RU192814U1 - LASER HIGH-SPEED THREE-DIMENSIONAL RANGE FOR THE NAVIGATION OF MOBILE ROBOTIC DEVICES - Google Patents

Abstract

The device relates to devices, sensors, sensors for technical vision or laser three-dimensional scanning, autonomous navigation systems of vehicles and robotic means. The device comprises a transmitting channel rigidly fixed in the housing, including a pulsed coherent source of infrared radiation and a collimator, a receiving channel including a photodetector with focusing optics, a processing and control unit and a microelectromechanical mirror with a two-coordinate suspension, located after the transmitting channel collimator and in front of the receiving focusing optics channel for simultaneously scanning the scene with a laser beam and a radiation receiver. The optical axes of the transmitting and receiving channels are combined by using an inclined mirror made with a hole in the center through which the collimated radiation beam of the transmitting channel passes, and after reflection from the object of scanning, the radiation beam is directed by the specified mirror to the receiving channel. The technical result is a reduction in the requirements for the viewing angle of the photodetector. 5 cp f-ly, 1 ill.

Description

The field of technology.

The technical solution relates to devices, sensors, sensors for technical vision or laser three-dimensional scanning, autonomous navigation systems of transport and robotic means.

State of the art

The prior art is known to US patent No. 7969558, published from 06/28/2011, "Lidar with high resolution." Velodyne's patent describes a lidar with a rotating transceiver head, which contains many laser-receiver pairs, as well as precision mechanics. The solution has high technical characteristics, accuracy, but at the same time, the complexity of the system significantly increases the cost and reduces reliability.

The prior art patent application US No. 2014211194 A1, published on 07/31/2014, "Multitasking lidar detector with low cost for the detection of multiple signals, including weak signals and method of its use." The document describes the design of a compact lidar with an improved reflection processing algorithm. Lidar is designed for transport and robotics. However, the design includes a motor and a rotatable optical unit, which increases the cost of the system and reduces reliability.

The technical problem and the technical result.

The technical task is to develop a lidar to build a three-dimensional image of the environment in real time with the ability to scan the scene with a laser beam and a radiation receiver at the same time.

The technical result is a reduced requirement for the viewing angle of the photodetector (the angle may be smaller).

Decision.

To solve this problem, it is proposed to use a laser scanning three-dimensional range finder, containing:

a. a transmitting channel including a pulsed coherent source of infrared radiation and a collimator,

b. a receiving channel, including a photodetector on an avalanche diode with focusing optics,

c. processing and control unit.

In this case, the range finder includes a microelectromechanical mirror for scanning the scene, and also has combined optical axes of the transmitting and receiving channels due to the use of an inclined mirror made with a hole in the center through which the collimated beam of radiation of the transmitting channel passes unhindered, and after reflection from the object being scanned a larger radiation beam is mainly directed by the indicated mirror into the receiving channel.

The device can be made in such a way that at least one laser diode emitting in the IR spectrum is a coherent light source. At least two laser diodes emitting in the IR spectrum can also be used, configured to alternately generate optical pulses in order to increase the repetition rate of the optical pulses by a multiple of the number of laser diodes used. In this case, the photodetector can be made on one or more avalanche photodiodes, and a microelectromechanical mirror with a two-coordinate suspension. The processing and control unit may be configured to transmit data to a remote device.

To implement the device, the elements should be rigidly fixed inside the housing in a dust and water tight design with windows transparent for IR radiation, made with the possibility of mounting on a vehicle.

Description of the drawings.

In FIG. 1 shows a large-block optical scheme of a lidar.

The following notation is introduced:

1 - source of pulsed laser radiation (OR1),

2 - collimator,

3 - mirror with a hole in the center,

4 - MEMS,

5 - lidar controller,

6 - ADC,

7 - TDC,

8 - peak detector,

9 - discriminator,

10 - amplifier

11 - APD.

Detailed description of the solution.

The object of patenting is a lidar (real-time laser scanning three-dimensional range finder) installed on vehicles operating indoors and outdoors and designed for on-line scanning of the environment / situation while the vehicle is in motion.

Using a lidar allows you to get a three-dimensional image of the surrounding objects in electronic digital form, which can then be transmitted via data channels and processed automatically on a computer using well-known algorithms to select objects in the image and classify them, as well as to build a route and map the vehicle, on which the lidar is mounted. The above algorithms are usually not part of the technical solution of the lidar, however in our lidar some of these algorithms are implemented in the lidar software.

The developed lidar includes the following main components.

1. The lidar transceiver path is made according to a coaxial scheme, which makes it possible to scan the scene with a laser beam and a radiation receiver at the same time. This reduces the requirements for the viewing angle of the photodetector (the angle may be smaller in this case).

The transceiver path consists of the following blocks:

1.1. A laser unit consisting of one or more laser diodes, collimating optics and terminal amplifiers of laser diodes, and operating in the wavelength ranges of 900–950 nm or 1500–1600 nm, providing increased eye safety and improved scanning quality in a cloudy environment. On the market are laser diodes manufactured by Osram and Excelitas operating at a laser wavelength of 905 nm, and laser diodes manufactured by Laser Components, Applied Optoelectronics, Seminex operating at a wavelength of 1550 nm.

1.2. The detection unit, which is based on one or more avalanche photodiodes and is equipped with an amplifier with special characteristics. The amplifier is broadband enough to amplify pulses with fronts up to 1 nanosecond without distortion. The amplifier is low noise enough to register returns on the detector with a 95% probability for a given measurement distance, the radiation power of the laser unit and the reflectivity of the object.

1.3. Scanner based on a two-coordinate MEMS mirror, providing high reliability / long operating time for lidar failure.

2. The computing unit that performs the following functions:

but. Calculation of distance according to the time-of-flight principle.

b. The formation of the scanning pattern (i.e., the trajectory of the laser beam when scanning the scene) and its translation into the scanning device. Moreover, the scanning patterns are standard and predefined, or user-defined.

at. Laser unit control: generation of clock signals to determine the exact coordinates of the delivery point of each laser pulse.

d. Pre-processing - execution of measurement data processing algorithms.

e. Formation of the output stream in a standard format or in a format defined by the user.

3. Firmware - provides processing of measurement results and implements an external lidar control interface.

In the process of reconfiguring the lidar operating mode, the following parameters can be changed (during operation or in maintenance mode):

- scanning pattern (path of the scanning laser beam along the stage)

- scan speed / frame rate / resolution

- radiation power

- output format

- output data rate

- format and method of transmitting diagnostic data

4. Housing - built-in, dust and water tight, vibration-proof.

Elements of a utility model are functionally related as follows (FIG. 1). OR1 (1) contains a pulsed source of infrared radiation on one or more laser diodes. It is connected with Ktr1 (5), which provides power and sends high-frequency clock signals to OR1 (1) to form laser pulses.

The collimator Kol1 (2) provides collimation (minimizes the divergence) of the laser beam OR1 (1), leading it to a diameter D1.

An angled mirror 3 passes a collimated laser beam through a hole passing in the center at an angle to its surface.

The scanner on a two-coordinate MEMS mirror (4) deflects the beam at arbitrary angles in two coordinates after it passes through mirror 3. After that, the beam leaves the lidar and is reflected from opaque objects from the outside. Scanner 4 receives control commands for forming the mirror deflection angles in two coordinates from Ktr1 (5).

Pulses reflected from external objects are reflected by mirror 3 and then are received by the APD detector (11).

Signals with an APD (11) are processed by an amplifier (10), a peak detector (8) and a discriminator (9), and then processed by Ktr1 (5) in order to calculate the distance for each pulse according to the time-of-flight principle and surface reflection coefficient.

The proposed lidar has the following distinctive technical features:

- the use of a scanning device based on a two-coordinate MEMS mirror,

- the use of a coaxial optical scheme with an inclined mirror,

- use of firmware for preprocessing measurement results and an external control interface,

- the use of a built-in housing as a component of a vehicle or a robot integrated in a common housing of a given vehicle. The design of the case involves external fasteners, technological holes and cooling radiators.

Claims (10)

1. The device is a laser scanning three-dimensional range finder containing rigidly mounted in the housing: a. a transmitting channel including a pulsed coherent source of infrared radiation and a collimator, b. a receiving channel including a photodetector with focusing optics, c. processing and control unit, characterized in that it includes a microelectromechanical mirror made with a two-axis suspension, placed after the collimator of the transmitting channel and in front of the focusing optics of the receiving channel, for simultaneously scanning the scene with a laser beam and a radiation receiver, and also has combined optical axes of the transmitting and receiving channels due to the use of an inclined mirror, made with a hole in the center through which the collimated beam of radiation of the transmitting channel passes unhindered, and this after reflection from the object scan larger radiation beam is preferably directed at said mirror receiving channel. 2. The device according to claim 1, characterized in that the coherent light source is a single laser diode emitting in the IR spectrum. 3. The device according to claim 1, characterized in that the coherent light source is two laser diodes emitting in the IR spectrum, configured to alternately generate optical pulses in order to increase the repetition rate of optical pulses by a multiple of the number of laser diodes used. 4. The device according to claim 1, characterized in that the photodetector is made on avalanche photodiodes. 5. The device according to claim 1, characterized in that the processing and control unit is configured to transmit data to a remote device. 6. The device according to p. 1, characterized in that the housing is made in dust and water tight performance with windows transparent to IR radiation, as well as with the possibility of mounting on a vehicle.

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