In this blog post, we will compare the differences between optical stabilization and digital stabilization technologies for image stabilization and examine which technology is better.
When ordinary users take pictures with a digital camera, the image becomes blurred due to slight hand movements, and when shooting while walking or running, the image becomes so shaky that it is difficult to identify. Image stabilization technology minimizes the effects of shaking.
Image stabilization technology includes optical technology that uses light and digital technology that uses software. Camera modules that use optical image stabilization (OIS) technology consist of a lens module, image sensor, gyro sensor, control device, and lens movement device. The lens module consists of multiple lenses, including correction lenses. Generally, light entering through the lens of a camera hits the image sensor, forming an image of the subject, and electrical signals proportional to the intensity of light at each pixel corresponding to a point on the subject are stored as an image on a storage medium. However, when the camera shakes, the intensity of light hitting each pixel of the image sensor changes. When OIS technology is activated, the gyro sensor detects the movement of the camera and transmits the direction and speed to the control device. The control device moves the lens to stabilize the image while maintaining the image of the subject.
One of the most common methods of moving the lens is to use a voice coil motor. Camera modules that include voice coil motors have coils and magnets arranged around the lens located in the center. When the camera shakes, an electric current flows through the coils by the control device, generating a force proportional to the magnitude of the electric current in the direction perpendicular to the magnetic field. This force moves the lens, canceling out the effects of shaking and maintaining the image of the subject. Another method is used to reduce shaking by moving the image sensor when the camera shakes. This optical stabilization technology is particularly effective in photography, helping to produce clear images even when shooting at night or using a zoom lens.
Although OIS technology can compensate for hand shake very well, the range of lens movement is limited, so the range of movement that can be compensated for is narrow. Digital image stabilization (DIS) technology is a technology that uses software to compensate for shake after shooting, and can be used to good effect when shooting videos in dynamic situations. This technology divides the recorded video into frames and estimates the movement of the subject between consecutive frames. One way to estimate movement is to use feature points. Feature points are selected based on their distinctiveness from their surroundings and brightness, such as the corners of a subject, which remain unchanged even when the image moves or rotates.
First, feature points are found in the kth frame, and then the same feature points are found in the k+1th frame. The movement of the image is estimated by calculating how much the same feature points have moved between these two frames. Then, the effect of shaking is reduced by correcting the position difference in the frame where the shaking is estimated to have occurred, and the corrected video becomes smoother. However, the more feature points there are, the longer the calculation takes. On the other hand, rotating the image during the correction process creates empty spaces in the frames. Cutting out the empty spaces reduces the size of the frames, but maintaining the original frame size results in a loss of image quality.
Image stabilization technology is widely used in various devices such as smartphones, action cameras, and drones. In particular, smartphone cameras, despite their small size, apply high-level stabilization technology to enable users to easily take high-quality photos and videos in everyday life. Action cameras are useful for capturing dramatic scenes by providing stable images even during sports and outdoor activities. Stabilization technology is also essential for drones when shooting from the air, playing a major role in obtaining smooth and clear images.
In conclusion, image stabilization technology plays an important role in various situations and is becoming increasingly advanced with technological developments. The combination of optical stabilization and digital stabilization technologies allows users to obtain shake-free images in any environment, and these technologies will continue to evolve to provide new shooting experiences in the future.
