Alignment lasers are industrial laser devices that provide precision alignment. They enable a variety of tasks such as tire positioning, textile and clothing cutting, freeze framing, defense and military targeting, laser cutting machining, marking and sewing, amongst others. Lasers have characteristics that make them ideal for alignment uses, such as monochromaticity (consisting of a single color), coherence, brightness, and precision. These features provide highly accurate calibration in a variety of conditions.

Types of Alignment Lasers

These lasers come in several types including spot, line, cross, and pattern projecting alignment. An array of colors is available such as red, green, blue violet, or 808nm or 980nm infrared depending on the intended use. Red lasers are applied in numerous applications using alignment lasers. They tend to be less expensive than green lasers, which have greater visibility given that the human eye is more sensitive to green. Optics can be integrated into laser modules to ensure that the output is as clear as possible.

Alignment laser types include: 

• Point or spot lasers: These lasers project dots or spots commonly used in drilling and other applications where precise targeting of a single point is needed. In drilling, it is vital to have an exact visual reference for initial drilling and then to follow from that point forward.
• Line lasers: These lasers project lines  for tasks such as aligning paper created in a mill, cutting metal in a machine shop, or sawing timber. The lens used for these lasers are chosen according to various fan angles for optimal line length.
• Cross lasers: These lasers project crosses that are preferred for tasks such as aligning textiles. An extra dimension is provided in the targeting process giving greater precision and improved accuracy.
• Laser projectors: These lasers are used to outline concrete forms.
• Pattern lasers: These lasers project patterns such as parallel lines, circles, or grids for more complex alignment processes.

Operation

Lasers are classes of devices that produce beams of light that are intense and consist of a pure single color. Such beams can be potent enough to destroy even hardened, heat-resistant material. The name laser comes from “light amplification by stimulated emission of radiation.” It reflects the process of exciting atoms or molecules from a low energy level to a high one in conjunction with light of a particular wavelength, thereby causing a powerful beam of light made up of a single pure color to be emitted. This is unlike the process seen in ordinary light sources in which many excited atoms or molecules give off light in a different wavelengths, directions, and colors.
 
The light emanating from lasers is more concentrated, coherent and powerful than that of other sources. Within laser devices, there is a great deal of diversity in the properties and power of the light beams emitted by the devices. As a result, there is no one-size-fits-all laser - different lasers are suitable for different purposes.
 
For the purpose of alignment, lasers work in a variety of ways. A laser that uses gas, a combination of helium and neon, can provide an almost perfectly straight line for a number of alignment applications. Such a beam may diverge by an amount smaller than 1/1000 of a part. The divergence of the beam can be further reduced by causing it to pass backward through a telescope. Over long distances the accuracy of the beam can be affected by atmospheric fluctuations.
 
By providing an easy to see visual tool, laser alignment devices have become common in a variety of industries and applications. In photography, the brightness of lasers, along with their coherence, make them well suited for freeze frame applications.
 
Measuring applications benefit from the high coherence shown by laser beams. As light beams are divided into two separate parts, they may either join again in-step or out-of-step. The brightness exhibited by the recombined beam produces interference that helps in measuring over long distances and in small increments.

Applications

A popular use of alignment lasers involves green line alignment for cutting purposes. This line projecting method relies on the brightness of 532nm green lasers to ensure line generation that is highly precise. These lasers may use a glass-coated optic lens to generate reference lines that are easy to see even at a distance. Another application is in large construction projects, whereusing lasers for laying pipes or digging tunnels overcomes difficulties associated with traditional methods of marking guide lines.

Other applications for alignment lasers include: 

• Sewing
• Tire positioning
• Mechanical sheet metal marking
• Laser cutting machine marking
• Textiles and clothing cutting
• Golf corrective positioning
• SMT positioning
• Freeze frame
• Steel plate printing positioning
• Stone cutting marking
• Sawing wood processing positioning
• Woodworking
• Defense and military targeting and positioning
• Measuring
• Towel printing
• Medical and cosmetic
• Stage lighting

• Construction

Selection

Considerations include the laser wavelength needed for best results, the size of the laser, voltage, color, the distance required, output power, and transverse operation.

Standards

NAS876 - Alignment lasers for optical tooling

Image credits:

World StarTechnologies | Laserglow Technologies