1. Apr 8, 2014

### regnar86

I'm developing a scanner that uses a laser for edge detection. It will be mounted on a hexacopter that will traverse a short distance through a cave/tunnel system and produce a 3D image. I'm still researching on ways to process this data but i'm thinking of using a edge detection algorithm in MatLab to produce a 3D image.

My question is determining the right kind of laser to do this. Because the environment will be in low light conditions this will help out. However, I'm not for sure if something around 75mW is enough or if I need to go up to 10W. Also, I will be testing the device in a building where there will be some light. Here is a link to a site I found that sells lasers. They are just pointers so I'm not for sure if they are powerful enough.

http://www.wickedlasers.com/

This is another link that has a 10W laser. I'm not familiar with specifications on lasers and this link defines this laser as a "waterproof 10000mW / 10W focusable burning Blue laser pointer". The word "burning" doesn't sound to great so would like some clarification on this.

http://www.dhgate.com/product/new-w...ble-burning/153993729.html#s1-12-1|2367005007

It should be able to perform out to distances of 50meters. Can someone give me some advice and guidance on exactly what laser specifications I need to consider and what might be suitable for this kind of operation.

Last edited: Apr 8, 2014
2. Apr 8, 2014

### AlephZero

IMO the only safe place for a 10W laser is in a proper laboratory, with locked doors, controlled entry, and mandatory safety training for everybody who is allowed access.

The safe power limit for laser pointers is 5 mW. Your 10W laser is 2000 times more powerful than that.

Even a 200mW laser can blind you in 1/10 of a second (that's faster than you can blink) at a range of 100 yards. Your 10W laser is 50 times more powerful than that.

FWIW it is probably not legal to own a high power laser, but it would almost certainly be illegal to operate even a 75mW laser it in the way you described, let alone a 10W.

3. Apr 9, 2014

### UltrafastPED

Your laser only needs to generate a return signal; look up "laser range finding" - such as LIDAR.

Since your distances are relatively short your power requirements are low. By modulating the laser output (bursts of light) you can estimate distances the same way as sonar or radar - hence the name LIDAR.

Here is a Kickstarter LIDAR project: $99! https://www.kickstarter.com/projects/1108292587/99-lidar-project Here is a commercial 3D LIDAR mapping system: https://wiki.csiro.au/display/ASL/Zebedee And another: http://velodynelidar.com/lidar/hdlproducts/hdl32e.aspx Note: these are all low-powered lasers. Class 1, near-infrared (invisible beams, < 5 mW total power). The typical 10 W laser available today is intended for machining/cutting applications. I have a several friends that have purchased this type of system for home workshop machining applications -$3,000 to \$6,000 for a complete 2D system. But these are class IV laser systems and require the proper safety goggles (for the intensity and wavelength), plus beam confinement. They are not for playing with!

4. Apr 13, 2014

### mrspeedybob

It seems to me like mapping the interior surface of a cave or structure would involve rapidly scanning said surface with the laser, hence the time spent and the energy delivered to any one spot would be very small, even for the largest of lasers. It seems to me like it would essentially become a 75 mw (or 10 W) point source of coherent light.

Is this incorrect? If so, why?

I do understand that safety precautions would have to be taken to ensure that the laser could not be on unless the scanning mechanism was operating correctly.

5. Apr 14, 2014

### UltrafastPED

I have served as laser safety officer in several labs; your "It seems to me" is a very dangerous statement, and could easily cost somebody their vision.

See the laser safety classification system: http://en.wikipedia.org/wiki/Laser_safety#Revised_system

The "eye safe" conditions require very low power levels because the eye is a near-perfect lens - and focuses the light onto a very delicate and irreparable surface, your retina.

As power levels increase you are subject to dangerous levels of light even from non-reflective surfaces - surface scattering.

A 10 watt laser is dangerous in many ways; they must be treated like a welding torch.

Rather than give a detailed safety lecture here - which I have done for many students new to an optics lab - I refer anybody interested to Sam's Laser FAQ:
http://www.repairfaq.org/sam/lasersam.htm

There are good sections on laser safety for the home hobbyist.