JP2017166851A - Encoder, lens device, imaging system, and machine tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an encoder that reduces the effect of an error and exhibits high accuracy.SOLUTION: An encoder (100) comprises a scale (20) having a first grating (21) consisting of a pattern string that modulates energy distribution by space, and a detector (10) having a second grating (12) cyclically provided in a first direction and detecting energy distribution from the pattern string, the scale and the detector being relatively movable in the first direction. The second grating includes a first grating area and a second grating area along a second direction perpendicular to the first direction, the first grating area having a first period smaller than the period of energy distribution on the second grating, the second grating area having a second period larger than the period of energy distribution on the second grating, each of the first period and the second period being constant in the first direction.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an encoder.

  Patent Document 1 discloses an encoder that detects a linear scale with an optical grating on the light receiver side formed at an equiangular pitch on an arc. Thereby, the fluctuation | variation of the sine wave signal by an alignment fluctuation | variation can be reduced. Further, position detection can be performed by converting a plurality of sine wave signals having different phases into position information using a signal processing circuit.

JP 2001-116592 A

  However, in the encoder disclosed in Patent Document 1, the spatial frequency response is asymmetric between a region having a large curvature radius and a region having a small curvature radius of the optical grating formed on the light receiver side. For this reason, when an error occurs in the projection magnification, the relative phase relationship of the plurality of sine wave signals varies. As a result, the interpolation error of the sine wave signal increases, and the position detection accuracy may decrease.

  Accordingly, an object of the present invention is to provide a highly accurate encoder, lens device, imaging system, and machine tool by reducing the influence of errors.

  An encoder according to one aspect of the present invention includes a scale having a first grating composed of a pattern sequence for spatially modulating an energy distribution, and a second grating periodically provided in a first direction, and the pattern A detector for detecting the energy distribution from a column, wherein the scale and the detector are relatively movable in the first direction, and the second grating is the first grid A first lattice region and a second lattice region are provided along a second direction perpendicular to the direction, and the first lattice region is smaller than a period of the energy distribution on the second lattice. The second grating region has a second period that is greater than the period on the second grating of the energy distribution, the first period and the second period; Each period is constant in the first direction

  A lens device according to another aspect of the present invention includes a lens that is displaceable in an optical axis direction, and the encoder that is configured to detect the position of the lens.

  An imaging system as another aspect of the present invention includes the lens apparatus and an imaging apparatus including an imaging element that performs photoelectric conversion of an optical image via the lens.

  A machine tool according to another aspect of the present invention includes a machine tool including a robot arm or a transport body that transports an assembly target, and the encoder configured to detect a position or a posture of the machine tool. .

  Other objects and features of the present invention are illustrated in the following examples.

  According to the present invention, it is possible to provide a highly accurate encoder, lens device, imaging system, and machine tool by reducing the influence of errors.

It is a block diagram of the encoder in Examples 1-3. It is a block diagram of the encoder as a modification in Examples 1-3. It is a block diagram of the encoder as a modification in Examples 1-3. 2 is a plan view of a light receiving element array in Embodiment 1. FIG. It is an optical path expansion view of the encoder in Examples 1-4. In Example 1, it is a figure which shows the relationship between the image magnification M, the projection image period P, and the grating | lattice periods Pa and Pb. In Example 1, it is a graph which shows the change of the amplitude of an A (+) phase signal with respect to the spatial frequency f, and a phase. In a comparative example, it is a graph which shows the change of the amplitude of an A (+) phase signal with respect to spatial frequency f, and a phase. 6 is a plan view of a light receiving element array in Example 2. FIG. In Example 2, it is a figure which shows the relationship between the image magnification M, the projection image period P, and the grating | lattice periods Pa, Pb, and Pc. In Example 2, it is a graph which shows the change of the amplitude of an A (+) phase signal with respect to the spatial frequency f, and a phase. 6 is a plan view of a light receiving element array in Embodiment 3. FIG. In Example 3, it is a graph which shows the change of the amplitude of an A (+) phase signal with respect to the spatial frequency f, and a phase. FIG. 10 is a configuration diagram of an encoder in Embodiment 4. 6 is a plan view of a light receiving element array in Example 4. FIG. 10 is a schematic cross-sectional view of an imaging system in Embodiment 5. FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  First, an encoder (position detection device) in Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a configuration diagram of an encoder 100 in the present embodiment. The encoder 100 includes a sensor unit 10 (detector) attached to a fixed part, and a scale 20 attached to a movable part (not shown). In this embodiment, the relationship between the fixed portion and the movable portion may be reversed, and the sensor unit 10 can be attached to the movable portion and the scale 20 can be attached to the fixed portion. That is, it is only necessary that the sensor unit 10 and the scale 20 are relatively movable.

  The sensor unit 10 is a light receiving / emitting integrated sensor unit in which a light source 11 composed of a current confining type LED and a light receiving IC 13 having a light receiving element array 12 are mounted in the same package. The light receiving element array 12 is configured by arranging a plurality of detection elements that detect the intensity distribution of reflected light from the pattern of the scale 20 in the X direction that is the moving direction (length measuring direction) of the scale 20 (or the movable portion). Has been. On the reflective surface on the scale 20, a scale grating 21 in which reflective portions and non-reflective portions are alternately formed in the length measuring direction (X direction) is formed. The scale grating 21 may be a phase grating in which steps are formed so that the optical path lengths are periodically different. For example, the diffraction efficiency of ± 1st order diffracted light that contributes to the signal can be increased by forming a step of a quarter of the wavelength and uniformly forming the reflective film. The cover glass 16 is bonded onto a transparent resin 17 that seals the light source 11 and the light receiving IC 13, and is optically integrated with the transparent resin 17.

  FIGS. 2 and 3 are configuration diagrams of encoders 100a and 100b as modifications of the present embodiment, respectively. As shown in FIG. 2, in this embodiment, an encoder 100 a in which a light shielding member 18 is provided between the light source 11 and the light receiving IC 13 may be used. The light shielding member 18 can suppress the internal reflection component that does not pass through the scale grating 21 from entering the light receiving element array 12, and can improve the signal contrast. Further, as shown in FIG. 3, in this embodiment, an encoder 100b in which an antireflection film 19 is provided at the interface between the cover glass 16 and air may be used.

  Next, the arrangement of the light receiving element array 12 in the light receiving IC 13 will be described with reference to FIG. FIG. 4 is a plan view of the light receiving element array 12 and shows the arrangement of the light receiving surfaces of the light receiving element array 12. The light-receiving element array 12 includes 32 light-receiving elements in two rows of a region A (first lattice region) and a region B (second lattice region). Arranged in the X direction). The light receiving element array 12 includes four light receiving elements arranged in order, an A (+) phase, a B (+) phase, an A (−) phase, and a B (−) phase. It is comprised by. Every fourth light receiving element in the position detection direction (X direction) is electrically connected, and is converted into a voltage as an addition output by the four IV conversion amplifiers in the subsequent stage. The outputs of the four IV amplifiers correspond to signal phases of 0 degree, 90 degrees, 180 degrees, and 270 degrees, and are converted into position information by arithmetic processing. In this embodiment, four-phase light receiving elements are arranged in series to directly detect a four-phase signal, but the present invention is not limited to this. It is also possible to place a transmissive diffraction grating arranged with a phase shift every 90 degrees or 270 degrees in front of the light receiving element surface and detect the amount of transmitted light with the light receiving element. In this case, the relative phase relationship of signals can be stabilized by arranging the diffraction gratings corresponding to the respective detection phases in a direction perpendicular to the fringe period direction of the scale image projected on the diffraction grating.

  In the region A, the distance between the centers of the light receiving elements adjacent to each other is 60 μm. Therefore, the interval between the light receiving elements to be added (the interval between every four light receiving elements), that is, the lattice period Pa of the region A (first lattice region) is 240 μm. In the region A, the length Ya in the direction (Y direction) perpendicular to the position detection direction of each light receiving element is 225 μm. In the region B, the distance between the centers of the light receiving elements adjacent to each other is 68 μm. Therefore, the interval between the light receiving elements to be added (the interval between every four light receiving elements), that is, the lattice period Pb of the region B (second lattice region) is 272 μm. In the region B, the length Yb in the direction (Y direction) perpendicular to the position detection direction of each light receiving element is 225 μm. In each row, the grating periods Pa and Pb in the periodic direction (X direction) of the stripes of the scale image reflected and projected on the light receiving elements are constant (in this embodiment, Pa = 240 μm and Pb = 272 μm, respectively). Constant).

  Next, the optical path in the encoder 100 will be described with reference to FIG. FIG. 5 is an optical path development view of the encoder 100. The divergent light beam emitted from the light source 11 composed of the current confining type LED is incident on the scale grating 21 formed on the scale 20. In the present embodiment, a current confined LED is used as the light source 11, but the present invention is not limited to this. For example, a semiconductor laser can be used, and a combination of an LED, an optical grating, and a pinhole may be used as a secondary point light source array. The distance from the light source 11 to the scale grating 21 is L0. The distance L1 from the scale grating 21 to the light receiving element array 12 is substantially equal to the distance L0 by mounting the light source 11 and the light receiving element array 12 in the same plane. The light beam reflected by the scale grating 21 forms a light intensity distribution as interference fringes on the light receiving element array 12 by diffraction and interference.

  The lattice image of the scale lattice 21 is projected onto the light receiving element array surface at an image magnification M. The image magnification M at this time is expressed as M = (L0 + L1) / L0. Since L0 = L1 at the design center, M = 2. However, an optical path difference is generated between the distance L1 and the distance L0 due to a mounting height difference between the light source 11 and the light receiving element array 12, a relative angular deviation between the scale grating 21 and the sensor unit 10, and the like. Strictly, the projection magnification M onto the light receiving surface includes an error. The projected image period P of the scale grating 21 formed on the light receiving element surface can be expressed as P = M × Ps, where Ps is the grating period of the scale grating 21. In this embodiment, Ps = 128 μm. Note that when using interference of ± primary light, a grating period image that is half of the grating period Ps of the scale grating 21 is formed. In this case, it is effectively replaced with P = M × Ps / 2. The spatial frequency f of the lattice image is expressed as f = 1 / P.

  Next, referring to FIG. 6, the relationship between the image magnification M, the projected image period P of the scale grating 21, the grating period Pa in the area A of the light receiving element array 12, and the grating period Pb in the area B of the light receiving element array 12. Will be described. FIG. 6 is a relationship diagram of the image magnification M, the projection image period P, and the grating periods Pa and Pb. In FIG. 6, the horizontal axis represents the image magnification M, and the vertical axis represents the period (μm). In this embodiment, there is a relationship of the grating period Ps = 128 μm of the scale grating 21, the grating period Pa = 240 μm in the region A of the light receiving element array 12, and the grating period Pa = 272 μm in the region B. Therefore, the light receiving element array 12 of the present embodiment has a grating region (region B) having a grating period Pb larger than the projected image period P (= M × Ps) in the range where the variation of the image magnification M is ± 6.25%. And a grating region (region A) having a grating period Pa smaller than the projected image period P.

  Next, changes in the amplitude and phase of the A (+) phase signal with respect to the spatial frequency f will be described with reference to FIG. FIGS. 7A and 7B show graphs relating to changes in the amplitude and phase of the A (+) phase signal with respect to the spatial frequency f (lattice image spatial frequency) of the scale lattice image on the light receiving element surface. 7A and 7B, the horizontal axis represents the spatial frequency f × 2Ps, and the vertical axis represents the amplitude or phase. The response characteristic of the sine wave signal output with respect to the spatial frequency f formed on the light receiving element array 12 has a characteristic in which f = 1 / Ppd is a peak with respect to the interval Ppd of the added light receiving elements.

  The amplitudes of the detection signals in the region A (first lattice region) and the region B (second lattice region) of the light receiving element array 12 differ depending on the variation of the spatial frequency f by satisfying the above relationship. It has a peak at f. As a result, the amplitude fluctuation after the addition is suppressed. In addition, the phase of each detection signal in region A (first lattice region) and region B (second lattice region) changes as the spatial frequency f varies, but the phase variation occurs by satisfying the above relationship. The weighting changes between the two areas to cancel. Thereby, the phase fluctuation after being added is suppressed. The same applies to the other B (+) phase, A (−) phase, and B (−) phase. In each of the areas A and B, the arrangement period (grating period Pa, Pb) of the light receiving elements to be added is constant with respect to the period direction (X direction) of the stripes of the scale image reflected and projected onto the light receiving elements. Therefore, the response characteristics with respect to fluctuations in the spatial frequency f are substantially symmetric. Thereby, a highly accurate phase fluctuation canceling effect can be obtained in a wider spatial frequency range.

  The light receiving element array 12 includes Q (32 in this embodiment) light receiving elements along the X direction (first direction). The light receiving element array 12 adds up and outputs signals for each of R (four in this embodiment) light receiving elements among the Q light receiving elements. Assume that the number G of sets of light receiving element arrays 12 (the number of sets of light receiving elements to be added) is G = Q / R (G = 32/4 = 8 in this embodiment). At this time, the lattice period Pa (first period) of the region A (first lattice region) and the lattice period Pb (second period) of the region B (second lattice region) are expressed by the following equation (1a): , (1b) is preferably satisfied.

P> Pa ≧ P · (G−1.5) / G (1a)
P <Pb ≦ P · (G + 1.5) / G (1b)
As shown in FIG. 6, the grating periods Pa and Pb satisfy the following formulas (2a) and (2b) with P · (G−1) / G and P · (G + 1) / G as references. More preferred.

P> Pa ≧ P · (G-1) / G (2a)
P <Pb ≦ P · (G + 1) / G (2b)
More preferably, the lattice periods Pa and Pb satisfy the following expressions (3a) and (3b).

P · (G−0.1) / G ≧ Pa ≧ P · (G−0.9) / G (3a)
P · (G + 0.1) / G ≦ Pb ≦ P · (G + 0.9) / G (3b)
In the present embodiment, for example, by satisfying the above-described equations, the encoder 100 (light receiving element array 12) causes the amplitude variation of each of the regions A and B with respect to the variation of the image magnification M to increase monotonously on one side and It is configured to be monotonously decreasing. With such a configuration, fluctuations in amplitude after being added can be more effectively suppressed.

  In this embodiment, a linear encoder using a linear scale as the scale 20 has been described as an example, but the present invention is not limited to this. The present embodiment can also be applied to a rotary encoder using a rotary scale as the scale 20, for example. In this embodiment, the reflective scale has been described as an example. However, the present invention is not limited to this, and the present embodiment can be applied to, for example, a transmissive scale, and can suppress the influence of a projection magnification error. Is more effective.

  In this embodiment, an optical encoder is used as the sensor unit 10, but the present invention is not limited to this. For example, the same effect can be obtained by using a magnetic encoder, a capacitance encoder, or the like. In the case of a magnetic encoder that uses a magnetic distribution as an energy distribution, a magnetic material is used for the scale 20 and the magnetic polarity distribution is formed in the same shape as the reflective film of the scale 20 of this embodiment. Then, magnetic field detection elements arranged in an array are arranged in proximity to the scale for detection. In the case of a capacitive encoder that uses electrical distribution as energy distribution, a conductive electrode pattern is formed in the same shape as the scale reflective film of this embodiment, and another array of electrode patterns is placed close to each other. May be detected.

(Comparative Example 1)
Next, a case where the configuration of the first embodiment is not applied will be described as a comparative example of the first embodiment. In the comparative example, the light receiving element array is described as being arranged at an angular pitch P = 2.16 deg along the arrangement axis on the arc having the curvature radius R = 1.698 mm, and the light receiving element array has a radial width of 450 μm.

  With reference to FIG. 8, changes in amplitude and phase of the A (+) phase signal with respect to the spatial frequency f will be described in the comparative example. FIG. 8 shows the response characteristics of the signal obtained by adding up each region and two regions to the spatial frequency f on the light receiving surface, where region A is smaller than the arc arrangement axis and region B is larger. . FIGS. 8A and 8B show graphs relating to changes in the amplitude and phase of the A (+) phase signal with respect to the spatial frequency f (lattice image spatial frequency) of the scale lattice image on the light receiving element surface. 8A and 8B, the horizontal axis represents the spatial frequency f × 2Ps, and the vertical axis represents the amplitude or phase.

  The response characteristics are asymmetric between the region A and the region B when the spatial frequency is shifted to the larger side and when the spatial frequency is shifted to the smaller side. As a result, the effect of canceling the phase fluctuation in the region A and the region B is reduced, and the phase cannot be stabilized in a wide range.

  Next, an encoder according to the second embodiment of the present invention will be described. The encoder of the present embodiment is different from the encoder 100 of the first embodiment in that a light receiving IC 13a having a light receiving element array 12a is provided instead of the light receiving IC 13 having the light receiving element array 12. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  The arrangement of the light receiving element array 12a in the light receiving IC 13a will be described with reference to FIG. FIG. 9 is a plan view of the light receiving element array 12a, and shows the arrangement of the light receiving surfaces of the light receiving element array 12a. The light receiving element array 12a includes 32 light receiving elements in three columns of a region A (first lattice region), a region B (second lattice region), and a region C (third lattice region). They are arranged in the periodic direction (X direction) of the stripes of the scale image to be reflected and projected.

  In the region A, the distance between the centers of the light receiving elements adjacent to each other is 56 μm. For this reason, the interval between the light receiving elements to be added (the interval between every four light receiving elements), that is, the lattice period Pa of the region A (first lattice region) is 224 μm. In the region A, the length Ya in the direction (Y direction) perpendicular to the position detection direction of each light receiving element is 112.5 μm.

  In the region B, the distance between the centers of the light receiving elements adjacent to each other is 72 μm. For this reason, the interval between the light receiving elements to be added (the interval between every four light receiving elements), that is, the lattice period Pb of the region B (second lattice region) is 288 μm. In the region B, the length Yb in the direction (Y direction) perpendicular to the position detection direction of each light receiving element is 112.5 μm.

  In the region C, the distance between the centers of the light receiving elements adjacent to each other is 64 μm. For this reason, the interval between the light receiving elements to be added (the interval between every four light receiving elements), that is, the lattice period Pc of the region C (third lattice region) is 256 μm. In the region C, the length Yc in the direction (Y direction) perpendicular to the position detection direction of each light receiving element is 225 μm.

  Next, the relationship between the image magnification M, the projected image period P of the scale grating 21, and the grating periods Pa, Pb, and Pc in the regions A, B, and C of the light receiving element array 12a will be described with reference to FIG. FIG. 10 is a relationship diagram of the image magnification M, the projection image period P, and the grating periods Pa, Pb, and Pc. In FIG. 10, the horizontal axis represents the image magnification M, and the vertical axis represents the period (μm).

  As shown in FIG. 10, when L0> L1, that is, M <2, the region A having the lattice period Pa acts as the first lattice region, and the region C having the lattice period Pc acts as the second lattice region. On the other hand, when L0 <L1, that is, M> 2, the region C having the lattice period Pc functions as the first lattice region as described in the first embodiment, and the region B having the lattice period Pb functions as the second lattice region.

  Next, changes in the amplitude and phase of the A (+) phase signal with respect to the spatial frequency f will be described with reference to FIG. FIGS. 11A and 11B show graphs relating to changes in the amplitude and phase of the A (+) phase signal with respect to the spatial frequency f (lattice image spatial frequency) of the scale lattice image on the light receiving element surface. 11A and 11B, the horizontal axis indicates the spatial frequency f × 2Ps, and the vertical axis indicates the amplitude or phase.

  As described above, in the present embodiment, the light receiving element array 12a (second grating) includes the region B (first grating region) provided between the region A (first grating region) and the region C (second grating region). 3 lattice regions). The region B has a grating period Pb (third period) between the grating period Pa (first period) and the grating period Pc (second period). Preferably, the lattice periods Pa, Pb, and Pc satisfy the following expressions (4a) to (4c).

P · (G−0.6) / G ≧ Pa ≧ P · (G−1.4) / G (4a)
P · (G + 0.6) / G ≦ Pb ≦ P · (G + 1.4) / G (4b)
P · (G−0.6) / G <Pc <P · (G + 0.6) / G (4c)
As shown in FIG. 10, the grating periods Pa, Pb, and Pc satisfy the following formulas (5a) and (5b) with P · (G−1) / G and P · (G + 1) / G as references. It is more preferable.

Pc> Pa ≧ P · (G-1) / G
(When M <2) (5a)
Pc <Pb ≦ P · (G + 1) / G
(When M> 2) (5b)
The light receiving element array of the present embodiment is stable against fluctuations in a wide spatial frequency f by combining the three regions A, B, and C as compared with the first embodiment in which the two regions A and B are combined. It is possible to obtain characteristics. In the present embodiment, the light receiving element array having three regions has been described. However, the present invention is not limited to this, and the present embodiment is applicable to a light receiving element array having four or more regions.

  Next, an encoder according to Embodiment 3 of the present invention will be described. The encoder of the present embodiment is different from the encoder 100 of the first embodiment in that it includes a light receiving IC 13b having a light receiving element array 12b instead of the light receiving IC 13 having the light receiving element array 12. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  The arrangement of the light receiving element array 12b in the light receiving IC 13b will be described with reference to FIG. FIG. 12 is a plan view of the light receiving element array 12b, and shows the arrangement of the light receiving surfaces of the light receiving element array 12b. In the present embodiment, the grating period Pa of the light receiving element array 12b continuously changes according to the position in the direction (Y direction) perpendicular to the length measurement direction (position detection direction: X direction). The length Ya of each light receiving element in the direction perpendicular to the position detection direction is 450 μm. The center of the light receiving element array 12b (center in the Y direction) is Y = 0, the position in the direction approaching the light source 11 (position on the light source 11 side) is Y> 0, and the position in the direction away from the light source 11 is Y <0. . At this time, the grating period Pa (Y) of the light receiving element array 12b follows a function represented by the following expression (6).

Pa (Y) = − Y · 32/225 + 256 (μm) (6)
At the end position where Y> 0 (Y = + 225 μm), the grating period Pa of the light receiving element array 12b is minimum, and the grating period Pamin (minimum value) is 224 μm. On the other hand, at the position of the end portion where Y <0 (Y = −225 μm), the grating period Pa (Pb) of the light receiving element array 12b is maximized, and the grating period Pbmax (maximum value) is 288 μm.

  Next, the operation of the light receiving element array 12b will be described. A straight line that passes through the position Y0 where Pa (Y0) = P and is parallel to the length measuring direction (X direction) is defined as a boundary line D. For example, when L0 = L1, since Pa (0) = P, the position of the boundary line D is Y = 0. When the image magnification M = (L0 + L1) / L0 changes, the position of the boundary line B shifts. At this time, a region satisfying Y> D acts as a first lattice region (region A having a lattice period Pa), and a region satisfying Y <D is defined as a second lattice region (region B having a lattice period Pb). Works.

  Referring to FIG. 13, the response characteristics of the signal obtained by adding up each region and the two regions with respect to the spatial frequency on the light receiving surface will be described with region A as Y> 0 and region B as Y <0. To do. FIGS. 13A and 13B show graphs relating to changes in the amplitude and phase of the A (+) phase signal with respect to the spatial frequency f (lattice image spatial frequency) of the scale lattice image on the light receiving element surface. 13A and 13B, the horizontal axis represents the spatial frequency f × 2Ps, and the vertical axis represents the amplitude or phase.

  Thus, in the present embodiment, the light receiving element array 12b (second grating) has a period that linearly changes along the second direction (Y direction). In addition, an area in the direction approaching the light source 11 with the predetermined position (boundary line D) in the second direction as a reference is a first lattice area (area A), and an area in a direction away from the light source 11 with the predetermined position as a reference. The second lattice region (region B) is assumed. When the minimum value of the first period (lattice period Pa) of the first grating region is Pamin and the maximum value of the second period (lattice period Pb) of the second grating region is Pbmax, the following equation (7a ) And (7b) are preferably satisfied.

P> Pamin ≧ P · (G−1.5) / G (7a)
P <Pbmax ≦ P · (G + 1.5) / G (7b)
At each position (each position in the Y direction), the grating period Pa (Y) (array period) of the light receiving elements added to the periodic direction (X direction) of the stripes of the scale image reflected and projected onto the light receiving elements is It is constant. For this reason, the response characteristic with respect to the fluctuation of the spatial frequency f becomes substantially symmetrical. As a result, a highly accurate phase fluctuation canceling effect can be obtained in a wider spatial frequency range.

  Next, with reference to FIG. 14, an encoder (position detection device) in Embodiment 4 of the present invention will be described. FIG. 14 is a configuration diagram of the encoder 100c in the present embodiment. The encoder 100 c is a rotary encoder, and includes a sensor unit 10 (detector) attached to a fixed portion, and a scale 20 attached to the rotating shaft 22 (movable portion) and rotatable around the rotating shaft 22. In this embodiment, the relationship between the fixed portion and the movable portion may be reversed, and the sensor unit 10 can be attached to the rotating shaft 22 and the scale 20 can be attached to the fixed portion. That is, it is only necessary that the sensor unit 10 and the scale 20 are relatively movable (rotatable).

  On the reflective surface on the scale 20, a scale grating 21 is formed in which reflective portions and non-reflective portions are alternately provided at a constant angular period in the length measurement direction (position detection direction: θ direction). The reflective part and the non-reflective part are formed radially so as to extend in a direction perpendicular to the length measuring direction (r direction). The scale grating 21 is formed with a grating of 256 periods per round, and the grating angle period is 1.40625 deg. The reading radius is set to 5.215 mm, and the center point on the radius between the centers of the light source 11 and the light receiving element array 12 of the sensor unit 10 is arranged to coincide with the reading center.

  Next, the arrangement of the light receiving element array 12c of the light receiving IC 13c in the present embodiment will be described with reference to FIG. FIG. 15 is a plan view of the light receiving element array 12c, and shows the arrangement of the light receiving surfaces of the light receiving element array 12c. The scale image reflected and projected on the light receiving element is formed as a radial stripe having a radius of curvature twice. Three regions (region A, region B, region C) having different arrangement periods of the light receiving elements with respect to the periodic direction (first direction, θ direction) of the stripes of the scale image reflected and projected on the light receiving elements are They are arranged in a direction (second direction, r direction) perpendicular to the periodic direction.

  In the region A, the curvature at the center position in the r direction is 10.59913 mm, and the angular interval between the centers of the light receiving elements adjacent to each other is 0.307617 deg. The interval between the light receiving elements to be added (the interval between every four light receiving elements), that is, the lattice period Pθa of the region A (first lattice region) is 1.230469 deg. The length Ra of each light receiving element in the direction (r direction) perpendicular to the position detection direction (θ direction) is 112.5 μm.

  In the region B, the curvature at the center position in the r direction is 10.26163 mm, and the angular interval between the centers of the light receiving elements adjacent to each other is 0.395508 deg. The interval between the light receiving elements to be added (the interval between every four light receiving elements), that is, the lattice period Pθc of the region B (second lattice region) is 1.582031 deg. The length Rb of each light receiving element in the direction (r direction) perpendicular to the position detection direction (θ direction) is 112.5 μm.

  In the region C, the curvature at the center position in the r direction is 10.43038 mm, and the angular interval between the centers of the light receiving elements adjacent to each other is 0.351563 deg. The interval between the light receiving elements to be added (the interval between every four light receiving elements), that is, the lattice period Pθc of the region C (third lattice region) is 1.40625 deg. The length Rc of each light receiving element in the direction (r direction) perpendicular to the position detection direction (θ direction) is 225 μm.

  In each of the areas A, B, and C, the grating periods Pθa and Pθb of the light receiving elements added together in the period direction (first direction: θ direction) of the stripes of the scale image reflected and projected onto the light receiving elements , Pθc (arrangement period) is constant. Therefore, the response characteristics with respect to the variation of the spatial frequency f are substantially symmetric. As a result, a highly accurate phase fluctuation canceling effect can be obtained in a wider spatial frequency range. In the present embodiment, the light receiving element array 12c has three regions, but is not limited to this. The present embodiment can also be applied to a light receiving element array having four or more regions and a light receiving element array configured such that the angular period continuously changes.

  Next, Embodiment 5 of the present invention will be described with reference to FIG. FIG. 16 is a schematic cross-sectional view of the imaging system 200 in the present embodiment. The imaging system 200 is an imaging system in which the encoder (position detection device) in each of the above embodiments is mounted on a lens device. The imaging system 200 includes an imaging device 200a and a lens device 200b (a lens barrel provided with an encoder) that can be attached to and detached from the imaging device 200a. However, this embodiment can also be applied to an imaging system in which an imaging device and a lens device are integrated.

  In FIG. 16, 53 is a sensor unit and 54 is a CPU. The sensor unit 53 and the scale 20 constitute the encoder (position detection device) of each of the above-described embodiments. In the present embodiment, the sensor unit 53 corresponds to the sensor unit 10 in the first to fourth embodiments. Reference numeral 51 denotes a lens unit, 52 denotes a driving lens, 55 denotes an imaging element, and 50 denotes a cylindrical body. The imaging system is mainly configured by these. The drive lens 52 (lens) constituting the lens unit 51 is, for example, an autofocus lens, and can be displaced in the Y direction that is the optical axis direction. The driving lens 52 may be another lens as long as it is driven, such as a zoom adjustment lens. The cylindrical body 50 in this embodiment is connected to an actuator (not shown) that drives the drive lens 52. The imaging element 55 is provided in the imaging apparatus 200a and performs photoelectric conversion of an optical image (subject image) via the lens unit 51 (lens).

  The lens device 200b of the present embodiment includes a drive lens 52 that can be displaced in the optical axis direction (Y direction), and an encoder that is configured to detect displacement of the drive lens 52. The scale 20 is attached to the cylindrical body 50. In such a configuration, the encoder detects the displacement of the drive lens 52 in the optical axis direction by acquiring the rotation amount (displacement) of the cylindrical body 50 around the optical axis direction.

  The scale 20 is a rotary scale configured by forming a reflection pattern on a donut-shaped disk surface, and is attached to the cylindrical body 50. The scale 20 may be a linear scale configured by forming a lattice pattern on a film-like substrate. In this case, the scale 20 is attached to the cylindrical surface along the rotation direction of the cylindrical body 50.

  When the cylindrical body 50 is rotated around the optical axis by an actuator or manually, the scale 20 is displaced relative to the sensor unit 53. As the scale 20 is displaced, the drive lens 52 is driven in the Y direction (arrow direction) that is the optical axis direction. Then, a signal corresponding to the displacement of the drive lens 52 obtained from the sensor unit 53 of the encoder is output to the CPU 54. The CPU 54 generates a drive signal for moving the drive lens 52 to a desired position. The drive lens 52 is driven based on the drive signal.

  The encoder in each embodiment can be applied to various devices other than the lens device and the imaging device. For example, by constructing a machine tool having a robot arm or a machine tool having a carrier for conveying an assembly object and an encoder of each embodiment for detecting the position or posture of the machine tool, the position of the carrier Can be detected with high accuracy.

  Thus, the encoder of each embodiment has the scale 20 and the detector (sensor unit 10). The scale 20 has a first lattice (scale lattice 21) formed of a pattern sequence for spatially modulating the energy distribution. The detector has a second grating (light receiving element arrays 12, 12 a, 12 b, 12 c) periodically provided in the first direction (length measurement direction or position detection direction), and energy distribution from the pattern row Is detected. The scale and the detector are relatively movable in the first direction. The second lattice has a first lattice region (region A) and a second lattice region (region B) along a second direction perpendicular to the first direction. The first lattice region has a first period (lattice period Pa) that is smaller than the period on the second lattice of the energy distribution. The second lattice region has a second period (lattice period Pb) that is larger than the period on the second lattice of the energy distribution. Each of the first period and the second period is constant in the first direction.

  Preferably, the period on the second grating of the energy distribution is a period of the projected image (projected image period P) on the second grating of the first grating. More preferably, the period of the projected image is determined by the product (P = M × Ps) of the image magnification M and the period of the first grating (grating period Ps). Preferably, the first direction is a periodic direction of the projected image, and the second direction is a direction perpendicular to the periodic direction.

  According to each of the above embodiments, it is possible to provide a highly accurate encoder, lens device, imaging system, and machine tool by reducing the influence of errors. Further, according to the encoders of the above embodiments, it is possible to detect the position with high accuracy without largely depending on the mounting accuracy of the sensor. Therefore, it is possible to provide an encoder that is easy to install at low cost.

  As mentioned above, although the preferable Example of this invention was described, this invention is not limited to these Examples, A various deformation | transformation and change are possible within the range of the summary.

10 Sensor unit (detector)
12 Light receiving element array (second grating)
20 scale 21 scale grid (first grid)
100 encoder

Claims (16)

A scale having a first grid of pattern rows that spatially modulate the energy distribution;
A second grating periodically provided in a first direction, and a detector for detecting the energy distribution from the pattern row,
The scale and the detector are relatively movable in the first direction;
The second lattice has a first lattice region and a second lattice region along a second direction perpendicular to the first direction,
The first lattice region has a first period smaller than a period on a second lattice of the energy distribution;
The second lattice region has a second period greater than the period on the second lattice of the energy distribution;
The encoder characterized in that each of the first period and the second period is constant in the first direction.   The encoder according to claim 1, wherein the period of the energy distribution on the second grating is a period of a projected image of the first grating on the second grating.   The encoder according to claim 2, wherein the period of the projected image is determined by a product of an image magnification and a period of the first grating. When the image magnification is M, the distance from the light source to the first grating is L0, and the distance from the first grating to the second grating is L1,
M = (L0 + L1) / L0
The encoder according to claim 3, wherein: The first direction is a periodic direction of the projected image,
The encoder according to any one of claims 2 to 5, wherein the second direction is a direction perpendicular to the periodic direction. The second grating is a light receiving element array including Q light receiving elements along the first direction,
The light receiving element array adds and outputs a signal for each of the R light receiving elements among the Q light receiving elements,
The number G of sets of the light receiving element arrays is G = Q / R, the period of the projected image is P, the first period of the first grating area is Pa, and the second period of the second grating area is When the period is Pb,
P> Pa ≧ P · (G-1.5) / G
P <Pb ≦ P · (G + 1.5) / G
The encoder according to any one of claims 2 to 5, wherein: The encoder is
P> Pa ≧ P · (G-1) / G
P <Pb ≦ P · (G + 1) / G
The encoder according to claim 6, wherein: The encoder is
P · (G−0.1) / G ≧ Pa ≧ P · (G−0.9) / G
P · (G + 0.1) / G ≦ Pb ≦ P · (G + 0.9) / G
The encoder according to claim 7, wherein: The second lattice further includes a third lattice region provided between the first lattice region and the second lattice region,
The encoder according to claim 6, wherein the third grating region has a third period between the first period and the second period. When the third period of the third lattice region is Pc,
P · (G−0.6) / G ≧ Pa ≧ P · (G−1.4) / G
P · (G + 0.6) / G ≦ Pb ≦ P · (G + 1.4) / G
P · (G−0.6) / G <Pc <P · (G + 0.6) / G
The encoder according to claim 9, wherein: The second grating has a period that varies linearly along the second direction;
When the minimum value of the first period of the first lattice region is Pamin and the maximum value of the second period of the second lattice region is Pbmax,
P> Pamin ≧ P · (G−1.5) / G
P <Pbmax ≦ P · (G + 1.5) / G
The encoder according to any one of claims 2 to 5, wherein:   The encoder according to any one of claims 1 to 11, wherein the scale is a linear scale.   The encoder according to any one of claims 1 to 11, wherein the scale is a rotary scale. A lens displaceable in the optical axis direction;
A lens apparatus comprising: the encoder according to claim 1 configured to detect a position of the lens. A lens device according to claim 14;
An imaging apparatus comprising: an imaging device including an imaging element that performs photoelectric conversion of an optical image through the lens. A machine tool including a robot arm or a transport body for transporting an assembly object;
14. A machine tool comprising: the encoder according to claim 1 configured to detect a position or a posture of the machine tool.