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By David Lashmet
Market Analyst, Microvision

At this year’s Consumer Electronics Show, Microvision unveiled our latest projector prototype, code-named “SHOW” TM. With SHOW, we can project a Wide VGA image (854 x 480) at video rates in full color, from a pico projector engine that’s only 5 cc’s – about the size of an Andes thin mint.

If you missed it, the new projector looks like this:



To understand how SHOW works, you can start with a television set. A TV works by scanning a beam of electrons across some phosphors painted on the inside of a glass tube. If you want a color TV – which since 1954 everyone does – then you use three lines of phosphors, one for each color.

Microvision’s SHOW projector prototype is like a TV set in its scanning pattern. But instead of a stream of electrons, we start with a beam of photons – and these already are colored. So we don’t need phosphors, or glass, or high voltage. It doesn’t even need a plug, because it’s battery powered.

In other words, it’s a mobile device, offering portable projections against any surface, in almost any lighting. So, instead of bringing color images to the home, our new projector brings color video anywhere. Even video that you capture yourself, or that is sent to you by your family and friends.



How this SHOW projector works is the real breakthrough. And for this Microvision Blog entry, I’d like to take you inside the box -- from the laser lights, to the scanning mirror.

Here’s the big idea: not all tiny projectors are created equal. In fact, we’re the smallest, the brightest and we offer the highest resolution. Our projectors are always in focus, without a projection lens. We’re also the most efficient with heat and power.

Fair to say, these advantages get our rivals pretty distressed. That’s because from the outset, we planned this device to work inside cellular phones, within automobile dashboards, and on consumer eyewear. It never started out as a desktop projector that we’re trying to shrink down.

The real difference is, we use one small mirror. Not hundreds of thousands of mirrors, nor hundreds of thousands of cells full of liquid crystals. This leads to a massive improvement in reliability: instead of millions of moving parts, there are four flexures: two so the mirror can pivot up and down, and two more so it pivots right and left.



You should know, these single X-Y mirrors are cheap, and reliable. We use them in our bar code scanner, called ROV. And the core technology is silicon on chip. So it’s an industrial grade product proven in the field.

Electromagnets drive the mirror through its paces, and in turn there are drive chips for the electromagnets. That’s why we call this device a micro-electric mechanical system, or MEMS for short.

This MEMS mirror is the heart of our projector solution. But without lasers, we’d be in the dark. In our decade of experience building MEMS mirrors, we’ve tried many different sorts of light sources. What draws us to small lasers is their optical efficiency. Let me explain…

WHY LASERS ARE THE BEST LIGHT SOURCES FOR PROJECTORS

What makes a laser different from a light-emitting diode (LED) is its ability to lase. Both pump electricity through a luminescent material – often the SAME material. But lasing means a quantum leap in the ability to produce photons – pretty much like Einstein predicted in his 1917 paper on electricity and quantum theory.

If you’re building a projector, lasers have a second advantage, too. Lasers make rays of light. And if you want all your light energy to go in one direction, it makes sense to do this from the start. The alternative is any sort of light source that throws light in all directions: LED, small halogen bulb, you name it. In these other cases, you need to redirect this light into a column using a concave mirror, like a flashlight does.

Unfortunately, no mirror is 100% reflective. So you’re burning watts and generating heat at the very start of your optical train. Which doesn’t bode well for system-wide optical efficiency. That’s why lasers are vastly better light sources for small projectors.

The small lasers we’re using are special in three other ways, too:

First, these are spectrally pure solid state laser diodes, in each of the primary colors. Like Isaac Newton proved with prisms, with red, green and blue you can blend light into any color of the rainbow, including white. We can also shut the lasers off, to create black. So, lasers produce the richest color palette – along with the broadest grey scale – that people can see.

Second, these solid state laser diodes make columns of coherent light. This appears brighter to most people, an effect first discovered by the physics gurus Helmholz and Kohlrausch. Depending on the person and the projection surface, the “H-K effect” gives up to a 50% boost to apparent brightness. So, just comparing lumens of output does not tell the full story. For human observers, laser projectors make brighter images than other projectors.

Third, the lasers we use are modulated very quickly. In fact, we turn them on and off 50 million times per second! That’s because we make each picture element (or ‘pixel’) individually, and that’s true for every pixel of every frame in a video display. In practice, this approach saves power and reduces heat inside a small device, because there’s no wasted light energy. This makes us “greener,” roughly by a factor of two.

For an example, think of a checker board pattern. To make alternating white and black sections within a single video frame, our lasers are off half the time. But everyone else has to pump out enough light over a whole array of pixels to illuminate the brightest pixels, then divert the extra light. In a small portable device, this light cost you battery power to generate. Basically, if it’s not usable light, it’s waste heat.

The open question is, where does all that extra heat go? If you add a fan, it’s easy: you just pump it out. But fans take even more electricity, and small bladed fans aren’t thermally efficient. They don’t quite help your form factor, either. So there’s definitely a thermal threshold, and Microvision’s projector is under it.

As far as we can tell, nobody else has reached this level of thermal efficiency. The practical consequence of being too hot is threatening the rest the system with thermal run-away. That’s why lasers and a MEMS mirror make such a useful combination. Our projector won’t burn up a PDA with its waste heat.

In the end, what makes a small projector different from an LCD or OLED panel is the projector’s limitless screen size. Compared to an iPhone, for instance, with its 4” diagonal screen, the SHOW projector prototype from Microvision can make an 80” diagonal image, from the same sized device.



Besides the projection engine itself, getting the image out of the projector is just as important as putting it in. And because Microvision’s pico projection engine uses lasers and a single scanning mirror, this is already a spreading image, as it leaves the MEMS. So, there’s no need for projection lenses. More importantly, the lasers provide infinite focus, even against uneven projection surfaces. So there’s no focusing knob, either.

HOW THE OTHER GUYS DO IT

For other small projection systems, the projection optics train is a crucial weakness. Besides such obvious limitations as added cost and added volume, a projection lens demands one of three sorts of focusing strategies:

[1] You can fix the focus, which means your projector only works at a set distance, and only if ambient light makes this size picture visible in the room you’re in – otherwise, you’ve got a picture that nobody can see;

[2] You can manually adjust the focus, but this requires either an open dial, or a closed servomotor system. The open system leaves your device vulnerable to the elements; the closed system adds considerable power requirements, mass, heat, and cost. They also require active support from the user – which might work on a showroom floor, but it’s much less effective in common practice.

[3] You can add an auto-focus feature. Unfortunately, given the size of the LC or LCOS panels used in other display engines, the lens you need to focus is huge: 10 mm or larger. Plus, you still have to measure the distance from the projector to the screen. So, you’ll end up building the same optics train as a high-end digital camera. And that’s not the sort of device that’s easily scaled into a PDA or a cell phone.

There’s a fourth alternative in projection lenses. If you use lasers as your light sources, and light up an array of pixels like in a liquid crystal, you don’t need to focus the image – you simply need to spread the image with a magnification lens, after it passes through the array.

But the problem with magnification lenses is that they introduce all sorts of image artifacts, including chromatic aberration. Correcting for such color changes requires multiple lenses. And the good ones – which do more complex corrections – are both big and expensive.

More to the point, the only competing system we know about that uses RGB lasers does so to make holograms. This is an over-the-edge technology, in terms of processing power. For example, holographic projector systems still can’t render holograms in real time. And even if they could, they are less than half the brightness of Microvision’s projector. So, this is basically a science project, for at least the next few years.

THE BIG PICTURE

It’s always difficult to predict the future – either for our own technology, or for someone else’s. Yet we strongly suspect that our size, power, heat, and resolution advantages will continue in successive generations. For instance, on our near-term technology roadmap, we expect to step up the MEMS mirror projector’s resolution. As we do this, our form factor shrinks even further, and our optical and power efficiency improve.



Bottom line, our small projector technology has sustainable advantages in resolution, size and heat and power.

Contact Information: David_Lashmet@Microvision.com

10 comments:

At February 4, 2008 at 6:05 PM Len said...

Thanks Ben,
This answers a whole host of questions about picoP vs. competition.

 
At February 4, 2008 at 6:23 PM Anonymous said...

Can you talk about speckle a little bit? How bad is it? What does it look like? Is it possible to fix speckle or is it always going to be there?

Also, you mentioned that you cannot compare lumens between laser and other projectors. Can you give us an example of a projector now on the market that would have similar real-world brightness to the Pico?

THanks for your informative post.

 
At February 4, 2008 at 10:25 PM Anonymous said...

Is this the same Dave Lashmet that worked with Porter Stansberry writing newsletters? Must be the same guy, since he recommended the company back in 2001.

I will give Dave this much, he can write a great PR release.

 
At February 4, 2008 at 10:32 PM Anonymous said...

I love this guy!

 
At February 4, 2008 at 11:23 PM Anonymous said...

"he can write a great press release..."

He also does great stock and technology research. Got me into NUAN, OLED and MVIS some time ago.

1 and 2 paid off big time. Gains from #3 will dwarf those returns, in due time.

Glad to see you at MVIS, Dave. Keep spreading the word.

 
At February 4, 2008 at 11:40 PM Anonymous said...

I would think they brought Dave onboard not only for his writing abilities, but his connections in the investment world. Getting the word out on MVIS from this point on is a whole new ballgame.

 
At February 5, 2008 at 12:11 PM Anonymous said...

"For instance, on our near-term technology roadmap, we expect to step up the MEMS mirror projector’s resolution."

What resolution, 720p or 1080p?

You guys should really focus on a product for the home theater projector market.

The holy grail of projectors is:

1. High contrast (no light projected with black image). WHICH THE SHOW CAN DO.
2. High resolution 720p or 1080p for sharper, larger images.
3. Great colors which because the SHOW uses lasers, color should be great.
4. A bright enough picture (obviously the SHOW with 20 lumens needs to be brighter, at least around 200-300 lumens.

If you can meet these goals, you could sell a HT projector for $3000 easily and actually as high as $5,000-6,000 (although if you can sell for less us penny pinchers would be pleased).

Good luck and keep us updated!

 
At February 5, 2008 at 3:29 PM Anonymous said...

Hey Dave,
What is up with the printer - the co-project with Epson you wrote about a couple of years ago?

 
At February 10, 2008 at 9:34 AM Anonymous said...

deafening silence about the speckle

 
At February 13, 2008 at 10:09 PM Ben said...

Here's everything on the blogpertaining to speckle.

 

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