1. a type of lens with a surface consisting of concentric grooves, designed to focus light while remaining thin and lightweight
Usage: often capitalized when referring to the Fresnel lens invented by Augustin-Jean Fresnel; commonly used in lighting equipment, lighthouses, and optical devices
2. a type of theatrical spotlight that uses a Fresnel lens to produce a soft-edged beam of light
Usage: theater and film production terminology

Examples

• The lighthouse used a large Fresnel lens to magnify and project the light beam across the ocean.
• Stage lighting technicians positioned several fresnels around the set to create the desired mood.
• Fresnel lenses are found in many modern car headlights because they are compact and efficient.
• The photographer used a fresnel to soften the harsh shadows in the studio.
• Fresnel lenses reduce weight while maintaining optical performance in camera viewfinders.