Liquid Lens for Optical Image Stabilization (OIS)
A second generation of liquid lenses has been developed for mobile digital image capture, in all situations where the quality of the picture counts, and/or when one cannot afford to try several times to get the good shot (for instance with children, friends etc…)
- mobile photography in medium light (indoors, at dusk…)
- mobile video
- mobile data capture
The progresses made in miniature camera modules optical quality have made the intrinsic blur coming from the camera itself negligible. Major source of blur are now extrinsic:
- Focus blur: if imagers are not equipped with an AF actuator, the lack of precise control of the focus impacts visual image quality.
- Handshake blur: the miniaturization of camera phones has degraded their light sensitivity; under medium light illumination, images are blurred due to longer exposure times. Optical Image Stabilization is a key requirement to produce a good picture, and Varioptic OIS liquid lens is the ideal solution to achieve a high image quality while keeping a very small camera format.
Varioptic is the first company to have developed a lens that effectively and simultaneously performs superior Auto-Focus and Optical Image Stabilization, correcting both major sources of blur.
This new generation of liquid lens, with a multi-electrodes design, allows tilting the light in all directions of space and, at the same time, refocusing the light.
The ability to tilt the light enables camera module manufacturers to use our liquid lens to activate Optical Image Stabilization by measuring the handshake and compensating in real time with the liquid lens. This lens uses 4 electrodes to enable tilts and non-symmetrical shapes necessary to simultaneously support Auto-Focus and Optical Image Stabilization:
The optical design of a camera module with the liquid lens OIS+AF obeys the same general rules as for the AF case: locate the liquid lens as close as possible to the aperture stop plane. The electronics design uses information coming from a gyroscope, either “image-dedicated”, or shared with multimedia applications. The gyroscope signal processing is very similar to DSC stabilizing systems, with some minor adaptations.
Main properties of the OIS liquid lens are:
- Effective correction of most of the handshake blur: with picture integration time up to 400ms, 90% of pictures have their maximal handshake blur within the tilt correction range of the liquid lens.
- Response frequencies optimized for mobile photography.
- Long exposure times enabled (up to 1s)
- In AF macro mode, focus range is maintained very wide, enabling excellent focus at distances from 5cm to infinity.