MULTIPLE WAVELENGTH SPECTROMETER

• US 3,877,812 A
• Filed: 01/31/1973
• Issued: 04/15/1975
• Est. Priority Date: 01/31/1973
• Status: Expired due to Term

• Current Assignee: The Foxboro Company (Schneider Electric SE)
• Original Assignee: Duane T. Thompson
• Inventors: Thompson, Duane T.
• Primary Examiner(s): Wibert, Ronald L.
• Assistant Examiner(s): Evans, F. L.
• Application Number:
  US05/328,240
• Time in Patent Office: 804 Days
• Field of Search: 356/51,83,97,100,186,188,205 250/226,233 350/273,274,315,318
• US Class Current: 356/418
• CPC Class Codes: G01J 2003/1213 Filters in general, e.g. dichroic, band
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0232 using shutters
• CPC Class Codes: G01N 21/314 with comparison of measurements at specific and non-specific wavelengths dual wavelength spectrometry G01J3/427

Abstract

There is disclosed a multiple wavelength infrared spectrometer. It includes an optical chopper and a pendulum-like filter carrier which inserts a plurality of filters sequentially into the radiation beam. Filter changes occur during an opaque period of the chopper and each filter remains in place for a predetermined number of radiation pulses. The radiation passes through the sample and onto a detector which produces an electrical signal. An electronic circuit operates upon the signal so produced to provide an output proportional to sample absorbance.

Claims

1. A multiple wavelength radiation analyzer which comprises:

means for detecting electromagnetic radiation from a radiation source;

a chopper intermediate said source and detecting means positioned to chop said radiation at a first frequency;

means for supporting a plurality of filters is close spatial relationship to said chopper; and

means driven by said chopper for positioning said supporting means to periodically, repetitively, and alternatively insert each of said filters into the path of said radiation between said source and detecting means for a preselected observation period greater than the chopping period and keeping each filter stationary during its respective observation period.

2. The analyzer of claim 1 wherein said supporting means comprises an oscillatory member having said filters thereon.

3. The analyzer of claim 1 wherein said chopper comprises a rotatable wheel having a plurality of opaque blades about its periphery.

4. The analyzer of claim 3 wherein said supporting means comprises an oscillatory member having said filters thereon;

and said positioning means comprises camming means driven by said wheel for positioning said oscillatory member in response to the rotational position of said wheel.

5. The analyzer of claim 4 wherein said wheel includes a substantially cup-shaped central portion having said blades extending radially outward from its rim portion.

6. The analyzer of claim 5 wherein said oscillatory member is a relatively thin flag supporting said filters in close spatial relationship to said blades.

7. The analyzer of claim 6 wherein said camming means are substantially enclosed within the cup-shaped portion of said wheel.

8. A multiple wavelength spectrometer which comprises:

a source of electromagnetic radiation;

means for directing said radiation to a sample to be analyzed;

means for detecting radiation leaving said sample;

a chopper intermediate said source and detecting means positioned to chop said radiation at a first frequency;

means for supporting a plurality of filters in close spatial relationship to said chopper; and

means driven by said chopper for positioning said supporting means to periodically, repetitively, and alternatively insert each of said filters into the path of said radiation between said source and detecting means for a preselected observation period greater than the chopping period and keeping each filter stationary driving its respective observation period.