JPS6230566B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Field of the Invention The present invention relates to an assembly accuracy measuring device for measuring the attachment accuracy of a plurality of objects attached along the circumferential direction of a rotating body.

(2) Prior art For example, in a VTR, two heads (objects) are mounted on a disk (rotating body) at an angle of 180 degrees.
They are mounted at different angles, and the screen signals are extracted by running these heads over the magnetic tape. Therefore, if the head is not attached precisely at a 180 degree angle in the circumferential direction of the disk, the image on the TV screen will be misaligned. Inspection is extremely important.

Conventionally, in order to inspect the assembly accuracy of the head relative to the disk, a pair of microscopes is placed at exactly 180 degrees to the rotation axis of the disk, and a pair of microscopes is placed on the end face of each head to be magnified by each microscope. Whether each head was assembled to the disk at a precise angle of 180 degrees was determined by whether the slit section was located at the center of the field of view of each microscope. However, with such measurement methods, it not only takes a great deal of effort to accurately align the optical axes of the pair of microscopes with the center of the rotational axis of the disk and to arrange them at opposing angles of 180 degrees, but it is also prone to errors. Furthermore, when making measurements, it is necessary to adjust the focus and look through a pair of microscopes, making the work extremely difficult. Moreover, since measurements made using a microscope are made by the person measuring them visually, there are variations in the criteria for judgment, and there is a limit to the improvement of measurement accuracy.

Therefore, a device was developed in which a laser beam is incident on a head that rotates with the disk at a constant speed, the laser beam is scattered and diffracted by a slit on the end face of the head, and the laser beam is received by a sensor, and the mounting angle of each head is determined from the timing of the reception of the laser beam. is being considered.

(3) Problems with the conventional technology Although it is true that the measuring means employing such a laser beam can measure the assembly accuracy of the head with high precision,
On the other hand, if there is dirt or scratches on the end face of the head, there is a problem that the laser light will be scattered and diffracted, which may cause a serious measurement error.

(4) Purpose of the Invention The present invention provides an assembly that uses laser light as a measuring medium to stably measure the mounting angle of an object with high precision and without measurement errors even when there is dirt or scratches. The purpose of the present invention is to provide an accuracy measuring device.

(5) Key points of the invention When measuring assembly accuracy by irradiating laser light onto multiple objects equipped with scattering parts that rotate together with the rotating body, the laser light scattered and diffracted by the scattering parts of the objects and dirt and scratches The purpose is to distinguish between the laser beam that is scattered and diffracted and to determine the mounting angle of each object using only the laser beam that is scattered and diffracted at the scattering section.

(6) An embodiment of the invention 1 in Fig. 1 is a disc-shaped rotating body.
This is a VTR disk, and a rotating shaft 2 is provided at the center of the disk 1. Also, on the upper surface of the disk 1, there are two heads 3a as objects,
3b is attached to the disk 1 at an angle of 180 degrees in the circumferential direction. As shown in FIG. 2, these pair of heads 3a and 3b have a substantially semicylindrical shape with one end surface curved, and a curved surface 3c protruding from the outer peripheral surface of the disk 1 has a scattering portion along the thickness direction. A slit portion 4 is provided. The disk 1 with the heads 3a and 3b assembled in this manner is configured such that the rotating shaft 2 is rotatably supported by a support (not shown) and is driven to rotate at a constant speed.

A pair of heads 3a and 3b are connected to the disk 1.
The measuring device 5 measures whether or not it is precisely provided at 180 degrees in the circumferential direction. To explain this measuring device 5, 6 in the figure is a laser oscillator, and this laser oscillator 6 can oscillate a laser beam 7 having linear polarization characteristics. Then, this laser beam 7 is focused by a first condensing lens 8, and the curved surfaces 3c of the heads 3a, 3b,
The light is incident (irradiated) on the curved surface 3c at a predetermined angle of incidence, and is specularly reflected on the curved surface 3c, and scattered on the slit portion 4 to perform a specific scattering diffraction. . Further, a light shielding plate 9 is disposed in the direction of reflection of the laser beam 7, and a second condenser lens 10 and a thin through hole 11 are arranged in the direction perpendicular to the slit portion 4 in the direction of scattering and diffraction.
Spatial filters 11 having holes a are provided in sequence. Therefore, the reflected light 7a is blocked by the light shielding plate 9, the polarized laser light other than the end faces of the heads 3a and 3b is removed by the spatial filter 11, and only the scattered light 7b from the slit portion 4 passes through the spatial filter 11. and is guided along an optical path 12. Further, a first sensor 13 and a second sensor 14 are provided at a position on the optical path 12 where the scattered light 7b forms an image of the slit portion 4. These sensors 13 and 14 are formed by joining two photodetectors side by side, and the first sensor 1 detects the image of the slit portion 4 that moves as the disk 1 rotates.
3, and then the second sensor 14 detects it. Of these sensors 13 and 14, the first sensor 13 is connected to the non-inverting input terminal of the differential amplifier 15, and the second sensor 13 is connected to the non-inverting input terminal of the differential amplifier 15.
The sensors 14 are each connected to an inverting input terminal, and constitute a first detection system 23. Further, the differential amplifier 15 includes a gate circuit 1 as a control circuit.
It is connected to the signal processing device 17 via 6.

On the other hand, numeral 18 in the figure is a beam splitter that is located after the spatial filter 11 and is provided on the optical path 12. This beam splitter 18 allows light having the same polarization characteristics as the laser light 7 to pass to the sensors 13 and 14 among the light incident on the beam splitter 18, and reflects the other light in a direction perpendicular to the optical path 12. It has the function of separating the Therefore, the scattered light 7c, which has a polarization characteristic different from that of the scattered light 7b scattered by the slit portion 4, is distinguished from the scattered light 7b. A second detection system 21 composed of a third sensor 19 composed of a photodetector and a photoamplifier 20 is provided in the direction in which the scattered light 7c is separated, and is capable of detecting the separated scattered light 7c. I'm starting to be able to do it. Further, the photoamplifier 20 constituting the detection system 21 is connected to the gate circuit 16, and controls and operates the gate circuit 16 using a detection signal. That is, in the gate circuit 16, a detection signal is output to the gate circuit 16 through the third sensor 19 and the photoamplifier 20, thereby blocking the output of the differential amplifier 15, and no detection signal is output to the gate circuit 16. At times, an operation is performed in which the output of the differential amplifier 15 is guided to the signal processing device 17 side. Then, in the signal processing device 17, the gate circuit 1
The period of the zero-crossing point of the signal of the difference between the output of the first sensor 13 and the output of the second sensor 14 of the differential amplifier 15 input through the differential amplifier 6 is calculated.

Next, the operation of the measuring device 5 configured as described above will be explained. While the disk 1 is rotated at a constant speed, the laser oscillator 6 is activated to output a laser beam 7. As a result, the laser beam 7 irradiates the head 3a rotating together with the disk 1.
Reflected light 7a generated by the laser beam 7 irradiating the curved surface 3c of the head 3a excluding the slit portion 4 is blocked by the light shielding plate 9. Further, the scattering hole 7b generated by irradiating the slit portion 4 is specifically scattered and diffracted, and an image is formed on the surface of the first sensor 13 through the focusing lens 10 and the spatial filter 11, and this image is further transferred to the second sensor. Moving on to 14. Then, the output of the differential amplifier 15 at the moment when the image of the slit portion 4 reaches the junction between the first sensor 13 and the second sensor 14 is zero (the output of the first sensor 13 and the second sensor 14 is zero). Calculate the zero crossing point where the outputs are equal). Next, disk 1
As the slit portion 4 of the head 3b rotates, the slit portion 4 of the head 3b also rotates.
The scattering hole 7b is detected, and the zero-crossing point at this time is calculated by the differential amplifier 15 in the same way as before. Then, the time from head 3a to head 3b being detected at this time is stored in the signal processing device 17 as a period T1.

Similarly, the time from the slit section 4 of the head 3b to the detection of the slit section 4 of the head 3a is stored in the signal processing device 17 as a period T2.
The signal processing device 17 compares and calculates the light reception timings of period T1 and period T2. Therefore, if the pair of heads 3a and 3b assembled to the disk 1 are attached at an angle of exactly 180 degrees,
Since the period T1 is equal to the period T2, the assembly accuracy of the pair of heads 3a and 3b can be determined by comparing and calculating the period T1 and the period T2.

In addition, when measuring the assembly accuracy, the head 3a
Alternatively, if there is dirt 22 on the curved surface 3c of the head 3b that causes malfunction (measurement error), the moment the laser beam 7 is incident on the dirt 22,
A portion of the laser beam 7 is scattered and diffracted. However, unlike the scattered light 7b of the slit portion 4 formed with a specific shape, groove depth, and other dimensions, this scattered light exhibits disordered scattered diffraction,
When the beam enters the beam splitter 18, it is reflected toward the third sensor 19 and separated from the optical path 12.
On the other hand, among the scattered light scattered by the dirt 22, the scattered light 7b from the slit portion 4 enters the first sensor 13 having the same characteristics as the scattered light 7b, but the third sensor 1
With the output of the photoamplifier 20 due to the detection operation of 9,
The gate circuit 16 is closed and no signal is output from the differential amplifier 15. In this way, the signals input to the signal processing device 17 are distinguished, and only the detection signal from the slit section 4 is input.

Therefore, the laser beam scattered and diffracted by the dirt 22 will not be detected and cause a malfunction in measurement, and stable and highly accurate assembly of the pair of heads 3a and 3b is guaranteed. Ru. In addition,
Not only the dirt 22 but also the curved surfaces 3 of the heads 3a and 3b.
The same can be said about the scratches on c.

(7) Other Embodiments of the Invention In the embodiment described above, a case was described in which two heads were assembled as objects on a disk which was a rotating body, but two heads were assembled on a rotating body.
The number is not limited to three, and may be three or more.

(8) Effects of the invention The second detection system and control circuit separate the scattered light incident on the first detection system into specific scattered light from the slit portion and other scattered light with different polarization characteristics. Since the signal processing device calculates the mounting angle of the object relative to the rotating body only based on the timing of the reception of scattered light from the slit, there is no possibility of measurement errors even if the object is dirty or scratched. It is possible to obtain stable and highly accurate assembly of objects without any problems.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a schematic diagram showing the entire measuring device, and FIG. 2 is a perspective view showing the head as an object. 1'... Disk (rotating body), 3a, 3b... Head (object), 6... Laser oscillator, 12... Optical path, 16... Gate circuit (control circuit), 17...
Signal processing device, 18...beam splitter, 21
...Second detection system, 23...First detection system.

Claims (1)

[Claims] 1. A laser oscillator that irradiates a laser beam with a linear polarization characteristic to a plurality of objects that rotate with the rotation of a rotating body that has a plurality of objects equipped with scattering parts that scatter light in a specific manner along the circumferential direction, and a scattering part of each object. a first detection system that receives the scattered light scattered and diffracted through the optical path; and signal processing that inputs the detection signal of this first detection system and calculates the mounting angle in the circumferential direction of the rotating body of the object based on the light reception timing. a beam splitter that is provided on the optical path from the object to the first detection system and separates light with polarization characteristics different from the scattered light scattered by the scattering part of the incident object from the optical path;
A second detection system detects the light separated by the beam splitter, and upon receiving the detection signal of the second detection system, the output of the first detection system is blocked and detected when the detection signal is input. An assembly accuracy measuring device comprising: a control circuit that controls passing when no signal is input.