Optical film, design method and application thereof

Abstract

The invention discloses an optical film, a design method and application thereof, and belongs to the technical field of vehicle-mounted display. The surface of the optical film is configured to have a plurality of microstructures arranged in an array, and the microstructures enable the optical film to have a visual angle regulation and control function; the microstructure is in an oval shape. The optical film is applied to the vehicle-mounted HUD system. The vehicle-mounted HUD system comprises a projection lens, the optical film, a first reflector, a second reflector and a windshield which are sequentially and optically connected. The projection lens, the optical film and the first reflecting mirror are sequentially arranged, the second reflecting mirror and the first reflecting mirror are oppositely arranged, and the windshield is arranged on a reflecting path of the second reflecting mirror. The horizontal view angle of the passing projection image can be enlarged, and view angle regulation and control are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of vehicle-mounted displays, and in particular relates to an optical film, a design method and applications thereof. Background Art

[0002] The head-up display (HUD) system can display information such as vehicle speed, rotation speed, fuel consumption, etc. on the car windshield. The driver can read the vehicle information without lowering his head, reducing traffic accidents caused by driving blind spots and improving driving safety and comfort. For car drivers, the horizontal movement of the head is much greater than the vertical movement, which means that the driver usually turns his head horizontally to observe the road and surrounding conditions, but rarely turns his head vertically. This requires that the horizontal viewing angle of the image displayed by the HUD is greater than the vertical viewing angle, ensuring that the brightness of the image observed by the driver when turning his head horizontally will not change significantly, thereby improving driving safety.

[0003] The vehicle HUD system usually includes a projection system, two or three reflectors and a windshield. The projection system includes an image source, a relay system, a projection lens, etc. The reflector is usually a free-form surface designed to match the curve of the windshield to fold the light path and reduce the size of the HUD. The image emitted by the projection lens enters the human eye after being reflected by the reflector and the windshield, and the horizontal and vertical viewing angles are the same. However, the horizontal viewing angle of the current optical film is limited and cannot meet the requirements of high-standard vehicle HUD. Figure 1 This is a schematic diagram of the common automotive head-up display optical system. As can be seen from the figure, since the reflector and windshield cannot change the viewing angle of the image emitted by the projection lens, Figure 1 In a system with Figure 4 As shown, the horizontal viewing angle and the vertical viewing angle are exactly the same (the two curves completely overlap). At the same time, according to the principle of light reversibility, the sunlight outside the car will converge to the projection lens, forming sunlight backflow, which will cause damage to the projection equipment. Summary of the invention

[0004] The present invention aims to solve one of the technical problems in the above-mentioned related art at least to a certain extent.

[0005] To this end, an object of the present invention is to provide an optical film, a design method and an application thereof, which can expand the horizontal viewing angle of a passing projected image and achieve viewing angle control.

[0006] In order to solve the above-mentioned technical problems, the present invention is achieved as follows:

[0007] An embodiment of the present invention provides an optical film, wherein the surface of the optical film is configured to have a plurality of microstructures arranged in an array, wherein the microstructures enable the optical film to have a viewing angle control function;

[0008] The microstructure is oval.

[0009] In addition, the optical film according to the present invention may also have the following additional technical features:

[0010] In some embodiments, the number of microstructures in the horizontal direction and the number of microstructures in the vertical direction on the optical film are respectively:

[0011]

[0012] Among them, N H is the number of microstructures in the horizontal direction, N V is the number of microstructures in the vertical direction, d 1 is the distance from the projection lens to the optical film, r is the radius of the projection lens, D H and DV are the length and width of the rectangular bottom surface of the microstructure, respectively, and θ is the output angle corresponding to the time when the brightness of the image emitted by the projection lens drops to 5% of the maximum brightness.

[0013] In some of the embodiments, the focal length of a single microstructure is:

[0014]

[0015] Among them, f H is the horizontal focal length, f V is the vertical focal length, d 2 is the distance between the optical film and the image after reflection, D H and D V are the length and width of the rectangular bottom of the microstructure, L H and W V are the length and width of the image formed by reflection from a single microstructure.

[0016] In some of the embodiments, the radius of curvature of a single microstructure is:

[0017] R H =f H (n-1),

[0018] R V =f V (n-1),

[0019] Among them, R H and R V are the horizontal and vertical curvature radii, n is the refractive index of the microstructure material, and f His the horizontal focal length of the microstructure, f V is the vertical focal length of the microstructure.

[0020] In some embodiments, the size of the ellipse of the microstructure is:

[0021]

[0022] Among them, a, b and c are the major semi-axis, minor semi-axis and half-height of the ellipse respectively, and D H and D V are the length and width of the rectangular bottom of the microstructure, R H and R V are the horizontal and vertical radii of curvature respectively.

[0023] An embodiment of the present invention further provides a method for designing an optical film, the method for designing an optical film as described in any one of the above items, the steps of the method comprising:

[0024] S1. Determine the length and width of the bottom surface of the microstructure, the radius of the projection lens, the distance from the projection lens to the optical film, and the distance from the optical film to the reflection imaging position;

[0025] S2. Obtain the length and width of the image reflected by the optical film according to the distance from the projection lens to the optical film, the distance from the optical film to the reflected image, the corresponding output angle when the brightness of the image emitted by the projection lens drops to 5% of the maximum brightness, and the corresponding horizontal and vertical angles when the brightness of the image drops to 5% of the maximum brightness after the image passes through the optical film;

[0026] S3, according to the distance from the projection lens to the optical film, the length and width of the bottom surface of the microstructure, the radius of the projection lens, and the corresponding output angle when the brightness of the image emitted by the projection lens drops to 5% of the maximum brightness, the number of microstructures in the horizontal direction and the vertical direction on the optical film is obtained;

[0027] S4, obtaining the size of the image formed by the microstructure at the reflected imaging location according to the length and width of the image formed by the reflection of the optical film obtained in S2 and the number of microstructures in the horizontal and vertical directions on the optical film obtained in S3;

[0028] S5, obtaining the horizontal focal length and vertical focal length of a single microstructure according to the length and width of the bottom surface of the microstructure, the distance from the optical film to the reflection imaging location, and the image size formed by the microstructure at the reflection imaging location obtained in S4;

[0029] S6. Obtain the curvature radius of the single microstructure in the horizontal direction and the vertical direction according to the horizontal focal length and the vertical focal length of the single microstructure obtained in S5 and the refractive index of the microstructure material;

[0030] S7, obtaining the major semi-axis, minor semi-axis and half-height of the elliptical microstructure according to the radius of curvature of the single microstructure obtained in S6 and the length and width of the bottom surface of the microstructure;

[0031] S8, performing array simulation on a single microstructure to obtain an optical film with required size requirements;

[0032] S9. According to the designed parameters of the optical film, the optical film is prepared by using direct writing lithography technology.

[0033] In addition, the design method of the optical film according to the present invention may also have the following additional technical features:

[0034] In some embodiments, the design method further comprises:

[0035] S1 0. Electroplating is performed on the surface of the cured optical film to form a metal master film, and then large-scale production of the optical film is performed by reprinting.

[0036] In some of the embodiments, step S8 includes: spin coating a photoresist on the substrate material, obtaining the designed microstructure morphology on the photoresist surface by direct write lithography technology, and then solidifying the microstructure morphology after development and heat baking.

[0037] In some embodiments, the length and width of the bottom surface of the microstructure are both in the range of 20-40 μm.

[0038] An embodiment of the present invention further provides an application of the optical film as described in any one of the above items, wherein the optical film is applied in a vehicle-mounted HUD system, wherein the vehicle-mounted HUD system comprises a projection lens, the optical film, a first reflector, a second reflector, and a windshield that are optically connected in sequence;

[0039] The projection lens, the optical film and the first reflector are arranged in sequence, the second reflector and the first reflector are arranged opposite to each other, and the windshield is arranged on the reflection path of the second reflector.

[0040] Compared with the prior art, the present invention has at least the following beneficial effects:

[0041] In an embodiment of the present invention, an optical film and a design method thereof are provided, wherein a viewing angle regulating optical film having a microstructure on the surface is added between the projection lens and the first reflector. After the image emitted by the projection lens passes through the optical film, the horizontal viewing angle is expanded, the visible range is optimized, and at the same time, damage to the projection equipment caused by backflow of sunlight can be effectively prevented.

[0042] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a HUD optical system evolved from the off-axis three-mirror structure of the prior art;

[0044] Figure 2 A HUD optical system with a viewing angle control optical film disclosed in one embodiment of the present invention;

[0045] Figure 3 A schematic diagram of design process parameters disclosed in one embodiment of the present invention;

[0046] Figure 4 Horizontal and vertical viewing angle curves of the prior art HUD optical system without adding a viewing angle control optical film, and the two curves completely overlap;

[0047] Figure 5 Horizontal and vertical viewing angle curves after adding a viewing angle regulating optical film disclosed in one embodiment of the present invention, blue is the horizontal viewing angle curve, and red is the vertical viewing angle curve;

[0048] Figure 6 A single microstructure morphology disclosed in one embodiment of the present invention;

[0049] Figure 7 A schematic diagram of an optical film formed by splicing single microstructures disclosed in one embodiment of the present invention. DETAILED DESCRIPTION

[0050] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] The embodiments of the present invention are described in detail below through specific embodiments and application scenarios in conjunction with the accompanying drawings.

[0052] See also Figure 2 As shown, in some embodiments of the present invention, an optical film and a design method thereof are provided, in which a viewing angle regulating optical film with a microstructure on the surface is added between the projection lens and the first reflector, which can not only expand the horizontal viewing angle and optimize the visible range, but also effectively prevent the damage to the projection equipment caused by the backflow of sunlight.

[0053] In some embodiments of the present invention, the design and preparation method of the optical film are as follows:

[0054] 1. Design steps of optical film

[0055] Step 1.1: Set the bottom surface of the microstructure to a rectangle with a length of D H , width is D v , the length and width dimensions are both 20-40 μm;

[0056] Step 1.2: Set the projection lens radius to r and the distance to the optical film to d 1 , optical film to reflector M 1 The distance is d 2 , projection lens to reflector M 1 The distance between is d, then d 1 +d 2 =d. Figure 3 As shown. The angle corresponding to when the brightness of the image emitted by the projection lens drops to 5% of the maximum brightness is set to θ, and the angle corresponding to when the brightness of the image in the horizontal direction drops to 5% of the maximum brightness after the image passes through the optical film is set to θ H , which can be understood as the horizontal divergence angle of the light after passing through the optical film and continuing to propagate forward, and the angle corresponding to the vertical brightness dropping to 5% of the maximum brightness is θv. According to the expected design viewing angle θ H The size of the imaging surface can be accurately calculated by θv and θv, avoiding unnecessary large-area display and high-brightness display, which can effectively reduce the power consumption of the HUD system. Especially for battery-powered vehicles or new energy vehicles with high energy consumption requirements, reducing the power consumption of the HUD system can help extend the vehicle's range and improve energy efficiency. H and θv to calculate the reflector M 1 The length L and width W of the image at position are calculated as follows:

[0057]

[0058] Step 1.3: Calculate the number N of microstructures in the horizontal and vertical directions on the optical film H and N V :

[0059]

[0060] Step 1.4: Calculate the reflector M 1 The image size formed by a single microstructure at position (here is the image size of the light after passing through a single microstructure at M 1 The image size formed at the position is similar to the concept of a single pixel), denoted as length L H and width W V :

[0061]

[0062] Step 1.5: Different from the traditional straight line structure, the microstructure designed in the present invention is composed of curved surfaces, with smoother connection transitions and more stable overall structures, which reduces the difficulty of processing. Calculating the horizontal focal length and vertical focal length of a single microstructure separately can achieve precise control of the final imaging horizontal and vertical viewing angles, which is conducive to achieving the expected goal of expanding the horizontal viewing angle alone. The calculation formula is as follows:

[0063]

[0064] In the formula, f H is the horizontal focal length, f V is the vertical focal length;

[0065] Step 1.6: Calculate the radius of curvature of a single microstructure:

[0066] R H =f H (n-1) (9)

[0067] R V =f V (n-1) (10)

[0068] Where n is the refractive index of the microstructure material.

[0069] Step 1.7: According to R H and R V Generate an ellipsoid, the major semi-axis, minor semi-axis and half-height of the ellipsoid are a, b and c respectively. a and b are calculated according to formula (11), and c is calculated according to formula (12):

[0070]

[0071] Step 1.8: Cropping

[0072] D H , width is D v The rectangular clipping satisfies the ellipsoid equation First, cut the ellipsoid along the plane formed by the major axis and the minor axis at half the height of the ellipsoid, cut the ellipsoid in half, and keep the bottom surface as the upper half of the ellipse. Then, use a length of D within the bottom surface of the ellipse. H , width is D v The ellipse on the bottom surface of the retained entity is selected by a rectangular box, extended to the vertex of the ellipsoid in space, and the excess part is cut off to obtain a single microstructure morphology.

[0073] Step 1.9: Stitching

[0074] Single microstructure horizontal expansion N H , vertical expansion N V to form a microstructure array.

[0075] Figure 2 This is a schematic diagram of the automotive head-up display optical system with a viewing angle control optical film. As can be seen from the figure, the horizontal viewing angle is expanded after the optical film (blue curve), and the horizontal viewing angle (blue curve) is significantly larger than the vertical viewing angle (red curve), forming Figure 5 At the same time, when the sunlight outside the car enters the system, the optical film will diffuse the light, preventing the backflow of sunlight from harming the projection equipment.

[0076] In the present invention, the single microstructure morphology obtained by cutting and the microstructure array obtained by splicing both belong to the category of simulation, and the photolithography preparation is performed after the various parameters of the microstructure are determined by simulation.

[0077] 2. Preparation steps of optical films

[0078] Step 2.1: Spin-coat photoresist on the substrate material, obtain the designed microstructure morphology on the photoresist surface by direct write lithography technology, and solidify the morphology after development and thermal baking.

[0079] Step 2.2: The surface of the cured optical adhesive is electroplated to form a metal master mold, which can then be mass-produced through replication.

[0080] Embodiment 1:

[0081] Step 1.1: Set the bottom surface of the microstructure to a rectangle with a length of D H , width is Dv, D H =30μm, Dv=30μm;

[0082] Step 1.2: Set the projection lens radius to r, r = 8 mm, and the distance to the optical film to d 1 , d 1 =60mm, optical film to reflector M 1 The distance from the projection lens to the reflector M is d2, d2 = 400 mm. 1 The distance between is d, then d 1 +d2=d,d=460mm. The angle corresponding to when the brightness of the image emitted by the projection lens drops to 5% of the maximum brightness is set to θ, θ=8°, and the angle corresponding to when the brightness of the image drops to 5% of the maximum brightness in the horizontal direction after the image passes through the optical film is θ H ,θ H =48°, the angle corresponding to the vertical brightness decreasing to 5% of the maximum brightness is θv, θv = 28°. H and θv to calculate the reflector M 1 The length L and width W of the image at position are calculated as follows:

[0083]

[0084]

[0085] Step 1.3: Calculate the number N of microstructures in the horizontal and vertical directions on the optical film H and Nv:

[0086]

[0087] Step 1.4: Calculate the reflector M 1 The image size formed by the microstructure at position is recorded as length L H And width Wv:

[0088]

[0089] Step 1.5: Calculate the focal length of a single microstructure:

[0090]

[0091] Step 1.6: Calculate the radius of curvature of a single microstructure:

[0092] R H =f H (n-1)=47.24×0.61=28.82mm (9)

[0093] R V =fv(n-1)=84.21×0.61=46.48mm (10)

[0094] Step 1.7: According to R H The ellipsoid is generated by Rv, and the major semi-axis, minor semi-axis and half-height of the ellipsoid are a, b and c respectively. a and b are calculated according to formula (11), and c is calculated according to formula (12):

[0095]

[0096] b=22μm,a=28.16μm,

[0097]

[0098] Step 1.8: Cropping

[0099] The length of the base is D H = 30 μm, and a rectangular clipped ellipsoid with a width of Dv = 30 μm, to obtain a single microstructure morphology, such as Figure 6 shown.

[0100] Step 1.9: Stitching

[0101] Single microstructure horizontal expansion N H= 814, vertical expansion Nv = 814, forming a microstructure array, such as Figure 7 shown.

[0102] Step 2.1: Spin-coat a photoresist on a substrate material, obtain a designed microstructure morphology on the surface of the photoresist by direct-write lithography, solidify the morphology after development and heat baking, and obtain an optical film with a microstructure on the surface.

[0103] Figure 4 It is the viewing angle curve of the image at the reflector before adding the optical film (the horizontal viewing angle curve and the vertical viewing angle curve coincide). Figure 5 This is the viewing angle curve of the image at the reflector after adding the optical film (blue is the horizontal viewing angle curve, red is the vertical viewing angle curve). It can be seen that the horizontal viewing angle is significantly expanded after adding the optical film. The horizontal viewing angle corresponding to the maximum brightness of 85% increases from 8° without the film to 28° with the film, the horizontal viewing angle corresponding to the maximum brightness of 50% increases from 14° without the film to 40° with the film, and the horizontal viewing angle corresponding to the maximum brightness of 15% increases from 18° without the film to 52° with the film.

[0104] The parts of the present invention that are not described in detail may refer to the prior art in the art or are known to those skilled in the art, and will not be described in detail here.

[0105] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. An optical film, characterized in that: The surface of the optical film is configured to have a plurality of microstructures arranged in an array, and the microstructures enable the optical film to have a viewing angle regulating function; The microstructure is oval.

2. The optical film according to claim 1, characterized in that: The numbers of microstructures in the horizontal direction and the vertical direction on the optical film are respectively: Among them, N H is the number of microstructures in the horizontal direction, N V is the number of microstructures in the vertical direction, d1 is the distance from the projection lens to the optical film, r is the radius of the projection lens, and D H and D V are the length and width of the rectangular bottom of the microstructure, respectively; θ is the output angle corresponding to when the brightness of the image emitted by the projection lens drops to 5% of the maximum brightness.

3. The optical film according to claim 1, characterized in that: The focal length of a single microstructure is: Among them, f H is the horizontal focal length, f V is the vertical focal length, d2 is the distance between the optical film and the image after reflection, D H and D V are the length and width of the rectangular bottom of the microstructure, L H and W V are the length and width of the image formed by reflection from a single microstructure.

4. The optical film according to claim 1, characterized in that: The radius of curvature of a single microstructure is: R H =f H (n-1), R V =f V (n-1), Among them, R H and R V are the horizontal and vertical curvature radii, n is the refractive index of the microstructure material, and f H is the horizontal focal length of the microstructure, f V is the vertical focal length of the microstructure.

5. The optical film according to claim 1, characterized in that: The dimensions of the ellipse of the microstructure are: Among them, a, b and c are the major semi-axis, minor semi-axis and half-height of the ellipse respectively, and D H and D V are the length and width of the rectangular bottom of the microstructure, R H and R V are the horizontal and vertical radii of curvature respectively.

6. A method for designing an optical film, characterized in that: The design method is used to design the optical film according to any one of claims 1 to 5, and the steps of the design method include: S1. Determine the length and width of the bottom surface of the microstructure, the radius of the projection lens, the distance from the projection lens to the optical film, and the distance from the optical film to the reflection imaging position; S2. Obtain the length and width of the image reflected by the optical film according to the distance from the projection lens to the optical film, the distance from the optical film to the reflected image, the corresponding output angle when the brightness of the image emitted by the projection lens drops to 5% of the maximum brightness, and the corresponding horizontal and vertical angles when the brightness of the image drops to 5% of the maximum brightness after the image passes through the optical film; S3, according to the distance from the projection lens to the optical film, the length and width of the bottom surface of the microstructure, the radius of the projection lens, and the corresponding output angle when the brightness of the image emitted by the projection lens drops to 5% of the maximum brightness, the number of microstructures in the horizontal direction and the vertical direction on the optical film is obtained; S4, obtaining the size of the image formed by the microstructure at the reflected imaging location according to the length and width of the image formed by the reflection of the optical film obtained in S2 and the number of microstructures in the horizontal and vertical directions on the optical film obtained in S3; S5, obtaining the horizontal focal length and vertical focal length of a single microstructure according to the length and width of the bottom surface of the microstructure, the distance from the optical film to the reflection imaging location, and the image size formed by the microstructure at the reflection imaging location obtained in S4; S6. Obtain the curvature radius of the single microstructure in the horizontal direction and the vertical direction according to the horizontal focal length and the vertical focal length of the single microstructure obtained in S5 and the refractive index of the microstructure material; S7, obtaining the major semi-axis, minor semi-axis and half-height of the elliptical microstructure according to the radius of curvature of the single microstructure obtained in S6 and the length and width of the bottom surface of the microstructure; S8, performing array simulation on a single microstructure to obtain an optical film with required size requirements; S9. According to the designed parameters of the optical film, the optical film is prepared by using direct writing lithography technology.

7. The method for designing an optical film according to claim 6, characterized in that: The steps of the design method also include: S10, electroplating is performed on the surface of the cured optical film to form a metal master film, and then large-scale production of the optical film is performed through reprinting.

8. The method for designing an optical film according to claim 6, characterized in that: Step S9 includes: spin coating photoresist on the substrate material, obtaining the designed microstructure morphology on the photoresist surface by direct write photolithography technology, and then solidifying the microstructure morphology after development and heat baking.

9. The method for designing an optical film according to claim 6, characterized in that: The length and width of the bottom surface of the microstructure are both in the range of 20-40 μm.

10. Use of the optical film according to any one of claims 1 to 5, characterized in that: The optical film is applied in a vehicle-mounted HUD system, wherein the vehicle-mounted HUD system comprises a projection lens, the optical film, a first reflector, a second reflector and a windshield which are optically connected in sequence; The projection lens, the optical film and the first reflector are arranged in sequence, the second reflector and the first reflector are arranged opposite to each other, and the windshield is arranged on the reflection path of the second reflector.

Images