See under Lens.
a very thin lens designed to be equivalent to a much thicker lens made the conventional way (see figure 23.14)
Optical lens named after its inventor Augustin-Jean Fresnel. Originally developed for light houses, since it allows the construction of huge lenses with low focal distance. Today it is used in overhead projectors and rear projection tvs.
Lens which produces a soft-edged beam of light.
Condenser lens used on a spotlight to gather together the rays of light coming from a source and direct them into a narrow beam.
Used to focus light. The lens is virtually flat.
A parabolic type lens invented by French physicist Augustin Fresnel, commonly used in lighthouses throughout the world. Classified by size into six "orders" based on the lens focal length. The First Order is the largest at 12 feet tall with a diameter of 6 feet and a focal length of 36 inches. The Sixth Order is the smallest at 2 feet tall with a diameter of 1 foot and a focal length of 5.9 inches. Click here to see a Second Order lens
lens composed of a number of small lenses arranged to make a lightweight lens of large diameter and short focal length
a 'flat' lens, or rather, the lens curve is collapsed down to a series of very fine concentric rings
a fraction of the size and weight of a conventional lens, and the image is more distorted
an accessory for a groundglass focusing screen
a Plano Convex lens that has been collapsed on itself to form a flat
a plastic flat lens with striations on it to focus light
a transparent plastic sheet with fine round grooves on the surface
A thin optical lens consisting of concentric rings of segmental lenses and having a short focal length.
This is the lens on a PIR. It is called a fresnel lens due to the grooves cut into it. It is these grooves that create the beam pattern. There are 4 main types, which are: 12 metre, 30 metre, Pet Alley or Curtain.
Acts as a large convex lens that gathers light from the CRTs (Cathode Ray Tubes) and prevents it from spreading throughout the viewing room, greatly enhancing picture brightness and contrast.
A flat lens that is composed of a series of closely spaced grooves that control the refraction of light. It is usually part of the stage.
A concentrating lens, positioned above and concave to a PV material to concentrate light on the material.
A type of optic consisting of a convex lens and many prisms of glass which focus and intensify the light through reflection and refraction.
Manufactured using a molding process that results in annular rings (or grooves) in thin plastic/acrylic. Each groove refracts the light as if it were a part of a whole conventional lens. The result is a lighter lens that can have a lower f/# than a conventional glass lens of the same focal length. The original design for this type of lens was made by A.J. Fresnel for use in lighthouses.
A system of annular prisms that refract and reflect into a beam; invented in 1821 by Augustine Fresnel; this system captures and focuses up to 70% of the light emitted from the illuminant. Fresnel designed a variety of lens system sizes which he defined by orders. Today, there are 9 modern equivalents to his original orders, first through sixth (including a 3 1/2 order), a meso radial, and hyper radial. The first-order lens is the largest and is typically used in coastal lights. The sizes of the lenses and their effective range decrease as the order number increases. Click here for a more detailed description.
A plano-convex lens constructed with the convex surface flattened into concentric rings that collect and direct light into parallel rays.
An optical device for concentrating light that is made of concentric rings that are faced at different angles so that light falling on any ring is focused to the same point.
An optical device that focuses light like a magnifying glass; concentric rings are faced at slightly different angles so that light falling on any ring is focused to the same point. Fresnel lenses are flat rather than thick in the center and can be stamped out in a mold.
A Fresnel lens is a type of lens invented by Augustin-Jean Fresnel (pronounced fre-NELL in scientific and lighting applications, although often pronounced FREZ-nell). Originally developed for lighthouses, the design enables the construction of lenses of large aperture and short focal length without the weight and volume of material which would be required in conventional lens design. Compared to earlier lenses, the Fresnel lens is much thinner, thus passing more light and allowing lighthouses to be visible over much longer distances.