焦距

The design of four-mirror anastigmat was analyzed, then a system with effective focal length of 1 200 mm and field of view of 0.8°×0.8° was designed , total length and f-number are 300 mm and F/6,respectively.The system has advantages of long focal length, relative short physical size and excellent ability in restraining stray lights.

分析了离轴四反的设计步骤，设计了一个焦距为1 200 mm，视场为0.8°×0.8°，相对孔径为F/6的光学系统，系统总长只有300 mm，并达到很好的光学性能，具有长焦距、小尺寸、良好的杂散光抑制能力等特点。

Measuring the focal length of concave lens using collimator;2. The relation between the focal length of a concave lens and its reflective image properties is analysed and deduced.

本文分析推导了透镜的凹面反射成像与凹透镜焦距的关系，介绍了利用此关系较方便地测量凹透镜焦距的方法。

But these methods limited by the expense of computing fundamental matrices and trifocal tensors or of the nonlinear optimization involved in computing epipolar tangencies. Through the studies of the invariants of the single axis motions, computational theories have been developed in this thesis to provide practical solutions for the problem of structure and motion from fitting the corresponding points in the whole sequence to its conic locus or conics for short.

在最近的研究中，一些研究人员利用视觉几何的方法从非定标的图象中对单轴旋转运动进行分析，提出了利用基本矩阵和三焦距张量求解单轴旋转运动中的关键参数——旋转角度的算法，但是该算法需要计算一系列相邻2图象的基本矩阵和一系列相邻3图象的三焦距张量，由于每个基本矩阵的自由度为7，每个三焦距张量的自由度为18，导致算法参数数量非常之大。

A dioptre is the inverse of the focal length of an optical system measured in metres.

屈光度是镜片焦距的倒数，其中焦距的计算以米为单位。

A dioptre is 1 divided by the focal length of the lens in centimetres. So a 1-dioptre lens has a focal length of 1m; a 2-dioptre lens has a focal length of 50cm; a 5D lens has a focal length of 20cm.

一屈光度是1除以该镜头焦距在厘米，所以一屈光度镜头焦距一米； 2屈光度镜头焦距50厘米； 1日5日镜头焦距二○厘米）。

Experimental results and values in theory were accordant well. Experimental results showed that the radius of focal spot would increase with the longer focal length, and focal depth would decrease with higher order of FZPs.

实验还发现，聚焦的焦斑半径会随着焦距的长度而增大，而聚焦深度则随着分形波带片的阶次的升高而减小，同时还对比了分形波带片和常规波带片的焦距调节方式和精度，理论研究表明分形波带片的调节焦距的方式具有更高的调节精度。

The merit of the invention are: 1 adopting free curved surface imaging method , three part reflection type Zernike polynomial free curved surface forms short focal distance bigger, relative apertures bigger fields of view angle imaging , rectifying optical aberration much better and its structure is simple; 2 adopting the reflection structure without optical lens, has removed the effect of various chromatic aberration , guarantee the imaging articulation; 3 adopt the design of short focal distance big fields of view angle, focal distance 8 - 15 mm, field of view angles 100 -135 degree, having 120 times multiplications under 250 mm imaging distance, having ultra-thin characteristic property; 4 adopting big relative apertures design ,the relative aperture is 2.0-2.4, having improved the illuminance of flat surface; 5 adopting image space telecentric imaging method , ensures that the image surface irradiance is homogeneous.

本发明的优点是：1采用自由曲面成像方法，三片反射式Zernike多项式自由曲面形成短焦距大相对孔径大视场角成像，更好地校正像差，结构简单；2采用无透镜形式的反射式结构，消除了各种色差影响，保证成像清晰度；3采用短焦距大视场角设计，焦距8～15mm，具有100～135度的视场角，在250mm成像距离下有120倍的放大倍数，具有超薄特性；4采用大相对孔径设计，相对孔径为2.0～2.4，提高像平面上的光照度；5采用像方远心成像方法，保证像面辐照度均匀。

Considering the thermal-induced birefringence, the g parameter coordinate system is analyzed, the formulas of radially polarized and azimuthally polarized focal lengths in three different cavity structures are deduced and the proper cavity structure to get the thermal focal length coefficients is presented.

考虑热致双折射效应，利用等效谐振腔的g参数坐标图进行分析，推导了三种不同腔型结构下径向热透镜焦距和切向热透镜焦距系数的计算方法，分析并得出了测量热透镜焦距系数所需的腔型结构。

A novel method of measuring plus lens's focus is given, which is based on LCD, CCD, and digital image processing It is also a discussion on photoelectric method of automatically measuring parameters of an optic system In this method, a LCD is used as a reticle of the collimator, while the image on the accepting side is transformed into digital image and is sent into a computer The focus can finally be calculated out through digital image processing and analysis The method of measurement is introduce...

讨论了一种基于LCD、CCD和数字图像处理的正透镜焦距测量方法，是光电法自动化测量光学系统多个参数的一种有益的探讨。用液晶屏显示分划图形取代平行光管的分划板，用CCD在接收方采集数字图像并送入计算机，通过图像处理和分析得出被测透镜的焦距。运用叠加的方法提高图像的信噪比；结合重心法和平行线拟合方法求取平行线对的间距；应用高精度焦距标准透镜标定数字图像和实际像之间的比例关系。详细介绍了测量和图像处理的方法，进行了公式推导和误差分析，并给出了实验结果

The optical trade offs compared to the SE are reduced eye relief from the shorter focal length eyepiece needed to produce the same magnification and higher levels of chromatic and spherical aberrations from the lower focal ratio objective (which may or may not actually be visible at 8X).

SE物镜焦距较长，E和E II为了紧凑而使用较短的焦距，但是就要有所牺牲。因为相同倍数需要用更短焦距的目镜，所以出瞳距离短了。

As she looked at Warrington's manly face, and dark, melancholy eyes, she had settled in her mind that he must have been the victim of an unhappy attachment.

每逢看到沃林顿那刚毅的脸，那乌黑、忧郁的眼睛，她便会相信，他一定作过不幸的爱情的受害者。

Maybe they'll disappear into a pothole.

也许他们将在壶穴里消失