CN220419998U - Passenger flow statistics ware and passenger flow statistics system based on dTOF sensor - Google Patents

Abstract

Disclosed are a traffic statistics device and a traffic statistics system based on dTOF sensors. The passenger flow statistics device comprises: the light source module is used for projecting invisible light to the tested space; a direct time-of-flight dtif sensor that generates a sensing signal characterizing a distance based on a time of receipt of return light for the projected invisible light; the controller is used for controlling the operation of the light source module and the dTOF sensor, performing head-shoulder detection based on the induction signal and generating a passenger flow count value according to the head-shoulder detection result; and a base for fixing the light source module, the dTOF sensor, and the controller. The utility model can be used in strong natural light scenes such as outdoors by arranging the dTOF sensor with high sensitivity to reflection light and large imaging area, and reduces false detection rate by head-shoulder detection for induction information.

Description

Passenger flow statistics ware and passenger flow statistics system based on dTOF sensor

Technical Field

The utility model relates to the field of digital image processing, in particular to a dTOF-based passenger flow statistics device and a passenger flow statistics system.

Background

The development of visualization technology and computer technology has been continuous, and instant, reliable traffic information has become possible. For shopping places such as shopping malls and supermarkets, public transportation systems such as railways, subways and buses, and public places such as exhibition halls, stadiums, libraries and airports with high public safety requirements, the importance of real-time and accurate passenger flow information is self-evident.

The traditional people counting method has the problems that manual counting or electronic equipment triggering counting is wasteful of manpower and low in efficiency, and the electronic equipment triggering counting cannot cope with the situation that the crowds are mutually blocked and overlapped. With the development and popularization of the stereoscopic vision technology, automatic passenger flow counting equipment based on stereoscopic vision has also been developed, but the equipment needs a large amount of computation for image matching, and has the problems of limited application scene, easy false detection and the like.

Disclosure of Invention

One technical problem to be solved by the present disclosure is to provide a passenger flow statistics device and a passenger flow statistics system based on a dtif sensor. The utility model can be used in strong natural light scenes such as outdoors by arranging the dTOF sensor with high sensitivity to reflection light and large imaging area, and reduces false detection rate by head-shoulder detection for induction information.

According to a first aspect of the present disclosure, there is provided a dtif sensor-based passenger flow statistics apparatus comprising: the light source module is used for projecting invisible light to the tested space; a direct time-of-flight dtif sensor that generates a sensing signal characterizing a distance based on a time of receipt of return light for the projected invisible light; the controller is used for controlling the operation of the light source module and the dTOF sensor, performing head-shoulder detection based on the induction signal and generating a passenger flow count value according to the head-shoulder detection result; and a base for fixing the light source module, the dTOF sensor, and the controller.

Optionally, the dtofs sensor comprises: an area array sensor composed of a plurality of avalanche photosensors is used.

Optionally, the light source module includes: a light emitting device for generating a laser beam; and a diffusion sheet disposed on a propagation path of the light beam to convert the laser beam into area array light.

Optionally, the light emitting device includes: a Laser Diode (LD); a Vertical Cavity Surface Emitting Laser (VCSEL); or a Light Emitting Diode (LED).

Optionally, the dtofs sensor is arranged such that the sensing area coincides at least partially with the projection area of the area array light of the light source module.

Optionally, the dtofs sensor is disposed separately from the light source module, and optical axes of the dtofs sensor and the light source module do not coincide.

Optionally, the base comprises a connection structure for fixing the traffic statistics downward on the traffic statistics path.

Optionally, the passenger flow statistics device further comprises: a single case for surrounding the surface light source module, the dtif sensor, the controller, and the base; and/or a reserve surface light source module detachably connected.

Optionally, the passenger flow counter further comprises a communication mechanism for sending the passenger flow count value to the outside and receiving a zero clearing operation.

According to a second aspect of the present disclosure, there is provided a passenger flow statistics system comprising: a plurality of traffic statistics machines according to the first aspect mounted on traffic statistics paths, each of the traffic statistics machines imaging a measured space that is at least partially non-overlapping with each other; and the calibration device is used for calibrating the tested space among the plurality of passenger flow statistics devices.

Optionally, the system further comprises: one or more doors defining a passenger flow path and one or more of said passenger flow counters mounted on the cross beam of each door.

Thus, the present utility model can be used in strong natural light scenes such as outdoors and the like by arranging a dtoh sensor having high sensitivity to reflection light and a large imaging area, and reduces the false detection rate by head-shoulder detection for the sensing information.

Drawings

The foregoing and other objects, features and advantages of the disclosure will be apparent from the following more particular descriptions of exemplary embodiments of the disclosure as illustrated in the accompanying drawings wherein like reference numbers generally represent like parts throughout exemplary embodiments of the disclosure.

FIG. 1 illustrates a schematic diagram of the use of a dTOF sensor-based passenger flow statistics device in accordance with one embodiment of the present utility model.

Fig. 2 shows a schematic composition of a dtif sensor based passenger flow statistic according to one embodiment of the disclosure.

Fig. 3 shows a schematic diagram of head-shoulder detection.

Fig. 4 shows a schematic diagram of the use of a passenger flow statistics system according to an embodiment of the utility model.

Detailed Description

Preferred embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While the preferred embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

FIG. 1 illustrates a schematic diagram of the use of a dTOF sensor-based passenger flow statistics device in accordance with one embodiment of the present utility model. The passenger flow statistics device comprises a camera part for actively projecting invisible light and acquiring corresponding reflected light, and a processing output part for performing data processing and output. Fig. 2 shows a schematic composition of a dtif sensor based passenger flow statistic according to one embodiment of the disclosure. The light source module and dtif sensor comprised by the camera part are shown in particular in fig. 2.

The composition of the dtif sensor-based traffic statistics of the present utility model and its use will be described in detail below in conjunction with fig. 1 and 2.

In the present utility model, for convenience of description, a horizontal plane may be defined as an xy plane, in which a direction parallel to a door is an x direction, a direction perpendicular to the door (i.e., a direction in which passenger flows enter or leave) is a y direction, and a vertical direction is defined as a z direction.

First, as shown in fig. 1, the traffic statistics device 1 of the present disclosure is a device for actively projecting light to a space to be measured, and performing traffic statistics based on reflected light of the projected light.

The passenger flow statistics 1 shown in fig. 1 is shown in fig. 2 as a device 200. Fig. 2 highlights the projection and imaging part comprised by the traffic statistics. As shown in fig. 2, the traffic volume 200 includes a light source module 210, a dtif sensor 220, and a base 230.

The light source module 210 is used for projecting invisible light to the tested space. Here, the light source module 210 may be a conventional light source module, for example, a light source module that projects area array light. In one embodiment, to project the area array light, the light source module 210 may include: a light emitting device for generating a laser beam; and a diffusion sheet disposed on a propagation path of the light beam to convert the laser beam into area array light. The light emitting device may emit laser light, and may be implemented as a Laser Diode (LD) or a Vertical Cavity Surface Emitting Laser (VCSEL). In certain embodiments, the light emitting device may even be implemented by a Light Emitting Diode (LED).

In order to be used under various conditions and to avoid interference of visible light with the sensor, the light source module 210 projects invisible light, which may be particularly infrared light, for example, 940nm infrared light having strong interference resistance may be preferably emitted. And in order to perform head-shoulder detection, the projection area of the light source module 210 needs to cover a large area, for example, as shown in a dark gray area in fig. 1.

As shown, the dtofs sensor 220 is disposed separately from the light source module 210, and the optical axes of the two are not coincident. The dtofs sensor 220 is configured to receive the spatial return light and generate an inductive signal. Specifically, the dtif sensor 220 generates a sensing signal characterizing the distance based on the time of receipt of the return light for the projected invisible light. Because the two are arranged in a paraxial manner and the light paths are not coincident, the light source module 210 comprises a single light outlet I, and the dTOF sensor 220 comprises a single light inlet II instead of sharing one light inlet.

The controller (not shown) is used to control the operations of the light source module 210 and the dtoh sensor 220, and performs head-shoulder detection based on the sensing signal generated by the dtoh sensor 220, and generates a passenger flow count value according to the result of the head-shoulder detection. The base 230 may be used to fix the light source module 210, the ToF sensor 220, and the controller, not shown. In one embodiment, the base 230 may be a circuit board on which the controller and other circuitry are disposed. The circuit board may be arranged perpendicular to the vertical direction (z-axis direction). It should be appreciated that for ease of installation and protection from dust intrusion, the flow counter also includes a housing that encloses and holds the above assembly, and that also includes light outlets and light inlets for spot laser projection and return light, respectively, as described above. As shown in fig. 1, the light source module 210, the dtif sensor 220, and the base 230 shown in fig. 2, as well as sensors not shown, may be enclosed in a housing, and the traffic statistics 1 enclosed in the housing may be fixed on the traffic statistics path downward. The passenger flow statistical path may be limited by a door or door-like structure, such as the door frame 2 shown in fig. 1. In this case, the base 230 or the housing may include a coupling mechanism for coupling and fixing the passenger flow counter to the door beam of the door frame 2 as shown in fig. 1.

For ease of understanding, fig. 3 shows a schematic diagram of head-shoulder detection. In the case where the passenger flow counter is provided in a top view as in fig. 1, the dtif sensor 220 may acquire depth information of the head and shoulder of the person passing through the door 2 as shown in the right side of fig. 3, and judge that the head and shoulder appearing in pairs are included in the sensing information according to the head-shoulder relationship within a predetermined range, thereby counting. In this case, since the people stream judgment is performed based on the head-shoulder relationship, not the simple circle, the article (for example, the top bag of the mountain climbing bag) is not simply mistaken as a person.

Here, in order to provide high-precision imaging, the imaging apparatus uses a direct time-of-flight (dtif) sensor that generates an induction signal based on the reception time of return light. ToF is an abbreviation of Time of flight, which translates into Time of flight, by continuously sending light pulses to a target, then receiving light back from the object with a sensor, and by detecting the flight (round trip) Time or phase of these transmitted and received light pulses to obtain the target distance.

The light source module of the ToF may be configured to emit light after high-frequency modulation, and a laser (e.g., VCSEL) may be used to emit high-performance pulsed light, with pulses up to about 100 MHz.

The most of the ToF techniques currently available on the market are based on continuous wave intensity modulation methods, and some are based on optical shutters.

A continuous wave-based modulation method emits a beam of illumination light, and a distance measurement is performed by using the phase change of an emitted light wave signal and a reflected light wave signal. The wavelength of the illumination module is generally in the infrared band, and high-frequency modulation is required. The ToF photosensitive module is similar to a common mobile phone camera module, and is composed of a chip, a lens, a circuit board and the like, each pixel of the ToF photosensitive chip records specific phases between a round-trip camera emitting light waves and an object respectively, the phase difference is extracted through a data processing unit, and depth information is calculated through a formula. The sensor structure is similar to a CMOS image sensor adopted by a common mobile phone camera module, but the pixel size of the sensor is larger than that of a common image sensor, and the pixel size is about 20 um. An infrared bandpass filter is also required to ensure that only light of the same wavelength as the illumination source is allowed to enter. The sensor using the modulation method described above may be referred to as an iToF (indirect time of flight) sensor.

The method based on the optical shutter emits a beam of pulse light waves, the time difference t of the light waves reflected back after irradiating the three-dimensional object is rapidly and accurately obtained through the optical shutter, and as the light speed c is known, the back-and-forth distance can be represented by d=t/2·c as long as the time difference between the irradiated light and the received light is known. In practical application, if the method is to achieve higher precision, the clock for controlling the optical shutter switch is required to have higher precision, short pulse with high precision and high repeatability can be generated, and the irradiation unit and the ToF sensing chip are required to be controlled by high-speed signals, so that high depth measurement precision can be achieved. If the clock signal between the illumination light and the ToF sensor is shifted by 10ps, this corresponds to a displacement error of 1.5 mm. The sensor using the above-described modulation method may be referred to as a dtofq (direct time of flight, d) sensor.

The principles of dtofs and itofs differ primarily in the difference between emitted and reflected light. The principle of dtofs is relatively straightforward, i.e. the time of flight of light can be obtained by directly emitting a light pulse and then measuring the time interval between the reflected light pulse and the emitted light pulse. In iToF, light is emitted that is not a pulse of light, but is modulated. A phase difference exists between the received reflected modulated light and the emitted modulated light, and by detecting this phase difference, the time of flight can be measured, thereby estimating the distance.

In principle, the biggest problem of iToF is the contradiction between maximum ranging distance and ranging accuracy. For example, if the current target distance is 0.15m, the time of flight for the entire emitted and reflected light is 1ns. At a modulation frequency of 100MHz (10 ns period) of the modulated light, a time difference of flight of 1ns is converted into a phase difference of 36 degrees, whereas if the modulation frequency of the modulated light is 10MHz (100 ns period), a time difference of flight of 1ns is converted into a phase difference of 3.6 degrees. Obviously, a phase difference of 36 degrees is easier to detect than a phase difference of 3.6 degrees, so the higher the modulation optical modulation frequency of iToF, the better the ranging accuracy. The higher the modulation frequency, the more limited the maximum ranging distance. In contrast, dtofs do not have a contradiction between this ranging distance and ranging accuracy.

In a specific implementation, dtofs are much more difficult than itofs. The difficulty with dtofs is that the optical signal to be detected is a pulsed signal and therefore the sensitivity of the detector to light needs to be very high. For this purpose, the dTOF sensor used in the present utility model may use SPAD (single-photon avalanche diode, single photon avalanche diode). The working area of the SPAD is located near the breakdown area of the diode, and when a single photon enters the SPAD, a large number of electron-hole pairs are generated, so that the SPAD can detect very weak light pulses. In other embodiments, the utility model may also use Avalanche Photodiodes (APDs) as dtofs sensors.

SPADs are photodiodes that operate in geiger mode, just like photon triggered switches, in either an "on" or "off" state. In one embodiment, the dtif sensor 220 of the present utility model may further include: an area array sensor composed of a plurality of avalanche photosensors is used. Thereby, a larger sensing area can be achieved, for example as shown in the light grey area of fig. 1. The area sensor in this case may be, for example, a silicon photomultiplier (SiPM) composed of a plurality of individual SPAD sensors. Sipms are comprised of multiple independent SPAD sensors, each with its own quench resistance, so as to be able to receive the return pulse more sensitively.

In addition, in order to image a larger area of the measured space, the dtoff sensor may be arranged such that the sensing area is at least partially coincident with the projection area of the area array light of the light source module, for example, the sensing area is substantially the same as the projection area as shown in fig. 1, thereby performing passenger flow statistics in the overlapping area (i.e., imaging area) of the sensing area and the projection area. In one embodiment, the traffic statistics may only count traffic in one direction. For example, only passenger flows in the entering direction (the "in" arrow in fig. 1) or only passenger flows in the leaving direction (the "out" arrow in fig. 1) are counted. At this time, it can be considered that the door 2 is specified as an entrance or an exit. In another embodiment, the passenger flow statistics device can distinguish the incoming and outgoing directions of passenger flows and respectively count the passenger flows. The passenger flow statistics device can distinguish the incoming passenger flow from the outgoing passenger flow by detecting the relative position of the head shoulder.

In addition, it should be appreciated that the laser pulses emitted by the light source module of the present disclosure need to be pulses outside the visible light band, such as near infrared pulses, thereby enabling the filtering of disturbances of extraneous ambient light in combination with a band pass filter. Because of the extremely high sensitivity of the dTOF sensor, very few return infrared light can be measured. The thus obtained passenger flow statistics device can be arranged outdoors and can count normally even under outdoor strong light conditions.

Since the outgoing light path of the light source module 210 and the incoming light path of the dtofs sensor 220 are each independently arranged (i.e., a "paraxial" rather than a "coaxial" arrangement), the dtofs sensor 220 may be a "wide-angle" dtofs sensor for sensing return light within the projection range of the light shadow module. In other words, toF sensor 220 can be provided with at least an imaging angle of α (e.g., α is greater than 90 °) in the x and y directions, respectively, so as to be able to sense return light over a large range.

Since conventional light sources are utilized, multiple light sources may be provided for this purpose in one embodiment to take turns or to facilitate replacement. At this time, the controller may include: and the switching device is used for switching one of the plurality of light source modules to project the area array light. In the case where the apparatus includes a plurality of light source modules, the traffic statistics of the present disclosure may also be implemented to include external (backup) light source modules for ease of replacement of the failed light source. In some embodiments, the light source module may be detachably connected with the main housing via the external cable. Thus, in case of a failure of, for example, one light source module, the failure removal can be achieved simply by removing the individual light source housing and replacing the new light source housing containing the light source module. The discrete arrangement of light sources is particularly suitable for use in the arrangement of spare light sources.

The traffic statistics of the present disclosure may be disposed vertically downward on the door beam as shown in fig. 1, thereby detecting head shoulder (depth) information shown in the right part of fig. 3. In other embodiments, the flow counter may be angled downward, i.e., not vertically downward, but at an angle to the z-axis. The passenger flow sensing signals acquired at this time are not pure top views, but angular half top views. In other embodiments, the flow counter may be located elsewhere than on the door beam, such as on the door upright.

In addition, although not shown in the drawings, the traffic counter may further include a communication mechanism for transmitting the traffic count value to the outside and receiving a zero clearing operation. In one embodiment, the communication mechanism may be a network interface or a wired interface such as RS 485.

The utility model can also be realized as a passenger flow statistics system. The passenger flow statistics system is suitable for the situation that a single passenger flow statistics device cannot cover all entrances and exits. If simultaneous statistics summary of multiple independent entrances and exits is desired, the traffic statistics system may include multiple traffic statistics devices as described above, each of which performs traffic statistics individually and is passed, for example, to a monitoring platform for summary of incoming and outgoing traffic. When a plurality of passenger flow statistical devices are needed to cooperate and passenger flow statistics is carried out on one entrance and exit, the calibration operation among the plurality of passenger flow statistical devices is involved.

Fig. 4 shows a schematic diagram of the use of a passenger flow statistics system according to an embodiment of the utility model. The traffic statistics system comprises a plurality of traffic statistics devices (shown as traffic statistics device 1 and traffic statistics device 1') mounted on the traffic statistics path and a calibration device 3. Each of the passenger flow statistical devices images the tested space which is at least partially not overlapped with each other, and the calibrating device 3 is used for calibrating the tested space among the passenger flow statistical devices.

As shown in the figure, the imaging area of the passenger flow counter 1 can only cover the left side of the wide door 2', and the passenger flow entering and exiting from the right side cannot be counted. For this purpose, a passenger flow counter 1 'is additionally installed on the right side of the door beam of the wide door 2', and a calibration device 3 is provided at the overlapping portion of the imaging area of the passenger flow counter 1 and the imaging area 'of the passenger flow counter 1'. The calibration means 3 may for example be present in the illustrated checkerboard pattern. Therefore, the imaging space of the two passenger flow statistics devices can be calibrated, and the passenger flow entering and exiting can be counted cooperatively. In one embodiment, the system may further comprise doors 2', each of which may have one or more of said traffic statistics mounted on the door beam.

The passenger flow statistics device and the passenger flow statistics system according to the present utility model have been described above in detail with reference to the accompanying drawings. The utility model can be used in strong natural light scenes such as outdoors by arranging the dTOF sensor with high sensitivity to reflection light and large imaging area, and reduces false detection rate by head-shoulder detection for induction information.

The foregoing description of embodiments of the utility model has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the various embodiments described. The terminology used herein was chosen in order to best explain the principles of the embodiments, the practical application, or the improvement of technology in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

Claims (11)

1. A dtif sensor-based passenger flow statistics machine, comprising:

the light source module is used for projecting invisible light to the tested space;

a direct time-of-flight dtif sensor that generates a sensing signal characterizing a distance based on a time of receipt of return light for the projected invisible light;

the controller is used for controlling the operation of the light source module and the dTOF sensor, performing head-shoulder detection based on the induction signal and generating a passenger flow count value according to the head-shoulder detection result; and

and the base is used for fixing the light source module, the dTOF sensor and the controller.

2. The passenger flow counter of claim 1, wherein the dtif sensor comprises:

an area array sensor composed of a plurality of avalanche photosensors is used.

3. The passenger flow counter of claim 1, wherein the light source module comprises:

a light emitting device for generating a laser beam; and

and a diffusion sheet disposed on a propagation path of the light beam to convert the laser beam into area array light.

4. A passenger flow counter as claimed in claim 3, wherein the light emitting means comprises:

a laser diode LD;

a vertical cavity surface emitting laser VCSEL; or (b)

A light emitting diode LED.

5. The traffic counter of claim 4, wherein the dtif sensor is arranged such that a sensing area at least partially coincides with a projection area of the area array light of the light source module.

6. The traffic counter of claim 1, wherein said dtif sensor is spaced apart from said light source module and the optical axes of both are not coincident.

7. The traffic statistic of claim 1, wherein said base includes a connection mechanism for securing said traffic statistic downwardly on said traffic statistic path.

8. The passenger flow statistics machine of claim 1, wherein the passenger flow statistics machine further comprises:

a single housing for enclosing the light source module, the dtif sensor, the controller, and the base; and/or

And the standby surface light source module is detachably connected.

9. The traffic counter of claim 1, further comprising a communication mechanism for externally transmitting the traffic count value and receiving a zero clearing operation.

10. A passenger flow statistics system, comprising:

a plurality of traffic statistics machines according to any one of claims 1-9 mounted on traffic statistics paths, each of said traffic statistics machines imaging a measured space that is at least partially non-overlapping with each other;

and the calibration device is used for calibrating the tested space among the plurality of passenger flow statistics devices.

11. The passenger flow statistics system of claim 10, further comprising:

one or more doors defining a passenger flow path and one or more of said passenger flow counters mounted on the cross beam of each door.