WO2022115090A2

WO2022115090A2 - Seeker working in three wavelengths

Info

Publication number: WO2022115090A2
Application number: PCT/TR2021/051288
Authority: WO
Inventors: Bilgen Birkan KURŞUN; Doğan Uğur SAKARYA
Original assignee: Roketsan Roket Sanayi ve Ticaret AS
Current assignee: Roketsan Roket Sanayi ve Ticaret AS
Priority date: 2020-11-26
Filing date: 2021-11-25
Publication date: 2022-06-02
Anticipated expiration: 2023-05-26
Also published as: WO2022115090A3; TR202019074A2

Abstract

The invention relates to a seeker working in three wavelengths and comprising a compact structure. In particular, the invention relates to seeker that enables the seeker to work in all infra-red bands simultaneously by separating three different wavelengths (SWIR, MWIR and LWIR) into three different detectors by means of the pentagon having a selectively permeable coating.

Description

SEEKER WORKING IN THREE WAVELENGTHS

Technical field of the invention:

The invention relates to a seeker working in three wavelengths and comprising a compact structure.

In particular, the invention relates to seeker that enables the seeker to work in all infra red bands simultaneously by separating three different wavelengths (SWIR, MWIR and LWIR) into three different detectors by means of the pentagon having a selectively permeable coating.

State of the art:

Air Force Systems are one of the most important security requirements of a country in terms of protecting the military installations, operation practices of the tactical forces and the border security. Missiles and rockets have an important place in the air force systems.

Guidance systems of missiles are generally referred to as seekers. Even though they do not have seeker elements, some missiles having systems such as GPS (Global Positioning System) and INS (Inertial Navigation System) also demonstrate guidance feature and track the target. The guidance system is a structure that enables the missile to lock on and track the target until hitting it. The “counter measure systems” of the enemy forms certain tricks to prevent the missile from hitting the target, whereas the guidance system of the missile aims to clear such preventions.

The most important property of the applications of military air vehicles to avoid the missiles is the technical capabilities of the seekers. Because escaping a missile is only possible by preventing the seeker from locking on the target. In the seeker part of missiles, radar or infra-red technologies are used. In addition to these technologies, INS, GPS, Passive Radiation Seeker, IMU (Inertial Measurement Unit) and Data-Link systems integrated to the missiles are also elements helping the guidance.

In the seeker parts of the missiles, generally one or two different types of wavelengths are used. The most frequently used wavelengths are SWIR, MWIR and LWIR wavelengths. Generally, one of these wavelengths are used, in certain embodiments, more than one wavelengths are used. Short Wave Infra-Red (SWIR) is a subset of the electromagnetic spectrum covering the wavelengths of the infra-red band between 1 micron and 3 microns. Middle Wave Infra-Red (MWIR) is a subset of the electromagnetic spectrum covering the wavelengths of the infra-red band between 3 microns and 5 microns. Long Wave Infra-Red (LWIR), is a subset of the electromagnetic spectrum covering the wavelengths of the infra-red band between 8 microns to 12 microns.

Using more than one wavelength in the seekers helps the seeker with counter-counter measure. Using more than one wavelength requires these wavelengths to be separated. This separation is generally performed by the help of filters.

Patent document no “2014/04394” in the state of the art was reviewed. In the abstract of the invention subject to the application, the following information is given: “This invention relates to an electro-optical sensor system that provides, in a single compact and ergonomic design, the sensors that sense within MWIR band defined as 3-5 pm wavelength with its high resolution thermal imaging sensor, viewpoints of the lens thereof providing a certain level of sight in narrow, middle and wide, containing colour day television sensor, harmless to eye laser distance meter, ground positioning sensor and digital magnetic compass units, meeting the requirements related to determination (detection, recognition, identification) of the target in a wide range, the thermal imaging sensor of which having the advantage to be used in both the day and night surveillance and target locating, able to detect the its own location as well as determine the location information of a possible threat with high precision and accuracy by means of its ground positioning sensor, performing all calculation processes with its own embedded software without requiring user intervention and using developed technologies different from one another.” Patent document no “2014/16238” in the state of the art was reviewed. In the abstract of the invention subject to the application, the following information is given: “The present invention propounds unit cell architecture comprising, for infra-red imaging, two input levels covering both low and high light levels and automated input selection circuit in it for the purpose of expanding the dynamic range. The invention, substantially, helps expanding the dynamic range of the near infra-red (NIR) and short wave infra-red (SWIR) imaging sensors by expanding the SNR value. The idea can be applied not only to infra-red bands comprising NIR, SWIR, MWIR and LWIR, but also to the entire light spectrum”.

Patent document no “EP2757356A1” in the state of the art was reviewed. In the invention subject to the application, a multi spectral optical device arranged between or within multi spectral optical systems is disclosed. The device subject to this invention has an active optical element such as reflecting optical systems, i.e. flexible mirror. In the device, beam splitters or filters are used to split the spectral channels. On the other hand, said invention does not comprise a prism, particularly a prism with a pentagonal structure.

Patent document no “US8326142B2” in the state of the art was reviewed. In the invention subject to the application, an optical imaging system comprising a first lens, a camera and a second lends and having a second sensor is disclosed. The system subject to this invention comprises a beam splitter to transfer the incident electromagnetic radiation beam with a first wavelength band to the focal plane array of the first camera and to reflect the incident electromagnetic radiation beam coming from a second wavelength. The system subject to this invention is neither used in a seeker nor comprises a prism with a pentagonal structure and a roll-pitch gimbal structure.

In the state of the art, structures working in dual wavelength are provided with filters. In the systems working in dual wavelength, the beam is split into two wavelengths with a filtered structure. Meanwhile, image distortions and editing challenges occur resulting from the filter.

Conclusively, due to the above-described problems and the insufficiency of the existing solutions made it necessary to make an improvement in the relevant technical field. The Aim of the invention

The most important aim of the invention is to enable the seeker to work in all infra-red bands simultaneously by separating the three different wavelengths (SWIR, MWIR and LWIR) into three different detectors by means of the pentagon having a selectively permeable coating.

Another aim of the invention is to form a seeker having three wavelengths by using the surfaces of the used pentagonal structure.

Another aim of the invention is to carry the beams in a system with roll-pitch gimbal structure from the dome of the seeker up to the pentagonal structure.

Another aim of the invention is to provide mountability and thereby to obtain a compact design.

Another aim of the invention is to make it more successful against the counter-counter measures by using three wavelengths simultaneously.

Another aim of the invention is to make other wavelengths usable in the counter measures or circumstances where one wavelength becomes insufficient. By this way, the reliability of the design is increased.

The structural and characteristic properties and all advantages of the invention will be understood more clearly via the figures given below and the detailed description written with reference to these figures. Therefore, the evaluation should also be made taking these figures and detailed description into account.

Description of drawings:

FIGURE-1 ; is the drawing presenting the image of the contexts of the seeker that is the subject of the invention.

FIGURE-2; is the drawing presenting the detailed image of the pentagonal prism of the seeker that is the subject of the invention. Reference Numbers:

100. Seeker 110. Seeker Dome 120. Mirror

130. Pentagonal Prism 140. Risley Prism

Description of the invention:

The invention enables the seeker (100) to work in all infra-red bands simultaneously by separating the three different wavelengths (SWIR, MWIR and LWIR) into three different detectors.

The seeker (100) that is the subject of the invention comprises, in general terms, the seeker dome (110), mirrors (120), pentagonal prism (130) and risley prisms (140). The system, preferably comprising four mirrors (120) and multiple risley prisms (140) transfer the beams from the seeker dome (110) up to the pentagonal prism (130) within a system having roll-pitch gimbal structure.

The seeker dome (110) enables the infra-red beams in different wavelengths to enter into the seeker (100). The seeker dome (1 10) has a dome structure and enables the transfer of wavelengths coming from any angle to the mirrors (120). The different wavelengths here are short wavelength infra-red (SWIR), middle wavelength infra-red (MWIR) and long wavelength infra-red (LWIR) beams. The beams arriving the seeker dome (110) may arrive the seeker dome (110) rectangularly or in different angles. Beams coming from physically different angles can rebound between mirrors.

There are preferably four mirrors (120) and are positioned within the seeker dome (110). They ensure that the infra-red beams coming to the seeker are reflected on them and transferred to the pentagonal prism (130) after passing through the seeker dome (110). Another reason for the use of the mirrors (120) is to obtain a more compact volume by keeping the stationary optical structure in the axis.

The pentagonal prism (130) splits the infra-red beams coming from the mirrors (120) into wavelengths and enables them to be transferred them to risley prisms (140) therefore to different detectors. Pentagonal prism (130), details of which are shown in Figure-2, has a selectively permeable coating. This selectively permeable coating helps the pentagonal prism (130) to separate the beams into different wavelengths and detectors. In the pentagonal prism (130), SWIR wavelength refracts in the first surface whereas MWIR and LWIR wavelengths are reflected. Wavelengths that cannot pass through the second surface are reflected on the third surface which is coated with a special coating. By this way, MWIR and LWIR wavelengths arrive on the third surface. On the third surface, there is a special coating that allows the MWIR wavelength to pass but reflects the LWIR wavelength. The LWIR being reflected from here refracts in the last surface.

Risley prisms (140) enable the infra-red beams the pentagonal prism (130) separates to be transferred to the detectors. In order to adjust the optic route difference occurring during the reflections within the pentagonal prism (130) and passes through the surfaces, risley prisms (140) are used. Risley prisms (140) decrease the optical defects by creating a route difference exactly opposite to this route difference.

To adjust the image distortions emerging due to the optical route distance inside and outside of the pentagonal prism (130), risley prisms (140) are used. Image quality is compensated by creating a route difference opposite to the emerging route difference. During the optical route travelled within the pentagonal prism (130), the distance the incident beams travel varies depending on the entrance pupil. This is why optical route differences occur within the pentagonal prism (130). To create a similar effect to this optical route difference, risley prisms (140) are chosen. The apical angle of this risley prisms (140) have a structure that can be adjusted. This optical route difference occurring in the light in the pentagonal prism (130) is reconstructed by adjusting the apical angle of the risley prism (140). By this way, equalising the sum of the two route difference is tried. By this way, beams are exposed to an effect as if they travel in a straight window. The working principle of the system and of the pentagonal prism are given in Figures 1 and 2. Accordingly, in the seeker (100) that is the subject of the invention, first infra red beams having different wavelengths are sent to the system in which the seeker (100) is installed. These beams are taken into the seeker by seeker dome (110). The beams entering in the seeker are transferred to the pentagonal prism (130) by means of mirrors (120). Three different wavelengths arriving the pentagonal prism (130) are separated into wavelengths here. In the first surface of the pentagonal prism (130), SWIR wavelength refracts while MWIR and LWIR are reflected. In the second surface, MWIR wavelength refracts while LWIR wavelength is reflected. In the last surface, LWIR refracts. Wavelengths are separated by this way. To rectify the image quality, rectifier risley prism (140) is used in all three wavelengths. Also, to save place and form a compact structure, mirrors (120) can also be used in the surfaces where MWIR and LWIR wavelengths refract.

Using more than one wavelength in seekers (100) helps the seeker in the matter of counter-counter measure. By enabling the use of three wavelengths in the seeker (100) that is the subject of this invention, it is made more successful against counter counter measures.

Claims

1. A seeker (100) working in three wavelengths and having a compact structure, characterized in that; it comprises;

• seeker dome (110) with a dome structure enabling the infra-red beams in different wavelengths to enter into the seeker (100);

• mirror (120), positioned in the seeker dome (110), ensuring that the infra-red beams coming to the seeker are transferred to the pentagonal prism (130) after passing through the seeker dome (110),

• pentagonal prism (130), having a selectively permeable coating and surface helping the separation of the beams into different wavelengths, ensuring that infra-red beams coming from the mirrors (120) are separated according to their wavelengths and transferred to the risley prisms (140),

• risley prisms (140), enabling the infra-red beams the pentagonal prism (130) separates to be transferred to the detectors and rectifying the reflections inside the pentagonal prism (130) and the optical route difference emerging during the passes

2. Seeker (100) according to Claim 1 , comprising pentagonal prism (130) that can separate infra-red beams belonging to different wavelengths as short wavelength infra-red (SWIR), middle wavelength infra-red (MWIR) and long wavelength infra-red (LWIR).

3. Seeker (100) according to Claim 1 or Claim 2, comprising the pentagonal prism (130) having the first surface in which SWIR wavelength refracts and MWIR and LWIR wavelengths are reflected, the second surface in which MWIR wavelength refracts and LWIR wavelength is reflected and the third surface in which LWIR wavelength refracts.

4. Seeker (100) according to Claim 1 , comprising, preferably four, mirrors (120), enabling to obtain a more compact volume by keeping the stationary optical structures in the same axis.

5. Seeker (100) according to Claim 1 , comprising risley prisms (140) enabling to reduce the optical defect by forming a route difference exactly opposite to the emerging route difference.

6. Seeker (100) according to Claim 1, comprising risley prisms (140) having a structure with an adjustable the apical angle.

7. Seeker (100) according to Claim 1 or Claim 5 or Claim 6, comprising risley prism (140) ensuring the reconstruction of the route difference by adjusting the apical angle for the emerging route difference in the light in pentagonal prism (130) to ensure that the sum of two route differences equalises.