WO2004051367A2

WO2004051367A2 - Systems and methods for shadowed image particle profiling and evaluation

Info

Publication number: WO2004051367A2
Application number: PCT/US2003/038610
Authority: WO
Inventors: Scott Samson; Lawrence Langebrake; James Patten; Chad Lembke
Original assignee: University Of South Florida
Priority date: 2002-12-04
Filing date: 2003-12-04
Publication date: 2004-06-17
Also published as: AU2003298902A1; WO2004051367A3; AU2003298902A8

Abstract

The systems and methods of the present invention provides for micro-particle analyzer that is capable of data reduction via a novel reduction circuit for improved resolution in identification and quantification of the particles. By virtue of using line scan or similar cameras (11, 12) the instant system (10) is capable of high resolution without as much interference as experienced with two-dimensional systems. The data reduction circuit (50) also enables the microscopic material to be analyzed and recorded with better adaptability to current computer storage systems.

Description

SYSTEMS AND METHODS FOR SHADOWED IMAGE PARTICLE PROFILING AND EVALUATION

GOVERNMENT SUPPORT This invention was supported in part by funds from the US Government, Department of the Navy, Grant No. N 00014-96-1-5020, and the US Government may therefore have certain rights to this invention.

FIELD OF THE INVENTION This invention relates to oceanographic imaging systems for capturing the images of microscopic particles. More specifically, the invention is directed to a high-speed digital line scan system for detection and identification of microscopic particles suspended in aqueous or gaseous medium using a high-resolution sampling system.

BACKGROUND OF THE INVENTION

Particulate matter in the ocean and other aqueous environments is derived from multiple sources. In the ocean, mostly flake-like particles dominate what is commonly referred to as marine snow. Marine aggregate particles also result from biological activities such as abandoned houses from gelatinous feeders, residual food from inefficient grazers, feeding webs from pteropods, mucus, and fecal pellets. Hidden among the assortment of marine snow particles are living zooplankton, fish larvae, eggs, long phytoplankton chains and other related biologic material. The varied origin of marine particles results in a very diverse set of shapes, sizes geometries and optical properties. These properties are not only molded by the biological and physical properties of the ocean but can affect them as well. The importance of marine particles in chemical processes has also been shown.

In order to unravel the intricacy of interaction between biological, chemical and physical processes in the ocean or other aqueous environment requires quantification, qualification and an understanding of distributions of marine particles as well as successful development of models of those environments. Many techniques for examining marine particles have been developed and experimented with over the past several decades. These techniques include both simple and complex methodologies, most of which are plagued with distinct disadvantages ranging from being massively labor intensive to being intrinsically error prone. Methods that have been traditionally used include water bottle sampling, human visual observation, underwater photography, remote cameras, in situ large volume pumps, holographic imaging and sediment traps. In general, results from these methods show high variation in the concentration and type and number generally from 10 to 500 per liter in surface waters, while only a few per liter are found in deeper waters. These, of course, also vary between fresh and salt-water environments.

Methodologies providing the best results were those using non-intrusive techniques. Non-intrusive methodologies use acoustic and optical means to preserve fragile particle structure thereby reducing error in qualification and quantification. In studies of oceanic ecosystems, it is very important to know the temporal variations and spatial distributions of zooplankton, which constitute secondary production in such ecosystems. To date, the abundance of zooplankton has been monitored through sampling with a plankton net. In this approach, a conventional microscope is used to count and identify preserved plankton species. However, in this technique fragile particles such as jellyfish and some of the marine snow for example, are destroyed in the net collection or preservation; hence there is a need for in situ optical recording techniques for accurate representation. Previous in situ recording methods have included underwater photography and camera-based video systems.

In order to accurately determine biomass and particle counts, it is desirable that the system used be capable of recording each particle only once. Unless the water velocity past the imaging system can be precisely controlled, particles recorded from two-dimensional (2- D) imaging arrays typically are either imaged multiple times or missed entirely, which introduces errors in the data. The resolution of a digital video camera is limited by the pixel count of its array. Analog tape recording or signal transfer systems further degrade the quality of images.

Both systems require an additional intermediate step of remotely digitizing the collected analog images before computer processing may be performed. Typically using reflective illumination techniques, these have the disadvantage of relatively low optical efficiency associated with collecting scattered light. High magnifications limit the depth of focus of these systems to a few millimeters. Holographic methods allow very high resolution imaging of a large volume of water and may be used to observe particle motion. However, holographic systems generally require bulky and expensive coherent laser illumination, precision optics, high-resolution single-use film, and a lab set-up for reconstructing and imaging the light fields using conventional optics, such as microscopes.

Computer examination of images can assist in identification and sizing of particles of interest. For speed and simplicity of processing, it is beneficial to have a system that is capable of generating in-focus quality digital data directly readable by a computer. Additionally, the volume of data generated by imaging instruments makes it imperative for development of automated particle recognition algorithms. Otherwise, users will spend as much time manually identifying particle images as they would identifying organisms under a microscope. To this effect, particle and image recognition software has been developed for plankton, but reported analysis of field data using these packages has been limited.

SUMMARY OF THE INVENTION The present invention relates to oceanographic imaging systems for capturing the images of microscopic particles. More specifically, the invention is directed to a high-speed digital line scan system for detection and identification of microscopic particles in aqueous environments using a high-resolution sampling system. The present invention is additionally applicable to particles suspended in other mediums, such as in gaseous environments. The sampling system provides a sample chamber adapted to temporarily contain a sample, a housing surrounding at least a portion of the sample chamber, an optical imaging system connected to the sampling chamber at least in part by the housing. The optical imaging system includes two sections that are arranged about the sampling chamber at a fixed angle, such as 90 degrees in the illustrated embodiment. Alternatively, the imaging system may be configured with a single section or multiple sections, as may be desired for a particular application. Each section has a light source generating a light beam that passes through the sample chamber and is received by a camera after passing through at least one optical lens. The light beams from the section intersect in the sampling chamber to create an orthogonal cross flow axis, providing for the imaging of each particle from two directions. By recording velocity information about the fluid flow in the sampling chamber the scale of the particle can be derived. The image data is compressed (or reduced in size) by a data manipulator circuit (also referred to herein as a data reduction circuit), and then the image data is transferred from the optical imaging system to a data store for further processing to identify the particles. By virtue of using line scan or similar cameras the present invention is capable of high resolution without as much interference as experienced with two-dimensional systems. The data reduction circuit also enables the microscopic material to be analyzed and recorded with better adaptability to current computer storage systems.

In accordance with an embodiment of the present invention, a system for analyzing microscopic particles suspended in a fluid or gaseous medium comprises a sample chamber adapted to temporarily contain a sample of the medium, an optical imaging system that is associated with the sample chamber and that generates image data from at least two different directions in response to variations in particles contained in the sample passing through the sample chamber, a data manipulation circuit that receives the image data and generates reduced quantity digital data based at least in part on the image data, and a data store that stores the reduced quantity digital data from the data manipulation circuit, h such a system, the optical imaging system may include an optical section for each direction of imaging, wherein at least two sections are substantially orthogonally aligned. In addition, the reduced quantity digital data can be determined utilizing time-averaged pixel value data.

In accordance with an aspect of the present invention, the optical imaging system may include a plurality of optical sections, at least one optical section including at least one optical source and at least one corresponding camera. In such a system, the optical imaging system may comprise a plurality of cameras, wherein the plurality of cameras defines a plurality of optical members, the members arranged at a fixed angle with respect to each other. The camera may be, for example, a line scan camera. In addition, the optical imaging system may further comprise a series of lenses disposed between the light source and the corresponding camera, and at least one lens may de-magnify light emitted from the light source before the light strikes the camera.

In accordance with another aspect of the present invention, the image data may be generating using back illumination. In addition, the system may further comprise circuitry adapted to quantify and identify particles in the sample based on the reduced quantity digital data. The system may further comprise a visual viewer in communication with the data store. In accordance with another embodiment of the present invention, a method of analyzing microscopic particles suspended in a fluid or gaseous medium comprises passing a sample of a medium through a sample chamber, generating image data in response to variations in particles contained in the sample passing through the sample chamber, the image data comprising data from at least two different directions, , and conveying the reduced image data to a data store. Such a method may further comprise the step of processing the reduced image data to provide quantitative and identification information about the particles in the fluid sample, and the step of conveying the sample through the chamber in a continuous flow. Another step may be collecting velocity data of the passing through the sample chamber for utilization in generating a scale image of a particle. In addition, the method may further comprise controlling the step of generating image data by a feedback mechanism with operator assistance capability, and the reduced quantity digital data can be determined utilizing time-averaged pixel value data.

In accordance with an embodiment of the present invention, a method for analyzing microscopic particles suspended in a fluid or gaseous medium comprises providing a sample chamber adapted to temporarily contain a sample of the medium, providing an optical imaging system that is associated with the sample chamber and that generates image data from at least two different directions in response to variations in particles contained in the sample passing through the sample chamber, providing a data manipulation circuit that receives the image data and generates reduced quantity digital data based at least in part on the image data, and providing a data store that stores the reduced quantity digital data from the data manipulation circuit. In addition, the reduced quantity digital data can be determined utilizing time-averaged pixel value data, and the image data can be generated utilizing back illumination.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic of the overall instrument in accordance with an embodiment of present invention.

FIG. 2 is a more detailed showing of one of the two optics systems in accordance with an embodiment of the present invention.

FIG. 3 shows an example of one image obtained by the instrument of the present invention.

FIG. 4 represents another image obtained by the instrument of the present invention. FIG. 5 is a third set of images obtained by the instrument of the present invention.

FIG. 6 is a fourth example of typical images obtained by the instrument of the present invention. FIG. 7 is a schematic representation of the data reduction circuitry of an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION The systems and methods of the present invention provide for an analyzer for particles in a fluid or gaseous medium, such as fluidic plankton or other micro-particles. The analyzer of the present invention has improved resolution in identification and quantification of the particles in the fluid due in part to data reduction via a reduction circuit. In addition, utilization of line scan or similar cameras in the disclosed configuration of the present invention enables high resolution. With reference to FIG. 1, the instrument 10 comprises two optical sections 11 and 12, which are located in housing 13 and are at substantially ninety degree angle with respect to each other. This duplication in the orthogonal cross flow axis allows imaging of each particle from two directions. With this geometry, the number of unidentifiable particles is reduced and it permits volumetric measurements to be made. Even though a ninety degree angle is depicted as the optimal angle, it is considered within the scope of the invention to orient the two optical systems at other angles with respect to each other to permit cross-sectional viewing of the sample chamber and the particles therein.

The housing 13 is made from any suitable material such as metals or engineering plastics as known to those of ordinary skill in the art. As shown, the housing 13 comprises six anodized aluminum pressure vessels with two 150 mm diameter cylindrical pressure vessels 14 containing the imaging system connected to two similar 100 mm diameter pressure vessels 15 containing laser or other appropriate optical source. The vessels 14 and 15 are fastened together with external clamps 18 and rods (not shown) defining a sample chamber 17. A specially designed optical interface member (not shown) serves to hold the vessels 14 and 15 in proper optical alignment with each other. As discussed earlier, this alignment is at a substantially ninety degree angle, but modifications of this angle are considered within the scope of the invention. A suitable power source 19 is also contained within the housing structure.

In addition to the four optical portions of the instrument and power source, the instant instrument also contains a digital data handling and storage system 51, housed in housing means 50. This electronics and software system allows for flexibility in configuration and operation and may also include optional real image or video screen viewing apparatus in addition to the capability of digitally storing information. In addition to data storage, the data handling and storage system 51 includes data synchronization electronics, a high-speed digital data storage mechanism and a Microsoft Windows™-based or equivalent processing and image-offload single board computer. These features are shown in FIG. 7. The entire instrument 10 is rigidly designed and is able to withstand rough handling without degradation in performance or optical alignment. Moreover, it is designed to prohibit ingress of fluid into the optical or electronic components.

Illustrative embodiments of the optical component systems 30 are shown in FIG. 2. The optics design is a balanced compromise of optical path length, depth of field and percentage coverage of the sampling tube. As shown, the optical pathway defines a specific geometry, however this geometry is dependent on the size of the overall instrument and the length and sensitivity of the optical resolution desired, so any other geometry is considered within the scope of ordinary skill in the art. Each of these systems consists of securing members 31a, 31b, 31c and 31d. These members, here depicted as rings, serve to secure the optical components to the housing 13. Since the external housing 13 illustrated in FIG. 1 is shown as generally cylindrical, the securing members 31 are designed to accommodate this geometry, but it is considered within the scope of the invention that other housing and securing shapes may be used. The securing numbers 31 are also able to be adjusted within the housing 13 by movement of their assembly in directions normal to the linear axis of the housing member. In addition, precise optical adjustments may be made by means of fine adjustment screws located within the securing means 31 themselves.

Contained within securing member 31a is the optical source means 32. In a preferred embodiment, a 3 mW, 635 nm diode laser, with diverging optic 32b, available from Power Technology, Inc. is used. This laser is only representative and other coherent and noncoherent optical sources as known to those of ordinary skill in the art may be substituted. The optical source means (also referred to herein as the light source) 32 is adjustably affixed to the housing 13 and can be moved in pitch, yaw and translation directions by virtue of a tilting member 33 to enable precise modifications of the beam direction to be made. A light beam 45 generated by the source then is deflected off a routing mirror 35 or other suitable deflecting means. The light beam 45 is then directed to a focusing lens 36. In a preferred embodiment of the invention, the distance between the light source 32 and this focusing lens 36 permits the light to be adjusted to a width of approximately 100 mm. The focusing lens 36 then collimates the beam into a sheet format. In the preferred embodiment a 280 mm focal length lens is used to form the beam into a 1 x 100 mm sheet format. Again, this may be modified by one of ordinary skill in the art depending on the optical properties desired. By the use of the mirror 35 the optical pathway is re-routed, without any loss of sensitivity enabling the total system to be of a more compact nature. The routing mirror 35 is adjustably affixed to the housing 13 and can be tilted by virtue of tilting member 35a to enable small modifications of the tilt angle to be made. Following the routing mirror 35 and collimating lens 36, the light path 45 then illuminates the sample chamber 43 area.

Before impinging on the routing mirror 35 and focusing lens 36, the light sheet may be optionally passed through a corrective lens 34. This lens serves to reduce the effect of mechanical vibration in the system on imaging performance by producing a thicker beam structure at a camera 41. In the preferred embodiment a plano-concave cylindrical lens is used, but any suitable lens which serves this purpose may be substituted.

The light sheet 45 passes through two sealed windows 37a and 37b (collectively referred to herein as windows 37) which define its path through the sample chamber 43. These windows 37 are thick optical windows made of any suitable material, such as acrylic or glass, that permits light transmission with minimal interference. The windows 37 are of a suitable thickness so that they are able to withstand pressure and handling conditions in underwater environments without possibility of failure and are mounted within the housing 13 with O-rings that seal the optical portions to prevent any fluid incursion. After passing through the sample chamber 43, the light is then directed onto two additional adjustable routing mirrors 38 and 39 before passing through an image focusing lens 40. Before entering the camera 41, the light sheet is passed through an imaging lens 40. This lens serves to sharply image particles within the sample chamber 43 onto the camera 41, with demagnification suitable to image substantially the entire sample chamber area onto the detecting portion of the camera. The lens is positioned coarsely and finely through the use of a securing member 31d and a translating lens mount 42. In the preferred embodiment a spherically-corrected doublet is used, but any suitable lens or lenses which serves the purpose of imaging with minimal aberrations may be substituted.

Because the method of imaging the objects in the sample chamber uses back- illumination, the system 10 of the instant invention has several advantages over the diffuse illumination typical of conventional diffuse illumination imaging schemes. The depth of field of this system is greater than that of other imaging schemes. Light passing through the sampling area and being imaged comes from within a narrow focused cone, thus providing a high f-number optical system. This high f-number provides a greater depth of field than that of a low f-system and back illumination maintains high light throughput. Conversely, with diffuse illumination, only a small percentage of the light created by the system would reach the active area of the camera, necessitating either more optical power or a lower f-number optical system. The semiconductor light source back-illumination system of the instant invention has the advantage of allowing lower power consumption, as less light is needed to illuminate the sample area. In the system 10, the resolution along the imaging line is fixed by the optics and number of camera pixels utilized. The resolution in the other direction is dependent on the water velocity and camera line scan rate. Because the particle flow past the underwater imaging system is unidirectional, the system 10, in its preferred embodiment, is configured with fast line scan cameras 41. Although other suitable camera or sensor systems may be used, line scan cameras are well suited for accurate particle counting in flowing applications when compared to other system including 2-dimensional array cameras. With the line scan camera, each section of the sampling volume 43 is imaged onto the imaging array once and only once, assuming non-turbulent flow characteristics are present. Conversely, a 2-D system offers the possibility of either missing particles or producing multiple images of them if they move more or less than a fixed distance between imaging frames. In the instant system, the independent duplication in the orthogonal cross flow axis permits imaging of each particle from two directions. This reduces the number of unidentifiable particles, and allows volumetric measurements to be made. Transient particle shadow images are captured in two directions to permit maximal characterization and 3-D reconstruction of sampled particles. Examples of the images obtained by the instant invention are shown in FIGs. 3-6. This imaging is facilitated by use of two high-speed line scan cameras, shown in FIG.

2 as camera 41. The two cameras may have the same resolution or may also be of differing resolutions. In the preferred embodiment a system containing two 4096 pixel cameras is used, such as the Dalsa PIRANHA™ series cameras. Each of these digital line scan cameras outputs approximately 90 million pixels per second with an 8-bit digital intensity resolution. In order to produce accurately scaled images, the particle velocity is required in the present embodiment. An additional instrument is used in-line to measure water velocity. Any suitable instrument capable of accurately measuring flow may be used, such as a GF- Signet paddlewheel flowmeter. Preferably, mechanical-type flowmeters should be installed downstream of the imaging area to prevent disruption of the particles being imaged. In order to reduce the data rate and post-processing requirements, a real-time threshold on the image data is performed within field programmable gate array (FPGA) based processing hardware. The threshold is set remotely by the user in a computer application, and is relayed to the hardware via an Ethernet data network link. Pixels darker than the threshold value are marked as black and those lighter are marked white. When the water contains no particles, all pixels are white.

The data network allows other parameters to be set, including data recording start and stop, and power down of inactive portions of the system to conserve energy. Information about the water flow rate can be relayed back to the user via the data network to facilitate separately altering the flow of water through the instrument. The thresholded image data from the two camera modules is combined into a synchronous parallel data stream within the data handling and storage system 51. Both cameras are synchronized so that each line contains information about an identical volume of water. The parallel data are buffered and sent to a Digital Data Recorder (DDR) or other analogous recorder, as known to one of ordinary skill in the art. The DDR stores clocked digital data onto single or multiple hard disks, at up to 23 million bytes/second. In addition to recording the data, the user may also preview images in near real time via embedded software and the data network connection. For example, in test mode, an image may be displayed on a multisync monitor.

In order to enable the data generated by the cameras 41, a specialized data handling and storage system 51 transforms the data into quantities that are compatible and convenient for the computer system. Because of the large amount of data generated by the pictorial imaging, prior art systems generally were incapable of being able to process the information generated by the camera systems. The present invention solves this problem by use of a novel data handling and storage system 51.

Referring now to FIG. 7, the data handling and storage system 51 has several functions. This circuit receives the digital camera data, converts the pixel information to a reduced-quantity digital stream, reformats the pixel locations to facilitate software reconstruction of images, and then digitally records the information for later evaluation. In order to do this effectively and quickly, the amount of information generated by the cameras is reduced using an electronic circuit as opposed to a software program. The receiving portion 52 of the circuitry receives the initial data output from the cameras 41 and conveys this information into the initial data reduction section 53. A monitoring circuit 54 is included to compare the instant pixel values to their average to compensate for any constant abnormalities in the illumination intensity. The data is then processed by a threshold comparison section 55 before being conveyed to a storage unit 56. The receiving portion 52 of the data handling and storage system 51 receives the data sent by the cameras in a time-serialized fashion. The camera data is sent to the digital processing circuitry contained in the data handling and storage system 51 using serialized differential signaling, so as to avoid erroneous transmission due to common-mode electromagnetic noise, and to minimize the number of electronic wires. The serialization at the camera, and deserialization of the data handling and storage system may be performed by using the Camera Link or Flat Link™ (Texas Instruments) standard or any other suitable standard as known to those of skill in the art. Serialization is the process of sending multiple synchronous data bits per unit of time in a multiplexed fashion, such that each of the large number of data bits are each sent over a reduced number of conductors. Similarly, deserialization is the conversion of serialized data into its original synchronous parallel form. Cameras which support the Camera Link standard may be used in the present system, or additional conversion hardware may be used to convert parallel output camera data into the serialized form. The digital processing circuitry contained in the data handling and storage system 51 has the appropriate circuitry 52 to receive the multiplexed or serialized information and deserialize this information prior to further processing. In operation, the receiving portion 52 circuitry comprises high-frequency termination resistors and a single or multiple integrated circuit. The output of this circuit represents a digital gray-scale representation of one or more pixels. In the preferred embodiment, the camera pixels are sent in a serialized fashion such that four pixels are received per unit of time or clock cycle.

The deserialized camera pixel information is then conveyed into the initial data reduction section 53. The monitoring circuitry 54 is included to store a time-averaged grayscale value of each pixel. This circuit serves to periodically compare the current pixel value to a stored average pixel value. If the current pixel value is greater than the stored average value for the same pixel number, the pixel's stored average value is incremented. If the current pixel value is less than the average value for the same pixel number, the pixel's average value is decremented. This simple averaging scheme allows the hardware to track the average pixel values using minimal computation time (a few nanoseconds). The average pixel value may thus be read during half a clock cycle and written during the other half clock cycle. The average value for each pixel is stored and retrieved from a fast asynchronous static random access memory (SRAM). The time-averaged gray-scale value of each pixel thus is used to compensate for lighting nonuniformati.es and optimize dynamic range of a reduced length binary code. The information is then conveyed into the threshold comparison section 55 of the data handling and storage system 51.

Using the average pixel value for each pixel as a reference, the gray-scale information is converted from 256 digital levels to 8. This allows the information to be represented by 3 bits per pixel instead of 8 bits per pixel. The data reduction is accomplished by determining the pixel value relative to the average pixel value and assigning a new pixel value based on that comparison. In the preferred embodiment, a pixel with a value greater than or equal to the pixel's average value is assigned a 10 maximum binary value, and a zero-valued pixel, or one that falls below the threshold value, is assigned a minimum binary value (zero). The resulting reduced-bit binary value may be a linear or nonlinear representation of the pixel value versus the average value. Using the pixel's time-averaged value versus the original binary maximum code as the basis of the data reduction enables maximum usage of the number of bits available in the reduced-bit code, corrects for uneven lighting, and compensated for slowly- varying changes in lighting versus time due to fouling of the optical windows, for example. The binary encoded information is then temporarily stored in a storage means 56, which in the preferred embodiment consists of a dual-port random access memory (DPRAM). This unit allows the control circuitry 53 to selectively store and retrieve specific pixels or groups of pixels at any given time, whether sequential or dissimilar in time order. The circuitry is optimal for reconfiguring the order of the pixels that are read into subsequent processing circuitry. This is especially useful when the instant invention is used with multi- tap cameras, where non-contiguous pixels are available from the cameras during each clock time cycle. In some multi-tap cameras, pixels are relayed in time, starting on the outsides of the linear array, followed by pixels nearer the center of the linear array. Finally, the center pixels are output. Because this gives a non-linear representation of the image, this format is inconvenient for reconstruction software or compression, since the pixels are not contiguous. The DPRAM circuitry 56 allows the hardware to reconfigure the pixels to be read as a contiguous image. In the preferred embodiment, the write addresses and read addresses are on two separate pages in memory. The write addresses are written to their appropriate pixel numbers during each clock cycle and the read addresses are read as contiguous pixel numbers from the previously written pixel data storage page. The multiple-page memory access structure obviates the possibility that pixels from separate lines are overwritten before being read.

In addition to the above circuitry, the processing circuitry of the present invention may also include an additional data reduction section 60 utilizing more thresholding 61 and data compression 62. In this thresholding step, the number of bits per pixel is reduced to one. Because thresholding is often the initial step in image, processing algorithms, and additionally reduces the data storage requirements, it is considered beneficial to compute this step in the hardware portion of the instrument as opposed to the software. In the preferred embodiment, the threshold is set as a fixed binary percentage of the reduced-bit binary of each pixel. The threshold value may be set by an external electronic signal 63, which is preferably operator-configurable over the existing data network, to allow for fine-tuning of the threshold if necessary.

Additional data reduction may also be accomplished through the use of widely known data compression technology, but this is considered an additional feature as opposed to the necessity of such technology in the prior art instruments. In a marine or other aqueous application, a run-length encoding scheme is convenient and realistic for hardware implementation. In a preferred embodiment, a suitable run-length encoding algorithm is implemented in a Field Programmable Gate Array (FPGA) integrated circuit. The run-length encoding can be implemented in a modest-capability FPGA (for example XILINX Spartan™ series by Xilinx, Inc.) with a suitably designed state diagram. Alternately, the implementation could be performed in a different type of integrated circuit or plurality of circuits, including an application specific integrated circuit (ASIC) or other as known to those of ordinary skill in the art.

In addition, circuitry may be included into the data handling and storage system 51 to allow for the inclusion of additional information to be processed with the data stream 62. These comprise, for example, camera identification, end-of-line marks, water or fluid velocity information, and compression scheme being implemented. These forms of additional information may be used alternately or additionally to aid in instrument operation, provide performance data desired by the operator, or facilitate software reconstruction of images. Further data manipulation in the data handling and storage system 51 includes a buffering portion 70 to modify the data stream into a format suitable for transferal to a digital storage unit 80. In the preferred embodiment of the invention, this is performed by using a first-in-first-out (FIFO) memory, which allows for dissimilar reading and writing rates for a short period of time. In alternate embodiments, a dual port memory with additional control circuitry may be substituted; these circuits are well known to those of ordinary skill in the art. The preferred embodiment of the instant invention also includes circuitry 71 to determine if the digital data storage mechanism 80 is ready to accept data. When the data storage mechanism is determined to be ready, and the circuitry is activated by the operator or control circuit 71, the buffer memory 70 is then read and transmittal is made to the data storage mechanism 80. It should be noted that the circuitry 71 is capable of performing this handshaking operation at rates sufficient to support data transfer without any loss of data. In addition, the processing circuitry 51 may include remotely located user capability to modify various parameters in the operation of the instrument. For example, in the preferred embodiment, this control comprises an embedded microcontroller 64 enabling TCP/IP communication of a visual interface and virtual control buttons linked to a world- wide- web browser that is capable of viewing HTML (Hyper Text Markup Language) or another suitable data network language. One particular microcontroller suitable for this purpose is the SitePlayer Ethernet web server by NetMedia, Inc.; other servers with digital input and output lines may be substituted, as readily known to those of ordinary skill in the art. As mentioned before, additional circuitry 90 may be provided in the data handling and storage system 51 to allow for attachment of one or several multi-synch video display units 91 to the instant instrument. This circuitry allows for generation of horizontal and vertical video synchronization signals to enable synchronization of the rate of the linescan camera to a video display unit. This circuitry produces an analog signal proportional to the corresponding line camera's digital pixel value, and its reduced form, with timing such that an image of the linescan appears as one or more lines simultaneously on the video display unit. This is accomplished by modification of the analog signal to produce an electrical voltage and current range suitable for the purpose of the display on the video unit. In addition, this modification may also be responsive to the signals to produce suitable automatic gain control in the video display unit. The circuitry 90 and the video display unit 91 is optimally used in pre-field testing to determine and adjust optical components of the instant instrument, without the need for expensive frame-grabbers or additional computers. In addition, a video display enables the operator to obtain visual data that is of interest for a number of reasons. Modification and variation can be made to the disclosed embodiments of the present invention without departing from the scope of the invention as described. Those skilled in the art will appreciate that the applications of the present invention herein are varied, and that the invention is described in the preferred embodiment. Accordingly, additions and modifications can be made without departing from the principles of the invention. Particularly with respect to the claims it should be understood that changes may be made without departing from the essence of this invention. In this regard it is intended that such changes would still fall within the scope of the present invention. Therefore, this invention is not limited to the particular embodiments disclosed, but is intended to cover modifications within the spirit and scope of the present invention as defined in the appended claims.

Claims

CLAIMSWhat is claimed is:

1. A system for analyzing microscopic particles in a fluid or gaseous medium, comprising: a sample chamber adapted to temporarily contain a sample of a medium; an optical imaging system that is associated with the sample chamber and that generates image data from at least two different directions in response to variations in particles contained in the sample passing through the sample chamber; a data manipulation circuit that receives the image data and generates reduced quantity digital data based at least in part on the image data; and a data store that stores the reduced quantity digital data from the data manipulation circuit.

2. The system of claim 2, wherein the camera is a line scan camera.

3. The system of claim 1, wherein the image data is generating utilizing back illumination.

4. The system of claim 1, further comprising circuitry adapted to quantify and identify particles in the sample based on the reduced quantity digital data.

5. The system of claim 1 , wherein the reduced quantity digital data is determined utilizing time-averaged pixel value data.

6. A method of analyzing microscopic particles in a fluid or gaseous medium, comprising: passing a sample of a medium through a sample chamber; generating image data in response to variations in particles contained in the sample passing through the sample chamber, the image data comprising data from at least two different directions; reducing the quantity of the image data; and conveying the reduced image data to a data store. .

7. The method of claim 6, further comprising the step of processing the reduced image data to provide quantitative and identification information about the particles in the fluid sample.

8. The method of claim 6, further comprising collecting velocity data of the sample passing through the sample chamber for utilization in generating a scale image of a particle.

9. The method of claim 6, wherein reducing the quantity of image data includes utilizing a time-averaged pixel value of the image data.

10. A method for analyzing microscopic particles in a fluid or gaseous medium, comprising: providing a sample chamber adapted to temporarily contain a sample of a medium; providing an optical imaging system that is associated with the sample chamber and that generates image data from at least two different directions in response to variations in particles contained in the sample passing through the sample chamber; providing a data manipulation circuit that receives the image data and generates reduced quantity digital data based at least in part on the image data; and providing a data store that stores the reduced quantity digital data from the data manipulation circuit.

11. The method of claim 10, wherein the reduced quantity digital data is determined utilizing time-averaged pixel value data.

12. The method of claim 10, wherein the image data is generating utilizing back illumination.