The invention provides a method of detecting the
surface shape of a reflection element based on dual-frequency orthogonal
grating projection. When the method is used to detect the reflection
optical surface shape, basic devices comprise a CCD sensor, a to-be-detected element, an LCD display and a computer. The LCD display sequentially displays phase-shifting fringe patterns generated by computer coding, and the CCD receives and obtains the deformed fringe patterns reflected through the surface of the to-be-detected element. If a physical
grating and a mechanical device are used for phase shifting in a measuring
system, switching in a vertical
grating and a horizontal grating needs to be carried out, and a corresponding phase shifting amount is further completed. In order to avoid grating switching in the two directions and realize the accurate phase shifting amount, a dual-frequency orthogonal grating phase shifting method based on
least squares iteration is proposed, the dual-frequency orthogonal grating is applied to phase deflectometry, no grating needs to be replaced in a measuring process, an accurate phase shifting amount is not needed either, and phase distribution in two directions can be acquired at the same time. The method has the beneficial effects of being high in measuring result accuracy and applicable to high-accuracy three-dimensional
surface shape measurement.