Patent Description:
A turbidimeter measures the turbidity of a liquid sample in a sample cuvette or vial. A nephelometric turbidimeter determines the concentration of solid particles suspended in a liquid sample within a sample cuvette by projecting a light beam into the liquid sample within the cuvette. A light detector detects the amount of light scattered by the suspended solid particles in a cone of solid angle, e.g., of <NUM>° centered at <NUM>° to the light beam axis.

If the light detector of a turbidimeter detects light scattered in one single sector of the circumference (of the cuvette, vial or sample vessel), the signal of the light detector is relatively low because much scattered light is being thrown away. Circular mirrors and/or prism arrangements have been designed to coaxially surround the liquid sample cuvette in an effort to direct radially scattered light (over the complete) circumference to the light detector. Such designs generally are acknowledged to increase the signal to noise ratio (SNR). However, many of these devices are sensitive to geometrical inaccuracies of their optical arrangements (directing the scattered light toward the light detector) and may be sensitive to non-homogenous samples (turbidity differences in the liquid sample).

Document "<NPL> describes a differential light scattering photometer which has been developed for rapid size analysis of single particles in flow. A fluid stream carrying individual particles in single file intersects a focused laser beam at the primary focal point of an annular strip of an ellipsoidal reflector situated in a scattering chamber.

Document <CIT> describes that values for one or more particle properties, such as an aerosol asymmetry parameter g, can be measured directly using a detector that measures scattered light. The detector can comprise two or more diffusers coupled to optical sensors responsive to scattered light that is incident on the surfaces of the diffusers. One or more weighing functions can be obtained based on diffuser geometry. In an example, the diffusers correspond to quadrants of a circular toroid.

Document <CIT> describes an improved optical scatterometer which includes a multiple detector array that enables the measurement of sample microstructure over an increased range of spatial frequency. One array of optical detectors is positioned in a plane perpendicular to the plane containing an incident laser beam and a specularly reflected beam to detect indications of back-scattered and forward-scattered light in that perpendicular plane. Two laser beams having different wavelengths may be employed to determine the optical characteristics of a film and an underlying substrate.

The claimed invention is defined by the features set forth in the appended independent claims.

For a better understanding of the embodiments, together with other and further features and advantages thereof, reference is made to the following description, taken in conjunction with the accompanying drawings.

It will be readily understood that the components of the embodiments, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations in accordance with the appended claims.

Reference throughout this specification to "one embodiment" or "an embodiment" (or the like) means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" or the like in various places throughout this specification are not necessarily all referring to the same embodiment.

Furthermore, the described features, structures, or characteristics may be combined in accordance with the appended claims. In the following description, numerous specific details are provided to give a thorough understanding of example embodiments. One skilled in the relevant art will recognize, however, that various embodiments can be practiced in accordance with the appended claims without one or more of the specific details, or with other methods, components, materials, et cetera. In other instances, well-known structures, materials, or operations are not shown or described in detail. The following description is intended only by way of example, and simply illustrates certain example embodiments.

The various embodiments described herein provide turbidimeters that detect light from an arc surrounding or substantially surrounding a sample vessel or cuvette. The embodiments permit such light detection without using complex light focusing geometries. Rather, embodiments provide mechanisms to directly detect light in an arc surrounding or substantially surrounding the sample vessel or cuvette. In other embodiments, light from an arc surrounding or substantially surrounding the sample vessel or cuvette is piped or redirected to a light detector.

An embodiment provides a nephelometric turbidimeter detector comprising a <NUM> degree element having a plurality of contiguous photodiode arrays capable of detecting radiation from about <NUM> to about <NUM> and arranged to capture scattered radiation at a <NUM> degree angle +/- about <NUM> degrees relative to the light beam axis. An exemplary not claimed arrangement comprises a detector including a <NUM> degree element having single flexible photodiode array that detects radiation from about <NUM> to about <NUM> and that is arranged to capture scattered radiation at a <NUM> degree angle +/- <NUM> degrees relative to the light beam axis. In the various embodiments forming nephelometric turbidimeter, these embodiments may include all of the standard elements, some of which are not described.

The illustrated examples and embodiments will be best understood by reference to the figures. The following description is intended only by way of example, and simply illustrates certain examples and embodiments.

<FIG> depicts a cross section of the <NUM> degree turbidimeter detector apparatus according to the claimed invention. The turbidimeter illustrated in <FIG> is substantially round when viewed from above or below. Vial <NUM> is a vial for holding sample solutions, e.g. water (waste water, drinking water, etc.). The vial (also referred to as a cuvette) <NUM> may be made from an optically clear material such as glass or quartz that is substantially transparent to radiation used to interrogate the sample, such as <NUM>, <NUM> or <NUM> radiation. The vial <NUM> may be configured as a cylinder, although sample vials may take any shape appropriate for the task. The vial <NUM> is supported by a vial holder <NUM> which itself is supported by a turbidimeter supporting skeleton (not shown in <FIG>).

In operation the vial <NUM> sits in vial holder <NUM> so that the vial is held stably. The vial holder <NUM> abuts detector housing <NUM>, which may be a generally circular shape and surround at least a portion of the mid-section of vial <NUM>. The inside of detector housing <NUM> is lined with light-absorbing material <NUM> which acts as a light baffle to absorb stray radiation that may emanate from vial <NUM> when illuminated. The light absorbing material <NUM> may also be placed in additional areas, e.g., along the length dimension of the vial to restrict light entry to a predetermined angular range. A non-limiting example light absorbing material is VANTABLACK of Surrey Nanosystems, UK.

The detector housing <NUM> also may act as the supporting structure for light detectors, e.g., photodiodes <NUM>, which capture the scattered radiation from sample liquid <NUM>. The photodiodes <NUM> in the embodiment of <FIG> are placed contiguously in a circle on the inside of detector housing <NUM> so that they make up a substantially continuous array of detectors that correspond to scattered radiation along a predefined arc of scattered radiation, shown as rays <NUM> emanating from collected volume <NUM>.

A light source <NUM> may be a broad-band visible light source, a laser, or a light emitting diode (LED). The light source <NUM> is selected according to the specific needs of the application and may also be used in combination with filters for selecting specific wavelengths. Typical wavelengths for turbidimeters are <NUM> and <NUM>, although these are non-limiting examples, e.g., <NUM> +/- <NUM> may be used.

The light source <NUM> may be provided through a slit or other optical element that results in a substantially collimated light beam <NUM> that impinges upon the clear vial bottom, thereby passing through vial <NUM> and sample liquid <NUM> to create an illuminated volume of sample liquid termed the collected volume <NUM>, shown by brackets in <FIG>.

Particles which are in collected volume <NUM> will be illuminated, thereby acting to scatter the light randomly but on average over <NUM> degrees. The collected scattered light will resemble a disk of light that is thicker at its edges than its middle. The scattered light will fall upon the photodiodes <NUM> arrayed along the interior of detector housing <NUM> and thereby cause a signal to be emitted from the photodiodes <NUM> that is proportional to the amount of scattered light, which in turn is proportional to the amount of turbidity (e.g., NTUs).

A not claimed example is shown in <FIG>, which is an elevational view of a <NUM> degree turbidimeter detector having a circular photodiode array (PDA) <NUM> arranged in a substantially circular manner around the vial <NUM>. As before, vial <NUM> is irradiated by collimated light beam <NUM>, thereby causing the scattering of light <NUM> from collected volume <NUM>.

Scattered light <NUM> impinges upon the inner surface of circular PDA <NUM> thereby generating a signal proportional to the number of particles scattering light in the collected volume <NUM>. A circular PDA may be formed by film-based organic photodiodes. However, other materials may be used, including other flexible photodiode materials or an array of photodiodes configured in separate components forming a substantially circular arc or array of detectors.

The example shown in <FIG> is a relatively narrow band or strip of PDA film <NUM> that is looped around the vial's <NUM> equator and is designed to capture a predefined vertical slice or portion of the available scattered radiation. In <FIG>, stray light management is not explicitly illustrated. In theory the sensitivity of the detector system may be tuned simply by changing the arc range of the flexible PDA <NUM>. The flexible photodiodes <NUM> may be configured in almost limitless orientations to take advantage of the specific directions of the omni-directional scattering of the scattered light <NUM>. For example, a diode array made addressable in the direction and subtended angle from which the light is being detected can be changed, giving the advantage that the turbidimeter may detect turbidity from samples with different physical characteristics. As will be appreciated, as with the embodiment illustrated in <FIG>, the arrangement of the detector(s) utilized may vary based on a variety of factors, e.g., the input light angle, the type of cuvette or sample vessel utilized, etc..

<FIG> illustrates an additional not claimed example. In this example, the turbidimeter includes an arc that is substantially circular about a mid point or portion of the sample vial <NUM>. Here, the arc captures the scattered light <NUM> and directs it to a light pipe or guide material <NUM>. In an example, the light guide or pipe material <NUM> may be fiber optics or another suitable waveguide, e.g., a light tube such as ALTAFUOR <NUM> available from Altaflo.

The fiber optic or waveguide <NUM> may start at the surface of the arc, where the flexible PDA is arranged, e.g., in the example illustrated in <FIG>. From there the waveguide <NUM> may curve about <NUM> degrees and meet up with all of the other waveguides, which ultimately provide the light to a single photodiode or an array thereof, e.g., as arranged in the example of <FIG>at <NUM>.

Thus, incoming light <NUM> (e.g., infrared) from a light source is provided entryway <NUM> through (or around) the light pipe <NUM> and provides light to a sample, which may be redirected, e.g., by a mirror <NUM>. In an example, the vial may be angled to prevent reflected light from damaging the source. This light penetrates the liquid sample in the sample vial <NUM> and particles in the liquid sample produce scattered light, a relevant portion thereof <NUM> being illustrated in <FIG>. The sample vial <NUM> may be housed in a manner, e.g., by light blockers <NUM> as shown in <FIG> (which may in turn include a light absorbing material, e.g., as described in connection with the light baffles of <FIG>, e.g., light absorbing VANTABLACK coating). The captured light <NUM> is then provided by the light guides <NUM> (e.g., optic fibers, etc.) to a photodiode, e.g., a circular photodiode <NUM> as illustrated in <FIG>.

The structure thus may include a plurality or collection of optical fibers or guides <NUM> arranged to provide light from the circular arc directly to the photodiode <NUM>. Alternatively, the light guides and the arc could be made of one unitary body so that light collection is not interrupted by the junctions that would inevitable product loss of signal and noise. The shape of such a unitary light collection device might resemble that of an onion with the fatter base of the onion surrounding the sample collection vial, and the apex of the onion being where the detector <NUM> sits. The inside of the onion would have a similar stray light absorber.

In another example, the components of the turbidimeter, e.g., the photodiode array and/or an arc element coupled with light guides, may be arranged to accommodate different sample holding structures, e.g., other than a standard cuvette or like sample vessel. A further not claimed example is illustrated in <FIG>.

In the illustrated example of <FIG>, a cylindrical or arc element <NUM>, e.g., including infrared photodiode(s), may be placed within a sample cell <NUM>. As illustrated in <FIG>, the cylindrical infrared photodiode <NUM> containing element is placed within the sample fluid <NUM>, e.g., suspended above a light source <NUM>, e.g., placed on a sample cell lid <NUM> of a sample cell <NUM>. As illustrated in <FIG>, the cylindrical detector <NUM> may be supported by one or more detector elements <NUM>. As with the other example turbidimeters described herein, the example of <FIG> may include a photodiode array <NUM> or may be configured with light guide(s) such that light from the sample <NUM>, and reflected by the sample (as indicated by <NUM>) is directed to a detector <NUM> that processes the detected light to determine a sample concentration. It should be noted that light of other wavelengths may also be used, such as in the visible and near UV ranges.

In yet another not claimed example depicted in <FIG>, there is shown in cross- section a cone-shaped optical structure that utilizes the phenomenon of total internal reflection to channel and capture scattered light. In the example illustrated in <FIG>, the light <NUM> scattered from a sample in vial <NUM> is measured at the bottom or base end of the device, i.e., the measurement of turbidity of the media is carried out at a <NUM> degree angle to the incident light <NUM>, with the light <NUM> being channeled by total internal reflection to a detector <NUM> that sits at the bottom of the device.

When incident light <NUM> is provided to the sample vial <NUM>, which sits in an upper collar portion of the cone-shaped collector, the scattered radiation <NUM> at <NUM> degrees from incident, in an angular range of <NUM> degrees around the cuvette or vial <NUM>, is collected by entry of the light <NUM> into a pathway <NUM> formed in the upper color portion of the cone shaped device. The scattered light <NUM> is collected in <NUM> degrees at an angle <NUM> degrees from the incident light <NUM>, plus or minus an angular range (which is modifiable) effectively and safely with little effort on a small optical receiver or detector <NUM> that sits at the end of the device.

As shown in <FIG>, an example utilizes internal surfaces <NUM>, <NUM> to form the pathway <NUM> around an outer periphery of the device. The internal surfaces <NUM>, <NUM> are made of a material such that light <NUM> entering the pathway <NUM> is subject to total internal reflection, channeling it along the pathway <NUM> to the detector <NUM>. The device, including internal surfaces <NUM>, <NUM>, may be produced by injection molding. The size of the device may be adapted to the measurement task (e.g., cuvette <NUM> size, device size, etc.). This example illustrated in <FIG> is only one example of a possible device configuration.

The device of <FIG> has at the top or collar portion an optically active aperture or light entryway <NUM> which receives the scattered radiation <NUM> from the sample vial <NUM> in <NUM> degrees. In an example, angled surfaces or slants <NUM>, <NUM> may be provided that reflect the light, e.g., via a coating appropriate surfaces of the slanted regions <NUM> or <NUM> with mirror or silvering material or coating. The angled surfaces <NUM>, <NUM> may be chosen to functionally limit the amount of light reflected along the pathway <NUM> to the detector <NUM>. For example, a slanted outer edge <NUM> in the structure dictates that only light at a certain height in the sample vial <NUM> is reflected along the light pathway <NUM>. A specific opening angle (e.g., +/- <NUM> degrees) may also be provided to the light entryway <NUM>, e.g., such that this additional light satisfies the total reflection condition of the subsequent light guide structure <NUM>. Only this light is guided in the structure's pathway <NUM> to the detector <NUM>. All other light which does not satisfy this condition is suppressed as scattered light.

The useful light <NUM> enters the light pathway <NUM> and is internally reflected to detector <NUM> due to surfaces <NUM><NUM> and <NUM>. At the end of the light pathway <NUM> the entire radiation is focused onto the detector <NUM>. An example detector is a Si receiver.

To avoid reflection losses or total reflections at the end of the light pathway <NUM>, the detector may be bonded with appropriate adhesives of suitable refractive index to direct the light onto the detector <NUM>. When using other receivers or detectors, the size of the lower opening proximate to the detector <NUM> may be adjusted accordingly. For example, an adaptation of the end of the pathway <NUM> to accommodate a rectangular receiver or detector is possible in place of circular detector <NUM>, as compared to the illustrated round opening. A rectangular receiver or detector may be dimmed according to the unused receiver surface. Also, the cuvette or sample vial <NUM> may be provided with a lens hood or appropriate covering structure (not illustrated in <FIG>) so that the light pathway <NUM> and consequently the detector <NUM> receive no direct or unintended light.

Also, a mirror or like reflective coating of an inclined or slanted lower part <NUM> may be utilized. This may make the device simpler to design and construct, i.e., since reflection rather than total internal reflection is used for the lower portion. If such an arrangement is utilized, it must then be ensured that no stray light reaches the mirrored portion. As with other configurations, light blocking material or coatings may be utilized, e.g., mirror or silvering on exterior surfaces, such that stray light is not permitted a pathway to the detector <NUM>.

The light from the photodiode/detector or photodiode array of any of the embodiments may be processed in a standard manner. The output from the photodiode or light pipes may be combined in a fashion that provides a summation of the signal. In the case of addressable photodiode arrays, photodiodes may be arranged to be summing, in circumferential groups providing the adjustment of collection angles. Thus, logic included with the turbidimeter or supporting components, e.g., a processor that executes instructions stored in a memory, may process the raw light data provided by the photodiodes such that the relative scattered light from the sample may be used to determine a concentration of particles in the sample.

Claim 1:
A nephelometric turbidimeter detector, comprising:
a substantially circular detection element (<NUM>) having a plurality of contiguous photodiode arrays that detect radiation, wherein
the substantially circular detection element (<NUM>) is configured to be arranged about a sample (<NUM>) to capture scattered radiation from said sample within a predetermined angular range, wherein said sample (<NUM>) is contained in a sample vial (<NUM>) and wherein said substantially circular detection element (<NUM>) is configured to be arranged outside of said vial (<NUM>) and to be centered at ninety degrees relative to an axis of an incident light beam (<NUM>),
characterized in that the plurality of contiguous photodiode arrays is placed on an inside of a detector housing (<NUM>), wherein the inside of the detector housing (<NUM>) is lined with a light-absorbing material (<NUM>) which acts as a light baffle to absorb stray radiation emanating from a sample vial (<NUM>) when illuminated.