The basic elements of the optical computer mouse (OCM) are; a light emitting diode
(LED), image acquisition system (IAS) which acquires images via the lens and a digital signal
processor (DSP) to implement the algorithm to determine direction and distance of motion. Here,
we describe the light speckles produced from different colour LEDs to design and implement a
new optical computer mouse. The speckle pattern will be used also to determine the velocity of
the device relative to the surface it slides on it. The most important and critical property of speckles is their average diameter, which is independent of the type of the surface being illuminated by coherent (He-Ne laser and diode laser) or partially coherent light (LEDs). The average diameter of a speckle pattern is function of the diameter of the illuminated area of the surface, the distance between the surface and the detector, and the wavelength of the used light. In this work, we replaced the laser source by a small powerful white light lamp with different optical coloured filters and studying the resulting coloured speckle patterns to investigate the effect of different wavelengths on the velocity of the device relative to the surface it slides on it.
The transverse interference pattern from a fusion-spliced optical fiber is obtained by illuminating the fiber with a laser sheet of light. The buckling on the fiber material in one direction of the spliced point is clear inside the transverse interference pattern. The buckling height ranges from 1 to 10 microns in a waveguide of a 50 micron core adn125 micron clad diameters. The refractive index profile inside the fiber core is calculated using a new method showing the change in the refractive index due to fusion splicing of the fiber. The refractive index profile is calculated by means of the transverse interference patterns obtained at different illumination directions. A CCD camera is used to record the transverse interference pattern from the fusion-spliced optical fiber. In order to calculate the visibility of the obtained fringe patterns and the deflection angle of light through the fiber (displaying the change in the refractive index) it is necessary to measure the fringe maximum and minimum intensities using a special software package.
In this technique the speckle shear interferometer is combined with the electronic speckle pattern interferometry technique. Two pinholes of the same diameter 'a', separated by a distance 'd' is used to image through object through an imaging lens. The formed speckle pattern which is the resultant of mutual interference between the two speckle patterns formed by each pinhole, is modulated by a grid structure inside it. This pattern is imaged by a CCD camera combined with a reference beam through a beam splitter. The object under investigation is now photographed in its first state, without any deformation, and this signal is allowed to be stored in the computer as a data file. During the object vibration or deformation, a second signal is to be sorted on the same data filet. A fast Fourier transform has been used to add such tow signals and after processing the two overlapped signals data one can obtain the deformation suffered by the object in the form of interference fringes displaying such deformation.
A loudspeaker at certain frequencies, producing vibrating sound wave causes periodic pressure variations in air. This pressure variation can be displayed in the form of a corresponding variations in the refractive index of air. The induced variation of the refractive index of air lead to a deflection of light rays traveling through the disturbed area of air by the vibrating sound waves. Speckle photography technique has been sued in this work to measure the light deflection along a certain cross-section of the integrated sound fields. The deflection angle of light rays can be measured as a speckle shift in the image plane leads to the formation of interference fringes similar to Young's fringes pattern. In the present work, a fringe pattern displaying the speckle shift due to the refractive index variation has been obtained using the electronic speckle pattern shearing interferometry. This fringe pattern in a measure of the speckle displacement due to light deflection caused by a vibrating sound source making a periodic pressure and refractive index variations of air.
The aim of this work is to present an overview about the speckles produced from many surfaces used in automotive industries using different illuminating wavelengths e.g. white light, Hg and Na light sources. In order to minimize the effect of the reflected speckle grains from such surfaces one has to calculate the speckle grain size and contrast at different wavelengths and the visibility of interference fringes obtained and also the roughness of the rough surface used. The speckles recorded at different angle of incidence for light used to achieve the proper scattering angles which gives minimum speckle brightness causing distortion of the formed image for a moment. Speckles produced from non-spectral light sources were photographed also to identify the difference between such pattern and the speckle pattern obtained with He- Ne laser light source and purely spectral light sources. The visibility of the interference fringe pattern obtained by speckle photography technique with different wavelengths has been investigated experimentally and theoretically.