Image sensing apparatus having a focus adjustment device, and control method thereof

Abstract

This invention has as its object to prevent a conventional problem in that the focal point position cannot be determined before and after an in-focus point, even in a slow shutter mode. To this end, a camera control microcomputer of a video camera determines the drive amount of a focus lens for one field in accordance with the rotation angle of a manual focus dial when the shutter speed is 1/60 sec, 1/30 sec, or 1/15 sec, and controls a focus compensation lens driver and focus compensation lens motor to drive the focus lens by the determined drive amount in a direction corresponding to the detected rotation direction of the manual focus dial.

1. A focus adjustment apparatus comprising:
 a focus adjustment device that drives a focus lens of an image sensing optical system to adjust a focal point of the image sensing optical system in response to a manual focusing operation by a user; of a user; 
 a change device that controls said focus focusing adjustment device to decrease a focus adjustment drive speed of the focus lens caused by the manual focusing operation by the user as a photoelectric conversion cycle in which an image sensing device converts an object image received via the image sensing optical system into an image signal becomes longer drive the focus lens in a first speed in response to the manual focusing operation of the user when a photoelectric conversion cycle in which an image sensing device photo-electrically converts an object image is a first cycle, and drive the focus lens in a second speed in response to the manual focusing operation of the user when the photoelectric conversion cycle is a second cycle, wherein the first speed is slower than the second speed and the fire cycle is longer than the second cycle; and 
 a display device that displays images corresponding to electric signals which are periodically and photo-electrically converted by the image sensing device. 
 
     
     
       2. The apparatus according to  claim 1 , wherein said change device changes a focus adjustment drive amount per unit time of said focus adjustment device corresponding to the manual operation in accordance with the cycle in which the image sensing device converts an object image received via the image sensing optical system into an image signal. 
     
     
       3. The apparatus according to  claim 1 , further comprising: a display device for displaying an image signal periodically converted by the image sensing device. 
     
     
       4. The apparatus according to  claim 1 , wherein said focus adjustment device drives to adjust a focal point at a drive speed corresponding to an operation speed of a manual operation member. 
     
     
       5. An image sensing apparatus comprising: a focus adjustment apparatus of  claim 1 . 
     
     
       6. A focus adjustment apparatus comprising:
 a focus adjustment device that drives a focus lens of an image sensing optical system to adjust a focal point of the image sensing optical system in response to a manual focusing operation by of a user; 
 a change device that controls said focus adjustment device to decrease a time in which said focus adjustment device moves the focus lens of the image sensing optical system in response to the manual focusing operation by the user as a photoelectric conversion cycle in which an image sensing device converts an object image received via the image sensing optical system into an image signal becomes longer; drive the focus lens within a first time of a unit cycle that is within a predetermined cycle in response to the manual focusing operation of the user when a photoelectric conversion cycle in which an image sensing device converts an object image is a first cycle, and drive the focus lens within a second time of the unit cycle in response to the manual focusing operation of the user when the photoelectric conversion cycle is a second cycle, wherein the first time is shorter than the second time and the first cycle is longer than the second cycle; and 
 a display device that displays images corresponding to electric signals which are periodically and photo-electrically converted by the image sensing device. 
 
     
     
       7. The apparatus according to  claim 6 , wherein said change device prolongs the response time of said focus adjustment device to the manual operation as the cycle in which the image sensing device converts an object image received via the image sensing optical system into an image signal becomes longer. 
     
     
       8. A focus adjustment method for driving a focus lens of an image sensing optical system to adjust a focal point of the image sensing optical system in response to a manual focusing operation by of a user, comprising the steps of:
 decreasing a focus adjustment drive speed of the focus lens caused by the manual focusing operation by the user as a photoelectric conversion cycle in which an image sensing device converts an object image received via the image sensing optical system into an image signal becomes longer;driving the focus lens in a first speed in response to the manual focusing operation of the user when a photoelectric conversion cycle in which an image sensing device photo-electrically converts an object image is a first cycle, and driving the focus lens in a second speed in response to the manual focusing operation of the user when the photoelectric conversion cycle is a second cycle, wherein the first speed is slower than the second speed and the first cycle is longer than the second cycle; and 
 displaying images corresponding to electric signals which are periodically and photo-electrically converted by the image sensing device on a display device. 
 
     
     
       9. A focus adjustment method for driving a focus lens of an image sensing optical system to adjust a focal point of the image sensing optical system in response to a manual focusing operation by of a user, comprising the steps of:
 decreasing a time in which the focus lens of the image sensing optical system is moved in response to the manual focusing operation by the user as a photoelectric conversion cycle in which an image sensing device converts an object image received via the image sensing optical system into an image signal becomes longer;driving the focus lens within a first time of a unit cycle that is within a predetermined cycle in response to the manual focusing operation of the user when a photoelectric conversion cycle in which an image sensing device converts an object image is a first cycle, and driving the focus lens within a second time of the unit cycle in response to the manual focusing operation of the user when the photoelectric conversion cycle is a second cycle, wherein the first time is shorter than the second time and the first cycle is longer than the second cycle; and 
 displaying images corresponding to electric signals which are periodically and photo-electrically converted by the image sensing device on a display device. 
 
     
     
       10. A computer readable medium that stores a control program for a focus adjustment apparatus, wherein the control program is executed by a processing unit for driving a focus lens of an image sensing optical system to adjust a focal point of the image sensing optical system in response to a manual focusing operation by of a user, comprising the steps of:
 decreasing a focus adjustment drive speed of the focus lens caused by the manual focusing operation by the user as a photoelectric conversion cycle in which an image sensing device converts an object image received via the image sensing optical system into an image signal becomes longer;driving the focus lens in a first speed in response to the manual focusing operation of the user when a photoelectric conversion cycle in which an image sensing device photo-electrically converts an object image is a first cycle, and driving the focus lens in a second speed in response to the manual focusing operation of the user when the photoelectric conversion cycle is a second cycle, wherein the first speed is slower than the second speed and the first cycle is longer than the second cycle; and 
 displaying images corresponding to electric signals which are periodically and photo-electrically converted by the image sensing device on a display device. 
 
     
     
       11. A computer readable medium that stores a control program for a focus adjustment apparatus, wherein the control program is executed by a processing unit for driving a focus lens of an image sensing optical system to adjust a focal point of the image sensing optical system in response to a manual focusing operation by of a user, comprising the steps of:
 decreasing a time in which the focus lens of the image sensing optical system is moved in response to the manual focusing operation by the user as a photoelectric conversion cycle in which an image sensing device converts an object image received via the image sensing optical system into an image signal becomes longer;driving the focus lens within a first time of a unit cycle that is within a predetermined cycle in response to the manual focusing operation of the user when a photoelectric conversion cycle in which an image sensing device converts an object image is a first cycle, and driving the focus lens within a second time of the unit cycle in response to the manual focusing operation of the user when the photoelectric conversion cycle is a second cycle, wherein the first time is shorter than the second time and the first cycle is longer than the second cycle; and 
 displaying images corresponding to electric signals which are periodically and photo-electrically converted by the image sensing device on a display device.