Optical system based on freeform mirror and electronic device

Abstract

Embodiments of the present application relate to the field of optical design, and disclose an optical system based on a free-form mirror and electronic equipment.The optical system based on the free-form mirror comprises: a free-form mirror, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and an imaging surface which are sequentially arranged along an optical axis direction; the free-form mirror is used for collecting light rays within a preset angle; wherein the preset angle is greater than 180 degrees; the first lens, the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens are used for focusing the light rays collected by the free-form mirror together, so that the light rays form a light spot on the imaging surface; wherein the first lens, the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens are all spherical lenses.The present application realizes 360-degree omnidirectional simultaneous imaging, guarantees high-quality imaging and reduces the cost of the optical system.

Description

TECHNICAL FIELD

[0001] The embodiment of the present application relates to the field of optical design, in particular to an optical system based on a free-form surface mirror and electronic equipment. BACKGROUND

[0002] In order to meet the demand of the azimuth coverage range of imaging in the application fields such as virtual reality (VR), sports camera, unmanned vehicle, reconnaissance satellite and monitoring system, the current optical system needs to realize panoramic imaging. At present, the ways to realize panoramic imaging include: obtaining panoramic image through 360-degree rotation scanning of a single camera, obtaining panoramic image through 360-degree rotation scanning of multiple cameras, and panoramic imaging through a fisheye lens.

[0003] The inventor finds that the above-mentioned imaging ways at least have the following problems: the way of obtaining panoramic image through 360-degree rotation scanning of a single camera cannot realize real-time imaging at each moment due to the time consumption in the scanning process, and some targets are easily missed, finally resulting in that the obtained image information does not have integrity. The way of obtaining panoramic image through 360-degree rotation scanning of multiple cameras needs to design multiple cameras in the optical system, resulting in that the overall volume of the system is relatively large, and the manufacturing cost is very high. The way of panoramic imaging through a fisheye lens has a larger imaging field of view than an ordinary lens, but the scene information captured by the fisheye lens will introduce a large amount of barrel distortion, causing the edge image to have a serious phenomenon of deformation and reduction. On the other hand, if a good imaging quality is needed, the fisheye lens system is generally composed of multiple lenses, resulting in that the lens processing is more troublesome, and the manufacturing cost also increases. SUMMARY

[0004] The embodiment of the present application aims to provide an optical system based on a free-form surface mirror and electronic equipment, realize 360-degree omnidirectional simultaneous imaging, and ensure high-quality imaging while reducing the cost of the optical system.

[0005] In order to solve one or more of the above-mentioned technical problems, the embodiment of the present application provides an optical system based on a free-form surface mirror, which comprises: a free-form surface mirror, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and an imaging surface which are sequentially arranged along the optical axis direction; the free-form surface mirror is used for collecting light within a preset angle; wherein the preset angle is greater than 180 degrees; the first lens, the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens are collectively used for focusing the light collected by the free-form surface mirror, so that the light forms a light spot on the imaging surface; wherein the first lens, the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens are all spherical lenses.

[0006] The embodiment of the present application also provides an electronic device, comprising: a camera module; the camera module comprises an optical lens, and the optical lens adopts the optical system based on the free-form surface mirror.

[0007] Compared with the prior art, the embodiment of the present application collects 360-degree light through the free-form surface mirror, realizes 360-degree omnidirectional simultaneous imaging, only six lenses are needed in the optical system, all the lenses are ordinary spherical mirrors, and the optical system is simple to manufacture and low in cost.

[0008] In addition, the image plane side of the first lens is a concave surface, the side close to the free-form surface mirror is a convex surface, and the equivalent focal length of the first lens is negative; the image plane side of the second lens is a convex surface, the side close to the free-form surface mirror is a convex surface, and the equivalent focal length of the second lens is positive; the image plane side of the third lens exposed to the outside of two sides is a convex surface, the side close to the free-form surface mirror is a concave surface, and the equivalent focal length of the third lens is negative; the image plane side of the fourth lens is a convex surface, the side close to the free-form surface mirror is a convex surface, and the equivalent focal length of the fourth lens is positive; the image plane side of the fifth lens is a convex surface, the side close to the free-form surface mirror is a convex surface, and the equivalent focal length of the fifth lens is positive; the image plane side of the sixth lens exposed to the outside of two sides is a concave surface, the side close to the free-form surface mirror is a convex surface, and the equivalent focal length of the sixth lens is positive.

[0009] In addition, the third lens and the sixth lens are both double-cemented lenses.

[0010] In addition, the equivalent focal length of the first lens is -13.821 mm; the equivalent focal length of the second lens is 19.734 mm; the equivalent focal length of the third lens is -20.6327 mm; the equivalent focal length of the fourth lens is 14.612 mm; the equivalent focal length of the fifth lens is 18.261 mm; and the equivalent focal length of the sixth lens is 15.97054 mm.

[0011] In addition, the curvature radius of the mirror on the image side of the first lens is -2.007 mm, and the curvature radius of the mirror on the other side is -3.773 mm; the curvature radius of the mirror on the image side of the second lens is 14.871 mm, and the curvature radius of the mirror on the other side is -80.932 mm; the curvature radius of the mirror on the image side of the third lens is 6.542 mm, and the curvature radius of the mirror exposed to the outside on the other side is 2.726 mm; the curvature radius of the mirror on the image side of the fourth lens is 9.001 mm, and the curvature radius of the mirror on the other side is -107.294 mm; the curvature radius of the mirror on the image side of the fifth lens is 10.890 mm, and the curvature radius of the mirror on the other side is -214.281 mm; the curvature radius of the mirror on the image side of the sixth lens is -75.153 mm, and the curvature radius of the mirror exposed to the outside on the other side is -7.437 mm.

[0012] In addition, the refractive index of the first lens and the second lens is the same; the refractive index of the fourth lens and the fifth lens is the same.

[0013] In addition, the distance between the free-form surface mirror and the first lens is 30.089 mm; the distance between the first lens and the second lens is 0.702 mm; the distance between the second lens and the third lens is 0.277 mm; the distance between the third lens and the fourth lens is 0.419 mm; the distance between the fourth lens and the fifth lens is 0.122 mm; the distance between the fifth lens and the sixth lens is 0.282 mm; and the distance between the sixth lens and the imaging surface is 5.708 mm.

[0014] In addition, the curvature radius of the free-form surface mirror is 14.230 mm, the conic coefficient is -1.832, and the optical radius is 6.061 mm.

[0015] In addition, the electronic device is a virtual reality device, a vehicle-mounted device, a reconnaissance satellite, or a monitoring device. BRIEF DESCRIPTION OF DRAWINGS

[0016] One or more embodiments are illustrated by way of example in the figures that form a part of this disclosure and which are shown by way of illustration in the drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts that serve a similar purpose. Figures in the drawings are not necessarily to scale, the emphasis instead being placed upon clearly illustrating the principles of the embodiments.

[0017] Figure 1 is a structural schematic diagram of an optical system based on a free-form surface mirror according to an embodiment of the present application;

[0018] Figure 2 is a structural schematic diagram of an optical system based on a free-form surface mirror according to another embodiment of the present application;

[0019] Figure 3is a MTF curve graph of the optical system at 50 LP / mm according to an embodiment of the present application;

[0020] Figure 4 is a MTF curve graph of the optical system at 100 LP / mm according to an embodiment of the present application;

[0021] Figure 5 is a MTF curve graph of the optical system at 200 LP / mm according to an embodiment of the present application;

[0022] Figure 6 is a spot diagram of the optical system according to an embodiment of the present application;

[0023] Figure 7 is a relative illuminance graph of the optical system according to an embodiment of the present application;

[0024] Figure 8 is a field curvature graph of the optical system according to an embodiment of the present application;

[0025] Figure 9 is a distortion graph of the optical system according to an embodiment of the present application;

[0026] Figure 10 is a defocus curve of the optical system according to an embodiment of the present application. DETAILED DESCRIPTION

[0027] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the embodiments of the present application will be described in detail below with reference to the drawings. However, those skilled in the art can understand that, in the embodiments of the present application, many technical details are presented in order to make the readers better understand the present application. However, the technical solutions claimed by the present application can be implemented even without these technical details and based on various changes and modifications of the following embodiments.

[0028] The division of the following embodiments is for the convenience of description, and should not constitute any limitation on the specific implementation modes of the present application. The embodiments can be combined and referenced with each other on the premise of no contradiction.

[0029] Embodiments of the present application relate to an optical system based on a freeform mirror, such as Figure 1As shown, the optical system comprises, in sequence along the optical axis direction, a free-form mirror 1, a first lens 2, a second lens 3, a third lens 4, a fourth lens 5, a fifth lens 6, a sixth lens 7 and an imaging surface 8; the free-form mirror 1 is used for collecting light rays within a preset angle; the preset angle is greater than 180 degrees; the first lens 2, the second lens 3, the third lens 4, the fourth lens 5, the fifth lens 6 and the sixth lens 7 are collectively used for focusing the light rays collected by the free-form mirror 1, so that the light rays form a light spot on the imaging surface 8; and the first lens 2, the second lens 3, the third lens 4, the fourth lens 5, the fifth lens 6 and the sixth lens 7 are all spherical lenses.

[0030] Compared with the prior art, the embodiment of the application collects 360-degree light rays through the free-form mirror 1, realizes 360-degree omnidirectional simultaneous imaging, only six lenses are needed in the optical system, and all the lenses are ordinary spherical mirrors, which are simple to manufacture and reduce the cost of the optical system.

[0031] In the embodiment of the application, the image plane side of the first lens is concave, the side close to the free-form mirror is convex, and the equivalent focal length of the first lens is negative; the image plane side of the second lens is convex, the side close to the free-form mirror is convex, and the equivalent focal length of the second lens is positive; in the two sides exposed to the outside of the third lens, the image plane side is convex, the side close to the free-form mirror is concave, and the equivalent focal length of the third lens is negative; the image plane side of the fourth lens is convex, the side close to the free-form mirror is convex, and the equivalent focal length of the fourth lens is positive; the image plane side of the fifth lens is convex, the side close to the free-form mirror is convex, and the equivalent focal length of the fifth lens is positive; in the two sides exposed to the outside of the sixth lens, the image plane side is concave, the side close to the free-form mirror is convex, and the equivalent focal length of the sixth lens is positive. The third lens 4 and the sixth lens 7 are both double-cemented lenses.

[0032] The basic parameters of the free-form mirror 1 and the lenses are shown in the following table:

[0033]

[0034] In addition, the radius of curvature of the mirror surface on the image side of the first lens 2 is -2.007 mm, and the radius of curvature of the mirror surface on the other side is -3.773 mm; the radius of curvature of the mirror surface on the image side of the second lens 3 is 14.871 mm, and the radius of curvature of the mirror surface on the other side is -80.932 mm; the radius of curvature of the mirror surface on the image side of the third lens 4 is 6.542 mm, and the radius of curvature of the mirror surface exposed to the outside is 2.726 mm; the radius of curvature of the mirror surface on the image side of the fourth lens 5 is 9.001 mm, and the radius of curvature of the mirror surface on the other side is -107.294 mm; the radius of curvature of the mirror surface on the image side of the fifth lens 6 is 10.890 mm, and the radius of curvature of the mirror surface on the other side is -214.281 mm; the radius of curvature of the mirror surface on the image side of the sixth lens 7 is -75.153 mm, and the radius of curvature of the mirror surface exposed to the outside is -7.437 mm. Among them, the third lens 4 and the sixth lens 7 are two lenses of different materials glued together, the radius of curvature of the bonding surface of the two lenses constituting the third lens 4 is 7.187 mm, and the radius of curvature of the bonding surface of the two lenses constituting the third lens 4 is 6.603 mm.

[0035] The lens thickness of the first lens 2 is 2.341 mm, the lens thickness of the second lens is 4.166 mm, the lens thickness of the third lens 4 is 1.635+3.632 mm, the lens thickness of the fourth lens 5 is 0.307 mm, the lens thickness of the fifth lens 6 is 1.447 mm, and the lens thickness of the sixth lens 7 is 2.073+1.296 mm.

[0036] In addition, the refractive index of different lenses changes according to the lens material, the lens material of the first lens 2 is H-ZF1, the lens material of the second lens 3 is H-ZF1, the third lens 4 is glued together by two lenses with lens materials of H-ZF62 and H-ZLAF56, the lens material of the fourth lens 5 is H-BAK7, the lens material of the fifth lens 6 is H-BAK7, and the sixth lens 7 is glued together by two lenses with lens materials of H-ZBAF52 and H-ZF62. Among them, the refractive index of the first lens 2 and the second lens 3 is the same; the refractive index of the fourth lens 5 and the fifth lens 6 is the same. All lenses in the optical system use high-cost-effective glass to achieve high-quality imaging effect, taking into account the cost while achieving high-quality imaging.

[0037] In addition to the above lens parameters, the effective focal length of the first lens 2 is -13.821 mm; the effective focal length of the second lens 3 is 19.734 mm; the effective focal length of the third lens 4 is -20.6327 mm; the effective focal length of the fourth lens 5 is 14.612 mm; the effective focal length of the fifth lens 6 is 18.261 mm; and the effective focal length of the sixth lens 7 is 15.97054 mm.

[0038] The relevant parameters for the freeform surface mirror 1 are shown in the table below:

[0039]

[0040] Wherein, *conic* represents the conic coefficient, which is -1.832, the optical radius is 6.061 mm, and the radius of curvature is 14.230 mm. *X1YO*, *X1Y1*, *X0Y1*, *X0Y2*, *X2Y0*, *X3Y0*, *X1Y2*, *X2Y1*, *X0Y3*, and *X4Y0* all represent the coordinates corresponding to the freeform surface. Based on the relevant parameters of the freeform surface mirror 1, the specific structure of the freeform surface mirror 1 can be determined using Zernike polynomials. The substrate material of the freeform surface mirror 1 is PMMA, and the surface is coated with a metallic reflective film; the surface material is aluminum (AL). The freeform surface mirror 1 receives light from infinity on the object side and converges it into a lens system composed of multiple lenses. Alternatively, as... Figure 2 As shown, in this embodiment of the invention, the object distance of the optical system is infinite (the distance between the geometric center of the optical axis where the object surface is located and the geometric center of the optical axis on the object side of the first lens 2 is set to infinity). Light is reflected by the mirror 30 to the freeform mirror 11, and then the light is reflected into the lens group 20.

[0041] In addition, such as Figure 1 As shown, the distance between the freeform mirror 1 and the first lens 2 is 30.089 mm, which can also be described as the distance from the geometric center of the optical axis of the rightmost face of the first lens 2 to the geometric center of the optical axis of the freeform mirror 1 is 30.089 mm; the distance between the first lens 2 and the second lens 3 is 0.702 mm, which can also be described as the distance from the geometric center of the optical axis of the rightmost face of the second lens 3 to the geometric center of the optical axis of the leftmost face of the first lens 2 is 0.702 mm; the distance between the second lens 3 and the third lens 4 is 0.277 mm, which can also be described as the distance from the geometric center of the optical axis of the rightmost face of the third lens 4 to the geometric center of the optical axis of the leftmost face of the second lens 3 is 0.277 mm; the distance between the third lens 4 and the fourth lens 5 is 0.419 mm, which can also be described as the distance from the geometric center of the optical axis of the rightmost face of the third lens 4 to the geometric center of the optical axis of the leftmost face of the second lens 3 is 0.419 mm. The distance between the geometric center of the optical axis of the rightmost face of lens 5 and the geometric center of the optical axis of the leftmost face of the third lens 4 is 0.419 mm; the distance between the fourth lens 5 and the fifth lens 6 is 0.122 mm, which can also be said to be the distance between the geometric center of the optical axis of the rightmost face of the fifth lens 6 and the geometric center of the optical axis of the leftmost face of the fourth lens 5; the distance between the fifth lens 6 and the sixth lens 7 is 0.282 mm, which can also be said to be the distance between the geometric center of the optical axis of the rightmost face of the sixth lens 7 and the geometric center of the optical axis of the leftmost face of the fifth lens 6; the distance between the sixth lens 7 and the imaging plane 8 is 5.708 mm, which can also be said to be the distance between the geometric center of the optical axis of the imaging plane 8 and the geometric center of the optical axis of the leftmost face of the sixth lens 7.

[0042] In the embodiment of the present application, the total optical length of the imaging lens set 20 is 24.406 mm, and the total length of the optical system TTL is 54.494 mm.

[0043] Regarding the performance parameter test of the optical system in the embodiment of the present application, the following results are obtained:

[0044] The MTF curve of the optical system in the embodiment of the present application is shown in FIG. 6, which is the MTF curve of the optical system at 50 LP / mm, 100 LP / mm and 200 LP / mm, respectively. Figures 3 to 5

[0045] The SPT point diagram of the optical system in the embodiment of the present application is shown in FIG. 7, and the point diagrams obtained by 8 groups of parameters are shown in FIG. 8, and each group of parameters is as follows: Figure 6 Figure 6

[0046]

[0047] The relative luminance diagram of the optical system in the embodiment of the present application is shown in FIG. 9, which is tested at a wavelength of 0.587562 microns. Figure 7

[0048] The field curvature diagram of the optical system in the embodiment of the present application is shown in FIG. 10, and the related test parameters of the field curvature diagram include: the maximum field of view is 50 degrees, the sagittal field curvature is 0.0038 mm, and the meridional field curvature is 0.0419 mm. Figure 8 The distortion diagram of the optical system in the embodiment of the present application is shown in FIG. 11, and the trend of the three different curves in the diagram is roughly coincided, and the related test parameters of the distortion diagram include: the maximum field of view is 50 degrees, and the maximum distortion is 23.0373%.

[0049] Figure 9 The defocus curve of the optical system in the embodiment of the present application is shown in FIG. 12, and the related test parameters of the defocus curve include: the spatial frequency is 50 cycles / mm.

[0050] In addition, regarding the imaging surface 8, a height-adapted multi-small-size CCD sensor or a 1 / 18 inch CMOS chip can be used, so as to improve the panoramic image accuracy under a large field of view. Figure 10

[0051]

[0052] ​​​​​​​Compared with the prior art, the embodiment of the present application optimizes the focal length of the lens to 0.65 mm, the horizontal full field of view reaches 360 degrees, the depression angle is 50 degrees, the elevation angle is 15 degrees, and the total length of the optical system is less than 55 mm, which is beneficial to the miniaturization of the device. In the optical system, no additional scanning components are needed, and the panoramic image can be obtained without combining the image stitching technology, which has the advantage of real-time acquisition of panoramic images. Finally, the aberration correction of the optical system in the embodiment of the present application is excellent, the field curvature is optimized to less than 0.03 mm, and the distortion is less than 25%; the optical system MTF performs excellently, and the structure and manufacturability are stable.

[0053] The embodiment of the present application also relates to an electronic device, comprising: a camera module; the camera module comprises an optical lens, and the optical lens adopts the optical system based on the free-form surface mirror.

[0054] The related parameters of the optical lens are shown in the following table:

[0055]

[0056] In addition, the electronic device is a virtual reality device, a vehicle-mounted device, a reconnaissance satellite or a monitoring device.

[0057] In the embodiment of the optical system based on the free-form surface mirror, the implementation details are consistent with the previous embodiment of the optical system based on the free-form surface mirror, and the related technical details mentioned in the embodiment of the optical system based on the free-form surface mirror are still effective in this embodiment. In order to reduce repetition, they will not be repeated here.

[0058] Those skilled in the art can understand that the above embodiments are specific embodiments for implementing the present application, and in actual application, various changes can be made in form and details without departing from the spirit and scope of the present application.

Claims

1. An optical system based on a freeform surface mirror, characterized in that, include: Along the optical axis, a freeform surface mirror, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and an imaging surface are arranged sequentially. The freeform surface mirror is used to collect light within a preset angle; wherein the preset angle is greater than 180 degrees; The first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are used together to focus the light collected by the freeform surface mirror so that the light forms a light spot on the imaging surface; wherein, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are all spherical lenses; The image plane side of the first lens is concave, and the side near the freeform mirror is convex, and the equivalent focal length of the first lens is negative. The image plane side of the second lens is convex, the side closer to the freeform mirror is convex, and the equivalent focal length of the second lens is positive. The third lens has two exposed external sides, with the image plane side being convex and the side closer to the freeform mirror being concave, and the equivalent focal length of the third lens is negative. The image plane side of the fourth lens is convex, the side closest to the freeform mirror is convex, and the equivalent focal length of the fourth lens is positive. The image plane side of the fifth lens is convex, the side closest to the freeform mirror is convex, and the equivalent focal length of the fifth lens is positive. The sixth lens has two exposed external sides, with the image plane side being concave and the side closer to the freeform mirror being convex, and the equivalent focal length of the sixth lens is positive.

2. The optical system based on a freeform surface mirror according to claim 1, characterized in that, Both the third lens and the sixth lens are cemented doublet lenses.

3. The optical system based on a freeform surface mirror according to claim 1, characterized in that, The equivalent focal length of the first lens is -13.821 mm; The equivalent focal length of the second lens is 19.734 mm; The equivalent focal length of the third lens is -20.6327 mm; The equivalent focal length of the fourth lens is 14.612 mm; The equivalent focal length of the fifth lens is 18.261 mm; The equivalent focal length of the sixth lens is 15.97054 mm.

4. The optical system based on a freeform surface mirror according to claim 1, characterized in that, The radius of curvature of the mirror surface on the image plane side of the first lens is -2.007 mm, and the radius of curvature of the mirror surface on the other side is -3.773 mm; The radius of curvature of the mirror surface on the image plane side of the second lens is 14.871 mm, and the radius of curvature of the mirror surface on the other side is -80.932 mm; The radius of curvature of the mirror surface on the image plane side of the third lens is 6.542 mm, and the radius of curvature of the mirror surface on the other side exposed to the outside is 2.726 mm. The radius of curvature of the mirror surface on the image plane side of the fourth lens is 9.001 mm, and the radius of curvature of the mirror surface on the other side is -107.294 mm. The radius of curvature of the image plane side of the fifth lens is 10.890 mm, and the radius of curvature of the other side of the lens is -214.281 mm. The radius of curvature of the image plane side of the sixth lens is -75.153 mm, and the radius of curvature of the other side of the lens exposed to the outside is -7.437 mm.

5. The optical system based on a freeform surface mirror according to claim 1, characterized in that, The first lens and the second lens have the same refractive index; the fourth lens and the fifth lens have the same refractive index.

6. The optical system based on a freeform surface mirror according to claim 1, characterized in that, The distance between the freeform surface mirror and the first lens is 30.089 mm; The distance between the first lens and the second lens is 0.702 mm; The distance between the second lens and the third lens is 0.277 mm; The distance between the third lens and the fourth lens is 0.419 mm; The distance between the fourth lens and the fifth lens is 0.122 mm; The distance between the fifth lens and the sixth lens is 0.282 mm; The distance between the sixth lens and the imaging surface is 5.708 mm.

7. The optical system based on a freeform surface mirror according to claim 1, characterized in that, The freeform mirror has a radius of curvature of 14.230 mm, a conic coefficient of -1.832, and an optical radius of 6.061 mm.

8. An electronic device, characterized in that, include: A camera module; the camera module includes an optical lens, and the optical lens employs an optical system based on a freeform surface mirror as described in any one of claims 1 to 7.

9. The electronic device according to claim 8, characterized in that, The electronic device is a virtual reality device, a vehicle-mounted device, a reconnaissance satellite, or a surveillance device.

Images