Chapter 1. Vision System Design

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

Chapter 3. Eye 
Design Illustrations

Chapter 4. Eye 
 Reproduction

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

 
 
 
 
 
 
 
 

EYE DESIGN BOOK
Chapter 2
Sections A, B and C
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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

Figure 2.1. Camera Type  Optical Design variations Fig 2.1a. Camera Eye Structure Durations 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)

Figure 2.2a. Example  of Camera Eye Figure 2.2b. Human  Camera Eye (Like Fig 3.44a)

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)

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)

Figure 2.4. Rod and Cone Details

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)

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.

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

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)

Figure 2.8 Example of Concave  Mirror Design in Scallop Eyes