Transmitter and receiver integrated coaxial laser radar optical system

Abstract

The present invention proposes a coaxial laser radar optical system with transmission and reception, wherein a transmitting end S and a receiving end D share an optical system; the starting end of the optical system is an external light signal input end and a detection light signal transmitting end of the laser radar, and the end is a rectangular polarization beam splitter prism P; the polarization beam splitter prism P is formed by connecting and fixing a 1 / 4 input wave plate P1, a right-angle prism P2, and a right-angle prism P3 which are sequentially arranged in the input direction of the external light signal; the inclined surface S2 of the right-angle prism P2 and the inclined surface S3 of the right-angle prism P3 are connected, and the connecting position is covered with a polarization beam splitter film; the installation positions of the transmitting end S and the receiving end D are interchangeable, and the installation position of the device is adjacent to the surface S1 of the polarization beam splitter prism P which is perpendicular to the wave plate P1 and the surface S8 which is parallel to the wave plate P1; the transmitting polarization beam splitter prism and the receiving polarization beam splitter prism of the present invention are the same and share the beam splitter prism, and the collimating transmitting mirror group and the focusing receiving mirror group are the same and share the mirror group, which is suitable for applications such as automatic driving of automobiles and distance detection.

Description

Technical Field

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

[0002] With the development of automobile autonomous driving, the wide application of laser radar optical systems has also led to an increasing demand. Among them, mechanical laser radar is one of the most widely used methods for autonomous driving. Mechanical laser radar uses two sets of mirrors. One set of mirrors is used for collimated emission of light sources. Multiple laser light source transmitters are arranged vertically at different heights of the focal plane of the collimated emission mirror group at a predetermined angle, and the vertical field of view angle is preset; the other set of mirrors is used for multiple photoelectric detectors to receive signals. The photoelectric detectors are arranged at different heights of the focal plane of the focusing receiving mirror group at predetermined positions. The array-type light source transmitters and array-type photoelectric detectors realize multi-channel signal detection and construct a 3D scene. Since the light source emission system and the detector receiving system are not completely coaxial, there is a certain blind spot when measuring distance. Many manufacturers choose to cut off a certain size of the two sets of mirrors to reduce the blind spot. However, such a solution still belongs to the paraxial system and cannot completely eliminate the blind spot, and it also increases the cost. Summary of the invention

[0003] The present invention proposes a coaxial laser radar optical system with transmission and reception, in which the transmitting polarization beam splitter prism and the receiving polarization beam splitter prism are the same and share the beam splitter prism, and the collimating transmitting mirror group and the focusing receiving mirror group are the same and share the mirror group. The system is suitable for applications such as automatic driving of automobiles and distance detection.

[0004] The present invention adopts the following technical solutions.

[0005] A transmitting and receiving integrated coaxial laser radar optical system, wherein the transmitting end S of the laser light source of the laser radar and the receiving end D of the photodetector share an optical system; the starting end of the optical system is the external light signal input end and the detection light signal transmitting end of the laser radar, and the end is a rectangular polarization beam splitter prism P; the polarization beam splitter prism P is formed by connecting and fixing a 1 / 4 input wave plate P1, a right-angle prism P2, and a right-angle prism P3 which are sequentially arranged in the input direction of the external light signal; the inclined surface S2 of the right-angle prism P2 and the inclined surface S3 of the right-angle prism P3 are connected, and the connecting position is covered with a polarization beam splitter film;

[0006] The transmitting end S and the receiving end D are installed at the device installation position of the laser radar. The installation positions of the transmitting end S and the receiving end D are interchangeable. The device installation position is adjacent to the surface S1 of the polarization splitter prism P perpendicular to the wave plate P1 and the surface S8 parallel to the wave plate P1.

[0007] The optical system includes a plurality of mirror devices, each of which is located on the same straight line. A mirror group is provided between the starting end of the optical system and the polarization beam splitter prism P; the mirror group is used for collimating the emission of the detection light signal and for focusing the detection light signal reflected by the external environment.

[0008] The lens group is provided with a meniscus positive lens L1, a double concave negative lens L2, a plano-convex cylindrical positive lens L3 and a double convex positive lens L4 in sequence in the input direction of the external light signal.

[0009] The signal receiving end D of the photoelectric detector is located at the focal plane D1 of the lens group; the 1 / 4 input wave plate P1, the right-angle prism P2, and the right-angle prism P3 are connected and fixed by gluing.

[0010] The central air gap between the meniscus positive lens L1 and the biconcave negative lens L2 is 4.027 mm; the central air gap between the biconcave negative lens L2 and the plano-convex cylindrical positive lens L3 is 6.548 mm; the central air gap between the plano-convex cylindrical positive lens L3 and the biconvex positive lens L4 is 0.949 mm; the central air gap between the biconvex positive lens L4 and the 1 / 4 input wave plate P3 is greater than 0.1 mm and less than 11 mm.

[0011] The focal length of the meniscus positive lens L1 is f1; the focal length of the double concave negative lens L2 is f2; the focal length of the plano-convex cylindrical positive lens L3 is f3; the focal length of the double convex positive lens L4 is f4; the following relationship is satisfied: <f1 / f2<-1; 0.15<f1 / f3<0.25;0.35<f1 / f4<0.8。

[0012] The refractive index of the optical glass material of the meniscus positive lens L1 is n1 and the Abbe number is v1, the refractive index of the optical glass material of the biconcave negative lens L2 is n2 and the Abbe number is v2, the refractive index of the optical glass material of the plano-convex cylindrical mirror is n3 and the Abbe number is v3, and the refractive index of the optical glass material of the biconvex positive lens is n4 and v4, which satisfy the following relationship: 1.8 <n1<2.1, 15<v1<35;1.5<n2<1.7, 50<v2<65;1.4<n3<1.55, 60<v3<80;1.4<n4<1.55, 60<v4<80。

[0013] The thickness of the 1 / 4 input wave plate is dp1=0.015~0.06mm, satisfying the following relationship: dp1=λ / 4(nO-ne), wherein n0 is the principal refractive index of the wave plate for o light with a wavelength of λ in vacuum, and ne is the principal refractive index of the wave plate for e light with a wavelength of λ in vacuum; the polarization splitter prism is composed of two isosceles right-angle prisms of the same size glued together, and the oblique surfaces of the isosceles right-angle prisms are coated with a polarization splitter film.

[0014] The laser radar uses the same set of lenses for light source emission and signal reception, and the lenses in the set are coaxially arranged; when the transmitting end S is adjacent to the surface S1 of the polarization beam splitter prism P, its light source signal is emitted from the light source signal surface of the transmitting end S, and then incident on the surface S1 of the polarization beam splitter prism, and the light signal is divided into P light and S light by the inclined surfaces S2 and S3 of the polarization beam splitter prism, and the P light is emitted from the S4 surface after passing through the inclined surface, and the S light is reflected by the inclined surface and passes through the 1 / 4 input wave plate P1 to form circularly polarized light, and the detection light signal is output through the lens group and the beginning of the optical system;

[0015] After the detection light signal reflected by the object surface O of the external environment enters the beginning of the optical system, it is incident on the S7 surface of the 1 / 4 input wave plate P1 through the lens group, converted into P light by the 1 / 4 input wave plate P1, and then transmitted by the right-angle prism P2 and the right-angle prism P3 and received by the signal receiving end D;

[0016] When the transmitting end S is adjacent to the surface S8 of the right-angle prism P2, the installation position of the signal receiving end D is replaced to the surface S1 of the right-angle prism P2. At this time, the object surface reflected detection light signal received by the signal receiving end D is S light.

[0017] The polarization beam splitter prism P may be replaced by an optical filter or a beam splitter prism with a preset ratio of reflectivity and transmittance.

[0018] The advantages of the present invention are:

[0019] 1. The light source emission and signal reception use the same set of lenses, and the lenses in the set are coaxially arranged to eliminate the blind spots caused by the rangefinder system;

[0020] 2. Simple structure and compact size. The paraxial optical system consisting of a transmitting optical system and a receiving optical system is transformed into a coaxial optical system integrating transmitting and receiving. The process of trimming the optical lens group to reduce the blind area is eliminated, which effectively reduces the cost.

[0021] 3. Combine the characteristics of polarization beam splitter and 1 / 4 entry glass to improve the utilization of optical signals in optical systems.

[0022] In the present invention, a polarization beam splitter prism is used to merge the transmitting light source and the receiving signal into a coaxial optical path, eliminating blind spots while reducing costs. A polarization beam splitter prism is used to convert non-polarized light into linearly polarized light, reflecting more than 95% of the S light and transmitting more than 95% of the P light; the linearly polarized light and the circularly polarized light are converted into each other through a 1 / 4 input wave plate, thereby reducing energy loss.

[0023] In addition, since the installation positions of the transmitting end S and the receiving end D are interchangeable in the present invention, the required performance can be achieved or the cost can be reduced by reasonably setting the transmitting end S and the receiving end D according to the different indicators of the optical device for S light and P light, as well as the different performance requirements of the laser radar. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0025] Attached Figure 1 is a schematic diagram of an optical system of the present invention;

[0026] Attached Figure 2 Schematic diagram of light propagation when the polarization beam splitter prism P is working (the emitting end S is adjacent to the surface S1 of the polarization beam splitter prism P);

[0027] Attached Figure 3 1 is a schematic diagram of the labeled surfaces of the polarization beam splitter prism P;

[0028] Attached Figure 4 It is a schematic diagram of the distortion of the laser radar optical system;

[0029] Attached Figure 5 It is a schematic diagram of the diffuse spot diameter of the laser radar optical system;

[0030] Attached Figure 6 It is a schematic diagram of the index data of each lens coaxially arranged in the lens group. DETAILED DESCRIPTION

[0031] As shown in the figure, a transmitting and receiving coaxial laser radar optical system is provided, wherein the transmitting end S of the laser light source of the laser radar and the receiving end D of the photodetector share an optical system; the starting end of the optical system is the external light signal input end and the detection light signal transmitting end of the laser radar, and the end is a rectangular polarization beam splitter prism P; the polarization beam splitter prism P is formed by connecting and fixing a 1 / 4 input wave plate P1, a right-angle prism P2, and a right-angle prism P3 which are sequentially arranged in the input direction of the external light signal; the inclined surface S2 of the right-angle prism P2 and the inclined surface S3 of the right-angle prism P3 are connected, and the connecting position is covered with a polarization beam splitter film;

[0032] The transmitting end S and the receiving end D are installed at the device installation position of the laser radar. The installation positions of the transmitting end S and the receiving end D are interchangeable. The device installation position is adjacent to the surface S1 of the polarization splitter prism P perpendicular to the wave plate P1 and the surface S8 parallel to the wave plate P1.

[0033] The optical system includes a plurality of mirror devices, each of which is located on the same straight line. A mirror group is provided between the starting end of the optical system and the polarization beam splitter prism P; the mirror group is used for collimating the emission of the detection light signal and for focusing the detection light signal reflected by the external environment.

[0034] The lens group is provided with a meniscus positive lens L1, a double concave negative lens L2, a plano-convex cylindrical positive lens L3 and a double convex positive lens L4 in sequence in the input direction of the external light signal.

[0035] The signal receiving end D of the photoelectric detector is located at the focal plane D1 of the lens group; the 1 / 4 input wave plate P1, the right-angle prism P2, and the right-angle prism P3 are connected and fixed by gluing.

[0036] The central air gap between the meniscus positive lens L1 and the biconcave negative lens L2 is 4.027 mm; the central air gap between the biconcave negative lens L2 and the plano-convex cylindrical positive lens L3 is 6.548 mm; the central air gap between the plano-convex cylindrical positive lens L3 and the biconvex positive lens L4 is 0.949 mm; the central air gap between the biconvex positive lens L4 and the 1 / 4 input wave plate P3 is greater than 0.1 mm and less than 11 mm.

[0037] The focal length of the meniscus positive lens L1 is f1; the focal length of the double concave negative lens L2 is f2; the focal length of the plano-convex cylindrical positive lens L3 is f3; the focal length of the double convex positive lens L4 is f4; the following relationship is satisfied: <f1 / f2<-1; 0.15<f1 / f3<0.25;0.35<f1 / f4<0.8。

[0038] The refractive index of the optical glass material of the meniscus positive lens L1 is n1 and the Abbe number is v1, the refractive index of the optical glass material of the biconcave negative lens L2 is n2 and the Abbe number is v2, the refractive index of the optical glass material of the plano-convex cylindrical mirror is n3 and the Abbe number is v3, and the refractive index of the optical glass material of the biconvex positive lens is n4 and v4, which satisfy the following relationship: 1.8 <n1<2.1, 15<v1<35;1.5<n2<1.7, 50<v2<65;1.4<n3<1.55, 60<v3<80;1.4<n4<1.55, 60<v4<80。

[0039] The thickness of the 1 / 4 input wave plate is dp1=0.015~0.06mm, satisfying the following relationship: dp1=λ / 4(nO-ne), wherein n0 is the principal refractive index of the wave plate for o light with a wavelength of λ in vacuum, and ne is the principal refractive index of the wave plate for e light with a wavelength of λ in vacuum; the polarization splitter prism is composed of two isosceles right-angle prisms of the same size glued together, and the oblique surfaces of the isosceles right-angle prisms are coated with a polarization splitter film.

[0040] The laser radar uses the same set of lenses for light source emission and signal reception, and the lenses in the set are coaxially arranged; when the transmitting end S is adjacent to the surface S1 of the polarization beam splitter prism P, its light source signal is emitted from the light source signal surface of the transmitting end S, and then incident on the surface S1 of the polarization beam splitter prism, and the light signal is divided into P light and S light by the inclined surfaces S2 and S3 of the polarization beam splitter prism, and the P light is emitted from the S4 surface after passing through the inclined surface, and the S light is reflected by the inclined surface and passes through the 1 / 4 input wave plate P1 to form circularly polarized light, and the detection light signal is output through the lens group and the beginning of the optical system;

[0041] After the detection light signal reflected by the object surface O of the external environment enters the beginning of the optical system, it is incident on the S7 surface of the 1 / 4 input wave plate P1 through the lens group, converted into P light by the 1 / 4 input wave plate P1, and then transmitted by the right-angle prism P2 and the right-angle prism P3 and received by the signal receiving end D;

[0042] When the transmitting end S is adjacent to the surface S8 of the right-angle prism P2, the installation position of the signal receiving end D is replaced to the surface S1 of the right-angle prism P2. At this time, the object surface reflected detection light signal received by the signal receiving end D is S light.

[0043] The polarization beam splitter prism P may be replaced by an optical filter or a beam splitter prism with a preset ratio of reflectivity and transmittance.

[0044] Example:

[0045] In this example, the specific performance parameters of this lidar optical system are:

[0046] (1) Focal length: EFFL = 58 mm

[0047] (2) Entrance pupil diameter ≥ 29

[0048] (3) Field of view: 2w = 31°

[0049] (4) The focal plane diameter is greater than Ф32mm

[0050] (5) Optical distortion < 0.8%

[0051] (6) The receiving end diffuse spot diameter is less than 200um

[0052] (7) Working spectrum: 905nm

[0053] (8) Total optical length TTL ≤ 80 mm

[0054] The laser radar optical system consists of a laser light source emitting surface S, a polarization beam splitter prism P, an optical lens group L, and a photoelectric detector receiving D. The laser light source is fixed on the focal plane S1 of the collimating emitting lens group at a specific position; the polarization beam splitter prism P is made of two high-precision right-angle prism bevels S2 and S7, respectively P2 and P3, with polarization beam splitting film coated on the bevel, and the 1 / 4 input wave plate P1 is glued on the polarization beam splitter prism S3 surface; the collimating emitting lens group and the focusing receiving lens group are composed of 4 pieces of optical glass, which are composed of a meniscus lens positive lens L1, a double concave negative lens L2, a plano-convex cylindrical positive lens L3, and a double convex positive lens L4 from the object plane O to the polarization beam splitter prism P; the photoelectric detector is fixed on the focal plane D1 through the focusing receiving lens group at a specific position.

[0055] After the light source signal is emitted from the light source signal surface, it is incident on the S1 surface of the polarization beam splitter prism. The polarization beam splitter prism bevel surface S2 and S3 divide the light signal into P light and S light. The P light passes through the bevel and then emits from the S4 surface. The S light is reflected from the bevel and then passes through the S5 and S6 surfaces of the 1 / 4 input wave plate and the bonding surface of the polarization beam splitter prism. The circularly polarized light is emitted from the S7 surface. Then it is incident on the lens group (which functions as a collimating lens group at this time). The light signal reflected from the object surface is incident on the S7 surface by the lens group (which functions as a focusing receiving lens group at this time), and is converted into P light through the S6 and S5 surfaces, and then passes through the S2 and S3 surfaces, and is emitted from the S8 surface to be received by the detector.

Claims

1. Transmitter-receiver coaxial laser radar optical system, characterized by: The transmitting end S of the laser light source of the laser radar and the receiving end D of the photodetector share an optical system; the starting end of the optical system is the external light signal input end and the detection light signal transmitting end of the laser radar, and the end is a rectangular polarization beam splitter prism P; the polarization beam splitter prism P is formed by connecting and fixing a 1 / 4λ wave plate P1, a right-angle prism P2, and a right-angle prism P3 which are sequentially arranged in the input direction of the external light signal; the inclined surface S2 of the right-angle prism P2 and the inclined surface S3 of the right-angle prism P3 are connected, and the connection position is covered with a polarization beam splitter film; The transmitting end S and the receiving end D are installed at the device installation position of the laser radar. The installation positions of the transmitting end S and the receiving end D are interchangeable. The device installation position is adjacent to the surface S1 of the polarization beam splitter prism P perpendicular to the wave plate P1 and the surface S8 parallel to the wave plate P1; The optical system includes a plurality of mirror devices, each of which is located on the same straight line, and a mirror group is provided between the starting end of the optical system and the polarization beam splitter prism P; the mirror group is used for collimating the emission of the detection light signal, and is also used for focusing and receiving the detection light signal reflected by the external environment; The lens group is provided with a meniscus positive lens L1, a double concave negative lens L2, a plano-convex cylindrical positive lens L3 and a double convex positive lens L4 in sequence in the input direction of the external light signal; The focal length of the meniscus positive lens L1 is f1; the focal length of the double concave negative lens L2 is f2; the focal length of the plano-convex cylindrical positive lens L3 is f3; the focal length of the double convex positive lens L4 is f4; the following relationship is satisfied: <f1 / f2<-1; 0.15<f1 / f3<0.25;0.35<f1 / f4<0.8; The refractive index of the optical glass material of the meniscus positive lens L1 is n1 and the Abbe number is v1, the refractive index of the optical glass material of the biconcave negative lens L2 is n2 and the Abbe number is v2, the refractive index of the optical glass material of the plano-convex cylindrical mirror is n3 and the Abbe number is v3, and the refractive index of the optical glass material of the biconvex positive lens is n4 and v4, which satisfy the following relationship: 1.8 <n1<2.1, 15<v1<35;1.5<n2<1.7, 50<v2<65;1.4<n3<1.55, 60<v3<80;1.4<n4<1.55, 60<v4<80。 2. The transmitting and receiving coaxial laser radar optical system according to claim 1, characterized in that: The signal receiving end D of the photoelectric detector is located at the focal plane D1 of the lens group; the 1 / 4λ wave plate P1, the right-angle prism P2 and the right-angle prism P3 are connected and fixed by gluing.

3. The transmitting and receiving coaxial laser radar optical system according to claim 1 is characterized in that: The central air gap between the meniscus positive lens L1 and the double concave negative lens L2 is 4.027mm; the central air gap between the double concave negative lens L2 and the plano-convex cylindrical positive lens L3 is 6.548mm; the central air gap between the plano-convex cylindrical positive lens L3 and the double convex positive lens L4 is 0.949mm; the central air gap between the double convex positive lens L4 and the 1 / 4λ wave plate P3 is greater than 0.1mm and less than 11mm.

4. The transmitting and receiving coaxial laser radar optical system according to claim 1, characterized in that: The thickness of the 1 / 4λ wave plate P1 is dp1=0.015~0.06mm, satisfying the following relationship: dp1=λ / 4(nO-ne), wherein n0 is the principal refractive index of the wave plate for o light with a wavelength of λ in vacuum, and ne is the principal refractive index of the wave plate for e light with a wavelength of λ in vacuum; the polarization splitter prism is composed of two isosceles right-angle prisms of the same size glued together, and the oblique surfaces of the isosceles right-angle prisms are coated with a polarization splitter film.

5. The transmitting and receiving coaxial laser radar optical system according to claim 1, characterized in that: The laser radar uses the same set of lenses for light source emission and signal reception, and the lenses in the set are coaxially arranged; when the transmitting end S is adjacent to the surface S1 of the polarization beam splitter prism P, its light source signal is emitted from the light source signal surface of the transmitting end S, and then incident on the surface S1 of the polarization beam splitter prism, and the light signal is divided into P light and S light by the inclined surfaces S2 and S3 of the polarization beam splitter prism, and the P light is emitted from the S4 surface after passing through the inclined surface, and the S light is reflected by the inclined surface and forms circularly polarized light through the 1 / 4λ wave plate P1, and the detection light signal is output through the lens group and the beginning of the optical system; After the detection light signal reflected by the object surface O of the external environment enters the beginning of the optical system, it is incident on the S7 surface of the 1 / 4λ wave plate P1 through the lens group, converted into P light by the 1 / 4λ wave plate P1, and then transmitted through the right-angle prism P2 and the right-angle prism P3 and received by the signal receiving end D; When the transmitting end S is adjacent to the surface S8 of the right-angle prism P2, the installation position of the signal receiving end D is replaced to the surface S1 of the right-angle prism P2. At this time, the object surface reflected detection light signal received by the signal receiving end D is S light.

6. The transmitting and receiving coaxial laser radar optical system according to claim 1, characterized in that: The polarization beam splitter prism P may be replaced by an optical filter or a beam splitter prism with a preset ratio of reflectivity and transmittance.

Images