共查询到19条相似文献,搜索用时 343 毫秒
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为提高针尖增强拉曼系统对焦准确性和效率,提出通过分析CCD相机拍摄的光斑图像的像素值实现自动对焦的方法。首先快速粗调焦缩小调焦范围,然后再慢速细调焦提高调焦精度。实验表明:与Tenengrad评价函数相比,方差评价函数更适用于针尖增强拉曼光谱测量系统自动对焦,聚焦到样品表面时对焦结果的无偏估计标准差<0.25μm,具有较高的重复性和鲁棒性;快速粗调焦可提高调焦效率,避免陷入局部最优解;慢速细调焦评价函数曲线在焦点附近呈现“M”形,可通过二次拟合提高调焦精度。 相似文献
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本文重点介绍眼科光学计量中对焦度计测量不确定度的评定,分别给出了使用顶焦度标准镜片对两种不同测量原理的焦度计进行强制检定时,检定证书中列出的被检焦度计的顶焦度修正值的不确定度。一、焦度计的分类焦度计从工作原理上被划分为基于自动对焦原理的焦度计和基于调焦原理的焦度计。基于自动对焦原理的焦度计,原理先进,操作简单,可自动读数,数字显示的分辨力为0.01m-1。基于调焦原理的焦度计主要有目视式和投影式两种。由于受人眼分辨力及光学系统成像等主、客观因素的影响,其刻度间隔一般为0.12m-1和0.25m-1。个别仪器经… 相似文献
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为了保证电动变焦数字监控摄像机的变焦步进电机和调焦步进电机的调节范围在厂家设计的可聚焦范围内,设计了一种基于变焦曲线的变焦电机和调焦电机的原点位置校正方法。首先,从镜头厂家提供的镜头变焦曲线中选定一条作为标准曲线。接着,利用自动调焦方法采集标准曲线对应距离下的实际变焦曲线。然后,计算标准变焦曲线的最高点和实际变焦曲线的最高点的偏移量。最后,在该偏移量附近的一个小范围内按照平方差最小的原则求出最佳偏移量即为原点位置的补偿值。在30倍光学变焦数字高清摄像机中实现了该方法,实验结果表明:48台采用本文方法成功校正的镜头在设计调节范围内均没有出现电机堵转和无法聚焦的现象,校正成功率96%,很好地解决了由于原点位置误差造成的问题。 相似文献
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倾斜镜面成像的自动调焦方法 总被引:1,自引:0,他引:1
倾斜镜面成像系统的像面与光轴倾斜,仅利用轴向自动调焦无法实现像面整体清晰。为此提出一种基于图像清晰度判断的自动调焦方法。该方法将轴向调焦与角度调焦相结合,通过步进方式平移和旋转像接收面,利用离焦函数判断聚焦情况,采用数据拟合回归的方法实现了像面整体清晰。该方法在椭偏成像系统的应用结果验证了其有效性,调焦精度达到微米量级。 相似文献
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摄影人都知道,不管作用微距镜头还是近摄附件,其近摄的景深都非常浅,调焦操作困难,有时甚至不能使用相机的自动对焦系统来完成对焦,必需改用手动调焦来完成精确的调焦需要。由于景深浅,使得焦点以外的景物模糊,无法表达清楚。 相似文献
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用步进电机实现连续变焦距光学镜头的变焦控制 总被引:7,自引:0,他引:7
根据望远镜的工作原理,对变焦距光学镜头的变焦运动进行了定性分析,并且根据理想光学系统的物像关系式推导出该镜头运动镜组的运动方程。该连续变焦控制的实验装置包括步进电机,电机驱动器以及控制平台,其控制程序用VisualC 编写。实验表明,该方法能方便地实现连续变焦距光学镜头的变焦控制。 相似文献
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Xiao Tang Pierre L’Hostis Yu Xiao 《Journal of research of the National Institute of Standards and Technology》2000,105(4):565-569
An auto-focusing method in a digital image system is demonstrated that uses a standard deviation of pixel gray levels as a feedback signal. In this system, an optical microscope and a charge coupled device (CCD) camera are used to create clear pit images of optical discs. A dynamic focusing scheme is designed in the system-control software, which is able to eliminate environmental disturbances and other noises so that a fast and stable focus can be achieved. The method shows an excellent focusing accuracy. The performance and possible applications of this method are discussed. The test results for optical discs are given in this paper. 相似文献
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A method is proposed for increasing the resolution of an object and overcoming the diffraction limit of an optical system installed on top of a moving imaging system, such as an airborne platform or satellite. The resolution improvement is obtained via a two-step process. First, three low resolution differently defocused images are captured and the optical phase is retrieved using an improved iterative Gershberg–Saxton based algorithm. The phase retrieval allows numerical back propagation of the field to the aperture plane. Second, the imaging system is shifted and the first step is repeated. The obtained optical fields at the aperture plane are combined and a synthetically increased lens aperture is generated along the direction of movement, yielding higher imaging resolution. The method resembles a well-known approach from the microwave regime called the synthetic aperture radar in which the antenna size is synthetically increased along the platform propagation direction. The proposed method is demonstrated via Matlab simulation as well as through laboratory experiment. 相似文献
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We describe a method of measuring the relative optical phase on reflection between amorphous and crystalline regions of the phase-change media of optical data storage. With a red He-Ne laser (wavelength, 632.8 nm) the relative phases on two quadrilayer optical disk stacks were measured and found to be ~40 degrees . The results are in good agreement with the calculated values based on the known layer thicknesses and refractive indices of the stacks. For calibration purposes the height of a known step on an otherwise flat silicon substrate was measured with the same apparatus. The proposed method is fairly simple to set up, can measure both front-surface and through-substrate types of optical disk, and can be used with any laser that has long coherence length. 相似文献
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根据傅里叶变换系统中物面平移其频谱面上光强分布不变的特点,提出一种利用二次傅里叶变换实现CCD精密定焦的方法。将CCD和其透镜作为逆变换系统,输入面为两个狭缝,与一个附加透镜组成一个正变换系统。通过镜组移动改变正、负傅里叶变换系统的距离,用软件比较CCD上两个波峰的间隔是否变化来对CCD进行定焦。根据傅里叶变换原理和几何光学成像原理对CCD正焦和离焦时的波峰特点进行了理论分析,证明了离焦时波峰间隔变化量与镜组移动量、离焦量、狭缝间隔成正比,与两透镜的焦距成反比,由此关系即可实现CCD定焦。实验表明,该方法的相对定焦误差为0.2%。 相似文献
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A highly accurate method of optical path-length measurement is introduced by use of a scanning heterodyne optical interferometer with no moving parts. The instrument has demonstrated the potential to measure optical path length at angstrom resolution over continuous thickness in the micrometer range. This optical path length can be used to calculate the thickness of any material if the refractive index is known or to measure the refractive index of the material if the thickness is known. The instrument uses a single acousto-optic device in an in-line ultra-stable reflective geometry to implement rapid scanning in the microsecond domain for thickness measurements of the test medium. 相似文献
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Materials that have subwavelength structure can add degrees of freedom to optical system design that are not possible with bulk materials. We demonstrate two lenses that are composed out of lithographically patterned arrays of elliptical cross-section silicon nanowires, which can dynamically reconfigure their imaging properties in response to the polarization of the illumination. In each element, two different focusing functions are polarization encoded into a single lens. The first nanowire lens has a different focal length for each linear polarization state, thereby realizing the front end of a nonmechanical zoom imaging system. The second nanowire lens has a different optical axis for each linear polarization state, demonstrating stereoscopic image capture from a single physical aperture. 相似文献