Front surface mirror

Coating

Single-side coating: Aluminium with an interference coating for reflectivity enhancement, deposited by magnetron sputtering under a high vacuum.

Surface protection

Following the visual inspections, the coated side of the front surface mirror is provided with a thin, easy-peel protective film to prevent damage during transport, removable without leaving any residue.

Optical requirements

Minimum reflective values at defined wavelenghts under differnt light incidence angles (directed reflection):

    Wavelength in mm     6° light incidence angle     45° light incidence angle
                 400                  ˃ 92%                  ˃ 92%
                 450                  ˃ 93%                  ˃ 93%
                 550                  ˃ 94%                  ˃ 94%
                 600                  ˃ 90%                  ˃ 90%

Front surface mirrors are optically opaque, meaning they have no measurable transmission.

Durability requirements

• Abrasion test, 200 strokes, 566 g, with cheesecloth
• Adhesion test with tape, Scotch 3M 8981
• Humidity test, 48 h, 95% relative humidity, 50°C
• Immersion test in salt solution, 37 g/l, 24 h at room temperature
• Salt spray test to ISO 9227 NSS, 48 h
• Wipe test (20 cycles) with isopropyl alcohol, acentone, 2h at room temperature
• Cycling test (4h at 80°C, 4h at -30°C, 16h at humidity to ISO 6270 Part 1), 4 cycles
• High-temperature storage (7 days at 100°C)

Following these tests, the coating must not show any defects such as stains, delaminations or pinholes. The required minimum reflectance values must also be exceeded after these tests.