Holographic microscopy is a technique not currently being utilized in studying in vivo biomedical problems. This paper reviews the current status of holographic microscopy, evaluates some of the optical processing techniques which could improve the reconstructed image quality, and assesses the current status of biomedical applications. A joint effort by designers and potential users is needed to get the holographic microscope out of the optics research laboratory and into the biomedical laboratory.

This editorial serves both a scientific purpose and a metascientific purpose. The scientific purpose is to introduce and tie together an outstanding group of papers. The metascientific purpose is to plead a cause related to coherent optical systems.

One of the most frequent complaints one hears is that a better job could have been done if there had been more money. The scientists and technicians who work with optics are not immune to this problem but they do have an alternative solution that does not require extensive paper work for proposals or budget modifications. The solution is contained with-in the researcher himself and is simply ingenuity and inven-tiveness. The most efficient way to surface the latent ideas that can help to solve the problems aggrevated by budget limitations is to visit other laboratories and see how they have solved similar problems. In addition it is always gratifying to discover that you can improve on someone else's idea.

One method of generating synthetic or computer-generated holograms is to first compute the Discrete Fourier Transform (DFT) of the desired image. The hologram is then formed by coding in some manner on photographic film the complex values of this DFT. This paper describes a method for generating synthetic binary holograms that avoids the necessity for computing the DFT of the desired image. The relationship between this new method and previously used techniques is discussed. An analogous method for generating kinoforms that does not require the calculation of the DFT is also described.

This paper concerns itself with the investigation of a method for solving the longstanding problem of longitudinal image distortion encountered in longwave (microwave or acoustic) holography that has so far prevented the exploitation of the three-dimensional imaging capability of holography. A scheme for real-time, distortionless image reconstruction from longwave holograms that has the potential of yielding three-dimensional images which can be viewed with the unaided eye is described. The scheme is based on combining the operations of a semiconductor spatial microwave modulator with that of a plasma chamber in which visualization is due to light emission caused by microwave-induced enhanced ionization and luminosity in a weakly ionized r.f. plasma. The scheme has the potential advantage of being implementable in real time when a light value is added. Relatively reasonable level millimeter microwave reconstruction power of .6 watts average is shown to be sufficient for the reconstruction of a three-dimensional image consisting of 1000 resolvable points using commercially available millimeter wave sources, assuming that the local enhanced luminosity is caused by a doubling of the ionization rate in a low frequency r.f. discharge plasma.

A holographic method for the measurement of pulsed infrared laser spectra is reported. The first application was the measurement of the pressure dependent emission spectrum of a pulsed HF-laser (10 Joules, 150 ns).

The Coherent Optics in Mapping Tutorial Seminar and Technology Utilization Program, jointly sponsored by the Society of Photo-Optical Instrumentation Engineers and the American Society of Photogrammetry in Rochester, New York, in May 1974 was the first of its kind to gather interested workers and users from both the topographic mapping and coherent optics communities for a common purpose, that purpose being to define how the expanding technology of coherent optics can assist the various processes associated with topographic mapping. The meeting was successful in that consen-sus indicated an optimistic enthusiasm and a desire to continue communication. This is the intent of the following papers.

Several potential applications of coherent optics in the field of topographic mapping have been identified.1 This paper outlines the motivation for applying coherent optics to topographic mapping, presents some additional applications not included in Ref. 1, and further discusses some applications developed in that reference.

A new, high-performance device has been developed for application to real-time coherent optical data processing. The new device embodies a CdS photoconductor, a CdTe light-absorbing layer, a dielectric mirror, and a liquid crystal layer sandwiched between indiumtin-oxide transparent electrodes deposited on optical quality glass flats. The non-coherent image is directed onto the photoconductor; this reduces the impedance of the photoconductor, thereby switching the ac vol-tage that is impressed across the electrodes onto the liquid crystal to activate the device. The liquid crystal is operated in a hybrid field effect mode. It utilizes the twisted nematic effect to create a dark off-state (voltage off the liquid crystal) and the optical birefringence effect to create the bright on-state. The liquid crystal modulates the polarization of the coherent read-out light so an analyzer must be used to create an intensity modulated output beam. Performance figures for the device include: Resolution 100 lines/mm; Input Sensitivity 160 iW/cm2 at 525 nm; Time Response on: 10. msec; off: 15 msec; Contrast >100 : 1 ; Aperture 1 inch by 1 inch.

We have used coherent optical data processing techniques to measure parallax in stereo aerial photographs. This is accomplished by cross-correlating one aerial photograph with a small region in another photograph. Experiments were performed on a breadboard system which was used both for making matched spatial filters (Fourier transform holograms) and for measuring parallax. This system has a 100-mm x 100-mm useful aperture which is scanned by a telecentric beam steering device controlled by a minicomputer. Parallax data obtained from this system proved to be in good agreement with similar data produced by an operational electronic stereo-compilation system. These experimental results and certain inherent advantages discussed in the paper lead us to conclude that coherent optical techniques may provide the basis for a fast, cost-effective automatic stereo-compilation system.

Three different approaches to record electrical signals by holographic techniques on moving data carriers are discussed. It is shown that, besides the well-known redundancy of holography and the possibility of attaining high storage densities, it is the flexibility of the holographic principle itself that makes holography an attractive recording method. Holographic parameters can be varied widely to meet specific boundary conditions imposed by the design of the data carrier or the storage medium. So, by using the "hy-brid" recording technique, holograms may be recorded which are invariant to hologram translations in two directions per-pendicular to one preferred axis, but with respect to this axis their sensitivity to displacements is increased by a factor of two. This hybrid technique combines the advantage of an increased linear storage density with drastically reduced precision requirements for guiding the data carrier and is thus very well suited for a holographic tape recorder.

The analytical flux monitoring technique has been used to evaluate the caustic surface and line spread function (energy flux distribution along a line) on different image planes for point source light passing through a model of the human eye. It is shown by comparison with the standard spot diagrams that the caustic is a valuable tool in evaluating the aberra-tions and performance of the model of the human eye.

Under sponsorship of the Naval Air Systems Command, an electronically variable neutral density filter for automatic background compensation has been successfully developed by the Naval Missile Center and Sandia Laboratories for use with vidicons. The same filter can also be used with film cameras, and with minor modifications, it can operate as a microsecond duration electro-optical shutter in infrared sys-tems. This article describes the filter operating principle, test configuration, and test results.

A portable battery-powered spectroradiometer has been constructed for the measurement of the apparent directional reflectance of natural targets. A silicon detector that is tripod mounted and positioned to monitor a horizontally oriented reference panel determines the target irradiance. A second detector for measurement of target radiance is mounted on the tripod swivel head. Electronic switching provides alter-nate detector references for the determination of apparent directional reflectance. Snap-on interference filters allow measurement in desired spectral bands. Equipment calibration procedures are discussed and typical experimental radiation data are given.

An electronically scannable electron-beam-pumped semicon-ductor laser device is described which provides laser emission from more than 1000 X 1000 randomly addressable spots. The device consists of a permanently sealed electron beam tube about 50 cm long. Attached to the inside of the face-plate is a 30 um thick cadmium sulfide single crystal wafer with typical lateral dimensions of 28 mm X 28 mm, which serves as the active laser element. Using a 50 ns pulsed elec-tron beam current of up to 2 mA, with an accelerating poten-tial of about 50 keV, laser emission is produced in a direction essentially coaxial with the pumping electron beam. A laser spot diameter of 25 um can be achieved with these devices. The emitted radiation is typically confined to a symmetric cone with a half angle less than 0.1 rad. The laser tube is capable of operation at room temperature or, for greater power output, may be conveniently cooled with conventional refrigeration to about -50°C. At this temperature, peak power outputs in excess of 5 watts have been produced from CdS at 515 nm wavelength. In preliminary tests, laser tubes have been operated at repetition rates up to 400 kHz for more than 2000 hours without significant decrease in laser emission. Applications of such devices include display, COM/CIM, and optically addressed holographic memories.

A conventional grating spectrometer has been modified to incorporate electronic spectral scanning through the use of a special purpose image dissector photomultiplier tube. The control of the deflection coils is synchronized with data storage location in a 1024 memory analyser thus ensuring precise wavelength repeatability during successive spectral scans. The control logic enables three selectable wavelengths to be sampled at repetition rates of up to 30 samples per second. The system has been applied to several problems encountered in aeronomical research where the spectrum under study is of varying intensity or where precise wavelength repeatability is required.

An oblique-incidence interferometer for testing the flatness of fine-ground surfaces is described. This uses reflecting diffraction gratings to divide and recombine the beams, resulting in a very compact optical system. In addition, the relative amplitudes of the interfering beams can be adjusted, by a suitable choice of the grating orders used, to give fringes of excellent visibility with surfaces having a wide range of refleetances.

A novel and promising technique for moire fringe interpolation using an electro-optic polarization rotator is described and the results of an initial feasibility study are presented. The possibility of very high-frequency operation using electro-optic crystals should permit high accuracy positional measurements on mechanical components moving with appreciable velocities. Resolution of displacements of 0.1 um was achieved with the best system. The main disadvantage of the electro-optic system is the sensitivity to temperature changes and mechanical misalignment.

With this issue of Optical Engineering the Society of Photo-Optical Instrumentation Engineers starts a new section devoted to short communications. Id here are many interesting and important aspects of optical engineering that are worth re porting in the literature but which are not suitable for a full-length paper. The mechanism of short communications can provide a format for such i formation. The subject matter of these contributions can include any material that can be considered optical engineering and may be theoretical results or predication of the behavior of optical systems, 'experimental data relating to optical system performance, engineering detail of new or improved optical systems, and new and unique laboratory or shop practice techniques.

The two terms "fringes of defocusing" and "fringes of lateral displacement" are used in the interferometric testing of lens aberrations. The definition of these terms can be related to the three-dimensional intensity distribution near the focus of a spherical wave. 14 In this note we will relate these two usages of the terms.

This being the first of a series of articles, I felt that it would be best to give the reader.an over-view of the topics with which I will deal. The concept of "vision" is a vastly complicated domain, involving the researcher, the clinician, and the manufacturer. There have been, in the past, the imposition of specific titles that served to distinguish facets of the examination and correction of vision. These names are Op-tometry, Ophthalmology, Opticianry, Optical Fabrication, and Eye Research. Even the word optician has to be subdivided into the fabricating optician who makes the eyewear, the dispensing optician who works with the public in fitting, adjusting, and selling of eye glasses, and in Great Britain there is the refracting optician who is comparable to the American optometrist. The present state of affairs shows that this division is in transition and the imposed barriers which dictated the responsi bility for a particular visual examination or visual-aid fabrication are changing.