The eyes have it, or die augen haben es

About 30m people around the world have grown legally blind due to retinal diseases. The EPI-RET project has looked for a technical solution for the past twelve years to help these patients resulting in a unique system – a fully implantable visual prosthesis.

For twelve years, experts fn the fields of microelectronics, neurophysics, information engineering, computer science, materials science and medicine worked to develop a visual prosthetic device for patients who have lost their sight through diseases of the retina. In September 2007, their effort was rewarded. In a clinical study including six patients, the team was able to demonstrate not only that a completely implantable vision prosthesis is technically feasible and proven functioning, but also that it enables patients to perceive visual images.

Dr. Hoc Khiem Trieu has been involved from the outset of this project, which was funded by the German Ministry of Education and Research. Together with Dr. Ingo Krisch and Dipl.-Ing. Michael Görtz, he translated the specifications given by the medical experts and material scientists into an implant and chip design. The scientists are to receive the Joseph von Fraunhofer Prize 2008 for their work.

“A milestone was reached when the prosthetic system finally operated wirelessly and remotely controlled,” explains Dr. Ingo Krisch. “A great deal of detailed work was necessary before the implant could be activated without any external cable connections."

“Designs became smaller and smaller, the materials more flexible, more robust and higher in performance, so the implant now fits comfortably in the eye,” reports Michael Görtz.

The system benefits from a particular disease pattern, and it uses a specific operating principle to restore sight to those suffering from retinitis pigmentosa.  Here the light sensitive cells are destroyed, but the connection of the nerve cells to the brain remains intact. The scientists have bypassed the defects of the retina by means of a visual prosthesis.

The complete system comprises the implant and an external transmitter integrated in a spectacle-frame. The implant system converts the image patterns into interpretable stimulation signals. Data and energy are transferred to the implant by a telemetric link. The nerve cells inside the eye are then stimulatedaccording to the captured images. Those intact cells are innervated by means of three-dimensional stimulation electrodes that rest against the retina like small studs.

EPI-RET GmbH, a spin-off of this project consortium, intends to market the vision prosthesis in about three years’ time after a new clinical study of selected patients has been completed with the final product.


Acute artificial compound eyes 

                                                                                        Winner of the Hugo Geiger Prize (1st place): Andreas Brückner.
Insects are a source of inspiration for technological development work with researchers world wide working on ultra-thin imaging systems based on insect eyes. The principle of hyperacuity has now been successfully incorporated in a technical model.

Insects have inspired scientists to transfer features which have been optimized over millions of years to present-day products. Research scientists at the Fraunhofer Institute for Applied Optics and Precision Engineering IOF in Jena, for example, are working on the development of an ultra-thin image sensor based on the insect eye. In the work for his degree dissertation “High-precision position determination with artificial compound eyes”, Andreas Brückner improved the imaging properties of these systems with regard to sensor applications.

Insects have not just two, but thousands of eyes. Each facet of their eye picks up one image point, and the numerous facets, each with its own lens and visual cells, are spread over the surface of a hemisphere. As a result, the insect eye can cover a wide viewing angle – though images resolution is not particularly high.

This is surprising, given that insects can fly very precise maneuvers. They are able to do so because of the principle of hyperacuity – seeing more than the images actually captured by their compound eyes because the visual fields of adjacent facets overlap. Brückner is replicating this phenomenon in a technical system.

“The aim was to develop micro-optical compound eyes which contain numerous parallel imaging channels and which are also extremely compact, thinner than 0.5mm,” reports Brückner. To achieve this, he began by analysing how images are created in artificial compound eyes. Given that each facet captures one image point, the challenge was to accomplish controlled overlapping in the technical system.

With a precise knowledge of the angular sensitivity, image signals of adjacent facets can then be compared with each other. This makes it possible to determine the position of the object viewed in a two-dimensional visual field with an accuracy which is many times higher than the image resolution.

 A comparison has shown that an artificial compound eye lens can transfer information with an effective image resolution of 625 x 625 pixels, although the number of actually available image pixels is limited to 50 x 50. As a result, the sensor can recognize simple objects, precisely determine their position and size, and also reliably detect movements. Brückner is to be presented with the Hugo Geiger Prize 1st place for the results of his dissertation.

Projects are already underway to implement the process, for instance as solar altitude sensors in automobiles, for recognising traffic lanes in driver assistance systems, and for machine vision.

Scanning photon microscope offers alternative to laser scanning
Internal assembly of the Scanning Photon Microscope  

Laser scanning microscopy is a well-established visualising method for different fields of application. Objects being detected are raster scanned by a focusing laser beam, and the light diffused from the samples surface is collected by a suitable mounted detector. However, systems currently available on the market, are very large  and cost-intensive limiting application  possibilities.

The Fraunhofer IPMS presents an alternative with its “Scanning Photon Microscope”. It works on a similar principle but uses a two- dimensional resonant microscanning mirror developed at the Fraunhofer IPMS for the deflection of light.. Various possibilities for miniaturisation of the system result from the minimal dimension of the mirror (4 x 3 mm2).

The presented demonstrator with a dimension of 4 x 10 x 20cm collects pictures of 1000 x 1000 pixels with a resolution of 10µm per pixel. So the image area is 1 x 1 cm.  By changing optical design it is possible to increase the performance parameters.

Highly interesting for future applications is the possibility to choose the wave length of the radiated light and therefore to activate processes like fluorescence and then to evaluate them by wave length specific. Non-destructive testing, to detect microcracks, or use in biotechnology are potential fields of THE SPM AND. Measurements are possible both in the illuminated area and in the dark field.

Source: http://www.fraunhofer.de/