Illumina Fresnel Lens for Shortest DIY Projector Focal Length 185mm India (Former Globalibay) Item DescriptionThe Fresnel lens reduces the amount of material required compared to a conventional lens by dividing the into a set of concentric annular sections. An ideal Fresnel would have infinitely many such sections. In each section, the overall thickness is decreased compared to an equivalent simple. This effectively divides the continuous surface of a standard into a set of surfaces of the same curvature, with step wise discontinuities between them.In some lenses, the curved surfaces are replaced with flat surfaces, with different angle in each section. Such a can be regarded as an array of prisms arranged in a circular fashion, with steeper prisms on the edges, and a flat or slightly convex center. In the first (and largest) Fresnel, each section was actually a separate prism. 'Single-piece' Fresnel lenses were later produced, being used for automobile headlamps, brake, parking, and turn signal, and so on. In modern times, computer-controlled milling equipment (CNC) might be used to manufacture more complex lenses.Fresnel design allows a substantial reduction in thickness (and thus mass and of material), at the expense of reducing the imagingof the, which is why precise imaging applications such as photography still use conventional bulky lenses.This is best fit for 7" and below LCD, It has holes at corners for proper fixing.Focal Length : 185mmSize: 120X180mmThickness: 2mmMaterial: PMMAGroove Pitch: 0.3.