JPH06267180A - Recording and reproducing circuit - Google Patents

Abstract

PURPOSE:To always obtain a stable control characteristic by revising the gain of a rotation control system according to the output of a disk detection means and revising the integration constant of a stop circuit system according to the output of a disk size detection means. CONSTITUTION:The information of the presence and the size of a disk are converted into a stable DC level by level detectors 33, 34 to be inputted to a disk size detection circuit. At this time, a switch 40 is operated according to the disk size, and the deterioration in the control characteristic due to the disk size is prevented by revising a phase compensation characteristic. By a waveform shaping circuit 45, the output of a rotation detector 24 is pulse formed to be inputted to an integration circuit 46. By the level detector 48, a switch circuit 42 is opened and operated so that no brake signal is impressed to a motor when the fact that the output of the integration circuit 46 becomes a below set level is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording / reproducing apparatus for recording or reproducing information by using a disc-shaped recording medium (hereinafter abbreviated as disc), and detecting the diameter of a disc mounted in the device, The constant of the control system that is affected by the diameter of the disk is automatically changed to always operate in an optimum state.

[0002]

2. Description of the Related Art An example of a disc diameter detecting method used in a conventional audio record will be briefly described with reference to FIG.

Reference numeral 1 is a turntable, which has one or a few holes at a portion smaller than the diameter of the EP board and at a portion larger than the diameter.
a and 1b are opened. 2 is a record, which is placed on the turntable of 1 and rotated by the motor of 3. A rotation detector 4 detects the rotation speed of the motor. Reference numerals 5 and 6 are reflection type photocouplers arranged below the holes 1a and 1b provided in the turntable. The outputs of these are shaped by the level detectors 7 and 8 and the record board is not placed. Only the photo coupler of outputs the pulse, and by the retriggerable mono-multi,
It is converted into a DC voltage and input to the record detection circuit 11, where presence / absence of a record and size are detected, and a performance start position and a rotation speed change signal are output. Reference numeral 12 is a crystal oscillating circuit, which outputs a rotation phase reference and is divided by a frequency divider 13 into a required frequency. The frequency divider 13 can change the frequency division ratio by the output according to the record size of the record detection circuit 11,
The number of rotations of the board and LP board can be changed automatically.

Reference numeral 14 denotes a waveform shaping circuit, which converts the output of the rotation detector 4 into a pulse and inputs the pulse into a phase comparator 15 so that a phase difference from the reference frequency output from the frequency divider 13 is obtained. It is detected, and the motor 3 is rotated through 16 drive circuits.

As described above, in the conventional record reproduction, the presence of the turntable is large, and as the factors affected by the record size, it is sufficient to change only the number of revolutions according to the standard and the change of the playing start point. there were.

On the other hand, in the recently proposed optical type video disc and the like, since light is applied from the lower side of the disc for reproduction, there is no turntable like a conventional audio record player, and the diameter is 90 mm. The turntable 1 has a small size for mounting. Therefore, the moment of inertia of the rotating system is almost determined by the disc, and the difference in the moment of inertia due to the size of the disc becomes very large.

In general, the moment of inertia J of a disk-shaped object is given by the following equation.

[0008]

[Equation 1]

Further, the mass m of the disk is expressed by the following equation.

[0010]

[Equation 2]

Substituting into (Equation 1)

[0012]

[Equation 3]

As described above, the moment of inertia is proportional to the fourth power of the radius, and the ratio of the moments of inertia of a disk having a diameter of 20 cm and a disk having a diameter of 30 cm is 5 times or more.

Therefore, in such a device,
In order to ensure the stability of the rotation control system, it is necessary to detect the size of the mounted disk and change the phase compensation or gain of the control system.

The time ts required to stop the rotating disk is given by the following equation.

[0016]

[Equation 4]

[0017]

As described above, the time required to stop the rotation of the disk is also determined by the moment of inertia including the disk. Conventionally used, detection of rotation stop detects that the level obtained by integrating the output of the rotation speed detector is below a certain level,
The timing to stop the driving force in the braking direction is created. Therefore, when the rotational moment of inertia changes greatly, unless the integral constant is changed, reverse runaway may occur, resulting in a very dangerous state.

[0018]

In order to solve the above-mentioned problems, the present invention detects the presence / absence of a disc at the time when the disc is mounted and, at the same time, provides information on the expected moment of inertia to a control system. The time constant is set to obtain an optimum control state and stop timing.

Further, the pickup device has a structure for restricting the pickup device from being fed beyond the diameter of the disc, based on the disc size information.

[0020]

According to the above-mentioned object, the gain of the rotation control system is changed according to the output of the disc size detecting means for detecting the size of the disc, and the integral constant of the stop circuit system is changed by the output of the disc size detecting means. Thus, the optimum stopping operation can be performed.
Further, since the pickup device is prohibited from being sent to the position where the disc does not exist, it is possible to ensure the stability of the rotation control system that controls the rotation by the synchronization signal read by the pickup device.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

Reference numeral 21 is a disk, which is mounted on a small-diameter turntable 22 and rotated by a motor 23. Reference numeral 24 is the rotation detector. A pickup device 25 includes a detector for reading information from the disk 21 and a servo actuator for following an information track, and is driven by a feed screw 26 and a feed motor 27 in the radial direction. Reference numeral 28 denotes a potentiometer as a position detector of the pickup, which is used for detecting the inner and outer limit positions of the disc, position control of the pickup device, and the like. Reference numerals 29 and 31 are light emitting elements, and reference numerals 30 and 32 are light receiving elements. A photocoupler for detecting the size of the disc is arranged with the disc sandwiched by the respective combinations, but this may also be a reflection type photocoupler as in the conventional example. Reference numerals 33 and 34 denote level detectors, which convert information about the presence or absence of a disk and size into a stable DC level, and 3
5 is input to the disk size detection circuit. The size detection circuit 35 is composed of a simple logic circuit. For example, when the output of the light receiving element 30 on the inner circumference side is high, it means that there is no disc, and the information that does not put the player in the reproduction state is as follows.
It is input to a command device such as a microcomputer. Or light receiving element 3
When the outputs of both 0 and 32 are low, it means that the disk size is large, and therefore serves to give the information to the rotation control system and the feed control system.

Reference numeral 36 denotes a crystal oscillator for generating a reference frequency for disc rotation, which is phase-compared by the phase comparator 38 with the output of the demodulation circuit 31 which demodulates the information signal output of the pickup device 25 to separate the synchronizing signal. The control signal of the rotation phase of is obtained. The output of the phase comparator 38 is given to the phase compensation circuit 39. At this time, the switch 40 operates according to the disk size, and the phase compensation characteristic is changed to prevent the deterioration of the control characteristic due to the disk size. Reference numeral 41 is a drive amplifier circuit, and the output of the drive amplifier circuit controls the motor 23 via the switch circuit 42. Reference numeral 43 is a command device for instructing the start and end of reproduction. When stopped, the brake voltage generating circuit 44 is operated to give an inversion signal to the amplifier 41 so as to generate a brake torque in the motor 23.

Reference numeral 45 is a waveform shaping circuit, which converts the output of the rotation detector 24 into a pulse and inputs it to an integrating circuit 46. The integration constant at this time is also changed by the switch circuit 47 according to the disk size. Four
Reference numeral 8 denotes a level detector, which detects that the output of the integrating circuit 46 has become equal to or lower than a set level, opens the switch circuit 42, and operates so that a brake signal is not given to the motor. The level detector 48 is configured so that the disk starts rotating from the stopped state and does not operate during the period until the disk reaches a predetermined number of rotations.

Reference numeral 49 denotes an outer circumference limit detecting circuit, which is used when the output of the position detector 28 of the pickup device in the preceding stage exceeds a certain level, that is, when the pickup device 25 goes out of a predetermined movement range. When the signal 51 is sent from the feed control circuit to the feed motor 27, it is opened. At this time, the disc size information is also input to the outer circumference limiting circuit 49, and the pickup device 25
However, it is configured so that it cannot be fed beyond the diameter of the disc.

[0026]

According to the present invention, the size of a disk is detected, and information about the disk diameter is fed back to the rotation control system, stop circuit system, and feed control system of the disk, so that stable control characteristics are always obtained. Is something that can be done.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a recording / reproducing apparatus of the present invention.

FIG. 2 is a block diagram showing an example of a conventional recording / reproducing apparatus.

[Explanation of symbols]

 21 Disk 22 Turntable 23 Motor 24 Rotational Speed Detector 25 Pickup Device 26 Feed Screw 27 Feed Motor 28 Position Detector 29,31 Light-Emitting Element 30,32 Light-Receiving Element 33,34,48 Level Detector 35 Size Detection Circuit 36 Crystal Oscillator 37 Sync Separation Circuit 38 Phase Comparator 39 Phase Compensation Circuit 40, 42, 47, 51 Switch Circuit 41 Amplifier 43 Command Device 44 Brake Circuit 45 Waveform Shaping Circuit 46 Integrating Circuit 49 Perimeter Limit Detection Circuit 50 Feed Control Circuit

Claims (2)

[Claims] 1. A disk size detecting means for generating an output according to a diameter of a disk placed on a turntable which is rotationally driven by a drive motor, a pickup means for reading a signal from the disk, and the pickup means. It has a feeding means that moves in the radial direction of the disc, and an outer circumference limit detecting means that limits the outer circumference movement position of the pickup means on the disk. The recording / reproducing apparatus is characterized in that the detection position of the outer circumference limitation detecting means is changed. 2. The outer peripheral position detecting means is provided between the pick-up means and the device fixing end and changes the position of the pick-up means into a voltage, and the output of the position detecting means differs according to the disc size. 2. The recording / reproducing apparatus according to claim 1, wherein the recording / reproducing apparatus is composed of two or more comparators for comparing with the reference voltage level.