Tessera on Mobile Imaging Trends

Mobile Handset DesignLine: Tessera's R&D Director Giles Humpston started a four-part article taking a look at the trends and design challenges of image acquisition and processing on cell phones. The first part discusses camera modules.

Some of the most sought-after camera module characteristics include:

• Low light sensitivity, especially the ability to take photographs indoors without flash. Flash photography is very power hungry in a product where battery life is often a major consideration for the consumer. Flash photography can also introduce undesirable image artifacts, such as red-eye, that then need correction.
• Focus, image stabilization and optical zoom. Clearly, photographs need to be in focus. Image stabilization is, in many ways, analogous to focus because it is also image blurring, but in a lateral direction. Because the distance of the object to the camera varies, what is required is the means of either adjusting the focus to suit or extending the depth of field. Optical zoom allows the user to get closer to the subject of the photograph and details of the scene to be magnified. Digital zoom degrades image quality, so is undesirable if the captured quality is already low.
• Higher resolution. Although higher resolution does not directly translate into higher picture quality, acquisition of additional information by a higher resolution imager facilitates effective image enhancement by software.
• Size reduction. The height of camera modules is one factor limiting the thinness of cell phones where the current fashion is for extreme thinness. Camera modules are typically around 5mm high, but would ideally be less than 1.5mm tall.
• Cost reduction. Camera modules and the associated image processor are relatively expensive components and contribute to the overall handset price. This is especially true for cell phones that have two cameras, where the cost of the cameras is around 12 percent of the total handset bill of materials [Semiconductor Insights, 2008]. A long-term goal of the industry is the $1 VGA camera module.

Part 2 of this article series looks at "revolutionary new hardware technology" (Tessera's one?) and its impact on camera module design and size. Part 3 will discuss how software enhanced lenses can favorably boost camera phone performance. Part 4 considers how numerical image enhancement and face detection can be embedded in mobile devices to bolster the image taking and viewing experience.