The former obtains the intensity distribution of reflected light through reflection, thus producing interference fringes; The latter is the superposition of diffracted wave fronts (or beams), and then the interference fringes are obtained. In addition, wavefront interferometry usually requires special instruments and equipment, which may bring some challenges to experimental operation and result analysis. But the advantage of this method is that it can measure tiny deformation more accurately, which is very important for many scientific research and application fields (such as engineering, material science, geology, etc.). ).
Fractional amplitude interference, also known as thin film interference, means that when a beam of white light shines on two reflecting surfaces, the light reflects and interferes. The reflected rays are superimposed on each other, resulting in interference fringes. These stripes are white because all wavelengths of light have the same phase. When observing, interference fringes are a group of concentric rings with alternating light and dark, which depends on the polarization state of incident light and the inclination of two reflecting surfaces.
Because this method uses the full beam of each reflector, it requires less equipment (such as mirrors, observation windows, etc.). It can also be applied to objects with rough surfaces, and emphasizes the interference fringes caused by the change of partially reflected wavefront. Fractional amplitude interference is very common in many practical applications, such as optical measurement, optical film preparation, hologram and so on.
Wavefront splitting interference uses two identical wavefronts (or beams) to interfere. It needs to use special instruments, such as special one-third wave plate, grating, laser and so on. Different from fractional amplitude interference, the interference fringes produced by fractional wavefront interference are not based on reflection, but on diffraction. This means that their shapes and positions are related to the shapes and sizes of objects.
By observing and analyzing the changes of interference fringes on some wave surfaces, the size and shape of the object can be determined. In addition, wavefront interferometry has some advantages, such as higher spatial frequency sensitivity and more accurate measurement of small deformation. In scientific research and industrial production, wavefront interferometry is widely used in optics, spectroscopy, micro-nano measurement and other fields.
Application of wavefront interferometry
1, optical interferometry: wavefront interferometry is widely used in optical interferometry, because it can separate two or more wave fronts in space and realize accurate measurement of light intensity. This method can measure tiny displacement, deformation and refractive index change, and is widely used in scientific research and industrial measurement.
2. Interference imaging: Wavefront interference can be used for interference imaging. By interfering with two or more wave fronts, interference fringes can be generated in spatial domain or frequency domain, thus realizing high-resolution imaging of the object surface. This technology can be used in microscope, holography and other fields.
3. Laser technology: Wavefront interference has important applications in laser technology, such as controlling the phase and amplitude of laser light, so as to realize the modulation, amplification and shaping of laser light.
4. Spectroscopy: Wavefront interference can be used in spectroscopy, and the frequency and phase of light can be measured through the generation and analysis of interference spectrum. This method can be used to analyze gas molecules, chemical reactions and so on.
5. Material Science: Wavefront interferometry can be used in the research of material science, which can produce interference fringes on the surface of materials through interference technology, so as to measure and analyze the surface morphology, refractive index and other characteristics of materials.
6. Biomedical engineering: wavefront interferometry is also applied in biomedical engineering, such as optical coherence tomography, which realizes high-resolution imaging of biological tissues through interference principle.