A pyroelectric infrared sensor and a method of manufacturing a dual pyroelectric element used therein

A pyroelectric infrared sensor includes a package (1) having a light-receiving window (26) and at least two dual pyroelectric elements (24,25) arranged in the package, each of the dual pyroelectric elements (24,25) having first and second unit pyroelectric elements (20a,20b;21a,21b), the first and second unit pyroelectric elements being connected in series or parallel with each other so as to have opposite polarities. The first and second light-receiving electrodes (14a,14b;15a,15b) and the first and second back electrodes (16a,16b;17a,17b) are formed such that an effective light-receiving electrode area of the first unit pyroelectric element (20b;21a) opposing a central portion of the light-receiving window (26) is smaller than an effective light-receiving electrode area of the second unit pyroelectric element (20a;21b) opposing a peripheral portion of the light-receiving window (26). A difference between secondary infrared rays incident on the first and second unit pyroelectric elements which is caused by a difference between angles of visibility of these elements with respect to the light-receiving window can be compensated. This invention also relates to a method of manufacturing the dual pyroelectric element.