Abstract: A meandering groove is formed in a digital disk (10) with a wobble signal that is wobbled to reproduce a clock signal. The wobble signal is read out by an optical head (26). An address detection circuit (40) detects an address signal that is multiplexed with the wobble signal. A PLL oscillation circuit (24) provides a clock signal in synchronization with the wobble signal. Data is modulated by a modulation circuit (16) according to the clock signal and a timing signal based on the address signal, and recorded on the digital disk (10). In reproduction, a RF signal in the wobble signal is converted into a digital signal by an A/D converter (42). The signal is demodulated by a demodulation circuit (44) for data output.

Abstract: A two-side video disc is manufactured by laminating a top side face disc having a HDTV video signal with red color signal component recorded and a back side face disc having a HDTV video signal with blue color signal component recorded at a position corresponding to the recorded signal on the top side face. Visual end marks are formed at the respective ends of recording tracks of the top side face and back side face discs. The two discs are laminated so that the positions of the end marks coincide with each other. This minimizes deviation in timings between the reproduced signals from the two sides of the disc to reduce significantly the memory capacity of a delay circuit.

Abstract: An FM-MUSE signal and a pilot signal are frequency-multiplexed, to be recorded on a video disc (D). In addition, a clamp level signal and an index signal are multiplexed on particular lines of a plurality of lines of the MUSE signal. The index signal is detected from the FM-MUSE signal reproduced from the video disc by a video disc player (100). Pulses of the reproduced pilot signal are counted, beginning at the time of this detection. Accordingly, the timing of generating the clamp level signal is specified, so that clamp pulses are generated. A clamping circuit (5) is provided in the video disc player, so that the clamp level signal is accurately clamped in response to the clamp pulse.

Abstract: Two recording tracks (T1) and (T2) are formed in parallel with each other on a stereoscopic video disc record (D). Image information for a right eye and audio information are serially recorded on one recording track (T1). Image information for a left eye and audio information are serially recorded on the recording track (T2) at a synchronized timing with the image information for a right eye and the audio information recorded on the adjacent recording track T1. Information can be easily recorded on such steroscopic video disc record (D) in a manner that the image information for right and left eyes and the audio information are recorded at the same time by two recording beams. On the other hand, stereoscopic image information can be reproduced by reproducing respective recording tracks at the same time by two reproducing means. Furthermore, a normal two dimensional image information can be reproduced by reproducing either one of the recording tracks serially by one reproducing beam.

Abstract: A frequency multiplexing circuit in an optical video disc recorder frequency-multiplexes a second signal comprising a digital sound signal on the low frequency band of a first signal comprising a frequency-modulated video signal to generate a recording signal. In addition, the recording signal is applied to a limiter to be limited. In this case, a noise component produced in a band of the second signal is extracted by using a Bessel filter and a subtractor and previously subtracted from the recording signal generated by frequency multiplexing. The recording signal including a negative noise component is applied to the limiter, so that harmonic noise and linear distortion noise essentially produced in an output of the limiter can be cancelled. Furthermore, a slice level of the limiter is suitably adjusted, so that asymmetrical noise in the output of the limiter can be also eliminated.

Abstract: A reproducing apparatus comprises a motor (9) for driving a digital audio disk (1), in which digital data and a synchronizing signal are recorded. The digital data is modulated in accordance with a predetermined digital modulating system such as an EFM modulating system, and is then recorded, while the synchronizing signal is recorded which includes the repetition number of the signals of the maximum period included in the digital data which repetition number is larger than that in the digital data. A signal is reproduced from the disk and the reproduced signal is subjected to FM demodulation and then a control signal is generated based on the FM demodulated signal. The generated control signal as well as a reference signal is applied to a phase comparator (7) constituting a phase locked loop (10), whereby the phase locked loop controls the rotational speed of the motor.