JP2592602B2 - Pick-up device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method in which a scanner is applied to the surface of an information recording disk (hereinafter abbreviated as a disk) on which information signals are recorded as concentric or spiral recording trajectories. The present invention relates to a pickup device of a reproducing apparatus that reproduces an information signal sequentially by contacting the information signals.

(Prior Art) FIG. 4 shows an example of a conventional pickup device. In FIG. 1, reference numeral 1 denotes a scanner (specifically, a reproduction needle or the like), and 2 denotes a disk. Reference numeral 3 denotes a scanner holder, 4 denotes a lead wire, 5 denotes a cantilever, and 6 denotes a magnet, which are integrally combined to form a pickup arm. A vibrating system is constituted by the elastic support 7 elastically supporting the vicinity of the magnet 6 of the pickup arm, and an electromagnetic coil 8 is provided above and spaced apart from the magnet 6 above. When a current flows through the electromagnetic coil 8, the pickup arm is given a rotating force about the elastic support 7, and a contact pressure of the scanner 1 attached to the tip with respect to the disk 2 is obtained. Reference numeral 9 denotes a constant contact pressure application circuit, the operation of which is started by a switch signal 10, supplies a constant current to the electromagnetic coil 8 through a drive circuit 11, and applies a prescribed contact pressure to the scanner 1. The lead wire 4 transmits a signal sensed by the scanner 1 to the signal detector 12. 13 is an output drop detection circuit, which is a signal detector.
12 to detect the fluctuation of the reproduction output obtained through
This detects the intervention of foreign matter between the disk and the disk 2. 14
Is an adder, which outputs a current corresponding to the output reduction level detected by the output reduction detection circuit 13 to the constant contact pressure application circuit 9.
Is added to the specified current from. With this configuration, foreign matter that is not removed under the specified contact pressure can be removed, and after the removal, the output returns to the original specified contact pressure when the output is restored.

(Problems to be Solved by the Invention) The above-described conventional configuration has the following disadvantages.

The disk 2 has surface waviness (undulation) generated during molding and with the passage of time, and generates vibration having various frequency components with rotation. A prescribed contact pressure is applied to the scanner 1 so as to follow this vibration. The relationship between the vibration acceleration amplitude A of the disk and the contact pressure W of the scanner is expressed by the relation A∝ω · W / Zm. Therefore, as the contact pressure W increases, the disk vibration A that the scanner can follow increases. In the above equation, ω is the angular frequency, and Zm is the mechanical impedance in the disk vibration direction at the scanning portion of the pickup vibration system. However, increasing the contact pressure of the scanner impairs the life of the disk and the scanner, which is a limitation.

FIG. 5 shows the relationship between the disk vibration and the tracking ability of the pickup (scanner). In the figure, reference numeral 15 denotes a disk vibration level, and reference numeral 16 denotes a follow-up capability level of the scanner when a constant contact pressure is applied to the scanner. Tracking ability level 16 of the scanning tool, as shown in FIG decreases by Q ₂ at a frequency indicated by F _2. It is the mechanical impedance of the scanning part (Zm) due to the configuration of the vibration system of the pickup.
There is for showing the frequency characteristic having a resonance point of the resonance value Q ₂ at a frequency of F _2, usually referred to as the resonance point and antiresonance point.

In the conventional configuration shown in FIG. 4, the response frequency of the output drop detection circuit 13 is relatively low, the detection target is a foreign substance between the scanner 1 and the disk 2, the detection frequency is extremely low, and most of the time, the contact pressure is constant, as described above, in FIG. 5, tracking capability level of the scanning body varies as 16, M ₁ to the vibration level 15 of the disk at low frequencies
While there is a margin, not take a only afford M ₂ is at the frequency F _2. The follow-up margin is important to be kept uniform in the entire frequency range, in the state described above, with respect to the disc having a large vibration components near the frequency F _2, exhibits a very unstable tracking state Will be. However, it also sets a prescribed contact pressure to ensure the same follow-up margin as M ₁ at the frequency F ₂ is not preferred from the viewpoint of the disc life, the scanning tool life is as described above.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pickup device which solves the conventional drawbacks and has a sufficient margin for following a disk having a vibration component near the anti-resonance frequency of the pickup.

(Means for Solving the Problems) In the pickup device of the present invention, a scanner for reading a signal by abutting on an information recording disk is attached to a front end of a pickup arm having a rear end elastically supported. Vibration system, means for detecting the vibration acceleration of the information recording disk,
A low-pass filter having a transfer characteristic whose peak frequency and peak value substantially match the frequency and resonance value of the anti-resonance point of the mechanical impedance in the vibration direction of the information recording disk in the scanning part of the vibration system; There is provided means for applying the contact pressure in accordance with the vibration acceleration and weighted by the transfer characteristic of the low-pass filter.

(Operation) According to the present invention, a necessary contact pressure is applied to the scanner in accordance with the mechanical impedance characteristics of the pickup, and a sufficient tracking allowance of the pickup is ensured in a wide frequency band.

Embodiment An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 shows a pickup device according to a first embodiment of the present invention. In the figure, the same parts as those of the conventional example shown in FIG. 4 are denoted by the same reference numerals, and the description thereof is partially omitted.

In FIG. 1, reference numeral 17 denotes a sensor for detecting the vibration of the disk 2, and reference numeral 18 denotes an acceleration detection circuit for detecting an output from the sensor 17 as acceleration. Reference numeral 19 denotes a low-pass filter which has a transfer characteristic as shown in FIG. ₂ and whose peak frequency F ₁ and peak value Q ₁ are substantially equal to the anti-resonance frequency F ₂ and its resonance value Q ₂ shown in FIG. Match. Reference numeral 11 denotes a drive circuit for driving the electromagnetic coil 8.

Regarding the pickup device configured as described above,
The operation will be described with reference to FIG. 1 and FIG.

The vibration amplitude signal of the disk 2 detected by the sensor 17 is converted into acceleration by the acceleration detection circuit 18 and detected, and a signal corresponding to the disk vibration level 15 shown in FIG. 5 is output. Next, the vibration level of the disk 2 is weighted by the low-pass filter 19. That is, it is considered that the apparent vibration level of the disk has increased by an amount corresponding to the drop in the following ability of the pickup in FIG. The signal level corresponding to the acceleration amplitude of the disk vibration weighted in this way is
The drive circuit 11 amplifies and drives the electromagnetic coil 8 so that the pickup applies a contact pressure having a certain margin to follow the weighted acceleration amplitude. Reference numeral 10 denotes a switch signal which turns on and off a series of operations according to the position of the pickup and other conditions.

As described above, according to the present embodiment, the acceleration detection circuit 18
By providing a low-pass filter having a peak characteristic almost coincident with the anti-resonance characteristic of the pickup, a necessary contact pressure of the scanner can be obtained according to the vibration level of the disk. It is possible to recover from the problem that the following ability is degraded at the anti-resonance point. That is, in FIG. 5, the tracking ability level of the pickup is improved to a line indicated by approximately 16 '.

FIG. 3 shows a pickup device according to a second embodiment of the present invention. 1 differs from FIG. 1 in that a comparator 20, a constant contact pressure applying circuit 9, and an adder 14 are provided.

Regarding the pickup device configured as described above,
The operation will be described.

In the present embodiment, a constant contact pressure is always applied to the scanner by the constant contact pressure application circuit 9 as in the conventional pickup device. This constant contact pressure (specified contact pressure) corresponds to the disk vibration level 15 in FIG.
Against the expected upper limit level, a value follow-up margin M ₁ is minimum ensured pickup.

The acceleration amplitude of the disk vibration weighted by the low-pass filter 19 is compared by the comparator 20 with the acceleration amplitude that the pickup can follow under the specified contact pressure. That is, an insufficient follow-up margin under the specified contact pressure is detected. Then, the current corresponding to the indefinite amount is added to the specified current from the constant contact pressure application circuit 9.

As described above, the comparator 20 and the constant contact pressure applying circuit 9
By providing the adder 14, the same effect as in the first embodiment can be obtained.

(Effects of the Invention) According to the present invention, a means for detecting the vibration acceleration of a disk, and transmission in which the peak frequency and the peak value match the frequency and the resonance value of the anti-resonance point of the mechanical impedance in the scanning portion of the pickup vibration system By providing a low-pass filter having characteristics and a means for applying the contact pressure of the scanner to the disk in accordance with the vibration acceleration and weighted by the transfer characteristics of the low-pass filter, the necessary pressure can be adjusted according to the mechanical impedance characteristics of the pickup. The contact pressure is applied to the scanning element, and a sufficient tracking allowance of the pickup can be secured in a wide frequency band, and the practical effect is great.

[Brief description of the drawings]

FIG. 1 is a block diagram of a pickup device according to a first embodiment of the present invention, FIG. 2 is a diagram showing transfer characteristics of a low-pass filter 19, and FIG. 3 is a block diagram of a pickup device according to a second embodiment of the present invention. FIG. 4 is a block diagram showing an example of a conventional pickup device, and FIG. 5 is a diagram showing the relationship between the disk vibration and the following ability of the pickup. 1 ... scanner, 2 ... disk, 3 ... scanner holder,
4 lead wire, 5 cantilever, 6 magnet, 7 elastic support, 8 electromagnetic coil, 9 constant contact pressure application circuit, 10 switch signal, 11 drive circuit, 12 ... Signal detector, 13 ... Output drop detection circuit, 14 ...
... Adder, 15 ... Disk vibration level, 16 ... Scanner tracking ability level, 16 '... Pickup tracking ability level, 17 ... Sensor, 18 ... Acceleration detection circuit, 19 ...
Low-pass filter, 20 ... Comparator.

Claims (1)

(57) [Claims] 1. A vibration system in which a scanner for reading a signal by contacting an information recording disk is attached to a distal end of a pickup arm having a rear end elastically supported, and a vibration acceleration of the information recording disk. And a low-pass filter having a transmission characteristic whose peak frequency and peak value substantially coincide with the frequency and resonance value of the anti-resonance point of the mechanical impedance in the vibration direction of the information recording disk in the scanning unit of the vibration system. A pickup device for applying a contact pressure of the scanner to the information recording disk in accordance with the vibration acceleration and weighted by a transfer characteristic of the low-pass filter.