This paper presents an endoscopic digital holographic interferometry system which is based on phase-shifting in-line digital holography. The system is able to measure both the shape and deformation of an object with the advantages of digital holography, such as real-time processing of the hologram. Two theoretical problems are briefly described: phase-shifting in- line holography and hologram data re-sampling for 2-wavelength contouring. In addition, initial experimental results of the deformation of a metal piece and surface 3D-shape measurement of a bottle cap are given.
The quality of interferograms is of the most concern in interferometric experiments. Present approaches to evaluate the contrast of interferograms are neither efficient to be carried out nor insensitive to noise. In this paper, we study the mean dynamic range and imbalance of grey levels on the basis of histograms. Analytical and calculation results show that these parameters are closely related to the contrast of interferograms. They are insensitive to noise disturbance and easy to be implemented with efficient computer algorithms and, therefore, can be used to estimate the quality of interferograms in real-time.
When the dimension of measurand is measured with a charge couple device (CCD), the measuring accuracy is limited in interval of array photosensor. It we want to improve the measuring resolution, we often finish it by improving the magnifying power of optical system. But if we do this, we shall limit the measuring range of CCD. If using a analog- digital converter, we can get the pulse amplitude of CCD array photosensor. Using numerical method to the pulse amplitude, we can change intersect value to continuous value. With the segmentation level, we can get a improving resolution. In this paper, we give a hardware frame chart and the calculation course.
In this paper, the design theory of a computer-generated quadruple focus holographic lens is described. The holographic lens is required to have the identical diffraction performance for the four focuses. Because the fringe pattern of the hologram can be expressed with mathematical equations, the principle of computer holographic interferogram is adopted. We present an area division method for the design of multi-focus computer- generated holograms. The mathematical model, computing process and an example of design ar given int his paper.
In this paper, a new kind of security hologram using an encoded reference wave is introduced. The hologram is produced with the interference of an encoded reference wave and a convergent object wave. The focus of the convergent wave can be reconstructed only by the illumination with a duplicate of the original encoded reference wave. Because the verification pattern is simply s spot peak rather than an image pattern, this kind of security hologram is suitable for machine inspection. A scheme of machine inspection by using this kind of security holograms is described.
In this paper, a new storage approach of color films by means of a single-wavelength laser and SLMs is presented. A color film is illuminated with a beam of incoherent white light but filtered into red one. Then a frame on the film is imaged on a CdS liquid crystal SLM. The red coherent light of a He-Ne laser projects on the SLM as a reading light. So the output light of the SLM is also a red coherent light that carries the image information of the red incoherent light. By replacing filters with green and blue ones, three images of red coherent light can be produced step by step. A rainbow holographic recording geometry is arranged to store the three coherent light waves. Therefore, an image frame of the color film is stored in a rainbow hologram which can be preserved forever.
A two-step method for fabricating miniaperture on-axis holographic lenses with high numerical apertures is presented. The first step is to record a bifocus off-axis master holographic lens using a plane wave and a divergent spherical wave. The second step is to record the miniaperture on-axis holographic lens using the conjugate reconstructed wave of the master holographic lens. A holographic lens array is made in our experiments in which the numerical aperture of each lens in the array reached 0.31.