At present, there are many specifications and varieties of laser lenses on the market, and the prices are also uneven. What are the differences in the materials used and the price differences of these lenses?
Here's a detailed introduction to the base material of optical lenses:
Optical glass (BK7/K9)
BK7(K9) is one of the common borosilicate crown glasses, with a transmission range of 380nm to 2100nm. It has high homogeneity, low bubble and impurity content, and can be directly used as a transmission optical material. BK7 has higher hardness and good scratch resistance. However, the coefficient of thermal expansion is large and not recommended for temperature-sensitive applications.
Fused silica materials are divided into JGS1, JGS2 and JGS3 for different applications.
● JGS1: usually used in ultraviolet and visible light bands, the material does not contain bubbles and impurities.
● JGS2: Usually used for mirror base, the material contains many small air bubbles.
● JGS3: It has good transmittance in infrared, but contains many bubbles, which limits its wide use.
In general, unless otherwise stated, we call UV Fused Silica fused silica. Ultraviolet fused silica is an extremely high-purity amorphous silica with a transmission range from ultraviolet 185nm to 2300nm. This amorphous, colorless quartz combines a very low coefficient of thermal expansion with good optical properties. Its transmission and homogeneity exceed that of crystalline form of quartz crystal (Crystal), and fused silica has a high damage threshold and is one of the ideal materials for high-energy lasers. Ultraviolet fused silica has high refractive index uniformity and low impurity content, and is suitable for both transmission and reflection optical systems and high-energy optical systems.
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In the field of laser cutting, fused silica is used to make various optical components. Compared with BK7, it is more suitable for fields requiring higher transmittance and higher damage threshold. According to the characteristics of different fused silica materials: JGS1 is better than JGS2 is better than JGS3.
In terms of cost, the JGS1 is expensive. JGS2 is relatively cheap, but has air bubbles inside. Therefore, at present, JGS2 materials are mainly used in the market, which are used to make small and medium power laser lenses, which are cost-effective. For low-demand cutting requirements, it can be satisfied, but for medium and high-power laser cutting, the performance of JGS2 will be much worse. In order to achieve better use results, JGS1 materials are generally used for better and more stable applications.
In addition to the difference in the base material of optical lenses, there are also great differences in coating. Different coating equipment, coating materials and ratios, coating time requirements, etc., have an impact on the transmittance, service life and use effect of the lens. . Therefore, the reference for choosing laser lenses is not only in terms of price, but also in quality.
Therefore, BK7 (K9) materials are susceptible to high temperature expansion and explosion, and are basically not used in the laser cutting range. Due to low cost, they are often used in low power (≤500W) laser welding fields.