Mitsubishi Denki Kabushiki Kaisha

Mitsubishi Denki Kabushiki

Keiji Hatanaka

Yoshiko Hatano

Takahiro Nakai

Ken Onishi

Hidetoshi Mishima

Taketoshi Hibi

Kihei Ido

Shinobu Ueda

Kenji Maeno

Katsuhiro Ookawa

Akiyoshi Hirano

Takashi Shiroshita

Yoshimitsu Nakajima

Yoshiyuki Shirasaki

Masami Itoga

In a method for performing magnetic recording and reproducing an apparatus is used which includes a magnetic head carried by a piezo-electric movable element, the position of the magnetic head is detected such that reproduction signals are maximized within the range of transverse movement of the magnetic head, i.e., the range of less than 1/3 of the track width is detected. Their corresponding pattern signals are inputted as renewed successively. The result of this method is that a good reproduction image can be obtained even from a magnetic tape having locally different record levels, following any track curvature change with time, without deteriorating the quality of image during reproduction.

Method and apparatus for following curved tracks on a tape

An inversion prevention device to prevent inversion and provide the best S/N ratio detects a point where the zero crossing is missing from a quantized FM signal. An output is provided by switching between the digital FM signal and the output signal of at least one sideband suppression filter based on a result of the inversion detection. Alternatively, an output is provided by switching between the digital FM signal and a specified value based on a result of the inversion detection. As a further alternative, an output is provided by switching between the digital FM signal, the output signal of a low-sideband emphasis filter and the output signal of a sideband suppression filter based on a result of the inversion detection.

Inversion prevention device

In program retrieval using a magnetic tape in which programs are classified by index signals recorded on the tape, an image at the beginning of each program is displayed in a list on a multi-screen, and a desired program is directly selected using a count value of index signals. In recording, an index signal is recorded at a starting point of recording. When preparing a multi-screen at the time of reproducing, an image reproduced a predetermined time after detection of an index signal is reduced and stored in a memory.

Recording and reproducing apparatus

An FM signal which is partly missing zero crossing points is supplied to an input terminal, to which a second polarity discriminating circuit and a lower side band suppressing circuit followed by a first polarity discriminating circuit are coupled together. A pulse extracting circuit receives the outputs of the first polarity discriminating circuit and a second polarity discriminating circuit to produce pulses corresponding only to portions of the FM signal at which the zero crossing points are absent. The pulses thus obtained are subsequently combined in a waveform reforming circuits with the FM signal from the input terminal, thereby permitting the FM signal to regain the zero crossing points.

Inversion phenomenon preventing circuit

Video image reproducing apparatus which eliminates a noise bar in the

A frequency demodulator which comprises a digital FM demodulating circuit for demodulating an inputted FM signal and outputting a digital demodulated signal, a discriminator for discriminating whether or not the value of the digital demodulated signal from the digital FM demodulating circuit deviates from an upper limit value or a lower limit value set for a normal demodulating range, and a circuit operable on the basis of a result of the discrimination performed by the discriminator for replacing the value of the demodulated signal deviating from the upper limit value or the lower limit value with a compensation value set to a value approximating the upper limit value in the case where the inputted FM signal which has been demodulated is of a type having upper and lower side-bands suppressed and emphasized, respectively, or with a compensation value set to a value approximating the lower limit value in the case where the inputted FM signal which has been demodulated is of a type having upper and lower side-bands emphasized and suppressed, respectively.

Frequency demodulator with reversal phenomenon compensation

A frequency demodulator includes an analog-to-digital converter for converting an inputted FM signal into a digital signal. A 90.degree. phase shifter is used to phase shift the converted digital signal. The phase shifted signal and the converted signal are utilized to determine the results of tan.sup.-1 (X/Y). X represents the converted signal, and Y represents the phase shifted signal. The result from the calculation is delayed for a period of time equal to one sampling cycle. The frequency demodulator also includes a subtractor for subtracting the delayed signal from the calculation result. A discontinuity corrector corrects any discontinuity in an output from the subtractor, and a reversal phenomenon compensator compensates the output from the discontinuity corrector when the output from the discontinuity corrector exceeds a predetermined range of levels. These levels correspond to an appearance of discrete lines of black or white color on a reproduced picture.

Digital FM demodulator with distortion correction

A video recording and reproducing apparatus which is designed to store a reproduced signal in a field memory when a level of the signal reproduced from the recorded magnetic tape is larger than a previously established predetermined level and to read out the stored content, including detection, circuit for measuring the recording track width on the basis of an envelope detection signal of the reproduced signal which is obtained when the magnetic head traverses the recording track on said magnetic tape; and a circuit for establishing said predetermined level at a level optimum to the reproduction of the signal on the basis of the measured result.

Growing community of inventors

Nagaokakyo, Japan

Keiji Hatanaka