OHARA INC.

These materials are optically homogeneous and have excellent internal transmittance and high durability against solarization (coloring by UV). They are used in semi-conductor production equipment (Stepper Cameras) and its peripherals (Illumination Systems, etc.).

• 01Internal Transmittance (τ)

  Internal transmittance of the glass is indicated as guaranteed minimum transmittance at 365nm (10 and 25 mm sample thickness). Please note this is internal transmittance, reflection losses are not included.

• 02Solarization

  The degree of solarization is indicated as a decrease in transmittance caused by radiation from a super high pressure mercury-vapor lamp. The detailed measurement method is described in the "Japanese Optical Glass Industrial Standard (JOGIS)".

• 03Optical Homogeneity

  Optical Homogeneity (Δn) is guaranteed by use of our He-Ne laser interferometers. The Δn specification is indicated for three diameter ranges (Φ 160 mm or less, Φ 210 mm or less, Φ 260 mm or less) due to the Δn variances caused by glass type, size, and shape. Please note, if the ordered thickness is less than 25 mm, we will use a 25 mm thick test piece for Δn measurement. Please contact us when lower Δn specifications are required.

• 04Refractive Index (ni) Variation within one Lot (Sn Standard)

  The indicated Sn value is the refractive index variation after annealing within a single batch (same melt, same annealing run). Example: ±1 (×10⁻⁵)

• 05Refractive Index Tolerance

  The standard refractive index (ni) of our i-line glasses is higher than our catalogue nominal values. This is due to the longer annealing times which are necessary to obtain the desired homogeneity levels. Longer annealing times result in higher refractive indices. Example: +20±20

– The format of this catalog is identical to OHARA’s master catalog for optical glass so that it may be used for optical systems other than i-line systems. For individual properties, refer to the detailed data [PDF]. However, the properties mentioned below differ from the detailed data [PDF].

– The refractive index represents values for 22 segments of the spectrum ranging from 326 nm to 2325 nm.

– Refractive indices for wavelengths not specified in the catalog may be calculated using Sellmeier’s dispersion formula, as they have traditionally been. Given that the scope of applications for the dispersion formula is broad, the data sheet shows the dispersion formula constant used for the 326 nm to 1129 nm wavelength range. For refractive indices in the 1129 nm to 2325 nm wavelength range, use the dispersion formula constant specified below.

– The internal transmittance shows both the value for the standard sample thickness of 10 mm (τ10) as well as the value for the thickness of 25 mm (τ25), which is suitable for practical application.

(Notice) Optical Homogeneity Guaranteed : Please consult us if you need tighter specification. In case the thickness of the material is 25mm or less, we will guarantee the Optical Homogeneity by measurement using 25mm or more thick material.

(Notice) Tolerance of Refractive Index: Please consult us if you need tighter specification.