Abstract: An aberration correcting apparatus is provided, which is capable of suppressing occurrence of abnormal operation in an actuator for a tracking servo by reducing track cross noise caused by astigmatism in a 45-degree direction in which influence is exerted on the tracking servo. A control is performed by using a CPU 12 and a selector 3 so as to optimize an astigmatism correction amount in a liquid crystal panel in a state where a tracking servo loop is open and in a state where the tracking servo loop is closed.

Abstract: An optical pickup system includes a light source, an objective lens, a beam splitter for splitting light received from the light source and reflected light from an optical disc, a detector for receiving the reflected light, a liquid crystal panel for providing passing light with a phase difference in accordance with a control signal and a control means for providing the control signal to the liquid crystal panel to eliminate an influence of birefringence of the optical disc.

Abstract: An optical pickup is disclosed which includes a first light source for emitting a first beam of light with a first wavelength; a second light source for emitting a second beam of light with a second wavelength, longer than the first wavelength; a condenser lens for condensing the first and second beam of light onto an information recording surface of a recording medium; and a diffractive optical element arranged in an optical path from the first and second light source to the condenser lens. The condenser lens condenses, for the first beam of light, a refracted beam of the first diffraction order of the first beam of light by means of the diffractive optical element as an information read beam or an information write beam. For the second beam of light, the condenser lens condenses a refracted beam of the second diffraction order, lower than the first diffraction order, of the second beam of light by means of the diffractive optical element as an information read beam or an information write beam.

Abstract: A liquid crystal driving signal generating apparatus comprises a PWM signal generator, a low pass filter for limiting a frequency band of a PWM signal outputted from the PWM signal generator, a liquid crystal panel connected to an output of the low pass filter, and a control means for controlling the PWM signal generator. The control means controls the PWM signal generator such that the PWM signal generator generates a PWM signal with a duty ratio corresponding to a refractive index to be set in the liquid crystal panel.

Abstract: A liquid crystal driving signal generating apparatus comprises a PWM signal generator, a low pass filter for limiting a frequency band of a PWM signal outputted from the PWM signal generator, a liquid crystal panel connected to an output of the low pass filter, and a control means for controlling the PWM signal generator. The control means controls the PWM signal generator such that the PWM signal generator generates a PWM signal with a duty ratio corresponding to a refractive index to be set in the liquid crystal panel.

Abstract: A searching method for an information record medium has: an initial value data preparing process of (i) performing a search for a plurality of sampling positions arranged in a radial direction on the information record medium, (ii) actuating a tilt servo to correct an error due to a tilt of an optical axis of a light beam emitted onto the information record medium from a normal line of a surface of the information record medium at each of the sampling positions, (iii) extracting a tilt correction amount after the tilt servo is stabilized for each of the sampling positions and (iv) storing the extracted tilt correction amount in relation to respective one of the sampling positions corresponding to the extracted tilt correction amount into a memory as initial value data of the tilt correction amount in advance; an initial value determining process for determining an initial value of the tilt correction amount at a search target position of the search when the search is to be performed, on the basis of a content

Abstract: A CPU is provided for producing a control signal. In accordance with the control signal, a modulated signal modulated in pulse width by the control signal is produced. The modulated signal has a predetermined duty ratio based on the control signal. A liquid crystal driving signal having the duty ratio based on the modulated signal is produced. The CPU is for producing the control signal for setting the duty ratio in accordance with a refractive index at each of the unit electrode of the liquid crystal panel.

Abstract: A tilt servo controlling apparatus is provided with: an optical pickup for emitting a light beam onto an optical record medium and detecting a reflection light from the optical record medium to thereby output a detection signal; a level detecting device for detecting a level of the detection signal outputted by the optical pickup; a tilt error correcting device for correcting a tilt error due to an aberration, which is generated by a tilt angle between (i) a normal line of a surface of the optical record medium at a position irradiated with the light beam and (ii) an optical axis of the light beam; and a tilt error correction controlling device for outputting a control signal to control a correction amount of the tilt error correcting device, by giving a variation to the control signal on a time base and adjusting the control signal so that the level detected by the level detecting device be optimized with respect to the variation of the control signal.

Abstract: A tilt servo apparatus in an optical disc reproducing apparatus operates promptly and certainly when reading recording information of an optical disc recorded at high density. The tilt servo apparatus is used in an optical disc reproducing apparatus having an optical pickup including a liquid crystal panel for an aberration correction on which a transparent electrode is formed and divided into segments of predetermined shapes, and irradiating a laser beam via the liquid crystal panel for the aberration correction and the objective lens, and receiving an obtained reflection light. The tilt servo apparatus has: tilt detecting for detecting a signal corresponding to a tilting angle in a radial direction between the information recording surface of the optical disc and an optical axis of the objective lens; and a driving circuit for variably driving voltages which are applied to the divided portions of the liquid crystal panel, respectively.

Abstract: An optical pickup for reading information recorded on a recording surface of an optical information storage medium such as a compact disc or a laser video disc has a light beam source for emitting a linear light beam, and an optical system including an objective lens for converging the linear light beam as a linear image on the recording surface and collecting and emitting a light beam reflected from the recording surface.

Abstract: A plurality of tracks are spirally arranged in a group on an optical disc. The tracks in the group are simultaneously radiated by laser beams. Adjacent tracks in the group are disposed at a radial distance d1, and adjacent spots of the laser beams on the tracks are disposed at a radial distance ds which is smaller than the distance d1.

Abstract: An optical information recording medium, to and from which information can be recorded or reproduced at a high density, uses more number of kinds of pits than those of a conventional optical disc. A reproducing apparatus for such a medium also is devised. Information is recorded onto the recording medium by using a plurality of pit lengths which are obtained by dividing a whole frequency band below a cut-off frequency of MTF characteristic of a reproducing system into a plurality of bands in correspondence to the band characteristic and by allocating a plurality of spatial frequencies to the divided bands.

Abstract: An optical pickup has a light source for generating a first light having a longer wavelength and a second light having a shorter wavelength, an objective, and a phase hologram disposed between the light source and the objective. The objective is designed to have a larger spherical aberration for the first light than a spherical aberration for the second light. The phase hologram is arranged to give a phase difference of an integer multiple of 2.pi. for the second light. The phase hologram is further arranged so that a spherical aberration given to the first light has an opposite polarity to the polarity of the spherical aberration given by the objective.

Abstract: An optical pickup for reading information recorded on a recording surface of an optical information storage medium has a light beam source for emitting a linear light beam, and an optical system including an objective lens for converging the linear light beam as a linear image on the recording surface and collecting and emitting a light beam reflected from the recording surface.