Patent ID: 7068571
Filing Date: 2006-06-27
Classification: G11B

Abstract:
1. An optical recording apparatus comprising: an optical system for diffracting an optical beam emitted from a light source to form a main beam and a succeeding sub-beam following the main beam and for irradiating a signal recording medium with the main beam and the succeeding sub-beam, wherein a main spot is formed on the signal recording medium by irradiation of the main beam and a succeeding sub-spot is formed on the signal recording medium by irradiation of the succeeding sub-beam; and a photodetector including a main light receiving region for receiving reflected light of the main spot on the signal recording medium and a succeeding light receiving sub-region for receiving reflected light of the succeeding sub-spot on the signal recording medium, wherein the optical system is set such that a distance between the succeeding sub-spot and the main spot in the direction orthogonal to an extending direction of a signal track on the signal recording medium corresponds to an amount defined by an expression (2k−1)P/4(k=a natural number), in which P denotes a distance between adjacent signal tracks on the signal recording medium, wherein the optical system diffracts the optical beam to further form a preceding sub-beam preceding the main beam, which forms a preceding sub-spot on the signal recording medium, wherein the photodetector further includes a preceding light receiving sub-region for receiving reflected light of the preceding sub-spot, wherein each of the main light receiving region, the succeeding light receiving sub-region, and the preceding light receiving sub-region is divided into two segment regions by a dividing line which extends in a direction corresponding to the extending direction of the signal track on the signal recording medium, the optical recording apparatus further comprises a first tracking error signal generating circuit for generating a tracking error signal in a Differential Push-pull method based on an output from each segment region of the main light receiving region, the succeeding light receiving sub-region, and the preceding light receiving sub-region, further comprising an evaluation circuit for evaluating the recording state of a recording signal recorded with the main beam on the signal track on the signal recording medium, wherein the evaluation circuit evaluates the recording state based on an output from a predetermined one of the two segment regions of the succeeding light receiving sub-region, further comprising a current-to-voltage conversion amplifier provided for each segment region of the succeeding light receiving sub-region for converting into a voltage signal from a current signal output from a corresponding segment region, and further comprising a buffer amplifier for gain adjustment provided downstream of each current-to-voltage conversion amplifier, for amplifying an output from a corresponding current-to-voltage conversion amplifier, and wherein an output from each buffer amplifier is supplied to the first tracking error generating circuit, and an output from the current-to-voltage conversion amplifier corresponding to the predetermined one of the two segment regions of the succeeding light receiving sub-region, prior to amplification by the buffer amplifier, is supplied to the evaluation circuit.