We here introduce a pedagogical method of theoretical simulation as one major means of the teaching process of “Engineering Optics” in course quality improvement action plan (Qc) in our school. Students, in groups of three to five, complete simulations of interference, diffraction, electromagnetism and polarization of light; each student is evaluated and scored in light of his performance in the interviews between the teacher and the student, and each student can opt to be interviewed many times until he is satisfied with his score and learning. After three years of Qc practice, the remarkable teaching and learning effect is obatined. Such theoretical simulation experiment is a very valuable teaching method worthwhile for physical optics which is highly theoretical and abstruse. This teaching methodology works well in training students as to how to ask questions and how to solve problems, which can also stimulate their interest in research learning and their initiative to develop their self-confidence and sense of innovation.
A method for the measurement of the thickness of transparent oil film on water based on laser trigonometry is introduced,
and the oil film thickness can be obtained using the displacement of imaging spot and the configuration parameter of the
imaging system. So calibration is needed to achieve the geometrical parameters of the imaging system. A simple
experimental calibration is performed, a series of corresponding thickness and displacement data can be obtained and a
calibration curve is fitted, and the system parameters the object distance of the imaging system and the incident angle of
the laser beam are acquired. The experiment is conducted with block gauge, diesel oil and lubricant oil. The research
results verify the feasibility of the method presented in this paper, which is applicable to dynamic on-line measurement
of oil film thickness of oil spill on sea surface.
An optical system of digital holography based on 4f system for microstructure measurement is studied. Fresnel off-axis
hologram generated by a magnified image of microstructure is recorded with a CCD, and the magnified reconstructed
image can be obtained by the angular spectrum method. The quantitative phase information of the microstructure under
test is obtained. A theoretical analysis is performed in detail and the experiment done, and the experimental results are
also given. The research shows that the method presented in this paper can be applied to micro-object imaging and its
A method for the measurement of low-density microporous polymeric foams with digital microscopic image plane holography is studied. An image plane hologram of microporous foam is recorded in an optical system of a Mach-Zender interferometer by CCD sensor, and the magnified image, which contains the quantitative information of the intensity and the phase of the microporous foam, is reconstructed numerically from the captured single interference pattern by twice
fast Fourier transform and digital filter processing of frequency spectrum. And the morphometry and the pore diameter of
the microporous foam under test can be obtained. A theoretical analysis has been performed and experimental results of
the polymeric foam are also given. The experimental results show that the method presented in this paper is feasible,
easy in data processing.
In order to ameliorate convergence of the algorithm to invert the particle-size distribution (PSD) from laser diffraction data, an improved conjugate gradient algorithm (ICGA) is proposed. This method is independent of any given a priori information of the particle-size distribution. In the algorithm, each objective function is constructed according to an equation of the system of equations. Then iterations are carried out continuously between objective functions by choosing conjugate gradient directions, and thus the objective functions are tied up. An iteration step-adjusting parameter is introduced, which depends on the row index vectors of the matrix equation. Two narrowly distributed particulate-certified reference materials, their mixture, and a widely distributed particle plate are used as samples to verify the algorithm. Experimental results show that the ICGA is sufficiently convergent and that the convergence points are stable. The presented method can be used to invert unimodal and multimodal PSD with high precision.
The improved Newton algorithm is proposed to apply to the inversion of the light-scattering data for particle sizing. A theoretical analysis is performed in detail and the experimental results are also given. The experimental results show that, compared with the projection algorithm and the improved projection algorithm, the presented improved Newton algorithm is much more stable and speedy and has high precision.
The simple hologram recording system of digital off-axis holography is designed. Holographic diffraction grating of low spatial frequency is introduced to digital holography, acting as a beam splitter, illuminated by the monochrome plane parallel light wave, and the three different plane parallel light waves, namely, the zero-order and the ±1order diffraction waves, are generated. An off-axis holography system is configurated between the +1/-1order diffraction waves and the zero-order wave. The theoretical analysis has been done in detail and the zero-order diffraction in the reconstructed image of digital off-axis holography is also analyzed theoretically. The experimental results are given. The feasibility of the experimental system presented in this paper was confirmed, simple in optical structure and easy in operation. In addition, the zero-order image can be eliminated by numerically processing the holograms of object with different recording parameters obtained by adjusting the reflecting mirror in the recording optical system to vary the incidence beam orientation in CCD to introduce a phase shift.
The theory and the method of digital holography and its application have been studied, and part of the study results mainly involving eliminating zero-order diffraction in digital off-axis holography, analysis of the influence factors of the reconstructed image quality, particle field measurement, etc. are reported, and the experimental results are also given. The preliminary investigative basic research in color digital holography has been done. Multiple-wavelength recording system is introduced in digital holography, and recording of hologram by CCD is no longer a single wavelength one, which is a beneficial tentative research for the development of color digital holography. The research and the results provide the initial theory and experimental basis for the further advancement of digital holography.
BP Neural Network Method and Linear Partition Method are proposed to search the mapping relationship between space points and their image points in CCD cameras, which can be adopted to calibrate three-dimensional digitization systems based on optical method. Both of the methods only need the coordinates of calibration points and their corresponding image points’ coordinates as parameters. The principle of the calibration techniques includes the formula and solution procedure is deduced in detail. Calibration experiment results indicate that the use of Linear Partition Method to coplanar points enables its measuring mean relative error to reach 0.44 percent and the use of BP Neural Network Method to non-coplanar points enables its testing accuracy to reach 0.5-0.6 pixels.
A method of numerical reconstruction of hologram recorded on a low resolution CCD with different perspectives is presented. The hologram generated by 3D object at any plane located in the Fresnel diffraction region is magnified by a lens and is then recorded on a low resolution CCD sensor and numerical reconstruction is obtained by using linear interpolation and FFT. The 3D reconstruction of the different perspectives can be gained by the method introducing a window in the digital hologram and moving this window inside the whole digital hologram. The experimental results are also given.
3D object recognition is now an increasing interest in the optical information processing. In this paper, a method of 3D particle shape recognition by using in-line digital holography and optical correlation techniques is presented. The complex amplitude distribution generated by particle field at any plane located in the Fresnel diffraction region is recorded directly by CCD. The original field is then reconstructed numerically by wavelet transform. The scale parameter of the wavelet family, ? , is related to the distance between the particle hologram and the plane of observation. The whole information of particle field can be obtained by changing the value of ? .Holographic information of the 3D reference object can also be gained by the same method, and act as complex filter. Correlation techniques are then applied to recognizing the particle shape, and experimental results are also given.
The thesis presents first that the distribution of the light field reflected by a local curve surface varies after through a lens. And the theoretical analysis is made on the basis of Fourier optical principle.