LAUSR

The key issue in phase measurement deflectometry is the solution of the incident light which is used to determine the surface normal. To restore the three-dimensional information of mirror surface, the line-planes deflectometry is proposed to determine the surface normal from the reflected light and the incident light planes containing the incident light. To this end, the point light source is used to replace the continuous surface light source of the traditional deflectometry. Accordingly, the incident light is calculated by the intersection of incident light planes which are determined by two or more projected lights of point light source. Finally, the precise mirror surface is restored through the radial basis function interpolation from the gradient which is transformed from the normal information. To verify the proposed method, a line–planes deflectometry system is developed with two projectors and one camera. The system can be applied for two measurement modes concerning different measurement requirements: 'line-plane model' and 'line-planes model'. The 'line-plane model' can be inferred with the measurement error less than 0.25 mm to measure the objects with low accuracy and non-connectivity. By contrast, the 'line-planes model' can be used to measure objects with high accuracy and good area connectivity, and the measurement error is about 1 µm.