Cassegrain telescope system

Abstract

The invention belongs to the technical field of optical structures, and particularly relates to a Cassegrain telescope system which comprises a first objective lens, a glued reflector and a plane reflector which share the same optical axis. The first objective lens is a first lens for light to enter the system and is used for converging light beams, and a hollow hole is formed in the middle part of the first objective lens; the glued reflecting mirror is plated with reflecting films, serves as a main reflecting mirror and is formed by gluing three lenses, and the two ends of the rear curved surface of the largest lens are plated with reflecting films; the plane reflector is used as an auxiliary reflector and is used for converging and reflecting the light again into the middle part of the glued reflector; the catadioptric system is formed by introducing the lens group, and the catadioptric system has the advantages of no chromatic aberration and high transmittance of a reflective system and the aberration correction capability of a refractive system.

Description

Technical Field

[0001] This invention belongs to the field of optical structure technology, specifically a Cassegrain telescope system. Background Technology

[0002] The Cassegrain telescope system is a classic reflecting telescope structure, primarily composed of a primary mirror and a secondary mirror. This system typically uses a combination of a concave primary mirror and a convex secondary mirror. Light is reflected by the primary mirror and converges to the secondary mirror, then reflected again and passes through an opening in the center of the primary mirror to reach the eyepiece or imaging device. This ingenious structure achieves a long focal length within a limited physical space, making the system relatively compact.

[0003] When using existing Cassegrain telescope systems, parallel rays emitted from the target first strike the system's primary mirror. The primary mirror reflects and converges these rays, guiding them to a secondary mirror located in the optical path. The secondary mirror then reflects the converged beam a second time, changing its propagation direction and causing it to pass through a central aperture in the primary mirror. Ultimately, the light forms a visible image of the target near the system's focal plane, which can be directly magnified and observed through the eyepiece or recorded by an image sensor at the rear.

[0004] Existing refracting telescopes suffer from chromatic aberration, bulkiness, and difficulties in manufacturing large-aperture telescopes. While reflecting telescopes have solved the chromatic aberration problem, they cannot correct off-axis astigmatism and coma. Some telescopes use a combination of a primary concave mirror and a secondary convex mirror to achieve long focal lengths and paraxial image quality, but off-axis image quality is poorly affected by coma, especially with a sharp drop in image quality at the edges in large field-of-view, large-aperture systems.

[0005] This patent aims to solve the off-axis image quality problem of classic Cassegrain telescopes by introducing a lens group to form a catadioptric system, correcting aberrations and improving image quality.

[0006] Therefore, the present invention provides a Cassegrain telescope system. Summary of the Invention

[0007] In order to overcome the shortcomings of the prior art, at least one technical problem raised in the background art is solved.

[0008] The technical solution adopted by the present invention to solve its technical problem is: a Cassegrain telescope system according to the present invention includes a first objective lens, a cemented mirror and a plane mirror, wherein the first objective lens, the cemented mirror and the plane mirror are coaxial;

[0009] The first objective lens is the first lens into which light enters the system, used to converge the light beam, and the middle part of the first objective lens is provided with a hollow hole;

[0010] The cemented reflector is coated with a reflective film and serves as the main reflector. It is composed of three lenses cemented together, with the largest lens having a reflective film coated at both ends of its rear curved surface.

[0011] The plane mirror serves as a secondary mirror, used to refocus and reflect light into the middle part of the cemented mirror.

[0012] The light rays passing through the first objective lens converge to the cemented mirror, are reflected by the cemented mirror, enter the plane mirror, are reflected again by the plane mirror, and enter the middle part of the cemented mirror. Finally, the light rays are converged by the lens group in the cemented mirror to form an image on the image plane.

[0013] The beneficial effects of this invention are as follows:

[0014] 1. The Cassegrain telescope system described in this invention forms a catadioptric system by introducing a lens group, which combines the advantages of a reflective system (no chromatic aberration and high transmittance) and a refractive system (aberration correction capability).

[0015] 2. The Cassegrain telescope system of the present invention adopts a cemented lens form, which cements the reflector and the lens together. A single lens group has both reflection and refraction functions, and the structure is simple. Attached Figure Description

[0016] The invention will now be further described with reference to the accompanying drawings.

[0017] Figure 1 It is a diagram showing the direction of light within the objective lens;

[0018] Figure 2 It is a dot plot of the imaging system;

[0019] Figure 3 It is the field-of-view view of the imaging system;

[0020] Figure 4 This is an aberration analysis diagram of the imaging system;

[0021] Figure 5 This is a structural diagram of the retroreflector assembly. Detailed Implementation

[0022] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0023] like Figures 1 to 5 As shown in the embodiment of the present invention, a Cassegrain telescope system includes a first objective lens 1, a cemented mirror 2, and a plane mirror 3, wherein the first objective lens 1, the cemented mirror 2, and the plane mirror 3 are coaxial.

[0024] The first objective lens 1 is the first lens into which light enters the system, used to converge the light beam, and the middle part of the first objective lens 1 is provided with a hollow hole;

[0025] The cemented reflector 2 is coated with a reflective film and serves as the main reflector. It is composed of three lenses cemented together, with the largest lens having a reflective film coated at both ends of its rear curved surface.

[0026] The plane mirror 3 serves as a secondary mirror, used to refocus and reflect light into the middle part of the cemented mirror.

[0027] The light rays passing through the first objective lens 1 converge to the cemented mirror 2, are reflected by the cemented mirror, enter the plane mirror 3, are reflected again by the plane mirror 3, and enter the middle part of the cemented mirror 2. Finally, the light rays are converged by the lens group in the cemented mirror 2 to form an image on the image plane.

[0028] The system has an aperture of F-number 2.3, a focal length of 108 mm, an entrance pupil size of 47 mm, a field of view of 9.5°, and a total system length of 61 mm.

[0029] The specific parameters of the lens are shown in the table below:

[0030] lens Radius (mm) Thickness (mm) glass materials Remark surface unlimited unlimited First objective lens 173.78 8.36 H-ZK9B 520 35.88 Glued mirror -167.49 6 H-LAK7A Aperture -236.6 -50.24 MIRROR plane mirror unlimited 41.9 MIRROR Glued mirror 42.658 3.76 H-K9L -42.658 4.58 H-ZBAF50 -167.49 6 H-LAK7A -236.6 4.38 Image unlimited -

[0031] The first objective lens has a radius of curvature of 173.78 mm, a thickness of 8.36 mm, and is made of H-ZK9B glass.

[0032] The cemented mirror comprises three lenses, whose radii of curvature, thickness, and materials are as follows:

[0033] The first objective lens has a radius of curvature of -167.49 mm and a thickness of 6 mm, and is made of H-LAK7A material; the second lens has a radius of curvature of -236.6 mm and a thickness of -50.24 mm, and is made of MIRROR material; the third lens has a radius of curvature of 42.658 mm and a thickness of 3.76 mm, and is made of H-K9L material.

[0034] The cemented reflector also includes a fourth lens with a radius of curvature of -42.658 mm, a thickness of 4.58 mm, and made of H-ZBAF50; a fifth lens with a radius of curvature of -167.49 mm, a thickness of 6 mm, and made of H-LAK7A; and a sixth lens with a radius of curvature of -236.6 mm and a thickness of 4.38 mm.

[0035] The plane mirror has an infinite radius of curvature, a thickness of 41.9 mm, and is made of MIRROR.

[0036] The system is a catadioptric telescope optical system that corrects off-axis aberrations through lens groups.

[0037] The cemented reflector has both reflection and refraction functions in a single lens group.

[0038] The reflex mirror assembly includes: first objective lens 1, cemented mirror 2, plane mirror 3, objective lens tube 4, focusing handwheel ring 5, connecting ring 6, rear mirror cover 7, washer 1 8, washer 2 9, connecting ring retaining ring 10, mirror retaining ring 11, lens spacer 12, lens retaining ring 13, plane mirror frame 14, plane mirror retaining ring 15, guide pin 16, and front mirror cover 17.

[0039] The objective lens barrel 4 serves as the main support for the entire assembly. The cemented mirror 2 is connected to the objective lens barrel 4 via a shaft-hole fit and end-face limiting method. The mirror retainer ring 11 is connected to the objective lens barrel 4 via a threaded connection. Tightening the mirror retainer ring 11 causes one end face to press against the other end face of the cemented mirror 2 to fix the position of the cemented mirror 2 within the objective lens barrel 4. The first objective lens 1 is connected to the plane mirror frame 14 via a hole-shaft fit and end-face limiting method. The plane mirror 3 is connected to the plane mirror frame 14 via a shaft-hole fit and end-face limiting method. The plane mirror retainer ring 15 is connected to the plane mirror frame 14 via a threaded fit and end-face limiting method. The first objective lens 1 is connected to the objective lens barrel 4 via a shaft-hole fit and end-face limiting method. The lens spacer ring 12 is connected to the objective lens barrel 4 via a shaft-hole fit, with one end face contacting the surface of the first objective lens 1 and the other end face contacting the lens retainer ring 13. The lens retaining ring 13 is threaded to the objective lens barrel 4; the connecting ring retaining ring 10 is threaded to the objective lens barrel 4; the washer 2 9 is fitted with the objective lens barrel 4 with a hole-shaft clearance fit; one end face of the washer 2 9 contacts the end face of the connecting ring retaining ring 10 and the other end face contacts the connecting ring 6; the connecting ring 6 is fitted with the objective lens barrel 4 with a hole-shaft fit; the threaded hole on the connecting ring 6 is aligned with the racetrack-shaped guide groove on the objective lens barrel 4; the washer 1 8 is fitted with the connecting ring 6 with a hole-shaft fit end face contact; the focusing handwheel ring 5 is threaded to the connecting ring retaining ring 10; the focusing handwheel ring 5 is fitted with the connecting ring 6 with a hole-shaft fit; the end face of the focusing handwheel ring 5 contacts the end face of the washer 1 8; the guide pin 16 is threaded to the connecting ring 6; the axial surface of the guide pin 16 contacts the racetrack-shaped guide groove surface of the objective lens barrel 4; the end hole ring of the front lens cap 17 is fitted onto the middle cylindrical outer surface of the objective lens barrel 4, and the front hole-shaft fit covers the front end face of the objective lens barrel 4.

[0040] During operation, light enters the first objective lens from the object plane, converges to the cemented mirror, is reflected by the reflective film, reaches the plane mirror, is reflected back to the middle part of the cemented mirror, and finally passes through the lenses in the cemented mirror to form an image on the image plane. The system corrects coma and astigmatism through the lens group, improving the image quality at the edges of the field of view.

[0041] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A Cassegrain telescope system, characterized in that: It includes a first objective lens (1), a cemented mirror (2), and a plane mirror (3), wherein the first objective lens (1), the cemented mirror (2), and the plane mirror (3) are coaxial; The first objective lens (1) is the first lens into which light enters the system, used to converge the light beam, and the middle part of the first objective lens (1) is provided with a hollow hole; The cemented reflector (2) is coated with a reflective film and serves as the main reflector. It is made of three lenses cemented together, with the largest lens having a reflective film coated at both ends of its rear curved surface. The plane mirror (3) serves as a secondary mirror, used to refocus and reflect light into the middle part of the cemented mirror. The light rays passing through the first objective lens (1) converge to the cemented mirror (2), are reflected by the cemented mirror and enter the plane mirror (3), are reflected by the plane mirror (3) and enter the middle part of the cemented mirror (2), and finally converge to form an image on the image plane through the lens group in the cemented mirror (2).

2. The Cassegrain telescope system according to claim 1, characterized in that: The system has an aperture of F-number 2.3, a focal length of 108 mm, an entrance pupil size of 47 mm, a field of view of 9.5°, and a total system length of 61 mm.

3. A Cassegrain telescope system according to claim 2, characterized in that: The first objective lens has a radius of curvature of 173.78 mm and a thickness of 8.36 mm.

4. A Cassegrain telescope system according to claim 1, characterized in that: The cemented mirror comprises three lenses, whose radii of curvature, thickness, and materials are as follows: The first objective lens has a radius of curvature of -167.49 mm and a thickness of 6 mm; The second lens has a radius of curvature of -236.6 mm and a thickness of -50.24 mm; The third lens has a radius of curvature of 42.658 mm and a thickness of 3.76 mm.

5. A Cassegrain telescope system according to claim 1, characterized in that: The cemented reflector also includes a fourth lens with a radius of curvature of -42.658 mm, a thickness of 4.58 mm, and made of H-ZBAF50; a fifth lens with a radius of curvature of -167.49 mm, a thickness of 6 mm, and made of H-LAK7A; and a sixth lens with a radius of curvature of -236.6 mm and a thickness of 4.38 mm.

6. A Cassegrain telescope system according to claim 1, characterized in that: The plane mirror has an infinite radius of curvature and a thickness of 41.9 mm.

7. A Cassegrain telescope system according to claim 1, characterized in that: The system is a catadioptric telescope optical system that corrects off-axis aberrations through lens groups.

8. A Cassegrain telescope system according to claim 1, characterized in that: The cemented reflector has both reflection and refraction functions in a single lens group.

9. A Cassegrain telescope system according to claim 1, characterized in that: It also includes a folding mirror assembly; the folding mirror assembly includes: a first objective lens (1), a cemented mirror (2), a plane mirror (3), an objective lens tube (4), a focusing handwheel ring (5), a connecting ring (6), a rear mirror cover (7), a washer one (8), a washer two (9), a connecting ring retaining ring (10), a mirror retaining ring (11), a lens spacer (12), a lens retaining ring (13), a plane mirror frame (14), a plane mirror retaining ring (15), a guide pin (16), and a front mirror cover (17); The objective lens barrel (4) is the main supporting body of the entire assembly. The cemented mirror (2) is connected to the objective lens barrel (4) by a shaft-hole fit and end face limiting method. The mirror retaining ring (11) is connected to the objective lens barrel (4) by a threaded connection. Tightening the mirror retaining ring (11) causes one end face to press against the other end face of the cemented mirror (2) to fix the position of the cemented mirror (2) inside the objective lens barrel (4). The first objective lens (1) is connected to the plane mirror frame (14) by a hole-shaft fit and end face limiting method. The mirror (3) and the plane mirror frame (14) are connected by a shaft hole fit and end face limiting connection; the plane mirror retaining ring (15) and the plane mirror frame (14) are connected by a thread fit and end face limiting connection; the first objective lens (1) and the objective lens barrel (4) are connected by a shaft hole fit and end face limiting connection; the lens spacer (12) and the objective lens barrel (4) are connected by a shaft hole fit, with one end face contacting the surface of the first objective lens (1) and the other end face contacting the lens retaining ring (13); the lens retaining ring (13) The connection between the connecting ring (6) and the objective lens tube (4) is threaded; the connection between the connecting ring (10) and the objective lens tube (4) is threaded; the connection between the washer (9) and the objective lens tube (4) is clearance-fitted; one end face of the washer (9) contacts the end face of the connecting ring (10) and the other end face contacts the connecting ring (6); the connection between the connecting ring (6) and the objective lens tube (4) is clearance-fitted; the threaded hole on the connecting ring (6) is aligned with the racetrack-shaped guide groove on the objective lens tube (4); the connection between the washer (8) and the connecting ring (6) is clearance-fitted. The focusing handwheel ring (5) and the connecting ring pressure ring (10) are connected by threads, and the focusing handwheel ring (5) and the connecting ring (6) are connected by a hole-shaft fit. The end face of the focusing handwheel ring (5) is in contact with the end face of the washer (8). The guide pin (16) is connected by threads to the connecting ring (6), and the axial surface of the guide pin (16) is in contact with the racetrack-shaped guide groove surface of the objective lens tube (4). The end hole ring of the front lens cover (17) is fitted onto the cylindrical outer surface in the middle of the objective lens tube (4), and the front hole-shaft fit covers the front end face of the objective lens tube (4).

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