Patent ID: 7738199

Claim:
A filter device comprising a frame comprising a window comprising two opposite sides and two rails being respectively attached to the sides of the window and each rail comprising multiple fastening portions; two coil-holding portions; an attaching portion being located between the two coil-holding portions and attached to one of the two opposite sides of the window; two coils being mounted between the rails and each coil being mounted between one coil-holding portion of one rail and one coil-holding portion of the other rail; an optical filter comprising two sliders, each slider comprising a first end and a second end; at least one lens mounted between the two sliders; two holders, one holder being attached to the first ends of the two sliders and the other being attached to the second ends of the two sliders and each holder having two ends; two magnetic members respectively held by the two holders; two covers holding the optical filter between the rails, each cover being a plate and comprising an opening aligned to the window; multiple fasteners formed on the cover and mounted respectively on the fastening portions of the frame; two sets of projections formed on the cover and each set limiting one of the sliders.