Transmission-type ultra-wideband multi-focal-plane optical system

Abstract

The invention discloses a transmission-type ultra-wideband multi-focal-plane optical system which comprises a first positive lens, a first negative lens, a second positive lens, a second negative lens and a third negative lens which are sequentially arranged along the same optical axis. Incident light of different wave bands sequentially passes through the first positive lens, the first negative lens, the second positive lens, the second negative lens and the third negative lens, differential focusing is formed by setting different back intercept, and a visible light wave band, a near-infrared wave band, a medium-wave infrared wave band and a long-wave infrared wave band respectively form independent focal planes which are axially separated. The transmission wave band of the optical system is 0.5-12 microns, visible light, near-infrared light, medium-wave infrared light and long-wave infrared light are covered, the common optical element and axial separation multi-focal plane design is adopted, different wave bands share the same set of optical elements, and the target can be detected only by placing the target on the corresponding focal plane. And optical collimation of different wavebands can be realized by changing the position of the focal plane.

Description

Technical Field

[0001] The present invention belongs to the field of optical design, and relates to an optical system covering visible light, near infrared, mid-wave infrared, and long-wave infrared. Background Art

[0002] In the detection and recognition of targets, optoelectronic detection is a common means. With the increasingly complex application background of optoelectronic detection, the information obtained when using a single-band system for detection is limited, resulting in a reduction in the accuracy rate during target detection or even the situation where the target cannot be recognized. Therefore, wide-band imaging or multi-band imaging is of great significance for the detection and recognition of targets.

[0003] During the development process of an optoelectronic detection system, various indicators need to be tested under different application scenarios to ensure that the detection system meets the requirements of the design indicators. However, the cost of simulating targets in a real environment is very high, and different meteorological conditions and environments will affect the test results, and all situations cannot be tested. The hardware-in-the-loop simulation system can simulate the target and can be tested repeatedly, and the collimating optical system can provide a target from an infinite distance for the detector.

[0004] Currently, the optical systems covering visible light, mid-wave infrared, and long-wave infrared mainly include two types: reflective and transmissive. However, the reflective optical system has a small field of view, which is difficult to meet the requirements of a large field of view in most cases and has a complex structure; the transmissive optical system mainly uses a beam-splitting element to split different bands, such as CN109407273B, where the working bands of 0.55μm - 0.75μm, 3.7μm - 4.8μm, and 7.5μm - 9.5μm are split by a beam-splitting prism in front of different detectors. However, this structure is very complex and the working bands are relatively narrow. Summary of the Invention

[0005] Aiming at the problems of the existing wide-band optical system, such as small field of view, relatively narrow transmission band, and complex structure, the present invention provides a transmissive ultra-wide-band, multi-focal-plane optical system. It adopts a fully transmissive structure to achieve continuous transmission in the ultra-wide band of 0.5 - 12μm, and uses a transmissive optical path design without central occlusion to eliminate the aperture occlusion effect and small field of view limitation of the reflective system. The optical system of the present invention has a simple structure, low processing and alignment difficulty, and can collimate targets in different bands by cooperating with a target, providing a target for the optoelectronic detection system to complete the test of the optoelectronic detection system.

[0006] The object of the present invention is achieved through the following technical solutions:

[0007] A transmissive ultra-wideband, multi-focal plane optical system, which adopts a fully transmissive structure to achieve continuous transmission in the ultra-wideband of 0.5 - 12μm. It includes a lens group composed of a first positive lens, a first negative lens, a second positive lens, a second negative lens, and a third negative lens arranged in sequence along the same optical axis. Incident light of different bands passes through the first positive lens, the first negative lens, the second positive lens, the second negative lens, and the third negative lens in sequence. By setting different back intercepts, independent focal planes separated axially are formed for the visible light band, the near-infrared band, the mid-wave infrared band, and the long-wave infrared band respectively. Each focal plane images a target corresponding to a specific band. The optical system accurately locates targets of different bands to the corresponding focal planes and outputs collimated parallel beams in reverse through the lens group.

[0008] Compared with the prior art, the present invention has the following advantages:

[0009] 1. The transmissive ultra-wideband, multi-focal plane optical system of the present invention has a transmission band of 0.5 - 12μm, covering visible light, near-infrared, mid-wave infrared, and long-wave infrared. It adopts a common optical element and axially separated multi-focal plane design, enabling different bands to share the same set of optical elements. Only by placing the target on the corresponding focal plane and changing the position of the focal plane can optical collimation for different bands be achieved.

[0010] 2. Compared with the existing wideband optical systems, the transmissive ultra-wideband, multi-focal plane optical system of the present invention has a wider covered band and a simpler structure, and can meet the requirements for various bands; compared with reflective optical systems, it can achieve a larger field of view and meet the requirements for a large field of view. Moreover, for the transmissive ultra-wideband, multi-focal plane optical system of the present invention, different bands share the same set of optical elements, the system alignment and adjustment are simple, there is no need for additional design of the optical system, which reduces the difficulty of the opto-mechanical system design. Only by preparing corresponding targets according to different bands can the requirements be met, greatly reducing the preparation difficulty and being convenient to use. Description of the Drawings

[0011] Figure 1 It is a structural diagram of the transmissive ultra-wideband, multi-focal plane optical system of the present invention.

[0012] Figure 2 It is an MTF diagram of the optical system of the present invention at 0.6 - 1μm.

[0013] Figure 3 It is an MTF diagram of the optical system of the present invention at 3 - 5μm.

[0014] Figure 4 It is an MTF diagram of the optical system of the present invention at 8 - 12μm.

[0015] Figure 5 It is a field curvature and distortion diagram of the optical system of the present invention at 0.6 - 1μm.

[0016] Figure 6 This is the field curvature distortion diagram of the optical system of the present invention at 3-5 μm.

[0017] Figure 7 This is the field curvature distortion diagram of the optical system of the present invention at 8-12 μm. Detailed implementation manners

[0018] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings, but it is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be covered by the protection scope of the present invention.

[0019] The present invention provides a transmissive ultra-wideband and multi-focal plane optical system. The optical system adopts a full-transmissive structure to achieve an ultra-wideband coverage of 0.5-12 μm. Through a lens group composed of a first positive lens 1, a first negative lens 2, a second positive lens 3, a second negative lens 4, and a third negative lens 5 arranged in sequence along the same optical axis, the incident light of different bands is differentially focused, so that the visible light band, the near-infrared band, the mid-wave infrared band, and the long-wave infrared band respectively form independent focal planes 6 separated axially.

[0020] In the present invention, the ultra-wideband of the optical system is achieved by using a variety of materials with wide-band transmission: the material of the first positive lens 1 is potassium bromide, the material of the first negative lens 2 is multi-spectral zinc sulfide, the materials of the second positive lens 3 and the third negative lens 5 are infrared glass IRG208, and the material of the second negative lens 4 is infrared glass HWS27; the multi-focal plane is achieved by the overall optimization method of dividing the bands. Specifically: for the visible light band, the short-wave infrared band, the mid-wave infrared band, and the long-wave infrared band, different back intercepts are set, and the parameters of the lens group are optimized as a whole, so that each band forms an independent focal plane 6 separated axially in the optical axis direction, while keeping all bands sharing the same set of optical elements; each focal plane 6 corresponds to the imaging of a target in a specific band. The optical system accurately positions the targets of different bands to the corresponding focal planes 6, and outputs collimated parallel beams in reverse through the lens group, providing an infinite far target simulation for a multi-spectral imaging system and an infrared / visible composite seeker to simultaneously verify the detection performance of multiple bands.

[0021] In the present invention, the rear surface of the first positive lens 1 and the front and rear surfaces of the second negative lens 4 are even aspherical surfaces, and the remaining surfaces are spherical surfaces or flat surfaces.

[0022] In the present invention, the distance between the first positive lens 1 and the third negative lens 5 is L 1 , and the back intercept of the optical system is L 2 , L 1 is a fixed value, and for different working bands, the value of L 2 is variable.

[0023] In the present invention, the optical system is a fully transmissive type, where all wavelength bands share the same set of optical elements, and different working wavelength bands have different focal planes.

[0024] In the present invention, an optical filter can be inserted between the third negative lens 5 and the focal plane 6.

[0025] In the present invention, the first positive lens 1, the first negative lens 2, the second positive lens 3, the second negative lens 4, the third negative lens 5, and the focal plane 6 are coaxially arranged. The working wavelength bands are 0.6 - 1 μm, 3 - 5 μm, and 8 - 12 μm. The target is placed on the focal plane, and the output through the optical system is parallel light, which can provide a target from infinity for the optoelectronic detection system. For different wavelength bands, there are different back intercepts. Just by placing the target on the focal plane corresponding to the wavelength band, optical collimation for different wavelength bands can be achieved.

[0026] In the present invention, the external parameters of the optical system are: aperture 80 mm, entrance pupil distance 100 mm, full field of view 9°, and the system working wavelength bands are visible - near infrared 0.6 - 1 μm, mid - wave infrared 3 - 5 μm, and long - wave infrared 8 - 12 μm.

[0027] In the present invention, the back intercepts of the three wavelength bands of visible - near infrared 0.6 - 1 μm, mid - wave infrared 3 - 5 μm, and long - wave infrared 8 - 12 μm are 14.814 mm, 15.253 mm, and 15.992 mm respectively.

[0028] In the present invention, the focal length of the optical system is 300 mm, the total length is 425 mm, and the F - number is 3.75.

[0029] In the present invention, the internal parameters of the system are shown in Table 1.

[0030] Table 1 Structural parameters of the optical system

[0031]

[0032] In Table 1, S2 - S11 respectively correspond to the first ten and the last ten surfaces of the lens. The even - order aspheric parameters of S3 are: second - order term 2.428E - 003, fourth - order term 9.735E - 008, sixth - order term - 7.389E - 012, and the rest are 0. The even - order aspheric parameters of S8 are: second - order term - 7.038E - 003, fourth - order term 1.996E - 007, sixth - order term - 1.056E - 010, and the rest are 0. The even - order aspheric parameters of S9 are: second - order term 5.365E - 004, fourth - order term 6.538E - 007, sixth - order term - 4.181E - 011, and the rest are 0.

[0033] As Figure 2As shown, in the 0.6 - 1μm band, the MTF is greater than 0.9 at 10 lp / mm and is close to the diffraction limit, with good imaging quality.

[0034] As Figure 3 shown, in the 3 - 5μm band, the MTF is greater than 0.6 at 10 lp / mm and is close to the diffraction limit, with good imaging quality.

[0035] As Figure 4 shown, in the 8 - 12μm band, the MTF is greater than 0.4 at 10 lp / mm and is close to the diffraction limit, with good imaging quality.

[0036] As Figure 5 shown, in the 0.6 - 1μm band, the maximum distortion is less than 1%, with good imaging quality.

[0037] As Figure 6 shown, in the 3 - 5μm band, the maximum distortion is less than 1%, with good imaging quality.

[0038] As Figure 7 shown, in the 8 - 12μm band, the maximum distortion is less than 1%, with good imaging quality.

Claims

1. A transmissive ultra-wideband, multi-focal optical system, characterized in that The optical system adopts a fully transmissive structure, and has an ultra-wide transmission band of 0.5 to 12 μm. The optical system includes a lens group consisting of a first positive lens, a first negative lens, a second positive lens, a second negative lens, and a third negative lens arranged in sequence along the same optical axis. Incident light of different bands passes through the first positive lens, the first negative lens, the second positive lens, the second negative lens, and the third negative lens in sequence. By setting different back intercepts, the visible light band, the near-infrared band, the medium-wave infrared band, and the long-wave infrared band respectively form axially separated independent focal planes, and each focal plane corresponds to a target imaging of a specific band. The optical system accurately positions targets of different bands to corresponding focal planes, and outputs collimated parallel light beams in reverse through the lens group.

2. The transmissive ultra-wideband, multi-focal optical system according to claim 1, characterized in that The material of the first positive lens is potassium bromide.

3. The transmissive ultra-wideband, multi-focal optical system according to claim 1, characterized in that The material of the first negative lens is multi-spectrum zinc sulfide.

4. The transmissive ultra-wideband, multi-focal optical system according to claim 1, characterized in that The material of the second positive lens and the third negative lens is infrared glass IRG208.

5. The transmissive ultra-wideband, multi-focal optical system according to claim 1, characterized in that The material of the second negative lens is infrared glass HWS27.

6. The transmissive ultra-wideband, multi-focal optical system according to claim 1, characterized in that The rear surface of the first positive lens and the front and rear surfaces of the second negative lens are even-order aspherical surfaces, and the remaining surfaces are spherical surfaces or plane surfaces.

7. The transmissive ultra-wideband, multi-focal optical system according to claim 1, characterized in that The distance between the first positive lens and the third negative lens is L1, and the back intercept of the optical system is L2. L1 is a fixed value, and the value of L2 can be changed for different working bands.

8. The transmissive ultra-wideband, multi-focal optical system according to claim 1, characterized in that An optical filter is inserted between the third negative lens and the focal plane.

9. The transmissive ultra-wideband, multi-focal optical system according to claim 1, characterized in that The working bands of the optical system are 0.6-1 μm, 3-5 μm, and 8-12 μm, and the back intercepts of the three bands are 14.814 mm, 15.253 mm, and 15.992 mm, respectively.

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