Patent Application
20080030730
As shown in
Additionally second and third light sensors 40 and 42 can be provided. The light sensor 40 detects light scattered at an angle of about 90° while the sensor 42 detects back scattered light, i.e., light scattered at an angle greater that 90°. These sensors 40 and 42 can be photosensor arrays similar to the photosensor array 30.
The data acquisition and processing system 32 includes stored light intensity patterns of known concentrations of known contaminants. These light intensity patterns can be prepared and stored in the system 32 by the procedure of
The selection of a water sample generating source 26 is also not critical. Any commercially available droplet production source should be sufficient, if the droplets are of sufficient size to provide statistically significant measurements and the instrumentation has been properly calibrated. A sample vial or tube may also be substituted for a droplet production source. The vial or tube should be designed so that a continuous stream of liquid can flow in and out of the vial or tube. The vial or tube may also be designed so that the sample can be maintained as a static fluid.
The selection of the light trap 24 is not critical. The light trap may be any commercially available suitable device or an equivalent device receiving and absorbing light to prevent non-scattered light from the light beam 22 from reaching the sensor array 30
The selection of the three photo sensor arrays 30, 40 and 42 is critical. The first photo sensor array 30 must have a sufficient number of segments to discriminate intensity measurements as a function of angular position at increments of 0.10° or less. In one embodiment the sensor array 30 is a commercial linear sensor device having 1024 elements with an aspect ratio of 100:1.
The second sensor 40 and the third sensor 42 may be identical to the first sensor. The sensors 40 and 42 can be selected from any commercially available sensor capable of taking at least one light intensity measurement. Alternatively, the sensors 30, 40 and 42 can be components of a sensor array which may or may not include a combination of the first sensor array 30, the second sensor 40, and/or the third sensor 42.
The selection of a data acquisition and processing system 32 is also not critical. The data acquisition 32 must be sufficiently fast to obtain and process at least a sufficient number of intensity measurements from the forward sensor array 30 at a rate that will provide near-real time measurements. In one embodiment the data acquisition and processing system comprises a 16 bit, 100 k. Hz analog-to-digital converter data acquisition board connected to a computer system, which will take the measurements and provide output to the water treatment facility through the connector 34. The system 32 includes a program with the procedure shown in
The type of connector 34 is also not critical. The connector connects the water treatment system 36 to the data acquisition and processing system 32. The water treatment system must be able to accept output from the data acquisition system, and change the water treatment conditions accordingly.
The operation of the system begins with the operation of the water sample generator 26 producing a water sample, such as a stream of droplets 28, a continuous water stream (not shown) or vials (not shown), suitable for measuring contaminants in the water source. The sample passes between the light source 20 and the light trap 24. A beam of light 22 from the light source 20 passes through the sample 28 from the light source to the light trap 24. Depending upon contaminants in the sample, the beam of light is scattered into the sensor arrays 30, 40 and 42. The light trap absorbs the light which is not reflected or refracted. The light strikes the sensors causing the sensors to convert the light into an electrical signal.
As shown in
The data acquisition system reads the voltages from the sensor arrays and stores the values of the voltages in its memory as an intensity patterns of the sample. The stored pattern of intensities is compared to the stored intensity patterns of a known calibration standards. The voltages may also be converted into the standard output signals for turbidimeters, particle counters, cytometers, or multi-angle light scattering measurement systems.
In the particle counter mode, the light source strikes the droplet and is scattered into the forward sensor array 30. The intensity of the light is measured at various angles and the measurements are collected by the data acquisition system 32. The pattern of light intensity as measured at various angles is compared to calibrated patterns for specific contaminants and pathogens. By comparing the patterns, the data acquisition system 32 can identify the contaminant. The data acquisition system can then provide that data to the water treatment system through the connector. The water treatment system can adjust the treatment process to eliminate or reduce the concentration of the contaminant.
In the turbidimeter mode, the light source strikes the droplet and is scattered into the forward sensor array 30. The intensity is measured by the sensors in the array and then sent to the data acquisition system. The intensity of the light that strikes the sensor array may be summed over the entire range of the array. The intensity may also be summed over specific ranges that conform to certain turbidimeter standards. The intensity should correspond to specific contaminant concentration ranges. The data may be used to adjust the water treatment process. The use of the forward sensor array allows turbidity measurements at low levels of turbidity.
The system may also operate as a turbidimeter by collecting intensity measurements at different angles. By collecting data at an angle perpendicular to the path of the light source, the system corresponds to the standard imposed by ISO. By collecting back scattered light, i.e., light reflected at angles greater than 90°, the system can collect data in high turbidity conditions.
In the cytometer mode the droplet generator 26 generates a droplet 28. Light from the light source passes through the droplet. The light that passes through the droplet but is scattered at different angles represents the intensity distribution that is used to provide the desired information. The excess light is caught in the light trap 24. The light scattered at different angles strikes individual detectors. The detectors provide a voltage reading based upon the intensity of the light striking the detector. The voltage readings can be used to calculate the ratio of the intensity at one standard cytometer sensor position to the intensity at the other standard cytometer position. In such a manner, the output is identical to standard cytometer output.
In the multi-angle mode, the droplet generator 26 generates a droplet 28. Light from the light source passes through the droplet. The light that passes through the droplet but is directed at different angles via scattering represents the light that is used to provide the desired information. The excess light is caught in the light trap 24. The light that is scattered at different angles strikes individual detectors or sensors in the sensor arrays 30, 40 and 42. The detectors provide voltage readings based upon the intensity of the light striking the detectors. The voltage readings are measured by the data acquisition and processing system 32, so that the light intensity as a function of angle can be determined. The high resolution of the system (angle increments less than 0.1°) allows the determination of the identity of microorganisms in the sample.
The output of all four modes can be compared to known standards for known contaminants. This comparison allows the system to determine the concentration of known contaminants. The standards may be obtained by passing water contaminated with known concentrations of contaminants through the system and taking measurements of the contaminant level. The measurements may also be stored in the, memory of the data acquisition system and recalled at the calibration time. The output may take the form of one specific voltage to reflect the degree of contamination, a simple on/off voltage output to reflect acceptable or unacceptable levels of contamination, or in the form of multiple voltages to reflect the different measurements of the different modes of operation. The output signal may also be in digital or analog form.
In one embodiment a water droplet sample flows from a source into a vial. A HeNe laser generates a light beam with a wavelength of 632.8 nm. The light beam passes through the sample in the vial. When the sample contains contaminants, scattered light strikes the sensor array 30. Excess light is trapped in a light trap. In this embodiment, the sensor array 30 is a monolithic self scanning linear photo diode optimized for application in spectroscopy. The sensor array comprises 1024 elements with an aspect ratio of 100:1. Thus light beam intensity of forward scattered light is measured at a plurality of positions on the sensor array elements at angles less than 90° relative to the beam 22. Each sensor array element generates a voltage signal proportional to the intensity of light impinging on the element. The sensor array 40 generates at least one proportional voltage signal at a position perpendicular to the beam 22; this signal allows the apparatus to obtain a measurement that is equivalent to a turbidimeter measurement. The sensor array 42 generates a least one proportional voltage signal from back scattered light at an angle less than 90° from the beam 22; this signal allows the apparatus to obtain a measurement that is equivalent to a cytometer measurement. The data acquisition and processing system 32 converts the voltage measurements into digital signals and stores the measurements in a data structure with voltages stored in positions corresponding to angular positions. A processor within the system compares the voltages to voltages for known or stored standards that correspond to the concentration of contaminants or specific optical response patterns.
As shown in
While the above description contains many specifics, these should not be construed as limitations on the scope of the inventions, but as an exemplification of one preferred embodiment thereof. Many other variations are possible. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their legal equivalents.
