JPS58150178A - Methd for correcting placing position of gramophone record - Google Patents

Abstract

PURPOSE:To match the center of a gramophone record to the rotating center, by measuring the angular displacement of an arm at the time of tracing, and detecting the eccentric peak position and its eccentric amount of the record against the rotating center, and correcting the placing position of the record. CONSTITUTION:A photodetector 7b outputs a pulse signal of a fixed cycle T in response to the rotation of a turntable which makes a uniform rotation. On the other hand, when the center of a gramophone record 1 does not coincide with the rotating center of the turntable 3, an angular displacement of an arm 5 occurs in response to the eccentric state, at a photodetector 7a therefore, the electric signal V attains the sine wave in accordance with the maximum and minimum eccentric positions, for example having the maximum level V1 and minimum level V2. Therefore, a detecting circuit 9 detects the maximum eccentric positions t1, t1',-or the minimum eccentric positions t2, t2', at one rotation of the turntable 3 which uses the detecting times t0, t0', - of a pulse signal P as the reference and the levels V1 or V2 which is the information regarding their eccentric amounts and controls a correcting means which corrects the placing position of the record 1, by a desired amount at a desired timing.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for correcting the placement position of a record so that the center of the record coincides with the center of rotation of a turntable.

When playing a record, if the center of the record and the center of rotation of the turntable that rotates the record do not coincide, wow occurs due to eccentricity, which deteriorates the playback characteristics.

For this reason, it is generally not possible to record records on a turntable.
A shaft part (commonly known as a spindle) is provided, and a record center hole is fitted into the shaft part to position the record relative to the rotation center of the turntable, and the diameter dimensions of each of these parts are specified by standards.

However, for example, according to the Japanese Industrial Standards, the outer diameter is 300/
In the case of an LP record of n, the eccentricity of the record itself is allowed up to 02 degrees, and the diameters of the center hole and the fitting shaft are 7.24~7.331111 and 705~7.15 degrees, respectively, and there is a distance between the two. There is always a gap when the record is inserted, and this gap can be quite large depending on the combination of record and player used.

Therefore, it is difficult to align the center of the record with the center of rotation of the turntable only by positioning the center hole and the fitting shaft, and in the past, records were played by being placed eccentrically on the turntable. was common, and the amount of eccentricity was largely influenced by how the record was placed.

In view of the above, the present invention provides a method for correcting the position of a record by which the center of the record placed on the turntable can be aligned with the center of rotation of the turntable. Explain in detail. In FIG. 1, reference numeral 1 is a record in which required grooves such as sound grooves are formed, and this record 1 is placed on a turntable 3 by fitting its center hole 1a into a shaft portion 2 [7]. An arm 5 rotatably supported by a support shaft 4
is equipped with a tracing needle (not shown) at its tip for tracing the grooves on the record l, and at its other end a light emitting element 6a such as a lamp and a photodetector 7a for receiving light from the light emitting element 6a. A shutter plate 8 is provided with a 1° interposition therebetween. The photodetector 7a outputs a required electrical signal (2) whose level changes in response to a change in the amount of light received due to the angular displacement of the arm 5, and this output is input to the detection circuit 9. Moreover, the light emitting element 6b and the photodetector 7b
An optical sensor means is provided to detect rotational position information of the turntable 3. One means of this optical sensor is
When the light reflecting member 10 attached to, for example, one point on the curve of the turntable 3 reaches its detection position, the photodetector 7
b outputs a pulse signal P, and this output is input to the detection circuit 9. The detection circuit 9 detects the peak eccentricity position and the amount of eccentricity of the record from the electrical signal V and the pulse signal P, and outputs a control signal S for correcting the placement position of the record 1. record 1
Among the various grooves formed above, the final groove lb is a concentric circle.
A case will be explained in which an eccentric state is detected by tracing with the tip of a tracing needle.

In response to the rotation of the turntable rotating at a constant speed, the photodetector 7b outputs a pulse signal P having a constant period of 1'', as shown in FIG. 2(a).

On the other hand, the photodetector 7a, as shown in FIG. 2(b),
When the center of the cord l and the rotation center of the turntable 3 are aligned and there is no eccentricity, there is no angular displacement of the arm 50, so
Constant level V. However, if the two do not match, an angular displacement of the arm 50 will occur in response to the eccentricity, so the electrical signal V will vary depending on the maximum and minimum eccentric positions, for example, the maximum level V1 and the minimum level. It becomes a sine waveform with v2.

Therefore, the detection circuit 9 has a detection time toXt of the pulse signal P.
Maximum eccentric position 'i', 'I', or minimum eccentric position' in one rotation of the turntable 3 based on o', -
2, '2', and level ■ or ■, which is information regarding the amount of eccentricity thereof, is detected, and in order to correct the placement position of the record I, a correction means to be described later is controlled by the required amount at the required timing.

Next, we will explain the case of detecting eccentricity by tracing the non-concentric sound $lc among the grooves on the record 1. Since the sound groove 1C etc. is usually formed by the variable pitch recording method, the photodetector As shown in Fig. 2 (C), the level of the electric signal V from 7a changes as shown by the dotted line according to the groove feed amount even when there is no eccentricity, and the change also varies depending on the location to be traced. If there is eccentricity in the case, the electric signal (2) becomes a sine waveform as shown by the solid line, and the frequency of this sine waveform varies from 33 rpm to 0.0 m for an LP record based on the rotational speed of the turntable 3.
Since it is known in advance to be 55Hz, the output of the photodetector 7a is set to 0.5Hz.
If the signal is input to the detection circuit 9 through a 5 Hz band-pass filter, the eccentricity peak position and eccentricity amount can be detected in the same manner as described above.

An example of a method for correcting the placement position of a record using the control signal S from the detection circuit 9 obtained by tracing the grooves on the record 1 will be explained below with reference to FIG. a main turntable 3 which has a multilayer structure and whose center of rotation is to coincide with the center of the record l;
corresponds to the turntable 3 in FIG. 1, and is directly driven by a drive motor M, for example, and has a light reflecting member 10 attached to its circumferential surface, and a sub-turntable 3 □ on its upper surface. is slidably mounted. A spindle 2 conforming to the standard is provided on the upper surface of the sub-turntable 32. 1 at the detection point a of the above-mentioned optical sensor means consisting of the light emitting element 6b and the photodetector 7b and the rotation angle.
The correction lever L, which presses the sub-turntable island in its radial direction at pressing points 80 degrees apart, normally receives the required urging force in the direction of the arrow, and is spaced apart from the circumferential surface of the sub-turntable island;
Only when the control motor m is driven, it is displaced by a controlled amount in the suppression direction and presses the sub-turntable 3□.

Here, regarding the eccentricity of the center of the record 1 with respect to the rotation center of the main turntable type, the maximum eccentricity position t1.11
',... and the level vI related to the amount of eccentricity is detected, the control motor ITI is driven in response to the arrival of the record 1 at the pressing point of the maximum eccentricity position, and the correction lever L is turned into the sub-turn. By pressing table 3□, the placement position of record l is corrected.

Further, when the minimum eccentric position t2.12',... is detected, the correction lever L is displaced in response to the arrival of the minimum eccentric position at the detection point a, and the record l
The mounting position of the record 1 is corrected so that the center of the record 1 and the rotation center of the main turntable 31 are aligned.

The mounting position can be corrected by detecting the peak eccentricity position and the amount of eccentricity in at least one revolution of the record, but it is also possible to use a closed-loop control system to carry out sequential corrections to reach the final target position.

In addition, the pressing point of the correction lever is not limited to the above-mentioned example, and it is also possible to have a configuration that directly moves the record without relying on the double turntable structure.Furthermore, the mounting position can be corrected by rotating the turntable. It is technically possible to do so either in the state or in a stopped state at a predetermined position.

Further, as the arm, a tone arm normally provided on a player can be used, or a dedicated arm can also be used.

According to the present invention, the eccentricity of the center of the record relative to the center of rotation of the turntable, which occurs due to the gap that inevitably exists between the center hole of the record and the spindle of the turntable, can be corrected. , it is possible to obtain excellent playback characteristics in record playback.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining an example of the method for detecting eccentricity of a record according to the present invention, FIG. 2 is a diagram for explaining the method for detecting eccentricity peak positions, etc. according to the present invention, and FIG. Figures illustrating an example of a method for correcting the placement position of a record according to the above are shown. Trecord, 3...Turnty full, 5...Arm, 6a, 6b light emitting element, 7a, 7b...photodetector, 9 detection circuit, L...correction lever, m...control motor. Patent applicant Nakamichi Co., Ltd. Representative Nakamichiguchi 6 (Den Figure 1)

Claims (3)

[Claims] (1) Trace a groove formed on a rotating record placed on a turntable with a tracing needle attached to an arm while the record rotates at least once, and measure the angular displacement of the arm during this tracing. detecting the eccentricity peak position and the amount of eccentricity of the center of the record with respect to the rotation center of the turntable; and correcting the mounting position of the record to align the center of the record with the rotation center. Features a method for correcting the placement position of records. (2) The record placement position correction method as set forth in claim 1, wherein the eccentricity peak position is the maximum eccentricity position. (3) The record placement position correcting method according to claim 1, wherein the eccentricity peak position is the minimum eccentricity position td.