Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Reexamination Certificate
1999-01-25
2002-03-12
Ham, Seungsook (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
C250S339030, C250S370060, C250S370150, C250S352000
Reexamination Certificate
active
06355930
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed generally to infrared optical instruments such as cameras and spectrometers, and particularly to such cameras and spectrometers as are able to obtain data at a high repetition rate. Infrared cameras and spectrometers capable of repeatedly obtaining data many times per second are desirable to provide detailed information in dynamic thermal situations such as occur in fires and high temperature manufacturing and processing operations.
Obtaining accurate information on the structure of fires is vital in a wide variety of situations. These include the detection of pollutant emissions and process variations requiring control in industrial applications as well as fire detection and safety situations. The structure of fires can be determined experimentally by measuring the gas velocity, gas species concentrations and temperatures in non-luminous flames. In luminous flames, additional information on the soot volume fraction or particulate concentrations is also important. In turbulent and transient flames, these measurements are preferably made simultaneously so that any cross-correlation between them can be computed as well.
Most combustion processes, whether accidental or in industrial burners, gas turbine engines or other machines that use hydrocarbon fuels, emit H
2
O and CO
2
as the major byproducts of combustion. In order to estimate flame or hot gas temperature, as well as gas species concentrations in reacting flows, it is critical to obtain simultaneously emission or absorption spectra from the fundamental H
2
O (2.7 &mgr;m) and CO
2
(4.4 &mgr;m) bands. In addition, most accidental and industrial flows are turbulent. Therefore, it is an object of the present invention to obtain the desired thermal spectra over very short periods of time to prevent blurring of the information. It is additionally desirable to provide a dynamic time-based set of data by obtaining the spectra repeatedly at a high interval rate reflecting the short period of time required to eliminate data blurring.
Likewise, many industrial processes involve the thermal treatment of flows of materials although not involving flames or combustion. The uniformity of the products of these industrial processes is often achieved through close control of the thermal characteristics. Thus, it is often desirable to continuously measure the thermal characteristics of a flow of materials, such as continuously extruded polymer films, to detect any thermal change that might portend an undesirable modification in the product. It is often desirable to measure the absorption of thermal energy over a large number of wavelengths at a sufficiently fast rate so as to enable on-line monitoring of a process, for example, in food and chemical processing lines. An object of the present invention is to have the thermal measurements preferably taken as often as possible over the smallest physical region possible so as to isolate any area of possible product change. At the same time, it is desirable to assay the entire product flow, not just discrete portions thereof, so that any changes in thermal characteristics can be identified as soon as they occur with some precision as to location. The thermal measurements are most desirably made by a thermal imaging camera having a data output that could possibly be used as an input for a closed loop process control.
The general design of cameras and spectrometers of the present invention that allow the above design objectives to be met are preferably constructed so as to be minimally affected by the vibration commonly present in industrial situations. The cameras and spectrometers of the present invention are preferably constructed using principally off-the-shelf elements that are competitively priced to maintain the cost of the overall instrument at a reasonable level.
The use of charge storing photon integration devices to form one and two-dimensional opto-electric arrays for converting infrared radiation into a suitable electronic signal is known, for example, from U.S. Pat. No. 5,166,755. The arrays generally consist of a specific arrangement of closely adjacent photosensitive sites, elements, or pixels situated on a monolithic substrate and directly coupled to electronic elements that permit interrogation of the array by scanning or polling. The information gathered by the interrogation can thereafter be processed and/or stored for contemporaneous or future readout or display. The arrays specifically take the form of CCDs, CIDs, DDPDs, SSPDs, or the like which include an integrated circuit which contains the electronics for sequentially scanning and reading the signal of each pixel in the array in a designated order. The electronic circuitry can also include elements for calibration, pixel spectral response correction, pixel uniformity corrections, background signal suppression, dark current suppression, time delay integration, and various other signal enhancements. The photosensitive pixels are disclosed to be constructed using materials specifically selected for infrared sensitivity such as PtSi, HgCdTe, or InSb, which are also disclosed to be used in U.S. Pat. No. 5,420,681. In some situations, electronic gating is employed in the place of a mechanical shutter to control the output signal in relation to the optical input. The arrays are specifically disclosed in relation to their use in infrared spectrometers, but other uses for similar devices are suggested such as in thermal imaging cameras. The systems are, however, unable to provide data over the whole range of from 1.2 to 5 &mgr;m at temperatures ranging from 210 to 293° K and require cooling with cryogenic liquids such as N
2
which is undesirable, particularly in the case of portable equipment.
The use of a sixty-four element PbS detector array in an infrared spectrometer is disclosed in U.S. Pat. No. 5,394,237. The array is coupled to a multiplexer which sequentially samples the signal level from each detector in the array to arrive at an output which is fed to an amplifier and then to an analog/digital converter. The digital output from the converter is controlled by a decoder coupled to receive signals from and send output signals to a standard parallel port of a personal computer for data storage, display, and/or processing. The spectrometer also includes a chopper-type shutter located at the entrance slit and controlled by control circuitry to open for a programmed number of read cycles of the decoder and to then close for another programmed number of read cycles. The output obtained during the closed shutter condition is employed to provide a dark current baseline measurement for correction of the light current measured signal. The entire spectra can be sampled at a rate of 80 Hz using this instrument. This instrument avoids the need to use liquid cryogenic cooling by adopting the more sensitive PbS array that is sensitive over the range of from 1.0 &mgr;m to 3.0 &mgr;m. However, the instrument as a whole fails to have a satisfactory useful spectral range due to the use of a grating that causes multiples of any given wavelength, e.g. 1.2 &mgr;m and 2.4 &mgr;m, to be dispersed to the same location on the array. Thus, the instrument is usefully functional only over a range of either from 1.0 &mgr;m to 2.0 &mgr;m, or from 1.5 &mgr;m to 3.0 &mgr;m. The upper limit of sensitivity of 3.0 &mgr;m also fails to include the hot CO
2
(4.4 &mgr;m) band which is very desirable in any analysis of combustion or other processes where hot CO
2
might be present. The sampling rate of 80 Hz is also less than desirable for use in high-speed industrial processes.
A near infrared analyzer employing a PbS array containing 256 pixels is disclosed in U.S. Pat. No. 5,422,483 for use in the range of from 1.0 &mgr;m to 2.6 &mgr;m. Alternatives for the PbS array are indicated to be made of InGaAs, InGaAsP, or PtSi. The array is used with a diffraction grating to analyze the infrared signature of, for example, processed foods for protein and water content. This analyzer omits not only the ho
Joseph Rony K.
Sivathanu Yudaya R.
Brinks Hofer Gilson & Lione
EN'URGA, Inc.
Ham Seungsook
Lee Shun
LandOfFree
Fast infrared linear image optical instruments does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fast infrared linear image optical instruments, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fast infrared linear image optical instruments will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2873406