2677 results about "Beam splitters" patented technology

The present disclosure relates to an active graded magnetic compensation system and method for an unshielded SERF magnetometer. The system comprises: a detection laser, a half-wave plate, a magnetic field compensation coil, a magnetic field modulation coil, a non-magnetic heating assembly, an alkali-metal atomic vapor cell, a polarizing beam splitter prism, a balanced photodetector, a graded feedback control module, a pump laser, a quarter-wave plate, a focusing lens and a photodetector. By means of the present disclosure, a graded compensation system is used to realize high-precision compensation for a magnetic field within a large dynamic range in a geomagnetic environment, thereby ensuring that an instrument carries out high-sensitivity magnetic field measurement under geomagnetic conditions.

The invention provides an optical measurement method and device, and belongs to the technical field of optical measurement, and the method comprises the steps: starting a light source with the wavelength changing dynamically to generate a sweep frequency optical signal; dividing the light into a measuring beam and a reference beam by using a light splitting component, guiding the measuring beam to irradiate a target to be measured and then return along the same path, and guiding the reference beam to enter an optical component of which the optical path changes along with the wavelength and then return; based on the low-coherence characteristic of the light source, when the optical paths of the two light beams meet the interference condition, detecting an interference signal by using a sensing component; the optical path difference is determined according to time information in the interference signal, and the thickness of each reflection interface is calculated by combining refractive index data of a target to be measured. Different from the traditional low-coherence interference measurement which depends on a motor and the like to control the movement of a reflector, the method avoids the limitation of mechanical driving on the measurement frequency, and achieves the high-speed optical thickness measurement.

The invention discloses a polarization-state-based optical fiber vibration sensing system and application, and relates to the technical field of optical fiber sensing, and the polarization-state-based optical fiber vibration sensing system mainly comprises a transmitting end and a receiving end. The transmitting end comprises a laser diode, a first erbium-doped optical fiber amplifier, a first circulator, a polarization scrambler, a single-mode optical fiber link, a second circulator and a second erbium-doped optical fiber amplifier which are connected in sequence; and the receiving end comprises a polarization beam splitter, a first shunt module, a second shunt module, an optical mixer, a first balanced photoelectric detector, a second balanced photoelectric detector, a third balanced photoelectric detector and a polarization analysis module. According to the optical fiber vibration sensing system based on the polarization state and the application, the vibration monitoring performance and reliability in a long-distance and high-noise environment can be improved.

The invention relates to the technical field of laser ranging, in particular to a double-optical-comb hybrid ranging device which comprises a signal detection optical path system and a signal demodulation optical path system. Wherein the signal detection optical path system comprises a first optical frequency comb, a first optical isolator, a first optical collimator, a first beam splitter prism, a reference mirror, a Faraday rotator, a convergence mirror and a target reflector; the signal demodulation optical path system comprises a second optical frequency comb, a second optical isolator, a second optical collimator, a half-wave plate, a second beam splitter prism, a third beam splitter prism, a first polarization controller, a first photoelectric detector, a reflector, a polarization beam splitter prism, a second polarization controller and a second photoelectric detector. A third polarization controller; and a third photoelectric detector. According to the invention, three ranging technologies of asynchronous optical sampling ranging, multi-heterodyne interference ranging and synthetic wavelength ranging are fused, and the problem that a large ranging range and high ranging precision cannot be simultaneously considered in the ranging process is solved.

The invention discloses a transparent part defect detection method and system based on dual-optical-path phase deflection, and belongs to the technical field of optical detection. The system comprises a camera, a reflection light source, a spectroscope, a backlight light source and a processing unit. The detection method comprises the steps of primary measurement, product overturning, secondary measurement and defect comprehensive analysis and classification. A depth map and a modulation degree map of the surface of a product are obtained through reflective measurement, a phase difference map and a backlight modulation degree map are obtained through transmission-type zero reference surface differential measurement, multi-dimensional data are fused, and accurate detection and classification of concave and convex points, foreign matter, scratches and other defects are achieved according to preset logic. The method can effectively eliminate inherent errors of the system, realizes double-sided full detection without omission, is high in detection precision and accurate in defect classification, and is suitable for defect detection of transparent parts such as multilayer transparent glass.

The invention provides a photon parallel matrix convolution operation chip which can be applied to the technical field of integrated photonics and optical calculation. The chip is integrated by a 1 * N array waveguide grating, a 1 * 2 beam splitter array, an input matrix modulator array, two N * 1 array waveguide gratings, two 1 * N beam splitters, a weight matrix modulator array, an M * M array waveguide grating detector array and a detector array. Main functional devices are integrated in a monolithic mode, the system is compact, the complexity and power consumption of the system can be effectively reduced, and the calculation efficiency is improved.

The invention discloses an external cavity tunable laser linewidth compression system for realizing wavelength phase locking based on mutual injection of gain chips. The external cavity tunable laser linewidth compression system comprises a red light semiconductor laser main gain chip, a first collimation optical system, a blazed grating, a tuning rotating mirror, a reflector, a power supply driving system and a double-path feedback amplification system, the double-path feedback amplification system comprises a first secondary gain chip, a second secondary gain chip, a second collimation optical system, a third collimation optical system and a polarization-free beam splitter prism; and the red light semiconductor laser main gain chip, the first secondary gain chip and the second secondary gain chip are all connected with the power supply driving system. Therefore, the technical problems of low output infrared light power, poor stability and narrow mode-hopping-free tuning range in the prior art are solved, and high-power, narrow-linewidth, high-stability and large-range mode-hopping-free continuous tuning red light output can be realized.

The invention discloses a parallel imaging OCT (Optical Coherence Tomography) system based on a metasurface area array, which relates to the technical field of medical instruments, is small in size and can realize intraocular single-shot area array imaging and a three-dimensional position depth perception function by using metasurface and optical coherence tomography imaging information in a sample tissue with a limited size. According to the technical scheme, a light beam emitted by a laser is divided into two paths through a beam splitter, and the two paths enter a sample arm module and a reference arm module respectively; the sample arm module is a probe and comprises a multi-core optical fiber and a first metasurface; the reference arm module comprises a collimator, a motor and a right-angle reflector; the probe enters a sample tissue, a light beam is focused on the sample tissue and then is backscattered, the backscattered light beam reversely passes through the first metasurface, the multi-core optical fiber, the beam splitter, the second metasurface, the third lens, the grating and the focusing lens and then forms a spectral line beam on the CCD sensor, and the computer reads a signal from the CCD sensor and performs three-dimensional reconstruction imaging on the sample tissue.

The invention relates to an electro-optical modulator, a preparation method thereof and an electro-optical chip. The electro-optical modulator comprises a substrate, an optical beam splitter, a first optical waveguide, a second optical waveguide, traveling wave electrodes and an electro-optical film, the traveling wave electrodes comprise a first signal electrode and a second signal electrode, the first signal electrode and the second signal electrode are sequentially arranged in the second direction, the first signal electrode and the second signal electrode form a differential electrode, and the first signal electrode and the second signal electrode are sequentially arranged in the second direction. The first signal electrode generates a first electric field when transmitting a first electric signal, the second signal electrode generates a second electric field when transmitting a second electric signal, the directions of the first electric field and the second electric field are opposite, and the refractive index of the electro-optical film is changed under the action of the electric fields to realize electro-optical modulation; part of the electro-optical film, the first optical waveguide overlaps with the first electric field, and the other part of the electro-optical film overlaps with the second electric field. According to the invention, the differential driving of the electro-optical modulator is realized based on the electro-optical film, and the anti-interference capability and the transmission distance of the electro-optical modulator are effectively improved.

The invention provides a laser radar ranging method based on parallel detection, which relates to the technical field of laser radar ranging, and comprises the following steps: generating N lasers with different wavelengths, splitting beams by a beam splitter, separating optical channels with N independent wavelengths by a demultiplexer, performing frequency shift processing, combining N paths of optical signals after frequency shift through a beam combiner, and combining the N paths of optical signals after frequency shift through a beam splitter; generating a beam of composite reference light containing N wavelengths, wherein each wavelength has a specific frequency shift; signal light returned from a target and the composite reference light are jointly input into a coupler for frequency mixing so as to generate an optical beat frequency signal, and operation processing is performed to calculate the target distance and the target radial speed corresponding to each wavelength. According to the laser radar ranging method provided by the invention, parallel detection of the laser radar can be realized, beat frequency signals corresponding to a plurality of different wavelengths can be distinguished only by integrating a group of detectors, a cross-group amplifier and an analog-to-digital converter, the cost is greatly reduced, and the complexity of the system is reduced.

The invention provides a compact hyperspectral imager optical system and an imaging method thereof, which are used for solving the technical problems that the overall size of a front telescopic assembly in a traditional hyperspectral imager optical system is difficult to compress, the installation and adjustment difficulty is relatively large, or the incident energy is lost and the space coverage capability is insufficient. And the technical problems of low energy utilization rate and difficulty in improving the sensitivity and the signal-to-noise ratio of the hyperspectral imager of the traditional Dyson type dispersion light splitting assembly are solved. The invention provides a compact hyperspectral imager optical system, which comprises an off-axis two-image-reflection telecentric optical path system based on a free-form surface and a Dyson light splitting system based on a curved surface prism, and realizes high regulation and control capability on light through multiple degrees of freedom of a curved surface shape. Compared with the prior art, the high-spectral imaging device has the advantages that the high-spectral imaging device is simple in structure, high image quality, small distortion and good telecentricity are achieved, meanwhile, the curved prism serves as a dispersion light splitting element, the whole spectrum has high light splitting efficiency, and the signal-to-noise ratio and sensitivity of the high-spectral imaging device can be improved.

The invention relates to the technical field of laser radars, in particular to a laser radar near-field saturation suppression method and device based on signal splicing. The method comprises the following steps: transmitting a pulse laser beam and receiving a scattering echo signal, dividing the echo signal into a transmission light signal and a reflection light signal through an intensity beam splitter prism, and respectively obtaining a far-field channel photon profile and a near-field channel photon profile through the transmission light signal and the reflection light signal; fusing and splicing the far-field channel photon profile and the near-field channel photon profile to obtain a corrected distance square signal profile; and performing atmospheric detection by using a laser radar system, and inverting atmospheric parameters by correcting a distance square signal profile. Meanwhile, the invention discloses a device for executing the method, by adopting the laser radar near-field saturation suppression method and device based on signal splicing, the problem of near-field signal saturation of a high-power laser radar can be effectively solved, and the overall performance index of the laser radar is greatly improved while the detection precision is guaranteed.

The invention relates to the field of wafer defect detection, in particular to a rapid zooming wafer detection microscope based on MEMS and a detection method. The microscope comprises an illumination part, a sample stage, a spectroscope, a microscope objective, an MEMS micromirror array zoom module, a CMOS image sensor, a laser interference distance measuring sensor and a synchronous control and processing module based on an FPGA. The MEMS micro-mirror array zoom module composed of a plurality of micro-mirror units is introduced into a light path, the deflection state of each micro-mirror unit is adjusted, a dynamic reflecting surface with a controllable equivalent curvature is formed, focusing regulation and control of imaging light beams are achieved, electronic focusing without mechanical movement is completed, the response speed is superior to that of traditional mechanical adjustment, and the imaging quality is improved. And the method is suitable for high-speed online detection.

The invention discloses a coherent interference-based coaxial transceiving line scanning three-dimensional profile measurement system and method. The system comprises a low-coherence light source; the beam splitter is used for collimating light emitted by the low-coherence light source and then dividing the light into two paths; the measuring light is focused into a linear light beam through the cylindrical lens and is emitted to the surface of the to-be-measured sample, and the measuring light reflected by the surface of the to-be-measured sample returns to the beam splitter along the original path; the reference light is emitted to a reference mirror with a certain inclination angle and is reflected back to the beam splitter through the reference mirror; the measuring light reflected by the surface of the sample to be measured and the reference light reflected by the reference mirror are subjected to beam combination interference through a beam splitter and are imaged to enter a camera for interference pattern acquisition; the signal processing system is used for processing the interference patterns to obtain height distribution of the to-be-measured sample on a line field, and three-dimensional profile measurement of the to-be-measured sample is realized by transversely moving or transversely scanning the to-be-measured sample and overlapping the interference patterns measured at different positions. Therefore, high-efficiency measurement can be realized while the micro-nano precision is kept.

The invention relates to the technical field of light quantum metering, in particular to a multifunctional standard single photon source generation and calibration device and a use method, and the device comprises a pumping laser light source, a nonlinear crystal, a signal optical filter, a beam splitter, a temperature control module, an idler frequency optical filter, a control module, a single photon detector group, a beam splitter, a multi-channel coincidence counter, and an optical switch. The pumping laser light source pumps the nonlinear crystal to generate two paths of single photon output of signal light and idler frequency light, the two paths of single photon output are filtered by the filter and then divided into multiple paths by the beam splitter, and standard single photons are directly output or the paths of the signal light or the idler frequency light are controlled by the optical switch to enter the single photon detector group for detection. External input single photons are controlled by the optical switch to enter the single-photon detector group for detection, and a count value of the single-photon detector group is accessed to the multichannel coincidence counter to record data. A pump light stable power system and a multi-path beam splitting coincidence counting system are introduced into a light path, so that standard single photon output with known brightness and g (2) (0) value can be realized.

The invention provides a series of polarization-independent beam splitters, a decoding end, a quantum key distribution system and a communication method, which can be applied to the technical field of quantum communication. The polarization independent beam splitter comprises an input optical channel, an input adiabatic evolution waveguide, a variable-width multimode waveguide, an output adiabatic evolution waveguide and an output optical channel, the variable-width multimode waveguide is in a strip shape and comprises a first end and a second end opposite to the first end, multiple waveguide sections with different width value changes are arranged between the first end and the second end, and the variable-width multimode waveguide is arranged between the first end and the second end. The signal photons are subjected to light field evolution in multiple waveguide sections with variable width values and then are subjected to beam splitting at a second end, and first beam splitting signal photons and second beam splitting signal photons are obtained; the length of the variable-width multimode waveguide is combined with different width values, so that the value of a target function is smaller than a target threshold value, and any beam splitting ratio can be realized on the premise of ensuring polarization independence through the combined asymmetric design.

The invention relates to the technical field of optics, in particular to blade front and tail edge polishing and correcting equipment which comprises a clamp for loading a to-be-detected guide vane, a polishing system is arranged beside the clamp, and the to-be-detected guide vane is vertically placed on the clamp; the system also comprises a laser interferometer system. The laser interferometer system comprises a laser and a beam splitter, and the beam splitter splits a measuring light beam and a reference light beam; linear collimating lenses are respectively arranged on light paths of the measuring light beam and the reference light beam, and the measuring light beam and the reference light beam respectively penetrate through the collimating lenses to form horizontal linear light beams. On-line real-time detection is achieved through the laser interferometer system, the defect portions of the front edge and the tail edge of the guide vane are accurately positioned, the polishing head can conveniently move to the defect portions to conduct fine polishing, the production period is shortened, and the production cost is reduced.

The invention relates to the technical field of information processing, in particular to the technical field of optical detection, and particularly relates to a two-dimensional material layer number identification method and equipment. A photoelectron chip composed of a semiconductor light source, a 2 * 2 waveguide beam splitter, a grating coupler, an on-chip spectrometer, a super lens and an optical detector is compact in structure and low in cost; a semiconductor light source emits an optical signal, the optical signal sequentially passes through a 2 * 2 waveguide beam splitter, a grating coupler and a super lens and then irradiates a two-dimensional material sample, a displacement table is used for carrying out accurate Z-axis focusing and XY plane scanning, reflection spectrum signals are collected in real time, spectrum characteristics are analyzed through an upper computer to determine layer number information, and finally a layer number distribution diagram is generated. According to the method, rapid, automatic and high-precision identification of the number of layers of the two-dimensional material is realized, and large-range scanning detection is facilitated.

The invention discloses a pattern wafer multi-parameter synchronous detection system and method based on double optical combs, and belongs to the field of wafer quality detection. The system comprises a signal light path, a reference light path, a detection light path and a synchronous detection module. After interference, the detection light beam and the reference light beam are decomposed into an H path and a V path through the polarization beam splitter, and are synchronously detected by the first camera and the second camera. The invention also provides a method which comprises the following steps: synchronously acquiring two paths of time domain interference data; fourier transform is carried out on each pixel point to obtain a plurality of spectrum pairs; the processing unit decodes in parallel based on the spectrum pair, and synchronously inverts multi-dimensional physical parameters such as three-dimensional morphology, stress and film parameters of the pattern wafer; and finally, comparing and identifying defects. According to the method, the problems of low detection efficiency and single information dimension in the prior art are solved, and wide-field, high-speed, high-precision and multi-parameter synchronous comprehensive characterization is realized.

A visualization system for dynamically visualizing an eye includes a laser module operable for outputting a primary laser beam along a beam axis, a beam splitter positioned in the beam axis and configured to direct a first beam portion along the beam axis and a second beam portion along a detection axis that is orthogonal to the beam axis. A microelectromechanical system (MEMS) scanner is arranged on the beam axis and configured, in response to the first beam portion, to output a scanning laser along a visualization path. An avalanche photodiode (APD) detector receives the second beam portion. A 4F correlator optical system has a spatial filter arranged along the visualization path. An optional optical flat may be disposed between the eye and the 4F correlator optical system to achieve stereo parallax.

The disclosure relates to an optical system for an augmented reality apparatus, comprising: an image projection source; and a polarizing beam splitter. The polarizing beam splitter is arranged such that light emitted from the image projection source is able to be non-perpendicularly incident on the beam splitting side and be at least partially reflected. The polarizing beam splitter is configured such that a polarized light component passes through the polarizing beam splitter and is transmitted through the transmission side thereof, and a polarized light component is reflected from the beam splitting side. The optical system also comprises a polarizer disposed between the image projection source and the polarizing beam splitter, and the polarizer is configured to allow polarized light, whose polarization is in the second direction, to be transmitted therethrough and polarized light, whose polarization is in the first direction to be absorbed.

A beamsplitter can include a first surface with a diffractive optical element, a second surface normal to the first surface, and a beam splitting surface arranged at an angle to the second surface that is less than 45 degrees. The beamsplitter may be configured to illuminate the entire second surface in response to an input beam at the first surface.

The invention relates to the technical field of steel wire rope state detection, in particular to a steel wire rope diameter measuring method and system based on event compensation correction. According to the technical scheme, the system comprises an imaging module, a boundary initial extraction module, a dynamic motion estimation module, a dynamic correction compensation module and a diameter calculation module. The imaging module comprises a traditional camera, an event camera, an optical component, a synchronous triggering device and a spectroscope. The traditional camera is used for collecting frame images of the steel wire rope. According to the method, on the basis of complementary advantages of an event camera and a traditional camera, systematic measurement deviation under the dynamic working condition is solved from the mechanism through an event-driven dynamic geometric compensation model, and quasi-static imaging dependence is broken through. The method does not need extra constraint or increase of frame rate, control cost and hardware complexity, avoids the problems of reduction of signal-to-noise ratio and the like, realizes high-precision stable measurement under high-speed and vibration working conditions, adapts to online monitoring of multiple industrial scenes, and is remarkable in practicability and application value.

A holographic near-eye display device with multi-angle simultaneous illumination comprises a light source module, a spatial light modulator, a beam splitter, an eyepiece, and a master controller. The light source module emits parallel light at different angles and simultaneously illuminates and covers effective working area of spatial light modulator which, loaded with a hologram, modulates incident parallel light at different angles to form diffracted parallel light at different angles, that is, virtual images at different viewing angles. Parallel light at different angles illuminates spatial light modulator. After modulated and diffracted by calculated hologram on spatial light modulator, the diffracted image light is converged by second lens to form different viewpoints for human eye to view. In multi-angle simultaneous illumination, additional time-sharing control of illumination unit is not needed. When size and position of human eye pupil change, clear virtual image is always seen, achieving expanding the eyebox.

The invention discloses a relay device and method for long-distance few-mode optical fiber communication, and belongs to the field of optical communication. According to the device, firstly, optical signals transmitted in a few-mode optical fiber are separated into a plurality of independent mode channels through a mode decomposition multiplexer; then, an adjustable light delay unit is configured in each channel, and compensation is carried out according to a difference mode group delay difference pre-calculated or actually measured by a few-mode optical fiber parameter; furthermore, a dimmable amplifier is used for amplifying the signal, power monitoring is carried out at the output end of the amplifier through an optical fiber beam splitter and a photoelectric detector, closed-loop feedback control is formed, and gain of each channel is adjusted in a self-adaptive mode to eliminate mode-dependent loss. According to the invention, signal distortion can be effectively suppressed in an optical domain, the complexity of digital signal processing of a receiving end is reduced, and the transmission distance and the transmission capacity of a few-mode optical fiber mode division multiplexing communication system are remarkably improved.

This invention presents a frequency-domain fluorescence lifetime imaging system, enhancing capabilities with a spatial beam attenuator and pinhole beam splitter. The spatial beam attenuator reshapes any beam into a circular Gaussian beam profile, being compact, cost-effective, with low loss and back reflection. Using digital printing technology, a thin optical film is deposited onto an optical substrate for precise local attenuation of the beam in either transmission or reflection mode. The pinhole beam splitter consists of an optical beam splitter with an active region the size of a pinhole, positioned near the beam's focus, which directs focused light into two paths based on acceptance or rejection by the pinhole. This configuration allows for two detectors to collect photons from both paths concurrently, facilitating dual-mode imaging. Consequently, the system can generate both confocal and conventional non-confocal laser scanning fluorescence lifetime images of the sample at the same time.

The invention discloses a coaxial laser confocal processing and measurement integrated system and an in-situ morphology measurement method thereof, and belongs to the technical field of ultrafast laser precision processing and in-situ measurement. The system comprises a laser confocal morphology measurement module, an ultrafast laser scanning processing module, a CCD (Charge Coupled Device) microscopic imaging module, a beam splitter prism, a low-pass dichroscope, a long-working-distance achromatic laser processing objective lens and a combined three-axis precision displacement table, the laser confocal morphology measurement module generates a measurement light beam to realize morphology measurement of a sample; the ultrafast laser scanning processing module generates a processing light beam to scan and process the surface of the sample; the CCD microscopic imaging module generates an illumination light beam to realize illumination of a processing position and acquisition of image information of a sample surface; a measurement light beam, a processing light beam and an illumination light beam form coaxial light beams through a low-pass dichroscope, the coaxial light beams are focused at the same position of the surface of a sample through a long-working-distance achromatic laser processing objective lens, and the coaxial in-situ measurement condition is achieved.

The invention discloses a femtosecond optical comb large-size precision absolute distance measurement system in a complex environment. Comprising a source module, a beam splitter, a third dichroic mirror, a fundamental frequency femtosecond optical comb reference detector, a frequency doubling femtosecond optical comb reference detector, a fourth dichroic mirror, a frequency doubling femtosecond optical comb measurement detector, a fundamental frequency femtosecond optical comb measurement detector, a phase discriminator, a ranging zero point mirror and a corner reflector. The source module comprises an atomic clock, a femtosecond optical comb, an optical fiber beam splitter, a signal generator, an electro-optical modulator, a lens, a frequency multiplication module, a first collimation beam expander, a second collimation beam expander, a first dichroic mirror and a second dichroic mirror. According to the scheme, the defects that in the prior art, the measurement range is insufficient, complex industrial sites are difficult to adapt, and the real-time performance is poor are overcome, and a new way is provided for breaking through the technical bottleneck of large-range, high-precision, dead-zone-free, rapid and real-time measurement in a complex environment; and a technical support is provided for engineering application of a femtosecond optical comb precision distance measurement technology and development of a subsequent measurement prototype.

The invention relates to the technical field of projection modules, and particularly discloses an LCOS laser projection module, which comprises a laser light source module, a laser speckle eliminator, a reflector, a diffuser, a collimating lens, a fly-eye lens, a relay lens, a first linear polarizer, a polarizing beam splitter, an LCOS chip, a second linear polarizer and a projection lens which are sequentially arranged along a light transmission path, the laser light source module is provided with a light source optical axis and is used for emitting light, and the light is projected by the projection lens after being modulated along a light transmission path to form a projection image. The light emitted by the laser light source has the advantages of narrow divergence angle, small light-emitting area and good light concentration and collimation, the resolution of a projected image can be improved, the projected image is bright in color and high in definition, and the requirements of simple structure and small size are met. Meanwhile, the laser speckle can be eliminated through the matching of the laser speckle eliminator and the diffusion sheet, and the projection image can meet the high contrast through the existence of the first linear polarizer and the second linear polarizer.

Provided is a substrate inspection apparatus which includes a stage to accommodate a substrate, an image sensor disposed on the stage, an objective lens disposed between the image sensor and the stage to project an image of the substrate, an imaging optical system disposed between the objective lens and the image sensor, a first main beam splitter disposed between the imaging optical system and the objective lens, a first illumination light source disposed at one side of the first main beam splitter to provide first illumination light to a first depth of the substrate, and a second illumination light source disposed adjacent to the first illumination light source to provide second illumination light source, which has a wavelength shorter than that of the first illumination light source, to a second depth, which is shallower than the first depth, through the first main beam splitter.