Projection optical systems and electronic devices

Abstract

This application relates to a projection optical system and an electronic device. The projection optical system, from the light-emitting side to the light-receiving side, includes a first lens with positive optical power, a second lens with negative optical power, a third lens group with positive optical power, and a fourth lens with positive optical power. The first lens has a convex light-emitting surface and a concave light-receiving surface; the second lens has both concave light-emitting and light-receiving surfaces; the third lens group includes at least three lenses with optical power; and the fourth lens has both convex light-emitting and light-receiving surfaces. Both the second lens and the third lens group are configured to move between the first and fourth lenses along the optical axis. The projection optical system provided in this application adjusts the focal length of the projection optical system by changing the distance between the second and first lenses along the optical axis, and compensates for the zoom of the second lens by adjusting the distance between the third lens group and the second lens, thereby improving image quality.

Description

Technical Field

[0001] This application relates to the field of optical equipment technology, and in particular to projection optical systems and electronic devices. Background Technology

[0002] Projection devices equipped with projection optics systems, such as projectors, spotlights, and advertising lights, are widely used in various scenarios. These devices project light sources onto patterns such as film, and then project the patterns onto the target using the projection optics system to create a clear image.

[0003] The projection optical system in the related technology has poor image quality when using the zoom function. Summary of the Invention

[0004] Therefore, it is necessary to provide a projection optical system and electronic device to address the problem of poor image quality in projection optical systems when using zoom functions in related technologies.

[0005] A projection optical system, the projection optical system comprising, from the light-emitting side to the light-incident side:

[0006] A first lens with positive optical power, wherein the light-emitting surface of the first lens is convex and the light-incident surface is concave;

[0007] A second lens with negative optical power, wherein both the light-emitting surface and the light-receiving surface of the second lens are concave.

[0008] A third lens group having positive optical power, the third lens group comprising at least three lenses having optical power; and,

[0009] A fourth lens with positive optical power, wherein both the light-emitting surface and the light-receiving surface of the fourth lens are convex.

[0010] Both the second lens and the third lens group are configured to move along the optical axis between the first lens and the fourth lens.

[0011] This application provides a projection optical system with a first lens of positive optical power and a second lens of negative optical power. The second lens is movable relative to the first lens along the optical axis, changing the distance between the second and first lenses on the optical axis, thereby adjusting the focal length of the projection optical system. The projection optical system also includes a third lens group and a fourth lens. The first lens, second lens, third lens group, and fourth lens are arranged sequentially from the light-emitting side to the light-receiving side along the optical axis, and the light beam passes through the fourth lens, third lens group, second lens, and first lens in sequence. The third lens group is movable relative to the first lens along the optical axis, thereby adjusting the distance between the second and third lens groups on the optical axis, and thus adjusting the change in the beam focusing position caused by the movement of the second lens, i.e., compensating for the zoom of the second lens, improving image quality and image sharpness. Combined with the fourth lens, the light beam is still focused at the focusing position before the second lens moved, thereby achieving zoom projection. It is understood that by setting up the second lens and the third lens group, the projection optical system of this application can change the focal length and form a clear image, that is, adjust and change the size of the projected image while keeping the projected image clear.

[0012] In one embodiment, the projection optical system includes a lens barrel element, wherein the second lens and the third lens group are coupled to the first lens and the fourth lens through the lens barrel element;

[0013] The lens barrel element is configured such that the amount of movement of one of the second lens and the third lens group along the optical axis is linearly related to the rotation angle of the lens barrel element, while the other of the second lens and the third lens group has a non-linear relationship with the rotation angle of the lens barrel element.

[0014] In one embodiment, the third lens group includes a first positive lens, a first cemented lens, and a first negative lens arranged sequentially along the optical axis. The first cemented lens includes a first sub-lens with negative optical power and a second sub-lens with positive optical power.

[0015] In one embodiment, the light-emitting surface of the first positive lens is convex, and the light-incident surface is convex; and / or

[0016] The first sub-lens has a convex light-emitting surface and a concave light-incident surface; and / or

[0017] The second sub-lens has a convex light-exit surface and a convex light-incident surface; and / or

[0018] The light-emitting surface of the first negative lens is concave, and the light-incident surface is also concave.

[0019] In one embodiment, the total optical length of the projection optical system is TTL1, the distance between the first lens and the second lens is a first air gap d1, the distance between the second lens and the third lens group is a second air gap d2, and the distance between the third lens group and the fourth lens is a third air gap d3.

[0020] The first air gap d1, the second air gap d2, and the third air gap d3 satisfy the formulas: 0.04≤d1 / TTL1≤0.27; 0.03≤d2 / TTL1≤0.38; 0.07≤d3 / TTL1≤0.18.

[0021] In one embodiment, the third lens group includes a second positive lens, a third positive lens, and a second cemented lens arranged sequentially along the optical axis.

[0022] The second cemented lens includes a third sub-lens with negative optical power and a fourth sub-lens with positive optical power.

[0023] In one embodiment, the light-emitting surface of the second positive lens is convex, and the light-incident surface is convex; and / or

[0024] The third positive lens has a convex light-emitting surface and a concave light-incident surface; and / or

[0025] The light-emitting surface of the third sub-lens is concave, and the light-incident surface is concave; and / or

[0026] The light-emitting surface of the fourth sub-lens is convex, and the light-incident surface is concave.

[0027] In one embodiment, the total optical length of the projection optical system is TTL2, the distance between the first lens and the second lens is a fourth air gap g4, the distance between the second lens and the third lens group is a fifth air gap g5, and the distance between the third lens group and the fourth lens is a sixth air gap g6.

[0028] The fourth air gap g4, the fifth air gap g5, and the sixth air gap g6 satisfy the following formulas: 0.05≤g4 / TTL2≤0.22; 0.04≤g5 / TTL2≤0.34; 0.08≤g6 / TTL2≤0.22.

[0029] In one embodiment, the projection optical system further includes an aperture stop disposed between the second lens and the third lens group.

[0030] According to another aspect of this application, an electronic device is provided, including the projection optical system described above. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of a projection optical system according to this application;

[0032] Figure 2 for Figure 1 The diagram shows the structure of the projection optical system at different focal lengths.

[0033] Figure 3 This is a schematic diagram of another projection optical system according to this application;

[0034] Figure 4 for Figure 3 The diagram shows the structure of the projection optical system at different focal lengths.

[0035] Explanation of reference numerals in the attached figures:

[0036] Projection optical system 100;

[0037] First lens 1; Second lens 2;

[0038] Third lens group 3; First positive lens 31; First sub-lens 32; Second sub-lens 33; First negative lens 34; Second positive lens 35; Third positive lens 36; Third sub-lens 37; Fourth sub-lens 38;

[0039] 4. Fourth lens; 5. Aperture; 6. Film; d1. First air gap; d2. Second air gap; d3. Third air gap; g4. Fourth air gap; g5. Fifth air gap; g6. Detailed Implementation

[0040] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0041] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0042] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0043] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0044] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0045] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0046] See Figure 1 and Figure 2 As shown, Figure 1 This is a schematic diagram of the structure of a projection optical system 100 according to this application. Figure 2 for Figure 1 The diagram shows the structure of the projection optical system 100 at different focal lengths. This application provides a projection optical system 100, which includes, from the light-emitting side to the light-receiving side, a first lens 1, a second lens 2, a third lens group 3, and a fourth lens 4. The first lens 1 has positive optical power, and its light-emitting surface is convex, while its light-receiving surface is concave. The second lens 2 has negative optical power, and both its light-emitting and light-receiving surfaces are concave. The third lens group 3 has positive optical power and includes at least three lenses with optical power. The fourth lens 4 has positive optical power, and both its light-emitting and light-receiving surfaces are convex. Both the second lens 2 and the third lens group 3 are configured to move between the first lens 1 and the fourth lens 4 along the optical axis.

[0047] It is understood that the projection optical system 100 provided in this application projects a light beam onto a target such as a screen after passing through the film 6 and the projection optical system 100, forming a clear pattern. The projection optical system 100 changes its effective focal length by moving the second lens 2 relative to the first lens 1 along the optical axis, thus achieving a zoom function, or in other words, changing the projection angle of the light beam, or changing the size of the light spot or pattern formed by the projected light beam. Simultaneously, compensation is achieved by moving the third lens group 3 along the optical axis, and in conjunction with the fourth lens 4, the light beam is adjusted to form a clear pattern. That is, the arrangement of the second lens 2 and the third lens group 3 enables the projection image to be zoomed while maintaining a clear image.

[0048] The projection optical system 100 includes a lens barrel element (not shown). A second lens 2 and a third lens group 3 are coupled to a first lens 1 and a fourth lens 4 via the lens barrel element, allowing the second lens 2 and the third lens group 3 to move between the first lens 1 and the fourth lens 4 along the optical axis. The lens barrel element is configured such that the amount of movement of one of the second lens 2 and the third lens group 3 along the optical axis is linearly related to the rotation angle of the lens barrel element, while the other of the second lens 2 and the third lens group 3 has a non-linear relationship with the rotation angle of the lens barrel element.

[0049] In some embodiments, the lens barrel element is configured as a lens barrel with an internal CAM groove, the second lens 2 and the third lens group 3 are disposed in the lens barrel through the CAM groove, and the second lens 2 and the third lens group 3 are adjusted to move along the optical axis by rotating the lens barrel.

[0050] In some embodiments, the relationship between the displacement distance of the second lens 2 and the third lens group 3 along the optical axis and the angle of rotation of the lens barrel can be accurately calculated by simulation software. This allows the rotation angle of the lens barrel to be set according to the calculation results, so that the displacement distance of the second lens 2 and the third lens group 3 along the optical axis can be precisely adjusted accordingly. This enables the coupling of the second lens 2, the third lens group 3 with the first lens 1 and the fourth lens 4, so that while adjusting the focal length of the second lens 2, compensation can be made by the third lens group 3, ensuring that the pattern projected after zooming is clear.

[0051] In some embodiments, the first lens 1 and the fourth lens 4 are disposed at both ends of the lens barrel, and the first lens 1 and the fourth lens 4 are configured to be movable along the optical axis, so that by fine adjustment of the first lens 1 and the fourth lens 4 along the optical axis, the projection pattern edge of the projection optical system 100 is clear under different focal length conditions.

[0052] It is understood that this application achieves zoom functionality by moving the second lens 2 relative to the first lens 1, thereby changing the distance between the two lenses and flexibly adjusting the focus. For example, the zoom magnification of the projection optical system 100 in this application can reach 1.8X or higher. Simultaneously, a third lens group 3 is provided on the light-incident side of the second lens 2 to achieve a compensation function. After the zoom adjustment of the second lens 2 is completed, the third lens group 3 moves along the optical axis to correct the sharpness, distortion, and other characteristics of the image, thereby improving image quality. Furthermore, the image quality can be further improved by fine-tuning the first lens 1 and the fourth lens 4 along the optical axis.

[0053] In some embodiments, see Figure 1 and Figure 2As shown, the projection optical system 100 also includes an aperture stop 5, which is disposed between the second lens 2 and the third lens group 3. The second lens 2 is movable between the first lens 1 and the aperture stop 5 along the optical axis, and the third lens group 3 is movable between the aperture stop 5 and the fourth lens 4 along the optical axis.

[0054] In some embodiments, see Figure 1 and Figure 2 As shown, the third lens group 3 includes a first positive lens 31, a first cemented lens, and a first negative lens 34 arranged sequentially along the optical axis. The first positive lens 31 has positive optical power, and the first negative lens 34 has negative optical power. The first cemented lens includes a first sub-lens 32 with negative optical power and a second sub-lens 33 with positive optical power.

[0055] In this embodiment, such as Figure 1 As shown, the light-incident surface of the first positive lens 31 can be set as a convex surface, and the light-exiting surface can also be set as a convex surface; the light-incident surface of the first sub-lens 32 can be set as a concave surface, and the light-exiting surface can be set as a convex surface; the light-incident surface of the second sub-lens 33 can be set as a convex surface, and the light-exiting surface can be set as a convex surface; the light-incident surface of the first negative lens 34 can be set as a concave surface, and the light-exiting surface can be set as a concave surface.

[0056] Table 1 below shows the parameter information of each lens in the projection optical system 100 in this embodiment. Numbers 1-16 in the table represent the surface numbers of the optical elements arranged sequentially from the light-emitting side to the light-receiving side of the projection optical system 100. Surfaces numbered 9 and 10 are the cementing surfaces of the first sub-lens 32 and the second sub-lens 33 of the first cemented lens of the third lens group 3, respectively. Thickness represents the distance along the optical axis from the corresponding surface to the next surface. Nd is the refractive index of the corresponding lens, and Vd is the Abbe number of the corresponding lens.

[0057] As shown in Table 1, the distance between the first lens 1 and the second lens 2 is the first air gap d1, which is the air gap along the optical axis from the light-emitting side to the second surface and then to the third surface on the light-incident side. Similarly, D4 is the air gap between the second lens 2 and the aperture 5, and D5 is the air gap between the aperture 5 and the third lens group 3. Let the distance between the second lens 2 and the third lens group 3 be the second air gap d2, then d2 = D4 + D5. The distance between the third lens group 3 and the fourth lens 4 is the third air gap d3. d1, D4, D5, and d3 can change as the second lens 2 and the third lens group 3 move along the optical axis.

[0058] Table 1

[0059]

[0060] Table 2 shows the values ​​of the first air gap d1, the air gap D4 between the second lens 2 and the aperture 5, the air gap D5 between the aperture 5 and the third lens group 3, and the third air gap d3 for the focal lengths of the projection optical system 100 in this embodiment, when the focal lengths are 50mm, 35mm, and 24mm. Table 2 also shows the projection angle of the projection optical system 100 at the corresponding focal lengths.

[0061] Table 2

[0062]

[0063] See also Figure 1 As shown in Tables 1 and 2, in this embodiment, the total optical length of the projection optical system 100 of this application is TTL1 = 79.71 mm, the focal length range is adjustable, a film 6 with a diameter of 15 mm is used, and the magnification is 2.1. The focal length f1 satisfies: 24 mm ≤ f1 ≤ 50 mm, and the projection angle is 16.77-35.4 degrees. The first air gap d1 satisfies the formula: 0.04 ≤ d1 / TTL1 ≤ 0.27, where when d1 / TTL1 = 0.04, d1 = 3.5 mm, and the focal length of the projection optical system is 24 mm; when d1 / TTL1 = 0.27, d1 = 21.90, and the focal length of the projection optical system is 50 mm. The second air gap d2 satisfies the formula: 0.03 ≤ d2 / TTL1 ≤ 0.38, where when d2 / TTL1 = 0.03, d2 = D4 + D5 = 2 + 0.38 = 2.38, and the focal length of the projection optical system is 50mm; when d2 / TTL1 = 0.38, d2 = D4 + D5 = 20.40 + 9.56 = 29.96, and the focal length of the projection optical system is 24mm. The third air gap d3 satisfies the formula: 0.07 ≤ d3 / TTL1 ≤ 0.18, where when d3 / TTL1 = 0.07, d3 = 5.24, and the focal length of the projection optical system is 24mm; when d3 / TTL1 = 0.18, d3 = 16.77, and the focal length of the projection optical system is 50mm. That is, by adjusting the size of the corresponding first air gap d1, second air gap d2 and third air gap d3, the projection optical system 100 can be adjusted to different focal lengths to achieve zoom function.

[0064] In some embodiments, see Figure 3 and Figure 4 As shown, Figure 2 This is a schematic diagram of another projection optical system 100 according to this application. Figure 4 for Figure 3The diagram shows the structure of the projection optical system at different focal lengths. In this embodiment, the third lens group 3 includes a second positive lens 35 with positive optical power, a third positive lens 36 with positive optical power, and a second cemented lens arranged sequentially along the optical axis. The second cemented lens includes a third sub-lens 37 with negative optical power and a fourth sub-lens 38 with positive optical power.

[0065] In this embodiment, such as Figure 3 As shown, the light-emitting surface of the second positive lens 35 can be set as a convex surface, and the light-incident surface can be set as a convex surface; the light-emitting surface of the third positive lens 36 can be set as a convex surface, and the light-incident surface can be set as a concave surface; the light-emitting surface of the third sub-lens 37 can be set as a concave surface, and the light-incident surface can be set as a concave surface; and the light-emitting surface of the fourth sub-lens 38 can be set as a convex surface, and the light-incident surface can be set as a concave surface.

[0066] Table 3 below shows the parameter information of each lens in the projection optical system 100 in this embodiment. Numbers 1-16 in the table represent the surface numbers of the optical elements arranged sequentially from the light-emitting side to the light-receiving side of the projection optical system 100. Surfaces numbered 11 and 12 are the cemented surfaces of the third sub-lens 37 and the fourth sub-lens 38 of the second cemented lens of the third lens group 3, therefore their corresponding data are the same. Thickness represents the distance along the optical axis from the corresponding surface to the next surface. Nd is the refractive index of the corresponding lens, and Vd is the Abbe number of the corresponding lens.

[0067] As shown in Table 3, the distance between the first lens 1 and the second lens 2 is the fourth air gap g4, which is the air gap along the optical axis from the light-emitting side to the second surface to the third surface along the light-incident side. G4 is the air gap between the second lens 2 and the aperture 5, and G5 is the air gap between the aperture 5 and the third lens group 3. Let the distance between the second lens 2 and the third lens group 3 be the fifth air gap g5, then g5 = G4 + G5. The distance between the third lens group 3 and the fourth lens 4 is the sixth air gap g6. g4, G4, G5, and g6 can change as the second lens 2 and the third lens group 3 move along the optical axis.

[0068] Table 3

[0069]

[0070] Table 4 shows the values ​​of the fourth air gap g4, the air gap G4 between the second lens 2 and the aperture 5, the air gap G5 between the aperture 5 and the third lens group 3, and the sixth air gap g6 for the focal lengths of the projection optical system 100 in this embodiment, when the focal lengths are 37.5mm, 60mm, and 75mm. Table 4 also shows the projection angle of the projection optical system 100 at the corresponding focal lengths.

[0071] Table 4

[0072]

[0073] See also Figure 3 As shown in Tables 3 and 4, in this embodiment, the total optical length of the projection optical system 100 of this application is TTL2 = 105 mm, a film 6 with a diameter of 25 mm is used, and the magnification is 2. The focal length range is adjustable, and the focal length f2 satisfies: 37.5 mm ≤ f2 ≤ 75 mm, and the projection angle is 18.59-37.59 degrees. In this embodiment, referring to Table 4 above, the fourth air gap g4 satisfies the formula: 0.05 ≤ g4 / TTL2 ≤ 0.22. When g4 / TTL2 = 0.05, g4 = 5.50 mm, and the focal length of the projection optical system is 75 mm. When g4 / TTL2 = 0.22, g4 = 22.97 mm, and the focal length of the projection optical system is 37.5 mm. The fifth air gap g5 satisfies the formula: 0.04 ≤ g5 / TTL2 ≤ 0.34. When g5 / TTL2 = 0.04, g5 = G4 + G5 = 2.50 + 1.50 = 4mm, and the focal length of the projection optical system is 37.5mm. When g5 / TTL2 = 0.34, g5 = G4 + G5 = 19.97 + 16.01 = 35.98mm, and the focal length of the projection optical system is 75mm. The sixth air gap g6 satisfies the formula: 0.08 ≤ g6 / TTL2 ≤ 0.22. When g6 / TTL2 = 0.08, g6 = 8.45mm, and the focal length of the projection optical system is 75mm. When g6 / TTL2 = 0.22, g6 = 22.96mm, and the focal length of the projection optical system is 37.5mm. By adjusting the sizes of the corresponding fourth air gap g4, fifth air gap g5, and sixth air gap g6, zoom adjustment can be achieved. The projected pattern after zooming has high imaging quality due to the setting of the third lens group 3. That is, the setting of the third lens group 3 can keep patterns of different sizes formed by zooming clear.

[0074] This application also provides an electronic device, including the aforementioned projection optical system 100. The electronic device further includes a light source, the light beam provided by which passes sequentially through a film 6, a fourth lens 4, a third lens group 3, a second lens 2, and a first lens 1, and is finally projected onto a corresponding position to form a projection pattern. This application configures the second lens 2 to move relative to the first lens 1 along the optical axis, changing its focal length. Furthermore, by configuring the third lens group 3 to move along the optical axis, the distance between the second lens 2 and the third lens group 3 can be adjusted, thereby achieving the effect of adjusting the image sharpness. It can be understood that, based on the relationship between focal length and field of view, a change in focal length will cause a change in the field of view, thereby changing the projection angle or the size of the projected light spot. The third lens group 3 of this application moves along the optical axis, ensuring that the edges of images of different sizes are sharp when the size of the projected light spot changes, thus achieving high sharpness while maintaining a high zoom ratio.

[0075] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0076] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A projection optical system, characterized in that, The projection optical system comprises seven lenses with optical power, and the projection optical system includes, from the light-emitting side to the light-receiving side, the following: A first lens with positive optical power, wherein the light-emitting surface of the first lens is convex and the light-incident surface is concave; A second lens with negative optical power, wherein both the light-emitting surface and the light-receiving surface of the second lens are concave. A third lens group having positive optical power, the third lens group comprising four lenses having optical power; and, A fourth lens with positive optical power, wherein both the light-emitting surface and the light-receiving surface of the fourth lens are convex. Both the second lens and the third lens group are configured to be movable between the first lens and the fourth lens along the optical axis; in: The third lens group includes a first positive lens, a first cemented lens, and a first negative lens arranged sequentially along the optical axis. The first cemented lens includes a first sub-lens with negative optical power and a second sub-lens with positive optical power. The light-emitting surface and the light-receiving surface of the first positive lens are convex. The light-emitting surface of the first sub-lens is convex, and the light-receiving surface is concave. The light-emitting surface and the light-receiving surface of the second sub-lens are both convex. The light-emitting surface and the light-receiving surface of the first negative lens are both concave. The total optical length of the projection optical system is TTL1, the distance between the first lens and the second lens is the first air gap d1, the distance between the second lens and the third lens group is the second air gap d2, and the distance between the third lens group and the fourth lens is the third air gap d3. The first air gap d1, the second air gap d2, and the third air gap d3 satisfy the following formulas: 0.04≤d1 / TTL1≤0.27; 0.03≤d2 / TTL1≤0.38; 0.07≤d3 / TTL1≤0.18; or, The third lens group includes a second positive lens, a third positive lens, and a second cemented lens arranged sequentially along the optical axis; the second cemented lens includes a third sub-lens with negative optical power and a fourth sub-lens with positive optical power; the light-emitting surface of the second positive lens is convex, and the light-receiving surface is convex; the light-emitting surface of the third positive lens is convex, and the light-receiving surface is concave; the light-emitting surface of the third sub-lens is concave, and the light-receiving surface is concave; the light-emitting surface of the fourth sub-lens is convex, and the light-receiving surface is concave. The total optical length of the projection optical system is TTL2, the distance between the first lens and the second lens is the fourth air gap g4, the distance between the second lens and the third lens group is the fifth air gap g5, and the distance between the third lens group and the fourth lens is the sixth air gap g6. The fourth air gap g4, the fifth air gap g5, and the sixth air gap g6 satisfy the following formulas: 0.05≤g4 / TTL2≤0.22; 0.04≤g5 / TTL2≤0.34; 0.08≤g6 / TTL2≤0.

22.

2. The projection optical system according to claim 1, characterized in that, The projection optical system includes a lens barrel element, and the second lens and the third lens group are coupled to the first lens and the fourth lens through the lens barrel element; The lens barrel element is configured such that the amount of movement of one of the second lens and the third lens group along the optical axis is linearly related to the rotation angle of the lens barrel element, while the other of the second lens and the third lens group has a non-linear relationship with the rotation angle of the lens barrel element.

3. The projection optical system according to claim 2, characterized in that, The first lens and the fourth lens are disposed at both ends of the lens barrel element, and the first lens and the fourth lens are configured to be movable along the optical axis.

4. The projection optical system according to claim 1, characterized in that, When the third lens group includes the first cemented lens, if d1 = 21.9mm, the focal length of the projection optical system is 50mm; if d1 = 13.83mm, the focal length of the projection optical system is 35mm; if d1 = 3.5mm, the focal length of the projection optical system is 24mm.

5. The projection optical system according to claim 1, characterized in that, When the third lens group includes the second cemented lens, if g4 = 22.97mm, the focal length of the projection optical system is 37.5mm; if g4 = 18.17mm, the focal length of the projection optical system is 60mm; if g4 = 5.5mm, the focal length of the projection optical system is 75mm.

6. The projection optical system according to claim 1, characterized in that, The projection optical system further includes an aperture stop, which is disposed between the second lens and the third lens group.

7. The projection optical system according to claim 6, characterized in that, The second lens is configured to move along the optical axis between the first lens and the aperture, and the third lens group is configured to move along the optical axis between the aperture and the fourth lens.

8. An electronic device, characterized in that, Includes the projection optical system as described in any one of claims 1-7.

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