A four-group zoom optical system

Abstract

A four-group zoom optical system, by dividing the traditional focusing lens group into two, with the fourth lens group 4 being fixedly set as part of the main optical path, effectively corrects system spherical aberration, reduces lens tolerance sensitivity, and improves pattern image quality. At the same time, it reduces the number of lenses in the focusing lens group 3, which helps to solve the problem that the focusing lens group 3 is too sensitive to the precision of sheet metal structure.

Description

Technical Field

[0001] This invention relates to the field of stage lighting technology, and more specifically, to a four-group zoom optical system. Background Technology

[0002] Pattern lights, moving head lights, and projected logo lights used in professional stage, outdoor cultural tourism, and landscape lighting industries typically employ zoom lenses composed of three lens groups: a front fixed group (light-emitting lens group), a magnifying group, and a focusing group. These three-group zoom lenses have been widely used in the field of stage entertainment lighting. The lens design and manufacturing costs are relatively low, and they can generally achieve clear projection of simple patterns with low resolution. They can also achieve a large zoom ratio under long stroke conditions. However, due to the small number of lens groups, they cannot achieve high-definition projection of complex and high-resolution patterns, and they lack the ability to achieve a wide zoom range, fine aberration adjustment, and balance under short stroke conditions. Summary of the Invention

[0003] This invention provides a four-group zoom optical system that solves the above-mentioned problems.

[0004] To address the problems of the prior art, the present invention adopts the following technical solution: A four-group zoom optical system includes four independent lens groups, which are coaxially mounted; the four lens groups include a fourth lens group, a third lens group, a second lens group, and a first lens group arranged sequentially along the principal optical axis. The first lens group is a front-fixed imaging lens group, including a first lens, a second lens, a third lens and a first lens barrel, wherein the first lens is a biconvex lens, the second lens is a plano-convex lens and the third lens is a plano-concave lens; The second lens group is a magnifying lens group, including a fourth lens, a fifth lens, a sixth lens, and a second lens tube, wherein the fourth lens is a plano-concave lens, the fifth lens is a biconcave lens, and the sixth lens is a concave-convex lens. The third lens group is the focusing lens group, which includes the seventh lens, the eighth lens and the third lens barrel, wherein the seventh lens is a plano-convex lens and the eighth lens is a plano-convex lens; The fourth lens group is a rear-fixed imaging lens group, including the ninth lens, the tenth lens, the eleventh lens, the twelfth lens, the thirteenth lens and the fourth lens tube. The ninth lens is a concave-convex lens, the tenth lens is a concave-convex lens, the eleventh lens is a concave-convex lens, the twelfth lens is a concave-convex lens, and the thirteenth lens is a biconvex lens. The first and fourth lens groups are fixed on the main optical axis, while the second and third lens groups are movably mounted on the main optical axis. Zooming is achieved by the relative or opposing movement of the second and third lens groups.

[0005] As a further improvement of the present invention, the total optical length L is 213 mm.

[0006] As a further improvement of the present invention, the system focal length is 40mm-126mm.

[0007] As a further improvement of the present invention, the aperture value is F / 1.5.

[0008] As a further improvement of the present invention, the field of view (FOV) is 10°≤FOV≤30°.

[0009] As a further improvement of the present invention, the stroke L1 of the second mirror group is L1≤47mm.

[0010] As a further improvement of the present invention, the stroke L2 of the third mirror group is L2≤11mm.

[0011] As a further improvement of the present invention, the minimum distance L3 between the third lens and the fourth lens is 3.4 mm, and the minimum distance L4 between the eighth lens and the ninth lens is 7.7 mm.

[0012] As a further improvement of the present invention, an aperture stop is also included, which is located between the sixth lens and the seventh lens.

[0013] As a further improvement of the present invention, the radius of curvature of the light-emitting surface of the fourth lens is 405 mm, and the radius of curvature of the light-incident surface of the fourth lens is 105 mm; the radius of curvature of the light-emitting surface of the fifth lens is -72 mm, and the radius of curvature of the light-incident surface of the fifth lens is 34 mm; the radius of curvature of the light-emitting surface of the sixth lens is 34 mm, and the radius of curvature of the light-incident surface of the sixth lens is 70 mm.

[0014] As a further improvement of the present invention, the radius of curvature of the light-emitting surface of the seventh lens is 378 mm, and the radius of curvature of the light-incident surface of the seventh lens is 66 mm; the radius of curvature of the light-emitting surface of the eighth lens is 58 mm, and the radius of curvature of the light-incident surface of the eighth lens is not limited.

[0015] As a further improvement of the present invention, all lenses in the four lens groups are spherical lenses. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the four mirror groups of the present invention mounted on the main optical axis.

[0017] Figure 2 This is a schematic diagram of the four lens barrels of the present invention being coaxially mounted.

[0018] Figure 3 a is a schematic diagram of the second and third mirror groups moving towards each other in this invention.

[0019] Figure 3 b is a schematic diagram of the relative motion between the second and third mirror groups of the present invention.

[0020] In the diagram: 1-First lens group; 11-First lens; 12-Second lens; 13-Third lens; 14-First lens barrel; 2-Second lens group; 21-Fourth lens; 22-Fifth lens; 23-Sixth lens; 24-Second lens barrel; 3-Third lens group; 31-Seventh lens; 32-Eighth lens; 33-Third lens barrel; 4-Fourth lens group; 41-Ninth lens; 42-Tenth lens; 43-Eleventh lens; 44-Twelfth lens; 45-Thirteenth lens; 46-Fourth lens barrel; 5-Principal axis; 6-Aperture stop; 7-Imaging object; 8-Light source. Detailed Implementation

[0021] Combined with appendix Figure 1 Appendix Figure 2 and attached Figure 3 A four-group zoom optical system includes four independent lens groups, which are coaxially mounted. The four lens groups include a fourth lens group 4, a third lens group 3, a second lens group 2, and a first lens group 1 arranged sequentially along the principal optical axis.

[0022] The first lens group 1 is a front fixed imaging lens group, including a first lens 11, a second lens 12, a third lens 13 and a first lens barrel 14, wherein the first lens 11 is a biconvex lens, the second lens 12 is a plano-convex lens and the third lens 13 is a plano-concave lens; the first lens group 1 can ensure that the image or light spot projected from the first lens group 1 can form a clear and stable image.

[0023] The second lens group 2 is a magnifying lens group, including a fourth lens 21, a fifth lens 22, a sixth lens 23, and a second lens tube 24. The fourth lens 21 is a plano-concave lens, the fifth lens 22 is a biconcave lens, and the sixth lens 23 is a concave-convex lens. All the lenses on the second lens group 2 are concave lenses. Concave lenses have a diverging effect on light. Therefore, the second lens group 2 is mainly used to change the size of the light spot or expand the range of the beam illumination.

[0024] The third lens group 3 is a focusing lens group, including the seventh lens 31, the eighth lens 32 and the third lens barrel 33, wherein the seventh lens 31 is a plano-convex lens and the eighth lens 32 is a plano-convex lens; by adjusting the position of the third lens group 3 on the principal optical axis 5, the focal length of the light emitted from the light source 8 can be changed, thereby achieving precise control over the size and sharpness of the light spot.

[0025] The fourth lens group 4 is a rear-fixed imaging lens group, including the ninth lens 41, the tenth lens 42, the eleventh lens 43, the twelfth lens 44, the thirteenth lens 45 and the fourth lens tube 46. Among them, the ninth lens 41 is a concave-convex lens, the tenth lens 42 is a concave-convex lens, the eleventh lens 43 is a concave-convex lens, the twelfth lens 44 is a concave-convex lens, and the thirteenth lens 45 is a biconvex lens. The first lens group 1 and the fourth lens group 4 are both fixed on the main optical axis 5, while the second lens group 2 and the third lens group 3 are movably mounted on the main optical axis 5. Zooming is achieved through the relative or opposing movement of the second lens group 2 and the third lens group 3. Figure 3 As shown in diagram a, when the second mirror group 2 and the third mirror group 3 move towards each other, the divergence effect of the second mirror group 2 on the light gradually increases, while the distance between the third mirror group 3 and the imaging object 7 gradually decreases. Therefore, the overall focal length of the optical system decreases accordingly. During this process, the light spot formed by the light rays propagating through the optical system gradually increases in size, and the position of this light spot gradually moves closer to the light source 8. Figure 3 As shown in Figure b, when the second mirror group 2 and the third mirror group 3 move relative to each other, the divergence effect of the second mirror group 2 on the light gradually weakens, while the distance between the third mirror group 3 and the imaging object 7 gradually increases. Therefore, the overall focal length of the optical system increases accordingly. During this process, the light spot formed by the light propagating through the optical system gradually decreases, and the location of this light spot gradually moves away from the light source 8.

[0026] Traditional zoom optical systems generally consist of three lens groups: a fixed imaging lens group, a magnifying lens group, and a focusing lens group. These include the first lens group (fixed imaging lens group) and the second lens group (magnifying lens group) mentioned above, and are not significantly different from the first lens group 1 and second lens group 2 described above. The focusing lens group differs significantly from the above. Traditional focusing lens groups have a larger number of lenses and are located between the second lens group (magnifying lens group) and the light source 8. For example, patent CN220603772U mentions that "the third lens group is a focusing lens group, including: a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens, and a third lens barrel." The large number of lenses in the focusing lens group results in a larger overall weight. Furthermore, the focusing lens group requires high precision in its sheet metal structure; low precision can easily lead to issues such as tilt and coaxiality, resulting in a light spot that is half clear and half blurry. Also, because traditional optical systems only have three lens groups, they cannot achieve high-definition projection of complex and high-resolution patterns.

[0027] The focusing lens group 3 in this invention differs from traditional focusing lens groups. In this embodiment, the focusing lens group 3 is the third lens group 3, which contains only two lenses. Compared to traditional focusing lens groups, the number of lenses in the focusing lens group 3 of this invention is greatly reduced. The reduction in the number of lenses simplifies installation, improves the coaxiality of the two lenses, and effectively solves the problem of the focusing lens group 3 being overly sensitive to the precision of structural components. Furthermore, compared to traditional optical systems, an additional lens group is added. Therefore, the system's optical power can be more evenly distributed across the four lens groups, effectively correcting system spherical aberration, reducing lens tolerance sensitivity, and improving image quality.

[0028] The third lens group 3 and the fourth lens group 4 of the present invention are equivalent to splitting the traditional focusing lens group into two parts. The fourth lens group 4 is fixedly set in the main light path as a part of it and cannot be moved.

[0029] More specifically, this invention differs from patent CN220603772U in the following ways: First: The optical system consists of four lens groups, with the addition of a rear fixed imaging lens group 4, and the number of lenses in the optical system has increased by four.

[0030] Second: The number of lenses in focusing lens group 3 has been reduced to two.

[0031] This invention has two beneficial effects: The first beneficial effect is that it increases the number of lenses in the optical system and adds a rear fixed imaging lens group 4, which allows the system's optical power to be more evenly distributed among the four lens groups, effectively corrects system spherical aberration, reduces lens tolerance sensitivity, and improves image quality.

[0032] The second beneficial effect is that it reduces the number of lenses in the focusing lens group 3, which helps to solve the problem that the focusing lens group 3 is too sensitive to the precision of the sheet metal structure.

[0033] As a new implementation method, combined with the appendix Figure 3 The total optical length is 213mm. Traditional optical systems typically have only three lens groups, and their total optical length is between 200-220mm; for example, patent CN220603772U mentions "composed of three independent lens groups, with a total optical length of 210mm." The optical system of this invention consists of four lens groups, that is, one more lens group is added; compared with patent CN220603772U, this invention adds one more lens group without increasing the total optical length, enabling high-definition projection of complex and high-resolution patterns.

[0034] As a new implementation method, combined with the appendix Figure 1 The system focal length is 40mm-126mm. Patent CN220603772U mentions that "the combined focal length is 27mm-132mm". In this embodiment, the system focal length of the present invention is less than the combined focal length mentioned in patent CN220603772U; that is, different focusing needs of the optical system can be achieved without changing the total optical length and with a shorter system focal length; the zoom ratio of the optical system is the ratio between the maximum system focal length and the minimum system focal length, therefore the zoom ratio of the present invention is 3x.

[0035] As a new implementation method, combined with the appendix Figure 1The aperture value is F / 1.5. The aperture value is the ratio between the effective focal length and the effective aperture diameter, used to represent the light transmission capability of an optical system. Compared with patent CN220603772U, the aperture value of this invention is relatively large. When the aperture value is large, the aperture diameter is small, and the depth of field will increase accordingly. Therefore, the range of clear imaging of this invention also increases accordingly. Furthermore, the aperture value must be compatible with the light source 8 to ensure that the light spot formed by the light projected by the optical system is bright and clear.

[0036] As a new implementation method, combined with the appendix Figure 1 The field of view (FOV) is 10° ≤ FOV ≤ 30°. As those skilled in the art will understand, the size of the FOV is related to the focal length of the optical system; the focal length determines the FOV. The longer the focal length, the smaller the FOV; the shorter the focal length, the larger the FOV. In this embodiment, when the system focal length is 41mm, the FOV of the optical system is 30°. At this time, the light rays passing through the optical system have a high degree of divergence, meaning the illumination range is wide, but the illumination distance is short. When the system focal length is 126mm, the FOV of the optical system is 10°. At this time, the illumination range of the light rays projected by the optical system is narrower, but it can illuminate a greater distance.

[0037] As a new implementation method, combined with the appendix Figure 3 The travel distance L1 of the second mirror group 2 is L1≤47mm. When the second mirror group 2 moves towards the light source 8, its divergence effect on the emitted light rays increases, resulting in a larger light spot; conversely, when the second mirror group 2 moves away from the light source 8, its divergence effect on the emitted light rays decreases, resulting in a smaller light spot. The advantage of this embodiment is that traditional second mirror groups typically only achieve clear projection of complex and high-resolution patterns under long travel conditions; while this invention can achieve high-definition projection of complex and high-resolution patterns under short travel conditions.

[0038] As a new implementation method, combined with the appendix Figure 3The travel distance L2 of the third lens group 3 is L2≤11mm. The third lens group 3 is mainly used to adjust the system focal length of the optical system. When the third lens group 3 moves towards the light source 8, the system focal length decreases, and the spot formation position will be relatively closer to the light source 8; at the same time, the system focal length decreases, and the field of view increases relatively, so the size of the formed spot will also increase with the increase of the field of view. When the third lens group 3 moves away from the light source 8, the system focal length increases, and the spot formation position will be relatively farther away from the light source 8; at the same time, the focal length increases, and the field of view decreases relatively, so the size of the formed spot will also decrease with the decrease of the field of view. The beneficial effect of this embodiment is that traditional optical systems can only achieve a large zoom ratio under the condition of a large travel distance, and they cannot perform high-definition projection of complex and high-resolution patterns; while the present invention can achieve a wide zoom range within a short travel distance compared with traditional optical systems, and improves the ability to finely adjust and balance aberrations, enabling high-definition projection of complex and high-resolution patterns.

[0039] As a new implementation method, combined with the appendix Figure 2 and attached Figure 3 The minimum distance L3 between the third lens 13 and the fourth lens 21 is 3.4 mm, and the minimum distance L4 between the eighth lens 32 and the ninth lens 41 is 7.7 mm. The third lens 13 is installed inside the first lens barrel 14, and the fourth lens 21 is installed inside the second lens barrel 24; the eighth lens 32 is located inside the third lens barrel 33, and the ninth lens 41 is located inside the fourth lens barrel 46; the first lens barrel 14 and the fourth lens barrel 46 remain fixed, while the second lens barrel 24 and the third lens barrel 33 move towards each other; at this time, the second lens barrel 24 moves towards the first lens barrel 14, and at the same time, the third lens barrel 33 moves towards the fourth lens barrel 46, until the fourth lens 21 and the third lens 13 in the second lens barrel 24 reach the position of minimum distance, and the eighth lens 32 and the ninth lens 41 in the third lens barrel 33 reach the position of minimum distance; combined with the above, it can be seen that when the fourth lens 21 reaches the position of minimum distance, the fourth lens 21 is within the stroke L1; when the eighth lens 32 reaches the position of minimum distance, the eighth lens 32 is within the stroke L2. As a new implementation method, combined with the appendix Figure 1 It also includes an aperture stop 6, which is located between the sixth lens 23 and the seventh lens 31. In this embodiment, the position of the aperture stop 6 moves with the movement of the third lens group 3, and the maximum diameter of the aperture stop 6 is smaller than the diameter of the seventh lens 31. The aperture stop 6 can change the light flux by adjusting its size, thereby adjusting the brightness of the lighting system. The aperture stop 6 can also prevent light from spilling into non-illuminated areas, reducing light loss and waste.

[0040] As a new implementation method, combined with the appendix Figure 3The radius of curvature of the light-emitting surface of the fourth lens 21 is 405 mm, and the radius of curvature of the light-receiving surface of the fourth lens 21 is 105 mm; the radius of curvature of the light-emitting surface of the fifth lens 22 is -72 mm, and the radius of curvature of the light-receiving surface of the fifth lens 22 is 34 mm; the radius of curvature of the light-emitting surface of the sixth lens 23 is 34 mm, and the radius of curvature of the light-receiving surface of the sixth lens 23 is 70 mm. There is a gap between the fourth lens 21 and the fifth lens 22, and the incident surface of the fifth lens 22 is in close contact with the exit surface of the sixth lens 23. As those skilled in the art can understand, a smaller radius of curvature makes the concave lens more divergent, meaning that the light will be more divergent after passing through the concave lens; a larger radius of curvature makes the concave lens less divergent. All lenses in the second lens group 2 are concave lenses. Furthermore, the optical power of the fourth lens is negative, and the fourth lens 21 has a divergent effect on the light. The optical powers of the fifth lens 22 and the sixth lens 23 are both negative and have small radii of curvature, so the fifth lens 22 and the sixth lens 23 have a strong divergent effect on the light. Moreover, the second lens group 2, composed of the fourth lens 21, the fifth lens 22, and the sixth lens 23, can achieve precise control over the degree of light divergence, thereby adjusting the size of the light spot. The beneficial effect of this embodiment is that the curvature radius of the lens in the optical system can directly affect the imaging quality of the optical system, effectively diverging the light and forming a clear light spot; and the design of the curvature radius of the lens in the second lens group 2 of the optical system can effectively control the degree of optical distortion within a range of less than or equal to 3.2%.

[0041] As a new implementation method, combined with the appendix Figure 3 The seventh lens 31 has an exit surface radius of 378 mm and an entrance surface radius of 66 mm. The eighth lens 32 has an exit surface radius of 58 mm, while its entrance surface radius is unrestricted. The seventh lens group 31 and the eighth lens group 32 are in contact. A prism is located on the side of the third lens group 3 furthest from the light source 8. As those skilled in the art will understand, the smaller the radius of curvature of a convex lens, the stronger its light-gathering effect; conversely, the larger the radius of curvature, the weaker its light-gathering effect. All lenses in the third lens group 3 are convex lenses. Furthermore, the seventh lens 31 and the eighth lens 32 have positive optical power, thus exhibiting strong light-gathering effects. The third lens group 3, composed of the seventh lens 31 and the eighth lens 32, allows for precise control of light refraction, thereby adjusting the position of the light spot. The setting of the lens radius of curvature parameters in the third lens group 3 can influence the system's focal length. The beneficial effect of this embodiment is that the curvature radius of the lens in the optical system can directly affect the imaging quality of the optical system, and the design of the curvature radius of the lens in the third lens group 3 of the optical system can effectively control the degree of optical distortion within a range of less than or equal to 3.2%.

[0042] Preferably, the setting of the curvature radius of multiple lenses in the optical system is beneficial to fixing the system focal length within the range of 40mm-126mm, so that the degree of optical distortion can be controlled within the range of less than 3.2%, and aberrations can be effectively reduced.

[0043] As a new implementation method, combined with the appendix Figure 3 All four lens groups contain spherical lenses. The advantages of this implementation are that spherical lenses have omnidirectional light-emitting characteristics, capable of uniformly scattering light into the surrounding environment; they also effectively reduce glare, making the light softer; compared to aspherical lenses, spherical lenses are relatively simple to manufacture, thus having a lower cost; their structure is also relatively simple, resulting in higher stability during use.

Claims

1. A four-group zoom optical system, characterized in that, It includes four independent lens groups, which are coaxially mounted; the four lens groups include a fourth lens group, a third lens group, a second lens group, and a first lens group arranged sequentially along the principal optical axis; The first lens group is a front-fixed imaging lens group, including a first lens, a second lens, a third lens and a first lens barrel, wherein the first lens is a biconvex lens, the second lens is a plano-convex lens and the third lens is a plano-concave lens; The second lens group is a magnifying lens group, including a fourth lens, a fifth lens, a sixth lens, and a second lens barrel, wherein the fourth lens is a plano-concave lens, the fifth lens is a biconcave lens, and the sixth lens is a concave-convex lens; The third lens group is a focusing lens group, including a seventh lens, an eighth lens and a third lens barrel, wherein the seventh lens is a plano-convex lens and the eighth lens is a plano-convex lens; The fourth lens group is a rear-fixed imaging lens group, including a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, a thirteenth lens and a fourth lens barrel, wherein the ninth lens is a concave-convex lens, the tenth lens is a concave-convex lens, the eleventh lens is a concave-convex lens, the twelfth lens is a concave-convex lens and the thirteenth lens is a biconvex lens. The first and fourth lens groups are fixed on the main optical axis, while the second and third lens groups are movably mounted on the main optical axis. Zooming is achieved by the relative or opposing movement of the second and third lens groups.

2. The four-group zoom optical system according to claim 1, characterized in that, The total optical length L is 213mm.

3. The four-group zoom optical system according to claim 1, characterized in that, The system's focal length is 40mm-126mm.

4. The four-group zoom optical system according to claim 1, characterized in that, The aperture value is F / 1.

5.

5. A four-group zoom optical system according to claim 1, characterized in that, The field of view (FOV) is 10° ≤ FOV ≤ 30°.

6. A four-group zoom optical system according to claim 1, characterized in that, The travel L1 of the second lens group is L1≤47mm, and the travel L2 of the third lens group is L2≤11mm.

7. A four-group zoom optical system according to claim 1, characterized in that, The minimum distance L3 between the third lens and the fourth lens is 3.4 mm, and the minimum distance L4 between the eighth lens and the ninth lens is 7.7 mm.

8. A four-group zoom optical system according to claim 1, characterized in that, It also includes an aperture stop, which is located between the sixth lens and the seventh lens.

9. A four-group zoom optical system according to claim 1, characterized in that, The radius of curvature of the light-emitting surface of the fourth lens is 405 mm, and the radius of curvature of the light-incident surface of the fourth lens is 105 mm; the radius of curvature of the light-emitting surface of the fifth lens is -72 mm, and the radius of curvature of the light-incident surface of the fifth lens is 34 mm; the radius of curvature of the light-emitting surface of the sixth lens is 34 mm, and the radius of curvature of the light-incident surface of the sixth lens is 70 mm.

10. A four-group zoom optical system according to claim 1, characterized in that, The radius of curvature of the light-emitting surface of the seventh lens is 378 mm, and the radius of curvature of the light-incident surface of the seventh lens is 66 mm; the radius of curvature of the light-emitting surface of the eighth lens is 58 mm, and the radius of curvature of the light-incident surface of the eighth lens is not limited.

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