RU2782303C1 - System of working with liquid and method for analysis of state of tip - Google Patents

Abstract

FIELD: optics.

SUBSTANCE: group of inventions relates to optical and photometric methods for control and analysis of a state of tips used in such systems. A system for working with liquid for dispensing a liquid sample from a tip contains a light source, the first and the second detectors, an analysis unit, and a time-of-flight component. The light source is made with the possibility of projection along the first optical path of the first light beam, which interacts with the tip or its content, and direction along the second optical path of the second light beam, which does not interact with the tip and its content. The first and the second detectors are made with the possibility of detection of the first and the second light beams. The analysis unit is made with the possibility of analysis of the state of the tip based on signals received from the first and the second detectors. The second detector is a normalizing detector made with the possibility of measurement of the intensity of the light source. The time-of-flight component contains the light source and the first detector, and it is made with the possibility of calculation of a distance to a surface of liquid in the tip.

EFFECT: increase in the accuracy of control of a tip and determination of a level of liquid, regardless environmental conditions and liquid characteristics.

16 cl, 20 dwg

Description

FIELD OF TECHNOLOGY

[1] The present invention relates to a fluid handling system and, in particular, to optical and photometric methods for monitoring and analyzing the condition of the tips used in such systems.

BACKGROUND OF THE INVENTION

[2] In manual pipettes and automated liquid handling devices (liquid handling robots), accurate pipetting requires reliable methods to detect and control the condition of the tip into which fluid will be aspirated. First, the tip must be immersed in the collected liquid to a certain depth. A precise volume of liquid is then aspirated and the handpiece is simultaneously lowered so that the lower end of the handpiece is below the surface of the liquid. Finally, the tip is positioned over the receiving container and some or all of the liquid is released into the container.

[3] As is known, to determine the level of liquid in a pipette tip, for example, pressure measurement or capacitance methods are used. These methods have many disadvantages. For highly viscous fluids, the change in liquid level is slower than the change in pressure, resulting in less accurate pressure-based liquid level control. Pressure measurement does not reliably detect partial tip end clogging in cases where air can still pass through the clog. In addition, ambient pressure and altitude affect the measured pressure values.

[4] EP 1 756 587 B1 discloses an aspiration system comprising an aspirator body element having a fluid passage through it, as well as first and second light guides configured to receive and/or transmit light through them. The controller detects the contact of the aspirator tip with the fluid based on the characteristics of the light received from the aspirator tip through at least one of the first and second light guides, and determines the level of the fluid based on the position of the aspirator body element upon detecting the contact of the aspirator tip with the fluid.

[5] In automatic analyzers, photometric methods were partly used:

[6] US 8203721 B2 discloses a photometric method for detecting a liquid-gas interface in a microtiter plate channel in an automatic liquid handling device. Light is simultaneously directed to a plurality of illumination points which are on a flat, convex or concave surface corresponding to the actual shape of the liquid interface to be detected.

[7] EP 1756587 B1 discloses a method for optical detection of liquid for an automatic aspiration system. According to this method, aspirator tips are used, characterized by a discrete change in outer diameter. Light passes through the tip material. Contact of the tip with the fluid is detected optically by detecting a change in the characteristics of light reflected from the outer surface of the tip upon contact of the interfaces and the fluid.

[8] The following publications disclose the use of special tips for the implementation of photometric determination of the level of liquid in a manual pipette:

[9] FI 120336 B describes an optical method for analyzing liquid in a pipette tip. The tip contains optical grating structures and light enters the liquid through the material of the tip and the grating. The light source and detection device are located in the body of the pipette.

[10] US 5,844,686 describes the incorporation of mirrors and windows into a pipette tip for photometric measurements.

[11] There is a need to develop an improved method for tip control and liquid level detection that is accurate, independent of environmental conditions and liquid characteristics, and that can be successfully used in both manual pipettes and automated pipetting systems over the entire range dispensing volumes along with conventional disposable tips.

[12] At least some embodiments of the present invention are intended to overcome at least some of the above disadvantages and limitations of known methods for analyzing and inspecting a tip and its contents in fluid handling devices.

DISCLOSURE OF THE INVENTION

[13] The present invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.

[14] According to a first aspect of the present invention, there is provided a liquid handling system for dispensing a liquid sample from a tip, comprising:

a light source configured to project, through the first optical path, a first beam of light that interacts with the tip or its contents, and configured to direct, through the second optical path, a second beam of light that does not interact with the tip and its contents;

a first detector configured to detect the first beam of light;

a second detector configured to detect the second beam of light; an analysis unit configured to analyze the state of the tip based on the signals received from the first and second detectors;

wherein the second detector is a normalizing detector configured to measure the intensity of the light source.

[15] Various embodiments of the first aspect may include at least one feature from the following bulleted list:

• The first and second detectors and the light source are located inside the cylinder of the liquid handling system, which is a manual pipette.

• The first and second detectors and the light source are located inside the cylinder of the liquid handling system, and the light source is located outside the cylinder.

• The first and second detectors, as well as the light source, are located outside the cylinder of the liquid handling system.

• The light source is located above the top edge of the tip and is configured to project light into the tip material.

• The light source is located on one side of the handpiece and is configured to project light towards the handpiece, and the fluid handling system is an automated fluid handling station.

• The barrel of the fluid handling system is configured to transmit light from a light source through the barrel material to the interior of the tip, preferably to the surface of the fluid.

• The system contains a time-of-flight component that contains a light source and a first detector.

• The system contains a time-of-flight component that is located inside the cylinder of the fluid handling system.

• The system includes a time-of-flight component, the light source in the time-of-flight component is located outside the fluid system cylinder, and the first detector in the time-of-flight component is located inside the fluid system cylinder.

• The system comprises an optical fiber extending from the light source into the inside of the tip, preferably towards the surface of the liquid inside the tip, and configured to direct the first beam of light from the light source onto the surface of the liquid.

• The system includes an optical component, such as a lens or a cone, positioned in front of the first detector and configured to focus a first beam of light from the inside of the tip, preferably from the surface of the liquid inside the tip, onto the first detector.

• The lower edge of the cylinder of the fluid handling system is shaped like a lens, and this cylinder is configured to transmit light from a light source through the material of the cylinder and said lower edge is shaped like a lens into the interior of the tip, preferably on the surface of the liquid, the cylinder is also configured to collecting light that has interacted with the tip or its contents, in particular the liquid surface, on the first detector.

• The system contains an optical component, which is an interchangeable lens system that connects the cylinder of the liquid handling system to the handpiece, and which is attached to the outer surface of the cylinder and the inner surface of the handpiece, said lens system being capable of transmitting light from a light source into the interior. the tip, in particular the surface of the liquid, and the lens system is also configured to collect light that has interacted with the tip or its contents, in particular the surface of the liquid, on the first detector.

• The system includes a support arm that is movable around and along the tip, and a first detector, and preferably a second detector, is attached to the support arm.

• The first detector, and preferably the second detector, is in the form of a linear sensor.

• The system includes a support arm that is movable around and along the tip, and the light source is attached to the support arm.

• The light source is located inside the cylinder of the liquid handling system.

• The system comprises two support arms on opposite sides of the tip, the light source is attached to one of said support arms, and the first detector is attached to the other of said support arms, the support arms being movable around the tip.

[16] According to a second aspect of the present invention, there is provided a method for analyzing the condition of a disposable handpiece used in a fluid handling system for sucking and dispensing fluid, comprising the following steps:

direction from the light source to the first detector along the first optical path of the first beam of light that interacts with the tip or its contents; and measurement of magnitude;

direction from the light source to the second detector along the second optical path of the second beam of light, which does not interact with the tip and its contents; measuring the intensity of the light source and

analyzing the state of the disposable tip based on the measured value and the measured intensity of the light source; wherein the second detector is a normalizing detector.

[17] Various embodiments of the second aspect may include at least one feature from the following bulleted list:

• The first beam of light interacts with the tip material or the liquid inside the tip, or both.

• The analysis includes one or more of the following: detecting the level of liquid in the tip, determining the volume of liquid in the tip, determining the contact between the tip and the liquid surface, determining the contact between the tip and the outer container, and determining the displacement of the tip.

• The analysis step involves determining the liquid level or volume of liquid in the tip, and the value is the reflectance.

• The analysis step involves determining the liquid level or volume of liquid in the tip, and the value is the absorption coefficient.

• The fluid handling system is a system according to the first aspect of the present invention.

[18] At least some embodiments of the present invention provide significant advantages over known liquid level detection and tip control methods in liquid handling devices. The present method makes it possible to accurately measure the liquid level, even for highly viscous liquids, and this method is independent of ambient pressure conditions and can reliably detect any clogging of the tip.

[19] At least some embodiments of the present invention provide versatile optical techniques that can be readily implemented for tip inspection in both manual and automated fluid handling devices.

BRIEF DESCRIPTION OF THE DRAWINGS

[20] FIG. 1 illustrates the principle of relative measurement using two detectors in accordance with at least some embodiments of the present invention;

[21] FIG. 2 shows an embodiment in which the main interaction between light and liquid in the tip is reflection;

[22] FIG. 3 and 4 show embodiments in which the main interaction between light and liquid in the tip is absorption;

[23] FIG. 5 and 6 show additional embodiments in which the main interaction between light and liquid in the tip is absorption;

[24] FIG. 7 and 8 show additional embodiments in which the main interaction between light and liquid in the tip is reflection;

[25] FIG. 9 and 10 show additional embodiments in which the main interaction between light and liquid in the tip is reflection;

[26] FIG. 11 and 12 show removable modules for photometric measurement in accordance with at least some embodiments of the present invention;

[27] FIG. 13 shows an embodiment in which the light source and detector are movable around the tip.

[28] FIG. 14 shows an embodiment in which the detector is movable around the tip.

[29] FIG. 15 shows an embodiment in which the light source and detector are movable around the tip.

[30] FIG. 16 illustrates an embodiment that uses a time-of-flight component located inside a cylinder.

[31] FIG. 17 and 18 illustrate embodiments that use a time-of-flight component located partially within the cylinder.

[32] FIG. 19 shows an experimental photometric measurement apparatus in accordance with one embodiment of the present invention.

[33] FIG. 20 is a graph depicting the measured signal versus the volume of fluid sucked in, in accordance with one embodiment of the present invention.

IMPLEMENTATION OF THE INVENTION

[34] DEFINITIONS

[35] As used herein, the term "fluid handling system" includes both manual pipettes and automated fluid handling stations or robots. These systems can be manual, electronic or electromechanical.

[36] As used herein, the term “tip” includes both disposable and reusable tips that are removable and that are used in manual pipettes or automated liquid handling stations or robots to receive a liquid sample to be transferred into a container, microplate, or etc. Such tips can be manufactured according to the needs of the customer or commercially from any suitable material, preferably from a plastic material. In a preferred embodiment, the tip is a disposable tip.

[37] In a fluid handling system such as a pipette, there is a linear actuator to provide longitudinal movement of the piston in the cylinder to aspirate and dispense fluid into and out of the pipette tip.

[38] As our observations have shown, optical measurements can be successfully applied to detect and control the various states of the handpiece during liquid handling or dispensing operations. As used herein, "tip condition" refers to, for example, the liquid level or volume of liquid in a pipette tip, stability of the tip, contact between the tip and an external liquid container, or contact between the tip and the surface of a liquid in the container. The present method is based on performing a relative measurement using two detectors. Using this principle, a surprisingly large set of working geometric measurement methods can be developed.

[39] The optical method can be based on the principle of transit time or on photometry. In photometric methods, the measured quantity is the light intensity.

[40] In some embodiments, implementation of the present invention, the light passes through certain optical paths on the tip or inside it to interact with the light with the tip and/or its contents in various ways. After the interaction, the light is collected and characterized in a detection device to analyze the state of the tip and any changes in it.

[41] The present method makes it possible to determine the liquid level in the tip, the stability of the tip, the volume of the liquid in the tip, and the contact between the tip and the surface of the liquid in the container using optical measurement.

[42] The geometric arrangement of the measurement means determines the type of interaction between the light and the tip or the liquid in the tip. The interaction may be, for example, reflection, absorption, refraction, scattering or interference. Preferably the interaction is either reflection or absorption. Factors that affect measurement dynamics include the direction and angle of incidence of the light, the location of the detector, the geometry of the tip, and the wavelength of the light.

[43] In a preferred embodiment, the light from the light source is split into two beams that travel along two different optical paths. By "different optical paths" is meant that said paths at least partially pass through different sections or material interfaces of the handpiece, the cylinder of the fluid handling system, or the fluid/air space within the handpiece; and/or the path length values are at least partially different and/or the angle of incidence is different. One or both of the optical paths may pass within the airspace of the handpiece. One or both of the optical paths may extend within the tip material or barrel material.

[44] Preferably, the optical measurement is performed using infrared, ultraviolet or visible light, or a combination thereof.

[45] In the photometric method, the light source is preferably an LED or a laser.

[46] FIG. 1 illustrates the principle of relative measurement using two optical detectors 11, 12. In this embodiment, the light from the LED 10 is split into two optical paths. The first optical path (measurement path) is configured to provide interaction with the tip 13, and the second optical path is configured to directly measure the intensity of the light source 10. The instability of the light source is compensated by measuring the relative value between the two detectors.

[47] In the first optical path, the interaction between light and liquid to be measured is mainly the reflection of light from the surface of the liquid. The relative reflectance is measured. The following equation 1 determines the relative reflection coefficient R as a function of the null and time dependent voltage signals from the detectors:

[48] In Equation 1, V _MB is the voltage of the measurement detector 11 at empty measurement when the tip is empty, and V _NB is the voltage of the normalizing detector 12 at empty measurement when the tip is empty. V _MK is the measurement detector voltage at time t _K when the tip contains liquid, and V _NK is the normalizing detector voltage at time t _K when the tip contains liquid.

[49] FIG. 2-18 the second optical path and the normalizing detector are not shown for clarity. Preferably, in the embodiments shown in FIG. 2-18, the second optical path is configured to provide a direct measurement of the intensity of the light source.

[50] As shown in FIG. 2, the light source 20 and the measurement detector 23 are located inside the pipette barrel 22. The main interaction to be measured between the light passing along the measurement path and the liquid is the reflection from the surface 21 of the liquid. Measure the relative reflection coefficient.

[51] As shown in FIG. 3 and 4, light passes into the material of the tip and is reflected off the bottom edge 31, 41 of the tip 33, 43. The tip is shaped to allow for optical measurements such that light travels from the tip to the liquid. The main interaction to be measured between the light passing through the measurement path and the liquid 32, 42 is absorption as the light passes through the liquid in the tip. The light source is 30, 40 and the measurement detector 34, 44.

[52] As shown by our observations, the geometric shapes shown in FIG. 2 and 4 provide the best reliability and performance.

[53] The embodiment shown in FIG. 3 is particularly suitable for use in automated fluid handling stations because the geometry of the illumination and detection means is approximately vertical in that the light source 30 and detector 34 are positioned above the tip 33.

[54] If the tip is in contact with the surface of the liquid in the outer container, a decrease in the measured signal may be observed, since the proportion of light reflected from the bottom edge of the tip decreases relative to the amount of light passing through the bottom edge. This is because the refractive indices of the tip material and the liquid are close to and different from those of air.

[55] As shown in FIG. 5 and 6, the tip is illuminated by a light source 50, 60 from outside and the light is reflected from the surfaces of the tip to the detector 51, 61. The effect of the liquid to be measured is based on absorption as light passes through the liquid and other optical phenomena.

[56] In the embodiments shown in FIG. 3, 4, 5 and 6, contact between the tip and the outer container can be detected.

[57] As shown in FIG. 7 and 8, the tip is illuminated by a light source 70, 80 from outside and the light is reflected from the tip and liquid surfaces to the detector 71, 81. The liquid action to be measured is based on reflection from the liquid surface 72, 82 and other optical phenomena.

[58] The embodiments shown in FIG. 5-7 provide flexible measurement options. By varying the angle of incidence, various reflections of light can be measured: reflection directly from the liquid surface; reflection from the optical interface between the liquid and the plastic material of the tip; or monitor the change in the light transmission of the plastic material of the tip.

[59] The embodiments shown in FIG. 5-8 are particularly suitable for use in automated fluid handling stations. At such stations, one can essentially freely choose the location and orientation of the light source and, for example, illumination of the tip from the side is possible.

[60] As shown in FIG. 9 and 10, light passes into the material of the cylinder 91 where it is refracted from the lower edge 92 of the cylinder towards the surface 93 of the liquid. The bottom edge 92 has a sloped surface or lens shape. The effect of a liquid to be measured is based on reflection from the surface of the liquid and other optical phenomena. The light source is designated 90 and the measurement detector is designated 94.

[61] The embodiment shown in FIG. 9 can be used in both a manual pipette and an automated liquid handling station. Geometric characteristics associated with the measurement provide a compact design.

[62] As shown in FIG. 10, the light that is reflected from the liquid surface 101 is collected in the maximum area by the lower edge 102 of the cylinder, which is shaped like a lens with a large diameter. The cylinder body 103 performs the function of a light guide, the passage of light inside which occurs due to total internal reflection. Total internal reflection occurs because the material of the cylinder has a much higher refractive index than the surrounding air. The light source is denoted by 100 and the measurement detector is denoted by 104. The embodiment shown in FIG. 10 can be used both in an automated liquid handling station and in a manual pipette.

[63] In the device shown in FIG. 11 and 12, a removable measuring module in the form of a lens system is used, which is fixed on the inner or outer surface of the cylinder.

[64] As shown in FIG. 11, the module 111 seals against the outer surface 112 of the cylinder. The module body functions as a light guide, and the bottom surface 113 of the module functions as a lens. The tip seals against the outer surface 114 of the module housing. The light source is 110 and the measurement detector is 116.

[65] The embodiment shown in FIG. 11 is particularly suitable for use in automated liquid handling stations.

[66] As shown in FIG. 12, the module 121 seals against the outer surface 122 of the cylinder. Light source 120 and detector 126 are located within the module: In one embodiment, they are enclosed in a shell. In another embodiment, they are cast inside the light guide that forms the module. The bottom surface 124 of the module is a surface that reflects light so that it is reflected towards the liquid surface. Alternatively, the smaller components may be directed towards the surface of the liquid within the module.

[67] When using photoconductors, the geometric configuration options shown in FIG. 1-11 can be implemented by moving the light source and detector to the desired location, for example, closer to the body of the pipette.

[68] As shown in FIG. 13, the light source 130 and the detector 133 are located on opposite sides of the handpiece and attached to a movable support frame 131. The frame may be in the form of two support arms. The tip is scanned by rotating the frame and moving it in the vertical direction. The tip and its contents can be scanned with very high accuracy. Based on measurement data, tip straightness, liquid volume, mixing of different liquids, and air space between two liquids in pipette dilution mode can be determined.

[69] FIG. 14 shows that a high resolution linear probe 142 is used as the detector. This sensor is mounted on a movable support arm 141. The sensor is rotated around the tip by moving and rotating the support arm. Thus, the tip and its contents can be quickly and accurately scanned. The topmost pixels of the sensor can be used as a measurement reference, so there is no longer a need for a separate reference detector to obtain relative measurement data. A 2D image sensor can also be used instead of a linear sensor.

[70] In FIG. 15 shows that the light source 150 is located at the lower end of the support arm 152, below the linear sensor 151. A portion of the light that has passed at a right angle through the outer surface of the tip is reflected from the opposite outer surface of the tip upwards towards the linear sensor.

[71] The embodiments shown in FIG. 13-15 are particularly suitable for use in automated liquid handling stations for determining liquid levels.

[72] In photometric measurement, the light source can generate waves of different wavelengths that alternate at high intervals in accordance with the principle of time division. The data of parallel measurements obtained in this way can be used to improve the accuracy of measurements for liquids of different colors. It becomes possible to analyze the mixture of different liquids inside the tip. You can easily create different wavelengths using the same light source component, such as an RGB LED.

[73] In photometric measurement, signal processing can be performed using the principle of phase-sensitive detection or a locking amplifier. The input signal to be measured modulates the carrier signal which has been generated by the intermittent operation of the light source. Thus, the input signal is shifted to a suitable higher frequency where it will not be affected by low frequency noise. Before sampling by the AD converter, an analog low-pass filter filters the signal. After demodulation, the signal is filtered with a narrow-band, steep digital low-pass filter so that the input signal can be separated from the noise.

[74] In addition to the traditional photometric measurement, a new and integrated time-of-flight component can be used to control movements of the pipette tip and determine the volume of liquid contained in the tip. The time-of-flight component measures the travel time of the light signal. The light transmitted by the specified component is reflected from the liquid surface to a detector located on the opposite edge of the component, which allows the component to calculate the distance to the liquid surface based on the light travel time. The advantage of transit time measurement is that it does not depend on the reflected light intensity, provided that the intensity exceeds a certain minimum level.

[75] As shown in FIG. 16, the time-of-flight component 160° is located entirely within the pipette barrel 161.

[76] As shown in FIG. 17, the time-of-flight component 170 is only partially located within the pipette barrel 171. The transmitting part of the component is located outside the cylinder. The light emitted by the transmitter is directed into the cylinder through a multi-mode optical fiber 172. One end of the fiber is made in the form of a lens that directs the light onto the surface 173 of the liquid. The light reflected from the surface of the liquid is collected over a maximum area by a lens 174 which focuses the collected light onto the detector of the measurement component. An optical fiber guides the incident light either past the lens or through the lens, which collects the reflected light to avoid direct reflection of the incident light from the lens to the detector. In this way, the maximum accuracy of the measurement result is achieved. The lens can be a Fresnel lens, in which case it will be light and thin.

[77] In the device shown in FIG. 18 uses the same time-of-flight component 180 as in FIG. 17. The lens that collects reflected light has been replaced with a cone 182 that collects light reflected from the liquid surface. The inner surface of the cone is reflective, whereby the cone effectively focuses the collected light onto the detector of the transit time measurement component. Instead of a cone, the collecting device may have the shape of a paraboloid.

[78] The embodiments shown in FIG. 16-18 can be used both in a manual pipette and in an automated liquid handling station.

[79] In some embodiments, light is transmitted and directed to the liquid surface or tip using an optical fiber or photoconductor.

[80] In some embodiments of the present invention, light is transmitted and directed to a detector using an optical fiber or photoconductor.

[81] The use of an optical fiber provides flexibility in terms of placement of the light source and/or detector in a liquid handling system, particularly in a manual pipette. In manual pipettes, the space available for adding additional components is limited.

[82] When the tip is illuminated from the outside, this makes it possible to determine the contact of the tip with the surface of the liquid in the container, which is separated from the pipette and which is used, for example, as a source of liquid or as a receiving container for the dispensed liquid.

[83] In some embodiments, the implementation of the light source and detectors can be located near the body of the pipette through the use of photoconductors.

[84] In one embodiment, infrared (IR) light is used in the measurement. An IR light source and/or an IR detector may be incorporated into, for example, the bottom of the sleeve to eject the tip of the liquid handling system.

[85] In some embodiments, light is projected (reflected) onto the measurement detector along two alternative paths: 1) through the material of the tip or 2) through the air space within the tip. The present invention makes it possible to optimize the power and accuracy of the signal in relation to the analyzed volume of liquid: For large volumes of liquid (for example, more than 0.5 ml, preferably more than 1 ml), path 2 is used. For small volumes of liquid (for example, less than 1 ml, preferably less than 0 .5 ml) use route 1. In addition, both routes can be used with different weighting factors.

[86] Preferably, the present method is applicable to the analysis of liquid volumes from 1 pl to about 10 ml, more preferably from 10 pl to 5 ml, for example, from 10 pl to 200 pl.

[87] Hysteresis phenomena can be used to analyze whether the conical lower end of the tip contains liquid.

[88] One advantage is that conventional disposable tips can be used. The tip must not contain any special means for transmitting or directing light, such as gratings, lenses, or irregular shapes.

[89] In some embodiments, there are vertical raised channels on opposite sides of the tip. Said channels are preferably made of the same material as the rest of the tip and are configured to transmit light from the light source to the detector. Light is directed from the light source down one channel and up to the measurement detector through another channel.

[90] The present method can be applied in a manual pipette or in an automated liquid handling station. In a liquid handling station, two independent methods of analyzing the liquid level at the tip can be used, for example, the present optical method and the pressure based method.

[91] This method allows you to accurately measure the volume of liquid in the range of pl.

[92] The present invention overcomes several disadvantages of pressure-based liquid level detection methods: The present invention is not affected by ambient pressure or altitude. The present invention allows tip clogging to be detected. In addition, the present method is suitable for detecting high viscosity liquids. The movement of such fluids lags behind the change in pressure inside the tip. The optical measurement according to the present invention makes it possible to detect the volume of liquid contained in the tip immediately, in real time.

[93] Next, the electronic circuitry and signal processing according to some embodiments will be described in more detail.

[94] Relative Measurement

[95] The instability of the light source, such as LED or laser, and its power supply is compensated by making a relative measurement between the two detectors. The light emanating from the light source is divided into two optical paths. One optical path interacts with the pipette tip, while the other optical path is configured to measure the intensity of the light source directly or at constant attenuation without any interaction with the pipette tip. The two detectors need not be identical if they are used within their linear range. The measurement accuracy is based on the linear response of the detectors.

[96] Noise Sources

[97] The term "noise" refers to everything that affects the measurement result, but does not depend on the measured parameter. In optical measurement of a pipette tip and the volume of liquid within it, the most significant noise is the noise in the optical signal. Scattered light from the environment and the current of the detector, which occurs without exposure to light, are detected in the measured signal as a constant component, and a component with a frequency of 100 Hz can be associated with the illumination of the room. The optical and electronic measurement structure also includes 1/f noise, white noise, and the 50 Hz and 150 Hz mains frequency components. With the exception of white noise, the most significant noise sources are mostly below 175 Hz.

[98] Modulation and Sampling

[99] In modulation, the input signal is shifted to a suitable higher frequency where it will not be affected by low frequency noise. The signal generated by the detector is modulated at a frequency that corresponds to the intermittent operation of the LED. In the sampling performed by the AD converter, one digital value is generated for each LED ON/OFF state. Thus, the sampling rate (FS) is twice the modulation frequency. The input signal is transmitted as an amplitude modulated signal, taking into account the sampling rate at the so-called minimum allowable sampling rate (FS/2).

[100] Analog Anti-Aliasing Filtering

[101] Before sampling performed by the AD converter, the signal is filtered using an analog low-pass filter. The so-called low-pass smoothing filter limits the aliasing of frequencies greater than half the sampling frequency (FS/2) in the sampled signal during sampling. Discretization in the AD converter is performed synchronously with modulation, i.e. the FS/2 signal must pass through an analog low-pass filter whose cutoff frequency (-3 dB) is set to FS/2 plus an appropriately small value.

[102] Demodulation and Filtering

[103] AM Input with

the minimum allowable sampling rate is demodulated, i.e. is shifted to zero frequency when it is multiplied by a cosine signal at the minimum allowed sample rate, having the form [1, -1, 1, -1, ...]. After amplitude modulation, the spectrum of the modulating signal is shifted near the carrier signal. To detect the pipette tip and determine the volume of liquid inside the tip, use the value of the signal intensity at zero frequency. After demodulation, the input signal is contained in the DC component, and the remaining AC component is considered noise from the measurement point of view. As a result of demodulation, the highest power noise observed near zero frequency is shifted to a location near the minimum allowed sampling rate. After demodulation, the signal is filtered with a narrow-band digital low-pass filter with the steepest possible response to prevent noise or interference from distorting the input signal. Thus, the principle of phase-sensitive detection or locking amplifier is realized.

[104] Example

[105] In FIG. 19 shows the measuring system built into a manual mechanical pipette (Sartorius, model Tarta). The operation of the system is based on photometric measurement. In this test system, a normalizing detector was not used. In all other respects, the system utilizes measurement related geometries as shown in FIG. 2. A 1000 pl tip was used during the measurement and the dispensed volume was set to 1000 pl. When liquid was sucked in, the detector signal was recorded. Digital low-pass filtering was carried out by averaging the instantaneous results of the AD converter, which were obtained by interrogating the measuring system. The results are shown in FIG. 20 as a graph of the measured signal intensity versus the volume of fluid in the tip. The results showed that the system is able to reliably detect the presence of liquid in the tip and ensure that it is successfully drawn into the tip.

[106] It should be understood that the disclosed embodiments of the present invention are not limited to the particular constructions, method steps, or materials disclosed herein, but also extend to their equivalents as those of skill in the art would suggest. In addition, it should be understood that the terminology used herein is used solely for the purpose of describing specific embodiments and is not intended to be limiting.

[107] Reference in this specification to one embodiment or any embodiment means that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the present invention. Thus, the expressions "in one embodiment" or "in some embodiment" in various places in this specification do not mean that they all necessarily refer to the same embodiment. When referring to a numeric value using a term such as "approximately" or "substantially", the exact numeric value is also disclosed.

[108] In the context of this document, a variety of elements, structural elements, compositional elements and/or materials for convenience can be represented in the general list. However, these lists should be construed as lists in which each element of the list can be independently identified as a separate and unique element. Thus, no individual element of such a list should be considered as the actual equivalent of any other element of the same list solely on the basis that they are represented in the general group, unless otherwise indicated. In addition, various embodiments and an example of the present invention may be referred to herein along with alternatives for various components thereof. It should be understood that such embodiments, examples, and alternatives should not be considered as actual equivalents of each other, but should be considered as separate and independent forms for presenting the present invention.

[109] In addition, the features, structures, or characteristics described may be combined in any suitable manner in one or more embodiments. This description provides numerous specific details, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of the embodiments of the present invention. However, it will be apparent to a person skilled in the art that the present invention may be practiced without one or more specific details, or using other methods, components, materials, etc. In other cases, well-known structures, materials or operations are not shown or described in detail in order to avoid obscuring aspects of the present invention.

[110] While the above examples illustrate the principles of the present invention in one or more specific applications, it will be apparent to those skilled in the art that numerous changes in form, use, and implementation details can be made without inventiveness and without departing from the principles and concepts of the present invention. inventions. Accordingly, the present invention is not intended to be limited except as set forth in the following claims.

[111] The verbs "comprise" and "include" are used in this document as open restrictions that do not exclude or require non-listed features. The features listed in the dependent claims can be freely combined, unless expressly stated otherwise. In addition, it should be understood that the use of singular grammatical forms throughout this document does not preclude plurality.

INDUSTRIAL APPLICABILITY

[112] At least some embodiments of the present invention find commercial application in manual pipettes and automated liquid handling stations.

LIST OF CITATIONS

Patent Literature

EP 1756587 B1

US 8203721 B2

EP 1756587 B1

FI 120336 B

US5844686

Claims (29)

1. A liquid handling system for issuing a liquid sample from a tip, comprising: a light source configured to project, through the first optical path, a first beam of light that interacts with the tip or its contents, and configured to direct, through the second optical path, a second beam of light that does not interact with the tip and its contents; a first detector configured to detect the first beam of light; a second detector configured to detect the second beam of light; an analysis unit configured to analyze the state of the tip based on the signals received from the first and second detectors; wherein the second detector is a normalizing detector configured to measure the intensity of the light source; wherein the fluid handling system comprises a time-of-flight component that includes said light source and said first detector and is configured to calculate the distance to the liquid surface at the tip. 2. The system of claim. 1, in which the first and second detectors, as well as a light source are located inside the cylinder of the system for handling liquid, and the system for handling liquid is a manual pipette. 3. The system of claim. 1, in which the first and second detectors are located inside the cylinder of the system for working with liquid, and the light source is located outside the cylinder. 4. The system of claim. 1, in which the first and second detectors, as well as a light source are located outside the cylinder of the system for working with a liquid. 5. The system of claim. 1, in which the light source is located above the upper edge of the tip and is configured to project light into the material of the tip. 6. The system of claim 1 wherein the light source is located on one side of the handpiece and configured to project light toward the handpiece, the fluid handling system being an automated fluid handling station. 7. The system of claim 1, wherein the cylinder of the fluid handling system is configured to transmit light from the light source through the material of the cylinder into the interior of the tip, preferably onto the surface of the fluid. 8. The system of claim 1 wherein the time-of-flight component is located within the cylinder of the fluid handling system. 9. The system of claim 1, wherein the light source in the TOF is located outside the fluid system cylinder and the first detector in the TOF is located inside the fluid system cylinder. 10. The system according to any one of the preceding claims, further comprising an optical fiber extending from the light source into the inside of the tip, preferably towards the surface of the liquid inside the tip, and configured to direct the first beam of light from the light source onto the surface of the liquid. 11. The system according to any of the preceding claims, further comprising an optical component, such as a lens or a cone, located in front of the first detector and configured to focus the first beam of light from the inside of the tip, preferably from the surface of the liquid inside the tip, onto the first detector. 12. The system of claim. 7, in which the lower edge of the cylinder of the fluid handling system is in the form of a lens, wherein said cylinder is configured to transmit light from a light source through the material of the cylinder and said lower lens-shaped edge into the interior of the tip, preferably onto the surface of the liquid, and the cylinder is also configured to collect light that has interacted with the tip or its contents, in particular the liquid surface, on the first detector. 13. The method of analyzing the state of the tip used in the system for working with liquid for suction and delivery of liquid, and includes the following steps: - the direction from the light source to the first detector along the first optical path of the first beam of light that interacts with the tip or its contents; and measurement of magnitude; - the direction from the light source to the second detector along the second optical path of the second beam of light, which does not interact with the tip and its contents; measuring the intensity of the light source and - analysis of the state of the disposable tip on the basis of the measured value and the measured intensity of the light source; wherein the second detector is a normalizing detector; wherein the fluid handling system comprises a time-of-flight component that includes said light source and said first detector and is configured to calculate the distance to the liquid surface at the tip. 14. The method of claim 13, wherein the first beam of light interacts with the material of the tip, or the liquid within the tip, or both. 15. The method according to any one of paragraphs. 13 and 14, wherein the analysis includes one or more of the following: determining the liquid level in the tip, determining the volume of liquid in the tip, determining the contact between the tip and the liquid surface, determining the contact between the tip and the outer container, and determining the displacement of the tip. 16. The method according to any one of paragraphs. 13-15, wherein the analysis step includes determining the liquid level or liquid volume in the tip, and said value is the reflectance or absorption coefficient.

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