CN112558084A

CN112558084A - Optical flow sensor and mobile robot

Info

Publication number: CN112558084A
Application number: CN201910912023.2A
Authority: CN
Inventors: 段思雨; 任玉斌
Original assignee: Ecovacs Robotics Suzhou Co Ltd
Current assignee: Ecovacs Robotics Suzhou Co Ltd
Priority date: 2019-09-25
Filing date: 2019-09-25
Publication date: 2021-03-26

Abstract

The invention discloses an optical flow sensor and a mobile robot. The optical flow sensor includes a light-filling device and an imaging device. The imaging device includes an imaging chip and a first lens. The light-filling device provides emitted light, and the first lens receives the emitted light and irradiates the object. The reflected light formed afterward is a parallel light beam, the first lens is arranged on the optical path of the reflected light, and the main optical axis of the first lens is parallel to the optical path of the reflected light. The present invention adopts parallel light for supplementary light, and a supplementary light device that emits parallel light beams can satisfy the light-filling requirements of the optical flow sensor when used on various grounds, the requirements for power and current are reduced, the imaging quality is obviously improved, and the ordinary resolution is The sensor chip can meet the positioning requirements of the optical flow sensor, which greatly reduces the cost of the chip. On the other hand, when the surface of the ground or obstacle is uneven, the displacement calculation of the optical flow sensor maintains high accuracy.

Description

Optical flow sensor and mobile robot

Technical Field

The invention relates to the technical field of robot positioning and light supplement of an optical flow sensor, in particular to an optical flow sensor and a mobile robot.

Background

The mobile robot is sometimes trapped in the process of traveling, and if the robot cannot find the condition in time, the positioning of the robot is deviated under a confidence state, so that the working effect is influenced.

In order to quickly obtain the moving state of the robot, a sensor for detecting the position movement, such as an optical flow sensor, may be mounted on the housing of the robot, and directly connected to the housing of the robot, so that when the wheels of the robot slip, the slipping state of the robot can be directly detected, and the slip-related action can be performed.

To make light stream sensor can both acquire the environment image under various illumination conditions, need introduce the light filling lamp and carry out the light filling, prior art need use the high resolution sensor chip that the price is more expensive in order to reach and can use on including the most subaerial including carpet, adopts the diffuse reflection light filling of a plurality of LED light filling lamps to need big drive current, measuring result still can have the problem of distortion.

Disclosure of Invention

The invention aims to provide an optical flow sensor and a mobile robot, which use a new light supplement scheme to solve the problems that a plurality of light supplement lamps, large driving current and high-resolution sensor chips are required to be used by the optical flow sensor on various grounds, and measurement distortion exists during use.

The purpose of the invention is realized by adopting the following technical scheme:

an optical flow sensor comprises a light supplementing device and an imaging device;

the imaging device comprises an imaging chip and a first lens, the light supplementing device provides emitted light, the first lens receives reflected light formed after the emitted light irradiates on an object,

the emitted light is a parallel light beam;

the first lens is arranged on the light path of the reflected light, and the main optical axis of the first lens is parallel to the light path of the reflected light.

Preferably, the first lens is disposed on an optical path of the specular reflection light of the emission light incidence reference surface.

Preferably, the light supplement device comprises a light source and a collimating lens;

the emitted light is formed by light emitted by the light source after passing through the collimating lens.

Preferably, the light supplement device is disposed above a reference surface, and a distance between the light supplement device and the reference surface is greater than or equal to 20mm and less than or equal to 60 mm.

Preferably, the imaging device is arranged above a reference surface, and the distance between the imaging device and the reference surface is greater than or equal to 20mm and less than or equal to 65 mm.

Preferably, the receiving field width of the imaging chip is greater than 0 and less than or equal to 10 mm.

Preferably, the foreground depth of the first lens is greater than 0 and equal to or less than 30mm, and the back depth of field of the first lens is greater than 0 and equal to or less than 10 mm.

Preferably, the included angle between the parallel light beams and the vertical direction is greater than or equal to 3 degrees and less than or equal to 15 degrees.

Preferably, the effective diameter of the parallel light beam is D, D ≧ [ L + (CD + FD). times.sin α × 2 ];

wherein L is the receiving field width of the imaging chip; CD is the foreground depth of the first lens, FD is the back depth of field of the first lens; and alpha is an included angle between the parallel light beams and the vertical direction.

Preferably, the effective diameter D of the parallel light beam is equal to or greater than 5mm and equal to or less than 25 mm.

Preferably, the receiving field width L of the imaging chip is greater than 0 and less than or equal to 10mm, the foreground depth CD of the first lens is greater than 0 and less than or equal to 30mm, the back field depth FD of the first lens is greater than 0 and less than or equal to 10mm, and the included angle α between the parallel light beams and the vertical direction is greater than or equal to 2 ° and less than or equal to 15 °.

Preferably, the divergence angle of the parallel light beam is equal to or greater than-5 ° and equal to or less than 5 °.

Preferably, the light intensity non-uniformity of the parallel light beam is less than 2%/mm.

Preferably, the light intensity uniformity of the parallel light beams is greater than 75% in the receiving field of view of the imaging chip.

A mobile robot comprising an optical flow sensor;

the optical flow sensor comprises a light supplementing device and an imaging device; the imaging device comprises an imaging chip and a first lens, the light supplementing device provides emitted light, the first lens receives reflected light formed after the emitted light irradiates on an object,

the emitted light is a parallel light beam;

Compared with the prior art, the invention has the beneficial effects that:

the invention discloses an optical flow sensor and a mobile robot, which comprise a light supplementing device and an imaging device, wherein the imaging device comprises an imaging chip and a first lens, the light supplementing device provides emitted light, the first lens receives reflected light formed after the emitted light irradiates an object, the emitted light is parallel light beams, the first lens is arranged on a light path of the reflected light, and a main optical axis of the first lens is parallel to the light path of the reflected light. The invention adopts the parallel light for light supplement, one light supplement device for emitting the parallel light beams can meet the light supplement requirement of the optical flow sensor when being used on various grounds, the requirements on power and current are reduced, the imaging quality is obviously improved, the positioning requirement of the optical flow sensor can be met by a sensor chip with common resolution, and the chip cost is greatly reduced. On the other hand, when the ground or the surface of the obstacle is uneven, the length of the shadow formed by the supplementary lighting does not change with the movement of the robot, the brightness of the area where the shadow is not formed does not change with the movement of the robot, and the displacement calculation of the optical flow sensor maintains high accuracy.

Drawings

The invention is further illustrated with reference to the following figures and examples.

Fig. 1 shows a schematic diagram of a light supplement effect of a mobile robot when a diffuse reflection light supplement is adopted;

FIG. 2 is a schematic diagram illustrating a light supplement effect of the mobile robot when the mobile robot passes through a position B during light supplement by diffuse reflection;

fig. 3 is a perspective view illustrating a mobile robot according to an embodiment of the present invention;

fig. 4 illustrates a bottom view of a mobile robot according to an embodiment of the present invention;

FIG. 5 is a schematic diagram illustrating the operation of an optical flow sensor according to an embodiment of the present invention;

fig. 6 is a schematic diagram illustrating an effect of a parallel light supplementary lighting scheme according to an embodiment of the present invention;

fig. 7 is a schematic diagram illustrating a light supplement effect of the mobile robot when the mobile robot passes through the position a during light supplement by using parallel light;

fig. 8 is a schematic diagram illustrating the light supplement effect of the mobile robot passing through the position B when parallel light is used for light supplement;

FIG. 9 shows an image formed by a general LED lamp diffuse reflection fill light on a black mouse pad;

fig. 10 illustrates an image formed on a black mouse pad by parallel light supplementary lighting according to an embodiment of the present invention.

In the figure: 100. an optical flow sensor; 1. a light supplement device; 11. a light source; 12. a collimating lens; 2. an imaging device; 21. an imaging chip; 22. a first lens; 3. a reference plane; 4. a close scene; 5. a distant view surface; 6. a parallel light compensating area; 7. an imaging area.

Detailed Description

The present invention will be further described with reference to the accompanying drawings and the detailed description, and it should be noted that any combination of the embodiments or technical features described below can be used to form a new embodiment without conflict.

In the embodiment of the invention, the plane of the road surface on which the mobile robot normally runs is taken as the reference plane 3, and the direction perpendicular to the reference plane 3 is taken as the vertical direction.

The light supplement mode in the prior art has the following disadvantages: because the field of view area of the optical flow sensor only occupies a small part of the lighting area of the LED lamp and is in a diffuse reflection light supplementing mode, the light energy utilization rate is low, and when a surface with low diffuse reflectivity, such as a black surface or a surface with strong specular reflection, meets the requirement of lighting intensity by driving the LED lamp light to emit light with large current; referring to fig. 1 and 2, when the mobile robot moves from the position a to the position B, since the light emitted from the LED lamp has a certain divergence angle, when the light is irradiated onto an object with a wavy surface, a shadow region formed on the backlight side changes, and the brightness of a region where no shadow is formed also changes, both of which cause measurement distortion; when the robot moves during multi-lamp light compensation, the position of a certain fluctuation characteristic of an object relative to a lamp group is different, so that the brightness distribution of a shadow area is changed, and measurement distortion is caused; since a high-resolution sensor chip is required, the sensor chip is high in cost.

Referring to fig. 3 to 5, an embodiment of the present invention provides a mobile robot including an optical flow sensor 100. The optical flow sensor 100 includes a light supplement device 1 and an imaging device 2. The imaging device 2 includes an imaging chip 21 and a first lens 22. The fill-in device 1 provides the emitted light, and the first lens 22 receives the reflected light formed after the emitted light is irradiated to the object. The emitted light is a parallel light beam, the first lens 22 is disposed on the light path of the reflected light, and the main optical axis of the first lens 22 is parallel to the light path of the reflected light.

The mobile robot in the embodiment of the invention can be a sweeping robot. The optical flow sensor 100 may be disposed at the bottom of the sweeping robot. When the sweeping robot works, the imaging chip 21 of the optical flow sensor 100 acquires image information on the ground through the first lens 22, and performs analysis and calculation on the image information at the previous moment and the image information at the next moment to obtain a displacement calculation result of the sweeping robot, and the current speed of the sweeping robot can be calculated according to the displacement calculation result. And when the current speed of the sweeping robot is 0 or the current speed of the sweeping robot is approximate to 0, judging that the sweeping robot slips.

Referring to fig. 6, during the operation of the sweeping robot, the light supplement device 1 of the optical flow sensor 100 provides parallel light supplement for the imaging device 2, 6 is a parallel light supplement region, and 7 is an imaging region. The light flux of the parallel light flux is concentrated, and the first lens 22 receives the reflected light on the optical path of the reflected light, so that the optical flow sensor 100 has high light energy utilization efficiency and does not need a large driving current to meet the illumination intensity requirement.

The shadow zone formed when the parallel light beam is irradiated on any type of floor, such as a carpet, remains unchanged. Referring to fig. 7 and 8, when the sweeping robot works on a carpet, the sweeping robot moves from the position a to the position B, the length of the shadow formed by the parallel light supplementary lighting does not change along with the movement of the sweeping robot, the brightness of the area where the shadow is not formed does not change along with the movement of the sweeping robot, and the displacement calculation of the optical flow sensor 100 maintains high precision.

The divergence angle of the parallel light beams is small, and the receiving view field width L of the imaging chip 21 is limited, so that in the view field range, no matter the sweeping robot works on a carpet or a smoother ground, most of the images received by the imaging chip 21 are generated by the parallel light.

In the embodiment of the present invention, the receiving field width L of the imaging chip 21 refers to a distance between two points which are farthest away in a cross section perpendicular to the main optical axis direction of the first lens 22 in the receiving field of view of the imaging chip 21. For example, when the reception field of view is a circle, the reception field of view width L is the diameter of the circle; when the reception field of view is a rectangle, the reception field of view width L is the length of the rectangle. The receiving field width L of the imaging chip 21 may be greater than 0 and 10mm or less. The receiving field of view is too small, and the image information obtained by the imaging chip 21 is not enough to help judge whether the sweeping robot slips or not. The receiving field of view is too large, the image data amount to be analyzed is large, the data processing time is prolonged, the time for the sweeping robot to wait for the judgment result is prolonged, and the situation of jamming can occur in the moving process; on the other hand, the effective diameter D of the parallel light beam required for light supplement is also correspondingly increased, and the light energy consumption is increased.

Fig. 9 and 10 show images of the optical flow sensor 100 formed on the black mouse pad by using diffuse reflection supplementary light and parallel light supplementary light on the same surface, respectively, and it can be seen that the image contrast of fig. 10 is higher than that of fig. 9. The higher the image contrast, the higher the imaging quality, which was measured to be 7387 for fig. 9 and 11049 for fig. 10. Through comparison, the imaging quality of an image formed by parallel light supplementary lighting is higher than that of an image formed by diffuse reflection supplementary lighting. The reason is that in the reflected light received by the first lens 22, the light reflected by the plane is strongest, and the light reflected by the micro-protrusions or the micro-recesses on the plane is relatively weaker, which enhances the contrast of the image, compared with diffuse reflection light filling, the characteristic points in the picture are more obvious, and the imaging chip 21 can obtain sufficient imaging quality without adopting a high-resolution sensor chip, thereby reducing the resolution requirement on the imaging chip 21 and avoiding the high cost caused by the use of the high-resolution sensor chip.

The first lens 22 may be disposed on the optical path of the specular reflection light of the emission light incident on the reference surface 3. At this time, the light reflected by the reference surface 3 is the strongest among the reflected lights received by the first lens 22.

The emitted light may be formed by light emitted from the light source 11 after passing through the collimating lens 12. The collimating lens 12 can achieve collimation of light beams and improve utilization rate of light energy. The light source 11 may include an LED and/or an LD, among others. The led (light Emitting diode) refers to a light Emitting diode. Ld (laser diode) refers to a semiconductor laser, also called a laser diode. Whether the light source 11 is an LED or an LD, the emitted light formed after the light emitted from the light source 11 passes through the collimator lens 12 is a parallel light beam. When the light source 11 is an LED, the combination of one LED and one collimating lens 12 can supplement light for the imaging device 2, and compared with a mode of supplementing light by a plurality of LEDs, the light energy utilization rate is high, and the cost is low.

The mode that the light supplementing device 1 emits the parallel light beams can be realized by one LD as long as the effective diameter D of the parallel light beams emitted by the LD meets the light supplementing requirement of the imaging device 2.

The light supplement device 1 may also be implemented by two or more parallel LDs. On the premise that the required effective diameter D of the parallel light beam is not changed, the scheme that a plurality of LDs provide the parallel light beam together can reduce the cost compared with the scheme of a single LD, because for an LD, increasing the diameter of the outgoing light beam causes the cost of the LD to increase rapidly. The multiple LDs share the same effect, and each LD only needs to provide an emergent light beam with a smaller effective diameter, so that the performance requirement on each LD is reduced, and the cost is controlled.

The position of light filling device 1 is too high, can make the overall height of robot of sweeping the floor too high, leads to it can't get into comparatively short space, for example carries out work under the tea table. However, the position of the light supplement device 1 cannot be too low, and if the light supplement device 1 is too close to the ground, the optical flow sensor 100 may contact with an obstacle on the ground, such as a pile or a cotton thread on a carpet, so that the light supplement device 1 may be damaged or soiled. Preferably, the light supplement device 1 may be disposed above the reference plane 3, and a distance P between the light supplement device 1 and the reference plane 3 is greater than or equal to 20mm and less than or equal to 60 mm.

The imaging device 2 is too high, which causes the overall height of the sweeping robot to be too high, and the sweeping robot cannot enter a short space to work. If the position of the imaging device 2 is too low, the first lens 22 is too close to the object to be photographed, the depth of field is too small, and the image received by the imaging chip 21 is blurred; on the other hand, light reflected by minute protrusions or depressions on the plane, such as pile or cotton threads on a carpet, also enters the first lens 22 more, reducing the contrast of the image. Preferably, the imaging device 2 may be disposed above the reference surface 3, and the distance Q between the imaging device 2 and the reference surface 3 is 20mm or more and 65mm or less.

In practical applications, the first lens 22 is close to the ground, and a large aperture is needed to realize a large depth of field of the first lens 22. However, an excessively large aperture causes a drastic increase in the cost of the first lens 22, and thus the depth of field of the first lens 22 cannot be excessively large. The front depth of field is greater than 0 and equal to or less than 30mm, and the rear depth of field is greater than 0 and equal to or less than 10mm, which is a selection range with high cost performance.

The angle α between the parallel light beam and the vertical direction may be 3 ° or more and 15 ° or less. An included angle α between the parallel light beam and the vertical direction cannot be too large, and in order to ensure that the receiving field width L of the imaging chip 21 reaches a predetermined size, as the included angle α between the parallel light beam and the vertical direction becomes larger, the effective diameter D of the parallel light beam must be correspondingly increased, so that the requirement on the light supplement device 1 is increased, and the cost is increased; on the other hand, the larger the included angle alpha between the parallel light beam and the vertical direction is, the lower the light energy utilization rate is, and the resource waste is caused. However, the included angle α between the parallel light beam and the vertical direction cannot be too small, when the parallel light beam is approximately parallel to the vertical direction and approximately perpendicular to the ground, the projection of the first lens 22 for receiving the reflected light and the projection of the light supplement device 1 on the reference plane 3 are approximately overlapped, and at this time, the light supplement device 1 can prevent the reflected light from entering the first lens 22, so that the light supplement effect is affected.

Referring to fig. 5, let the effective diameter of the parallel light beam be D, the minimum value of D is required to satisfy that the reflected light of the near view plane 4, the far view plane 5 and the plane therebetween can all reach the receiving view field width L of the imaging chip 21, that is:

d is not less than [ L + (CD + FD). times.sin alpha.x 2 ]; wherein L is the receiving field width of the imaging chip 21; CD is the foreground depth of the first lens 22 and FD is the back depth of field of the first lens 22; alpha is the included angle between the parallel light beam and the vertical direction. The near view plane 4 is the plane in which the foreground depth CD of the first lens 22 lies. The distant view plane 5 refers to a plane in which the back depth FD of the first lens 22 is located.

The requirement for the light supplement device 1 is increased by the too large effective diameter D of the parallel light beam, for example, the brightness of the light source 11 is increased, the effective diameter of the emergent light beam is increased, and the cost is increased. And the effective diameter D of the parallel light beam is too small, and when the parallel light beam is similar to a light beam, once the parallel light beam encounters a protrusion or a recess, for example, when the floor sweeping robot works on a carpet, the reflected light cannot enter the first lens 22, so that the light supplementing effect cannot be achieved. Preferably, the effective diameter D of the parallel light beam takes a value between 5mm and 25 mm.

According to the above formula, the receiving field width L of the imaging chip 21, the foreground depth CD of the first lens 22, the back field depth FD of the first lens 22, and the range of the angle α between the parallel light beam and the vertical direction directly affect the effective diameter D of the parallel light beam, preferably, the receiving field width L of the imaging chip 21 is greater than 0 and less than or equal to 10mm, the foreground depth CD of the first lens 22 is greater than 0 and less than or equal to 30mm, the back field depth FD of the first lens is greater than 0 and less than or equal to 10mm, the angle α between the parallel light beam and the vertical direction is greater than or equal to 2 ° and less than or equal to 15 °, and the minimum value of the effective diameter D of the corresponding parallel light beam is between 0 and 22 mm. It is further preferable that the receiving field width L of the imaging chip 21 is 3mm, the foreground depth CD of the first lens 22 is 15mm, the back field depth FD of the first lens 22 is 5mm, the angle α of the parallel light beam with the vertical direction is 6 °, and the minimum value of the effective diameter D of the corresponding parallel light beam is 7 mm.

The divergence angle of the parallel light beams is too large, the light beams are not concentrated enough, and the problem of diffuse reflection light filling in the above can occur. Therefore, the divergence angle of the parallel light beam is preferably equal to or greater than-5 ° and equal to or less than 5 °.

The non-uniformity of the light intensity of the parallel light beam means a ratio of a decrease in the light intensity every distance from a predetermined length with reference to the strongest brightness at the center of the light beam. In an embodiment of the invention, this may be the light intensity drop ratio per 1mm away. The larger the light intensity nonuniformity is, the more rapidly the light beam is attenuated, and the reflected light entering the first lens 22 is greatly reduced, which affects the light supplement effect. Therefore, the light intensity non-uniformity of the parallel light beam is preferably less than 2%/mm.

The intensity uniformity of the parallel light beam refers to the degree to which the intensity of the parallel light beam is uniformly distributed. The uniform distribution of the parallel light beams can make the reflected light entering the first lens 22 be uniformly distributed, so that the light supplementing effect in the receiving field range of the imaging chip 21 is uniform. The uniformity of the intensity of the parallel light beam may be greater than 75% across the receiving field of view of the imaging chip 21.

The invention has been described in terms of its several purposes, including but not limited to, and it is to be understood that such terms are merely intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

Claims

1. An optical flow sensor comprises a light supplementing device and an imaging device;

the imaging device comprises an imaging chip and a first lens, the light supplementing device provides emitted light, and the first lens receives reflected light formed after the emitted light irradiates an object,

the emitted light is a parallel light beam;

2. The optical flow sensor according to claim 1, wherein the first lens is disposed on an optical path of the specular reflection light of the emission light incidence reference surface.

3. The optical flow sensor according to claim 1, wherein the light supplementing device comprises a light source, a collimating lens;

4. The optical flow sensor according to claim 1, wherein the light supplement device is disposed above a reference surface, and the distance between the light supplement device and the reference surface is greater than or equal to 20mm and less than or equal to 60 mm.

5. The optical flow sensor according to claim 1, wherein the imaging device is disposed above a reference surface, and a distance between the imaging device and the reference surface is 20mm or more and 65mm or less.

6. The optical flow sensor according to claim 1, wherein the receiving field width of the imaging chip is greater than 0 and 10mm or less.

7. The optical flow sensor according to claim 1, wherein the foreground depth of the first lens is greater than 0 and equal to or less than 30mm, and the back depth of field of the first lens is greater than 0 and equal to or less than 10 mm.

8. The optical flow sensor according to claim 1, characterized in that the angle of the parallel light beam with the vertical direction is greater than or equal to 3 ° and less than or equal to 15 °.

9. The optical flow sensor according to claim 1, wherein the effective diameter of the parallel light beam is D, D ≧ L + (CD + FD) x sin α x 2;

10. The optical flow sensor according to claim 9, characterized in that the effective diameter D of the parallel light beam is greater than or equal to 5mm and less than or equal to 25 mm.

11. The optical flow sensor according to claim 9, wherein the receiving field width L of the imaging chip is greater than 0 and 10mm or less, the foreground depth CD of the first lens is greater than 0 and 30mm or less, the back field depth FD of the first lens is greater than 0 and 10mm or less, and the angle α between the parallel light beams and the vertical direction is greater than or equal to 2 ° and 15 ° or less.

12. The optical flow sensor according to claim 1, wherein the divergence angle of the parallel light beams is equal to or greater than-5 ° and equal to or less than 5 °.

13. The optical flow sensor according to claim 1, characterized in that the light intensity non-uniformity of the parallel light beam is less than 2%/mm.

14. The optical flow sensor according to claim 1, wherein the uniformity of the intensity of the parallel light beam is greater than 75% over the receiving field of view of the imaging chip.

15. A mobile robot comprising an optical flow sensor;

the optical flow sensor comprises a light supplementing device and an imaging device; the imaging device comprises an imaging chip and a first lens, the light supplementing device provides emitted light, and the first lens receives reflected light formed after the emitted light irradiates an object,

the emitted light is a parallel light beam;