Research On The Technology Of High Dynamic Near Infrared Dental Imaging Based On DMD

The detection of tooth diseases by near-infrared light has a good application prospect in medical tooth detection imaging,because the enamel is almost transparent under irradiation of near-infrared light.However,In the near-infrared scene,due to uneven tooth thickness,using a common near-infrared image acquisition device will show highly exposed parts of the acquired tooth image,and the dynamic range is limited.Doctors can't accurately observe the disease information of teeth,which limits the application of near-infrared light in the tooth detection.At present,how to effectively improve the dynamic range of tooth images under near infrared light is very important for near infrared light tooth detection.In this paper,a high dynamic near-infrared tooth detection technology based on the digital micro mirror device(DMD)is proposed.Based on the unique working mode of the DMD chip,we can adjust the light intensity collected by each pixel of the image sensor.The image exposure can be changed by adjusting the intake of near-infrared light intensity in different positions of teeth.It reducing the light intensity intake of the high-exposure part while keeping the normal exposure part of the image unchanged can reduce the high-exposure level effectively.At this time,the image sensor can simultaneously detect the details of bright or dark images caused by uneven tooth thickness under near infrared light.Therefore,the dynamic range of the entire dental imaging system is improved,and it has a good application prospect.In this paper,a light intensity adjusting algorithm based on space modulation and PWM pulse modulation is designed.The algorithm designed a 4: 1 correspondence between the number of DMD lenses and the image sensor,which ensures the full use of DMD lens resources and accelerates the speed of light intensity adjustment.The required steps are only 1/4 of the traditional way.We use DDR2 SDRAM to cache the image data to ensure the system frame rate(40 frames / second),It shortens the waiting time for loading data in the DMD flip process,and successfully implements the flip control of the 8-bit grayscale image of the DMD.Imaging system dynamic range increased by 60.21 dB combined with two design strategies successfully.The system mainly includes an optical imaging system,host computer processing software and DMD hardware control platform.The main function of the optical imaging system is the optical adjustment of the DMD micro mirror lens and image sensor.The main function of the host computer processing software is to realize the acquisition of camera image data and the realization of a light intensity adjustment algorithm.We have designed a host computer control method that combines manual dimming and automatic dimming,which improves the dimming efficiency and makes the DMD control process more user-friendly.The main functions of the DMD hardware control platform are image data writing,data clearing,data resetting and lens floating control timing.We used a 48 dB near-infrared camera to test the near-infrared imaging system.The experimental results show that the imaging results of the simulated high-dynamic scene meet the observation requirements.The contrast of the collected image is strong,there is no oversaturated area.This system tests the imaging effect under different dimming weights to prove that this system does have the purpose of adjusting the intensity of the beam entering the image sensor.In this paper,imaging tests were performed on four groups of teeth exposed to near-infrared light.The results show that,with the addition of this system,the clarity of teeth images has been significantly improved.Teeth outline and details are clearer.