JP2661025B2 - Double-sided playback video disc player - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video disc player suitable for reproducing a video disc having video information recorded on both sides. [Summary of the Invention] The present invention provides two optical heads capable of reproducing information facing the front and back of a video disc,
After the front surface of the optical disk is reproduced by the first optical head without reversing the front and back surfaces of the video disk and the rotation direction of the spindle motor, the second optical disk is continuously reproduced.
The optical head can reproduce the back surface of the optical disk. 2. Description of the Related Art A video disc on which a movie program or an educational program is recorded can be made a long-time recording disc by recording video information on the front and back surfaces. [Problems to be Solved by the Invention] However, when reproducing such a double-sided recording disc, the video disc is once pulled out from the player when the disc is moved from the front side (side A) to the back side (side B). It was necessary to invert the side B and load again. Therefore, two optical pickups (optical heads) mounted on a video disk player are arranged on the upper and lower surfaces of the disk, the first optical head faces the surface of the disk A, and the second optical head is mounted on the disk. By disposing the disk so as to face the surface B, it is possible to eliminate the hassle of turning over and mounting the disk when moving from the surface A to the surface B. However, since both sides A and B have a format in which recorded information is read out in the same rotation direction so that they can be reproduced by a normal player, for example, the first optical head facing the side A causes the first optical head to face the side A. When the reproduction of is completed, the second optical head facing the surface B
In order to continuously reproduce the surface, it is necessary to reverse the rotation direction of the spindle motor. By the way, the rotation speed of the video disc is at least 1800 rpm on the inner circumference side, and a very large braking voltage is required to reverse the disc rotating at 1800 rpm at 1800 rpm, and a large spindle A motor is required. Since the reversal time is long, it is extremely difficult to continuously reproduce the double-sided disc by reversing the spindle motor. The present invention has been made in view of such a problem, and an object of the present invention is to provide a video disc player capable of continuously reproducing a reproduction RF signal from a surface A to a surface B without interruption. [Means for Solving the Problems] FIG. 1 shows a schematic diagram of a double-sided playback video disc according to the present invention. Reference numeral 10 denotes a video disc having video information returned to both sides (hereinafter simply referred to as a disc). 1) 1A and 1B are first and second optical heads disposed on the lower surface and the upper surface of the disk 10, respectively. These are a servo circuit (not shown) and a thread feed, as in the conventional optical head. It outputs a reproduced RF signal while tracking. 2 is a switching circuit, 3 is a signal processing circuit for demodulating a video signal from an RF signal, 4 is a memory means capable of recording the demodulated video signal for at least two fields and reading it out, and 5 is the first, 2 shows a control unit for controlling the optical head (1A, 1B) switching circuit 2 and the memory means 4. [Operation] First, the A side of the disk is reproduced from the inner periphery to the outer periphery by the first optical head 1A. Then, the switching circuit 2 is inverted so that the reproduction signal of the second optical head 1B in the standby state is output at the same time when the reproduction of the last track on the side A is completed. Then, at least two fields of signals are input to the rewritable memory means 4 via the signal processing circuit 3. In this case, the second
When the rotation direction of the track viewed from below the surface A of the disk is counterclockwise as shown by the arrow A as shown in FIG. 7A, the rotation direction of the surface B when viewed from above in the same rotation direction Is in the direction of arrow B, and the spot irradiated on the track follows the track in the direction of arrow b. Therefore, the reproduction RF signal S _b B-side to the reproduction RF signal S _a of A surface as shown in FIG. 2 (b) and at the same time the time axis of the signal is reversed, when the tracking is applied, The irradiated spot is controlled to move to the inner peripheral side of the spiral track. Therefore, in the present invention, a jump signal for stepping toward the outer periphery for each field is output from the control unit 5 as shown in FIG. 2 (a) during the B-side reproduction, and the control unit 5 controls the memory means 4. Reproduced RF stored in reverse time
When reading the signal _Sb from the memory means 4, control is performed so as to read from the last line address signal. As a result, the reproduced RF signal S _{b on the} surface B shown in FIG.
That is read from the arrow direction as indicated by the dotted line, and outputs the normal video signal similarly to the reproduced waveform S _a of read from the memory means 4 as shown in the signal waveform S _c of FIG surface A it can. [Embodiment] FIG. 3 is an embodiment showing a main part of the present invention, in which 10 is a double-sided recording type video disc, and 11A and 11B are for searching tracks on the A and B sides of the double-sided recording video disc. Reference numerals 12 and 13A, 13A and 13B denote first and second optical heads which can be reproduced and reproduced, and RF signal amplifiers and demodulators. 14A and 14B are D / A and A / D converters for recording or reading video signals in the frame memories 15A and 15B. The frame memories 15A and 15B have independent write / read addresses. A dual port type that can be accessed is used. Reference numeral 16 denotes a reference signal source for reading, and 17 denotes a variable oscillator for forming a clock signal for writing. A burst signal is input to the variable oscillator (VCO) via a burst gate 19 in order to synchronize the demodulated video signal with a frequency four times as high as the frequency of the color subcarrier _fsc extracted via the filter circuit 18. I have. The video signal output from the filter circuit 18 is input to the synchronization signal separation circuit 24, and the extracted horizontal synchronization signal (H
D) is input to the horizontal counter 26, and the vertical synchronizing signal (VD) is input to the system controller 23 as a jump command signal in the signal forming circuit 25. Note that the horizontal synchronization signal
By controlling the VCO 17 by HD, a TBC function (time axis compensation) is added. Reference numerals 20 and 21 denote an inverse frame number decoder and an address control circuit which show the features of the present invention. The inverse frame number decoder forms the frame number of the reproduced signal to a normal value during B-side reproduction. The address control circuit 21 is provided for the frame memory 15.
A read address is supplied to A and 15B. For example, a line address signal is formed by dividing the sample frequency, and this line address signal is supplied to the frame memories 15A and 15B at the time of reading or writing. Reference numeral 22 denotes a control unit (CPU) constituting a central control unit of the double-sided reproduction disk player of the present invention, and reference numeral 22 denotes a system controller. Reference numeral 27 denotes a low-pass filter, reference numeral 28 denotes an output amplifier, and a signal processing circuit, a dropout compensation circuit, and various servo circuits of an audio system are omitted. Hereinafter, an embodiment of the present invention will be described with reference to the waveform diagram of FIG. As shown in FIG.
First, the A-side is reproduced by the first optical head 11A. The reproduced RF signal is supplied to an amplifier 13A and a demodulator 13B.
Is converted into a composite video signal via an A / D converter 14A (which also compensates for dropout if necessary), and is sampled at, for example, 4f _sc (where f _sc is the color subcarrier frequency), and the clock of the VCO 17 Is input to the first memory 15A. VCO17 jitter when read in TBC (time base collector) as well as including the jitter component clock signal and is for that input to the memory 15A field data A ₁ to A _n a reference signal (4f _sc) The components are removed. When the odd-order frame data A is read from the first memory 15A, the second memory 15B is used for reading subsequent even-order frame data (A '). Then, when the second memory 15B is being read, the next field data is written to the first memory 15A. In this way, when the reproduction of the A side of the double-sided recording type video disc 10 approaches the end point, the second optical head is controlled to the standby state by the command from the control unit 22, and the start frame (B _{1) of the} B side ) Is set to a state for still playback. At the same time as the recording of the last frame data (A _n ′) on the side A is completed as shown by [I] in FIG. 4, the control is performed so that the start frame data (B ₁ ) on the side B is recorded. The reading of the last frame data (A _n ′) on the A side is completed, and the start frame data (B ₁ ) on the B side is read. In this case, since the time axis of the recording on the side B is reversed, the read address is supplied to the address control circuit 21 in the order opposite to that on the side A. The reproduction of the surface B is performed by the second optical head 1B.
As shown in FIG. 7A, the operation is performed while jumping one step toward the outer periphery in the vertical synchronization signal period. By the way, the end time of the last playback frame on the A side, and B
The start time of the start frame of the surface may not match on the front and back surfaces of the disc. In this case, the last frame data (A _n ′) of the A plane is transmitted twice, as shown in [II] in FIG. 4, and the still plane (A _n ″) of one field is transmitted. Is output, and the still image is transmitted, and then the start frame data (B ₁ ) on the side B is read out. When connecting, a skew of 0.5H occurs. As is well known, a still image (A _n ″) is read as, for example, a 263H line, and the next field (B ₁ ) is read as a 262H line. Can be solved by [Effects of the Invention] As described above, the screen recording disk reproducing apparatus of the present invention faces the first and second disks on the front and back surfaces of the disk, and simultaneously completes the reproduction of the A surface with the B surface. In addition to controlling the reproduction to start, the reproduction of the B side is performed by reading the reproduced frame data from the frame memory in reverse time while driving the second optical head by one-step jump. There is an effect that the side A can be continuously reproduced from the side A in the set state without changing the rotation direction of the spindle motor.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a basic outline of a player according to the present invention, and FIGS. 2 (a) and 2 (b) show reproduction tracks of an optical disk on a B side and reproduction waveforms thereof. FIG. 3, FIG. 3 is a block diagram showing an embodiment of the present invention, and FIG.
It is an RF data diagram. In the figure, 1A and 1B are first and second optical heads, 2 is a switching circuit, 3 is a signal processing circuit, 4 is a memory means, 5 is a control unit,
Reference numeral 10 denotes a double-sided recording disk.

Claims (1)

(57) [Claims] First and second optical heads arranged on both sides of a video disc for reading information stored on the front and back sides of the video disc; and reading from both sides of the video disc by the first and second optical heads A switching circuit for selecting the selected signal, and a reproduction signal based on an output signal from the first or second optical head selectively output by the switching circuit for at least one frame. A first and a second memory unit; and a control unit for controlling the operation of the first and second optical heads and the first and the second memory unit. When the operation of reproducing one of the surfaces of the video disc using one of the second optical heads is nearing completion, the other optical head is controlled to a standby state. When the operation of reproducing one surface of the video disk by the one optical head is completed, the switching circuit is switched to start reading of information recorded on the other surface of the video disk by the other optical head. At the same time, the reproduction signal read by the other optical head is written in the first and second memory means while the other optical head is jumped by one step, and stored in the first and second memory means. A double-sided reproduction video disc player, characterized in that the data is read out in the reverse order of the reproduction signal read out by the one optical head.