The correction of visual defects and human eye diseases by laser surgery is becoming more and more popular. Higher order aberrations of the eye are normaly not taken into account for ophtalmologic surgery. This leads to the fact, that normal vision can not be fully restored.
The measurement of higher order aberrations opens the path to supervision, a vision of more than 100%, which is the populations average. To get accurate measurements of the aberrations, the backscattered image of the retina has to be analyzed with a sensor of high speed and accuracy.
The high resolution retina scanner project was started in 1996 at the Kirchhoff institute. A Hartmann-Shack sensor determines the characteristic parameters of the wavefront by measuring the lateral shifts of focal spots from a lens array. The main emphasis of this work is, to overcome the limitations in speed and accuracy of ccd cameras, which are normaly used to localize the focal spots. The ccd camera is therefore replaced by a fast vision chip, which integrates analog and digital signal processing on one single chip.
The work is done at the ASIC laboratory in cooperation with the Kirchhoff Institute and 20/10 Perfect Vision from Heidelberg.
The picture shows an overview of the Hartmann-Shack sensor.