Abstract: In recording data on a disk-shaped information recording medium having formed thereon a plurality of concentric or spiral tracks each being divided into a plurality of sectors each having an ID field and a data field, a data mark is selected from a plurality of distinct data marks according to an address of a target sector such that the selected data mark is different from a data mark recorded in an adjacent sector which is contained in an adjacent track. The selected data mark is recorded at the start position of the data field of the target sector. In reproducing the recorded data, a data mark is selected from the plurality of distinct data marks according to an address of a target sector, and is compared with a data mark reproduced from the target sector to detect whether the reproduced data mark coincides with the selected data mark. Sector data in the target sector is reproduced only when the reproduced data mark coincides with the selected data mark.

Abstract: In an optical data recording and reproducing apparatus comprising an information signal generator, a sample/hold switching signal generator, a write/read switching signal generator, a laser beam source, a reference voltage generator, a comparator and a photo detector, a dummy signal is added to the information signal modulating the laser beam or generation of the laser beam is forcedly stopped after a data write servo mode so as to prevent generation of the laser beam of an excessively high level at the time of change-over from the data write servo mode to a data write hold mode or from the data write hold mode to a data read mode, or the level of the write/read switching signal is changed before the level of the sample/hold switching signal is changed at the time of change-over from the data write hold mode to the data read mode, or the duration of emission of the laser beam is extended slightly before the level of the sample/hold switching signal is changed.

Abstract: An optical recording and reproducing apparatus which records information on the optical disc to reproduce the information from the optical disc. It is necessary to detect the abnormal condition, when the abnormal condition has been caused while the information is recording on the optical disc, to change the optical power level of the laser light source into the non-recording condition so that the abnormal data may not be recorded on the optical disc. The track skipping which is not intended, unnecessary during the recording operation, the condition which is not the record power with the record power level being set, the motor which is rotating the optical disc causes the abnormal rotation, are the abnormal condition during the recording operation.

Abstract: A drive circuit for a semiconductor laser in an apparatus for recording/playback of data utilizing an optical recording medium includes circuit elements for establishing recording and playback operating conditions respectively in which output light levels from the laser are set to suitable values for recording and playback, and for controlling the laser output light levels during recording and playback operation at fixed values, and moreover for modulating the laser output light in accordance with a recording signal during recording operation. A changeover control signal which executes changeover between the recording and playback conditions is derived such as to begin in coincidence with the start of a leading pulse of a series of recording signal pulses, and to end immediately following the final recording signal pulse, to thereby avoid excessive laser drive current levels following changeover between playback and recording operating conditions.

Abstract: An optical disk for optical recording and reproducing data has a spiral track and further includes a single index field and a plurality of sectors. The index field includes an index mark that indicates the position at which an optical head of the optical recording and reproducing apparatus retraces a spiral track by jumping a specific portion of the guide track. Each of the sectors has a sector header, which comprises a sector mark located at the start of the sector and an address field including a track address, sector address, and an error detecting and correcting code. The index mark in the field is detected, and the optical head is made to perform a jumping operation in response to the resulting signal, whereby the jumping operation is rendered certain. When there is a failure to read the address fields, the signal produced by detecting the index mark starts a counter which counts the signal produced by detecting a sector mark, for recovering the sector address.

Abstract: A semiconductor laser drive circuit functioning as a light source of an optical recording/reproducing apparatus using an optical disk. In the recording mode, the input light of a semiconductor laser is modulated by a recording signal, the output light of the semiconductor laser is detected as a monitor signal by a photo sensitive device, the peak value of this monitor signal is held by a peak-hold circuit, a differential compensation control signal is obtained from the output of the peak-hold circuit and is fed back, and a photo control system to control the output light to a constant level is constituted, thereby controlling in such a way that the output light of the semiconductor laser becomes a certain constant modulation amplitude. Even upon recording, the output light can be stably controlled within a wide temperature range even if the characteristic of the semiconductor laser changes with the elapse of time. Also, this drive circuit can be realized by a simple arrangement.

Abstract: An optical recording and reproducing apparatus in which a laser beam is converged to a tiny beam spot and projected onto an optical disc to change thermally the optical disc, thereby effecting recording and reproducing of a signal and which detects a mark (17) for determining a recording polarity of the optical disc which is provided on an optical disc or a disc jacket and effects switching between analog gate switches (23a), (23b) in accordance with the result of the detection thereby to control a polarity of a signal to be recorded or reproduced in a positive or negative direction, whereby it is made possible to stably effect recording and reproduction of signals on optical discs which provide reproduced signals of different polarities because of the characteristics of their recording materials, such as erasable optical discs and unerasable optical discs, by using one and the same recording and reproducing apparatus.

Abstract: A drive circuit drives a liquid crystal display device of the type in which liquid crystal fills a space between an X-Y matrix substrate having a number of picture elements each including a switching element, and a common electrode plate. The drive circuit provides an optimum picture displayed to an observer in accordance with ambient conditions such as light and temperature. To this end, a DC bias voltage to determine the operating point of the liquid crystal display device is applied to the common electrode. The brightness of the displayed picture may be controlled by adjusting the DC bias voltage. The DC bias is changed in accordance with a change in an amount of ambient light or ambient temperature. Furthermore, in accordance with the fall of the ambient temperature the DC voltage applied to the common electrode is made to oscillate at a frequency to which the liquid crystal is insensitive, with respect to the bias point. At this time, the amplitude of the oscillation is made large.

Abstract: The present invention relates to a driving method for displaying television signals on an X-Y matrix type liquid crystal display panel having both switching elements and memory elements for respective picture elements which utilizes the phenomenon that high frequencies reduce the erasing time of the liquid crystals. According to the present invention, when a panel is driven by means of a line at a time process, each horizontal scanning period is divided into two periods, a video signal period and a erasing signal period, thereby to provide a composite signal having a video signal portion and an erasing signal portion so that a first pulse corresponding to the video signal period writes the video signal on that panel and a plurality of second pulses corresponding to the erasing signal period applies the erasing signal to the panel for erasing.