Convergent light path parallel plate light splitting machine system and method based on free-form surface lens

Abstract

The invention discloses a convergent light path parallel plate light splitting system and method based on a free-form surface lens, and belongs to the field of photoelectric imaging optical design. The system comprises a common focusing lens, a medium-wave light path and a long-wave light path, wherein the medium-wave light path comprises the common focusing lens, a medium / long-wave infrared spectroscope, a medium-wave convergent light path and a medium-wave detector which are sequentially arranged along the light path; the long-wave light path comprises a common focusing lens, a medium / long-wave infrared spectroscope, a free-form surface correction lens, a turning lens, a first long-wave convergent lens, a second long-wave convergent lens and a long-wave detector which are sequentially arranged along the light path; long-wave infrared rays are transmitted to the free-form surface correction mirror through the medium / long-wave infrared spectroscope, and asymmetric aberration generated by light splitting in a convergent light path is compensated. According to the invention, the problem of non-rotational symmetry aberration caused by the fact that medium-long wave light splitting cannot be realized in parallel light in a limited space is solved.

Description

Technical Field

[0001] The invention belongs to the field of optoelectronic imaging optical design, and in particular relates to a convergent light path parallel flat plate light splitting system and method based on a free-form surface lens. Background Art

[0002] Optoelectronic detection equipment is mainly used for searching, tracking and identifying distant targets during aerial missions. Long-wave infrared is mainly used for long-distance search and tracking, and medium-wave performs high-definition imaging after the system enters stable tracking to realize the recognition of aerial target features, such as aircraft contours, number of vertical tails, vertical tail angles, etc., and cooperates with image machines to determine whether it is a third-generation aircraft or a fourth-generation aircraft, or a specific model.

[0003] Airborne optoelectronics has strict constraints on available space, and it is an inevitable trend for multi-band systems to share telescopes, fast-reflection mirrors, focusing mirrors, and black bodies. Among them, sharing telescopes, fast-reflection mirrors, and black bodies is more common, while sharing focusing in medium and long waves is relatively rare.

[0004] Medium and long wave splitting is generally realized in a parallel optical path. This splitting method does not introduce additional aberrations, and the optical path design after splitting is relatively conventional.

[0005] Some systems are space-constrained and require medium and long waves to share a set of focusing mirrors, a set of focusing motors, guide rails and other mechanical structures; and the splitting position is limited, with only a certain space behind the focusing mirror. This results in the need to set the beam splitter in the converging optical path of non-parallel light. At this time, the beam splitter will introduce certain non-rotational symmetric aberrations, which are difficult to correct in the subsequent optical path.

[0006] The commonly used converging and splitting methods are:

[0007] 1. Prism spectrometry: two half-cubic prisms are glued together to form a complete cubic prism. The glued surface is coated with a spectroscopic film. The transmitted light passes through the optical path symmetrically without introducing additional aberrations. It is mainly limited by the refractive index of the optical glue. The maximum refractive index that can be achieved is 1.8. Only BaF2 material can be used as a prism, and it can only reflect long waves and transmit medium waves. BaF2 has serious absorption in the long-wave band after 10μm. This type of spectrometry has a very serious loss in detection performance. It is more suitable for testing equipment, which does not require high extreme transmittance.

[0008] 2. Double orthogonal plate splitting, using two parallel plates, plate 1 is tilted at 45° in azimuth, and plate 2 is tilted at 45° in elevation. This splitting configuration can greatly reduce the aberration introduced in the converging light path. The main disadvantage is that an extra plate requires a certain length of space, which is more suitable for optoelectronic systems with relatively loose space. Summary of the invention

[0009] Technical issues to be solved:

[0010] In order to avoid the shortcomings of the prior art, the present invention provides a convergent light path parallel plate spectroscopic system and method based on a free-form surface lens, provides a common focusing lens for medium and long-wave infrared, uses a 45° plate to split the convergent light behind the focusing lens, and uses a free-form surface lens to eliminate the aberration introduced by the plate in the convergent light; this method performs medium and long-wave spectroscopic in a non-parallel light path, and uses a free-form surface correction lens to achieve spectroscopic aberration correction. The present invention solves the problem that medium and long-wave spectroscopic cannot be performed in parallel light in a limited space, resulting in non-rotationally symmetric aberrations.

[0011] The technical scheme of the present invention is: a convergent optical path parallel plate spectroscopic system based on a free-form surface lens, comprising a common focusing mirror and a medium-wave optical path and a long-wave optical path, wherein the medium-wave optical path comprises a common focusing mirror, a medium / long-wave infrared spectroscope, a medium-wave converging optical path and a medium-wave detector arranged in sequence along the optical path; the long-wave optical path comprises a common focusing mirror, a medium / long-wave infrared spectroscope, a free-form surface correction mirror, a folding mirror, a first long-wave converging mirror, a second long-wave converging mirror and a long-wave detector arranged in sequence along the optical path;

[0012] The telescopic optical path is incident on the medium / long-wave infrared spectrometer through the common focusing mirror, and the medium-wave infrared rays are reflected by the medium / long-wave infrared spectrometer to the medium-wave converging optical path and the medium-wave detector. The long-wave infrared rays are transmitted to the free-form surface correction mirror through the medium / long-wave infrared spectrometer to compensate for the asymmetric aberration caused by the splitting in the converging optical path, and then reflected by the folding mirror to the first long-wave converging mirror, the second long-wave converging mirror, and the long-wave detector.

[0013] A further technical solution of the present invention is: a cut-in black body is arranged behind the common focusing mirror to perform multi-temperature segment non-uniform correction on the medium / long wave optical path and the medium / long wave detector respectively.

[0014] A further technical solution of the present invention is that the medium / long wave infrared spectroscope forms an angle of 45° with the incident light beam.

[0015] A further technical solution of the present invention is that the optical parameters of each mirror group in the convergent light path parallel plate beam splitter system are as follows:

[0016]

[0017]

[0018] A further technical solution of the present invention is that the common focusing lens is a lens or a lens group composed of multiple lenses, which has a focusing effect on medium and long wave infrared and is made of single crystal germanium, zinc selenide or chalcogenide glass.

[0019] A further technical solution of the present invention is: the surface coefficients of the free-form surface correction mirror are: C2 = -8.2479e-4; C4 = -1.7800e-2; C6 = -1.7836e-2; C7 = 2.8537e-09; C9 = -5.0644e-08; C11 = -2.8470e-06; C13 = -5.6945e-06; C15 = -2.8540e-06; C16 = -2.7617e-10; C18 = -1.1301e-10;

[0020] C20=-1.6980e-10; C22=-7.8388e-11; C24=-4.3859e-10; C26=-3.5177e-10;

[0021] C28=-1.2920e-10; C29=8.1544e-13; C31=-3.1138e-13; C33=-1.5783e-13;

[0022] C35=3.8950e-13; C37=-3.5102e-13; C39=-6.0983e-13; C41=-1.6749e-12;

[0023] C43=-9.4566e-13; C45=-2.3250e-13; C46=-9.8313e-13; C48=7.7327e-16;

[0024] C50=-4.8711e-16; C52=3.76933e-16; C54=-4.0675e-16; C56=1.5422e-16;

[0025] C58=-1.9500e-16; C60=1.61478e-16; C62=4.5909e-16; C64=1.35188e-17;

[0026] C66=4.9096e-18.

[0027] A further technical solution of the present invention is that the free-form surface correction mirror is made of single crystal germanium.

[0028] A further technical solution of the present invention is that the angle between the folding mirror and the incident light is 45°, and the light path is folded by 90°.

[0029] A method for parallel plate light splitting of a convergent light path based on a free-form surface lens, the specific steps are as follows:

[0030] The telescope optical path is incident on the common focusing lens, and the medium and long wave infrared are focused through the common focusing lens;

[0031] A medium / long-wave infrared spectroscope is arranged on the optical path passing through the common focusing lens, the medium-wave infrared is reflected to the medium-wave converging optical path and the medium-wave detector through the medium / long-wave infrared spectroscope, and the long-wave infrared is transmitted through the medium / long-wave infrared spectroscope;

[0032] A free-form surface correction mirror is arranged in the transmission light path of the mid-wave / long-wave infrared spectroscope to compensate for the asymmetric aberration caused by the splitting in the converging light path;

[0033] The compensated long-wave infrared is reflected by the folding mirror to the first long-wave converging mirror, the second long-wave converging mirror and the long-wave detector.

[0034] A photoelectric device comprises the convergent light path parallel plate spectroscopic system based on free-form surface lens, wherein the system light path includes long-wave infrared 8-10.5 μm, long-wave F#2.6, medium-wave 3.7-4.8 μm, and medium-wave F#5.

[0035] Beneficial Effects

[0036] The beneficial effects of the present invention are as follows: the present invention adopts a medium / long-wave infrared spectroscope to reflect the medium-wave infrared of the incident light and transmit the long-wave infrared, and by arranging a free-form surface correction mirror behind the medium / long-wave infrared spectroscope, the asymmetric aberration caused by the splitting in the converging light path is compensated, thereby solving the problem that the medium and long-wave splitting cannot be realized in parallel light and the non-rotationally symmetric aberration is generated.

[0037] The free-form surface correction mirror arranged in the optical path of the present invention can split the medium and long waves under the condition of relatively tight installation space and ensure the imaging quality. Therefore, the present invention has certain application prospects in some systems with relatively tight space and requiring a common focusing mirror for medium and long waves.

[0038] The system of the present invention has a compact structure, occupies a small space, and ensures imaging quality on the basis of realizing medium and long wave spectrometry. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is an optical configuration diagram in an embodiment of the present invention;

[0040] Figure 2 is a diagram of the optical transfer function of the telescope group at room temperature in the laser emission band in an embodiment of the present invention;

[0041] Explanation of the reference numerals: 1. Common focusing mirror, 2. Cut-in black body, 3. Medium / long-wave infrared spectrometer, 4. Medium-wave converging optical path and medium-wave detector, 5. Free-form surface correction mirror, 6. Folding mirror, 7. First long-wave converging mirror, 8. Second long-wave converging mirror, 9. Long-wave detector. DETAILED DESCRIPTION

[0042] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0043] Based on the existing conventional converging light splitting method, the detection performance is seriously damaged by using prism splitting, and the space required for using double orthogonal plate splitting is relatively large. The present invention provides a converging light path parallel plate splitting system based on free-form surface lens, including a common focusing mirror and a medium-wave light path and a long-wave light path. The medium-wave light path includes a common focusing mirror, a medium / long-wave infrared spectroscope, a medium-wave converging light path and a medium-wave detector arranged in sequence along the light path; the long-wave light path includes a common focusing mirror, a medium / long-wave infrared spectroscope, a medium-wave converging light path and a medium-wave detector arranged in sequence along the light path. Optical mirror, free-form surface correction mirror, folding mirror, first long-wave converging mirror, second long-wave converging mirror, long-wave detector; the telescopic optical path is incident on the medium / long-wave infrared spectroscope via the common focusing mirror, the medium-wave infrared rays are reflected to the medium-wave converging optical path and the medium-wave detector via the medium / long-wave infrared spectroscope, the long-wave infrared rays are transmitted to the free-form surface correction mirror via the medium / long-wave infrared spectroscope, the asymmetric aberration caused by the spectral splitting in the converging optical path is compensated, and then reflected to the first long-wave converging mirror, the second long-wave converging mirror, and the long-wave detector via the folding mirror.

[0044] The present invention provides a convergent light path parallel plate spectrometry method based on a free-form surface lens, and the specific steps are as follows:

[0045] Step 1: The telescopic optical path is incident on the common focusing lens, and the medium and long wave infrared are focused through the common focusing lens;

[0046] Step 2: Set a medium / long-wave infrared spectroscope on the optical path passing through the common focusing lens, reflect the medium-wave infrared to the medium-wave converging optical path and the medium-wave detector through the medium / long-wave infrared spectroscope, and transmit the long-wave infrared through the medium / long-wave infrared spectroscope;

[0047] Step 3: A free-form surface correction mirror is arranged in the transmission light path of the mid-wave / long-wave infrared spectroscope to compensate for the asymmetric aberration caused by the splitting in the converging light path;

[0048] Step 4: The compensated long-wave infrared is reflected by the folding mirror to the first long-wave converging mirror, the second long-wave converging mirror, and the long-wave detector.

[0049] The above technical solution is further described below with reference to the accompanying drawings and examples:

[0050] This embodiment mainly describes a method for splitting light in a converging light path. The main background is some space-constrained optoelectronic systems that need to share a focusing lens, and the splitting needs to be set up behind the focusing lens group. The main bands are long-wave infrared 8-10.5μm, long-wave F#2.6, medium-wave 3.7-4.8μm, and medium-wave F#5.

[0051] Reference Figure 1 As shown, this embodiment provides a design method for sharing a focusing mirror for medium and long wave infrared, splitting the converged light behind the focusing mirror through a 45° flat plate, and using a free-form surface lens to eliminate the aberration introduced by the flat plate in the converged light. The system mainly includes a shared focusing mirror 1, a cut-in black body 2, a medium / long wave infrared spectroscope 3, a medium wave convergent optical path and a medium wave detector 4, a free-form surface correction mirror 5, a folding mirror 6, a long wave convergent mirror 17, a long wave convergent mirror 28, and a long wave detector 9.

[0052] Figure 1 The front end of the optical path shown has a telephoto optical path, which eliminates aberrations in multiple bands. There are many papers and materials related to the telephoto optical path, which will not be described in detail in this patent.

[0053] The common focusing lens group 1 can be a lens group composed of one lens or multiple lenses, which can focus the medium and long wave infrared. This focusing is mainly used in high and low temperature environments, when the optical system is thermally defocused, and the focusing lens is used to compensate. Considering that the medium and long waves have high transmittance, the lens group mainly uses single crystal germanium, zinc selenide, chalcogenide glass and other materials. Single crystal silicon and calcium fluoride cannot be used, and zinc sulfide and barium fluoride are not recommended.

[0054] The insertable black body 2 is mainly used for the non-uniform correction of multi-temperature background of medium and long wave detectors. When correction is required, the black body is cut into the optical path; when it is not in working state, it is cut out of the optical path.

[0055] The middle / long wave infrared spectroscope 3, considering the difficulty of coating, generally has a spectroscopic order of transmitting long waves and rejecting middle waves; it can also transmit middle waves and reject long waves according to the space situation. The material of the spectroscope is preferably zinc selenide.

[0056] The medium wave convergent optical path and the detector 4 do not introduce additional aberrations due to the use of a splitting reflection surface, and the design is the same as that of a conventional medium wave optical path, so no special description is given.

[0057] The free-form surface correction lens 5 has a free-form surface in the form of an xy polynomial on one surface. The front beam splitter is tilted at 45°, which will introduce a non-rotationally symmetrical aberration, which is an axisymmetric aberration in a certain direction. Therefore, it cannot be corrected using a conventional rotationally symmetrical aspheric surface, and an axisymmetric free-form surface is required. The free-form surface can be selected to be symmetrical relative to the xz plane or the yz plane according to the tilt direction of 45°. The order of the polynomial can be determined based on the optimization design effect.

[0058] The deflecting mirror 6 is used to deflect the optical path. Generally, it is set at 45°, and the optical path is deflected by 90°, which is convenient for assembly and alignment. In special cases, due to space limitations, it is necessary to rotate a specific angle to achieve space compactness.

[0059] The converging mirrors 7 and 8 converge the front light path to the image plane.

[0060] The long-wave detector 9 converts the infrared energy convergence imaging into a digital image output.

[0061] The lens curvature, thickness, spacing, and material parameters of the above-mentioned lens assembly are shown in Table 1, and the aspheric coefficients are shown in Table 2, wherein the curvature radius, spacing thickness, and the signs of the aspheric coefficients comply with the general principles of optical design and are not repeated here.

[0062] The main parameters of the optical path are focal length 72.7mm, F#2.6, detector field of view 640×512, and single pixel 25μm.

[0063] Table 1

[0064] name surface Radius of curvature Thickness\Interval Material Focusing mirror Front surface -47.64mm 8.15mm Single Crystal Germanium Back surface 50.65mm 70mm Bold 34.88mm Beamsplitter Front surface flat 4 Zinc Selenide Back surface flat 2.65mm Free-form surface correction mirror Front surface 52.19mm 8.47mm Single Crystal Germanium Back surface -47.65mm 25mm Folding mirror Front surface flat -25mm Quartz glass Converging lens 1 Front surface -30.37mm -5.10 Zinc Selenide Back surface -20.3 -2.89 Converging lens 2 Front surface -29.76 -4 Single Crystal Germanium Back surface -41.76 -6 Long wave infrared detector

[0065] Table 2

[0066]

[0067]

[0068] The surface coefficients of the free-form surface correction mirror are: C2 = -8.2479e-4; C4 = -1.7800e-2; C6 = -1.7836e-2; C7 = 2.8537e-09; C9 = -5.0644e-08; C11 = -2.8470e-06; C13 = -5.6945e-06;

[0069] C15=-2.8540e-06; C16=-2.7617e-10; C18=-1.1301e-10; C20=-1.6980e-10;

[0070] C22=-7.8388e-11; C24=-4.3859e-10; C26=-3.5177e-10; C28=-1.2920e-10;

[0071] C29=8.1544e-13; C31=-3.1138e-13; C33=-1.5783e-13; C35=3.8950e-13;

[0072] C37=-3.5102e-13; C39=-6.0983e-13; C41=-1.6749e-12; C43=-9.4566e-13;

[0073] C45=-2.3250e-13; C46=-9.8313e-13; C48=7.7327e-16; C50=-4.8711e-16;

[0074] C52=3.76933e-16; C54=-4.0675e-16; C56=1.5422e-16; C58=-1.9500e-16;

[0075] C60=1.61478e-16; C62=4.5909e-16; C64=1.35188e-17; C66=4.9096e-18.

[0076] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A convergent light path parallel plate spectroscopic system based on a free-form surface lens, characterized in that: It includes a common focusing mirror, a medium-wave optical path, and a long-wave optical path. The medium-wave optical path includes a common focusing mirror, a medium / long-wave infrared spectroscope, a medium-wave converging optical path, and a medium-wave detector arranged in sequence along the optical path; the long-wave optical path includes a common focusing mirror, a medium / long-wave infrared spectroscope, a free-form surface correction mirror, a folding mirror, a first long-wave converging mirror, a second long-wave converging mirror, and a long-wave detector arranged in sequence along the optical path; The telescopic optical path is incident on the medium / long-wave infrared spectrometer through the common focusing mirror, and the medium-wave infrared rays are reflected by the medium / long-wave infrared spectrometer to the medium-wave converging optical path and the medium-wave detector. The long-wave infrared rays are transmitted to the free-form surface correction mirror through the medium / long-wave infrared spectrometer to compensate for the asymmetric aberration caused by the splitting in the converging optical path, and then reflected by the folding mirror to the first long-wave converging mirror, the second long-wave converging mirror, and the long-wave detector.

2. According to claim 1, a convergent light path parallel plate spectroscopic system based on a free-form surface lens, characterized in that: A cut-in black body is arranged behind the common focusing mirror to perform multi-temperature section non-uniform correction on the medium / long wave optical path and the medium / long wave detector respectively.

3. According to claim 2, a convergent light path parallel plate spectroscopic system based on a free-form surface lens, characterized in that: The mid / long wave infrared spectroscope forms an angle of 45° with the incident light beam.

4. According to claim 3, a convergent light path parallel plate spectroscopic system based on a free-form surface lens, characterized in that: The optical parameters of each mirror group in the parallel plate beam splitter system of the converging light path are as follows:

5. The convergent light path parallel plate spectroscopic system based on free-form surface lens according to claim 4, characterized in that: The shared focusing lens is a lens or a lens group composed of multiple lenses, which plays a focusing role on medium and long wave infrared and is made of single crystal germanium, zinc selenide or chalcogenide glass.

6. The convergent light path parallel plate spectroscopic system based on free-form surface lens according to claim 4, characterized in that: The surface coefficient of the free-form surface correction mirror is: C2=-8.2479e-4; C4=-1.7800e-2; C6=-1.7836e-2; C7=2.8537e-09; C9=-5.0644e-08; C11=-2.8470 e-06; C13=-5.6945e-06; C15=-2.8540e-06; C16=-2.7617e-10; C18=-1.1301e-10; C20=-1.6980e-10; C22=-7.8388e-11; C24=-4.3859e-10; C26=-3.5177e-10; C28=-1.2920e-10; C29=8.1544e-13; C31=-3.1138e-13; C33=-1.5783e-13; C35=3.8950e-13; C37=-3.5102e-13; C39=-6.0983e-13; C41=-1.6749e-12; C43=-9.4566e-13; C45=-2.3250e-13; C46=-9.8313e-13; C48=7.7327e-16; C50=-4.8711e-16; C52=3.76933e-16; C54=-4.0675e-16; C56=1.5422e-16; C58=-1.9500e-16; C60=1.61478e-16; C62=4.5909e-16; C64=1.35188e-17; C66=4.9096e-18.

7. The convergent light path parallel plate spectroscopic system based on free-form surface lens according to claim 6, characterized in that: The free-form surface correction mirror is made of single crystal germanium.

8. The convergent light path parallel plate spectroscopic system based on free-form surface lens according to claim 1, characterized in that: The angle between the folding mirror and the incident light is 45°, and the light path is folded by 90°.

9. A method for parallel plate spectrometry of a convergent light path based on a free-form surface lens, implemented based on the parallel plate spectrometry system of any one of claims 1 to 8, characterized in that The specific steps are as follows: The telescope optical path is incident on the common focusing lens, and the medium and long wave infrared are focused through the common focusing lens; A medium / long-wave infrared spectroscope is arranged on the optical path passing through the common focusing lens, the medium-wave infrared is reflected to the medium-wave converging optical path and the medium-wave detector through the medium / long-wave infrared spectroscope, and the long-wave infrared is transmitted through the medium / long-wave infrared spectroscope; A free-form surface correction mirror is arranged in the transmission light path of the mid-wave / long-wave infrared spectroscope to compensate for the asymmetric aberration caused by the splitting in the converging light path; The compensated long-wave infrared is reflected by the folding mirror to the first long-wave converging mirror, the second long-wave converging mirror and the long-wave detector.

10. An optoelectronic device, characterized in that: The invention comprises a convergent optical path parallel plate spectroscopic system based on a free-form surface lens as described in any one of claims 1 to 8, wherein the system optical path includes long-wave infrared 8-10.5 μm, long-wave F#2.6, medium-wave 3.7-4.8 μm, and medium-wave F#5.

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