Design And Implementation Of Illumination Detection Sysytem Based On CMOS Image Sensor

With the development of IOT, intelligent lighting system is becoming one of the hot spots of current research. Because of that traditional light sensor can’t meet the requirements of precision testing and measurement range of intelligent lighting due to its inherent attribute, a fast and accurate intensity of illumination and illumination distribution test system is developed, to achieve precise lighting control requirements of intelligent lighting system, which is the premise to realize comfort and energy-saving lighting.This topic studies methods around detection of illumination intensity in intelligent lighting system. Through the analysis of existing disadvantages of traditional light sensor and problems existing in the engineering application, the CMOS image sensor applied to lighting environment illumination measurement method is proposed. The feasibility of illumination measurement by using CMOS image processing has been analyzed. The methods of image acquisition, image preprocessing and illumination intensity by image measurement has been studied in-depth. The embedded illumination intensity detection system based on CMOS image sensor has been designed and realized the function of real-time illumination distribution measurements, and the system has been tested. The content of the subject research includes the following several aspects:(1)The idea of applying the method of detecting environment illumination by using CMOS image sensor to intelligent lighting is put forward, and the embedded system based on CMOS image sensor is developed. The relationship between illumination and the factors such as image gray scale, sensor gain, exposure time, objects reflectivity is analyzed in theory, and the feasibility of CMOS image sensor used in illumination intensity measurement is demonstrated.(2)Image gray scale normalization processing is put forward, and using the least square method and fitting curve through experimental data, the function relationship between image gray scale and brightness is established. According to the relationship between object brightness and illumination intensity, parameter has been calibrated and the reflectivity of the object has been established, and then realized the measurement of illumination intensity and distribution.(3)The design of overall architecture of system is accomplished, the system development of technology roadmap is determined, the function of system is defined. Through the program comparison, regarding STM32F407ZE which has the capability of data processing of high-speed floating point as the core, regarding OV7670 as CMOS image sensor, combining image acquisition with storage circuits, the hardware structure is determined.(4)The software design of system is completed. The three-tier software architecture including hardware driver layer, operating system layer, and application layer is established. The writing of underlying driver, transplant of μC/OSⅡ- real-time operating system is completed, and application layer tasks such as image acquisition, illumination measurement, parameter configuration is accomplished. Through combining DCMI with DMA transfer unit to improve the speed of image acquisition, using floating point arithmetic unit (FPU) to improve the computing speed, and completing the image processing algorithm, the real-time performance of the system is ensured.(5) The system has been tested. Through development of the PC configuration tool, illumination measurement system calibration and parameters configuration, the illumination intensity and illumination partition measurement in the lighting environment, and the image acquisition, intensity of illumination measurement is realized. The functions including image acquisition, illumination measurement, parameters configuration have been tested. The results show that the system can meet the illumination measurement demand of intelligent lighting system and has certain actual application value.