Lens arrangement for intrusion detection device

A sensing device for use in detecting the presence of persons or animals and capable of being mounted on either a wall or a ceiling, comprising:

• (a) sensitive means for detecting radiation having a predetermined characteristic wavelength;
• and
• (b) a lens grouping adapted to refract incident radiation having said predetermined characteristic wavelength, said lens grouping being mounted in a predetermined location with respect to said sensitive means and said lens grouping having a central axis and defining respective mutually perpendicular first and second planes each including said central axis, and said lens grouping having at least five lens elements, each of said lens elements having an optical axis, radiation having said predetermined wavelength and traveling along each said optical axis being focused generally on a focal point located proximate said sensitive means, said at least five lens elements including:
• (i) a primary lens element having an optical axis oriented in a preferred direction relative to said lens grouping and having an incident-radiation-gathering ability, said first plane including said optical axis of said primary lens element;
• (ii) a plurality of secondary lens elements in addition to said primary lens element, each secondary lens element having a respective optical axis oriented in a respective secondary direction relative to said lens grouping and having a respective incident-radiation-gathering ability no greater than that of said primary lens element, said optical axes of said primary lens element and at least two of said secondary lens elements defining a third plane mutually perpendicular with said first plane but not parallel with said second plane;
• and
• (iii) a plurality of tertiary lens elements in addition to said primary lens element and said secondary lens elements, each tertiary lens element having a respective optical axis oriented in a respective tertiary direction relative to said lens grouping and having a respective incident-radiation-gathering ability less than that of any of said primary lens element and said secondary lens elements, some of said plurality of tertiary lens elements being arranged in an arcuately curved row located in said lens grouping on one side of said second plane, said optical axes of said plurality of tertiary lens elements in said row defining partially the surface of a cone containing therein said optical axis of said primary lens element.

A sensing device with a masking system for detecting the presence of persons or animals and capable of being mounted on either a wall or a ceiling, comprising:

• (a) sensitive means for detecting radiation having a predetermined characteristic wavelength;
• (b) a lens grouping adapted to refract incident radiation having said predetermined characteristic wavelength, said lens grouping having a central axis and defining respective mutually perpendicular first and second planes each including said central axis, and said lens grouping having at least five lens elements, each of said lens elements having an optical axis, radiation having said predetermined wavelength and traveling along each said optical axis being focused generally on a focal point located proximate said sensitive means, said at least five lens elements including:
• (i) a primary lens element having an optical axis oriented in a preferred direction relative to said lens grouping and having an incident-radiation-gathering ability, said first plane including said optical axis of said primary lens element;
• (ii) a plurality of secondary lens elements in addition to said primary lens element, each secondary lens element having a respective optical axis oriented in a respective secondary direction relative to said lens grouping and having a respective incident-radiation-gathering ability no greater than that of said primary lens element, said optical axes of said primary lens element and any two of said secondary lens elements defining a third plane mutually perpendicular with said first plane but not parallel with said second plane;
• and
• (iii) a plurality of tertiary lens elements in addition to said primary lens element and said secondary lens elements, each tertiary lens element having a respective optical axis oriented in a respective tertiary direction relative to said lens grouping and having a respective incident-radiation-gathering ability less than that of any of said primary lens element and said secondary lens elements;
• (c) housing means for carrying said lens grouping thereon in a predetermined location with respect to said sensitive means;
• (d) unitary mask means, opaque to radiation of said predetermined characteristic wavelength, located adjacent said lens grouping, for preventing radiation from reaching said sensitive means through selected ones of said lens elements, said mask means defining an opening therein to permit passage of radiation of said predetermined characteristic wavelength toward said sensitive means, said mask means being stiff yet resiliently flexible and having marginal portions, and;
• (e) attachment means, associated with said marginal portions of said unitary mask means, for releasably fastening said mask means to said housing means adjacent said lens grouping.