A new two-DOF rotational optical image stabilizer

Abstract

This work proposes design, optimization and validation of a new two degree-of-freedom (DOF) rotational optical image stabilizer (OIS) that is suitable for installing into a mobile-phone-camera. This OIS differs from the previous designs since it stabilizes the lens holder directly by two-DOF translational mechanisms that are actuated by voice coil motors. The work can be divided into three main parts: (1) designs of mechanism and genetic algorithm (GA) optimization of magnetic field, (2) establishments of the dynamic model and equation of motions (EOM) of a dual-axis rotational structure, and (3) realizations of a sliding mode control (SMC) controller with fine performance. The dynamic of the dual-axis rotational OIS system has been analyzed and the EOM has been derived. Based on the Lagrange's method, the motions of the OIS have been modeled through considering kinetic energy and electromagnetic torques. In the last part, the theory of SMC is applied, and the associated simulations are conducted. Based on the simulation results, the SMC controller is forged with the assistances from MATLAB pre-simulation and tested by a microprocessor module. After a series of experiments and verifications, the prototype of the novel OIS is finally accomplished with satisfactory performance of vibration reduction.

Control Design and Digital Implementation of a Fast 2-Degree-of-Freedom Translational Optical Image Stabilizer for Image Sensors in Mobile Camera Phones

“…The basic optical principle underlying OIS is illustrated in Figure 3 , where the movement of the lens and image sensor due to hand shaking are exaggerated for the sake of clarity [ 13 , 16 ]. Note that hand shaking by users while shooting photos on a camera phone induces not only translational but also rotational movements in all six DOFs of the camera.…”

“…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 ]. On the other hand, OIS equips the lens in the camera with mechanical suspension and the associated actuating voice coil motors to move the lens fast enough to compensate for image blurs [ 2 , 9 , 10 , 11 , 12 , 13 , 14 ]. As compared to DIS, OIS tries to eliminate image blurs based on basic optics rather than working on imaged digital pixel data as DIS does.…”

“…Thus, OIS remains viable as an important technology, even with DIS also applied, to tackle the image blur caused by hand shaking as long as the performance of the designed OIS can meet the required specifications [ 11 ]. According to their different image stabilization goals, varied OIS structures have been proposed, such as, translational [ 9 , 12 ], rotational [ 13 ] as well as a special one using a deformable freeform mirror [ 14 ]. The study herein focuses on the translational OIS, since it is most suitable for compensating for the disturbances caused by hand shaking on a mobile phone camera, which is mostly translational.…”

“…Compared to all prior reported works, the work presented herein is the first to design a simple lead-lag controller based on complete, complicated nonlinear equations of motion of the OIS, especially including the coupling dynamics between different DOFs being treated as uncertainties during control design. Furthermore, the designed lead-lag controller is easy to implement by using an FPGA chip that is capable of achieving a faster response with the required precision than those reported in prior works [ 9 , 12 , 13 , 15 ].…”

Design and Simulation of Novel 3-DOF Spherical Voice Coil Motor

“…To provide these functions, voice coil motors (VCMs) or voice coil actuators (VCAs) have been widely used because they afford advantages such as a simple structure, compact size, high positioning accuracy, and high power efficiency [8,9]. VCMs with 1-and multi-DOF motion have been developed to realize 1-DOF AF [10][11][12][13], 2-DOF OIS [14][15][16][17][18], 2-DOF OZ [7], 3-DOF AF/OIS [19], and 5-DOF AF/OIS [9]. However, these VCMs have a cubic shape, which limits their scope of application.…”