Compact television camera with switching noise prevention

• US 5,555,021 A
• Filed: 03/14/1995
• Issued: 09/10/1996
• Est. Priority Date: 12/14/1993
• Status: Expired due to Term

• Current Assignee: Watec America Corporation
• Original Assignee: Watec America Corporation
• Inventors: Igarashi, Shigemi
• Primary Examiner(s): GARBER, WENDY RAE
• Application Number:
  US08/403,577
• Time in Patent Office: 546 Days
• Field of Search: 348/207, 348/372, 348/222, 348/217, 348/241, 348/625, 348/312, 330/199
• US Class Current: 348/222.1
• CPC Class Codes: H04N 25/745 Circuitry for generating timing or clock signals
• CPC Class Codes: H04N 5/21 Circuitry for suppressing or minimising disturbance, e.g. moiré or halo

Abstract

An object of the present invention is to provide a compact television camera having a circuit that prevents switching noises by that a transistor of a power supply circuit being switched on for a dc-dc converter only during a blanking period eliminates the need for a transformer and shielding box for the dc- dc converter circuit and a low-pass filter circuit, thereby allowing the camera body to be made smaller. The compact television camera circuit, comprises in combination, a synchronizing signal generator (1), a timing signal generator (2) for generating a timing signal from said synchronizing signal generator (1) output, a vertical driver (3) and a horizontal driver (4) for generating vertical and horizontal scanning signals using the timing signal, a CCD pick-up device (5), a low-pass filter (8) for eliminating the high-frequency components of a video signal (b) output of said CCD pick-up device (5), and an output amplifier (11) for feeding out the video output signal (a). The low-pass filter (8) is an active low-pass filter formed of an emitter follower amplifier having a unity gain of 1. The power supply circuit (20) is formed of a charging circuit of the double-voltage charging type, wherein a trigger signal (c) of the synchronizing signal generator (1) for triggering said power supply circuit (20) is a signal (c1) or (c2) having a rising edge and a falling edge during a blanking period BLK of the video signal (b).

Claims

1. A circuit for improving the compactness of a compact television camera comprising;

synchronizing signal generating means;

a voltage doubling charging power supply connected to receive a synchronizing pulse from said synchronizing signal generating means, said voltage doubling charging power supply having an input switching transistor receiving said synchronizing pulse from said synchronizing signal generating means for turning said voltage doubling charging power supply on and off at preselected periods;

timing signal generating means connected to receive a timing pulse from said synchronizing signal generating means;

a vertical driver and a horizontal driver receiving the output from said timing signal generating means for generating vertical and horizontal scanning signals respectively;

CCD pick-up means receiving said vertical and horizontal scanning signals from said timing signal generating means and outputting a video signal;

a fourth harmonic active low pass filter means receiving a video signal from said CCD pick-up means, said fourth harmonic active low pass filter means comprised of a pair of second harmonic active filters in tandem having emitter follower amplifiers with a gain of one for eliminating high frequency components of said video signal;

blanking circuit means for blanking said circuit video signal received from said fourth harmonic active low pass filter means;

output amplifying means receiving the output of said fourth harmonic active low pass filter for amplifying and producing a video output signal;

said synchronizing signal generating means producing said pulse to turn said voltage doubling charging power supply on or off during a blanking period produced by said blanking circuit means;

said on and off pulses from said signal generating means having a falling and rising edge during a blanking period or a falling edge during a first blanking period and a rising edge during the next blanking period;

said rising and falling edges being synchronized with the beginning and end of said blanking period; and

an image enhancing circuit comprised of a parallel RC circuit, a series RC circuit in series with said parallel RC circuit receiving the output of said fourth harmonic active low pass filter means for heightening the contour of an image;

whereby the size of said compact television camera can be reduced.