JPS6364828B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording and reproducing apparatus for recording and reproducing signals on a disc-shaped double-sided recordable recording medium.

An optical recording and reproducing device, which is an example of such a recording and reproducing device, uses a photosensitive material to form a disk, rotates the disk, and irradiates it with light from a laser or the like with a diameter of 1 micron or less. By narrowing the irradiation to a small diameter, signals can be recorded or reproduced with high density on the disk as irregularities or changes in shading.

For example, optical video discs are well known among the above-mentioned technologies as a device that only plays back signals recorded in advance at high density.

Further, the above-mentioned recording technique is used in an apparatus for making a master disc of a video disc.

Furthermore, in a disk-shaped recording medium, recording is performed on both the front and back surfaces in order to increase the capacity of recorded information.

However, when reproducing a double-sided disc, the following problems occur. Namely: (1) During playback, the disc rotates, making it difficult to determine whether the front side or the back side is being played back.

(2) In general, disks rotate at high speed, so
For safety reasons, it is covered with a protective cover, so you cannot look directly into the disk.

Therefore, it is extremely difficult to directly visually determine whether the disk is front or back.

The present invention, for example, like a video disc,
When reproducing a disk-shaped recording medium that rotates at high speed, it is necessary to check whether the start bit string of the search address signal, which is recorded differently depending on whether it is on the front side or the back side, matches the start bit string on the front side or the back side. It detects and determines whether it is front or back.

An embodiment of the present invention will be described below based on the drawings. FIG. 1 shows a part of an example of the configuration of an optical recording/reproducing device. 1 is a disk using a photosensitive material,
2 is a turntable, 3 is a disk holder, and the disk 1 rotates around a spindle 4 of a disk motor 5. This rotation speed is, for example,
It rotates at 1800 rpm to record one frame of NTSC video signal per rotation.

6 indicates an optical system unit (optical head). 6
Reference numeral 1 indicates a light source such as a laser, which generates light a. 6
2 is a condensing optical system for concentrating the light from the light source 61;
3 is a known tracking mirror, and 64 is an objective lens for focusing the light a to a minute diameter and irradiating it onto the disk 1. This objective lens 64 performs focus control using a known voice coil or the like. b shows the reflected light from the disk. A beam splitter 65 separates light b from the optical path of light a and directs it toward a photoelectric converter 66. 66 is a high-speed photoelectric converter such as a PIN diode, which detects the signal recorded on the disk 1, and also detects a focus error signal and a tracking error signal using a known divided PIN diode. Reference numeral 67 indicates a preamplifier of the photoelectric converter 66. The following description will be made assuming that a reproduced signal is output to the terminal Q. Reference numeral 7 indicates a laser driving device, and a signal to be recorded (for example, an FM-modulated video signal) is input to a terminal P.

Reference numeral 8 indicates a transfer screw for transferring the optical system unit 6 relative to the disk in either direction of arrows A or B. Reference numeral 9 indicates a transfer motor that provides rotational power to the transfer screw 8, and is composed of a DC motor or the like.
Reference numeral 10 indicates a rotation angle detector using a rotary encoder or the like. This rotary encoder is used to intermittently move the optical system unit in steps when forming concentric tracks on the disk 1 using the transfer motor 9. That is, the rotation angle of the transfer screw is detected, and the transfer motor is stopped when the transfer screw has rotated by a certain angle. 11 is a transfer motor control circuit, and 12 is an operation panel.

FIG. 2 shows an example of a disk used in the apparatus shown in FIG. A fan-shaped area V in FIG. 2 shows a place where a vertical synchronization signal of a recorded video signal is recorded. In the section of the vertical synchronizing signal of each track, a search information signal (address unique to each track) is recorded for each track by a known technique, superimposed on the video signal. The search information signal is used as a search address when randomly searching and reproducing an arbitrary track of a recorded video signal.

Next, the present invention will be specifically explained using the drawings from FIG. 3 onwards. FIG. 3 is a block diagram of a search information signal decoding circuit and a disk front/back discrimination circuit used in the present invention, and FIG. 4 is a waveform diagram of each part of FIG. 3.
FIG. 5 shows an enlarged view of the search information signal section. Fourth
The symbols attached to the waveforms in the figures and FIG. 5 correspond to the symbols attached to the lines in FIG. In this embodiment, a phase encode method is used as a modulation method for the search information signal, and the search address signal is BCD converted and "1" is set to high level.
It is recorded in positive logic such that "0" is a low level. However, it goes without saying that the present invention is not limited to any particular modulation method.

Generally, in digital modulation systems, a start bit sequence is placed before the start of effective information bits to ensure that the decoding operation on the decoding side can be performed reliably. Especially in the case of BCD conversion, the decimal number 1
Requires 4 bits per digit. So BCD
4-bit permutation (1010) that cannot occur in conversion,
(1011), (1100), (1101), (1110), (1111) 6
By using one of these as the start bit string, it is possible to distinguish between the search address and the start bit string.

In this embodiment, this start bit string is recorded differently on the front and back sides of the disk, and during playback, this start bit string is read to automatically determine whether the disk is front or back. In the following explanation, (1111) for heads and (1010) for tails are used as start bit sequences.

First, the operation in FIG. 3 will be explained in conjunction with the waveform diagram in FIG. 4. The terminal Q is connected to the preamplifier 67 shown in FIG.
The output of is input. Reference numeral 41 denotes an FM demodulator for demodulating the output of the preamplifier 67 into a video signal, and the video signal is output to line i. 42
is a synchronization signal removal circuit which removes the synchronization signal contained in the video signal and outputs the signal excluding the synchronization signal to line j. 43 is a synchronization signal separation circuit which separates a vertical synchronization signal and a horizontal synchronization signal from the demodulated video signal and outputs them to line k. 44 is an address extraction pulse generation circuit. Generally, the search information signal is inserted in the blanking section after the vertical synchronization signal, and therefore, as an address extraction pulse,
With the vertical synchronization signal as a reference, a pulse is generated that extracts a horizontal synchronization signal section equal to the interval in which the subsequent search information signal is superimposed, and is output to line 1. 45 is a search information signal extraction gate circuit which extracts only the address signal from the demodulated video signal via the address extraction pulse and outputs it to line m. A self-clock generator 46 generates a self-clock from the address signal and outputs it to line n. 47 is a serial/parallel conversion shift register which reads the address signal on line m from the self-clock output on line n as shown in FIG. That is, when the self-clock on line n is at high level, the address signal output on line m is read as "1" when it is at high level, and "0" when it is at low level, and is output to line _B0 . Each time the self-clock on line n goes high, the new read data goes to line B ₀ , the previous line B ₀ output goes to line B ₁ , and the previous line B ₁
The output moves one bit to the right, to line B ₂ , and so on. 48 and 49 are inverting circuits, and when the input is at a high level, the output is at a low level, and when the input is at a low level, the output is at a high level. 50,
51 is a NAND circuit whose output is low level only when all four inputs are high level, and high level otherwise. 52 is a reset flip-flop circuit, and when the S input becomes low level, the T
When the output becomes high level and the R input becomes low level, the T output becomes low level.

When the start bit sequence is (1111), as can be seen in FIG. 5, the output of the NAND circuit 50 on line _P1 becomes low level, and as already mentioned, the T output becomes high level. Similarly, when the start bit string is (1010), the NAND circuit 51 of line _P2
The output becomes low level, and the T output switches to low level. Therefore, if the start bit string on the front side is (1111) and the start bit string on the back side is (1010), the T output will change between the front side and the back side of the disc during playback, and when the T output is at a high level, the output of the disc will change. This means that the front side of the disc is being played back, and when the T output is at a low level, it means that the back side of the disc is being played back.

As is clear from the above explanation, by checking whether the T output of the reset flip-flop circuit 52 shown in FIG. 3 is at a high level or a low level,
It can be determined whether the information track currently being played is on the front or back side of the disc.

In the above description, a method was used in which the start bit sequence of phase modulation is changed between the front side and the back side of the disk in order to include information on distinguishing between the front and rear sides of the disk in the search information signal. Another method of adding parity bits to the search information signal is to add a bit indicating whether the disk is on the front or back side in addition to the parity bit for checking the search address, so that the front side has an even parity and the back side has an odd parity. It will be done.

Further, in this embodiment, only the method for including information on distinguishing between the front and rear sides of the disc in the search address signal has been described, but as another embodiment, a method for including information on the front and rear side of the disc in the search address signal, but it is possible to Information on distinguishing between the front and rear sides of the disc may be inserted between the horizontal synchronization signals using another code, independent of the search address signal.

As described above, according to the present invention, it is possible to easily identify whether the reproduced track is on the front side or the back side during playback by the start bit string of the search address signal, so there is no need to directly visually determine whether the disk is on the front side or the back side. Even if a protective cover is in use, you can know for sure. Furthermore, since the start bit string of the search address signal of the information track is changed and used as a signal for identifying the front and back sides of the disk surface, there is no need to add a separate signal, which has the advantage of being very convenient to use.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the configuration of an optical recording/reproducing device, FIG. 2 is a schematic plan view of a disk, and FIG. 3 is a circuit for determining whether the disk is front or back, which is a main part of the recording/reproducing device according to the present invention. FIG. 4 is a waveform diagram of each part of FIG. 3, and FIG. 5 is an enlarged view of the search information signal extraction section of FIG. 4. 1...Disk, 6...Optical system unit, 44
... Address extraction pulse generation circuit, 45 ... Search information extraction gate circuit, 46 ... Self-clock generator, 47 ... Serial-to-parallel conversion shift register, 50, 51 ... NAND circuit, 52
...Set-reset flip-flop circuit.

Claims (1)

[Claims] 1. A start bit sequence of a search address signal of the information track is recorded on a disk-shaped recording medium having information tracks on both sides, with the start bit sequence changed between the front side and the back side of the disk-shaped recording medium, and when the disk-shaped recording medium is reproduced, A means is provided for detecting whether the start bit string matches a start bit string on the front side or the back side, so that it is possible to identify whether the surface being reproduced is the front side or the back side of the disk-shaped recording medium. Configured recording/playback device.