CN114690151A - Filter and sensor protective cover - Google Patents

Abstract

The invention provides an optical filter, which contains a multi-layer laminated film structure; the average transmittance of the optical filter in the near-infrared wavelength band is >90%, and the haze is <3%. In the development of autonomous driving, ADAS technology and various types of intelligence, sensors such as lidar and infrared cameras have been or will be widely used as an important type of sensor. Considering that in the prior art, when the infrared sensor is unprotected and the surface is damaged due to weather, impact, etc., the detection sensitivity, accuracy, and maximum detection distance of the sensor are degraded. In addition, based on the integrated design of the final product, it is desirable to cover the infrared sensor with a decorative protective cover without affecting the detection of the sensor. When mounted on products such as automobiles that are designed to have a long service life and are used in harsh environments, a protective cover that can provide decoration, infrared signal transmission and weather resistance at the same time is required.

Description

A filter and sensor protection cover

technical field

The invention relates to an optical filter applied to an infrared sensor for filtering stray light, shielding and decoration, and an infrared transparent sensor protective cover containing the optical filter.

Background technique

In the development of autonomous driving, ADAS technology and various types of intelligence, sensors such as lidar and infrared cameras have been or will be widely used as an important type of sensor. With the application of infrared sensors, sensor failure due to external noise and wear during use has become an important issue that may affect vehicle safety. In addition, the inconsistency between the sensor itself and the design of the vehicle body results in the placement of the sensor being limited by the exterior design of the vehicle body. To a certain extent, the automaker must choose between the most suitable sensor location and appearance. Therefore, there is a need for a protective cover that can shield the ambient light, shield the sensor, and can provide a certain decorative effect and have certain weather resistance to solve the above problems.

As a specific example of the above protective cover, for example, a product including an optical filter disclosed in patent CN201780007792.7, the product can selectively transmit infrared wavelengths by using fillers with specific particle size distribution. , and make the product appear white, so that the sensor is first blocked by visible light, making the sensor invisible, but the sensor in the infrared band can still work normally.

In addition, for example, an all-polymer cold mirror disclosed in CN93118964.0 can transmit light in a specific infrared band by controlling the thickness of the multilayer laminated film. The light source using the cold mirror reduces the light in the near-infrared wavelength band irradiating the illuminated object. Therefore, the heating and photoaging effects of the light source on the illuminated object are reduced without affecting the lighting effect.

The products or cold mirrors described in the above technologies cannot provide a protective cover that shields ambient light and sensors, and can provide a certain decorative effect and certain weather resistance.

SUMMARY OF THE INVENTION

Considering that in the prior art, when the infrared sensor is unprotected and the surface is damaged due to weather, impact, etc., the detection sensitivity, accuracy, and maximum detection distance of the sensor are degraded. In addition, based on the integrated design of the final product, it is desirable to cover the infrared sensor with a decorative protective cover without affecting the detection of the sensor. The loss of the signal caused by the reflection or absorption of the protective cover provided by the prior art can mask the sensor, and the performance of the corresponding sensor, such as the detection sensitivity, accuracy, and maximum detection distance, will also be degraded. When used on products with a long service life and harsh environments, a protective cover that can provide decoration, infrared signal transmission and weather resistance at the same time is required.

In order to solve the defects of the prior art, the present invention provides an optical filter that can transmit infrared signals but basically does not transmit visible light, and a filter that can transmit infrared signals and basically does not transmit visible light, and has certain decorative properties and weather resistance. sensor cover.

The invention provides an optical filter, which contains a multi-layer laminated film structure; the transmittance of the optical filter in the near-infrared band is >90%, and the haze is <3%. The multi-layer laminated film structure is a multi-layer laminated film structure capable of interference reflection in all or a part of wavelength bands in the visible light wavelength range. The multi-layer laminated film can be designed according to the design principles of general multi-layer films. It is produced by biaxial stretching after co-extrusion using two polymer materials with different refractive indices. The multilayer laminate films can also be heat treated to adjust their mechanical and optical properties. During the stretching process or after the stretching is completed, an easy-bonding layer can also be coated on the surface of the film to improve the affinity of the film surface to ink and adhesive.

In the present invention, in consideration of the signal passability of the infrared optical sensor, and some high-precision, high-sensitivity sensors require higher signal passability, the transmittance of the filter in the near-infrared band is preferably >95%, and The haze is preferably <1%.

More specifically, when the sensor is a lidar and a transparent object is set on the detection path of the lidar, in the point cloud detected by the lidar, among the points in the range blocked by the transparent object, the same Compared with the point cloud detected without the transparent object, the ratio of the number of points whose position deviation is >1cm or cannot be detected due to occlusion to the total number of points is defined as the point cloud loss rate. Preferably, when the filter is set on the laser radar optical path in the near-infrared band, the point cloud loss rate is <= 10%. And it can be further preferably <=1%.

Generally speaking, infrared sensors also respond to visible light in a part of the band, and this part of the response generates noise signals, which reduces the signal-to-noise ratio of the sensor, thereby reducing the accuracy and sensitivity of the sensor. In extreme cases, the sensor may not be able to obtain meaningful signals, or false signals may be generated, resulting in misjudgment by the control program. Therefore, in the present invention, considering the filtering of visible light noise, the present invention provides an optical filter that substantially does not transmit visible light. The visible light transmittance of the optical filter is preferably 1% or less, and may preferably be 0.1% or less.

The visible light transmittance is obtained by increasing the visible light reflectivity or visible light absorptivity of the optical filter, so the optical filter also contains a coating that can absorb all or part of the wavelength band in the visible light range. The visible light reflectance is mainly caused by the interference reflection of the multilayer laminate film, and the visible light absorption is mainly caused by the coating. The coating is also substantially transparent to infrared signals.

In the present invention, in consideration of decoration, the visible light absorbing coating contained in the optical filter provided by the present invention may be a coating having absorption in a part of wavelength bands in the visible light range, and the absorbing coating has a color. Further, the visible light absorbing coating contained in the optical filter provided by the present invention may contain a plurality of regions of the coating having absorption in a part of wavelength bands in the visible light range, and the absorption wavelength bands of the coatings may be different. The regions may partially or fully overlap each other. The visible light absorbing coating can be applied to the multilayer build-up film from infrared transparent ink via ink jet printing, gravure printing, screen printing, but is not limited to.

In the present invention, considering the decorativeness, the optical filter provided by the present invention has formability under the thermoforming process. The optical filter is formed by high pressure or ultra-high pressure under suitable temperature and pressure conditions, and can withstand 150% area stretch rate without cracking and delamination. Due to the inherent characteristics of the multi-layered film, its reflection band will be shifted due to stretching and thinning. Specifically, the optical filter of the present invention may change its appearance and color. In order to ensure a certain formability, the filter provided by the present invention is designed with a reflection band from the short-wave end of the near-infrared region to the detection wavelength of the sensor. The existence of the reflection band can make the filter in the thermoforming process. Process withstands 110% areal stretch without discoloration. The thermoforming process includes, but is not limited to, vacuum forming, high-pressure gas-assisted forming, thermocompression forming, and non-preformed film insert injection molding.

The present invention also provides a sensor protective cover containing the above-mentioned optical filter, the protective cover contains a substrate layer, a first main surface and a second main surface; the first main surface and the second main surface are opposite in shape The size deviation of the designed shape is <=10 μm; and when the protective cover is arranged on the laser radar optical path in the near-infrared band, the point cloud loss rate is <=10%. Considering that the refraction caused by the protective cover with a certain thickness will produce a lens effect, the shape and surface roughness of the protective cover need to be strictly controlled. Preferably, the dimensional deviation of the shape of the first main surface and the second main surface relative to the designed shape is <= 1 μm.

In the present invention, the protective cover needs to have filter performance similar to the above-mentioned filter. Therefore, the protective cover contains any one of the optical filters described above. In addition, the protective cover needs to have a certain shape, and therefore, the protective cover contains one or more substrate layers. The substrate layer may be rigid or flexible. In particular, when applied to the exterior of automobiles or other industrial products, considering the cost, the substrate layer is polycarbonate or polymethyl methacrylate. The substrate and filter can be combined by, but not limited to, dry lamination, cold lamination, in-film injection molding. After the lamination is completed, the protective cover can be further thermoformed and punched as a whole to obtain the desired shape.

In the present invention, in order to meet the requirements of weather resistance and scratch resistance of the product, the protective cover further contains a hardened coating, and the hardened coating has a surface hardness of 2H or above. The hard coat may also contain UV absorbers to enhance light resistance properties. The hard coating can be applied to the surface of the protective cover by, but not limited to, die coating, flow coating, spray coating, evaporation and other processes.

In the present invention, in order to meet the weather resistance and scratch resistance requirements of the product, the near-infrared transmittance of the protective cover changes after any one of the xenon lamp aging test, high temperature treatment, weather cycle, or wear test test. rate <5%, and the near-infrared haze change rate of the protective cover is <5%, and when the protective cover is placed on the laser radar optical path in the near-infrared band, the point cloud loss rate is <=10%, and can be More preferably, it is <=1%.

In the present invention, when the protective cover is used in rainy and snowy weather or in a humid environment, water droplets, ice or snow may be attached to the surface, thereby affecting the detection sensitivity, accuracy and maximum detection distance of the infrared sensor. Therefore, preferably, the protective cover further contains a conductive layer, and the conductive layer can keep the surface temperature of the protective cover between 35 and 45° C. after electrification. The conductive layer may be discontinuous. The conductive layer is substantially transparent in the near infrared region. The conductive layer may be pre-applied to the substrate layer by burial, or may be pre-applied to the filter by screen printing. Preferably, the conductive layer can withstand 150% stretching without breaking or cracking. Preferably, the conductive layer is transparent to visible light.

In the present invention, the protective cover can shield other types of sensors, such as millimeter-wave radar, while shielding the infrared sensor. In addition, the protective cover may need to meet the electromagnetic compatibility of various wireless communications. Therefore, preferably, the two-way transmission loss of the protective cover to electromagnetic waves in the frequency range of 50-100 GHz is less than -10 dBm, and more preferably less than -5 dBm, -3 dBm, -1 dBm.

The present invention provides a protective cover that can shield ambient light, shield sensors, provide certain decorative effects and have certain weather resistance. The protective cover can reduce ambient light noise and make the sensor invisible to the naked eye while satisfying the overall design on the premise that the detection signal of the sensor can pass when the sensor is mounted on a product with complex usage scenarios and strict weather resistance requirements such as automobiles. Appearance requirements to reduce sensor aging due to environmental factors. Further, the protective cover can also be self-heated to reduce the influence of rain and snow on the sensor. Further, the protective cover can also shield the millimeter-wave sensor at the same time, so as not to affect the passage of the detection signal thereof.

Description of drawings

FIG. 1 is a schematic structural diagram of a protective cover.

Among them, 1 is a hard coating, 2 is a substrate layer, 3 is an adhesive layer, 4 is a conductive layer, 5 is a coating that absorbs all or part of the wavelength band in the visible light range, and 6 is a multilayer laminate The thin film, 7 is a coating having absorption in all or a part of the wavelength band in the visible light range, and 8 is an AR treatment layer.

Detailed ways

The present invention is described in more detail by the following examples, but the examples do not constitute a limitation of the present invention.

The test methods used in the examples and comparative examples are as follows, for all tests, if the test temperature is not explicitly stated, the test is carried out at 25°C:

<Average transmittance Tnir and reflectance Rnir in near-infrared band>

Measured over a wavelength range of 830 to 1100 nm using a JASCO V-670 spectrophotometer, and averaged over this wavelength range.

<Average visible light transmittance Tvis, reflectance Rvis>

Measured in a wavelength range of 360 to 830 nm using a JASCO V-670 spectrophotometer, and averaged over this wavelength range.

<Haze nir in the near-infrared band>

Using a JASCO V-670 spectrophotometer in the wavelength range of 830 to 1100 nm, the incident angle was measured as 0°, and the quotient of the light intensity with a scattering angle of 1° or more and the sum of all scattered light intensities was calculated as the near-infrared haze.

<Lidar point cloud loss rate>

Using Leishen Technology C16-700B mechanical lidar, place the protective cover 100mm in front of the lidar detection area. Take the white standard plate 2m away from the center of the lidar as the target, and read its point cloud. Compare whether there are missing target points in the range covered by the protective cover in the point cloud with or without protective cover, and count the number of missing points.

<shape size>

Measured using a Keyence VR 3200, 3D scanner.

<Surface hardness>

Measured using pencil hardness tester VF2380-152

<Xenon lamp aging test>

Xenon lamp aging test is carried out under the following conditions

Xenon lamp illumination 75W/m2@300～400nm

Blackboard temperature 53℃

Irradiation dose 350MJ/m2

<High temperature treatment>

High temperature treatment under the following conditions

90℃ for 500 hours

<Climate Cycle>

The climate cycle test is carried out under the following conditions, and the cycle is 50 times

40min/23℃/RH30%→

90min/(23℃ to -35℃)/RH30%→

60min/-35℃/RH30%→

80min/(-35℃ to 50℃)/RH80%→

120min/50℃/RH80%→

30min/(50℃ to 80℃)/RH30%→

240min/80℃/RH30%→

60min/(80℃ to 23℃)/RH30%

<Abrasion Test>

The test was performed according to the American standard ASTM D4060 using a Taber Abrasion Tester Model 5135.

The raw materials used in the examples and comparative examples are as follows:

<Film>

A: 125 μm polyester multilayer laminate film, PICASUS CM, manufactured by Toray Industries, Ltd.

B: 70 μm polyester multilayer laminate film, PICASUS DC, manufactured by Toray Industries, Ltd.

C: 125 μm polyester multilayer laminate film, PICASUS GH, manufactured by Toray Industries, Ltd.

D: 100 μm thick aluminized film, produced by Toray Film Processing Co., Ltd.

<Substrate>

I: PMMA/PC/PMMA sheet, TST310, produced by Meisaka Vacuum Industry Co., Ltd., thickness 1.5mm

II: PC resin for injection molding, Markrolon AL2467, produced by Covestro Polymers (China) Co., Ltd.

<Inks and adhesives>

a: Infrared transparent black ink, TABK-4727 manufactured by Toray Co., Ltd.

b: Infrared transparent blue ink, manufactured by Toray Co., Ltd.

c: Infrared transparent red ink, manufactured by Toray Co., Ltd.

d: Infrared transparent yellow ink, produced by Toray Co., Ltd.

e: Infrared transparent green ink, produced by Toray Co., Ltd.

f: Adhesive for in-film injection molding, UPX930, provided by Mingno Trading

g: conductive layer

h: Optical clear adhesive, SP-700, produced by Toyo Kemei Co., Ltd.

i: Ink for injection molding in film, IPX-HF-979 black, produced by Caihuang

<AR processing>

1. Coating a single layer of low refractive index material by coating

2. Alternate vapor deposition of high and low refractive index materials by vapor deposition

<Hard coating>

Using UVHC5000 hardening coating, produced by Momentive High-tech Materials Group

The samples for each example and comparative example were prepared according to the protocol listed in Table 1. The test results are shown in Table 2.

Example 1

filter, use only film A.

Example 2

Filter, AR treatment on Film A in Mode 1

Example 3

For the optical filter, a layer of infrared transparent black ink a is printed on the film A by ink jet printing, and dried.

Example 4

On the basis of Example 3, the filter was pattern-printed with inks a, b, c, d, and e on the unprinted surface, and dried.

Example 5

The protective cover, on the basis of Example 4, was coated with an optically transparent glue h on the pattern printing surface using a microgravure method, and after drying, it was attached to the base material I

Example 6

The protective cover, on the basis of Example 5, uses ultra-high pressure molding to make the protective cover described in Example 5 produce a 3D shape, and punch out the excess part

Example 7

Protective cover, as shown in Figure 1, but without layer 4 (conductive layer), on the basis of Example 4, after printing a layer of adhesive f for in-film injection molding on the pattern printing surface using screen printing, high pressure Forming, punching. The die-cut samples were placed into injection molds and in-film injection molded using Substrate II. After injection molding, a hardcoat is applied by spraying on the exposed surfaces of the substrate.

Example 8

Protective cover, as shown in Figure 1, but without layer 4 (conductive layer), compared with Example 7, the design thickness of the injection molded part is 3.68mm (including coating)

Example 9

Protective cover, as shown in Figure 1, but without layer 4 (conductive layer), compared with Example 7, the film used in it is film B, and the rest are the same

Example 10

The protective cover, as shown in FIG. 1 , is compared with Example 7, wherein before printing the adhesive f, a conductive layer g is printed by screen printing and dried.

Comparative Example 1

filter, use only film C.

Comparative Example 2

filter, use only film D.

Comparative Example 3

Protective cover, compared to Example 7, where AR treatment is used in Mode 2

Comparative Example 4

Protective cover, in which shape control accuracy is poor compared to Example 7

The xenon lamp aging test, high temperature treatment, weather cycle, or abrasion test was carried out in Example 7.

Table 1

Table 2

Tnir Tvis Haze nir Point cloud loss rate Shape size deviation Example 1 92.00% 10.00% 0.90% 1% - Example 2 95.00% 13.00% 0.95% 1% - Example 3 91.00% 1.00% 1.76% 1% - Example 4 90.00% 0.70% 2.10% 1% - Example 5 87.00% 0.50% 2.10% 5% 2μm Example 6 87.00% 0.50% 2.10% 5% 8μm Example 7 91.00% 0.70% 2.30% 2% 3μm Example 8 91.00% 0.70% 2.30% 2% 3μm Example 9 91.00% 0.70% 2.30% 2% 3μm Example 10 90.00% 0.70% 2.40% 2% 3μm Comparative Example 1 30.00% 30.00% 1.10% 90% - Comparative Example 2 0.10% 0.10% can't test 100% - Comparative Example 3 - - - - -(Surface rupture) Comparative Example 4 91.00% 0.70% 2.30% 12% 17μm

Example 7 After the xenon lamp aging test, high temperature treatment, climate cycle, or abrasion test test, the near-infrared transmittance change rate is less than 5%, and the near-infrared haze change rate of the protective cover is less than 5%, And when the protective cover is set on the laser radar optical path in the near-infrared band, the point cloud loss rate is <=10%.

Example 9 The static millimeter wave transmission attenuation test was carried out, and the two-way signal attenuation was -3.0dBm.

All patent documents and non-patent documents mentioned in this specification are incorporated herein by reference. Reference in this specification to "a plurality" includes all instances of more than one, ie, "one or more" includes one, two, three, . . . and the like. In this specification, when an upper limit and a lower limit are respectively described for a certain numerical range, or when a certain numerical range is described in the form of a combination of the upper limit and the lower limit, each upper limit and each lower limit described therein can be arbitrarily combined into a new numerical range, which is different from the direct and explicit description. The description form of the numerical range combined should be regarded as the same. Those skilled in the art can make changes and improvements to the present invention without departing from the gist of the present invention, and these are also included in the scope of the present invention.

Claims (13)

1. An optical filter, characterized by: contains a multi-layered laminated film structure; the average transmission of the filter in the near infrared band is > 90% and the haze is < 3%.

2. The filter of claim 1, wherein the filter has an average transmission of > 95% in the near infrared band and a haze of < 1%.

3. The filter of claim 1, wherein: when the optical filter is arranged on a laser radar light path of a near infrared band, the point cloud loss rate is less than 10%.

4. The filter of claim 3, wherein: when the optical filter is arranged on a laser radar light path of a near infrared band, the point cloud loss rate is less than 1%.

5. The filter of claim 1 further comprising a coating that absorbs in all or a portion of the visible range.

6. The filter of claim 1, wherein the filter has an average visible light transmittance of 1% or less.

7. The filter of claim 1, wherein the filter has an average visible light transmittance of 0.1% or less.

8. A sensor protective cover comprising the optical filter according to any one of claims 1 to 7, wherein: the protective cover comprises a substrate layer, a first main surface and a second main surface; a dimensional deviation of the first and second main surface shapes from a design shape of 10 μm; and when the protective cover is arranged on a laser radar light path of a near-infrared band, the point cloud loss rate is less than 10%.

9. The sensor protection cover of claim 8, wherein: the first main surface and the second main surface have a shape having a dimensional deviation of 1 μm from a design shape.

10. The sensor protective cover of claim 8, wherein said protective cover further comprises a hardened coating having a surface hardness of 2H or greater.

11. The protective cover of claim 8, wherein: after any one of a xenon lamp aging test, a high-temperature treatment, a climate cycle or a wear-resistant test, the change rate of the near-infrared transmittance of the protective cover is less than 5%, the change rate of the near-infrared haze of the protective cover is less than 5%, and when the protective cover is arranged on a laser radar light path of a near-infrared band, the point cloud loss rate is less than 10%.

12. The sensor protective cover of claim 8, wherein said protective cover further comprises a conductive layer; after the conducting layer is electrified, the surface temperature of the protective cover can be kept between 35 and 45 ℃; the conductive layer may be discontinuous.

13. The sensor protective cover of claim 8, wherein: the bidirectional transmission loss of the protective cover to electromagnetic waves in the frequency range of 50-100 GHz is less than-10 dBm.

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