CN112684609B - A compact broadband polarization simultaneous imaging device and system with sub-aperture - Google Patents

Abstract

The invention relates to a compact broadband polarization simultaneous imaging device and system with divided apertures. The purpose of the present invention is to solve the technical problem that it is difficult to realize real-time detection and recognition of targets, especially high-speed moving targets, under the complex background of low contrast or target camouflage in the existing polarization imaging system. The first reflecting mirror, the first lens group, the second lens group, the third reflecting mirror and the fourth reflecting mirror of the device are arranged in sequence along the optical axis; the second reflecting mirror is located between the first reflecting mirror and the third reflecting mirror, The center of the second reflecting mirror and the third reflecting mirror is provided with a light-passing hole a; the first lens group and the second lens group are arranged at the light-passing hole a on the second reflecting mirror; the first reflecting mirror and the second reflecting mirror The reflecting surfaces of the mirrors are opposite to each other, and the third reflecting mirror is opposite to the reflecting surface of the fourth reflecting mirror; the telescopic objective lens unit and the zooming and collimating objective lens unit form an afocal system; the entrance pupil surfaces of the four imaging objective lens units are all located in the on the exit pupil of the afocal system.

Description

A compact broadband polarization simultaneous imaging device and system with sub-aperture

technical field

The invention relates to a simultaneous polarization imaging device and system, in particular to a compact broadband polarization simultaneous imaging device and system with divided apertures.

Background technique

The existing target detection imaging methods mainly include photometric imaging, spectral imaging and polarization imaging.

Photometric imaging is difficult to recognize the target when the target light intensity is similar to the background light intensity. With the development of new special (camouflage and concealment) materials and their application on targets, the camouflage and concealment performance of targets has been greatly improved, and photometric imaging has gradually become incompetent. However, spectral imaging is easily disturbed, has poor stability, and has a short spectral range, making it difficult to adapt to complex application environments such as diverse targets. Therefore, in complex backgrounds such as low contrast, the existing photometric imaging and spectral imaging methods are difficult to achieve accurate detection and recognition of objects, and it is even more difficult to accurately identify camouflaged targets and potential threats in complex backgrounds.

Polarization imaging realizes polarization imaging by collecting information on the polarized light generated by the reflected natural light of the target. The technical processing of the collected information can improve the contrast information of the target image to be detected, and at the same time, the appearance characteristics and surface materials of the target image can be obtained. Multidimensional information such as properties and surface roughness.

Existing polarization imaging systems mainly include sequential polarization imaging systems, interference polarization imaging systems and spatial polarization imaging systems. Among them, the time series polarization imaging system cannot collect the polarization information of the target in real time, and has the defect of large information error, so it is difficult to realize the real-time collection of the polarization information of the moving target, especially the high-speed moving target. The interferometric polarization imaging system not only has the problem of single working wavelength and multi-band crosstalk, but also requires a certain amount of time to solve the interference fringes, which requires high computer performance. The environment of the imaging site is generally difficult to meet the interference polarization imaging The system is more demanding. For the spatial polarization imaging system, due to the use of the sub-amplitude structure, there are mutual exclusions in terms of high resolution and compactness, resulting in problems such as bulky volume, low resolution and difficult assembly. The structural form of simultaneous acquisition by multiple systems has the disadvantages of large size, heavy weight, poor stability and high cost.

The Chinese invention patent with publication number CN111750997A discloses an optical imaging detection device based on polarization time division spectral synchronization. The optical system of the device is divided into an imaging unit and a time division conversion polarization spectrum unit. feature to obtain different polarization information of the target. This optical system has the disadvantages of low spatial resolution and too long axial length of the system. When imaging a moving target, it cannot collect different polarization properties of the target at the same time in real time, and cannot meet the high resolution of high-speed moving targets in complex environments. imaging, and there are insurmountable shortcomings such as large principle errors and low data reliability.

To sum up, under complex backgrounds such as low contrast or target camouflage, it is difficult for existing polarization imaging systems to achieve real-time detection and recognition of targets, especially high-speed moving targets.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the technical problem that the existing polarization imaging system is difficult to realize real-time detection and recognition of targets, especially high-speed moving targets under complex backgrounds such as low contrast or target camouflage, and to provide a compact broadband polarization with different apertures Simultaneous imaging device and system.

For solving the above-mentioned technical problems, the technical solutions provided by the present invention are as follows:

The present invention provides a compact broadband simultaneous imaging device with split aperture, which is characterized by:

Including a telescopic objective lens unit for collecting target information, a reduced focus collimating objective lens unit with the same compression and collimation optical paths, and four imaging objective lens units for polarized imaging;

The telescopic objective lens unit includes a first reflection mirror, a second reflection mirror and a first lens group;

The zooming and collimating objective lens unit includes a third reflecting mirror, a fourth reflecting mirror and a second lens group;

the first reflecting mirror, the first lens group, the second lens group, the third reflecting mirror and the fourth reflecting mirror are arranged in sequence along the optical axis;

The second reflecting mirror is arranged along the optical axis and is located between the first reflecting mirror and the third reflecting mirror, and the center of the second reflecting mirror and the third reflecting mirror is provided with a light-passing hole a; the first lens group and the second reflecting mirror The lens group is arranged at the light-passing hole a on the second reflector for residual aberration correction;

The first reflecting mirror is opposite to the reflecting surface of the second reflecting mirror to form a first folding structure, and the third reflecting mirror is opposite to the reflecting surface of the fourth reflecting mirror to form a second folding structure for compressing the axial length ;

The telescopic objective lens unit and the zooming and collimating objective lens unit form an afocal system; the entrance pupil surfaces of the four imaging objective lens units are all located on the exit pupil surface of the afocal system, and are centered along the same optical axis. Evenly distributed around the circumference to realize the splicing of the afocal system and the four imaging objective lens units.

Further, the imaging objective lens unit includes a fifth reflector, a sixth reflector, a third lens group and a polarizer that are coaxially arranged in sequence;

The center of the sixth reflector is provided with a light-passing hole c;

The fifth reflecting mirror is opposite to the reflecting surface of the sixth reflecting mirror to form a third folding structure;

The third lens group is used for residual aberration correction.

： Further, the compression ratio of the axial length of the afocal system is

:

；

;

in,

为望远物镜单元的有效焦距；

is the effective focal length of the telescopic objective lens unit;

为缩焦准直物镜单元的有效焦距；

is the effective focal length of the zooming and collimating objective lens unit;

TTLA is the axial distance from the front surface of the first mirror to the rear surface of the fourth mirror.

，

。 Further, the angular magnification of the afocal system is

,

.

Further, the deviation distances of the four imaging objective lens units from the optical axis are all d, and the deviation distance d and the total focal length ƒ of the telescopic objective lens unit, the zooming and collimating objective lens unit and the imaging objective lens unit satisfy the following relationship:

；

;

The total focal length ƒ of the telescopic objective lens unit, the zooming and collimating objective lens unit, and the imaging objective lens unit, and the overall length TTL from the rear surface of the first reflecting mirror to the rear image surface b of the polarizing plate of the imaging objective lens unit, and the exit surface of the third lens group to The axial distance BFL of the image plane b satisfies the following relationship:

。

.

与第六反射镜的直径

满足以下关系式：

。 Further, the diameter of the third mirror

with the diameter of the sixth mirror

Satisfy the following relation:

.

满足下式： Further, the total focal length of the first lens group and the second lens group

Satisfy the following formula:

。

.

Further, the four polarizers of the four imaging objective lens units are sequentially 0°, 60° and 120° polarizers along the circumferential direction, and circular polarizers.

Further, the first reflection mirror, the third reflection mirror, the fourth reflection mirror, the fifth reflection mirror and the sixth reflection mirror are all hyperbolic mirrors; the second reflection mirror is a parabolic mirror.

The present invention also provides a compact broadband polarization simultaneous imaging system with sub-aperture, which is characterized in that: based on the above-mentioned compact broadband polarization simultaneous imaging device with sub-aperture, it also includes a computer and four detectors connected to it, The four detectors are located at the four image planes b, and are used to obtain four sets of polarization images containing only a single polarization state information. The computer is used to process and calculate the four sets of polarization images to obtain the Stokes matrix of the target. information.

Compared with the prior art, the present invention has the following beneficial effects:

1. The present invention provides a compact wide-band polarization simultaneous imaging device and system with different apertures. By adopting the optical scheme of forming an afocal system in the form of a fold-back structure, the axial length of the system is compressed and the compactness of the system is improved. , to achieve a compression ratio greater than 10 times the axial length of the front afocal system, which greatly reduces the volume, length and weight of the system.

2. The present invention provides a compact wide-band polarization simultaneous imaging device and system with different apertures. The system adopts wide-spectrum imaging and can cope with the characteristic response spectrum of different targets in complex environments, so it can be adapted to complex environments. And provide high reliability and sensitivity.

3. The present invention provides a compact wide-band polarization simultaneous imaging device and system with different apertures. The afocal system and four fold-back imaging objective lens units are spliced together to form a polarized imaging device, and the four imaging objective lens units realize split-aperture imaging. The structure has the advantages of good real-time performance, compact device structure, and high energy density in the device. Compared with the traditional time-sharing polarization imaging system, the system can collect real-time information on moving targets and realize real-time response to the target.

4. The present invention provides a compact wide-band polarization simultaneous imaging device and system with different apertures, which can obtain multi-dimensional information such as target surface material characteristics and surface roughness that cannot be measured by traditional means by processing the collected information, and then reconstruct the data through three-dimensional reconstruction. technology, a 3D model containing information such as the target surface material can be obtained.

5. A compact wide-band polarization simultaneous imaging device and system with different apertures provided by the present invention can reduce the difficulty of size, design and assembly due to the advantages of introducing a pre-amplifying telescope (telephoto objective lens unit) structure. In addition, another important advantage is that the total luminous flux is increased through the front group, so that the luminous flux density per unit section in the optical path of the rear group is larger, which is beneficial to make up for the energy loss caused by the polarizer, increase the image signal-to-noise ratio, and can be used for a shorter time. The integration time can be used to avoid image shift caused by insufficient energy and prolong the integration time, which will lead to the deterioration of image quality.

Description of drawings

Fig. 1 is the structure schematic diagram of the compact broadband polarization simultaneous imaging device of sub-aperture of the present invention;

2 is a schematic structural diagram of the first lens group and the second lens group of the compact broadband polarization simultaneous imaging device of the present invention;

3 is a schematic structural diagram of an imaging objective lens unit on a single polarized light channel of a compact broadband polarization simultaneous imaging device with sub-aperture of the present invention;

4 to 6 are arrow indication diagrams of the 25 lens surfaces in Table 1 in the embodiment, wherein the ninth surface is a virtual surface (a surface that does not exist in reality, so it is not shown in the figure);

Fig. 7 is the MTF (modulation transfer function) curve when the 0° polarized light channel of the present invention obtained by simulation works in the spectral range of 450nm to 850nm, indicating the imaging quality in the meridional direction;

8 is the MTF (modulation transfer function) curve obtained by simulation when the 60° polarized light channel of the present invention operates in the spectral range of wavelength 450nm~850nm, indicating the imaging quality in the sagittal direction.

Description of reference numbers:

101-first reflector, 102-second reflector, 103-first lens group;

201-third mirror, 202-fourth mirror, 203-second lens group;

301-fifth reflector, 302-sixth reflector, 303-third lens group, 304-polarizer.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and embodiments.

Referring to FIG. 1 and FIG. 2 , the present invention provides a compact broadband polarization simultaneous imaging device with different apertures, which can realize real-time detection and recognition of targets, especially high-speed moving targets, under complex backgrounds such as low contrast or target camouflage. The device consists of three parts, including a telescopic objective lens unit for collecting target information, a reduced focus collimating objective lens unit with the same compression and collimation optical paths, and four for polarized imaging (which will contain information about different polarization states of the target). The first two units form an afocal system; the telescopic objective lens unit includes a first reflecting mirror 101, a second reflecting mirror 102 and a first lens group 103; the The focusing and collimating objective lens unit includes a third reflecting mirror 201 , a fourth reflecting mirror 202 and a second lens group 203 ; the first reflecting mirror 101 , the first lens group 103 , the second lens group 203 , and the third reflecting mirror 201 and the fourth reflecting mirror 202 are arranged in sequence along the optical axis; the second reflecting mirror 102 is arranged along the optical axis, between the first reflecting mirror 101 and the third reflecting mirror 201, the second reflecting mirror 102 and the third reflecting mirror 201 A light-passing hole a is opened in the center of the lens; the combination of the first lens group 103 and the second lens group 203 is set at the light-passing hole a on the second mirror 102 as a correction lens combination for residual aberration correction; the The reflecting surfaces of the first reflecting mirror 101 and the second reflecting mirror 102 are opposite to form a first fold-back structure, and the reflecting surfaces of the third reflecting mirror 201 and the fourth reflecting mirror 202 are opposite to form a second fold-back structure for compressing the shaft to length.

The entrance pupil planes of the four imaging objective lens units are all located on the exit pupil plane of the afocal system to divide the exit pupils, and are evenly distributed along the same circumference with the optical axis as the center, that is, at the exit pupil of the afocal system, with The optical axis is the origin to establish an xy coordinate system, and the entire four imaging objective lens units are deviated by d in the ±x and ±y directions respectively around the optical axis, so as to realize the splicing of the afocal system and the four imaging objective lens units, and the afocal system and the four return The polarized imaging device is formed by splicing the single-type imaging objective lens units, and the structure has the advantages of good real-time performance, compact device structure, and high energy density in the device.

The imaging objective lens unit includes a fifth reflector 301, a sixth reflector 302, a third lens group 303 and a polarizer 304 that are coaxially arranged in sequence; the sixth reflector 302 is provided with a light through hole c in the center; The fifth reflecting mirror 301 is opposite to the reflecting surface of the sixth reflecting mirror 302, forming a third fold-back structure, and the three-group fold-back structure can significantly compress the axial length of the device; the third lens group 303 is used for residual aberration correction . Of course, the imaging objective lens unit can be replaced with a transmissive structure, but this will increase the overall length and weight of the system.

The first reflecting mirror 101, the third reflecting mirror 201, the fourth reflecting mirror 202, the fifth reflecting mirror 301 and the sixth reflecting mirror 302 are all hyperbolic mirrors; the second reflecting mirror 102 is a parabolic mirror (hyperbolic mirror). one of the mirrors).

： The compression ratio of the axial length of the afocal system is

:

；

;

in,

为望远物镜单元的有效焦距；

is the effective focal length of the telescopic objective lens unit;

为缩焦准直物镜单元的有效焦距；

is the effective focal length of the zooming and collimating objective lens unit;

TTLA is the axial distance from the front surface of the first reflector 101 to the back surface of the fourth reflector 202 , that is, the total length of the afocal system.

，

，通过无焦系统的放大倍率压缩无 焦系统出瞳直径，提升无焦系统出瞳处以及出瞳后端成像物镜单元内的能量密度。 The angular magnification of the afocal system is

,

, through the magnification of the afocal system, the diameter of the exit pupil of the afocal system is compressed, and the energy density at the exit pupil of the afocal system and in the imaging objective lens unit behind the exit pupil is increased.

The deviation distances of the four imaging objective lens units from the optical axis are all d, and the deviation distance d is related to the total focal length ƒ of the telescopic objective lens unit, the zooming and collimating objective lens unit and the imaging objective lens unit, which satisfies the following relationship:

；

;

The total focal length of the telescopic objective lens unit, the zooming and collimating objective lens unit and the imaging objective lens unit (that is, the total focal length of the device) ƒ, and the total length from the rear surface of the first reflecting mirror 101 to the rear image surface b of the polarizing plate 304 of the imaging objective lens unit ( That is, the overall length of the device) TTL , and the axial distance BFL from the exit surface of the third lens group 303 to the image plane b, the three satisfy the following relationship:

。

.

与第六反射镜 302的直径（成像物镜单元的入瞳直径）

满足以下关系式： The diameter of the third reflecting mirror 201 (that is, the clear aperture of the reduced-focus collimating objective lens unit)

and the diameter of the sixth mirror 302 (the entrance pupil diameter of the imaging objective lens unit)

Satisfy the following relation:

。

.

满足下式： The total focal length of the first lens group 103 and the second lens group 203

Satisfy the following formula:

。

.

Figure 3 is a schematic diagram of an imaging objective lens unit with a single polarized light channel. The total system has four groups of channels; the polarizers 304 in their respective states in the four groups of channels are 0°, 60°, 120° and circularly polarized polarizers in sequence along the circumference. . Among them, the 0° polarized light channel is located in the +x direction; the 60° polarized light channel is located in the +y direction; the 120° polarized light channel is located in the -x direction.

The present invention also provides a compact broadband polarization simultaneous imaging system with divided apertures, based on the above-mentioned compact broadband polarization simultaneous imaging device with divided apertures, further comprising a computer and four detectors connected thereto, the four detectors Located at the four image planes b, it is used to obtain four sets of polarization images containing only a single polarization state information. The computer is used to process and calculate the four sets of polarization images to obtain the Stokes matrix information of the target. Technical processing obtains information on other dimensions of the target.

In the above-mentioned device and system, all three units adopt a folded structure, especially the first two units adopt a folded structure, which greatly compresses the axial length of the system, and the compression ratio is greater than 10 times.

The working process of the whole system is as follows:

The light reflected or emitted by the target is collected into the system by the second mirror 102, and reaches the primary image plane b in the first lens group 103 through the first mirror 101; 201 is collimated and emitted; it enters the imaging objective lens unit at the exit pupil, and after passing through the polarizer 304, a polarized image containing only a single polarization state information is obtained at the image plane b. Stokes matrix information can be processed by other technologies to obtain information of other dimensions of the target (multi-dimensional information such as the material properties and surface roughness of the target surface that cannot be measured by traditional methods can be obtained by processing the collected information, and through 3D reconstruction technology, it can be obtained. 3D model with information such as target surface material).

Example

The technical indicators are as follows:

Optical system total length TTL : 830mm;

System total focal length ƒ: 2000mm;

：6； Afocal system angular magnification

:6;

Optical system aperture FNO: 10;

Field of view of optical system: 0.42°;

Optical system using wavelength range: 450nm ~ 850nm.

Structural parameters of each lens in a compact broadband polarization simultaneous imaging device with different apertures:

In the table, Mirror is a mirror, and SILICA_SPECIAL is fused silica. Figures 4 to 6 are arrow indication diagrams of the 25 lens surfaces in Table 1 above, wherein the ninth surface is a virtual surface (a surface that does not exist in reality, so it is not shown in the figure);

Figure 7 shows the MTF (modulation transfer function) curve of the simulated 0° polarized light channel operating in the spectral range of 450nm to 850nm, indicating the imaging quality in the meridian direction. It can be seen from the figure that the Nyquist frequency At 50 lp/mm, the MTF values of 0, 0.5, 0.707, 0.866 and 1 field of view are all above 0.4 and close to the diffraction limit (dashed line in the figure), achieving good imaging quality.

Figure 8 is the MTF (modulation transfer function) curve of the simulated 60° polarized light channel operating in the wavelength range of 450nm~850nm, which indicates the imaging quality in the sagittal direction. It can be seen from the figure that the Nyquist frequency At 50 lp/mm, the MTF values of 0, 0.5, 0.707, 0.866 and 1 field of view are all above 0.4 and close to the diffraction limit, achieving good imaging quality.

Of course, the material of each lens is not limited to the above table, and the material of each lens can be adjusted according to specific needs during use.

In addition, when the working wavelength band is wider or high transmittance is pursued, the correction lens combination of the first lens group 103 and the second lens group 203 can be removed. In this way, the image quality of the afocal system will be degraded, but the aberration can be appropriately corrected by adding a correction lens group in the imaging objective lens unit at the rear, or by adding the first reflecting mirror 101, the second reflecting mirror 102, and the third reflecting mirror 201 The aspheric surface or free-form surface is introduced into the fourth reflecting mirror 202 to perform aberration compensation correction, and the refractive surface is reduced by reducing the number of lenses, so that the energy loss of the system will be improved.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them. For those of ordinary skill in the art, the specific technical solutions recorded in the foregoing embodiments can be modified. , or equivalently replace some of the technical features, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions protected by the present invention.

Claims (10)

1. A kind of wide band polarization of compact that divides the aperture is formed the image device at the same time, characterized by:

the device comprises a telescope objective unit for collecting target information, a focusing collimator objective unit which is the same as a compression and collimation optical path, and four imaging objective units for polarization imaging;

the telescopic objective lens unit comprises a first reflector (101), a second reflector (102) and a first lens group (103);

the zooming collimating objective unit comprises a third reflector (201), a fourth reflector (202) and a second lens group (203);

the first reflector (101), the first lens group (103), the second lens group (203), the third reflector (201) and the fourth reflector (202) are sequentially arranged along an optical axis;

the second reflector (102) is arranged along the optical axis and is positioned between the first reflector (101) and the third reflector (201), and the centers of the second reflector (102) and the third reflector (201) are both provided with a light through hole a; the first lens group (103) and the second lens group (203) are arranged at a light-passing hole a on the second reflector (102) and used for residual aberration correction;

the first reflector (101) is opposite to the reflecting surface of the second reflector (102) to form a first folding structure, and the third reflector (201) is opposite to the reflecting surface of the fourth reflector (202) to form a second folding structure for compressing the axial length;

the telescope objective lens unit and the focus-reducing collimator objective lens unit form an afocal system; the entrance pupil surfaces of the four imaging objective lens units are all located on the exit pupil surface of the afocal system and are uniformly distributed along the same circumference by taking the optical axis as the center, so that the afocal system and the four imaging objective lens units are spliced.

2. The apertured compact wide-band simultaneous polarization imaging device according to claim 1, wherein:

the imaging objective unit comprises a fifth reflector (301), a sixth reflector (302), a third lens group (303) and a polaroid (304) which are coaxially and sequentially arranged;

the center of the sixth reflector (302) is provided with a light through hole c;

the reflecting surface of the fifth reflector (301) is opposite to the reflecting surface of the sixth reflector (302) to form a third folding structure;

the third lens group (303) is used for residual aberration correction.

3. The small aperture compact wide band simultaneous polarization imaging device of claim 1 or 2, wherein:

the compression ratio of the axial length of the coke-free system is

：

；

Wherein,

is the effective focal length of the telescopic objective lens unit;

is the effective focal length of the convergent-collimation objective lens unit;

TTLAis the axial distance from the front surface of the first mirror (101) to the rear surface of the fourth mirror (202).

4. The apertured compact wide-band simultaneous polarization imaging device according to claim 3, wherein:

the angular magnification of the afocal system is

，

。

5. The apertured compact wide-band simultaneous polarization imaging device according to claim 4, wherein:

the deviation distances between the four imaging objective lens units and the optical axis are d, and the deviation distances d are equal to the total focal length of the telescopic objective lens unit, the zooming collimation objective lens unit and the imaging objective lens unit

The following relational expression is satisfied:

；

total focal length of telescopic objective lens unit, focusing collimator objective lens unit and imaging objective lens unit

And the total length from the rear surface of the first reflector (101) to the rear image surface b of the polarizer (304) of the imaging objective unitTTLAnd the axial distance from the exit surface of the third lens group (303) to the image surface bBFLThe three satisfy the following relational expression:

。

6. the apertured compact wide-band simultaneous polarization imaging device according to claim 5, wherein:

diameter of the third reflector (201)

And the diameter of the sixth reflector (302)

The following relation is satisfied:

。

7. the apertured compact wide-band simultaneous polarization imaging device according to claim 6, wherein:

a total focal length of the first lens group (103) and the second lens group (203)

Satisfies the following formula:

。

8. the apertured compact wide-band simultaneous polarization imaging device according to claim 7, wherein:

the four polarizers (304) of the four imaging objective units are 0 °, 60 ° and 120 ° polarizers in order in the circumferential direction, and a circularly polarizing polarizer.

9. The apertured compact wide-band simultaneous polarization imaging device according to claim 8, wherein:

the first reflector (101), the third reflector (201), the fourth reflector (202), the fifth reflector (301) and the sixth reflector (302) are hyperboloidal reflectors; the second mirror (102) is a parabolic mirror.

10. The utility model provides a wide band polarization simultaneous imaging system of compact of branch aperture which characterized in that: the aperture-dividing compact wide-band polarization simultaneous imaging device according to any one of claims 5 to 9, further comprising a computer and four detectors connected to the computer, wherein the four detectors are located at the four image planes b and are used for obtaining four groups of polarization images only containing single polarization state information, and the computer is used for processing and calculating the four groups of polarization images to obtain stokes matrix information of a target.

Images