Patent Application
20150002658
The present invention relates to a liquid level measuring device, and more particularly to a liquid level measuring device for accurately and precisely measuring a liquid level in a detection region by using a digital electronic device to capture images, using an inclined partition structure and a light-transmission part and performing an image processing technology (e.g. a sub-pixel accuracy analysis).
In Taiwan, heavy rainfall may easily occur in the plum rain season or in the typhoon season. As known, the steep terrain of the mountains in Taiwan may cause the rapid flowing rivers and short collecting time of the rivers. If the hillsides are over-developed or the hydraulic facilities have not been installed before the flood season, the occurrence of heavy rainfall often causes landslides in mountains, serious flood in the urban regions, midstream and downstream of rivers, or other serious disasters. Nowadays, the climate change causes the increased frequency of the extreme and violent weather events. Due to these meteorological factors, the possibility of causing natural disasters will increase. Therefore, the government should make efforts in prevention, early warning or preparation of such disasters.
For accurately and early warning the possible disasters caused by rainfall in associated regions, in addition to the quantitative precipitation forecast beforehand, it is essential to observe the water level and the water flow rate of these regions. As for water level observation, the water levels or flooding depths of rivers, lakes, reservoirs, embankments, roads, undergrounds or other regions are observed. In case that the water level reaches a warning line or the water level is high enough to affect safety, the relevant personnel should alert, announce or provide information to relevant organizations in order to avoid expansion of the disaster. In other words, it is important to observe the water levels of these regions in an actual and real-time manner.
In accordance with the conventional technologies, the water level is manually measured, or a graduation line around the water body is directly observed. Moreover, the conventional water level observation devices include for example float-type water level gauges, pressure-type water level gauges, acoustic-type water level gauges, radar-type water level gauges, or the like. According to the water fluctuation, these conventional water level observation devices can realize the corresponding water levels by specified detection and calculation methods. However, these water level observation devices still have some drawbacks. For example, since some of these devices are read by human judgment, the accuracy and the real-time measuring efficacy are usually unsatisfied. In addition, some of these devices have high fabricating cost and thus fail to be widely installed. Moreover, since some of these devices measure the water level by contacting the devices with water surfaces, it is difficult to maintain the devices.
On the other hand, some of the conventional water level observation devices have the automatic observing functions or are equipped with image capturing devices to shoot the water surfaces. These technologies are disclosed in for example Taiwanese Patent No. 1384205 (entitled “Measure method for the height of a liquid surface”) and Korean Patent No. 1020120003746 (entitles “Method and device for measuring a rainfall”). However, the approaches of transmitting the observed data to a back-end device and processing the observed data in the back-end device are complicated. Moreover, since the processes of capturing images are readily interfered by the ambient light beams, the results of the water level judgment are neither accurate nor precise.
Therefore, there is a need of providing an improved liquid level measuring device in order to overcome the above drawbacks.
The present invention provides a liquid level measuring device. The liquid level measuring device has a digital electronic device for capturing images. Moreover, by means of an inclined partition structure and a light-transmission part and by analyzing a sub-pixel accuracy of the captured images, the liquid level change can be measured more accurately and precisely. Consequently, the liquid level of the liquid in a detection region can be accurately realized. Moreover, the container is made of an opaque material, and the outer appearance of the container is designed as a sealed structure. Since the ambient light beams are nearly blocked from entering the container, the processes of capturing images are not interfered by the ambient light beams. Moreover, since the known digital electronic device and the known light source are employed for capturing images, processing and analyzing images, transmitting signals and illuminating the detection plane, the installation cost of the liquid level measuring device is reduced, and associated images and information can be immediately provided.
In accordance with an aspect of the present invention, there is provided a liquid level measuring device. The liquid level measuring device includes a container and a digital electronic device. The container is located at a detection region. The container has an opening, so that a liquid is permitted to flow into the container through the opening. The digital electronic device is combined with the container. The digital electronic device includes a lens, and an optical axis of the lens is directed to and perpendicular to a detection plane. A light source illuminates the detection plane. The lens is operated in a fixed-focus mode to shoot the detection plane to acquire an image stream. Each image frame of the image stream contains a corresponding liquid surface image. After an image analyzing operation is performed on the corresponding liquid surface image to calculate the corresponding liquid surface image, a liquid level of the liquid is realized.
In an embodiment, for performing the image analyzing operation, an area of the liquid surface image contained in each image frame is calculated, or changes of liquid surface edges of two image frames are calculated and compared with each other, and a Gaussian distribution method or a Centroid method is further used to analyze a sub-pixel accuracy, so that the corresponding liquid level is acquired.
In an embodiment, the liquid level measuring device further includes a partition structure. The partition structure is disposed within the container and inclined relative to a lower portion of the container. The partition structure includes a light-transmissible part with a linear slope. The corresponding liquid surface image is an image of the liquid which is visible through the light-transmissible part, and the corresponding liquid surface image is indicated as a bright fringe.
In an embodiment, the partition structure is a flat plate, a trapezoidal pyramid structure or a cone structure. In addition, the light-transmissible part is arranged in an oblique line or a helical line.
In an embodiment, the opening is formed on an upper portion of the container, and a water collector is disposed in the opening of the container. The partition structure is a pipe structure with a fixed diameter and connected with the water collector.
In an embodiment, for performing the image analyzing operation, positions of the bright fringes of any two image frames are calculated and compared with each other, and a Gaussian distribution method or a Centroid method is further used to analyze a sub-pixel accuracy, so that the corresponding liquid level is acquired.
In accordance with another aspect of the present invention, there is provided a liquid level measuring device. The liquid level measuring device includes a shielding container and a digital electronic device. The shielding container is located at a detection region. The shielding container has an opening, so that a liquid is permitted to flow into the container through the opening. The digital electronic device is disposed within the shielding container. The digital electronic device includes a lens, and an optical axis of the lens is directed to a detection plane. A light source illuminates the detection plane. The lens shoots the detection plane to acquire an image stream. Each image frame of the image stream contains a corresponding liquid surface image. After an image analyzing operation is performed on the corresponding liquid surface image to calculate the corresponding liquid surface image, a liquid level of the liquid is realized.
The above objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which:
Hereinafter, a liquid level measuring device of a first embodiment of the present invention will be illustrated.
In this embodiment, the liquid level measuring device 100 further comprises a light source 13 and an external power source 14. The digital electronic device 11 comprises a lens 12 for capturing images or taking photos. In this embodiment, the light source 13 is composed of at least one light emitting diode unit. The container 10 is a cylindrical or tubal structure with a closed top end. In addition, the container 10 is made of an opaque material. That is, except for the opening 10a, the inner portion and the outer portion of the container 10 are isolated from each other. Since a great portion of the ambient light beams fail to be introduced into the container 10, the interference of the ambient light beams will be minimized. In other words, the light source 13 is used for supplementing brightness while the lens 12 captures images. The light emitting diode unit has many benefits such as high brightness, low power consumption and long use life. Consequently, the light emitting diode unit can provide the lighting efficacy for a long time. In some embodiments, the light emitting diode unit of the light source 13 is designed to be operated in a synchronous flash control mode. That is, when the lens 12 captures images, the light emitting diode unit of the light source 13 synchronously flashes. Under this circumstance, it is not necessary for the light source 13 to lengthily or continuously provide the light beams.
Generally, the digital electronic device 11 has a built-in storage battery that provides electric power required for its operations. However, for continuously measuring the liquid level, the electric power to be supplied to the digital electronic device 11 should be stable and sustained. The external power source 14 is used for providing the electric power to the digital electronic device 11 and the light source 13. For example, the external power source 14 is a utility power source, a solar energy supply unit or a wind power supply unit. For installing the external power source 14, the isolation between the inner portion and the outer portion of the container 10 should be taken into consideration. For example, a solar panel of the solar energy supply unit or a wind turbine of the wind power supply unit is located at the outer portion of the container 10 for transferring electric power to the inner portion of the container 10 through a power cable. Moreover, the electric power is stored in a storage battery within the container 10 or directly transferred to the digital electronic device 11.
In this embodiment, the light source 13 and the digital electronic device 11 are separate units. Alternatively, in some other embodiments, the light source 13 is included in the digital electronic device 11. For example, the light source 13 is a flash lamp of the digital electronic device 11. In particular, the digital electronic device 11 is a smart phone, a tablet personal computer or a notebook computer. In the state-of-the-art technology, the smart phone, the tablet personal computer or the notebook computer is usually equipped with a camera module or a lens having the functions of capturing images or taking photos. That is, the digital electronic device 11 is equipped with a charge coupled device (CCD) or a complementary metal-Oxide-semiconductor (CMOS), which is well known in the art. Moreover, the digital electronic device 11 further comprises a memory unit, a central processing unit and a signal transmission unit (not shown). After the tasks of capturing images or taking photos are performed, the associated images are stored, processed and transmitted by the memory unit, the central processing unit and the signal transmission unit, respectively.
Please refer to
Moreover, under the illumination of the light source 13, the lens 12 shoots the liquid to acquire an image stream. Each image frame of the image stream contains a liquid surface image corresponding to the liquid. In this embodiment, the lens 12 is operated in a fixed focus mode to capture images. That is, without manual manipulation, the lens 12 is programmed to capture images at fixed focal length, wherein the zooming in function and the zooming out functions of the lens 12 are not done. Consequently, the displaying regions of the images captured at different time points indicate the target regions with the same size. By means of this design, the target images will have a fixed range and a fixed scaling factor in the subsequent image processing and analyzing processes. Consequently, the measurement and judgment of the liquid level can be corresponding performed.
According to the photographing principles, the zooming-in action of the lens generates an image-capturing result with a smaller viewing angle and a larger target region, and the zooming-out action of the lens generates an image-capturing result with a larger viewing angle and a smaller target region. In this embodiment, the focal length of the lens 12 has been previously set. Consequently, each image frame of the image stream contains not only the liquid surface image (i.e. the whole image of the surface of the liquid), but also an image of a part of an inner wall 10b of the container 10. Please refer to
It is noted that the image frame at the first time point and the image frame at the second time point are different. In
Moreover, after an image analyzing operation is performed on a liquid surface image, a corresponding liquid level is obtained. The image analyzing operation is a well-known image processing and analyzing technology. For example, a Gaussian distribution method or a Centroid method may be used to analyze the sub-pixel accuracy. For example, since the liquid surface image and the inner wall image are obviously different in colors and brightness values, the Gaussian distribution method may be employed to distinguish from the peak values of the pixels of the image in order to judge which pixels of the image frame indicate the liquid surface or the inner wall or whether the pixels representative of the liquid surface are increased or decreased.
In this embodiment, the central processing unit is used for processing the image stream and storing the image stream into the memory unit. The image analyzing operation is performed by the central processing unit to calculate the area of the liquid surface image contained in each image frame. Alternatively, for performing the image analyzing operation, the unchanged portions of the liquid surfaces of two image frames are not taken into consideration, but only the changes of the liquid surface edges of the two image frames are calculated and compared.
Then, according to a sub-pixel accuracy algorithm, a sub-pixel displacement from a peak value of the Gaussian distribution curve to a peak value of an image brightness distribution curve is calculated to acquire the displacement or the change amount of the liquid surface edge. For example, if the peak value of the image brightness distribution curve has a coordinate (m,n), according to the following Gaussian distribution equation (1), the sub-pixel displacement Δx from the peak value of the Gaussian distribution curve to the peak value m of the image brightness distribution curve can be obtained. Consequently, the displacement of the liquid surface edge in the x-direction is equal to m+Δx. Similarly, the displacement of the liquid surface edge in the y-direction is equal to n+Δy. In particular, if the calculation of the sub-pixel displacement is not performed, the precision is only one half of a pixel. Whereas, if the calculation of the sub-pixel displacement is performed, the precision is enhanced (e.g. several tenths to several hundredths of one pixel).
In equation (1), Zn, is the image intensity of the pixel m
Consequently, if the relationship between each pixel of the image frame and the actual height or distance has been previously known, the sub-pixel displacement can be converted into the actual rising or lowering extent of the liquid level. In particular, after all image frames are continuously subjected to the above calculation or the image frames separated by a specified time interval are subjected to the above calculation, the calculating result about the rising or lowering extent of the liquid level is accumulated or compared with the initial value that is obtained in the beginning of the measurement. Consequently, the change of the liquid level within an operating time period and the actual liquid level of the liquid in the detection region can be realized.
Moreover, the central processing unit may be programmed to generate a corresponding warning signal when the liquid level reaches a preset value. The warning signal is transmitted to a back-end device through the signal transmission unit in order to prompt or warn the user or the guarder. Moreover, in addition to the warning signal, the acquired image stream is also transmitted through the signal transmission unit simultaneously. Alternatively, according to the practical requirements, the image stream may be transmitted to the back-end device at a specified time point. Under this circumstance, the real scene can be watched in real time while avoiding transmitting huge amount of data.
Moreover, if the signal transmission unit of the digital electronic device 11 has a wireless transmission function, associated signals are transmitted by a wireless transmission technology. Alternatively, the digital electronic device 11 may be connected with the back-end device through a network cable, and associated signals are transmitted by a wired transmission technology. Moreover, the image analyzing operation may be directly performed by the central processing unit of the digital electronic device 11 at the local end. Alternatively, the image analyzing operation may be performed by the back-end device. For example, the digital electronic device is a web camera. The web camera is only able to capture images. Moreover, the image stream is simultaneously transmitted to the back-end device, and analyzed by the back-end device.
Hereinafter, a liquid level measuring device of a second embodiment of the present invention will be illustrated.
It is noted that numerous modifications and alterations of the light-transmissible part may be made while retaining the teachings of the invention. For example, in another embodiment, the partition structure is a deeply-colored flat plate, and the light-transmissible part comprises a groove and a transparent sheet. That is, for forming the light-transmissible part, an oblique groove with a specified inclined angle is firstly formed in the flat plate, and then the transparent sheet (e.g. an acrylic sheet or a plastic sheet) is disposed within the groove. Alternatively, in some other embodiments, an oblique line is painted on a flat plate, wherein the oblique line and the flat plate have high color contrast. As long as the position of the liquid surface is visible according to the different refractive indices of the liquid and air, the design of the oblique line is not restricted.
Please refer to
In the imaging formula U×Z=I×B, both of Z and B are in linear variation. That is, U/I=B/Z=constant. Consequently, when the lens 12 is operated in the fixed focus mode to shoot the second region 102, the focal length I is fixed, and the image length U is fixed. That is, even if the depths Z of the object at different, the image length U is identical. In this embodiment, since the inclined flat plate has an oblique light-transmissible part 21, the change of the liquid surface may be realized by observing the image of the light-transmissible part 21. For a specified depth Z, there is a difference ΔB between the B value of the light-transmissible part 21 and the B value of the central axis of the inclined flat plane. Since ΔU/I=ΔB/Z, ΔU is in direct proportion to ΔB. In other words, the change of ΔB of the light-transmissible part 21 indicates the change of the liquid surface.
In
For example, if the liquid level change is 2 meters and the width of the flat plate of the partition structure 20 is 0.3 meter, one unit of displacement of the image in the width direction may indicate 6.67 units of the liquid level change (i.e. 2/0.3=6.67). In case that one unit of displacement of the image is recorded by 1000 pixels, each pixel indicates 0.3 millimeter (i.e. 0.3 m/1000=0.3 mm). In other words, one pixel of displacement of the image indicates 2 mm of the actual liquid level change (i.e. 0.3 mm×6.67=2 mm or 2 m/1000=2 mm).
According to the image processing and analyzing technologies described in the first embodiment and in the prior art, if the calculation of the sub-pixel displacement is not performed (i.e. only the calculation of the integer pixel is done), the precision is only one half of a pixel. That is, in this example, the precision is one millimeter (i.e. 2 mm×0.5=1 mm). Whereas, if the calculation of the sub-pixel displacement is performed, the precision is enhanced (e.g. several tenths to several hundredths of one pixel). Consequently, after the positions of the bright fringes shown on two image frames are calculated and compared with each other (i.e. the calculation of the sub-pixel displacement is performed), the liquid level change may be acquired. Under this circumstance, the actual liquid level of the liquid in the detection region is realized. Moreover, the use of the partition structure 20 can increase the measuring precision.
Moreover, in case that the slope of the light-transmissible part 21 is adjusted, the measuring precision is correspondingly adjusted. From the above discussions, as the slope of the light-transmissible part 21 decreases, the measuring precision increases.
In this embodiment, the light source 13 illuminates the second region 102 that does not contain the liquid. However, since the liquid and the air have different refractive indices, even if the light source 13 illuminates the first region 101 containing the liquid, the interface between the liquid surface and the air is clearly visible. Alternatively, in some other embodiments, the second region 102 also has an opening for allowing the liquid to flow through. Under this circumstance, the liquid level in the first region 101 is equal to the liquid level in the second region 102, and the obvious light reflection occurs under the irradiation of the light beams of the light source 13.
It is noted that numerous modifications and alterations of the partition structure 20 may be made while retaining the teachings of the second embodiment.
Hereinafter, a liquid level measuring device of a third embodiment of the present invention will be illustrated.
As shown in
In
For example, if the liquid level change is 2 meters and the diameter of the bottom surface of the cone-shaped partition structure 30 is 0.3 meter and the diameter of the circular trajectory of the bright fringe is recorded by 1000 pixels, the circular trajectory of the bright fringe is recorded by 3141 pixels (i.e. π×1000=3141). In other words, one pixel of displacement of the image indicates 0.64 mm of the liquid level change (i.e. 2 m/3141=0.64 mm). Consequently, after the positions of the bright fringes shown on any two image frames are calculated and compared with each other (i.e. the calculation of the sub-pixel displacement is performed), the liquid level change may be acquired. Under this circumstance, the actual liquid level of the liquid in the detection region is realized. Moreover, in comparison with the inclined flat plate, the use of the cone-shaped partition structure 30 can further increase the measuring precision.
Moreover, in case that the slope of the light-transmissible part 31 is adjusted, the measuring precision is correspondingly adjusted. From the above discussions, as the slope of the light-transmissible part 31 decreases, the measuring precision increases. Moreover, the decrease of the slope of the light-transmissible part 31 indicates more turns of travelling the light-transmissible part 31 from the bottom to the top of the partition structure 30.
It is noted that numerous modifications and alterations of the partition structure may be made while retaining the teachings of the second embodiment and the third embodiment. For example, in some other embodiments, the partition structure is a trapezoidal pyramid structure. The trapezoidal pyramid structure has a square bottom surface and four trapezoidal lateral surfaces. Moreover, the trapezoidal pyramid structure is inclined relative to the lower portion of the container, the inner portion of the trapezoidal pyramid structure is hollow, and a square hole is formed in a top surface of the trapezoidal pyramid structure. Moreover, the light-transmissible part is traveled around the four lateral surfaces of the trapezoidal pyramid structure. According to such design, the bright fringe is moved along a square trajectory. Similarly, after the calculation of the sub-pixel displacement is performed, the liquid level change may be acquired.
From the above embodiments and possible variant examples, the liquid level measuring device of the present invention is capable of effectively measuring the liquid level in the detection region and the liquid level change that varies with time. However, in the above embodiments, since the opening of the liquid level measuring device for allowing the liquid to flow through is located at the lower portion of the container, the applications of the liquid level measuring device is restricted. For example, it is difficult to use the liquid level measuring devices of the above embodiments to measure the quantity of rainfall.
Hereinafter, a liquid level measuring device of a fourth embodiment of the present invention will be illustrated.
Since the partition structure 40 is a pipe structure with a fixed diameter, the cross section area of the pipe structure is fixed. The product of the cross section area of the pipe structure multiplied by the depth of the liquid is equal to the quantity of rainfall. Moreover, the quantity of rainfall divided by the area of the water collector is equal to the rainfall depth per unit area. Moreover, the partition structure 40 also has a light-transmissible part (not shown). The way of forming the light-transmissible part and the corresponding image analyzing operation are similar to those of the second embodiment, and are not redundantly described herein.
Moreover, by referring to the teachings of the fourth embodiment, the liquid level measuring device of the third embodiment may be modified to measure the quantity of rainfall. For example, the outer appearance of the container and the partition structure within the container match each other. That is, the outer appearance of the container is also cone-shaped. Consequently, the first region that contains the liquid has a uniform diameter. After an opening (or more than one opening) is formed in the upper portion of the container or a corresponding water collector (or more than one water collector) is installed, the efficacy of accurately measuring the quantity of rainfall is also achievable.
From the above descriptions, the present invention provides a liquid level measuring device. For effectively measuring the liquid level and applying to different situations, an opening may be located at a lower portion or an upper portion of a container. Moreover, although the container is not completely sealed, as shown in the above drawings, a digital electronic device and a lens of the liquid level measuring device are still disposed within a relatively sealed environment. That is, since the ambient light beams are nearly blocked from entering the container, the quality of the captured image is not interfered by the ambient light beams. Since the container of the liquid level measuring device of the present invention is capable of blocking the ambient light beams and shielding the inner components, the container may be also referred as a shielding container.
In the above embodiments, the lens is operated in the fixed focus mode. However, for acquiring an appropriate image frames or displaying range, the lens may be manually manipulated (e.g. remotely controlled) to be zoomed in or zoomed out according to the liquid level change. Moreover, in some practical situations, the liquid level measuring device is not ideally installed in the detection region. For example, if the terrain in the detection region is bumpy, the optical axis of the lens is not ideally perpendicular to the detection plane (i.e. the liquid surface). That is, the optical axis of the lens may be tilted. After associated image analyzing technologies are performed to calculate and convert the image data of the liquid surface image, the liquid level at the detection region can also be effectively realized.
Alternatively, in some embodiments, the partition structure may be designed as a cylindrical structure. Under this circumstance, the cylindrical structure is not inclined relative to the lower portion of the container. Whereas, the cylindrical structure is perpendicular to the lower portion of the container. The slope of the light-transmissible part is non-linear. In particular, the slope of the light-transmissible part is inversely related to the water level. That is, the slope of the light-transmissible part varies with the altitude of the light-transmissible part relative to the bottom surface of the cylindrical structure. For example, the slope of the light-transmissible part corresponding to the lower altitude of the cylindrical structure is smaller, and the slope of the light-transmissible part corresponding to the higher altitude of the cylindrical structure is larger. In such design, if the liquids at different depths have the identical liquid level change, the image distance is identical. Consequently, the uniform measuring precision is achievable.
In the liquid level measuring device of the above embodiments, the container is made of an opaque material, and the outer appearance of the container is designed as a sealed structure. Since the ambient light beams are nearly blocked from entering the container, the processes of capturing images are not interfered by the ambient light beams. Moreover, since the known digital electronic device and the known light source are employed for capturing images, processing and analyzing images, transmitting signals and illuminating the detection plane, the installation cost of the liquid level measuring device is reduced, and associated images and information can be immediately transmitted to the back-end device to be used and watched by the user. Moreover, by means of the inclined partition structure and the light-transmission part and by analyzing the sub-pixel accuracy of the captured images, the liquid level change can be measured more accurately and precisely. Consequently, the liquid level of the liquid in the detection region can be accurately realized.
As a consequence, the liquid level measuring device of the present invention is effective to solve the problems encountered from the prior art technology and achieve industrial advance and development.
While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102123307 | Jun 2013 | TW | national |
