JP2009042544A - Vibration prevention control circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vibration prevention control circuit that calculates the moving amount of an imaging apparatus without using a CPU, and obtains an image signal of high image quality with less influence of camera-shake while reducing power consumption. <P>SOLUTION: The vibration prevention control circuit to control an optical component driving element for moving optical components loaded to the imaging apparatus includes: a high-pass filter for removing low frequency components of the signal outputted by a vibration detection element; a moving amount calculation circuit to calculate the moving amount of the imaging apparatus based on the signal outputted by the high-pass filter; a servo circuit for generating a correction signal to correct the position of the optical component based on the output signal of the moving amount calculation circuit and outputting the correction signal to the optical component driving element. The high-pass filter includes a digital filter circuit and a register. The digital filter circuit is configured to perform filtering based on a filtering coefficient stored in the register. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image stabilization control circuit that suppresses blurring (hand shake) of a subject caused by vibration applied to an imaging apparatus such as a digital still camera.

  In recent years, an imaging apparatus such as a digital still camera or a digital video camera has realized high image quality by increasing the number of pixels of an imaging element provided therein. On the other hand, as another method for realizing high image quality of the image pickup apparatus, it is desired that the image pickup apparatus has a camera shake correction function in order to prevent subject shake caused by hand shake with the image pickup apparatus. .

  Specifically, the imaging apparatus includes a detection element such as a gyro sensor, and drives an optical component such as a lens or an imaging element according to an angular velocity component generated by vibration of the imaging apparatus to prevent subject blurring. Accordingly, even when the imaging apparatus vibrates, the vibration component is not reflected in the acquired video signal, and a high-quality video signal without image blur can be acquired.

  FIG. 2 shows a block diagram of a conventional image stabilization control circuit 100 used for realizing the camera shake correction function. The image stabilization control circuit 100 is provided in the imaging apparatus and operates in accordance with control of a main control circuit (not shown) provided in the imaging apparatus. The image stabilization control circuit 100 is connected to the position detection element 200, the lens driving element 300 and the vibration detection element 400.

  The position detection element 200 detects the position of a lens provided in the imaging apparatus. More specifically, the position detection element 200 can be a Hall element, generates an induced current corresponding to the absolute position of the lens, and outputs a voltage signal.

  The lens driving element 300 moves the lens position in accordance with the lens driving signal output from the image stabilization control circuit 100. The lens driving element 300 can be a voice coil motor, and the image stabilization control circuit 100 controls the position of the moving coil of the voice coil motor, that is, the position of the lens by adjusting the voltage value applied to the lens driving element 300. . The lens driving element 300 drives the lens in a plane perpendicular to the optical axis of the imaging device.

  The vibration detection element 400 detects the vibration of the imaging device and outputs the result to the image stabilization control circuit 100. The vibration detection element 400 can be a gyro sensor, generates an angular velocity signal corresponding to the vibration applied to the imaging device, and outputs it to the image stabilization control circuit 100.

  Each of the position detection element 200, the lens driving element 300, and the vibration detection element 400 is preferably composed of at least two elements, and a plurality of components corresponding to a horizontal component and a vertical component in a plane perpendicular to the optical axis of the imaging device. Are provided to control lens position detection, lens movement, and vibration detection of the imaging apparatus.

  Next, the image stabilization control circuit 100 will be described in detail. The image stabilization control circuit 100 includes a servo circuit 120, a lens driver 140, an analog-digital conversion circuit (ADC) 142, a CPU 160, and a digital-analog conversion circuit (DAC) 162.

The servo circuit 120 generates a signal for controlling the lens driving element 300 in accordance with the voltage signal output from the position detection element 200. The servo circuit 120 is configured to include an analog filter circuit including an external resistor element, a capacitor, and the like, and a lens driving element so that the optical axis of the lens coincides with the center of the imaging element provided in the imaging device. A signal for controlling 300 is generated. The lens driver 140 generates a lens driving signal for driving the lens driving element 300 based on the signal output from the servo circuit 120.

  The ADC 142 converts an analog angular velocity signal output from the vibration detection element 400 into a digital signal. The CPU 160 generates an angle signal indicating the amount of movement of the imaging device based on the digital angular velocity signal. The CPU 160 is connected to a memory (not shown), and performs an angle signal generation process based on software stored in the memory. The DAC 162 converts the digital angle signal generated by the CPU 160 into an analog signal.

Here, the servo circuit 120 generates a lens driving signal for driving the lens driving element 300 according to a signal obtained by adding the analog angle signal output from the DAC 162 and the voltage signal output from the position detection element 200. . That is, in order to prevent subject shake due to camera shake, the position of the lens is changed based on an angle signal indicating the amount of movement of the imaging device, thereby suppressing blurring of the subject image on the image sensor. Thus, it is possible to obtain a high-quality video signal while suppressing blurring of the subject image due to camera shake.
JP-A-10-213832

  The conventional image stabilization control circuit 100 shown in FIG. 2 realizes its function by software using the CPU 160 when generating an angle signal indicating the amount of movement of the imaging device from the angular velocity signal obtained from the vibration detection element 400. Yes. At this time, the image stabilization control circuit 100 is required to have a high processing speed, and the CPU 160 needs to be operable with a high-speed clock. For example, when the imaging device captures 30 frames of images per second to obtain a moving image, it is necessary to control the lens position to change with a resolution faster than 1/30 seconds.

  When the CPU 160 is driven using a high-speed clock, power consumption in the image stabilization control circuit 100 increases. The imaging device on which the image stabilization control circuit 100 is mounted is driven using a secondary battery such as a lithium ion battery as a power source. For this reason, if the power consumption of the image stabilization control circuit 100 increases, the secondary battery is consumed quickly, so that the driving time of the imaging device is shortened, so that the shooting time of moving images is shortened and the number of still images shot is reduced. Problem arises. Since the camera shake correction function of the imaging apparatus is often executed not only during shooting of a moving image or a still image but also during a preview during preparation for shooting, reduction of power consumption related to the camera shake correction function is desired.

  An object of the present invention is to provide an image stabilization control circuit that obtains a high-quality video signal and reduces power consumption in view of the above-described problems of the prior art.

  The present invention is an image stabilization control circuit for controlling an optical component driving element that moves an optical component provided in an imaging apparatus based on a signal output from a vibration detection element provided in the imaging apparatus. An analog-digital conversion circuit that converts an analog signal output from the digital signal into a digital signal, a high-pass filter that removes a low-frequency component of the digital signal, and a movement amount that calculates the movement amount of the imaging device based on the signal output from the high-pass filter A calculation circuit; and a servo circuit that generates a correction signal for correcting the position of the optical component based on the output signal of the movement amount calculation circuit and outputs the correction signal to the optical component driving element. And the digital filter circuit performs a filtering process based on the filter coefficient stored in the register. And, characterized by.

According to the present invention, since the movement amount of the imaging apparatus can be calculated without using a CPU, it is possible to obtain a high-quality video signal that suppresses the influence of camera shake while reducing power consumption.

  FIG. 1 is a schematic block diagram of an image stabilization control circuit 10 according to an embodiment of the present invention. The image stabilization control circuit 10 includes ADCs 12 and 42, a servo circuit 20, a lens driver 40, a high-pass filter (HPF) 44, a pan / tilt determination circuit 46, a gain adjustment circuit 48, an integration circuit 50, and a centering processing circuit 52. Is done. The image stabilization control circuit 10 is connected to the position detection element 200, the lens driving element 300, and the vibration detection element 400, which are the same as those described in the prior art.

  The ADC 12 converts an analog voltage signal output from the position detection element 200, for example, a Hall element, into a digital signal. The Hall element generates an induced current corresponding to the magnetic force generated by the magnet fixed to the lens. That is, the Hall element outputs a voltage signal indicating the position of the lens according to the distance from the lens, and the ADC 12 converts the voltage signal into a digital signal and outputs it as a position signal SP. The ADC 12 is configured to output a signal indicating a reference, for example, a digital value indicating “0”, when the optical axis of the lens matches the center of the image sensor provided in the image pickup apparatus.

  The servo circuit 20 generates a correction signal SR for controlling the driving of the lens driving element 300 according to a signal obtained by adding a position signal SP output from the ADC 12 and a vibration component signal SV described later. The servo circuit 20 includes a register 22 and a digital filter circuit (not shown), and performs a filter process using a filter coefficient stored in the register 22.

  The DAC 30 converts the digital correction signal SR into an analog signal. The lens driver 40 generates a lens driving signal for driving the lens driving element 300 based on the analog correction signal SR.

  The ADC 42 converts an analog angular velocity signal output from the vibration detection element 400, for example, a gyro sensor, into a digital signal. The HPF 44 removes a direct current component included in the angular velocity signal, and extracts a high frequency component of the angular velocity signal reflecting the vibration of the imaging device.

  The pan / tilt determination circuit 46 detects the pan operation and tilt operation of the imaging apparatus based on the angular velocity signal output from the HPF 44. Moving the imaging device in the horizontal direction according to the movement of the subject is called a panning operation, and moving the imaging device in the vertical direction is called a tilting operation. When the imaging device is moved according to the movement of the subject, the vibration detection element 400 outputs an angular velocity signal corresponding to the movement. However, the fluctuation of the angular velocity signal due to the pan operation or the tilt operation is not caused by camera shake, so there is a case where it is not necessary to correct the optical system such as a lens. The pan / tilt determination circuit 46 is provided to realize the control as described above. Specifically, the pan / tilt determination circuit 46 determines that the pan operation or the tilt operation is being performed when it is detected that the angular velocity signal exceeds a predetermined value for a certain period.

  The gain adjustment circuit 48 changes the amplification factor of the angular velocity signal output from the HPF 44 according to the determination result of the pan / tilt determination circuit 46. For example, when the pan operation or tilt operation is not being performed, the gain adjustment circuit 48 performs gain adjustment so as to maintain the intensity of the angular velocity signal output from the HPF 44. When the pan operation or the tilt operation is being performed, the gain adjustment circuit 48 performs gain adjustment so that the intensity of the angular velocity signal output from the HPF 44 is attenuated and the output becomes zero.

The integration circuit 50 integrates the angular velocity signal output from the gain adjustment circuit 48 to generate an angle signal indicating the amount of movement of the imaging device. The integration circuit 50 is preferably configured to include a digital filter (not shown), and obtains an angle signal, that is, a movement amount of the imaging device by performing filter processing according to a filter coefficient set in a register (not shown).

  The centering processing circuit 52 subtracts a predetermined value from the angle signal output from the integration circuit 50 to generate a vibration component signal SV indicating the amount of movement of the imaging device. When camera shake correction processing is performed in the imaging apparatus, the lens position gradually moves away from the reference position while the correction processing is continuously performed, and may reach the vicinity of the limit point of the movable range of the lens. At this time, if the camera shake correction process is continued, the lens can move in one direction but cannot move in the other direction. The centering processing circuit 52 is provided to prevent this, and performs control so as not to approach the limit point of the movable range of the lens by subtracting a predetermined value from the angle signal.

  The centering process 52 preferably includes a digital filter (not shown), and performs a process of subtracting a predetermined value from the angle signal by performing a filter process according to a filter coefficient set in a register (not shown). Do.

  The lens movement control for correcting the shake of the subject due to the camera shake using the image stabilization control circuit 10 shown in FIG. 1 will be described.

  First, a case where there is no subject shake due to camera shake will be described. Since the optical axis of the lens driven by the lens driving element 300 coincides with the center of the image sensor provided in the image pickup apparatus, the ADC 12 outputs a digital position signal SP indicating “0”. When the value of the position signal SP is “0”, the servo circuit 20 outputs a correction signal SR for controlling the lens driving element 300 so as to maintain the current lens position.

  If the lens position does not match the center of the image sensor, the ADC 12 outputs a digital position signal SP indicating a value different from “0”. The servo circuit 20 outputs a correction signal SR for controlling the lens driving element 300 so that the value of the position signal SP becomes “0” according to the value output from the ADC 12. By repeating the above operation, the lens position is controlled so that the lens position and the center of the image sensor coincide.

  Next, a case where the subject shakes due to camera shake will be described. Since the optical axis of the lens driven by the lens driving element 300 coincides with the center of the image sensor provided in the image pickup apparatus, the ADC 12 outputs a digital position signal SP indicating “0”. On the other hand, since the image pickup apparatus moves due to camera shake, the integration circuit 50 and the centering processing circuit 52 output an angle signal indicating the amount of movement of the image pickup apparatus based on the angular velocity signal detected by the vibration detection element 400.

  The servo circuit 20 generates a correction signal SR according to a signal obtained by adding the position signal SP indicating “0” output from the ADC 12 and the angle signal output from the centering processing circuit 52. At this time, although the position signal SP is “0”, since the angle signal that is not “0” is added, the servo circuit 20 generates the correction signal SR for moving the lens. Since the lens driving element 300 moves the lens based on the correction signal SR output from the servo circuit 20, the image pickup element provided in the image pickup apparatus can obtain a signal in which blurring of the subject due to camera shake is suppressed. By repeating such control, the image stabilization control circuit 10 realizes camera shake correction control.

In the embodiment of the present invention, when generating an angle signal indicating the amount of movement of the imaging device from the angular velocity signal obtained from the vibration detection element 400, the HPF 44, the integration circuit 50, and the centering processing circuit 52 are used to generate the angle signal. . As a result, it is not necessary to use a CPU for generating an angle signal, and power consumption in the image stabilization control circuit 10 can be reduced.

  In the embodiment of the present invention, the image stabilization control circuit 10 includes the HPF 44, the integration circuit 50, and the centering processing circuit 52, so that the circuit area can be reduced as compared with the configuration in which the CPU is provided. . As a result, the cost of the semiconductor chip on which the image stabilization control circuit 10 is mounted can be reduced.

  In the embodiment of the present invention, the servo circuit 20, the HPF 44, the integration circuit 50, and the centering processing circuit 52 provided in the image stabilization control circuit 10 include a digital filter circuit. In the prior art shown in FIG. 2, since the servo circuit 120 is configured to include an analog filter circuit, external components such as a resistance element and a capacitor are required. When the filter coefficient of the servo circuit 120 is changed in order to adjust the control characteristics of the conventional image stabilization control circuit 100, it is difficult to change the filter coefficient easily because external parts must be replaced. However, in the image stabilization control circuit 10 of the present invention, when changing the filter coefficient, the filter coefficient stored in a register such as the register 22 may be changed, and the control characteristics of the image stabilization control circuit 10 can be easily adjusted. be able to.

  In the embodiment of the present invention, the position detecting element 200, the lens driving element 300, and the vibration detecting element 400 are a hall element, a voice coil motor, and a gyro sensor, respectively, but the present application is not limited thereto. For example, the lens driving element 300 can be a stepping motor or a piezo element. When a stepping motor is used as the lens driving element 300, a stepping motor can also be used as the position detection element 200. The lens is driven by the stepping motor, and the control signal of the stepping motor can be used as a signal indicating the position of the lens. it can. Further, the vibration detection element 400 can be configured to detect vibration of the imaging device based on an acceleration signal using a sensor that detects acceleration in a linear direction.

  In the embodiment of the present invention, the lens shift method is performed in which the lens is driven to perform the camera shake correction process. However, the present invention is not limited to this. For example, the present invention can also be applied to a CCD shift method in which an image pickup device such as a CCD device is shifted according to the shake of the image pickup apparatus. At this time, the position detection element 200 can detect the position of the imaging element, and the lens driving element 300 (the optical component driving element described in the claims) can be an element that drives the imaging element.

It is a schematic block diagram of the image stabilization control circuit of embodiment of this invention. FIG. 10 is a schematic block diagram of a conventional image stabilization control circuit.

Explanation of symbols

  10, 100 Anti-vibration control circuit, 12, 42, 142 ADC, 20, 120 Servo circuit, 22 registers, 30, 162 DAC, registers, 40, 140 Lens driver, 44 HPF, 46 Pan / tilt determination circuit, 48 Gain adjustment Circuit, 50 integrating circuit, 52 centering processing circuit, 1200 position detecting element, 300 lens driving element, 400 vibration detecting element.

Claims (4)

An image stabilization control circuit that controls an optical component driving element that moves an optical component provided in the imaging apparatus based on a signal output from a vibration detection element provided in the imaging apparatus,
An analog-digital conversion circuit that converts an analog signal output from the vibration detection element into a digital signal;
A high pass filter for removing low frequency components of the digital signal;
A movement amount calculation circuit for calculating a movement amount of the imaging device based on a signal output from the high-pass filter;
A servo circuit that generates a correction signal for correcting the position of the optical component based on the output signal of the movement amount calculation circuit and outputs the correction signal to the optical component driving element;
And the high-pass filter includes a digital filter circuit and a register, and the digital filter circuit performs a filtering process based on a filter coefficient stored in the register. In the image stabilization control circuit according to claim 1,
The movement amount calculation circuit includes a digital filter circuit and a register, and the digital filter circuit performs a filter process based on a filter coefficient stored in the register. In the image stabilization control circuit according to claim 1,
A pan / tilt determination circuit that compares a signal output from the high-pass filter with a predetermined threshold value and determines the presence or absence of a pan operation or a tilt operation according to the comparison result;
An amplifying circuit for amplifying a signal output from the high-pass filter;
The image stabilization control circuit, wherein the amplification circuit changes an amplification factor according to a determination result of the pan / tilt determination circuit. In the image stabilization control circuit according to claim 1,
An anti-vibration control circuit further comprising a centering processing circuit that subtracts a predetermined value from the output signal of the movement amount calculation circuit and outputs the result to the servo circuit.

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