Bench Talk

Video cameras dropped in price by three orders of magnitude in the last couple of decades. A reasonably sensitive full HD video camera cost thousands of dollars in the 1990s, but now you can purchase these HD video cameras—which come in a module smaller than a sugar cube—in high volume for around five dollars. What if reasonably bright HD video projectors currently priced around five hundred dollars followed a similar path? Where would we put those little, cheap projectors? How could you use massively parallel arrays of projectors? What sorts of new services could result? Let us have a look at some possibilities.

There are several possible ways to implement inexpensive, compact, power-efficient video projectors. The first thing that comes to mind is not really a video projector, but more of a structured light engine. If you ever looked closely at a modern Light-Emitting Diode (LED) lightbulb, there are often a dozen or so individual LEDs. What if we control them individually, and therefore are able to adjust the brightness of light that exits the device from various angles? You could do this by placing a 2D array of small LED chips—either white or RGB—on a substrate that can remove their heat and individually control their brightness. You would place that substrate into an optical system that projects an image of the array into the far field as large numbers of partially overlapping beams. The optical system could be in the form of:

• A micro-lens array
• A fish-eye lens
• A holograph

If you mounted such a device in a ceiling light fixture and used a local processor to accept commands via Wi-Fi and individually control the brightness of each of the LEDs, occupants of the room could choose the brightness emitted from each angle of the source, thereby controlling illumination of every corner of a room. So, for example in a retail or entertainment setting, the LED beams directed at work areas or merchandise display cases could be bright; and adjacent LEDs directed at walkways or dining tables could be dimmer. As people move about or activities change, the processor adjusts the structured light patterns accordingly.

Using some of today’s smallest Red, Green, Blue (RGB) surface-mount LEDs, which are 0.65mm², a 50 x 50 pixel structured light array could fit in the 35mm focal plane of a standard 180° fish-eye lens. This would draw about 100W at full brightness. For example, if you installed the pixel structured light array in the center of a 5m² room with a 3m ceiling height, it would make 2500 individually controllable light pools on the walls and floor, each about 25cm².

However, 2500 pixels from the example above is a far cry from the two million pixels of an HD image or the eight million pixels of a 4K image. Fortunately, there are video projection engines that produce multi-megapixel images in very compact and energy-efficient packages. These video projection engines are sometimes called “pico projectors.” Several technologies, products, and techniques are available to support these video projection engines. One technology for their implementation includes the Digital Micromirror Devices perfected by Texas Instruments. Another is Liquid Crystal on Silicon, which you can use as a light modulator for bright LED sources. A third technology involves using deflected laser sources. No matter which technique is chosen, you can use these video projection engines to project high-resolution images on walls, floors, and objects in a room.

Implementing a Five-Direction Projector

Now, let’s consider a device about the size of a standard lightbulb. But, instead of LED emitters, it has five pico video projection modules—one facing down, and one each facing north, south, east and west. A processor in the device receives five High-Definition (HD) or Ultra-High Definition (UHD) video streams from an external control computer via Wi-Fi, and blasts the light out of its five pico projectors. If developers design the optics correctly, the five beams slightly overlap, blanketing the room and all objects within it with controlled, high-resolution light and imagery. Besides controlling the brightness of regions as a sort of dynamic task light as in the above example, this device—if implemented with 4K projectors—could provide ~1.3mm pixel size on all four walls and floor of a 5m x 5m room, and any object surfaces that the device can “see.” This permits virtualization of environments—think holodeck—artwork, or redecorating on-demand, full surround video programs, and fully immersive video conference environments.

Troubleshooting with a Five-Direction Projector

Let’s go one step further to try to address some possible shortcomings of the five-direction projector described above. What if we use a coordinated array of several of those five-direction projectors? We could mount about four of them spaced out on the ceiling of our 5m x 5m room, and perhaps a fifth one in a small transparent “bump” in the center of the floor—to cover the ceiling and the walls from a lower perspective. In this scenario, the multiple projectors can “see” almost every square centimeter of the room’s walls, floor, and ceiling. If they are coordinated carefully via the external control computer with geometric transforms and calibration, the same images arrive from different angles to each point on the wall. So, if a person or piece of furniture happens to block the viewpoint of one of the projectors, there are up to four other projectors that can still illuminate that surface. Cameras in the room—perhaps also mounted on the five sides of the same devices that houses the pico projectors—can monitor the displays to calibrate and compensate for obstructions of the projected beams. If the cameras can detect the eye position and faces in the room, you could instruct the projectors to ‘mute” the few pixels that would intercept the eyes, eliminating the glare from the projectors.

Designing Large Installations

What if we went really big—say with 1000 of these projectors across a stadium, campus, or retail store? The projectors could be controlled as a large, contiguous video array, permitting very versatile services and advertising. There could be a navigation mode, where the projectors render a path marker in front of moving occupants, guiding them to the shelves where their desired merchandise is located or their seats in a concert or sports venue. Cameras detect the movement of all patrons, the central control processor recalculates the video on-the-fly, and multiple projectors paint the graphics from multiple angles, performing seamless handoffs as people move around. In the event of an emergency, the system can render very easy-to-follow evacuation instructions. If you want to learn more, my US Patent 9,508,137 describes the details of a system that can do this.

Conclusion

As the cost, size, and power consumption of pico video projectors and other structured lighting sources comes down, many interesting products and innovative services become possible. Eventually, these structured lighting and video projection engines could cost on the same order of magnitude as a smart lightbulb. At that point, why not have the ultimate control over the direction, brightness, and color of light, and enable it to respond to the needs of the occupants of a space?

Key Points:

• Structured light engines like LED arrays and pico video projectors are on a steep cost decline.
• You can equip multiple projectors to blanket all the walls, floors, and objects in a room with dynamically controlled lighting and imagery.
• New services are enabled by ubiquitous video projection—including convenience, comfort, entertainment, and emergency services.
• By coordinating multiple projection heads, a unified system can provide “wall-to-wall” imagery.