Project: Smart Autofocus

Digital Photography is a market with a very fast growth rate, with very fast technical evolutions. Not only digital cameras have replaced traditional cameras for their traditional usage, but they created new ones. In particular, social networks, dedicated to photography (Flickr, Picasa…) or not (Facebook, MySpace…) have created a new interest in photography, and new fast ways to exchange pictures. _x000D__x000D_Camera phones (smartphones in particular) have very user friendly interfaces to directly connect (via 3G or Wifi) to social networks in order to upload or download images on a server, transfer the image on a computer or a printer for visualization on larger display. As a matter of fact, the camera with the most images on Flickr in 2009 is a smartphone!_x000D__x000D_Until now, the quality of camera phones has not been very good, due to the small size of the sensors and the small aperture of the lenses. However, digital image processing has allowed an important improvement of image quality, and has made camera phone good enough for most common use-cases. Image quality has become a major concern for camera phones manufacturer, since they became direct competitors to compact cameras. However, there are other constraints at least as much important as image quality: size, power consumption, and cost._x000D_Until a recent period, most camera phones have been using fixed focal length lenses. This implies that the depth of field of the camera is determined by the lens design and the sensor characteristics. For low resolutions (<2Mpix), the lack of sharpness of the lenses is not a big problem because the blur spot reCOs relatively small compared to the pixel size. However, when the number of megapixels increases, and the optical format of the sensor reCOs the same, the size of the pixels decreases, and images tend to become more and more blurry (when displayed at full resolution). _x000D_The depth of field of cameras decreases as the number of megapixels increases. _x000D_The limitation of depth of field of fixed focal lenses has become critical for 3Mpix camera, and is not viable for 5Mpix cameras. Alternative technologies are needed for these higher resolution. Optics with an extended depth of field (EDoF) is an elegant and cheap solution that has been adopted for some low cost cameras, from 3MPix to 8Mpix, but VCM (Voice Coil Motors) is still the most common solution for a pure optical solution. DxO Labs is one of the two providers of EDoF technology on the market, while poLight supply a compeeting pure optical solution._x000D_For high-end cameras, manufacturers have chosen autofocus solutions. This solution guarantees that it is possible to obtain sharp images at far and very close distance. However, the autofocus adds a significant cost to the overall camera. Moreover, in terms of user experience, autofocus on camera phones do not offer the same comfort as for high-end cameras as DSLRs. In particular, DSLR cameras focus very, fast allowing a very short time-to-shoot. On camera phones, the autofocus is usually much slower and less reliable. _x000D_The reason for this difference is that DSLR and camera phones use completely different technologies to track the best focus. DSLR cameras use phase-autofocus that relies on splitting the incoming light beam in two sub-beams and focus them on two dedicated sensors (different from the CO imaging sensors). This system is very costly and bulky, and therefore not applicable on camera phones. _x000D_On the contrary, camera phones estimate the defocus directly from the preview image on the sensor. All the solutions on the market compute the relative difference of sharpness of two images focused at difference positions by comparing their contrast. In particular, there is no absolute measure of the camera defocus. _x000D_This has several consequences for the autofocus. First, it is not obvious to detect that the camera is not at focus. Second, when the camera is not at focus, it is not possible to know if the object is too close or too far. Finally, it is not possible to know what amount of defocus should be applied to the lens to obtain an image at focus almost immediately. _x000D_For the final user, this yields a very slow autofocus: sometimes more than 2s between pressing the button and the actual acquisition of the image. Also, autofocus in video mode is not reliable, because there is no way to find out in what direction to move the autofocus when the object distance has changed. _x000D__x000D_The objective of this project is to answer to the CO objections that can be made to the usage of autofocus on camera-phones. We intend to build the smallest, fastest and cheapest autofocus camera module on the market. _x000D__x000D_This purpose will be obtained by three major ingredients:_x000D_1. Wafer level lenses technology for smaller and cheaper lenses._x000D_2. DxO Digital Optics technology, consisting in a co-design of the lens and digital processing. _x000D_3. Fast and low power consumption, thanks to the deformable polymer based technology of poLight.

Acronym SmartAF (Reference Number: 6808)
Duration 20/04/2012 - 15/10/2014
Project Topic We will build the smallest, cheapest and fastest autofocus on the market, dedicated to mobile phone industries. The key innovations rely on a co-design of the lens and digital image processing, waferlevel optics and polymer based autofocus with no moving parts.
Project Results
(after finalisation)
The CO result of this project is an autofocus camera module for 5Mpix sensor with a very fast and continuous autofocus for still images and a very fast estimate of defocus position for real time video. The SmartAF autofocus module is small, cheap to produce and doesn't contain any moving parts. Such performance is acheived through a co-design of polymer based autofocus lens and digital image processing._x000D_
Network Eurostars
Call Eurostars Cut-Off 7

Project partner

Number Name Role Country
2 DxO Labs Coordinator France
2 poLight as Partner Norway