CN118294016A - Ultrafast single-pixel imaging enhancement system based on spatial optical filter - Google Patents

Abstract

The present invention provides an ultrafast single-pixel imaging enhancement system based on a spatial optical filter, wherein a laser light source is connected to a first end of a circulator through a dispersive medium, a second end of the circulator is connected to a first end of a beam splitter prism through a collimator, a second end of the beam splitter prism is connected to a sample to be tested through a cylindrical mirror, a VIPA, a volume grating, and a first lens in sequence, and a third end of the beam splitter prism is connected to an oscilloscope through a coupler and a second detector in sequence; the third end of the circulator is connected to the oscilloscope through the first detector, and a spatial optical filter is located between the third end of the beam splitter prism and the coupler, and/or between the collimator and the first end of the beam splitter prism. The oscilloscope simultaneously performs two-dimensional imaging of a part and a whole of an irradiated area on the sample to be tested according to electrical signals of filtered and unfiltered spatial optical signals returned by the sample to be tested, and by adopting a volume grating and a first lens, the signal-to-noise ratio of an incident light signal array can be improved, thereby ensuring imaging accuracy.

Description

Ultrafast single-pixel imaging enhancement system based on spatial optical filter

Technical Field

The invention belongs to the field of imaging, and in particular relates to an ultrafast single-pixel imaging enhancement system based on a spatial optical filter.

Background technique

At present, in order to improve the imaging efficiency, when imaging the sample to be tested, the pulsed laser is usually divided into two paths, one path is used as a reference signal, and the other path is converted into an incident light signal array to irradiate the sample to be tested. The incident light signal array is composed of multiple parallel spectral components with different wavelengths, and each spectral component is incident on a different position of the sample to be tested, so as to achieve surface scanning of the sample to be tested. After receiving the incident light signal array, the sample to be tested reflects the spatial light signal back, and the spatial light signal is used as a measurement signal to beat with the reference signal to generate an interference signal, and the deformation at each position on the sample to be tested is detected based on the interference signal. The existing imaging system can only perform overall imaging of the irradiated area on the sample to be tested, but cannot perform prominent imaging of the local area within the irradiated area.

Summary of the invention

The present invention provides an ultrafast single-pixel imaging enhancement system based on a spatial optical filter, so as to solve the problem that the current imaging system can only perform overall imaging of an irradiated area on a sample to be tested, but cannot perform prominent imaging of a local area within the irradiated area.

According to a first aspect of an embodiment of the present invention, there is provided an ultrafast single-pixel imaging enhancement system based on a spatial light filter, comprising a laser light source, a dispersive medium, a circulator, a collimator, a beam splitter, a cylindrical mirror, a virtual imaging phase array VIPA, a volume grating, a first lens, a first detector, an oscilloscope, a coupler, a second detector and a spatial light filter, wherein the laser light source is connected to the first end of the circulator through the dispersive medium, the second end of the circulator is connected to the first end of the beam splitter through the collimator, the second end of the beam splitter is connected to a sample to be measured through the cylindrical mirror, the VIPA, the volume grating and the first lens in sequence, the third end of the beam splitter is connected to the oscilloscope through the coupler and the second detector in sequence; the third end of the circulator is connected to the oscilloscope through the first detector; the spatial light filter is located between the third end of the beam splitter and the coupler, and/or between the collimator and the first end of the beam splitter.

In an optional implementation, when the spatial light filter is only located between the third end of the beam splitter and the coupler, the dispersive medium performs time domain stretching on the pulsed laser output by the laser light source, and transmits the time domain stretched pulsed laser to the collimator through the circulator; the pulsed laser is collimated by the collimator and then transmitted to the beam splitter, and the beam splitter transmits the collimated pulsed laser to the VIPA through the cylindrical mirror;

The VIPA performs spatial dispersion on the received pulsed laser to separate it into a plurality of incident light signals. After the plurality of incident light signals pass through a volume grating whose dispersion direction is orthogonal to the VIPA, an incident light signal array is formed. Spectral components of different wavelengths in the incident light signal array are vertically irradiated to different positions on the sample to be tested through the first lens, thereby realizing surface scanning of the sample to be tested. The spatial light signals reflected back from different positions on the sample to be tested are transmitted to the beam splitter prism in sequence through the first lens, the volume grating, the VIPA and the cylindrical mirror according to the original path.

The beam splitter prism splits the spatial light signal into two paths, one path is transmitted to the first detector through the collimator and the circulator in sequence, and the other path is transmitted to the spatial light filter; the first detector converts the spatial light signal into an unmodulated electrical signal; the spatial light filter performs spectrum filtering on the other spatial light signal, and the filtered spatial light signal is transmitted to the second detector through the coupler, and is converted into a modulated electrical signal by the second detector;

The oscilloscope performs two-dimensional imaging of a part of the irradiated area on the sample to be tested according to the light intensity of the modulated electrical signal; the oscilloscope performs two-dimensional imaging of the entire irradiated area on the sample to be tested according to the light intensity of the unmodulated electrical signal. The light intensity reflects the reflectivity of each position on the sample to be tested, thereby reflecting the characteristics of each position on the sample to be tested.

In another optional implementation, when the spatial light filter is only located between the collimator and the first end of the beam splitter, the dispersive medium performs time domain stretching on the pulsed laser output by the laser light source, and transmits the time domain stretched pulsed laser to the collimator through the circulator; the pulsed laser is collimated by the collimator and then transmitted to the spatial light filter, the spatial light filter performs spectrum filtering on the pulsed laser, the filtered pulsed laser is transmitted to the beam splitter, and the beam splitter transmits the filtered pulsed laser to the VIPA through the cylindrical mirror;

The VIPA performs spatial dispersion on the received pulsed laser to separate it into a plurality of incident light signals. After the plurality of incident light signals pass through a volume grating whose dispersion direction is orthogonal to the VIPA, an incident light signal array is formed. Spectral components of different wavelengths in the incident light signal array are vertically irradiated to different positions on the sample to be tested through the first lens, thereby realizing surface scanning of the sample to be tested. The spatial light signals reflected back from different positions on the sample to be tested are transmitted to the beam splitter prism in sequence through the first lens, the volume grating, the VIPA and the cylindrical mirror according to the original path.

The beam splitter splits the spatial light signal into two paths, one path is transmitted to the spatial light filter, and the other path is transmitted to the second detector through the coupler; the spatial light filter performs spectrum filtering on the spatial light signal, and the filtered spatial light signal is transmitted to the first detector through the collimator and the circulator in sequence, and is converted into a modulated electrical signal by the first detector; the second detector converts the other path of the spatial light signal into an unmodulated electrical signal;

The oscilloscope performs two-dimensional imaging of a part of the irradiated area on the sample to be tested according to the light intensity of the modulated electrical signal; the oscilloscope performs two-dimensional imaging of the entire irradiated area on the sample to be tested according to the light intensity of the unmodulated electrical signal. The light intensity reflects the reflectivity of each position on the sample to be tested, thereby reflecting the characteristics of each position on the sample to be tested.

In another optional implementation, when the spatial light filter is respectively present between the collimator and the first end of the beam splitter prism and between the third end of the beam splitter prism and the coupler, the dispersive medium performs time domain stretching on the pulsed laser output by the laser light source, and transmits the time domain stretched pulsed laser to the collimator through the circulator; the pulsed laser is collimated by the collimator and then transmitted to the spatial light filter, the spatial light filter performs spectrum filtering on the pulsed laser, the filtered pulsed laser is transmitted to the beam splitter prism, and the beam splitter prism transmits the filtered pulsed laser to the VIPA through the cylindrical mirror;

The VIPA performs spatial dispersion on the received pulsed laser to separate it into a plurality of incident light signals. After the plurality of incident light signals pass through a volume grating whose dispersion direction is orthogonal to the VIPA, an incident light signal array is formed. Spectral components of different wavelengths in the incident light signal array are vertically irradiated to different positions on the sample to be tested through the first lens, thereby realizing surface scanning of the sample to be tested. The spatial light signals reflected back from different positions on the sample to be tested are transmitted to the beam splitter prism in sequence through the first lens, the volume grating, the VIPA and the cylindrical mirror according to the original path.

The beam splitter prism divides the spatial light signal into two paths, which are respectively transmitted to corresponding spatial light filters, wherein one spatial light filter performs spectrum filtering on the spatial light signal, and the filtered spatial light signal is sequentially transmitted to the first detector through the collimator and the circulator, and is converted into an unmodulated electrical signal or a modulated electrical signal by the first detector; another spatial light filter performs spectrum filtering on the other spatial light signal, and the filtered spatial light signal is transmitted to the second detector through the coupler, and is converted into a modulated electrical signal or an unmodulated electrical signal by the second detector;

The oscilloscope performs two-dimensional imaging of a part of the irradiated area on the sample to be tested according to the light intensity of the modulated electrical signal; the oscilloscope performs two-dimensional imaging of the entire irradiated area on the sample to be tested according to the light intensity of the unmodulated electrical signal. The light intensity reflects the reflectivity of each position on the sample to be tested, thereby reflecting the characteristics of each position on the sample to be tested.

In another optional implementation, it also includes an optical amplifier arranged between the laser light source and the first end of the circulator, the optical amplifier amplifies the pulse laser and transmits the amplified pulse laser to the collimator through the circulator.

In another optional implementation, the oscilloscope also filters out other electrical signals except the modulated electrical signal from the unmodulated electrical signal, and performs two-dimensional imaging of other areas in the irradiated area on the sample to be tested except the corresponding local area according to the light intensity of the other electrical signals.

In another optional implementation, the spatial light filter is a 4f optical system, and the spatial light filter is also connected to a filter controller, and the filter controller locally stores the correspondence between the different wavelength spectral components in the incident light signal array and the various positions on the sample to be tested;

The spatial light filter comprises a second lens, a spatial modulator SLM and a third lens, wherein the distance from the beam splitter to the second lens, the distance from the second lens to the SLM, the distance from the SLM to the third lens and the distance from the third lens to the coupler or collimator are all f, and f is any value greater than 0;

When the second lens or the third lens in the spatial light filter receives the optical signal, the received optical signal is firstly Fourier transformed so that the center point on the spectrum plane behind the second lens or the third lens corresponds to zero frequency, and the farther from the center point, the higher the corresponding frequency; after receiving the position information to be displayed on the sample to be tested, the filter controller generates a corresponding amplitude grayscale image according to the wavelength of the spectral component corresponding to the position information, and loads the amplitude grayscale image to the SLM, so that the voltages loaded at both ends of the SLM are different in magnitude. After the corresponding voltages are loaded at both ends of the SLM, the liquid crystal molecules therein are polarized at different angles, so that in the optical signal after Fourier transformation, only the spectral components of the corresponding wavelength pass through; correspondingly, the third lens or the second lens performs inverse Fourier transformation on each spectral component passing through the SLM to obtain a filtered optical signal.

In another optional implementation, the spatial light filter includes a second lens, a pinhole located on the spectrum plane, and a third lens, wherein the distance from the beam splitter prism to the second lens, the distance from the second lens to the pinhole, the distance from the pinhole to the third lens, and the distance from the third lens to the coupler or collimator are all f;

When the second lens or the third lens in the spatial optical filter receives the optical signal, the received optical signal is firstly subjected to Fourier transformation, so that the center point on the spectrum plane behind the second lens or the third lens corresponds to zero frequency, and the farther from the center point, the higher the corresponding frequency; after receiving the position information on the sample to be tested, the filter controller adjusts the size of the pinhole, so that only the spectral component corresponding to the wavelength passes through the optical signal after Fourier transformation; correspondingly, the third lens or the second lens performs inverse Fourier transformation on each spectral component passing through the pinhole to obtain a filtered optical signal;

When the spatial light filter is located between the third end of the beam splitter and the coupler, the optical signal received by the spatial light filter is a spatial light signal; when the spatial light filter is located between the collimator and the first end of the beam splitter, the optical signal received by the spatial light filter is an incident pulsed laser and a spatial light signal.

In another optional implementation, the field of view of the system is affected by the cavity length of the VIPA, the number of grating lines of the transmissive body, the focal length of the first lens, and the spectral bandwidth of the pulsed laser.

In another optional implementation, the imaging resolution of the system in the Y-axis direction is mainly affected by the spectral resolution, angular dispersion and focal length of the first lens of the VIPA; the imaging resolution of the system in the X-axis is mainly affected by the free spectral range of the VIPA and the angular dispersion of the volume grating.

The beneficial effects of the present invention are:

1. The present invention can realize simultaneous overall and local imaging of the irradiated area on the sample to be tested, and the present invention replaces the ordinary diffraction grating with a volume grating, which can improve the signal-to-noise ratio of the incident light signal array. The first lens is arranged after the volume grating to convert the noise signal carried in the light signal into parallel light, thereby further reducing the influence of the noise signal on the incident light signal array, thereby further improving the signal-to-noise ratio of the incident light signal array irradiated on the sample to be tested; when the signal-to-noise ratio of the incident light signal array is high, imaging is performed according to the spatial light signal returned by the sample to be tested, which can achieve simultaneous overall and local imaging while ensuring imaging accuracy;

In addition, the present invention uses ultrafast pulsed lasers to perform single-pixel acquisition of surface information on the sample to be tested, and the acquisition frequency can reach the nanosecond level, so that rapid reconstruction of two-dimensional images can be achieved; the present invention combines VIPA and volume grating to obtain a planar array spot, directly illuminating the corresponding plane of the sample to be tested, and realizing a one-to-one mapping between the frequency domain and the spatial domain; the present invention sets two detectors, which can simultaneously obtain ultrafast single-pixel images before and after filtering, and can perform real-time and intuitive image comparison and subsequent image processing; the present invention can selectively highlight the features of the area of interest in the overall image or suppress (mask) the features of certain unnecessary areas in the image, so that the image can be matched with the actual response features. The present invention can reflect the edge and local effective information of the sample to be tested in real time within the ultra-transient time, and is also suitable for signal or defect detection;

The present invention sets the spatial light filter between the collimator and the first end of the beam splitter prism, and by adjusting the filtering characteristics of the spatial light filter, the imaging system can complete a series of coherent and logical imaging operations; on this basis, the spatial light filter is set between the third end of the beam splitter prism and the coupler, and by adjusting the filtering characteristics of the two spatial light filters, the diversity of the coherent imaging operation can be increased; the present invention sets the spatial light filter between the collimator and the first end of the beam splitter prism, and can also improve the quality of the incident light spot on the sample to be measured, while improving the compactness of the optical path structure;

2. The present invention can ensure that the signal-to-noise ratio of the spatial optical signal after splitting is still high by setting an optical amplifier;

3. The spatial light filter of the present invention adopts a 4f optical system including a second lens, an SLM and a third lens, wherein the SLM is used to perform spectral filtering on the spatial light signal, so that the data required for two-dimensional image reconstruction can be obtained within the nanometer range, without the need for subsequent filtering processing by a subsequent algorithm; when the spatial light filter of the present invention includes a second lens, a pinhole located on the spectrum plane and a third lens, all data passing through the pinhole are low-frequency data, and high-frequency filtered data can only be obtained after removing the low-pass filtered data from the unfiltered data. The present invention adopts a low-pass filtering method to indirectly obtain high-pass filtered data, which can effectively avoid the problem of low power existing in direct high-pass filtering, and avoid the use of single-photon detectors.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic structural diagram of an embodiment of an ultrafast single-pixel imaging enhancement system based on a spatial optical filter of the present invention;

FIG2 is a schematic structural diagram of another embodiment of an ultrafast single-pixel imaging enhancement system based on a spatial optical filter according to the present invention;

FIG3 is a schematic structural diagram of another embodiment of an ultrafast single-pixel imaging enhancement system based on a spatial optical filter according to the present invention;

FIG4 is a schematic structural diagram of an embodiment of a spatial light filter of the present invention;

FIG5 is a schematic structural diagram of another embodiment of the spatial light filter of the present invention;

FIG6 is a schematic structural diagram of another embodiment of an ultrafast single-pixel imaging enhancement system based on a spatial optical filter according to the present invention.

Detailed ways

In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention and to make the above-mentioned purposes, features and advantages of the embodiments of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings.

In the description of the present invention, unless otherwise specified and limited, it should be noted that the term "connection" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the internal connection of two elements. It can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

As shown in Figures 1 to 3, the ultrafast single-pixel imaging enhancement system based on the spatial light filter may include a laser light source, a dispersive medium, a circulator, a collimator, a beam splitter, a cylindrical mirror, a virtual imaging phase array VIPA, a volume grating, a first lens, a first detector, an oscilloscope, a coupler, a second detector and a spatial light filter, wherein the laser light source is connected to the first end of the circulator through the dispersive medium, the second end of the circulator is connected to the first end of the beam splitter through the collimator, the second end of the beam splitter is connected to the sample to be measured through the cylindrical mirror, VIPA, volume grating and first lens in sequence, the third end of the beam splitter is connected to the oscilloscope through the coupler and the second detector in sequence; the third end of the circulator is connected to the oscilloscope through the first detector; the spatial light filter is located between the third end of the beam splitter and the coupler, and/or between the collimator and the first end of the beam splitter.

The working principle of the present invention is: when the spatial optical filter is only located between the third end of the beam splitter and the coupler, as shown in FIG1 , the dispersive medium performs time domain stretching on the pulsed laser output by the laser light source, and transmits the time domain stretched pulsed laser to the collimator through the circulator; the pulsed laser is transmitted to the beam splitter after being collimated by the collimator, and the beam splitter transmits the collimated pulsed laser to the VIPA through the cylindrical mirror; the VIPA performs spatial dispersion on the received pulsed laser to separate it into a plurality of incident light signals, and the plurality of incident light signals form an incident light signal array after passing through a volume grating whose dispersion direction is orthogonal to the VIPA, and the spectral components of different wavelengths in the incident light signal array are vertically irradiated to different positions on the sample to be tested through the first lens, thereby realizing the surface scanning of the sample to be tested; the light reflected from different positions on the sample to be tested is reflected back to the VIPA. The spatial light signal is transmitted to the beam splitter prism in accordance with the original path, through the first lens, volume grating, VIPA and cylindrical mirror in sequence; the beam splitter prism divides the spatial light signal into two paths, one path is transmitted to the first detector through the collimator and circulator in sequence, and the other path is transmitted to the spatial light filter; the first detector converts the spatial light signal into an unmodulated electrical signal; the spatial light filter performs spectrum filtering on the other spatial light signal, and the filtered spatial light signal is transmitted to the second detector through the coupler, and is converted into a modulated electrical signal by the second detector; since the features at various positions on the sample to be tested are different (the features may include textures, contours, etc.), the reflectivity is correspondingly different, and the intensity of the light reflected back after receiving the light signal is different, so the reflectivity at the corresponding position on the sample to be tested can be determined according to the light intensity, thereby determining the features of the corresponding position on the sample to be tested. In order to facilitate user viewing, different colors can be used to render different features on the sample to be tested. The oscilloscope in the present invention can perform two-dimensional imaging of a part of the irradiated area on the sample to be tested according to the light intensity of the modulated electrical signal; the oscilloscope can perform two-dimensional imaging of the entire irradiated area on the sample to be tested according to the light intensity of the unmodulated electrical signal, and the light intensity reflects the reflectivity of each position on the sample to be tested, thereby reflecting the characteristics of each position on the sample to be tested.

When the spatial light filter is only located between the collimator and the first end of the beam splitter, as shown in FIG2 , the dispersive medium performs time domain stretching on the pulsed laser output by the laser light source, and transmits the time domain stretched pulsed laser to the collimator through the circulator; the pulsed laser is collimated by the collimator and then transmitted to the spatial light filter, the spatial light filter performs spectrum filtering on the pulsed laser, and the filtered pulsed laser is transmitted to the beam splitter, and the beam splitter transmits the filtered pulsed laser to the VIPA through the cylindrical mirror; the VI The PA performs spatial dispersion on the received pulsed laser and divides it into a plurality of incident light signals. After the plurality of incident light signals pass through a volume grating whose dispersion direction is orthogonal to the VIPA, an incident light signal array is formed. The spectral components of different wavelengths in the incident light signal array are vertically irradiated to different positions on the sample to be tested through the first lens, thereby realizing surface scanning of the sample to be tested. The spatial light signals reflected back from different positions on the sample to be tested are transmitted to the beam splitter prism in sequence through the first lens, the volume grating, the VIPA and the cylindrical mirror along the original path.

The beam splitter divides the spatial light signal into two paths, one path is transmitted to the spatial light filter, and the other path is transmitted to the second detector through the coupler; the spatial light filter performs spectrum filtering on the spatial light signal, and the filtered spatial light signal is transmitted to the first detector through the collimator and the circulator in turn, and is converted into a modulated electrical signal by the first detector; the second detector converts the other spatial light signal into an unmodulated electrical signal. The oscilloscope performs two-dimensional imaging of a part of the irradiated area on the sample to be tested according to the light intensity of the modulated electrical signal; the oscilloscope performs two-dimensional imaging of the entire irradiated area on the sample to be tested according to the light intensity of the unmodulated electrical signal.

When the spatial light filter is respectively present between the collimator and the first end of the beam splitter prism and between the third end of the beam splitter prism and the coupler, as shown in FIG3 , the dispersive medium performs time domain stretching on the pulsed laser output by the laser light source, and transmits the time domain stretched pulsed laser to the collimator through the circulator; the pulsed laser is collimated by the collimator and then transmitted to the spatial light filter, the spatial light filter performs spectrum filtering on the pulsed laser, the filtered pulsed laser is transmitted to the beam splitter prism, and the beam splitter prism transmits the filtered pulsed laser to the VIPA through the cylindrical mirror; the VIPA performs spatial dispersion on the received pulsed laser and divides it into a plurality of incident light signals, and the plurality of incident light signals form an incident light signal array after passing through a volume grating whose dispersion direction is orthogonal to the VIPA, and the spectral components of different wavelengths in the incident light signal array are vertically irradiated to different positions on the sample to be tested through the first lens, thereby realizing the surface scanning of the sample to be tested ; The spatial light signals reflected from different positions on the sample to be tested are transmitted to the dichroic prism in sequence through the first lens, volume grating, VIPA and cylindrical mirror according to the original path; the dichroic prism divides the spatial light signal into two paths, and transmits them to corresponding spatial light filters respectively, one of which performs spectrum filtering on the spatial light signal, and the filtered spatial light signal is transmitted to the first detector through the collimator and circulator in sequence, and is converted into a modulated electrical signal or an unmodulated electrical signal by the first detector; the other spatial light filter performs spectrum filtering on the other spatial light signal, and the filtered spatial light signal is transmitted to the second detector through the coupler, and is converted into an unmodulated electrical signal or a modulated electrical signal by the second detector; the oscilloscope performs two-dimensional imaging of a part of the irradiated area on the sample to be tested according to the light intensity of the modulated electrical signal; the oscilloscope performs two-dimensional imaging of the entire irradiated area on the sample to be tested according to the light intensity of the unmodulated electrical signal.

Existing imaging systems usually use a combination of VIPA and diffraction grating to generate an incident light signal array. If an ordinary diffraction grating is used, the incident light signal array output by the diffraction grating has a low signal-to-noise ratio. Although the signal-to-noise ratio of the incident light signal array in the existing imaging system is low, since the measurement signal reflected back by the incident light signal array is beat with the reference signal, and the image is reconstructed according to the interference signal generated by the beat, the reference signal does not include the noise signal, and the noise signal carried by the incident light signal array will not beat, so the noise signal carried by the incident light signal array will not have much impact on the imaging. It can be seen that the existing imaging system does not have to consider the signal-to-noise ratio of the incident light signal array. The present invention requires simultaneous imaging of the entire and local irradiation area on the sample to be tested. If imaging is based on the beat signal, it will be difficult to separate the local imaging signal that needs to be highlighted from the beat signal, and it is impossible to achieve simultaneous imaging of the entire and local areas. However, when imaging is not based on the beat signal, the imaging signal has a low signal-to-noise ratio.

In order to solve the problem that overall and local imaging cannot be achieved simultaneously when imaging is based on beat frequency signals, and the imaging signal has a low signal-to-noise ratio when imaging is not based on beat frequency signals, the present invention removes the beat frequency branch in the traditional imaging system, splits the spatial light signal returned from the sample to be tested, and uses one spatial light signal as the overall imaging signal, and uses the other spatial light signal as the local imaging signal after spectrum filtering, thereby achieving overall and local simultaneous imaging, and replacing the ordinary diffraction grating with a volume grating when performing surface scanning, and adding a first lens after the volume grating. Since the volume grating has a diffraction characteristic that is independent of polarization, it can maintain a high diffraction efficiency for incident light signals of different polarization states. Therefore, the present invention replaces the ordinary diffraction grating with the volume grating, which can improve the signal-to-noise ratio of the incident light signal array; in addition, the first lens is arranged after the volume grating in the present invention, so that the noise signal carried in the light signal can be converted into parallel light, thereby further reducing the influence of the noise signal on the incident light signal array, thereby further improving the signal-to-noise ratio of the incident light signal array irradiated on the sample to be tested.

Since only light signals of corresponding wavelengths can pass through the spatial light filter, the noise signals carried in the light signals cannot pass through the spatial light filter. Therefore, a branch with a spatial light filter between the beam splitter prism and the oscilloscope can be set as the first branch, and a branch without a spatial light filter between the beam splitter prism and the oscilloscope can be set as the second branch. The beam splitter prism can make the spatial light signal on the first branch have a lower light intensity, and at the same time make the spatial light signal on the second branch have a higher light intensity, so that the light intensity of the spatial light signal on the second branch will be greater than the intensity of the noise signal. In this way, when overall imaging is performed based on the light signal on the second branch, even if the spatial light signal carries a noise signal, the required target spatial light signal can be screened out according to the light intensity, thereby ensuring the accuracy of the overall imaging.

In addition, after receiving the modulated electrical signal and the unmodulated electrical signal, the oscilloscope can also filter out other electrical signals except the modulated electrical signal from the unmodulated electrical signal, and perform two-dimensional imaging of other areas except the corresponding local area in the irradiated area on the sample to be tested according to the light intensity of the other electrical signals. The present invention reconstructs two-dimensional images of other areas except the local area in the irradiated area according to other electrical signals except the modulated electrical signal filtered out from the unmodulated electrical signal, thereby increasing the diversity of the areas to be highlighted that can be displayed simultaneously with the overall irradiated area.

When the spatial light filter is only provided between the third end of the beam splitter and the coupler in the present invention, since the pulse laser irradiated onto the sample to be tested is fixed, the oscilloscope can only display the entire irradiation area and the corresponding local part, and cannot adjust the size of the irradiation area. When the spatial light filter is provided between the collimator and the first end of the beam splitter, not only the pulse laser irradiated onto the sample to be tested will be spectrally filtered, but also the spatial light signal returned from the sample to be tested will be spectrally filtered. After the pulse laser after spectrally filtering is irradiated onto the sample to be tested, in order to image the local part in the irradiation area, the filtering characteristics of the spatial light filter will change. At this time, the pulse laser provided by the laser light source will be reduced in the corresponding irradiation area after passing through the spatial light filter. When the irradiation area can be gradually reduced, a series of coherent and logical imaging operations can be completed by changing the filtering characteristics of the spatial light filter. For example, when the spatial light filter is only provided between the collimator and the first end of the beam splitter prism in the present invention, the filtering characteristics of the spatial light filter are adjusted so that the irradiated area is gradually reduced and the centers of the irradiated areas formed each time overlap, thereby enabling the area centered on a certain position on the sample to be tested to be gradually enlarged and imaged, and each imaging can simultaneously present the overall and local images.

For another example, when the spatial light filter is provided between the collimator and the first end of the beam splitter prism and between the third end of the beam splitter prism and the coupler of the present invention, after the pulsed laser after spectrum filtering is irradiated onto the sample to be tested, the filtering characteristics of the two spatial light filters are adjusted so that the spatial light filter between the collimator and the first end of the beam splitter prism can pass the spectral components of the local area to be compared, and the spatial light filter between the third end of the beam splitter prism and the coupler can pass the spectral components of the corresponding area outside the local area to be compared, and at this time, a comparative imaging diagram of the local area to be compared and its external corresponding area is displayed; after the next cycle of pulsed laser passes through the spatial light filter with adjusted filtering characteristics, the area irradiated onto the sample to be tested is the local area to be compared, and at this time, the filtering characteristics of the spatial light filter between the third end of the beam splitter prism and the coupler are adjusted so that the spectral components of the corresponding area within the local area to be compared can pass, and at this time, a comparative imaging diagram of the local area to be compared and its internal corresponding area is displayed, thereby realizing comparative imaging of a certain area with the external area and the internal area in turn.

It can be seen that the present invention sets the spatial light filter between the collimator and the first end of the beam splitter prism, and by adjusting the filtering characteristics of the spatial light filter, the imaging system can complete a series of coherent and logical imaging operations; on this basis, the spatial light filter is also set between the third end of the beam splitter prism and the coupler, and by adjusting the filtering characteristics of the two spatial light filters, the diversity of the coherent imaging operation can be increased.

In this embodiment, the spatial light filter can be a 4f optical system, and the spatial light filter can also be connected to a filter controller, and the filter controller locally stores the correspondence between the different wavelength spectral components in the incident light signal array and the various positions on the sample to be tested. In one example, as shown in Figure 4, the spatial light filter can include a second lens, a spatial modulator SLM (which can be transmissive) and a third lens, wherein the distance from the beam splitter to the second lens, the distance from the second lens to the SLM, the distance from the SLM to the third lens, and the distance from the third lens to the coupler or collimator are all f, and f can be any value greater than 0; when the second lens or the third lens in the spatial light filter receives an optical signal, the optical signal is first Fourier transformed so that the center point on the rear spectrum plane of the second lens or the third lens corresponds to zero frequency, and the farther away from the center point, the higher the corresponding frequency.

In order to perform two-dimensional imaging, the present invention can first establish a two-dimensional coordinate system, in which the plane where the X-Y axis is located is perpendicular to the incident light signal array. According to the Fourier analysis method, the light field f(x, y) of the spatial light signal can be expanded into a superposition of countless complex functions:

Wherein, f _x and f _y are the spatial frequencies in the X and Y directions respectively, and F(f _x ,f _y ) is the spatial spectrum of f(x,y), representing the weighting factor of each frequency component of (f _x ,f _y );

In this embodiment, the second lens and the third lens may be convex lenses and the focal length may be f. After the spatial light signal f(x, y) is Fourier transformed by the second lens, the above spectrum F(f _x , f _y ) is obtained on the back focal plane of the second lens:

Among them, λ represents the wavelength, x′ and y′ represent the coordinates of the spectrum surface, because Therefore, when the focal length f of the second lens is constant, the center point on the rear spectrum surface (i.e., rear focal plane or output spectrum surface) of the second lens corresponds to zero frequency, and the farther away from the center point, the higher the corresponding frequency. The transmissive SLM placed on the spectrum surface can realize the functions of various spatial filters according to filtering needs.

When using SLM to implement filtering, first, after receiving the position information to be displayed on the sample to be tested, the filter controller generates a corresponding amplitude grayscale image according to the wavelength of the spectral component corresponding to the position information, and loads the amplitude grayscale image to the SLM, so that the voltages loaded at both ends of the SLM are different. After the corresponding voltages are loaded at both ends of the SLM, based on the electrically controlled birefringence and distortion effect of the liquid crystal molecules, the liquid crystal molecules therein are polarized at corresponding angles, thereby realizing light wave characteristic modulation, so that only the spectral components of the corresponding wavelengths pass through the optical signal after Fourier transformation; correspondingly, the third lens or the second lens performs inverse Fourier transformation on each spectral component passing through the SLM to obtain a filtered optical signal.

In this embodiment, when the filter controller loads the amplitude grayscale image into the SLM, the impulse response of the SLM is h(x,y), the filter function is H( _fx , _fy ), and the light field immediately after the filter is proportional to The light field complex amplitude distribution (ignoring constant coefficients) of the filtered spatial light signal output at the rear focal plane of the third lens can be expressed as: g(x,y)=f(x,y)*h(x,y).

The spatial optical filter of the present invention adopts a 4f optical system including a second lens, an SLM and a third lens, wherein the SLM is used to perform spectral filtering on the optical signal, so that the data required for two-dimensional imaging can be obtained within the nanometer range without the need for subsequent algorithm filtering processing.

In another example, as shown in FIG5 , the spatial light filter may include a second lens, a pinhole located on a spectrum plane, and a third lens, wherein the distance from the beam splitter prism to the second lens, the distance from the second lens to the pinhole, the distance from the pinhole to the third lens, and the distance from the third lens to the coupler or collimator are all f; when the second lens or the third lens in the spatial light filter receives an optical signal, the received optical signal is firstly Fourier transformed so that the center point on the spectrum plane behind the second lens or the third lens corresponds to zero frequency, and the farther from the center point, the higher the corresponding frequency; after receiving the position information on the sample to be tested, the filter controller adjusts the size of the pinhole so that only the spectral components corresponding to the wavelength pass through the optical signal after Fourier transformation; correspondingly, the third lens or the second lens performs an inverse Fourier transform on each spectral component passing through the pinhole to obtain a filtered optical signal.

Wherein, when the spatial light filter is located between the third end of the beam splitter and the coupler, the optical signal received by the spatial light filter is a spatial light signal; when the spatial light filter is located between the collimator and the first end of the beam splitter, the optical signal received by the spatial light filter is a pulsed laser and a spatial light signal. The present invention sets a spatial light filter between the collimator and the first end of the beam splitter, which can also improve the quality of the incident light spot on the sample to be tested, and at the same time improve the compactness of the optical path structure; in addition, when the spatial light filter of the present invention includes a second lens, a small hole located on the spectrum plane, and a third lens, the data passing through the small hole are all low-frequency data, and high-frequency filtered data can only be obtained after removing the low-pass filtered data from the unfiltered data. The present invention uses low-pass filtering to indirectly obtain high-pass filtered data, which can effectively avoid the problem of low power in direct high-pass filtering and avoid the use of single-photon detectors.

In this embodiment, the pulse laser can be: an ultrafast pulse laser with a spectral range of more than ten nanometers and a pulse repetition frequency greater than megahertz. The dispersive medium acts as a dispersive Fourier transform DFT module to stretch the pulse laser in the time domain, thereby realizing the mapping of the frequency domain and the time domain. After the spatial domain information is mapped to the frequency domain, the optical pulse propagates in a medium with group velocity dispersion. When the loss is ignored and only the second-order dispersion is considered, the frequency domain information of the pulse itself has a one-to-one correspondence with the time domain information, thereby obtaining the corresponding relationship between wavelength and time. That is, the wide spectrum information of the ultrafast laser is mapped to the time domain through time stretching, and is collected by using a high-frequency photoelectric converter to realize high-speed detection of the sample to be tested (the collection speed can reach MHz). The spectral components of different wavelengths in the incident light signal array are irradiated to different positions on the sample to be tested, thereby realizing the one-to-one mapping of spatial and frequency domain information. Compared with the traditional spectrometer, the present invention uses a dispersive medium to realize the one-to-one mapping of the frequency domain and the spatial domain, and uses Fourier transform technology to record the spectrum, which can ensure the spectral resolution while enabling the spectral information to be directly collected by the detector, thereby making the sampling rate higher.

Wherein, the circulator can be a multimode circulator, and the collimator can couple the collimated optical signal into the optical fiber after collimating the optical signal received by it, so as to transmit the collimated optical signal to the beam splitter (as shown in FIG. 1 ), or to the circulator (as shown in FIG. 1 and FIG. 2 ), or to the spatial optical filter (as shown in FIG. 2 ) through the optical fiber; the coupler can couple the optical signal received by it into the optical fiber, so as to transmit the optical signal received by it to the second detector through the optical fiber. The cylindrical mirror, VIPA, volume grating and first lens constitute a two-dimensional spatial dispersion component. After the pulsed laser is incident on the two-dimensional spatial dispersion component, the two-dimensional spatial dispersion component performs spatial domain spectroscopy on it, and irradiates different spectral components in the incident optical signal array formed to different positions on the sample to be tested, thereby realizing a one-to-one mapping of two-dimensional plane spatial information and frequency domain information.

Among them, the transmission spectrum of VIPA shows multiple resonance peaks separated by the free spectral range (FSR), which is multi-beam interference. Since the output beam of VIPA is periodically aliased, it is necessary to combine VIPA with volume grating to expand the spectrum in two dimensions, so as to achieve one-to-one mapping of different wavelengths and different positions in space. Compared with volume grating, VIPA can produce greater angular dispersion, and its wavelength resolution is also an order of magnitude higher.

The field of view of the system of the present invention is determined by the dispersion capability of the two-dimensional space disperser, the focal length of the lens and the spectral bandwidth of the pulsed laser. The two-dimensional space disperser is composed of a VIPA and a volume grating, and is specifically mainly affected by the cavity length of the VIPA, the number of lines of the transmission volume grating, the focal length of the first lens and the spectral bandwidth of the pulsed laser. The imaging resolution of the system is mainly affected by the spectral resolution and spatial resolution. For reconstructing a two-dimensional image, the factors affecting its longitudinal (Y-axis direction) imaging resolution and transverse (X-axis direction) imaging resolution are different. The imaging resolution of the system in the Y-axis direction is mainly affected by the spectral resolution, angular dispersion and focal length of the first lens of the VIPA; the imaging resolution of the system on the X-axis is mainly affected by the free spectral range of the VIPA and the angular dispersion of the volume grating. Therefore, when realizing spectral imaging through two-dimensional mapping, it is necessary to consider the imaging resolution on the X-axis and the Y-axis at the same time to achieve the best imaging effect. The scanning rate of the system mainly depends on the pulse repetition frequency of the pulsed laser and the response time of the photoelectric converter such as the detector. Usually, the pulse frequency of the ultrafast laser is greater than megahertz, so the scanning rate can reach the nanosecond level.

It can be seen from the above embodiments that the present invention can realize simultaneous overall and local imaging of the irradiated area on the sample to be tested, and the present invention replaces the ordinary diffraction grating with a volume grating, which can improve the signal-to-noise ratio of the incident light signal array. The first lens is arranged after the volume grating so that the noise signal carried in the light signal can be converted into parallel light, thereby further reducing the influence of the noise signal on the incident light signal array, thereby further improving the signal-to-noise ratio of the incident light signal array irradiated on the sample to be tested; when the signal-to-noise ratio of the incident light signal array is high, imaging is performed based on the spatial light signal returned by the sample to be tested, which can achieve simultaneous overall and local imaging while ensuring imaging accuracy.

In addition, the present invention uses ultrafast pulse laser to collect single pixel surface information on the sample to be tested, and the collection frequency can reach the nanosecond level, so that the two-dimensional image can be quickly reconstructed; the present invention combines VIPA and volume grating to obtain a planar array spot, directly illuminate the corresponding plane of the sample to be tested, and realize a one-to-one mapping between the frequency domain and the spatial domain; the present invention sets two detectors, which can simultaneously obtain ultrafast single pixel images before and after filtering, and can perform image comparison and subsequent image processing in real time and intuitively; the present invention can selectively highlight the features of the area of interest in the overall image or suppress (cover up) the features of some unnecessary areas in the image, so that the image can be matched with the actual response features. The present invention can reflect the edge and local effective information of the sample to be tested in real time within the ultra-transient time, and is also suitable for signal or defect detection.

The present invention sets the spatial light filter between the collimator and the first end of the beam splitter prism and between the third end of the beam splitter prism and the coupler. By adjusting the filtering characteristics of the spatial light filter, the imaging system can complete a series of coherent and logical imaging operations; on this basis, the spatial light filter is set between the third end of the beam splitter prism and the coupler. By adjusting the filtering characteristics of the two spatial light filters, the diversity of the coherent imaging operation can be increased. The present invention sets the spatial light filter between the collimator and the first end of the beam splitter prism, which can also improve the quality of the incident light spot on the sample to be tested and improve the compactness of the optical path structure.

See FIG6, which is a schematic diagram of the structure of another embodiment of the ultrafast single pixel imaging enhancement system based on the spatial optical filter of the present invention. The difference between FIG6 and the system shown in FIG1 is that it can also include an optical amplifier arranged between the laser light source and the first end of the circulator, and the optical amplifier amplifies the pulse laser and transmits the amplified pulse laser to the collimator through the circulator. By setting the optical amplifier, the present invention can ensure that the signal-to-noise ratio of the spatial optical signal after splitting is still high.

In one example, a laser light source is used to output an ultrafast pulse laser with a central wavelength of 1566nm, a spectral bandwidth of 15nm, and a repetition frequency of 7.4MHz. The pulse laser is amplified to 140mW by an optical amplifier and injected into a dispersion medium (1530ps/nm) after amplification. After dispersion stretching, it is injected into a beam splitter prism by a collimator. The transmitted light through the beam splitter prism is subjected to spatial spectral splitting by a two-dimensional spatial dispersion component to form an incident light signal array. The two-dimensional spatial dispersion component is composed of a cylindrical mirror (focal length 250mm), a virtual image phase array VIPA, a volume grating (600 lines) and a plano-convex lens (i.e., the first lens, with a focal length of 200mm). The incident light signal array is collimated by a plano-convex lens and irradiated onto the sample to be tested, realizing a one-to-one mapping of two-dimensional plane spatial information and frequency domain information. The spatial light signal that collected the sample information is reflected back along the original optical path to the beam splitter prism, and the transmitted spatial light signal light is coupled into the optical fiber by the collimator, and finally collected by the high-speed photodetector (i.e., the first detector, with a bandwidth of 8 GHz) at the 3-port of the multimode circulator; the reflected spatial light signal enters the spatial light filter, which is a 4f optical system composed of two convex lenses with equal focal lengths and a transmissive SLM on the spectrum plane. The reflected spatial light signal is Fourier transformed by the first convex lens, and targeted spectrum filtering is achieved by the SLM on the spectrum plane. The filtered spatial light signal is inversely Fourier transformed by the second convex lens, coupled into the optical fiber by the coupler, and finally collected by another high-speed photodetector (i.e., the second detector, with a bandwidth of 8 GHz). The light collected by the two detectors is displayed and recorded by a high-frequency oscilloscope, and the sampling rate of the oscilloscope is 50 Gsa/s. The sampling time should be greater than the pulse time after the dispersion light is stretched. The recorded and stored data is processed by a computer, and a two-dimensional intensity matrix is divided according to the free spectrum range of the VIPA, and finally the two-dimensional intensity matrix is used to reconstruct the image before filtering and the enhanced image after filtering.

Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the present invention are indicated by the following claims.

It will be appreciated that the invention is not limited to the precise construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from its scope. The scope of the invention is governed solely by the appended claims.

Claims (10)

1. The ultra-fast single-pixel imaging enhancement system based on the space optical filter is characterized by comprising a laser light source, a dispersion medium, a circulator, a collimator, a beam splitter prism, a cylindrical mirror, a Virtual Imaging Phase Array (VIPA), a volume grating, a first lens, a first detector, an oscilloscope, a coupler, a second detector and a space optical filter, wherein the laser light source is connected with the first end of the circulator through the dispersion medium, the second end of the circulator is connected with the first end of the beam splitter prism through the collimator, the second end of the beam splitter prism is sequentially connected with a sample to be detected through the cylindrical mirror, the VIPA, the volume grating and the first lens, and the third end of the beam splitter prism is sequentially connected with the oscilloscope through the coupler and the second detector; the third end of the circulator is connected with the oscilloscope through the first detector; the spatial light filter is positioned between the third end of the beam-splitting prism and the coupler and/or between the collimator and the first end of the beam-splitting prism.

2. The spatial light filter-based ultrafast single-pixel imaging enhancement system, as recited in claim 1, wherein when the spatial light filter is located only between the third end of the beam splitter prism and the coupler, the dispersion medium performs time-domain stretching on the pulsed laser output by the laser light source, and the time-domain stretched pulsed laser is transmitted to the collimator through the circulator; the pulse laser is transmitted to the beam splitting prism after being collimated by the collimator, and the beam splitting prism transmits the collimated pulse laser to the VIPA through the cylindrical mirror;

The VIPA performs space dispersion on the received pulse laser and is divided into a plurality of incident light signals, the plurality of incident light signals form an incident light signal array after passing through a volume grating with the dispersion direction orthogonal to the VIPA, and spectral components with different wavelengths in the incident light signal array vertically irradiate different positions on the sample to be detected through the first lens, so that the surface scanning of the sample to be detected is realized; the space optical signals reflected from different positions on the sample to be detected are sequentially transmitted to the beam splitting prism through the first lens, the volume grating, the VIPA and the cylindrical mirror according to the original path;

the beam splitting prism divides the space optical signal into two paths, one path of the space optical signal is transmitted to the first detector through the collimator and the circulator in sequence, and the other path of the space optical signal is transmitted to the space optical filter; the first detector converts the spatial light signal into an unmodulated electrical signal; the space optical filter carries out frequency spectrum filtering on the other path of space optical signals, the space optical signals after filtering are transmitted to the second detector through the coupler, and the space optical signals are converted into modulated electric signals by the second detector;

the oscilloscope performs two-dimensional imaging on the local part of the irradiation area on the sample to be detected according to the light intensity of the modulated electric signal; and the oscilloscope performs two-dimensional imaging on the whole irradiation area on the sample to be detected according to the light intensity of the unmodulated electric signal, and the light intensity reflects the reflectivity of each position on the sample to be detected, thereby reflecting the characteristics of each position on the sample to be detected.

3. The spatial light filter-based ultrafast single-pixel imaging enhancement system, as recited in claim 1, wherein when the spatial light filter is positioned only between the collimator and the first end of the beam splitting prism, the dispersion medium performs time-domain stretching on the pulsed laser light output by the laser light source, and the time-domain stretched pulsed laser light is transmitted to the collimator through the circulator; the pulse laser is collimated by the collimator and then transmitted to the spatial optical filter, the spatial optical filter carries out frequency spectrum filtering on the pulse laser, the filtered pulse laser is transmitted to the beam splitting prism, and the beam splitting prism transmits the filtered pulse laser to the VIPA through the cylindrical mirror;

The VIPA performs space dispersion on the received pulse laser and is divided into a plurality of incident light signals, the plurality of incident light signals form an incident light signal array after passing through a volume grating with the dispersion direction orthogonal to the VIPA, and spectral components with different wavelengths in the incident light signal array vertically irradiate different positions on the sample to be detected through the first lens, so that the surface scanning of the sample to be detected is realized; the space optical signals reflected from different positions on the sample to be detected are sequentially transmitted to the beam splitting prism through the first lens, the volume grating, the VIPA and the cylindrical mirror according to the original path;

the beam splitting prism divides the space optical signal into two paths, one path is transmitted to the space optical filter, and the other path is transmitted to the second detector through the coupler; the space optical filter carries out frequency spectrum filtering on the space optical signal, and the filtered space optical signal is transmitted to the first detector through the collimator and the circulator in sequence and is converted into a modulated electric signal by the first detector; the second detector converts the other path of space optical signal into an unmodulated electrical signal;

the oscilloscope performs two-dimensional imaging on the local part of the irradiation area on the sample to be detected according to the light intensity of the modulated electric signal; and the oscilloscope performs two-dimensional imaging on the whole irradiation area on the sample to be detected according to the light intensity of the unmodulated electric signal, and the light intensity reflects the reflectivity of each position on the sample to be detected, thereby reflecting the characteristics of each position on the sample to be detected.

4. The spatial light filter-based ultrafast single-pixel imaging enhancement system, as recited in claim 1, wherein when the spatial light filter exists between the collimator and the first end of the beam-splitting prism and between the third end of the beam-splitting prism and the coupler, respectively, the dispersion medium performs time-domain stretching on the pulse laser output by the laser light source, and the time-domain stretched pulse laser is transmitted to the collimator through the circulator; the pulse laser is collimated by the collimator and then transmitted to the spatial optical filter, the spatial optical filter carries out frequency spectrum filtering on the pulse laser, the filtered pulse laser is transmitted to the beam splitting prism, and the beam splitting prism transmits the filtered pulse laser to the VIPA through the cylindrical mirror;

The VIPA performs space dispersion on the received pulse laser and is divided into a plurality of incident light signals, the plurality of incident light signals form an incident light signal array after passing through a volume grating with the dispersion direction orthogonal to the VIPA, and spectral components with different wavelengths in the incident light signal array vertically irradiate different positions on the sample to be detected through the first lens, so that the surface scanning of the sample to be detected is realized; the space optical signals reflected from different positions on the sample to be detected are sequentially transmitted to the beam splitting prism through the first lens, the volume grating, the VIPA and the cylindrical mirror according to the original path;

The beam splitting prism divides the space optical signal into two paths, and transmits the two paths of the space optical signal to corresponding space optical filters respectively, wherein one space optical filter carries out frequency spectrum filtering on the space optical signal, and the filtered space optical signal sequentially passes through the collimator and the circulator and is transmitted to the first detector, and is converted into an unmodulated electric signal or a modulated electric signal by the first detector; the other space optical filter carries out frequency spectrum filtering on the other path of space optical signals, the filtered space optical signals are transmitted to the second detector through the coupler, and the second detector converts the space optical signals into modulated electric signals or unmodulated electric signals;

The oscilloscope performs two-dimensional imaging on the local part of the irradiation area on the sample to be detected according to the light intensity of the modulated electric signal; and the oscilloscope performs two-dimensional imaging on the whole irradiation area on the sample to be detected according to the light intensity of the unmodulated body electric signal, and the light intensity reflects the reflectivity of each position on the sample to be detected, thereby reflecting the characteristics of each position on the sample to be detected.

5. The spatial light filter-based ultrafast single pixel imaging enhancement system, as recited in any one of claims 1 to 4, further comprising an optical amplifier disposed between the laser light source and the first end of the circulator, the optical amplifier amplifying the pulsed laser light and transmitting the amplified pulsed laser light through the circulator to the collimator.

6. The spatial light filter-based ultrafast single-pixel imaging enhancement system of any one of claims 2 to 4, wherein the oscilloscope further screens out other electrical signals except for the modulated electrical signal from the unmodulated electrical signal, and performs two-dimensional imaging on other areas except for the corresponding local areas in the illuminated area on the sample to be measured according to the light intensity of the other electrical signals.

7. The spatial light filter-based ultrafast single-pixel imaging enhancement system of claim 1, wherein the spatial light filter is a 4f optical system, the spatial light filter is further connected with a filter controller, and the filter controller locally stores the correspondence between different wavelength spectral components in the incident light signal array and each position on the sample to be measured;

The spatial light filter comprises a second lens, a spatial modulator (SLM) and a third lens, wherein the distance from the beam splitting prism to the second lens, the distance from the second lens to the SLM, the distance from the SLM to the third lens and the distance from the third lens to the coupler or the collimator are all f, and f is any value larger than 0;

when a second lens or a third lens in the spatial optical filter receives the optical signal, firstly performing Fourier transform on the received optical signal so that a center point on a rear spectrum surface of the second lens or the third lens corresponds to zero frequency, and the frequency corresponding to the farther from the center point is higher; after receiving position information to be displayed on the sample to be detected, the filter controller generates a corresponding amplitude gray scale map according to the wavelength of a spectrum component corresponding to the position information, and loads the amplitude gray scale map to the SLM, so that voltages loaded at two ends of the SLM are different, and after the corresponding voltages are loaded at two ends of the SLM, liquid crystal molecules in the SLM are polarized at different angles, so that only the spectrum component with the corresponding wavelength in the optical signal after Fourier transformation passes; and performing inverse Fourier transform on each spectral component passing through the SLM by the third lens or the second lens respectively to obtain a filtered optical signal.

8. The spatial light filter-based ultrafast single pixel imaging enhancement system, as recited in claim 1, wherein the spatial light filter comprises a second lens, an aperture located on a spectral plane, and a third lens, wherein the distance of the splitting prism to the second lens, the distance of the second lens to the aperture, the distance of the aperture to the third lens, and the distance of the third lens to the coupler or collimator are all f;

When a second lens or a third lens in the spatial optical filter receives the optical signal, firstly performing Fourier transform on the received optical signal so that a center point on a rear spectrum surface of the second lens or the third lens corresponds to zero frequency, and the frequency corresponding to the farther from the center point is higher; the filter controller adjusts the size of the small hole after receiving the position information on the sample to be detected, so that only spectrum components corresponding to the wavelength in the optical signal after Fourier transformation pass through; performing inverse Fourier transform on each spectrum component passing through the aperture by the third lens or the second lens correspondingly to obtain a filtered optical signal;

When the space optical filter is positioned between the third end of the beam splitter prism and the coupler, the optical signal received by the space optical filter is a space optical signal; when the space optical filter is positioned between the collimator and the first end of the beam splitting prism, the optical signals received by the space optical filter are incident pulse laser and space optical signals.

9. The spatial light filter-based ultrafast single pixel imaging enhancement system, as recited in claim 1, wherein the field of view of the system is affected by the cavity length of the VIPA, the number of lines of the transmission grating, the first lens focal length, and the pulse laser spectral bandwidth.

10. The spatial light filter-based ultrafast single pixel imaging enhancement system, as recited in claim 1 or 9, wherein the imaging resolution of the system in the Y-axis direction is primarily affected by the spectral resolution of the VIPA, angular dispersion, and first lens focal length; the imaging resolution of the system on the X-axis is mainly influenced by the free spectral range of the VIPA and the angular dispersion of the volume grating.