This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2009-037403 filed on Feb. 20, 2009.
1. Technical Field
The present invention relates to a shake detecting sensor and an image blur correcting device, and more particularly, to a shake detecting sensor capable of improving the S/N ratio (signal-to-noise ratio) of an output signal (shake signal) and an image blur correcting device.
2. Related Art
An image blur correcting device for a television camera has been proposed in which an anti-shake lens is provided in an imaging optical system so as to be movable in the plane orthogonal to an optical axis, and when a shake occurs in the camera (the imaging optical system of the camera), the anti-shake lens is driven by an actuator such that image blur caused by the shake is removed, thereby correcting the image blur (for example, see Patent Document 1 (JP-A-2001-142103 corresponding to U.S. Pat. No. 7,339,612) and Patent Document 2 (JP-A-2003-107554)). In addition to the method of using the anti-shake lens that is moved in the plane orthogonal to the optical axis, other image blur correcting methods have been proposed. In the image blur correcting methods, an image displacement unit optically or electronically displaces the position of the image formed by the optical system on an image surface in the horizontal direction or the vertical direction and the amount of displacement of the image by the image displacement unit is controlled such that image blur is removed. In this way, the image blur is corrected.
In addition, a shake detecting sensor, such as a gyro sensor, is provided in the camera and a camera shake is detected by a shake signal output from the shake detecting sensor.
However, the voltage of the shake detecting sensor is not constant and noise is generated from the shake detecting sensor even in a stationary state in which no shake occurs. It is difficult to discriminate the noise from the shake signal output from the shake detecting sensor when a shake occurs actually. Therefore, the noise generated from the shake detecting sensor is also processed as the shake signal generated due to a shake, and an image blur correcting process is also performed on the noise. As a result, a ‘fluctuation phenomenon’ occurs in which, even though no shake occurs, image blur occurs.
The invention has been made in order to solve the above-mentioned problems, and an object of the invention is to provide a shake detecting sensor capable of improving the S/N ratio of an output shake signal and appropriately preventing a fluctuation phenomenon by correcting image blur caused by noise when it is used in an image blur correcting device, and an image blur correcting device.
[1] According to an aspect of the invention, a shake detecting sensor includes: a plurality of shake detecting sensors that detects a shake; and an adder circuit that adds shake signals output from the plurality of shake detecting sensors. A signal added by the adder circuit is output as a shake signal output from one sensor.
[2] According to the shake detecting sensor of [1], the plurality of shake detecting sensors, or the plurality of shake detecting sensors and the adder circuit may be incorporated into one package.
[3] According to the shake detecting sensor of [19 or [2], each of the plurality of shake detecting sensors may be a gyro sensor.
[4] According to another aspect of the invention, an image blur correcting device includes: a shake detecting sensor that outputs a shake signal corresponding to a shake which occurs in an optical system; an image displacement unit that displaces an image formed by the optical system on an imaging surface; and an image blur correcting unit that removes image blur caused by the shake occurring in the optical system using the image displacement unit, on the basis of the shake signal. The shake detecting sensor includes: a plurality of shake detecting sensors that detects the shake; and an adder circuit that adds shake signals output from the plurality of shake detecting sensors. A signal added by the adder circuit is output as a shake signal output from one sensor.
[5] According to the image blur correcting device of [4], the plurality of shake detecting sensors, or the plurality of shake detecting sensors and the adder circuit may be incorporated into one package.
[6] According to the image blur correcting device of [4] or [5], each of the plurality of shake detecting sensors may be a gyro sensor.
With the configuration of [1] to [6], it is possible to improve the S/N ratio of the shake signal output from the shake detecting sensor. When the shake detecting sensor is used in an image blur correcting device, it is possible to appropriately prevent a fluctuation phenomenon by correcting image blur caused by noise.
Hereinafter, a lens device including an anti-shake shift lens according to an exemplary embodiment of the invention will be described in detail with reference to the accompanying drawings.
A shake detecting sensor 14 shown in
The shake signal output from the shake detecting sensor 14 is converted into a digital signal by an A/D converter 16. Then, the digital signal is transmitted to a CPU 18. The CPU 18 calculates position data indicating a target position to which the anti-shake lens 10 will be moved, on the basis of the shake signal acquired from the shake detecting sensor 14. For example, when a gyro sensor is used as the shake detecting sensor 14, an angular velocity signal is transmitted as the shake signal from the gyro sensor to the CPU 18. In this case, the CPU 18 performs, for example, an integration process on the acquired angular velocity signal to convert the angular velocity signal into a signal indicating an angle (angular signal) and calculates the position (position data indicating a target position) of the anti-shake lens 10 where image blur is corrected, on the basis of the angular signal.
As described above, the position data indicating the target position calculated by the CPU 18 is output as a position instruction signal to a D/A converter 20. The D/A converter 20 converts the position instruction signal into an analog voltage signal and outputs the position instruction signal to a driving circuit 22.
The driving circuit 22 drives the motor 12 to move the anti-shake lens 10 to the target position indicated by the position instruction signal. Then, the anti-shake lens 10 is moved to the target position calculated by the CPU 18 and image blur caused by a camera shake is corrected (prevented).
However, the voltage of the shake detecting sensor 14 is not constant and noise is generated from the shake detecting sensor 14 even in a stationary state in which no shake occurs. It is difficult to discriminate the noise from the shake signal output from the shake detecting sensor 14 when a shake occurs actually. Therefore, the noise generated from the shake detecting sensor 14 is also processed as the shake signal generated due to a shake, and an image blur correcting process is also performed on the noise. As a result, a ‘fluctuation phenomenon’ occurs in which, even though no shake occurs, image blur occurs.
In order to solve the above-mentioned problem, as shown in
In
The shake signal output from each of the shake detecting sensors S1, S2, . . . , SH is input to the adder circuit 30, and the adder circuit 30 adds the shake signals output from all the shake detecting sensors S1, S2, . . . , SH. Then, the shake signal added by the adder circuit 30 is output as the output of one shake detecting unit 14′ to the A/D converter 16. The process after the A/D converter 16 is the same as that shown in
According to the above-mentioned structure, the shake signal that is output from the adder circuit 30 as the output of the shake detecting unit 14′ has an S/N ratio higher than that of the shake signal that is output from the shake detecting sensor 14 including one sensor shown in
Meanwhile, if the sum of the outputs from the plurality of shake detecting sensors S1, S2, . . . , SH is used as the output of one shake detecting unit 14′ as shown in
Where, H indicates the number of shake detecting sensors S1, S2, . . . , SH.
The signal range Vn′ of the noise output from the shake detecting unit 14′ shown in
Therefore, the S/N ratio of the shake signal output from the shake detecting unit 14′ shown in
As described above, the image blur correcting device according to this embodiment of the invention treats the shake signal obtained by adding the outputs of a plurality of shake detecting sensors as the output of one shake detecting sensor. Therefore, it is possible to correct image blur on the basis of a shake signal with a high S/N ratio and prevent the problems, such as the above-mentioned ‘fluctuation phenomenon’. In addition, it is possible to manufacture an inexpensive sensor with a high S/N ratio using an inexpensive sensor with a low S/N ratio.
As shown in
Each of the shake detecting sensors S1, S2, S3, and S4 includes a power supply terminal and a ground terminal for operation, and the power supply terminals are connected to a power supply and the ground. The output terminals of the detecting sensors S1, S2, S3, and S4 from which the shake signals are output are connected to the corresponding resistors Rs, Rs, Rs, and Rs, as described above.
According to the above-mentioned structure, a shake signal with the following voltage Vo is output from the output terminal of the operational amplifier OP that is connected to the input terminal of the A/D converter 16 shown in
In this case, since currents (V1−E)/Rs, (V2−E)/Rs, (V3−E)/Rs, and (V4−E)/Rs flow through the resistors Rs, Rs, Rs, and Rs, the sum {(V1−E)+(V2−E)+(V3−E)+(V4−E)}/Rs of the currents flows through the feedback resistor Rf. Therefore, the voltage Vo of the shake signal output from the output terminal of the operational amplifier OP is represented by the following Expression 3:
Vo=E−{(V1−E)+(V2−E)+(V3−E)+(V4−E)}·Rf/Rs=(1−4·Rf/Rs)·E−(V1+V2+V3+V4)·Rf/Rs=A−(V1+V2+V3+V4)·B [Expression 3]
where A and B are integers.
That is, a shake signal corresponding to a voltage obtained by adding the voltages V1, V2, V3, and V4 of the shake signals is output as the output signal of the shake detecting unit 14′.
The shake detecting unit 14′ shown in
In addition, a plurality of shake detecting sensors S1, S2, SH and the adder circuit 30 may be incorporated into one package to manufacture one shake detecting unit 14′. That is, in
In the above-described embodiment, a gyro sensor is given as an example of the shake detecting sensor. However, the invention can be applied to any sensors capable of detecting a shake, in addition to a gyro sensor.
The shake detecting unit 14′ according to the above-described embodiment is not limited to the image blur correcting device, but it may be applied to other devices.
Number | Date | Country | Kind |
---|---|---|---|
P2009-037403 | Feb 2009 | JP | national |