JP2013002874A - Encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that an absolute rotary encoder for detecting an absolute position requires as many light receiving elements as the number of coding bits of a certain absolute pattern such as gray code, and to enhance the resolution entails an increase in the number of coding bits and accordingly a more complex structure, leading to high cost.SOLUTION: An absolute encoder is provided that measures the distance to a reflecting plate of a rotating disk, whose reflecting plate linearly varies in height with the rotational angle of the rotating body, with an optical sensor and calculates the absolute position of the rotating body from the measured distance.

Description

  The present invention relates to an absolute position detection technique.

  Optical encoders are widely used to detect physical analog quantities relating to movements such as the movement amount, angle, position, and speed of a rotating body as digital quantities. A general rotary encoder irradiates a rotary signal plate provided with a necessary signal pattern with uniform light from one side by a light emitting element such as a light emitting diode or LED, and transmits light after passing through the signal pattern, or Reflected light from the signal plate is received and detected by a light receiving element such as a photodiode or a phototransistor. In terms of functionality, there are incremental and absolute rotary encoders.

  Incremental rotary encoders generally output a pulse signal corresponding to the rotation angle of the rotating shaft. Specifically, light is irradiated to a binary signal (bright / dark) pattern at equal intervals or a rotating signal plate provided with equally spaced transmission / shielding slits concentrically, and reflected light from each pattern, Alternatively, the rotation angle and the rotation amount from the reference point are relatively detected by integrating and counting regular pulse signals obtained by converting the transmitted light from each slit into digital. In addition, this incremental rotary encoder has a feature that an initialization for setting a reference point is required every time the power is turned on.

  On the other hand, an absolute type rotary encoder generally converts an absolute value of a rotation angle of a rotary shaft into a binary value and outputs the binary value. Specifically, a plurality of tracks formed concentrically are irradiated with light on a rotating signal plate on which a desired signal pattern (absolute pattern) is formed, and reflected light or transmitted light from each signal pattern is irradiated. , The binary bits “0” and “1” are read to detect the absolute rotational angle and rotational position of the rotating body. Further, this absolute rotary encoder can detect the current position by reading the above-mentioned absolute pattern when the power is turned on, so that initialization is unnecessary.

In the absolute type rotary encoder, the resolution of the encoder is determined by the number of code bits of the absolute pattern formed concentrically on the rotation signal plate. If the number of code bits is n, an encoder signal obtained by dividing one rotation (360 degrees) by 2 to the power of n is obtained. For example, if a 10-bit absolute pattern is used, an encoder signal obtained by dividing one rotation into 2 to the 10th power (= 1024) can be obtained.
Patent Document 1 discloses an optical absolute that forms a curve whose radius varies according to a rotation angle on a rotating disk and outputs a two-phase signal based on a signal obtained by measuring the radius at two locations and an incremental signal. An encoder is disclosed.

JP-A-9-096544

The absolute encoder has a feature that an absolute position can be detected. On the other hand, when trying to increase the resolution, a multi-bit absolute pattern and a number of sensors are used to detect the pattern. There is a problem that the configuration is complicated and the cost is drastically increased.
The present invention has been made in view of the above problems, and provides an absolute encoder technique that simplifies the configuration of the entire apparatus and reduces the cost.

  In order to solve the above-described problem, a position detection device according to the present invention is an absolute encoder that detects an absolute value of a rotation angle of a shaft, and rotates in conjunction with an irradiation unit that emits light and a shaft. A rotating member, reflecting means for reflecting light from the irradiating means, and changing a position from the irradiating means to the reflecting surface according to a rotation angle of the shaft; and light receiving for receiving reflected light reflected by the reflecting means Means, a measuring means for measuring the distance from the irradiating means to the reflecting surface of the reflecting means based on the reflected light received by the light receiving means, and the rotation of the shaft based on the distance measured by the measuring means Output means for outputting the absolute value of the corner.

  According to the present invention, since the absolute position is detected by measuring the distance to the reflector, it is possible to obtain absolute values with high resolution without forming a complex absolute pattern or using a large number of light receiving sensors. It is possible to detect the position. Further, since the configuration is simple, the cost of the entire apparatus can be reduced.

It is a block diagram of an optical sensor part. It is a wave form diagram which shows the output waveform of a light receiving element. It is a block diagram of an absolute encoder. It is a block diagram of an absolute position detection part. It is an internal block diagram of a signal processing part. It is a flowchart which shows the process of absolute position detection. It is a block diagram of an absolute encoder (Embodiment 2). It is a block diagram of an absolute encoder (third embodiment). It is a block diagram of an absolute position detection part. It is an internal block diagram of a signal processing part. It is a flowchart which shows the process of absolute position detection. It is a block diagram of an absolute encoder (Embodiment 4).

(Embodiment 1)
Hereinafter, Embodiment 1 which is one embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic diagram illustrating a configuration of an optical sensor unit 110 of an absolute encoder as a position detection device according to the first embodiment. The optical sensor unit 110 includes a light source 101 having a laser diode, an LED, and the like, a condensing lens 102 that condenses light from the light source on the surface of the reflection plate 105, and light reception that forms an image of light reflected from the reflection plate 105 on a light receiving element. A lens 103 and a light receiving element array 104 that captures a spatial intensity distribution of an image formed on the light receiving lens are provided. Although details of the reflecting plate will be described later, it is assumed that the reflecting plate has a function of varying the position from the light receiving element array to the reflecting surface in accordance with the rotation angle of the rotating shaft.

  FIG. 2 shows an output waveform from the light receiving element array 104.

  The graph of FIG. 2 shows a peak waveform in which the center outputted from the light receiving element array 104 is maximum, with the vertical axis representing “light quantity” and the horizontal axis representing “light receiving element position”. Reference numeral 201 denotes a reflection waveform at a certain reflection position. Similarly, reference numeral 202 denotes a reflection waveform at a reflection position different from 201.

  Thus, the reflected light images are formed at different positions on the light receiving element array 104 in accordance with the difference in reflection position (the difference in distance from the optical sensor unit 110 to the reflection plate 105). By detecting the peak position (center position) of the reflected waveform when the light is reflected by the reflecting plate 105, the distance from the optical sensor unit 110 to the reflecting plate 105 is measured. The configuration in FIG. 1 and the mechanism in FIG. 2 are general contents as a laser displacement meter using triangulation.

  FIG. 3 shows the configuration of the absolute encoder of the first embodiment.

  The absolute encoder shown in FIG. 3 is configured on a rotating disk part (rotating member) 302 that rotates in conjunction with the rotation of the rotating shaft 301 of the motor, and is reflected on the rotating angle of the rotating shaft. A reflection plate 303 and an optical sensor unit 110 are formed so that the height of the surface changes linearly. In the configuration of FIG. 3, the light source 101 irradiates the reflector 303 from the axial direction of the rotating shaft 301.

  First, when the rotating shaft 301 of the motor rotates, the rotating disk portion 302 rotates in conjunction with it. Since the height of the reflection plate 303 changes linearly according to the rotation angle of the rotation shaft 301, the distance from the reflection plate 303 is measured using the optical sensor unit every time it rotates. Next, based on the measured distance value, the absolute position of the motor (the absolute value of the rotation angle) is calculated with reference to the value of the absolute position conversion table 510 described later. In the absolute position conversion table 510, the absolute position value of the motor corresponding to the distance between the optical sensor unit 110 and the reflecting plate 303 is stored in advance. As a storage method, for example, the absolute position value of the motor corresponding to the measured distance value may be stored in the absolute position conversion table 510 at the time of product shipment or during periodic calibration.

  FIG. 4 shows a configuration diagram of an absolute position detection unit including the optical sensor unit 110.

  As shown in FIG. 4, the absolute position detection unit converts the reflection waveform obtained from the optical sensor unit 110 and the light receiving element array 104 into a digital signal, and stores a digital signal and a storage unit 401 and a storage unit 401. The signal processing unit 402 calculates the absolute position of the motor from the reflected waveform data stored in the.

  FIG. 5 is a block diagram illustrating a schematic configuration of the signal processing unit 402 that calculates the absolute position of the motor from the reflected waveform data captured by the light receiving element array 104.

  The peak detector 501 detects the peak position indicating the highest intensity of the reflected waveform data stored in the storage unit 401. The light receiving element position detection unit 502 detects the position of the light receiving element that images the peak position of the reflected waveform data detected by the peak detection unit 501. The distance calculation unit 503 calculates the distance between the optical sensor unit 110 and the reflection plate 303 based on the position of the light receiving element that captures the peak position of the reflected waveform data. The absolute position conversion table 510 stores a value of the absolute position of the motor corresponding to the distance between the optical sensor unit 110 and the reflection plate 303 in advance. Based on the distance value calculated by the distance calculation unit 503, the absolute position calculation unit 504 refers to the value stored in the absolute position conversion table 510 and calculates the absolute position of the motor.

  FIG. 6 is a flowchart showing a process for detecting the absolute position of the motor.

  In step S101, the light source 101 emits light. In step S102, the light receiving element array 104 receives the reflected light. In step S103, the storage unit 401 stores the received reflected waveform data. In step S104, the peak detector 501 detects the peak of the reflected waveform data. In step S105, the light receiving element position detection unit 502 detects the position of the light receiving element that has received the detected peak. In step S106, the distance calculation unit 503 calculates the distance from the position of the light receiving element to the reflecting surface. In step S107, the absolute position calculation unit 504 calculates the absolute position of the motor with reference to the values in the absolute position conversion table.

  As described above, according to the first embodiment, since the absolute position of the rotating body is detected by measuring the distance to the reflecting plate, a complicated absolute pattern or the like is formed on the rotating disk, The absolute position of the motor can be detected with high resolution without using a light receiving sensor.

(Embodiment 2)
FIG. 7 is a schematic diagram illustrating a configuration of an absolute encoder according to the second embodiment. In addition, about the structure similar to Embodiment 1, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted about what does not change functionally.

  The absolute encoder shown in FIG. 7 includes a reflecting plate 703 on the outer periphery, and has a rotating disc portion 702 whose radius from the rotating shaft to the light source direction changes linearly according to the rotating angle of the rotating shaft. Therefore, the optical sensor unit 110 irradiates light substantially perpendicularly to the rotating shaft 301 in order to measure the distance from the reflecting plate 703.

First, when the rotating shaft 301 of the motor rotates, the rotating disk portion 702 rotates in conjunction with it. Since the reflection plate 703 linearly changes its rotation radius according to the amount of rotation of the rotation shaft 301, the optical sensor unit is used for each rotation to measure the distance from the reflection plate 703. Based on the measured distance value, the absolute position of the motor is calculated with reference to the value in the absolute position conversion table 510.
As in the first embodiment, the absolute position conversion table 510 stores an absolute position value corresponding to the distance between the optical sensor unit 110 and the reflection plate 303 in advance.

  As described above, in the second embodiment, the distance from the reflector to the optical sensor unit is measured and the absolute position of the motor is detected by using a rotating disk whose rotation radius changes linearly according to the rotation amount of the motor. ing.

(Embodiment 3)
In Embodiment 1, the example which measures the distance from a reflecting plate to an optical sensor part by the structure using a reflecting plate formed so that height changes linearly according to the rotation amount of a motor was shown. However, this is based on the premise that the rotating disk part is ideally rotated horizontally, and the position of the reflector formed on the rotating disk part is delicately affected by uneven rotation and eccentricity of the motor. It was not taken into account that it would shake up and down. Therefore, in this embodiment, attention is paid to the blurring of the position of the reflecting plate.

  FIG. 8 shows a configuration diagram of an absolute encoder in the third embodiment.

  The rotating shaft 301 of the motor, the rotating disk portion 802 that rotates in conjunction with the rotating shaft 301, and the rotating disk portion 802 are configured so that the height changes linearly according to the amount of rotation of the rotating shaft. Further, a reference reflector 803 is provided which is configured on the reflector 303 and the rotating disk portion 802 and formed so as to have a constant height regardless of the amount of rotation of the rotating shaft. However, “the height is constant regardless of the amount of rotation of the rotating shaft” does not include the position blur of the reflector due to the influence of rotation unevenness or the like. In the optical sensor unit, a light source 101 composed of a laser diode or the like, a spectroscopic lens 801 that divides and condenses light from the light source on the surfaces of the reflector 303 and the reference reflector 803, the reflector 303, and the reference The light receiving lens 103 forms an image of the light reflected from the reflecting plate 803 on the light receiving element, and the light receiving element array 104 picks up the spatial intensity distribution of the image formed on the light receiving lens.

  In the configuration diagram of FIG. 8, the light source, the spectroscopic lens, the light receiving lens, and the light receiving element array are shown to be used in common, but the configuration is not particularly limited here. The light source, the condensing lens, the light receiving lens, and the light receiving element array may be separately provided for the light source and the reference reflector 803, respectively. It is also possible to use a combination of what is commonly used and what is used separately.

  First, the distance between the reflection plate 303 whose height changes linearly according to the amount of rotation of the rotating shaft 301 and the optical sensor unit is measured, and then the reference is constant regardless of the amount of rotation of the rotating shaft 301. The distance between the reflector 803 and the optical sensor unit is measured. And the height of the reflecting plate 303 is detected by taking the difference between the measured distances. This is expressed by the following equation.

“Distance from optical sensor unit to reference reflector 803” − “Distance from optical sensor unit to reflector 303” = “Height of reflector 303”
The height value of the reflection plate 303 is not affected even if there is rotation unevenness or eccentricity of the motor, and can be handled as an invariable value.

  Next, based on the measured height value of the reflector 303, the absolute position of the motor is calculated with reference to values in an absolute position conversion table 1010 described later. In this absolute position conversion table 1010, it is assumed that the absolute position value corresponding to the height value of the reflector 303 is stored in advance. As a storage method, for example, the absolute position value of the motor corresponding to the measured height of the reflector 303 may be stored in the absolute position conversion table 1010 at the time of product shipment or during periodic calibration.

  FIG. 9 shows a configuration diagram of an absolute position detection unit including an optical sensor unit.

  As shown in FIG. 9, the absolute position detection unit includes the above-described optical sensor unit (light source 101, spectroscopic lens 801, light receiving lens 103, light receiving element array 104), and a reflector (first optical element) obtained from the light receiving element array 104. The waveform (first waveform data) of the reflected light (first reflected light) from the reflecting plate 303 is converted into a digital signal, and the digital signal is stored in the storage unit 901 and the reference reflecting plate (second reflecting plate) 803. The waveform (second waveform data) of the reflected light (second reflected light) is converted into a digital signal, and the storage unit 902 that stores the digital signal, the storage unit 901, and the reflected waveform data stored in the storage unit 902, the first The signal processing unit 903 is configured to acquire a first distance corresponding to the reflected light and a second distance corresponding to the second reflected light, and to calculate the absolute position of the motor based on the difference between them.

  FIG. 10 shows an internal block of the signal processing unit 903 that calculates the absolute position of the motor from the reflected waveform data captured by the light receiving element array 104.

  The peak detector 1001 detects the peak position (first and second center positions) indicating the highest intensity of the reflected waveform data stored in the storage unit 901. The peak detection unit 1002 detects the peak position indicating the highest intensity of the reflected waveform data stored in the storage unit 902.

  The light receiving element position detection unit 1003 detects the position of the light receiving element that images the peak position of the reflected waveform data detected by the peak detection unit 1001. The light receiving element position detection unit 1004 detects the position of the light receiving element that images the peak position of the reflected waveform data detected by the peak detection unit 1002.

  The distance calculation unit 1005 calculates the distance between the optical sensor unit and the reflection plate 303 based on the position of the light receiving element that captures the peak position of the reflected waveform data. The distance calculation unit 1006 calculates the distance between the optical sensor unit and the reference reflector 803 based on the position of the light receiving element that captures the peak position of the reflected waveform data.

  The difference detection unit 1007 obtains a difference between the calculated distance between the optical sensor unit and the reflection plate 303 and the calculated distance between the optical sensor unit and the reference reflection plate 803.

  The absolute position conversion table 1010 stores the absolute position value of the motor corresponding to the height value of the reflector 303 in advance. The absolute position calculation unit 1008 calculates the absolute position of the motor with reference to the value stored in the absolute position conversion table 1010 based on the height value of the reflector 303 calculated by the difference detection unit 1007.

  FIG. 11 shows a flow of detecting the absolute position of the motor in the third embodiment.

  Step S201 represents a step of irradiating light from the light source 101. Step S202 represents a step of splitting the irradiation light with the spectroscopic lens. Step S <b> 203 represents a step of receiving reflected light by the light receiving element array 104.

  Step S204 represents a step of storing the reflected waveform data from the reflector 303 in the storage unit 901. Step S205 represents a step of detecting the peak of the reflected waveform data. Step S206 represents a step of detecting the position of the light receiving element that has received the detected peak. Step S207 represents a step of calculating the distance from the optical sensor unit to the reflecting plate 303 based on the position of the light receiving element.

  Step S208 represents the step of storing the reflected waveform data from the reference reflector 803 in the storage unit 902. Step S209 represents a step of detecting the peak of the reflected waveform data. Step S210 represents a step of detecting the position of the light receiving element that has received the detected peak. Step S211 represents a step of calculating the distance from the optical sensor unit to the reflection plate 803 based on the position of the light receiving element.

  Step S212 represents a step of calculating a difference between the distance from the optical sensor unit to the reflecting plate 303 and the distance from the optical sensor unit to the reference reflecting plate 803. The difference value calculated here is the height value of the reflector 303. Step S213 represents a step of calculating the absolute position of the motor with reference to the value of the absolute position conversion table 1010 based on the calculated height value of the reflector 303.

  As described above, according to the third embodiment, the difference between the distance from the optical sensor unit to the reflection plate 303 and the distance from the optical sensor unit to the reference reflection plate 803 is calculated, and the motor is calculated from the height value of the reflection plate 303. The absolute position of was detected. This makes it possible to detect the absolute position of the motor with high accuracy without being affected by the rotating disk portion 802 that is slightly shaken up and down due to uneven rotation or eccentricity of the motor. .

(Embodiment 4)
FIG. 12 shows a configuration diagram of the absolute encoder according to the fourth embodiment as viewed from above. Since the configuration other than the configuration diagram of FIG. 12 is the same as that of the third embodiment, the description other than FIG. 12 is omitted.

  The rotating shaft 301 of the motor, the rotating disc portion 1002 that rotates in conjunction with the rotating shaft 301, and the radius of the rotating disc portion 1002 are formed to change linearly according to the amount of rotation of the rotating shaft. A reflection plate 703 is provided on the outer periphery of the disc portion 1002. A reference reflector 1003 is provided on the outer periphery of a perfect circle that is configured on the rotating disk portion 1002 and has a rotation axis as a center. In the optical sensor unit, a light source 101 composed of a laser diode or the like, a spectroscopic lens 801 for reflecting and condensing light from the light source onto the respective surfaces of the reflecting plate 703 and the reference reflecting plate 1003, a reflecting plate 703, and a reference The light receiving lens 103 forms an image of light reflected from the reflecting plate 1003 on the light receiving element, and the light receiving element array 104 picks up the spatial intensity distribution of the image formed on the light receiving lens.

  In the configuration diagram of FIG. 12, the light source, the spectroscopic lens, the light receiving lens, and the light receiving element array are commonly used. However, the configuration is not particularly limited, and for example, the reflector 703 is used. The light source, the condensing lens, the light receiving lens, and the light receiving element array may be separately provided for the light source and the reference reflector 1003. It is also possible to use a combination of what is commonly used and what is used separately.

  First, the distance between the reflection plate 703 whose radius changes linearly according to the rotation amount of the rotation shaft 301 and the optical sensor unit is measured, and then the reference reflection plate whose radius is constant regardless of the rotation amount of the rotation shaft 301. The distance between 1003 and the optical sensor unit is measured. And the distance from the reference | standard reflecting plate 1003 to the reflecting plate 703 is detected by taking the difference of each measured distance. This is expressed by the following equation.

“Distance from optical sensor unit to reference reflector 1003” − “Distance from optical sensor unit to reflector 703” = “Distance from reference reflector 1003 to reflector 703”
The value of the distance from the reference reflecting plate 1003 to the reflecting plate 703 can be handled as an invariant value without being affected even if there is uneven rotation or eccentricity of the motor.

Next, based on the measured value of the distance from the reference reflector 1003 to the reflector 703, the absolute position of the motor is calculated with reference to the value of the absolute position conversion table 1010.
As in the third embodiment, the absolute position conversion table 1010 stores the absolute position value of the motor corresponding to the distance from the reflecting plate 703 to the reference reflecting plate 1003 in advance.

  As described above, according to the fourth embodiment, the difference between the distance from the optical sensor unit to the reflection plate 703 and the distance from the optical sensor unit to the reference reflection plate 1003 is calculated, and from the reference reflection plate 1003 to the reflection plate 703. The absolute position of the motor is detected from the distance value. As a result, even if the rotating disk portion 1002 rotates eccentrically due to uneven rotation or eccentricity of the motor, the absolute position of the motor can be accurately detected without being affected by the rotation.

  In the above-described embodiment, a single rotary encoder has been described. For example, the present invention can be applied to a surveillance camera or the like.

  Assuming a case where the supply of power is temporarily stopped due to a power failure or the like and is restored again, in the case of a surveillance camera equipped with a conventional incremental rotary encoder, an initialization operation is performed immediately after the restoration of the power. That is, the lens part of the surveillance camera is once moved to the initial position, and after the initialization operation, the lens is returned to the position when the power is stopped. The procedure of resuming video recording was essential.

  However, in the case of a surveillance camera equipped with the absolute rotary encoder of the present invention, there is no need for initialization, so that when the power is restored, video recording can be resumed at the current position. is there. In addition, unlike Patent Document 1, it is not necessary to detect an absolute position using a plurality of signals, the position detection process is simple, and there is no need to provide a large number of sensors, so that the apparatus can be reduced in size and cost. It becomes possible.

  In the above-described embodiment, an example using a triangulation optical sensor has been described. However, a laser focus optical sensor may be used. Further, since the present invention is a method of changing the position of the measurement reference plane according to the rotation angle of the rotation shaft, the present invention can be similarly applied even if another displacement measurement method is used. However, since it is a rotating body, it is preferably a non-contact type non-contact displacement meter.

  Further, although the displacement meter has been described as measuring the distance from the sensor to the reflecting surface each time it rotates, it may be measured simply at a predetermined sampling period. In addition, sampling may be started in response to an external trigger (power on, predetermined mode start). In the above description, the absolute encoder used for the rotating member has been described. However, not only the rotating member but also other moving members that move such as parallel movements are detected from reports perpendicular to the moving direction of the moving member. The present invention can be widely applied to position detection technology. In this case, it is preferable that the moving member is provided with a member that varies the distance measured by the displacement meter according to the moving amount of the moving member.

Claims (8)

An absolute encoder that detects the absolute value of the rotation angle of the shaft,
Irradiating means for irradiating light;
A rotating member that rotates in conjunction with the shaft;
Reflecting means for reflecting light from the irradiating means and changing the position from the irradiating means to the reflecting surface according to the rotation angle of the shaft;
A light receiving means for receiving the reflected light reflected by the reflecting means;
Measuring means for measuring a distance from the irradiating means to the reflecting surface of the reflecting means based on the reflected light received by the light receiving means;
An absolute encoder having output means for outputting an absolute value of the rotation angle of the shaft based on the distance measured by the measuring means.   The light receiving means further includes an image pickup means for picking up waveform data corresponding to reflected light reflected by the reflection means, and a detection means for detecting a center position of the waveform data picked up by the image pickup means. 2. The absolute encoder according to claim 1, wherein the means measures the distance from the irradiating means to the reflecting surface of the reflecting means based on the center position detected by the detecting means.   The reflecting means is provided on a surface substantially perpendicular to the axis of the rotating member so that the height of the reflecting surface changes linearly according to the rotation angle of the axis, and the irradiating means is arranged on the axis with respect to the reflecting means. The absolute encoder according to claim 1, wherein light is emitted from the axial direction of the encoder.   The reflecting means is provided on the outer periphery of the rotating member such that the height of the reflecting surface changes linearly according to the rotation angle of the shaft, and the irradiating means emits light from a direction perpendicular to the axis with respect to the reflecting means. The absolute encoder according to claim 1, wherein the absolute encoder is irradiated. An absolute encoder that detects the absolute value of the rotation angle of the shaft,
Irradiating means for irradiating light;
A rotating member that rotates in conjunction with the shaft;
First reflecting means for reflecting light from the irradiating means as first reflected light, and varying a position from the irradiating means to the reflecting surface according to a rotation angle of the shaft;
Second reflecting means for reflecting light from the irradiation means as second reflected light regardless of the rotation angle of the shaft;
Light receiving means for receiving the first and second reflected lights reflected by the first and second reflecting means, and an absolute value of the rotation angle of the shaft based on the first and second reflected lights received by the light receiving means An absolute encoder.   The light receiving means includes an image pickup means for picking up first and second waveform data corresponding to the first and second reflected light reflected by the first and second reflection means, and a first image picked up by the image pickup means, The output means further comprises detection means for detecting the first and second center positions of the second waveform data, and measurement means for acquiring the first and second distances based on the center position detected by the detection means. 6. The absolute encoder according to claim 5, wherein an absolute value of a rotation angle of the shaft is output based on a difference between the first and second distances.   An absolute encoder that detects an absolute position of a moving member from a direction perpendicular to a moving direction of the moving member, and includes a non-contact displacement meter and a non-contact displacement meter according to a movement amount of the moving member. An absolute type encoder comprising: displacement means for varying a displacement to be measured; and output means for outputting an absolute position of the moving member based on a distance measured by the non-contact displacement meter. A first reflector attached to an outer periphery of a circle configured to rotate in conjunction with an axis and linearly change a radius of the circle according to a rotation angle;
A rotating disk portion having a second reflector attached to the outer periphery of a circle configured so that the radius of the circle is constant regardless of the rotation angle;
Irradiating means for irradiating light to the first and second reflectors;
Imaging means for imaging waveform data corresponding to reflected light reflected by the first and second reflectors;
Detecting means for detecting a center position of the waveform data imaged by the imaging means;
Measurement means for measuring the distance to the reflection position of the reflector based on the center position detected by the detection means;
Output means for outputting an absolute value of the rotation angle of the shaft based on a difference between the distance to the first reflecting plate and the distance to the second reflecting plate measured by the measuring means. An absolute encoder.

Images