Automatic focusing circuit for automatically matching focus in response to video signal and zoom position

An automatic focusing circuit for automatically matching the focus in response to a video signal obtained from image sensing means having a focusing lens, a zoom lens, zoom lens moving means for moving said zoom lens in the direction of an optical axis and an image sensor, comprising:

• zoom position detecting means for detecting the zoom position of said zoom lens,
• focus evaluating value detecting means for detecting a level of a high frequency component of a video signal obtained from said image sensing means every constant period, converting the level into a focus evaluating value which takes the maximum value in the in-focus position or a focus evaluating value which takes the minimum value in the in-focus position and sequentially supplying the same, and
• focus control means connected to said zoom position detecting means and responsive to the change of the focus evaluating value supplied from said focus evaluating value detecting means for performing control in a predetermined characteristic so that said focusing lens is held in the in-focus position, said predetermined characteristic being switched in response to the zoom position detected by said zoom position detecting means;
• said focus control means including focusing lens position changing means for changing the relative position in the direction of the optical axis of said focusing lens relative to said image sensor;
• said focusing lens position changing means including a piezoelectric element for moving the focusing lens or the image sensor in the direction of the optical axis.

An automatic focusing circuit for automatically matching the focus in response to a video signal obtained from image sensing means having a focusing lens, a zoom lens, zoom lens moving means for moving said zoom lens in the direction of an optical axis and an image sensor, comprising:

• zoom position detecting means for detecting the zoom position of said zoom lens,
• focus evaluating value detecting means for detecting a level of a high frequency component of a video signal obtained from said image sensing means every constant period, converting the level into a focus evaluating value which takes the maximum value in the in-focus position or a focus evaluating value which takes the minimum value in the in-focus position and sequentially supplying the same, and
• focus control means connected to said zoom position detecting means and responsive to the change of the focus evaluating value supplied from said focus evaluating value detecting means for performing control in a predetermined characteristic so that said focusing lens is held in the in-focus position, said predetermined characteristic being switched in response to the zoom position detected by said zoom position detecting means;
• said focus evaluating value detecting means including:
• synchronizing signal separating means for separating a vertical synchronizing signal and a horizontal synchronizing signal from said video signal,
• gate means for passing every said constant period said video signal in a sampling area set in response to said vertical synchronizing signal and said horizontal synchronizing signal separated by said synchronizing signal separating means,
• filtering means for extracting a level of a high frequency component of the video signal which passed through said gate means,
• integrating means for integrating the level of the high frequency component of the video signal extracted by said filtering means, and
• analog/digital converting means for converting an output of said integrating means into a digital value.

An automatic focusing circuit for automatically matching the focus in response to a video signal obtained from image sensing means having a focusing lens, a zoom lens, zoom lens moving means for moving said zoom lens in the direction of an optical axis and an image sensor, comprising:

• zoom position detecting means for detecting the zoom position of said zoom lens,
• focus evaluating value detecting means for detecting a level of a high frequency component of a video signal obtained from said image sensing means every constant period, converting the level into a focus evaluating value which takes the maximum value in the in-focus position or a focus evaluating value which takes the minimum value in the in-focus position and sequentially supplying the same, and
• focus control means connected to said zoom position detecting means and responsive to the change of the focus evaluating value supplied from said focus evaluating value detecting means for performing control in a predetermined characteristic so that said focusing lens is held in the in-focus position, said predetermined characteristic being switched in response to the zoom position detected by said zoom position detecting means;
• said focus control means including focusing lens position changing means for changing the relative position in the direction of the optical axis of said focusing lens relative to said image sensor;
• said focus control means including first control means connected to said focus evaluating value detecting means for controlling said focusing lens position changing means so that the position of said focusing lens is once fixed in the position where said focus evaluating value takes the maximum value or the minimum value;
• said first control means further including:
• means for initializing the direction of the change of the relative position of said focusing lens immediately after said automatic focus matching operation is started,
• a first memory for always holding the maximum value of the minimum value of said focus evaluating value, held in said first memory with the focus evaluating value outputted from said focus evaluating value detecting means and determining that the position of said focusing lens passed through the position where said focus evaluating value takes the maximum value or the minimum value, and
• means responsive to determination by said first comparing means for reversing the direction of the change of the position of said focusing lens and controlling said focusing lens position changing means so that the position of said focusing lens is returned to the position where said focus evaluating value takes the maximum value or the minimum value.

An automatic focusing circuit for automatically matching the focus in response to a video signal obtained from image sensing means having a focusing lens, a zoom lens, zoom lens moving means for moving said zoom lens in the direction of an optical axis and an image sensor, comprising:

• zoom position detecting means for detecting the zoom position of said zoom lens,
• focus evaluating value detecting means for detecting a level of a high frequency component of a video signal obtained from said image sensing means every constant period, converting the level into a focus evaluating value which takes the maximum value in the in-focus position or a focus evaluating value which takes the minimum value in the in-focus position and sequentially supplying the same, and
• focus control means connected to said zoom position detecting means and responsive to the change of the focus evaluating value supplied from said focus evaluating value detecting means for performing control in a predetermined characteristic so that said focusing lens is held in the in-focus position, said predetermined characteristic being switched in response to the zoom position detected by said zoom position detecting means;
• said focus control means including focusing lens position changing means for changing the relative position in the direction of the optical axis of said focusing lens relative to said image sensor;
• said focus control means including first control means connected to said focus evaluating value detecting means for controlling said focusing lens position changing means so that the position of said focusing lens is once fixed in the position where said focus evaluating value takes the maximum value or the minimum value;
• said focus control means further including:
• second control means for changing, by a very small amount, the position of said focusing lens and detecting the change of a focus evaluating value corresponding to the very small change after the position of said focusing lens is once fixed by said first control means and then, correcting the position of said focusing lens at the maximal point or the minimal point of said focus evaluating value,
• switching means for resuming controlling the position of the focusing lens by said first control means when the correction amount of the position of said focusing lens by said second control means exceeds a predetermined value, and
• means responsive to the zoom position detected by said zoom position detecting means for switching said predetermined value.

An automatic focusing circuit for automatically matching the focus in response to a video signal obtained from image sensing means having a focusing lens, a zoom lens, zoom lens moving means for moving said zoom lens in the direction of an optical axis and an image sensor, comprising:

• zoom position detecting means for detecting the zoom position of said zoom lens,
• focus evaluating value detecting means for detecting a level of a high frequency component of a video signal obtained from said image sensing means every constant period, converting the level into a focus evaluating value which takes the maximum value in the in-focus position or a focus evaluating value which takes the minimum value in the in-focus position and sequentially supplying the same, and
• focus control means connected to said zoom position detecting means and responsive to the change of the focus evaluating value supplied from said focus evaluating value detecting means for performing control in a predetermined characteristic so that said focusing lens is held in the in-focus position, said predetermined characteristic being switched in response to the zoom position detected by said zoom position detecting means;
• said focus control means including focusing lens position changing means for changing the relative position in the direction of the optical axis of said focusing lens relative to said image sensor;
• said focus control means including first control means connected to said focus evaluating value detecting means for controlling said focusing lens position changing means so that the position of said focusing lens is once fixed in the position where said focus evaluating value takes the maximum value or the minimum value;
• said focus control means further including:
• a memory for holding said focus evaluating value at the time point when the position of said focusing lens is once fixed by said first control means,
• comparing means for comparing the focus evaluating value held in said second memory with the focus evaluating value outputted from said focus evaluating value detecting means after said focusing lens position is once fixed and indicating resumption of control of the position of the focusing lens by said first control means when the difference therebetween exceeds a predetermined threshold value, and
• means responsive to the zoom position detected by said zoom position detecting means for switching said predetermined threshold value.