When we talk about microlens we are referring to small lens that possess a diameter that is smaller than a millimeter and are most often about 10 micrometres in size. From a design standpoint, the miniscule size of the lenses provides a feature that offers excellent optical quality but can be prone to some unwanted effects like optical diffraction.

Microlens typically can be a single element that contains a plain surface and a single spherical convex surface for the purpose of refracting the light. The fact that microlenses are quite miniscule, the substrate that supports them is most often thicker than the lens and therefore should be considered in the design. Advanced lenses may use aspherical surfaces while others may feature several layers of optical material for them to achieve the desired design performance.

GRIN LENSAnother kind of microlens contains a couple of flat as well as parallel surfaces and the concentrating effect is achieved through a variation of refractive index across the lens and is known as gradient-index lenses or GRIN. There are some microlenses that attain their focusing effect through both the variation in refractive index as well as the surface shape.

Microlens arrays feature several lenses formed in a one dimensional or two dimensional arrays on a supporting substrate. In the case where each of the lenses contains circular apertures and hence not allowed to overlap with one another, the solution is placement in a hexagonal array so as to achieve the best coverage of the substrate. What you need to know is that there will still be gaps between the lenses which can only be reduced by making the microlenses with non-circular apertures. For optical sensor arrays these feature tiny lens systems that focus and concentrate the light source onto what is called a photodiode surface as opposed to making it come in contact with non-photosensitive sections of the pixel device.

Another kind of microlens also known as micro Fresnel lenses can focus light via refraction through a set of concentric curved surface. These lenses can be made quite thin and very lightweight. On the other hand, binary focus lenses concentrate light via the diffraction process. The contain grooves that feature stepped edges or multilevels that estimate the most ideal form. They are quite advantages in replication and fabrication like semiconductor processes featured in photolithography.

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