Patent ID: 7019295
Filing Date: 2006-03-28
Classification: G01J

Abstract:
1. A digitally-controlled pyroelectric signal sampling circuit, which comprises: a trigger-signal generating unit for generating a trigger signal, a first sampling signal, and a second sampling signal, which are substantially fixed in frequencies and timings irrespective of temperature changes in the ambient environment; a light source module, which is triggered by the trigger signal from the trigger-signal generating unit to emit an alternating light beam; a pyroelectric sensor module for sensing the emitted alternating light beam from the light source module to thereby generate an alternating pyroelectric signal; a first sample-and-hold circuit, which is clocked by the first sampling signal generated by the trigger-signal generating unit, to sample each upper peak of the alternating pyroelectric signal from the pyroelectric sensor module and thereby generate a first sampled signal; a second sample-and-hold circuit, which is clocked by the second sampling signal generated by the trigger-signal generating unit, to sample each bottom peak of the alternating pyroelectric signal from the pyroelectric sensor module and thereby generate a second sampled signal; and a subtraction circuit for performing a subtraction operation on the first sampled signal generated by the first sample-and-hold circuit and the second sampled signal generated by the second sample-and-hold circuit to thereby obtain a difference signal; wherein the difference signal from the subtraction circuit is substantially a direct current (DC) output and serves as an output of the digitally-controlled pyroelectric signal sampling circuit.