Design Of High Frequency Direct Current Dental X-ray Machine

X-ray was discovered by Roentgen in 1895,which establishes foundation of Medical Imaging.X-ray machine experiences three phase:ion X-ray tube,electron X-ray tube and rotating anode X-ray tube.with the development of power electronic technology and microcomputer technology, the development direction of X-ray machine is high performance and low cost. High voltage generator is processing from power-frequency to middle frequency(400-20KHz)and High Frequency(more than 20KHz),the bulk of high voltage generator is reduced.Control circuit adopts microcomputer technology,high precision close-loop control is used to control tube current and tube voltage,and time of exposure is controlled accurately.High frequency technology was used,direct tube current and tube voltage are acquired and the damage to human is reduced.In this paper,high frequency direct current dental X-ray machine is manufactured,frequency of high-voltage circuit is 40KHz,instantaneous power is 1600W,output tube voltage can be adjusted in 50～100KV,output tube current can be adjusted in3～8mA,power factor is not less than 0.92,the whole efficiency is not less than 90%,tube size is 50×120×125.The high frequency power of this machine adopts advance IGBT switch apparatus and high frequency syntony inverter,dependability of output tube voltage and tube current is high,anode voltage is stable.Microprocessor are used to control tube voltage and tube current.Safeguard is perfect,and it has over input voltage,over tube current,over filament and over power protect;can self-diagnoses the connect station of system parts,and displays the status. Man-machine interface is friendly,and a large liquid crystal display are used to display Chinese characters or English.More spots exposing keys are used to guarantee the personal safety mostly and operating convenience.X-ray exposure can use close tube keys exposure,long-distance cable exposure,and remote infrared exposure.In addition,the movement rack is designed,through the balance design, the assemble head can keep still while shooting pictures;through machinery design,the assemble head can make 360°rotation on the level of the surface, and make 280°rotation on the vertical level,and ruler with 10°degrees value is also designed to show relative rotation;equipped with rollers,the chassis can be fixed and also can be moved,and it is convenient to acquire picture.Five sets of prototype are manufactured,circuit aging test, anti-interference test,dielectric strength test are made,tests results show that performance is excellent.Prototype exposures every three minutes,after 100 hours of continuous experiments,it can still work properly.Using CCD imaging system,the 20μm micron integrated circuits interior lines can be seen clearly,the teeth marrow can be seen clearly.Using dental film,the teeth marrow can also be seen clearly.A new way to measure the focal spot to skin distance of dental X-ray Machine was developed,using dental X-ray machine to get the image of material object,and the image is transmitted to the computer through CCD image sensor,after the measure of image and material object size ratio, through similar Triangle principle to derive the focal spot to skin distance. focal spot to skin distance got by this method is only 8mm longer than the real focal spot to skin distance,which is 205mm.This method is simple,fast,and has practical value.