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Tham khảo tài liệu 'mcgraw-hill - the robot builder's bonanza episode 2 part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 616 ROBOTIC EYES FIGURE 37.13 A penlight laser diffraction grating filter and video camera can be used to create a lowcost machine vision system. FIGURE 37.14 When projected onto a flat surface the beams from the diffracted laser light form a regular grid. sound to quickly and efficiently navigate through dark caves. So accurate is their sonar that bats can sense tiny insects flying a dozen or more feet away. Similarly robots don t always need light-sensitive vision systems. You may want to consider using an alternative system either instead of or in addition to light-sensitive vision. The following sections outline some affordable technologies you can easily use. ULTRASONICS Like a cave bat your robot can use high-frequency sounds to navigate its surroundings. Ultrasonic transducers are common in Polaroid instant cameras electronic tape-measuring devices automotive backup alarms and security systems. All work by sending out a high-frequency burst of sound then measuring the amount of time it takes to receive the reflected sound. GOING BEYOND LIGHT-SENSITIVE VISION 617 Ultrasonic systems are designed to determine distance between the transducer and an object in front of it. More accurate versions can map an area to create a type of topographical image showing the relative distances of several nearby objects along a kind of 3-D plane. Such ultrasonic systems are regularly used in the medical field. Some transducers are designed to be used in pairs one transducer to emit a series of short ultrasonic bursts another transducer to receive the sound. Other transducers such as the kind used on Polaroid cameras and electronic tape-measuring devices combine the transmitter and receiver into one unit. An important aspect of ultrasonic imagery is that high sound frequencies disperse less readily than do low-frequency ones. That is the sound wave produced by a high-frequency source spreads out much less broadly than the sound wave from a low-frequency source. This phenomenon .
