ABSTRACT
Sophisticated non-mechanical technology for LIDARs is needed to realize safe autonomous cars. We have confirmed the operating principle of a non-mechanical LIDAR by combining concentric circular-grating couplers (CGCs) with a coaxially aligned rod lens. Laser light incident vertically on the center of the inner CGC along the center axis of the lens is radiated from the outer CGC and passes through the side surface of the lens. It is converted to a parallel beam that scans in two axes by applying voltages to two area-segmented electrode layers sandwiching the CGCs and a liquid crystal layer formed on the CGCs. We have demonstrated scanning whose motion ranges were 360 degrees horizontally and 10° vertically. A beam with a spread angle of 0.3° × 0.8° at a minimum swept vertically up to a frequency of 100 Hz and ten equally spaced beams scanned rotationally with a 6-degree cycle variation of spread of between 0.8° and 3.5°.
ABSTRACT
Interferometers are widely used in science and industry to measure small displacements, changes in refractive index, and surface irregularities. In all interferometers, including phase-contrast microscopes and DICs (differential interference contrast microscopes), light from a single source is split into two beams that travel along different optical paths. They are then recombined to produce interference. The fundamental operation of beam separation makes device configuration more complex and adds to the bulk of the equipment. In this study we propose a new method of observing phase-contrast images without beam separation by using self-interference inside a grating coupler structure disposed on the observation plane. We experimentally demonstrate that the self-interference principle can generate phase-contrast images using a simple configuration. From measurements using a multilevel phase plate, we confirm its phase-contrast depth resolution to approach one- tenth of a wavelength.
