Autofocus system

Abstract

An autofocus system includes (i) an illumination path configured to illuminate a sample with illumination beams forming a plurality of spot arrays on the sample, the spot arrays including an upstream set of spot arrays formed on a first side of an imaging region and a downstream set of spot arrays formed on another side of the imaging region; (ii) a collection path including an entrance pupil and configured to collect a collected beam emitted from the sample and focus the collected beam along a first axis while imaging the entrance pupil along a second axis to provide an optically processed beam. A sensor is configured to generate a detection signal representative of the optically processed beam. A controller is configured to determine a focus state of an evaluation beam incident on the imaging region.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit and priority of U.S. Patent Application No. 18 / 762,546, filed July 2, 2024, entitled “Autofocus using multi-position illumination,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The embodiments disclosed herein generally relate to autofocus systems. Background Technology

[0004] In high-volume optical inspection systems, autofocus plays a crucial role in ensuring an accurate and efficient inspection process. These systems are designed to inspect samples, such as wafers or lithographic masks, to quickly identify defects or anomalies.

[0005] One of the key challenges of these systems is maintaining consistent focus over large areas of the sample surface. Variations in sample thickness, curvature, or surface topography can affect the focal plane. Without autofocus capabilities, inspection systems may struggle to maintain optimal focus, leading to inaccurate or incomplete inspection results.

[0006] There is an increasing need for efficient and accurate autofocus systems and methods. Utility Model Content

[0007] An autofocusing system and method are provided, as illustrated in this application.

[0008] An autofocusing system is provided, comprising (i) an illumination path configured to illuminate a sample using illumination beams forming a plurality of spot arrays on the sample, the spot arrays including an upstream group of spot arrays formed on a first side of an imaging region and a downstream group of spot arrays formed on the other side of the imaging region; and (ii) a collection path including an entrance pupil and configured to collect a collected beam emitted from the sample and focus the collected beam along a first axis while imaging the entrance pupil along a second axis to provide an optically processed beam. A sensor is configured to generate a detection signal representing the optically processed beam. A controller is configured to determine the focusing state of an evaluation beam incident on the imaging region.

[0009] A method for autofocusing by an autofocusing system is provided, the method comprising (a) illuminating a sample with illumination beams forming a plurality of spot arrays on the sample, wherein the spot arrays include an upstream group of spot arrays formed on a first side of an imaging region and a downstream group of spot arrays formed on the other side of the imaging region; (b) collecting the collected beams emitted from the sample along a collection path including an entrance pupil; (c) focusing the collected beams along a first axis while imaging the entrance pupil along a second axis to provide an optically processed beam; (d) generating a detection signal representing the optically processed beam; and (e) determining the focus state of an evaluation beam incident on the imaging region. Attached Figure Description

[0010] The subject matter considered as an embodiment is specifically pointed out and explicitly claimed at the end of the specification. However, the embodiments, features, and advantages of both the organization and the method of operation can be best understood by referring to the following detailed description in conjunction with the accompanying drawings.

[0011] Figure 1 Examples of autofocus systems and associated evaluation systems are shown;

[0012] Figure 2 An example of a sample and the spots formed on that sample is shown;

[0013] Figure 3 An example is given of the effect of a mask with an off-axis slit and the wavefront on light rays leaving the mask;

[0014] Figure 4 An example of an optical process applied through a slit in a mask is shown;

[0015] Figure 5 An example of distance-based focus sensing is shown;

[0016] Figure 6 Examples of at least some components of an autofocus system are shown;

[0017] Figure 7 Examples of at least some components of an autofocus system are shown;

[0018] Figure 8 Examples of at least some components of an autofocus system are shown;

[0019] Figure 9 Examples of at least some components of an autofocus system are shown;

[0020] Figure 10 Examples of at least some components of an autofocus system are shown;

[0021] Figure 11Examples of at least some components of an autofocus system are shown;

[0022] Figure 12 Examples of at least some components of an autofocus system are shown;

[0023] Figure 13 An example of a splitter is shown;

[0024] Figure 14 Examples of at least some components of an autofocus system are shown;

[0025] Figure 15 Examples of at least some components of an autofocus system are shown;

[0026] Figure 16 Examples of at least some components of an autofocus system are shown;

[0027] Figure 17 Examples of at least some components of an autofocus system are shown;

[0028] Figure 18 An example of a spot formed on a sensor is shown;

[0029] Figure 19 Examples of at least some components of an autofocus system are shown;

[0030] Figure 20 An example of the method is shown;

[0031] Figure 21 An example of the method is shown; and

[0032] Figure 22 An example of the method is shown.

[0033] It should be understood that, for the sake of simplicity and clarity, the elements shown in the accompanying drawings are not necessarily drawn to scale. For example, for clarity, the dimensions of some elements may be exaggerated relative to others. Additionally, element symbols may be repeated between drawings where deemed appropriate to indicate corresponding or similar elements. Detailed Implementation

[0034] Optical systems, particularly those used in large field-of-view and high numerical aperture (NA) imaging applications such as inspection tools, face significant challenges in managing complexity while maintaining performance. These systems typically require complex optics to achieve the desired magnification and resolution over a wide field of view. However, the high NA required for such performance typically necessitates complex optical arrangements, which introduce distortion and reduce transmitted intensity. This is particularly problematic when the specimen or the sample being inspected is sensitive to the intensity and quality of illumination.

[0035] Existing solutions to these challenges typically involve using multiple lenses and compensating optics to correct field curvature and other aberrations. While feasible, these approaches tend to increase complexity and sensitivity to alignment and manufacturing tolerances. Furthermore, the combination of numerous optical components can lead to reduced transmitted intensity due to light loss at each interface, which is particularly detrimental in applications where the sample cannot tolerate high-intensity illumination, as the intensity of the illumination must be increased to compensate for the significant loss. Additionally, the complexity of these systems often results in increased susceptibility to misalignment and manufacturing deviations, which can impair optical performance and necessitate more stringent and costly production controls.

[0036] This system addresses these and other problems by providing a simplified optical solution that separates the field and utilizes field splitting to achieve near-diffraction-limited spot arrays. The system includes a double-slit array (in...) Figure 1 The mask marked as 112 (in) Figure 1 (Illustrated as 110), this mask maintains the original optical axis and uses only an off-center slit to preserve optical performance. In doing so, the system introduces only field curvature, which is efficiently managed using simple window-based optical path compensation techniques, such as the first field curvature compensator 144 and the second field curvature compensator 174, which are segmented optical elements (see...). Figure 14 The advantage of this solution lies in the reduced system complexity, which allows for a high level of performance with minimal sensitivity to tolerances. The system's design, incorporating a smaller number of lenses, not only enhances transmission intensity but also improves sensitivity without the risk of damaging the sample.

[0037] Additionally, the system's splitter (in) Figure 1 The method (indicated by 130) operates along a common optical axis, thereby minimizing overlap between adjacent fields and enabling the sample to be illuminated using a staggered speckle array. This innovative approach for autofocusing and field splitting represents a significant advancement, providing a less complex, more robust, and highly efficient solution for high-NA and large-field imaging systems.

[0038] In aerial imaging, practitioners frequently face challenges related to the limited field of view (FOV) captured by camera systems. Traditional methods for extending the FOV typically involve using multiple cameras placed adjacent to each other. The goal of this configuration is to extract the maximum FOV from the scene while minimizing the number of optical repeaters required. However, such an arrangement can lead to increased complexity, cost, and size of the imaging apparatus, as well as potential alignment problems between individual camera units.

[0039] Existing solutions for FOVs used to enhance aerial imaging tools typically require a large number of repetitive optical components, which can be cumbersome and cost-inefficient. Furthermore, using multiple cameras to cover a large area can introduce complexity in image processing and stitching, potentially impacting overall image quality. Additionally, each camera requires multiple optical repeaters to focus the image, which can further complicate system design and reduce imaging efficiency.

[0040] This system addresses these challenges by introducing splitters strategically positioned near the image plane downstream of the mask. FLS effectively separates the field of view onto the wafer or mask without requiring additional optical repeaters to bring the image to the camera. By utilizing the relatively small area of ​​view (NA) in the image space, the system minimizes the field of view separation on the wafer or lithographic mask. The system also identifies the optimal location for splitting the field from a temporary image, ensuring that light is not cut off, which typically requires the use of a knife mirror. This innovative approach allows for extended FOV with minimal repetitive capture of optical components, simplifying the design of the imaging system and reducing associated costs.

[0041] According to one embodiment, an autofocusing system is provided, comprising: an illumination path configured to illuminate a sample using illumination beams forming a plurality of spot arrays on the sample, the spot arrays including a first set of spot arrays formed on a first side of an imaging region and a second set of spot arrays formed on the other side of the imaging region; a sensor; a controller; a collection path including an entrance pupil and configured to collect a collection beam emitted from the sample and focus the collection beam along a first axis while imaging the entrance pupil along a second axis to provide an optically processed beam; wherein the sensor is configured to generate a detection signal representing the optically processed beam; and wherein the controller is configured to determine the focusing state of an evaluation beam incident on the imaging region.

[0042] The imaging area is provided using aerial illumination.

[0043] According to one embodiment, the controller is configured to generate an initial autofocus estimate of the future focus state obtained when the evaluation beam reaches the defined position of the first set of spot arrays.

[0044] According to one embodiment, the controller is configured to update the initial autofocus estimate when the imaging region approaches a defined position.

[0045] According to one embodiment, the first set of spot arrays includes a first spot array, a second spot array, and a third spot array.

[0046] According to one embodiment, the second set of spot arrays includes a fourth spot array, a fifth spot array, and a sixth spot array.

[0047] According to one embodiment, each of the plurality of spot arrays and the first group of spot arrays are interleaved along a first axis and a second axis.

[0048] According to one embodiment, each of the speckle arrays is a linear speckle array.

[0049] According to one embodiment, the optically processed beam forms a pair of spots for each of a plurality of spot arrays, wherein the distance between each pair of spots indicates the focus state associated with the corresponding spot array.

[0050] According to one embodiment, the controller is configured to ignore detection signals based on sample elements irradiated by at least a portion of the illumination beam.

[0051] According to one embodiment, the controller is configured to determine at least one of the pitch angle and roll angle of the irradiation beam.

[0052] Figure 20 An example of an autofocus method 500 for an autofocus system (10) is illustrated, the method comprising:

[0053] a. Irradiating 510 samples using irradiation beams, which form multiple speckle arrays on the samples, including a first set of speckle arrays formed on a first side of the imaging region and a second set of speckle arrays formed on the other side of the imaging region.

[0054] b. Collect the 520 beams emitted from the sample along the collection path, including the entrance pupil.

[0055] c. Focus the beam along the first axis 530 through the collecting beam, while simultaneously imaging the entrance pupil along the second axis to provide the optically processed beam.

[0056] d. Generate a detection signal of 540 representing the optically processed beam.

[0057] e. Determine the focus state of the evaluation beam incident on the imaging region at 550°. The detection signal indicates the focus at multiple locations on the sample (forming a multidimensional array of two or more locations per axis) and from different sides of the imaging region (thus inferring that the focus state of the evaluation beam is direct).

[0058] f. Respond to the focus state 590. The response may include changing the focus state of the evaluation system.

[0059] According to one embodiment, the method includes generating an initial autofocus estimate of the future focus state obtained when the evaluation beam reaches a defined position of a first set of spot arrays.

[0060] According to one embodiment, the method includes updating the initial autofocus estimate when the imaging region approaches a defined position.

[0061] According to one embodiment, the first set of spot arrays includes a first spot array, a second spot array, and a third spot array.

[0062] According to one embodiment, the second set of spot arrays includes a fourth spot array, a fifth spot array, and a sixth spot array.

[0063] According to one embodiment, each of the plurality of spot arrays and the first group of spot arrays are staggered along a first axis and a second axis. This staggering along the two axes reduces the number of sharding elements required to separate the plurality of spot arrays.

[0064] According to one embodiment, each of the speckle arrays is a linear speckle array.

[0065] According to one embodiment, the optically processed beam forms a pair of spots for each of a plurality of spot arrays, wherein the distance between each pair of spots indicates the focus state associated with the corresponding spot array.

[0066] According to one embodiment, method 500 includes ignoring detection signals based on sample elements irradiated by at least a portion of the illumination beam.

[0067] According to one embodiment, step 540 includes determining at least one of the pitch angle and roll angle of the irradiation beam.

[0068] According to one embodiment, an autofocusing system is provided, the autofocusing system comprising:

[0069] a. An illumination path configured to illuminate a sample using illumination beams that form multiple speckle arrays on the sample, the speckle arrays comprising a first set of speckle arrays formed on one side of the imaging region and a second set of speckle arrays formed on the other side of the imaging region.

[0070] b. Controller.

[0071] c. A collection path configured to receive a first and a second collection bundle from the sample. The collection path includes:

[0072] i. A mask located at the entrance pupil, the mask comprising a pair of off-axis slits for truncating each collected beam to provide a pair of rays for each collected beam.

[0073] ii. A splitter configured to (i) direct a first ray associated with a first collected beam to a first branch, and (ii) direct a ray associated with a second collected beam to a second branch.

[0074] iii. A sensor, connected after the first and second branches, and configured to receive a pair of spots for each of a plurality of spot arrays, wherein the distance between each pair of spots indicates the focusing state associated with the corresponding spot array. The optical axis of the first branch is oriented relative to the optical axis of the second branch.

[0075] According to one embodiment, the controller is configured to receive detection signals from at least one of a first sensor and a second sensor, and to determine the focus state of the evaluation beam. According to another embodiment, the controller is configured to change the focus of the evaluation system by controlling one or more engines, such as by moving a lens or other optical component of the evaluation system, by changing the position of the evaluation system, by changing the position of a sample, etc., to set the focus of the evaluation system.

[0076] According to one embodiment, the first branch includes a first spherical telescope, a first field curvature compensator, and a first longitudinal collimation repeater.

[0077] According to one embodiment, the second branch includes a second spherical telescope, a second field curvature compensator, and a second laminar collimation repeater.

[0078] According to one embodiment, the first field curvature compensator differs from a lens and is essentially composed of a first segment of optical elements, which includes segments with different refractive indices. The first segment of optical elements is located at positions where the field associated with the light rays is very small (discrete).

[0079] According to one embodiment, the second field curvature compensator differs from the lens and is essentially composed of a second segment of optical elements, which includes segments with different refractive indices.

[0080] According to one embodiment, each of the optical elements in the first segment and the optical elements in the second segment is located at a position where the field associated with the light is very small.

[0081] According to one embodiment, the first ray includes a pair of first central rays (in) Figure 12 The middle label is 66-2, 67-2) and two pairs of first marginal rays (the first pair of marginal rays (in Figure 12 The middle markings are 66-1 and 67-1) and the second pair of edge rays (in Figure 12 The first field curvature compensator is the first segment of the optical element, which is basically composed of the following: (i) the first segment of the first refractive index (in Figure 14 (i) marked as 144-1), a pair of first central rays propagate through this segment, and (ii) the second segment of the second refractive index (in Figure 14(Illustrated as 144-2), the two first pair of edge rays propagate through this segment, where the first refractive index is different from the second refractive index.

[0082] According to one embodiment, the second ray includes a pair of second central rays (in...) Figure 12 The markings are 68-2 and 69-2) and two pairs of marginal rays (including a pair of first marginal rays (in Figure 12 The middle markings are 68-1 and 69-1) and a pair of second edge rays (in Figure 12 The winning designation is indicated as 68-3 or 69-3).

[0083] According to one embodiment, the second curvature compensator (in...) Figure 14 The optical element marked 174 is the second segment, which is basically composed of the following: a first segment (174-1) with a first refractive index, through which a set of second central rays (including the third pair of marginal rays 68-2 and the fourth pair of marginal rays 69-2) propagate, and a second segment with a second refractive index (in... Figure 14 (Illustrated as 174-2), two pairs of edge rays propagate through this segment, where the first refractive index is different from the second refractive index.

[0084] According to one embodiment, the first spherical telescope is configured to provide a reduced image of the entrance pupil (the reduction factor may be in the range of six to twelve, or equal to ten, or any other value) on the focal plane of the output lens of the first spherical telescope.

[0085] According to one embodiment, the second spherical telescope is configured to provide a reduced image of the incident pupil on the focal plane of the output lens of the second spherical telescope.

[0086] According to one embodiment, the first collimated repeater includes a first repeater input spherical lens and a first repeater output spherical lens.

[0087] According to one embodiment, the second collimated repeater includes a second repeater input spherical lens and a second repeater output spherical lens.

[0088] According to one embodiment, the autofocus system includes a pair of first prisms located at the focal plane of the output lens of a first spherical telescope.

[0089] According to one embodiment, the autofocus system includes a pair of second prisms located at the focal plane of the output lens of the second spherical telescope. These second prisms deflect the rays of the first pair of light rays away from each other.

[0090] According to one embodiment, the autofocus system includes a first collimator repeater moving mechanism configured to change the distance between a first repeater input spherical lens and a first repeater output spherical lens.

[0091] According to one embodiment, a first collimator repeater moving mechanism moves a first repeater output spherical lens and also moves a first sensor to maintain the distance between the first repeater output spherical lens and the first sensor. According to one embodiment, the first collimator repeater moving mechanism includes a first motor.

[0092] According to one embodiment, the autofocus system includes a second collimator repeater moving mechanism configured to change the distance between a second repeater input spherical lens and a second repeater output spherical lens.

[0093] According to one embodiment, the second collimator repeater moving mechanism moves the second repeater output spherical lens and the second sensor to maintain the distance between the second repeater output spherical lens and the second sensor. According to one embodiment, the second collimator repeater moving mechanism includes a second motor.

[0094] According to one embodiment, different distances between the relay input spherical lens and the relay output spherical lens are associated with different trade-offs between the dynamic range and sensitivity of the autofocus system. A larger dynamic range is associated with lower sensitivity. Different distances are associated with different effective focal lengths via the collimating repeater.

[0095] According to one embodiment, the different distances between the first relay input spherical lens and the first relay output spherical lens are associated with different effective focal lengths of the first collimated repeater.

[0096] According to one embodiment, the first collimating repeater is essentially composed of a first repeater input spherical lens and a first repeater output spherical lens.

[0097] The repeater includes a repeater input spherical lens and a repeater output spherical lens with defects or aberrations, such that the optical power at different points in either of the repeater spherical lenses differs from each other. The different optical powers even introduce residual optical power along a second axis of either of the repeater spherical lenses. According to one embodiment, the value of the optical power at a point in the repeater spherical lens is related to the spatial relationship between the center of the repeater spherical lens and that point. The optical power is associated with magnification.

[0098] According to one embodiment, the first collimating repeater exhibits primary optical power along the main axis, and when receiving deflected rays (off-axis rays) oriented relative to the main axis of the collimating repeater and the collimating axis of the collimating repeater, the deflected rays are incident on a point (off-center point) located outside the center of the repeater spherical lens and exhibit optical power along both axes.

[0099] The deflected light rays are deflected in part due to the non-zero angle between the optical axis formed between the mask and the splitter and the optical axis of each of the first and second branches.

[0100] According to one embodiment, the autofocus system includes a selectable depth-of-field unit configured to select a reference focal plane for the autofocus system.

[0101] According to one embodiment, the selectable depth-of-field unit includes a first selectable depth-of-field unit that is selectively positioned within or outside the first branch. According to another embodiment, the first selectable depth-of-field unit is a first window selectively positioned within the first spherical telescope. When positioned within the first spherical telescope, the depth of field of the first branch is at a first position; when positioned outside the first spherical telescope, the depth of field of the first branch is at a second position different from the first position.

[0102] According to one embodiment, the selectable depth-of-field unit includes a second selectable depth-of-field unit that is selectively positioned within or outside the second branch. According to another embodiment, the second selectable depth-of-field unit is a second window selectively positioned within the second spherical telescope. When positioned within the second spherical telescope, the depth of field of the second branch is located at a third position; when positioned outside the second spherical telescope, the depth of field of the second branch is located at a fourth position different from the first position.

[0103] Figure 21 An example of an autofocus method 501 for an autofocus system (10) is illustrated, the method comprising:

[0104] a. The sample is irradiated (510) using irradiation beams (30), which form multiple speckle arrays (40) on the sample, wherein the speckle arrays include a first set of speckle arrays (42) formed on a first side of the imaging region (39) and a second set of speckle arrays (44) formed on the other side of the imaging region (39).

[0105] b. Collect (520) the collected beam emitted from the sample along the collection path including the entrance pupil.

[0106] c. Focus (530) the collecting beam along the first axis (91) while imaging the entrance pupil along the second axis (92) to provide the optically processed beam.

[0107] d. Generate (540) to represent the detection signal (100) of the optically processed beam.

[0108] e. Determine (550) the focusing state of the evaluation beam (38) incident on the imaging region (39).

[0109] f. Respond to the focus state (590). The response may include changing the focus state of the evaluation system.

[0110] According to one embodiment, steps 510-550 are repeated multiple times at different time points.

[0111] According to one embodiment, step 540 is followed by step 560, which generates an initial autofocus estimate of the future focus state obtained when the evaluation beam reaches the defined position of the first set of spot arrays. Step 560 may be included in step 590.

[0112] For example—assuming the sample is scanned such that the first set of speckle arrays precedes the evaluation beam—then the initial autofocus estimate can be based on the focus information embedded in the first set of speckle arrays. The initial autofocus estimate can be equal to, or different from, the focus state reflected by the first set of speckle arrays.

[0113] For example—assuming the sample is scanned such that the second set of speckle arrays precedes the evaluation beam—then the initial autofocus estimate can be based on the focus information embedded in the second set of speckle arrays. The initial autofocus estimate may be equal to the focus state reflected by the second set of speckle arrays, or it may be different from the focus state reflected by the second set of speckle arrays.

[0114] According to one embodiment, method 501 includes step 570, namely, updating the initial autofocus estimate when the imaging region (39) approaches a defined position. Step 570 may be included in step 590.

[0115] The update may be based on the focus state of the imaging region obtained during one or more iterations of steps 510-550 after the iteration that provides the initial autofocus estimate (or based on the focus of any set of speckle arrays).

[0116] For example, see Figure 2 . Figure 2 The right-hand portion illustrates sample 99 and a first set of speckle arrays and a second set of speckle arrays at a first time point, during which an initial autofocus estimate of the focus state of imaging region 39 is made based on the focus information embedded in the first set of speckle arrays. Step 570 may update the initial autofocus estimate before imaging region 39 reaches the position of the first set of speckle arrays (at the first time point). Figure 2 The left portion illustrates the imaging region 39 at the location of the first set of speckle arrays (at the first time point).

[0117] According to one embodiment, each of the plurality of spot arrays (40) and the first set of spot arrays (42) are interleaved along the first axis (91) and the second axis (92).

[0118] According to one embodiment, one, some, or all of the spot arrays are linear spot arrays.

[0119] According to one embodiment, one, some, or all of the spot arrays are nonlinear spot arrays.

[0120] According to one embodiment, an optically processed beam forms a pair of spots for each of a plurality of spot arrays, wherein the distance between each pair of spots (at the sensor plane) indicates the focus state associated with the corresponding spot array.

[0121] According to one embodiment, step 550 includes ignoring detection signals (100) based on at least a portion of the irradiation beam (30) irradiating the sample element. Ignoring other types of information may be based on design information or indications of regions of the sample (e.g., high-density logic element regions) that would provide low signal-to-noise ratio signals and / or diffraction signals once irradiated.

[0122] According to one embodiment, step 550 includes determining at least one of the pitch angle and roll angle of the illumination beam. Any of these angles can be detected by comparing focusing information from different spot arrays.

[0123] According to one embodiment, at least one of method 500 and method 501 includes adjusting the distance between optical elements in the collection path of the evaluation system to optimize the focusing state of the evaluation beam.

[0124] According to one embodiment, adjusting the distance between optical elements includes moving a lens or mirror in the collection path of the evaluation system.

[0125] According to one embodiment, the method includes adjusting the intensity of the irradiation beam used by the evaluation system to optimize the focusing state of the evaluation beam.

[0126] According to one embodiment, adjusting the intensity of the irradiation beam of the evaluation system includes controlling the power of the light source or adjusting the aperture of the irradiation path of the evaluation system.

[0127] According to one embodiment, at least one of method 500 and method 501 includes determining the depth of field of the autofocus system based on the focus state of the evaluation beam.

[0128] According to one embodiment, at least one of method 500 and method 501 includes adjusting the position of the imaging region based on a determined depth of field.

[0129] According to one embodiment, at least one of method 500 and method 501 includes compensating for aberrations in the collection path to improve the focus state of the evaluation bundle 38.

[0130] According to one embodiment, aberration compensation includes adjusting the position or shape of one or more optical elements in the collection path of the evaluation system.

[0131] According to one embodiment, at least one of methods 500 and 501 includes determining a focus metric based on a detection signal to quantify the focus state of the evaluated bundle. The focus metric may indicate focus along any axis, relative focus error between bundles, etc.

[0132] According to one embodiment, step 590 includes adjusting the focus state of the evaluation beam based on a determined focus metric.

[0133] According to one embodiment, step 590 includes capturing an image of the sample by an evaluation system associated with the autofocus system based on the focus state of the evaluation beam.

[0134] According to one embodiment, step 590 includes analyzing the captured image to extract information about the sample.

[0135] According to one embodiment, step 590 includes adjusting the position or orientation of the sample based on the focusing state of the evaluation beam.

[0136] According to one embodiment, step 590 includes determining a focus error signal based on the detection signal (100) to provide feedback for adjusting the focus state of the evaluation beam.

[0137] According to one embodiment, step 590 includes using a focus error signal to control the position or movement of one or more optical elements of the evaluation system.

[0138] According to one embodiment, an autofocus system (10) is provided, the autofocus system comprising:

[0139] a. An illumination path configured to illuminate a sample using illumination beams that form multiple speckle arrays on the sample, the speckle arrays including a first set of speckle arrays formed on a first side of the imaging region and a second set of speckle arrays formed on the other side of the imaging region.

[0140] b. Controller.

[0141] c. Collection path, which includes:

[0142] i. A first branch comprising a first spherical telescope, a first field curvature compensator, a pair of first prisms, and a first collimating repeater consisting essentially of a first relay input spherical lens and a first relay output spherical lens.

[0143] ii. A second branch comprising a second spherical telescope, a second field curvature compensator, a pair of second prisms, and a second collimating repeater consisting essentially of a second relay input spherical lens and a second relay output spherical lens;

[0144] iii. A sharing module configured to (i) receive a first and a second collection beam, (ii) optically process the first collection beam to provide a pair of first rays to a first segment for each first collection beam, and (iii) optically process the second collection beam to provide a pair of second rays to a second segment for each second collection beam;

[0145] d. A sensor, which is connected after the first branch and the second branch, and is configured to generate a detection signal indicating the light output from the first branch and the light output from the second branch.

[0146] According to one embodiment, the shared module includes a mask located at the entrance pupil, the mask including a pair of off-axis slits for truncating each collection beam to provide a pair of light rays per collection beam.

[0147] According to one embodiment, the sharing module further includes a splitter configured to (i) direct a first ray associated with a first collected beam to a first branch, and (ii) direct a ray associated with a second collected beam to a second branch.

[0148] According to one embodiment, the first collimated repeater exhibits primary optical power along the main axis and residual optical power along the second axis.

[0149] According to one embodiment, the autofocus system includes a selectable depth-of-field unit configured to select a reference focal plane for the autofocus system.

[0150] According to one embodiment, the selectable depth-of-field unit includes a first window selectively positioned within a first spherical telescope and a second window selectively positioned within a second spherical telescope.

[0151] According to one embodiment, a system is provided, the system comprising:

[0152] a. An illumination path configured to illuminate a sample using illumination beams that form multiple speckle arrays on the sample, the speckle arrays including a first set of speckle arrays formed on a first side of the imaging region and a second set of speckle arrays formed on the other side of the imaging region.

[0153] b. Sensors.

[0154] c. Controller.

[0155] d. A collection path configured to receive a first and a second collection bundle from the sample. The collection path includes:

[0156] i. A mask located at the entrance pupil, the mask comprising a pair of off-axis slits for truncating each of the collected beams to provide a pair of light rays per collected beam;

[0157] ii. A splitter comprising an optical splitting element including (i) a first reflective surface configured to guide a first ray associated with a first collected beam to a first branch, and (ii) a second reflective surface oriented relative to the first reflective surface and configured to guide a second ray associated with a second collected beam to a second branch. The first and second reflective surfaces are located at reflective surface positions that: (a) are outside the image plane, and (b) are separated from the second ray.

[0158] According to one embodiment, the optical splitter element is a prism.

[0159] According to one embodiment, the prism is a knife-edge right-angle prism.

[0160] According to one embodiment, the shape and position of the optical splitter element are configured to prevent vignetting of either the first ray or the second ray.

[0161] According to one embodiment, the shape and position of the optical splitter element are set at the position furthest from the intermediate image plane, at which neither the first ray nor the second ray will be cut off by the prism.

[0162] According to one embodiment, the splitter includes a housing and a mechanical interface connected to the housing and the optical splitting element.

[0163] According to one embodiment, the housing includes an input opening, a first light output opening, and a second light output opening.

[0164] Figure 22 Here is an example of a method (600) for field manipulation, which includes:

[0165] a. Irradiating (610) the sample with irradiation beams, which form multiple speckle arrays on the sample, including a first set of speckle arrays formed on a first side of the imaging region and a second set of speckle arrays formed on the other side of the imaging region.

[0166] b. Collect (620) the first and second meridian collection bundles from the sample.

[0167] c. Use a mask (110) located at the entrance pupil to truncate (630) each wavelength collection beam, wherein the mask (110) includes a pair of slits (112) that are off-axis slits to provide a pair of rays for each wavelength collection beam.

[0168] d. Using the first reflective surface of the optical splitter element located at a reflective surface position outside the intermediate image plane, the first ray associated with the first collected beam is guided to a first part (640) of the system. This first part may be a first branch or any other part not used for autofocus.

[0169] e. Using a second reflective surface of an optical splitter element to guide a second ray associated with a second collected beam to a second portion (650) of the system, wherein the second reflective surface is oriented relative to the first reflective surface. This second portion may be a second branch or any other portion not used for autofocus.

[0170] According to one embodiment, steps 640 and 650 are based on the separation between the first ray and the second ray at the reflective facet position.

[0171] According to one embodiment, steps 610-650 are used in an automatic focusing measurement system.

[0172] According to one embodiment, steps 610-650 are used for purposes other than autofocus.

[0173] According to one embodiment, the optical splitter element is a prism.

[0174] According to one embodiment, the prism is a knife-edge right-angle prism.

[0175] According to one embodiment, the method includes setting the shape and position of the optical splitter element to prevent vignetting of either the first ray or the second ray.

[0176] According to one embodiment, the method includes setting the shape and position of the optical splitter element at a location furthest from the intermediate image plane, where neither the first ray nor the second ray will be cut off by the prism.

[0177] According to one embodiment, the method includes connecting a mechanical interface to the housing and optical splitting elements of the splitter (130).

[0178] Figure 1An example of an autofocus system 10 and an evaluation system 11 is illustrated, which uses the autofocus system 10 to maintain the evaluation beam at the desired focused position on the sample 99. The evaluation system 11 includes an evaluation illumination device 11, an evaluation system beam splitter 14, and an evaluation sensor 13. The evaluation system outputs an evaluation beam 38, which passes through a first dichroic mirror 24 and is focused by an objective lens 19 to be incident on the sample 99 to form a return beam collected by the objective lens 19. This return beam is guided by the first dichroic mirror 24 to the evaluation system beam splitter 14 and then to the evaluation sensor 13.

[0179] The first dichroic mirror 24 and the objective lens 19 are also used by the autofocus system 10.

[0180] The autofocus system 10 includes an autofocus (AF) illumination unit 19, an initial mirror 21, an illumination / collection beam splitter 22, a third mirror 23, a mask 110 (with a slit 112), a splitter 130, a first mirror 125, a first branch 140, a first sensor 50-1, a second mirror 126, a second branch 170, and a second sensor 50-2.

[0181] The first branch 140 includes a first spherical telescope 142, a first field curvature compensator 144, and a first meridian collimation repeater 146.

[0182] The second branch 170 includes a second spherical telescope 172, a second field curvature compensator 174, and a second meridian collimation repeater 176.

[0183] Figure 1 The first conjugate plane 111 and the first conjugate plane 113 of the mask pupil are illustrated.

[0184] Figure 2 Examples of sample 99 and multiple speckle arrays at two different time points are shown.

[0185] The multiple spot arrays include a first group of spot arrays 42 and a second group of spot arrays 44, which are interleaved along a first axis 91 and a second axis 92.

[0186] The first group of spot arrays 42 includes a first spot array 42-1, a second spot array 42-2, and a third spot array 42-3.

[0187] The second group of spot arrays 44 includes the fourth spot array 44-1, the fifth spot array 44-2, and the sixth spot array 44-3.

[0188] Figure 3The diagram illustrates the relationship between the focused state of a collected beam having a wavefront 31 reaching a mask 110 and the light rays exiting from a slit 112, which is an off-axis slit. When focused, the wavefront 31 is parallel to the mask, and the light rays passing through the slit are parallel to each other and perpendicular to the mask. When unfocused, the wavefront is convex (wavefront 32) or concave (wavefront 33), and the light rays passing through the slit are oriented relative to each other and are not perpendicular to the mask.

[0189] Figure 4 The illustration shows how the slit 112 of mask 110 converts each of the first and second set of spot arrays into a pair of spaced-apart rays. When the value x is between 1 and 3, spot array 42-x is converted into a pair of rays 46-x and 47-x, while spot array 44-x is converted into a pair of rays 48-x and 49-x.

[0190] Following mask 110, the distance between rays in a single ray pair indicates the focus state associated with that ray pair. Figure 4 Examples of distances are given: D1 45-1 between the first ray 46-1 and 47-1, D2 45-2 between the second ray 46-2 and 47-2, D3 45-3 between the third ray 46-3 and 47-3, D4 45-4 between the fourth ray 48-1 and 49-1, D5 45-5 between the fifth ray 48-2 and 49-2, and D6 45-6 between the sixth ray 48-3 and 49-3.

[0191] Figure 4 Also shown is a reduced image 51 of the entrance pupil at the focal plane of the output lens of the first spherical telescope.

[0192] Figure 5 This illustrates the effect of the wavefront of light at the focal plane of the output lens of a spherical telescope on how the light is sensed by the sensor.

[0193] The focusing phase should be determined based on the distance between the light rays incident on the sensor. When the wavefront 1031 is parallel to the sensor, this distance clearly indicates the focusing state. When the wavefront 1032 is concave or convex 1033, this distance may be blurred, depending on the position of the focal spot associated with that light ray. To resolve the blurring, a pair of light rays is spaced apart by using a prism or a pair of prisms.

[0194] Figure 6-8 and Figure 9-18 An example is an autofocus system or a component of such an autofocus system having a fixed collimation repeater. Figure 9An autofocus system with a collimator repeater moving mechanism is illustrated, which is configured to change the distance between the relay input spherical lens and the relay output spherical lens of the collimator repeater. According to one embodiment, Figure 6-8 and Figure 9-18 Any autofocus system includes a collimator repeater movement mechanism.

[0195] Figure 6 and Figure 7 The autofocus system is exemplified as including an entrance pupil 80, a mask 110, a splitter 130, a first mirror 125, a second mirror 126, a first spherical telescope input lens 142-1, a first selectable depth-of-field unit 203-1, a first field curvature compensator 144, a first spherical telescope output lens 142-2, a first prism 145, a first relay input spherical lens 146-1, a first relay output spherical lens 146-1, a first sensor 50-1, a second spherical telescope input lens 172-1, a second selectable depth-of-field unit 203-2, a second field curvature compensator 174, a second spherical telescope output lens 172-2, a second prism 175, a second relay input spherical lens 176-1, a second relay output spherical lens 176-1, and a second sensor 50-2.

[0196] Figure 8 The top portion illustrates an autofocus system having a first selectable depth-of-field unit 203-1 within a first branch 140 and a second selectable depth-of-field unit 203-2 within a second branch 170.

[0197] Figure 8 The bottom portion illustrates an autofocus system having a first selectable depth-of-field unit 203-1 outside the first branch 140 and a second selectable depth-of-field unit 203-2 outside the second branch 170.

[0198] Depth of focus is determined by moving the second selectable depth of field unit and the first selectable depth of field unit, while other optical components of the first and second branches remain stationary, which improves the accuracy of the autofocus system.

[0199] Figure 9 An autofocus system is illustrated at two different distances between lenses at two time points and collimating repeaters.

[0200] The autofocus system includes:

[0201] a. A first lower folding mirror 222-5 and a first upper folding mirror 222-4, which are located between a first relay input spherical lens 146-1 and a first relay output spherical lens 146-2.

[0202] b. A second upper folding mirror 222-6 and a second lower folding mirror 222-7, which are located between the second relay input spherical lens 176-1 and the second relay output spherical lens 176-2.

[0203] c. A first collimator repeater moving mechanism 202-1, which is configured to change the distance between the first repeater input spherical lens 146-1 and the first repeater output spherical lens 146-2.

[0204] d. A second collimator repeater moving mechanism 202-2, which is configured to change the distance between the second repeater input spherical lens 176-1 and the second repeater output spherical lens 176-2.

[0205] Figure 8 The autofocus system allows for continuous variation of the effective focal length via a collimation repeater.

[0206] Figure 10 and Figure 11 Examples are shown for mask 110, first mirror 125, second mirror 126, first spherical telescope input lens 142-1 and second spherical telescope input lens 172-1, splitter 130 for separating two pairs of light rays, first mirror 125 for deflecting pairs of light rays 66-2 and 67-2, and second mirror 126 for deflecting pairs of light rays 68-2 and 69-2.

[0207] Figure 12 Slit 112 of mask 110 is illustrated to convert each of the first and second set of spot arrays into a pair of spaced-apart rays and a splitter spot formed on splitter 130. For a refractive index x value between 1 and 3, spot array 42-x is converted into a pair of rays forming splitter spots 66-x and 67-x, while spot array 44-x is converted into a pair of rays forming splitter spots 68-x and 69-x.

[0208] Figure 13 A splitter 130A is illustrated, which includes an optical splitting element (such as a prism 133) including a first reflective facet 131 and a second reflective facet 132. The splitter 130A also includes a housing 134 and a mechanical interface. The housing includes a housing top 135, an input opening 136, a first light output opening 137, and a second light output opening 138.

[0209] Figure 14 and Figure 15 The optical processing of paired light rays by the various components of the first and second branches is illustrated.

[0210] exist Figure 14The components include a first spherical telescope input lens 142-1, a first selectable depth-of-field unit 203-1, a first field curvature compensator including a first segment 144-1 and a second segment 144-2, a first spherical telescope output lens 142-2, a first prism 145 and a first relay input spherical lens 146-1, a second spherical telescope input lens 172-1, a second selectable depth-of-field unit 203-2, a second field curvature compensator including a third segment 174-1 and a fourth segment 174-2, a second spherical telescope output lens 172-2, a second prism 175, and a second relay input spherical lens 176-1.

[0211] exist Figure 15 The components include a first field curvature compensator 144, a first spherical telescope output lens 142-2, a first prism 145, a first relay input spherical lens 146-1, a first relay output spherical lens 146-1, a first sensor 50-1, a second field curvature compensator 174, a second spherical telescope output lens 172-2, a second prism 175, a second relay input spherical lens 176-1, a second relay output spherical lens 176-1, and a second sensor 50-2.

[0212] Figure 14 and Figure 15 The first pair of rays 401 is illustrated (including) Figure 4 The first pair of rays 46-1 and 47-1), and the second pair of rays 402 (including Figure 4 The second pair of rays 46-2 and 47-2), and the third pair of rays 403 (including Figure 4 The third pair of rays 46-3 and 47-3), and the fourth pair of rays 411 (including Figure 4 The fourth pair of rays 48-1 and 49-1, and the fifth pair of rays 412 (including...) Figure 4 The fifth pair of rays (48-2 and 49-2) and the sixth pair of rays (413) (including Figure 4 The sixth ray (48-3 and 49-3 in the middle).

[0213] Figure 16 The optical processing of paired light rays by the various components of the first and second branches is illustrated.

[0214] The components include a first selectable depth-of-field unit 203-1, a first field curvature compensator 144, a first spherical telescope output lens 142-2, a first prism 145, and a first relay input spherical lens 146-1.

[0215] Figure 16 Examples include first rays 46-1 and 47-1, first pair of rays 401, second rays 46-2 and 47-2, second pair of rays 402, third rays 46-3 and 47-3, and third pair of rays 403.

[0216] Figure 17 The optical processing of paired light rays by the various components of the first and second branches is illustrated.

[0217] The components include a first spherical telescope output lens 142-2, a first prism 145, a first relay input spherical lens 146-1, and a first relay output spherical lens 146-2. Dashed line 1463 illustrates the propagation of second rays 46-2 and 47-2.

[0218] Figure 17 First rays 46-1 and 47-1 are illustrated. The first rays are located on a dashed line oriented relative to the main axis 1462 of the collimator repeater and relative to the auxiliary axis 1461 of the collimator repeater, and are affected by the main optical power of the collimator repeater.

[0219] Figure 18 An example is shown of spots where paired light rays are incident on the first sensor 50-1 and the second sensor 50-2.

[0220] The first pair of light rays 66-1 and 67-1 form a first spot 281-1 and a second spot 281-2 on the first pair of pixels of the first sensor 50-1. The first spot 281-1 and the second spot 281-2 are spaced apart from the first sensor distance DS1 271.

[0221] The second pair of light rays 66-2 and 67-2 form a third spot 282-1 and a fourth spot 282-2 on the second pair of pixels of the first sensor 50-1. The third spot 282-1 and the fourth spot 282-2 are spaced apart from the second sensor by a distance DS2 272.

[0222] The third pair of light rays 66-3 and 67-3 form the fifth spot 283-1 and the sixth spot 283-2 on the third pair of pixels of the first sensor 50-1. The fifth spot 283-1 and the sixth spot 283-2 are spaced apart from the third sensor at a distance of DS3 273.

[0223] The fourth pair of light rays 68-1 and 69-1 form the seventh spot 284-1 and the eighth spot 284-2 on the fourth pair of pixels of the second sensor 50-2. The seventh spot 284-1 and the eighth spot 284-2 are spaced apart from the fourth sensor at a distance of DS4 274.

[0224] The fifth pair of light rays 68-2 and 69-2 form the ninth spot 285-1 and the tenth spot 285-2 on the fifth pair of pixels of the second sensor 50-2. The ninth spot 285-1 and the tenth spot 285-2 are spaced apart from the fifth sensor at a distance of DS5 275.

[0225] The sixth pair of light rays 68-3 and 69-3 form the eleventh spot 286-1 and the twelfth spot 286-2 on the sixth pair of pixels of the second sensor 50-2. The eleventh spot 286-1 and the twelfth spot 286-2 are spaced apart from the sixth sensor distance DS6276.

[0226] The sensor distance indicator shows the focusing status.

[0227] Figure 19 An example of an autofocus system is shown, which includes:

[0228] a. A first turntable having a set of first spherical telescope output lenses (collectively referred to as 351) with different focal lengths to provide different sensitivities for the autofocus system.

[0229] b. A second turntable having a set of second spherical telescope output lenses (collectively referred to as 352) with different focal lengths to provide different sensitivities for the autofocus system.

[0230] Any reference to a sensor shall apply to either the first sensor or the second sensor.

[0231] Any reference to light should be modified as necessary to apply to the bundle.

[0232] Any reference to light should be modified as necessary to apply to spots formed by light.

[0233] Any reference to a beam of light should be modified as necessary to apply it to the light ray.

[0234] Any reference to a beam should be modified as necessary to apply to the spots formed by the beam.

[0235] In the foregoing detailed description, numerous specific details have been set forth in order to provide a thorough understanding of embodiments of the present disclosure.

[0236] However, those skilled in the art will understand that the current embodiments of this disclosure can be practiced without these specific details. In other instances, well-known methods, processes, and components have not been described in detail so as not to obscure the current embodiments of this disclosure.

[0237] The subject matter considered as embodiments of this disclosure is specifically pointed out and explicitly claimed at the end of the specification. However, the embodiments of this disclosure relating to both organization and operation methods, as well as their objectives, features, and advantages, can be best understood by referring to the following detailed description in conjunction with the accompanying drawings.

[0238] It should be understood that, for the sake of simplicity and clarity, the elements shown in the figures are not necessarily drawn to scale. For example, the dimensions of some elements may be exaggerated relative to others for clarity. Additionally, reference numerals may be repeated in the figures where appropriate to indicate corresponding or similar elements.

[0239] Since most of the illustrative embodiments of this disclosure can be implemented using optical components and circuits known to those skilled in the art, no further details will be described in detail as deemed necessary for understanding and comprehending the basic concepts of the current embodiments of this disclosure, so as not to obscure or distract from the teachings of the current embodiments of this disclosure.

[0240] Any references to the method in the specification should be modified as necessary to suit the system capable of performing the method.

[0241] Any references to the system in the specification should be modified as necessary to apply to methods that can be performed by the system.

[0242] The term "and / or" means additionally or alternatively. For example, A and / or B means only A, or only B, or A and B.

[0243] In the foregoing description, numerous specific details have been set forth in order to provide a penetrating understanding of embodiments of the present disclosure.

[0244] However, those skilled in the art will understand that the current embodiments of this disclosure can be practiced without these specific details. In other instances, well-known methods, processes, and components have not been described in detail so as not to obscure the current embodiments of this disclosure.

[0245] The subject matter considered as embodiments of this disclosure is specifically pointed out and explicitly claimed at the end of the specification. However, the embodiments of this disclosure relating to both organization and operation methods, as well as their objectives, features, and advantages, can be best understood by referring to the following detailed description in conjunction with the accompanying drawings.

[0246] It should be understood that, for the sake of simplicity and clarity, the elements shown in the figures are not necessarily drawn to scale. For example, the dimensions of some elements may be exaggerated relative to others for clarity. Additionally, reference numerals may be repeated in the figures where appropriate to indicate corresponding or similar elements.

[0247] In the foregoing specification, embodiments of the present disclosure have been described with reference to specific examples of examples. However, it will be apparent that various modifications and changes may be made therein without departing from the broader spirit and scope of the appended claims.

[0248] Furthermore, the terms “front,” “back,” “top,” “bottom,” “above,” “below,” etc., used in the specification and claims are for descriptive purposes and are not necessarily used to describe permanent relative positions. It should be understood that such terms are interchangeable where appropriate, such that embodiments of this disclosure described herein can operate, for example, on orientations other than those illustrated or otherwise described herein.

[0249] Any reference to the terms “comprising”, “having”, or “including” shall be modified as necessary to apply to “consisting of” and / or as necessary to “consisting substantially of”.

[0250] However, other modifications, variations, and alternatives are also possible. Therefore, the specification and drawings should be considered illustrative rather than restrictive.

[0251] In the claims, any reference numerals placed between parentheses shall not be construed as limiting the claim. The word 'comprising' does not exclude the presence of elements or steps other than those listed in the claim. Furthermore, the terms "an" or "a" as used herein are defined as one or more. Moreover, introductory phrases used in the claims, such as "at least one" and "one or more," should not be construed as implying that the introduction of another claim element by the indefinite article "an" or "a" limits any particular claim containing such an introduced claim element to an embodiment containing only one such element, even if the same claim includes the introductory phrase "one or more" or "at least one" and indefinite articles such as "an" or "a." The same applies to the use of definite articles. Unless otherwise stated, terms such as "first" and "second" are used to arbitrarily distinguish the elements described by these terms. Therefore, these terms are not necessarily intended to indicate the time or other priority of these elements. The fact that certain measures are referenced in mutually different claims does not mean that a combination of these measures cannot be advantageous.

[0252] While certain features of the embodiments have been illustrated and described herein, many modifications, substitutions, alterations, and equivalents will now arise in those skilled in the art. Therefore, it should be understood that the appended claims are intended to cover all modifications and alterations consistent with the true spirit of the embodiments.

Claims

1. An automatic focusing system, characterized in that, The autofocus system includes: An illumination path is configured to illuminate a sample using an illumination beam that forms a plurality of spot arrays on the sample, the spot arrays including an upstream group of spot arrays formed on a first side of the imaging region and a downstream group of spot arrays formed on the other side of the imaging region. sensor; Controller; and A collection path, including an entrance pupil, is configured to collect a collected beam emitted from the sample and focus the collected beam along a first axis while imaging the entrance pupil along a second axis to provide an optically processed beam; wherein the sensor is configured to generate a detection signal representing the optically processed beam; and wherein the controller is configured to determine the focusing state of an evaluation beam incident on the imaging region.

2. The autofocus system of claim 1, wherein the controller is configured to generate an initial autofocus estimate of the future focus state of the evaluation beam as it reaches a defined position of the upstream group of spot arrays.

3. The autofocus system of claim 2, wherein the controller is configured to update the initial autofocus estimate when the imaging region approaches a defined position.

4. The autofocusing system as claimed in any of the preceding claims, wherein the upstream spot array comprises a first upstream spot array, a second upstream spot array, and a third upstream spot array.

5. The autofocusing system of claim 4, wherein each of the speckle arrays is a linear speckle array.

6. The autofocusing system of claim 4, wherein the optically processed beam forms a pair of spots for each of the plurality of spot arrays, wherein the distance between each pair of spots indicates the focus state associated with the corresponding spot array.

7. The autofocusing system of claim 4, wherein the controller is configured to ignore detection signals based on sample elements irradiated by at least a portion of the illumination beam.

8. The autofocusing system of claim 4, wherein the controller is configured to determine at least one of the pitch angle and roll angle of the illumination beam.

9. The autofocus system of claim 4, wherein the downstream spot array comprises a first downstream spot array, a second downstream spot array, and a third downstream spot array.

10. The autofocus system of claim 9, wherein each of the plurality of spot arrays and the upstream group of spot arrays are staggered along the first axis and the second axis.

11. The autofocusing system according to any one of claims 1-3, 9 and 10, wherein each of the spot arrays is a linear spot array.

12. The autofocusing system of any one of claims 1-3, 9 and 10, wherein the optically processed beam forms a pair of spots for each of the plurality of spot arrays, wherein the distance between each pair of spots indicates the focus state associated with the corresponding spot array.

13. The autofocusing system of any one of claims 1-3, 9 and 10, wherein the controller is configured to ignore detection signals based on sample elements irradiated by at least a portion of the illumination beam.

14. The autofocusing system of any one of claims 1-3, 9 and 10, wherein the controller is configured to determine at least one of the pitch angle and roll angle of the illumination beam.

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