Supersonic Wave Filter
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The Supersonic Wave Filter (SSWF) is a dust reduction system developed by Olympus to overcome the negative effect of dust particles landing on the image sensor of digital SLRs. Dust may enter the camera body during lenses changes, so it is particularly D-SLR cameras that are susceptible to this problem. Even the tiniest dust particles or other contaminants that settle on the image sensor may become visible in the image as small grey specks. Olympus introduced the first ever dust reduction technology together with their first digital SLR, the E-1 in 2003, and has incorporated it in all their E-System D-SLRs since.
The Supersonic Wave Filter works like this:
(1) Ultrasonic dust removal
Through the ultrasonic vibrations (35kHz), dust particles that have adhered to the surface of the SSWF are removed. They are then captured on an adhesive strip at the bottom of the filter. The material used for the filter is free from any kind of reflection. The SSWF consists of a discoid plate and a piezoelectric element.
(2) Preventing dust from reaching the image sensor
The dust reduction system prevents dust from settling on the image sensor by hermetically sealing the space between the SSWF and the image sensor surface. This is achieved by applying a special rubber seal between the image sensor and low pass filter as well as the low pass Filter and SSWF.
(3) Preventing dust from appearing in the image
Due to the space between the sensor surface and the SSWF, dust is not projected clearly therefore it does not block the light and won't appear in the image. In addition, the SSWF is hermetically shielded by a rubber seal so the ultrasonic vibrations do not affect other components. Applying a frequency voltage of more than 35kHz to the piezoelectric element activates the resonant vibrations of the SSWF. The vibrations are flexed vibrations, making it possible to effectively remove dust from the SSWF.
