Products
Fluoride crystal, typically exemplified by fluorite, has to be grown in a vacuum ambient atmosphere with a high temperature of 1,000°C or higher, requiring advanced devices as well as high-level processing technology. Canon Optron succeeded in mass production of fluorite in 1968. Since then, we have continued to provide a wide range of optical crystal materials that are produced using our long accumulated technologies for high-temperature vacuum and temperature control. These crystal materials demonstrate the optical properties not found in conventional optical glass, and are widely used in optical devices such as telephoto lenses as well as analyzers, helping to dramatically expand the potential of optical equipment.
Fluorite (CaF2)
Fluorite has a wide transmittance wavelength region, and has the properties of low refraction, low dispersion, and anomalous partial dispersion. Because of these characteristics, fluorite is used in various products, ranging from a super achromatic (apochromat) telephoto lens that completely eliminates the secondary color aberration to a zoom lens, television camera, and astronomical telescope. UV grade is available, which is excellent in transmittance in the vacuum ultraviolet region.
Barium Fluoride (BaF2)
Barium fluoride exhibits a wide transmittance wavelength range of up to 13 μm in the infrared region, the widest among fluorides. Due to this property, barium fluoride is commonly used for optical materials used in analysis devices that employ infrared waves as well as high power infrared lasers.
Crystal Material Physical Property Values
| Name of crystal material | CaF2 | BaF2 |
|---|---|---|
| Transmittance wavelength range （µm） | 0.13～10 | 0.15～13 |
| Refractive index | 1.435 （0.546µ） |
1.4756 (0.546µ) |
| Color | Colorless | Colorless |
| Density（g/cc） | 3.18 | 4.83 |
| Melting point (℃) | 1418 | 1280 |
| Thermal conductivity （cal/cm・sec･℃） | 0.0241（50℃） | 0.028（13℃） |
| Coefficient of thermal expansion （/℃） | 0.000024 （20～60℃） |
0.000018 （0～300℃） |
| Hardness（knoop） | 158.3 | 82.0 |
| Specific heat（cal/ｇ・℃） | 0.211（50℃） | 0.098（27℃） |
| Solubility（ｇ/100ｇH2O） | 0.00151（20℃） | 0.162（30℃） |
| Molecular weight | 78.08 | 175.36 |
| Crystal system | Cubic crystal system | Cubic crystal system |
| Crystal structure | Fluorite type | Fluorite type |
| Cleavage plane | ｛１１１｝ | ｛１１１｝ |
Technologies
Canon Optron has been working on the development of large, ultra-high quality fluorite crystals, used in semiconductor exposure devices. For our achievements in this area, we were recognized with a technology prize from the Japanese Association for Crystal Growth in 2005.
High-Purification Technology
Ultra-high purity fluorite can be produced using our technology for refining the material to high purity. These fluorites are excellent in transmittance in the vacuum ultraviolet region, now being used in a UV grade lens for UV light.
Large Crystal Production Technology
We have made advancements in our crystal growth and anneal technologies, succeeding in the growth of large diameter fluorite crystals with low birefringence and high homogeneity. These products have been employed in the large diameter, refracting astrometric telescopes at astronomical observatories in Japan.