Information
VZ Growth Academy-A Comprehensive Guide to Beam Expanders
10 Jun,2025
A laser beam expander is an optical component used to increase the diameter of a laser beam and reduce its divergence angle, mainly to improve the collimation and focusing performance of the laser. In the laser marking industry (such as laser marking, welding, etc.), the commonly used type of beam expander is the Galilean beam expander, which has no internal focus, a compact design, and high power adaptability, fully meeting industrial requirements. The following is a detailed introduction to the laser beam expander:
I. Core Functions
Expand beam diameter: Enlarge the laser beam diameter through an optical system, for example, converting a fine beam into a wider parallel beam.
Reduce divergence angle: The divergence angle is inversely proportional to the beam expansion ratio (θ' = θ/x, where x is the beam expansion ratio). After beam expansion, the beam is closer to an ideal collimated state, which is beneficial for long-distance transmission or high-precision focusing.
Improve focusing effect: The beam after expansion can be focused to a smaller spot. The product of the spot size and the divergence angle (optical invariant) remains unchanged, but the improved collimation helps increase the power density at the focus.
II. Working Principle
Based on the diffraction limit theory: Due to the diffraction effect, laser beams naturally have a divergence angle. The beam expander reduces the divergence angle by increasing the beam diameter, thereby improving collimation.
Lens combination design: Common beam expanders are based on the Galilean telescope principle, consisting of an input concave lens and an output convex lens. They correct the beam path through refraction or reflection to achieve collimated beam expansion.
III. Main Types
1. Galilean beam expander
- Applicability: Galilean beam expanders consist of a concave lens (negative focal length) and a convex lens (positive focal length), with no internal focus. They have a compact structure and are suitable for high-power laser applications.
- Advantages:
- No thermal focusing issue: In high-power lasers, the absence of an internal focus avoids wavefront errors caused by air ionization or thermal effects.
- Small size: Compared to Keplerian beam expanders, Galilean beam expanders are shorter in length, making them easier to integrate into industrial equipment.
- Low spherical aberration: The combination of positive and negative lenses reduces aberrations and improves beam quality.
- Typical scenarios: High-power scenarios such as laser marking and welding, where collimated beams are needed to enhance focusing effects.
2. Keplerian beam expander
- Applicability: Composed of two groups of positive lenses with an internal focus in the middle, it is suitable for low-power applications or those requiring spatial filtering.
- Limitations:
- At high power, the internal focus may cause air ionization or thermal distortion, affecting beam stability.
- The structure is complex and bulky, typically used in laboratory settings or for low-power ranging applications.
- Special uses: If spatial filtering is needed in a laser marking system (such as purifying the beam mode), a Keplerian design may be used locally.
There are other types of beam expanders, but they will not be elaborated on here.
IV. Key Factors in Industry Selection
- Power Demand: For high-power laser marking equipment, the Galilean type is preferred to avoid thermal effects.
- Cost and Volume: Industrial equipment pursues miniaturization and economy, and the Galilean type has more advantages.
- Beam Quality: The Galilean type improves collimation by reducing spherical aberration, meeting the requirements of laser marking for fine spots.
*******************************
From this, it can be concluded that the beam expander used in our equipment is of the Galilean type.
10 Jun,2025
Classification：
Information
Latest Contents
Message Inquiry
Welcome to leave a message, we will contact you in time!
Welcome to leave a message, we will contact you in time!
CONTACT US
E-mail：info@vzjet.com
Address: 24/F, Building 7, Oceanwide International Soho Town, Jianghan District, Wuhan, Hubei, China
