The Study Of Stability Of Phase-shift Holographic Interferometry System

People’s demand for scientific and technological progress promotes the development of theholographic technology, and also make the digital phase-shift holographic technology.Due tothe digital phase-shift holographic technology combine optical holography with computertechnology, it is widely used in our production and life.Phase shifting technology can makedigital hologram reproducing four kinds of optical waves include direct hologram image,amutual interference image, the original image and conjugate image, and this system canreproduce either of the four pure light.In established a stable phase shifting holographic optical system, we move the grating onthe basis of the spatial light modulator through computer control, realize the interferencestreak phase shift accurately, and obtain a stable phase shift of light waves.The main contentsinclude:First, the digital phase-shift holographic interferometry optical system is established.Thesystem selects the Mach interference light path to realize the phase shift of plane waves.Phaseshifter in the system replace traditional piezoelectric ceramic with spatial light modulator torealize the phase shift.Its advantage is that with the spatial light modulator we can move thephase shift with people’s need, and the movement points are very accurate.In addition, byadding Fourier transform optical system, the waves of light can be realized the Fouriertransform and the inverse transformation.With the CCD detector obtains the interferenceimage, finally we can achieve the gather continuously of interference fringes which phasechanges alternately.Second, the acquisition method of phase-shifting hologram is presented.The holographicsystem can be implemented through recording the image of experiment fast, which realizesgetting a lot of phase shifting interference fringes in a short time. The cosine grating imageproduced by computer is inputted to the spatial light modulator, and then the grating periodalternated by computer control. This method can make the interference fringe phase beforeand after in pairs. Due to the interference of external factors, such as vibration, the differencebetween each pair of fringe phase will be different. Therefore, CCD is used to fast shooting4to5images in each phase fringe, that is to say, each phase image must be continuouslycollected thousands of pictures.Third, the computer program to calculate the phase shift value is designed.We pick out300pairs of pictures from continuous acquisition of images, and calculate the phase shift value by computer program. Selecting a pair of picture from the images, which is the mostclose to the theoretical value. After calculation, the error between the pair of picture and thetheoretical value is low, which indicates that the system and the method has high accuracyand validity.Fourth, to verify the effectiveness of the system. Puts a lens in the optical path,making the spherical waves as light waves and plane waves interfere to form ahologram.Four-step phase-shifting method is used to registration phase which are0、π/2、π and3π/2. Using the above method deal with the results of the experiment, the error betweenthe optimal phase shift and the theoretical value can still be low, which proves theeffectiveness of this system once again.