JPS6027110B2 - scanning needle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a scanning needle, which scans an information signal recorded on a circular or spiral track on a disc-shaped recording medium and reproduces it as a capacitance change. By flattening the shape of the electrode forming surface so that it maintains a predetermined shape regardless of the degree of wear, the life of the scanning needle can be extended, and information signals can be reproduced with a good S/N ratio over a long period of time. An object of the present invention is to provide a scanning needle that is both flexible and easy to process.

In recent years, so-called video disk devices have been developed that reproduce information signals including video signals from a disk-shaped recording medium (disk) on which information signals are recorded at high density as changes in geometrically uneven shapes. In some cases, a scanning needle that moves relative to the bottom of a needle guide groove of a track formed on a disk detects and reproduces changes in mechanical vibration or capacitance.

FIG. 1 shows the shape of the tip of an example of the conventional scanning needle mentioned above.

As shown in the figure, the scanning needle 1 is made of a material such as diamond or saphire, which has excellent wear resistance, and has a triangular apex 2 at which it slides against the disk surface. An electrode part 3 is formed on the end face formed perpendicularly to the electrode part 3, in which a conductive material such as hafnium or titanium is deposited by sputtering to a film thickness on the order of angstroms. A ridgeline portion 4 is formed. During playback, this scanning needle 1 has a spiral guide groove at the bottom of which the information signal including the video signal recorded as a change in the geometrical uneven shape is transferred to the top part 2 of the sliding tip. The signal is tracked by the movement and detected and reproduced as a capacitance change with the electrode section 3, which is exactly the same as the signal pickup means in a conventional sound record.

However, because the information bandwidth of a video signal is more than 200 times that of an audio signal, in conventional video disc devices, the groove pitch must be kept at a few mm or less due to high-density recording. Moreover, in order to slide the top part 2 of the tip of the sardine and its vicinity into the guide area, the contact area is limited (for example, the electrode width p is about 3 m, the contact length 1 is about 6 meters), Therefore, the high speed rotation of the disk (for example, 45
(pm), the needle pressure per unit area of the scanning needle is extremely large, leading to extremely severe wear, and due to the structure, the width p of the electrode part increases proportionally with this wear, so that the width p is substantially equal to that of the disk. When it reaches a track pitch of (for example, about 4.5 mm), it has no choice but to call it the end of its life.
For example, in the case of the Safya needle, the lifespan of the needle is only a few tens of hours at most, which is a fatal shortcoming.

In addition, the needle pressure is 30/9 due to severe needle wear.
There is no choice but to use a very small front and rear pressure, which has disadvantages such as so-called needle skipping, which tends to cause dirt to adhere to it.

Furthermore, as the width p of the electrode portion 3 increases due to wear, information signals from adjacent tracks may be reproduced, resulting in beat disturbance.

The present invention eliminates the above-mentioned drawbacks, and each embodiment thereof will be explained with reference to the drawings from FIG. 2 onwards. FIG. 2 shows a schematic mechanical diagram of an example of a disc playback device in which the scanning needle according to the present invention is used.

In FIG. 2, reference numeral 5 denotes a turntable, which is synchronously rotated in the direction of arrow 8 at a speed of, for example, 450 to 180 pm with a disk 6 mounted on its rotating surface by a disk motor (not shown). Here, the disk 6 may have a needle guide groove like the slave, but for convenience of explanation, it is assumed that the information bit 7 is formed in a spiral or D-circular shape without forming a needle guide groove. do. That is, the disk 6 has at least the first adjacent track of the main information signal, as in the method previously proposed by the present applicant in Japanese Patent Application No. 51-38809 (Hakama Kaisho No. 52-123205).
At least one reference signal for tracking control is simultaneously recorded in bits in the second signal-free portion. The disk 6 may also be an information recording medium having a fly-guiding layer and a military layer as shown in Samurai Kaisho No. 47-37415, for example. Reference numeral 9 denotes a capacitance-type scanning needle according to the present invention, which will be described later. A lead wire 10 is connected to the electrode portion of the scanning needle 9, and a thin pipe-shaped cantilever 11, 11' made of glass or aluminum and a damper 12 are connected. , 12' to the bracket 13.

Further, 14 is a so-called moving coil mechanism created based on the same operating principle as the well-known moving linear voice coil mechanism, and is composed of a permanent magnet, a driving coil, a yoke, a damper, and a moving shaft 16. The moving shaft 16 is displaced in a predetermined direction and amplitude as indicated by an arrow 18 in accordance with the polarity and magnitude of the electric power obtained by detecting and discriminating the reference signal applied to the coil terminal 15. As a result, the scanning needle 9 is always controlled to track in the radial direction of the disk 6 stably and reliably. On the other hand, the entire signal pickup body including the moving coil mechanism 14 and the scanning needle 9 is moved by the pickup body transport mechanism (
(not shown), and is linearly transported in the disk radial direction 17 in synchronization with the track pitch on the disk 6. In addition, cantilevers 11, 11' and damper 1
The reason for forming two sets of 2 and 12' into a V shape is as follows.
Only the vertical movement of the scanning needle 9 in the vertical direction is allowed to trace the information board surface with low pressure, while the free movement in the horizontal track direction is completely restricted and applied to the moving coil mechanism 14. This is because the tracking control operation can be performed faithfully using the control power from the tracking servo.

Next, to explain the scanning needle according to the present invention, FIG.
- E' are respectively shown enlarged perspective views of essential parts for explaining the manufacturing method of the first embodiment of the scanning needle according to the present invention, and the initial shape of the contact surface and its shape after wear.

In the case of the apparatus explained in FIG.
A frame video signal is recorded for 30 minutes on a disk 6 with a diameter of 3, and the pitch interval of information bits 7 is 1.6~
It is about 5 mm. Therefore, the width of the electrode part is about 1 to 5 m, but if the finished width of the final electrode part is difficult to process due to fine dimensional accuracy, by manufacturing as follows, all polishing processes can be done by plane polishing. It can be manufactured by finishing and therefore can be processed reliably. First, as the needle material, Tiremond, which has the highest abrasion resistance, may be used, but Safya is used in consideration of material cost, workability, etc.

This Safya material is made into a regular square prism with one side of the bottom having a length d (for example, about 0.2 side), and only one side of the square prism is mirror-polished. Next, the processed side surface is finished by mirror polishing cutting at a bevel angle Q from a position a length h from the upper bottom surface toward the bottom surface. In addition, in the example, the oblique angle Q is l0o, and h is 3
~loAm. Next, in order to form an electrode on the mirror-finished side surface, a well-conducting material such as tantalum is deposited to a film thickness of about 500 to 3000 Å using a well-known sputtering technique, as shown in FIG. 3A. Rod-shaped processed body 19
get. Here, since unnecessary parts of the good conductor film shown by diagonal lines in FIG. Next, in order to form the tip shape of the needle, a portion 2 of the workpiece 19 shown by a broken line in FIG.
0 and 20' are removed by grinding to form the cut portion 22 as shown in FIG.
, 22' is formed.

Here, the electrode forming surface on which the electrode, which is the guiding body film, is formed is connected to the bottom surface part 24, so that the first electrode forming surface 23 has a width of p over a height range of h; It is connected to this with an oblique angle of angle Q, and the opening angle is 8 (for example, 40
o approximately). By using the processed body 21 as a scanning needle and scanning the disk 6 which does not have a guide groove so that the bottom surface portion 24 slides, the recorded signal can be reproduced, and as the wear progresses, the contact area increases. Therefore, the scanning needle can have an extremely long life. However, in order to improve the relationship between the electrode part and the information bit surface, and furthermore to make it possible to play secondary discs with guide grooves, the bottom part 2
4. In other words, the portions shown by broken lines 25 and 25' in FIG. 3B may be polished away so that they have a triangular shape when viewed from the sliding surface. As a result, as shown in FIG.
A scanning needle having a tip shape having a triangular bottom portion 27 on which electrodes are attached and formed as shown by diagonal lines on the first and second electrode forming surfaces 23 and 23' is obtained. At the initial stage of use, the contact surface shape of the scanning needle is triangular with a contact length of 1 and an apex angle of 0, as shown in Figure 3D, and after a sufficiently long period of use, as shown in Figure 3E. It is clear that the shape has a contact width 29 and a contact length L that are larger than the electrode width p and the contact length 1.

Incidentally, the contact length 1 may be sufficiently long to about 40 m when applied to a device as shown in FIG.

According to Fujito Honde's prototype test results, for example, the number of disk rotations is 1.
80 ratio pm, p = lAm, h = 10rm, needle pressure 3
When using the Safya needle of 0.0 mm, the scanning needle was able to withstand use for more than 300 q hours. However, when the scanning needle according to the present invention is used to reproduce a 5-disk having a secondary guide groove, if the contact length 1 is made extremely long, the tracking accuracy with respect to the guide groove will deteriorate.
It is desirable to carry out the process by finishing the process to a thickness of less than m. FIGS. 4A to 4C are enlarged perspective views of essential parts for explaining the manufacturing method of the 20th embodiment of the scanning needle according to the present invention.

In the figure, the same parts as in Figures 3A to 3E are given the same reference numerals.
The explanation will be omitted. From the bar-shaped workpiece 19 shown in FIG. 4A, a portion indicated by a broken line having a width of p and diagonally rearward at a predetermined angle is ground 5, and a portion indicated by 30 is removed.
As a result, the grinding section and the first
and second electrode forming surfaces 23 and 23' are formed. Next, the portion indicated by the broken line in Figure B is ground, and the portion indicated by 32 is removed. Thereby, like the scanning needle shown in FIG. 3B, when used in the apparatus shown in FIG. 2, it can be used as a scanning needle that can fulfill the initial purpose of the present invention. but,
In order to improve the contact situation between the electrode part and the information bit on the sliding surface, it is preferable to further remove the portion 32 shown by the broken line in FIG. It is finished into a shape having a bottom portion and a ridgeline portion 34 as shown at 33. In this embodiment, since one side surface 19a can be polished into the final needle shape while remaining flat, there is no difference from each of the above embodiments.
All of them are advantageous in terms of the processing process.

In the above first and second embodiments, the side opposite to the electrode part was explained as the introduction part during sliding, but the scanning needle according to the present invention limits the scanning direction of the sliding surface of the needle tip. Needless to say, this is not the case, and even if the electrode section 3 is arranged in advance and used as an introduction section, the signal can be similarly reproduced without any problem.

As described above, the scanning needle according to the present invention has an electrode forming surface on which electrodes for forming a capacitance with the track are formed.
It is composed of a first electrode forming surface connected to a sliding surface with the track and a second electrode forming surface connected thereto, and the first electrode forming surface is relative to the second electrode forming surface. The first electrode forming surface is formed so as to have a pair of side edges substantially parallel to the wear direction.
The first and second electrode formation surfaces can be manufactured by flat surface polishing for all polishing processes, so they can be processed with fine dimensional accuracy.Also, since they can be processed by a mechanical grinding process, the needle tip is The shape is extremely small compared to the shape of the needle tip of the Onto cord, which makes it difficult to process. However, it can be processed well and easily, is inexpensive, and even if worn, the first electrode Since the formation surface is always approximately constant, the electrode width at this part is also approximately constant,
Therefore, information signals with a good S/N ratio can be reproduced for a long period of time compared to conventional methods, and crosstalk from adjacent tracks does not occur even when reproducing a disk having a conventional needle guide groove. In addition, as the wear progresses, the contact area of the sliding surface with the recording medium increases, so that the life span of the rotating needle can be significantly extended compared to the conventional method. 1st
And since the recording medium has at least one reference signal for tracking control other than the information signal recorded in the second information signal non-recorded part, the contact area of the sliding surface with the recording medium can be expanded to a desired value. Therefore, there are no blinds that damage the information recording track, so there is no signal loss due to dust adhesion, and it has many features such as being able to perform good quality playback because it does not interfere with the current situation with the track. It is something.

[Brief explanation of drawings]

FIG. 1 is a perspective view of the tip shape of an example of a conventional scanning needle, FIG. 2 is a schematic mechanical diagram of an example of a disc playback device in which the scanning needle of the present invention is used, and FIGS. 3A to 3E are FIGS. 4A to 4C are an enlarged perspective view of essential parts for explaining the manufacturing method of the first embodiment of the scanning needle according to the present invention, and a diagram showing the initial shape of the contact surface and its shape after wear. FIG. 6 is an enlarged perspective view of a main part for explaining a manufacturing method of a second embodiment of a scanning needle according to the present invention. 1, 9... Scanning needle, 3... Electrode, 6...
...Disc-shaped recording medium (disk), 23...
...First electrode forming surface, 23'... Second electrode forming surface, 27, 33... Bottom surface portion (sliding contact surface). Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. In a scanning needle that slides on a concentric or spiral track on a disc-shaped recording medium on which an information signal is recorded as a change in geometric shape and reproduces the information signal as a capacitance change, The electrode forming surface on which the electrode for forming a capacitance is formed is composed of a first electrode forming surface connected to the sliding surface with the track and a second electrode forming surface continuous thereto, The first electrode forming surface is inclined relative to the second electrode forming surface,
A scanning needle characterized in that the first electrode forming surface is configured to have a pair of side edges substantially parallel to the wear direction.