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You’ve just bought a surplus helium-neon gas laser at a local swap meet. You get it home, plug it in, and marvel at the incredibly bright, red spot it projects on the wall. Your friends and family seem interested, but they keep asking you “What’s it good for?” You mumble something about holography and gun sights, but your interest soon wanes.
You grow tired of playing “laser tag” with the cat or bouncing the beam off reflective objects in your living room. Your toy soon finds its place in the dusty confines of the closet. You’ve run out of things to do with the laser and you soon move on to other hobbies.
It’s time to get that laser out of the closet! This guide shows you over 88 inexpensive laser-based projects from experimenting with laser optics to constructing a laser optical bench to using lasers to make stunning holograms. All the projects are geared towards garage/shop tinkering with a special emphasis on minimizing the budget.
The guide mixes the history of lasers, how lasers work, and practical applications in an easy-to-read and fun text that’s suitable for experimenters of all ages. Among the topics in this guide, you’ll learn how to use lasers for:
* holography
* optics and optical experiments
* laser guns
* laser light shows
* laser beam intrusion and detection systems
* aerodynamics and airflow study
* coherent-light seismology
* laser beam communication
* laser and fiber optics computer data link
* precision measurement
Though the laser is a relatively new invention, it has undergone many refinements and improvements since the first successful prototype was tested by Theodore Mainian in 1960. And its cost has been drastically reduced. Today, lasers are inexpensive, al most throw-away devices and are used in numerous consumer products and electronic systems. Lasers are everywhere—from the phone lines that connect home to office to the electronics that play back sound and pictures encoded on a videodisc to the bar-code scanning system used at the supermarket.
Lasers are available to even the most budget-conscious hobbyists, so if you don’t already have one (whether in the closet or not), don’t despair. Surplus laser kits can be purchased for less than $100, and the latest semiconductor lasers—the kind used in videodisc and audio compact disc players—cost under $15. The tools are here to bring laser technology to the common masses. All that’s needed is a guide to show how the pieces fit together. Such a resource is this guide.
WHO THIS GUIDE IS FOR
This guide is written for a wide variety of readers. If you’re into electronics, you’ll enjoy the many circuits you can build, including one that lets you carry your voice over a beam of light, or the project that can detect the presence of intruders around a campsite. A number of the projects are excellent springboards for science fairs. These include measuring—with astonishing accuracy—the speed of light, seismology, and hydrodynamics. Lastly, this guide is a gold mine for the gadgeteer. Lasers represent the ultimate in space-age technology, but this guide presents numerous laser- based gadgets that you can readily build in your garage.
In all cases, the designs used in This guide have been thoroughly tested in prototype form. I encourage you to improve on the basic designs, but you can rest assured that the projects have actually been tried and field tested.
The projects in this guide include all the necessary information on how to construct the essential building blocks of high-tech laser projects. Suggested alternative approaches, parts lists, and sources of electronic and mechanical components are also provided, where appropriate.
HOW TO USE THIS GUIDE
This guide is divided into 24 sections. Most sections present one or more actual hands-on projects that you can duplicate for your own laser creations. Whenever practical, I designed the components as discrete building blocks, so you can combine the blocks in just about any configuration you desire. That way, you are not tied down to one of my designs. You’re free to experiment on your own!
If you have some experience in electronics, mechanics, or lasers in general, you can skip around and read only those sections that provide the information you’re looking for. Like the laser designs presented, the sections are very much stand-alone modules. This allows you to pick and choose, using your time to its best advantage.
However, if you’re new to lasers and the varied disciplines that go into them, you should take a more pedestrian approach and read as much of the guide as possible. In this way, you’ll get a thorough understanding of how lasers tick and the myriad ways you can use them.
CONVENTIONS USED IN THIS GUIDE
You need little advance information before you can jump head-first into this guide, but you should take note of a few conventions I’ve used in the description of electronic parts and in the schematic diagrams for the electronic circuits.
TTL integrated circuits are referenced by their standard 74XX number. The “LS” identifier is assumed. I built most of the circuits using LS TTL chips, but the projects should work with the other TTL-family chips—the standard (non-LS) chips, as well as those with the S, ALS, and C identifiers. If you use a type of TTL chip other than LS, you should consider current consumption, fan-out, and other design criteria, because these factors can affect the operation or performance of the circuit.
In some cases, however, a certain TTL-compatible IC is specified in a design. Unless the accompanying text recommends otherwise, you should use only the chip specified.
ill. 1-1. Conventions used in the schematic diagrams in this guide.
Certain CMOS TTL-compatible chips offer the same functions as a sister IC, but the pinouts and operation might differ.
The chart in ill. 1-1 details the conventions used in the schematic diagrams. Note that unconnected wires are shown by a direct cross of lines, a broken line, or a “looped” line. Connected wires are only shown by a connecting dot.
Details on the specific parts used in the circuits are provided in the parts list tables that accompany each schematic. Refer to the parts list for information on resistor and capacitor type, tolerance, and wattage or voltage ratings.
In all schematics, the parts are referenced by component type and number.
* IC# means an integrated circuit (IC).
* R# means a resistor or potentiometer (variable resistor).
* C# means a capacitor.
* D# means a diode, a zener diode, and sometimes a light-sensitive photodiode.
* Q# means a transistor and sometimes a light-sensitive phototransistor.
* LED# means a light-emitting diode (most any visible LED will do unless the parts list specifically calls for an infrared LED).
* XTAL# means a crystal or ceramic resonator.
* S# means a switch, RL# means a relay, SPKR# means a speaker, and MIC# means a microphone.
SAFETY FIRST
It’s hard to imagine that something as fun as lasers can be potentially dangerous. While the types of lasers commonly available to experimenters don't pose a great radiation emission hazard, they can do damage if mishandled. This point is reiterated in later sections, but it’s worth mentioning here: NEVER LOOK DIRECTLY INTO THE LASER BEAM. The intensity and needle-sharp focus of the beam can do your eyes harm.
Perhaps more importantly, gas lasers, such as the helium-neon type, require high voltage power supplies. These power supplies generate from 1,000 to 10,000 volts. Though the current provided from these power supplies is low (generally under 7 milliamps), a 5,000- or 10,000-volt jolt is enough to at least knock you down. The power supply of a laser isn't a toy and should be considered potentially lethal.