Windshield correction optics for front-facing camera

Abstract

A windshield correction optical system includes a motor vehicle having a windshield. A camera is positioned within a passenger compartment of the motor vehicle, toward the windshield and to receive light rays through the windshield. A sensor is configured to receive the light rays. A correction element is configured to allow the light rays to pass through the correction element to the sensor. The correction element corrects aberrations of the light rays caused by passing through the windshield before the light rays reach the sensor.

Description

Technical Field

[0001] This disclosure relates to a windshield camera system for motor vehicles. Background Technology

[0002] Motor vehicle windshields typically house cameras positioned within the passenger compartment and associated observation systems. These systems receive light images through the windshield and monitor objects appearing within the camera's field of view (FOV). Windshields are usually angled to reduce air resistance and minimize impact damage from objects striking them. This angle introduces aberrations, degrading the resulting camera view image and potentially reducing the performance of the observation system's perception algorithms. FOV degradation is most pronounced in the tangential (vertical) direction, which coincides with the windshield's angle.

[0003] Therefore, although current motor vehicle windshield camera systems have achieved their intended purpose, there is a need for new and improved systems and methods for motor vehicle forward windshield cameras. Summary of the Invention

[0004] According to several aspects, a windshield correction optical system includes a motor vehicle having a windshield. A camera positioned within the passenger compartment of the motor vehicle faces the windshield and is positioned to receive light passing through the windshield. A sensor is configured to receive light passing through the windshield. A correction element is positioned to allow light to pass through the correction element to the sensor. The correction element is configured to correct aberrations in the light caused by passing through the windshield before the light reaches the sensor.

[0005] In another aspect of this disclosure, the windshield is oriented at a tilt angle; and the correction element is oriented at a correction angle substantially opposite to the tilt angle.

[0006] In another aspect of this disclosure, the correction element is positioned within the camera.

[0007] In another aspect of this disclosure, the sensor and calibration element are fixed inside the camera, with the calibration element located between the windshield and the sensor.

[0008] In another aspect of this disclosure, the camera includes at least a first lens group and a second lens group, wherein the first lens group, the second lens group, and the sensor are arranged in sequence away from the windshield.

[0009] In another aspect of this disclosure, the first lens group and the second lens group are positioned between the correction element and the sensor.

[0010] In another aspect of this disclosure, the correction element is located between the first lens group and the second lens group, and also includes a light intersection point caused by the aperture stop located between the correction element and the second lens group.

[0011] In another aspect of this disclosure, the correction element is located between the first lens group and the second lens group, and also includes a ray intersection point caused by the aperture stop located between the first lens group and the correction element.

[0012] In another aspect of this disclosure, the correction element is located between the second lens group and the sensor, and also includes a light intersection point caused by the aperture stop located between the first lens group and the second lens group.

[0013] In another aspect of this disclosure, the PK1 glass material is defined as an exemplary material for the correction element; however, the correction element material may be other types of glass or polymer materials.

[0014] According to several aspects, a windshield correction optical system includes a motor vehicle having a windshield and an occupant compartment oriented at an angle. A camera is positioned within the occupant compartment, facing the windshield, and receives light passing through the windshield and within the camera's field of view (FOV). A sensor within the camera receives the light. A correction element positioned in front of the sensor within the camera allows light to pass through the correction element to the sensor. The correction element corrects for aberrations in the light passing through the windshield caused by the windshield's angle before the light reaches the sensor.

[0015] In another aspect of this disclosure, the camera includes at least a first lens group and a second lens group, wherein the first lens group, the second lens group, and the sensor are arranged in sequence away from the windshield.

[0016] In another aspect of this disclosure, the aberrations of light caused by the radius of curvature of the windshield in the vertical direction are contained in the geometry of the correction element, such that the correction element defines annular or cylindrical optics.

[0017] In another aspect of this disclosure, a first antireflective coating is applied to a first side of the correction element, and a second antireflective coating is applied to the opposite second side of the correction element.

[0018] In another aspect of this disclosure, the camera includes an imaging system, and the imaging system is adapted to generate, transmit, and receive lidar signals.

[0019] In another aspect of this disclosure, the correction element is substantially flat, having parallel opposing surfaces.

[0020] In another aspect of this disclosure, the PK1 glass material is defined as an exemplary material for the correction element; however, the correction element material may be other types of glass or polymer materials.

[0021] According to several aspects, a method for correcting aberrations in light passing through a windshield includes: tilting the windshield of a motor vehicle at an angle; mounting a camera inside the passenger compartment of the motor vehicle, facing the windshield and receiving light passing through the windshield; positioning a sensor within the camera to receive the light; and positioning a correction element in front of the sensor within the camera to allow light to pass through the correction element to reach the sensor, and correcting aberrations in light passing through the windshield caused by the tilt angle of the windshield before the light reaches the sensor.

[0022] In another aspect of this disclosure, the method further includes oriented a correction element at a correction angle substantially opposite to the tilt angle.

[0023] In another aspect of this disclosure, the method further includes arranging at least a first lens group, a second lens group, and a sensor sequentially within the camera away from the windshield.

[0024] Other areas of application will become apparent from the description provided herein. It should be understood that the descriptions and specific examples are intended for illustrative purposes only and are not intended to limit the scope of this disclosure. Attached Figure Description

[0025] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of this disclosure in any way.

[0026] Figure 1 This is a schematic diagram of a windshield correction optical system according to an exemplary aspect;

[0027] Figure 2 is a graph showing the modulus of a known windshield design compared to its spatial frequency (cycles per millimeter), which introduces aberrations into the camera's field of view (FOV) across multiple ranges.

[0028] Figure 3 The curve in Figure 2 is a modified version of the curve after incorporating the correction element of this disclosure;

[0029] Figure 4 Yes Figure 1 Modify the diagram to incorporate the aperture stop;

[0030] Figure 5 It is a presentation Figure 1 A schematic diagram of another aspect of the system;

[0031] Figure 6 It is a presentation Figure 1 A schematic diagram of another aspect of the system; and

[0032] Figure 7 It is a presentation Figure 1 A diagram illustrating another aspect of the system. Detailed Implementation

[0033] The following description is exemplary in nature and is not intended to limit this disclosure, application, or use.

[0034] refer to Figure 1 A windshield correction optics system 10 is incorporated into the optics system 12 of a camera 14, which is positioned within the passenger compartment 16 of the vehicle 18. The camera 14 receives light and image data through the tilted windshield 20. The tilt angle alpha (α) of the windshield 20 creates distortion or aberration 22 in the synthesized image, which may degrade the performance of the perception algorithms applied in the imaging system 24 of the camera 14. The imaging system 24 comprises multiple imaging lenses, which, for simplicity, are described herein as including a first lens group 26 and a second lens group 28. Each of the lens groups may include one, two, or more lenses. Typically, imaging lens designs use one, two, three, or more lenses. In practice, lenses are typically subdivided into sets called “groups,” where a group may contain as few as one lens or any other magnification. Subdividing the lens design into groups facilitates the association of lens function, the position of elements relative to the “aperture” described below, and other design-related features of the overall lens design. Imaging system 24 receives and interprets light and image data via sensor 30. To correct aberration 22 caused by tilt angle α, correction element 32 is positioned within the optical path 34 of optical system 12 between windshield 20 and sensor 30 to eliminate or reduce the magnitude of aberration 22 and restore resolution to the nominal performance of imaging system 24.

[0035] Note that the windshield correction optics system 10 is applicable to camera lenses designed without taking into account the geometry and material of the vehicle's windshield. For example, when using a known or "conventional" camera lens, where the field of view is degraded due to aberration 22 caused by the windshield geometry, additional modifications of the correction element 32 of this disclosure should be used. This differs from camera lenses specifically designed for use behind windshields, which are designed to take into account the windshield geometry and any aberrations caused by the windshield. Such camera lenses do not require correction element 32.

[0036] According to several aspects, the correction element 32 may define an inclined polymeric material (such as a plastic sheet or glass plate) inserted between the windshield 20 and the first optical surface 36 of the imaging system 24. The correction element 32 is oriented with a correction angle beta (β), which, according to several aspects, is substantially opposite to the tilt angle α of the windshield 20. For example, if the windshield 20 is tilted (sloped) by 60 degrees, the correction element 32 should be tilted to -60 degrees. Note that this orientation angle of the correction element 32 is oversimplified, as the exemplary correction element angle β works for cases with a narrow field of view (FOV).

[0037] According to several aspects, the corrective element 32 is PK1 glass; however, the selected material is not limiting, as the corrective element 32 can also be a different type of glass or polymeric material, such as polycarbonate plastic. The refractive index of the corrective element 32 is selected to be similar to that of the windshield 20 and can be modified to suit the material and location of the corrective element 32, as well as its geometry. According to several aspects, the corrective element 32 is substantially flat, having parallel opposing surfaces; however, according to other aspects, one or both of the opposing surfaces of the corrective element 32 can be curved.

[0038] In some vehicle designs, the field of view (FOV) of camera 14 can be significant, for example, 28 degrees or greater in the horizontal or sagittal direction 38. The focal ratio (F#) of the imaging lenses, including the first lens group 26 and the second lens group 28, can be considered to be 1.8 or smaller (large aperture). Therefore, a simple correction element angle β of correction element 32, which is oriented substantially opposite to the tilt angle α of windshield 20, may not be sufficient for all applications. Therefore, for a given tilt angle α of windshield 20 and specific parameters of camera 14, standard optical design techniques can be used to optimize the correction element angle β.

[0039] The windshield 20 is typically made of multiple layers of material, including glass and plastic. The refractive index of the correction element 32 is approximately matched to the total refractive index of the materials of the windshield 20. Standard optical design techniques can be used to determine the optimal glass or plastic material for the correction element 32.

[0040] The deterioration of the field of view (FOV) is most pronounced in the tangential (vertical) direction 40, which coincides with the windshield tilt angle α. Therefore, additional parameters for aberration correction include the radius of curvature 42 of the windshield 20 in the vertical direction 40, resulting in the correction element 32 being either a ring-shaped or cylindrical optics. While the correction element 32 includes a tilt angle, improved correction can be achieved by combining the tilt angle with the radius of curvature.

[0041] Refer to Figure 2 and again Figure 1For a windshield with a known design that introduces aberrations into the field of view (FOV), graph 44 presents the modulus 46 relative to the spatial frequency, in cycles per millimeter. The first curve 50 presents the optimal modulation transfer function (MTF) in the tangential direction. The second curve 52 shows significant performance degradation and deviates from the first curve 50 in the sagittal direction. The third curve 54 deviates from the first curve 50 in the tangential direction and therefore shows a deviation in the MTF. The fourth curve 56 deviates from the third curve 54 in the sagittal direction and also deviates relative to the first curve 50. The fifth curve 58 shows a significant deviation from the first curve 50 in the tangential direction, and the sixth curve 60 deviates from the fifth curve 58 in the sagittal direction and therefore shows a deviation in the MTF.

[0042] refer to Figure 3 And refer to again Figure 1 As shown in Figure 2, curve 62 presents curve 64, which has virtually no gaps between the sagittal and tangential curves across the FOV, and therefore shows virtually no MTF degradation. Curve 62 presents data for the application of correction elements, such as the correction element 32 of this disclosure positioned between the windshield 20 and the sensor 30 of the camera 14. Curve 64 presents a well-corrected lens with good, consistent performance across the FOV.

[0043] refer to Figure 4 And refer to again Figure 1 According to several aspects, the windshield correction optics system 10 provides a standard two-lens assembly for the imaging system 24, having a first lens group 26 and a second lens group 28 mounted behind the windshield 20, with a correction element 32 positioned in front of the two lens groups. A single principal ray 66 passing through the correction element 32 is directed into the first lens group 26. The aperture stop used here is generated by the opening of the lens, which physically restricts the solid angle of light rays passing through the system from an object point on the axis, to produce in space the point where the principal rays in the camera's field of view typically intersect. According to several aspects, the aperture stop of the windshield correction optics system 10 causes an intersection point 68 of the principal rays in the field of view and is located in front of the first lens group 26.

[0044] refer to Figure 5 And refer to again Figure 4 According to several aspects, the windshield correction optics system 70 is modified from the windshield correction optics system 10 to position the correction element 32 between the first lens group 26 and the second lens group 28. According to several aspects, an aperture stop generates an intersection 72 for the windshield correction optics system 70, which is located between the correction element 32 and the second lens group 28.

[0045] refer to Figure 6 And refer to again Figure 4 and Figure 5 According to several aspects, the windshield correction optics system 74 is modified from the windshield correction optics system 70 to position the aperture stop and create an intersection point 76 between the first lens group 26 and the correction element 32. Similar to the windshield correction optics system 70, the correction element 32 of the windshield correction optics system 74 is positioned between the first lens group 26 and the second lens group 28.

[0046] refer to Figure 7 And refer to again Figures 4 to 6 According to several aspects, the windshield correction optical system 78 is modified from windshield correction optical systems 10, 70, and 74 as follows. In this aspect, the correction element 32 is positioned behind both the first lens group 26 and the second lens group 28, and in front of the sensor 30, with both the first lens group 26 and the second lens group 28 positioned behind the windshield 20. According to several aspects, the aperture stop of the windshield correction optical system 78 is formed at the intersection point 80 between the first lens group 26 and the second lens group 28.

[0047] Continue to refer to Figure 7 And refer to again Figures 1 to 6 The first anti-reflective coating 82 can be applied to the first surface 84 of the correction element 32, and the second anti-reflective coating 86 can be applied to the opposite second surface 88 of the correction element 32.

[0048] The correction element 32 disclosed herein can be added to a standard imaging lens design to correct aberrations caused by the windshield tilt angle α. The correction element 32 is located between the windshield 20 and the sensor 30, and can be mounted between the windshield 20 and the lens group, between lens groups, or between the lens group and the sensor 30. Instead of receiving light representing the FOV of the camera 14, the imaging system 24 can be modified, according to several aspects, to generate, transmit, and receive optical detection and ranging (LIDAR) signals. LiDAR provides a method for determining a variable range by aiming a laser at an object and measuring the time it takes for the reflected light to return to the receiver or sensor. The correction element 32 can be modified accordingly.

[0049] The correction element 32 of this disclosure can be positioned before or between lens groups; before or after the intersection of aperture stops. Provided there is sufficient mechanical space to allow for such a position, the correction element 32 can also be positioned after the last lens element of a second lens group 28 and before the sensor 30. The refractive index of the correction element material can be selected from a variety of standard glasses. For example, glass such as PK1 (Nd = 1.5038Vd = 66.922) can be used for optimization; however, the correction element 32 can also be provided by other glass types or polymeric materials. For the first iterative analysis, the glass radius can be taken as infinite, and the correction angle or tilt angle β of the correction element 32 can be substantially opposite to the tilt angle α of the windshield 20. Depending on several aspects, the tilt angle α of a typical motor vehicle windshield can range from about 50 degrees to 70 degrees, and the correction element 32 is designed to correct aberrations over the entire angular range; however, the correction element 32 can be designed to function substantially for any windshield tilt angle. Although the windshield 20 is described in some aspects herein, the windshield correction optics system disclosed herein can be applied to any window of a motor vehicle 18.

[0050] The windshield correction optics system disclosed herein offers several advantages. These include providing windshield optical correction elements that avoid the use of complex design components, such as freeform lenses, and their subsequent design and manufacturing costs. The correction elements disclosed herein can be applied to a variety of windshield designs with multiple tilt angles, simplifying implementation in various vehicle programs in production.

[0051] The description in this disclosure is exemplary in nature only, and variations thereof without departing from the spirit and scope of this disclosure are intended to fall within its scope. Such variations should not be considered as departing from the spirit and scope of this disclosure.

Claims

1. A windshield correction optical system, comprising: A motor vehicle having a windshield oriented at an angle; A camera, positioned inside the passenger compartment of the motor vehicle, facing the windshield, and configured to receive light passing through the windshield; A sensor configured to receive light passing through the windshield; A correction element, positioned to allow light to pass through it to the sensor, the correction element being configured to correct aberrations of the light caused by the tilt angle of the windshield as it passes through it before reaching the sensor, the correction element being positioned within the camera, the camera being located in the line of sight of the windshield such that the light propagates directly from the windshield to the camera; and The correction element is oriented at a correction angle opposite to the tilt angle, the absolute value of the tilt angle is equal to the absolute value of the correction angle, the tilt angle has a positive value, the correction angle has a negative value, the camera extends along the camera axis, the windshield extends along the windshield axis, the tilt angle is defined as the distance from the camera axis to the windshield axis, the correction element extends along its axis, the correction angle is defined as the distance from the camera axis to the element axis, the correction element has a first refractive index, the windshield has a second refractive index, and the first refractive index is equal to the absolute value of the tilt angle. The second refractive index is specified, the correction element has a first surface and a second surface opposite to the first surface, the first surface is planar, the second surface is planar, and the first surface is parallel to the second surface; the windshield correction optical system further includes a first anti-reflective coating applied to the first surface of the correction element, and the windshield correction optical system further includes a second anti-reflective coating applied to the second surface of the correction element; the first refractive index is 1.5038, the correction element has an Abbe number of 66.922, the tilt angle is 60 degrees, and the correction angle is -60 degrees.

2. The windshield correction optical system according to claim 1, wherein the sensor and the correction element are fixed inside the camera, and the correction element is located between the windshield and the sensor.

3. The windshield correction optical system according to claim 2, wherein the camera includes at least a first lens group and a second lens group, and the first lens group, the second lens group and the sensor are arranged in sequence away from the windshield.

4. The windshield correction optical system according to claim 3, wherein the first lens group and the second lens group are positioned between the correction element and the sensor.

5. The windshield correction optical system of claim 3, wherein the correction element is located between the first lens group and the second lens group, and further includes a light intersection point caused by an aperture stop located between the correction element and the second lens group.

6. The windshield correction optical system of claim 3, wherein the correction element is located between the first lens group and the second lens group, and further includes a ray intersection point caused by an aperture stop located between the first lens group and the correction element.

7. The windshield correction optical system of claim 3, wherein the correction element is located between the second lens group and the sensor, and further includes a light intersection point caused by an aperture stop located between the first lens group and the second lens group.

8. The windshield correction optical system according to claim 1, wherein the correction element is formed of PK1 glass material.

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