Abstract: Provided is a photo detecting element that has a simplified structure and that is easily manufactured and assembled, and an optical pick-up device including the photo detecting element.

Abstract: A linear motor for a laser beam recorder for mastering of optical media. The linear motor has a base and an actuator, the actuator being mounted to the base in a flexible way, such as via a leaf spring. The actuator may have a balance mass as a counter mass. The balance mass is preferably formed by an essential component of the linear motor.

Abstract: [PROBLEMS] To perform highly accurate focus control in an optical recording medium of multilayer structure having an interface of each layer with a reflectance reduced as much as possible. [SOLVING ELEMENT] In a focus control apparatus with optical pickup for use in an optical recording medium of multilayer structure, laser light irradiating device including a laser light source (50) and an objective lens (54) irradiates laser light to an optical recording medium (D), a photodetector (55) detects an optical characteristic change associated with multiphoton absorption caused when the laser light is condensed to at least one of recording layers, and in accordance with the detection result, focus control in the optical pickup is performed for an arbitrary recording layer (L1 to Ln).

Abstract: A method and system for obtaining focus optimization in an optical disc system is disclosed. The focus offset of a recording unit is set to a first of a plurality of predetermined values. A HF quality value is measured and stored for the selected focus offset value of the recording unit. The focus offset is then set to a best-known focus offset value. Tracks on the optical media being read are then jumped. The above steps are then repeated for each of the plurality of predetermined focus offset values. The optimal focus setting is then determined from the stored HF quality measurements.