Photography – Camera shake sensing
Reexamination Certificate
1998-02-24
2001-01-09
Perkey, W. B. (Department: 2851)
Photography
Camera shake sensing
C396S055000
Reexamination Certificate
active
06173121
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims priority of a Japanese Patent Application No. 09-064386 filed Mar. 18, 1997, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a motion compensation device which detects vibration of an optical system caused by hand tremors and other sources of undesired vibration. In particular, the present invention relates to a device which can discriminate between undesired movement or vibration of photographic equipment and intentional movement of the photographic equipment and compensate for the undesired movement while not compensating for the desired movement.
2. Description of the Related Art
Optical systems project an image onto an image plane. Conventional image blur suppression device suppress, or reduce, blurring of the image. A motion compensation device is a type of image blur suppression device, and compensates for motion incident upon the optical system. Motion is typically imparted to the optical system by vibrations in the optical system, or in a surrounding holding member. In general, conventional motion compensation devices cause a compensation lens to shift counter to the motion of the optical system so as to shift the image projected by the optical system relative to the optical system. Conventional cameras use a motion compensation device to suppress image blur resulting from motion of the camera. Such motion is typically caused by hand tremors of the photographer.
A motion compensation in the prior art has a structure as disclosed in Japanese Laid-Open Patent Publication JP-A-4-76525 In FIG. 3 of JP-A-4-76525, the overall structure of a prior art optical system which performs motion compensation is shown. A camera having the motion compensation capability of JP-A-4-76525 is equipped with a blurring motion compensation lens which is capable of parallel motion in a plane at right angles to the optical axis. A drive actuator is used to drive the blurring motion compensation lens in up and down, and left and right directions. This drive actuator includes: a lens frame member which supports the blurring motion compensation lens; a plate member which supports this lens frame member; four wires mounted on the plate member; a body which supports these wires; a wound coil; a yoke; and a permanent magnet. A position detection device is included in the drive actuator and detects the position of the blurring motion compensation lens. This position detection device includes a light generating element and a light receiving element.
The operation of the prior art motion compensation devices will be described below with reference to FIG.
8
.
FIG. 8
is a block diagram of a prior art blurring motion compensation device.
In
FIG. 8
an angular velocity sensor
10
would include a piezoelectric vibration type of angular velocity sensor used to detect a Coriolis force, and is a sensor to monitor the vibration of the camera. The output signal of the angular velocity sensor
10
is input to an integration unit
40
which integrates this output signal over time. After the integration unit
40
has converted the output signal of the angular velocity sensor
10
into a blurring motion angle of the camera, this angle is converted into target drive information for the blurring motion detection lens. A servo circuit
100
is used to drive the blurring motion compensation lens according to the target drive position information. The servo circuit
100
calculates the difference in the target drive position information and the position information of the blurring motion compensation lens, and outputs a signal to an actuator
110
. The actuator
110
, based on this signal, drives the blurring motion compensation lens within a plane at right angles to the optical axis. A position detection device
120
monitors the movement of the blurring motion compensation lens and feeds it back to the servo circuit
100
.
In the prior art of motion compensation devices, once the integration unit
40
integrates the output signal of the angular velocity sensor
10
, the information is converted into angular displacement information. As a result of this conversion, when the integration unit integrates the output signal of the angular velocity sensor
10
over time, it is necessary to set a constant of integration (referred to as a “standard value” hereinafter) including the target value of control. The output signal (referred to as “omega zero” hereinafter) of the angular velocity sensor, when the camera is stationary, is generally used as this standard value. This method of calculating the standard value is shown in FIG. 17 and FIG. 18 of Japanese Laid-Open Patent Publication JP-A-4-211230.
The blurring motion sensor of the motion compensation device disclosed in JP-A-4-211230 is equipped with an angular velocity sensor which detects Coriolis force. A drift component detection unit which includes a central processing unit (“CPU”) and a memory, calculates the average value of the output signal of the angular velocity sensor sampled in an interval from the present time to a predetermined earlier time. By subtracting the average value of the output signal of the angular velocity sensor the drift component detection unit eliminates the drift portion of the motion detected and outputs this subtraction value.
Output signals of the angular velocity sensor are input every 10 ms into the drift component detection unit. Thereby fifty output signals are input every 0.5 second (10 ms×50). The calculated average value (referred to as “average 1” hereinafter) of these fifty output signals is stored in the memory of the drift component detection unit. After ten seconds (0.5 seconds×20) has elapsed, the average 1 of a further 20 samples is input. Accordingly, after ten seconds have elapsed from the start, the average can be calculated of 1,000 (50×20) output signals of the angular velocity sensor.
In the motion compensation devices of the prior art a problem is encountered when a large and usually intentional movement is detected. These large movements are usually a result of the camera operator changing the composition of the photograph by panning the camera to follow a moving subject or to focus on another subject (referred to as “field of view angle changes” hereafter). As far as the motion compensation device is concerned, these field of view angle changes are random and cannot be distinguished easily from other sources of vibration. The motion compensation device driving the blurring motion compensation lens in an attempt to compensate for these field of view angle changes runs into the movement limits (referred to as “drive limits” hereafter) of the blurring motion compensation lens which distorts the photograph taken and possibly damages the motion compensation device.
FIG.
9
A and
FIG. 9B
are diagrams depicting examples of the output signal of an angular velocity sensor and the resulting drive amount of the blurring motion compensation lens over a period of time when photographic composition changes occur.
Referring to
FIG. 9A
, when the camera is completely stationary the angular velocity detected is 0 deg/s. As shown in
FIG. 9A
, the output signal suddenly rises when there is a change in the picture composition. Prior to this sudden change in photographic composition, the camera is approximately stationary in position. The camera is not completely stationary due to the addition of undesired motion such as hand tremors which must be accounted for in this example. For the sake of simplicity, these operator hand tremors are drawn as a sine wave.
FIG. 9B
shows the drive amount of the blurring motion compensation lens resulting from the angular velocity sensor of
FIG. 9A
integrating the output signal as the target value equal to 0. The blurring motion compensation lens, as shown in
FIG. 9B
, moves in unison with the output signal shown in FIG.
9
A. However, as shown by the broken line in
FIG. 9B
, there exists a drive l
Tomita Hiroyuki
Yamaguchi Hideki
Nikon Corporation
Perkey W. B.
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