20 July 2011

Osram launches IR LED for low-profile small- and medium-size touch-screen displays

Osram Opto Semiconductors GmbH of Regensburg, Germany says that its new ChipLED SFH 4053 infrared emitter (IRED) combines tiny dimensions with high efficiency, suiting the demands for low-profile and powerful infrared components in all-in-one computer, tablet PC and laptop displays. The new IRED is so small that it can also be easily integrated into smart-phones.

Optical touch screens are available in a wide variety of designs, but they share a common principle in that the touch of a finger will either cast a shadow or reflect light. In basic versions, an array of infrared emitters (IREDs) and detectors create a grid of vertical and horizontal beams. The components are housed in a low-profile frame, known as the bezel, measuring a 0.5–1mm in depth around the screen. “To make this frame even shallower requires particularly small IREDs and detectors,” says product marketing manager Bianka Schnabel. “This is especially important for mobile devices such as tablet PCs and laptops because of the positive effect on the design aspect.” The ChipLED SFH 4053 measures just 0.5mm x 1mm, so it takes up very little space. Combined with a height of 0.45mm in industry standard 0402 (length/width), it is one of the smallest IREDs on the market, the firm claims.

In addition to their small size, the high light output of the components plays a key role, particularly for camera-based touch screens, Osram Opto adds. Such a display setup requires considerably fewer IR emitters than the traditional version, but the emitters must have a very high output because they flood the display with infrared light from two corners. Next to the IR emitters are camera chips that detect a change in the signal when a pen or finger touches the display.

Due to Osram’s thin-film chip technology, the SFH 4053 provides high output from a very small package for this application, rated at 35mW from an operating current of 70mA. In pulse mode, it can achieve as much as 260mW from 700mA. “This ChipLED provides enough light to make it easy and cost effective to expand camera-based touch-screen systems to larger diagonal sizes,” Schnabel notes. 

The ChipLED SFH 4053 is part of a broad range of components being used in an increasing number of touch-screen applications – from narrow-angle emitters for light grids to low-profile components for optimum coupling into light guides. Osram Opto’s ChipLEDs are available in 0603 sizes with lens types from ±40° to ±10° and with different chip technologies, including thin film and nanostack.

The firm adds that the wavelength of the ChipLED suits the requirements of these applications. At 850nm, light from the IRED is barely discernible to the human eye, but receiver components are highly sensitive to this wavelength.

Tags: Osram IR LEDs

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