OSRAM Opto Semiconductors' two new SMT proximity sensors (SFH7740 and SFH7741) use distance measurements to detect a mobile device's operating status without physical contact to the sensor itself. This technology allows for the automatic shut-off of displays and keypads when no longer needed, improving performance and efficiency of products such as cell phones and digital cameras. The proximity sensors can also be used to adjust the volume of the device's speakers.
The SFH7740 proximity sensor with optical touch switch measures just 3.7 x 3.7 x 1.0 mm and reacts to distances between 0.5 and 4.0 mm. These compact dimensions allow it to be unobtrusively integrated into unusual designs, such as extremely low-profile devices. The SFH7741 proximity sensor reacts at a typical working distance of 20mm and is suitable for a wide range of applications. For example it can detect when the phone is moved close to the ear, taking the display and the keypad out of sight of the user. The backlighting is then switched off and the volume adjusted. The sensor can also help save energy in digital cameras, switching off the display lighting whenever users holds the camera up to their eyes and use the viewfinder instead of the screen.
The two SMT sensors draw a current of only 50 µA (approx.). They make use of integrated ambient light suppression and therefore operate reliably in all lighting conditions.