Compared with monocular eye, compound eye is the main visual organ of insects, which usually occupies a prominent position in the head of insects. It is made up of many small eyes. Each eye has cornea, lens vertebrae, pigment cells, retinal cells, rods and other structures, and is an independent photosensitive unit. Axons extend backward from retinal cells, pass through basement membrane, and synthesize optic nerve.
Some arthropods have pigment cells in their compound eyes. When the light is very strong, the pigment cells will extend. Only direct light can reach the rod and be felt by the optic nerve. Oblique light is absorbed by pigment cells and not felt by optic nerve. In this way, each small eye can only form one image point, and the image points formed by many small eyes are combined into an image.
The difference between human eye and compound eye:
Because the small eyes in the compound eye open in different directions, the objects in the compound eye can be seen in three dimensions, and the objects behind the head can be seen, for example, some compound eyes of bees open to the back of the head, so the single eye on the compound eye can see a larger field of vision. In short, the range of compound eyes is as big as the object you see, which is a bit like a wide-angle lens. In fact, the function of compound eyes is the same as our human eyes, and they are all used to see things.
The eye of advanced animals is an evolutionary version of compound eye, so the imaging of compound eye is different from that of advanced animals. Generally, the eyes of advanced animals are imaged as retina, just as we see a whole when we see a picture, and the picture seen by compound eyes is often composed of countless points.