Stack structure coefficient determination method, filter design method, and filter

Abstract

The application provides a method for determining a stack structure coefficient of a cutoff filter film, a design method of a filter and the filter. The method comprises obtaining a center wavelength of a to-be-cutoff spectral segment corresponding to the cutoff filter film; and determining the stack structure coefficient of the cutoff filter film according to the center wavelength of the to-be-cutoff spectral segment and a center wavelength of the FP cavity filter. In the design method of the filter and the filter, the stack structure coefficient of the cutoff filter film is obtained by using the method. The stack structure coefficient of the cutoff filter film is designed by using the method, so that the light leakage outside the free spectral range can be greatly suppressed, the side mode suppression ratio of the spectral filtering is greatly improved, and the performance of the spectral imaging micro sensor is improved.

Description

Technical Field

[0001] This invention relates to the field of spectral analysis technology, and to a method for determining stacked structure coefficients, a filter design method, and a filter, particularly to a method for determining the stacked structure coefficients of a cutoff filter film, a filter design method, and a filter. Background Technology

[0002] Each pixel in a standard RGB color image contains data for color identification. However, the photosensitive spectral range of a standard RGB color image is too wide, making it impossible to distinguish many targets with similar spectral information. To differentiate between targets with similar spectral information, narrowband filtering is needed on the three wide RGB bands to extract the target's characteristic spectral bands and achieve target differentiation. Since the characteristic spectral bands of various targets to be identified are different, narrowband filtering at different wavelengths needs to be implemented at different pixels.

[0003] Variable cavity Fabry-Perot (FP) spectral filters can be integrated onto CMOS image sensors, achieving unified imaging sensor functionality. The materials used in fabricating FP filters are semiconductor materials compatible with CMOS sensors. The optical cavity of a FP filter includes a light-transmitting layer, an upper mirror, and a lower mirror. Bragg mirrors made of semiconductor materials (Si3N4 and SiO2), fabricated through overlapping growth, achieve reflectivity exceeding 99% and can be used as FP cavity mirrors.

[0004] The three key parameters of a FP filter are its free spectral range (FSR), cavity precision, and cavity filter bandwidth. All three parameters depend on the effective cavity length and the effective reflectivity of the cavity mirrors. Changing the cavity length of the FP cavity by varying the cavity structure can alter the filter's midline wavelength. However, due to limitations in semiconductor materials compatible with CMOS processes, the free spectral range is limited to 350 nm. For silicon-based detectors, the response spectral range is above 400 nm (500–900 nm). Leakage outside the free spectral range severely impacts the performance of multispectral imaging microsensors. Therefore, suppressing leakage outside the free spectral range is a significant challenge for multispectral imaging microsensors. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art or related art.

[0006] Therefore, the present invention provides a method for determining the stacking structure coefficients of a cutoff filter film, a filter design method, and a filter.

[0007] The technical solution of the present invention is as follows:

[0008] According to one aspect, a method for determining the stacking structure coefficient of a cutoff filter film is provided, the cutoff filter film being formed on an FP cavity filter to cut off interference bands, wherein the stacking structure of the cutoff filter film is an α-stacked structure unit, and α is a stacking structure coefficient; the method includes:

[0009] Obtain the center wavelength of the spectral band to be cut off corresponding to the cutoff filter film;

[0010] The stacking coefficient α of the cutoff filter film is determined based on the center wavelength of the spectral band to be cut off and the center wavelength of the FP cavity filter.

[0011] Furthermore, the center wavelength of the spectral band to be cut off corresponding to the cutoff filter film is obtained by the following formula:

[0012]

[0013] Where λ0 is the center wavelength of the spectral band to be cut off; λ1 and λ2 are the upper and lower limits of the spectral band to be cut off, respectively.

[0014] Furthermore, the center wavelength of the spectral band to be cut off corresponding to the cutoff filter film is obtained by the following formula:

[0015]

[0016] Where λ0 is the center wavelength of the spectral band to be cut off; λ1 and λ2 are the upper and lower limits of the spectral band to be cut off, respectively.

[0017] Furthermore, the stacking structure coefficient α of the cutoff filter film is determined according to the center wavelength of the spectral band to be cut off and the center wavelength of the FP cavity filter using the following formula:

[0018]

[0019] Where λ0 is the center wavelength of the spectrum to be cut off; λ is the center wavelength of the FP cavity filter.

[0020] According to another aspect, a filter design method is provided, the design method comprising:

[0021] Step 1: Design the filter, including an FP cavity filter;

[0022] Step 2: Determine whether the filter, including a cutoff filter, needs to be designed based on the filtering effect of the FP cavity filter; if so, proceed to Step 3.

[0023] Step 3: Determine the number of cutoff filter films and the corresponding spectral bands to be cut off;

[0024] Step 4: Determine the stacking structure coefficient of the cutoff filter membrane according to the above method for determining the stacking structure coefficient.

[0025] Further, the number of cutoff filter films and the corresponding spectral bands to be cut off are determined, including:

[0026] The leakage spectral band is determined based on the filtering effect of the FP cavity filter;

[0027] The number of cutoff filter films and the corresponding cutoff spectral segments are determined based on the leaked spectral band, the free spectral range of the FP cavity filter, the first set bandwidth threshold, and the second set bandwidth threshold.

[0028] Further, determining the number of cutoff filter films and the corresponding cutoff spectral bands based on the leaked spectral band, the free spectral range of the FP cavity filter, the first set bandwidth threshold, and the second set bandwidth threshold includes:

[0029] If the upper limit of the leaky spectral range does not exceed the lower limit of the free spectral range of the FP cavity filter, then

[0030] If the difference between the upper and lower limits of the leaked spectral segment does not exceed the first set bandwidth threshold, then the leaked spectral segment is a segment to be cut off; if the difference between the upper and lower limits of the leaked spectral segment is greater than the first set bandwidth threshold, then the leaked spectral segment is split to obtain at least two segments to be cut off, wherein the difference between the upper and lower limits of any one of the at least two segments to be cut off does not exceed the first set bandwidth threshold.

[0031] If the lower limit of the leaky spectral range is not less than the upper limit of the free spectral range of the FP cavity filter, then

[0032] If the difference between the upper and lower limits of the leaked spectral segment does not exceed the second set bandwidth threshold, then the leaked spectral segment is a segment to be cut off; if the difference between the upper and lower limits of the leaked spectral segment is greater than the second set bandwidth threshold, then the leaked spectral segment is split to obtain at least two segments to be cut off, wherein the difference between the upper and lower limits of any one of the at least two segments to be cut off does not exceed the second set bandwidth threshold.

[0033] The number of cutoff filter films is equal to the number of spectral bands to be cut off.

[0034] Furthermore, the first set bandwidth threshold is 100nm; the second set bandwidth threshold is 150nm.

[0035] According to another aspect, a filter is provided, the filter comprising an FP cavity filter and at least one cutoff filter diaphragm, wherein...

[0036] The FP cavity filter includes a pixel photosensitive unit and a narrowband filter film. The narrowband filter film is integrally grown on the pixel photosensitive unit, and the narrowband filter film has an FP cavity structure.

[0037] When there is one cutoff filter, the cutoff filter is formed on the narrowband filter; when there are more than two cutoff filter, the stacking coefficients of the cutoff filter are all different, and the cutoff filter is alternately arranged on the narrowband filter.

[0038] The stacking structure coefficients of the cutoff filter film are obtained using the method described above.

[0039] Furthermore, the cutoff filter film is integrally deposited on the narrowband filter film.

[0040] By applying the above technical solution, the stacking structure coefficient of the cutoff filter film is determined by the center wavelength of the spectral band to be cut off and the center wavelength of the FP cavity filter. In this way, when the cutoff filter film with the stacking structure coefficient is formed on the FP cavity filter, leakage light outside the free spectral range can be greatly suppressed, the side mode suppression ratio of spectral filtering is greatly improved, and the performance of the spectral imaging micro sensor is improved. Attached Figure Description

[0041] The accompanying drawings, which form part of this specification, are provided to further illustrate embodiments of the invention and, together with the textual description, explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0042] Figure 1 The filtering effect diagram of the FP cavity filter (with a cutoff filter film and stacking coefficients determined according to the method of the embodiment of the present invention) provided in the first embodiment of the present invention is shown.

[0043] Figure 2 The first comparative example of the first embodiment is a filtering effect diagram of the FP cavity filter (without a cutoff filter film);

[0044] Figure 3 The second comparative example of the first embodiment is a filtering effect diagram of an FP cavity filter (with a cutoff filter film added, and the stacking coefficient is not determined according to the method of the embodiment of the present invention);

[0045] Figure 4 The filtering effect diagram of the FP cavity filter (with a cutoff filter film and the stacking coefficient determined according to the method of the embodiment of the present invention) provided in the second embodiment of the present invention is shown.

[0046] Figure 5The first comparative example of the second embodiment is a filtering effect diagram of the FP cavity filter (without a cutoff filter film);

[0047] Figure 6 The second comparative example of the second embodiment is a filtering effect diagram of an FP cavity filter (with a cutoff filter film added, and the stacking coefficient is not determined according to the method of the embodiment of the present invention);

[0048] Figure 7 The filtering effect diagram of the FP cavity filter (with a cutoff filter film and the stacking coefficient determined according to the method of the embodiment of the present invention) provided in the third embodiment of the present invention is shown.

[0049] Figure 8 The first comparative example of the third embodiment is a filtering effect diagram of the FP cavity filter (without a cutoff filter film);

[0050] Figure 9 The second comparative example of the third embodiment is a filtering effect diagram of an FP cavity filter (with a cutoff filter film added, and the stacking coefficient is not determined according to the method of the embodiment of the present invention);

[0051] Figure 10 This is a flowchart illustrating a method for determining the stacking structure coefficients of a cutoff filter film according to an embodiment of the present invention. Detailed Implementation

[0052] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0054] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0055] In one embodiment of the present invention, such as Figure 10 As shown, a method for determining the stacking structure coefficients of a cutoff filter film is provided. The cutoff filter film is used to form on an FP cavity filter to cut off interference bands. The stacking structure of the cutoff filter film is an α-stacked structure unit, where α is the stacking structure coefficient. The method includes:

[0056] Step 1: Obtain the center wavelength of the spectral band to be cut off corresponding to the cutoff filter film;

[0057] Step 2: Determine the stacking structure coefficient α of the cutoff filter film based on the center wavelength of the spectrum to be cut off and the center wavelength of the FP cavity filter.

[0058] In this embodiment, the spectral band to be cut off corresponding to the cutoff filter membrane is a known condition.

[0059] In this embodiment, the FP cavity filter is a variable cavity Fabry-Perot (FP) spectral filter. The filter includes a pixel photosensitive unit and a narrowband filter film integrally grown on the pixel photosensitive unit, i.e., an FP cavity filter film. Each optical cavity includes a light-transmitting layer, an upper reflector, and a lower reflector. A cutoff filter film is formed on the narrowband filter film to cut off interference bands. The center wavelength of the FP cavity filter usually refers to the center wavelength of the narrowband filter film.

[0060] In this embodiment, the stacked structure unit of the cutoff filter film can be ((HL)^nH, which is the general film system structure of existing cutoff filter films, where H is a high refractive index material, L is a low refractive index material, and n is the number of overlaps. Among them, the number of overlaps (HL) only affects the degree of cutoff, that is, the degree of light opacity, but does not change the cutoff wavelength. Therefore, this embodiment of the invention does not specifically limit the stacked structure unit.

[0061] For example, H can be SI3N4, and L can be SiO2.

[0062] By applying the above configuration method, the cutoff filter film is optimized. Specifically, the stacking structure coefficient of the cutoff filter film is determined by the center wavelength of the spectrum to be cut off and the center wavelength of the FP cavity filter. When the cutoff filter film with the stacking structure coefficient is formed on the FP cavity filter, the leakage light outside the free spectrum range can be greatly suppressed, the side mode suppression ratio of the spectral filter is greatly improved, and the performance of the spectral imaging micro sensor is improved.

[0063] According to one embodiment of the present invention, in order to accurately obtain the spectral band to be cut off, the spectral band to be cut off can be determined by the missing spectral band.

[0064] According to one embodiment of the present invention, in order to obtain the center wavelength of the spectral band to be cut off, the center wavelength of the spectral band to be cut off can be determined by the following formula based on the upper limit and lower limit of the spectral band to be cut off:

[0065]

[0066] Where λ0 is the center wavelength of the spectral band to be cut off; λ1 and λ2 are the upper and lower limits of the spectral band to be cut off, respectively.

[0067] According to one embodiment of the present invention, in order to obtain the center wavelength of the spectral band to be cut off more accurately, the center wavelength of the spectral band to be cut off can also be determined according to the upper limit and lower limit of the spectral band to be cut off by the following formula:

[0068]

[0069] Where λ0 is the center wavelength of the spectral band to be cut off; λ1 and λ2 are the upper and lower limits of the spectral band to be cut off, respectively.

[0070] In this embodiment, the formula is applied. Obtain the center wavelength of the spectral band to be cut off, and use this wavelength to calculate the stacking structure coefficient of the cutoff filter film. This allows for better suppression of light leakage outside the free spectral range when forming a cutoff filter film with this stacking structure coefficient on an FP cavity filter (compared to the formula). (Obtain the center wavelength of the spectral band to be cut off).

[0071] According to one embodiment of the present invention, in order to obtain the stacking structure coefficient of the cutoff filter film, the stacking structure coefficient α of the cutoff filter film is determined by the following formula based on the center wavelength of the spectral band to be cut off and the center wavelength of the FP cavity filter:

[0072]

[0073] Where λ0 is the center wavelength of the spectrum to be cut off; λ is the center wavelength of the FP cavity filter.

[0074] Among them, from Figure 1-9 As can be seen, by designing the stacked junction structure coefficient of the cutoff filter film using the method of the embodiments of the present invention and forming the cutoff filter film with the coefficient in the FP cavity filter, leakage light outside the free spectrum range is greatly suppressed (the following embodiments will describe this in detail).

[0075] According to another embodiment of the present invention, a filter design method is provided, the design method comprising:

[0076] Step 1: Design the filter, including an FP cavity filter;

[0077] Step 2: Determine whether the filter, including a cutoff filter, needs to be designed based on the filtering effect of the FP cavity filter; if so, proceed to Step 3.

[0078] Step 3: Determine the number of cutoff filter films and the corresponding spectral bands to be cut off;

[0079] Step 4: Determine the stacking structure coefficient of the cutoff filter membrane according to the above method for determining the stacking structure coefficient.

[0080] For example, the presence of a leakage spectral range can be determined based on the filtering effect of the FP cavity filter. If a leakage spectral range exists, a cutoff filter film needs to be designed to block it. Furthermore, those skilled in the art know that for SI-based detectors responding to the 500nm–900nm spectral range, FP cavity filters typically exhibit very severe light leakage.

[0081] By applying the above configuration method, when the filter includes a cutoff filter film, the cutoff filter film is optimized. Specifically, the stacking structure coefficient of the cutoff filter film is determined by the center wavelength of the spectrum to be cut off and the center wavelength of the FP cavity filter. When the cutoff filter film with the stacking structure coefficient is formed on the FP cavity filter, leakage light outside the free spectrum range can be greatly suppressed, the side mode suppression ratio of spectral filtering is greatly improved, and the performance of the spectral imaging micro sensor is improved.

[0082] According to one embodiment of the present invention, in order to accurately obtain the number of cutoff filter films required for the filter and the corresponding cutoff spectral bands, the number of cutoff filter films and the cutoff spectral bands corresponding to the cutoff filter films can be determined in the following manner:

[0083] The leakage spectral band is determined based on the filtering effect of the FP cavity filter;

[0084] The number of cutoff filter films and the corresponding cutoff spectral segments are determined based on the leaked spectral band, the free spectral range of the FP cavity filter, the first set bandwidth threshold, and the second set bandwidth threshold.

[0085] According to an embodiment of the present invention, in order to accurately obtain the number of cutoff spectral bands and the corresponding cutoff spectral bands, the step of determining the number of cutoff filter films and the cutoff spectral bands corresponding to the cutoff filter films based on the leaked spectral band, the free spectral range of the FP cavity filter, a first set bandwidth threshold, and a second set bandwidth threshold includes:

[0086] If the upper limit of the leaky spectral range does not exceed the lower limit of the free spectral range of the FP cavity filter, then

[0087] If the difference between the upper and lower limits of the leaked spectral segment does not exceed the first set bandwidth threshold, then the leaked spectral segment is a segment to be cut off; if the difference between the upper and lower limits of the leaked spectral segment is greater than the first set bandwidth threshold, then the leaked spectral segment is split to obtain at least two segments to be cut off, wherein the difference between the upper and lower limits of any one of the at least two segments to be cut off does not exceed the first set bandwidth threshold.

[0088] If the lower limit of the leaky spectral range is not less than the upper limit of the free spectral range of the FP cavity filter, then

[0089] If the difference between the upper and lower limits of the leaked spectral segment does not exceed the second set bandwidth threshold, then the leaked spectral segment is a segment to be cut off; if the difference between the upper and lower limits of the leaked spectral segment is greater than the second set bandwidth threshold, then the leaked spectral segment is split to obtain at least two segments to be cut off, wherein the difference between the upper and lower limits of any one of the at least two segments to be cut off does not exceed the second set bandwidth threshold.

[0090] The number of cutoff filter films is equal to the number of spectral bands to be cut off.

[0091] Using the above configuration method, the spectrum is first grouped according to the upper and lower limits of the leaked spectrum and the lower and upper limits of the free spectral range of the FP cavity filter, that is, divided into truncated waves and long waves. Then, based on this, the required cutoff spectrum is determined according to the difference between the upper and lower limits of the leaked spectrum, the first set bandwidth threshold and the second set bandwidth threshold. One cutoff spectrum corresponds to one cutoff filter film. In this way, the number of cutoff filter films and the cutoff spectrum corresponding to the cutoff filter films can be accurately obtained.

[0092] According to one embodiment of the present invention, in order to better avoid light leakage, the first set bandwidth threshold can be set to 100nm; and the second set bandwidth threshold can be set to 150nm.

[0093] According to another embodiment of the present invention, a filter is also provided, the filter comprising an FP cavity filter and at least one cutoff filter membrane, wherein,

[0094] The FP cavity filter includes a pixel photosensitive unit and a narrowband filter film. The narrowband filter film is integrally grown on the pixel photosensitive unit, and the narrowband filter film has an FP cavity structure.

[0095] When there is one cutoff filter, the cutoff filter is formed on the narrowband filter; when there are more than two cutoff filter, the stacking coefficients of the cutoff filter are all different, and the cutoff filter is alternately arranged on the narrowband filter.

[0096] The stacking structure coefficients of the cutoff filter film are obtained using the method described above.

[0097] In this embodiment, the pixel photosensitive unit may be a CMOS pixel photosensitive unit.

[0098] It is evident that at least one cutoff filter is placed on the narrowband filter film of the FP cavity filter. This cutoff filter has been optimized, that is, the stacking structure coefficient of the cutoff filter is designed. Specifically, the stacking structure coefficient of the cutoff filter is determined by the center wavelength of the spectrum to be cut off and the center wavelength of the FP cavity filter. In this way, when the cutoff filter with this stacking structure coefficient is formed on the FP cavity filter, it can greatly suppress light leakage outside the free spectrum range, greatly improve the side mode suppression ratio of spectral filtering, and improve the performance of the spectral imaging micro sensor.

[0099] Preferably, the cutoff filter membrane included in the filter can be designed using the above-described design method.

[0100] According to one embodiment of the present invention, the cutoff filter film is integrally deposited on the narrowband filter film.

[0101] For example, when there is one cutoff filter, it is integrally deposited and grown on the narrowband filter. When there are multiple cutoff filters, they are integrally deposited and grown on the narrowband filter and arranged alternately (that is, one cutoff filter is first integrally deposited and grown on the narrowband filter, then a second cutoff filter is deposited on the first cutoff filter, and so on, with the remaining cutoff filters deposited in sequence).

[0102] This configuration involves integrally depositing the cutoff filter film onto the narrowband filter film, and then integrally depositing the narrowband filter film onto the pixel photosensitive unit. There are no gaps between the cutoff filter film, the narrowband filter film, and the pixel photosensitive unit, resulting in high spectral transmittance, reduced energy loss, and a single-stage fabrication process that is unaffected by external environmental contamination, offering better robustness, higher fabrication efficiency, and greater integration. Compared to existing technologies that externally bond the cutoff filter film, integrating the cutoff filter film and the narrowband filter film into the spectral imaging chip structure significantly improves quantum efficiency and spectral transmittance.

[0103] The filtering effect of the filter will be described in detail below with reference to the accompanying drawings and specific embodiments:

[0104] In the following embodiments, the cutoff filter membranes (including the number and the corresponding cutoff bands) required for the filter are designed according to the above design method.

[0105] 1. The first embodiment and the corresponding first and second comparative examples

[0106] Taking the design of an FP cavity filter with a center wavelength of 650nm as an example, if no cutoff filter is added, i.e., the first comparative example is obtained, its filtering effect is as follows: Figure 2 As shown, narrowband filtering was only achieved in the 575nm–740nm range, while severe light leakage occurred in the 500nm–575nm and 750nm–900nm bands. This is a serious light leakage problem for SI-based detectors responding to the 500nm–900nm spectral range, and these two bands need to be suppressed.

[0107] In the first embodiment, based on the leakage spectral ranges of 500nm–575nm and 750nm–900nm, two cutoff filter layers are integrally deposited on the FP cavity filter. One layer is used to suppress leakage light in the 500nm–575nm range, with a center wavelength of [missing information]. The center wavelength was determined to be 534.88 nm; the corresponding stacking coefficient α1 is 534.88 nm / 650 nm = 0.82; similarly, another layer suppresses light leakage in the 750 nm–900 nm range, with a center wavelength of... The center wavelength is determined to be 818.18 nm; the corresponding stacking structure coefficient α2 is 818.18 nm / 650 nm = 1.26.

[0108] In the second comparative example, the only difference from the first embodiment is that the coefficients α1 and α2 are 0.7 and 1.4 respectively, that is, the stacking structure coefficients are not determined according to the method of the embodiment of the present invention.

[0109] Figure 1 The above diagram shows the filtering effect of the FP cavity filter provided in the first embodiment. Figure 3 The filtering effect diagram of the FP cavity filter provided in the second comparative example above shows that the cutoff filter film, with the stacking structure coefficients determined according to the embodiments of the present invention, can greatly suppress light leakage outside the free spectral range. Conversely, if the stacking structure coefficients are not determined according to the method of the embodiments of the present invention, even if a cutoff filter film is added and the coefficients differ very little, it is difficult to effectively suppress light leakage outside the free spectral range, or even solve the light leakage problem.

[0110] 2. The second embodiment and the corresponding first and second comparative examples

[0111] Taking the design of an FP cavity filter with a center wavelength of 790nm as an example, if no cutoff filter is added, that is, the first comparative example, its filtering effect is as follows: Figure 5 As shown, a very serious light leakage phenomenon occurs in the 500nm to 700nm spectral range. This is a very serious light leakage problem for SI-based detectors that respond to the 500nm to 900nm spectral range, and this spectral range needs to be suppressed.

[0112] In the second embodiment, based on the leakage spectral range of 500nm to 700nm, the leakage spectral range is divided into 500nm to 600nm and 600nm to 700nm to meet the first set bandwidth threshold requirement, resulting in two spectral ranges to be cut off. Two cutoff filter films (single-sided cutoff) are integrally deposited on the FP cavity filter. One layer is used to suppress leakage light in the range of 500nm to 600nm, with a center wavelength of 545.45nm; the corresponding stacking structure coefficient α1 is 0.69. Similarly, the other layer suppresses leakage light in the range of 600nm to 700nm, with a center wavelength of 646.15nm, and the corresponding stacking structure coefficient α2 is 0.818.

[0113] In the second comparative example, the only difference from the second embodiment is that the coefficients α1 and α2 are 0.59 and 0.718 respectively, that is, the stacking structure coefficients are not determined according to the method of the embodiment of the present invention.

[0114] Figure 4 The above diagram shows the filtering effect of the FP cavity filter provided in the first embodiment. Figure 6 The filtering effect diagram of the FP cavity filter provided in the second comparative example above shows that the cutoff filter film, with the stacking structure coefficients determined according to the embodiments of the present invention, can greatly suppress light leakage outside the free spectral range. Conversely, if the stacking structure coefficients are not determined according to the method of the embodiments of the present invention, even if a cutoff filter film is added and the coefficients differ very little, it is difficult to effectively suppress light leakage outside the free spectral range, or even solve the light leakage problem.

[0115] 3. The second embodiment and the corresponding first and second comparative examples

[0116] Taking the design of an FP cavity filter with a center wavelength of 550nm as an example, if no cutoff filter is added, i.e., the first comparative example is obtained, its filtering effect is as follows: Figure 5 As shown, a very serious light leakage phenomenon occurs in the 650nm to 900nm spectral range. This is a very serious light leakage problem for SI-based detectors that respond to the 500nm to 900nm spectral range, and this spectral range needs to be suppressed.

[0117] In the third embodiment, based on the leakage spectral range of 650nm to 900nm, the leakage spectral range is divided into 650nm to 775nm and 775nm to 900nm to meet the second set bandwidth threshold requirement, resulting in two spectral ranges to be cut off. Two cutoff filter films (single-sided cutoff) are integrally deposited on the FP cavity filter. One layer is used to suppress leakage light in the range of 650nm to 775nm, with a center wavelength of 707nm; the corresponding stacking structure coefficient α1 is 1.28. Similarly, the other layer suppresses leakage light in the range of 775nm to 900nm, with a center wavelength of 832.83nm, and the corresponding stacking structure coefficient α2 is 1.514.

[0118] In the second comparative example, the difference from the third embodiment is only that the coefficients α1 and α2 are 1.18 and 1.414 respectively, that is, the stacking structure coefficients are not determined according to the method of the embodiment of the present invention.

[0119] Figure 7 The above diagram shows the filtering effect of the FP cavity filter provided in the first embodiment. Figure 9 The filtering effect diagram of the FP cavity filter provided in the second comparative example above shows that the cutoff filter film, with the stacking structure coefficients determined according to the embodiments of the present invention, can greatly suppress light leakage outside the free spectral range. Conversely, if the stacking structure coefficients are not determined according to the method of the embodiments of the present invention, even if a cutoff filter film is added and the coefficients differ very little, it is difficult to effectively suppress light leakage outside the free spectral range, or even solve the light leakage problem.

[0120] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0121] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0122] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for determining the stacking structure coefficients of a cutoff filter membrane, characterized in that, The cutoff filter film is formed on the FP cavity filter to cut off the interference band. The stacking structure of the cutoff filter film is as follows: Stacked structural units, The stacking structure coefficient is (HL)^nH, where H is a high-refractive-index material, L is a low-refractive-index material, and n is the number of overlaps. The method includes: Obtain the center wavelength of the spectral band to be cut off corresponding to the cutoff filter film; The stacking coefficient of the cutoff filter film is determined based on the center wavelength of the spectral band to be cut off and the center wavelength of the FP cavity filter. As shown in the following formula: ； in, The center wavelength of the spectral band to be cut off; The center wavelength of the FP cavity filter; The FP cavity filter includes a pixel photosensitive unit and a narrowband filter film integrally grown on the pixel photosensitive unit, i.e., the FP cavity filter film. Each optical cavity includes a light-transmitting layer, an upper reflector and a lower reflector. The cut-off filter film is integrally deposited on the narrowband filter film to cut off interference bands. The number of cutoff filters and the corresponding spectral bands to be cut off are determined in the following ways: The leakage spectral band is determined based on the filtering effect of the FP cavity filter; The number of cutoff filter films and the corresponding cutoff spectral bands are determined based on the leaked spectral band, the free spectral range of the FP cavity filter, the first set bandwidth threshold, and the second set bandwidth threshold, including: The determination of the number of spectral bands to be cut off based on the leaked spectral band, the free spectral range of the FP cavity filter, the first set bandwidth threshold, and the second set bandwidth threshold includes: If the upper limit of the leaky spectral range does not exceed the lower limit of the free spectral range of the FP cavity filter, then If the difference between the upper and lower limits of the leaked spectral segment does not exceed the first set bandwidth threshold, then the leaked spectral segment is a segment to be cut off; if the difference between the upper and lower limits of the leaked spectral segment is greater than the first set bandwidth threshold, then the leaked spectral segment is split to obtain at least two segments to be cut off, wherein the difference between the upper and lower limits of any one of the at least two segments to be cut off does not exceed the first set bandwidth threshold. If the lower limit of the leaky spectral range is not less than the upper limit of the free spectral range of the FP cavity filter, then If the difference between the upper and lower limits of the leaked spectral segment does not exceed the second set bandwidth threshold, then the leaked spectral segment is a segment to be cut off; if the difference between the upper and lower limits of the leaked spectral segment is greater than the second set bandwidth threshold, then the leaked spectral segment is split to obtain at least two segments to be cut off, wherein the difference between the upper and lower limits of any one of the at least two segments to be cut off does not exceed the second set bandwidth threshold. The number of cutoff filter films is equal to the number of spectral bands to be cut off.

2. The method for determining the stacking structure coefficients of a cutoff filter membrane according to claim 1, characterized in that, The center wavelength of the spectral band to be cut off corresponding to the cutoff filter membrane is obtained by the following formula: ； in, The center wavelength of the spectral band to be cut off; and These are the upper and lower limits of the spectral segment to be cut off, respectively.

3. The method for determining the stacking structure coefficients of a cutoff filter membrane according to claim 1, characterized in that, The center wavelength of the spectral band to be cut off corresponding to the cutoff filter membrane is obtained by the following formula: ； in, The center wavelength of the spectral band to be cut off; and These are the upper and lower limits of the spectral segment to be cut off, respectively.

4. A filter design method, characterized in that, The design method includes: Step 1: Design the filter, including an FP cavity filter; Step 2: Determine whether the filter, including a cutoff filter, needs to be designed based on the filtering effect of the FP cavity filter; if so, proceed to Step 3. Step 3: Determine the number of cutoff filter films and the corresponding spectral bands to be cut off; Step 4: Determine the stacking structure coefficient of the cutoff filter film using the stacking structure coefficient determination method according to any one of claims 1-3; The determination of the number of cutoff filter films and the corresponding spectral bands to be cut off includes: The leakage spectral band is determined based on the filtering effect of the FP cavity filter; The number of cutoff filter films and the corresponding cutoff spectral segments are determined based on the leaked spectral segment, the free spectral range of the FP cavity filter, the first set bandwidth threshold, and the second set bandwidth threshold. The step of determining the number of cutoff filter films and the corresponding cutoff spectral bands based on the leaked spectral band, the free spectral range of the FP cavity filter, the first set bandwidth threshold, and the second set bandwidth threshold includes: The determination of the number of spectral bands to be cut off based on the leaked spectral band, the free spectral range of the FP cavity filter, the first set bandwidth threshold, and the second set bandwidth threshold includes: If the upper limit of the leaky spectral range does not exceed the lower limit of the free spectral range of the FP cavity filter, then If the difference between the upper and lower limits of the leaked spectral segment does not exceed the first set bandwidth threshold, then the leaked spectral segment is a segment to be cut off; if the difference between the upper and lower limits of the leaked spectral segment is greater than the first set bandwidth threshold, then the leaked spectral segment is split to obtain at least two segments to be cut off, wherein the difference between the upper and lower limits of any one of the at least two segments to be cut off does not exceed the first set bandwidth threshold. If the lower limit of the leaky spectral range is not less than the upper limit of the free spectral range of the FP cavity filter, then If the difference between the upper and lower limits of the leaked spectral segment does not exceed the second set bandwidth threshold, then the leaked spectral segment is a segment to be cut off; if the difference between the upper and lower limits of the leaked spectral segment is greater than the second set bandwidth threshold, then the leaked spectral segment is split to obtain at least two segments to be cut off, wherein the difference between the upper and lower limits of any one of the at least two segments to be cut off does not exceed the second set bandwidth threshold. The number of cutoff filter films is equal to the number of spectral bands to be cut off.

5. The filter design method according to claim 4, characterized in that, The first set bandwidth threshold is 100nm; the second set bandwidth threshold is 150nm.

6. A filter, characterized in that, The filter includes an FP cavity filter and at least one cutoff filter membrane, wherein, The FP cavity filter includes a pixel photosensitive unit and a narrowband filter film. The narrowband filter film is integrally grown on the pixel photosensitive unit, and the narrowband filter film has an FP cavity structure. When there is one cutoff filter, the cutoff filter is formed on the narrowband filter; when there are more than two cutoff filter, the stacking coefficients of the cutoff filter are all different, and the cutoff filter is alternately arranged on the narrowband filter. The stacking structure coefficient of the cutoff filter film is obtained by the method described in any one of claims 1-3.

7. A filter according to claim 6, characterized in that, The cutoff filter film is integrally deposited on the narrowband filter film.

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