A new method of using photo-electromotive force in detecting gas and controlling sensitivity is proposed. Photo-electromotive force on the heterojunction between porous silicon thin layer and crystalline silicon wafer depends on the concentration of ammonia in the measurement chamber. A porous silicon thin layer was formed by electrochemical etching on p-type silicon wafer. A gas and light transparent electrical contact was manufactured to this porous layer. Photo-EMF sensitivity corresponding to ammonia concentration in the range from 10 ppm to 1,000 ppm can be maximized by controlling the intensity of illumination light.

The 8‐bit RGB image of a cracked concrete surface, obtained with a high‐resolution camera based on a close‐distance photographing and using an optical microscope, is used to estimate the geometrical parameters of the crack. The parameters such as the crack’s width, depth, and morphology can be determined by the pixel intensity distribution of the image. For the estimation, the image is transformed into 16‐bit gray scale to enhance the geometrical parameters of the crack and then a mathematical relationship relating the intensity distribution with the depth and width is derived based on the enhanced image. This relationship enables to estimate the width and depth with ±10% and ±15% accuracy, respectively, for the crack samples used for the experiments. It is expected that the accuracy can be further improved if the 8‐bit RGB image is synthesized by the images of the cracks obtained with different illumination directions.

Hyperspectral images in the spectral wavelength range of 500 nm to 650 nm are used to detect green mold pathogens, which are parasitic on the surface of lemons. The images reveal that the spectral range of 500 nm to 560 nm is appropriate for detecting the early stage of development of the pathogen in the lemon, because the spectral intensity is proportional to the infection degree. Within the range, it was found that the dominant spectral wavelengths of the fresh lemon and the green mold pathogen are 580 nm and 550 nm, respectively, with the 550 nm being the most sensitive in detecting the pathogen with spectral imaging. The spectral intensity ratio of the infected lemon to the fresh one in the spectral range of 500 nm to 560 nm increases with the increasing degree of the infection. Therefore, the ratio can be used to effectively estimate the degree of lemons infecting by the green mold pathogens. It also shows that the sudden decrease of the spectral intensity corresponding to the dominant spectral wavelength of the fresh lemon, together with the neighboring spectral wavelengths can be used to classify fresh and contaminated lemons. The spectral intensity ratio of discriminating the fresh lemon from the infected one is calculated as 1.15.

The light intensity distributions in the front space of a contact-type multiview 3-D imaging system are measured to estimate the effects of the differences in real and nominal values of parameters and alignment errors on the quality of 3-D images. The distributions clearly reveal how the viewing zone cross section is formed and how the mixed images are formed. For these measurements, a 1×4 Fresnel lens array and a projector are used as the viewing zone forming optics and image source, respectively. The results are graphically represented in terms of crosstalk. Both the misalignments and the inaccuracies greatly increase the crosstalk.

Changes in electric parameters of a mesoporous silicon treated by a plasma chemical etching with fluorine and hydrogen ions, under the adsorption of NEPO (Nematodetransmitted Polyhedral) plant viruses such as TORSV (Tomato Ringspot Virus), GFLV (Grapevine Fan Leaf Virus) and protein macromolecule from TORSV particles are described. The current response to the applied voltage is measured for each virus particle to investigate the material parameters which are sensitive to the adsorbed particles. The peculiar behaviors of the response are modeled by the current-voltage relationship in a MOSFET. This model explains the behavior well and the double gate model of the MOSFET informs that the mesoporous silicon is a highly sensitive means of detecting the viruses in the size range less than 50 nm.

This paper proposes an adsorption sensitivity control method that uses a wireless network and illumination light intensity in a photo-electromagnetic field (EMF)-based gas sensor for measurements in real time of a wide range of ammonia concentrations. The minimum measurement error for a range of ammonia concentration from 3 to 800 ppm occurs when the gas concentration magnitude corresponds with the optimal intensity of the illumination light. A simulation with LabView-engineered modules for automatic control of a new intelligent computer system was conducted to improve measurement precision over a wide range of gas concentrations. This gas sensor computer system with wireless network technology could be useful in the chemical industry for automatic detection and measurement of hazardous ammonia gas levels in real time.