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Chapter 1. Vision System Design

Chapter 2.
Eye Designs
A. Camera
B. Pinhole
C. Concave mirror
D. Apposition
E. Neural
F. Refraction
G. Reflection
H. Parabolic
I. Multiple sensor 
types and 
combinations of types

Chapter 3. Eye 
Design Illustrations

Chapter 4. Eye 

Chapter 5. Optical 
 Systems Design 

Chapter 6. The Eye Designer

Related Links

Appendix A - Slide Show & Conference Speech by Curt Deckert

Appendix B - Conference Speech by Curt Deckert

Appendix C - Comments From Our Readers

Appendix D - Panicked Evolutionists: The Stephen Meyer Controversy
















Chapter 2
Sections A, B and C
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     Biological eye designs are classified into a number of broad categories. Some primitive eyes, plant eyes and eyes of some creatures do not have image-forming optical designs. These can be noted as multiple sensor types, but there are also creatures with a mix of image forming and non-image forming sensors. There are considerable optical variations within each of the eye design type. For example, we find variations in the use of simple or highly corrected compound lenses, sensor combinations, focusing, light control, color pigments in cells, resolution over field of view, maximum resolution, eye-supporting and pointing structures, and in other features. This section is divided into nine broad image-forming optical design types as follows: 
A. Camera 
B. Pinhole 
C. Concave mirror
D. Apposition compound 
E. Apposition-Neural superposition compound
F. Refracting superposition compound
G. Reflecting superposition compound
H. Parabolic superposition compound
I. Multiple sensor types and combinations of types
A . Camera
      Camera-type eye designs form an image on a retina (instead of film) from eye lenses. They are found in animals of all complexities and sizes such as humans, vertebrate animals, some aquatic creatures, spiders, and other creatures. In general, slightly different designs are required for small aquatic creatures such as jellyfish. 
     Figure 2.1 illustrates typical optical designs for a camera-type eye, where it forms an inverted image on the retina. (p.300, Fig. 2, Vision Optics & Evolution by Dan E. Nilsson, Biosciences, Vol. 39, No. 5, May 1989) 
      The following variations in Camera Eye structure illustrates applications for particular animals requiring different optical designs for their vision systems. All are based on the same design themes.
Figure 2.1a Camera Eye Structure Durations
(Reference: Figure 5.7, p. 83, Animal Eyes, Michael F. Land, Dan-Eric Nilsson, Oxford Animal Biology series, Oxford University Press, 2002- Please see their book for more details )
     There are many different approaches taken to focus camera type eyes. The following figure illustrates some of the extent of different focusing mechanisms.Figure 2.1b Camera Eye Focus
(Reference: Figure 5.9, p. 85, Animal Eyes, Michael F. Land, Dan-Eric Nilsson, Oxford Animal Biology series, Oxford University Press, 2002- Please see their book for more details )
      Good focus is not possible in all creatures having camera-type eyes. This is especially true in small eyes with a fixed focal distance between lens and retina, such as those in some fish and other aquatic animals. Precision focusing results from interactive controls between the eye and brain. This function is much like auto-focus lenses on man-made cameras. Some camera-type eyes focus by changing the shape of the lens instead of moving the lens relative to the retina. In an eye this takes place by muscles

fig2-01TN.gif Camera Type Optical Design variations 400x187
Figure 2.1. Camera Type 
Optical Design variations

fig2- Camera Type Opti01aTN.jpg Camera Eye Structure Durations 196x200
Fig 2.1a. Camera Eye
Structure Durations

fig2- Camera Type Opti01bTN.jpg Camera Eye Focus 278x200
Fig 2.1b. Camera
Eye Focus
changing the effective curvature of the lens from a shorter focal length to a longer focal length.
       Some camera eye focusing takes place using hydraulic methods. Here, fluid is moved in and out of chambers to adjust a fixed focal length lens relative to the retina to achieve focus. In addition, amphibious animals using this technique often need to provide radical water pressure accommodations using hydraulic controls.        Lens materials, photoreceptors' or light sensors' resolution, shape, size controls, color vision, and field coverage can be slightly different for eyes of different creatures. Large creatures typically have large visual fields with good resolution. The camera type eyes of birds, may have very close photoreceptor cell spacing for high resolution to see small targets at long distances. An example of an actual camera eye is shown in Figure 2.2. (Fig 2.2a by Bruce Chambers) (Fig 2.2b adapted from 1999 Eye Poster from Anatomical Chart Co. Skokie, IL)
fig2-02aTN.jpg Example of Camera Eye 400x251
Figure 2.2a. Example 
of Camera Eye
fig2-02bTN.jpg Human Camera Eye 200x163 Figure 2.2b. Human 
Camera Eye (Like Fig 3.44a)
     The density of photoreceptors at a specific point determines the resolution available at that point in the total field. In some variations of less-precise camera type eyes, the lens is so close to the retina that a clear image cannot be focused at very close or very far object distances. Some aquatic camera eyes use gradient index material to help correct the lens design. Gradient index surfaces are even difficult for man to define and to reproduce under ideal conditions, yet many cells, with very slight variations, grow into these unique patterns. 
     Some animals use eye scanning to achieve a larger effective field of vision with a smaller number of sensors. Typically, eye-pointing controls in the brain move the eye's center of vision to the area of interest. Normally, eye resolution is far less at the edges of the field of view than near the center where most detail is seen. This is typical of camera lens systems design, especially in wide field applications, where it is difficult to achieve high resolution over a large angular field of view. The placement and integration of each eye sensor indicates intelligent optical design.
     Human eye photo- receptors consist of rods and cones. Rods operate in dim light and cones are responsible for visual acuity and color perception. Small animals with just a few photo- receptor cells in small retina fields have very limited resolution. Figure 2.3 contains a cross section of the human retina to illustrate the design complexity of the layered sensor arrangement. (P. 31, The Computational Eye, Frank Werblin, Adam Jacobs, Jeff Teeters, IEEE SPECTRUM, May 1996) 
fig2-03TN.gif Cross Section of Human Retina 410x400
Figure 2.3 Cross Section of Human Retina
     There are many different configurations of rods and cones in camera-type eyes. Rods and cones are shown by Figure 2.4. (P. 548, Fig. 7, Science & Technology Encyclopedia, McGraw Hill)  fig2-04bTN.jpg Rod and Cone Details
Figure 2.4. Rod and Cone Details
     In some creatures, rods will have different color pigments to see efficiently in specific color environments. Others are packaged more densely for higher resolution and have less emphasis on detecting many different colors. Some retinas require light to pass through multiple retina layers more than once instead of just falling onto a single absorbing surface. Most biological eyes have wide-angle vision; however, some have wide-angle scanning capability where the moving eye provides only narrow angle vision at each image. 

B. Pinhole
      The pinhole eye design occurs in the eyes of the nautilus, the eyes of a planarian (flat worm) and the eyes of other simple animal forms. This is a less complex optical design 
that does not require a lens. Light is not focused with a lens like the camera eye. An example of this optical design is the pinhole box camera that came out during the 1930's and 1940's. This camera worked, without any lenses, by using natural optical light diffraction to form an image. Those cameras were easily improved upon with simple lenses. Figure 2.5 illustrates the pinhole optical design. As one of the less complex optical designs it may be the most likely to occur naturally without much intelligent optical design. This, of course, assumes the existence of the right mix and configuration of cells to make up this type of eye. 
(p.300, Fig. 2, Vision Optics & Evolution by Dan E. Nilsson, Biosciences, Vol. 39, No. 5, May 1989) 
fig2-05TN.jpg Pinhole Optical Design 200x250
Fig 2.5 Pinhole Optical Design (Like Fig. 6-2)
     The pinhole eye retina is relatively simple and similar to the camera eye retina. It does not have a lens (or much of a lens) so it does not provide fine optical corrections like the
camera eye, the resultant image is less clear. Variable pupils are used to adapt to a variety of lighting situations. It takes more light to detect a given scene because a bright image on the retina from a pinhole eye requires a large pupil (small f/no.) while a sharp image focus on the retina requires a small pupil (large f/no.). Therefore it is difficult to obtain sharp faint images using a pinhole optical design.  fig2-06TN.jpg Pinhole Eye of Nautilus 200x116
Fig 2.6. Pinhole Eye of Nautilus 
     Insects with compound eyes, such as flies, do not have a retina that can pre-process data, like creatures with pinhole or camera optics. For most insects, the total eye volume required for a scaled-down pinhole design would be much larger for a given angular field than more complex multifaceted eyes taking into account the expected light gathering power and resolution of each facet. 
     Insects achieve a greater field of vision in small packages than they would using the pinhole approach. An example of a pinhole eye is shown in Figure 2.6. (P. 281, Readers Digest, Exploring the Secrets of Nature, 1994)
C. Concave mirror
     The concave mirror design is found in a few small eyes. For example, when a clam opens its protective shell it exposes multiple eyes with a small concave mirror design. Each small concave mirror eye forms an inverted image on small retinas like the design shown in Figure 2.7. (p. 299, Fig. 1, Vision Optics & Evolution by Dan E. Nilsson, Biosciences, Vol. 39, No. 5, May 1989)
The large arrow represents the object the eye is looking at and the small arrow represents the image of the large arrow on the retina.
     Concave mirror eyes are more complex than pinhole eyes, since they use internal concave mirrors to form images. 
     Reflective mirrors are used as a substitute for lenses to form images on retinas. Potentially, they can have more total image resolution in a small space
fig2-07TN.jpg Concave Mirror Optical Design 240x334
Figure 2.7 Concave 
Mirror Optical Design.
than pinhole eyes, because they provide better-corrected optics in a small space. Typically, images are focused on transparent retinas, made up of arrays of transparent eye sensors. 
     This type of eye is like a reflective telescope design using one concave mirror instead of a camera lens. These are not as well-known eye designs as camera type eyes. It is difficult to achieve a wide field of view with high resolution using this type of design. Adapting this design of an eye from another type would be difficult. An example of the concave mirror type of eye is shown in Figure 2.8. (P. 322, Readers Digest, Exploring the Secrets of Nature, 1994 fig2-08TN.jpg Example of Concave Mirror Design in Scallop Eyes 400x291
Figure 2.8 Example of Concave 
Mirror Design in Scallop Eyes



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Related Links
Appendix A - Slide Show & Conference Speech by Curt Deckert
Appendix B - Conference Speech by Curt Deckert
Appendix C - Comments From Our Readers
Appendix D - Panicked Evolutionists: The Stephen Meyer Controversy
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