JPS5845094B2 - Recording signal detection device for disc records - Google Patents

Description

[Detailed Description of the Invention] A light beam capable of producing a light spot (light spot) with a diameter sufficiently small compared to the shortest recording wavelength of the recording signal recorded in the sound groove of a disc record is transmitted to the disc record. An optical pickup means for recording signals on a disc record, which is projected onto the record and optically detects the recorded signal from the disc record in a non-contact manner, does not damage the sound groove when detecting the recorded signal. It also has the advantage of being able to faithfully reproduce recorded signals, and various formats have been proposed in the past.

Figure 1 a, b, Figure 2 a, b, Figure 3, etc., show that the recording signal is at the depth of the sound groove, as in the case where the disc record is a 45-45 stereophonic disc record. and/or the state of projection of the light beam in some cases in which a recording signal is optically detected from a disc record recorded as a lateral positional change of each wall of the sound groove. and the state of reflection (Fig. 1 a, b, Fig. 2 a, Fig. 3), and the state of the light spot on the board surface (Fig. 2)
etc., and are illustrated and explained in Figures 1a and 2a.
Figures 3 and 3 are longitudinal cross-sectional views of the sound groove, and figures 1 and 2 are plan views, respectively. (Only the light beam or spot is shown to detect the recording signal on one side).

In each figure, 1 is a disc record, G is a tone groove, 2, 3
, 2a and 3a are the walls of the sound groove G, 4 and 4a are projected light beams, 41 and 4al are reflected lights, 5 is the moving direction of the disc record 1, and 4P is a light spot, respectively.

1A and 1B show the wall surface on which the light beam 4 is projected by projecting the light beam 4 onto the wall surface 3 of the sound groove G of the disc record 1 and detecting the change in the amount of light reflected from the wall surface 3. This method is designed to obtain a recording signal at 3, and FIGS.
straddles both the wall surface 3 of the sound groove G on the board surface and the land section, and by detecting the change in the amount of light reflected from the land section, the light beam 4 is projected on the wall surface 3 of the sound groove G. This is a method for obtaining recording signals, and furthermore,
FIG. 3 shows that the walls 2 and 3 of the sound groove G are 2a
, 3a, the optical path length becomes (4+4
1) to (4a+4al), this method obtains a recording signal on the wall surface on the side on which the light beam is projected by detecting the change in the optical path length.

In addition to the above-mentioned methods illustrated with reference to FIGS. 1 to 3, in many other optical detection methods for recording signals, light is projected onto the disc surface for detecting recording signals. It is necessary for the beam to correctly follow the sound groove in the required condition, but disc records generally have warpage or uneven thickness on the disc body, and also usually have eccentricity or deviation from a perfect circle. Therefore, it is necessary to use a focus servo system and a tracking servo system in order to make the light beam projected onto the disc surface always follow the sound groove correctly in the required state as described above.

However, the above-mentioned focus servo systems and tracking servo systems have complex configurations, many technical difficulties, and high prices.

Therefore, in the detection device for recording signals on disc records of the present invention, the advantages of the non-contact type obtained in the above-mentioned optical detection method of recording signals are retained, and at the same time, the focus detection system, which has various problems, can be avoided. - Instead of using a servo system and a tracking servo system, a guide needle is used to trace the sound groove, thereby successfully solving the above-mentioned conventional problems.

Hereinafter, specific contents of the present invention will be explained with reference to the accompanying drawings.

FIG. 4 is an enlarged sectional view of a part of an embodiment of a pickup device used to implement the recording signal detection device for a disc record of the present invention, and in FIG. 4, 6 is a cantilever of the pickup. , 7 is a holder fixed to the cantilever 6.

A guide needle 9 is provided on the holder 7 via a damper member (or buffer member) 8 such as rubber, and
A focusing lens 10 is fixed.

An optical fiber 11 is connected to the focusing lens 10, and a light beam 4 from a light source (not shown) is transmitted and focused through the optical fiber 11 and the focusing lens 10, thereby forming a light spot 12 with a minute diameter on the board surface. is projected, and reflected light 41 from the board surface is sent to a detector (not shown) via a focusing lens 10 and an optical fiber 11.

It is desirable that the position of the tip of the guide needle 9 and the position of the focal point of the focusing lens 10 (position of the light spot 12) be as close as possible, and the position of the guide needle 9 should be such that it is aligned with the sound groove G. It is necessary to avoid damaging the recording waveform carved in the sound groove when tracing the sound groove.

The vibration of the guide needle 9 is caused by a damper member (or buffer member) 8.
Since the vibration of the guide needle 9 is transmitted to the holder 7 via the damper member (or buffer member) 8, the frequency band of the recorded signal recorded in the sound groove and a higher frequency band are transmitted to the holder 7 through the vibration of the guide needle 9. By using a material that can absorb the vibrations of the disc record, the holder 7 is free from warping, uneven thickness, and
Only low-frequency vibrations generated in the guide needle due to eccentricity and deviation from a perfect circle are transmitted, and therefore a light spot is created by the light beam focused by the focusing lens 10 fixed to the holder 7. 12 is always correctly projected in the required state to the sound groove near the tip of the guide needle.

(When the guide needle 9 and the holder 7 are fixed and the vibration of the guide needle 9 is completely transmitted to the holder 7, the guide needle 9 is faithful to the recorded waveform of the sound groove. If the recording signal were to be followed, the recorded signal cannot be detected with such a device because no change based on the recorded signal appears in the reflected light from the light spot 12.

) As described above, in the recording signal detection device for a disc record of the present invention, a light beam is projected onto the disc surface in order to optically detect a recording signal from the sound groove of the disc record in a non-contact manner. The projection position of the dot is regulated by the guidance of a guide needle placed very close to the light spot, which is not necessary in conventional non-contact recording signal detection methods. This eliminates the need for a complicated servo system, and the vibration of the guide needle that follows the sound groove is used to regulate the position of the light beam via a mechanical low-pass filter. The recorded signals inside are optically detected with high fidelity.

Furthermore, the guide needle used is different from the playback needle in a normal pink-up, which is used to extract the recorded signal from the sound groove, and is used only to obtain information about the position and condition of the sound groove. Therefore, it is only necessary to have a structure that does not damage the recorded waveform in the sound groove.

As described above, according to the recording signal detection device for a disc record of the present invention, all the problems of the conventional example described above can be solved satisfactorily, and by applying the device of the present invention, high performance can be achieved. It becomes possible to manufacture and provide a high-performance disc record playback device at low cost.

[Brief Description of the Drawings] Figures 1a and b, Figures 2a and b, and Figure 3 are longitudinal cross-sectional views of sound grooves (Figs. Figure 1a, Figure 2a, Figure 3) and plan view (
FIG. 1, FIG. 2) and FIG. 4 are partially enlarged sectional views of an embodiment of a pick amplifier device used to implement the device of the present invention. 1... Disc record, 2, 3... Sound groove wall, 4.4a... Light beam, 41.4 a
l...Reflected light, 6...Pickup cantilever, 7...Holder, 8...
Damper member (or buffer member), 9... Guide needle, 10... Focusing lens, 11... Optical fiber, 12... Light spot, G ...Sound groove.

Claims (1)

[Claims] 1. A guide needle passing through the tone groove is passed through a damper member to a hard record in which a recording signal is recorded as the depth of the tone groove and/or various lateral positional changes of the tone groove. A light beam for optically detecting a recording signal in a sound groove attached to a holder and a part of the holder is guided in a desired state to the sound groove near the tip of the guide needle. a light beam forming means is provided, and a material capable of absorbing vibrations in a frequency band of a recording signal recorded in the sound groove and a frequency band higher than that is used as the damper member,
The light beam guided in the required state to the sound groove near the tip of the guide needle is caused to reach the lowest frequency in the recorded signal recorded in the sound groove during the movement of the guide needle in the sound groove. 1. A detecting device for a recorded signal in a disc record, characterized in that it tracks only signals having frequency components lower than that of the disc record.