Abstract: The astigmatic aberration in an optical system is to be adjusted. Specifically, in an optical disc device on which can be selectively loaded a first optical disc having a first index of double refraction or a second optical disc having a second index of double refraction larger than said first index of double refraction, and which includes a liquid crystal device 31 between a light source 11 and an objective lens 15 converging a light beam radiated from said light source on the optical disc 2 loaded on the optical disc device, the voltage applied to the liquid crystal device 31 is adjusted to correct the coma aberration or the astigmatic aberration for the first disc or the second disc, respectively.

Abstract: An information system according to the invention comprises a record carrier and a playback apparatus. The record carrier has information marks along a track thereof and exhibits first variations caused by existence and nonexistence of the information marks along the track. The first variations represent an information signal recorded on said record carrier. The record carrier further exhibits second variations caused by variations associated with the information marks. The phase of the second variations is coupled to the phase of the first variations.

Abstract: In a multimedia copy control system, digital contents data stored in the digital data recording medium includes a first copy control information of a digital format and a second copy control information of an analog embedded format, and encryption of the reproduction output data from the recording medium is decrypted and judged for each digital contents unit under reproduction, and even in the case of detecting no first copy control information, the reproduction of the digital contents data is controlled based on the second copy control information.

Abstract: A predetermined synchronization pattern (40), a so-called VFO field, in, for example, the headers 3 of an information carrier. The predetermined synchronization pattern contains a first part with marks having a first length of (d+1) times the channel bit length, and spaces having a second length of (d+1) times the channel bit length, and a second part with marks having a third length of (k+1) times the channel bit length and spaces having a fourth length of (k+1) times the channel bit length and a third part, which third part contains marks having a length of (k?d) times the channel bit length and spaces having a length of (k?d) times the channel bit length. This sequence of patterns is advantageous for setting the dynamic range of an Automatic Gain Controlled (AGC) amplifier located within a device reading the information carrier.

Abstract: An information recording device for writing information in a circumferential direction of a disk-type recording medium, with a substantially constant linear density.

Abstract: This invention provides a method of acquisition of binary information that has been stored physically in a periodic storage medium. The method, referred to as matrix-method deconvolution (MMD), is useful for use with optical storage media using an optical addressing system that reads and writes binary information in a periodic array of nano-particles. With this MMD method, the density of existing memory systems can be boosted to between 10 and 100 Terabytes of data per cubic centimeter. This matrix-method deconvolution method compensates for the effects of the optical addressing system's point spread function. Prior knowledge of a system's point spread function and inter memory-center spacing is used.

Abstract: An optical disk is provided for recording data of a signal modulated according to a predetermined modulation method in a form of concavo-convex pits. The optical disk includes a first area having a reflecting film partly removed, and a second area for recording pits which are different from pits satisfying requirements of the predetermined modulation method. The first area having the reflecting film partly removed includes a portion which is formed by removing the reflecting film, and has a length longer than a maximum pit length determined by the modulation method in a circumferential direction of the optical disk. When the pits recorded on the optical disk are physically copied as they are, physical copying of the optical disk can be prevented by utilizing such a difference that the authorized optical disk differs from a pirated copy in a combination of the respective reproduced signals of the first and second areas.

Abstract: To stably carry out recording and reproducing to and from a high density optical disk without using a double servo in the optical disk using a high NA objective lens. A detection of a spherical aberration and a detection of a coma aberration in a radial direction are simultaneously performed, and the coma aberration generated with the offset of an objective lens 109 is corrected in real time, thus enlarging an allowable offset amount of the objective lens. In order to simultaneously detect the spherical aberration and the coma aberration, focal shift and tracking shift signals in an inside region and outside region of reflected light flux are detected respectively, and the differential signals are set as spherical aberration and coma aberration signals.

Abstract: An optical recording medium having an information layer with a reflective film on which an information recording portion is formed by physical change of shape at least in one direction of thickness and track width, the reflective film having such a structure that additional recording can be performed by thermal recording, and that the reflectance of the reflective film changes in the range of 0.5%<(|R0−R1|/R0)×100%<17%, where R0 is reflectance of non-recording state and R1 is reflectance of recording state for reproducing beam. Such optical recording medium can be manufactured at low cost with additional recording.