【作者】 王学仁；

【导师】 董威；

【作者基本信息】 西安工业大学 ， 测试计量技术及仪器， 2011， 硕士

【摘要】 在各种CCD成像系统中,必须对CCD器件进行非均匀性校正,这是由于半导体制造技术中存在的实际问题,在相等照度下CCD各像元的输出并不相等,CCD的这种像元响应不均匀性直接影响其应用性能,因此必须对整个系统的非均匀性进行校正。CCD非线性校正最常用的方法是采用积分球光源作为标准光源对CCD进行非均匀化校准。这类装置通常由标准灯、积分球、滤光片和可变光阑组成,利用积分球的均光特性提供均匀光场,光场照度由光源入射光阑控制。然而这种传统的方法受到标准灯自身的光稳定性以及积分球体积的限制,使标准光源光通量的变化范围和稳定性均受到不同程度的制约。大功率白光LED的出现为CCD器件的校正提供了一种新型光源。特别是针对用积分球作为校准光源而言,LED的高光效、低光衰、短的响应时间、体积小等突出特点,使其成为目前用于CCD校正的很合适、很有前途的照明光源。用LED作为CCD校准光源时,为了产生高光通量,通常由多颗LED按某种形式排列组合成阵列的形式,通过积分球的匀光技术最终达到CCD校准所要求的光照度条件。但多颗LED光源组合使用中也存在一些问题,福州大学的吴海彬等人在研究多颗LED组合照明设计的关键技术时总结：多个LED组成阵列时不同的连接方式、环境温度、p-n结结温、驱动方式等因素都将影响各个LED电流的均衡性,进而影响电光转换效率的变化并最终导致光源的不稳定,使标准光源无法对CCD器件进行有效校准。因此大功率白光LED光源光通量的稳定性成为CCD器件校准的关键问题。中科院安徽光机所陈风等人设计了一种LED光谱分布可调光源,其面非均匀性达到0.53%,角度特性在±10。以内,最大偏差为0.77%。这种新型光源可做为光辐射测量中的量值传递标准使用。本文从LED的工作原理和实际工程设计出发,结合国内外LED工程应用领域的最新发展,研究LED阵列的光稳定性问题,重点围绕LED阵列的连接方式、供电方式和LED的工作状态等方面来展开研究。本课题围绕LED在CCD校正用标准光源的工程应用展开,根据CCD校准用光源的要求,对LED进行选型,设计并搭建了LED光通量测量平台,包括积分球测量基准及LED靶板测量装置,分别展开LED在不同连接方式下的光通量稳定性测量。最后采用正交实验法对影响LED阵列光稳定性的正向电流,连接方式等因素进行了优化处理。实验结果表明当LED阵列采用不同的串、并联方式时,光源的光稳定性也不同,其中采用2×2模式,也就是先串后并的LED连接模式为基本单元设计的LED阵列光源的光稳定性较好,八小时稳定性可达99%,能够很好地满足CCD校准用光源的要求。更多还原

【Abstract】 In CCD imaging system, because of the practical problems in the semiconductor manufacturing technology, the outputs of each CCD pixel are not the same when it is irradiated in the same light intensity. This non-uniformity of CCD pixel response affects the application performance of CCD directly, so the whole imaging system must calibrate the non-uniformity of CCD. It is the normal method that using integrating sphere as a standard light source to calibrate the CCD. This light source is usually consisted by the standard lamp, integrating sphere, optical filters and iris diaphragm. In this light source, the integrating sphere provides uniform light field, and iris diaphragm controls the illumination. However, this traditional approach is limited by the standard lamp’s own light stability and the size of the integrating sphere. And the changes range of light flux and stability of the standard light source are subject to different constraints. The emergence of the high-power white LED provides a new light source for CCD calibration, especially for the use of integrating sphere as the calibration light source. Now LED is the appropriate and promising light source for CCD calibration, because of its high efficiency, low-light decline, short response time and small size.When using LED as the light source for CCD calibration, it usually combined a number of LED into an array by some form. Thus, it can reach the required illumination conditions of CCD calibration in the integrating sphere light source. However, there are also some problems in the combination of multiple LED light source. Fuzhou University, Wu Haibin pointed out: when using multiple LED to compose LED array, the different connection way, ambient temperature, p-n junction temperature and drive type of LED would affect the balance of each LED current, thereby led to the changes in electro-optical conversion efficiency and instability of the light source. This resulted that the standard light source could not be effective on the calibration of CCD device. Therefore, the stability of high-power white LED light source’s luminous flux is the key issue in the calibration of CCD. Anhui Optics and Fine Mechanics of Chinese Academy of Sciences, Chen Feng, who designed spectral tunable LED light source, pointed out:the uniformity of this light source was 0.53%, and the performance of the angle was 0.77% in±10°. This new type of LED light source could be used as a transfer standard for radiometric application. This article starts research from the working principle of LED and the actual engineering design, on the basis of the latest developments in LED engineering applications at home and abroad, and research the stability of LED light array. It is the key technology to solve this problem that researching on the connection type of LED array, the drive type of LED array’s power supply and the work condition of LED.This article researches LED light source surrounding the engineering applications of the LED light source as the standard light source for CCD calibration. According to the requirements of light source for CCD calibration, the type of the LED is selected. A LED luminous flux measurement platform is designed and built, including integrating sphere measurements reference and LED target plate measurement device. Through this measurement system, the stability of the luminous flux is researched when LEDs are connected in a different way. Finally, using orthogonal experimental design, LED forward current and connection way of LED array, which can affect the light stability of LED array, are optimized. Experimental results show that when the LED array is in different series and parallel mode, the stability of light source is different. Using 2×2 LED array that series first and then parallel as the basic unit of the LED array, the illumination stability of light source can reach to 99% in 8 hours, and this light source can well meet the requirements of the light source for CCD calibration.更多还原