JPS5836032Y2 - level detection device - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a level detection device.

Furthermore, the present invention relates to a level detecting device (more specifically, a level detecting device having a level detecting section and a calculating section consisting of an optical system and an electric system, with high accuracy and high follow-up speed).

Conventionally, several devices have been proposed that attempt to detect the surface level of an object (for example, a liquid in a tank, powder, etc.) in a non-contact manner.

For example, a device has been proposed that focuses reflected and scattered light on the surface of an object through a lens and detects changes in the level of the object based on changes in the length of the image projected onto a light receiver (
(Japanese Patent Application Laid-Open No. 51-60563).

However, this device has a drawback in that the light-receiving element can clearly identify the shape of the object and can detect a level change only when the shape of the object does not change.

A method has also been proposed in which the reflected and scattered light of the luminous flux irradiated onto the object is focused through a lens and projected onto a receiver, and the change in the object level is detected by the change in the projection position of the focused light. (Japanese Unexamined Patent Publication No. 52-57842).

However, with this device, if the surface level of the object changes constantly at a high speed or if bubbles occur on the surface, the detection speed of the receiver itself is too slow to follow the level changes. However, if the irradiation light source and receiver are placed close together, the accuracy will drop significantly due to the principle of measurement, making detection impossible. Therefore, it has been difficult to provide the irradiation light source and the light receiver close to each other and to reduce the detection window of the device.

The purpose of the present invention is to overcome the drawbacks of such conventional devices,
It can be detected even when the shape of the object is unclear or changing, and it can also be detected when the surface level of the object changes drastically or when bubbles have formed on the surface. It is an object of the present invention to provide an excellent level detection device which enables level detection to be carried out in the same manner, and furthermore, allows the irradiation light source and the light receiver to be disposed close to each other so that the detection window of the device can be made small.

In order to achieve this object, the level detection device of the present invention consists of a level detection section consisting of illumination/reception means, and an arithmetic section that processes signals from the detection section, and the illumination means is located above the surface to be detected. The light receiving means comprises an optical system that irradiates a detection surface with a pair of light beams having respective optical axes in directions that intersect with each other. and the arithmetic unit is characterized by comprising a computer and an output converter capable of statistically averaging the output of the -dimensional image sensor.

Hereinafter, the present invention will be specifically explained with reference to Figure Q.

FIG. 1 is a schematic diagram of a level detection device according to an embodiment of the present invention.

As shown in the figure, the level detection device 1 installed above the storage tank 9 intersects above the detection surface 8 of the object (liquid in this example), and is linearly symmetrical to the normal n. A pair of lasers 2, 2' having respective optical axes, cylindrical lenses 3, 3' placed on the optical axes, an imaging lens 4 provided perpendicular to the normal line n, an imaging lens 4 A one-dimensional image sensor 5, a -dimensional image sensor 5 that receives an image of
The computer 6 receives the output of the computer 6, and the D/A converter 7 converts the output of the computer 6.

Laser 2, 2', J: emitted light beam l, l'
4, a slit-shaped projected image m9m' is formed on the detection surface 8 through the cylindrical lenses 3 and 3', respectively.

FIG. 2 is a plan view of the detection surface 8 seen from above the normal line n.

The projected images m and m'l are received by the imaging lens 4 and the one-dimensional image sensor 5 and subjected to surface image processing.

-Output of the dimensional image sensor 5 (an example is shown in FIG. 3).

C: constant, ■: lightning voltage t: time) is processed by the computer 6 as follows.

Now, assuming that the distance between the projected images m and m' is X, and the distance between the detection surface 8 and the imaging lens 4 is L, the following equation holds between X and L.

L=aX+b (a, b: constants) That is, the projected image m on the detection surface 8 by the pair of lasers 2 and 2',
By detecting the distance X between m', the imaging lens 4 (
The vertical distance between the detected surface 8 and the detected surface 8 is calculated.

The values of X and L are statistically averaged in a computer.

The output of the computer 6 is converted into an analog quantity by the D/A converter 7, and then recorded on a recorder or the like (not shown), thereby making it possible to monitor level fluctuations on the detection surface 8.

In the present invention, not only the laser as in the above embodiment but also other light beam generating devices can be used as the illumination means.

In short, any illumination means that can provide a clear projected image on the surface to be detected can be used, but a laser is particularly preferred.

Further, the cylindrical lens is used to make the projected image into a slit shape rather than a spot shape, and it is preferable to have a cylindrical lens in terms of obtaining a clearer projected image.

The optical axes of the light beams emitted from these pair of optical systems are preferably symmetrical with respect to the normal to the detection surface, but even if they are asymmetrical, they can be easily calibrated.

The imaging lens does not need to be a single lens; for example, a camera-like lens system can also be used.

This lens system is preferably installed perpendicular to the normal to the surface to be detected, but it can also be easily calibrated even if it is not perpendicular.

A one-dimensional image sensor is a self-scanning image sensor that also has a built-in scanning function, and has a large number of photodiodes that are densely arranged in one dimension to convert the incident light pattern into electrical signals.
In addition, an address switch for addressing each photodiode and a scanning circuit are integrated on a single substrate.

The features of this -dimensional image sensor are high detection accuracy due to high resolution and high tracking speed (on the order of m5ec) due to high scanning ability.

As the computer, a microcomputer (including an interface) or the like can be used.

A normal D/A converter can be used as the output converter.

According to the level detection device of the present invention, projection images are formed at two locations on the detection surface using the optical system that generates a pair of intersecting light beams.
Even when bubbling occurs, a pair of clear images is projected onto the detection surface, and this projected image is received by the one-dimensional image sensor through the imaging lens, so the distance between the images can be determined with extremely high precision. It is possible to stably track cases where the level of the surface to be detected is constantly repeating vertical movements.

Furthermore, since the output signals of this dimensional image sensor are processed by a computer, the calculation accuracy is high and the speed is high.

Therefore, if the level detection device of the present invention is used, even if the shape of the object is unclear or changes,
In addition, it is also possible to level the surface with extremely high accuracy and high speed even when the target has bubbles on the surface or has severe changes in vertical movement, which would be difficult to track or be impossible to track with conventional equipment. It becomes possible to detect.

In particular, it is extremely effective and suitable for level detection at interfaces where bubbles occur on the surface and are constantly moving up and down, such as in various reaction tanks and polymerization tanks in the chemical industry.

Moreover, since the optical axes of the light beams intersect, the illuminating means and the light receiving means can be installed close to each other, and therefore the detection window provided in the apparatus can be made very small.

Furthermore, if a laser spot is used as the light beam, the surface level can be accurately detected without being affected by the measurement environment such as temperature, pressure, and brightness, the shape of the object, or the surface composition.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a level detection device according to an embodiment of the present invention, FIG. 2 is a plan view of a surface to be detected, and FIG. 3 is an output waveform diagram of a one-dimensional image sensor. code, 1 two-level detection device, 2, 2': laser, 4:
Imaging lens, 5 one-dimensional image sensor, 6: computer,
7: D/A converter, 8: detection surface.

Claims (1)

[Scope of utility model registration request] It consists of a level detection section consisting of illumination and light reception means, and a calculation section that processes the signal from the detection section, and the illumination means includes:
It consists of an optical system that irradiates the detection surface with a pair of light beams whose respective optical axes extend in directions that intersect above the detection surface.
The light receiving means includes a lens system and a one-dimensional image sensor provided between the pair of optical systems, and the one-dimensional image sensor detects the distance between the pair of light beam images on the detection surface as an electrical signal. and the calculation unit calculates the level of the detection surface from the output of the -dimensional image sensor according to a mathematical formula, and further statistically averages the results to improve accuracy; and A level detection device comprising an output converter.