West Electric Co., Ltd.

Matsushita Electric Industrial Co., Ltd.

Wataru Hasegawa

Hiroshi Iwata

Katsuji Ishikawa

Hiroshi Makino

Osamu Kawasaki

Kazuou Murata

An AC driving signal of a frequency in the vicinity of the resonance frequency of a piezoelectric transformer is generated by a variable oscillation circuit and the waveform of the output signal of the variable oscillation circuit is shaped so as to be substantially sinusoidal by a waveform shaping circuit and the output of the waveform shaping circuit is subjected by a driving circuit to current amplification or voltage amplification so as to be amplified to a level sufficient for driving the piezoelectric transformer and the output of the driving circuit is subjected to current limitation, and then input to the piezoelectric transformer and the output signal of the transformer is applied to a cold cathode fluorescent lamp so that the cold cathode fluorescent lamp is lit and even if the impedance of the cold cathode fluorescent lamp decreases, the piezoelectric transformer cannot supply a large current.

Cold cathode fluorescent lamp driving apparatus using a piezoelectric

There are video and sound recording devices such as movie cameras or video cameras with an automatic focusing system of the type for setting a photographic lens to a position at which an object can be sharply focused in response to the signal which is representative of a distance from the camera to the object and obtained by measuring the time interval from the time when the ultrasonic waves are transmitted at a predetermined repetition frequency to the object to the time when the echo from the object is received. Such devices have a common defect that a microphone picks up impulse-like noise generated from an ultrasonic transducer especially at the start point of ultrasonic waves. To overcome this problem, the present invention provides an audible noise elimination or suppression means or a control circuit which operates in synchronism with the ultrasonic wave transmission so that an audio signal processing system attenuates the audio output signal.

Video and sound recording device with automatic focusing system

An ultrasonic wave transmission apparatus built in an image producing apparatus with an auto-focusing apparatus has features that transmission timings are determined by processing a vertical synchronization signal produced in the video camera and that transmission operations are made within blank times of the vertical synchronization signal thereby eliminating noise troubles in image reproduction made in the video camera.

Apparatus and method for transmitting ultrasonic wave

An automatic focusing camera is provided with an ultrasonic distance measuring instrument capable of varying the directivity of an ultrasonic beam to be transmitted depending upon the angle of view of a photographic lens used. A plurality of circuit components one of which is selected so as to determine the oscillation frequency of an oscillator mounted in a camera body depending upon the angle of view of a photographic lens attached to the camera are mounted on the camera body, and a selecting means is mounted on the lens mount of a photographic lens at a position corresponding to the angle of view thereof so that when the photographic lens is attached to the camera body, its selecting means establishes an electrical connection of a predetermined one of said circuit components to said oscillator, whereby the latter oscillates at a predetermined frequency and consequently the ultrasonic beam transmitted has a predetermined directivity corresponding to the angle of view of the photographic lens.

Automatic focusing camera

An automatic focusing camera wherein after the distance to object has been measured automatically by an ultrasonic or optical distance measuring means, a photographic lens is automatically shifted from the minimum focusing distance position to the infinity position and a shutter is released automatically without stopping the lens when the lens is shifted to such a position where the image of an object is in sharp focus.

Growing community of inventors

Sakai, Japan

Wataru Hasegawa