RESUMEN
A rigid fiber-optic imaging element with high fidelity, high resolution, and high contrast is applied in low-level-light night vision and particle detection devices. Any optical fiber in elements is an image transmission unit. However, the independence and integrity of image transmission are disturbed constantly, resulting in blemishes. This paper studies the formation mechanism of the blemishes of rigid fiber-optic imaging elements. The existence of defects with different sizes in or among the optical fibers, and fiber deformation decreasing light transmission ability are simulated theoretically. Then experiments are carried out to verify the simulation results. It is theoretically concluded that a blemish forms when the equivalent sphere radius (RES) of a stone defect is greater than 1.2 µm in a normal fiber, and 1.1 µm in a taper fiber. The RES of a bubble defect is greater than 1.3 µm in the fiber, which can form blemishes. Excessive deformation of fibers behaving as a clad layer with thickness less than 0.3 µm also results in the formation of blemishes. When fiber deformation and the existence of stone are considered, blemishes can occur as long as the size of the stone defect among the fibers is greater than 0.823 µm. The results provide data support and theoretical guidance in solving blemishes and other fixed pattern noises, and significantly improve the engineering and application level of fiber-optic imaging elements.
RESUMEN
Based on the mathematical models proposed by the image spherizing algorithm, a novel planeness detecting method for a micro-channel plate (MCP) is presented. After describing the theory of the image spherizing algorithm, a straight line image is chosen as a standard picture, and the imaging simulation for a deformed MCP is performed. According to the simulated results, the deformation characteristic of the MCP and the mechanism of the image twisting phenomenon were analyzed. Finally, the double lines method, which specializes in planeness detection, is proposed. The experimental result obtained by interferometer shows that the profile characteristics of a deformed MCP are consistent with the theoretical analysis. To verify the effectiveness of the double lines method, we measured the planeness of 100 pieces of MCP and then defined the detecting standard: a micro-channel plate will be treated as a defective product when the twisting angle of the two orthogonal lines in the reflected image is greater than 40°, whereas the product will meet the military standard when the twisting angle is smaller than 7°. In this method, the planeness detection could be completed only by observing the reflected image of the MCP, even in a harsh environment. In particular, the accuracy can reach 1 µm and it has been applied to the MCP production process.