Method and apparatus for automatic deployment of camera lens
First Claim
1. A method of automatically positioning a camera lens during an autofocus operation comprising the steps of:
- initiating a picture taking sequence;
determining a destination focus position of the lens;
enabling a lens motor drive with a first motor drive signal to initiate movement of the lens from a starting position toward the focus destination positiongenerating signal pulses as a function of movement of the lens, the destination focus position being a determined number of said signal pulse away from said lens starting position;
at a first intermediate position in advance of the destination focus position, calculating motor drive speed and determining, from said calculated motor drive speed, a second motor drive signal that will result in the lens arriving at a near focus destination position at a predetermined arrival speed;
operating said motor drive with said second motor drive signal until the lens reaches said near focus destination position; and
when the lens arrives at the near focus destination position, initiating a predetermined motor stopping sequence.
1 Assignment
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Accused Products
Abstract
Camera autofocus apparatus and method employing an autoranging device to determine a lens destination focus position in terms of a target number of signal pulses from a lens motion sensor photo-interrupter. A lens drive motor is initially driven at maximum speed by a 100% pulse width modulated drive signal. At a fixed number of signal pulses in advance of the target, the average motor speed is calculated and a reduced pulse with modulated drive signal, determined based on the calculated motor speed, is applied to the drive motor to cause the lens to arrive at a uniform speed at a near destination focus position that is suitable for application of a standard motor stopping routine. During the motor stopping routine, the motor is initially "plugged" (reverse polarity drive signal) and the signal pulse period is monitored until a predetermined period is reached. At this point, the plug is removed and an electrical brake (short circuit) is applied to the motor to bring the lens to a rest at the destination focus position.
21 Citations
10 Claims
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1. A method of automatically positioning a camera lens during an autofocus operation comprising the steps of:
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initiating a picture taking sequence; determining a destination focus position of the lens; enabling a lens motor drive with a first motor drive signal to initiate movement of the lens from a starting position toward the focus destination position generating signal pulses as a function of movement of the lens, the destination focus position being a determined number of said signal pulse away from said lens starting position; at a first intermediate position in advance of the destination focus position, calculating motor drive speed and determining, from said calculated motor drive speed, a second motor drive signal that will result in the lens arriving at a near focus destination position at a predetermined arrival speed; operating said motor drive with said second motor drive signal until the lens reaches said near focus destination position; and when the lens arrives at the near focus destination position, initiating a predetermined motor stopping sequence. - View Dependent Claims (2)
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3. Apparatus for deploying a camera taking lens outwardly to a destination focus position comprising:
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means for initiating a picture taking operation; means for determining a subject range and a destination focus position for the lens corresponding to the subject range; a taking lens motor drive responsive to a motor drive signal for moving the taking lens toward the destination focus position; and control means for initiating movement of said, taking lens toward the destination focus position in response to a first drive signal and, at an intermediate position a fixed distance in advance of the destination position, for changing to a second drive signal determined on the basis of motor drive speed at the intermediate position that will cause the lens to arrive at a near destination focus position at a predetermined motor speed and, when said lens reaches said near destination focus position, for initiating a predetermined motor stopping sequence. - View Dependent Claims (4, 5, 6, 7)
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8. A method of automatically positioning a camera lens during an autofocus operation comprising the steps of:
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initiating a picture taking sequence; determining a destination focus position of the lens; enabling a lens motor drive with a first motor drive signal to initiate movement of the lens toward the focus destination position; calculating motor speed at a first intermediate position a fixed distance in advance of the destination focus position; determining and setting a second motor drive signal based on said calculated motor speed that will result in the lens arriving at a near focus destination position at a predetermined arrival speed and operating said motor drive with said second motor drive signal until the lens reaches said near focus destination position; and when the lens arrives at the near focus destination position, initiating a predetermined motor stopping sequence. - View Dependent Claims (9)
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10. A method of automatically positioning a camera lens during an autofocus operation comprising the steps of:
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initiating a picture taking sequence; determining a destination focus position of the lens; enabling a lens motor drive with a first motor drive signal to initiate movement of the lens toward the focus destination position; generating signal pulses as a function of movement of the lens, the destination focus position being a function of the number of said signal pulses from a starting position of the lens to the focus destination position; at a first intermediate position a fixed distance in advance of the destination focus position, setting a second motor drive signal that will result in the lens arriving at a near focus destination position at a predetermined arrival speed and operating said motor drive with said second motor drive signal until the lens reaches said near focus destination position, said first intermediate position being a first predetermined number of signal pulses in advance of said destination position and said near focus position being a second predetermined number of signal pulses in advance of the destination focus position, said second predetermined number of signal pulses being less than said first predetermined number of signal pulses; and when the lens arrives at the near focus destination position, initiating a predetermined motor stopping sequence wherein said motor stopping sequence comprises the steps of reversing current in said lens motor drive when the lens reaches a position corresponding to said second predetermined number of signal pulses;
thereafter monitoring the duration of each signal pulse; and
, when the signal pulse duration reaches a predetermined value, applying an electrical brake to cause said lens motor drive to stop at said destination position.
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Specification