Laser radar transmitting lens optical system

Abstract

The invention provides an optical system of a laser radar transmitting lens. The optical system comprises a first lens, a second lens, a diaphragm, a third lens, a fourth lens, a fifth lens, an optical filter, protective glass and an image surface which are arranged in a direction from an object side to an image side. According to the invention, by reasonably using the lenses with specific shapes and structures and limiting the focal power of each lens, the field angle of the optical system is increased to 150 degrees and the relative illumination is greater than 90%, the radar detection field of view is wider and clearer, the F-theta distortion is less than 1%, the CRA is less than 1 degree, the detection distance and precision are improved, and the detection cost is reduced. According to the utility model, more accurate distance measurement data and farther detection distance can be provided, TTL is 29 mm, the size is small, miniaturization can be realized, the camera can be arranged in a vehicle, the matching of 2G3P glass and plastic enables the whole optical system to optimize high and low temperature excursion compensation, it is ensured that the lens does not have virtual focus at high and low temperatures, the cost is more advantageous, and the cost performance is higher.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging technology, and in particular to a laser radar transmitting lens optical system. Background Art

[0002] In recent years, intelligent recognition technology has gained increasing attention. As a key component of intelligent detection technology, LiDAR (Lidar) has emerged. LiDAR, short for Laser Detection and Ranging System, is typically composed of a laser transmitter and a laser receiver. LiDAR uses a transmitting lens to send a detection signal toward a target. The receiving lens set in front of the LiDAR detector focuses the reflected light onto the detector. The signal reflected from the target is compared with the transmitted signal and, after appropriate processing, information such as the target's reflected energy, the amplitude, frequency, and phase of the reflected wave spectrum can be obtained. This information can then be used to determine parameters such as the target's distance, height, and speed, enabling detection, tracking, and identification.

[0003] However, current LiDAR transmitting lenses generally suffer from a limited field of view, resulting in a narrow field of view. Furthermore, these lenses often utilize a 4G2P structure, comprising four glass lenses. This not only increases manufacturing costs, driving up mass production costs, but also results in an excessively long optical system, occupying a large space and hindering installation within a vehicle. Summary of the Invention

[0004] The present invention proposes a laser radar transmitting lens optical system, which takes into account the characteristics of large field of view, high illumination, small distortion, low cost, small CRA and high and low temperature drift compensation capability.

[0005] The above technical objectives of the present invention are achieved through the following technical solutions: a laser radar transmitting lens optical system: Along the optical axis, from the object plane to the image plane, it includes: the first lens, the second lens, the aperture, the third lens, the fourth lens, the fifth lens, the filter, the protection glass and the image plane; The first lens is a meniscus lens with negative optical power; the second lens is an M-type lens with negative optical power; the third lens is a biconvex lens with positive optical power; the fourth lens is a concave-convex lens with positive optical power; and the fifth lens is a biconvex lens with positive optical power. The ratio of the focal lengths of the first to fifth lenses to the focal length of the lens satisfies the following relationship: 3.7 < |f1 / f| < 4.1, 3.0 < |f2 / f| < 3.5, 3.0 < |f3 / f| < 3.4, 13.3 < |f4 / f| < 14.2, 6.0 < |f5 / f| < 6.5, 2.0 < f4 / f5 < 2.4; where f1 represents the effective focal length of the first lens, f2 represents the effective focal length of the second lens, f3 represents the effective focal length of the third lens, f4 represents the effective focal length of the fourth lens, f5 represents the effective focal length of the fifth lens, and f represents the effective focal length of the optical system.

[0006] Further, the refractive indices of the third lens, the fourth lens, and the fifth lens are all greater than 1.4 and less than 1.65; the Abbe numbers of the second lens, the third lens, the fourth lens, and the fifth lens are all greater than 50 and less than 59.

[0007] Further, the maximum field angle FOV of the optical system: 150° ≤ FOV ≤ 155°.

[0008] Further, the relative illumination of the optical system at the maximum field angle: RI ≥ 90%.

[0009] Further, the chief ray angle of incidence CRA of the optical system: CRA < 1°. Further, the optical system satisfies the following conditional formula: 0.2 < (h / 2) / (f × tan(FOV / 2)) < 0.6.

[0010] Where: f represents the effective focal length of the optical system, FOV represents the maximum field angle of the optical system, and h represents the maximum full image height of the optical system.

[0011] Further, the surface of the first lens facing the object side is convex, and the surface facing the image side is concave; the surface of the second lens facing the object side is concave, and the surface facing the image side is concave; the surface of the third lens facing the object side is convex, and the surface facing the image side is convex; the surface of the fourth lens facing the object side is concave, and the surface facing the image side is convex; the surface of the fifth lens facing the object side is convex, and the surface facing the image side is convex.

[0012] Further, the total optical length TTL of the optical system and the maximum full image height h corresponding to the maximum field angle satisfy: 4.8 < TTL / h < 5.3.

[0013] Further, the maximum full image height h corresponding to the maximum field angle of the optical system and the aperture FNO of the optical system satisfy: 3.2 < h / FNO < 3.8.

[0014] In summary, the present invention has the following beneficial effects: by rationally using lenses of specific shapes and structures and limiting the optical focal length of each lens, the present invention increases the field of view of the optical system to 150 degrees and the relative illumination is greater than 90%. The radar detection field of view is wider and clearer, the F-theta distortion is less than 1%, and the CRA is less than 1 degree, thereby improving its detection distance and accuracy, and being able to provide more accurate ranging data and a longer detection distance. The TTL is 29mm, the volume is small, which is conducive to miniaturization and convenient placement in the car. At the same time, the combination of 2G3P glass and plastic optimizes the high and low temperature drift compensation of the entire optical system, ensuring that the lens is not out of focus at high and low temperatures, and the cost is more advantageous and the cost performance is higher, ensuring the reliability and cost-effectiveness of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic structural diagram of an optical system provided in an embodiment of the present invention; Figure 2 Provided for the embodiment of the present invention is an MTF analysis diagram of the optical system corresponding to incident light of 940nm infrared wavelength at 20°C; Figure 3 Provided for the embodiment of the present invention is a defocus curve diagram of the optical system corresponding to the incident light having an infrared wavelength of 940nm at 20°C; Figure 4 Provided for the embodiment of the present invention is a defocus curve diagram of the optical system corresponding to the incident light having an infrared wavelength of 940nm at 85°C; Figure 5 Provided for the embodiment of the present invention is a defocus curve diagram of the optical system corresponding to the incident light having an infrared wavelength of 940nm at -40°C; Figure 6 Provided for the embodiment of the present invention is a field curvature diagram of the optical system corresponding to incident light having an infrared wavelength of 940 nm; Figure 7 Provided for the embodiment of the present invention is an F-THETA distortion diagram of the optical system corresponding to incident light of infrared wavelength of 940nm; Figure 8 Provided for the embodiment of the present invention is an illumination diagram of the optical system corresponding to incident light having an infrared wavelength of 940 nm. DETAILED DESCRIPTION

[0016] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0017] In the description of the present invention, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0018] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0019] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0020] like Figure 1 As shown, the present invention provides a laser radar transmitting lens optical system, which includes, along the optical axis from the object plane to the image plane, a first lens E1, a second lens E2, an aperture STO, a third lens E3, a fourth lens E4, a fifth lens E5, a filter IR, a protective glass CG and an image plane IMA; the structure of the optical system is a 2G3P structure, the glass lenses are the first lens E1 and the third lens E3, and the plastic lenses are the second lens E2, the fourth lens E4 and the fifth lens E5, and the plastic lenses are aspherical lenses.

[0021] The first lens E1 is a meniscus lens with negative optical power; the second lens E2 is an M-type lens with negative optical power; the third lens E3 is a biconvex lens with positive optical power; the fourth lens E4 is a meniscus lens with positive optical power; and the fifth lens E5 is a biconvex lens with positive optical power. The ratio of the focal length of the first lens E1 to the fifth lens E5 to the focal length of the optical system satisfies the following relationship: 3.7 < |f1 / f| < 4.1, 3.0 < |f2 / f| < 3.5, 3.0 < |f3 / f| < 3.4, 13.3 < |f4 / f| < 14.2, 6.0 < |f5 / f| < 6.5; where f1 represents the effective focal length of the first lens E1, f2 represents the effective focal length of the second lens E2, f3 represents the effective focal length of the third lens E3, f4 represents the effective focal length of the fourth lens E4, f5 represents the effective focal length of the fifth lens E5, and f represents the effective focal length of the optical system.

[0022] It should be noted that for the effective focal length f of the optical lens, the focal length f1 of the first lens E1 and the focal length f2 of the second lens E2 satisfy: -4.1 < f1 / f < -3.7; -3.5 < f2 / f < -3.0. Meeting the above range can make the first lens E1 and the second lens E2 have appropriate negative optical power, which is beneficial for large-angle light to enter the optical lens, and then increases the field angle of the optical lens. For the effective focal length f of the optical lens and the focal length f4 of the fourth lens E4, they satisfy: 13.3 < f4 / f < 14.2; the focal length f4 of the fourth lens E4 and the focal length f5 of the fifth lens E5 satisfy: 2.0 < f4 / f5 < 2.4. Meeting the above range is beneficial for expanding the width of the light beam. After the light is refracted by the fourth lens E4 and the fifth lens E5, the width of the light beam entering the optical lens is larger, and then it can be fully transmitted to the high-pixel imaging surface, enabling the optical lens to obtain a wider field range. At the same time, it is also beneficial for the optical lens to achieve high-pixel and large-image-plane imaging.

[0023] As an improvement, the refractive indices of the third lens E3, the fourth lens E4, and the fifth lens E5 are all greater than 1.4 and less than 1.65; the Abbe numbers of the second lens E2, the third lens E3, the fourth lens E4, and the fifth lens E5 are all greater than 50 and less than 59. It should be noted that meeting the above range, by reasonably selecting optical materials and ensuring that the refractive indices of adjacent lens materials match each other, the light exit angle can be reduced, thereby reducing the CRA of the lens; it is beneficial for the chip to match the lens.

[0024] As an improvement, the maximum field angle FOV of the optical system: 150° ≤ FOV ≤ 155°.

[0025] As an improvement, the relative illumination RI of the optical system at the maximum field angle: RI ≥ 90%.

[0026] As an improvement, the chief ray angle of incidence CRA of the optical system: CRA < 1°. As an improvement, the effective focal length f of the optical system, the maximum field angle, and the maximum holographic height h corresponding to the maximum field angle satisfy: 0.2 < (h / 2) / (f×tan(FOV / 2)) < 0.6. Satisfying the above range can further reduce the F-THETA distortion of the optical system and improve the imaging picture accuracy.

[0027] As an improvement, the total optical length TTL of the optical lens and the maximum holographic height h corresponding to the maximum field angle satisfy: 4.8 < TTL / h < 5.3. Satisfying the above range can balance the relationship between the image height and the total optical length of the optical lens, reduce the lens volume, and is conducive to miniaturization.

[0028] As an improvement, the maximum holographic height h corresponding to the maximum field angle of the optical lens and the aperture FNO of the optical system satisfy: 3.2 < h / FNO < 3.8. Satisfying the above range can improve the edge brightness of the lens picture, enhance the relative illuminance of the entire optical system, and optimize the imaging quality.

[0029] Where: f represents the effective focal length of the optical system, FOV represents the maximum field angle of the optical system, and h represents the maximum holographic height of the optical system.

[0030] As an improvement, the object side S1 of the first lens E1 is a convex surface, and the image side S2 of the first lens E1 is a concave surface; the object side S3 of the second lens E2 is a concave surface, and the image side S4 of the second lens E2 is a concave surface; the object side S6 of the third lens E3 is a convex surface, and the image side S7 of the third lens E3 is a convex surface; the object side S8 of the fourth lens E4 is a concave surface, and the image side S9 of the fourth lens E4 is a convex surface; the object side S10 of the fifth lens E5 is a convex surface, and the image side S11 of the fifth lens E5 is a convex surface.

[0031] This specific embodiment is only an explanation of the present invention, and it is not a limitation of the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present invention, it is protected by the patent law.

[0032] Among them, the parameters of each lens in this embodiment are listed in Table 1 below, and the aspherical coefficients of the lenses are shown in Table 2 below.

[0033] Table 1 Physical parameters of each lens

[0034] Table 2 Aspherical coefficients of lenses

[0035]

[0036] The aspheric coefficients satisfy the following equation:

[0037] Among them, z is the aspheric surface sag, c is the aspheric surface paraxial curvature, y is the lens aperture, k is the cone coefficient, a4 is the 4th aspheric surface coefficient, a6 is the 6th aspheric surface coefficient, a8 is the 8th aspheric surface coefficient, and a10 is the 10th aspheric surface coefficient.

[0038] Specifically, the R value and thickness of each lens surface in this embodiment are shown in Table 1, and the aspheric surface parameters are shown in Table 2. The R value (radius of curvature), thickness (Thickness), refractive index (Index), Abbe coefficient (ABB), and lens focal length (EFL-E) of each lens surface in this embodiment are shown in Table 1, and the aspheric surface parameters are shown in Table 2. In Table 1, Surf represents the mirror surface number, and INFINITY represents infinity. In Table 2, R1 represents the curvature radius of the corresponding lens surface facing the object side, and R2 represents the curvature radius of the corresponding lens surface facing the image side. A positive curvature radius indicates that the mirror surface is curved toward the object side, and a negative curvature radius indicates that the mirror surface is curved toward the image side.

[0039] The optical system provided in Table 1 has an effective focal length of 2.13mm, a total TTL optical length of 29mm, a maximum full image height of 5.71mm, an F-theta distortion of less than 1%, a relative illumination of 90%, a maximum field of view of 150 degrees, and a CRA of less than 1 degree. In Table 1, mirror numbers 1 and 2 represent the two mirror surfaces of lens 1 along the direction of light incidence, mirror numbers 3 and 4 represent the two mirror surfaces of lens 2 along the direction of light incidence, mirror numbers 6 and 7 represent the two mirror surfaces of lens 3 along the direction of light incidence, mirror numbers 8 and 9 represent the two mirror surfaces of lens 4 along the direction of light incidence, and mirror numbers 10 and 11 represent the two mirror surfaces of lens 5 along the direction of light incidence. In an embodiment of the present invention, Figure 2 This is a modulation transfer function (MTF) curve for the infrared light band, representing the comprehensive resolution capability of the optical system. The horizontal axis represents the spatial frequency (in cycles / mm), and the vertical axis represents the value of the modulation transfer function (MTF). The MTF value is used to evaluate the imaging quality of the lens, ranging from 0 to 1. It is particularly pointed out that the optical transfer function is a relatively accurate, intuitive, and common way to evaluate the imaging quality of an optical system. The higher and smoother the curve is, the better the imaging quality of the system is and the stronger the ability to restore the real image is. Figure 2 It can be seen that the MTF of the infrared light band in the imaging area near the center is greater than 0.9, and the imaging quality is good. Figure 3 From the defocus curve, we can see that the MTF concentration of this lens is good, which makes focusing easy. Figure 3 The vertical axis is the MTF value, and the horizontal axis is the offset: mm. Figure 4 and Figure 5 It can be seen that the defocus curves at both high and low temperatures meet high resolution, the focus change of the defocus curve is small, and the thermal drift effect is stable; Figure 6 Represented as a field curvature diagram, Figure 6 It can be seen that the field curvature value is controlled between -40um and 40um. The smaller the field curvature value, the better the imaging quality of the lens. Figure 7 It is expressed as F-THETA distortion diagram. The smaller the F-THETA distortion, the smaller the compression of the image edge. Figure 8 It is expressed as a relative illumination diagram. The higher the relative illumination, the higher the overall brightness of the captured image. Figure 8 The vertical axis represents "relative illuminance" and the horizontal axis represents "field of view: angle".

Claims

1. A lidar transmitting lens optical system, characterized in that: Along the optical axis from the object plane to the image plane, it sequentially includes: a first lens, a second lens, a diaphragm, a third lens, a fourth lens, a fifth lens, a filter, a protective glass, and an image plane; The first lens is a meniscus lens with a negative optical power; the second lens is an M-shaped lens with a negative optical power; the third lens is a biconvex lens with a positive optical power; the fourth lens is a convex-concave lens with a positive optical power; the fifth lens is a biconvex lens with a positive optical power; Among them, the ratio of the focal lengths of the first lens to the fifth lens to the focal length of the lens satisfies the following set relationship: 3.7 < |f1 / f| < 4.1, 3.0 < |f2 / f| < 3.5, 3.0 < |f3 / f| < 3.4, 13.3 < |f4 / f| < 14.2, 6.0 < |f5 / f| < 6.5, 2.0 < f4 / f5 < 2.4; where f1 represents the effective focal length of the first lens, f2 represents the effective focal length of the second lens, f3 represents the effective focal length of the third lens, f4 represents the effective focal length of the fourth lens, f5 represents the effective focal length of the fifth lens, and f represents the effective focal length of the optical system.

2. The laser radar transmitting lens optical system according to claim 1, characterized in that: The refractive indices of the third lens, the fourth lens, and the fifth lens are all greater than 1.4 and less than 1.65; the Abbe numbers of the second lens, the third lens, the fourth lens, and the fifth lens are all greater than 50 and less than 59.

3. A laser radar transmitting lens optical system according to any one of claims 1 or 2, characterized in that: The maximum field of view angle FOV of the optical system: 150° ≤ FOV ≤ 155°.

4. A laser radar transmitting lens optical system according to any one of claims 1 or 2, characterized in that: The relative illumination of the optical system at the maximum field of view angle: RI ≥ 90%.

5. A laser radar transmitting lens optical system according to any one of claims 1 or 2, characterized in that: The chief ray angle of incidence CRA of the optical system: CRA < 1°.

6. A laser radar transmitting lens optical system according to any one of claims 1 or 2, characterized in that: The optical system satisfies the following conditional formula: 0.2 < (h / 2) / (f × tan(FOV / 2)) < 0.

6. Where: f represents the effective focal length of the optical system, FOV represents the maximum field of view angle of the optical system, and h represents the maximum full image height of the optical system.

7. A laser radar transmitting lens optical system according to any one of claims 1 or 2, characterized in that: The surface of the first lens facing the object side is convex, and the surface facing the image side is concave; the surface of the second lens facing the object side is concave, and the surface facing the image side is concave; the surface of the third lens facing the object side is convex, and the surface facing the image side is convex; the surface of the fourth lens facing the object side is concave, and the surface facing the image side is convex; the surface of the fifth lens facing the object side is convex, and the surface facing the image side is convex.

8. The laser radar transmitting lens optical system according to claim 1, characterized in that: The total optical length TTL of the optical system and the maximum full image height h corresponding to the maximum field of view angle satisfy: 4.8 < TTL / h < 5.

3.

9. The laser radar transmitting lens optical system according to claim 1, characterized in that: The maximum full image height h corresponding to the maximum field of view angle of the optical system and the aperture FNO of the optical system satisfy: 3.2 < h / FNO < 3.8.

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