JPS58203679A - Pickup - Google Patents

Abstract

PURPOSE:To smoothen and make smaller the noise level of an audio output in an audio frequency band, by arranging the supporting point of a needle arm so that the resonance frequency of the needle arm related to a distance between a supporting part and supporting point of a scanning needle becomes higher than the audio frequency. CONSTITUTION:A needle arm 40 consists of a base part 41, axis part 42 and an intermediate part 70 which is arranged between the base part and axis part and has larger sectional area than that of the axis part 42. The intermediate part 70 is formed integral with the base part 41 and axis part 42 and consists of the 1st part 71 having the same sectional area as that of the axis part 42, and the 2nd part 72 of a flat plate shape mounted on the top surface of the 1st part. Actually, they are constituted by mounting the 2nd part 72 on the axis part on the base side of a conventional needle arm. The supporting point of the needle arm 40 exists in the boundary part between the axis part 42 and the intermediate part 70, and a distance Z between the supporting point P' and needle supporting part becomes shorter by the length R of the intermediate part 70 than that of the conventional one. Namely, a distance Z' is nearly halved, and a resonance frequency becomes about four times to exceed the upper limit of the audio frequency band.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pickup applied to a capacitance sensing type video disc player, and its main purpose is to improve audio frequency characteristics during playback.

A recording medium (for example, a video disc) K has a superimposed signal of an FM video signal and an FM audio signal recorded thereon so as to have a geometrical shape change along its track, and the pickup in contact with the recording medium K has a geometric shape that changes along its track. A scanning needle is provided to detect a change in the capacitance value corresponding to the change as a change in the quantity of electricity, and the above-mentioned superimposed signal is extracted.

FIG. 1 shows a schematic block diagram of this type of big block used in the CKD system. In the figure, (1) is a base such as a cartridge case, (
2) is a support that is fixed to this base and allows displacement of the scanning needle in the track extending direction; (3) is fixed to this support and allows displacement of the scanning needle in the vertical and horizontal directions. It's a damper. A first arm (4) made of a metal tube is connected to this damper (31), and this first arm (4) is connected to the damper (31).
j82 made of plastic that runs along the free end side of the arm
A scanning needle (6) having an electrode (not shown) on the scanning surface (6&) is fixed to the arm (5) (hereinafter, this second arm will be referred to as the needle arm). In addition, a metal strip-like elastic body called a fly lead (7) is connected to the electrode of the scanning needle (6), which maintains smooth tracking of the scanning needle, applies appropriate needle pressure, and furthermore, the reproducing circuit ( (not shown). Fly lead (7)
) is introduced into the resonator that constitutes the playback circuit of the player via the output terminal (9) attached to the adjustment ball (8) fitted to the base (1). When the magnetic field of the built-in coil acts on the scanning needle (displaces the 6th order in the track cross direction,
It is designed to support a so-called lock groove release, in which the scanning needle repeatedly scans the same track, and a visual search function, which moves the scanning needle faster than during standard playback.

FIG. 2 shows a frequency characteristic diagram of noise in the audio band when a CmD test video disc is played back using the above pickup (PU).

The test video disc had a 1KH2 carrier (71
6KH2) is modulated by 50%, and a non-modulated area where no such modulation is performed. When the above modulation region is reproduced, the spectrum analyzer is set to zero dB.
This shows the reproduction characteristics in the non-modulated region when As is clear from this Fig. 2, the above pickup (PU
) has a noise peak near 13KHz. It has been recognized that this noise beak is a non-negligible hindrance to faithful chapter reproduction (for example, the generation of a harsh hissing sound). As a result of various studies, it was found that this noise peak was caused by resonance caused by the needle arm (5).

Figure 3 is a schematic diagram of the needle arm used in a conventional CED pickup, where (a) is a perspective view and (b) is a perspective view.
shows a side view. This needle arm (5) is j[! 1
is fixed to the arm (cantilever) (4);
D, a shaft portion (to) whose central axis substantially coincides with the first arm (4) K, and a fly lead (7) configured on the free end side of the shaft portion for attachment. A needle support part (with a through hole (to) for holding the splicing part and the scanning needle (6)
) are integrally molded with synthetic resin (cellulose propionate). The base 6D has a main body part trowel having a first hole (to) for inserting the arm (4) of @1 and a second hole 67 for inserting the magnet uI, and the main body part is Conical part 11 for alignment with @! It is equipped with J. This needle arm (5) has a total length (3) of approximately 9.4
ym, the length 7) of the base 6υ is designed to be approximately 3.2 cm, and the length and slope from the fulcrum (g) of the shaft part to the needle support part (to) is approximately 6 cm, and the shaft part The cross-sectional shape of the tether is designed to be a square with each side approximately 0.5 m. Such a needle arm (5) is connected to a scanning needle (6) from a video disc.
It has been found that when an impact force is applied via the fulcrum, the details vibrate around the fulcrum, and this resonance causes the noise peak in the frequency characteristics shown in Figure 2. In order to make the resonance frequency (Fr) of this noise peak higher than the upper limit of the audible frequency band (for example, 25 KHIg), from the relational expression Fr=k・''/2 (where k is a constant and l is the slope of the length mentioned above), By the way, simply shortening the length (2) leads to shortening the overall length (the slope) of the needle arm (5), which is relative to the rotation plane of the video disc. This leads to the approach of a first arm arranged at a certain angle (for example 5°) to the video disc and also the approach of the first arm to the fly lead (7), thus leading to signal extraction. A problem with the system is floating accommodation between the first arm and the video disk and fly lead, respectively.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a pickup in which the noise level of audio output is reduced and leveled in the audible frequency band. That is, by arranging the fulcrum of the needle arm so that the resonance frequency of the needle arm is higher than the audible frequency, resonance in the audible frequency band is suppressed, thereby obtaining good frequency characteristics. Therefore, the needle arm of the present invention has a base portion fixed to the first arm, a shaft portion extending toward the free end, and a cross-sectional area disposed between these portions that is larger than that of the shaft portion. The fulcrum that determines the resonance frequency is located at the boundary between the shaft portion and the middle portion, and the middle portion (resonance suppressor) is connected to the base portion and the shaft portion. It can be provided by either all being molded as one piece, or by attaching a separate piece on top of something that is partially molded as one piece.

Next, the present invention will be explained according to examples. FIG. 4 shows a perspective view of a needle arm according to an embodiment of the present invention. The construction of the needle arm is as follows.The other components are the same as those shown in FIG. 1, and their explanation will be omitted.

The needle arm hook has a base fixed to the first arm (4) (same configuration as the base 6υ in Fig. 1) and a shaft whose central axis substantially coincides with the first arm (4). (42 (the only difference is the axial length from the shaft part @ in Figure 1), and an intermediate part σG which is located between these base parts and the shaft part and whose cross-sectional area is larger than that of the tree. The middle part f71 is the base part (41
) and the shaft (41) and a first part (2) having the same cross-sectional area as that of the shaft (42), and a flat second part (2) placed and fixed on the top surface of the first part. (for example, a luminaire plate with a length of 3 cm, a medium Q, 5 tm, and a thickness of 0.2 m), and in this embodiment, substantially tζ is smaller than that of the conventional needle arm shown in FIG. The second part (
2). The fulcrum of this needle arm f4 (l exists at the boundary between the shaft part (@) and the intermediate part (7G), and the distance between the fulcrum (6) of this embodiment and the needle support part (the slope is that of FIG. 1) Compared to the slope, the length of the middle part m is shortened by an equal amount.In other words, the distance It!t(Z) is about half, and the resonant frequency is calculated to be about 4 times larger, exceeding the upper limit of the audible frequency band. When the same characteristics as shown in FIG. 2 were obtained using the pickup of this embodiment, it was possible to obtain a pickup having no noise peak within the audible frequency band as shown in FIG.

6(A) to 6(S) all show main parts (intermediate parts) of other embodiments of the present invention, and (A) to 6) show the conventional parts similar to the embodiment of FIG. 4. A second needle is attached to the proximal shaft of the needle arm.
On the other hand, (E) to (S) are those in which the intermediate part is integrally molded to the base and shaft part. next,
We will give an overview of these. A) is a flat plate-like second part (72 mm) similar to that shown in Figure 4 attached to the bottom of the first part, and (B) is a shaft part (with a U-shaped cross section that matches the outer shape of the cutter). The second part (72B) is arranged to span the first part.The latter is advantageous over the former in that the second part can be placed accurately on the first part. (
C) is a structure in which a tube made of heat-shrinkable resin is adhered to the first part to form the second part (72c);
The second part (72D) is made by applying boxy adhesive to the circumference of the first part, including the base (the conical part +41), over a length of about 2 kami (K). When the characteristics similar to those shown in FIG. 2 were obtained for the latter example, the characteristics (indicated by the broken line (S) in FIG. 5) almost the same as the water child characteristics were obtained in FIG.

(E) ~ (1st sentence) As mentioned above, the middle part (70K) ~ (70
The base (41) and the detail (4 sides) are integrally molded, and both are molded so that the conical part provided in the conventional isthmus 6υ is incorporated into these intermediate parts. The appropriate length is about 2 to 3 m, and the inclination angle of the slope in the examples (e), (e) and (1) (wa) is selected to be about 10°.However, depending on these values, Needless to say, changes may be made as appropriate within the scope of achieving the object of the present invention without being limited to the above.This also applies to the shape of the intermediate portion or the material of the second portion.

As described above, the present invention provides a needle arm that supports a scanning needle such that the fulcrum of the needle arm is located closer to the free end of the needle arm than in conventional needle arms, for example, between the shaft and the base. An intermediate part that functions in the same way as the base is placed in between, and the overall length of the shaft is shortened to 1. This is useful because it can eliminate noise peaks in the audio signal and improve the S/N frequency characteristics of the reproduced audio signal.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the pickup of the Juto, Fig. 2 is a frequency characteristic diagram of the noise level of the audio output of this big rtube, and Fig. 3 (A) (C4 is a perspective view of the configuration of the needle arm of the Juto. FIG. 4 is a perspective view of the configuration of a needle arm applied to the pickup of the present invention, and FIG. 5 is a frequency characteristic diagram of bright light shown in FIG. 2 of a pickup to which this needle arm is applied. Figures (A) to (S) are partial views of other embodiments of the needle arm applied to the present invention. Explanation of main figure numbers ...
Shaft part, 1'7G (70A) ~ (70 pieces)...middle part. Applicant Sanyo Electric Co., Ltd. - Σ) Representative Patent Attorney Shizuo Sano'y, -1j,, H~nee, 7/
＼Knee Figure 1 Figure 2 0 5 10 15
20 25th million l (in H7) Figure 3 rAl+

Claims (4)

[Claims] (1) In a pickup including a needle arm supporting a scanning needle that detects a change in capacitance value corresponding to a change in a geometrical shape extending along a track of a recording medium as a change in electric quantity, the needle arm is A pickup characterized in that the fulcrum is arranged in such a way that the resonance frequency of the needle arm, which is related to the distance between the supporting part of the scanning needle and the fulcrum, is higher than the audible frequency. (2) The needle arm has a base portion fixed to the cantilever, a shaft portion extending toward the free end, and a cross-sectional area located between the base portion and the oil portion that is larger than the cross-sectional area of the shaft portion. The pickup according to claim 1, wherein the pickup has an intermediate portion having a certain area, and the fulcrum is located at a boundary between the shaft portion and the intermediate portion. (3) The pickup according to claim (2), wherein the intermediate portion is integrally molded with the base portion and the shaft portion. (4) The intermediate part is composed of a first part integrally molded with the base part and the shaft part, and a second part attached to the first part. Pickup described in scope item (2).