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Photon-counting sensing is a widely used technique for low-light-level imaging applications. This paper proposes a distance information extraction method with photon-counting passive sensing under low-lightlevel conditions. The photo-counting passive sensing combined with integral imaging generates a photon-limited elemental image array. Maximum-likelihood estimation (MLE) is used to reconstruct the photon-limited image at certain depth levels. The distance information is extracted at the depth level that minimizes the sum of the standard deviation of the corresponding photo-events in the elemental image array. Experimental and simulation results confirm that the proposed method can extract the distance information of the object under low-light-level conditions.

Nitrogen oxides (NOx) and carbon monoxide (CO) are among the most dangerous chemical species to human health present in the atmosphere. Acute CO toxicity leading to unconsciousness, respiratory failure or death can occur after 1 hr of exposure when ambient CO levels reach 1000 ppm, whilst increase of NOx emissions can contribute to acid deposition, pollution of groundwater, eutrophication of surface waters, and tropospheric ozone and ecosystem damage. In this work, pure SnO2 sensors for CO and NOx were prepared by spin coating solutions derived from a washed Gel-precipitate followed by a calcining step. SnO2 sensors of nanometer grain size prepared by this process showed good sensitivity to CO and NOx gases. The increase of calcining temperature not only affected grain size and surface morphology, but also caused a decrease in sensitivity of the SnO2 sensors.

Indium tin oxide (ITO) films are widely used in optical devices for their high electrical conductivity and high transparency to visible light. Some relevant papers reported ITO thin films showed favorable sensitivity to NO2 and NO gases. However, researches on gas sensing with ITO films, especially thick films, had not been actively conducted until now. The crystal structure and particle size of ITO can be controlled in nanometer accuracy by coprecipitation method. To investigate the effects of crystal structure and particle size of nano-sized ITO powder on gas sensing properties, two kinds of ITO sensors, having cubic and rhombohedral crystal structures with 15 nm particle sizes, were investigated, and three kinds of ITO sensors having 15, 30, and 70 nm particle sizes, with the rhombohedral crystal structure, were investigated. Gas sensing properties were examined in a chamber with dry air (less than 1 ppm humidity concentration) or gaseous ethanol diluted in dry air. ITO gas sensors with the finer the particle sieze have better sensitivity than of large particle size. The sensitivity of ITO thick films were evaluated by sensing of gaseous ethanol.

Nano-sized materials, have much bigger surface-bulk ratio than coarse materials. Thus, surface properties become paramount, which makes these materials particularly appealing in applications in which such properties are exploited, as in gas sensors. The purpose of this work is that investigates the gas sensing characteristics of the nanocrystalline ITO thick films with various particle sizes. At first, we synthesized nano-sized ITO powders with particle size of 15, 30 and 70nm in an equivalent diameter via coprecipitation method. And then, the sensitivity of ITO thick films was measuresd for ethanol(C2H5OH) as target gas and some Volatile Organic Compounds(VOCs) such as Toluene, Methanol, Benzene, Chloroform. XRD, BET, TEM, SEM, XPS were used to investigated characteristics of ITO powders and thick films.