855 results about "Autofocus" patented technology

The invention belongs to the technical field of lens calibration, and particularly discloses and provides an optical lens production intelligent calibration system which comprises an environment coupling module, an optical detection module, a self-adaptive calibration decision module and an automatic focusing adjustment module. According to the invention, various environmental data are collected in real time through the environmental coupling module to form a time-space correlation parameter set, so that a basis is provided for suppressing environmental interference; the optical detection module generates a dynamic target sequence and synchronously acquires various parameters of the lens, so that a calibration path can be dynamically optimized; the adaptive calibration decision module not only can establish a mapping relation between environment and optical distortion, but also can calculate a focusing adjustment parameter based on multiple parameters when an error exceeds a threshold value; and the automatic focusing adjustment module controls the focusing device in real time according to the adjustment parameters and verifies the adjustment parameters, so that sorting and recalibration of qualified and unqualified lenses are realized, the calibration accuracy is comprehensively improved, and the scene adaptability of an AF algorithm is enhanced.

The invention relates to a tin ring automatic focusing laser soldering tin fixing and 3D welding spot detecting system, and belongs to the technical field of industrial automatic laser processing. The system is characterized in that a tin ring preparation module identifies pins in real time and dynamically optimizes winding parameters through visual positioning and a self-adaptive winding head, and performs defect identification and pre-repair analysis through multispectral imaging; the soldering tin positioning module is used for switching stations through a rotary table, and precise positioning and clamping of a product are realized by combining laser contour sensing and a focusing compensation algorithm; the laser tin soldering module can visually identify tin materials and automatically call welding parameters, laser power and action time are regulated and controlled in real time by establishing a regional heat conduction model, and gradient cooling is implemented after welding; and the 3D detection module adopts dual-mode scanning, constructs a welding spot three-dimensional model based on fusion data, recognizes microcracks through super-resolution processing, and discriminates the welding spot quality. And automation and intellectualization of the whole process from tin ring preparation to welding spot quality detection are achieved.

The invention discloses a patterned wafer defect detection system and method based on double-optical-comb space-time coding, and the system comprises a double-optical-comb light source module, a space coding illumination module, a time programming control module, a signal collection and processing module, and a data analysis and processing module. And the data analysis processing module receives and analyzes the restored three-dimensional shape information of the surface of the wafer to be detected, extracts defect related characteristics, establishes a mapping relation between spectral characteristics and defects, and identifies the defects on the surface of the wafer to obtain corresponding defect types and position information. According to the invention, a wafer defect detection technology based on double-optical-comb space-time coding is adopted, rapid scanning and parallel detection are realized by using a double-optical-comb interference technology, the detection efficiency is greatly improved, and absolute distance information of the wafer surface can be obtained. The result is fed back to the precise air floating motion platform, so that an automatic focusing optical path system and a feedback control part can be omitted, the detection efficiency is improved, and the size, complexity and cost of the whole wafer detection system are reduced.

Particular embodiments are directed to passthrough image generation for a mixed-reality experience. A device may determine, using an eye-tracking system of a head-mounted device, eye-tracking data associated with a user of the head-mounted device. The device may determine, based on the eye-tracking data, a desired scene depth for the user. The device may instruct a first autofocus camera of the head-mounted device to adjust a first focus distance based on the desired scene depth and capture a first image of a real-world environment of the user. The device may generate a first passthrough image based on the first image. The device may display the first passthrough image to a first eye of the user via a first display of the head-mounted device.

The invention belongs to the technical field of digital holographic measurement, and particularly relates to an optical element stress measurement and defect identification method based on a digital holographic photoelastic method. The method is realized based on a transmission-type off-axis digital holographic light path system; light beams emitted by the laser assembly are divided into reference light and object light, the object light is reflected by the surface of a sample and carries sample information, the object light and the reference light intersect in front of the CMOS camera to generate interference, the CMOS converts an interference light intensity signal into an electric signal, and holographic image processing is performed by the computer; the hologram before and after external force loading is reconstructed to obtain surface topography distribution, and the reconstruction precision is improved through the steps of positive first-order spectrum extraction, angular spectrum reconstruction automatic focusing and the like; the phase difference before and after external force loading is calculated through reconstruction complex amplitude phase extraction, and then the direction and size distribution of the principal stress of the sample are measured and calculated based on a digital photoelastic method and a stress optical law; and the defect of the optical element is identified by measuring the stress value change under the same external force loading, so that the method has important practical significance.

The invention provides a microscopic automatic focusing method and system based on image gray histogram characteristics, and the method comprises the steps: collecting an image sequence under different focal lengths, carrying out the fuzzy processing, extracting a gray histogram of each frame of image, and calculating the peak position and full width at half maximum of the histogram as the evaluation characteristics of the image definition; calculating the variance of each feature and automatically allocating a weight according to the relative response degree; and finally, comprehensively evaluating the image definition through a weighted definition scoring function, and selecting the focal length corresponding to the image with the optimal score as the optimal focusing position. The method is based on the global features of the gray histogram, is high in anti-noise capability, is adaptive to different imaging scenes through weight adaptive adjustment, is low in calculation complexity, supports real-time focusing, is especially suitable for high-noise fluorescence microscopic imaging scenes, is high in system portability, is low in operation threshold, and effectively improves the accuracy and stability of microscopic automatic focusing.

A system includes one or more memories configured to store a camera image captured with a camera; and processing circuitry in communication with the one or more memories. The processing circuitry is configured to identify, in the camera image, a first camera image portion and a second camera image portion, apply primary phase detection autofocus (PDAF) to the first camera image portion, and apply the primary PDAF and secondary PDAF to the second camera image portion. Additionally, the processing circuitry is configured to control, based on applying the primary PDAF to the first camera image portion and without applying the secondary PDAF to the first camera image portion and based on applying the primary PDAF and the secondary PDAF to the second camera image portion, the camera to bring the first camera image portion and the second camera image portion into focus.

The invention discloses a portable long-distance automatic focusing laser emission system, and relates to the technical field of automatic focusing of optical instruments. The system comprises a ranging and focusing quantization module, a focal length regulation and control module and a light spot quality quantization and regulation and control module. The focusing adaptation degree is obtained through the obtained focusing regulation and control deviation parameter, whether focal length regulation and control are carried out or not is judged, after the focal length is qualified, the light spot regulation and control deviation degree is obtained in combination with the light spot quality parameter obtained in the pre-emission process of the laser emitter, and whether light spot regulation and control are carried out or not is judged. After the light spot is qualified, a laser emission wire-mounted foreign matter removing instruction is sent to carry out laser emission for removing the target object, so that the focusing and emission precision and the light spot form in the process of emitting laser to remove the target object through the laser emission device are improved; the problem that in the prior art, when the foreign matter on the high-voltage line is removed through laser, the focusing and transmitting precision is low due to the fact that position fluctuation of the foreign matter is not fully considered is solved.

The invention discloses a reticulocyte recognition and grading system based on a blood smear, and particularly relates to the field of medical cell morphology examination, and the system comprises an image acquisition module, a staining normalization module, an instance segmentation module, an erythrocyte classification module, a reticulocyte grading module and a statistics output module. The image acquisition module adopts an automatic microscope platform to continuously scan the blood smear under a 100-time visual field, acquires a high-quality bright field channel image through an automatic focusing technology, and monitors image definition, contrast and illumination uniformity; the statistical output module is used for calculating the proportion and bluish violet intensity statistics of reticulocytes of each level, and generating a visual quality control result and a diagnostic report; according to the invention, full-automatic processing from samples to reports is realized, interpretability and high classification precision are both considered, subjective difference and omission ratio of manual microscopic examination are significantly reduced, and efficiency and consistency of clinical detection are improved.

The invention provides an automatic focusing system, an automatic focusing method and a surface defect detection method, and the method comprises the steps: controlling a plurality of light sources in a light source array to be lightened one by one according to a preset time sequence, and enabling a light beam emitted by each light source to be reflected by a corresponding to-be-detected sub-region on the surface of a to-be-detected device, and one part of the reflected light is detected as a defocus detection light spot by the defocus information acquisition unit, and the other part of the reflected light forms a detection image on the main detection camera. As the position of the defocus detection light spot and the position of the microscope objective have a mapping relation, defocus information corresponding to the defocus detection light spot can be obtained through the mapping relation, and therefore automatic focusing of the microscope objective is achieved. According to the lighting sequence of the light source, automatic focusing and imaging are sequentially carried out on each to-be-detected sub-region, so that the image detection precision can be improved, the light path hardware requirement can be reduced, the height information of the surface of the to-be-detected device can be obtained through defocusing information, surface defect detection on an object with complex three-dimensional morphology characteristics is facilitated, and the detection efficiency is improved. And the detection flexibility and precision are improved.

Various structures for a hybrid pixel array are disclosed. The hybrid pixel array includes a combination of square photodiode (PD) pixel structures and split PD pixel structures. Square PD pixel structures include one photodiode per pixel unit while split PD pixel structures include two photodiodes per pixel unit. In certain instances, square PD pixel structures are used for green light pixels and split PD pixel structures are used for blue and red light pixels in the hybrid pixel array. The combination of square PD pixel structures and split PD pixel structures provides autofocus capability with higher signal strengths. Various techniques for row addressing and readout from the hybrid pixel array are also disclosed.

The invention discloses a laser automatic focusing method, system and device for a multi-height plane and a medium, and relates to the field of automatic focusing. The method comprises the following steps: acquiring a laser spot image; according to the gray value of each column of pixel points in the laser spot image, dividing continuous pixel columns formed by plane reflection from different heights; based on the width of the to-be-focused plane and the width corresponding relation, determining a continuous pixel column formed by reflection of the to-be-focused plane as a first pixel column; and calculating a first defocusing amount of the to-be-focused plane based on the first pixel column. On the basis of the above processing, in consideration of different pixel values of laser spots reflected by the planes at different heights, continuous pixel columns reflected by the planes at different heights are divided. According to the method, the first pixel column is determined according to the width and the width corresponding relation between the height planes, and then the defocusing amount of the to-be-focused plane is calculated, so that the adverse effect caused by light spots reflected by other height planes is avoided, and the accuracy of automatic focusing is improved.

The invention discloses a stray light gray value acquisition method, an automatic focusing processing method and an automatic focusing processing system, and relates to the field of automatic focusing. The method is applied to the microscopic automatic focusing device, and comprises the following steps: adjusting the distance between a microscope objective and a reflection point corresponding to light passing through the microscope objective, or the reflection angle of the light, so that the adjusted distance or reflection angle exceeds the focusing range of the microscope objective; or an extinction assembly is additionally arranged on the outer side of the microscope objective, so that the light penetrating through the microscope objective is eliminated; theoretical light spot areas formed by stray light on the surface of the first sensor at different axial height positions of the microscope objective are calculated; and gray values corresponding to theoretical light spot areas in the actual light spot images of the microscope objective at different axial height positions are extracted and used for correcting the light spot image of the object to be measured, so that the influence of stray light on a defocusing amount calculation result is reduced. Therefore, the influence of stray light reflected by the surface of the microscope objective on the defocusing amount calculation is reduced, and the accuracy of the defocusing amount calculation is improved.

A method for detecting circularity of silicon carbide micro powder relates to the technical field of silicon carbide detection, and comprises the following steps: S1, turning on a flowing particle imager, preheating and then carrying out background detection; s2, adding standard particles into the sample pool, and enabling the flowing particle imager to perform automatic focusing; s3, adding the prepared silicon carbide micro powder sample into a sample pool, and detecting by using a flowing particle imager; and S4, storing the detection result, checking the silicon carbide micro powder particle image, and recording the detection result. The preparation of the silicon carbide micro-powder sample comprises the following steps: S31, adding the dried silicon carbide sample into a dry and clean beaker; s32, sequentially adding an impregnating compound, a dispersing agent and deionized water into the beaker; s33, carrying out ultrasonic dispersion; and S34, taking out the uniformly mixed sample. The method can solve the technical problem of detection failure caused by easy agglomeration of the silicon carbide sample when the flowing particle imager is used for detecting the circularity of the silicon carbide micro powder.

The invention discloses a CSAR self-focusing imaging method based on ABP sub-aperture processing and incoherent superposition, and the method comprises the steps: generating a plurality of sub-aperture data according to the to-be-imaged data, and carrying out the coarse imaging of all sub-aperture data, and obtaining a corresponding coarse image; performing feature extraction on all the coarse images to obtain corresponding projection vectors; performing self-focusing processing on all the projection vectors to obtain corresponding self-focusing images; and obtaining an imaging image corresponding to the to-be-imaged data through image matching and incoherent superposition processing according to the self-focusing imaging picture. According to the invention, the precision and efficiency of CSAR imaging can be improved.

The invention discloses an airborne camera equipment intelligent control method and system based on edge calculation, and relates to the field of unmanned aerial vehicle intelligent control, and the method comprises the steps: carrying out the self-inspection and initialization of an unmanned aerial vehicle after the unmanned aerial vehicle is started, and planning a flight path and a shooting point according to an inspection task issued by a control station; the unmanned aerial vehicle flies according to a planned path, airborne camera equipment starts to shoot, and an edge calculation unit processes image data in real time and performs fine identification and automatic focusing; a sensor loaded on the unmanned aerial vehicle senses the flight environment in real time, and an edge calculation unit adjusts camera parameters and flight attitudes according to sensed data; and after the inspection task is completed, the unmanned aerial vehicle automatically returns, and the ground control station analyzes and processes the collected data. By automatically planning a flight path and a shooting point, manual intervention is reduced, an edge calculation unit is introduced, automatic focusing and real-time adjustment of camera parameters can be realized according to image data and perception data, high-quality image acquisition is ensured, and secondary re-flight caused by inaccurate focus is avoided.

The invention discloses a wafer six-surface detection automatic focusing method comprising the following steps: correcting the crystal grain position through a feeding XYR platform, and obtaining a to-be-detected crystal grain image; according to a to-be-detected crystal grain image, edge points in the edge contour of the crystal grain are converted into geometric parameters by using a Hough transform algorithm, and a position compensation value of the crystal grain is calculated; determining an optimal focus position of a front / back detection station of the to-be-detected crystal grain according to the optical characteristics, the light deflection angle and the incident light intensity of the crystal grain, and adjusting the focus position of the focusing module; according to the position compensation value of the crystal grain, an electric sliding table is controlled to carry an optical camera to move in place and focus and image; and by comparing actual detection data with prediction results of the refraction deviation correction model and the crystal grain front / back focus adjustment model, the accuracy of the model is evaluated and optimized. According to the invention, the problems of position error, optical characteristic difference, refraction deviation and the like in the prior art are effectively solved, and efficient and accurate crystal grain detection is realized.

To provide a zoo lens which has a large aperture ratio and a minimized total length, offers less shift in the center of gravity while zooming and focusing and quiet autofocusing, and is suitable for video shooting.SOLUTION: A zoom lens of the present invention consists of a first lens group G1 having negative refractive power, an intermediate lens group GM having positive refractive power as a whole, a rear lens group GR, and a final lens group GN arranged in order from the object side, the intermediate lens group GM consisting of three or more lens groups including a focusing lens group configured to move along an optical axis while focusing from infinity to a short distance, and the rear lens group consisting of one or more lens groups. When zooming from the wide-angle end to the telephoto end, distances between the lens groups change as the intermediate lens group GM moves toward the object side, increasing the distance between the intermediate lens group GM and the rear lens group GR. The first lens group G1 and the final lens gup GN are stationary while zooming and focusing.SELECTED DRAWING: Figure 1

The invention relates to an infrared measurement device and a measurement method thereof, and belongs to the technical field of infrared measurement, and the infrared measurement method comprises the following steps: S100, feeding and conveying an object to be measured; step S200, acquiring and processing an image of an object to be detected, extracting and identifying an edge closed contour of the object to be detected, capturing center position data and attitude data of the object to be detected according to the edge closed contour of the object to be detected, and sending the data to a control unit; height data of the object to be measured and the height measuring unit are collected and sent to the control unit; and step S300, the control unit adjusts the position of the infrared measurement unit according to the central position data and the attitude data of the to-be-measured object and the height data of the to-be-measured object and the height measurement unit so as to focus the to-be-measured object, and performs infrared irradiation on the to-be-measured object to form infrared imaging. According to the invention, automatic focusing infrared measurement of the to-be-measured object can be realized, manual intervention is not needed, and the precision and efficiency of infrared measurement are effectively improved.

The invention discloses laser positioning / welding and laser cleaning synchronous integrated equipment and a laser positioning / welding and laser cleaning synchronous integrated method. The equipment realizes real-time positioning and automatic focusing based on welding seam tracking and optical signal processing, links two lasers to synchronously emit welding and cleaning light beams, acts on a welding pool at the same time, and is matched with shielding gas pre-injection, smoke discharge and slag removal and a special clamp to remove impurities in the welding pool in real time, generate micro-vibration stirring and promote grain refinement in the welding process. According to the equipment, key links such as workpiece clamping and positioning, automatic focusing, welding and cleaning are combined, the technological process is greatly simplified, and the compactness and the mechanical property of a welding seam of a plated part are improved.

The invention discloses an automatic focusing method, device, equipment and system of laser processing equipment and a medium, the laser processing equipment comprises a first light output module and a second light output module, the first light output module is used for outputting light spots for laser processing, and the second light output module is used for outputting light spots for indication. The automatic focusing method comprises the following steps: controlling the first light output module to output a first light spot to a workpiece, and controlling the second light output module to output a second light spot to the workpiece; controlling the first light output module to descend, and acquiring a plurality of images of the workpiece comprising the first light spot and the second light spot at different distances to obtain a plurality of images; obtaining an image with the minimum distance between the first light spot and the second light spot in the plurality of images, and taking the image as a target image; and based on the target image, adjusting the focus of the first light output module to enable the focus to be located on the machining surface of the workpiece. The problem that automatic focusing cannot be achieved is solved.

Disclosed are systems and techniques for improving focus performance. For example, a computing device can categorize each grid of a plurality of grids of a region of interest (ROI) of one or more images into one of a first category or a second category based on a respective confidence value corresponding to a respective defocusing value for each grid of the plurality of grids. The computing device can adjust at least one confidence value corresponding to at least one defocusing value for at least one grid of the plurality of grids categorized into the first category to be lower than a confidence value threshold. The computing device can determine a position for a lens of the camera based on defocusing values of the plurality of grids having corresponding confidence values that are higher than the confidence value threshold.

An autofocus control method and an imaging device are provided. [Solution] The method includes collecting an image of a subject, and if the image includes a face area, determining a first target focus adjustment evaluation area, and if the image includes a face area, determining a target provisional area in the first target focus adjustment evaluation area and a second target focus adjustment evaluation area excluding the target provisional area, wherein the target provisional area includes at least one of an eye area, an eyeglass area, and a teeth area, adjusting a focus lens position and collecting an image after the adjustment, obtaining a contrast value at each focus lens position in the second target focus adjustment evaluation area, calculating a corresponding focus adjustment evaluation value for the first target focus adjustment evaluation area based on at least the contrast value of the second target focus adjustment evaluation area, determining a target focus position based on the focus adjustment evaluation value, and adjusting the position of the focus lens to the target focus position.

The invention discloses an automatic focusing method and system based on a TFT liquid crystal panel, and particularly relates to the technical field of TFT liquid crystal panels. By acquiring image data of a shooting scene, calculating an optimal focal length adjustment parameter and applying a control voltage to dynamically adjust the refractive index of a liquid crystal panel, focus adjustment of an optical system is realized, an adjusted image is acquired, image quality is compared by using a definition evaluation algorithm, if the definition does not reach a preset threshold value, voltage control is iteratively optimized, and the image quality is improved. And after the focus is determined, the system maintains the current voltage state, and the focusing process is automatically optimized in combination with a scene change detection mechanism. The problems of optical distortion, halo, aberration and the like caused by the uniformity and response characteristics of liquid crystal molecules in the optical adjustment process of an existing liquid crystal panel are solved; the automatic focusing method and the automatic focusing device are particularly suitable for high-resolution and large-aperture application scenes, and stability and adaptability of automatic focusing are improved.

The invention discloses an automatic focusing lens module and method, and relates to the technical field of optical equipment, and the lens module comprises an outer sleeve, the inner side surface of which is provided with a thread; the inner sleeve is internally provided with an objective lens, the outer side surface is provided with threads and teeth, and the inner sleeve is inserted into the outer sleeve and screwed together; a rotating shaft of the motor is provided with a driving gear, and the driving gear is meshed with teeth of the inner sleeve; a driving plate; and the upper computer is provided with automatic focusing software, and the automatic focusing software controls the motor to work through the driving plate, so that the inner sleeve is driven by the motor to rotate, and then moves in the outer sleeve along the axial direction. The lens module can adapt to most of traditional manual microscopes, the upgrading cost is saved for a laboratory, and the service life of old equipment is prolonged.

The utility model discloses a high-stability automatic focusing module, which comprises a fixed base, a gear motor assembly, a movable focusing ring and a movable mirror frame, the movable focusing ring is sleeved on the periphery of a cylinder part of the base and is driven by the gear motor assembly, and the movable mirror frame is movably embedded in a light through hole of the base; the movable mirror frame is provided with a guide column, the guide column and the movable mirror frame are of an integrated structure through injection molding, and the outer end of the guide column penetrates through the vertical through groove and extends into the spiral groove. A magnetic attraction assembly is arranged between the fixed base and the movable mirror frame, the magnetic attraction assembly comprises a first magnetic attraction piece fixed to the inner wall of a light through hole of the base in a dispensing mode and a second magnetic attraction piece fixed to the outer side wall of the movable mirror frame in a dispensing mode, and the first magnetic attraction piece and the second magnetic attraction piece are arranged in a staggered mode in the Z-axis direction; and the movable mirror frame is subjected to the combined action of the radial retention force and the axial retention force under the magnetic action of the first magnetic attraction piece on the second magnetic attraction piece. By means of the structural design, the focusing device has the advantages of being novel in design, good in stability and reliability and high in focusing precision.

The invention discloses an automatic focusing method and system of a cell slide scanner, and relates to the related field of optical equipment focusing technology.The method comprises the steps that a slide is previewed and scanned, a multi-mode preview image and physical height sensing data are synchronously collected and preprocessed, and then the pre-processed image is obtained; the multi-modal preview image and the corresponding height data are input into a pre-training focus prediction model, a focusing strategy graph aligned with a slide coordinate space is output, and the graph comprises the predicted optimal focus offset, the focusing function recommendation identifier, the focus verification confidence coefficient and the search radius of each view point; according to the focusing strategy graph, a final focus is determined through feedforward positioning, limited verification and conditional adjustment, a scanner objective table is controlled to carry out formal scanning at the final focus position, and a complete scanning image of the cell slide is collected. The problems that a traditional focusing method is long in time consumption and poor in adaptability to complex samples with low contrast, high background fluorescence and scratch pollution are solved, and the adaptive capacity of the focusing process is improved.

The invention discloses a high-precision lightweight focusing window intelligent selection method based on improved YOLOv8, and the method comprises the steps: carrying out the optimization of a mark focusing window into a target detection task, and achieving the precise focusing imaging of a mark in a wafer image. By introducing a deformable convolution DCN module, the learning ability of the network for complex mark structure features is enhanced, and the diversity of wafer mark shapes can be more flexibly adapted; in combination with an attention mechanism CBAM module, the attention of the network to the key mark area is enhanced, and the ability of understanding complex images and predicting features is effectively improved; a Shape-IoU loss function is adopted to optimize regression of a target bounding box, so that the prediction precision is improved, and the target positioning capability of the model is enhanced; and the network is improved by using the lightweight Ghost module, so that the calculation complexity and the parameter quantity are remarkably reduced, and the detection efficiency is improved. According to the invention, intelligent selection of the wafer marking image focusing window in the automatic focusing process is realized.

The embodiment of the present application provides a camera module and electronic device, wherein the camera module is used to be installed in the electronic device, and the camera module includes: a bracket, an optical image stabilization motor, an autofocus motor, a reflective prism, a lens, and a lens mount; the reflective prism is arranged in the optical image stabilization motor, the lens is arranged in the autofocus motor, the lens and the lens mount are connected, the optical image stabilization motor, the autofocus motor, and the lens mount are arranged in the bracket and arranged in sequence in a first direction, the first direction being the optical axis direction of the lens, and the plane where the lens mount is located is arranged perpendicular to the optical axis direction; the lens includes a plurality of lenses arranged in sequence from the light input side to the light output side, the side of the lens facing the reflective prism is the light input side, and the first lens is closer to the light input side among the plurality of lenses, and the aperture of the lens is arranged on the peripheral side of the first lens or on the side of the first lens facing the reflective prism. The embodiment of the present application provides a camera module and electronic device, which can reduce the stacking height.

The purpose of the present invention is to provide a microscope with an autofocus mechanism that achieves both high-speed focus tracking and focus accuracy. In a microscope according to the present invention, the position of a collimator lens is moved so that light that has passed through an objective lens is focused on the surface of a cover glass, and a reflected light from a sample is detected as a focus error signal indicating the amount of deviation of the focal point of the light that has passed through the objective lens from the surface to be focused (see fig. 1).