Four-frame optical system

Abstract

This invention discloses a four-lens optical system, belonging to the field of optical imaging. Along the optical axis from the object plane to the image plane, the system comprises: a first lens L1, a second lens L2, a third lens L3, a fourth lens group L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, and an image plane L9. The first, third, fourth lens group, fifth, seventh, and eighth lenses have positive optical power, while the second and sixth lenses have negative optical power. The four lenses in the fourth lens group L4... 41 、l 42 、l 43 、l 44 Similarly, in the optical system, the four single-channel aperture stops are located at the lens l. 41 、l 42 、l 43 、l 44 The optical system of this invention uses only one detector, but has the function of simultaneous four-band imaging of the same imaging target. This invention also has the advantages of small distortion, no vignetting across the entire field of view, compact structure, and low research and development cost.

Description

Technical fields:

[0001] This invention relates to an optical system, and more particularly to a four-frame optical system, belonging to the field of optical imaging. Background technology:

[0002] Traditional multispectral cameras typically use beam-splitting prisms for beam splitting. Systems using beam-splitting prisms require sufficient backstop to accommodate them, increasing the length and design complexity of the optical system. Furthermore, a crucial factor is the need for multiple detectors to receive images from different spectral bands, which not only increases development costs but also enlarges the system's size and weight. The use of multiple detectors also introduces asynchrony in multispectral imaging; therefore, synchronization circuitry is required for simultaneous multispectral imaging. Summary of the Invention:

[0003] To overcome the problems of high R&D costs, large size and weight, and complex control circuits of traditional multispectral frame cameras, the main purpose of this invention is to provide a four-frame optical system. This system uses only one detector but has the function of simultaneous imaging of the same imaging target in four bands. The system also has the advantages of low distortion, no vignetting in the entire field of view, compact structure, and low R&D costs.

[0004] The solution to the technical problem of this invention is:

[0005] This invention discloses a four-lens optical system, comprising, along the optical axis from the object plane to the image plane, the following components arranged sequentially: a first lens L1, a second lens L2, a third lens L3, a fourth lens group L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, and an image plane L9. The fourth lens group L4 includes lens 1. 41 l 42 l 43 l 44 The first lens, third lens, fourth lens group, fifth lens, seventh lens, and eighth lens have positive optical power, while the second lens and sixth lens have negative optical power. The four lenses in the fourth lens group L4... 41 l 42 l 43 l 44 Similarly, in the optical system, the four single-channel aperture stops are located at the lens l. 41 l 42 l 43 l 44 The side of the object.

[0006] To achieve chromatic aberration and focus position compensation while ensuring functionality, and to reduce chromatic aberration and distortion of the lens, each lens group of the optical system must meet the following conditions:

[0007] 0.075 <f / f 13 <0.31;

[0008] 0.54 <f / f4<0.78;

[0009] 0.30 <f / f 58 <0.51;

[0010] Where f is the focal length of the entire optical system, f 13 f is the total focal length of the first, second, and third lenses, and f4 is the focal length of a single lens in the fourth lens group. 58 This is the total focal length of the fifth, sixth, seventh, and eighth lenses.

[0011] The focal length parameters of each lens group in the optical system are obtained through multiple iterations of optimization based on experience, on the initial structure of the optical system. The constraints of these parameters determine that the combination of the optical system in this patent can achieve the minimum chromatic aberration and distortion effect.

[0012] Furthermore, the lens l 43 and lens l 44 The line connecting the centers is the X-axis, and the lens l 43 and lens l 42 The line connecting the centers is the Y-axis, and the optical axis is the Z-axis.

[0013] Furthermore, the lens l 41 l 42 l 43 l 44 Translation only exists on the X and Y axes, and the lens l 41 l 42 l 43 l 44 The absolute values ​​of the translations on the X and Y axes are equal.

[0014] Furthermore, the lens l 41 l 42 l 43 l 44 180 along the optical axis 0 Rotational symmetry.

[0015] Furthermore, the imaging area of ​​the detector is divided into four equal parts, with each of the four single-channel imaging regions in the optical system occupying one part.

[0016] Furthermore, the incident light rays parallel to the optical axis are imaged at the center of the imaging area corresponding to each channel.

[0017] Furthermore, the detector has a 100% utilization rate.

[0018] Furthermore, the optical system exhibits no vignetting across the entire field of view in each channel.

[0019] Beneficial effects:

[0020] 1. The present invention discloses a four-frame optical system in which the focal length parameters of each lens group of the optical system are constructed based on the initial structure of the optical system through multiple iterations of parameter constraint model. The constructed parameter constraint condition enables the optical system to adapt to multiple combination methods. Under the premise of ensuring function in multiple combination methods, chromatic aberration and focal position compensation are achieved, thereby reducing the chromatic aberration and distortion of the optical system.

[0021] 2. The present invention discloses a four-segment optical system, which adopts a segment imaging structure, wherein the fourth lens is divided into four single channels, and the target is imaged in the four quadrants of the same detector. Only one detector is used, but it has the function of synchronous imaging of the same imaging target in four bands. The system also has the advantages of small distortion, no vignetting in the whole field of view, compact structure, and low research and development cost. Attached image description:

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a three-dimensional structural diagram of the optical system of the present invention;

[0024] Figure 2 This is a two-dimensional structural diagram of the optical system of the present invention. Detailed implementation method:

[0025] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0026] like Figure 1 As shown, the four-frame optical system disclosed in this embodiment has the following components arranged sequentially along the optical axis from the object plane to the image plane: a first lens L1, a second lens L2, a third lens L3, and a fourth lens group L4 (including lens 1). 41 l 42 l 43 l 44The system comprises a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, and an image plane L9. The first, third, and fourth lens groups, the fifth, seventh, and eighth lenses have positive optical power, while the second and sixth lenses have negative optical power. The fourth lens group L4 contains four lenses... 41 l 42 l 43 l 44 Similarly, in the optical system, the four single-channel aperture stops are located at the lens l. 41 l 42 l 43 l 44 The side of the object.

[0027] As a specific implementation of this solution and not a limitation, each lens of this optical system satisfies the following conditions:

[0028] 0.075 <f / f 13 <0.31;

[0029] 0.54 <f / f4<0.78;

[0030] 0.30 <f / f 58 <0.51;

[0031] Where f is the focal length of the entire optical system, f 13 f is the total focal length of the first, second, and third lenses, and f4 is the focal length of a single lens in the fourth lens group. 58 This is the total focal length of the fifth, sixth, seventh, and eighth lenses.

[0032] The lens l 43 and lens l 44 The line connecting the centers is the X-axis, and the lens l 43 and lens l 42 The line connecting the centers is the Y-axis, and the optical axis is the Z-axis.

[0033] The lens l 41 l 42 l 43 l 44 Translation only exists on the X and Y axes, and the lens l 41 l 42 l 43 l 44 The absolute values ​​of the translations on the X and Y axes are equal.

[0034] The lens l 41 l 42 l 43 l 44 180 along the optical axis 0Rotational symmetry.

[0035] The imaging area of ​​the detector is divided into four equal parts, with each of the four single-channel imaging areas in the optical system occupying one part, resulting in 100% utilization of the detector.

[0036] The incident light rays parallel to the optical axis are imaged at the center of the imaging area corresponding to each channel.

[0037] All lenses in this embodiment are spherical lenses, which reduces the difficulty of processing and assembly, helps to ensure the manufacturability and assembly yield of the four-frame optical system, and reduces development costs.

[0038] For ease of description, the light-incident surface of the lens is referred to as the front surface, and the light-exiting surface of the lens is referred to as the rear surface.

[0039] As a further preferred embodiment, the radius of curvature of the front surface of the first lens L1 is -1929.1 mm, the radius of curvature of the rear surface is -32.9 mm, the center thickness is 4.5 mm, and the lens aperture is Φ21.5 mm.

[0040] The second lens L2 has a front surface radius of curvature of -10.8mm, a rear surface radius of curvature of 13.9mm, a center thickness of 3.7mm, and a lens aperture of Φ12.1mm.

[0041] The third lens L3 has a front surface radius of curvature of 46.5 mm, a rear surface radius of curvature of -12.1 mm, a center thickness of 4.5 mm, and a lens aperture of Φ12.3 mm.

[0042] Lens l 41 The radius of curvature of the front surface is -88.2mm, the radius of curvature of the rear surface is -10.1mm, the center thickness is 4.5mm, and the lens aperture is Φ4.2mm.

[0043] The fifth lens L5 has a front surface radius of curvature of -34.3mm, a rear surface radius of curvature of -11.1mm, a center thickness of 3.5mm, and a lens aperture of Φ12.0mm.

[0044] The sixth lens L6 has a front surface radius of curvature of -11.5mm, a rear surface radius of curvature of 19.7mm, a center thickness of 1.2mm, and a lens aperture of Φ12.7mm.

[0045] The seventh lens L7 has a front surface radius of curvature of 28.4 mm, a rear surface radius of curvature of -14.8 mm, a center thickness of 3.3 mm, and a lens aperture of Φ12.0 mm.

[0046] The eighth lens L8 has a front surface radius of curvature of 31.7 mm, a rear surface radius of curvature of 96.4 mm, a center thickness of 1.3 mm, and a lens aperture of Φ13.0 mm.

[0047] As a further preferred embodiment, the distance between the first lens L1 and the second lens L2 is 6.0 mm; the distance between the second lens L2 and the third lens L3 is 1.4 mm; and the distance between the third lens L3 and lens L1 is... 41 The distance is 0.5mm; lens l 41 The distance between the fifth lens L5 and the sixth lens L6 is 1.1 mm; the distance between the fifth lens L5 and the sixth lens L6 is 0.4 mm; the distance between the sixth lens L6 and the seventh lens L7 is 0.7 mm; the distance between the seventh lens L7 and the eighth lens L8 is 0.1 mm; and the distance between the eighth lens L8 and the image plane L9 is 4.2 mm.

[0048] The first lens L1 is made of ZF7, the second lens L2 is made of F4, and the third lens L3 is made of H-ZLAF50D. 41 The material of the fifth lens L5 is ZF7, the material of the sixth lens L6 is ZF6, the material of the seventh lens L7 is H-ZLAF50D, and the material of the eighth lens L8 is ZF7.

[0049] As a further preferred implementation method, in the first channel of the optical system, lens l 41 Translate 2.4mm along the X-axis and 3.2mm along the Y-axis; in the second channel of the optical system, lens l 42 Translation along the X-axis by -2.4mm, and along the Y-axis by 3.2mm; in the third channel of the optical system, lens l 43 Translation along the X-axis -2.4mm, translation along the Y-axis -3.2mm; in the fourth channel of the optical system, lens l 44 Translate 2.4mm along the X-axis and -3.2mm along the Y-axis;

[0050] Among them, lens l 43 and lens l 44 The line connecting the centers is the X-axis, and the lens l 43 and lens l 42 The line connecting the centers is the Y-axis, and the optical axis is the Z-axis.

[0051] The specific parameters of the four-frame optical system disclosed in this embodiment are as follows:

[0052] Focal length 10.2mm; single-channel relative aperture F / 4.3; horizontal full field of view 26.5°. 0The spectral range is 900nm~1700nm; there is no vignetting across the entire field of view; the maximum distortion across the entire field of view is <2.5%; the total length of the optical system (from the first surface of the optical system to the image plane) is 40mm.

[0053] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A four-frame optical system, characterized in that, Along the optical axis from the object plane to the image plane, the following lenses are arranged sequentially: a first lens L1, a second lens L2, a third lens L3, a fourth lens group L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, and an image plane L9; the fourth lens group L4 includes lens l 41 l 42 l 43 l 44 The first lens, third lens, fourth lens group, fifth lens, seventh lens, and eighth lens have positive optical power, while the second lens and sixth lens have negative optical power. The four lenses in the fourth lens group L4... 41 l 42 l 43 l 44 Similarly, in the optical system, the four single-channel aperture stops are located at the lens l. 41 l 42 l 43 l 44 The side of the object; Each lens group of the optical system satisfies the following condition: (1)0.075<f / f 13 <0.31; (2) 0.54 <f / f4<0.78; (3)0.30<f / f 58 <0.51; Where f is the focal length of the entire optical system, f 13 f is the total focal length of the first, second, and third lenses, and f4 is the focal length of a single lens in the fourth lens group. 58 This is the total focal length of the fifth, sixth, seventh, and eighth lenses.

2. The four-frame optical system according to claim 1, characterized in that, Lens l 43 and lens l 44 The line connecting the centers is the X-axis, and the lens l 43 and lens l 42 The line connecting the centers is the Y-axis, and the optical axis is the Z-axis.

3. The four-frame optical system according to claim 1, characterized in that, Lens l 41 l 42 l 43 l 44 Translation only exists on the X and Y axes, and the lens l 41 l 42 l 43 l 44 The absolute values ​​of the translations on the X and Y axes are equal.

4. The four-frame optical system according to claim 1, characterized in that, Lens l 41 l 42 l 43 l 44 180 along the optical axis 0 Rotational symmetry.

5. The four-frame optical system according to claim 1, characterized in that, The detector's imaging area is divided into four equal parts, with each of the four single-channel imaging regions in the optical system occupying one part.

6. The four-frame optical system according to claim 1, characterized in that, Incident rays parallel to the optical axis are imaged at the center of the imaging area corresponding to each channel.

7. The four-frame optical system according to claim 1, characterized in that, The detector is 100% utilized.

8. The four-frame optical system according to claim 1, characterized in that, The optical system has no vignetting across the entire field of view in each channel.

9. The four-frame optical system according to claim 1, characterized in that, The optical system uses only one detector and, through a combination of lenses that meet parameter constraints, has the function of simultaneous imaging of the same imaging target in four bands.

Images