The history of naval camouflage is briefly reviewed with particular stress on the work of Dayton R. E. Brown during and immediately after World War II. Submarine concealment in particular was a difficult problem with the requirement for both surfaced and submerged operations in the battle environment. Aircraft camouflage also underwent important evolutions during the war with the development of unusual schemes such as Yehudi and Black Widow. These needs instigated important research efforts both within the Navy and in the camouflage section of NDRC where work was carried out by Duntley and others principally at MIT and at the Tiffany Foundation. Research work encompassed the natural environment, human vision, as well as camouflage design.

In this introductory survey of optical oceanography we first present the fundamental inherent and apparent optical properties of natural waters. Relationships between these inherent and apparent optical properties, as related through the radiative transfer equation, are then presented. Following the first three theoretical sections brief discussions describing the application of ocean optics to geophysics, biological oceanography, and ocean remote sensing are then presented. Authorship for each section is indicated by initials after the section heading.

It is shown how the exact two-flow model for upward and downward irradiance fields in the sea can yield numerical determinations of the coefficients of the model. These coefficients are interpretable as the local optical properties of the sea. Knowledge of the upward and downward irradiances at any two distinct depths in the sea will generally allow such a determination of the average local optical properties of the sea between the the chosen depths. From such determinations we can in principle find the four global optical pro-perties of each layer of the sea, namely the transmittance and reflectance factors for the upward and downward irradiances, associated with each layer of the sea. Finally, knowledge of both local and global properties, together with measured upward and downward irradiances at each depth, allow the detection and deter-mination of internal sources of radiant energy in the sea (e.g. fluorescent phenomena). The procedures for irradiance just described can be elevated without essential change to the radiance level.

The diffuse attenuation coefficient for downwelling irradiance (Kd), the coefficient used to describe the attenuation of irradiance as a function of depth in natural waters, is an apparent optical property. As such, it is a function of the geometry of measurement and other factors which alter the radiance distribution as a function of depth. In spite of this, measurements of downwelling irradiance versus depth and sun zenith angle show that Kd is relatively insensitive to changes in sun angle, thus displaying "quasi-inherent" characteristics, except for very large sun zenith angles. Data will be shown to demonstrate this for a highly productive water type.

Laboratory measurements of the irradiance distribution due to a laser beam and the radiance distribution due to a point source in a hydrosol have been made and the results analyzed. The analysis indicated that after proper accounting for absorption, the distri-butions may be scaled as a function of the scattering length rather than the more commonly used parameter, the attenuation length. The two distributions have also been shown to be equivalent as required by the optical reciprocity theorem. The measurements have given new insight into understanding the spreading of light underwater.

The research reported here was initially stimulated by a contradiction in the literature that suggested there was no significant performance advantage for manipulator operators employing stereo versus conventional TV systems, while typical direct-viewed results indicate that binocular performance is always superior to monocular performance in tasks requiring depth judgment or distance estimation. This paper presents an analysis of the inter-action of several important variables involved in visual display research, with particular reference to our own research comparing mono and stereo TV displays in simulated underwater environments. Three experiments were conducted in our lab to assess the impact of degraded visibility on remote manipulator operator performance using either mono or stereo TV. Subjects were required to perform tasks which differed markedly in the number and type of depth cues available. As predicted, the results indicate that stereo performance was superior to mono under most conditions tested; however, the amount of improvement was shown to be a complex function of visibility, task, and learning factors. Conclusions and recommendations for further research aimed at understanding the relative contributions of these and additional display factors are presented for discussion.

In recent years there has been an increased emphasis on ocean exploration by both government and private agencies of the world. A large portion of these marine activities involve human occupancy of pressure vessels, also known as hyperbaric chambers. The most common chambers of this type are diving submersibles and diver decompression chambers. As their' use by private agencies has grown, so has the requirement that the marine construction codes include more definitive guidelines in design and production of windows for the occupants to view thru the chamber walls.

An increase in the incidence of solar ultraviolet radiation upon oceans and lakes, as a consequence of anthropogenic diminishing of the ozone in the stratosphere, might well have a significant effect upon primary producers and other aquatic organisms in these waters. Existing data were inadequate for accurately estimating the penetration of biologically effective dosages of present and potential future levels of UV irradiance into various natural waters. An underwater spectroradiometer, designed specifically to measure spectral irradiance in the middle ultraviolet (MUV, 280-340 nm), has been designed, constructed and used to obtain ecologically important data.

The light output of He-Ne lasers has been found to be sensitive to acoustic pressures applied to the lasers. It is theorized that the variation in the laser output is due to the following pressure effects: (1) microscopic mechanical deformations, both linear and angular and (2) pressure changes of the He-Ne gas. A one mw laser in air responds to sound waves with fair sensitivity from 80 Hz to 10 kHz and as a hydrophone with somewhat better sensitivity from 500 Hz to 50 kHz.

The Continental Margin Sediment Dynamics program of the U.S. Geological Survey has been using a variety of optical instruments to monitor water turbidity as part of our studies of sediment transport. Although we suspect that optical devices will eventually be supplanted by more direct measures of suspended sediments, results of several field experiments indicate that for now transmissometers and nephelometers offer the best solution to the problem of long term environmental monitoring in the ocean. The Continental Margin Sediment Dynamics (CMSD) program of the U.S. Geological Survey is structured to investigate those oceanographic and geological processes which influence and control the active transport of sediments and other materials over continental margins. The focus of this program is on active sedimentary processes, the mechanisms which create them, and the effects they produce (see Figure 1 for a diagrammatic depiction). Basically, we design our experiments to investigate (1) transport mechanisms of oceanic sediments and other materials as suspended load and bed load, and (2) relationships of erosion and deposition to the dynamical characteristics of oceanic bottom boundary layers. The purpose of this report is to describe briefly those aspects of equipment and experiments that relate to our study of suspended particulate matter and water turbidity. Much of our understanding of the spatial distribution and temporal variability of suspended sediments depends upon measurements from optical instruments. In this report we describe those instruments and give examples of their use and some results of two field experiments.

The effect of shape on the fall velocity of silt-size mineral particles was investigated by recording sequential transmission holograms of settling particles. Particles with similar densities and settling speeds varied in their sphere-equivalent radii by a factor of 5. The large particles were edgewise-settling thin flakes while the smaller particles were much more compact. Variations of the Stokes settling equation for thin disks accurately described the settling data for large thin flakes. The fall velocities for small, compact, fast-settling particles were much greater than for volume-equivalent spheres and were adequately described by the Stokes equation for elliptical cylinders. An unresolved problem remains in that the theoretical drag on thin disks is about four times that on flat elliptical cylinders of the same surface area.

Measurements of light scattering and light attenuation were made for suspensions of formazin and diatomaceous earth. Light scattering was measured for light of wavelength 632.8 nm at angles from 0.1° to 1.0° and for light of wavelengths 400, 500, 550, 600, 650, and 700 nm at 45°. Light attenuation was measured over a 25 cm pathlength for light of 660 nm. These measurements were made for suspensions which varied from 0 to 40 Jackson Turbidity Units of formazin and 0 to 40 mg/1 of diatomaceous earth. The results indicate the necessity for multiple optical measurements for determinations of turbidity of water. In addition the tables and curves presented may be used in the calibration of light scattering meters and transmissometers which are used for turbidity studies.

The characteristics of the Coastal Zone Color Scanner (CZCS) are described. The factors affecting the apparent radiance signature at the satellite are presented along with some representative examples of measured spectral radinces, irradiances and transmittances in the ocean and in the atmosphere. Finally an example is presented of the spectral radiance components measured and computed for an experiment conducted in southern California coastal waters for the purpose of obtaining surface validation data at the time of a satellite overpass.

A multi-stage experiment has been conducted over Lake Ontario during the summer season of 1979 in conjunction with CZCS overpasses. Airborne data were acquired with a multi-spectral 11 channel imager, a two channel experimental pushbroom imager, a profiling 4 channel photometer and a 500 spectral element profiling spectrometer. Ground based radiance measurements of the atmospheric attenuation coefficient and sky radiance were made at six wavelengths. The airborne and atmospheric measurements were made to coincide with CZCS overpasses and in-situ measurements were made from a ship which traversed the lake along the same line from the Niagara River to Toronto during the same day. The remote experimental data will be corrected for atmospheric effects and inverted to predict water quality parameters. The experiment and some preliminary results will be discussed.

An application of characteristic vector analysis to ocean color spectra for the detection of pollutants in water is described. The technique can be useful for detecting and distinguishing among a variety of substances in the water. The analysis also illustrates the variability of the water color spectra with both concentration and depth distribution. Both concentration and depth information may be extractable from passive multispectral data under certain circumstances.

This paper describes experimental remote sensing of subsurface water temperature using the Raman spectroscopic technique. Using a pulsed laser and range gating detection techniques, Raman scattering is analyzed as a function of depth in a radar-like echo mode, and thus subsurface profiles of temperature and transmission are obtained. Experiments are described in which Raman data using polarization spectroscopy has been obtained from a ship as a function of depth in ocean water near Grand Bahama Island. Spectral temperature accuracy of °C has been obtained from this data in the first two optical attenuation lengths. Raman data obtained from ocean water using the NASA airborne oceanographic lidar is also presented.

A novel procedure for remote determination of the statistics of the ocean surface geometry is presented. A simplified treatment of the concept and a computational evaluation of some sources of error are given.

A new device intended to measure internal wave phenomena, benthic transport phenomena and propulsion system hydrodynamics is introduced. This device, in measuring vorticity, is able to investigate small scale fluid behavior, a behavior that is difficult to capture by the turbulence measuring techniques presently employed. The vorticity meter approach introduced utilizes Laser Doppler Velocimeter techniques. This approach has the promise of providing rotational sensitivities of from 10^-3 to 10^-4 radians sec^-1 at scale sizes ranging from 1 mm. to 10 m. An additional benefit of the technique is that it provides a remote sensing capability with a 10 to 20 meter standoff range under favorable water conditions. A proposed two-dimensional display of the output of this instrument should greatly enhance the recognition of the hydrodynamic phenomena taking place.

A computer model is presented which allows the image components of an underwater camera system to be computed. Input parameters to the model are system geometry, source properties, and water optical properties. Output products are the irradiances due to non scattered object light, scattered object light and backscattered light. From these basic quantities other useful parameters such as contrast transmittances and signal to noise ratio can be calculated over the entire field of view of the camera. Sample calculations are presented.

A mathematical model, Visibility Evaluation of Underwater Systems (VEUS), used to predict the optical response of deep-sea viewing systems, is under development. The model predicts the scene modulation (target contrast), target irradiance, and total exposure at the focal plane as a function of the following: (1) viewing and lighting geometry, (2) spectral water characteristics, (3) spectral light source emittance, (4) spectral camera and film characteristics, and (5) target and background reflectance. The model sums light energy over the visible spectrum contributed by discrete water slabs between the viewing system and the target. Water clarity characteristics (volume scattering function, diffuse attenuation coefficient and volume attenuation coefficient) were measured in several different areas and this data formed the basis for a test comparison between the mathematical model and actual photographs taken with TELEPROBE, a deep-tow viewing system. This test has shown the model produces data that agree with photographic response.

Some optical measurements may be greatly simplified by invoking the principle of reciprocity. The particular case of measuring point spread functions along long vertical paths in seawater is demonstrated, and the equivalence of this data to beam spread functions over the same paths is pointed out.

This paper traces the evolution of early underwater television work, right through. today's hardware and into tomorrow's technology. It discusses basic design criteria of the camera electronics, lens and view port physics, housing materials, and lighting requirements -- thus providing a valuable insight into the overall mechanism of an underwater closed circuit viewing system.

Optical transmission through the atmosphere is degraded both by the turbulence-induced fluctuation of the optical index, described by Cn², the turbulence structure constant for index, and also by extinction due to molecular absorption and scattering by fog or aerosols. Various techniques for direct optical measurement of Cn² and extinction are compared and the results shown to depend differently on the distribution of turbulence along the path. Tech- niques of field optical measurements of Cn² and extinction coefficient developed at NPS are presented. Results are compared with thermal and humidity fluctuations, and Knollenberg particle size spectra.