two dots from laser

[SirSyko]

I bought a 150mw green laser from ebay. Sometimes when its on for like 10 seconds the dot from the laser will turn into two dots that are close to eachother. When I let go of the button and turn it back on its a single dot agian. It seems to turn into two dots randomly. Does anyone know why this is?
It also does this withought any lenses but its less noticable, turns more into a disorted ovel.

 

[allthatwhichis]

Sounds like it is mode hopping. And while I can tell you what it sounds like it is doing, I can't tell you why... Somebody else can and will though.

 

[Led_Blind]

Its probably a missalignment of all the crystals.

I have one that is a bit similar. Hold it one way and you get a single dot surrounded by spatter that is perfectly comuminated with the main beam. Hold it another and you get a perfect single dot.

 

[SenKat]

The two dots close together can be seen REALLY clear if you shine it through a magnifying glass. That is normally referred to as TEM01 - it has two distinct beams coming out - it could be misalignment of hte crystals, or it could be the diode pooping out early in its' life. The majority of the Blue portables are TEM01 and last a long time, so I think it could be an "urban legend" that is spells doom for the diode. If it is still within its' warranty period, then I suggest return it for one that only projects one beam.

 

[The_LED_Museum]

This definitely sounds like mode hopping to me.
It is not uncommon, especially in lower cost DPSS lasers.

I would also seek warranty replacement with one that produces a TEM00 beam (a single spot).

 

[luvlasers]

The two dots close together can be seen REALLY clear if you shine it through a magnifying glass. That is normally referred to as TEM01 - it has two distinct beams coming out - it could be misalignment of hte crystals, or it could be the diode pooping out early in its' life. The majority of the Blue portables are TEM01 and last a long time, so I think it could be an "urban legend" that is spells doom for the diode. If it is still within its' warranty period, then I suggest return it for one that only projects one beam.

Don't both TEM 01 and TEM 10 produce two dots? Both modes been identical but with a 180 degree difference?

 

[The_LED_Museum]

I believe TEM10 is an annular (doughnut-shaped) beam.