"photodetector" - 1 õppematerjal

Elektroonika Alused

) The light then passes through the 1/4 wave plate again. Since it is going the reverse direction, it will be polariz perpendicular to the original beam (in other words, the light polarization is now vertical with respect to the paper). When the vertically polarized light hits the polarizing beam splitter this time, it will be reflected (not transmitt as before). Thus, it will reflect though the focusing lens and then the cylindrical lens and be imaged on the photodetector array. The cylindrical lens is important in the auto-focusing mechanism. E. Three beam autofocus If the objective lens is closer to the compact disk than the focal length of the object lens, then the cylindrical le creates an elliptical image on the photodetector array. If the objective lens is further away from the compact disk than the focal length of the object lens, then the cylindrical lens again creates an elliptical image on the photodetector array. However, this elliptical image is