焦距

According to the obtained characteristics of focal points and principal planes, using the expressions of focal point, focal plane, focal length, principal point, and principal plane of geodesic lenses, the geometry graphic imaging formation principles of geodesic lenses are developed to get the object-image-relation of geodesic lenses .

利用短程透镜焦点、焦平面、焦距、主点、主平面等的表达式，根据短程透镜在大口径范围内理想聚焦，主平面为以焦点为圆心、以焦距为半径、在原点相切的两个圆弧等性质，推导出了短程透镜物像关系的作图法求取原则。

According to range of the focal distance, dropping UV glue which is crystalline and unexpensive into lens cavity with UV rays, and then forms as soon as solidifies the convex lens. Combining UV curing glue convex lens and variable focus lens, the focal distance range achieves the 8.3~24.5 mm low focal distance effect.

於此之后根据变焦效果的需要，利用UV胶透光性佳、成本低，将UV胶滴定於透镜腔体中，形成一凸透镜，藉由变焦透镜与UV胶透镜结合，焦距变化达到8.3~24.5mm范围的低焦距效果。

Therefore based on image line observation, the adjustment model of correlation between line and vanishing point is constructed to determine the location of vanishing point from the viewpoint of photogrammetry.

分析了长焦距相机因视场角小在应用灭点标定时遇到的问题，首次研究了专门针对长焦距、小视场角相机的基于点线混合的标定方法。

In this paper,we use direct linear transformation algorithm to compute the homographic matrix between the known ground control points with equal elevation and the corresponding points on the image plane, then establish the relationships between the homographic matrix and the collinearity equations, and finally give the mathematic models for computing the intrinsic and extrinsic parameters of the aerial camera.

该方法根据单张航空像片估计伞载空中摄像机焦距及摄像机在世界坐标系中的位置和姿态角等外参数，利用直接线性变换算法求取已知等高地面控制点与对应像点之间的单应矩阵，建立了单应矩阵与共线条件方程之间的关联关系，最后根据关联关系推导出计算航空摄像机焦距、纵横比、位置和姿态角等内外参数的数学模型。

The result proves that the thermal lensing effect of slab has been improved due to adoptation of adiabatic construction.

板条热透镜效应实验结果表明，在500Hz重复频率下，未装绝热结构的板条热焦距为0.78m，而装有绝热结构的板条的热焦距为1.93m，热聚焦大为改善。

The focus of the collimating lens has effects on the slope of the visual magnification curve while the focus of the imaging lens affects visual magnification of the whole moving range in the same way.

系统中视力板移动检测时，准直透镜焦距影响视觉放大率变化快慢，决定视觉放大率曲线的平缓程度；成像透镜焦距对视觉放大率产生整体影响，使视觉放大率曲线产生整体平移。

The calculated uncertainty is in range of ±0.05 mm with different numbers of beamlets.

实验得到的焦距为23.2mm，焦斑直径1.3mm，实验结果表明焦距绝对误差在3.5 cm范围内，焦斑直径绝对误差在0.4mm范围内。

It will decrease when the pointing angle increases,and vice versa.By giving a pixel size of 20 μm for a detector,an orbit altitude of 600 km and a beam deflexion angle low than 30° for the imaging spectrometer, the effective focal length of the telescope was calculated(400,470 or 435 mm),and the relation curves between the relative ratios of ground resolution and the beam deflexions were presented.

给定成像光谱仪探测器像元尺寸为20 μm，飞行轨道高度为600 km，光线摆角≤30°，以星下点、最大摆角和整个运动补偿段地面分辨率中值为30 m为依据来计算望远系统的焦距，求得望远系统焦距为400、470、435 mm，并给出了此时的地面分辨率相对比值与光线摆角的关系曲线。

Also, the shorter focal lengths are desirable, because most digital SLR cameras have image sensors whose dimensions are considerably smaller than a 35mm negative (usually by a factor of 1.3X to 1.7X), making the lens' angle of view equivalent to that of a longer lens on 35mm cameras.

而且，更短的焦距更是想要的，因为绝大多数数码单反相机的图象传感器的尺寸比35 mm负片小(通常要乘1.3x 到1.7x)，从而使镜头的视角相当于一个在35mm相机上的更长焦距镜头的视角。

For that I want only your face to be in-focus, and the rest of the picture will be out-of-focus.

我只使你的脸在焦距内，其它的在焦距外

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。