LED Flash for Smart Phones
Nov 2010OSRAM Opto Semiconductors Inc.Request Info
NORTHVILLE, Mich., Nov. 30, 2010 — Researchers from Osram Opto Semiconductors Inc. have developed an LED chip that makes it possible to offer smaller pocket projectors, vehicle headlights and cell phone camera flashes.
The new UX:3 chip is 50% brighter than the previous package. With an optimized lens, the light is much better distributed. The chip is used in the Oslux LED, which is therefore more efficient at high currents than previous LEDs and delivers high luminous efficiency over a small area.
At a distance of 1 m, such an LED flash evenly illuminates a diagonal of 90 cm, sufficient for capturing sharp images even under unfavorable light conditions. At 150 lx, the LED with the UX:3 chip is 50 lx brighter than its predecessor. As a result, high-quality images can be taken even with very flat cell phones or smart phones.
Normally, when taking photos at night with a camera phone, the flash can provide relatively bright illumination of the middle of the image area, but the corners appear somewhat dark because the luminosity of the LED is too low and the lens doesn’t distribute the light evenly enough. This creates a bright circle with dark edges, an effect that occurs especially under unfavorable light conditions. To correct this, the researchers rearranged the internal layout of the LED chip.
The chip consists of a metallic lattice and two semiconductor layers. The lattice conducts the current to the upper layer, from where the electrons move to the lower layer and release energy in the form of light. With conventional LEDs, however, the metallic lattice is positioned above both layers and thus diminishes the light. The effect is similar to what would happen when a dark cloth is placed over a lightbulb. The researchers moved the lattice all the way to the bottom, enabling them to increase the wall plug efficiency, which describes the relationship between the radiant flux of the chip and the electrical power that flows through it.