Robot Vision
Dateline: 12/09/99
Incorporating machine vision techniques into a home-built robot is probably one of the greatest achievements for the typical hobbyist. Only a few years ago such project would cost a fortune due to the high prices of quality cameras and frame-grabbers, not to mention the physical size of the related equipment that simply couldn't fit the requirements. Imaginative as always, some robot builders even used some DRAM chips with top lids removed as a simple (but ineffective) cameras. However, with the advent of VVL1070 from VLSI Vision Ltd. and similar chips, serious machine vision hardware became accessible even to the developers on limited budget.
We'll start with an older, but still very interesting project. It is cheap, easy to build, easy to program, easy to explain - a beginner's dream. Kevin Ross from Seattle Robotics Society built a Low Resolution Vision System using only 8 Cadmium-Sulfide cells and a 68HC11E2 microcontroller. The final system is able to detect and track motion in the environment. If left alone for a little while, it will eventually focus in on whatever is moving, and as author says, "the way that the two lenses are mounted on the head gives the robot a certain amount of personality that is hard to resist". Slight improvements could bring much better resolution (8x8, for example), and the ability to follow smaller lines or find small patterns.
Want something more advanced, but still very affordable? There are numerous sites on the Web describing how to "hack" QuickCam and similar commercial Web cams, or even cheaper "toy cams". Some people use TYCO VideoCam that includes a small camera module, microphone, and preamplifier boxed up together with a battery holder. Game Boy Camera is another toy cam that can take and store 30 black and white images, and has an impressive collection of fun image manipulation tools. Images can be flipped, mirrored, and stretched - one of the best resources for this type of camera is Jeff Frohwein's GameBoy Tech Page . Linux users should definitely visit Connectix QuickCam and Linux mini_HOWTO. Another site that deserves recommendation is The Cookbook CCD Camera Home Page, established to help amateur astronomers who build their own CCD cameras.
As for the more advanced vision hardware, Spectronix and similar companies offer a wide range of small CMOS camera modules. These products are not as cheap as off- the-shelf Web cams, but the details of their operation are fully disclosed. These units is intended to provide full control over the CMOS imager for robotic and machine vision apps.
EyeBot is another interesting project for builders developing advanced robotic vision projects. It consists of a 32-bit microcontroller (MC68332) board with a graphics display and a digital grayscale or color camera. The camera is directly connected to the robot board - there's no need for additional frame grabber, which allows for writing powerful control algorithms without having to sacrifice vision - the most important sensor. The EyeCam itself is a full color (24 bit), low resolution (80 x 60 pixels) digital camera which can be used directly on an EyeBot controller or with an adapter cable on a PC, using the Improv software.
Transmitting video signal no longer requires large, complicated and expensive units. The Aegis VidLink 100 is so small that the transmitter, a video camera and battery will fit into a cigarette pack. Its full 100 mW RF power output gives you a realistic range of more than 500 feet and an optimum range of over 2,500 feet with gain antenna.
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Utilizing the VISION VV5300 "Camera on a chip" CMOS Image Sensor, the RoboCam camera board (99 USD) is a great choice for robot developers and experimenters interested in CMOS image sensor operation and applications. The sensor adjusts it's exposure and gain settings based on the scene, simplifying requirements of the host system. It supports B/W images up to 164x124 in size and frame rates up to 60 frames per second. The module supports 1, 4, and 8 bits/ pixel data formats as well as 4 or 8 bit conversion.
Other, more advanced units, like RAMCAM (209 USD) combine a high integration CMOS Image sensor with a high speed frame capture storage RAM. It provides a fully functional digital storage camera with 164 x 124 pixel resolution and automatic exposure control.