The Current Art of Underwater Imaging Πwith a Glimpse of The
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PAPER The Current Art of Underwater Imaging – With a Glimpse of the Past and Vision of the Future AUTHORS ABSTRACT Donna M. Kocak This State of Technology Report on Underwater Imaging provides a historical synopsis Green Sky Imaging, LLC of underwater imaging, discusses current state of the art, and suggests future possibilities Chair, MTS Underwater Imaging Committee for continued advancement of the field. The history presented herein provides information Frank M. Caimi assembled in a manner not found in previous reviews. Present work is grouped according Green Sky Imaging, LLC to imaging methodology wherein foremost research and technical innovations of the field are highlighted, with a focus on the past five years. Trends in research and development are also discussed as they relate to emerging underwater imaging techniques and technologies. INTRODUCTION bservation and exploration of the underwater realm has been of interest since ■ Electromagnetic (EM) methods that vances are often associated with imaging Oancient times and has forged the development utilize transparent regions of the spectrum hardware and methodology, credit must also of many technological advances. Advance- (near infrared, ultraviolet, visible, and very be given to developments in computer vi- ments in diving apparatus, submersibles, un- low frequency [VLF]); sion and pattern recognition that allow ex- derwater cameras and optics, underwater light- ■ Acoustic imaging techniques that include traction or interpretation of useful informa- ing, sonar, remotely operated vehicles (ROV), 3-D reconstruction and mosaicking; and tion from raw imagery or data. This focus and autonomous underwater vehicles (AUV) ■ Temporally discriminant or signal-coded has been noted in a recent publication that are the most notable. Although the quest to methods that support multidimensional underscores the difficulties and challenges travel to ocean depths has been pursued for image representations. of underwater imaging, which is written for centuries, emphasis on recording and obtain- Detailed descriptions of many of these the computer vision community (Murino ing or interpreting information beyond that preceding methods have been published else- and Trucco, 2000a). available from the human visual system is an where (Potter, 1999; Kocak and Caimi, 2001), important recent endeavor. Various hardware, and in Jaffe et al., 2001, where an emphasis is software, and algorithmic advancements, as placed on extended range imaging. A Glimpse of the Past well as better understanding of ocean physical Historically, imaging developments have “We can chart our future clearly and wisely parameters make this possible. For example: been slow to evolve and have taken decades only when we know the path which has led to ■ Conventional imaging methods that to reach the present state of the art. This has the present.” utilize standard cameras; been due, in part, to limitations stemming Adlai E. Stevenson (1900-1965) ■ Extended range imaging techniques that from incomplete understanding of radia- utilize time-gating or angular field restriction tive transfer in optical media such as air and “The farther back you can look, the farther for- to reduce unwanted image noise resulting seawater, limitations in image sensor elec- ward you are likely to see.” from optical scatter in the transmissive medium; tronic and optical hardware, and restrictions Winston Churchill (1874-1965) ■ Laser line scan methods that produce 2-D in data transfer, recording, and signal pro- or 3-D imagery; cessing throughput. Continued advance- Many advancements have enabled the ■ Holographic or other techniques that ments in these areas have effectively coun- evolution of underwater imaging, including: exploit spatial coherency; tered contrast and range reduction resulting direct methods for observation such as scuba, ■ Optical methods using frequency conversion from severe physical effects of light propa- underwater housing technology and vessels; (fluorescence, Raman, etc.) to develop gation in seawater. Similar observations hold development of the electronic camera, pho- higher-dimensional image data; for sound propagation and acoustic imag- tography, video recording and light sources; ■ Multiple-perspective methods that achieve ing. In 1999, a review of the field revealed invention of the laser and fluorometric analy- range depth or 3-dimensional (3-D) image dramatic advances in video technology, elec- sis; as well as the fields of information process- formation and display (including mosaics); tronic ballasting of HMI lighting, laser tech- ing, artificial intelligence and computer vision. ■ Image intensity algorithms based on image nology, mechanically and electronically Some key milestones in these topics are illus- processing techniques that exploit effects scanned sonar, and sonar processing algo- trated in the timeline shown in Figure 1 and such as shading, filtering, or motion; rithms (Olsson, 1999). Although these ad- are summarized on the following pages. Fall 2005 Volume 39, Number 3 5 FIGURE 1 Historical timeline of events leading to present day underwater imaging. Direct Observation Techniques they could pick up bottom sediment to deter- derwater visualization techniques. Dive appa- As early as 4500 B.C., diving provided a mine the topography (Hohler, 2002). ratus inventions included the first practical means for food gathering, commerce or war- Increasingly, direct observations were SCUBA in 1825 by William James, a diving fare for coastal cultures such as those found in sought by traveling into the depths of the sea. helmet converted from a patented “smoke Greece, Mesopotamia, and China. In 360 The first successful submersible vessel was built helmet” for firefighters in 1828 by Charles B.C., Aristotle wrote of sponge fishers using around 1620 by Cornelius Van Drebbel. The Anthony Deane, and, that same year, the first an air-supply diving bell; and in 332 B.C. watertight vessel was wood-framed and sheathed known buoyancy compensator by Lemaire Alexander the Great was reported to have in leather, capable of carrying a total of 20 people d’Augerville. However, it was not until 1869 made several dives in a crude glass diving bell to a depth of 20 m. In 1667, Robert Boyle when Jules Vern’s novel entitled 20,000 Leagues for observation (Bachrach, 1998). In the observed a gaseous bubble in the cornea of a Under the Sea was published that the inven- 1500’s, Leonardo da Vinci envisioned the first snake during his experiments with compres- tions of SCUBA were introduced to the world. known self-contained underwater breathing sion and decompression; however, many years apparatus (SCUBA) that combined an air sup- passed before Boyle’s discovery was put to prac- Camera, Photography and Video ply and buoyancy control in a single system. tical use in humans (Borrillo, 2001). John Scott Along with advancements allowing travel In the 1850’s, mariners recorded depth mea- Haldane created a procedure for staged decom- into the ocean depths, other inventions pro- surements, called soundings, by lowering a hemp pression to avoid “the bends” in 1908, which vided a means of documenting what was be- rope marked in equal distances with a lead ball culminated in the publication of the first U.S. ing seen both above and below the ocean’s on the end until the tension in the rope Navy dive tables in 1912. surface. The Chinese philosopher Mo Ti pro- changed to indicate that the ball had reached Developments enabling man to remain vides perhaps the earliest written mention of bottom. By covering the ball with grease, submerged for longer periods led to early un- imaging in his description, dating from the 5th 6 Marine Technology Society Journal century B.C., of images formed by a small ber of plates. Three years later Eastman an- Technologies, 2005). In 1979, National Geo- opening. In 4 B.C., Aristotle made similar nounced the invention of photographic film graphic was the first to use a CCD television observations. Ibn al-Haitham (Alhazen) re- in rolls and, in 1888, provides the first Kodak (TV) camera in the deep ocean. The story ported this concept in 10 A.D. and was cred- camera designed to use roll film. With these behind this expedition is provided here, para- ited with inventing the pinhole camera. In inventions, Eastman established the Eastman phrased from Emory Kristof (2005): the 1500’s, many artists used a dark box or Kodak Company (Bellis, 2005a). In early 1977, the hot water vents room with a hole in one end, known as a The world’s first underwater exposure are discovered about 100 miles north of camera obscura (Latin for dark room), to project was recorded at a depth of 6 m in 1856, the Galapagos Islands at 8,500 feet inverted images onto the opposite wall where when William Thompson published his ex- (2,590.8 m). National Geographic pub- they could be traced. Giovanni Battista della periment in the Journal of the Society of Arts lishes the first story on the vents in 1977. Porta’s writings in 1591 document the first (Baker, 1997). Thompson took the photo- A decision is made by the National Sci- use of a camera obscura with lens, to increase graph from the surface using a camera at- ence Foundation (NSF) to fund a second brightness and clarity (Hammond, 1981). In tached to a pole (a precursor to the ROV) Galapagos Rift Expedition with biolo- the early 1800’s, William Hyde Wollaston in- with an exposure time of 10 minutes. Not gists. National Geographic decides to pro- troduced a camera lucida (Latin for light room), surprisingly, the camera flooded but the im- duce a second story and a one-hour PBS which was merely a prism mounted above a age survived. In 1872, Ernest Bazin alleg- TV show. My investigations into TV drawing board that allowed an artist to trace edly took photos at an underwater observa- camera technology reveal that 3 tube cam- the superimposed image in ambient light. tory using an electric lighting system; however, eras are too large to package for exterior use All of these discoveries led up to the in- none of the photographs have been found on ALVIN, and that the quality of 1 vention of photography, a term coined by Sir (Gilbert and Alary, 1996).