CN201681207U - A coaxial three-reflection optical system used in a full field of view - Google Patents

Abstract

The utility model relates to a coaxial three-reflection optical system used in a full field of view. The CCDs on the image surface of the optical system are arranged as follows: 1) According to the focal length f of the optical system, the field of view angle 2w, the coefficient α of the line blocking system, Calculate the image plane range of the optical system, the scope of the vignetting area and the scope of the non-vignetting area; 2) Calculate the length of the required CCD according to the diameter range _D1 of the vignetting area, assuming that the effective pixel length of a single CCD is d, it should make nd ≥ 2r (n=1, 3, 5, ...), and at the same time, the CCD is arranged in the non-vignetting area along the radial direction of the image plane, so that the CCD participating in the push-broom imaging All are within the vignetting-free zone. The utility model reduces the difficulty of assembly and completely eliminates the aberration of the optical system through the design of the shape of the folding axis reflector and the arrangement of various reflectors; it fully utilizes the field of view of the optical system to expand the ground coverage of the camera width.

Description

A coaxial three-reflection optical system used in a full field of view

technical field

The utility model belongs to the optical application technology, and in particular relates to a coaxial three-reflection optical system with a long focal length and a full field of view.

Background technique:

The coaxial three-mirror optical system commonly used in space cameras now will cause a vignetting area on the image surface due to the central obstruction caused by the secondary mirror to the system. In order to prevent the CCD from being in the vignetting area and resulting in uneven illumination on the image surface, Generally, the partial field of view is used, but the coaxial three-mirror optical system used in the partial field of view will make the effective field of view of the optical system smaller, and the field of view of the optical system cannot be effectively used, which is not conducive to improving the ground width of the camera. wide, reducing the efficiency of the camera system.

Utility model content:

The purpose of the utility model is to solve the defects of the existing coaxial three-mirror optical system used in the partial field of view described in the background art that the effective viewing angle becomes smaller and the width decreases.

However, a folded axis triple-mirror optical system with a long focal length and a full field of view is provided, which fully utilizes the field of view of the optical system. It can meet the use requirements of the space camera imaging in the form of push-broom.

The solution of the utility model is: a coaxial three-reflection optical system used in a full field of view, which is special in that: the CCDs on the image surface of the optical system are arranged as follows:

1) According to f of the focal length of the optical system, the angle of view 2w, and the coefficient α of the line obscuration system, calculate the range of the image plane, the range of the vignetting area and the range of the non-vignetting area of the optical system:

Calculate the image height H of the optical system by formula (1):

H＝f×tan w (1)

The range of the image plane is D:

D=πH ² (2)

The radius r of the vignetting area is calculated by formula (3):

r＝H×α (3)

The range of the vignetting area is:

D ₁ =πr ² (4)

The range of the vignetting-free zone is:

D ₀ =DD ₁ =π(H ² −r ² ); (5)

2) Calculate the length of the required CCD according to the diameter range _D1 of the vignetting area, assuming that the effective pixel length of a single CCD is d, then it should be nd ≥ 2r (n=1, 3, 5, ...), At the same time, the CCDs are arranged in the non-vignetting area along the radial direction of the image plane, so that all the CCDs participating in the push-broom imaging are located in the non-vignetting area.

By rationally arranging the CCDs on the final image plane, the image sensor is completely in the non-vignetting area, which avoids the problem of uneven illumination on the image plane caused by vignetting.

One of the optical systems used: comprising a primary reflector 1 and a secondary reflector 2, composed of a folded axis reflector 4 placed at an angle of 45° to the optical axis of the primary and secondary mirrors, a third reflector 3 and an image plane 5; The special feature of this system is that the refractive axis reflector 4 placed at an angle of 45° with the optical axis of the primary and secondary mirrors not only reflects the incident light of the primary and secondary mirrors, but also reflects the reflected light of the three mirrors from the refractive axis. Pass through the mirror 4, and the light beams of the two must be completely separated without interference. Therefore, the utility model designs a horseshoe-shaped folding axis reflector 4 and its shape is composed of a rectangle with a light hole in the center and a trapezoid. Bottoms are connected, and the bottom width of the trapezoid is equal to the side length of the side of the rectangle connected to it; the reflecting surfaces of these two kinds of folding mirrors 4 are used to reflect the main, The reflected light of the secondary mirror, the light hole in the middle is used to pass through the reflected light of the third reflecting mirror 3.

Because the processing and manufacturing of the above two folding axis mirrors 4 have certain difficulties, the utility model provides another optical system, which still has a main reflector 1, a secondary reflector 2, a third reflector 3, and a refraction mirror. Axis reflector 4 and image plane 5 are formed, and main reflector 1, secondary reflector 2, the 3rd reflector 3 are coaxially arranged, folded axis reflector 4 can be formed in the optical axis of it and the 3rd reflector 3 Place it near the exit pupil at any position within the angle range of 35°～55°.

In order to avoid the secondary occlusion problem, the utility model also provides a third folding axis reflector 4 , which is in the shape of a cuboid with rounded corners.

The utility model reduces the difficulty of assembly and completely eliminates the aberration of the optical system through the design of the shape of the folding axis reflector and the arrangement of various reflectors; the optical system of the utility model is suitable for line The CCD camera with push-broom imaging makes full use of the field of view of the optical system to expand the camera's ground coverage width.

Description of drawings:

Fig. 1 is a schematic diagram of the arrangement of CCDs on the image plane of the optical system of the present invention.

Fig. 2 is the optical path schematic diagram of the present utility model;

Fig. 3 is the outline schematic diagram one of folding axis mirror of the present utility model;

Fig. 4 is the outline schematic diagram II of the folding mirror of the present invention;

Fig. 5 is another kind of optical path schematic diagram of the present utility model;

6 is a schematic diagram of another folding mirror of the optical system of the present invention;

Fig. 7 is the imaging quality of the optical system of the present utility model.

Detailed ways:

Referring to Fig. 1, the utility model relates to a coaxial three-reflection optical system used in a full field of view, and the CCDs on the image surface of the optical system are arranged as follows:

1) According to f of the focal length of the optical system, the angle of view 2w, and the coefficient α of the line obscuration system, calculate the range of the image plane, the range of the vignetting area and the range of the non-vignetting area of the optical system:

Calculate the image height H of the optical system by formula (1):

H＝f×tan w (1)

The range of the image plane is D:

D=πH ² (2)

The radius r of the vignetting area is calculated by formula (3):

r＝H×α (3)

The range of the vignetting area is:

D ₁ =πr ² (4)

The range of the vignetting-free zone is:

D ₀ =DD ₁ =π(H ² −r ² ); (5)

2) Calculate the length of the required CCD according to the diameter range _D1 of the vignetting area, assuming that the effective pixel length of a single CCD is d, then it should be nd ≥ 2r (n=1, 3, 5, ...), At the same time, the CCDs are arranged in the non-vignetting area along the radial direction of the image plane, so that all the CCDs participating in the push-broom imaging are located in the non-vignetting area.

According to the parameters of the optical system, the range of the image plane, the range of the vignetting area and the range of the non-vignetting area of the optical system are calculated. Then calculate the image plane length of the CCD according to the diameter range of the vignetting area, and then make all the CCDs participating in the push-broom imaging be in the non-vignetting area through a reasonable arrangement of the CCDs, so as to effectively use the entire field of view.

Referring to Fig. 2, the coaxial three-mirror optical system used in the full field of view is reflected by the main reflector 1 and the secondary reflector 2, and the optical axis of the main reflector 1 (secondary reflector 2) is placed at an angle of 45°. mirror 4, the third reflector 3 and the image plane 5, wherein the optical axes of the main reflector 1 and the secondary reflector 2 coincide and the secondary reflector 2 is set on the reflected light path of the main reflector 1, and the folding axis reflector 4 is set On the reflection optical path of the secondary reflection mirror 2, the third reflection mirror 3 is arranged on the reflection optical path of the folding axis reflection mirror 4, and the reflected light of the third reflection mirror 3 passes through the middle light hole incident on the reflection surface of the folding axis reflection mirror 4 Go to image surface 5.

Referring to Fig. 3, 4, two kinds of folding axis reflectors 4 of different forms provided by the utility model, wherein, a kind of shape is horseshoe-shaped (the hollow part of horseshoe shape is used as light hole), and another kind of shape is formed by the center The rectangle with the light hole is connected to the bottom of a trapezoid, and the width of the bottom of the trapezoid is equal to the side length of one side of the rectangle connected to it; these two kinds of refractive mirrors The reflection surface of 4 is used to reflect the reflected light of the main reflector 1 (secondary reflector 2 ), and the middle aperture is used to pass the reflected light of the third reflector 3 .

This folding axis reflector 4 will not only reflect the reflected light of the main reflector 1 (secondary reflector 2), but also make the reflected light of the third reflecting mirror 3 pass through the folded axis reflecting mirror 4, and the light beams of the two must be Complete separation cannot interfere. Simultaneously, the folding axis reflector 4 has a certain thickness, so the central light hole arranged on it needs to have a certain outward inclination Q, that is, the light hole is from the reflecting surface of the folding axis reflecting mirror to the back side of the folding axis reflecting mirror. The inclination angle, the calculation formula is as follows:

Q=arctan(H/D)

Where: H is the height of the image plane of the optical system, D is the distance from the exit pupil to the image plane.

Please describe clearly the direction of the inclination angle and mark it in the diagram.

Referring to Figure 5, the field of view layout on the image plane of the optical system still adopts the form of Figure 1, and the optical system is still composed of the main reflector 1, the secondary reflector 2, the third reflector 3, the folding axis reflector 4 and the image surface 5 components, and the main reflector 1, the main reflector 2, and the third reflector 3 are coaxially arranged, which completely eliminates the aberration of the optical system, and the refractive axis reflector 4 can be used in the light between it and the third reflector 3 In the 35°～55° angle range formed by the axis, it is placed near the exit pupil at any position. Here, the folding axis reflector 4 is placed at the exit pupil position, and its size is the same as that of the exit pupil.

Referring to Fig. 6, since the shapes of the above two folding axis reflectors are relatively complex and difficult to manufacture, the application is limited to a certain extent. For this reason, the utility model designs a third mirror on the basis of the optical system shown in Fig. 5 A folded axis reflector of this shape, the folded axis reflector is not only small in size, but also has a relatively simple shape structure. By placing the folded axis reflector near the exit pupil position, the outgoing light of the third reflector can be completely reflected, and at the same time It can avoid blocking the outgoing light of the primary and secondary mirrors, and will not cause the problem of secondary blocking.

Referring to Fig. 7, the imaging quality of the two optical systems of the present invention is close to the diffraction limit, and the imaging quality is intact.

It is worth noting that the two optical systems of the present invention are suitable for linear array push-broom imaging CCD cameras used in a full field of view, making full use of the field of view of the optical system and expanding the ground coverage width of the camera.

Claims (7)

1. A coaxial three-reflection optical system used in a full field of view is characterized in that: the CCD on the image plane of the optical system is arranged as follows: 1) According to f of the focal length of the optical system, the angle of view 2w, and the coefficient α of the line obscuration system, calculate the range of the image plane, the range of the vignetting area and the range of the non-vignetting area of the optical system: Calculate the image height H of the optical system by formula (1): H＝f×tanw (1) The range of the image plane is D: D=πH ² (2) The radius r of the vignetting area is calculated by formula (3): r＝H×α (3) The range of the vignetting area is: D ₁ =πr ² (4) The range of the vignetting-free zone is: D ₀ =DD ₁ =π(H ² −r ² ); (5) 2) Calculate the length of the required CCD according to the diameter range D ₁ of the vignetting area, assuming that the effective pixel length of a single CCD is d, then it should make nd≥2r (n=1, 3, 5,....) , and at the same time, the CCDs are arranged in the non-vignetting area along the radial direction of the image plane, so that all the CCDs participating in the push-broom imaging are located in the non-vignetting area. 2. The coaxial three-reflection optical system used in the full field of view according to claim 1, characterized in that: the system includes a primary reflector, a secondary reflector arranged on the reflected light path of the primary reflector, and a secondary reflector arranged on the secondary reflector. A folded axis reflector on the reflected light path of the reflector and a third reflector arranged on the reflected light path of the folded axis reflector, the optical axes of the primary reflector and the secondary reflector coincide; the reflection of the folded axis reflector A light hole is arranged on the surface, and the refractive axis reflector is set at an angle of 45° to the optical axis of the secondary reflector; the reflected light of the third reflector is incident on the imaging surface through the light hole. 3 . The coaxial three-reflection optical system used in a full field of view according to claim 2 , characterized in that: the folding axis mirror is horseshoe-shaped, and the hollow part of the horseshoe-shape forms a light hole. 4 . 4. The coaxial three-reflection optical system used in the full field of view according to claim 2, characterized in that: the shape of the folding axis mirror is formed by connecting a rectangle with a light hole in the center and a trapezoidal bottom , and the width of the bottom of the trapezoid is equal to the side length of one side of the rectangle connected to it. 5. The coaxial three-reflection optical system used in the full field of view according to claim 3 or 4, wherein the optical hole is from the reflective surface of the folding axis mirror to the back side of the folding axis mirror The inclination angle is Q=arctan(H/D), wherein: H is the height of the image plane of the optical system, and D is the distance from the exit pupil to the image plane. 6. The coaxial three-reflection optical system used in the full field of view according to claim 1, characterized in that: the system includes a primary reflector, a secondary reflector arranged on the reflected light path of the primary reflector, and a secondary reflector arranged on the secondary reflector. The third reflecting mirror on the reflection optical path of the reflecting mirror and the folding axis reflecting mirror arranged on the reflecting optical path of the third reflecting mirror, the optical axes of the main reflecting mirror, the secondary reflecting mirror and the third reflecting mirror coincide; The axis reflection mirror is arranged at the position of the exit pupil, and is placed at an angle of 35°-55° with the optical axis of the third reflection mirror; the size of the axis reflection mirror is the same as that of the exit pupil. 7 . The coaxial three-reflection optical system used in a full field of view according to claim 6 , wherein the shape of the folding axis mirror is a cuboid, and the four corners of the cuboid are all rounded. the

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