Sapphire Optics

Understanding Surface Flatness in Sapphire Components

Custom fabricated sapphire windows & lenses which are chemically inert and operate over a wide spectrum for use in blood gas monitors, centrifuges, and other instruments are available from AOG Sapphire Optics Co.,Ltd.

Surface Flatness in Sapphire Components

Surface Flatness of Sapphire Windows

Surface flatness is a type of surface accuracy specification that measures the deviation of a flat surface such as that of a mirror, window, prism, or plano-lens. This deviation can be measured using an optical flat, which is a high quality, highly precise flat reference surface used to compare the flatness of a test piece. When the flat surface of the test optic is placed against the optical flat, fringes appear whose shape dictates the surface flatness of the optic under inspection. If the fringes are evenly spaced, straight, and parallel, then the optical surface under test is at least as flat as the reference optical flat. If the fringes are curved, the number of fringes between two imaginary lines, one tangent to the center of a fringe and one through the ends of that same fringe, indicate the flatness error. The deviations in flatness are often measured in values of waves (λ), which are multiples of the wavelength of the testing source. One fringe corresponds to ½ of a wave. 1λ flatness is considered typical grade, λ/4 flatness is considered precision grade, and λ/20 is considered high precision grade.

Why Surface Flatness Matters for Sapphire Components

Optical Performance - Sapphire windows, lenses, and wafers must maintain precise flatness to prevent distortions in optical systems. Flatness variations can cause wavefront errors, reducing imaging accuracy in high-precision applications like lasers and cameras.

Semiconductor Applications - In semiconductor processing, sapphire wafers require ultra-flat surfaces to ensure uniform deposition and etching of thin films. Poor flatness can lead to defects and inconsistent device performance.

Mechanical and Structural Integrity - For mechanical components such as bearings and seals, flatness ensures proper contact and load distribution, improving durability and reducing wear.

How Surface Flatness Is Measured

Surface flatness is typically measured using interferometry, a high-precision optical technique that analyzes light wave interference to detect surface deviations. The results are commonly expressed as:

λ/4, λ/10, λ/20 (for optical components, where λ represents a reference wavelength, often 632.8 nm from a HeNe laser)

Microns (µm) for industrial sapphire parts requiring strict mechanical tolerances

Factors Affecting Sapphire Surface Flatness

Several factors influence the flatness of sapphire surfaces during manufacturing:

Material Quality - Internal stresses and inclusions in sapphire can impact its ability to maintain a flat surface after processing.

Polishing Techniques - High-precision polishing using chemical-mechanical polishing (CMP) or diamond lapping helps achieve superior flatness.

Manufacturing Process Control - Advanced metrology tools and strict quality control help minimize deviations and ensure consistent flatness.

Applications Requiring High Surface Flatness

Laser Windows & Optical Lenses

To prevent beam distortion and maintain optical clarity

Sapphire Wafers

Used in microelectronics and LED manufacturing

Scientific Instruments

Precision measurement devices require extremely flat surfaces for accurate results

Notes

AOG SAPPHIRE is a leading custom sapphire glass parts manufacturer specializing in the production of custom sapphire crystal parts. Our comprehensive solutions for custom sapphire optical parts fabrication encompass shaping, grinding, drilling, and polishing. Additionally, we offer coating solutions tailored to enhance and optimize performance across a wide spectrum of applications.

Backed by over 20 years of diverse experience, AOG SAPPHIRE offers effective methods for polishing custom sapphire parts, ensuring low roughness, high surface quality, and precise surface accuracy.

If need other specifications and quantities products, please contact us(sales@sapphire-window.com).