Photonics as a domestic aid

The new textile scanner from BSH Hausgeräte GmbH needs just one second to determine the type of textile and also the composition of stains using near infrared (NIR) spectroscopy. The handy high-tech device then uses the measurement results to derive the optimum pretreatment and program settings, which, if requested, it sends fully automatically to the networked washing machine. Shrunken and faded laundry items could be a thing of the past, along with stains that are not completely removed.

BSH uses NIR-Sensorik from the Finnish material sensing expert Spectral Engines. The NIRONE Sensor X analyzes the spectrum in the wavelength range from 1550 to 1950 nanometers (nm) and also has an RGB color sensor. According to the Finnish company, the construction volume is 16x32x35 mm. Within this are a light source made from tungsten wire and what the company claims is the smallest NIR spectral sensor on the market. This is based on a microelectromechanical (MEMS) Fabry-Perot Interferometer that can be adjusted within the specified NIR range—and can be programmed. Among other things, the user can define whether it scans the entire wavelength range or just selected wavelengths.

Saving water with optical sensors

While the textile scanner from BSH and Spectral Engines is designed as a standalone device, optical sensors are also installed inside modern washing machines and dishwashers. These turbidity sensors analyze the rinsing water and, based on the turbidity, decide whether to add more fresh water or even if an additional rinsing cycle is required. The sensors consist of an LED, which emits light in the NIR range, and a photodiode as a receiver, which converts the incoming light into electrical signals. The transmitter and receiver are integrated into two probes that are immersed in the rinsing water. The more turbid the water is, the more light it absorbs, which results in weaker electrical signals. When sufficient light reaches the receiver, the stronger signal switches the next program level: pumping and spinning with washing machines or pumping and drying with dishwashers. In other words, optical sensors ensure effective cleaning with minimized water and energy consumption.

Smart baking?—Not without photonics

In smart homes, optical sensors are also able to take over more control in food preparation. For example, in its latest generation of ovens, Miele has integrated a camera system that sends cooks true-color pictures in HD quality to their smartphone or tablet. With the FoodView function, they can not only observe the cooking progress remotely, but also adjust the temperature or change the programmed cooking time if necessary. The camera takes one photo per minute, which replaces the previous photo in the memory. In other words, users receive only the latest picture. According to Miele, the camera optical system is so sturdy that it can even withstand the 440 degree Celsius self-cleaning program.

In addition to the cameras, infrared sensors are integrated in the oven’s control panel. On the one hand, they ensure safety in the operation of appliances that are installed behind furniture fronts. When the front is closed while the oven is operating, the sensor system warns the user with a loud audible signal. If no action is taken, the oven switches off automatically. On the other hand, Miele enables more convenience with its sensor system. When users are within 40 centimeters of the oven, the lighting switches on automatically. Photonics also plays a role here: For efficiency reasons Miele uses LED technology for its oven lighting.

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