What type of lens is typically used to collimate light from an LED?

A convex lens is typically used to collimate light from an LED because it converges the diverging light rays emitted from the LED into a parallel beam of light. LEDs generally emit light in a wide dispersion angle, meaning the light is not traveling in a straight line but rather spreading out from the source. By positioning a convex lens in front of the LED, the lens bends the light rays towards the optical axis.

When the light passes through the convex lens, the shape of the lens allows the rays to exit as parallel rays, which is the definition of collimation. This is particularly useful in applications where focused or directed light is needed, such as in illumination systems, projectors, and optical sensors.

The other types of lenses mentioned do not serve the same purpose effectively. A concave lens diverges light, a planar lens does not change the path of light rays significantly, and a cylindrical lens mainly focuses light in one direction rather than creating a parallel beam. Therefore, the choice of a convex lens is the most suitable for collating light from an LED.