How do they make lcd led backlight?

[Isaac Newton]

I really wanted to know how do they make those LED diffusers that make a nice and evenly illuminated backlight in LCD displays like those on some multimeters or wrist watches. Do they sell them separately?

[c4757p]

You'd be surprised how well diffused the backlight on a small display like that can be with a solution of "completely jack shit". It's often just a plain plastic panel.

[Isaac Newton]

So, no black magic going on?

[c4757p]

Not in something like that. Occasionally they'll even use multiple LEDs to spread the light more evenly!  It doesn't take much to get good diffusion over a small display area.

[Isaac Newton]

So, what kind of plastic do they use?

[george graves]

Sometimes the edges of the diffuser are pained or covered in something reflective.  Sometimes the surface of the diffuser is like frosted glass. But mostly, the light just bounces around behind the screen till it gets out.

[Isaac Newton]

True, I just took apart my multimeter and the backlight is just a LED shining through one of the sides of a plastic material. Around the plastic, there is just a reflective sheet. On the top of the defuser, is a white difused plastic sheet and behind it there is another reflective sheet. I'm preaty impressed by the fact that it has a very good spread of light in it. Nice.

[retiredcaps]

This video is somewhat related and less than 5 minutes long.  I really like how he (engineerguyvideo) describes things in his videos in simple terms and some of the early videos had a lot of tongue in cheek humor.

[Jon Chandler]

Here's a link to some pictures of an LCD backlight I dissassembled.. Many LEDs which explains how the backlight can draw 200-300 mA.

[jeroen74]

That's LED backlighting the oldskool way before LEDs got really bright. That panel can now be backlit with one or two LEDs at a fraction of the current.

The plastic used is mostly likely PMMA with little dots on the main surface to get the light out.

[ptricks]

You can use one led for a backlight and the plastic used is just ordinary acrylic . You can make these at home by using sand paper on a piece of acrylic, scuff it up  and it will diffuse the light.

[Isaac Newton]

The billions of sheets that are used to make those lcd monitors are nice, but for the little and inexpensive LCD's, I guess they have to use just simple methods. I think it is good engineering to come up with simple solutions like this with just a single LED and a sheet of plastic...

[nukie]

Many optical designers who work hard to keep light transmission efficiency as high as possible while making sure the light is even spread out are not going to be happy when they read this... It might look like a plain plastic panel but some have micro optics on them if you look carefully. It is a simple yet elegant solution for stuffing backlight into places as thin as your mobile phone.

You'd be surprised how well diffused the backlight on a small display like that can be with a solution of "completely jack shit". It's often just a plain plastic panel.

[Isaac Newton]

I know, I know. I was just analizing the alternative ways to make this work even without so much resources.

[jeroen74]

A few of my Casio watches use EL backlighting, some use a couple of yellow LEDs in a ring. The latter does not really work, but the EL on my newest Casio watch is really beatiful.

[Baliszoft]

Watch Daves video about his led ceiling lights.

[T4P]

My vote for the best LED backlighting for a watch goes to TI : I wear their EZ430-Chronos development watch
At least the screen is not some white back-plated LCD screen and has great contrast but the backlighting is not so bright but it's good enough plus it's VERY even green, i can hardly tell where the LEDs at placed at