84 results about "Wavefront sensor" patented technology

The invention relates to the technical field of free space optical communication, in particular to an atmospheric turbulence adaptive optical compensation method for wireless laser communication, which comprises the following steps of: performing light beam coarse tracking by using a fast reflector to eliminate tilt drift; monitoring the received light intensity of the wavefront sensor in real time, and setting a threshold value for mode judgment; when a channel is good, a Kalman filtering algorithm is adopted to predict and compensate system delay, modal decoupling is carried out on reconstructed wavefront, a large-stroke deformable mirror is controlled to correct low-frequency large-amplitude aberration, and a micro-electro-mechanical deformable mirror is controlled to correct high-frequency residual error; and when the channel is in deep fading or the detector fails, the blind optimization mode is automatically switched, the state of the large-stroke deformable mirror is locked, and SPGD iterative control is applied to the micro-electro-mechanical deformable mirror based on the communication light intensity. According to the invention, through a double-deformable mirror frequency division cooperation and hybrid sensing strategy, the problems of insufficient bandwidth, limited stroke, easy interruption and the like of a traditional system under strong turbulence are effectively solved, and the optical fiber coupling efficiency and the robustness of a communication link are significantly improved.

The invention provides a fundus camera system integrated with adaptive optics and a correction method, and relates to the technical field of ophthalmology imaging. The fundus camera system comprises a beacon light source, an imaging light source and an imaging sensor; the device comprises a wavefront sensor, a wavefront correction device and a control module, and the wavefront correction device comprises a focusing lens group and a deformable reflector; the focusing lens group and the deformable reflector are arranged in the same light path from the beacon light source to human eyes and from the human eyes to the wavefront sensor; moreover, the control module executes a two-step closed-loop control strategy of first focusing and second correction: firstly, based on a first measurement result of the wavefront sensor, the focusing lens group is driven to move so as to compensate low-order aberration; and after the focusing is completed, the deformable reflector is driven to deform based on the subsequent measurement result of the wavefront sensor so as to compensate the high-order aberration in a closed-loop manner. On the basis of inheriting the advantage of rapid focusing in the prior art, the self-adaptive optical technology is further integrated, so that the limitation of high-order aberration on resolution is solved.

This invention relates to an interferometric measurement method and apparatus for large warp wafers, belonging to the field of optical detection and semiconductor measurement technology. The detection light is polarized and birefringently split to form P-beams and S-beams, which are then further divided into P-reference beams, S-silicon beams, S-reference beams, and P-silicon beams, respectively. By adjusting the spatial orientation of the reference mirror and the wafer under test, and using an aperture for spatial filtering, the P-reference beam and S-silicon beam are allowed to enter the subsequent optical path, while the S-reference beam and P-silicon beam are blocked. The S-silicon beam forms a measurement wavefront carrying information about the surface shape of the wafer under test. The P-reference beam is modulated by a deformable mirror to form a modulated reference wavefront similar to the measurement wavefront. The two form a resolvable interference fringe pattern at the camera. A wavefront sensor measures the surface shape information of the deformable mirror, and a calculation system obtains the surface shape information of the wafer under test based on the deformable mirror surface shape information and the relative surface shape change. This invention can reduce the interference fringe density in the detection of large warp wafers, reduce splicing measurement errors, and improve detection efficiency and accuracy.

This invention relates to the field of optical measurement technology and discloses a distortion measurement method for a PDV and Hartmann wavefront sensor optical system. The method includes acquiring interference data of the measurement environment in which the optical system is located, analyzing and calculating the interference correction index of the measurement environment, classifying the measurement environment into weak or strong interference environments, and correcting the initial distortion in a strong interference environment. This invention introduces a measurement contribution coefficient calculation mechanism based on signal-to-noise ratio, spatial coverage, and dynamic response time constant, which adaptively allocates the weights of different sensors in the fusion process, thereby improving the accuracy and reliability of distortion reconstruction. More importantly, by constructing an environmental interference correction model that includes temperature, vibration acceleration, and air refractive index, and by quantitatively evaluating the measurement environment through the interference correction index, it can effectively correct the initial distortion results in a strong interference environment.

The invention discloses a laser powder bed sheet pattern distortion real-time correction system and method based on a phase type light valve, and relates to the technical field of metal additive manufacturing. The system comprises a polarization laser, a beam expanding and collimating unit, a reflecting mirror, a phase-type spatial light modulator, a reflecting mirror, a relay optical system, a galvanometer / field lens system, a movable spectroscope, a reference plane mirror and a forming cylinder. A double-loop correction system with a position sensitive detector as an absolute reference and a wavefront sensor as direct feedback is constructed, information of the position sensitive detector and the wavefront sensor is unified in a phase domain through a frequency domain fusion algorithm, and a comprehensive compensation phase diagram capable of completing pattern generation and distortion correction at the same time is generated. And loading to a phase type light valve to carry out high-power laser patterning modulation, and melting metal powder of a powder bed.

The present application relates to the technical field of laser detection, in particular to a laser striking target detection device and method for terminal defense. Firstly, the peak intensity of the light spot and the deflection vector of each channel of the wavefront sensor are collected in a single frame detection period, the real-time light intensity characteristics and the circuit noise are combined to generate a servo light intensity filtering threshold, the effective channel set with calculation value is screened out by dynamically adapting to the battlefield noise fluctuation; the direction consistency of the deflection vectors of the adjacent effective channels is calculated, the light spot connected weight network with coherent weight is constructed, the sub-aperture grouping area is obtained by clustering, and the automatic aggregation of the scattered same target light spots is realized; then the integrated light intensity connectivity is generated by fusing the peak intensity of the light spot and the local connected weight, the signal intensity and the spatial correlation attribute are considered, the real target tracking effective area is accurately stripped out, and finally the calculation accuracy is greatly improved by relying on the channel number characteristics and the deflection vector calculation servo command in the area.

Device for modulating a laser beam, including a deformable mirror with a reflective surface to receive an incident laser beam and to reflect a corresponding reflected laser beam provided with an output wavefront, and an actuator for deforming the reflective surface. The device also includes a detection system having an electromagnetic radiation source to emit a control beam incident on the reflective surface, and a wavefront sensor to intercept the reflected control beam reflected by the reflective surface to detect measurements of the wavefront of the reflected control beam and generate corresponding measurement signals. The device further includes a logic control unit, which receives the measurement signals, associates them with corresponding forms of the output wavefront of the reflected laser beam, actuates the actuator to deform the reflective surface in order to feedback control the output wavefront of the reflected laser beam.

The invention discloses a phase difference wavefront-image estimation method based on depth image prior. The method comprises the following steps: firstly, constructing a forward physical model of an incoherent imaging system, and generating an observation image with out-of-focus aberration by introducing phase difference; and then using a depth image prior network to jointly optimize image domain loss and wavefront domain loss under the condition of no external training data by taking the consistency of an observation image and a model generation image as a constraint so as to simultaneously obtain a high-quality recovered image and accurate wavefront estimation. The method provided by the invention can realize accurate wavefront estimation and high-quality image recovery under the condition of large aberration under the condition of only needing a small number of acquired images, and has the advantages of strong anti-noise capability, no need of an additional wavefront sensor and low system complexity. The method can be widely applied to fluorescence microscopic imaging and other high-resolution microscopic imaging technologies, and the imaging resolution and the image quality are improved.

The invention discloses an optical view field expansion and dynamic distortion compensation method for light field display, and particularly relates to the technical field of light field display, and the method comprises the steps: determining a configuration scheme through building a collaborative structure parameter model of a microlens array and a free-form surface optical element; then, the focal length distribution of the micro-lens array and the curvature distribution of the free-form surface optical element are adjusted, so that the expansion of an optical view field is realized; acquiring light information in an expanded view field range by using a wavefront sensor, and establishing an optical distortion mathematical model; calculating wavefront error distribution based on an optical error inversion algorithm and generating a compensation control signal; and adjusting response parameters of the optical element according to the compensation control signal, correcting the light wavefront, feeding back the corrected light field information to update wavefront error distribution, and iteratively generating a new compensation control signal. According to the invention, a light field display field angle can be effectively expanded, distortion after field expansion is reduced, and good application compatibility is achieved.

This invention discloses a method for restoring turbulent degradation images based on complex amplitude detection, belonging to the field of computational optics imaging technology. This method constructs a computational optics imaging system without a hardware correction unit. It utilizes a wavefront sensor and an imaging sensor to simultaneously acquire Hartmann images and target degradation images. A computational unit performs wavefront complex amplitude reconstruction and aberration correction. Based on this, a physically constrained end-to-end neural network architecture is designed. By reconstructing the wavefront complex amplitude, it achieves accurate mapping and inference from the Hartmann image to the point spread function of the imaging system. Finally, a multi-scale deconvolutional network is combined to complete high-quality restoration of the turbulent degradation image. This invention eliminates the need for a hardware corrector, overcomes the physical limitations of traditional adaptive optics, effectively solves the problem of insufficient point spread function accuracy, and enables time-delay-free and highly efficient turbulent image restoration under low-cost conditions.

The invention discloses a defect detection method based on light wavefront. The defect detection method comprises the following steps: arranging an object to be detected on a base; providing a laser device which comprises a laser pump and a laser light source and emits a first laser beam towards the detection part of the object to be detected; providing a first light wavefront sensor, wherein the first light wavefront sensor receives first reflected light of the first laser beam reflected by the detection part of the to-be-detected object to generate a first reflected light signal, or receives first penetrating light of the first laser beam penetrating through the detection part of the to-be-detected object to generate a first penetrating light signal; providing a waveform generator which is electrically connected with the first optical wavefront sensor, and receiving the first reflected light signal or the first penetrating light signal by the waveform generator to generate a first detection oscillogram; the invention further provides a defect detection system based on the light wavefront.

This invention discloses a calibration method, apparatus, device, medium, and product. The calibration method relates to the field of active alignment calibration technology in optical module production. The method includes: controlling a first sensor conveying platform to move an image sensor to a first position; controlling a second sensor conveying platform to move a wavefront sensor to the first position, and determining a reference Zernike coefficient based on a second image acquired by the wavefront sensor; controlling an active calibration gripper to tilt multiple times, and determining a sensitivity parameter and an offset based on a third image acquired by the wavefront sensor after each tilt and the reference Zernike coefficient; constructing a target model based on the reference Zernike coefficient, sensitivity parameter, and offset; controlling the second sensor conveying platform to move the wavefront sensor to a second position, and determining a target tilt angle based on the current vertical tilt coefficient, the current horizontal tilt coefficient, and the target model; and performing calibration based on the target tilt angle.

This invention provides a multi-channel receiving SLM partition-controlled adaptive optics alignment system and method. The method includes: a beam to be aligned in a perturbed channel is decomposed into a target beam and a reference beam after passing through a beam splitter; a wavefront sensor receives the reference beam, acquires the intensity distribution and phase distribution of the reference beam, and inputs them into a processor; the processor uses a preset SLM multi-zone control algorithm to partition the liquid crystal of the phase-type SLM, and matches each selected zone with each optical receiver one by one, generating a phase hologram for each selected zone and inputting it into the liquid crystal controller; each selected zone of the SLM liquid crystal performs partition alignment and outputs the received target beam; this invention can achieve multi-point focusing, dynamic alignment, and power allocation of the received beam through a single SLM, supports multi-point simultaneous alignment and arbitrary power allocation of a multi-channel receiving UOWC system under dynamic conditions, and has outstanding advantages such as high flexibility, good real-time performance, and strong scalability.

The application provides a complex amplitude SLM adaptive optical path alignment system and method for aligning a to-be-aligned light beam in a disturbed channel, wherein the to-be-aligned light beam in the disturbed channel is decomposed into target light and reference light after passing through a beam splitter; a wavefront sensor receives the reference light, acquires phase information of the reference light and inputs the phase information into a processor; the processor calculates a superimposed compensation amount of complex amplitude regulation according to an alignment position and generates a phase hologram, and inputs the phase hologram into a liquid crystal controller; the phase hologram comprises a plurality of concentric circles, and is used for simulating a ring-shaped blazed grating of focused light rays at a preset alignment position; a liquid crystal of a phase SLM receives the target light, the liquid crystal controller converts the phase hologram into a control voltage, and controls the liquid crystal to perform alignment output on the target light; and the application can continuously correct and align the light beam transmitted in the disturbed optical channel based on pure phase SLM complex amplitude regulation.

A wavefront tester for measuring the wavefront of a sample via an optical path, the wavefront tester including a mirror, an imaging lens, an aperture, a beam splitter, a wavefront sensor, a lens selection system including a plurality of optical lenses, a suitable optical lens of which is commensurate with the sample and selected to be disposed in the optical path and a light source directed in a first direction through the optical path by the beam splitter through the suitable optical lens and the sample to the mirror such that the light source is redirected in a second direction opposite the first direction through the optical path and the beam splitter, the aperture and the imaging lens to be received at the wavefront sensor.

The application discloses a kind of adaptive optics real-time controller hardware architecture based on multi-core CPU and GPU.Shack-Hartmann wavefront sensor sub-aperture slope calculation, wavefront recovery and wavefront control are completed in parallel by multi-core CPU and GPU using the real-time controller hardware architecture.The application uses general multi-core CPU and GPU as computing platform, after receiving image data in multi-core CPU, part of sub-aperture image data is transmitted to GPU by PCIE bus using a CPU core, and wavefront calculation task of the part of sub-aperture is completed by GPU;At the same time, the remaining CPU core is used to complete the remaining sub-aperture wavefront calculation task in parallel, to reduce the purpose of real-time controller calculation delay.The application uses multi-core CPU and GPU in parallel to complete wavefront calculation task, to reduce the effect of adaptive optics real-time controller calculation delay, to meet the real-time requirement of adaptive optics system to real-time controller, especially suitable for next-generation large-aperture ground-based telescope adaptive optics system real-time control.

The invention relates to the technical field of optical precision detection, in particular to a method and a device for calibrating core parameters of a Shack-Hartmann wavefront sensor, which can obtain the distance between a micro-lens array and a camera target surface and the size of a micro-lens unit which are highly related to detection precision through superposition calibration based on plane waves and spherical waves. The theoretical model has high precision. In the calibration scheme, simple and rapid switching based on plane waves and spherical waves can be realized by removing / adding the microscope objective, and few error sources are introduced. In the calibration scheme, high-precision rotation angle monitoring based on an autocollimator and high-precision displacement monitoring based on a displacement sensor are arranged, so that high-precision calibration is ensured.

The utility model relates to a special-shaped light spot wavefront sensing device, measuring instrument and equipment, comprising a micro-lens array and an imaging device, the micro-lens array is arranged at one side of the imaging device close to incident light, the micro-lens array is divided into a plurality of units arranged regularly, the micro-lens array comprises a plurality of micro-lenses, and the micro-lenses are arranged on the side of the imaging device close to incident light. The microlens array comprises a special-shaped mark area formed by at least one unit, so that a special-shaped shadow area is formed in the middle or on the periphery of a light spot array formed on the imaging device. The special-shaped mark area comprising at least one unit is arranged on the microlens array, so that the reference position can be accurately determined by taking the special-shaped mark area as a special mark, and the corresponding position relation between the light spot array and the microlens array is determined based on the corresponding special-shaped shadow area on the imaging device; manual grid division of the imaging field of view of the imaging device is avoided, and the wavefront measurement efficiency and precision are greatly improved.

A reciprocal lattice image, which represents a lattice point group of a reciprocal lattice, is generated by performing a two-dimensional Fourier transform on a target image. In addition, a target lattice, in which an arrangement of the lattice point group approximates an arrangement of a target focal spot group, is estimated with reference to a lattice vector of the reciprocal lattice. Then, lattice coordinates of a lattice point, which is closest to a target focal spot, of the target lattice are assigned to each corresponding target focal spot, thereby pairing the target focal spot with a reference focal spot.

Techniques are disclosed for systems and methods for providing dry eye and / or tear film hydration monitoring in the context of ocular aberrometry. An ocular aberrometry system (100) includes a wavefront sensor (120) configured to provide wavefront sensor data associated with an optical target (102) monitored by the ocular aberrometry system (100) and a logic device (140) configured to communicate with the wavefront sensor (120). The logic device (140) can be configured to receive (1102) ocular aberrometry output data including at least wavefront sensor data provided by the wavefront sensor (120), determine (1106) a tear film hydration state associated with the optical target based at least in part on the received ocular aberrometry output data, and generate (1110) user feedback corresponding to the determined tear film hydration state based at least in part on the received aberrometry output data and / or the determined tear film hydration state.

The present application relates to the field of confocal modulation of a mosaic telescope, and specifically provides a large-aperture mosaic telescope partition multi-stage confocal method, comprising: performing finite element analysis on a mosaic mirror to obtain a deformation coupling relationship of mosaic sub-mirrors, dividing the mosaic sub-mirrors of the mosaic mirror into multiple structural functional areas, independently confocally adjusting the mosaic sub-mirrors in each structural functional area by using a digital micromirror device, detecting wavefront information of each structural functional area after independent confocal adjustment by using a wavefront sensor, and adjusting all the mosaic sub-mirrors in the structural functional area as a whole according to the wavefront information of each structural functional area, so that the area focal points of all the structural functional areas are collectively converged at a final system focal point of the mosaic mirror. The present application realizes initial misadjustment detection and high-precision confocal correction in a large dynamic range, and reduces confocal adjustment cost and complexity.

An apparatus, and corresponding method, for determining a property of an eye includes a housing with a proximal port that receives an eye and also light from the eye. The housing further includes a distal port, and the two ports together form a visual channel providing an open view to enable the eye to see target indicia external to and spaced away from the housing. A wavefront sensor within the housing is configured to receive the light from the eye via the optical path and to measure a wavefront of the light. A determination module determines an objective refractive correction based on the wavefront and predicts a subjective refractive preference of a person having the eye based on the objective refractive correction. Embodiments can be handheld, and binocular, and predict subjective refraction based on demographic and other information.

The invention discloses a large-aperture diffraction structure direct writing online calibration and error suppression system, which relates to the technical field of diffraction structure direct writing and comprises an error detection module, a compensation generation module, a dynamic execution module and a closed loop feedback module. The error detection module is provided with a workpiece carrying table and a wavefront sensor, obtains a residual light field, separates a tilt term, an out-of-focus term, an astigmatism term and a coma term caused by mechanical vibration of the carrying table through Zernike polynomial decomposition, and generates an error source feature vector. The compensation generation module generates geometric correction and an aberration compensation matrix through a reverse optical path tracing algorithm; the dynamic execution module feeds the correction amount and the compensation matrix back to the carrying table and the transmission-type spatial light modulator respectively, and pre-modulation and wavefront pre-shaping are completed; and the closed-loop feedback module scans the morphology through the confocal detection array and compares the morphology to generate an error distribution diagram for closed-loop input. According to the system, accurate error traceability and two-way synchronous pre-compensation are realized, and direct writing errors are effectively inhibited.

The invention discloses a high-precision intelligent super-resolution wavefront restoration method, and the method comprises the steps: designing a neural network model based on an optical imaging mechanism and a signal processing method, and building a nonlinear relation between a Shack-Hartmann wavefront sensor light spot array image and a Zernike coefficient through model training; a Gabor filter of which the bandwidth and the direction can be trained is used for replacing a convolution kernel of a traditional convolutional neural network, an SH-GaborNet model applied to a Shack-Hartmann wavefront sensor is constructed, high-frequency and low-frequency characteristics in dispersed light spots are efficiently separated and extracted, and high-resolution and high-precision wavefront restoration is achieved. According to the method, the limitation of spatial resolution is broken through, and the mode confusion error caused by inaccurate slope measurement is effectively inhibited; according to the method, higher precision is shown in a super-resolution wavefront reconstruction task, and an efficient and reliable technical solution is provided for the fields of wavefront detection with high precision and high resolution and the like.

The invention relates to the technical field of confocal modulation of spliced telescopes, and particularly provides a large-aperture spliced telescope partition multistage confocal method, which comprises the following steps: carrying out finite element analysis on a spliced mirror surface to obtain a deformation coupling relationship of spliced sub-mirrors, and dividing the spliced sub-mirrors of the spliced mirror surface into a plurality of structural functional areas, a digital micro-mirror device is used for carrying out independent confocal adjustment on spliced sub-mirrors in each structural functional area, then a wavefront sensor is used for detecting wavefront information of each structural functional area subjected to independent confocal adjustment, and all spliced sub-mirrors in the structural functional area are integrally adjusted according to the wavefront information of each structural functional area. And converging the regional focuses of all the structural functional regions together to a final system focus of the spliced mirror surface. According to the invention, large-dynamic-range initial imbalance detection and high-precision confocal correction are realized, and confocal adjustment cost and complexity are reduced.

The present application relates to a kind of big warping wafer interference measurement method and device, belong to optical detection and semiconductor measurement technical field.Detection light is converted and diffracted after birefringence, and P light and S light are formed, and P reference light, S silicon light, S reference light and P silicon light are formed respectively;By adjusting the spatial posture of reference mirror and the wafer to be measured, and cooperating with spatial screening of diaphragm, P reference light and S silicon light enter subsequent optical path, while S reference light and P silicon light are blocked;S silicon light forms the measurement wave front carrying the wafer to be measured surface shape information, P reference light is modulated as the modulation reference wave front similar to the measurement wave front by deformable mirror, and the two form analytical interference fringe pattern at camera;Wave front sensor measures deformable mirror surface shape information, and the computing system obtains the surface shape information of the wafer to be measured according to deformable mirror surface shape information and relative surface shape variation amount.The present application can reduce the interference fringe density in the detection of big warping wafer, reduce splicing measurement error, improve detection efficiency and accuracy.

An optical system includes an optical antenna configured to receive and / or transmit laser beams through a first aperture, a gimbal-mounted deformable mirror (GDM) configurable to correct aberrations of a received laser beam, a power selector configurable to split the received laser beam into a first light beam and a second light beam, a wavefront sensor configured to measure a wavefront of the first light beam, a collimator configured to couple the second light beam into an optical fiber, and a controller configured to control the GDM for laser beam tracking and for correcting the aberrations of the received laser beam based on the wavefront of the first light beam measured by the wavefront sensor. The GDM is configurable to scan, within a field of regard (FOR), a beacon beam to be transmitted for laser beam tracking; or scan within the FOR to acquire a beacon beam transmitted by a terminal.

The invention belongs to the technical field of optical measurement, and discloses a wavefront sensor parameter configuration method and related equipment, and the method comprises the steps: obtaining the measurement demand parameters of human eye wavefront aberration, gradually determining the basic size parameters, calculating the focal length upper limit of a micro lens, determining the focal length and the pixel size, and verifying the sensitivity. The configuration of the sensor can be dynamically adjusted according to actual requirements, so that the problem that the measurement precision and the application range are limited due to fixed parameters in the prior art is solved, and the wavefront sensor parameters can be dynamically configured according to actual measurement requirement parameters, so that large-dynamic-range and high-resolution measurement is considered; and the detection precision and the application range of the wavefront sensor are systematically improved.

The application provides a mirror convergence method and device based on double feedback surface shape regulation and optimization, which comprises the following steps: monitoring the wavefront component after the surface shape of a deformed mirror is modulated in real time by using a wavefront sensor; judging whether the surface shape coefficient residual of the wavefront component is greater than or equal to a set threshold; if yes, quickly calculating the surface shape reconstruction voltage by using an influence function matrix, and making the deformed mirror quickly converge based on the surface shape reconstruction voltage; if no, monitoring the change of light intensity distribution or imaging definition by using an image sensor, and taking the change as an evaluation parameter of the correction degree of the distorted wavefront; and based on the evaluation parameter, improving the surface shape reconstruction precision by using a search optimization algorithm. The application makes up for the defects that the control precision of the closed-loop control algorithm based on the influence function is affected by the measurement precision of the influence function matrix, and the closed-loop control algorithm without the influence function has low calculation efficiency and is easy to converge to a local optimal value, and can meet the requirements of a non-moving zoom steady image system.

The application provides an optical system of a fundus camera, which comprises an ocular lens, an aperture diaphragm, an aberration-correcting lens group, a field lens group, a half-transmission half-reflection mirror and an imaging lens group, light of a light source is irradiated to a pupil through the ocular lens, the light goes out from the pupil and sequentially passes through the ocular lens, the aperture diaphragm, the aberration-correcting lens group and the field lens group to reach the half-transmission half-reflection mirror, 50% of the light transmits through the half-transmission half-reflection mirror to the imaging lens group and is imaged on a CCD, and the other 50% of the light is reflected by the half-transmission half-reflection mirror and is used for connection with a wavefront sensor, and the field lens group comprises a deformable mirror.The application realizes synchronous and efficient collection of high-resolution fundus imaging and high-precision wavefront sensing by optimizing the structure of the aberration-correcting lens group, integrating the field lens group and the deformable mirror and adopting the half-transmission half-reflection mirror light splitting design, and the imaging quality, light energy utilization rate and functional integration degree of the system are improved, and the high-performance requirement of the fundus camera in modern ophthalmic diagnosis and treatment is met.