CN118169843A - Long-focus 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

Long-focus optical system and lens

Technical Field

The invention relates to the technical field of optical imaging, in particular to a long-focus optical system and a lens.

Background

Tele optical systems typically have a relatively long focal length and are well suited for capturing scenes and objects at long distances. However, a tele optical system requires more correction of system chromatic aberration, astigmatism, off-axis astigmatism, and the like, and besides, tele requires more control considering the total optical length of the system.

Disclosure of Invention

The invention aims to overcome the technical problems and provides a long-focus optical system and a lens.

In order to achieve the above and other objects, the present invention is achieved by the following technical solutions: the utility model provides a long focal optical system, including from object side to image side along the optical axis of long focal optical system's optical filter that sets gradually, first lens, first cemented lens, liquid lens, second cemented lens, second lens and third lens, adjust the focusing position of long focal optical system through controlling the drive voltage or the drive electric current of 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.

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

Further, 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, the curvature radius is 8mm, the image surface of the fourth lens is a convex spherical surface, the curvature radius is-13.4 mm, the object surface of the fifth lens is a concave spherical surface, the curvature radius is-13.4 mm, and the image surface of the fifth lens is a concave spherical surface, and the curvature radius is 7.6mm.

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

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

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

Further, an optical interval between the optical filter and the first lens is between 0.18mm and 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.

Further, the optical filter is arranged on the left side of the first lens, the optical filter is an IR optical filter, the object plane of the IR optical filter is a plane, and the image plane of the IR optical filter is a plane.

Further, the liquid lens further comprises an aperture diaphragm, and the aperture diaphragm is arranged in the liquid lens.

Further, the working wavelength of the long-focus optical system is between 486nm and 650 nm.

Further, the aperture of the system is F/6.6, the focal length is 50mm, the diagonal field angle is 7.74 DEG, and the CRA is 9 deg.

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

Another aspect of the present invention also provides a lens including a tele optical system as described above.

The invention has small distortion and small light energy attenuation, and adopts the liquid lens to replace the driven manual focusing, so 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 a picture in a small visual angle range.

Drawings

Fig. 1 is a schematic structural view of a tele optical system according to the present invention.

FIG. 2 shows a graph of the light ray fan (RayFan) of the present invention at different fields of view at operating wavelengths 486nm, 588nm and 656 nm.

FIG. 3 shows a plot of field curvature (FieldCurvature) and Distortion (dispersion) for the present invention at operating wavelengths 486.1nm, 588.6nm, and 656.3 nm.

Fig. 4 shows a plot of the modulation transfer function (FFTMTF) for the fourier transform of the present invention over the operating band.

Fig. 5 shows the image plane illumination at an operating wavelength of 587.6nm according to the present invention.

FIG. 6 shows dispersion circles for the present invention at operating wavelengths 486.1nm, 588.6nm and 656.3 nm.

Detailed Description

Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. It should be understood that numerous specific details are set forth in the following description in order to provide a thorough understanding of the present invention, but that the present invention may be practiced otherwise than as described herein, and therefore the scope of the invention is not limited to the specific embodiments disclosed below. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the present invention, the surface of each lens closest to the focusing object plane is referred to as "object plane", the surface of each lens closest to the imaging plane a is referred to as "image plane", and when the lens object plane is convex or the image plane is concave, the object plane curvature or the image plane curvature is positive, and when the lens object plane is concave or the image plane is convex, the object plane curvature or the image plane curvature is negative.

As shown in fig. 1, the invention provides a long-focus optical system, the object plane of the long-focus optical system is at left, the initial focusing object plane is at infinity, the image plane a is at right, and the image distance is 6mm. The long-focus optical system is sequentially provided with an optical 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 along a main optical axis of the long-focus optical system from a focused object to an imaging surface A according to a specific optical interval, and the curvature characteristic of the liquid lens 13 is changed by applying a driving voltage through software control so as to adjust the focusing position of the long-focus optical system and realize focusing of the long-focus optical system. In one embodiment, the filter is an IR filter.

In this example, the total optical length of the tele optical system (from the object plane curvature center of the first lens 11 to the imaging plane a) is 61.44mm. The optical interval parameters between the lenses of the tele optical system are as follows: the optical interval between the optical filter 10 and the first lens 11 is 0.2mm, and the tolerance is +/-0.02 mm; an optical space between the first lens 11 and the first cemented lens 12 is 0.61mm, and a tolerance is + -0.02 mm; the optical interval between the first cemented lens 12 and the liquid lens 13 is 2.4mm, and the tolerance is + -0.02 mm; an optical interval between the liquid lens 13 and the second cemented lens 14 is 2.4mm, and a tolerance is + -0.02 mm; the optical interval between the second cemented lens 14 and the second lens 15 is 1mm, and the tolerance is + -0.02 mm; the optical interval between the second lens 15 and the third lens 16 is 0.65mm, and the tolerance is + -0.02 mm. It should be noted that the optical interval may be flexibly adjusted according to the need, and is not limited to the above-listed dimensions.

The above-described optical spacing parameters are primarily based on three factors: diagonal field angle, aperture, and CRA value. The aperture of the long-focus optical system is F/6.6, the focal length is 50mm, the angle of view of a diagonal line is 7.74 degrees, the CRA is 9 degrees, and the diameter of an image surface is 6.8mm. According to the focal length of the lens being 50mm and the image plane diameter being 6.8mm, the visual angle of the lens can be calculated to be 7.74 degrees; f/6.6 aperture value of the lens is realized, and the lens is matched with a liquid lens of A39, wherein the light transmission caliber of the liquid lens is 3.9mm; the lens also needs to meet the requirement of an image space CRA within 10 degrees so as to ensure that imaging color spots, edge illumination attenuation and other anomalies can not occur when the lens is matched with a chip. From these three factors, we calculated the angle and the incidence height of the first and second chief rays at the incidence and exit surfaces of each lens of the tele optical system, respectively. Specifically, the incident height of the first principal ray and the second principal ray on the surface of the optical filter 10 is front 12mm and rear 11.91mm, the incident height on the surface of the first lens 11 is front 11.596mm and rear 10.362mm, and the incident height on the surface of the first cemented lens 12 is front 8.54mm and rear 4.926mm; the incident height on the surface of the second cemented lens 14 is forward 2.608mm, backward 3.246mm, the incident height on the surface of the second lens 15 is 3.464mm, backward 3.894mm, and the incident height on the surface of the third lens 16 is forward 5.496mm, and backward 5.97mm. The incidence angles of the first principal ray and the second principal ray on the surface of the optical filter 10 are 3.89 degrees at the front and 2.563 degrees at the back; the incident angle on the surface of the first lens 11 is 10 degrees at the front and 7.536 degrees at the back; the incident angle on the surface of the first cemented lens 12 is front 1.239 deg., and back 4.092 deg.; the incidence angle of the surface of the bonding sheet 4 is front 8.179 degrees and rear 3.681 degrees; the incidence angle of the surface of the lens 5 is the front 0.462 degrees and the back 12.274 degrees; the angle of incidence on the surface of the lens 6 is at a front 35.48 deg., and at a back 3.122 deg., the acceptable deviation of the angle of inflection and the initial height value of the light at each lens translates into optical spacing from lens to lens and tolerance values.

The specific parameters of each lens are described in detail below. Referring to fig. 1 again, the object plane of the optical filter 10 is a plane, the image plane of the optical filter 10 is also a plane, and the center thickness of the optical filter 10 is 0.21mm; the object plane of the first lens 11 is a convex spherical surface, the curvature radius is 8.14mm, the image plane of the first lens 11 is a plane, the center thickness of the first lens 11 is 4mm, and the tolerance is +/-0.02 mm; the first cemented lens 12 is a double cemented lens, and includes a fourth lens 121 and a fifth lens 122, and an image plane of the fourth lens 121 and an object plane of the fifth lens 122 may be fixed by optical colloid, or may be clamped and fixed by mechanical means (such as a positioning groove). The curvature of the image surface of the fourth lens 121 is equal to the curvature of the object surface of the fifth lens 122, specifically, the object surface of the fourth lens 121 is a convex spherical surface, the radius of curvature is 8mm, the image surface of the fourth lens 121 is a convex spherical surface, the radius of curvature is-13.4 mm, the center thickness of the fourth lens 121 is 3.5mm, the tolerance is + -0.02 mm, the object surface of the fifth lens 122 is a concave spherical surface, the radius of curvature is-13.4 mm, the image surface of the fifth lens 122 is a concave spherical surface, the radius of curvature is 7.6mm, the center thickness of the fifth lens 122 is 1.3mm, and the tolerance is + -0.02 mm; the second cemented lens 14 also adopts a double cemented lens, and includes a sixth lens 141 and a seventh lens 142, and an image plane of the sixth lens 141 and an object plane of the seventh lens 142 may be fixed by optical colloid, or may be clamped and fixed by mechanical means (such as a positioning groove). The object plane of the sixth lens 141 is a concave spherical surface, the radius of curvature is-6.63 mm, the image plane of the sixth lens 141 is a concave spherical surface, the radius of curvature is 3mm, the center thickness of the sixth lens 141 is 1mm, and the tolerance is +/-0.02 mm; the object plane of the seventh lens 142 is a convex spherical surface, the radius of curvature is 3mm, the image plane of the seventh lens 142 is a convex spherical surface, the radius of curvature is-6 mm, the center thickness of the seventh lens 142 is 1.52mm, and the tolerance is +/-0.02 mm; the object plane of the second lens 15 is a concave spherical surface, the curvature radius is-6 mm, the image plane of the second lens 15 is a convex spherical surface, the curvature radius is-50 mm, the center thickness of the second lens 15 is 0.8mm, and the tolerance is +/-0.02 mm; the object plane of the third lens 16 is a convex spherical surface, the curvature radius is 13mm, the image plane of the third lens 16 is a convex spherical surface, the curvature radius is-13 mm, the center thickness of the third lens 16 is 3.5mm, and the tolerance is +/-0.02 mm. The surface type tolerance of all curvatures is aperture 3-5, and the local aperture 0.3-0.5 is detected by adopting an interferometer.

As one embodiment, an aperture stop (not shown) is also disposed in the liquid lens 13, for example, the aperture stop may be disposed at a packaging filter position in the liquid lens 13, and the aperture stop is used to limit the size of the on-axis imaging beam.

In this example, all lenses other than the liquid lens 13 are glass. The liquid lens 13 may be Corning-a25H of Corning company, of course, other types of liquid lenses capable of meeting the light path requirement may be adopted, and the optical filter 10 may be schottky float glass (d 263 teco), for example; the first lens 11 may be, for example, a heavy phosphorus crown glass (h-zpk a); the fourth lens 121 may be, for example, heavy phosphorus crown glass (h-zpk a), and the fifth lens 122 may be, for example, heavy lanthanum flint glass (h-zlaf 76 a); the sixth lens 141 may be, for example, heavy flint glass (h-zf 52 gt), and the seventh lens 142 may be, for example, heavy crown glass (h-zk 14); the second lens 15 may be, for example, heavy flint glass (h-zf 1 a); the third lens 16 may be, for example, heavy flint glass (h-zf 1 a).

In the example, the working environment of the long-focus optical system is a visible light environment, the working wavelength is between 486nm and 650nm, and the axial chromatic aberration and the vertical chromatic aberration of the whole system are compensated and corrected through the cemented lenses with different refractive indexes and different chromatic dispersion coefficients. Firstly, the system adopts a double Gaussian optical structure as an initial structure of the system, and the liquid lens 13 is designed symmetrically front and back, so that chromatic aberration caused by band difference can be reduced to the greatest extent while spherical aberration of the tele optical system is reduced. Secondly, we use a combination of heavy phosphorus crown glass (h-zpk a) and heavy flint glass (h-zf 52 gt) in such a way that a combination of high refractive index low dispersion and low refractive index high dispersion, which respectively generate opposite magnitudes of dispersion aberration before and after the aperture stop, minimizes the aberration of the tele optical system.

The two groups of cemented lenses are symmetrical to the front and back of the liquid lens (aperture diaphragm), and positive and negative chromatic aberration before and after the diaphragm is corrected by a symmetrical structure on the basis of utilizing refractive index dispersion difference of the cemented lenses. The two groups of the cemented lenses 12 and 14 are cemented by a combination of biconvex and biconcave, and the concave surfaces of the two cemented lenses are opposite to the direction of the aperture diaphragm, so that a larger light-emitting angle can be ensured while chromatic aberration is corrected, and the aperture diaphragm can be the minimum position of the system light-transmitting aperture.

The technical scheme of the long-focus optical system can effectively correct chromatic aberration, astigmatism and off-axis astigmatism of the system. The optical filter can effectively intercept stray light with a certain wave band and enter the lens, so that the defect that imaging chromatic aberration is caused by extra correction of stray light with a non-designed wave band by the long focal lens is avoided. And plays a role in protecting the lens from dust, water, collision and the like.

Referring to fig. 2, fig. 2 shows a light Ray Fan (Ray Fan) diagram of the tele optical system in different view areas when the working wavelength is 486nm, 588nm and 656nm, and fig. 2 shows a set of aberrations generated in different view areas, and each view area can see the difference of meridional surface and sagittal surface aberrations.

Referring to fig. 3, fig. 3 shows a graph of field curvature (Field Curvature) and Distortion (dispersion) of the tele optical system at operating wavelengths 486.1nm, 587.6nm, and 656.3 nm. In the left graph, the abscissa is millimeter, the ordinate corresponds to the (semi) field of view interval y+ of the tele optical system, the solid lines represent meridian planes at the working wave bands of 486.1nm, 587.6nm and 656.3nm in sequence from left to right, and the dotted lines represent sagittal planes at the working wave bands of 486.1nm, 587.6nm and 656.3nm in sequence from left to right, and as can be seen from the left graph, the maximum deviation of the field curvature is not more than 0.0510mm and can be ignored. In the right graph, the abscissa is the Distortion percentage, the ordinate corresponds to the (half) field interval y+ of the focusing optical system, 3 curves respectively represent the Distortion (dispersion) graphs of the focusing optical system at the wavelengths of 486.1nm, 587.6nm and 656.3nm, the maximum Distortion of the focusing optical system occurs at the edge position of the whole field, and the maximum Distortion is 0.5012%, so as to meet the design requirement.

Referring to fig. 4, fig. 4 shows a graph of a modulation transfer function (FFTMTF) of fourier transform of the focusing optical system in an operating band, in fig. 4, an abscissa represents spatial frequency, and represents logarithm/millimeter, where logarithm/millimeter represents distinguishable detail information of an image, one pair is a black-and-white stripe, that is, a plurality of pairs can be resolved within a width range of 1 millimeter, and a larger value represents a smaller distinguishable detail and a higher resolution. The ordinate is the optical transfer function coefficient (ModulusoftheOTF), which represents sharpness, i.e., the difference in brightness and darkness of an image, and the larger the difference value is, the higher the gray level difference of the image is, so that the sharper the outline of the image can be seen. The solid line represents a meridian curve and the dashed line represents a sagittal curve, from which it can be seen that in the operating band, the spatial transfer function of the focusing optical system, which is one of the performance parameters of the focusing optical system operating in this band, is the way the resolution of the whole system is evaluated, the graphs of the corresponding meridians and the sagittal for the different fields of view being shown. In general, the more the diffraction limit of the system is approached, the optimal is all the lines in an ideal state.

Referring to fig. 5, fig. 5 shows an image plane illumination diagram of the focusing optical system at an operating wavelength of 587.6nm, and in fig. 5, an abscissa represents a (half) field of view interval and an ordinate represents relative illumination (RelativeIllumination). The relative illumination mainly shows the illumination distribution condition in different areas of the image surface after the light passes through the optical system, shows the attenuation condition of the illumination of different fields of view, and is an important index for evaluating the illumination of the image surface of the whole optical system. The image plane illuminance at the edge in fig. 5 can reach 97% or more of the center image plane illuminance, which means that the uniformity of the illuminance changes with the size of the field of view, and the image plane illuminance gradually decreases with the increase of the field of view. In general, the illuminance of the image surface at the edge of the long-focus optical system should not be lower than 80% of the illuminance of the central image surface, so that the situation that the edge of the image is darkened can be ensured to be observed by naked eyes; if the content is less than 80%, the dark image edge is clearly perceived by the naked eye. In the fields of machine vision, etc., the higher the requirement for the image, the higher the value. The long-focus optical system meets the requirement of illumination attenuation by controlling the angle of view of the diagonal line of the principal ray to be 7.74 degrees.

Referring to fig. 6, fig. 6 shows a dispersion circle diagram of the tele optical system when the working wavelength is 486.1nm, 587.6nm and 656.3nm, which is a diffusion condition that all the entrance pupil light rays in different visual field areas converge on the imaging plane a, and different curves represent different wavelengths, which is also an important way to evaluate the overall imaging characteristics of one optical system. It can be seen from fig. 6 that both the center field of view diffuse spots and the edge field of view diffuse spots can be within 9.455 microns over the design wavelength range. Because of the limitation of the aperture diaphragm, any imaging system can have diffraction spots, under the visible light wave band and in the state of aperture F/6.6, the radius of the theoretical diffraction spots is 4.795 microns, the diameter is 9.59 microns, and the maximum diameter 9.455 microns of the dispersion spots of the tele optical system which is actually designed by us is smaller than the diameter of the theoretical diffraction spots, so that the optical aberration of the tele optical system can meet the requirements.

The invention also provides a lens, which comprises the long-focus optical system, and is suitable for industrial cameras with the imaging surface diameter of 11.2mm and below.

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.