CN105301600B - A kind of no-raster laser three-dimensional imaging device based on taper reflection - Google Patents

Abstract

A non-scanning laser three-dimensional imaging device based on a conical mirror, comprising a laser (1), a transmitting conical mirror (2), a receiving conical mirror (3), a receiving lens (4), and a CCD camera (5) and image processing module (6). The laser (1) emits a circular spot laser along the axis of the emitting conical reflector (2), and after being reflected by the emitting conical reflector (2), a laser beam is formed in a plane perpendicular to the axis of the emitting reflector (2). Circular ring, the echo of the laser ring irradiating the 360° range target returns to the receiving conical mirror (3), and is focused on the CCD camera (5) by the receiving lens (4) through the receiving conical mirror (3) Form a closed curve image, and the image processing module (6) obtains the distance and the angle of the 360 ° range target by calculating the angle and distance of each image point on the closed curve image, and then obtains the 360 ° through Cartesian coordinate transformation The 3D Cartesian coordinates of the range target.

Description

A Scanning Laser 3D Imaging Device Based on Conical Mirror

technical field

The invention relates to a laser three-dimensional imaging device, which can realize laser three-dimensional imaging in a range of 360 degrees in a plane perpendicular to the moving direction.

Background technique

In the field of lidar and laser 3D scanners, rotating mechanical scanning is often used to achieve target detection in a range of 360°. Mechanical scanning usually requires a high-precision encoder and a stable scanning servo system, resulting in the bulky size and high cost of the entire laser radar and laser 3D scanner. In addition, mechanical scanning will also cause the problem of long measurement time, and high-speed mechanical scanning will reduce the service life of the instrument.

At present, new scanning technologies have been introduced into the field of laser three-dimensional imaging, including crystal scanning, piezoelectric scanning and MEMS scanning. Crystal scanning has the characteristics of high speed and high reliability, but the usual scanning angle is very small, and the transmittance of the crystal to the laser light is low, which will lead to a decrease in optical efficiency. Piezoelectric scanning uses the characteristics of piezoelectric ceramics to achieve mirror deflection. A single lens can achieve high-speed two-dimensional scanning. It has the characteristics of high speed, high reliability and miniaturization. However, this method has a small scanning angle and requires more complicated The feedback system controls and collects the scanning angle. MEMS scanning is a micro-electromechanical system developed on the basis of microelectronics technology. It has the advantages of miniaturization, low power consumption and high reliability. The scanning function is integrated in the chip, which can realize fast scanning at a large angle. However, its scanning The size of the mirror surface is only a few millimeters, which is difficult to meet the current requirements of receiving and detecting.

Non-scanning technology has also been introduced into 3D imaging lidar by using area detection devices. The main surface detection devices include focal plane photodiode (PIN) detector, focal plane avalanche photodiode (APD) detector and image intensified CCD (ICCD). Each pixel of the focal plane PIN detector and focal plane APD detector is equivalent to a PIN detector and APD detector, and has independent time measurement capability. Therefore, the area array PIN detector and APD detector can face the target Carry out distance measurement, i.e. achieve three-dimensional imaging of the target. The image enhancement part of the ICCD has a gain control function, which can perform gate imaging at a fixed time, and in this way can realize three-dimensional imaging of the opposite target. The above-mentioned surface detection device can realize three-dimensional measurement in a certain angle range without scanning, but the pixel resolution of this type of device is low, resulting in low angular resolution, and the price is very high, which is not suitable for conventional commercial laser three-dimensional imaging equipment use on.

In order to achieve high-speed, high-resolution, miniaturized and low-cost laser 3D scanners, a laser 3D imaging device that does not need to scan, has high angular resolution and low cost is urgently needed.

Contents of the invention

The technical solution of the present invention is: Aiming at the reliability and miniaturization problems faced by the current scanning system, as well as the index and cost problems faced by the non-scanning technology, a non-scanning laser three-dimensional imaging device based on a conical mirror is proposed. The device can simultaneously have the technical advantages of non-scanning, miniaturization, high resolution and low cost, and realize 360-degree laser three-dimensional imaging without scanning.

The technical solution of the present invention is: a kind of non-scanning laser three-dimensional imaging device based on conical reflector, comprising laser, emitting conical reflector, receiving conical reflector, receiving lens, CCD camera and image processing module, emitting cone The surface shapes of both the conical reflector and the receiving conical reflector are conical, wherein the conical angle of the emitting conical reflector is 90° and the cone angle faces the laser, and the axes of the receiving conical reflector and the emitting conical reflector are consistent The cone angle is in the opposite direction, and the cone angle of the receiving conical reflector is greater than 90°; the laser emits a circular spot laser along the axis of the emitting conical reflector. A laser ring is formed in the plane of the axis of the reflector, and the echo of the laser ring irradiated to the 360° range target returns to the receiving conical reflector, and is reflected to the receiving lens by the receiving lens. Focus the laser echo on the CCD camera to form a closed curve image, and the image processing module calculates the angle and distance of each image point on the closed curve image to obtain the distance and angle of the target in the 360° range, and then through the Cartesian coordinates Transform to obtain the three-dimensional rectangular coordinates of the 360° range target.

The three-dimensional Cartesian coordinates of the 360 ° range target are (x, y, z), where x=R×cosα, y=R×sinα, and z is the reflection of the circular spot laser from the emission point to the emission cone reflector The distance of the point, α is the angle of the image point on the image of the closed curve, R=d×tg[arctg(r/f)-(θ/2-45)×2], d is the reflection of the conical reflector The distance between the plane where the laser light is located and the plane where the half-height circular section of the receiving conical reflector is located, f is the focal length of the receiving lens, r is the radius of the closed curve, and θ is the cone angle of the receiving conical reflector.

The diameter of the emitting light spot of the laser is the same as that of the emitting conical reflector.

The diameter 5mm of described transmitting conical reflector, the cone angle of described receiving conical reflector is 120 °, diameter 30mm, the plane where the laser light reflected by transmitting conical reflector and the half-height circle of receiving conical reflector The distance d of the plane where the shaped section is located is 20mm.

The laser is a semiconductor laser with a wavelength of 808nm. The receiving lens is a double-convex lens with a diameter of 30 mm and a focal length of 50 mm. The resolution of the CCD camera is 2592×1944, and the size of the photosensitive surface is 0.5 inches.

The advantage of the present invention compared with prior art is:

(1) The present invention adopts the emitting conical reflector to form a circular emitting light, which can continuously cover the 360° range without scanning, realizes 360° non-scanning detection, saves the rotating structure and motor, and has more advantages than the rotating scanning three-dimensional imaging technology High reliability and compactness;

(2) The present invention receives the echo of the circular emitted light through the coaxial receiving conical mirror and images it on the CCD focal plane device, and measures the target according to the distance from the closed curve of the received echo to the central pixel on the CCD focal plane Distance, with the help of high-resolution CCD to achieve high-resolution angles and 360° range continuous light imaging, compared with point-scanning laser 3D imaging, the point density depends on multiple factors such as laser repetition frequency, scanning speed and spot diameter , the spatial resolution of continuous light imaging is only limited by the resolution of the imaging device. Demand for low-cost laser 3D imaging;

(3) The present invention carries out continuous imaging to the laser echo signal, calculates the target distance according to the distance from the image point to the image center, and calculates the angle of the target according to the plane angle of the image point on the image, which requires high-speed sampling compared to scanning three-dimensional imaging technology and a high-speed digital processing circuit to increase the detection rate, the device of the invention only needs to adopt a low-speed imaging device (such as a CCD) and perform simple image coordinate calculation, which has lower cost and technical difficulty.

Description of drawings

Fig. 1 is a schematic diagram of the composition and measurement principle of the imaging device of the present invention.

Detailed ways

As shown in Figure 1, it is a schematic diagram of the composition and measurement principle of the non-scanning laser three-dimensional imaging device based on the conical mirror of the present invention. The device of the present invention mainly includes a laser 1, a transmitting conical reflector 2, a receiving conical reflector 3, Receiving lens 4, CCD camera 5 and image processing module 6.

The laser 1 emits circular spot laser light along the axial direction of the emission cone reflector 2, and the laser light is incident on the apex of the emission cone reflector 2 with a cone angle of 90°. After the laser is reflected by the emitting conical reflector 2, a laser ring is formed in a plane perpendicular to the axis of the emitting conical reflector 2. The ring irradiates the echoes of the 360° target and returns to the receiving conical reflector 3 . The axis center of the receiving conical mirror 3 is consistent with that of the transmitting conical mirror 2, but the direction of the apex is opposite. The receiving conical mirror 3 reflects the target echo to the receiving lens 4, and the receiving lens 4 focuses it on the CCD camera 5. Form a closed curve image, that is, the target laser echo image formed on the CCD camera 5 is a closed curve around the origin, the center pixel of the CCD camera 5 is the origin, and the image points on the curve correspond to the targets in the 360° range. The angle corresponds to the angle of the target, and the distance from the image point to the origin corresponds to the distance of the target. The image processing module 6 obtains the distance of the target at the corresponding angle by measuring the distance from any angle point on the closed curve on the focal plane of the CCD camera 5 to the origin, and the rectangular three-dimensional coordinates of the target can be calculated in combination with the angle.

The non-scanning laser three-dimensional imaging device based on the conical mirror of the present invention can be installed on a mobile platform, and emits a ring laser on a two-dimensional plane perpendicular to the moving direction.

The laser 1 adopts a semiconductor laser, for example, the laser wavelength is 808nm. The emission conical reflector 2 is a conical reflector with an apex angle of 90° and a diameter of 5 mm. The receiving conical reflector 3 is a conical reflector with an apex angle greater than 90°, for example, 120°, and a diameter of 30mm. The receiving lens 4 is a doublet convex lens with a diameter of 30 mm and a focal length of 50 mm. The resolution of the CCD camera 5 is 2592×1944, and the size of the photosensitive surface is 0.5 inches.

The diameter of the laser spot emitted by the laser 1 is the same as the diameter of the emitting conical reflector 2, and the apex angle of the emitting conical reflector 2 is 90°, and the spot width of the annular spot after passing through the emitting conical reflector 2 is equal to Laser 1 emits spot radius.

The apex angle of the receiving conical reflector 3 must be greater than 90°. The larger the apex angle, the greater the distance from the imaging point to the origin of the target echo on the focal plane of the CCD camera 5, and the higher the corresponding angular resolution. The plane of emitting light (the intersection line between the laser light reflected by the emitting conical reflector 2 and the target at a distance R) and the half-height plane of the receiving conical reflector 3 (the plane perpendicular to the axis of the cone at the half-height of the receiving conical reflector 3) The larger the spacing, the greater the distance from the imaging point to the origin of the target echo on the focal plane of the CCD camera 5 at the same distance, and the higher the corresponding angular resolution. However, increasing the cone angle and spacing of the receiving cone mirror 3 will increase the volume of the receiving cone mirror 3 and the volume of the entire optical path at the same height of the receiving cone mirror 3 (representing the receiving aperture). Therefore, in engineering applications, appropriate cone angle and spacing should be selected, taking into account resolution and volume.

Using single-lens imaging, the CCD image point and the target point are axisymmetric (the axis of the transmitting conical mirror 2 and the receiving conical mirror 3), that is, the angle of the image point and the angle of the target point are one-to-one axisymmetric relationship , the angle of the target point can be calculated from the angle of the image point through coordinate transformation.

The image processing module 6 takes the central pixel of the CCD camera 5 as the origin, and the image points on the curve correspond to targets in the range of 360°, the angle α of the image points is consistent with the angle of the target, and the distance r from the image point to the origin corresponds to the distance R of the target. The plane of emitting light (the intersection line between the laser light reflected by the emitting conical reflector 2 and the target at a distance R) and the half-height plane of the receiving conical reflector 3 (the plane perpendicular to the axis of the cone at the half-height of the receiving conical reflector 3) The pitch is d, the focal length of the receiving lens 4 is f, and the vertex angle of the receiving conical reflector 3 is θ, then according to the triangular geometric relationship, the image processing module 6 can be according to the formula R=d×tg[arctg(r/f) -(θ/2-45)×2] Calculate the target distance R, according to the angle α of the image point, the target angle can be calculated as α, and then according to the Cartesian coordinate transformation formula x=R×cos(α) and y=R Cartesian coordinate transformation of ×sin(α), combined with the height z of the emitting laser ring, can obtain the three-dimensional rectangular coordinates (x, y, z) of the target in the 360° range.

The content that is not described in detail in the description of the present invention belongs to the well-known technology of those skilled in the art.

Claims (6)

1. A kind of 1. no-raster laser three-dimensional imaging device based on taper reflection, it is characterised in that：Including laser (1), hair Penetrate taper reflection (2), receive taper reflection (3), receiving lens (4), CCD camera (5) and image processing module (6), hair The face shape for penetrating taper reflection (2) and reception taper reflection (3) is cone, wherein the cone of transmitting taper reflection (2) Angle is 90 ° and cone angle is towards laser (1), and reception taper reflection (3) is consistent with the axle center of transmitting taper reflection (2) and bores Angle is towards on the contrary, the cone angle for receiving taper reflection (3) is more than 90 °；Axle center of the laser (1) along transmitting taper reflection (2) Circular light spot laser is launched in direction, and laser is after transmitting taper reflection (2) reflection, perpendicular to transmitting taper reflection (2) A laser annulus is formed in the plane in axle center, the echo that the laser annulus is irradiated to 360 ° of scope targets returns to reception cone Shape speculum (3), and received taper reflection (3) reflexes to receiving lens (4), is gathered return laser beam by receiving lens (4) It is burnt to forming closed curve picture in CCD camera (5), image processing module (6) by the closed curve as on each picture point Angle and distance calculates, and obtains the distance and angle of 360 ° of scope targets, then described in obtaining by rectangular coordinates transformation The three-dimensional rectangular coordinate of 360 ° of scope targets；The three-dimensional rectangular coordinate of 360 ° of scope targets is (x, y, z), wherein x=R × Cos α, y=R × sin α, z are the circular light spot laser from launch point to the distance of the pip of transmitting taper reflection (2), α For the angle of picture point on the closed curve picture, R=d × tg [arctg (r/f)-(θ/2-45) × 2], d are transmitting taper reflection The distance of plane where plane where the laser that mirror (2) reflects and half high circular cross-section of reception taper reflection (3), f is to connect The focal length of lens (4) is received, r is the radius of the closed curve, and θ is the cone angle of the reception taper reflection (3).
2. 2. a kind of no-raster laser three-dimensional imaging device based on taper reflection according to claim 1, its feature exist In：The diameter 5mm of described transmitting taper reflection (2), the cone angle of described reception taper reflection (3) is 120 °, diameter Where half high circular cross-section of 30mm, plane where the laser of transmitting taper reflection (2) reflection and reception taper reflection (3) The distance d of plane is 20mm.
3. 3. a kind of no-raster laser three-dimensional imaging device based on taper reflection according to claim 1, its feature exist In：The diameter of described laser (1) launch spot is identical with the diameter of transmitting taper reflection (2).
4. 4. a kind of no-raster laser three-dimensional imaging device based on taper reflection according to claim 1, its feature exist In：Described laser (1) is wavelength 808nm semiconductor laser.
5. 5. a kind of no-raster laser three-dimensional imaging device based on taper reflection according to claim 1, its feature exist In：Described receiving lens (4) are diameter 30mm doublet lens, focal length 50mm.
6. 6. a kind of no-raster laser three-dimensional imaging device based on taper reflection according to claim 1, its feature exist In：Described CCD camera (5) resolution ratio is 2592 × 1944, and photosurface size is 0.5 inch.