TWI242636B - An optical angle encoder - Google Patents

Abstract

An optical angle encoder is disclosed, which includes one first circular grating; one second circular grating parallel to the first circular grating with the same axle center; one rotational bearing connecting to the second circular grating and making the second circular grating rotatable; one bulk for fixing the first circular grating; one light source for generating a beam of light parallel to the axle center before the light reaching the first circular grating; one focusing lens for focusing the light when the light leaves the first circular grating and the second circular grating; and one light detector located at the focus of the focusing lens to detect the Moire fringe.

Description

1242636 发明 Description of the invention: [Technical field to which the invention belongs] The present invention relates to an optical angle winding »flat horse, especially an optical angle encoder suitable for a high-precision rotary shaft. [Previous technology] At present, the optoelectronic industry such as the semiconductor industry and thin film transistor display is constantly growing. Nano technology has also become one of the world's most popular research directions, and the technical standards are also increasing. These industries are all optoelectronics Integrating the 10-type industry 'In order to meet this technical requirement, the precision machinery industry has been paid more attention by comparison. In the precision machinery industry, high-precision grinding machines, CNC lathes, CNC milling machines, etc. are often used. These guarding machines, in addition to requiring accurate displacement, must also have high-precision angular rotation axes to meet processing requirements. In addition, because of the distance of observation in aviation, it is also necessary to measure with a high degree of angular rotation to prevent errors. Existing high-precision rotating shafts use encoders for their angular positioning sensors. They include a disc (or grating) with countless gaps. Light emitters and sensors are installed on both sides of the disc. When moving the grating disk, the grating will block the light, and the sensor will receive the intermittent light source. The 20 computer will use the signal received by the light sensor to calculate the displacement. The optical angle encoder of the single-unit type is a thin slot with a thin disk and other angles, and then the sensor detects the light and dark changes of the light beam through the slit. For example, it is used in a mouse encoder, but its The size of the slit that can sense the change of light and darkness is limited, that is, the slit is too small to be sensed; the light 1242636 learning encoder used in industry is shown in Figure i, which contains the main light thumb and the auxiliary light thumb 20. The light thumb is like a thin disk, with equal angle radial engraved lines on the disk, while the auxiliary light thumb 20 is only the size of the main grating U) or 1/2 () of the disk, and the light source% passes through the main After the grating H) ', then pass through the secondary varnish, use-light sensor (reading head) 5 4 (H 测 measuring light signal changes, the two grating lines are parallel, when the rotation of the center of the circle direction, a cycle will occur The change in the lightness and darkness is the so-called Moire (m.㈣ fringe). The corresponding rotation angle can be converted by calculating the number of Moire fringes. Recently, different optical methods have been used to apply optical diffraction interference to generate interference fringes. The number of stripes is converted to the corresponding rotation angle. These 10 optical encoders Both include angular errors caused by processing and assembly.

When the rotation angle of accuracy is required, it becomes important to try to eliminate these angle errors. In order to solve the angular error caused by eccentricity, Can0n Inc • designed a k-1 optical path type optical encoder, which is characterized in that two interference optical paths are incident on the reflecting surface of 15 symmetrical positions (phase difference 180.), and then reflected back. Gather together to generate interference. When the eccentricity occurs in the direction of the vector formed by the symmetrical position, the error will be automatically compensated to reduce the eccentric shadow vector. In addition, the German Federal Institute of Physics and Technology has designed an optical encoder with 8 read heads to offset the angular error. The more the read head of the optical encoder, the more the g 'optical encoder can reduce the effect of the angle 20 error, so the present invention adopts an optical method to design a pseudo-infinite: the read head can completely offset the effect of the angle error. [Summary of the invention] 1242636 Cry, two f: The main purpose is to provide an optical angle coding to enable the encoder to completely eliminate i ′ caused by guarding and assembly to achieve zero error angle measurement. 10 15 In order to achieve the above object, the optical angle encoder of the present invention includes a circular weaving grid with a plurality of fine slit grooves arranged in a radial pattern:. The angle between any two adjacent narrow slits extending to the center of the circle is equal; a second circular coded grating has a plurality of thin slits arranged in a radial pattern. The included angles to the center of the circle are all equal, and are arranged parallel to the first-round coded grating and share a central axis; two rotation axes are connected to the second round-coded grating to drive the second round-coded grating Rotate;-the body is used to fully or partially accommodate the rotating shaft, sub-fixing the first circular coded grating;-light source, generating-a light beam, when reaching the first circular coded grating and the second circular coded grating , The beam path is parallel to the center and axis of the circular encoding grating, and the riding range covers the perimeter of the first circular encoding grating; a condenser lens, the parallel beam passes through the first circular encoding grating and the The plurality of narrow slit grooves of the second circular coded grating are used to focus the parallel beam; and-a light sensor is placed at the focus of the focusing lens; t position is used to know the change of the moire fringe, and Turn optical signals into telecommunications signals. [Embodiment] In the 2001 International Optical Engineering Conference (pr〇c · spiE) No. 44〇1, pages 267 ~ 274, "Automatic high precision calibration system f0r angle enc〇der" proposed by Tsukasa Watanabe, Suppose that the angle 20 1242636 degree encoder has an error of 5 due to processing and assembly. Because the encoder is 疋 I one circle 疋 2π, the angle is misunderstood. The difference 5 is a periodic function with a period of 2π. , 5 can be expanded by Fourier bismuth of order η

Expansion), we can get the theorem of formula 1: 5 10 15 s = ζΈΕ] ύηϋ ~ + β.), Where Ej is the amplitude of the jth term, and is the phase angle of the jth term. When the average 'm points are taken within the range of 2π, that is, the phase difference between each f, A ^ ^ point is k / m, the function value of the corresponding function & is shown in Equation 2: 2) • 0 :: 'm 1 After adding the corresponding function values of 坆 m points, take the average dry ^ = mean is equal to the sum of all _ multiple items of the Fu Li # sequence towel, table: Divide = multiple items of m in the sequence In addition, other terms will be lost. Expressed as an equation: mm τ Ύα: I ~ sin (plus 苎 + ~) ............ ........ 3) Read on the circle: This: The reason for the encoder design 'if there is. 1 equidistant sub-head: U value 2 homing' the average value of the angular error reading of the code 11 It is the mean value of several terms of Qin m, the original angle resident part will be offset, and only the residual I / 'is left. At this time, the angle error is as shown in Equation 3. If m is close to the number of two :: Yes Fourier items are offset. Only the Fourier class and people are left. For the trans system, the amplitude of the higher item will be 20

I 1242636 4 ',' Therefore, the amplitude of 彳 next to the infinite term approaches zero, and the error δ approaches zero at this time. For example, the optical encoder of the 8 read heads designed by the German Federal Institute of Physics and Technology has the amplitudes of the Fourier series 0 to 7 multiples of the angular error are zero, and the amplitudes of the remaining 8 multiples are not zero (that is, the first 8, 16, 24, 32 ... order amplitude 5 is not zero), the overall angular error is less than 0.006 ". 4 Optical encoders of this specification, the first circular encoder grating and the second circular encoder encoder It is preferred that there is a light-equivalent line on the transparent substrate. When the first circle $, the flat code grating and the second circular code grating are displaced relative to each other, the period I * produces a change in light and shade, which is Moire. ) Streak, Moire fringe light 10 signal detection, you can use transmitted light or reflected light, and then calculate the moire fringe number to convert the corresponding rotation angle. In this optical angle encoder, the rotation axis is better In order to pass through the central axis of the second circular coded grating, or to be connected outside the thumb of the second circular coded light source, the light source is preferably a point light source, and a parallel light beam is generated through a collimating lens. When the central axis position, it first guides the light beam through a refractive lens Llj lance toward the first encoder plate-shaped, and extends through the center axis of the focus. M, 20

Yang Mingchun uses the reflected light to calculate the number of Moire fringes in exchange for the rotation angle. At this time, the light source and the light sensor are located in the -circular series: the grating is on the same side, and the beam passes through the first-shaped encoding grating and the third grating. ， Reflected back to the second circular series * 7 A young circular group was used to be pinched by a light sensor. According to the present invention, if the number of penetration n is used to convert the corresponding rotation angle 廑, the bar is at this time. The light source and the light sensor are located at this time. 10 1242636 Circular coded grating—the opposite side of the circular coded grating, then The light beam penetrates the first and second circular coded gratings for detection by a light sensor. On the light path of the present invention, the light beam is shot by a human in parallel with the first __coded light album /, and a circular coded light beam is obtained, and a light signal with a moiré pattern that penetrates or reflects is obtained. After encoding with the second circle, after collimating the lens, the light beam will be focused on the light sensor. This is equivalent to the signal of countless light sensor read heads. When the light sensor Tianshan type 3 is known to be infinite, then All Fourier terms are offset == when the error 5 is zero. 10 In order to allow your review committee to better understand the technical content of the present invention, the second preferred embodiment is described below. Embodiment 1 The optical angle encoder in this embodiment is shown in FIG. 2 and includes a first circular encoding grating 110 having a plurality of fine slits arranged radially at equal angular positions; The angular position has a second circular coded grating 12 with a plurality of fine slits arranged in a radial pattern, which are arranged parallel to the first-rounded coded thumb 110 and share the middle axis; and the second-rounded code The rotating shaft 13o connected to the outer edge of the grating 120 is used to drive the rotation of the second circular coded grating 20 120. It also shares a central axis with the first circular coded grating 110, and a rotary shaft 130 is set for 70 Wanggu The body 140 of the first circular encoding grating 丨 丨 0 is fixed. A light beam is generated by a point light source 15 located outside the first circular coded grating “ο and deviated from the central axis, and directs the light beam in the direction of the first circular coded grating 11 through a spectroscopic conversion lens 16o. The light beam is extended and focused on the central axis of the first circular coded grating 11 °, and then converted into a parallel light beam through a collimating lens 1242636 170. The irradiation range of the light beam completely covers the first circular coded grating 110 and the first circular The coded grating i 20 is then reflected back to the second circular coded grating 120 and the first-rounded coded grating 11 10, and then passes through the spectroscopic conversion lens 160 to be placed in the light sensor 5 at the focusing position of the spectroscopic conversion lens 160. Detect changes in moire fringes to convert optical signals into electrical signals. Because the point light source 150 and the light sensor 丨 800 are on the same side of the first circular encoder grating 110, the second circle is driven. The rotation axis 1 of the encoder grating 1 is not obstructed by rotation, and is relatively easy to be controlled by the user. In this embodiment, the rotation axis 13 of the second circular encoder grating 12 can also be encoded with the second 10 circle. Inner edge phase of the grating 120 And pass through the central axis of the second circular encoding grating 120. In this embodiment, since the detected light beam covers the entire circumference of the circular encoding grating in the irradiation range, it is then focused on the light sensor to obtain an average Value, so it is equivalent to the signals from countless light sensor read heads, which are output by the light sensor U after being gathered. According to Equation 3, the error account is zero at this time, so the position of the grating sub-drawing line at the time of manufacture can be eliminated. Error, and eliminate the error caused by the inconsistency between the measured centerline and the centerline of the rotating shaft when the encoder is installed (the so-called eccentricity). Embodiment 2 20 The optical angle encoder in this embodiment is shown in Figure 3. A first circular encoding grating 210 having a plurality of fine slit grooves arranged radially at an equiangular position; a second circular encoding grating 220 having a plurality of fine slit grooves arranged radially at an angular position It is arranged parallel to the first circular encoding grating 210 and shares a central axis; a rotating shaft 230 connected to the outer edge of the second circular encoding light 25 grid 220 is used to drive the second circular encoding grating 12 1242636 The rotation of 220 is also related to A circular coded grating 21 0 shares a central axis; a body 240 for completely accommodating the rotating shaft 230 and fixing the first circular coded grating 21 0. A light beam is located on the central axis of the first circular coded grating. Generated by the point light source 250, it is first converted into a parallel beam by a collimating lens 27, and then passes through the first circular coded grating 210 and the second circular coded grating 22, and passes through a focusing lens 260 to convert the parallel beam. Focus on-The 28G light sensor placed at the focusing position of the focusing lens 260 is used to detect the change of the moire fringe to convert the optical signal into a telecommunication signal.

/ Because the light beam leaves the first and second rounded coding gratings 10 and 10, it will be 'focused to the light sensor' as shown in the embodiment i, and its error will be zero. This optical angle encoder can completely eliminate processing and grouping during measurement. For example, the scope of the present invention is not limited to the above. The above embodiments are only for the convenience of explanation of the scope of the claimed rights. The patent application is based on the above embodiments. 20 [Schematic description] Figure 1 is a schematic diagram of a conventional optical angle encoder

Fig. 2 is a diagram of an optical angle encoder according to the present invention Fig. 3 is a diagram of another preferred embodiment of the optical angle encoder according to the present invention

[Illustration of drawing number] 30 light source 10 ± light ^ book 20 pairs of grating 40 light sensor 13 1242636 110 first circular code 120 second circular code 130 rotary grating grating 140 body 150 point light source 160 splitting lens 170 collimation Lens 180 Light sensor 210 First circular code 220 Second circular code 230 Rotary axis grating grating 240 Body 250 Point light source 260 Focusing lens 270 Collimation lens 280 Light sensor

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Claims (1)

1242636 The scope of patent application: 1. An optical angle encoder, including a 11-shaped encoder grating, with a plurality of fine slits arranged in a radial pattern, in which the two adjacent fine slit grooves The included angles extending to the center of the circle are all equal;-the second circular coding grating has a plurality of fine slit grooves arranged in a radial pattern: wherein the included angles of any two adjacent narrow slit grooves extending to the center of the circle are equal to each other and equal to the first — Gj-shaped encoder gratings are parallel to each other and share a mandrel; The rotating shaft and the second circular coded grating are connected to each other to rotate the second circular coded grating; a body that completely or partially houses the rotating shaft with 卩 and fixes the first circularly coded light Peach; a beam is generated, upon reaching the first-.-shaped coded grating # 15 'when the second circular coded grating', the beam path is parallel to the far center axis of the "shaped-coded optical phase" and the irradiation range covers the first-circle Perimeter of shape-coded grating Two focusing lenses' after the parallel light beam passes through the first-circle-coded optical phase 14 »the first circular-coded grating of the plurality of fine slits to focus the -beam; and a light sensor , Placed at the focusing position of the focusing lens to detect the change of the 20 moire fringes, so as to convert the optical signal into an electrical signal. 2. The optical angle encoder as described in the first item of the patent application scope, wherein the rotation axis passes through the center axis of the second circular encoder grating, or the outer edge of the circular encoder grating相 连接。 Phase connection. 15 1242636 3. The optical angle knitting horse as described in item 1 of the scope of patent application, wherein the light source is a point light source, and the flat beam is generated through a collimating lens. 4. According to the optical angle coding described in item 3 of the scope of patent application, 5 When the light source is located at a position other than the central axis, the light beam is first directed toward the first circular coded light through a splitting lens The thumb is extended to focus on the central axis of the first circular coding light peach. 5. According to the optical angle deduplication device described in item 3 of the patent application scope, wherein the light source and the light sensor are located on the side of the first circular coded light peach gate 10, the light beam passes through the The first circular coded grating and the second circular coded light are reflected back to the second circular coded light and the first circular coded stone horse grating to be detected by the light sensor. 6. The optical angle encoder as described in item 3 of the scope of patent application, wherein the light source and the light sensor are located on the | 15 side of the first circular encoder grating, and the light beam penetrates the first encoder. A circular encoder grating and the second circular kinematic horse grating are detected by the light sensor. 16