Camera elements

图像处理

背光补偿、曝光区域和宽动态范围是网络摄像机提高图像质量的三种功能。

背光补偿

尽管摄像机自动曝光功能极力使图像显示的亮度与人眼看到的场景相同,但很可能适得其反。强背光会造成前景中的物体变暗。配有背光补偿功能的网络摄像机尽力忽略有限的高亮区域,如同不存在一样。这样,即使明亮区域感光过度,仍然可以看到前景中的物体。这种照明状况也可以通过提高摄像机动态范围来处。

曝光区

除处理有限高亮区外,网络摄像机自动曝光还必须选择图像中需要确定曝光值的区域。例如,背景(一般为图像底部)所含信息可能比天空(一般为图像顶部)等前景中的更重要。场景中不重要的部分应确定为非过度曝光区。采用高级安讯士网络摄像机,用户可以选择场景中部、左部、右部、顶部或底部作为曝光区,从而更加准确地曝光。

宽动态范围

有些安讯士网络摄像机具有宽动态范围功能,可处理照明变化大的场景。区域过亮或过暗,或人位于玻璃幕墙背光场景中,一般摄像机生成的图像,处于暗区中的物体很难清晰看到。宽动态范围技术采用场景中不同物体不同曝光率等方法解决这一问题,使得明暗区域中的物体都能看得很清楚。

左图,未采用宽动态范围的图像。右图,采用宽动态范围的图像。

Noise reduction

Any image or video will contain a certain amount of noise, i.e. pixel values that are not correct representations of the scene and that negatively impact the viewing experience, aesthetically or practically. The noise is picked up from a variety of sources including the image sensor and the other electronic components of the camera, but also from the light itself.

Different factors work in favor or against reduced noise levels. For example, high resolution cameras typically have smaller pixels in their image sensors than standard resolution cameras. Smaller pixels are more sensitive to noise, in turn making megapixel and HDTV cameras more sensitive.

To reduce noise is thus a key task in a video surveillance camera. Modern network cameras that offer high processing capacity in their chips are well equipped to analyze and reduce noise levels, even in high resolution and full frame rate conditions. One technique for minimizing noise is built on spatial processing, where a single image frame is analyzed to find pixels that are very different in color or intensity from their surrounding pixels. Another technique is temporal processing, where consecutive image frames are compared to find artifacts in the images that are not static over time and can be regarded as potential noise.

网络摄像机的安装