JPH0722765Y2 - Constant linear velocity rotation control circuit based on pickup position - Google Patents

Description

[Detailed Description of the Invention] (Industrial field of application) The present invention relates to a linear velocity constant rotation (CLV) control circuit based on a pickup position, and in particular, enables improvement of CLV control accuracy even if the resolution of the pickup position scale is low. And a constant linear velocity rotation control circuit.

(Prior Art) Conventionally, in a CLV control circuit that adjusts the disk rotation speed according to the pickup position, a pickup position scale is installed and the motor rotation speed is variably controlled for each count of this scale. That is, as shown in the processing flow in FIG. 4, after reading the pickup position data (step S51), calculation for obtaining the motor rotation speed control signal is performed (step S52), and the frequency division ratio is set. By (step S53), the number of rotations of the motor is controlled.

(Problems to be Solved by the Invention) As described above, the conventional CLV control circuit controls the motor rotation speed for each 1 count (scale pitch) of the pickup position scale, and therefore is shown by the solid line in FIG. As described above, the stepwise rotation speed changes for each scale pitch. This change is not preferable because the deviation from the required linear change is large. If the resolution of the scale is improved, it is possible to get closer to the CLV rotational speed characteristic line, but there is a limit to the improvement of the resolution of the scale, and there is a problem in terms of cost.

Therefore, an object of the present invention is to provide a CLV control circuit that can improve the CLV accuracy without improving the resolution of the position scale.

(Means for Solving the Problems) In order to solve the above problems, a CLV control circuit according to the present invention detects a pickup position with respect to a disc by a linear scale, and rotationally drives the disc based on the detected position information. A linear speed constant rotation control circuit based on a pickup position for controlling a constant rotation speed of a motor, wherein a circuit for generating a pulse for each rotation of the motor, a linear scale for outputting rough data from the pickup position, and A constant linear velocity rotation comprising: a track counter for counting pulses and outputting track counter data; and a rotation control means for controlling the rotation speed of the motor based on the rough data and the track counter data. And a control circuit.

(Example) Next, this invention is demonstrated, referring drawings.

FIG. 1 is a block diagram showing an embodiment of a CLV control circuit according to the present invention.

In this invention, an optical pickup 2 is provided which follows the track groove of a disk 1 having a spiral track groove. The optical pickup 2 is
It is also driven by the linear motor 3. These operate by a focus tracking sled servo circuit.

The position of the pickup 2 is detected by the linear scale 4. Pickup 2 detected by linear scale 4
The position information of is converted into absolute position data in the thread position counter 7 and sent to the CPU 8.

The disk 1 is rotationally driven by a spindle motor 5. The spindle motor 5 is provided with a rotary encoder 6 to extract a rotation signal proportional to the rotation angle of the motor. The rotation signal is amplified by the amplifier 11, converted into a TTL level signal by the comparator 12, and supplied to the counter 10.

The counter 10 receives the output signal from the comparator 12,
One pulse is output for each rotation of the disk (motor). The track counter 9 counts the pulses from the counter 10 and sends the count output to the CPU 8.

The output of the comparator 12 is also supplied as one input of the phase frequency comparator 15.

The 1 / N frequency divider 17 is a frequency divider whose frequency division ratio from the CPU 8 is controlled, and divides the reference clock generated by the oscillator 16 by 1 / N. The frequency-divided output divided by the 1 / N divider 17 is the phase comparator 2
It is input to 0 and is phase-compared with the frequency-divided output from the 1/2560 frequency divider 18.

A low-pass filter (LPF) 21 extracts low-frequency components from the output of the phase comparator 20, and a voltage-controlled oscillator (VCO) 22
Is output as a control signal.

The oscillation frequency of the VCO 22 is controlled by the signal from the LPF 21, and the oscillation frequency is output to the frequency dividers 18 and 19. Divider 18,1
9. The phase comparator 20, LPF21, VCO22 constitute a normal PLL circuit.

The phase frequency comparator 15 compares the output from the comparator 12 with the output of the frequency divider 19 to generate a rotation signal of the motor corresponding to the phase difference, and outputs the low pass filter (LP
F) Supply to 14.

The output of the LPF 14 is input to the driver circuit 13, and the drive signal of the spindle motor 5 is supplied to the spindle motor 5 by the driver circuit 13.

Now, the relationship between the pickup position (the position where the position signal is currently detected) and the number of rotations is as follows: linear velocity v (m / sec), radial position r from the center of the disc 1 of the pickup.
(M), the rotation speed N (rpm) at that time is represented by N = 60 · v / 2πr.

In FIG. 1, the signal corresponding to the output of the rotary encoder 6 and the signal corresponding to the reference signal from the frequency divider 17 are compared in phase by the phase comparator 20 to control the rotation speed of the motor. Therefore, it becomes possible to control the rotation speed of the motor by changing the frequency division ratio data of the frequency divider 17 with a signal from the CPU 8.

When the number of output pulses from the rotary encoder 6 per rotation is p and the reference clock frequency is Ck (Hz), the frequency division ratio is expressed as A = (2πCk / vp) · r, and the frequency division ratio A is 2πCk / v · p is a coefficient k, and r
Proportional to.

FIG. 3 is a flow chart showing a processing procedure of CLV control according to the present invention. The process will be described below with reference to FIG.

First, as an initial operation, the pickup is returned to the innermost circumference, and this position is set as a recording start position. Also, the thread position counter 7 and the track counter 9 are reset.

From the disk center, and the distance to the position and r _0, the division ratio data k · r ₀ at a distance r ₀ as the initial value, (the number of counts of the threads position counter 7) The distance r ₀ from the pickup moving amount Is Δr, the division ratio is kΔr
It becomes + kΔr ₀ . These calculations are performed in the CPU 8 in a cycle sufficiently shorter than one rotation of the disk to control the frequency divider 17.

First, the sled position counter 7 detects the position data of the pickup 2 by the linear scale 4 and multiplies the position data by the linear velocity coefficient k to obtain the frequency division ratio A (step
S31).

Next, the frequency division ratio B is obtained by adding the initial frequency division ratio data at the initial pickup position to the frequency division ratio A (step
S32). This value changes for each scale resolution of the linear scale 4, and does not change if the pickup position changes within the scale resolution. For example, the scale resolution is 0.1mm / 1
When counting, the division ratio does not change when the pickup position changes within 0.1 mm. This value is used as the coarse frequency division ratio data, and whether or not the value B does not change is determined in step S33.
If it is determined that the data is not the coarse frequency division ratio data, the coarse frequency division ratio data is updated (step S39), and the obtained coarse frequency division ratio data is used as the frequency division data (step S40). The counter 9 is reset (step S41). After that, the frequency division ratio data is set in the frequency divider 17.

On the other hand, in step S33, when B is determined to be the coarse frequency division ratio data (when the frequency division ratio data B does not change), the pickup position change within 0.1 mm is interpolated based on the count value by the track counter 9. Ask. That is, since the pickup 2 follows the track, when the disc 1 makes one rotation, the pickup 2 moves by one track pitch. Therefore, if one pulse signal per rotation from the counter 10 is counted, the increment is within 0.1 mm (position change).
Is detected based on the track pitch resolution.

The track counter 9 is reset each time the count number of the thread position counter 7 changes, and increases every time the disk rotates once. Therefore, if Δr moves 0.1 mm,
The coarse division ratio data is set and the track counter 9 is reset, and the division ratio for correction is added to the coarse division ratio every time the disk makes one revolution, and apparently the resolution of the scale is improved.

That is, in step S34, the count data of the track counter 9 is multiplied by the linear velocity coefficient k, and the obtained multiplication result is divided by the number of tracks in one pickup scale count to obtain the frequency division ratio data as C, The added value of the frequency division ratio data C and B is used as the frequency division ratio data D (step S35).

Thereafter, the frequency division ratio data is updated (step S37), and the obtained frequency division ratio data is set in the frequency divider 17 (step S3).
8).

As a result, the disc rotation speed control for the pickup position from the center of the disc is not the conventional control for each scale pitch, but fine adjustment is possible for each track pitch within the scale pitch, and constant linear velocity rotation (CLV) is possible. Become.

That is, the dotted line portion in FIG. 2 is the control characteristic obtained by the above-mentioned device, and as is apparent from the partially enlarged view in the same figure, in this device, the control characteristic line is compared with that for each track pitch. Almost linear characteristics can be obtained.

(Effect of Device) As described above, in this device, the change in the pickup position within the resolution (scale pitch) of the linear scale for detecting the pickup position is obtained by interpolating based on the track count data. Appropriate speed control according to minute position changes within the scale pitch becomes possible.

Therefore, a scale with low resolution can be used, it is inexpensive, and only a circuit for counting the zero-point signal of the rotary encoder is added.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a CLV control circuit according to the present invention, FIG. 2 is a view showing the relationship between pickup position and rotation speed, and FIG. 3 is a main operation in the embodiment shown in FIG. FIG. 4 is a flow chart showing the processing procedure, and FIG.
It is a figure which shows the process sequence of CLV control. 1 ... Disc, 2 ... Pickup, 3 ... Linear scale, 5 ... Spindle motor, 6 ... Rotary encoder, 7 ... Thread position counter, 8 ... CPU,
9 …… Track counter, 10 …… Counter, 11 …… Amplifier, 12 …… Comparator, 13 …… Driver, 14,21 ……
Low-pass filter, 15 …… Phase frequency type comparator, 16 ……
Oscillator, 17,18,19 …… divider, 20 …… phase comparator, 22 ・ ・ ・
… Voltage controlled oscillator (VCO).

Claims (1)

[Scope of utility model registration request] 1. A linear scale constant rotation control based on a pickup position, which detects a pickup position with respect to a disc by a linear scale, and controls a rotational speed of a motor for rotationally driving the disc based on the detected position information. In the circuit, the linear scale that outputs rough data from the pickup position, a circuit that generates a pulse for each rotation of the motor, a track counter that counts the pulse and outputs track counter data, and the rough data And a rotation control means for controlling the rotation speed of the motor based on the track counter data, a constant linear velocity rotation control circuit.