Head mounted DMD based projection system for natural and prosthetic visual stimulation in freely moving rats

Novel technologies are constantly under development for vision restoration in blind patients. Many of these emerging technologies are based on the projection of high intensity light patterns at specific wavelengths, raising the need for the development of specialized projection systems. Here we present and characterize a novel projection system that meets the requirements for artificial retinal stimulation in rats and enables the recording of cortical responses. The system is based on a customized miniature Digital Mirror Device (DMD) for pattern projection, in both visible (525 nm) and NIR (915 nm) wavelengths, and a lens periscope for relaying the pattern directly onto the animal's retina. Thorough system characterization and the investigation of the effect of various parameters on obtained image quality were performed using ZEMAX. Simulation results revealed that images with an MTF higher than 0.8 were obtained with little effect of the vertex distance. Increased image quality was obtained at an optimal pupil diameter and smaller field of view. Visual cortex activity data was recorded simultaneously with pattern projection, further highlighting the importance of the system for prosthetic vision studies. This novel head mounted projection system may prove to be a vital tool in studying natural and artificial vision in behaving animals.

Extending the depth of focus for enhanced three-dimensional imaging and profilometry: an overview

We overview the benefits that extended depth of focus technology may provide for three-dimensional imaging and profilometry. The approaches for which the extended depth of focus benefits are being examined include stereoscopy, light coherence, pattern projection, scanning line, speckles projection, and projection of axially varied shapes.

Extended depth of focus imaging with birefringent plate

In this paper we present a simple approach to obtain extended depth of field for any optical imaging system just by adding a birefringent plate between the lens and the detector. The width of the plate is properly designed such that one polarization state contains in-focus near field information while the other polarization state contains in-focus far field details. Both images are superimposed one on top of the other and thus an all-optical spatially sharp imaging is obtained containing both fields. The width of the plate is also designed such that there is a longitudinal overlapping of the two regions (the near and the far) such that continuously well focused imaging is generated. The presented approach for extending the depth of focus is significantly simple compared to the use of birefringent and bi-focal lenses published recently. Preliminary numerical as well as experimental results verify the proposed approach.

Optical realization of Viterbi decoder for communication network

The advantages of optics that include processing speed and information throughput, modularity and versatility could be incorporated into one of the most interesting and applicable topics of digital communication related to Viterbi decoders. We aim to accelerate the processing rate and capabilities of Viterbi decoders applied for convolution codes, speech recognition, inter symbol interference (ISI) mitigation problems. The suggested configuration for realizing the decoder is based upon fast optical switches. The configuration is very modular and can easily be increased to Viterbi decoder based upon state machine with larger number of states and depth of the trellis diagram.