JPS606011B2 - optical disc player - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical disc player, such as a video or audio disc player or a PCM laser sound disc breaker, which is capable of obtaining a constant playback waveform regardless of the location of the disc. be.

An example of a conventional optical disc breaker will be described with reference to FIGS. 180 enemies. p. While rotating at a constant speed of m, a beam 4 is projected from a beam projection device 3 onto the disk 1, and the beam projection bag layer 3 is further sent in the radial direction of the disk by a feeding device 5, so that the beam 4 spirally scans the disk. It is configured to read signals while

More specifically, the laser light emitted from the laser light source 6 is converged via a concave lens 7, a beam splitter 8, a 1'4 input plate 9, a circular mirror IQ for minute beam movement, and a condenser lens 11. This beam 4 becomes a reproduction beam 4 and is projected onto the disk 1.If the recording track of the disk 1 is scanned with the beam 4, a reflected beam 12 corresponding to the presence or absence of a recording signal is obtained, and this reflected beam 12 The light passes through the condensing lens 11, rotating mirror 10, 1/4 input plate 9, and beam splitter 8 to a photodetector 13 for recording signal recording, where it is converted into an electrical signal and sent to a demodulation circuit.
Although not shown in FIG. 1, a tracking control device and a focus control device are also provided.The disk 1 used in the device shown in FIG. Information such as a video signal or an audio signal is transferred to a spiral track 1 by an array of target recesses or bits 14.
This was recorded on FM on 5th. The width of the bit 14 on this disk 1 is, for example, 1 mm, and the depth of the bit is approximately 1 mm.
In the case of a video disc, the bit length differs depending on the inner and outer sides, and is, for example, 1.5 to 6 meters. Bit 1 like this
4, a transparent resin layer 16 having an uneven surface corresponding to the bit 14, a reflective film IT coated on the uneven surface of the resin layer as shown in FIG. A protective film 18 protects the reflective film. The diameter of the reproduction beam 4, which is shown explanatory in FIG. 2, is larger than the width of the bit 14, and when scanning the bit 14, the reflected light inside the bit and the reflected light outside the bit cancel each other out. When the area where the bit 14 is not provided is scanned, no cancellation occurs, so the reflected output becomes large.

Therefore, bit 3 as a unit recording area in the photodetector 13
The presence or absence of 4 and this sequence can be read. By the way, even if the frequency signal is the same, the length and interval of the bits 14 differ depending on the radial position of the disk.

FIG. 4A shows the bit length and interval in the inner track, and FIG. 5A shows the bit length and interval in the outer track of the same signal as FIG. 4A. As is clear from these comparisons, the bit length increases toward the outer periphery even for the same signal. At the inner circumference where the bit length is small, the reproduced waveform is as shown in Figure 4B, whereas at the outer circumference where the bit length is large, the reproduced waveform is distorted as shown in Figure 5B. Faithful reproduction becomes impossible.
If the spot of beam 4 is made larger, the waveform distortion will be reduced even at the outer periphery as shown in Fig. 5C, but the reproduction output level will decrease (decrease in modulation degree) at the inner periphery as shown in Fig. 4C. arise.

Therefore, it is an object of the present invention to provide an optical disc breaker that can obtain distortion-free reproduced waveforms regardless of changes in the radial position of the disc.

To achieve the above object, the present invention uses an optical playback disk in which information is recorded in an array of unit recording areas in which information can be optically negotiated so that the carrier frequency is higher in the outer track than in the inner track. and a beam projection device for projecting an information processing beam onto the disk, a disk rotation device for rotating the disk at a constant speed, and a device for transmitting the beam in the radial direction of the disk. an information detection device that detects information based on a reflected or transmitted beam obtained by reflecting or transmitting the beam on the disk; a beam scanning position signal generating device that generates a signal; and a frequency converting circuit that converts the output carrier frequency of the information detecting device into a carrier frequency that does not depend on the beam scanning position based on the output of the beam scanning position signal generating device. The present invention relates to an optical disc player characterized by comprising:

According to the present invention, a unit recording area is optically negotiated using a disk in which the carrier frequency increases toward the outer circumference, and then the frequency is converted so that the carrier frequency becomes constant. It becomes possible to obtain substantially the same reproduced waveform regardless of the outer circumference.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical recording and reproducing system for audio signals according to an embodiment of the present invention will be described below with reference to the drawings.

First, FIG. 6, which shows a recording method for making a disc according to the present invention, will be described.

When forming information bits on the disk 2 shown in FIG. 6 using a laser beam, the disk 21 is rotated at a constant speed by a motor 22, and a beam projection device 24 is sent in the radial direction of the disk 21 by a feeding device 23. The beam projection device 24 modulates the laser light emitted from the laser light source 25 with an optical modulator 26 to obtain a modulated beam corresponding to the signal, and passes this modulated beam through an optical system 27 including a condensing lens etc.
1. When a modulated beam is projected onto the disk 21, the photoresist is exposed in a state corresponding to the signal, and bits corresponding to the signal can be obtained through development processing. By the way, in this case, the optical modulator 26
Rather than supplying normal audio FM modulated waves to
FM modulated waves with different carrier frequencies are supplied according to changes in the radial position of the disk 21.

For this purpose, the Numa mover 28 is coupled to the beam projection device 24,
The movement of the slider 28 on the resistor 29 is detected by a position detection circuit 30. That is, a voltage corresponding to the beam scanning position is obtained by the position detection circuit 3M. Of course, a sawtooth wave (triangular wave) having a constant slope may be generated in synchronization with the start of recording without performing such position detection. In this embodiment, since the audio signal is recorded as FM, the input terminal 31
After passing through a buffer amplifier 32 and a low-pass filter 33 that passes below the second HZ, the audio signal is input to a pre-emphasis circuit .

Then, in order to improve the signal-to-noise ratio, the high pitch is lifted by the preamplifier circuit 34 and applied to the AGC, that is, the automatic gain control circuit 35.The automatic gain control circuit 35 is controlled by the output of the radial position detection circuit 30. Therefore, the amplitude of the signal gradually increases from the inner circumference to the outer circumference of the disk. That is, as shown in FIG. 7, at the inner circumference of the disk 21, the amplitude between the peaks is V3-V, However, at the outer periphery, the amplitude between peaks is V6-V4 as shown in waveform B. In this case, of course, V6-V4>
V3-V. Further, in order to change the carrier frequency according to the position in the disk radial direction, an adder 36 adds the output of the automatic gain control circuit 35 and the output of the position detection circuit 30. A waveform A is obtained, and a waveform B shown in FIG. 7 is obtained corresponding to the outer circumference of the disk. Although only two waveforms are shown in FIG. 7, the waveforms gradually change as the disk radial position changes. The output of adder 36 is a voltage controlled oscillator or VC.
037, a frequency signal corresponding to the VCO input voltage value can be obtained. When recording a signal on the inner track of the disk, oscillation frequencies of f and fa are obtained corresponding to waveform A as shown in FIG. On the other hand, when recording a signal on the outer track of the disk, an oscillation frequency of f2±fb corresponding to waveform B is obtained. That is, by changing the beam scanning position from the inner circumference to the outer circumference, the signal center level changes from V2 to V5 for the same input signal, and the oscillation frequency, that is, the carrier frequency of VC037 also changes from f to f2. Since the relationship between the input voltage and the oscillation frequency in VC037 is linear as shown by straight line C in Fig. 7, the carrier frequency also increases toward the outer circumference following the movement of the beam scanning position in the disk radial direction. changes linearly. The output of VC037 is 11 mitter 38
, a low-pass filter 39, and a level adjuster 40, the waveform is shaped by a symmetrical limiter 41, and the signal is supplied to the optical modulator 25.

As a result, the beam emitted from the light source 25 becomes an intermittent beam modulated by the FM signal. In other words, it becomes an intermittent beam in which only the positive half-wave of the FM wave passes through, and the negative half-wave does not pass. The period (frequency) of this intermittent beam also corresponds to the oscillation frequency of VC037,
The period (frequency) of bits on the disk 21 is also VC0.
Information is recorded in bits in a state where the carrier frequency increases toward the outer circumference of the disk 21, corresponding to the oscillation frequency of 37. Therefore, on a disc recorded using this method, if the signal is the same on both the inner and outer peripheries of the disc, the same bit length and bit interval will be the same. 2 and 3.Next, referring to FIG. 8, a disk 21 is used in which the carrier frequency increases from the inner track toward the outer track. A disc player for obtaining playback signals will be explained.

However, since the parts indicated by numerals 2 to 13 in FIG. 8 are substantially the same as the parts with the same numerals in FIG. 1, their explanation will be omitted. In this disk player as well, bits as information are captured by constant speed rotation and constant speed feeding, similar to the conventional device shown in FIG. However, since signals with different carrier frequencies are obtained from the photodetector 13 even though they contain the same information, it is necessary to align the carrier frequencies. Since the slider 54 slides on the resistor 55, a voltage signal corresponding to the beam scanning position is obtained from the L position detection circuit 42. The corresponding high frequency signal is amplified by an amplifier 43 and then supplied to a frequency conversion circuit 44 for adjusting the carrier frequency to a constant value.
VC045, whose oscillation frequency changes according to the output voltage of the position detection circuit 42, is also connected to the amplifier 4.
Balanced modulation is performed between the output frequency fs of VC045 and the output frequency fc of VC045, and a frequency signal of fs±fc is output. That is, the frequency conversion circuit 441 converts the frequency of the same information signal so that it becomes the same carrier signal regardless of the beam scanning position. The output of the frequency conversion circuit 44 is passed through an obijo filter 46 and a limiter 47.
The signal is supplied to the FM detection circuit 48 via the FM detection circuit 48, where it is demodulated into an audio signal.The detection circuit 481 receives the same carrier frequency signal that is aligned with the carrier frequency of the inner circumference of the disk, so it performs the well-known FM detection. The FM detection output is attenuated by the differential amplifier 49 to have a flat characteristic and is sent to the AGC circuit, that is, the automatic gain control circuit 50. During recording, as shown in waveform B in Figure 7, the circuit increases the amplitude as it approaches the outer periphery of the disk and returns it to its original state. The amplitude is controlled so that the amplitude is the same on both the inner and outer circumferences of the disk.Therefore, the audio signal obtained at the output terminal 53 via the low-pass filter 51 and amplifier 52 is as shown in FIG. The audio signal is approximately the same as the audio signal applied to input terminal 3.If the disk 21 is configured as described above and the disk 21 is used for reproduction in the manner described above, the beam spot will be as shown in FIG. 4B. As described above, even if the reproduction is made smaller, the reproduced output waveform on the outer track is not distorted as shown in FIG. 5B, and it becomes possible to obtain the same reproduced waveform on all tracks.

Therefore, reproduction output with good characteristics can be obtained over all tracks. In addition, according to this method, performance can be improved by changing only the electrical part from the mechanical part as in the past, making it easier to manufacture the device. is not limited to the above-mentioned embodiments, and can be further modified. The beam scanning position in the disk radial direction may be determined by detecting and counting.Also, the address signal may be recorded during the vertical erasure period of the composite video signal or the corresponding period of the composite PCM signal, and the "detection of the address signal during play" may be performed. The beam scanning position in the disk radial direction may be obtained by using the resistor.Also, when reproducing from the inner or outer track, a predetermined sawtooth wave (triangular wave) may be sent as the beam scanning position layer signal. The position is not limited to detection using the body 55 and the slider 54, but may also be determined by an optical method.Furthermore, when a semiconductor laser is used as the light source 6, the state of the semiconductor laser changes depending on the incidence of the reflected beam. This can also be used to read information using a transmitted beam on a disk.It can also be applied to the same circular track. There is no harm in changing it in stages.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a conventional disc player, Fig. 2 is an explanatory plan view of the disc, Fig. 3 is an enlarged sectional view of the disc, and Fig. 4 is the bit arrangement and reproduction waveform in the inner track of the disc. FIG. 5 is an explanatory diagram showing the bit arrangement and reproduced waveform on the outer track of the disc. FIG. 6 is a block diagram showing a recording apparatus for obtaining a disc according to the present invention. Input voltage and VC
FIG. 8 is a block diagram showing a disk player according to an embodiment of the present invention. In addition, in the symbols used in the drawings, 2 is the motor, 3
4 is a beam projection device, 4 is a beam, 6 is a light source for the 5G feeder, 54 is a slider, and 55 is a resistor. 42 is a position detection circuit, 44 is a frequency conversion circuit, and 45 is a VCO. Figure 2 Figure 3 Figure 4 Figure 5 Blind drawing Figure 6 Figure 8

Claims (1)

[Claims] 1. A reproduction signal is generated using an optical reproduction disk in which information is recorded in an array of optically readable unit recording areas such that the carrier frequency is higher on the outer track than on the inner track. a beam projection device that projects an information reading beam onto the disk; a disk rotation device that rotates the disk at a constant speed;
a beam radial sending device that sends the beam in a radial direction of the disk; an information detection device that detects information based on a reflected or transmitted beam obtained by reflecting or transmitting the beam on the disk; a beam scanning position signal generating device that generates a signal corresponding to a radial beam scanning position; and a beam scanning position signal generating device that generates a signal corresponding to a beam scanning position in the radial direction; An optical disc player characterized by comprising a frequency conversion circuit that converts the frequency into a frequency. 2. The beam scanning position signal generating device detects the beam scanning position in the disk radial direction in response to the feeding operation by the feeding device, and generates a signal corresponding to the detected output. Optical disc player as described. 3. The beam scanning position signal generating device detects the beam scanning position in the disk radial direction based on the detection of a synchronization signal recorded on the disk, and generates a signal corresponding to this detection output. The optical disc player according to scope 1. 4. The beam scanning position signal generating device detects the beam scanning position in the disk radial direction based on the detection of an address signal recorded on the disk, and generates a signal corresponding to the detection output. The optical disc player according to scope 1.