Optics: measuring and testing – Of light reflection
Reexamination Certificate
1999-08-20
2001-03-13
Font, Frank G. (Department: 2877)
Optics: measuring and testing
Of light reflection
C356S039000
Reexamination Certificate
active
06201607
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to body fluid analysis instruments and more particularly to a blood analysis device for determining levels of different types of sugar in a blood sample.
BACKGROUND OF THE INVENTION
Devices for enabling patients to test their own blood are well known in the art. One such device is shown in U.S. Pat. No. 4,552,458, to Lowne, which deals with a compact reflectometer to enable the exposure of a reagent to different light beams, one red and one green. The light beams are folded by a reflecting surface, which redirects the beams through a transparent glass plate onto a reagent strip. Light is reflected back from the strip along a similar folded path onto a detector located in the same plane as the light sources.
Other patents describing various optical arrangements for illuminating and detecting the light reflected from reagent strips are U.S. Pat. No. 4,632,559, to Miles, for an optical read head for measuring non-specular, i.e. non-mirror-like, reflections from a reagent test strip; U.S. Pat. No. 4,787,398, to Garcia, for a glucose medical monitoring system and U.S. Pat. No. 4,985,205 for a test carrier analysis system.
The latter '205 patent describes a reference measurement using the same optical elements by using the same reference layer so as to avoid a two tier testing process. The reference measurement uses two LED's for illuminating the same color formation layer from different directions. The LED's are preferably activated successively so that the measurements can then be averaged.
U.S. Pat. No. 5,039,225 describes a device for measuring optical density with a light transmissive plate inserted between the light source and the surface being measured. The light is directed at an angle relative to a surface of the plate so that a portion is reflected back to a detector for obtaining a reference measurement while another detector is oriented to detect diffuse light for analysis.
Other patents related to body fluid analysis are U.S. Pat. Nos. 5,114,350; 5,279,294 for a glucose diagnostic device which can fit inside a shirt pocket; U.S. Pat. No. 5,321,492 using a dual function read head for a glucose level detector; U.S. Pat. No. 5,424,035 for a glucose test strip positioning structure; U.S. Pat. No. 5,424,545 for a non-invasive spectro-photometric technique to determine glucose levels; U.S. Pat. Nos. 5,518,689 and 5,611,999 for a diffused light reflectance technique wherein the reagent sample is held at a particular angle relative to the incident beam to obtain an improved performance; U.S. Pat. Nos. 5,563,042 and 5,597,532 for particular types of glucose test strips.
None of the these patents describe or disclose a small personally useable body fluid diagnostic instrument with which both glucose and fructosamine levels in a blood sample can be detected.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to provide a diagnostic apparatus for determining the levels of both glucose and fructosamine in a blood sample using respectively different reagents in strips and which undergo a color change when exposed to a blood sample containing glucose or fructosamine. A light source is used to illuminate the blood exposed reagent strip to enable a light detector to determine what color is reflected by the strip.
It is a further object of the invention to enable a precise compensation for wavelength changes in a light source, which is used to detect the level of a chemical in a reacted reagent by sensing color changes in the reflectance characteristics of a reacted reagent.
When the wavelength of the light source increases, which can be the result of an increase in the temperature of the LED used for the light source or to a change in the drive current to the LED, the reflectance measured with a light detector, whose sensitivity increases with wavelength (i.e. provides more output signal) is also increased. With no control over the light source's optical output power, the reflectance measured with this type of detector would tend to increase as the wavelength increase, causing an erroneous measurement.
One apparatus for practicing the invention includes a control loop with which an accurate compensation for variations in the characteristics of a light source used in the analysis of the reagent can be obtained for a reliable measurement of the blood sample. This is achieved with one embodiment in accordance with the invention by employing a reference detector to control the amplitude output level from the light source.
When the reference detector has a particular response characteristic to different wavelengths generated by the light source used to analyze the blood exposed reagent strip, this response can be used to compensate for the wavelength changes in the light source. Hence, as the wavelength of the light source alters over time, a reference detector compensates for this change to produce a correspondingly changed output level from the light source. When a main detector, sensitive to the reflectance from the blood exposed reagent strip, is a similar detector as the reference detector, the output signal from the main detector will exhibit the same changed level and thus produce a constant output signal despite the change in wavelength of the light source.
Different types of light detectors can be used for the reference and main detectors so as to achieve different compensations useful for the compensation for other portions of the optical system used in the apparatus. For example, compensation for the sensitivity of the transmittance of the optical system to different wavelengths can be obtained in this manner, as well different dyes can be used in the optical system to force a different wavelength response to achieve a particular response characteristic for the reagent reflected light detection system.
One particular apparatus for practicing the invention comprises a housing, an optical beam generating structure comprising an optical element, two spaced apart light beam generators selected to enable the investigation of different reagents on strips, a reference detector positioned to detect and control light from a light source, and a main detector to detect light reflections from a reagent strip aligned with an aperture and passing through the optical element. The output signal from the reference detector is used in a control loop to regulate the light output from the light source.
It is, therefore, a further object of the invention to provide a diagnostic apparatus of the above character wherein an automatic compensation for changes in the wavelength from the light source is obtained for an accurate detection of the color change in a reagent strip.
It is yet another object of the invention to provide a diagnostic apparatus of the above character wherein the optical beam generating structure includes a base plate and a cover plate adapted to intermesh with each other to form an optical path enclosure, the optical path enclosure including two converging paths retaining two different light wavelength beam generators, the two converging paths encompassing the two beam axes.
The above objects and advantages of the invention are accomplished by a diagnostic apparatus for determining the levels of both glucose and fructosamine in a blood sample using respectively different reagent strips with reagents that undergo a color change when exposed to a blood sample containing glucose or fructosamine. One apparatus in accordance with the invention comprises a housing, an optical beam generating structure, a reference detector and a main detector. The optical beam generating structure further comprises an optical element and two spaced apart light beam generators for illuminating respectively different reagent strips. The housing has a surface for receiving the reagent strips and an optical aperture through which an optical beam from inside the housing can illuminate the reagent on a test strip aligned with the aperture.
The optical beam generating structure is positioned inside the housing a
Paolini Gregory P.
Roth G. Thomas
Font Frank G.
Merlino Amanda
MIT Development Corporation
St. Onge Steward Johnston & Reens LLC
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