Calculation of MTF for Optical Disk Modulator by Using Fractal Function

Optical modulator is an important component in optical systems. It is a device, which changes the angle between the vision line to the target and coordinate to electrical signal. The optical modulator modulates the optical signal by a frequency depending on the shape and number of sectors. The optical modulator takes various circular shapes due to the need for it. Through this study we have designed an optical modulator consisting of three concentric circles (C0, C1, C2). Each circle is divided to transmittance and oblique sectors, the numbers of sectors chosen equal to (20,40,60) respectively, and increases progressively with
increasing the number of circles. And thickness of each circle chosen equal to (Ro=1.5) cm, that means the radius of optical disk is (Rr=4.5)cm. The central circle was designed using fractal geometry with a modified program to draw and enhance fractal figures including the fractal optical disk. The final shape of the proposed disk was designed using (Auto-CAD) software. The efficiency of this optical modulator disk was tested by applying the modulation transfer function (MTF), where we found that the results converge, the maximum chopping frequencies in circles (C0, C1, C2) are (2.5,5,10)KHZ at (t=0.004)sec, and minimum chopping frequencies are (0.05,0.1,0.2)KHZ at (t=0.2)sec, and the best modulation at spot light size equal to (2 mm 2), and that the proposed optical modulator disk could be used in optical systems.