Schlieren Imaging
Make invisible changes in pressure, temperature, density, and refractive index visible with high-speed schlieren, shadowgraph, and background-oriented schlieren imaging.
Visualizing the Invisible
Schlieren imaging reveals changes in a transparent medium by showing how variations in density and refractive index bend light. These variations can be caused by changes in pressure, temperature, gas composition, or shock-wave propagation.
When paired with a high-speed camera, schlieren systems provide detailed slow-motion visualization of rapidly changing air and gas flow that cannot be seen directly by the human eye.
Why Use High-Speed Schlieren?
Fast imaging adds temporal detail to an optical method that is already highly sensitive to refractive-index changes.
Capture Transient Waves
Resolve rapidly propagating shock fronts, compression waves, expansion fans, and pressure disturbances frame by frame.
Observe Thermal Flow
Visualize hot-gas plumes, heat transfer, convection, buoyancy-driven flow, and temperature gradients in air.
Study Flow Boundaries
Identify jets, shear layers, mixing regions, boundary layers, flow separation, and aerodynamic disturbances.
Schlieren Imaging Methods
Each method uses refracted light differently and offers a different balance of sensitivity, setup complexity, field size, and quantitative capability.
Schlieren
Collimated light passes through the test region and is focused at a cutoff, such as a knife edge, to convert small angular deflections into visible brightness changes.
- High sensitivity to density gradients
- Clear visualization of flow direction
- Common in wind tunnels and combustion labs
- Requires precise optical alignment
Shadowgraph
A light source projects intensity variations caused by refractive-index changes directly onto the camera, often without a knife edge or complex focusing optics.
- Simpler setup than classical schlieren
- Effective for strong shock waves
- Useful for explosions and ballistics
- Highlights rapid spatial changes
Background-Oriented Schlieren
A patterned background is imaged before and during the event. Software measures apparent pattern displacement caused by refractive-index gradients in the flow.
- Minimal specialized optical hardware
- Suitable for large fields of view
- Supports qualitative or quantitative analysis
- Useful in laboratories and outdoor testing
Common Schlieren Applications
Schlieren and shadowgraph methods are widely used wherever transparent flow contains strong pressure, temperature, or density gradients.
Aerospace Aerodynamics
Visualize airfoil flow, shock formation, boundary layers, supersonic jets, transonic buffet, and high-speed wind-tunnel behavior.
Combustión
Track flame fronts, ignition, hot-gas movement, mixing, pressure waves, and combustion-induced density changes.
Balística
Observe projectile bow shocks, muzzle blast, blast-wave propagation, gas expansion, and high-speed impact events.
Explosions & Pressure Waves
Capture blast fronts, compression zones, reflected waves, expansion regions, and interactions with nearby structures.
Heat Transfer
Visualize convection, thermal plumes, hot surfaces, cooling airflow, leakage, and temperature-driven density gradients.
Jets & Gas Mixing
Study nozzle flow, gas injection, exhaust plumes, shear layers, mixing boundaries, and underexpanded jets.
Typical Schlieren Workflow
A successful setup depends on optical geometry, a stable light source, careful alignment, sharp focus, short exposure, and timing matched to the test event.
Selecting a Camera for Schlieren
Camera performance directly affects the ability to resolve small optical distortions, fast shock fronts, low-contrast thermal gradients, and rapidly evolving flow structures.
Need help configuring a schlieren system?
Share your test speed, field of view, optical method, light source, expected density gradients, and recording duration with Photron.