Which type of PIR lens is least effective for wide area surveillance?

The curtain lens is designed to provide a vertical detection pattern, making it more suited for monitoring specific areas, such as doorways or windows, rather than covering vast, open spaces. This vertical orientation limits its effectiveness in wide area surveillance, where a broader horizontal detection range is typically needed to capture movements across large areas.

In contrast, other lens types, such as wide angle lenses and standard lenses, are designed specifically for broader detection ranges, which allows them to cover larger areas effectively. Therefore, the curtain lens is considered the least effective for wide area surveillance due to its specialized design that emphasizes height over breadth.