A differential mixing technique is described whereby the Doppler shift of light reflected from a shock wave can be measured in the laboratory. Results are given for the application of the technique to shock waves produced in a conventional pressure‐driven shock tube, and it is found that measurements of shock wave velocity can be performed with a spatial resolution ∼10−5m, and of shock wave curvature with a resolution up to 10−1m−1. Deliberate optimization of the various design parameters involved is expected to improve the sensitivity of either of these measurements by about an order‐of‐magnitude.