JPS6136293B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION High-density recording of signals on a disc-shaped light-sensitive disk is generally performed, for example, in the production of master discs for optical and other video discs. In addition, with the recent development of highly sensitive optical recording materials, in addition to the playback-only function of conventional video discs, they can also record and play back signals themselves in real time. . Such recording generally involves irradiating a disk coated with a photosensitive recording material with light whose strength is modulated by a recording signal, thereby producing changes in unevenness or refractive index on the disk.
This is done in real time by changing optical properties such as reflectance.

In the above-mentioned optical recording/playback device, like a conventional video disk, a disk rotating at 1800 rpm has a track pitch of 2.5 μm, and for example, when recording still images concentrically, a disk with a diameter of 30 cm is used. Approximately 40,000 still images can be recorded on a 20cm diameter disk.

In the above optical recording/reproducing apparatus, it is very inconvenient to use the system in which 40,000 or 20,000 frames of still images are prepared in advance and then the still image signals are recorded on a specific disk. 20,000~
Even if all 40,000 frames of still images are not available, it is convenient to record the still images to the disk each time they are prepared as a still image file. That is, it is useful as an apparatus to perform necessary recording each time a still image to be recorded occurs, and to search and reproduce video files as needed. Therefore, it is necessary to have a function for additionally recording still images generated later on the unrecorded portion of the disk.
Furthermore, if the disk can be removed from the device and used for reproduction or recording in another device between the preceding recording and the next recording, the usefulness of the device will be significantly improved. Therefore, even if the rotation center of the disk and the center of a previously recorded signal track are offset (eccentric), the additional recording function can record a new signal without intersecting the previously recorded track. form a track,
It becomes necessary to record a new still image. This is necessary both to preserve the quality of previously recorded still images and to ensure that newly recorded still images are recorded with good quality.

Above we have explained the case where still images are recorded on a disk while forming concentric tracks.
The same thing can be said when several sets of short moving pictures are recorded on one disk using spiral tracks.

It is an object of the present invention to provide that when a new signal is to be recorded on a disk on which signals have already been recorded, the track formed on the disk by the newly recorded signal is different from the track formed by the previously recorded signal. To provide an optical recording and reproducing device that does not cross or overlap tracks.

In order to achieve the above object, the recording light source and the driving device for the light source are automatically controlled according to the signal reproduced from the disk, and so-called double recording is performed by eliminating the crossing and overlapping of the recording tracks. This is to prevent

Furthermore, even if there is no intersection or overlap of the recorded tracks, the previously recorded track and the newly recorded track are abnormally close to each other over the entire circumference or a part of the circumference of the track. (for example, when the tracks are closer than 1.5μ), the signal crosstalk between each track becomes large and may deteriorate the quality of the reproduced signal of both tracks. It also achieves the prevention of

An embodiment of the present invention will be explained below based on the drawings. First, an example of the configuration of an optical recording/reproducing apparatus will be explained with reference to FIG. Reference numeral 10 denotes an optical unit in which an optical system necessary for recording and reproduction of this apparatus is mounted. 10
Reference numeral 1 indicates a light source such as a semiconductor laser, which generates light L having relatively good coherency. Reference numeral 102 denotes a conventionally known tracking mirror, which is used for changing the optical path and performing known tracking control. 10
Reference numeral 3 denotes an aperture lens composed of an objective lens, etc., which narrows the light L of the semiconductor laser 101 to a minute diameter light and irradiates it onto the optical recording material surface 13 coated on the transparent disk base material 12 of the disk 11. . 104
A beam splitter separates the reflected light from the disk 11 from the optical path and directs it toward the photodetector 105. A photodetector 105 detects the reflected light from the disk 11 and reproduces a signal and generates a conventionally known focus control error signal and tracking control error signal. The optical unit 10 is composed of the above main elements.

14 is a shaft of a disk motor 15 that rotates the disk 11, and 16 is a turntable. Reference numeral 17 indicates a transfer screw for moving the optical unit 10 in the radial direction of the disk 11. 18
indicates a drive motor for the transfer screw 17, and a step motor or a DC motor may be used depending on the purpose, such as when forming concentric tracks on the disk 11 or when forming a spiral track. Reference numeral 19 denotes a drive circuit for the drive motor 18. Under the control of this drive circuit 19, the drive motor 18 can arbitrarily send the optical unit 10 in the direction of the inner circumference or the direction of the outer circumference of the disk via the transfer screw 17. can. Reference numeral 20 denotes a semiconductor laser drive circuit, which controls the light emission output (reproduction power, recording power) of the semiconductor laser.

Reference numerals 21, 22, 23, and 24 show examples of the configuration of electronic paths when one field of still images is recorded in one rotation of the disk using the apparatus shown in FIG. Details of its operation will be described later. Reference numeral 25 indicates a drive circuit for the disk motor 15, and FIG. 1 shows an example in which the disk motor 15 rotates at 1800 rpm in synchronization with a vertical synchronizing signal of a video signal input from line RO. A preamplifier 26 amplifies the electrical signal from the photodetector 105, and outputs a reproduced signal recorded on the disk to a terminal OU.

FIG. 2 shows an example of a disk in which signals are recorded only on a part of the disk using the apparatus shown in FIG. Tracks T ₁ and T ₂ indicate concentric tracks on which signals have been previously recorded. The center of T ₁ and T ₂ is point C. Next, when this disk is installed in the device shown in Figure 1, the center of rotation of the disk will be shifted due to the eccentricity.
Assuming point C' (deviated by Δ1 from point C), the trajectory of the light irradiating the disk at this time is shown by a solid line _T3 .
Therefore, if recording light is applied while irradiating this T ₃ , at the point where it intersects with the tracks T ₁ and T ₂ previously recorded on the disk, and at the point quite close to T ₁ and T ₂ , Since a new signal is recorded, not only the signals on tracks T ₁ and T ₂ are damaged, but also the quality of the signal recorded on track T ₃ is degraded due to the influence of the signals on T ₁ and T ₂ . I'll wake you up.

The present invention provides a novel device that prevents such recording errors. A more detailed explanation will be given based on the drawings from FIG. 3 onwards. FIG. 3 is a diagram for explaining the operating characteristics of the semiconductor laser used in the device of FIG. 1. When the horizontal axis represents the forward current flowing through the semiconductor laser and the vertical axis represents the corresponding light emission output, a characteristic as shown by line A is shown. I _th indicates a threshold current, and a current greater than or equal to I _th enters the laser region.
The reproducing power P _R with respect to the reproducing current I _R indicates the operating point used when reproducing a signal already recorded on the disk in the apparatus shown in FIG. Further, the recording power P _W with respect to the recording current I _W indicates the operating point when a signal is recorded on a disk using the apparatus shown in FIG. As shown in the figure, when the recording signal current _Is is applied around the recording current _IW , the recording light is Pmin~
A recording L _W whose intensity is modulated between Pmax is obtained,
The resulting Pmax changes the physical properties of the recording material, forming recording bits.

FIG. 4 shows a configuration example of a semiconductor laser drive circuit 20 having the above operating characteristics. In this figure, parts corresponding to the configuration in FIG. 1 are given the same numbers. In FIG. 4, LD indicates a semiconductor laser. This LD is configured to conduct current to a negative voltage -V through an inductance L, a transistor Tr, and a resistor _R3 . The transistor Tr constitutes a constant current circuit. The switch _S3 connected to the base of the transistor Tr is a high-speed switch consisting of an analog gate, etc.
By the signal entering gate terminal _G2 from terminal N,
Switch terminal 1 is connected to terminal 2 or 3.
By switching this switch _S3 , the current flowing through the semiconductor laser LD is set to the reproducing current I _R or the recording current I _W. Further, the switch _S2 corresponds to the gate circuit 24 in FIG. 1, and is composed of an analog gate like the switch _S3 . A _signal is to be recorded is applied to the terminal M, and the terminal 1 of the switch _S2 is connected to the terminal 2 or 3 depending on the signal input from the terminal N to the gate terminal _G1 . terminal 1
is connected to terminal 3, a recording signal i _s input from terminal M is applied to semiconductor laser LD through capacitor C, and the light intensity is modulated.

The states of switches S ₂ and S ₃ in FIG. 4 indicate a reproducing state (a state in which the reproducing current I _R of FIG. 3 is provided). If the level of terminal N becomes high in this state,
Terminal 1 and terminal 3 of each switch are connected, and the recording state (recording current I _W and recording signal current _{I s} in Figure 3)
supply state).

Figure 5 shows one field in the apparatus shown in Figure 1.
a circuit 21 for creating an FM modulated video signal;
A time chart for explaining the operations of 22, 23, and 24 is shown.

Reference numeral 21 in FIG. 1 is a synchronization separation circuit for extracting a vertical synchronization signal from the composite video signal inputted to the terminal IN, and generates a 30 Hz signal shown in FIG. 5a on line RO. This signal also serves as a reference signal for the disk motor 15, which rotates at 1800 rpm. 22 is an FM modulation circuit, and the FM modulated video signal shown in FIG. 5d is outputted to line C. 23 is a gate circuit 24 which inputs the video signal of one field (i.e. disk 1).
In the video signal for rotation, the recording signal current i
_s ) (FIG. 5e), generates an arbitrary signal shown in FIG. 5B through switch _S1 in the gate signal generation circuit for supplying to the semiconductor laser drive circuit 20, and outputs this signal. A gate signal (Fig. 5 c) in the interval from the synchronizing signal (2 in Fig. 5 a) to the next synchronizing signal (3 in Fig. 5 a) generated immediately after is generated, and the gate signal (Fig. 5 c) is During this time, the switches S ₂ and S ₃ are turned on, and the recording current I _W is supplied to the semiconductor laser LD, and the recording signal current I _s is supplied from the terminal M through the line H.

An example of the operation of each part of the apparatus shown in FIG. 1 has been described above. Next, a method for preventing the above-mentioned double recording or abnormally approaching recording of trucks using this apparatus will be described. Figure 6 shows, for example, after changing the disk, it is detected whether the light irradiation trajectory T ₃ intersects with the previously recorded tracks T ₁ and T ₂ or approaches them abnormally, as shown in Figure 2. A circuit block diagram for this purpose is shown, and FIG. 7 shows waveforms of each part thereof. In FIG. 6, 26 is the preamplifier described in FIG. A photodetector 105 detects the reflected light (or transmitted light) from the disk, converts it into an electrical signal, amplifies it, and outputs it to the terminal OU. FIG. 7a shows the same synchronization signal as FIG. 5a, and if the reproduction light crosses or approaches a previously recorded track as shown in FIG. Envelope signal E ₁ as shown in FIG. 7b
~E ₃ is output from the preamplifier 25. Second
In the case of the figure, one rotation of the disk motor (in Figure 7)
One or more envelopes are generated (one revolution is made in each section of V ₁ , V ₂ , V ₃ , V ₄ , V ₅ ) (one envelope is representative in Figure 7b) . Reference numeral 201 in FIG. 6 is a rectifier/integrator circuit, which amplifies the signal from the preamplifier 26, rectifies it, integrates it with an appropriate time constant, and sends this output to the waveform shaping circuit 20.
Supply to 2. This waveform shaping circuit 20 is configured such that the level at which the input is cut off can be changed by changing the threshold voltage _Vth , for example. By doing this, for example, the seventh
Even if the amplitude of the envelope signal shown in FIG. b becomes small, it can be detected. That is, when the disk is mounted in the apparatus shown in FIG. ₁ in the state described in FIG. There comes a point where it no longer intersects with the lap record track T ₂ . However, in this case, there is a situation where the cross stroke between T ₂ and T ₃ partially exceeds -40 dB, although they do not cross. Even in such a case, in order to maintain good recording signal quality, it is desirable that the waveform shaping circuit 202 be able to detect the envelope. Therefore, by adjusting and setting the threshold voltage V _th , the crosstalk is set to a level below a specified amount. Waveform shaping circuit 202
7c depending on the input envelope signal.
Generates formatted output as shown below. 203 is composed of, for example, a little gable monostable multivibrator, and once triggered, the time required for one rotation of the disk is longer (for example, the time longer than V ₁ in FIG. 7a, which corresponds to T ₁ in FIG. _7d ) V ₁ ) This is a circuit that holds that state. In this way, the seventh
As shown in FIG. d, as long as the envelope signal exists within one rotation period of the disk (or one field period of the recorded video signal), the low level is maintained, and in this state, the optical unit 10 is moved. When the envelope disappears or falls below a specified value, a signal that returns to a high level is obtained. By using this signal to control the signal indicated by line 2 in FIGS. 1 and 4, even in the presence of the above-mentioned track crossing and crosstalk, no deviation in the recording current and recording signal current is caused to flow through the semiconductor laser. Thus, it is possible to obtain a device in which only the reproduction current flows.

FIG. 8 shows an example of a specific method for controlling the signal shown in line d in FIG. 1 with the signal at terminal P in FIG. FIG. 8a shows a circuit that inputs the output of the gate signal generation circuit 23 in FIG. No signal is generated to command recording. FIG. 8b shows a circuit with an equivalent function using an analog gate AG.

As described above, according to the present invention, if a track on which a signal is to be optically recorded on a disk intersects with a track on which a signal has been previously recorded, or if the crosstalk is even partially larger than a specified value. Furthermore, it is possible to obtain an apparatus that prevents strong recording light from being irradiated onto the disk, thereby protecting previously recorded tracks and also capable of reliably recording new signals.

In the above explanation, a case has been described in which concentric still images are recorded, but the same effect can be obtained also when a short-time moving image is recorded in a spiral manner. It can also be applied to recording other than video signals.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing an example of the configuration of an optical recording/reproducing device, Figure 2 is an explanatory diagram showing the mutual relationship of signal tracks formed on a disk, and Figure 3 is an illustration of the operating characteristics of a semiconductor laser and the time of signal reproduction. Figure 4 is a circuit diagram showing an example of the configuration of a semiconductor laser drive circuit, and Figure 5 is a waveform diagram of each part when recording a still image on a concentric track using the device shown in Figure 1. , Figure 6 is a circuit diagram for detecting the presence of a reproduction envelope signal at a location on the disk where the reproduction signal is irradiated, Figure 7 is a waveform diagram of each part in Figure 6, and Figures 8a and b are recording commands. This is a concrete circuit that prohibits a signal with a reproduction envelope. DESCRIPTION OF SYMBOLS 10... Optical unit for recording and reproduction, 101... Semiconductor laser, 11... Disk, 20... Semiconductor laser drive circuit, 21... Synchronization separation circuit, 22... FM modulation circuit, 23... Gate signal generation circuit, 24... Gate circuit, 201... Rectifier/integrator circuit, 202... Waveform shaping circuit, 203... Retriggerable monostable multivibrator.

Claims (1)

[Claims] 1. In a device that records and reproduces signals by focusing light from a semiconductor laser or the like into a minute diameter and irradiating it onto an optical recording disk, the optical power of the light source is defined as the power at the time of signal reproduction. and a means for setting the signal recording power to the signal recording power, and detecting the presence or absence of an envelope of the reproduced signal by irradiating the signal recording area of the disk with the reproduction power in advance, and detecting the presence or absence of an envelope of the reproduced signal, and detecting the presence or absence of an envelope of the reproduced signal. means for generating a pulse, means for always being triggered by the pulse to maintain a specific level for a period of time required for one revolution of the disk after the trigger pulse; and means for maintaining the light source while the specific level is maintained. An optical recording/reproducing device having means for preventing the power from generating the power necessary for recording. 2. The optical recording and reproducing apparatus according to claim 1, wherein the switching from the reproducing power of the light source to the recording power is performed by switching the forward current value of the semiconductor laser and applying a recording signal.