Microlens arrays are used for increasing the optical fill factor in charged coupled devices (CCDs) that suffer from reduced aperture because of metal shielding. Such tiny systems act to focus light onto the photodiode surface rather than letting it fail on non-photosensitive areas of the device, where it’s lost from the imaging information the CCD collects. The microlenses may be circular, hexagonal, or square while the array may be square, hexagonal, or geometric shape. Microlens arrays are also used in light field cameras and optical microscopes, as well as for 3D imaging and displays.
Manufacturers produce both 1- and 2- dimensional arrays in various configurations, focal lengths, and sizes. Such arrays are made from high-quality fused silica. Photolithographic techniques and semiconductor processing technology lets manufacturers produce precisely positioned arrays that have very accurate shaping of the lens profile. Also, they work with customers to produce custom micro lens arrays based on their specifications.
Microlens arrays offer a large field of view angles, low aberration and distortion, high temporal resolution, and infinite depth of field. Such properties make them the right design component in 3D imaging. Microlens arrays can be used with different light emitters to homogenize light. But, they are particularly useful for optical applications that require non-Gaussian uniformity and high efficiency.
Microlens arrays can be used in a digital projector to focus light on to the LCD’s active area to generate the image to be projected. A LED pico-projector novel design includes the use of a special array of 45 microlenses on the display coverglass. The array lets the projector be highly compact and robust while having the capability to produce bright, crisp imagery.
Kinds of Microlens Arrays
Below are some of the types of microlens arrays available:
- Fly’s eye arrays. These arrays consist of individual square or rectangular microlenses mounted on a substrate in a close-packed configuration. Typically, they have 7-11 channels in every direction, optically overlapped in the illumination plane. These microlenses have surfaces that may be anamorphic or spherical.
- Square microlens arrays. These arrays are mainly used for beam homogenization and shaping. They have a very high fill factor (up to 98%) that eliminates zero-order hot spots in the illuminated field. Manufacturers can produce a standard square microlens with 10mm x 10mm configuration, but they can also produce custom sizes upon request. Customers can choose from a variety of focal lengths and lens pitch options.