Television – Camera – system and detail – Camera image stabilization
Reexamination Certificate
1997-12-12
2004-10-05
Garber, Wendy R. (Department: 2612)
Television
Camera, system and detail
Camera image stabilization
Reexamination Certificate
active
06801247
ABSTRACT:
The entire disclosure of Japanese Patent Application Nos. 8-331848, 8-331856, 9-093479, 9-168273, 9-258857 including specifications, claims, drawings and summaries is incorporated herein by reference in their entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vibration detecting device for detecting vibration in a camera or an image pickup device for a video movie or the like, and a vibration reduction device for compensating the vibration. The invention also relates to a micro signal processing circuit which can be used in a vibration detecting circuit.
2. Related Background Art
For example, as a prior-art vibration detecting device known is a device which detects acceleration or angular velocity occurring in an apparatus by using an acceleration sensor, an angular velocity sensor or the like. In general, because the acceleration sensor or the angular velocity sensor itself outputs only a slight voltage in relation to a given vibration, an appropriate amplifier is provided outside the sensor for emitting a necessary voltage.
However, the vibration detecting sensor, especially a vibration sensing gyroscope of piezoelectric type generally used in a camera or the like outputs a remarkably unstable output for several tens to hundreds of milliseconds immediately after power turns on, and generates a low-frequency output drift even after the power turns on. Also, a voltage under the state in which no vibration is given (hereinafter, referred to as a stationary output voltage) is not always constant, and remarkably much varied with variation among vibration sensing gyroscopes or change in operational environment, especially with operation temperature. Such variation in output when power turns on is considerably large as compared with a level of an output signal for the vibration to be originally detected in accordance with the acceleration or the angular velocity, and in some case excessively large.
As a vibration detecting device in which an influence of the variation in output when power turns on is minimized, for example, a vibration detecting circuit disclosed in a publication of Japanese Patent Application Laid-Open No. 7-218953 is heretofore known. The vibration detecting circuit is constituted of an angular velocity sensor, a high pass filter for cutting an output of a tolerably low frequency relative to a frequency of a vibration to be detected from an output of the angular velocity sensor and an amplifying portion for amplifying a signal passed through the high pass filter.
FIG. 20
is a circuit diagram showing a vibration detecting circuit in the prior-art vibration detecting device. A vibration sensing gyroscope
1
detects an angular velocity caused by vibration in the device with a piezoelectric element. A circuit
2
is a three-dimensional low pass filter circuit for removing high-frequency components from an output of the vibration sensing gyroscope
1
. In a circuit
3
, a capacitor C
4
and a resistor R
4
constitute a high pass filter for removing low-frequency components which are not caused by the vibration, and an operational amplifier OP
2
and resistors R
6
and R
7
constitute an amplifying circuit which amplifies an output signal of the circuit
2
in a non-inverting manner. The cut-off frequency which is a low frequency to be determined by the capacitor C
4
and the resistor R
4
, needs to be sufficiently low relative to the frequency of the vibration to be detected, so that the cut-off frequency has no influence on the vibration which occurs in the apparatus. For the purpose, a numeric value of the cut-off frequency is, for example, set to about 0.1 Hz.
A switch SW
1
is an analog switch which shifts the cut-off frequency to a high frequency when it is on and which is maintained on for a predetermined time after power is turned on so as to minimize an influence exerted on an output signal Vout by the variation in output when the power supply to the vibration sensing gyroscope
1
is started. When the switch SW
1
is turned off, the low frequency of the cut-off frequency is determined by the capacitor C
4
and the resistor R
4
. A power circuit
4
supplies a stable power to the vibration sensing gyroscope
1
and the circuits
2
and
3
. In one chip computer (hereinafter, referred to as the MCU)
5
, the output signal Vout from the circuit
3
is digitized by a built-in A/D converter
5
a
, the vibration occurring in the apparatus is detected, and also an operation of the power circuit
4
is controlled in accordance with a control signal PC of a control signal generator
5
d
. Further, in the MCU
5
the turning on/off of the analog switch SW
1
is controlled in accordance with an operation signal SSW of an operation signal generator
5
b.
Also, in each of vibration detecting devices disclosed in publications of Japanese Patent Application Laid-Open Nos. 7-253604 and 8-82820, an output of a vibration sensing gyroscope and a reference voltage are differentially amplified by a differential amplifying portion, and a vibration occurring in the apparatus is detected from the output. An influence of an output drift of the vibration sensing gyroscope when power turns on and an influence of variations in stationary output voltage among individual vibration sensing gyroscopes are eliminated by controlling the output differentiated/amplified by changing the reference voltage within a dynamic range of the output.
However, the prior-art vibration detecting device has a first problem with the dynamic range of the vibration to be detected and a detecting resolution.
For example, when an angular velocity of a vibration is detected in a camera which uses a silver salt (or silver halide) film and has a function of reducing the vibration, at the time of usually shooting, a stationary object, a maximum value of the vibration angular velocity is approximately 20° to 30° per second though it varies depending on the individual users. On the other hand, when the camera pans, flows or picks up an object moving at a high speed, a very large angular velocity occurs as compared with in the case of shooting the stationary object. For example, the angular velocity exceeding 50° per second occurs. When considering even the angular velocity which may occur at the time of shooting the object other than the stationary object, the dynamic range of the angular velocity up to 50° per second or more needs to be secured.
In the camera having the vibration reducing function and using the silver salt film, a video movie or the like, as shown in
FIG. 20
, the detected output signal Vout is quantized to a digital value by using the A/D converter
5
a
, and the vibration reduction is usually performed based on the quantized vibration signal. In this case, since a quantization unit of the A/D converter
5
a
is finite, the resolution per bit of quantization needs to be increased by setting large an amplification factor for amplifying the output of the vibration sensing gyroscope
1
. For the purpose, to enhance a ratio (S/N) of the signal to be detected with a noise included in the output of the operational amplifier OP
2
, a gain of the amplifying circuit constituted of the operational amplifier OP
2
, the resistors R
6
and R
7
and the like needs to be set large. However, since the output range of the operational amplifier OP
2
is limited, the dynamic range of the angular velocity that can be detected is decreased when the resolution per bit of quantization is enhanced. In this manner, when priority is given to the dynamic range of the vibration to be detected, the resolution per bit of quantization or the ratio S/N is deteriorated. On the other hand, when priority is given to the resolution per bit of quantization or S/N, the dynamic range of vibration which can be detected is disadvantageously narrowed.
Secondly, a problem is caused by a time constant of the high pass filter.
The cut-off frequency of the high pass filter constituting the vibration detecting device has to be set sufficiently low relative to the frequency bandwidth of the vibr
Ohishi Sueyuki
Taguchi Fumiya
Garber Wendy R.
Nikon Corporation
Staas & Halsey , LLP
Tillery Rashawn N.
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