JPH0727576A - Absolute encoder - Google Patents

Abstract

(57) [Abstract] [Purpose] Even if dust adheres to the linear image sensor, the rotation angle can be measured more accurately. [Structure] Light emitted from a light emitting diode 4 is projected onto a pattern forming portion of a rotating disk 2 in which a pattern Ps corresponding to a rotation angle is continuously formed in a circumferential direction, and the pattern Ps
The linear image sensor 9 receives the light that has passed through.
The image sensor 9 includes, for example, three sensor units 1
A CCD in which 0 ₁ , 10 ₂ , and 10 ₃ are arranged in parallel, and three sensor units 1 that read one pattern Ps
Even if _one of the outputs 0 ₁ , 10 ₂ , and 10 ₃ is erroneous data due to the adhesion of dust, if the other two data match, it is output as accurate data and the angle measurement value is displayed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an absolute encoder used, for example, in an angle measuring instrument.

[0002]

2. Description of the Related Art A conventional absolute encoder projects light from a light emitting unit onto, for example, a rotating disk, and allows a linear image sensor to receive the light transmitted through a slit pattern of the rotating disk through a lens of an imaging system. The rotation angle of the disk is calculated by the arithmetic processing circuit based on the signal corresponding to the slit pattern output from the sensor.

[0003]

In the absolute encoder described above, since the CCD which is the linear image sensor is formed by arranging a large number of light receiving elements having a size of, for example, 14 μm × 14 μm continuously. If dust adheres to or is defective on the pattern forming position of the disc or the light receiving element of the CCD, it causes a reading error. That is, dust and defects are 10 μm
In many cases, the size of the slit pattern is larger or larger, and the shadow of the defect appears on the light receiving element of the CCD, so that the slit pattern cannot be accurately read.

An object of the present invention is to provide an absolute encoder capable of reading a more accurate movement amount, for example, a rotation angle, even if dust is attached and the linear image sensor has a defect.

[0005]

In order to achieve the above-mentioned object, the present invention projects a moving body in which a pattern corresponding to a moving amount is continuously formed in the moving direction and a pattern forming position of the moving body. A light emitting unit and a linear light-receiving unit that receives light corresponding to the pattern obtained by projecting light from the light emitting unit onto the moving body and outputs a signal corresponding to the pattern.
In an absolute encoder provided with an image sensor and an arithmetic processing means for arithmetically processing a moving amount of the moving body from an output signal of the linear image sensor, in the linear image sensor, light receiving elements are continuously arranged. A plurality of sensor units configured as described above are arranged at predetermined intervals and arranged in an odd number, and when the output signals of more than half of the sensor units match, the arithmetic processing means outputs the mobile unit from the output signals. Is calculated.

[0006]

In the linear image sensor, a plurality of sensor units are provided in the width direction of the moving body at a predetermined distance from each other, and an odd number is provided, so that the light from the light emitting portion is projected onto the moving body. The plurality of odd-numbered sensor units simultaneously receive the light of the pattern corresponding to the movement amount obtained by the above. Therefore, even if less than half of the entire sensor unit erroneously reads the pattern corresponding to the movement amount due to adhesion of dust or the like, the remaining sensor units of more than half of the entire unit accurately read the pattern corresponding to the movement amount, The arithmetic processing means obtains the moving amount of the moving body based on the output signals of the sensor units of more than half of the rest.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the structure of a pattern reading unit according to an embodiment of the present invention.

In the figure, 1 is a light emitting part, 2 is a rotating disk, and 3 is a light receiving part. The light emitting unit 1 is, for example, red 66
Light-emitting diode (LED) that emits 0 μm visible light
4, a collimation lens 5 and a prism 6 for projecting the visible light to the pattern forming position of the rotary disk 2. The rotary disc 2 has a slit pattern Ps corresponding to a rotation angle formed in the radial direction.
Are continuously formed in the circumferential direction. The light receiving section 3 is composed of a prism 7, an image forming system lens 8 and a linear image sensor 9, and the linear image sensor 9 is connected to an arithmetic processing means described later. The above configuration is not particularly different from the conventional one.

The linear image sensor (CC of the present invention
D) 9 is, for example, three Cs arranged side by side at a predetermined interval.
Sensor units 10 ₁ , 10 ₂ , 1 composed of CD units
0 ₃ , each sensor unit 10 ₁ , 10 ₂ , 10 ₃
Is configured such that the light receiving elements are continuously arranged in the tangential direction of the rotating disk 2.

FIG. 2 is a block diagram of another embodiment of the present invention. In the figure, the light emitting diode 4 is an LED drive circuit 12 operated by an LED drive timing circuit 11.
The linear image sensor 9 is connected to the A / D converter 15 via the CCD waveform shaping circuit 14 and is operated by the CCD operation timing circuit 13. The A / D converter is operated by the A / D converter timing circuit 16. Reference numeral 15 is connected to the CPU 17. Reference numeral 18 is a ROM, 19 is a RAM, and 20 is a key and display unit. The LED drive timing circuit 11, C
The CD operation timing circuit 13 and the A / D converter timing circuit 16 are both controlled by the CPU 17.

The operation of this embodiment will be described with reference to the flow chart shown in FIG. The LED drive timing circuit 11 operates the LED drive circuit 12 to turn on the light emitting diode 4, and this light is converted into parallel light by the collimation lens 5 and projected onto the slit pattern Ps of the rotating disk 2. The light transmitted through the slit pattern Ps is imaged on the linear image sensor 9 via the prisms 6 and 7 and the imaging system lens 8, and the photo diode array is set (steps S ₁ and S _2). ). Next, the CCD operation timing circuit 13 is activated, and _first the photo diode of the sensor unit 10 ₁ of the linear image sensor 9 is connected.
The charges of the array are sent to the transfer gate by the transfer gate (step S ₃ ), the light emitting diode 4 is turned off (step S ₄ ), and then the CCD transfer register is shifted, reset, and sampled and held to correspond to the slit pattern. The signal is output from the linear image sensor 9. Similarly, the remaining sensor units 10 ₂ and 10 ₃ are sequentially operated to sequentially output signals corresponding to the slit patterns on the sensor units 10 ₂ and 10 ₃ from the linear image sensor 9 (step S ₅ ). Linear image sensor 9
The output signal of is waveform-shaped by the CCD waveform shaping circuit 14 and input to the A / D converter 15, converted from an analog signal to a digital signal (step S ₆ ), and stored in the memory (RAM) 19 (step S ₆ ). S ₇ ), CPU
In 17, the ROM and the code pattern data corresponding to the slit pattern stored in the memory (RAM) 19
The code pattern data stored in 18 is compared and converted into an angle (step S ₈ ). CPU17
Determines whether or not the two or more angular positions obtained by the sensor units 10 ₁ , 10 ₂ , and 10 ₃ match (step S ₉ ), and if they do not match, an error is displayed on the display unit 20. (step S _10),
When a match two or more displays an angle corresponding to the slit pattern (step S _11). The present invention can also be applied to a linear encoder.

[0013]

As described above, according to the present invention, a plurality of linear image sensors (sensor units each of which is formed by continuously arranging light receiving elements) are arranged at a predetermined interval and are arranged in an odd number. When the output signals of more than half of the sensor units match, the arithmetic processing means calculates the moving amount of the moving body from the output signals.
Even if dust adheres to the image sensor and is defective, the accuracy of the measured value can be increased.

[Brief description of drawings]

FIG. 1 is a perspective view of a pattern reading unit according to an embodiment of the present invention.

FIG. 2 is a block diagram of another embodiment of the present invention.

FIG. 3 is a flowchart of the present invention.

[Explanation of symbols]

1 Light emitting part 2 Rotating disk 3
Light receiving part 4 Light emitting diode 9 Linear image sensor 10 ₁ , 10 ₂ , 10 ₃ Sensor unit 17
CPU 18 ROM 19 RAM

Claims (1)

[Claims] 1. A moving body in which a pattern corresponding to a moving amount is continuously formed in a moving direction, a light emitting section that projects light to a pattern forming position of the moving body, and light from the light emitting section is projected onto the moving body. Linear that receives light corresponding to the pattern obtained by illuminating and outputs a signal corresponding to the pattern
In an absolute encoder provided with an image sensor and an arithmetic processing means for arithmetically processing a moving amount of the moving body from an output signal of the linear image sensor, in the linear image sensor, light receiving elements are continuously arranged. A plurality of sensor units configured as described above are arranged at predetermined intervals and arranged in an odd number, and when the output signals of more than half of the sensor units match, the arithmetic processing means outputs the mobile unit from the output signals. An absolute encoder characterized in that it calculates the amount of movement of the.