Still video camera having video synchronized to drive motor phase

摘要

A still video camera produces a still signal for recording on a magnetic disk and a movie signal for displaying in an electronic viewfinder. In recording the still picture . . . after previewing the scene in the viewfinder . . . , a vertical synchronizing signal is recorded in predetermined relation to a reference position on the disk. Instead of phase locking the disk drive to the vertical synchronizing signal, the time base of the camera is "locked" to variations in the location (phase) of the reference position. The camera is thus affected by a relatively instantaneous reset of the time base rather than an inertially-limited adjustment of the drive motor, which tends to "blind" the electronic viewfinder for the duration and renders previewing unacceptable. By attempting the video reset only after the disk has been stabilized at a standard velocity (by a velocity servo) and by "windowing" the reference position for "acceptable" phase error, the viewfinder is further unburdened of visually-disruptive effects that impede effective still photography.