System for high-speed time-resolved holography of transient events

Abstract

A configuration for sequential holographic recording based on a new system for obtaining a train of spatially separated light pulses at frequencies ranging from 6 to 35 MHz has been developed. The multipulse system uses a high-energy Q-switched Nd:YAG laser as a light source and incorporates a phase-front-preserving optical delay line and a specially graded beam splitter to produce as many as ten spatially separated light pulses of nearly equal energy. The temporal spacing between successive output pulses may be varied discretely in increments of 28.3 ns from 28.3 to 169.8 ns. The system is currently used for high-speed time-resolved holography of dynamic events with lifetimes between 100 ns and 1.5 micros. Other applications include using the system either as a single point or sequential-array source for laser generation of ultrasound.

Fourier Holography for Enhanced Visualization of Volume Phase Objects through Exploitation of Non-Linearities Associated with Silver Halide Emulsions

“…For an object placed a distance f-d behind a lens of focallength f, and assurning that the object is of smaller spatial extent than the illurnination, the field distribution at the focal plane, Ur ( Xr, y f), can be written as a function of the object's spatial frequency spectrum T(f.,fy) [4]: The irradiance distribution at the focal plane will be proportional to the magnitude squared of the sum of the field distributions, which can be cast into a general irradiance distribution expression: (2) where Ibis the average value ofthe intensity, M is the modulation index ofthe irradiance pattem, and g(xr ,y r) is the phase variation across the film plane. For the specific case described here, it can be shown that [11]: The resulting transmittance recorded on the film can be approximated to the first order as [12]: (6) where Tb is the transmission of the film associated with the biasing exposure, ß is the slope of the Transmission-Exposure (T-E) curve at the biasing point, and M is the modulation.…”

“…This system incorporated a White cell delay line and a custom designed hyperharmonic beamsplitter which provided equal energy for each exposure. With this capability, two particle sturlies were performed by initiating detonation in one particle, and holographically recording the subsequent shock wave and plasma generation, propagation, and interaction with the second particle [2].…”

Optically produced true-time delays for phased antenna arrays

“…20 Other uses indirectly related to time delays include acoustic pulsing 21 and cineholography. 22 The White cell has even been adapted for optical computing. 23 We start in Section 2 by describing the details of operation of the TTD device.…”

Holographic recording of fast events on a CCD camera

“…A sequence of holograms, i.e., a holographic movie, can be recorded by use of multiplexing techniques. In previous research, recording techniques included spatial 2,3 and angular multiplexing. 4,5 In recording a fast holographic movie, the sensitivity and response speed of the recording material are two very important issues.…”