焦距

The ratio of the focal length to the diameter of a lens system.

相机镜头直径焦距比。

The rotary connection can be carried out in free space and hi-direction transmission of optical signal can be performed. Through analyzing the design principle of the optical structure and optical path calculation, it is found that when the ratio between the focal lengths for two lens is 20~50 and off-axis distance is in the range of 4~10mm, the interference will not be occurred between two optical channels and signal transmission can be lasted.

在自由空间可以实现旋转连接并实现光信号的双向传输，通过分析该光学结构设计原理和光路计算，发现每组透镜中两个透镜焦距之比为20-50，离轴距离为4-10mm范围时，才能保证光通道之间不发生干扰且信号持续传输。

I appraised the light, adjusted the lens setting and distance, locked a bulb in the flashgun

于是，我对好光，调好焦距，又安了一个闪光灯泡，然后举起像机，将这一场面在取景器中定格。

I appraise d the light, adjusted the lens setting and distance, locked a bulb in the flashgun, raised the camera and composed the scene in the viewfinder

于是，我对好光，调好焦距，又安了一个闪光灯泡，然后举起像机，将这一场面在取景器中定格。

I appraised the light, adjusted the lens setting and distance, locked a bulb in the flashgun, raised the camera and composed the scene in the viewfinder

于是，我对好光，调好焦距，又安了一个闪光灯泡，然后举起像机，将这一场面在取景器中定格。

I appraised the light, adjusted the lens setting and distance, locked a bulb in the flashgun, raised the camera and composed the scene in the viewfinder .

于是，我对好光，调好焦距，又安了一个闪光灯，然后举起相机，将这一场面在取景器中定格。

Then the experimental setup for the focusing performance is described, and the focusing performance of the PMMA compound high-energy X-ray lens is tested under the inradiation of the 8 keV monochromatic X-ray.

最后给出8 keV单色X射线辐射下，PMMA材料X射线组合透镜的聚焦性能的测试结果，对实际测试结果进行了分析和讨论，得出结论，焦距等参量与理论计算结果基本吻合。

To avoid the shortcoming of magnification change with wavelength, which will cause the spectral image pixel registration error and provide inaccurate relative spectral signal strength in the classical diffractive optic imaging spectrometer, a novel hybrid refraction/diffraction telecentric optical system combining a diffractive lens with an achromatic lens system is presented, and the working principle is then established.

为了克服在传统衍射光学成像光谱仪中，衍射透镜的焦距随波长变化引起系统放大率随波长变化，从而导致光谱图像的像元配准误差，得到并不精确的相对光谱信号强度，提出了将衍射透镜与消色差透镜系统相结合的新型折/衍混合、二组元复合远心成像光学系统的技术方案，具体分析推导了该系统的成像理论。

The focus of Fresnel zone lens is related to both the radius and the number of loops, however is independent to its phase grades.

在环带相位深度P为2p 时，菲涅耳波带透镜的焦距与其半径和环带数有关，而与相位阶数L无关。

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。