Design method of ultra-wide cut-off band 50nm wide-band rectangular wave bandpass filter film

Abstract

The invention belongs to the technical field of optical thin films and discloses a substrate of H-K9L or other colorless glass with high transmittance in the range of 400nm to 1100nm, with a central wavelength λ in the range of 400nm to 1100nm. 0 =515nm, passband width Δλ=λ 0 ±25nm=50nm, cutoff band λ≠λ 0 A design method for a 50nm wide-band rectangular wave bandpass filter film with an ultra-wide cutoff band of ±40nm. This method is aimed at electron beam thermal evaporation coating equipment, uses Ti2O3 as a high-refractive index thin film material, uses SiO2 as a low-refractive index thin film material, and uses a quartz crystal control method to monitor the film thickness. The designed and prepared film system has the characteristics of thin total film thickness, small film stress, strong environmental adaptability, low requirements for thin film deposition equipment, simple preparation method, and low production cost. The method described in the present invention is universal for 50nm wide-bandpass filter films with other central wavelengths in the 400nm to 1100nm band.

Description

Technical Field

[0001] The invention belongs to the technical field of optical films and relates to a design method for a rectangular wave bandpass filter film with an ultra-wide cut-off band of 50nm. Background Art

[0002] Bandpass filter refers to an optical thin film device that has a high reflection / cutoff area except for a short section of high transmission within a certain band. With the continuous expansion of the spectral band of optoelectronic products and the increase in the use of variable angle filters, the demand for ultra-wide cutoff rectangular wave wide bandpass filter applications is increasing. The design method, preparation method, film performance and cost control of ultra-wide cutoff rectangular wave wide bandpass filter are particularly important.

[0003] The traditional design methods of bandpass filter films include FP narrowband filter films and bandpass filter films that are a combination of long-wave and short-wave cutoff films.

[0004] For a 50nm wide-bandpass filter film, when the central wavelength λ0=515nm, the transmission band width of the FP type filter film cannot meet the requirements and cannot be used for the preparation of the filter film of the present invention.

[0005] Since the film layer is required to cut off the entire wavelength range of 400nm to 1100nm, the bandpass filter film composed of long-wave and short-wave cutoff films has a very thick film layer, poor monitoring accuracy, and large film layer stress; at the same time, the principle of optical thin film determines that its rectangularity is poor and there is a half-wave hole effect. In order to meet the rectangularity requirement, the film layer thickness will be further increased, and the half-wave hole effect cannot be completely eliminated, resulting in a significant reduction in passband transmittance, which cannot meet the passband transmittance requirements of the filter film described in the present invention. Therefore, the bandpass filter film composed of long-wave and short-wave cutoff films is not suitable for designing the ultra-wide cutoff band 50nm wide-band rectangular wave bandpass filter film described in the present invention.

[0006] In summary, the design method for the ultra-wide cut-off band 50nm wide-band rectangular wave bandpass filter film has not been reported yet. Summary of the invention

[0007] (I) Purpose of the invention

[0008] The purpose of the present invention is to propose a high-precision, low-cost, high-performance ultra-wide cut-off band 50nm wide-band pass rectangular wave bandpass filter film design method for electron beam thermal evaporation coating deposition equipment.

[0009] (II) Technical solution

[0010] In order to solve the above technical problems, the present invention provides a design method for a high-precision, low-cost, high-performance ultra-wide cut-off band 50nm wide-band rectangular wave bandpass filter film suitable for electron beam thermal evaporation deposition equipment. The design content includes the following aspects:

[0011] 1) The ultra-wide cut-off band 50nm wide-band pass rectangular wave band-pass filter film comprises three parts: a double-sided polished H-K9L or other colorless flat glass substrate with high transmittance in the range of 400nm to 1100nm, a wide-band pass rectangular wave filter film designed and deposited on the A side, and an ultra-wide cut-off band long-wave cut-off film designed and deposited on the B side;

[0012] 2) The broadband rectangular wave filter film deposited on the A surface contains partial cut-off bands on both sides of the passband, and its passband width, passband transmittance, and rectangularity all meet the passband width, passband transmittance, and rectangularity required by the final film system;

[0013] 3) The transmission band of the ultra-wideband long-wave cutoff film deposited on the B side is the same as the passband of the broadband rectangular wave bandpass filter film on the A side, and its cutoff band is the full-band cutoff of 400nm to 1100nm except the cutoff band of the broadband rectangular wave bandpass filter film on the A side.

[0014] 4) After the transmittance spectra of the broadband rectangular wave filter film deposited on the A side and the ultra-wide cut-off band long-wave cut-off film deposited on the B side are spliced, the spectrum requirements of the ultra-wide cut-off band 50nm broadband rectangular wave band-pass filter film are met, and the central ultra-wide cut-off band 50nm broadband rectangular wave band-pass filter film of the present invention is obtained. In the 400nm-1100nm band, the central wavelength λ0=515nm, the passband width Δλ=λ0±25nm=50nm, the passband average transmittance τ—>95%, the cut-off band λ≠λ0±40nm, the cut-off band transmittance τ in the 400nm-575nm and 555nm-1100nm cmax <0.1%, absorbance OD>3, film transmittance rectangularity 0.82, upward steepness S 上行 =0.97%, downward steepness S 下行 =1.17%;

[0015] In the A mask series and the B mask series, the high refractive index thin film material used is Ti2O3 thin film material, and the low refractive index material is SiO2 thin film material.

[0016] The electron beam thermal evaporation deposition technology uses the quartz crystal control method to monitor the film thickness and prepare the A-side wide-band rectangular wave bandpass filter film and the B-side ultra-wide cutoff band long-wave cutoff film.

[0017] (III) Beneficial effects

[0018] The design method of the ultra-wide cut-off band 50nm wide-band rectangular wave bandpass filter film provided by the above technical solution is to obtain an ultra-wide cut-off band 50nm wide-band rectangular wave bandpass filter film with better spectral performance, environmental adaptability, preparation cost and other performances by splicing the spectrum of the wide-band rectangular wave bandpass filter film on the A side and the spectrum of the ultra-wide cut-off band long-wave cut-off film on the B side; the ultra-wide cut-off band 50nm wide-band rectangular wave bandpass filter film designed by this method is suitable for monitoring the film thickness using the quartz crystal control method, and has the advantage of low preparation cost. The method described in the present invention is universal for 50nm wide-band filter films with other central wavelengths in the 400nm to 1100nm band. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of a sample of a 50nm wide-band rectangular wave bandpass filter film of the present invention, wherein the A and B surfaces can be switched arbitrarily;

[0020] Figure 2a This is the design transmittance curve of the single-sided wide-band rectangular wave bandpass filter film;

[0021] Figure 2b In accordance with Figure 2a Actual transmittance test curve of single-sided wide-band rectangular wave bandpass filter film prepared by designed film system;

[0022] Figure 3a This is the design transmittance curve of the single-sided ultra-wide cut-off band long-wave cut-off film;

[0023] Figure 3b In accordance with Figure 3a Actual transmittance test curve of single-sided ultra-wide cut-off band long-wave cut-off film prepared by designed film system;

[0024] Figure 4a The designed transmittance curve of the ultra-wide cut-off band 50nm rectangular wave bandpass filter film of the present invention;

[0025] Figure 4b In accordance with Figure 4a Actual transmittance test curve of the ultra-wide cutoff band 50nm rectangular wave bandpass filter film prepared by the designed film system. DETAILED DESCRIPTION

[0026] In order to make the purpose, content and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below in conjunction with the drawings and examples.

[0027] The present invention is suitable for designing and preparing a high-precision, low-cost, high-performance, ultra-wide cutoff band 50nm wide-band rectangular wave bandpass filter film on a double-sided polished H-K9L or other colorless flat glass substrates with high transmittance in 400nm-1100nm, using Ti2O3 thin film material as a high-refractive index thin film material and SiO2 thin film material as a low-refractive index material, using a quartz crystal control method and an electron beam thermal evaporation deposition device, and specifically includes the following steps:

[0028] Step 1: Determine the wideband rectangular wave bandpass filter film system on side A

[0029] The transition band of the traditional FP narrowband filter film can meet the rectangularity requirements of the bandpass filter film, but it cannot meet the passband width of the broadband rectangular wave bandpass filter film. In order to meet the passband width, rectangularity and passband transmittance requirements of the broadband rectangular wave bandpass filter film, multi-cavity FP narrowband filter films with different wavelengths are staggered and connected as the basic film system to achieve the purpose of increasing the passband width. However, since the passband transmittance will be seriously affected by the staggered wavelength of the FP filter film, the basic film system often has extremely low transmittance, so it is necessary to optimize the thickness of each layer to improve the passband transmittance. At the same time, in order to ensure the rectangularity, the weight of the cutoff band should be increased when setting the film system optimization target.

[0030] Based on the above analysis, when designing the broadband rectangular wave bandpass filter film, the central wavelength λ 01 =505nm and λ 02 = 515nm two double cavity narrow band filter film connected, that is, the basic film system is Glass|(0.98H0.98L)^ 3 1.96H(0.98L0.98H)^ 3 L(1.02H1.02L)^ 3 2.04H(1.02L1.02H)^ 3 |Air, Ti2O3 thin film material is a high refractive index material, and SiO2 thin film material is a low refractive index material; the optimization target is the passband wavelength, passband transmittance and rectangularity of the bandpass filter film, and the weights of the cutoff bands at both ends are increased. After optimization, a broadband rectangular wave bandpass filter film system on the A surface can be obtained.

[0031] The wide-band rectangular wave bandpass filter film on the A side includes cut-off bands on both sides of the passband, and its center wavelength, passband width, passband transmittance, and rectangularity all meet the center wavelength, passband width, passband transmittance, and rectangularity required by the final film system;

[0032] The broadband rectangular wave bandpass filter film on the A side of the present embodiment is within the range of 400nm to 1100nm, with a central wavelength λ0=515nm, a passband width Δλ=λ0±25nm=50nm, a passband average transmittance τ—>95%, a cutoff band λ≠λ0±40nm, and a transmittance τ in the cutoff bands of 400nm to 575nm and 555nm to 1100nm. cmax <0.1%,absorbance OD>3,rectangularity of the overall transmittance of the film layer is 0.82,upward steepness S 上行 =0.97%, downward steepness S 下行 =1.17%.

[0033] Step 2: Determine the B-side ultra-wide cutoff band long-wave cutoff film system

[0034] The ultra-wide cutoff band long-wave cutoff film on the B side should match the cutoff band of the wide-band rectangular wave bandpass film on the A side to achieve the full-band cutoff effect of 400nm to 1100nm described in the present invention. It can be seen that the ultra-wide cutoff band long-wave cutoff film on the B side should have high transmittance characteristics in the passband described on the A side in addition to the ultra-wide cutoff band. Since there is a "half-wave hole" effect between the passband and the cutoff band described in the present invention, the ultra-wide cutoff band long-wave cutoff film on the B side uses non-waiting periodic film stacks of different wavelengths as the basic film system. At the same time, in order to ensure the absorbance OD3 of the cutoff band, the optimization target setting should increase the weight of the cutoff band.

[0035] Combined with the transmission band and cutoff band of the wide-band rectangular wave bandpass filter film in step 1, according to the above process, for the ultra-wide cutoff band long-wave cutoff film on the B surface, the central wavelength is selected as λ = 400nm, and the periodic film stacks with different central wavelengths and non-uniform thickness are connected, that is, the basic film system is: Glass|(HL)^ 12 1.4(0.8HL)^ 10 1.6(0.8HL)^ 10 |Air, Ti2O3 thin film material is a high refractive index material, and SiO2 thin film material is a low refractive index material; the optimization target is the passband band and passband transmittance of the bandpass film, and the weights of the cutoff bands at both ends are increased. After optimization, a broadband rectangular wave bandpass filter film system on the B surface can be obtained.

[0036] The transmission band of the ultra-wide cutoff band long-wave cutoff film on the B side is the same as the passband of the broadband rectangular wave bandpass filter film on the A side. Its cutoff band is the full-band cutoff of 400nm to 1100nm except the cutoff band of the broadband rectangular wave bandpass filter film on the A side.

[0037] Step 3: Place the A and B film systems on both sides of the substrate respectively, and use TFCale software to calculate the transmittance of the entire film system.

[0038] The substrate is a double-sided polished H-K9L or other colorless flat glass substrate with high transmittance (transmittance>95%) in the range of 400nm to 1100nm.

[0039] After splicing the transmittance spectra of the two film systems, the broadband rectangular wave bandpass filter film deposited on the A side and the ultra-wide cutoff band long wave cutoff film deposited on the B side, the spectral requirements of the ultra-wide cutoff band 50nm broadband rectangular wave bandpass filter film are met, and the broadband rectangular wave bandpass filter film with a central wavelength of 515nm and an ultra-wide cutoff band of 50nm described in the present invention is obtained.

[0040] The method for designing an ultra-wide cutoff band 50nm wide-band pass rectangular wave bandpass filter film described in the present invention uses a quartz crystal control method to monitor the film thickness, which can greatly reduce the preparation cost of such ultra-wide cutoff wide-band pass rectangular wave filter film and has high practical value.

[0041] Example

[0042] refer to Figure 2a In order to simultaneously meet the requirements of center wavelength, passband width, passband transmittance and rectangularity, the FP type narrowband filter film is used as the basic film system, and the passband center wavelength, passband transmittance, passband width and rectangularity indicators are used as the target. The TFCale software is used to optimize the design with Ti2O3 thin film material as the high refractive index material and SiO2 thin film material as the low refractive index material to obtain the design transmittance curve of the A-side broadband rectangular wave bandpass filter film, as shown in the figure. Figure 2a described.

[0043] refer to Figure 3a In order to meet the requirements of passband transmittance and cutoff band width at the same time, the non-uniform thickness periodic film layer is used as the basic film system, and the passband center wavelength, passband transmittance, passband width and cutoff band width are taken as the targets. The TFCale software is used to optimize the design with Ti2O3 thin film material as the high refractive index material and SiO2 thin film material as the low refractive index material to obtain the design transmittance curve of the B-side ultra-wide cutoff band long-wave cutoff film, as shown in the figure. Figure 3a shown.

[0044] refer to Figure 4a The designed single-sided A-side rectangular wave wide-band pass filter film and the B-side ultra-wide cut-off band long-wave cut-off film are placed on both sides of the sample, and the spliced ​​spectrum is calculated using TFCale software to obtain the designed transmittance curve of the ultra-wide cut-off band 50nm wide-band pass rectangular wave bandpass filter film of the present invention, as shown in FIG. Figure 4a shown.

[0045] refer to Figure 2bOn a blank substrate, a Beiyi ZZSX-800M vacuum coating machine equipped with an Infukang IC5 quartz crystal controller was used to deposit a wide-band rectangular wave bandpass filter film on the A side by electron beam thermal evaporation and quartz crystal control method to monitor the film deposition thickness. The transmittance curve was tested as shown in Figure 2b shown.

[0046] refer to Figure 3b On a blank substrate, a Beiyi ZZSX-800M vacuum coating machine equipped with an Infukang IC5 quartz crystal controller was used to deposit a B-side ultra-wide cutoff band long-wave cutoff film by electron beam thermal evaporation and quartz crystal control method to monitor the film deposition thickness. The transmittance curve was tested as shown in Figure 3b shown.

[0047] refer to Figure 4b On the other side of the A-side broadband rectangular wave bandpass filter film sample, a North Instrument ZZSX-800M vacuum coating machine equipped with an Infukang IC5 quartz crystal controller was used to deposit the B-side ultra-wide cutoff band long-wave cutoff film by electron beam thermal evaporation and crystal control method to monitor the film deposition thickness, and the final ultra-wide cutoff band 50nm broadband rectangular wave bandpass filter film was obtained. The test curve is shown in Figure 4b shown.

[0048] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A design method for a 50nm ultra-wide cut-off band wide-band rectangular wave bandpass filter film, characterized in that: The process includes: Step 1: Determine the wideband rectangular wave bandpass filter film system on side A The wide-band rectangular wave bandpass filter film on the A side includes cut-off bands on both sides of the passband, and its center wavelength, passband width, passband transmittance, and rectangularity all meet the requirements of the center wavelength, passband width, passband transmittance, and rectangularity required for the final formation of the overall filter film system; Step 2: Determine the B-side ultra-wide cutoff band long-wave cutoff film system The transmission band of the ultra-wide cut-off band long-wave cut-off film on the B side is the same as the passband of the wide-band rectangular wave band-pass filter film on the A side, and its cut-off band is the full-band cut-off of 400nm to 1100nm except the cut-off band of the wide-band rectangular wave band-pass filter film on the A side; Step 3: The wide-band rectangular wave band-pass filter film system on the A side determined in step 1 and the ultra-wide cut-off band long-wave cut-off film system on the B side determined in step 2 are formed on both sides of the substrate respectively, and the transmittance of the overall film system is calculated using TFCale software; The substrate is a double-sided polished H-K9L or other colorless flat glass substrate with high transmittance in the range of 400nm to 1100nm; In the A-face film system, multi-cavity FP-type narrow-band filter films of different wavelengths are staggered and connected as the basic film system, and the thickness of each layer is optimized to improve the passband transmittance, and the weight of the cutoff band is increased to ensure the rectangularity; When designing a mask system, the central wavelength λ 01 =505nm and λ 02 = 515nm two double cavity narrow band filter film connected, that is, the basic film system is Glass|(0.98H0.98L)^ 3 1.96H(0.98L0.98H)^ 3 L(1.02H1.02L)^ 3 2.04H(1.02L1.02H)^ 3 |Air, Ti2O3 thin film material is a high refractive index material, SiO2 thin film material is a low refractive index material; In the B-face membrane system, the non-waiting periodic membrane stacks with different wavelengths are selected as the basic membrane system, and the weights of the cutoff bands at both ends are increased for optimization to meet the absorbance of the cutoff bands; When designing the B-face film system, the central wavelength is selected as λ=400nm, and periodic film stacks with different central wavelengths and non-uniform thickness are connected. The basic film system is: Glass|(HL)^ 12 1.4(0.8HL)^ 10 1.6(0.8HL)^ 10 |Air, Ti2O3 thin film material is a high refractive index material, SiO2 thin film material is a low refractive index material; When the A-face mask system and the B-face mask system are prepared and formed on the substrate, the electron beam thermal evaporation deposition technology is adopted, and the quartz crystal control method is used to monitor the film thickness; After the transmittance spectra of the A-film system and the B-film system are spliced, they meet the spectral requirements of the ultra-wide cut-off band 50nm wide-band rectangular wave bandpass filter film; After the transmittance spectra of mask series A and mask series B are spliced, in the 400nm~1100nm band, the central wavelength λ0=515nm, the passband width Δλ=λ0±25nm=50nm, and the passband average transmittance Cut-off band λ≠λ0±40nm, cut-off band transmittance τ at 400nm~575nm, 555nm~1100nm cmax <0.1%, absorbance OD>3, film transmittance rectangularity 0.82, upward steepness S 上行 =0.97%, downward steepness S 下行 =1.17%.

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