JPH11108838A - Turbidity measuring method and turbidity measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To permit highly accurate measurement without being affected by scattering light by receiving a beam transmitted through an object to be measured on the light-receiving plane of a photo detector through the use of a Fourier transform lens and setting an area of light reception of the photo detector smaller than an area of its light convergence. SOLUTION: This measuring device is provided with a light source 1, a beam magnifying device 2, a glass cell 3, a Fourier transform lens 5, a photo detector 6, etc. A laser tube to generate parallel and strong light is used for the light source 1. The beam magnifying device 2 is used so as to measure even a substance with a small concentration with high accuracy, and a beam with a magnified diameter is brought to be incident on the glass cell 3. Light transmitted through the glass cell 3 is condensed by the Fourier transform lens 5 arranged so that its axis may be in parallel with incident light. The photo detector 6 has an area of light reception corresponding to the diameter of a condensed beam, extremely reduces the amount of scattering light into an ignorable degree, and detects light transmittance with high accuracy. By this, it is possible to obtain the turbidity of a sample 4 with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for measuring the turbidity of an object to be measured.

[0002]

2. Description of the Related Art Conventionally, there is a transmitted light method as a method for measuring the turbidity of a sample such as a liquid. This method uses the principle that the intensity of transmitted light is inversely proportional to the concentration of a suspended substance in an exponential manner. Although not shown in the figure, a light source light is generally applied to a sample in a liquid tank. Then, an apparatus is used in which the transmitted light is received and detected by a photodetector.

[0003]

In the above-described conventional turbidity measuring device, the light transmitted through the sample is directly detected by the photodetector, so that not only the transmitted light but also the scattered light from the substance in the sample can be detected. There is a problem that turbidity cannot be measured with high accuracy because the turbidity is detected by the photodetector.

[0004] The present invention has been made in view of such circumstances,
It is an object of the present invention to provide a turbidity measuring method and a turbidity measuring instrument that can measure turbidity with high accuracy while being hardly affected by scattered light.

[0005]

According to the present invention, means for solving the above-mentioned problems are constituted as follows. That is, in the method of the first aspect, the light beam transmitted through the measurement object is condensed on the light receiving surface of the photodetector by the Fourier transform lens, and the light receiving area of the photodetector is equal to the condensing area. By setting it to be smaller or smaller, the transmitted light intensity is detected under a state where the amount of scattered light received is extremely reduced, and the turbidity of the measurement object is obtained based on the detected value. .

According to a second aspect of the present invention, an object to be measured is arranged between the Fourier transform lens and the photodetector.
The light transmitted through the object to be measured is condensed on the light receiving surface of the photodetector, and the light receiving area of the photodetector is set to be equal to or smaller than the light condensing area. The transmitted light intensity is detected in a state where the value is extremely reduced, and the turbidity of the measurement object is obtained based on the detected value.

According to a third aspect of the present invention, there is provided a light source, a measuring object arranged in an optical path of a light beam emitted from the light source, a Fourier transform lens for condensing light transmitted through the measuring object, A photodetector that receives the light condensed by the Fourier transform lens, and the light receiving area of the photodetector is equal to or smaller than the condensed area condensed by the Fourier transform lens. It is characterized by being set.

[0010] According to the present invention, a light source, a Fourier transform lens for condensing a light beam emitted from the light source, an object to be measured, and a condensed light transmitted through the object to be measured are received. And a light receiving area of the light detector is set to be equal to or smaller than a light condensing area condensed by the Fourier transform lens.

By setting the light receiving area of the photodetector to be equal to or smaller than the light condensing area of the Fourier transform lens, the amount of scattered light received can be extremely reduced. , The light transmittance with high accuracy can be obtained, and the turbidity can be obtained with high accuracy without requiring compensation for scattered light. The measurement object may be any of a gas, a liquid, and a solid.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the turbidity measuring device of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a basic configuration of a turbidity measuring device. Reference numeral 1 denotes a light source (laser tube) that generates a laser beam, and 2 denotes a beam expander that appropriately expands the laser beam into a wide light beam. For example, it is composed of a combination of two convex lenses (not shown). Reference numeral 3 denotes a glass cell into which, for example, a liquid sample (hereinafter referred to as a sample) 4 is taken in, reference numeral 5 denotes a Fourier transform lens for condensing a parallel light beam transmitted through the glass cell 3, and reference numeral 6 denotes light receiving elements 61 to 64 comprising photodiodes. Photodetector.

In the photodetector 62, the light receiving area, that is, the area of the four light receiving elements 61 to 64 is determined by the light condensing area s (for example, 50) condensed by the Fourier transform lens 5.
(φμm). With such a setting, the amount of scattered light received from the substance in the sample 4 itself can be extremely reduced, and a highly accurate turbidity can be obtained based on the light transmittance detected under the state. Become. The Fourier transform lens 5 is a lens unit that is set to satisfy the relational expression of h = f · sin θ when the incident angle θ of the light beam with respect to the optical axis, the focal length f, and the height h of the image are parallel light. Has the optical property of condensing light at the center.

More specifically, in the configuration shown in FIG. 1, first, a laser tube is used as a light source 1 that generates parallel and intense light, and a beam expander 2 is used to accurately measure even a substance having a small turbidity. The beam diameter is expanded by using and the light is incident on the glass cell 3, and the light transmitted through the glass cell 3 is
The light is condensed by a Fourier transform lens 5 arranged in parallel with the axis of the incident light, and as described above, the amount of scattered light is negligible by the photodetector 6 having a light receiving area equivalent to the condensed beam diameter. Thus, the light transmittance can be accurately detected. Note that an aperture or masking may be used as a method for setting the light receiving area of the photodetector 6. In addition, a point light source may be used as the light source 1, and any light source may be used as long as it is a parallel light flux when entering the measurement object.

With such a configuration, the turbidity of the sample 4 can be determined with high accuracy, for example, according to the flow shown in FIG. First, the optical axis is adjusted without injecting the sample 4 into the glass cell 3 (S1). The optical axis is adjusted by moving the Fourier transform lens 5 or the photodetector 6 with respect to the optical axis by an actuator (not shown) so that the light receiving intensities of the four light receiving elements 61 to 64 of the photodetector 6 are all equal. This is performed by moving in the XY axis directions on the orthogonal plane. The light receiving element of the photodetector 6 is
The division is for performing the optical axis adjustment, but the present invention does not specify the configuration of the light receiving element,
Any configuration is possible as long as it has a light receiving area at least equal to the light condensing area s of the Fourier transform lens 5.

Next, the intensity of the transmitted light, that is, the light intensity A is measured while the sample 4 is not injected into the glass cell 3 (S2). Thereafter, the sample 4 is injected into the glass cell 3 and the optical axis is adjusted in the same manner (S3). Thereafter, in a state where the sample 4 is injected,
The light intensity B is measured (S4). Then, by dividing the light intensity B obtained in S4 by the light intensity A obtained in S2, the light transmittance of the sample 4 can be obtained, and a highly accurate turbidity can be efficiently calculated from the light transmittance. (S5).

In the present invention, as described above, of the light transmitted through the sample 4 in the glass cell 3, all components parallel to the incident light are condensed on the photodetector 6, while other scattered light, etc. By preventing the stray light from being incident on the photodetector 6 and performing the optical axis adjustment as described above, highly accurate measurement of the light transmittance becomes possible, and the turbidity is accurately calculated. be able to. In particular, the light detector 6
By reducing the amount of scattered light received by the system to a negligible level, it is possible to omit a separate operation for compensating for the amount of scattered light. In addition to the above, the influence of ambient conditions and the like can be reduced, and a highly reliable measured value can be obtained. It should be noted that the present invention does not specify the measuring method in the flow of FIG. 2, and it goes without saying that the measuring method may be appropriately selected.

FIG. 3 shows a different embodiment, in which
A glass cell 3 is arranged between the Fourier transform lens 5 and the photodetector 6, and light transmitted through the glass cell 3 is condensed on a light receiving element (see FIG. 1) of the photodetector 6.
The light collecting area s (see FIG. 1) and the light receiving area of the light receiving element are set to be equal. As described above, by giving a degree of freedom to the internal layout, it becomes easy to deal with the design conditions of the turbidity measuring device. Note that the measurement method can be performed according to the same flow as in the previous embodiment.

[0017]

As described above, according to the first or third aspect of the present invention, the light transmitted through the object to be measured is condensed on the light receiving surface of the photodetector by the Fourier transform lens. Since the light receiving area of the photodetector is set to be equal to or smaller than the light condensing area, the amount of scattered light received can be reduced to a negligible level, and the light transmittance of the sample can be highly accurate. The turbidity can be accurately calculated based on the light transmittance.

According to the second or fourth aspect of the present invention, the object to be measured is arranged between the Fourier transform lens and the photodetector, and the light transmitted through the object to be measured is transmitted to the photodetector. Since the light is condensed on the light receiving surface and the light receiving area of the photodetector is set to be equal to or smaller than the light condensing area, also in this case, the light receiving area is high as in the invention of claim 1 or 3. Turbidity can be determined with accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a turbidity measuring device according to the present invention.

FIG. 2 is a flowchart for explaining the measurement method.

FIG. 3 is a schematic configuration diagram showing the different embodiment.

[Description of Signs] 4 ... Measurement object (sample), 5 ... Fourier transform lens, 6 ... Photodetector, s ... Condensing area.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kiyoshi Morimoto 71-11 Kamo, Mishima City, Shizuoka Prefecture

Claims (4)

[Claims] 1. A light beam transmitted through an object to be measured is condensed on a light receiving surface of a photodetector by a Fourier transform lens, and a light receiving area of the photodetector is set to be equal to or smaller than the light condensing area. Wherein the transmitted light intensity is detected under a state where the amount of scattered light received is extremely reduced, and the turbidity of the measurement object is obtained based on the detected value. 2. An object to be measured is arranged between a Fourier transform lens and a photodetector, and light transmitted through the object to be measured is condensed on a light receiving surface of the photodetector. By setting the area equal to or smaller than the condensing area, the transmitted light intensity is detected under a state where the amount of scattered light received is extremely reduced, and the turbidity of the measurement object is determined based on the detected value. A turbidity measuring method characterized by determining a degree. 3. A light source, a measuring object arranged in an optical path of a light beam emitted from the light source, a Fourier transform lens for condensing light transmitted through the measuring object, and condensing by the Fourier transform lens A light detector that receives the light that has been focused on, and a light receiving area of the light detector is set to be equal to or smaller than a light condensing area condensed by the Fourier transform lens. Turbidity meter. 4. A light source, a Fourier transform lens for condensing a light beam emitted from the light source, an object to be measured, and a photodetector for receiving the condensed light transmitted through the object to be measured. A turbidity measuring device characterized in that the light receiving area of the photodetector is set to be equal to or smaller than the light collecting area condensed by the Fourier transform lens.