Four-group zoom optical system

Abstract

A four-group type zoom optical system comprises four independent lens groups, and the four lens groups are coaxially installed. The four lens sets include the fourth lens set, the third lens set, the second lens set and the first lens set which are sequentially arranged along the main optical axis, a traditional focusing lens set is divided into two, and the fourth lens set 4 serves as a part to be fixedly arranged on the main optical path, so that the system spherical aberration is effectively corrected, the lens tolerance sensitivity is reduced, and the pattern image quality is improved; meanwhile, the number of lenses in the focusing lens group 3 is reduced, and the problem that the focusing lens group 3 is too sensitive to the precision of a metal plate structure is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of stage light, more particularly, to a four-group zoom optical system. BACKGROUND

[0002] The pattern lamp, computer head lamp and projection LOGO lamp used in professional stage, outdoor travel and landscape lighting industry generally use a zoom lens composed of a front fixed group (light-emitting lens group), an amplification group and a focusing group. The zoom lens composed of three groups has been widely used in the field of stage entertainment light, and the lens design and manufacturing cost are relatively low. The zoom lens can basically realize clear projection of simple patterns with low resolution, and can also realize large zoom ratio under the condition of large stroke. However, due to the small number of lens groups, the zoom lens cannot realize high-definition projection of complex and high-resolution patterns, and lacks the ability to realize wide zoom range, fine adjustment and balance of aberration under the condition of short stroke. SUMMARY

[0003] The present application provides a four-group zoom optical system, which solves the above problems.

[0004] To solve the problems of the prior art, the present application adopts the following technical solutions:

[0005] A four-group zoom optical system, comprising four independent lens groups, which are coaxially installed; the four lens groups comprise a fourth lens group, a third lens group, a second lens group and a first lens group arranged in sequence along the main optical axis;

[0006] The first lens group is a front fixed imaging lens group, comprising a first lens, a second lens, a third lens and a first lens barrel, wherein the first lens is a double convex lens, the second lens is a plano-convex lens, and the third lens is a plano-concave lens;

[0007] The second lens group is an amplification lens group, comprising 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 double concave lens, and the sixth lens is a concave-convex lens;

[0008] The third lens group is a focusing lens group, comprising 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;

[0009] The fourth lens group is a rear fixed imaging lens group, comprising 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 double convex lens;

[0010] The first and fourth mirror groups are fixed on the main optical axis, and the second and third mirror groups are movably installed on the main optical axis, and the zooming is realized by the opposite or relative movement of the second and third mirror groups.

[0011] As a further improvement of the present application, the total optical length L is 213 mm.

[0012] As a further improvement of the present application, the system focal length is 40 mm-126 mm.

[0013] As a further improvement of the present application, the aperture coefficient is F / 1.5.

[0014] As a further improvement of the present application, the field of view FOV is 10°≤FOV≤30°.

[0015] As a further improvement of the present application, the stroke L1 of the second mirror group is L1≤47 mm.

[0016] As a further improvement of the present application, the stroke L2 of the third mirror group is L2≤11 mm.

[0017] As a further improvement of the present application, 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.

[0018] As a further improvement of the present application, a diaphragm is further included, and the diaphragm is located between the sixth lens and the seventh lens.

[0019] As a further improvement of the present application, the curvature radius of the light-emitting surface of the fourth lens is 405 mm, the curvature radius of the light-entering surface of the fourth lens is 105 mm; the curvature radius of the light-emitting surface of the fifth lens is -72 mm, the curvature radius of the light-entering surface of the fifth lens is 34 mm; the curvature radius of the light-emitting surface of the sixth lens is 34 mm, and the curvature radius of the light-entering surface of the sixth lens is 70 mm.

[0020] As a further improvement of the present application, the curvature radius of the light-emitting surface of the seventh lens is 378 mm, and the curvature radius of the light-entering surface of the seventh lens is 66 mm; the curvature radius of the light-emitting surface of the eighth lens is 58 mm, and the curvature radius of the light-entering surface of the eighth lens is not limited.

[0021] As a further improvement of the present application, the lenses in the four mirror groups are all spherical lenses. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The schematic diagram for the four mirror groups of the present application installed on the main optical axis.

[0023] Figure 2 The schematic diagram for the coaxial installation of the four lens barrels of the present application.

[0024] Figure 3 Fig. 2 is a schematic diagram of the movement of the second and third mirror groups of the present application.

[0025] Figure 3 Fig. 3 is a schematic diagram of the movement of the second and third mirror groups of the present application. Figure 3 Fig. 4 is a schematic diagram of the movement of the second and third mirror groups of the present application.

[0026] Fig. 1 is a schematic diagram of the four-group zoom optical system of the present application. DETAILED DESCRIPTION

[0027] In combination with Figs. 1, 2, 3 and 4, the four-group zoom optical system comprises four independent mirror groups, which are coaxially arranged; the four mirror groups comprise, in order along the main optical axis, a fourth mirror group 4, a third mirror group 3, a second mirror group 2 and a first mirror group 1. Figure 1 Figure 2 The first mirror group 1 is a front fixed imaging mirror group, which comprises 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 double convex lens, the second lens 12 is a plano-convex lens, and the third lens 13 is a plano-concave lens; the first mirror group 1 can ensure that the light projected from the first mirror group 1 can form a clear and stable image or light spot. Figure 3 The second mirror group 2 is a magnifying mirror group, which comprises a fourth lens 21, a fifth lens 22, a sixth lens 23 and a second lens barrel 24, wherein the fourth lens 21 is a plano-concave lens, the fifth lens 22 is a double concave lens, and the sixth lens 23 is a concave-convex lens; all the lenses arranged on the second mirror group 2 are concave lenses, which have a diverging effect on light, so the second mirror group 2 is mainly used to change the size of the light spot or expand the range of light beam irradiation.

[0028] The third mirror group 3 is a focusing mirror group, which comprises a seventh lens 31, an eighth lens 32 and a 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 mirror group 3 on the main optical axis 5, the focal length of the light emitted from the light source 8 can be changed, thereby realizing accurate control of the size of the light spot and the degree of virtuality.

[0029]

[0030]

[0031] ​​​The fourth lens group 4 is a rear fixed imaging lens group, which comprises a ninth lens 41, a tenth lens 42, an eleventh lens 43, a twelfth lens 44, a thirteenth lens 45 and a fourth lens barrel 46, wherein the ninth lens 41 is a meniscus lens, the tenth lens 42 is a meniscus lens, the eleventh lens 43 is a meniscus lens, the twelfth lens 44 is a meniscus lens, and the thirteenth lens 45 is a double convex lens.

[0032] The first lens group 1 and the fourth lens group 4 are fixed on the main optical axis 5, and the second lens group 2 and the third lens group 3 are movably mounted on the main optical axis 5, and the zooming is realized by the approaching or opposite movement of the second lens group 2 and the third lens group 3. Figure 3 a, when the second lens group 2 and the third lens group 3 move towards each other, the diverging effect of the second lens group 2 on the light rays gradually increases, and the distance between the third lens group 3 and the imaging object 7 gradually decreases. Therefore, the overall focal length of the optical system decreases. In this process, the light spot formed by the light rays propagating through the optical system gradually increases, and the formation position of the light spot gradually approaches the light source 8. Figure 3 b, when the second lens group 2 and the third lens group 3 move away from each other, the diverging effect of the second lens group 2 on the light rays gradually decreases, and the distance between the third lens group 3 and the imaging object 7 gradually increases. Therefore, the overall focal length of the optical system increases. In this process, the light spot formed by the light rays propagating through the optical system gradually decreases, and the formation position of the light spot gradually moves away from the light source 8.

[0033] The conventional zoom optical system generally consists of three lens groups, namely the fixed imaging lens group, the magnifying lens group and the focusing lens group, that is, it includes the first lens group (fixed imaging lens group) and the second lens group (magnifying lens group) mentioned above, and there is little difference between the first lens group 1 and the second lens group 2 mentioned above; the biggest difference from the above is the focusing lens group. In the traditional focusing lens group, the number of lenses is large, and it is located between the second lens group (magnifying lens group) and the light source 8. For example, in the patent CN220603772U, it is mentioned that "the third lens group is a focusing lens group, which comprises 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 large overall weight; and the focusing lens group has high precision requirements for the sheet metal structure, and the low precision of the sheet metal structure is prone to cause the phenomenon that one half of the formed light spot is clear and the other half is blurred due to inclination and coaxiality; and since the conventional optical system only has three lens groups, it cannot realize high-definition projection of complex and high-resolution patterns.

[0034] The focusing lens group 3 in the application is different from the traditional focusing lens group, in the embodiment, the focusing lens group 3 is the third lens group 3, the number of lenses in the third lens group 3 is only two, compared with the traditional focusing lens group, the number of lenses in the focusing lens group 3 of the application is greatly reduced; the reduction of the number of lenses is beneficial to simplify the installation, improve the coaxiality of the installation of the two lenses, and also effectively solve the problem that the focusing lens group 3 is too sensitive to the precision of the structural member; and compared with the traditional optical system, one more lens group is added; therefore the system focal power can be more evenly distributed to the four lens groups, effectively correct the system spherical aberration, reduce the lens tolerance sensitivity, and improve the pattern image quality.

[0035] The third lens group 3 and the fourth lens group 4 of the application are equivalent to dividing the traditional focusing lens group into two parts, the fourth lens group 4 is fixedly arranged on the main light path as one part and cannot be moved.

[0036] More specifically, compared with the patent CN220603772U, the application has the following differences:

[0037] Firstly, the optical system is composed of four lens groups, one more rear fixed imaging lens group 4 is added, and the number of lenses in the optical system is increased by four.

[0038] Secondly, the number of lenses in the focusing lens group 3 is reduced, and the number of lenses in the focusing lens group 3 is two.

[0039] The application has two beneficial effects:

[0040] The first beneficial effect is that the number of lenses in the optical system is increased, and one more rear fixed imaging lens group 4 is added, the system focal power can be more evenly distributed to the four lens groups, effectively correct the system spherical aberration, reduce the lens tolerance sensitivity, and improve the pattern image quality.

[0041] The second beneficial effect is that the number of lenses in the focusing lens group 3 is reduced, which is beneficial to solve the problem that the focusing lens group 3 is too sensitive to the precision of the metal structure.

[0042] As a new embodiment, the application is described in combination with the accompanying drawings Figure 3 The optical total length is 213mm. The traditional optical system generally has only three lens groups, and the optical total length is also between 200-220mm; for example, the patent CN220603772U mentions that "it is composed of three independent lens groups, and the optical total length is 210mm." The optical system of the application is composed of four lens groups, that is, one more lens group is added; compared with the patent CN220603772U, the application adds one more lens group without increasing the optical total length, which can realize high-definition projection of complex and high-resolution patterns.

[0043] As a new embodiment, the application is described in combination with the accompanying drawings Figure 1, the system focal length is 40mm-126mm. Patent CN220603772U mentions that the combined focal length is 27mm-132mm. In the present embodiment, the system focal length of the present application is smaller than the combined focal length mentioned in patent CN220603772U; that is, the different focusing needs of the optical system can be achieved under the condition of not changing the total optical length and under 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, so the zoom ratio of the present application is 3x.

[0044] As a new embodiment, in combination with the accompanying drawings Figure 1 , the aperture coefficient is F / 1.5. The aperture coefficient is the ratio between the effective focal length and the effective aperture diameter, which is used to represent the strength of the light transmission capacity of the optical system; compared with patent CN220603772U, the aperture coefficient of the present application is larger; when the aperture coefficient is large, the aperture diameter is small, and the depth of field will increase accordingly, so the clear range of the present application is also increased accordingly; and the aperture coefficient should be adapted to the light source 8, so that the light spot formed by the light projected by the optical system is bright and clear.

[0045] As a new embodiment, in combination with the accompanying drawings Figure 1 , the field of view FOV is 10°≤FOV≤30°. As can be understood by those skilled in the art, the size of the field of view is related to the focal length in the optical system, and the focal length determines the field of view of the optical system; the longer the focal length, the smaller the field of view; the shorter the focal length, the larger the field of view; in the present embodiment, when the system focal length is 41mm, the field of view of the optical system is 30°; at this time, the degree of divergence of the light passing through the optical system is high, that is, the illumination range is wide, but the illumination distance is short; when the system focal length is 126mm, the field of view of the optical system is 10°; at this time, the illumination range of the light projected by the optical system is narrower, but it can illuminate a farther distance.

[0046] As a new embodiment, in combination with the accompanying drawings Figure 3 , the stroke L1 of the second lens group 2 is L1≤47mm. When the second lens group 2 moves towards the light source 8, the divergence of the second lens group 2 to the outgoing light will increase, and the formed light spot will be larger; when the second lens group 2 moves away from the light source 8, the divergence of the second lens group 2 to the outgoing light will weaken, and the formed light spot will be smaller. The beneficial effect of this embodiment is that the traditional second lens group can usually only achieve clear projection of complex and high-resolution patterns under the condition of large stroke; while the present application can achieve high-definition projection of complex and high-resolution patterns under the condition of short stroke.

[0047] As a new embodiment, in combination with the accompanying drawings Figure 3The stroke L2 of the third lens group 3 is L2≤11mm. The third lens group 3 is mainly used for adjusting the system focal length of the optical system. When the third lens group 3 moves towards the light source 8, the system focal length becomes smaller, and the forming position of the light spot is relatively close to the light source 8. At the same time, the system focal length becomes smaller, and the field of view angle is relatively increased, so the size of the formed light spot is also increased with the increase of the field of view angle. When the third lens group 3 moves away from the light source 8, the system focal length becomes larger, and the forming position of the light spot is relatively far away from the light source 8. At the same time, the focal length becomes larger, and the field of view angle is relatively decreased, so the size of the formed light spot is also decreased with the decrease of the field of view angle. The beneficial effect of this embodiment is that the traditional optical system can only realize a large zoom ratio under the condition of a large stroke, and it cannot project high-definition patterns of complex and high resolution. The present application can realize a wide zoom range in a relatively short stroke compared with the traditional optical system, and improve the ability of aberration fine adjustment and balance, and can realize high-definition projection of complex and high-resolution patterns.

[0048] As a new embodiment, combined with the accompanying drawings Figure 2 and the accompanying drawings Figure 3 The minimum distance L3 between the third lens 13 and the fourth lens 21 is 3.4mm, and the minimum distance L4 between the eighth lens 32 and the ninth lens 41 is 7.7mm. The third lens 13 is installed in the first lens barrel 14, and the fourth lens 21 is installed in the second lens barrel 24. The eighth lens 32 is located in the third lens barrel 33, and the ninth lens 41 is located in 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 the third lens barrel 33 moves towards the fourth lens barrel 46, until the fourth lens 21 in the second lens barrel 24 reaches the minimum distance position with the third lens 13, and the eighth lens 32 in the third lens barrel 33 reaches the minimum distance position with the ninth lens 41. As can be known from the above, when the fourth lens 21 reaches the minimum distance position, the fourth lens 21 is located in the stroke L1. When the eighth lens 32 reaches the minimum distance position, the eighth lens 32 is located in the stroke L2. As a new embodiment, combined with the accompanying drawings Figure 1 It also includes a diaphragm 6 located between the sixth lens 23 and the seventh lens 31. In this embodiment, the position of the diaphragm 6 moves with the third lens group 3, and the maximum diameter of the diaphragm 6 is smaller than the diameter of the seventh lens 31. The diaphragm 6 can change the flux of light by adjusting its size, so as to adjust the brightness of the illumination system. The diaphragm 6 can also prevent light from overflowing to the non-illumination area, reducing the loss and waste of light.

[0049] As a new embodiment, combined with the accompanying drawings Figure 3, the curvature radius of the light-out surface of the fourth lens 21 is 405mm, and the curvature radius of the light-in surface of the fourth lens 21 is 105mm; the curvature radius of the light-out surface of the fifth lens 22 is -72mm, and the curvature radius of the light-in surface of the fifth lens 22 is 34mm; the curvature radius of the light-out surface of the sixth lens 23 is 34mm, and the curvature radius of the light-in surface of the sixth lens 23 is 70mm. There is a space between the fourth lens 21 and the fifth lens 22, and the light-in surface of the fifth lens 22 is in close contact with the light-out surface of the sixth lens 23; as can be understood by those skilled in the art, a smaller curvature radius makes the diverging effect of a concave lens on light stronger, i.e., the light is more divergent after passing through the concave lens; a larger curvature radius makes the diverging effect of a concave lens on light relatively weaker; the lenses in the second lens group 2 are all concave lenses; and the optical power of the fourth lens is negative, the fourth lens 21 has a diverging effect on light, the optical power of the fifth lens 22 and the sixth lens 23 are both negative and the curvature radius is small, so the fifth lens 22 and the sixth lens 23 have a strong diverging effect on light; and the second lens group 2 composed of the fourth lens 21, the fifth lens 22 and the sixth lens 23 can accurately control 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 lenses in the optical system can also directly affect the imaging quality of the optical system, effectively diverging the light, and thus forming a clear light spot; and the design of the curvature radius of the lenses in the second lens group 2 in the optical system can effectively control the degree of optical distortion to be less than or equal to 3.2%.

[0050] As a new embodiment, in combination with the accompanying drawings Figure 3 , the curvature radius of the light-out surface of the seventh lens 31 is 378mm, and the curvature radius of the light-in surface of the seventh lens 31 is 66mm; the curvature radius of the light-out surface of the eighth lens 32 is 58mm, and the curvature radius of the light-in surface of the eighth lens 32 is not limited. The seventh lens group 31 and the eighth lens group 32 are in close contact, and the third lens group 3 is provided with a triangular prism on the side away from the light source 8; as can be understood by those skilled in the art, the smaller the curvature radius of a convex lens, the stronger the converging effect of the lens on light; the larger the curvature radius, the relatively weaker the converging effect of the lens on light; the lenses in the third lens group 3 are all convex lenses; and the optical power of the seventh lens 31 and the eighth lens 32 is positive, so the seventh lens 31 and the eighth lens 32 have a strong converging effect on light; the third lens group 3 composed of the seventh lens 31 and the eighth lens 32 can accurately control the refraction of light, thereby adjusting the position formed by the light spot; and the setting of the curvature radius parameter of the lenses in the third lens group 3 can affect the size of the system focal length. The beneficial effect of this embodiment is that the curvature radius of the lenses in the optical system can also directly affect the imaging quality of the optical system, and the design of the curvature radius of the lenses in the third lens group 3 in the optical system can effectively control the degree of optical distortion to be less than or equal to 3.2%.

[0051] Preferably, the curvature radius of the plurality of lenses in the optical system is arranged to fix the focal length of the system in the range of 40mm-126mm, so that the degree of optical distortion can be controlled in the range of less than 3.2%, and the aberration can be effectively reduced.

[0052] As a new implementation, in combination with the accompanying drawings Figure 3 The lenses in the four mirror groups are all spherical lenses. The implementation has the beneficial effects that the spherical lenses have all-around light emitting characteristics, can uniformly scatter light to the surrounding environment, can effectively reduce glare, and make the light more soft; compared with aspherical lenses, the manufacturing process of the spherical lenses is relatively simple, so the cost is relatively low; and the structure is relatively simple, so it has high stability in use.

Claims

1. A four-group zoom optical system characterized in that, The four independent mirror groups are coaxially arranged, and the four mirror groups include a fourth mirror group, a third mirror group, a second mirror group and a first mirror group arranged in sequence along a main optical axis; The first mirror group is a front fixed imaging mirror group, and includes a first lens, a second lens, a third lens and a first lens barrel, wherein the first lens is a double convex lens, the second lens is a plano-convex lens, and the third lens is a plano-concave lens; The second mirror group is a magnifying mirror group, and includes 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 double concave lens, and the sixth lens is a meniscus lens; The third mirror group is a focusing mirror group, and includes 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 mirror group is a rear fixed imaging mirror group, and includes 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 meniscus lens, the tenth lens is a meniscus lens, the eleventh lens is a meniscus lens, the twelfth lens is a meniscus lens, and the thirteenth lens is a double convex lens; The first mirror group and the fourth mirror group are fixed on the main optical axis, and the second mirror group and the third mirror group are movably arranged on the main optical axis, and the zooming is realized by the relative movement of the second mirror group and the third mirror group.

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

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

4. The four-group zoom optical system of claim 1, wherein The aperture coefficient is F / 1.

5.

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

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

7. A four-group zoom optical system according to claim 1, wherein 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, A diaphragm is further included, and the diaphragm is located between the sixth lens and the seventh lens.

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

10. The four-group zoom optical system of claim 1, wherein The curvature radius of the light emitting surface of the seventh lens is 378 mm, the curvature radius of the light incident surface of the seventh lens is 66 mm, the curvature radius of the light emitting surface of the eighth lens is 58 mm, and the curvature radius of the light incident surface of the eighth lens is not limited.

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