Face-to-face vision is a type of view characteristic of the insect, crustaceans and some other invertebrates, which is characterized by the presence of facet eye. Facial eyes have a complex structure and consist of small structural units (ommatidiyev), the shape of the cornea of a lens which is similar to a convex hexagon (face).
The facet of vision is characterized by a poor distinction of small details, but the good ability to distinguish between frequent flashing of light - up to 250-300 Hz, while for a human the limiting frequency is 50 Hz.
Features of the facet view of insects
The facet of the insects is immobile, unlike the human eye, for example, which has a characteristic binocular vision. The eyes of the grandma occupy almost the entire surface of her head and consist of 30 thousand structural particles. The number of ommatyids in different types of insects is different: in the working ant they are in the eye of about 100, in bees - 5 thousand, in the room flies - 4 thousand, and in butterflies - up to 17 thousand.
What is the difference between the facet type of vision and the binocular? Binocular vision of a person gives him the opportunity to perceive the world volumetric, coordinate their movements while walking, jumping, navigate the locality, assessing the distance to the object and the location of objects relative to each other.
However, human vision is limited by space with an angle of about 46 °. If we need a bigger look, we reflexively move the eyeball to the side or turn our head. The facet of vision of insects through the arrangement of the eyes in the form of two hemispheres with a large number of ommatydiev allows the insect to see objects and the surrounding space on all sides without turning their heads.
The image perceived by the facet type of view looks like a mosaic, where each element is perceived by one structural unit of the eye, and together they reproduce the overall picture. Each human eye, due to the presence of a lens, perceives and focuses the image by sending a signal to the brain where a single picture is formed.
Varieties of facial eyes
Anatomical ommatydiev, providing face-to-face vision, and their optical properties in different insects are different. Depending on this, there are three types of facial eyes:
- Apozitsionnye - are found in daytime insects. The opaque pigment constantly separates the facets that are close, so the receptors of the eye perceive only that world, which coincides with the axis of this ommatydia;
- Opto-soperpositivnye - found in the twilight and night-time insects and crustaceans. The pigment has the ability to move and isolate ommatydia alternately, which increases the sensitivity of the eyes in low light;
- Neurosuperpozitsionnye. The sight cells that are in different ommatydia, but receive light from one and the same point of space, sum up the signal.
The features of the facet view of insects, which consist in a broad space review, gave rise to a new direction in the development of applied optics, aimed at the development of artificial face-to-face, which can be used in miniature video surveillance and control systems.