Polymeric security window
First Claim
1. A security window system comprising:
- a window panel;
a waveguide having first and second ends and extended length therebetween, said waveguide being joined to said window panel, said waveguide having a different acoustic impedance for compression waves than that of said window panel.
1 Assignment
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Accused Products
Abstract
A security window is a laminated pair of polymeric window panels having waveguides sandwiched therebetween for transmission of ultrasonic compression waves. The waveguide transmission medium is glass fibers extending from edge to edge of the plastic panels and distributed in plastic strips which cover the entire window area. The index of refraction of the glass fibers is as identical as possible to that of the surrounding plastics, making the waveguides substantially invisible. A transducer initiates an ultrasonic compression wave which travels the length of the waveguide, and is detected by a transducer at the other end of the waveguide. The received signal amplitude diminishes when the waveguide is damaged and such change is used to trigger an external alarm system.
39 Citations
23 Claims
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1. A security window system comprising:
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a window panel; a waveguide having first and second ends and extended length therebetween, said waveguide being joined to said window panel, said waveguide having a different acoustic impedance for compression waves than that of said window panel. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method for detecting penetration of a transparent window panel, comprising the steps:
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(a) applying a waveguide to said panel in the region of prospective penetration, said waveguide being substantially indistinguishable visually from said panel and having a different acoustic impedance for compression waves than said panel, said waveguide having a first and a second end; (b) inducing a compression wave in said waveguide at said first end, said compression wave being transmitted toward said second end; (c) detecting said compression wave arriving at said second end of said waveguide; (d) comparing a characteristic of said detected compression wave against a preselected standard of waveguide transmission performance; and (e) producing a signal indicative of deviation of said arriving wave from said standard.
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22. A method for detecting penetration of a transparent window panel, comprising the steps:
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(a) applying a waveguide to said panel in the region of prospective penetration, said waveguide being substantially indistinguishable visually from said panel and having a different acoustic impedance for compression waves than said panel, said waveguide having a first and a second end; (b) inducing a compression wave in said waveguide at said first end, said compression wave being transmitted toward said second end and at least in part being reflected therefrom; (c) detecting said reflected compression wave arriving at said first end of said waveguide; (d) comparing a characteristic of said detected compression wave against a preselected standard of waveguide transmission performance; and (e) producing a signal indicative of deviation of said arriving wave from said standard.
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23. In a security system for a panel having a layer which is transparent to visible light:
waveguide means which is transparent to visible light and is embedded in said panel so as to extend thereacross and is constructed so as to be substantially indistinguishable visually from the panel itself, said waveguide means having a different acoustic impedance for compression waves than said panel.
Specification