Myeong-Gyu Song

Design of a Voice-Coil Actuator for Optical Image Stabilization Based on Genetic Algorithm

In this paper, a design method based on genetic algorithm is proposed. Proposed design method is useful for inexperienced engineers to select a concept design and it also offers optimized result. A voice-coil actuator for optical image stabilization system in mobile phone camera is designed by using this method. To reduce the size, the optical image stabilization system is integrated with auto-focusing module and the Hall Effect sensor shares a magnet with a voice-coil. Combined electromagnetic analysis is used to reduce computing time. The final design from genetic algorithm is fabricated and verified experimentally. Experiment result shows that combined electromagnetic analysis is reliable and the final design has good performance.

Development of Small Sized Actuator With Compliant Mechanism for Optical Image Stabilization

In this paper, a voice-coil actuator for OIS integrated in mobile phone camera is developed. The actuator with compliant mechanism is free from friction, so open loop control becomes possible and the performance of optical image stabilization can be improved. The compliant mechanism that consist 4 wires is designed for the OIS actuator and the electromagnetic part is also design and improved by using design of experiments. After all, the final design is fabricated and verified experimentally. The experiment result shows that the developed actuator has sufficient performance and good linearity for open loop control.

Effects of motion of an imaging system and optical image stabilizer on the modulation transfer function

This paper analyzes the effects due to the angular motion of a small-sized imaging system equipped with an optical image stabilizer (OIS) on image quality. Accurate lens moving distances for the OIS required to compensate the ray distortion induced by the angular motion are determined. To calculate the associated modulation transfer function, the integrated and the compensated point spread functions are defined. Finally, the deterioration of the image resolution due to angular motion and the restorative performance of the OIS are analyzed by isolating seven types of angular motion.

Development of small sized actuator for optical image stabilization

In this paper, 2-axis voice coil actuator of optical image stabilization which is a technique to compensate a trembling of camera caused by a vibration of users hand is suggested. The actuator is designed for mobile phone camera. Considering total size and application of auto focusing module, the concept of the moving auto-focusing module is selected for optical image stabilization. The handshake of mobile phone is measured to define the specification of the actuator. Two kinds of 2-axis mechanisms made of two prismatic joints are designed and united the electromagnetic part which is already designed. Finally, two types are fabricated and verified experimentally.

Improvement of Dynamic Characteristics for Symmetric-Type Slim Optical Pickup Actuator by Changing Coil Shape

As rotational speed and track density of disk media in optical disk drives increases, an optical pickup actuator must have a high servo bandwidth for its focusing and tracking control to follow disk fluctuations. In this paper, we propose an efficient method to improve control bandwidth of actuators through changing the shape of cross section of coils without redesigning structural parts

Optimal Design of Moving-Magnet Type Actuators for Optical Disk Drives Considering Effect of Coil Electromagnet

This paper suggests a method for analyzing moving-magnet type actuators for optical pickups. To move the objective lens to the desired position, voice coil actuators use the electromagnetic force, which is the force exerted on a charge moving in a magnetic field. When an electric current passes through a coil, the coil becomes an electromagnet by the solenoid effect. This causes the force between a coil electromagnet and a permanent magnet. The force affects flexible modes of voice coil actuators because it is dynamic force with the frequency same as that of a driving current. Therefore, the analysis, which considers both the electromagnetic force and that between a coil electromagnet and a permanent magnet, is suggested. The moving-magnet-type actuator is fabricated and its dynamic behaviors are measured experimentally to demonstrate and validate the analysis method. As a result, it is verified that the analysis method offers more exact simulations than current methods. Finally, the dynamic behaviors of the moving-magnet-type actuator are improved using the analysis method.

Design of a Leaf Spring Using a Genetic Algorithm

This paper describes a design method of a leaf spring using a genetic algorithm. To avoid disconnected shape, a novel genetic representation which contains travel points and their order is proposed. A two-stage search is performed to improve the convergence and compared with the single stage search. To demonstrate the proposed method, it is applied to a leaf spring for an optical disc drive (ODD) actuator. The final result of the genetic algorithm has unnecessary parts, and thus manual mending process is needed. The obtained design of the leaf spring satisfies the required specification. The proposed design method is very simple, and hence it is expected that the proposed design method can be easily applied to other applications.

Improvement of Dynamic Characteristics of an Optical Image Stabilizer in a Compact Camera

Optical image stabilization is a device to compensate the camera movement in the exposure time. The compensation is implemented by movable lens or image sensor that adjusts the optical path to the camera movement. Generally, the camera is moved by a handshake, thus the handshake is considered as an external disturbance. However, there are many other vibrations such as car and train vibration. In this paper, the optical image stabilization system in high frequency region is presented. Notch filter and lead compensator are designed and applied to improve the stability without changing the actuator. To verify the performance of the optical image stabilization system in high frequency region, the experiment equipment with moving object is established. It is confirmed that the opticalimage stabilization system does not diverge at the resonance frequency.

Design of Moving Magnet Type Optical Pickup Actuator with High Frequencies of the Flexible Modes

Data transfer rate and storage capacity are main criteria of the performance of the optical disk drive. The highest data transfer rate and the largest storage capacity is most desirable. To increase these performances, the actuator of the optical disk drive should have a high servo bandwidth to compensate the vibration of an optical disk. The servo bandwidth is limited by some flexible modes of the actuator, thus it is essential to increase the natural frequencies of the flexible modes. In this paper, we suggested a moving magnet type actuator having high frequencies of the flexible modes. Generally, the moving magnet type actuator has an advantage to increase the natural frequencies of the flexible modes because the moving magnet type actuator has simple structure and the Young`s modulus of magnet is high. However, large moving mass and inefficiency of EM(electromagnetic) circuit cut down driving sensitivities of the actuator. To improve driving sensitivities, we designed the model with the closed electromagnetic circuit for tracking direction. In addition, driving sensitivities and the natural frequencies of the flexible modes were improved by using DOE(design of experiments) for electromagnetic circuit and modifying the lens holder.