Illumination device

An illumination device comprising an optical plate extending over a plurality of LEDs arranged on a PCB main surface of a PCB, in a mounted configuration said PCB and optical plate are mutually connected by a plurality of fasteners,

• wherein each fastener extends through a respective, associated through hole in the optical plate in a direction transverse to said PCB main surface,
• wherein said associated through hole has a wide portion extending over a depth D from a first main surface of the optical plate facing away from the PCB towards a second main surface of the optical plate facing towards the PCB, which through hole is narrowed to a neck portion at said depth D, and
• wherein each fastener extends through said through hole with play S in a plane P parallel to said PCB main surface and rests on a respective, associated resilient washer seated in the wide portion of said associated through hole,
• wherein the wide portion comprises a tapered portion which gradually, preferably continually, tapers along depth D, and
• wherein the washer is a toothed washer, preferably with teeth extending outward.