GB2046901A

GB2046901A - Measurement of blood bilirubin concentration

Info

Publication number: GB2046901A
Application number: GB8012607A
Authority: GB
Original assignee: American Optical Corp
Current assignee: American Optical Corp
Priority date: 1979-05-14
Filing date: 1980-04-17
Publication date: 1980-11-19
Also published as: FR2456948A1; FR2456948B1; CA1139124A; AT370524B; GB2046901B; ATA250680A; HK18985A; JPS55152443A; DE3018343A1

Abstract

Electro-optical system to test for bilirubin in blood samples comprises means for directing a beam of light through a sample and a beam divider 16 to create separate optical paths after transmission through the sample. A different band pass filter 18 in each of the paths provides transmitted light at two specific wavelengths such that the effect of hemoglobin, on the compared light intensities is eliminated. A gradient density filter 32 in one path is moved in response to imbalance to a position at which intensities of light transmitted along the paths are equal. The filter position is correlated to a reading of bilirubin concentration. An automated sample handling system receives a sample, moves it into operative position and signals the optical system to function, and returns the sample for removal. <IMAGE>

Description

SPECIFICATION Apparatus for measurement of blood biliru bin concentration This invention relates to testing of blood se rum samples for measurement of bilirubin concentration. More particularly, the invention is a novel apparatus for performing such mea surement.

The general testing method used herein involves directing a beam of light through a blood sample, then along parallel optical paths through a narrow band pass filter, 460 nm in one path and 550 nm in the other path, then to compare the light transmittance or attenuation in the two optical paths as an indication of bilirubin concentration in the blood sample. This method is more fully de scribed in United States Patent &num;3569721 to Goldberg and Polanyi, the specification of which is incorporated herein by reference.

Goldberg and Polanyi also disclose an appa ratus for performing their test method. It is an optical system including light source and con denser for transilluminating a blood sample, collimating optics for light transmitted by the sample, and a beam divider to create parallel optical paths. A 461 nm band pass filter in one path and a 551 nm band pass filter in the other path transmit light to respective photo detectors which are in turn connected to a galvonometer to indicate balance or imbalance of the intensity of light transmitted along the two optical paths. A variable aperture in the path of light to the 551 nm filter adjustably attenuates the light transmission in that path.

This variable aperture is calibrated to indicate bilirubin concentration when its setting is such that the galvonometer is at a null condition.

Adjustment of the variable aperture to reach a null condition is manual.

According to one aspect of the present invention we provide a system for measuring the concentration of bilirubin in a test sample of blood serum, including: a light source to direct light along an optical axis to illuminate a test station, an objective lens to project light further along said optical axis from said test station, a beam divider disposed on said optical axis to receive light from said objective lens and to partially reflect and partially transmit same along parallel optical paths, a band pass filter in each of said parallel optical paths to transmit substantially only light of one wavelength, a photodetector behind said band pass filter in each of said parallel optical paths to receive light transmitted thereby, an adjustable light attenuator in one of said parallel optical paths for adjustably varying the intensity of light transmitted therethrough to the associated photodetector, said photodectors electrically connected to a carriage motor which is responsive to any imbalance in the signals from said photodetectors to move said light attenuator to a position at which the photodetector signals to said motor are in balance, the resulting position of said light attenuator being correlated to bilirubin concentration in said test sample.

reference is now made to the accompanying drawing; in which: Figure 1 is a plan view of the system of this invention, partly in the section.

Figure 2 is a sectional elevation taken along the line ll-ll of Fig. 1.

Figure 3 is a detail elevation taken along the line Ill-Ill of Fig. 1.

Figure 4 is an elevation view of a detail of the system.

Figure 5 is a sectional plan view of the detail of Fig. 4, taken along the line V-V of Fig. 4.

Fig. 1 shows the system of this invention, in plan view, supported on a frame generally indicated at 2. A light source 4, a condenser lens 6, a first reflector 8, a second reflector 10, and an objective lens 12 are disposed on an optical axis 1 4. From objective lens 1 2 onward, the optical system is best seen with reference also to Fig. 2 and includes a beam divider 1 6 which divides the optical axis 14 into parallel optical paths 14r and 14t. The term "parallel" is used herein to describe optical paths in the same sense as "parallel" electric circuits and the like, and not in the geometric sense to denote spatial parallelism.

Beam divider 1 6 is shown in Fig. 2 supported by, and depending from, frame 2 which is actually above the system; all the elements described hang from frame 2 above.

The reflected optical path 1 4r leads from beam divider 1 6 through a 460 nm band pass filter 1 8 to a first photo detector 20.

Transmitted optical path 1 4t leads from beam divider 1 6 through a 550 nm band pass filter 22 to a second photo detector 24.

A pair of parallel guide rails 26 are stationarily mounted to the frame 2 and extend forward and back to slidably support a carriage member 28 thereon. Carriage member 28 is mounted for sliding back and forth, in the directions indicated, on rails 26 by suitable V-blocks or the like at 30. Carriage member 28 carries an optical filter wedge 32 for movement of wedge 32 relative to the optical path 14t. Wedge 32 is, in essence, a filter element having a gradient density from one end to the other so that by moving it across the optical path 14t, transmission along path 14t is varied. Wedge 32 is calibrated from end to end so that its lateral position relative to the optical path 1 4t is correlated to its light attenuation at that position.

Carriage 28 is connected at 34 to a drive belt which in turn is mounted on suitable pulleys 38 and connected by a drive pulley 39 to a carriage drive motor 40. Motor 40 is a reversible stepper motor, operatively connected to the electrical outputs from photo detectors 20 and 24 so that an imbalance in the signals from the two photo detectors 20 and 24 signals the motor 40 to move carriage 28 and optical wedge 32 to a null position in which the equal or balanced signals from the photo detectors mean that light intensities through the 460 nm filter and the 550 nm filter are equal. A normally closed limit switch 42 is frame-mounted and positioned in the way of the travel of carriage 28 at each end point of its travel. As an equipment protective measure, when either switch 42 is abutted by the carriage 28, the drive circuit is broken and motor and carriage stopped.Switches 42 are electrically connected to the motor 40 though this is not shown in the drawing.

A blood sample handling system is also shown in Fig. 1 and is mounted to frame 2. A sample drive motor 50, which is a reversible stepper motor, is operatively connected at its output shaft 52 to a sample holder shaft 54 which extends through and is supported for rotation by a housing 56. A sample holder assembly 58 is fastened for rotation on shaft 54. Sample holder 58 is shown in detail in Figs. 4 and 5. The end of shaft 54 supports a cam 60 which is operatively connected to a limit switch 62 which is in turn electrically connected to sample drive motor 50. The cam 60, limit switch 62 interaction can be more clearly seen in Fig. 3 in which the switch 62 is open and the sample drive motor 50 therefore operative. Housing 56 includes a pair of apertures 64 to transmit light along the optical axis 14.

The sample holder assembly is shown in a rest or reference position to receive a blood sample. In this position, a reference aperture 66 in the holder assembly is in line with apertures 64 of the housing and passes light, unmodified by a blood sample, from the light source 4 to the photo detectors 20 and 24.

This permits calibration, or a check on calibration, of the instrument prior to every actual blood sample measurement.

Referring now to Figs. 4 and 5 particularly, sample holder 58 includes a sample insert/removal station 68 in which a blood sample, typically between two glass plates, is placed and held by leaf springs 70. The sample holder includes a sample test aperture 72 positioned to direct light through the blood sample when it is in place. Sample holder 58 is rotatable 90 on shaft 54 to move a blood sample from its insert/removal position shown to its test position in which the test aperture 72 is where reference aperture 66 is now shown, i.e. on the optical axis 14. Sample drive motor 50 is connected to a detent switch 74 which coacts with the sample holder 58 to seat (and thereby close the switch) at each end of the 90' arc travel of the holder 58.

The operation of the system will now be described with the sample holder 58 at its Fig. 1, Fig. 4 position as a starting point. A reference reading is continually made in the optical system with light passing through reference aperture 68, carriage motor 40 being energized and always at or seeking a balance position. A blood sample is inserted in station 68 and sample drive motor 50 actuated as by a manual switch. Momentary switch actuation starts the rotation of the sample holder 58.

The consequent unseating and opening of the detent switch 74 de-energizes carriage motor 40 until the holder reaches its test position in which test aperture 72 is aligned at the optical axis 1 4 and the detent switch again seats to energize the carriage motor 40 and stops sample motor 50. While the blood sample is thus in the optical axis, light transmitting through it to the photo detectors 20 and 24 signals the carriage motor 40 to position the filter wedge 32 in response to any imbalance in photo detector signals until a null condition is reached. At this point the desired reading is made. The manual switch again starts motor 50, this time in the reverse direction, and again detent switch 74 unseats and opens to de-energize the carriage motor 40 until the initial position is reached with reference aperture 66 once again in the optical axis and the sample holder accessible for removal of the sample. At this point, motor 50 stops when cam 60 actuates limit switch 62.

Claims

1. A system for measuring the concentration of bilirubin in a test sample of blood serum, including: a light source to direct light along an optical axis to illuminate a test station, an objective lens to project light further along said optical axis from said test station, a beam divider disposed on said optical axis to receive light from said objective lens and to partially reflect and partially transmit same along parallel optical paths, a band pass filter in each of said parallel optical paths to transmit substantially only light of one wavelength, a photodetector behind said band pass filter in each of said parallel optical paths to receive light transmitted thereby, an adjustable light attenuator in one of said parallel optical paths for adjustably varying the intensity of light transmitted therethrough to the associated photodetector, said photodetectors electrically connected to a carriage motor which is responsive to any imbalance in the signals from said photodetectors to move said light attenuator to a position at which the photodetector signals to said motor are in balance, the resulting position of said light attenuator being correlated to bilirubin concentration in said test sample.

2. A system as defined in Claim 1 in which said light attenuator is a gradient density filter.

3. A system as defined in Claim 1 or 2 in which said gradient density filter forms an optical wedge.

4. A system as defined in any of claims 1 to 3, further including a sample handling system for presentation of test samples of blood serum at said test station, said sample holding system including: a sample holder adapted to hold a blood sample placed thereon and movable relative to said optical axis in a defined locus between a reference position in which the sample is out of the optical axis, and a test position in which the sample is on the optical axis at said test station.

5. A system as defined in Claim 4 in which said sample holder forms a reference aperture and a test aperture which are sequentially positoned at said test station when said sample holder is at its reference and test positions respectively.

6. A system as defined in Claim 4 or 5 further including means responsive to the position of said sample holder to energize said carraige motor when said sample holder is in its reference and test positions and to deenergize said carriage motor at all other positions of said sample holder.

7. A system as defined in Claim 4,5 or 6 further including a sample drive motor operatively connected to said sample holder to move the same from said reference position to said test position and from said test position to said reference position, and switch means to start and stop said sample drive motor at said reference and test positions.

8. A system for measuring the concentration of bilirubin in a test sample of blood serum, including an optical system disposed on an optical axis and a sample handling system disposed to present test samples to said optical system; said optical system including: a. means to direct light along said optical axis to a test station to transilluminate a test sample of blood serum disposed at said test station, b. means to transmit light from said test station and to direct the same along parallel optical paths, c. a narrow band pass filter in each of said optical paths and a photodetector behind each to receive light transmitted thereby, d. an adjustable light attenuator in the optical path of said second band pass filter to adjustably vary the intensity of light transmitted therethrough to the associated photodetector, and e. balance means responsive to signals from said photodetectors and the balance condition thereof to position said light attenuator relative to its optical path to reach a balance condition of said signals, the resulting balance position of said light attenuator being correlated to bilirubin concentration in said test sample, said sample handling system including: a. sample holder means to releasbly hold a test sample and to carry said sample from an insert/removal station at which said holder is in a reference position to said test station at which said holder is in a test position, b. said sample holder means permitting light transmission along said optical axis in both said reference and test positions, and c. means responsive to the position of said sample holder to energize said balance means when said sample holder is in its reference and test positions and to deenergize said balance means at all other positions of said sample holder, whereby said balance means positions said light attenuator at a balance position when said sample holder is in said reference and test positions.

9. A system for measuring the concentration of bilirubin in blood serum substantially as herein described with reference to and as shown in the drawings.