Camera as Small as a Grain of Salt Built
BERLIN, March 23, 2011 — A microcamera for endoscopy applications developed by a German collaboration promises to be so inexpensive as to be disposable.
Endoscopy has gone through amazing advancements in recent years. Microcameras on the tip of endoscopes supply images from the inside of the human body at a higher resolution than ever, which often makes it possible to identify tumors at an early stage. Endoscopes have some downsides, however: They are expensive and, because of their multiple usages, must be put through time-consuming and exhaustive cleaning procedures each time they are used.
This new microcamera is no larger than a grain of coarsely ground salt, enabling it to fit perfectly into the tip of an endoscope. (Image: Awaiba GmbH)
The latter problem might be solved by the new camera developed by Fraunhofer Institute for Reliability and Microintegration (IZM) and Awaiba GmbH with the support of the Fraunhofer Institute for Applied Optics and Precision Engineering in Jena.
"We can produce microcameras so inexpensively with our technology that doctors can dispose of endoscopes after using them only once," said Martin Wilke, a scientist at Fraunhofer IZM. “This is made possible by a new type of manufacturing process.”
Digital camera systems consist of two components: a lens and a sensor that transforms the image into electrical signals. Electrical contacts on the sensor allow access to these signals and therefore also to the information of the image. Due to the way they are manufactured, these contacts are located between the sensor and the lens. The sensors are manufactured simultaneously in large numbers, like computer chips.
"You have to think of a book full of postage stamps, where many thousand stamps are printed in one step,” Wilke said. “If you want to use them, you have to separate one from another.”
Instead of a sheet of paper, he added, image sensors have silicon wafers. About 28,000 image sensors fit onto one wafer and, until recently, each one was sawed out, wired and mounted on the lens that was still missing. That means wiring them 28,000 times and mounting them just as often.
The researchers at Fraunhofer IZM streamlined this process by developing a way to access the electrical contacts. Now, the wiring process is faster, and the entire camera system is smaller. The trick lies in the fact that they do not reach the contacts of each individual image sensor via the side but rather, simultaneously, with all sensors via their reverse side while they are still connected as a wafer. That means one no longer must mount the individual lenses. Instead, you can connect them with the image sensor wafers as lens wafers. Only then is the stack of wafers sawed apart into individual microcameras.
Another upside is the fact that the sensor supplies razor-sharp pictures even with very thin endoscopes. To date, the camera systems built into endoscopes had to be divided because of their size. The lens was at the tip of the endoscope and the sensor at the other end of the glass fiber strand. The new microcamera is small enough for the tip of the endoscope. It has a resolution of 62,500 pixels and transmits the image information through the endoscope via an electrical cable. Stephan Voltz, the CEO of Awaiba GmbH, said that "at 1 × 1 × 1 mm, the camera is as small as a coarsely ground grain of salt – the smallest camera that we are aware of."
"Starting in 2012, using Fraunhofer's expertise, we will be able to bring disposable endoscopes to market for only a few euros – we already have the prototype," Voltz said.
Besides the medical field, the automotive industry is interested in the tiny camera, with one possibility being the replacement of outside rearview mirrors on cars with microcameras. This would reduce flow resistance and energy consumption. Beyond this, installed in fittings, this camera could calculate the driver's eye movements and prevent him from nodding off for a few seconds.
For more information, visit: www.izm.fraunhofer.de
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