JPH07270690A - Optical chopper - Google Patents

Abstract

PURPOSE:To drastically reduce the weight of a light shielding board so as to make torque for rotating the light shielding board small by forming the light shielding board in a state where a synthetic resin sheet is coated with a fluororesin having a function for shielding infrared ray. CONSTITUTION:This optical chopper is constituted of a semicircular light shielding board 3 which shields infrared ray, a pivot 4 integrated to the light shielding board 3, a fixing member 5 fixing the pivot 4 and the light shielding board 3, a rotor 6 constituted of a permanent magnet fixed to the pivot 4, an electromagnet coil 7, and a stator 8. A voltage is impressed on the coil 7 so as to rotate the light shielding board 3. The light shielding board 3 is formed in a state where the surface of a polyester resin sheet containing carbon is coated with the fluororesin having the function for shielding the infrared ray. Thus, the light shielding board 3 coated with the fluororesin is excellent in chemical resistance, corrosion resistance, and weather resistance, and has w good function for shielding infrared ray in a measuring wavelength region(8-10mum).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical chopper incorporated in infrared applied equipment such as a radiation thermometer and an infrared gas analyzer.

[0002]

2. Description of the Related Art A radiation thermometer or an infrared gas analyzer using a pyroelectric infrared detector is provided with an optical chopper for chopping infrared light incident on an infrared detector.

The optical chopper is constructed such that a light-shielding plate made of a thin plate of stainless steel or aluminum formed in a semi-arcuate shape is attached to a rotary shaft of a motor, a synchronous motor, a pulse motor, or the like to be driven to rotate.

[0004]

For example, in the case of forming a small portable radiation thermometer, in order to reduce the size and cost, and to reduce the current consumption, the torque required for rotating the motor is required. Is desired to be reduced.

As the light shield plate, a metal plate is usually used in order to obtain a perfect light shield property. In particular, in order to reduce the weight of the light shielding plate, a thin plate of stainless material (thickness of about 0.1 mm) was often used. However, further thinning has many problems in terms of mechanical strength, and there is a limit to weight reduction. Therefore, the weight of the shading plate cannot be neglected, and it is necessary to devise the shape in order to balance the rotation, it is necessary to provide a counter weight, and special consideration must be given to wear on the bearing. there were.

Therefore, as one method, it is conceivable to form the light shielding plate with a thin plate material (or sheet) made of resin. For example, a polyester resin sheet has a specific gravity of 1.3.
8 to 1.39 (Source: Industrial Material Vol 21, No.
8), it is possible to reduce the weight by 1/5 to 1/6 as compared with the conventional stainless steel plate (specific gravity 7.7 to 7.8) when used as a light shielding plate for a chopper motor. However, there is no material having a perfect light-shielding ability in the measurement wavelength range of a radiation thermometer. For example, when a polyester resin plate mixed with carbon having a thickness of 50 μm is used, it is 2 to around 8 to 10 μm.
There was a transmission of about 4%, and there was a limit to thinning.

The present invention has been made in view of such circumstances.
An object of the present invention is to provide an optical chopper provided with a light-shielding plate that requires a small torque required for rotation.

[0008]

The present invention comprises means for solving the above-mentioned problems as follows. That is, the light shielding plate for chopping the infrared light incident on the infrared detecting section is characterized in that a thin plate of a synthetic resin material is coated with a fluororesin having an infrared shielding ability.

[0009]

[Function] A thin plate of synthetic resin is used as a base, and a fluororesin having an infrared shielding ability in the wavelength band of 8 to 10 μm is coated thereon to form a light shielding plate, so that the weight of the light shielding plate is significantly reduced. Therefore, the required torque for rotating the light shielding plate can be small.

[0010]

Embodiments of the optical chopper of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a plan view of an optical chopper 2 of the radiation thermometer 1, and FIG. 2 is a cross-sectional view of a main part. In each drawing, reference numeral 3 is a semicircular shading plate that blocks infrared light,
Reference numeral 4 denotes a pivot integrated with the light shielding plate 3, 5 a fixing member for fixing the pivot 4 and the light shielding plate 3, 6 a rotor made of a permanent magnet fixed to the pivot 4, 7 an electromagnetic coil, 8 In the stator, the optical chopper 2 is constituted by these, and by applying a voltage to the electromagnetic coil 7, the light shielding plate 3 rotates at a rotation angle of 180 ° per pulse. Reference numeral 10 is a pyroelectric infrared detector, a is a window, b is a light receiving electrode, 11 is a lower holder, and 12 is an upper holder.

FIG. 3 shows the whole structure of the radiation thermometer 1, 13 is an object to be measured, 14 is a hood, 15 is a condenser lens, 16 is a slit, 17 is a pulse consisting of the rotor 6 and the electromagnetic coil 7, etc. A motor, 18 is a drive circuit for the pulse motor 17, and 19 is an amplifier circuit for amplifying a detection signal output from the pyroelectric infrared detector 10. Although not shown, a space is provided in the main body for accommodating a dry battery as a driving power source of the pulse motor 17.

The light shielding plate 3 has a thickness of 50 to 125 μm.
It is preferable that the surface of a carbon-containing polyester resin plate of about 1 μm is coated with a fluororesin having an infrared shielding ability, and it is very lightweight. Even when it is formed in a semicircular shape, a counterweight is provided especially. With a minimal torque, it can rotate smoothly, and bearing wear is extremely low, improving durability. Further, it can be driven with a pulse having a large duty ratio (see FIG. 4), and the current stabilizing circuit of the pulse motor 17 may be simple, and the pulse motor 17 can be made lightweight and compact.
The power consumption is low, the battery consumption can be reduced, and the radiation thermometer 1 can be made compact.

For the coating of the fluororesin, a general method can be adopted, and a physical method such as vacuum deposition, sputtering or thermocompression bonding with a heating heater and a pressure roller, or a chemical method of dipping in a fluororesin solution diluted with a solvent. Any of the target methods can be adopted. In the case of dipping, for example, a Fluorinert solution or a perfluoro solvent can be used as a solvent for the fluororesin. For example, the fluororesin is melted and diluted with these solvents to a concentration of about 5%, and the solution is kept at room temperature. The polyester resin plate may be dipped (soaked) in the inside, taken out, and then dried in a drying furnace at 180 ° C. for about 1 hour, which is inexpensive.

As described above, the light shielding plate 3 coated with the fluororesin has good chemical resistance, corrosion resistance and weather resistance, and has a good infrared shielding ability in the measurement wavelength range (8 to 10 μm). Is.

Incidentally, in the case of a polyester plate having a thickness of 50 μm (for example, amorphous perfluorocarbon), as shown by arrows A and B in FIG.
Although there is an infrared light transmission band of about 4%, the fluororesin film with a thickness of about 1 μm formed by dipping the above-mentioned 5% fluororesin solution has a red color near a wavelength of 8.5 μm as indicated by an arrow C in FIG. Since there is a large absorption of outside light, the transmission of infrared light can be effectively suppressed. Therefore, in the polyester coated with the fluororesin, the arrow D,
As indicated by E, the infrared transmittance is significantly reduced, and the light shielding plate 3 has a sufficient infrared shielding ability. In addition, as the light-shielding plate 3, PVF ₂ (hydrogen molecule of hydrocarbon is replaced by fluorine atom) or crystalline PTFE is also used.
(Polytetrafluoroethylene), PFA (copolymer of tetrafluoroethylene and perfluoroaceter vinyl ether), and FEP (copolymer of tetrafluoroethylene and hexafluoropropylene) can be used.

FIG. 6 shows a non-dispersive gas analyzer (NDIR) 2
1 shows an application example, reference numeral 22 is an infrared light source, 23 is a cell tube for gas analysis, 24 is a window material for infrared transmission, 25 is a gas inlet, 26 is a gas outlet, and 27 is a gas to be measured. Accordingly, it is an infrared bandpass filter that transmits only light of a specific wavelength. Even in this case, it is possible to reduce power consumption, reduce weight and size, and improve durability.

[0017]

As described above, according to the present invention, a thin plate made of a synthetic resin material is coated with a fluororesin having an infrared shielding ability in a specific wavelength region so as to cover its own transmission wavelength region. Since a plate is used, sufficient light blocking characteristics can be obtained in the measurement wavelength range, the weight of the light blocking plate is significantly reduced, the torque required to rotate the light blocking plate can be small, and the motor can be downsized. In addition to this, there is an effect that wear on the bearing is reduced, the life is extended, and power consumption is reduced. It is needless to say that the present invention does not specify the shape of the light shielding plate as that of the embodiment, and that the shape may be appropriately set according to the application.

[Brief description of drawings]

FIG. 1 is a plan view of a main part of a radiation thermometer showing an embodiment of an optical chopper of the present invention.

FIG. 2 is a sectional view taken along line XX of FIG.

FIG. 3 is a main configuration diagram of the radiation thermometer.

FIG. 4 is a diagram showing a chopping pattern of the optical chopper driving pulse and infrared light.

FIG. 5 is a graph showing infrared transmittances of the polyester plate and the fluororesin.

FIG. 6 is a main configuration diagram of the non-dispersive gas analyzer (NDIR).

[Explanation of symbols]

2 ... Optical chopper, 3 ... Shading plate, 10 ... Pyroelectric infrared detector.

Claims (1)

[Claims] 1. An optical chopper characterized in that a light-shielding plate for chopping infrared light incident on an infrared detector is formed by coating a thin synthetic resin material with a fluororesin having an infrared shielding ability. .