Zoom optical lens with large image plane and large zoom ratio

Abstract

The invention discloses a large-image-plane large-zoom-ratio zoom optical lens which is composed of a transmission group G1 with positive focal power, a transmission group G2 with negative focal power, an aperture diaphragm, a transmission group G3 with positive focal power, a transmission group G4 with positive focal power, an optical filter and an image plane which are sequentially arranged in the direction from the object side to the image side. The focal length is changed through the movement of the transmission group G2 along the optical axis, and a position can be found through the matched movement of the transmission group G4 along the optical axis, so that the image plane position of the optical system is not changed, the imaging is clear, and large-zoom-ratio optical imaging is realized under the condition of matching a large image plane. Therefore, the performance and the appearance size of the product are well matched, and the method can be widely applied to the technical field of security monitoring and the like.

Description

Technical Field

[0001] The invention belongs to the field of optical technology, and in particular relates to a zoom optical lens with a large image plane and a large magnification ratio. Background Art

[0002] With the continuous advancement of CMOS device technology, the photosensitive surface of image sensors is getting larger and larger, allowing the optical system to receive more light energy. In the field of security monitoring, there is a great demand for sensors with large image surfaces. In large squares, wide roads, border defenses, forest protection and other occasions, it is necessary to view the overall range and track key local ranges. This requires a large zoom ratio optical system that can match the large image surface and take into account wide angle and telephoto.

[0003] The existing zoom optical systems either have a large zoom ratio but a small image surface, or a large image surface but a small zoom ratio. It is impossible to have an optical system with a large zoom ratio and a large image surface at the same time. Summary of the invention

[0004] In order to overcome the above-mentioned shortcomings, a large image plane and large zoom ratio optical lens is proposed, which changes the focal length by moving the transmission group G2 along the optical axis, and can find a position by the coordinated movement of the transmission group G4 along the optical axis, so that the image plane position of the optical system remains unchanged and the image is clear. Under the condition of matching the large image plane sensor, large zoom ratio optical imaging is achieved at the same time, so that the product performance and appearance size are well matched, so that it can be widely used in technical fields such as security monitoring.

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: to provide a large image plane and large zoom ratio optical lens. It is composed of a transmission group G1 with positive focal power, a transmission group G2 with negative focal power, an aperture stop, a transmission group G3 with positive focal power, a transmission group G4 with positive focal power, a filter and an image plane, which are arranged in sequence from the object side to the image side; The transmission group G1 is composed of a first lens, a second lens, a third lens and a fourth lens arranged in sequence from the object side to the image side, wherein the first lens is a negative lens, and the second lens, the third lens and the fourth lens are positive lenses; The transmission group G2 is composed of a fifth lens, a sixth lens, a seventh lens and an eighth lens arranged in sequence from the object side to the image side, wherein the fifth lens and the sixth lens are negative lenses, and the seventh lens and the eighth lens are positive lenses; The transmission group G3 is composed of a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, and a thirteenth lens arranged in sequence from the object side to the image side, wherein the tenth lens and the twelfth lens are negative lenses, and the ninth lens, the eleventh lens, and the thirteenth lens are positive lenses; The transmission group G4 consists of a fourteenth lens, a fifteenth lens and a sixteenth lens arranged in sequence from the object side to the image side, wherein the fifteenth lens is a negative lens, and the fourteenth lens and the sixteenth lens are positive lenses.

[0006] According to the large image plane and large magnification ratio zoom optical lens of the present invention, a further preferred technical solution is: At the short focal position, the ratio of the focal length of the transmission group G1 to the focal length of the entire optical system is in the range of (5.18, 7.51), the ratio of the focal length of the transmission group G2 to the focal length of the entire optical system is in the range of (-1.42, -1.25), the ratio of the focal length of the transmission group G3 to the focal length of the entire optical system is in the range of (4.27, 4.82), and the ratio of the focal length of the transmission group G4 to the focal length of the entire optical system is in the range of (2.88, 3.11); At the mid-focus position, the ratio of the focal length of the transmission group G1 to the focal length of the entire optical system is in the range of (0.66, 0.93), the ratio of the focal length of the transmission group G2 to the focal length of the entire optical system is in the range of (-0.26, -0.08), the ratio of the focal length of the transmission group G3 to the focal length of the entire optical system is in the range of (0.27, 1.82), and the ratio of the focal length of the transmission group G4 to the focal length of the entire optical system is in the range of (0.23, 0.51); At the telephoto position, the ratio of the focal length of the transmission group G1 to the focal length of the entire optical system is in the range of (0.13, 0.62), the ratio of the focal length of the transmission group G2 to the focal length of the entire optical system is in the range of (-0.08, -0.06), the ratio of the focal length of the transmission group G3 to the focal length of the entire optical system is in the range of (0.22, 0.32), and the ratio of the focal length of the transmission group G4 to the focal length of the entire optical system is in the range of (0.09, 0.22).

[0007] According to the zoom optical lens with a large image surface and a large magnification ratio described in the present invention, a further preferred technical solution is: the first lens and the second lens of the transmission group G1 form a cemented lens group; the sixth lens and the seventh lens of the transmission group G2 form a cemented lens group; the tenth lens and the eleventh lens of the transmission group G3 form a cemented lens group, and the twelfth lens and the thirteenth lens form a cemented lens group; the fourteenth lens and the fifteenth lens of the transmission group G4 form a cemented lens group.

[0008] According to the large image plane and large magnification ratio zoom optical lens of the present invention, a further preferred technical solution is that the surface of the first lens facing the object plane is convex, and the surface facing the image plane is concave; The surface of the second lens facing the object plane is convex, and the surface facing the image plane is convex; The surface of the third lens facing the object plane is convex, and the surface facing the image plane is concave; The surface of the fourth lens facing the object plane is convex, and the surface facing the image plane is concave; The surface of the fifth lens facing the object plane is convex, and the surface facing the image plane is concave; The surface of the sixth lens facing the object plane is concave, and the surface facing the image plane is concave; The surface of the seventh lens element facing the object plane is convex, and the surface facing the image plane is concave; The surface of the eighth lens facing the object plane is convex, and the surface facing the image plane is concave; The surface of the ninth lens facing the object plane is convex, and the surface facing the image plane is convex; The surface of the tenth lens facing the object plane is convex, and the surface facing the image plane is concave; The surface of the eleventh lens facing the object plane is convex, and the surface facing the image plane is concave; The surface of the twelfth lens facing the object plane is convex, and the surface facing the image plane is concave; The surface of the thirteenth lens facing the object plane is convex, and the surface facing the image plane is concave; The surface of the fourteenth lens facing the object plane is convex, and the surface facing the image plane is convex; The surface of the fifteenth lens facing the object plane is concave, and the surface facing the image plane is convex; The surface of the sixteenth lens facing the object plane is convex, and the surface facing the image plane is convex.

[0009] According to the large image surface and large magnification ratio zoom optical lens of the present invention, a further preferred technical solution is: among the first to sixteenth lenses, the third lens and the ninth lens are aspherical lenses, and the remaining lenses are spherical lenses.

[0010] According to the large image plane and large zoom ratio optical lens of the present invention, a further preferred technical solution is that the transmission groups G2 and G3 are moving groups, and the transmission groups G1 and G4 are fixed groups.

[0011] Compared with the prior art, the technical solution of the present invention has the following advantages / benefits: The present invention changes the focal length by moving the transmission group G2 along the optical axis, and can find a position by coordinating the movement of the transmission group G4 along the optical axis, so that the image plane position of the optical system can be kept unchanged and the image can be clear. Under the condition of matching the large image plane, large zoom ratio optical imaging can be achieved at the same time, so that the product performance and appearance size are well matched, and it can be widely used in technical fields such as security monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0013] Figure 1 The present invention is a schematic structural diagram of a large image plane and large magnification ratio zoom optical lens.

[0014] Figure 2 This is a light fan diagram of a zoom optical lens with a large image surface and a large magnification ratio at short focal length in Example 2 of the present invention.

[0015] Figure 3 This is a light fan diagram of a large image surface and large magnification ratio zoom optical lens embodiment 2 of the present invention at medium focus.

[0016] Figure 4 This is a light fan diagram of a large image surface and large magnification ratio zoom optical lens embodiment 2 of the present invention at a long focal length.

[0017] Figure 5 This is a point arrangement diagram at short focal length in Example 2 of a zoom optical lens with a large image surface and a large magnification ratio according to the present invention.

[0018] Figure 6 This is a point arrangement diagram of a zoom optical lens with a large image surface and a large magnification ratio in Embodiment 2 of the present invention at mid-focus.

[0019] Figure 7 This is a point arrangement diagram of a large image surface and large magnification ratio zoom optical lens embodiment 2 of the present invention at a long focus.

[0020] The marks in the figure are: 1. first lens, 2. second lens, 3. third lens, 4. fourth lens, 5. fifth lens, 6. sixth lens, 7. seventh lens, 8. eighth lens, 9. ninth lens, 10. tenth lens, 11. eleventh lens, 12. twelfth lens, 13. thirteenth lens, 14. fourteenth lens, 15. fifteenth lens, 16. sixteenth lens, 17. filter, 18. image plane. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention. Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention.

[0022] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and thus, once an item is defined in one drawing, it may not be further defined or explained in the subsequent drawings.

[0023] Embodiment 1: like Figure 1 As shown, a large image plane and large zoom ratio optical lens is composed of a transmission group G1, a transmission group G2, an aperture stop (STO), a transmission group G3, a transmission group G4, a filter 17 and an image plane 18 arranged in sequence from the object side to the image side. The transmission group G2 and the transmission group G3 are moving groups, and the transmission group G1 and the transmission group G4 are fixed groups.

[0024] The transmission group G1 is a transmission group with positive optical power, including a first lens 1, a second lens 2, a third lens 3 and a fourth lens 4. The first lens 1 is a negative lens, and the second lens 2, the third lens 3 and the fourth lens 4 are positive lenses. The first lens 1 and the second lens 2 form a cemented lens group. The surface of the first lens 1 facing the object plane is convex, and the surface facing the image plane 18 is concave; the surface of the second lens 2 facing the object plane is convex, and the surface facing the image plane 18 is convex; the surface of the third lens 3 facing the object plane is convex, and the surface facing the image plane 18 is concave; the surface of the fourth lens 4 facing the object plane is convex, and the surface facing the image plane 18 is concave.

[0025] The transmission group G2 is a transmission group with negative optical power, including a fifth lens 5, a sixth lens 6, a seventh lens 7 and an eighth lens 8. The fifth lens 5 and the sixth lens 6 are negative lenses, and the seventh lens 7 and the eighth lens 8 are positive lenses. The sixth lens 6 and the seventh lens 7 form a cemented lens group. The surface of the fifth lens 5 facing the object plane is convex, and the surface facing the image plane 18 is concave; the surface of the sixth lens 6 facing the object plane is concave, and the surface facing the image plane 18 is concave; the surface of the seventh lens 7 facing the object plane is convex, and the surface facing the image plane 18 is concave; the surface of the eighth lens 8 facing the object plane is convex, and the surface facing the image plane 18 is concave.

[0026] The transmission group G3 is a transmission group with positive optical power, including a ninth lens 9, a tenth lens 10, an eleventh lens 11, a twelfth lens 12 and a thirteenth lens 13. The eleventh lens 11, the twelfth lens 12 and the thirteenth lens 13 are negative lenses. The ninth lens 9 and the tenth lens 10 are positive lenses. The tenth lens 10 and the twelfth lens 12 are negative lenses, and the ninth lens 9, the eleventh lens 11 and the thirteenth lens 13 are positive lenses. The surface of the ninth lens 9 facing the object plane is convex, and the surface facing the image plane 18 is convex; the surface of the tenth lens 10 facing the object plane is convex, and the surface facing the image plane 18 is concave; the surface of the eleventh lens 11 facing the object plane is convex, and the surface facing the image plane 18 is concave; the surface of the twelfth lens 12 facing the object plane is convex, and the surface facing the image plane 18 is concave; the surface of the thirteenth lens 13 facing the object plane is convex, and the surface facing the image plane 18 is concave.

[0027] The transmission group G4 is a transmission group with positive power, including a fourteenth lens, a fifteenth lens 15 and a sixteenth lens 16. The fifteenth lens 15 is a negative lens, and the fourteenth lens 14 and the sixteenth lens are positive lenses. The fourteenth lens 14 and the fifteenth lens 15 form a cemented lens group. The surface of the fourteenth lens 14 facing the object plane is convex, and the surface facing the image plane 18 is convex; the surface of the fifteenth lens 15 facing the object plane is concave, and the surface facing the image plane 18 is convex; the surface of the sixteenth lens 16 facing the object plane is convex, and the surface facing the image plane 18 is convex.

[0028] At the short focal position, the ratio of the focal length of the transmission group G1 to the focal length of the entire optical system is in the range of (5.18, 7.51), the ratio of the focal length of the transmission group G2 to the focal length of the entire optical system is in the range of (-1.42, -1.25), the ratio of the focal length of the transmission group G3 to the focal length of the entire optical system is in the range of (4.27, 4.82), and the ratio of the focal length of the transmission group G4 to the focal length of the entire optical system is in the range of (2.88, 3.11); At the mid-focus position, the ratio of the focal length of the transmission group G1 to the focal length of the entire optical system is in the range of (0.66, 0.93), the ratio of the focal length of the transmission group G2 to the focal length of the entire optical system is in the range of (-0.26, -0.08), the ratio of the focal length of the transmission group G3 to the focal length of the entire optical system is in the range of (0.27, 1.82), and the ratio of the focal length of the transmission group G4 to the focal length of the entire optical system is in the range of (0.23, 0.51); At the telephoto position, the ratio of the focal length of the transmission group G1 to the focal length of the entire optical system is in the range of (0.13, 0.62), the ratio of the focal length of the transmission group G2 to the focal length of the entire optical system is in the range of (-0.08, -0.06), the ratio of the focal length of the transmission group G3 to the focal length of the entire optical system is in the range of (0.22, 0.32), and the ratio of the focal length of the transmission group G4 to the focal length of the entire optical system is in the range of (0.09, 0.22).

[0029] Among the first to sixteenth lenses, the third lens 3 and the ninth lens 9 are aspherical lenses, and the remaining lenses are spherical lenses.

[0030] Embodiment 2: Based on Example 1, the actual situation of a large image plane and large magnification ratio zoom optical system is as follows: The ratio range of the focal length of the transmission group G1 to the focal length of the entire optical system at short focus is 6.20, the ratio range of the focal length of the transmission group G1 to the focal length of the entire optical system at mid focus is 0.69, and the ratio range of the focal length of the transmission group G1 to the focal length of the entire optical system at long focus is 0.34.

[0031] The ratio range of the focal length of the transmission group G2 to the focal length of the entire optical system at short focus is -1.28, the ratio range of the focal length of the transmission group G2 to the focal length of the entire optical system at mid focus is -0.14, and the ratio range of the focal length of the transmission group G2 to the focal length of the entire optical system at long focus is -0.07.

[0032] The ratio range of the focal length of the transmission group G3 to the focal length of the entire optical system at short focus is 4.39, the ratio range of the focal length of the transmission group G3 to the focal length of the entire optical system at mid-focus is 0.49, and the ratio range of the focal length of the transmission group G3 to the focal length of the entire optical system at long focus is 0.25.

[0033] The ratio range of the focal length of the transmission group G4 to the focal length of the entire optical system at short focus is 2.92, the ratio range of the focal length of the transmission group G4 to the focal length of the entire optical system at medium focus is 0.33, and the ratio range of the focal length of the transmission group G4 to the focal length of the entire optical system at long focus is 0.16.

[0034] The physical parameters of each lens of a large image plane and large zoom ratio optical lens in this embodiment meet the data requirements shown in Table 1: Table 1 Physical parameters of each lens

[0035] The equation for an aspheric surface is as follows:

[0036] The definition of aspherical shape is explained below: y: radial coordinate from the optical axis.

[0037] z: The offset in the direction of the optical axis starting from the intersection point of the aspherical surface and the optical axis.

[0038] r: The radius of curvature of the reference sphere of the aspheric surface.

[0039] k is the cone constant, A4, A6, A8, A10, A12 are the 4th, 6th, 8th, 10th, 12th aspheric coefficients.

[0040] Surfaces 4 and 5 of the third lens are aspherical surfaces. Surfaces 16 and 17 of the ninth lens are aspherical surfaces (the above all refer to surface numbers).

[0041] In Table 2, the 4th, 6th, 8th, 10th, and 12th order aspheric coefficients A4, A6, A8, A10, A12 and the cone constant k of the aspheric surface are given together.

[0042] Table 2 Aspheric parameters

[0043] The optical system provided by the large image plane and large zoom ratio optical lens in this embodiment has the following optical technical indicators: Working band: 435 nm-656 nm; Total optical length TTL<82mm; Focal length f: 5.6 mm (W) ~ 100.8 mm (T); Field of view: 70°(W)~3.8°(T); Optical distortion: -9.5% (W) ~ +2.6% (T); Image size: Φ7mm.

[0044] Note: W stands for short focal length and T stands for long focal length.

[0045] like Figure 2-Figure 4 As shown in the figure, the light aberration curves of the large image plane and large zoom ratio zoom optical system at short focal length, medium focal length and long focal length are given. It can be seen that the meridional aberration and sagittal aberration of the large image plane and large zoom ratio zoom optical system are both small in the full focal length. In the figure, ex: light aberration x component, ey: light aberration y component, px: x entrance pupil coordinate, py: y entrance pupil coordinate.

[0046] like Figure 5-Figure 7As shown in the figure, the field curvature and distortion curves of the large image plane and large zoom ratio zoom optical system at short focal length, medium focal length and long focal length are given. It can be seen that the absolute value of the distortion in the full spectrum and full field of view of the large image plane and large zoom ratio zoom optical system at short focal length is better than 9.5%, and the absolute value of the distortion in the full spectrum and full field of view of the long focal length is better than 2.6%.

[0047] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0048] The above are only preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limiting the present invention, and the protection scope of the present invention should be based on the scope defined by the claims. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A zoom optical lens with a large image area and a large magnification ratio, characterized in that: It is composed of a transmission group G1 with positive optical power, a transmission group G2 with negative optical power, an aperture stop, a transmission group G3 with positive optical power, a transmission group G4 with positive optical power, a filter and an image plane, which are arranged in sequence from the object side to the image side; The transmission group G1 is composed of a first lens, a second lens, a third lens and a fourth lens arranged in sequence from the object side to the image side, wherein the first lens is a negative lens, and the second lens, the third lens and the fourth lens are positive lenses; The transmission group G2 is composed of a fifth lens, a sixth lens, a seventh lens and an eighth lens arranged in sequence from the object side to the image side, wherein the fifth lens and the sixth lens are negative lenses, and the seventh lens and the eighth lens are positive lenses; The transmission group G3 is composed of a ninth lens, a tenth lens, an eleventh lens, a twelfth lens and a thirteenth lens arranged in sequence from the object side to the image side, wherein the tenth lens and the twelfth lens are negative lenses, and the ninth lens, the eleventh lens and the thirteenth lens are positive lenses; The transmission group G4 consists of a fourteenth lens, a fifteenth lens and a sixteenth lens arranged in sequence from the object side to the image side, wherein the fifteenth lens is a negative lens, and the fourteenth lens and the sixteenth lens are positive lenses.

2. The large image plane and large magnification ratio zoom optical lens according to claim 1, characterized in that: At the short focal position, the ratio of the focal length of the transmission group G1 to the focal length of the entire optical system is in the range of (5.18, 7.51), the ratio of the focal length of the transmission group G2 to the focal length of the entire optical system is in the range of (-1.42, -1.25), the ratio of the focal length of the transmission group G3 to the focal length of the entire optical system is in the range of (4.27, 4.82), and the ratio of the focal length of the transmission group G4 to the focal length of the entire optical system is in the range of (2.88, 3.11); At the mid-focus position, the ratio of the focal length of the transmission group G1 to the focal length of the entire optical system is in the range of (0.66, 0.93), the ratio of the focal length of the transmission group G2 to the focal length of the entire optical system is in the range of (-0.26, -0.08), the ratio of the focal length of the transmission group G3 to the focal length of the entire optical system is in the range of (0.27, 1.82), and the ratio of the focal length of the transmission group G4 to the focal length of the entire optical system is in the range of (0.23, 0.51); At the telephoto position, the ratio of the focal length of the transmission group G1 to the focal length of the entire optical system is in the range of (0.13, 0.62), the ratio of the focal length of the transmission group G2 to the focal length of the entire optical system is in the range of (-0.08, -0.06), the ratio of the focal length of the transmission group G3 to the focal length of the entire optical system is in the range of (0.22, 0.32), and the ratio of the focal length of the transmission group G4 to the focal length of the entire optical system is in the range of (0.09, 0.22).

3. The large image plane and large variable magnification zoom optical lens according to claim 1, characterized in that: The first lens and the second lens of the transmission group G1 form a cemented lens group; the sixth lens and the seventh lens of the transmission group G2 form a cemented lens group; the tenth lens and the eleventh lens of the transmission group G3 form a cemented lens group, and the twelfth lens and the thirteenth lens form a cemented lens group; the fourteenth lens and the fifteenth lens of the transmission group G4 form a cemented lens group.

4. The large image plane and large variable magnification zoom optical lens according to claim 1, characterized in that: The surface of the first lens facing the object plane is convex, and the surface facing the image plane is concave; The surface of the second lens facing the object plane is convex, and the surface facing the image plane is convex; The surface of the third lens facing the object plane is convex, and the surface facing the image plane is concave; The surface of the fourth lens facing the object plane is convex, and the surface facing the image plane is concave; The surface of the fifth lens facing the object plane is convex, and the surface facing the image plane is concave; The surface of the sixth lens facing the object plane is concave, and the surface facing the image plane is concave; The surface of the seventh lens element facing the object plane is convex, and the surface facing the image plane is concave; The surface of the eighth lens facing the object plane is convex, and the surface facing the image plane is concave; The surface of the ninth lens facing the object plane is convex, and the surface facing the image plane is convex; The surface of the tenth lens facing the object plane is convex, and the surface facing the image plane is concave; The surface of the eleventh lens facing the object plane is convex, and the surface facing the image plane is concave; The surface of the twelfth lens facing the object plane is convex, and the surface facing the image plane is concave; The surface of the thirteenth lens facing the object plane is convex, and the surface facing the image plane is concave; The surface of the fourteenth lens facing the object plane is convex, and the surface facing the image plane is convex; The surface of the fifteenth lens facing the object plane is concave, and the surface facing the image plane is convex; The surface of the sixteenth lens facing the object plane is convex, and the surface facing the image plane is convex.

5. The large image plane and large magnification ratio zoom optical lens according to claim 1, characterized in that: Among the first to sixteenth lenses, the third lens and the ninth lens are aspherical lenses, and the remaining lenses are spherical lenses.

6. The large image plane and large variable magnification zoom optical lens according to claim 1, characterized in that: The transmission group G2 and the transmission group G3 are moving groups, and the transmission group G1 and the transmission group G4 are fixed groups.

Images