JPS58153243A - Pickup - Google Patents

Abstract

PURPOSE:To improve S/N, by adding a buffer body which has large buffer effect to a stylus arm which supports an electrostatic capacity variation type scanning stylus, and flattening the peak value of the resonance frequency of a pickup oscillation system. CONSTITUTION:The buffer body 30 is added to some part of the back surface 5a of the stylus arm 5 which supports the electrostatic capacity variation type scanning stylus 6. The buffer body 30 is made of, for example, bloom rubber with 50-degree Shore hardness, having 0.5mm. high, 0.5mm. wide, and 6mm. long as shown by 31, 32, and 33. Consequently, the resonance frequency of the pickup oscillation system decreases to suppress Q low, during resonation obtaining flat frequency characteristics. The buffer body may be added symmetrically to both flanks of the stylus arm, or extended surrounding the back surface and both flanks in a channel shape.

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 superimposed signal of an FM video signal and an FM audio signal is recorded on a recording medium (e.g., a video disk) so as to have a geometrical shape change along the track, and a pickup in contact with the recording medium changes the geometric shape along the 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 diagram of this type of pickup used in the CED 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, and (3) is a damper that is fixed to this support and allows displacement of the scanning needle in the vertical and horizontal directions. It is. A first arm (4) made of a metal tube is connected to this damper (3), and a second arm (4) made of plastic is connected to the other end of this first arm.
5) (The @2 arm with the following is called the needle arm) has a scanning needle (6a l) with an electrode (not shown) on the scanning surface (6a l).
) is fixed. In addition, the electrode of the scanning needle (6) has 7
A metal band-like elastic body called ReiLead (7) is connected,
This maintains smooth tracking of the scanning needle, applies appropriate front needle pressure, and also serves as an output lead to a reproducing circuit (not shown). 7 Rei lead (7) is the base (
Output terminal (9) attached to adjustment bulb (8) fitted to
), and the signal output is introduced through this output terminal (9) to a resonator that constitutes the playback circuit of the player.

(The IQ is a magnet, and when the magnetic field of the coil built into the player acts during playback operation, it gives displacement to the scanning needle (6) in the track crossing direction, and the scanning needle repeatedly scans the same track. It is compatible with a visual search function that releases the lock groove and moves the scanning needle faster than during standard playback.

Generally, the resonant frequency fh of the pickup vibration system is:
ad is the equivalent stiffness due to the elasticity of the disk, etc.
Sp is the stiffness of the support that supports the pickup system (for example, the damper (3)), and M is the stiffness of the pickup vibration chamber (for example, the arm (4), the needle arm (5), the scanning needle (6)
), magnet QQ, and fly lead (7)). When a CED type video disc is played back using the above pickup (pu), experiments have shown that the noise component caused by this resonance frequency/h is a non-negligible hindrance to the reproduction of faithful sound. is recognized. Possible measures to reduce this unpleasant noise include moving the resonant frequency fh to a higher frequency side or suppressing the output level of the resonant frequency fb. (1
According to the equation ), it can be seen that in order to increase the value of the resonance frequency/h, it is effective to decrease the equivalent mass M when the equivalent stiffness (Fid + Sp) is constant. In particular, in the pickup vibration system, the tip (
Various studies have shown that the mass (for example, in the vicinity of the scanning needle and needle arm) does not have a large effect on the frequency characteristics of the output level. The above facts will now be explained in more detail based on experimental examples.

Figures 2 and 3 show the output of the preamplifier when the masses of the scanning needle and needle arm are selected as shown in sample 1.2 in the table below in the pickup shown in Figure 1.
) and noise level (characteristic B).

Here, to measure the preamplifier output, pick up a sample (Pυ
) Related to the preamplifier (goods)
and is applied to the spectrum analyzer (to) via the amplifier (2).

In the case of the CED method, the test disk has an unmodulated 7
The 16xnz carrier wave is recorded with the color par modulated signal, and the 25KH of the spectrum analyzer (c) is recorded.
As shown in the figure, in the range up to z, an output that depends on the sample pickup vibration system is obtained, and from the resonance frequency and sharpness of this characteristic A, the approximate noise characteristics of the sample pickup can be known. The measurement of the noise level of the audio output is carried out as shown in FIG. 8(b). In the figure, (2) is a discriminator that demodulates the 0υ output of the 7° reamplifier, and (c) is an amplifier that amplifies the discriminator output in order to provide it to the spectrum analyzer (c). For this measurement, a carrier (716K) is attached to the test disk.
It includes a modulation region obtained by modulating the frequency (Hz) by 50 degrees, and a non-modulation region. Characteristic B shows the reproduction characteristic of the non-modulated region when the spectrum analyzer input when reproducing this modulated region is set to OdB.

As is clear from Figure 2, in sample 1, 11KH
Corresponding to the peak value of the preamplifier output that exists near z, the maximum noise is also seen in the audio output noise level near 11 KHz. )% B, for example, the noise level difference between 5KHz and the peak (near 11KHz) reaches 8 to 9 dB, and the peak noise level is -38
~-39dB. This peak noise is recognized as a harsh phonetic sound, and is a cause of deteriorating the quality of the sound. Sample 2 has a scanning needle and a needle arm each about 1/longer and 24% lower than that of Sample 1.
As shown in the frequency characteristic diagram of this sample in FIG. 3, it is recognized that the resonance frequency has shifted to around 13 KHz and the peak of the noise level has also shifted accordingly. Looking at characteristic B, the difference between the 5KHz level and the peak level is 4 to 5 dB, and the maximum noise level is -48 dB.
B to -49 dB, both of which are improved compared to sample 1. These results show that reducing the mass of the tip of the pickup contributes to reducing the noise level.

Samples 3 and 4 have different mass combinations of the scanning needle and needle arm compared to samples 1 and 2, but sample 3
Although there was a slight improvement effect compared to the frequency characteristics of sample 1 (Figure 2), the effect was small, whereas in sample 4, a significant effect was seen compared to sample 3, but compared to sample 2. It was inferior. As described above, it can be seen that the frequency characteristics of sample 2 are superior to the other samples, but the occurrence of some noticeable noise was observed and was not satisfactory.

The object of the present invention is to provide a pickup in which the noise level of the audio output is reduced and flattened in the audio frequency range, and as described above, the level of the resonant frequency fh of the pip-up and vibration system is In view of its influence on the noise level, the objective is to smooth out the level in this resonant frequency region to lower the level of this resonant frequency and to flatten the noise level as well.

The invention is therefore characterized in that the needle arm is loaded with a suitable damping element. Further, the present invention seeks to provide a pickup characterized in that the load of the buffer is provided on the needle arm symmetrically with respect to an imaginary plane perpendicular to the video disc and extending in the track direction. It is.

Next, the present invention will be explained according to examples. FIG. 4a shows a perspective view of a main part (a portion corresponding to IV-N in FIG. 1) of an embodiment of the present invention. This is the back side (5a) of the needle arm (5).
) with the exception of providing a buffer (to)
This is the same as shown in FIG.

The buffer body (7) is made of butyl rubber with a shear hardness of 50°, and the length, width, and length r31)■ (to) are 0 and 5, respectively.
．． It has the dimensions of 0°5.6 cod, ib, and the mass is about 1
．． It is Cape 5. The frequency characteristics of a pickup (Sample 5) in which this buffer (to) was attached to the needle arm of Sample 1 are as shown in FIG. Compared to FIG. 2, the noise level is suppressed and significantly reduced, but the occurrence of noise is still observed.

Note that the reason why the resonant frequency is shifted to the lower side is due to the buffer body (7
) due to the load. Figure 6 shows the above buffer (to)
It is a frequency characteristic diagram of a 20-needle sample loaded onto an arm. Compared to FIG. 5, the resonant frequency of the preamplifier output is lowered by the mass of the buffer member due to its load, and the Q value at resonance is suppressed low. Furthermore, the audio output exhibits no noise at all and has extremely flat frequency characteristics. As you can see, the difference in characteristics between the two is obvious. However, it should be noted that the masses of the tips of both pickups are about the same as shown in the table above.

FIG. 4 (1, 1) shows another embodiment in which the needle arm (5)
Buffers (b) and (b) are fixed to the sides (5b) and (5c), respectively. Each buffer (b) (b) should be mounted symmetrically with respect to an imaginary plane that is perpendicular to the video disc and extends in the track direction.

This is because if it is unbalanced, tracking and visual search functions will be affected. Figure (c) shows the six sides of the needle arm (5), namely the sides (5m) (5b) (5
A U-shaped buffer body (c) is fixed along c). In addition, (d) and (e) of the same figure show a ring or tube-shaped buffer c@Gη with an angular and circular outer shape, respectively.
These are each fitted onto a needle arm. The cushioning bodies in each of these examples are molded from rubber, flexible plastic, and plastic foam. , that is, any type of cushioning material that has a greater cushioning effect than the needle arm can be used. FIG. 7 shows a different embodiment of the needle arm for securing the shock absorber. The same figure (a) shows the needle arm (which is equipped with an O recess (51) on the back of the ladle to accommodate the buffer (to), and the same figure (b) also shows the needle arm with the back 1i.
In addition, in the same figure (c), a shock absorber is installed in the recess shown in (a), and the shock absorber (to) is fixed with a heat-shrinkable chain (53). This is what I did.

As described above, the present invention can reduce the noise level of the buffer which has a greater buffering effect than the needle arm that supports the scanning needle, and can very easily improve the frequency characteristics of 87H of the reproduced audio signal. Useful.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a pickup for the CED system. FIGS. 2 and 5 are frequency characteristic diagrams of the noise levels of the preamplifier output and audio output of samples with different bit ups (samples 1 and 2), respectively. FIG. 4(a) is a partial perspective view of one embodiment of the present invention;
b) and (c) are partial perspective views of different embodiments, and figures (d) and (e) are perspective views of different embodiments of the buffer body. 5 and 6 are frequency characteristic diagrams of different samples (sample 5.6) in FIG. 4(a), respectively. FIGS. 7(a) and 7(b) are perspective views of different embodiments of the needle arm, and FIG. 7(e) is a perspective view showing a state in which a buffer body is attached to the needle holder shown in FIG. 7(&). FIGS. 8(a) and 8(b) are measurement circuit diagrams used to measure each of the above characteristics. Explanation of main drawing numbers (5)...needle arm, (to)...buffer procedure
Amendment (spontaneous) April 2rr, 1980, Director General of the Japan Patent Office, 1982 Patent Application No. 5568jS 2, Pick up name of invention 6, Patent applicant address of person making amendment Moriguchi type Keihan Hondori 2nd completion 18 Address name (188) Sanyo Electric Co., Ltd. Representative Kaoru Iue 4, agent address 2-18 Keihan Hondori, Moriguchi-shi Contact information: Telephone (Tokyo) 835-1111 Patent Center Representative Kamata 6, subject to amendment + 11 Specification ``Detailed Description of the Invention'' column. 6. Contents of amendment (1) Specification page 6 I/! 11! Line 1 "Resonance wave number JY of the vibration system. Correct it to "Resonance frequency in the high range of the vibration system." (21, page 5, line 18, “For example, a damper (31J
v. "For example, needle arm (corrected as May. 31, page 6, line 19, [for example, arm (4),"
, correct it as ``for example.'' . (4) In the table on page 5, the column for tip mass of Chimp N5 has been corrected to r7.2J and r8.2J. that's all

Claims (1)

[Claims] Q! The needle arm that supports the scanning needle that detects changes is loaded with a buffer that has a larger buffering effect than the needle arm. 1. ll pickup. (2) The load of the buffer is provided on the support arm symmetrically with respect to a virtual plane that is orthogonal to the recording medium and extends in the track direction. Range No. (Pickup 0 listed in item 11)