Pioneer Corporation

Pioneer Electronic Corporation

Hiroshi Hikima

Junji Tanaka

Takeo Tobe

A prepit detecting apparatus which uses an optical recording medium having information recording tracks on which information is recorded and guide tracks each of which guides a light beam to the information recording track and on which prepits for saving pre-information are formed such that the light beam is applied to the information track of the optical recording medium, the prepit detecting apparatus comprising: light receiving means divided into a first divided light receiving portion and a second divided light receiving portion divided along an optically parallel division line in a direction of tangent of the information tracks and arranged to receive reflected light of the light beam with which the optical recording medium has been irradiated; and a difference calculator for calculating the difference between a first read signal output from the first divided light receiving portion and a second read signal output from the second divided light receiving portion so that the prepit is detected in response to a differential signal output from the difference calculator, wherein the difference calculator incorporates amplitude correction means for causing the amplitudes of the first read signal and the second read signal to coincide with a reference level, and the difference between the first read signal and the second read signal corrected by the amplitude correction means is calculated.

Prepit detecting apparatus

When first and second read signals generated on the basis of the outputs of electrical signals from a light receiving portion are input to an amplitude correcting circuit, the first and second read signals are added to generate an addition signal. Then the amplitudes of the first and second read signals are corrected for the each RF signal component corresponding to each recording pit, which is contained in the first and second read signals on the basis of the addition signal. Finally, the difference between the first and second read signals is computed to generate a difference signal so that a pre-pit signal will be detected on the basis of the difference signal.

Pre-pit detecting apparatus

A prepit detection unit for detecting prepits in an optical recording and reproducing apparatus for recording and reproducing information on a recordable, optical record medium including preinformation such as address information in a prepit form. In the prepit detection unit, for first and second divisional RF signals output from a pickup being divided into a first divisional light reception part and a second divisional light reception part by a division line optically parallel to the tangential direction of an information track for receiving reflected light from the optical record medium, mark sections and space sections are clamped by potential correction circuits and a difference is found by a radial push-pull circuit.

Prepit detection unit

An information detecting device detects information recorded in a form of pre-pits on a storage medium which is recorded with movement control information recorded by wobbling information tracks at a frequency corresponding to the movement control information and the recording control information recorded by forming the pre-pits on neighboring tracks of the information track. The device includes: a pickup for irradiating a light beam on the information track and the neighboring tracks at the same time and for outputting a reproduction signal based on the light beam reflected by the information track and the neighboring tracks; a wobbling signal extracting unit for extracting only the wobbling signal indicating the movement control information from the reproduction signal outputted; a pre-pit signal detector for detecting a pre-pit signal mixed with the wobbling signal from the reproduction signal outputted; a measuring unit for measuring a pre-pit signal absent period, in which the pre-pit signal detector detects no pre-pit signal, on a wobbling signal period basis; and a detection enabling unit for judging whether or not the pre-pit signal absent period accords with a first predetermined period, and for enabling the pre-pit signal detection by the pre-pit signal detector in a second predetermined period determined on the basis of the wobbling signal period if the pre-pit signal absent period accords with the first predetermined period.

Apparatus for and method of detecting pre-pit information

The reading position of a first reading head jumps when it is located in a vertical blanking period section of a video disc and the reading position of a second reading head jumps when it is located outside a predetermined portion of the vertical blanking period section in which a PCM audio signal is recorded. An output of the first reading head that is produced by reading sections other than the vertical blanking period section is employed as a video reading signal, and an output of the second reading head that is produced by reading the vertical blanking period section is employed as an audio reading signal.

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Saitama, Japan

Hiroshi Hikima