Laser scanning method and laser scanning system

Abstract

A method (and corresponding apparatus) for scanning a laser over a field of view, comprising: rasterizing a laser beam over a first subarea of ​​the field of view; deflecting the laser beam to a second subarea of ​​the field of view; rasterizing the laser beam over the second subarea of ​​the field of view; and capturing image information produced by the laser beam such that, for each subarea of ​​the field of view, the rasterized laser beam defines a plurality of image segments; calculating an image correction for each segment; and applying the correction to the laser according to the image correction calculated for the segment.

Description

[Technical Field]

[0001] Embodiments relate to a laser scanning system for use in optical systems such as microscopes, laser lithography, laser writing, laser engraving, and corresponding laser scanning methods. [Background Art]

[0002] In any system where light or other electromagnetic radiation is manipulated, there are numerous factors that limit the performance of the system. For example, in an optical system, one of the most important factors may be changes in refractive index at different positions within a sample. Other examples include optical distortion in the optical train, such as laser scanning units and field curvature. These changes can make it difficult to obtain optimal results from the system over space and / or time.

[0003] "Adaptive optics" is a term commonly used to refer to the use of one or more active optical components to correct small variations in optical characteristics that affect a system. Generally, this includes determining the range of optical aberrations to be corrected, calculating the correction, and implementing the correction.

[0004] There are various methods for determining the required correction. One example relies on a wavefront detector, which is susceptible to inaccuracies arising from defocused light. When a wavefront sensor is used, the levels of dark noise, background noise, and crosstalk between each detector on a 2D array can limit the performance of the above system.

[0005] Many existing correction approaches fail to On the fly adapt to sample distortion. Unless scanning is paused or restricted to a fixed scan field, spatially varying aberrations cannot be On the fly achieved. [Summary of Invention]

[0006] One embodiment provides a method for scanning a laser beam across a field of view, the method comprising: We provide a laser for generating a laser beam. The laser beam is rasterized on the first sub-area of ​​the field of view, By deflecting the laser beam to a second sub-area of ​​the field of view, The laser beam is rasterized in the second sub-area of ​​the field of view. For each sub-area of ​​the field of view, the image information generated by the laser beam is captured so that the rasterized laser beam defines multiple image segments. For each segment, an image correction is calculated, and the correction is applied to the laser according to the image correction calculated for that segment.

[0007] Corrections may be applied to each segment.

[0008] Each segment and each correction may be time-recorded. Time recording may include recording the relative time at which the segments are scanned. The relative time will establish the sequence of segments so that the correction to the laser can be applied to the corresponding segments when the corresponding segments are rasterized.

[0009] This method may further include the step of applying corrections when the corresponding segment is being scanned by a laser.

[0010] The field of view may be related to the target. This method may include moving the target relative to one or more optical elements, such as a rasterizing mirror, or / or, in addition, moving the optical elements relative to the target. The optical elements may include an objective lens. The field of view can be defined at a given position of the target relative to the optical elements. Thus, in the embodiment, neither the target nor the optical elements are moved while the segment is being scanned.

[0011] The temporal correlation between image segments and corrections can lead to a time-division multiplexing approach to correction. Using a time-division multiplexing approach makes it easier to broaden the effective field of view at a specific target location. A time-division multiplexing approach may also facilitate improvements in laser intensity. By segmenting the field of view, different corrections can be applied to spatially different regions at different times.

[0012] The embodiments can provide different corrections that can be applied to different optical properties of the system and / or different optical properties of the target.

[0013] Image correction calculations may include deriving wavefront masks. Each correction may include a corresponding wavefront mask.

[0014] Image correction calculations may include applying an iterative image-based wavefront detection loop to each segment. The loop may include a hill-climbing algorithm applied to the measured intensity. The measured intensity may be measured for each segment. Image correction calculations may include identifying the Zernike mode for each segment and deriving one or more wavefront masks based on the identified Zernike mode.

[0015] Applying corrections may involve adjusting a deformable mirror. The deformable mirror can be adjusted according to the corresponding wavefront mask.

[0016] The only optical correction that can be applied is that which can be applied by a deformable mirror.

[0017] Rasterizing a laser beam may involve moving the laser beam in two directions. The laser beam can be moved in a first direction corresponding to the x-axis and a second direction corresponding to the y-axis. The movement of the laser beam in the x-axis direction may be faster than the movement of the laser beam in the y-axis direction. In embodiments, the x and y axes are orthogonal to each other and lie in the plane of the target. In embodiments, the x and y axes can be arbitrarily selected because there is no difference in the optical properties of the system in the plane of the target.

[0018] By deflecting the laser beam to a second sub-area of ​​the field of view, the laser beam can be directed x This may include deflection in the direction of the axis.

[0019] The deformable mirror can be synchronized with the movement of the laser beam in the y-axis. Therefore, embodiments may not require a high-speed deformable mirror capable of achieving aberration correction at video frame rates (approximately 20 frames per second with a residence time of approximately 5 μs). In one embodiment, the deformable mirror can implement 200 waveform masks per second. The deformable mirror may have 30 to 50 actuators. In one embodiment, the deformable mirror may have approximately 40 actuators. Synchronization may include saving the captured image information along with the time the image information was captured. Then, corrections can be applied to the image information corresponding to a segment by applying corrections to the laser at the corresponding time during rasterization of the segment. It should be understood that by comparing the relative timing of the image information corresponding to all segments, the system can determine the sequence and timing for applying each correction to the laser.

[0020] In this embodiment, an iterative approach is applied to the calculation of image correction. The correction applied to the laser can be updated with each iteration.

[0021] Each sub-area may cover the same area of ​​the field of view, or the first sub-area may cover a different area of ​​the field of view than the second sub-area.

[0022] A further embodiment provides a system for scanning a laser beam across a field of view. The system comprises the following. a laser for generating a laser beam,[] a first movable deflector for rasterizing the laser beam over a first sub-area of the field of view,[] a second movable deflector for deflecting the laser beam such that the first movable deflector rasterizes a second sub-area of the field of view,[] an image digitizer for digitizing image information generated by the laser beam interacting with a target,[] a computer processor for capturing the image information generated by the image digitizer such that, for each sub-area of the field of view, the rasterized laser beam defines a plurality of image segments, the computer processor calculating an image correction for each segment,[] further, an optical correction element for applying correction to the laser beam in accordance with the calculated image correction.

[0023] The system may comprise three movable deflectors for rasterizing the sub-areas. The movable deflectors are formed of three scanning mirrors. The system may include a rotating polygon mirror and two galvanic mirrors. The first movable deflector for rasterizing the laser beam across a sub-area of the field of view may include the rotating polygon mirror and a first galvanic mirror. The second movable deflector for deflecting the laser beam to rasterize a second sub-area of the field of view may include a second galvanic mirror.

[0024] The field of view may be associated with a target. The target may be movable relative to one or more optical elements such as a rasterizing mirror, or additionally / in addition, the optical element may be movable relative to the target. The optical element may comprise an objective lens. The field of view may be defined at a given position of the target relative to the optical element. Accordingly, in an embodiment, neither the target nor the optical element is moved while a segment is being scanned.

[0025] Rasterizing the laser beam may comprise moving the laser beam in two directions. The laser beam can move in a first direction corresponding to the x-axis and a second direction corresponding to the y-axis. Movement of the laser beam in the x-direction during rasterizing may be faster than movement of the laser beam in the y-direction.

[0026] During rasterizing, a rotating polygon mirror may move the laser beam along the x-axis, and a first galvanic mirror may move the laser beam along the y-axis. The x-axis and the y-axis may be orthogonal to each other.

[0027] Movement of a second galvanic mirror may cause the laser beam to x deflect in the axial direction, thereby deflecting the laser beam to a second sub-area of the field of view.

[0028] The processor may calculate an image correction for each segment. The image correction may be a calculated wavefront mask.

[0029] The processor may apply a timestamp to each segment and each correction.

[0030] The processor may apply the correction when a corresponding segment is being scanned by the laser.

[0031] The temporal correlation between image segments and corrections can lead to a time-division multiplex approach to correction. Using a time-division multiplex approach makes it easier to broaden the effective field of view at a specific target location. By segmenting the field of view, different corrections can be applied to spatially different regions at different times.

[0032] The embodiments can provide different corrections that can be applied to different optical characteristics of the system.

[0033] Image correction calculations may include deriving wavefront masks. Each correction may include a corresponding wavefront mask.

[0034] The embodiments can improve imaging performance. For example, the point image distribution function, spatial-bandwidth product, and / or fluorescence intensity can be improved compared to known configurations without optically splitting the detected signal. Therefore, embodiments may not be limited by the sensitivity of the wavefront detector or the number of image splitters.

[0035] Image correction calculations may include applying an iterative image-based wavefront detection loop to each segment. The loop may include a hill-climbing algorithm. Image correction calculations may include identifying the Zernike modes for each segment and deriving one or more wavefront masks based on the identified Zernike modes.

[0036] The optical correction element may include a deformable mirror. The deformable mirror may be adapted so as to be adjusted by a processor according to the corresponding wavefront mask.

[0037] The optical correction element can consist of a deformable mirror. The system may include just one deformable mirror or other adaptive optics elements. The deformable mirror may be a low-resolution deformable mirror. The deformable mirror may be a high-speed deformable mirror. In one embodiment, the deformable mirror is adapted to implement 200 waveform masks per second. The deformable mirror may have 30 to 50 actuators. In one embodiment, the deformable mirror may have about 40 actuators.

[0038] The embodiment can extend the imaging field of view with complete or near-complete recovery of the point image distribution function.

[0039] Optical correction elements may include digital micromirrors and / or spatial light modulators.

[0040] The deformable mirror may be synchronized with the movement of the laser beam in the y-axis or in the x-axis. Therefore, the embodiment may not require a high-speed deformable mirror that can achieve aberration correction at video frame rates (approximately 20 frames per second with a residence time of approximately 5 μs).

[0041] Each sub-area may cover the same area of ​​the field of view, or the first sub-area may cover a different area of ​​the field of view than the second sub-area.

[0042] Further embodiments include a method for scanning a laser beam in a field of view, and include the following steps: The laser beam is sequentially raster-scanned within multiple sub-areas of the field of view. Here, the sub-areas are positioned in a first direction of the field of view. Multiple image segments are defined for each sub-area. Here, the image segments of a particular sub-area are positioned in a second direction of the field of view, perpendicular to a first direction. This captures image information from each image segment, specifically image information associated with the illumination of the field of view by a laser beam. Image correction is calculated for each segment. Here, the image correction is configured so that the laser beam is corrected when it is next raster-scanned over the corresponding segment.

[0043] Another further embodiment is a system for scanning a laser across a field of view, which includes: A laser used to generate a laser beam. A first movable deflector for raster scanning the laser beam. A second movable deflector for deflecting the laser beam to sequentially raster scan multiple sub-areas of the field of view, where the sub-areas are positioned in a first direction of the field of view. Image capture means configured to capture image information of each image segment, which is associated with the illumination of the field of view by a laser beam. The processor is configured as follows: Multiple image segments are defined for each sub-area. Here, the image segments of a particular sub-area are positioned in a second direction of the field of view, perpendicular to a first direction. This captures image information from each image segment, specifically image information associated with the illumination of the field of view by the laser beam. For each segment, image correction is calculated. Here, the image correction is configured to allow correction of the laser beam when the laser beam is next raster-scanned over the corresponding segment.

[0044] Furthermore, this embodiment can be retrofitted to an existing laser scanning system. [Brief explanation of the drawing]

[0045] The embodiments will be described with reference to the attached drawings below. [Figure 1] A schematic diagram of the optical elements of a laser scanning microscope according to one embodiment. [Figure 2] Schematic diagram of electronic components in a laser scanning microscope, Figure 1. [Figure 3] Figure 1 shows the segmentation of the field of view image from a laser scanning microscope. [Figure 4] A diagram illustrating a method for scanning a laser according to one embodiment. [Figure 5] A diagram showing the correlation between an image segment and a wavefront mask according to one embodiment. [Figure 6] Figure 1 shows further segmentation of the field of view of the laser scanning microscope. [Figure 7] A diagram showing multiple segments and sub-areas of the field of view, and the wavefront masks calculated for each. [Figure 8] A diagram showing the effects of various wavefront corrections on different segments. [Figure 9A] A diagram showing the results of a photolithography process without correction. [Figure 9B] A diagram showing the results of a photolithography process with correction applied. [Figure 9C] Figures 9A and 9B show the intensity profiles of selected portions. [Figure 10] A figure showing improvements in intensity profile and resolution between the uncorrected and corrected images of the beads. [Modes for carrying out the invention]

[0046] Figure 1 shows a laser scanning microscope 10. The laser scanning microscope 10 is used to image a sample 12 on a target sample stage 14 by directing a laser beam onto the sample 12 through the microscope's optical elements and collecting image information using a photomultiplier tube 34. While this embodiment utilizes a photomultiplier tube 34, it should be understood that any other device for converting optical information into electronic information can be used instead.

[0047] The microscope 10 includes a laser 16 that generates a laser beam, as shown in the figure. A deformable mirror 18 is used to apply a wavefront mask to correct optical aberrations in the microscope 10, the target holding the sample 12 in use, and / or the surrounding environment. The embodiment relates to adaptive optics, and aspects of the embodiment that can be learned from the field of adaptive optics should be understood as not being described in detail herein.

[0048] A polygonal scanning mirror 22 is used to scan the laser beam in the manner described below. Two galvanic mirrors 26 and 28 are also used to change the position of the laser beam relative to the target 12. The Y-axis galvanic mirror 26 changes the direction of the laser beam along the y-axis (perpendicular to the plane in the drawing of Figure 1), while the X-axis galvanic mirror 28 changes the direction of the laser beam along the x-axis (in and out of the plane in the drawing of Figure 1).

[0049] In the embodiments of the disclosure, the microscope 10 includes three sets of telescoping lenses 20, 24, and 30 that focus and direct the laser beam. A filter 32 (in this embodiment, a dichroic long-pass filter) reflects the emitted fluorescence signal to a photomultiplier tube 34. An objective lens 36 focuses the laser beam, which has passed through the optical elements of the microscope 10, onto a target 12. The image information is then captured by the photomultiplier tube 34.

[0050] It should be understood that the laser scanning microscope 10 shown in Figure 1 is only one example of an application of the present invention. Additional embodiments should be understood to find applications in other types of microscopes and in fields other than microscopy, as described below.

[0051] Figure 2 shows the electronic components of the microscope 10. The deformable mirror 18, polygonal mirror 22, and galvanic mirrors 26 and 28 are connected to the processor 40 (for example, in the form of a personal computing unit). The processor 40 includes a central processing unit 42 attached to a clock 44. The processor 40 is attached to a storage device 46 used for storing information. The photomultiplier tube 34 is connected to the processor 40 so that image information captured by the photomultiplier tube 34 can be manipulated by the processor and stored in the storage device 46.

[0052] The processor 40 and other electronic components shown in Figure 2 are shown in schematic form only. Therefore, for example, the clock 44 may be provided as part of the central processing unit 42 or separately. Furthermore, it should be understood that the processor 40 and memory 46 may instead be provided in separate locations connected to the microscope 10 via a network, and as a further example, they may be provided as cloud computing.

[0053] The clock 44 provides a timing mechanism to synchronize the image information, the relative positions of the polygon mirror 22 and the galvanic mirrors 26 and 28, and the operation of the deformable mirror 18 in the manner described below.

[0054] Figure 3 shows scanned image information representing a sub-area or portion 50 of the field of view provided by the objective lens 36. As shown, the portion 50 has an x-axis (horizontal) and a y-axis (vertical). The rotating polygonal mirror 22 scans the laser beam along the x-axis, and the Y-axis galvanic mirror 26 scans the laser beam along the y-axis. Thus, the scanned image information of the sub-area 50 consists of rows of scanned image information forming a specific column. Therefore, the sub-area 50 is raster-scanned with the laser by the combined action of the rotating polygonal mirror 22 and the Y-axis galvanic mirror 26.

[0055] Next, embodiments of the present invention define a segment 52 of subarea 50 by grouping some of these scanned rows together. In the embodiment shown in Figure 3, there are five segments 52A, 52B, 52C, 52D, and 52E. As shown, each segment 52 consists of multiple scanned rows. For example, segment 52A is rows 1 to 102, and segment 52E is row 408 Starting from 512, the intermediate rows are assigned to the remaining segments 52B, 52C, and 52D. Adjacent segments 52 are preferably bounded between adjacent rows. For example, segment 52A ends at row 102 and segment 52B begins at row 103. In this way, segment 52 covers the entire sub-area 50.

[0056] According to one embodiment, the X-axis galvanic mirror 28 remains stationary during the scanning process to define the sub-area 50. However, as will be explained in detail below with reference to Figure 6, when the scanning process reaches the bottom of the column of the sub-area 50, the galvanic mirror 28 moves the laser beam to the adjacent sub-area 50, and the laser beam scans the adjacent sub-area. Figure 6 shows sub-areas 50A, 50B, and 50C, each with five segments 52A(A) through 52 E (C) is present. Therefore, in the diagram, a specific segment 52 is associated with a row and a column, and the value in parentheses represents a specific sub-area within 50A-50C.

[0057] Figure 4 shows a method 80 for scanning a laser using the scanning laser microscope 10 shown in Figure 1. In the first step, step 82, the sample is scanned with the laser beam and the corresponding image information is stored in the memory device 46. During this step, the rotating polygon mirror 22 and the galvanic mirrors 26 and 28 work together to scan the field of view provided by the objective lens 36 by scanning multiple adjacent columns as described above.

[0058] In one embodiment, the field of view is defined by an objective lens 36 that focuses a laser beam onto the sample 12. The field of view is provided relative to a given position of the objective lens 36.

[0059] In the next step, step 84, the segments are defined. This step determines the number of scan rows to be allocated to each segment. This step may also include determining how much of the potential field of view needs to be processed. Defining the segment size determines the relative speed of the rotating polygon mirror 22 and the galvanic mirrors 26 and 28. As the image information for each segment is digitized and stored, a timestamp provided by the clock 44 is stored for that segment. This allows for tracking and synchronizing corrections for each segment.

[0060] It should be understood that segment size can be selected depending on the optical characteristics of the target and / or system. In particular, segment size may be changed to find the optimal correction for the current field of view. Therefore, segment size may be changed during rasterization.

[0061] In step 86, segment processing begins. This process starts with the first segment and loads the next segment repeatedly until all segments have been processed. In step 88, the metric (intensity in this case) is calculated, and in the next step, step 90, the wavefront is estimated using a hill-climbing algorithm. The hill-climbing method is achieved by moving through the first 13th order of Zernike modes (excluding tip, tilt, and piston) from lower order (Z4) to higher order (Z15) to identify the optimal set of Zernike masks for each correction. Each step is a 0.05 step value of the Zernike amplitude. The optimization takes into account the measured intensity (higher is better), but not the gradient between each point (the difference between each measurement).

[0062] Please be aware that the step value may be changed to meet specific requirements.

[0063] In step 92, the amplitude of the Zernike mode is set. In step 94, a wavefront mask corresponding to the current segment is generated and stored in the memory device 46. Thus, the image correction calculation involves applying an iterative image-based wavefront detection loop for each segment.

[0064] Next, the process returns to step 86, where the next segment is considered, and the process cycles through steps 88, 90, 92, and 94 again to generate the wavefront mask for the next segment. In this way, the wavefront mask for each segment is generated.

[0065] During operation, samples are continuously scanned. Therefore, when the processor determines that a segment for which a wavefront mask has been previously generated and stored is being scanned, the processor uses that wavefront mask to deform the deformable mirror and applies the resulting wavefront mask to correct aberrations in that segment. As shown in Figure 5, wavefront masks 102A, 102B, 102C, 102D, and 102E correspond to segments 52A, 52B, 52C, 52D, and 52E.

[0066] In one embodiment, for each segment 52, the determined wavefront mask 102 is continuously updated during each scan. For example, segment 52 can be imaged using the calculated wavefront mask 102 to generate output (e.g., to a display or data store). This newly obtained image of segment 52 can also be used to determine a new wavefront mask 102 (as in the embodiments described herein). Conveniently, since this newly determined wavefront mask 102 is determined from the image generated with the previous wavefront mask 102, a more accurate correction can be produced. Such a correction process may proceed during the imaging of sample 12. In most cases, the resulting image can be expected to continuously improve, although the improvement in subsequent captures is slight. In some cases, the most effective correction may be obtained after several updates.

[0067] Figure 6 illustrates how the scan sub-areas 50 are offset. The middle column corresponds to the sub-areas 50 shown in Figure 3 above. The X-axis galvanic mirror 28 is controlled to provide an offset in the x-axis, thereby defining different sub-areas 50. For example, sub-area 50A is offset relative to sub-area 50B, which itself is offset relative to sub-area 50C. By applying a series of offsets, the system can advantageously expand the scanned effective field of view. This is because different corrections via the deformable mirror 18 are expected to be required across the range of the field of view in the x-direction. This is similar to the various corrections required in the y-direction, although the differences in the y-direction are naturally accounted for by the direction of the raster scan. Advantageously, by dividing the x-axis into different sub-areas 50, the field of view is sufficiently corrected in both the x and y directions, enabling improved imaging of sample 12.

[0068] Figure 7 shows an example where multiple sub-areas 50A–50J are defined in a two-dimensional grid. As shown, each sub-area 50A–50J contains five segments 52, and therefore, as a result, there are 50 segments 52. Each segment 52 is shown along with its calculated wavefront mask 102. As can be seen, each segment 52 has its own wavefront mask 102, which depends on the distortion specific to the corresponding image area.

[0069] Figure 7 illustrates the advantage that a relatively wide area can be imaged (i.e., a relatively high field of view) by dividing the field of view into individual regions (i.e., segments 52) and determining a unique wavefront mask 102 in each region. An advantage of the present invention would be the balance between the number of wavefront masks 102 determined and the operating speed. A large number of individual unique wavefront masks 102 would significantly enable useful adaptive optics correction while maintaining, for example, video-level frame rates (e.g., 20 frames per second).

[0070] As shown in Figure 7, the size of each segment 52 (i.e., the extent within the field of view) can vary. For example, segment 52A (A) This is segment 52 A(B) This is a different size. In this figure, the segment size changes in the x direction and essentially corresponds to the line length during raster scanning (i.e., laser scanning). In one embodiment, the number of lines per segment 52 can also be changed. This changes the size in the y direction. In one embodiment, changes in line length and the number of lines can be applied to each segment 52, thereby allowing the size of the segment 52 to be changed in both the x and y directions.

[0071] Figure 8 shows the various improvements measured in two segments 52, TMy1 and TMy5. Here, a lower “axial FWHM” (“full width at half maximum”) indicates higher resolution, i.e., improved results, and a higher fluorescence intensity indicates improved results. In both TMy1 and TMy5, each measured parameter is improved by wavefront correction (“RAO”) compared to no wavefront correction (“no RAO”), but the improvement is much more pronounced in the case of TMy5. In the actual samples measured to generate Figure 8, the wavefront correction required for TMy5 was more complex than for TMy1, because the aberrations were more complex.

[0072] The embodiment may be capable of operating at speeds comparable to video storage and playback (approximately 20 fps and a dwell time of approximately 5 μs) for wavefront optimization of selected segments, potentially eliminating the need to slow down the scan speed or reduce the region of interest.

[0073] Generally, when imaging a sample 12 using a laser scanning microscope 10 without correction according to the embodiments described herein, optical aberrations and sample aberrations result in an odd-isoplanar illumination field. The embodiments described herein can favorably improve the illumination field toward an ideal odd-isoplanar illumination field, and in particular, embodiments in which the wavefront mask 102 is continuously updated can provide effective iterative modification of the wavefront mask 102 toward an odd-isoplanar illumination field.

[0074] Figure 10 shows an intensity plot of images of beads suspended in a capillary tube. The top image shows the uncorrected bead image, and the line profile in the right image corresponds to the line shown in the left image. The bottom image shows the corrected bead image, and the line profile in the right image corresponds to the line shown in the left image. As you can see, the peaks are more clearly shown in the corrected image, and the line profile does not contain false peaks.

[0075] The effectiveness of the embodiment (measured, for example, by improvement in signal strength) may correlate with the number of segments. Up to a certain threshold, a larger number of segments leads to greater improvement in signal strength; beyond that threshold, it becomes difficult to quantify the improvement in signal strength with increasing the number of segments. However, increasing the number of segments also increases the processing resources required, and if there is a delay between wavefront mask generation and retrieval, the usefulness of the embodiment may decrease, which is particularly problematic when a scanning objective lens is used. Therefore, there may be a trade-off between the number of segments processed and a useful frame rate.

[0076] While embodiments related to laser scanning microscopes have been illustrated and discussed, it should be understood that further embodiments may find applications outside the field of microscopy research. For example, in the field of photolithography, laser scanning is used, and it may be important to maximize the laser power across the objective lens's field of view during such processes. Using embodiments for such applications, the effective field of view of the objective lens can be expanded and / or the laser intensity increased by applying different wavefront masks to different sub-areas or parts of the field of view. Expanding the effective field of view of the objective lens can reduce stage or objective lens movement, potentially improving accuracy. Increasing the laser intensity allows for the effective application of lithography or "laser writing" processes to a wider range of materials and applications.

[0077] Figures 9A and 9B show the results of two-photon laser writing (i.e., photolithography) patterns formed on a fluorescent UV-curable adhesive in a glass capillary tube. These figures show the cured adhesive obtained under fluorescent conditions, and the visible features correspond to the preceding laser writing step. Figure 9A shows an image of the result of laser writing without wavefront correction, while Figure 9B shows the result of writing with wavefront correction. The visible features in Figure 9B demonstrate that the embodiment described herein, which applies a wavefront mask 102 to correct a segment 52 of the field of view of the laser writing process, corrects aberrations caused by the curved glass capillary tube (compared to Figure 9A). As indicated by the residual fluorescence intensity across each spot, the elongation of the lithography pattern is reduced and the laser power is more evenly distributed. Figure 9C shows plots of fluorescence intensity for the enlarged uncorrected laser-written features (Figure 9A) and the enlarged corrected laser-written features (Figure 9B). As can be seen, the corrected image shows improvement in excessive intensity and finer features. It should be noted that wavefront correction was performed using a low-power laser to determine the wavefront mask 102 for each segment 52. Laser writing was then performed using a laser with sufficient power and the determined wavefront mask 102.

[0078] It should be understood that further embodiments can find applications in any system using a scanning laser, for example, in the fields of laser cutting and distance measurement.

[0079] Where prior art publications are referenced herein, it should be understood that such references do not constitute an endorsement that such publications form part of the general knowledge in the art in Australia or any other country.

[0080] In the following claims and the preceding description, unless the context otherwise requires explicit wording or necessary implications, the word “comprise,” or variations such as “comprises” or “comprising,” is used in a comprehensive sense; that is, it identifies the presence of the described features but does not preclude the presence or addition of further features in various embodiments. Similarly, the term “device” is used in a broad sense and is intended to cover components provided as a whole, and examples of one or more components provided separately from one another.

Claims

1. A method of scanning a laser in the field of view, We provide a laser for generating a laser beam. The laser beam is raster-scanned over a first sub-area of ​​the field of view. The laser beam is deflected to a second sub-area of ​​the field of view. The laser beam is raster-scanned in the second sub-area of ​​the field of view. For each sub-area of ​​the field of view, image information generated by the laser beam is captured such that the raster-scanned laser beam defines multiple image segments. For each of the plurality of image segments (let's call it image segment A), an image correction is calculated using the scanned image information of image segment A, and when image segment A is next raster-scanned by the laser, optical aberration correction is applied to the laser according to the calculated image correction for image segment A. This includes assigning a timestamp to each optical aberration correction and each of the multiple image segments, and using the timestamp to establish a time correlation between the image segments and the optical aberration correction, thereby employing a time-division multiplex approach for the optical aberration correction, The scanned image information of the first sub-area and the second sub-area each consists of a number of rows of scanned image information, and the scanned image information of the image segment each consists of a number of rows of scanned image information. method.

2. The method according to claim 1, wherein the field of view is related to a target, Using an objective lens, the laser beam is focused onto the target. A method that further includes this.

3. The method according to any one of claims 1 to 2, wherein calculating the image correction includes deriving a wavefront mask that compensates for the wavefront of the laser beam and corrects optical aberrations.

4. The method according to claim 3, wherein each of the optical aberration corrections includes a corresponding wavefront mask.

5. The image correction calculation involves repeatedly applying a loop consisting of wavefront detection, wavefront mask generation, and application of the wavefront mask to the laser for each image segment. The method according to any one of claims 1 to 4.

6. The method according to any one of claims 1 to 5, wherein the application of the optical aberration correction includes adjusting a deformable mirror.

7. The method according to any one of claims 1 to 6, wherein the raster scan of the laser beam includes moving the laser beam in a first direction corresponding to the x-axis and a second direction corresponding to the y-axis.

8. The method according to claim 7, wherein the movement of the laser beam in the x-axis direction is faster than the movement of the laser beam in the y-axis direction.

9. The method according to claim 7 or claim 8, wherein deflecting the laser beam to the second sub-area of ​​the field of view includes deflecting the laser beam in the direction of the x-axis.

10. The method according to any one of claims 7 to 9, wherein the deformable mirror is synchronized with the movement of the laser beam in the y-axis.

11. The image segment covers the field of view completely and without overlap in the x-axis and y-axis directions. The method according to any one of claims 7 to 10.

12. The method according to any one of claims 1 to 11, wherein each of the sub-areas covers the same area of ​​the field of view.

13. The method according to any one of claims 1 to 11, wherein the first sub-area covers a different region of the field of view from the second sub-area.

14. A system for scanning a laser within a field of view, A laser for generating a laser beam, A first movable deflector for raster scanning the laser beam across a first sub-area of ​​the field of view, A second movable deflector for deflecting the laser beam such that the first movable deflector raster scans a second sub-area of ​​the field of view, An image digitizer for digitizing image information generated by the laser beam interacting with a target, A computer processor for capturing image information generated by the image digitizer so that the raster-scanned laser beam defines a plurality of image segments for each sub-area of ​​the field of view, comprising: a computer processor for calculating image correction for each image segment (let's call it image segment A) using the scanned image information of image segment A; Furthermore, when the image segment A is next raster-scanned by the laser, the optical correction element is used to apply optical aberration correction to the laser beam according to the image correction calculated for the image segment A, The scanned image information of the first sub-area and the second sub-area each consists of a number of rows of scanned image information, and the scanned image information of the image segment each consists of a number of rows of scanned image information. A time-division multiplexing approach is used for optical aberration correction by assigning a timestamp to each optical aberration correction and each of the multiple image segments, and by providing a time correlation between the image segments and the optical aberration correction using the timestamp. system.

15. The system according to claim 14, comprising three movable mirrors.

16. The system according to claim 15, The first movable deflector for raster scanning the laser beam across the sub-area of ​​the field of view includes a rotating polygonal mirror and a first galvanic mirror, The second movable deflector for deflecting the laser beam to raster scan the second sub-area of ​​the field of view includes a second galvanic mirror. system.

17. The system according to claim 16, wherein the rotating polygonal mirror moves the laser beam along the x-axis, and the first galvanic mirror moves the laser beam along the y-axis.

18. The system according to claim 17, wherein the movement of the second galvanic mirror deflects the laser beam in the x-axis direction, thereby deflecting the laser beam to a second sub-area of ​​the field of view.

19. The system according to any one of claims 14 to 18, wherein the computer processor calculates the image correction for each of the image segments.

20. The system according to any one of claims 14 to 19, wherein the computer processor assigns a timestamp to each image segment and each optical aberration correction.

21. The system according to any one of claims 14 to 20, further comprising an objective lens for focusing the laser beam onto the target.

22. The system according to any one of claims 14 to 21, wherein the optical correction element is a deformable mirror.

23. The system according to claim 22, wherein the deformable mirror is synchronized with the movement of the laser beam in one of the x-axis or the y-axis.

24. The system according to any one of claims 14 to 23, wherein each of the sub-areas covers the same area of ​​the field of view.

25. The system according to any one of claims 14 to 23, wherein the first sub-area covers a different region of the field of view from the second sub-area.

26. A method of scanning a laser beam in the field of view, The steps include sequentially raster scanning the laser beam within a plurality of sub-areas arranged in a line within the field of view, A step of defining a plurality of image segments for each sub-area, wherein the direction of the single-row arrangement is a first direction, and the image segments of a particular sub-area are arranged in a second direction perpendicular to the first direction, A step of capturing image information for each of the image segments, wherein the image information is associated with the illumination of the field of view by the laser beam, For each image segment (referred to as image segment A), the step of calculating image correction using the scanned image information of the image segment A, wherein the image correction is configured so that the laser beam can be optically aberrated when the laser beam is next raster-scanned on the image segment A; The steps include: assigning a timestamp to each of the optical aberration corrections and each of the plurality of image segments, and using the timestamp to provide a time correlation between the image segment and the optical aberration correction when the image segment is next raster scanned, thereby employing a time-division multiplex approach for the optical aberration correction; The scanned image information of the aforementioned sub-area consists of numerous rows of scanned image information, and the scanned image information of the aforementioned image segment consists of multiple rows of scanned image information. method.

27. The method according to claim 26, Later, when raster scanning the laser beam, the optical aberration correction calculated using an optical correction element is applied to the laser beam for each image segment. A method that further includes this.

28. A system for scanning a laser within a field of view, A laser for generating a laser beam, A first movable deflector for raster scanning the laser beam, A second movable deflector for deflecting the laser beam and sequentially raster scanning multiple sub-areas arranged in a line within the field of view, Image capture means configured to capture image information of each image segment, which is associated with the illumination of the field of view by the laser beam, Includes a processor, The aforementioned processor, With the aforementioned single-row arrangement direction as the first direction, a plurality of image segments are defined for each sub-area where the image segments of a particular sub-area are arranged in a second direction perpendicular to the first direction. Capture the image information of each image segment, which is associated with the illumination of the field of view by the laser beam. For each image segment (let's call it image segment A), an image correction is calculated using the scanned image information of image segment A, which is configured to enable optical aberration correction of the laser beam when the laser beam is next raster-scanned on image segment A. Each of the optical aberration corrections and / or each of the plurality of image segments is given a timestamp, and when the image segment is next raster scanned, a time-division multiplex approach is applied to the optical aberration correction by providing a time correlation between the image segment and the optical aberration correction using the timestamp. The scanned image information of the aforementioned sub-area consists of numerous rows of scanned image information, and the scanned image information of the aforementioned image segment consists of multiple rows of scanned image information. system.

29. The system according to claim 28, The laser beam is further provided with an optical correction element for correcting the laser beam. The processor is configured to control the optical correction element so that when the laser beam is later raster-scanned, the optical aberration correction calculated for each image segment is applied to the laser beam. system.

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