Power lens and camera system

A power zoom lens having a zooming lens unit and a zoom mechanism which supports the zooming lens unit to move in an optical axis direction, comprising:

• a motor for driving said zoom mechanism to move said zooming lens unit in said optical axis direction;
• detecting means for generating detection signals in association with an operation of said motor at a predetermined time interval corresponding to a predetermined displacement of said motor;
• speed setting means for setting an operational speed of said motor to a time interval corresponding to an output of said detection signals by said detecting means;
• power supply means for at least one of continuously and discontinuously supplying electrical power to said motor, wherein said power supply means comprises means for controlling a duty ratio of a discontinuous electrical power supply time and a discontinuous electrical power non-supply time so that said power supply means discontinuously supplies electrical power to said motor with a fixed frequency;
• and
• supply control means for shortening said discontinuous electrical power supply time by a predetermined time unit, determined by said fixed frequency, by changing said duty ratio when said detection signals are outputted by said detection means within said predetermined time interval, and for lengthening said discontinuous electrical power supply time by said predetermined time unit when no detection signal is outputted by said detecting means within said predetermined time interval, said supply control means setting said discontinuous electrical power supply time to a predetermined minimum discontinuous electrical power supply time when said motor is actuated from a predetermined state.

A camera system comprising:

• a camera body;
• a power zoom lens detachably mountable to said camera body, said power zoom lens having a zooming lens unit and a zoom mechanism which supports said zooming lens unit to move in an optical axis direction;
• a motor for driving said zoom mechanism to move said zooming lens unit in said optical axis direction;
• detecting means for generating detection signals in association with an operation of said motor at a predetermined interval corresponding to a predetermined displacement of said motor;
• speed setting means for setting an operational speed of said motor to a time interval corresponding to an output of said detection signals by said detecting means;
• power supply means for at least one of continuously and discontinuously supplying electrical power to said motor, wherein said power supply means comprises means for controlling a duty ratio of a discontinuous electrical power supply time and a discontinuous electrical power non-supply time so that said power supply means discontinuously supplies electrical power to said motor with a fixed frequency;
• and
• supply control means for shortening said discontinuous electrical power supply time by a predetermined time unit, determined by said fixed frequency, by changing said duty ratio when said detection signals are outputted by said detecting means within said time interval, and for lengthening said discontinuous electrical power supply time by said predetermined time unit when no detection signal is outputted by said detecting means within said time interval, said supply control means setting said discontinuous electrical power supply time to a predetermined minimum discontinuous electrical power supply time when said motor is actuated from a predetermined state.

A lens driving apparatus in an optical system that includes a movable lens unit and a lens moving mechanism which supports said movable lens unit to move in an optical axis direction, comprising:

• a motor for driving said lens moving mechanism to move said movable lens unit;
• a power supply for at least one of continuously and discontinuously supplying electrical power to said motor, said power supply operating with a fixed frequency and comprising means for controlling a duty ratio of a discontinuous electrical power supply time and a discontinuous electrical power non-supply time;
• a detector that generates detection signals in association with an operation of said motor at a predetermined interval corresponding to a predetermined displacement of said motor;
• means for setting an operational speed of said motor to a time interval corresponding to an output of said detection signals by said detecting means;
• and
• means for changing said duty ratio of said power supply to shorten said discontinuous electrical power supply, by a time determined by said fixed frequency, by changing said duty ratio when said detection signals are outputted by said detecting means within said predetermined interval, and for lengthening said discontinuous electrical power supply time by said time determined by said fixed frequency by changing said duty ratio when no detection signal is outputted by said detecting means within said predetermined interval, wherein said changing means sets said discontinuous electrical power supply time to a predetermined minimum discontinuous electrical power supply time when said motor is actuated from a predetermined state.

An apparatus for driving a movable lens in an optical axis direction, comprising:

• means for driving said movable lens unit;
• a power supply for at least one of continuously or discontinuously supplying electrical power to said driving means, a duty ratio being defined by a discontinuous electrical power supply time and a discontinuous electrical power non-supply time when said power supply discontinuously supplies electrical power to said driving means;
• means for generating detection signals in association with an operation of said driving means at a predetermined time interval corresponding to a predetermined displacement of said driving means;
• and
• means for changing said discontinuous electrical power supply time by a predetermined time unit in response to said detection signals outputted by said detecting means to control an operational speed of said driving means, wherein a sum of said discontinuous electrical power supply time and said discontinuous electrical power non-supply time remains constant as said duty ratio is changed, said changing means setting said discontinuous electrical power supply time to a predetermined minimum discontinuous electrical power supply time when said driving means is actuated from a predetermined state.