The importance of optical image quality and the trend toward thinner smart-phones have pushed manufacturers to increase the number of cameras in order to provide cellphones with better zoom, low-light-exposure, high-quality photography. But adding additional lenses to a miniaturized optical configuration and driving light focusing with an electronic device is difficult, particularly at small scales or in confined spaces.
The integration of an adjustable-dynamic zoom lens in a millimeter-thick cellphone, miniaturized microscope, or the remote end of a medical endoscope requires complex lenses that can handle the full optical spectrum and be reshaped electrically within milliseconds. Until now, a class of soft materials known as liquid crystal spatial light modulators has been the tool of choice for high-resolution light shaping but their implementation has proven to have limits in terms of performance, bulkiness, and cost.
A dynamically tunable lens capable of achieving almost any complex optical function was developed that manipulates light without any mechanical movement. In this Smartlens, a current is passed through a well-optimized micrometer-scale resistor and the heating locally changes the optical properties of the transparent polymer plate holding the resistor. In much the same way as a mirage bends light passing through hot air to create illusions of distant lakes, this microscale hot region is able to deviate light. Within milliseconds, a simple slab of polymer can be turned into a lens and back. Small, micrometer-scale Smartlenses heat up and cool down quickly and with minimal power consumption. They can even be fabricated in arrays and several objects located at very different distances can be brought into focus within the same image by activating the Smartlenses located in front of each of them, even if the scene is in color.
By modeling the diffusion of heat and the propagation of light and using algorithms inspired by the laws of natural selection, a properly engineered resistor can shape light with a very high level of control and achieve a wide variety of optical functions. If the right resistor is imprinted on it, a piece of polymer could be activated or deactivated at will to generate a given “freeform” and correct specific defects in eyesight or the aberrations of an optical instrument.