Abstract: An optical recording-reproducing apparatus includes a laser light source, an objective lens for concentrating a luminous flux from the laser light source onto a disk medium, an actuator for controlling the position of the objective lens, a tilt-adjusting circuit for adjusting a tilt of the objective lens with respect to the disk medium, a circuit for determining laser power for recording a recording mark on the disk medium, and a circuit for detecting symmetry of the recording mark based on reflected light from the disk medium. In recording, the tilt of the objective lens is adjusted by the tilt-adjusting circuit based on an amount of change of the symmetry of the recording mark.

Abstract: An optical head includes a laser light source of emitting laser, an objective lens which focuses the laser emitted from the laser light source on an optical recording medium and an optical element placed between the light source and the optical recording medium, of which the transmittance varies depending on a voltage applied. The voltage applied to the optical element is switched so that the optical element has a lower transmittance upon reproducing a signal on the optical recording medium than upon recording a signal on the optical recording medium, at times when recording a signal on the optical recording medium and when reproducing a signal on the optical recording medium.

Abstract: Problem: To provide a recording and reproducing device that is capable of improving in its reproduction quality by efficiently detecting a reproduction signal having small low frequency noises even when reproducing data on a super-resolution optical disk including recording marks smaller than a diffraction limit. Means for Solving the Problem: By using an aperture control means that makes an exit pupil diameter of an objective lens that is provided across a beam return path to make an effect on the reflection light from the optical disk, larger than an exit pupil diameter of the lens provided across a beam return path, peripheral portion's light of the reflection light with a low frequency noise rate is efficiently received and detected without a high-NA objective lens requiring a lot of manufacturing costs, so that a reproduction signal is obtained in good quality.

Abstract: An optical pickup device includes light sources for respectively emitting a plurality of different wavelengths of light, a unit structured for causing at least a part of the light emitted from the light sources to pass a same optical path; and a focusing unit for focusing the light. The focusing unit includes at least first and second focusing parts, the first focusing part being to focus mainly a wavelength of light different from a wavelength of light to be mainly focused by the second focusing part. The optical pickup device and optical disk device are capable of realizing at least one of thickness reduction, size reduction and suppression against characteristic deterioration even where coping with various wavelengths of laser including a blue laser.

Abstract: A gap controller according to the present invention can set a reference level reasonably for a gap control that needs to be done to keep the gap between a solid immersion lens (SIL) and an optical disc constant. With the gap varied at a substantially regular step, gap detection signal levels are logged to find an extreme value of its second-order difference. And the gap control reference level is determined by the gap detection signal level that results in that extreme value.

Abstract: A hybrid objective lens has a refractive lens and a diffractive optical element constructed by plural coaxial ring-shaped zones on at least one optical surface thereof. When n1, n2 and n3 each is a diffraction order of a diffracted ray having a maximum light amount among diffracted rays of each of first, second and third light flux having wavelength ?1, ?2 and ?3 when respective light flux comes to be incident into the diffractive structure respectively, the following formulas are satisfied: |n1|>|n2|, and |n1|>|n3|, and the hybrid objective lens converges a n1-th, n2-th and n3-th order diffracted ray of the first, second and third light flux onto an information recording plane of each of the first, second ant third optical information recording medium respectively so as to form an appropriate wavefront within respective prescribed necessary image side numerical apertures.