阅读说明：本技术 一种光学像移补偿方法及装置 (Optical image motion compensation method and device ) 是由 张新 张建萍 史广维 王灵杰 于 2020-12-28 设计创作，主要内容包括：本发明属于光学技术领域,提出一种双反射镜像移补偿方法,利用置于远心或近似远心的会聚光路中的两块平行反射镜进行同步旋转,补偿光学系统与目标发生相对运动时所产生的像移,从而实现对像方光束快速、精准的像移补偿。(The invention belongs to the technical field of optics, and provides a double-reflector image motion compensation method, which utilizes two parallel reflectors arranged in a telecentric or approximately telecentric convergent light path to synchronously rotate to compensate image motion generated when an optical system and a target move relatively, thereby realizing rapid and accurate image motion compensation of image side light beams.)

1. An optical image motion compensation method, comprising the steps of:

s1, placing two first reflectors (31) and two second reflectors (32) which are placed in parallel, rotate synchronously and have fixed axial center distance in a telecentric convergence light path;

s2, the optical system and the target generate relative motion, and the first reflecting mirror (31) and the second reflecting mirror (32) rotate synchronously to compensate the image shift of the target on the focal plane of the detector (4).

2. The optical image motion compensation method according to claim 1, wherein the angle α of the synchronous rotation is obtained by the following equation:

ΔW+Lsin(2α)＝0 (1)

the axial defocusing amount of the image plane caused by the synchronous rotation of the first reflector (31) and the second reflector (32) is required to be less than the focal depth of the optical system, namely the following formula is satisfied:

L(1-cos2α)＜2λF² (2)

wherein, Δ W is the variation of the field angle generated on the telecentric optical path by the movement of the target,

l is the axial distance between the first reflector (31) and the second reflector (32),

f is the F number of the optical system,

λ is the wavelength of the optical system.

3. The optical image motion compensation method according to claim 1, wherein aw is obtained by the following equation:

ΔS₁＝ΔW (3)

wherein, Delta S₁The image shift amount generated in the vertical axis direction of the image plane is the target.

4. An optical image motion compensation device, comprising: the image motion compensation unit (3) is arranged in the telecentric convergent light path, and the image motion compensation unit (3) comprises a first reflector (31) and a second reflector (32) which are arranged in parallel, rotate synchronously and have fixed axial center distance; the optical system and the target generate relative motion, and the first reflecting mirror (31) and the second reflecting mirror (32) synchronously rotate to compensate the image movement of the target on the focal plane of the detector.

5. The optical image motion compensation device according to claim 4, wherein the angle α of the synchronous rotation is obtained by the following equation:

ΔW+Lsin(2α)＝0 (1)

the axial defocusing amount of the image plane caused by the synchronous rotation of the first reflector (31) and the second reflector (32) is required to be less than the focal depth of the optical system, namely the following formula is satisfied:

L(1-cos2α)＜2λF² (2)

wherein, Δ W is the variation of the field angle generated on the telecentric optical path by the movement of the target,

l is the axial distance between the first reflector (31) and the second reflector (32),

f is the F number of the optical system,

λ is the wavelength of the optical system.

6. The optical image motion compensation device according to claim 4, further comprising: the imaging lens group comprises a diaphragm (1), an imaging lens group (2) and a detector (4), wherein the diaphragm (1), the imaging lens group (2), an image motion compensation unit (3) and the detector (4) are sequentially arranged along a main optical axis of an incidence direction.

7. The optical image motion compensation device according to claim 6, wherein the imaging lens group (2) is an ideal optical system.

8. The optical image motion compensation device of claim 4, wherein F/# ≧ 4 of the telecentric converging light path.

Technical Field

The invention belongs to the technical field of optics, and particularly relates to an optical image motion compensation method and device.

Background

With the development of the photoelectric imaging detection technology, a modern photoelectric detection and tracking system requires that a camera has the capability of acquiring a large-field-of-view high-resolution target image under the condition of high-speed flight, and an image formed by a scene image on a focal plane detector and the detector move relatively within the integral imaging time of the detector, so that image shift is generated on the focal plane of the detector, image blurring can be caused by the image shift, the target detail resolution capability is influenced, the number of pixels of the detector occupied by a target is increased, and the type of the target is misjudged. In order to obtain a clearer image and reduce the influence of image motion on the system, a design for performing image motion compensation on a high-resolution photoelectric system is needed.

In conventional optical image space scanning, a mirror is often used as a compensation element to realize image motion compensation in one direction through rotation and swing. If a single reflector is directly placed in a convergent light path, the arc motion of an image surface generated by scanning causes the phenomenon of bending of a scanned image surface, influences the compensation effect, and is particularly not suitable for the swing scanning image motion compensation of large-area staring imaging. The mirror is often placed in a parallel optical path. In order to reduce the size of the compensating mirror, increase the scanning speed and compensation range, and ensure the compensation accuracy and the staring imaging quality, it is usually necessary to manufacture a beam-shrinking afocal system inside the system to meet the requirements. The added light path inevitably increases the length and complexity of the optical system, which is not beneficial to simplifying the structure and compressing the cylinder length.

Disclosure of Invention

The optical compensation method is an important way for realizing image motion compensation, light rays move reversely by rotating the reflector, the optical wedge and the lens to offset image motion caused by the motion platform, the volume of the reflector adopted by the method is relatively small, the reflector is easy to control by lightweight design, and the method is mainly used for a long-focus high-resolution camera.

The optical compensation method of the quick reflector is adopted, so that the direction of light rays is changed according to a specific rule, and the stability of a visual axis in the integration time is ensured. The scanning mode using the reverse scanning compensation comprises object scanning and image scanning, wherein the object scanning means that a reverse scanning compensation device is added in an optical path in front of an objective lens to directly scan the scenery. The object space scanning mode is simpler in principle and can meet the optical double-angle relation, but the defects are that the caliber of the reflector is usually larger, and when the reflector swings in a large range, particularly two-dimensional scanning swing, a system device is complex and heavy. The image scanning means that a reverse scanning compensation device is added between the objective lens and the detector to perform compensation scanning on the image beam. Compared with the object space scanning scheme, the scheme has compact structure and the size of the scanning element can be small.

The image space scanning converging light compensation has the advantages that the structure is relatively simple, the structure of the light path for converging light compensation is basically unchanged from the original imaging light path, only a compensating reflector is added, and the image space scanning converging light compensation is particularly suitable under the condition that the requirements on parameters such as the appearance, the weight and the like of a system are strictly limited.

The invention provides an optical image motion compensation method and a device, wherein the method utilizes two parallel reflectors arranged in a telecentric or approximately telecentric convergent light path to synchronously rotate to compensate the image motion generated when an optical system and a target move relatively. In order to achieve the purpose, the invention adopts the following specific technical scheme:

an optical image motion compensation method, comprising the steps of:

s1, placing two first reflectors and two second reflectors which are placed in parallel, rotate synchronously and have fixed axial center distance in a telecentric convergence light path;

s2, the optical system and the target move relatively, and the first reflector and the second reflector rotate synchronously to compensate the image shift of the target on the focal plane of the detector.

Preferably, the angle α of the synchronous rotation is found by the following equation:

ΔW+L sin(2α)＝0 (1)

the axial defocusing amount of the image plane caused by the synchronous rotation of the first reflector and the second reflector is required to be less than the focal depth of the optical system, namely the following formula is satisfied:

L(1-cos 2α)＜2λF² (2)

wherein, Δ W is the variation of the field angle generated on the telecentric optical path by the movement of the target,

l is the axial distance between the first reflector (31) and the second reflector,

f is the F number of the optical system,

λ is the wavelength of the optical system.

Preferably, Δ W is obtained using the formula:

ΔS₁＝ΔW (3)

wherein, Delta S₁The image shift amount generated in the vertical axis direction of the image plane is the target.

An optical image motion compensation device comprising: the image motion compensation unit is arranged in the telecentric convergent light path and comprises a first reflector and a second reflector which are arranged in parallel, rotate synchronously and have fixed axial center distance; the optical system and the target generate relative motion, and the first reflecting mirror and the second reflecting mirror rotate synchronously to compensate the image shift of the target on the focal plane of the detector.

Preferably, the angle α of the synchronous rotation is found by the following equation:

ΔW+L sin(2α)＝0 (1)

the axial defocusing amount of the image plane caused by the synchronous rotation of the first reflector and the second reflector is required to be less than the focal depth of the optical system, namely the following formula is satisfied:

L(1-cos 2α)＜2λF² (2)

wherein, Δ W is the variation of the field angle generated on the telecentric optical path by the movement of the target,

l is the axial distance between the first reflector and the second reflector,

f is the F number of the optical system,

λ is the wavelength of the optical system.

Preferably, the method further comprises the following steps: the diaphragm, the imaging lens group, the detector, the diaphragm, the imaging lens group, the image motion compensation unit and the detector are sequentially arranged along a main optical axis of an incidence direction.

Preferably, the imaging optics are ideal optical systems.

Preferably, F/# ≧ 4 of the telecentric convergence light path.

The invention can obtain the following technical effects:

1. the reasonable matching setting of the view field change and the rotating angle of the reflector is utilized, the image motion compensation of the system is realized, the imaging quality is not affected, and the performance is stable.

2. The image motion compensation problem of the planar array staring imaging in the scanning process in the convergent light path is solved.

3. An afocal light path does not need to be manufactured in an optical system to place an image motion compensation mirror, the length of an optical cylinder is shortened, the system structure is simplified, and the miniaturization of optical loads is facilitated.

4. In the focal plane detector integration time, the target is static relative to the detector, the integration time is long, and the system action distance is increased.

Drawings

FIG. 1 is a schematic diagram illustrating a relationship between a field-of-view variation angle and an image shift in an optical image shift compensation method according to an embodiment of the present invention;

FIG. 2 is a schematic diagram illustrating the relationship between the rotation angle and the image shift of a dual reflector according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a two-mirror image motion compensation system according to an embodiment of the present invention;

FIG. 4 is a schematic structural diagram of an optical image motion compensation device according to an embodiment of the present invention;

FIG. 5a is a graph of MTF for a target at a fixed position relative to an optical system with a 0 degree field angle, in accordance with an embodiment of the present invention;

FIG. 5b is the MTF plot for a relative motion between the object and the optical system at a field angle of 1 °;

FIG. 5c is a graph of MTF for a-1 degree field angle for relative motion of the object and the optical system.

Reference numerals:

the device comprises a diaphragm 1, an imaging lens group 2, an image motion compensation unit 3, a first reflecting mirror 31, a second reflecting mirror 32 and a detector 4.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not to be construed as limiting the invention.

The invention aims to provide an optical image motion compensation method and device, which utilize two parallel reflectors arranged in a telecentric or approximately telecentric convergent light path to synchronously rotate to compensate image motion generated when an optical system and a target move relatively, thereby realizing rapid and accurate image motion compensation of light beams on an image side. The following describes an optical image motion compensation method and apparatus provided by the present invention in detail with specific embodiments.

As shown in FIG. 1, the object is moved in the vertical axis direction of the image plane of the detector 4 based on the relative movement between the optical system and the object, and the image shift amount Δ S is obtained₁Obtained according to the following formula:

ΔS₁＝ΔW (3)

at this time, the defocusing amount Δ l of the image plane is determined by changing the axial direction of the target in the image plane based on the relative motion between the optical system and the target₁Defocus amount Δ l thereof₁Obtained according to the following formula:

Δl₁＝0 (4)

as shown in fig. 2, the object is moved in the vertical axis direction of the image plane by the angle α based on the synchronous rotation of the first mirror 31 and the second mirror 32, and the image shift amount Δ S is obtained₂Obtained according to the following formula:

ΔS₂＝L sin(2α) (5)

at this time, the defocusing amount Δ l of the image plane is determined by changing the axial direction of the target in the image plane based on the relative motion between the optical system and the target₂The defocus amount is obtained according to the following formula:

Δl₂＝L(1-cos 2α) (6)

as shown in fig. 3, when the optical system and the object move relatively, the first mirror 31 and the second mirror 32 rotate synchronously by α to compensate the movement of the object on the focal plane of the detector 4, so that the object is still at rest relative to the detector 4 in the position of the T2 and the original T1 within the integration time of the detector 4. To achieve the above object, the following two conditions are satisfied:

the first condition is as follows: the image motion of the target in the vertical axis direction and the image motion caused by the rotation of the reflector need to satisfy the conditions of the same size and the opposite directions, and the following formula is adopted:

ΔS₁+ΔS₂＝0 (7)

substituting equations (3) and (5) into the above equation yields equation (1), i.e.:

ΔW+L sin(2α)＝0 (1)

and a second condition: axial defocusing amount delta l of image surface caused by rotation of two reflectors₂Must be less than the depth of focus of the system, i.e.:

|Δl₂|＜2λF² (8)

substituting equation (6) into equation (2), i.e.:

L(1-cos 2α)＜2λF² (2)

in a preferred embodiment of the present invention, considering the influence of system defocus on the image quality, the compensation method of the present invention is not limited by the relative aperture theoretically, and considering the restriction of the structure size and the size of the mirror, the optimal applicable range of F/# of the optical path in which the present invention is placed is: f/# ≧ 4.

Fig. 4 is a schematic structural diagram of an optical image motion compensation apparatus according to the present invention, which is arranged in the following manner: the image motion compensation unit 3 is placed in an image space telecentric convergent light path of the optical system, and a diaphragm 1, an imaging lens group 2, the image motion compensation unit 3 and a detector 4 are sequentially arranged along a main optical axis of an incidence direction. The first mirror 31 and the second mirror 32 in the image motion compensation unit 3 are disposed in parallel, and rotate synchronously at a, i.e., the axial distance L between the two mirrors is always a fixed value when performing image motion compensation.

It should be noted that, since the present embodiment mainly emphasizes the arrangement of the image motion compensation unit 3, the imaging lens group 2 is replaced by an ideal optical system.

In another embodiment of the present invention, the design optical system specifications are as follows:

the working wave band is as follows: 486nm to 656 nm;

focal length: 150 mm;

f number: 10;

distance L between the first mirror 31 and the second mirror 32: 20 mm.

The correspondence relationship between the field change Δ W due to the target position and the mirror rotation angle α is shown in table 1:

TABLE 1

As shown in fig. 5a, 5b, and 5c, the MTF of the system is close to the diffraction limit in all three cases, which shows that the image motion compensation apparatus of the present invention can perform good image motion compensation.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

The above embodiments of the present invention should not be construed as limiting the scope of the present invention. Any other corresponding changes and modifications made according to the technical idea of the present invention should be included in the protection scope of the claims of the present invention.