Tag Archives: DLP

SLI: Sensing Without Touching

MEMS is revolutionizing technology, causing microminiaturization and increasing the precision of conventional solutions. Ubiquitous MEMS applications are emerging as the next most promising frontier by removing the need for touch in structured light illumination or SLI.

DLPs or digital light processors from Texas Instruments contain millions of mirrors. TI is pioneering SLI that works by projecting moving stripes of light onto objects. It then measures the deformities in the reflected patterns by reconstructing their 3-D shapes using algorithms. The biggest customers so far are OEMs that manufacture touch-free fingerprint scanners.

These scanners are different from the traditional, as they do not require the traditional ink-blotter protocol. Therefore, SLI is revolutionizing biometric, facial, dental and medical scanning by opening up a whole new frontier in DLP applications. That includes the entire range from scientific instrumentation to industrial inspection systems.

So far, TI already has OEM development kits with DLPs and algorithm libraries. These can recognize 3D shapes, contours, surfaces, discontinuities and roughness. Operating on light sources ranging from near-infrared to ultra-violet, they enable accurate, fast and non-contact 3D scanning and recognition systems.

With its new DLP LightCarrier development platform, TI will be using nearly half a million micro-mirrors for illuminating simultaneously almost anything with structured light. That will allow almost instant recognition and characterization of 3D objects without touching them.

For example, TI uses FlashScan3D in DLP technology to capture far greater detail of fingerprints with higher accuracy than any other SLI solution can. That helps in cutting down on the possibilities of technician error and fraud. Moreover, the new DLP LightCrafter can scan faster and store data internally as against on a separate storage device such as a laptop. Therefore, it helps in building even smaller and more portable SLI applications.

YoungOptics Inc. of Taiwan origin manufactures the DLP LightCrafter as a plug-n-play module for TI. YoungOptics also manufactures TI’s DLP Optical Engine for OEMs that make projection televisions. LightCrafter, along with TI’s DLP 0.3 WVGA chipset, is ready to be used by OEMs for research and development. However, it can serve as the main subsystem in their finished end-user products as well.

Along with the DLP chip that contains exactly 415,872 micro-mirrors is an ASIC or Application-Specific Integrated Circuit acting as a second custom controller. There is also a DVP or a DaVinci digital video processor with its own 128MB NAND flash memory for storing patterns, a configurable IO trigger for integrating cameras, sensors and other peripherals needed for SLI.

Users can optionally add an FPGA, thereby speeding up the SLI patterns that LightCrafter displays, making them faster up to 4,000 per second. Finally, LightCrafter is capable of generating 20 lumens of light as it has an integrated light-emitting diode array for generating red, blue and green light.

OEMs can also use embedded Linux for developing their software to run the DaVinci DVP in the LightCrafter. That makes it an evaluation module compact enough for integrating projected light for scientific, medical and industrial applications, creating faster development cycles for end equipment needing high-speed pattern display with a small form factor, intelligent and lower cost.

How do battery powered pico-projectors work?

Once upon a time, very long ago, the projector world was ruled by the intense light of arcs. As they were rather unwieldy, xenon lamps took their place. With the unrelenting march of innovation, the era of OHPs or overhead projectors that could project images of transparencies, came into existence. These soon became obsolete as computers evolved and could be directly connected to projectors with LCD screens. The latest in line is the Pico-projector, which uses tiny batteries and the light from LEDs to project large displays.

Although Pico-projectors are small – as small as mobile phones, and sometimes even smaller – they can project large displays, sometimes up to 100 inches. Even though their brightness and resolution is not up to the mark of their bigger brethren, Pico-projectors are relatively new in the innovation chain, and as the market expands, they are expected to develop further.

Several companies have developed their own methods of producing battery-powered Pico-projectors. Of them, the three major technologies are DLP or Digital Light Processing, LCoS or Liquid Crystal on Silicon and LBS or Light Beam Steering. DLP and LCoS use a white light source and a system of filtering techniques to create different color and brightness of each pixel. On the other hand, LBS uses a small liquid crystal display to control the amount of light going to each pixel.

Digital Light Processing or DLP is pioneered by Texas Instruments (TI). Their idea is to use tiny mirrors on a chip to direct the light. Each mirror controls how much light goes onto each pixel of the display. The mirror can be turned on or turned off on command many times a second, and the on to off time ratio defines the brightness of the pixel. For color, there is a color wheel in front of the light source, splitting the beam into red, green and blue. Each mirror controls all the three light beams.

Liquid Crystal on Silicon or LCoS, as the name suggests, uses an LCD to control the amount of light reaching the pixel of the display. For color, two techniques are used. One is the Color Filter where three sub pixels are used, and they each have their own color, Red, Green and Blue. The other is the FSC or Field Sequential Color that requires a fast LCD and a color filter to split the image into RGB, the three main colors sequentially. The LCD is refreshed three times, once for each color. For LCoS, the light source could be an LED or a diffused Laser.

Laser Beam Steering or LBS creates the image one pixel at a time. The technique uses three directed laser beams, red, green and blue. The three beams are combined using optics and are guided using mirrors. So that the eye does not notice the pixel-by-pixel design, the image is scanned at over 60Hz.

LBS has some advantages over the other two techniques. The size is small and power consumption lowest, as the darker pixels require less energy, while the black pixel does not require any energy at all. The image from an LBS system is always focused, even on curved surfaces. On the other hand, lasers are expensive, cause random intensity patterns and are a concern for eye safety.