Scheimpflug-integrated focusing schlieren: imaging tilted planes in three-dimensional high-speed flows.

Conventional focusing schlieren is fundamentally restricted to measurement planes normal to the optical axis, limiting visualization of arbitrarily oriented flow structures. We present a Scheimpflug-integrated focusing schlieren technique that enables sharply focused visualization of strongly tilted measurement planes (up to ±60∘ in the present configuration) in high-speed flows while preserving quasi-two-dimensional imaging capability. A dot-array calibration procedure corrects geometric distortion and reconstructs the true spatial coordinates of the inclined measurement plane. The technique is demonstrated in a confined quasi-two-dimensional jet and in a Mach-6 hypersonic flow over a compound delta wing, revealing flow structures inaccessible to conventional schlieren configurations. The approach establishes a tilted-plane optical-sectioning capability for schlieren imaging and provides a flexible diagnostic framework for three-dimensional high-speed flow visualization.