Optical: systems and elements – Image stabilization – By movable refractive structure
Reexamination Certificate
1999-05-26
2001-03-27
Nguyen, Thong (Department: 2872)
Optical: systems and elements
Image stabilization
By movable refractive structure
C359S407000, C359S554000
Reexamination Certificate
active
06208464
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a tremble preventing device mounted in an optical device, for example, binoculars.
2. Description of the Related Art
Conventionally, an optical device, for example, binoculars, is provided with a tremble preventing device which corrects a tremble of a focused image due to camera-shake and so on. In the tremble preventing device, correction optical systems are moved by a predetermined amount such that a movement of the optical device is canceled, enabling the tremble of the focused image to be corrected. Direct-drivetype actuators that include a stepping motor are utilized as a driving device of the correction optical systems. A rotational motion of the stepping motor is transmitted to the correction optical systems, after being converted to a two-dimensional rectilinear motion of the correction optical systems by a transmitting mechanism, on a plane perpendicular to optical axes of the correction optical systems.
A driving amount of the correction optical systems corresponding to one rotation step of the stepping motor is determined due to an angular degree through which one rotation of the stepping motor moves and a construction of the transmitting mechanism. Accordingly, the driving amount of the correction optical systems can be controlled by a step amount of the stepping motor, so that a position of the correction optical systems can be easily determined.
For example, a gear mechanism or a screw mechanism is utilized as the transmitting mechanism. However, play exists in the engaging portion of such a gear mechanism and a screw mechanism. Thus, when a direction of drive of the engaging portion is reversed, an initial rotational motion of the stepping motor is spent in taking-up the backlash, and is not transmitted to the correction optical systems.
Namely, even if the stepping motor is driven by pulses calculated based on a trembling amount of the focused image, the correction optical systems are not accurately driven due to the aforementioned backlash. In order to prevent the inaccurate driving due to the backlash, a spring member may be mounted, urging the engaging portion in a predetermined direction such that a positional engagement remains unchanged at all times when the driving operation starts.
However, the mounting of the spring member causes an increase in a number of members in the optical device, a rise in a manufacturing cost, and an enlargement in an overall size and weight of the optical device.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a tremble preventing device that drives correction optical systems accurately without backlash.
In accordance with an aspect of the present invention, there is provided a tremble preventing device comprising: a detector that detects an amount of an optical device tremble; correcting optical systems that correct a tremble of a focused image due to the optical device tremble; driving systems that include an actuator and a transmitting mechanism that transmits a motion of the actuator to the correction optical systems, the driving systems driving the optical systems along a predetermined axis on a plane perpendicular to optical axes of the correction optical systems; and a controller that controls the driving systems such that a difference between the amount of the optical device tremble detected by the detector and positional data of the optical systems is canceled.
When the correction optical systems are moved in a moving direction opposite a previous moving direction in which the correction optical systems were previously moved, the controller controls the driving systems such that a backlash of the transmitting mechanism and the difference is canceled.
The controller comprises: an operator that operates a driving amount and a driving direction of the actuator whereby the correction optical Systems are moved such that the difference is canceled; and a driving direction checker that judges whether the driving direction of the actuator changes from a previous driving direction of the actuator.
When the driving direction checker judges that the driving direction changes, the operator calculates the driving amount of the actuator that includes a backlash driving amount component compensating the backlash.
The optical device further comprises a memory that stores the backlash driving amount component. When the driving direction checker determines that the driving direction changes, the operator reads the backlash driving amount component from the memory, and adjusts the driving amount of the actuator by the backlash driving amount component to cancel.
When the previous moving direction is a first direction along the predetermined axis and the moving direction is a second direction that is prolonged at an angle of 180 degrees against the first direction, being along the predetermined axis, the operator adds the backlash driving amount component to the driving amount that cancels the difference, and when the previous direction is the second direction and the opposite direction is the first direction, the operator subtracts the backlash driving amount component from the driving amount that cancels the difference.
The memory comprises a nonvolatile memory that is erasable and programable, and the actuator comprises a stepping motor. A rotational motion of the stepping motor is converted to a rectilinear motion by the transmitting mechanism.
For example, the transmitting mechanism comprises: a gear that is fixedly mounted on a free end of a rotational shaft of the stepping motor, opposite a journal of the rotational shaft; and a rack that is fixed on a supporting member of the correction optical systems, engaging the gear.
Further, for example, the transmitting mechanism comprises: a screw portion that is fixedly mounted on a tip of a rotational shaft of the stepping motor; and a nut portion that is fixed on a supporting member of the optical systems, engaging the screw portion.
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Hirunuma Ken
Tsukamoto Shinji
Asahi Kogaku Kogyo Kabushiki Kaisha
Greenblum & Bernstein P.L.C.
Nguyen Thong
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