The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 19, 1977
Filed:
Apr. 28, 1975
Barry Block, Los Altos Hills, CA (US);
Harry E Aine, Mountain View, CA (US);
Diax Corporation, Sunnyvale, CA (US);
Abstract
An infrared laser absorption spectrometer is disclosed wherein a pair of detector cells are disposed serially along the laser beam path. The laser beam is modulated to produce a modulation of the absorption by the sample materials in the two cells. Modulated absorption by the samples produces an acoustic wave in each cell which is detected by a suitable microphone and subtracted so as to produce a difference signal corresponding to the difference in infrared absorption between the two cells so that undesired background effects common to both cells are cancelled. A pressure controller, which is responsive to the pressure difference between the sample pressure in the two cells at a frequency substantially below the beam modulation frequency is employed for controlling the pressure differential. In one embodiment the pressure controller includes a compliant membrane partitioning the two cells so that the membrane may move so as to equalize the pressures. In a second embodiment, deflection of the diaphragm of a differential microphone coupled into both cells is employed to derive an output utilized to control either the flow through the cells and/or the volume of the respective cells to control the pressure difference between the cells.