The present disclosure provides improved optical systems for particle processing (e.g., cytometry including microfluidic based sorters, drop sorters, and/or cell purification) systems and methods. More particularly, the present disclosure provides advantageous micro-lens array optical detection assemblies for particle (e.g., cells, microscopic particles, etc.) processing systems and methods (e.g., for analyzing, sorting, processing, purifying, measuring, isolating, detecting, monitoring and/or enriching particles.