KR20100079701A - Digital camera having improved control-performance for driving mechanism - Google Patents

Abstract

PURPOSE: A digital camera having control feature which improved about dynamic device is provided to adaptively change wave form of a driving signal according to a current operation mode. CONSTITUTION: An actuator drives a dynamic implement unit. A PWM(Pulse Width Modulation) driving control unit(160) includes a control unit(161), a voltage adjusting unit(163), and PWM signal generation unit(165). The PWM driving control unit sanctions a PWM driving signal to the actuator. The PWM driving control unit changeably controls on voltage and duty ratio of the PWM driving signal.

Description

Digital camera having improved control-performance for driving mechanism

The present invention relates to a digital camera, and more particularly, to a digital camera capable of adaptively varying a waveform of a driving signal according to a current operation mode in consideration of a driving force and a control resolution.

With recent advances in technology, digital reduction is possible by moving the lens or image sensor to perform dust reduction, and by moving the lens or image sensor with the information of the gyro sensor for human hand movement to obtain a shake-free image. Cameras are being developed. The DAC (Digital to Analog Converter) or PWM (Pulse Width Modulation) method is used to move a lens or an image sensor.

According to the control method, when the voltage level of the power stage input to the DAC or PWM device is low, the control resolution may be increased, but the driving power is low, and the power stage input to the DAC or PWM device is reduced. If the voltage level is high, the driving force is high but the control resolution is low.

SUMMARY OF THE INVENTION An object of the present invention is to provide a digital camera capable of adaptively varying a waveform of a driving signal according to a current operation mode in consideration of a driving force and a control resolution.

In order to achieve the above object and other objects, the digital camera of the present invention,

An actuator for driving the dynamic mechanism; And

And applying a PWM driving signal to the actuator, wherein the PWM driving control unit variably controls an on voltage and a duty ratio of the PWM driving signal.

In one embodiment of the present invention, the PWM drive control unit,

A controller configured to output a first control signal and a second control signal relating to a target on voltage and a target duty ratio;

A voltage adjusting unit outputting a variable voltage according to the first control signal; And

And a PWM signal generator for adjusting an on voltage according to the variable voltage and adjusting a duty ratio of the PWM driving signal according to the second control signal.

In one embodiment of the present invention, the dynamic mechanism unit includes at least one of a lens unit into which the image of the subject is introduced, and an image sensor for capturing the image of the subject.

Preferably, the PWM drive control unit adjusts the on voltage of the PWM drive signal according to the current operation mode. At this time, the on voltage Von1 of the first operation mode requiring precise control of the dynamic mechanism and the on voltage Von2 of the second operation mode requiring a rapid response or a large movement amount of the dynamic mechanism are Von1 <Von2. It is desirable to satisfy the relationship of.

For example, the first operation mode includes an image stabilization mode for compensating for camera shake, and the second operation mode includes a vibration mode for removing foreign matter on the lens surface.

According to the digital camera of the present invention, in driving a dynamic mechanism such as a lens unit or an image sensor, the waveform of the drive signal is optimized in consideration of the driving force point and the control resolution point. Accordingly, the waveform of the drive signal can be adaptively changed according to the current operation mode by increasing the voltage level of the drive signal in an environment requiring driving force and lowering the voltage level of the drive signal in an environment requiring precise control resolution. .

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Through this specification, a digital camera is designed to be suitable for a mobile environment so that a user can carry and move, and as a mobile device having an appropriate photographing function, it simply means a negotiated camera classified based on a morphological feature called a camera. In addition, it is used in a broad sense to encompass all mobile devices that combine portability and shooting functions such as camcorders, mobile phones, PDAs, and the like.

1 is a block diagram showing the overall structure of a digital camera according to a preferred embodiment of the present invention. Referring to the drawings, the digital camera includes a lens unit 110 for forming an image of a subject on an image pickup surface, and an image sensor 120 for converting an image of the subject via the lens unit 110 into an electric image signal. ), An analog front end (AFE) circuit for processing the output signal of the image sensor 120 and converting it into a quantized digital video signal, and temporarily converting the video signal to provide a working area for image processing. Dynamic Random Access Memory (DRAM) 140, a recording medium 135 in which image data of a subject is stored in the form of a still image or a video file, and a digital signal processor which collectively controls the overall data flow and each component ( 150, Digital Signal Processor).

The lens unit 110 includes a zoom lens (not shown) for moving back and forth along the optical axis direction and changing a focal length, or a focus lens (not shown) for adjusting the focus of an image of an image formed on the image sensor 120. can do. The image sensor 120 is, for example, a Charged Coupled Device (CCD) or a Complementary Metal Oxide Semiconductor (CMOS) image sensor, and converts an image of a subject incident through the lens unit 110 into an electrical image signal. do. The lens unit 110 and the image sensor 120 are moved on a vertical plane of the optical axis and fixed to an image forming position of the subject in order to compensate for the shaking of the image caused by the hand shake according to the driving of the VCM motor 170 (Voice Coil Motor). The state can perform stable stabilization (OIS) operations. In addition, the lens unit 110 and the like may perform a vibration operation forcibly dropping these substances attached to the lens surface while vibrating at a high frequency according to the driving force of the VCM motor 170. The lens unit 110 and the image sensor 120 are dynamic mechanisms driven by the driving of the VCM motor 170, and become subjects to perform image stabilization, and perform vibration to effectively remove dust or the like attached to the lens surface. Can be removed However, in the illustrated embodiment, both the lens unit 110 and the image sensor 120 are illustrated as a dynamic mechanism to be driven by the VCM motor 170, but this is not intended to limit the technical scope of the present invention. For example, even if only one of the lens unit 110 or the image sensor 120 is configured as a dynamic mechanism, the technical principles of the present invention may be applied in the same manner. In addition, the VCM motor 170 is an example of an actuator for driving a dynamic mechanism, it may be made of a pair of a drive coil and a magnet (not shown), other than a VCM motor 170, such as a DC motor or a step motor Of course, a kind of actuator may be applied.

The analog front-end circuit 125 (AFE circuit) outputs from the image sensor 120 by performing a correlated double sampling (CDS) process and an analog digital conversion (ADC) process on the output signal of the image sensor 120. The analog image signal is converted into a digital image signal. The digital video signal is transmitted to the encoder / decoder 130, converted into encoded data according to a prescribed compression method, and stored in the recording medium 135. The DRAM 140 or SDRAM provides a work area for data processing of the encoder / decoder 130 and the digital signal processor 150.

The digital signal processor 150 executes a program recorded in the EEPROM (155, Electrically Erasable and Programmable ROM), and collectively controls each component of the digital camera. In particular, the digital signal processor 150 functions to control the operation of the dynamic unit such as the lens unit 110 and / or the image sensor 120 via the PWM driving controller 160.

In connection with an OIS operation for image stabilization, the digital camera includes a gyro sensor 191, a hall sensor 181, and a gyro filter 193 and a hall filter 183 disposed at an output side thereof. The gyro sensor 191 detects each speed of the camera with respect to the horizontal axis and the vertical axis, and extracts only the necessary components through the gyro filter 193 having a selection characteristic for a specific band. Then, the amount of shaking of the camera is calculated and then transferred to the digital signal processor 150 through proper integration processing in the arranged calculator 195. The hall sensor 181 detects a coordinate value of the current position of the lens unit 110 or the image sensor 120, which is the same as below. The detection signal of the current position removes a noise component. It is delivered to the digital signal processor 150 through.

The digital signal processor 150 captures the shake amount output from the gyro sensor 191, calculates a target position of the lens unit 110 to cancel the captured shake, and is output from the hall sensor 181. The control signal corresponding to the difference between the target position and the current position is output to the PWM driving controller 160 according to the result of comparison with the current position of the lens unit 110.

2 shows a detailed configuration of the PWM drive control unit 160. Referring to the drawing, the PWM drive controller 160 generates a PWM drive signal to be output to the VCM motor 170, and includes a controller 161, a voltage adjuster 163, and a PWM signal generator 165. . The controller 161 calculates a target voltage and a target duty ratio of the PWM driving waveform to be output to the VCM motor 170 according to the instructions of the digital signal processor 150. The first control signal defining the target voltage is output to the voltage adjusting unit 163, and the second control signal defining the target duty ratio is output to the PWM signal generator 165. The voltage adjustor 163 generates a variable voltage proportional to the first control signal and outputs the variable voltage to the PWM signal generator 165. The PWM signal generator 165 generates a PWM driving signal having a target voltage and a target duty by using a second control signal indicating a target duty and a variable voltage of the voltage adjusting unit indicating the target voltage. Although not shown in the drawing, for example, the PWM signal generator 165 inputs an analog sine wave having a frequency proportional to the second control signal as a signal waveform and a triangular wave with a constant frequency as a carrier waveform to the comparator. The switching element connected to the driving power source is turned on / off according to the magnitude relationship. At this time, the PWM driving signal having the target duty ratio and the target voltage can be generated by utilizing the variable voltage from the voltage adjusting unit as the driving power source.

According to the digital camera of the present invention, by varying both the duty ratio and the voltage level of the PWM driving signal applied to the VCM motor 170, it is possible to optimize the driving environment according to the current requirements. For example, when a dynamic mechanism such as the lens unit 110 needs to be moved at a rapid speed or needs to increase the stroke, the response level of the drive and the stroke are increased by increasing the voltage level of the PWM driving signal and maximizing the driving force. Can kill. On the other hand, when it is necessary to precisely control the dynamic mechanism such as the lens unit 110, it is possible to improve the control resolution by minimizing the voltage level of the PWM drive signal, thereby enabling precise control.

If the voltage level of the PWM drive signal is fixed at a constant constant voltage, i.e., if the power stage generating the PWM drive signal is fixed, the control resolution of the control signal (e.g., the second control signal) for adjusting the duty ratio is fixed. It is limited to n bits, and the amount of movement per unit bit cannot be controlled more precisely. In addition, depending on the voltage level of the fixed power supply stage, despite the maximum n bit (full bit) control signal (ex. Second control signal), the dynamic mechanism does not reach the required stroke or the response performance. There is also the problem of not meeting this requirement. In the present invention, since the duty ratio of the PWM drive signal as well as the voltage level can be varied in accordance with the required driving conditions, sufficient driving force and precise control resolution can be selected according to the requirements. By changing, the effect of reducing power consumption can also be obtained.

As an operation mode for operating the dynamic mechanism of the lens unit 110 or the image sensor 120, an OIS mode for image stabilization and a vibration mode for removing foreign matter attached to the optical lens may be exemplified. The OIS mode is an operation mode for fixing an imaging position of a subject while moving a dynamic object to compensate for shaking of an image generated by hand shaking. The vibration mode is an operation mode for forcibly removing the foreign matter attached to the lens surface by vibrating the dynamic mechanism quickly.

The controller 161 checks the current operation mode, and if it is determined that the OIS mode, the controller 161 lowers the on voltage of the PWM driving signal so that the dynamic mechanism can be controlled with high resolution. In the OIS mode, it is essential to precisely control the instrument to the target position in order to detect and compensate for minute hand shake. Therefore, it is desirable to increase the control resolution per unit bit of the control signal by lowering the on voltage of the PWM driving signal. will be. 3 shows the amount of movement of the dynamic instrument according to the number of bits of the control signal. The profiles S1 and S2 respectively show the amount of movement of the dynamic instrument when the on voltage is controlled to low voltage / high voltage. Comparing the movement amount per unit bit, it can be seen that the movement amount d1 at the low voltage is much smaller than the movement amount d2 at the high voltage. That is, the control resolution per unit bit can be improved by adjusting the on voltage of the PWM driving signal to a low voltage.

In the vibration mode, it is required to drive the lens unit 110 at a high frequency and a large amount of movement per unit time for the purpose of preventing optical interference due to the foreign matter by removing the foreign matter attached to the lens surface. That is, in the vibration mode, it is desirable to increase the speed and driving force per unit bit by increasing the on voltage of the PWM driving signal to actively vibrate the dynamic mechanism. As can be seen in FIG. 3, it can be seen that the movement amount per unit bit of the control signal is much larger at the high voltage d2 than at the low voltage d1, and the driving force per unit bit can be increased accordingly.

In conclusion, according to the current operation mode, the controller 161 achieves precise driving control by lowering the on voltage of the PWM driving signal in the OIS mode, and the on voltage of the PWM driving signal in the vibration mode. By increasing, it is possible to maximize the driving force applied to the dynamic mechanism.

Although the present invention has been described with reference to the embodiments illustrated in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

1 is a block diagram showing the overall configuration of a digital camera according to a preferred embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of the PWM driving controller shown in FIG. 1.

3 is a diagram showing the amount of movement of the dynamic mechanism according to the number of bits of the control signal, each showing the amount of movement when the on voltage of the PWM is adjusted to a low voltage / high voltage.

<Explanation of symbols for the main parts of the drawings>

110: lens unit 120: image sensor

125: analog front end circuit 130: encoder / decoder

135: recording medium 140: DRAM

150: digital signal processor 155: EEPROM

160: PWM drive control unit 161: control unit

163: voltage adjusting unit 165: PWM signal generating unit

170: VCM motor 181: Hall sensor

183 Hall Filter 191 Gyro Sensor

193: gyro filter 195: operator

Claims (6)

An actuator for driving the dynamic mechanism; And And a PWM driving controller for applying a PWM driving signal to the actuator to variably control an on voltage and a duty ratio of the PWM driving signal. The method of claim 1, The PWM drive control unit, A controller configured to output a first control signal and a second control signal relating to a target on voltage and a target duty ratio; A voltage adjusting unit outputting a variable voltage according to the first control signal; And And a PWM signal generator for adjusting an on voltage according to the variable voltage and adjusting a duty ratio of the PWM driving signal according to the second control signal. The method of claim 1, The dynamic mechanism unit comprises at least one of a lens unit into which the image of the subject is introduced, and an image sensor for capturing the image of the subject. The method of claim 1, And the PWM driving controller adjusts an on voltage of the PWM driving signal according to a current operation mode. The method of claim 4, wherein The on voltage Von1 of the first operation mode requiring precise control of the dynamic mechanism part and the on voltage Von2 of the second operation mode requiring a rapid response or large amount of movement of the dynamic mechanism part have a relationship of Von1 <Von2. Digital camera, characterized in that to satisfy. The method of claim 5, The first operation mode includes an image stabilization mode for compensating for camera shake, and the second operation mode includes a vibration mode for removing foreign matter on the lens surface.

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