Abstract:
A method of offset compensation for solid-state imaging devices is provided. In the method a first and second detection signal are obtained. The two signals are compared to obtain a difference value. A variable voltage is output according to the difference value to drive a magnetic element. The solid-state imaging device is moved by the magnetic element to compensate the offset of the solid-state imaging device. A system of offset compensation of the solid-state imaging device is also disclosed.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a system and method for compensating offset of a solid-state imaging device, and more particularly to a system and method for compensating offset of a solid-state imaging device used in a camcorder. 
     2. Description of the Related Art 
     Generally, a vibration problem exists in camcorders, particularly in lightweight digital cameras. While a shutter button is pressed, a user may cause camera vibration due to shaking hands or pressure on the shutter button. Thus, user instability may result in blurry images. 
     A camcorder typically has an angular velocity sensor and a position sensor to detect moving angle variation and position variation while the camcorder operates, and to generate corresponding sensing signals respectively. The angular velocity sensor, such as a gyro sensor, detects variation of angle, angular velocity, or angular acceleration while the camcorder operates. The position sensor, such as Hall effect sensor, is used to detect position variation while the camcorder operates. Subsequent to movement amount detection by the sensors, detected data can be calculated to determine the required compensating movement. Compensating for the direction and amount of movement through a set of compensating lens can thus eliminate vibration. This method, however, requires at least two sensors, and must work with the set of compensating lens. The described design, however, is both difficult to implement and expensive to produce. 
     Thus, a reduced cost compensation system capable of eliminating blur from vibration is desirable. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention provides a system and method of offset compensation for solid-state imaging devices capable of eliminating blur due to camcorder vibration. 
     One embodiment, according to the invention, provides a system of offset compensation for solid-state imaging devices. The system comprises a sensor, a calculating circuit, a delay circuit, an auto-control device, a driving device, and a magnetic element. The sensor, coupled to a solid-state imaging device, is configured to continuously detect the solid-state imaging device to generate a sensing signal. The calculating circuit is configured to receive and process the sensing signal to generate a first signal. The delay circuit is configured to delay the first signal to generate a second signal. The auto-control device is configured to receive and compare the first and second signals to obtain an error value, and to output an error-control signal according to the error value. The driving device is configured to receive the error-control signal, and to generate an electric signal according to the error-control signal. The electric signal drives the magnetic element for generating magnetic force to move the solid-state imaging device, thus offset of the solid-state imaging device is compensated. 
     Another embodiment of the invention, provides a method of offset compensation for solid-state imaging devices. The method comprises obtaining a first sensing signal, wherein the first sensing signal is first movement data of a solid-state imaging device. Next, a second sensing signal is obtained, wherein the second sensing signal is second movement data of a solid-state imaging device. Next, the first and second sensing signals are compared to obtain an error value representing an offset value of the solid-state imaging device. Next, an electric signal is output according to the error value to drive a magnetic element. Finally, the magnetic element is utilized to move the solid-state imaging device for compensating the offset value of the solid-state imaging device. 
     The system and method of the invention provide a simplified and low cost optical anti-vibration effect for reducing blur resulting from movement while capturing images. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
         FIG. 1  shows a system of offset compensation for solid-state imaging devices; 
         FIG. 2  shows an embodiment of a system of offset compensation for solid-state imaging devices of the invention; 
         FIG. 3  shows another embodiment of a system of offset compensation for solid-state imaging devices of the invention; 
         FIG. 4  shows another embodiment of a system of offset compensation for solid-state imaging devices of the invention; 
         FIG. 5  shows another embodiment of a system of offset compensation for solid-state imaging devices of the invention; and 
         FIG. 6  shows another embodiment of a method of offset compensation for solid-state imaging devices of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a system of offset compensation for solid-state imaging devices. The system is used in a camcorder  100 , which comprises a sensor  102 , a calculating circuit  104 , a delay circuit  106 , an auto-control device  108 , a driving device  110 , and a magnetic element  112 . Sensor  102 , coupled to a solid-state imaging device  114 , is configured to continuously detect the variation of movement data to generate a sensing signal while the solid-state imaging device  114  operates. Sensor  102  can be a dip sensor or an acceleration sensor. The solid-state imaging device  114  can be a charge-coupled device (CCD). Calculating circuit  104  is configured to receive and process the sensing signal output from sensor  102  to output a calculating signal, wherein calculating circuit  104  can be an integrator, a differentiator, or a multiplier. Delay circuit  106  is configured to postpone the calculating signal output from calculating circuit  104 , and to provide a delay signal for comparison with the calculating signal. Auto-control device  108  receives an error value and outputs an error-control signal according to the error value. The error value is obtained by comparing a calculating signal output from calculating circuit  104  with a delay signal. The delay signal is a previous calculating signal output from delay circuit  106 . Auto-control device  108  can be a proportional-integral-derivative (PID) controller. Driving device  110  receives the error-control signal output from auto-control device  108  and generates a variable voltage or a pulse-width-modulation (PWM) signal according to the error-control signal. Driving device  110  can be a motor driver. Magnetic element  112  generates magnetic force according to the variable voltage output from driving device  110  for compensating the solid-state imaging device  114 . The magnetic element  112  can be an induction coil. 
       FIG. 2  shows an embodiment of a system of offset compensation for solid-state imaging devices. In this embodiment, camcorder  200  uses a dip sensor, such as gyro sensor  202 , to detect the angular variation of CCD  204 . When detecting the angular acceleration of CCD  204  for error comparison, gyro sensor  202  continuously detects the movement of CCD  204  to output an angular speed signal. The angular speed signal is passed to differentiator  206  for conversion to an angular acceleration signal. The angular acceleration signal is compared with its previous angular acceleration signal delayed by delay circuit  210  to obtain an angular acceleration error value. PID controller  208  outputs a PWM signal according to the angular acceleration error value. Motor driver  212  generates a variable voltage according to the PWM signal to drive induction coil  214 . Induction coil  214  induces magnetic force to move CCD  204  for compensating the offset of CCD  204  due to vibration. 
       FIG. 3  shows an embodiment of a system of offset compensation for solid-state imaging devices. In this embodiment, camcorder  200   a  also uses gyro sensor  202  to detect the angular variation of CCD  204 . When detecting the angular speed of CCD  204  for error comparison, gyro sensor  202  continuously detects the movement of CCD  204  to output an angular speed signal. The angular speed signal is multiplied by a constant through multiplier  306  to modify the angular speed signal within a specific range. Subsequently, the angular speed signal is compared with its previous angular speed signal delayed by delay circuit  210  to obtain an angular speed error value. PID controller  208  receives the angular speed error value and outputs a PWM signal according to the angular speed error value. Motor driver  212  generates a variable voltage according to the PWM signal to drive induction coil  214 . Induction coil  214  induces magnetic force to move CCD  204  for compensating the offset of CCD  204  due to vibration. 
       FIG. 4   a  shows an embodiment of a system of offset compensation for solid-state imaging devices. In this embodiment, camcorder  200   b  uses acceleration sensor  402  to detect the position variation of CCD  204 . When detecting the speed of CCD  204  for error comparison, acceleration sensor  402  continuously detects the movement of CCD  204  to output an acceleration signal. Integrator  406  receives and calculates the acceleration signal to output a speed signal. The speed signal is subsequently compared with its previous speed signal delayed by delay circuit  210  to obtain a speed error value. PID controller  208  receives the speed error value and outputs a PWM signal according to the speed error value. Motor driver  212  generates a variable voltage according to the PWM signal to drive induction coil  214 . Induction coil  214  induces magnetic force to move CCD  204  for compensating the offset of CCD  204  due to vibration. 
       FIG. 5  shows an embodiment of a system of offset compensation for solid-state imaging devices. In this embodiment, camcorder  200   c  also uses acceleration sensor  402  to detect the position variation of CCD  204 . When detecting the acceleration of CCD  204  for error comparison, acceleration sensor  402  continuously detects the movement of CCD  204  to output an acceleration signal. The acceleration signal is multiplied by a constant through multiplier  506  to modify the acceleration signal within a specific range. The acceleration signal is subsequently compared with its previous acceleration signal delayed by delay circuit  210  to obtain an acceleration error value. PID controller  208  receives the speed error value and outputs a PWM signal according to the speed error value. Motor driver  212  generates a variable voltage according to the PWM signal to drive induction coil  214 . Induction coil  214  induces magnetic force to move CCD  204  for compensating the offset of CCD  204  due to vibration. 
       FIG. 6  shows an embodiment of a method of offset compensation for solid-state imaging devices. In the method, a sensing signal is obtained though a sensor, by continuously detecting the movement variation of a solid-state imaging device while operating (step  600 ). The sensing signal is the movement variation data of a solid-state imaging device, and the solid-state imaging device can be a CCD. The sensor subsequently obtains another sensing signal (step  602 ) for comparison with the previous sensing signal. When a dip sensor is used, such as gyro sensor, to detect the movement variation, both sensing signals can be angular speed signals or angular acceleration signals. When an acceleration sensor is used to detect the movement variation, both sensing signals can be speed signals or acceleration signals. 
     Two sensing signals, subsequently generated at different times, are compared to obtain an error value representing an offset of the solid-state imaging device (step  604 ). An error-control signal is output corresponding to the error value for compensation (step  606 ), for example, outputting a PWM signal by a PID controller. Additionally, a variable voltage or a PWM signal is generated according to the error-control signal to drive a magnetic element (step  608 ). The magnetic element can be an induction coil. Finally, the solid-state imaging device is shifted by magnetic force induced from the magnetic element for compensating the offset of the solid-state imaging device (step  610 ). At this point, if the solid-state imaging device has not been compensated completely so as to return to its original position, the method returns to step  602  to obtain another sensing signal for comparison until compensation is complete. 
     The system and method of offset compensation for solid-state imaging devices provides an optical anti-vibration effect for reducing blurry images resulting from vibration while capturing images. The anti-vibration design is simplified and can reduce production costs. 
     While the invention has been described by way of examples and in terms of preferred embodiments, it is to be understood that the invention is not limited thereto. Any variation or modification can be made by those skilled in art without departing from the spirit or scope of the invention. Therefore, the scope of the appended claims should be accorded the broadest interpretation to encompass all such modifications and similar arrangements.