Advanced imaging with dynamic focus and extended depth using integrated FR4 platform

Abstract

A two-degrees-of-freedom scanned beam imaging system with large dynamic range and dynamic focusing is demonstrated. The laser diode, photo-detector and the optical components are integrated on a moving platform that is made of FR4 (Flame-Retardant 4), a common polymeric substrate used in printed circuit boards. A scan angle of 52 degrees is demonstrated at 60 Hz resonant frequency while the laser is moved 250 um in the out-of-plane direction to achieve dynamic focusing. The laser is scanned by physically rotating the laser diode and the collection optics to achieve high signal-to-noise ratio and good ambient light rejection. The collection optics is engineered such that the collection efficiency decreases when collecting light from close distances to avoid detector saturation. The detection range is extended from contact distance up to 600 mm while the collected power level varies only by a factor of 30 within this long range. Slight modifications will allow increasing the detection range up to one meter. This is the first demonstration of a laser scan engine with such a high degree of integration of electronics, optoelectronics, optics and micromechanics on the same platform.

Dichroic Scanning Nonlinear Optical Microscope With Photodetecting Polymer Scanner and Objective Lens With External Back Focal Plane

“…The polymer material called FR4 (flame retardant) glass epoxy is a popular and versatile high-pressure thermoset plastic laminate with excellent strength to weight ratio. As a composite material, FR4 has been used to form low-cost optical scanners and NIR spectrometers [19][20][21][22][23][24]. In this research the type I FR4 scanner has a rotating dichroic filter rather than a common reflective mirror plate to reflect the excitation beam and allow the transmission of emission photons which are received by an external photodetector.…”