An image is formed using the normal passband of the optical device. It is a matter, Randi argues, of trick photography using a simple hand-held optical device. Phantasmagoria is a type of horror show using an optical device to display moving images. Both channels have a telescope, a spectrometer, and an optical device which focuses light. Randi claimed Serios used "a simple handheld optical device" to perform his photographic trickery. There was an optical device for the initial visual acquisition of the target. Insight Technology, Inc. is an optical device manufacturer based in Londonderry, New Hampshire, USA. A saturable absorber is an optical device that exhibits an intensity-dependent transmission. This holographic mirror-like optical device was invented by the Japanese firm Dentsu. A camera lucida is an optical device used as a drawing aid by artists. A depolarizer or depolariser is an optical device used to scramble the polarization of light. A null corrector is an optical device used in the testing of large aspheric mirrors.