Pinhole camera for ship-based helicopter landing aid optical system

Abstract

The application discloses a pinhole camera for a carrier-based helicopter landing optical system and belongs to the field of carrier-based helicopter landing optics. The pinhole camera is composed of a six-piece spherical lens group, an aperture stop and a detector. The first lens and the second lens are combined to correct the field curvature in the optical system. The third lens, the fourth lens and the fifth lens are combined to improve the distortion in the system. The sixth lens of the lanthanide series glass corrects the field curvature of the system again, and the seventh surface focuses the imaging surface to be received. The aperture stop is located at the front surface of the fourth lens of the system to limit the light entering the optical system. The infrared camera lens on both sides of the flight deck tracks and shoots two groups of infrared laser beacons on the fuselage, captures the position of the carrier-based helicopter, corrects the aberration of the system according to the positive and negative focal lengths of the lenses in the infrared optical system, and improves the imaging precision of the carrier-based helicopter landing optical system.

Description

Technical Field

[0001] This invention relates to a pinhole camera for a shipborne helicopter landing aid optical system, belonging to the field of shipborne helicopter landing aid optics. Background Technology

[0002] With the continuous advancement of technology, modern naval warfare has diversified, and the battlefield is no longer confined to the sea. The role of shipborne helicopters is increasingly evident. The vast skies are gradually becoming a second battlefield in naval warfare. Shipborne helicopters, based on aircraft carriers or other warships, must perform crucial tasks in the air, including search and rescue, equipment transport, anti-submarine warfare, amphibious assault, airborne early warning, and modern electronic warfare and torpedo warfare. Shipborne helicopters have become an indispensable component of modern naval warfare, serving as a vital armed force for seizing and maintaining air and sea supremacy. Without the involvement of deck personnel, shipborne helicopters utilize their electro-optical landing system, employing two cameras on either side of the flight deck to track and photograph two sets of infrared laser beacons on the helicopter's fuselage. The images acquired by the cameras are processed in real-time to determine the helicopter's relative position and attitude to the flight deck, thereby activating the rapid-locking device on the ship's deck to quickly engage the helicopter's extended main probe and complete the landing operation.

[0003] Indel Technologies of Canada developed the first truly functional shipboard helicopter landing system to date: the "E System." Using the E System for shipboard helicopter landings, a winch mounted on the helicopter fuselage lowers a tension cable; then, deck crew secure the cable to a fixed connection on the deck; the winch on the helicopter rewinds the tension cable to achieve a gradual descent, maintaining tension on the cable until the helicopter touches the deck; finally, the fuselage is aligned for retrieval, completing the recovery operation. However, the entire operation takes over 10 minutes, and the total weight of the system is nearly 9 tons. Later, ITI, another Canadian company, further developed the now widely used "Landing, Assist, Securing, and Towing System" based on the helicopter descent-assisted landing system. This system uses a grid-shaped quick-locking device, but the tension cable is placed on the flight deck. When a helicopter is about to land on a ship, the pilot first releases the guide cable for the deck crew to secure the tension cable. The pilot then rewinds the tension cable and secures it to the helicopter's boom. The deck crew rewinds the tension cable to ensure a smooth landing and that the boom accurately enters and is quickly engaged by the quick-release device. Finally, deck crew install a cable at the tail, and a winch rotates the helicopter to the docking direction, completing the retrieval along the track. Therefore, developing a highly automated, short-operation-time, simple, and lightweight shipborne helicopter landing system is of paramount importance for the execution of maritime missions, the integrity of ordnance and equipment, and the safety of pilots.

[0004] In conclusion, how to research and develop a safe and reliable pinhole camera for shipborne helicopter landing aid optical systems is a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The main objective of this invention is to provide a pinhole camera for a shipborne helicopter landing aid optical system. This pinhole camera, which assists shipborne helicopters in landing and operates in the near-infrared (0.8μm-0.815μm) range, tracks and captures two sets of infrared laser beacons on the fuselage through infrared camera lenses on both sides of the flight deck, thereby capturing the position of the shipborne helicopter. At the same time, it corrects various aberrations of the system by allocating the positive and negative optical powers of each lens in the infrared optical system, thereby improving the optical imaging accuracy of shipborne helicopter landing aids.

[0006] The objective of this invention is achieved through the following technical solution.

[0007] This invention discloses a pinhole camera for a shipborne helicopter landing aid optical system, comprising a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh focusing imaging surface. The first, second, third, fourth, fifth, and sixth lenses constitute a six-element spherical lens group. Through the allocation of optical power and element spacing of the first, second, third, fourth, fifth, and sixth lenses, the optical power equation is... With the cooperation of various factors, the aberrations can be reduced and optimized, where h is the aberration. i The height of the paraxial marginal ray on the i-th lens is given. The first and second lenses are combined to correct the field curvature in the optical system. The third, fourth, and fifth lenses are combined to improve distortion in the system. The sixth lanthanide glass further corrects the field curvature and is received at the seventh focusing imaging surface. The refractive indices of the materials for the first, second, third, fourth, and sixth lenses are 1.55–1.58, 1.74–1.76, 1.65–1.68, 1.52–1.54, 1.70–1.72, and 1.72–1.74, respectively. The front surface of the fourth lens is the aperture stop. The seventh surface is the focusing imaging surface, and it is where the detector is located.

[0008] The first lens has a thickness of 1.085mm to 1.09mm, a front surface radius of curvature of 10.95mm to 10.99mm, a rear surface radius of curvature of 3.573mm to 3.58mm, and a distance of 3.34mm to 3.35mm from the front surface of the second lens. The refractive index of the material is 1.55 to 1.58. Preferably, the first lens has a thickness of 1.089mm, a front surface radius of curvature of 10.970mm, a rear surface radius of curvature of 3.575mm, and a distance of 3.347mm from the front surface of the second lens. The material is H-BAK8.

[0009] The second lens has a thickness of 2.083mm to 2.088mm, a front surface radius of curvature of 28.34mm to 28.35mm, a rear surface radius of curvature of -27.06mm to -27.055mm, and is 0.45mm to 0.54mm away from the third lens. The refractive index of the material is 1.74 to 1.76. Preferably, the second lens has a thickness of 2.086mm, a front surface radius of curvature of 28.344mm, a rear surface radius of curvature of -27.057mm, and is 0.5mm away from the third lens. The material is H-LAK3.

[0010] The third lens has a thickness of 1.9mm to 1.906mm, a front surface radius of curvature of 10.53mm to 10.536mm, a rear surface radius of curvature of -8.058mm to -8.053mm, and a distance of 0.715mm to 0.722mm from the front surface of the fourth lens. The refractive index of the material is 1.65 to 1.68. Preferably, the third lens has a thickness of 1.902mm, a front surface radius of curvature of 10.531mm, a rear surface radius of curvature of -8.055mm, and a distance of 0.719mm from the front surface of the fourth lens. The material is H-LAK1.

[0011] The fourth lens has a thickness of 1.08mm to 1.085mm, its front surface is an aperture stop, which is set as a plane, its rear surface has a radius of curvature of 4.95mm to 4.967mm, and its distance from the front surface of the fifth lens is 1.255mm to 1.26mm. The refractive index of the material is 1.52 to 1.54. Preferably, the fourth lens has a thickness of 1.082mm, a front surface (i.e., the aperture stop surface) with a radius of curvature of ∞, a rear surface with a radius of curvature of 4.959mm, and a distance from the front surface of the fifth lens is 1.257mm. The material is H-K51.

[0012] The fifth lens has a thickness of 1.033mm to 1.042mm, a front surface radius of curvature of -8.18mm to -8.168mm, a rear surface radius of curvature of -4.47mm to -4.45mm, and a distance of 0.76mm to 0.8mm from the front surface of the sixth lens. The refractive index of the material is 1.70 to 1.72. Preferably, the fifth lens has a thickness of 1.038mm, a front surface radius of curvature of -8.175mm, a rear surface radius of curvature of -4.461mm, a distance of 0.78mm from the front surface of the sixth lens, and is made of H-LAK7A material.

[0013] The sixth lens has a thickness of 0.98mm to 1.06mm, a front surface radius of curvature of -62.9mm to -62.88mm, a rear surface radius of curvature of -12.95mm to -12.94mm, a distance from the imaging plane of 5.15mm to 5.23mm, and a material refractive index of 1.72 to 1.74; preferably, the sixth lens has a thickness of 1mm, a front surface radius of curvature of -62.892mm, a rear surface radius of curvature of -12.945mm, a distance from the imaging plane of 5.2mm, and is made of H-LAK54.

[0014] The seventh surface is a focusing imaging surface, which can be a short-wave infrared detector with a specification of 1024×1024 and a pixel size of 10μm.

[0015] The present invention discloses a pinhole camera for a shipborne helicopter landing aid optical system, which is installed on both sides of the flight deck. Its observation band is the near-infrared band of 0.8μm-0.815μm; the observation field of view is 45°; the system focal length is 6mm; the relative aperture is 1:5.5; the total system length is 20mm; and the detector pixel size is 10μm.

[0016] The present invention discloses a method for operating a pinhole camera for a shipborne helicopter landing-aid optical system as follows:

[0017] The shipborne helicopter's position is captured by tracking and photographing two sets of infrared laser beacons on the fuselage using infrared cameras on both sides of the flight deck. Simultaneously, various aberrations in the system are corrected by rationally allocating the positive and negative optical powers of each lens in the infrared optical system. The first and second lenses combine to correct field curvature in the optical system. The third, fourth, and fifth lenses combine to significantly improve distortion. A sixth lanthanide glass element further corrects field curvature, and the image is finally received on the seventh focusing surface. The pinhole camera used in the shipborne helicopter landing aid optical system operates in the near-infrared band, tracking and photographing the two sets of infrared laser beacons on the fuselage through infrared cameras on both sides of the flight deck.

[0018] Beneficial effects:

[0019] As the military value of shipborne helicopters continues to be explored, the demand from navies around the world is also increasing, leading to higher requirements for their safety and stability during return and landing. The pinhole camera system for shipborne helicopter landing assistance optical systems of this invention offers the following beneficial effects in practical applications:

[0020] 1. The present invention discloses a pinhole camera for a shipborne helicopter landing optical system, which adopts a large field of view, so that the system can have a larger observation range. Unlike the aberrations caused by the large field of view in general systems, the camera system of the present invention has excellent aberration correction capability and imaging performance close to the diffraction limit.

[0021] 2. The pinhole camera disclosed in this invention for a shipborne helicopter landing aid optical system adopts a relatively simple optical system structure. While ensuring aberrations, it consists of only six lenses and is very small in size, thus achieving a good concealment effect.

[0022] 3. The present invention discloses a pinhole camera for a shipborne helicopter landing optical system. The system operates in the infrared optical band of 0.8μm-0.815μm, which can operate normally at night or in bad weather, reducing the impact of the environment on the optical system. At the same time, due to the narrow operating wavelength range, it is not easily affected by other signals.

[0023] 4. This invention discloses a pinhole camera for a shipborne helicopter landing aid optical system. By allocating optical power between lenses and element spacing, various aberrations are reduced, enabling the camera system to acquire images with minimal distortion. The distortion is less than 1.66% across the entire field of view. Simultaneously, the system exhibits near-diffraction-limited imaging quality; at a Nyquist frequency of 50 lp / mm, the modulation transfer function of the camera system is greater than 0.37 in all fields of view except the maximum field of view, demonstrating excellent observation performance. Attached Figure Description

[0024] Figure 1 Optical path diagram of the pinhole camera in the shipborne helicopter landing aid optical system;

[0025] Figure 2 A dot diagram of the pinhole camera in the shipborne helicopter landing aid optical system;

[0026] Figure 3 A graph showing the root mean square radius of the image plane of the pinhole camera in the shipborne helicopter landing aid optical system as a function of wavelength.

[0027] Figure 4 A graph showing the root mean square radius of the image plane blur spot of the pinhole camera in the shipborne helicopter landing aid optical system as a function of the field of view.

[0028] Figure 5 Modulation transfer function curve of pinhole camera in shipborne helicopter landing aid optical system;

[0029] Figure 6 A graph showing the energy fraction of the image plane surrounding the circle of the pinhole camera in the shipborne helicopter landing aid optical system as a function of the radius.

[0030] Figure 7 Wavefront aberration of the pinhole camera in the edge field of view of the shipborne helicopter landing aid optical system;

[0031] Figure 8 Field curvature aberration curves and distortion aberration curves of pinhole cameras in shipborne helicopter landing aid optical systems;

[0032] Figure 9 A graph showing the root mean square radius of the image plane of the pinhole camera in the shipborne helicopter landing aid optical system as a function of the system's defocusing amount.

[0033] Figure 10 Axial chromatic aberration curve of the pinhole camera in the shipborne helicopter landing aid optical system;

[0034] Figure 11 Magnification chromatic aberration curve of the pinhole camera in the shipborne helicopter landing aid optical system;

[0035] Figure 12A schematic diagram of the pinhole camera in the shipborne helicopter landing aid optical system during practical application.

[0036] Among them, 1—first lens, 2—second lens, 3—third lens, 4—fourth lens, 5—fifth lens, 6—sixth lens, and 7—seventh focusing imaging surface. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0038] like Figure 1 As shown, the pinhole camera of the shipborne helicopter landing aid optical system disclosed in this embodiment includes a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6, and a seventh focusing imaging surface 7. The first lens 1, second lens 2, third lens 3, fourth lens 4, fifth lens 5, and sixth lens 6 constitute a six-element spherical lens group. Various aberrations are reduced through the allocation of optical power of the lenses. Specifically, the first lens 1 is made of H-BAK8 material, the second lens 2 is made of H-LAK3 material, the third lens 3 is made of H-LAK1 material, the fourth lens 4 is made of H-K51 material, the fifth lens 5 is made of H-LAK7A material, and the sixth lens 6 is made of H-LAK54 material. The front surface of the fourth lens 4 is an aperture stop. The seventh surface 7 is the focusing imaging surface, which is the location of the detector.

[0039] The first lens 1 has a thickness of 1.089 mm, a front surface curvature radius of 10.970 mm, a rear surface curvature radius of 3.575 mm, and a distance of 3.347 mm from the front surface of the second lens 2. The material is H-BAK8.

[0040] The second lens 2 has a thickness of 2.086 mm, a front surface curvature radius of 28.344 mm, a rear surface curvature radius of -27.057 mm, and is 0.5 mm away from the third lens 3. The material is H-LAK3.

[0041] The third lens 3 has a thickness of 1.902 mm, a front surface curvature radius of 10.531 mm, a rear surface curvature radius of -8.055 mm, and is 0.719 mm away from the front surface of the fourth lens 4. The material is H-LAK1.

[0042] The fourth lens 4 has a thickness of 1.082 mm, a flat front surface (i.e., aperture stop), a radius of curvature of 4.959 mm on its rear surface, and a distance of 1.257 mm from the front surface of the fifth lens 5. The material is H-K51.

[0043] The fifth lens 5 has a thickness of 1.038 mm, a front surface curvature radius of -8.175 mm, a rear surface curvature radius of -4.461 mm, and is 0.78 mm away from the front surface of the sixth lens 6. The material is H-LAK7A.

[0044] The sixth lens 6 has a thickness of 1 mm, a front surface curvature radius of -62.892 mm, a rear surface curvature radius of -12.945 mm, a distance of 5.2 mm from the imaging surface 7, and is made of H-LAK54 material.

[0045] The seventh surface is a focusing imaging surface 7, which can be a short-wave infrared detector with a specification of 1024×1024 and a pixel size of 10μm.

[0046] The pinhole camera used in the shipborne helicopter landing optical system is installed on both sides of the flight deck. Its observation band is the near-infrared band of 0.8μm-0.815μm; the observation field of view is 45°; the system focal length is 6mm; the relative aperture is 1:5.5; the total system length is 20mm; and the detector pixel size is 10μm.

[0047] Figure 2 This is a distribution diagram of the image plane blur pattern of the pinhole camera system in the shipborne helicopter landing aid optical system according to an embodiment of the present invention, under full field of view. Figure 3 This is a graph showing the variation of the root mean square radius of the speckle on the image plane of the pinhole camera system in the shipborne helicopter landing aid optical system, an example of the present invention, with the field of view. Figure 4 This is a graph showing the root mean square radius of the image plane blur spot of the pinhole camera in the shipborne helicopter landing aid optical system according to an embodiment of the present invention, as a function of the field of view. Figure 5 This is a modulation transfer function curve of the pinhole camera in the shipborne helicopter landing aid optical system according to an embodiment of the present invention. Figure 6 This is a graph showing the energy fraction of the image plane surrounding the circle of the pinhole camera in the shipborne helicopter landing aid optical system according to an embodiment of the present invention, as a function of the radius. Figures 2-6 The curves all indicate that the imaging quality of the pinhole camera system in the embodiments of the present invention is close to the diffraction limit.

[0048] Figure 7 This invention relates to wavefront aberration of the pinhole camera in the shipborne helicopter landing aid optical system at the edge of the field of view, as described in an embodiment of the invention. Figure 8 The field curvature aberration curve and distortion aberration curve of the pinhole camera in the shipborne helicopter landing aid optical system of this embodiment of the invention are shown. Figure 9This is a graph showing the root mean square radius of the image plane of the pinhole camera in the shipborne helicopter landing aid optical system according to an embodiment of the present invention, as a function of the system's defocusing amount. Figure 10 This is an axial chromatic aberration curve of the pinhole camera in the shipborne helicopter landing aid optical system according to an embodiment of the present invention. Figure 11 This is a magnification chromatic aberration curve of the pinhole camera in the shipborne helicopter landing aid optical system according to an embodiment of the present invention. Figures 7-11 The curves all show that the field curvature, distortion, defocus, axial chromatic aberration, and magnification chromatic aberration of the pinhole camera system in the embodiments of the present invention are well corrected, and the wavelet aberration of the system is far superior to the Rayleigh criterion.

[0049] Figure 12 This is a schematic diagram illustrating the operation of the pinhole camera in the shipborne helicopter landing aid optical system of this invention in practical application. Two cameras on either side of the flight deck track and photograph two sets of infrared laser beacons on the helicopter fuselage. Within one second of the shipborne helicopter entering the field of view of the infrared cameras, the infrared laser beacon points on the helicopter can be detected. The helicopter's attitude information is calculated every 1 / 30th of a second, providing the pilot with real-time relative attitude information of the helicopter relative to the flight deck coordinate system, until the rapid locking device engages with the main probe of the shipborne helicopter, correcting the fuselage orientation and completing the safe landing and storage of the shipborne helicopter.

[0050] In summary, the pinhole camera of the shipborne helicopter landing assistance optical system of the present invention employs a simple optical structure, reducing the system's size and weight. Operating in the infrared band reduces the impact of the environment on the optical system while also improving its anti-interference capabilities. Through the rational combination of optical and structural materials and the appropriate allocation of lens power, the system achieves excellent imaging quality. This invention can be used for shipborne helicopter landing assistance, improving the safety and stability of return and landing operations.

[0051] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A pinhole camera for a shipborne helicopter landing-aid optical system, characterized in that: It consists of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh focusing imaging surface; the first, second, third, fourth, fifth, and sixth lenses form a six-element spherical lens group. The optical power and element spacing of the first, second, third, fourth, fifth, and sixth lenses are allocated according to the optical power equation. With the cooperation of various factors, the aberrations can be reduced and optimized, where h is the aberration. i The height of the paraxial marginal ray on the i-th lens; the first and second lenses combine to correct the field curvature in the optical system; the third, fourth, and fifth lenses combine to improve distortion in the system; the sixth lanthanide glass further corrects the field curvature and is received at the seventh focusing imaging surface; the refractive index of the first lens material is 1.55~1.58, the refractive index of the second lens material is 1.74~1.76, the refractive index of the third lens material is 1.65~1.68, the refractive index of the fourth lens material is 1.52~1.54, the refractive index of the fifth lens material is 1.70~1.72, and the refractive index of the sixth lens material is 1.72~1.74; the front surface of the fourth lens is the aperture stop; the seventh surface is the focusing imaging surface, which is the location of the detector; The first lens has a thickness of 1.085mm to 1.09mm, a front surface radius of curvature of 10.95mm to 10.99mm, a rear surface radius of curvature of 3.573mm to 3.58mm, and a distance of 3.34mm to 3.35mm from the front surface of the second lens. The second lens has a thickness of 2.083mm to 2.088mm, a front surface radius of curvature of 28.34mm to 28.35mm, a rear surface radius of curvature of -27.06mm to -27.055mm, and a distance of 0.45mm to 0.54mm from the third lens. The third lens has a thickness of 1.9mm to 1.906mm, a front surface radius of curvature of 10.53mm to 10.536mm, a rear surface radius of curvature of -8.058mm to -8.053mm, and a distance of 0.715mm to 0.722mm from the front surface of the fourth lens. The fourth lens has a thickness of 1.08mm to 1.085mm, its front surface is an aperture stop set as a plane, its rear surface has a radius of curvature of 4.95mm to 4.967mm, and its distance from the front surface of the fifth lens is 1.255mm to 1.26mm. The fifth lens has a thickness of 1.033mm to 1.042mm, a front surface radius of curvature of -8.18mm to -8.168mm, a rear surface radius of curvature of -4.47mm to -4.45mm, and a distance of 0.76mm to 0.8mm from the front surface of the sixth lens. The sixth lens has a thickness of 0.98mm to 1.06mm, a front surface radius of curvature of -62.9mm to -62.88mm, a rear surface radius of curvature of -12.95mm to -12.94mm, and a distance of 5.15mm to 5.23mm from the first imaging plane.

2. A pinhole camera for a shipborne helicopter landing aid optical system as described in claim 1, characterized in that: The first lens has a thickness of 1.089 mm, a front surface curvature radius of 10.970 mm, a rear surface curvature radius of 3.575 mm, and a distance of 3.347 mm from the front surface of the second lens. The material is H-BAK8. The second lens is 2.086mm thick, with a front surface radius of curvature of 28.344mm and a rear surface radius of curvature of -27.057mm. It is 0.5mm away from the third lens and is made of H-LAK3 material. The third lens has a thickness of 1.902 mm, a front surface curvature radius of 10.531 mm, a rear surface curvature radius of -8.055 mm, and is 0.719 mm away from the front surface of the fourth lens. The material is H-LAK1. The fourth lens is 1.082mm thick, with a front surface (aperture stop) radius of curvature of ∞, a rear surface radius of curvature of 4.959mm, and a distance of 1.257mm from the front surface of the fifth lens. The material is H-K51. The fifth lens has a thickness of 1.038mm, a front surface curvature radius of -8.175mm, a rear surface curvature radius of -4.461mm, and is 0.78mm away from the front surface of the sixth lens. The material is H-LAK7A. The sixth lens is 1mm thick, with a front surface radius of curvature of -62.892mm, a rear surface radius of curvature of -12.945mm, a distance of 5.2mm from the imaging plane, and is made of H-LAK54 material. The seventh surface is a focusing imaging surface, and a short-wave infrared detector with a specification of 1024×1024 and a pixel size of 10μm is selected.

3. A pinhole camera for a shipborne helicopter landing aid optical system as described in claim 1 or 2, characterized in that: Installed on both sides of the flight deck, its observation band is the near-infrared band of 0.8μm-0.815μm; the observation field of view is 45°; the system focal length is 6mm; the relative aperture is 1:5.5; the total system length is 20mm; and the detector pixel size is 10μm.

Images