Apparatus and method utilizing a slope for automatically focusing an object in a video camera

Claim 1

An apparatus for automatically focusing an object in a video camera, comprising: a lens for receiving a light beam from the object; a lens motor driver for moving said lens; an iris for adjusting an amount of the light beam being received by said lens; a solid state image sensing means for converting the light beam of the amount adjusted by said iris into an electrical signal and outputting a video signal; an amplification means for amplifying the video signal from said solid state image sensing means; a video signal processing means for processing the video signal amplified by said amplification means so that the amplified video signal can be displayed on a screen; a plurality of high pass filters for filtering the video signal amplified by said amplification means, each of said high pass filters having a different cut-off frequency and respectively outputting an output signal; control means for calculating a slope value of the video detect data corresponding to the signal outputted from a first one of said plurality of high pass filters having a first cut-off frequency when a peak value is not set and controlling a speed and direction of the lens motor driver according to the calculated slope value thereof until the calculated slope value is less than a first predetermined value, and for calculating a difference value of a video detect data corresponding to the signal outputted from a second one of said plurality of high pass filters having a higher cut-off frequency than said first one when the calculated difference value is less than a second predetermined value and controlling a speed and a direction of the lens motor driver according to the calculated difference value thereof; a switching means for selecting the video signal output from one of said plurality of high pass filters in accordance with a control signal output from said control means; a video division means for dividing the video signal selected by said switching means in the unit of a field; a low pass filtering means for filtering the video signal divided by said video division means at a low frequency band; an analog/digital conversion means for converting the video signal filtered by said low pass filtering means into a digital signal; and an integration means for integrating the digital signal from said analog/digital conversion means to output video detect data for focusing the object.

Claim 2

An apparatus for automatically focusing an object in a video camera, comprising: a lens for receiving a light beam from the object; a lens motor driver for moving said lens; an iris for adjusting an amount of the light beam being received by said lens; a solid state image sensing means for converting the light beam of the amount adjusted by said iris into an electrical signal and outputting a video signal; an amplification means for amplifying the video signal from said solid state image sensing means; a video signal processing means for processing the video signal amplified by said amplification means so that the amplified video signal can be displayed on a screen; a plurality of high pass filters for filtering the video signal amplified by said amplification means, each of said high pass filters having a different cut-off frequency and respectively outputting an output signal; control means for calculating a slope value of the video detect data corresponding to the signal outputted from a first one of said plurality of high pass filters having a first cut-off frequency when a peak value is not set and controlling a speed and direction of the lens motor driver according to the calculated slope value thereof until the calculated slope value is less than a first predetermined value, and for calculating a difference value of a video detect data corresponding to the signal outputted from a second one of said plurality of high pass filters having a higher cut-off frequency than said first one when the calculated difference value is less than a second predetermined value and controlling a speed and a direction of the lens motor driver according to the calculated difference value thereof; a switching means for selecting the video signal output from one of said plurality of high pass filters in accordance with a control signal output from said control means; a video division means for dividing the video signal selected by said switching means in the unit of a field; a low pass filtering means for filtering the video signal divided by said video division means at a low frequency band; an analog/digital conversion means for converting the video signal filtered by said low pass filtering means into a digital signal; and an integration means for integrating the digital signal from said analog/digital conversion means to output video detect data for focusing the object.

Claim 4

A method of automatically focusing an object in a video camera having a plurality of high pass filters, comprising the steps of: (a) calculating a slope value of a video detect data from a first high pass filter having a cut-off frequency when a peak value is not set and controlling a speed and a direction of a lens motor driver responsive to the calculated slope thereof; (b) calculating a difference value of a video detect data from a second high pass filter having a higher cut-off frequency than said first high pass filter if the slope of the video detect data calculated at said step (a) is less than a first predetermined reference value and controlling the speed and the direction of the lens motor driver responsive to the calculated difference thereof; and (c) repeating said step (b) until the difference value calculated at step (b) is less than a second predetermined value and controlling the speed and the direction of the lens motor driver so that a lens is driven thereby to a focus position where the peak value is set.

Claim 5

A method of automatically focusing an object in a video camera having a plurality of high pass filters, comprising the steps of: (a) calculating a slope value of a video detect data from a first high pass filter having a cut-off frequency when a peak value is not set and controlling a speed and a direction of a lens motor driver responsive to the calculated slope thereof; (b) calculating a difference value of a video detect data from a second high pass filter having a higher cut-off frequency than said first high pass filter if the slope of the video detect data calculated at said step (a) is less than a first predetermined reference value and controlling the speed and the direction of the lens motor driver responsive to the calculated difference thereof; and (c) repeating said step (b) until the difference value calculated at step (b) is less than a second predetermined value and controlling the speed and the direction of the lens motor driver so that a lens is driven thereby to a focus position where the peak value is set.