CN118169843A - A telephoto optical system and lens - Google Patents

Abstract

The invention provides a long-focus optical system, which comprises an optical filter, a first lens, a first cemented lens, a liquid lens, a second cemented lens, a second lens and a third lens which are sequentially arranged from an object side to an image side along a main optical axis, wherein the focusing position of the long-focus optical system is adjusted by controlling the driving voltage or the driving current of the liquid lens; the design of the invention ensures that the lens can complete quick focusing by adjusting the voltage or the driving current of the liquid lens when the long-focus optical system takes the image in a small visual angle range.

Description

A telephoto optical system and lens

Technical Field

The present invention relates to the field of optical imaging technology, and in particular to a telephoto optical system and a lens.

Background technique

Telephoto optical systems usually have a relatively long focal length and are well suited for capturing scenes and subjects at a distance. However, telephoto optical systems require more correction of system chromatic aberration, astigmatism, and off-axis astigmatism, etc. In addition, telephoto requires more consideration of the control of the total optical length of the system.

Summary of the invention

The purpose of the present invention is to overcome the above technical problems and provide a telephoto optical system and a lens.

In order to achieve the above purpose and other purposes, the present invention is implemented through the following technical solutions: a telephoto optical system is provided, comprising a filter, a first lens, a first cemented lens, a liquid lens, a second cemented lens, a second lens and a third lens, which are sequentially arranged along the main optical axis of the telephoto optical system from the object side to the image side, and the focus position of the telephoto optical system is adjusted by controlling the driving voltage or driving current of the liquid lens; the first cemented lens comprises a fourth lens and a fifth lens, the image plane of the fourth lens is fixedly connected to the object plane of the fifth lens, the object plane of the fourth lens is a convex spherical surface, the image plane of the fourth lens is a convex spherical surface, the object plane of the fifth lens is a concave spherical surface, and the image plane of the fifth lens is a concave spherical surface; the second cemented lens comprises a sixth lens and a seventh lens, the image plane of the sixth lens is fixedly connected to the object plane of the seventh lens, the object plane of the sixth lens is a concave spherical surface, the image plane of the sixth lens is a concave spherical surface, the object plane of the seventh lens is a convex spherical surface, and the image plane of the seventh lens is a convex spherical surface.

Furthermore, the object surface of the first lens is a convex spherical surface with a curvature radius of 8.14 mm, and the image surface of the first lens is a plane.

Furthermore, the first cemented lens includes a fourth lens and a fifth lens, the image plane of the fourth lens is fixedly connected to the object plane of the fifth lens, the object plane of the fourth lens is a convex spherical surface with a curvature radius of 8 mm, the image plane of the fourth lens is a convex spherical surface with a curvature radius of -13.4 mm, the object plane of the fifth lens is a concave spherical surface with a curvature radius of -13.4 mm, and the image plane of the fifth lens is a concave spherical surface with a curvature radius of 7.6 mm.

Furthermore, the second cemented lens includes a sixth lens and a seventh lens, the image plane of the sixth lens is fixedly connected to the object plane of the seventh lens, the object plane of the sixth lens is a concave spherical surface with a curvature radius of -6.63mm, the image plane of the sixth lens is a concave spherical surface with a curvature radius of 3mm, the object plane of the seventh lens is a convex spherical surface with a curvature radius of 3mm, and the image plane of the seventh lens is a convex spherical surface with a curvature radius of -6mm.

Furthermore, the object surface of the second lens is a concave spherical surface with a curvature radius of -6 mm, and the image surface of the second lens is a convex spherical surface with a curvature radius of -50 mm.

Furthermore, the object surface of the third lens is a convex spherical surface with a curvature radius of 13 mm, and the image surface of the third lens is a convex spherical surface with a curvature radius of -13 mm.

Furthermore, the optical spacing between the filter and the first lens is between 0.18mm-0.22mm; the optical spacing between the first lens and the first cemented lens is between 0.59mm-0.63mm; the optical spacing between the first cemented lens and the liquid lens is between 2.38mm-2.42mm; the optical spacing between the liquid lens and the second cemented lens is between 2.38mm-2.42mm; the optical spacing between the second cemented lens and the second lens is between 0.08mm-1.02mm; and the optical spacing between the second lens and the third lens is between 0.63mm-0.67mm.

Furthermore, it also includes a filter, which is arranged on the left side of the first lens, and is an IR filter. The object surface of the IR filter is a plane, and the image surface of the IR filter is a plane.

Furthermore, it also includes an aperture stop, and the aperture stop is arranged in the liquid lens.

Furthermore, the operating wavelength of the telephoto optical system is between 486nm and 650nm.

Furthermore, the system has an aperture of F/6.6, a focal length of 50 mm, a diagonal field of view of 7.74°, and a CRA of 9°.

Furthermore, the image plane diameter of the optical system is 6.8 mm.

Another aspect of the present invention provides a lens, which includes the telephoto optical system described above.

The design of the present invention has small distortion and small light energy attenuation, and adopts a liquid lens instead of a manual focus adjustment of the transmission, so that when the telephoto optical system takes images within a small viewing angle range, the voltage or driving current of the liquid lens can be adjusted to enable the lens to quickly focus. Compared with the focusing method of the transmission mechanical method, the solution of the present invention improves the focusing efficiency and accuracy, and the user experience is greatly improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural diagram of a telephoto optical system of the present invention.

FIG. 2 shows a RayFan diagram of the present invention in different fields of view when the working wavelengths are 486 nm, 588 nm and 656 nm.

FIG. 3 shows a field curvature diagram and a distortion diagram of the present invention when the working wavelength is 486.1 nm, 588.6 nm and 656.3 nm.

FIG. 4 shows a Fourier transformed modulation transfer function (FFTMTF) diagram of the present invention within the working band.

FIG. 5 shows an image plane illumination diagram of the present invention when the working wavelength is 587.6 nm.

FIG. 6 shows the diffusion circle diagram of the present invention when the working wavelength is 486.1 nm, 588.6 nm and 656.3 nm.

Detailed ways

The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. It should be noted that many specific details are set forth in the following description to facilitate a full understanding of the present invention, but the present invention can also be implemented in other ways different from those described herein, and therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

In the present invention, the surface of each lens closest to the focused object plane is called the "object plane", and the surface of each lens closest to the imaging plane A is called the "image plane". When the object plane of the lens is convex or the image plane is concave, the object plane curvature or the image plane curvature is positive; when the object plane of the lens is concave or the image plane is convex, the object plane curvature or the image plane curvature is negative.

As shown in FIG1 , the present invention provides a telephoto optical system, wherein the object plane of the telephoto optical system is on the left, the initial focus object plane is at infinity, the image plane A is on the right, and the image distance is 6 mm. The telephoto optical system is provided with a filter 10, a first lens 11, a first cemented lens 12, a liquid lens 13, a second cemented lens 14, a second lens 15, and a third lens 16 in sequence along the main optical axis of the telephoto optical system from the focus object plane to the imaging plane A according to specific optical intervals, and the curvature characteristics of the liquid lens 13 are changed by applying a driving voltage controlled by software to adjust the focus position of the telephoto optical system and realize the focus of the telephoto optical system. In one embodiment, the filter is an IR filter.

In this example, the total optical length of the telephoto optical system (from the object surface curvature center of the first lens 11 to the imaging surface A) is 61.44 mm. The optical spacing parameters between the lenses of the telephoto optical system are as follows: the optical spacing between the filter 10 and the first lens 11 is 0.2 mm, with a tolerance of ±0.02 mm; the optical spacing between the first lens 11 and the first cemented lens 12 is 0.61 mm, with a tolerance of ±0.02 mm; the optical spacing between the first cemented lens 12 and the liquid lens 13 is 2.4 mm, with a tolerance of ±0.02 mm; the optical spacing between the liquid lens 13 and the second cemented lens 14 is 2.4 mm, with a tolerance of ±0.02 mm; the optical spacing between the second cemented lens 14 and the second lens 15 is 1 mm, with a tolerance of ±0.02 mm; the optical spacing between the second lens 15 and the third lens 16 is 0.65 mm, with a tolerance of ±0.02 mm. It should be noted that the optical spacing can be flexibly adjusted as needed and is not limited to the sizes listed above.

The above-mentioned optical spacing parameters are mainly based on three factors: diagonal field angle, aperture and CRA value. The aperture of the telephoto optical system is F/6.6, the focal length is 50mm, the diagonal field angle is 7.74°, the CRA is 9°, and the image diameter is 6.8mm. According to the focal length of the lens of 50mm and the image diameter of 6.8mm, it can be calculated that the viewing angle of the lens is 7.74°; to achieve an aperture value of F/6.6, the lens needs to be matched with an A39 liquid lens, and the clear aperture of the liquid lens is 3.9mm; the lens also needs to meet the image side CRA within 10° to ensure that there will be no abnormalities such as imaging spots or edge illumination attenuation when paired with the chip. Based on these three factors, we calculated the angles and incident heights of the first principal ray and the second principal ray on the incident surface and the exit surface of each lens in the telephoto optical system. Specifically, the incident heights of the first principal ray and the second principal ray on the surface of the filter 10 are 12 mm in the front and 11.91 mm in the back, the incident heights on the surface of the first lens 11 are 11.596 mm in the front and 10.362 mm in the back, and the incident heights on the surface of the first cemented lens 12 are 8.54 mm in the front and 4.926 mm in the back; the incident heights on the surface of the second cemented lens 14 are 2.608 mm in the front and 3.246 mm in the back, the incident heights on the surface of the second lens 15 are 3.464 mm and 3.894 mm in the back, and the incident heights on the surface of the third lens 16 are 5.496 mm in the front and 5.97 mm in the back. The incident angles of the first principal ray and the second principal ray on the surface of the filter 10 are 3.89° at the front and 2.563° at the back; the incident angles on the surface of the first lens 11 are 10° at the front and 7.536° at the back; the incident angles on the surface of the first cemented lens 12 are 1.239° at the front and 4.092° at the back; the incident angles on the surface of the cemented sheet 4 are 8.179° at the front and 3.681° at the back; the incident angles on the surface of the lens 5 are 0.462° at the front and 12.274° at the back; the incident angles on the surface of the lens 6 are 35.48° at the front and 3.122° at the back. The acceptable deviations of the turning angles and starting height values of the light at each lens are converted into optical spacing and tolerance values between lenses.

The specific parameters of each lens are introduced in detail below. Combined with Figure 1, the object plane of the filter 10 is a plane, the image plane of the filter 10 is also a plane, and the center thickness of the filter 10 is 0.21mm; the object plane of the first lens 11 is a convex spherical surface with a radius of curvature of 8.14mm, the image plane of the first lens 11 is a plane, and the center thickness of the first lens 11 is 4mm, with a tolerance of ±0.02mm; the first cemented lens 12 is a double cemented lens, including a fourth lens 121 and a fifth lens 122, and the image plane of the fourth lens 121 and the object plane of the fifth lens 122 can be fixed by optical colloid, or clamped and fixed by mechanical means (such as positioning grooves). The image surface curvature of the fourth lens 121 is equal to the object surface curvature of the fifth lens 122. Specifically, the object surface of the fourth lens 121 is a convex spherical surface with a curvature radius of 8 mm, the image surface of the fourth lens 121 is a convex spherical surface with a curvature radius of -13.4 mm, the center thickness of the fourth lens 121 is 3.5 mm, and the tolerance is ±0.02 mm. The object surface of the fifth lens 122 is a concave spherical surface with a curvature radius of -13.4 mm, the image surface of the fifth lens 122 is a concave spherical surface with a curvature radius of 7.6 mm, and the center thickness of the fifth lens 122 is 1.3 mm, and the tolerance is ±0.02 mm. The second cemented lens 14 also adopts a double cemented lens, including a sixth lens 141 and a seventh lens 142. The image surface of the sixth lens 141 and the object surface of the seventh lens 142 can be fixed by optical colloid, or can be clamped and fixed by mechanical means (such as positioning grooves). The object surface of the sixth lens 141 is a concave spherical surface with a curvature radius of -6.63mm, the image surface of the sixth lens 141 is a concave spherical surface with a curvature radius of 3mm, the center thickness of the sixth lens 141 is 1mm, and the tolerance is ±0.02mm; the object surface of the seventh lens 142 is a convex spherical surface with a curvature radius of 3mm, the image surface of the seventh lens 142 is a convex spherical surface with a curvature radius of -6mm, the center thickness of the seventh lens 142 is 1.52mm, and the tolerance is ±0.02 mm; the object surface of the second lens 15 is a concave spherical surface with a curvature radius of -6mm, the image surface of the second lens 15 is a convex spherical surface with a curvature radius of -50mm, the center thickness of the second lens 15 is 0.8mm, and the tolerance is ±0.02mm; the object surface of the third lens 16 is a convex spherical surface with a curvature radius of 13mm, the image surface of the third lens 16 is a convex spherical surface with a curvature radius of -13mm, the center thickness of the third lens 16 is 3.5mm, and the tolerance is ±0.02mm. The surface tolerances of all the above curvatures are aperture 3-5, local aperture 0.3-0.5, and are all detected by interferometer.

As one of the implementation modes, an aperture stop (not shown) is also provided in the liquid lens 13. For example, the aperture stop can be provided at the packaged filter position in the liquid lens 13. The aperture stop is used to limit the size of the on-axis imaging light beam.

In this example, all lenses except the liquid lens 13 are made of glass. The liquid lens 13 can be Corning-A25H of Corning, and of course other types of liquid lenses that can meet the optical path requirements can also be used. The filter 10 can be, for example, Schott's float glass (d263teco); the first lens 11 can be, for example, heavy phosphorus crown glass (h-zpk1a); the fourth lens 121 can be, for example, heavy phosphorus crown glass (h-zpk1a); the fifth lens 122 can be, for example, heavy lanthanum flint glass (h-zlaf76a); the sixth lens 141 can be, for example, heavy flint glass (h-zf52gt); the seventh lens 142 can be, for example, heavy crown glass (h-zk14); the second lens 15 can be, for example, heavy flint glass (h-zf1a); the third lens 16 can be, for example, heavy flint glass (h-zf1a).

In this example, the working environment of the telephoto optical system is a visible light environment, and the working wavelength is between 486nm-650nm. The axial chromatic aberration and the vertical chromatic aberration of the entire system are compensated and corrected by cemented lenses with different refractive indices and dispersion coefficients. First, the system adopts a double Gaussian optical structure as the initial structure of the system, and the liquid lens 13 adopts a symmetrical design before and after, which can reduce the spherical aberration of the telephoto optical system while also minimizing the chromatic aberration caused by the band difference. Secondly, we use a combination of heavy phosphorus crown glass (H-ZPK1A) and heavy flint glass (H-ZF52GT). This combination is a combination of high refractive index and low dispersion and low refractive index and high dispersion. They produce dispersion aberrations of opposite magnitude before and after the aperture stop, respectively, thereby minimizing the aberration of the telephoto optical system.

The two sets of cemented lenses are symmetrical to the front and back of the liquid lens (aperture stop). Based on the difference in refractive index dispersion of the cemented lenses, the positive and negative chromatic aberrations before and after the stop are corrected through a symmetrical structure. The two sets of cemented lenses 12 and 14 are bonded in a combination of double convex and double concave, and the two cemented concave surfaces are both facing the direction of the aperture stop. Therefore, while correcting the chromatic aberration, a larger light output angle can be guaranteed, so that the aperture stop can be the minimum position of the system's aperture.

The technical solution of the telephoto optical system of the present invention can effectively correct system chromatic aberration, astigmatism and off-axis astigmatism. The filter can effectively block stray light of a certain wavelength from entering the lens, avoiding the need for the telephoto lens to additionally correct stray light of non-designed wavelengths, resulting in poor imaging chromatic aberration. It also provides dust, water, and impact protection for the lens.

Please refer to Figure 2, which shows a ray fan diagram of the telephoto optical system in different field of view areas when the working wavelength is 486nm, 588nm and 656nm. Figure 2 shows the aberration set generated in different field of view areas, and the difference in meridian and sagittal plane aberrations can be seen in each field of view area.

Please refer to Figure 3, which shows the field curvature and distortion diagrams of the telephoto optical system when the working wavelengths are 486.1nm, 587.6nm and 656.3nm. In the left figure, the horizontal axis is millimeters, the vertical axis corresponds to the (half) field of view interval Y+ of the telephoto optical system, the solid lines represent the meridian plane when the working wavelengths are 486.1nm, 587.6nm and 656.3nm from left to right, and the dotted lines represent the sagittal plane when the working wavelengths are 486.1nm, 587.6nm and 656.3nm from left to right. It can be seen from the left figure that the maximum deviation of the field curvature does not exceed 0.0510mm, which can be ignored. In the right figure, the horizontal axis is the distortion percentage, the vertical axis corresponds to the (half) field of view interval Y+ of the focusing optical system, and the three curves represent the distortion diagrams of the focusing optical system at wavelengths of 486.1nm, 587.6nm and 656.3nm. The maximum distortion of the focusing optical system occurs at the edge of the entire field of view, and the maximum distortion is 0.5012%, which meets the design requirements.

Please refer to FIG. 4 , which shows a modulation transfer function (FFTMTF) diagram of the Fourier transform of the focusing optical system in the working band. In FIG. 4 , the horizontal axis is the spatial frequency, which represents the number of line pairs/mm. The number of line pairs/mm represents the detail information that can be distinguished in the image. One line pair is a black and white stripe, that is, multiple groups of line pairs can be distinguished within a width of 1 mm. The larger the value, the smaller the detail that can be distinguished, and the higher the resolution. The vertical axis is the optical transfer function coefficient (ModulusoftheOTF), which represents sharpness. Sharpness is the difference between the brightness and darkness of the image. The larger the difference value, the higher the grayscale difference of the image, so that the image contour that can be seen is sharper. The solid line represents the meridian curve, and the dotted line represents the sagittal curve. It can be seen from the figure that the spatial transfer function of the focusing optical system in the working band is one of the performance parameters of the focusing optical system working in this band, and is a way to evaluate the resolution of the entire system. The figure shows the corresponding meridian and sagittal curves of different fields of view. In general, the ideal state is that the closer all lines are to the diffraction limit of the system, the better.

Please refer to Figure 5, which shows the image plane illumination diagram of the focusing optical system when the working wavelength is 587.6nm. In Figure 5, the horizontal axis is the (half) field of view interval, and the vertical axis is the relative illumination (RelativeIllumination). Relative illumination mainly reflects the distribution of light in different areas of the image plane after the light passes through the optical system, reflects the attenuation of light illumination in different fields of view, and is an important indicator for evaluating the image plane illumination of the entire optical system. The image plane illumination at the edge in Figure 5 can reach more than 97% of the central image plane illumination, indicating that the uniformity of illumination will also change accordingly with the change of the field of view size. As the field of view increases, the image plane illumination gradually decreases. In general, the image plane illumination at the edge of the telephoto optical system should not be lower than 80% of the illumination of the central image plane to ensure that the naked eye cannot clearly observe the darkening of the image edge; if it is lower than 80%, the naked eye can clearly perceive the darkening of the image edge. In fields such as machine vision, the higher the requirements for images, the higher this value will be. The telephoto optical system of the present invention meets the illumination attenuation requirement by controlling the diagonal field angle of the chief light to 7.74°.

Please refer to Figure 6, which shows the diffusion circle diagram of the telephoto optical system when the working wavelength is 486.1nm, 587.6nm and 656.3nm. It is the diffusion of all pupil light rays in different field of view areas converging to the imaging surface A. Different curves represent different wavelengths, which is also an important way to evaluate the overall imaging characteristics of an optical system. It can be seen from Figure 6 that the central field of view dispersion spot and the edge field of view dispersion spot can reach within 9.455 microns within the design wavelength range. Due to the limitation of the aperture diaphragm, any imaging system will have a diffraction spot. In the visible light band and the state of aperture F/6.6, the theoretical radius of the diffraction spot is 4.795 microns and the diameter is 9.59 microns. The maximum diameter of the dispersion spot of the telephoto optical system we actually designed is 9.455 microns, which is smaller than the diameter of the theoretical diffraction spot, indicating that the optical aberration of the telephoto optical system has met the requirements.

The present invention also provides a lens, comprising the telephoto optical system described above, wherein the lens is suitable for industrial cameras with an imaging surface diameter of 11.2 mm or less.

Claims (13)

1. The long-focus optical system is characterized by comprising a first lens, a first cemented lens, a liquid lens, a second cemented lens, a second lens and a third lens which are sequentially arranged from an object side to an image side along a main optical axis, and the focusing position of the long-focus optical system is adjusted by controlling the driving voltage or the driving current of the liquid lens;

The first cemented lens comprises a fourth lens and a fifth lens, an image surface of the fourth lens is fixedly connected with an object surface of the fifth lens, the object surface of the fourth lens is a convex spherical surface, an image surface of the fourth lens is a convex spherical surface, an object surface of the fifth lens is a concave spherical surface, an image surface of the fifth lens is a concave spherical surface, the second cemented lens comprises a sixth lens and a seventh lens, the image surface of the sixth lens is fixedly connected with the object surface of the seventh lens, the object surface of the sixth lens is a concave spherical surface, the image surface of the sixth lens is a concave spherical surface, the object surface of the seventh lens is a convex spherical surface, and the image surface of the seventh lens is a convex spherical surface.

2. The tele optical system of claim 1, wherein the object plane of the first lens is a convex sphere, the radius of curvature is 8.14mm, and the image plane of the first lens is a plane.

3. The tele optical system according to claim 2, wherein the first cemented lens comprises a fourth lens and a fifth lens, an image surface of the fourth lens is fixedly connected with an object surface of the fifth lens, the object surface of the fourth lens is a convex spherical surface, a radius of curvature is 8mm, the image surface of the fourth lens is a convex spherical surface, a radius of curvature is-13.4 mm, the object surface of the fifth lens is a concave spherical surface, a radius of curvature is-13.4 mm, and the image surface of the fifth lens is a concave spherical surface, a radius of curvature is 7.6mm.

4. A tele optical system according to claim 3, wherein the second cemented lens comprises a sixth lens and a seventh lens, the image surface of the sixth lens is fixedly connected with the object surface of the seventh lens, the object surface of the sixth lens is a concave spherical surface, the radius of curvature is-6.63 mm, the image surface of the sixth lens is a concave spherical surface, the radius of curvature is 3mm, the object surface of the seventh lens is a convex spherical surface, the radius of curvature is 3mm, the image surface of the seventh lens is a convex spherical surface, and the radius of curvature is-6 mm.

5. The tele optical system of claim 4, wherein the object plane of the second lens is a concave sphere with a radius of curvature of-6 mm, and the image plane of the second lens is a convex sphere with a radius of curvature of-50 mm.

6. The tele optical system of claim 5, wherein the object plane of the third lens is a convex sphere, the radius of curvature is 13mm, and the image plane of the third lens is a convex sphere, the radius of curvature is-13 mm.

7. The tele optical system of claim 6, wherein an optical separation between the optical filter and the first lens is between 0.18mm-0.22 mm; the optical interval between the first lens and the first cemented lens is between 0.59mm and 0.63 mm; the optical interval between the first cemented lens and the liquid lens is between 2.38mm and 2.42 mm; the optical interval between the liquid lens and the second cemented lens is between 2.38mm and 2.42 mm; the optical interval between the second cemented lens and the second lens is between 0.08mm and 1.02 mm; the optical spacing between the second lens and the third lens is between 0.63mm and 0.67 mm.

8. The tele optical system of claim 1, further comprising an optical filter disposed to the left of the first lens, the optical filter being an IR optical filter, an object plane of the IR optical filter being a plane, and an image plane of the IR optical filter being a plane.

9. The tele optical system of any one of claims 1-8, further comprising an aperture stop disposed within the liquid lens.

10. The tele optical system of claim 9, wherein the operating wavelength of the tele optical system is between 486nm and 650 nm.

11. A tele optical system according to claim 9, characterized in that the system has an aperture F/6.6, a focal length of 50mm, a diagonal field angle of 7.74 °, CRA of 9 °.

12. A tele optical system according to claim 9, characterized in that the image plane diameter of the optical system is 6.8mm.

13. A lens comprising a tele optical system according to any one of claims 1-12.