A liquid level continuous measuring instrument based on the principle of total internal reflection of light

Abstract

The present invention discloses a liquid level continuous measuring instrument based on the principle of total internal reflection of light, which relates to the field of optoelectronic detection technology and includes an optoelectronic unit and a sensing unit; the optoelectronic unit includes: a linear light source, a linear light source driving circuit, a linear array photodetector, and a linear array photodetector driving circuit; the sensing unit includes a straight quadrangular prism optical prism and a reflection grating; the linear array photodetector and the linear array photodetector driving circuit are both arranged on the first side surface of the straight quadrangular prism optical prism; the linear light source and the linear light source driving circuit are both arranged on the second side surface of the straight quadrangular prism optical prism; the reflection grating is arranged on the third side surface of the straight quadrangular prism optical prism. The measuring instrument provided by the present invention can achieve precise measurement of continuously changing liquid levels.

Description

Technical Field

[0001] The present invention relates to the technical field of optoelectronic detection, and particularly to a liquid level continuous measuring instrument based on the principle of total internal reflection of light. Background Art

[0002] The measurement of liquid level is widely used in industries such as petroleum, medicine, food, and metallurgy, and is a relatively common and important measurement parameter in the industrial production process. Current liquid level measurement methods include:

[0003] 1. Buoy type measurement. This measurement method is a mechanical detection method, which detects the change of liquid level through the lifting amplitude of the buoy. The detection accuracy is affected by liquid density and buoyancy of the buoy, and the repeatability accuracy is poor. When measuring different liquids, the measurement scale of the buoy needs to be recalibrated. It is not suitable for viscous or impurity-containing liquids.

[0004] 2. Tuning fork vibration measurement. This measurement method is a physical measurement method. When liquid or bulk materials fill between two vibrating tuning forks, the resonance frequency changes and a switch signal is sent out. The tuning fork type measurement only outputs switch quantities and cannot be used for continuous monitoring of liquid height.

[0005] 3. Ultrasonic measurement. The liquid level height is calculated by detecting the time difference between ultrasonic wave transmission and reflection, and is easily affected by the energy loss of ultrasonic wave propagation. Therefore, when used in an environment with wave absorption such as foam, the measurement effect is severely limited.

[0006] 4. Laser measurement. Laser sensors are based on the principle of optical detection, and detect by reflecting light from the object surface to the receiver. It is not suitable for use in transparent liquids (transparent liquids are easy to refract light, resulting in the inability of light to be reflected to the receiver), environments containing foam or steam (unable to penetrate foam or easily interfered by steam), fluctuating liquids (easy to cause false actions), vibration environments, etc.

[0007] 5. Capacitive measurement. Capacitive measurement measures the material level height by detecting the change of capacitance value caused by the change of liquid level or bulk material height. Capacitive sensors are easily affected by different container materials and solution properties, such as plastic containers and hanging materials, which easily affect the capacitive sensors with analog output.

[0008] 6. Hydrostatic pressure measurement. This measurement method uses a pressure sensor installed at the bottom to detect the liquid pressure at the bottom and converts and calculates the liquid level height. This measurement method requires the use of a high-precision, flush-mounted pressure sensor.

[0009] 7. Photoelectric refraction measurement. In this detection method, a light source is emitted inside the sensor. The light source is totally reflected by the transparent resin to the sensor receiver. However, when it encounters the liquid surface, part of the light will be refracted into the liquid. Thus, the sensor monitors the liquid level by detecting the decrease in the amount of light reflected back by total reflection. This detection method is inexpensive and simple to install and debug, but it can only be applied to transparent liquids and only outputs digital signals.

[0010] The above-mentioned several measurement methods can be used alone or in combination, but their applications in industrial environments such as high voltage and strong magnetic fields are restricted. Summary of the Invention

[0011] The purpose of the present invention is to provide a liquid level continuous measuring instrument based on the principle of optical total reflection to achieve accurate measurement of continuously changing liquid levels.

[0012] To achieve the above purpose, the present invention provides the following solution:

[0013] A liquid level continuous measuring instrument based on the principle of optical total reflection includes a photoelectric unit and a sensing unit;

[0014] The photoelectric unit includes: a linear light source, a linear light source driving circuit, a linear array photodetector, and a linear array photodetector driving circuit;

[0015] The sensing unit includes a straight quadrangular prism optical prism and a reflection grating;

[0016] The linear array photodetector and the linear array photodetector driving circuit are both arranged on the first side surface of the straight quadrangular prism optical prism; the linear light source and the linear light source driving circuit are both arranged on the second side surface of the straight quadrangular prism optical prism; the reflection grating is arranged on the third side surface of the straight quadrangular prism optical prism.

[0017] Optionally, the first side surface and the third side surface of the straight quadrangular prism optical prism are parallel to each other.

[0018] Optionally, the second side surface of the straight quadrangular prism optical prism is perpendicular to the first side surface and the third side surface respectively.

[0019] Optionally, the straight quadrangular prism optical prism further includes a fourth side surface; the included angle formed by the fourth side surface and the third side surface is α, where α < 45°.

[0020] Optionally, the reflection grating includes a reflection surface and a non-reflection surface; the non-reflection surface of the reflection grating is perpendicular to the reflection surface of the reflection grating; the included angle between the reflection surface of the reflection grating and the third side surface is β, where β ≥ (90° - 3α / 2).

[0021] Optionally, the straight quadrangular prism optical prism is a right trapezoid; the linear array photodetector is located on the upper base surface of the right trapezoid, and the linear light source is located on the waist surface of the right trapezoid, so that the light emitted by the linear light source is reflected by the straight quadrangular prism optical prism to the linear array photodetector; wherein, the waist surface is the waist surface perpendicular to the upper base surface.

[0022] Optionally, the liquid level continuous measuring instrument based on the principle of total internal reflection of light is also provided with a photoelectric unit sealed protective cover; the photoelectric unit is sealed in the photoelectric unit sealed protective cover.

[0023] Optionally, the sensing unit is also provided with a sealed protective cover; the reflection grating is sealed in the sealed protective cover.

[0024] Optionally, the reflection grating is arranged in the third side area close to the fourth side.

[0025] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0026] The present invention provides a liquid level continuous measuring instrument based on the principle of total internal reflection of light. Based on the principle of total internal reflection of light, by effectively separating the active optical device from the passive optical device, that is, isolating the photoelectric unit and the sensing unit, the active optical device, that is, the optoelectronic device, can measure or give an early warning of the liquid level without being immersed in the liquid. Through the difference in the light intensity signals received by the linear array photodetector in the photoelectric unit, the continuous and accurate measurement of the liquid level measuring instrument is realized. Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0028] Figure 1 It is a schematic structural diagram of the liquid level continuous measuring instrument based on the principle of total internal reflection of light in Embodiment 1 of the present invention;

[0029] Figure 2 It is a schematic structural diagram of the straight quadrangular prism optical prism of the liquid level continuous measuring instrument based on the principle of total internal reflection of light in Embodiment 1 of the present invention;

[0030] Figure 3 It is a vertical cross-sectional view of the liquid level continuous measuring instrument based on the principle of total internal reflection of light in Embodiment 1 of the present invention;

[0031] Figure 4It is the light intensity signal curve graph detected by the linear array photodetector of the liquid level continuous measuring instrument based on the optical total reflection principle in Embodiment 1 of the present invention;

[0032] Figure 5 It is the structure schematic diagram of the liquid level continuous measuring instrument based on the optical total reflection principle in Embodiment 2 of the present invention;

[0033] Figure 6 It is the light intensity signal curve graph detected by the linear array photodetector of the liquid level continuous measuring instrument based on the optical total reflection principle in Embodiment 2 of the present invention.

[0034] Symbol description:

[0035] 1 - linear light source, 2 - linear array photodetector, 3 - straight quadrangular prism optical prism, 4 - reflection grating, 5 - linear light source drive circuit, 6 - linear array photodetector drive circuit, 7 - photoelectric unit airtight protective cover, 8 - airtight protective cover, 9 - liquid to be measured, 10 - liquid container, 12 - first linear array photodetector, 13 - second linear array photodetector, 16 - first linear array photodetector drive circuit, 17 - second linear array photodetector drive circuit, 18 - overall airtight protective cover, 19 - right-angled triangular prism, 20 - obtuse-angled triangular prism. Specific implementation manners

[0036] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0037] The purpose of the present invention is to provide a liquid level continuous measuring instrument based on the optical total reflection principle to achieve accurate measurement of continuously changing liquid levels.

[0038] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the drawings and specific implementation manners.

[0039] Embodiment 1

[0040] As Figure 1As shown in the figure, the present invention provides a liquid level continuous measuring instrument based on the principle of total internal reflection of light. The liquid level continuous measuring instrument based on the principle of total internal reflection of light includes an optoelectronic unit and a sensing unit. The optoelectronic unit includes: a linear light source 1, a linear light source driving circuit 5, a linear array photodetector 2, and a linear array photodetector driving circuit 6. The sensing unit includes a straight quadrangular prism optical prism 3 and a reflection grating 4. The linear light source 1 and the linear array photodetector 2 are vertically bonded to two side surfaces of the straight quadrangular prism optical prism 3. The linear array photodetector 2 and the linear array photodetector driving circuit 6 are both arranged on the first side surface of the straight quadrangular prism optical prism 3. The linear light source 1 and the linear light source driving circuit 5 are both arranged on the second side surface of the straight quadrangular prism optical prism 3. The reflection grating 4 is arranged on the third side surface of the straight quadrangular prism optical prism 3.

[0041] Wherein, the first side surface and the third side surface of the straight quadrangular prism optical prism 3 are parallel to each other. The second side surface of the straight quadrangular prism optical prism 3 is perpendicular to the first side surface and the third side surface respectively.

[0042] In addition, if the straight quadrangular prism optical prism 3 further includes a fourth side surface. The included angle formed by the fourth side surface and the third side surface is α, where α < 45°.

[0043] In addition, as Figure 2 shown, the reflection grating 4 includes a reflection surface and a non-reflection surface. The non-reflection surface of the reflection grating 4 is perpendicular to the reflection surface of the reflection grating 4. As Figure 3 shown, the included angle between the reflection surface of the reflection grating 4 and the third side surface is β, where β ≥ (90° - 3α / 2). The reflection grating 4 is arranged in the area of the third side surface close to the fourth side surface. The reflection grating 4 is a two-dimensional grating made on the right side of the straight quadrangular prism, and the grating grooves are at the position of the third side surface as Figure 3 shown, and the grating grooves are perpendicular to the paper surface.

[0044] Preferably, as Figure 1-2 shown, the straight quadrangular prism optical prism 3 is a right trapezoid. The linear array photodetector 2 is located on the upper bottom surface of the right trapezoid, and the linear light source 1 is located on the waist surface perpendicular to the upper bottom surface, so that the light emitted by the linear light source 1 is reflected by the straight quadrangular prism optical prism 3 to the linear array photodetector 2. Wherein, the waist surface is the waist surface perpendicular to the upper bottom surface.

[0045] In order to better meet the actual application, the liquid level continuous measuring instrument based on the principle of total internal reflection of light is also provided with an optoelectronic unit sealed protective cover 7. The optoelectronic unit is sealed in the optoelectronic unit sealed protective cover 7. Other optoelectronic components of the optoelectronic unit are also sealed in the optoelectronic unit sealed protective cover 7.

[0046] To better conform to practical applications, the sensing unit is further provided with a sealed protective cover 8; the reflection grating 4 is sealed within the sealed protective cover 8.

[0047] In addition, when the liquid level continuous measuring instrument based on the principle of total internal reflection of light is in use, the light intensity signal curve detected by the linear array photodetector 2 is as Figure 4 shown.

[0048] Working principle of the liquid level continuous measuring instrument based on the principle of total internal reflection of light:

[0049] During use, the sensing unit is placed inside the liquid container 10, and the liquid level continuous measuring instrument based on the principle of total internal reflection of light is perpendicular to the liquid surface of the liquid to be measured 9.

[0050] Under the action of the linear light source driving circuit 5, the linear light source 1 in the optoelectronic unit emits a light beam that vertically enters the straight quadrangular prism optical prism 3. The incident light beam is transmitted to the lower inclined surface, i.e., the fourth side surface of the straight quadrangular prism optical prism 3, where it is reflected. The reflected light beam is transmitted to the reflection grating 4 on the right side surface, i.e., the third side surface of the straight quadrangular prism optical prism 3. The reflection grating 4 reflects the transmitted reflected light beam again to the linear array photodetector 2 on the left side surface, i.e., the first side surface of the straight quadrangular prism optical prism 3. Under the action of the linear array photodetector driving circuit 6, the linear array photodetector 2 converts the light signal reflected by the reflection grating 4 into an electrical signal.

[0051] When the liquid surface of the liquid to be measured 9 reaches a certain height, total internal reflection occurs for the incident light beam in the part above the liquid surface. The light beam after total internal reflection is reflected into the linear array photodetector 2 under the action of the reflection grating 4. Since the light beam emitted by the linear light source 1 can all return to the linear array photodetector 2, at this time, the light signal intensity detected by the linear array photodetector 2 is the largest. For the light beam transmitted below the liquid surface, since the condition of total internal reflection is not satisfied, part of the light beam is transmitted into the liquid to be measured 9, resulting in attenuation of the light intensity of the light beam that is reflected to the reflection grating 4 and then reflected into the linear array photodetector 2 again. Therefore, a jump occurs among all the light intensity signals received by the linear array photodetector 2, as Figure 4 shown. By calculating the position change of the jump in the photoelectric signal received by the linear array photodetector 2, continuous measurement of the liquid level is achieved.

[0052] For different liquids to be measured, linear light sources and linear array photodetectors with different spectral bands can be selected.

[0053] Embodiment 2

[0054] As Figure 5 shown, in this embodiment, a right-angled triangular prism 19 and an obtuse-angled triangular prism 20 are glued together to form a straight quadrangular prism optical prism. The straight quadrangular prism optical prism is a right-angled trapezoid body;

[0055] The first linear photodetector 12 and the first linear photodetector driving circuit 16 are both disposed on the first side surface of the straight quadrangular prism optical prism; the linear light source 1 and the linear light source driving circuit 5 are both disposed on the second side surface of the straight quadrangular prism optical prism; the second linear photodetector 13, the second linear photodetector driving circuit 17 and the reflection grating 4 are disposed on the third side surface of the straight quadrangular prism optical prism. Among them, the second linear photodetector 13 and the second linear photodetector driving circuit 17 are disposed in the area of the third side surface close to the second side surface. The reflection grating 4 is disposed in the area of the third side surface close to the fourth side surface.

[0056] Among them, the first side surface and the third side surface of the straight quadrangular prism optical prism are parallel to each other. The second side surface of the straight quadrangular prism optical prism is perpendicular to the first side surface and the third side surface respectively.

[0057] In addition, if the straight quadrangular prism optical prism further includes a fourth side surface; the included angle formed by the fourth side surface and the third side surface is α, where α < 45°.

[0058] In addition, the reflection grating 4 includes a reflection surface and a non-reflection surface; the non-reflection surface of the reflection grating 4 is perpendicular to the reflection surface of the reflection grating 4. The included angle between the reflection surface of the reflection grating 4 and the third side surface is β, where β ≥ (90° - 3α / 2). The reflection grating 4 is a two-dimensional grating fabricated on the right side of the straight quadrangular prism, and the grating grooves are perpendicular to the paper surface.

[0059] Preferably, the first linear photodetector 12 is located on the upper bottom surface of the right trapezoid body, and the linear light source 1 is located on the waist surface of the right trapezoid body, where the waist surface is the waist surface perpendicular to the upper bottom surface. The second linear photodetector 13 is located on the lower bottom surface of the right trapezoid body, so that the light emitted by the linear light source 1 is reflected by the straight quadrangular prism optical prism to the second linear photodetector 13.

[0060] To better meet the actual application, the liquid level continuous measuring instrument based on the principle of total internal reflection of light is further provided with an overall airtight protective cover 18. The first linear photodetector 12, the first linear photodetector driving circuit 16, the second linear photodetector 13, the second linear photodetector driving circuit 17, the linear light source 1 and the linear light source driving circuit 5 are all disposed inside the overall airtight protective cover 18.

[0061] When the outgoing light beam of the line light source 1 is perpendicularly incident on the bonding surface of the right-angled triangular prism 19 and the obtuse-angled triangular prism 20, the reflected light beam of the bonding surface exits from a right-angled side surface of the right-angled triangular prism 19 and enters the first linear photodetector 12 to realize the monitoring of the output light intensity of the line light source 1; the light beam transmitted by the bonding surface is incident on the other obtuse hypotenuse of the obtuse-angled triangular prism 20. Above the liquid level of the liquid to be measured 9, total reflection occurs for the light beam transmitted by the bonding surface; the light beam after total reflection is incident on the reflection grating 4, and the reflection grating 4 reflects the light beam back to the bonding surface again; the bonding surface exits the light beam from the bottom edge of the obtuse-angled triangular prism 20.

[0062] For the light beam below the liquid level of the liquid to be measured 9, since the total reflection condition is not satisfied, the transmitted light enters the liquid to be measured 9, and part of the reflected light beam exits from the bottom edge of the obtuse-angled triangular prism 20 after being reflected by the reflection grating 4 and the bonding surface and enters the second linear photodetector 13.

[0063] As Figure 6 shown, due to the presence of the liquid to be measured 9, the light intensity curve detected by the second linear photodetector 13 undergoes a sudden change at the position corresponding to the liquid level.

[0064] The present invention also provides a method for continuously measuring the liquid level based on the principle of optical total reflection, which is applied to the liquid level continuous measuring instrument based on the principle of optical total reflection in any one of Embodiment 1 and Embodiment 2, and specifically includes:

[0065] Obtain the light intensity information detected by the linear photodetector;

[0066] Judge whether there is a jump in the light intensity information detected by the linear photodetector; if so, calculate the position change where the jump occurs to obtain the liquid level position.

[0067] The device provided by the present invention is based on the principle of optical total reflection. A straight quadrangular prism optical prism with a part of one side surface having the function of reflecting light beams after being processed by a special process is used as the sensing unit in the optical fiber sensing ring, and a line light source and a linear photodetector are used as the optoelectronic unit. Since the optoelectronic unit is not immersed in the liquid to be measured, all the sensing units immersed in the liquid are passive devices. Therefore, accurate measurement of continuously changing liquid levels can be achieved under the influence of harsh environments such as external high voltages and strong magnetic fields. The general optoelectronic components used greatly reduce the cost of the liquid level measuring instrument and expand the application scenarios.

[0068] The liquid level continuous measuring instrument based on the principle of optical total reflection provided by the present invention has the following advantages:

[0069] 1. A liquid level testing device assembled with optical components such as a line light source, a linear photoelectric detector, and a straight quadrangular prism optical prism. The photoelectric unit (line light source and linear photoelectric detector) is located above the liquid surface to be measured, and only the sensing unit (straight quadrangular prism optical prism, mainly the lower inclined surface of the straight quadrangular prism optical prism and the reflection grating with a sealed cover) is in direct contact with the liquid to be measured. The reflection grating returns the light beam totally reflected by the lower inclined surface of the straight quadrangular prism optical prism along the original incident light path, avoiding the equipment failure caused by the immersion of the linear photoelectric detector in the liquid and restricting the application scenarios of the liquid level measuring instrument.

[0070] 2. A liquid level testing method based on the principle of total internal reflection and reflection principle of optics. When the incident light beam enters the lower inclined surface of the straight quadrangular prism optical prism, at the position where there is no liquid to be measured on the lower inclined surface, the incident light beam will undergo total internal reflection. The light beam after total internal reflection is reflected to the left side surface of the straight quadrangular prism optical prism at the reflection grating interface, and the linear photoelectric detector converts the received optical signal into an electrical signal; at the position where there is a liquid surface to be measured and below, the condition of total internal reflection of the incident light beam cannot be satisfied, a part of the light beam refracts into the liquid, and the other part of the reflected light beam is transmitted to the reflection grating, and the light beam after reflection returns to the linear photoelectric detector. According to the difference in the light intensity signals received by the linear photoelectric detector, the accuracy of the liquid level measuring instrument is achieved.

[0071] 3. The combination of the straight quadrangular prism optical prism and the reflection grating in the structure of the liquid level tester. The reflection grating reflects the light beam totally reflected by the lower inclined surface of the straight quadrangular prism optical prism to the linear photoelectric detector adhered to the left side surface at an acute angle, which greatly reduces the volume of the straight quadrangular prism.

[0072] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other.

[0073] In this article, specific examples are used to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, based on the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A liquid level continuous measuring instrument based on the principle of total internal reflection of light, characterized in that, the liquid level continuous measuring instrument based on the principle of total internal reflection of light includes a photoelectric unit and a sensing unit; the photoelectric unit includes: a linear light source, a linear light source driving circuit, a linear array photodetector, and a linear array photodetector driving circuit; the sensing unit includes a straight quadrangular prism optical prism and a reflection grating; the first side and the third side of the straight quadrangular prism optical prism are parallel to each other; the second side of the straight quadrangular prism optical prism is perpendicular to the first side and the third side respectively; the linear array photodetector and the linear array photodetector driving circuit are both arranged on the first side of the straight quadrangular prism optical prism; the linear light source and the linear light source driving circuit are both arranged on the second side of the straight quadrangular prism optical prism; the reflection grating is arranged on the third side of the straight quadrangular prism optical prism.

2. The liquid level continuous measuring instrument based on the principle of total internal reflection of light according to claim 1, characterized in that, the straight quadrangular prism optical prism further includes a fourth side; the included angle formed by the fourth side and the third side is α, where α < 45°.

3. The liquid level continuous measuring instrument based on the principle of total internal reflection of light according to claim 2, characterized in that, the reflection grating includes a reflection surface and a non-reflection surface; the non-reflection surface of the reflection grating is perpendicular to the reflection surface of the reflection grating; the included angle between the reflection surface of the reflection grating and the third side is β, where β ≥ (90° - 3α / 2).

4. The liquid level continuous measuring instrument based on the principle of total internal reflection of light according to claim 1, characterized in that, the straight quadrangular prism optical prism is a right trapezoid; the linear array photodetector is located on the upper base surface of the right trapezoid, and the linear light source is located on the waist surface of the right trapezoid, so that the light emitted by the linear light source is reflected by the straight quadrangular prism optical prism to the linear array photodetector; wherein, the waist surface is the waist surface perpendicular to the upper base surface.

5. The liquid level continuous measuring instrument based on the principle of total internal reflection of light according to claim 1, characterized in that, the liquid level continuous measuring instrument based on the principle of total internal reflection of light is also provided with a photoelectric unit airtight protective cover; the photoelectric unit is sealed in the photoelectric unit airtight protective cover.

6. The liquid level continuous measuring instrument based on the principle of total internal reflection of light according to claim 1, characterized in that, the sensing unit is also provided with an airtight protective cover; the reflection grating is sealed in the airtight protective cover.

7. The liquid level continuous measuring instrument based on the principle of total internal reflection of light according to claim 1, characterized in that, the reflection grating is arranged in the area of the third side close to the fourth side.

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