Metasurface lens, optical system, and optical apparatus

Abstract

The invention provides a metasurface lens, an optical system and optical equipment, and the metasurface lens can be applied to a spectrograph, and is used for solving the problem of high cost of the spectrograph in the prior art. The metasurface lens provided by the invention can be used for carrying out dispersion and focusing processing on an optical signal to obtain N point light spots, the N point light spots are in one-to-one correspondence with N wavelength sections, and the central wavelengths of T wavelength sections in the N wavelength sections are adjacent in sequence according to a first wavelength difference, the central wavelengths of the S wavelength sections in the N wavelength sections are sequentially adjacent according to a second wavelength difference, and the first wavelength difference is not equal to the second wavelength difference. According to the method provided by the invention, the metasurface lens can perform different degrees of light splitting on the optical signals of the T wavelength bands and the optical signals of the S wavelength bands, and the cost of the spectrograph can be reduced on the basis of meeting the light splitting requirement.

Description

Technical Field

[0001] The present application relates to the field of optical technology, and in particular to metasurface lenses, optical systems and optical devices. Background Art

[0002] Spectrometers are widely used in agriculture, astronomy, automobiles, biology, chemistry, coatings, colorimetry, environmental monitoring, membrane industry, food, printing, papermaking, Raman spectroscopy, semiconductor industry, component detection, color mixing, matching, etc. For example, spectrometers can be used in biomedical applications, fluorescence measurement, gemstone component detection, oxygen concentration sensors, vacuum chamber coating process monitoring, film thickness measurement, emission spectrum measurement, UV and visible absorption spectrum measurement, color measurement, etc.

[0003] One working principle of a spectrometer is as follows: after receiving an optical signal, the spectrometer uses a dispersion element to evenly disperse the optical signal into multiple light beams according to the wavelength in space, and uses a focusing element to focus each of the multiple light beams on an imaging point, and uses a detection element to measure the light intensity of each image point, thereby obtaining a spectrum. Among them, the number of image points determines the fineness of the spectrum. Generally speaking, the higher the fineness of the spectrum, the more accurate the detection result of the spectrometer. Therefore, with the widespread application of spectrometers, spectrometers have increasingly higher requirements for the fineness of the spectrum.

[0004] However, as the precision of the spectrum increases, the cost of the spectrometer will also increase. Summary of the invention

[0005] The present application provides a metasurface lens, an optical system and an optical device, which are used to solve the problem of high cost of spectrometers in the prior art.

[0006] In the first aspect, the present application provides a metasurface lens, which can be applied to a spectrometer. The metasurface lens can be used to: perform dispersion processing on an optical signal incident on the metasurface lens and emit the optical signal obtained by the dispersion processing, wherein the optical signal emitted by the metasurface lens is focused to obtain N point light spots, N is an integer, and the N point light spots correspond to N wavelength bands one by one, and each of the N point light spots is a point light spot obtained by focusing the optical signal of the corresponding wavelength band in the optical signal incident on the metasurface lens, and the center wavelengths of the T wavelength bands in the N wavelength bands are adjacent in sequence according to a first wavelength difference, and the center wavelengths of the S wavelength bands in the N wavelength bands are adjacent in sequence according to a second wavelength difference, the first wavelength difference is not equal to the second wavelength difference, T and S are both positive integers, and the sum of T and S is less than or equal to N.

[0007] In the present application, the first wavelength difference is not equal to the second wavelength difference, which means that the distribution density of the T point light spots and the S point light spots is different.

[0008] According to the different distribution densities of the point light spots, the distribution area of ​​the point light spots can be divided into a first area and a second area. As an example, the first area may include T point light spots, and the second area may include S point light spots.

[0009] The point light spot in the first area may be a point light spot obtained by focusing a light signal of the first wavelength band through the metasurface lens, and the point light spot in the second area may be a point light spot obtained by focusing a light signal of the second wavelength band through the metasurface lens. The working wavelength band of the metasurface lens includes the first wavelength band and the second wavelength band.

[0010] As an example, when the first area includes T light spots, the first wavelength band may include T wavelength bands corresponding to the T light spots. When the second area includes S light spots, the second wavelength band may include S wavelength bands corresponding to the S light spots.

[0011] In the present application, the distribution density of T point light spots and S point light spots is different, indicating that the metasurface lens can split the optical signals of the first band and the second band to different degrees, or in other words, the metasurface lens can independently phase-control the light of the first band and the second band. In this way, when the information demand of any band is high, the number of point light spots corresponding to any band can be increased based on the information demand of any band, and the number of point light spots of other bands can remain unchanged, so that the cost of the spectrometer can be reduced while ensuring that the distribution density of the point light spots corresponding to any band meets its information demand.

[0012] In some possible designs, the metasurface lens includes a first unit, which is the smallest unit in the metasurface lens that performs dispersion processing on an incident light signal and focuses the outgoing light signal to obtain the N point light spots; wherein the minimum wavelength in the T wavelength bands and the maximum wavelength in the S wavelength bands are the same wavelength, and the phase curve of the first unit has an inflection point at the same wavelength.

[0013] The same wavelength may be a boundary wavelength between the first wavelength band and the second wavelength band.

[0014] The phase curve of the first unit has an inflection point at the same wavelength, so that the first unit can have different light responses between the first band and the second band, which is beneficial for the first unit to independently control the phase of light in the first band and the second band.

[0015] In the present application, the metasurface lens may include one or more first units.

[0016] In some possible designs, the first unit includes a first subunit and a second subunit, and a shape of the first subunit is different from a shape of the second subunit.

[0017] Optionally, the first subunit and the second subunit may be nanocolumns. A first unit may include two nanocolumns, and resonance and interference may exist between the two nanocolumns, thereby facilitating different light responses of the first unit in the first band and the second band.

[0018] In some possible designs, the first subunit and the second subunit meet the following conditions: a refractive index greater than or equal to 2.4, an elliptical or rectangular shape, a material of gallium nitride, and a height greater than or equal to 1500 nanometers.

[0019] In the present application, the metasurface lens is obtained by phase-controlling the shape and size of the first unit. When the shapes of the first subunit and the second subunit in the first unit are elliptical or rectangular, there are more variables related to phase control, and the structures and sizes of the first unit that meet the phase control conditions are more, which is more conducive to obtaining a metasurface lens that meets the phase control conditions.

[0020] In the present application, the greater the refractive index of the first subunit and the second subunit, the stronger the dispersion effect of the first unit on light.

[0021] In the present application, gallium nitride can not only meet the refractive index requirement, but also the spectral range obtained based on gallium nitride is relatively wide.

[0022] In the present application, the higher the height of the first subunit and the second subunit is, the higher the phase control strength of the first unit is. Therefore, in an ideal state, the higher the height of the first subunit and the second subunit is, the better. Optionally, affected by the semiconductor process, the height of the first subunit and the second subunit can also be less than 3000nm.

[0023] In some possible designs, the light transmittance of the first unit is greater than or equal to a preset threshold.

[0024] As an example, the preset threshold may be 70%.

[0025] In the present application, the light transmission rate of the first unit is greater than or equal to a preset threshold value, which can ensure that sufficient light passes through the metasurface lens, thereby obtaining a clearer point light spot.

[0026] In some possible designs, the phase of the optical signal of any wavelength band in the N wavelength bands of the first unit satisfies the following formula:

[0027]

[0028] Wherein, (x, y) represents the first coordinate of the first unit in the coordinate system of the metasurface lens, (x ′ ,y ′ ) represents the offset between the coordinates of the point light spot corresponding to the arbitrary wavelength band on the coordinate system and the first coordinate, f represents the focal length of the point light spot corresponding to the arbitrary wavelength band, and λ represents the central wavelength of the arbitrary wavelength band.

[0029] The formula is a phase condition that the first unit needs to satisfy when forming the N point light spots, and the structure and size of the first unit can be determined based on the formula.

[0030] In the present application, since the structure and size of the first unit satisfy the formula, the first unit can achieve the N point light spots after the optical signal passes through the metasurface lens, thereby realizing independent dispersion control of the first band and the second band by the metasurface lens.

[0031] In some possible designs, the phase offset of the first unit between different wavelengths satisfies the following formula:

[0032]

[0033] in, is the phase of the first unit at the first wavelength, represents the phase of the first unit at the second wavelength, where the first wavelength and the second wavelength are any two wavelengths in the N wavelength bands.

[0034] The formula is another phase condition that the first unit needs to satisfy when forming the N point light spots, and the structure and size of the first unit can be determined based on the formula.

[0035] In the present application, the phase shift of the first unit at the first wavelength and the second wavelength is less than or equal to This is beneficial to achieve a high degree of dispersion of the first unit with large lateral displacement at different wavelengths.

[0036] In some possible designs, the S wavelength bands are located in the ultraviolet light band, and the T wavelength bands are located in the visible light band.

[0037] In a second aspect, the present application provides an optical system, comprising the metasurface lens as described in the first aspect and N detection elements, where N is an integer.

[0038] The metasurface lens is used to perform dispersion processing on the optical signal incident on the metasurface lens and emit the optical signal obtained by the dispersion processing, wherein the optical signal emitted by the metasurface lens is focused to obtain N point light spots, the N point light spots correspond one-to-one to N wavelength bands, each of the N point light spots is a point light spot obtained by focusing the optical signal of the corresponding wavelength band in the optical signal incident on the metasurface lens, the central wavelengths of T wavelength bands in the N wavelength bands are adjacent in sequence according to a first wavelength difference, the central wavelengths of S wavelength bands in the N wavelength bands are adjacent in sequence according to a second wavelength difference, the first wavelength difference is not equal to the second wavelength difference, T and S are both positive integers, and the sum of T and S is less than or equal to N; the N detection elements correspond one-to-one to the N point light spots, and each of the N detection elements is used to detect the intensity of the corresponding point light spot.

[0039] In a third aspect, the present application provides an optical device, wherein the optical device comprises the optical system as described in the second aspect.

[0040] It can be understood that the effects that can be obtained in the second and third aspects can refer to the description in the first aspect and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of the structure of a traditional spectrometer;

[0042] Figure 2 A schematic diagram of the spectral distribution of a traditional spectrometer;

[0043] Figure 3 A schematic diagram of a traditional spectrometer's spectral channel;

[0044] Figure 4 A schematic diagram of the structure of a metasurface lens 400 provided in one embodiment of the present application;

[0045] Figure 5 A schematic diagram of the light splitting of a metasurface lens 400 provided in one embodiment of the present application;

[0046] Figure 6 A schematic diagram of a light splitting channel of a metasurface lens 400 provided in one embodiment of the present application;

[0047] Figure 7 An exemplary structural diagram of a first unit 420 provided in one embodiment of the present application;

[0048] Figure 8 An example diagram of the structural dimensions of the first unit 420 provided in one embodiment of the present application;

[0049] Fig. 9An example diagram of the angle between the first unit 420 and the substrate 410 provided in one embodiment of the present application;

[0050] Fig.10 A schematic diagram of the relationship between the phase and light transmission rate of the first unit 420 and the wavelength provided in one embodiment of the present application;

[0051] Fig.11 A phase distribution diagram corresponding to different central wavelengths of the first unit 420 provided in one embodiment of the present application;

[0052] Fig.12 A schematic flow chart of a method for determining a second target unit from a first target unit provided in one embodiment of the present application;

[0053] Fig.13 A schematic diagram of the planar distribution of a metasurface lens 400 provided in one embodiment of the present application;

[0054] Fig.14 A schematic diagram of an optical system provided for this application. DETAILED DESCRIPTION

[0055] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

[0056] In order to facilitate the clear description of the technical solutions of the embodiments of the present application, in the embodiments of the present application, the words "first" and "second" are used to distinguish the same items or similar items with substantially the same functions and effects. For example, the first information and the second information are only used to distinguish different information, and their order is not limited. Those skilled in the art can understand that the words "first" and "second" do not limit the quantity and execution order, and the words "first" and "second" do not necessarily limit them to be different.

[0057] In the embodiments of the present application, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can represent: a, b, c; a and b; a and c; b and c; or a and b and c. Among them, a, b, c can be single or multiple.

[0058] Spectrometers can be widely used in agriculture, astronomy, automobiles, biology, chemistry, coatings, colorimetry, environmental monitoring, membrane industry, food, printing, papermaking, Raman spectroscopy, semiconductor industry, component detection, color mixing, matching, etc. More specifically, spectrometers can be used in biomedical applications, fluorescence measurement, gem component detection, oxygen concentration sensors, vacuum chamber coating process monitoring, film thickness measurement, emission spectrum measurement, ultraviolet and visible absorption spectrum measurement, color measurement, etc.

[0059] Figure 1 Figure 1 is a schematic diagram of the structure of a traditional spectrometer. Figure 1 As shown, the spectrometer includes an incident port, optical elements and detection elements.

[0060] The incident port is used to receive the optical signal and transmit the optical signal to the optical element.

[0061] The incident port of the spectrometer usually adopts a slit design. In some embodiments, the incident port can also be called an incident slit.

[0062] The optical element may be used to receive an optical signal from an incident port, split the optical signal, and transmit the split light beam to a detection element. As an example, the optical element may include a collimating element, a dispersing element, and a focusing element.

[0063] The collimating element can convert the received optical signal into parallel light. Optionally, the collimating element can be an independent lens, a reflector, or directly integrated on the dispersion element, such as a concave grating in a concave grating spectrometer.

[0064] The dispersion element can uniformly disperse the parallel light into multiple light beams according to wavelength in space. Optionally, the dispersion element is usually a grating.

[0065] The multiple light beams correspond to the multiple wavelength bands one by one, and each of the multiple light beams is a light beam obtained after the optical signal of the corresponding wavelength band passes through the dispersion element.

[0066] Uniformly dispersing into multiple light beams by wavelength can be understood as: the wavelength difference between the center wavelengths of the wavelength bands corresponding to any two adjacent light beams is the same as the wavelength difference between the center wavelengths of the wavelength bands corresponding to any other two adjacent light beams, or in other words, the wavelength difference between any two adjacent wavelength bands is the same.

[0067] The focusing element can be used to focus the dispersed light beam so that it forms a series of light spots (foci or image points) on the focal plane, wherein each light spot corresponds to a wavelength band.

[0068] The detection element can be used to measure the light intensity of each spot, and the detection element is usually placed on the focal plane. In some embodiments, the detection element can be a sensor, a detector array, or a charge-coupled device (CCD).

[0069] Based on the different working band ranges, spectrometers can be divided into visible light spectrometers, shortwave infrared spectrometers, ultraviolet spectrometers, etc.

[0070] Among them, the working band of the visible light spectrometer includes the visible light band. The visible light spectrometer can be used to identify the color of objects or analyze some chemical substances.

[0071] The working band of the shortwave infrared spectrometer includes the shortwave infrared light band. The shortwave infrared spectrometer can be used to obtain some special components that are difficult to identify with the naked eye, such as some minerals, chemical pesticides, and fructose proteins of the biological clock.

[0072] The working band of the ultraviolet spectrometer includes the ultraviolet light band. The ultraviolet spectrometer can be used to obtain images that are not visible to the human eye, and can even be used to obtain some hidden information under low light conditions.

[0073] However, for some complex detection environments, such as remote sensing detection in the aerospace field, quality inspection in the food industry, and medical diagnosis in the medical field, it is often necessary to collect spectral information of multiple spectral bands of the target scene or sample to compare and fuse them, which can more effectively realize target recognition, classification and tracking, etc. These requirements cannot be achieved by a single-band spectrometer. Therefore, a wide-band spectrometer is proposed, which can realize wide-band spectral imaging. Among them, the wide band can contain two or more bands. The wide-band optical wave meter can also be called a multi-band spectrometer.

[0074] As an example, it is assumed that the working band of a spectrometer ranges from 350 nm (nanometers) to 650 nm, and the working band includes a part of the ultraviolet light band (350 nm to 450 nm) and a part of the visible light band (450 nm to 650 nm).

[0075] In the spectrometer, optical signals within the working wavelength band can be evenly dispersed into multiple light beams according to wavelength, and the multiple light beams can be focused into multiple light spots on the focal plane.

[0076] As an example, the conventional spectrometer can be shown as Figure 2 shown. Figure 2 In the invention, the optical element can receive light signals of different wavelengths, evenly split the light signals according to the wavelengths, and transmit the split light beams to the focal plane.

[0077] The area between points A and B in the optical element represents the area where the light signal irradiates the optical element. The light signal received by the optical element is complex light. The solid line represents the light beam within the ultraviolet light band, and the dotted line represents the light beam within the visible light band.

[0078] In this example, the spot light spots on the focal plane are evenly distributed on the focal plane. That is, the distribution density of the spot light spots focused on the focal plane by the light beam in the ultraviolet light band is the same as the distribution density of the spot light spots focused on the focal plane by the light beam in the visible light band. The distribution density of the spot light spots can be understood as the wavelength difference between the center wavelengths of the two wavelength bands corresponding to two adjacent spot light spots.

[0079] The distribution density of the point light spots focused on the focal plane by the light beam in the ultraviolet band may be equal to the ratio of the band width of the ultraviolet band to the number of the point light spots focused on the focal plane by the light beam in the ultraviolet band.

[0080] The distribution density of the point light spots focused on the focal plane by the light beam in the visible light band may be equal to the ratio of the band width of the visible light band to the number of the point light spots focused on the focal plane by the light beam in the visible light band.

[0081] In this example, the band width of the ultraviolet light band is 100nm, the number of point spots focused on the focal plane by the light beam in the ultraviolet light band is 3, and the distribution density of the point spots focused on the focal plane by the light beam in the ultraviolet light band is 100 / 3. The band width of the visible light band is 200nm, the number of point spots focused on the focal plane by the light beam in the visible light band is 6, and the distribution density of the point spots focused on the focal plane by the light beam in the visible light band is 200 / 6. The distribution density of the point spots focused on the focal plane by the light beams in these two bands is the same.

[0082] In this example, the point light spot gathered on the focal plane by the light beam in the ultraviolet light band can be located in the first area on the focal plane, and the point light spot gathered on the focal plane by the light beam in the visible light band can be located in the second area on the focal plane. Since the point light spots on the focal plane are evenly distributed, and in the working band of the spectrometer, the ultraviolet light band is narrower than the visible light band, the area of ​​the first area is smaller than the area of ​​the second area.

[0083] The number of the point light spots in the first area is the same as the number of channels in the ultraviolet light band, and the number of channels in the ultraviolet light band is equal to the number of light beams obtained after the light signal in the ultraviolet light band passes through the optical element.

[0084] The number of the point light spots in the second area is the same as the number of channels in the visible light band, and the number of channels in the visible light band is equal to the number of light beams obtained after the light signal in the visible light band passes through the optical element.

[0085] Accordingly, the spectroscopic channels of the spectrometer can be Figure 3 shown. Figure 3 In the figure, the solid lines represent channels within the wavelength range of 350nm to 450nm, and the dotted lines represent channels within the wavelength range of 450nm to 650nm. There are three channels in the wavelength range of 350nm to 450nm, and there are six channels in the wavelength range of 450nm to 650nm.

[0086] In some scenarios, different bands require different levels of spectral precision. For example, in makeup photography, the visible light band only needs three channels to determine its color information, while the ultraviolet light band requires multiple channels to obtain spectral imaging information.

[0087] Combination Figure 2 or Figure 3 , assuming that the ultraviolet band requires six channels, the number of point spots gathered on the focal plane by the light beam in the ultraviolet band is six. Since the point spots on the focal plane are evenly distributed on the focal plane, the number of point spots gathered on the focal plane by the light beam in the visible light band is twelve, that is, the number of channels in the visible light band is twelve, which exceeds the number of channels required for the visible light band. In other words, when the number of channels required for a band increases, the number of channels in the entire working band of the spectrometer needs to be increased. The spectrometer has a high degree of precision for the entire spectrum, and the cost of the spectrometer is high.

[0088] Therefore, how to reduce the cost of the spectrometer on the basis of satisfying the spectral fineness is a technical problem to be solved urgently in this application.

[0089] The present application provides a metasurface lens, which can be used as an optical element in an optical system, and the optical system can also include a detection element, which is usually placed on the focal plane of the metasurface lens. As an example, the detection element can be a sensor.

[0090] In the present application, the metasurface lens can receive an optical signal, perform dispersion processing on the optical signal incident to the metasurface lens and emit the optical signal obtained by the dispersion processing. The optical signal emitted by the metasurface lens is focused to obtain N point light spots, where N is an integer, and the N point light spots correspond one-to-one to N wavelength bands. Each of the N point light spots is a point light spot obtained by focusing the optical signal of the corresponding wavelength band in the optical signal incident on the metasurface lens.

[0091] The optical signal received by the metasurface lens is polychromatic light, and the distribution density of the N point light spots obtained by focusing the optical signal through the metasurface lens is uneven. The uneven distribution density of the N point light spots can be understood as: the wavelength difference between the center wavelengths of the two wavelength bands corresponding to at least two adjacent point light spots is different from the wavelength difference between the center wavelengths of the two wavelength bands corresponding to at least two other adjacent point light spots.

[0092] As an example, according to the difference in the distribution density of the point light spot, the distribution area of ​​the point light spot can be divided into a first area and a second area, and the distribution density of the point light spot in the first area and the point light spot in the second area is different. The distribution density of the point light spot in the first area and the point light spot in the second area is different, indicating that the metasurface lens has different degrees of light splitting in the first band and the second band.

[0093] The point light spot in the first area can be a point light spot obtained by focusing the light signal of the first wavelength band through the metasurface lens, and the point light spot in the second area can be a point light spot obtained by focusing the light signal of the second wavelength band through the metasurface lens. The number of the point light spots in the first area is one or more, and the number of the point light spots in the second area is also one or more.

[0094] As an example, assuming that the first region includes T point light spots, and these T point light spots correspond to T wavelength bands one by one, then the first wavelength band includes these T wavelength bands, and T is a positive integer. Assuming that the second region includes S point light spots, and these S point light spots correspond to S wavelength bands one by one, then the second wavelength band includes these S wavelength bands, S is a positive integer, and the sum of T and S is less than or equal to N.

[0095] The distribution density of the spot light in the first region can be obtained based on the number of spot light in the first region and the band width of the first band. For example, the distribution density of the spot light in the first region can be equal to the ratio of the band width of the first band to the number of spot light in the first region.

[0096] The distribution density of the spot light in the second region can be obtained based on the number of spot light in the second region and the band width of the second band. For example, the distribution density of the spot light in the second region can be equal to the ratio of the band width of the second band to the number of spot light in the second region.

[0097] In the present application, the distribution density of the point light spots in the first area is uniform, and the distribution density of the point light spots in the second area is uniform.

[0098] The distribution density of the point light spots in the first region is uniform, indicating that the wavelength difference between the central wavelengths of the wavelength bands corresponding to each two adjacent point light spots in the first region is equal. The distribution density of the point light spots in the second region is uniform, indicating that the wavelength difference between the central wavelengths of the wavelength bands corresponding to each two adjacent point light spots in the second region is equal.

[0099] Assume that the wavelength difference between the central wavelengths of the wavelength band corresponding to each two adjacent point light spots in the first area is the first wavelength difference, and the wavelength difference between the central wavelengths of the wavelength band corresponding to each two adjacent point light spots in the second area is the second wavelength difference, and the first wavelength difference is not equal to the second wavelength difference.

[0100] As an example, it is assumed that the first region includes T point light spots, the T point light spots correspond to T wavelength bands one by one, and the central wavelengths of the T wavelength bands are adjacent in sequence according to the first wavelength difference. It is assumed that the second region includes S point light spots, the S point light spots correspond to S wavelength bands one by one, and the central wavelengths of the S wavelength bands are adjacent in sequence according to the second wavelength difference.

[0101] The number of point light spots in the first area is the same as the number of channels in the first band, and the number of channels in the first band is equal to the number of light beams obtained after the optical signal of the first band passes through the metasurface lens.

[0102] The number of point light spots in the second area is the same as the number of channels in the second band, and the number of channels in the second band is equal to the number of light beams obtained after the optical signal of the second band passes through the metasurface lens.

[0103] In the present application, the distribution densities of the point light spots in the first area and the point light spots in the second area are different. The metasurface lens can independently control the dispersion of different bands based on the spectral requirements of different bands, which is beneficial to saving the cost of the spectrometer.

[0104] Next, this application will combine Figures 4 to 14 , the solution of this application is introduced in detail.

[0105] Figure 4 FIG. 4 is a schematic diagram of the structure of a metasurface lens 400 provided in one embodiment of the present application. Figure 4 As shown, the metasurface lens 400 may include a substrate 410 and at least one first unit 420 .

[0106] The substrate 410 may be disposed at the bottom of at least one first unit 420 to support the at least one first unit 420 to ensure the stability of the structure of the metasurface lens 400 .

[0107] Optionally, one first unit 420 may correspond to one base unit, and the base unit may be used to support the corresponding first unit 420. Accordingly, the base 410 may include a plurality of base units, and the plurality of base units may correspond to the plurality of first units 420 one by one.

[0108] The plurality of first units 420 can be used to receive optical signals and gather optical signals of different wavelength bands to a designated position to form a point light spot based on the wavelength band. The optical signals received by the plurality of first units are complex color lights.

[0109] As an example, N point light spots can be obtained based on the metasurface lens 400, where N is an integer. The N point light spots correspond one-to-one to the N wavelength bands, and each of the N point light spots is a point light spot obtained by focusing the light signal of the corresponding wavelength band in the light signal incident on the metasurface lens 400. In the present application, the first unit 420 is the smallest unit in the metasurface lens 400 that performs dispersion processing on the incident light signal and focuses the outgoing light signal to obtain the N point light spots.

[0110] In some embodiments, the first unit may also be referred to as a super unit, a structure unit, or a lens unit.

[0111] In this embodiment, the distribution density of the point light spot obtained by focusing the light signal through the metasurface lens 400 is uneven. The point light spot is located on the focal plane, which can be equivalent to the plane where the sensor is located, and the focal plane is perpendicular to the propagation direction of the light beam.

[0112] According to the difference in distribution density of the point light spots, the distribution area of ​​the point light spots can be divided into a first area and a second area, and the distribution densities of the point light spots in the first area and the point light spots in the second area are different.

[0113] Among them, the point light spot in the first area can be the point light spot obtained by focusing the light signal of the first band after passing through the metasurface lens 400, and the point light spot in the second area can be the point light spot obtained by focusing the light signal of the second band after passing through the metasurface lens 400.

[0114] As an example, assuming that the first region includes T point light spots, and these T point light spots correspond to T wavelength bands one by one, then the first wavelength band includes these T wavelength bands, and T is a positive integer. Assuming that the second region includes S point light spots, and these S point light spots correspond to S wavelength bands one by one, then the second wavelength band includes these S wavelength bands, S is a positive integer, and the sum of T and S is less than or equal to N.

[0115] In the present application, the central wavelengths of the T wavelength bands are adjacent in sequence according to a first wavelength difference, and the central wavelengths of the S wavelength bands are adjacent in sequence according to a second wavelength difference, and the first wavelength difference is not equal to the second wavelength difference.

[0116] The distribution density of the spot light in the first region can be obtained based on the number of spot light in the first region and the band width of the first band. For example, the distribution density of the spot light in the first region can be equal to the ratio of the band width of the first band to the number of spot light in the first region.

[0117] The distribution density of the spot light in the second region can be obtained based on the number of spot light in the second region and the band width of the second band. For example, the distribution density of the spot light in the second region can be equal to the ratio of the band width of the second band to the number of spot light in the second region.

[0118] The distribution densities of the point light spots in the first region and the point light spots in the second region are different, indicating that the metasurface lens 400 has different degrees of light splitting in the first band and the second band.

[0119] Optionally, Figure 5 A schematic diagram of the light splitting of a metasurface lens 400 provided for one embodiment of the present application. The area between points A and B represents the area where the light signal is irradiated onto the metasurface lens 400, and the solid line represents the light beam obtained after the light signal of the first wavelength band passes through the metasurface lens 400, and the point light spot irradiated onto the focal plane by the light beam is located in the first area of ​​the focal plane. The dotted line represents the light beam obtained after the light signal of the second wavelength band passes through the metasurface lens 400, and the point light spot irradiated onto the focal plane by the light beam is located in the second area of ​​the focal plane.

[0120] Assuming that the first wavelength band is 350nm to 450nm, and the second wavelength band is 450nm to 650nm, the optical signal of the first wavelength band obtains six light beams after passing through the metasurface lens 400, and the number of point light spots distributed in the first area is 6, and the optical signal of the second wavelength band obtains three light beams after passing through the metasurface lens 400, and the number of point light spots distributed in the second area is 3. Then the distribution density of the point light spots in the first area is 100 / 6, and the distribution density of the point light spots in the second area is 200 / 3. In this example, the area of ​​the first area is larger than the area of ​​the second area, or in other words, the coordinate range of the first area is larger than the coordinate range of the second area.

[0121] In this embodiment, the number of point light spots in the first area is the same as the number of channels in the first band, and the number of channels in the first band is equal to the number of light beams obtained after the optical signal of the first band passes through the metasurface lens 400.

[0122] The number of point light spots in the second area is the same as the number of channels in the second band, and the number of channels in the second band is equal to the number of light beams obtained after the optical signal of the second band passes through the metasurface lens 400.

[0123] Optionally, an example of the light splitting channel of the metasurface lens 400 can be as follows Figure 6 In this example, the solid line indicates the number of channels in the first band, and the dotted line indicates the number of channels in the second band. The number of channels in the first band is six, and the number of channels in the second band is three.

[0124] In this example, the first band has six channels, based on which the imaging information of the object can be determined, and the number of channels of the first band can be equal to the minimum number of channels required to determine the imaging information of the object. The second band has three channels, based on which the color information of the object can be determined, and the number of channels of the second band can be equal to the minimum number of channels required to determine the color information of the imaging of the object.

[0125] That is to say, the light splitting requirements of the first band and the second band are different. The metasurface lens 400 of the present application can independently control the dispersion of different bands based on the light splitting requirements of the first band and the second band, so that the number of channels of the first band can be equal to the minimum number of channels required to determine the imaging information of the object, and the number of channels of the second band can be equal to the minimum number of channels required to determine the color information of the object. Compared with the spectrometer in the prior art that evenly splits the first band and the second band, the number of channels of the second band in the present application can be less than the number of channels of the second band in the prior art, which can avoid the waste of unnecessary channels in the second band, thereby reducing the cost of the spectrometer.

[0126] In the present application, the number of light beams obtained after the optical signal passes through the metasurface lens 400 can be determined based on the phase condition satisfied by the metasurface lens 400 and the structure and size of the metasurface lens 400. In other words, the distribution density of the point light spot on the focal plane can be determined based on the phase condition satisfied by the metasurface lens 400 and the structure and size of the metasurface lens 400.

[0127] In the present application, the metasurface lens 400 includes one or more first units 420 , and each of the one or more first units 420 may include a first subunit and a second subunit.

[0128] For any first unit 420, the shape of the first subunit and the shape of the second subunit may be different. Optionally, the size of the first subunit and the size of the second subunit may also be different.

[0129] As an example, Figure 7 This is a structural example diagram of a first unit 420 provided in one embodiment of the present application. In this example, the first unit 420 may include a first subunit 4201 and a second subunit 4202 .

[0130] In this example, the first subunit 4201 and the second subunit 4202 may be elliptical nanocolumns. Alternatively, the first subunit 4201 and the second subunit 4202 may also be nanocolumns of other shapes. For example, the first subunit 4201 may also be a rectangular nanocolumn, and the second subunit 4202 may also be a rectangular nanocolumn. The shapes of the first subunit 4201 and the second subunit 4202 may be arbitrarily combined.

[0131] In this example, the first subunit 4201 and the second subunit 4202 may be placed in parallel, that is, the long axis of the first subunit 4201 is parallel to the long axis of the second subunit 4202. Alternatively, the first subunit 4201 and the second subunit 4202 may not be placed in parallel, that is, there may be a deflection angle between the long axis of the first subunit 4201 and the long axis of the second subunit 4202.

[0132] In this example, the height of the first subunit 4201 may be greater than or equal to 1500nm, and the height of the second subunit 4202 may be greater than or equal to 1500nm. The higher the height of the first subunit 4201 and the second subunit 4202, the higher the phase control strength of the first unit 420. Therefore, in an ideal state, the higher the height of the first subunit 4201 and the second subunit 4202, the better. Optionally, affected by the semiconductor process, the height of the first subunit 4201 and the second subunit 4202 can also be less than 3000nm.

[0133] In this example, the refractive index of the first subunit 4201 and the second subunit 4202 may be greater than or equal to 2.4. The greater the refractive index of the first subunit 4201 and the second subunit 4202, the stronger the dispersion effect of the first unit 420 on light.

[0134] Optionally, the material of the first subunit 4201 and the second subunit 4202 may be gallium nitride, which not only meets the refractive index requirement but also has a wider spectral range.

[0135] In the present application, for any first unit 420 , the phase curve of the first unit 420 needs to have an inflection point (or turning point) at a first wavelength, and the first wavelength is a boundary wavelength between the first wavelength band and the second wavelength band.

[0136] As an example, assuming that the first wavelength band includes T wavelength bands, and the second wavelength band includes S wavelength bands, the minimum wavelength among the T wavelength bands and the maximum wavelength among the S wavelength bands may be the same wavelength, and the same wavelength may be the first wavelength.

[0137] In the actual design process, for any first unit 420, the sizes of the first subunit 4201 and the second subunit 4202 need to meet the first condition: the phase curve of the first unit 420 has an inflection point at the second wavelength, and the wavelength difference between the second wavelength and the first wavelength is less than or equal to the first threshold.

[0138] The first threshold may be a smaller value, for example, 30 nm.

[0139] Assuming that the first wavelength range is 350 nm to 450 nm and the second wavelength range is 450 nm to 650 nm, the first wavelength may be 450 nm and the second wavelength may be between 420 nm and 480 nm.

[0140] The phase curve of the first unit 420 can be obtained by scanning the first unit 420. As an example, in combination with Figure 7, the positions of the point light spots corresponding to the light beams of different wavelength bands can be obtained by scanning the first unit 420 once. The phase curve of the first unit 420 can be obtained based on the positions of the point light spots corresponding to the light beams of different wavelength bands.

[0141] The phase curve of the first unit 420 is associated with the size of the first unit 420. When the size of the first unit 420 changes, the obtained phase curve of the first unit 420 also changes.

[0142] In the present application, the size that meets the first condition can be determined based on the phase curves of the first unit 420 at different sizes. Here, the first unit whose size meets the first condition can be referred to as the first target unit.

[0143] like Figure 8 As shown, assuming that the first subunit 4201 includes two axes, the sizes of the two axes can be recorded as W1 and L1 respectively. In one example, W1 represents the size of the short axis of the first subunit 4201, and L1 represents the size of the long axis of the first subunit 4201. In another example, W1 represents the size of the long axis of the first subunit 4201, and L1 represents the size of the short axis of the first subunit 4201.

[0144] Assuming that the second subunit 4202 includes two axes, the sizes of the two axes can be recorded as W2 and L2 respectively. In one example, W2 represents the size of the short axis of the second subunit 4202, and L2 represents the size of the long axis of the second subunit 4202. In another example, W2 represents the size of the long axis of the second subunit 4202, and L2 represents the size of the short axis of the second subunit 4202.

[0145] Among them, the value range of W1 and W2 can be [40nm, 120nm], and the value range of L1 and L2 can be [60nm, 340nm].

[0146] The distance between the first subunit 4201 and the second subunit 4202 can be denoted as a, and the value range of a can be [10 nm, 50 nm].

[0147] like Fig. 9 As shown, the angle between the first unit 420 and the substrate 410 can be recorded as θ, and the value range of θ can be [0°, 180°]. Among them, the angle θ between the first unit 420 and the substrate can be the angle between the positive axis of the first unit 420 and the positive axis of the substrate 410. In this example, the positive axis of the first unit 420 can be parallel to the long axis of the first subunit or the second subunit, and the positive axis of the substrate 410 can be parallel to the substrate 410 and the direction is horizontal to the right.

[0148] In the present application, by modifying any one or more variables among W1, L1, W2, L2, a and θ, multiple phase curves of the first unit 420 at different sizes can be obtained, and then the first target unit is determined based on these multiple phase curves, and the phase curve of the first target unit has an inflection point at the second wavelength.

[0149] In addition, the light transmission rate (or light transmittance) of the first unit can also be greater than or equal to a preset threshold. As an example, the preset threshold can be 70%. The light transmission rate of the first unit is greater than or equal to the preset threshold, which can ensure that enough light passes through the metasurface lens, thereby obtaining a clearer point light spot.

[0150] The light transmission rate of the first unit is also related to the size of the first unit.

[0151] In some possible implementations, any one or more variables among W1, L1, W2, L2, a and θ may be modified based on a control variable method.

[0152] As an example, W1 and W2 can be taken from 40nm to 120nm with a step size of 10nm; L1 and L2 can be taken from 60nm to 340nm with a step size of 20nm; a can be taken from 10nm to 50nm with a step size of 5nm; θ can be taken from 0° to 180° with a step size of 10°.

[0153] Assuming that W1=50nm, L1=100nm, W2=80nm, L2=150nm, a=20nm, θ=60°, the relationship between the phase and light transmission rate of the first unit 420 and the wavelength can be as follows: Fig.10 shown. Fig.10 , the solid line represents the phase curve of the first unit 420 , and the dotted line represents the optical transmission rate of the first unit 420 .

[0154] In this example, the phase curve of the first unit 420 has a turning point near 460 nm, and the light transmission rate of the first unit 420 is about 90%, so the first unit 420 at this size is determined as the first target unit.

[0155] It can be understood that at least one first target unit can be obtained according to a plurality of phase curves.

[0156] In the present application, when the focal plane includes N point light spots, the phase of the optical signal of any wavelength band in the N wavelength bands corresponding to the N point light spots by the first unit 420 satisfies formula (1):

[0157]

[0158] Wherein, (x, y) represents the first coordinate of the first unit 420 in the coordinate system of the metasurface lens 400, (x ′ ,y ′ ) represents the offset between the coordinates of the point light spot corresponding to any wavelength band on the coordinate system and the first coordinate, f represents the focal length of the point light spot corresponding to any wavelength band, and λ represents the central wavelength of any wavelength band.

[0159] Among them, any wavelength band is within the working band range of the metasurface lens 400, and f can be equal to the distance between the metasurface lens 400 and the detection element that receives the point light spot corresponding to the arbitrary wavelength band.

[0160] Accordingly, based on formula (1), we can get Fig.11 The dotted line may represent the phase distribution diagram corresponding to the metasurface lens 400 when the central wavelength in any wavelength band is 350nm, the solid line may represent the phase distribution diagram corresponding to the metasurface lens 400 when the central wavelength in any wavelength band is 450nm, and the dotted line may represent the phase distribution diagram corresponding to the metasurface lens 400 when the central wavelength in any wavelength band is 650nm.

[0161] For any first unit 420 , the phase of the first unit 420 also needs to satisfy a second condition: a phase difference between a first phase of the first unit 420 and a second phase of the first unit 420 is less than or equal to a second threshold.

[0162] The first phase of the first unit 420 refers to a phase obtained after scanning the first unit 420, and the second phase of the first unit 420 refers to a phase calculated based on formula (1).

[0163] The phase difference between the first phase of the first unit 420 and the second phase of the first unit 420 includes multiple phase differences, and the multiple phase differences correspond to multiple center wavelengths one by one. Accordingly, the phase difference between the first phase of the first unit 420 and the second phase of the first unit 420 can be equal to the sum of the phase differences corresponding to each center wavelength in the multiple center wavelengths.

[0164] Optionally, based on the second condition, a second target unit may be determined from the first target units, where the second target unit is a first target unit whose phase satisfies the second condition among the first target units.

[0165] In a possible implementation manner, the method of determining the second target unit from the first target unit based on the second condition may be implemented by a first algorithm.

[0166] Optionally, the first algorithm may be any optimal algorithm, which is not limited in the present application. As an example, the first algorithm may be a genetic algorithm.

[0167] Taking the first algorithm as a genetic algorithm as an example, the method of determining the second target unit from the first target unit can be as follows: Fig.12 shown.

[0168] S1201, randomly generate an initial population, which includes the initial positions of the point light spots corresponding to the two boundary wavelengths of the first band on the focal plane, the initial positions of the point light spots corresponding to the two boundary wavelengths of the second band on the focal plane, and the initial values ​​of phase compensation corresponding to the boundary wavelengths of the first band and the second band.

[0169] S1202, calculating a phase difference between a first phase and a second phase of each of the plurality of first target units based on a residual function, and performing fitness calculation based on a fitness function.

[0170] Optionally, the residual function can be as shown in formula (2):

[0171]

[0172] Among them, R i represents the residual function, N represents the number of light spots, represents the first phase of the optical signal of the first target unit for the i-th wavelength band, represents the second phase of the optical signal of the first target unit for the i-th wavelength band.

[0173] Optionally, the fitness function can be as shown in formula (3):

[0174]

[0175] Among them, F represents the fitness function, M represents the number of first units, φ shift (i) represents the phase compensation of the optical signal corresponding to the i-th spot.

[0176] S1203, determining whether there is at least one first target unit among the plurality of first target units and whether the phase of the first target unit satisfies the second condition. If so, executing S1204; if not, executing S1205.

[0177] S1204: Determine the first target unit with the highest fitness among the at least one first target unit as the second target unit.

[0178] S1205, perform selection, crossover and mutation to obtain a new population, and repeat S1202.

[0179] In the present application, when the focal plane includes N light spots, the phase shift of the first unit 420 between different wavelengths can be as shown in formula (4):

[0180]

[0181] in, is the phase of the first unit 420 at the first wavelength, represents the phase of the first unit 420 at the second wavelength, where the first wavelength and the second wavelength are any two wavelengths in the N wavelength bands corresponding to the N point light spots.

[0182] For any first unit 420, the phase of the first unit 420 also needs to satisfy the third condition: the phase offset between the first wavelength and the second wavelength of the first unit 420 is less than or equal to

[0183] In the present application, the structure and size of the metasurface lens 400 can be determined based on the coordinates, structure and size of each first unit 420 .

[0184] Optionally, the planar distribution diagram of the metasurface lens 400 can be as follows: Fig.13 shown.

[0185] In the present application, the first band and the second band may be any two bands. As an example, assuming that the first band includes T wavelength bands and the second band includes S wavelength bands, the T wavelength bands may be in the visible light band and the S wavelength bands may be in the ultraviolet light band.

[0186] In the present application, the metasurface lens 400 can be applied to an optical system. Fig.14 This is a schematic diagram of an optical system provided in this application. Fig.14 As shown, optical system 1400 may include a metasurface lens and a detection element.

[0187] The metasurface lens is used to perform dispersion processing on the optical signal incident to the metasurface lens and emit the optical signal obtained by the dispersion processing, wherein the optical signal emitted by the metasurface lens is focused to obtain N point light spots, the N point light spots correspond to N wavelength bands one by one, each of the N point light spots is a point light spot obtained by focusing the optical signal of the corresponding wavelength band in the optical signal incident to the metasurface lens, the central wavelengths of T wavelength bands in the N wavelength bands are adjacent in sequence according to a first wavelength difference, the central wavelengths of S wavelength bands in the N wavelength bands are adjacent in sequence according to a second wavelength difference, the first wavelength difference is not equal to the second wavelength difference, T and S are both positive integers, and the sum of T and S is less than or equal to N. The structure of the metasurface lens and the conditions met can be as follows Figures 4 to 13 The above is not repeated here.

[0188] The detection element is used to receive N point light spots and detect the intensity of the N point light spots. As an example, the detection element can be a sensor.

[0189] In a possible implementation, the optical system 1400 may include N detection elements, and the N detection elements correspond one-to-one to the N point light spots. Each of the N detection elements can be used to detect the intensity of the corresponding point light spot.

[0190] Optionally, the aforementioned steps of determining the first target unit, the second target unit, and determining the structure and size of the metasurface lens 400 can be performed by a detection element in the optical system 1400, or by a controller or control chip outside the optical system 1400.

[0191] In this embodiment, the optical system 1400 can be applied to an optical device, such as a spectrometer.

[0192] In the various embodiments of the present application, unless otherwise specified or provided in a logical conflict, the terms and / or descriptions between the different embodiments are consistent and may be referenced to each other, and the technical features in the different embodiments may be combined to form new embodiments according to their inherent logical relationships.

[0193] It is understood that the various numbers involved in the embodiments of the present application are only for the convenience of description and are not used to limit the scope of the embodiments of the present application. The size of the sequence number of the above-mentioned processes does not mean the order of execution, and the execution order of each process should be determined by its function and internal logic.

Claims

1. A metasurface lens, characterized in that: The metasurface lens is used for: The optical signal incident on the metasurface lens is subjected to dispersion processing and the optical signal obtained by the dispersion processing is emitted, wherein the optical signal emitted by the metasurface lens is focused to obtain N point light spots, N is an integer, and the N point light spots correspond to N wavelength bands one by one. Each point light spot of the N point light spots is a point light spot obtained by focusing the optical signal of the corresponding wavelength band in the optical signal incident on the metasurface lens, the center wavelengths of T wavelength bands in the N wavelength bands are adjacent in sequence according to a first wavelength difference, the center wavelengths of S wavelength bands in the N wavelength bands are adjacent in sequence according to a second wavelength difference, the first wavelength difference is not equal to the second wavelength difference, T and S are both positive integers, and the sum of T and S is less than or equal to N.

2. The metasurface lens according to claim 1, characterized in that: The metasurface lens includes a first unit, which is a minimum unit in the metasurface lens that performs dispersion processing on an incident light signal and focuses the outgoing light signal to obtain the N light spots; The minimum wavelength in the T wavelength bands and the maximum wavelength in the S wavelength bands are the same wavelength, and the phase curve of the first unit has an inflection point at the same wavelength.

3. The metasurface lens according to claim 2, characterized in that: The first unit includes a first subunit and a second subunit, and a shape of the first subunit is different from a shape of the second subunit.

4. The metasurface lens according to claim 3, characterized in that: The first subunit and the second subunit meet the following conditions: a refractive index greater than or equal to 2.4, an elliptical or rectangular shape, a material of gallium nitride, and a height greater than or equal to 1500 nanometers.

5. The metasurface lens according to any one of claims 2 to 4, characterized in that: The light transmission rate of the first unit is greater than or equal to a preset threshold.

6. The metasurface lens according to any one of claims 1 to 5, characterized in that: The phase of the optical signal of any wavelength band in the N wavelength bands of the first unit satisfies the following formula: Wherein, (x, y) represents the first coordinate of the first unit in the coordinate system of the metasurface lens, (x ′ ,y ′ ) represents the offset between the coordinates of the point light spot corresponding to the arbitrary wavelength band on the coordinate system and the first coordinate, f represents the focal length of the point light spot corresponding to the arbitrary wavelength band, and λ represents the central wavelength of the arbitrary wavelength band.

7. The metasurface lens according to any one of claims 1 to 6, characterized in that: The phase shift of the first unit between different wavelengths satisfies the following formula: in, is the phase of the first unit at the first wavelength, represents the phase of the first unit at the second wavelength, where the first wavelength and the second wavelength are any two wavelengths in the N wavelength bands.

8. The metasurface lens according to any one of claims 1 to 7, characterized in that: The S wavelength bands are located in the ultraviolet light band, and the T wavelength bands are located in the visible light band.

9. An optical system, characterized in that: The optical system comprises a metasurface lens as claimed in any one of claims 1 to 8 and N detection elements, where N is an integer; The metasurface lens is used to perform dispersion processing on the optical signal incident to the metasurface lens and emit the optical signal obtained by the dispersion processing, wherein the optical signal emitted by the metasurface lens is focused to obtain N point light spots, the N point light spots correspond one-to-one to N wavelength bands, each of the N point light spots is a point light spot obtained by focusing the optical signal of the corresponding wavelength band in the optical signal incident to the metasurface lens, the central wavelengths of T wavelength bands in the N wavelength bands are adjacent in sequence according to a first wavelength difference, the central wavelengths of S wavelength bands in the N wavelength bands are adjacent in sequence according to a second wavelength difference, the first wavelength difference is not equal to the second wavelength difference, T and S are both positive integers, and the sum of T and S is less than or equal to N; The N detection elements correspond to the N point light spots one by one, and each of the N detection elements is used to detect the intensity of the corresponding point light spot.

10. An optical device, characterized in that: The optical device comprises the optical system according to claim 9.

Images