1343Views14Replies

Author Options:

Why are there magnets around the DVD laser player? Answered


I just disassembled an old DVD player. The laser is 'suspended' between two fairly powerful small batteries. Any idea WHY the batteries are there?

The link below shows the laser and the magnets.
Video

Discussions

0
None
steveastrouk

Best Answer 8 years ago

They are used to focus the laser

0
None
kelseymhsteveastrouk

Answer 8 years ago

I'm glad Frollard clarified your description, Steve! Otherwise, I would have posted something highly sarcastic about linear Maxwell's equations and the inability of magnetic fields to affect the propagation of light.

It does make a lot of sense to use non-mechanical actuators to adjust the laser position. Much faster response and tighter control.

0
None
steveastroukkelseymh

Answer 8 years ago

In the same spirit, I am honour bound to point out that moving a lens around has to count as mechanical actuation.....

0
None
kelseymhsteveastrouk

Answer 8 years ago

:-D Yeah, yeah. Though using a non-contact method (magnets) is generally better than gears and levers.

0
None
kelseymhsteveastrouk

Answer 8 years ago

Ah, stupid me, making the spherical cow approximation again.

0
None
frollardsteveastrouk

Answer 8 years ago

Yup, in conjunction with a small coil (electromagnet) the laser can be moved with insanely good precision - limited only by the accuracy of the circuit controlling the coil.

0
None
lemonie

8 years ago

magnets and coils of wire = movement. L

0
None
steveastrouklemonie

Answer 8 years ago

Since we're on a picky kick today courtesy of Dr. K...magnets and coils = force. Movement is optional.

0
None
lemoniesteveastrouk

Answer 8 years ago


level 3 pickyness:
magnets and energised coils.

L

0
None
steveastrouklemonie

Answer 8 years ago

I'll see you and raise you to level 4. A shorted coil will also exhibit a force if moved.

0
None
lemoniesteveastrouk

Answer 8 years ago


you excite it with the magnetic-field, so technically it would still be energised/excited?

L

0
None
kelseymhsteveastrouk

Answer 8 years ago

F = dp/dt = m dv/dt + v dm/dt. You could use force to change mass, but that's probably a lot more difficult than changing velocity :-)

Isn't pointless Talmudic debate fun?