Compound eye

A compound eye is a visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidia, which are tiny independent photoreception units that consist of a cornea, lens, and photoreceptor cells which distinguish brightness and color. The image perceived by this arthropod eye is a combination of inputs from the numerous ommatidia, which are oriented to point in slightly different directions.

Compared with single-aperture eyes, compound eyes have poor image resolution; however, they possess a very large view angle and the ability to detect fast movement and, in some cases, the polarization of light.
Because a compound eye is made up of a collection of ommatidia, each with its own lens, light will enter each ommatidium instead of using a single entrance point.
The individual light receptors behind each lens are then turned on and off due to a series of changes in the light intensity during movement or when an object is moving, creating a flicker-effect known as the flicker frequency, which is the rate at which the ommatidia are turned on and off– this facilitates faster reaction to movement; honey bees respond in 0.

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Source: Wikipedia · Image: Wikimedia Commons · CC BY-SA 3.0