Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer
Reexamination Certificate
2000-11-30
2004-03-30
Evans, F. L. (Department: 2877)
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrometer
C356S333000, C356S334000
Reexamination Certificate
active
06714298
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The instant invention most generally relates to spectrometers and spectral instruments. Particularly this invention relates to the manipulating and the directing of electromagnetic beams, preferably within the optical spectrum. More particularly, using appropriate optical elements, a plurality of non-interfering beams paths are created and each of which beams are controlled, directed as to the paths, and shaped, dispersed, diffracted and otherwise manipulated. The manipulation, directing, redirecting, diffracting, frequency selection and the like, accomplished to each of the beams of the plurality of beams is accomplished by some of the same elements. More particularly, there are two beams, a first or an in beam and a second or an out beam going in substantially opposing directions and passing through the same control, manipulation and direction elements concurrently and without interference. One beam manipulating element is a means for diffraction which diffracts or spatially separates the wavelengths within the spectrum of each of the beams concurrently and without interference with gains in the discrimination of the wavelength from the spectrum. The preferred means for diffraction is a concave spherical shaped grating with a specially configured hyperbolic shaped holographic grating surface designed to diffract and reflect the beam off of the optical axis of the grating structure. Even more particularly, the invention is a spectral instrument which combines the functions of several optical instruments usually used separately in spectrometry measurements. The instrument may have any combination of elements such as means for coupling a beam to be measured into the instrument, a monochromator which monochromator preferably has the dual and non-interfering optical beam paths, means for scanning the optical spectrum, such as a motor and drive mechanism which causes the means for diffracting to move through an arc and consequently discriminate a particular set of wavelengths, means for sorting out harmonics or orders of the monochromatic beam, such as filters, means for chopping or modulating the beam being measured, means for detection of the selected frequency/wavelength and means for amplification of the power level of the detected wavelength. Most particularly, the invention is a spectral system which includes the spectral instrument and which may have at least a power module and one or a combination of such as a means for remotely controlling the scanning, the filtering/sorting functions and the control of the power to the instrument. The instrument may preferably have a housing or casing, within which the optical elements of the instrument are housed, which housing protects the contents from changes in or unwanted characteristics in ambient conditions including spatial orientation, atmosphere and mechanical shock. The operation of the preferred system and the instrument requires no adjustments or manipulations by an operator or user. Scanning, order sorting and the measured output of the instrument are all controllable and available to the user from a PC (Personal Computer). Access to the instrument, using the system may be by remote connection such as by telephone lines via a modem or by any form of dedicated communication with the instrument.
2. Description of Related Art
A spectrometer is an instrument which is used in the analysis of the characteristics of electromagnetic energy over a certain identified spectrum or frequency distribution. The frequencies normally considered to be in the spectrum have wavelengths from as long as 10,000 nanometers (nm) to as short as 100 nm all of which frequencies are within the spectrum of the optical portion of the electromagnetic spectrum. The instrument may be used for any combination of functions such as observing, resolving, recording and amplitude measuring of frequency distribution and the amplitudes or power levels of the various frequencies or wavelengths which make up the spectra of the observed optical spectrum. A spectroradiometer is a spectrometer that is more specifically equipped with scales for measuring the positions of spectral lines of radiation and the level of energy of each of the wavelengths which relate to the spectral lines. A spectrophotometer is used for measuring the intensity of a particular spectrum in comparison to the intensity of light from a standard spectral source to determine the concentration and the composition of the substance that emits or absorbs spectral lines of the spectrum.
Currently, a spectrometer that performs spectrometry, spectroradiometry, and spectrophotometry is a large, immobile device, not amenable to mobile applications. The current practice is to assemble individual components such as input optics, at least one monochromator, filters to eliminate unwanted harmonics or orders, detectors and amplifiers. That is, if one wishes to do a spectroradiometric measurement of a particular optical beam, the individual components are carefully selected and positioned in order to carry out the radiometric measurements. In addition, many of these currently-available devices do not have the resolution nor the precision to accomplish the many tasks for which a spectrometer could be useful. One common problem is inadequate stray light rejection. Stray light rejection, which is express as a “scatter figure”, is the ability of the system to measure only light of a specified wavelength and to ignore all other light. Other issues with currently-available spectrometers, which issues are considered to be of disadvantage or inconvenience, include complex operating procedures, frequent recalibration requirements, and the oxidation of the optics. Most spectroscopy systems which are reasonably priced and which are relatively easy to use do not provide for accurate and stable measurements. There are many polychromator systems that are reasonably affordable however, the scatter rejection is inadequate thereby making it difficult to obtain absolute measurements that represent true and accurate readings of the character of the spectrum. Purity (scatter) in the current technology often causes gross errors in the readings. In fact, the scatter figure for some current systems is not good enough for accurate measurements of modest signals from broadband sources. Other inexpensive systems fall short when it comes to high resolution, wide band coverage, small signal amplification, and order sorting.
U.S. Pat. No. 4,867,563 in class 356/328 discloses a silicon photodiode for receiving light: (1) having a bandwidth in the range of between 2 and 15 nm (nanometers) from a pivotable concave holographic diffraction grating within the wavelength range of between 250 and 1150 nm at a scanning rate in the range of 20 to 100 nm per second; (2) having stray light of high intensity and undesired frequencies and the shorter wavelength harmonics of the selected frequency range blocked by filters; and (3) having flux of at least 10 microwatts per square meter of diffuser plate for each nanometer of bandwidth. Automatic electrical zeroing is obtained by blocking all light at the beginning of each scan, obtaining an electrical drift-related signal and using the drift signal to adjust the measured signal during the scan. Several different sensing interfaces can be used, including a quartz, light fiber probe having at least a 50% packing density and a cone angle of at least 24 degrees. The data and the programming storage are at least 30 K bytes but the instrument uses relatively little power when the instrument is not scanning. The purpose of this invention defined in the '563 Patent is to provide sufficient sensitivity, spectral resolution and speed for environmental measurements in the field using a portable spectroradiometer.
U.S. Pat. No. 5,528,364 discloses a monochromator which employs a spherical mirror, a traveling plane mirror with simultaneous rotation, and a varied spacing plane gratin
Dishong George W.
Evans F. L.
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