Abstract:
An apparatus including a treated tape, an adjustable color source, a photodiode, and a processor is provided. The adjustable color source emits a first radiation toward the treated tape and operates at each of a plurality of different target wavelengths in a spectrum. The photodiode measures a second radiation reflected from the treated tape, and the processor analyzes measurements from the photodiode to determine a peak wavelength from the plurality of target wavelengths. Based on the peak wavelength, the processor determines a color and darkness of a color stain on the treated tape. Based on the determined color and darkness of the color stain, the processor also determines a type and concentration of gas to which the treated tape is exposed.

Description:
FIELD 
       [0001]    The present invention relates generally to gas detection. More particularly, the present invention relates to the detection of multiple types of gases using an adjustable color source and wavelength spectrum analysis. 
       BACKGROUND 
       [0002]    Gas detectors using treated tape to measure gases are known in the art. For example, some gas detectors using treated tape can measure a low concentration gas that comes into contact with the tape. 
         [0003]    In known gas detectors, the treated tape can include a chemically treated paper that reacts to a target gas flow delivered by, for example, a sample extraction system inside of the gas detector. The treated tape can react to the gas flow by changing color at the spot where the target gas contacts the tape. 
         [0004]    Different types of target gas can cause different color stains on the tape. Similarly, different concentrations of the target gas can alter the color stains on the tape. For example, a higher concentration of target gas can produce a darker stain. 
         [0005]    Known gas detectors using treated tape to measure the concentration of gases have incorporated an LED. The LED can have a calibrated intensity and can act as a source of light directed onto the tape. The reflection of light from the tape, and any stains thereon, can be measured by a photodiode. Thus, the darkness of the stain can be measured and the concentration of the target gas can be determined. 
         [0006]    Some known gas detectors using treated tape have only employed single wavelength LEDs. Single wavelength LED gas detectors have a high sensitivity to a single stain color caused by one particular type of gas. That is, single wavelength LED gas detectors are highly sensitive to detecting a single type of gas because the wavelength of the LED is calibrated for the particular tape color caused by the one particular type of gas. However, these single wavelength LED gas detectors have a reduced and/or minimal sensitivity to stain colors caused by other types of gas. Thus, single wavelength LED gas detectors have a poor sensitivity for detecting multiple types of gas. 
         [0007]    Therefore, there is a continuing, ongoing need for gas detectors that detect multiple types of gases. Preferably, these gas detectors use an adjustable color source and wavelength spectrum analysis. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a block diagram of a system in accordance with the present invention; and 
           [0009]      FIG. 2  is a flow diagram of a method in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    While this invention is susceptible of an embodiment in many different forms, there are shown in the drawings and will be described herein in detail specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention. It is not intended to limit the invention to the specific illustrated embodiments. 
         [0011]    Embodiments of the present invention include gas detectors that detect multiple types of gases using an adjustable color source and wavelength spectrum analysis. In embodiments of the present invention, the wavelength and intensity of the adjustable color source be adjusted, and light from the adjustable color source can be directed onto a treated tape. A photodiode can measure a reflection from the treated tape, and a microprocessor can analyze results from the photodiode to determine the type and concentration of gas exposed to the tape. 
         [0012]    For example, an adjustable color source in accordance with the present invention can include a RGB (Red-Green-Blue) LED. An adjustable color source in accordance with the present invention can also include a separate Red LED, Green LED, and Blue LED. 
         [0013]    The adjustable color source can be controlled by a microprocessor so that the net output radiation from the source is adjusted to a target wavelength. For example, the intensity of each of the Red, Green, and Blue elements in the source can be adjusted to achieve a net output radiation at the target wavelength. In embodiments of the present invention, the microprocessor can control the source to separately or simultaneously output radiation at each of a plurality of target wavelengths in a spectrum. 
         [0014]    In embodiments, of the present invention, the wavelength of the source output can be adjusted to target wavelengths along a spectrum, for example, the visible radiation spectrum. In some embodiments, the microprocessor can adjust the wavelength of the adjustable color source from approximately 450 nm to approximately 650 nm. After the wavelength of the source output has been adjusted to each of the target wavelengths along the desired color spectrum, the source completes a color scan. 
         [0015]    In accordance with the present invention, radiation from the adjustable color source can act as a source of light and be directed onto a treated tape. A photodiode can measure the reflected radiation from the tape and any stain thereon. In some embodiments, the photodiode can measure the wavelength and intensity of reflected radiation. 
         [0016]    The photodiode can measure the reflected radiation while the wavelength of the source is adjusted along the spectrum. Thus, the photodiode can obtain a plurality of measurements corresponding to plurality of source output wavelengths along the spectrum. 
         [0017]    When the microprocessor receives measurements from the photodiode, the microprocessor can perform a spectrum scan analysis to determine the color of the stain on the tape as well as the darkness of the color stain. Based on this determination, the microprocessor can determine the type of gas to which the treated tape has been exposed. In some embodiments, the microprocessor can also determine the concentration of the gas to which the tape has been exposed. Accordingly, systems and methods of the present invention can detect the presence of different types of gases without losing sensitivity to any one particular type of gas. 
         [0018]    To determine the type of gas to which the treated tape has been exposed, systems and methods of the present invention can determine which source wavelength in the spectrum has the highest sensitivity to the tape and any color stain thereon. In some embodiments, the concentration of the gas to which the tape has been exposed can also be determined by determining which source wavelength has the highest sensitivity. 
         [0019]    To determine the source wavelength with the highest sensitivity, systems and methods in accordance with the present invention can perform a data analysis on the measurements from the photodiode. For example, in some embodiments of the present invention, systems and methods can perform a Fast Fourier Transform (FFT) on the measurements from the photodiode in the frequency domain. The result of the FFT can be indicative of the source wavelength with the highest response to the color stain that was caused by gas exposure. 
         [0020]    Once the wavelength with the highest sensitivity is determined, systems and methods of the present invention can identify a corresponding color and darkness of the stain on the treated tape. Then, systems and methods of the present invention can determine the type and concentration of gas to which the tape was exposed. For example, systems and methods of the present invention can access a cross-reference table to identify, based on the identified wavelength, the relevant color and darkness of the stain and the relevant type and concentration of the gas that caused the stain. 
         [0021]    In embodiments in which the adjustable color source includes a RGB LED, the wavelength of the RGB LED output can be adjusted by controlling the wavelength of each of the Red, Green, and Blue elements. For example, the current flow through each of the Red, Green, and Blue junctions can be adjusted to alter the intensity of each element. The net output of the RGB LED can be altered when the wavelength of the three junctions diffuse. 
         [0022]    Systems and methods in accordance with the present invention can verify that the actual output of the adjustable color source is consistent with the target output of the source. That is, systems and methods can verify that the actual wavelength and intensity of radiation emitted by the source are consistent with the target wavelength and intensity output. For example, in some embodiments, the target wavelength output can be compared to the driven current at the LED using an optical parameter stored in the microprocessor. In some embodiments, a color sensor can measure the actual Red, Green, and Blue optical output of the source, and systems and methods can calculate the mixed wavelength and intensity of the source. 
         [0023]    In some embodiments, the actual output of the source can be verified by measuring the current and voltage drop for each of the Red, Green, and Blue elements. Then, the radiation actually emitted from the source can be measured, and the wavelength and intensity of the actual source output can be measured. 
         [0024]    When the actual output is not consistent with the target output, systems and methods in accordance with the present invention can adjust the intensity of each of the Red, Green, and Blue elements. For example, systems and methods in accordance with the present invention can dim the output of any of the Red, Green, or Blue elements to dim the output of the source. 
         [0025]    In some embodiments, the tolerance on the optical performance of the source can be reduced. For example, the temperature at the source can be measured, and the temperature drift on the optical output can be compensated by the microprocessor. 
         [0026]    In some embodiments, systems and methods of the present invention can use a white color source in lieu of an adjustable color source. In these embodiments, systems and methods can employ adjustable color detection using, for example, a color filter, or a camera. 
         [0027]      FIG. 1  is a block diagram of a system  100  in accordance with the present invention. As seen in  FIG. 1 , the system  100  can include a microprocessor  110 , an adjustable color source  120 , a color sensor  130 , a treated tape  140 , and a photodiode  150 . In some embodiments of the present invention, the adjustable color source  120  can include a RGB LED. In some embodiments of the present invention, any or some of the microprocessor  110 , adjustable color source  120 , color sensor  130 , treated tape  140 , and photodiode  150  can be housed in a housing  160 . 
         [0028]    The microprocessor  110  can include executable control software  112  stored on a non-transitory computer readable medium as would be understood by one of ordinary skill in the art. The microprocessor  110  can also include a memory  114 . In some embodiments, the memory  114  can be an internal database, and in some embodiments, the memory  114  can be external database that can be accessed by the microprocessor  110 . 
         [0029]    The microprocessor  110  can control the adjustable color source  120  to adjust the wavelength of the source  120  along a spectrum. That is, the microprocessor  110  can adjust the source  120  so that the source outputs radiation at a plurality of target wavelengths in the spectrum. In some embodiments, the microprocessor  110  can adjust the wavelength of the source  120  within the visible light spectrum. In some embodiments, the microprocessor  110  can output radiation at different wavelengths sequentially or simultaneously. 
         [0030]    The color sensor  130  can receive and measure radiation emitted by the source  120 . The color sensor  130  can then transmit measurements related to the received radiation to the microprocessor  110 , and the microprocessor can determine whether wavelength of the radiation actually output by the source  120  is consistent with the target wavelength of the source. When the target wavelength and the actual output wavelength are not consistent, the microprocessor can adjust the source  120  until consistency is achieved. 
         [0031]    The treated tape  140  can be exposed to gas. For example, the treated tape  140  can be exposed to ambient air, or the treated tape can be exposed to air flow delivered by an extraction system. It is to be understood that the method in which the tape  140  is exposed to air and gas is not a limitation of the present invention. 
         [0032]    When the treated tape  140  is exposed to air, gases in the air can cause a stain on the tape  140 . Different gases can cause different color stains, and different concentrations of gas can cause different levels of stain darkness. 
         [0033]    Radiation emitted by the source can be directed onto the treated tape  140 , and radiation reflected by the tape  140  can be measured by the photodiode  150 . Radiation reflected by any color stains on the tape  140  can also be measured by the photodiode  150 . Thus, the photodiode  150  can measure any radiation reflected by the tape  140  and detect any color stains on the tape  140  regardless of stain color or darkness. 
         [0034]    Measurements obtained by the photodiode  150  can be transmitted to the microprocessor  110 , and the microprocessor  110  can analyze these measurements to determine the type and concentration of gas to which the tape  140  has been exposed. 
         [0035]      FIG. 2  is a flow diagram of a method  200  in accordance with the present invention. In embodiments of the present invention, a microprocessor, for example, the microprocessor  110  shown in  FIG. 1  can execute the method  200 . 
         [0036]    The method  200  can determine if a color scan has been completed as in  210 . In accordance with the present invention, a color scan is completed when a source has output radiation at each of the target wavelengths within a spectrum. 
         [0037]    If the color scan has not been completed, then the next target color wavelength and intensity can be selected as in  215 . Then, the R/G/B (Red/Green/Blue) element intensity can be adjusted as in  220  to adjust the output wavelength of the source to the target wavelength and intensity. After these adjustments, the R/G/B element current and voltage can be measured as in  225 . The R/G/B light intensity can be captured as in  230 , and the actual color wavelength and intensity can be calculated as in  235 . 
         [0038]    The method  200  can determine if the output color is consistent with the target color as in  240 . If not, then the method can again adjust the R/G/B element intensity as in  220 , measure the R/G/B element current and voltage as in  225 , capture the R/G/B light intensity as in  230 , and calculate the actual color wavelength and intensity as in  235 . 
         [0039]    When the output color is consistent with the target color as determined in  240 , the output from the photodiode can be measured as in  245 . Then, the method  200  can again determine if the color scan is complete as in  210 . 
         [0040]    When color scan is complete as determined in  210 , the method  200  can perform a data analysis as in  250 . The most sensitive wavelength can be determined as in  255 , and the stain color on the treated tape can be determined as in  260 . Finally, the gas family and the concentration of the gas can be determined, as in  265 . 
         [0041]    Although a few embodiments have been described in detail above, other modifications are possible. For example, the logic flows depicted in the figures do not require the particular order shown, or sequential order, to achieve desirable results. Other steps may be provided, or steps may be eliminated, from the described flows, and other components may be added to, or removed from, the described systems. Other embodiments may be within the scope of the following claims. 
         [0042]    From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific system or method illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the spirit and scope of the claims.