Discrete frequency colorimeter

• US 3,994,590 A
• Filed: 04/29/1975
• Issued: 11/30/1976
• Est. Priority Date: 04/29/1975
• Status: Expired due to Term

• Current Assignee: Raymond G. Di Martini, Stephen Chopyak
• Original Assignee: Raymond G. Di Martini, Stephen Chopyak
• Inventors: Di Martini, Raymond G., Chopyak, Stephen
• Primary Examiner(s): McGraw, Vincent P.
• Application Number:
  US05/572,928
• Time in Patent Office: 581 Days
• Field of Search: 356/73, 356/180, 356/181, 356/184, 356/190, 356/201, 356/205, 356/178, 250/552, 250/553, 250/573, 250/565
• US Class Current: 356/407
• CPC Class Codes: G01J 2001/4242 Modulated light, e.g. for synchronizing source and detector circuit
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0272 Handheld
• CPC Class Codes: G01J 3/10 Arrangements of light sources specially adapted for spectrometry or colorimetry
• CPC Class Codes: G01N 21/255 Details, e.g. use of specially adapted sources, lighting or optical systems

Abstract

A compact and portable colorimeter, including an integrally-formed probe having both a solid-state source of relatively monochromatic light and an optically coupled photodetector mounted therein. A power oscillator gating means is connected to the light source for pulsing same, to provide a chopped optical input. A demodulating circuit receives the output from the photodetector. The power oscillator gate signal is provided to a synchronous detector at the demodulating circuit, to synchronize detection with the chopping. The output from the demodulator is converted to a signal and read-out indicative of the concentration of that component of the sample which has absorbance characteristics correlated with the wavelength of the monochromatic source. The light source may comprise an LED, a laser diode or the like; and a tunable diode or array of LED'"'"'s may also be used so as to enable a plurality of discrete frequency outputs, which outputs correlate with a plurality of chemical species the concentrations of which are to be determined.

Claims

1. A compact and portable colorimeter comprising in combination:

a casing including an integrally-formed probe portion;

a pulsable solid state source of relatively monochromatic light mounted in said probe;

photodetector means at said probe, said detector means being optically coupled to said light source through a sample receiving path at said probe;

a power oscillator gating means connected to said light source for pulsing same to thereby provide a chopped optical input during a colorimetric measurement of said sample;

a demodulating circuit including synchronous detector means, being connected to receive the output from said photodetector means, said power oscillator gate signal being provided to said demodulator means to synchronize the rate of detection with the rate of said chopping;

a difference amplifier connected to receive the output from said demodulator circuit means as one input thereto;

the other input to said difference amplifier being provided from said power oscillator gating means, and the levels of said inputs being initially adjustable for balance at said difference amplifier in the presence of a reference sample, whereby the output from said difference amplifier is linearly related to the concentration of the chemical component to be measured in said samples; and

measurement and read-out means for converting the output from said difference amplifier to a signal and read-out indicative of at least one of either the absorbance or transmission of said sample with respect to the wavelength of said monochromatic light.

2. Apparatus in accordance with claim 1, wherein said measurement and read-out means converts the output from said demodulator circuit to a signal and read-out indicative of the concentration of that component of said sample having absorbance characteristics correlated with the wavelength of said monochromatic light.

3. Apparatus in accordance with claim 1, wherein said light source comprises a light emitting diode providing an optical output at a narrow wavelength range determinatively related to the absorption characteristics of the chemical component to be measured in said sample.

4. Apparatus in accordance with claim 1, wherein said light source comprises a diode laser providing an optical output at a narrow wavelength range determinatively related to the absorption characteristics of the chemical component to be measured in said sample.

5. Apparatus in accordance with claim 1, wherein said light source comprises a tunable diode, and wherein said colorimeter includes control circuit means for selectively varying the optical output from said diode to provide an optical output at a narrow range determinatively related to the absorption characteristics of the chemical component to be measured in said sample.

6. Apparatus in accordance with claim 1, including a plurality of discrete solid state light sources mounted at said probe;

each said source providing an optical output predominantly at a predetermined wavelength, whereby to provide a series of optical outputs at differing discrete wavelengths.

7. Apparatus in accordance with claim 6, including at said probe a plurality of photodetectors, each of said photodetectors being optically coupled to one each of said light sources.

8. Apparatus in accordance with claim 6, wherein said light sources are light-emitting diodes.