阅读说明：本技术 一种提高视场选通成像系统视场占空比的方法 (Method for improving field duty ratio of field gating imaging system ) 是由 方亮 张辉 廖志远 程欣 谭述亮 范真节 于 2021-08-20 设计创作，主要内容包括：本发明公开了一种提高视场选通成像系统视场占空比的方法,该方法包括：在视场选通成像系统一次像面附近添加一组微透镜阵列,与后组微透镜阵列形成微透镜阵列组；添加的一组微透镜阵列中,每个微透镜单元均作为场镜,用于将选通视场内的边缘视场光线偏转,并使其通过后组微透镜单元,从而减小选通视场内成像的渐晕。另一方面,利用分光镜将视场选通成像系统一次像面一分为二,分别对两个一次像面进行视场选通,且选通的视场范围相互交错。本发明所述的一种提高视场选通成像系统视场占空比的方法可以解决现有视场选通成像系统边缘视场由于渐晕而导致成像分辨率低以及视场占空比不足等问题,为实现强背景光下的多星探测提供一种有效的技术途径。(The invention discloses a method for improving the field duty ratio of a field gating imaging system, which comprises the following steps: adding a group of micro-lens arrays near a primary image surface of the field-of-view gated imaging system, and forming a micro-lens array group with the rear group of micro-lens arrays; in the added group of micro lens array, each micro lens unit is used as a field lens and is used for deflecting the light rays of the marginal field of view in the gating field of view and enabling the light rays to pass through the rear group of micro lens units, so that the vignetting of the image in the gating field of view is reduced. On the other hand, the primary image surface of the field gating imaging system is divided into two parts by using the spectroscope, the field gating is respectively carried out on the two primary image surfaces, and the gated field ranges are mutually staggered. The method for improving the field duty ratio of the field gating imaging system can solve the problems of low imaging resolution, insufficient field duty ratio and the like caused by vignetting of the marginal field of the existing field gating imaging system, and provides an effective technical approach for realizing multi-satellite detection under strong background light.)

1. A method for improving a field duty cycle of a field gating imaging system, the method comprising:

1) a spectroscope (2) is used for dividing a primary image surface of a field gating imaging system into a primary image surface (31) of a transmission light path and a primary image surface (32) of a reflection light path;

2) a first front group micro-lens array (41) is arranged between the primary image surface (31) of the transmission optical path and a first rear group micro-lens array (51) arranged behind the primary image surface, and the first front group micro-lens array (41) and the first rear group micro-lens array (51) form a micro-lens array group; each microlens unit in the first front group microlens array (41) is used as a field lens and is used for deflecting marginal field rays in the corresponding gating field so that chief rays of the marginal field can pass through the microlens units in the first rear group microlens array (51);

3) a group of second front group micro lens arrays (42) is arranged between the primary image surface (32) of the reflected light path and a second rear group micro lens array (52) arranged behind the primary image surface, the second front group micro lens arrays (42) and the second rear group micro lens array (52) form a micro lens array group, each micro lens unit in the second front group micro lens array (42) is used as a field lens and is used for deflecting marginal field light rays in a corresponding gating field, and principal rays of the marginal field can pass through the micro lens units in the second rear group micro lens array (52).

2. The method for improving the field duty cycle of a field gated imaging system of claim 1, wherein: the gating field of view of the transmission optical path primary image surface (31) and the gating field of view of the reflection optical path primary image surface (32) are mutually staggered, and the total effective field of view of the whole field gating imaging system is approximately equal to the sum of the effective field of view of the transmission optical path and the effective field of view of the reflection optical path.

3. The method for improving the field duty cycle of a field gated imaging system of claim 1, wherein: the primary image surface of the view field gating imaging system is the imaging surface of the front-end telescope (1); after light rays of the primary image surface (31) of the transmission optical path pass through a micro lens array group consisting of a first front group micro lens array (41) and a first rear group micro lens array (51), the light rays are gated by a first micro switch array (61) and then imaged on a detector (81) by a first rear-end imaging objective lens (71); after light rays of the primary image surface (32) of the reflection optical path pass through a micro lens array group consisting of a second front group micro lens array (42) and a second rear group micro lens array (52), the light rays are gated by a first micro switch array (62) and then imaged on a detector (82) by a second rear end imaging objective lens (72).

Technical Field

The invention belongs to the technical field of all-day star sensor optical imaging, and relates to a method for improving the field duty ratio of a field gating imaging system.

Background

The star sensor is a high-precision attitude sensitive measuring instrument, and is commonly used for navigation of space spacecrafts such as satellites, spacecrafts, rockets and the like. In recent years, with the rapid development of the satellite-inertial integrated navigation technology, the application of the star sensor navigation technology is gradually expanded from the application of an extraterrestrial space-based platform to the application of a near-earth space platform, so that the near-earth space platforms such as near-earth space aircrafts, ships, airplanes and the like are expected to get rid of the dependence on a satellite navigation system, and the star sensor navigation technology has wide application prospects and important strategic significance.

Compared with a space-based star sensor, the ground-near space star sensor is interfered by strong sky background light, and in order to realize the detection of dark and weak star targets under the strong sky light background condition, a certain method is required to be adopted to inhibit the sky background light, so that the detection signal-to-noise ratio of the system is improved. The traditional near-earth space star sensor usually adopts a small-field imaging system to inhibit sky background light, and realizes tracking detection of a single star by combining a two-dimensional turntable scanning detection means, and the working system generally has the defects of large system, low precision and the like, and has a plurality of limitations in miniaturized platforms and high-precision application occasions.

The optical imaging system based on the field gating technology adopts a large-field telescope to collect the star, utilizes the micro lens and the micro switch array to realize the rapid gating of the instantaneous field, can simultaneously obtain a larger field and stronger sky background light inhibition capability, has the advantages of small volume, light weight, high precision and the like, and is very suitable for the application of the near-earth space all-day star sensor.

However, in this system, the relative aperture of the front-end telescope is usually large, and the light focused on the primary image plane has a large field angle, which will cause that when the subsequent microlens unit images the primary image plane in the gating field, the light of the marginal field cannot pass through the microlens unit completely, thereby generating a significant vignetting phenomenon. The effective aperture of the light beam corresponding to the vignetting area is reduced, so that the airy disk size in the area is larger. If the system requires near diffraction limit imaging, the spot size of the vignetting region is significantly larger than that of the non-vignetting region, and the requirement for energy concentration cannot be met, which results in a reduction of the effective area in the gated field corresponding to the microlens unit. On the other hand, the distribution of the microlens units in the microlens array itself is also difficult to achieve a 100% duty cycle. Therefore, the total effective field duty ratio of the optical imaging system based on the field gating technology is small, and the detection probability of multiple stars is difficult to guarantee. In order to promote the practical application of the optical imaging system based on the field gating technology in the all-day-hour star sensor, a method for effectively improving the field duty ratio needs to be explored, and a technical foundation is laid for the research of the all-day-hour star sensor with miniaturization, high precision and high autonomy.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: aiming at the problem of low effective field duty ratio of the existing optical imaging system based on the field gating technology, a method for improving the effective field duty ratio of the system is provided. The method can increase the effective field of view of the field-of-view gated optical imaging system and improve the detection probability of the system on a plurality of fixed stars in the daytime environment.

The technical scheme adopted by the invention for solving the technical problems is as follows: a method of increasing a field duty cycle of a field gated imaging system, the method comprising:

1) dividing a primary image surface of a field gating imaging system into a primary image surface of a transmission light path and a primary image surface of a reflection light path by using a spectroscope;

2) a group of first front group micro-lens arrays are arranged between the primary image surface of the transmission light path and a first rear group micro-lens array arranged behind the primary image surface of the transmission light path, and the first front group micro-lens array and the first rear group micro-lens array form a micro-lens array group; each microlens unit in the first front group of microlens arrays is used as a field lens and is used for deflecting marginal field rays in the corresponding gating field so that principal rays of the marginal field can pass through the microlens units in the first rear group of microlens arrays; therefore, the imaging vignetting phenomenon in each gating field in the transmission light path is reduced, the imaging quality in the gating field is ensured, and the effective area of the gating field is improved;

3) a group of second front group micro lens arrays are arranged between a primary image surface of a reflection light path and a second rear group micro lens array arranged behind the primary image surface, the second front group micro lens arrays and the second rear group micro lens array form a micro lens array group, each micro lens unit in the second front group micro lens array is used as a field lens and is used for deflecting marginal field rays in a corresponding gating field, and the main rays of the marginal field can pass through the micro lens units in the second rear group micro lens array, so that the vignetting phenomenon of imaging in each gating field in the reflection light path is reduced, the imaging quality is ensured, and the effective area of the gating field is improved.

Furthermore, the gating view field of the primary image surface of the transmission light path and the gating view field of the primary image surface of the reflection light path are mutually staggered, and the total effective view field of the whole view field gating imaging system is approximately equal to the sum of the effective view field of the transmission light path and the effective view field of the reflection light path.

Further, a primary image surface of the view field gating imaging system is an imaging surface of the front-end telescope; after light rays of the primary image surface of the transmission light path pass through a micro lens array group consisting of a first front group micro lens array and a first rear group micro lens array, the light rays are gated by a first micro switch array and then imaged on a detector by a first rear-end imaging objective lens; and the light rays of the primary image surface of the reflection light path pass through a micro lens array group consisting of a second front group micro lens array and a second rear group micro lens array, are gated by a first micro switch array, and are imaged on a detector by a second rear-end imaging objective lens.

The first front group micro lens array can be used for deflecting marginal field-of-view rays in the gating field of view, and an optimized curved surface is added, so that the imaging quality of the field-of-view gating imaging system can be optimized.

The effective gating field range refers to an area without vignetting phenomenon in the gating field; the effective field of view of the system is the sum of effective gating fields corresponding to all the microlens units; the field duty ratio of the system refers to the ratio of the sum of effective gating fields corresponding to all the microlens units to the field of the front-end telescope.

An optical imaging system based on a field gating technology is a new system imaging system applied to a full-time star sensor, and mainly faces the problems of low effective field duty ratio and the like in practical application. The invention provides a solution for improving the field duty ratio of a field gating imaging system, which aims at solving the problems that the existing field gating imaging system has a lower effective field and the like. Compared with the prior art, the invention has the following advantages:

1. the vignetting area in the gating field range is reduced, the problems that the vignetting area is large, the concentration ratio of light spot energy in the vignetting area is not enough and the like in the existing field gating technology are solved to a certain extent, and the effective area in the gating field is improved;

2. because a group of micro-lens arrays are added in the optical system, an optimized curved surface is added in each gating channel, which is beneficial to optimizing the imaging quality of the field-of-view gating imaging system;

3. the primary image plane is divided into two parts by the spectroscope to respectively carry out field gating, so that the effective area of the gated field and the effective field of the system can be greatly improved.

Drawings

FIG. 1 is a schematic structural diagram of an original field-of-view gated imaging system in an embodiment of the present invention;

in the figure: the imaging system comprises a front-end telescope 1, a front-end telescope 11, a micro lens array 2, a micro switch array 3, a rear-end imaging objective 4 and an array detector 5, wherein the front-end telescope images a fixed star.

FIG. 2 is a schematic diagram of optical paths at unit microlenses in an original field-of-view gated imaging system in an embodiment of the present invention;

in the figure: 11 is a primary image surface of the front-end telescope for imaging the fixed star, and 22 is a micro-lens unit in the micro-lens array;

FIG. 3 is a schematic view of an effective field range of an original field-of-view gated imaging system in an embodiment of the present invention;

in the figure: 1 is a square field of view of the front-end telescope, 2 is a gating field of view of the micro-lens array, and 3 is an effective gating field of view of the micro-lens array;

FIG. 4 is a schematic diagram of a method for increasing the duty cycle of the field of view of an original field-of-view gated imaging system in an embodiment of the present invention;

in the figure: the system comprises a front-end telescope 1, a spectroscope 2, a primary image plane 31 of a transmission optical path, a microlens array 41 of a transmission optical path used as a field lens, a microlens array 51 of a transmission optical path used for field gating, a microswitch array 61 of a transmission optical path, a confocal plane imaging system 71 of the transmission optical path, an array detector 81 of the transmission optical path, a primary image plane 32 of a reflection optical path, a microlens array 42 of a reflection optical path used as a field lens, a microlens array 52 of a reflection optical path used for field gating, a microswitch array 62, a confocal plane imaging system 72 of the reflection optical path, and an array detector 82 of the reflection optical path.

FIG. 5 is a schematic diagram of an optical path at a microlens of a unit after a method for increasing a field duty ratio of an original field gating imaging system is adopted in an embodiment of the present invention;

in the figure: 11 is a primary image surface of the front-end telescope for imaging the fixed star, 21 is a micro-lens unit in the added micro-lens array, and 22 is a micro-lens unit in the original micro-lens array;

FIGS. 6(a) and 6(b) are schematic views of a field-of-view gated area of a transmitted optical path and a field-of-view gated area of a reflected optical path, respectively, in an embodiment of the present invention;

in the figure: 1 is a square field of view of a front-end telescope in a transmission light path, 2 is a gating field of view of a micro-lens array in the transmission light path, and 3 is an effective gating field of view of the micro-lens array in the transmission light path; 11 is the square field of view of the front telescope in the reflection optical path, 22 is the gating field of view range of the micro lens array in the reflection optical path, and 33 is the effective gating field of view range of the micro lens array in the reflection optical path.

Detailed Description

The invention is described in detail below with reference to the figures and the detailed description. The following examples are only for explaining the present invention, the scope of the present invention shall include the whole contents of the claims, and those skilled in the art can realize the whole contents of the claims of the present invention by the following examples.

Example 1:

the embodiment 1 of the invention is a method for improving the duty ratio of a view field gated imaging system with the aperture of 100mm, the F number of 15, the working wave band of 1.3-1.7 mu m and the total view field of 5 degrees multiplied by 5 degrees.

Fig. 1 is a schematic structural diagram of an original field-of-view gated imaging system. The system comprises: the device comprises a front-end telescope 1, a micro lens array 2, a micro switch array 3, a rear-end imaging objective lens 4 and an array detector 5. Wherein the view field of the front-end telescope 1 is 5 degrees multiplied by 5 degrees, the caliber is phi 100mm, and the focal length is 300 mm; the unit aperture of the micro lens array 2 is phi 3.8mm, the focal length is 6mm, and the unit number is 7 multiplied by 7; the unit aperture of the micro switch array 3 is phi 3.8mm, and the unit number is 7 multiplied by 7; the aperture of the rear-end imaging objective 4 is 30mm, and the focal length is 30 mm; the pixel size of the array detector 5 is 20 μm, and the effective pixel array number is 512 × 512.

Multiple fixed star signal lights at infinity are imaged on a primary image surface by the front-end telescope 1, and the imaging quality reaches a near diffraction limit; then subdividing and gating the field of view of the primary image plane by the micro lens array 2 and the micro switch array 3; since the F number of the front-end telescope 1 is 3, the field angle of each image point ray on the primary image surface is 19 degrees; the schematic diagram of the optical path at the unit microlens is shown in fig. 2, and it can be seen that the gated view field range AC on the primary image plane 11 corresponding to the unit microlens 21 is consistent with the aperture size of the unit microlens 21. However, only a part of the light rays of the fringe field a or C can pass through the unit microlens within the range of the gated field, and thus there is a significant vignetting phenomenon. According to the formula of Airy spotsIt can be seen that the effective aperture D of the light beam corresponding to the vignetting area is reduced, so the airy disk size in the area becomes larger. In the embodiment, the central field B area in the gating field range is a non-vignetting area, the Airy spot size is about 55 μm, and the Airy spots are distributed within 3 x 3 pixels and meet the requirement of energyThe amount centralizes the requirements. And the marginal field A or C in the gating field range is a vignetting area, the size of the Airy spot is about 80 μm and exceeds the range of 3 multiplied by 3 pixels, and the requirement of energy concentration cannot be met. This indicates that only the central field of view is valid and the peripheral field of view is invalid within the gated field of view. FIG. 3 shows a schematic diagram of the effective field of view of the system, wherein the square region 1 is 5 degrees of the field of view of the front-end telescope, the gating field of view 2 is phi 0.72 degrees, the radius of the effective region of the gating field of view is only 50 percent of the radius of the gating field of view, and the total effective field of view of the system is only 7 x pi x (0.36 x 50 percent)²＝4.98°²The total effective field duty ratio of the system is only 4.98 °²/25°²＝19.9％。

Fig. 4 is a schematic diagram of a method for increasing the duty cycle of the field of view of the original field-of-view gated imaging system in embodiment 1 of the present invention, which includes a front-end telescope 1, a beam splitter 2, a primary image plane 31 of a transmission optical path, a microlens array 41 used as a field lens in the transmission optical path, a microlens array 51 used for field-of-view gating in the transmission optical path, a microswitch array 61 of the transmission optical path, a confocal plane imaging system 71 of the transmission optical path, an array detector 81 of the transmission optical path, a primary image plane 32 of a reflection optical path, a microlens array 42 used as a field lens in the reflection optical path, a microlens array 52 used for field-of-view gating in the reflection optical path, a microswitch array 62, a confocal plane imaging system 72 of the reflection optical path, and an array detector 82 of the reflection optical path. The main difference from the original field-of-view gated imaging system configuration in fig. 1 is that a beam splitter is introduced to divide the primary image planes into two, and microlens arrays 41 and 42, which serve as field lenses, are introduced in the transmission and reflection optical paths. Fig. 5 is a schematic diagram of an optical path at the microlens set of the transmission optical path unit. Due to the introduction of the microlens unit 22 serving as a field lens, the light rays of the marginal fields a and C within the gated field range AC are deflected and can pass through the microlens unit 21 of the rear group, thereby greatly reducing the vignetting area and improving the effective area of the gated field. Assuming that the radius of the effective area of the gating field of view is increased to 80% of the radius of the gating field of view, the total effective gating field of view of the transmission optical path is 7 × 7 × π × x (0.36 ° × 80%)²＝12.7°²Total gated field of view of transmitted light pathThe duty ratio can reach 12.7 °²/25°²51 percent. Similarly, the total effective gating field of view in the reflection light path is also 12.7 °²The total gating field duty ratio of the reflection optical path can also reach 51%. And arranging the gating area of the primary image surface by the micro lens array in the reflection optical path and the gating area of the primary image surface by the micro lens array in the transmission optical path in a mutually staggered manner, so that the total effective gating field of view of the system can be approximately regarded as the sum of the effective gating field of view in the reflection optical path and the effective gating field of view in the transmission optical path. Fig. 6(a) and 6(b) are schematic diagrams of the field-of-view gating region of the transmission optical path and the field-of-view gating region of the reflection optical path in the embodiment of the present invention. Obviously, the effective gating fields in the reflected optical path and the effective gating fields in the transmitted optical path are distributed in a staggered manner, and the total gating field duty cycle of the system can approach 100% except for the overlapped area.

Example 2

The embodiment 2 of the invention is a method for improving the duty ratio of a view field gated imaging system with the aperture of 80mm, the F number of 20, the working wave band of 700 nm-900 nm and the total view field of 6 degrees multiplied by 6 degrees.

Fig. 1 is a schematic structural diagram of an original field-of-view gated imaging system. The system comprises: the device comprises a front-end telescope 1, a micro lens array 2, a micro switch array 3, a rear-end imaging objective lens 4 and an array detector 5. Wherein the view field of the front-end telescope 1 is 6 degrees multiplied by 6 degrees, the caliber is phi 80mm, and the focal length is 320 mm; the unit aperture of the micro lens array 2 is phi 3mm, the focal length is 7mm, and the unit number is 11 multiplied by 11; the unit aperture of the micro switch array 3 is phi 3mm, and the unit number is 11 multiplied by 11; the aperture of the rear-end imaging objective lens 4 is 35mm, and the focal length is 35 mm; the pixel size of the array detector 5 is 13 μm, and the effective pixel array number is 1024 × 1024. Multiple fixed star signal lights at infinity are imaged on a primary image surface by the front-end telescope 1, and the imaging quality reaches a near diffraction limit; then subdividing and gating the field of view of the primary image plane by the micro lens array 2 and the micro switch array 3; because the F number of the front-end telescope 1 is 4, the field angle of each image point ray on the primary image surface is 14.3 degrees; the schematic diagram of the optical path at the unit microlens is shown in fig. 2, and it can be seen that the gated field range AC on the primary image plane 11 corresponding to the unit microlens 21 and the unit microlensThe sizes of the 21 calibers are consistent. However, only a part of the light rays of the fringe field a or C can pass through the unit microlens within the range of the gated field, and thus there is a significant vignetting phenomenon. According to the formula of Airy spotsIt can be seen that the effective aperture D of the light beam corresponding to the vignetting area is reduced, so the airy disk size in the area becomes larger. In the embodiment, the central field B region in the gated field range is a non-vignetting region, the airy disk size is about 39 μm, and the airy disk size is distributed within 3 × 3 pixels, so as to meet the requirement of energy concentration. And the marginal field A or C in the gating field range is a vignetting area, the size of the Airy spot is about 50 μm and exceeds the range of 3 multiplied by 3 pixels, and the requirement of energy concentration cannot be met. This indicates that only the central field of view is valid and the peripheral field of view is invalid within the gated field of view. FIG. 3 shows a schematic diagram of the effective field of view range of the system, wherein the square region 1 is the field of view of the front-end telescope 6 degrees by 6 degrees, the gating field of view 2 has a range of phi 0.54 degrees, the radius of the effective area of the gating field of view is only 55 percent of the radius of the gating field of view, and the total effective field of view of the system is only 11 x pi x (0.27 degrees by 55 percent)²＝8.38°²The total effective field duty ratio of the system is only 8.38 °²/36°²＝23.3％。

Fig. 4 is a schematic diagram of a method for increasing the duty cycle of the field of view of the original field-of-view gated imaging system in embodiment 1 of the present invention, which includes a front-end telescope 1, a beam splitter 2, a primary image plane 31 of a transmission optical path, a microlens array 41 used as a field lens in the transmission optical path, a microlens array 51 used for field-of-view gating in the transmission optical path, a microswitch array 61 of the transmission optical path, a confocal plane imaging system 71 of the transmission optical path, an array detector 81 of the transmission optical path, a primary image plane 32 of a reflection optical path, a microlens array 42 used as a field lens in the reflection optical path, a microlens array 52 used for field-of-view gating in the reflection optical path, a microswitch array 62, a confocal plane imaging system 72 of the reflection optical path, and an array detector 82 of the reflection optical path. The main difference from the original field-of-view gated imaging system structure in FIG. 1 is that a spectroscope is introduced to divide one primary image plane into twoMicrolens arrays 41 and 42, which act as field lenses, are introduced in both the transmitted and reflected light paths. Fig. 5 is a schematic diagram of an optical path at the microlens set of the transmission optical path unit. Due to the introduction of the microlens unit 22 serving as a field lens, the light rays of the marginal fields a and C within the gated field range AC are deflected and can pass through the microlens unit 21 of the rear group, thereby greatly reducing the vignetting area and improving the effective area of the gated field. Assuming that the radius of the effective area of the gating field of view is increased to 90% of the radius of the gating field of view, the total effective gating field of view of the transmission optical path is 11 × 11 × pi × (0.27 ° × 90%)²＝20°²The total gating view field duty ratio of the transmission light path can reach 20 DEG²/36°²55.6 percent. Similarly, the total effective gating field of view in the reflection light path is also 20 °²And the total gating field duty ratio of the reflection optical path can also reach 55.6%. And arranging the gating area of the primary image surface by the micro lens array in the reflection optical path and the gating area of the primary image surface by the micro lens array in the transmission optical path in a mutually staggered manner, so that the total effective gating field of view of the system can be approximately regarded as the sum of the effective gating field of view in the reflection optical path and the effective gating field of view in the transmission optical path. Fig. 6(a) and 6(b) are schematic diagrams of the field-of-view gating region of the transmission optical path and the field-of-view gating region of the reflection optical path in the embodiment of the present invention. Obviously, the effective gating fields in the reflected optical path and the effective gating fields in the transmitted optical path are distributed in a staggered manner, and the total gating field duty cycle of the system can approach 100% except for the overlapped area.

The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can understand that the modifications or substitutions within the technical scope of the present invention are included in the scope of the present invention.