CN205157871U - A small imaging system with large aperture and wide angle - Google Patents

Abstract

The utility model discloses a large-aperture wide-angle small imaging system, which is provided with an aperture diaphragm, a first lens, a second lens, a third lens, a fourth lens, a light filter and a light sensitive sheet in sequence from an object plane to an image plane; the first lens is a positive focal length lens, one surface of the first lens facing the object surface is a convex aspheric surface, and the other surface of the first lens facing the image surface is a concave aspheric surface; the second lens is a biconcave negative focal length lens, and both concave surfaces of the second lens are aspheric surfaces; the third lens is a positive focal length lens, one surface of the third lens facing the object surface is a concave aspheric surface, and the other surface of the third lens facing the image surface is a convex aspheric surface; the fourth lens is a negative focal length lens, and the surface shapes of the two surfaces are both of M-shaped structures facing the direction of the object plane. The utility model discloses all adopt plastics aspheric surface structure, so optical system's geometric transfer function obtains very big improvement, can make tax degree, transmittance, color reducibility of this product obtain showing and promote. Meanwhile, the total length of the lens can be greatly shortened, so that the total volume of the lens is greatly reduced.

Description

A small imaging system with large aperture and wide angle

【Technical field】

The utility model relates to a small-sized imaging system with a large aperture and a wide angle, in particular to a super 80-degree field of view wide-angle optical imaging system loaded with a small volume.

【Background technique】

The small optical system currently used has some disadvantages. The aperture is small, and the FNO is generally in the range of 2.0-2.4. The imaging picture has a bright center and a dark and uneven periphery, and the field of view angle is controlled around 70 degrees.

This utility model just proposes based on the shortcoming that above-mentioned prior art exists.

【Content of utility model】

The technical problem to be solved by this utility model is to provide a small imaging system with large aperture and wide angle, which includes 4 lenses in total. For a more stringent real shooting environment, the required loading space is also relatively economical.

In order to achieve the above object, this utility model has adopted following technical scheme:

A small-sized imaging system with large aperture and wide angle is characterized in that: an aperture stop 0, a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, and an optical filter are arranged successively from the object plane to the image plane 5 and a photosensitive sheet 6; the first lens 1 is a positive focal length lens, one side facing the object plane is a convex aspheric surface, and the other side facing the image plane is a concave aspheric surface; the second lens 2 is a double-concave negative focal length lens , both of its concave surfaces are aspheric; the third lens 3 is a positive focal length lens, and its side facing the object plane is a concave aspheric surface, and its other side facing the image plane is a convex aspheric surface; the fourth lens 4 is For negative focal length lenses, the surface shapes of both surfaces are M-shaped structures facing the direction of the object plane.

2. As described in a large-aperture wide-angle small-scale imaging system, it is characterized in that:

1) The focal length of the first lens 1 is f1, the focal length of the second lens 2 is f2, the focal length of the third lens 3 is f3, and the focal length of the fourth lens 4 is respectively f4, satisfying: -4<f2/f1<0; -1.5<f4/f3<0;

2) The dispersion coefficient of the first lens 1 is (lens1), the dispersion coefficient of the second lens 2 is (lens2), the dispersion coefficient of the third lens 3 is (lens3), and the dispersion coefficient of the fourth lens 4 (lens4) , satisfy the following conditions: 50<(lens1)<60; 50<lens3<60; 50<lens4)<60; 20<(lens2)<30; 30<(lens1)-(lens2)<40.

A large-aperture wide-angle small imaging system as described above is characterized in that: the distance between the first lens 1 and the second lens 2 is A1, the distance between the second lens 2 and the third lens 3 is A2, and the distance between the second lens 2 and the third lens 3 is A2. The distance between the third lens 3 and the fourth lens 4 is A3, the distance between the fourth lens 4 and the optical filter 5 is A4, and the distance between the first lens 1 and the photosensitive sheet 6 is TL, so that: 1<A2 /A3<1.3; 0.18<A2/A1<0.2; 0.18<A2/A4<0.2; 0.14<A1+A2+A3+A4/TL<0.15.

A small-sized imaging system with large aperture and wide angle as described above is characterized in that the central thickness of the first lens 1 is T1, the central thickness of the second lens 2 is T2, and the central thickness of the third lens 3 is T3, the central thickness of the fourth lens 4 is T4, satisfying: 0.2<T2/T3<0.23; 0.36<T2/T1<0.39; 1.23<T3/T4<1.25; 0.3<T1+T2+T3+T4/ TL<0.4; where T1+(T2)+(T3)+(T4 and A1+(A2)+(A3)+(A4 meet the following conditions: 2.35<(T1+(T2)+(T3)+T4)/(A1+( A2)+(A3)+(A4)<2.45.

A large-aperture wide-angle small imaging system as described above is characterized in that the focal length of the lens is f, which satisfies: 0.6<f/TL<0.8.

A small imaging system with large aperture and wide angle as described above is characterized in that the first lens 1 , the second lens 2 , the third lens 3 and the fourth lens 4 are all plastic lenses.

As mentioned above, a small imaging system with large aperture and wide angle is characterized in that the height of the photosensitive sheet is (IMC), and the distance between the first lens 1 and the photosensitive sheet 6 is TL, which satisfies: TL/IMC<0.8.

A large-aperture wide-angle small imaging system as described above is characterized in that the filter 6 is an IR filter.

A small-sized imaging system with a large aperture and wide angle as described above is characterized in that the first lens 1, the second lens 2, the third lens 3 and the fourth lens 4 are all aspherical, and the shape of the aspheric surface satisfies the equation: $Z={\mathrm{cy}}^2/\left\{1+\sqrt{\&lsqb;1-(1+k)c2\mathrm{the\; y}2\&rsqb;}\right\}+{\mathrm{\&alpha;}}_1{\mathrm{the\; y}}^2+{\mathrm{\&alpha;}}_2{\mathrm{the\; y}}^4+{\mathrm{\&alpha;}}_3{\mathrm{the\; y}}^6+{\mathrm{\&alpha;}}_4{\mathrm{the\; y}}^8+{\mathrm{\&alpha;}}_5^{10}\mathrm{the\; y}+{\mathrm{\&alpha;}}_6{\mathrm{the\; y}}^{12}+$ ${\mathrm{\&alpha;}}_7{\mathrm{the\; y}}^{14}+{\mathrm{\&alpha;}}_8{\mathrm{the\; y}}^{16},$ In the formula, the parameter c is the curvature corresponding to the radius, y is the radial coordinate, and its unit is the same as the lens length unit, and k is the coefficient of the conic conic curve; when the k coefficient is less than -1, the surface curve of the lens is double curve, when the k coefficient is equal to -1, the surface curve of the lens is a parabola; when the k coefficient is between -1 and 0, the lens surface curve is an ellipse, when the k coefficient is equal to 0, the lens surface curve The curve is circular, and when the k coefficient is greater than 0, the surface curve of the lens is oblate; α ₁ to α ₈ respectively represent the coefficients corresponding to each radial coordinate.

Compared with the existing technology, this utility model has the following advantages:

1. In the optical structure, the aperture stop is in front, -4<(f2)/(f1)<0, -1.5<(f4)/(f3)<0, which can solve the wide-angle field of view compression problem of this utility model , can effectively reduce the height of large-angle light on the main surface of the system, make the system ultra-thin and reduce structural tolerance sensitivity.

2. The first lens and the third lens are located on both sides of the second lens, which are similar to symmetrical lenses. The second lens can effectively eliminate chromatic aberration, and the fourth lens is a negative focal length lens. The surface shapes of the two surfaces are facing the direction of the object plane. The M-shaped structure can effectively correct the system distortion.

3. In the optical structure, the lens should meet: 50<(lens1)<60; 50<(lens3)<60; 50<(lens4)<60; 20<(lens2)<30; 30<(lens1)-( lens2)<40, it can well correct the system chromatic aberration and meet the high image quality requirements.

4. The utility model can realize a wide-angle camera of more than 80°.

5. The overall image surface of the utility model is uniform, with high brightness and large aperture (aperture number reaches F1.8).

6. The TV distortion of the lens of the present utility model is less than 1%.

7. The utility model adopts plastic aspherical structure, so the geometric transfer function of the optical system is greatly improved, and the tax rate, transmittance, and color reproduction of the product can be significantly improved. At the same time, the total length of the lens can be greatly shortened, so that the overall volume of the lens is greatly reduced.

【Description of drawings】

Fig. 1 is the structural representation of the utility model.

【detailed description】

Below in conjunction with accompanying drawing this utility model is described in further detail.

The utility model is provided with an aperture stop 0, a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, an optical filter 5 and a photosensitive sheet 6 sequentially from the object plane to the image plane; the first lens 1 is a positive focal length lens, and its side facing the object plane is a convex aspheric surface, and the other side facing the image surface is a concave aspheric surface; the second lens 2 is a double-concave negative focal length lens, and its two concave surfaces are both aspherical surfaces; The third lens 3 is a positive focal length lens, and its side facing the object plane is a concave aspheric surface, and the other side facing the image plane is a convex aspheric surface; the fourth lens 4 is a negative focal length lens, and the surface shapes of both surfaces are the same. It is an M-shaped structure facing the direction of the object plane; the first lens 1, the second lens 2, the third lens 3 and the fourth lens 4 are all plastic lenses.

In addition, the first lens 1, the second lens 2, the third lens 3 and the fourth lens 4 are all aspherical surfaces, which have the characteristics of low cost of plastic lenses, and the characteristics of aspheric surfaces greatly improve the geometric transfer function of the optical lens. The tax rate, transmittance, and color reproduction of the product have been significantly improved, and the total length of the lens can be greatly shortened, so that the overall volume of the lens is greatly reduced.

The shape of an aspheric surface satisfies the equation: $Z={\mathrm{cy}}^2/\left\{1+\sqrt{\&lsqb;1-(1+k)c2\mathrm{the\; y}2\&rsqb;}\right\}+{\mathrm{\&alpha;}}_1{\mathrm{the\; y}}^2+$ ${\mathrm{\&alpha;}}_2{\mathrm{the\; y}}^4+{\mathrm{\&alpha;}}_3{\mathrm{the\; y}}^6+{\mathrm{\&alpha;}}_4{\mathrm{the\; y}}^8+{\mathrm{\&alpha;}}_5{\mathrm{the\; y}}^{10}+{\mathrm{\&alpha;}}_6{\mathrm{the\; y}}^{12}+a_7{\mathrm{the\; y}}^{14}+{\mathrm{\&alpha;}}_8{\mathrm{the\; y}}^{16},$ In the formula, the parameter c is the curvature corresponding to the radius, y is the radial coordinate (its unit is the same as the lens length unit), k is the coefficient of the conic conic curve; when the k coefficient is less than -1, the surface curve of the lens is Hyperbola, when the coefficient k is equal to -1, the surface curve of the lens is a parabola; when the coefficient k is between -1 and 0, the surface curve of the lens is an ellipse; when the coefficient k is equal to 0, the surface curve of the lens is The shape curve is a circle, and when the k coefficient is greater than 0, the surface shape curve of the lens is an oblate circle; α ₁ to α ₈ respectively represent the coefficients corresponding to each radial coordinate.

The focal lengths of the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4 are respectively f1, f2, f3, f4, and the first lens 1, the second lens 2, the third lens 3, the The dispersion coefficients of the four lenses 4 are lens1, lens2, lens3 and lens4 respectively, the distance between the first lens 1 and the second lens 2 is A1, the distance between the second lens 2 and the third lens 3 is A2, and the distance between the first lens 1 and the second lens 2 is A2. The distance between the third lens 3 and the fourth lens 4 is A3, the distance between the fourth lens 4 and the filter 5 is A4, and the distance between the first lens 1 and the photosensitive sheet 6 is TL.

The central thickness of the first lens 1 is T1, the central thickness of the second lens 2 is T2, the central thickness of the third lens 3 is T3, the central thickness of the fourth lens 4 is T4, and the height of the photosensitive sheet is IMC , the distance between the first lens 1 and the photosensitive sheet 6 is TL, and the filter 6 is an IR filter.

The above parameters meet the following conditions, summarized as follows:

I.-4<(f2)/(f1)<0

II.-1.5<(f4)/(f3)<0

III.50<(lens1)<60;

IV.50<(lens3)<60;

V.50<(lens4)<60;

VI.20<(lens2)<30

VII.30<(lens2)-(lens1)<40

VIII.1<(A2)/(A3)<1.3

IX.0.18<(A2)/(A1)<0.2

X.0.18<(A2)/(A4)<0.2

XI.0.14<((A1)+(A2)+(A3)+(A4))/TL<0.15

XII.0.2<(T2)/(T3)<0.23

XIII.0.36<(T2)/(T1)<0.39

XIV.1.23<(T3)/(T4)<1.25

XV.0.3<((T1)+(T2)+(T3)+(T4))/TL<0.4

XVI.2.35<((T1)+(T2)+(T3)+(T4))/((A1)+(A2)+(A3)

+(4))<2.45

XVII.0.6<(f)/(TL)<0.8

XVIII. (TL)/(IMC)<0.8.

Claims (9)

1. the small-sized imaging system of large aperture wide-angle, is characterized in that: it is provided with aperture diaphragm (0), the first lens (1), the second lens (2), the 3rd lens (3), the 4th lens (4), optical filter (5) and sensitive film (6) successively by object plane to image planes; Described first lens (1) are positive focal length lens, and its one side towards object plane is convex aspheric surface, and the another side towards image planes is concave surface aspheric surface; Described second lens (2) are concave-concave negative focal length lens, and its two concave surface is aspheric surface; Described 3rd lens (3) are positive focal length lens, and its one side towards object plane is concave surface aspheric surface, and its another side towards image planes is convex aspheric surface; Described 4th lens (4) are negative focal length lens, and the surface configuration in two faces is all towards the M character form structure in object plane direction.

2. the small-sized imaging system of a kind of large aperture wide-angle according to claim 1, is characterized in that:

1) focal length of the first lens (1) is (f1), the focal length of the second lens (2) is (f2), the focal length of the 3rd lens (3) is (f3), the focal length of the 4th lens (4) is respectively (f4), meets :-4< (f2)/(f1) <0;-1.5< (f4)/(f3) <0;

2) abbe number of described first lens (1) is (lens1), the abbe number of the second lens (2) is (lens2), the abbe number of the 3rd lens (3) is (lens3), the abbe number (lens4) of the 4th lens (4), meets following condition: 50< (lens1) <60; 50< (lens3) <60; 50< (lens4) <60; 20< (lens2) <30; 30< (lens1)-(lens2) <40.

3. the small-sized imaging system of a kind of large aperture wide-angle according to claim 1, it is characterized in that: described first lens (1) are (A1) with the spacing of the second lens (2), described second lens (2) are (A2) with the spacing of the 3rd lens (3), described 3rd lens (3) are (A3) with the spacing of the 4th lens (4), described 4th lens (4) are (A4) with the spacing of optical filter (5), described first lens (1) are (TL) with the spacing of sensitive film (6), then meet: 1< (A2)/(A3) <1.3, 0.18< (A2)/(A1) <0.2, 0.18< (A2)/(A4) <0.2, 0.14< ((A1)+(A2)+(A3)+(A4))/TL<0.15.

4. the small-sized imaging system of a kind of large aperture wide-angle according to claim 1, it is characterized in that the center thickness of described first lens (1) is for (T1), the center thickness of described second lens (2) is (T2), the center thickness of described 3rd lens (3) is (T3), the center thickness of described 4th lens (4) is (T4), meets: 0.2< (T2)/(T3) <0.23; 0.36< (T2)/(T1) <0.39; 1.23< (T3)/(T4) <1.25; 0.3< ((T1)+(T2)+(T3)+(T4))/TL<0.4; Wherein (T1)+(T2)+(T3)+(T4) and (A1)+(A2)+(A3)+(A4) meet the following conditions: 2.35< ((T1)+(T2)+(T3)+(T4))/((A1)+(A2)+(A3)+(A4)) <2.45.

5. the small-sized imaging system of a kind of large aperture wide-angle according to claim 1, is characterized in that the focal length of described camera lens is for (f), meets: 0.6< (f)/(TL) <0.8.

6. the small-sized imaging system of a kind of large aperture wide-angle according to claim 1, is characterized in that described first lens (1), the second lens (2), the 3rd lens (3) and the 4th lens (4) are plastic lens.

7. the small-sized imaging system of a kind of large aperture wide-angle according to claim 1, it is characterized in that sensitive film height is for (IMC), described first lens (1) are (TL) with the spacing of sensitive film (6), meet: (TL)/(IMC) <0.8.

8. the small-sized imaging system of a kind of large aperture wide-angle according to claim 1, is characterized in that described optical filter (6) is for IR infrared fileter.

9. the small-sized imaging system of a kind of large aperture wide-angle according to claim 1, it is characterized in that described first lens (1), the second lens (2), the 3rd lens (3) and the 4th lens (4) are aspheric surface, aspherical surface shape meets equation: $Z={\mathrm{cy}}^2/$ $\{1+\sqrt{\&lsqb;1-(1+k)c2y2\&rsqb;}\}+{\mathrm{\&alpha;}}_1{y}^2+{\mathrm{\&alpha;}}_2{y}^4+{\mathrm{\&alpha;}}_3{y}^6+{\mathrm{\&alpha;}}_4{y}^8+{\mathrm{\&alpha;}}_5{y}^{10}+{\mathrm{\&alpha;}}_6{y}^{12}+{\mathrm{\&alpha;}}_7{y}^{14}+{\mathrm{\&alpha;}}_8{y}^{16},$ In formula, the curvature of parameter (c) corresponding to radius, (y) is radial coordinate, and its unit is identical with length of lens unit, and (k) is circular cone whose conic coefficient; When (k) coefficient is less than-1, the face shape curve of lens is hyperbolic curve, and when (k) coefficient equals-1, the face shape curve of lens is para-curve; When (k) coefficient is between-1 to 0, the face shape curve of lens is oval, and when (k) coefficient equals 0, the face shape curve of lens is circular, and when (k) coefficient is greater than 0, the face shape curve of lens is oblate; (α ₁) to (α ₈) represent coefficient corresponding to each radial coordinate respectively.