37 results about "Köhler illumination" patented technology

The invention provides a microscope objective optimization method and electronic equipment, and relates to the technical field of microscopic imaging. The method comprises the following steps: acquiring initial design parameters of a microscope objective; respectively calculating the imaging quality of the microscope objective and the total ghost image intensity of the microscope objective based on the Kohler illumination system according to the initial design parameters of the microscope objective; according to the imaging quality and the total ghost image intensity of the microscope objective, a preset lens evaluation function is constructed, and the target design parameters of each target lens when the imaging quality meets the first preset requirement and the total ghost image intensity meets the second preset requirement are iteratively calculated, so that compared with an existing mode of determining through multiple tests, the optimization efficiency can be improved; and through introduction of the preset lens evaluation function, comprehensive evaluation can be realized, and the optimization effect is ensured.

The invention provides an adjustment method of detection equipment, and the detection equipment sequentially comprises an objective lens, a spectroscope, a barrel lens and a detector from an object space to an image space, and also comprises a Kohler illumination module. The illumination light beam is emitted from the Kohler illumination module and is transmitted to the objective lens through the spectroscope, when the object to be detected is arranged on one side, far away from the spectroscope, of the objective lens, the illumination light beam emitted from the objective lens is reflected to obtain a reflected light beam, and the reflected light beam sequentially passes through the objective lens, the spectroscope and the barrel lens to reach the detector. After an aperture diaphragm is inserted into the Kohler illumination module and an auxiliary lens is arranged between the barrel lens and the detector, obtaining a first light spot position of a light spot formed by the aperture diaphragm at an entrance pupil of the objective lens through the detector; and under the condition that the Kohler illumination module does not provide the illumination light beam and the light source is used as an object to be detected, acquiring a second light spot position of the light spot of the entrance pupil of the objective lens through the detector, adjusting the position of the aperture diaphragm according to the first light spot position and the second light spot position, and aligning the illumination optical axis and the imaging optical axis.

The embodiments of the present disclosure provide a method for an image simulation generation based on a near-field simulation of a computational electromagnetic field, the method comprising: constructing a simulated three-dimensional model based on model parameters; constructing a simulated Kohler illumination model based on a light source parameter; using a degree of similarity change in a synthesized image under incremental aperture diaphragm sampling points as a criterion for approximate convergence of the simulation to determine a count of samples to be used for a balancing combination of simulation cost and accuracy; an optical simulation is performed based on the simulated three-dimensional model and the simulated Kohler illumination model, and a far-field electromagnetic field distribution data is obtained to obtain a simulated image by synthesizing the image. In the generation of a large count of simulated images on the basis of pseudo-random defect dataset generation may be further realized, in the acquisition of a large count of datasets, the dataset of defect inspection model may be trained, in order to achieve a direct detection for patterned wafer defective images and solve the problem of difficult access to reference images in a process of patterned wafer defect detection.

The invention provides a super-structure lens condenser and a microscopic imaging lighting device, and belongs to the technical field of microscopic imaging. The technical problems that a traditional Kohler illumination collecting lens is large in caliber, thickness and weight, high in price and not beneficial to light weight and miniaturization of a microscopic system are solved, the technical scheme is that the super-structure lens collecting lens achieves abrupt change of a light field phase through interaction of a micro-nano structure and the light field, and the light field phase change is achieved through the super-structure lens collecting lens. Therefore, the light propagation direction is changed, and the micro-nano structures of the plane lens and the super-structure lens condenser for realizing light beam convergence are periodically arranged according to a certain interval. The beneficial effects are that the super-structure lens is utilized to perform light beam deflection and convergence on a plane by utilizing phase mutation, the limitation that a traditional lens needs a convex surface type or a plurality of lenses to realize large numerical aperture condensation is solved, the limitation on the surface curvature and the transverse size during processing is solved, the longitudinal size of the condensing lens is reduced, and the processing efficiency is improved. And miniaturization of a microscopic imaging system is facilitated.

This invention relates to the field of water radiance measurement technology, and particularly to an enhanced water radiance sensor based on a polarizing filter. The sensor comprises a polarizing filter, a Kohler illumination system, a shaping fiber bundle, a spectrometer, and a host computer, arranged sequentially. The polarizing filter is positioned at a preset position at the front end of the optical path of the Kohler illumination system, which converts natural light from the water surface into a uniform and controllable light source. The incident end of the shaping fiber bundle is connected to the Kohler illumination system, and the exit end is connected to the spectrometer. The spectrometer is connected to the host computer. The water radiance passes sequentially through the polarizing filter, the Kohler illumination system, and the shaping fiber bundle before entering the spectrometer. The spectrometer converts the received optical signal into an electrical signal and transmits it to the host computer. The advantage of this invention is that by employing the Kohler illumination system, the field of view of the enhanced water radiance sensor is reduced to ±2°, solving the problem of poor glare suppression under large field of view in traditional sensors.

The invention discloses an angle continuously adjustable super-resolution microscope illumination device and method. The device comprises a light beam coupling assembly; an LED-DMD excitation light path and a digital micromirror array perform intensity modulation on Kohler illumination light according to a loaded intensity distribution reference pattern, a first light beam is reflected, and the first light beam is projected to a sample plane through a light beam coupling assembly and a conjugate light path in sequence; an SLM-Laser excitation / light control light path, a spatial light modulator performs phase modulation on parallel light according to a loaded phase distribution reference pattern to generate a second light beam, and the second light beam is coupled with the first light beam through a light beam coupling assembly and then is projected to a sample plane; the excitation mode switching module is used for switching a conjugate surface to realize TIRF illumination or spot scanning excitation; the control system realizes seamless switching between a preset light control imaging mode and a real-time light control imaging mode. The problems that a traditional super-resolution microscope is single in function, high in phototoxicity, poor in adaptability and the like are solved, and a more powerful imaging platform can be provided for biomedical research.

According to the full-field coherence tomography device and method based on ultrasonic rotation and bidirectional interference, a Kohler illumination system forms parallel light which enters an interference and shunt unit, and the interference and shunt unit divides the entering light into a reference arm and a sample arm; the sample arm unit divides a sample arm light path into two sample light paths to irradiate the upper side and the lower side of the same sample; the reference arm unit realizes optical path selective matching of phase displacement and two sample optical paths; the ultrasonic rotating unit enables the sample to be in a non-contact suspension state and rotate according to a set angle so as to obtain multi-direction interference information; the imaging and acquisition unit focuses and detects light returned by the reference arm and the sample arm; and the switching and fusion unit switches the state of the reference arm, so that the reference arm is respectively matched with the two sample light paths, interference acquisition, demodulation and three-dimensional reconstruction of interference fringes and fusion of up-down bidirectional and multi-angle data are completed, and a high-penetration three-dimensional imaging result is obtained. According to the invention, the penetration depth can be enhanced, the three-dimensional reconstruction quality is improved, and non-contact operation is realized.

The application discloses an optical element subsurface defect detection method and system based on phase contrast digital holography, and belongs to the field of precision measurement technology; the system adopts annular Bessel beam Kohler illumination, utilizes polarization modulation technology and a specially-made polarization contrast ring to realize synchronous four-step phase shift high-speed quantitative phase measurement in a U-shaped light path; the method acquires complex amplitude through a polarization camera, compensates for resolution loss by using a self-supervision super-resolution reconstruction algorithm fused with a physical model; full-field and local inverse diffraction reconstruction is carried out based on angular spectrum diffraction theory, high-precision depth positioning is realized based on the diffraction light complex amplitude distribution characteristics as a focusing criterion; three-dimensional information representation of defects is realized in combination with an optical field scattering and diffraction model and a machine learning algorithm; the application can realize high-sensitivity, high-signal-to-noise ratio, real-time in-situ quantitative detection and three-dimensional reconstruction of submicron defects without significantly increasing the cost.

The invention relates to the technical field of semiconductor manufacturing, and discloses a mask detection device and method based on a light path technology, and the device comprises an optical imaging system, a dark field illumination system, a reflection coaxial light illumination system, a transmission coaxial light illumination system, and an automatic focusing system. Wherein the dark field illumination system is arranged in the bottom area of the optical imaging system, a mask to be detected is arranged at the bottom of the dark field illumination system, the reflection coaxial light illumination system is arranged in the side edge area of the optical imaging system, and the transmission coaxial light illumination system is arranged in the bottom area of the mask. A transmission light path adopts a four-stage compression design of a light source, a light receiving lens, a field lens and a condensing lens, and is matched with a plane reflector to fold the light path, so that the total length is shortened by 35% compared with that of a Kohler illumination system, and the Kohler illumination system is shorter in light path, smaller in occupied space and convenient to integrate and use compared with a traditional Kohler illumination system.

The invention provides an adjustment method of detection equipment, and the detection equipment sequentially comprises an objective lens, a spectroscope, a barrel lens and a detector from an object space to an image space, and also comprises a Kohler illumination module. The illumination light beam is emitted from the Kohler illumination module and is transmitted to the objective lens through the spectroscope, when the object to be detected is arranged on one side, far away from the spectroscope, of the objective lens, the illumination light beam emitted from the objective lens is reflected to obtain a reflected light beam, and the reflected light beam sequentially passes through the objective lens, the spectroscope and the barrel lens to reach the detector. After an aperture diaphragm is inserted into the Kohler illumination module and a first auxiliary lens is arranged between a barrel lens and a spectroscope, acquiring a first light spot position of a light spot formed by the aperture diaphragm at an entrance pupil of an objective lens through a detector; under the condition that the Kohler illumination module does not provide the illumination light beam and the light source is used as an object to be detected, acquiring a second light spot position of the light spot of the entrance pupil of the objective lens through the detector; and adjusting the position of the aperture diaphragm according to the first light spot position and the second light spot position, and aligning the illumination optical axis and the imaging optical axis.

The invention discloses a microscopic imaging system for dual-band LED illumination and a use method thereof.The microscopic imaging system comprises a dual-band illumination module, a double telecentric objective lens, a high-power imaging system and a low-power imaging system.The dual-band illumination module adopts a red light and blue light dual-band LED light source and combines the Kohler illumination technology to achieve the high-uniformity illumination effect; the high-magnification imaging system and the low-magnification imaging system both adopt double telecentric optical design, telecentric degrees of an object space and an image space are ensured to be smaller than or equal to 0.2 degree, meanwhile, the characteristic of large depth of field is obtained through collaborative design of optical parameters, a high-precision automatic focusing module is integrated, imaging definition is judged through an image definition evaluation algorithm, a high-magnification telecentric imaging lens group and a low-magnification telecentric imaging lens group are automatically adjusted, and rapid focusing is achieved. The problems that a traditional microscopic system is large in magnification error, insufficient in depth of field, low in focusing efficiency and poor in illumination stability are solved, and high-magnification and low-magnification simultaneous imaging is achieved.

Disclosed in this disclosure is a method for super-resolution microscopic interferometric measurement based on broadband annular radially polarized light, where a broad-spectrum light source with an extended surface is selected; uniform illumination covering a to-be-tested FOV and having a certain aperture angle is provided using a Kohler illumination system; a two-stage relay system is designed, and amplitude and polarization of a full-FOV beam is modulated by a liquid crystal spatial light modulator and a vortex waveplate; broadband annular radially polarized light is focused based on the extended surface light source and a microscopic objective lens with a high numerical aperture to implement super-resolution microscopic interference imaging of a sample; and super-resolution topography measurement directed at a surface of a microstructure is implemented combined with phase-shifting interferometry.

A microscope is configured for brightfield and darkfield illumination using Kohler illumination. An illuminator provides a first radiation pattern that passes through the microscope's objective lens for brightfield illumination and provides at least one second radiation pattern that also passes through the objective lens for darkfield illumination.

The present application provides a method for calibrating the optimal diffuser position of a Kohler illumination system. First, an initial measured object dynamic image is collected by an image sensor when a diffuser rotates to an initial position, and whether the deviation displacement vector of at least one speckle keeps converging in a predetermined range is analyzed according to the initial measured object dynamic image. Then, if the deviation displacement vector of the speckle keeps converging in the predetermined range, the initial position of the diffuser is defined as the optimal diffuser position with the best light field uniformity. Otherwise, the position of the diffuser is adjusted until the deviation displacement vector of the speckle keeps converging in the predetermined range, and the corrected position of the diffuser is defined as the optimal position with the best light field uniformity.

The application discloses a low-cost universal virtual phase contrast method and device based on a cylindrical lens; the method comprises the following steps: adding a cylindrical lens in a common bright field microscope of a Kohler illumination structure, so that the illumination light source forms asymmetric illumination, and a bright field image is obtained; a strong image carries more phase information; the obtained bright field image is input into a conditional generative adversarial neural network under credibility negative feedback after training, and a virtual phase contrast image is generated, so that the effect equivalent to a standard phase contrast image is realized at low cost. The application not only realizes the effect similar to the standard phase contrast microscope at low cost, but also is superior to the image of the standard phase contrast microscope in some applications (cell segmentation, cell recognition, etc.), and expands the application potential of the application in the fields of biomedicine, material science and the like.

The utility model relates to the technical field of optical detection, in particular to a lighting system. By adopting the illumination structure formed by coupling at least two light sources, the problem of insufficient illumination brightness in a tiny area can be solved, the system can be used in cooperation with multiple line scanning cameras at the same time, the detection rate can be improved, the system adapts to a specific rapid detection field lens, and implementation is easy. The whole lighting system is clear in modular structure, the number of lenses is reduced, and production cost is reduced. According to the double telecentric Kohler illumination, high-brightness and high-uniformity illumination can be realized, a fuzzy edge caused by diffuse reflection can be eliminated, and the illumination view field and the angle of incident light can be controlled through the view field diaphragm and the pupil control module, so that the defect detection precision is improved.

The invention provides a method for adjusting the position of an optimized diffusion sheet of a Kohler lighting system, which is used for correcting the Kohler lighting system, and comprises the following steps: firstly, when a diffusion sheet rotates, acquiring an initial dynamic image of a measured object when the diffusion sheet is positioned at an initial position by using an image sensor; analyzing whether a deviation displacement vector of at least one speckle is converged in a preset range or not according to the initial dynamic image of the measured object; then, if the deviation displacement vector of the speckle is kept converged in a preset range, defining the initial position of the diffusion sheet as an optimized diffusion sheet position with the optimal light field uniformity, otherwise, adjusting the position of the diffusion sheet until the deviation displacement vector of the speckle is kept converged in the preset range, and defining the corrected position of the diffusion sheet as the optimal position with the optimal light field uniformity.

The present invention provides a semiconductor measurement system and measurement method, and a storage medium. The semiconductor measurement system comprises a Köhler illumination module, an optical module, and a detection module. The Köhler illumination module sequentially comprises a broad-spectrum light source, a wavelength selection unit, a first lens, a field diaphragm, a second lens, aperture diaphragms, and objective lenses. The optical module comprises a first light splitting unit and a second light splitting unit. The detection module comprises a spectrograph and a camera. By simultaneously providing the Köhler illumination module having the wavelength selection unit, the high-magnification first objective lens, the low-magnification second objective lens, the spectrograph, and the camera, the present invention can implement both large-area thin film thickness measurement, and small-area thin film thickness measurement and microstructure detection, can implement "one-stop" measurement of various semiconductor parameters, and thus can effectively reduce the economic cost of semiconductor measurement and improve the semiconductor measurement efficiency.

The invention belongs to the related technical field of nanoscale three-dimensional shape measurement, and discloses a flying shooting type three-dimensional white light interference shape measurement system, which comprises a linear displacement table (13), a Kohler illumination system (100), a Linnik type interference objective lens (200), an imaging lens (11) and a high-speed camera (12), the Linnik type interference objective lens (200) comprises an objective lens I (8), a spectroscope (7), a reflector (10) and an objective lens II (9); the Kohler illumination system (100), the spectroscope (7), the objective lens II (9) and the reflector (10) are sequentially arranged on a horizontal illumination light path (14); and the objective lens I (8), the spectroscope (7), the imaging lens (11) and the high-speed camera (12) are sequentially arranged on a vertical imaging light path (15). The system can realize high-speed, high-precision, large-view-field and large-measurement-range three-dimensional shape measurement.

The present invention belongs to the technical field related to nanoscale three-dimensional shape measurement, and discloses a flying-type three-dimensional white light interferometric shape measurement system, comprising a linear translation stage (13), a Kohler illumination system (100), a Linnik-type interference objective lens (200), an imaging lens (11), and a high-speed camera (12); the Linnik-type interference objective lens (200) comprises an objective lens 1 (8), a beam splitter (7), a reflector (10), and an objective lens 2 (9); the Kohler illumination system (100), the beam splitter (7), the objective lens 2 (9), and the reflector (10) are sequentially arranged on a horizontal illumination light path (14); the objective lens 1 (8), the beam splitter (7), the imaging lens (11), and the high-speed camera (12) are sequentially arranged on a vertical imaging light path (15). The system can realize high-speed, high-precision, large-field-of-view, and large-measurement-range three-dimensional shape measurement.

The invention discloses a device and method for capturing and operating biomass aerosol based on optical fiber optical tweezers, and the device comprises a laser device, and an isolator, a beam expanding assembly, a first half-wave plate and a polarization beam splitter which are sequentially arranged along a light path of a laser beam, wherein the polarization beam splitter is used for dividing the laser beam into a first laser beam and a second laser beam; the system further comprises a single-mode optical fiber, a multimode optical fiber, a spatial light modulator and an aerosol capturing chamber. The first laser beam and the second laser beam are respectively coupled into the input ends of the multimode optical fiber and the single-mode optical fiber, and the output ends of the multimode optical fiber and the single-mode optical fiber enter the aerosol capturing chamber; the spatial light modulator is used for modulating an input light field of the multimode optical fiber to create an optimized focus in an output light field; the aerosol capture chamber is equipped with a first CMOS camera, a long focal length objective lens and a Kohler illumination system. According to the device for capturing and operating the biomass aerosol, the two limitation problems that traditional single biomass aerosol particles are difficult to capture and control are solved.

The invention relates to a surface topography measuring method, which is used for measuring the relative height of a surface partition of an object to be measured by using a Kohler illumination system, and comprises the following steps of: firstly, capturing a dynamic image of the object to be measured by using an image sensor when a diffusion sheet of the Kohler illumination system rotates; dividing the dynamic image into a plurality of regional dynamic images according to the plurality of analysis regions, and analyzing the plurality of speckles for the plurality of regional dynamic images to generate a plurality of deviation displacements corresponding to the plurality of analysis regions; and finally, establishing a corresponding relation between a displacement range and the relative heights, thereby defining a plurality of relative heights corresponding to the plurality of analysis areas.

The present application provides an optimization method for a microscope objective lens and an electronic device, relating to the field of microscopic imaging technology. The method includes: obtaining initial design parameters of the microscope objective lens; respectively calculating the imaging quality of the microscope objective lens and the total ghost image intensity of the microscope objective lens based on a Köhler illumination system according to the initial design parameters of the microscope objective lens; constructing a preset lens evaluation function according to the imaging quality and the total ghost image intensity of the microscope objective lens, and iteratively calculating the target design parameters of each target lens when the imaging quality meets a first preset requirement and the total ghost image intensity meets a second preset requirement. Compared with the existing method determined through multiple experiments, the optimization efficiency can be improved, and through the introduction of the preset lens evaluation function, comprehensive evaluation can be realized to ensure the optimization effect.

The invention discloses a light current microscopic device with light modulation and real-time monitoring functions and a modulation method. The device comprises a bottom plate, a microscopic system support, a sample table, an objective lens, a microscopic imaging layer, a wide-field light excitation layer and a point focusing light excitation layer. Wherein the microscopic imaging layer collimates, filters, reflects and focuses broadband light to a rear focal plane of the objective lens to realize Kohler illumination, and sample light returned by the objective lens is reflected and imaged to the camera; the wide-field light excitation layer collimates the wide-field light, adjusts the power, polarization direction and light spot shape, and reflects and focuses the wide-field light to the rear focal plane of the objective lens to realize wide-field light excitation; after the point focusing light excitation layer collimates and reflects laser and adjusts power, the polarization direction and the spot size are adjusted, and the laser is focused to a sample table through an objective lens after being reflected for multiple times to achieve point focusing light excitation. The device can modulate the laser wavelength, power and the like, monitors the optical power in real time, meets the excitation light modulation requirement, is compatible with more tests and reduces the operation complexity.

The invention discloses an angle resolution spectrum and surface shape in-situ measurement device and method based on white light interference. The measurement device comprises an illumination module, a microscopic interference module, a rear focal plane image acquisition module and an object plane image acquisition module. White light emitted by the illumination module is converted into linearly polarized light through the polarizer and the relay system, and the linearly polarized light is relayed to a rear focal plane of an objective lens of the microscopic interference module to form Kohler illumination. After being split by a beam splitter prism in the microscopic interference module, illumination light is respectively reflected by a reference mirror and a sample to be measured and generates interference, an object plane interference pattern and a rear focal plane interference pattern are synchronously acquired by the image acquisition module, and in-situ measurement of a sample surface shape and a corresponding angular resolution spectrum under the same field of view can be realized by analyzing the interference patterns. The method has important significance for representing optical parameters of wafers, surface shapes of micro-nano optical devices such as photonic crystals and metasurfaces, a momentum space dispersion relation and key parameters such as momentum space phase distribution.

The application discloses a device and method for capturing and operating biomass aerosol based on fiber optical tweezers, which comprises a laser, an isolator, a beam expander assembly, a first half-wave plate and a polarization beam splitter for splitting the laser beam into a first laser beam and a second laser beam, which are arranged along the optical path of the laser beam in sequence, and a single-mode optical fiber, a multi-mode optical fiber, a spatial light modulator and an aerosol capture chamber; the first laser beam and the second laser beam are coupled into the input ends of the multi-mode optical fiber and the single-mode optical fiber respectively, and the output ends of the multi-mode optical fiber and the single-mode optical fiber enter the aerosol capture chamber; the spatial light modulator is used for modulating the input light field of the multi-mode optical fiber to create an optimized focal point in the output light field; and the aerosol capture chamber is provided with a first CMOS camera, a long-focus objective lens and a Kohler illumination system. The device for capturing and operating biomass aerosol of the application overcomes the two major limiting problems of traditional single biomass aerosol particle capture and operation.

The utility model discloses a kind of wafer thickness measurement systems, including pedestal, motion module, microscopic imaging module, white light interference thickness measurement module and industrial control linkage control unit. Microscopic imaging module includes microscopic illumination light source, Kohler illumination component, first light splitting module, microscopic objective lens, barrel lens, second light splitting module and imaging module;White light interference thickness measurement module includes white light source, fiber coupler, spectrometer and fiber receiving end. Imaging module and fiber receiving end are connected with shared microscopic objective lens, barrel lens via second light splitting module, and fiber receiving end is equipped with Z direction adjusting mechanism and XY adjusting mechanism;Control unit controls two light sources time-sharing work. The system can realize the visualization positioning and film thickness measurement of sample measurement area.

Systems, methods, and devices for providing Köhler illumination for inspection, under a microscope, of end connectors of fiber optic cables. In one aspect, a microscopy system provides Köhler illumination where a numerical aperture of the illumination (NAIL) is greater than a numerical aperture of imaging (NAIM). In another aspect, a reflected light microscopy system includes an array of light sources which illuminate a diffuser, which, in turn, projects the diffused light to reflect off of a beamsplitter and through an objective / condenser upon the end connector. In yet another aspect, the array of light sources may provide different light patterns to illuminate the end connector, and each light pattern may correspond to a different type of radiused end connector.

Systems, methods, and devices for providing Köhler illumination for inspection, under a microscope, of end connectors of fiber optic cables. In one aspect, a microscopy system provides Köhler illumination where a numerical aperture of the illumination (NAIL) is greater than a numerical aperture of imaging (NAIM). In another aspect, a reflected light microscopy system includes an array of light sources which illuminate a diffuser, which, in turn, projects the diffused light to reflect off of a beamsplitter and through an objective / condenser upon the end connector. In yet another aspect, the array of light sources may provide different light patterns to illuminate the end connector, and each light pattern may correspond to a different type of radiused end connector.

This application provides a method for adjusting a detection device. The detection device, from the object side to the image side, includes an objective lens, a beam splitter, a telescope, and a detector, and also includes a Kohler illumination module. An illumination beam is emitted from the Kohler illumination module, transmitted through the beam splitter to the objective lens. When the object to be tested is placed on the side of the objective lens away from the beam splitter, a reflected beam is obtained by reflecting the illumination beam emitted from the objective lens. The reflected beam passes sequentially through the objective lens, beam splitter, and telescope to the detector. After inserting an aperture stop in the Kohler illumination module and placing a first auxiliary lens between the telescope and the beam splitter, the detector obtains the first spot position of the light spot formed by the aperture stop at the entrance pupil of the objective lens. When the Kohler illumination module does not provide an illumination beam and the light source is used as the object to be tested, the detector obtains the second spot position of the light spot at the entrance pupil of the objective lens. The position of the aperture stop is adjusted according to the first and second spot positions to align the illumination optical axis and the imaging optical axis.