Laser Electronics Ltd

Information Section.

Lasers:

Lasers can be defined to three current types, Gas (Ion lasers), Solid State Lasers (DPSS and Direct coupled diodes, CW) or Q-Switched (Pulsed Lasers) each suited for a different purpose. The definition of Laser is an Acronym (Light amplification by stimulated emission of radiation) this was originally taken from the Acronym Maser (Mass amplification by stimulated emission of radiation). Laser devices are present in a lot of everyday products such as CD Players, laser levels, laser pointers, measurement devices, commercial video projectors, medical devices, radar range finding systems (such as speed detection devices that use lasers operating in the near IR).  Care and caution should be taken when being exposed to what could be determined as dangerous and unacceptable levels, as the actual level of output from some laser devices can be far greater than the MPE levels given within the current guidelines from the FDA, CDRH, BSI and IEC guidelines. Lasers over 5-10 mw are dangerous to the eye when low divergence of the primary source allows the eye to focus the emission to sub-micron levels, direct viewing should be avoided. Laser emissions that are pulsed within the visible or infrared should never be viewed as the peak power levels can exceed the damage threshold of the tissue absorbing the laser output (even at relatively low power levels).

Laser Classification:

Lasers have been classified by wavelength and maximum output power into four classes and a few subclasses since the early 1970s. The classifications categorize lasers according to their ability to produce damage in exposed people, from class 1 (no hazard during normal use) to class 4 (severe hazard for eyes and skin). There are two classification systems, the "old system" used before 2002, and the "revised system" being phased in since 2002. The latter reflects the greater knowledge of lasers that has been accumulated since the original classification system was devised, and permits certain types of lasers to be recognized as having a lower hazard than was implied by their placement in the original classification system. The revised system is part of the revised IEC 60825 standard. From 2007, the revised system is also incorporated into the US-oriented ANSI Laser Safety Standard (ANSI Z136.1). Since 2007, labeling according to the revised system is accepted by the FDA on laser products imported into the US. The old and revised systems can be distinguished by the 1M, 2M and 3R classes used only in the revised system and the 2A and 3A classes used only in the old system. Class numbers were designated using Roman numerals (I–IV) in the US under the old system and Arabic numerals (1–4) in the EU. The revised system uses Arabic numerals (1–4) in all jurisdictions.

The classification of a laser is based on the concept of accessible emission limits (AEL) that are defined for each laser class. This is usually a maximum power (in W) or energy (in J) that can be emitted in a specified wavelength range and exposure time. For infrared wavelengths above 4 μm, it is specified as a maximum power density (in W/m2). It is the responsibility of the manufacturer to provide the correct classification of a laser, and to equip the laser with appropriate warning labels and safety measures as prescribed by the regulations. Safety measures used with the more powerful lasers include key-controlled operation, warning lights to indicate laser light emission, a beam stop or attenuator, and an electrical contact that the user can connect to an emergency stop or interlock. Below we will deal with the revised classification system as this is generally the adopted method for current manufactured laser systems.

Revised classification system:

Warning label for class 2 and higher:

Below, the main characteristics and requirements for the classification system from 2002 are listed, along with typical required warning label text. Additionally, classes 2 and higher must have the triangular warning label and other labels are required in specific cases indicating laser emission, laser apertures, skin hazards, and invisible wavelengths.

Class 1:

CLASS 1 LASER PRODUCT

A class 1 laser is safe under all conditions of normal use. This means the maximum permissible exposure (MPE) cannot be exceeded. This class includes high-power lasers within an enclosure that prevents exposure to the radiation and that cannot be opened without shutting down the laser. For example, a continuous laser at 600 nm can emit up to 0.39 mw, but for shorter wavelengths, the maximum emission is lower because of the potential of those wavelengths to generate photochemical damage. The maximum emission is also related to the pulse duration in the case of pulsed lasers and the degree of spatial coherence.

Class 1M:

LASER RADIATION
DO NOT VIEW DIRECTLY WITH OPTICAL INSTRUMENTS
CLASS 1M LASER PRODUCT

A Class 1M laser is safe for all conditions of use except when passed through magnifying optics such as microscopes and telescopes. Class 1M lasers produce large-diameter beams, or beams that are divergent. The MPE for a Class 1M laser cannot normally be exceeded unless focusing or imaging optics are used to narrow the beam. If the beam is refocused, the hazard of Class 1M lasers may be increased and the product class may be changed. A laser can be classified as Class 1M if the total output power is below class 3B but the power that can pass through the pupil of the eye is within Class 1.

Class 2:

LASER RADIATION
DO NOT STARE INTO BEAM
CLASS 2 LASER PRODUCT

A Class 2 laser is safe because the blink reflex will limit the exposure to no more than 0.25 seconds. It only applies to visible-light lasers (400–700 nm). Class-2 lasers are limited to 1 mw continuous wave, or more if the emission time is less than 0.25 seconds or if the light is not spatially coherent. Intentional suppression of the blink reflex could lead to eye injury. Many laser pointers are class 2 but always clarify with the manufacturer as some exceed this classification.

Class 2M:

LASER RADIATION
DO NOT STARE INTO BEAM OR VIEW
DIRECTLY WITH OPTICAL INSTRUMENTS
CLASS 2M LASER PRODUCT

A Class 2M laser is safe because of the blink reflex if not viewed through optical instruments. As with class 1M, this applies to laser beams with a large diameter or large divergence, for which the amount of light passing through the pupil cannot exceed the limits for class 2.

Class 3R:

LASER RADIATION
AVOID DIRECT EYE EXPOSURE
CLASS 3R LASER PRODUCT

A Class 3R laser is considered safe if handled carefully, with restricted beam viewing. With a class 3R laser, the MPE can be exceeded, but with a low risk of injury. Visible continuous lasers in Class 3R are limited to 5 mw. For other wavelengths and for pulsed lasers, other limits apply.

Class 3B:

LASER RADIATION
AVOID EXPOSURE TO THE BEAM
CLASS 3B LASER PRODUCT

A Class 3B laser is hazardous if the eye is exposed directly, but diffuse reflections such as from paper or other matte surfaces are not harmful. Continuous lasers in the wavelength range from 315 nm to far infrared are limited to 0.5 W. For pulsed lasers between 400 and 700 nm, the limit is 30 mJ. Other limits apply to other wavelengths and to ultrashort pulsed lasers. Protective eyewear is typically required where direct viewing of a class 3B laser beam may occur. Class-3B lasers must be equipped with a key switch and a safety interlock.

Class 4:

LASER RADIATION
AVOID EYE OR SKIN EXPOSURE TO
DIRECT OR SCATTERED RADIATION
CLASS 4 LASER PRODUCT

Class 4 lasers include all lasers with beam power greater than class 3B. By definition, a class-4 laser can burn the skin, in addition to potentially devastating and permanent eye damage as a result of direct or diffuse beam viewing. These lasers may ignite combustible materials, and thus may represent a fire risk. Class 4 lasers must be equipped with a key switch and a safety interlock. Many industrial, scientific, and medical lasers are in this category.

Hints:

All lasers will fit into one of the above classification categories and below we will look at just a few of the types of lasers available and some of the associated components that go with these lasers for use in such industries as the laser Light show one.

Direct coupled diode lasers:

Direct coupled diodes are semiconductor devices that produce coherent light from a quantum well structure, much the same as Led’s, the typical color is red(635 to 650nm). When encapsulation in a close proximity and the addition of a short cavity, frequency doubling can be attained by the doubling crystals being layered sequentially after the primary pump source to give alternate output frequencies (colors such as green and blue). The non frequency doubled devices are typically red in color but over the past few years other devices have been made commercially available. Red diodes have typical power ranges from 1-4000mw. The most popular of these being a 5mw hand held pointing device. These devices typically run of batteries or 5vdc and weigh several ounces. Their typical cost is, $10- $1000 new, $5-$700 used. Higher power units run off of 110-230vac and can weigh several pounds. 2000-4000mw units typically cost $5,000-$30,000 new

Helium Neon (He-Ne):

These lasers typically emit red (special types may be yellow or green). Typical power levels are 2-20mw, with the most popular being 5mw. Their sizes can be 1-2 ft. long, 2" cylindrical, with a small power supply that runs off of 110-240VAC and consumes less than 1 amp. Typically they weigh 1-10 pounds and prices range, $200- $2000 new, $10-$800 used.

Argon Ion (air cooled):

These lasers emit visible light from the UV spectrum through to the Green. The typical power ranges are 30-1000mw, with the most popular being 100mw and greater. They can measure 1-2 ft. long, 8" square, with a similar sized power supply. The typical power requirements can be 110-240 vac @ 10-30 amps, their weights can be from 30-90 pounds and typical prices can be $2000-$12,000 new, $500-$8000 used.

Argon Ion (water cooled):

As with the air cooled version these lasers emit visible light from the UV spectrum through to the Green. The typical power ranges are 2W to 30W, with the most popular being 5W. The typical dimension of a 5 watt laser system is 3-6 ft. long by 8" square, with a large power supply that requires 220-440 vac, 3 phase @ 40-60 amps and weighs 80-400 pounds. Typical prices $6000-$70,000 new, $3000-$30,000 used.

Krypton (water cooled):

Unknown to most people these lasers emit visible light from the UV spectrum through to the Red spectrum. The typical power ranges are 100mw to 7W, with the most popular power range being around 1.2W. The average size can be 3-6 ft. long by 8" square, with a large power supply that requires 220-440VAC 3 phase @ 30-60 amps and weighs 30-500 pounds. The typical costs can range from $6000-$70,000 new, $3000-$30,000 used.

White Light Ar/Kr gas lasers (water cooled / air cooled):

The typical power ranges are from 100mw air-cooled to1-12W water-cooled, with the most popular being within the 3-5 watt range and measuring 3-6 ft. long * 8" square. The power supply is normally quite large and typically requires a power input requirement of 220 vac 3 phase @ 40-60 amps. The typical weights can be 80-200 pounds and prices vary from $5000-$50,000 new, $2000-$15,000 used, depending on the system.

DPSS lasers (Frequency doubled CW 344-671nm):

The typical power ranges are from 10mw to 8W, with the most popular being within the 1-5 watt range and measuring 5 to 24 inches long. The power supply is normally quite small and typically requires a power input requirement of 110 – 230 vac and 1 – 7 amps. The typical weights can be 1-40 pounds and prices vary from $200-$50,000 new, $100-$25,000 used, depending on the system. These systems can come in various output frequency configurations with the most popular being 473 and 460nm (blue), 532nm (green) and 651 and 671nm (red).

ND-Yag lasers (Frequency doubled Pulsed 532nm(Green):

 With typical output powers 20W to 60W, with the most popular being 40W. 2-3 ft. cube, including power supply 220VAC 3 phase @ 10-30 amps, weighs 100-400 pounds. Typical prices $50,000-$100,000 new, $20,000-$50,000 used, $10,000-$40,000 for converted medical units. These lasers are extremely high output powers and under no circumstances should they ever be used for audience scanning.

Hints:
Be sure to check the power socket with a voltmeter to make sure your power source matches your laser power supply specification, before turning the supply on. If the unit is 3 phase, check to see if the power supply is delta or wye. With delta power, one of the phases will measure twice as much as the other two, referenced to ground. This double voltage leg is sometimes called the "stinger" leg, and will blow up many laser power supplies.
Never disable the water flow interlock on a water cooled system. You may need to "kink" the output hose slightly (to cause back pressure), in order to activate some flow sensors. Cool down the laser at low power before shutting off the fan or water flow.
Keep the optics clean. Use reagent grade methyl alcohol or acetone and a very clean, non abrasive paper such as lens cleaning tissue. Do not rub, but rather drag the wet paper over the optics, then immediately dry or blow with a can of compressed air. When replacing or cleaning optics, only work with one at a time. Fire the laser and realign before going on to the next one. Try not to loose the beam completely when adjusting.

Beam table:

The classic beam table is an optical breadboard consisting of a 1/4 inch thick aluminum plate, drilled and tapped every square inch with 1/4-20 holes. The entire assembly is usually black anodized to reduce potentially dangerous reflections. Mounts holding mirrors, galvos, actuators, fiber feeds, and various optical elements can be moved around and easily repositioned. If the laser is fastened to the table, the entire system becomes immune to unintentional misalignment. The beam is directed around the beam table and into the various effects by actuator arms with mirrors on them.

Flat optical breadboard table:
A large plate up to 4' x 6' in size is used to mount all components, including the laser. Newer technologies such as PCAOM's, DPSS lasers and other devices have reduced the need for such large beam table areas. Due to it's large size and weight, this type of table is mostly suited for permanent installations.

Upper/Lower configuration tables:
Two optical breadboards can be stacked on top of each other, spaced apart by support beams to make a box. This allows more equipment to be packed into a smaller area, and also acts as an enclosure to protect the parts. Typically the laser (or at least the front part of the laser) is mounted on the bottom plate, along with color modulation and electronic components, power supplies, etc. The beam is bounced up to the top through one of the 1/4-20 holes, and the top is left free for any desired optical configuration. This type of system is easily transported because the laser can be mounted in such a way as to be easily removable.

Custom tables:

Classic beam tables are expensive. With a hole every square inch, a one foot square breadboard has 144 holes. Even medium sized breadboards can have thousands of holes. Drilling and tapping 1/4 inch aluminum is not cheap. In a production environment, there will certainly be taps broken and breadboards ruined, which must be factored into the per-unit cost. Some manufacturers drill only the holes that are needed, and drill and tap extra holes when a change has to be made. Metal chips from drilling the hole can get into the laser or electronics, so partial disassembly is usually required.

Hints:
Use solid, repeatable mounts in all locations, bolted down firmly. Make sure the weight is distributed evenly, so moving the unit will not cause flexing of the optical breadboard and subsequent misalignment.
Keep beam paths as short as possible. The longer the throw to the next optical component, the easier it is to put the system out of alignment. Use as few mirrors as possible, because each mirror bounce will add a loss of the overall laser output power, and also causes the beam to expand slightly.
If your system does not have a permanent output mask (safety beam block), make a temporary one out of "black wrap" aluminum foil. Before the audience is present purposely scan where the audience would be, and adjust the beam block until it masks the audience area.

Galvos(Scanners):

A galvo (scanner) is basically a high speed motor that rotates only slightly from side to side, instead of spinning continuously in one direction. When a mirror is attached, a galvo can deflect the laser beam very accurately. The main determining factor for a galvo is speed, which is measured in thousands of points per second, or KPPS. Faster galvos produce images that appear to have less flicker than slower galvos because they can move the beam position faster. There are several types of galvos available and we will deal with just a few models.

General Scanning G138, G120, 124:
General Scanning was the inventor of the modern day mass produced high speed galvo. The G120 position detecting galvo used feedback, which allowed the projection of modern day laser graphics without overshoot. Although not specifically designed for laser lightshow use, the G120 quickly became the standard of the industry during the 1980’s. Their patents on moving-iron armatures, torsion bar centering suspension, and capacitive feedback technology, held the rest of the industry at bay for years. Newer versions have increased speed and deflection. These galvos run at the standard 12K ILDA speed, although new amplifier designs pump enough current into them to allow 24K or higher speeds.
The G124 galvo is similar to the wide angle G138 without the feedback section. Although this would typically result in massive overshoot, recently developed amplifiers allow them to operate at near 12K performance. The 124 galvos and "accelerator" amps were very popular because of their low cost, medium performance, and almost indestructible characteristics.

Cambridge Technology Scanners 6800HP, 6210H, 6215HB, 6215H:
Cambridge Technology is a hi-tech company which started making a line galvos specifically for the laser lightshow industry. The 6800HP (H stands for high performance, P for dual position detector) is characterized by very high speeds of up to 40k points per second or more, and a wide output swing of as much as 80 degrees. The design uses optical feedback for stability, and no torsion bar for reliability and low power consumption.

Eye-Magic EMS3080 EMS4000:
The early Eye Magic EMS 3080 brought laser enthusiast a few desirable features such as no fuse to blow and the ability to grab the mirror while projecting without causing any damage to the scanner or amplifier. The newer EMS 4000 has improved on the early EMS 3080 design with very low heat amplifiers and a 300 degree C coating around the magnet to prevent the magnet from flaking and jamming the rotor. These scanners have exceptionally wide deflection angles and are very reliable and we feel represent a very good investment for the serious enthusiast.

Hints:
If you feel the need to rotate the mirror/armature assembly with your fingers, do so gently. Most non-Cambridge style galvos have a torsion bar suspension that will easily break. Keep mirrors as small as possible, and the galvo mount as sturdy as possible. Never plug in or unplug a galvo when the galvo amp is on as this can cause fatal damage to the amp or galvo.

ServoAmps(Drivecards):

A galvo amp is similar to a Hi-Fi stereo amplifier which is DC coupled from input to output, and uses a special feedback circuit to determine the galvo mirror position. This feedback allows the amp to give the galvo a reverse feed in the opposite direction, to help slam on the brakes when the galvo starts to overshoot. Many amps have balanced inputs which help cancel hum and other interference when using long cable runs. All galvo amps have a servo feedback and dampening adjustment. The more servo feedback you tune in, the more current is pumped into the galvo, and the faster it will go.

G120:
Manufactured by many different companies, the GS style galvo amp was the standard of the industry for years. Recent amp improvements allow faster scanning speeds than previously thought possible using this type of galvo.

Cambridge:
These are manufactured by several different vendors, the Cambridge Technology amps use optical feedback, which is inherently more accurate and stable than most other feedback methods. The Cambridge amp has a built-in protection circuit called a coil temperature calculator, which basically monitors the instantaneous power dissipation of the galvo, and reduces the gain if an offending input signal is applied.

G124:
This amp can fake a non-feedback galvo into acting like a feedback galvo by sensing inductive kickback (reverse EMF). The amp automatically corrects for overshoot on a microsecond basis.

Hints:
Galvo mirrors should be kept as small as possible to reduce mass and increase speed. However, you may want to consider using two "Y" mirrors on your X/Y set in order to avoid different amplifier tuning between channels.
You can tune your galvo amp without an oscilloscope by using your controller software to project a low speed square consisting of 4 dots. Slowly turn up the servo gain (not to be confused with the input gain, or size) until the beam overshoots on the corners, and get rid of the overshoot with the dampening. Increase the servo gain to get more overshoot, and get rid of it with the dampening again. Repeat until the image isn't stable any more and then reduce the settings. If you are tuning a Cambridge style amp, use the low frequency dampening first, then when the corners start to overshoot and undershoot at the same time, adjust the low frequency dampening to get equal amounts of overshoot and undershoot, then get rid of it with the high frequency dampening adjustment before continuing.
For safety: During the tuning procedure, be ready to turn off power if the galvos start to squeal. Only use as much input gain as necessary to get the job done. Only use the factory rated galvo fuse, typically 2 amps. Never plug in or unplug a galvo when the galvo amp is on. Check your galvos and amps every once in a while, to make sure they are not getting too hot and they are heat sunk correctly.

Blanking:

Blanking is the ability to turn the beam on and off at a high speed. Most complex graphic images require blanking, in order to eliminate the flyback lines that would otherwise be visible. There are several different ways to blank.

Flag blanking:
The least complex method is to have a galvo move a beam block into the beam path. This method is very slow, and usually causes "tails" on the beam as it is being blanked. Flag blanking is usually used only in economy situations.

Mirror/pinhole blanking:
A faster method is to have the beam bounce off of a galvo mirror, and travel some distance (a few inches) to a pinhole in a beam block. A slight movement of the galvo causes the beam to move out of the pinhole and to hit the beam block. The distance between the galvo acts as an optical lever, speeding up the blanking tremendously.

Retro reflector blanking:
The best of all mechanical blanking mechanisms. The beam bounces from a mirror to a retro reflector and back to the same mirror again, before entering the X-Y set. The long throw acts as an optical lever, and the retro section cancels out the "hooks" on the end of the blanking tails that would otherwise be visible.

A/O blanking:
Acousto optic blanking with an electronic crystal is the fastest method possible. The beam passes through the crystal and is diffracted when an RF signal is applied by the driver. Standard A/O blanking is only 50 to 80% efficient, so be prepared for some power loss.

Hints:
Use a high quality feedback galvo for blanking if possible, or the overshoot will cause the beam to "stutter". If you are using a pinhole, make it as big as possible without getting performance degradation.

Mirrors, Splitters and Dichros:

Mirrors, splitters and dichros are all basically the same type of optical element, except for the percentage and wavelength of light they reflect or pass.

Mirrors:
For high power laser lightshow purposes, dielectric mirrors are normally used. Dielectric mirrors have many layers of material vacuum deposited on them, in order to reflect the desired band of wavelengths (colors). In most cases, these mirrors are optimized for Argon, and will take 10, 20, or even 30 watts of laser power. If many more layers of material are deposited, the mirror will reflect red as well as blue and green, in which case it is called a white-light mirror (typically much more expensive). For low power (less than one or two watts) purposes, you can use aluminized mirrors which are very cheap, and are by nature white-light reflective.

Splitters:
A beam splitter is a partially mirrored piece of glass, that can be coated to reflect virtually any percentage, and let the rest pass through. The most common values are 50% and 33%.

Dichros:
Sometimes it is desirable to reflect certain colors, and let the other colors pass through. A dichro can be used as either a color selective mirror, or a filter. That is, the desired band such as blue and green can be passed through, and the remaining red can be reflected. Conversely, the same end result can be accomplished by reflecting the blue and green, then passing the red. These two categories of dichros are referred to as RGB (red, green, blue) and CMY (cyan, magenta, yellow). Color blending and mixing can therefore be additive or subtractive.
Dichros can also be used to combine beams of different colors. For instance, a "reflect red" dichro can be placed in front of an Argon laser at a 45 degree angle, and a red Krypton or HeNe beam can be aimed at the same spot on the dichro. The blue/green passes through, and the red is reflected in the same direction as the blue/green, combining the beams into white light. The 45 degree dichro is "tweaked" with a MM1 mirror positioner, until the two "far" beam spots (some distance away), are on top of each other. In a combining setup, a small percentage of the light is reflected off of the back of the dichro and lost.

Hints:
For cleaning, use methyl alcohol or acetone and a very clean, non abrasive paper. Do not rub, but rather drag the wet paper over the optics, then immediately dry or blow with a can of compressed air.
Do not use superglue to mount glass elements. Superglue causes a haze to form which may not be removable. Superglue contracts when it dries, causing the mirror to bend, and causing any beam that hits it to expand. Most laserists use five minute epoxy for permanent installations, or silicone sealant for removability.

Poly Chromatic Acousto Optic Modulators:

The PCAOM has changed the way we do color modulation in the laser lightshow industry. The old way was to flip dichros on the end of actuator arms (slow), or use three A/O's with a beam blending setup (difficult to align). The PCAOM can instantaneously change beam color and intensity, with minimum setup and alignment hassle.

Color selection.

Most multi-channel PCAOM’s have eight channels of selectable wavelengths (color). The RF driver puts out a different frequency for each channel, and the crystal reacts to each frequency by diffracting a different wavelength. The output of each channel is proportional to the DC input level, so you can select any of eight colors (or combination of colors) and adjust the brightness of each. There are several ways to change colors with a PCAOM.

(a) RGB. Tie all of the red channels together, all of the green channels together, and all of the blue channels together. You can adjust the brightness level of each of the three groups of channels, to blend the colors together. This gives dozens, hundreds, or even thousands of color combinations, but many of the blended colors lack the inherent eye-catching brilliance of pure laser colors. Since you are attenuating (cutting down the brightness) of the outputs in order to get a certain color, this method can be somewhat inefficient.

(b) Color Combining. The channels are turned off and on in combinations. For instance, bright red combined with dark blue, to get a rich purple color. This method gives brilliant colors, and does not attenuate any of the inputs, so it is inherently efficient. The drawback is that there are only a limited number of color combinations available.

(c) Individual wavelength modulation. Some systems allow complete analog control of all inputs. This is similar to the RGB system, but allows millions of colors.

Efficiency.

Although the typical efficiency of a high performance PCAOM is about 85%, this only applies to each of the eight colors that can be selected. There may be a dozen or more "lines" of color in the spectrum analysis of the beam of a given laser. This means that these other colors are being thrown away, even when all of the PCAOM channels are full on. Admittedly, these wavelengths are of little use, but nonetheless add up to a percentage of the lasers output. The real world efficiency figure ends up being more like 70-75%. The remaining 25% or so is in the "waste" (throw away) beam output, but can be used for other purposes on the projector, such as a simultaneous nebula effect.

The following is the "quick" alignment procedure for the popular NEOS PCAOM
(1) Turn down the laser power to less than one watt, and adjust the crystal so that it is vertical (not tilted).
(2) Center the beam in the input window, and turn up the laser power to the desired level.
(3) Project a known color, and adjust the brag angle by slowly tilting the RF connector away from the laser.
(4) The selected color will be deflected out of the main beam, when the angle is correct (5-10 degrees).
(5) There will be more than one angle where the selected color is visible. Pick the brightest one.

Hints:
Be very careful when making the electronic connections. When purchasing, pay the extra to get input/output windows, so as to avoid damage to the raw crystal itself. If you don't have windows, be careful to follow the factory cleaning instructions, and stay away from the tiny delicate gold wires on the inside.

Fiber input and output couplers, collimators:

Sometimes you can't get the projector where you want it. The good news is that a fiber optic "light pipe" can get the beam to virtually any desired location, even hundreds of feet away. The bad news is that you will have to put up with at least some power loss and beam degradation.

Fiber:
In general, the best fiber to use is step index silica/silica, although it is possible to get good performance with gradient index plastic fiber. The connectors on the end can be several different types, but SMA seems to be prevalent due to it's low cost and availability. Use 50 micron for graphics and 100 micron for high power beams where divergence is not as important. Divergence is the rate at which the diameter of a beam gets bigger with distance.

Fiber input couplers:
The most important part of a fiber system is the input coupler. The beam must be focused down to enter the exact center "core" of the fiber for best performance. An input coupler has a method of moving the focal point of the beam onto the end of the fiber in all three directions, X, Y, and Z.

Fiber output couplers:
The output coupler is almost a mirror image of the input coupler. Adjusting the X and Y axis is either not as important, or not important at all, depending who you talk to. The output coupler usually consists of a simple single lens to refocus the output of the fiber into a beam again, adjustable in the Z axis only. The output beam diameter is usually 1/4 to 1/2 inch in diameter, and usually diverges considerably faster than the original raw beam.

Collimators:
Also known as beam expanders, a collimator will make the laser beam smaller at a distance (far dot size), at the expense of having a fatter beam coming out of the collimator (near dot size). If the near dot size is too big, it makes the beam hard to manage because of the need for larger galvo mirrors etc.

Hints:
It is important to keep the fiber ends and lenses clean, especially on the input coupler end. Specifically, a single speck of dust on the tip of the input fiber will turn into black carbon as soon as it is hit with several watts of focused laser power. At that point it will start to absorb power and generate heat, destroying the end of the fiber.
When adjusting the input coupler, turn the laser power down to less than one watt to avoid burning the end. Aim the raw output end of your fiber at the wall or similar surface several feet away, and adjust the input coupler for best beam quality. First adjust the X and Y, then the Z for maximum brightness. Repeat the X, Y, and Z adjustment for fine tuning. Attach the output coupler and adjust the focus of the output coupler for the smallest far dot size. It is now safe to advance the laser power.

Actuators:

Actuators are used to change the direction of the beam on a beam table, and reroute it to a different effect. An actuator must be continuous duty, be capable of moving considerable mass, and do it at a fairly high rate of speed. In many respects, it is a slow galvo.

General Scanning GM20:
The classic laser lightshow actuator. Rugged, very repeatable, requires about 12-18vdc at about 1 amp. Capable of swinging in both directions.

MFE:
A GM20 clone at lower price, more than acceptable performance, and slightly larger in size. Many people have recommended this as the only true alternative to the GM20.

Rotary Solenoid:
Much cheaper ($20-30 vs. $100-150). Not very repeatable, the rotary solenoid will come to a slightly different resting place every time. For some applications, this is OK. A good cheap alternative if you can stand the noise.

Actuator Amps:
Amplifiers for actuators can be a simple TIP 120 transistor with a 2.2k resistor in the base, or they can approach galvo amp complexity, depending on the speed required. Prices range from as little as $10 per channel to over $80 per channel.

Unipolar vs. Bipolar:
Most actuators, with the exception of rotary solenoids, can be driven in both directions (plus and minus 10 or 20 degrees) by reversing the polarity of the drive signal. A unipolar driver moves an actuator to a given position, and then lets it spring back to it's resting position.

Hints:
Make sure your actuator is capable of continuous duty, by making sure it doesn't get to hot after 10-20 minutes of "constant on" operation.
Count the total number of actuators that can be on at one time, and make sure your power supply can handle it. Usually, one or two actuators are on at a time, requiring 2-3 amps total.

Other effects:

There are many different effects that can be achieved with simple optical elements. There are probably hundreds of different effects that can be achieved by sticking something into the beam. Here are a couple of the most common.

Nebula effect:
The Nebula effect, or Astro cloud, is one of the easiest effects to produce. Take a piece of plastic or glass and smear some clear silicone on it. Let it dry, and put a beam through it. If you want to get really fancy, put your newly created effect on a fractional RPM motor (1 RPM to 1/4 RPM). For high power applications, use "shower glass". Try different types of glass for different sized effects at different distances, and put the beam through a prism (or use the "waste beam" of a PCAOM) for color effect. Use an actuator to steer the beam into the effect.

Diffraction gratings:
Diffraction gratings make a fan or burst of beams when interacting with a beam. They can be made out of scribed plastic or glass, grooved metal, or a thin plastic holographic simulation of one of the above. A "line" or "fan" grating produces a beam pattern similar to that at the top of this page. Put a sheet of this grating over a bounce mirror to throw the pattern back in the opposite direction. A "burst" or "X-Y" grating produces a beam pattern of dozens or even hundreds of beams going in all directions. A burst style grating can be placed in front of a set of galvos, and cause the projected image to multiply. The "Machida" diffraction grating (named after the company that manufactures it) is made of fiber optic strands closely butted up against each other side to side, and creates a very wide angle, full color, closely spaced fan of beams. Somewhat expensive, but a very dramatic effect.

HOE:
The Holographic Optical Element can simulate just about anything that can be achieved in nature, plus some that can't. Various adaptations of this technology can produce spirals and even company logos by simply passing a beam through the holographic film.

3D:
A very plausible 3D image can be made by projecting two slightly different images in different colors or polarizations from two sets of galvos. The viewer wears glasses with different colors or polarization planes in each eye, to allow different images to be viewed by the right and left eyes. Other types of glasses allow different colored objects to be perceived as different depths.

Hints:
Be very careful when using any optical effect. Unexpected reflections and out of alignment actuators can cause permanent eye damage. Keep the power in the low milliwatt levels until you get it right.