Sharp's Infrared Laser Diode Safe for Eyes

Mar 18, 2014
Tsunoru Nakashima, Nikkei Electronics
The newly-developed infrared laser diode (right)
The newly-developed infrared laser diode (right)
[Click to enlarge image]

Sharp Corp announced an infrared laser diode integrated with a component that reduces damage to eyes March 12, 2014.

Sharp expects that the laser diode will be used as light sources of 3D sensors that realize (1) gesture-based inputs to game consoles and (2) object detection capability of security devices. The company will start to ship samples April 18, 2014, and begin volume production in July. The price of the sample is ¥5,000 (approx US$49.14) per unit, excluding tax.

3D sensors using infrared light measure the location of or distance to an object by emitting infrared light from a light source and detecting the reflected light. As a source of infrared light, an LED or laser diode is mainly used.

While laser diodes consume less energy and respond more quickly than LEDs, their energy densities are high because the sizes of their light sources are small and they have high directivities. If light from a laser diode is seen with the naked eye as it is, there is a risk of damaging retinae. To ensure safety and a strong light at the same time, some measures have to be taken such as using a diffuser to increase the size of a light source.

With conventional laser diodes, it is necessary to adopt such safety measures, making device designs complicated and increasing the size and cost of a light source. As a result, LEDs are currently preferred to laser diodes.

In light of that, Sharp added a cap-like device made of plastic to the tip of the light source unit as a safety measure. The device contains minute substances called "filler," and they scatter light. The fillers scatter incoming laser light and increase the size of a light source to a diameter of about 2mm, which is large enough not to damage retinae.

The new product is the industry's first infrared laser diode integrated with a safety device, Sharp said. The upper part of the diode has a lenticular shape and radiates infrared light with a radiation angle of 30°.

The maximum output and power conversion efficiency of the laser diode are 700mW and 36%, respectively. Its has an operating voltage of 1.8V, threshold current of 270mA and peak oscillation wavelength of 830nm. Sharp aims to replace existing laser diodes and LEDs with the new product by leveraging the fact that it does not require any additional safety measure and can be used as easily as LEDs.