All-reflective panoramic optical system consisting of coaxial mirror group and off-axis mirror group

Abstract

The full reflection panoramic optical system composed of coaxial mirror group and off-axis mirror group belongs to the panoramic imaging optical technology field. The prior art needs to be further miniaturized, large field of view, small blind area and high quality. The even-ogive aspheric coaxial mirror group is located on the object side of the optical system, and the XY polynomial off-axis mirror group is located on the image side of the optical system; in the even-ogive aspheric coaxial mirror group, the large-aperture incident mirror and the small-aperture return mirror both have even-ogive surface type; in the XY polynomial off-axis mirror group, the tangent lines of the vertexes of the incident off-axis mirror, the return off-axis mirror and the exit off-axis mirror are distributed in a triangular shape, and the three mirrors sequentially form a positive-negative-positive focal length structure; the position and attitude of the XY polynomial off-axis mirror group satisfy that the light returned by the small-aperture return mirror can pass through the window between the return off-axis mirror and the exit off-axis mirror and irradiate on the incident off-axis mirror.

Description

Technical Field

[0001] This invention belongs to the field of panoramic imaging optical technology. Background Technology

[0002] A panoramic optical system is a system that uses planar cylindrical projection for instantaneous imaging. Through the refraction and reflection of optical elements, it projects objects within an ultra-large field of view onto a cylindrical surface. This type of optical system can map a 360° view around the optical axis of the imaging optical system onto the corresponding cylindrical surface and compress this view into a ring-shaped image plane. This unique imaging method enables imaging of ultra-hemispherical, ultra-large field-of-view areas.

[0003] Existing ultra-hemispherical panoramic optical systems with extra-large field of view employ either transmissive panoramic ring systems or reflective panoramic telescoping systems, both of which fundamentally include a head unit and a relay system. Currently, improvements to ultra-hemispherical panoramic optical systems with extra-large field of view in the field of panoramic imaging optics have focused on the head unit, neglecting the optimization of the relay system. This current state of research has made it difficult to further reduce the radial and axial distances of ultra-hemispherical panoramic optical systems with extra-large field of view, and the imaging quality cannot meet the requirements of many application areas.

[0004] Below are two examples of existing panoramic optical systems.

[0005] The first is a technical solution disclosed in a Chinese patent application with publication number CN115469436A, entitled "Compact Panoramic Ring Optical System." This solution's panoramic ring head unit consists of two coaxially distributed Q-con aspherical mirrors, and the relay system is a lens group including two cemented doublet lenses and a field lens, serving convergence and aberration correction functions. This solution simplifies the structure and improves image quality while ensuring fabrication feasibility. However, precisely because of its structural limitations, this panoramic ring optical system has a radial distance of 67.5 mm, an axial distance of 55 mm, and a field of view of 42°~82°, which cannot meet current requirements for miniaturization, a large field of view, and a small blind zone in panoramic optical devices.

[0006] The second proposal is from a 2023 dissertation titled "Design of a Q-type Catadioptric Inner Wall Imaging Optical System," uploaded to CNKI (https: / / www.cnki.net / ). This dissertation optimizes the head unit of the panoramic catadioptric system. However, it also fails to address improvements to the relay system. The imaging system has a radial distance of 82mm, an axial distance of 60mm, and an effective field of view of 65°~115°. While the field of view is expanded, it does not meet current requirements for miniaturization and small blind spots in panoramic optical devices.

[0007] In fact, since the relay system of the prior art is a refractive imaging system, it inevitably has aberrations including chromatic aberration and spherical aberration, and imaging quality is the goal that panoramic optical system design always pursues.

[0008] In addition, the existing head unit reflector uses a Q-type surface (including Q-con aspherical surface) for forced optimization. Since the curvature change near the optical axis of the even-order Q-type surface is not smooth enough, it is easy to introduce high-order aberrations during the optimization process, making it difficult to maintain good image quality. Summary of the Invention

[0009] To further miniaturize, expand the field of view, reduce the blind zone, and improve the quality of panoramic imaging optical systems, this invention proposes a technical solution entitled "Total Internal Reflection Panoramic Optical System Composed of Coaxial Mirror Group and Off-Axis Mirror Group".

[0010] The total internal reflection panoramic optical system of the present invention, composed of a coaxial mirror group and an off-axis mirror group, is characterized in that, as Figure 1 , Figure 2 As shown, the even-ogive aspherical coaxial mirror group is located on the object side of the optical system, and the XY polynomial off-axis mirror group is located on the image side of the optical system.

[0011] In the even-ogive aspherical coaxial mirror assembly, such as Figure 1 , Figure 2 As shown, a large-aperture incident light reflector 1-1 receives light from the object side and reflects it to a small-aperture retroreflector 1-2; both reflectors have an even-ogive surface; a window 1-1-1 is opened in the central region of the large-aperture incident light reflector 1-1, and the aperture of the small-aperture retroreflector 1-2 is smaller than the aperture of the large-aperture incident light reflector 1-1 but larger than the aperture of the window 1-1-1; an aperture stop 1-3 is located at the convergence point of the reflected light path of the large-aperture incident light reflector 1-1; and the window 1-1-1 is located at the convergence point of the reflected light path of the small-aperture retroreflector 1-2.

[0012] In an XY polynomial off-axis mirror assembly, such as Figures 1-3 As shown, the tangents at the vertices of the incident off-axis reflector 2-1, the reflecting off-axis reflector 2-2, and the exiting off-axis reflector 2-3 are distributed in a triangular pattern. All three reflectors have a freeform surface defined by an XY polynomial and sequentially form a positive-negative-positive optical power structure. The reflecting off-axis reflector 2-2 is located on the optical path between the incident off-axis reflector 2-1 and its virtual image point p1', while the exiting off-axis reflector 2-3 is located on the optical path between the reflecting off-axis reflector 2-2 and its virtual image point p2'.

[0013] like Figures 1-3As shown, the position and orientation of the XY polynomial off-axis mirror group satisfy the condition that the light reflected by the small-aperture reflecting mirror 1-2 can pass through the window between the reflecting off-axis mirror 2-2 and the exiting off-axis mirror 2-3 and illuminate the incident off-axis mirror 2-1; the light from the object side is reflected twice by the large-aperture incident light reflecting mirror 1-1 and the small-aperture reflecting mirror 1-2, and then reflected three times by the incident off-axis mirror 2-1, the reflecting off-axis mirror 2-2, and the exiting off-axis mirror 2-3, and finally imaged onto the real image point p3' of the exiting off-axis mirror 2-3.

[0014] The imaging process of the total internal reflection panoramic optical system is described below. For example... Figure 1 , Figure 2 As shown, natural light (imaging band is visible light) from the super-hemispherical extra-large field of view first illuminates the large-aperture incident light reflector 1-1. After reflection, it passes through the aperture 1-3 and then enters the small-aperture retroreflector 1-2. After being reflected twice, it enters the XY polynomial off-axis reflector group. Then, it is reflected three times in succession by the incident off-axis reflector 2-1, the retroreflector 2-2, and the exit off-axis reflector 2-3, and finally enters the image plane 3 to complete the panoramic imaging.

[0015] The technical advantage of this invention lies in the fact that the even-ogive aspherical coaxial mirror group, composed of a large-aperture incident light reflector 1-1 and a small-aperture retroreflector 1-2, can quickly gather incident light within a super-hemispherical, extra-large field of view. The even-ogive aspherical surface, in particular, possesses sufficiently strong refractive power and maintains good image quality near the optical axis. In other words, when a panoramic optical system requires significant refraction of light near the optical axis, the reflector surface near the optical axis should exhibit a steeper shape change. The XY polynomial off-axis mirror group, composed of an incident off-axis mirror 2-1, a retroreflector 2-2, and an exit off-axis mirror 2-3, can effectively compensate for and correct the aberrations of the even-ogive aspherical coaxial mirror group. The three off-axis mirrors in the XY polynomial off-axis mirror group are arranged in a triangular configuration, resulting in a compact structure.

[0016] One embodiment of the present invention has a radial distance of 64.33 mm and an axial distance of 44 mm, which is reduced compared to the prior art; it achieves imaging of a super-large field of view with a small blind zone and an effective field of view of 19°~94°. These effects are attributed to the design of the even-ogive aspherical coaxial mirror group, such as the large-aperture incident light reflector 1-1 and the small-aperture folding reflector 1-2 using even-ogive aspherical surfaces, and at most second-order surfaces, the design of the large and small apertures, the adoption of the planar cylindrical projection method, and the internal triangular structure design of the XY polynomial off-axis mirror group.

[0017] Furthermore, the design concept of the even-ogive aspherical surface originates from the E-oval (ogive) curve with good curvature continuity. Its quadratic surface substrate can provide stronger inherent refractive power under the same light-transmitting aperture, while having a more natural and smooth curvature transition. This characteristic makes it more outstanding in controlling light deflection and suppressing aberrations in a large field of view, especially beneficial for improving image quality such as illumination and distortion in the edge field of view. During the imaging process, the large-aperture incident light mirror 1-1 receives natural light from the ultra-hemispherical extra-large field of view and plays a role in rapid focusing. The small-aperture reflecting mirror 1-2 receives light from the large-aperture incident light mirror 1-1, further focuses and performs aberration compensation, so that the light smoothly enters the XY polynomial off-axis mirror group as a relay system. This process has a significant advantage in improving the imaging performance of the panoramic optical system.

[0018] Furthermore, in the off-axis mirror assembly defined by the XY polynomial, the incident off-axis mirror 2-1, the returning off-axis mirror 2-2, and the exiting off-axis mirror 2-3 are arranged in an approximately isosceles triangle, with a positive-negative-positive optical power distribution according to the light path direction. Each mirror is a non-rotationally symmetric freeform surface. Through precise surface curvature adjustment and optical power distribution, off-axis aberrations can be effectively compensated, further improving the imaging quality of the panoramic optical system. During the imaging process, the incident off-axis mirror 2-1 receives the converging light from the head unit and initially adjusts the beam direction, providing a suitable incident angle for subsequent reflection. The returning off-axis mirror 2-2, as a negative optical power element, reverses the light beam, playing a role in aberration equalization and stabilization. The exiting off-axis mirror 2-3 converges the light again, guiding the beam to the image plane to complete the final imaging.

[0019] The technical effect can be verified by testing an example of the present invention:

[0020] like Figures 5-7 As shown, the three figures are the semi-axial distortion curves of the total internal reflection panoramic optical system of the present invention at the defined wavelength. The X-axis represents the normalized field of view, and the Y-axis represents the linear distortion. It can be seen from the three figures that the distortion of the system has been well compensated.

[0021] For example Figures 8-10 As shown, the three figures are the relative illumination curves of the total internal reflection panoramic optical system of the present invention at the defined wavelength. The X-axis represents the normalized field of view, and the Y-axis represents the relative illumination. It can be seen from the three figures that the relative illumination of the system has been well corrected.

[0022] The imaging quality of the total internal reflection panoramic optical system of the present invention can also be verified by the following test of an example of the present invention:

[0023] like Figure 11As shown in the figure, this is a standard spot diagram of the total internal reflection panoramic optical system of the present invention at a reference wavelength of 0.588 μm. The X-axis represents the relative field of view, and the Y-axis represents the root-mean-square spot radius in mm. As can be seen from the figure, the spot radius of this example in multiple fields of view is not significantly different from the Airy disk radius of 2.785 μm, indicating that the spherical aberration of the system is well compensated, resulting in high imaging quality.

[0024] For example Figure 12 As shown, this figure is a graph of the MTF (modulation transfer function) of an optical system, where the X-axis represents the number of line pairs per millimeter. lp / mm The Y-axis represents the MTF value. As can be seen from the figure, at a spatial frequency of 40 lp / mm, the MTF value in all regions except the maximum field of view in the off-axis region can reach above 0.5, which indicates the excellent imaging performance of the system in a large field of view.

[0025] An additional technical advantage of this invention is that, since it is a total internal reflection imaging invention, it can theoretically operate across the entire wavelength range. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure and half-field-of-view (HFOV) optical path of the total internal reflection panoramic optical system of the present invention, which is also included as an abstract figure.

[0027] Figure 2 This is a schematic diagram of the structure and field of view (FOV) optical path of the total internal reflection panoramic optical system of the present invention.

[0028] Figure 3 This is a schematic diagram of the structure and optical path of the XY polynomial off-axis mirror group in the total internal reflection panoramic optical system of the present invention.

[0029] Figure 4 This is a schematic diagram of the structure and optical path of the even-ogive aspherical coaxial mirror group in the total internal reflection panoramic optical system of the present invention.

[0030] Figure 5 This is a curve of the Y-axis positive semi-axis distortion (sagittal plane) of the total internal reflection panoramic optical system of this invention.

[0031] Figure 6 This is a curve of the Y-axis negative half-axis distortion (sagittal plane) of the total internal reflection panoramic optical system of the present invention.

[0032] Figure 7 This is a graph showing the X-axis positive semi-axis distortion (meridian plane) curve of the total internal reflection panoramic optical system of this invention.

[0033] Figure 8 This is a curve showing the relative illumination (sagittal plane) of the positive half-axis of the total internal reflection panoramic optical system of this invention.

[0034] Figure 9 This is a curve showing the relative illumination (sagittal plane) of the Y-axis negative half-axis of the total internal reflection panoramic optical system of this invention.

[0035] Figure 10 This is a graph showing the relative illumination (meridian plane) of the positive half-axis of the X-axis of the total internal reflection panoramic optical system of this invention.

[0036] Figure 11 This is a standard dot matrix diagram of the total internal reflection panoramic optical system of this invention.

[0037] Figure 12 This is the MTF curve of the total internal reflection panoramic optical system of the present invention. Detailed Implementation

[0038] This invention introduces the initial structure calculation method of the relay system into the design of the panoramic optical system. By adjusting the optical power and surface complexity of the five reflective mirrors, the radial and axial distances are shortened while maintaining the image quality of the panoramic optical system, thereby reducing the volume of the panoramic optical system.

[0039] The surface shape of the large-aperture incident light reflector 1-1 and the small-aperture retroreflector 1-2, which constitute the even-ogive aspherical coaxial mirror group, is an even-ogive aspherical surface, using the second-order term at most. This surface shape is defined by the following formula:

[0040] ,

[0041] in:

[0042] ,

[0043] ,

[0044] In the formula: x, y, and z are the three coordinate values ​​of any point on the surface of revolution in the rectangular coordinate system, z is the sagitta of the surface of revolution, which represents the difference between the coordinate values ​​of any point on the surface of revolution and the vertex in the direction of the optical axis of the even-ogive aspherical coaxial mirror group, and r is the radial coordinate of the surface of revolution; is the compensation value, which is the distance between the rotation axis of the complete even-ogive surface and the rotation axis of the tail even-ogive surface; c is the curvature of the vertex of the surface of revolution; k is the conic coefficient of the surface of revolution. The coefficient of the linear term, The coefficient of the quadratic term;

[0045] The expressions for the radius of curvature R and conic coefficient k of the large-aperture incident light reflector 1-1 are as follows:

[0046] ,

[0047] ;

[0048] The expressions for the radius of curvature R and the conic coefficient k of the small-aperture catadioptric mirror 1-2 are as follows:

[0049] ,

[0050] ;

[0051] In the above formula: such as Figure 4 As shown, L1 is the distance between P2 and P3, L2 is the distance between P3 and P1, and L3 is the distance between P1 and P4; P1 is the vertex of the large-aperture incident light reflector 1-1, P2 is the vertex of the small-aperture reflecting mirror 1-2, P4 is the intersection of the extension of the incident natural light at a 90° half-field angle with the optical axis, and P3 is the intersection of the incident natural light after reflection by the large-aperture incident light reflector 1-1 with the optical axis.

[0052] The surface shapes of the incident off-axis mirror 2-1, the reflecting off-axis mirror 2-2, and the exiting off-axis mirror 2-3, which constitute the XY polynomial off-axis mirror group, are free-form surfaces defined by the XY polynomial, which is:

[0053] ,

[0054] In the formula: Z, X, Y are the coordinate values ​​in the Cartesian coordinate system, and n is the order of the XY polynomial, with the highest order term being fourth. These are the polynomial coefficients.

[0055] like Figure 3 As shown, p1, p2, and p3 are the vertices of the incident off-axis mirror 2-1, the reflecting off-axis mirror 2-2, and the exiting off-axis mirror 2-3, respectively. p1' and p2' are the virtual image points of the incident off-axis mirror 2-1 and the reflecting off-axis mirror 2-2, respectively, and p3' is the real image point of the exiting off-axis mirror 2-3. Therefore, the radii of curvature at each vertex of the incident off-axis mirror 2-1, the reflecting off-axis mirror 2-2, and the exiting off-axis mirror 2-3 are... R 1 、R 2 、R 3 Determined by the following formula:

[0056] ,

[0057] ,

[0058] ,

[0059] in, , TA=tanθ 1 ≈tanθ 3 TB=tanθ 2 CA=cosθ 1 ≈cosθ 3 ， CB=cosθ 2 ;

[0060] In the above formula: l Let p1 be the distance from p2. θ 1 θ 2 θ 3 The reflection angles at the vertices of the incident off-axis reflector 2-1, the returning off-axis reflector 2-2, and the exiting off-axis reflector 2-3 are, in order. The normals of the incident off-axis reflector 2-1 and the exiting off-axis reflector 2-3 with respect to the vertex p2 of the returning off-axis reflector 2-2 are approximately symmetrical, and θ1≈θ3.

[0061] The distance from p3 to p1' is 1.5. l , ml Let p2 be the distance from p1'. nl Let m be the distance from p3 to p2', m be a value in the interval [0.8, 1.5], and n be a value in the interval [1, 1.8].

[0062] The radii of curvature at the vertices of the incident off-axis mirror 2-1, the reflecting off-axis mirror 2-2, and the exiting off-axis mirror 2-3 are as described above. R 1 、R 2 、R 3 The three formulas only contain R , θ , l With three variables, it can be seen that the initial structural design of the XY polynomial off-axis mirror assembly involves the distance from p1 to p2. l start, l , θ This determined the positional relationship and orientation of the three reflectors.

[0063] The following is an example of the total internal reflection panoramic optical system of the present invention.

[0064] The specific parameters of each reflector in this example are listed in Table 1.

[0065] Table 1 Specific parameters of each reflector

[0066]

[0067] In the table, the units for radius of curvature R and spacing are mm. By default, the direction from the large-aperture incident mirror 1-1 to the exiting off-axis mirror 2-3 is considered the positive direction of the optical axis. A negative spacing value indicates that the mirror is positioned on the image side of the next mirror, while a positive value indicates that the mirror is positioned on the object side of the next mirror. Originally... R 1 、R 2 、R 3 The value is extremely large. After optimization by optical design software, the final result of this example is set to infinity.

[0068] Distance from p2 to p1' ml of m The value is 1, representing the distance from p3 to p2'. nl of n The value is 1.3.

[0069] The aspherical parameters for this example, even-ogive, are listed in Table 2.

[0070] Table 2. Aspherical parameters of even-ogive

[0071]

[0072] The XY polynomial coefficients in this example The data is listed in Table 3.

[0073] Table 3. Polynomial coefficients of XY data

[0074]

[0075] This example has a focal length of 1.698mm, an F-number of 3.88, an overall optical power of 0.364, a radial distance of 64.33mm, an axial distance of 44mm, and an axis rotationally symmetric field of view range of 19°~94°.

Claims

1. A total internal reflection panoramic optical system consisting of a coaxial mirror group and an off-axis mirror group, characterized in that, The even-ogive aspherical coaxial mirror group is located on the object side of the optical system, and the XY polynomial off-axis mirror group is located on the image side of the optical system. In the even-ogive aspherical coaxial mirror assembly, a large-aperture incident light mirror (1-1) receives light from the object side and reflects it to a small-aperture retroreflector (1-2); both mirrors have an even-ogive surface shape; a window (1-1-1) is opened in the central region of the large-aperture incident light mirror (1-1), and the aperture of the small-aperture retroreflector (1-2) is smaller than the aperture of the large-aperture incident light mirror (1-1) but larger than the aperture of the window (1-1-1); an aperture stop (1-3) is located at the convergence point of the reflected light path of the large-aperture incident light mirror (1-1); the window (1-1-1) is located at the convergence point of the reflected light path of the small-aperture retroreflector (1-2). In the XY polynomial off-axis mirror group, the tangents at the vertices of the incident off-axis mirror (2-1), the reflecting off-axis mirror (2-2), and the exiting off-axis mirror (2-3) are distributed in a triangular pattern. The three mirrors each have a free-form surface defined by the XY polynomial and form a positive-negative-positive optical power structure in sequence. The reflecting off-axis mirror (2-2) is located on the optical path between the incident off-axis mirror (2-1) and the virtual image point p1' of the incident off-axis mirror (2-1), and the exiting off-axis mirror (2-3) is located on the optical path between the reflecting off-axis mirror (2-2) and the virtual image point p2' of the reflecting off-axis mirror (2-2). The position and orientation of the XY polynomial off-axis mirror group satisfy the following conditions: the light reflected by the small-aperture reflecting mirror (1-2) can pass through the window between the reflecting off-axis mirror (2-2) and the exiting off-axis mirror (2-3) and illuminate the incident off-axis mirror (2-1); the light from the object side is reflected twice by the large-aperture incident mirror (1-1) and the small-aperture reflecting mirror (1-2), and then reflected three times by the incident off-axis mirror (2-1), the reflecting off-axis mirror (2-2), and the exiting off-axis mirror (2-3), and finally imaged onto the real image point p3' of the exiting off-axis mirror (2-3).

2. The total internal reflection panoramic optical system comprising a coaxial mirror group and an off-axis mirror group according to claim 1, characterized in that, The large-aperture incident light reflector (1-1) and the small-aperture retroreflector (1-2) constituting the even-ogive aspherical coaxial mirror group have an even-ogive aspherical shape, using the second-order term at most. This shape is defined by the following formula: ， in: ， ， In the formula: x, y, and z are the three coordinate values ​​of any point on the surface of revolution in the rectangular coordinate system, z is the sagitta of the surface of revolution, which represents the difference between the coordinate values ​​of any point on the surface of revolution and the vertex in the direction of the optical axis of the even-ogive aspherical coaxial mirror group, and r is the radial coordinate of the surface of revolution; is the compensation value, which is the distance between the rotation axis of the complete even-ogive surface and the rotation axis of the tail even-ogive surface; c is the curvature of the vertex of the surface of revolution; k is the conic coefficient of the surface of revolution; The coefficient of the linear term, The coefficient of the quadratic term; The expressions for the radius of curvature R and conic coefficient k of the large-aperture incident light reflector (1-1) are as follows: ， ； The expressions for the radius of curvature R and the conic coefficient k of the small-aperture catadioptric mirror (1-2) are as follows: ， ； In the above formula: L1 is the distance between P2 and P3, L2 is the distance between P3 and P1, and L3 is the distance between P1 and P4; P1 is the vertex of the large-aperture incident light reflector (1-1), P2 is the vertex of the small-aperture reflecting mirror (1-2), P4 is the intersection of the extension of the incident natural light at a 90° half-field angle with the optical axis, and P3 is the intersection of the incident natural light after reflection by the large-aperture incident light reflector (1-1) with the optical axis.

3. The total internal reflection panoramic optical system comprising a coaxial mirror group and an off-axis mirror group according to claim 1, characterized in that, The incident off-axis mirror (2-1), the reflecting off-axis mirror (2-2), and the exiting off-axis mirror (2-3) constituting the XY polynomial off-axis mirror group have surface shapes defined by the XY polynomial, which is: ， In the formula: Z, X, Y are the coordinate values ​​in the Cartesian coordinate system, and n is the order of the XY polynomial, with the highest order term being fourth. These are the polynomial coefficients.

4. The total internal reflection panoramic optical system comprising a coaxial mirror group and an off-axis mirror group according to claim 1, characterized in that, p1, p2, and p3 are the vertices of the incident off-axis mirror (2-1), the reflecting off-axis mirror (2-2), and the exiting off-axis mirror (2-3), respectively. p1' and p2' are the virtual image points of the incident off-axis mirror (2-1) and the reflecting off-axis mirror (2-2), respectively. p3' is the real image point of the exiting off-axis mirror (2-3). Therefore, the radii of curvature at each vertex of the incident off-axis mirror (2-1), the reflecting off-axis mirror (2-2), and the exiting off-axis mirror (2-3) are... R 1 、R 2 、R 3 Determined by the following formula: ， ， ， in, , TA=tanθ 1 ≈tanθ 3 TB=tanθ 2 CA=cosθ 1 ≈cosθ 3 , CB= cosθ 2 ; In the above formula: l Let p1 be the distance from p2. θ 1 θ 2 θ 3 The reflection angles at the vertices of the incident off-axis mirror (2-1), the reflecting off-axis mirror (2-2), and the exiting off-axis mirror (2-3) are respectively; the normals of the incident off-axis mirror (2-1) and the exiting off-axis mirror (2-3) are approximately symmetrical with respect to the vertex p2 of the reflecting off-axis mirror (2-2), and θ1≈θ3.

5. The total internal reflection panoramic optical system comprising a coaxial mirror group and an off-axis mirror group according to claim 4, characterized in that, The distance from p3 to p1' is 1.

5. l , ml Let p2 be the distance from p1'. nl Let m be the distance from p3 to p2', m be a value in the interval [0.8, 1.5], and n be a value in the interval [1, 1.8].

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