The Spectrum of the Smart City

­Light is a form of electromagnetic radiation that has a constant influence on people, flora, fauna, and on technologies. The different wavelengths of this radiation are used in a variety of established, as well as cutting-edge, applications. Since the end of the 20th century, it was impossible to imagine medical diagnostics without short-wave X-rays. The particularly long-wavelength radio ensures the wireless transmission of data. With advancing technologies, UV, infrared (IR) and artificially generated laser radiation are also gaining new fields of application. The latter - especially as LiDAR (light detection and ranging) - and IR are gaining additional importance in the realization of smart living concepts.

Light Creates the Perfect Atmosphere

The knowledge of how humans, animals, and nature are influenced by different lighting scenarios is already being used in shopping centers, production facilities, and agriculture:

Lighting similar to daylight, for example, ensures greater concentration and safety in the workplace and is also established in retail, as colors and color differences are easy to recognize with a color temperature of 6,000 Kelvin, a bright, clear, and radiant white. A "warmer" lighting concept with 2,700 Kelvin, on the other hand, is more conducive to relaxation and calm.

Light as an Artificial Sun for Smart City & Urban Farming

The combination of sensor technology and lighting enables comprehensive lighting concepts that combine various tasks. Here, energy-efficient and long-lasting LEDs take over the illumination of indoor and outdoor areas. The light sources can be controlled almost in real-time to adapt intensity and color to the respective situation. This significantly increases safety in both private and public spaces, while being much more energy-efficient than permanent lighting. In addition, special emitting UV LEDs make the urban farming concept a reality for almost any city.

Especially in outdoor areas, this could be supplemented by energy harvesting technologies: Here, floor plates convert friction caused by footsteps or movement into energy that can be used to power integrated sensor systems.

Light Opens Doors

The integration of high-power infrared LEDs, such as those from ams OSRAM's OSLON® P1616 product range, extends the smart city security concept, for example as night vision cameras, 2D face recognition for user authentication, and intelligent doorbells. Due to their small size of 1.6 mm x 1.6 mm, the products are perfect for all space-critical applications while maintaining high optical performance, efficiency, and reliability. Due to the wide temperature range from -40 to +105 °C, they are suitable for a wide range of applications.

This product range is also suitable for the realization of eye-tracking applications, which, for example, enable people with a physical impairment to participate more actively and independently in social life again. The IR technology is used primarily to detect fixations (eyes remain fixed on a point for a long time) and saccades (eyes move quickly) and to execute commands based on these. One application scenario, for example, would be menu navigation on smartphones, computers, and vending machines, but also the opening of doors and the use of checkout systems.

Using Light to Prevent Food Waste

This does not just mean the production of vitamin D, which is important for the human body. With infrared (IR) sensors integrated into mobile devices, such as the ams OSRAM BIOFY series, it is possible to check the freshness of food at any time - using IR spectroscopy. Spoiled stomachs can thus be easily avoided in the future. This technology is already being used successfully in the food industry and thus also offers a reliable solution for counteracting food waste. ams OSRAM offers the P1616 SFH4737 broadband emitter for this purpose with a spectral emission range of 650 nm to 1050 nm, a particularly small design (1.6 mm x 1.6 mm x 0.9 mm) and an emission angle of 130°, which means that light can be absorbed within a larger area. The broad homogeneous spectrum of the wavelength range enables a wide coverage of infrared light sources.

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Figure 1: LIDAR detecting various items including humans

Light Saves Lives

Biomonitoring sensors also make it possible to monitor blood oxygen levels and heart rate without interruption. Especially in the care of people in need of care, this means a bit more freedom for those affected, because handy and, above all, significantly smaller devices replace bulky, medical monitoring devices. A discreet smartwatch does not disturb the wearer in everyday life, but provides the necessary security: If the sensor registers irregularities, an emergency call can be made immediately. It is also possible to detect medication using IR spectroscopy, an advantage for caregivers. This is an advantage for caregivers because senior citizens living alone are often confused when taking medication, which can lead to dangerous interactions. If the watch also has an acceleration sensor that can detect a fall and a GNSS positioning function, the nearest emergency services are alerted and receive a very accurate emergency scenario, which saves a considerable amount of time.

Light Regulates Traffic

Mobility concepts for a smart city require reliable and precise technologies to prevent accidents, ensure the safety of people and animals, and create optimum efficiency. LiDAR, for example, is used to measure distances around vehicles and thus the distance to potential obstacles. In LiDAR sensors, a pulsed IR laser diode emits a light pulse. If this is reflected by an obstacle, the sensor detects it. The distance between the sensor and the obstacle can be determined from the time between the emission and arrival of the light waves, the time of flight (ToF).

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Figure 2: LIDAR detecting various items including humans

A ToF camera can help increase driving safety in the interior of a vehicle, for example by monitoring the driver, passengers, and objects in the passenger compartment. Then the system can detect when the driver is distracted or tired before an accident occurs. Interior monitoring also makes it possible to detect head and body positions, for example for optimal airbag alignment; it can also be used to control controls by gesture. Outside the vehicle, a ToF solution can support assisted and autonomous driving.

The demo board is equipped with a VCSEL (Verical Cavity Surface Emitting Laser) from Lextar's PV85Q series. It features high efficiency and narrow spectral bandwidth (1.8 nm). Its various optical power options enable multiple object detection, 3D depth assistance, and presence detection. For eye safety, the VCSEL includes a photodiode. The fully integrated MLX75027 VGA (640 x 480) optical ToF image sensor comes with 10 x 10 µm DepthSense® pixels.

Not All Light is the Same

Thanks to an extensive LED manufacturer portfolio, Rutronik offers the optimum solution for a wide range of requirements. The associated technologies for thermal management, for example, and of course sensor technology can also be provided from a single source. This provides Rutronik's interdisciplinary experts with a deeper understanding of a complex overall system. That allows them to advise and oversee the implementation of an individually suitable solution for the realization of smart city, smart, and urban farming concepts.

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