LIDAR window integrated optical filter

Abstract

A LIDAR vehicle window integrated optical filter is disclosed, the filter comprising a vehicle window made of a polymer material for absorbing visible light bands and transmitting near infrared bands; and an upper reflection layer and a lower reflection layer formed on the upper surface and the lower surface of the vehicle window. The upper reflection layer and the lower reflection layer may be formed to include titanium dioxide (TiO 2 ) and silicon dioxide (SiO 2 ) film.

Description

Technical Field

[0001] The present invention relates to a light detection and ranging (LiDAR) vehicle window integrated optical filter for integratedly realizing the functions of an optical filter and a cover constituting a LiDAR system for autonomous driving. Background Art

[0002] Conventionally, optical filters are mainly used in digital imaging devices such as cameras and smartphones to block near-infrared light to achieve natural colors as seen by the human eye. Therefore, images are achieved by transmitting visible light and blocking near-infrared light to prevent interference of light. However, since LiDAR components use infrared light as the main light source, the performance of blocking visible light and transmitting infrared light is very important, unlike optical filters applied to cameras and smartphones. For example, by using the time it takes for infrared light emitted from the LiDAR component to hit the target and return, the LiDAR component can be used in the time-of-flight method to measure the distance to an object. For example, Figure 1A As shown, in the prior art, the upper / lower near-infrared absorption layer 20a, 20b is coated on the transparent substrate 10a that does not absorb visible light with a solution made of a near-infrared absorption dye and a binder resin, and then dried. In addition, the near-infrared reflection layer 30a, 30b can be formed on the upper and lower parts of the near-infrared absorption layer by chemical vapor deposition (CVD). However, the coating thickness may not be uniform because it is made by a solution coating process, and a uniform film thickness may not be formed on a curved substrate. In addition, as Figure 1B As shown, light with a wavelength of 905 nm may not be used for LiDAR because it blocks near-infrared light.

[0003] Next, Figure 2A and Figure 2B An optical filter with high visible light blocking rate and high infrared light transmittance in the prior art is shown. Conventional technology forms a low-reflection coating 13b on the upper part of glass ceramic 11b, and forms a multilayer thin film 12b on the lower part thereof. However, the substrate of the conventional technology is limited to glass ceramic, the multilayer thin film is alternately laminated by Si and Ti, the thin film is 10 to 50 layers, and the thickness is 1μm to 100μm, thereby increasing the manufacturing cost. In particular, since glass-based optical filters may be easily broken, they need to be processed and their mechanical durability is weak, which may cause the following problems: when manufacturing glass with a curved surface, the processing cost of the glass increases.

[0004] The transmittance at the infrared wavelength of 905nm band used in LiDAR is about 89%. In LiDAR, Figure 3AAs shown, only the 905nm band should be transmitted, and the remaining wavelengths should be cut off. That is, there should be a bandpass filter function. Therefore, in the related art, wavelengths other than the 905nm signal sent by the LiDAR may be received, causing sensor failure.

[0005] At the same time, when using Figure 3A In the case of the optical filter having the characteristics shown, since the transmittance at a wavelength of 905 nm is lower than the level of 55%, the efficiency of signal transmission and reception is reduced.

[0006] In addition, if Figure 3B The glass-based optical filter shown also requires a bandpass filter function of approximately ±100 nm based on a central wavelength of 905 nm.

[0007] A disadvantage is that, until now, conventional technology has used a method of attaching an optical filter deposited with inorganic materials to a glass substrate by separately manufacturing a sensing chip (semiconductor) and the optical filter, thereby increasing process and manufacturing costs.

[0008] That is, in the LiDAR system, if Figure 4 As shown, an avalanche photodiode (APD) chip 1 and an optical filter 2 for image sensing are configured to be bonded to an interior of a plastic cover 4 of a front portion of a vehicle by an adhesive 3 .

[0009] The matters described in the description of the related art are to help understanding the background of the present invention and may include matters that are previously unknown to those skilled in the art to which the present invention belongs. Summary of the invention

[0010] In a preferred aspect, a LiDAR vehicle window integrated optical filter is provided, which can reduce manufacturing costs and processes while being used as an optical filter for a LiDAR system.

[0011] The LiDAR vehicle window integrated optical filter includes: a vehicle window including a polymer material; an upper reflection layer formed on the upper surface of the vehicle window; and a lower reflection layer formed on the lower surface of the vehicle window. The polymer material can appropriately absorb visible light and transmit near infrared light. Each of the upper reflection layer and the lower reflection layer can be formed to include titanium dioxide (TiO 2 ) and silicon dioxide (SiO 2 For example, titanium dioxide (TiO 2 ) layer and silicon dioxide (SiO 2 ) layer to form a film. Preferably, such a film layer (including TiO 2 and SiO 2 Film) is a thin film layer.

[0012] In addition, each of the upper reflection layer and the lower reflection layer may be formed in a multi-layer film on the vehicle window by vapor deposition.

[0013] Each of the upper reflection layer and the lower reflection layer can be formed by laminating a plurality of SiO 2 Layer and TiO 2 layer to form a thin film.

[0014] In addition, the thickness of the upper reflection layer may be appropriately in the range of about 4 μm to about 7 μm.

[0015] In addition, each upper reflection layer may be deposited as a multi-layer structure of 25 to 30 layers, and the upper reflection layer reflects infrared light having a wavelength of about 1400 nm to 1600 nm.

[0016] In addition, the thickness of the low reflection layer may be appropriately in the range of about 4 μm to about 7 μm.

[0017] In addition, the low reflection layer may be deposited as a multi-layer structure of 25 to 30 layers, and the low reflection layer reflects infrared light having a wavelength of about 1100 nm to 1400 nm.

[0018] Preferably, a thickness difference between the upper reflection layer and the lower reflection layer may be less than about 2 μm.

[0019] Meanwhile, the vehicle window may include a transparent plastic material to which a visible light absorbing material is added, and may suitably have a thickness of about 2 mm to 4 mm.

[0020] As used herein, the term "transparent" material or "transparent" resin may refer to a material having a substantial transmittance of light, such as visible light. For example, a large amount of visible light, such as about 50%, about 60%, about 70%, about 80%, about 90%, about 95%, about 99% or more of the visible light may be transmitted or passed through the transparent material or resin.

[0021] Therefore, the transmittance at a wavelength of 905 nm may be about 90% or more, and the transmittance at a wavelength of 1550 nm may be about 1% or less.

[0022] In one aspect, a LiDAR window integrated optical filter is provided, which may include: a window including a polymer material that absorbs visible light with a wavelength of about 350nm to 780nm; an upper reflection layer laminated on the upper surface of the window to reflect infrared light with a wavelength of about 1400nm to 1600nm; and a lower reflection layer laminated on the lower surface of the window to reflect infrared light with a wavelength of about 1100 to 1400nm.

[0023] In addition, the transmittance at a wavelength of 905 nm may be approximately 90% or more.

[0024] In addition, the transmittance at a wavelength of 1550 nm may be approximately 1% or less.

[0025] According to various exemplary embodiments of the LiDAR window integrated optical filter of the present invention, for example, by manufacturing a separate optical filter, the light absorbing additive and the multilayer film can be integrated on the plastic cover of the LiDAR component without being attached to the APD chip. Therefore, the LiDAR window itself performs the function of a 905nm bandpass filter, thereby playing the role of a bandpass filter.

[0026] Therefore, the manufacturing cost and the manufacturing process can be reduced.

[0027] In addition, for autonomous driving, the sensing performance of LiDAR can be further improved compared to before, thereby further ensuring the safety of drivers and pedestrians. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figures 1A to 4 is a diagram for explaining a conventional LiDAR system and an optical filter in the related art.

[0029] Figure 5 Schematic diagram of a LiDAR window integrated optical filter according to an exemplary embodiment of the present invention.

[0030] Fig. 6A is a diagram showing an optical filter according to Comparative Example 1, and Figure 6B is a graph showing filter characteristics according to Comparative Example 1.

[0031] Fig. 7A is a diagram showing an exemplary optical filter according to an exemplary embodiment of the present invention, and Figure 7B is a diagram illustrating exemplary filter characteristics according to an exemplary embodiment of the present invention.

[0032] Fig. 8A is a diagram illustrating an exemplary upper surface of an exemplary multilayer structure of an exemplary optical filter according to an exemplary embodiment of the present invention, and Figure 8B is a diagram illustrating an exemplary lower surface of an exemplary multilayer structure of an exemplary optical filter according to an exemplary embodiment of the present invention.

[0033] Fig. 9 is a diagram showing the incident angle of 95 nm-band infrared laser incident on an exemplary LiDAR vehicle window integrated optical filter of the present invention.

[0034] Fig. 10A is a diagram showing an optical filter according to Comparative Example 2, and Fig. 10B is a graph showing filter characteristics of Comparative Example 2.

[0035] Fig. 10C and Fig. 10D 3 is a diagram showing the bending phenomenon of Comparative Example 2.

[0036] Fig.11A is a diagram illustrating an exemplary optical filter according to an exemplary embodiment of the present invention compared with Comparative Example 2.

[0037] Fig. 11B and Fig. 11C is a diagram showing whether the optical filter according to the embodiment of the present invention has been bent.

[0038] Fig.12 is a diagram showing a configuration for test evaluation of a LiDAR vehicle window integrated optical filter.

[0039] Fig.13A is a graph showing evaluation results according to Comparative Example 1, and Fig. 13B is a diagram showing evaluation results according to an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The terms used herein are only used for the purpose of describing specific exemplary embodiments, rather than to limit the present invention. As used herein, the singular forms "one", "an" and "the" are also intended to include plural forms, unless the context clearly states otherwise. It will be further understood that when used in this specification, the terms "include" and / or "comprise" specify the presence of the features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. As used herein, the term "and / or" includes any and all combinations of one or more related listed items.

[0041] Unless otherwise specified or obvious from the context, as used herein, the term "about" should be understood as being within the normal tolerance range in the art, such as within 2 standard deviations of the mean. "About" can be understood as being within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clearly indicated from the context, all numerical values ​​provided herein are modified by the term "about".

[0042] For a fuller understanding of the invention, its operating advantages and objectives attained by practice of its implementation, reference should be made to the accompanying drawings which illustrate preferred embodiments of the invention and the matter described therein.

[0043] In describing various exemplary embodiments of the present invention, well-known techniques or repeated descriptions that may unnecessarily obscure the subject matter of the present invention will be shortened or omitted.

[0044] Figure 5 is a schematic diagram of an exemplary LiDAR vehicle window integrated optical filter according to an exemplary embodiment of the present invention.

[0045] The LiDAR window integrated optical filter according to an exemplary embodiment of the present invention is used for a LiDAR system, and the window integrated optical filter is arranged in front of a LiDAR sensor (APD chip) and serves to simultaneously perform the functions of a conventional optical filter and a cover.

[0046] LiDAR is an essential sensor for autonomous driving, and can calculate the distance to a target by using infrared light with a wavelength of 905nm to hit the target and return the signal. Among other things, optical filters are used to minimize noise interference (such as sunlight and other signals from the outside world) during transmission and reception.

[0047] To this end, the LiDAR window integrated optical filter of the present invention is configured to include a window 10, an upper reflection layer 20 and a lower reflection layer 30, and the window 10 is a polymer material and, for example, is formed of a transparent plastic (11, PC) to which a visible light absorbing material 12 is added, and the reflection layers 20, 30 are formed of thin-film multilayer deposition films by vacuum deposition.

[0048] Therefore, visible light may be absorbed by the vehicle window 10 , and infrared light of a target wavelength or more may be reflected by the reflective layers 20 , 30 .

[0049] The thickness, number of layers, etc. of the vehicle window 10 and the reflective layers 20 , 30 are summarized in Table 1.

[0050] Table 1

[0051]

[0052] That is, the upper reflective layer 20 is made of SiO 2 and TiO 2 The thickness of the thin film multilayer deposition film deposited on the upper portion of the vehicle window 10 may be approximately 4 μm to 7 μm and 25 to 30 layers.

[0053] In addition, the lower reflection layer 30 is made of SiO 2 and TiO 2 The thickness of the thin film multilayer deposition film deposited on the lower portion of the vehicle window 10 may be approximately 4 μm to 7 μm and 25 to 30 layers.

[0054] The thickness difference between the upper reflection layer 20 and the lower reflection layer 30 may be less than about 2 μm because bending may occur when the thickness difference is about 2 μm or more.

[0055] Furthermore, the vehicle window 10 may suitably have a transmittance of 85% to 92% at a wavelength of 905 nm and a thickness of approximately 2 mm to 4 mm.

[0056] In addition, the surface of the upper reflection layer 20 may include a low reflection coating material, a hard coating layer, or both a low reflection coating layer and a hard coating layer.

[0057] When referring to FIG. 6A to FIG. 7B When describing in more detail, such as Fig. 6A As shown, when only the visible light absorbing material is added to the base plastic (polycarbonate, 5) without adding the infrared reflective deposition film, the infrared light is transmitted and only the visible light is absorbed, making it impossible to achieve the Figure 6B The bandpass filter shown.

[0058] On the contrary, Fig. 7A In the case of the LiDAR window integrated optical filter according to the exemplary embodiment of the present invention, the infrared band can be reflected according to the type, thickness, and number of layers of each deposited film corresponding to the upper reflection layer 20 and the lower reflection layer 30. Therefore, as shown in FIG. Figure 7B As shown, a bandpass filter with high transmittance around 905nm can be realized. Since the LiDAR window integrated optical filter has a high transmittance of more than about 90% at a wavelength between 825nm and 1025nm, it is suitable for LiDAR systems.

[0059] Specifically, since the transmittance of a wavelength of 905 nm used for LiDAR is about 90% or more, and the transmittance of a wavelength of 1550 nm is about 0.1%, there is no noise crosstalk with LiDAR using the wavelength band of 1550 nm.

[0060] In this example, the low reflection layer 30 may be deposited with 30 layers of SiO 2 and TiO 2 To reflect wavelengths of about 1100nm to 1400nm, and the upper reflective layer 20 may be deposited with 27 layers of SiO 2 and TiO 2 To reflect wavelengths of approximately 1400nm to 1600nm.

[0061] Fig. 8A and Figure 8B The structure of the multilayer film is analyzed by FIB / SEM. The pretreatment layer can be a temporary layer for analysis. Fig. 8A corresponds to an upper surface of the multilayer film structure of the optical filter, and Figure 8BThe bottom surface of the multilayer film structure corresponding to the optical filter. The actual infrared reflection layer is marked between the pre-treatment layer and the base material. Fig. 8A In the figure, the actual thickness is 5918 μm, while in Figure 8B The actual thickness is 5478 μm. Fig. 9 As shown, the incident light is incident on the LiDAR window integrated optical filter 100 at a constant angle.

[0062] Therefore, it is important to maintain a transmittance of 95% or more at a wavelength of 905 nm even when the incident light changes from 0 degrees to 40 degrees. In addition, it is important to have a transmittance within 1% at a wavelength of 1550 nm, and this can be achieved by the present invention.

[0063] Fig. 10A An optical filter according to Comparative Example 2 is shown, and Fig. 10B The filter characteristics of Comparative Example 2 are shown. Comparative Example 2 is a case where the infrared reflection layer 6 is formed only on one surface of the base plastic 5, and since Comparative Example 2 performs infrared reflection in a wide range of 1100nm to 1600nm in order to show the bandpass characteristics, the infrared reflection layer 6 can only increase the number of layers of the deposited film. For example, 59 layers and a thickness of about 10202μm may be required.

[0064] In order to form a thick deposited film having a large number of layers, the base plastic 5 having a relatively low heat deformation temperature during a high temperature deposition process is exposed, thereby causing bending.

[0065] Fig. 10C This bending phenomenon is shown in Fig. 10D Shows Fig. 10C , and this is summarized in Table 2. In the experiment, it was confirmed that the thickness of the base plastic was 2 mm, and an average bending of 286 μm occurred.

[0066] Table 2

[0067]

[0068] In addition, when the deposited film is formed only on one surface, it can be confirmed that the transmittance is about 15% when the incident angle is 50 degrees in the 1550nm band. That is, since the noise signal of the LiDAR using the 1550nm band may pass as it is, the LiDAR signal is distorted due to the bending.

[0069] The purpose of the present invention is to have high transmittance at 905 nm and low transmittance at 1550 nm, and this purpose cannot be achieved by the configuration as in Comparative Example 2. Instead, Fig.11A 1 shows an optical filter according to an embodiment of the present invention, Fig. 11Band Fig. 11C It is shown whether the optical filter according to the exemplary embodiment of the present invention is bent, and is summarized as shown in Table 3. In the experiment, it was confirmed that the thickness of the base plastic was 2 mm, and an average bending of 286 μm occurred.

[0070] Table 3

[0071]

[0072] As can be seen from Table 3, when the reflective layers are deposited on the upper and lower surfaces as in the present invention, the bow after deposition can be an insignificant about 53 μm even at a thickness of 2 mm to minimize the bow phenomenon and thus not affect the LiDAR signal.

[0073] Fig.12 It is an experimental configuration for evaluating the sensing (signal sensing) capability of LiDAR when the LiDAR window integrated optical filter of the present invention is applied.

[0074] in addition, Fig.13A Shown by Fig.12 Evaluation results of Comparative Example 1 of the experimental configuration, and Fig. 13B Shown by Fig.12 Evaluation results of an exemplary embodiment of the present invention of an experimental configuration.

[0075] In the experiment, the illuminance of light used was 5500 cd to 5800 cd, the illuminometer used was CL200-A, the glossmeter used was AG-446, and the artificial daylight used was SOLAX XC-500.

[0076] Artificial sunlight (S) acts as noise to interfere with the normal operation of LiDAR (L). LiDAR uses a wavelength of 905nm in infrared light, and APD also only receives the 905nm wavelength without converting it into an electrical signal, and also changes some peripheral wavelengths into electrical signals, so a high filter performance that selectively transmits only the 905nm wavelength at maximum is required in the optical filter.

[0077] It can be confirmed that when the light reflected from the artificial sunlight (S) on the wall (W) is incident on the LiDARL as noise, in the case of the plastic cover having only the visible light absorption function, such as Fig.13A As shown, the LiDAR signal is cut off by sunlight. On the contrary, it can be confirmed that when the optical filter according to the present invention is applied, only the band of 905nm±100nm is transmitted due to the functions of infrared reflection and visible light absorption, so a lot of noise is filtered out, and therefore, as a result of evaluating the 8-channel LiDAR signal, the LiDAR signal can retain 6 channels.

[0078] This means that when the LiDAR window integrated optical filter according to various exemplary embodiments of the present invention is used in an actual autonomous driving vehicle, the sensing performance can be significantly improved to ensure the safety of drivers and pedestrians.

[0079] The LiDAR used in the experiment is an 8-channel LiDAR, and 8 channels (layers) are formed vertically. Fig.13A and Fig. 13B It is a picture seen from the front of the LiDAR, and the green line indicates with a dotted line the signal after the infrared light of the LiDAR reflected on the target (wall surface) is converted into an electrical signal by the point cloud technology.

[0080] As described above, compared with the conventional technology, according to various exemplary LiDAR window integrated optical filters of the present invention, the cover itself can be used as an optical filter without having to include a separate optical filter on the LiDAR, thereby reducing manufacturing costs, etc., but it is more effective for LiDAR reception performance.

[0081] Although the present invention as described above has been described with reference to the exemplary drawings, the present invention is not limited to the described embodiments, and it is obvious to those skilled in the art that various modifications and changes can be made without departing from the spirit and scope of the present invention. Therefore, modifications or changes should be included in the claims of the present invention, and the scope of the present invention should be interpreted based on the appended claims.

Claims

1. A light detection and ranging LiDAR vehicle window integrated optical filter, comprising: Vehicle windows, including polymeric materials; an upper reflective layer formed on an upper surface of the vehicle window to reflect infrared light; as well as a lower reflection layer formed on the lower surface of the vehicle window to reflect infrared light; Wherein, the polymer material absorbs visible light and transmits near infrared light, wherein each of the upper reflection layer and the lower reflection layer is formed as a film containing titanium dioxide and silicon dioxide; wherein each of the upper reflection layer and the lower reflection layer is formed by laminating a plurality of silicon dioxide layers and titanium dioxide layers; Wherein, the upper reflection layer reflects infrared light with a wavelength of 1400nm to 1600nm; Wherein, the lower reflection layer reflects infrared light with a wavelength of 1100nm to 1400nm; Wherein, the thickness difference between the upper reflection layer and the lower reflection layer is less than 2 μm.

2. The LiDAR window integrated optical filter according to claim 1, in, Each of the upper reflection layer and the lower reflection layer is formed as a multi-layer film by vapor deposition.

3. The LiDAR window integrated optical filter according to claim 1, in, The thickness of the upper reflection layer is 4 μm to 7 μm.

4. The LiDAR window integrated optical filter according to claim 1, in, The upper reflective layer is deposited into a multilayer structure of 25 to 30 layers.

5. The LiDAR window integrated optical filter according to claim 1, in, The thickness of the low reflection layer is 4 μm to 7 μm.

6. The LiDAR window integrated optical filter according to claim 5, in, The lower reflection layer is deposited into a multilayer structure of 25 to 30 layers.

7. The LiDAR window integrated optical filter according to claim 1, in, The vehicle window comprises a transparent plastic material to which a visible light absorbing material is added and has a thickness of 2 mm to 4 mm.

8. The LiDAR window integrated optical filter according to claim 1, in, The transmittance of the vehicle window at a wavelength of 905 nm is greater than 90%.

9. The LiDAR window integrated optical filter according to claim 8, in, The transmittance of the vehicle window at a wavelength of 1550 nm is less than 1%.

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