Interfacing of Vision Sensors
Interfacing of Vision Sensors
Vision sensors are a relatively new technology with few common features. Interfacing these sensors therefore requires an in depth knowledge of the individual sensor being used and commands strict adherence to the manufacturer or, more generally the research establishment, data sheets.
Figure 1. Interfacing the I-SCAN vision sensor (based on the CCDlll linescan camera; courtesy of Fairchild, 1984)
Although internally very complex these sensors, however, usually require few external control signals and, as a general guideline, need the less handshaking the more local intelligence they have. An example of basic interfacing is shown in Figure 1 for the Fairchild ISCAN 1-D vision sensor as extracted from the manufacturer CCD catalog (Fairchild, 1984).
This sensor is based on the 1-D optical array transducer CCDll1 (i.e. a linescan camera) and generates internally all the necessary waveforms shown in Figure 2, thus requiring only an external clock for synchronization purposes, an exposure signal (if the image exposure needs to be under software control) and the supply lines in order to provide the output image on a serial line.
Figure 2. I-SCAN vision sensor timing diagram (courtesy of Fairchild, 1984)
Another example of specific yet simple vision sensor interfacing is provided by the EV1 sensor manufactured by Micro Robotics. This device is based on the IS-32 DRAM chip and, once again, generates internally all the necessary waveforms thus requiring only 3 signals: a clock signal of between 1 and 10 f..l,S, a reset signal and a separate logic signal to determine which half of the DRAM is being used (this latter is only needed because of the particular optical arrangement of the IS-32 chip). Figure 3 shows the interfacing of the EV1 to the Applelle microcomputer as reported by Marr (1986).
Figure 3. Interfacing the EV1 vision sensor (based on the IS-32 DRAM camera) to the Apple lIe microcomputer (after Marr, 1986 and courtesy of Apple User)
