JP2007278998A - Optical image focusing type liquid level sensor, and method of measuring liquid level displaced in inside of transparent tube using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical image-focusing type liquid level sensor, capable of measuring accurately and steplessly a liquid level displaced in the inside of a transparent tube installed vertically, and to provide a method of measuring the liquid level displaced in the inside of transparent tube that uses the same. <P>SOLUTION: The present invention provides the optical image focusing type liquid level sensor, comprising a light source 1 capable of illuminating the transparent tube A of a measuring object as a whole, an optical image-focusing system 2, and a linear light-receiving part 3 capable of image-focusing the transparent tube A of the measuring object as a whole, and the method of measuring the liquid level displaced in the inside of transparent tube by using the optical image-focusing type liquid level sensor, capable of image-focusing the light transmitted through the transparent tube A as a whole by the optical image-focusing system 2, on the linear sensor 3 capable of image-focusing the whole transparent tube A of the measuring object, by illuminating the transparent tube A of the measuring object as a whole, by using the linear light source 1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical imaging type liquid level sensor and a method for measuring a liquid level that displaces in a transparent tube using the same, and more particularly, to accurately and without disposing a liquid level that displaces in a transparent tube installed in a vertical direction. The present invention relates to an optical imaging type liquid level sensor capable of measuring in stages and a method for measuring a liquid level displaced in a transparent tube using the same.

  Conventionally, as a method of measuring the liquid level that displaces in a transparent tube, multiple light sources are installed in stages and projected, and multiple light receiving units (light receiving sensors) corresponding to the light sources are received by a tube filled with liquid. A method of measuring by changing the light quantity from the liquid surface by arranging at a possible position has been performed (see Patent Document 1).

  However, in this case, measurement was possible only at the installation interval of the light source and the corresponding light receiving sensor, and continuous fine reading was impossible.

JP 2004-301707 A

  The present invention solves the above-mentioned conventional problems, and uses a liquid imaging type liquid level sensor capable of accurately and continuously measuring a liquid level displaced in a transparent tube installed in a vertical direction. It is an object of the present invention to provide a method for measuring a liquid level displaced in a transparent tube.

That is, the present invention according to claim 1 is a linear light source having a light source having means for illuminating the entire transparent tube to be measured, an optical imaging system, and a linear shape capable of imaging the entire transparent tube to be measured. An optical imaging type liquid level sensor comprising a light receiving unit is provided.
The present invention according to claim 2 is a light source having means for illuminating the entire transparent tube to be measured when measuring the liquid level displaced in the transparent tube installed in the vertical direction, an optical imaging system, An optical imaging type liquid level sensor consisting of a linear light-receiving unit that can image the entire transparent tube to be measured, and the entire transparent tube to be measured is illuminated using the light source and transparent. The light transmitted through the entire tube is imaged on a linear light-receiving unit that can image the entire transparent tube to be measured by an optical imaging system, and the variation in the liquid level is measured by the light intensity. A method for measuring a liquid level displaced in a transparent tube is provided.

According to the present invention, it is possible to accurately and steplessly measure the liquid level displaced in the transparent tube installed in the vertical direction.
That is, since the present invention has an optical imaging system, the position of the liquid level can be accurately reproduced by the linear light receiving unit, and the displacement amount of the liquid level is measured in time series. be able to.
Moreover, the displacement of the liquid level can be measured steplessly as well as in time series.
Moreover, it is easy to apply optical restrictions, such as a polarizing plate, on a structure, and the stray light generated from a liquid level can be prevented.
Furthermore, even if the length of the transparent tube to be measured changes, it can be dealt with by changing the imaging magnification without changing the length of the light receiving section.

  An optical imaging type liquid level sensor according to a first aspect of the present invention forms an image of a light source having means for illuminating the entire transparent tube to be measured, an optical imaging system, and the entire transparent tube to be measured. It is composed of a linear light-receiving part that can be used.

  Hereinafter, the present invention according to claim 1 will be described in detail with reference to the drawings. FIG. 1 is an explanatory view showing an aspect of the optical imaging type liquid level sensor according to the first aspect of the present invention. In the figure, reference numeral 1 denotes a light source, reference numeral 2 denotes an optical imaging system, and reference numeral 3 denotes a linear light receiving unit. Reference symbol A is a transparent tube.

  The optical imaging type liquid level sensor of the present invention according to claim 1 includes a light source 1 having means for illuminating the entire transparent tube A to be measured, an optical imaging system 2, and the entire transparent tube A to be measured. And a linear light receiving portion 3 capable of forming an image.

  The transparent tube A to be measured is installed in the vertical direction and needs to have visible light permeability, and is specifically made of a glass tube or the like.

In the optical imaging type liquid level sensor of the present invention according to claim 1, the light source 1 has means for illuminating the entire transparent tube A to be measured.
In other words, the light source 1 needs to be able to illuminate the entire transparent tube A to be measured.
Specifically, as such a light source 1, for example, a linear light source (line light source) having a length equal to or greater than that of the transparent tube A to be measured can be cited. More specifically, examples of this type include LEDs arranged in a vertical direction, tube lighting such as a fluorescent lamp, and a light source having means for expanding a point light source in a slit shape.
When an LED is used, the amount of light can be diffused by a diffuser plate (diffuser) 5 so that the entire transparent tube A to be measured can be illuminated uniformly, and unevenness in the light intensity of the limiting light can be eliminated. it can.
If necessary, the S / N ratio of the linear light receiving unit 3 can be improved by providing a slit-shaped diaphragm 4 between the light source 1 and the transparent tube A, and Stray light can be prevented. Further, by providing the slit-shaped diaphragm 4 in this way, the light receiving part can be determined at an arbitrary position. FIG. 2 is an explanatory view showing an example of the slit-shaped diaphragm 4.
Furthermore, linearly polarized light such as a laser diode can be used as the light source 1, and one or two or more thereof are combined and irradiated in a linear (line) or sheet form. When such linearly polarized light is used, an adverse effect on measurement due to stray light or the like can be prevented by placing a linearly polarizing plate in front of the light receiving unit 3 and restricting it.

Next, as the optical imaging system 2, any optical system can be used as long as it can image light from the linear light source 1 onto the linear light receiving unit 3, and a convex lens is usually used.
In the present invention, since the optical imaging system 2 is used, the linear light receiving unit 3 can be further downsized.
In the present invention, an image is formed using the optical imaging system 2 as described above, and the positional deviation of the imaging system is electrically captured by the linear light receiving unit 3 described below.

In addition, the light receiving unit 3 needs to be a line sensor that can form an image of the entire view of the transparent tube A to be measured. Specifically, for example, a line CCD, PSD or the like is used.
When the length of the light receiving unit 3 is long, a limiting mask that limits the measurement range may be provided.
As described above, when linearly polarized light is used, the linear polarizing plate 6 is placed in front of the light receiving unit 3 to restrict the adverse effect on measurement due to stray light or the like.

The optical imaging type liquid level sensor according to the first aspect of the present invention is basically as described above, but a reading device for reading the potential level of the light imaged on the light receiving unit 3 is required.
Examples of such a reader include analog and digital output arithmetic circuits for defect detection / measurement / image processing.

In order to measure the liquid level displaced in the transparent tube A installed in the vertical direction by using the optical imaging type liquid level sensor according to the first aspect of the present invention as described above, as described in the second aspect, According to the method.
That is, from a light source 1 having means for illuminating the entire transparent tube A to be measured, an optical imaging system 2, and a linear light receiving unit 3 capable of imaging the entire transparent tube A to be measured. An optical imaging type liquid level sensor is used to illuminate the entire transparent tube A to be measured using the linear light source 1, and light transmitted through the entire transparent tube A is optically imaged by the optical imaging system 2. The entire transparent tube A to be measured is imaged on a linear light receiving portion 3 that can form an image, and the variation in the liquid level is measured by the light intensity, thereby the inside of the transparent tube A installed in the vertical direction. What is necessary is to measure the liquid level which displaces.
The specific liquid level may be measured using a reader for reading the potential level of the light imaged on the light receiving unit 3 as described above.

[Measurement principle]
The principle of measuring the liquid level displaced in the transparent tube installed in the vertical direction according to the present invention as described above will be described as follows.
That is, as the light source 1, light emitted from a linear (line-shaped) light source or a light source that emits in a slit shape is used, and this is limited by a slit or a polarizing plate, if necessary.
In the case where the light intensity is uneven in the limited light spread in a slit shape, the dark current of the light receiving unit 3 is reduced with respect to the signal by inserting a diffuser 5 or the like.
When the liquid is filled in the transparent tube A, the light intensity incident on the light receiving unit 3 is substantially constant and does not change.
For example, when polarized light is used, if the liquid is filled in the transparent tube A, the light incident on the light receiving unit 3 maintains zero polarization characteristics, so that the amount of light incident on the light receiving unit 3 is zero.
However, when the liquid surface position is displaced, the light intensity changes at the boundary surface due to the difference in refractive index between air and the liquid surface, and a high potential point can be obtained as in the potential level graph shown at the right end of FIG. it can.
By making a table of the relationship between this point and the liquid volume in advance, if the potential point is known, the liquid level (flow rate) can be determined from the level of the liquid surface, and the displacement is continuously measured. can do.

[Measurement flow]
The measurement flow is described as follows.
(1) The liquid level is completely filled.
(2) The potential level is automatically calibrated in this state.
(3) Detect a potential level that is programmed in advance and is above a certain threshold.
However, when the imaging state is poor, the potential level does not exceed the threshold value.
(4) Since the threshold value is arbitrarily calculated and set with respect to the dark potential, it is possible to cope with changes in the external environment.
(5) However, when a direct dark light enters the optical system or the like becomes higher than a certain dark potential, a notice indicating that measurement is impossible is given.
(6) With these measures, it is possible to cope with changes in the brightness of the external environment where the liquid level gauge is installed.
(7) The liquid level displacement measurement ends with vignetting at an optically off-point or a mask in front of the line sensor.
(8) If the signal sampling time from the sensor is shortened, the liquid level displacement can be detected with higher resolution (for example, 1 μL).

This sensor uses a series of pipes filled with liquid to measure the non-light-transmissive flow rate to be detected. It is applied as a means for measuring the flow rate of liquid.
In addition, since the fluid image is captured at every fixed flow rate, the potential level sensed by the liquid level sensor can be used as a capture trigger signal, and the liquid at the time of a certain liquid volume passage without causing a time lag. It makes it possible to observe the situation.

According to the present invention, it is possible to accurately and steplessly measure the liquid level displaced in the transparent tube installed in the vertical direction.
Therefore, the present invention can be effectively used for measuring the liquid level.

It is explanatory drawing which shows the one aspect | mode of the optical image formation type liquid level sensor of this invention which concerns on Claim 1. It is explanatory drawing which shows an example of the slit-shaped aperture_diaphragm | restriction.

Explanation of symbols

A Transparent tube 1 Light source 2 Optical imaging system 3 Linear light receiving part 4 Slit-shaped stop 5 Diffusion plate 6 Linear polarizing plate

Claims (2)

  An optical imaging liquid comprising a light source having means for illuminating the entire transparent tube to be measured, an optical imaging system, and a linear light receiving unit capable of imaging the entire transparent tube to be measured. Surface sensor.   When measuring the liquid level displaced in a transparent tube installed in the vertical direction, a light source having means for illuminating the entire transparent tube to be measured, an optical imaging system, and an image of the entire transparent tube to be measured An optical imaging type liquid level sensor consisting of a linear light-receiving unit that can be used to illuminate the entire transparent tube to be measured using the light source, and optically transmit the light transmitted through the entire transparent tube. Displacement in the transparent tube is characterized by the fact that the entire transparent tube to be measured is imaged by the imaging system on a linear light receiving part that can image and the variation in the liquid level is measured by the light intensity. To measure the liquid level.

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