Multi-magnification imaging system axial deviation detection system and method

Abstract

The embodiment of the invention discloses a multi-magnification imaging system axial deviation detection system and method. The system comprises an objective lens, a plurality of tube lenses, a tube lens switching structure, a Z-direction motion table, a camera, a beam splitter and a marking plate. According to the detection method, on the basis of a reference light beam and defocus imaging of a measured object, a reflected light beam of a beam splitter is adopted as the reference light beam, the defocus imaging method of the measured object is combined, and through position changes of a reference light spot and an imaging light spot in different Z-direction positions of a camera and inclination of a measurement optical axis, axial deviation measurement of a multi-magnification tube lens module and an objective lens is achieved. The reflected light beam of the beam splitter is used as a reference light beam during axial deviation measurement, and correction is carried out in a result, so that the measurement precision is irrelevant to the motion axis of the camera, the inclination influence of the motion axis of the camera is eliminated, and the detection precision is further improved.

Description

Technical Field

[0001] The present invention relates to the field of industrial detection, and in particular to the field of semiconductor imaging detection. Background Art

[0002] In the field of industrial inspection, such as semiconductor imaging inspection, Figure 1 As shown, the imaging detection system is composed of a large numerical aperture objective lens 4, multiple magnification tube lenses, a tube lens switching structure 30, a Z-axis motion stage 2, and a camera 1, etc.; wherein the tube lens switching structure 30 moves in the horizontal direction to realize the switching of different tube lenses including the first tube lens 31, the second tube lens 32, and the third tube lens 33; the camera 1 is installed on the Z-axis motion stage 2, and can move up and down and focus the image plane. When the system performs imaging detection on the object 5 such as a wafer, the coaxiality deviation of the tube lens and the objective lens will affect the image quality and cause the center of the imaging field of view to deviate, so precise control is required to minimize or avoid the coaxiality deviation.

[0003] Therefore, in one of the prior art axis deviation measurement methods, the coaxiality of the tube lens and the objective lens is detected by offline three-coordinate calibration and mechanical dimension chain transmission. However, in the above method, due to factors such as equipment accuracy, assembly error and dimension chain transmission error, the measurement error accumulates, so the coaxiality measurement accuracy is not high. Summary of the invention

[0004] The main technical problem solved by the present invention is to improve the accuracy of measuring the axis deviation of an imaging system.

[0005] Accordingly, firstly, in one embodiment of the present invention, a method for detecting axis deviation of a multi-magnification imaging system is provided; the method comprises the following steps: 1) Beam splitter settings: A beam splitter is arranged on the opposite side of the tube image, and a parallel reference beam is used to calibrate the attitude of the beam splitter until the light spots formed by at least two beams emitted by the beam splitter overlap on the camera; 2) Measurement of the first imaging light spot position: The camera is located at the first axial position, a marking plate for imaging measurement is placed on the object side of the objective lens, the illumination beam of the objective lens imaging is turned on, and the absolute position of the objective lens imaging light spot on the camera target surface is counted as the first imaging light spot position P11; 3) First reference light spot position measurement: the camera is located at the first axial position, the parallel reference beam is turned on, and the absolute position of the light spot formed by the parallel reference beam is recorded as the first reference light spot position P10; 4) Second imaging spot position measurement: the camera is located at the second axial position, a marking plate for imaging measurement is placed on the object side of the objective lens, the illumination beam of the objective lens imaging is turned on, and the absolute position of the objective lens imaging spot on the camera target surface is counted as the second imaging spot position P21; 5) Second reference light spot position measurement: the camera is located at the second axial position, the parallel reference beam is turned on, and the absolute position of the light spot formed by the parallel reference beam is recorded as the second reference light spot position P20; 6) Calculation of axis offset: Record the axial movement distance ΔZ between the first axial position and the second axial position of the camera; Calculate the change in the center distance M between the imaging spot position and the reference spot position under different camera axial positions, which is calculated as ΔM=(P11-P10)-(P21-P20); According to tanα=ΔM / ΔZ, where α is the inclination angle of the optical axis of the tube lens after removing the influence of the camera motion axis inclination; calculate the value of α; According to the formula tanα=ΔL / f, where f is the focal length of the tube lens, the corresponding axis offset ΔL= f·tanα of the tube lens is calculated; The execution order of step 2) is any one of the following: before step 1), after step 1) and before step 6); the execution order of step 4) is any one of the following: before step 1), after step 1) and before step 6).

[0006] In one embodiment of the above-mentioned method for detecting axis deviation of a multi-magnification imaging system, in the step of setting the beam splitter, the step of calibrating the posture of the beam splitter includes: A reference reflective element is provided on the mirror image square mechanical reference plane of the tube; The beam splitter is arranged between the camera and the reference reflective element, and the parallel reference beam is irradiated into the beam splitter; The beam splitter splits the parallel reference beam into at least two beams; one beam passes through the beam splitter-reference reflective element-beam splitter-camera, and the other beam passes through the beam splitter-camera; the two beams form two light spots on the camera; The posture of the beam splitter is adjusted so that the two light spots overlap on the camera. At this time, the posture of the beam splitter relative to the reference reflective element has been adjusted to be parallel.

[0007] In one embodiment of the multi-magnification imaging system axis deviation detection method, the method further includes the step of calibrating the parallel reference beam: A calibration reflective element is arranged on the side of the square mechanical reference plane of the tube image, and the reflective surface of the calibration reflective element is perpendicular to the square mechanical reference plane of the tube image; The light beam emitted by the parallel light generator is irradiated onto the surface of the calibration reflective element, and then returns to the parallel light generator after being reflected; According to the measurement indication of the parallel light generator, the posture of the parallel light generator is adjusted so that the outgoing light beam of the parallel light generator is perpendicular to the reflective surface of the calibration reflective element; At this time, the outgoing light beam is calibrated as the parallel reference light beam.

[0008] In one embodiment of the above-mentioned method for detecting axis deviation of a multi-magnification imaging system, the beam splitter is a cubic beam splitter prism, and the cubic beam splitter prism splits the parallel reference beam into two paths.

[0009] In one embodiment of the above-mentioned method for detecting axial deviation of a multi-magnification imaging system, the first interface, the second interface and the third interface of the cubic beamsplitter prism are high-transmittance surfaces coated with an anti-reflection film, the fourth interface is a reflective surface coated with a reflective film, and the fifth interface is a semi-transparent and semi-reflective surface coated with a dichroic film.

[0010] Secondly, an embodiment of the present invention provides an axial deviation detection system for a multi-magnification imaging system, which includes an objective lens, a plurality of tube lenses, a tube lens switching structure, a Z-axis motion stage, a camera, a beam splitter and a marking plate; the tube lens switching structure carries the plurality of tube lenses and is used to move in the horizontal direction to achieve switching of different tube lenses; the camera is installed on the Z-axis adjustment structure and can move up and down and focus the image plane; the beam splitter is arranged between the tube lens object side and the camera object side, and is calibrated in posture until the light spots formed on the camera by at least two light beams generated by parallel reference light beams overlap; the marking plate is used to be placed on the object side of the objective lens and form an imaging light spot on the camera.

[0011] The above-mentioned multi-magnification imaging system axis deviation detection system, in one embodiment, also includes a reference reflective element, which is arranged on the mechanical reference plane of the tube image; and is used for: when the reference light beam is split into at least two light beams by the beam splitter, one of the light beams passes through the beam splitter-reference reflective element-beam splitter-camera, and the other light beam passes through the beam splitter-camera; the two light beams form two light spots on the camera; the posture of the beam splitter is adjusted so that the two light spots overlap on the camera, and at this time, the posture of the beam splitter relative to the reference reflective element has been adjusted to be parallel.

[0012] The above-mentioned multi-magnification imaging system axis deviation detection system, in one embodiment, also includes a parallel light generator and a calibration reflective element, wherein the parallel light generator and the calibration reflective element are respectively arranged on the side of the beam splitter, and the reflective surface of the calibration reflective element is perpendicular to the square mechanical reference surface of the tube image; it is used for: the outgoing light beam from the parallel light generator is irradiated to the surface of the calibration reflective element, and returns to the parallel light generator after reflection; according to the measurement indication of the parallel light generator, the posture of the parallel light generator is adjusted so that the outgoing light beam of the parallel light generator is perpendicular to the reflective surface of the calibration reflective element; at this time, the outgoing light beam is calibrated as the parallel reference beam.

[0013] In one embodiment of the above-mentioned multi-magnification imaging system axis deviation detection system, the beam splitter is a cubic beam splitting prism.

[0014] According to the method and / or system of the above-mentioned embodiment, based on the reference beam and the defocused imaging of the object to be measured, the reflected beam of the beam splitter is used as the reference beam, and in combination with the defocused imaging method of the object to be measured, the position change of the reference light spot and the imaging light spot at different Z positions of the camera is used to measure the tilt of the optical axis, thereby realizing the measurement of the axis deviation of the tube lens module and the objective lens with multiple magnifications; because the reflected beam of the beam splitter is used as the reference beam for the axis deviation measurement, and the axis deviation of the Z motion axis is corrected in the result, the measurement accuracy of the present invention is independent of the camera motion axis, the influence of the camera motion axis tilt is eliminated, and the detection accuracy is further improved.

[0015] According to the method and / or system of the above-mentioned embodiment, further, the posture of the beam splitter is first adjusted using a reference reflective element, so that the beam splitting of the beam splitter can be ensured to be in a parallel state relative to the axial angle of the tube lens, thereby ensuring the accuracy and precision of the beam splitter position, and further ensuring the accuracy of the axial deviation measurement of the present invention.

[0016] According to the method and / or system of the above-mentioned embodiment, further, a parallel light generator and a calibration reflective element are used to calibrate the parallel reference light of the incident beam splitter, thereby ensuring the accuracy of the parallel performance of the parallel reference light beam and further ensuring the accuracy of the axial deviation measurement of the present invention.

[0017] According to the method and / or system of the above-mentioned embodiment, further, the beam splitter uses a cubic beam splitter prism, which has a simple structure, is easy to debug, and is convenient for measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the imaging detection system; Figure 2 Schematic diagram of the principle of the defocus imaging axis deviation measurement method of the present invention; Figure 3 A schematic diagram of a light spot of a method for measuring the axis deviation of defocused imaging in the present invention; Figure 4 A schematic diagram of a prism attitude calibration process according to an embodiment of the present invention; Figure 5 A schematic diagram of a prism posture calibration after completion of an embodiment of the present invention; Wherein: camera 1, camera target surface 10, imaging spot 100, axial first position 11, axial second position 12, Z-axis motion stage 2, tube lens 3, tube lens switching structure 30, first tube lens 31, second tube lens 32, third tube lens 33, objective lens 4, object to be measured 5, cubic beam splitter prism 6, prism optical axis 60, first interface 61, second interface 62, third interface 63, fourth interface 64, fifth interface 65, reference reflection flat crystal 71, calibration reflection flat crystal 72, aperture 8, parallel reference beam 90. DETAILED DESCRIPTION

[0019] The present invention is further described in detail below by specific embodiments in conjunction with the accompanying drawings. Wherein similar elements in different embodiments use associated similar device numbers. In the following embodiments, many detailed descriptions are intended to enable the present application to be better understood. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other devices, materials, and methods. In some cases, some operations related to the present application are not shown or described in the specification, in order to avoid the core part of the present application being overwhelmed by too much description, and for those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations based on the description in the specification and the general technical knowledge in the art.

[0020] In addition, the features, operations or characteristics described in the specification can be combined in any appropriate manner to form various implementations. At the same time, the steps or actions in the method description can also be interchanged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for the purpose of clearly describing a certain embodiment and are not meant to be a required sequence, unless otherwise specified that a certain sequence must be followed.

[0021] The serial numbers assigned to the components herein, such as "first", "second", etc., are only used to distinguish the objects described and do not have any sequential meaning. The "connection" and "coupling" mentioned in this application, unless otherwise specified, include direct and indirect connections (couplings).

[0022] In the embodiment of the present invention, a defocused imaging axis deviation measurement method is used. Figure 2 , Figure 3As shown, the rearward deviation of the tube lens axis introduces a tilt of the image-side optical axis. When the camera is at different Z-positions for measurement, the position of the imaging spot 100 on the camera target surface 10 will shift. The imaging spot when the camera is at the second axial position 12 has a positional shift of ΔX relative to the imaging spot when the camera is at the first axial position 11.

[0023] The measurement method can be summarized as follows: the camera moves slightly along the Z axis, and the defocus amount is recorded as ΔZ; the translation ΔX of the imaging spot on the camera target surface is obtained, and tanθ=ΔX / ΔZ is calculated, where θ is the inclination angle of the optical axis.

[0024] The optical axis inclination angle is directly related to the axis offset of the tube lens. Assuming that the focal length of the tube lens is f and the axis offset is ΔL, then tanθ=ΔL / f; therefore, by measuring θ, the axis offset of the tube lens ΔL= f·tanθ can be calculated.

[0025] However, in the above-mentioned defocused imaging axis deviation measurement method, the axis deviation of the tube mirror will be coupled with the motion axis tilt of the detector, which will introduce a large measurement error. Therefore, the measurement result is greatly affected by the motion axis tilt of the detector.

[0026] Therefore, further, in an embodiment of the present invention, a multi-magnification imaging system axis deviation detection system is proposed, and the system includes: an objective lens, a plurality of tube lenses, a tube lens switching structure, a Z-axis motion stage, a camera, a beam splitter and a marking plate; the tube lens switching structure carries a plurality of tube lenses of different magnifications, and is used to move in the horizontal direction to realize the switching of tube lenses of different magnifications; the camera is installed on the Z-axis motion stage for up and down movement and image plane focusing; the beam splitter is arranged between the tube lens side and the camera object side, and the beam splitter is calibrated through posture so that at least two light beams generated by parallel reference light beams overlap the light spots formed on the camera target surface; the marking plate is used to be placed on the object side of the objective lens and form an imaging light spot on the camera; the aperture is arranged between the tube lens and the objective lens, and is used to control the amount of light, reduce stray light and glare, and thus improve image contrast and clarity.

[0027] Meanwhile, in an embodiment of the present invention, a method for detecting axis deviation of a multi-magnification imaging system is proposed, which is applicable to an imaging detection system, such as a semiconductor imaging detection system, and includes the following steps: 1) Beam splitter setting: Set the beam splitter on the opposite side of the tube image, and use a parallel reference beam to calibrate the beam splitter until the spots formed by at least two beams emitted by it overlap on the camera, and the calibration is completed; 2) Imaging spot position measurement: The camera is located at the first axial position, a marking plate for imaging measurement is placed on the object side of the objective lens, the illumination beam of the objective lens imaging is turned on, and the absolute position of the objective lens imaging spot on the camera target surface is counted as the imaging spot position P1. 3) Reference spot position measurement: The camera is located at the first axial position, the parallel reference beam is turned on, and the absolute position of the spot formed by the parallel reference beam on the camera target surface is recorded as the reference spot position P0; 4) Calculation of axis offset: The camera moves ΔZ in the axial direction; the change of the center distance M between the imaging spot position P1 and the reference spot position P0 under different camera axial positions is calculated as ΔM; According to tanα=ΔM / ΔZ, where α is the inclination angle of the optical axis of the tube lens after removing the influence of the tilt of the camera motion axis; the value of α is calculated; according to the formula tanα=ΔL / f, where f is the focal length of the tube lens, the corresponding axis offset of the tube lens is calculated; The execution order of step 2) is any one of the following: before step 1), after step 1) and before step 4).

[0028] The camera referred to in the embodiment of the present invention is a camera that only includes a camera body but does not have a lens.

[0029] Embodiment 1: Please refer to Figure 4 As shown, the axis deviation detection system of the multi-magnification imaging system of this example includes: a camera 1, a beam splitter, a parallel light tube (not shown in the figure) and a reflective element; wherein the reflective element includes a reference reflective flat crystal 71 and a calibration reflective flat crystal 72, and the beam splitter adopts a cubic beam splitting prism 6, which has a simple structure and is easy to operate by splitting light. The first interface 61, the second interface 62 and the third interface 63 of the cubic beam splitting prism 6 are high-transmittance surfaces coated with an anti-reflection film, the fourth interface 64 is a reflective surface coated with a reflective film, and the fifth interface 65 is a semi-transparent and semi-reflective surface coated with a spectroscopic film.

[0030] The multi-magnification imaging system axis deviation detection method of this example is applicable to semiconductor imaging detection, and specifically includes the following steps: Step 1: Calibration of parallel reference beam of collimator A calibration reflection flat crystal 72 is placed on the side of the mechanical reference plane on the image side of the tube lens 3, and the reflection surface of the calibration reflection flat crystal is perpendicular to the mechanical reference plane on the image side of the tube lens 3; no cubic beam splitter prism is placed at this time; the parallel reference light beam 90 emitted by the collimator irradiates the reflection surface of the calibration reflection flat crystal 72, and returns to the collimator after reflection; according to the measurement indication of the collimator, the posture of the collimator is adjusted so that the parallel reference light beam 90 emitted by the collimator is perpendicular to the reflection surface of the calibration reflection flat crystal 72, and at this time, the calibration of the parallel reference light beam 90 is completed.

[0031] Step 2: Prism attitude calibration Please combine Figure 4 and Figure 5As shown, a reference reflection flat crystal 71 is placed on the mechanical reference plane above the tube lens 3, and a cubic beam splitter prism 6 is placed between the camera 1 and the reference reflection flat crystal 71. The calibrated parallel reference light beam 90 emitted by the parallel light tube is irradiated into the cubic beam splitter prism 6; the parallel reference light beam 90 is divided into two paths by the cubic beam splitter prism 6, one of which passes through the second interface 62-fifth interface 65-third interface 63-reference reflection flat crystal-third interface 63-fifth interface 65-first interface 61-camera; the other light beam passes through the second interface 62-fifth interface 65-fourth interface 64-fifth interface 65-first interface 61-camera; the two light beams form two light spots on the camera.

[0032] The attitude of the cubic beam splitter prism 6 is adjusted so that the two light spots overlap on the target surface of the camera 1. At this time, the attitude of the cubic beam splitter prism 6 relative to the reference reflection flat crystal 71 has been adjusted to be parallel. The overlapping light spot is counted as P0 and used as the reference light spot for subsequent measurement.

[0033] If the camera's Z-axis of motion is tilted, the position of the light spot P0 on the camera target surface changes when the camera 1 moves along the Z direction.

[0034] Therefore, the change of P0 position during the Z-direction movement of the camera can be used to characterize the inclination of the camera's Z-direction movement axis, and a reference deduction can be performed in subsequent measurements. The calculation after deducting the position change can correct the influence of the inclination of the Z-direction movement axis to ensure that the inclination will not affect the measurement result of the tube lens axis offset, thereby further improving the detection accuracy.

[0035] Step 3: Defocus Imaging Measurement Remove the reference reflective flat crystal 71; A marking plate for measurement (not shown in the figure) is placed on the object side of the objective lens 4, and the marking plate has suitable markings, such as crosshairs, star holes or circular holes, etc., for imaging measurement; the cubic beam splitter prism 6 after the posture adjustment is retained; and the parallel reference beam 90 and the illumination beam for imaging the objective lens (not shown in the figure) are turned on at the same time; When the camera 1 is located at the first axial position 11, the absolute position of the imaging spot of the objective lens on the camera target surface is counted as the first imaging spot P11; the absolute position of the spot of the parallel reference beam on the camera target surface is counted as the first reference spot P10; The camera 1 moves axially by ΔZ to a second axial position 12, the absolute position of the imaging spot of the objective lens on the target surface of the camera is counted as the second imaging spot P21, and the absolute position of the spot of the parallel reference beam on the target surface of the camera is counted as the second reference spot P20; Step 4: Calculation of axis offset The change in the distance M between the objective imaging spot and the reference spot at different Z positions is calculated as ΔM, and ΔM=(P11-P10)-(P21-P20); then tanα=ΔM / ΔZ, where α is the inclination angle of the optical axis of the tube lens after removing the influence of the tilt of the camera motion axis.

[0036] According to the formula tanα=ΔL / f, the corresponding axial deviation of the tube lens ΔL= f·tanα is calculated.

[0037] The multi-magnification imaging system axial deviation detection method and system of this example measures the axial deviation of the tube lens and the objective lens based on the reference beam and defocus imaging method, uses the reflected beam of the cubic beamsplitter prism as the reference beam, and combines the defocus imaging method to measure the optical axis tilt, thereby realizing the axial deviation measurement of the tube lens module and the objective lens with multiple magnifications. Moreover, because the reflected beam of the cubic beamsplitter prism is used as the reference beam for axial deviation measurement, the measurement accuracy is independent of the camera's motion axis, thereby eliminating the influence of the camera's motion axis tilt, and further improving the detection accuracy.

[0038] Embodiment 2: The difference between this example and the first embodiment is mainly that the order of executing the steps is different, as follows: Step 1: Defocus Imaging Measurement A marking plate (not shown in the figure) for measurement is placed on the object side of the objective lens 4, and the marking plate has suitable markings, such as crosshairs or star holes, for imaging measurement; an illumination beam (not shown in the figure) for imaging the objective lens is turned on; When the camera 1 is located at the first axial position 11, the absolute position of the imaging spot of the objective lens on the target surface of the camera is counted as the first imaging spot P11; The camera moves axially by ΔZ to a second axial position 12, and the absolute position of the imaging spot of the objective lens on the target surface of the camera is counted as the second imaging spot P21; Step 2: Collimator Equal Reference Beam Calibration A calibration reflection flat crystal 72 is placed on the side of the mechanical reference plane on the image side of the tube lens 3, and the reflection surface of the calibration reflection flat crystal 72 is perpendicular to the mechanical reference plane on the image side of the tube lens 3; no cubic beam splitter prism is placed at this time; the parallel reference light beam 90 emitted by the collimator (not shown in the figure) is irradiated to the reflection surface of the calibration reflection flat crystal 72, and returns to the collimator after reflection; according to the measurement indication of the collimator, the posture of the collimator is adjusted so that the parallel reference light beam 90 emitted by the collimator is perpendicular to the reflection surface of the calibration reflection flat crystal 72. At this time, the calibration of the parallel reference light beam 90 is completed.

[0039] Step 3: Prism attitude calibration Please combine Figure 4 and Figure 5As shown, a reference reflection flat crystal 71 is placed on the mechanical reference plane above the tube lens 3, and a cubic beam splitter prism 6 is placed between the camera 1 and the reference reflection flat crystal 71. The calibrated parallel reference light beam 90 emitted by the parallel light tube is irradiated into the cubic beam splitter prism 6; the parallel reference light beam 90 is divided into two paths by the cubic beam splitter prism 6, one of which passes through the second interface 62-fifth interface 65-third interface 63-reference reflection flat crystal 71-third interface 63-fifth interface 65-first interface 61-camera; the other light beam passes through the second interface 62-fifth interface 65-fourth interface 64-fifth interface 65-first interface 61-camera; the two light beams form two light spots on the camera.

[0040] The cubic beam splitter prism 6 is adjusted so that the two light spots overlap on the camera target surface 10 of the camera 1. At this time, the cubic beam splitter prism 6 is adjusted to be parallel to the reference reflection flat crystal 71. The overlapping light spot is recorded as P0 and used as the reference light spot for subsequent measurement.

[0041] If the Z-axis of the camera is tilted, the position of the spot P0 on the camera target surface will change when the camera 1 moves in the Z direction. Therefore, the change in the position of P0 during the Z-axis movement of the camera can be used to characterize the tilt of the Z-axis of the camera, and a reference deduction can be made in subsequent measurements. After deducting the position change, the calculation can correct the tilt of the Z-axis, thus avoiding the tilt affecting the measurement result of the tube lens axis offset.

[0042] Step 4: Reference spot imaging measurement Remove the reference reflective flat crystal 71; Keep the cubic beam splitter prism 6 after adjusting the posture, and start the parallel reference beam 90; When the camera 1 is located at the first axial position, the absolute position of the spot of the parallel reference beam 90 on the camera target surface is counted as the first reference spot P10; The camera moves axially ΔZ to a second axial position, and the absolute position of the spot of the parallel reference beam 90 on the camera target surface is counted as the second reference spot P20; Step 5: Calculation of axis offset The change in the distance M between the objective imaging spot and the reference spot at different Z positions is calculated as ΔM, and ΔM=(P11-P10)-(P21-P20); then tanα=ΔM / ΔZ, where α is the inclination angle of the optical axis of the tube lens after removing the influence of the tilt of the camera motion axis.

[0043] According to the formula tanα=ΔL / f, the corresponding axial deviation of the tube lens ΔL= f·tanα is calculated.

[0044] The multi-magnification imaging system axial deviation detection method and system of this example measures the axial deviation of the tube lens and the objective lens based on the reference beam and defocus imaging method, uses the reflected beam of the cubic beamsplitter prism as the reference beam, and combines the defocus imaging method to measure the optical axis tilt, thereby realizing the axial deviation measurement of the tube lens module and the objective lens with multiple magnifications. Moreover, because the reflected beam of the cubic beamsplitter prism is used as the reference beam for axial deviation measurement, the measurement accuracy is independent of the camera's motion axis, thereby eliminating the influence of the camera's motion axis tilt, and further improving the detection accuracy.

[0045] Embodiment three: In this example, on the basis of the above-mentioned embodiment, the calibration reflection unit and the reference reflection unit are combined, that is, the two adopt an integrated structure, the calibration reflection flat crystal 72 and the reference reflection flat crystal 71 are perpendicular to each other, and are integrated into an L-shaped reflection flat crystal. In this way, when setting, one arm of the L-shaped reflection flat crystal is directly set on the mechanical reference plane of the image side of the tube lens 3, as the reference reflection flat crystal 71; at this time, the other arm is perpendicular to the mechanical reference plane of the image side of the tube lens 3, as the calibration reflection flat crystal 72. The position adjustment of the two relative to the mechanical reference plane of the image side of the tube lens 3 is completed at one time, and it is more accurate.

[0046] The above specific examples are used to illustrate the present invention, which is only used to help understand the present invention and is not intended to limit the present invention. For technicians in the technical field to which the present invention belongs, they can also make some simple deductions, deformations or substitutions based on the ideas of the present invention. For example, the beam splitter can also use other types of beam splitters, as long as one of the light beams remains perpendicular to the mechanical surface of the tube lens and can be irradiated to the camera for the purpose of monitoring and calibrating the camera motion axis. As for the axis deviation detection method for a multi-magnification imaging system of the present invention, those skilled in the art can also change or adjust the execution order in the specific execution steps according to the specific circumstances, and still achieve the purpose of the present invention.

Claims

1. A method for detecting axis deviation of a multi-magnification imaging system; comprising the following steps: 1) Beam splitter settings: A beam splitter is arranged on the opposite side of the tube image, and a parallel reference beam is used to calibrate the attitude of the beam splitter until the light spots formed by at least two beams emitted by the beam splitter overlap on the camera; 2) Measurement of the first imaging light spot position: The camera is located at the first axial position, a marking plate for imaging measurement is placed on the object side of the objective lens, the illumination beam of the objective lens imaging is turned on, and the absolute position of the objective lens imaging light spot on the camera target surface is counted as the first imaging light spot position P11; 3) First reference light spot position measurement: the camera is located at the first axial position, the parallel reference beam is turned on, and the absolute position of the light spot formed by the parallel reference beam is recorded as the first reference light spot position P10; 4) Measurement of the second imaging spot position: The camera is located at the second axial position, a marking plate for imaging measurement is placed on the object side of the objective lens, the illumination beam of the objective lens imaging is turned on, and the absolute position of the objective lens imaging spot on the camera target surface is counted as the second imaging spot position P21; 5) Second reference light spot position measurement: the camera is located at the second axial position, the parallel reference beam is turned on, and the absolute position of the light spot formed by the parallel reference beam is recorded as the second reference light spot position P20; 6) Calculation of axis offset: Record the axial movement distance ΔZ between the first axial position and the second axial position of the camera; Calculate the change in the center distance M between the imaging spot position and the reference spot position under different camera axial positions, which is calculated as ΔM=(P11-P10)-(P21-P20); According to tanα=ΔM / ΔZ, where α is the inclination angle of the optical axis of the tube lens after removing the influence of the camera motion axis inclination; Calculate the value of α; According to the formula tanα=ΔL / f, where f is the focal length of the tube lens, the corresponding axis offset ΔL= f·tanα of the tube lens is calculated; The execution order of step 2) is any one of the following: before step 1), after step 1) and before step 6); the execution order of step 4) is any one of the following: before step 1), after step 1) and before step 6).

2. The method for detecting axis deviation of a multi-magnification imaging system according to claim 1, characterized in that: In the beam splitter setting step, the step of calibrating the beam splitter posture includes: A reference reflective element is arranged on the image-side mechanical reference plane of the tube lens; The beam splitter is arranged between the camera and the reference reflective element, and the parallel reference beam is irradiated into the beam splitter; The beam splitter splits the parallel reference beam into at least two beams; One path of the light beam passes through a beam splitter-reference reflective element-beam splitter-camera, and the other path of the light beam passes through a beam splitter-camera; the two paths of the light beam form two light spots on the camera; The posture of the beam splitter is adjusted so that the two light spots overlap on the camera. At this time, the posture of the beam splitter relative to the reference reflective element has been adjusted to be parallel.

3. The method for detecting axis deviation of a multi-magnification imaging system according to claim 2, characterized in that: The method also includes the step of calibrating the parallel reference beam: A calibration reflective element is arranged on the image side mechanical reference plane of the tube lens, wherein the reflective surface of the calibration reflective element is perpendicular to the image side mechanical reference plane of the tube lens; The light beam emitted by the parallel light generator is irradiated onto the surface of the calibration reflective element, and then returns to the parallel light generator after being reflected; According to the measurement indication of the parallel light generator, the posture of the parallel light generator is adjusted so that the outgoing light beam of the parallel light generator is perpendicular to the reflective surface of the calibration reflective element; At this time, the outgoing light beam is calibrated as the parallel reference light beam.

4. The method for detecting axis deviation of a multi-magnification imaging system according to claim 2 or 3, characterized in that: The beam splitter is a cubic beam splitter prism, which splits the parallel reference beam into two paths.

5. The method for detecting axis deviation of a multi-magnification imaging system according to claim 3, characterized in that: The parallel light generator is a parallel light tube.

6. The method for detecting axis deviation of a multi-magnification imaging system according to claim 3, characterized in that: The calibration reflective element and the reference reflective element are reflective flat crystals.

7. The method for detecting axis deviation of a multi-magnification imaging system according to claim 2 or 3, characterized in that: The marking plate carries markings suitable for imaging measurement, including but not limited to crosshairs, star holes or circular holes.

8. The method for detecting axis deviation of a multi-magnification imaging system according to claim 4, characterized in that: The first interface, the second interface and the third interface of the cubic beam splitter prism are high-transmittance surfaces coated with anti-reflection films, the fourth interface is a reflective surface coated with a reflective film, and the fifth interface is a semi-transparent and semi-reflective surface coated with a beam splitting film.

9. The method for detecting axis deviation of a multi-magnification imaging system according to claim 6, characterized in that: The calibration reflective element and the reference reflective element are integrated into an L-shaped reflective flat crystal, and two arms of the L-shape are perpendicular to each other.

10. A multi-magnification imaging system axis deviation detection system, characterized in that: It comprises an objective lens, a plurality of tube lenses, a tube lens switching structure, a Z-axis motion stage, a camera, a beam splitter and a marking plate; the tube lens switching structure carries the plurality of tube lenses and is used to move in the horizontal direction to realize the switching of different tube lenses; the camera is mounted on the Z-axis adjustment structure and can be moved up and down and the image plane can be focused; the beam splitter is arranged between the image side of the tube lens and the object side of the camera, and is calibrated in posture until the light spots formed on the camera by at least two light beams generated by parallel reference light beams overlap; the marking plate is used to be placed on the object side of the objective lens and form an imaging light spot on the camera.

11. The multi-magnification imaging system axis deviation detection system according to claim 10, characterized in that: It also includes a reference reflective element, which is arranged on the image-side mechanical reference plane of the tube lens; and is used for: when the reference light beam is split into at least two light beams by the beam splitter, one of the light beams passes through the beam splitter-reference reflective element-beam splitter-camera, and the other light beam passes through the beam splitter-camera; the two light beams form two light spots on the camera; the posture of the beam splitter is adjusted so that the two light spots overlap on the camera, and at this time, the posture of the beam splitter relative to the reference reflective element has been adjusted to be parallel.

12. The multi-magnification imaging system axis deviation detection system according to claim 11, characterized in that: It also includes a parallel light generator and a calibration reflective element, wherein the parallel light generator and the calibration reflective element are respectively arranged on the side of the beam splitter, and the reflective surface of the calibration reflective element is perpendicular to the image side mechanical reference surface of the tube lens; Used to: irradiate the outgoing light beam of the parallel light generator to the surface of the calibration reflective element, and return to the parallel light generator after reflection; adjust the posture of the parallel light generator according to the measurement indication of the parallel light generator, so that the outgoing light beam of the parallel light generator is perpendicular to the reflective surface of the calibration reflective element; at this time, the outgoing light beam is calibrated as the reference light beam.

13. The multi-magnification imaging system axis deviation detection system according to claim 11 or 12, characterized in that: The beam splitter is a cubic beam splitter prism.

14. The multi-magnification imaging system axis deviation detection system according to claim 12, characterized in that: The parallel light generator is a parallel light tube.

15. The multi-magnification imaging system axis deviation detection system according to claim 12, characterized in that: The calibration reflective element and the reference reflective element are reflective flat crystals.

16. The multi-magnification imaging system axis deviation detection system according to claim 13, characterized in that: The first interface, the second interface and the third interface of the cubic beam splitter prism are high-transmittance surfaces coated with anti-reflection films, the fourth interface is a reflective surface coated with a reflective film, and the fifth interface is a semi-transparent and semi-reflective surface coated with a beam splitting film.

17. The multi-magnification imaging system axis deviation detection system according to claim 15, characterized in that: The calibration reflective element and the reference reflective element are integrated into an L-shaped reflective flat crystal, and two arms of the L-shape are perpendicular to each other.

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