ISO 19741:2018 PDF

Overview - ISO 19741:2018 (striae in infrared optical materials)

ISO 19741:2018 establishes a standardized test method for detecting and quantifying striae (localized refractive-index deviations) in infrared optical materials. It applies to materials such as infrared optical glass that are opaque in the visible and transmit beyond 0.78 µm. The standard defines the principle, apparatus, environmental conditions, sample requirements, measurement procedures (projection and Schlieren), data processing and reporting needed for consistent, reproducible striae assessment.

Key topics and technical requirements

• Principle: Illuminate a sample with collimated infrared radiation and image refractive-index disturbances using either a projection (beam-contracting telescope) or Schlieren measurement (knife edge + camera) system.
• Apparatus: Collimating IR light source, sample stage, projection optical system (lens 1, lens 2, knife edge/diaphragm), infrared image sensor and computer image-processing/display system.
• Light and sensor:
  • Emission spectrum must cover the sample’s transmission band.
  • Light intensity non-uniformity ≤ 5%.
  • Image sensor working spectrum within sample transmission; spatial resolution ≤ 0.25 mm.
• Environmental conditions:
  • Temperature: stable between 15 °C and 35 °C (±2 °C tolerance).
  • Relative humidity: **