135 results about "Picosecond" patented technology

The invention discloses a PCB blind hole machining method and device, laser drilling equipment and a storage medium, the laser drilling equipment comprises a picosecond or femtosecond laser device and a CO2 laser device, after a first machining parameter of the picosecond or femtosecond laser device and a second machining parameter of the CO2 laser device are determined, on one hand, the first machining parameter of the picosecond or femtosecond laser device and the second machining parameter of the CO2 laser device are determined; the picosecond or femtosecond laser performs cold machining on the surface copper layer to form the annular heat insulation groove, the surface copper layer can be prevented from generating suspended copper at the opening of the blind hole, on the other hand, heat generated when the CO2 laser machines the blind hole can be prevented from being diffused to the opening of the blind hole in the surface copper layer through the annular heat insulation groove, suspended copper is further prevented from being generated, and on the other hand, the heat dissipation efficiency is improved. The picosecond or femtosecond laser device with low processing efficiency is adopted for annularly cutting the annular heat insulation groove in the surface copper layer, then the CO2 laser device with high processing efficiency is used for removing materials in the area in the outer contour of the annular heat insulation groove to achieve drilling, the processing efficiency of the two laser devices with different processing efficiency is considered, and the laser drilling efficiency is improved.

The invention discloses an OEO amplifier with a high-speed hard switching function and an optical transmission system, and relates to the technical field of optical amplifiers, the OEO amplifier comprises three magneto-optical switches, an optical splitter group, a photoelectric detector group, a real-time comparison circuit, a logic gate control circuit and a driving circuit; the photoelectric detector group collects optical signal power to generate an electric signal; the real-time comparison circuit performs voltage threshold judgment on the electric signal; the logic gate control circuit is connected with the output end of the real-time comparison circuit so as to synchronously control the switching states of the three magneto-optical switches according to a voltage threshold judgment result; the driving circuit is used for driving the magneto-optical switch to synchronously execute a switching action; when the OEO amplifier detects that optical signals in any direction are interrupted, all the magneto-optical switches finish synchronous switching within 100 microseconds, and the end-to-end optical signal switching time difference is smaller than 2 picoseconds. The method is suitable for a single-fiber bidirectional optical communication environment requiring high frequency, high precision and high stability.

The invention discloses a miniaturized ultra-strong and ultra-short laser dispersion compensation device and method. The miniaturized ultra-strong and ultra-short laser dispersion compensation device comprises a stretcher, a pre-compensation compressor, an amplifier and a compressor. The pulse laser is firstly broadened by the stretcher, partial second-order and third-order dispersion is compensated by the pre-compensation compressor, partial high-order dispersion is increased, then the pulse laser is amplified by the amplifier, and finally the pulse laser is compressed to be close to the Fourier limit pulse width by the compressor. According to the invention, the pulse laser can be broadened to hundreds of picoseconds or even nanoseconds to be amplified under the existing condition and then compressed to be close to the Fourier limit pulse width, and good light beam quality is ensured.

The invention provides a covalent organic framework material as well as a preparation method and application thereof, 1, 3, 6, 8-tetra (4-aminophenyl) pyrene is selected as a central construction unit, and a trap state is realized in a covalent organic framework (COFs) by regulating and controlling the symmetry of active sites (benzothiadiazole, BT). Compared with a centrosymmetric counterpart in the COFs, by breaking the symmetry of the center BT core, the trap state density in the COFs can be remarkably reduced, and the service life of the shallow trap state can be prolonged to 1160.02 picoseconds. Therefore, more photo-induced electrons can participate in the photocatalytic reaction, and the remarkable performance (greater than 99%) of photocatalytic reduction of uranium (VI) is finally realized. According to the invention, the key effect of symmetric breaking in inhibition of excited state decay of COFs is clarified for the first time, and a profound solution is provided for understanding how to improve the photocatalytic performance of COFs in environmental restoration.

The invention discloses a photoconductive switch, a manufacturing method and a high-voltage-resistant picosecond electric pulse device, relates to the technical field of semiconductor devices and can also be applied to the field of microelectronics, and the photoconductive switch comprises a substrate layer, and a low-temperature gallium arsenide layer, a top insulating layer and a top electrode layer which are sequentially stacked on the substrate layer, wherein the top electrode layer comprises a first pin and a second pin, and the first pin and the second pin are embedded into the low-temperature gallium arsenide layer through the top insulating layer. According to the technical scheme, the electrode with a certain depth is embedded into the gallium arsenide growing at low temperature, so that the current density can be reduced, and the heat dissipation performance and the voltage resistance of the photoconductive switch are enhanced.

The invention relates to the technical field of integrated circuits, and discloses a data generation circuit for a high-speed transmitter. The circuit adopts a two-stage structural design, a first-stage circuit unit generates a narrow pulse signal through cooperation of an input tube, a pre-discharge control tube, a reset control tube and a pre-charge control tube, and a second-stage circuit unit converts a non-full-swing pulse signal into a full-swing signal through a pull-down tube and a plurality of pull-up tubes and outputs the full-swing signal. According to the invention, stable and reliable signal generation and shaping in an ultra-high-speed scene with a unit time interval less than or equal to 10 picoseconds are realized, and the device is suitable for a high-speed transmitter with a 1 / 4 rate or a 1 / 8 rate, and has the characteristics of simple structure and accurate time sequence.

The invention provides a dual-wavelength coaxial aiming system capable of achieving automatic collimation. The dual-wavelength coaxial aiming system is used for inertial confinement nuclear fusion (ICF) picosecond terminal light path cone target posture adjustment and target spot positioning aiming. The system comprises an automatic collimation light path and an aiming light path with different working wavelengths, the automatic collimation light path comprises a light source, a beam splitter prism, a secondary mirror, a reflector and a CCD detector. The aiming light path consists of a primary mirror, a secondary mirror, a lens group, a beam splitter prism and a CCD (Charge Coupled Device) detector which are coaxial; according to the system, a secondary mirror is multiplexed, and automatic collimation and positioning aiming are achieved through transmission and reflection of different wavelengths; the flint and the crown glass are combined to correct color differences of different wavelengths; dual-wavelength light path image planes are at the same position; the system adopts a coaxial two-reflector structure, and is compact in structure and small in size.

The present invention discloses a system and method for continuous observation of multiple time scales during femtosecond laser processing. The system comprises a femtosecond laser light source, a laser processing system, a pulse shaping system, and a multi-time scale continuous observation system. The multi-time scale continuous observation system comprises a femtosecond ultrafast continuous imaging system, a picosecond-nanosecond ultrafast pump-probe system, a nanosecond-millisecond ICCD continuous imaging system, and a microsecond-second high-speed camera system. Compared to other ultrafast imaging systems, the present invention enables ultrafast continuous observation of femtosecond laser processing across multiple time scales. Its observation time range extends over 13 orders of magnitude, from hundreds of femtoseconds to seconds, encompassing the entire physical and chemical reaction process. This system plays a crucial role in providing a deeper understanding and understanding of a range of nonequilibrium and nonlinear ultrafast phenomena in femtosecond laser processing.

The present disclosure provides a time compensation method and system for interference test equipment. The method includes: obtaining a first delay time and a second delay time; decomposing the first delay time and the second delay time to obtain a nanosecond scale delay time corresponding to the first delay time and a picosecond scale delay time corresponding to the second delay time; performing lead compensation for the nanosecond scale delay time by a configurable lead compensation and output module to obtain a nanosecond scale lead compensation time; performing lag compensation for the picosecond scale delay time by a delay compensation module to obtain a picosecond scale delay compensation time, and calculating a sum of the nanosecond scale lead compensation time and the picosecond scale delay compensation time to obtain a picosecond scale lead compensation time; and applying an interference signal on a controller area network, CAN, bus based on the picosecond scale lead compensation time. Therefore, by using a plurality of timing controllers connected in cascade in the delay compensation module, the picosecond scale delay compensation time is realized.

The present invention provides an optical member and a method for manufacturing the same, the method comprising: a removal step for partially removing an antireflection film having a multilayer structure in which a low-refractive-index layer and a high-refractive-index layer are laminated, the antireflection film being formed so as to cover an optical surface of an optical substrate, by irradiation with an ultra-short pulse laser light, and performing non-heat processing on the antireflection film by irradiation with an ultra-short pulse laser light to form an antireflection film having a multilayer structure in which a low-refractive-index layer and a high-refractive-index layer are laminated; the pulse width of the ultra-short pulse laser is 0.1 picosecond or more and less than 100 picoseconds, and in the removal step, the ultra-short pulse laser is irradiated to remove the low refractive index layer, which is the outermost layer of the multilayer structure, or the low refractive index layer, which is the outermost layer, and the conductive layer, which is a layer immediately adjacent to the low refractive index layer. The non-heating processing is a processing for suppressing thermal damage to the high refractive index layer, which is a lower layer of the conductive layer, and the processing for suppressing thermal damage is a processing in which the ratio t1 / t2 of the thickness t1 of a portion removed by the removal step to the thickness t2 of a portion not removed in the high refractive index layer is within the range of 0.90-1.00.

The present disclosure provides a real-time holographic system and a real-time optical reconstruction method, which relate to the field of holographic technology. The system comprises: a first laser, adapted to generate nanosecond pulse light; a first beam splitter, adapted to split the nanosecond pulse light into reference light and detection light, the detection light being incident on an object to be measured and generating object light having information about the object to be measured; a reconstruction light timing module, adapted to generate reconstruction light having timed femtosecond pulse information; a dichroic mirror, adapted to generate combined light based on the incident reference light and reconstruction light; a holographic dry plate, adapted to receive the combined light and object light, so that the reference light and object light in the combined light interfere on the holographic dry plate to form a phase grating, thereby recording optical information; and a multi-frame imaging module, adapted to receive the reconstruction light and form a diffraction wave based on the phase grating, thereby reading the optical information with a time resolution of the order of picoseconds.

The invention discloses a broadband FP (Fabry-Perot) cavity transmission spectral line calibration method and a calibration spectral line generation device, and belongs to the field of astronomical spectrum calibration. According to the invention, the laser frequency comb is utilized to carry out precise calibration on the FP cavity, the precision is an Hz magnitude, and the calibration precision of the radial velocity of the FP cavity can reach m / s; by tuning laser frequency comb parameters, all transmission peaks are supplemented, and broadband coverage is achieved; the high precision requirement for FP cavity coating is avoided, the accuracy of transmission spectral lines is ensured, frequent calibration is performed on the FP cavity, and the problem that the FP cavity cannot provide long-term stability of frequency is solved; a low-repetition-frequency picosecond white light source is used, the spectrum is wide and flat, the spectrum is not sensitive to the position of a transmission peak of an FP cavity, and the light enters a calibrated FP cavity array to generate a calibration spectral line with a high signal-to-noise ratio and multiple frequency intervals, so that the calibration precision of the astronomical spectrometer reaches the cm / s-level radial velocity calibration precision. The method is applied to the calibration of the astronomical spectrometer for extrasolar planet search.

1. Name of the Design Product: Laser Freckle Remover (Picosecond). 2. Use of the Design Product: For laser freckle removal. 3. Design Key Points of the Design Product: Lies in the shape. 4. Picture or Photo that Best Illustrates the Design Key Points: Perspective view.

The invention relates to a radio frequency millimeter wave ultra-low noise single-stage sampling phase-locked loop comprising a sampling phase discriminator used for carrying out instantaneous sampling on a reference signal according to a picosecond-level narrow pulse signal and outputting a sampling voltage, the reference signal and the picosecond-level narrow pulse signal having the same frequency; the series resonance voltage-controlled oscillator based on the transformer is connected with the sampling phase discriminator and used for adjusting the oscillation frequency of the series resonance voltage-controlled oscillator according to the sampling voltage and outputting a high-frequency signal; the frequency divider is connected with the voltage-controlled oscillator and is used for carrying out frequency division on the high-frequency signal and outputting a clock control signal; and the clock generation module is connected with the frequency divider and the sampling phase discriminator and is used for generating a picosecond-level narrow pulse signal according to the clock control signal. The sampling phase-locked loop provided by the invention realizes effective suppression of noise, and has the advantages of low phase noise, low reference stray and small area.

An inspection device includes: a light source for outputting pulsed excitation light with a time width of 10 picoseconds to 10 nanoseconds; a nonlinear optical crystal for generating a terahertz wave by optical wavelength conversion of the pulsed excitation light; a polarization part for reflecting at least a part of a reflected wave of the terahertz wave reflected by an inspection target; and a detector for detecting the reflected wave reflected by the polarization part.

The invention provides an FPGA-based programmable periodic pulse signal generation method and application thereof, and belongs to the technical field of electronic measurement. In order to solve the problems that the large dynamic range and the high resolution are difficult to consider at the same time and hardware resources are consumed synchronously by multiple channels in the prior art, according to the method, coarse delay is achieved through FPGA system clock counting, and next pulse parameters are calculated through accumulation of remaining decimal parts; picosecond-level fine delay is realized by constructing a three-level cascade architecture consisting of a lookup table, a coarse carry chain and a fine carry chain; and XOR synthesis waveforms after rising edges and falling edges are independently generated respectively. In addition, the inter-channel transmission delay difference is compensated by correcting the initial calculation parameters. According to the multi-channel pulse signal generation circuit, high-precision, low-jitter and strictly-aligned-phase multi-channel pulse signals can be generated only by utilizing pure logic resources of the FPGA.

The invention relates to the technical field of laser processing, in particular to a metal surface solder mask processing method and device. Comprising the steps that a laser emits ultraviolet laser; adjusting the position and the size of a focusing light spot of the ultraviolet laser; the position of the metal product to be machined is adjusted, so that the light spot of the ultraviolet laser is focused on the metal product to be machined; controlling the laser to emit laser according to a set frequency and a set light emitting method to process a solder mask on the surface of the to-be-processed metal product; the set light emitting method is a light emitting processing method in which the light emitting time t1 picosecond and then the non-light emitting time t2 picosecond are taken as a light emitting period and n light emitting periods are taken as a processing cycle. According to the metal surface solder mask layer machining method, submicron-level accurate energy deposition is achieved, the non-equilibrium phase change process is triggered, the metal surface is promoted to generate a highly-ordered microcrystalline structure, and the uniformity and consistency of the solder mask layer are improved.

Disclosed is a process for cutting a metallic-glass strip, comprising applying to the strip a pulsed laser beam of wavelength shorter than or equal to 555 nanometers, the pulsed laser beam being formed of a succession of pulses each having a duration shorter than 10 picoseconds, and advantageously shorter than 1 picosecond, the crystallization temperature of the metallic glass being below 500° C., and the light energy of the laser beam incident on the strip being comprised between 1 and 10 microjoules per pulse.

This invention provides a covalent organic framework material, its preparation method, and its applications. The invention selects 1,3,6,8-tetra(4-aminophenyl)pyrene as the central building block and achieves trapped states within covalent organic frameworks (COFs) by controlling the symmetry of the active site (benzothiadiazole, BT). Compared to its centrosymmetric counterpart, by breaking the symmetry of the central BT core, the density of trapped states in COFs can be significantly reduced, and the lifetime of shallow trapped states can be extended to 1160.02 picoseconds. This allows more photogenerated electrons to participate in the photocatalytic reaction, ultimately achieving significant photocatalytic reduction of uranium (VI) (>99%). This invention elucidates for the first time the crucial role of symmetry breaking in suppressing excited-state decay in COFs, providing profound insights into how to improve the photocatalytic performance of COFs in environmental remediation.

The present invention provides an ultrafast time-compressed image acquisition method based on on-chip storage, which is used to address the technical problem that the ultrafast compression imaging technology of a streak camera for a target scene is limited by the working principle of the streak tube, resulting in a time resolution of the order of picoseconds to sub-nanoseconds and a low spatial resolution. The method of the present invention comprises: selecting pixel areas with pixel resolutions of M×N and M×L as imaging photosensitive areas and imaging storage areas, respectively; making a pseudo-random mask plate to cover the imaging photosensitive area, and covering the imaging storage area with an opaque mask plate; imaging the target scene on the imaging surface of the imaging photosensitive area; exposing the target scene and performing an initial image, and transferring the image of the imaging photosensitive area as a whole by one row along the charge storage transfer direction; after the transfer is completed, exposing the imaging photosensitive area and continuing to acquire the image, and executing i=i+1 after the exposure is completed; if i≤L, outputting the next row of images, and so on until i>L, thereby obtaining a time-compressed image of the target scene.

The invention discloses a carving machining method and system based on vector pulse laser, and belongs to the technical field of laser carving, the carving machining method based on the vector pulse laser comprises the steps that linear polarization femtosecond pulse laser is split into femtosecond pre-pulse laser and picosecond main pulse laser; adjusting the pulse time delay between the femtosecond pre-pulse laser and the picosecond main pulse laser; combining the femtosecond pre-pulse laser and the picosecond main pulse laser after delay regulation and control; the femtosecond pre-pulse laser is converted into an angularly polarized femtosecond pre-pulse light beam, the picosecond main pulse laser is converted into a radially polarized picosecond main pulse light beam, and a double-pulse light beam combination of the angularly polarized femtosecond pre-pulse light beam and the radially polarized picosecond main pulse light beam is formed; and the to-be-machined workpiece is ablated and engraved through the double-pulse light beam combination. And by means of the synergistic effect of double pulses and precise time delay, the width and fusion damage of a heat affected zone are remarkably reduced, and high-precision and low-damage carving machining is achieved.

The invention relates to the technical field of lasers, and discloses a composite pulse width laser which comprises a first laser seed source, a second laser seed source, an acousto-optic modulator, a polarization beam combiner and an amplification module, the output end of the first laser seed source is connected with the input end of the acousto-optic modulator, and the output end of the second laser seed source is connected with the input end of the polarization beam combiner. The output end of the acousto-optic modulator is connected with one input end of the polarization beam combiner, the output end of the second laser seed source is connected with the other input end of the polarization beam combiner, the output end of the polarization beam combiner is connected with the input end of the amplification module, and the first laser seed source is in a normally open state. The acousto-optic modulator is used for controlling on-off of laser output by the first laser seed source, the first laser seed source is used for outputting laser with the pulse width range of picosecond magnitude or smaller than picosecond magnitude, and the second laser seed source is used for outputting laser with the pulse width range of nanosecond magnitude or larger than nanosecond magnitude. According to the invention, the composite pulse width laser with a larger pulse width range can be obtained, and the method can adapt to more processing scenes.

The present invention provides a high-repetition-rate extreme ultraviolet radiation light source and an EUV lithography machine light source, wherein a portion of the target laser pulses is incident on a megawatt-class optical gain cavity to generate a second infrared laser pulse with a megawatt average power; another portion of the target laser pulses is incident on a room-temperature very high frequency photocathode microwave electron gun after frequency doubling and shaping, driving the room-temperature very high frequency photocathode microwave electron gun to generate a continuous picosecond electron beam with a repetition rate of hundreds of megahertz; the continuous picosecond electron beam is incident on the megawatt-class optical gain cavity and undergoes inverse Compton scattering with the second infrared laser pulse to generate radiation in the extreme ultraviolet band; further, by adjusting the energy of the continuous picosecond electron beam and the laser incident angle, the wavelength of the scattered light can be adjusted within a certain range, thereby realizing a high-repetition-rate extreme ultraviolet radiation light source.

The invention discloses a lens switching mechanism of a picosecond transient absorption spectrum system, and belongs to the technical field of spectrometers. The mechanism comprises a driving assembly, a reflector assembly, a supporting assembly and a limiting assembly, the driving assembly comprises a driving motor, a sliding rail and a sliding block, the sliding block is installed on the sliding rail, a protruding part is arranged on the sliding block, and the driving motor drives the sliding block to longitudinally move along the sliding rail; the reflecting mirror assembly comprises a rotating arm and a reflecting mirror, the reflecting mirror is arranged at the first end of the rotating arm, and the protruding part is located over the second end of the rotating arm; the supporting assembly comprises a support and a rotating shaft, the rotating arm is connected with the supporting frame through the rotating shaft, and the two ends of the rotating arm rotate in the vertical plane with the rotating shaft on the supporting frame as the center. The limiting assembly comprises a limiting support and a limiting ball head and is fixed below the first end of the rotating arm, a limiting hole matched with the limiting ball head is formed in the limiting support, and the limiting ball head is fixed to the first end of the rotating arm. According to the mechanism, automatic switching of internal light paths is realized, and the measurement precision of the system is improved.

The application discloses a kind of ultrafast pulse laser autocorrelation measurement system and method, comprising: beam splitting unit;Reference light path;Delay light path;Adjustable delay unit;Delay light mirror group;Reference light mirror group;Combining unit;Focusing unit;Asymmetric air nanoslit photodetector, for receiving the light beam output by combining unit and focusing unit, and output corresponding photocurrent signal;Signal acquisition and processing unit, for acquiring photocurrent signal, and obtaining the intensity autocorrelation curve of ultrafast pulse laser according to the time delay change relationship of photocurrent signal, and inversion obtains the pulse width information of ultrafast pulse laser.The application utilizes asymmetric air nanoslit photodetector to directly output photocurrent signal, realizes the autocorrelation measurement of ultrafast pulse laser, without nonlinear crystal, compact structure, easy to integrate, suitable for measuring femtosecond or picosecond ultrafast pulse laser.

The full-automatic cutting disc production equipment comprises a machine frame, one side in the machine frame is connected with a moving platform which is of a step mechanism, the moving platform is connected with a first jacking and transplanting mechanism and a second jacking and transplanting mechanism which are the same in mechanism, and the lower step of the moving platform of the step mechanism is connected with an X-axis sliding platform; the X-axis sliding platform is connected with a Y-axis sliding platform, the Y-axis sliding platform is connected with a Z-axis lifting platform, the Z-axis lifting platform is connected with a cutting head, the cutting head and a picosecond cutting light path device installed in the rack form a cutting light path, and an upper step of the moving platform is connected with a galvanometer splitting gantry. A galvanometer splitting machining head is connected to the galvanometer splitting gantry, the galvanometer splitting gantry and a CO2 light path device installed in the rack form a CO2 light path, and the galvanometer splitting machining head and the cutting head both move in the first jacking and transplanting mechanism and the second jacking and transplanting mechanism. The working efficiency can be improved.

1. Name of the product in this design: Infrared Picosecond Cutting Machine. 2. Application of this design: for cutting glass, ceramics, monocrystalline silicon, etc. 3. The key design feature of this product is its shape. 4. The image or photograph that best illustrates the design's key points: a 3D model.

The utility model discloses ultrashort pulse purple picosecond PCB laser cutting equipment, and relates to the technical field of laser cutting equipment, the ultrashort pulse purple picosecond PCB laser cutting equipment comprises a lower machine body, four supporting legs are fixedly arranged at the lower end of the lower machine body, a plurality of heat dissipation holes are formed in the two sides of one end of the lower machine body, and an upper machine body is fixedly arranged at the upper end of the lower machine body; a baffle is fixedly arranged between the inner walls of the two sides of the upper machine body, and guide rails are fixedly arranged on the inner walls of the two sides of the upper machine body. According to the ultra-short pulse purple picosecond PCB laser cutting equipment, high-precision adjustment of the position of a laser cutting piece can be achieved, the cutting accuracy and precision are ensured, and the production efficiency is improved. When a complex PCB pattern is cut, the falling point of laser can be accurately controlled, errors are avoided, for PCBs of different specifications, the position of the platform can be rapidly adjusted, the working efficiency is improved, the marble platform has good stability and precision retentivity, and vibration and errors in the cutting process are reduced.

A device for the generation of ultrashort pulses, wherein an oscillator is formed by: a first and a second non-overlapping transmission band-pass filter, which can serve as reflecting end element of the oscillator; optically transparent means with non-linear Kerr coefficient χ(3) different from zero configured to achieve a spectral broadening by self-phase modulation of the signal transiting through these means; an optical waveguide that produces a positive gain; a node configured to receive a trigger signal designed to activate the operation of the oscillator; a trigger signal generating device comprising: a laser source, for example a microchip, configured to generate a laser pulse, preferably with a minimum bandwidth, having a duration of hundreds of ps, up to the ns; a coupling system designed to introduce the pulse of the trigger laser into a waveguide made of an optically transparent material characterised by a non-linear Kerr coefficient χ(3) different from zero, which is configured to produce two distinct effects in order to spectrally broaden the pulse of the trigger laser, and precisely: a) self-phase modulation four-wave mixing; the output of the waveguide supplies the trigger signal to the node. The pulses produced by the oscillator typically have a duration of the order of the picosecond and are easily reduced to the Fourier limit of circa 100 femtoseconds by means of a dispersive device.

An image acquisition method comprising: a step of generating an optical excitation pulse group comprising a plurality of repeated optical excitation pulses; a step of emitting the optical excitation pulse group toward an object containing a fluorescent dye; a step of detecting fluorescence intensities generated at a plurality of locations on the object due to the emission of the optical excitation pulse group; and a step of generating a fluorescent image based on the fluorescence intensities at the plurality of locations on the object. In the step of generating the optical excitation pulse group, a time interval between the plurality of optical excitation pulses is set to be equal to or shorter than a relaxation time between excited triplet states of the fluorescent dye or shorter than 10 picoseconds.