The technological advances that have been made in the field of network-based surveillance in the last few years are astounding. High definition (HD) and megapixel (MP) cameras were introduced onto the market and the question arose: Which are more suitable for professional video surveillance of ports, HD or megapixel cameras? But since then, even that discussion is already outdated. A new technology, known as multifocal sensor technology, has taken the market by storm and is paving the way for a whole range of previously inconceivable surveillance and analysis capabilities.
When the first HD and megapixel cameras were launched onto the market a few years ago, they were clearly superior to the predecessor standard definition cameras, with much higher resolutions. HD cameras are impressive because of a technology that is derived from the field of video – that is to say relating to moving images. On the other hand, the roots of megapixel technology are in the field of static photography, even though they can reach higher pixel values than are possible with HD cameras. But before any discussions begin as to whether HD or megapixel cameras are more suitable for modern surveillance tasks, one point must be considered: resolution on its own is not everything. In order to be able to use the images from surveillance cameras
efficiently and analyse them successfully, other dimensions besides resolution are important, such as effective image breakdown, recording of the overall image or analysis in the past. Whereas both HD and megapixel cameras very soon reach the limits of their capabilities in these areas, a new technology, multifocal sensor technology, performs flawlessly.
Unlike HD and megapixel cameras, which are equipped with a single lens, the multifocal sensor systems work with several lenses, each of which has a different focal length. Thanks to this new sensor concept, the camera can be adapted optimally to the area for surveillance, so details are still clearly visible, not only close up but also at very long distances, and individuals can be recognised. However, that is not the only way it stands apart from conventional cameras.
Efficient image breakdown
One of the main arguments advanced by the defenders of high definition cameras is that HD uses the widescreen format with an aspect ratio of 16:9 compared with the 4:3 format of the megapixel cameras. This corresponds more closely to the human field of vision, and makes it possible to record yet more information laterally as well.
But real scenes seldom correspond to either of these two formats. However, in order to cover all areas of interest, it is often accepted that unimportant expanses, such as the sky, will be captured as well. In this case, pixels and the recording and storage capacity they take up are all wasted needlessly. But there is a more elegant solution: instead of forcing a scene for surveillance into a given format, with multifocal sensor systems there are no rigid, pre-set aspect ratios. They adapt the pixel ratio to the situation at hand. The image is split efficiently without being locked into specific aspect ratios such as 16:9 or 4:3. Thus for example aspect ratios like 5:1, 10:1 or 3:4 can be used without any difficulty.
Constant resolution over the entire object space
It is true that HD and megapixel cameras use progressive resolution options, but they quickly reach their limits precisely when it is important to be able to recognise details even at long distances. “Movies or television programmes like CSI often suggest to viewers that even blurry pictures can be transformed into high quality police wanted posters with just a few clicks”, explains Roland Meier, team leader, Panomera® Multifocal Sensor Systems at Dallmeier. “But pixels are still just pixels: if there is no additional image information present, for example because an HD or MP camera only represents a person at a distance of 50 metres with a collection of coarse blocks, this information cannot be conjured out of thin air afterwards. So you are aware that something is happening here, but it is completely impossible to even recognise, much less identify a person. And that is precisely the objective of a professional video system.”