The Automatically Focimeter Developed

Focimeter, one of the necessary instruments for the spectacle manufacturer, is used for the specificationes of lenses. China, where many people wear spectacles, focimeters are in high demand. The automatic focimeter is both fast and accurate, and is widely used in the big spectacle shops. For a long time, the automatic focimeter has been mainly imported and the related document is limited. Based on the patent of the foreign automatic focimeter and document, this project studies in details the principle and realization of the automatic focimeter.The automatic focimeter is usually made up of the optical system, precise mechanical system, photoelectricity detecting devices (CCD sensers are commonly used), and electrical controls, involving the optical technology, mechanical technology, electrical technology, etc. The background, implication, definition and clasification of the focimeter are discussed first, and then the system principle of the focimeter and the overal plan are analysed. The design of the software and hardware of the system is followed. In the section of the hardware design, the embedded platform consisted of ARM processor is used in this project. ARM system structure is acknowledged as the leading embeded RISC processing core, which has such advantages as low power consumption and cost, and high performance. The company's partners are worldwide. Sumsung's ARM IC is used in this project as the controller, and the IC capability is fully made use of, realizing LCD display, AD sampling, SDRAM control, etc. The system I/O is extended through the bus. The design of the hardware is low in cost and power consumption, and high in operating speed. In the software μC/OS-Ⅱ operating system is used, which is simple, free, etc. RTOS software is easy to design and extend. The system used in the project involves the design of person to computer interface, where the structure of windows is followed, so that each interface has the identical structure, which is good for the program maintenance.A prototype focimeter is made according to the design discussed in this paper. Some standard lenses have been measured with the focimeter and the results are of a satisfactory. However, there are some rooms to improve, which are analyzed in the end of the paper.