WO2018133089A1 - Tof distance measurement system and movable platform - Google Patents

Abstract

A TOF distance measurement system and a movable platform. The TOF distance measurement system comprises: a light emitter (11), a receiver (12), a controller (13) and an optical system (14), the optical system (14) comprising at least one of a first optical signal processing apparatus (141) and a second optical signal processing apparatus (142); an optical signal emitted by the light emitter (11) passing through the first optical signal processing apparatus (141) so as to improve the radiation power density of the optical signal emitted by the light emitter (11); and an optical signal reflected by a target object (15) passing through a second optical signal processing apparatus (142) so as to improve the intensity of the optical signal reflected by the target object (15) and received by the receiver (12). By means of improving the radiation power density of the optical signal emitted by the light emitter (11) and/or improving the intensity of the optical signal reflected by the target object (15) and received by the receiver (12), the signal-to-noise ratio of a TOF distance measurement system can be improved, so that the TOF distance measurement system can detect a target object far away from the TOF distance measurement system, thereby improving the distance measurement range of the TOF distance measurement system.

Description

TOF ranging system and mobile platform Technical field

Embodiments of the present invention relate to the field of ranging, and in particular, to a TOF ranging system and a movable platform.

Background technique

Currently, mobile platforms (such as unmanned aerial vehicles, detection robots, etc.) are provided with detection devices for detecting obstacles around the movable platform to prevent the movable platform from colliding with surrounding obstacles.

Time Of Flight (TOF) is a commonly used ranging method. The TOF ranging method includes phase modulation method. The phase modulation method refers to the emission of a light source of a TOF ranging system on a movable platform. An amplitude-modulated continuous optical signal, which is usually a Light Emitting Diode (LED). When a continuous optical signal is irradiated to an obstacle around the movable platform, the obstacle returns a reflected optical signal to the TOF ranging system, TOF. The ranging system calculates the distance between the obstacle and the movable platform based on the phase of the reflected light signal.

However, in the TOF ranging system, on the one hand, as the measuring distance increases, the intensity of the returned optical signal decreases, resulting in insufficient intensity of the optical signal received by the receiver. On the other hand, in order to obtain sufficient optical signal strength, it is necessary to increase the integration time. The electric power and optical power consumed at this time will increase. Therefore, the current TOF ranging system can only detect relatively close obstacles and cannot detect obstacles at a long distance.

Summary of the invention

The embodiment of the invention provides a TOF ranging system and a movable platform to improve the ranging range of the TOF ranging system.

An aspect of an embodiment of the present invention provides a TOF ranging system including: an illuminator, a receiver, a controller, and an optical system;

An illuminator for emitting an optical signal;

a receiver for receiving an optical signal reflected by the target object;

The controller is configured to determine a distance between the target object and the ranging system according to an optical signal emitted by the illuminator and an optical signal received by the receiver and reflected by the target object;

The optical system includes at least one of the following:

a first optical signal processing device, wherein an optical signal emitted by the illuminator passes through the first optical signal processing device to increase a radiation power density of an optical signal emitted by the illuminator;

The second optical signal processing device passes the optical signal reflected by the target object through the second optical signal processing device to increase the intensity of the optical signal reflected by the target object received by the receiver.

Another aspect of the present invention provides a TOF ranging system including: an illuminator, a receiver, a controller, and an external driving circuit;

An illuminator for emitting an optical signal;

a receiver for receiving an optical signal reflected by the target object;

The controller is configured to determine a distance between the target object and the ranging system according to an optical signal emitted by the illuminator and an optical signal received by the receiver and reflected by the target object;

The external driving circuit is configured to increase an output power of the illuminator.

Another aspect of the present invention provides a mobile platform, comprising: the TOF ranging system described in any of the above.

The TOF ranging system and the movable platform provided in this embodiment, by providing an optical system in the TOF ranging system, the optical system includes at least one of a first optical signal processing device and a second optical signal processing device, so that the TOF measurement The optical signal emitted from the illuminator in the system passes through the first optical signal processing device, and/or the receiver in the TOF ranging system receives the optical signal reflected by the target object through the second optical signal processing device, the first optical signal processing The device can increase the radiation power density of the light signal emitted by the illuminator, and the second light signal processing device can increase the intensity of the light signal reflected by the target object received by the receiver, by increasing the radiation power density of the light signal emitted by the illuminator, and/ Or improve the optical signal intensity reflected by the target object received by the receiver, which can improve the signal-to-noise ratio of the TOF ranging system, so that the TOF ranging system can detect the target object far from the TOF ranging system, thereby improving the TOF measurement. The range of ranging from the system.

DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments will be briefly described below. It is obvious that the drawings in the following description are the present invention. For some embodiments, other drawings may be obtained from those of ordinary skill in the art in light of the inventive workability.

1 is a structural diagram of a TOF ranging system according to an embodiment of the present invention;

2 is a schematic diagram of a light signal emitted by an illuminator in the prior art;

3 is a structural diagram of a TOF ranging system according to an embodiment of the present invention;

4 is a structural diagram of a TOF ranging system according to an embodiment of the present invention;

FIG. 5 is a structural diagram of a TOF ranging system according to an embodiment of the present invention; FIG.

FIG. 6 is a structural diagram of a TOF ranging system according to an embodiment of the present invention; FIG.

FIG. 7 is a structural diagram of a TOF ranging system according to an embodiment of the present invention; FIG.

8 is a schematic diagram of a receiver receiving an optical signal in the prior art;

FIG. 9 is a structural diagram of a TOF ranging system according to an embodiment of the present invention; FIG.

FIG. 10 is a structural diagram of a TOF ranging system according to an embodiment of the present invention; FIG.

11 is a structural diagram of a TOF ranging system according to an embodiment of the present invention;

FIG. 12 is a structural diagram of a TOF ranging system according to an embodiment of the present invention; FIG.

FIG. 13 is a structural diagram of a TOF ranging system according to an embodiment of the present invention; FIG.

14 is a structural diagram of a TOF ranging system in the prior art;

15 is a structural diagram of a TOF ranging system according to an embodiment of the present invention;

16 is a diagram showing relationship between driving current and luminous intensity of an illuminator according to an embodiment of the present invention;

FIG. 17 is a structural diagram of a TOF ranging system according to another embodiment of the present invention; FIG.

FIG. 18 is a structural diagram of an unmanned aerial vehicle according to an embodiment of the present invention.

Reference mark:

11-emitter 12-receiver 13-controller

14-Optical system 15-target object 141-First optical signal processing device

142-second optical signal processing device 21-light emitting diode

22-plane 31-first converging lens 41-mirror

51-first aperture 91-second convergence lens 92-filter

131-second aperture 151-drive source 152-control circuit

150-external power supply 16-external drive circuit 161-external drive power supply

162-switching element 163-resistor

17-one end of the resistor 163 connected to the switching element 162 100-unmanned aerial vehicle

107-motor 106-propeller 117-electronic governor

118-Flight Controller 108-Sensor System 110-Communication System

102-Supporting equipment 104-Photographing equipment 112-Ground station

114-Antenna 116-Electromagnetic Wave 119-TOF Ranging System

detailed description

The technical solutions in the embodiments of the present invention will be clearly described with reference to the accompanying drawings in the embodiments of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

It should be noted that when a component is referred to as being "fixed" to another component, it can be directly on the other component or the component can be present. When a component is considered to "connect" another component, it can be directly connected to another component or possibly a central component.

All 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, unless otherwise defined. The terminology used in the description of the present invention is for the purpose of describing particular embodiments and is not intended to limit the invention. The term "and/or" used herein includes any and all combinations of one or more of the associated listed items.

Some embodiments of the present invention are described in detail below with reference to the accompanying drawings. The features of the embodiments and examples described below can be combined with each other without conflict.

Embodiments of the present invention provide a TOF ranging system. FIG. 1 is a structural diagram of a TOF ranging system according to an embodiment of the present invention. As shown in FIG. 1, the TOF ranging system includes an illuminator 11, a receiver 12, a controller 13, and an optical system 14, and the optical system 14 includes at least one of the first optical signal processing device 141 and the second optical signal processing device 142. In the present embodiment, the optical system 14 includes a first optical signal processing device 141 and a second optical signal processing device 142. In other embodiments, the optical system 14 includes a first optical signal processing device 141 and a second optical Signal processing Any one of the devices 142.

The TOF ranging system provided in this embodiment may be disposed on a movable platform, and the movable platform includes at least one of the following: an unmanned aerial vehicle, a movable robot, and a vehicle. The TOF ranging system is configured to detect a target object around the movable platform, and the target object may be an obstacle or an object of interest, and the TOF ranging system is specifically configured to detect a distance between the target object and the TOF ranging system, And determining the distance between the target object and the movable platform according to the distance between the target object and the TOF ranging system.

The illuminator 11 is used to emit an optical signal. Specifically, the illuminator 11 can be a Light Emitting Diode (LED) or a Laser Diode (LD). When the light signal emitted by the illuminator 11 illuminates the target object around the movable platform, the target object returns a reflected light signal to the TOF ranging system, and the receiver 12 in the TOF ranging system is configured to receive the light signal reflected by the target object. Optionally, the receiver 12 includes a photosensitive element, and the photosensitive element includes at least one of the following: a photodiode, an avalanche photodiode, and a charge coupled device.

As shown in FIG. 1, the controller 13 is connected to the illuminator 11 and the receiver 12, respectively, and the controller 13 determines the target based on the optical signal emitted by the illuminator 11 and the optical signal reflected by the target object 15 received by the receiver 12. The distance between the object 15 and the TOF ranging system. Specifically, the controller 13 is configured to determine a phase difference between the optical signal emitted by the illuminator 11 and the optical signal reflected by the target 12 received by the receiver 12, and determine the target object 15 and the TOF ranging according to the phase difference. The distance between the systems.

In the present embodiment, the optical signal emitted by the illuminator 11 is directed to the target object 15 via the first optical signal processing device 141, and the first optical signal processing device 141 functions to increase the radiant power of the optical signal emitted by the illuminator 11. Density, optionally, the first optical signal processing device 141 has a function of concentrating optical signals, that is, the first optical signal processing device 141 can concentrate the optical signals emitted by the illuminator 11 to reduce the optical signal emitted by the illuminator 11. The divergence angle increases the radiation power density of the optical signal emitted by the illuminator 11.

For example, as shown in FIG. 2, the illuminator 11 is a light-emitting diode 21, which is usually a divergent light source, and the light signal emitted by the LED is a diverging light beam. In the absence of the first optical signal processing device 141, assuming that the luminous power of the LED is P, the divergence angle of the optical signal emitted by the LED is θ, on a plane 22 that is d from the LED, perpendicular to the optical axis of the LED. , The radius of the spot formed by the beam projection of the LED is r, and r is determined according to the following formula (1):

r=d tan(θ) (1)

In addition, the radiation power density E of the optical signal emitted by the LED is determined according to the following formula (2):

In order to increase the radiant power density E of the optical signal emitted by the LED, the first optical signal processing device 141 is disposed in front of the LED such that the optical signal emitted by the LED passes through the first optical signal processing device 141 to the plane 22, the first light. The signal processing device 141 is capable of concentrating the optical signals emitted by the LEDs. In the case where the illuminating power P of the LEDs is constant, the first optical signal processing device 141 can reduce the divergence angle θ of the optical signals emitted by the LEDs to increase the The radiant power density E of the optical signal emitted by the LED.

In addition, after the optical signal emitted by the illuminator 11 is directed to the target object 15 by the first optical signal processing device 141, the target object 15 returns a reflected optical signal to the TOF ranging system, and the optical signal reflected by the target object 15 is received by the optical system 14. The second optical signal processing device 142 receives, and the optical signal reflected by the target object 15 is received by the receiver 12 after passing through the second optical signal processing device 142, and the receiver 12 transmits the optical signal reflected by the target object 15 to the controller 13, and controls The device 13 determines the distance between the target object 15 and the TOF ranging system based on the optical signal emitted by the illuminator 11 and the optical signal received by the receiver 12 and reflected by the target object 15. The second optical signal processing device 142 functions to increase the intensity of the optical signal reflected by the target object 15 received by the receiver 12. Optionally, the second optical signal processing device 142 can aggregate the optical signals reflected by the target object 15 so that more optical signals in the optical signal reflected by the target object 15 can be received by the receiver 12, thereby improving the receiver. 12 Received light signal intensity reflected by the target object 15.

Optionally, the target object 15 is an obstacle, and the optical signal reflected by the obstacle is a reflected beam, and the reflection of the obstacle on the optical signal can be regarded as a Lambertian reflection, and the reflected beam of the obstacle is distributed within a solid angle of π, If the second optical signal processing device 142 is not provided, only a small portion of the reflected light beam of the obstacle is received by the receiver 12. In this embodiment, the second optical signal processing device 142 is disposed in front of the receiver 12. The second optical signal processing device 142 is capable of concentrating the reflected beam of the obstacle so that more reflected beams of the reflected beam of the obstacle are received by the receiver 12, thereby improving the reflection of the obstacle received by the receiver 12. Optical signal strength.

The TOF ranging system provided by the embodiment provides an optical system in the TOF ranging system, the optical system including at least one of the first optical signal processing device and the second optical signal processing device, such that the TOF ranging system The optical signal emitted by the illuminator passes through the first optical signal processing device, and/or the receiver in the TOF ranging system receives the optical signal reflected by the target object through the second optical signal processing device, and the first optical signal processing device can improve the illuminating The radiant power density of the optical signal emitted by the device, the second optical signal processing device capable of increasing the intensity of the optical signal reflected by the target object received by the receiver, by increasing the radiant power density of the optical signal emitted by the illuminator, and/or by increasing the receiver The received optical signal intensity reflected by the target object can improve the signal-to-noise ratio of the TOF ranging system, so that the TOF ranging system can detect the target object far from the TOF ranging system, thereby improving the measurement of the TOF ranging system. Distance range.

Embodiments of the present invention provide a TOF ranging system. 3 is a structural diagram of a TOF ranging system according to an embodiment of the present invention; FIG. 4 is a structural diagram of a TOF ranging system according to an embodiment of the present invention; and FIG. 5 is a structural diagram of a TOF ranging system according to an embodiment of the present invention; FIG. 6 is a structural diagram of a TOF ranging system according to an embodiment of the present invention; FIG. 7 is a structural diagram of a TOF ranging system according to an embodiment of the present invention.

In the present embodiment, the first optical signal processing device 141 in the embodiment shown in FIG. 1 includes at least one of a first converging lens, a mirror, and a first aperture. As shown in FIGS. 3-7, 11 denotes an illuminator, and the illuminator 11 may be a light emitting diode or a laser diode, and 22 denotes a plane perpendicular to the optical axis of the illuminator 11, which plane may serve as a surface of the target object.

In addition, in other embodiments, the first optical signal processing device 141 may include both the first converging lens and the mirror, or the first optical signal processing device 141 may include both the first converging lens and the first aperture.

Specifically, the first optical signal processing device 141 can have the following forms:

The first:

As shown in FIG. 3, the first optical signal processing device 141 is specifically a first converging lens 31. The distance between the first converging lens 31 and the plane 22 is d. The first converging lens 31 includes at least one of the following: a plano-convex lens, Lenticular lens, lens combination. The first converging lens 31 has a function of concentrating optical signals, that is, the first converging lens 31 can converge the optical signals emitted by the illuminator 11 to The divergence angle of the optical signal emitted by the illuminator 11 is reduced. As shown in FIG. 3, after the optical signal emitted by the illuminator 11 passes through the first converging lens 31, the divergence angle of the optical signal emitted by the illuminator 11 is as shown in FIG. θ is reduced to θ1 shown in FIG. 3, and correspondingly, the radius of the spot formed by the light signal emitted from the illuminator 11 after being projected on the plane 22 after passing through the first converging lens 31 is r1, and in the case where d is large, r1 It can be approximated according to the following formula (3):

R1=d tan(θ1) (3)

As shown in FIG. 3, the radiation power density E1 of the optical signal emitted from the illuminator 11 is determined according to the following formula (4):

Comparing FIG. 2 and FIG. 3, after increasing the first converging lens 31, the radius of the spot formed by the optical signal emitted by the illuminator 11 projected on the plane 22 is reduced from r=d tan(θ) to r1=d tan(θ1). Correspondingly, the radiant power density of the optical signal emitted by the illuminator 11 is

raise to

If will

versus

The ratio of the radiation power density of the optical signal emitted by the illuminator 11 is increased by M, and M can be determined according to the following formula (5):

For example, when θ is 10 degrees, after the optical signal emitted by the illuminator 11 passes through the first converging lens 31, the divergence angle θ1 of the optical signal emitted by the illuminator 11 is reduced to 3 degrees, and the radiant power of the optical signal emitted by the illuminator 11 is obtained. Density increase

That is, E1 is 11.3 times that of E.

Further, in the present embodiment, the position of the illuminator 11 is determined in accordance with the back focus of the first converging lens 31. Alternatively, the illuminator 11 is located at the back focus of the first converging lens 31.

Second:

As shown in FIG. 4, the first optical signal processing device 141 is specifically a mirror 41. The mirror surface of the mirror 41 is a paraboloid that at least partially surrounds the illuminator 11. Generally, the light signal emitted by the light emitting diode has a large divergence angle, as shown by the solid arrows 1 and 2 shown in FIG. The angle of the emission is large. When the beams indicated by the solid arrows 1 and 2 are directed toward the paraboloid of the mirror 41, the mirror 41 reflects the beams indicated by the solid arrows 1 and 2, according to the reflection principle of the mirror surface. The light beam indicated by the line arrow 1 is reflected as the light beam 3, and the light beam indicated by the solid line arrow 2 is reflected as the light beam 4. The emission angle of the light beam 3 is smaller than the emission angle of the light beam indicated by the solid line arrow 1, and the emission angle of the light beam 4 is The angle of the light beam indicated by the line arrow 2 is small. It can be seen that the mirror 41 has the function of concentrating the light signal, that is, the mirror 41 can converge the light signal emitted by the illuminator 11 to reduce the light signal emitted by the illuminator 11. The divergence angle similarly increases the radiation power density of the optical signal emitted by the illuminator 11.

Further, in the present embodiment, the curvature of the paraboloid of the mirror 41 is determined according to at least one of the following parameters: the size of the illuminator 11, and the energy distribution of the optical signal emitted by the illuminator 11.

The third type:

As shown in FIG. 5, the first optical signal processing device 141 is specifically a first aperture 51. The first aperture 51 is at least partially disposed around the illuminator 11, and the axis of the aperture of the first aperture 51 is The optical axes of the illuminators 11 are parallel. The light beam indicated by the solid arrow shown in FIG. 5 is blocked by the inner wall of the first aperture 51 after being directed toward the first aperture 51, and cannot pass through the aperture of the first aperture 51, as compared with FIG. The light signal emitted by the illuminator 11 projects the radius of the spot formed on the plane 22. It can be seen that the first aperture 51 also has the function of concentrating the optical signal, that is, the first aperture 51 can also converge the optical signal emitted by the illuminator 11 to reduce the divergence angle of the optical signal emitted by the illuminator 11, and the same reason. The radiation power density of the optical signal emitted by the illuminator 11 is increased. Specifically, the first aperture 51 may be a sleeve, and the sleeve may have a circular shape, a rectangular shape, a square shape, or the like.

In addition, the divergence angle of the light signal emitted by the illuminator 11 after passing through the first aperture 51 is determined according to at least one of the following parameters: the length of the first aperture 51, the aperture of the aperture of the first aperture 51, and the first light. The position of the crucible 51 relative to the illuminator 11. Further, the size of the first aperture 51 can also be determined according to the size of the illuminator 11.

Fourth:

As shown in FIG. 6, the first optical signal processing device 141 includes a first converging lens 31 and a mirror 41. As shown in FIG. 3, for example, the illuminator 11 is a light-emitting diode. Generally, the light signal emitted by the light-emitting diode has a large divergence angle. As shown in FIG. 3, some of the light signals emitted by the illuminator 11 cannot be emitted. The first converging lens 31, for example, a light beam indicated by an arrow a and an arrow b, has a large angle of emission and cannot be directed toward the first converging lens 31, so that the light emitted by the illuminator 11 The signal cannot be effectively utilized, resulting in a decrease in the utilization efficiency of the illuminating power of the illuminator 11, and at the same time, the efficiency of the first concentrating lens 31 concentrating the optical signal emitted by the illuminator 11 is lowered. To solve the problem, as shown in FIG. On the basis of Fig. 3, a mirror 41 is added, and the mirror 41 in Fig. 6 coincides with the mirror 41 shown in Fig. 4. For example, the light beams indicated by the arrow a and the arrow b in FIG. 3 cannot be directed toward the first converging lens 31, and after the beam indicated by the arrow a and the arrow b in FIG. 6 is directed toward the paraboloid of the mirror 41, the mirror 41 is opposed. The light beams indicated by the arrows a and b are reflected, and the light beams reflected by the mirror 41 can be directed to the first converging lens 31, that is, the mirror 41 can reflect the large-angle beam emitted by the illuminator 11 into a small-angle beam. In order to enable more light beams to be emitted from the illuminator 11 to the first concentrating lens 31, the optical signal emitted by the illuminator 11 can be effectively utilized, thereby improving the utilization efficiency of the illuminating power of the illuminator 11. The efficiency at which the first converging lens 31 converges the optical signal emitted by the illuminator 11 is increased.

The fifth one:

As shown in FIG. 7, the first optical signal processing device 141 includes a first converging lens 31 and a first aperture 51. Since the first converging lens 31 has a function of concentrating the optical signals, that is, the first converging lens 31 can converge the optical signals emitted by the illuminators 11 to reduce the divergence angle of the optical signals emitted by the illuminators 11, as shown in FIG. On the basis of FIG. 5, a first converging lens 31 is added in front of the illuminator 11, and the optical signal emitted by the illuminator 11 is first concentrated by the first aperture 51 to reduce the optical signal emitted by the illuminator 11. The divergence angle, after the light signal emitted by the illuminator 11 passes through the first aperture 51, part of the optical signal is blocked by the inner wall of the first aperture 51, and the light aperture of the first aperture 51 cannot be emitted, and the first aperture 51 is emitted. The light signal of the light-passing hole is again incident on the first converging lens 31, and the first converging lens 31 re-converges the optical signal that emits the light-passing hole of the first aperture 51. The divergence angle of the optical signal transmitted through the first converging lens 31 in FIG. 7 is smaller than the divergence angle of the optical signal of the light-passing aperture of the first aperture 51 in FIG. 5, and therefore, the first convergent lens 31 is added. Thereafter, the divergence angle of the optical signal emitted by the illuminator 11 can be further reduced.

In the TOF ranging system provided by this embodiment, the first optical signal processing device may be at least one of a first converging lens, a mirror and a first aperture, the first converging lens, the mirror and the first aperture. Any one of the foregoing can converge the optical signal emitted by the illuminator, and provides various implementation manners for reducing the divergence angle of the optical signal emitted by the illuminator; in addition, the first optical signal processing device can also be the first converging lens And a mirror capable of reflecting a large-angle beam emitted by the illuminator into a beam of a small angle so that more of the beam emitted by the illuminator can be directed toward the first a converging lens enables the optical signal emitted by the illuminator to be effectively utilized, improving the utilization efficiency of the illuminating power of the illuminator, and improving the efficiency of the optical signal emitted by the first concentrating lens concentrating illuminator; further, the first optical signal processing The device may further be a first converging lens and a first aperture, and the optical signal emitted by the illuminator is first concentrated by the first aperture to reduce a divergence angle of the optical signal emitted by the illuminator, and the first aperture is emitted. The optical signal of the hole is again directed to the first converging lens, and the first converging lens re-converges the optical signal of the light passing through the first aperture to further reduce the divergence angle of the optical signal emitted by the illuminator, thereby further improving The radiant power density of the optical signal emitted by the illuminator.

Embodiments of the present invention provide a TOF ranging system. FIG. 9 is a structural diagram of a TOF ranging system according to an embodiment of the present invention. The embodiment shown in FIG. 3-7 improves the radiant power density of the optical signal emitted by the illuminator 11 by reducing the divergence angle of the optical signal emitted by the illuminator 11, so as to improve the signal-to-noise ratio of the TOF ranging system. The example improves the signal-to-noise ratio of the TOF ranging system by increasing the receiving aperture of the receiver 12. The receiving aperture of the receiver 12 determines the intensity of the optical signal reflected by the target object 15 received by the receiver 12, as shown in Fig. 8, 12 denotes a receiver, the receiver 12 comprises a photosensitive element, and the photosensitive element comprises at least one of the following : Photodiode, avalanche photodiode, charge coupled device. 15 denotes a target object, which may be an obstacle. The optical signal reflected by the obstacle is a reflected beam, and the reflection of the obstacle on the optical signal can be regarded as a Lambertian reflection, and the reflected beam of the obstacle is distributed in a stereoscopic shape of π. Within the corner, if the second optical signal processing device 142 is not provided, only a small portion of the reflected light beam of the obstacle is received by the receiver 12, assuming that only the solid angle of the reflected beam of the obstacle is within Ω. The beam is received by the receiver 12, the distance between the receiver 12 and the target object 15 is d, and the area of the receiver 12 is A. The relationship between Ω, d and A can be determined by the following formula (6):

Ω=A/d ² (6)

In order to increase the receiving aperture of the receiver 12, in this embodiment, a second optical signal processing device 142 is disposed in front of the receiver 12. As shown in FIG. 9, the second optical signal processing device 142 includes a second converging lens 91, and the second convergence. The lens 91 includes at least one of a plano-convex lens, a lenticular lens, and a lens combination. The second converging lens 91 is specifically configured to increase the receiving aperture of the receiver 12 to increase the intensity of the optical signal reflected by the target object 15 received by the receiver 12. Second converging lens 91 The area is A1, the focal length is f, and the area A1 of the second converging lens 91 is larger than the area A of the receiver 12, as shown in FIG. 9, in the optical signal reflected by the target object 15, which is directed to the second converging lens 91. The optical signal is focused by the second converging lens 91 on the receiver 12, that is, the optical signal in the solid angle Ω1 of the optical signal reflected by the target object 15 is received by the receiver 12, assuming the second converging lens 91 and the target object The distance between 15 is d, and the relationship between Ω1, d and A1 can be determined by the following formula (7):

Ω1=A1/d ² (7)

Since the area A1 of the second converging lens 91 is larger than the area A of the receiver 12, Ω1 is larger than Ω, and if the area A of the receiver 12 is 1 mm 2 and the area A1 of the second converging lens 91 is 100 mm 2 , Ω 1 is 100 times of Ω, the intensity of the optical signal reflected by the target object received by the receiver 12 will be increased by 100 times, that is, by adding the second converging lens 91 in front of the receiver 12, the receiving aperture of the receiver 12 can be increased, thereby improving The intensity of the optical signal reflected by the target object received by the receiver 12.

Additionally, in other embodiments, the position of the receiver 12 is determined based on the back focus of the second converging lens 91. Alternatively, the receiver 12 is located at the back focus of the second converging lens 91.

In addition, in other embodiments, the first converging lens 31 and the second converging lens 91 may be the same lens or different lenses.

The TOF ranging system provided in this embodiment provides a converging lens in front of the receiver, and the optical signal reflected by the target object is collected by the convergent lens and received by the receiver. The area of the converging lens is larger than the area of the receiver, so that the area of the converging lens is larger than that of the receiver. More optical signals reflected by the target object can be received by the receiver, which improves the receiving aperture of the receiver, thereby improving the intensity of the optical signal reflected by the target object received by the receiver, further improving the TOF ranging. The signal-to-noise ratio of the system improves the accuracy of the measurement results of the TOF ranging system.

Embodiments of the present invention provide a TOF ranging system. 11 is a structural diagram of a TOF ranging system according to an embodiment of the present invention; FIG. 12 is a structural diagram of a TOF ranging system according to an embodiment of the present invention; and FIG. 13 is a structural diagram of a TOF ranging system according to an embodiment of the present invention. .

As shown in FIG. 10, in the TOF ranging system, the receiver 12 receives the optical signal concentrated by the second converging lens 91, and also receives the background light, the background light is randomly generated, and the receiver 12 may Receiving background light in all directions, the background light will not only affect the receiver 12 The received optical signal intensity reflected by the target object, and the background light also brings a large noise, which has a great influence on the measurement result of the TOF ranging system, thereby reducing the measurement accuracy of the TOF ranging system, in order to solve For this problem, the present embodiment limits the intensity of the background light received by the receiver 12 in the following two ways, which are described in detail below:

The first:

The second optical signal processing device 142 includes a filter, as shown in FIG. 11, the filter 92 is located on the side of the second converging lens 91 near the receiver 12, or, as shown in FIG. 12, the filter 92 is located at the The side of the second converging lens 91 away from the receiver 12, as shown in FIG. 11 or 12, the filter 92 can filter out part of the background light, and let the light signal reflected by the target object 15 pass, thereby avoiding excessive background light being Received by the receiver 12 to increase the signal to noise ratio of the received optical signal.

In addition, the transmission wavelength of the filter 92 is determined according to the wavelength of the optical signal emitted from the illuminator 11. For example, the wavelength of the optical signal emitted by the illuminator 11 is 850 nm, and the transmission wavelength of the filter 92 can be set in the range of 830 nm to 870 nm.

Second:

The optical system 14 also includes a second aperture, as shown in Figure 13, with a second aperture 131 positioned between the receiver 12 and the second converging lens 91 for blocking background light in a predetermined direction. Since the background light is randomly generated, and the receiver 12 may receive the background light in each direction, the direction of the light signal reflected by the target object 15 is concentrated, as shown in FIG. 13, the light signal reflected by the target object 15 is concentrated. In the solid angle Ω1, the embodiment may block the background light of the preset direction by the second aperture 131, and the preset direction may be the direction of the light signal reflected by the target object 15, thereby avoiding excessive background light being received by the receiver. 12 received. In addition, by adjusting the size of the second aperture 131 to adjust the amount of background light blocked by the second aperture 131, the preset direction can also be adjusted by adjusting the placement angle of the second aperture 131.

In the TOF ranging system provided by this embodiment, a filter is disposed on a side of the second converging lens close to the receiver or a side of the second converging lens away from the receiver, and the filter can filter part of the background light, and Passing the optical signal reflected by the target object, thereby avoiding excessive background light being received by the receiver, improving the signal-to-noise ratio of the optical signal received by the receiver; and, by setting between the receiver and the second converging lens The second aperture, the second aperture is used to block the background light in the preset direction, and the excessive background light is also received by the receiver, thereby reducing the intensity of the light signal reflected by the background light on the receiver receiving the target object. Influence, at the same time, avoid the larger background light Noise, reducing the influence of background light on the measurement results of the TOF ranging system, further improves the accuracy of the measurement results of the TOF ranging system.

Embodiments of the present invention provide a TOF ranging system. FIG. 15 is a structural diagram of a TOF ranging system according to an embodiment of the present invention. Based on the above embodiment, the controller 13 shown in FIG. 1 can determine not only the target object 15 and the TOF measurement based on the optical signal emitted by the illuminator 11 and the optical signal reflected by the target object 15 received by the receiver 12. The distance from the system can also drive the illuminator 11 to emit a modulated optical signal at a predetermined period, while the controller 13 can also control the intensity of the optical signal emitted by the illuminator 11. As shown in FIG. 14, the controller 13 is internally provided with a driving circuit. The driving circuit built in the controller 13 includes a driving source 151 and a control circuit 152. The driving source 151 is connected with an external power source 150, and the external power source 150 provides a constant voltage to drive the driving source. 151, so that the driving source 151 can be used as a constant current source, where the constant current source refers to a current having a maximum current of a fixed value, for example, 200 mA, and a minimum current of 0, and the control circuit 152 can include a register inside the controller 13. The register can perform pulse width modulation (PWM) on the constant current source, so that the current flowing to the illuminator 11 is a pulse current. Specifically, the control circuit 152 can control the start time of the PWM waveform and continue. Time, duty cycle and other parameters. The pulse current controlled by the control circuit 152 flows to the illuminator 11, and the illuminator 11 emits an optical signal when the pulse current is at a high level, and the illuminator 11 does not emit an optical signal when the pulse current is at a low level, that is, the controller 13 The illuminator 11 is controlled to perform switching modulation illumination. Since the highest current of the constant current source is fixed, the improvement cannot be continued, and the optical power output from the illuminator 11 as shown in FIG. 14 is fixed, and higher optical power cannot be output. The illuminator 11 can be a Light Emitting Diode (LED) or a Laser Diode (LD).

In view of the above problem, the present embodiment improves the circuit as shown in FIG. 14, as shown in FIG. 15, on the basis of FIG. 14, the TOF ranging system further includes: an external driving circuit 16, an external driving circuit 16 and control. The illuminator 13 and the illuminator 11 are respectively connected for increasing the output power of the illuminator 11. Specifically, the external driving circuit 16 includes an external driving power source 161 for driving the illuminator 11, the external driving power source 161 provides a voltage greater than the voltage supplied from the external power source 150, and the controller 13 outputs a control signal I, the control signal I is the pulse current flowing to the illuminator 11 in FIG. 14, and unlike FIG. 14, the control signal I does not directly control the illuminating. The device 11 controls the external drive circuit 16.

As shown in FIG. 15, the external driving circuit 16 includes a switching element 162, and the illuminator 11 is connected to the switching element 162. The control signal I outputted by the controller 13 controls the switching element 162 when the control signal I output from the controller 13 is at a high level. The switching element 162 is turned on. When the control signal I outputted by the controller 13 is low level, the switching element 162 is turned off, that is, when the control signal I outputted by the controller 13 is at a high level, the external driving circuit 16 is turned on when controlling When the control signal I outputted by the device 13 is at a low level, the external drive circuit 16 is turned off, thereby realizing control of the external drive circuit 16 by the control signal I output from the controller 13. In the present embodiment, the switching element 162 includes at least one of a metal oxide semiconductor field effect transistor, a triode, and a device for amplitude modulating the illumination of the illuminator. Optionally, the switching element 162 is a Metal Oxide Semi-Conductor Field Effect Transistor (MOS FET).

In addition, the external driving circuit 16 further includes a resistor 163, and the resistor 163 is connected to the switching element 162. Controlling the switching element 162 by the control signal I to implement the control of the external driving circuit 16 includes: the control signal I is loaded in the resistor 163 and connected to the switching element 162. One end 17, the control signal I is used to control the opening or closing of the switching element 162 to effect control of the external drive circuit 16. Specifically, after the control signal I, that is, the pulse current I outputted by the controller 13 flows through the resistor 163, a partial pressure U is formed on the resistor 163, and the relationship between the divided voltage U, the pulse current I, and the resistance R of the resistor 163 is as follows: Equation (8) determines:

U=I*R (8)

When the pulse current I outputted by the controller 13 is at a high level, the divided voltage U is greater than the turn-on voltage of the MOS FET, causing the MOS FET to be turned on, at which time the external driving circuit 16 is turned on, and the illuminator 11 is externally driven by the power source 161. Drives to illuminate.

When the pulse current I outputted by the controller 13 is at a low level, the divided voltage U formed on the resistor 163 by the pulse current I is smaller than the turn-on voltage of the MOS FET, and the MOS FET is not turned on, and the external driving circuit 16 is not turned on at this time. The illuminator 11 does not emit light, that is, the pulse current I outputted by the controller 13 controls the external drive circuit 16 by controlling the opening or closing of the switching element 162, thereby causing the illuminator 11 to be switched under the driving of the external driving power source 161. Modulate illumination. Since the voltage supplied from the external driving power source 161 is greater than the voltage supplied from the external power source 150, the illuminator 11 can output higher optical power under the driving of the external driving power source 161, thereby improving the receiver 12. The signal-to-noise ratio of the received optical signal improves the power of the optical signal received by the receiver 12, so that the ranging range of the TOF ranging system is larger and the measurement result is more accurate.

In addition, in other embodiments, the magnitude of the voltage provided by the external driving power source 161 can be adjusted according to the volt-ampere characteristics of the illuminator 11 to achieve the maximum output power of the illuminator 11 and is not driven by the driving circuit provided inside the controller 13. The impact of driving capabilities.

As shown in Fig. 16, the horizontal axis represents the magnitude of the driving current I flowing through the illuminator 11, and the vertical axis represents the ratio of the illuminating intensity of the illuminator 11 driven by the driving current I and Ie, where Ie indicates that the illuminator 11 is The nominal luminous power at 100 mA. For example, the maximum current of the pulse current I outputted by the controller 13 is fixed at 200 mA. In FIG. 14, the maximum value of the pulse current I flowing through the illuminator 11 is 200 mA. According to FIG. 16, when the driving current I is 200 mA, The luminous intensity of the illuminator 11 is twice the Ie. As shown in FIG. 15, the voltage supplied from the external driving power supply 161 is fixed at 2.4 V, and the driving current through the illuminator 11 is 1 A. According to FIG. 16, when the driving current I is 1 A, the luminous intensity of the illuminator 11 is 7 times. The Ie is equivalent to a 3.5-fold increase in the luminous power of the illuminator 11.

The TOF ranging system provided in this embodiment increases the output power of the illuminator by using an external power source to drive the power source by adding an external driving circuit to the TOF ranging system. Specifically, the external driving circuit includes an external driving power source. And the switching element, the external driving power source drives the illuminator, and the control signal outputted by the controller does not directly control the illuminator, but controls the opening or closing of the switching element to realize the control of the external driving circuit, so that the illuminator is externally driven The switch modulates the illumination under the driving of the power source, and the voltage driven by the external driving power source drives the illuminator to output an optical signal with higher optical power, thereby improving the signal-to-noise ratio of the optical signal received by the receiver, and improving the optical signal received by the receiver. The optical power makes the TOF ranging system have a larger range of measurement and more accurate measurement results.

Embodiments of the present invention provide a TOF ranging system. FIG. 17 is a structural diagram of a TOF ranging system according to another embodiment of the present invention. As shown in FIG. 17, the TOF ranging system includes an illuminator 11, a receiver 12, a controller 13, and an external driving circuit 16, the illuminator 11 is for emitting an optical signal, and the receiver 12 is for receiving an optical signal reflected by the target object. The controller 13 is configured to determine a distance between the target object and the TOF ranging system according to the optical signal emitted by the illuminator 11 and the optical signal reflected by the target 12 received by the receiver 12; the external driving circuit 16 is configured to increase Illuminate The output power of the device 11.

As shown in FIG. 15, the external drive circuit 16 includes an external drive power source 161 for driving the illuminator 11. The controller 13 is connected to an external drive circuit 16, which is also used to output a control signal to control the external drive circuit 16.

The external drive circuit 16 includes a switching element 162, and the illuminator 11 is coupled to the switching element 162. The controller 13 is specifically configured to output a control signal, and the switching element 162 is controlled by the control signal to effect control of the external driving circuit 16.

In addition, the external driving circuit 16 further includes a resistor 163, and the resistor 163 is connected to the switching element 162. Controlling the switching element 162 by the control signal to realize the control of the external driving circuit 16 includes: the control signal is loaded at the end of the connection between the resistor 163 and the switching element 162. Control of the external drive circuit 16 is accomplished using control signals to control the opening or closing of the switching element 162.

Optionally, the switching element 162 includes at least one of a metal oxide semiconductor field effect transistor, a triode, and a device for amplitude modulating the illumination of the illuminator.

The controller 13 is specifically configured to determine a phase difference between an optical signal emitted by the illuminator 11 and an optical signal reflected by the target object received by the receiver 12, and determine, between the target object and the ranging system, according to the phase difference. distance.

The specific principles and implementation manners of the external driving circuit 16 provided by the embodiment of the present invention are similar to the embodiment shown in FIG. 15 and will not be further described herein.

The embodiment of the invention provides a mobile platform, which comprises the TOF ranging system described in the above embodiments. The mobile platform includes an unmanned aerial vehicle.

Embodiments of the present invention provide an unmanned aerial vehicle. FIG. 18 is a structural diagram of an unmanned aerial vehicle according to an embodiment of the present invention. As shown in FIG. 18, the unmanned aerial vehicle 100 includes: a fuselage, a power system, and a control device 118. The power system includes at least one of the following: a motor 107. A propeller 106 and an electronic governor 117 are mounted to the fuselage for providing flight power; the control device 118 may specifically be a flight controller.

In addition, as shown in FIG. 18, the unmanned aerial vehicle 100 further includes: a sensing system 108, a communication system 110, a supporting device 102, a photographing device 104, and a TOF ranging system 119, wherein the sensing system is configured to detect the unmanned Aircraft speed, acceleration, attitude parameters (pitch angle, roll angle, The yaw angle, etc.) or the attitude parameters of the pan/tilt (pitch angle, roll angle, yaw angle, etc.), etc., the support device 102 may specifically be a pan/tilt, and the communication system 110 may specifically include a receiver and/or a transmitter, and receive The machine is configured to receive wireless signals transmitted by the antenna 114 of the ground station 112. The communication system 110 can also transmit wireless signals (e.g., image information, status information of the unmanned aerial vehicle, etc.) to the ground station, 116 indicating the communication process of the communication system 110 and the antenna 114. Electromagnetic waves generated in.

The specific principles and implementations of the TOF ranging system 119 provided by the embodiments of the present invention are similar to the TOF ranging system of the foregoing embodiment, and are not described herein again.

In the several embodiments provided by the present invention, it should be understood that the disclosed apparatus and method may be implemented in other manners. For example, the device embodiments described above are merely illustrative. For example, the division of the unit is only a logical function division. In actual implementation, there may be another division manner, for example, multiple units or components may be combined or Can be integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some interface, device or unit, and may be in an electrical, mechanical or other form.

The units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, may be located in one place, or may be distributed to multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above integrated unit can be implemented in the form of hardware or in the form of hardware plus software functional units.

The above-described integrated unit implemented in the form of a software functional unit can be stored in a computer readable storage medium. The above software functional unit is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) or a processor to perform the methods of the various embodiments of the present invention. Part of the steps. The foregoing storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk, and the like, which can store program codes. .

A person skilled in the art can clearly understand that for the convenience and brevity of the description, only the division of each functional module described above is exemplified. In practical applications, the above function assignment can be completed by different functional modules as needed, that is, the device is installed. The internal structure is divided into different functional modules to perform all or part of the functions described above. For the specific working process of the device described above, refer to the corresponding process in the foregoing method embodiment, and details are not described herein again.

Finally, it should be noted that the above embodiments are merely illustrative of the technical solutions of the present invention, and are not intended to be limiting; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art will understand that The technical solutions described in the foregoing embodiments may be modified, or some or all of the technical features may be equivalently replaced; and the modifications or substitutions do not deviate from the technical solutions of the embodiments of the present invention. range.

Claims (32)

1. A TOF ranging system includes: an illuminator, a receiver, a controller, and an optical system, wherein

   An illuminator for emitting an optical signal;

   a receiver for receiving an optical signal reflected by the target object;

   The controller is configured to determine a distance between the target object and the ranging system according to an optical signal emitted by the illuminator and an optical signal received by the receiver and reflected by the target object;

   The optical system includes at least one of the following:

   a first optical signal processing device, wherein an optical signal emitted by the illuminator passes through the first optical signal processing device to increase a radiation power density of an optical signal emitted by the illuminator;

   The second optical signal processing device passes the optical signal reflected by the target object through the second optical signal processing device to increase the intensity of the optical signal reflected by the target object received by the receiver.
2. The system according to claim 1, wherein said first optical signal processing device is specifically configured to reduce a divergence angle of an optical signal emitted by said illuminator to increase an optical signal emitted by said illuminator Radiated power density.
3. A system according to claim 1 or 2, wherein said first optical signal processing means comprises at least one of a first converging lens, a mirror and a first aperture.
4. The system of claim 3 wherein the position of the illuminator is determined based on a back focus of the first concentrating lens.
5. The system of claim 4 wherein said illuminator is located at a back focus of said first concentrating lens.
6. A system according to any one of claims 3-5, wherein the mirror of the mirror is a paraboloid, the paraboloid at least partially surrounding the illuminator.
7. The system of claim 6 wherein the curvature of the paraboloid is determined based on at least one of the following parameters:

   The size of the illuminator, the energy distribution of the optical signal emitted by the illuminator.
8. The system according to any one of claims 3-7, wherein the first aperture is at least partially disposed around the illuminator, and an axis of the aperture of the first aperture is The optical axes of the illuminators are parallel.
9. The system according to any one of claims 1-8, wherein the second optical signal processing device comprises a second converging lens, and the second converging lens is specifically configured to increase a receiving aperture of the receiver, To increase the intensity of the optical signal reflected by the target object received by the receiver.
10. The system of claim 9 wherein the position of the receiver is determined based on a back focus of the second concentrating lens.
11. The system of claim 10 wherein said receiver is located at a rear focus of said second converging lens.
12. A system according to any one of claims 9-11, wherein the area of the second converging lens is larger than the area of the receiver.
13. A system according to any one of claims 9 to 12, wherein said second optical signal processing device further comprises a filter, said filter being located adjacent said receiver of said second converging lens One side or a side remote from the receiver is used to filter out background light.
14. The system of claim 13 wherein the transmission wavelength of the filter is determined based on a wavelength of an optical signal emitted by the illuminator.
15. A system according to any one of claims 9-14, wherein said second The optical signal processing apparatus further includes a second aperture between the receiver and the second converging lens for blocking background light in a predetermined direction.
16. The system according to claim 3 or 9, wherein the converging lens comprises at least one of the following:

    Plano-convex lens, lenticular lens, lens combination.
17. A system according to any one of claims 1 to 16, further comprising: an external drive circuit;

    Wherein, an external driving circuit is connected to the controller and the illuminator for increasing the output power of the illuminator.
18. The system of claim 17 wherein said external drive circuit comprises an external drive power source;

    The external driving power source is for driving the illuminator.
19. The system according to claim 17 or 18, wherein said controller is further configured to output a control signal to control said external drive circuit.
20. The system according to claim 19, wherein said external drive circuit comprises a switching element, said illuminator being coupled to said switching element;

    The controller is specifically configured to output a control signal, and the control element is used to control the switching element to implement control of the external driving circuit.
21. The system according to claim 20, wherein said external drive circuit further comprises a resistor, said resistor being coupled to said switching element;

    The controlling the switching element by the control signal to implement control of the external driving circuit comprises:

    The control signal is loaded at one end of the resistor connected to the switching element, and the control signal is used to control the opening or closing of the switching element to implement the external driving circuit. control.
22. A system according to claim 20 or 21, wherein said switching element comprises at least one of the following:

    A metal oxide semiconductor field effect transistor, a triode, a device for amplitude modulating the illumination of the illuminator.
23. The system according to any one of claims 1 to 2, wherein the controller is specifically configured to determine a phase difference between an optical signal emitted by the illuminator and an optical signal reflected by a target object received by the receiver Determining a distance between the target object and the ranging system based on the phase difference.
24. A TOF ranging system includes: an illuminator, a receiver, a controller, and an external driving circuit, wherein

    An illuminator for emitting an optical signal;

    a receiver for receiving an optical signal reflected by the target object;

    The controller is configured to determine a distance between the target object and the ranging system according to an optical signal emitted by the illuminator and an optical signal received by the receiver and reflected by the target object;

    The external driving circuit is configured to increase an output power of the illuminator.
25. The system of claim 24 wherein said external drive circuit comprises an external drive power source;

    The external driving power source is for driving the illuminator.
26. The system according to claim 24 or 25, wherein said controller is further configured to output a control signal to control said external drive circuit.
27. The system according to claim 26, wherein said external drive circuit comprises a switching element, said illuminator being coupled to said switching element;

    The controller is specifically configured to output a control signal, and the control element is used to control the switching element to implement control of the external driving circuit.
28. The system according to claim 27, wherein said external drive circuit further comprises a resistor, said resistor being coupled to said switching element;

    The controlling the switching element by the control signal to implement control of the external driving circuit comprises:

    The control signal is loaded at one end of the resistor connected to the switching element, and the control signal is used to control the opening or closing of the switching element to implement control of the external driving circuit.
29. A system according to claim 27 or 28, wherein said switching element comprises at least one of the following:

    A metal oxide semiconductor field effect transistor, a triode, a device for amplitude modulating the illumination of the illuminator.
30. The system according to any one of claims 24 to 29, wherein the controller is specifically configured to determine a phase difference between an optical signal emitted by the illuminator and an optical signal reflected by a target object received by the receiver Determining a distance between the target object and the ranging system based on the phase difference.
31. A movable platform, comprising: the TOF ranging system according to any one of claims 1 to 23, or the TOF ranging system according to any one of claims 24-30.
32. The mobile platform of claim 31 wherein said movable platform comprises an unmanned aerial vehicle.

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