JPS58155502A - Method for correcting loading position of record disc - Google Patents

Abstract

PURPOSE:To make the center of a record disc placed on a turntable coincident with the rotating center of the turntable, by detecting a peak position and the amount of eccentricity in one revolution of the record disc. CONSTITUTION:When positions of maximum eccentricity t1, t1'- and a level V1 of an eccentricity for the center eccentricity of the record disc 1 to the rotating center of a main turntable 31 are detected at a phtodetector 9, a control motor (m) is driven in response to the maximum eccentricity of the disc 1 incoming to a pressing point (b) and a correcting level L depresses a subturntable 32 to correct the loading position of the disc 1. In detecting positions of minimum eccentricity t2, t2'-, the correcting lever L is displaced in response to the positions of minimum eccentricity incoming to a detecting point (a) to correct the loading position of the disc 1, allowing to make the center of the disc 1 coincident with the rotating center of the main turntable 31, resulting that the eccentricity of the disc center is corrected and excellent reproducing characteristics are obtained.

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 rotation centers of the turntable that rotates the center of the record do not match, wow occurs due to eccentricity, and the playback characteristics deteriorate.

For this reason, generally, a turntable is provided with a record-fitting shaft (commonly known as a spindle), and a record center hole is fitted into this to position the record relative to the turntable's center of rotation. etc. are stipulated in the standards.

However, for example, in the case of an LP record with an outer diameter of 30 degrees according to Japanese Industrial Standards, the eccentricity of the record itself is 0.2 Il.
Up to 1 is allowed, and 1. The diameter dimensions of the center hole and the fitting shaft are 7.24~7.331111 and 7.05~, respectively.
7.151111, and there is always a gap between the two when they are inserted, and this gap can be large depending on the combination of record and player used.

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

In view of this, the present invention provides a method for correcting the placement 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, l is a record on which required grooves such as a sound groove 1a and a final groove 1b are formed, and this record is placed on a turntable 3 by fitting the center hole 1c into the shaft part 2. be done. In this embodiment, the arm 5 rotatably supported by the support shaft 4 is a tone arm used in a normal player, and the tip of the arm 5 has a groove on the record 1 connected to the tip of a playback needle (not shown). The cartridge is equipped with an IJ cartridge 6 which converts the movement of the needle into an electrical signal by converting the movement of the needle into an electrical signal.The electrical signal V from this cartridge 6 is input to the detection circuit 7 via an amplifier etc. 8 and a photodetector 9 outputs a pulse signal P from the photodetector 9 when a light reflecting member 10 provided, for example, at one location on the circumference of the turntable 3 reaches its detection position. This pulse signal P, which provides rotational position information of the turntable, is input to the detection circuit 7. The detection circuit 7 detects the eccentricity peak position and the amount of eccentricity of the record from the electric signal V from the cartridge 6 and the pulse signal P from the optical sensor means, and generates a control signal S for correcting the mounting position of the record 1. First, a case will be described in which, among the various grooves formed on the record 1, the final groove 1b, which is an unmodulated concentric circle, is traced by the cartridge 6 to detect an eccentric state. Such tracing is performed with the horizontal rotation of the arm 5 being suppressed at the position where the needle tip of the cartridge 60 traces the final groove 1b. In response to the rotation of the turntable 3, which rotates at a constant speed, the photodetector 9 outputs a pulse signal P having a constant period T, as shown in FIG. 2(a).

On the other hand, the electric signal ν from the cartridge 6 is
), the center of record 1 and turntable 3
When the rotation centers of the two coincide and there is no eccentricity, the playback needle does not move, so the level is 0. However, if the two do not match, the playback needle moves horizontally in response to the eccentricity, so the maximum and minimum Depending on the eccentric position, for example, the waveform becomes a sine wave with a maximum level v1 and a minimum level 2.

Note that the electric signal V having a sinusoidal waveform is
Depending on the type of cartridge, for example a velocity proportional cartridge, or the amplifier that amplifies it, the phase may change and the peak position of the sine waveform may not correspond to the peak position of the eccentricity. The following explanation will be given assuming that in this embodiment, phase correction is performed so that the peak positions of the two correspond to each other.

As described above, the detection circuit 7 to which the electric signal (2) and the pulse signal P are inputted has a detection time t of the pulse signal P. The maximum eccentric position t1, tζ, ... or the minimum eccentric position t2.12' in one rotation of the turntable 3 based on %'O'...
... and the level VI or v2, which is information regarding the amount of eccentricity thereof, is detected, and in order to correct the placement position of the record 1, a correction means to be described later is controlled by the required amount at the required timing.

Next, a case will be described in which an eccentric state is detected by tracing a non-concentric sound groove 1a among the grooves of the record 1 with the cartridge 6 while the horizontal rotation of the arm 5 is similarly suppressed. The sound grooves 1a and the like are normally formed by the variable pitch recording method, and since the recording signal is still recorded in the sound groove 1a, the electric signal V from the cartridge 6 is subject to the groove feeding amount in addition to the signal caused by eccentricity. Includes signals and playback signals of recorded signals. However, the frequency of the above-mentioned sinusoidal waveform signal due to eccentricity varies from the rotational speed of the turntable 3, for example, 33 rpm in the case of an LP record, to 0.5 rpm in the case of an LP record.
55Hz in advance, and since this frequency is outside the frequency band of the recording signal, if the electric signal V is input to the detection circuit 7 via a 0.55Hz bandpass filter in the case of an LP record, the same as described above can be achieved. The eccentricity peak position and amount of eccentricity can be detected.

An example of a method for correcting the placement position of the υ record using the control signal S from the detection circuit 7 obtained by tracing the groove on the record 1 will be explained below with reference to FIG. The table has a double structure, and the main turntable 3 whose rotation center should coincide with the center of record 1
．． corresponds to the turntable 3 shown in FIG. 1, and is directly driven by, for example, a drive motor M. A light reflecting member 10 is attached to one place on its circumferential surface, and a sub-turntable 3 □ is attached to 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 8 and the photodetector 9 and the rotation angle.
The correction lever L, which presses the sub-turntable 3□ in its radial direction at a pressing point 80 degrees apart, normally receives the required biasing force in the direction of the arrow. Only when m is driven, the sub turntable 32 is displaced by a controlled amount in the pressing direction and presses the sub turntable 32.

Here, main turntable 3. Regarding the eccentricity of the center of record 1 with respect to the rotation center of , the maximum eccentricity position 1. ．． 1
ζ, . . . and the level ■ related to the amount of eccentricity are detected, the control motor m is driven in response to the arrival of the record 1 at the pressing point of the maximum eccentric position, and the correction lever L is moved to the secondary position. Press the turntable 32 to record 1
The placement position of is corrected. Also, the minimum eccentric position t2
, t;, in response to the arrival of the minimum eccentric position at detection point a, the correction lever L is displaced, the placement position of record 1 is corrected, and record 1 is
The center of the main turntable 3I coincides with the rotation center of the main turntable 3I.

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. In addition, it is technically possible to use the tone arm normally provided in a player as the arm, or it may be configured with a dedicated arm.

According to the present invention, the eccentricity of the center of the record with respect to the rotational center 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, is corrected, and the Excellent reproduction characteristics can be obtained during reproduction.

[Brief explanation of the drawing]

FIG. 1 is an explanation of an example of the receipt eccentricity detection method according to the present invention, FIG. 2 is an explanation of the detection of eccentricity peak positions, etc. according to the present invention, and FIG. 3 is an explanation of the record placement position correction according to the present invention. Figures illustrating an example of the method are shown. 1 ・Record, 1a... sound groove, 1b... final groove,
3... Turntable, 5... Arm, 6 Cartridge, 77 Detection circuit, 8 Light emitting element, 9 Photodetector,
L・・Corrected/<-1m・−Control motor. Patent applicant Nakamichi Co., Ltd. Representative Hitoshi Nakamichi (0) ” ” →kai

Claims (3)

[Claims] (1) Tracing the grooves formed on a record placed on a turntable and rotating with a playback stylus attached to an arm whose rotation in the horizontal direction is suppressed during at least one revolution of the record, An electrical signal responsive to the movement of the playback stylus caused by the eccentricity of the center of the record with respect to the rotation center of the table is generated, an eccentric peak position and the amount of eccentricity of the record are detected from the electrical signal, and the record is 1. A method for correcting a record placement position, comprising: aligning the center of the record with the rotation center by correcting the placement position of the record. (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.