焦距

This making of a composition can take a very short time (because of midges I had to retreat from the field of Buchaille Etive Mor within 10 seconds), sometimes it has me puzzled and it takes a long time: a bit to the left, some sky or not, telephoto or standard, no - this way is best.

这幅构图的形成只花了我很短的时间（因为蚊子我不得不在10秒之内从Buchaille Etive Mor的田野撤离），有时则令我为难，花很长时间：左边的一小点，天空要一些还是不要，长焦距镜头还是标准镜头－－这个方法是最好的。

Development of optical manufacturing, especially aspherical manufacturing, boosted the developing of space optics. Aspheric testing for large departures from reference wavefronts becomes the bottleneck of optical manufacturing. Off-axis TMA system presented in space cameras for large field, high resolution, long focal length challenges the manufacturing and testing for aspheric components .

光学制造技术的发展，尤其是非球面加工技术的兴起，促进了空间光学的发展，大视场、高分辨率、长焦距的航天相机离轴三反系统设计的引进对非球面的加工和检测都是很大的挑战，非球面的检测技术越来越成为光学加工的瓶颈，本文从检测角度出发，提出了基于电子虚拟样板的非球面检测技术概念，建立电子虚拟样板的数学模型。

It allows for versatile adjustment by panning, tilting and rotating the varifocal lens to any camera angle desired.

它还可以对镜头进行水平、垂直及焦距的调节，以满足用户对摄像机视角调节的需要。

New from Vicon Industries, Inc., of Hauppauge, New York, are six infrared varifocal lenses that can be used with true day/night cameras to provide sharp, focused images in daylight and at night, particularly in the presence of IR light.

源自美国纽约州Vicon实业公司的新型产品，六款红外变焦距镜头，各类日夜交替式摄像机，可以应用到在白昼、夜晚、尤其是红外光照射的环境下生成清晰的图像。

A varifocal f-theta lens was designed for Nd:YAG laser making scan focusing system, so that it apply to differ making area but change a lens necessarily. the system consists of four lens ,made by glass BK7, SF18 and SF11. The total length of the system is 122.96mm, working at 1064m.

为Nd：YAG激光打标机设计了变焦距f-theta镜扫描系统，以使它适用于不同的打标面积而不必更换镜头，系统由四片透镜组成，材料分别为BK7，SF18和SF11，系统总长度为122.96mm，工作波长1064nm。

The unit includes a removable infrared cut filter, digital signal processing circuitry with a 1/3-inch IT 410,000 pixel CCD, and backlight compensation. A 4x digital zoom complements the 2.5- to 6.0-millimeter varifocal, auto iris lens to ensure detailed close-ups.

摄像机还包括红外可拆卸截止滤光片，数字信号处理电路，1/3英尺IT的41万像素CCD以及背光补偿。4倍数字变焦补偿2.5到6.0毫米的变焦距，自动虹膜镜头确保详细的特写镜头。

Eyepieces can be found with shorter eye reliefs than that, but they are not comfortable to use for long periods.

目镜中有不少是小于8MM焦距的，但是长时间的观测会非常的不舒服。

Using the K20 eyepiece included as standard equipment, about 45x magnification, it's easy to see the Andromeda Galaxy and its smaller satellite galaxy M32. When compared to 60mm refractors, the Powerseeker 114 brings out much more detail in the Orion Nebula, reveals many more stars in Perseus' Double Cluster and even brings out a few individual stars in globular clusters like M13. Saturn looks quite small at 45x with the K20 eyepiece, but using my own 7.5mm eyepiece (120x) I can easily detect the shadow cast by the planet on the rings, and even glimpse the ring's Cassini Division. When the mirrors are properly lined up or "collimated," the images are reasonably sharp up to magnifications of 225x.

使用标准配件中的K20 目镜，可以得到45倍放大率，这时候很容易看到仙女座星系，还有较小的星系M32；和60毫米口径的折射望远镜相比，114 EQ可以看清更多猎户座星云的细节；瞄准英仙座双星团，看到的星体数量更多，显得更加壮丽；对于球状星团，比如M13，甚至可以显出其中少数独立的恒星；在K20 目镜下（放大45倍）的土星显得相当小，但换成我自己的7.5毫米焦距的目镜(得到120倍)，可以轻松的看到光环在土星上的投影，甚至可以瞥见土星光环内的卡西尼缝隙。

But wide angle oculars with long focal lengths have large field lenses, which require large prisms to be illuminated to the edges of the field, and this leads to an expensive and bulky instrument.

但宽视野又长焦距的目镜含有广角镜片，这需要大棱镜照亮视场边缘，导致价格昂贵和体积巨大。

This paper disuissed the deduction of the focal distance f using the Gauss method and the total yoke method in an imperfect situation,namely a situation where thin lens merely involve light core errors.

在普通物理光学实验中，在理想状态下测定薄透镜焦距常采用的方法有高斯法、共扼法、自准直法等。

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。