The field of view (FOV) of a nonlinear optical microscope (NLOM) is expected to be large enough for employing high-speed raster scanning on a mesoscale volumetric biological sample. Concurrently, three-dimensional (3D) visualization of fine sub-micron biological structures requires high enough lateral and axial resolutions, enforcing a high numerical aperture (NA) objective lens to be employed, thereby limiting the FOV of an NLOM. The invention is directed to a laser scanning NLOM, or to a large-angle optical raster scanning system, for deep biological tissue imaging with a large FOV of more than one square millimeter, up to 1.6×1.6 mm2, while simultaneously maintaining a sub-femtoliter effective 3D resolution by means of a high-NA and low magnification objective lens and further maintaining a high acquisition speed with synchronized sampling, limited by the repetition rate of a high repetition rate pulsed laser source, thereby exceeding Nyquist Criterion for resolving micro-optical resolution throughout a horizontal FOV of more than one millimeter.