焦距

Further,it puts forward a new method,which is based on the lens' assemble plane and realizes the purpose of optical system imaging clearly by refacing revolution mechanic part two times and adjusting imaging distance.

简单的家用相机，摄相机等含有光学系统的成像仪器，它们所包含的镜头焦距短，相对孔径大，成像像面小，成像质量要求较低，通过机械和光学的加工可以保证，只

Finaly many experiments are completed in the lab in diffrient conditions , which contains illuminance of crack 、 contrast of image 、 distance of shotting and focal length, to review the accuracy of the new system and to analys the rule of th effection of the accuracy .

在论文的后阶段，设计了实验室中进行的两个层次的考核和标定试验，并对应用中必然遇到的物面光照度、图像对比度、测量距离和焦距的改变，对试验样本测量精度的规律作出了初步分析，为新方法的进一步完善提供了有价值的工作基础。

More interesting candid pictures happen when the photographer moves around the subject, tilts the camera, and stoops down of finds a higher point of view.

家庭生活场景是摄影师用来练习构图和布光技巧的很好的素材，要深入体会各种视角、镜头、焦距对于景深和画面的影响。

Theory analysis and computer simulation show that the precision and focus of star tracker, the divergence angle of down beam influence the probability of laser link setting up.

理论分析和计算机仿真都表明，星敏感器的测量精度和焦距，下行信号光的束散角将影响激光链路成功建立概率。

Compared with traditional methods,the novel calibration approach expands the applications of the multi cameras and can find out the internal and external parameters simultaneously without the constraint for the ball bar movement.

与传统方法相比，本方法扩展到了多台摄像机应用场合并允许摄像机焦距各不相同，不需要对球杆的运动做任何限制，能够同时求解出摄像机内外参数，而改进的模拟退火进化策略改善了算法收敛速度和全局收敛性能。

Finally, the law that laser reflection characteristics varies with the parameters of the transmitting laser beam and the cat eye optical lens, including aperture, focus and focal shift etc, is achieved.

得出了猫眼效应反射光特性随着入射激光参数以及猫眼光学镜头的基本参数——口径、焦距、离焦量变化的规律。

To enlarge the measurement range of a potential vision meter and improve its measurement accuracy for patients with high error of refraction, the imaging characteristics of its optical system were investigated. The visual magnification equation of the system was derived. The influence of the focal length variation of the collimating lens and the imaging lens on the magnification was analyzed respectively.

针对潜在视功能检测仪临床使用中量程有限和对高度屈光不正患者检测结果有一定误差的现象，研究了其光学系统成像特性，建立了系统对视力板成像的视觉放大率公式，分析了准直透镜、成像透镜焦距变化对视觉放大率的影响。

The lens axicon is based on the use of the spherical aberration of the mirror surfaces,which is inexpensive and easy to manufacture into a element with large apertures as compared with diffractive axicons,refractive cone axicons,and earlier lens axicons with aspheric surfaces;the opaque disk can offer the Bessel beams with long non-diffracting distances,and the diameter of the central peak is adjusted by choosing the focal length of the collimating lens;the tunable fluidic conical lens is a new device for generating Bessel beams,which can obtain the Bessel beams with different parameters by varying the refractive indexes of the solution which is filled in the device.

双透镜轴棱锥法主要基于透镜球面像差的运用，与衍射轴棱锥、折射轴棱锥和早期的非球面轴棱锥相比，具有加工简单、便宜，易于制作大尺寸的特点；不透明障碍物法得到的贝塞尔光束具有很长的无衍射距离，其直径可通过选择不同焦距的准直透镜来得到调节；可调流体轴棱锥是一种产生贝塞尔光束的新型器件，它可以很容易地通过改变注入器件的液体的折射率来得到不同参量的贝塞尔光束。

The box beam external dimensions are big , are away from the ground to be high , carries on the dog-legged single shade beam crack detection from the opposite side , the focal distance is long , and is not easy to operate.

箱形梁外形尺寸较大，距离地面较高，从对侧进行双壁单影射线探伤，焦距偏长且不易操作。

And much is changing in countries, in the world and in the international situation. Therefore, we all have the task of "adjusting the focus and apertures."

当前，各国的情况、世界的情况都发生了很大变化，所以我们大家都存在如何&调焦距、对光圈&这样一个任务。

I didn't watch TV last night, because it .

昨晚我没有看电视，因为电视机坏了。

Since this year, in a lot of villages of Beijing, TV of elevator liquid crystal was removed.

今年以来，在北京的很多小区里，电梯液晶电视被撤了下来。