摘要:
An optical head apparatus capable of stably obtaining a detection signal of spherical aberration even with a high density optical disk. A spherical aberration error signal is obtained by: dividing the returning light from the optical disk into a transmitted light and a diffracted light; reproducing information with the transmitted light having a larger amount of light while dividing the diffracted light having a small amount of light into two regions, i.e., region near the optical axis and a region distant from the optical axis; determining amounts of focus deviation in respective regions as focus error signals; and taking the difference signal therebetween. Thus, it is possible to detect the amount of spherical aberration with the SN ratio of the information reproducing signal kept at high level.
摘要:
An optical head device includes a light source for emitting light; a collection optical system for collecting the light emitted by the light source to an information memory medium including tracks having prescribed grooves; a light detector having a plurality of detection areas for receiving the light reflected by the information memory medium and outputting a signal in accordance with a light amount of the light received; a tracking error signal generator for receiving the signals output from the light detector and generating a tracking error signal based on the signals; and a light division element for dividing a reflected light reflected by the information memory medium. A relationship λ/(NA·Tp)≧1 is satisfied where λ is the wavelength of the light emitted from the light source, NA is the numerical aperture of the collection optical system, and Tp is the distance from a center of the track in the information memory medium to a center of the adjacent track; and the tracking error signal generator generates a tracking error signal from an area except for an overlapping area of the reflected light, the overlapping area being an area of overlapping two circles each having a radius of 1 and having a center of one circle being apart from a center of the reflected light beam at a distance of λ/(NA·2Tp) in a direction orthogonal to the track from a center of a cross-section of the reflected light, when the cross-section of the reflected light on the light division element in a circle having a radius of 1.
摘要:
An optical head device includes a light source for emitting light; a collection optical system for collecting the light emitted by the light source to an information memory medium including at least one of a track having a mark or a space selectively arranged, and a track having a prescribed groove; a light detector having a plurality of detection areas for receiving the light reflected by the information memory medium and outputting a signal in accordance with a light amount of the light received; a division element for dividing the light reflected by the information memory medium and allowing the light to be received by the light detector; a switch element for receiving a first signal and a second signal, which are respectively obtained in accordance with the reflected light incident on a first prescribed area and a second prescribed area of the division element and outputting either one of the first signal or the second signal, the first and second prescribed areas being obtained by dividing the division element along at least one division line; and an information reproduction signal generator for receiving the signal output by the switch element and generating information recorded on the track. The switch element outputs either one of the first signal and the second signal in accordance with a distance and e positional relationship between a light collection point of the light output from the collection light system and the track.
摘要:
An optical head device includes a light source for emitting at least one of a coherent beam and a quasi-monochromatic beam; a collection optical system for collecting the beam to an information memory medium having a track which has at least one mark and at least one space; a light detector having a plurality of detection areas for receiving the beam reflected by the information memory medium and outputting a signal in accordance with a light amount of the beam received; and a tracking error signal generator for receiving the signals output from the light detector and generating a tracking error signal based on the signals. The tracking error signal generator reduces a difference between a first signal amplitude and a second signal amplitude. The first signal amplitude is an absolute value of a difference between first and second signal levels. The second signal amplitude is an absolute value of a difference between the first and third signal levels. The first signal level is a value of the tracking error signal obtained when the beam emitted by the light source is radiated to a center of the track. The second and third signal levels are, respectively, a maximum value and a minimum value of the tracking error signal obtained when the information memory medium is scanned by the beam emitted by the light source in a direction perpendicular to the track.
摘要:
In a magnetic recording medium to detect tracking error signals optically where an optical head and a magnetic head scan different tracks, two signals having phases different by .pi./2 are generated and added or subtracted. By changing the amplitude of the two signals with a changeable gain amplifying means, a phase of a tracking error signal is changed so that the servo operation is conducted at the middle of the amplitude of the tracking error signal to keep the magnetic head on track.
摘要:
An optical head device includes a light source for emitting light; a collection optical system for collecting the light emitted by the light source to an information memory medium including at least one of a track having a mark or a space selectively arranged, and a track having a prescribed groove; a light detector having a plurality of detection areas for receiving the light reflected by the information memory medium and outputting a signal in accordance with a light amount of the light received; a division element for dividing the light reflected by the information memory medium and allowing the light to be received by the light detector; a switch element for receiving a first signal and a second signal, which are respectively obtained in accordance with the reflected light incident on a first prescribed area and a second prescribed area of the division element and outputting either one of the first signal or the second signal, the first and second prescribed areas being obtained by dividing the division element along at least one division line; and an information reproduction signal generator for receiving the signal output by the switch element and generating information recorded on the track. The switch element outputs either one of the first signal and the second signal in accordance with a distance and a positional relationship between a light collection point of the light output from the collection light system and the track.
摘要:
An optical head device includes a light source for emitting light; a collection optical system for collecting the light emitted by the light source to an information memory medium including at least one of a track having a mark or a space selectively arranged, and a track having a prescribed groove; a light detector having a plurality of detection areas for receiving the light reflected by the information memory medium and outputting a signal in accordance with a light amount of the light received; a division element for dividing the light reflected by the information memory medium and allowing the light to be received by the light detector; a switch element for receiving a first signal and a second signal, which are respectively obtained in accordance with the reflected light incident on a first prescribed area and a second prescribed area of the division element and outputting either one of the first signal or the second signal, the first and second prescribed areas being obtained by dividing the division element along at least one division line, and an information reproduction signal generator for receiving the signal output by the switch element and generating information recorded on the track. The switch element outputs either one of the first signal and the second signal in accordance with a distance and a positional relationship between a light collection point of the light output from the collection light system and the track.
摘要:
An optical head device includes a light source for emitting at least one of a coherent beam and a quasi-monochromatic beam; a collection optical system for collecting the beam to an information memory medium having a track which has at least one mark and at least one space; a light detector having a plurality of detection areas for receiving the beam reflected by the information memory medium and outputting a signal in accordance with a light amount of the beam received; and a tracking error signal generator for receiving the signals output from the light detector and generating a tracking error signal based on the signals. The tracking error signal generator reduces a difference between a first signal amplitude and a second signal amplitude. The first signal amplitude is an absolute value of a difference between first and second signal levels. The second signal amplitude is an absolute value of a difference between the first and third signal levels. The first signal level is a value of the tracking error signal obtained when the beam emitted by the light source is radiated to a center of the track. The second and third signal levels are, respectively, a maximum value and a minimum value of the tracking error signal obtained when the information memory medium is scanned by the beam emitted by the light source in a direction perpendicular to the track.
摘要:
An inclination detection apparatus is provided which includes an optical system for collecting a beam emitted by a light source onto an information memory medium. The inclination detection apparatus further includes a light detector for generating a detection signal in accordance with a light amount of the beam reflected by the information memory medium, the light detector including a first light receiving section and a second light receiving section. In addition, the inclination detection apparatus includes a signal processing section for processing the detection signal. The signal processing section generates an inclination detection signal based on a difference between a first sum signal and a second sum signal, the first sum signal being based on a sum of a first light receiving section signal and a second light receiving section signal, the second sum signal being based on a sum of a third light receiving section signal and a fourth light receiving section signal. Moreover, the signal processing section generates a tracking error signal based on a difference between a fifth light receiving section signal and a sixth light receiving section signal.
摘要:
In a magnetic recording medium to detect tracking error signals optically where an optical head and a magnetic head scan different tracks, two signals having phases different by &pgr;/2 are generated and added or subtracted. By changing the amplitude of the two signals with a changeable gain amplifying means, a phase of a tracking error signal is changed so that the servo operation is conducted at the middle of the amplitude of the tracking error signal to keep the magnetic head on track.