Optics: measuring and testing – Dimension – Volume
Reexamination Certificate
2000-03-13
2002-10-29
Rosenberger, Richard A. (Department: 2877)
Optics: measuring and testing
Dimension
Volume
C356S628000, C356S630000, C250S559290, C250S559310
Reexamination Certificate
active
06473190
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to volume measurement devices, and, more particularly, to an optical volume sensor for measuring the volume of a drop of blood.
BACKGROUND OF THE INVENTION
It is often necessary to quickly and inexpensively measure the volume of an object. One example of a need for volume measurement is in connection with a blood glucose monitoring system where it may be necessary to measure the volume of a drop of blood.
Those who have irregular blood glucose concentration levels are medically required to regularly self-monitor their blood glucose concentration level. An irregular blood glucose level can be brought on by a variety of reasons including illness such as diabetes. The purpose of monitoring the blood glucose concentration level is to determine the blood glucose concentration level and then to take corrective action, based upon whether the level is too high or too low, to bring the level back within a normal range. The failure to take corrective action can have serious implications. When blood glucose levels drop too low—a condition known as hypoglycemia—a person can become nervous. shaky, and confused. That person's judgment may become impaired and that person may eventually pass out. A person can also become very ill if their blood glucose level becomes too high—a condition known as hyperglycemia. Both conditions, hypoglycemia and hyperglycemia, are both potentially life-threatening emergencies.
One method of monitoring a person's blood glucose level is with a portable, hand-held blood glucose testing device. A prior art blood glucose testing device
100
is illustrated in FIG.
1
. The portable nature of these devices
100
enables the users to conveniently test their blood glucose levels wherever the user may be. The glucose testing device contains a test sensor
102
to harvest the blood for analysis. The device
100
contains a switch
104
to activate the device
100
and a display
106
to display the blood glucose analysis results. In order to check the blood glucose level, a drop of blood is obtained from the fingertip using a lancing device. A prior art lancing device
120
is illustrated in FIG.
2
. The lancing device
120
contains a needle lance
122
to puncture the skin. Some lancing devices implement a vacuum to facilitate the drawing of blood. Once the requisite amount of blood is produced on the fingertip, the blood is harvested using the test sensor
102
. The test sensor
102
, which is inserted into a testing unit
100
, is brought into contact with the blood drop. The test sensor
102
draws the blood to the inside of the test unit
100
which then determines the concentration of glucose in the blood. Once the results of the test are displayed on the display
106
of the test unit
100
, the test sensor
102
is discarded. Each new test requires a new test sensor
102
.
One problem associated with some lancing devices is that the requisite amount of blood for accurate test results is not always obtained. Roughly thirty percent of lances to do not produce enough blood for accurate analysis. The amount of blood obtained from each lance varies between zero and ten microliters (“&mgr;l”). For an accurate result, at least two &mgr;l of blood must be obtained. If less than this amount is produced, the test results may be erroneous and a test sensor is wasted. More serious an issue, however, is that the user may be relying on inaccurate results. Obviously, because of the serious nature of the medical issues involved, erroneous results are not preferred.
Another problem associated with conventional lancing devices is that there is no mechanism to let the user know whether the correct amount of blood has been obtained for accurate analysis. Typically, the test units come with instructions containing a graphical illustration of the actual size of the blood drop required for accurate testing. However, this visual comparison is subjective and often produces inconsistent results. To insure the requisite amount of blood is produced, users often overcompensate by squeezing or otherwise manipulating their fingers to produce larger than necessary drops of blood. However, this adds more time to the overall testing process and also results in an increased amount of wasted blood.
The inconsistent results produced by conventional lances has impeded the integration of the lancing device, the harvesting device, and the blood glucose analysis device into a single unit. Because the analysis may begin even though the requisite amount of blood has not been obtained, it appears problematic to combine the lancing with the actual harvesting due to the potentially inaccurate results.
SUMMARY OF THE INVENTION
According to one embodiment of the present invention, there is an optical sensor for determining the volume of an object. One application of the optical sensor is for use in a blood glucose monitoring system which integrates the lancing device. the harvesting device, and the blood glucose analysis device into a single unit. In accordance with the present invention, the optical sensor comprises a source of light and a light sensor adapted to measure an amount of light reflected off the side and off the top of a drop of blood, wherein the measured amount of the light reflected off the side and the top correlates to a height and a diameter of the blood drop. At least one optical device is adapted to direct light reflected off the side of the object to the light detector, and at least one optical device is adapted to direct light reflected off the top of the object to the light detector.
The above summary of the present invention is not intended to represent each embodiment, or every aspect, of the present invention. Additional features and benefits of the present invention will become apparent from the detailed description, figures, and claims set forth below.
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patent: 5184733 (1993-02-01), Arnarson et al.
patent: 5555090 (1996-09-01), Schmutz
patent: 5699161 (1997-12-01), Woodworth
patent: 6061645 (2000-05-01), Bengala et al.
patent: 6069696 (2000-05-01), McQueen et al.
patent: 6202493 (2001-03-01), Cantral et al.
Bayer Corporation
Jeffers Jerome L.
Nguyen Sang H.
Rosenberger Richard A.
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