CN112014940A - Large-aperture high-low temperature confocal imaging system - Google Patents

Abstract

The invention discloses a large-aperture high-low temperature confocal imaging system which comprises a first glass spherical lens L1 with convex-concave negative focal power, a second glass spherical lens L2 with convex-concave negative focal power, a third plastic aspheric lens L3 with convex-concave positive focal power, a fourth glass spherical lens L4 with double convex positive focal power, a fifth glass spherical lens L5 with double convex positive focal power, a sixth plastic aspheric lens L6 with convex-concave negative focal power and a sixth plastic aspheric lens L7 with double convex positive focal power, which are sequentially arranged along the light incidence direction; the lens adopts a 4G3P structure, so that the cost is reduced. The lens structure is compact by reasonably distributing focal power, so that tolerance sensitivity is greatly reduced, various aberrations are well corrected by reasonably adopting the plastic aspheric lens, and the imaging quality is greatly improved; a large aperture of F0.95 is achieved in terms of aperture; meanwhile, the focal length ratio is reasonably controlled, so that the system is not defocused under the environmental condition of-40 ℃ to +85 ℃.

Description

Large-aperture high-low temperature confocal imaging system

Technical Field

The invention mainly aims at security monitoring and ensures that the large-aperture imaging system is not defocused at the temperature of-40-85 ℃.

Background

At present, the domestic closed circuit monitoring industry (CCTV) is developed towards miniaturization, multifunction and strong environment adaptability, and under the form of extremely intense domestic competition, the fixed focus lens cannot meet the requirements of customers in different regions, for example, the northeast market of China requires a designed monitoring device which is placed outdoors and is not defocused all the year round, the temperature of the northeast of China is often minus 30 ℃ in winter, and the highest temperature of the northeast of China can reach about 31 ℃ in summer. If the circuit heating factor of the monitoring camera is considered, it becomes necessary to design an imaging system with a large aperture and a focal plane which is not deviated within-40 ℃ to 85 ℃. Performing data statistics according to authority statistics of public security organs: nearly 70% of crimes occur at night or in dark regions, and darkness becomes a natural protective umbrella for criminals, and in view of color loss, unclear details and insufficient brightness under the infrared light supplement of the existing camera, the imaging quality of the current front-end camera under the weak light is difficult to find out to become a short plate for security and protection big data development, so that a large-aperture camera capable of realizing bright, clean and colorful pictures under low illumination is very necessary.

Disclosure of Invention

The invention mainly provides a large-aperture imaging system which is not defocused at the temperature of-40-85 ℃ during security monitoring.

In order to meet the design requirements, the technical scheme provided by the invention is as follows:

A4G 3P glass-plastic mixed structure high-low temperature confocal imaging system with a focal length of 8mm comprises a first glass spherical lens L1 with convex-concave negative focal power, a second glass spherical lens L2 with convex-concave negative focal power, a third plastic aspheric lens L3 with convex-concave positive focal power, a fourth glass spherical lens L4 with double convex positive focal power, a fifth glass spherical lens L5 with double convex positive focal power, a sixth plastic aspheric lens L6 with convex-concave negative focal power and a seventh plastic aspheric lens L7 with double convex positive focal power, which are sequentially arranged along the light incidence direction; the focal length and the refractive index of seven lenses and the curvature radius of four glass lenses of the system respectively satisfy the conditions of the following table 1:

f1＝-17.46±5％	n1＝1.517±5％	R11＝34.93±5％	R12＝7.11±5％
				f2＝-37.27±5％	n2＝1.523±5％	R21＝-7.84±5％	R22＝-15.11±5％
f3＝47.62±5％	n3＝1.535±5％
				f4＝30.32±5％	n4＝1.497±5％	R41＝17.76±5％	R42＝-93.45±5％
f5＝21.18±5％	n5＝1.497±5％	R51＝13.66±5％	R52＝-40.49±5％
				f6＝-12.55±5％	n6＝1.636±5％
f7＝12.72±5％	n7＝1.535±5％

TABLE 1

In the above table: f. of₁-f₇The focal lengths of the first glass spherical lens L1 and the seventh plastic aspheric lens L7 respectively correspond to the first glass spherical lens L1 and the seventh plastic aspheric lens; n is₁-n₇The refractive indexes of the first glass spherical lens L1 and the seventh plastic aspheric lens L7 respectively correspond in sequence; the R is₁₁And R₁₂Corresponding to the curvature radius of the first glass spherical lens L1, R₂₁And R₂₂Corresponding to the radius of curvature of the second spherical glass lens L2, R₄₁And R₄₂Corresponding to the radius of curvature of the fourth spherical glass lens L4, R₅₁And R₅₂Corresponds to the radius of curvature of the fifth aspherical lens L5, wherein "-" indicates that the direction is a negative direction.

The aspherical equations of the aspherical lenses L3, L6, and L7 satisfy:

in the above formula, the parameter c is a curvature radius, y is a radial coordinate, and k is a conic coefficient, wherein the third plastic aspheric lens L3 includes an R element₃₁Face and R₃₂The sixth plastic aspheric lens L6 includes opposite R₆₁Face and R₆₂The seventh plastic aspheric lens L7 includes opposite R₇₁Face and R₇₂Wherein R is₃₁Flour, R₃₂Flour, R₆₁Flour, R₆₂Flour, R₇₁Face and R₇₂The parameters of the face are:

TABLE 2

The invention mainly controls the sum of the focal powers of two positive lenses and the focal power of one negative lens in the focal powers of 3 plastic non-spherical lenses.

Namely, it is

Wherein f is₃，f₆，f₇See table 1.

Values of FNO. in the present invention are in the following ranges

Where f is the system focal length and D is the entrance pupil diameter.

The imaging system provided by the invention can effectively ensure that the imaging system can not defocus in the temperature change of-40-85 ℃. And reasonable adoption of the plastic aspheric surface can well improve the edge image quality and ensure high imaging quality. The large aperture makes the lens form clear image under weak light.

Drawings

Fig. 1 is a lens assembly diagram according to a first embodiment of the invention.

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

FIG. 3 is a MTF graph of the present invention at a low temperature of 20 ℃;

FIG. 4 is a MTF graph of the present invention at room temperature to 40 deg.C;

FIG. 5 is a MTF graph of the present invention at a high temperature of 85 ℃.

Detailed Description

The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some but not all of the relevant aspects of the present invention are shown in the drawings.

Referring to fig. 1 and 2, the present invention includes a first glass spherical lens L1 with convex-concave negative focal power, a second glass spherical lens L2 with convex-concave negative focal power, a third plastic aspheric lens L3 with convex-concave positive focal power, a fourth glass spherical lens L4 with double convex positive focal power, a fifth glass spherical lens L5 with double convex positive focal power, a sixth plastic aspheric lens L6 with convex-concave negative focal power, and a sixth plastic aspheric lens L7 with double convex positive focal power, which are sequentially arranged along the light incidence direction; wherein the lens L1 comprises opposite R₁₁Face and R₁₂The lens L2 includes opposite R₂₁Face and R₂₂The lens L3 includes opposite R₃₁Face and R₃₂The lens L4 includes opposite R₄₁Face and R₄₂The lens L5 includes opposite R₅₁Face and R₅₂The lens L6 includes opposite R₆₁Face and R₆₂The lens L7 includes opposite R₇₁Face and R₇₂And (5) kneading.

The focal length and the refractive index of seven lenses and the curvature radius of four glass lenses of the system respectively meet the following conditions:

f1＝-17.46±5％	n1＝1.517±5％	R11＝34.93±5％	R12＝7.11±5％
				f2＝-37.27±5％	n2＝1.523±5％	R21＝-7.84±5％	R22＝-15.11±5％
f3＝47.62±5％	n3＝1.535±5％
				f4＝30.32±5％	n4＝1.497±5％	R41＝17.76±5％	R42＝-93.45±5％
f5＝21.18±5％	n5＝1.497±5％	R51＝13.66±5％	R52＝-40.49±5％
				f6＝-12.55±5％	n6＝1.636±5％
f7＝12.72±5％	n7＝1.535±5％

TABLE 1

The aspherical equations of the aspherical lenses L3, L6, and L7 satisfy:

in the above formula, the parameter c is a curvature radius, y is a radial coordinate, and k is a conic coefficient, wherein the third plastic aspheric lens L3, L6, and L7 include opposite surfaces: r₃₁Flour, R₃₂Flour, R₆₁Flour, R₆₂Flour, R₇₁Face and R₇₂The parameters of the face are:

TABLE 2

When the focal length and the refractive index of the seven lenses and the curvature radius and the thickness of the two glass lenses respectively meet the conditions in the table 1, the MTF curves do not have serious defocusing phenomenon under the limit conditions of 20 ℃ normal temperature, minus 40 ℃ low temperature, minus 85 ℃ high temperature and the like as can be seen from fig. 3, 4 and 5.

The present invention is not limited to the above preferred embodiments, and any modifications, equivalent replacements, improvements, etc. within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (4)

1. The large-aperture high-low-temperature confocal imaging system is characterized by comprising a first glass spherical lens L1 with convex-concave negative focal power, a second glass spherical lens L2 with convex-concave negative focal power, a third plastic aspheric lens L3 with convex-concave positive focal power, a fourth glass spherical lens L4 with double convex positive focal power, a fifth glass spherical lens L5 with double convex positive focal power, a sixth plastic aspheric lens L6 with convex-concave negative focal power and a sixth plastic aspheric lens L7 with double convex positive focal power, which are sequentially arranged along the light incidence direction; the focal length and the refractive index of the seven lenses of the imaging system and the curvature radius of the four glass lenses respectively meet the following conditions:

f₁＝-17.46±5％ n₁＝1.517±5％ R₁₁＝34.93±5％ R₁₂＝7.11±5％ f₂＝-37.27±5％ n₂＝1.523±5％ R₂₁＝-7.84±5％ R₂₂＝-15.11±5％ f₃＝47.62±5％ n₃＝1.535±5％ f₄＝30.32±5％ n₄＝1.497±5％ R₄₁＝17.76±5％ R₄₂＝-93.45±5％ f₅＝21.18±5％ n₅＝1.497±5％ R₅₁＝13.66±5％ R₅₂＝-40.49±5％ f₆＝-12.55±5％ n₆＝1.636±5％ f₇＝12.72±5％ n₇＝1.535±5％

in the above table: f. of₁-f₇The focal lengths of the first glass spherical lens L1 and the seventh plastic aspheric lens L7 respectively correspond to the first glass spherical lens L1 and the seventh plastic aspheric lens; n is₁-n₇The refractive indexes of the first glass spherical lens L1 and the seventh plastic aspheric lens L7 respectively correspond in sequence; the R is₁₁And R₁₂Corresponding to the curvature radius of the first glass spherical lens L1, R₂₁And R₂₂Corresponding to the radius of curvature of the second spherical glass lens L2, R₄₁And R₄₂Corresponding to the radius of curvature of the fourth spherical glass lens L4, R₅₁And R₅₂Corresponds to the radius of curvature of the fifth aspherical lens L5, wherein "-" indicates that the direction is a negative direction.

2. The large aperture high and low temperature confocal imaging system of claim 1, wherein: the aspheric surface equations of the third plastic aspheric lens with concave-convex positive focal power L3, the sixth plastic aspheric lens with concave-convex negative focal power L6 and the seventh plastic aspheric lens with double convex positive focal power L7 satisfy that:

in the above formula, the parameter c is a curvature radius, y is a radial coordinate, and k is a conic coefficient, wherein the third plastic aspheric lens L3 includes an R element₃₁Face and R₃₂The sixth plastic aspheric lens L6 includes opposite R₆₁Face and R₆₂The seventh plastic aspheric lens L7 includes opposite R₇₁Face and R₇₂Wherein R is₃₁Flour, R₃₂Flour, R₆₁Flour, R₆₂Flour, R₇₁Face and R₇₂The parameters of the face are as follows:

3. the large aperture high and low temperature confocal imaging system of claim 1, wherein: also satisfies that the sum of the focal powers of two positive lenses and the focal power of one negative lens in the focal powers of the three plastic non-spherical lenses is within the following range

4. The large aperture high and low temperature confocal imaging system of claim 1 further satisfying FNO

Where f is the system focal length and D is the entrance pupil diameter.

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