Abel Eric, Fotiadis Nikolaos, Miah Mohammed, White Paul
School of Engineering, University of Dundee, Dundee, United Kingdom.
Laryngoscope. 2015 Mar;125(3):561-6. doi: 10.1002/lary.24971. Epub 2014 Oct 24.
OBJECTIVES/HYPOTHESIS: To describe lens and perspective distortion using new measures that have practical meaning to the surgeon, and to apply these measures to show the extent of optical distortion in rigid endoscopes used in endoscopic sinus surgery.
Laboratory measurements on rigid endoscopes.
Barrel and perspective distortion were measured in 4-mm diameter 0°, 30°, 45°, and 70° rigid sinus endoscopes. Images of square grids were obtained with the endoscopes aligned in a specially constructed test rig. The terms relative size (RS) and relative distance (RD) were introduced to describe size and distance errors; and the term relative angle (RA) was used for assessing perspective errors.
All the endoscopes exhibited similar barrel distortion. RS of the image at the periphery was 52%; RD was 80%. For RA values of 30°, 45°, and 70°, RS values were 77%, 58%, and 32%, respectively. Objects at the edge of the surgical field appear significantly more distant than suggested by their screen position. Perspective distortion occurs, unless RA = 0°. Barrel distortion of the lens helped to offset the effects of perspective distortion.
Optical distortion can be quantified and understood using straightforward definitions. High levels of distortion are common, particularly due to perspective distortion, which is dependent on RA but independent of barrel distortion and the viewing angle of the endoscope.
目的/假设：使用对外科医生具有实际意义的新测量方法来描述透镜和透视畸变，并应用这些测量方法来显示鼻内窥镜手术中使用的硬性内窥镜的光学畸变程度。
对硬性内窥镜进行实验室测量。
在直径4毫米的0°、30°、45°和70°硬性鼻窦内窥镜中测量桶形畸变和透视畸变。在内窥镜对准专门构建的测试装置的情况下获取方形网格的图像。引入相对大小（RS）和相对距离（RD）这两个术语来描述大小和距离误差；并使用相对角度（RA）这一术语来评估透视误差。
所有内窥镜均表现出相似的桶形畸变。周边图像的RS为52%；RD为80%。对于30°、45°和70°的RA值，RS值分别为77%、58%和32%。手术视野边缘的物体看起来比其在屏幕上的位置所显示的距离要远得多。除非RA = 0°，否则会发生透视畸变。透镜的桶形畸变有助于抵消透视畸变的影响。
可以使用简单的定义对光学畸变进行量化和理解。高水平的畸变很常见，尤其是由于透视畸变，它取决于RA，但与桶形畸变和内窥镜的视角无关。
