METHOD FOR OPERATING AN ACOUSTIC SCRATCH MICROSCOPE AND ACOUSTIC SCRATCH MICROSCOPE

Abstract

The invention relates, inter alia, to a method for operating a scanning-acoustic microscope, in particular an ultrasound scanning microscope, in which method: a sample is scanned in an X-Y plane by means of a transducer unit (10), in particular having one or more transducer elements (1, 2, 3, 4, 12, 14) each comprising a transducer (20) and a lens (21, 22); in order to scan the sample linearly, the transducer unit (10) is moved in the X direction; after the or a linear scanning operation of the sample by means of the transducer unit (10), the transducer unit (10) is shifted in the Y direction by a shifting step size (U, W); in order to scan the sample, the magnitude of the shifting step size (U, W) of the transducer unit (10) is varied in the Y direction; in particular after shifting the transducer unit (10) in the Y direction, at least one further linear scanning operation of the sample is carried out by means of the transducer unit (10) in the Y direction.

Description

[0001] Method for operating an acoustic scanning microscope and acoustic scanning microscope

[0002] Description

[0003] The invention relates to a method for operating an acoustic scanning microscope, in particular an ultrasonic scanning microscope, and to an acoustic scanning microscope, in particular an ultrasonic scanning microscope.

[0004] Ultrasonic microscopes or acoustic microscopes, also known as scanning acoustic microscopes (SAM), are used to scan samples using ultrasound and to process the reflected sound waves to create images of the sample's structures.

[0005] Ultrasound microscopes are equipped with an ultrasound head, also known as a transducer head. The ultrasound head consists of an acoustic lens and a connected transducer.

[0006] In acoustic microscopy, water is used as the coupling medium between the acoustic transducer and the sample under investigation to ensure good transmission of the sound waves emitted by the transducer to the sample. This requires a coupling medium with good sound conduction properties.

[0007] In ultrasonic microscopy, which operates in the frequency range from 1 MHz to 5 GHz, it is common for samples to be submerged in a water basin and placed on a sample holder, with the sample being examined using an immersion ultrasound microscope. Another method uses a water jet, which is formed between the transducer and the sample, to ensure good sound coupling into the sample.

[0008] Ultrasound microscopes, in which a sample is scanned using ultrasound and the transmitted or reflected sound waves are processed to create an image, are well known in the art. Image generation is non-destructive, providing information about the internal structure of a sample. The images obtained using the scanning process enable analysis or monitoring of materials, electronic components, etc.

[0009] Furthermore, multi-channel transducers are used in acoustic microscopy, in which a large number of individual elements with a fixed focal length are arranged next to one another. The pixel size in the Y direction, i.e. perpendicular to the scanning direction in the X direction, corresponds to the distance between the individual transducer elements. When using such multi-channel transducers, many parallel linear scanning lines are recorded simultaneously, depending on the number of transducer elements. In the transducer elements of the multi-channel transducers, the distance between the individual elements is constant and cannot be changed, whereby the height of a line of a linear scan is fixed and the pixel size in the Y direction, i.e. perpendicular to the scanning direction in the X direction, always corresponds to the width of the individual transducer elements and is constant. Due to the small dimension of the individual elements in the Y direction, i.e.perpendicular to the scanning direction in the X-direction, the aperture of the lenses of the transducer elements is very small in this direction, which means that the resolution in the Y-direction is low.

[0010] One object of the invention is to expand the application possibilities of acoustic scanning microscopy or of an acoustic microscope for examining samples, such as wafers, etc. A further object of the invention is to examine large-volume or large-area samples, particularly with a high data throughput, in an efficient and simple manner using an acoustic microscope, in particular an ultrasonic scanning microscope.

[0011] The object is achieved by a method for operating an acoustic scanning microscope, in particular an ultrasonic scanning microscope, wherein a sample is scanned in an XY plane by means of a transducer unit, in particular with one or more transducer elements each having a transducer and a lens, wherein the transducer unit is moved in the X direction for a linear scanning of the sample, wherein after the one or more linear scannings of the sample by the transducer unit, the transducer unit is displaced in the Y direction by an offset step size, wherein the size of the offset step size of the transducer unit in the Y direction is varied for the scanning of the sample, wherein in particular after the displacement of the transducer unit in the Y direction, at least one further linear scanning of the sample is carried out by means of the transducer unit in the Y direction.

[0012] A particular advantage of the method is that during an examination of a sample using the raster method, the offset step size of the transducer unit in the Y direction is changed while the raster method is being carried out, which makes it possible to scan or examine specific areas of a sample with a higher (pixel J) resolution and other less interesting areas of the sample with a lower (pixel) resolution. This can shorten the time required for an entire examination of the sample.

[0013] A further advantage of the method is that the scanning process enables the use of transducer units with multiple transducer elements, where the lateral dimension of the transducer elements is larger than the pixel size. The method according to the invention avoids restrictions on the free choice of pixel size and losses in resolution and detection sensitivity. In particular, a deviation of the individual transducer elements from a reference position is measured and entered, for example, in a calibration table. For transducer units with transducer elements of the same focal length, the area of ​​the sample to be scanned is divided, with each individual transducer element scanning the sample line by line.The acoustic microscope, in particular an ultrasonic scanning microscope, for carrying out the method comprises a positioning system, at least one transducer unit, in particular with a plurality of transducer elements, a pulse generator unit for the transducer unit, preferably pulse generators with a number corresponding to the transducer elements, and a receiving unit, in particular a receiving device for each transducer element. Furthermore, the acoustic microscope comprises a data processing system and a module for digitizing the analog received ultrasound signals.

[0014] In the method according to the invention, it is preferred that, in a transducer unit with multiple transducer elements, the lateral spacing of the individual transducer elements is taken into account on the basis of a (pre-)calibration, so that the area of ​​a sample to be examined and scanned is scanned in an optimized manner. In this case, with a continuous line-by-line, i.e., linear, scanning (in the X direction) with a predetermined and configurable number of pixels per line, the line-to-line spacing in the Y direction is freely selectable.Preferably, the line-shaped scannings are carried out with the same small offset step sizes in the Y direction until the maximum distance between the transducer elements of the same properties is reached and then the transducer unit is moved in the Y direction by this distance with a larger offset step size in the Y direction, so that a high-resolution image of the areas to be examined is created at an increased analysis speed.

[0015] In a further development of the method, it is provided that several linear scans of the sample (in the X-direction) are carried out by the transducer unit, wherein the transducer unit is displaced by a small, preferably constant, offset step size in the Y-direction after each linear scan of the sample and after a predetermined number n (n > 2, 3, ...) of several linear scans of the sample, the transducer unit is displaced by a large, preferably constant, offset step size that is greater than the small offset step size in the Y-direction and / or that after a linear scan of the sample, the transducer unit is displaced by a large, preferably constant, offset step size in the Y-direction and after the displacement of the transducer unit by the large offset step size, several n (n > 2, 3, ...) linear scanning of the sample is carried out by the transducer unit, wherein after each of the plurality of linear n (n > 2, 3, ...) scannings of the sample, the transducer unit is displaced by a small, preferably constant, displacement step size in the Y direction, which is smaller than the large displacement step size.

[0016] This results in a high-resolution image of the sample areas to be examined, in which, for example, the pixel size or the spacing of the linear scans (in the Y direction) is smaller than the spacing of the individual transducer elements (in the Y direction) of a preferably linear array of transducer elements. In particular, the ratio of pixel size or spacing of the linear scans to the spacing of the individual transducer elements (in the Y direction) is less than 1:10, in particular less than 1:100, and more particularly 1:1000.

[0017] Furthermore, it is preferred in the method if the transducer unit is moved in a meandering pattern in the XY plane relative to the sample. For this purpose, a corresponding positioning system is provided to move the transducer unit relative to the sample under investigation. According to a further exemplary embodiment, the method provides that a.) the sample is scanned using a transducer unit for an acoustic scanning microscope, in particular an ultrasonic scanning microscope, with a plurality of transducer elements, each having a transducer and a lens, wherein at least two transducer elements have different focal lengths, or b.) that the sample is scanned using a transducer unit with a plurality of transducer elements each having a transducer and a, preferably acoustic, lens, wherein in particular the transducer elements have the same focal length and / or the transducer elements are arranged next to one another in a linear or diamond-shaped arrangement in the Y direction.

[0018] Furthermore, a further development of the method is characterized in that the transducer unit has a plurality of transducer elements arranged in the Y direction, preferably one behind the other and / or linearly, wherein a plurality of linear m (m > 2, 3, 4, ... ) scannings are carried out in the X direction by means of the respective transducer elements, wherein the distances of the linear m (m > 2, 3, 4, ... ) scannings by the respective transducer elements in the Y direction are equidistant and after the linear m (m > 2, 3, 4, ... ) scannings have been carried out by the transducer unit, the transducer unit is moved in the Y direction with the offset step size which corresponds to the product of the equidistant distance of the linear scannings with the number of linear m (m > 2, 3, 4, ... ) scannings and the number of transducer elements of the transducer unit in Y-direction.Advantageously, the image resolution achieved with this method is independent of the distance and arrangement of the individual transducer elements, e.g., an array. Furthermore, the individual transducer elements can be freely adjusted or optimized with regard to their resolution and signal intensity.

[0019] The image resolution achieved or to be achieved by the method is independent of the distance and arrangement of the individual transducer elements of a transducer unit or a transducer array, whereby in particular the individual transducer elements can be configured with regard to their resolution and focal length depending on the requirements.

[0020] By using transducer elements of different focal lengths in a transducer unit, the surfaces or planes of a sample to be examined are scanned in one or more depth planes, which are or will be determined by the corresponding focal lengths of the individual transducer elements of the transducer unit or transducer array, according to one embodiment of the method. Furthermore, according to a further aspect, the lateral deviation of each individual transducer element is measured and the scan field is enlarged by the corresponding amount. During image creation, possible deviations are corrected to produce seamless and perfectly overlapping images.

[0021] In a further embodiment of the method, it is provided that the transducer unit, preferably with a plurality of transducer elements, has a length in the Y direction, wherein after a plurality of linear scans in the X direction by the transducer unit, the transducer unit is offset in the Y direction with an offset step size that corresponds to the length of the transducer unit, wherein the respective distances of the plurality of linear scans carried out before the offset of the transducer unit in the Y direction with the offset step size that corresponds to the length of the transducer unit correspond to a natural fraction of the length of the transducer unit (length of the transducer unit / 1, t > 2, 3, 4, ... ).

[0022] Furthermore, a method according to a further development is provided in which the transducer unit has a plurality of transducer elements arranged in the Y direction, preferably next to one another and / or linearly, wherein the transducer elements each have a preferably constant width in the Y direction, wherein a plurality of linear p (p > 2, 3, 4, ... ) scans are carried out in the X direction, wherein the distances between the linear p (p > 2, 3, 4, ... ) scans correspond to a fraction of the width of the transducer elements (width of the transducer elements / p, p > 2, 3, 4, ... ), and after the linear p (p > 2, 3, 4, ... ) scans have been carried out, the transducer unit is offset in the Y direction with the offset step size which corresponds to a multiple of the width of the transducer elements.

[0023] In one embodiment of the method, it is preferred that the, in particular large, offset step size of the transducer unit in the Y direction is corrected by a tolerance correction value after the multiple linear scans have been carried out by the transducer unit, wherein in particular the tolerance correction value is formed such that the distance in the Y direction of the last linear scan before the displacement of the transducer unit by the large offset step size to the first linear scan after the displacement of the transducer unit by the large offset step size corresponds to the distance of the multiple linear scans before and / or after the displacement of the transducer unit by the large offset step size in the Y direction or wherein in particular the tolerance correction value is formed such that the distance between all linear scans by the transducer unit is constant.

[0024] In particular, the transducer unit comprises a plurality of transducer elements, wherein the transducer elements are operated in parallel. Preferably, the pulse generators for each transducer element and / or the receiving devices for each transducer element are operated in parallel. Alternatively, in one embodiment, pulse operation occurs with a temporal offset of the total decay time for the transducer signals, wherein crosstalk between the individual transducer elements is minimized and / or the signals of a transducer element caused by sound waves do not interfere with neighboring transducer elements.

[0025] Within the scope of the invention, it is possible that a transducer unit with several transducer elements with a compact design with separate transducer elements or with a monolithic block for the transducer elements is provided for carrying out the method.

[0026] Furthermore, in one embodiment of the method, the distance between the transducer unit and the surface of the sample is monitored by means of a transducer element. Alternatively, the distance between the transducer unit and the sample can be monitored using a weighted value, for example, using a corresponding algorithm, of the various transducer elements. To implement the method, a transducer unit for an acoustic scanning microscope, in particular an ultrasonic scanning microscope, is provided, comprising a plurality of transducer elements, each having a transducer and a, preferably acoustic, lens, wherein at least two transducer elements have different focal lengths.

[0027] When using the transducer unit in an acoustic scanning microscope, several linear scans are performed simultaneously in one, preferably single, scanning process. Due to the different focal lengths of the transducer elements of the transducer unit, the scans occur simultaneously in different planes of the sample. Thus, different scan fields of the sample to be examined are obtained in different planes of the sample during one scanning process.

[0028] In addition to a transducer for generating a sound signal and an acoustic lens for focusing, the individual transducer elements also have a pulse generator, a transmit / receive switch, a receiver for receiving the sound signals reflected or transmitted by the sample, and an A / D converter for converting the received sound signals into digital values ​​for displaying (grayscale) images. The ultrasound signals reflected or transmitted by the sample are measured and converted to generate the image. In addition, the propagation times of the signals or their phase shifts can be obtained as further image information. In a raster method, the sample is scanned pixel by pixel and line by line. The transducer unit or the transducer elements are moved relative to the sample to be examined.For this purpose, in a preferred development of the transducer unit, it is provided that, preferably exclusively, two transducer elements with different focal lengths relative to an XY plane are arranged next to one another in a linear arrangement in the Y direction or one behind the other in the X direction, or that, preferably exclusively, two transducer elements with different focal lengths relative to an XY plane are arranged offset from one another in the X direction and in the Y direction, in particular diagonally.

[0029] In addition, a further embodiment of the transducer unit is characterized in that the transducer unit has a plurality of transducer elements, each with a first focal length, and a plurality of transducer elements, each with a second focal length that differs from the first focal length, relative to an XY plane, wherein an array of transducer elements arranged next to one another, in particular linearly, in the Y direction with the first focal length and an array of transducer elements arranged next to one another, in particular linearly, in the Y direction with the second focal length are arranged one behind the other in the X direction, or wherein an array of transducer elements arranged next to one another, in particular linearly, in the Y direction with the first focal length and an array of transducer elements arranged next to one another, in particular linearly, in the Y direction with the second focal length in the X direction and in the Y direction, in particular diagonally,are arranged offset from one another or wherein transducer elements with the first focal length and transducer elements with the second focal length are arranged one behind the other, in particular linearly, in an alternating sequence in the Y direction. According to an advantageous development, the transducer unit has, in particular, more than two transducer elements, each with a first focal length, and more than two transducer elements, each with a second focal length. By using, in particular in parallel or simultaneously, multiple arrays with multiple transducer elements for an acoustic microscope, in particular with more than two transducer elements of a first focal length and with more than two transducer elements of a second focal length, the application possibilities of the acoustic microscope are increased,This is because, in a single sample examination, transducer elements with different focal lengths simultaneously acquire multiple images in different planes. The arrays also shorten the time required for a scanning examination, as multiple transducer elements of the same focal length scan the sample over a larger width in the Y direction or a wider scan field.

[0030] Furthermore, the object is achieved by an acoustic scanning microscope, in particular an ultrasonic scanning microscope, wherein the acoustic scanning microscope is configured as a transducer unit, as described above, or the acoustic scanning microscope is configured to carry out the above-described method for operating an acoustic microscope, in particular according to one of claims 1 to 11. To avoid repetition, express reference is made to the above statements.

[0031] Furthermore, within the scope of the invention, a method for operating an acoustic scanning microscope, in particular an ultrasonic scanning microscope, is provided as an independent subject matter of the invention, wherein a sample is scanned in an XY plane by means of a transducer unit as described above, in particular with one or more transducer elements each having a transducer and a lens, wherein the transducer unit is moved in the X direction for a linear scanning of the sample, wherein after the one or more linear scannings of the sample in the X direction by the transducer unit, the transducer unit is displaced in the Y direction by a constant displacement step size in the Y direction, wherein in particular after the displacement of the transducer unit in the Y direction, at least one further linear scanning of the sample is carried out by means of the transducer unit in the Y direction.

[0032] The sample to be examined is moved by the transducer unit in a raster method with a constant displacement step size in the Y direction after each line-like scanning in the X direction. Preferably, the transducer unit has several transducer elements, with the transducer elements being operated in parallel. In particular, according to a further aspect, the transducer unit is moved in a meandering pattern in the XY plane relative to the sample.

[0033] Further features of the invention will become apparent from the description of embodiments of the invention together with the claims and the accompanying drawings. Embodiments of the invention may incorporate individual features or a combination of several features.

[0034] Within the scope of the invention, features marked with “in particular” or “preferably” are to be understood as optional features.

[0035] The invention is described below, without limiting the general inventive concept, using exemplary embodiments with reference to the drawings, whereby express reference is made to the drawings for all details of the invention not explained in more detail in the text. They show:

[0036] Fig. 1 a, 1 b schematically show perspective cross-sectional views of transducer units for an acoustic microscope;

[0037] Fig. 2a, 2b schematically show perspective cross-sectional views of further transducer units for an acoustic microscope;

[0038] Fig. 3 schematically shows a single scan field of a transducer unit of an acoustic microscope for examining a sample;

[0039] Fig. 4 schematically shows an entire scan field of a transducer unit of an acoustic microscope for examining a sample;

[0040] Fig. 5 a schematic representation of a meandering scan path of a transducer unit over a sample surface in the section and

[0041] Fig. 6 schematically shows the scan fields for another transducer unit.

[0042] In the drawings, identical or similar elements and / or parts are provided with the same reference numbers, so that a repeated presentation is omitted.

[0043] Fig. 1 a and Fig. 1 b each show schematic perspective views of transducer units 10 for an acoustic microscope, in particular an ultrasonic scanning microscope, in cross section.

[0044] The transducer unit 10 in Fig. 1a has transducer elements 1, 2, 3, 4 arranged side by side in a linear array in the Y direction, i.e., perpendicular to the scanning direction of the transducer unit 10 in the X direction, all of which have the same focal length. The transducer elements 1, 2, 3, 4 are structurally identical and each have a transducer 20 and an acoustic lens 21 arranged on the transducer 20 for focusing the ultrasound signals onto a sample to be examined.

[0045] In the embodiment in Fig. 1b, the transducer unit 10 has transducer elements 1, 12, 3, and 14 in a linear arrangement in the Y direction in an alternating sequence. The transducer elements 1 and 3 each have a (first) focal length, and the transducer elements 12 and 14 have a (second) focal length, wherein the focal length of the transducer elements 1 and 3 and the focal length of the transducer elements 12 and 14 differ. The transducer elements 12 and 14 have a lens 22 whose focal length is different from the focal length of the lens 21 for the transducer elements 1 and 3.

[0046] In Fig. 2a and Fig. 2b, schematic perspective views of transducer units 10 according to other embodiments for an acoustic microscope, in particular an ultrasonic scanning microscope, are shown in cross section.

[0047] The designs of the additional transducer units 10 according to Fig. 2a and Fig. 2b differ from the designs of the transducer units 10 according to Fig. 1a and Fig. 1b in the arrangement of the transducer elements. In the design of the transducer unit 10 according to Fig. 2a, compared to the transducer unit 10 in Fig. 1a, the transducer elements 1 and 3 are offset in the X direction relative to the transducer elements 2 and 4. The transducer elements 1, 2, 3, and 4 each have the same focal length.

[0048] In the configuration of the transducer unit 10 according to Fig. 2b, the transducer elements 1 and 3 are offset in the X direction relative to the transducer elements 12 and 14 compared to the transducer unit 10 in Fig. 1b. The transducer elements 1 and 3 each have the same focal length, which differs from the focal length of the transducer elements 12 and 14.

[0049] Fig. 3 schematically shows a single first scan field 100.1 of the transducer unit 10 according to the embodiment of Fig. 1a with transducer elements 1, 2, 3, 4 that have the same focal length, for a sample to be examined. By means of the transducer elements 1, 2, 3, 4 in the Y position Y1, the image lines Y1 - transducer element 1, Y1 - transducer element 2, Y1 - transducer element 3, Y1 - transducer element 4 are obtained simultaneously in a linear scan of the sample as a representation, for example, on a monitor, corresponding to the received reflected signals for the transducer elements 1, 2, 3, 4 from the sample during a scan in the X direction.

[0050] Subsequently, in a final position, the transducer unit 10 is moved from the Y position Y1 to the Y position Y2 by a small offset increment LJ in the Y direction (see Fig. 5), so that in a linear scan of the sample, the image lines Y2 transducer element 1, Y2 transducer element 2, Y2 transducer element 3, Y2 transducer element 4 are obtained from the sample. The transducer unit 10 is then moved from the Y position Y2 to the Y position Y3 by a small offset increment LJ (see Fig. 5), whereby the image lines Y3 transducer element 1, Y3 transducer element 2, Y3 transducer element 3, Y3 transducer element 4 are subsequently obtained by means of the transducer elements 1, 2, 3, 4. In an analogous manner, the transducer unit 10 is moved from the Y-position Y3 to the Y-position Y4 by a small offset step size LJ in the Y-direction (cf. Fig.5) is moved further in order to then simultaneously obtain the image lines Y4 transducer element 1, Y4 transducer element 2, Y4 transducer element 3, Y4 transducer element 4 in a linear scanning in the X direction.

[0051] Fig. 4 schematically illustrates a total scan field 100 of the transducer unit 10 of an acoustic microscope for examining a sample. After capturing the entire scan field 100.1 with four linear scans in the X direction, as shown in Fig. 3, the transducer unit 10 is offset in the Y direction by a displacement step width W (see Fig. 5) that is greater than the displacement step width U (see Fig. 5) between the Y positions Y1, Y2, Y3, Y4. In particular, the offset step width W of the transducer unit 10 in the Y direction corresponds to the length resulting from the product of the equidistant distance U of the linear scans with the number of linear scans m (in the present case m = 4) and the number of transducer elements (in the present exemplary case: four) of the transducer unit 10 in the Y direction.

[0052] In another embodiment, the Y-spacings of the four linear scans in the positions Y1, Y2, Y3 and Y4 correspond to a fraction of the width of the transducer elements 1, 2, 3, 4, wherein after the four linear scans in the X-direction have been carried out, the transducer unit is offset in the Y-direction with the offset step size which corresponds to a multiple of the width of the transducer elements.

[0053] After the acquisition and complete display of the scan field 100.1, the transducer unit 10 is moved, as described in Fig. 3, and after an offset in the Y direction by a large offset step width W (cf. Fig. 5) from the Y position Y4 to the Y position Y5 for the acquisition of a subsequent scan field 100.2, wherein the transducer unit 10 is then moved from the Y position Y5 to the further Y positions Y6, Y7 and Y8 in a meandering manner in the raster method for the acquisition of a scan field 100.2 in order to generate the respective image lines for the four Y positions Y5, Y6, Y7 and Y8 by means of the transducer elements 1, 2, 3, 4 by linear scanning of the sample. These process steps between the individual Y-positions of the transducer unit 10 and between two consecutive scan fields are repeated several times in a corresponding manner until the last scan field 100.n for the Y positions Yn, Yn+1, Yn+2, Yn+3 is scanned by means of the transducer elements 1, 2, 3, 4 and the corresponding image lines are generated.

[0054] Within the scope of the invention, it is possible, instead of the transducer unit 10 from Fig. 1a, to use a transducer unit 10 according to the schematic embodiments according to Fig. 1b or Fig. 2a or Fig. 2b or another transducer unit with several transducer elements that are arranged in a predetermined arrangement in the X-direction and / or in the Y-direction and / or have different focal lengths, for the acquisition of an overall scan field 100, wherein the transducer units 10 are each moved according to a, in particular meander-shaped, raster method with different offset step sizes in the Y-direction during the raster method. Fig. 5 shows a detail schematic representation of the scan path of the transducer unit 10 (cf. Fig. 4) with the four transducer elements 1, 2, 3, 4 over a section of a sample surface of the sample. For the acquisition of the scan fields 100.1 and 100.2, the transducer unit 10 is moved between the several Y positions Y1, Y2, Y3, Y4 respectively.Y5, Y6, Y7, Y8 of the respective scan field 100.1 or 100.2 are moved by the (small) offset step size LJ in the Y direction and after acquisition of a scan field 100.1 or 100.2 by the offset step size W, which is larger than the offset step size LJ.

[0055] The movement of the transducer unit 10 takes the form of a meander 30, whereby the sample is scanned in a meandering manner. The Y-step size of the meander 30 for the transducer unit 10 is varied in the Y direction to capture the entire scan field 100 with the offset step sizes LJ and W.

[0056] In the embodiment of Fig. 6, a transducer unit 10 with two transducer elements 1 and 12 as well as the total scan fields 101 and 112 for the two transducer elements 1 and 12 are shown schematically. In this embodiment, the transducer elements 1 and 12 have different focal lengths.

[0057] As can be seen from Fig. 6, the transducer elements 1 and 12 are arranged diagonally offset in the X direction and in the Y direction on the transducer unit 10, whereby when scanning a sample, the total scan field 101 for the transducer element 1 and the total scan field 112 for the transducer element 12 are also formed with an offset in the X direction and in the Y direction. Accordingly, the generated total scan images 101, 102, which are obtained with the transducer elements 1 and 12, are displayed with an offset. In one embodiment, the transducer unit 10 is moved in a meandering pattern over the sample for a linear scan using the transducer elements 1 and 12, wherein the Y step size between two linear scans is constant.

[0058] In a further embodiment (not shown here), instead of the transducer unit 10 shown in Fig. 6, the transducer unit 10 shown in Fig. 2b, for example, is used for capturing the total scan fields 101 and 112, wherein the transducer unit 10 is moved in the Y direction according to a raster method, in particular a meandering raster method, with different offset increments. Other embodiments of the raster method can also be implemented using transducer units with multiple transducer elements having different focal lengths, wherein the transducer units are moved in the Y direction according to raster methods, in particular a meandering raster method, with different offset increments during the capture of a total scan field.

[0059] All mentioned features, including those that can be inferred from the drawings alone, as well as individual features disclosed in combination with other features, are considered essential to the invention, both individually and in combination. Embodiments according to the invention may be fulfilled by individual features or a combination of several features. List of reference symbols

[0060] 1 , 2, 3, 4 Transducer element

[0061] 10 Transducer unit

[0062] 12, 14 Transducer element

[0063] 20 transducers

[0064] 21 , 22 lens

[0065] 30 meanders

[0066] 100 total scan field

[0067] 101 total scan field

[0068] 100.1 , 100.2, ... , 100. n Scan field 1 12 Total scan field

[0069] U Offset step width w Offset step width

Claims

Method for operating an acoustic scanning microscope and acoustic scanning microscope Patent claims 1. A method for operating an acoustic scanning microscope, in particular an ultrasonic scanning microscope, wherein a sample is scanned in an XY plane by means of a transducer unit (10), in particular with one or more transducer elements (1, 2, 3, 4, 12, 14) each having a transducer (20) and a lens (21, 22), wherein the transducer unit (10) is moved in the X direction for a linear scanning of the sample, wherein after the or a linear scanning of the sample by the transducer unit (10), the transducer unit (10) is displaced in the Y direction by an offset step size, wherein for the scanning of the sample the size of the offset step size of the transducer unit (10) in the Y direction is varied, wherein in particular after the displacement of the trans- ducer unit (10) in the Y direction at least one further linear scanning of the sample is carried out by means of the transducer unit (10) in the Y direction.

2. Method according to claim 1, characterized in that several linear scans of the sample are carried out by the transducer unit (10), wherein the transducer unit (10) is displaced in the Y direction by a small, preferably constant, offset step size (LJ) after each linear scan of the sample and after a predetermined number n (n > 2, 3, ...) of several linear scans of the sample, the transducer unit (10) is displaced in the Y direction by a large, preferably constant, offset step size (W), which is greater than the small offset step size (LJ) and / or that after a linear scan of the sample, the transducer unit (10) is displaced in the Y direction by a large, preferably constant, offset step size and after the displacement of the transducer unit (10) by the large offset step size (W), several n (n > 2, 3, ...) linear scanning of the sample is carried out by the transducer unit (10), wherein after each of the plurality of linear n (n > 2, 3, ...) scannings of the sample, the transducer unit (10) is displaced by a small, preferably constant, displacement step width (LJ) in the Y direction, which is smaller than the large displacement step width (W).

3. Method according to claim 1 or 2, characterized in that the transducer unit (10) is moved in a meandering course in the XY plane relative to the sample.

4. Method according to one of claims 1 to 3, characterized in that a.) the sample is scanned using a transducer unit (10) for an acoustic scanning microscope, in particular an ultrasonic scanning microscope, with a plurality of transducer elements (1, 2, 3, 4, 12, 14) each having a transducer (20) and a lens (21, 22), wherein at least two transducer elements (1, 2, 3, 4, 12, 14) have different focal lengths, or b.) that the sample is scanned using a transducer unit (10) with a plurality of transducer elements (1, 2, 3, 4, 12, 14) each having a transducer (20) and a lens (21, 22), wherein in particular the transducer elements (1, 2, 3, 4, 12, 14) have the same focal length and / or the transducer elements (1, 2, 3, 4, 12, 14) are arranged next to each other in a linear or diamond-shaped arrangement in the Y direction.Method according to one of claims 1 to 4, characterized in that the transducer unit (10) has a plurality of transducer elements (1, 2, 3, 4, 12, 14) arranged in the Y direction, preferably one behind the other and / or linearly, wherein a plurality of linear m (m > 2, 3, 4, ...) scannings are carried out in the X direction by means of the respective transducer elements (1, 2, 3, 4, 12, 14), wherein the distances of the linear m (m > 2, 3, 4, ...) scannings by the respective transducer elements (1, 2, 3, 4, 12, 14) in the Y direction are equidistant and after the linear m (m > 2, 3, 4, ...) scannings have been carried out by the transducer unit (10), the transducer unit (10) in the Y-direction with the offset step size, which corresponds to the product of the equidistant distance of the line-shaped scans with the number of line-shaped scans m (m > 2, 3, 4, ... ) and the number of transducer elements (1 , 2, 3, 4,. 12, 14) of the transducer unit (10) in the Y direction. Method according to one of claims 1 to 5, characterized in that the transducer unit (10), preferably with a plurality of transducer elements (1, 2, 3, 4, 12, 14), has a length in the Y direction, wherein after a plurality of linear scans in the X direction by the transducer unit (10), the transducer unit (10) is offset in the Y direction with an offset step size that corresponds to the length of the transducer unit (10), wherein the respective distances of the plurality of linear scans carried out before the offset of the transducer unit (10) in the Y direction with the offset step size that corresponds to the length of the transducer unit (10) correspond to a natural fraction of the length of the transducer unit (10) (length of the transducer unit (10) / 1, t > 2, 3, 4, ... ).Method according to one of claims 1 to 5, characterized in that the transducer unit (10) has a plurality of transducer elements (1, 2, 3, 4, 12, 14) arranged in the Y direction, preferably next to one another and / or linearly, wherein the transducer elements (1, 2, 3, 4, 12, 14) each have a preferably constant width in the Y direction, wherein a plurality of linear p (p > 2, 3, 4, ...) scannings are carried out in the X direction, wherein the distances of the linear p (p > 2, 3, 4, ...) scannings correspond to a fraction of the width of the transducer elements (1, 2, 3, 4, 12, 14) (width of the transducer elements (1, 2, 3, 4, 12, 14) / p, p > 2, 3, 4, ... ), and after carrying out the line-shaped p (p > 2, 3, 4, ... ) scannings, the transducer unit (10) in the Y direction with the. Offset step width, which corresponds to a multiple of the width of the transducer elements (1, 2, 3, 4, 12, 14). Method according to one of claims 5 to 7, characterized in that the, in particular large, offset step width (W) of the transducer unit (10) in the Y direction is corrected by a tolerance correction value after the execution of the multiple linear scannings by the transducer unit (10), wherein in particular the tolerance correction value is formed in such a way,that the distance in the Y direction of the last linear scan before the displacement of the transducer unit (10) by the large displacement step size (W) to the first linear scan after the displacement of the transducer unit (10) by the large displacement step size (W) corresponds to the distance of the multiple linear scans before and / or after the displacement of the transducer unit (10) by the large displacement step size (W) in the Y direction, or wherein in particular the tolerance correction value is formed such that the distance between all linear scans by the transducer unit (10) is constant. Method according to one of claims 1 to 8, characterized in that the transducer unit (10) has a plurality of transducer elements (1, 2, 3, 4, 12, 14), wherein the transducer elements (1, 2, 3, 4, 12, 14) are operated in parallel. Method according to one of claims 4 to 9, characterized in that, in particular in case a.), preferably exclusively,two transducer elements (1, 2, 3, 4, 12, 14) with different focal lengths relative to an XY plane in a linear arrangement in the Y direction next to each other or in the X, direction are arranged one behind the other or that, preferably exclusively, two transducer elements (1, 2, 3, 4, 12, 14) with different focal lengths relative to an XY plane in the X direction and in the Y direction, in particular diagonally, are arranged offset from one another. 1 . Method according to one of claims 4 to 10, characterized in that, in particular in case a.), the transducer unit (10) comprises a plurality of transducer elements (1, 2, 3, 4, 12, 14) each with a first focal length and a plurality of transducer elements (1, 2, 3, 4, 12, 14) each having a second focal length which differs from the first focal length, relative to an XY plane, wherein an array of transducer elements (1, 2, 3, 4, 12, 14) arranged next to one another, in particular linearly, in the Y direction with the first focal length and an array of transducer elements (1, 2, 3, 4, 12, 14) arranged next to one another, in particular linearly, in the Y direction with the second focal length are arranged one behind the other in the X direction or wherein an array of transducer elements (1, 2, 3, 4, 12, 14) arranged next to one another, in particular linearly, in the Y direction 4, 12, 14) with the first focal length and an array of transducer elements (1, 2, 3, 4, 12, 14) with the second focal length arranged next to one another in the Y direction, in particular linearly, are arranged offset from one another in the X direction and in the Y direction, in particular diagonally, or wherein transducer elements (1, 2, 3, 4, 12, 14) with the first focal length and transducer elements (1, 2, 3, 4, 12, 14) with the second focal length are arranged one behind the other, in particular linearly, in an alternating sequence in the Y direction. Acoustic scanning microscope, in particular ultrasonic scanning microscope, wherein the acoustic scanning microscope is configured to carry out the method according to one of claims 1 to 11.