Modulation transfer function (MTF) evaluation in the imaging of the optical lenses with poorly corrected geometric distortion involves sampling region of interest (ROI) images that are affected by geometric distortion, reducing its accuracy. A based liquid-crystal-device MTF (LMTF) method is proposed for this purpose by evaluating MTF of the medical rigid endoscope. This method establishes a mathematical model of geometric distortion and analyzes two sampling ROI image manners in MTF evaluation. Compared with the distortion factor (DF) manner, the distortion correction manner relaxes the value of the DF to twice the maximum non-distortion value, extends the sampling ROI image to twice the size, reduces the average RRMSE value to 6%, and improves average accuracy on MTF by 1.2%. The experimental results provide good agreement with the theoretical prediction. Therefore, the proposed LMTF method can be referential for the other optical lenses with poorly corrected distortion.
Optical waveguide directional couplers can perform some very useful functions in a variety of integrated optical
applications, especially when the branch arm incorporates gain. In this paper, the performance of three-dimensional
active optical waveguide directional coupler is analyzed by
finite-difference beam propagation method (FD-BPM). The
paper analyses the impact of normalized gain difference and normalized phase difference on optical power transfer
characteristics. The transmission characteristics of
three-dimensional active waveguide coupler in phase matching and
mismatching are discussed in detail. In addition, the influence of geometric parameters of three-dimensional waveguide
coupler on the transmission characteristics is analyzed. The result of above analysis can be helpful for optimizing the
active coupler designing.
Today, circular bubble is tested mainly by manual work that leads to lower efficiency and limited precision. A new testing method based on CCD image system is proposed in which the bubble is laid on an inclinable workbench, and then digital images of the bubble are captured by CCD image system. After the displacement between the center of the bubble and the scale circle is detected through a revised randomized Hough transform, the scale unit and the sensibility of circular bubble can be obtained.
KEYWORDS: Liquids, Laser range finders, Sensors, Intelligence systems, Safety, Laser systems engineering, Control systems, Telecommunications, Data communications, Ranging
Using laser range finder DISTO as a sensor, we developed an intelligent liquid surface measuring system that can be used to measure the depth of liquid. Many problems such as liquid surface reflected in fixed direction, measuring errors caused by reflex reflections and liquid surface fluctuation are solved. Now it is proved by our experiments on the spot that the system would be used in measuring depth of all kind of liquid, especially in combustible or explosive oil and liquefaction gas with the accuracy of +/-3mm.
Concerning automatic interpretation of interference fringes, current algorithms, such as typical hit-or-miss transform, always extract the characters by binary images, which are sure to lose some available information. Hence a new automatic interpretation algorithm of interference fringes is proposed, which uses their own gray characters and designs an appropriate weight function, then solves a series of curves to which the integrals of the square of the distance from each point of the fringes is minimal, that is to say, resolves expectations of fringes under the weight function designed. Furthermore the new algorithm has the functions of extracting the multiplicity of fringes as well as image processing. And the algorithm is insensitive to the random noise when the weight function is an odd function of gray.
Optical fiber connection with beveled endface is applied to enhance return loss in optical fiber communication, so the angle of endface is an important parameter of the optical fiber that needs to be tested before connection. Perfect optical fiber endface is an area in an intersection plane across a cylinder of the optical fiber and the projection of the area is an ellipse or line relative to the beveled angle. Because imaging of microscope objective follows the principle of geometric projection, when the optical fiber endface is imaged in CCD by a microscope objective, the image is the amplified projection of the optical fiber endface. With a video capture card, the digital image is formed in the computer. The equation of the projection is resolved by means of digital image processing, and then the angle degree is calculated. In course of image processing, edge detection and thinning of the image is based on mathematical morphology and curve fitting is based on least square method. It is shown by the result that the precision of the angle degree is between 0.2° in the method.
This paper shows an approach using tunable narrowband speckle pattern generated by a double-slit aperture laid behind a new microcrystalline glass material scattering screen, for testing MTF of FPA between zero and twice Nyquist frequency. The measurement near to the Nyquist frequency, this method proved highly effective much better than that obtained by the Wide-band Laser Speckle.
Based on the statistical properties of laser speckle, the response for laser speckle passing through a linear shift- invariant system is studied. This paper presents a method for testing the modulation transfer function (MTF) of charge-coupled devices below the Nyquist frequency. A new scattering microcrystalline glass material generates laser speckle. The instrument is designed and test results show that this technique is a variable MTF measurement approach. The difference of the results of each test is within 0.03.
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