micro lens by pant
Apr 07, 2018 Written by Anurag Pant Lens
1.A microlens is a small lens, generally with a diameter less than a millimetre and often as small as 10 micrometres The small sizes of the lenses means that a simple design can give good optical quality but sometimes unwanted effects arise due to optical diffraction at the small features.
2.Micro-lens arrays contain multiple lenses formed in a one-dimensional or two-dimensional array on a supporting substrate. If the individual lenses have circular apertures and are not allowed to overlap, they may be placed in a hexagonal array to obtain maximum coverage of the substrate.
3.The optical efficiency of diffracting lenses depends on the shape of the groove structure and, if the ideal shape can be approximated by a series of steps or multilevels, the structures may be fabricated using technology developed for the integrated circuit industry, such as wafer-level optics.
4.Advances in technology have enabled micro-lenses to be designed and fabricated to close tolerances by a variety of methods. In most cases multiple copies are required and these can be formed by or embossing from a master lens array.
5.Single micro-lenses are used to couple light to optical fibres while microlens arrays are often used to increase the light collection efficiency of CCD arrays. They collect and focus light that would have otherwise fallen onto the non-sensitive areas of the CCD.
6.Combinations of microlens arrays have been designed that have novel imaging properties, such as the ability to form an image at unit magnification and not inverted as is the case with conventional lenses.
7.Micro-lens arrays have been developed to form compact imaging devices for applications such as photocopiers and mobile-phone cameras.
8.In order to characterize micro-lenses it is necessary to measure parameters such as the focal length and quality of transmitted wavefront. Special techniques and new definitions have been developed for this.
9.It is useful to know the distance at which the maximum amount of light is concentrated in the fibre aperture and these factors have led to new definitions for focal length.
10.micro-optics are to be found in nature ranging from simple structures to gather light for photosynthesis in leaves to compound eyes in insects. As methods of forming micro-lenses and detector arrays are further developed then the ability to mimic optical designs found in nature will lead to new compact optical systems.