An optical system with small zoom, large image surface and large aperture

Abstract

The present invention provides an optical system with small zoom, large image surface and large aperture, which can solve technical problems such as small image surface, low definition, small aperture and infrared incomplete confocality. The optical system comprises a first lens group, an aperture, a second lens group, a third lens group, a filter and a photosensitive chip which are arranged in sequence from the object surface to the phase surface. The focal length of the third lens group is a negative value and the third lens group is fixed relative to the photosensitive chip. The focal length of the first lens group is a negative value and the first lens group can move forward and backward along the object image direction relative to the photosensitive chip. The focal length of the second lens group is a positive value and the second lens group can move forward and backward along the object image direction relative to the photosensitive chip. The second lens group comprises a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens and a ninth lens which are arranged in sequence along the object image direction. The fourth lens and the ninth lens are glass aspherical lenses.

Description

[Technical field]

[0001] The invention relates to the field of monitoring systems, in particular to an optical system with small zoom, large image surface and large aperture. [Background technology]

[0002] At present, the zoom optical system used for monitoring generally has such shortcomings, that is, the system has low definition, small aperture, and cannot ensure complete confocality of each focal length infrared during zooming, etc. At present, there is no lens on the market that fully takes into account the above characteristics. There are only a few lenses that improve one aspect at the expense of other aspects. For example, in order to achieve ultra-high definition and infrared confocality, the aperture is designed to be small, which cannot meet the definition requirements of monitoring lenses under low illumination conditions. [Summary of the invention]

[0003] The technical problem to be solved by the present invention is to provide an optical system with small zoom, large image surface and large aperture which can solve the technical problems of small image surface, low definition, small aperture and incomplete confocality of infrared.

[0004] The object of the present invention is achieved in that:

[0005] An optical system with small zoom, large image surface and large aperture comprises a first lens group, an aperture, a second lens group, a third lens group, a filter and a photosensitive chip which are arranged in sequence from the object plane to the image plane, the focal length of the third lens group is a negative value and the third lens group is fixed relative to the photosensitive chip, the focal length of the first lens group is a negative value and the first lens group can move forward and backward relative to the photosensitive chip along the object image direction, the focal length of the second lens group is a positive value and the second lens group can move forward and backward relative to the photosensitive chip along the object image direction, the second lens group comprises a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens and a ninth lens which are arranged in sequence along the object image direction, and the fourth lens and the ninth lens are glass aspherical lenses.

[0006] In the optical system with small zoom, large image surface and large aperture as described above, the optical power of the fourth lens, the fifth lens, the seventh lens and the ninth lens are positive, the optical power of the eighth lens is negative, and the optical power of the sixth lens is positive or negative.

[0007] As described above, an optical system with small zoom, large image surface and large aperture, the first lens group includes a first lens, a second lens and a third lens arranged in sequence along the object image direction, the third lens group includes a tenth lens, an eleventh lens and a twelfth lens arranged in sequence along the object image direction, and the first lens, the second lens, the third lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the tenth lens, the eleventh lens and the twelfth lens are all glass spherical lenses.

[0008] In the optical system with small zoom, large image surface and large aperture as described above, the aspherical surface types of the fourth lens and the ninth lens satisfy the following equation:

[0009]

[0010] Among them, k, a1, a2, a3, a4, a5, a6, a7 and a8 are aspheric coefficients, Z and y are the horizontal and vertical coordinates of the lens surface in the Cartesian coordinate system, and c is the reciprocal of the radius R corresponding to the lens surface.

[0011] In an optical system with small zoom, large image surface and large aperture as described above, the spacing distance between the first lens group and the aperture can be adjusted within the range of 19.41 mm to 1.83 mm, and the spacing distance between the second lens group and the aperture can be adjusted within the range of 11.035 mm to 0.43 mm.

[0012] Compared with the prior art, the present invention has the following technical features:

[0013] 1. Most zoom lenses on the market currently use a large number of glass spherical and aspherical lenses to achieve high-definition image quality, large aperture and infrared confocality, resulting in high costs. The present invention reasonably considers the lens layout and controls the cost.

[0014] 2. The zoom lenses commonly used in the market usually have a significant drop in image quality when switched to infrared imaging mode when the visible band is fully focused, or infrared confocality is only achieved in a smaller focal length range. The present invention achieves complete confocality in the visible band and infrared band, ensuring the imaging clarity of the visible band and infrared band during the 6.6-19mm zoom process.

[0015] 3. Most zoom lenses on the market, especially those with a focal length greater than 10mm, will be in focus at room temperature of 20°C, but will be out of focus or blurry at high temperatures of 70°C or low temperatures of -30°C. The present invention ensures complete confocality at all magnifications and high and low temperatures.

[0016] 4. Most zoom lenses on the market currently have a small image plane (generally less than φ8.8mm). With the same pixel size, the pixel will be low, resulting in the picture clarity effect not meeting expectations. The image plane of the present invention can reach φ13.1mm, and the corresponding resolution can reach more than 4K. The entire process from low magnification to high magnification can capture a clear, high-contrast image of the entire picture.

Brief Description of the Drawings

[0017] The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings, wherein:

[0018] Figure 1It is a structural schematic diagram of the present invention. [Specific implementation method]

[0019] An optical system with small zoom, large image surface and large aperture comprises a first lens group 1, an aperture 2, a second lens group 3, a third lens group 4, a filter 5 and a photosensitive chip 6 which are arranged in sequence from the object plane to the image plane, the focal length of the third lens group 4 is a negative value and the third lens group 4 is fixed relative to the photosensitive chip 6, the focal length of the first lens group 1 is a negative value and the first lens group 1 can move forward and backward relative to the photosensitive chip 6 along the object image direction, the focal length of the second lens group 3 is a positive value and the second lens group 3 can move forward and backward relative to the photosensitive chip 6 along the object image direction, the second lens group 3 comprises a fourth lens 31, a fifth lens 32, a sixth lens 33, a seventh lens 34, an eighth lens 35 and a ninth lens 36 which are arranged in sequence along the object image direction, and the fourth lens 31 and the ninth lens 36 are glass aspherical lenses.

[0020] The refractive powers of the fourth lens 31 , the fifth lens 32 , the seventh lens 34 and the ninth lens 36 are positive, the refractive power of the eighth lens 35 is negative, and the refractive power of the sixth lens 33 is positive or negative.

[0021] The first lens group 1 includes a first lens 11, a second lens 12 and a third lens 13 which are sequentially arranged along the object-image direction. The third lens group 4 includes a tenth lens 41, an eleventh lens 42 and a twelfth lens 43 which are sequentially arranged along the object-image direction. The first lens 11, the second lens 12, the third lens 13, the fifth lens 32, the sixth lens 33, the seventh lens 34, the eighth lens 35, the tenth lens 41, the eleventh lens 42 and the twelfth lens 43 are all glass spherical lenses.

[0022] The second lens 12 and the third lens 13 are bonded together using optical glue, and the seventh lens 34 and the eighth lens 35 are bonded together using optical glue.

[0023] The aspheric surfaces of the fourth lens 31 and the ninth lens 36 satisfy the following equation:

[0024]

[0025] Among them, k, a1, a2, a3, a4, a5, a6, a7 and a8 are aspheric coefficients, Z and y are the horizontal and vertical coordinates of the lens surface in the Cartesian coordinate system, respectively, and c is the reciprocal of the radius R corresponding to the lens surface, that is, c = 1 / R.

[0026] The spacing distance between the first lens group 1 and the aperture 2 can be adjusted within the range of 19.41 mm to 1.83 mm, and the spacing distance between the second lens group 3 and the aperture 2 can be adjusted within the range of 11.035 mm to 0.43 mm.

[0027] The specific parameters of the best embodiment of the present invention are listed below:

[0028]

[0029]

[0030] Aspheric coefficients of each surface of the fourth lens 31 and the ninth lens 36:

[0031]

[0032] In order to achieve complete confocality in infrared, the complementarity of the refractive index and Abbe number of different lens materials is fully considered during the design. While ensuring small chromatic aberration in the visible band, the resolution effect in the infrared band is also guaranteed, achieving a perfect match of lens materials.

[0033] In order to achieve ultra-high resolution, purple edge control and infrared full-power confocal, the design uses the change in the conjugate distance of the first lens group 1 to offset the change in the conjugate distance after longitudinal magnification of the second lens group 3 to achieve image compensation. The first lens group 1 uses a single lens and a cemented lens, which can not only correct the chromatic aberration of the lens well and ensure infrared confocality, but also correct the spherical aberration and sine aberration at high magnification positions. The lens of the second lens group 3 uses a glass aspheric surface and a quasi-cemented structure after the aperture 2. It is a perfect achromatic structure, which not only realizes the correction of high-order aberrations but also ensures the correction of chromatic aberrations. It not only eliminates the chromatic aberration of the entire system, but also balances the aberration of the entire system and realizes the correction of chromatic aberration. The lens of the third lens group 4 cooperates with the first lens group 1 to form a symmetrical structure, which plays a good role in correcting chromatic aberration and various aberrations. The clarity of the entire system is guaranteed, and ultra-high-definition resolution and infrared full-power full-power confocality are achieved. Finally, by setting a certain amount of vignetting, the surrounding stray light can be blocked without affecting the illumination of the image plane, so that the resolution of the center of the image plane is high while the edge can also achieve a very high resolution.

[0034] In order to achieve high and low temperature confocality of the system, the changes in the refractive index and Abbe number of various glass materials at high and low temperatures were fully considered during the design process, while matching the changes in surface shape and air spacing, achieving the matching of various high and low temperature elements, thereby achieving synchronization and clarity of the image surface at high and low temperatures.

Claims

1. An optical system with small zoom, large image surface and large aperture, characterized in that The invention comprises a first lens group (1), an aperture (2), a second lens group (3), a third lens group (4), a filter (5) and a photosensitive chip (6) which are arranged in sequence from the object plane to the image plane. The focal length of the third lens group (4) is a negative value and the third lens group (4) is fixed relative to the photosensitive chip (6). The focal length of the first lens group (1) is a negative value and the first lens group (1) can move forward and backward relative to the photosensitive chip (6) along the object image direction. The focal length of the second lens group (3) is a positive value and the second lens group (3) can move forward and backward relative to the photosensitive chip (6) along the object image direction. The second lens group (3) is composed of a fourth lens (31), a fifth lens (32), a sixth lens (33) which are arranged in sequence along the object image direction. 3), a seventh lens (34), an eighth lens (35) and a ninth lens (36); the fourth lens (31) and the ninth lens (36) are glass aspherical lenses; the optical focal lengths of the fourth lens (31), the fifth lens (32), the seventh lens (34) and the ninth lens (36) are positive, the optical focal length of the eighth lens (35) is negative, and the optical focal length of the sixth lens (33) is positive; the first lens group (1) is composed of a first lens (11), a second lens (12) and a third lens (13) which are arranged in sequence along the object-image direction; the third lens group (4) is composed of a tenth lens (41), an eleventh lens (42) and a twelfth lens (43) which are arranged in sequence along the object-image direction.

2. The optical system with small zoom, large image area and large aperture according to claim 1, characterized in that The first lens (11), the second lens (12), the third lens (13), the fifth lens (32), the sixth lens (33), the seventh lens (34), the eighth lens (35), the tenth lens (41), the eleventh lens (42) and the twelfth lens (43) are all glass spherical lenses.

3. The optical system with small zoom, large image area and large aperture according to claim 1, characterized in that The aspheric surface shapes of the fourth lens (31) and the ninth lens (36) satisfy the following equation: Among them, k, a1, a2, a3, a4, a5, a6, a7 and a8 are aspheric coefficients, Z and y are the horizontal and vertical coordinates of the lens surface in the Cartesian coordinate system, and c is the reciprocal of the radius R corresponding to the lens surface.

4. The optical system with small zoom, large image area and large aperture according to claim 1, characterized in that The spacing distance between the first lens group (1) and the aperture (2) may be in the range of 19.41 mm to 1.83 mm.

Images