Abstract
We demonstrated a unique monolithic integration of Fresnel elliptical zone plate (EZP) objective on a 2-axis staggered vertical comb-drive micromirror with 500 μm by 800 μm surface area via direct patterning of reflective binary phase modulation elements on a silicon chip. The need for focusing optics is thus obviated, simplifying the micro-endoscope assembly and improving its form factor. The design of binary phase EZP was guided by simulations based on FFT based Rayleigh-Sommerfeld diffraction model. For dual-axis scanning angles up to 9º by 9º at the image plane, the simulated diffracted Airy disks on a spatial map have been demonstrated to vary from 10.5 μm to 28.6 μm. Micromirrors scanning ±9º (optical) about both axes are patterned with elliptical zones designed for 7 mm focal length and 20þ off-axis 635-nm illumination using 635 nm laser. Videos of samples acquired with ~15 μm lateral resolution over 1mm × 0.35 mm field of view (FOV) at 5.0 frames/second using the device in both transmission and reflectance modes bench-top single-fiber laser scanning confocal microscope confirmed the applicability of the device to micro-endoscopy.
Highlights
In vivo optical imaging is an important tool for medical diagnosis in situations where biopsy is difficult, and for image-guided microsurgery and photodynamic therapy [1]
As a special form of Fresnel zone plate, the elliptical zone plate (EZP) is designed by projecting the circular zone plate annular pattern onto a plane tilted at an angle which will determine the off-axis angular position for reflection
Novel monolithic integration of reflective binary-phase modulation elements on two-axis Microelectromechanical system (MEMS) scanning micromirrors is demonstrated for simultaneous beam scanning and focusing in a compact single-chip solution
Summary
In vivo optical imaging is an important tool for medical diagnosis in situations where biopsy is difficult, and for image-guided microsurgery and photodynamic therapy [1]. Toward minimizing the system form factor and assembling complexity, in other literatures MEMS micromirrors with both refractive [12] and diffractive [13] lenses were fabricated for distal scanning imaging. These techniques suffer from slow scan rates and increased optical aberrations. High accordance of the experimental measurements with the simulation demonstrated the feasibility of the EZP design. Both theoretical analysis and testing results proved its applicability to a novel fastimaging handheld lens-free micro endoscope
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