What is the difference between BK7 and B270?

Difference Between BK7 and B270

BK7 and B270 are both popular types of optical glass used in the manufacturing of lenses, prisms, and other optical components. Despite their similarities, they have distinct properties that make them suitable for different applications.

Composition

• BK7: A high-quality optical glass that is part of the borosilicate family. It is known for its high purity and excellent optical properties.
• B270: Also known as 'Superwite' or 'Crown glass', it is a soda-lime glass that is less expensive and has slightly lower optical qualities compared to BK7.

Optical Properties

• BK7: Offers excellent transmission in the visible and near-infrared spectra. It has a refractive index of 1.5168 at 587.6 nm.
• B270: Has good optical transmission in the visible spectrum but is slightly inferior to BK7, especially in the ultraviolet (UV) range. Its refractive index is slightly lower than that of BK7.

Physical Properties

• BK7: Exhibits high durability and resistance to thermal shock, making it suitable for high-precision optical applications.
• B270: While it has good physical properties, it is not as resistant to thermal shock as BK7. However, it is easier to mold and shape, making it a cost-effective choice for less demanding applications.

Applications

• BK7: Widely used in high-quality lens systems, telescopes, microscopes, and other precision optical instruments.
• B270: Often used in less critical applications such as simple lenses, windows, and display glass where cost is a more significant factor than optical performance.

Cost

Due to its superior optical properties and higher production costs, BK7 is generally more expensive than B270, which is considered a more economical option for many applications.