further, the angle theta between the light E and the light F is twice the theta _2, the light E and the optical F is by having the angle theta (= 2 [Theta] _2), the optical cross-section of the collimated light Interference fringes are generated. The relationship between the pitch Λ _{0 of the} interference fringes and the diffraction angle θ ₂ is expressed by the following equation.

[0087]

## EQU14 ## sin θ ₂ = λ / (2Λ ₀ )

Using Equations 13 and 14, Λ ₁ , Λ ₂ and Λ ₀
The relationship with and is calculated by the following equation.

[0089]

(15) 1 / (2Λ ₀ ) = 1 / Λ ₁ −1 / Λ ₂

[0090] From Equation 15, the pitch lambda ₀ of the interference fringes, only related to the pitch lambda ₂ pitches lambda ₁ and the mobile diffraction grating 54 of the fixed diffraction grating 53, the wavelength λ of the light from the light source 1 is It becomes completely irrelevant and is not affected by the wavelength change even when a light source having a large wavelength change such as a semiconductor laser is used as the light source 1.

Further, as schematically shown in FIG. 16, when the diameter of the collimated light is W ₀ and the diameter W ₀ of the light is multiplied by the right side and the left side of Expression 15, the following equation is obtained.

[0092]

(W ₀ / Λ ₀ ) / 2 = W ₀ / Λ ₁ −W ₀ / Λ ₂

Here, W ₀ / Λ ₀ is the number of interference fringes generated within the light diameter, and W ₀ / Λ ₁ and W ₀ / Λ ₂ are the light in the fixed diffraction grating 53 and the movable diffraction grating 54, respectively. It is the number of diffraction gratings within the diameter. That is, the following equation is derived from the equation 16.

[0094]

[Equation 17] (Number of interference fringes) / 2 = (Number of fixed diffraction gratings) − (Number of movable diffraction gratings)

From Equation 17, it is possible to obtain an arbitrary number of interference fringes by appropriately setting Λ ₁ and Λ ₂ . For example,
When using a very high-density diffraction grating with Λ ₁ = 0.948 μm for high resolution, in order to obtain a large Λ ₀ = 1 mm, Λ ₂ = 0.94768 μm, and Λ ₁ and Λ ₂ Although the difference is as small as about 0.03%, it is possible to form the diffraction gratings 53 and 54 in which the pitches Λ ₁ and Λ ₂ are slightly different from each other. in this case,
If the light diameter of the collimated light is set to about 2 mm, one or two interference fringes will be observed.

Since the interference fringes move in accordance with the movement of the moving diffraction grating 54, if the interference light is received by one light receiving element 57 having a light receiving surface smaller than the pitch of the interference fringes,
A sinusoidal signal as shown in FIG. 17 is obtained. If the first-order light and the −1st-order light are used as in the configuration of FIG. 14, the phase difference generated in the diffraction grating 54 as the pitch moves by one pitch occurs in the opposite direction, and the sine wave signal is output for two cycles. To be done.

As described above, in the collimator device of the second embodiment, since the pitch Λ _{0 of the} interference fringes is completely unrelated to the wavelength of light, even if the wavelength of light from the light source 1 changes, the movement amount This does not have any influence on the measurement of etc., so that the highly accurate movement amount can always be stably measured.

[0098] Further, in this second embodiment, by slightly different and pitch lambda ₂ pitches lambda ₁ and the mobile diffraction grating 54 of the fixed diffraction grating 53, similar to the encoder apparatus of FIG. 8, Even if light is not condensed by the condenser lens, interference fringes can be directly generated from the lights E and F from the moving diffraction grating 54, and the moving diffraction grating 54 can be moved in the direction of arrow R. The accompanying movement of the interference fringes, that is, the change in the light amount of the interference light between the light E and the light F can be detected by one light receiving element 57. This makes it possible to obtain information about the movement of the moving diffraction grating 54 and measure the amount of movement of the diffraction grating 54 with a simple configuration without providing a condenser lens. Further, since a large interference fringe can be generated in the collimated light, the light receiving element 57 can be arranged at a predetermined position in the collimated light, and the movement amount can be reduced as compared with the case where it is arranged at the condensing position of the condenser lens. The arrangement and assembly adjustment of the light-receiving element 57 required for accurate measurement are facilitated.

In the example of FIG. 14, only the ± 1st-order light is used, and the ± 1st-order light has a high diffraction efficiency.
Because there is less noise compared to the light above the next light,
Using ± first-order light is superior to using higher-order light. However, in a type of encoder device using a diffraction grating, since the resolution is proportional to the diffraction angle, it may be desired to use higher-order light in order to increase the resolution.

The present invention is not limited to the case of using only ± first-order light as in the example of FIG. 14, but can be extended to the case of using higher-order light. That is, the fixed diffraction grating 53
The + n-order light (n is positive) generated by the moving diffraction grating 54 and the -m-order light (m is positive) generated by the moving diffraction grating 54 and the -n-order light (n is positive) generated by the fixed diffraction grating 53. And the moving diffraction grating 5
The + mth order light of 4 (m is positive) can also be used to obtain information (movement amount, moving direction, etc.) regarding the movement of the diffraction grating 54.

In this case, the diffraction condition of the fixed diffraction grating 53 is expressed by the following equation.

[0102]

(18) sin θ ₁ = nλ / Λ ₁

Here, n is the order. Further, the diffraction condition in the moving diffraction grating 54 is expressed by the following equation.

[0104]

## EQU19 ## −sin θ ₂ + sin θ ₁ = mλ / Λ ₂

Here, m is the order. Number 18 and number 19
From, the following equation is derived for the diffraction angle θ ₂ of the moving diffraction grating 54.

[0106]

## EQU20 ## sin θ ₂ = λ (n / Λ ₁ −m / Λ ₂ )

Further, using Equations 14 and 20, Λ ₁ and Λ ₂
The relation between and Λ ₀ is calculated as

[0108]

1 / (2Λ ₀ ) = n / Λ ₁ −m / Λ ₂

From equation 21, even when high-order light is used,
As in the case of using the primary light, the pitch Λ _{0 of the} interference fringes is
The pitch Λ ₁ of the fixed diffraction grating 53 and the movable diffraction grating 54
The only related to the pitch lambda _2, it becomes completely unrelated to the wavelength of the light from the light source, even if a large source of wavelength variation such as a semiconductor laser light source 1 is used, not affected by the wavelength change.

Further, when the diameter of the collimated light is W ₀ and the diameter W ₀ of the light is multiplied by the right side and the left side of the equation 21, the following equation is obtained.

[0111]

[Number 22] _{(W 0 / Λ 0) /} 2 = nW 0 / Λ 1 -mW 0 / Λ 2

Here, W ₀ / Λ ₀ is the number of interference fringes generated within the light diameter, and nW ₀ / Λ ₁ and mW ₀ / Λ ₂ are the light in the fixed diffraction grating 53 and the movable diffraction grating 54, respectively. It is obtained by multiplying the number of in-diameter diffraction gratings by each order.
That is, the following equation is derived from the equation 22.

[0113]

(23) (Number of interference fringes) / 2 = Order × (Number of fixed diffraction gratings) −Order × (Number of movable diffraction gratings)

Thus, by appropriately setting the pitch, interference fringes can be generated as described above, and the function of the encoder can be realized.

By using Equation 17, it is possible to obtain an arbitrary number of interference fringes by appropriately setting Λ ₁ and Λ ₂ . For example,
When using a very high-density diffraction grating with Λ ₁ = 0.948 μm for high resolution, in order to obtain a large Λ ₀ = 1 mm, Λ ₂ = 0.94768 μm, and Λ ₁ and Λ ₂ Although the difference is as small as about 0.03%, it is possible to form the diffraction gratings 53 and 54 in which the pitches Λ ₁ and Λ ₂ are slightly different from each other. in this case,
If the light diameter of the collimated light is set to about 2 mm, one or two interference fringes will be observed.

Since the interference fringes move in accordance with the movement of the moving diffraction grating 54, if the interference light is received by one light receiving element 57 having a light receiving surface smaller than the pitch of the interference fringes,
A sinusoidal signal as shown in FIG. 17 is obtained. If the first-order light and the −1st-order light are used as in the configuration of FIG. 14, the phase difference generated in the diffraction grating 54 as the pitch moves by one pitch occurs in the opposite direction, and the sine wave signal is output for two cycles. To be done.

As described above, in the collimator device of the second embodiment, since the pitch Λ _{0 of the} interference fringes is completely unrelated to the wavelength of light, even if the wavelength of light from the light source 1 changes, the movement amount This does not have any influence on the measurement of etc., so that the highly accurate movement amount can always be stably measured.

[0118] Further, in this second embodiment, by slightly different and pitch lambda ₂ pitches lambda ₁ and the mobile diffraction grating 54 of the fixed diffraction grating 53, similar to the encoder apparatus of FIG. 8, Even if light is not condensed by the condenser lens, interference fringes can be directly generated from the lights E and F from the moving diffraction grating 54, and the moving diffraction grating 54 can be moved in the direction of arrow R. The accompanying movement of the interference fringes, that is, the change in the light amount of the interference light between the light E and the light F can be detected by one light receiving element 57. This makes it possible to obtain information about the movement of the moving diffraction grating 54 and measure the amount of movement of the diffraction grating 54 with a simple configuration without providing a condenser lens. Further, since a large interference fringe can be generated in the collimated light, the light receiving element 57 can be arranged at a predetermined position in the collimated light, and the movement amount can be reduced as compared with the case where it is arranged at the condensing position of the condenser lens. The arrangement and assembly adjustment of the light-receiving element 57 required for accurate measurement are facilitated.

By the way, in the above-mentioned example, as shown in FIG. 15, for the light E, the nth-order diffracted light (diffraction angle θ ₁ ) at the fixed diffraction grating 53 and the − at the moving diffraction grating 54 are used. m
The next diffracted light (diffraction angle θ ₂ ) is used, and for the light F, the −n th diffracted light (diffraction angle θ
₁ ), assuming that the diffracted light of the m-th order (diffraction angle θ ₂ ) in the moving diffraction grating 54 is used, the diffracted light of the same order n, m and the same diffractive angle θ ₁ , θ ₂ of the light E and the light F, respectively. However, it is also possible to use diffracted lights of different orders and different diffraction angles for the light E and the light F. Next, a more expanded (generalized) case in which diffracted lights having different orders and different diffraction angles for the light E and the light F can be used will be described.

[0120] Figure 18, for light E is n _1-order diffracted light with a fixed diffraction grating 53 (diffraction angle theta _1), m _1-order diffracted light (diffraction angle in moving the diffraction grating 54 theta ₂ ) and use the light F
In the case of using the n ₂ -order diffracted light (diffraction angle φ ₁ ) at the fixed diffraction grating 53, the m ₂ -order diffracted light (diffraction angle φ ₂ ) at the moving diffraction grating 54 is shown. .

In this case, for the light E, the following relationship is established.

[0122]

## EQU23 ## sin θ ₁ = n ₁ λ / Λ ₁

[0123]

## EQU25 ## −sin θ ₂ + sin θ ₁ = m ₁ λ / Λ ₂

From the equations 24 and 25, the following equation is derived for the diffraction angle θ ₂ of the moving diffraction grating 54.

[0125]

Sin θ ₂ = λ (n ₁ / Λ ₁ −m ₁ / Λ ₂ )

Similarly, for the light F, the following equation holds.

[0127]

Sin φ ₂ = −λ (n ₂ / Λ ₁ −m ₂ / Λ ₂ )

The pitch Λ _{0 of the} interference fringes is expressed by the following equation.

[0129]

Λ ₀ = λ / (sin θ ₂ + sin φ ₂ )

Further, using Equations 26, 27, and 28, the relationship between Λ ₁ , Λ ₂ and Λ ₀ can be obtained by the following equation.

[0131]

Λ ₀ = 1 / [(n ₁ −n ₂ ) / Λ ₁ − (m ₁ −m ₂ ) / Λ ₂ ]

From Equation 29, the light E and the light F have the same order (n ₁ = n ₂ , m ₁ = m ₂ ) and the same diffraction angle (θ ₁ = φ ₁ , θ _2).
= Φ ₂ ), not only when using higher-order light of
Even in the case of using the high-order light of different diffraction angles, pitch lambda ₀ of the interference fringes, only related to the pitch lambda ₂ pitches lambda ₁ and the mobile diffraction grating 54 of the fixed diffraction grating 53, the wavelength of the light from the light source It has no relation to the above, and it can be seen that even if a light source having a large wavelength change such as a semiconductor laser is used as the light source 1, it is not affected by the wavelength change.

In this case, by appropriately setting Λ ₁ and Λ ₂ and the diffraction orders n ₁ , n ₂ , m ₁ and m ₂ , it is possible to obtain interference fringes of an arbitrary number. Since the interference fringes move in accordance with the movement of the moving diffraction grating as described above, a sinusoidal signal can be obtained by receiving light with one light receiving element having a light receiving area smaller than the pitch Λ _{0 of the} interference fringes. , N ₁ -order light (or m ₁ -order light), as the diffraction grating 54 moves one pitch, a phase difference occurs in the opposite direction, and the sinusoidal signal is generated by the moving diffraction grating 54. The period is twice the order (2 | m ₁ | or 2 | n ₁ |). In this case, since the moving diffraction grating is 54, the sinusoidal signal has a period of 2 | m ₁ |.

Further, as a method of selecting the diffraction orders n ₁ , n ₂ , m ₁ and m ₂ , since the two outgoing lights from the two diffraction gratings 53 and 54 must be substantially parallel, the fixing diffraction grating and m _1-order light in the moving diffraction grating 54 a n ₁ order light 53, and m ₂ order light by moving the diffraction grating 54 a n ₂ order light at a fixed diffraction grating 53 For interference, Λ ₁ ≈ Λ
Taking ₀ as an example, the following expression must be satisfied.

[0135]

[Equation 30] n ₁ + m ₁ = n ₂ + m ₂

For example, the first-order light from the fixed diffraction grating 53 and the 0th-order light from the movable diffraction grating 54, and the −second-order light from the fixed diffraction grating 53 and the movable diffraction grating 54. Of 3
The interference with the next light is “1 + 0 = −2 + 3”,
It can be used because it satisfies the condition of 0.

When high-order light is also used as described above, the sensitivity can be improved. That is, the sensitivity is determined by the diffracted light (that is, the second diffracted light) from the moving diffraction grating 54, and when only the first-order light of the moving diffraction grating 54 is used, the sine wave obtained by moving one pitch of the diffraction grating is 1 Only the period, but m ₁ + when high-order light is used
m ₂ times. In the case of the above-mentioned example, “0 + 3 = 3” is set, and the sensitivity can be tripled as compared with the case where only the primary light is used.

[0138] Further, by using such high-order light, it can also be significantly different the pitch lambda ₂ pitches lambda ₁ and the mobile diffraction grating 54 of the fixed diffraction grating 53.
As a specific example, the pitch Λ ₁ is Λ ₁ =
When a very high-density diffraction grating of 1 μm is used and the pitch Λ _{0 of} interference fringes is set to a large _value of 2 mm (about the diameter of collimated light), the diffraction orders are n ₁ = 1 and n ₂ = −1, m ₁ = -2,
If m ₂ = 2, the pitch Λ ₂ of the moving diffraction grating 54 is
Λ ₂ = 2,00005 μm, which is about twice as large as the pitch Λ ₁ of the fixed diffraction grating 53, is sufficient. If the pitch lambda ₁ of the fixed diffraction grating 53 and the pitch lambda ₂ moving diffraction grating 54 it does not differ only slightly, when a large pitch lambda ₀ of the interference fringes, the fixed diffraction grating 53 lambda ₁ =
It is necessary to make the diffraction grating with a very high density of 1 μm and also the moving diffraction grating 54 to have a very high density of about Λ ₁ = 1 μm. However, since the pitch Λ ₂ of the moving diffraction grating 54 can be made significantly different from the pitch Λ ₁ of the fixing diffraction grating 53 as described above, the fixing diffraction grating 53 is very high. Even with a high-density diffraction grating, the moving diffraction grating 54 can be manufactured as a low-density diffraction grating as compared with the fixed diffraction grating 53, whereby a problem in accuracy can be avoided.

In each of the above examples, the moving diffraction grating 5 is used.
4 moves linearly in the direction of the arrow R, and thus is configured as a linear encoder device, but in the second embodiment as well, as in the first embodiment, Not only the linear encoder device, but also a rotary encoder device can be configured.

19 and 20 are diagrams showing a configuration example of the rotary encoder device according to the present invention. First, FIG.
The rotary encoder device includes a light source 1, a lens 2 that collimates light from the light source 1, and a fixing diffraction grating 63.
And a moving diffraction grating 64 formed on a cylindrical surface and rotatable about the axis X, and a light receiving element 67.

The rotary encoder device shown in FIG. 20 is formed on the light source 1, the lens 2 for collimating the light from the light source 1, the fixing diffraction grating 73, and the disk, and the axis X.
A moving diffraction grating 74 rotatable around the
7 and 7.

Also in the rotary encoder device of FIGS. 19 and 20, the influence of the wavelength change is obtained by using the ± m-order light (more generally, m ₁ and m ₂ -order light) from the diffraction gratings 64 and 74. The pitch of the fixed diffraction gratings 63 and 73 and the movable diffraction gratings 64 and 74 can be reduced.
By slightly different from the pitch of, the moving amount (rotation amount, rotation speed, etc.) of the moving diffraction grating is highly accurate with a simple configuration that does not require a condenser lens as in the linear encoder device described above. Can be measured.

FIG. 21 is a block diagram of the third embodiment of the encoder apparatus according to the present invention. The encoder device shown in FIG. 21 is the same as the encoder device shown in FIG. 13 or 18 except that the second diffraction grating (moving diffraction grating) 54 is opposite to the first diffraction grating (fixing diffraction grating) 53. To
Reflecting means (for example, a mirror) 81 is further arranged, and
A splitting means (for example, a beam splitter) 82 is further arranged between the lens 2 and the fixing diffraction grating 53, and the light receiving element 7 as the movement information detecting means is arranged so as to receive the light emitted from the splitting means. It has become a thing. In addition,
The reflecting means 81 may be provided separately from the diffraction grating 54 as shown in FIG. 21, but the diffraction grating 5 of the diffraction grating 54 may be provided.
It may be integrally formed with the diffraction grating 54 on the surface on the side opposite to 3.

In such a structure, the collimated light collimated by the lens 2 passes through the dividing means 82 and enters the fixed diffraction grating 53 and the moving diffraction grating 54. The diffracted light from the moving diffraction grating 54 is reflected by the reflecting means 81, undergoes the moving diffraction grating 54 and the fixing diffraction grating 53 again, is divided by the dividing means 82, and enters the light receiving element 7. At this time, on the light receiving element 7, interference fringes are generated by the diffracted light incident on the light receiving element 7.

Such an optical system is equivalent to a symmetrical four-times diffraction grating system as shown in FIG. The state of the diffracted light will be described in more detail with reference to FIG. Similar to the above-described embodiment, it is assumed that the interference fringes are generated by the two lights E and F, and the light E is n in the fixing diffraction grating 53.
_First- order diffracted light (diffraction angle θ ₁ ), m in the moving diffraction grating 54
_First- order diffracted light (diffraction angle θ ₂ ), m in the moving diffraction grating 54
_First- order diffracted light (diffraction angle θ ₃ ), n in the fixed diffraction grating 53
_First- order diffracted light (diffraction angle θ ₄ ) is sequentially generated, and as for the light F, n ₂ -th-order diffracted light (diffraction angle φ ₁ ) at the fixed diffraction grating 53 and m at the moving diffraction grating 54. _2nd- order diffracted light (diffraction angle φ ₂ ), m _2nd- order diffracted light (diffraction angle φ ₃ ) at the moving diffraction grating 54, n _2nd- order diffracted light (diffraction angle φ ₄ ) at the fixed diffraction grating 53 ) Shall be generated sequentially.

For simplification of explanation, assuming that the collimated light is vertically incident on the fixing diffraction grating 53, as in the above-described embodiment, the following relationship is established for the light E.

[0147]

Sin θ ₁ = n ₁ λ / Λ ₁ sin θ ₁ −sin θ ₂ = m ₁ λ / Λ ₂ sin θ ₂ + sin θ ₃ = m ₁ λ / Λ ₂ sin θ ₃ + sin θ ₄ = n ₁ λ / Λ ₁

Accordingly, θ ₄ is expressed by the following equation.

[0149]

(32) sin θ ₄ = 2λ (n ₁ / Λ ₁ −m ₁ / Λ ₂ )

Similarly, for the light F, the following equation holds.

[0151]

(33) sin φ ₄ = −2λ (n ₂ / Λ ₁ −m ₂ / Λ ₂ )

Λ ₀ is expressed by the following equation.

[0153]

Λ ₀ = λ / (sin θ ₄ + sinφ ₄ )

From equations 32, 33 and 34, the pitch Λ _{0 of the} interference fringes is expressed by the following equation.

[0155]

Λ ₀ = 1 / [2 ((n ₁ −n ₂ ) / Λ ₁ − (m ₁ −m ₂ ) / Λ ₂ )]

From this, it can be seen that Λ ₀ does not depend on the wavelength. Further, since the interference fringes move in accordance with the movement of the moving diffraction grating, a sinusoidal signal can be obtained by receiving light with one light receiving element smaller than the pitch of the interference fringes. Also, n
_{By using the 1st-} order light (or m _1st- order light) for reciprocal movement, the phase difference generated in each direction as the diffraction grating moves 1 pitch occurs in the opposite direction, and the sinusoidal signal is the order of the moving diffraction grating. 4 times (4 | m ₁ | or 4 | n ₁ |). In the above example, the moving diffraction grating is 54, so
It becomes a period of | m ₁ |.

Compared with the encoder device having the structure shown in FIG. 18, the fixed diffraction grating 53 and the moving diffraction grating 54 are each caused to experience light twice, so that the moving amount detection sensitivity is 4 times.
Can be doubled.

In the first and second embodiments described above, as the light source 1, only a point light source (for example, a semiconductor laser or a light emitting diode having a light emitting surface of several tens of μm or less) can be used. Although it is not possible to use a light emitting diode having a wide surface (hereinafter, a light emitting diode is simply referred to as a light emitting diode having a wide light emitting surface) or the like, in the third embodiment, as the light source 1, a point light source (for example, a semiconductor) is used. Not only a laser but also a light emitting diode or the like can be used. That is, when the light source 1 is a point light source such as a semiconductor laser, the light E and the light F are emitted from the same point light source as shown in FIG. Interference with each other, interference fringes occur,
Although it functions as an encoder device, in the case of a light emitting diode, as shown in FIG. 23 (b), since the light E and the light F are not emitted from the same place, the first and second embodiments In the above configuration, no interference fringe is generated, and therefore the light emitting diode cannot be used as the light source 1.

On the other hand, in the third embodiment, the light reflected by the reflection means 81 returns to the original light through the same optical path by the reflection means 81. Therefore, when a light emitting diode is used for the light source 1, for example, The light reaching the reflecting means 81 is not emitted from the point light source and no interference fringes are generated, but the reflected light from the reflecting means 81 is the moving diffraction grating 5.
4, the light reaching the light receiving element 7 via the fixing diffraction grating 53 and the dividing means 82 is equivalent to that emitted from the point light source, and therefore, the interference fringes should be generated on the light receiving element 7. And can function as an encoder device.

FIG. 24 is a diagram showing a modification of the encoder device of FIG. In the encoder device of FIG. 24, the encoder device of FIG.
Instead of the reflecting means 81 of the encoder device, the reflecting means 84 is provided on the diffraction grating surface of the moving diffraction grating 54. That is, in the example of FIG. 24, the moving diffraction grating 54 is a reflection type diffraction grating in which a metal such as aluminum is formed on the diffraction grating surface by vapor deposition or sputtering. In this case, it is formed by vapor deposition or sputtering. The formed metal film functions as the reflecting means 84. Further, in this modified example, the pitch Λ ₂ of the moving diffraction grating 54 is about ½ of the pitch Λ ₁ of the fixed diffraction grating 53.

In the encoder device having such a configuration, the light from the light source 1 experiences the fixed diffraction grating 53 twice and the movable diffraction grating 54 once before reaching the light receiving element 7. , The pitch Λ of the interference fringes generated on the light receiving element 7
₀ is represented by the following equation.

[0162]

Λ ₀ = 1 / [2 (n ₁ −n ₂ ) / Λ ₁ − (m ₁ −m ₂ ) / Λ ₂ ]

The above equation is derived from the equation 35 as follows. That is, to simplify the explanation,
If ± 1st order light is used as n ₁ , n ₂ , m ₁ and m ₂ ,
5 is transformed into the following equation.

[0164]

Equation 37] _{Λ 0 = 1 / [4 (} 1 / Λ 1 -1 / Λ 2)] = 1 / {2 [2 / Λ 1 -1 / (Λ 2/2)]}

In this modified equation, 1 / Λ ₁ becomes 2 / Λ ₁ ,
Moreover, lambda ₂ has become a lambda _2/2, Where this means, the fixed diffraction grating 53 of the pitch lambda ₁ experienced twice a pitch of half (lambda _2/2) moving the diffraction grating 54 of the It means that it is possible to have a configuration in which the user experiences once. Expression 36 can be derived based on this modified formula.

According to this modification, the n ₁ -order light (or m ₁
As the diffraction grating moves one pitch by using (next light), the sine wave signal is four times the order of the moving diffraction grating.
In the case of (4 | n ₁ |, m _1st- order light), the period becomes 2 | m ₁ | When the m ₁ -order light is used for movement, the movement period of the sine wave signal is 1/2 as compared with the encoder device of FIG. 21, but the pitch Λ ₂ is substantially smaller than the pitch Λ ₁ of the fixed diffraction grating. Since it is half, the sensitivity is four times that of the encoder devices of the first and second embodiments, as in the encoder device of FIG.

Further, similarly to the encoder device shown in FIG. 21, even when a light emitting diode or the like is used for the light source 1 by the reflecting means 84, it functions well as an encoder device.

In the examples of FIGS. 21 and 24, the collimated light is transmitted through the beam splitter 82 and the diffraction grating 5
3 and 54, the reflected light is reflected by the beam splitter 82 and directed to the light receiving element 7, but the collimated light is reflected by the beam splitter 82 and diffracted by the diffraction gratings 53 and 54.
Alternatively, the reflected light may be transmitted through the beam splitter 82 and directed to the light receiving element 7. In this case, the diffraction gratings 53 and 54 are arranged on the reflection side of the beam splitter 82, and the light receiving element 7 is arranged on the transmission side of the beam splitter 82.

FIG. 25 is a block diagram of the fourth embodiment of the encoder apparatus according to the present invention. The encoder device of FIG. 25 is the same as the encoder device shown in FIG. 21, except that a third diffraction grating 86 is further provided between the diffraction grating 54 and the reflecting means 81, and a total of three diffraction gratings 53, 54,
It is composed of 86. In this case, for example, 1
The second and third diffraction gratings 53 and 54 are fixed diffraction gratings, and the third diffraction grating 86 is a moving diffraction grating.

Such an optical system is equivalent to a symmetrical 6-times diffraction grating system as shown in FIG. The state of the diffracted light will be described in more detail with reference to FIG. Similar to the above-described embodiment, it is assumed that interference fringes are generated by the two lights E and F. Regarding the light E, the n ₁ -th order diffracted light (diffraction angle θ ₁ ) at the _first diffraction grating 53 and the second _1st order diffracted light (diffraction angle θ ₂ ) at the diffraction grating 54 of the third diffraction grating 86
_1st- order diffracted light (diffraction angle θ ₃ ) at the 3rd diffraction grating 8
6, diffracted light of the 1 _1st order (diffraction angle θ ₄ ), diffracted light of the m _1st order at the second diffraction grating 54 (diffraction angle θ ₅ ), diffraction of the n _1st order at the _first diffraction grating 53 Light (diffraction angle θ ₆ ) is sequentially generated, and for light F, n ₂ -order diffracted light (diffraction angle φ ₁ ) at the _first diffraction grating 53 and m ₂ at the second diffraction grating 54.
Next diffracted light (diffraction angle φ ₂ ), l _{2 nd-} order diffracted light at the third diffraction grating 86 (diffraction angle φ ₃ ), l _{2 nd-} order diffracted light at the third diffraction grating 86 (diffraction angle φ 3 ₄ ) m ₂ -order diffracted light (diffraction angle φ ₅ ) at the second diffraction grating 54, first diffraction grating 53
The n ₂ -order diffracted light (diffraction angle φ ₆ ) is sequentially generated.

For simplification of explanation, assuming that the collimated light is vertically incident on the fixing diffraction grating 53 as in the above-mentioned embodiment, the following relationship is established for the light E.

[0172]

(38) sin θ₁= N₁λ / Λ₁ sin θ₁+ Sin θ₂= M₁λ / Λ₂ sin θ₂+ Sin θ₃= L₁λ / Λ₃ -Sin θ₃+ Sin θ_Four= L₁λ / Λ₃ sin θ_Four+ Sin θ_Five= M₁λ / Λ₂  sin θ_Five+ Sin θ₆= N₁λ / Λ₁

Accordingly, θ ₆ is expressed by the following equation.

[0174]

Sin θ ₆ = 2λ (n ₁ / Λ ₁ −m ₁ / Λ ₂ + l ₁ / Λ ₃ ).

Similarly, for the light F, the following equation holds.

[0176]

Sin φ ₆ = −2λ (n ₂ / Λ ₁ −m ₂ / Λ ₂ + l ₂ / Λ ₃ )

Λ ₀ is expressed by the following equation.

[0178]

Λ ₀ = λ / (sin θ ₆ + sin φ ₆ )

From Equations 39, 40 and 41, the pitch Λ _{0 of the} interference fringes is expressed by the following equation.

[0180]

Λ ₀ = 1 / [2 ((n ₁ −n ₂ ) / Λ ₁ − (m ₁ −m ₂ ) / Λ ₂ + (l ₁ −l ₂ ) / Λ ₃ )]

From this, it can be seen that Λ ₀ does not depend on the wavelength. Further, since the interference fringes move in accordance with the movement of the moving diffraction grating, a sinusoidal signal can be obtained by receiving light with one light receiving element smaller than the pitch of the interference fringes. Also, n
_{Since the 1st-} order light and the n _2nd- order light (or the m _1st- order light and the m _2nd- order light) are used in a reciprocating manner, the phase difference generated as the diffraction grating moves by one pitch occurs in the opposite direction, and the sine wave shape is generated. The signal is twice the order of the moving diffraction grating (2 (| m ₁ | + | m
₂ |) or 2 (| n ₁ | + | n ₂ |) or 2 (| l ₁ | + |
l ₂ |).

Also in the fourth embodiment, not only a point light source (for example, a semiconductor laser) but also a light emitting diode or the like can be used as the light source 1 as in the third embodiment.

FIG. 27 is a diagram showing a modification of the encoder device of FIG. The encoder apparatus of FIG. 27 corresponds to the encoder apparatus shown in FIG. 24, and instead of the reflecting means 81 of the encoder apparatus of FIG. 25, the reflecting means 84 is provided on the diffraction grating surface of the third diffraction grating 86. Is provided. That is, in the example of FIG.
The second diffraction grating 86 is a reflection type diffraction grating in which a metal such as aluminum is formed on the diffraction grating surface by vapor deposition or sputtering. Further, in this modification, the pitch Λ ₃ of the _third diffraction grating 54 is equal to the pitch of the first and second diffraction gratings 53,
It is about 1/2 of the pitches Λ ₁ and Λ ₂ of 54.

In the encoder device having such a configuration, the light from the light source 1 reaches the first,
The pitch Λ ₀ of the interference fringes generated on the light receiving element 7 when the second diffraction gratings 53 and 54 are experienced twice and the third diffraction grating 86 is experienced once is expressed by the following equation.

[0185]

Λ ₀ = 1 / [2 ((n ₁ −n ₂ ) / Λ ₁ − (m ₁ −m ₂ ) / Λ ₂ ) + (l ₁ −l ₂ ) / Λ ₃ ]

The above equation is derived from the equation 42 as follows. That is, to simplify the explanation,
If ± 1st order light is used as n ₁ , n ₂ , m ₁ , and m ₂ ,
2 is transformed into the following equation.

[0187]

Equation 44] _{Λ 0 = 1 / [4 (} 1 / Λ 1 -1 / Λ 2 + 1 / Λ 3)] = 1 / {2 [2 / Λ 1 -2 / Λ 2 + 1 / (Λ 3/2) ]}

[0188] The modified _{formula, 1 / Λ 1, 1 /} Λ 2 are respectively _{2 / Λ 1, 2 / Λ} 2 , and the addition, lambda ₃ has become a lambda _3/2, means of this deformation type However, the pitch Λ ₁ ,
Lambda ₂ of the diffraction grating 53 and 54 experienced twice respectively, is that possible configuration that pitch will experience once the moving diffraction grating 86 half (Λ _3/2). Equation 43 can be derived based on this modified equation.

According to this modification, the n ₁ -order light and the n ₂ -order light
(Or m _1st- order light, m _2nd- order light) makes the diffraction grating 1
As the pitch shifts, the sinusoidal signal becomes twice the order of the moving grating (2 (| m ₁ | + | m ₂ |) or 2
(| N ₁ | + | n ₂ |)). Also, l ₁ , l ₂
Is used, the cycle becomes (| l ₁ | + | l ₂ |) times. At this time, compared with the encoder device of FIG. 25, the moving period of the sine wave signal is 1/2, but the pitch Λ ₃ is about half the pitch Λ ₁ , Λ ₂ of the _first and second diffraction gratings. Therefore, the sensitivity is similar to that of the encoder device of FIG.
It is four times as large as that of the encoder devices of the first and second embodiments.

Further, similarly to the encoder device of FIG. 25, the reflection means 84 allows the light source 1 to use a light-emitting diode or the like, and thus functions well as an encoder device.

Although the three diffraction gratings 53, 54 and 86 are provided in the encoder device of FIGS. 25 and 27, it is also possible to provide three or more diffraction gratings.

In the third and fourth embodiments described above, the moving diffraction grating 54 moves linearly in the direction of the arrow R, which constitutes a linear encoder device. However, also in the third and fourth embodiments, as with the first and second embodiments, not only such a linear encoder device but also a rotary encoder device can be configured.

FIGS. 28 to 35 are diagrams showing a configuration example of the rotary encoder device according to the third and fourth embodiments. The rotary encoder device shown in FIGS. 28, 30, 32 and 34 is, for example, as shown in FIG. The configuration is compatible with the rotary encoder device. Also, FIG. 29 and FIG.
The rotary encoder device of FIGS. 1, 33, and 35 has a configuration corresponding to, for example, the rotary encoder device of FIG.

Further, the rotary encoder device of FIGS. 28 and 29 is provided with the reflecting means 81 on the side opposite to the movable diffraction gratings 64 and 74, and has a structure corresponding to the encoder device of FIG. There is. Also, FIG. 30 and FIG.
In the rotary encoder device of 1, reflection means are formed on the diffraction grating surfaces of the movable diffraction gratings 64 and 74,
It has a configuration corresponding to the encoder device of FIG.
The rotary encoder device shown in FIGS. 32 and 33 is
A third diffraction grating 86 and a reflecting means 81 are provided on the side opposite to the rotatable moving diffraction gratings 64 and 74, as shown in FIG.
The configuration is compatible with the encoder device of. Also,
In the rotary encoder device of FIGS. 34 and 35, a third diffraction grating 86 is provided on the side opposite to the rotatable moving diffraction gratings 64 and 67, and the reflecting means 84 is provided on the diffraction grating surface of the third diffraction grating. It is formed and has a configuration corresponding to the encoder device of FIG.

As described in each of the above-mentioned embodiments, in the present invention, higher order light can also be used, and a unique effect can be obtained by using the higher order light, but interference fringes of a large pitch are generated and a small pitch is generated. In order to make the size of the light receiving element 7 larger and easier to set than in the case of the interference fringes, it is preferable that the lights to be interfered be close to each other.

When high-order diffracted light is used, the pitch does not have wavelength dependency as described above, but the phase of the interference fringe has wavelength dependency. In order to eliminate the wavelength dependence of the phase of the interference fringes, the two lights are made to be completely symmetrical optical systems. That is, the two lights generated in each diffraction grating have the same order. For example, in the first diffraction grating, ± first-order lights are included, in the second diffraction grating, ± 3rd-order lights are included. Of these, the primary light is most suitable because it has the highest efficiency.

For example, in the case of the encoder device shown in FIG.
Taking n ₁ = 1, n ₂ = −1, m ₁ = 1, m ₂ = −1 as an example, Λ
_{When 1} = 1 μm, to obtain Λ ₀ = 2 mm, Λ ₂ =
1.00025 μm, the difference between Λ ₁ and Λ ₂ is about 0.0
It becomes 25%.

Further, in the case of the encoder device of FIG. 21, n
Taking ₁ = 1 and n ₂ = -1, m ₁ = 1 and m ₂ = -1 as an example, Λ ₁
= 1 μm, to obtain Λ ₀ = 2 mm, Λ ₂ = 1.
It becomes 000125 μm.

In the case of the encoder device of FIG. 24, n
Taking ₁ = 1 and n ₂ = -1, m ₁ = 1 and m ₂ = -1 as an example, Λ ₁
= 1 μm, to obtain Λ ₀ = 2 mm, Λ ₃ = 0.
It is 5000625 μm.

In the case of the encoder device of FIG. 25, n
Taking ₁ = 1 and n ₂ = -1, m ₁ = 1 and m ₂ = -1 as an example, Λ ₁
= 1 μm and Λ ₂ = 0.5 μm, Λ ₃ = 0.9999875 μm in order to set Λ ₀ = 2 mm.

By the way, in each of the above-mentioned embodiments, the interference
A type for detecting information about the movement of a diffraction grating based on fringes.
Encoder device (for example, FIG. 1, FIG. 2, FIG. 3, FIG.
8, FIG. 10, FIG. 11, FIG. 12, FIG. 13, FIG.
8, FIG. 19, FIG. 20, FIG. 21, FIG. 24, FIG. 25, FIG.
7, FIG. 28, FIG. 29, FIG. 30, FIG. 31, FIG. 32, FIG.
3, the encoder device as shown in FIGS. 34 and 35)
Causes the moving diffraction grating to move, which causes interference fringes.
When moving, as a movement information detection means,
A light receiving element with a light receiving surface smaller than the gap or a pin with a small hole
If holes are used, one light receiving element can be used as shown in FIG.
A sinusoidal signal as shown in 7 can be obtained. This
The sinusoidal signal of this species has a valley-to-peak ratio (t₂/ T₁; Aspe
The better the quality, the better the quality
And the sinusoidal signal from the bias component t ₁To have
The sinusoidal signal of is not good quality.

36 to 42 show various signal detecting methods according to the present invention for improving the quality of the sinusoidal signal, in other words, various structural examples of the moving information detecting means. ing. In the following description, for convenience, the encoder device is based on the configuration of FIG. 13. First, in FIG. 36, when light and dark of interference fringes are generated one by one in a light diameter (circle in the drawing) in which light is overlapped,
Interval corresponding to the light and shade of interference fringes (half the pitch of interference fringes)
A configuration is shown in which two light receiving elements 58 and 59 are arranged so as to extend from each other and a difference between outputs of the respective light receiving elements 58 and 59 is obtained.

FIG. 37 shows the output signal O1 of one light receiving element 58, the output signal O2 of the other light receiving element 59, and the difference signal (O1-O2) of the outputs of the two light receiving elements 58, 59 in the configuration of FIG. It is a figure which respectively shows. As can be seen from FIG. 37, since the two light receiving elements 58 and 59 are arranged at an interval half the pitch of the interference fringes, the light receiving element 5
The output signals O1 and O2 of 8 and 59 have a phase difference of 180 °, and therefore the outputs O1 and O1 of the two light receiving elements 58 and 59 are
With taking difference signal the difference between O2 (O1-O2), it is possible to remove the bias component t _1, it is possible to obtain a high aspect ratio good sinusoidal signal, thereby, more accurate The amount of movement can be measured. Further, in this case, as shown in FIG. 38, by reducing the width H of the light receiving elements 58 and 59, the bias component t ₁ can be further reduced, and the difference signal (O1-
It is possible to increase the amplitude of O2), and it is possible to obtain a more nearly perfect quality sinusoidal signal. However, if the width H is reduced, the amount of light received also decreases. Therefore, the width H of the light receiving elements 58 and 59 should be designed to be appropriate according to the application.

In FIG. 36, two light receiving elements 5 are formed with an interval (half the pitch of the interference fringes) corresponding to the contrast of the interference fringes.
Although 8 and 59 are arranged, as shown in FIG. 39, an interval half the interval of light and dark of the interference fringes (a quarter of the pitch of the interference fringes).
It is also possible to dispose two light receiving elements 58 and 59 with an angle. That is, it is possible to arrange one light receiving element 58 in, for example, a bright portion and the other light receiving element 59 in an intermediate position between light and dark (an intermediate position of the light diameter).

FIG. 40 shows the output signal O1 of one light receiving element 58, the output signal O3 of the other light receiving element 59, and the difference signal (O of the two light receiving elements 58, 59 in the configuration of FIG.
It is a figure which respectively shows 1-O3). As shown in FIG. 39,
The distance between the two light-receiving elements 58 and 59 is 4 with the pitch of the interference fringes.
When the two light receiving elements 58 and 59 are arranged so that the light receiving elements 58 and 59 are halved (half the dark and light intervals), the output signals O1 and O3 of the two light receiving elements 58 and 59 are 90 ° as shown in FIG. There will be a phase difference. That is, two sine wave signals (that is, an A-phase signal and a B-phase signal) having a 90 ° phase difference generally required for an encoder can be output from the light receiving elements 58 and 59 as output signals O1 and O3, respectively. In this case, the A-phase signal O1, which has a phase difference of 90 °,
The B-phase signal O3 can be used as a direction discrimination signal for detecting the moving direction of the diffraction grating, and the difference between the A-phase signal and the B-phase signal, that is, the difference between the output signal O1 and the output signal O3 is obtained. By setting (O1-O3), this difference signal (O1-O3) can be used for the measurement of the actual moving distance. Then, the difference signal (O1-O
By using 3), a sine wave of good quality can be obtained, and the amount of movement can be measured with high accuracy, as described above. That is, in the configuration of FIG. 39, as the information on the movement of the diffraction grating 54, a signal for discriminating the movement direction and a signal for measuring the movement amount can be obtained with high accuracy.

Further, in order to obtain a signal of high quality (high aspect ratio), as shown in FIG. 41, the distance between adjacent elements should be set to 1/4 of the pitch of interference fringes.
It is also possible to arrange one light receiving element 60, 61, 62.

FIG. 42 shows output signals O1 and O from the three light receiving elements 60, 61 and 62 in the configuration of FIG.
3, O2 is a diagram showing the difference signal (O1-O3) of the outputs of the two light receiving elements 60, 61 and the difference signal (O3-O2) of the outputs of the two light receiving elements 61, 62, respectively. As shown in FIG. 41, when the three light receiving elements 60, 61, 62 are arranged so that the distance between the adjacent elements becomes a quarter of the pitch of the interference fringes, as shown in FIG. , 6
The output signals O1, O3, O2 of 1, 62 have a phase difference of 90 °. Therefore, the difference signal (O1-O3) and the difference signal (O3-O2) have a phase difference of 90 ° with each other, and The sine wave is closer to perfection (higher quality).
In this case, a difference signal (O1-O3) having a 90 ° phase difference,
By using (O3-O2) as the A-phase signal and the B-phase signal, it is possible to detect the moving direction of the diffraction grating 54 with high precision, and the individual difference signals (O1-O3) and (O3).
The movement amount of the diffraction grating 54 can be accurately measured by -O2) itself.

Further, in the encoder device of each of the above-mentioned embodiments, at least one (for example, one of) the diffraction grating 53, the diffraction grating 54, and the diffraction grating 86, as shown in FIG. It is also possible to divide into two areas u _a and u _b . That is, the regions u _a and u _b have the same pitch Λ ₁ (or Λ ₂ and Λ ₃ ), but the pitch phases are different from each other. By doing this,
As shown in FIG. 43 (b), the optical section 60 in the respective regions u _a collimator light, u 2 types of interference fringes with different phases corresponding to _b I _a, I _b (each of the interference fringes I _a, I _b the pitch can generate lambda _0), the interference fringes I _a, and arranged two light receiving elements (e.g., photodiodes, etc.) 7a in the stripe direction Y of I _b, and 7b, the respective light receiving elements 7a, 7b It is also possible to obtain a predetermined signal from each.

Here, the light receiving elements 7a and 7b have a light receiving surface smaller than the interval of the interference fringes. Further, the phase difference β ₁ of the diffraction grating pitch between the two regions u _a and u _b is 2π / (4 |
n−m |) is preferable. Note that n and m are the diffraction orders of the diffraction grating whose regions are separated. For example, if the first diffraction grating 53 is divided into two regions, n and m are n ₁ and m ₁ , respectively. Further, if the second diffraction grating 54 is divided into two regions,
n and m are n ₂ and m ₂ , respectively. Therefore, for example, in FIG.
As in the configuration of No. 4, the first-order light of the first diffraction grating 53 and −
If the first-order light is used (n ₁ = 1 and m ₁ = −1) and the −1st-order light and the first-order light of the second diffraction grating 54 are used (n ₂
= -1, m ₂ = 1), the second diffraction grating 54 is set to 2
When dividing into two areas, the phase difference β of the diffraction grating pitch
_It is good to set ₁ to 2π / 8.

When the -1st-order light and the 1st-order light of the second diffraction grating 54 are used, each region u _a of the diffraction grating 54,
The phase difference β _{0 of the} interference fringes I _a and I _b with respect to the phase difference β _{1 of} u _b
Is as follows: That is, the second diffraction grating 5
When the −1st order light and the 1st order light of 4 are used, the phase shift of the interference fringes is 1 with respect to the phase shift of the second diffraction grating 54.
Since − (− 1) = 2 times, the following formula is derived.

[0211]

Β ₀ = 2β ₁

Therefore, in the second diffraction grating 54,
The phase difference β ₁ between the pitches of the regions I _a and I _b is 2 as described above.
When set to π / 8, the phase difference β ₀ between the pitches of the interference fringes I _a and I _b becomes 2π / 4, and each light receiving element 7
From a and 7b, the pitch of the interference fringes is shifted by 1/4, 90 °
It is possible to obtain two sine wave signals (that is, an A-phase signal and a B-phase signal) each having a phase difference of. As a result, the A-phase signal and the B-phase signal having a phase difference of 90 ° can be used as direction discrimination signals for detecting the moving direction of the diffraction grating, and the difference between the A-phase signal and the B-phase signal can be obtained. so,
This difference signal can be used to measure the actual distance traveled. Then, by using the difference signal for measuring the movement distance, a good quality sine wave can be obtained, and the movement amount can be measured with high accuracy. That is, the diffraction grating 54
As the information regarding the movement of, the signal for discriminating the movement direction and the signal for measuring the movement amount can be obtained with high accuracy.

The A-phase signal and the B-phase signal as described above can be realized also in the encoder device of FIG. 39, for example, as described above. However, in the encoder device of FIG. 39, since the A phase and the B phase are detected from one interference fringe,
When the interference fringes are displaced, there is a problem that the phases of the A phase and the B phase are likely to be displaced and a detection error in the moving direction is likely to occur.

On the other hand, the diffraction grating 53 or 54 is divided into two regions to generate two interference fringes I _a and I _b ,
Two light receiving elements 7a and 7b are arranged side by side in the direction Y of the interference fringes, and two interference fringes I _a ,
When the A-phase and B-phase signals are directly obtained from I _b, it is possible to reduce the detection error with respect to the inclination of the interference fringes due to the deviation of the diffraction grating 53 or 54. The phase of the B-phase signal is less likely to shift, and the occurrence of detection error in the moving direction can be significantly reduced.

In this case as well, not only ± 1st order light,
It can be extended to use higher order light. That is, for example, as shown in FIG. 44, the first diffraction grating 53
N _1st- order light generated by the second diffraction grating 54 n ₂
And the next light, a m _1-order light generated by the first diffraction grating 53, the diffraction grating 5 and the second m ₂ order light of the diffraction grating 54
It can also be used to obtain information (movement amount, moving direction, etc.) regarding the movement of No. 4.

In this case, the diffraction condition at the first diffraction grating 53 is expressed by the following equation.

[0217]

Sin θ ₁₁ = n ₁ λ / Λ ₁ sin θ ₁₂ = m ₁ λ / Λ ₁

The diffraction condition of the second diffraction grating 54 is expressed by the following equation.

[0219]

-Sin θ ₂₁ + sin θ ₁₁ = n ₂ λ / Λ ₂ −sin θ ₂₂ + sin θ ₁₂ = m ₂ λ / Λ ₂

The following equation is derived from the equations 46 and 47.

[0221]

Sin θ ₂₁ = λ (n ₂ / Λ ₂ −n ₁ / Λ ₁ ) sin θ ₂₂ = λ (m ₂ / Λ ₂ −m ₁ / Λ ₁ ).

The pitch of the interference fringes formed by the light having the angles of θ ₂₁ and θ ₂₂ is expressed by the following equation.

[0223]

Λ ₀ = λ / (sin θ ₂₁ + sin θ ₂₂ )

Using Equations 48 and 49, Λ ₁ , Λ ₂ and Λ ₀
The relationship with and is calculated by the following equation.

[0225]

Λ ₀ = 1 / [(n ₂ + m ₂ ) / Λ ₂ − (n ₁ + m ₁ ) / Λ ₁ ]

From Equation 50, even when high-order light is used,
As in the case of using the primary light, the pitch Λ _{0 of the} interference fringes is
Pitch lambda ₁ of the first diffraction grating 53 and only related to the second pitch lambda ₂ of the diffraction grating 54, it is completely independent of the wavelength of the light from the light source, the wavelength change, such as a semiconductor laser light source 1 Even if a large light source is used, it is not affected by the wavelength change.

Note that, as a method of selecting the higher order light, as described above, the two outgoing lights from the two diffraction gratings 53 and 54 must be substantially parallel, so that the n ₁ -th order in the _first diffraction grating 53 is used. M ₁ at the second diffraction grating 4 which is light
_2nd order light and n _2nd order light at the first diffraction grating 53
In the interference with the m ₂ -order light at the th diffraction grating 4, Λ ₁ ≈Λ ₀
For example, Equation 30 must be satisfied.

Further, as described above, the second diffraction grating 54
When using the higher order light of, or the first diffraction grating 5
When the third-order light of 3 is used, the phase difference β ₀ of the interference fringes is as follows with respect to the phase difference β ₁ of the regions u _a and u _b of the diffraction grating. That is, when the n ₂ -order light and the m ₂ -order light of the second diffraction grating 54 are used, the phase shift of the interference fringes is (n ₂ −m _{2) with} respect to the phase shift of the second diffraction grating 54. ) Times, the following formula is derived.

[0229]

Β ₀ = (n ₂ −m ₂ ) β ₁

Therefore, if β ₀ = π / 2, then β ₁ = π /
[2 (n ₂ −m ₂ )].

By the way, for example, in the encoder device of FIGS. 13 and 14, the sinusoidal signal obtained from each of the light receiving elements 7a and 7b has a bias component t ₁ as shown in FIG.
Since the waveforms are superimposed, the reading is likely to be erroneous if they are left as they are. In other words, this type of sinusoidal signal is better in quality as the valley-to-peak ratio (t ₂ / t ₁ ; aspect ratio) is larger, but the sinusoidal signal from one light receiving element 7a or 7b is biased. Since it has the component t ₁ , this sinusoidal signal is not of good quality.

Therefore, as shown in FIG. 45, when light and dark of interference fringes are generated one by one in a light diameter (circle in the figure) in which light is overlapped, the light receiving elements 7a and 7b are respectively affected. , spaced apart corresponding to the brightness of the interference fringes (half lambda _0/2 of the pitch lambda ₀ of the interference fringes), further, the light receiving elements 8a, arranged 8b, the difference between the output of the light receiving element 7a and the light receiving element 8a, It is also possible to adopt a configuration in which the difference between the outputs of the light receiving elements 7b and 8b is taken.

FIG. 46 shows the output signal a1 of the light receiving element 7a and the output signal _a of the light receiving element 8a in one region of the diffraction grating 53 or 54, for example u _a, in the structure of FIG.
A difference signal (a1−a2) between the outputs of the two light receiving elements 7a and 8a.
It is a figure which respectively shows a2). As can be seen from FIG. 46, since the light receiving elements 7a and 8a are arranged at intervals of half the pitch of the interference fringes, the output signals a1 and a2 of the light receiving elements 7a and 8a have a phase difference of 180 °, and The bias component t ₁ can be removed by obtaining the difference signal (a1-a2) between the outputs a1 and a2 of the light receiving elements 7a and 8a, and a good sinusoidal signal with a high aspect ratio can be obtained. You can The difference signal (a1-a2) between the outputs of the light receiving elements 7a and 8a and the difference signal (b1-b2) between the outputs of the light receiving elements 7b and 8b are as shown in FIG.
By making (a1-a2) and (b1-b2) the final outputs, a good A-phase signal having a phase difference of 90 °,
Since the B-phase signal can be obtained, the movement amount can be measured with higher accuracy. Further, in this case, as shown in FIG. 48, by reducing the width H of the light receiving elements 7a, 8a; 7b, 8b, the bias component t ₁ can be further reduced, and the amplitude of the difference signal is increased. Therefore, it is possible to obtain a more nearly perfect quality sinusoidal signal. However, if the width H is reduced, the amount of light received also decreases. Therefore, the width H of the light receiving elements 7a, 8a; 7b, 8b should be designed appropriately according to the application. Further, in the above-described example, the light receiving elements 7a and 8 are provided with an interval (half the pitch of the interference fringes) corresponding to the contrast of the interference fringes.
Although a; 7b and 8b are arranged, the present invention is not limited to such an arrangement example, and various modifications are possible.

In the encoder device (linear encoder device, rotary encoder device) of each of the above-mentioned embodiments,
First diffraction grating 3, 23, 33, 43, 53, 6
3 and 73 are fixed and the second diffraction gratings 4, 24 and 3
4, 44, 54, 64, 74 are used for movement, but the first diffraction gratings 3, 23, 33, 43, 53, 63, 73
Is used for moving (that is, a moving diffraction grating), and the second diffraction grating 4, 24, 34, 44, 54, 64, 74
Can be fixed (that is, a fixed diffraction grating).

Furthermore, the first diffraction gratings 3, 23,
Both 33, 43, 53, 63, 73 and the second diffraction gratings 4, 24, 34, 44, 54, 64, 74 are used for movement, and the first diffraction gratings 3, 23, 33, 43 are used. ，
53, 63, 73 and the second diffraction grating 4, 24, 3
It is also possible to configure so as to measure the amount of movement relative to 4, 44, 54, 64, 74.

Similarly, in the fourth embodiment, the first and second diffraction gratings 53 and 54 may be used for moving and the third diffraction grating 86 may be used for fixing.

The present invention is not limited to the case where the light from the light source 1 is vertically incident on the diffraction grating, and is applicable even when the light is not vertically incident.

[0238]

As described above, according to the first to twelfth aspects of the invention, the information about the movement of the diffraction grating is detected based on the twice-diffracted light and the twice-transmitted light. Therefore, even when the wavelength of the light from the light source changes, the influence of the wavelength change can be reduced without lowering the sensitivity, and the information regarding the movement of the diffraction grating can be accurately measured.

In particular, according to the second aspect of the present invention, the semiconductor laser is used as the light source, whereby a large output can be obtained without increasing the size of the device, and the semiconductor laser is used as the light source. As a result, even if the wavelength of the light changes due to the temperature change, the influence of the wavelength change can be reduced, and the information regarding the movement of the diffraction grating can be accurately measured.

According to the present invention, the first diffraction grating and the second diffraction grating have the same pitch, and the grating surfaces are arranged in parallel with each other. In addition, since the non-parallelizing means for non-parallelizing the two-time diffracted light and the two-time transmitted light into the movement information detection means is further provided, the two-time diffracted light is It is possible to form an interference fringe with a predetermined pitch by making an angle between the two-time transmitted light.

According to the eighth to tenth aspects of the present invention, since the information about the movement of the diffraction grating is detected by utilizing the rotation of the polarized light, it is possible to obtain a perfect sinusoidal signal. Therefore, highly accurate measurement can be performed.

According to the eleventh and twelfth aspects of the invention, whether the first diffraction grating and the second diffraction grating are arranged so that their grating directions are slightly different from each other,
Alternatively, since the pitches are slightly different, it is possible to form interference fringes at a predetermined interval without providing a condenser lens or the like.

According to the thirteenth aspect of the present invention, the first diffracted light of the ± n-order light from the first diffraction grating is changed to the second diffraction light having a pitch slightly different from that of the first diffraction grating. Since the second diffracted light of ± m-order light is generated by diffracting by the grating, it is possible to reduce the influence of the wavelength change of the light, and further, without using the condenser lens, the interference fringes at the predetermined intervals. Can be generated, and the amount of movement of the diffraction grating and the like can be accurately measured.

Further, according to the invention of claim 14, ±
By appropriately selecting the nth order light and the ± mth order light, the pitch and the number of the interference fringes can be selected with a high degree of freedom, and the generation of the interference fringes can be flexibly controlled. In particular, when the ± 1st order light is used as the ± nth order light and the ± 1st order light is used as the ± mth order light, the diffraction efficiency is high, so that it is not necessary to amplify the output of the light receiving element that receives the interference fringes. A wide band amplifier can be used to achieve high speed, and in this case, since the efficiency of light of the secondary light or higher is low, noise is small and the amount of movement can be measured with high accuracy. Furthermore, + 1st order light and −
By using the first-order light, a phase difference is generated in the opposite direction between the + 1st-order light as the + mth-order light and the -1st-order light as the -mth-order light, as the diffraction grating moves by one pitch. From the light receiving element, it is possible to obtain an output signal for two cycles per pitch of the diffraction grating. On the other hand, ± n-order light, ±
When high-order light is used as the m-order light, the sensitivity can be improved, the pitch difference between the two diffraction gratings can be increased, and the allowable range of the grating manufacturing error between the two diffraction gratings can be increased. You can

According to the fifteenth aspect of the invention, the light source and the light from the light source are diffracted to generate the _first diffracted light of the n ₁ -order light and the n ₂ -order light (n ₁ and n ₂ are integers). The first diffraction grating to be generated and the first diffracted light of the n ₁ -order light and the n ₂ -order light from the first diffraction grating are diffracted respectively to m ₁ -order light,
A second diffraction grating for generating a second diffracted light of m ₂ -order light (m ₁ and m ₂ are integers), and m from the second diffraction grating
To generate interference fringes by interference between the _primary beam and the m ₂ order light,
A movement information detecting means for detecting information on the movement of the diffraction grating based on the interference fringes that move with the movement of at least one of the first diffraction grating and the second diffraction grating. Therefore, the orders and diffraction angles of the two light beams to be interfered can be different from each other. For example, even when the first diffraction grating is a very high-density diffraction grating, Compared with the first diffraction grating, the diffraction grating can be made as a low-density diffraction grating,
As a result, accuracy problems can be avoided.

According to the sixteenth and eighteenth inventions, the _first light source and the first diffracted light of the n ₁ -order light and the n ₂ -order light (n ₁ and n ₂ are integers) are generated. And a second diffraction grating for generating a second diffracted light of m ₁ -order light and m ₂ -order light (m ₁ and m ₂ are integers) (further, l ₁ -order light, l ₂
The third diffracted light for generating the third diffracted light of the next light (l ₁ and l ₂ are integers)
The second diffraction grating, and a reflection means for causing the light from the light source to experience the first diffraction grating, the second diffraction grating, and the third diffraction grating twice, respectively, and the light source. Light has undergone the first, second and (third) diffraction gratings, and is then reflected by the reflecting means to (third,) the second and first diffraction gratings again. When the light is emitted from the first diffraction grating, interference fringes are generated by the emitted diffracted light, and the first diffraction grating and the second diffraction grating are generated.
A third diffraction grating, and (3rd) diffraction grating, and movement information detecting means for detecting information on the movement of the diffraction grating based on the interference fringes that move with the movement of at least one diffraction grating. Therefore, the detection sensitivity of the movement amount is increased,
In addition, interference fringes can be generated even when a light source such as a light emitting diode is used.

According to the seventeenth and nineteenth aspects of the invention, the _first light source and the first diffracted light of the n ₁ -order light and the n ₂ -order light (n ₁ and n ₂ are integers) are generated. And a second diffraction grating for generating the second diffracted light of m ₁ -order light and m ₂ -order light (m ₁ and m ₂ are integers), and l ₁ -order light and l ₂ -order light (l ₁ ,
(l ₂ is an integer) The third diffraction grating for generating the third diffraction light, and the light from the light source are caused to experience the first diffraction grating and the second diffraction grating twice, respectively, and The reflecting means for causing the first diffraction grating to experience once, and the light from the light source experiences the first, second, and third diffraction gratings, and is reflected by the reflecting means to become the second and first diffraction gratings. When the first diffraction grating is re-experienced and the first diffraction grating is emitted, the first diffraction grating, the second diffraction grating,
The third diffraction grating has movement information detecting means for detecting information on the movement of the diffraction grating based on the interference fringes that move along with the movement of at least one diffraction grating. Interference fringes can be generated even when a light source is used.

According to the twentieth aspect of the invention, the interference fringes are received by the two light receivers arranged at intervals of half the pitch of the interference fringes, and the phase is 18 from the two light receivers.
Two output signals differing by 0 ° are obtained, and information on the movement of the diffraction grating is detected based on the difference between the two signals. By taking the difference between the two output signals, the bias component is detected. It is possible to obtain a sinusoidal signal having a high aspect ratio and good quality, and the amount of movement of the diffraction grating can be measured more accurately using this signal.

According to the twenty-first aspect of the present invention, the distances of two quarters of the interference fringes are arranged at intervals of one quarter.
One photoreceiver receives the interference fringes, two photoreceivers obtain two output signals whose phases are different from each other by 90 °, and information on the movement of the diffraction grating is detected based on the two output signals. By using the above two output signals as direction discrimination signals, the moving direction of the diffraction grating can be detected, and by taking the difference between the two output signals, a good sinusoidal signal with high aspect ratio can be obtained. It is possible to measure the moving amount of the diffraction grating with higher accuracy using this signal.

According to the twenty-second aspect of the present invention, the three elements are arranged at intervals of a quarter of the pitch of the interference fringes.
One photoreceiver receives the interference fringes, and two more perfect two sinusoidal signals with a phase difference of 90 ° are obtained from the three photoreceivers, and the two signals with a phase difference of 90 ° are discriminated from each other. By using it as a signal, the moving direction of the diffraction grating can be detected with higher accuracy, and the moving amount of the diffraction grating can be accurately measured by the individual signals themselves.

According to the twenty-third aspect of the present invention, in the encoder device of the first aspect, at least one diffraction grating has diffraction grating regions having different phases, and the A phase and the B phase are output from respective outputs. Is detected, stable interference fringes can be obtained and stable A and B phases can be obtained.

Further, according to the invention described in claim 24, it is possible to provide a highly accurate linear encoder device, and according to the invention described in claims 25 to 26, a simpler structure than the conventional structure can be provided. A highly accurate rotary encoder device can be provided.

[Brief description of drawings]

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

FIG. 2 is a diagram for explaining diffracted light and transmitted light from two diffraction gratings of the encoder device of FIG.

FIG. 3 is a diagram showing a change in light amount based on interference fringes that move with the movement of a diffraction grating in the encoder device of FIG.

FIG. 4 is a diagram showing a modified example of the encoder device of FIG. 1.

FIG. 5 is a diagram showing another configuration example of an encoder device using polarization rotation.

FIG. 6 is a diagram showing another configuration example of an encoder device that uses rotation of polarized light.

FIG. 7 is a diagram showing another configuration example of an encoder device that uses rotation of polarized light.

FIG. 8 is a diagram showing still another configuration example of the encoder device according to the first embodiment of the present invention.

9 is a diagram showing output signals in the encoder device of FIG. 8. FIG.

FIG. 10 is a diagram showing still another configuration example of the encoder device according to the first embodiment of the present invention.

FIG. 11 is a diagram showing a configuration example of a rotary encoder device according to the present invention.

FIG. 12 is a diagram showing a configuration example of a rotary encoder device according to the present invention.

FIG. 13 is a configuration diagram of a second embodiment of an encoder device according to the present invention.

14 is a diagram showing a configuration in a case where ± 1st-order light beams from two diffraction gratings are used in the encoder device of FIG.

FIG. 15 is a diagram for explaining the operation principle of the encoder device having the configuration shown in FIG. 14.

16 is a diagram for explaining interference fringes generated by the encoder device having the configuration shown in FIG.

17 is a diagram showing a signal output from the light receiving element of the encoder device having the configuration shown in FIG.

FIG. 18 is a diagram showing a configuration example of a more extended encoder device of the second embodiment.

FIG. 19 is a diagram showing a configuration example of a rotary encoder device according to the present invention.

FIG. 20 is a diagram showing a configuration example of a rotary encoder device according to the present invention.

FIG. 21 is a configuration diagram of a third embodiment of an encoder device according to the present invention.

22 is a diagram showing an equivalent optical system of the encoder device of FIG. 21. FIG.

FIG. 23 is a diagram for explaining a point light source.

FIG. 24 is a diagram showing a modification of the encoder device of FIG. 21.

FIG. 25 is a configuration diagram of a third embodiment of the encoder apparatus according to the present invention.

FIG. 26 is a diagram showing an equivalent optical system of the encoder device of FIG. 25.

FIG. 27 is a diagram showing a modified example of the encoder device of FIG. 25.

FIG. 28 is a diagram showing a configuration example of a rotary encoder device according to the present invention.

FIG. 29 is a diagram showing a configuration example of a rotary encoder device according to the present invention.

FIG. 30 is a diagram showing a configuration example of a rotary encoder device according to the present invention.

FIG. 31 is a diagram showing a configuration example of a rotary encoder device according to the present invention.

FIG. 32 is a diagram showing a configuration example of a rotary encoder device according to the present invention.

FIG. 33 is a diagram showing a configuration example of a rotary encoder device according to the present invention.

FIG. 34 is a diagram showing a configuration example of a rotary encoder device according to the present invention.

FIG. 35 is a diagram showing a configuration example of a rotary encoder device according to the present invention.

FIG. 36 is a diagram showing a configuration example of an encoder device in which two light receiving elements are arranged at intervals of half the pitch of interference fringes.

37 is a diagram showing an output signal from each light receiving element of the encoder device configured as shown in FIG. 36;

FIG. 38 is a diagram showing a state where the width of each light receiving element is reduced in the encoder device having the configuration of FIG. 36.

[Fig. 39] Fig. 39 is a diagram illustrating a configuration example of an encoder device in which two light receiving elements are arranged at intervals of a quarter of the pitch of interference fringes.

40 is a diagram showing an output signal from each light receiving element of the encoder device configured as shown in FIG. 39. FIG.

[FIG. 41] The distance between adjacent elements is 4 times the pitch of interference fringes.
It is a figure which shows the structural example of the encoder apparatus in which the three light receiving elements are arrange | positioned so that it may become 1/10.

42 is a diagram showing an output signal from each light receiving element of the encoder device having the configuration of FIG. 41. FIG.

FIG. 43 is a diagram showing a configuration example of a diffraction grating and an example of generation of interference fringes.

FIG. 44 is a diagram showing a configuration when high-order light from two diffraction gratings is used.

[Fig. 45] Fig. 45 is a diagram illustrating a configuration example of an encoder device in which light-receiving elements are arranged at intervals of half the pitch of the interference fringes with respect to each of the light-receiving elements arranged side by side in the direction of the interference fringes.

FIG. 46 is a diagram showing an output signal from the light receiving element in one region of the encoder device configured as shown in FIG. 45.

47 is a diagram showing a final output signal of the encoder device of FIG. 45. FIG.

FIG. 48 is a diagram showing a state where the width of each light receiving element is reduced in the encoder device of FIG. 45.

FIG. 49 is a configuration example of a conventional encoder device.

50 is a diagram for explaining diffracted light generated from two diffraction gratings of the encoder device of FIG. 49.

51 is a diagram for explaining diffracted light generated from two diffraction gratings of the encoder device of FIG. 49.

[Explanation of symbols]

1 light source 2,9 lens 3,23,33,43,53,63,73 first diffraction grating 4,24,34,44,54,64,74 second diffraction grating 5 condensing lens 7, 27,37 light receiving element 11,12 polarizing plate 13 beam splitter 14 polarizing beam splitter 15 λ / 4 plate 16 polarizing beam splitter 17a, 17b light receiving element 18 polarizing plate 81 reflecting means (mirror) 82 splitting means ( Beam splitter) 84 Reflecting means 86 Third diffraction grating 90 Movement information detecting means

Claims (26)

[Claims] 1. A light source, a first diffraction grating on which light from the light source is incident, a second diffraction grating on which light from the first diffraction grating is incident, and the first diffraction grating. And a movement information detection means for detecting information regarding movement of at least one diffraction grating of the second diffraction grating,
The movement information detecting means is a diffracted light from the first diffraction grating and is also diffracted by the second diffraction grating (twice diffracted light), and a light from the first diffraction grating. An encoder device for detecting information about movement of a diffraction grating on the basis of transmitted light (light transmitted twice) which is also transmitted through the second diffraction grating. 2. The encoder apparatus according to claim 1, wherein a semiconductor laser is used for the light source. 3. The encoder apparatus according to claim 1, wherein the first diffraction grating and the second diffraction grating have the same pitch and the grating surfaces are arranged in parallel with each other. An encoder device characterized by. 4. The encoder apparatus according to claim 1, wherein the movement information detecting means includes the two-time diffracted light and the two-time diffracted light.
An encoder device for detecting information about movement of a diffraction grating based on movement of interference fringes formed by interference with transmitted light. 5. The encoder apparatus according to claim 1, wherein the first diffraction grating and the second diffraction grating have the same pitch, and the grating surfaces are arranged in parallel with each other. In addition, an encoder is further provided which is provided with an uncollimating means for uncollimating the twice-diffracted light and the twice-transmitted light before they enter the movement information detecting means. apparatus. 6. The encoder apparatus according to claim 5, wherein the non-parallelizing means is a condenser lens provided between the second diffraction grating and the movement information detecting means. An encoder device characterized by. 7. The encoder apparatus according to claim 5, wherein the decollimating means is a lens provided between the light source and the first diffraction grating. apparatus. 8. The encoder apparatus according to claim 1, wherein the movement information detecting means includes the two-time diffracted light and the two-time diffracted light.
Linearly-polarizing means for linearly polarizing the transmitted light in directions orthogonal to each other, superimposing means for superimposing the linearly polarized light of the twice-diffracted light and the linearly polarized light of the twice-transmitted light, and a superimposing means. Circularly polarized light conversion means for converting the linearly polarized light of the twice-diffracted light and the linearly polarized light of the twice-transmitted light, which are superimposed on each other, into circularly polarized light having different rotation directions, and the light from the circularly polarized light conversion means is incident. , And a means for separating the incident light into two polarizations orthogonal to each other, and by measuring the light quantity ratio of the two polarizations separated by the separation means, information about the movement of the diffraction grating is detected. Encoder device characterized in that 9. The encoder apparatus according to claim 1, wherein the second diffraction grating emits twice-diffracted light and twice-transmitted light in a linearly polarized state orthogonal to each other, and these are overlapped with each other. In this case, the movement information detecting means converts the superimposed linearly polarized light of the twice-diffracted light and linearly polarized light of the twice-transmitted light into circularly polarized light having different rotation directions, respectively. And a separating means for separating the light from the circularly polarized light converting means into two polarizations orthogonal to each other, and by detecting the light quantity ratio of the two polarizations separated by the separating means, information regarding the movement of the diffraction grating is detected. An encoder device characterized by being adapted to. 10. The encoder apparatus according to claim 8 or 9, wherein the pitches of the first diffraction grating and the second diffraction grating are smaller than the wavelength of light from the light source. An encoder device characterized by the following. 11. The encoder apparatus according to claim 1, wherein the first diffraction grating and the second diffraction grating have the same pitch, and the grating surfaces are parallel to each other, and
An encoder device characterized in that it is arranged with the grating directions being slightly different. 12. The encoder apparatus according to claim 1, wherein the first diffraction grating and the second diffraction grating have slightly different pitches. 13. A light source and ± n obtained by diffracting light from the light source.
The first diffraction grating that generates the first diffracted light of the next light (n is positive) is slightly different in pitch from the first diffraction grating, and ± n from the first diffraction grating is used. A second diffraction grating that diffracts the first diffracted light of the next light to generate the second diffracted light of the ± m-order light (m is positive), and the ± m-order light from the second diffraction grating Interference between them causes interference fringes,
A movement information detecting means for detecting information on the movement of the diffraction grating based on the interference fringes that move with the movement of at least one of the first diffraction grating and the second diffraction grating. An encoder device characterized in that. 14. The encoder apparatus according to claim 13, wherein the difference between the number of diffraction gratings that the light from said light source experiences in said first diffraction grating and the number of diffraction gratings experienced in said second diffraction grating. Is one or more, and the −m-order light in the second diffracted light of the + n-order light of the first diffracted light and the first diffracted light
The −n-order light of the diffracted light and the + m-order light of the second diffracted light are caused to interfere with each other to generate interference fringes having a pitch according to the difference in the number of the diffraction gratings. Information on the movement of the diffraction grating is detected based on the interference fringes that move along with the movement of at least one of the second diffraction grating and the second diffraction grating. Encoder device. 15. A light source and n ₁ by diffracting light from the light source.
A first diffraction grating for generating a first diffracted light of the _second light and the n2 th light (n ₁ and n ₂ are integers), and n 1 th light and n ₂ th light from the _first diffraction grating Second diffractive grating for diffracting the first diffracted light of the above to generate second diffracted light of m ₁ -order light and m ₂ -order light (m ₁ and m ₂ are integers), and the second diffraction grating. Interference fringes are generated by the interference between the m ₁ -order light and the m ₂ -order light from the grating, and with the movement of at least one of the first diffraction grating and the second diffraction grating, An encoder device, comprising: a movement information detection unit that detects information regarding the movement of the diffraction grating based on the moving interference fringes. 16. A light source and n ₁ by diffracting light from the light source.
A first diffraction grating for generating a first diffracted light of the _second light and the n2 th light (n ₁ and n ₂ are integers), and n 1 th light and n ₂ th light from the _first diffraction grating The second diffractive grating for diffracting the first diffracted light of the above to generate the second diffracted light of m ₁ -order light and m ₂ -order light (m ₁ and m ₂ are integers), and the light from the light source Reflecting means for causing the first diffraction grating and the second diffraction grating to experience each two times, and a reflecting means after the light from the light source has experienced the first and second diffraction gratings. When the light is reflected by the second diffraction grating, the second diffraction grating and the first diffraction grating are re-experienced. When the diffraction grating is emitted from the first diffraction grating, interference fringes are generated by the emitted diffracted light, and the first diffraction grating and the first diffraction grating. The movement of the diffraction grating is determined based on the interference fringes that move with the movement of at least one diffraction grating of the second diffraction grating. The encoder apparatus characterized by and a movement information detecting means for detecting that information. 17. A light source and n ₁ by diffracting light from the light source.
A first diffraction grating for generating a first diffracted light of the _second light and the n2 th light (n ₁ and n ₂ are integers), and n 1 th light and n ₂ th light from the _first diffraction grating. The second diffractive grating for diffracting the first diffracted light of the above to generate the second diffracted light of m ₁ -order light and m ₂ -order light (m ₁ and m ₂ are integers), and the light from the light source Reflecting means for causing the first diffraction grating to experience twice and allowing the second diffraction grating to experience once, and light from the light source experiences the first and second diffraction gratings and is reflected. The first diffraction grating is re-experienced after being reflected by the means, and when emitted from the first diffraction grating, interference fringes are generated by the emitted diffracted light, and the first diffraction grating and the second diffraction grating are generated.
An encoder device, comprising: movement information detection means for detecting information regarding the movement of the diffraction grating based on the interference fringes that move with the movement of at least one diffraction grating of the th diffraction grating. 18. A light source, and n _1st- order light and n _2nd- order light (n ₁ , n ₂
Is an integer)) and a second diffraction grating that generates a first diffracted light of m ₁ -order light and m ₂ -order light (m ₁ , m ₂ is an integer). A diffraction grating, a third diffraction grating that generates third diffracted light of l ₁ -order light and l ₂ -order light (where l ₁ and l ₂ are integers), and light from a light source as the first diffraction grating. After the reflecting means for causing the second diffraction grating and the third diffraction grating to experience each two times, and the light from the light source has experienced the first, second, and third diffraction gratings. When the third diffraction grating, the second diffraction grating, and the first diffraction grating, which have been reflected by the reflecting means, are re-experienced and emitted from the first diffraction grating, interference fringes are generated by the emitted diffracted light. It moves with the movement of at least one of the first diffraction grating, the second diffraction grating, and the third diffraction grating. The encoder apparatus characterized by and a movement information detecting means for detecting information on the movement of the diffraction grating based on the interference fringes. 19. A light source, and n _1st- order light and n _2nd- order light (n ₁ , n ₂
Is an integer)) and a second diffraction grating that generates a first diffracted light of m ₁ -order light and m ₂ -order light (m ₁ , m ₂ is an integer). A diffraction grating, a third diffraction grating that generates third diffracted light of l ₁ -order light and l ₂ -order light (where l ₁ and l ₂ are integers), and light from a light source as the first diffraction grating. Reflecting means for causing the second diffraction grating to experience each two times and the third diffraction grating to experience once,
The light from the light source goes through the first, second and third diffraction gratings, and is reflected by the reflecting means to become the second and first diffraction gratings.
When the first diffraction grating is re-experienced and emitted from the first diffraction grating, at least one diffraction grating of the first diffraction grating, the second diffraction grating, and the third diffraction grating moves. An encoder device, comprising: a movement information detection unit that detects information regarding the movement of the diffraction grating based on the interference fringes that move with it. 20. In an encoder device of a type that detects information on the movement of a diffraction grating based on interference fringes, two encoders arranged at intervals of half the pitch of the interference fringes.
Two photoreceivers are provided, the two photoreceivers receive the interference fringes, two output signals having phases different by 180 ° are obtained from the two photoreceivers, and a diffraction grating is obtained based on a difference between the two output signals. An encoder device, which is adapted to detect information about movement of the. 21. An encoder device of the type for detecting information on the movement of a diffraction grating based on interference fringes, comprising two light receivers arranged at intervals of a quarter of the pitch of the interference fringes. , The two light receivers receive the interference fringes, two output signals having phases different by 90 ° are obtained from the two light receivers, and information on the movement of the diffraction grating is detected based on the two output signals. An encoder device characterized in that 22. An encoder device of the type for detecting information on the movement of a diffraction grating based on interference fringes, comprising three light receivers arranged at intervals of a quarter of the pitch of the interference fringes. An encoder device, wherein the three light receivers receive the interference fringes and two signals having phases different by 90 ° are obtained from the three light receivers. 23. The encoder apparatus according to claim 1, wherein at least one diffraction grating has diffraction grating regions having different phases, and the A phase and the B phase are detected from respective outputs. Characteristic encoder device. 24. The encoder apparatus according to claim 1, wherein the moving diffraction grating of at least one of the first diffraction grating and the second diffraction grating is configured to move linearly. , An encoder device configured as a linear encoder. 25. The encoder according to claim 1, wherein a moving diffraction grating of at least one of the first diffraction grating and the second diffraction grating is formed on a cylindrical surface. An encoder device characterized by being configured as. 26. The encoder according to claim 1, wherein a moving diffraction grating of at least one of the first diffraction grating and the second diffraction grating is formed on a disc. An encoder device characterized by being configured as.