JP2862448B2 - Optical displacement sensor and drive system using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention utilizes the fact that when a light beam irradiated on a displaced object is diffracted or scattered, the diffracted or scattered light beam undergoes a phase modulation action in accordance with the displacement or moving speed of the object. The present invention relates to an optical displacement sensor such as an encoder, a speed sensor, and an acceleration sensor for measuring a displacement and a speed of an object.

[0002]

2. Description of the Related Art Conventionally, an optical displacement sensor for irradiating an object with light to obtain a physical quantity such as movement or displacement of the object with high accuracy, for example, an optical encoder, a laser Doppler velocimeter,
Laser interferometers and the like are widely used mainly in the fields of NC machine tools, OA equipment, robots, and the like. As a conventional example of such a displacement sensor, for example, an optical encoder is disclosed in Japanese Utility Model Laid-Open No. 1-180615 and Japanese Patent Application Laid-Open No. 62-121314. Further, Japanese Patent Application Laid-Open No. Hei 2-262604 discloses an example of a laser Doppler velocimeter.

[0003]

Considering application of the displacement sensor to a wider field, further miniaturization (size on the order of millimeters) and higher precision and higher resolution (on the order of 0.1 μm) are considered. ) Is desired. With a millimeter size, it can be used, for example, by directly attaching it to an object to be measured with an adhesive or the like, so that it can be used for a smaller device and the field of application is dramatically expanded. However, the conventional displacement sensor has a limit in pursuing both miniaturization and high accuracy and high resolution.

SUMMARY OF THE INVENTION It is a first object of the present invention to provide an optical sensor and a system using the same, which achieve both miniaturization and high precision and high resolution at a very high level.

It is a second object of the present invention to provide an optical displacement detection sensor which can be miniaturized and which can fix a main part of an optical element to reduce an error factor to enable high-precision measurement. I do.

A third object of the present invention is to provide an optical displacement detection sensor capable of performing measurement with high accuracy even when a rotation error occurs between the sensor head side and the diffraction grating side.
The purpose of.

[0007]

A preferred example of the optical displacement sensor according to the present invention for solving the above-mentioned problems is a housing having an optical window, a light emitting element and a light receiving element built in the housing, and A light-transmitting member provided in the vicinity of the window, a first optical functional element provided on the light-transmitting member, for splitting light generated by the light-emitting element into a plurality of light beams, and emitting the light; A second optical function element provided on the optical member, for guiding the light that has been emitted to the relative displacement object and is modulated by the light to the light receiving element.

In another preferred embodiment of the present invention, a light source, a light beam converting element for converting the divergent state of the light beam from the light source, and a light beam converted by the light beam converting element are separated into first and second light beams. And a diffractive light generated corresponding to each light beam from the test object illuminated by the first and second light beams. And a detection system for detecting the displacement of the test object based on the detection result of the detection system.

Still another preferred embodiment of the present invention is an optical displacement sensor for measuring a relative displacement between a diffraction grating to be measured, and a light emitting element and a divergent and divergent light beam emitted from the light emitting element. An optical unit for converting a state, a first diffraction grating for splitting a light beam from the light emitting element into a first light beam and a second light beam, and each of the first light beam and the second light beam applied to the measured diffraction grating. A second diffraction grating for combining generated diffracted light beams to obtain an interference light beam; and a light receiving element for receiving the interference light beam, such that the wavefront of the interference light beam incident on the light receiving element is spherical. It is arranged in.

[0010]

【Example】

<Embodiment 1> FIG. 1 shows an optical encoder according to a first embodiment of the present invention.
It is the block diagram seen from the direction, (A) shows a side view, (B) shows a top view, and (C) shows a front view. FIG. 2 is a perspective view of a main part.

The member 1 is a light emitting element for generating light, and has a size on the order of several hundreds of μm. The light emitting device of this embodiment is a semiconductor laser device that generates laser light having a wavelength of 780 nm. In addition, as the light emitting element, a light emitting diode or the like can be used in addition to the semiconductor laser. Light generated and emitted from the horizontally disposed light emitting element 1 is reflected by the mirror 2 having a mirror surface with a 45-degree inclination and directed in the vertical direction. Note that a prism can be used instead of the mirror. A transparent glass plate 3, which is a light transmitting member, is provided in the direction in which the light is directed. On one surface (inner surface) of the glass plate 3, three replica lens portions 31A, 31B,
On the other surface (outer surface), three replica diffraction grating portions 32A, 32B, and 32C having the same pitch are formed.
It is formed so as to face the two lens portions. The pitch P of each diffraction grating portion was 1.6 μm in this embodiment. In addition, three light receiving elements 4A, 4B, and 4C each having a size on the order of several hundred μm are provided for receiving light and performing photoelectric conversion. Specific examples of the light receiving element include a photodiode, an avalanche photodiode, a pin photodiode, a CCD, and a light receiving I / O having a circuit for amplifying or processing a photocurrent output from the light receiving section.
C and the like. The light beam emitted from the rear surface of the semiconductor laser element 1 is guided to the light receiving element 4A, and the light quantity can be monitored, and is used for feedback such as APC (Auto Power Control) control. The light receiving elements 4B and 4C detect signals having a phase difference from each other, and
Reference numeral 1C is provided to allow only the necessary light beam to be stably incident on the minute light receiving elements 4B and 4C.

Light emitting element 1 and light receiving elements 4A, 4B, 4C
Is sealed in a ceramic light-shielding housing 5, and the glass plate 3 is attached to an optical window on the upper surface of the housing 5 to hermetically seal the inside. In addition, two shielding plates 6 are inserted between the light emitting element and the light receiving element so that light from the light emitting element does not directly enter the light receiving element. An electrode pattern is connected to each of the light emitting element 1 and the light receiving elements 4A, 4B, 4C, and an end of each electrode pattern is exposed to the outside of the housing 5. When a signal processing circuit is built in the housing, an output signal of the circuit is output to the exposed electrode pattern. The housing 5 has a size on the order of several mm, and constitutes a very small sensor unit.

On the other hand, at a position facing the sensor unit, a transparent scale 20 is attached to an object that moves relatively to the sensor unit, and a reflective diffraction grating 21 serving as a scale is formed on the scale. . The pitch P of the diffraction grating 21 is 1.6 μm as in the above-described diffraction grating.

The divergent light beam emitted from the light emitting element 1 horizontally mounted in the housing of the sensor unit has its path vertically bent by a mirror 2 and is formed on the inner surface of a glass plate 3 mounted on a window. The light is converted into a substantially parallel light beam by the lens 31A. This luminous flux is a glass plate 3
Is transmitted and diffracted by a diffraction grating 32A formed on the outer surface of the light-emitting device, and is divided into a plurality of light beams including three _0-order diffracted light R ₀ , + 1st-order diffracted light R ₊₁ , and -1st-order diffracted light R ₋₁ and emitted. I do.

Of these, the light flux R traveling straight through the diffraction grating 32A
₀ is reflected and diffracted at a point P1 on the diffraction grating 21 formed on the scale 20, is divided into ⁺ 1st-order diffracted light R ₀ ⁺¹ and −1st-order diffracted light R ₀ ^-1 and is phase-modulated. When the scale 20 moves relatively, the phase of the + 1st-order diffracted light R ₀ ⁺¹ is shifted by + 2πx / P, and the phase of the −1st-order diffracted light R ₀ ^-1 is shifted by −2πx / P. Here, x is the amount of movement of the diffraction grating 21, and P is the pitch of the diffraction grating 21.

The + 1st-order diffracted light R ₀ ⁺¹ is being transmitted diffracted by the diffraction grating 32B formed on the surface of the glass plate 3, 0-order diffracted light R ₀ ⁺¹ _0, -1-order diffracted light R ₀ ⁺¹ _-1 and The light beam is split into other light beams, of which the -1st-order diffracted light R ₀ ⁺¹ _-1 is extracted perpendicular to the diffraction grating surface, and the phase of the wavefront at this time is + 2πx /
It becomes P. Also, the -1st-order diffracted light R ₀ ^-1 is being transmitted diffracted by the diffraction grating 32C formed on the surface of the glass plate 3, 0-order diffracted light R ₀ ^-1 _0, + 1-order diffracted light R ₀ ^-1 ₊₁ and other + 1st-order diffracted light R ₀ ^-1 ₊₁ is taken out perpendicular to the diffraction grating surface, and the phase of the wavefront at this time is -2πx
/ P.

Here, the diffraction grating 32B is shifted from 32C with respect to 32C.
If the phase relation of the lattice arrangement is shifted by P / 4, +1
The second-order diffracted light R ₀ ^-1 ₊₁ has a wavefront phase of −2π (P / 4).
/ P = -2πx / P-π / 2 shifted by -π / 2.

On the other hand, the light beam R ₊₁ diffracted + 1st-order by the diffraction grating 32A formed on the surface of the glass plate 3 is
The light is reflected and diffracted at a point P2 on the upper diffraction grating 21, and -1
Order diffraction light R ₊₁ ^-1, 0 is divided into order diffracted light R ₊₁ ⁰ and other light beams are respectively phase-modulated. Among them, the phase of the ^-1st-order diffracted light R ₊₁ ^-1 is shifted by -2πx / P and the diffraction grating 3
0B diffracted light R ₊₁ incident on 2B and traveling straight there
The phase of the wavefront of ^-1 is -2? X / P.

The light beam R _-1 diffracted -1st-order by the diffraction grating 32A formed on the surface of the glass plate 3 is reflected and diffracted at a point P3 on the diffraction grating 21 on the scale 20, and the + 1st-order diffracted light is reflected. The light is split into R _-1 ⁺¹ , 0th-order diffracted light R _- ^10, and other light beams, and each is phase-modulated. Among them, the phase of the + 1st order diffracted light R _-1 ⁺¹ is shifted by + 2πx / P, and the diffraction grating 3
0C diffracted light R _-1 which is incident on 2C and goes straight there
The phase of the ⁺¹ wavefront is + 2πx / P.

[0020] by the diffraction grating 32B, the light beam was superposed an optical path R ₊₁ ^-1 ₀ and the light beam R ₀ ⁺¹ _-1 are taken with interference light is condensed by the lens 2B is incident on the light receiving element 4B . The interference phase at this time is as follows: {+ 2πx / P} − {− 2πx / P} = 4πx / P, and a light-dark signal of one cycle is generated each time the diffraction grating 21 on the scale 20 moves by ピ ッ チ pitch.

The light beam R _-1 ⁺¹ ₀ and the light beam R ₀ ^-1 ₊₁ whose optical paths are superimposed on the diffraction grating 32C become interference light, which is condensed by the lens 2C and enters the light receiving element 4C. . The interference phase at this time is {-2πx / P-π / 2}-{+ 2πx / P} =-4π
x / P−π / 2, and a light-dark signal of one cycle is generated every time the diffraction grating 21 on the scale 20 moves by ピ ッ チ pitch.
The timing of light and dark is shifted by 1/4 cycle.

As described above, with the displacement of the scale, the periodic signals A and B whose phases are shifted from each other by 1/4 cycle (90 degrees) are obtained by the light receiving elements 4B and 4C. Based on this, it is possible to detect a relative displacement state between the sensor unit and the scale using a known signal processing circuit such as an amplifier, a signal interpolation circuit, a binarization circuit, and a direction determination circuit.
In this embodiment, the integration is enhanced by incorporating some or all of these signal processing circuits in the sensor unit.

The diffraction grating in this embodiment employs a phase grating, that is, a so-called relief type diffraction grating, and is designed under the following optimum conditions. In each of the embodiments of the encoder described later, the optimum design is similarly made.

FIG. 3 is a cross-sectional view of the relief type diffraction grating. If the duty (the ratio of the width in the arrangement direction of the groove bottom and the groove upper part in the arrangement direction) is 50% (a = b in FIG. 3), even-order diffraction is performed. Since no light is generated, it is convenient for the encoder having the configuration of the present embodiment. The duty of the diffraction grating is 50
%, Μ is the diffraction order, C ₁ is a constant, λ is the wavelength of light, π is the circular constant, N is the refractive index of the material of the phase grating, and d is the step of the phase grating. (Μ) is I (μ) = C ₁ {[sin (πμ / 2)] / (πμ / 2)} ² × {1 + (− 1) μcos (2π (N−1) d / λ)} ... (1) Thus, zero-order diffracted light intensity I ₀ and 1-order diffracted light intensity I _{1 is, I 0 = C 1 {1} + cos (2π (N-1) d / λ)} ···· (2) I 1 = C 1 ( 2 / π) ² {1-cos (2π (N−1) d / λ)} (3) Therefore 0 complex optical I _01-order diffracted light and 1-order diffracted light is the product of these diffracted light intensity and (2) (3).

[0025] ^{_{I 01 = C 1 2 (2}} / π) 2 {1-cos 2 (2π (N-1) d / λ)} ···· (4)

Here, the numerical value N = 1.5 in the present embodiment.
FIG. 4 shows a graph of the diffracted light intensity at 3348, λ = 780 nm. The condition of the step d _{M at which} the composite light intensity I ₀₁ becomes maximum is obtained by using (4), and I ₀₁ ′ (d _M ) = 0 I ₀₁ ″ (d _M ) <0 (5) Here, “′” is a derivative with respect to the step d. From this, the step d _{M at} which the composite light I ₀₁ becomes the maximum is obtained from (4) and (5), and d _M = (2n + 1) λ / (4 (N− 1)) (6) n = 0, 1, 2, 3,...

In the encoder according to the present embodiment, in which the interference light is formed by the composite light of the ± 1st-order diffracted light and the 0th-order diffracted light, it is desirable that the intensity of the composite light is as large as possible and the fluctuation of the intensity of the composite light is small. Further, in order to receive signal light and perform processing such as electric division using a signal converted into an electric signal by a light receiving element, it is desirable that the intensity fluctuation of the composite light be suppressed to within 10%. 10% intensity fluctuation of composite light
The conditions to be held down are as follows from (4) to (6).

{Λ / [4π (N−1)]} 2nπ + cos ⁻¹ (−0.8)} ≦ d _{> 90} ≦ {λ / [4π (N−1)]} 2 (n + 1) π− cos ⁻¹ (−0.8)｝ n = 0, 1, 2, 3, 4,... (7) Here, the step d _M at which the composite light intensity I ₀₁ is the maximum is 90, %
When the difference d _{> 90} is obtained, λ = 780 nm, N
= 1.53348 is applied to the equations (6) and (7) and is obtained as follows.

D _M = 365.524 nm 290.653 nm ≦ d _{> 90} ≦ 440.396
nm The above d _M is the optimum value of the groove depth in the encoder of the present embodiment, and d _{> 90} is an allowable value. By designing the groove depth of the relief transmission type diffraction grating in this way, the relief transmission type diffraction grating can be obtained. The variation in the intensity of the diffracted light generated by the grating is suppressed to a small value, and a composite diffracted light is obtained with high efficiency.

In the encoder of the present embodiment described above, the interference optical system is composed of lenses, diffraction gratings, and diffraction gratings on a scale formed on both surfaces of a glass plate by a replica method or the like. An encoder that is small in size, low in cost, and capable of high-accuracy and stable displacement detection is realized, but further has the following significant features.

Three sets of diffraction gratings (32A, 21, 32)
B or 32C) using + 1st and -1st diffraction, 0
Since the interference optical system is configured to perform the next diffraction one time at a time, even if the wavelength of the light source fluctuates and the diffraction angle fluctuates, it is corrected in the opposite direction by the second diffraction, and the diffraction grating (32
B or 32C), the angles (0 °) emitted from them are all kept constant, and the overlapping state of the two light beams and the mutual difference in the traveling direction are preserved. Therefore, a semiconductor laser in which wavelength fluctuation is inevitable can be used without a temperature compensation function such as temperature control. If a sensor with higher stability is required, these temperature compensation functions may be added.

Even if the parallelism between the scale 20 and the glass plate 3 is slightly deviated, the directions in which the optical paths of the two interfering light beams deviate coincide with each other. Is a highly accurate encoder that is not affected by the scale mounting accuracy. In other words, the mounting accuracy of the scale 20 may be somewhat coarse, or the scale 20 can be used in an adverse environment where the mounting accuracy is deteriorated. Considering that the sensor unit is integrated into one chip, the environment resistance against a bad environment such as temperature fluctuation and vibration becomes very high.

The luminous flux is synthesized at two places (3
2B and 32C) and are separated from each other. Therefore, if the diffraction gratings 32B and 32C are formed to be shifted in phase, a desired phase difference can be obtained without preparing a split optical system in order to obtain a two-phase signal. Since a signal is obtained, the design of the optical system is easy. Further, the phase difference does not depend on a subtle difference in the cross-sectional shape of the diffraction grating, and an amplitude grating can be used.

Since the division and combination of the luminous flux by the diffraction grating are performed at different places to separate the optical paths, even if there is reflected return light on each surface, it does not enter the light receiving element and cause a problem. . Furthermore, since the shielding plate 6 is inserted, the optical path on the outward path and the optical path on the return path are completely optically insulated in the housing, and the influence of unnecessary light is eliminated.

Since the reciprocating optical path is separated, forming a small-diameter microlens with a short focal length can reduce the distance between the light emitting element and the lens, which is advantageous for miniaturization and thinning.

Since the light path from the light emitting element is bent by the reflective element, the optical path can be bent by the reflecting element. Therefore, even if the glass plate and the light emitting element are brought close to each other, the lens and the light emitting element can be separated by a desired focal length, and the thickness can be reduced. Is advantageous.

The smaller the pitch of the diffraction grating on the scale, the larger the diffraction angle. Even if the distance to the scale is small, the diffracted light can be sufficiently spatially separated, so that it is easy to reduce the size. In other words, miniaturization and high precision
Both high resolution can be improved at the same time.

Since a glass plate-shaped optical component is overlapped and sealed on the window of the housing, the bonding work of the light emitting element, the light receiving element, the chip electronic circuit and the electrode, the manufacturing work of the glass plate shaped optical functional part, Since the joining operation of the two is independent, the assembling property is good.

By optimally designing the shape of the relief transmission type diffraction grating, composite diffracted light can be obtained with high efficiency.

<Embodiment 2> Next, as a second embodiment of the present invention, FIG. 5 shows an encoder in which the above embodiment is modified to further improve the stability. In the drawing, the same reference numerals as those in the previous embodiment represent the same or equivalent members. In the following embodiments, the same components as those in the previous embodiment are partially omitted from explanation and the like. The present embodiment is characterized in that a four-phase signal whose phase is shifted by 1/4 cycle (90 degrees) is obtained, and a two-phase signal is generated based on this.

The lenses 31B and 31C are compound lenses formed on a glass plate, and include four diffraction gratings 32B ₁ , 3B.
2B ₂ , 32C ₁ , and 32C ₂ are arranged out of phase with each other as shown in the figure. When thinking diffraction grating 32B ₁ relative to the phase to be 0 degrees, the diffraction grating 32C ₁ phase 9
0 degrees, and the phase 180 degrees diffraction grating 32B _2, diffraction grating 3
The phase of 2C ₂ is shifted by １ ／ cycle of 270 degrees and is arranged. Thus the diffraction grating (32B ₁ and 32B _2, 3
2C ₁ and 32C ₂ ), diffracted lights having different phases are emitted and each is separately collected by each lens element of the compound lens. Further, in order to detect the light amount of each light beam that has passed through each diffraction grating and separately collected by each lens element, four light receiving elements 4B ₁ , 4B ₂ , 4C ₁ ,
4C ₂ is arranged as shown. With these light receiving elements, a four-phase signal whose phase is shifted by １ ／ cycle is obtained. These four-phase signals are connected to a push-pull as shown in the figure, and signals having opposite phases having a phase difference of 180 degrees are differentially amplified.
The phase signals A and B are generated.

By adopting such a configuration, the DC fluctuation of the periodic signal obtained according to the phase of the scale is removed, so that a defect on the scale side (scale mounting inclination, dust on the scale, scale failure due to manufacturing defect). Even if there are irregularities in reflectivity, etc., or defects on the light source side (fluctuations in the light amount of the light source, fluctuations in the light source wavelength, mixing of unnecessary light, etc.), these effects are canceled, and a stable signal can be obtained even in a poor environment. Encoder.

Further, since the interference signals having different phases are spatially separated and made incident on different light receiving elements by using the compound lens, the phase shift and the decrease in S / N are small. The compound lens can be easily manufactured by a replica manufacturing method.

<Embodiment 3> Next, an encoder according to a third embodiment of the present invention will be described with reference to FIG. Very small components on the order of millimeters used in the embodiments require a very high assembling accuracy since the optical path is greatly displaced and the detection accuracy is greatly deteriorated even if the displacement is on the order of tens of μm. Therefore, in this embodiment, the adjustment of the optical system is facilitated by providing an adjusting mechanism. The principle of detection of the encoder itself is the same as that described in the first embodiment.

In FIG. 6, a light emitting element 1 is provided in a housing 5.
Optical members such as the mirror 2, the light receiving elements 4A, 4B, and 4C are fixed, and a transparent glass plate 11 for hermetic sealing is attached to an opening on the upper surface thereof by bonding. On the other hand, case 5
A fixed frame 12 is arranged around the frame, and a glass plate 3 on which an optical function element is formed is mounted on the upper surface of the fixed frame. By adjusting the relative positional relationship between the fixed frame 12 and the housing 5, the alignment between the optical member fixed in the housing 5 and the optical functional element such as a lens or a diffraction grating formed on the surface of the glass plate 3 is performed. Can be performed. After the adjustment, it is fixed by screw mechanisms 13 provided on four sides of the fixed frame 12, and the gap is filled with an adhesive to increase the stability. As described above, in the present embodiment, since the components of the encoder are unitized into two units and the units are adjusted relative to each other, the adjustment at the time of assembly is easy and the encoder has high accuracy.

Further, the housing containing the light emitting element generates a large amount of heat. High heat is not preferable for optical functional elements such as replica lenses and diffraction gratings on a glass plate, and especially the pitch of diffraction gratings fluctuates due to thermal expansion,
It may directly affect the detection accuracy of the encoder. On the other hand, in this embodiment, the heat conduction from the housing 5 to the glass plate 3 can be considerably suppressed by using the housing 5 and the glass plate 3 as separate units. Further, the transparent glass plate 11
Also have a heat blocking effect.

Also, immediately after the mounting operation of the electronic components such as the light emitting element and the light receiving element, if the transparent glass plate 11 for hermetic sealing is bonded to the window of the housing 5, the semiconductor laser element will be air-tight during the assembly operation. The reduction in reliability due to exposure inside can be minimized. In addition, there is an advantage that it is easy to design the package while paying attention to airtightness and gas generation.

<Embodiment 4> Next, a description will be given of a fourth embodiment in which the component arrangement of the encoder is changed. FIG. 7 is a three-sided configuration diagram of the present embodiment, and FIG. 8 is a perspective view of a main part. In the drawing, the same reference numerals as those in the previous embodiment represent the same or equivalent members.

The light receiving elements 4A, 4B, 4C are arranged in parallel on the same substrate. The mirror 2 is larger than that of the previous embodiment, reflects the emitted light from the light emitting element 1 and emits it, and reflects the light reflected and incident on the scale and guides it to the light receiving elements 4B and 4C. Also, prism mirror 1
Numeral 0 reflects the light for monitoring emitted from the rear surface of the light emitting element 1 and directs it to the light receiving element 4A, and also reflects the light from the scale reflected and reflected by the mirror 2 and the light receiving elements 4B and 4C. Oriented to

In this embodiment, as compared with the previous embodiment, the light receiving elements are arranged in parallel on one substrate, and the mirrors 2, 1
Since 0 is an optical component that is relatively large compared to the housing,
It has the feature that the assemblability is good.

Further, since the light receiving elements are arranged in a line, the signal light takes an optical path to be condensed between the mirrors 2 and 10, and for example, a perforated light shielding plate is provided at the condensing position. By inserting the above, signal light having a good S / N ratio can be incident on the light receiving element. Furthermore, since the prism mirror 10 is mounted on the light receiving elements arranged in a line, the surface other than the surface on which the signal light is incident is masked with a light-shielding paint or the like, so that the surface other than the signal light incident direction is masked. The ghost light can be blocked, and the surface on which the signal light is incident is coated with a thin film or the like that reflects the light incident at an angle larger than the incident angle of the incident light, so that the angle larger than the incident angle of the incident light Can block all incident ghost light, and a signal with good S / N can be obtained.

<Embodiment 5> FIG. 9 shows a fifth embodiment in which the same technical concept as the fourth embodiment is applied to the configuration of FIG. In FIG. 9, the same reference numerals denote the same or equivalent members. In the present embodiment, similarly to the embodiment of FIG. 5, an encoder which is miniaturized to the order of millimeter and has extremely high environmental resistance can be obtained. In addition, it is more preferable that the lenses 31B and 31C be a compound lens similar to that of FIG.

<Embodiment 6> FIG. 10 is a structural view of an optical encoder according to a sixth embodiment of the present invention viewed from three directions, and FIG. 11 is a perspective view of a main part.

In the above embodiments, the light beam incident on the diffraction grating 21 of the scale 20 and the light beam reflected and diffracted by the diffraction grating 21 are included in the same plane. On the other hand, by making the light incident at an angle deviated from the vertical direction, the surface containing the light incident on the diffraction grating 21 and the surface containing the reflected light are made different. As a means for this, the angle of the mirror surface of the mirror 2 is set to a value larger than 45 degrees (for example, 55 degrees) with respect to the direction of the light beam generated from the light emitting element 1. As a result, the light beam reflected by the mirror 2 is tilted in the direction (7
0 degrees). The light reflected and diffracted by the diffraction grating 21 passes through the optical function element of the glass plate 3 and the light receiving element 4B,
It is led to 4C. Further, the monitor light emitted from the rear surface of the light emitting element 1 is turned back by the prism 10 and the light receiving element 4A
Is led to. These light receiving elements 4A, 4B, 4C are arranged and formed in a line on one substrate.

As described above, in the present embodiment, since the light beams before and after the diffraction grating 21 are separated, unnecessary light is not mixed into the light receiving element, and the signal light can be obtained with a high S / N.
Further, since the diameter of the light beam can be increased, the influence of dust and the like on the scale can be reduced. In addition, it is possible to increase the size of optical components such as lenses, so that processing and assembling of components are facilitated, and the number of components can be reduced.

<Embodiment 7> FIG. 12 shows a seventh embodiment having the same technical concept as the sixth embodiment. In this embodiment, as a means for making the light incident on the diffraction grating 21 at an angle deviated from the vertical direction, the optical axis of the lens 31A is shifted with respect to the optical axis of the light beam from the light emitting element 1 that is vertically reflected by the mirror 2. This refracts the light beam passing through the lens 31A. Thereby, the diffraction grating 2 is formed in the same manner as in the sixth embodiment.
The incident light and the reflected light on 1 are included in different planes and can be separated from each other. Further, by inserting the light shielding plate 16 as shown in the figure, unnecessary light is prevented from entering the light receiving elements 4B and 4C. If the mirror 2 is made the same size as the light-shielding plate 16 and a light-shielding process such as applying a light-shielding paint to the light-receiving elements 4B and 4C of the mirror 2 is performed, the same operation as when the light-shielding plate 16 is provided. And the light shielding plate 16 can be omitted.

<Embodiment 8> FIG. 13 is a block diagram of an encoder according to an eighth embodiment of the present invention. In the drawings, the same reference numerals as those described above denote the same or equivalent members. Reference numeral 30 denotes a mask having a circular opening. The path of the divergent light beam emitted from the light emitting element 1 is bent by the mirror 2, and the divergent light beam R having an appropriate diameter is formed by the mask 30. This divergent light beam R is applied to the diffraction grating 3A. Diffraction grating 32A, 3
2B and 32C are formed on one surface of the transparent glass plate as in the previous embodiments, and the principle of detection of the encoder itself is the same as in the previous embodiments.

The configuration for forming the divergent light beam is not limited to the embodiment shown in FIG. 13, and an appropriate divergent light beam may be formed by using a lens 31 instead of the mask as shown in FIG.

The feature of this embodiment is that a divergent light beam, that is, a spherical wave, is incident on the light receiving element. FIG. 18 is a diagram for comparing the case where the light beam is a parallel light beam (plane wave) with the case of a divergent light beam (spherical wave). In the embodiments described above, the light beam is a parallel light beam, that is, a plane wave.
As shown on the left side of FIG. 8, the pitch P ₂ of the interference fringes in the interference between the parallel light beams is determined by the angle θ ₂ of the two light beams. Therefore, as shown in FIG. 17, if the scale has an attachment error in the rotation direction of the arrow with respect to the encoder head, the interference state changes. That is, in the case of a plane wave, a high level is required for the mounting accuracy of the scale to the encoder head.

On the other hand, as shown on the right side of FIG.
Interfering two light beams A, if B are both divergent light (spherical wave), the pitch P ₁ of the interference fringe light beam A, regardless of the angle theta ₁ of the principal ray of B is to be repeatedly , Emission points A, B
And the ratio (ΔX / R) of the separation amount ΔX of the light emitting point and the distance R from the light emitting point to the observation surface (the curvature 1 / R of the spherical wave on the observation surface). As ΔX / R approaches 0, the pitch P _{1 of the} interference fringes increases, and as a result, the change in the interference state decreases. Accordingly, by setting R as large as possible with respect to the separation amount ΔX between the light emitting points A and B, the output fluctuation with respect to the mounting error in the rotation direction of the scale as shown in FIG.

In this embodiment, the mask 30 or the lens 3
By causing the divergent luminous flux (spherical wave) having an appropriate curvature as described above to enter the light receiving surfaces of the light receiving elements 4B and 4C by the method 1, the influence on the output due to the mounting error of the scale 21 as shown in FIG. 17 is reduced. In addition, an encoder that is easy to assemble and assemble and that is resistant to environmental changes has been achieved.

<Embodiment 9> FIG. 15 shows the configuration of an encoder according to a ninth embodiment in which a spherical wave is incident on a light receiving element in the same manner as in the eighth embodiment. In the figure, a lens 31A converts light emitted from a light emitting element into a converged light beam or a parallel light beam, and lenses 31B and 31C are provided for converting the light into appropriate divergent light and entering the light receiving elements 4B and 4C. Can be
These lenses 31A, 31B, 31C and diffraction grating 3
2A, 32B and 32C are formed on the surface of the transparent glass plate as in the previous embodiments.

The divergent light beam emitted from the light emitting element 1 is bent by the mirror 2 and converted into a condensed light beam or a substantially parallel light beam R by the lens 31A, and is irradiated on the diffraction grating 32A. Although detection principle itself of the encoder is similar to the previous embodiments, it focused or collimated light beams superimposed optical paths by the diffraction grating 32B R ₊₁ ^-1 ₀ and the light beam R ₀ ⁺¹ _-1
Is converted into appropriate divergent interference light (spherical wave) by the lens 31B and is incident on the photoelectric element 4B. Also, the diffraction grating 32C
Focused or parallel light flux R _-1 with light paths superimposed at
^{The +1} ₀ and the light flux R ₀ ^-1 ₊₁ are converted into appropriate divergent interference light (spherical waves) by the lens 31C and enter the photoelectric element 4C.

As described above, in this embodiment, the photoelectric elements 4B, 4B
In order to make the interference light divergent just before C, the photoelectric element 4B,
The amount of light incident on 4C can be increased. Therefore, in addition to the effect of the eighth embodiment, an effect of obtaining a stable signal with a better S / N can be obtained.

<Embodiment 10> As the tenth embodiment, FIG. 16 shows a configuration of an encoder for making an appropriate spherical wave incident on a light receiving element as in the eighth and ninth embodiments. Lens 31
A converges the light emitted from the light emitting element 1 and once condenses it in the vicinity of the scale diffraction grating 21, further diverges light from the light and enters the photoelectric elements 4B and 4C.

In this state, even if the alignment between the scale diffraction grating 21 and the diffraction gratings 32A, 32B, 32C is shifted, the position of the point light source of the two incident spherical waves as viewed from the sensor surface is changed to the scale diffraction grating. Since it is in the vicinity, it is hardly affected by misalignment. That is, as described in the eighth embodiment, the separation amount of the light-emitting points A and B △
Since X becomes almost 0, the pitch P _{1 of the} interference fringes becomes almost infinite regardless of the number of θ ₁ , and the interference state hardly changes.

<Embodiment 11> As an eleventh embodiment, FIG. 19 shows a configuration of an encoder for making an appropriate spherical wave incident on a light receiving element as in the eighth to tenth embodiments. In this embodiment, by converging the light flux to an intermediate point on the optical path from the divided diffraction grating to the combined diffraction grating, it is possible to suppress a change in the interference state caused by an attachment error to a small extent. As a result, output fluctuations due to changes in the interference state on the light receiving surface are reduced, and S / S is less affected by mounting errors.
A signal with a good N ratio can be obtained. Also, since the encoder is composed of one light emitting element, at least one mask or lens, three diffraction gratings provided on the measuring head, a diffraction grating provided on the scale, and at least two photoelectric elements, mounting and assembling are possible. An inexpensive encoder that is easy, compact, highly accurate, simple in structure, and easy to handle can be constructed.

Hereinafter, description will be made with reference to FIG.

FIG. 19 is a diagram showing the configuration of the optical encoder according to the present embodiment. In the drawing, the same members as those in the above-described embodiment are denoted by the same reference numerals. The divergent light flux emitted from the light emitting element 1 is deflected by the mirror 2 to form a lens 3
1A makes the beam converged appropriately, and the diffraction grating 32A
Are transmitted and diffracted by the first order diffracted light R ₀ , the + 1st order diffracted light R
₊₁ and -1 order diffracted light R- ₁ are divided into three and emitted.

[0070] Light beam R ₀ with straight diffraction grating 32A is reflected and diffracted at a point P1 on the diffraction grating 21 formed on the scale, + 1-order diffracted light R ₀ ^+1, -1 order diffracted light R ₀ ^-1 The light is divided and phase-modulated, and converges at points 011 and 012 near the diffraction grating 21, respectively.

The phase of the + 1st-order diffracted light R ₀ ⁺¹ is + 2πx / P
The phase of the ^-1st-order diffracted light R ₀ ^-1 is -2πx / P
Just shift. Where x is the amount of movement of the diffraction grating 21 and P
Is the pitch of the diffraction grating 21.

The ⁺ 1st-order diffracted light R ₀ ⁺¹ is transmitted and diffracted by the diffraction grating 32B, and the 0th-order diffracted light R ₀ ⁺¹ ₀ and the −1st-order diffracted light R _{0 are} transmitted.
^-1 -1 and other light beams are divided, and the -1st-order diffracted light R ₀ ⁺¹ _-1 is taken out perpendicular to the diffraction grating surface. The phase shift of the wavefront of this light beam is + 2πx / P if there is no phase shift in the diffraction grating 32B.

[0073] -1-order diffracted light R ₀ ^-1 is being transmitted diffracted by the diffraction grating 32C, 0-order diffracted light R ₀ ^-1 _0, + 1-order diffracted light R ₀
^-1 ₊₁ and other light beams are divided, and the + ^1st-order diffracted light R ₀ ^-1 ₊₁ is extracted perpendicular to the diffraction grating surface. If there is no phase shift in the diffraction grating 32C, the phase shift of the wavefront of this light beam is -2πx / P.

Here, the diffraction grating 32B is set at 32C with respect to 32C.
If the arrangement phase relation of the lattice is shifted by P / 4, +1
The diffracted light R ₀ ^-1 ₊₁ has a wavefront phase of −2π (P /
4) / P = -2πx / P-π / 2 shifted by -π / 2
become.

Light beam R diffracted by + 1st order at diffraction grating 32A
₊₁ converges at a point 02 in the vicinity of the diffraction grating 21 and is reflected and diffracted at a point P2 on the diffraction grating 21 on the scale to be a -1st-order diffracted light R ₊₁ ^-1 , a 0th-order diffracted light R ₊ ^10, and others. , And phase-modulated. Among -1 order diffraction light R ₊₁ ^-1 phase is shifted by -2πx / P, incident on the diffraction grating 32B, where the remains straight and the zero-order diffracted light R ₊₁ ^-1 ₀ wavefront phase is - 2πx / P.

Light beam R diffracted by -1st order at diffraction grating 32A
_-1 converges at a point 03 near the diffraction grating 21 and is reflected and diffracted at a point P3 on the diffraction grating 21 on the scale, and the + 1st-order diffraction light R _-1 ⁺¹ , the 0th-order diffraction light R _- ^10, and others. , And phase-modulated. Among + 1st-order diffracted light R _-1 ⁺¹ of phase, + 2.pi.x / P only displaced, incident on the diffraction grating 32C, where this remains straight and the zero-order diffracted light R _-1 ⁺¹ ₀ of the wavefront phase is, + 2.pi.x / P It is.

The convergence point of each light beam described above is set at an intermediate optical path length position of the light path length of the light path from the grating 32A to 32B or 32C of each light beam. That is, for example, from the diffraction grating 21 of the light beam R ₊₁ ^-1 and the light beam R ₀ ⁺¹ to the diffraction grating 3
Assuming that the optical path lengths before reaching 2B are L and L ', respectively, the optical path length from the diffraction grating 32B is approximately (L + L') /
The light beam R ₊₁ ^-1 (that is, the light beam R ₊₁ ) and the light beam R ₀ are located at the position 2.
It is set so that a convergence point of ⁺¹ is formed. Luminous flux R
_The same applies to _-1 ⁺¹ and light flux R ₀ ^-1 .

[0078] Light beams superimposed optical path R ₊₁ ^-1 ₀ and the light beam R ₀ ⁺¹ _-1 are at the diffraction grating 32B, become interference light incident on the photoelectric element 4B. The interference phase at this time is as follows: {+ 2πx / P} − {− 2πx / P} = 4πx / P, and a light-dark signal of one cycle is generated every time the diffraction grating 21 on the scale moves by ピ ッ チ pitch.

The light beams R _-1 ⁺¹ ₀ and R ₀ ^-1 ₊₁ whose optical paths are overlapped by the diffraction grating 32C are incident on the photoelectric element 4B as interference light. The interference phase at this time is as follows: {-2πx / P} −π + 2πx / P｝ =-4πx / P, and every time the diffraction grating 21 on the scale moves by ピ ッ チ pitch, a light-dark signal of one cycle is generated. The light / dark timing is shifted from the photoelectric element 4B by １ ／ cycle.

In the above apparatus, the interference optical system has a very simple configuration. If a lens and a diffraction grating are formed on both sides of glass by a replica manufacturing method or the like, a small and inexpensive encoder can be realized. This embodiment has the following advantages.

1) Diffraction gratings (32A, 32B, 32C) for dividing and synthesizing the light beam with the diffraction grating 21 on the scale
The interference signal is stably output even if an arrangement is made with an angle deviation between the two. The reason will be described below with reference to FIGS.

FIG. 20 shows the principle of the device shown in FIG. 19 and is shown without the mirror 2. With respect to the two interference light beams detected on the respective sensor surfaces, if the diffraction grating 21 side and the diffraction gratings 32A, 32B, 32C side are in the original state in which there is no rotational displacement, the interference 2
The principal rays of the two light beams coincide, and the spherical waves of both light beams are always concentric. However, when these two light beams are given an azimuth angle shift θ as shown in FIG.
As shown in FIG. 21, an angle difference (θ1) occurs between the two principal rays. In this case, although the degree is much smaller than that of the plane wave, the interference between the two spherical waves causes some unevenness of the interference on the sensor surface.

FIG. 22 schematically shows a state where the principal rays of the two light beams A and B having spherical waves have an angle difference. Point O _A, O _B are each two light beams A, B of the focal point, _A A, A _B Each two beams A, principal rays of B, W denotes the wavefront. In such a ray state, it appears that the principal rays intersect at a certain specific position (point C in FIG. 22). The position that appears to intersect will be described as an intersection position in the future. If the convergence position of the light beam does not coincide with the intersection position, the two point light sources (convergence points) will be separated. Since the point light source coincides with the center of the spherical wave of each light beam, the spherical waves of both light beams are non-concentric, and interference fringes occur on the sensor surface as shown by "bright" and "dark" in FIG. The pitch P1 of the interference fringes on the sensor surface is independent of the angle θ1 of the principal ray of the light beams A and B, regardless of the angle, and the separation amount ΔX of the focal points A and B and the distance from the point light source to the observation surface. R
(The curvature 1 / R of the spherical wave on the observation surface) depending on the ratio (ΔX / R). As ΔX / R approaches 0, the pitch P1 of the interference fringes increases, and as a result, the change in the interference state decreases. In an extreme example, if ΔX = 0, then θ1
No matter how many times, the pitch P1 of the interference fringes becomes infinite and the interference state does not change. By bringing the convergence points A and B closer to the intersection C of the principal rays of the two interference light beams, the separation amount ΔX can be made as small as possible. Here, the intersection position of the principal rays of the two interference light beams will be described. FIG. 2 shows the intersection of the principal rays of the two interference light beams, the ratio of the wavelength to the grating pitch, and FIG.
The relationship between the rotation angle (azimuth angle) θ of zero and the lattice distance L
If the unit length is 2, the graph shown in FIG. 25 is obtained in the case of the optical system of FIG. 20. (The intersection position of the two interference light beams is represented by the distance from the gratings 32B and 32C for combining the light beams, and the sign is negative. In the case of, the grid 32 viewed from the sensor surfaces 4b and 4c
B, 32C, in the direction away from it, and in the positive case, it is the direction to approach). From this, the intersection position of the two interference light beams is almost constant in this optical system irrespective of the wavelength λ, the pitch P of the grating, and the azimuth angle θ, and the optical paths 32A to 32B between the gratings (the light split by the grating 32A Optical path from the reflection and diffraction of the light to the incidence on the grating 32B), or 32A
To an intermediate optical path length position of .about.32C (an optical path where the light split by the grating 32A is reflected and diffracted by the scale 21 and enters the grating 32C), that is, an optical path length half the optical path length of the optical path from the grating 32A to 32B or 32C. It will be the corresponding position. This also allows the focal point as shown in FIG.
An optical path length position at half the optical path length of the optical path from A to 32B or 32C (when the optical path lengths until two interfering diffracted lights reach the diffraction grating 32B or 32C from the diffraction grating 21 are L and L ', respectively) In a device in which the optical path length from the diffraction grating 32B or 32C is set to approximately (L + L ') / 2), the intersection position of the two interfering light beams and the converging position are substantially the same, and the spherical waves of the two light beams are concentric. Which indicates that no interference fringes theoretically occur on the sensor surface.

FIG. 26 is a graph showing the relationship between the azimuth angle θ and the intersection position. As will be understood from the graph, the intersection position actually moves slightly in the direction approaching the scale 21 as the azimuth angle θ increases. . The reason is as follows. When the azimuth angle θ is given to the scale, the direction of reflection and diffraction starts to shift in the Y-axis direction and the X-axis direction in FIG.
However, the deviation in the Y-axis direction can be ignored when the azimuth angle θ is small or when the diffraction angle is small. That is, at this time, the intersection position of the two interference beams can be calculated only by the displacement in the X-axis direction, and substantially coincides with the above-mentioned intermediate position of the optical path length between the gratings. If the azimuth angle θ becomes larger or the diffraction angle becomes larger than this, the deviation in the Y-axis direction cannot be ignored and the position of the intersection of the two interference light beams moves in a direction approaching the scale. However, the movement amount is almost negligible as compared with the inter-grating distance as understood from FIG.

As described above, the collimator lens 31A converges a light beam at a position corresponding to a substantially middle position of the optical path length between the gratings, so that the diffraction gratings 32A and 32B for separating and synthesizing the scale and the light beam are provided. A decrease in output due to a relative angle (azimuth angle) with 32C can be suppressed. For example, in the embodiment, the distance between lattices is 1 mm, and P =
Assuming that 1.6 μm and λ = 0.78 μm, the ideal convergence position is-from the diffraction gratings 32B and 32C that combine the light flux.
1.072657 mm.

Next, the deviation between the ideal convergence position and the actual convergence position will be specifically verified. First, the relationship between the incident angle and the exit angle with respect to the diffraction grating and the direction in which the grating exists will be clarified. Therefore, the incident vector on the diffraction grating is expressed as U
₀ (u _0x , u _0y , u _0z ), and the ejection vector as U ₁ (u _1x , u
_1y , u _1z ), a grid exists on the xy plane of the Cartesian coordinates, and the pitch of the grid is P (Px in the x direction, Py is y
Direction pitch. ) When the diffraction order is m and the wavelength of light is λ, the following relationship is established.

[0087] _{u 1x = u 0x + mλ /} Px u 1y = u 0y + mλ / Py u 1x 2 + u 1y 2 + u 1z 2 = 1 u 0x 2 + u 0y 2 + u 0z 2 = 1 ( or formula (8)) The Based on the relationship, the relative angle θ between the scale 20 and the gratings 32A to 32C for dividing and synthesizing the light flux as shown in FIG.
When the rotation of the (azimuth angle) occurs, the grid combining light beams ^{_{R 0 +1 -1, R +1 -1}} 0 which is taken out as an interference light 32B
Are as follows (the direction of incidence on the grating 32A is positive).

The emission vector U ₂ (u _2x , u _2y , u _2z ) of the light beam R ₀ ⁺¹ _{-1 from} the grating 32B is

[0089]

[Outside 1] Next, the injection vector U ₂ from the light beam R ₊₁ ^-1 ₀ grating _{32B '(u 2x', u} 2y ', u 2z') is

[0090]

[Outside 2] Becomes The angle difference θ ₁ between the two beams of interference is θ ₁ = ArcCos
Considering [U ₂ · U ₂ '] (• is the inner product of vectors), the following is obtained from equations (9) and (10).

Θ ₁ = ArcCos [(2λ / P) ² (co
sθ-1) +1] Since the azimuth angle is about several minutes, if the approximation to the second order of θ is used, the above relational expression becomes θ ₁ = (2λ / P) θ (θ≪1) (11) Become. From this, the relationship between the angular difference θ ₁ of the two interference light beams, λ / P, and the azimuth angle θ is as shown in FIG. 23, and λ = 0.78
If μm and P = 1.6 μm, the result is as shown in FIG.

[0092] then focused on the light flux incident on the 32B, the interference two light beams R ₀ ⁺¹ _-1, determine the position of the intersection as viewed from the sensor surface of the main ray of the R ₊₁ ^-1 _0. The vectors of the luminous flux emitted from the two-beam synthesizing grating 32B are expressed by the equations (9) and (10), respectively.
Given by Using the relational expression of Expression (8) and the distance between the diffraction gratings, the intersection of the two light rays with each diffraction grating can be obtained. From this, the intersections of each light beam and the grating 32B, that is, the light emission positions P ₀ and P ₊₁ on the grating 32B are obtained. From this, a straight line passing through the point P ₀ and parallel to the vector (U ₂ ) shown in the equation (9) and a straight line passing through the point P _{+ 1} and being parallel to the vector (U ₂ ′) shown in the equation (10) are obtained. If the position where these two straight lines intersect is obtained, the position is the intersection position to be obtained. This intersection position is considered assuming that the grating 32B for combining the two light beams is the origin of the Z axis and the direction of the scale 20 is negative. The positions in the X and Y directions are considered as follows. A perpendicular perpendicular to the grid 32B;
Two light beams R ₀ ⁺¹ _-1 which is separated by the azimuth angle of the R ₊₁ ^-1 ₀ is substantially the same in the opposite directions. Thus, the position in the X and Y directions where the two straight lines intersect is near the optical axis when there is no azimuth. That is, as for the position where the two straight lines intersect, only the position in the optical axis direction when there is no azimuth, that is, the position in the Z direction may be considered. In the following description, only the position in the Z direction is considered. Gratings 32A, 3 for splitting and combining light beams
2B, 32C and when the distance L ₂ between the grating 21 on the scale and unit length the intersection position Z and azimuth angle θ and the wavelength /
The relational expression of the pitch λ / P is obtained by using these relations. FIG. 25 is a graph of this equation (the origin of the coordinates is a diffraction grating for synthesizing light flux, and the direction approaching the sensor from the diffraction grating is positive, and the direction away from the sensor is negative).
If λ = 0.78 μm and P = 1.6 μm, the result is as shown in FIG. Further, the relational expression shown as a graph in FIG.
When expanded with

[0093]

[Outside 3] And ignoring the second and higher order terms of θ,

[0094]

[Outside 4] Becomes When the average optical path length of the different optical path lengths from the scale 21 to the grating 32B is calculated, the average optical path length substantially matches the distance Z shown in the equation (13). This equation (13) is
Under the conditions of λ = 0.78 μm and P = 1.6 μm, the value becomes −1.07265. -1.0 in FIG. 26
It can be seen that the position 72 is an average distance of two different optical path lengths for synthesizing a light beam from the scale 21 that is substantially reflected and diffracted. Therefore, the approximation of Expression (13) holds in a region of about θ ≦ 5 degrees. Since the position of the scale is -1 in this case, -1.072
It is also understood that the position is near the scale. Furthermore, it can be understood from FIG. 25 or equation (13) that the intersection position of the two interference light beams is substantially constant unless the ratio of λ / P is smaller than 1 and close to 1 even when the azimuth angle is changed. .

As described above, if the light beam converges at the intersection of the two interference light beams, the change in the interference state due to the azimuth angle hardly occurs as described above. However, when the light beam converges to a position shifted from the ideal light beam convergence position, the interference state changes and leads to a decrease in output.
Next, the number of interference fringes on the sensor due to the deviation of the light beam convergence position is obtained.

As shown in FIG. 29, the distance from the intersection of the sensor surface with the normal drawn from the ideal light beam convergence position to the sensor surface (which is set at the center of the sensor surface) is R _S ,
The distance between the sensor end and the focal point is represented by L _S , L _S ′ (L _S <L _S ′),
Assuming that the distance between the diffraction grating 32B for synthesizing the two light fluxes and the sensor 4B is L ₃ , the ideal focusing position is L _i , and the deviation amount in the Z direction therefrom is D _Z.

[0097]

[Outside 5] The optical path difference ΔL between these two optical paths is as follows: ΔL = | L _S ′ −L _S | When ΔL = λ / 2, the sensor center becomes the brightest and the sensor edge becomes the darkest. As a result, one interference fringe is formed on the entire sensor surface. Therefore, the number of interference fringes H _0n on the sensor surface is

[0098]

[Outside 6] Next, where theta ₁ is a function of the azimuth angle theta from equation (11), if the expression L _i also take an optical system of FIG. 16 (13)
As derived in

[0099]

[Outside 7] Where H _0n is a relation of H _0n = R _S n where n is the number of interference fringes per unit length.

[0100]

[Outside 8] Becomes

Next, the relationship between the sensor output and the number of interference fringes on the sensor surface will be described. When an interference fringe occurs on the sensor surface, the output amplitude of the light receiving element decreases. When the number of interference fringes approaches zero on the sensor surface, the output amplitude of the light receiving element becomes maximum. If the contrast of the interference fringes is V, then V
Is as follows.

[0102] _{V = (I max -I min)} / (I max + I min)

Here, I _max and I _min are the maximum and minimum of the output amplitude of the light receiving element. Then, assuming that the number of interference fringes in the sensor area is n _S and the maximum and minimum of the light receiving element output are V _max and V _min

[0104]

[Outside 9] Next, the relation of the interference fringe and the light receiving sensor outputs X, the maximum outputs 1 to the _{X = sin (πn S) /} πn S next _n S = nR since it is _{S X = sin (πnR s)} / πnR S (16 ).

For example, in the embodiment, the inter-grating distance is 1 m.
m, P = 1.6 μm, and λ = 0.78 μm, the ideal focusing position is the diffraction grating 32B, 3
The position is -1.072657 mm from 2C. At this time, the relationship between the azimuth angle θ, the number n of interference fringes, and the deviation D _Z from the ideal focusing position is as shown in FIGS. 27 and 28 from the equation (15). Here, the sensor output decreases by 20%
Within this range, the maximum number of interference fringes generated on the sensor surface can be defined by the conditional expression (16). 1m sensor diameter
m, the maximum number of stripes allowed is 0.36, and if the allowable range of the azimuth angle is specified as a maximum of 480 seconds (8 minutes), the deviation D _Z from the ideal focusing position corresponding thereto is defined.
In FIG. 28, the area that satisfies the above condition is indicated by oblique lines. According to this, it can be understood that the objective stability can be obtained if an optical system that condenses light in the range of −0.29 mm ≦ D _Z ≦ 0.22 mm is obtained.

Thus, with the configuration as shown in FIG. 16, there is little effect on the output due to the mounting error of the scale.
An encoder that is easy to assemble can be realized.

Further, the angle shift between the diffraction grating 21 on the scale and the diffraction gratings (32A, 32B, 32C) for dividing and synthesizing the luminous flux with the X axis and the Y axis as rotation axes as shown in FIG. , The apparent emission points of the two spherical waves are substantially the same, so that the wavefront angle between the two interfering light beams does not shift, and the interference signal is stably output. .

Then, the grids of 32C and 32B are set to pitch 1
By arranging in the grid arrangement direction by shifting by / 4,
The phases of the signals output from the sensors 4C and 4B are 90
A two-phase signal can be obtained as a signal shift and a signal output.

<Embodiment 12> Next, an encoder according to a twelfth embodiment will be described. The present embodiment provides an optical encoder that uses a wavelength selection filter to receive only necessary signal light and cut off unnecessary light, thereby obtaining a detection signal with good S / N.

FIG. 31 is a sectional view of the optical encoder of this embodiment. In FIG. 1, reference numeral 1 denotes a semiconductor laser light emitting element that emits infrared light having a wavelength of 780 nm;
0 is a glass epoxy board on which the light receiving element 4 is mounted, 41
Is a through hole provided at the center of the substrate 40 for transmitting light from the light emitting element 1. 42 is a holder of the semiconductor laser unit, and 43 is an optical unit holder. Reference numeral 44 denotes an optical unit which is a characteristic member of the present embodiment, and has an operation of transmitting only light in the infrared region, and has three plano-convex lenses 31 on the lower surface of the optical unit corresponding to the position of the light receiving element 4. Is provided with a diffraction grating on the upper surface. 4
Reference numeral 7 denotes a cylindrical non-reflective member for removing unnecessary light emitted from the light emitting element 1 in an oblique direction. Reference numeral 20 denotes a displacement scale on which a diffraction grating is formed along the displacement direction.

FIG. 32 is a sectional view of the optical unit 44. In the figure, reference numeral 401 denotes an optical filter that transmits light only in a wavelength band (mainly an infrared light region) of light emitted from the light emitting element 1 and that blocks light in other wavelength bands. Reference numeral 31 denotes a plano-convex lens formed of resin, and 32 denotes a diffraction grating formed of resin, which is formed on each surface of the optical filter 401 by using a replica technique.

FIG. 33 shows a modification of the optical unit 44. This is because two glass substrates 402 each have a lens 3
1. A diffraction grating 32 formed by a replica technique is prepared, and these are filtered by a filter 40 having the same action as described above.
The optical unit 44 is formed by bonding the optical unit 44 to both surfaces of the optical unit 1.

FIG. 34 shows a further modification of the optical unit 44. Two filters 401-1 and 401-2 having different transmittances depending on the wavelength band are attached to each other, and a lens 31 and a diffraction grating 32 are formed on the respective surfaces.

A cold mirror (a filter that reflects visible light and transmits infrared light) or an interference filter (a filter having high monochromaticity that transmits only a specific wavelength and reflects other wavelength bands) by vapor deposition on one side of a glass substrate. ) Can be formed to substantially replace the filter 401.

Next, the manufacturing procedure of the device of this embodiment will be described. First, the light receiving element 4 is fixed at a predetermined position on the glass epoxy substrate 40 on which a wiring pattern is drawn in advance by die bonding, and then the light receiving element 4 is fixed by a wire bonder device.
And the wiring of the glass epoxy substrate 40 are connected with gold wires. Also, an output signal can be obtained from the end of the glass epoxy substrate 40 using a lead wire, a flexible substrate, or the like. Next, after positioning is performed so that the positional relationship between the light emitting element 1 and the light receiving element 4 incorporated in the holder 42 becomes a predetermined positional relationship, the holder 42 and the glass epoxy substrate 40 are bonded to each other by bonding. And Also, the holder 43 is attached to the optical unit 44 and the second
Unit. Here, the first unit is covered with the second unit, and after positioning, both are fixed with an adhesive.

According to the above-described embodiment, since only the wavelength of the signal light is selected by the filter to eliminate the influence of external light on the light receiving element, an optical encoder capable of performing stable and highly accurate detection is provided. Can be provided.

<Thirteenth Embodiment> Next, an encoder according to a thirteenth embodiment will be described. In the above embodiments, a transparent glass plate having an optical functional element formed on the surface is attached to the window of the housing. In these cases, light emitted obliquely from the light emitting element reflects inside the glass plate. There is a possibility that the light will repeatedly reach the light receiving element as noise light. Therefore, the present embodiment is characterized in that a light shielding means for blocking ghost light due to multiple reflection is provided by providing light shielding means on a glass plate. As a specific example of this light shielding means,
A groove may be formed between the region through which the emitted light transmits and the region through which the signal light transmits, or a light-blocking paint or metal may be provided inside the groove. Further, the light shielding region may be formed inside the optical component instead of the surface. By providing such a light-blocking region, the reflected light does not propagate to the region where the signal light is transmitted, or even if it propagates, the light intensity is greatly reduced.

FIG. 35 is a sectional view of the optical encoder of this embodiment. The same reference numerals as those of FIG. 31 of the twelfth embodiment denote the same or similar members. Reference numeral 45 denotes an optical unit similar to the optical unit 44 of the twelfth embodiment, and has a filter function of selecting only infrared light from the light emitting element. On the surface of the optical unit 45 on which the diffraction grating 32 is formed, a light-shielding groove 46 for blocking multiple reflected light is formed. The light shielding groove 46 is formed using a dicing saw. Therefore, the side surface of the groove is a ground surface at the time of forming the groove and becomes a scattering surface for light, so that the internally reflected light is scattered by the side surface of the groove 46 and cannot reach the signal light region.

Note that, as shown in FIG.
The light-shielding groove 46 may be formed on the surface on which the fifth lens 31 is formed. If the inside of the light-shielding groove 46 is filled with a light-shielding member such as a non-reflective paint, transmission of internal reflection can be more completely prevented.

FIG. 37 shows a further modification of the optical unit 45, in which a light shielding portion 46 is formed inside the optical unit. This is to prepare two translucent substrates of glass or infrared transmitting filter, provide a groove on one side of each,
The grooves are filled with a light-shielding resin paint to form light-shielding portions 46. Then, a diffraction grating and a plano-convex lens are formed on the other surface of each substrate by a replica technique. Next, the optical unit 45 is produced by bonding the two substrates produced separately to each other.

According to the present embodiment, the optical unit for separating outgoing light and combining incident light is provided with a light shielding area so that the internally reflected light does not propagate to the area where the signal light is transmitted. The ghost light due to the reflected light is suppressed, and the modulated signal light can be monitored at a high S / N ratio. This means that a stable optical signal can be obtained, and high precision can be achieved. In addition, since the ghost light due to the internally reflected light is prevented by forming a light shielding area from the surface of the optical unit to the inside, the versatility is small and the use environment is not selected without increasing the size and thickness of the optical unit. It is possible to provide an optical displacement sensor.

<Embodiment 14> FIG. 38 is an embodiment showing an application example of the above encoder, and is a system configuration diagram of a drive system using the encoder. An encoder 101 is attached to a drive output unit of a drive unit 100 having a drive source such as a motor, an actuator, or an engine, or a moving unit of a driven object, and detects a displacement state such as a displacement amount and a displacement speed. As this encoder, the first to thirteenth
Use any of the examples. The detection output of the encoder 101 is fed back to the control means 102, and the control means 102 transmits a drive signal to the drive means 100 so as to be in the state set by the setting means 103. By configuring such a feedback system, the driving state set by the setting unit 103 can be obtained. Such drive systems are, for example, office equipment such as typewriters, printers, copy machines, and facsimile machines, as well as video equipment such as cameras and video equipment, as well as information recording / reproducing equipment, robots, machine tools, manufacturing equipment, transportation equipment, Further, the present invention is not limited to these, and can be widely applied to all devices having a driving unit.

<Embodiment 15> Although the example of the encoder has been described above, the optical displacement sensor of the present invention can be applied not only to the encoder but also to a Doppler displacement sensor. This will be described below. FIGS. 39A and 39B are three-side configuration diagrams of the Doppler displacement sensor according to the present embodiment viewed from three directions. FIG. 39A is a side view, FIG. 39B is a top view, and FIG.

The member 1 is a light-emitting device (semiconductor laser device) for generating light, and has a size on the order of several hundred μm. Light generated and emitted from the horizontally disposed light emitting element 1 is reflected by the mirror 2 having a mirror surface at an angle larger than 45 degrees (for example, 55 degrees) and directed in a direction deviated from the vertical direction. I do. Note that a prism can be used instead of the mirror. A transparent glass plate 7 is provided in the direction in which the light is directed, and two transparent glass plates 8 are provided on the transparent glass plate 7 with a spacer interposed therebetween. A replica lens portion 35 is formed on the inner surface of the glass plate 7, a diffraction grating 36 is formed on the inner surface of the glass plate 8, and two replica diffraction grating portions 37A and 37B and a replica lens portion 38 are formed on the outer surface. . With this configuration, the two emitted light beams intersect at the focal point. Further, a light receiving element 4 having a size on the order of several hundred μm is provided for receiving light and performing photoelectric conversion. Specific examples of the light receiving element include a photodiode, an avalanche photodiode, a pin photodiode, a CCD, and a light receiving IC having a circuit for amplifying or processing a photocurrent output from the light receiving unit.

The light-emitting element 1 and the light-receiving element 4 are sealed in a ceramic light-shielding case 5, and the glass plate 7 is attached to a window on the upper surface of the case 5 to hermetically seal the inside. . An electrode pattern is connected to each of the light emitting element 1 and the light receiving element 4, and an end of the electrode pattern is exposed outside the housing 5. When a signal processing circuit is built in the housing, an output signal of the circuit is output to the exposed electrode pattern. The housing 5 has a size on the order of several mm, and constitutes a very small sensor unit.

An arrangement in which two laser beams are emitted from the sensor unit and a scattered / reflective object 23 (such as fine particles or a scattered / reflective surface) relatively moving to the converging intersection 22 of the laser beams is located. Relationship.

The divergent light beam emitted from the light emitting element 1 is bent by the mirror 2 and then converted by the lens 35 formed on the back surface of the glass plate 7 into a condensed light beam R (or parallel light beam). is transmitted diffracted by the diffraction grating 36 formed on the rear surface of the 8, + 1st-order diffracted light is bent by an angle theta _a by the diffraction, -1 is split order diffracted light, and the 0-order diffracted light traces of straight. Since the 0th-order diffracted light (straight light flux) R ₀ transmitted through the diffraction grating 36 does not contribute to the detection signal, much required ± 1st-order diffracted light is emitted,
It is preferable to appropriately design the sectional shape of the diffraction grating 32A so that the zero-order light becomes weak.

The light flux R ₋₁ diffracted by the diffraction grating 36 at ± 1 order,
R ₊₁ is bent by the diffraction gratings 37A and 37B, and is incident on the target point 22 near the test object 23 at the incident angles θ _B and θ _C.
The light is collected at. These quantitative relations are as follows.

[0129] + 1-order diffracted light beam _{R +1: sinθ A = + λ} / P A sinθ B = -λ / P B + sinθ A -1 -order diffracted light beam _{R -1: sinθ A = -λ /} P A sinθ C = + λ / P _C + sin θ _A P _C = P _B

These are as follows.

Sin θ _B = + λ / (P _A −P _B ) sin θ _C = −sin θ _B where PA is the pitch of the diffraction grating 36, P _B is the pitch of the diffraction grating 37 _A , and PC is the pitch of the diffraction grating 37 _C. , Λ is the wavelength of the light beam (P _A > P _B , P _A > P _C ).

At this time, since the two light beams intersect near the target point 22, interference fringes occur in space. The pitch P of the interference fringes
₀ is as follows.

[0133] _{P 0 = λ / (sinθ B} + sinθ C) = λ / {λ / (P A -P B) + λ / (P A -P C)} = (P A -P B) + (P A - _{P C) = (P A -P} B) / 2

In this space, the velocity v in the direction crossing the interference fringes
When microparticles are inspected object is moved by, occur brightness of scattered light in accordance with the brightness of the space, the frequency _{f, f = v / P 0 =} 2 · v (P A -P B) becomes, lambda Becomes irrelevant.

The Doppler signal (light / dark signal) component is condensed on the light receiving element 4 by the lens 38, and thereafter, is proportional to the moving speed v by a known signal processing circuit such as an amplifier, a filter, and a binarization circuit. If a pulse signal of a frequency is output, the moving speed of the test object can be detected. If a part or all of these signal processing circuits are incorporated in the sensor unit, the integration will be further enhanced, which is more preferable. Note that the focusing state of the light beam irradiated on the test object can be changed to parallel light or the like according to the state of the scattering particles and the scattering surface of the test object.

In this embodiment, as in the previous embodiment, the interference optical system has a structure in which an optical element in which lenses and diffraction gratings are formed on both sides of a glass plate by a replica manufacturing method or the like is very simple, small, and low in cost. In addition, a laser Doppler displacement sensor capable of detecting a speed with high accuracy and stability can be realized, and further has the following significant features.

Two sets of diffraction gratings (36, 37A or 37)
Since the separation angle θ _A and the incident angle θ _B of the light beam are set using B), even if the wavelength λ of the light source fluctuates and the incident angle θ _B to the test object fluctuates, the Doppler frequency f Can be used without a temperature compensation function such as temperature control, which has no influence and wavelength fluctuation is inevitable. or,
If a more stable sensor is required, these temperature compensation functions may be added. Considering that the detection signal is not affected by the temperature fluctuation and that the sensor unit is formed as a one-chip component, the environment resistance against a bad environment such as temperature fluctuation and vibration becomes very high.

Since a condenser lens with a large NA is required to widely pick up the scattered light from the test object, the optical path of the light beam projected onto the test object is inclined as in the embodiment to further reduce the NA. Then, by irradiating the test object using the minute diffraction gratings 36, 37A, 33B and the lens 35, the optical path of the return path for picking up the scattered light from the object is shifted and condensed by the lens having a large NA. If a high-quality Doppler signal can be obtained, the optical path for reciprocation can be easily separated at the same time. Therefore, even if an optical system for displacing the optical path such as a half mirror is not provided to obtain the Doppler signal, the optical path deviates from the light source. Light can be received by the light receiving element 4 disposed at the position, and the number of components of the optical system can be reduced.

Since the reciprocating optical paths are separated, even if there is reflected light returning from each surface of the plurality of glass plate optical elements, it does not enter the light receiving element and cause a problem.

Since the reciprocating optical path is separated, the distance between the light emitting element and the lens can be reduced by forming a small-diameter microlens having a short focal length, which is advantageous for miniaturization and thinning.

Since the light path from the light-emitting element is bent by the reflection element, the structure in which the lens and the light-emitting element are separated by a desired focal length even when the glass plate and the light-emitting element are brought close together is possible, and the thickness is reduced. Is advantageous.

By making the pitch of the diffraction grating 36 fine,
Diffraction grating 37A separation angle theta _A due to diffraction becomes large, 3
Even if the distance to 7B is small (that is, even if the glass plate 8 is thin), the diffracted light can be sufficiently separated spatially.
Sufficient working distance is obtained, and an easy-to-handle Doppler velocimeter is easy to design. That is, it can be designed to be easy to handle even if it is made smaller and thinner. Diffraction grating 37A at the conditions, and more precisely the pitch of 37B, the incident angle theta _B increases and the Doppler shift to the inspected object is made large, high sensitivity, high resolution Doppler displacement sensor can be realized. In other words, high sensitivity and high resolution, miniaturization and thinning,
All of the ease of handling is satisfied.

Embodiment 16 Next, a Doppler displacement sensor according to a sixteenth embodiment of the present invention will be described with reference to FIG. The micro parts of the millimeter order used in the embodiment require a very high assembling accuracy because the optical path is largely shifted and the detection accuracy is greatly deteriorated even if the displacement is on the order of tens of μm. Therefore, in this embodiment, the adjustment of the optical system is facilitated by providing an adjusting mechanism. The detection principle of the Doppler displacement sensor itself is the same as in the above embodiment.

In FIG. 40, a fixed frame 12 is provided around a housing 5 in which optical members such as a light emitting element 1 and a mirror 2 are incorporated.
Is disposed, and a glass plate 7 on which an optical functional element similar to that of the above embodiment is formed is attached to the upper surface of the fixed frame 12. Further, a fixed frame 15 is arranged around the fixed frame 12,
On the upper surface of the fixed frame 15, a glass plate 8 on which an optical functional element similar to that of the above embodiment is formed is attached. By adjusting the relative positional relationship between the housing 5, the fixed frame 12 and the fixed frame 15, an optical member fixed in the housing 5 and lenses, diffraction gratings, and the like formed on the surfaces of the glass plates 7 and 8. Can be aligned with the optical function element. After the adjustment, it is fixed by screw mechanisms 13 and 14 provided on the four sides of the fixed frames 12 and 15, and the gap is filled with an adhesive to increase the stability. As described above, in this embodiment, the components of the Doppler displacement sensor are unitized into three units, and the relative adjustment between the units is performed. Therefore, the Doppler displacement sensor can be easily adjusted during assembly and has high accuracy.

<Embodiment 17> FIG. 41 is a three-view configuration diagram of the Doppler displacement sensor of the seventeenth embodiment viewed from three directions.
(A) is a side view, (B) is a top view, and (C) is a front view.

The member 1 is a light emitting element (semiconductor laser element) for generating light, and has a size on the order of several hundreds of μm. Light generated and emitted from the horizontally disposed light emitting element 1 is reflected by the mirror 2 having a mirror surface at an angle larger than 45 degrees (for example, 55 degrees) and directed in a direction deviated from the vertical direction. I do. Note that a prism can be used instead of the mirror. A transparent glass plate 7 is provided in the direction in which the light is directed, and two transparent glass plates 8 are provided on the transparent glass plate 7 with a spacer interposed therebetween. In this embodiment, the first
Unlike the fifth embodiment, a replica lens portion 35 is formed on the inner surface of the glass plate 7 and the diffraction grating 3 is formed on the outer surface.
6 and two replica diffraction gratings 37A and 37B and a replica lens portion 38 are formed on the outer surface of the glass plate 8. With this configuration, the two emitted light beams intersect at the focal point. Further, a light receiving element 4 having a size on the order of several hundred μm is provided for receiving light and performing photoelectric conversion. As a specific example of the light receiving element,
Photodiodes, avalanche photodiodes,
Examples include a pin photodiode, a CCD, and a light receiving IC having a circuit for amplifying or processing a photocurrent output from the light receiving unit.

The light-emitting element 1 and the light-receiving element 4 are sealed in a ceramic light-shielding housing 5, and the glass plate 7 is attached to a window on the upper surface of the housing 5 to hermetically seal the inside. . An electrode pattern is connected to each of the light emitting element 1 and the light receiving element 4, and an end of the electrode pattern is exposed outside the housing 5. When a signal processing circuit is built in the housing, an output signal of the circuit is output to the exposed electrode pattern. The housing 5 has a size on the order of several mm, and constitutes a very small sensor unit.

An arrangement is made such that two laser beams are emitted from the sensor unit, and a scattered / reflective object 23 (such as fine particles or a scattered / reflective surface) relatively moving to the converging intersection 22 of the laser beams is located. Relationship.

The divergent light beam emitted from the light emitting element 1 is bent by the mirror 2 and then converted into a condensed light beam R (or a parallel light beam) by a lens 35 formed on the back surface of the glass plate 7. is transmitted diffracted by the diffraction grating 36 formed on the rear surface of the 8, + 1st-order diffracted light is bent by an angle theta _a by the diffraction, -1 is split order diffracted light, and the 0-order diffracted light traces of straight. Since the 0th-order diffracted light (straight light flux) R ₀ transmitted through the diffraction grating 36 does not contribute to the detection signal, much required ± 1st-order diffracted light is emitted,
It is preferable to appropriately design the sectional shape of the diffraction grating 32A so that the zero-order light becomes weak.

The light flux R ₋₁ diffracted by the diffraction grating 36 at the ± 1st order,
The path of R _{+ 1} is bent by the diffraction gratings 37A and 37B, and is converged on the target point 22 near the test object 23 at the incident angles θ _B and θ _C. These quantitative relations are as follows.

[0151] + 1-order diffracted light beam _{R +1: sinθ A = + λ} / P A sinθ B = -λ / P B + sinθ A -1 -order diffracted light beam _{R -1: sinθ A = -λ /} P A sinθ C = + λ / P _C + sin θ _A P _C = P _B

These are as follows.

[0153] _{sinθ B = + λ / (P} A -P B) sinθ C = -sinθ B where, P _A is the pitch of the diffraction grating 36, P _B is the diffraction grating 3
7A pitch, the P _C pitch of the diffraction grating 37C, lambda is the wavelength of the light beam _{(P A> P B, P} A> P C).

At this time, since the two light beams intersect in the vicinity of the target point 22, interference fringes occur in space. The pitch P of the interference fringes
₀ is as follows.

[0155] _{P 0 = λ / (sinθ B} + sinθ C) = λ / {λ / (P A -P B) + λ / (P A -P C)} = (P A -P B) + (P A - _{P C) = (P A -P} B) / 2

In this space, the velocity v in the direction crossing the interference fringes
When microparticles are inspected object is moved by, occur brightness of scattered light in accordance with the brightness of the space, the frequency _{f, f = v / P 0 =} 2 · v (P A -P B) becomes, lambda Becomes irrelevant.

This Doppler signal (bright and dark signal) component is condensed on the light receiving element 4 by the lens 38, and thereafter, is proportional to the moving speed v by a known signal processing circuit such as an amplifier, a filter, and a binarization circuit. If a pulse signal of a frequency is output, the moving speed of the test object can be detected. If a part or all of these signal processing circuits are incorporated in the sensor unit, the integration will be further enhanced, which is more preferable. Note that the focusing state of the light beam irradiated on the test object can be changed to parallel light or the like according to the state of the scattering particles and the scattering surface of the test object.

In this embodiment, as in the previous embodiment, the interference optical system has a structure in which an optical element in which lenses and diffraction gratings are formed on both surfaces of a glass plate by a replica manufacturing method or the like is very simple, small, and low in cost. In addition, a laser Doppler displacement sensor capable of detecting a speed with high accuracy and stability can be realized, and further has the following significant features.

Two sets of diffraction gratings (36, 37A or 37)
Since the separation angle θ _A and the incident angle θ _B of the light beam are set using B), even if the wavelength λ of the light source fluctuates and the incident angle θ _B to the test object fluctuates, the Doppler frequency f Can be used without a temperature compensation function such as temperature control, which has no influence and wavelength fluctuation is inevitable. or,
If a more stable sensor is required, these temperature compensation functions may be added. Considering that the detection signal is not affected by the temperature fluctuation and that the sensor unit is formed as a one-chip component, the environment resistance against a bad environment such as temperature fluctuation and vibration becomes very high.

Since a large NA condenser lens is required to widely pick up the scattered light from the test object, the optical path of the condensed light beam to the test object is inclined as in the embodiment to further reduce the NA. Then, by irradiating the test object using the minute diffraction gratings 36, 37A, 33B and the lens 35, the optical path of the return path for picking up the scattered light from the object is shifted and condensed by the lens having a large NA. If a high-quality Doppler signal can be obtained, the optical path for reciprocation can be easily separated at the same time. Therefore, even if an optical system for displacing the optical path such as a half mirror is not provided to obtain the Doppler signal, the optical path deviates from the light source. Light can be received by the light receiving element 4 disposed at the position, and the number of components of the optical system can be reduced.

Since the reciprocating optical paths are separated, even if there is light reflected and returned on each surface of the plurality of glass plate optical elements, it does not enter the light receiving element and cause a problem.

Since the reciprocating optical path is separated, the distance between the light emitting element and the lens can be reduced by forming a small-diameter microlens having a short focal length, which is advantageous for miniaturization and thinning.

Since the light path from the light-emitting element is bent by the reflection element, the light path can be bent. Therefore, even if the glass plate and the light-emitting element are brought close to each other, the lens can be separated from the light-emitting element by a desired focal length. Is advantageous.

When the pitch of the diffraction grating 36 is reduced,
Diffraction grating 37A separation angle theta _A due to diffraction becomes large, 3
Even if the distance to 7B is small (that is, even if the glass plate 8 is thin), the diffracted light can be sufficiently separated spatially.
Sufficient working distance is obtained, and an easy-to-handle Doppler velocimeter is easy to design. That is, it can be designed to be easy to handle even if it is made smaller and thinner. Diffraction grating 37A at the conditions, and more precisely the pitch of 37B, the incident angle theta _B increases and the Doppler shift to the inspected object is made large, high sensitivity, high resolution Doppler displacement sensor can be realized. In other words, high sensitivity and high resolution, miniaturization and thinning,
All of the ease of handling is satisfied.

<Embodiment 18> Next, a Doppler displacement sensor according to an eighteenth embodiment of the present invention will be described with reference to FIG. The micro parts of the millimeter order used in the embodiment require a very high assembling accuracy because the optical path is largely shifted and the detection accuracy is greatly deteriorated even if the displacement is on the order of tens of μm. Therefore, in this embodiment, similarly to the embodiment of FIG. 40, the adjustment of the optical system is facilitated by providing an adjusting mechanism. The detection principle of the Doppler displacement sensor itself is the same as in the above embodiment.

In FIG. 42, a fixed frame 12 is provided around a housing 5 in which optical members such as a light emitting element 1 and a mirror 2 are built.
And a glass plate 7 on which an optical function element similar to that of the seventeenth embodiment is formed is attached to the upper surface of the fixed frame 12. Further, a fixed frame 15 is arranged around the fixed frame 12, and a glass plate 8 on which the same optical functional element as that of the above-described seventeenth embodiment is formed is mounted on the upper surface of the fixed frame 15. By adjusting the relative positional relationship between the housing 5, the fixed frame 12 and the fixed frame 15, an optical member fixed in the housing 5 and lenses, diffraction gratings, and the like formed on the surfaces of the glass plates 7 and 8. Can be aligned with the optical function element. After the adjustment, it is fixed by screw mechanisms 13 and 14 provided on the four sides of the fixed frames 12 and 15, and the gap is filled with an adhesive to increase the stability. Thus, in the present embodiment, the components of the Doppler displacement sensor are 3
Since the configuration is made into a single unit and the relative adjustment between the units is performed, the Doppler displacement sensor can be easily adjusted at the time of assembly and has high accuracy.

<Embodiment 19> FIG. 43 is an embodiment showing an application example of the above-mentioned Doppler displacement sensor, and is a system configuration diagram of a drive system mainly used in an image recording apparatus and an image reading apparatus. A displacement object 110 such as a recording sheet is moved by a driving unit 112 having a driving mechanism including a driving motor and a rotating roller. The moving speed and the moving amount of the displacement object 110 are detected in a non-contact manner by the displacement sensor 111 of any one of the above-described embodiments 15 to 18.
The detection output of the displacement sensor is fed back to the control means 113, and the control means 113 transmits a drive signal to the drive means 112 so as to be in the state set by the setting means 114. By configuring such a feedback system, the displacement object 110 can be moved as set by the setting unit 114. Such drive systems are, for example, office equipment such as typewriters, printers, copy machines, and facsimile machines, as well as video equipment such as cameras and video equipment, as well as information recording / reproducing equipment, robots, machine tools, manufacturing equipment, transportation equipment, Further, the present invention is not limited to these, and can be widely applied to all devices having a driving unit.

<Modifications> Although the embodiments of the encoder and the Doppler displacement sensor have been described above, the present invention is not limited to the above embodiments, and various modifications may be made within the technical idea of the present invention. It is possible.

For example, in the above embodiment, the semiconductor chip or C
Although a light-shielding ceramic package generally used as a package for a CD light receiving element or the like is used as the housing, a metal can package may be used without being limited to this. Further, a transparent resin may be used instead of the glass plate.

In place of the replica lens used in the embodiments, a lens having the same optical function as a Fresnel lens or a zone plate may be used.

[0171]

According to the present invention, it is possible to provide an optical sensor which achieves both miniaturization, high precision and high resolution at a very high level, and which has high environmental resistance.

[Brief description of the drawings]

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

FIG. 2 is a perspective view showing a configuration of a main part of the first embodiment.

FIG. 3 is a cross-sectional view of the phase grating of the embodiment.

FIG. 4 is a graph showing the diffraction efficiency of a diffraction grating.

FIG. 5 is a configuration diagram of a second embodiment.

FIG. 6 is a configuration diagram of a third embodiment.

FIG. 7 is a configuration diagram of a fourth embodiment.

FIG. 8 is a perspective view showing a configuration of a main part of a fourth embodiment.

FIG. 9 is a configuration diagram of a fifth embodiment.

FIG. 10 is a configuration diagram of a sixth embodiment.

FIG. 11 is a configuration diagram of a sixth embodiment.

FIG. 12 is a configuration diagram of a seventh embodiment.

FIG. 13 is a configuration diagram of an eighth embodiment.

FIG. 14 is a configuration diagram of a modification of the embodiment of FIG.

FIG. 15 is a configuration diagram of a ninth embodiment.

FIG. 16 is a configuration diagram of a tenth embodiment.

FIG. 17 is a diagram for explaining an adverse effect of a mounting error of the scale 21;

FIG. 18 is a diagram comparing a case where a parallel light beam (plane wave) enters a light receiving surface of a light receiving element and a case where a divergent light beam (spherical wave) enters.

FIG. 19 is a configuration diagram of an eleventh embodiment.

FIG. 20 is a principle diagram for explaining a relative mounting error of the scale with respect to the head.

FIG. 21 is a perspective view for explaining a relative mounting error of the scale with respect to the head.

FIG. 22 is an explanatory diagram showing an interference state in a spherical wave.

FIG. 23 is a graph showing the relationship between the angle difference between two interference light beams, the relative mounting error angle (azimuth angle) of the scale with respect to the head, and the ratio between the wavelength of the light emitting source and the pitch of the grating.

FIG. 24 is a graph showing a relationship between an angle difference between two beams of interference and a relative mounting error angle (azimuth angle) of the scale with respect to a head.

FIG. 25 is a graph showing a relationship between an intersecting position between two interference light beams, a relative mounting error angle (azimuth angle) of the scale with respect to a head, and a ratio between a wavelength of a light emitting source and a pitch of a grating.

FIG. 26 is a graph showing the relationship between the intersection position between two interference light beams and the relative mounting error angle (azimuth angle) of the scale with respect to the head.

FIG. 27 is a graph showing the relationship between the number of interference fringes per 1 mm, the relative mounting error angle (azimuth angle) of the scale with respect to the head, and the deviation from the ideal focusing position.

FIG. 28 is a graph showing the relationship between the number of interference fringes per 1 mm, the relative mounting error angle (azimuth angle) of the scale with respect to the head, and the deviation from the ideal focusing position.

FIG. 29 is a schematic diagram of a positional relationship between a light-converging position and a sensor.

FIG. 30 is a principle view for explaining another relative mounting error of the scale with respect to the head.

FIG. 31 is a configuration diagram of a twelfth embodiment.

FIG. 32 is a sectional view of an optical unit according to a twelfth embodiment.

FIG. 33 is a modification of the optical unit in FIG. 32;

FIG. 34 is a modification of the optical unit in FIG. 32;

FIG. 35 is a configuration diagram of a thirteenth embodiment.

FIG. 36 is a modification of the embodiment of FIG. 35;

FIG. 37 is a modification of the embodiment of FIG. 35;

FIG. 38 is a configuration diagram of an embodiment of a drive system having an encoder.

FIG. 39 is a configuration diagram of a laser Doppler displacement sensor according to a fifteenth embodiment.

FIG. 40 is a configuration diagram of a sixteenth embodiment.

FIG. 41 is a configuration diagram of a laser Doppler displacement sensor of a seventeenth embodiment.

FIG. 42 is a configuration diagram of an eighteenth embodiment.

FIG. 43 is a configuration diagram of an embodiment of a drive system having a Doppler displacement sensor.

[Explanation of symbols]

 Reference Signs List 1 light emitting element 2 mirror 3 transparent glass plate 31A, 31B, 31C lens 32A, 32B, 32C diffraction grating 4, 4A, 4B, 4C light receiving element 5 housing 7, 8 transparent glass plate 20 relative movement scale 21 diffraction grating scale 22 2 Convergent crossing point of the laser beam of the book 23 Scattering / reflection object to be relatively moved 35 Lens 36, 37A, 37B Diffraction grating 38 Lens

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroshi Kondo 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-62-172203 (JP, A) JP-A-61 -17016 (JP, A) JP-A-63-311121 (JP, A) JP-A-4-2116 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01B 11/00 G01D 5/38

Claims (26)

(57) [Claims] 1. A housing having an optical window, a light emitting element and a light receiving element built in the housing, a light transmitting member provided in the vicinity of the window, and a light transmitting element provided on the light transmitting member. A first optical function element for splitting the generated light into a plurality of light beams and emitting the light, provided on the light-transmitting member, and irradiating the emitted light onto a relative displacement object and modulating the light; An optical displacement sensor, comprising: a second optical function element for leading to the light receiving element. 2. A drive mechanism for displacing an object, an optical displacement sensor for detecting a displacement state of the object, and control means for controlling the drive mechanism based on a detection output of the sensor. A drive system using an optical displacement sensor. 3. The displacement sensor according to claim 1, wherein the optical displacement sensor is an encoder, and the relative displacement object is a diffraction grating scale. 4. The drive system according to claim 1, wherein the optical displacement sensor is a Doppler displacement sensor, and the relative displacement object is a scattering reflective object. 5. The displacement sensor according to claim 1, wherein the light emitting element is a semiconductor laser element. 6. The displacement sensor according to claim 1, wherein a plurality of said light receiving elements are provided. 7. At least two light receiving elements for detecting signals having a phase difference of １ ／ period from each other.
A displacement sensor or drive system as described. 8. The displacement sensor according to claim 1, wherein the light transmitting member is a transparent plate, and a lens portion is provided on one surface and a diffraction grating portion is provided on the other surface. 9. The displacement sensor according to claim 1, wherein a plurality of transparent plates each provided with a lens portion or a diffraction grating portion are attached in a multiplex manner near the window portion. 10. The displacement sensor according to claim 1, wherein a signal processing circuit for processing a signal obtained by the light receiving element is built in the housing. 11. The relief grating of claim 1, wherein the refractive index of the material of the diffraction grating is N, and the wavelength of light generated by the light emitting element is λ. 4. The displacement sensor or drive system according to claim 3, wherein d satisfies the following condition. {Λ / [4π (N−1)]} 2nπ + cos ⁻¹ (−0.8)} ≦ d ≦ {λ / [4π (N−1)]} 2 (n + 1) π−cos ⁻¹ (− 0.8)｝ n = 0,1,2,3,4, ... 12. The displacement sensor according to claim 1, further comprising a mechanism for adjusting a relative positional relationship between said housing and said light transmitting member. 13. The displacement sensor according to claim 1, wherein a surface including a light beam directed to the displacement object is different from a surface including a light beam reflected from the displacement object. 14. The displacement sensor according to claim 3, wherein the optical system is configured such that light of a spherical wave is incident on the light receiving element. 15. The displacement sensor or the drive system according to claim 14, wherein the optical system is configured so that light generated by the light emitting element is collected near the diffraction grating scale. 16. The displacement sensor according to claim 1, wherein said light transmitting member has a filter function of selectively transmitting a wavelength range of light generated by said light emitting element. 17. The displacement sensor according to claim 1, wherein the light-transmitting member has a light-blocking means for blocking multiple reflected light. 18. A lens bonded to an inner surface of the light transmitting member and collimating light generated by the light emitting element, provided on an outer surface of the light transmitting member, and dividing the collimated light beam into a plurality of light beams for diffraction. A first diffraction grating directed to a grating scale, a second diffraction grating provided on an outer surface of the light transmitting member, and a second and third diffraction grating for combining and interfering a plurality of light fluxes returned from the diffraction grating scale; The respective interference lights provided on the inner surface of the light transmitting member and taken out in the substantially vertical direction from the second and third diffraction gratings are focused on a plurality of light receiving elements respectively corresponding to the inside of the housing. , The first, second, and third diffraction gratings all have the same pitch, and the second and third diffraction gratings are arranged with their phases shifted from each other. 4. The method according to claim 3, wherein Position sensors or drive system. 19. The displacement sensor or drive system according to claim 18, wherein said plurality of light receiving elements are arranged in parallel on the same substrate. 20. A first diffraction grating provided on an inner surface of the light transmitting member and dividing a light beam into a plurality of light beams, and a first diffraction grating provided on an outer surface of the light transmitting member and divided by the first diffraction grating. Second and third diffraction gratings for bending the traveling direction of the light beam and directing the beam to a relative displacement object; a Doppler light provided on the translucent member and reflected and scattered from the relative displacement object and phase-modulated, and The displacement sensor or the drive system according to claim 4, further comprising a lens for allowing the light to enter the light receiving element. 21. The displacement sensor according to claim 20, further comprising a light transmitting member provided with a lens for collimating the light generated by the light emitting element, separately from the light transmitting member, wherein the light transmitting members are arranged in a multiplex manner. Or drive system. 22. A light source, a light beam conversion element for converting the divergent state of light beams from the light source, and a separation optical element for separating the light beam converted by the light beam conversion device into first and second light beams. A transparent member integrally provided above, and a detection system for combining two diffracted lights generated from the test object illuminated by the first and second light fluxes corresponding to the respective light fluxes to cause interference and detection. A displacement detection device for measuring information on displacement of the object to be detected based on a detection result of the detection system. 23. An optical displacement sensor for measuring a relative displacement between a diffraction grating to be measured, a light emitting element, and an optical means for converting a convergence and divergence state of a light beam emitted from the light emitting element; The light beam from the light emitting element is divided into a first light beam and a second light beam.
A first diffraction grating for splitting into a light beam, a second diffraction grating for synthesizing diffracted light beams generated from the first light beam and the second light beam applied to the measured diffraction grating to obtain an interference light beam, A light receiving element for receiving the interference light beam,
An optical displacement sensor, wherein the wavefront of the interference light beam incident on the light receiving element is arranged to be spherical. 24. An optical displacement sensor for measuring a relative displacement between a diffraction grating to be measured, a light emitting element, and an optical means for converting a convergence and divergence state of a light beam emitted from the light emitting element. The light beam from the light emitting element is divided into a first light beam and a second light beam.
A first diffraction grating that divides the light into a light beam, and a second diffraction light beam that combines two diffracted light beams generated from the first light beam and the second light beam applied to the measured diffraction grating to obtain an interference light beam.
A diffraction grating, and a light receiving element for receiving the interference light beam, wherein the optical path lengths of the two diffracted lights from the measured diffraction grating to the second diffraction grating are L and L ', respectively.
When the optical path length from the second diffraction grating is substantially (L +
L ′) / 2, the first and second light beams or the second light beam
An optical displacement sensor, wherein the optical means is set so that a focal point of two diffracted lights is formed. 25. An optical displacement sensor for measuring a relative displacement between a diffraction grating to be measured, a light emitting element, and an optical means for converting a convergence / divergence state of a light beam emitted from the light emitting element; The light beam from the light emitting element is divided into a first light beam and a second light beam.
A first diffraction grating that divides the light into a light beam, and a second diffraction light beam that combines two diffracted light beams generated from the first light beam and the second light beam applied to the measured diffraction grating to obtain an interference light beam.
An optical path including a diffraction grating and a light receiving element for receiving the interference light beam, and in each of the first and second light beams or the two diffracted lights, an optical path from the first diffraction grating to the second diffraction grating An optical displacement sensor, wherein the optical means is set so that a focal point of the two diffracted lights is formed at a position of an optical path length substantially in the middle of the length. 26. The optical displacement sensor according to claim 24, wherein the converging point is located near the diffraction grating to be measured.