JPH08233557A - Rotational information detector and drive controller using the same - Google Patents

Abstract

PURPOSE: To provide a rotational information detector in which the reduction in size, the simplification in a structure and high detecting accuracy are realized and a drive controller using the same. CONSTITUTION: A scale side radiating diffraction grating GT and body side radiating diffraction gratings GBS2, GBS3 disposed in parallel with the grating GT are used, the luminous flux from the source LGT is separated, deflected and synthesized by the diffraction, the generated interference light is detected by a photodetector SA to detect the relative rotational information of an article. In this case, the grating pitches of the scale side grating and the body side grating and the order of the diffraction of the used diffraction light are N1, N2, N3 and n1, n2, n3 in the incident order of the fluxes, and so set as to satisfy N1×n1+N2×n2+N3×n3=0.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation information detecting device and a drive control device using the same. The present invention irradiates a radial diffraction grating of a disk attached to a relative rotating object with a light beam, and detects a phase-modulated signal light obtained from the light beam, thereby detecting the rotational position of the disk, the rotational position shift amount,
The present invention can be applied particularly well to a rotary encoder that detects a rotational displacement direction, a rotational speed, a rotational acceleration, and the like.

[0002]

2. Description of the Related Art Conventionally, an incremental rotary encoder has been used for the purpose of highly accurately measuring rotation information (rotational displacement amount, speed, acceleration, etc.) of an object.

A high-precision incremental linear encoder illuminates a monochromatic light flux on a micrometer-order fine grating recorded on a scale, extracts at least two of the diffracted light obtained there, and causes them to interfere with each other. , An incremental encoder signal is output by creating a periodic change in the amount of light with the movement of the grating and detecting it with a photoelectric element.

[0004]

As a recent trend, there is a demand for miniaturization of a rotary encoder (EX.Φ10 mm disc). The principle of the miniaturized linear encoder as described above is the rotary encoder. However, it was difficult to use it for different configurations. In particular, when adopting such a principle in a rotary encoder, there has been no specific configuration for accurately interfering diffracted light.

In view of the above, it is an object of the present invention to provide a rotation information detecting device that realizes downsizing, simplification of configuration, and high detection accuracy, and a drive control device using the same.

[0006]

A first aspect of the present invention for achieving the above object is to provide a scale-side radial diffraction grating provided on an object whose relative rotation information is to be detected, and a scale-side radial diffraction grating arranged parallel to the radial diffraction grating. A plurality of main body side radial diffraction gratings, a light source means and a light receiving means provided on the main body side, and the light flux from the light source means using the scale side radial diffraction grating and the main body side radial diffraction grating. Are arranged so that the relative light information of the object can be detected by detecting the interference light generated by separating, deflecting and combining by the diffraction of the scale side radial diffraction grating and the body side radial direction. The number of gratings corresponding to one round of the diffraction grating is N1, N2, N3 in the order of incidence of the light flux, and the diffraction order of the diffracted light used from the scale-side radial diffraction grating and the body-side radial diffraction grating is the order of emission of the light flux. As n1, n2, n3, N1 · n1 + N2
The rotation information detecting device is characterized in that the optical path is configured so as to satisfy n2 + N3 · n3 = 0.

The second invention is further characterized in that the scale side radial diffraction grating and the main body side radial diffraction grating are phase type diffraction gratings.

A third aspect of the present invention is a drive control device for performing relative rotation drive control of the object using the relative rotation information detected by the rotation information detection device.

[0009]

1 to 3 are explanatory views of a rotary encoder according to a first embodiment of the present invention. FIG. 1 is an optical layout diagram of the apparatus of this embodiment, FIG. 2 is a schematic optical path diagram of the apparatus, and FIG.
FIG. 3 is a diagram showing a shape of a pattern in the same device. In the figure, all members except the disk D and the pattern formed thereon are fixedly arranged on the apparatus main body (not shown) on the fixed side, and the disk D is a rotating member (not shown) such as a shaft. It is installed with the disk center aligned with the center of rotation.

A light beam emitted from a light source LGT such as an LED is converted into a parallel light beam R by a collimator lens LNS and illuminated on a disk D which rotates relative to one another.

On the disk D, a transmissive radial diffraction grating GT (the number of gratings corresponding to one rotation is N1 / circle) having the disk center as the radiation center is recorded over the entire circumference of the disk D. Further, on the light emitting side of the radial diffraction grating in the main body of the apparatus, a transmission type radial diffraction grating GBS2 (the number of gratings corresponding to one round is N2 /
Circumference), and similarly, a transmission type radial diffraction grating GBS3 (where the number of gratings corresponding to one circumference is N3 /
Circumference) is arranged substantially parallel to the disk D. The diffraction gratings GBS2 and GBS3 are partially provided on the entire circumference of the disc D. For example, the diffraction grating GBS2 is 1
If only / 12 are formed, the number of diffraction gratings GBS2 formed will be N2 / 12. An example of a specific pattern shape of the diffraction gratings GT, GBS2, GBS3 is shown in FIG.

Here, the diffraction gratings GBS2, GBS3 and the radiation grating GT preferably have a fine structure so that the 0th order diffracted light is not generated in the lamella grating.

Radial diffraction grating GT irradiated with parallel light flux R
From the number of gratings equivalent to one round N1 / circle, + N first-order diffracted light flux R
+, -N first-order diffracted light flux R- is generated. These diffracted light beams R + and R- are generated by the diffraction grating GBS2 (the number of gratings N2 per circle)
-N 2nd order and + n 2nd order are diffracted and the optical path is bent,
The luminous flux becomes R +-, R- +. The diffraction grating GBS3 is arranged at a point 0 on the space where the light fluxes R +-and R- + intersect, and the light fluxes R +-and R-
-+ Is this diffraction grating GBS3 (number of gratings equivalent to one round N3 / circle)
Are diffracted by + n3rd order and -n3rd order respectively, and luminous fluxes R +-+ and R-+-
become.

Here, the relationship between the number of gratings N1, N2, N3 corresponding to one round in the diffraction gratings GT, GBS2, GBS3 and the diffraction orders n1, n2, n3 of the diffracted light used for the signal light is N1.n1 + N2.・ N2 + N3 ・ n3 = 0. ． ． (1) Since the optical path is configured so as to satisfy (N1, N2, N3, n1, n2, n3 are arbitrary natural numbers), the luminous flux R +-+, R-+-finally used as the signal light Are emitted in parallel with each other.
The light fluxes R +-+ and R-+-are overlapped with each other with the same optical path length, and interfere with each other to be emitted as a bright / dark signal.

FIG. 2 schematically shows the above optical path.

Light fluxes R +-+, R diffracted from the diffraction grating GBS3
-+-Are emitted so that the optical axes of the optical axes are overlapped with each other and the optical axes are parallel to each other, and the symmetry of all the optical paths from the light source is maintained and interfere with each other.

At this time, when the radial diffraction grating GT of the diffracted light R +-+ moves by one pitch due to the rotation of the disk, the phase of the wavefront is shifted by + 2π, and the diffracted light R-+-is rotated by the disk D. When the GT moves one pitch, the wavefront phase shifts by -2π. Therefore, when the radial diffraction grating GT moves by one pitch due to the rotation of the disk,
The light and dark changes twice in a sine wave.

Here, as shown in FIG. 3, the diffraction grating GBS3 is divided into four regions with the point P0 as a boundary, and the phases of the arrangement of the gratings are shifted by 1/8 pitch. is there. Therefore, the interference phase (brightness phase) of the interference light flux emitted from each region is shifted by 1/4 cycle and becomes 2 in a sinusoidal shape.
Change times. Since the interference light from each of these areas is incident on the light receiving elements SA, SB, S bar A, S bar B,
From SA, SB, S bar A, and S bar B, sinusoidal analog signal currents that are shifted by 1/4 cycle of 2N1 cycles are generated in one rotation. The four cyclic signals are signal-processed by a signal processing system (not shown) to calculate the rotation amount and the rotation direction. Since the method of calculating the rotation amount and the rotation direction at this time is well known,
Description is omitted.

Since the luminous flux R illuminating the disc D has a spread, it is diffracted by the radial diffraction grating GT and the diffraction grating GB
Even when the light reaches S2, the two signal diffracted lights are almost overlapped with each other and pass through the diffraction gratings GBS2 and GBS3 to receive the light receiving elements SA and S.
Guided to B, S bar A, S bar B.

For example, the luminous flux diameter for illumination is 500 μm, the number of radial diffraction gratings is N1 = 2500, and the recording radius on the disc D is r = 50.
Assuming 00μm and LED wavelength λ = 0.86μm, first-order diffraction angle θ
Is θ = arcsin {λ · N1 / (2πr)} = 3.92 °. In this case, the gap between the radial diffraction grating GT and the diffraction grating GBS2 is h = 500 μm, and the separation amount is 68.5 μm.

In the embodiment described above, the diffraction grating G
Number of grids N1, N2, N3 corresponding to one round in T, GBS2, GBS3
And the relationship between the diffraction orders of the diffracted light used for the signal light, n1, n2, n3, is N1 ・ n1 + N2 ・ n2 + N3 ・ n3 = 0 (N1, N2, N3, n1, n2, n3 are any natural numbers. Since the optical path is configured so as to satisfy (1), in the rotation information detection using the radial diffraction grating, a stable interference light flux can be easily obtained by the two diffraction gratings provided in the vicinity of the disc D, and It is also possible to downsize the device configuration. In particular, by achieving such a condition with a phase grating configured to prevent 0th-order light, it is possible to perform highly accurate rotation detection while preventing the generation of noise light as much as possible even in the configuration in which these diffraction gratings are close to each other. .

4 to 6 are explanatory views of a rotary encoder according to the second embodiment of the present invention. FIG. 4 is an optical layout diagram of the apparatus of this embodiment, FIG. 5 is a schematic optical path diagram of the apparatus, and FIG.
FIG. 3 is a diagram showing a shape of a pattern in the same device. The same members as those described above are given the same reference numerals.

In this embodiment, the reflected diffracted light from the radial diffraction grating GT on the disk D is used. That is,
The radial diffraction grating GT is modified by partially modifying the optical system of the first embodiment.
Is a reflection type diffraction grating, and the diffraction diffraction light is generated from the radial diffraction grating GT, separated and combined by the diffraction grating GBS4, and the interference signal light is projected onto the light receiving element. The radial diffraction grating GT is basically the same as that of the first embodiment except that it is a reflection type phase diffraction grating (preferably a lamella phase grating having a fine structure that does not generate 0th-order diffracted light). It has the same configuration as the one.

The light beam emitted from the light source LGT such as an LED is converted into a parallel light beam R by the collimator lens LNS1, and half the amount of light passes through the beam splitter BS and reaches the diffraction grating GBS4. This diffraction grating GBS4 (the number of gratings corresponding to one rotation is N2 / circle) provided in the main body of the device is a transmission type radial diffraction grating whose radiation center is substantially the center of the disc, and is arranged substantially parallel to the disc D. There is. The diffraction grating GBS4 is a disc
It is partially provided around the entire circumference of D. Here, the diffraction grating GBS4 preferably has a fine structure that does not generate 0th-order diffracted light in the lamella grating.

From the diffraction grating GBS4 (the number of gratings corresponding to one round N2 / circle) irradiated with the parallel light flux R, the + n second-order diffracted light R +
Then, -n second-order diffracted light R- is generated and illuminated on the disk D that rotates relative to each other.

On the disk D, as described above, the reflection type radial diffraction grating GT (the number of gratings N1 / circle corresponding to one round) is recorded.

Radial diffraction grating irradiated with diffracted lights R + and R-
-N1 from GT (N1 grid per lap / lap)
Next, + N first-order reflected diffracted light fluxes R +-and R- + are generated. Diffracted light flux R
+-, R- + are the diffraction grating GBS4 (the number of gratings corresponding to one round N2 /
(Circumference), the light is diffracted by + n2nd order and -n2nd order respectively and then emitted.

Here, the relationship between the number of gratings N1 and N2 in the diffraction gratings GT and GBS4 and the diffraction orders n1 and n2 of the diffracted light used for the signal light is N2.n2 + N1.n1 + N2.n2 = 0 ( N1, N2, n1, and n2 have an optical path that satisfies any natural number), so the light fluxes R +-+ and R-+-that are finally used as signal light overlap in parallel and interfere with each other. To do.
The light fluxes R +-+ and R-+-are overlapped with each other with the same optical path length, and interfere with each other to be emitted as a bright / dark signal.

FIG. 5 schematically shows the above optical path.

Light flux R +-+ re-diffracted from the diffraction grating GBS4,
The R-+-are emitted so that the optical paths of the optical axes are overlapped with each other and the optical axes are parallel to each other, and the symmetry of all the optical paths from the light source is maintained and interfere with each other.

At this time, when the radial diffraction grating GT moves by one pitch due to the rotation of the disk D, the diffracted light R +-+ is shifted in phase by + 2π, and the diffracted light R-+-is radially diffracted by the rotation of the disk D. When the grating moves by one pitch, the wavefront phase shifts by -2π. Therefore, the interference light changes its brightness twice in a sine wave shape when the radial diffraction grating moves by one pitch due to the rotation of the disk.

As shown in FIG. 6, the diffraction grating GBS3 is divided into four regions with the point P0 as a boundary, and the phases of the grating arrangements are shifted by 1/8 pitch. is there. Therefore, the interference phase (brightness phase) of the interference light flux emitted from each region is shifted by 1/4 cycle and becomes 2 in a sinusoidal shape.
Change times. The interference light from each of these areas is reflected by the beam splitter BS by half the amount of light, and the light receiving elements SA, SB,
Since it is incident on S-bar A and S-bar B, each photodetector SA, SB, S
From the bar A and the bar B, sinusoidal analog signal currents of 2N cycles, which are deviated from each other by ¼ cycle, are generated in one rotation. The four cyclic signals are signal-processed by a signal processing system (not shown) to calculate the rotation amount and the rotation direction. Since the method of calculating the rotation amount and the rotation direction at this time is well known, the description thereof will be omitted.

Since the luminous flux R illuminating the disc D has a divergence, it is diffracted by the diffraction grating GBS4 and is then a radial diffraction grating.
Even after reaching the GT, the two diffracted light fluxes are almost overlapped and go through the diffraction grating GBS4 and then the light receiving elements SA, SB, S bar A, S bar B.
Be led to.

For example, assuming that the illuminating luminous flux diameter is 500 μm, the number N2 of the radial diffraction grating GT corresponding to one round is N2 = 2500, the recording radius on the disc D is r = 5000 μm, and the LED wavelength is λ = 0.86 μm, the disc illumination light incident angle θ is , Θ = arcsin {λ · N2 / (4πr)} = 1.96 °. Gap between radial grating GT and grating GBS h
= 500 μm, the separation amount = 34.2 μm.

In the embodiment described above, the diffraction grating G
The relationship between the number of gratings N1 and N2 corresponding to one round in T and GBS4 and the diffraction orders n1 and n2 of the diffracted light used for the signal light is N2 ・ n2 + N1 ・ n1 + N2 ・ n2 = 0 (N1, N2, n1 , n2 have an optical path configured to satisfy an arbitrary natural number), so that in the rotation information detection using the radial diffraction grating, a stable interference light flux can be easily generated by one diffraction grating provided near the disk D. As a result, the overall size of the device can be reduced. In particular, such conditions
By achieving this with a phase grating configured to prevent 0th-order light, it is possible to perform highly accurate rotation detection while preventing the generation of noise light even in the configuration in which these diffraction gratings are arranged close to each other. Since the above equation is a method of passing through the same diffraction grating twice, N3 · n3 in the equation (1) is replaced by N2 · n2, and the order is also different, but substantially the equation (1) Is the same as.

FIG. 7 is a schematic configuration diagram of a motor driver system according to a third embodiment of the present invention. In the figure, DH is the light source LGT in any of the above-described first and second embodiments.
A detection head in which all optical configurations except the disk D from the light receiving element to the light receiving element are arranged, and the PU processes the output from each light receiving element, performs incremental rotation amount and rotation direction measurement, and generates a control signal. Processing circuit, IM is an input section for inputting a rotation command to the signal processing circuit PU, MD is a motor driver that receives the control signal from the signal processing circuit PU and controls the drive of the motor, MT is a motor, SF is a motor It is a shaft that is rotationally driven to transmit the driving force to a driven part (not shown).

The signal processing circuit PU generates a control signal based on the output from each light receiving element and the command input information from the input section, and thereby the rotational drive of the shaft SF by the motor MT is controlled.

With the above-described structure, the detection head DH is downsized, and a more compact motor driver system is realized.

In addition, the optical system can be modified by the following modifications. (1) When the entire circumference is not recorded, the number of the radial diffraction gratings corresponding to one round does not need to be an integer, and may be a number after the decimal point. For example, N2 and N3 of the first embodiment, N2 of the second embodiment
Corresponds to this. By the way, in the first embodiment, n1 = +
It is assumed that 1, n2 = -1, n3 = + 1, N1 = 2500, N2 = 5000, N3 = 2500. (2) The number of divisions of the diffraction grating (GBS3 in the first embodiment, GBS4 in the second embodiment) and the phase shift amount may be changed (two divisions, and the grating arrangement phases are mutually shifted by 90 degrees. , 6 divisions and 60 degree shifts).

[0040]

As described above, according to the first aspect of the present invention, stable and stable interference light flux can be easily obtained, the overall size of the apparatus can be reduced, and a small, simple, and highly accurate apparatus can be realized. It

Further, according to the second aspect of the present invention, the generation of zero-order light can be avoided, so that it is possible to perform a more accurate measurement with such a miniaturized device.

Further, according to the third aspect of the invention, a drive controller which is small, simple, and capable of highly accurate measurement is realized.

[Brief description of drawings]

FIG. 1 is an optical layout diagram of a rotary encoder according to a first embodiment of the present invention, and an optical path schematic diagram of the same device.

FIG. 2 is a schematic diagram of the optical path of the device.

FIG. 3 is a diagram showing a shape of a pattern in the device.

FIG. 4 is an optical layout diagram of a rotary encoder device according to a second embodiment of the present invention.

FIG. 5 is a schematic diagram of the optical path of the device.

FIG. 6 is a diagram showing a shape of a pattern in the device.

FIG. 7 is a schematic configuration diagram of a motor driver system according to a third embodiment of the invention.

[Explanation of symbols]

 LGT light source R parallel light flux LNS, LNS1 lens D disk GBS2 to GBS4 radial diffraction grating radial diffraction grating on GT disk SA, S bar A, SB, S bar B interference light receiving element

Claims (3)

[Claims] 1. A scale-side radial diffraction grating provided on an object whose relative rotation information is to be detected, one or a plurality of body-side radial diffraction gratings arranged in parallel with the radial diffraction grating, and a body-side radial diffraction grating. Interference light generated by separating, deflecting, and combining the luminous flux from the light source means by diffraction using the scale-side radial diffraction grating and the main-body-side radial diffraction grating. Arranged so that the relative rotation information of the object detected by the light receiving means is detected, and the number of gratings corresponding to one circumference of the scale side radial diffraction grating and the main body side radial diffraction grating is N1, N2 in the order of incidence of the light flux. , N3, the diffraction orders of the used diffracted light emitted from the scale-side radial diffraction grating and the main-body-side radial diffraction grating are n1, n2, and n3 in the order of emission of the light flux, and N1 · n1 + N2
A rotation information detecting device characterized in that an optical path is configured so as to satisfy n2 + N3 · n3 = 0. 2. The rotation information detecting device according to claim 1, wherein the scale side radial diffraction grating and the main body side radial diffraction grating are phase type diffraction gratings. 3. A drive control device that performs relative rotation drive control of the object using the relative rotation information detected by the rotation information detection device according to claim 1.