New developments in German research - miniature LED projectors on smartphones

Smartphones have replaced some of the desktop and notebook functions to some extent, and others have begun using smart phones to display data. However, due to screen size limitations, it is difficult for smartphones to clearly display image details. Now, with an LED-based projector, you can project a clear, bright A4 image on your desktop by placing your smartphone on the coffee table and standing it up. If the user wants to zoom in on one part of the image, just touch the screen to zoom in, and the projected image will respond the same way.

The special feature of the LED projector is that it can display very clear images even in the case of reflective angles and unsmooth desktops. In general, this can cause distortion and blurring of the picture. The technicians of the Fraunhofer Institute for Applied Optics and Precision Engineering IOF in Germany, which is responsible for the development of such projectors, have solved these problems. "Our projectors are made up of hundreds of tiny micro projectors in an array. In the middle, each micro-projector can produce a complete image," said IOF scientist Marcel Sieler. "This technology is known as array projection technology. It mainly mimics natural mechanisms, such as the compound eyes of some insects. This is the first time we have developed an ultra-thin, ultra-bright, powerful imaging projection system."

In the simplest application scenario—where the projector is placed vertically and projected onto a horizontal plane, these tiny projections project the same image onto a user-visible surface. Hundreds of independent images will overlap and present a sharp and bright overall image. However, if the angle of the device is facing a screen, the image projected by each small projector will be slightly different. In order to project a sharp overall image, these individual images must also seek the most suitable projection angle and the geometry of the screen. This is due to the fact that the overall scene perspective of each projector in the array is slightly different. The larger microlens depth of field means that there is almost no screen size limit, and even a curved screen can be used. Experts say this can be seen as a focus function tailored to the projector. Each individual image is computed using software. Researchers have developed positioning sensors and smart phone-specific cameras that provide the necessary geometric information to allow the software to calculate each individual image and the focus settings of those images. .

Its optical equipment is fabricated on wafers and contains approximately 300 chips, each of which contains 200 lenses for microprojectors. “This process is very suitable for mass production, which makes new equipment more economical,” says Sieler. It is a very advanced technology to communicate whether the user uses the information such as these projectors or the like to the smartphone. “These images overlap with infrared rays that are invisible to the human eye,” Sieler explains. “If the user’s finger breaks one of these infrared rays, the sensor temporarily stores the image and immediately moves to the next image. However, it may take three to four years for such a projector to actually come out, because the new projection technology requires a very high pixel density on the components of the digital imaging system. The researchers plan to showcase the new LED projector prototype at the Optatec trade fair in Frankfurt this May, which was initially suitable for playing still images. The device is said to be only 2 cm x 2 cm in size.