GB2536206A

GB2536206A - System and method for the detection of light transmission and light reflection

Info

Publication number: GB2536206A
Application number: GB1503582.7A
Authority: GB
Inventors: Barth Matthias; Grossmann Jens; Trump Martin
Original assignee: Stratec Biomedical Systems AG
Current assignee: Stratec Biomedical Systems AG
Priority date: 2015-03-03
Filing date: 2015-03-03
Publication date: 2016-09-14
Also published as: GB201503582D0

Abstract

Light from an emitter 110, which may be an LED, is guided by at least one light guide 130 to reaction vessel 140, for example a transparent or translucent cuvette or microtiter plate. After being transmitted through or reflected from the vessel the light is then guided to detector 120, possibly a photo-diode, by at least one guide 160. The light guides may comprise a light guide head such as a prism and a plastic optical fibre (POF), which may be exchangeable. The vessel material and light wavelength used may be chosen to ensure low transmission, for instance using polypropylene and 430nm (blue) light respectively. Uses may include detection of liquid level or air bubbles within or integrity of the vessel, or of the presence or position of it. The reaction vessel may comprise a position marker such as a rib or rough surface.

Description

System and method for the detection of light transmission and light reflection

Field of the invention

[0001] The present invention is directed to a system and a method for detecting a light transmission through a reaction vessel or for detecting a light reflection from a reaction vessel. The invention also relates to a use of the system.

Background of the invention

[0002] In automatic analyser systems for clinical diagnostics, it is necessary to detect the presence of reaction vessels, i.e. cuvettes or microliter plates, at certain positions for process control. Often these reaction vessels are made of transparent or translucent plastic materials.

[0003] Contactless optical presence detection of translucent reaction vessels is known in the state in the art.

[0004] Contactless optical presence detection has been, for example, achieved with a reflex light barrier. The reflex light barrier combines light emitter and light receiver in one single housing. The reaction vessel is being detected by reflecting the light coming from the light emitter hack to the light receiver. The sensor is placed on a separate printed card board (PCB). A sophisticated mechanical interface is integrated. However, the light barrier only detects the bottom of the reaction vessel so that information about liquid level or positioning accuracy of the reaction vessel cannot be provided.

[0005] A through-beam light barrier with separate emitter 1R-LED and receiver photodiode for detecting a reaction vessel is also known in the state of the art. The reaction vessel is being detected by interrupting the beam coming from the emitter to the receiver. Light emitter and light receiver must he connected to a separate printed card hoard (PCB). A sophisticated mechanical interface is integrated. However, the wavelength of the light emitter UR) is not adapted to transmission properties of reaction vessels. Additional information about liquid level or positioning accuracy of the reaction vessel can thus not be provided.

[0006] Another possible setup is a through-beam light barrier with a separate laser emitter and receiver photodiode. The reaction vessel is being detected by interrupting the laser beam coming from the laser emitter to the receiver photodiode. This setup also integrates a sophisticated mechanical interface. The laser emitter must be connected to a printed card board (PCB) and the laser beam must be precisely directed and aligned to the receiver photodiode. Again, the wavelength of the laser emitter (for example, red, 650nm) is not adapted to the transmission properties of the reaction vessel. Additional information about liquid level or positioning accuracy of the reaction vessel cannot be provided.

[0007] The detection of translucent reaction vessels with optical sensors and simple electronics is difficult. Standard optoelectronic components like LEDs and photodiodes have high tolerances. These tolerances can only be reduced by the expensive selection of components with a rather tight tolerance range. However, even with selected components additional information about liquid level or positioning accuracy of the reaction vessel cannot he provided.

[0008] If using a laser diode as a light emitter it is necessary to precisely assemble and align the sensor parts.

[0009] For the known available solutions the system into which the sensor is integrated must provide sophisticated mechanical interfaces, cable connections and printed circuit boards.

[0010] Contactless optical detection is the preferred technology regarding the requirements of installation space, robustness, reliability and cost efficiency. But optical detection is difficult due to the fact that the optical detection of transparent or translucent objects usually does not provide sufficient signal-to-noise ratio. The needed accuracy and precision throughout the lifetime cannot be ensured.

Obiect of the Invention [0011] It is thus an object of the present invention to provide a system and a method for detecting a light transmission through a reaction vessel or for detecting a light reflection from a reaction vessel which is contactless and reliable and wherein information about liquid level and/or one or more air bubbles or positioning accuracy of the reaction vessel or the integrity of the reaction vessel can be provided.

Summary of the Invention

[0012] A system for detecting a light transmission through a reaction vessel or for detecting a light reflection from a reaction vessel is provided. The system comprises a light barrier which comprises at least one light emitter and at least one light receiver, wherein the at least one light receiver serves for receiving light emitted from the at least one light emitter. The system further comprises at least one light guide for guiding the light emitted from the at least one light emitter and at least one light guide for guiding the light received by the at least one light receiver.

[0013] The light emitter may be an LED and the light receiver may be a photodiode.

[0014] In one aspect of the invention, the light guide comprises one or more components.

[0015] The light guide may comprise a light guide head and a plastic optical fibre (POE).

[0016] The light guide head and the plastic optical fibre may be exchangeable.

[0017] In one aspect of the disclosure, the light emitter and the light receiver are located on a printed circuit hoard.

[0018] In another aspect of the disclosure, the reaction vessel is a cuvcttc or a microtiter plate.

[0019] The disclosure also teaches that the reaction vessel may he transparent or translucent.

[0020] The reaction vessel may he made from a material comprising polypropylene.

[0021] In one aspect of the disclosure, the at least one light emitter emits pulsed light and/or the at least one light guide and/or the at least one light receiver comprises an electrical filter.

[0022] In another aspect of the disclosure, the POF is of a cylindrical shape.

[0023] The system may further comprise a signal controller.

[0024] The system may further comprise a reaction vessel comprising at least one position marker.

[0025] The at least one position marker may be at least one rib located on the reaction vessel or a rough surface of the reaction vessel.

[0026] A method for the detection of light transmission through a reaction vessel or for the detection of light reflection from a reaction vessel is also provided. The method comprises the following steps: - emitting light from a light emitter guiding the light through a light guide to a reaction vessel - guiding the light that is transmitted through the reaction vessel or the light that is reflected from the reaction vessel to a light receiver receiving the light by the light receiver - detecting if light is received by the light receiver.

[0027] In one aspect of the disclosure, the method comprises the further step of measuring and adjusting by a signal controller a signal received from the light receiver.

[0028] In another aspect of the disclosure, the light that is received by the light receiver is filtered light.

[0029] Use of the above system for the detection of a presence of a reaction vessel, for the detection of a liquid level or one or more air bubbles in a liquid inside the reaction vessel, for the detection of a position of the reaction vessel or for the detection of an integrity of the reaction vessel is also provided.

Summary of the Figures

[0030] The invention will now be described on the basis of the figures. It will be understood that the embodiments and aspects of the invention described in the figures are only examples and do not limit the protective scope of the claims in any way. The invention is defined by the claims and their equivalents. It will be understood that features of one aspect or embodiment of the invention can be combined with a feature of a different aspect or aspects and/or embodiments of the invention.

[0031] Fig. 1 is an example of a system of the present invention comprising a through-beam light barrier.

[0032] Fig. 2 is an example of a system of the present invention comprising a reflex light barrier.

[0033] Fig. 3 illustrates a light guide comprising a light guide head and a plastic optical fibre (POF).

[0034] Fig. 4 displays a bent plastic optical fibre (POF).

[0035] Fig. 5 shows an inventive system where the light emitter and the light receiver are located on a printed circuit board (PCB).

[0036] Fig. 6 shows only the light guides, the light emitter and the light receiver and the printed circuit board (PCB).

[0037] Fig. 7 illustrates three different detection/measurement positions.

[0038] Fig. 8 is a close view of a detection/measurement position.

[0039] Fig. 9 shows a top view of two detection/measurement positions.

[0040] Fig. 10 shows two light guides inside a housing.

[0041] Fig. 11 illustrates a side view of an inventive system th a reaction vessel and a housing.

[0042] Figure 12 shows counterbores and slots.

Detailed Description of the Invention and the Figures [0043] The present disclosure provides a system for detecting a light transmission through a reaction vessel or for detecting a light reflection from a reaction vessel. The system comprises a light barrier which comprises at least one light emitter and at least one light receiver, wherein the at least one light receiver serves for receiving light emitted from the at least one light emitter. The system further comprises at least one light guide for guiding the light emitted from the at least one light emitter and at least one light guide for guiding the light received by the at least one light receiver.

[0044] One embodiment of the system is illustrated in Figure 1. The light is emitted from the light emitter 110 and received by the light receiver 120. The light is guided through the light guide 130 for guiding the light emitted from the at least one light emitter and directed at the reaction vessel 140 at the detection/measurement position 150. The optical signal may be reduced due to a position marker, such as at least one rib located on the reaction vessel and/or a rough surface of the reaction vessel. The light that is received by the light guide 160 is guided to the light receiver 120 receiving the light. The optical path 170 is also shown.

[0045] The detection/measurement position can be defined as the position where the light beam is directed at the reaction vessel or at the empty position in case there is no reaction vessel.

[0046] The present invention ensures contactless optical presence detection of reaction vessels (which may be translucent or transparent) with high accuracy and precision throughout the lifetime and production. Beyond the presence detection, the optical sensor provides further information like the liquid level inside the reaction vessel, the detection of one or more air bubbles in a liquid inside the reaction vessel, information about the positioning accuracy of the reaction vessel and/or if reaction vessels are defective.

[0047] The reaction vessels arc being detected by interrupting a through-beam light barrier or a reflex light barrier. In case of the reflex light barrier, a reflecting surface on the reaction vessel may be useful. The reaction vessel is being detected by reflecting the light coming from the light emitter to the light receiver. The electronic evaluation is basically the same for the through-beam light barrier and the reflex light barrier. The system comprising a reflex light barrier is shown in Figure 2. The thick black arrows show the optical path 210.

[0048] The light emitter may be an LED and the light receiver may be a photodiode. The wavelength of the LED has to be chosen according the optical properties of the reaction vessel. Ideally, the wavelength of the LED must match the wavelength where optical transmission of the material of the reaction vessel is low. In case the reaction vessel is made of polypropylene, the transmission for blue light is low. Therefore, the wavelength of the emitter LED may be 430nm. Light guides with optical filter properties, which match the LED wavelength may be used in order to reduce the influence of ambient light.

[0049] The position where the reaction vessel is being detected/measured is not where the optoelectronic components are located. Optical components that guide the light to and from the reaction vessel are located between optoelectronics and the detection/measurement position of the reaction vessel. The light guiding components on light emitter and light receiver side are identical. The light guide may comprise one or more components. The light guide may comprise an element that works like a prism and directs the light towards the reaction vessel (a light guide head, 310) and a plastic optical fibre (POF) 320. Such a setup is illustrated in Figure 3. Both parts, POF and light guide head may be inseparably glued together but they can also be exchangeable. The area, where the light exits the light guide head and where it is being emitted towards the reaction vessel is kept as small as possible. The detection is thus concentrated on an area of the reaction vessel which is as small as possible. This setup makes it possible to measure at different spots on the reaction vessel. Using a reaction vessel with a certain shape and/or features like ribs or a rough surface decreases the optical transmission. These shapes or features are helpful to interrupt the light harrier properly in order to get a better signal-to-noise ratio.

[0050] By using longer or shorter light guides, the light bather can be adapted to different measuring heights or to other devices where the distance between optoelectronics and detection/measurement position is different.

[0051] Alternatively, the light guide may be made out of one piece (Figure 4). The plastic optical fibre may be bent instead of a straight fibre with an attached light guide head to direct the beam to the reaction vessel. This setup needs more installation space than the setup with plastic optical fibre and attached light guide head. Due to the circular area where light exits and enters the light guide (in the one-piece-setup), the geometric properties of the reaction vessels and the aperture design in the housing have to he adapted [0052] The plastic optical fibre may thus be of a cylindrical shape. Different shapes arc also possible.

[0053] The optoelectronic components to detect the reaction vessel (i.e. the light emitter and the light receiver) may be located on a printed circuit board (PCB). This PCB is used to control the functionality of the whole system in which the reaction vessel is to be detected. No additional PCBs or cable connections are needed and the time used to assemble the device is reduced. Figure 5 shows an exemplary system. Two light guides 510, a reaction vessel 520, a light emitter 530, a light receiver 540 and a printed circuit board 550 are displayed. A housing 560 surrounds the light guides. Figure 6 illustrates only two light guides 610, a light emitter 620, a light receiver 630 and a printed circuit hoard 640, where the light emitter 620 and the light receiver 630 are located.

[0054] The reaction vessel may be a cuvette or a microtiter plate. Other reaction vessels are also possible. The reaction vessel may he transparent or translucent. The reaction vessel may be made from a material comprising polypropylene. The reaction vessel may comprise at least one position marker. The position marker may be at least one rib located on the reaction vessel or a rough surface of the reaction vessel. Features like ribs partially increase the thickness and therefore change the optical properties of the reaction vessel. By ribs, a rough surface or other position markers, and in combination with the rather small emitting area of the light guide there can be several detection/measurement positions on the reaction vessel. The several detection/ measurement positions can be used to detect the presence of the reaction vessel detect the liquid level or one or more air bubbles in a liquid inside the reaction vessel detect if the reaction vessel is correctly positioned, i.e. detect the position of the reaction vessel detect defective reaction vessels, i.e. detect the integrity of the reaction vessel.

[0055] The different purposes are illustrated in Figures 7, 8 and 9. Fig. 7 shows three different detection/measurement positions. In Fig. 7A, ribs 710 of the reaction vessel are shown to reduce transmission. The reaction vessel is not in detection/measurement position so that the system will detect that there is no reaction vessel. Fig. 7B shows that the reaction vessel is in position for presence detection. The ribs will reduce transmission and the system will detect that the reaction vessel is in the correct position. In Fig. 7C, the detection/measurement position is in between the ribs where a clear surface 720 allows the system to detect the liquid level or one or more air bubbles in the liquid. The clear surface 720 has a high transmission.

[0056] Fig. 8 is a close view of a detection/measurement position. A rib 810 of a reaction vessel is in detection/measurement position so that the presence of a reaction vessel can be detected by the system. A light guide 820 for guiding the light is also shown.

[0057] Fig. 9A shows a top view of a reaction vessel 910 in a detection/measurement position. . The light guide 920 is directed at the reaction vessel 910. The presence of the reaction vessel 910 can be detected. In Fig. 9B, the same reaction vessel in the same detection/measurement position as in Fig. 9A is shown but the very top part of the reaction vessel is cut off so that a rib 930 is visible which can be detected by the system beause the light guide 940 is directed at the rib of the reaction vessel.

[0058] Figures 7, 8 and 9 thus show that depending on the presence and position of the reaction vessel, the four above purposes are achieved.

[0059] The system may further comprise a signal controller. The at least one light emitter may emit pulsed light and/or the at least one light guide and/or the at least one light receiver may comprise an electrical filter. The electrical filter may be a high-pass filter.

Light emitter and light receiver, an electrical filter and amplifier circuits may be connected to a signal controller which measures the voltage level, adjusts all necessary parameters and communicates with a higher level controller.

[0060] To eliminate production tolerances and ambient light influence, the following measures may be taken.

Choosing a pulsed light emitter in combination with an electrical filter at the detector side at the light guide or light receiver, which blocks a constant voltage offset (or signals with low frequency) caused by ambient light, to compensate for ambient light fluctuations.

- Automatically adjusting the light emitter (for example, LED) current by the signal controller firmware.

S

[0061] The signal controller adjusts the light emitter current to achieve a certain (higher) voltage at its signal input when no reaction vessel is present between the light emitter and the light receiver. The signal controller may additionally adjust the gain of the amplifier to achieve a certain (lower) voltage when a reaction vessel is present.

[0062] The threshold to detect a reaction vessel has to be at a certain value between higher and lower voltage and will he calculated and stored during the automatic adjustment process. The threshold parameter may be 20%.

Vthreshold=(Vhith-Vlow) * threshold_parameter + Vio".

[0063] In addition, a readjustment of the reaction vessel sensor, i.e. the system, is possible to counteract aging effects of the optical and electronic components. This readjustment can be performed automatically by the control unit that drives the light emitter and the light receiver depending on the received signal. The transmitted pulses can also be used for function monitoring, i.e. plausibility check of the sensor signal.

[0064] Every time the measured voltage is lower than VthreshoId, the signal controller indicates a present reaction vessel to the higher level controller. To improve signal evaluation different algorithms can be used. For example, calculation of a mean value of a certain number or measured values can be used to reduce noise.

[0065] A method for the detection of light transmission through a reaction vessel or for the detection of light reflection from a reaction vessel is also provided. The method comprises the following steps: - emitting light from a light emitter - guiding the light through a light guide to a reaction vessel - guiding the light that is transmitted through the reaction vessel or the light that is reflected from the reaction vessel to a light receiver - receiving the light by the light receiver - detecting if light is received by the light receiver.

[0066] The method thus allows to determine by the transmitted or reflected light whether a reaction vessel is present, the level of the liquid inside the reaction vessel, the presence or absence of one or more air bubbles inside the reaction vessel and the integrity of the reaction vessel.

[0067] In one aspect of the disclosure, the method comprises the further step of measuring and adjusting by a signal controller a signal received from the light receiver as explained above.

[0068] In another aspect of the disclosure, the light that is received by the light receiver is filtered light. An optical filter allows, for example, to eliminate the influence of ambient light.

[0069] Use of the above system for the detection of a presence of a reaction vessel, for the detection of a liquid level or one or more air bubbles in a liquid inside the reaction vessel, for the detection of a position of the reaction vessel or for the detection of an integrity of the reaction vessel is also provided. The way these different uses can he achieved is explained above.

[0070] The PCB where the optoelectronic components may he placed on may he mounted to a housing. The light guiding parts may also be inserted into the housing. In that case, the mechanical interface of housing and light guide head is designed in a way that the light guide heads of emitter and receiver side are automatically directed to each other. No manual alignment is necessary. If the plastic optical fibre is of a cylindrical shape, the shape only requires cylindrical holes to reach from the detection/measurement position to the optoelectronics. The light guiding pails may be kept in the housing by press-fit or glue.

[0071] This setup is for example illustrated in Figures 10 and 11. Figure 10 shows two light guides 1010 inside a housing 1020. Figure 11 illustrates a side view of an inventive system with a housing 1110, where two light guides 1120 are integrated. The housing 1110 comprises a channel 1130 where a reaction vessel 1140 is inserted into. The printed circuit board 1150 is also shown.

[0072] The channel 1130, where the reaction vessel 1140 is inserted, and the printed circuit board (PCB) 1150 are separated by the housing 1110. The PCB 1150 is thus covered or separated from the reaction vessel 1140 that can be filled with liquid. It is ensured that liquid coming from the reaction vessel 1140 due to a leakage cannot get in contact with the PCB 1150. The risk of damage or failure of the PCB 1150 is reduced to a minimum.

[0073] Figure 12 shows counterbores and slots 1210 for the correct alignment of the light guiding parts. The only cut-outs of the housing are thus the exemplary circular gaps between light guides and housing. As these light-guide cut-outs are separated from the reaction vessel channel and the detection/measurement position is at the top of the reaction vessel the risk of liquid coming from the reaction vessel through the light-guide hole to the PCB is reduced to a minimum. In addition, due to the exemplary circular interface the round gaps between light guide head and housing can be easily closed/sealed by glue or 0-rings. However, rectangular gaps or other shapes of the gaps are also possible.

[0074] Advantages of the present invention are: "Robust" optical contactless detection of reaction vessels (which may be transparent or translucent) by a through-beam or reflex light barrier with precise repeatability because of -using optoelectronic components that are chosen according to the optical transmission properties of the reaction vessel that is to he detected a "decoupled" arrangement of electronic components and detection/measurement position by using light guides. This measure prevents liquid dripping on electronic components and therefore minimizes the risk of electronic failures - Recalibration/readjustment possible to reduce or eliminate aging effects of the components.

-The light-barrier is created by "standard" optoelectronic components that do not have to he selected to get tighter tolerances.

- Use of pulsed light possible to eliminate the influence of ambient light.

- Beyond the presence detection of a reaction vessel, it is also possible to detect the liquid level or one or more air bubbles inside the reaction vessel, to detect the 0 position of the reaction vessel, i.e. to get information about the positioning accuracy, to detect the integrity of the reaction vessel (i.e. if reaction vessels are defective). These uses can he achieved due to partially different thicknesses, for example by a position marker, or surface properties of the reaction vessel that is to be detected. The different thicknesses or surface properties lead to changes in light transmission that can be measured by the light barrier.

By using light guides the optoelectronics/ PCB can he positioned in order - to protect the PCB from liquid or other influences that can be harmful to the PCB - to combine the circuit to run the optoelectronics together with other circuits on a single PCB.

- The mechanical interfaces are designed in a way that manufacturing and assembly of the optical components and the housing are time-efficient and cost-efficient.

List of reference numerals light emitter light receiver light guide for guiding the light emitted from the light emitter reaction vessel detection/measurement position light guide for guiding the light received by the light receiver optical path 210 optical path 310 light guide head 320 plastic optical fibre (POF) 410 bent plastic optical fibre (POF) 510 light guide 520 reaction vessel 530 light emitter 540 light receiver 550 printed circuit board (PCB) 560 housing 610 light guide 620 light emitter 630 light receiver 640 printed circuit hoard (PCB) 710 ribs 720 clear surface 810 rib 820 light guide 910 reaction vessel 920 light guide 930 rib 940 light. guide 1010 light guide 1020 housing 1110 housing 1120 light guide 1130 channel 1140 reaction vessel 1150 printed circuit board (PCB) 1210 counterbores and slots

Claims

-17-Claims 1. A system for detecting a light transmission through a reaction vessel or for detecting a light reflection from a reaction vessel, comprising a light barrier which comprises at least one light emitter and at least one light receiver, wherein the at least one light receiver serves for receiving light emitted from the at least one light emitter, further comprising at least one light guide for guiding the light emitted from the at least one light emitter and at least one light guide for guiding the light received by the at least one light receiver.
2. The system according to claim 1, wherein the light emitter is an LED and the light receiver is a photodiode.
3. The system according to claim 1 or 2, wherein the light guide comprises one or more components.
4. The system according to any of the preceding claims, wherein the light guide comprises a light guide head and a plastic optical fibre (POP).
5. The system according to claim 4, wherein the light guide head and the plastic optical fibre are exchangeable.
6. The system according to any of the preceding claims, wherein the light emitter and the light receiver arc located on a printed circuit board.
7. The system according to any of the preceding claims, wherein the reaction vessel is a cuvette or a microtiter plate.
8. The system according to any of the preceding claims, wherein the reaction vessel is transparent or translucent.
9. The system according to any of the preceding claims, wherein the reaction vessel is made from a material comprising polypropylene.
10. The system according to any of the preceding claims, wherein the at least one light emitter emits pulsed light and/or the at least one light guide and/or the at least one light receiver comprises an electrical filter.
11. The system according to any of the preceding claims, wherein the POF is of a cylindrical shape.
12. The system according to any of the preceding claims, further comprising a signal controller.
13. The system according to any of the preceding claims, further comprising a reaction vessel comprising at least one position marker.
14. The system according to claim 13, wherein the at least one position marker is at least one rib located on the reaction vessel or a rough surface of the reaction vessel.
15. A method for the detection of light transmission through a reaction vessel or for the detection of light reflection from a reaction vessel comprising the following steps: - emitting light from a light emitter guiding the light through a light guide to a reaction vessel guiding the light that is transmitted through the reaction vessel or the light that is reflected from the reaction vessel to a light receiver - receiving the light by the light receiver detecting if light is received by the light receiver.
16. The method according the claim 15, wherein the method comprises the further step of measuring and adjusting by a signal controller a signal received from the light receiver.
17. The method according to claim 15 or 16, wherein the light that is received by the light receiver is filtered light.
18. Use of the system according to claim 1 for the detection of a presence of a reaction vessel, for the detection of a liquid level or one or more air bubbles in a liquid inside the reaction vessel, for the detection of a position of the reaction vessel or for the detection of an integrity of the reaction vessel.