We present an all-optoelectronic THz imaging system based on photomixing of two continuous-wave laser beams using photoconductive antennas. For a specific biological sample, we compare continuous-wave THz imaging and pulsed THz imaging at 1 THz with respect to data-acquisition time and signal-to-noise ratio, and discuss image formation from both amplitude and phase data. In addition, we introduce the application of hyperboloidal lenses which allow tighter focusing and a corresponding improvement in spatial resolution compared to off-axis paraboloidal mirrors.

We present an all-optoelectronic THz imaging system for ex vivo biomedical applications based on photomixing of two continuous-wave laser beams using photoconductive antennas. The application of hyperboloidal lenses is discussed. They allow for f-numbers less than 1/2 permitting better focusing and higher spatial resolution compared to off-axis paraboloidal mirrors whose f-numbers for practical reasons must be larger than 1/2. For a specific histological sample, an analysis of image noise is discussed.

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This paper presents a multi-modal automotive dictation editor (codenamed ECOR) used to compose and correct text messages while driving. The goals are to keep driver's distraction minimal while achieving good task completion rates and times as well as acceptance by users. We report test results for a set of 28 native US-English speakers using the system while driving a standard lane-change-test (LCT) car simulator. The dictation editor was tested (1) without any display, (2) with a display showing the full edited text, and (3) with just the "active" part of text being shown. In all cases, the system provided extensive text-to-speech feedback in order to prevent the driver from having to look at the display. In addition, cell phone messaging and GPS destination entry were evaluated as reference tasks. The test subjects were instructed to send text messages containing prescribed semantic information, and were given a list of destinations for the GPS task. The levels of driver distraction (evaluated by car's deviation from an ideal track, reaction times, number of missed lane change signs, eye gaze information etc.) were compared between the 3 ECOR and the 2 reference tasks, and also to undistracted driving. Task completion was measured by the number and quality of messages sent out during a 4 minute LCT ride, and subjective feedback was collected via questionnaires. Results indicate that the eyes-free version keeps the distraction level acceptable while achieving good task completion rate. Both multi-modal versions caused more distraction than the eyes-free version and were comparable to the GPS entry task. For native speakers, the missing display for the eyes-free version did not impact quality of dictated text. By far, the cell phone texting task was the most distracting one. Text composition speed using dictation was faster than cell phone typing.

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