Photography – Camera shake sensing – Having stabilization system
Reexamination Certificate
2001-07-31
2003-09-02
Perkey, W. B. (Department: 2851)
Photography
Camera shake sensing
Having stabilization system
Reexamination Certificate
active
06614994
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of the following priority applications are incorporated herein by reference: Japanese Patent Applications, No. 2000-233831 filed on Aug. 2, 2000 and No. 2000-239531 filed on Aug. 8, 2000.
FIELD OF THE INVENTION
The present invention relates to a shake detection device that detects vibration due to a shake or the like in an optical device such as binoculars and in a shooting device such as a camera and relates to an optical device, a camera system, and a interchangeable lens in each of which the shake detection device is built.
BACKGROUND OF THE INVENTION
FIG. 12
is a block diagram illustrating a basic configuration of a blur correction device including a shake detection device. Referring to the Figure, the mechanism of the blur correction device will be described.
Angular velocity sensor
10
is a sensor that first detects a shake to which a camera is subjected. Typically, angular velocity sensor
10
is implemented utilizing a piezoelectric oscillation-type angular velocity sensor that detects Coriolis force. An output from angular velocity sensor
10
is transmitted to reference value calculator
52
. Reference value calculator
52
is a unit that calculates a reference shake value using the output from angular velocity sensor
10
. Thereafter, the reference shake value is subtracted from a shake signal from angular velocity sensor
10
, and then the remainder is transmitted to integrator
54
. Integrator
54
is a unit that time-integrates a shake signal expressed in the angular velocity unit to convert it into a shake angle of a camera.
Target drive position calculator
56
calculates target drive position information for driving blur correction lens
80
, by adding information such as the focal length of the camera lens to the shake angle information sent from integrator
54
.
Drive signal calculator
58
, in order to move blur correction lens
80
in response to the target drive position information sent from target drive position calculator
56
, calculates a differential between the target drive position information and the present position information of blur correction lens
80
and then supplies a drive current to coil
73
.
Actuator
70
is provided to move blur correction lens
80
and is constituted of yoke
71
, magnet
72
, coil
73
, etc. Coil
73
is positioned within a magnetic circuit formed by yoke
71
and magnet
72
, and thus when an electric current is supplied to coil
73
, a force is generated in actuator
70
in accordance with the Fleming's left-hand rule.
As shown in
FIG. 12
, coil
73
is attached to lens barrel
82
, which accommodates blur correction lens
80
. Because blur correction lens
80
and lens barrel
82
are configured so that they can move perpendicularly to the optical axis I, blur correction lens
80
can be driven perpendicularly to the optical axis I by supplying an electric current to coil
73
.
Optical position detector
74
is provided to monitor the movement of blur correction lens
80
and is constituted of infrared ray emitting diode (hereinafter, IRED)
75
, slit plate
76
, slit
76
A, PSD (position sensitive device)
77
, etc. A light ray from IRED
75
first passes through slit
76
A with the width of the light ray being thus diminished and then reaches PSD
77
. PSD
77
is a device that outputs a signal indicative of a light position on its light-receiving surface.
Because slit plate
76
is attached to lens barrel
82
as shown in
FIG. 12
, the movement of blur correction lens
80
provides the movement of slit
76
A, inducing thus the movement of the light ray on the light-receiving surface of PSD
77
. Therefore, the position of the light ray on the light-receiving surface of PSD
77
is equivalent to the position of blur correction lens
80
. A signal detected by PSD
77
is fed back as position signal
78
.
Such a blur correction device is built mainly in a shooting device such as a camera and in an optical device such as binoculars. When those devices are used while being held with a user's hands, the blur correction device effectively works for correcting image blurring due to a shake from the user. However, the blur correction device need not be operated when the optical devices are fixed, e.g., when they are fixed on a tripod or the like.
The reason why the blur correction device need not be operated in such a situation is that if it is operated, higher power consumption results, the blur correction device unnecessarily operates because of, e.g., noise in the output of the angular velocity sensor, and the image is blurred all the more.
To address those problems, some methods have been proposed to determine whether an optical device with a blur correction device is fixed on a tripod or the like or is held with hands. For example, in Japanese Laid-open Patent Application Hei Nos. 9-304802 and 5-53168 are disclosed methods wherein whether or not the device is fixed is determined by providing a switch on the device's portion to which a tripod is to be attached.
Also in Japanese Laid-open Patent Application Hei Nos. 10-161172, 11-38461, and 11-64911 are disclosed methods wherein whether or not the device is fixed is determined based on the level or the frequency of the output from the shake detection sensor.
In each category of the patent applications above, when it is determined that the device is fixed on a tripod, a process follows in which blur correction is stopped or the blur correction control is more suppressed than when the device is held with hands.
The above-described prior art determination methods, however, may cause the following problems.
In the case of the first category methods, i.e., where a switch is provided on the device is portion to which a tripod is to be attached, because the switch equally turns to be on either when a tripod is attached to the device or when a unipod is attached to the device, it cannot be identified which of the two is attached.
In other words, attaching a unipod may simply results in recognition of the device being attached with a tripod. When a camera is used being mounted on a unipod, the camera still vibrates due to a shake, although the vibration is decreased a little more than when the camera is supported solely with hands. Thus, blur correction should preferably be done when a camera is mounted on a unipod.
But the first category methods cannot distinguish a tripod from a unipod, and thus being attached with a unipod is recognized as being attached with a tripod, which results in stopping or suppressing the blur correction. Attaching a unipod, therefore, would be susceptible to image blurring.
Moreover, when, not using a tripod or the like, a camera is fixed with the camera being mounted on a base, the methods cannot determine the supporting condition, and thus blur correction is performed even if the camera itself is not vibrating, which results in losing valuable power or in image blurring all the more.
In the case of the second category methods, wherein determination is made by monitoring outputs (amplitude, frequency, etc.) from the shake detection sensor, it may be determined whether the camera is attached to a unipod or to a tripod, through some ingenuities applied to the methods. However, such methods may err in the determination if the sensor is subjected to certain large disturbances.
Illustratively, when the blur correction device is started while the camera is kept in a state of being fixed on a tripod, the device determines that the camera is fixed on the tripod. Notably, however, operations such as a mirror flipping up and down operation, a shutter curtain running operation, and a motor driving operation, which produce vibration of the camera itself, are performed during the camera's shooting operation. Because the shake detection sensor then also detects the vibration, it is well conceivable that the output amplitude of the shake detection sensor becomes larger during the shooting operation. Thus, even when the camera is fixed on a tripod, it is determined that the camera is held with
Hiroyuki Tomita
Ohishi Sueyuki
Nikon Corporation
Perkey W. B.
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