AUTOMATIC FOCUSING CIRCUIT USING A TWO PERIOD DETECTION INTERVAL TO COMPENSATE FOR MOTION OCCURRING WITHIN A FIELD OF VIEW

摘要

jrrABSTRACT OF THE DISCLOSUREIn an automatic focusing circuit of a videocamera, an automatic focusing operation is performed by afocus evaluating value produced in response to a videosignal obtained in an image sensing circuit. A focusingmotor control circuit controls rotation of a focusing motorso that a focusing lens is once fixed in the position wherethe focusing evaluating value takes the maximum value.Then, a control circuit resumes the automatic focusingoperation after a lapse of a second time period when it isdetermined that the focus evaluating value was decreased toa predetermined level during a first time period andmaintained the level over the second time period, and doesnot resume the automatic focusing operation when it isdetermined that the focus evaluating value did not maintainthe level. On the other hand, the control circuit resumesthe automatic focusing operation after a lapse of the firsttime period when it is determined that a time period whichis more than the first time period is required until thefocus evaluating value attains the predetermined level.