JPH0996560A - Electromagnetic-wave chopper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to make a device using a chopper small-sized by making the rotary shaft of a planar body made of the electromagnetic impermeability material in the intended wavelength region cross at a right angle with an optical axis. SOLUTION: A rotary shaft 13 is provided so as to cross an optical axis 14 at a right angle. The extended line of the rotary shaft crosses the optical axis 14. A planar body 11 having an approximately equal cross-sectional area as luminous flux (and a detector 15) is attached to the rotary shaft 13. When a current is loaded on a motor 12 to rotate the motor, the rotary shaft 13 is rotated, and the planar body 11 is also rotated. when the planar body 11 is located at the vertical position, an optical path is cut off by the planar body 11. At this time point, the motor 12 is rotated by 90 degrees. When the planar body 11 comes to the horizontal position, the optical path is opened. Thus, on and off of the light are repeated at every 90-degree rotation of the planar body 11. The chopper like this is mainly used as the chopper when only the change of the amount of the light is measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for intermittently modulating an electromagnetic wave and modulating the electromagnetic wave, and is mainly used for a measuring device for measuring a physical / chemical property of a substance by using the electromagnetic wave. The present invention is particularly suitable as an electromagnetic wave chopper of a measuring device using a pyroelectric detector such as a gas analyzer for measuring carbon dioxide and nitrogen oxides and a moisture meter.

[0002]

2. Description of the Related Art In the optical path of an electromagnetic wave, a plate made of an electromagnetic wave non-transmissive material in a desired wavelength range is rotated, and the plate is alternately cut off and opened to interrupt the electromagnetic wave. As an electromagnetic wave chopper that is modulated by modulation, the one shown in FIG. 5 is conventionally known. FIG. 5 is an illustration of an optical chopper for visible light. In FIG. 5, 51 is a plate-like body,
The motor 52 rotates as it rotates, but its rotation axis 53 is parallel to the optical axis 54 of the optical path. FIG. 5b is a view of the conventional optical chopper viewed from the direction of the light source. As shown in FIG. 5 b, when the plate-shaped body 51 rotates about the rotation axis 53, the plate-shaped body 51 blocks the optical path of the light entering the detector 55, or the notch of the plate-shaped body 51. When the light enters the optical path, the optical path is opened so that the plate-like body 51 intermittently interrupts the light entering the detector 55 and modulates the light.

[0003]

In the conventional electromagnetic wave chopper, the diameter of the plate member needs to be at least twice the diameter of the optical axis, and there is a limit to miniaturize the electromagnetic wave chopper.

[0004]

In order to solve such a problem, an electromagnetic wave chopper according to the present invention rotates a plate made of an electromagnetic wave non-transmissive material in a target wavelength range in an optical path of an electromagnetic wave. , The optical path is alternately blocked by the plate-shaped body.
In an electromagnetic wave chopper that opens and closes to modulate an electromagnetic wave, the rotation axis of the plate-shaped body is orthogonal to the optical axis.

In the present invention, electromagnetic waves refer to X-rays, ultraviolet rays, visible rays, infrared rays, microwaves and the like.

In the present invention, the electromagnetic wave non-transmissive material in the wavelength range of interest includes lead for X-rays, black metal for ultraviolet and visible rays, aluminum whose surface is polished for infrared rays, and the like. Can be mentioned.

Further, in the present invention, the orthogonal relationship between the rotation axis and the optical axis is not limited to the case where the two or both extension lines intersect at one point in space, but the two are orthogonal, but the two or both extension lines intersect. It also includes the case where there is no twisting positional relationship.

[0008]

1 is an explanatory view for explaining a first embodiment of the present invention, in which a is a front view and b is a side view. 1 in Figure 1
1 is a plate-shaped body, 12 is a motor, 13 is a rotating shaft of the motor 12, and the plate-shaped body 11 is connected to the other end. Also,
Reference numeral 14 is an optical axis, and 15 is a detector.

The first embodiment is an example of a visible light chopper, in which a tungsten lamp is used as a light source, a black painted iron plate is used as the plate-shaped body 11, and a photomultiplier is used as the detector 15. When the visible light chopper of the first embodiment is used as a part of an absorption spectrometer, a measuring cell is usually attached between the plate-shaped body 11 and the detector 15, which is shown in the explanatory diagram. Absent.

In the first embodiment, the rotary shaft 13 is provided orthogonal to the optical axis 14, and the extension line of the rotary shaft 13 is the optical axis 14.
Intersect with. A light beam (and a detector 15) is applied to the rotation axis 13
A plate-like body 11 having a cross-sectional area substantially equal to is attached. When a current is applied to the motor 12 to rotate the motor, the rotating shaft 13 rotates and the plate-shaped body 11 also rotates. When the plate-shaped body is in the illustrated position, that is, in the vertical position, the optical path is blocked by the plate-shaped body 11. Motor 1 from this point
When 2 rotates 90 degrees and the plate-shaped body 11 reaches the horizontal position, the optical path is opened. In this way, the light is intermittently repeated every 90 ° rotation of the plate-shaped body 11.

The waveform of the light quantity after passing through the visible light chopper of the first embodiment when the motor 12 is rotated at the same angular velocity is shown in FIG. Such a chopper can be mainly used as a chopper when measuring only the change in the light amount. For example, it is a case of implementing the present invention as an infrared chopper of a human body detection device using a pyroelectric infrared detector.

Further, when a stepping motor having a step angle of 90 degrees is used as the motor 12, the waveform of the light quantity after passing through the visible light chopper of the first embodiment has a shape close to a rectangle as shown in FIG. Become. Such a chopper can be used when absolute light quantity measurement is required. For example, when the present invention is implemented as an ultraviolet chopper of an ultraviolet spectrophotometer.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 4 is an explanatory view for explaining the second embodiment of the present invention, in which a is a front view and b is a side view. FIG.
Among them, 41 is a plate-like body, 42 is a motor, 43 is a motor 42
The plate-like body 41 is connected to the other end of the plate-like body 41. Further, 44 is an optical axis, and 45 is a detector.

The second embodiment is an example of an infrared chopper, in which a nichrome wire is used as a light source, a mirror-polished aluminum plate is used as the plate-like body 41, and a pyroelectric detector is used as the detector 45.

In the second embodiment, the rotary shaft 43 of the plate member 41 is orthogonal to the optical axis 44, but these two shafts are in a twisted positional relationship, and the extension line of the rotary shaft 43 is the optical axis 44. Does not intersect

When a current is applied to the motor 42 to rotate the motor, the rotating shaft 43 rotates and the plate-like body 41 also rotates. When the plate-shaped body is in the illustrated position, that is, in the vertical position, the optical path is blocked by the plate-shaped body 41. From this point, the motor 42 rotates 90 degrees and the optical path is opened when the plate-shaped body 41 reaches the horizontal position. In this way, light is intermittently repeated every 90 ° rotation of the plate-shaped body 41.

[0017]

According to the present invention, a small electromagnetic chopper can be manufactured. As a result, downsizing of the device using the chopper can be realized.

Further, in the first embodiment, when the optical path is in the open state, the light in the optical path is blocked by the thickness of the plate-like member. However, as in the second embodiment, the chopper rotation axis is the optical axis. With more deviation, the device can be made slightly larger, but the light path can be completely opened. .

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating a chopper according to a first embodiment of the present invention.

FIG. 2 is a waveform diagram showing an example of a light amount waveform after passing through the chopper of the first embodiment.

FIG. 3 is a waveform diagram showing another example of the light amount waveform after passing through the chopper of the first embodiment.

FIG. 4 is an explanatory diagram illustrating a chopper according to a second embodiment of the present invention.

FIG. 5 is an explanatory diagram illustrating a conventional chopper.

[Explanation of symbols]

 11 plate-like body 12 motor 13 rotating shaft 14 optical axis

Claims (1)

[Claims] 1. An electromagnetic wave is interrupted by rotating a plate made of an electromagnetic wave non-transmissive material in a target wavelength range in the optical path of the electromagnetic wave and alternately blocking and opening the optical path by the plate. An electromagnetic wave chopper that modulates by modulating the rotation axis of the plate-shaped body orthogonal to the optical axis.