Showing papers on "Depth of field published in 1974"
TL;DR: Holography provides a method of storing the information (size and relative position) of a dynamic three-dimensional distribution of particles so that a stationary image can be produced for detailed study.
Abstract: Holography provides a method of storing the information (size and relative position) of a dynamic three-dimensional distribution of particles so that a stationary image can be produced for detailed study. The depth of field is considerably better than normal image formation. The major technique involves forming an in-line Fraunhofer hologram; this hologram is the interference pattern formed between the far field diffraction pattern of the particles and an in-line background. Off-axis holography can also be used. The basic principles of these methods are described, and practical limitations and advantages discussed. Application of the methods to fog, mist, sprays, rocket engine studies, two phase flow, bubble chamber photography, electron beam holography, etc. are reviewed.
127 citations
TL;DR: Operation against a daylit background then requires minimizing the system etendue, which cancels the inverse square range effect on signal strength, making the signal range independent (if atmospheric absorption is neglected).
Abstract: Sensitivity often restricts remote Raman spectrometers to operate at ranges inside their very large hyperfocal distances. Operation against a daylit background then requires minimizing the system etendue. This can be done by focusing the system at the range of interest; the depth of field is then etendue limited and varies with the square of the range. For the usual case of depth of field limited sampling depth, this cancels the inverse square range effect on signal strength, making the signal range independent (if atmospheric absorption is neglected). This concept is proven analytically and experimentally.
36 citations
TL;DR: In this article, the angular extent of a hologram's zero-order light is derived from that of a set of collimating lenses, and the effect of a reference source of nonzero area is obtained from the Airy disk of a lens.
Abstract: The angular extent of a hologram’s zero-order light is derived from that of a set of collimating lenses. The effect of a reference source of nonzero area is obtained from the Airy disk of a lens. The finite temporal coherence of the reference source is modeled in terms of the depth of field of a lens. Finally, sampled holograms, such as those usually obtained in microwave or acoustical work, are modeled by a lens with a complicated pupil function. For the first time, these disparate topics in holography are treated in terms of simple lens properties; such a treatment is extremely useful for gaining an increased intuitive understanding of holography.