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Laser Hobbyists - Hobby FAQ

        A page with some of the more Frequently Asked Questions about hobbyist laser systems.  We welcome your submissions and suggestions for this page.

Q: I want a low cost laser but I am not sure if I should buy a HeNe or a diode laser?
A: HeNe lasers are usually more collimated (the beam spreads less) than diode lasers. HeNe lasers are usually made of glass making them less rugged and they generally require AC power. Diode lasers are now available in the 5 mW range and are solid state devices making them more rugged. Theoretically a diode laser will last forever while the gas in a HeNe will eventually be consumed. Diode lasers can often be run from battery power making them ideal for portable applications.
Another option which is a bit more costly, but is much brighter to the eye, is buying one of the green DPSS laser modules - many of these have a modulation input allowing the laser to be turned on and off rapidly.  This is ideal if you later plan to do graphics as the modulation input can be used for blanking.

Q: What does DPSS stand for?
A:  DPSS stands for Diode Pumped Solid State Laser.  In a DPSS laser, an infra red diode laser is used to pump a crystal that up converts the frequency to 532 nM which is a bright lime green.  The eye is very sensitive to this frequency so that a 5 mW 532 nm laser appears as bright to the eye as a 15 mW HeNe laser.  Other combinations of pump diodes and crystals can be used to produce red and ble lasers so it is possible to have an all solid state RGB (full colour) laser.

Q: What is the most powerful laser I can use without a license?
A: The rules on maximum permissible power for public displays vary from jurisdiction to jurisdiction. In the United States the maximum is about 5 mW [contact the CDRH for full details]. Other countries follow the international standards which are approximately 1 mW for 1 second into a 7 mm aperture rule. For the exact details you should contact the regulatory authorities in your country.
For more information about laser safety in various countries, see the Safety Regulations page in the Safety Section.

Q: Can low power lasers be dangerous?
A: YES. You should observe the same kinds of safety rules that laser professionals use. NEVER shine a laser in anyone's eyes. The concentrating effect of the lens in the eye [see Basic Laser Safety for more info] can cause damage even with a low power laser. If you turn professional later, you will have good working and safety habits.

Q: I bought some GAL2 scanners. Why can't I do graphics with them?
A: The GAL2 scanners and other low budget scanners do not go fast enough to produce graphics. The speed of galvos for graphics systems is rated in PPS [Points Per Second] but all galvos can be speed rated in Hz when using an analogue sine wave as a test signal. The GAL2 and other low cost scanners usually don't go much faster then 300 Hz. The slowest scanner you can use for graphics, the G124, has a speed of 700 Hz while professional closed-loop scanners can attain speeds up to 7,000 Hz. The much slower consumer oriented galvos lack the speed and accuracy needed to follow the complex graphics signals. They can still be used for abstract generation and some beam effects.

Q: Can you use sound cards from computers to generate scanned effects?
A: You can use a sound card to generate scan signals if you first modify it to pass DC signals as graphics scanners require DC to produce images. Warning: this probably voids your warrantee and may damage your speakers or sound system. You will have to design your own sound control software to generate the effects.

Q: I have programming skills and I want to make my own laser graphics system.  Is there any info on software and hardware for making my own graphics system?
A: The design of a laser graphics system is a complex and time consuming task.  The first and most important part is a hardware interface or display processor to take the computer data and output it to the scanners.  These cards are not readily available as each laser company designs/builds a hardware interface to suit their needs and market.  There are a few companies that will sell you a card with the code to drive it.  Once you have that, you will need to program all of the software and design a GUI to make the images and animations with will take you hundreds of hours.
Laser F/X would like to encourage Linux programmers to work on this kind of project using the "open source" model but to date, we have not found any volunteers.

Q: I have seen those wispy 'gas cloud' effects they use at laser shows, how do they do that?
A: The effect is called a lumia and is generated by a lumia wheel. You can build one by using a 1 RPM [or slower] motor with a disk of bumpy glass or plastic attached. Simply shine the laser through the disk and watch the results on the wall.
If you use plastic with a very regular pattern such as the pyramid embossed type found on fluorescent lights, you will get a simple repeating pattern. If you use glass with a more random bumpy surface such as that found in old style shower doors, you will get a more interesting irregular pattern. Glass or plastic that is only waved [the bumps are not large] will spread the beam less while glass that is very bumpy will spread the laser more making a larger projected pattern.
The best way to find glass or plastic materials for lumia wheels is to go to a stained glass or art glass supply house. As them for some small samples to try out. Once you have found some you like, you can have them cut them into handy disks.  A simple way to make the disks interchangeable is to epoxy a 25 mm [1 inch] square of 'Velcro' type hook material on the hub and a matching square of loop onto the wheel. Note that these can come loose over time from vibrations and your disks may fall off and shatter.

Q: I have heard people talking about a "Liquid Sky" effect.  What is that?
A: "Liquid Sky" is a fancy name for a very simple effect.  By scanning a flat sheet (straight line) just above the audience's head, it appears they are under a "sky" the colour of the laser beam.  Since the beam is almost one dimensions in the vertical direction, it lights up smoke particles in a cross section so the swirling of the smoke due to air currents become readily visible.

Q: Can I build my own laser?
A: To build your own laser, you would have to have access to a machine shop, have glassblowing skills, vacuum equipment and access to rare gasses. I would be like trying to build your own light bulb or fluorescent tube. It is simpler to purchase a laser and low cost HeNe and diode lasers are readily available.
For those who would like to build their own laser, we have provided some resources on the Laser Construction page.

Q: I need more technical information about lasers. Where can I look?
A: The Backstage area of LaserFX.com contains a lot of technical information about laser light show applications.  For more technical information about the lasers themselves, Sam Goldwasser maintains Sam's Laser FAQ which is filled with technical details on a variety of lasers - LaserFX.com is pleased to act as a gateway for Sam's Laser FAQ 


DISCLAIMER: Some of the information in the Backstage area is provided by the persons or companies named on the relevant page(s). Laser F/X does NOT endorse or recommend any products/services and is NOT responsible for the technical accuracy of the information provided.  We provide this information as a service to laserists using the Backstage area. 

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