JPH0263162B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that uses an encoder to automatically test the amount of eccentricity accompanying the rotation of a scale disc of an electronic goniometer or the like.

Electronic goniometers using encoders generally measure the angle of rotation by rotating one of two scale disks with radial slit rows relative to the other, and photoelectrically counting the moiré fringes that occur at this time. It is something. Therefore, if the axis of rotation of the scale disk is eccentric, the photoelectric detection signal will undergo amplitude modulation, resulting in a large angle measurement error. This eccentricity of the rotating shaft is caused by purely mechanical factors such as unadjusted rotational axis and eccentricity of the center hole of the scale disk. The method that has been used is
First, the roundness of the circumference of the scale disc is ensured by precision machining, and the eccentricity is adjusted by reading the indicator scale while contacting the outer edge with a filler such as a micro indicator. Circular marking lines are provided on the outer edge of the scale area of the disc, or marks are provided at constant radius positions every 90° to 180°, and the radial direction of the marking lines or marks as the disc rotates. There is a method that measures the fluctuations in using a reading microscope.

These methods have traditionally been used to adjust optical theodolites and circumferential scale marking machines, and although they achieve the initial purpose of eliminating eccentricity of the rotating shaft, the first method described above Not only does this require precision machining to ensure the circularity of the disc, but it also has to prevent eccentricity between the circumference and the scale lines, which requires advanced processing technology and increases component costs. In addition, the second method requires considerable skill in order to perform highly accurate reading on the micron order using a microscope, takes a long time to measure, and has the problem of being subject to reading errors.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide an inexpensive automatic eccentricity testing device with a relatively simple configuration that can perform rapid and highly accurate automatic measurement of eccentricity. do. Therefore, in the automatic eccentricity inspection device according to the present invention, there is provided a light source that illuminates the circular marking line provided on the outer edge of the rotating disk that is the object to be inspected, and a light source that illuminates the circular marking line provided opposite to the light source. an optical system that forms an image of the marked line; a PSD (Positon Sensitive Device) that detects the image position of the image of the circular marked line formed by the optical system; the light source; the optical system; a rotation axis that rotates the PSD integrally relative to the rotating disk; two photocurrents i 1 proportional to the distance from each electrode to the image position, each output from two electrodes of the _PSD ; A current-voltage converter that converts i ₂ into photovoltages v ₁ and v ₂ respectively, an adder that outputs the sum output V ₁ + v ₂ of each photo voltage v ₁ and v ₂ , and each photo voltage v ₁ and v ₂ The difference output v ₁ − v ₂
an eccentricity consisting of a subtracter that outputs , a divider that outputs the ratio of the sum output v ₁ + v ₂ and the difference output v ₁ - v ₂ , and a display connected to the output of the divider. The above objective is achieved by constructing an automatic inspection device and adopting a method of determining the amount of eccentricity by photoelectric detection.

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows the relationship between the eccentricity d and the error angle dθ. Circle K ₁ is a reference circle with center O ₁ and radius r without eccentricity, and circle K ₂ is centered on O ₂ and has eccentricity.
O ₁ O ₂ = a circle with d. Now, the circle K ₁ and the circle K ₂ are opposite to each other with a small distance between them, and the circle K 1 is opposite to the fixed circle K ₁ .
Consider K ₂ to rotate around the rotation axis O ₂ .
Further, the circle _K1 can be regarded as a fixed scale disc in an electronic goniometer, and the circle _K2 can be regarded as a rotatable scanning scale plate. The angle measurement error dθ is maximum at the positions B ₁ , Q ₁ , B ₂ , Q ₂ perpendicular to the eccentricity O ₁ O ₂ , and dθ = ∠
B ₁ O ₂ Q ₁ = d/r, and the _two points B ₁ and B advance to the error angle, and since there is a delay, the total maximum error is 2dθ
It is. On the other hand, points A ₁ and A ₂ on the extension line of eccentricity O ₁ O ₂
In this case, the error angle is 0, but the eccentricity is at most _{2 2} =
A ₁ P ₁ =d. Now, suppose that the eccentricity observation points are the two intersections C ₁ and _C 2 of the diameter C 1 C ₂ and the circle K ₁ as shown in the figure, and the eccentricities _{1 1} and _{2 2} are _the maximum values _{1 1}
and ₂ less than ₂ . In order to obtain the true eccentricity _{12 and} the direction _of eccentricity _A2A1 , it is necessary to rotate the circle _K1 and move the observation points _C1 and _C2 to the points _A2 and _A1 , respectively.

Therefore, as described later, after performing this movement operation while continuously measuring the amount of eccentricity using PSD, the circular
Fix _K1 .

FIG. 2 shows an embodiment of an automatic eccentricity testing device according to the present invention. A transparent scale disk 3 having a circumferential scale 2 is fixed to the first rotating shaft 1, and a second rotating shaft 4 having an eccentricity d with respect to the first rotating shaft 1 has the scale markings. A rotating disk 6 having the same circumferential scale 5 as the disk 2 is fixed. Further on the outer edge of the outer circumferential circle of the circumferential scale 5, a circular marking line 7 is provided for use in eccentricity measurement. The scale disc 3 and the rotary disc 6 are arranged to face each other with the circumferential scales 2 and 5 separated by a minute interval. Arms 8 and 9 fixed to the first rotating shaft 1 are each equipped with a light-receiving unit that is an integrated unit of an LED 10, a lens 11, and a PSD 12, and is arranged on the central axis of the observation point _C1 . , said LED1
The light beam emitted from 0 illuminates the circular marked line 7, and the image 1 of the circular marked line 7 is formed by the imaging light flux that passes through the lens 11.
3 enters the light receiving surface of the PSD 12. The PSD12
is a sensor for inspecting the position of a light spot, and the light spot position is internally divided by the resistance value up to electrodes P ₁ and P ₂ (see Figure 3) arranged in the radial direction, and PSD1
2 outputs a pair of photocurrents i ₁ and i ₂ corresponding to the division ratio as position signals. The LED 10 is
It is driven by a stabilized power supply 14, and the
The output of the PSD 12 is converted by an electronic circuit 15 into an amount of eccentricity in μm units, and is displayed on a display 16.

As the PSD 12, for example, a one-dimensional PSDS1543 manufactured by Hamamatsu Photonics Co., Ltd. can be used in practice, and its position resolution is 0.2 μm and response speed is 5 μsec, allowing for quick and highly accurate position detection.

FIG. 3 is a block diagram of the electronic circuit 15. The PSD 12 outputs photocurrents i 1 , i ₂ that are proportional to the distances of the light spot 13 from the electrodes P ₁ , P ₂ , and these photocurrents _{i 1 ,} i ₂ are transferred to current-voltage converters 151 , 152 .
are converted into photovoltages V ₁ and V ₂ respectively. The photovoltages V ₁ and V ₂ are input to an adder 153 and a subtracter 154 to obtain a sum output V ₁ +V ₂ and a difference output V ₁ -V ₂ , respectively. The divider 155 outputs the sum output V ₁ +V ₂ and the difference output.
The ratio V _{1 −V 2} /V ₁ +V ₂ of V ₁ −V 2 is calculated and the amount of eccentricity in μm is output. The eccentricity amount, which is the output of the divider 155, is displayed on the display 16.

Here, the operation of continuous measurement of eccentricity will be explained with reference to FIG. 2 again.

When the first rotating shaft 1 is slowly rotated, the arms 8 and 9, the LED 10, the lens 11, and the PSD 12 are rotated in conjunction with each other. The rotating disk 6 is the first rotating shaft 1
Since it is mounted eccentrically with respect to the display 16, the amount of eccentricity appearing on the display 16 changes continuously, and shows the maximum and minimum values at points _A1 and _A2 in FIG. 1, respectively. When the rotating shaft 1 is stopped at this position, the maximum eccentricity value and its direction can be confirmed.

In this embodiment, the eccentricity measurement of the transparent scale disk 3 and rotating disk 6 in an electronic goniometer has been described, but the eccentricity measurement of an opaque rotating disk can be performed in the same manner. In this case, the illumination system using LEDs, etc. and the PSD are placed on one side of the rotary plate instead of facing each other, so the illumination is half-field illumination or epi-illumination through a semi-transparent prism, and the illumination system and detection system are What is necessary is to perform optical path division. Further, the signal processing by the electronic circuit 15 can be performed by an appropriate microcomputer, and the eccentricity amount is outputted to the built-in CRT or printer.

Furthermore, although the eccentricity observation point in this embodiment was one, there is no problem in performing the measurement at two diametrically opposed points or three points including the intermediate point thereof.

As described above, the automatic eccentricity inspection device according to the present invention uses a relatively simple optical configuration and an inexpensive mechanism, and utilizes the accurate position detection function of the PSD to quickly and accurately detect eccentricity. Core measurement becomes possible.

Furthermore, the PSD used in the present invention divides the position of the optical spot according to the resistance value up to the two electrodes, and outputs a pair of photocurrents to each electrode according to the division ratio. The output is an analog signal. Therefore, it is possible to detect infinitely small widths, and the claimed invention using such a PSD can be put to practical use, for example, as an automatic eccentricity inspection device used to adjust the eccentricity of the scale of electronic goniometers, etc. It is sufficiently durable.

The automatic eccentricity testing device according to the present invention can be applied not only to the encoder of an electronic goniometer, but also to the eccentricity measurement of optical instruments and precision measuring instruments having transparent discs and opaque discs. It can be widely applied.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the relationship between eccentricity and error angle.
FIG. 2 is a side view of one embodiment of the present invention, and FIG. 3 is a block diagram of an electronic circuit according to one embodiment of the present invention. 4... Rotating shaft, 6... Rotating disk, 7... Circular marking line, 10... LED (light source), 12... PSD (position detection element), 15... Electronic circuit, 16... Display device.

Claims (1)

[Claims] 1. A light source that illuminates a circular marked line provided on the outer edge of a rotating disk that is a test object, an optical system that is provided opposite to the light source and forms an image of the circular marked line, and a A PSD (PositTon Sensitive Device) that detects the image position of the image of the circular marked line thus formed.
, a rotation axis through which the light source, the optical system, and the PSD are integrally rotated relative to the rotating disk, and a distance from each electrode to the image position output from the two electrodes of the PSD, respectively. A current-voltage converter that converts two photocurrents i ₁ and i ₂ proportional to , respectively, into photovoltages v ₁ and v ₂ , and a sum output v ₁ of each photovoltage v ₁ and v ₂ .
an adder that outputs +v ₂ , a subtracter that outputs the difference output v ₁ −v ₂ of each photovoltage v ₁ and v ₂ , and the sum output v ₁ +v ₂
and a divider that outputs the ratio of difference output v ₁ −v ₂ , and a display connected to the output of the divider.