JPH08145883A - Light beam type gas concentration measuring device - Google Patents

Abstract

PURPOSE: To easily change a spot diameter of beam of a light emitting means housed in a body from outside. CONSTITUTION: Relating to a light beam type gas concentration measuring device body, an infrared light source 10 which makes an self-regressive reflecting plate, through a collimator lens 11 at the center, irradiated with the light beam from an aperture 4, and a measuring beam sensor 15 which detects incident light from the periphery of the collimator lens 11 through a paraboric mirror 12 are housed in a body 3 on one side of which an aperture 4 sealed with a transmissive board material is formed. A correcting lens 21 which changes focal distance of the collimator lens 11 is fixed, while detachable by a correcting lens rim 22, on the body 3, so that, a spot diameter of infrared ray beam is changed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas measuring device for irradiating a light beam so as to traverse the environment to be measured and measuring the concentration of gas in the environment to be measured based on the attenuation rate at the light receiving side. .

[0002]

2. Description of the Related Art When a gas leak is detected in a site where production facilities are installed or in a wide environment such as a tunnel, a large number of gas detection heads are required, resulting in high cost. There is. For this reason, a measuring device main body in which the light beam irradiating means and the light receiving means are incorporated in the same housing in the environment to be monitored, and a reflecting plate having a self-regressive property for reflecting in the incident direction at a predetermined distance from this are installed. However, a method of irradiating a light beam that matches the absorption spectrum of the gas to be monitored from the measuring device toward the reflector and measuring the concentration of gas in the environment from the attenuation rate of the light from the reflector is used. .

In this device, the distance between the reflection plate and the main body of the measuring device is in the range of several meters to several tens of meters and can be set arbitrarily according to the measurement environment. The diameter changes greatly, and the measurement result will include an error.

Of course, the spot diameter of the light beam can be changed by adjusting the relative distance between the light emitting means and the collimator lens, but for that purpose, it is necessary to open the case, and the work at the site is required. There is the problem of complexity.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to easily change the spot diameter of a measurement light beam from outside the housing. It is to provide a novel light beam type gas concentration measuring device that can be used.

[0006]

In order to solve such a problem, in the present invention, a casing having a window sealed with a light-transmitting material is formed in the center, and a collimator lens is provided in the center. A light emitting means for irradiating the autoregressive reflection plate with a light beam from the window through the light receiving means, and a light receiving means for receiving the light reflected by the autoregressive reflection plate and incident from the outer periphery of the collimator lens through a converging optical system. In a light beam type gas concentration measuring device accommodating and, a correction lens for changing the focal length of the collimator lens is fixed to the outside of the casing by a frame body that can be positioned at a position facing the collimator lens. Allows you to
The focal length of the condensing optical system is changed to change the spot diameter of the light beam to the optimum size.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments. FIG. 1 shows an embodiment of the present invention. In the figure, reference numeral 1 is a measuring device main body fixed to a supporting base 2, and a window 4 is provided on one side surface of a housing 3 to transmit light therethrough. The plate member 5 is configured to be fixed to the housing 3 with screws 6, 6, 6 so that an infrared beam for measurement is irradiated to an autoregressive reflecting plate described later and infrared rays reflected by the reflecting plate can be received. It is configured.

FIG. 2 shows an embodiment of the above-mentioned measuring apparatus. In the figure, reference numeral 10 is an infrared light emitting means, and a collimator lens 11 is arranged on the window 4 side thereof. The infrared rays from the light emitting means 10 are converged and irradiated as infrared rays from the window 4.

Reference numeral 12 denotes a parabolic mirror having a diameter larger than that of the collimator lens 11 and reflecting the infrared ray transmitted through the window 4 to the parabolic mirror 12 side by the plane mirror 13 and arranging it on this optical path. The half mirror 14 is provided so that the measurement light sensor 15 and the comparison light sensor 16 are made incident. A measurement light filter 17 is arranged on the measurement light sensor 15 side of the half mirror 14. In the figure, reference numeral 18 indicates a comparative optical filter.

FIG. 3 shows an embodiment of the correction lens mounting body 20. A plurality of arms 23, 23, 23, ... Are radially provided from a lens mounting frame 22 for fixing the correction lens 21.
Are radially projected, and the projections of the housing 3 are provided at the tips thereof, and in this embodiment, insertion holes 24, 24 that can be fitted into the screws 6, 6, 6 fixing the transparent plate member 5 to the housing 1. , 24 ...

In this embodiment, the measuring device body 1 and
When the self-regressive reflection plate 30 arranged on the optical path of the infrared beam to be emitted is arranged at a predetermined distance L1 (FIG. 5 (a)), the infrared beam emitted from the measuring device body 1 is The gas existing on the optical path is absorbed and reflected by the reflection plate 30, and again absorbed by the gas on the optical path to reach the measuring device body 1.

The infrared rays entering through the window 4 are parabolic mirrors 12.
After being converged by, the light is reflected by the reflection optical systems 13 and 14 and is incident on the measurement optical sensor 15 and the comparison optical sensor 16, the intensity thereof is detected, and the light is detected based on the ratio of the signal levels of the sensors 15 and 16. The concentration of gas on the road is measured.

By the way, when the distance between the measuring device main body 1 and the autoregressive reflecting mirror 30 is increased to change to the distance L2 (FIG. 5B), the light emitting source of the light emitting means 10 has a finite size. Since the light passing through the collimator lens 11 is not converged into a perfect parallel light, the spot diameter of the infrared beam reaching the reflection plate 30 spreads as shown by the dotted line in FIG.

When the size of the reflection plate 30 is larger than the size of the reflection plate 30 as described above, the correction lens 21 having an appropriate focal length is selected, and the insertion holes 24, 24 of the mounting body 20 are inserted.
24 ... Is inserted into the screws 6, 6, 6 ... of the casing 1,
The correction lens 21 is set at a position facing the collimator lens 11.

As a result, the focal length of the condensing optical system is changed by the collimator lens 11 and the correction lens 21, so that the spot diameter of the infrared beam irradiating the reflecting plate 30 is indicated by the solid line in FIG. It is narrowed down as shown in.

By narrowing the spot diameter of the infrared beam in this way, even when the distance between the measuring device body 1 and the reflection plate 30 becomes large, or when a small-sized reflection plate 30 is used, reflection occurs. The infrared beam that has reached the plate 30 can be reflected without escaping, and by attaching another correction lens 21 having a different focal length to expand the spot of the infrared beam, the measuring device body 1 and the reflecting mirror 30 can be separated. The reflector can be effectively used even when the distance becomes short.

Further, in an environment where ground vibration is severe, such as in a civil engineering construction site, the spot diameter of the infrared beam is narrowed by the correction lens 21 so that the reflection plate 30 can reliably receive the light and the measuring device body 1 Not only is it possible to prevent fluctuations in the amount of reflected light due to vibration by reflecting the light on the screen, but even in a limited space such as a tunnel, a small-sized reflector can be used, which hinders work. It is possible to measure the gas without doing so.

FIG. 6 shows a second embodiment of the correction lens mounting body. In the drawing, reference numeral 32 is a correction lens mounting frame, and bolts 33 are provided at symmetrical positions thereof. The bolts 33 are inserted into the long grooves 35 of the horizontally extending arms 34 fixed by the screws 6 of the casing 1, and then fixed by nuts 36 and 37 so as to sandwich the arms 34.

According to this embodiment, the nuts 36 and 37 are loosened, and the bolt 33 is moved in the long groove 35 to move the bolt 33 in the horizontal position.
The position in the vertical direction can be adjusted by adjusting the relative position with respect to 7, and the correction lens 24 can be set at the optimum position. Since the correction lens mounting frame 32 is in contact with the translucent plate member 5, the correction lens does not rattle even when subjected to vibration.

[0020]

As described above, according to the present invention, in a housing having a window sealed with a translucent material on one side, a light beam is passed through the collimator lens in the central portion of the window. A light beam type gas containing a light emitting means for irradiating an autoregressive reflection plate from the light receiving means and a light receiving means for receiving the light reflected by the autoregressive reflection plate and incident from the outer periphery of the collimator lens through a converging optical system. In the density measuring device, the correction lens that changes the focal length of the collimator lens is fixed by a frame that can be positioned at a position facing the collimator lens, so it is not necessary to open the case each time. , You can easily change to the optimum spot diameter.

[Brief description of drawings]

FIG. 1 is a schematic view of an apparatus showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the structure of the same device.

FIG. 3 is a diagram showing an example of a correction lens attachment body.

FIG. 4 is a diagram showing a state in which a correction lens is attached to a housing.

5 (a) and 5 (b) are diagrams showing a state of an infrared beam in the same apparatus, respectively.

FIG. 6 is a view showing another embodiment of the correction lens attachment body in a state where it is attached to a housing.

[Explanation of symbols]

 1 Measuring Device Main Body 2 Support Stand 3 Housing 4 Window 5 Light Transmitting Plate Material 6 Screw 10 Infrared Light Source 11 Collimator Lens 12 Parabolic Mirror 15 Measuring Light Sensor 16 Comparative Light Sensor 20 Correcting Lens Mount 21 Correcting Lens 22 Lens Mounting Frame 23 Arm 24 Insertion hole

Claims (1)

[Claims] 1. A housing having a light-transmitting window sealed on one side with a light-transmitting material is irradiated with a light beam from the window to a self-regressing reflector through a collimator lens in the center. In the light beam type gas concentration measuring device, which contains a light emitting means and a light receiving means for receiving the light reflected by the autoregressive reflection plate and incident from the outer periphery of the collimator lens through a converging optical system, the collimator A light beam type gas concentration measuring device in which a correction lens for changing the focal length of the lens is fixed to the outside of the casing by a frame body that can be positioned at a position facing the collimator lens.