Abstract: In glass bottle inspection, a pulse of acoustic wave is injected into a portion of the glass bottle forming a closed path for the propagation of the acoustic wave pulse so that the injected acoustic wave pulse travels round the closed plath, and acoustic wave pulse is detected while it is travelling round the closed path. Whether there is a defect along the closed path is judged in accordance with the magnitude of the detected acoustic wave pulse.

Abstract: Optical transmittances of a combination of a liquid to be detected and a container wall are measured in order to select two optical pass-bands, one of which is relatively high transmittance level while the other of which is relatively low transmittance. The light transmission quantities of the container at the selected two pass-bands are measured by one or more detecting elements. The light transmission quantities are converted into two electric signals, one of which is divided by the other in a signal process circuit.

Abstract: Irregularities in a coating on a substrate in which the coating includes optical scattering centers can be detected by irradiating the coating with polarized light and examining light from the coating through a filter which removes light having the same polarization as the initial beam. Light scattered by the optical scattering centers is transmitted through the filter, while specularly reflected light from the top surface of the coating, from the substrate exposed by gaps in the coating, or reflected by alien material on the coating is filtered out. As a result irregularities can be detected as intensity minima of the transmitted radiation.

Abstract: A method of lightening a radiation-darkened optical element in wich visible optical energy or electromagnetic radiation having a wavelength in the range of from about 2000 to about 20,000 angstroms is directed into the radiation-darkened optical element; the method may be used to lighten radiation-darkened optical element in-situ during the use of the optical element to transmit data by electronically separating the optical energy from the optical output by frequency filtering, data cooling, or interlacing the optic energy between data intervals.