As Digital Still Cameras (DSC) become smaller, cheaper and higher in resolution, photographs are increasingly prone to blurring from shaky hands. Optical image stabilization (OIS) is an effective solution that addresses the quality of images, and is an idea that has been around for at least 30 years. It has only recently made its way into the low-cost consumer camera market, and will soon be migrating to the higher end camera phones. This paper provides an overview of common design practices and considerations for optical image stabilization and how silicon-based MEMS dual-axis gyroscopes with their size, cost and performance advantages are enabling this vital function for image capturing devices

1. Optical Image Stabilization Technology
Dept. of Electronics and Communication, HIT Nidasoshi 1
CHAPTER 1
INTRODUCTION
Image Stabilization (IS) technology has been considered essential to delivering improved image
quality in professional cameras. More recently, as a result of advancing technology, IS has become
increasingly popular to handheld device makers who want to propose high-end features for their
products. So, manufacturers like ST have worked hard on its technologies and methods for image
stabilization to significantly improve camera shutter speed and to offer precise suppression of camera
vibration. Today, from the technologic point of view, Digital Image Stabilization (DIS), Electronics
Image Stabilization (EIS) and Optical Image Stabilization (OIS) are the best understood and the
easiest to integrate in digital still cameras and smartphones, though they can produce different
image- quality results: in fact, DIS and EIS require large memory and computational resources on the
hosting devices, while OIS acts directly on the lens position itself and minimizes memory and
computation demands on from the host. As an electro-mechanical method, lens stabilization (optical
unit) is the most effective method for removing blurring effects from involuntary hand motion or
shaking of the camera.
Whether capturing still images or recording moving video, image stabilization will always be a
major factor in reproducing a near perfect digital replica. A lack thereof will result in image
distortion through pixel blurring and the creation of unwanted artifacts. While media capturing
devices such as digital cameras, digital camcorders, mobile phones, and tablets have decreased in
physical size, their requirements for pixel count density and resolution quality have increased
drastically over the last decade and will continue to rise. The market shift to compact mobile devices
with high megapixel capturing ability has created a demand for advanced stabilization techniques.
Two methods, electronic image stabilization (EIS) and optical image stabilization (OIS), are the most
common implementations.

2. Optical Image Stabilization Technology
Dept. of Electronics and Communication, HIT Nidasoshi 2
CHAPTER 2
IMAGE STABILIZATION TECHNIQUES
There are two types of techniques
1. Optical image stabilization
2. Electronic image stabilization
2.1 OPTICAL IMAGE STABILIZATION:
An optical image stabilization system usually relies on gyroscopes or accelerometers to detect and
measure camera vibrations. The readings, typically limited to pan and tilt, are then relayed to
actuators that move a lens in the optical chain to compensate for the camera motion. In some designs,
the favored solution is instead to move the image sensor, for example using small linear motors.
Either method is able to compensate the shaking of camera and lens, so that light can strike the
image sensor in the same fashion as if the camera was not vibrating. Optical image stabilization is
particularly useful when using long focal lengths and works well also in low light conditions.
Optical image stabilization is used to reduce blurring associated with motion and/or shaking of the
camera during the time the image sensor is exposed to the capturing environment. However, it does
not prevent motion blur caused by movement of the target subject or extreme movements of the
camera itself, only the relatively small shaking of the camera lens by the user – within a few optical
degrees. This camera-user movement can be characterized by its pan and tilt components, where the
angular movements are known as yaw and pitch, respectively. Camera roll cannot be compensated
since 'rolling' the lens doesn't actually change/compensate for the roll motion, and therefore does not
have any effect on the image itself, relative to the image sensor.

3. Optical Image Stabilization Technology
Dept. of Electronics and Communication, HIT Nidasoshi 3
2.2 ELECTRONIC IMAGE STABILIZATION:
EIS is a digital image compensation technique which uses complex algorithms to compare frame
contrast and pixel location for each changing frame. Pixels on the image border provide the buffer
needed for motion compensation. An EIS algorithm calculates the subtle differences between each
frame and then the results are used to interpolate new frames to reduce the sense of motion. Though
the advantage with this method is the ability to create inexpensive and compact solutions, the
resulting image quality will always be reduced due to image scaling and image signal post-
processing artifacts and more power will be required for taking additional image captures and for the
resulting image processing.
EIS systems also suffer when at full electronic zoom (long field-of-view) and under low-light
conditions. Electronic image stabilization, also known as digital image stabilization, has primarily
been developed for video cameras. Electronic image stabilization relies on different algorithms for
modeling camera motion, which then are used to correct the images. Pixels outside the border of the
visible image are used as a buffer for motion and the information on these pixels can then be used to
shift the electronic image from frame to frame, enough to counterbalance the motion and create a
stream of stable video.
Although the technique is cost efficient, mainly because there is no need for moving parts, it has one
shortcoming which is its dependence on the input from the image sensor. For instance, the system
can have difficulties in distinguishing perceived motion caused by an object passing quickly in front
of the camera from physical motion induced by vibrations.

4. Optical Image Stabilization Technology
Dept. of Electronics and Communication, HIT Nidasoshi 4
CHAPTER 3
COMPARISON OF OIS & EIS TECHNIQUES
Fig.3.1 OIS and EIS Image Quality Comparison
Comparison to EIS, OIS systems reduce image blurring without significantly sacrificing image
quality, especially for low-light and long-range image capture. However, due to the addition of
actuators and the need for power driving sources compared to no additional hardware with EIS, OIS
modules tend to be larger and as a result are more expensive to implement.
 EIS suffers when at full electronic zoom (Long field of view) and under low light conditions.
 EIS requires large memory & computational resources on the hosting device compared to
OIS

5. Optical Image Stabilization Technology
Dept. of Electronics and Communication, HIT Nidasoshi 5
CHAPTER 4
OIS BEHAVIOR
OIS is a mechanical technique used in imaging devices to stabilize the recording image by
controlling the optical path to the image sensor. The two main methods of OIS in compact camera
modules are implemented by either moving the position of the lens (lens shift) or the module itself
(module tilt).Camera movements by the user can cause misalignment of the optical path between the
focusing lens and center of the image sensor. In an OIS system using the lens shift method, only the
lens within the camera module is controlled and used to realign the optical path to the center of the
image sensor. In contrast, the module tilt method controls the movement of the entire module,
including the fixed lens and image sensor.
Module tilt allows for a greater range of movement compensation by the OIS system, with the largest
tradeoff being increased module height. Minimal image distortion is also achieved with module tilt
due to the fixed focal length between the lens and image sensor. Overall, in comparison to EIS, OIS
systems reduce image blurring without significantly sacrificing image quality, especially for low-
light and long-range image capture. However, due to the addition of actuators and the need for power
driving sources compared to no additional hardware with EIS, OIS modules tend to be larger and as a
result are more expensive to implement.
Fig.4.1 Main Methods of OIS Compensation

6. Optical Image Stabilization Technology
Dept. of Electronics and Communication, HIT Nidasoshi 6
CHAPTER 5
OIS PRINCIPLE
Fig. 5.1 OIS compensation
The basic principle underlying OIS is simplified in Figure 5.1 where the movement effects are
amplified and represented on a single axis, for the sake of clarity. Let’s suppose we take a picture of
a non-moving object in which the shutter remains open for a time interval equal to ∆t; if no
compensation occurs (Figure a), the involuntary rotation of the camera generates a distribution of the
light cone, over a single pixel, splattered on a segment indicated in Figure a by A-B. Clearly, this
phenomenon occurs across the whole image sensor, causing a blurred image.
Otherwise, when optical stabilization occurs (Figure b), the lens moves opposite to the direction of
the camera shake and the image results to be stabilized (i.e. the subject acquired in t1 coincides with
image acquired in t 0).

7. Optical Image Stabilization Technology
Dept. of Electronics and Communication, HIT Nidasoshi 7
CHAPTER 6
BLOCK DIAGRAM OF OIS
Fig. 6.1 OIS High level block diagram.
Blur due to hand jitter is reduced by mechanically stabilizing the camera. A two axis gyroscope is
used to measure the movement of the camera, and a microcontroller directs that signal to small linear
motors that move the image sensor, compensating for the camera motion. Other designs move a lens
somewhere in the optical chain within the camera. A typical high-level block diagram. With either
method, the result is that the body of the camera may shake, but light strikes the pixels of the image
sensor as though the camera were not shaking.

8. Optical Image Stabilization Technology
Dept. of Electronics and Communication, HIT Nidasoshi 8
1) Sensor Requirements:
For an OIS system to function properly, the sensors, actuators, and electronics must be carefully
chosen. A newcomer to this field may immediately wonders why gyroscopes are used in image
stabilization, rather than other sensors, such as accelerometers. A gyroscope Measures the rotation
about an axis, where rotations about X, Y, and Z axes for a given Object are referred to as roll, pitch,
and yaw.
2) Gyroscopes:
Gyroscopes are employed in IS systems to sense pitch and yaw with low noise and high sensitivity in
order to resolve the small movements associated with hand jitter. Typically, these systems require a
full-scale range of +/-30 degrees per second, with at least 10-bit resolution.
3) Actuator Requirements:
Actuators for OIS systems must be small, low-power, and accurate for tiny movements. The range of
movement required by an OIS actuator depends on the optics of the system, but the desired outcome
is an ability to compensate for ±1º of rotation. The most common actuator is the voice coil, an
electromagnetic linear motor, used to drive the lens.

9. Optical Image Stabilization Technology
Dept. of Electronics and Communication, HIT Nidasoshi 9
CHAPTER 7
ADVANTAGES & DISADVANTAGES
7.1 ADVANTAGES
 OIS systems reduce image blurring without significantly sacrificing image quality, especially
for low-light and long-range image capture.
 Optical Image Stabilization technology is an effective solution for minimizing the effects of
involuntary camera shake or vibration.
 Optical image stabilization directly acts on the lens position itself it reduces memory
requirement.
 Optical image stabilization minimizes computational resources on the hosting device.
7.2DISADVATAGES
 Two main challenges in the development of OIS in smartphones and digital cameras are size
and cost. The additional hardware required to implement OIS it increases the total cost of
camera, and increases the camera’s size.

10. Optical Image Stabilization Technology
Dept. of Electronics and Communication, HIT Nidasoshi 10
CHAPTER 8
APPLICATIONS
 Smartphones: The introduction of optical Image Stabilization in several mobile platforms
has been a significant added value for photography lovers and especially for younger users,
who replaced their traditional and bulky cameras with brand-new smartphones—or had
cameras available to record memories simply because those cameras were embedded in the
mobile platform they were already carrying.
 Digital cameras: Optical Image Stabilization technology is an effective solution for
minimizing the effects of involuntary camera shake or vibration in digital cameras. It senses
the vibration on the hosting system and compensates for these camera movements to reduce
hand-jitter effects.

11. Optical Image Stabilization Technology
Dept. of Electronics and Communication, HIT Nidasoshi 11
CONCLUSION
Gyroscope-based optical and electronic image stabilization systems are mature and proven
technologies that address the quality of images. OIS has been penetrating the DSC market rapidly,
and as camera resolutions continue to increase, optical image stabilization is expected to become as
standard a function as autofocus on every DSC. As engineers struggle to pack advanced technologies
into the scarce and premium real estates of handsets, small size and low cost are at the top of their
lists. With the fast pace of increased CMOS sensors pixel densities and feature offerings, such as
auto focus and optical zoom, OIS entered into the camera phone market as a prominent feature.

12. Optical Image Stabilization Technology
Dept. of Electronics and Communication, HIT Nidasoshi 12
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