CN106249385A - A kind of long-focus apochromatism optical lens being applicable to remote imaging - Google Patents

Abstract

The invention relates to the technical field of optical lenses, and specifically discloses a long focal length apochromatic optical lens suitable for long-distance imaging. Along the incident direction of light, this optical lens includes first lens group, aperture stop, second lens group, third lens group, image plane; , the second refraction positive lens and the second refraction negative lens; the second lens group includes the third refraction positive lens and the third refraction negative lens; the third lens group includes the fourth refraction positive lens and the fourth refraction negative lens. The apochromatic optical lens with meter-level focal length is realized by using a simple Petzval structure, which has the characteristics of large relative aperture, small relative distortion, excellent on-axis and off-axis imaging quality and high consistency.

Description

A long-focal-length apochromatic optical lens suitable for long-distance imaging

technical field

The invention relates to the technical field of optical lenses, and specifically discloses a long focal length apochromatic optical lens suitable for long-distance imaging.

Background technique

In many application fields, in order to obtain high resolution and good image plane illumination, the optical imaging system is required to have a large aperture and a long focal length; in addition, due to the development and progress of detection devices, the spectral response range is getting wider and wider. Put forward the demand of wide spectrum band. For long-focal-length high-resolution optical imaging lenses based on the principle of refraction, the secondary spectrum is an important factor restricting the imaging quality, and its correction is the focus and difficulty in optical design.

For the catadioptric optical system, its total reflection front group has the inherent advantage of chromatic aberration correction and can share most of the focal power. The focal length of the rear refractor group is generally small and the aperture is small, and chromatic aberration correction is relatively easy. However, the field of view of the total reflection system is difficult to enlarge, the processing is difficult, the cost is high, or there are factors such as central occlusion that affect the imaging quality and detection capability. The advantage of the refraction system is that there is no obstruction, it is easy to achieve a large field of view, the processing and adjustment methods are conventional, the system is stable, and the stray light is easy to control; the disadvantage is that the size is limited and the secondary spectral correction is difficult.

The invention adopts a complicated Petzval objective lens structure, reasonably selects optical materials, and realizes the apochromatic design of the long focal length imaging optical lens. The invention can realize the apochromatic design of the optical lens with a focal length above the meter level and a field of view of about 10°, and has imaging quality close to the diffraction limit and good practicability.

Contents of the invention

The technical problem to be solved by the present invention is to provide an easy-to-implement large-aperture and long-focus apochromatic optical imaging lens based on the principle of refraction, with a compact structure and an image quality that reaches or approaches the diffraction limit. To achieve the above object, the present invention provides a complex Petzval structured optical lens for long-distance high-resolution imaging.

The Petzval objective lens in the prior art is composed of two lens groups separated by "++", which is a photographic objective lens suitable for large relative aperture and small field of view, and the structure itself is beneficial to the correction of the secondary spectrum. The spherical aberration and coma aberration of the Petzval objective lens can be well corrected, the relative aperture is relatively large, and the image quality of the central field of view is excellent; but its structural characteristics make it difficult to correct the Petzval sum, and it will produce a larger field of view with the increase of the field of view curved, which is not conducive to large field of view design.

In order to realize the purpose of long focal length apochromatism, the present invention adopts the following technical solutions:

The invention provides a long focal length apochromatic optical lens suitable for long-distance imaging, which sequentially includes a first lens group, an aperture stop, a second lens group, a third lens group, and an image surface along the incident direction of light;

The first lens group includes a first refraction positive lens, a first refraction negative lens, a second refraction positive lens and a second refraction negative lens arranged in sequence;

Alternatively, the first lens group is a double-single lens, including a first refraction positive lens, a first refraction negative lens and a second refraction positive lens arranged in sequence;

Or, the first lens group is a single-double lens, including a first refraction positive lens, a second refraction positive lens, and a first refraction negative lens arranged in sequence;

The second lens group includes a third positive refraction lens and a third negative refraction lens;

Or, the second lens group only includes the third positive refractive lens;

The third lens group includes a fourth refractive positive lens and a fourth refractive negative lens.

Further, the first refraction negative lens, the second refraction negative lens, the third refraction negative lens and the fourth refraction negative lens are all made of domestic TF3 glass with special relative partial dispersion; the first refraction positive lens, the second refraction positive lens The materials of the third, third positive refracting lens and the fourth positive refracting lens are all made of ordinary glass.

Further, the aperture stop is located in the middle of the first lens group and the second lens group, and is used to adjust the symmetry of the system to correct the vertical aberration.

Further, the relative aperture is 1:6, the focal length is 1000mm, the field of view is 8°, and the working wavelength range is 470nm-750nm.

Further, the light aperture of the first lens group is 200mm, the light aperture of the second lens group is 170mm, and the light aperture of the third lens group is 150mm.

Further, the focal length ratio of the three groups of lenses is about 34:1:-3.6.

Further, the distance between the first lens group and the second lens group is 230 mm, and the distance between the second lens group and the third lens group is 320 mm; the aperture stop is located 110 mm behind the first lens group.

The beneficial effects of the present invention are: apochromatic aberration with long focal length, strict correction of distortion, excellent image quality, and consistent imaging quality throughout the field of view; at the same time, not only at the characteristic frequency of the photoelectric system, there is a higher optical transfer function value (MTF) , also has a higher optical MTF in the middle and low frequencies, so as to improve the low contrast resolution ability and keep the image rich in layers. The optical lens of the invention is suitable for mass production.

Description of drawings

Figure 1 is the basic structure of the Petzval objective lens;

Fig. 2 is a schematic diagram of the optical path of an optical lens according to an embodiment of the present invention;

Fig. 3 is an aberration curve according to an embodiment of the present invention;

Fig. 4 is a transfer curve according to an embodiment of the present invention;

The names of the parts indicated by the numerals in the accompanying drawings are as follows:

1-first lens group, 2-second lens group, 3-third lens group, 4-aperture stop, 5-image plane, 11-first refraction positive lens, 12-first refraction negative lens, 13- The second refraction positive lens, 14-the second refraction negative lens, 21-the third refraction positive lens, 22-the third refraction negative lens, 31-the fourth refraction positive lens, 32-the fourth refraction negative lens.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, but not to limit the present invention.

Fig. 1 is the basic structural diagram of Petzval objective lens, and Fig. 2 is the optical lens shown in the present invention, comprises first lens group 1, aperture stop 4, second lens group 2, the 3rd lens group 3 and Image surface 5. The first lens group 1 is made up of 3 or 4 lenses, and when there are 4 lenses, the first refraction positive lens 11, the first refraction negative lens 12, the second refraction positive lens 13 and the second refraction negative lens 14, form The first lens group 1 with the structural form of "+-+-"; when there are 3 lenses, it is a double-single lens or a single-double lens, and when it is a double-single lens, it includes the first refraction positive lens 11 arranged in sequence, and the first refraction The negative lens 12 and the second positive lens 13 of refraction form the first lens group 1 whose structural form is "+-+"; when it is a single-double lens, it includes the first positive lens 11 of refraction arranged in sequence, the second positive lens of refraction 13 and The first refraction negative lens 12 forms the first lens group 1 of "++-"; the double lens can be a double split lens or a doublet lens; the second lens group 2 is composed of 1 or 2 lenses, and the lens is 2 pieces Include the third refraction positive lens 21 and the third refraction negative lens 22 arranged in sequence, when the lens is one piece, only the third refraction positive lens 21 is included, forming the second lens group with the structural form of "+-" or "+" 2; The third lens group 3 is composed of 2 lenses, which are the fourth positive refraction lens and the fourth negative refraction lens in turn, forming the third lens group 3 with a structure of "+-"; the aperture stop 4 is located in the lens group 1 In the middle position spaced from the lens group 2 , the image plane 5 is arranged behind the third lens group 3 . With reference to Fig. 2, the system described in this embodiment is a complication of the Petzval optical lens. For the first lens group 1, after changing the double cement in the standard structure into a double split lens, add a set of double split lenses, and use more lenses to share most of the increased relative aperture; add a set of double split second lenses Group 2 also has the function of increasing the relative aperture, and is used to correct the secondary spectrum, spherical aberration, coma, and chromatic aberration of the system; it uses special optical materials and combines the characteristics of the Petzval structure to realize the correction of the secondary spectrum. The aperture stop 4 is located in the middle of the first lens group 1 and the second lens group 2, and is used to adjust the symmetry of the system to correct the vertical aberration.

The relative aperture of the long focal length apochromatic imaging optical lens described in this embodiment is 1:6, the focal length is 1000mm, the field of view angle is 8°, the working waveband is 470nm～750nm, the characteristic wavelengths are 480nm, 546.07nm, 730nm, and the relative illumination center is 100%. , the edge is 98.5%, the distortion is better than 0.001% as shown in Figure 3, and the transfer function is high as shown in Figure 4.

The light aperture of the first lens group 1 is 200mm, the light aperture of the second lens group 2 is 170mm, and the light aperture of the third lens group 3 is 150mm; the focal length ratio of the three groups of lenses is about 34:1:-3.6; The components are separated to correct chromatic aberration and off-axis aberration, the distance between the first lens group 1 and the second lens group 2 is 230mm, and the distance between the second lens group 2 and the third lens group 3 is 320mm; the aperture stop 4 is located on the first lens Position 110mm behind Group 1.

In order to facilitate processing and mass production, the selection of lens materials in this embodiment follows the principle of the simplest design. There are 8 lenses in the entire optical lens, and 2 kinds of optical materials are selected, the first refraction negative lens 12, the second refraction negative lens 14, The third refraction negative lens 22 and the fourth refraction negative lens 32 are all made of domestic TF3 glass with special relative partial dispersion; the first refraction positive lens 11, the second refraction positive lens 13, the third refraction positive lens 21 and the fourth refraction positive lens The positive lens 31 is made of ordinary glass.

Combining Figure 3 and Figure 4, the spherical aberration curves of the three characteristic wavelengths of the optical system intersect at a point near the field of view of 0.7, which realizes the design correction of apochromatic aberration; the maximum distortion of the system is designed to be one millionth, which is close to zero ; The transfer function (MTF) of the full field of view of the optical lens at the characteristic frequency of 50lp/mm is greater than 0.37, indicating that the system has a high resolution.

The characteristics of the present invention are: based on the Petzval structure, the apochromatism of the meter-level focal length refracting optical lens is realized after complication, has a relatively large relative aperture and a large field of view, and the relative distortion reaches one millionth. The off-axis imaging quality is excellent and the image quality is highly consistent. In summary, the imaging quality of the system described in this embodiment can fully meet the requirements of high-quality application levels.

The specific embodiments of the present invention described above do not constitute a limitation to the protection scope of the present invention. Any other corresponding changes and modifications made according to the technical concept of the present invention shall be included in the protection scope of the claims of the present invention.

Claims (7)

1. A long focal length apochromatic optical lens suitable for long-distance imaging, said lens along the incident direction of light successively comprises a first lens group, an aperture stop, a second lens group, a third lens group, and an image plane; The first lens group includes a first refraction positive lens, a first refraction negative lens, a second refraction positive lens and a second refraction negative lens arranged in sequence; Alternatively, the first lens group is a double-single lens, including a first positive refracting lens, a first negative refracting lens and a second positive refracting lens arranged in sequence; Alternatively, the first lens group is a single-double lens, including a first refraction positive lens, a second refraction positive lens, and a first refraction negative lens arranged in sequence; The second lens group includes a third positive refraction lens and a third negative refraction lens; Or, the second lens group only includes a third positive refractive lens; The third lens group includes a fourth positive refraction lens and a fourth negative refraction lens. 2. The optical lens according to claim 1, wherein the material of the first refracting negative lens, the second refracting negative lens, the third refracting negative lens and the fourth refracting negative lens are all made of The domestic TF3 glass with special relative partial dispersion; the first refractive positive lens, the second refractive positive lens, the third refractive positive lens and the fourth refractive positive lens are all made of ordinary glass. 3. The optical lens according to claim 2, wherein the aperture stop is located in the middle of the first lens group and the second lens group, and is used to adjust the symmetry of the system to correct the vertical axis image Difference. 4. The optical lens according to claim 3, wherein the relative aperture is 1:6, the focal length is 1000 mm, the field of view is 8°, and the working wavelength range is 470 nm to 750 nm. 5. The optical lens according to claim 4, wherein the light aperture of the first lens group is 200mm, the light aperture of the second lens group is 170mm, and the light aperture of the third lens group is 150mm . 6. The optical lens according to claim 5, wherein the ratio of the focal lengths of the three groups of lenses is about 34:1:-3.6. 7. The optical lens according to claim 6, wherein the distance between the first lens group and the second lens group is 230mm, and the distance between the second lens group and the third lens group is 320mm; The aperture stop is located 110 mm behind the first lens group.