For use in a helical scan magnetic tape record/reproduce apparatus, disclosed is a rotary head scanner including a reflective tachometer/headwheel assembly. The rotary head scanner includes a plurality of magnetic record/reproduce heads mounted on a headwheel which has a reflective tachometer disposed on one side of the headwheel. A radiation source and radiation sensor are located adjacent to the reflective tachometer. The radiation sensor senses radiation reflected from the tachometer and produces a signal which is a function of the rotational position and/or rotational speed of the headwheel.
An error component such as an eccentricity implicated in an encoder itself is superimposed upon a detected value from an FG due to an assembly error of assemblies themselves and in the manufacturing process. As a result, a speed could not be controlled with a high accuracy and wow and flatter could not be reduced. A tape speed (TSS) signal detected and corrected from the tape transport by FG and PG is inputted into a PLL loop within a data controller (TBC) of a reproducing system. A reproduced signal is converted by an A/D converter in response to a reference clock generated therein and this data is temporarily stored in an FIFO. When this data is reconverted by a D/A converter into an analog signal, if this data is sequentially converted at a timing of an absolute control clock of a quartz oscillator, then it is possible to eliminate the error component superimposed upon the head reproduced signal. Thus, from a theory standpoint, it becomes possible to erase the wow and flatter of the drive mechanism system from the head reproduced signal.
A drum for a rotatable cylinder head includes an opaque disc-shaped member having a plurality of opaque fins affixed thereto and arranged substantially normal to the disc-shaped member. A first plurality of the fins has a first width and a second plurality of the fins has a second width broader than the first width. Every fin has a distal end remote from the disc-shaped member, and an opaque circumferential ring is affixed to the distal end of each fin. The disc-shaped member, the fins and the circumferential ring form a plurality of apertures about the drum.
A method of determining the rotational speed of a three-phase brushless DC-motor, which comprises scanning at least one signal trace disposed on a revolving rotor of a three-phase brushless DC-motor by means of three sensors, each emitting a signal having two possible signal states, the signal trace and the sensors being of such construction and arrangement that eight values are realized by a logical combination of the two possible signal states, respectively, of the three sensors; detecting the rotor position with six of the values; and determining the rotational speed with the other two values.
