JPH03177800A - Pyramid dome for infrared sensor - Google Patents

Abstract

PURPOSE:To permit coping with the high-speed of a missile, improve durability and permit the manufacture of the title dome inexpensively by a method wherein the dome is provided with the configuration of hollow pyramid as well as a specified vertical angle and a thickness. CONSTITUTION:The configuration of the whole of a dome is pyramid and, therefore, air resistance upon high-speed flying is small, the design of a high-speed missile is permitted and temperature rise due to the aerodynamic heating of the fore end of the missile is reduced. On the other hand, the colliding angle (angle of incidence) of sand grains, ice grains, rain drops and the like becomes large and, therefore, the durability of the dome may be improved remarkably. The vertical angle is designed so as to be larger than 20 deg. and smaller than 100 deg.. When the vertical angle is less than 20 deg. in this case, the angle of incidence of infrared rays with respect to the surface of the dome becomes large and, therefore, detection by an infrared sensor becomes difficult. When the same angle exceed 100 deg., the air resistance becomes large and the angle of collision of the sand grains, ice grains, rain drops and the like becomes small. The thickness of the dome is within the range of 2-8 mm. When the thickness is less than 2 mm, the strength of the dome is weak but when the thickness exceeds 8 mm, the permeation coefficient of infrared rays is reduced remarkably even when the vertical angle of the pyramid dome is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dome for protecting an infrared sensor attached to the tip of an infrared light guided missile.

[Conventional technology]

For infrared guided missiles, the ROC! A protective cover called a dome is used to protect the infrared sensor such as D from the external environment such as wind pressure.

Such a dome for an infrared sensor needs to sufficiently transmit infrared light emitted by a target object, so as the +4 material, magnesium fluoride, zinc sulfide, etc., which have good infrared light transmittance, are used.

Further, the shape of a conventional dome for an infrared sensor is a hollow hemisphere as shown in FIG. This is because it was important that the transmittance of infrared light was always constant, so the infrared sensor 2
The dome 1 has a hollow hemispherical shape so that the thickness of the dome 1 is the same in any direction with respect to the movement of the dome 1.

However, in response to the demand for faster missiles in recent years,
Conventional hollow hemispherical domes have high air resistance, which limits their aerodynamic speed, and they also have drawbacks such as the tip of the dome rising in temperature due to aerodynamic heating and emitting infrared noise. In addition, the surface of a hollow hemispherical dome is easily damaged by collisions with sand particles, ice particles, raindrops, etc. floating in the atmosphere when the missile flies at high speed, and there is a problem that the translucency decreases due to surface damage. Ta.

Furthermore, in order to manufacture a hollow hemispherical dome, it is often necessary to create a cylindrical or hemispherical integral object, and then machine it from this material and process it into a curved surface, making it difficult to manufacture. This resulted in poor yields and high costs.

[Problem to be solved by the invention]

In view of such conventional circumstances, the present invention has been developed to provide a red dome that has low air resistance and can cope with high speed missiles, has excellent durability such as a surface that is less likely to be scratched compared to conventional hollow hemispherical domes, and can be manufactured at a low cost. The purpose is to provide a dome for external sensors.

[Means to solve the problem]

In order to achieve the above object, the infrared sensor dome of the present invention has a hollow pyramidal shape, and its apex angle is 20.
It is characterized by having an angle of at least 100 degrees and a wall thickness of 2 to 8 mm.

The material used for the dome of the present invention is an infrared light transmitting material that has been used in conventional domes for infrared sensors, and is required based on the infrared light transmitting area required by the infrared sensor and the speed design of the missile. selected based on the required mechanical strength. For example, the wavelength required by an infrared sensor is 3 to 5μ.
In the case of m-band, single crystal or polycrystalline silicon (Si)
, magnesium fluoride (MgF>, calcium fluoride (C
ar ), spinel (MgAlO), ittria (y
o ), zinc oxynitride alsulfide (ZnS), zinc selenide (znse), calcium lanthanum sulfide (OLLLa S ), and the like are preferred.

The pyramidal dome of the present invention is manufactured by making an isosceles triangular plate made of the above-mentioned material, and bonding or joining the two equal sides of which the end faces are ground obliquely by bringing them into contact with each other.

Figures 1 to 3 show specific examples of hollow pyramidal domes made by gluing or joining isosceles triangular plates 3, and the apex angle θ is 90 degrees in Figure 1 and 50 degrees in Figure 2, respectively. degree, figure 3 is 3
It is 0 degrees.

(Function) Since the pyramidal dome for infrared sensors of the present invention has a pyramidal overall shape, the air resistance during high-speed flight is smaller than that of the conventional hollow hemispherical dome, which makes it possible to design high-speed missiles. This is possible, and the temperature rise due to aerodynamic heating at the tip is much smaller than that of a hollow hemispherical dome. In addition, the pyramidal shape increases the angle at which sand grains, ice grains, raindrops, etc. collide (angle of incidence), resulting in significantly improved durability compared to conventional hemispherical domes even when made from the same material. be done.

The reason why the apex angle of the pyramidal dome is limited to 20 degrees or more and 100 degrees or less is that the smaller the apex angle, the lower the air resistance, which is advantageous for increasing speed. This is because the transmittance of infrared light decreases significantly compared to normal incidence regardless of the material because of the large size, making detection by an infrared sensor difficult. Also, the apex angle is 100
If the angle is exceeded, air resistance increases and the angle at which sand grains, ice grains, raindrops, etc. collide with each other becomes smaller, so there are fewer aerodynamic advantages compared to conventional hemispherical domes, and there are also advantages in terms of durability. becomes less.

Further, the wall thickness of the hollow pyramidal dome varies slightly depending on the material, but is generally in the range of 2 to 8 mm. If the wall thickness is less than 2 layers, the strength will be weak, and even if it is pyramidal, sufficient durability will not be obtained, and if it exceeds 8 layers, the infrared light transmittance will be significantly reduced even if the apex angle of the pyramidal dome is made thicker. This is because it decreases.

The pyramidal dome is preferably a square pyramid, a hexagonal pyramid, an octagonal pyramid, or a decagonal pyramid. This is because the optical symmetry when the infrared sensor is oriented in various directions is better for even-numbered pyramids than for odd-numbered pyramids. This is not preferable because a large proportion of the corners are exposed, and there are many areas that do not transmit infrared light.

[Example] Example 1 Polycrystalline ZnS material was cut, ground and polished to a diameter of 1
A disc-shaped plate material with a thickness of 70 mm and a wall thickness of 3 mm was obtained. The infrared light transmittance of this plate material was 70% on average in the wavelength band of 8 to 10 μm. Using 4 equilateral triangles cut out from this board with sides of approximately 85 mm, the end surfaces were ground diagonally and then glued together with epoxy adhesive, so that the diagonal length of the bottom surface was approximately 120 cm and the height was 6
A regular square pyramidal dome with an apex angle of Q-450 was fabricated with zero friction.

An infrared sensor was installed at the center of the inside of this square pyramidal dome, and the infrared light transmittance of the dome was measured in various directions.The average transmittance of the dome was 65% in the wavelength range of 8 to 10 μm, which is sufficient for practical use. It turned out to be a gift.

In addition, the manufacturing cost of this regular square pyramid dome is
The height and wall thickness of the hemispherical dome was approximately 173 cm.

Example 2 A polycrystalline MgF material produced by hot pressing was cut, ground and polished to produce six isosceles triangular plates with a base of 40 m5, a height of 150 m, and a wall thickness of 3.5 m. The infrared light transmittance of this plate material is 90% on average in the wavelength range of 3 to 5 μm.
Met. The end faces of equal sides of this plate were obliquely ground and then bonded with epoxy adhesive to produce a hexagonal pyramidal dome with a regular hexagonal base with a diameter of 80 m5, a height of about 140 m, and an apex angle θ = 300.

An infrared sensor was installed at the center of the inside of this hexagonal pyramidal dome, and the infrared light transmittance of the dome was measured in various directions.The average transmittance of the dome was 70% in the wavelength range of 3 to 5 μm, which is sufficient for practical use. It turned out to be scales.

〔Effect of the invention〕

According to the present invention (d), the infrared sensor dome has low air resistance and can cope with high speed missiles, has excellent durability such as a surface that is less likely to be scratched compared to conventional hollow hemispherical domes, and can be manufactured at a low cost. can be provided.

[Brief explanation of drawings]

1 to 3 are side views of pyramidal domes showing specific examples of the present invention, in which FIG. 1 shows a square pyramid with an apex angle of 90 degrees, FIG. 2 shows a hexagonal pyramid with an apex angle of 50 degrees, and FIG. Figure 3 shows a dome consisting of a hexagonal pyramid with an apex angle of 30 degrees. FIG. 4 is a cross-sectional view of a conventional hemispherical dome.

Claims (2)

[Claims] (1) A dome for protecting an infrared sensor attached to the tip of an infrared light-guided missile is shaped like a hollow pyramid and has an apex angle of 20 degrees or more and 100 degrees or less,
A pyramidal dome for an infrared sensor, characterized by a wall thickness of 2 to 8 mm. (2) The pyramidal dome for an infrared sensor according to claim (1), which has a hollow square pyramid, hexagonal pyramid, octagonal pyramid, or decagonal pyramid shape.