An intelligent camera that is as tiny as a sugar cube and has the computer power of a Core2Duo in a fashionable black housing - sounds good, but unfortunately such a camera is still a figment of our imagination today. Nonetheless, even those of us who could live with a camera that may not be the size of a sugar cube but one that is actually about the size of a package of sugar, would want this camera to have heads that are as small and compact as possible, even if they cannot be shrunk down to the size of a sugar tube either. In such an application, the computer cube would be set up several meters from the camera cubes and would actually be equipped with a dual core CPU. Eltec now offers an innovative camera concept boasting a flexible and scalable image processing solution that meets virtually every expectation.
It is a common phenomenon for innovative concepts to arise from challenges. In the case in point, Eltec was working on a project that involved the development of a successor for a small intelligent camera that had become too slow for today's applications due to its limited computer speed. The objective was to come up with an intelligent camera that substantially boosts data speeds as a result of increased performance and that is still compact enough to fit into a weather guard housing. However, after having been customized for the special requirements of the application, this successor model turned out very differently. It now has up to two offset cameras, utilizes an innovative cable concept for digital image transfer and performs computations with the assistance of a geode CPU on an ETX module. Despite all of these extras it still fits into the weather guard housing.
Figure 1: Innovative camera concept with small offset camera heads
CMOS for Compact Designs
The objective was to design cameras that were as small as possible so that two of them could be used right next to each other. Additionally, they were to be equipped with a full frame shutter to get the disturbing oval distortions caused by a rolling shutter out of the picture. CMOS sensors designed for compact structures appeared to be an ideal solution, given that they offer high read-out rates and because they are relatively inexpensive considering their high resolution. However, those that comes with the desired shutter, which can freeze an entire image frame upon an impulse, are few and far between. Nonetheless, Eltec found one equipped with a sensor that directly delivers the digital data from the sensor, which made the implementation in a serial LVDS format for the transfers very easy to achieve. The selection of optimum transmission frequencies allows the use of budget priced patch cables for Gigabit Ethernet applications. The lengths of these cables can range from 20cm to 15m, which makes it easy to create set-ups that extend from compact to highly distributed. Eltec uses CMOS sensors with wide VGA resolution and a frame rate of 50Hz (non-interlaced), which are equipped with a freeze frame shutter to ensure the true-to-reality recording of moving objects and make it possible to achieve LVDS transmissions at rates of up to 700Mbps per channel. Nonetheless, CCD sensor solutions that make it possible to meet special requirements, such as reduced noise levels, are also available. The camera heads, which include the sensors, are small and lightweight.
Complete PC functionality on a card
The next engineering challenge was boosting the computing power of the CPU. Even at a 400MHz cycle, power conservation wizards can be found. The company chose an ETX module that offers all of the functions of a PC on a card. It even has a graphics outlet so that a full operating system with a graphic interface can actually be used. The key specifications of the ETX CPU module comprise the following: one Geode LX-800 CPU boasting 500MHz, one graphics controller in the chip set with up to 1280 1024 (85Hz), one PCI interface with 32bits / 33MHz and a 512MB SO-DIMM memory on-board.
Figure 2: Cost-effective cabling with Ethernet patch cables
ETX and COM modules sit on carrier cards, which also provide project-specific I/Os. For the image acquisition process, this particular application called for an interface between the digital camera interface and the hard disk, which is filled by the DMA. An FPGA handles this specific task with power and flexibility. All control outputs utilize the Profibus, i.e. a field bus. Pre-fabricated complete interfaces, which frequently master critical real-time communications and which can be optimally triggered via dual port RAMs, are available on the market. The 160mmx100mm format media card contains what is needed for the power supply, which operates at a voltage of only 24V / 20VA (12 typ.), as well as video inputs via RJ45 plugs, the DMA controller as well as the Profibus interface DP Slave.