Memory chips could lead the way to gigapixel cameras
October 14, 2009
Image sensors embedded in digital cameras are expensive, and issues with their circuitry limit the quality and resolution in the pictures they produce. Now a research group from the Netherlands believes a cheaper solution could be right before our eyes - the team's "gigavision" technique exploits the high light sensitivity of memory chips to produce inexpensive gigapixel sensors that perform very well, especially in extreme lighting conditions.
Today's image sensors in digital cameras are based on CCD or CMOS technology, which is effective but relatively complex and not very energy-efficient. With CMOS sensors, as light hits the objective its intensity is translated to an analog voltage for each pixel; the voltage is then transferred to the edge of the chip, where it's converted to a greyscale value between 0 and 255 by an analog-to-digital converter (ADC) in a process that often compromises image quality.
Memory chips store digital information as an electrical charge, which needs to be very small to make read and write operations faster and store more data on the same surface area. However, this makes them very sensitive to external sources of noise such as light, which can easily alter the bits' values as photons hit the transistors in the chip.
A team led by Edoardo Charbon of the Technical University of Delft, Netherlands, decided to exploit this phenomenon by conceptually "removing" the black plastic packages that protect memory chips from interfering photons. The team mapped the light hitting the camera's objective directly to the chip's memory cells, which act as a myriad of miniaturized digital sensors.
The main advantage with this approach is the better resolution with reduced complexity, because it can achieve imaging with 100 times as many pixels on a chip of the same area, reducing the cost in the meantime. Since most digital cameras can now take pictures at 10 megapixels, this means affordable gigapixel cameras could be easily manufactured.
This could pave the way for inexpensive digital cameras in cell phones or other devices that can take better pictures especially in conditions of very dim or very bright light, two areas in which digital cameras tend to struggle.
There is however one catch: each bit can only be set to either "0" or "1," as opposed to a the traditional greyscale sensor that is translated to one of 256 possible levels. This means that sensing the right level of gray accurately is trickier and requires an algorithm to consider not just one, but rather a few adjacent bits at a time.
The team is still working on developing an efficient algorithm for greyscale detection, and is hoping to have a first version of a gigavision memory chip manufactured late this year and a definitive version early next year.
Via New Scientist.