JPH02145940A - Diffracted light detector for laser diffraction type particle size distribution measuring apparatus - Google Patents

Abstract

PURPOSE:To enable accurate measurement with a simple operation by forming a channel having a pn junction surface held at a ground potential between a detecting section for measuring non-diffraction light and a detecting section for measuring diffraction light provided nearest the detecting section. CONSTITUTION:In a detector 12, a laser beam irradiates a measuring cell and non-diffraction light via a condenser lens enters a detecting section 7 for measuring non-diffraction light while diffraction light into detecting sections 8A and 8B for measuring diffraction light and converted into electricity to obtain detection signals S7, SA and SB. At this point, even if an electric charge generated at the detecting section 7 is leaked, it is trapped by a channel 13 provided in an insulation layer 9a between the detecting sections 7, 8A and 8B and flows into the earth to reduce an inflow of the electric charge to the detecting sections 8A and 8B, thereby achieving a higher measuring accuracy of the diffraction light.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement of a diffraction light detector of a laser diffraction type particle size distribution measuring device.

[Conventional technology]

Fig. 2 shows the main parts of a general laser diffraction particle size distribution measuring device. A measurement cell is connected to an ultrasonic dispersion bath (not shown) via a 100-degree ultrasonic dispersion bath (not shown), and a sample liquid is continuously supplied by a circulation pump (not shown); 5 is a lens that condenses the light transmitted through the measurement cell 3;
6 is a detector made of, for example, a silicon photodiode, which detects the light from the condensing lens 5.

In the above laser diffraction particle size distribution measuring device, while the sample liquid is continuously supplied to the measurement cell 3,
When the measurement cell 3 is irradiated with laser light, a part of the laser light irradiates the particles in the sample liquid in the measurement cell 3 and becomes diffracted light, and most of the remaining light passes between the particles. It passes through and becomes undiffracted light. Then, both the diffracted light and the undiffracted light reach the detector 6 via the condenser lens 5.

By the way, as shown in FIG. 3(A), the detector 6 is formed so that its shape in plan view is approximately 90@ fan-shaped, and the non-diffracted light is formed in the main part of the fan shape. A non-diffracted light measuring portion 7 is formed to detect the
Concentrically around this non-diffracted light measurement detection section 7,
A plurality of diffracted light measurement detecting sections 8A, 8B, 8C... for detecting the diffracted light are each provided with an appropriate insulating layer 9.
It is provided via a... 10 is a detection section 7 for non-diffracted light measurement and a detection section 8A, 8B for diffracted light measurement;
These are lead portions made of aluminum, for example, connected to each of 8C....

FIG. 3(B) shows a cross section of the detector 6, in which 9 is an n layer as an insulating layer, and the insulating layer is formed on one surface (light incident surface side) of this 0 layer 9. A plurality of p layers are formed through 9a..., and these are connected to the non-diffraction light measurement detection section 7 and the diffraction light measurement detection section 8A, 8B, respectively.
It is formed in 8C... Further, 11 is the n-layer 9
The n-layer formed on the other surface of the 1-layer is held at ground potential.

In the detector 6 configured in this way, when the undiffracted light and the diffracted light are incident through the condensing lens 5, the p layer (the detection section 7 for measuring the undiffracted light and the detection section 7 for measuring the diffracted light) photoelectric conversion is performed between the portions 8A, 8B, 8C, . . .
The signals are output as detection signals to the outside via lead portions 10 connected to the terminals 8C, . . ., respectively.

[Problem to be solved by the invention]

By the way, the undiffracted light is much stronger than the diffracted light (
104 times or more of the diffracted light), therefore, in the conventional detector 6 described above, the diffracted light measurement detection section 8A provided in the vicinity of the non-diffracted light measurement detection section 7 has a non-diffracted light measurement detection section. Charges generated by the light detected in step 7 flow in, and as a result, an error may occur in the measured value of the diffraction light measurement detection section 8^.

In order to eliminate such inconveniences, the insulating layer 9a between the non-diffraction light measurement detection section 7 and the diffraction light measurement detection section 8A is formed to be large. However, this method makes it difficult to measure diffracted light due to particles with large diameters, and if the particle diameter measurement range is about 2 decades, it is necessary to prepare multiple condensing lenses 5 with different focal lengths. It is necessary to use it properly, and the condenser lens 5
Each time the detector 6 is replaced, the position of the detector 6 must be readjusted, which requires troublesome operations and is difficult to handle.

It is also possible to make the portion corresponding to the non-diffracted light measurement detection section 7 open, but in this case,
It is necessary to separately provide a non-diffracted light measurement detection section 7 for measuring the non-diffracted light, which complicates the structure.

The present invention has been made with the above-mentioned considerations in mind, and its purpose is to reduce the flow of charge from the detection section for measuring non-diffracted light to the detection section for measuring diffracted light. It is an object of the present invention to provide a diffraction light detector of a laser diffraction type particle size distribution measuring device that can measure diffracted light with high precision through operation and has a simple structure.

[Means to solve the problem]

In order to achieve the above object, the diffraction light detector of the laser diffraction particle size distribution measuring device according to the present invention includes at least a detection section for measuring non-diffracted light and a detection section for measuring non-diffracted light provided closest to the detection section for measuring non-diffracted light. A feature is that a channel having a pn junction surface held at ground potential is formed between the detector and the detector for measuring diffracted light.

[Effect]

According to the above configuration, even if charges generated by light incident on the non-diffracted light measurement detection section leak out from the non-diffracted light measurement detection section, they are captured by the channel and flow into the ground, so that the non-diffracted light The flow of the charge into the diffraction light measurement detection section provided in the vicinity of the light measurement detection section is significantly reduced, and the above object is completely achieved.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1(A) and 1(B) show an example of the diffraction light detector of the laser diffraction particle size distribution measuring device according to the present invention. Items identical to those shown refer to the same or equivalent items.

Now, in the diffraction photodetector 12 shown in FIGS. 1(A) and 1(B), channels 13 . . . are held at ground potential and have pn junction surfaces 13 a .
The insulating layer 9a... is provided on the surface of the insulating layer 9a. That is, the insulating layer 9a between the detection section 7 for non-diffracted light measurement and the detection section 8A for diffracted light measurement and the insulating layer 9a between the detection section 8A for diffracted light measurement and the detection section 8B for diffracted light measurement are channel 13
... are provided for each. In addition, Fig. 1 (A)
In, S? , SA, and Ss are the detection section 78 for non-diffracted light measurement, the detection section 8A for diffracted light measurement, and the detection section 8B for diffracted light measurement.
The detection signal output from the is shown.

Therefore, in the diffraction light detector 12 having the above configuration, the second
The non-diffracted light that has passed through the condensing lens 5 shown in the figure is sent to the non-diffracted light measurement detection section 7, and the diffracted light is sent to the diffraction light measurement detection section 8A,
8B, etc., and is photoelectrically converted in each detection section to produce a detection signal S? .

SA, S, is obtained.

At this time, even if the charge generated by the light incident on the non-diffracted light measurement detection section 7 leaks out of the non-diffracted light measurement detection section 7, it will be captured by the channels 13 and 13 and connected to the ground. Therefore, the detection units 8A, 8 for diffracted light measurement are provided near the detection unit 7 for non-diffracted light measurement.
The flow of the charge into B is significantly reduced, and therefore the measurement accuracy of the diffracted light is significantly improved.

In the above-mentioned embodiment, the detection unit 8A for diffracted light measurement,
A channel 13 is also provided in the insulation Ji 19a between 8B, but at least a channel 13 is provided between the diffracted light measurement detection section 8A closest to the non-diffracted light measurement detection section 7 and the non-diffracted light measurement detection section 7. Further, the position of the channel 13 is not limited to the surface of the insulating layer 9a, but may be located near the surface.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to significantly reduce the flow of charge from the non-diffraction light measurement detection section to the diffraction light measurement detection section, thereby improving the measurement accuracy of diffracted light. In addition, it is easy to measure diffracted light from particles with large diameters, and it is possible to measure a wide range of particles from small particles to large particles. Moreover, unlike conventional methods, multiple condensing lenses with different focal lengths can be used. There is no need to prepare and use different detectors or readjust the position of the detector, which simplifies measurement operations.

[Brief explanation of the drawing]

FIGS. 1(A) and 1(B) show an embodiment of the present invention, FIG. 1(A) is a plan view showing a diffraction photodetector, and FIG. 1(B) is a B-B in FIG. FIG. Fig. 2 is a configuration diagram showing the main parts of a general laser diffraction particle size distribution measuring device, Figs. 3 (A) and (B) show a conventional diffraction photodetector, and Fig. 3 (A) is a plan view. , the same figure (B) is the same figure (
It is a BB line sectional view in A). 7...Detection section for non-diffracted light measurement, 8^, 8B...Detection section for diffracted light measurement, 13...Channel, 13a...
pn junction surface.

Claims (1)

[Claims] A laser diffraction particle size distribution measuring device comprising a detection section for measuring non-diffracted light and a plurality of detection sections for measuring diffracted light formed in an arc shape or concentrically around the detection section for measuring non-diffracted light. In the diffraction light detector, at least the detecting section for measuring the non-diffracted light and the detecting section for measuring the diffracted light provided closest to the detecting section for measuring the non-diffracted light are held at a ground potential and pn A diffraction photodetector for a laser diffraction particle size distribution measuring device, characterized in that a channel having a bonded surface is formed.