Is this normal?

[bucrepus]

I have just completed a PHR-805T build and am pushing between 120-150mW. I have a question about the Ax module. I can only focus a pinpoint up to about 6 inches or less. < 6 inches will focus to a very small point (pinhead size) and burn. Greater than 6" it becomes much wider(oval shape). At 1' about 3/4" wide, at 2' about 2-3" wide, at 3' about 4-6" wide. Screwing the mod out makes the beam more circular but wider by about 1.5 times than being screwed in. Is this normal? I though you could focus this thing better than this. At 10-15 feet, it's almost to wide to even see. The diode is flush in the module..

Thanks

 

[Trevor]

Are you trying to focus to infinity - just get a regular laser beam?

Are you trying to focus the laser to a point anywhere between the aperture and infinity? That's not doable...

-Trevor

 

[RA_pierce]

405nm light is near the edge of humans' ability to perceive...

Because the wavelength is so short, the lens of your eye focuses the light at a point above your retina rather than on it. This causes us to perceive a sort of Myopic effect or near-sightedness to short wavelengths of light.

Because of this, the dot at a distance becomes blurry and difficult to focus on.

It is easier to focus the laser with goggles on.
Try focusing the laser at ten feet or so and then walk up to the dot and take a closer look at it. You may find that the beam is not as wide as it appears from farther back.

Assuming you have the lens installed correctly, the laser should focus fine at more than 10 feet or so.

Also, keep in mind that after a certain distance, you can no longer focus the beam to a very small point. There are limits to lasers.
Try reading up on "refraction," "refractive index," and "myopia."

 

[bucrepus]

Thanks for the responses. Maybe I am expecting to much.. The lens was already installed.. it's in the tip of the module, do I need to mess with it? At 5 feet the beam has about a 7-8 inch diameter. At 10 feet about a 11-12 inch diameter? I thought the beam would be a little tighter than this, my cheap laser level has a 3" beam at 25 feet.

 

[Cyparagon]

The blurriness isn't a focus issue, it's a fluorescence issue. Here's my eye with a UV LED pointed at it:

 

[chipdouglas]

even if you had goggles to take way the scatter, you will see you can only focus pretty much every focusable laser to a "pin point" anywhere with in 12" or so of the aperature. if you want to burn/pop/ignite at a distance you are going to have to make up for that with good optics and raw power. on the hobby level, the 12x blu ray is king at distance burning. and the 445nm is the king at shorter range max power.


michael.

 

[lasersbee]

The only way to focus a 405nm Laser is with Laser Safety
Goggles/Glasses...
It is next to impossible to do without them... there is way
too much fluorescent glare... At least for me...

Jerry