JPH07225138A - Rotary encoder - Google Patents

Abstract

PURPOSE:To measure absolute angle position with high precision by comparing reference image data generated by irradiating each predetermined rotational position of a rotary disk with laser beams with an input image signal to measure a rotational angle of the rotary disk. CONSTITUTION:A laser beam from a laser light source 1 is converged into a spot of a predetermined size by a lens 2 and irradiates a disk 3. A reflected beam is detected by a TV camera 4, and a two-dimensional image signal for one round of the annular shade on the disk 3 surface where a two-dimensional image signal is outputted is converted by an A/D conversion circuit 7 and stored into a reference memory 9. Before an angle is measured, a two-dimensional image signal from a camera 4 corresponding to a rotational angle position of the disk 3 is converted by the circuit 7 and inputted into a control circuit 8. The circuit 8 compares an inputted two-dimensional digital signal with a reference image data called from the memory 9 by means of a correlator 10, senses an angle from an address of the memory 9 as obtained from the correlator 10, and displays it on a display device 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary encoder, and more particularly to a rotary encoder using a speckle pattern generated when a received laser beam is scattered.

[0002]

2. Description of the Related Art A conventional optical rotary encoder uses a rotating disk having an optical pattern or a diffraction grating to detect a rotation angle by utilizing a regular optical pattern and the action of light. Was configured into.

[0003]

However, in such a conventional encoder configuration, the performance of the encoder depends on the accuracy of the optical pattern. Therefore, it is necessary to form an accurate optical pattern on the rotating disk, and if higher resolution is to be obtained, the structure becomes complicated and expensive, and there is also a restriction on the optical pattern detection means and rotation speed. . In principle, it is impossible to compensate for errors due to deterioration of the rotating disk and temperature changes.

The object of the present invention is to detect the speckle pattern at each angular position on the scattering surface of the rotating disk, and to detect the absolute angular position with high precision and resolution with a relatively simple structure. To provide an encoder.

[0005]

In order to achieve the above object, the rotary encoder of the present invention comprises a laser light irradiating means for irradiating a rotating disc with a laser beam, and a laser at each predetermined rotating position of the rotating disc in advance. A storage means for storing reference image data having a speckle pattern generated by irradiating light, and an input image signal corresponding to a rotation position of the rotating disc are compared with the reference image data to rotate the rotating disc. The gist is to have a calculating means for measuring an angle.

[0006]

Operation: The rotating disk is irradiated with laser light, and the rotation angle of the disk is measured using the speckle pattern generated on the irradiation surface at each rotation angle position. This speckle pattern is unique to each angular position of the disk generated by the fine irregularities on the surface of the disk, so if you measure this speckle pattern in advance at each angular position, It can be used as each angular position information.

[0007]

Embodiments of the present invention shown in the drawings will be described below.
FIG. 1 shows an embodiment of a rotary encoder according to the present invention. In the figure, 1 is a laser light source composed of a semiconductor laser, 2 is a focusing lens, 3 is a rotating disk, 4 is a television camera composed of an imaging lens 5 and a two-dimensional sensor 6, etc., 7 is an A / D conversion circuit, 8 Is a control circuit including a microcomputer, 9 is a reference memory, 10 is a correlator, and 11 is a display.

Laser light from the laser light source 1 is focused on a spot having a predetermined size by a lens 2 and illuminates a disc 3. The reflected light due to this is detected by the television camera 4 and a two-dimensional image signal (analog signal) is output. Since this two-dimensional image signal has a speckle pattern specific to each angular position of the disc 3 generated by the fine irregularities on the surface of the disc 3 as described above, this speckle pattern is the disc 3 It can be used as the above rotation angle position information.

Therefore, for example, a two-dimensional image signal for one round of an annular shaded portion on the surface of the disk 3 is converted into a digital signal by the A / D conversion circuit 7 and referred to in advance as reference data corresponding to each angular position information. It is stored in the memory 9. Then, when measuring the angle, the two-dimensional image signal from the television camera 4 corresponding to the rotation angle position of the disc 3 is converted into a two-dimensional digital signal by the A / D conversion circuit 7 and input to the control circuit 8. The control circuit 8 inputs the input two-dimensional digital signal and the reference image data called from the reference memory 9,
Is added to the correlator 10 and the correspondence between the two is compared. That is, as shown in FIG. 2, the reference image data is stored in the reference memory 9 in one round AA 'to BB' of the disk 3, so that the input two-dimensional digital signal is held at the same time. The window 9a (address) of the reference memory 9 is moved to perform a search, and if it matches the called reference data, the correlator 10 obtains a correlation output. The angle can be detected from the address of the reference memory 9 when this correlation output is obtained, and the angle is displayed on the display 11. Note that AA 'and BB' are duplicated as circular data on the disk 3. Further, the two-dimensional digital signal is a multi-valued image signal having two or more values. However, since the degree of image coincidence is not sufficiently obtained with two values, it is preferable to use a multi-valued image signal having more than that. Further, the spot 1a (irradiation range) of the laser light with which the disc 3 is irradiated needs to be wider than the imaging range 1b incident on the sensor 6 as shown in FIG.

The sensor 6 may use a one-dimensional line sensor 6'as shown in FIG. In this case, the one-dimensional image signal is converted into a one-dimensional digital signal by the A / D conversion circuit 7, and as shown in FIG. 5, the one-dimensional digital signal and the one-dimensional reference image data are searched for a match to determine the rotation angle. Ask.

FIG. 6 shows an example of the input data f and the reference data g in the example of FIG. In this example, each data is
For example, the angle is obtained by moving the window (address) of the reference memory 9 and searching the address of the place matching the input data with digital data composed of multi-valued gradations. The degree of coincidence h _{j in} this case, after being subjected to normalization processing and the like,

[Equation 1] j = 0, 1, 2, ..., N-1, (where j is_n= J₀, J_{n + 1}
= J₁... ) Ask. Degree of coincidence h_jAddress j of the reference memory showing the maximum value of
The angle can be calculated from This j is an integer
However, as shown in FIG. 7, for example, j−1, j, j + 1
The maximum value j from the three points in the quadratic approximation_maxInterpolation calculation such as obtaining
To obtain the degree of coincidence with the coordinate accuracy of the pixel unit of the image or less
You can also

It is effective for adjustment to form a simple pattern in advance in addition to the speckle pattern at each predetermined angular position of the disk 3. Further, it is preferable to regularly update the speckle pattern (reference data) stored in the memory.

[0013]

As described above, according to the present invention, the speckle pattern for one round is stored in the memory in advance without providing the disc with the optical pattern for accurate angle detection as in the conventional case. It is possible to perform accurate angle detection only by setting it in advance, and it is possible to obtain an inexpensive encoder with a relatively simple structure. Moreover, by periodically updating the speckle pattern, it is possible to compensate for errors due to deterioration of the disk and temperature changes.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of the above embodiment.

FIG. 3 is an explanatory diagram showing a relationship between a laser light irradiation range and an imaging range.

FIG. 4 is a block diagram showing another embodiment of the present invention.

FIG. 5 is an operation explanatory diagram of the embodiment in FIG.

FIG. 6 is a diagram showing an example of input data and reference data.

FIG. 7 is an explanatory diagram of an interpolation calculation for obtaining the maximum value of the degree of coincidence.

[Explanation of symbols]

 1 Laser Light Source 3 Disc 4 TV Camera 6 Sensor 7 A / D Conversion Circuit 8 Control Circuit 9 Memory 10 Correlator 11 Display

Claims (1)

[Claims] 1. A laser light irradiating means for irradiating a rotating disk with a laser beam, and reference image data having a speckle pattern generated by irradiating a predetermined rotating position of the rotating disk with the laser beam in advance is stored. A rotary encoder comprising: a storage unit; and a calculation unit that compares an input image signal corresponding to a rotation position of the rotating disc with the reference image data to measure a rotation angle of the rotating disc. .