JPH0327985B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric motor rotation control apparatus, and more particularly to an electric motor rotation control apparatus for driving a digital audio disk, which requires recording of information while maintaining a constant linear velocity.

Conventionally, information is recorded on a disk-shaped recording medium such as an LP record while being rotated at a constant rotational speed, such as 33 1/3 rotations, that is, while keeping the angular velocity constant. Therefore, the linear velocity of the disk-shaped recording medium differs between the outer circumferential portion and the inner circumferential portion, and the linear velocity cannot be kept constant.

Digital audio disks, which have made remarkable progress in recent years, converge a laser beam onto a photoresist or the like thinly coated on the surface of the disk, and change the intensity of the laser beam in accordance with the information to be recorded. When the disk surface is then subjected to a development process, small holes called pits are formed on the disk surface.

In this way, a master recording is produced, and based on this, a copy is produced by press working or the like.

The digital audio disk produced as described above is particularly superior to conventional disks in the following points.

Since recording is performed using the pulse code modulation method (PCM), it has excellent S/N ratio, frequency characteristics, crosstalk, etc.

Since the pit width on a digital audio disk is less than 1 μm, the track width is
A diameter of about 2 μm is sufficient, and a disk with a diameter of 12 cm allows long-term recording of about 1 hour.

Since it is recorded as a digital value, the playing time,
It is possible to record information other than audio information such as the composer's name and performer's name, display this information on a playback device, and easily find the beginning of a song using address information, etc. Has excellent operability.

The invention relates to a device for achieving the above features. That is, when a digital audio disk is driven by a conventional device that maintains the angular velocity constant, the linear velocity v at a point at a distance r from the center of rotation is given by the following equation, where w is the angular velocity.

v=r・w Therefore, when the distance r from the center of rotation changes,
The linear velocity v also changes in direct proportion.

On the other hand, digital audio discs
Since recording is performed using PCM, the required band spans several MHz, and current optical technology can only focus laser beams down to about 1 μm, so these conditions require the required linear velocity v. will be determined.

Therefore, if a digital audio disk is to be driven by the conventional device described above, the digital audio disk must be rotated at the required number of rotations at the _radius r ₀ of the innermost circumference to be recorded. As for the part that goes beyond
Information is recorded at a linear velocity that exceeds the required linear velocity, which is extremely uneconomical.

Furthermore, since there are restrictions on the performance of the electric motor, the upper limit of the rotational speed is limited, and therefore the radius r ₀ of the innermost circumference that can be recorded is also limited, and it is not possible to record very far into the inner circumference.

The present invention solves the above drawbacks by providing means for detecting the recording radius and means for controlling the rotation speed of the electric motor using the output of the detection means as input so that the product of the rotation speed and the recording radius is constant. This will be explained in detail below with reference to the accompanying drawings showing embodiments.

FIG. 1 is a block diagram of the apparatus of the present invention, which includes a motor 2 for rotationally driving a digital audio disk 1, and a motor 3 for moving a reflecting mirror 5 for reflecting a laser beam 16 in the radial direction. Reference numeral 4 denotes a fine movement feed and movement amount detection device that receives power from the motor 3 to move the reflecting mirror 5, detects the amount of movement of the reflecting mirror 5, and inputs a detection signal to a control circuit 6, which will be described later. 6 inputs the output signal from the fine movement feed and movement amount detection device 4, and calculates the oscillation frequency or control voltage of a voltage controlled oscillator (hereinafter abbreviated as VCO) that has been set in advance after the recording radius has changed. This is a control circuit that outputs a reference signal for the comparators 7 and 10. Further, the comparator 7 uses the output signal of the frequency generator 8 provided integrally with the motor 2 as a comparison signal, outputs a difference signal from the reference signal from the control circuit 6, and outputs a difference signal from the reference signal from the control circuit 6. This is to control the rotation of the motor 2. Furthermore, the comparator 10 uses the output signal of the rotation detector 11 provided integrally with the motor 3 as a comparison signal, and outputs a difference signal between the reference signal from the control circuit 6 and the output signal via the drive circuit 12. This is to control the rotation of the motor 3.

In addition, 13 is a laser oscillation tube, 14 is an optical modulator, 1
5 is a converging lens that moves integrally with the reflecting mirror 5.

Therefore, if one pulse signal is output when the recording position moves by 1 mm by the fine movement feed and movement distance detection device 4, the pulse output is input to the control circuit 6, so that the control circuit 6 , preset VCO after recording radius moves by 1mm
The rotational speed of the motors 2 and 3 can be controlled by applying the oscillation frequency or VCO control voltage to the comparators 7 and 10 as a reference signal.

By repeating the above operations over the entire recording range, the recording radius and digital audio
A preset relationship with the disk can be maintained within tolerance.

FIG. 2 is a block diagram showing the control circuit 6 in more detail, and includes a reference oscillator 17 made of a component having a stable oscillation frequency such as a crystal resonator, and a reference oscillator 17 which uses the output of the reference oscillator 17 as an input and outputs a predetermined frequency. a phase comparator 19 that compares the output frequency of the frequency divider 18 with the output frequency of a frequency divider 22 (described later); and the output of the phase comparator 19 is inputted via a low-pass filter 20. applied to the terminal
A VCO 21, frequency dividers 22 and 23 that divide the output of the VCO 21, and a multiplexer 24 that selects the output frequencies of the VCO 21 and the frequency divider 23,
An attenuator 25 that compresses the control voltage of the VCO 21 to 1, 1/2, 1/2 ² , ... 1/2 ⁿ , an initial value setting circuit 26 that sets the initial value of the frequency divider 22, and a moving distance detection signal The frequency division ratio setting circuit 27 sets the frequency division ratio of the frequency divider 22 that advances one step by
2 ² , 2 ³ , . . . , 2 ⁿ ).

The frequency divider 22 divides the output frequency of the VCO 21 by 2, ^{2 2} , 2 ³ . . . , 2 ⁿ .

The operation of the control circuit 6 having the above configuration is as follows.

The output frequency of the reference oscillator 17 is o, and the frequency divider 1
The frequency division ratio of 8 is N, the oscillation frequency of VCO21 is,
If the current frequency division ratio of the frequency divider 22 is M, then o/N=/M.

Therefore, =M×o/N.

Here, since o and N are constant values, VCO
The oscillation frequency of 21 is proportional to the frequency division ratio M of the frequency divider 22.

Therefore, if a predetermined value, for example 1, is added to or subtracted from the frequency division ratio M every time one pulse of the moving distance detection signal is input thereafter, the relationship between the oscillation frequency of the VCO 21 and the moving distance can be expressed as follows. , a proportional relationship expressed by a straight line with a predetermined slope.

Further, the outputs of the initial value setting circuit 26 and the frequency division ratio setting circuit 27 are applied to the range determination circuit 28, and the slope of the straight line is set to 1, 2, ^{2 2} , . . . depending on the movement start position and the movement distance. ²ⁿ , and applies the determined output to the multiplexer 24 and the attenuator 25. The multiplexer 24 and the attenuator 25 select a frequency or voltage based on the determined output and apply it to the comparators 7 and 10.

By applying the reference signal obtained as described above to the comparators 7 and 10, the product of the rotation speed and the recording radius can be kept constant.

Figure 3 shows a curve showing the theoretical relationship between the recording radius and the disk rotation speed when recording information on a digital audio disk while keeping the linear velocity constant, and a curve that shows the theoretical relationship between the recording radius and the disk rotation speed when the linear velocity is kept constant. ,4,
8, 16, 32, and 64. In this case, the error when the curve was approximated by the broken lines was about 3% or less.

Note that the ranges “0”, “1”, “2”, etc. in Figure 3 are
“6” indicates the output from the range determining circuit 28.

As described above, the present invention makes it possible to create various relationships between the recording radius and the rotational speed of the disk simply by changing the numerical values of the ROM, etc.
Since the variable frequency range of the VCO is at most twice as large and the linearity of the control voltage and oscillation frequency is good, it is possible to use a VCO, which has the unique effect of increasing the rotational control information of the motor.

In addition, since the feed motor of the moving distance detection device and the disk drive motor are rotated to correct the linear velocity of the laser spot on the disk to be constant, the correction range of one motor is small. What's more, the time required for corrections is reduced accordingly.
Good followability.

It should be noted that the present invention is not limited to the above embodiments at all, and it goes without saying that various design changes can be made without changing the gist of the present invention.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention; FIG. 1 is a block diagram of the apparatus of the present invention, FIG. 2 is a block diagram of the control circuit, and FIG. 3 is a diagram showing the relationship between the recording radius and the rotation speed of the disk. . DESCRIPTION OF SYMBOLS 1...Disk, 2, 3...Motor, 4...Fine movement feed and movement amount detection device, 5...Reflector, 6...
... Control circuit, 7, 10 ... Comparison circuit, 8 ... Frequency generator, 9, 12 ... Drive circuit, 11 ... Rotation detector, 17 ... Reference oscillator, 19 ... Phase comparator, 21 ... Voltage controlled oscillator, 22, 23... Frequency divider, 24... Multiplexer, 25... Attenuator, 26... Initial value setting circuit, 27... Frequency ratio setting circuit, 28... Range determination circuit.

Claims (1)

[Scope of Claims] 1. A fine movement feed and movement distance detection device that guides a laser beam onto the audio disk surface and detects the spot position of the laser beam from the center of rotation on the disk surface, and the detection device is connected to the radius of the disk. a control circuit having a feed motor for moving in the direction, a voltage controlled oscillator for receiving an output signal from the detection device and generating an oscillation frequency or a control voltage as a reference signal, and interlocking with the feed motor of the movement distance detection device. a comparison circuit that obtains a difference signal between the output signal from the rotation detector and the reference signal from the control circuit; a drive circuit that operates the motor based on the output from the comparison circuit; and a disk drive circuit that rotates the disk. a motor, a comparison circuit that compares the output from the frequency generator that detects the rotational speed of the motor and the output from the control circuit to obtain a difference output; and a disk drive motor according to the output from the comparison circuit. The distance from the rotation center of the disk to the spot position obtained by the movement distance detection device, and
A rotation control device for an electric motor, characterized in that a disk drive motor is controlled so that the product of the travel distance detection device and the rotation speed of a feed motor is always kept constant. 2. Consisting of a fine movement feed and movement distance detection device that detects the distance between the recording position and the center of rotation of a disk rotationally driven by a motor, and a control circuit that changes the output state of the voltage controlled oscillator based on the output signal from the device, The disk driving motor is operated so that the product of the distance from the center of the disk to the recording device obtained by the distance detecting device and the rotational speed of a motor that provides a feeding operation to the moving distance detecting device is always kept constant. The rotation control device for an electric motor according to claim 1, wherein the rotation control device for an electric motor is configured to control the rotation of an electric motor. 3. If the relationship between the distance from the center of the disk to the recording position and the motor rotation speed is a curve, this curve is a broken line consisting of line segments with slope ratios of 1, 2, ^{2 2} ,...2 ⁿ . A range determination circuit that approximates and determines each range of the broken line, and a frequency divider that outputs the output signal or control voltage of the voltage controlled oscillator at a ratio of 1, 2, ^{2 2} , ... 2 ⁿ . A rotation control device for an electric motor according to claim 2.