What is inside a DVD player? (5 of 5)
About this video
A narrated look at how a DVD player reads a disc. A motor spins the disc, a laser diode shines light through a lens onto a reflector and the disc, and a light collector reads the reflected pattern of pits and bumps, converting it into electrical pulses for the processor. The laser assembly uses magnets and copper coils to move the lens for fine focus.
You'll be able to
- trace the path of light from the laser diode to the light collector
- explain how pits and bumps on the disc become electrical pulses
- describe why the lens is mounted on wires and moved by coils and magnets
Key words
- Laser diode
- The small light source that shines the laser beam onto the reflector.
- Light collector
- The sensor that reads reflected light and turns it into electrical pulses.
- Pits and bumps
- The pattern on the disc surface that encodes the stored data.
- Neodymium magnet
- A very strong rare-earth permanent magnet used in the lens assembly.
Transcript
- [Narrator] Okay so the way a DVD player works is there's a spinning disc right here. That's our DVD. And so it spins around and there is underneath of it there is a motor, and that motor spins causing the disc to spin. And then there is a lens and a reflector, and a laser diode. And the laser diode shines the light on the reflector, it goes through the lens focuses on the DVD, and this whole part right here moves out as the DVD spins. And what happens is the DVD reflects the light back down here and there is a light collector. So the light collector says oh, okay. This is a pit or a bump and it sends that information via pulses of electricity back to the micro processor.
So now we're gonna look at the laser assembly. It's comprised of a number of parts. It has a laser diode. It has a series of reflectors. It has a lens. It has a laser or a light sensor. And it has an adjustment mechanism. So the first thing I'm gonna do is take this covering off. I had already loosened it to make it a little easier to get off.
And you can see right here there are two neodymium magnets. I think they're neodymium because they're very, very strong for their size. And that means it's a rare earth magnet and they tend to be very, very powerful permanent magnets. And then, right here you can see there are two different coils out of copper.
And there are two coils out of copper there. And the lens is mounted on these wires in between and it can shift and move. So I suspect that that mechanism allows for fine tuning adjustments of the lens. All right. So let's go ahead and see if we can take apart this DVD player. So we'll pop this prism off here.
So this sensor collects the reflected light and sends that information back. Now let's see if we can there we go. And there's the laser diode. So that's the little guy that shines the light, the laser light that gets read, that hits the disc and gets reflected and read by this sensor.
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