|M.Sc Student||Zabar Yoel|
|Subject||IR Super - Resolution in Far Field|
|Department||Department of Mechanical Engineering||Supervisors||Professor Emeritus Stephen Lipson|
|Dr. Erez Ribak|
In order to measure the internal spatial response of a pixel in a detector, it is scanned by a beam smaller than its size. This becomes difficult as the wave length grows and becomes comparable to the pixel size, such as in the infra red.
To overcome this difficulty, a special phase mask which makes the beam narrower was designed, constructed, and tested successfully.
The mask was made from five alternating transparent rings, where the rings had half a wave phase difference between them. The beam was scanned with and without the mask in two dimensions in fine steps by a much smaller detector and its response was taken. The spot width dropped by 19% at half its height and by 42% at tenth its height, a significant narrowing. Moreover, even a focus error of 20mm did not render it much wider. A slight focus error even provided a benefit, by smearing the side-lobes somewhat, so that their magnitude was even less than the calculated 8%.
The scan was repeated with the full detector pixel. That beam scan served as a deconvolution kernel and allowed the pixel point spread function (spatial response), the pixel modulation transfer function and the optical cross talk between the pixels to be found. In the future, with smaller pixels, PSF measurements with the phase mask might be even more important for improvement of the measurement accuracy.
The design of the phase mask presented in this work is unique and more complicated because the source is not a laser and has a 10% band width. The system is planned for mid-IR radiation - a fact which restricts the choice of materials which can be used.