JP4176935B2 - Imaging device with camera shake prevention function - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an imaging apparatus with a camera shake prevention function, such as a digital camera.
[0002]
[Prior art]
In recent years, digital cameras have begun to spread widely from business to personal. However, in the future, blurring of images due to camera shake at the time of shooting will be a major problem for digital cameras. The reasons include the following factors (1) to (3).
(1) Digital cameras are becoming smaller and lighter due to user demands. However, since a small but low-sensitivity CCD is adopted, the camera shake becomes conspicuous because the exposure time increases.
(2) Due to the use of liquid crystal viewfinders and the like, there are an increasing number of devices that do not have an optical viewfinder such as a silver salt camera. For this reason, a shooting style such as moving the digital camera away from the body or holding it with one hand has arisen, and stability during shooting is reduced.
(3) Due to differentiation from other companies' products, it is expected that a camera with a high-power zoom lens will appear, and camera shake is conspicuous due to the high-power zoom lens.
[0003]
In the video camera, a method {circle around (1)} of detecting image shake from image shake and suppressing image blur by controlling an image area cut out from the field memory according to the amount of movement is described in, for example, the Journal of Television Society, Vol. 49, No. 2, PP, 131-134 (1995).
In addition, as a camera shake prevention method that can be applied to video cameras, a system that obtains an image with little blurring by moving the optical axis in accordance with the movement of the camera due to camera shake using a parallel movement with respect to the optical axis of the lens or a variable apex angle prism. There are 2 ▼.
[0004]
Japanese Patent No. 2672267 describes a signal processing device applied to an image blur prevention device that removes an offset component included in a camera shake detection signal by sequentially calculating an average value of the camera shake detection signal. .
Japanese Patent Application Laid-Open No. 7-20521 describes a camera shake detection apparatus that removes an offset component included in a camera shake detection signal by detecting a peak value of camera shake angular acceleration.
Japanese Patent Application Laid-Open No. 7-218953 describes a camera shake detection device that removes an offset component included in a camera shake detection signal from the maximum value and the minimum value of a camera shake angular velocity.
[0005]
[Problems to be solved by the invention]
Image blur due to camera shake in a digital camera (digital still camera) is caused by camera shake within the capture time of one frame. Therefore, the method (1) cannot be used for a digital camera. This is because the method {circle around (1)} used in the video camera corrects the shift between frames and does not take into account the camera shake during capturing one frame.
[0006]
In the method {circle around (2)} that can also be applied to a digital camera, a sensor that mechanically detects the motion of the camera, such as a gyro, is often used for camera shake detection. However, since the signal of such a sensor is minute or noisy, it generally passes through a filter circuit or an amplifier circuit. A slight offset generated in these sensors and circuits greatly affects the effect of camera shake correction, and therefore it is preferable to remove as much as possible. However, since this offset value changes depending on conditions such as temperature, it is desirable to remove it adaptively.
[0007]
On the other hand, in order to solve the above problem, methods for detecting an offset component from a signal from the circuit are described in the above-mentioned Japanese Patent No. 2672267, Japanese Patent Laid-Open No. 7-20521, and Japanese Patent Laid-Open No. 7-218953. Yes. However, these methods are based on the assumption that the time average of a signal with camera shake is 0, and there is a high possibility that camera shake correction will fail.
[0008]
That is, in the signal processing device applied to the image blur prevention device described in the above-mentioned Japanese Patent No. 2672267, long time detection is required to obtain an accurate offset value, and it cannot be used for a digital camera. The camera shake detection device described in Japanese Patent Laid-Open No. 7-20521 is susceptible to noise and is not realistic. In the camera shake detection apparatus described in Japanese Patent Laid-Open No. 7-218953, the assumed ideal camera shake waveform is often different from the camera shake waveform within the actual exposure time. high.
[0009]
An object of the present invention is to provide an imaging apparatus with a camera shake prevention function that can improve the reliability of camera shake detection.
An object of the present invention is to provide an image pickup apparatus with a camera shake prevention function that enables offset removal with a simple configuration.
An object of the invention according to claim 3 is to provide an image pickup apparatus with a camera shake prevention function that can obtain a more suitable offset value and can remove the offset with higher accuracy.
[0010]
An object of the present invention according to claim 4 is to provide an imaging device with a camera shake prevention function capable of improving the accuracy of camera shake detection.
An object of the invention according to claim 5 is to provide an imaging apparatus with a camera shake prevention function capable of further improving the reliability of camera shake detection.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 includes a camera shake detecting means for detecting a camera shake, a signal converting means for shaping / amplifying a camera shake signal from the camera shake detecting means, and a converted signal from the signal converting means. the in an imaging apparatus having a camera shake correction function to suppress blurring of the image due to camera shake based on a reference signal generating means for generating a reference signal for measuring the offset component included in the signal conversion means, to said signal converting means The reference signal from the reference signal generation means is input to the signal conversion means prior to the detection of the shake, and the input signal is switched to either the shake signal from the shake detection means or the reference signal from the reference signal generation means. and the signal, a first switching means for an input signal to the hand shake signal from the hand shake detecting means when performing vibration detection to said signal converting means , It calculates the offset voltage, by obtaining the signal after the offset removal by using the offset voltage, in which a first offset removing means for removing an offset of the signal converting means.
[0012]
According to a second aspect of the present invention, in the imaging apparatus with a camera shake preventing function according to the first aspect, the reference signal generating means generates a reference signal which is a ground voltage or a predetermined DC voltage.
[0013]
According to a third aspect of the present invention, in the imaging apparatus with a camera shake preventing function according to the first aspect , the reference signal generating means generates a reference signal that is a predetermined AC voltage.
[0014]
According to a fourth aspect of the present invention, in the imaging apparatus with a camera shake preventing function according to the first, second, or third aspect, the offset is further removed from the signal from which the offset of the signal converting unit is removed by the first offset removing unit. 2 An offset removing means is provided.
[0015]
According to a fifth aspect of the present invention, in the imaging apparatus with a camera shake prevention function according to the first, second, third, or fourth aspect, a third offset removing unit that removes an offset of the camera shake signal, the first offset removing unit, and the Second switching means for switching to third offset removing means is provided.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an outline of a camera shake prevention mechanism in Embodiment 1 of the present invention. The first embodiment is an embodiment of the invention according to claims 1 to 3, and is an example of an imaging apparatus with a camera shake preventing function including a digital camera with a camera shake preventing function. The first embodiment is a well-known digital camera provided with the camera shake prevention mechanism shown in FIG. 1. The subject image is captured by an imaging unit and an image signal from the imaging unit is stored in a field memory. A subject image is displayed by a finder as a display device based on an image signal from an imaging unit or an image signal in a field memory.
[0017]
The camera shake detection sensors 1 and 2 serving as camera shake detection means detect motion caused by camera shake of the image pickup apparatus according to the first embodiment, and the camera shake signals from the camera shake detection sensors 1 and 2 are respectively converted into the conversion circuit 3 serving as signal conversion means, 4 is shaped and amplified, and input to a microcomputer (hereinafter referred to as a microcomputer) 5 as a calculation means. The microcomputer 5 has an A / D conversion function and a D / A conversion function, digitizes the conversion signal from the conversion circuits 3 and 4 by the A / D conversion function, and sets the control target of the correction mechanisms 6 and 7 from the digital signal. calculate. That is, when the camera shake detection sensors 1 and 2 are gyros that mechanically detect the movement of the first embodiment, the signals from the conversion circuits 3 and 4 are integrated to obtain the exposure start time t = 0. The posture angle of the first embodiment is set to the reference θ (0), the posture angle θ (T) of the first embodiment at the current time t = T is calculated, and the image shift caused by this θ (T) is corrected. Then, the movement amount (control target) of the correction mechanisms 6 and 7 is calculated.
[0018]
The microcomputer 5 transmits the control target as an analog signal to the drive circuits 8 and 9 by the D / A conversion function, and the drive circuits 8 and 9 drive and move the correction mechanisms 6 and 7 by the analog signal from the microcomputer 5. . The correction mechanisms 6 and 7 may be a correction lens or a variable apex prism that moves an image, or may be a mechanism that moves an image sensor (or a substrate including the image sensor) in order to change a region to be photographed. Good.
[0019]
In FIG. 1, the camera shake detection system including the camera shake detection sensors 1 and 2 and the conversion circuits 3 and 4 is shown as two sets, and the camera shake correction system including the drive circuits 8 and 9 and the correction climates 6 and 7 is shown as two sets. In general, the change in the yaw angle and pitch angle of the first embodiment is detected by each camera shake detection sensor, and the correction mechanism is generally driven so as to correct each component. However, the camera shake detection system and the camera shake correction system may each be one set or three or more sets.
[0020]
Further, the number of sets may be different between the camera shake detection system and the camera shake correction system. Note that the calculation contents in the camera shake detection system and the microcomputer 5 are not limited to those described above, and may be configured to change the cutout position of an image stored in a field memory, for example. However, in the application to a still camera, the former example is preferable.
[0021]
FIG. 2 shows an example of the conversion circuits 3 and 4. The input terminal 11 receives an output signal of the camera shake detection sensor. This signal is a low-pass filter composed of an operational amplifier A1, capacitors C1, C2 and resistors R1, R2, and a high-pass filter composed of an operational amplifier A2, a capacitor C3 and a resistor R3. Are amplified at a predetermined magnification and output from the output terminal 12.
[0022]
Since human hand shake does not include a high frequency, a high-frequency component of a signal from a hand shake detection sensor such as a gyro is removed by the low-pass filter. Further, the signal from the camera shake detection sensor generally includes an offset voltage, and the offset voltage is removed by the high-pass filter. The conversion circuit amplifies the signal so that sufficient accuracy can be obtained by the A / D conversion function.
[0023]
FIG. 3 shows in detail the input side of the conversion circuit 1 of the first embodiment. The first switching means 13 switches between the signal from the camera shake detection sensor 1 and the reference signal from the reference signal generating means 14 and inputs them to the conversion circuit 3.
First, prior to camera shake detection, the reference signal generating means 14 and the conversion circuit 3 are connected by the first switching means 13. Here, the reference signal from the reference signal generating means 14 is O (t). Further, the ideal value of the output value of the conversion circuit 3 expected when O (t) is input to the conversion circuit 3 is V ₁ (t), and the actual output value of the conversion circuit 3 is V ₁ ′ (t). The first offset removing means 15 calculates the offset voltage δV from V ₁ (t) and V ₁ ′ (t). An example of a calculation formula for calculating the offset voltage δV from V ₁ (t) and V ₁ ′ (t) in the first offset removing means 15 is shown in the following formula (1).
[0024]
_{δV = E (V 1 '(} t) -V 1 (t)) ··· (1)
Here, E () means time average, and the average value of the difference between the actual measurement value V ₁ ′ (t) and the ideal value V ₁ (t) within the measurement time is obtained. The first offset removing means 15 stores the offset voltage δV in an internal memory. At this time, by using the reference signal generation means 14 that outputs a ground voltage or a known DC voltage as the reference signal O (t), the configuration of the reference signal generation means 14 becomes extremely simple. Further, by using the reference signal generating means 14 that outputs an alternating voltage having a similar waveform close to camera shake as the reference signal O (t), it is possible to know the offset characteristics in a frequency band close to camera shake, and to achieve higher accuracy. Offset removal can be realized.
[0025]
Next, when camera shake detection is performed, the camera shake detection sensor 1 and the conversion circuit 3 are connected by the first switching unit 13. Then, the first offset removing means 15 calculates the signal V ₃ (t) after offset removal by the following equation (2), where V ₂ (t) is the output voltage of the conversion circuit 3.
_{V 3 (t) = V 2} (t) -δV ··· (2)
The microcomputer 5 calculates the movement amount (control target) of the correction mechanism from the signal V ₃ (t) after the offset removal.
[0026]
The first offset removing unit 15 may be realized by the microcomputer 5 (including its peripheral circuit and software) or may be software in the microcomputer 5. The first switching means 13 similarly switches the signal from the camera shake detection sensor 2 and the reference signal from the reference signal generation means 14 and inputs them to the conversion circuit 4, and the first offset removing means 15 similarly offsets before the camera shake detection. The voltage is calculated, and the offset of the signal from the conversion circuit 4 is removed when camera shake is detected. The microcomputer 5 calculates the movement amount (control target) of the correction mechanism from the signal after the offset removal.
[0027]
According to the first embodiment, camera shake detection sensors 1 and 2 as camera shake detection means for detecting camera shake, and a conversion circuit 3 as signal conversion means for shaping and amplifying the camera shake signals from the camera shake detection means 1 and 2, 4 and an image pickup apparatus having a microcomputer 5, a drive circuit 8, 9 and a correction climate 6, 7 as a camera shake correction function for suppressing blurring of an image due to camera shake based on the converted signals from the signal conversion means 3, 4. A first switching means 13 for switching an input signal to the signal conversion means 3 and 4 to either a shake signal from the shake detection means 1 or 2 and a reference signal from a reference signal generation means 14; Since the first offset removing means 15 for removing the offset of the means 3 and 4 is provided, it is possible to accurately measure the yaw set component possessed by the signal converting means, and to detect camera shake. It is possible to increase the dependability.
[0028]
Further, according to the first embodiment, the reference signal generating means 14 generates a reference signal that is a ground voltage (0 V) or a known DC voltage, without incorporating a special mechanism as the reference signal generating means. Offset removal is possible with a simple configuration, space saving, and low cost.
[0029]
Further, according to the first embodiment, the reference signal generating means 14 generates a reference signal which is a predetermined AC voltage, so that the characteristics of the circuit close to the time of camera shake can be reproduced and a more suitable offset value can be obtained. Thus, offset removal can be performed with higher accuracy.
[0030]
FIG. 4 shows an offset prevention system in Embodiment 2 of the present invention. The second embodiment is an embodiment of the invention according to claim 4, and in the first embodiment, the second offset removing means 16 is provided after the first offset removing means 15. The second offset removing means 16 removes offset values other than the offset voltage that the conversion circuits 3 and 4 have. For example, when gyroscopes are used as the camera shake detection sensors 1 and 2, the gyroscope immediately after power-on has a low-frequency offset variation, and it is difficult to remove the offset with a high-pass filter in the conversion circuits 3 and 4.
[0031]
Therefore, the second offset removing unit 16 removes the gyro offset voltage from the output signal of the first offset removing unit 15. In calculating the gyro offset voltage, the second offset removing means 16 obtains the gyro offset voltage by referring to the look-up table according to the time from the power-on time measured by the time measuring means or the temperature measured by the temperature sensor. The offset signal may be removed from the output signal of the first offset removing means 15, or the gyro offset voltage may be removed from the output signal of the first offset removing means 15 by the same processing as in the prior art.
[0032]
The microcomputer 5 calculates the movement amount (control target) of the correction mechanism from the signal after the offset removal from the second offset removal means 16. As a result, offset removal with higher accuracy can be realized. The second offset removing means 16 may be realized by the microcomputer 5 (including its peripheral circuit and software) or may be software in the microcomputer 5. Further, the first offset removing unit 15 may have the function of the second offset removing unit 16 together.
[0033]
According to the second embodiment, the second offset removing means 16 for further removing the offset from the signal from which the offset of the signal converting means 2 and 4 has been removed by the first offset removing means 15 in the first embodiment is provided. Therefore, the accuracy of camera shake detection can be improved.
[0034]
FIG. 5 shows an offset prevention system in Embodiment 3 of the present invention. The third embodiment is an embodiment of the invention according to claim 5. In the first embodiment, the second switching means 17 is arranged between the conversion circuits 3, 4 and the first offset removing means 15. The second switching means 17 switches the signals from the conversion circuits 3 and 4 to the first offset removing means 15 and the third offset removing means 18 and inputs them.
[0035]
The third offset removing unit 18 does not receive the reference signal from the reference signal generating unit, and removes the offset component from the signals from the conversion circuits 3 and 4 by the same processing as in the prior art. The microcomputer 5 calculates the movement amount (control target) of the correction mechanism from the signal after offset removal from the first offset removal means 15 or the third offset removal means 18 selected by the second switching means 17.
[0036]
When the second switching means 17 selects the first offset removing means 15 and inputs the signals from the conversion circuits 3 and 4 to the first offset removing means 15, the first offset removing means 15 or the microcomputer 5 calculates the offset value. If it is determined that the state is not normal, the second switching unit 17 selects the third offset removing unit 18 and the signals from the conversion circuits 3 and 4 are input to the third offset removing unit 18.
[0037]
The fourth embodiment of the present invention is another embodiment of the invention according to claim 5, and in the second embodiment, the second switching means 17 is provided between the conversion circuits 3 and 4 and the first offset removing means 15. The signals from the conversion circuits 3 and 4 are switched and input to the first offset removing means 15 and the third offset removing means 18 by the second switching means 17. The microcomputer 5 calculates the movement amount (control target) of the correction mechanism from the signal after the offset removal from the second offset removal means 16 or the third offset removal means 18 according to the selection operation of the second switching means 17.
[0038]
When the second switching means 17 selects the first offset removing means 15 and inputs the signals from the conversion circuits 3 and 4 to the first offset removing means 15, the first offset removing means 15 or the second offset removing means 16 or If the microcomputer 5 determines that the offset value calculation is not normal, the second switching means 17 selects the third offset removing means 18 and the signals from the conversion circuits 3 and 4 are input to the third offset removing means 18. Is done.
[0039]
According to the third and fourth embodiments, in the first or second embodiment, the third offset removing unit 18 that removes the offset of the camera shake signal, the first offset removing unit 15, and the third offset removing unit. Since the second switching means 17 for switching to 18 is provided, the reliability of camera shake detection can be further improved.
[0040]
In addition, this invention is not limited to the said Example, It is possible to apply similarly to imaging devices other than the said Example.
[0041]
【The invention's effect】
As described above, according to the first aspect of the invention, the reliability of camera shake detection can be improved.
According to the invention of claim 2, it is possible to remove the offset with a simple configuration. According to the invention of claim 3, a more suitable offset value can be obtained, and offset removal can be performed with higher accuracy.
[0042]
According to the invention of claim 4, the accuracy of camera shake detection can be improved. According to the fifth aspect of the present invention, the reliability of camera shake detection can be further improved.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating an outline of a camera shake prevention mechanism according to a first embodiment of the invention.
FIG. 2 is a circuit diagram showing an example of a conversion circuit in the first embodiment.
FIG. 3 is a block diagram illustrating in detail a conversion circuit input side according to the first embodiment;
FIG. 4 is a block diagram showing an offset prevention system in Embodiment 2 of the present invention.
FIG. 5 is a block diagram showing an offset prevention system in Embodiment 3 of the present invention.
[Explanation of symbols]
1, 2, camera shake detection sensor 3, 4 conversion circuit 5 microcomputer 6, 7 correction mechanism 8, 9 drive circuit 13 first switching means 14 reference signal generating means 15 first offset removing means 16 second offset removing means 17 second switching means 18 Third offset removing means

Claims (5)

Camera shake detection means for detecting camera shake, signal conversion means for shaping / amplifying a camera shake signal from the camera shake detection means, and a camera shake correction function for suppressing image blur due to camera shake based on the converted signal from the signal conversion means; In an imaging apparatus having
Reference signal generating means for generating a reference signal for measuring an offset component included in the signal converting means, an input signal to the signal converting means, a hand shake signal from the hand shake detecting means, and a reference signal from the reference signal generating means Prior to camera shake detection, the reference signal from the reference signal generator is used as an input signal to the signal converter, and when camera shake is detected, the camera shake signal from the camera shake detector is converted to the signal. First switching means as an input signal to the means;
With a camera shake prevention function , comprising: a first offset removing means for removing an offset of the signal converting means by calculating an offset voltage and obtaining an offset-removed signal using the offset voltage Imaging device.   2. The imaging apparatus with a camera shake preventing function according to claim 1, wherein the reference signal generating means generates a reference signal which is a ground voltage or a predetermined DC voltage. 2. The imaging apparatus with a camera shake preventing function according to claim 1 , wherein the reference signal generating means generates a reference signal having a predetermined AC voltage.   4. The imaging apparatus with a camera shake preventing function according to claim 1, further comprising second offset removing means for further removing an offset from the signal from which the offset of the signal converting means has been removed by the first offset removing means. An image pickup apparatus with a camera shake prevention function.   5. The imaging apparatus with a camera shake prevention function according to claim 1, wherein the third offset removing means for removing an offset of the camera shake signal, the first offset removing means, and the third offset removing means are switched. An imaging apparatus with a camera shake prevention function, comprising: a second switching unit.

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