【作者】 朱海金；

【导师】 程萍；

【作者基本信息】 合肥工业大学 ， 光学工程， 2010， 硕士

【摘要】 光学投影三维测量系统主要由投影系统和接收系统组成。投影系统投影出光栅条纹的质量是取得高精度测量的关键,因此光栅元件是投影系统中的核心部件。本文针对光栅元件的高质量、高精度等要求,提出制作高质量光栅元件的方法。其中,一组编码元件中灰度正弦光栅的制作方法是本文的重点。制作灰度正弦光栅有很多种方法,针对光栅元件中灰度正弦光栅的特殊要求,本文选择运用空间滤波成像的方法制作高精度灰度正弦光栅。阐述了该灰度正弦光栅制作的基本理论和光路参数计算。该方法可以方便的精确调整所需要的条纹频率和在线观测条纹质量。制作的光栅条纹平行度及均匀性好,光栅常数控制精确,而且畸变小,能获得良好的正弦性条纹分布。针对光路的不足之处,在光路中引入双散斑屏消除激光强相干性对成像质量的影响,并用背景光照射像面使像面因而产生不为零的最低光强,使得正弦干涉条纹光强分布达到全息干板的特性曲线的线性区。实验过程中,首先制作高质量的朗奇光栅作为成像系统中的物光栅,在像面上用高质量全息干板在不同实验条件下拍摄像面上的灰度正弦光栅图;然后在光学投影系统中对光栅进行投影,通过CCD摄取干板的透过条纹图,对图像的数据处理可得出光栅的透过率曲线,用标准的正弦曲线拟合透过率曲线,通过比较两者的差别可得出干板条纹图正弦性的优劣和条纹的反衬度;最后根据检测结果得出制作正弦性优、反衬度高、质量高灰度光栅的最佳实验条件。实验结果表明,基于空间滤波成像原理的消激光散斑成像系统,可以通过低频二值化的光栅得到较高频率的正弦光栅,可方便调整光栅常数,且所制作的光栅常数准确,获得条纹均匀性和平行度好,相干噪声小的投影正弦条纹。为保证线性记录和线性显影,采取引入合适的背景光曝光量和总曝光量,控制正弦干涉条纹曝光量在所用干板的线性区域,在水溶比为10:1的稀释显影液中显影,制作出了高质量反衬度满足要求的灰度正弦光栅。更多还原

【Abstract】 Structured-Light Three-Dimension Measuring System is primarily composed of projection system and the receiving system. The quality of the grating which is projected by the projection system is key to achieve hight-precision measurements, and the grating component is the core of the projection system. In this paper, a fabrication method of high quality grating components is proposed to meet the demand Structured-Light Three-Dimension Measuring System, among them, the production of sinusoidal grating of a group of coding elements is the focus of this article.There are many ways to produce sinusoidal grating. Weighing the special requirement of the sinusoidal, we choose space filter imaging process to make high-precision sinusoidal grating. The basic theory and optical parameters of making gray sinusoidal grating are described. In this way, the required frequencies can be easily adjusted and we can on-line observe fringe quality. It can produce grating fringe with high parallelism and uniformity reliably, control grating constant accurately with very small distortion and obtain favorable sinusoidal fringe distribution efficiently. To improve the shortcoming of optical path, pairs of speckle screen is introduced in the light path to eliminate the laser’s strong coherence which effects on image quality, and a background light is introduced to expose the image so that the intensity distribution of the sinusoidal interference fringes can reach the linear region of the characteristic curve of holographic plane.During the experiment,first, we produce high-quality Ronchi grating which we put on object plant of the imaging system. Sinusoidal grating image in the image plane is recorded on holographic plane with high-quality under different experimental conditions. Second, the grating is projected in the optical projection system, after the processing date of the picture shot by CCD, we obtain the transmittance curve of holographic plane. By comparing the difference between the transmittance curve and the standard sinusoid which we fit with the actual curve, is or no and the contrasting degrees of the picture are obtained. At last, according to test results we obtain optimal experimental conditions of producing favorable sinusoidal fringe distribution, high contrasting degrees, high-quality sinusoidal grating.Experimental results show the we can obtain a higher frequency sinusoidal grating with lower frequency binary grating, adjust grating constant conveniently, and finally obtain the sinusoidal grating’s projection imaging with accurate frequency, high parallel, as well as very small coherent noise distribution. In order to ensure liner recording and linear imaging, appropriate light exposure of the background and total exposure are introduced, and we control the sinusoidal interference fringes exposure in the linear region of the characteristic curve of holographic plane and develop the holographic plane in Water-soluble ratio of 10:1 DEVELOPER, then we can make contrasting degrees to meet the requirement of high-quality gray sinusoidal grating.更多还原