Supersonic Wave Filter
The Supersonic Wave Filter ( SSWF ) is a dust protection system developed by Olympus . It prevents the negative effects of dust particles on the image sensor of digital SLR cameras . Dust and dirt particles can get into the camera housing when changing lenses or when air is sucked in when zooming. Even the smallest of impurities that stick to the image sensor can become visible as gray spots in the image. With its first digital SLR, the E-1 , Olympus introduced the first dust protection system for D-SLRs in 2003 and has since equipped all E-System cameras with it. Panasonic and Leica also use Olympus technology for their D-SLRs, while other manufacturers have developed their own processes.
Protection of the sensor from dust
The hermetic sealing of the space between SSWF and image sensor prevents dust from reaching the actual image sensor surface. For this purpose, special rubber seals are attached both between the image sensor and the low-pass filter and between the low-pass filter and the SSWF.
Ultrasonic dust removal
Ultrasonic vibrations (35 kHz) loosen particles adhering to the surface of the SSWF, which are then caught by adhesive strips in the camera housing. The SSWF consists of a reflection-free glass plate and a piezoelectric element. The vibrations of the SSWF are caused by resonance . This is triggered by applying an alternating voltage with a frequency of 35 kHz to the piezoelectric element. This creates bending vibrations that throw the dust off the filter surface. Since the SSWF is encased in rubber all around, its vibrations are not transmitted to other camera parts.
Dust remains invisible
The distance between the sensor surface and the SSWF also prevents dust particles from blocking the incidence of light on the sensor and thus being depicted as shadows.