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The step-frequency radar is proposed as a means of detecting targets imbedded in high loss media. The radar derives information on target distance by exploiting the phase and amplitude characteristics of the returned signal. With a given frequency change, the phase angle change from a faroff target is larger, and therefore its phasor rotates faster, than that from a closeby target. Distance information is conveniently derived by applying the Fast Fourier Transform algorithm. The radar is able to offset an arbitrary distance and zoom to the targets, thereby obtaining fine resolution. With Wiener filtering, the resolution of the radar is high enough to identify the type, as well as the orientation, of the buried targets. A subtraction feature has also been incorporated which allows scattering from unwanted targets to be cancelled out from that of the wanted targets. The radar was successfully demonstrated for the detection and identification of various targets buried in sand, moist clay soils, underwater, as well as for the mapping of thin ice.

It is a remarkable book on a rapidly growing fascinating subject. The book deals with the enginecring aspects of optics and is intended both for the physics student who wants to apply his knowledge of optics and for the student of other subjects who wants to untlerstand the physical principles of optics. Basic tools are developed in the earlier chaptt Coriiplicated iliathematics have been oinitted.The 15 chapters cover the whole field at the border between optics and technology. I n the beginning an introduction to the foundations of physical optics is given. Catchwords which illustrate the content are the history of optics, means of describing waves ~~heno~inr~nologi-cally, Kirehhoff's and Fresnel's theories of diffraction, gtwmetrical optics, Fmuier opties ant1 fast Fourier transform.S O I I~P of the subsequent chapters are devoted to holography and its applications. To p u t i t into practice the fabrication of a hologram is described as a step-by-stcp guide to the cxperiinrnt. Nunierous valuablc hints are given to the newconicr.Whcwas up to this point problein solving in optics has been dealt with fro111 thc spaw domain view point, the spatical frequency domain is now introduced. This liiakes various applied probleins easier t o present.Applications covered in that way are optical signal processing using cwhercnt and incoherent light including tomography, fiber optical coniinunication, electro ant1 aceusto optics as well as integrated optics.The inost iiiiportant advantage of the present book is its didactics. The inaterial is arranged in an order that can progressively increase the studtmt's comprehension of the subject. A large number of exercises and problems is included to assist the reader in gctting through the material. Last but not least excellent figures provide both very rlear instruction and pleasant relaxation. P. PAUFLER