TWI878181B - Imaging lens for satellite star tracker - Google Patents

Abstract

An imaging lens for star tracker includes, in order from an object to image, a first lens group (G1) having negative-negative-positive-positive refractive power lenses, a second lens group (G2) having negative refractive power lenses (G21), and the rear group of the second lens group having positive-positive-negative-positive refractive power lenses; and is an optical system in which the aperture stop located in the middle of the lens with symmetric principle; using the Petzval Sum, the number of positive and negative refractive power elements are balance and the pair of L8、L9 with “New Glass” construction to keep a flat image plane; this imaging lens for star tracker having characterizations of large aperture (F/1.4) and large field of view (Full FOV~29∘).

Description

Star-guided optical lens

The invention discloses a star image guiding optical lens, which is particularly applicable to a star image taking lens for positioning artificial satellites.

At present, inertial gyroscopes are the most commonly used navigation equipment in aircraft and ship navigation applications. They have high transient attitude measurement accuracy, but they drift greatly under long-term working conditions, and the errors accumulate over time, requiring external information to correct the errors. The constant star tracker uses the invariance of the relative position of stars in the celestial coordinate system, and there is no attitude accumulation error. Therefore, the constant star guidance optical lens (star tracker) has become the best system for correcting inertial navigation measurement errors. As the main component of the artificial satellite positioning system, the performance of the constant star imaging lens determines the function of artificial satellite positioning. With the booming development of the satellite industry, cameras have a wide range of applications. In low illumination, high temperature change and vacuum environments, higher requirements are placed on imaging lenses with large aperture, high resolution, low distortion and small chief ray angle. In the space environment, the temperature difference is large and the thermal expansion of the lens material is uneven, so two or three-piece glued lens groups cannot be used. The lenses disclosed in the prior art such as US 7209300 and CN108459399 are large aperture lenses, but there are two sets of double glued optical elements in the lens, so they are not suitable for the space environment.

Currently, many optical lenses use a mixture of glass and plastic, such as the lens disclosed in CN 207946588. However, in the space application environment, the high and low temperature changes are large, and plastic materials are not suitable for the space environment. All-glass optical materials must be used.

In modern optical lenses, many optical surfaces use aspherical surfaces to improve performance, such as the lens disclosed in US 7301578 B2. However, in the process of rocket-propelled space vehicles entering space orbit, the space vehicle instruments must withstand severe vibration environments and large changes in high and low temperatures in the space application environment. Therefore, only spherical glass lenses with larger manufacturing tolerances can be used. Another prior art, US 4025169, is a large aperture imaging lens with an aperture of F/1.33. Part of the optical surfaces use aspherical surfaces. Considering that the manufacturing tolerance and the precision of the aspherical surface are relatively sensitive to changes in the temperature of the application environment, aspherical surfaces are not applicable to this case. Therefore, the lens of the present invention is a lens assembly in which each lens element is separated, all glass, and the entire spherical surface is formed.

Among modern space imaging lenses, the star image optical imaging system used for attitude control and positioning of space vehicles uses a catadioptric optical system, such as CN 105467570, but its size is large and the field of view is relatively small, which is not suitable for the application requirements of microsatellite structures with limited size and weight. Therefore, the present invention adopts a two-group lens structure.

A star tracker is an optical device that uses a camera to measure the position of stars. Since the positions of many stars have been measured and located with high precision, star trackers on satellites can be used to determine the satellite's direction or attitude relative to the stars. To do this, the star tracker must acquire images of the stars, measure their observed positions in the satellite's reference frame, and identify the stars so that their positions can be compared to known absolute positions in star catalogs. A star tracker may include a processor for identifying stars by comparing observed star patterns to known star patterns in the sky.

In order to view the complete star image of the stars, the lens needs to have a smaller distortion specification, so the aperture of the lens should be at the optimal position in the center of the lens, and the front and rear groups must have certain symmetry restrictions. Therefore, the lens of the present invention has the characteristic of symmetry. The present invention provides a star image-taking lens, which includes, from the object side to the image side, a first lens group G1 and a second lens group G2. In order to view the complete star image of the stars, a larger field of view is required, and the ratio of the effective focal length of the lens to the diagonal length of the digital sensor (image sensor) of the recording medium must have certain restrictions. Therefore, the lens of the present invention has a feature similar to that of an inversed telephoto, that is, the total length TTL of the lens is greater than the effective focal length EFL of the lens, satisfying (1)

In order for the lens to obtain a relatively flat image field, the lens structure must have a balanced combination of positive refractive lenses and negative lenses. Therefore, the number of convex and concave lenses in the lens of the present invention must be balanced to comply with the Petzval Sum image field formula. (2) To achieve the flat field requirement of a ratio of the curvature radius of the field curvature to the effective focal length of the lens greater than 3 times, the front and rear groups of this lens each have the characteristics of balanced positive and negative refraction. The selection of materials is subject to special restrictions. The L9 of the second group has a thick meniscus shape, which can help reduce the field curvature. According to the Anastigmat New Glass theory of eliminating field curvature, the positive refractive L9 should be made of a material with a high refractive index and low dispersion, while the negative refractive L8 should be made of a material with a low refractive index and high dispersion. (3) Where, Δn, Δ They are the refractive index difference and Abbe number difference between L8 and L9 respectively.

In order to facilitate the capture of distant stars and ensure the consistent traceability of the star tracker lens assembly and focus adjustment verification status, the focus point of the lens is usually set at twice the depth of field near point (Near Point), that is, the focus point is usually set at the hyperfocal distance (Hyperfocal Distance). (4) Where C is the diameter of the blur circle, F/# is the aperture number, and EFL is the effective focal length, which makes the far point of this lens at infinity.

The present invention provides a star image-taking lens, which includes, from the object side to the image side, a first lens group G1, which is composed of a plurality of lens elements G11 with negative refractive power, and a plurality of lens elements G12 with positive refractive power. The ratio of the focal length of the first lens group to the effective focal length of the lens is less than 2.32 and greater than 1.47; 1.47 < FL_G1/EFL < 2.32                                           (5) Wherein, FL_G1 is the front group focal length, and EFL is the effective focal length of the star image-taking lens. The second lens group G2 is composed of a negative refractive power lens element G21, and a plurality of positive, positive, negative, and positive refractive power lens element groups G22 to form a rear group. The ratio of the focal length of the second lens group to the effective focal length of the star-guided optical lens is less than 0.92 and greater than 0.76; 0.76 ＜ FL_G2/EFL ＜ 0.92                                (6) Since the refractive power of the front lens group is lower than that of the rear lens group, the lens structure of the two lens groups has a slight inversed telephoto feature, which can obtain the advantages of a larger field of view and a larger aperture.

The ratio of the first negative lens element G21 of the second lens group of the star-guided optical lens to the effective focal length of the lens is less than -0.59 and greater than -0.71. -0.71 < FL_G21/EFL < -0.59                            (7) Wherein, FL_G21 is the focal length of the negative refractive power lens of the rear group. The rest of the rear group is composed of a plurality of lens elements G22, and the ratio of the focal length of the rear group G22 of the second lens group to the effective focal length of the star-guided optical lens is less than 0.55 and greater than 0.45. 0.45 ＜ FL_G22/EFL ＜ 0.55                                      (8) Wherein, FL_G22 is the focal length of the multiple lens elements with positive refractive power in the rear group.

Embodiment 1

FIG1 is a best embodiment 1 of the present invention, which is a 2-group 9-lens lens, wherein the first lens group, from the object side 100 to the image side 200, has the first lens group G1: four lenses with negative, negative, positive, and positive refractive power; diaphragm; the second lens group G2: five lenses with negative, positive, positive, negative, and positive refractive power. The wavelength applicable to the lens of the best embodiment 1 is greater than 0.4 microns and less than 1.0 microns. The aperture number (F-number) of Example 1 is 1.4; the effective focal length is 16.2mm, wherein the focal length of the first lens group G1 is 35.8mm, and the ratio of the effective focal length is 2.21, wherein the focal length of the front negative lens G21 of the second lens group is -10.6mm, and the ratio of the effective focal length of the lens is -0.65; and wherein the focal length of the rear refractive lens group G22 of the second lens group is 7.7mm, and the ratio of the effective focal length of the lens is 0.48.

FIG2 is a ray tracing diagram of the lens of the best embodiment 1 of the present case, which shows that the focusing performance of the lens is good. FIG3 is a longitudinal spherical aberration diagram, astigmatism and field curvature diagram, and distortion diagram of the lens of the best embodiment 1. From FIG4, the resolution of the lens of the best embodiment 1 is greater than 25% when there are 75 pairs of black and white lines per millimeter. FIG5 is an MTF diagram of the lens of the best embodiment 1 through the focal plane for different fields of view, showing that the peak of the MTF is very concentrated.

The detailed radius of curvature, thickness, refractive index and Abbe number of the lens of Example 1 are all shown in Table 1. The first column in Table 1 is the lens number, the second column is the number of the lens surface, the third column is the lens surface characteristics are all spherical, no aspherical surface is used, the fourth column is the radius of curvature of the lens surface number, the fifth column is the lens thickness or air thickness behind the lens surface, the sixth column is the glass material behind the lens surface number, and the Glass Code shows the conventional representation of the glass material. The first 3 digits of the Glass Code are the 3 digits after the decimal point of the glass refractive index n-1, and the last 3 digits of the Glass Code are the dispersion parameter Vd *10. Table 1 The best example 1 of this case is a 2-group 9-element lens. Effective focal length 16.2mm, aperture F/1.4, FOV=28∘ Optical component number Optical surface number Surface morphology Radius of curvature [mm] Thickness spacing[mm] Glass Material Code L1 S1 Sphere 71.454 8.00 458.677 S2 Sphere 26.120 3.50 L2 S3 Sphere 209.638 1.00 740.277 S4 Sphere 23.976 0.97 L3 S5 Sphere 26.222 7.05 882.407 S6 Sphere -55.359 0.30 L4 S7 Sphere 19.753 4.23 834.427 S8 Sphere 25.547 9.78 STOP S9 Sphere Infinity 1.32 L5 S10 Sphere -11.697 1.00 672.320 S11 Sphere 18.126 1.08 L6 S12 Sphere 71.441 4.45 743.493 S13 Sphere -12.709 0.30 L7 S14 Sphere 12.026 5.24 691.548 S15 Sphere -52.750 0.30 L8 S16 Sphere 74.097 1.00 717.295 S17 Sphere 7.363 0.97 L9 S18 Sphere 8.701 6.66 882.407 S19 Sphere 23.705 2.50 CG Cover Glass Sphere Infinity 0.4 523.544 Sphere Infinity 0.125 IMG Sphere Infinity 0 Embodiment 2

FIG6 is a best embodiment 2 of the present invention, which is a 2-group 9-lens lens, wherein the first lens group, from the object side 100 to the image side 200, sequentially comprises the first lens group G1: four lenses of negative, negative, positive, and positive refractive power; diaphragm; the second lens group G2: five lenses of negative, positive, positive, negative, and positive refractive power. The wavelength applicable to the lens of the best embodiment 2 is greater than 0.4 microns and less than 1.0 microns. The aperture number (F-number) of Example 2 is 1.4; the effective focal length is 16.2mm, wherein the focal length of the first lens group G1 is 26.98mm, and the ratio of the effective focal length is 1.66, wherein the focal length of the front negative lens G21 of the second lens group is -10.6mm, and the ratio of the effective focal length of the lens is -0.65; and wherein the focal length of the rear refractive lens group G22 of the second lens group is 8.2mm, and the ratio of the effective focal length of the lens is 0.51.

FIG7 is a ray tracing diagram of the lens of the best embodiment 2 of this case, which shows that the focusing performance of the lens is good. FIG8 is a longitudinal spherical aberration diagram, astigmatism and field curvature diagram, and distortion diagram of the lens of the best embodiment 2. From FIG9, the resolution of the lens of the best embodiment 2 is greater than 25% when there are 75 pairs of black and white lines per millimeter. FIG10 is an MTF diagram of each different field of view of the lens of the best embodiment 2 through the focal plane, showing that the peak of the MTF is very concentrated.

The detailed curvature radius, thickness, refractive index and Abbe number of the lens of Example 2 are shown in Table 2. Table 2 The best example 2 of this case is a lens with 2 groups and 9 elements. Effective focal length 16.2mm, aperture F/1.4, FOV=28∘ Optical component number Optical surface number Surface morphology Radius of curvature [mm] Thickness spacing[mm] Glass Material Code L1 S1 Sphere 18.374 9.00 698.301 S2 Sphere 11.450 4.47 L2 S3 Sphere -1343.501 1.00 846.237 S4 Sphere 17.195 0.83 L3 S5 Sphere 18.437 6.09 882.407 S6 Sphere -31.527 0.30 L4 S7 Sphere 14.413 3.98 846.237 S8 Sphere 20.166 3.55 STOP S9 Sphere Infinity 1.16 L5 S10 Sphere -16.761 1.00 717.295 S11 Sphere 13.767 1.25 L6 S12 Sphere 356.464 3.95 882.407 S13 Sphere -15.111 0.30 L7 S14 Sphere 14.013 5.05 691.548 S15 Sphere -22.562 0.30 L8 S16 Sphere 999.630 1.00 740.277 S17 Sphere 7.863 0.90 L9 S18 Sphere 8.963 6.22 882.407 S19 Sphere 29.950 2.5 CG Cover Glass Sphere Infinity 0.4 523.544 Sphere Infinity 0.125 IMG Sphere Infinity 0 Embodiment 3

FIG11 is a best embodiment 3 of the present invention, which is a 2-group 9-lens lens, wherein the first lens group, from the object side 100 to the image side 200, has the first lens group G1: four lenses with negative, negative, positive, and positive refractive power; diaphragm; the second lens group G2: five lenses with negative, positive, positive, negative, and positive refractive power. The wavelength applicable to the lens of the best embodiment 3 is greater than 0.4 microns and less than 1.0 microns. The aperture number (F-number) of Example 3 is 1.4; the effective focal length is 16.2mm, wherein the focal length of the first lens group G1 is 33.5mm, and the ratio of the effective focal length is 2.06; wherein the focal length of the front negative lens G21 of the second lens group is -10.1mm, and the ratio of the effective focal length of the lens is -0.62; and wherein the focal length of the rear refractive lens group G22 of the second lens group is 7.7mm, and the ratio of the effective focal length of the lens is 0.47.

FIG12 is a ray tracing diagram of the lens of the best embodiment 3 of the present case, which shows that the focusing performance of the lens is good. FIG13 is a longitudinal spherical aberration diagram, astigmatism and field curvature diagram, and distortion diagram of the lens of the best embodiment 3. From FIG14, the resolution of the lens of the best embodiment 3 is greater than 25% when there are 75 pairs of black and white lines per millimeter. FIG15 is an MTF diagram of each different field of view of the lens of the best embodiment 3 through the focal plane, showing that the peak of the MTF is very concentrated.

The detailed curvature radius, thickness, refractive index and Abbe number of the lens of Example 3 are shown in Table 3. Table 3 The best example 3 of this case is a lens with 2 groups and 9 elements. Effective focal length 16.2mm, aperture F/1.4, FOV=28∘ Optical component number Optical surface number Surface morphology Radius of curvature [mm] Thickness spacing [mm] Glass Material Code L1 S1 Sphere 26.599 8.00 516.641 S2 Sphere 15.585 3.98 L2 S3 Sphere 214.188 1.00 846.237 S4 Sphere 21.615 0.83 L3 S5 Sphere 22.305 6.54 882.407 S6 Sphere -42.894 0.30 L4 S7 Sphere 16.474 4.01 846.237 S8 Sphere 19.750 6.65 STOP S9 Sphere Infinity 1.30 L5 S10 Sphere -12.464 1.00 717.295 S11 Sphere 17.133 1.07 L6 S12 Sphere 59.217 4.39 882.407 S13 Sphere -13.516 0.30 L7 S14 Sphere 12.574 5.31 691.548 S15 Sphere -21.708 0.30 L8 S16 Sphere -29.838 1.00 717.295 S17 Sphere 7.722 0.90 L9 S18 Sphere 8.907 6.19 882.407 S19 Sphere 34.517 2.50 CG Cover Glass Sphere Infinity 0.4 523.544 Sphere Infinity 0.125 IMG Sphere Infinity 0 Embodiment 4

FIG16 is a best embodiment 4 of the present invention, which is a 2-group 9-lens lens, wherein the first lens group, from the object side 100 to the image side 200, has the first lens group G1: four lenses with negative, negative, positive, and positive refractive power; diaphragm; the second lens group G2: five lenses with negative, positive, positive, negative, and positive refractive power. The wavelength applicable to the lens of the best embodiment 4 is greater than 0.4 microns and less than 1.0 microns. The aperture number (F-number) of Example 4 is 1.4; the effective focal length is 16.2mm, wherein the focal length of the first lens group G1 is 25.2mm and the ratio of the effective focal length is 1.55, wherein the focal length of the front negative lens G21 of the second lens group is -10.97mm and the ratio of the effective focal length of the lens is -0.68; and wherein the focal length of the rear refractive lens group G22 of the second lens group is 8.4mm and the ratio of the effective focal length of the lens is 0.52.

FIG17 is a ray tracing diagram of the lens of the best embodiment 4 of the present case, which shows that the focusing performance of the lens is good. FIG18 is a longitudinal spherical aberration diagram, astigmatism and field curvature diagram, and distortion diagram of the lens of the best embodiment 4. From FIG19, the resolution of the lens of the best embodiment 4 is greater than 25% when there are 75 pairs of black and white lines per millimeter. FIG20 is an MTF diagram of the lens of the best embodiment 4 through the focal plane for different fields of view, showing that the peak of the MTF is very concentrated.

The detailed curvature radius, thickness, refractive index and Abbe number of the lens of Example 4 are shown in Table 4. Table 4 The best example 4 of this case is a lens with 2 groups and 9 elements. Effective focal length 16.2mm, aperture F/1.4, FOV=28∘ Optical component number Optical surface number Surface morphology Radius of curvature [mm] Thickness spacing [mm] Glass Material Code L1 S1 Sphere 16.402 9.86 790.266 S2 Sphere 9.898 4.41 L2 S3 Sphere 450.687 1.42 846.237 S4 Sphere 14.362 0.84 L3 S5 Sphere 15.834 5.83 788.473 S6 Sphere -25.457 0.30 L4 S7 Sphere 13.048 3.92 846.237 S8 Sphere 20.542 2.36 STOP S9 Sphere Infinity 1.11 L5 S10 Sphere -19.978 1.00 728.284 S11 Sphere 13.130 1.35 L6 S12 Sphere -108.842 3.81 882.407 S13 Sphere -15.824 0.30 L7 S14 Sphere 15.555 4.77 691.548 S15 Sphere -24.431 0.30 L8 S16 Sphere 29.947 1.00 728.284 S17 Sphere 7.825 0.87 L9 S18 Sphere 8.595 6.18 785.442 S19 Sphere 24.033 2.50 CG Cover Glass Sphere Infinity 0.4 523.544 Sphere Infinity 0.125 IMG Sphere Infinity 0 Embodiment 5

FIG. 21 shows the best embodiment 5 of the present invention, which is a 2-group 9-lens lens, wherein the first lens group, from the object side 100 to the image side 200, has the first lens group (G1): four lenses with negative, negative, positive, and positive refractive power; diaphragm; the second lens group (G2): five lenses with negative, positive, positive, negative, and positive refractive power. The wavelength applicable to the lens of the best embodiment 5 is greater than 0.4 microns and less than 1.0 microns. The aperture number (F-number) of Example 5 is 1.4; the effective focal length is 16.2mm, wherein the focal length of the first lens group G1 is 25.7mm and the ratio of the effective focal length is 1.58, wherein the focal length of the front negative lens G21 of the second lens group is -10.96mm and the ratio of the effective focal length of the lens is -0.68; and wherein the focal length of the rear refractive lens group G22 of the second lens group is 8.37mm and the ratio of the effective focal length of the lens is 0.52.

FIG22 is a ray tracing diagram of the lens of the best embodiment 5 of the present case, which shows that the focusing performance of the lens is good. FIG23 is a longitudinal spherical aberration diagram, astigmatism and field curvature diagram, and distortion diagram of the lens of the best embodiment 5. From FIG24, the resolution of the lens of the best embodiment 5 is greater than 25% when there are 75 pairs of black and white lines per millimeter. FIG25 is an MTF diagram of each different field of view of the lens of the best embodiment 5 through the focal plane, showing that the peak of the MTF is very concentrated.

The detailed curvature radius, thickness, refractive index and Abbe number of the lens of Example 5 are shown in Table 5. Table 5 The best example 5 of this case is a lens with 2 groups and 9 elements. Effective focal length 16.2mm, aperture F/1.4, FOV=28∘ Optical component number Optical surface number Surface morphology Radius of curvature [mm] Thickness spacing[mm] Glass Material Code L1 S1 Sphere 17.760 9.14 846.237 S2 Sphere 10.549 3.90 L2 S3 Sphere 81.252 1.17 846.237 S4 Sphere 14.756 0.83 L3 S5 Sphere 15.530 6.21 743.447 S6 Sphere -24.410 0.30 L4 S7 Sphere 12.221 3.94 846.237 S8 Sphere 15.660 2.50 STOP S9 Sphere Infinity 1.07 L5 S10 Sphere -21.100 1.00 728.284 S11 Sphere 12.649 1.33 L6 S12 Sphere -245.528 3.85 882.407 S13 Sphere -15.519 0.30 L7 S14 Sphere 14.324 4.92 691.548 S15 Sphere -23.160 0.30 L8 S16 Sphere 117.768 1.00 728.284 S17 Sphere 8.051 0.87 L9 S18 Sphere 8.959 6.01 882.407 S19 Sphere 26.907 2.50 CG Cover Glass Sphere Infinity 0.4 523.544 Sphere Infinity 0.125 IMG Sphere Infinity 0

Table 4: Summary of focal length structures of various groups in various embodiments of the present invention. First lens group Second lens group FL_G1/EFL FL_G21/EFL FL_G22/EFL Embodiment 1 2.21 -0.65 0.48 Embodiment 2 1.66 -0.65 0.51 Embodiment 3 2.06 -0.62 0.47 Embodiment 4 1.55 -0.68 0.52 Embodiment 5 1.58 -0.68 0.52

Generally, the ratio of the field curvature radius of a lens to its focal length is designed to be 3 times. (diopter) Rp field curvature radius (mm) /EFL Ratio of field curvature radius to focal length Embodiment 1 -16.2 -61.41 -3.78 Embodiment 2 -16.6 -60.01 -3.70 Embodiment 3 -15.9 -62.77 -3.87 Embodiment 4 -18.1 -55.22 -3.40 Embodiment 5 -17.9 -55.64 -3.43 in, is the effective focal length, and Rp/EFL is the ratio of the field curvature radius to the effective focal length. The field curvature radius of the lens of the present invention reaches more than 3.4 times the effective focal length, which is a fairly flat field lens.

The above-mentioned specific embodiments may be partially adjusted in different ways by technical personnel in this field without departing from the principles and limitations of the present invention. The protection scope of the present invention shall be based on the claims and is not limited to the above-mentioned specific embodiments. All embodiments within its scope are subject to the constraints of the present invention.

The structure and technical method of the present invention can be understood by referring to the detailed description of the following embodiments and the accompanying drawings, and the invention purpose mentioned above can be achieved: [Figure 1] Schematic diagram of the structure of the 9 lenses of the best embodiment 1. [Figure 2] Light tracing diagram of the structure of the 9 lenses of the best embodiment 1. [Figure 3] Longitudinal spherical aberration diagram, astigmatism diagram, and distortion diagram of the 9 lenses of the best embodiment 1. [Figure 4] MTF diagram of the 9 lenses of the best embodiment 1. [Figure 5] MTF diagram of the 9 lenses of the best embodiment 1 through the focal plane. [Figure 6] Schematic diagram of the structure of the 9 lenses of the best embodiment 2. [Figure 7] Light tracing diagram of the structure of the 9 lenses of the best embodiment 2. [Figure 8]  Longitudinal spherical aberration diagram, astigmatism diagram, and distortion diagram of the 9-lens lens of the best embodiment 2. [Figure 9]  MTF diagram of the 9-lens lens of the best embodiment 2. [Figure 10]  MTF diagram of the 9-lens lens of the best embodiment 2 through the focal plane. [Figure 11]  Schematic diagram of the 9-lens structure of the best embodiment 3. [Figure 12]  Ray tracing diagram of the 9-lens structure of the best embodiment 3. [Figure 13]  Longitudinal spherical aberration diagram, astigmatism diagram, and distortion diagram of the 9-lens lens of the best embodiment 3. [Figure 14]  MTF diagram of the 9-lens lens of the best embodiment 3. [Figure 15]  MTF diagram of the 9-lens lens of the best embodiment 3 through the focal plane. [Figure 16] Schematic diagram of the 9-lens structure of the best embodiment 4. [Figure 17] Light tracing diagram of the 9-lens structure of the best embodiment 4. [Figure 18] Longitudinal spherical aberration diagram, astigmatism diagram, and distortion diagram of the 9-lens of the best embodiment 4. [Figure 19] MTF diagram of the 9-lens of the best embodiment 4. [Figure 20] MTF diagram of the 9-lens of the best embodiment 4 through the focal plane. [Figure 21] Schematic diagram of the 9-lens structure of the best embodiment 5. [Figure 22] Light tracing diagram of the 9-lens structure of the best embodiment 5. [Figure 23] Longitudinal spherical aberration diagram, astigmatism diagram, and distortion diagram of the 9-lens of the best embodiment 5. [Figure 24]  MTF diagram of the 9 lenses of the best embodiment 5. [Figure 25]  MTF diagram of the 9 lenses of the best embodiment 5 through the focal plane.

G1: First lens group

G11: Negative group before the first lens group

G12: Positive group after the first lens group

G2: Second lens group

G21: Negative group before the second lens group

G22: Positive group after the second lens group

L1: The first lens of the first lens group

L2: The second lens of the first lens group

L3: The third lens of the first lens group

L4: The 4th lens of the first lens group

L5: The first lens of the second lens group

L6: The second lens of the second lens group

L7: The third lens of the second lens group

L8: The 4th lens of the second lens group

L9: The fifth lens of the second lens group

100: Physical side

200: Like side

t1: Thickness of the first lens of the first lens group

t3: Thickness of the second lens of the first lens group

t5: Thickness of the third lens in the first lens group

t7: Thickness of the 4th lens of the first lens group

t8: The distance from the 4th lens of the first lens group to the aperture

t9: The distance from the aperture to the first lens of the second lens group

t12: Thickness of the second lens of the second lens group

t14: Thickness of the third lens of the second lens group

t16: Thickness of the 4th lens of the second lens group

t18: Thickness of the fifth lens of the second lens group

Claims (9)

A star image guiding optical lens, from the object side to the image side, has: a first lens group, which is composed of a plurality of lens elements, the ratio of the focal length of the first lens group to the effective focal length of the star image guiding optical lens is greater than 1.47 and less than 2.32, wherein the first lens group, from the object side to the image side, has: negative, negative, positive, positive, a total of four lenses; and A second lens group, which is composed of a plurality of lens elements, and the ratio of the focal length of the second lens group to the effective focal length of the star image guidance optical lens is greater than 0.76 and less than 0.92, wherein the second lens group has, from the object side to the image side, five lenses in total: negative, positive, positive, negative, positive. As described in claim 1, the second lens group, from the object side to the image side, sequentially comprises an aperture, a negative lens, and a rear group of the second lens group; the ratio of the focal length of the negative lens to the effective focal length of the star-guided optical lens is greater than -0.71 and less than -0.59; and the rear group of the second lens group, from the object side to the image side, sequentially comprises: the focal lengths of the four lenses, positive, positive, negative, and positive, and the ratio of the effective focal length of the star-guided optical lens is greater than 0.45 and less than 0.55. The star-guided optical lens as described in claim 2, wherein the rear group of the second lens group, from the object side to the image side, has four lenses, namely positive, positive, negative, and positive, in sequence; the third lens is made of a material with a low refractive index and high dispersion; the fourth lens has a thick meniscus shape; the fourth lens is made of a material with a high refractive index and low dispersion, satisfying 0.011 < Δn/ΔVd < 0.015, Δn and ΔVd are respectively the refractive index difference and Abbe number difference between the third lens and the fourth lens. A star-guided optical lens as described in claim 1, wherein the ratio of the total length from the first surface to the image plane of the star-guided optical lens to the effective focal length is less than 3.9 and greater than 3.0. A star-steering optical lens as described in claim 1, wherein the dispersion parameter Vd of the first lens of the first lens group is less than 68.1 and greater than 26.5. As described in claim 1, the aperture number of the star-guided optical lens is greater than 1.4 and less than 1.6. As described in claim 1, the star-guided optical lens has a full field of view angle greater than 25 degrees and less than 28 degrees. The star-steering optical lens as described in claim 1, wherein the applicable wavelength of the lens is greater than 0.4 microns and less than 1.1 microns. A star-steering optical lens as described in claim 1, wherein the resolution of the lens is greater than 25% at a contrast ratio of 75 black and white line pairs per millimeter.