JP6111852B2 - Encoder device - Google Patents

Description

  The present invention relates to an encoder device.

  In recent years, as a scanning encoder device, a scale that has a grating that moves with a moving body and that is periodically formed along the moving direction is irradiated with irradiation light modulated based on a predetermined modulation signal, An encoder apparatus that detects position information of a scale by comparing the reflected light or transmitted light with a modulation signal has been proposed (Patent Document 1).

US Pat. No. 6,639,686

  However, in the encoder device described in Patent Document 1, for example, the light is emitted from the light source due to the influence of heat or the like emitted from the light source, the variation of the holding member that holds the light source or the moving body, the temporal variation of the light source, and the like. In some cases, the wavelength center of the light drifts. In such a case, an error is included in the position detection result of the moving body, which causes a problem that a very large error occurs as a high resolution sensor. Further, the encoder device described in Patent Document 1 has a problem that an error occurs in the position detection result of the moving body when the light emitted from the light source is blocked by a foreign substance or the like. The present invention has been made in view of the above points, and provides an encoder apparatus capable of reducing an error included in a position detection result of a moving body.

One embodiment of the present invention includes a light modulation unit that modulates at least part of light emitted from a light source unit, and an incident surface on which a plurality of light beams from the light are incident, and is relatively movable in at least one direction A moving member, at least two light receiving units that respectively receive interference fringes generated in at least two regions on the moving member, and output light reception signals based on the received interference fringes, and at least of the light receiving units Calculation for calculating the relative movement amount of the moving member based on the light reception signal output from one light receiving unit, at least one of the light reception signals output from each of the at least two light receiving units. A signal selection unit that is selected as a signal, and a movement amount calculation unit that calculates the relative movement amount of the moving member based on the calculation signal selected by the signal selection unit , And a amplitude detector for detecting the amplitude of the received light signal in which the light receiving unit outputs, the signal selection unit, amplitude the amplitude detection unit detects that the received signal is within the predetermined amplitude, It is an encoder apparatus selected as the calculation signal.
One aspect of the present invention is a light modulation unit that modulates at least part of light emitted from a light source unit;
The light receiving unit has a light incident surface on which a plurality of light beams are incident, and receives a moving member that is relatively movable in at least one direction and interference fringes generated in at least two regions on the moving member. The at least two light receiving units that respectively output light receiving signals based on the interference fringes, and the light receiving units that are output by at least two light receiving units based on the light receiving signals output by at least one light receiving unit among the light receiving units. A signal selection unit that selects at least one of the signals as a calculation signal for calculating a relative movement amount of the movement member; and the movement member based on the calculation signal selected by the signal selection unit. And a storage unit for storing information indicating the light reception signal output from the light receiving unit. An amount calculation unit is an encoder that calculates the relative movement amount of the moving member based on the calculation signal selected by the signal selection unit and information indicating the light reception signal stored in the storage unit Device.

  ADVANTAGE OF THE INVENTION According to this invention, the error contained in the position detection result of a moving body can be reduced.

It is the schematic which shows the structure of the encoder apparatus which concerns on one embodiment of this invention. It is the schematic for demonstrating the complex phase of the light ray in the encoder apparatus of this embodiment. It is a schematic diagram which shows an example when the big foreign material has adhered to the moving grid of this embodiment. It is a schematic diagram which shows an example in case the small foreign material has adhered to the moving grid of this embodiment. It is a block diagram which shows an example of the specific structure of the movement amount detection apparatus with which the encoder apparatus of this embodiment is provided. It is a table | surface which shows an example of the calculation of the count process part of this embodiment. It is a wave form diagram which shows an example of the amplitude waveform of the photoelectric conversion signal which the amplitude detection circuit of this embodiment detects an amplitude. It is a graph which shows an example of the result of having detected the movement amount by the movement amount detection apparatus of this embodiment. It is the schematic of the encoder apparatus which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows an example of a structure of the count process part of this embodiment. It is a table | surface which shows an example of the calculation of the signal selection part of this embodiment.

[First Embodiment]
Hereinafter, an embodiment of an encoder according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a configuration of an encoder apparatus 1 according to an embodiment of the present invention. The encoder device 1 is a so-called diffraction interference type encoder, and is an optical encoder that detects the moving direction, moving amount, or displacement of a moving body (moving grating) that moves in a predetermined direction (for example, the X-axis direction). In order to describe the positional relationship of the encoder according to the present embodiment, the direction toward the upper side of the paper is the positive direction of the Y axis, the right direction of the paper is the positive direction of the X axis, and the direction from the back surface to the front surface of the paper surface. The positive direction of the Z axis will be described below.

  As shown in FIG. 1, the encoder device 1 of the present embodiment includes a light source unit 11, an optical branching member 12, an optical modulation unit 13, a glass block 14, an index grating 15, two light receiving elements 17 and 18, and a movement amount detection device. 20 and a moving grid 16 provided so as to be relatively displaceable with respect to these constituent members.

The light source unit 11 includes a light source 11a and a collimator lens 11b. The light source unit 11 may not include the collimator lens 11b.
The light source 11 a is a laser element that emits laser light, for example, and emits coherent light whose wavelength is modulated by the light modulation unit 13 toward the −Y axis direction side.
The collimator lens 11b receives the light emitted from the light source 11a and deflects it into parallel light in the Y-axis direction.

  The light branching member 12 receives the light emitted from the light source unit 11 and divides the received light into a plurality of light beams L1, L2, and L3. That is, the light branching member 12 is composed of a mask having partially different transmittances, for example, transmitting light at positions corresponding to the optical paths A, B, and C, and blocking the light at other portions. A light receiving surface is disposed at a position (X-axis direction) orthogonal to the optical axis (Y-axis direction) of parallel light emitted from 11b. Therefore, the parallel light incident on the light branching member 12 is branched into the light beams L1 to L3 and emitted from the positions corresponding to the optical paths A, B, and C.

  For example, the light modulation unit 13 periodically changes the wavelength of light emitted from the light source 11a by changing a current supplied to the light source 11a. For example, the light modulation unit 13 changes the wavelength λ = 850 nm of the light emitted from the light source 11a by Δλ = ± 5 nm. That is, the light modulation unit 13 changes the wavelength of light emitted from the light source 11a in a range of λ = 845 to 855 nm. That is, the light modulation unit 13 modulates at least a part of the light emitted from the light source unit 11. A specific configuration of the light modulator 13 will be described later with reference to FIG.

  The glass block 14 is an optical path length changing unit that changes the optical path length of at least some of the plurality of light beams emitted from the light source unit 11, and is, for example, between the light branching member 12 and the moving grating 16. It arrange | positions on the optical path B and permeate | transmits the light ray L2 inject | emitted from the light branching member 12. FIG.

  The glass block 14 has a predetermined refractive index N1, and has a predetermined thickness D in the traveling direction of the light beam L2 emitted from the light branching member 12 (for example, the Y-axis direction). Therefore, the optical path length of the light beam L2 that passes through the glass block 14 depends on the refractive index N (for example, the refractive index N1) and the thickness D, and the optical paths of the light beam L1 and the light beam L3 that pass through the air, for example. Longer than the length. That is, the glass block 14 is disposed only on the optical path B of the light beam L2 with respect to the distance between the light beams L1 and L2 having the same substantial distance as the optical path in the moving grating 16 from the light source 11a, so that the light beams L1 and L2 The optical path lengths of the light beams L2 are changed relatively, and the optical path length of the light beam L2 is made longer than the optical path length of the light beam L1. Similarly, between the light beams L2 and L3, the glass block 14 is disposed only on the optical path B of the light beam L2, so that the optical path lengths of the light beams L2 and L3 are relatively changed by the glass block 14. As a result, the optical path length of the light beam L2 becomes longer than the optical path length of the light beam L3.

  In other words, the optical path length from the light source 11a to the moving grating 16 for the light beam L2 is longer than the optical path length from the light source 11a to the moving grating 16 for the light beam L1 and the light beam L3. The optical path lengths of a plurality of light beams incident on the region can be relatively changed. As a result, the phase of the wavefront of the light beam L2 transmitted through the glass block 14 is delayed at the incident surface of the moving grating 16 even if the substantial distance as the light path is the same as the light beams L1 and L3. Here, the optical path length is an optical distance obtained by multiplying a spatial distance by a refractive index.

  The index grating 15 is an optical deflection member that deflects the traveling directions of the plurality of light beams L1 to L3 emitted from the optical branching member 12 so as to form at least two intersecting regions on the moving grating 16. Specifically, the index grating 15 is a diffraction grating in which a lattice-like pattern is formed at the same pitch as the moving grating 16, for example, and has a diffraction pattern periodically formed along the X-axis direction. It is a transmission type diffraction grating.

  The index grating 15 generates a plurality of diffracted lights based on the incident light, for example, diffracts the predetermined incident light into ± first-order diffracted lights. That is, the index grating 15 diffracts incident light rays L1 to L3 into ± first-order diffracted lights, respectively, and + 1st-order diffracted light Lp1 (third light) based on the light L1, and −1st-order diffracted light Lm2 (first light based on the light L2). + 1st order diffracted light Lp2 (second light beam) and −1st order diffracted light Lm3 (fourth light beam) based on the light beam L3 are emitted. Hereinafter, the −1st order diffracted light Lm2 is also simply referred to as a light beam Lm2. Further, the −1st-order diffracted light Lm3 is hereinafter also simply referred to as a light beam Lm3. Further, the + 1st order diffracted light Lp1 is hereinafter also simply referred to as a light beam Lp1. Hereinafter, the + 1st order diffracted light Lp2 is also simply referred to as a light beam Lp2.

  As described above, the + 1st order diffracted light Lp1 and the −1st order diffracted light Lm3 have the same optical path length from the light source unit 11 to the moving grating 16 (hereinafter referred to as the first optical path length), and the −1st order diffracted light based on the light beam L2. The optical path lengths of the Lm2 and the + 1st order diffracted light Lp2 from the light source unit 11 to the moving grating 16 (hereinafter referred to as the second optical path length) are equal, and the second optical path length is longer than the first optical path length. Further, as described above, the + 1st order diffracted light Lp1 and the −1st order diffracted light Lm3 are composed of the same light, and the −1st order diffracted light Lm2 and the + 1st order diffracted light Lp2 based on the light beam L2 are composed of the same light.

  The moving grating 16 is a diffraction grating provided on a moving body that is displaced relative to the light source unit 11, the light branching member 12, the light modulating unit 13, the glass block 14, the index grating 15, and the light receiving elements 17 and 18. is there. The moving grating 16 is a diffraction grating in which a diffraction pattern periodically formed along the moving direction (for example, the X-axis direction) due to this displacement is formed. That is, the moving grating 16 (moving member) has an incident surface on which a plurality of light beams by the light modulated by the light modulation unit 13 is incident, and is relatively movable in at least one direction.

  The moving grating 16 has an incident surface on which at least a plurality of light rays out of the light emitted from the light source unit 11 are incident. Further, the moving grating 16 is positioned so that a plurality of intersecting areas M1 and M2 where the diffracted lights diffracted by the index grating 15 overlap are formed on the incident surface, and the diffracted light incident on the plurality of intersecting areas M1 and M2 is formed. Injecting from the exit surface so that the traveling direction is substantially the same direction. That is, the + 1st order diffracted light Lp1 and the −1st order diffracted light Lm2 incident on the intersecting region M1 on the moving grating 16 interfere with each other by overlapping, and are emitted as interference light L12 to the −Y axis direction side. Further, the + 1st order diffracted light Lp2 and the −1st order diffracted light Lm3 incident on the intersecting region M2 on the moving grating 16 interfere with each other by overlapping, and as the interference light L23, −− in the substantially same direction as the interference light L12. Injected in the Y-axis direction. Here, the intersecting region is a region where a plurality of incident light overlaps on the incident surface of the moving grating 16 and an interference fringe is formed.

  That is, the −1st order diffracted light Lm2 incident on the intersecting region M1 on the moving grating 16 and the + 1st order diffracted light Lp2 incident on the intersecting region M2 on the moving grating 16 are opposite to each other with respect to the incident surface direction of the moving grating 16. From the direction, the light enters the entrance surface of the moving grating 16. Here, “entering in directions opposite to each other” means, for example, that −1st order diffracted light Lm2 and + 1st order diffracted light Lp2 incident on different intersecting regions M1 and M2 on the moving grating 16 are incident on the moving grating 16. In the virtual surface (for example, XY plane) orthogonal to the surface, it means that the light enters the moving surface of the moving grating 16 from different directions. In other words, “entering in directions opposite to each other” refers to an arbitrary virtual line parallel to the optical axis (Y-axis direction) of the plurality of light beams L1 to L3 orthogonal to the incident surface of the moving grating 16. It is incident from the reverse direction and has an incident angle in the reverse direction (+ X direction side and −X direction side) in the X axis direction with respect to this virtual line.

  The incident angles with respect to the moving grating 16 may be the same or different, and even if they are not exactly the same incident angles, they are almost the same angle within the range of design errors. There may be.

  Although not shown, the −1st order diffracted light Lm2 incident on the intersecting region M1 on the moving grating 16 and the + 1st order diffracted light Lp2 incident on the intersecting region M2 on the moving grating 16 are before entering the moving grating 16, respectively. In addition, the predetermined axis perpendicular to the incident surface of the moving grating 16 may cross the predetermined axis from opposite sides. In this case, the −1st order diffracted light Lm2 and the + 1st order diffracted light Lp2 are incident on different crossing regions on the moving grating 16 from opposite directions after crossing.

  Further, of the light rays incident on the moving grating 16, the −1st order diffracted light Lm2 incident on the intersecting region M1 on the moving grating 16 and the + 1st order diffracted light Lp2 incident on the intersecting region M2 on the moving grating 16 are moved. It is symmetric with respect to a predetermined axis perpendicular to the incident surface of the grating 16. The predetermined axis serving as the symmetry axis may be substantially perpendicular to the incident surface of the moving grating 16 and includes a range of design errors.

  The optical paths of the + 1st order diffracted light Lp1 and the −1st order diffracted light Lm2 incident on the intersecting region M1 of the moving grating 16 are, for example, substantially perpendicular to the moving direction (X axis direction) of the moving grating 16 in the intersecting region M1. Symmetric with respect to a straight line (in the Y-axis direction, that is, the optical axis of light emitted from the light source unit 11), and the incident angles incident on the moving grating 16 are the same angle. Similarly, the + 1st order diffracted light Lp2 and the −1st order diffracted light Lm3 incident on the intersecting region M2 of the moving grating 16 are also symmetric with respect to the Y-axis direction in the intersecting region M2 and are incident on the moving grating 16, for example. Are at the same angle. The substantially vertical straight line includes a range of design errors.

  The moving grating 16 is, for example, a transmissive diffraction grating. The moving grating 16 emits interference lights L12 and L23 toward a plurality of light receiving elements (here, the light receiving elements 17 and 18) arranged on the emission surface side of the moving grating 16. In other words, the interference light L12 based on the + 1st order diffracted light Lp1 and the −1st order diffracted light Lm2 is incident on the light receiving element 17 (first light receiving unit), and the interference light L23 based on the + 1st order diffracted light Lp2 and the −1st order diffracted light Lm3 is The light enters the light receiving element 18 (second light receiving portion).

The light receiving element 17 receives the interference light L12 emitted from the moving grating 16, and outputs a photoelectric conversion signal Sig1 indicating the interference intensity of the interference light L12.
The light receiving element 18 receives the interference light L23 emitted from the moving grating 16, and outputs a photoelectric conversion signal Sig2 indicating the interference intensity of the interference light L23.
Here, the interference light L12 and the interference light L23 are emitted from different positions of the moving grating 16, respectively. That is, the light receiving elements 17 and 18 respectively receive the interference lights L12 and L23 emitted from different positions of the moving grating 16, and output the photoelectric conversion signals Sig1 and Sig2 indicating the interference intensities of the interference lights L12 and L23. To do. That is, the light receiving elements 17 and 18 respectively receive interference fringes generated in at least two regions on the moving grating 16 (moving member), and output light reception signals based on the received interference fringes.

  The movement amount detection device 20 is connected to the light receiving elements 17 and 18, respectively, and receives photoelectric conversion signals converted by the light receiving elements 17 and 18. The movement amount detection device 20 calculates movement amount information (position information) of the moving grating 16 based on the photoelectric conversion signals detected by the light receiving elements 17 and 18. The movement amount detection device 20 outputs a position signal Sig3 indicating the calculated movement amount information (position information).

  The moving grating 16 is not limited to the transmission type, and may be, for example, a reflection type diffraction grating. In this case, the light receiving elements 17 and 18 can receive reflected light (for example, the incident surface of the moving grating 16). Side).

[Interference light detection method]
Next, an example of the interference light detection method by the encoder device 1 will be described.
The modulated light whose wavelength is modulated by the light modulator 13 is emitted from the light source 11a to the −Y axis direction side. The modulated light emitted from the light source 11a passes through the collimator lens 11b and is deflected into parallel light. The parallel light deflected by the collimator lens 11b enters the light branching member 12, and is divided into a plurality of light beams L1 to L3. Light rays L1 to L3 emitted from the light branching member 12 and traveling along the optical paths A to B travel in a direction parallel to the optical axis of the parallel light deflected by the collimator lens 11b (Y-axis direction) and enter the index grating 15. .

  Among the plurality of light beams L1 to L3, the light beams L1 and L3 enter the index grating 15 as they are, and are diffracted by the index grating 15 into the light beam Lp1 or the light beam Lm3, respectively. On the other hand, the light beam L2 passes through the glass block 14, enters the index grating 15, and is diffracted into the light beam Lm2 and the light beam Lp2.

  The light beam Lp1 and the light beam Lm2 diffracted by the index grating 15 are incident on the intersection region M1 on the incident surface of the moving grating 16, are further diffracted by the moving grating 16, and are emitted as interference light L12 to the −Y axis direction side. The Similarly, the light beam Lp2 and the light beam Lm3 are incident on the intersecting region M2 on the incident surface of the moving grating 16, are further diffracted by the moving grating 16, and are emitted as interference light L23 to the −Y axis direction side. Interference fringes that periodically change in the first direction are formed in the intersection region M1 of the moving grating 16, and interference fringes that periodically change in a second direction different from the first direction are formed in the intersection region M2. Is done.

  As described above, the interference light L12 emitted from the moving grating 16 enters the light receiving element 17 and is converted into a photoelectric conversion signal Sig1 indicating the interference intensity of the interference light. Further, the interference light L23 emitted from the moving grating 16 enters the light receiving element 18 and is converted into a photoelectric conversion signal Sig2 indicating the interference intensity of the interference light.

  As described above, (1) the wavelengths of the light beams L1 to L3 emitted from the light source unit 11 are modulated, and among the light beams based on the interference lights L12 and L23 emitted from the moving grating 16, the light beam Lm2 and the light beam Lp2 is a light beam based on the same light beam L2 in which the same optical path length difference is given to each of the light beams L1 and L3 based on the same light beam.

  (2) The light beam Lm2 and the light beam Lp2 emitted from the index grating 15 are emitted in directions opposite to each other with respect to the moving direction (X-axis direction) of the moving grating 16. Furthermore, the optical system (light branching member 12, glass block 14, index grating 15) from the light source unit 11 to the moving grating 16 is on the optical axis (Y-axis direction) of the light beam L2 orthogonal to the incident surface direction of the moving grating 16. The optical paths of the light beams L1 to L3 are symmetrical with respect to the optical axis (predetermined axis) of the light beam L2 or an axis parallel to the optical axis (predetermined axis).

  As a result, (3) interference light L12 (first interference light) due to interference between the + 1st order diffracted light Lp1 and the −1st order diffracted light Lm2 incident on the intersecting region M1 on the moving grating 16 and the intersecting region M2 on the moving grating 16 The interference light L23 (second interference light) generated by the + 1st order diffracted light Lp2 and the −1st order diffracted light Lm3 incident on the light has opposite phases. Further, the interference intensity based on each of the interference lights L12 and L23 detected by the light receiving elements 17 and 18 is expressed by a mathematical formula in which numerical items related to the modulation given by the light modulation unit 13 are in opposite phases. Therefore, by adding the interference intensities based on the interference lights L12 and L23 detected by the light receiving elements 17 and 18, the numerical items related to the modulation can be canceled with each other.

  Note that the interference lights L12 and L23 in this case are in reverse phase, for example, with respect to one of the plurality of light beams forming each interference light in the plurality of interference lights emitted from the moving grating 16. The other light beam having the same optical path length difference is incident on the moving grating 16 from the straight line (Y-axis direction) orthogonal to the moving direction (X-axis direction) of the moving grating 16 toward the opposite directions. By doing so, the numerical items relating to the modulation representing the phase difference include that they are in opposite phases. In other words, in each of the intersecting regions M1 and M2, the other light beam having the same optical path length difference with respect to one of the light beams constituting the interference light is incident on the incident surface of the moving grating 16. On the other hand, the numerical items relating to the modulation representing the phase difference by the incidence on the opposite direction side with respect to the moving direction of the moving grating 16 at the same incident angle include that the phases are opposite to each other.

  Further, the light beam Lp1 and the light beam Lm2 based on the modulated light emitted from the light source 11a and the light beam Lp2 and the light beam Lm3 have a predetermined phase difference in a state where they interfere with each other in the moving grating 16, whereby the encoder device 1 For example, interference fringes that periodically change (or move) in the movement direction (X-axis direction) can be obtained on the moving grating 16. Note that the periodic change of the interference fringes is based on the periodic change of the wavelength modulated by the light modulator 13, and the photoelectric conversion signals (photoelectric conversion signal Sig1, photoelectric conversion signal obtained by the light receiving elements 17 and 18). The conversion signal Sig2) is expressed by the position information of the moving grating 16 modulated by the modulation signal supplied to the light modulation unit 13. Therefore, the photoelectric conversion signal Sig1 and the photoelectric conversion signal Sig2 obtained by the light receiving elements 17 and 18 are based on both the positional information of the moving grating 16 and the periodic change of the modulated light emitted from the light source 11a. Based on the photoelectric conversion signal Sig1 and the photoelectric conversion signal Sig2, the position information of the moving grating 16 can be obtained using the modulation information of the light modulator 13 that is already known.

  Therefore, (4) interference fringes in the intersecting region M1 (first region) and the intersecting region M2 (second region) on the moving grating 16 periodically change, and the interference lights L12 and L23 are in opposite phases as described above. Therefore, the interference fringes in the intersection region M1 periodically change in the first direction (for example, the −X axis direction), and the interference fringes in the intersection region M2 have a second direction (for example, different from the first direction). , + X axis direction) periodically. That is, the interference fringes generated in each of the at least two intersecting regions M1 and M2 on the moving grating 16 move in opposite directions with the modulation of the light modulation unit 13.

  In addition, each member which concerns on this Embodiment is not limited to the said expression by having the above structures. For example, the light modulation unit 13 may be configured to modulate at least a part of the light emitted from the light source unit 11, and may modulate, for example, the wavelength or phase of the light. The light modulator 13 configured in this way relatively modulates the wavelengths of the light beam Lp1 and the light beam Lm2 incident on the intersection region M1, and relatively modulates the wavelengths of the light beam Lp2 and the light beam Lm3 incident on the intersection region M2. Can be modulated.

[Calculation of position information based on interference light]
Next, the interference light L12 emitted from the moving grating 16 will be described in detail with reference to FIG.
FIG. 2 is a schematic diagram for explaining the complex phase of the light beam in the encoder device 1 of the present embodiment. For convenience of explanation, in FIG. 2, the light beam Lp1 and the light beam Lm2 that interfere with each other in the intersecting region M1 of the moving grating 16 are described by shifting in the X-axis direction. The presence or absence is shown separately.

  As shown in FIG. 2, the index grating 15 and the moving grating 16 are transmissive diffraction gratings having diffraction patterns with the same grating pitch formed periodically along the X-axis direction. The index grating 15 diffracts the incident light beam L1 into + 1st order diffracted light and diffracts the incident light beam L2 into −1st order diffracted light.

  The + 1st order diffracted light Lp1 diffracted from the light beam L1 by the index grating 15 is further diffracted by the moving grating 16 into the −1st order diffracted light L10 and enters the light receiving element 17. The complex phase of the −1st order diffracted light L10 is expressed as in Equation 1. In Equation 1, “k” is the wavelength, “L” is the ray distance between the index grating 15 and the moving grating 16 as shown in FIG. 2, and “P” is the index grating 15 and the moving grating 16. “X” is relative positional information in the X-axis direction between the index grating 15 and the moving grating 16.

  Similarly, the −1st order diffracted light Lm 2 diffracted from the light beam L 2 by the index grating 15 is further diffracted into the + 1st order diffracted light L 20 by the moving grating 16 and is emitted to the light receiving element 17. The complex phase of the + 1st order diffracted light L20 is expressed as Equation 2.

  The interference intensity S1 in the case where the −1st order diffracted light L10 and the + 1st order diffracted light L20 interfere with each other is expressed as Expression 3.

  Therefore, when either the index grating 15 or the moving grating 16 moves one pitch in the movement direction (X-axis direction), the movement amount detection device 20 performs two cycles (4π) based on the photoelectric conversion signal Sig1 of the light receiving element 17. ).

  On the other hand, like the light beam L2 according to the present embodiment, by passing through the glass block 14 before entering the index grating 15, the complex of the + 1st order diffracted light beam L20 that gives an optical path length difference to the light beam L1. The phase is expressed as Equation 4.

  Here, when Expression 2 and Expression 4 are compared, the complex phase E′2 differs from the complex phase E2 by the phase difference ΔL. Therefore, the interference intensity S′1 when the −1st order diffracted light L10 interferes with the + 1st order diffracted light L20 transmitted through the glass block 14 is expressed by Equation 5.

  That is, as can be seen from Equation 3 and Equation 5, the interference intensity of the interference light including the + 1st order diffracted light L20 that has passed through the glass block 14 also differs by the phase difference ΔL. As shown in Equations 3 and 5, since the interference intensity obtained by the light receiving elements 17 and 18 does not include a variable term depending on the wavelength, the interference intensity pattern does not change even if the wavelength is changed.

  Here, the phase difference ΔL is expressed by ΔL = (N−1) · D · Δk, and when the light modulation unit 13 modulates the wavelength of light from λ1 to λ2, Δk = (1 / λ1-1 / λ2), the wavelength is modulated as Δλ = λ0−sinωt, and therefore Δk = A0 · sinωt and ΔL = (N−1) · D · A0 · sinωt. When this phase difference ΔL = (N−1) · D · A0 · sin ωt is substituted into Equation 5, it is expressed as Equation 6. Here, “N” represents the refractive index of the glass block 14, “D” represents the thickness of the glass block 14, “A0” represents a predetermined set value determined at the time of design, and “ωt” represents the angular phase.

  That is, as shown in Expression 6, the interference intensity of the interference light L12 between the light beam Lp1 and the light beam Lm2 detected by the light receiving element 17 is modulated by the modulation signal supplied to the light modulation unit 13 from the positional information X of the moving grating 16. It is a thing. When the photoelectric conversion signal Sig1 having the interference intensity shown in Equation 6 is output to the movement amount detection device 20 (position calculation unit), the movement amount detection device 20 calculates the position information X of the movement grating 16.

  Similarly, the interference intensity S2 of the interference light L23 is expressed as in Expression 7.

  Thus, the interference intensity S′1 of the interference light L12 shown in Expression 6 and the interference intensity S2 of the interference light L23 shown in Expression 7 are in opposite phases. Therefore, by adding these and dividing by 2, that is, by calculating (S′1 + S2) / 2, the modulation element modulated by the light modulator 13 is eliminated. That is, by calculating (S′1 + S2) / 2, the position information X of the moving grating 16 that does not include a modulation element can be calculated by the movement amount detection device 20.

  Therefore, for example, even when the wavelength center of the light from the light source unit 11 drifts, the position information X of the moving grating 16 calculated by the movement amount detection device 20 shifts the wavelength center of the light. An error is not included in the generated position detection result of the moving grid 16, and the accuracy of the position detection result of the moving grid 16 by the encoder device 1 can be improved.

  In addition, since it is not necessary to provide a compensation mechanism or the like for detecting an error included in the position detection result of the moving grating 16, it is possible to simplify the configuration of the encoder device 1 and reduce the cost for providing the compensation mechanism or the like. it can.

Incidentally, as shown in FIG. 3, in this encoder device 1, the light receiving elements 17 and 18 may not normally receive the light from the light source unit 11.
FIG. 3 is a schematic diagram illustrating an example of a case where a relatively large foreign object adheres to the moving grid 16 of the present embodiment. As shown in FIG. 3, for example, when light from the light source unit 11 cannot pass through these gratings because a foreign matter such as relatively large dust DS1 adheres to the index grating 15 or the moving grating 16, the light receiving element 17. , 18 may not receive light from the light source unit 11 in some cases. Even when light from the light source unit 11 cannot normally pass through these gratings due to a part of the moving grating 16 being damaged, the light receiving elements 17 and 18 are In some cases, light from the light source unit 11 cannot be received.

  As described above, when neither of the light receiving elements 17 and 18 can receive the light from the light source unit 11, the movement amount detection device 20 cannot detect the position of the moving grating 16. Here, when the movement amount detection device 20 cannot detect the position of the movement grid 16, for example, the movement amount detection device 20 can prevent the value output as the position signal Sig3 from being changed. . With this configuration, the external device that uses the position signal Sig3 output from the movement amount detection device 20 can detect that an abnormality has occurred in the encoder device 1. That is, the external device can detect that an abnormality has occurred in the encoder device 1 by detecting that the position signal Sig3 has not changed.

As shown in FIG. 4, in this encoder device 1, one of the light receiving elements 17 and 18 cannot receive light from the light source unit 11, and the other can receive light from the light source unit 11. There is a case.
FIG. 4 is a schematic diagram illustrating an example of a case where a relatively small foreign object is attached to the moving grid 16 of the present embodiment. As shown in FIG. 4, for example, when light from the light source unit 11 cannot pass through these gratings due to adhesion of foreign matters such as dust DS2 to the moving grating 16, whichever of the light receiving elements 17, 18 is used. One of the light receiving elements may not receive light from the light source unit 11 in some cases. Specifically, as shown in FIG. 4A, when the dust DS2 is attached near the intersection region M1 on the moving grid 16, the light receiving element 17 cannot receive light from the light source unit 11. However, the light receiving element 18 can receive light from the light source unit 11. As shown in FIG. 4B, when the dust DS2 is attached in the vicinity of the intersecting region M2 on the moving grid 16, the light receiving element 17 can receive the light from the light source unit 11, The element 18 cannot receive light from the light source unit 11.

  As described above, when one of the light receiving elements 17 and 18 cannot receive the light from the light source unit 11 and the other can receive the light from the light source unit 11, the movement amount detection device 20 The difference between the interference light received by the light receiving elements 17 and 18 cannot be calculated correctly, and the position information X of the moving grating 16 may be calculated incorrectly. Therefore, the encoder device 1 according to the present embodiment detects a state where the light receiving elements 17 and 18 cannot receive light from the light source unit 11. Thereby, the encoder apparatus 1 can prevent calculating the position information X of the moving grid 16 by mistake. Hereinafter, a specific configuration of the movement amount detection device 20 included in the encoder device 1 will be described with reference to FIG.

  FIG. 5 is a configuration diagram illustrating an example of a specific configuration of the movement amount detection device 20 included in the encoder device 1 of the present embodiment. As described above, the encoder device 1 includes the encoder 10, the light modulation unit 13, and the movement amount detection device 20.

  The optical modulation unit 13 includes a modulation signal generation unit 13a that generates a modulation signal Sig4, and outputs the generated modulation signal Sig4 to the light source 11a of the light source unit 11 via the DA converter 13b and the light source drive circuit 13c. . In addition, the optical modulation unit 13 outputs the modulation signal Sig4 generated by the modulation signal generation unit 13a to the movement amount detection device 20.

  The movement amount detection device 20 includes a set of amplitude detection circuits (a first amplitude detection circuit 211 and a second amplitude detection circuit 212), a set of decoders (a first decoder 221 and a second decoder 222), and a set of An amplifier circuit (first amplifier circuit 241 and second amplifier circuit 242), a set of AD converters (first AD converter 251 and second AD converter 252), and a count processing unit 230 are provided. Among these, first, the first amplification circuit 241, the first AD converter 251, the first amplitude detection circuit 211, and the first decoder 221 that process the photoelectric conversion signal Sig1 output from the light receiving element 17 will be described.

The first amplifier circuit 241 amplifies the photoelectric conversion signal Sig 1 output from the light receiving element 17 and outputs the amplified photoelectric conversion signal Sig 1 to the first AD converter 251.
The first AD converter 251 performs AD (analog-digital) conversion on the photoelectric conversion signal Sig 1 output from the first amplifier circuit 241, and outputs a digital signal of the photoelectric conversion signal Sig 1 to the first amplitude detection circuit 211.
The first amplitude detection circuit 211 detects the amplitude of the digital signal of the input photoelectric conversion signal Sig1, and outputs an amplitude detection signal Sig5 indicating the detection result to the count processing unit 230. Further, the first amplitude detection circuit 211 outputs the digital signal of the input photoelectric conversion signal Sig1 to the first decoder 221 as the digital signal Sig7.

  The first decoder 221 generates a decoded signal Sig9 by decoding the digital signal Sig7 of the input photoelectric conversion signal Sig1 based on the modulation signal Sig4 generated by the modulation signal generator 13a. The number of pulses of the decoded signal Sig9 indicates the relative amount of movement between the index grating 15 and the moving grating 16. By counting the number of pulses of the decoded signal Sig9, the relative movement amount between the index grating 15 and the moving grating 16 can be calculated. The first decoder 221 outputs the generated decoded signal Sig9 to the count processing unit 230.

  Next, the second amplification circuit 242, the second AD converter 252, the second amplitude detection circuit 212, and the second decoder 222 that process the photoelectric conversion signal Sig2 output from the light receiving element 18 will be described.

The second amplifier circuit 242 amplifies the photoelectric conversion signal Sig2 output from the light receiving element 18 and outputs the amplified photoelectric conversion signal Sig2 to the second AD converter 252.
The second AD converter 252 performs AD (analog-digital) conversion on the photoelectric conversion signal Sig <b> 2 output from the second amplifier circuit 242, and outputs a digital signal of the photoelectric conversion signal Sig <b> 2 to the second amplitude detection circuit 212.
The second amplitude detection circuit 212 detects the amplitude of the digital signal of the input photoelectric conversion signal Sig2, and outputs an amplitude detection signal Sig6 indicating the detection result to the count processing unit 230. Further, the second amplitude detection circuit 212 outputs the digital signal of the input photoelectric conversion signal Sig2 to the second decoder 222 as the digital signal Sig8.

  The second decoder 222 generates the decoded signal Sig10 by decoding the digital signal Sig8 of the input photoelectric conversion signal Sig2 based on the modulation signal Sig4 generated by the modulation signal generator 13a. The number of pulses of the decoded signal Sig10 indicates the relative amount of movement between the index grating 15 and the moving grating 16, similarly to the number of pulses of the decoded signal Si9 described above. Therefore, by counting the number of pulses of the decoded signal Sig10, the relative movement amount between the index grating 15 and the moving grating 16 can be calculated. Further, the second decoder 222 outputs the generated decoded signal Sig10 to the count processing unit 230.

  Next, the count processing unit 230 will be described. The count processing unit 230 calculates the relative movement amount of the moving grid 16 included in the encoder 10. Specifically, the count processing unit 230 receives the decoded signal Sig9 output from the first decoder 221 and the decoded signal Sig10 output from the second decoder 222. As described above with reference to Equation 6 and Equation 7, the modulation element is obtained by adding the interference intensity S′1 and the interference intensity S2 and dividing by 2, that is, calculating (S′1 + S2) / 2. It is possible to calculate the position information X of the moving grid 16 that does not include. Here, the decoded signal Sig9 is a signal indicating the above-described interference intensity S′1. The decoded signal Sig10 is a signal indicating the above-described interference intensity S2. Therefore, the count processing unit 230 can calculate the position information X of the moving grating 16 that does not include a modulation element, based on the decoded signal Sig9 and the decoded signal Sig10.

  Specifically, the count processing unit 230 calculates the count value cnt1 by counting the number of pulses of the decoded signal Sig9. Further, the count processing unit 230 counts the number of pulses of the decoded signal Sig10 and calculates a count value cnt2. The count processing unit 230 adds the calculated count value cnt1 and the count value cnt2 and divides by 2, and adds a value indicating the current position to the divided value to calculate the position information X. That is, the count processing unit 230 calculates the position information X by calculating the current position + (count value cnt1 + count value cnt2) / 2. In this way, the count processing unit 230 calculates the position information X of the moving grating 16 that does not include a modulation element.

  So far, the calculation of the count processing unit 230 when no abnormality is detected in the amplitude of the photoelectric conversion signal (photoelectric conversion signal Sig1 or photoelectric conversion signal Sig2) has been described. Next, the calculation of the count processing unit 230 when an abnormality is detected in the amplitude of the photoelectric conversion signal (photoelectric conversion signal Sig1 or photoelectric conversion signal Sig2) will be described with reference to FIGS.

  FIG. 6 is a table showing an example of the calculation of the count processing unit 230 of the present embodiment. The count processing unit 230 switches the calculation method of the position information X based on whether the amplitude of the photoelectric conversion signal Sig1 is normal and whether the amplitude of the photoelectric conversion signal Sig2 is normal.

  Here, when the amplitude of the photoelectric conversion signal Sig1 is normal, the first amplitude detection circuit 211 sets the value of the amplitude detection signal Sig5 to a value indicating “normal” (for example, a value of 0) and sets the amplitude detection signal. Sig5 is output to the count processing unit 230. In addition, when the amplitude of the photoelectric conversion signal Sig1 is abnormal, the first amplitude detection circuit 211 sets the value of the amplitude detection signal Sig5 to a value indicating “abnormal” (for example, value 1) and sets the amplitude detection signal Sig5. Is output to the count processing unit 230. That is, the first amplitude detection circuit 211 (amplitude detection unit) detects the amplitude of the light reception signal output from the light receiving element 17 (light reception unit).

  In addition, when the amplitude of the photoelectric conversion signal Sig2 is normal, the second amplitude detection circuit 212 sets the value of the amplitude detection signal Sig6 to a value indicating “normal” (for example, value 0), and sets the amplitude detection signal Sig6. Is output to the count processing unit 230. In addition, when the amplitude of the photoelectric conversion signal Sig2 is abnormal, the second amplitude detection circuit 212 sets the value of the amplitude detection signal Sig6 to a value indicating “abnormal” (for example, value 1) and sets the amplitude detection signal Sig6. Is output to the count processing unit 230. That is, the second amplitude detection circuit 212 (amplitude detection unit) detects the amplitude of the light reception signal output from the light receiving element 18 (light reception unit).

  When the amplitude detection signal Sig5 and the amplitude detection signal Sig6 are both values indicating normality, the count processing unit 230 sets the current position + (count value cnt1 + count value cnt2) / 2 as described above. The position information X is calculated by calculation.

  Next, the case where the amplitude detection signal Sig5 or the amplitude detection signal Sig6 is a value indicating abnormality (for example, value 1) will be described. First, the photoelectric conversion signal Sig1 among the photoelectric conversion signals will be described. First, an example of the amplitude of the photoelectric conversion signal Sig1 detected by the first amplitude detection circuit 211 will be described with reference to FIG.

  FIG. 7 is a waveform diagram showing an example of an amplitude waveform of a photoelectric conversion signal whose amplitude is detected by the amplitude detection circuit of the present embodiment. Of the amplitude waveforms of the photoelectric conversion signal shown in FIG. 7, the waveform WA is an example of the amplitude of the photoelectric conversion signal Sig <b> 1 detected by the first amplitude detection circuit 211.

  The waveform WA of the photoelectric conversion signal Sig1 will be described by taking as an example a case where dust DS2 is attached on the moving grid 16, as shown in FIG. 4 described above. When the moving grid 16 moves in the + X direction, the dust DS2 attached to the moving grid 16 moves in the + X direction in accordance with the movement of the moving grid 16. As shown in FIG. 7, when the moving grating 16 moves in the + X direction together with the dust DS2, and the amount of movement becomes the grating moving amount X1, the dust DS2 begins to block the interference light L12 received by the light receiving element 17. When the moving grid 16 further moves in the + X direction together with the dust DS2, the range in which the dust DS2 blocks the interference light L12 gradually increases. Further, when the moving amount of the moving grating 16 becomes the grating moving amount X2, the range in which the dust DS2 blocks the interference light L12 becomes the widest. Further, when the moving grid 16 moves in the + X direction together with the dust DS2, the range in which the dust DS2 blocks the interference light L12 is gradually narrowed. Further, when the moving amount of the moving grating 16 becomes the grating moving amount X3, the dust DS2 does not block the interference light L12.

  That is, when the dust DS2 on the moving grating 16 moves in the + X direction from the grating movement amount X1 to X3, the range of the interference light L12 blocked by the dust DS2 changes according to the movement amount of the moving grating 16. Therefore, the intensity of the interference light L12 received by the light receiving element 17 changes according to the amount of movement of the moving grating 16. As a result, the amplitude of the photoelectric conversion signal Sig1 output from the light receiving element 17 changes like a waveform WA shown in FIG.

  Here, among the signal amplitudes shown in FIG. 7, the reference potential Lv0 is the potential of the photoelectric conversion signal when the interference light L12 is received by the light receiving element 17 without being blocked by the dust DS2. The amplitude standard value Lv1 is a standard value indicating the potential of the photoelectric conversion signal that can be normally decoded by the decoder (the first decoder 221 and the second decoder 222). The decodable limit value Lv2 is a limit value (for example, a lower limit value) of the signal amplitude of the photoelectric conversion signal that can be normally decoded by these decoders. That is, the decoder decodes the potential in the vicinity of the reference potential Lv0 to the digital value 0 (zero), and the potential between the amplitude standard value Lv1 and the decodable limit value Lv2 as the digital value 1 of the photoelectric conversion signal. That is, when a photoelectric conversion signal having a potential lower than the decodable limit value Lv2 is input, the decoder cannot normally decode the photoelectric conversion signal. Therefore, when a photoelectric conversion signal having a potential lower than the decodable limit value Lv2 is input to the decoder, the count processing unit 230 cannot perform the count process normally. As a result, the count processing unit 230 may output incorrect position information X.

  Therefore, when the amplitude detection signal Sig5 is a value indicating abnormality (for example, value 1) and the amplitude detection signal Sig6 is a value indicating normal (for example, value 0), the count processing unit 230 is shown in FIG. As shown, the current position + (count value cnt2) is calculated to calculate the position information X. Here, the case where the amplitude detection signal Sig5 is a value indicating abnormality is a case where the amplitude of the photoelectric conversion signal Sig1 is abnormal. That is, the count processing unit 230 does not use the count value cnt1 based on the photoelectric conversion signal Sig1 for calculating the position information X when the amplitude of the photoelectric conversion signal Sig1 is abnormal.

  That is, the count processing unit 230 (signal selection unit) is based on the light reception signal output from at least one light reception element 17 (light reception unit) among the light reception elements 17 and 18 (light reception unit). At least one of the received light signals output from each of the 18 (light receiving units) is selected as a calculation signal for calculating the relative movement amount of the moving grid 16 (moving member). Further, the count processing unit 230 (movement amount calculation unit) calculates the relative movement amount of the moving grid 16 (moving member) based on the calculation signal selected by the count processing unit 230 (signal selection unit). The count processing unit 230 (signal selection unit) outputs at least two light receiving elements 17 and 18 (light receiving unit) based on the amplitude of the light receiving signal detected by the first amplitude detection circuit 211 (amplitude detection unit). At least one received light signal is selected as a calculation signal. At this time, the count processing unit 230 (signal selection unit) selects a light reception signal whose amplitude detected by the first amplitude detection circuit 211 (amplitude detection unit) is within a predetermined amplitude range as a calculation signal. Thus, the count processing unit 230 can calculate the position information X even if the amplitude of the photoelectric conversion signal Sig1 is abnormal.

  Next, of the photoelectric conversion signals, the photoelectric conversion signal Sig2 will be described again with reference to FIG. The waveform WB in FIG. 7 is an example of the amplitude of the photoelectric conversion signal Sig2 detected by the second amplitude detection circuit 212. The amplitude of the photoelectric conversion signal Sig2 also changes in the same manner as the photoelectric conversion signal Sig1.

  That is, when the moving grid 16 moves in the + X direction, the dust DS2 attached to the moving grid 16 moves in the + X direction according to the movement of the moving grid 16. As shown in FIG. 7, when the moving grating 16 moves in the + X direction together with the dust DS2, and the moving amount thereof becomes the grating moving amount X4, the dust DS2 starts to block the interference light L23 received by the light receiving element 18. Further, when the moving grid 16 moves in the + X direction together with the dust DS2, the range in which the dust DS2 blocks the interference light L23 gradually increases. Further, when the moving amount of the moving grating 16 becomes the grating moving amount X5, the range in which the dust DS2 blocks the interference light L23 becomes the widest. Further, when the moving grid 16 moves in the + X direction together with the dust DS2, the range in which the dust DS2 blocks the interference light L23 is gradually narrowed. Further, when the moving amount of the moving grating 16 becomes the grating moving amount X6, the dust DS2 does not block the interference light L23.

  That is, when the dust DS2 on the moving grid 16 moves in the + X direction from the grid moving amount X4 to X6, the range of the interference light L23 blocked by the dust DS2 changes according to the moving amount of the moving grid 16. Therefore, the intensity of the interference light L23 received by the light receiving element 18 changes according to the amount of movement of the moving grating 16. As a result, the amplitude of the photoelectric conversion signal Sig2 output from the light receiving element 18 changes like a waveform WB shown in FIG.

  The count processing unit 230 calculates the position information X in the same manner as the amplitude detection signal Sig5 even when the amplitude of the amplitude detection signal Sig6 is abnormal. That is, when the amplitude detection signal Sig5 is a value indicating normality (for example, value 0) and the amplitude detection signal Sig6 is a value indicating abnormality (for example, value 1), the count processing unit 230 The position information X is calculated by calculating (count value cnt1). Here, the case where the amplitude detection signal Sig6 is a value indicating abnormality is a case where the amplitude of the photoelectric conversion signal Sig2 is abnormal. That is, the count processing unit 230 does not use the count value cnt2 based on the photoelectric conversion signal Sig2 for the calculation of the position information X when the amplitude of the photoelectric conversion signal Sig2 is abnormal.

  That is, the count processing unit 230 (signal selection unit) is based on the light reception signal output from at least one light reception element 18 (light reception unit) among the light reception elements 17 and 18 (light reception unit). At least one of the received light signals output from each of the 18 (light receiving units) is selected as a calculation signal for calculating the relative movement amount of the moving grid 16 (moving member). Further, the count processing unit 230 (movement amount calculation unit) calculates the relative movement amount of the moving grid 16 (moving member) based on the calculation signal selected by the count processing unit 230 (signal selection unit). The count processing unit 230 (signal selection unit) outputs at least two light receiving elements 17 and 18 (light receiving units) based on the amplitude of the light receiving signal detected by the second amplitude detection circuit 212 (amplitude detection unit). At least one received light signal is selected as a calculation signal. At this time, the count processing unit 230 (signal selection unit) selects a light reception signal whose amplitude detected by the first amplitude detection circuit 211 (amplitude detection unit) is within a predetermined amplitude range as a calculation signal. Thus, the count processing unit 230 can calculate the position information X even if the amplitude of the photoelectric conversion signal Sig2 is abnormal.

  Further, the count processing unit 230 stops the calculation of the position information X when both the amplitude detection signal Sig5 and the amplitude detection signal Sig6 are values indicating abnormality (for example, value 1). Thereby, the count processing unit 230 can prevent erroneous position information X from being output.

  FIG. 8 is a graph illustrating an example of a result of detection of the movement amount by the movement amount detection device 20 of the present embodiment. 8A is a graph showing a case where the movement amount detection device 20 stops detecting the movement amount when an abnormality occurs in the amplitude of the photoelectric conversion signal (photoelectric conversion signal Sig1, photoelectric conversion signal Sig2). It is. Here, a case where an abnormality occurs in the amplitude of the photoelectric conversion signal Sig1 in a section where the moving amount of the moving lattice 16 is the lattice moving amounts X11 to X12 will be described. Since the photoelectric conversion signal Sig2 is the same as the photoelectric conversion signal Sig1, description thereof is omitted.

  First, the case where the movement amount detection device 20 stops outputting the position information X when an abnormality occurs in the amplitude of the photoelectric conversion signal Sig1 will be described. In the section of the lattice movement amount 0 to X11 shown in FIG. 8A, that is, when there is no abnormality in the amplitude of the photoelectric conversion signal Sig1, the movement amount detection device 20 changes the count value cnt1 from the value 0 to the value cnt11. Is calculated normally (see waveform W1-1). Thereby, the movement amount detection device 20 outputs position information X indicating the accurate movement amount of the moving grid 16. Further, in the section of the lattice movement amounts X11 to X12 shown in FIG. 8A, that is, when an abnormality occurs in the amplitude of the photoelectric conversion signal Sig1, the movement amount detection device 20 normally calculates the count value cnt1. If the count value cannot be calculated, for example, the calculation of the movement amount is stopped when the count value reaches the value cnt12 (see waveform W1-2).

  When the movement amount detection device 20 stops outputting the position information X in this way, a device using the position information X (for example, a processing apparatus such as a semiconductor exposure device or an optical lens cutting / polishing device). )), The amount of movement of the moving grid 16 becomes unknown. In this case, the apparatus using the position information X may have to return the moving grid 16 to the origin and process the workpiece again. For this reason, when the movement amount detection apparatus 20 stops outputting the position information X, time and cost for processing the workpiece again may occur.

  Next, a case where the movement amount detection device 20 continues to output the position information X when an abnormality occurs in the amplitude of the photoelectric conversion signal Sig1 will be described. In the section of the lattice movement amounts X11 to X12 shown in FIG. 8B, that is, when an abnormality occurs in the amplitude of the photoelectric conversion signal Sig1, the count processing unit 230 of the movement amount detection device 20 By switching the calculation method as shown in FIG. 6, the output of the position information X is continued (see waveform W2-2). That is, the count processing unit 230 continues to output the position information X while switching the calculation method of the position information X in the section of the lattice movement amount 0 to X13 shown in FIG.

  As described above, according to the movement amount detection device 20 of the present embodiment, even when the amplitude of the photoelectric conversion signal Sig1 is abnormal, it is possible to prevent an error in the position information X from increasing. Therefore, according to the movement amount detection device 20, the output of the position information X can be continued, and even when the amplitude of the photoelectric conversion signal Sig1 is abnormal, it is not necessary to return the moving grid 16 to the origin. Therefore, according to the movement amount detection apparatus 20, the time and cost for processing a workpiece again can be reduced.

  As described above, the encoder device 1 includes the movement amount detection device 20. According to the movement amount detection device 20, as described above, errors included in the position detection result of the moving body can be reduced. Therefore, according to the encoder device 1, the output of the position information X can be continued even when there is an abnormality in the amplitude of the photoelectric conversion signal.

[Second Embodiment]
Next, a second embodiment according to the encoder device of the present invention will be described with reference to FIGS. FIG. 9 is a schematic diagram of an encoder device 1a according to the second embodiment of the present invention. In addition, about the structural member which has the same or equivalent function and structure as 1st Embodiment, detailed description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  The encoder device 1a includes a movement amount detection device 20a. This movement amount detection device 20a differs from the movement amount detection device 20 described above in that it includes a count processing unit 230a, an error output circuit 270, and a storage unit 280.

FIG. 10 is a block diagram illustrating an example of the configuration of the count processing unit 230a of the present embodiment.
The count processing unit 230 a includes a low pass filter (LPF) 261, a movement amount detection unit 262, and a signal selection unit 263.

  The movement amount detection unit 262 calculates the count value cnt1 by counting the number of pulses of the decoded signal Sig9 output from the first decoder 221. Further, the movement amount detection unit 262 calculates the count value cnt2 by counting the number of pulses of the decoded signal Sig10 output from the second decoder 222. Further, the movement amount detection unit 262 outputs a position signal Sig3a indicating movement amount information (position information) of the moving grating 16 corresponding to the counted number of pulses. Specifically, the movement amount detection unit 262 calculates the position information X by calculating the current position + (count value cnt1 + count value cnt2) / 2 based on the decoded signal Sig9 output from the first decoder 221; A position signal Sig3a indicating the calculated position information X is output.

Further, the movement amount detection unit 262 outputs a position signal Sig3b indicating position information corresponding to the counted number of pulses.
FIG. 11 is a table showing an example of the calculation of the signal selection unit 263 of the present embodiment. As shown in FIG. 11, the movement amount detection unit 262 calculates position information X based on the amplitude detection signal Sig5 and the amplitude detection signal Sig6, and outputs a position signal Sig3b indicating the calculated position information X.

The LPF 261 outputs the position signal Sig3b ′ from which the high frequency component of the position signal Sig3b output from the movement amount detection unit 262 has been removed to the signal selection unit 263.
As shown in FIG. 11, the signal selection unit 263 determines whether the position signal output by the movement amount detection unit 262 is normal or abnormal based on the amplitude detection signal Sig5 and the amplitude detection signal Sig6. Further, the signal selection unit 263 calculates position information as shown in FIG. 11 based on the determined result. Further, the signal selection unit 263 outputs a position signal Sig3 indicating the calculated position information.

  As a result, the count processing unit 230a can reduce noise components included in the count value. Therefore, since the encoder device 1a can obtain a stable count value compared to the case where no low pass filter is provided, the error included in the position detection result of the moving body is reduced, and the position detection result of the moving body is reduced. Accuracy can be improved.

  Returning to FIG. 9, the error output circuit 270 outputs an error signal Sig11 based on the amplitude detection signal Sig5 and the amplitude detection signal Sig6. Specifically, the first amplitude detection circuit 211 outputs the amplitude detection signal Sig5 to the count processing unit 230a and the error output circuit 270. As described above, the amplitude detection signal Sig5 is a signal indicating the result of the first amplitude detection circuit 211 detecting the amplitude of the digital signal of the photoelectric conversion signal Sig1. That is, the amplitude detection signal Sig5 is a signal indicating a result of determining whether the amplitude of the digital signal of the photoelectric conversion signal Sig1 is normal or abnormal. The second amplitude detection circuit 212 outputs the amplitude detection signal Sig6 to the count processing unit 230a and the error output circuit 270. As described above, the amplitude detection signal Sig6 is a signal indicating the result of the second amplitude detection circuit 212 detecting the amplitude of the digital signal of the photoelectric conversion signal Sig2. That is, the amplitude detection signal Sig6 is a signal indicating a result of determining whether the amplitude of the digital signal of the photoelectric conversion signal Sig2 is normal or abnormal.

  The error output circuit 270 outputs an error signal Sig11 based on the amplitude detection signal Sig5 output from the first amplitude detection circuit 211 and the amplitude detection signal Sig6 output from the second amplitude detection circuit 212. Specifically, the error output circuit 270 indicates that an abnormality has occurred when at least one of the amplitude detection signal Sig5 and the amplitude detection signal Sig6 is a value indicating abnormality (for example, value 1). The error signal Sig11 shown is output.

  That is, the amplitude detection circuit (first amplitude detection circuit 211, second amplitude detection circuit 212) (determination unit) includes at least one light receiving element 17, 18 (light receiving unit) among the light receiving elements 17, 18 (light receiving unit). Based on the light reception signal to be output, it is determined whether the light reception signal is normal or abnormal. Further, the error output circuit 270 (output unit) outputs a result determined by the amplitude detection circuit (the first amplitude detection circuit 211 and the second amplitude detection circuit 212). Thereby, when the external device receives the error signal Sig11, the external device can detect that the amplitude detection signal is abnormal.

  Further, in the storage unit 280, information indicating the decoded signal Sig9 decoded by the first decoder 221 and information indicating the decoded signal Sig10 decoded by the second decoder 222 are associated with the movement amount of the moving grid 16 in advance. It is remembered. The information indicating the decoded signal Sig9 and the information indicating the decoded signal Sig10 are the first decoder 221 and the second decoder when no abnormality is detected in the amplitude of the photoelectric conversion signal (photoelectric conversion signal Sig1 or photoelectric conversion signal Sig2). This is information indicating the output of 222.

  When an abnormality is detected in the amplitude of either the photoelectric conversion signal Sig1 or the photoelectric conversion signal Sig2, the count processing unit 230a receives information indicating the decoded signal Sig9 or information indicating the decoded signal Sig10 from the storage unit 280. Is read. Here, a specific example in the case where an abnormality is detected in the amplitude of the photoelectric conversion signal Sig1 will be described. When an abnormality is detected in the amplitude of the photoelectric conversion signal Sig1, the count processing unit 230a reads information indicating the decoded signal Sig9 from the storage unit 280. Next, the count processing unit 230a, based on the information indicating the decoded signal Sig9 read from the storage unit 280 and the decoded signal Sig10 output from the second decoder 222, the current position + (count value cnt1 + count value cnt2) / 2 is calculated to calculate the position information X.

  The same applies to the case where an abnormality is detected in the amplitude of the photoelectric conversion signal Sig2. That is, the count processing unit 230a reads information indicating the decoded signal Sig10 from the storage unit 280 when an abnormality is detected in the amplitude of the photoelectric conversion signal Sig2. Next, the count processing unit 230a, based on the information indicating the decoded signal Sig10 read from the storage unit 280 and the decoded signal Sig9 output from the first decoder 221, the current position + (count value cnt1 + count value cnt2) / 2 is calculated to calculate the position information X.

  That is, the memory | storage part 280 memorize | stores the information which shows the light reception signal which the light receiving elements 17 and 18 (light receiving part) output. Further, the count processing unit 230a (movement amount calculation unit) is based on the calculation signal selected by the count processing unit 230a (signal selection unit) and the information indicating the received light signal stored in the storage unit 280. The relative movement amount of 16 (moving member) is calculated. With this configuration, even when an abnormality is detected in the amplitude of the photoelectric conversion signal, the position information X can be calculated based on information indicating the photoelectric conversion signal stored in advance. Thereby, the encoder apparatus 1a can reduce the error contained in the position detection result of a moving body.

  In the above description, the storage unit 280 has been described with an example in which information indicating the decoded signal decoded by the decoder is stored in advance. However, the present invention is not limited to this. For example, when no abnormality is detected in the amplitude of the photoelectric conversion signal, the count processing unit 230a may write the decoded signal output by the decoder (the first decoder 221 and the second decoder 222) in the storage unit 280. Further, the count processing unit 230a may periodically write the decoded signal output from the decoder into the storage unit 280. That is, the count processing unit 230a (update unit) may update the information indicating the received light signal stored in the storage unit 280 based on the calculation signal selected by the count processing unit 230a (signal selection unit). With this configuration, the information indicating the light reception signal stored in the storage unit 280 is updated, so the encoder device 1a can further reduce errors included in the position detection result of the moving body. .

In addition, in each embodiment mentioned above, although the glass block 14 demonstrated using the example arrange | positioned on any one optical path which comprises interference light L12, L23, this invention is not limited to this, For example, A configuration in which the glass block 14 is disposed on the optical paths of both the light beams constituting the interference light may be provided on the condition that a relative optical path length difference is given to the light beams constituting the interference light.
Moreover, in each embodiment mentioned above, although the light branching member 12 demonstrated the example which divides the light from the light source part 11 into the three light rays L1-L3, this invention is not limited to this, It is four or more light rays. You may divide. For example, when two interference lights are generated by causing two light beams to interfere with each other based on the light beams divided into four by the light branching member 12, on the optical path of the two light beams constituting one of the interference lights The structure by which the glass block 14 is arrange | positioned, respectively may be sufficient.

  Furthermore, the encoder device 1 (or the encoder device 1a) according to the present invention has a sufficient optical path difference ΔL compared to the wavelength variable range even when the wavelength variable range of the modulated light emitted from the light source unit 11 is small. If it enlarges, the change according to the periodic change of the modulated light inject | emitted from the light source part 11 can be given to the interference fringe formed on the moving grating | lattice 16. FIG. For example, when a light emitting laser diode is used as the light source 11a, the center wavelength of the modulated light emitted from the light source unit 11 is set to 850 nm, and the drive current supplied to the light emitting laser diode is changed within a range of 2 ± 0.5 mA. Then, the wavelength of the light emitted from the light source unit 11 changes in a range of 850 ± 1 nm (wavelength variable range). At this time, when the glass block 14 having an optical path difference ΔL of 1 mm is used, the optical path difference ΔL is sufficiently larger than the wavelength variable range, so that the interference fringes formed on the moving grating 16 change periodically. The light receiving elements 17 and 18 can obtain a photoelectric conversion signal.

  The modulation method of the modulated light emitted from the light source 11a is based on the current change by the above-described light modulation unit 13, and for example, various variable wavelength lasers used for the purpose of optical communication or the like can be used. it can. Further, the modulation method of the modulated light emitted from the light source 11a is not limited to the method based on the current change. For example, the apparatus periodically changes the wavelength by changing the temperature of the laser element used as the light source 11a. Can be used.

Moreover, the glass block 14 should just be a medium which permeate | transmits light and has the predetermined refractive index N different from the circumference | surroundings, for example, may be transparent media, such as a crystal | crystallization.
Furthermore, in each of the above-described embodiments, the ± first-order diffracted light diffracted by the index grating 15 has been described as an example of the interference light, but it may be zero-order diffracted light or other orders of diffracted light. Good.
Further, in each of the above-described embodiments, the description has been given using the example in which the two intersecting regions M1 and M2 are formed on the moving grid 16. However, the present invention is not limited to this, and at least two or more intersecting regions M1 and M2 are provided. (Interference fringes) may be formed.

  Moreover, in each embodiment mentioned above, although the encoder 10 was demonstrated using the example which is a linear encoder to which the moving grating | lattice 16 moves linearly (for example, X direction), this invention is not limited to this. For example, the encoder 10 may be a rotary encoder in which the moving grid 16 rotates.

  In each of the above-described embodiments, the encoder 10 has been described using an example in which the light receiving elements 17 and 18 receive the light emitted from the light source 11a and transmitted through the index grating 15 and the moving grating 16. However, the present invention is not limited to this. For example, the encoder 10 may be a reflective encoder that receives light emitted from the light source 11a and is received by the light receiving elements 17 and 18.

  DESCRIPTION OF SYMBOLS 1, 1a ... Encoder apparatus, 10 ... Encoder, 11 ... Light source part, 12 ... Light branching member, 13 ... Light modulation part, 16 ... Moving grating (moving member), 17, 18 ... Light receiving element (light receiving part), 20, 20a ... Movement amount detection device (position calculation unit), 211, 212 ... Amplitude detection circuit (amplitude detection unit, determination unit), 230, 230a ... Count processing unit (signal selection unit, movement amount calculation unit, update unit), 261 262, low-pass filter (filter unit), 270, error output circuit (output unit), 280, storage unit

Claims (8)

A light modulator that modulates at least part of the light emitted from the light source unit;
A moving member that has an incident surface on which a plurality of light beams from the light is incident, and that is relatively movable in at least one direction;
Receiving at least two interference fringes generated in at least two regions on the moving member, respectively, and outputting at least two light receiving signals based on the received interference fringes; and
Based on the light reception signal output by at least one light receiving unit among the light receiving units, at least one signal among the light receiving signals output by each of the at least two light receiving units is used as a relative movement amount of the moving member. A signal selection unit that selects as a calculation signal for calculating
A movement amount calculation unit that calculates the relative movement amount of the moving member based on the calculation signal selected by the signal selection unit;
An amplitude detection unit for detecting the amplitude of the received light signal output by the light receiving unit ,
The signal selector is
An encoder device that selects, as the calculation signal, the received light signal whose amplitude detected by the amplitude detection unit is within a predetermined amplitude range. A storage unit for storing information indicating the received light signal output by the light receiving unit;
The movement amount calculation unit
Wherein a calculation signal by the signal selecting section selects, based on the information indicating the receiving signal stored in the storage unit, according to claim 1 for calculating the amount of relative movement of the moving member Encoder device.   A light modulator that modulates at least part of the light emitted from the light source unit;
  A moving member that has an incident surface on which a plurality of light beams from the light is incident, and that is relatively movable in at least one direction;
  Receiving at least two interference fringes generated in at least two regions on the moving member, respectively, and outputting at least two light receiving signals based on the received interference fringes; and
  Based on the light reception signal output by at least one light receiving unit among the light receiving units, at least one signal among the light receiving signals output by each of the at least two light receiving units is used as a relative movement amount of the moving member. A signal selection unit that selects as a calculation signal for calculating
  A movement amount calculation unit that calculates the relative movement amount of the moving member based on the calculation signal selected by the signal selection unit;
  A storage unit for storing information indicating the received light signal output by the light receiving unit;
  With
  The movement amount calculation unit
  The relative movement amount of the moving member is calculated based on the calculation signal selected by the signal selection unit and information indicating the light reception signal stored in the storage unit.
  Encoder device. The signal selecting unit based on the calculated signal has been selected, the encoder apparatus according to 請 Motomeko 2 or claim 3 Ru comprising an update unit for updating the information indicating the receiving signal stored in the storage unit. The encoder apparatus according to any one of claims 4 to 請 Motomeko 1 Ru provided with a filter unit that removes a high-frequency component from the relative movement amount the movement amount calculating section is output. A determination unit that determines whether or not the light reception signal is normal based on the light reception signal output by at least one light reception unit of the light reception units;
The determination unit is an encoder device according to any one of claims 5 請 Motomeko 1 Ru and an output unit for outputting the result of judgment.   The light modulator modulates the wavelength of the light or the phase of the light.
  The encoder apparatus as described in any one of Claims 1-6.   The signal selection unit does not select, as the calculation signal, the light reception signal whose amplitude of the detected light reception signal is out of a predetermined amplitude range among the light reception signals output from the at least two light reception units, respectively.
  The encoder apparatus as described in any one of Claims 1-7.

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