CN110988898A

CN110988898A - Laser rangefinder and robot

Info

Publication number: CN110988898A
Application number: CN201911216147.3A
Authority: CN
Inventors: 张志淳; 李华强; 潘珂
Original assignee: Beijing Rockrobo Technology Co Ltd
Current assignee: Beijing Rockrobo Technology Co Ltd
Priority date: 2019-12-02
Filing date: 2019-12-02
Publication date: 2020-04-10
Also published as: TW202127061A; TWI767428B; WO2021109912A1

Abstract

The invention discloses a laser ranging device and a robot. The laser ranging device comprises a transmitting unit and a receiving unit. The transmitting unit includes a transmitter for transmitting pulsed laser light to a target object to be measured and a transmitting lens for passing the transmitted pulsed laser light. The receiving unit includes a photodetector for receiving the pulse laser light reflected from the target object and a receiving lens for passing the reflected pulse laser light. Wherein the angle of view of the receiving unit is greater than the angle of view of the transmitting unit, and the distance between the outer edge of the receiving lens and the outer edge of the transmitting lens is less than or equal to 3 mm. The laser ranging device and the robot are suitable for short-distance high-frequency ranging in an indoor environment by adopting a flight time method, and are high in ranging precision and low in cost.

Description

Laser rangefinder and robot

Technical Field

The present invention relates generally to the field of smart home technology, and more particularly to a laser ranging device and a robot.

Background

In the civil and commercial fields, laser ranging methods for environmental detection and map construction can be broadly divided into two categories according to technical routes: one is Time of Flight (TOF) and the other is triangulation. In which TOF is insensitive to deformation caused by temperature changes, and its distance measurement accuracy, especially in long-distance measurement, is higher than that of triangulation. However, TOF is mostly applied in long-distance ranging scenes, such as unmanned aerial vehicles or autopilot. Triangulation is mostly applied in high frequency (e.g. above 1000 times/second) ranging scenarios at relatively short distances (e.g. below 30 meters) in indoor environments. This is mainly because the cost of the apparatus using TOF ranging is higher, and the reflected stray light is too much during short-range ranging, and the signal-to-noise ratio of the received light is too low for various reasons, so that the ranging accuracy is poor. These factors limit the application of TOF ranging in high frequency sub-ranging scenarios of relatively short distance in indoor environments.

To this end, the present invention provides a laser ranging apparatus and a robot to at least partially solve the problems of the prior art.

Disclosure of Invention

In this summary, concepts in a simplified form are introduced that are further described in the detailed description. This summary of the invention is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

In order to at least partially solve the above technical problem, the present invention provides a laser ranging apparatus, including:

a transmitting unit including a transmitter for transmitting a pulse laser to a target object to be measured and a transmitting lens for passing the transmitted pulse laser; and

a receiving unit including a photodetector for receiving the pulse laser light reflected from the target object and a receiving lens for passing the reflected pulse laser light;

wherein a field angle of the receiving unit is larger than a field angle of the emitting unit, and a distance between an outer edge of the receiving lens and an outer edge of the emitting lens is less than or equal to 3 mm.

According to the laser ranging apparatus of the present invention, the angle of view of the receiving unit is larger than the angle of view of the transmitting unit. The emission angle of the emission unit is thus small, enabling laser pulses to be sent over greater distances with limited power. The receiving unit can have an optical field as large as possible, so that the overlapping area of the transmitting visual field and the receiving visual field is larger, the blind area is smaller, more light intensity can be received, and the signal-to-noise ratio of the received signal can be improved. In addition, the outer edge distance between the transmitting lens and the receiving lens is not more than 3mm, the blind areas of the transmitting view field and the receiving view field can be further reduced, and objects close to the transmitting lens and the receiving lens can be avoided being not detected. These characteristics make the laser ranging apparatus according to the present invention suitable for ranging short distances and high frequencies in an indoor environment using TOF.

According to another aspect of the present invention, there is also provided a robot including the laser ranging apparatus as described above.

According to the robot provided by the invention, the laser distance measuring device is suitable for short-distance and high-frequency distance measurement in an indoor environment by adopting TOF (time of flight), the distance measurement precision is higher, and the cost is lower.

Drawings

The following drawings of the invention are included to provide a further understanding of the invention. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings:

FIG. 1 is a perspective view of a laser ranging device in accordance with a preferred embodiment of the present invention;

FIG. 2 is a perspective view of a ranging assembly of the laser ranging device of FIG. 1;

FIG. 3 is a cross-sectional view of the laser ranging assembly shown in FIG. 2;

FIG. 4 is a perspective view of a circuit board of a receiving unit of the laser ranging device shown in FIG. 1;

FIG. 5 is a perspective view of a light shield of the laser ranging device shown in FIG. 1; and

fig. 6 is an exploded view of the laser ranging device shown in fig. 1.

Detailed Description

In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that embodiments of the invention may be practiced without one or more of these specific details. In other instances, well-known features have not been described in detail so as not to obscure the embodiments of the invention.

In the following description, a detailed structure will be presented for a thorough understanding of embodiments of the invention. It is apparent that the implementation of the embodiments of the present invention is not limited to the specific details familiar to those skilled in the art.

The invention provides a laser ranging device which can emit laser pulses to a target object to be ranged, then receive the laser pulses reflected by the target object, and analyze and calculate the received laser pulses so as to obtain the distance between the target object and the laser ranging device. The laser ranging apparatus according to the present invention is suitable for short-range (e.g. below 30 meters) high frequency (e.g. above 1000 times/second) ranging in indoor environments using TOF. The following detailed description is made with reference to the accompanying drawings.

As shown in fig. 1, a laser ranging apparatus 1 according to a preferred embodiment of the present invention mainly includes a ranging assembly 10 and an outer case 20. The distance measuring assembly 10 is a core component of the laser distance measuring device 1 for realizing the distance measuring function.

The outer housing 20 is generally configured as a circular cake, and covers the outside of the distance measuring assembly 10 for fixing and protecting. It is understood that in other embodiments, the outer housing 20 may also be configured in the shape of an oval pie, cube, or the like. The outer case 20 is provided with a first opening 21 through which the emitted laser pulses pass and a second opening 22 through which the laser pulses reflected by the target object to be measured pass.

Although not shown in the drawings, those skilled in the art will understand that the laser ranging device 1 may further include a fixing base. The outer housing 20 is fastened to the fixing base, and a substantially closed inner space is formed between the outer housing and the fixing base, and the distance measuring assembly 10 is accommodated in the inner space. Can also set up the mounting structure such as screw hole or buckle on the fixing base, can be fixed to robot, unmanned aerial vehicle etc. with the installation of laser rangefinder 1 through mounting structure.

As shown in fig. 2 and 6, the ranging assembly 10 includes a transmitting unit 11, a receiving unit 12, and a frame 13. The transmitting unit 11 and the receiving unit 12 are respectively fixed to the frame 13 to form an integral body.

As shown in fig. 3, the emission unit 11 includes an emitter 111, an emission circuit board 112, and an emission lens 113. The transmitter 111 is used to transmit laser pulses for ranging. In the present embodiment, the emitter 111 is configured as a laser diode. The laser diode is integrally provided on the transmitting circuit board 112. The frame 13 is provided with a first optical cavity 131. The emission circuit board 112 and the emission lens 113 are fixed to the frame 13 and are located at both ends of the first optical cavity 131, respectively. The laser pulses emitted by the emitter 111 may be passed out through the emission lens 113. The emitter lens 113 is capable of focusing and collimating the laser pulses passing therethrough. It will be appreciated that in other embodiments, other devices capable of lasing may also be used as the emitter.

Preferably, the transmitting unit 11 further comprises a regulator 114. The emission lens 113 is mounted on the adjuster 114, and the adjuster 114 is adjustably disposed within the first optical cavity 131 of the frame 13. Thus, the position of the emission lens 113 with respect to the emitter 111 can be adjusted by changing the position of the adjuster 114 within the first optical cavity 131 to adjust the optical path of the collimating emission unit 11. Wherein the direction of the position adjustment may include a direction along and a direction perpendicular to the direction of the laser pulse delivery.

In the embodiment shown in fig. 3 and 6, the regulator 114 has a cylindrical configuration. The outer side of the actuator 114 and the inner side of the first optical cavity 131 are provided with threads, respectively. The actuator 114 is movably disposed within the first optical cavity 131 by way of a threaded engagement. At the time of calibration, the adjuster 114 may be screwed to adjust the position of the emission lens 113. The manner of adjustment is relatively simple. After the emission lens 113 is adjusted in position, the adjuster 114 and the emission lens 113 may be fixed in position by a process such as dispensing.

To accommodate ranging in indoor environments, the center wavelength of the laser pulses emitted by emitter 111 may be 905nm or 850 nm. The light with the wavelengths can be distinguished from the ambient light under the common indoor environment, so that the influence of the ambient light can be weakened, and the accuracy of distance measurement is improved. It is understood that since there is a lot of stray light with a wavelength close to 850nm in outdoor ambient light, a laser pulse with a center wavelength of 850nm is not suitable for use in outdoor environments, but can be applied only to indoor environment ranging.

The receiving unit 12 includes a photodetector 121, a receiving circuit board 122, and a receiving lens 123. The optical detector 121 is used for sensing the laser pulse reflected by the target object and generating a corresponding photoelectric signal to be transmitted to the receiving circuit board 122. The analysis circuit on the receiving circuit board 122 analyzes and calculates the photoelectric signal to obtain the distance between the target object and the laser ranging device 1. The photodetector 121 is packaged in a package module 124 as shown in fig. 4 and is integrally provided on the receiving circuit board 122. Further, a second optical cavity 132 is provided on the frame 13 to be isolated from the first optical cavity 131. The receiving circuit board 122 and the receiving lens 123 are fixed to the frame 13 and are located at both ends of the second optical cavity 132, respectively. The laser light pulses reflected back by the target object may be focused and collimated by a receive lens 123 before being sensed by a photodetector 121.

In order to receive the laser pulses reflected by the target object as much as possible, so as to increase the received light intensity and improve the signal-to-noise ratio, the receiving unit 12 is preferably provided with a receiving window as large as possible, that is, the receiving lens 123 is as large as possible. However, as shown in fig. 1 and 6, there is a limitation in installation space, and the laser ranging apparatus 1 itself has a limited size in consideration of miniaturization. It will be appreciated that the outer housing 20 generally defines the outer profile of the laser ranging device 1. The dimension of the laser distance measuring device 1 in the thickness direction (i.e. the axial direction of the aforementioned pie shape) is thus significantly smaller than its dimension in a direction parallel to the end face 23 of the outer housing 20 (i.e. the radial direction of the aforementioned pie shape). Therefore, as shown in fig. 2, the receiving lens 123 is disposed such that its dimension in the direction parallel to the end face 23 is larger than its dimension in the above-described thickness direction to form a receiving window as large as possible. For example, the receiving lens 123 may be configured to have a rectangular projection on a plane perpendicular to its optical axis AX2 (see fig. 3), where the long side of the rectangle is parallel to the end face 23 and the short side of the rectangle is perpendicular to the end face 23.

Further, an outer surface of at least one of the transmitting lens 113 and the receiving lens 123 is configured as a free-form surface. That is, the outer surface of the lens described above satisfies the following formula:

in the above formula, z is the value in the thickness direction of the lens, r is the polar coordinate value of any point on the curved surface, k is the coefficient of the quadric surface, c is the radius of curvature of the fixed point of the curved surface, and a plurality of α_iIs the parameter to be set. The free-form surface is preferably a quadratic surface, which has good focusing and collimating effects. Therefore, a single lens may be used without providing a lens group including a plurality of lenses. Further, the lens focal length of at least one of the emission lens 113 and the reception lens 123 is set to be less than or equal to 50 mm. In addition, the thickness of the receiving lens 123 may be set to be less than or equal to 5 mm. So set up, the size of lens is less, is favorable to laser rangefinder's miniaturization.

Laser rangefinders are commonly used as part of sensing systems in application scenarios such as robotic, unmanned or unmanned aerial vehicles. The robot or the unmanned aerial vehicle and the like need to construct an environment map according to the surrounding environment information sensed by the laser ranging device. Therefore, the robot or the unmanned aerial vehicle can plan a moving path in the constructed environment map and actively avoid obstacles, so that autonomous movement is realized. Therefore, the laser ranging apparatus cannot have a blind area, particularly a near blind area. The conventionally arranged laser ranging device inevitably causes the occurrence and even expansion of a blind area when being miniaturized, which is an irreconcilable natural contradiction.

In addition, the ranging accuracy is a basic index for measuring the performance of the laser ranging device. The premise of realizing accurate distance measurement is that the signal-to-noise ratio can reach a preset index, otherwise, the accuracy of the distance measurement cannot be mentioned. Therefore, the occupation ratio of the received laser pulse is improved as much as possible, the introduction of other optical signal noises is reduced, and the problem that the whole design process of the optical path of the laser ranging device needs to be considered is solved.

In summary, the design optimization of the laser distance measuring device needs to solve the problems of blind areas, signal-to-noise ratio, speed drift, error control, etc., and various factors need to be considered and balanced.

Fig. 3 schematically shows the angle of view θ of the transmitting unit 11 and the angle of view β of the receiving unit 12 the laser ranging device 1 according to the present invention is arranged such that the angle of view β of the receiving unit 12 is larger than the angle of view θ of the transmitting unit 11 as can be seen from fig. 3, according to this arrangement, the overlapping area of the receiving field of view and the transmitting field of view is the sum of the a-area and the B-area, and the blind area therebetween is only the D-area.

In contrast, when the angle of view of the receiving unit 12 is the same as the angle of view of the transmitting unit 11 (both are θ), the overlapping area of the receiving field of view and the transmitting field of view is the a area, and the blind areas therebetween are the C area and the D area. It is understood that when the angle of view of the receiving unit is smaller than that of the transmitting unit, the overlapping area of the fields of view of the two is further decreased and the blind area is further increased.

Therefore, according to the invention, the receiving unit can have the optical field as large as possible, the receiving visual field and the transmitting visual field can have larger overlapping area and reduce or even eliminate blind area, the receiving unit can receive more light intensity, and the signal-to-noise ratio of the received signal can be improved. In addition, the emission angle of the emission unit is small, and the laser pulse can be sent to a longer distance under the condition of limited power, so that the distance measurement is facilitated.

Further, the transmitting unit 11 and the receiving unit 12 are arranged at a spacing in the lateral direction. From what is shown in fig. 3, it can be seen that the larger the distance L between the outer edge of the transmitting lens 113 and the outer edge of the receiving lens 123, the larger the distance between the optical axes AX1 and AX2 thereof. Accordingly, the larger the area of the triangle of the D region. I.e., the larger the blind areas of the transmit and receive fields of view. Therefore, in order to reduce the blind zone, the outer edge distance L of the transmitting lens 113 and the receiving lens 123 should be made as small as possible. According to the present invention, the interval L between the outer edge of the emission lens 113 and the outer edge of the reception lens 123 is set to be less than or equal to 3 mm. Therefore, blind areas of the transmitting visual field and the receiving visual field can be reduced as much as possible, and the situation that a near object cannot be detected can be avoided. These characteristics make the laser ranging apparatus according to the present invention suitable for ranging short distances and high frequencies in an indoor environment using TOF.

Currently, most of laser distance measuring devices that measure distance outdoors using TOF use Avalanche Photodiodes (APDs) as photodetectors. This is because APDs have a large magnification, and are suitable for laser ranging in outdoor environments because they can capture and amplify relatively weak reflected laser pulses for analysis and calculation even in outdoor environments. However, the APD amplifies the reflected laser pulse and also amplifies the received ambient light noise by an equal ratio. Therefore, it is usually necessary to provide an optical filter to filter the amplified ambient light noise so as to avoid the influence on the analysis and calculation result, which may result in inaccurate distance measurement.

In the laser distance measuring device 1 according to the present invention, a P-type semiconductor-impurity-N-type semiconductor (PIN) common photodiode may be used as the photodetector 121. The PIN photodiode itself is low in price, and thus the cost of the laser ranging apparatus 1 can be reduced.

Further, the amplification factor of the PIN photodiode is much smaller than that of the APD detector. In the distance measurement, even if the PIN photodiode amplifies the laser pulse reflected by the target object and the ambient light noise in an equal ratio, the amplified ambient light noise is still below the passing threshold of the PIN photodiode due to the small amplification factor, and therefore the amplified ambient light noise cannot pass through the PIN photodiode. Thus, the PIN photodiode essentially acts to filter ambient light. Therefore, the laser ranging device according to the present invention does not include an optical filter, so that the cost can be further reduced. That is, the invention replaces APD and optical filter with low cost PIN, still can obtain higher signal to noise ratio, simplifies the design of the optical circuit of the laser distance measuring device while reducing the cost, and reduces the design and implementation difficulty. The optical receiving end can be simplified, and the design of the whole optical path is benefited, so that the optical signal received by the receiving end is strong enough, and the ambient light noise is weak enough.

In addition, in a high-frequency environment, a filter capacitor electrically connected with the PIN photodiode can be arranged, and high-frequency noise is filtered in an alternating current blocking mode, so that the accuracy of distance measurement is ensured.

As shown in fig. 4, the photodetector 121 is packaged in a package module 124. The encapsulation module 124 is opposite to the receiving lens 123 through the second optical cavity 132, so that the laser pulse reflected by the target object can be sensed by the optical detector 121. During ranging, the laser pulse light reflected by a nearby obstacle (for example, within 30 cm) has a strong intensity, and enters the second optical cavity 132 through the receiving lens 123, and is reflected by the outer surface of the package module 124 of the receiving unit 12, so as to form stray light. Generally, the outer surface of the package module 124 is a light-colored metal substrate such as silver gray, and the reflected stray light causes the light pulse width received by the light detector 121 to increase. The optical pulse width here represents a pulse signal whose horizontal axis represents time and vertical axis represents voltage representing energy. In TOF (time of flight) ranging is based on the time difference between the emission and reception of laser pulses, and the time difference is calculated by a method related to the start and end positions of the pulse width of light, and not simply taking the middle position of the pulse width for calculation, so that the increase of the pulse width of light causes inaccurate ranging.

In view of the above problem, as shown in fig. 4, at least an outer surface 124a of the encapsulation module 124 encapsulating the optical detector 121 and facing the receiving lens 123 is configured as an extinction surface, so as to reduce the reflection of the outer surface 124a, thereby reducing or even eliminating stray light and avoiding the interference of the stray light on TOF ranging.

Specifically, the outer surface 124a may be coated with a matting material. For example, the outer surface 124a may be matte treated with a matting agent such as a polyacrylate resin or other matting powder, matting varnish, or the like coated thereon to form a matte surface. Alternatively, the outer surface 124a may be covered with an extinction film. Still alternatively, the outer package of the package module 124 may be made directly from a dark (e.g., black) base material, so that at least the outer surface 124a is formed as a matte surface.

As can be seen from the above description, the outer edge distance between the receiving lens 123 and the transmitting lens 113 of the laser ranging device 1 according to the present invention is 3mm at the maximum. Therefore, it is easy to occur that a part of the laser pulse emitted by the emitting unit 11 is not emitted to an external target object yet, that is, has been received by the receiving unit 12 by reflection of internal parts, thereby causing strong noise light, so that the signal-to-noise ratio is greatly lowered, and ranging cannot be achieved.

In order to avoid the above, as shown in fig. 1 and 5, the laser ranging apparatus 1 according to the present invention further includes a light shield 30. The light shield 30 has a first channel 31 and a second channel 32, which are disposed between the ranging assembly 10 and the outer housing 20. Wherein both ends of the first channel 31 are respectively butted with the transmitting lens 113 and the first opening 21 of the outer housing 20, and both ends of the second channel 32 are respectively butted with the receiving lens 123 and the second opening 22 of the outer housing 20. Further, a light-impermeable light-blocking wall 33 is provided between the first channel 31 and the second channel 32 to completely separate them. Therefore, the laser pulse emitted by the emitting unit 11 after passing through the emitting lens 113 can only be emitted to the outside via the first channel 31 and the first opening 21, and cannot be reflected to the receiving lens 123 inside the laser ranging device 1, so that the reduction of the signal-to-noise ratio caused by internal reflection is avoided, and the accuracy of TOF ranging is improved.

According to another aspect of the present invention, there is also provided a robot. The robot may include the above-described laser ranging apparatus, which is capable of acquiring and constructing a map of an indoor environment by TOF ranging in the indoor environment through the laser ranging apparatus, and autonomously moving according to the constructed map.

In one embodiment, the robot may be an intelligent cleaning device that can autonomously move over the floor to perform a sweeping function. For example, the intelligent cleaning device may be a sweeping robot, a mopping robot, or a sweeping and mopping integrated robot, etc. The intelligent cleaning device may include a cleaning system, a sensing system, a control system, a drive system, and the like. The perception system is used for perceiving the external environment such as the terrain by the intelligent cleaning equipment. The laser ranging device forms part of a sensing system, which may be located in front of or on top of the intelligent cleaning apparatus. The control system controls the driving system to drive the intelligent cleaning device to move autonomously based on the sensing result of the sensing system and selectively controls the cleaning system to perform the cleaning function.

According to the laser distance measuring device and the robot of the present invention, the angle of view of the receiving unit of the laser distance measuring device is larger than the angle of view of the transmitting unit. The emission angle of the emission unit is thus small, enabling laser pulses to be sent over greater distances with limited power. The receiving unit can have an optical field as large as possible, so that the overlapping area of the transmitting visual field and the receiving visual field is larger, the blind area is smaller, more light intensity can be received, and the signal-to-noise ratio of the received signal can be improved. In addition, the outer edge distance between the transmitting lens and the receiving lens is not more than 3mm, the blind areas of the transmitting view field and the receiving view field can be further reduced, and objects close to the transmitting lens and the receiving lens can be avoided being not detected. These characteristics make the laser ranging apparatus suitable for short-distance high-frequency ranging in an indoor environment using TOF.

Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Terms such as "disposed" and the like, as used herein, may refer to one element being directly attached to another element or one element being attached to another element through intervening elements. Features described herein in one embodiment may be applied to another embodiment, either alone or in combination with other features, unless the feature is otherwise inapplicable or otherwise stated in the other embodiment.

The present invention has been described in terms of the above embodiments, but it should be understood that the above embodiments are for purposes of illustration and description only and are not intended to limit the invention to the scope of the described embodiments. It will be appreciated by those skilled in the art that many variations and modifications may be made to the teachings of the invention, which fall within the scope of the invention as claimed.

Claims

1. A laser ranging device, comprising:

2. The laser ranging device as claimed in claim 1, wherein the receiving unit comprises a package module in which the light detector is packaged, and a side of the package module facing the receiving lens is configured as an extinction surface.

3. The laser ranging device as claimed in claim 2, wherein the light extinction surface is formed by coating a light extinction material on a side surface of the encapsulation module.

4. The laser rangefinder apparatus of claim 2 wherein the matt surface is formed by covering the side of the encapsulation module with an matt film.

5. The laser ranging device as claimed in claim 2, wherein at least one side of the packaging module facing the receiving lens is made of a black base material.

6. The laser rangefinder apparatus of claim 1 wherein the light detector is a PIN photodiode.

7. The laser ranging device as claimed in claim 6, wherein the optical path of the receiving unit does not include an optical filter at a front end of the optical detector.

8. The laser ranging device as claimed in claim 6, wherein the receiving unit further comprises a filter capacitor electrically connected to the light detector.

9. The laser rangefinder apparatus of claim 1 further comprising a light shield having a first channel and a second channel, the first channel and the second channel separated by a light blocking barrier, the transmit lens interfaced with the first channel, the laser pulse transmitted by the transmit unit being transmitted through the first channel to an exterior of the laser rangefinder apparatus, the receive lens interfaced with the second channel, the pulsed laser reflected from the target object being received by the receive unit through the second channel.

10. A robot, characterized in that the robot comprises a laser ranging device according to any one of claims 1 to 9.