Post by dkennedy on Mar 17, 2005 21:06:40 GMT -5
The Clicker: DLP TVs!
Posted Mar 17, 2005, 4:36 PM ET by Peter Rojas
Each week Stephen Speicher contributes The Clicker, a weekly column on television and technology:
I’m not one to primp or preen. I haven’t partaken in the metrosexual boom. Well… with the exception of that one Mystic Tan, but really how could I be expected to pass up the promise of an instant deep-golden tan? All this down-to-earth-ness and yet I live in a home with nearly one million mirrors! Am I vain? Nope. I just loves me my DLP!
DLP is one of those technologies that’s incredibly simple in concept and yet nearly unbelievable in practice. Here’s how it works:
At the heart of every one-chip DLP projector is a Digital Micromirror Device (DMD). The DMD is chip that holds a rectangular array (one per pixel) of tiny hinge-mounted mirrors each approximately 15 microns square (or about one fifth the width of a strand of hair). Each of these mirrors is designed to tilt into one of two positions: either towards the lens or away from the lens. If the mirror is tilted towards the lens, the pixel is white. If the mirror is tilted away from the lens, the pixel is black. It’s simple, right?
I hear what you’re saying: what about grays? Here’s where is starts to get interesting. Because it’s a mirror, it can’t actually produce grays. Instead, it relies on its ability to switch on and off really quickly (about one thousand times per second!). Let’s say, for instance, that you want to produce a medium gray. The mirror would simply pulse between on and off. As such, it would allow about half as much light to pass to the lens. Your brain would then do the rest. By using this technique (binary pulsewidth modulation), DLPs can achieve over a thousand levels of gray.
You want more? You want color? Darn you’re picky. That’s OK. DLPs can also do color (or colour for those of you across the pond). Here is where the color wheel comes into play. Much like the lighting gels that theaters have been using for decades, the DLP’s color wheel tints the light that is being delivered to the DMD. Here’s where it starts to get really cool. That color wheel is always spinning and alternating between different color gels. This spinning and coloring is done in unison with the DMD determining when to tilt a mirror towards the lens. Yeah – that sounded way too complicated. An example is in order.
Let’s look at the previous example of grey. In that example we were assuming that the light was white. Suppose on the other hand that we wanted to produce a purple of medium darkness. In that case the DMD still needs to tilt the mirror towards the lens half of the time. However, now it also needs to be careful when it’s doing so. It will only tilt the mirror towards the lens when the light is being colored red or blue. So a short sequence of light bursts might look like:
OFF BLUE OFF RED OFF BLUE OFF, etc.
Your mind then blends that series into something it understands; in our case, that’s purple.
Q: I’ve heard about something called the “Rainbow Effect” with DLPs. What is that?
A: The whole concept behind the DLP projectors is to trick people into thinking that they’re seeing a color. The problem is that not everyone is tricked. While the majority of the population will average the bursts of color into one color, that isn’t always the case. Some people’s eyes are aware of the color wheel. Ergo, they see the same “rainbow” of colors that the color wheel is using to color the light. Now, it should be noted that modern DLP projectors do a much better job than early projectors, and seeing “rainbows” is much less common these days.
Q: Why DLP over other technologies?
A: There are two main reasons why people buy DLPs over other technologies such as plasma or LCD. First, they don’t wear out. DLP projectors can’t suffer from burn-in and there is nothing to fade or wear out. The picture from a two year old DLP Television (with a new bulb) will look exactly like the day you brought it home. Second, there is no screen-door effect*. The mirrors on the DMD are very close together. This means that more of the screen is used to display content.
Q: What’s next week column going to be about?
A: Good question! Beats me – I just finished this one.
Like always, feel free to drop me a line with comments or suggestions at theclicker@theevilempire.com. Until next week, save my seat!
*The screen door effect is where each pixel is surrounded by unused space. This can make the picture look a little like you’re watching through screen windows.
Posted Mar 17, 2005, 4:36 PM ET by Peter Rojas
Each week Stephen Speicher contributes The Clicker, a weekly column on television and technology:
I’m not one to primp or preen. I haven’t partaken in the metrosexual boom. Well… with the exception of that one Mystic Tan, but really how could I be expected to pass up the promise of an instant deep-golden tan? All this down-to-earth-ness and yet I live in a home with nearly one million mirrors! Am I vain? Nope. I just loves me my DLP!
DLP is one of those technologies that’s incredibly simple in concept and yet nearly unbelievable in practice. Here’s how it works:
At the heart of every one-chip DLP projector is a Digital Micromirror Device (DMD). The DMD is chip that holds a rectangular array (one per pixel) of tiny hinge-mounted mirrors each approximately 15 microns square (or about one fifth the width of a strand of hair). Each of these mirrors is designed to tilt into one of two positions: either towards the lens or away from the lens. If the mirror is tilted towards the lens, the pixel is white. If the mirror is tilted away from the lens, the pixel is black. It’s simple, right?
I hear what you’re saying: what about grays? Here’s where is starts to get interesting. Because it’s a mirror, it can’t actually produce grays. Instead, it relies on its ability to switch on and off really quickly (about one thousand times per second!). Let’s say, for instance, that you want to produce a medium gray. The mirror would simply pulse between on and off. As such, it would allow about half as much light to pass to the lens. Your brain would then do the rest. By using this technique (binary pulsewidth modulation), DLPs can achieve over a thousand levels of gray.
You want more? You want color? Darn you’re picky. That’s OK. DLPs can also do color (or colour for those of you across the pond). Here is where the color wheel comes into play. Much like the lighting gels that theaters have been using for decades, the DLP’s color wheel tints the light that is being delivered to the DMD. Here’s where it starts to get really cool. That color wheel is always spinning and alternating between different color gels. This spinning and coloring is done in unison with the DMD determining when to tilt a mirror towards the lens. Yeah – that sounded way too complicated. An example is in order.
Let’s look at the previous example of grey. In that example we were assuming that the light was white. Suppose on the other hand that we wanted to produce a purple of medium darkness. In that case the DMD still needs to tilt the mirror towards the lens half of the time. However, now it also needs to be careful when it’s doing so. It will only tilt the mirror towards the lens when the light is being colored red or blue. So a short sequence of light bursts might look like:
OFF BLUE OFF RED OFF BLUE OFF, etc.
Your mind then blends that series into something it understands; in our case, that’s purple.
Q: I’ve heard about something called the “Rainbow Effect” with DLPs. What is that?
A: The whole concept behind the DLP projectors is to trick people into thinking that they’re seeing a color. The problem is that not everyone is tricked. While the majority of the population will average the bursts of color into one color, that isn’t always the case. Some people’s eyes are aware of the color wheel. Ergo, they see the same “rainbow” of colors that the color wheel is using to color the light. Now, it should be noted that modern DLP projectors do a much better job than early projectors, and seeing “rainbows” is much less common these days.
Q: Why DLP over other technologies?
A: There are two main reasons why people buy DLPs over other technologies such as plasma or LCD. First, they don’t wear out. DLP projectors can’t suffer from burn-in and there is nothing to fade or wear out. The picture from a two year old DLP Television (with a new bulb) will look exactly like the day you brought it home. Second, there is no screen-door effect*. The mirrors on the DMD are very close together. This means that more of the screen is used to display content.
Q: What’s next week column going to be about?
A: Good question! Beats me – I just finished this one.
Like always, feel free to drop me a line with comments or suggestions at theclicker@theevilempire.com. Until next week, save my seat!
*The screen door effect is where each pixel is surrounded by unused space. This can make the picture look a little like you’re watching through screen windows.