Laser safety with no lid.

[joe58]

Hello

Basically have a cd Walkman from a friend and I want to rebuild it into a new case with other features. However I want to do it without the lid(although there may be a acrylic cover) and just have it spinning open.

What are the safety concerns with this, as I have seen other diy-ers do it before. Although an old Philips glass topped Mini Hifi had a silver foil section where the laser was and the lid is always closed when 'play' is pressed and have seen others like this.

My basic questions are; what does the laser shine through? Does it stop say at a 'sticker' I could put on the acrylic lid. Does the laser 'shine' through the cd?

Better safe than sorry.

Thanks

 

[SoNic_real_one]

It will "shine" in somebody eye if you don't have a CD in, don't have a cover on and press play...

 

[theAnonymous1]

I don't think it's that much of a concern really. I played around plenty with CDP lasers when I was younger and never went blind.

They are low power Class-I lasers and the focal length is only a few mm.

Laser Safety

Class I laser products produce no accessible laser emissions. For example, a CD player or DVD player/recorder contains an internal laser to read or write data, but does not actually emit any laser light. Products of this type are Class I laser systems. Class I lasers products present no hazard at all unless they are disassembled to gain access to the internal components.

 

[imix500]

I agree, with the optics the divergence makes it a non issue at a couple inches or so. You would have to stare directly at a class I laser for a very long time without blinking to do any sort of damage.

 

[stratus46]

Isn't the usual startup ?
1:Laser on
2:attempt focus. No focus=stop
3:spin disc. No data=stop
4lay

Since the disc is nearly opaque I don't see a problem. The light is only concentrated at the focal point and the beam diverges a lot to not see surface dust. Still it would be better to cover it and protect the optical block.

 

[joe58]

When your talking about the length is that the wavelength or the actual length the laser 'shines' up to and runs out of power and 'stops'?

Also I didn't know if the disks were quite opaque as when I've looked through discs before I've been able to see the cover art sticker. Also is it a visible laser like infrared?

Another thing I've thought of is that a walkman doesn't auto close the lid, so you may be able to press play with the lid open and no disc? I will try and test this, although they're may be a mechanism/ procedure to stop this.

And this is the link from the other post: http://www.homebuilthifi.com/project/204

 

[SoNic_real_one]

The lid has a microswitch to "tell" the controller that it is closed.

 

[joe58]

I also remember seeing this, which is all over the web. It doesn't have anything in the way of stopping you not putting the cd in and playing and therefore activating the laser from what I can see. Is it safe? Not an area of expertise as the only stuff I know about laser etc is what is in a A-level. And rather be safe than sorry.

link: Make a Muji Wall Mounted CD Player | VVANK

 

[Mooly]

Remember most of the energy from the laser is in the near infra-red so your eyes don't register it as visible but it still passes into the eye and can conceivably do damage particularly if viewed close too. If you could see it, it would be dazzlingly bright.

All the comments re focal length are correct but it's better to be safe than sorry...

 

[joe58]

Information taken from laser marking company. Link.

CLASS I

Class I lasers are low powered devices that are considered safe from all potential hazards. Some examples of Class I laser use are: laser printers, CD players, etc. No individual, regardless of exposure conditions to the eyes or skin, would be expected to be injured by a Class I laser.

Then on class 2 they talk about they are harmful and if pointed in someone eyes it can cause damage. However on another site it tells me that higher power lasers can also be classified as class 1, but built so as no contact can come into the laser beam with an example being cd players, which I take as being the lid and the microswitch. Plus on the bottom of the player it tells me that radiation can occur if interlock defeated and lid open.

Therefore I won't bother and make something with a little more protection. I still don't know how the other open cd players do it and how damaging it could be, but I will not risk it as I need my eyes for jobs I want in the future. What's a designer with no eyes... Thanks for the comments and help above.

 

[DF96]

Does Class 1 (etc.) classify the laser, or the equipment containing the laser? If the latter, then a potentially hazardous laser can be used provided that the (unmodified) equipment renders it safe with appropriate interlocks.

 

[imix500]

AFAIK, the "Class" designation has to do with the output power at the laser aperture. For instance, some DPSS lasers might use a 1W pump diode, but only output 100mW or so. That would be the difference between Class IIIB and IV.

 

[joe58]

Yes it is to do with the power as some websites say with the example being the one posted in the last post. However it can also involve higher powered lasers if they have safety measures. There seems to be many conflicting views.

 

[joe58]

Reading Wikipedia(I know I know) using the new system Class 1 is totally safe. The old system says that class 1 is safe and also other items can be safe due to the enclosure and therefore still classed as 1. I might try and contact one(if I can find a email address)of the ones who has built one of these open cd players and see what they say and if they did research into these aspects.

 

[joe58]

A link to a real 'open' cd player by a real company. So how do they go about it? Is there a microswitch that the cd presses on to tell it it has a disc in and a little rubber wheel on the end for when the disc is spinning?

Edit: I have found a image of the Muji with no disc. If you look closely at the other side to the actual laser, it looks like it must have some sort of other 'laser' to tell it a disc is in.

 

[theAnonymous1]

Probably just an IR led and photodiode, not another laser.

Honestly, it sounds like you are trying to convince yourself there's some kind of serious risk of blindness when there really isn't any.

 

[Steven505]

Hello Joe58

Known the fact that I do a lot of repair bussiness on CD-players and I can still read this threat, the laser will not do any harm to your eyes. The numerical aperture of the objective is about 45, so the laserbeam is very divergent.
Without a disc on the turntable, the laser cuts out after focussing so again no danger.

Make sure you use a proper clamp to keep the disc on!! Otherwise it behaves like a frisbee.

The things you see on the side of the laser on the photo are the laser- and photodiodes. It is a so called flat optical pick-up.

 

[joe58]

Thank you for that. Although this project will have to wait until Christmas time when I actually get time and then I'll 'play' around with designs that could work. It will be a walkman anyway, so it has the bearing type clamp system already there.