Determination of defocus in image data related to an adjusted blood sample

Abstract

Disclosed is a method for determining blurring in image data regarding a conditioned blood sample by a blood analyzer. Image data regarding the conditioned blood sample arranged in an inspection space is obtained by an imaging system. The image data includes data related to at least one imaging plane corresponding to the depth of the conditioned blood sample. When analyzing the image data, an object region is identified in the obtained image data. The object region includes a group of pixels corresponding to an object physically present in the conditioned blood sample in the image data. Further, optical features of the identified object region are identified. The optical features are derived from a difference in refractive index between the object and the medium of the conditioned blood sample, and the optical features act as extra artifacts that do not represent an object physically present in the conditioned blood sample in the image data. Based on the appearance of the identified optical features, at least the direction of blurring is determined in the image data.

Description

Technical Field

[0001] The present invention relates to a method for determining out-of-focus in image data related to a prepared blood sample.

Background Art

[0002] Background of the Invention The analysis of biological fluid samples such as prepared blood samples can be time-consuming and may require a large number of steps, adjustments, resources, and advanced equipment. When the analysis is performed by an optical system such as a microscope, it is required to focus on the object to be analyzed such as blood cells in order to ensure proper, reliable, and rapid analysis.

[0003] US2020 / 0358946A1 discloses a system and method for capturing an entire slide image of a sample, and a camera is configured to capture a digital image of the sample. This system captures a bright-field image of the sample, a digital image of the sample illuminated from a first incident angle at a first wavelength, and a digital image of the sample illuminated from a second incident angle at a second wavelength. This system can determine whether the sample is out of focus based on the transitional shift between the first wavelength channel and the second wavelength channel of the captured digital image.

Summary of the Invention

[0004] An object of an embodiment of the present invention is to provide a method that enables easy, rapid, and more reliable determination of out-of-focus in image data related to a prepared blood sample. The present invention provides a method for determining out-of-focus in image data related to a prepared blood sample by a blood analyzer. The blood analyzer includes an imaging system and a probing volume, and this method includes - a step of placing a prepared blood sample in the inspection space of the blood analyzer, - A step of obtaining image data regarding an adjusted blood sample by an imaging system of a blood analyzer, wherein the image data includes data related to at least one imaging plane corresponding to the depth of the adjusted blood sample. - A step of analyzing the obtained image data. - A step of identifying an object region in the obtained image data, wherein the object region corresponds to an object physically present in the adjusted blood sample and includes a pixel group in the image data. - A step of identifying optical features of the identified object region, wherein the optical features are derived from the difference in refractive index between the object and the medium of the adjusted blood sample, the optical features act as extra artifacts in the image data, and do not represent an object physically present in the adjusted blood sample. including the steps. - A step of determining at least the direction of defocus in the image data based on the appearance of the identified optical features. including.

[0005] That is, the method according to the present invention is a method for determining defocus in image data regarding an adjusted blood sample. In the context of this specification, the expression "determining defocus" shall be construed to include determining whether a given portion of the image data is in focus, determining which portions of the image data may be considered in focus or out of focus respectively, determining to what extent the blurred portions of the image data are out of focus, i.e., how "off" the defocused portions are, determining the direction towards focus for the defocused portions of the image data, i.e., determining whether the imaging plane is in front of or behind the focal plane, and / or any other type of determination suitable for providing information regarding focus and defocus of the image data, and shall be interpreted to be included within that scope.

[0006] In the context of this specification, the term "prepared blood sample" shall be construed to mean a blood sample that has undergone one or more preparation steps to ensure that an appropriate analysis can be performed on the blood sample. Such preparation steps can include, for example, dilution, application of chemicals, application of reagents, culturing, stabilization, and the like.

[0007] In the context of this specification, the term "image data" shall be construed to mean optical data derived from a prepared blood sample or optical data related to a prepared blood sample. Thus, the image data includes information regarding the prepared blood sample to be analyzed.

[0008] The method is performed by a blood analyzer, i.e., by an apparatus configured to perform an analysis of a prepared blood sample. The blood analyzer comprises an imaging system, i.e., a system configured to generate image data, and an examination space, i.e., a space configured to receive the prepared blood sample to be analyzed. The imaging system may, for example, be a microscope and / or an imaging device based on holography, or may comprise these.

[0009] In the method according to the invention, the prepared blood sample is placed in the examination space of the blood analyzer in an initial state. Next, image data regarding the prepared blood sample is obtained by the imaging system of the blood analyzer. This may include, for example, the step of emitting a light beam towards the prepared blood sample and the step of detecting the light leaving the prepared blood sample as a result. This light includes, for example, light that has undergone scattering, reflection, deflection, diffraction, etc. by an object within the prepared blood sample. Alternatively or in addition, the obtained image data may include at least one holographic image.

[0010] The image data thus obtained includes data related to at least one imaging plane corresponding to the depth of the adjusted blood sample, and thus includes data related to the distance from the detector of the imaging system. This will be described in more detail below.

[0011] Next, the obtained image data is analyzed as follows. Identify the object regions in the obtained image data. The object regions include a group of pixels corresponding to an object physically present in the adjusted blood sample in the image data. That is, the object is an actual physical entity that is actually contained in the adjusted blood sample to be analyzed, i.e., forms a part of it. Thus, the object regions represent the images of the objects physically present in the adjusted blood sample in the image data, i.e., represent the part of the image data corresponding to the object regions that contain information about this object. In this way, based on the part of the image data corresponding to the object regions in the image data, an analysis of the object can be appropriately performed.

[0012] Furthermore, identify the optical characteristics of the identified object regions. This optical characteristic is caused by the difference in refractive index between the object and the medium of the adjusted blood sample. This optical characteristic acts as an extra artifact in the image data. Thus, unlike the object described above, the optical characteristic does not represent an object physically present in the adjusted blood sample. Instead, the optical characteristic represents a purely optical phenomenon caused by optical properties at the boundary between the actual physical object visible in the image data and the surrounding medium, and is not an image of the actual physical object.

[0013] When light intersects an interface between two media with different refractive indices, refraction occurs according to Snell's law, which generates optical features that can be observed as optical artifacts in image data. That is, when the incident light strikes an object within the conditioned blood sample and the refractive index of this object is different from that of the medium of the conditioned blood sample, and thus different from the refractive index of the medium in which the object is located, it can be inferred that recognizable optical features will occur as optical artifacts in the image data in or near the object region. However, as described above, such optical features, i.e., artifacts, do not represent actual physical objects present within the conditioned blood sample.

[0014] The inventors of the present invention have discovered that information regarding the blurriness of image data can be derived from such optical features, i.e., artifacts. By way of example, optical features caused by refraction can sometimes act as extra or virtual objects or artifacts in the image data, and the appearance of this extra artifact in the image data depends on whether a given observed imaging plane of the image data coincides with the focal plane of the imaging system. Furthermore, in the case of blurriness, it also depends on whether the focal plane is located near or far from the objective lens or detector of the imaging system. Therefore, by observing the appearance of the optical features in the image data, it becomes possible to extract information regarding the blurriness in the image data.

[0015] Therefore, based on the observation of the appearance of the identified optical features, at least the direction of blurriness in the image data is ultimately determined. In this way, at least it is determined whether a given imaging plane of the image data coincides with the focal plane of the imaging system. If they do not coincide, it is determined whether the focal plane is located nearer to or farther from the objective lens or detector of the imaging system than the imaging plane.

[0016] Thus, according to the present invention, in the obtained image data, at least the direction of defocus can be determined easily, quickly, reliably, and robustly. As a result, the possibility of defocus can be taken into account, or defocus can be processed quickly, reliably, and robustly, and by doing so, it becomes possible to perform the automatic analysis of the adjusted blood sample with high reliability and robustness. For example, the appearance of the optical characteristics can be derived from the image data regarding one imaging surface, and thus, it becomes possible to determine at least the direction of defocus without requiring image data from various imaging surfaces, illumination with various wavelengths, etc.

[0017] In addition to being related to the difference in refractive index, the observed optical characteristics cited above can also be related to the shape of the object. The step of obtaining the image data regarding the adjusted blood sample may include the step of emitting a light beam toward the adjusted blood sample with a numerical aperture smaller than the numerical aperture of the objective lens of the imaging system.

[0018] According to this embodiment, the light beam emitted toward the adjusted blood sample, that is, the incident or illumination light beam, has a numerical aperture smaller than the numerical aperture of the objective lens of the imaging system, and thus, has a numerical aperture smaller than the numerical aperture of the detection unit of the imaging system. In the context of this specification, the term "numerical aperture" shall be interpreted to mean a dimensionless number that characterizes the range of angles within which an optical system can emit or receive light.

[0019] That is, according to this embodiment, the light cone of the incident light beam determined by the emission angle range of the light source is smaller than the acceptance cone of the objective lens of the imaging system. For example, the numerical aperture of the light beam may be made smaller than 80% of the numerical aperture of the objective lens of the imaging system, such as between 5% and 50% of the numerical aperture of the objective lens of the imaging system, or may be between 10% and 40% of the numerical aperture of the objective lens of the imaging system.

[0020] By applying a numerical aperture of a light beam that is small compared to the numerical aperture of the objective lens of the imaging system, it can be obtained that the entire light beam can be accommodated within the acceptance angle of the objective lens of the imaging system. Further, by applying a small numerical aperture of the light beam, the blood sample being adjusted is illuminated by the incident light within a narrow angular range, whereby the determination of the direction of defocus becomes very accurate and robust.

[0021] The step of obtaining the image data may include the step of obtaining at least one hologram image. In such a hologram image, optical features of the types described above can be observed. That is, according to this embodiment, subsequent analysis is performed on at least one obtained hologram image, and at least the direction of defocus is determined from the appearance of the optical features that appear and are identified in the hologram image.

[0022] The object may be a blood cell such as a white blood cell, a red blood cell, or a platelet. According to this embodiment, an interface defining a transition from a region having one refractive index to a region having another refractive index may be formed by the membrane of the blood cell.

[0023] The blood cells have a shape that causes them to act as optical lenses. Thereby, when the incident light collides with the blood cells, a lens effect is generated, and thus, in the final image data, recognizable optical features that act as extra artifacts are generated.

[0024] As an example, in the case of red blood cells, due to the combination of the refractive index of the blood cell and the shape of the blood cell, the red blood cell acts as a concave lens and focuses behind the blood cell. Similarly, in the case of white blood cells, due to the combination of the refractive index of the blood cell and the shape of the blood cell, the white blood cell acts as a convex lens and focuses in front of the blood cell. This is due to the fact that the shapes of red blood cells and white blood cells are different from each other in that red blood cells have a substantially concave shape while white blood cells have a substantially convex shape.

[0025] For determining the blurring of image data, it is advantageous to use image data regarding blood cells. This is because, by doing so, it is to be analyzed, and the blurring is determined based on the objects already present in the prepared blood sample, and thus, there is no need to add separate objects such as microbeads or contrast agents to the prepared blood sample. Further, it is directly determined whether the blood cells (cells) to be analyzed are in focus.

[0026] Instead, the object may be of any other suitable type as long as it is an object that is present in the prepared blood sample and is desired to be analyzed. As another alternative, the object may be an object that is present in the prepared blood sample and whose sole purpose is to determine blurring in the image data.

[0027] Thus, the optical characteristics can be caused, for example, as described above, by the lens effect caused by the object. The step of identifying the optical characteristics of the identified object region may include the step of identifying a first annular characteristic and a second annular characteristic, and the step of determining at least the direction of blurring in the image data may include the step of determining the relative positions of the first and second annular characteristics.

[0028] When the object is of a type that produces a lens effect, for example, a blood cell as described above, this results in an optical characteristic in the form of two annular objects arranged to surround the periphery of the object in the image data, i.e., it can produce extra artifacts. Here, one of the annular objects appears as a dark ring and the other annular object appears as a bright ring.

[0029] When the object acts as a convex lens and the observed imaging plane is closer to the objective lens and the detector than the focal plane, the bright ring is arranged closer to the object than the dark ring. However, when the observed imaging plane is farther from the objective lens and the detector than the focal plane, the dark ring is arranged closer to the object than the bright ring. Therefore, the position of the focal plane is where the positions of the dark ring and the bright ring are interchanged.

[0030] Similarly, when the object acts as a concave lens, the positions of the annular features are reversed. That is, in this case, when the observed imaging plane is closer to the objective lens and the detector than the focal plane, the dark ring is arranged closer to the object than the bright ring, and when the observed imaging plane is farther from the objective lens and the detector than the focal plane, the bright ring is arranged closer to the object than the dark ring.

[0031] Therefore, from the mutual position of the annular objects, it is clarified whether the observed imaging plane is closer to the objective lens and the detector than the focal plane or farther from the objective lens and the detector. Thus, the direction of defocus can be derived from this information alone. As described above, only the image data related to one imaging plane is required for this.

[0032] Furthermore, the annular object becomes increasingly "blurred" as the observed imaging plane is located farther from the focal plane. Thus, information regarding the size or magnitude of defocus can also be derived from the appearance of the annular object.

[0033] The step of determining at least the direction of defocus in the image data may further be based on applying knowledge about the object. This may include, for example, applying knowledge about the optical properties of the object, such as whether the object produces a lens effect and, if so, whether it acts as a concave lens or a convex lens.

[0034] As described above, it is presumed that red blood cells act as concave lenses, while white blood cells are presumed to act as convex lenses. That is, if it is known whether the observed object is a red blood cell or a white blood cell, the direction of defocus can be easily derived from the order of the dark and bright rings observed in the image.

[0035] This method may further include the step of determining the magnitude or degree of defocus in the image data. This can be performed, for example, based on how the identified optical features appear "blurred" in the image data, as described above.

[0036] The image data may include a plurality of images, each related to an imaging plane. Thus, the image data forms a stack of images related to a plurality of imaging planes, and this method may further include the step of identifying the imaging plane in which the image of the object is in focus among the plurality of imaging planes.

[0037] According to this embodiment, the image data is in the form of a stack of images, each image being obtained at a specific depth of the prepared blood sample and thus corresponding to a specific imaging plane. By doing so, the stack of images will include various images of the same object at various depths and thus at various distances from the objective lens and detector of the imaging system. It is also possible to compare the images of the object at various imaging planes, specifically, to compare the appearance of the identified optical features across these imaging planes. By doing so, it becomes possible to determine which of the imaging planes are located closer to the objective lens and detector than the focal plane and which are located farther away. Thus, it is possible to identify the imaging plane closest to the focal plane, that is, the imaging plane in which the object can be considered to be in focus.

[0038] For example, when the object is of a type that produces a lens effect, such as a blood cell, and the identified optical features are of a type that includes a first annular feature and a second annular feature, the imaging surface where the positions of the annular features are swapped can be identified as the imaging surface on which the image of the object is in focus.

[0039] Subsequently, based on the portion of the image data that represents the in-focus object, that is, based on the image of the identified imaging surface, analysis of the object can be performed. The embodiments described above are very suitable for a setting in which the adjusted blood sample is substantially stationary, and thus various images can be obtained at various depths of the adjusted blood sample.

[0040] Alternatively, the image data may include data from only one imaging surface, and this method may further include the step of adjusting at least one setting of the imaging system based on the determined defocus direction.

[0041] According to this embodiment, image data from only one imaging surface is obtained, and based on this, at least the defocus direction is determined as described above, that is, by simply observing the identified optical features, that is, the appearance of the artifacts. For example, when the object is of a type that produces a lens effect, such as a blood cell, and the identified optical features are of a type that includes a first annular feature and a second annular feature, as described above, the defocus direction can be immediately determined by simply observing the order of the rings. Once the defocus direction is determined, at least one setting of the imaging system can be adjusted to focus the image of the object. Subsequently, analysis can be performed on the object based on the focused image.

[0042] This embodiment is very suitable for a setting where the adjusted blood sample moves, such as a flowing blood sample, and thus it is not possible to obtain various images of the same object at various depths of the adjusted blood sample, or a setting that is not realistic.

Brief Description of the Drawings

[0043] Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. In the drawings,

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0044] FIG. 1 is a schematic diagram of a blood analyzer 1 that executes the method according to an embodiment of the present invention. The blood analyzer 1 includes an inspection space 2 that holds a prepared blood sample 3. The blood analyzer 1 further includes an imaging system 4 that includes a light source 5 that illuminates the prepared blood sample 3 through an in-focus lens 6. Further, the blood analyzer 1 also includes an objective lens 7. The objective lens 7 collects light from the prepared blood sample 3 and supplies the collected light to a detector 8. Note that although only one in-focus lens 6 is shown in FIG. 1, it should be noted that the case where the imaging system 4 includes two or more in-focus lenses 6 is not excluded.

[0045] The blood analyzer 1 in FIG. 1 can operate as follows. The prepared blood sample 3 is illuminated by the light source 5 and through the in-focus lens 6. Accordingly, the light of the light source 5 is focused on the focal plane in the prepared blood sample 3. During this time, the imaging system 4, that is, by the objective lens 7 and the detector 8, and based on the light from the prepared blood sample 3, image data is obtained. The numerical aperture of the illumination light beam is smaller than the numerical aperture of the objective lens 7, thereby ensuring that the illumination light beam is included in the acceptance cone of the objective lens 7.

[0046] The obtained image data can include a plurality of images, and each image is related to an imaging plane corresponding to the depth of the adjusted blood sample 3. In this case, the obtained image data forms a set of images representing various depths of the adjusted blood sample 3. Alternatively, the obtained image data may be related to only one imaging plane corresponding to only one depth of the adjusted blood sample 3.

[0047] Next, the obtained image data is analyzed to determine at least the direction of defocus in the image data. This can be done as follows. In the obtained image data, an object region is identified. The object region includes a group of pixels corresponding to an object such as a blood cell in the adjusted blood sample 3 within the image data. Accordingly, an image representation of the object is identified in the image data. The object is a real physical object that physically exists within the adjusted blood sample 3.

[0048] Next, the optical characteristics of the identified object region are identified. Here, the optical characteristics are caused by the difference in refractive index between the object and the medium of the adjusted blood reagent 3. The optical characteristics may also be caused by diffraction, for example. The optical characteristics act as extra artifacts in the image data and do not represent a real physical object that physically exists within the adjusted blood sample 3, as opposed to the object.

[0049] Finally, at least the direction of defocus in the image data is determined based on the appearance of the identified optical characteristics. FIG. 2 is a diagram of image data in the form of a set of images obtained as part of an embodiment according to the present invention. The image data can be obtained, for example, by the blood analyzer of FIG. 1. The images are obtained at 15 different depths of the adjusted blood sample and 7 different numerical aperture setting values for the illumination light beam, and are arranged in 15 columns and 7 rows. Accordingly, each of the 105 images shown in FIG. 2 represents a depth and a numerical aperture corresponding to the column and row in which the image is located, respectively.

[0050] Each of the images shows an object region representing an object in the form of blood cell 9 in the adjusted blood sample. Therefore, all of these images show the same blood cell 9, but they were obtained with different settings regarding the numerical aperture of the illumination light beam at various depths of the adjusted blood sample. The numerical aperture of the objective lens of the imaging system is maintained constant.

[0051] Blood cell 9 defines a refractive index different from that of the surrounding medium of the adjusted blood sample. Further, the shape of blood cell 9, in combination with the difference in refractive indices, introduces a lens effect in the sense that blood cell 9 acts as a convex lens. This lens effect appears in the image data in the form of a pair of annular features 10 arranged so as to surround the periphery of blood cell 9. That is, the pair of annular features 10 do not represent real physical objects physically present in the adjusted blood sample, but rather are extra artifacts in the image data. This artifact is caused by the optical properties at the boundary between blood cell 9 and the surrounding medium of the adjusted blood sample, as described in detail above.

[0052] The pair of annular features 10 includes a first ring that appears dark and a second ring that appears bright. When the depth of the adjusted blood sample is located above the focal plane of the system, that is, closer to the objective lens and the detector than the focal plane, it can be seen that the bright ring is placed closer to blood cell 9 than the dark ring. Conversely, when the depth of the adjusted blood sample is located below the focal plane, that is, farther from the objective lens and the detector than the focal plane, the order of the rings is reversed. That is, the dark ring is placed closer to blood cell 9 than the bright ring. Therefore, whether the depth at which a given image was obtained is above or below the focal plane of the system is elucidated from the relative positions of the pair of annular features 10. In this way, simply by examining the pair of annular features 10, the direction of the blurring of the image data can be easily derived, which can be done by examining only one of the 105 images shown in FIG. 2.

[0053] It can be further understood that the further away from the focal plane, the more "blurred" the pair of annular features 10 appear. That is, information regarding the size or degree of defocus can also be derived from the image data. Finally, the focal plane of the system can be identified as the depth at which the positions of the dark and bright rings are swapped, which corresponds to the image marked with a square.

[0054] Furthermore, it can also be seen that in the image obtained by reducing the numerical aperture of the illumination light beam, the effects described above are much more prominent than in the image obtained by increasing the numerical aperture of the illumination light beam. This is due to the fact that at a low numerical aperture, the range of angles at which the light is emitted from the light source is narrow, and thus the light reaching the conditioned blood sample contains almost only components that are substantially perpendicular to the conditioned blood sample. This causes the lens effect of the blood cells 9 to appear clearly. Therefore, it is advantageous to apply a low numerical aperture of the illumination light beam to the objective lens of the imaging system. This is because it enables the direction of defocus, and if possible, also the position of the focal plane, to be determined quickly, accurately, reliably, and more robustly.

[0055] Once the direction of defocus has been determined as described above, a focused image of the blood cells 9 can be obtained quickly and easily, for example, by selecting the image obtained at the focal plane or by adjusting the settings of the blood analyzer until the blood cells 9 are in focus. Subsequently, based on the focused image, an automatic analysis of the conditioned blood sample, especially of the blood cells 9, can be performed. Since the image data used for the analysis is ensured to be in focus, the analysis is reliable and robust.

[0056] FIG. 3 shows simulations of the image of blood cell 9 in various settings of the numerical aperture and the image depth, and illustrates the effects described above with reference to FIG. 2. The blood cell 9 is simulated as a hollow convex lens-shaped object. In this simulated image, the dark ring 10a and the bright ring 10b can be clearly seen. It can also be seen that the rings 10a and 10b are interchanged at the focal plane, and that the effect is most prominent at a low numerical aperture.

Claims

1. A method for determining defocus in image data regarding a prepared blood sample by a blood analyzer comprising an imaging system and an examination space, comprising: - placing a prepared blood sample within the examination space of the blood analyzer; - obtaining, by the imaging system of the blood analyzer, image data regarding the prepared blood sample, the image data including data regarding at least one imaging plane corresponding to the depth of the prepared blood sample; - analyzing the obtained image data, comprising: - identifying an object region within the obtained image data, the object region including a group of pixels corresponding to an object physically present within the prepared blood sample in the image data; - identifying an optical feature of the identified object region, the optical feature resulting from a difference in refractive index between the object and the medium of the prepared blood sample, the optical feature acting as an extra artifact not representing the object physically present within the prepared blood sample in the image data; - including; - determining at least the direction of defocus in the image data based on the appearance of the identified optical feature. A method comprising the above steps.

2. The method according to claim 1, wherein the step of obtaining image data regarding the prepared blood sample includes emitting a light beam towards the prepared blood sample with a numerical aperture smaller than the numerical aperture of the objective lens of the imaging system.

3. The method according to claim 2, wherein the numerical aperture of the light beam is smaller than 80% of the numerical aperture of the objective lens of the imaging system.

4. The method according to claim 3, wherein the numerical aperture of the light beam is between 5% and 50% of the numerical aperture of the objective lens of the imaging system.

5. The method according to claim 1, wherein the step of obtaining the image data includes obtaining at least one hologram image.

6. The method according to any one of the preceding claims, wherein the object is a blood cell.

7. The method according to any one of the preceding claims, wherein the optical feature is caused by a lens effect caused by the object.

8. In the method according to any one of the preceding claims, the step of identifying the optical characteristics of the identified object region includes the step of identifying a first annular characteristic and a second annular characteristic, and the step of determining at least the direction of defocus in the image data includes the step of determining the relative positions of the first and second annular characteristics.

9. In the method according to any one of the preceding claims, the step of determining at least the direction of defocus in the image data is further based on applying knowledge regarding the optical characteristics of the object.

10. A method according to any one of the preceding claims, further comprising the step of determining the amount of defocus in the image data.

11. In the method according to any one of the preceding claims, the image data includes a plurality of images, each image being associated with an imaging plane, whereby the image data forms a set of images associated with a plurality of imaging planes, and the method further includes the step of identifying, from among the plurality of imaging planes, the imaging plane on which the image of the object is in focus.

12. In the method according to any one of claims 1 to 10, the image data includes data from only one imaging plane, and the method further includes the step of adjusting at least one setting of the imaging system based on the determined direction of defocus.

Images