Traditional projection systems were meant to be used in classrooms, boardrooms, and other stationary locations. They typically were perched atop a desk or table and were used to project pictures, presentations, and other forms of information. They were often heavy and hard to move; they needed a specific type of surface to project off of; and images were often blurry or skewed depending on the light source.
In today’s fast paced knowledge distribution world, the need to provide data and the means of dissemination have changed. For example, mobile (or pico or pocket) projectors can instantly project photos, videos, and presentations on any light-colored surface, at a small-screen size, with excellent image quality and a range of colors. These new projectors are small (0.9-in. x 2.4 x 4.7-in.) and extremely lightweight (6 oz or less).
A mobile projector consists of a light source, optics to collect the light, an imager device, and the associated electronics to drive the light source and the imager. The optics in the system collect the light and deliver it to the imager device, which modulates it to create the display image on the projection screen.
Projection systems require a light source that delivers high luminance from a small emission area because the imager, whether micro-electro-mechanical (MEMS) or liquid crystal on silicone (LCoS), cannot collect more light than emitted from the equivalent of the area “X” in the solid angle of the imager. Therefore, there is a need for high emission from a small area.
The light source best suited for this application are light emitting diodes (LEDs), which are very efficient surface emitters and are well suited for projection applications. These small, bright, energy-saving LEDs are the key to developing micro projectors. Besides the requirements for high luminance and a small emission area, the LED needs to be small in size to fit into the projector housing, whether it is used in an embedded cell phone system or in a standalone companion projector. The LED must also deliver high efficiency for optimal battery operation.
The OSRAM OSTAR SMT family of LED products are small, efficient, and designed to meet the requirements for pico-projectors. OSTAR LEDs are available in RGB version with one red chip, two green chips and one blue chip for single optical channel systems. For systems requiring higher output, the OSTAR SMT LED is available for use in a two-channel system by combining a bicolor red-blue module with a monochrome green module. For higher output using a three-channel system, three LED modules can be used with each module supplying a single color.
All OSTAR SMT LEDs use OSRAM Opto Semiconductors’ proprietary Thinfilm chip technology and a specially developed LED enclosure that delivers light in small spaces. The LEDs’ low energy consumption also conserves the projector’s battery and ensures longer operating times. This feature will benefit mobile applications. The LED lifetime of more than 20,000 hours is said to be more than adequate for this type of equipment. The use of a lithium-ion battery can provide up to four hours or more between charges. Thinfilm LEDs are reflow-solderable – they can be used with standard soldering processes with a minimal footprint and low profile for easy integration into the manufacturing process.
OSRAM Opto Semiconductors
Filed Under: Electronics • electrical, Lights • signal lamps • indicators