Design and Manipulation 3D Imaging System by using Photodiode Grid

Introduction: Radiation imaging is one of the applicable methods in diagnostic medicine and nondestructive testing for industrial applications. In nondestructive 3D imaging, in addition to the radiation source, there is a requirement for a suitable detection system, data acquisition system, mechanical sections for moving objects, reconstruction algorithm and finally a computer for processing and control. Method and Materials: One of the most important components of a digital radiation imaging system is its detector. Light photodiode is a new light sensor which is used in digital imaging systems because of its high efficiency. In the present research, a photodiode grid has been implemented to design and make a detection system. The photodiode grid has an array of 10×10 photodiodes in a 50×50 mm2 area. Beside the photodiode grid, a control board has been designed. Furthermore, a mechanical system has been designed to move the objects in the horizontal and vertical directions, and also rotate it around its own axis. The maximum displacement in the horizontal and vertical directions is 60 cm with step accuracy of about 0.015 mm. Step accuracy of the rotational movement is about 0.9 degrees.  Results: After the imaging system was constructed, background and uniformity of the system were tested. All the photodiodes in the imaging system showed good uniformity. The image data was transferred to a computer and processed using a MATLAB program to display the images on a monitor. As the physical resolution of the system is about the pixel size (5 mm), only the overall images of the object's dimensions were expected to be produced. Discussion and Conclusion: The fidelity of the detection system has been successfully tested using a visible light source and several test samples. The presented system is able to reconstruct 3D images and obtain cross-sectional images of the objects, by using the image processing algorithm specifically designed for it.