WO2021142837A1 - Projection lens - Google Patents

Abstract

The present invention provides a projection lens, comprising, in order from an object side to an image side: a first lens having positive refractive power, a second lens having positive refractive power, a third lens, and a fourth lens having positive refractive power. The focal lens of the projection lens is f, the focal length of the first lens is f1, the focal lens of the second lens is f2, the radius of curvature of an object side surface of the second lens is R3, the radius of curvature of an image side surface of the second lens is R4, the refractive index of the second lens is n2, and the following relational expressions are satisfied: 0.80≤f2/f≤1.50; 1.67≤n2≤2.20; 1.20≤f1/f≤2.00; and 4.50≤(R3+R4)/(R3-R4)≤15.00. The projection lens provided by the present invention has good optical properties, and also meets wide-angle and ultra-thin design requirements.

Description

Projection lens Technical field

The invention relates to the field of optical lenses, in particular to a projection lens suitable for portable terminal devices such as smart phones and digital cameras.

Background technique

With the rapid development of smart phones, innovative technologies such as 3D imaging technology continue to emerge in the camera function of smartphones. This optical sensing technology based on 3D structured light can be used for face and gesture recognition, enhanced camera functions, and Come to AR new applications to convert optical images from the past two-dimensional to three-dimensional space, thereby bringing a more realistic and clear perception experience.

3D structured light means that after specific laser information is projected onto the surface of an object, it is collected by a camera, and information such as the position and depth of the object is calculated according to the changes in the light information caused by the object, thereby restoring the entire three-dimensional space. Specific laser information is a very important indicator in 3D structured light technology, so the projection lens that projects the laser information onto the surface of the measured object is very demanding. This kind of projection lens that projects the array point light source with a specific solid angle emission on the surface of the VCSEL (Vertical Cavity Surface Emitting Laser) laser onto the surface of the measured object is a key link in the quality of 3D imaging.

technical problem

In the existing projection lens products, there is a problem that the focal length f of the lens changes greatly with the change of the use environment temperature, which will cause the angle of the light projected by the lens to change significantly, and change the original light information, resulting in Errors in the calculation of the entire system affect the accuracy of the contour restoration of the three-dimensional object; there is also the problem that the image point of the projection becomes larger with the change of the ambient temperature, which will also cause the resolution of the system to restore the three-dimensional object to decrease.

In order to effectively reduce the length of the system, increase the latitude of the system structure design and reduce the sensitivity of the focal length to the ambient temperature, the present invention proposes a projection lens.

Technical solutions

In view of the above-mentioned problems, the object of the present invention is to provide a projection lens which has good optical performance and meets the design requirements of ultra-thin and wide-angle.

In order to solve the above technical problems, embodiments of the present invention provide a projection lens, which sequentially includes from the object side to the image side: a first lens with positive refractive power, a second lens with positive refractive power, and a third lens, And a fourth lens with positive refractive power;

The focal length of the projection lens is f, the focal length of the first lens is f1, the focal length of the second lens is f2, the radius of curvature of the object side of the second lens is R3, and the second lens is The radius of curvature is R4, the refractive index of the second lens is n2, and the following relationship is satisfied:

0.80≤f2/f≤1.50;

1.67≤n2≤2.20;

1.20≤f1/f≤2.00;

4.50≤(R3+R4)/(R3-R4)≤15.00.

Preferably, the on-axis thickness of the third lens is d5, and the on-axis distance from the image side surface of the third lens to the object side surface of the fourth lens is d6, which satisfies the following relationship:

10.00≤d5/d6≤12.00.

Preferably, the radius of curvature of the object side surface of the third lens is R5, and the radius of curvature of the image side surface of the third lens is R6, which satisfies the following relationship:

-15.00≤(R5+R6)/(R5-R6)≤-5.00.

Preferably, the focal length of the fourth lens is f4, which satisfies the following relationship:

5.00≤f4/f≤9.00.

Preferably, the curvature radius of the object side surface of the first lens is R1, the curvature radius of the image side surface of the first lens is R2, the axial thickness of the first lens is d1, and the total optical length of the projection lens is TTL , Satisfies the following relationship:

-14.93≤(R1+R2)/(R1-R2)≤-1.51;

0.03≤d1/TTL≤0.13.

Preferably, the focal length of the third lens is f3, the on-axis thickness of the third lens is d5, the total optical length of the projection lens is TTL, and the following relationship is satisfied:

-102.60≤f3/f≤10.34;

0.05≤d5/TTL≤0.21.

Preferably, the radius of curvature of the object side surface of the fourth lens is R7, the radius of curvature of the image side surface of the fourth lens is R8, the axial thickness of the fourth lens is d7, and the total optical length of the projection lens is TTL , And satisfy the following relationship:

-4.85≤(R7+R8)/(R7-R8)≤-0.90;

0.16≤d7/TTL≤0.50.

Preferably, the angle of view of the projection lens is FOV, which satisfies the following relationship:

FOV≥69°.

Preferably, the second lens is made of glass.

Beneficial effect

The beneficial effects of the present invention are: through the above-mentioned lens configuration, not only can the lenses with different refractive indexes and focal lengths be effectively used to achieve clear imaging, but also can effectively reduce the length of the system and reduce the space occupied by the system. In addition, the system is sensitive to the environmental temperature. Insensitive, the performance can remain stable at different temperatures, the projection angle is not significantly changed, and the optical information is well preserved. Therefore, the system has better projection performance and is more suitable for portable high-power laser projection devices.

Description of the drawings

In order to explain the technical solutions in the embodiments of the present invention more clearly, the following will briefly introduce the drawings needed in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative work, other drawings can be obtained based on these drawings, among which:

FIG. 1 is a schematic diagram of the structure of the projection lens of the first embodiment;

Fig. 2 is a schematic diagram of field curvature and distortion of the projection lens shown in Fig. 1;

Fig. 3 is a point diagram of the projection lens shown in Fig. 1;

4 is a schematic diagram of the structure of the projection lens of the second embodiment;

FIG. 5 is a schematic diagram of field curvature and distortion of the projection lens shown in FIG. 4;

Fig. 6 is a point diagram of the projection lens shown in Fig. 4;

FIG. 7 is a schematic diagram of the structure of the projection lens of the third embodiment;

Fig. 8 is a schematic diagram of field curvature and distortion of the projection lens shown in Fig. 7;

Fig. 9 is a point diagram of the projection lens shown in Fig. 7.

Embodiments of the present invention

In order to make the objectives, technical solutions and advantages of the present invention clearer, the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, a person of ordinary skill in the art can understand that, in each embodiment of the present invention, many technical details are proposed for the reader to better understand the present invention. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solution claimed by the present invention can be realized.

(First Embodiment)

Please refer to the drawings. The present invention provides a projection lens 10. FIG. 1 shows a projection lens 10 according to a first embodiment of the present invention. The projection lens 10 includes four lenses. Specifically, the projection lens 10, from the object side to the image side, includes: an aperture S1, a first lens L1 with positive refractive power, a second lens L2 with positive refractive power, a third lens L3, and a lens with positive refractive power. The fourth lens L4 of refractive power.

In this embodiment, the focal length of the projection lens 10 is defined as f, and the focal length of the second lens L2 is defined as f2, which satisfies the following relationship: 0.80≤f2/f≤1.50, which specifies the focal length of the second lens L2 and The ratio of the focal length of the projection lens 10, within the range of the conditional expression, can effectively balance the spherical aberration and field curvature of the system. Preferably, 0.81≤f2/f≤1.47.

The refractive index of the second lens L2 is n2, which satisfies the following relational expression: 1.67≤n2≤2.20, which specifies the refractive index of the second lens L2. Within the range of the conditional expression, it is beneficial to improve the stability of the system to the ambient temperature. Good retention of optical information. Preferably, 1.68≤n2≤2.13.

The focal length of the first lens L1 is f1, which satisfies the following relationship: 1.20≤f1/f≤2.00, which specifies the ratio of the focal length of the first lens L1 to the focal length of the projection lens 10, which can effectively balance the spherical aberration of the system and The amount of field curvature. Preferably, 1.30≤f1/f≤1.99.

The curvature radius of the object side surface of the second lens L2 is R3, and the curvature radius of the second lens image L2 side surface is R4, which satisfies the following relationship: 4.50≤(R3+R4)/(R3-R4)≤15.00, which is specified The shape of the second lens L2 can relax the degree of deflection of the light passing through the lens within the scope of the conditional formula, and effectively reduce aberrations. Preferably, 4.75≤(R3+R4)/(R3-R4)≤14.74.

The on-axis thickness of the third lens L3 is defined as d5, and the on-axis distance from the image side surface of the third lens L3 to the object side surface of the fourth lens L5 is d6, which satisfies the following relationship: 10.00≤d5/d6≤12.00 , Specifies the ratio of the on-axis thickness of the third lens L3 to the on-axis distance from the image side surface of the third lens L3 to the object side surface of the fourth lens L5. The conditional expression range helps to compress the total length of the optical system, Achieve ultra-thin effect. Preferably, 10.17≤d5/d6≤11.23.

Define the radius of curvature of the object side surface of the third lens L3 as R5, and the radius of curvature of the image side surface of the third lens as R6, satisfying the following relationship: -15.00≤(R5+R6)/(R5-R6)≤-5.00 , Stipulates the shape of the third lens L3. When the condition is within this range, it is beneficial to the molding of the third lens L3 and avoids poor molding and stress generation due to excessive surface curvature. Preferably, -14.80≤(R5+R6)/(R5-R6)≤-5.05.

The focal length of the fourth lens L4 is defined as f4, which satisfies the following relationship: 5.00≤f4/f≤9.00, which specifies the ratio of the focal length of the fourth lens L4 to the focal length of the projection lens 10, so that the system has better imaging quality And lower sensitivity. Preferably, 5.05≤f4/f≤8.68.

Define the curvature radius of the object side surface of the first lens L1 as R1, and the curvature radius of the image side surface of the first lens L1 as R2, which satisfies the following relationship: -14.93≤(R1+R2)/(R1-R2)≤- 1.51. Within the scope of the conditional formula, reasonably control the shape of the first lens L1 so that the first lens L1 can effectively correct the spherical aberration of the system. Preferably, -9.33≤(R1+R2)/(R1-R2)≤-1.89.

The total optical length of the projection lens 10 is TTL, and the on-axis thickness of the first lens L1 is d1, which satisfies the following relationship: 0.03≦d1/TTL≦0.13. Within the range of the conditional expression, it is beneficial to realize ultra-thinness. Preferably, 0.06≤d1/TTL≤0.10.

The focal length of the third lens L3 is defined as f3, the focal length of the projection lens 10 is f, and the following relational expression is satisfied: -102.60≤f3/f≤10.34, within the scope of the conditional expression, through reasonable distribution of optical power , So that the system has better imaging quality and lower sensitivity. Preferably, -64.13≤f3/f≤8.27.

The axial thickness of the third lens L3 is d5, and the total optical length of the projection lens 10 is TTL, which satisfies the following relationship: 0.05≤d5/TTL≤0.21. Within the range of the conditional expression, it is beneficial to realize ultra-thinness. Preferably, 0.07≤d5/TTL≤0.17.

Define the radius of curvature of the object side surface of the fourth lens L4 as R7, and the radius of curvature of the image side surface of the fourth lens L4 as R8, satisfying the following relationship: -4.85≤(R7+R8)/(R7-R8)≤ -0.90. The shape of the fourth lens L4 is specified. Within the scope of the conditional expression, with the development of ultra-thin and wide-angle, it is beneficial to correct the aberration of the off-axis angle of view. Preferably, -3.03≤(R7+R8)/(R7-R8)≤-1.13.

The axial thickness of the fourth lens L4 is d7, and the total optical length of the projection lens 10 is TTL, which satisfies the following relationship: 0.16≤d7/TTL≤0.50. Within the range of the conditional expression, it is beneficial to achieve ultra-thinness. Preferably, 0.26≤d7/TTL≤0.40.

Further, the total optical length of the projection lens 10 is defined as TTL, and the image height of the projection lens 10 is IH, which satisfies the following relationship: TTL/IH≤2.70, which is conducive to achieving ultra-thinness.

Further, the field of view of the projection lens is FOV, which satisfies the relationship: FOV≥69°.

Further, the second lens L2 of the projection lens is made of glass. Since the glass material has a high refractive index and good light transmittance, the optical performance of the projection lens 10 can be effectively improved, and the glass material has better thermal properties. Stability, so that the optical system has good performance stability at different temperatures.

When the above relationship is satisfied, the projection lens 10 can not only have good optical imaging performance, but also meet the design requirements of ultra-thin and wide-angle; the system has better projection performance and is more suitable for portable high-power laser projection devices.

Hereinafter, the projection lens 10 of the present invention will be explained with an example. The symbols described in each example are as follows. The unit of focal length, distance on axis, radius of curvature, thickness on axis, position of inflection point, and position of stagnation point is mm.

TTL: total optical length (the on-axis distance from the object side of the first lens L1 to the image plane Si), the unit is mm;

Preferably, the object side and/or the image side of the lens can also be provided with inflection points and/or stagnation points to meet high-quality imaging requirements. For specific implementations, refer to the following.

Table 1 shows focal length data of the projection lens 10 according to the first embodiment of the present invention.

【Table 1】

The meaning of each symbol is as follows: f: the focal length of the projection lens 10;

f1: the focal length of the first lens L1;

f2: the focal length of the second lens L2;

f3: the focal length of the third lens L3;

f4: the focal length of the fourth lens L4.

Table 2 and Table 3 show design data of the projection lens 10 according to the first embodiment of the present invention.

【Table 2】

Among them, the meaning of each symbol is as follows.

S1: aperture;

R: The radius of curvature of the optical surface, when the lens is the central radius of curvature;

R1: the radius of curvature of the object side surface of the first lens L1;

R2: the radius of curvature of the image side surface of the first lens L1;

R3: the radius of curvature of the object side surface of the second lens L2;

R4: the radius of curvature of the image side surface of the second lens L2;

R5: the radius of curvature of the object side surface of the third lens L3;

R6: the radius of curvature of the image side surface of the third lens L3;

R7: the radius of curvature of the object side surface of the fourth lens L4;

R8: the radius of curvature of the image side surface of the fourth lens L4;

R9: the curvature radius of the object side surface of the optical filter GF;

R10: the radius of curvature of the image side surface of the optical filter GF;

D: the on-axis thickness of the lens and the on-axis distance between the lenses;

D0: the on-axis distance from the aperture S1 to the object side of the first lens L1;

D1: the on-axis thickness of the first lens L1;

D2: the on-axis distance from the image side surface of the first lens L1 to the object side surface of the second lens L2;

D3: the on-axis thickness of the second lens L2;

D4: the on-axis distance from the image side surface of the second lens L2 to the object side surface of the third lens L3;

D5: the on-axis thickness of the third lens L3;

D6: the on-axis distance from the image side surface of the third lens L3 to the object side surface of the fourth lens L4;

D7: the on-axis thickness of the fourth lens L4;

D8: the on-axis distance from the image side surface of the fourth lens L4 to the object side surface of the optical filter GF;

D9: the on-axis thickness of the optical filter GF;

D10: the on-axis distance from the image side surface of the optical filter GF to the image surface;

Nd: the refractive index of d-line;

Nd1: the refractive index of the d-line of the first lens L1;

Nd2: the refractive index of the d-line of the second lens L2;

Nd3: the refractive index of the d-line of the third lens L3;

Nd4: the refractive index of the d-line of the fourth lens L4;

Ndg: the refractive index of the d-line of the optical filter GF;

Νd: Abbe number;

Ν1: Abbe number of the first lens L1;

Ν2: Abbe number of the second lens L2;

Ν3: Abbe number of the third lens L3;

Ν4: Abbe number of the fourth lens L4;

Νg: Abbe number of optical filter GF.

Table 3 shows the aspheric surface data of each lens in the projection lens 10 according to the first embodiment of the present invention.

【table 3】

Among them, k is the conic coefficient, and A4, A6, A8, A10, A12, A14, and A16 are the aspheric coefficients.

y=(x ² /R)/{1+[1-(k+1)(x ² /R ² )] ^1/2 }+A4x ⁴ +A6x ⁶ +A8x ⁸ +A10x ¹⁰ +A12x ¹² +A14x ¹⁴ +A16x ¹⁶ (1)

For convenience, the aspheric surface of each lens surface uses the aspheric surface shown in the above formula (1). However, the present invention is not limited to the aspheric polynomial form represented by the formula (1).

Table 4 and Table 5 show the design data of the inflection point and stagnation point of each lens in the projection lens 10 according to the first embodiment of the present invention. Among them, P1R1 and P1R2 represent the object side and image side of the first lens L1 respectively, P2R1 and P2R2 represent the object side and image side of the second lens L2 respectively, and P3R1 and P3R2 represent the object side and image side of the third lens L3 respectively. P4R1 and P4R2 represent the object side surface and the image side surface of the fourth lens L4, respectively. The corresponding data in the “reflection point position” column is the vertical distance from the reflex point set on the surface of each lens to the optical axis of the projection lens 10. The data corresponding to the “stationary point position” column is the vertical distance from the stationary point set on the surface of each lens to the optical axis of the projection lens 10.

【Table 4】

【table 5】

FIG. 2 shows a schematic diagram of field curvature and distortion of light with a wavelength of 940 nm after passing through the projection lens 10 of the first embodiment. The field curvature S in FIG. 2 is the field curvature in the sagittal direction, and T is the field curvature in the meridian direction.

FIG. 3 shows a point diagram of the projection lens 10 of the first embodiment.

The following Table 16 shows the values corresponding to the various numerical values in the first, second, and third embodiments and the parameters that have been specified in the conditional expressions.

As shown in Table 16, the first embodiment satisfies various conditional expressions.

In this embodiment, the entrance pupil diameter of the projection lens is 0.675mm, the image height IH of the projection lens is 1.283mm, and the field angle in the diagonal direction is 72.00°, making the projection lens 10 wide-angle , Ultra-thin, its on-axis and off-axis chromatic aberrations are fully corrected, and it has excellent optical characteristics.

(Second Embodiment)

The second embodiment is basically the same as the first embodiment, and the meaning of the symbols is the same as that of the first embodiment. The structure of the projection lens 20 of the second embodiment is shown in FIG. 3, and only the differences are listed below.

Table 6 shows focal length data of the projection lens 20 according to the first embodiment of the present invention.

【Table 6】

Table 7 and Table 8 show design data of the projection lens 20 according to the second embodiment of the present invention.

【Table 7】

Table 8 shows the aspheric surface data of each lens in the projection lens 20 according to the second embodiment of the present invention.

【Table 8】

Table 9 and Table 10 show the design data of the inflection point and stagnation point of each lens in the projection lens 20 according to the second embodiment of the present invention.

【Table 9】

【Table 10】

FIG. 4 shows a schematic diagram of field curvature and distortion of light with a wavelength of 930 nm after passing through the projection lens 20 of the second embodiment. The field curvature S in FIG. 4 is the field curvature in the sagittal direction, and T is the field curvature in the meridian direction.

The following Table 16 lists the numerical values corresponding to each conditional expression in this embodiment according to the above-mentioned conditional expressions. Obviously, the projection lens 20 of this embodiment satisfies the above-mentioned conditional expression.

In this embodiment, the entrance pupil diameter of the projection lens 20 is 0.678mm, the image height of the projection lens is 1.283mm, and the diagonal field angle is 69.00°, so that the projection lens 20 has a wide angle. , Ultra-thin, its on-axis and off-axis chromatic aberrations are fully corrected, and it has excellent optical characteristics.

(Third Embodiment)

The third embodiment is basically the same as the first embodiment, and the meaning of the symbols is the same as that of the first embodiment. Please refer to FIG. 7 for the structure of the projection lens 30 of the third embodiment. Only the differences are listed below.

Table 11 shows focal length data of the projection lens 30 according to the first embodiment of the present invention.

【Table 11】

Table 12 and Table 13 show design data of the projection lens 30 according to the third embodiment of the present invention.

【Table 12】

Table 13 shows the aspheric surface data of each lens in the projection lens 30 of the third embodiment of the present invention.

【Table 13】

Table 14 and Table 15 show the design data of the inflection point and stagnation point of each lens in the projection lens 30 according to the third embodiment of the present invention.

【Table 14】

【Table 15】

FIG. 6 shows a schematic diagram of field curvature and distortion of light with a wavelength of 930 nm after passing through the projection lens 30 of the third embodiment. The field curvature S in FIG. 6 is the field curvature in the sagittal direction, and T is the field curvature in the meridian direction.

The following Table 16 lists the numerical values corresponding to each conditional expression in this embodiment according to the above-mentioned conditional expressions. Obviously, the projection lens 30 of this embodiment satisfies the above-mentioned conditional expression.

In this embodiment, the entrance pupil diameter of the projection lens 30 is 0.678mm, the image height of the projection lens is 1.283mm, and the diagonal field angle is 69.00°, which makes the projection lens 30 wide-angle , Ultra-thin, its on-axis and off-axis chromatic aberrations are fully corrected, and it has excellent optical characteristics.

【Table 16】

A person of ordinary skill in the art can understand that the above-mentioned embodiments are specific embodiments for realizing the present invention, and in practical applications, various changes can be made to them in form and details without departing from the spirit and spirit of the present invention. scope.

Claims (10)

1. A projection lens, characterized in that, from the object side to the image side, the projection lens includes in order from the object side to the image side: a first lens with positive refractive power, a second lens with positive refractive power, a third lens, and a third lens with positive refractive power. The fourth lens of force;

   The focal length of the projection lens is f, the focal length of the first lens is f1, the focal length of the second lens is f2, the radius of curvature of the object side of the second lens is R3, and the second lens is The radius of curvature is R4, the refractive index of the second lens is n2, and the following relationship is satisfied:

   0.80≤f2/f≤1.50;

   1.67≤n2≤2.20;

   1.20≤f1/f≤2.00;

   4.50≤(R3+R4)/(R3-R4)≤15.00.
2. The projection lens according to claim 1, wherein the on-axis thickness of the third lens is d5, and the on-axis distance from the image side surface of the third lens to the object side surface of the fourth lens is d6, which satisfies the following Relationship:

   10.00≤d5/d6≤12.00.
3. The projection lens according to claim 1, wherein the curvature radius of the object side surface of the third lens is R5, and the curvature radius of the image side surface of the third lens is R6, which satisfies the following relationship:

   -15.00≤(R5+R6)/(R5-R6)≤-5.00.
4. The projection lens according to claim 1, wherein the focal length of the fourth lens is f4, which satisfies the following relationship:

   5.00≤f4/f≤9.00.
5. The projection lens according to claim 1, wherein the curvature radius of the object side surface of the first lens is R1, the curvature radius of the image side surface of the first lens is R2, and the axial thickness of the first lens is d1, the total optical length of the projection lens is TTL, which satisfies the following relationship:

   -14.93≤(R1+R2)/(R1-R2)≤-1.51;

   0.03≤d1/TTL≤0.13.
6. The projection lens according to claim 1, wherein the focal length of the third lens is f3, the axial thickness of the third lens is d5, and the total optical length of the projection lens is TTL, and the following relationship is satisfied Mode:

   -102.60≤f3/f≤10.34;

   0.05≤d5/TTL≤0.21.
7. The projection lens of claim 1, wherein the radius of curvature of the object side of the fourth lens is R7, the radius of curvature of the image side of the fourth lens is R8, and the on-axis thickness of the fourth lens is d7, the total optical length of the projection lens is TTL, and satisfies the following relationship:

   -4.85≤(R7+R8)/(R7-R8)≤-0.90;

   0.16≤d7/TTL≤0.50.
8. The projection lens of claim 1, wherein the total optical length of the projection lens is TTL, and the image height of the projection lens is IH, and the following relationship is satisfied:

   TTL/IH≤2.70.
9. The projection lens according to claim 1, wherein the field of view of the projection lens is FOV, which satisfies the following relationship:

   FOV≥69°.
10. The projection lens of claim 1, wherein the second lens is made of glass.