Patent ID: 7414236

Claim:
A security surveillance device comprising: an electromagnetic wave sensor for sensing an electromagnetic wave of an external electromagnetic wave source; and an anti-tampering arrangement comprising: a detection window forming a partition between said external electromagnetic wave source and said electromagnetic wave sensor, said detection window comprising an outer corrugated surface facing said electromagnetic wave source; an optical arrangement for deploying an optical surveillance beam wherein optical surveillance beam comprises a first beam portion and a second beam portion, said first beam portion being a beam emitted by said optical arrangement towards said detection window, and said second beam portion being due to multiple reflections of said first beam portion at said outer corrugated surface of said detection window; and control circuitry for detection of a variation of said second beam portion, wherein the variation of said second beam portion is indicative of tampering of said detection window, said control circuitry generating an alarm signal upon detection of a variation of said second beam portion, wherein said second beam portion is a partial reflection of said first beam portion and wherein said outer corrugated surface is profiled with at least a pair of side walls such that a surveillance beam emitted by said optical source impinging upon said corrugated surface is partially reflected by said pair of side walls.