Copyright Goodheart-Willcox Co., Inc. 508 Section 5 Electrical and Electronic Systems Technology autonomous parking. These sensors may also be called sonar sensors. Infrared Sensors An infrared sensor sends an infrared light beam that bounces off objects in front of the vehicle and returns to the sensor. (The light beam is not visible to the human eye.) The amount of time it takes for the light beam to return to the sensor is used by the computer system to determine a safe driving distance for the current road speed of the vehicle. Camera Sensors Various types of camera sensors are used with safety, navigation, and advanced driver assistance systems. The types of cameras used include video, 2D and 3D, infra- red, and 360° cameras. Depending on their sophistica- tion, camera sensors detect objects, classify objects, and determine the distance from them. In general, medium-range cameras (between 100 and 275 yards) can identify pedestrians, cyclists, motor vehicles, side strips, bridge abutments, and road margins. Medium-range cameras warn the driver about cross-traffic (rear and front), pedestrians, and emer- gency braking in the car ahead. High-range cameras typically recognize traffic signs and signals, use video- based distance control, and provide road guidance. The number of camera sensors on a vehicle vary by manufacturer and the vehicle’s range of systems. For example, 3D cameras require four to six cameras to pro- vide a realistic image. Camera-based sensors do have limitations, including the following: • Difficulty detecting objects in low-visibility conditions, such as fog, rain, snow, and darkness. • Difficulty distinguishing objects with colors similar to the background or with low contrast between the objects and the background. • Require a clear lens to see properly, which limits where they are placed. Backup Camera A backup camera shows the view from the rear of the vehicle when the vehicle is in reverse. A small camera is mounted inside the rear body or bumper, Figure 38‑7. The camera aims straight behind the rear center to show the area directly behind the vehicle. The display screen gives the driver a better view of what is behind the car than the side-view or rear-view mirrors, whose views are blocked by the rear body structure. Surround-View Camera A surround-view camera (SVC) system uses four wide-angle cameras to provide the driver a 360° view of his or her vehicle. The front camera is in the center of the grille, the side cameras are typically under the left and right mirrors, and the fourth is at the rear of the vehicle, above the license plate or in the handle of the tailgate. The ECM stitches the overhead view with images from each camera. The computer inserts a proportional graphic of the vehicle in the center of the image on the screen. See Figure 38‑8. The camera is useful for viewing parking lot lines, curbs, adjacent vehicles, and moving objects, such as children and pets. The system activates when the vehicle is turned on and when it is put in reverse. It typically only works below 10 mph (16 kph). An SVC system is also called a surround-view monitor system. Adaptive Cruise Control An adaptive cruise control (ACC) system alters vehicle speed automatically when approaching another vehicle too quickly. These systems use a front-mounted radar and/or cameras that work with the vehicle’s on-board computer to maintain a safe distance between a vehicle and the vehicle in front of it. It can increase, decrease, or maintain vehicle speed and, if needed, apply the brakes, Figure 38‑9. This type of system may also be called intelligent speed adaptation (ISA). AVN Photo Lab/Shutterstock.com Figure 38-6. Proximity sensors are placed around the perimeter of the vehicle. The appearance and location vary by vehicle make and model. KUDZELKA YURY/Shutterstock.com