Infrared band-pass optical filter and sensor system

Abstract

The utility model discloses a band-pass optical filter and a sensor system, and relates to the technical field of optical filters, the band-pass optical filter has at least one passband in a near-infrared band, and the band-pass optical filter comprises a substrate, a first structure arranged on the upper surface of the substrate and a second structure arranged on the lower surface of the substrate; the first structure is an absorption layer, and the absorption layer can absorb ultraviolet light and visible light; the second structure is a band-pass filtering laminated layer and comprises a plurality of high-refractive-index layers and a plurality of low-refractive-index layers, the high-refractive-index layers and the low-refractive-index layers are alternately stacked, the light transmittance of the band-pass optical filter in a cut-off band is smaller than or equal to 1%, the light transmittance of the band-pass optical filter in a passband is larger than or equal to 90%, and the band-pass optical filter has the properties of cut-off band depth cut-off and passband high transmittance. Meanwhile, the manufacturing cost can be greatly reduced.

Description

Technical Field

[0001] The utility model relates to the field of optical filters, in particular to a bandpass filter and a sensor system. Background Art

[0002] A bandpass filter is an electronic filter that allows only signals within a specific frequency range to pass through, while blocking signals in other frequency ranges. The main uses of bandpass filters include but are not limited to: Communication systems: In communication systems such as modems, radio receivers and transmitters, bandpass filters can be used to select signals within a specific frequency range to improve the quality and reliability of the signal; Audio processing: In audio equipment, bandpass filters can be used to remove noise or reverberation, and improve the clarity and quality of audio signals; Biomedical applications: In the biomedical field, bandpass filters can be used to process biological signals such as electrocardiograms (ECGs) and electroencephalograms (EEGs) to extract useful information and remove interference; Signal processing: In signal processing applications, bandpass filters can be used to select signals within a specific frequency range and filter out unwanted frequency components to achieve signal analysis and processing.

[0003] In general, bandpass filters are widely used in various fields and can help select signals within a specific frequency range and improve signal quality and reliability. Traditional bandpass filters are generally vacuum-deposited with a visible light cutoff film layer (about 40 to 50 layers) on one side of the substrate and an infrared bandpass film layer (about 50 to 60 layers) on the other side. The spectral uniformity is poor and the production cost is high. There is a strong urgency to develop a high-performance and low-cost infrared bandpass filter. Utility Model Content

[0004] In order to solve the problems of poor spectral uniformity and high manufacturing cost in the prior art, the utility model provides a bandpass filter and a sensor system.

[0005] The purpose of the utility model can be achieved through the following technical solutions:

[0006] A bandpass filter comprises a substrate, a first structure arranged on the upper surface of the substrate, and a second structure arranged on the lower surface of the substrate;

[0007] The first structure is an absorption layer, and the absorption layer is used to absorb ultraviolet light, visible light and part of near-infrared light;

[0008] The second structure is a bandpass filter stack, which is composed of a plurality of high refractive index layers and a plurality of low refractive index layers stacked alternately.

[0009] Furthermore, the substrate is composed of one or more of a common transparent glass layer, an organic glass layer or a plastic film layer; the thickness of the substrate is in the range of greater than 0.05 mm and less than 3 mm.

[0010] Furthermore, it has at least one passband in the wavelength range of 800nm ​​to 1200nm, and has cutoff bands in the wavelength ranges of 400-790nm and 950-1100nm.

[0011] Furthermore, the thickness of the first structure is greater than 1 um and less than 10 um, and the wavelength range of the light that can be absorbed is between 350 nm and 800 nm.

[0012] Furthermore, when the number of layers of the second structure is greater than 30 and less than or equal to 70, the second structure is a filtering structure layer; in the filtering structure layer, the thickness range of each of the high refractive index layers is greater than or equal to 5 nm and less than or equal to 400 nm, and the thickness range of each of the low refractive index layers is greater than or equal to 10 nm and less than or equal to 500 nm.

[0013] Furthermore, the light transmittance in the cut-off band is less than 1%, and the light transmittance in the pass band is greater than 90%.

[0014] A sensor system further includes a light source and a sensor device;

[0015] The light source is arranged corresponding to the bandpass filter, and the bandpass filter is connected to the sensor device; the light source is used to emit light; the bandpass filter is used to filter the light emitted by the light source; and the sensor device is used to detect the light transmitted by the bandpass filter.

[0016] The beneficial effects of the utility model are as follows: by adopting the first structure in combination with the second structure, the bandpass filter is sequentially formed from the absorption layer, the substrate and the bandpass filter stack from bottom to top. By selecting an absorption coating material of a specific infrared passband and combining the high and low refractive index layer film system design, a film layer structure with a large ratio of high refractive index layer thickness to low refractive index thickness and an alternately deposited vacuum evaporation method are further provided, which greatly improves the performance of the bandpass filter, and the manufacturing process is relatively simple and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to facilitate understanding by those skilled in the art, the present invention is further described below in conjunction with the accompanying drawings.

[0018] Figure 1 It is a structural cross-sectional view of the bandpass filter of the utility model;

[0019] Figure 2 It is a transmittance curve diagram of the first structure of the utility model;

[0020] Figure 3 It is a transmittance curve diagram of the second structure of the utility model;

[0021] Figure 4 It is a transmittance curve diagram of the bandpass filter of the utility model;

[0022] Figure 5 It is a structural diagram of the sensor system of the utility model.

[0023] Description of reference numerals: 100, bandpass filter; 110, substrate; 120, first structure; 130, second structure; 200, light source; 300, sensor device. DETAILED DESCRIPTION

[0024] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined purpose of the utility model, the specific implementation method, structure, characteristics and effects of the present invention are described in detail below in combination with the accompanying drawings and preferred embodiments.

[0025] See also Figure 1-Figure 5 A bandpass filter comprises a substrate 110, a first structure 120 arranged on the upper surface of the substrate 110, and a second structure 130 arranged on the lower surface of the substrate 110; wherein the first structure 120 is an absorption layer that can absorb ultraviolet light, visible light and part of near-infrared light; the second structure 130 is a bandpass filter film layer, which is composed of a plurality of high refractive index layers and a plurality of low refractive index layers alternately stacked.

[0026] In the present embodiment 1, the substrate 110 is one of ordinary transparent glass, organic glass or plastic film or a composite thereof; preferably German Schott glass (model: D263Teco) or American Corning glass (model: Eagle XG), preferably 0.21mm or 0.3mm thick. The aforementioned two types of glass have excellent photoelectric properties, and the light wave transmittance in the wavelength range of 400nm to 1200nm is greater than 91%.

[0027] In the present embodiment 1, there is at least one passband in the wavelength range of 800nm ​​to 1200nm. The number of passbands can be set according to the actual application scenario of the bandpass filter 100. Preferably, the wavelength of the passband of the bandpass filter 100 in the present embodiment 1 includes 850nm, CENTER WAVELENGTH (CWL): 850±10nm.

[0028] In the present embodiment 1, the thickness of the absorption layer of the first structure 120 is greater than 1um and less than 10um, preferably, the thickness is 5 to 6um. And the absorbable light wavelength range is between 350nm and 800nm. The components of the absorption layer include modified acrylic resin (35 to 50%), hexamethylene diisocyanate (8 to 14%), carbon black (0 to 40%), fumed silica (0 to 1%), hexamethyldisiloxane (0.5 to 1.2%), and isophorone (15 to 25%). The absorption layer can be made by screen printing, spin coating or atomization spraying. It should be noted that, according to the actual application needs of the product, a layer of anti-reflection film can be plated on the upper surface of the absorption layer to further improve the light wave transmittance of the passband.

[0029] In this embodiment 1, the high refractive index layer of the second structure 130 includes at least one of titanium pentoxide, titanium dioxide, niobium oxide, tantalum pentoxide, aluminum oxide or zirconium oxide; the low refractive index layer of the second structure 130 includes at least one of silicon dioxide or magnesium fluoride. Preferably, the high refractive index layer is titanium pentoxide; the low refractive index layer is silicon dioxide.

[0030] Through experiments, Ti3O5 was selected as the high refractive index coating material and the coating parameters and process were optimized, so that the titanium oxide film with the highest refractive index can be obtained under the premise of low absorption. The specific coating parameters are set as follows:

[0031] 1. The initial vacuum degree of coating is 1.0x10-3Pa, the substrate constant temperature is 80℃~150℃, and the substrate constant temperature time is 30~90min.

[0032] 2. When coating the titanium pentoxide layer, set the evaporation rate to <4A / sec, the coating vacuum to 1.0x10-2~1.6x10-2Pa, the ion source current to 900~1200mA, the voltage to 900~1200V, and the oxygen filling amount to 40~80sccm.

[0033] 3. When coating the silicon dioxide layer, set the evaporation rate to <12A / sec, the coating vacuum to 1.0x10-2~1.6x10-2Pa, the ion source current to 600~1200mA, the voltage to 600~1200V, and the oxygen filling amount to 40~70sccm.

[0034] In this embodiment 1, when the number of layers of the second structure 130 is greater than 30 and less than or equal to 70, the second structure 130 is a filter structure layer. Preferably, the number of layers of the second structure 130 is 51; in the filter structure layer, the thickness range of each high refractive index layer is greater than or equal to 5nm and less than or equal to 400nm, and the thickness range of each low refractive index layer is greater than or equal to 10nm and less than or equal to 500nm. See the following bandpass filter film layer material and film thickness table 1 for details.

[0035]

[0036] like Figure 4 As shown, in this embodiment 1, the light transmittance of the bandpass filter 100 in the wavelength ranges of 400-790nm and 950-1100nm is 0.12% and 0.37% respectively; and the light transmittance in the wavelength range of 830-890nm is greater than or equal to 94%, and the transmittance is the highest value when the wavelength is 857nm, and the highest transmittance T>97.2%. The light transmittance in the cut-off band is less than 1%, and the light transmittance in the passband is greater than 90%. It has the performance of deep cut-off in the cut-off band and high transmittance in the passband, and the manufacturing cost can be greatly reduced.

[0037] like Figure 5 As shown, this embodiment 2 also provides a sensor system, which also includes a light source 200 and a sensor device 300.

[0038] The light source 200 is arranged corresponding to the bandpass filter 100, and the bandpass filter 100 is connected to the sensor device 300; the light source 200 is used to emit light; the bandpass filter 100 is used to transmit the light in the passband of the light emitted by the light source 200; the sensor device 300 is used to detect the light transmitted by the bandpass filter 100. The sensor device 300 can be a distance sensor for obtaining the distance of the target; or it can be a three-dimensional imaging system based on TOF or structured light for obtaining a three-dimensional image of the target.

[0039] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. An infrared bandpass filter, characterized in that: comprising a substrate, a first structure disposed on an upper surface of the substrate, and a second structure disposed on a lower surface of the substrate; The first structure is an absorption layer, and the absorption layer is used to absorb ultraviolet light, visible light and part of near-infrared light; The second structure is a bandpass filter stack, which is composed of a plurality of high refractive index layers and a plurality of low refractive index layers stacked alternately.

2. An infrared bandpass filter according to claim 1, characterized in that: The substrate is composed of one or more of a common transparent glass layer, an organic glass layer or a plastic film layer; the thickness of the substrate is greater than 0.05 mm and less than 3 mm.

3. The infrared bandpass filter according to claim 1, characterized in that: The invention has at least one pass band in the wavelength range of 800nm ​​to 1200nm and has cut-off bands in the wavelength ranges of 400-790nm and 950-1100nm.

4. The infrared bandpass filter according to claim 1, characterized in that: The thickness of the first structure is greater than 1 um and less than 10 um, and the wavelength range of the light that can be absorbed is between 350 nm and 800 nm.

5. The infrared bandpass filter according to claim 1, characterized in that: The number of layers of the second structure is greater than 30 and less than or equal to 70, and the second structure is a filter structure layer; In the filter structure layer, the thickness of each high refractive index layer is greater than or equal to 5 nm and less than or equal to 400 nm, and the thickness of each low refractive index layer is greater than or equal to 10 nm and less than or equal to 500 nm.

6. The infrared bandpass filter according to claim 3, characterized in that: The light transmittance in the cut-off band is less than 1%, and the light transmittance in the pass band is greater than 90%.

7. A sensor system, using the infrared bandpass filter according to any one of claims 1 to 6, characterized in that: It also includes a light source and a sensor device; The light source is arranged corresponding to the bandpass filter, and the bandpass filter is connected to the sensor device; the light source is used to emit light; the bandpass filter is used to filter the light emitted by the light source; and the sensor device is used to detect the light transmitted by the bandpass filter.

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