Sanyo Electric Co., Ltd.

Other

Koichi Tada

Shuichi Ichiura

Hiroshi Watanabe

Naoyuki Takagi

Ken Hirose

Shinichi Ohe

Yoichi Tsuchiya

Seiji Kajiyama

Yasuyuki Kanou

Toshio Harada

Masami Shimizu

Kenji Asano

Katsutoshi Hibino

Toshihide Hamaguchi

Shigekazu Minechika

Tadashi Okajima

Hideaki Yano

Shigeki Hori

Toshitaka Kuma

Takashi Onaka

Junko Onaka

The invention provides a disk playback device wherein a disk () is irradiated with a laser beam from an optical head () to reproduce signals from the disk, and which comprises an external synchronizing signal producing circuit () and a delay circuit () for producing a reproduction synchronizing signal providing reference timing at which a reproduced signal is detected by reading an output signal from the optical head (), a circuit () for detecting the reproduced signal by reading the output signal from the optical head () based on the reproduction synchronizing signal, and a system controller () for determining an optimum phase for a normal reproduction operation by altering the phase of the reproduction synchronizing signal and executing a reproduction operation, the controller () being operable to make a phase adjustment for the reproduction synchronizing signal prepared by the delay circuit (). A normal reproduction operation can be performed at all times by assuring the reproduction synchronizing signal of the optimum phase.

Disk reproduction device

A disk reproducing apparatus includes a variable gain amplifier (VCA) (), and the VCA applies a radial push-pull signal including an address signal and an FCM leakage-in signal to a switch (). The switch outputs only the address signal to a peak-hold circuit () on the basis of an FCM mask signal from a mask signal generation circuit (). The peak-hold circuit generates a peak-hold signal of the address signal so as to be output to a DSP (), and the DSP controls a gain of the VCA on the basis of the peak-hold signal. Then, the radial push-pull signal in which the gain is controlled on the basis of the address signal is applied to an address detection circuit (), and the address signal is detected therein.

Disk reproducing apparatus for precisely determining a value of an address signal reproduced from the disk

A digital signal processor () arithmetically determines a comparison level for comparing each signal component by determining a comparison level of comparators (and) for comparing a fine clock mark signal such that a larger weight is assigned to the comparison level of the signal component already compared. The comparators (and) compare the fine clock mark signal with reference to a level set on a peak side and a level set on a bottom side. When digital signal processor () receives the comparison signal from one of the comparators (and) prior to the comparison signal sent from the other, the digital signal processor produces a fine clock mark detection signal FCMT based on the comparison signal sent from a comparator (). Thereby, the clock can be accurately produced based on the fine clock mark signal even when a signal component having a larger amplitude than that of the fine clock mark signal is detected.

Optical disk apparatus capable of generating clock accurately

A defect detecting circuit generates a defect detection signal when the level of a sum signal obtained from an optical sensor in an optical pickup is lower than a predetermined level, and a gate circuit responds to the defect detection signal to set the level of a fine clock mark signal to zero, that is a difference signal obtained from the optical sensor in the optical pickup. A fine clock mark is thus distinguished from any defect such as scratch and a correct fine clock mark signal is accordingly generated. Alternatively, the value of a sum signal, which indicates the total amount of reflected light output from the optical pickup, is compared with a predetermined threshold. When the period in which the value of the sum signal is smaller than the threshold lasts for a predetermined threshold time period, it is determined that focus of an objective lens deviates from an optical disk and accordingly focus servo control is stopped. The threshold is defined by gradually reducing a drive signal while detecting peak and bottom values of the sum signal which is generated as the objective lens is moved in the direction of its optical axis, and then setting the threshold between the detected peak and bottom values. In this way, defocus of the objective lens is surely detected.

Apparatus for recording/reproducing signal on/from optical disk

A disk apparatus includes a DSP core, and executes processing for focal point positioning when turning on the power to the apparatus main body or exchanging the MO disk. The DSP core detects maximum and minimum values of outputs (focus error signal) of an FE signal detector circuit while moving the objective lens from an uppermost position of not contacted with a disk surface to a lowermost position. The DSP core calculates a middle position using positions of the objective lens upon fetching maximum and minimum values (uppermost and lowermost positions). Subsequently, the DSP core determines a range narrower than a range to be determined by the uppermost and lowermost positions, by the use of the middle point and amount of surface deflection of the MO disk. Then, the DSP core wobbles the objective lens within the narrow range and detects a focal point based on a level of the focus error signal.

Disk apparatus with enhanced focal positioning

A disk apparatus includes a DSP core. When turning on power to the apparatus main body or exchanging the MO disk, setting processing of focus offset (offset) values is performed. The DSP core extracts fine clock mark (FCM) signals out of the reproduced signal through tracking on the land/groove. Specifically, in a range that mean value of FCM signal levels is equal to or greater than a predetermined level, FCM signal levels are detected at positions shifted left and right by a predetermined amount from a present offset value. In this manner, scanning is made throughout the range while being shifted by a predetermined amount, each time of which a difference is detected. An offset value where the difference assumes a minimum is determined as an optimal offset value. The optimal offset values are determined respectively for the land and the groove, which are switched according to a track (land/groove) upon reproduction.

Disk apparatus for focusing and adjusting a laser beam

In order to reproduce signals from a double-layer optical disc having two signal recording surfaces, a focus jump that the focusing of an objective lens from the one signal recording surface to the other signal recording surface is quickly achieved, is necessary. When a focus error signal (FE) from a pickup ( ) reaches a predetermined threshold value (Vcomp), a deceleration signal for decelerating the objective lens ( ) is supplied to an actuator ( ). Preferably, a deceleration pulse voltage is lowered step by step. The deceleration pulse voltage is determined in accordance with the maximum value (DFEmax) of a differential focus error signal (DFE) generated by differentiating the focus error signal (FE). Preferably, the address seeking is done simultaneously with the focus jump. The focus jump is performed in accordance with the layer-to-layer distance which is measured beforehand. The focus jump is performed by using a lens ( ) having a controllable focal distance. Preferably, whether the layer is the first layer or the second layer is judged based on the reflected luminous power. If the focus error signal (FE) from the other layer is not obtained even when a certain time passages after the focus jump is started, the objective lens ( ) is moved in the reverse direction.

Optical disk device

Optical disc device

An apparatus for discriminating optical disks has an optical pickup provided with an objective lens having an effective numerical aperture of 0.55 to 0.65, which can compatibly reproduce information from a CD and an SD. The apparatus discriminates presence/absence of waveforms of two focus error signals detected when the effective numerical aperture of the objective lens is set at 0.55 to 0.65 and 0.20 to 0.45 respectively in a process of performing focus servo control, thereby discriminating various types of optical disks from each other. Thus, optical disks having different substrate thicknesses, different track pitches, different minimum pit lengths and different reflectivity can be quickly and simply discriminated from each other.

Apparatus for discriminating optical recording media of different thicknesses from each other and reproducing information therefrom

Optical pick-up device

An optical pickup apparatus including a polarization plane rotary unit arranged between a semiconductor laser and an objective lens, and a polarizing film arranged between the polarization plane rotary unit and the objective lens. The polarization plane rotary unit includes liquid crystal, two glass plates sandwiching the liquid crystal, and transparent electrodes patterned to a predetermined configuration on an inner face of these glass planes. The polarization plane rotary unit permits passage of the laser beam without rotating the plane of polarization of the entire laser beam at the time of recording, and permits passage of the laser beam with the plane of polarization of the center portion of the laser beam rotated and the plane of polarization of the remaining outer portion of the laser beam not rotated at the time of reproduction. Only the outer portion of the laser beam is focused on a magneto-optical disk in a reproduction mode, so that a main beam of a small spot is formed by mutual interference. Since the plane of polarization of the laser beam directed on the magneto-optical disk is not rotated, the Kerr angle of rotation can be detected at high accuracy. As a result, the reproducibility is improved.

Growing community of inventors

Gifu, Japan

Koichi Tada