Optics: measuring and testing – By shade or color – Fluid color transmission examination
Reexamination Certificate
1999-06-08
2002-03-26
Rosenberger, Richard A. (Department: 2877)
Optics: measuring and testing
By shade or color
Fluid color transmission examination
C356S436000
Reexamination Certificate
active
06362887
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a device for measuring changes in parameters within transparent objects.
BACKGROUND INFORMATION
There is a demand, in particular in medical applications, for detection of different parameters of fluids stored in containers and/or passed through tubing.
U.S. Pat. No. 5,644,402 discloses an optical measurement device for detecting red blood cells, which can be used, in particular, in an artificial kidney. The measurement device has an infrared transmitter, an infrared receiver and two mirrors, which are arranged around a length of medical tubing in such a way that when the tubing is empty, the light emitted goes to the receiver by simple reflection. If the tubing is filled with blood, the light emitted reaches the receiver at least partially by multiple reflection due to refraction. Since multiple reflection occurs only in the presence of red blood cells, it is possible with this device to detect even the lowest concentrations of blood in a fluid.
European Patent Application No. 634,642 A1 discloses an optical measurement device for measuring concentrations of certain substances such as glucose, red blood cells, or proteins in fluids. The measurement principle is based on the Lambert-Beer law which describes the relationship between the concentration of a solution and its light absorption. Consequently, the measurement device has a light source which supplies approximately parallel light, a measurement object with a variable optical path length and an optical sensor which detects the intensity of the light from the light source passing through the object for various optical path lengths. Devices are provided which permit multiple measurements for different optical path lengths at one time as well as devices with which only one optical path length can be measured at one time. The signals of the optical sensor are analyzed by a computer unit in which the Lambert-Beer law is implemented.
German Patent Application No. 41 32 965 A1 discloses an optical measurement device which detects the separation boundary between red blood cells and blood plasma in a blood centrifuge, where a light source is directed at the components in a blood centrifuge and the reflected light is picked up by an optical line sensor. The signals received by the line sensor are relayed to a computer unit where a brightness between the blood plasma and the red blood cells is analyzed. A control unit is driven according to the brightness, causing a plasma pump to be operated until a certain brightness limit can no longer be detected and there are only red blood cells in the blood centrifuge.
One disadvantage of the above-described optical measurement devices is that a special design must be provided for each application, which necessitates special adjustments and new developments for product series with different sensors for each product, which ultimately leads to higher costs on the whole.
SUMMARY OF THE INVENTION
An object of this invention is to create an optical measurement device which can be used universally for various applications.
A first embodiment of the present invention includes a device for measuring changes in parameters within transparent objects, in particular for medical applications, with a light sensor, with an optical line sensor detecting the intensity of the light from the light source passing through the object as function of the location in at least one extension direction of the object, and with a computer unit which compares the distribution of the light intensities detected by the optical line sensor as a function of the location with at least one predetermined reference distribution.
This embodiment according to the present invention is based on the finding that with this arrangement, a wide variety of optical parameters of a transparent object can be analyzed by the computer unit. Possible parameters may include turbidity, coloration, scattering, optical refraction, irregularities in the object as well as the motion or size of particles. Stored in the computer unit is at least one predetermined reference distribution so that the light intensities detected by the optical line sensor can be compared as a function of location. The reference distribution is preferably recorded once before the actual measurement on the basis of an object with known parameters. Thus in this way, changes in parameters can be determined easily with respect to the known object without requiring an absolute determination of the respective parameters. This also has the advantage that the same disturbance variables are averaged out in the device in recording the reference distribution and in the actual measurement.
According to a preferred embodiment, the light source is a point light source. Such a light source has a beam of light emitted in the direction of the optical line sensor. With objects with parallel bordering faces which also extend parallel to the optical line sensor, use of a point light source has the advantage that a defined optical refraction can be established on the parallel walls. In addition, due to the inverse-square law, a characteristic intensity distribution which is especially suitable for comparison with a predetermined reference distribution is obtained on the optical line sensor.
According to another preferred embodiment, however, a light source which supplies approximately parallel light may also be used. Such a light source in turn makes use of the fact that there happens to be no optical refraction on an object with parallel walls aligned perpendicular to the parallel beams of light. Thus, optical refraction can be prevented in a controlled manner with such a light source if there happens to be no interest in this parameter.
The two types of light sources also may be used together in combination. In this case, the analysis of the light from the light sources can be performed with a time offset, in which case the other light source is then turned off. However, a simultaneous analysis of both light sources with two optical line sensors may occur if crosstalk of the light of the two light sources is avoided through appropriate partitions.
The optical line sensor preferably has a CCD sensor (CCD=charge coupled device). With such a sensor it is possible to determine the light intensities in one extension direction as well as in two extension directions of the respective objects. If a two-dimensional CCD sensor is used, the device according to the present invention functions accordingly if a two-dimensional reference distribution is used as the basis instead of a one-dimensional reference distribution. A two-dimensional determination of the light intensities may have the advantage that the respective changes in parameters can be determined even more accurately.
In each instance, the reference distributions are recorded on the basis of a reference object. The intensities are converted by an AD converter into digital values and stored in the computer unit. The computer unit usually has a microprocessor and/or a signal processor as well as memory units and peripherals connected to it. A reference distribution is preferably recorded first without any influence by an object or an “empty” object (e.g., an empty fluid line) between the light source and the optical line sensor and then stored in the computer unit. The object which is between the light source and the optical line sensor and has neutral optical properties is referred to below as the “dummy object.”
With a reference distribution on the basis of a dummy object, changes in the measured light intensity on the optical line sensor can be detected. If the measurement of the light intensity is to be color-selective, the optical line sensor will usually have separate color sensors, in particular for the colors red, green and blue. Separate reference distributions are preferably recorded for each of these color sensors, so that there can be a color-selective change in light intensities as well. It is also possible to use color filters instead of color-sensitive sensors. This is a
Fresenius AG
Kenyon & Kenyon
Rosenberger Richard A.
LandOfFree
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