Metasurface lens, optical system and optical device

Abstract

This application provides a metasurface lens, an optical system, and an optical device. The metasurface lens can be applied to spectrometers to address the high cost of existing spectrometers. The metasurface lens provided in this application can be used to disperse and focus optical signals to obtain N point spots. These N point spots correspond one-to-one with N wavelength bands. The center wavelengths of T wavelength bands are sequentially adjacent according to a first wavelength difference, and the center wavelengths of S wavelength bands are sequentially adjacent according to a second wavelength difference. The first wavelength difference and the second wavelength difference are not equal. The method of this application allows the metasurface lens to split optical signals of T wavelength bands and S wavelength bands to different degrees, thereby reducing the cost of the spectrometer while meeting the splitting requirements.

Description

Technical Field

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

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

[0003] One working principle of a spectrometer is as follows: After receiving a light signal, the spectrometer uses a dispersive element to uniformly disperse the light signal into multiple beams according to wavelength in space. A focusing element then focuses each beam individually to form an image point, and a detection element measures the light intensity at each image point, thus obtaining the spectrum. The number of image points determines the fineness of the spectrum. Generally, the higher the fineness of the spectrum, the more accurate the spectrometer's detection results. Therefore, with the widespread application of spectrometers, the requirements for spectral fineness are becoming increasingly stringent.

[0004] However, as the required level of spectral precision increases, the cost of spectrometers also rises. Summary of the Invention

[0005] This application provides a metasurface lens, optical system, and optical device to address the problem of high cost of spectrometers in the prior art.

[0006] In a first aspect, this application provides a metasurface lens that can be applied in a spectrometer. The metasurface lens can be used to: perform dispersion processing on an incident light signal and output the dispersion-processed light signal, wherein the output light signal from the metasurface lens is focused to obtain N point spots, where N is an integer, and the N point spots correspond one-to-one with N wavelength bands. Each of the N point spots is a point spot obtained by focusing the light signal of the corresponding wavelength band incident on the metasurface lens. The center wavelengths of T wavelength bands among the N wavelength bands are sequentially adjacent according to a first wavelength difference, and the center wavelengths of S wavelength bands among the N wavelength bands are sequentially adjacent according to a second wavelength difference. The first wavelength difference and the second wavelength difference are not equal, T and S are both positive integers, and the sum of T and S is less than or equal to N.

[0007] In this application, the first wavelength difference and the second wavelength difference are not equal, indicating that the distribution density of T spot lights and S spot lights is different.

[0008] Based on the different distribution densities of the spotlights, the distribution area of ​​the spotlights can be divided into a first region and a second region. As an example, the first region may include T spotlights, and the second region may include S spotlights.

[0009] The first region's spot can be a spot obtained by focusing a first-band optical signal through a metasurface lens, and the second region's spot can be a spot obtained by focusing a second-band optical signal through a metasurface lens. The metasurface lens operates in both the first and second bands.

[0010] As an example, when the first region includes T spot lights, the first band can include the T wavelength bands corresponding to these T spot lights. When the second region includes S spot lights, the second band can include the S wavelength bands corresponding to these S spot lights.

[0011] In this application, the different distribution densities of the T and S spot lights indicate that the metasurface lens can split the optical signals of the first and second wavebands to different degrees. In other words, the metasurface lens can independently phase-modulate the light in the first and second wavebands. Thus, when the information demand is high in any one waveband, the number of spot lights corresponding to that waveband can be increased based on that demand, while the number of spot lights in other wavebands can remain unchanged. This ensures that the distribution density of the spot lights corresponding to that waveband meets its information requirements while also reducing the cost of the spectrometer.

[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 the incident light signal and focuses the emitted 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 can be the boundary wavelength between the first band and the second band.

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

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

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

[0017] Optionally, the first subunit and the second subunit can be nanopillars. A first unit may include two nanopillars, and resonance and interference may exist between these two nanopillars, which is beneficial for achieving different photoresponses in the first and second wavelength bands.

[0018] In some possible designs, the first sub-unit and the second sub-unit satisfy the following conditions: refractive index greater than or equal to 2.4, elliptical or rectangular shape, gallium nitride material, and height greater than or equal to 1500 nanometers.

[0019] In this application, the metasurface lens is obtained by phase-modulating the shape and size of the first unit. When the first and second sub-units in the first unit are elliptical or rectangular in shape, there are more variables related to phase modulation, and the structure and size of the first unit that satisfy the phase modulation conditions are more numerous, which is more conducive to obtaining a metasurface lens that satisfies the phase modulation conditions.

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

[0021] In this application, gallium nitride not only meets the refractive index requirements, but also provides a wider spectral range.

[0022] In this application, the higher the height of the first sub-cell and the second sub-cell, the stronger the phase modulation capability of the first sub-cell. Therefore, ideally, the higher the height of the first sub-cell and the second sub-cell, the better. Optionally, due to the influence of semiconductor process technology, the height of the first sub-cell and the second sub-cell can also be less than 3000nm.

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

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

[0025] In this application, the light transmittance of the first unit is greater than or equal to a preset threshold, which ensures that enough light passes through the metasurface lens, thereby obtaining a relatively clear spot.

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

[0027]

[0028] Where (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 spot corresponding to the arbitrary wavelength segment in the coordinate system and the first coordinate, f represents the focal length of the point spot corresponding to the arbitrary wavelength segment, and λ represents the center wavelength of the arbitrary wavelength segment.

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

[0030] In this application, since the structure and size of the first unit satisfy the formula, the first unit can realize that the light signal can obtain the N point light spots after passing through the metasurface lens, thereby realizing the independent dispersion control of the first band and the second band by the metasurface lens.

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

[0032]

[0033] in, The phase of the first unit at the first wavelength. This indicates the phase of the first unit at the second wavelength, where the first wavelength and the second wavelength are any two wavelengths from the N wavelength segments.

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

[0035] In this application, the phase offset of the first unit at the first wavelength and the second wavelength is less than or equal to... This is beneficial for achieving high dispersion with large lateral displacement of the first unit 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, this application provides an optical system comprising a 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 light signal incident on the metasurface lens and to output the dispersion-processed light signal. The light signal output from the metasurface lens is focused to obtain N point spots, each of which corresponds to one of N wavelength bands. Each of the N point spots is a point spot obtained by focusing the light signal of the corresponding wavelength band incident on the metasurface lens. The center wavelengths of T wavelength bands among the N wavelength bands are sequentially adjacent according to a first wavelength difference, and the center wavelengths of S wavelength bands among the N wavelength bands are sequentially adjacent according to a second wavelength difference. The first wavelength difference and the second wavelength difference are not equal. 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 with the N point spots, and each of the N detection elements is used to detect the intensity of the corresponding point spot.

[0039] Thirdly, this application provides an optical device, which includes the optical system described in the second aspect.

[0040] It is understandable that the effects achievable in the second and third aspects can be referred to the description in the first aspect, and will not be repeated here. Attached Figure Description

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

[0042] Figure 2 This is a schematic diagram of the spectroscopic activity of a traditional spectrometer.

[0043] Figure 3 This is a schematic diagram of the spectroscopic channel of a traditional spectrometer.

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

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

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

[0047] Figure 7 A structural example diagram of the first unit 420 provided in one embodiment of this application;

[0048] Figure 8 Example diagram of the structural dimensions of the first unit 420 provided in one embodiment of this application;

[0049] Figure 9An example diagram showing the angle between the first unit 420 and the substrate 410 provided in one embodiment of this application;

[0050] Figure 10 A schematic diagram illustrating the relationship between the phase and optical transmittance and wavelength of the first unit 420 provided in one embodiment of this application;

[0051] Figure 11 A phase distribution diagram of the first unit 420 at different center wavelengths provided in one embodiment of this application;

[0052] Figure 12 This is a schematic flowchart of a method for determining a second target unit from a first target unit according to an embodiment of this application;

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

[0054] Figure 14 A schematic diagram of an optical system provided in this application. Detailed Implementation

[0055] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0056] To facilitate a clear description of the technical solutions in the embodiments of this application, the terms "first" and "second" are used in the embodiments of this application to distinguish identical or similar items with essentially the same function and effect. For example, "first information" and "second information" are only used to distinguish different information and do not limit their order. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and the terms "first" and "second" are not necessarily different.

[0057] In this application embodiment, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer 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. Here, a, b, and c can be single or multiple.

[0058] Spectrometers have a wide range of applications in agriculture, astronomy, automotive, biology, chemistry, coatings, colorimetry, environmental monitoring, membrane industry, food, printing, papermaking, Raman spectroscopy, semiconductor industry, component analysis, color mixing, and matching. More specifically, spectrometers can be used in biomedical applications, fluorescence measurement, gemstone composition analysis, oxygen concentration sensors, vacuum chamber coating process monitoring, film thickness measurement, emission spectroscopy measurement, ultraviolet and visible absorption spectroscopy measurement, and color measurement.

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

[0060] The incident port is used to receive optical signals and transmit them to optical elements.

[0061] The entrance port of a spectrometer is typically designed as a slit; in some embodiments, the entrance port may also be referred to as an entrance slit.

[0062] Optical elements can be used to receive optical signals from an incident port, split the optical signals, and transmit the split beam to a detection element. As examples, optical elements may include collimating elements, dispersing elements, and focusing elements.

[0063] The collimating element converts the received optical signal into parallel light. Optionally, the collimating element can be a separate lens, a mirror, or directly integrated into the dispersive element, such as a concave grating in a concave grating spectrometer.

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

[0065] Multiple light beams correspond one-to-one with multiple wavelength bands. Each of these multiple light beams is the light beam obtained after the light signal of the corresponding wavelength band passes through the dispersive element.

[0066] Distributing the wavelength evenly into multiple beams can be understood as follows: the wavelength difference between the center wavelengths of any two adjacent beams is the same as the wavelength difference between the center wavelengths of any two adjacent beams, or in other words, the wavelength difference between any two adjacent wavelength segments is the same.

[0067] Focusing elements can be used to focus a dispersed light beam, causing it to form a series of point spots (focal points or image points) on the focal plane, where each point spot corresponds to a wavelength band.

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

[0069] Based on the different operating wavelength ranges, spectrometers can be divided into visible light spectrometers, short-wave 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 to analyze some chemical substances.

[0071] Short-wave infrared spectrometers operate in the short-wave infrared band. They 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 related to the biological clock.

[0072] Ultraviolet spectrometers operate in the ultraviolet light band. They can be used to obtain images that are invisible to the human eye, and even to obtain hidden information under low light conditions.

[0073] However, for complex detection environments, such as remote sensing in aerospace, quality inspection in the food industry, and medical diagnosis, it is often necessary to collect spectral information from multiple bands of the target scene or sample, compare and fuse them, and more effectively achieve target identification, classification, and tracking. These requirements cannot be met by single-band spectrometers. Therefore, wideband spectrometers have been proposed, which can achieve spectral imaging across a wide range of wavelengths. The wide band can include two or more bands. Wideband spectrometers can also be called multi-band spectrometers.

[0074] As an example, suppose a spectrometer operates in the range of 350 nm to 650 nm, which includes a portion of the ultraviolet band (350 nm to 450 nm) and a portion of the visible band (450 nm to 650 nm).

[0075] In this spectrometer, optical signals within the operating wavelength range can be uniformly dispersed into multiple beams according to wavelength, and these multiple beams can be focused into multiple spotlights on the focal plane.

[0076] As an example, a traditional spectrometer's spectroscopic diagram can be shown as follows: Figure 2 As shown. Figure 2 In this optical element, the light signal can be received at different wavelengths, the light signal can be split evenly according to the wavelength, and the split light beam can be transmitted to the focal plane.

[0077] In an optical element, the area between points A and B represents the area where light signals illuminate the optical element. The light signals received by the optical element are polychromatic light. Solid lines represent light beams within the ultraviolet band, and dashed lines represent light beams within the visible light band.

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

[0079] The distribution density of the spot light focused on the focal plane by a beam of light in the ultraviolet band can be equal to the ratio of the bandwidth of the ultraviolet band to the number of spot light focused on the focal plane by a beam of light in the ultraviolet band.

[0080] The distribution density of the point spot of a beam of light in the visible light band focused on the focal plane can be equal to the ratio of the bandwidth of the visible light band to the number of point spots of a beam of light in the visible light band focused on the focal plane.

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

[0082] In this example, the spot of light focused on the focal plane by a beam in the ultraviolet band can be located in a first region of the focal plane, while the spot of light focused on the focal plane by a beam in the visible light band can be located in a second region of the focal plane. Since the spot of light on the focal plane is uniformly distributed, and the ultraviolet band is narrower than the visible light band in the operating band of the spectrometer, the area of ​​the first region is smaller than the area of ​​the second region.

[0083] The number of spotlights in the first region is the same as the number of channels in the ultraviolet band. The number of channels in the ultraviolet band is equal to the number of light beams obtained after the ultraviolet light signal passes through the optical element.

[0084] The number of spotlights in the second region is the same as the number of channels in the visible light band. The number of channels in the visible light band is equal to the number of beams obtained after the visible light signal passes through the optical element.

[0085] Accordingly, the spectrometer's dispersive channels can be as follows: Figure 3 As shown. Figure 3 In the diagram, solid lines represent channels in the 350nm to 450nm band, and dashed lines represent channels in the 450nm to 650nm band. There are three channels in the 350nm to 450nm band and six channels in the 450nm to 650nm band.

[0086] In some scenarios, different wavelengths require different levels of spectral detail. For example, in makeup photography, only three channels are needed in the visible light band to determine color information, while multiple channels are needed in the ultraviolet light band to obtain spectral imaging information.

[0087] Combination Figure 2 or Figure 3 Assuming the ultraviolet (UV) band requires six channels, the number of point spots formed by the UV beam on the focal plane is six. Since these point spots are uniformly distributed on the focal plane, the number of point spots formed by the visible light beam on the focal plane is twelve. This means the visible light band requires twelve channels, exceeding the required number of channels. In other words, increasing the required number of channels for a particular band necessitates increasing the total number of channels across the entire operating band of the spectrometer. While this increases the precision of the spectrometer across the entire spectrum, it also increases its cost.

[0088] Therefore, how to reduce the cost of the spectrometer while ensuring the required spectral precision is a technical problem that this application urgently needs to solve.

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

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

[0091] In this system, the light signal received by the metasurface lens is polychromatic light, and the distribution density of the N point spots obtained by focusing the light signal through the metasurface lens is non-uniform. The non-uniform distribution density of the N point spots can be understood as follows: the wavelength difference between the center wavelengths of the two wavelength segments corresponding to at least two adjacent point spots is different from the wavelength difference between the center wavelengths of the two wavelength segments corresponding to at least another two adjacent point spots.

[0092] As an example, based on the different distribution densities of the spotlights, the distribution area of ​​the spotlights can be divided into a first region and a second region, with different distribution densities in the first and second regions. This difference in distribution density indicates that the metasurface lens exhibits different degrees of beam splitting in the first and second wavelength bands.

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

[0094] As an example, suppose the first region includes T spot lights, each corresponding to one of T wavelength segments. Then the first band includes these T wavelength segments, where T is a positive integer. Suppose the second region includes S spot lights, each corresponding to one of S wavelength segments. Then the second band includes these S wavelength segments, where 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 spotlights in the first region can be obtained based on the number of spotlights in the first region and the bandwidth of the first band. For example, the distribution density of the spotlights in the first region can be equal to the ratio of the bandwidth of the first band to the number of spotlights in the first region.

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

[0097] In this application, the distribution density of the spotlights in the first region is uniform, and the distribution density of the spotlights in the second region is also uniform.

[0098] The uniform distribution density of the spotlights in the first region indicates that the wavelength difference between the center wavelengths of the corresponding wavelength segments of every two adjacent spotlights in the first region is equal. Similarly, the uniform distribution density of the spotlights in the second region indicates that the wavelength difference between the center wavelengths of the corresponding wavelength segments of every two adjacent spotlights in the second region is equal.

[0099] Assume that the wavelength difference between the center wavelengths of the wavelength segments corresponding to each two adjacent spot points in the first region is the first wavelength difference, and the wavelength difference between the center wavelengths of the wavelength segments corresponding to each two adjacent spot points in the second region is the second wavelength difference. The first wavelength difference and the second wavelength difference are not equal.

[0100] As an example, suppose the first region includes T spot lights, each of which corresponds to one of T wavelength segments, and the center wavelengths of the T wavelength segments are sequentially adjacent according to a first wavelength difference. Suppose the second region includes S spot lights, each of which corresponds to one of S wavelength segments, and the center wavelengths of the S wavelength segments are sequentially adjacent according to a second wavelength difference.

[0101] The number of spotlights in the first region is the same as the number of channels in the first band. The number of channels in the first band is equal to the number of beams obtained after the optical signal of the first band passes through the metasurface lens.

[0102] The number of spotlights in the second region is the same as the number of channels in the second band. The number of channels in the second band is equal to the number of beams obtained after the optical signal of the second band passes through the metasurface lens.

[0103] In this application, the distribution density of the spot light in the first region and the spot light in the second region 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 This application provides a detailed description of its proposed solution.

[0105] Figure 4 This is a schematic diagram of the structure of a metasurface lens 400 provided in one embodiment of this 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 can be deployed at the bottom of at least one first unit 420 to support the at least one first unit 420 and ensure the stability of the structure of the metasurface lens 400.

[0107] Optionally, one first unit 420 may also correspond to one base unit, which can be used to support the corresponding first unit 420. Accordingly, the base 410 may include multiple base units, which may correspond one-to-one with the multiple first units 420.

[0108] These multiple first units 420 can be used to receive optical signals and focus optical signals of different wavelength bands onto a designated location to form a spot light. The optical signals received by these multiple first units are polychromatic light.

[0109] As an example, N point spots can be obtained based on the metasurface lens 400, where N is an integer. Each of the N point spots corresponds one-to-one with N wavelength bands, and each point spot is a focused spot obtained by focusing the light signal of the corresponding wavelength band incident on the metasurface lens 400. In this 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 emitted light signal to obtain these N point spots.

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

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

[0112] Based on the different distribution densities of the spotlights, the distribution area of ​​the spotlights can be divided into a first region and a second region, with different distribution densities of spotlights in the first region and the second region.

[0113] The spot in the first region can be the spot obtained by focusing the light signal of the first band through the metasurface lens 400, and the spot in the second region can be the spot obtained by focusing the light signal of the second band through the metasurface lens 400.

[0114] As an example, suppose the first region includes T spot lights, each corresponding to one of T wavelength segments. Then the first band includes these T wavelength segments, where T is a positive integer. Suppose the second region includes S spot lights, each corresponding to one of S wavelength segments. Then the second band includes these S wavelength segments, where S is a positive integer, and the sum of T and S is less than or equal to N.

[0115] In this application, the center wavelengths of the T wavelength segments are sequentially adjacent according to the first wavelength difference, and the center wavelengths of the S wavelength segments are sequentially adjacent according to the second wavelength difference. The first wavelength difference and the second wavelength difference are not equal.

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

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

[0118] The different distribution densities of the spotlights in the first and second regions indicate that the metasurface lens 400 has different degrees of beam splitting in the first and second wavebands.

[0119] Optionally, Figure 5 This is a schematic diagram of the beam splitting of a metasurface lens 400 according to an embodiment of this application. The area between points A and B represents the region where the light signal illuminates the metasurface lens 400. The solid line represents the light beam obtained after the first-band light signal passes through the metasurface lens 400, and the spot of this light beam illuminating the focal plane is located in the first region of the focal plane. The dashed line represents the light beam obtained after the second-band light signal passes through the metasurface lens 400, and the spot of this light beam illuminating the focal plane is located in the second region of the focal plane.

[0120] Assuming the first wavelength band is 350nm to 450nm and the second wavelength band is 450nm to 650nm, the light signal in the first wavelength band, after passing through the metasurface lens 400, results in six beams, with 6 spotlights distributed in the first region. Similarly, the light signal in the second wavelength band, after passing through the metasurface lens 400, results in three beams, with 3 spotlights distributed in the second region. Therefore, the spotlight density in the first region is 100 / 6, and the spotlight density in the second region is 200 / 3. In this example, the area of ​​the first region is larger than the area of ​​the second region, or in other words, the coordinate range of the first region is larger than the coordinate range of the second region.

[0121] In this embodiment, the number of spotlights in the first region is the same as the number of channels in the first band. The number of channels in the first band is equal to the number of light beams obtained after the light signal of the first band passes through the metasurface lens 400.

[0122] The number of spotlights in the second region is the same as the number of channels in the second band. The number of channels in the second band is equal to the number of light beams obtained after the light signal of the second band passes through the metasurface lens 400.

[0123] Alternatively, one example of the beam-splitting channel of the metasurface lens 400 can be as follows: Figure 6 As shown in the example, the solid line represents the number of channels in the first band, and the dashed line represents the number of channels in the second band. The first band has six channels, and the second band has three channels.

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

[0125] In other words, the spectral requirements for the first and second bands are different. The metasurface lens 400 of this application can independently adjust the dispersion of different bands based on the spectral requirements of the first and second bands, so that the number of channels in the first band can be equal to the minimum number of channels required to determine the object's imaging information, and the number of channels in the second band can be equal to the minimum number of channels required to determine the object's color information. Compared with the existing spectrometers that uniformly disperse the first and second bands, the number of channels in the second band of this application can be less than the number of channels in the second band of the existing technology, which can avoid the waste of unnecessary channels in the second band, thereby reducing the cost of the spectrometer.

[0126] In this 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. Alternatively, the distribution density of the point 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 this application, the metasurface lens 400 includes one or more first units 420, and each of these one or more first units 420 may include a first subunit and a second subunit.

[0128] For any given first unit 420, the shape of the first sub-unit and the shape of the second sub-unit can be different. Optionally, the size of the first sub-unit and the size of the second sub-unit can 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 this 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 can be elliptical nanopillars. Optionally, the first subunit 4201 and the second subunit 4202 can also be nanopillars of other shapes. For example, the first subunit 4201 can also be a rectangular nanopillar, and the second subunit 4202 can also be a rectangular nanopillar. The shapes of the first subunit 4201 and the second subunit 4202 can be arbitrarily combined.

[0131] In this example, the first sub-unit 4201 and the second sub-unit 4202 can be placed parallel to each other, that is, the major axis of the first sub-unit 4201 is parallel to the major axis of the second sub-unit 4202. Optionally, the first sub-unit 4201 and the second sub-unit 4202 can also be placed non-parallel, that is, there can be an angle of deflection between the major axis of the first sub-unit 4201 and the major axis of the second sub-unit 4202.

[0132] In this example, the height of the first sub-unit 4201 can be greater than or equal to 1500 nm, and the height of the second sub-unit 4202 can be greater than or equal to 1500 nm. The higher the height of the first sub-unit 4201 and the second sub-unit 4202, the stronger the phase modulation capability of the first unit 420. Therefore, ideally, the higher the height of the first sub-unit 4201 and the second sub-unit 4202, the better. Optionally, due to the influence of semiconductor manufacturing processes, the height of the first sub-unit 4201 and the second sub-unit 4202 can also be less than 3000 nm.

[0133] In this example, the refractive index of the first subunit 4201 and the second subunit 4202 can 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 first subunit 4201 and the second subunit 4202 can be made of gallium nitride. Gallium nitride not only meets the refractive index requirements, but also provides a wider spectral range.

[0135] In this 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, which is the boundary wavelength between the first band and the second band.

[0136] As an example, suppose the first band includes T wavelength segments and the second band includes S wavelength segments. The minimum wavelength in the T wavelength segments and the maximum wavelength in the S wavelength segments can be the same wavelength, which can be the first wavelength.

[0137] In the actual design process, for any first unit 420, the dimensions of the first sub-unit 4201 and the second sub-unit 4202 need to meet the first condition: the phase curve of the first unit 420 needs to have 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 can be a small value. For example, the first threshold can be 30nm.

[0139] Assuming the first band is 350nm to 450nm and the second band is 450nm to 650nm, then the first wavelength can be 450nm and the second wavelength can be between 420nm and 480nm.

[0140] The phase curve of the first unit 420 can be obtained by scanning the first unit 420. As an example, combined with Figure 7By scanning the first unit 420 once, the positions of the spot beams corresponding to different wavelength bands can be obtained. Based on the positions of the spot beams corresponding to different wavelength bands, the phase curve of the first unit 420 can be obtained.

[0141] The phase curve of the first unit 420 is related to the size of the first unit 420. When the size of the first unit 420 changes, the resulting phase curve of the first unit 420 also changes.

[0142] In this application, the size that meets the above-mentioned 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 above-mentioned first condition can be referred to as the first target unit.

[0143] like Figure 8 As shown, assume the first sub-unit 4201 includes two axes, the dimensions of which can be denoted as W1 and L1, respectively. In one example, W1 represents the dimension of the minor axis of the first sub-unit 4201, and L1 represents the dimension of the major axis of the first sub-unit 4201. In another example, W1 represents the dimension of the major axis of the first sub-unit 4201, and L1 represents the dimension of the minor axis of the first sub-unit 4201.

[0144] Suppose that the second sub-unit 4202 includes two axes, the dimensions of which can be denoted as W2 and L2, respectively. In one example, W2 represents the dimension of the minor axis of the second sub-unit 4202, and L2 represents the dimension of the major axis of the second sub-unit 4202. In another example, W2 represents the dimension of the major axis of the second sub-unit 4202, and L2 represents the dimension of the minor axis of the second sub-unit 4202.

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

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

[0147] like Figure 9 As shown, the angle between the first unit 420 and the base 410 can be denoted as θ, and the value of θ can be in the range of [0°, 180°]. Specifically, the angle θ between the first unit 420 and the base can be the angle between the positive axis of the first unit 420 and the positive axis of the base 410. In this example, the positive axis of the first unit 420 can be parallel to the major axis of the first sub-unit or the second sub-unit, and the positive axis of the base 410 can be parallel to the base 410 and directed horizontally to the right.

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

[0149] In addition, the light transmittance (or light transfer rate) of the first unit can be greater than or equal to a preset threshold. For example, the preset threshold can be 70%. A light transmittance greater than or equal to the preset threshold ensures that sufficient light passes through the metasurface lens, resulting in a clearer point light spot.

[0150] The optical transmittance of the first unit is also related to the size of the first unit.

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

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

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

[0154] In this example, the phase curve of the first unit 420 has an inflection point near 460nm, and the optical transmission rate of the first unit 420 is about 90%. Therefore, the first unit 420 of this size is determined as the first target unit.

[0155] It is understandable that at least one first target unit can be obtained based on multiple phase curves.

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

[0157]

[0158] Where (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 spot corresponding to any wavelength band and the first coordinate in the coordinate system, f represents the focal length of the point spot corresponding to any wavelength band, and λ represents the center wavelength of any wavelength band.

[0159] Wherein, any wavelength band is within the operating band 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 spot light corresponding to any wavelength band.

[0160] Accordingly, based on formula (1), we can obtain the following: Figure 11 The phase distribution diagram is shown below. The dashed line represents the phase distribution of the metasurface lens 400 at a center wavelength of 350 nm in any wavelength range; the solid line represents the phase distribution of the metasurface lens 400 at a center wavelength of 450 nm in any wavelength range; and the dotted dashed line represents the phase distribution of the metasurface lens 400 at a center wavelength of 650 nm in any wavelength range.

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

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

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

[0164] Optionally, a second target unit can be determined from the first target unit based on the second condition. The second target unit is the first target unit whose phase satisfies the second condition.

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

[0166] Optionally, the first algorithm can be any optimal algorithm, and this application does not limit it. As an example, the first algorithm can be a genetic algorithm.

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

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

[0169] S1202, calculate the phase difference between the first phase and the second phase of each first target unit in multiple first target units based on the residual function, and perform fitness calculation based on the fitness function.

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

[0171]

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

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

[0174]

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

[0176] S1203, determine whether there exists a first target unit whose phase satisfies the second condition. If yes, execute S1204; otherwise, execute S1205.

[0177] S1204, the first target unit with the highest fitness among the at least one first target unit is determined as the second target unit.

[0178] S1205 involves selection, crossover, and mutation to obtain a new population, and then S1202 is repeated.

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

[0180]

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

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

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

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

[0185] In this application, the first band and the second band can be any two bands. As an example, suppose the first band includes T wavelength segments and the second band includes S wavelength segments. The T wavelength segments can be located in the visible light band and the S wavelength segments can be located in the ultraviolet light band.

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

[0187] The metasurface lens is used to disperse the incident light signal and output the dispersed light signal. The output light signal is focused into N point spots, each corresponding to one of N wavelength bands. Each point spot is a focused spot of the corresponding wavelength band of the incident light signal. The center wavelengths of T wavelength bands are sequentially adjacent according to a first wavelength difference, and the center wavelengths of S wavelength bands are sequentially adjacent according to a second wavelength difference. The first wavelength difference and the second wavelength difference are not equal. 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 it satisfies can be described as follows: Figures 4 to 13 As previously mentioned, this will not be 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 one possible implementation, the optical system 1400 may include N detection elements, each of which corresponds one-to-one with N spot lights. Each of the N detection elements can be used to detect the intensity of the corresponding spot light.

[0190] Optionally, the steps of determining the first target unit, the second target unit, and the structure and size of the metasurface lens 400 can be performed by the 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 this application, unless otherwise specified or in case of logical conflict, the terminology and / or descriptions of different embodiments are consistent and can be referenced by each other. The technical features of different embodiments can be combined to form new embodiments according to their inherent logical relationship.

[0193] It is understood that the various numerical designations used in the embodiments of this application are merely for descriptive convenience and are not intended to limit the scope of the embodiments of this application. The order of the process numbers described above does not imply the order of execution; 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 light signal incident on the metasurface lens is subjected to dispersion processing, and the resulting light signal is emitted. The light signal emitted by the metasurface lens is focused to obtain N point spots, where N is an integer. The N point spots correspond one-to-one with N wavelength segments. Each of the N point spots is a point spot obtained by focusing the light signal of the corresponding wavelength segment of the light signal incident on the metasurface lens. The center wavelengths of T wavelength segments among the N wavelength segments are sequentially adjacent according to a first wavelength difference, and the center wavelengths of S wavelength segments among the N wavelength segments are sequentially adjacent according to a second wavelength difference. The first wavelength difference and the second wavelength difference are not equal. 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 the smallest unit in the metasurface lens that performs dispersion processing on the incident light signal and focuses the emitted 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.

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

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

5. The metasurface lens according to any one of claims 2 to 4, characterized in that, The optical 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 2 to 4, characterized in that, The phase of the optical signal in the first unit for any wavelength band among the N wavelength bands satisfies the following formula: ， Where (x, y) represents the first coordinate of the first unit in the coordinate system of the metasurface lens, , () represents the offset between the coordinates of the point spot corresponding to the arbitrary wavelength band in the coordinate system and the first coordinate. This represents the focal length of the spot corresponding to the arbitrary wavelength band. This refers to the center wavelength of the arbitrary wavelength band.

7. The metasurface lens according to any one of claims 2 to 4, characterized in that, The phase shift of the first unit between different wavelengths satisfies the following formula: ， in, The phase of the first unit at the first wavelength. This indicates the phase of the first unit at the second wavelength, where the first wavelength and the second wavelength are any two wavelengths from the N wavelength segments.

8. The metasurface lens according to claim 1 or 2, 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 includes a metasurface lens as described 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 light signal incident on the metasurface lens and to output the dispersion-processed light signal. The light signal output by the metasurface lens is focused to obtain N point spots. The N point spots correspond one-to-one with N wavelength segments. Each of the N point spots is a point spot obtained by focusing the light signal of the corresponding wavelength segment of the light signal incident on the metasurface lens. The center wavelengths of T wavelength segments in the N wavelength segments are sequentially adjacent according to a first wavelength difference. The center wavelengths of S wavelength segments in the N wavelength segments are sequentially adjacent according to a second wavelength difference. The first wavelength difference and the second wavelength difference are not equal. 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 with the N spot lights, and each of the N detection elements is used to detect the intensity of the corresponding spot light.

10. An optical device, characterized in that, The optical device includes the optical system as described in claim 9.

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