Fresnel lenses (also known as threaded lenses) are widely used in LED lighting lens, projection photography lighting, spotlights, and human infrared sensing products. The optical system of LED lens and spotlights consists of multiple Fresnel lenses. By utilizing the principles of light transmission and refraction, dispersed light sources can be focused into light spots or evenly distributed in parallel. In addition, in photographic lighting equipment, the luminous body of the light source can be focused at the center position of the spherical reflector through a Fresnel lens. Through the focus adjustment mechanism, the light source and reflector can move forward and backward along the optical axis of the Fresnel lens, thereby obtaining a beam of light with constantly changing angle sizes.
Fresnel lenses (another process is non threaded lenses) are usually pressed with various patterns of turtle shell or honeycomb patterns to scatter light appropriately, resulting in a soft and uniform lighting effect. There are no obvious boundaries in the illuminated light field, making it easy to receive light. The beam angle of this lamp can be adjusted within the range of 15 ° to 60 °. There is a sunshade called a sunshade outside the lightbox, and there is usually a frame in front of the lens that can be used to install light paper.
Most of the Fresnel lens spotlights used in cinematography lighting use tungsten halogen lamps as the light source, forming a series of lamps ranging from 200 watts to 20 kilowatts depending on the power of the light source. In addition to tungsten halogen lamps, there are also Fresnel lens spotlights with carbon arc as the light source, commonly referred to as carbon lamps. Carbon lamps have complex mechanical structures, heavy weight, large volume, and are contaminated by cyanide gas and smoke. However, due to the high luminous intensity and wide beam projection surface of carbon lamps, they can form high illuminance and are still difficult to be replaced by other types of lamps. In the 1980s, Fresnel lens spotlights using metal halide lamps as light sources entered the practical stage and gradually improved.
