阅读说明：本技术 光编码器和光编码器的计算方法 (Optical encoder and calculation method of optical encoder ) 是由 加藤庆显 于 2020-03-27 设计创作，主要内容包括：一种光编码器,包括：标尺；头部,其包括光源、图像捕获器和具有第一透镜和第二透镜的透镜阵列；和计算器。该计算器包括：信号生成器,其生成正弦波信号；分析区域提取器,其提取第一分析区域和第二分析区域；信号组合器,其基于区域间距离,使用第二分析区域的正弦波信号来生成延伸到第一分析区域的第一端的正弦波信号,使得生成的正弦波信号与第一分析区域的正弦波信号重叠,并且将第一分析区域的正弦波信号与该生成的正弦波信号进行组合；以及位移量计算器,其基于由信号组合器组合的正弦波信号来计算相对位移量。(An optical encoder, comprising: a scale; a head including a light source, an image capturer, and a lens array having a first lens and a second lens; and a calculator. The calculator includes: a signal generator that generates a sine wave signal; an analysis region extractor that extracts a first analysis region and a second analysis region; a signal combiner that generates a sine wave signal extending to a first end of the first analysis region using the sine wave signal of the second analysis region based on the inter-region distance such that the generated sine wave signal overlaps with the sine wave signal of the first analysis region, and combines the sine wave signal of the first analysis region with the generated sine wave signal; and a displacement amount calculator that calculates a relative displacement amount based on the sine wave signals combined by the signal combiner.)

1. An optical encoder, comprising:

a scale having a periodic scale pattern disposed along a measurement direction;

a head portion that faces the scale and is displaced relative to the scale along the measurement direction, the head portion including:

a light source that emits light to the scale;

an image capturer that captures an image of light from the light source that arrives via the scale; and

a lens array disposed between the scale and the image capturer, the lens array comprising:

a first lens that forms an image on the image capturer that arrives via the scale pattern; and

a second lens that is arranged parallel to the first lens along the measurement direction and forms an image arriving via the scale pattern on the image capturer, and

a calculator to calculate a signal based on relative displacement between the scale and the head, the calculator comprising a processor and a memory storing a set of executable instructions, wherein when the processor executes the executable instructions the calculator operates as:

a signal generator that generates respective sine wave signals from an image formed by the first lens and an image formed by the second lens captured by the image capturer;

an analysis region extractor that extracts a sine wave signal of at least one cycle from the sine wave signal of the image formed by the first lens to serve as a first analysis region, and extracts a sine wave signal of the same cycle number as that of the first analysis region from the sine wave signal of the image formed by the second lens to serve as a second analysis region;

a signal combiner that generates a sine wave signal extending to a first end of the first analysis region using the sine wave signal of the second analysis region based on an inter-region distance that is a distance from the first end of the first analysis region to a first end of the second analysis region such that the generated sine wave signal overlaps with the sine wave signal of the first analysis region, and combines the sine wave signal of the first analysis region with the generated sine wave signal based on the sine wave signal of the second analysis region; and

a displacement amount calculator that calculates a relative displacement amount between the scale and the head portion based on the sine wave signals combined by the signal combiner.

2. The optical encoder of claim 1, wherein:

the image capturer includes light receivers arranged in parallel along the measuring direction at a placement pitch p,

the analysis region extractor extracts the first analysis region and the second analysis region from a sine wave signal of an image formed by the first lens and a sine wave signal of an image formed by the second lens in such a manner that one period Λ is multiplied by an integer Q, and

the light receivers are arranged in parallel as a multiple of an integer q so that the light receivers are divisible by one period Λ and the placement pitch p.

3. The optical encoder according to claim 2, wherein when a point on a first end of the first analysis region is defined as N-1, a point on a second end of the first analysis region is defined as N-m, a point on a first end of the second analysis region is defined as N-m +1, a point on a second end of the second analysis region is defined as N-N, a signal intensity of the nth point is defined as yn, one period included in the first analysis region and the second analysis region is defined as Λ, the inter-region distance is defined as d, a placement pitch of the optical receiver is defined as p, and a phase is defined as Φ, the signal combiner and the displacement amount calculator combine the signals using formula (1),

and calculating a relative displacement amount between the scale and the head.

4. A calculation method of an optical encoder including a scale having a periodic scale pattern arranged along a measurement direction, a head facing the scale and displaced relative to the scale along the measurement direction, the head portion includes a light source that emits light toward the scale, an image capturer that captures an image of the light from the light source that reaches via the scale, and a lens array disposed between the scale and the image capturer, wherein the lens array includes a first lens and a second lens, wherein the first lens forms an image on the image capturer that arrives via the scale pattern, and the second lens is arranged parallel to the first lens along the measurement direction and forms an image arriving via the scale pattern on the image capturer, the method comprising:

generating respective sine wave signals from an image formed by the first lens and an image formed by the second lens captured by the image capturer;

extracting a sine wave signal of at least one cycle from a sine wave signal of an image formed by the first lens to be used as a first analysis area,

extracting a sine wave signal of the same number of cycles as the number of cycles of the first analysis area from a sine wave signal of an image formed by the second lens to serve as a second analysis area;

generating a sine wave signal extending to a first end of the first analysis region using the sine wave signal of the second analysis region based on an inter-region distance that is a distance from the first end of the first analysis region to the first end of the second analysis region such that the generated sine wave signal overlaps with the sine wave signal of the first analysis region;

combining the sine wave signal of the first analysis region with the generated sine wave signal based on the sine wave signal of a second analysis region; and

calculating a relative displacement amount between the scale and the head based on the combined sine wave signal.

Technical Field

The present invention relates to an optical encoder including a lens array, and a calculation method of the optical encoder.

Background

Conventionally, there is known an optical encoder including a scale having a periodic scale pattern disposed along a measurement direction, a head facing the scale and displaced relative to the scale along the measurement direction, and a calculator calculating a signal based on a relative displacement between the scale and the head. The head includes a light source that emits light to the scale, an image capturer that captures an image of the light from the light source that reaches via the scale, and a lens that is disposed between the scale and the image capturer. The calculator calculates a relative displacement amount between the scale and the head based on the light from the light source captured by the image capturer.

Fig. 7A and 7B are graphs illustrating a method of performing phase analysis on a sinusoidal signal using a conventional calculator. For example, as shown in fig. 7A, the calculator generates a sine wave signal from light captured in an image capture area H, which is an area in the image capture device where light can be captured. One period of the sine wave signal is represented by Λ. The calculator calculates the amount of relative displacement between the scale and the head by performing phase analysis on the generated sine wave signal. At this time, the calculator may perform high-precision analysis using fourier transform in phase analysis.

In this example, the size of the optical encoder depends on the focal length of the optical system (lens). Specifically, light from the light source is emitted to the image capturer via the scale and the lens, but in order to clearly emit an image (light) that arrives via the scale, the focal length of the lens must be adjusted. In order to focus the system so that the entire image emitted to the image capturer (i.e., the entire image capturing area H) is clearly formed, a certain amount of distance must be provided between the scale and the lens and between the lens and the image capturer. Further, the size of the lens is configured to be a size proportional to the image capturing area H. Therefore, the optical encoder can be made large in association with the size of the lens, the focal length, and the size of the image capturing area H.

In response to these problems, for example, in japanese unexamined patent publication No. 2005-522682 and japanese patent laid-open publication No. 2012-32295, a lens array having a plurality of small-diameter lenses is used instead of a single lens. The plurality of small-diameter lenses in the lens array each have a small image capturing area and a short focal length, and therefore, the optical encoder can be made smaller than when a single lens is used. However, when the lens array is used, an image cannot be formed at the boundary between the plurality of small-diameter lenses, and as shown in fig. 7B, an image emitted to the image capturer is formed in a state where each small-diameter lens is isolated, for example, as in the first image capturing area H1 and the second image capturing area H2.

In view of these problems, an optical encoder of japanese unexamined patent publication No. 2005-522682 (photoelectric encoder) is configured to balance the arrangement of each small-diameter lens so that images formed by photodetectors (image capturers) are overlapped with a coordinate phase, and by adjusting the periodicity of the lens array, no isolation occurs in the images formed by the photodetectors. Further, when the lens array is formed of, for example, plastic, characteristics such as the focal length of each small-diameter lens may vary due to temperature changes such as thermal expansion, but the optical encoder of japanese patent laid-open publication No. 2012-32295 corrects the amount of variation in each small-diameter lens using, for example, the least square method. In the isolated sine wave signals as in the first image-capturing region H1 and the second image-capturing region H2, the phase can be analyzed with the same accuracy as when fourier transform is employed using the least squares method.

However, in the optical encoder of japanese patent laid-open publication No. 2012-32295, even when the phase can be analyzed with high accuracy by the calculation, unstable matrix calculation occurs when the optical encoder is mounted in, for example, a microcomputer, and a significant phase error may occur due to, for example, the influence of rounding errors. In addition, phase analysis using the least squares method has a very large amount of calculation content compared to fourier transform, and thus requires time for calculation.

Disclosure of Invention

An advantage of the present invention is to provide an optical encoder that can calculate the relative displacement amount between a scale and a head with high accuracy even when a lens array having a plurality of small-diameter lenses is used.

An optical encoder according to the present invention is an optical encoder including a scale having a periodic scale pattern provided along a measurement direction, a head facing the scale and displaced relative to the scale along the measurement direction, and a calculator that calculates a signal based on a relative displacement between the scale and the head, and the head includes: a light source that emits light to the scale; an image capturer that captures an image of light from the light source that reaches via the scale; and a lens array disposed between the scale and the image capturer. The lens array includes a first lens and a second lens, wherein the first lens forms an image arriving via the scale pattern on the image capturer, and the second lens is arranged parallel to the first lens along the measurement direction, and forms an image arriving via the scale pattern on the image capturer. The calculator includes: a signal generator that generates respective sine wave signals from an image formed by the first lens and an image formed by the second lens captured by the image capturer; an analysis region extractor that extracts a sine wave signal of at least one cycle from the sine wave signal of the image formed by the first lens to serve as a first analysis region, and extracts a sine wave signal of the same cycle number as that of the first analysis region from the sine wave signal of the image formed by the second lens to serve as a second analysis region; a signal combiner that generates a sine wave signal extending to the first end of the first analysis region using the sine wave signal of the second analysis region based on an inter-region distance that is a distance from the first end of the first analysis region to the first end of the second analysis region such that the generated sine wave signal overlaps with the sine wave signal of the first analysis region, and combines the sine wave signal of the first analysis region with the generated sine wave signal based on the sine wave signal of the second analysis region; and a displacement amount calculator that calculates a relative displacement amount between the scale and the head portion based on the sine wave signals combined by the signal combiner.

According to the present invention, in the calculator, a sine wave signal extending to the first end of the first analysis region is generated from the sine wave signal of the second analysis region based on the inter-region distance using the signal combiner so that the generated sine wave signal overlaps with the sine wave signal of the first analysis region, and the sine wave signal of the first analysis region is combined with the generated sine wave signal based on the sine wave signal of the second analysis region, and the relative displacement amount between the scale and the head is calculated based on the sine wave signal combined by the signal combiner using the displacement amount calculator. Therefore, the signal of the image not formed at the boundary between the first lens and the second lens (which is a plurality of small-diameter lenses) can be interpolated without any complicated calculation or correction. Therefore, even when a lens array having a plurality of small-diameter lenses is used, the optical encoder can calculate the relative displacement amount between the scale and the head with high accuracy.

In this case, preferably, the image capturer includes light receivers arranged in parallel along the measurement direction at a placement pitch p, the analysis region extractor extracts the first analysis region and the second analysis region from the sine wave signal of the image formed by the first lens and the sine wave signal of the image formed by the second lens in such a manner that one period Λ is multiplied by an integer Q, and the light receivers are arranged in parallel as a multiple of the integer Q so that the light receivers are divisible by both the one period Λ and the placement pitch p.

According to this configuration, the analysis region extractor performs extraction on the first analysis region and the second analysis region, respectively, in such a manner that one period Λ of the sine wave signal is multiplied by an integer Q, and the optical receivers are arranged in parallel as a multiple of the integer Q so that the optical receivers are divisible by both the one period Λ and the placement pitch p, and thus, for example, fourier transform can be used to analyze the phase. Therefore, even when a lens array is used, the optical encoder can analyze the phase with high accuracy using fourier transform.

In this case, preferably, when a point on the first end of the first analysis region is defined as N ═ 1, a point on the second end of the first analysis region is defined as N ═ m, a point on the first end of the second analysis region is defined as N ═ m +1, a point on the second end of the second analysis region is defined as N ═ N, the signal intensity of the nth point is defined as yn, one period included in the first analysis region and the second analysis region is defined as Λ, the inter-region distance is defined as d, the placement pitch of the optical receivers is defined as p, and the phase is defined as Φ, the signal combiner and the displacement amount calculator combine signals using formula (1) provided in the following embodiments, and calculate the relative displacement amount between the scale and the head.

According to such a configuration, the calculator can calculate the relative displacement amount between the scale and the head portion using the formula (1), and therefore, the present invention can be easily mounted on, for example, a microcomputer.

A calculation method of an optical encoder according to the present invention is a calculation method of an optical encoder including a scale having a periodic scale pattern provided along a measurement direction, a head facing the scale and displaced relative to the scale along the measurement direction, and a calculator that calculates a signal based on a relative displacement between the scale and the head, and the head includes a light source that emits light to the scale; an image capturer that captures an image of light from the light source that reaches via the scale; and a lens array disposed between the scale and the image capturer. The lens array includes a first lens and a second lens, wherein the first lens forms an image arriving via the scale pattern on the image capturer, and the second lens is arranged parallel to the first lens along the measurement direction, and forms an image arriving via the scale pattern on the image capturer. The calculator includes: a signal generating step of generating respective sine wave signals from an image formed by the first lens and an image formed by the second lens captured by the image capturer; an analysis region extraction step of extracting a sine wave signal of at least one cycle from the sine wave signal of the image formed by the first lens to be used as a first analysis region, and extracting a sine wave signal of the same cycle number as the cycle number of the first analysis region from the sine wave signal of the image formed by the second lens to be used as a second analysis region; a signal combining step of generating a sine wave signal extending to a first end of a first analysis region using a sine wave signal of a second analysis region based on an inter-region distance that is a distance from the first end of the first analysis region to the first end of the second analysis region such that the generated sine wave signal overlaps with the sine wave signal of the first analysis region, and combining the sine wave signal of the first analysis region with the generated sine wave signal based on the sine wave signal of the second analysis region; and a displacement amount calculating step of calculating a relative displacement amount between the scale and the head portion based on the sine wave signals combined in the signal combining step.

According to the present invention, in the calculator, a sine wave signal extending to the first end of the first analysis region is generated from the sine wave signal of the second analysis region based on the inter-region distance in the signal combining step so that the generated sine wave signal overlaps with the sine wave signal of the first analysis region, and the sine wave signal of the first analysis region is combined with the generated sine wave signal based on the sine wave signal of the second analysis region, and in the displacement amount calculating step, the relative displacement amount between the scale and the head is calculated based on the combined sine wave signal. Therefore, the signal of the image not formed at the boundary between the first lens and the second lens (which is a plurality of small-diameter lenses) can be interpolated without any complicated calculation or correction. Therefore, even when the optical encoder uses a lens array having a plurality of small-diameter lenses, the calculation method of the optical encoder can calculate the relative displacement amount between the scale and the head with high accuracy.

Drawings

The present invention is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein:

FIG. 1 is a perspective view of an optical encoder according to an embodiment of the present invention;

FIG. 2 is a block diagram illustrating an optical encoder;

FIG. 3 is a flowchart showing a method of calculating the relative displacement amount with a calculator of an optical encoder;

fig. 4A to 4C are graphs showing a method of calculating the relative displacement amount with a calculator of an optical encoder;

fig. 5D and 5E are graphs showing a method of calculating the relative displacement amount with a calculator of an optical encoder;

fig. 6A and 6B are perspective views of an optical encoder according to a modification; and

fig. 7A and 7B are graphs illustrating a method of performing phase analysis on a sinusoidal signal using a conventional calculator.

Detailed Description

The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the forms of the invention may be embodied in practice.

Hereinafter, an embodiment of the present invention is described with reference to fig. 1 to 4C. In each drawing, the long direction of the scale 2 is shown as the X direction, the short direction is shown as the Y direction, and the height direction is shown as the Z direction. Hereinafter, the terms X-direction, Y-direction, and Z-direction may be simply used to provide description. FIG. 1 is a perspective view of an optical encoder 1 according to an embodiment of the present invention. As shown in fig. 1, the optical encoder 1 includes a long scale 2 and a head 3, and the head 3 faces the scale 2 and is displaced relative to the scale 2 along the X direction (measurement direction). The optical encoder 1 is a linear encoder used in a linear scale which is a measuring device not shown in the figure. The optical encoder 1 is disposed inside the linear scale. The linear scale detects the position of the head 3 relative to the scale 2 by displacing the head 3 relative to the scale 2 along the X direction (measurement direction), and outputs the detection result to a display component, such as a liquid crystal display, which is not shown in the figure.

The head 3 includes a light source 4 that emits light toward the scale 2, a lens array 5 having a plurality of small-diameter lenses, and an image capturer 6 that captures an image of the light from the light source 4 that reaches via the scale 2. The head 3 is provided so as to be able to advance and retreat in the X direction with respect to the scale 2. The light source 4, lens array 5 and image capturer 6 are configured to be displaced integrally with respect to the scale 2.

The scale 2 is formed of, for example, glass, and is provided with a periodic scale pattern 20 arranged along the X direction (measurement direction) on one surface. The scale pattern 20 is reflective, and includes a reflective portion 21 that reflects light from the light source 4 and a non-reflective portion 22 that does not reflect the light. The scale pattern 20 has reflective portions 21 and non-reflective portions 22 alternately arranged in parallel at a predetermined pitch along the X direction: so-called incremental patterns. A sine wave signal (incremental signal) is generated from light arriving via the incremental pattern, which light is captured by the image capturer 6. The optical encoder 1 calculates the relative displacement amount between the scale 2 and the head 3 by analyzing the sine wave signal.

For example, the light source 4 is a Light Emitting Diode (LED). The light source 4 is installed at an appropriate angle for emitting light to the scale 2. The light source 4 is not limited to LEDs; any desired light source may be used. A lens array 5 is arranged between the scale 2 and the image capturer 6. The lens array 5 is formed of, for example, plastic. The lens array 5 includes a first lens 51 and a second lens 52 as a plurality of small-diameter lenses, wherein the first lens 51 forms an image arriving via the scale pattern 20 on the image capturer 6, and the second lens 52 is arranged parallel to the first lens 51 along the X direction (measuring direction), and forms an image arriving via the scale pattern 20 on the image capturer 6. For convenience of description, the two small-diameter lenses arranged at the center of the lens array 5 are regarded as the first lens 51 and the second lens 52, but any small-diameter lens may be regarded as the first lens 51 and the second lens 52 as long as the lenses are arranged in parallel along the X direction. In addition, the lens array 5 may be formed of any transparent material, such as glass, instead of plastic.

The image capturer 6 includes light receivers 61 arranged in parallel along the X direction (measurement direction) at a placement pitch p. A Photo Diode Array (PDA) is used for the light receiver 61. The image capturer 6 is not limited to the PDA, and any detection device such as a Position Sensitive Detector (PSD) or a charge-coupled device (CCD) may be used. The image capturer 6 is mounted facing the + Z direction (upper side on the drawing plane) of the lens array 5 so as to overlap the lens array 5. In other words, the scale 2 and the image capturer 6 are arranged to face each other so as to overlap each other with the lens array 5 sandwiched therebetween.

Fig. 2 is a block diagram showing the optical encoder 1. As shown in fig. 2, the optical encoder 1 further includes a calculator 7 that calculates a signal based on the relative displacement between the scale 2 and the head 3. The calculator 7 is configured to include a signal generator 71, an analysis region extractor 72, a signal combiner 73, and a displacement amount calculator 74. For example, the calculator 7 may include, but is not limited to, a microcomputer having a processor and a memory storing a set of instructions executable by the processor for performing the operations described herein.

The signal generator 71 generates respective sine wave signals from the image formed by the first lens 51 and the image formed by the second lens 52 captured by the image capturer 6. The analysis region extractor 72 extracts a sine wave signal of at least one cycle from the sine wave signal of the image formed by the first lens 51 to serve as a first analysis region, and extracts a sine wave signal of the same cycle number as that of the first analysis region from the sine wave signal of the image formed by the second lens 52 to serve as a second analysis region. A specific method of extracting the analysis region with the analysis region extractor 72 is described below with reference to fig. 3 to 5E.

Based on the inter-area distance (distance from the first end of the first analysis area to the first end of the second analysis area), the signal combiner 73 generates a sine wave signal extending to the first end of the first analysis area using the sine wave signal of the second analysis area so that the generated sine wave signal overlaps with the sine wave signal of the first analysis area, and combines the sine wave signal of the first analysis area with the generated sine wave signal based on the sine wave signal of the second analysis area. A specific signal combining method using the signal combiner 73 is described below with reference to fig. 3 to 5E. The displacement amount calculator 74 calculates the relative displacement amount between the scale 2 and the head 3 based on the sine wave signals combined by the signal combiner 73.

Fig. 3 is a flowchart illustrating a method of calculating the relative displacement amount with the calculator 7 of the optical encoder 1, and fig. 4A to 5E are graphs illustrating a method of calculating the relative displacement amount using the calculator 7 of the optical encoder 1. The reference numerals are divided into fig. 4 and 5, but graphs (a) to (E) show the flow of a single sequence in the method of calculating the relative displacement amount using the calculator 7. Hereinafter, a specific method for calculating the relative displacement amount in the optical encoder 1 is described with reference to fig. 3 to 5E.

First, as shown in fig. 3, a signal generation step is performed in which, when the light receiver 61 in the image capturer 6 captures an image of light from the light source 4 arriving via the scale 2, the signal generator 71 generates a corresponding sine wave signal using each of the image formed by the first lens 51 and the image formed by the second lens 52 captured by the image capturer 6 (step ST 01). In the signal generation step performed by the signal generator 71, as shown in fig. 4A, a sine wave signal is generated from an image captured in a first image capturing area h1, which is a range in which the first lens 51 can perform image capturing, and a sine wave signal is generated from an image captured in a second image capturing area h2, which is a range in which the second lens 52 can perform image capturing, h 2.

Next, as shown in fig. 3 and 4A, an analysis region extraction step is performed in which the analysis region extractor 72 extracts a sine wave signal of two cycles from the sine wave signal of the image of the first image capturing region H1 of the first lens 51 to serve as a first analysis region H1, and extracts a sine wave signal of the same number of cycles as that in the first analysis region H1 (i.e., a sine wave signal of two cycles) from the sine wave signal of the image of the second image capturing region H2 of the second lens 52 to serve as a second analysis region H2 (step ST 02).

The analysis region extractor 72 extracts the first analysis region H1 and the second analysis region H2 from the sine wave signal of the image of the first image capturing region H1 of the first lens 51 and the sine wave signal of the image of the second image capturing region H2 of the second lens 52 in such a manner that one period Λ is multiplied by an integer Q (H1 ═ Λ Q, H2 ═ Λ Q). At this time, the relationship is required: (first analysis region H1) ═ second analysis region H2 ═ Λ Q. In addition, the light receivers 61 are arranged in parallel as a multiple of an integer q so that the light receivers 61 are divisible by one period Λ and the placement pitch p. This is because the optical encoder 1 uses fourier transform to analyze the phase.

Next, a signal combining step is performed in which, based on the inter-area distance D, that is, the distance from the first end (left side on the drawing sheet) of the first analysis area H1 to the first end (left side on the drawing sheet) of the second analysis area H2, as shown in fig. 4B and 4C, the signal combiner 73 uses the sine wave signal of the second analysis area H2 to generate a sine wave signal (indicated by a broken line in the drawing) extending to the first end of the first analysis area H1 such that the generated sine wave signal overlaps with the sine wave signal of the first analysis area H1, and, as shown in fig. 5D, combines the sine wave signal of the first analysis area H1 with the generated broken line sine wave signal based on the sine wave signal of the second analysis area H2 (step ST 03). Fig. 4B shows a case in which a broken-line sine wave signal based on the sine wave signal of the second analysis region H2 is generated, and therefore, the positions of the first analysis region H1 and the second analysis region H2 are depicted as being arranged offset in the vertical direction on the plane of the drawing sheet, but actually the broken-line sine wave signal is generated in the state shown in fig. 4C.

In addition, as shown in fig. 3, a displacement amount calculating step is performed in which the displacement amount calculator 74 calculates the relative displacement amount between the scale 2 and the head 3 based on the combined sine wave signal from the signal combining step of the signal combiner 73 (step ST 04). Specifically, when the signal combiner 73 combines the sine wave signals in fig. 5D, the displacement amount calculator 74 moves the second analysis region H2 by the amount of the interval between the signals generated by the first lens 51 and the second lens 52 along the sine wave signals (i.e., until the second end (right side on the drawing sheet) of the first analysis region H1 and the first end of the second analysis region H2 come into contact), as shown in fig. 5E, and calculates the relative displacement amount between the scale 2 and the head 3 based on the sine wave signals within the analysis region H3, the analysis region H3 combining the first analysis region H1 and the second analysis region H2.

The signal combiner 73 and the displacement amount calculator 74 combine the two sine wave signals using the following formula, which is a fourier transform, and calculate the relative displacement amount between the scale 2 and the head 3. Specifically, when a point on the first end of the first analysis region H1 is defined as N ═ 1, a point on the second end of the first analysis region H1 is defined as N ═ m, a point on the first end of the second analysis region H2 is defined as N ═ m +1, a point on the second end of the second analysis region H2 is defined as N ═ N, the signal intensity of the nth point is defined as yn, one period included in the first analysis region H1 and the second analysis region H2 is defined as Λ, the inter-region distance is defined as d, the placement pitch of the light receivers 61 is defined as p, and the phase is defined as Φ, the signals are combined using formula (1), and the relative displacement amount between the scale 2 and the head 3 is calculated.

[ equation 1]

Even when a sine wave signal for finding a phase cannot be obtained by merely isolating sine wave signals generated by the first lens 51 and the second lens 52 in this way using the calculator 7 and simply adding the isolated sine wave signals together using the respective properties of the first lens 51 and the second lens 52, the two isolated signals can be combined and corrected and interpolated by the signal combiner 73, and thus the relative displacement amount between the scale 2 and the head 3 can be calculated with high accuracy.

In this way, the following effects and advantages can be achieved according to the present embodiment:

(1) in the calculator 7, a sine wave signal extending to the first end of the first analysis region H1 is generated from the sine wave signal of the second analysis region H2 based on the inter-region distance d using the signal combiner 73 such that the generated sine wave signal overlaps with the sine wave signal of the first analysis region H1, and the sine wave signal of the first analysis region H1 is combined with the generated sine wave signal based on the sine wave signal of the second analysis region H2. Using the displacement amount calculator 74, the relative displacement amount between the scale 2 and the head 3 is calculated based on the sine wave signals combined by the signal combiner 73. Therefore, the signal of the image not formed at the boundary between the first lens 51 and the second lens 52 (which are a plurality of small-diameter lenses of the lens array 5) can be interpolated without any complicated calculation or correction. Therefore, even when the lens array 5 is used, the optical encoder 1 can calculate the relative displacement amount between the scale 2 and the head 3 with high accuracy.

(2) The analysis region extractor 72 performs extraction on the first analysis region H1 and the second analysis region H2, respectively, in such a manner that one period Λ of the sine wave signal is multiplied by an integer Q, and the light receivers 61 are arranged in parallel as a multiple of the integer Q so that the light receivers 61 are divisible by the one period Λ and the placement pitch p. Thus, the fourier transform can be used to analyze the phase. Therefore, even when the lens array 5 is used, the optical encoder 1 can analyze the phase with high accuracy using fourier transform.

(3) The calculator 7 can calculate the relative displacement amount between the scale 2 and the head 3 using the formula (1), and therefore, the present invention can be easily mounted on, for example, a microcomputer.

(4) In the calculator 7, in the signal combining step, a sine wave signal extending to the first end of the first analysis region H1 is generated from the sine wave signal of the second analysis region H2 based on the inter-region distance d so that the generated sine wave signal overlaps with the sine wave signal of the first analysis region H1, and the sine wave signal of the first analysis region H1 is combined with the generated sine wave signal based on the sine wave signal of the second analysis region H2, and in the displacement amount calculating step, the relative displacement amount between the scale 2 and the head 3 is calculated based on the combined sine wave signal. Therefore, the signal of the image that is not formed at the boundary between the first lens 51 and the second lens 52 can be interpolated without any complicated calculation or correction. Therefore, even when the optical encoder 1 uses the lens array 5, the calculation method of the optical encoder 1 can calculate the relative displacement amount between the scale 2 and the head 3 with high accuracy.

Modifying

Further, the present invention is not limited to the above-described embodiments, and includes modifications and improvements within a range in which the advantages of the present invention can be achieved. For example, in the above-described embodiment, the optical encoder 1 is used in a linear scale serving as a measuring apparatus, but the optical encoder may also be used in another measuring apparatus, such as a dial indicator (test indicator) or a micrometer. That is, the optical encoder is not particularly limited in terms of the form, method, and the like of the measuring apparatus to which it is applied, and may also be used in other measuring apparatuses, and the like. The optical encoder of the present invention is not particularly limited in terms of its installability. In addition, the optical encoder may be used in devices other than the measurement device (such as a sensor).

In the above embodiment, the optical encoder 1 is a linear encoder, but the optical encoder may be a rotary encoder. In addition, in the above-described embodiment, the image capturer 6 includes the light receiver 61, but the image capturer need not include the light receiver. Any component may be used as long as light from the light source arriving via the scale can be captured. In the above-described embodiment, the calculator 7 is, for example, a microcomputer, but the calculator need not be a microcomputer, but may be, for example, an externally connected personal computer. The calculator may be configured by any component as long as the component can perform calculation.

In the above-described embodiment, the analysis-area extractor 72 performs the analysis-area extracting step in which two periods of sine-wave signals are extracted from the sine-wave signals of the image of the first image-capturing area H1 of the first lens 51 to serve as the first analysis area H1, and similarly two periods of sine-wave signals are extracted from the sine-wave signals of the image of the second image-capturing area H2 of the second lens 52 to serve as the second analysis area H2. However, the analysis region extractor does not need to specify two periods of the sine wave signal as the first analysis region and the second analysis region, and may extract at least one period of the sine wave signal as the first analysis region and the second analysis region. That is, the analysis region extractor may extract a sine wave signal of at least one cycle from a sine wave signal of an image formed by the first lens to be used as the first analysis region, and may extract a sine wave signal of the same cycle number as that of the first analysis region from a sine wave signal of an image formed by the second lens to be used as the second analysis region.

In the above-described embodiment, in fig. 4A to 5E, the first analysis region H1 is shown on the left side of the drawing sheet and the second analysis region H2 is shown on the right side, but the left side of the drawing sheet may be regarded as the second analysis region H2 and the right side of the drawing sheet may be regarded as the first analysis region H1. Also, based on the inter-area distance d, which is the distance from the first end (left side on the drawing sheet) of the first analysis area H1 to the first end (left side on the drawing sheet) of the second analysis area H2, as shown in fig. 4B and 4C, the signal combiner 73 generates a sine wave signal (indicated by a broken line in the drawing) extending to the first end of the first analysis area H1 using the sine wave signal of the second analysis area H2 such that the generated sine wave signal overlaps with the sine wave signal of the first analysis area H1. However, as long as the sine wave signal of the second analysis region can be used to generate a sine wave signal that extends to the first end of the first analysis region so as to overlap with the sine wave signal of the first analysis region, the left or right direction of the drawing sheet may be regarded as the first end.

In the above-described embodiment, the signal combiner 73 and the displacement amount calculator 74 combine two sine wave signals (the sine wave signal of the first analysis region H1 acquired via the first lens 51 and the sine wave signal of the second analysis region H2 acquired via the second lens 52) using the formula (1), and calculate the relative displacement amount between the scale 2 and the head 3. However, a third lens aligned in parallel to the second lens 52 in the X direction (measurement direction) may be further provided, which forms an image arriving via the scale pattern on the image capturer 6, and the signal combiner 73 and the displacement amount calculator 74 may combine three sine wave signals using the sine wave signals of the third analysis region acquired via the third lens and calculate the relative displacement amount between the scale and the head. In this case, due to the third sine wave signal, the third term similar to the second term of the formula (1) must be used, and the inter-region distance is not the distance from the first end of the first analysis region H1 to the first end of the second analysis region H2, but must be calculated as the inter-region distance d' from the first end of the second analysis region H2 to the first end of the third analysis region. That is, the signal combiner is not limited to two sine wave signals, but may combine signals of sine wave signals generated according to the number of the plurality of small-diameter lenses existing in the lens array.

Also, the signal combiner 73 and the displacement amount calculator 74 perform combination using formula (1) which is fourier transform, and calculate the relative displacement amount between the scale 2 and the head 3. However, it is not necessary to perform the calculation using equation (1) or another fourier transform, and the calculation may be performed in another method. That is, based on the inter-area distance, i.e., the distance from the first end of the first analysis area to the first end of the second analysis area, the signal combiner may generate the sine wave signal extending to the first end of the first analysis area using the sine wave signal of the second analysis area such that the generated sine wave signal overlaps with the sine wave signal of the first analysis area, and may combine the sine wave signal of the first analysis area and the sine wave signal based on the generated sine wave signal of the second analysis area. The displacement amount calculator may calculate the relative displacement amount between the scale and the head portion based on the sine wave signals combined by the signal combiner.

Fig. 6A and 6B are perspective views of an optical encoder according to a modification. Specifically, fig. 6A is a perspective view of an optical encoder 1A according to a first modification, and fig. 6B is a perspective view of an optical encoder 1B according to a second modification. In the above-described embodiment, the scale 2 of the optical encoder 1 includes the reflective scale pattern 20.

In the first modification, the scale 2A of the optical encoder 1A is different from the above-described embodiment in that the scale 2A has a transparent type scale pattern 20A, as shown in fig. 6A. The scale pattern 20A includes a transparent portion 21A through which light from the light source 4 passes and an opaque portion 22A through which light does not pass, and the optical encoder 1A calculates the amount of relative displacement between the scale and the head by analyzing a sine wave signal generated by light arriving via the scale pattern 20A, similarly to the case when the scale pattern is a reflection type. By so doing, even when the optical encoder 1A has a transparent type scale pattern, the optical encoder 1A can be made smaller using the lens array 5, and the relative displacement amount between the scale 2A and the head 3 can also be calculated with high accuracy.

In the second modification, as shown in fig. 6B, the optical encoder 1B is different from the first modification in that the optical encoder 1B further includes a reflection member 10 that reflects light from the light source 4. The reflective member 10 is, for example, a mirror, but may be any member capable of reflecting light from the light source 4 toward the scale 2A. Therefore, the position of the light source 4 in the optical encoder 1B can be freely designed, and thus the degree of freedom in designing the optical encoder 1B can be improved.

As described above, the present invention can be advantageously applied to an optical encoder including a lens array, and a calculation method of the optical encoder.

It should be noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to exemplary embodiments, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope of the present invention in its aspects. Although the invention has been described herein with reference to particular structure, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein; rather, the invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.

The present invention is not limited to the above-described embodiments, and various changes and modifications are possible without departing from the scope of the present invention.