Abstract
This study presents design, digital implementation and performance validation of a lead-lag controller for a 2-degree-of-freedom (DOF) translational optical image stabilizer (OIS) installed with a digital image sensor in mobile camera phones. Nowadays, OIS is an important feature of modern commercial mobile camera phones, which aims to mechanically reduce the image blur caused by hand shaking while shooting photos. The OIS developed in this study is able to move the imaging lens by actuating its voice coil motors (VCMs) at the required speed to the position that significantly compensates for imaging blurs by hand shaking. The compensation proposed is made possible by first establishing the exact, nonlinear equations of motion (EOMs) for the OIS, which is followed by designing a simple lead-lag controller based on established nonlinear EOMs for simple digital computation via a field-programmable gate array (FPGA) board in order to achieve fast response. Finally, experimental validation is conducted to show the favorable performance of the designed OIS; i.e., it is able to stabilize the lens holder to the desired position within 0.02 s, which is much less than previously reported times of around 0.1 s. Also, the resulting residual vibration is less than 2.2–2.5 μm, which is commensurate to the very small pixel size found in most of commercial image sensors; thus, significantly minimizing image blur caused by hand shaking.
Highlights
Image stabilization (IS) technology [1,2,3] has been considered essential for delivering high image quality with minimized image blur in professional cameras
Hz,simulated which inresponse fact correspond the main harmonics of common relative to ground with the lead-lag controller designed and applied to both the x- and y-direction of hand shakings
optical image stabilizer (OIS), andstarted was followed by designing a simple lead-lag controller based on of motion (EOMs) for the OIS, and was followed by designing a simple lead-lag controller based on this nonlinear model, in order to take advantage of simple digital computation via a field-programmable gate array (FPGA) board to this nonlinear model, in order to take advantage of simple digital computation via a FPGA board to
Summary
Image stabilization (IS) technology [1,2,3] has been considered essential for delivering high image quality with minimized image blur in professional cameras. The image blurs are usually caused by the inevitable motion of the camera while shooting. This IS technology has been applied to mobile phone cameras to reduce image blur and for meeting new customer demands in the industrial field [1,2,3]. DIS technology employs varied techniques of digital image processing to reduce image blurs caused by hand shaking while shooting photos [1,3,4,5,6,7,8]. OIS remains viable as an important technology, even with DIS applied, to tackle the image blur caused by hand
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