An automated digital microscope system and method for testing a biological sample

Abstract

Automated digital microscope system for testing a biological sample, the system comprising a housing (4), a slide slot (11) configured to receive and hold a slide (21) containing a biological sample (22), an illumination device (12) arranged on a first side (SI) of the slide slot (11), an image sensor (13) arranged on a second side (S2) of the slide slot (11) opposite to and coaxially with the illumination device (12), a focusing and magnification unit (14) placed at a linear distance from the image sensor (13) on the second side (S2) of the slide slot (11), the focusing and magnification unit (14) comprising an objective lens (141) providing optical magnification and placed coaxially with the illumination device (12) and / or image sensor (13) and a focusing actuator(142) configured to move the objective lens (141). The slide slot (11), the illumination device (12), the image sensor (13) and the focusing and magnification unit (14) are arranged within the housing (4). A processing unit is configured to receive one or more images obtained by the image sensor (13), processing the one or more images, and based on the processing of the one or more images determine a focus distance between the objective lens (141) and the biological sample (22) wherein a focused image of the biological sample (22) is produced on the image sensor (13), and a drive unit is configured to control the focusing actuator (142) to move the objective lens (141) towards or away from the biological sample (22) such that a distance between the objective lens (141) and the biological sample (22) equals the determined focus distance.

Description

[0001] AN AUTOMATED DIGITAL MICROSCOPE SYSTEM AND METHOD FOR TESTING A BIOLOGICAL SAMPLE

[0002] Technical field

[0003] The present disclosure relates to a system for testing a biological sample, preferably semen. The disclosure further relates to a method for testing a biological sample.

[0004] Background art

[0005] Analysis of biological samples, such as semen, can be slow and expensive, limiting practicality and accessibility. Conventional light microscopy equipment used for semen analysis is complex and costly, requiring manual handling and adjustment by experienced personnel, resulting in time-consuming and expensive procedures.

[0006] The high cost of the equipment, combined with labour, can make semen analysis relatively expensive, limiting access for many patients. Therefore, there is a need for new and innovative technologies that can overcome these limitations, providing faster, more accurate, and cost-effective solutions for the analysis of biological samples, including semen.

[0007] WO2017 / 197072 Al describes a system including a sample carrier with a specimen holding area and a detachable cover placed on top of the specimen holding area and including a magnifying component configured to align with the specimen holding area, at least a first image sensor module arranged to capture images of the first holding area, and a processor for performing analytic processes on the captured images.

[0008] Summary

[0009] According to a first aspect, the disclosure relates to a system for testing a biological sample, preferably semen, the system comprising a slide slot configured to receive and hold a slide containing a biological sample; an illumination device arranged on a first side of the slide slot, the illumination device being configured to emit light that illuminates and at least partly propagates through the biological sample when the slide containing the biological sample is placed in the slide slot; an image sensor arranged on a second side of the slide slot opposite to and coaxially with the illumination device and configured to receive at least a part of the emitted light that has propagated through the biological sample; a focusing and magnification unit placed at a linear distance from the image sensor on the second side of the slide slot, the focusing and magnification unit comprising an objective lens providing optical magnification and placed coaxially with the illumination device and / or image sensor and a focusing actuator configured to move the objective lens; a processing unit configured to receive one or more images obtained by the image sensor, processing the one or more images, and based on the processing of the one or more images determine a focus distance between the objective lens and the biological sample wherein a focused image of the biological sample is produced on the image sensor; and a drive unit configured to control the focusing actuator to move the objective lens towards or away from the biological sample such that a distance between the objective lens and the biological sample equals the determined focus distance.

[0010] Consequently, a system with low-cost point of care testing capabilities may be provided. Further, the system provides autofocusing of the biological sample by determination of a focus distance for which a final image recording may be performed.

[0011] It may also be regarded as a further advantage that a small and compact microscope system is provided. This may make it easy to implement in small laboratories, e.g., a field laboratory compared to state of the art microscope systems.

[0012] The system is based on the principles of finite conjugate light microscopy.

[0013] By the slide slot being configured to receive and hold a slide it may be understood to constitute that the slot has dimensions which accommodate the slide and that the slide slot comprises fixation means, which allow the slide to be fixated.

[0014] The slide slot may be adapted to receive the slide by having inner dimensions substantially matching the outer dimension of the slide. The slide slot may have a repositioning means adapted to reposition the slide with respect to the through hole. The slide slot may be provided with a clip, which secures the slide. The slide slot may be provided with a spring-loaded release mechanism for releasing the slide. The slide may preferably be a glass slide or optical plastic slide.

[0015] The illumination device may comprise a light source such as an LED- light, a light bulb or a reflector reflecting a natural light source or an electrical light source onto the sample. The light source may be powered by an internal power source or an external power source. The light source may have a spectrum in the visible light spectrum, ultraviolet spectrum, or the infrared spectrum. The illumination device may comprise optical components for collimating and homogenizing the light source, such that a homogenous illumination distribution is produced on the sample plane. The illumination components may be movable and / or replaceable.

[0016] Alternatively, or additionally, the illumination device may comprise an optical diffuser, such as a diffuser film, a diffractive optical element (DOE), or a reflective element.

[0017] Alternatively, or additionally, the illumination device may comprise a condenser lens such as a DOE, a hologram, a zone plate, plano-convex lens, or the like. The condenser lens could be made of plastic or glass.

[0018] By illuminating the biological sample, a transmission image of the biological sample is created, which may be detected by the image sensor. By light partly propagating through the biological sample it is understood that part of the emitted light may be lost due to absorption or scattering within the biological sample. Furthermore, part of the light may be lost if the illuminated area of the biological sample is larger than the dimensions of the image sensor, or if all the illuminated image is not aligned to the image sensor.

[0019] The image sensor is configured to obtain one or more images.

[0020] The image sensor may be any suitable image sensor, such as a CMOS or CCD sensor. The image sensor may be part of a camera. The camera may further comprise a Printed Circuit Board Assembly (PCBA).

[0021] Alternatively, or additionally, the image sensor may be part of a PCBA comprising of but not limited to, the circuitry required to process the images and drive unit for controlling the focusing actuator.

[0022] By arranging the focusing and magnification unit between the slide and the image sensor it may be understood that the image generated by the illumination of the slide propagates through the focusing and magnification unit before reaching the image sensor.

[0023] By placing the focusing and magnification unit at a linear distance from the image sensor it may be understood that the focusing and magnification unit and the image sensor are separated such that they are not in direct physical contact or abuts, however they may be indirectly linked or connected via other components or elements.

[0024] The objective lens may magnify the image, such that the image of the sample formed on the image sensor is increased in dimensions compared to the size of the biological sample.

[0025] The objective lens may be a ball lens, a concave lens, a convex lens, an aspheric lens, a plano-convex lens, a meniscus lens, a GRIN lens, or a lens assembly.

[0026] The objective lens may be a made of or comprise a glass or plastic material.

[0027] The linear magnification is defined as the ratio of the size of the image formed on the sensor yi to the actual size of the object y0i.e., ML= -— , where y0the minus sign indicates an inverted image. The linear magnification provided by the objective lens may be 2-3 times, preferably 3-4 times, more preferably 4-5 times, or higher of the true size of the image of the biological sample.

[0028] The focusing actuator may comprise a piezoelectric motor, voice coil motor actuator (VCM), and / or mechanical displacement.

[0029] The focusing actuator may be configured to hold the objective lens.

[0030] The focusing actuator may provide coaxial movement of the objective lens, i.e. focusing actuator and the objective lens are both placed coaxially with the illumination device and the movement of the objective lens is along the common axis.

[0031] The focusing and magnification unit may be positioned substantially at a distance from the image sensor and / or camera and / or PCBA.

[0032] Focusing may also be achieved by moving the sample slide linearly or in multiple axes, utilizing a microstage, which may also involve stepper or DC motors.

[0033] The processing unit may be any circuit and / or device suitably adapted to perform the functions described herein. In particular, the above term comprises general purpose or proprietary programmable microprocessors, Digital Signal Processors (DSP), Application Specific Integrated Circuits (ASIC), Programmable Logic Arrays (PLA), Field Programmable Gate Arrays (FPGA), special-purpose electronic circuits, etc., or a combination thereof.

[0034] The processing unit may be part of an external apparatus which may be connected to the image sensor and remaining features of the system. The connection may be wired or wireless. A wireless connection may be made by a Wi-Fi or Bluetooth connection.

[0035] Alternatively, the system may be one integrally formed apparatus.

[0036] The one or more images may be obtained at various objective lens positions.

[0037] Processing the one or more images may be done by use of an autofocus algorithm, i.e. an algorithm that is able to detect the objective lens position relative to the biological sample, such that a sharp image of the biological sample can be registered on the image sensor. The specific autofocus technique can rely on detecting the actual distance between the objective lens and the biological sample, or alternatively, it can rely on a specialized image sensor for detecting focus.

[0038] Alternatively, or additionally, the processing may involve comparing the one or more images obtained by the image sensor to each other or a threshold, e.g. compare the contrast of the one or more images. By comparing the one or more images the processing unit can determine a focus distance between the objective lens and the biological sample.

[0039] The drive unit may be a circuit or component used to control another circuit or component by regulating current flow thereto, such as a driver IC or the like.

[0040] The drive unit is especially configured to control the focusing actuator but may also control other components of the system.

[0041] The system may be made substantially from plastic or metal, in particular the structural parts of the system may be 3D printed, thermoformed injection moulded, or pressed.

[0042] In some embodiments, the system further comprises a housing, wherein the slide slot, the illumination device, the image sensor and the focusing and magnification unit are arranged within the housing.

[0043] The housing may provide a protective cover for other parts of the system. The housing may be a shell or a casing or a circumferentially extending wall. A shape of the housing may be substantially round and / or spherical, cylindrical, parallelepipedal, ellipsoidal or any other suitable shape. The housing may be made of a hard and / or rigid and / or solid and / or robust material.

[0044] The housing may be made from plastic or metal, and produced by being 3D printed, thermoformed injection moulded, or pressed. The housing may be in one piece, two pieces and / or integrally shaped. The housing may comprise an opening. The opening may be closed with a cover, the cover being part of the housing. The slide slot may be placed onto the cover, preferably in the centre of the cover.

[0045] By having the slide slot, the illumination device, the image sensor and the focusing and magnification unit are arranged within the housing is it understood that the housing encompasses these parts of the system.

[0046] The entrance of the slide slot enables the insertion of a slide in the slide slot from the exterior.

[0047] The housing may be detachable, allowing for replacement of illumination device, lens, and / or other internal mechanism.

[0048] In some embodiments, the one or more images of the biological sample are obtained at one or more respective distances.

[0049] By respective distances it is meant that each of the one or more images has a corresponding one or more distances at which the image is obtained by the image sensor.

[0050] The one or more respective distances may be a distance measured between the objective lens and the biological sample.

[0051] By obtaining the more than one image of the biological sample at one more than one respective distances, a set of images comprising the more than one images may be obtained. The set of images may provide for further evaluation of the sample.

[0052] By obtaining one or more images at one or more distances the quality of the one or more images at one or more distances may be compared. Quality parameters may include contrast, dynamic range, spatial resolution, noise, and artifacts in the obtained one or more images. The focus distance may be determined based on comparing the one or more images at the one or more distances.

[0053] Alternatively, or additionally, the focus distance may be based on a determined quality of the one or more images.

[0054] In some embodiments, the processing unit and drive unit is comprised by a control unit arranged within the housing. Thereby making the system a standalone system, with no need of external processing.

[0055] In alternative embodiments, the processing unit may be part of an external apparatus or computing apparatus, and thus the processing is done externally from the remaining system.

[0056] In some embodiments, the focusing actuator is a voice coil motor actuator. Thereby providing a low-cost focusing actuator which enables focusing and autofocusing capabilities of the system.

[0057] In some embodiments, the system further comprises a display arranged externally on the housing. Thereby, enabling a user interface or displaying of information to a user.

[0058] Information may e.g. be results, required inputs or instructions for guiding a user.

[0059] In some embodiments, the system further comprises a distancing element, connected to and arranged between the image sensor and the focusing and magnification unit thereby defining the linear distance between the image sensor and the focusing and magnification unit, wherein the distancing element has an adjustable length, thereby enabling adjustment of the linear distance between the image sensor and the focusing and magnification unit.

[0060] By providing a distancing element with adjustable length, the system allows for changing magnification levels by moving the focusing and magnification unit towards or away from the image sensor.

[0061] The distancing element may also be used to adjust the magnification and / or focusing of the sample. The adjustable length hence provides a further adjustability of magnification and / or focusing of the sample. The distancing element may enable automatic or manual adjustment of the linear distance. The distancing element may by telescopic. The distancing element may be a simple piece of plastic, functioning to define and create the linear distance between the image sensor and the focusing and magnification unit. The distancing element may be a cylindrical, square or rectangular tube.

[0062] The distancing element may function as an optical baffle for limiting or preventing unwanted stray light from reaching the image sensor.

[0063] In a second aspect, the present disclosure relates to a method for determining the quality of a biological sample, preferably semen, comprising the steps of: placing a slide containing the biological sample in a slide slot of a system according to the first aspect; obtaining one or more images of the biological sample at one or more distances; processing the one or more images to determine a parameter value for each of the one or more images, thereby yielding one or more parameter values; determining, based on the one or more parameter values, a focus distance between the objective lens and the biological sample; moving the magnification lens to the focus distance; recoding a video of the biological sample at focus distance; identifying a plurality of biological cells in the biological sample based on the recorded video; determining a location of a first biological cell of the plurality of biological cells in a first frame of the recorded video; identifying the first biological cell in a second frame of the recorded video; determining a location of the first biological cell in the second frame; returning a detected cell characteristic of the plurality of biological cells in the biological sample.

[0064] Consequently, the cost associated with performing an analysis of the sample is reduced by reducing manual handling time.

[0065] The returned detected cell characteristic of the plurality of biological cells in the biological sample may be based on the identified plurality of biological cells and / or the determined location of the first biological cell in the first and second frame.

[0066] By identifying a plurality of biological cells, it is understood that cells are distinguished from their surroundings. The detected cell characteristic may be sperm concentration, sperm motility (A, B, C and D), other sperm motility parameters, sperm morphology, sperm aggregation / agglutination, round cell infiltration, debris, sperm viability, vitality or sperm DNA fragmentation.

[0067] By measuring the concentration, it is understood that from the number of detected cells within a certain area and with knowledge of the thickness of the sample reservoir, the average number of cells per volume can be inferred.

[0068] By measuring the motility of the detected cells, it is understood that the detected cells are divided into two categories of cells that are moving and not moving, by taking the ratio of the moving cells to the total number of cells the motility is deduced. Velocity and movement pattern may be used to determine normal motility.

[0069] By returning the detected motility and / or concentration of the plurality of biological cells in the biological sample, it is understood that the measured values are stored and / or presented on a display.

[0070] The display may be comprised by the system or an external apparatus, such as a computing apparatus.

[0071] The external apparatus may be a smartphone, tablet, or computer. The video may be recorded in the standard video recording application of the external apparatus. Alternatively, the video may be recorded in an application, which also performs the analysis.

[0072] The biological cells in the recorded video may be detected using stains.

[0073] The biological cells may be detected using their shape and / or their movement.

[0074] The steps of: determining a location of a first biological cell of the plurality of biological cells in a first frame of the recorded video, identifying the first biological cell in a second frame of the recorded video, and determining a location of the first biological cell in the second frame may be repeated a number of times. By repeating these steps of the method, the frames of the video may be processed a number of times to identify a number of biological cells of the plurality of biological cells.

[0075] The returned detected cell characteristic of the plurality of biological cells in the biological sample may be based on one or more of the identified number of biological cells of the plurality of biological cells. In some embodiments, the method further comprises the step of providing a system according to the first aspect of the disclosure. The method may comprise the step of connecting the external apparatus with the system. The connection may be wired or wireless. A wireless connection may be made by a Wi-Fi or Bluetooth connection.

[0076] In some embodiments, the method further comprises the step of uploading the recorded video, the detected motility, concentration of the biological sample, or any combination of the former to an external apparatus.

[0077] Consequently, further analysing capacity is available. Furthermore, the recorded video and data can be backed-up and shared among the user's apparatuses.

[0078] The step of uploading the recorded video and / or the measured motility and concentration of the detected biological cells to an external apparatus may occur at any step after the video has been recorded. The identification of biological cells may occur in either internally in the system or in an external apparatus.

[0079] The measured values may be stored on the external apparatus.

[0080] The external apparatus may be a server or a computer.

[0081] In some embodiments, the method further comprises the step of providing a digital label of the detected cells.

[0082] Consequently, a simple characterization scheme is obtained, which may be used to guide decision making in the process of conceiving. Furthermore, by labelling samples with low concentration for additional analysis, erroneous labelling due to user error can be avoided or users with critically low concentration can be referred to experts.

[0083] The digital labelling of the measured cell concentration may be provided as a classification system.

[0084] The additional analysis may comprise of recording a secondary video and performing a secondary analysis. The additional analysis may be performed by a software application. Alternatively, the additional analysis may be performed by a human operator.

[0085] In some embodiments, the method further comprises the step of connecting an external apparatus with the system according to the first aspect of the disclosure, such that the processing unit of the external apparatus is used as processing unit for the system, the step preferably being performed before the step of recording a video of the biological sample.

[0086] Consequently, the system provides a stable, illuminated, and magnified image of the biological sample for the external apparatus to process.

[0087] The different aspects of the present disclosure can be implemented in different ways including a system for testing a biological sample and a method for testing a biological sample described above and in the following, each yielding one or more of the benefits and advantages described in connection with at least one of the aspects described above, and each having one or more embodiments corresponding to the embodiments described in connection with at least one of the aspects described above and / or disclosed in independent claims. Furthermore, it will be appreciated that embodiments described in connection with one of the aspects described herein may equally be applied to the other aspects.

[0088] Brief description of the drawings

[0089] Fig. 1 shows a cross-sectional side view of a system for testing a biological sample according to an embodiment of the disclosure.

[0090] Fig. 2 shows a front view of a system for testing a biological sample according to an embodiment of the disclosure.

[0091] Fig.3 shows a perspective view of a system for testing a biological sample according to an embodiment of the disclosure.

[0092] Fig.4 shows a side view of a system for testing a biological sample according to an embodiment of the disclosure.

[0093] Fig. 5 shows a perspective view of a housing of a system for testing a biological sample according to an embodiment of the disclosure.

[0094] Fig. 6 shows a front view of a housing of a system for testing a biological sample according to an embodiment of the disclosure.

[0095] Fig. 7 shows an example of a method for determining the quality of a biological sample according to an embodiment of the disclosure.

[0096] Fig. 8 shows an example of a method for determining the quality of a biological sample according to an embodiment of the disclosure. Detailed description of embodiments

[0097] In the following description, reference is made to the accompanying figures, which show by way of illustration how the disclosure may be practiced.

[0098] Figs 1 to 4 show a system 1 for testing a biological sample 22 according to an embodiment of the disclosure.

[0099] The system 1 has a slide slot 11 (better shown in fig. 5) configured to receive and hold a slide 21 containing a biological sample 22 and an illumination device 12 arranged on a first side SI of the slide slot 11. The illumination device 12 is configured to emit light 31 that illuminates and at least partly propagates through the biological sample 22 when the slide 21 containing a biological sample 22 is placed in the slide slot 11.

[0100] On a second side S2 of the slide slot is an image sensor 13 arranged opposite to and positioned coaxially with the illumination device 12. The image sensor 13 is configured to receive at least a part of the emitted light 31' that has propagated through the biological sample 22. Also placed on the second side S2 is a focusing and magnification unit 14 placed at a linear distance di. from the image sensor 13. The focusing and magnification unit 14 comprises an objective lens 141 placed in line with the illumination device 12 and image sensor 13 and a focusing actuator 142 which is configured to move the objective lens toward and / or away from the biological sample such that a distance dr is increased or decreased.

[0101] In the shown embodiment of fig. 1, a drive unit 15, such as a driver IC, is shown for controlling the focusing actuator 142. The drive unit 15 is electrically connected to the focusing actuator 142 and is adapted to control current flow to it, in order to control the movement of the objective lens, such that the distance dl can be adjusted.

[0102] The system 1 is further connected to a processing unit configured to receive images obtained at by the image sensor 13, and processing images to determine a focus distance between the objective lens and the biological sample based on the processing of the images. The processing unit can be built into system 1 or be part of an external device to which the system is connected, either via a wired connection, e.g. via USB-cable, or wireless connection such as WIFI, Bluetooth or cloud-based.

[0103] The processing unit may process the images to determine a focus distance by use of an autofocus algorithm, e.g. a contrast autofocus algorithm. Many contrast autofocus algorithms exist but one way it may work is as follows:

[0104] A. conduct a coarse scan by obtaining one or more images by the image sensor at one or more objective lens positions relative to the biological sample. This may e.g. be done by using the focusing actuator, such as a voice coil motor actuator, to scan the whole range of objective lens positions at various position steps.

[0105] B. Conduct contrast calculation for each of the one or more images obtained. Each one or more image may be convolved with a Gaussian kernel to smooth out the noise and may later be followed by a convolution with a Laplacian kernel. Alternatively, these two kernels may be combined to create a Laplacian of Gaussian (LoG) kernel such that the operation can be done in one convolution. The statistical variance of the resulting data which corresponds to a quantitative measure of contrast is calculated for each one or more image.

[0106] C. conduct a fine scan by determining the position at which the largest contrast value is detected with the coarse scan in B and conduct a finer scan with smaller steps around this position again using the algorithm outlined in step B. Hereafter a contrast dataset C(x) may be generated where C(x) is the contrast value and x is the objective lens position.

[0107] D. Make a curve fitting on the resulting position-contrast graph. A curve fitting operation may be performed onto a gaussian line shape which has the following form:

[0108] Where Ao, Ai, xo and o are optimization parameters corresponding to offset, amplitude, centre position of the objective lens and the standard deviation respectively. To ensure a good fit these parameters are initially estimated. Ao is estimated as the minimum contrast value detected in the fine scan. Ai is estimated as the maximum contrast value detected in the fine scan with Ao subtracted i.e. A, = max(C(x)) - / 1(). The parameter xo is initially estimated as the position of the highest contrast value and ->o value is initially estimated at the factory. After the curve fit operation is performed and the parameters optimized the value xo corresponds to the determined focus distance.

[0109] Turning to figures 5 and 6, which shows an embodiment of a housing 4 for a system 1 according to the disclosure. The housing 4 has an opening 41 which opens to the slide slot 11 of the system, thereby allowing a slide 21 to be inserted into the system 1. The housing 4 may e.g. be made from a low- cost durable polymer which is suited for mass production, e.g. via 3D printing, casting, CNC machining or molding.

[0110] Referring to Fig. 7 showing an embodiment of the method for determining the quality of a biological sample. In 701 a slide containing a biological sample is placed in a slide slot of a system according to first aspect of the disclosure. In 702 one or more images of the biological sample is obtained by the image sensor at one or more distances. In 703 the one or more images are processed to determine a parameter value for each of the one or more images. In 704 a focus distance between the objective lens and the biological sample is determined based on the one or more parameter values. In 705 the objective lens is moved to the focus distance. In 706 a video of the sample is recorded at focus distance. In 707 software automatically identify a plurality of cells in the recorded video of the biological sample. In 708 a location of a first biological cell of the plurality of biological cells is determined in the first frame of the recorded video. In 709 the first biological cell is determined in the subsequent frames of the recorded video. In 710 the locations of the first biological cell is used to determine the movement pattern of the cell. In 711 cell characteristics, e.g. concentration, motility, morphology, and DNA fragmentation of the detected cells are detected based on the determination of cell location and cell appearance. In 712, the measured motility and concentration is returned.

[0111] The method may optionally further comprise the step of uploading the recorded video and / or the detected motility, concentration of the biological sample, or any combination of the former to an external apparatus. And / or further comprises the step of providing a digital label to the detected concentration of cells.

[0112] Fig. 8 shows an embodiment of the method for determining the quality of a biological sample. In 801, a video of the sample is recorded. In 802 the recorded video is uploaded to an internet-connected system. In 803 software automatically detects cells in the biological sample. In 804 the cell characteristics, e.g. concentration, motility, morphology, and DNA fragmentation of the detected cells are measured. In 805 the measured cell characteristics are returned. Although some embodiments have been described and shown in detail, the disclosure is not restricted to them, but may also be embodied in other way within the scope of the subject matter defined in the following claims. In particular, it is understood that other embodiments may be utilised, and structural and functional modifications may be made without departing from the scope of the present disclosure.

Claims

CLAIMS1. Automated digital microscope system for testing a biological sample, preferably semen, the system comprising: a housing; a slide slot configured to receive and hold a slide containing a biological sample; an illumination device arranged on a first side of the slide slot, the illumination device being configured to emit light that illuminates and at least partly propagates through the biological sample when the slide containing the biological sample is placed in the slide slot; an image sensor arranged on a second side of the slide slot opposite to and coaxially with the illumination device and configured to receive at least a part of the emitted light that has propagated through the biological sample; a focusing and magnification unit placed at a linear distance from the image sensor on the second side of the slide slot, the focusing and magnification unit comprising an objective lens providing optical magnification and placed coaxially with the illumination device and / or image sensor and a focusing actuator configured to move the objective lens; where the slide slot, the illumination device, the image sensor and the focusing and magnification unit are arranged within the housing; the system further comprising : a processing unit configured to receive one or more images obtained by the image sensor, processing the one or more images, and based on the processing of the one or more images determine a focus distance between the objective lens and the biological sample wherein a focused image of the biological sample is produced on the image sensor; and a drive unit configured to control the focusing actuator to move the objective lens towards or away from the biological sample such that a distance between the objective lens and the biological sample equals the determined focus distance.

2. System according to claim 1, wherein the focusing actuator is a voice coil motor actuator.

3. System according to claim 1, wherein the more than one image of the biological sample are obtained at one or more respective distances between the objective lens and the biological sample.

4. System according to claim 1, wherein the processing unit and drive unit is comprised by a control unit arranged within the housing.

5. System according to any one of the preceding claims, wherein the illumination device comprises an LED light source.

6. System according to claim 5, wherein the illumination device further comprises at least one of an optical diffuser and a condenser lens.

7. System according to any one of the preceding claims, further comprising a display arranged externally on the housing.

8. System according to any one of the preceding claims, further comprising a distancing element, connected to and arranged between the image sensor and the focusing and magnification unit thereby defining the linear distance between the image sensor and the focusing and magnification unit, wherein the distancing element has an adjustable length, thereby enabling adjustment of the linear distance between the image sensor and the focusing and magnification unit.

9. Method for determining the quality of a biological sample, preferably semen, comprising the steps of: placing a slide containing the biological sample in a slide slot of a system according to any of one of claim 1 to 8; obtaining one or more images of the biological sample at one or more distances; processing the one or more images to determine a parameter value for each of the one or more images, thereby yielding one or more parameter values;determining, based on the one or more parameter values, a focus distance between the objective lens and the biological sample; moving the objective lens to the focus distance; recording a video of the biological sample at the focus distance; identifying a plurality of biological cells in the biological sample based on the recorded video; determining a location of a first biological cell of the plurality of biological cells in a first frame of the recorded video; identifying the first biological cell in a second frame of the recorded video; determining a location of the first biological cell in the second frame; returning a detected cell characteristic of the plurality of biological cells in the biological sample based on the identified plurality of biological cells and / or the determined location of the first biological cell in the first and second frame.

10. Method according to claim 9, wherein the cell characteristic is motility, morphology and / or concentration of the plurality of biological cells in the biological sample.

11. Method according to any one of claim 9 to 10, where the method further comprises a step of staining the biological sample to detect further characteristics, including morphology, viability, or DNA fragmentation.

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