US4412744A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Absolute spectrophotometer
Assignee: EIDP Inc
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Filing: 1981-06-01
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Granted: 1983-11-01
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Expires: 2001-06-01
Abstract
Abstract An improved spectrophotometer having a light source, a scanning type monochromator that provides light beams of different wavelengths over a light spectrum being scanned, and an object photometer for measuring the intensity of reflected light from an object being tested and generating an electrical signal proportional to the intensity of the light measured and connected to means for recording the signal as a function of wavelength measured, the improvement used therewith comprising: (a) a beam splitter that divides the beam exiting from the monochromator into first and second light beams, whereby the first beam is incident upon the object; (b) a reference photometer that measures the flux of the second light beam and generates an output electrical signal proportional to the intensity of the light measured; and (c) a light source control, connecting the reference photometer and the light source, which receives the electrical signal from the reference photometer and generates a feedback electrical signal to adjust the intensity of the light source to maintain the reference photometer output electrical signal level constant across the light spectrum that is being scanned. The spectrophotometer is useful for determining standard color values for coatings on substrates or for any colored surface.
Inventors
- 👤 Jerald D. Lee
- 👤 Charles D. Reilly
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 06:39
CPC Classifications
G; G01; G01J; G01J3/00; G01J3/28; G01J3/42
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
235 words
In a spectrophotometer having a light source, a scanning type monochromator having an entrance slit and an exit slit for a light beam from the light source and containing a light dispersing or selection element and a wavelength drive mechanism to provide light beams of different wavelengths over a light spectrum constantly being scanned, beam-shaping optics at the exit slit of said monochromator and an object photometer for measuring the intensity of reflected or transmitted light from an object being tested and generating an electrical signal proportional to the intensity of the light measured and electrically connected to means for recording said electrical signal as a function of wavelength measured, the improvement used therewith comprising: (a) a beam splitter, positioned between said beam-shaping optics and said object, for dividing the beam exiting from the monochromator into first and second light beams, whereby the first beam is incident upon the object; (b) a reference photometer measuring the flux of the second light beam and generating an output electrical signal proportional to the intensity of the light measured; and (c) a light source control, connecting said reference photometer with said light source, which receives the electrical signal from the reference photometer and generates a feedback electrical signal to adjust the intensity of the light source by means of a proportional/integral controller to maintain the reference photometer output electrical signal level constant across the light spectrum being scanned.
Claim 2
Dependent Claim
235 words
In a spectrophotometer having a light source, a scanning type monochromator having an entrance slit and an exit slit for a light beam from the light source and containing a light dispersing or selection element and a wavelength drive mechanism to provide light beams of different wavelengths over a light spectrum constantly being scanned, beam-shaping optics at the exit slit of said monochromator and an object photometer for measuring the intensity of reflected or transmitted light from an object being tested and generating an electrical signal proportional to the intensity of the light measured and electrically connected to means for recording said electrical signal as a function of wavelength measured, the improvement used therewith comprising: (a) a beam splitter, positioned between said beam-shaping optics and said object, for dividing the beam exiting from the monochromator into first and second light beams, whereby the first beam is incident upon the object; (b) a reference photometer measuring the flux of the second light beam and generating an output electrical signal proportional to the intensity of the light measured; and (c) a light source control, connecting said reference photometer with said light source, which receives the electrical signal from the reference photometer and generates a feedback electrical signal to adjust the intensity of the light source by means of a proportional/integral controller to maintain the reference photometer output electrical signal level constant across the light spectrum being scanned.
Claim 3
Dependent Claim
39 words
The spectrophotometer of claim 1 in which the electrical signal from the object photometer and reference photometer are separately amplified by two-stage amplifiers in which the voltage level at the output of the first stage is at virtual ground.
Claim 4
Dependent Claim
19 words
The spectrophotometer of claim 1 in which the object photometer and the reference photometer have similar spectral response characteristics.
Claim 5
Dependent Claim
40 words
The spectrophotometer of claim 1 in which the recording means comprise a voltage to frequency converter and said converter is electrically connected to an internal processor which is connected to a computer to provide a readout in standard color values.
Claim 6
Dependent Claim
30 words
The spectrophotometer of claim 4 in which the monochromator is a double-grating type monochromator being continuously driven and wherein measurements are taken at different wavelengths selected by the internal processor.
Claim 7
Dependent Claim
21 words
The spectrophotometer of claim 2 in which the feedback resistance of the two-stage amplifier for the object photometer is electrically guarded.
Claim 8
Dependent Claim
16 words
The spectrophotometer of claim 3 in which the object photometer and reference photometer comprise vacuum diodes.
Claim 9
Dependent Claim
21 words
The spectrophotometer of claim 1 in which the object photometer signal is measured at wavelength intervals provided by the shaft encoder.
Claim 10
Dependent Claim
14 words
The spectrophotometer of claim 1 in which the recording means comprises an A/D converter.
Claim 11
Dependent Claim
29 words
The spectrophotometer of claim 1 in which the recording means comprises a voltage to frequency converter electrically connected to a microprocessor which provides a readout in standard color values.
References Cited (Backward Citations)
US3245305A
Cited
US3506358A
Cited
US3561872A
Cited
US3431054A
Cited
US3646331A
Cited
US3806258A
Cited
US3874799A
Cited
US4176957A
Cited
US4093991A
Cited
US4227811A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-10-31 | 1987-05-02 | 1987-11-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-10-31 | 1991-05-02 | 1991-11-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-10-31 | 1995-05-02 | 1995-11-01 | $7700.00 | Window Closed / Lapsed |