Light path calibration system and method

Abstract

The invention relates to an optical path calibration system and method. The system comprises a calibration sheet; the illumination assembly is used for illuminating the calibration sheet; the calibration sheet is placed between the illumination assembly and the first objective lens, and the calibration sheet is located in a front focal plane of the first objective lens; the beam splitter prism is located on the side, away from the calibration piece, of the first objective lens and used for receiving the emergent light beam of the first objective lens to form a first reflection light beam and a first transmission light beam, the first reflection light beam enters the first light path assembly to be imaged, and the first transmission light beam enters the second light path assembly to be imaged. By adopting the system, two light paths can be directly coupled by adopting a coaxial interconnection mode, and the deviation of the optical axes of the upper light path and the lower light path can be better processed in light path alignment.

Description

Technical Field

[0001] The present application relates to the field of semiconductor equipment, and in particular to an optical path calibration system and method. Background Art

[0002] Semiconductor bonding is a key link in advanced packaging technology. The imaging optical system is the core component of alignment bonding, and its recognition accuracy and system alignment accuracy determine the bonding accuracy of the equipment.

[0003] Figure 1 It is a wafer mark identification and bonding step, including an upper wafer and a lower wafer. The upper wafer is located above the lower wafer, and the upper wafer and the lower wafer are continuously moved. The objective lens is used to observe whether the mark is aligned and whether the wafers are successfully bonded. The Face to Face optical system of existing semiconductor wafer bonding equipment generally uses two sets of upper and lower microscope systems to respectively identify the upper and lower wafer marks to complete the alignment. By avoiding the upper wafer, the upper lens is used to identify the lower wafer mark to obtain the precise coordinates, and then by avoiding the lower wafer, the lower lens is used to identify the upper wafer mark to obtain the precise coordinates. After the mark alignment is completed, the high-precision platform is used to achieve movement and bonding.

[0004] Figure 2 This is a schematic diagram of the composition structure of the calibration piece. The basic components of the calibration piece include a pattern and a substrate. The pattern is on the upper surface or inside the calibration piece. The pattern serves as the foreground, and a suitable material needs to be selected to contrast with the background for easy identification. The substrate is generally a material with high transmittance, including but not limited to quartz or optical glass.

[0005] Figure 3 The optical path structure of the existing optical system is as follows: the upper optical path system includes camera 1, tube lens 1, reflector 1, and objective lens 1; the lower optical path system includes objective lens 2, reflector 2, tube lens 2, and camera 2. First, a calibration sheet with a specific pattern or mark is placed at the object plane position of the upper optical path system and the lower optical path system. It can pass through objective lens 1, reflector 1, and tube lens 1 to form an image in camera 1, or it can pass through objective lens 2, reflector 2, and tube lens 2 to form an image in camera 2. The position of the calibration sheet can be fine-tuned to be located in the central area of ​​the field of view of camera 1 and camera 2, such as Figure 4 , Figure 4 Schematic diagram for adjusting the calibration patch to the center of the camera's field of view. Figure 3The optical system includes an upper optical path system and a lower optical path system, which are combined into one by calibrating two separate optical paths. The optical axis deviation of the upper and lower optical paths is prone to occur in the optical path alignment. One side of the calibration sheet faces objective lens one, and the other side faces objective lens two. At least one side of the upper and lower optical path systems needs to be imaged through the substrate. Therefore, the calibrated system has inevitable on-axis aberrations, and the upper and lower optical paths cannot be directly connected, nor can the deviation between the optical axis and the mechanical axis be determined, which will also cause off-axis aberrations. Not only does it need to place an additional calibration sheet in the system, but it also needs to adjust the position of the calibration sheet and perform a series of tasks such as pitching when performing optical path calibration, which makes it difficult to improve work efficiency. Summary of the invention

[0006] Based on this, it is necessary to provide an optical path calibration system and method to address the above technical issues.

[0007] In a first aspect, the present application provides an optical path calibration system, the system comprising:

[0008] Calibration sheet;

[0009] an illumination component, the illumination component being used to illuminate the calibration sheet;

[0010] A first objective lens, wherein the calibration sheet is placed between the illumination assembly and the first objective lens, the calibration sheet is coaxially arranged with the first objective lens, and the calibration sheet is located in a front focal plane of the first objective lens;

[0011] The beam splitter prism is located on the side of the first objective lens away from the calibration plate, and is used to receive the output light beam of the first objective lens to form a first reflected light beam and a first transmitted light beam, the first reflected light beam enters the first optical path component to form an image, and the first transmitted light beam enters the second optical path component to form an image.

[0012] In one embodiment, the first optical path component comprises:

[0013] a plane reflector, located on the path of the first reflected light beam, and used to reflect the first reflected light beam again to form a second reflected light beam, and the second reflected light beam enters the beam splitter prism to form a second transmitted light beam;

[0014] a first tube lens, the first tube lens being located on a path of the second transmitted light beam;

[0015] The first camera is located at a side of the first tube lens away from the beam splitter prism and is used to receive the output light beam of the first tube lens to form an image of the calibration sheet.

[0016] In one embodiment, the second optical path component comprises:

[0017] a second objective lens, the second objective lens being located on a path of the first transmitted light beam;

[0018] a third objective lens, the third objective lens being located on a side of the second objective lens away from the beam splitter prism, and a front focal plane of the third objective lens and a rear focal plane of the second objective lens being coplanar; wherein the first objective lens, the second objective lens and the third objective lens are coaxially arranged;

[0019] a reflecting prism, the reflecting prism being located at a side of the third objective lens away from the second objective lens and being used for reflecting an outgoing light beam from the third objective lens;

[0020] A second tube lens, used for receiving the outgoing light beam of the reflecting prism;

[0021] The second camera is located at a side of the second tube lens away from the reflecting prism and is used to receive the output light beam of the second tube lens to form an image of the calibration sheet.

[0022] In one embodiment, the system further comprises:

[0023] An electronic shutter is placed between the beam splitter prism and the plane reflecting mirror.

[0024] In one embodiment, the system further comprises:

[0025] An electronic shutter, wherein the electronic shutter is placed in the first optical path component and / or the second optical path component.

[0026] In one embodiment, a calibration pattern is formed on a surface of the calibration sheet facing the first objective lens.

[0027] In a second aspect, the present application further provides an optical path calibration method, which is applied to any of the above optical path calibration systems, and the method comprises:

[0028] Turning on the illumination assembly and the electronic shutter so that the calibration sheet is imaged on the first camera and the second camera;

[0029] Based on the images of the calibration sheet captured by the first camera and the second camera, the exposure time of the electronic shutter is adjusted.

[0030] In one embodiment, the method further comprises:

[0031] Fine-tune the position of the calibration sheet so that the calibration pattern on the calibration sheet appears in the central area of ​​the field of view of the first camera;

[0032] The second optical path component is roughly adjusted so that the calibration pattern on the calibration sheet is located in the central area of ​​the field of view of the second camera.

[0033] In one of the embodiments, when the calibration pattern on the calibration sheet cannot be adjusted to the central area of ​​the field of view of the second camera, the position of the calibration sheet is fine-tuned so that the calibration pattern of the calibration sheet is imaged in the central area of ​​the field of view of the second camera.

[0034] In one embodiment, after the calibration pattern of the calibration sheet is imaged in the central area of ​​the field of view of the second camera, the position of the first camera is fine-tuned to image the calibration pattern of the calibration sheet in the central area of ​​the field of view of the first camera.

[0035] The above optical path calibration system has at least the following beneficial effects:

[0036] In the embodiment scheme provided by the present disclosure, an illumination component is placed above the first optical path component, and the illumination component is used to illuminate the calibration plate. The calibration plate is located in the front focal plane of the first objective lens, and the dichroic prism is located on the side of the first objective lens away from the calibration plate, and receives the outgoing light beam of the first objective lens to form a first reflected light beam and a first transmitted light beam. The first reflected light beam enters the first optical path component to form an image, and the first transmitted light beam enters the second optical path component to form an image. The two optical paths are directly coupled by coaxial interconnection, and the deviation of the optical axes of the upper and lower optical paths can be better handled in the optical path alignment. When the optical path needs to be calibrated, the calibration plate image can be seen by turning on the illumination component, and the calibration plate is built into the optical path calibration system, which does not affect the bonding process of the equipment and also improves the optical path calibration efficiency.

[0037] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0039] Figure 1 Marking wafers for identification and bonding steps;

[0040] Figure 2 Schematic diagram of the composition structure of the calibration piece;

[0041] Figure 3 The optical path structure of the existing optical system;

[0042] Figure 4 Schematic diagram for adjusting the calibration patch to the center of the camera's field of view;

[0043] Figure 5A schematic diagram of an optical path calibration system in one embodiment;

[0044] Figure 6 is a schematic diagram of a first optical path including a first optical path component in one embodiment;

[0045] Figure 7 is a schematic diagram of a second optical path including a second optical path component in one embodiment;

[0046] Figure 8 FIG. 4 is an optical path structure of an optical system in one embodiment. DETAILED DESCRIPTION

[0047] In order to enable ordinary persons in the art to better understand the technical solutions of the present disclosure, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings.

[0048] It should be noted that the terms "first", "second", etc. in the specification and claims of the present disclosure and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present disclosure described here can be implemented in an order other than those illustrated or described here. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. On the contrary, they are only examples of devices and methods consistent with some aspects of the present disclosure as detailed in the attached claims. The terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, product or device including a series of elements includes not only those elements, but also other elements that are not explicitly listed, or also includes elements inherent to such process, method, product or device. In the absence of more restrictions, it is not excluded that there are other identical or equivalent elements in the process, method, product or device including the elements. For example, if the words first, second, etc. are used to represent the name, they do not represent any specific order.

[0049] The present disclosure provides an optical path calibration system which can be applied to Figure 5 In the application environment shown, Figure 5 FIG. 4 is a schematic diagram of an optical path calibration system in an embodiment.

[0050] The illumination component 502 is placed above the calibration sheet 504 to illuminate the calibration sheet 504. The illumination component may be a lighting backlight source, which may provide a uniform light source to ensure that the pattern on the calibration sheet 504 is clearly visible. By adjusting the illumination intensity, the brightness of the calibration sheet may be controlled, thereby improving the imaging quality.

[0051] The calibration sheet 504 is placed between the illumination assembly 502 and the first objective lens 506, and the calibration sheet 504 is located in the front focal plane of the first objective lens 506. Each point on the calibration sheet will generate a set of parallel light rays through the objective lens, that is, the light rays on the calibration sheet 504 are coupled to infinity. The calibration sheet 504 is coaxially arranged with the first objective lens 506.

[0052] The beam splitter prism 508 is located on the side of the first objective lens 506 away from the calibration sheet 504, and is used to receive the outgoing light beam of the first objective lens 506 to form a first reflected light beam and a first transmitted light beam, wherein the first reflected light beam enters the first optical path component 510 to form an image, and the first transmitted light beam enters the second optical path component 512 to form an image. In the embodiment of the present disclosure, the first optical path component may include a first camera, and the second optical path component may include a second camera, so that the pattern of the calibration sheet can be observed in the two optical path components at the same time to ensure the alignment accuracy of the upper and lower optical paths.

[0053] In the above optical path calibration system, an illumination component is placed above the first optical path component. The illumination component is used to illuminate the calibration plate. The calibration plate is located in the front focal plane of the first objective lens. The dichroic prism is located on the side of the first objective lens away from the calibration plate. The outgoing light beam of the first objective lens is received to form a first reflected light beam and a first transmitted light beam. The first reflected light beam enters the first optical path component to form an image, and the first transmitted light beam enters the second optical path component to form an image. The two optical paths are directly coupled by coaxial interconnection, and the deviation of the optical axes of the upper and lower optical paths can be better handled in the optical path alignment. When the optical path needs to be calibrated, the calibration plate image can be seen by turning on the illumination component, and the calibration plate is built into the optical path calibration system, which does not affect the bonding process of the equipment and also improves the efficiency of the optical path calibration.

[0054] In some embodiments of the present disclosure, Figure 6 FIG. 5 is a schematic diagram of a first optical path including a first optical path component in an embodiment. The first optical path component 510 includes a plane reflector 602 , a first tube lens 604 , a first camera 606 , and may further include an electronic shutter 608 .

[0055] The plane reflector 602 is located on the path of the first reflected light beam and can adjust the direction of the light to ensure that the light can propagate along the expected path. It is used to reflect the first reflected light beam again to form a second reflected light beam, and the second reflected light beam enters the beam splitter prism 508 to form a second transmitted light beam.

[0056] The first tube lens 604 is located on the path of the second transmitted light beam. After further processing by the first tube lens 604, the second transmitted light beam finally forms a clear image on the first camera 606. The focal length of the first tube lens 604 can be adjusted to ensure that the outgoing light beam of the first tube lens 604 can form a clear image on the photosensitive element of the first camera 606.

[0057] The first camera 606 is located on the side of the first tube lens 604 away from the beam splitter prism 508, and is used to receive the outgoing light beam of the first tube lens 604 to form an image of the calibration sheet 504. The first camera 606 is used to capture the calibration sheet pattern imaged by the first tube lens 604, convert the light signal into a digital signal, and store it as image data. During debugging and calibration, the first camera 606 can provide real-time image feedback to help adjust the optical path alignment.

[0058] In some embodiments of the present disclosure, Figure 7 Schematic diagram of a second optical path including a second optical path component in one embodiment. The second optical path component 512 includes a second objective lens 702 , a third objective lens 704 , a reflecting prism 706 , a second tube lens 708 , and a second camera 710 .

[0059] The second objective lens 702 is located on the path of the first transmitted light beam and can receive and amplify the first transmitted light beam to prepare for subsequent imaging.

[0060] The third objective lens 704 is located on the side of the second objective lens 702 away from the beam splitter prism 508, and the front focal plane of the third objective lens 704 is coplanar with the back focal plane of the second objective lens 702. The third objective lens 704 couples the light to infinity to form parallel light. The first objective lens 506, the second objective lens 702 and the third objective lens 704 are coaxially arranged.

[0061] The reflection prism 706 is located on the side of the third objective lens 704 away from the second objective lens 702, and is used to reflect the outgoing light beam from the third objective lens 704. The reflection prism 706 is used to change the direction of the light path, receive the outgoing light beam from the third objective lens 704, and reflect it to another direction.

[0062] The second tube lens 708 is used to receive the outgoing light beam from the reflection prism 706 and further process the outgoing light beam, which may include re-magnification, aberration correction, etc., to ensure the quality of the final image.

[0063] The second camera 710 is located on a side of the second tube lens 708 away from the reflecting prism 706 and is used to receive the light beam emitted by the second tube lens 708 to form an image of the calibration sheet.

[0064] In some embodiments of the present disclosure, the system further comprises:

[0065] The electronic shutter 608 is placed between the beam splitter prism 508 and the plane mirror 602 .

[0066] When imaging of a certain section of the light path is required, the electronic shutter 608 is opened to allow light to enter and be captured by the sensor. When imaging of a certain section of the light path is not required, the electronic shutter 608 is closed to prevent light from entering and being captured by the sensor.

[0067] In some embodiments of the present disclosure, the system further comprises:

[0068] The electronic shutter 608 is placed in the first optical path component and / or the second optical path component.

[0069] The electronic shutter 608 may be placed in the first optical path component and / or the second optical path component. For example, when the first optical path component is required for imaging, the electronic shutter in the first optical path component is opened. For example, when the second optical path component is not required for imaging, the electronic shutter in the second optical path component is closed.

[0070] In some embodiments of the present disclosure, a calibration pattern is formed on a surface of the calibration sheet facing the first objective lens.

[0071] The calibration sheet is engraved with a pattern on only one side, thus avoiding the additional axial aberration that may be caused by using double-sided patterns. The calibration sheet is formed with a calibration pattern on the side facing the first objective lens, which can minimize the interference of the substrate on the light, thereby avoiding the aberration caused by the substrate.

[0072] Figure 8 FIG. 4 is an optical path structure of an optical system in one embodiment.

[0073] In some embodiments of the present disclosure, a light path calibration method is provided, which is applied to any of the above light path calibration systems, and the method includes:

[0074] Turn on the illumination assembly 502 and the electronic shutter 608 so that the calibration patch image is imaged on the first camera 606 and the second camera 710;

[0075] Based on the calibration patch images captured by the first camera 606 and the second camera 710 , the exposure time of the electronic shutter 608 is adjusted.

[0076] Turn on the illumination assembly 502 and ensure that the illumination assembly 502 is in the on state to provide sufficient brightness to illuminate the calibration sheet. Ensure that the electronic shutter 608 is in the on state to allow light to enter the camera for imaging. Observe the display screens of the first camera 606 and the second camera 710 to ensure that the image of the calibration sheet is clearly visible.

[0077] In some embodiments of the present disclosure, the method further includes:

[0078] Fine-adjusting the position of the calibration sheet 504 so that the calibration pattern on the calibration sheet 504 appears in the central area of ​​the field of view of the first camera;

[0079] The second optical path component is roughly adjusted so that the calibration patch pattern is located in the central area of ​​the field of view of the second camera 710 .

[0080] In some embodiments of the present disclosure, when the calibration pattern on the calibration sheet 504 cannot be adjusted to the central area of ​​the field of view of the second camera 710, the position of the calibration sheet 504 is fine-tuned so that the calibration pattern of the calibration sheet 504 is imaged in the central area of ​​the field of view of the second camera 710.

[0081] In some embodiments of the present disclosure, after the calibration pattern of the calibration sheet 504 is imaged in the central area of ​​the field of view of the second camera 710 , the position of the first camera 606 is fine-tuned to image the calibration pattern of the calibration sheet 504 in the central area of ​​the field of view of the first camera 606 .

[0082] The calibration pattern of the calibration sheet 504 is observed on the display screen of the first camera 606 to confirm whether the calibration pattern is located in the center of the field of view of the first camera 606. If the calibration pattern fails to reach the center of the field of view of the first camera 606, the position of the calibration sheet 504 is fine-tuned so that the calibration pattern appears in the center of the field of view of the first camera 606. The calibration pattern of the calibration sheet 504 is observed on the display screen of the second camera 710, and the second optical path component is roughly adjusted so that the calibration pattern is located in the center of the field of view of the second camera 710.

[0083] If the calibration pattern cannot be positioned in the center of the field of view of the second camera 710 by coarsely adjusting the second optical path component, the position of the calibration sheet 504 is finely adjusted so that the calibration pattern is imaged in the center of the field of view of the second camera 710. After the calibration pattern is imaged in the center of the field of view of the second camera 710, it is possible that the calibration pattern is not in the center of the field of view of the first camera 606, and the position of the first camera 606 is finely adjusted so that the calibration pattern is imaged in the center of the field of view of the first camera 606.

[0084] After the calibration is completed, the illumination assembly 502 and the electronic shutter 608 are turned off, and the wafer can be used for wafer alignment and bonding.

[0085] It should be understood that, although the various steps in the flowcharts involved in the above-mentioned embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps does not have a strict order restriction, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-mentioned embodiments can include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0086] The device may include a system (including a distributed system), software (application), module, component, server, client, etc. that uses the method described in the embodiments of this specification and is combined with necessary implementation hardware. Based on the same innovative concept, the device in one or more embodiments provided in the embodiments of the present disclosure is as described in the following embodiments. Since the implementation scheme and method of the device to solve the problem are similar, the implementation of the specific device in the embodiments of this specification can refer to the implementation of the aforementioned method, and the repetitions will not be repeated. As used below, the term "unit" or "module" can be a combination of software and / or hardware that implements a predetermined function. Although the device described in the following embodiments is preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceived.

[0087] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0088] The above-described embodiments only express several implementation methods of the present disclosure, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present disclosure, and these all belong to the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be subject to the attached claims.

Claims

1. An optical path calibration system, characterized in that: The system comprises: Calibration sheet; an illumination component, the illumination component being used to illuminate the calibration sheet; A first objective lens, wherein the calibration sheet is placed between the illumination assembly and the first objective lens, the calibration sheet is coaxially arranged with the first objective lens, and the calibration sheet is located in a front focal plane of the first objective lens; The beam splitter prism is located on the side of the first objective lens away from the calibration plate, and is used to receive the output light beam of the first objective lens to form a first reflected light beam and a first transmitted light beam, the first reflected light beam enters the first optical path component to form an image, and the first transmitted light beam enters the second optical path component to form an image.

2. The system according to claim 1, characterized in that The first optical path component comprises: a plane reflector, located on the path of the first reflected light beam, and used to reflect the first reflected light beam again to form a second reflected light beam, and the second reflected light beam enters the beam splitter prism to form a second transmitted light beam; a first tube lens, the first tube lens being located on a path of the second transmitted light beam; The first camera is located at a side of the first tube lens away from the beam splitter prism and is used to receive the output light beam of the first tube lens to form an image of the calibration sheet.

3. The system according to claim 1, characterized in that The second optical path component comprises: a second objective lens, the second objective lens being located on a path of the first transmitted light beam; a third objective lens, the third objective lens being located on a side of the second objective lens away from the beam splitter prism, and a front focal plane of the third objective lens and a rear focal plane of the second objective lens being coplanar; wherein the first objective lens, the second objective lens and the third objective lens are coaxially arranged; a reflecting prism, the reflecting prism being located at a side of the third objective lens away from the second objective lens and being used for reflecting an outgoing light beam from the third objective lens; A second tube lens, used for receiving the outgoing light beam of the reflecting prism; The second camera is located at a side of the second tube lens away from the reflecting prism and is used to receive the output light beam of the second tube lens to form an image of the calibration sheet.

4. The system according to claim 2, characterized in that The system further comprises: An electronic shutter is placed between the beam splitter prism and the plane reflecting mirror.

5. The system according to claim 1, characterized in that The system further comprises: An electronic shutter, wherein the electronic shutter is placed in the first optical path component and / or the second optical path component.

6. The system according to claim 1, characterized in that A calibration pattern is formed on a surface of the calibration sheet facing the first objective lens.

7. A method for optical path calibration, characterized in that: Applied to the optical path calibration system of any one of claims 1 to 6, the method comprising: Turning on the illumination assembly and the electronic shutter so that the calibration sheet is imaged on the first camera and the second camera; Based on the images of the calibration sheet captured by the first camera and the second camera, the exposure time of the electronic shutter is adjusted.

8. The method according to claim 7, characterized in that The method further comprises: Fine-tune the position of the calibration sheet so that the calibration pattern on the calibration sheet appears in the central area of ​​the field of view of the first camera; The second optical path component is roughly adjusted so that the calibration pattern on the calibration sheet is located in the central area of ​​the field of view of the second camera.

9. The method according to claim 8, characterized in that When the calibration pattern on the calibration sheet cannot be adjusted to the central area of ​​the field of view of the second camera, the position of the calibration sheet is fine-tuned so that the calibration pattern of the calibration sheet is imaged in the central area of ​​the field of view of the second camera.

10. The method according to claim 9, characterized in that After the calibration pattern of the calibration sheet is imaged in the central area of ​​the field of view of the second camera, the position of the first camera is finely adjusted to image the calibration pattern of the calibration sheet in the central area of ​​the field of view of the first camera.

Images