JPS627630B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an apparatus for sequentially recording or reproducing signals as spiral recording trajectories (tracks) on a rotating recording medium. The present invention relates to a variable feed pitch device which is characterized in that it can be set variably with high precision and that the set pitch can be directly read.

In the high-density information recording media such as video discs and PCM audio discs that have been proposed recently, track pitch has an impact on recording time, interference with adjacent groove signals (crosstalk), playback stability, etc. For example, to increase the recording time, set the track pitch within the allowable range of the recording device.
This is possible by narrowing the width, but during playback,
Interference with adjacent signals will increase, and the stability of reproduction will deteriorate due to the influence of dust and the like adhering to the disk surface. Therefore, by making the track pitch variable according to the required recording time, it is possible to make maximum effective use of the recording surface of the recording medium, and it is also possible to adjust the S/N of the signal depending on the content of the recorded information. Depending on the situation, you can record a disc with good image quality and a short program, or a disc with a long program and sacrifice some image quality.
Can be played. Furthermore, the present invention is also applicable to cases where the rotational speed of the recording medium changes continuously depending on the recording position, such as constant linear velocity (CLV) recording where the relative speed between the recording medium and the pickup device is always the same. It is possible. Also, during playback, even on disks that do not have a feedback loop for controlling feed from the tracking servo, the setting pitch information is recorded on the disk during recording, and that information is recorded during playback. By reading this, recording and playback on a variable setting track pitch disk becomes possible.

One embodiment will be described below with reference to the drawings.

FIG. 1 is a block diagram of the present invention, in which 1 is a turntable and a recording medium, which are rotated by a turntable motor 2 at a required rotational speed.

3 is a rotation detector that outputs a frequency proportional to the rotation of the turntable motor 2, and the output thereof is multiplied by a variable frequency multiplier circuit 4 to a frequency that is a necessary integral multiple. In the embodiment, a synthesizer circuit composed of a PLL is used. 5 is a frequency divider having a frequency division ratio determined by the reduction ratio and the constant of the rotation detector of each motor. Reference numeral 6 denotes a head device for recording or reproducing, which is driven in the radial direction through a feed screw 7 and a reduction gear 8 in accordance with the rotation of a feed motor 9. 10 is a rotation detector that outputs a frequency proportional to the rotation of the feed motor 9, which is input to a phase comparator 11, and is compared with the output of the frequency divider 5 to detect a rotation error;
It is input to the feed motor 9 through the drive circuit 12 and is operated in synchronization with the turntable motor 2 at a rotational speed determined by the multiplication number of the variable multiplier circuit 4 and the frequency division ratio of the frequency divider 5.

FIG. 2 shows an embodiment of the multiplier circuit 4 in FIG. 1.

13 is a phase comparator, which outputs a voltage proportional to the phase difference between two frequency inputs, and passes it through a low-pass filter 14 to a voltage controlled oscillator (VCO) 1.
5 and its frequency is controlled. VCO
The output of 15 is connected to a frequency divider 16 and a variable setting frequency divider 18.
The two inputs are phase-locked by being frequency-divided by , input to the phase comparator 13, and compared with the frequency of the rotation detector 3 shown in FIG. 1 in this example.
Frequencies are kept equal. A programmable counter is used as the variable setting frequency divider 18, and the frequency is divided by the value of the variable digital switch 17 for pitch setting. The decimal point and units displayed on this digital switch may be displayed in pitch units (for example, μm) for easy direct reading, and the frequency division number is an integer indicated by all digits of the switch.

As a result, the output frequency of the VCO 15 becomes a frequency multiplied by the output frequency of the rotation detector of the turntable motor, and the multiplier is an integer whose common divisor is an integer value represented by the necessary number of digits of the numerical value indicating the track pitch. becomes.

The feed accuracy when using this configuration will be calculated below.

P _T ...Set track pitch (μm) F _T ... Rotation speed of turntable motor 2 (r.
ps) F _S ...Rotational speed of the feed motor 9 (rps) P _S ...Pitch of the feed screw 7 (μm) 1/G ... Assuming the reduction ratio of the reducer 8, the required rotation speed F _S of the feed motor 9 is , F _S =F _T ×P _T ×G/P _S ...(1) Furthermore, the rotation speed F _S ' obtained with the configuration of the present invention is K ₁ ...the number of pulses per rotation of the rotation detector 3 ( p/r) K ₂ ... Number of pulses per rotation of rotation detector 10 (p/r) A ... Frequency division number of frequency divider 16 B ... Frequency division number n of frequency divider 5 ... Track pitch If the required number of digits Pi is the nearest integer value of Pi=P _T ×10 ^n-1 , then F _S ′×K ₂ = F _T ×K ₁ ×Pi×B/A ……(2) F _S ′=F _T ×K ₁ × Pi × B / (A × K ₂ ) …(3) Furthermore, the actual track pitch Pr is F _S ′ in equation (3).
Since this is P _T obtained when substituting F ₃ in Equation 1, Pr = K ₁ × Pi × B × P _S / (G × A × K ₂ ) … (4) Also, P _T = Pi / 10 ^{n- 1} , the track pitch error △P _T is as follows: △P _T = Pr/P _T = {K ₁ × B × P _S × 10 ^n-1 / (K ₂ × A × G) − 1} ……(5 ) From the above equation (5), it can be seen that the track pitch error of this configuration can be sufficiently adjusted by the number of digits n of the track pitch and the frequency division numbers A and B.

Substituting the numerical values from the example and calculating: P _O = 500 (μ) A = 8 K ₁ = 70 (p/r) B = 1703 K ₂ = 15 (p/r) G = 548 If n = 3 ΔP=0.000095, and the error is less than 0.01% for all three-digit track pitch setting values.

In this way, by configuring the turntable motor and feed motor to operate synchronously, it is possible to adapt even when the rotational speed of the turntable motor changes, and furthermore, the frequency proportional to the rotational speed of the turntable motor can be adjusted. By inserting a circuit that multiplies and divides the frequency, it is possible to control the track pitch with very high precision. Even when the track pitch is variable, the structure of the reducer can be simple, and the multiplier can be By multiplying the value by an integer including the value of , the desired track pitch can be set with a simple operation, and the set value of the track pitch can be read directly.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is a block diagram of the main parts. 1... Recording medium (turntable), 2... Turntable motor, 3, 10... Rotation detector,
4...Variable frequency multiplier circuit, 5...Frequency divider, 6...
...Head device, 7...Feed screw, 8...Reducer,
9...Feed motor, 11...Phase comparator, 12...
...Drive circuit.

Claims (1)

[Scope of Claims] 1. A rotation detector that outputs a frequency proportional to the number of rotations of a motor that rotates a disc-shaped recording medium, and a variable frequency multiplier that multiplies the frequency of the output of the rotation detector by an integer of a set value. a frequency divider that divides the multiplied frequency that is the output of the variable frequency multiplier circuit, and a rotation that outputs a frequency proportional to the rotation of the feed motor that moves the head device in the radial direction of the disc-shaped recording medium. Comparing means for comparing the phases of the output of the detector and the output of the frequency divider,
A recording/reproducing apparatus characterized in that the feed motor is synchronously controlled in accordance with the output of the comparing means. 2. The recording/reproducing apparatus according to claim 1, wherein the multiplication number of the variable frequency multiplier circuit is selected to be an integral multiple of the required number of digits of the track pitch value.