BIOLOGICAL VISION has a dual character. It is designed to provide a comprehensive overview of the operation of the visual system of any animal (including humans) while simultaneously providing a guide to the larger work, PROCESSES IN BIOLOGICAL VISION. The latter work is currently available in draft form on the World Wide Web. The larger work provides a more comprehensive analysis of each subject addressed in BIOLOGICAL VISION. It also provides an extensive list of references in support of it.

BIOLOGICAL VISION contains nine chapters. The first chapter begins with a phylogenic tree of the animal kingdom based on vision. The last ends with a series of figures defining the overall performance of the human visual system. Contrary to superficial statements in the recent literature, it shows that animals have enjoyed color vision for at least the last 500 years, long before the arrival of man. It also shows that biological vision is characteristically tetrachromatic; it involves four separate and distinct spectral detection channels. The work takes a major step forward in showing that the human retina is also tetrachromatic, although the overall performance of the human visual system is partially blocked by the absorption of the lens system. The resulting human visual system is best described as a blocked tetrachromat.

Chapter Two addresses the three fundamental forms of eyes found in the animal kingdom. It shows the frequently defined dichotomies within the animal kingdom are inappropriate when discussing vision. The families of Arthropoda, Mollusca and Chordata exhibit unique visual features that justify the use of a trichotometric approach when discussing the phylogeny of vision.

Chapter Three presents the overall architecture and signaling schematics found in animal vision. It defines the previously unrecognized role of the thalamus and other elements of the diencephalon in vision. It shows why the "primary visual cortex" does not play the primary role long envisioned in the literature. The primary role in the vision of the higher chordates is shown to be played by the thalamus. The thalamus is key to the ability of humans to analyze fine detail and to read. For the first time, the crucial role of the thalamic reticular nucleus in controlling the overall operation of the sensory systems of the organism is described. The chapter defines the multiple signaling modes involved in sensing and responding to the environment. These include the awareness, analytical, alarm and volition modes.

Chapter Four focuses on the operation of the neuron in its various forms required to support the overall operation of the neural system. The internal electrolytic operation of the neuron is presented for the first time. This presentation includes the description of its signal amplifying mechanism based on the Activa. The Activa is the electrolytic liquid-crystalline semiconductor equivalent of the man-made transistor. The Activa being a three-terminal device results in a major redefinition of the fundamental morphological and physiological characteristics of the neuron. It is demonstrated that, while the neuron is the fundamental morphological element of the neural system, it is not the fundamental electrophysiological element.

Chapters Five, Six and Seven focus on the unique characteristics, and close integration, of the photoreceptor cells, their associated retinal pigmented epithelium (RPE) cells and the inter-photoreceptor-matrix (IPM) between the two cell types.

Chapter Five is devoted to describing the unique characteristics and operation of the photoreceptor cell from a multitude of perspectives. Like other sensory cells, it is shown to exhibit a neuro-secretory nature. In common with tactile sensory cells, it secretes a protein substance, opsin, used to produce the disks associated with it. Unlike, the tactile cells, the photoreceptor cells sense energy absorbed by the chromophores of vision rather than the energy due to bending of the individual hairs associated with the cells. The chromophores of vision are shown to originate in the RPE cells rather than, as previously thought, the photoreceptor cells themselves.

Chapter Six reviews the photochemistry of biological vision and shows there are four (not three) chromophores associated with vision. The formation of these four chemical species within the RPE cells, and their delivery via the IPM, is examined in detail.

Chapter Seven explores the morphogenesis of the chordate eye, with its reversed retina. It then explores the physical (cytological) dynamics of the photoreceptor cells. It shows that the so-called cones of vision are in fact immature or nonfunctional photoreceptor cells. This leads to the demonstration that all photoreceptor cells are morphologically rod-shaped and physically identical. They differ only in the type of chromophore used to coat their individual disk stacks.

Chapter Eight addresses a variety of features of the visual system architecture not widely appreciated. A top level schematic of the entire visual system is provided along with a top-level functional diagram. These two diagrams support the computational anatomy employed to simplify the mathematical calculations required in the neural system. It is shown that computational anatomy frees the neural system from the need to perform transcendental arithmetic. Finally, the unique two-dimensional associative correlator employed within the perigeniculate nucleus/pulvinar couple to extract features associated with the imaged scene is presented. This couple is key to the abilities of higher chordates, to interpret fine detail (and in the case of homo sapiens, to read).

Chapter Nine culminates in a summary of the performance achievable in human vision. The focus is on the five major performance characteristics. First, the transient response of the detection process. Second, the overall spectral performance (luminous efficiency function)of the visual system. Third, the chromatic (color rendition) capabilities of the system. Fourth, the dynamic sensitivity control (adaptation) capability of the system and the associated phenomenon of color constancy. And fifth, the temporal and spatial contrast performance of the system.

For the first time, the complete photoexcitation/de-excitation mechanism and equation of visual sensing are described. It shows the equation, proposed by Hodgkin during the 1960's as part of a piecewise solution, is actually a special case of the general mathematical solution. The special case of the long wavelength spectral channel is also developed. It is shown why the spectral performance of the visual system in the long wavelength region is lost as the scene illumination is reduced. For the first time, a cogent description of the transition from hypertopic, through photopic and mesotopic to scotopic vision is presented. Using the schematics presented earlier, the chapter provides a physiologically based Chromaticity Diagram for the first time. This three-dimensional diagram is shown to be conformal over the entire spectral range of the tetrachromatic eye. A two-dimensional simplification of this Chromaticity Diagram is presented that is adequate (with caveats) for most studies in human vision. This diagram leads directly to the definition of a unique color set sought by the vision community for many years. When transformed into the coordinate system of the CIE (1935) Chromaticity Diagram, the non-conformality and general limitations of that presentation are highlighted. The new Diagram also leads to a theoretically precise three-dimensional lightness-chrominance space for the first time.

A brief section is presented on the mechanisms of perception and cognition. References are provided to the broader discussion in the larger work, PROCESSES IN BIOLOGICAL VISION.

James Fulton began his professional career in the late 1950's as an officer in the military-- supporting the Office of Special Projects under the Secretary of the Air Force. A very early task was to evaluate and compare the ultimate performance of television, photographic and human visual techniques as applied to high performance reconnaissance systems. This study clearly showed the superior performance of the eye in terms of ultimate sensitivity (quantum efficiency) but its limited signal amplification performance compared to the other systems. A quick series of projects implemented the same adaptation technique used in vision to the television cameras used in guided weapons such as the maverick. The use of this same technique led to the remarkable color-constancy achieved by the early vidicon-based color television cameras. This level of color constancy is again being sought in the non-vidicon commercial industry today.

To optimize a wide range of intelligence gathering equipment, understanding the photochemistry used in the visual process was important. This was successfully determined to be analogous to the photochemistry of color photographic film during the mid 1960's. The precise molecular structure of each chromophore was presented along with its unique liquid crystalline requirements.

Another critical task was the determination of the bandwidth and time delay found in the human visual system needed to optimize hand-eye coordination in the control of air-launched guided missiles.

The above studies led to a variety of military system implementations based on analogs of the biological visual system. A particularly interesting application was the emulation of the eye of a frog in a space-borne missile tracking system. Like the frog's eye, and the human eye in the absence of tremor, the sensor was blind to the scene presented to it except for targets that moved. This greatly simplified the data processing demanded of early (1970's) transistor-based computers.

Subsequently, the author patented one of the earliest examples of the two-dimensional retina used in current video cameras. This device incorporated many signal processing circuits found initially in the animal retina.

Recently, the author also patented the Activa, the man-made equivalent of the electrolytically-based amplifier found within each neuron of any neural system. This liquid-crystalline state semiconductor device is a direct analog of the man-made solid state semiconductor device known as a transistor.

The author held major engineering management positions within Grumman Aerospace Corporation and Hughes Aircraft Company. He was a Vice President of Hughes Optical Products, Inc. He retired from industry after leading the largest design and manufacturing operation in the world devoted to man-made retinas for the military. He is currently Director of Research for Vision Concepts of Corona Del Mar, California.

After applying the principles of visual science to military reconnaissance and intelligence for more than thirty years, the time came to reverse this process and describe the operation of the biological visual system for the unclassified community. This effort resulted in a very large and comprehensive work (2400 pages including more than 1000 figures), "Processes in Biological Vision," available at www.4colorvision.com. That work explores all aspects of vision in detail.

The size of the above work suggested that a more manageable introductory work was needed. The current work, "Biological Vision: A 21st Century Tutorial," is the outgrowth of that need.