Abstract
The design of optical transfer function (OTF) is of significant importance for optical information processing in various imaging and vision systems. Typically, OTF design relies on sophisticated bulk optical arrangement in the light path of the optical systems. In this letter, we demonstrate a surface-wave-interferometry aperture (SWIA) that can be directly incorporated onto optical sensors to accomplish OTF design on the pixel level. The whole aperture design is based on the bull’s eye structure. It composes of a central hole (diameter of 300 nm) and periodic groove (period of 560 nm) on a 340 nm thick gold layer. We show, with both simulation and experiment, that different types of optical transfer functions (notch, highpass and lowpass filter) can be achieved by manipulating the interference between the direct transmission of the central hole and the surface wave (SW) component induced from the periodic groove. Pixel level OTF design provides a low-cost, ultra robust, highly compact method for numerous applications such as optofluidic microscopy, wavefront detection, darkfield imaging, and computational photography.
Highlights
Optical transfer function (OTF) characterizes the response of an imaging system as a function of spatial frequency of the input signal
While these implementation methods allow for good control of OTF, they do come with the associated cost of sophisticated bulk optical arrangement
The Surface-Wave-Interferometry Aperture (SWIA) can be directly incorporated onto the pixel level of a modern CMOS active pixel sensor (APS) design, creating a new scheme for on chip OTF engineering that are much more compact and robust than those currently achievable options with bulk optical arrangements
Summary
Optical transfer function (OTF) characterizes the response of an imaging system as a function of spatial frequency of the input signal. The implementation of spatial filtering can be achieved by inserting a mask (phase, amplitude or both phase and amplitude) into the Fourier plane of a 4f system [1], or by using a spatial light modulator (SLM) to modify the phase and amplitude in real time [2]. While these implementation methods allow for good control of OTF, they do come with the associated cost of sophisticated bulk optical arrangement. The ability to modify the spatial response of single aperture on pixel level is beneficial to the design of various aperture based imaging devices [14]
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