Filtering structure for infrared camera, infrared camera and virtual reality equipment

Abstract

The embodiment of the invention discloses a filtering structure for an infrared camera, the infrared camera and virtual reality equipment. According to one specific embodiment, the light filtering structure comprises at least one layer of thin film, the at least one layer of thin film comprises at least one dichroic dye, the dichroic dye is used for absorbing visible light, the molecular orientation of the dichroic dye of the at least one layer of thin film is at least two target directions, and any two of the at least two target directions are not parallel. According to the embodiment, visible light can be absorbed in at least two different directions, and the reflectivity of the visible light is reduced.

Description

Technical Field

[0001] The disclosed embodiments relate to the field of optical filtering technology, and more particularly to a filtering structure for an infrared camera, an infrared camera, and a virtual reality device. Background Art

[0002] The application range of infrared cameras is very wide. They can be used in various occasions and various devices. For example, they can be used in virtual reality (VR) devices to realize eye tracking function. Eye tracking uses infrared LED to emit infrared light to the human eye, so that the infrared camera can capture the infrared light reflected by the human eye and identify the dynamics of the human eye in real time, thereby realizing the interaction between the human eye and the machine. Summary of the invention

[0003] The embodiments of the present application provide a filter structure for an infrared camera, an infrared camera, and a virtual reality device.

[0004] In a first aspect, an embodiment of the present disclosure provides a filtering structure for an infrared camera, comprising: at least one thin film, the at least one thin film comprising at least one dichroic dye, the dichroic dye being used to absorb visible light, the molecules of the dichroic dye of the at least one thin film being oriented in at least two target directions, and any two of the at least two target directions being not parallel.

[0005] In some embodiments, at least one thin film comprises at least two dichroic dyes, the at least two dichroic dyes comprising a dichroic dye that absorbs in a blue color range and a dichroic dye that absorbs in a red color range.

[0006] In some embodiments, the at least one film is at least two layers, and the molecules of the dichroic dye in each of the at least two films are oriented in the same direction.

[0007] In some embodiments, at least two target directions are determined based on the absorbance of visible light by the dichroic dye.

[0008] In some embodiments, the molecular orientation of the dichroic dye of each film layer matches the direction in which the dichroic dye of that film layer has the highest absorption rate of visible light.

[0009] In some embodiments, the at least one film is composed of two layers, and the molecular orientations of the dichroic dyes in the two films are perpendicular to each other.

[0010] In some embodiments, the filter structure further includes at least one of the following: an anti-reflection film for visible light, a phase delay film for visible light, and a circularly polarized light filter structure for infrared light.

[0011] In some embodiments, the anti-reflection film is formed by pressing a nano-material having a moth-eye structure.

[0012] In some embodiments, at least one film is prepared using ordered molecules, molecules of at least one dichroic dye are constrained by the ordered molecules, and the ordered molecules are oriented in at least two target directions.

[0013] In some embodiments, the ordered molecules are stretched linear polymers.

[0014] In some embodiments, the ordered molecules are aligned liquid crystal molecules.

[0015] In some embodiments, the molecules of the dichroic dye are alignable, and the molecules of the dichroic dye with alignability are aligned so that the molecules are oriented in at least two target directions.

[0016] In some embodiments, the dichroic dye is an azo-based dichroic dye.

[0017] In a second aspect, an embodiment of the present disclosure provides an infrared camera, comprising: an infrared camera body and the filtering structure of the first aspect.

[0018] In a third aspect, an embodiment of the present disclosure provides a virtual reality device, including: an infrared camera and the filter structure of the first aspect.

[0019] The filter structure for an infrared camera, the infrared camera and the virtual reality device provided by the embodiments of the present disclosure include: at least one layer of thin film, the at least one layer of thin film contains at least one dichroic dye, the dichroic dye is used to absorb visible light, the molecules of the dichroic dye of the at least one layer of thin film are oriented in at least two target directions, any two directions of the at least two target directions are not parallel, so that the visible light is absorbed in at least two different directions, thereby reducing the reflectivity of the visible light. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and other features, advantages and aspects of the embodiments of the present disclosure will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings. Throughout the accompanying drawings, the same or similar reference numerals represent the same or similar elements. It should be understood that the drawings are schematic and the originals and elements are not necessarily drawn to scale.

[0021] Figure 1 is a schematic diagram of an embodiment of a filter structure for an infrared camera according to the present application;

[0022] Figure 2 is a schematic diagram of another embodiment of a filter structure for an infrared camera according to the present application;

[0023] Figure 3 is a schematic diagram of another embodiment of a filter structure for an infrared camera according to the present application;

[0024] Figure 4 is a schematic diagram of another embodiment of a filter structure for an infrared camera according to the present application;

[0025] Figure 5 is a schematic structural diagram of an embodiment of an infrared camera according to the present application;

[0026] Figure 6 It is a structural schematic diagram of an embodiment of a virtual reality device according to the present application. DETAILED DESCRIPTION

[0027] The present application will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It should also be noted that, for ease of description, only the parts related to the relevant invention are shown in the accompanying drawings.

[0028] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0029] Figure 1 FIG. 1 is a schematic diagram showing an embodiment of a filter structure for an infrared camera according to the present application. Figure 1 As shown, the filter structure may include at least one thin film 101. The at least one thin film 101 may contain at least one dichroic dye. The dichroic dye is usually used to absorb visible light.

[0030] Dichroic dyes usually have different optical absorption spectra for incident light of different polarization directions, and usually have the highest absorption coefficient for polarized light in a certain direction, and the lowest absorption coefficient for polarized light in another direction (generally perpendicular to the direction with the highest absorption coefficient). Dichroic dyes may include, but are not limited to, anthraquinone dichroic dyes, triphenoxadiazine and its derivative dichroic dyes, monomethine and polymethine dichroic dyes.

[0031] It should be noted that if at least one layer of the film contains at least two dichroic dyes, the at least two dichroic dyes may be the same dichroic dye or different dichroic dyes.

[0032] The molecular orientation of the dichroic dye contained in at least one layer of film 101 can be at least two target directions, as shown by the directions indicated by icons 102 and 103, and any two of the at least two target directions are generally non-parallel. As an example, the angle between the two directions can be 30°-90°, or more specifically, 60°-90°.

[0033] Here, the order parameter can be used to define any direction of the dye molecule (generally the direction of its length) as its main axis direction, and the main axis directions of all dye molecules have an average direction. Assuming that the main axis directions of all dye molecules are along the average direction, that is, the orientations of all dye molecules are arranged in a uniform manner, then the order parameter S = <3 / 2cos^2θ-1 / 2> = 1, where θ is the angle between the main axis of each dye molecule and the average direction, <> means averaging all molecules, and if the dye molecules are completely disordered, the order parameter S is 0.

[0034] As an example, the filter structure may be a thin film, and the molecular orientation of the dichroic dye contained in the thin film may be at least two target directions, for example, two target directions.

[0035] Here, the above-mentioned filter structure can be a filter film formed by stacking the above-mentioned at least one layer of thin film together, or it can be a filter (for example, filter glass), and the filter can be obtained by coating the above-mentioned at least one layer of thin film on a glass plate.

[0036] The filter structure for the infrared camera disclosed in the present invention can absorb visible light in at least two different directions, thereby reducing the reflectivity of visible light. In addition, the filter structure can be highly transparent to the working wavelength of the infrared camera, thereby improving the transmittance of infrared light.

[0037] In some optional implementations, at least one layer of the film may include at least two dichroic dyes, and the at least two dichroic dyes may include a dichroic dye that absorbs the blue light color domain and a dichroic dye that absorbs the red light color domain. The dichroic dye that absorbs the blue light color domain can be understood as a dye with a more obvious dichroic property in the blue light band, and the dichroic dye that absorbs the red light color domain can be understood as a dye with a more obvious dichroic property in the red light band.

[0038] Since some dichroic dye molecules have a more obvious dichroism for the blue light band, and some dichroic dye molecules have a more obvious dichroism for the red light band, and blue light and red light are almost at the two ends of the visible light range, the use of dichroic dyes that absorb the blue light color range and dichroic dyes that absorb the red light color range can absorb most of the visible light bands. In this way, the reflectivity of most visible light can be further reduced.

[0039] In some optional implementations, at least one layer of film can be at least two layers, and the at least two layers of film can be directly superimposed on each other, or can be superimposed via a bonding layer (e.g., an optically clear adhesive (OCA)). The molecular orientation of the dichroic dye of each layer of the at least two layers of film can be in the same direction, that is, for each layer of the at least two layers of film, the molecular orientation of the dichroic dye of the layer of film is usually in the same direction. If the order parameter S is used to define the orientation of the dye molecules, the molecular orientation of the dichroic dye preferentially points in one direction, which can be understood as the order parameter S>0.3, or more specifically, S>0.7. It should be noted that the larger the order parameter, the more uniform the orientation of the molecules.

[0040] As an example, if at least one thin film may be two layers, the molecular orientations of the first thin film in the two thin films are all in the same direction, the molecular orientations of the second thin film are all in the same direction, and the molecular orientations of the two thin films are not parallel.

[0041] In some optional implementations, at least two target directions can be determined based on the absorptivity of the dichroic dye to visible light. Generally speaking, the absorptivity of a dichroic dye to visible light in different directions on a plane is different, and at least two target directions can be determined by the absorptivity. For example, at least two directions corresponding to absorptivity greater than an absorptivity threshold can be selected as target directions, or at least two directions can be selected in descending order of absorptivity as target directions. After determining the target direction, a corresponding film containing a dichroic dye can be prepared for the target direction. In this way, the absorption effect of the filter structure on visible light can be improved.

[0042] In some optional implementations, the molecular orientation of the dichroic dye of each layer of film can be matched with the direction of the highest absorption rate of the dichroic dye of the film to visible light, that is, the molecular orientation of the dichroic dye of each layer of film preferentially points to the same direction, so that the plane of the film has the direction with the highest absorption rate for visible light in macroscopic terms. In other words, once the molecular orientation of the dichroic dye is determined, the direction with the highest absorption rate for visible light is determined, and when preparing the filter structure, the determined direction with the highest absorption rate can be used as the above target direction. In this way, the absorption effect of the filter structure on visible light can be further improved.

[0043] In some optional implementations, the at least one film may be two films, and the molecular orientations of the dichroic dyes of the two films may be perpendicular to each other, that is, the angle between the two directions is 90°. When the two directions of the molecular orientation are perpendicular to each other, the absorption rate of visible light can reach a higher value. As an example, Figure 2 As shown, Figure 2 FIG. 2 is a schematic diagram showing another embodiment of a filter structure for an infrared camera according to the present application. Figure 2 In the embodiment, the filter structure includes two layers of thin films, namely, thin film 201 and thin film 202. The molecular orientation of the dichroic dye of thin film 201 is in the north-south direction, as shown in icon 203. The molecular orientation of the dichroic dye of thin film 202 is in the east-west direction, as shown in icon 204. Then, thin film 201 absorbs visible light in the north-south direction, and thin film 202 absorbs visible light in the east-west direction, that is, these two layers of thin films can absorb visible light in most directions. In this way, the absorption effect of the filter structure on visible light can be further improved, so that the filter structure can absorb most visible light.

[0044] In some optional implementations, the filter structure may also include at least one of the following: an anti-reflection film for visible light, a phase delay film for visible light, and a circularly polarized light filter film for infrared light. The anti-reflection film can also be called an anti-reflection film. Its main function is to reduce or eliminate the reflected light from optical surfaces such as lenses, prisms, and plane mirrors, thereby increasing the light transmittance of these components and reducing or eliminating the stray light of the system. The phase delay film reduces the reflectivity of visible light by delaying the phase of visible light. Anti-reflection films and phase delay films are usually attached to the outer surface of infrared cameras.

[0045] Here, the anti-reflection film can be composed of multi-layer metal oxides deposited by physical vapor deposition (PVD), or porous nano-oxide particles coated by wet method. Physical vapor deposition technology refers to the technology of using physical methods to vaporize the surface of the material source (solid or liquid) into gaseous atoms or molecules, or partially ionize into ions under vacuum conditions, and deposit a thin film with some special functions on the surface of the substrate through a low-pressure gas (or plasma) process.

[0046] Light whose rotating electric vector endpoints trace a circular trajectory is called circularly polarized light. When two plane polarized lights with the same propagation direction, perpendicular vibration directions and a constant phase difference of φ = (2m ± 1 / 2) π are superimposed, circularly polarized light with a regularly changing electric vector can be synthesized. The circularly polarized light filter can be attached to the outer surface of the infrared camera, or it can be attached between at least two layers of film, or it can be attached to the inner surface of the infrared camera.

[0047] This method can use anti-reflection film or phase delay film to reduce the reflectivity of visible light. In addition, anti-reflection film can also increase the transmittance of infrared light. Circular polarization filter film can reduce infrared ghosting of infrared cameras.

[0048] In some optional implementations, the anti-reflection film can be pressed from a nanomaterial with a moth-eye structure. When the sub-micrometer structure on the surface of the material is smaller than the wavelength of light, the light wave will not be able to recognize the microstructure, so the refractive index on the surface of the material changes continuously along the depth direction, which can reduce the reflection phenomenon caused by the sharp change of the refractive index. The moth-eye anti-reflection structure has an excellent anti-reflection and anti-transmission effect in the infrared band.

[0049] In some optional implementations, at least one layer of film 101 may be prepared using ordered molecules, and at least one dichroic dye molecule incorporated into the film may be constrained and oriented by the ordered molecules in the film. At this time, the ordered molecules are usually oriented in at least two target directions, so that the dichroic dye molecules are oriented in at least two target directions. In this way, other ordered molecules may be used to constrain the dichroic dye molecules for orientation.

[0050] In some optional implementations, the ordered molecules may be stretched linear polymers, which are usually long chains, such as polyvinyl alcohol (PVA).

[0051] In some optional implementations, the above-mentioned ordered molecules can be aligned liquid crystal molecules. These liquid crystal molecules are generally dissolved in a solvent first, and can be formed into a thin film by coating, and then the molecular orientation of the dichroic dye is constrained to preferentially point to one direction through any one of the alignment methods of light alignment, electric field alignment and shear force alignment. Light alignment technology usually refers to the use of ultraviolet light to irradiate the liquid crystal alignment film so that the liquid crystal molecules are arranged in a certain order. Electric field alignment usually refers to the use of an electric field to arrange the liquid crystal molecules in a certain order. Shear force alignment usually refers to the use of a force that can cause shear deformation of the material to cause the liquid crystal molecules to be arranged in the direction of the force.

[0052] In some optional implementations, the molecules of the dichroic dye have an alignable property, for example, a rod-shaped molecule with dichroism. The molecules of the dichroic dye having an alignable property are aligned so that the molecules are oriented in the above-mentioned at least two target directions. Here, any alignment method of light alignment, electric field alignment and shear force alignment can be used for alignment.

[0053] In some optional implementations, the dichroic dye used may be an azo dichroic dye, such as a disazo or trisazo dichroic dye. Azo dichroic dyes can simultaneously achieve extremely high visible light absorptivity and extremely high infrared light transmittance.

[0054] As an example, Figure 3 As shown, Figure 3FIG. 2 is a schematic diagram showing another embodiment of a filter structure for an infrared camera according to the present application. Figure 3 In the filter structure, two layers of films with azo dichroic dye molecules can be included, one of which is a PVA polarizing film with a thickness of 35 μm (micrometers), and the other is also a PVA polarizing film with a thickness of 30 μm. The two films are bonded together with a 15 μm optical pressure-sensitive adhesive so that the axial angle with the highest absorption rate of the two films is close to 90°.

[0055] In order to further reduce the visible light reflectivity and increase the near-infrared light transmittance, an anti-reflection film with an anti-reflection coating can be attached to the outside of the above-mentioned composite film with an optical pressure-sensitive adhesive. The anti-reflection coating may be pressed by nanomaterials with a moth-eye structure, which also has excellent anti-reflection and anti-transmission effects in the infrared band. The average reflectivity of the filter structure obtained in this way (400-700nm) is less than 1%, and the transmittance of the working wavelength of 850nm commonly used by eye tracking infrared cameras can reach >95%.

[0056] As another example, Figure 4 As shown, Figure 4 FIG. 2 is a schematic diagram showing another embodiment of a filter structure for an infrared camera according to the present application. Figure 4 In the method, a 40 μm TAC (Tri-Aacetyl Cellulose) film is selected as the bonding layer of two stacked films with dichroic dyes. On both surfaces of the TAC film, a lyotropic liquid crystal coating with a dry film thickness of 2 μm is applied by slit coating. The lyotropic liquid crystal coating can be obtained by aligning the liquid crystal molecules by the shear force during coating. In this way, by changing the coating direction on the front and back sides, the orientation of the liquid crystal films on the front and back sides can be respectively oriented to the x and y directions, that is, the orientation axis is 90°. Then it is immersed in a solution containing azo dichroic molecules for dyeing. The azo dichroic molecules form a polarizing film with a maximum absorption rate direction of 90° on both sides of the TAC film. Next, an optical pressure-sensitive adhesive is applied to one side of the film, and a hardening coating and an anti-reflection coating are applied to the other side, thus forming a filter structure with one side of adhesive, extremely thin thickness, and suitable for attaching to the curved surface of the camera lens.

[0057] It should be noted that the above examples are only schematic diagrams of forming the filter structure described in the present disclosure, but do not cover the scope of the present disclosure. For example, the film with dichroic dyes, in addition to the PVA and shear-aligned lyotropic liquid crystals mentioned above, can also be photo-aligned lyotropic liquid crystals and their alignment layers, and the corresponding formation method can also be to coat two layers of films with dichroic dyes in different orientations on one side of a film such as TAC / SRF / PMMA (Polymethyl Methacrylate) / COP.

[0058] Please refer to Figure 5 , Figure 5 FIG. 1 is a schematic diagram of the structure of an infrared camera according to an embodiment of the present application. Figure 5 In the embodiment, the infrared camera may include an infrared camera body and a filter structure 502 as described in the embodiment of the present application. The filter structure 502 may be a filter film, in which case the filter film may be attached to the outer surface of the lens 501 of the infrared camera body. The filter structure 502 may also be prepared as a separate filter, which may be used in conjunction with the infrared camera body to obtain an infrared camera with a filter structure. The infrared camera with a filter structure may absorb visible light in at least two different directions, thereby reducing the reflectivity of visible light and reducing the imaging stray light ghost caused by the lens reflecting visible light. In addition, the filter structure may be highly transparent to the working wavelength of the infrared camera, thereby improving the transmittance of infrared light.

[0059] Further references Figure 6 , Figure 6 is a structural diagram of an embodiment of a virtual reality device according to the present application. Figure 6 In the virtual reality (VR) device, an infrared camera is placed between the VR lens and the screen, so that the infrared signal is received by the infrared camera through the lens. In this way, from the human eye, the infrared camera is hidden in the lens, which is more conducive to the miniaturization of the device and the immersive feeling without interference from the near-eye side when worn.

[0060] However, the infrared camera receives infrared signals through the lens, which means that its lens must face the VR lens. Since the infrared lens is made of infrared sensitive materials, the transmittance and reflectivity of infrared light are optimized, and its visible light reflectivity cannot be optimized, resulting in strong visible light reflection. When the VR device is working, the infrared camera will reflect the visible light in the optical system to the lens surface, interfering with imaging and causing ghost images and stray light.

[0061] exist Figure 6 In the figure, the dotted line indicates that the screen light is reflected by the back of the lens, and then reflected by the infrared camera, entering the light path, forming a stray light ghost; the solid line indicates that the screen light is reflected by the left surface of the lens, and then reflected by the infrared camera, entering the light path, forming a stray light ghost; the long dotted line indicates that the screen light is directly reflected by the infrared camera, entering the light path, forming a stray light ghost.

[0062] Here, the filter structure described in the embodiment of the present application can be combined with Figure 6The lenses of the infrared camera shown are used together, so that the visible light reflectivity of the infrared camera surface is extremely low, and basically no stray light ghosting of visible light is brought about, but the impact on the infrared light transmittance of the infrared camera's working wavelength is minimal, so that eye tracking based on infrared light can be carried out normally.

[0063] It should be noted that Figure 6 The VR device shown is only an example. The filter structure described in the embodiment of the present application may be a filter film, which may be attached to the outer surface of the lens of any VR device including an infrared camera to achieve the above functions. The filter structure described in the embodiment of the present application may also be prepared as a separate filter, which may be used in conjunction with the lens of the VR device including an infrared camera to achieve the above functions.

[0064] It should also be noted that the filter structure disclosed in the present invention can be used not only on VR devices for eye tracking, but also in multiple application scenarios such as shielding infrared sensors, removing visible light interference from infrared sensors or cameras, and removing interference of visible light on infrared cameras.

[0065] The above description is only a preferred embodiment of the present disclosure and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the embodiments of the present disclosure is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the above-mentioned inventive concept. For example, the above-mentioned features are replaced with the technical features with similar functions disclosed in the embodiments of the present disclosure (but not limited to) to form a technical solution.

Claims

1. A filter structure for an infrared camera, characterized in that: include: At least one film, the at least one film comprises at least one dichroic dye, the dichroic dye is used to absorb visible light, the molecules of the dichroic dye of the at least one film are oriented in at least two target directions, and any two directions of the at least two target directions are not parallel.

2. The filter structure according to claim 1, characterized in that: The at least one thin film comprises at least two dichroic dyes, wherein the at least two dichroic dyes include a dichroic dye that absorbs a blue light color range and a dichroic dye that absorbs a red light color range.

3. The filter structure according to claim 1, characterized in that: The at least one thin film is at least two layers, and the molecules of the dichroic dye in each of the at least two thin films are oriented in the same direction.

4. The filter structure according to claim 3, characterized in that: The at least two target directions are determined according to the absorbance of the dichroic dye to visible light.

5. The filter structure according to claim 4, characterized in that: The molecular orientation of the dichroic dye of each layer of the film matches the direction in which the absorption rate of the dichroic dye of the film to visible light is the highest.

6. The filter structure according to claim 3, characterized in that: The at least one film is composed of two layers, and the molecular orientations of the dichroic dyes in the two films are perpendicular to each other.

7. The filter structure according to claim 1, characterized in that: The filter film also includes at least one of the following: an anti-reflection film for visible light, a phase delay film for visible light, and a circularly polarized light filter film for infrared light.

8. The filter structure according to claim 7, characterized in that: The anti-reflection film is formed by pressing a nano material with a moth-eye structure.

9. The filter structure according to claim 1, characterized in that: The at least one film is prepared by using orderly arranged molecules, the molecules of the at least one dichroic dye are constrained by the orderly arranged molecules, and the orientation of the orderly arranged molecules is the at least two target directions.

10. The light filtering structure according to claim 9, characterized in that: The orderly arranged molecules are straight-chain polymers formed by stretching.

11. The light filtering structure according to claim 9, characterized in that: The orderly arranged molecules are aligned liquid crystal molecules.

12. The light filtering structure according to claim 1, characterized in that: The molecules of the dichroic dye are alignable, and the molecules of the dichroic dye with alignability are aligned so that the molecules are oriented in the at least two target directions.

13. The filter structure according to claim 1, characterized in that: The dichroic dye is an azo dichroic dye.

14. An infrared camera, characterized in that: include: An infrared camera body and a filter structure as described in any one of claims 1-13.

15. A virtual reality device, characterized in that: include: An infrared camera and a filter structure as claimed in any one of claims 1 to 13.

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