Nakamichi Corporation

Gohji Uchikoshi

Tosihiko Otomo

Akio Terada

Toshiko Otomo

Keiji Sano

An error detection circuit for a helical scanning type magnetic reproducing apparatus including a rotary drum having a first head and a second head provided on the periphery thereof for reproducing pilot signals recorded on a first area and a second area of respective tracks of a magnetic tape adjacent to the widthwise edges of the tape whereby height error of the heads, an inclination error of the rotary drum and tracking error due to the height error or inclination error are detected on the pilot signals so that tracking control is made. The error detection circuit includes at least two sample and hold circuits to sequentially sample and hold a level difference between a pair of pilot signals on either of the first or second tracks. The pilot signals are detected by one of the first or second heads with different first and second timings in synchronization with a detection of a synchronizing signal recorded on another track which corresponds to either of the first or second areas. An operational circuit estimates the selected ones of the outputs from the sample hold circuits.

Tracking error detection circuit using pilot signals during tape

A method of controlling reel drive so that a magnetic tape is transported from one reel of first and second reels to the other between them at predetermined transport velocity including the steps of forming a control signal obtained by operationally determining predetermined expressions having functions of the rotational numbers of the two reels, indicating a variation in the turn numbers of the magnetic tape on the reels and of the winding radii of the reels and controlling at least one of the reels based on a comparison of the control signal with informations of rotational angular velocity of the one reel actually detected.

Method of controlling reel drive

A moving velocity detection circuit to detect the moving velocity and direction of motion for an optical spot. Detectors provide sine wave signals having periods inversely proportional to the moving velocity and having phases advanced or delayed opposite the direction of rotation. Deformed and differential signals derived from the detection signals are used to provide half wave signals which are added and subtracted in a predetermined combination, the polarity of which indicate direction of movement and the absolute value of which indicate velocity.

Recording medium transducing light spot moving velocity detection circuit

A control system having an open loop transfer function G expressed by a transfer function G.sub.2 of one control component having at least one integration element and a mass transfer function G.sub.1 of other control components and a saturation level of the other components expressed by the transfer function G.sub.2 set lower than that of the component expressed by G.sub.1.

Control system

A clock formation circuit to form, from a digital signal, a formation clock signal corresponding to a data clock controlling an inversion timing of the digital signal and providing an information signal of the phase difference between the digital signal and the formation clock signal and also providing a formation clock signal having a frequency controlled so as to be coincidental with a data clock frequency of the digital data signal and a phase not offset from that of the digital data signal.

Clock formation circuit with phase locked loop control

A clock formation circuit to form from a digital data signal a formation clock signal corresponding to a data clock controlling an inversion timing of the digital data signal having a circuitry which provides an information signal of the phase difference between the digital data signal and the formation clock signal and circuitry which outputs the formation clock signal having a frequency controlled based at least on an integrated information signal obtained by limiting a current flowing through a capacitor having a terminal voltage there across varying in accordance with the phase difference information signal.

Clock formation circuit

An optical spot position detection device for an optical disk apparatus able to detect a track position of an optical spot on the recording tracks of an optical disk by dividing a space between centers of adjacent recording tracks into four areas and indicating one of the four areas where the optical spot exists so that a control signal for the optical spot can be provided.

Optical spot position detection device for an optical disk apparatus

A signal processing circuit for an optical disk apparatus to detect a sine wave tracking error signal obtained when an optical spot on an optical disk moves in a direction of a radius of the optical disk and a sine wave whole reflection light quantity signal having a component of phase offset by 90 degrees relative to that of the tracking error signal and to deform the sine wave whole reflection light quantity signal so that a deformed signal is provided which has states of 'H' and 'L' selected on timing when the whole reflection light quantity signal traverses a center level of its amplitude.

Signal processing circuit for detecting a tracking error for an optical

A tracking control method in which at least an objective lens within an optical pick-up is so controlled as to be driven in a radius direction of an optical disk having grooves (in a direction traversing track of the optical disk) relative to detectors of two-divided detector means for detecting reflected light quantities of reflected beam obtained by irradiating laser convergent beam of spot diameter defined by .lambda./NA on the optical disk in a manner in which a detection range is divided in the radius direction by estimating a difference information between the detected reflected light quantities, a range of the reflected beam irradiating the detectors being so set that the detectors detect the reflected light quantity equal to each other at a track-on state of irradiation point even though the objective lens moves in the radius direction.

Tracking control method for eliminating a tracking error due to a

A two-phase encoder circuit for detecting a moving status of a moving article in accordance with first and second detecting signals which are input having a phase offset of 90 degrees and having repeated status of 'H' and 'L' according to the movement of said moving article, wherein the first detecting signal is taken in synchronization with a clock signal and an output received signal is sequentially output while a delay circuit having an input from at least the received signal outputs a delay signal more delayed than the received signal by less than one period of the clock signal, a pulse signal circuit having an input from at least the received signal outputs, a pulse signal in synchronization with an inversion of status of the received signal and the number of pulses of the pulse signal is counted while counted up or down according to the status of the delay signal with the counting operation being made when the second detecting signal has one status of ''H' and 'L'.

Two-phase encoder circuit

A tape feed control device is configured to detect resolutions of respective reels so as to supply respective reel motors with tension currents i.sub.t1 and i.sub.t2 for setting a tape tension to establish a predetermined tape tension of a tape extending between the reels, and so as to supply the reel motors with acceleration and deceleration currents i.sub.s1 and i.sub.s2 based on an acceleration/deceleration current ratio .alpha. to transport the tape. In this fashion, a desired tape speed is obtained, maintaining a constant tape tension.

Tape feed control device

This invention relates to a servo system for positioning and driving a movable member such as a pickup head of an optical reading system, for example. A sinewave signal is generated by a position detector in response to movement of the movable member. A first reference signal is used with the sinewave signal to position the movable member. A second reference signal is used with a modified signal which is generated by differentiating and rectifying the sinewave signal, to drive the movable member.

Servo system for positioning and driving a movable member using two

This invention relates to a method of converting a digital signal into an analog signal and a digital-to-analog converter therefor. In the invention, a digital signal having varying pulse width values is converted into a first pulse width signal, with each pulse varying in its pulse width in response to its respective data values and with the center of each pulse width being at a fixed time position within a respective sampling period, while a complement of the digital signal is converted into a second pulse width signal with each pulse varying in its pulse width in response to its respective data value and relative to said center of each respective pulse width. The first and second pulse width signals, after one of them is inverted, are mixed and pass through a smoothing filter to demodulate the digital signal into the analog signal.

Method of converting a digital signal into an analog signal and a

In the invention, a digital signal consisting of upper and lower bits is sampled while the upper and lower bits are divided. The sampled digital signal components of upper and lower bits are converted into upper and lower pulse width signals having a pulse width responding to their data value, respectively. Thereafter, the upper and lower pulse width signals are mixed and pass through a smoothing filter to convert the digital signal into an analog signal. The upper pulse width signal is formed of a pulse signal varying in a pulse width in response to the data value of the upper bits relative to a center of pulse width which has a fixed time position within a sampling period. The lower pulse width signal is formed of a combination of pulse signals varying in each pulse width in response to the data value of the lower bits relative to each center of pulse width which is at each pulse edge of the upper pulse width signal.

This invention relates to a signal conversion circuit, and more particularly to a signal conversion circuit to convert a digital signal sampled in synchronism with a sampling pulse into a pulse width signal having a pulse width corresponding to the digital value of the digital signal. A first counter is preset to a first count value corresponding to the digital value of the sampled digital signal and begins to count a first clock signal having a predetermined pulse period from the first count value. A second counter is preset to a second count value which is a complement of the first count value and begins to count a second clock signal having a pulse period twice as many as that of the first clock signal from the second count value in response to the detection of a full count of the first counter. A rising edge of the pulse width signal responds to the detection of the full count of the first counter and a falling edge thereof responds to the detection of a full count of the second counter whereby the center of a pulse width of the pulse width signal has a predetermined phase relation to the sampling pulse.

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Higashimurayama, Japan

Gohji Uchikoshi