JPS58115347A - Detecting device of scattered light - Google Patents

Abstract

PURPOSE:To simplify the structure of the titled device without strengthening the light from a light source by arranging a light absorbing element, a focusing lens and a photodetector in order in front of an object to be detected and positioning the light absorbing element on the optical path of non-scattered light passed through the object to be detected. CONSTITUTION:In a scattered light detecting device, the light absorbing element 6, the focusing lens 4 and the photodetector 1 are arranged in order in front of the object 3 to be detected and the light absrobing element 6 is positioned on the optical path of the non-scattered light L4 passed through the object 3 to be detected. Consequently, scattered light irradiated forward out of the whole scattered light can be detected and non-scattered light is absorbed to increase SNR, so that it is unnecessary to strengthen light from the light source, and the photodetector made of a semiconductor, is used to simplify the structure and to produce an inexpensive product in addition.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a scattered light detection device that detects scattered light scattered within an object to be inspected out of a beam of light (hereinafter simply referred to as light) irradiated onto an object to be inspected from a light source.

Scattered light detection devices are generally used, for example, to inspect tap water for foreign substances. This scattered light detection device has a light source, an input lens, and tap water installed in sequence, and the light source irradiates the tap water through the input lens. The light hits this foreign object and is scattered, and this scattered light is detected to inspect the foreign object.

Conventionally, in the above-mentioned scattered light detection device, when trying to detect the scattered light on the optical path of the non-scattered light that passes through tap water without being scattered, the non-scattered light increases the SNR (signal
noise ratio) will decrease. Therefore, other than the above-mentioned optical path, for example, as shown in FIG.
SNH using non-scattered light is detected by detecting scattered light from
was prevented from decreasing.

However, this method has the disadvantage that the intensity of the scattered light is weak, so the light from the light source must be made stronger, and a highly sensitive detector such as a photomultiplier must be used, resulting in an increase in cost.

This invention has been made in view of this point, and includes providing a light absorber in front of the object to be inspected and on the optical path of the non-scattered light that has passed through the object to be inspected, and condensing the light in front of the light absorber. By arranging a lens and a photodetector in this order and detecting only scattered light, a scattered light detection device is provided that can easily detect strong scattered light with a high 5NRi.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

As shown in FIGS. 1 and 2, reference numeral 1 denotes a scattered light detection device, which illuminates a test object 8 with light from a light source 12 and detects scattered light inside the test object 3. be.

The light source 2 is composed of a laser light source, etc., an input lens 4 is installed in front of the light source 2, the object to be inspected 3 is installed in front of the input lens 4, and the light L1 from the light source 2 enters the input lens. 4 and irradiates the object 3 to be inspected. The entrance lens 4 focuses the incident light from the light source 2 into a narrow beam L2 (Lx=ji). This beam diameter d is determined by D: incident light diameter λ: light wavelength f: focal length of the incident lens 4. Then, D or f2 is selected so that this beam diameter d becomes approximately the size of the scatterer 5 of the object 3 to be inspected. Note that this f is limited by the length across the object to be inspected 3 and the size of the entire apparatus.

The object to be inspected 3 is various fluids such as tap water, and foreign matter such as dust contained therein becomes the scatterer 5. The beam L2 that has passed through the incident lens 4 is scattered by the scatterer 5 and becomes scattered light L8, while the non-scattered lights I and 4 that are not scattered go straight ahead and pass through the object 3 to be inspected.

In front of the object to be inspected 3, there is a light absorber 6 and a condensing lens 7.
and a photodetector 8 are arranged in this order - this light absorber 6
is installed on the optical path of the non-scattered light L4, and absorbs this non-scattered light L4=i.

The condensing lens 7 focuses the scattered light Lai scattered toward the front within the test object 8.

Further, the photodetector 8 receives the scattered light L8 focused by the condenser lens 7, converts it into an electrical signal, and outputs the electrical signal.

Next, the operation of the scattered light detection device 1 will be explained. The light L1 (laser light) emitted from the light source 2 is focused into a narrow beam L2 by the entrance lens 4, and is irradiated onto the object 3 to be inspected.

This beam L2 passes through the object to be inspected 811, for example, tap water, but if there is a scatterer 5 such as dust, it is separated into non-scattered light L4 and scattered light L8. That is, the beam L4 that does not hit the scatterer 5 goes straight and crosses the object to be inspected 8 as non-scattered light L4, while the beam L2 that hits the scatterer 5 is refracted and crosses the object to be inspected 3 as scattered light L8. pass.

The non-scattered light L4 and the scattered light L8 are received in front of the object to be inspected 8, but the non-scattered light L4 becomes noise since the device obtains the scattered light L8. After passing through the object to be inspected 3, this non-scattered light L4 hits the light absorber 6 and is absorbed. On the other hand, the forward scattered light L8 is focused by the condenser lens 7, supplied to the photodetector 8, converted into an electrical signal, and output.

As shown in FIG. 1, the band in the center is the noise caused by the non-scattered light L4, and the impulsive part that protrudes from this band is the scattered light L8, and the non-scattered light L4= It is removed by the i-light absorber 6 to improve the 8NR (signal/noise ratio).

In addition, since the photodetector 8 detects the high-intensity scattered light Lsffi, it may be composed of a semiconductor, and conversely, if it is composed of a highly sensitive photomultiplier, the light source 2 may be composed of a weak one. .

Furthermore, it goes without saying that the object to be inspected 3 is not limited to tap water, but may be any other type of fluid.

FIG. 3 shows another example of the scattered light detection device 1, which is of a multi-pass type in which the beam L2 is caused to pass through the object 8 to be inspected by reciprocating a plurality of times.

That is, reflective mirrors 9α and 9bf are installed in front and behind the inspected object 3,
The beam L2 passing through the input lens 4 is reflected by both reflecting mirrors 9α and 9b.
The light is reflected and passes back and forth through the object to be inspected 3 from the first part to the lower part.

This expands the inspection area. The rest is the same as in the previous embodiment.

As described above, according to the present invention, a light absorber, a condensing lens, and a photodetector are sequentially arranged in front of the object to be inspected, and the light absorber is used to absorb the non-scattered light that has passed through the object to be inspected. Since it is located on the road and detects only the scattered light in front of the object to be inspected, it is possible to detect the strong scattered light directed forward among the scattered light, and at the same time absorb the non-scattered light to improve the SNR.
Since the light intensity of the light source can be increased, there is no need to increase the intensity of the light from the light source, and since a photodetector such as a semiconductor can be used, the structure can be manufactured easily and at low cost. Furthermore, if a highly sensitive photodetector is used, the light source can be weakened, so it can be manufactured easily and at low cost.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is an explanatory diagram showing an example of detection of scattered light, FIG. 2 is a schematic side view of a scattered light detection device, and FIG. 8 is an illustration of another method for detecting scattered light. FIG. 2 is a schematic side view showing the device. 1: Scattered light detection device, 2: Light source, 8: Test object, 4: Incident lens, 6: Scattering body. 6: light absorber, 7: condensing lens, 8: photodetector,
9a., 9h: Reflector, L8: Scattered light. L4: non-scattered light. Patent applicant: Shimadzu Corporation

Claims (1)

[Claims] A light absorber is provided in front of the test object and on the optical path of the non-scattered light that has passed through the test object. A scattered light detection device comprising: a condensing lens for condensing scattered light, a photodetector provided in front of the condensing lens, and the photodetector detecting only the scattered light. .