CN108802963A - fixed focus lens - Google Patents

Abstract

The present invention discloses a fixed-focus lens, comprising two lens groups separated by an aperture, wherein the lens group close to the magnification side comprises three lenses, and the lens group close to the reduction side comprises four lenses. When focusing, the distances between the first lens group, the aperture and the second lens group are fixed and move along the optical axis relative to the light valve. The first lens group and the second lens group each have an aspherical lens. The ratio of the back focal length to the effective focal length of the fixed-focus lens is greater than or equal to 1.3.

Description

fixed focus lens

technical field

The invention relates to an optical lens, in particular to a fixed-focus lens.

Background technique

With the advancement of optoelectronic technology, image devices such as projectors, digital video cameras, and digital cameras have been widely used in daily life. One of the core components of these imaging devices is an optical lens. By adjusting the optical lens, the image is clearly focused on the screen or the charge-coupled device for imaging. Therefore, the image quality is closely related to the optical quality of the optical lens. In the highly competitive market, various manufacturers are committed to improving the optical quality of the fixed-focus lens, and reducing its weight, volume and production cost, so as to enhance the competitive advantage of the above-mentioned imaging devices. Therefore, how to manufacture a miniaturized and high-performance fixed-focus lens with low aberration, large aperture, low cost and high resolution is one of the important tasks for those skilled in the art.

Contents of the invention

Other purposes and advantages of the present invention can be further understood from the technical features disclosed in the embodiments of the present invention.

According to an aspect of the present invention, a fixed-focus lens is proposed, which sequentially includes a first lens group, an aperture and a second lens group from the zoom-in side to the zoom-out side. The first lens group includes a first lens, a second lens and a third lens in sequence, and the first lens group includes at least one aspheric lens; the second lens group includes a fourth lens, a fifth lens, A sixth lens and a seventh lens, and the second lens group includes a cemented lens and an aspheric lens;

Moreover, BFL (Back focal length equivalent in air) is the back focal length of the fixed-focus lens, EFL (Effective focal length) is the effective focal length of the fixed-focus lens, and the fixed-focus lens meets the condition of BFL/EFL≧1.3.

If a glass lens is used as the first lens of the fixed-focus lens in the embodiment, it solves the problems of being easily scratched, manufacturability and high cost when using an aspheric lens. In addition, if two lenses with opposite diopters are installed in the front and rear groups, it also solves the problem of thermal drift of the lens in a high-temperature environment. Furthermore, the use of cemented lenses can reduce the residual lateral chromatic aberration in the system. Therefore, it is possible to provide a fixed-focus lens design that has good aberration elimination ability, is easy to miniaturize, and can provide better imaging quality.

The above description is only an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention, it can be implemented according to the contents of the description, and in order to make the above and other purposes, features and advantages of the present invention more obvious and understandable , the following preferred embodiments are specifically cited, and in conjunction with the accompanying drawings, the detailed description is as follows.

Description of drawings

FIG. 1 is a schematic diagram of a fixed-focus lens according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a fixed-focus lens according to a second embodiment of the present invention.

FIG. 3 is a schematic diagram of a fixed-focus lens according to a third embodiment of the present invention.

Detailed ways

The aforementioned and other technical contents, features and effects of the present invention will be clearly presented in the following detailed descriptions of multiple embodiments with reference to the drawings. The directional terms mentioned in the following embodiments, such as "upper", "lower", "front", "rear", "left", "right", etc., are only referring to the directions of the attached drawings. Accordingly, the directional terms are used to illustrate, not to limit, the invention. In addition, the terms "first" and "second" used in the following embodiments are used to identify the same or similar elements, and are not used to limit the elements. In addition, the following embodiments only further illustrate the present invention, and those skilled in the art can apply the present invention to any desired situation according to actual needs. The so-called lens in the present invention means that at least part of the light can be allowed to penetrate, and the radius of curvature of at least one of its light entrance and light exit surfaces is not infinite; in other words, at least one of the light entrance and light exit surfaces of the lens Those need not be plane. For example, flat glass is not the lens referred to in the present invention. In addition, the so-called magnification side of the present invention refers to the side closer to the projection surface (such as a projection screen) when the designated focal lens is applied in the projection system; the reduction side refers to the side closer to the light valve when the designated focal lens is applied in the projection system. side. When the fixed-focus lens is used in the imaging system, the zoom-in side refers to the side closer to the object to be photographed, and the zoom-out side refers to the side closer to the photosensitive element. The so-called lens group in the present invention includes one or more than one lens.

An embodiment of the invention provides a fixed-focus lens. Through the design of the embodiments of the present invention, a fixed-focus lens design with good aberration elimination ability, easy miniaturization and better imaging quality can be provided.

FIG. 1 is a schematic diagram of a fixed-focus lens according to an embodiment of the present invention. Please refer to FIG. 1 , in this embodiment, the fixed-focus lens 1 has a lens barrel (not shown), and elements such as a first lens group 10 , an aperture 20 , and a second lens group 30 are accommodated in the lens barrel. The aperture 20 is disposed between the first lens group 10 and the second lens group 30 . That is, with the aperture 20 as the dividing line, the fixed-focus lens 1 can include two lens groups (the first lens group 10 and the second lens group 30), and the side of the second lens group 30 relative to the reduction side can be further It is equipped with a transmissive smooth image device TSP (Transmissive Smooth Picture), a prism PR, a protective glass cover CG and a light valve LV. In this example, focusing can be achieved by moving the whole of the first lens group 10 , the aperture 20 and the second lens group 30 forward and backward along the optical axis A relative to the imaging plane. That is, when focusing, the interval (Interval) between the first lens group 10 , the aperture 20 and the second lens group 30 of the fixed-focus lens 1 is constant. In this example, however, the imaging plane is coplanar with the surface of the light valve LV. The so-called light valve LV in the present invention refers to an optical device that can convert illumination light into image light, such as DMD, LCD, LCOS, etc., which are known to those skilled in the art. In this example, however, the light valve is a DMD. In addition, in this example, the fixed-focus lens 1 is not only a telecentric lens, but also an inverted telescopic lens (Inverted telenes). For example, when the lens has two parts, when the sum of the diopters of the part closer to the magnification side (such as lenses L1, L2) is negative, and the corresponding diopter of the other part (such as lenses L3-L8) When the sum is positive, the lens is a retrograde lens.

In this example, the first lens group 10 has positive diopter, and the second lens group 30 has positive diopter. The first lens group 10 includes a lens L1 , a lens L2 and a lens L3 arranged in sequence along the optical axis A from the enlargement side (left side in FIG. 1 ) to the reduction side (right side in FIG. 1 ). The second lens group 30 includes a lens L4 , a lens L5 , a lens L6 , a lens L7 , and a lens L8 arranged in sequence along the optical axis from the enlargement side to the reduction side. The diopters of the lenses L1-L8 are respectively negative, negative, positive; positive, negative, positive, negative and positive. In addition, the sum of the diopters of the lenses L1 and L2 is negative, while the sum of the diopters of the lenses L1 , L2 and L3 is positive; and the sum of the diopters of the lenses L4 to L8 is positive. The materials of the lenses L1-L8 are respectively glass, plastic, glass; plastic, glass, glass, glass and glass. In addition, assuming that S is a spherical lens and ASP is an aspheric lens, the lenses L1-L8 are respectively S, ASP, S, ASP, S, S, S, and S. In addition, the optical surface shapes of the lenses L1-L8 are respectively convex-concave, convex-concave, convex-convex; concave-convex, concave-concave, convex-convex, concave-convex, convex-flat.

The design parameters of the fixed-focus lens 1 and its surrounding components are shown in Table 1. However, the information listed below is not intended to limit the present invention. Anyone with ordinary knowledge in the field may make appropriate changes to its parameters or settings after referring to the present invention, but it still belongs to the scope of the present invention. within the category.

Table I

Furthermore, * shown in the table means that the surface is an aspheric surface, and if it is not marked, it means a spherical surface. In each of the following design examples of the present invention, the aspheric polynomial is represented by the following formula:

In the above formula, x is the offset (sag) in the direction of the optical axis A, c' is the reciprocal of the radius of the Osculatingsphere, that is, the reciprocal of the radius of curvature near the optical axis A, and k is the conic coefficient ( Conicconstant), y is the height of the aspheric surface, which is the height from the center of the lens to the edge of the lens. A-G respectively represent the aspheric coefficients of each order of the aspheric polynomial. Table 2 lists the values of aspheric coefficients and quadric surface coefficients of each order of each lens surface in the lens in the first embodiment of the present invention.

Table II

S3 S4 S8 S9 k -9.17E-01 -9.76E-01 0.00E+00 -4.07E+00 A -1.11E-03 -1.50E-03 -1.00E-04 -2.86E-04 B 1.02E-05 1.66E-05 -4.88E-06 -2.49E-07 C -1.41E-08 7.74E-10 2.05E-07 -1.95E-09 D. -9.17E-10 -3.42E-09 -9.16E-09 -8.27E-10 E. 9.75E-12 4.59E-11 1.91E-10 1.47E-11 f -3.26E-14 -2.07E-13 -1.93E-12 -1.89E-13 G 1.08E-01 -4.71E-05 -2.67E-07 5.07E-09

According to the design of the above-mentioned embodiment, in order to solve the problems of being easily scratched, manufacturability and high cost when using aspherical lenses, in this example, the first piece of the front group (magnification side) and the rear group (reduction side) are the last A glass spherical lens is used for one lens, and the lens L2 and the lens L4 are designed as aspherical lenses, and the lens L2 and the lens L4 are respectively arranged on two sides of the aperture instead of on the same side.

In addition, in order to solve the easy-to-produce focus shift of the lens in high-temperature environment, when the diopters of lens L2 and lens L4 in the previous example are designed to be positive and negative, the amount of focus shift in the system must be offset and slowed down. In addition, the first and last lenses in the previous example use spherical lenses, and there will be more lateral color remaining in the system. Therefore, lenses L5, L6, and L7 are arranged as triplet lenses to reduce the residual color in the system. Lateral chromatic aberration. That is, the lenses L5, L6, and L7 include two lenses cemented together. It should be noted that, in this example, the triplet lens is located between the aperture and the reduction side. In the present invention, the so-called cemented lenses or cemented lenses refer to a lens group formed by a plurality of lenses fixed to each other and fixed, but the fixing means is not limited to glue. For example, in this example, the three lenses are fixed with optical colloid, but it is not limited to this. When necessary, the three lenses can also be clamped by mechanical means (such as positioning grooves, etc.) Hold, fix.

In addition, the EFL referred to in the present invention refers to the effective focal length of the system. And TTL refers to the total length of the optical path, that is, in the fixed-focus lens, it is measured from the first surface of the first lens L1 on the magnification side to the imaging plane along the optical axis of the lens toward the reduction side. In this embodiment, the surface S22 is coplanar with the imaging plane of the fixed-focus lens 1 . The so-called back focus length or BFL in the present invention designates the air back focus length of the focal lens. For example, the back focus length BFL is when all elements outside the lenses L1-L8 are replaced with air, the lens L1-L8 The equivalent back focal length measured by L8. In this example, the second lens group 30 is provided with a TSP toward the reduction side, so its BFL is larger than that of ordinary lenses. For example, the BFL can be between 9-20mm, preferably around 10-16mm. On the other hand, usually BFL/EFL will be between 1 and 5, for example greater than 1.3, or, alternatively, will be between 1.3 and 2.

In this example, the aperture value of prime lens 1 is about 1.6; the EFL is about 8.842mm; the TTL is about 87.977mm; and the BFL is about 13.11mm. And BFL/EFL is about 1.4826. The small EFL and small TTL characteristics of the fixed-focus lens allow the above-mentioned fixed-focus lens to be used in a portable projector with a built-in battery and no external power supply.

In addition, it is worth mentioning that in another embodiment, in addition to the above-mentioned lenses, the lens 1 can also optionally include the transmissive smooth image device TSP marked on the surface S16 and S17; the surface S18 and the prism PR marked by S19; any one of the protective glass covers marked by surfaces S20 and S21 and the light valve LV on the surface S22 is placed inside the lens barrel.

The design of the second specific embodiment of the fixed-focus lens of the present invention will be described below. Considering that its design is similar to that of the first specific embodiment, only the differences will be described separately, and the rest will not be repeated because they correspond to the first specific embodiment.

In this example, the design parameters of the lens and its peripheral elements in the fixed-focus lens 1 are shown in Table 3.

Table three

Table 4 lists the values of aspheric coefficients and quadric surface coefficients of each order of each lens surface of the lens in the second embodiment of the present invention.

Table four

S3 S4 S8 S9 S14 S15 k -1.36E+00 -1.11E+00 0.00E+00 -4.27E+00 1.22E+00 0.00E+00 A -1.20E-03 -1.65E-03 -1.02E-04 -2.67E-04 -2.47E-05 -2.57E-05 B 1.90E-05 3.06E-05 -5.07E-06 -1.03E-06 -5.34E-07 -4.24E-07 C -1.40E-07 -2.41E-07 2.01E-07 9.47E-09 5.72E-09 1.76E-09 D. -1.94E-11 -1.32E-09 -9.14E-09 -9.74E-10 -1.18E-10 -6.23E-11 E. 7.25E-12 3.84E-11 1.91E-10 1.58E-11 6.96E-13 5.35E-13 f -3.34E-14 -2.07E-13 -1.93E-12 -1.89E-13 0.00E+00 0.00E+00 G -1.36E+00 -1.11E+00 0.00E+00 -4.27E+00 1.22E+00 0.00E+00

It can be seen from Table 3 and Table 4 that the main difference between the second embodiment and the first embodiment is that the two surfaces S14 and S15 of the last lens near the reduction side of the fixed-focus lens 1 are both aspherical. Also, in this example, BFL/EFL is approximately 1.4828.

The design of the third specific embodiment of the fixed-focus lens of the present invention will be described below. Considering that its design is similar to that of the first specific embodiment, only the differences will be described separately, and the rest will not be repeated because they correspond to the first specific embodiment.

In this example, the design parameters of each lens and its peripheral elements in the fixed-focus lens 1 are shown in Table 5.

Table five

Table 6 lists the aspheric coefficients and quadric coefficient values of each lens surface of the lens in the third embodiment of the present invention.

Table six

It can be seen from the above two tables that the main difference between the third embodiment and the first embodiment is that the two surfaces of the last lens near the reduction side of the fixed-focus lens 1 are both aspherical. Additionally, in this case, the rear group includes two sets of doublets. In this example, BFL/EFL is about 1.451.

Furthermore, in another embodiment of the present invention, a projector is disclosed. In addition to using the fixed-focus lens 1 in the above-mentioned embodiments, it also includes the above-mentioned light valve and lighting source and other components, which can be used for An image is imaged on a projection surface such as a projection screen.

Moreover, in another embodiment of the present invention, a kind of imaging device such as a video camera is disclosed. In addition to using the fixed-focus lens 1 in the above-mentioned embodiments, it also includes a photosensitive element, which can be used to capture An object's image light.

It can be known from the above embodiments that the glass lens is used as the first lens of the fixed-focus lens, which solves the problems of being easily scratched, manufacturability and high cost when using an aspherical lens. In addition, by arranging two lenses with opposite diopters in the front and rear groups, it also solves the problem of the lens shifting easily in high-temperature environments. Furthermore, the residual lateral chromatic aberration in the system can be reduced by the use of cemented lenses. Therefore, it is possible to provide a fixed-focus lens design that has good aberration elimination ability, is easy to miniaturize, and can provide better imaging quality.

The parameters listed in Table 1 to Table 6 are only for illustration and not for limiting the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be defined by the appended claims. In addition, any embodiment or claims of the present invention need not achieve all the objects or advantages or features disclosed in the present invention. In addition, the abstract and the title are only used to assist in searching patent documents, and are not used to limit the claims of the present invention.

Claims (11)

1. a kind of tight shot, which is characterized in that from Zoom Side to reduced side, include sequentially：

One first lens group, an aperture and one second lens group；

Wherein, first lens group, includes sequentially one first lens, one second lens and a third lens, and described first Lens group includes an at least non-spherical lens；

Second lens group, including one the 4th lens, one the 5th lens, one the 6th lens and one the 7th lens, and described Two lens groups include a balsaming lens and a non-spherical lens；

Moreover, BFL is the back of the body focal length degree of the tight shot, EFL is the effective focal length of the tight shot, the tight shot Meet the condition of BFL/EFL≤1.3.

2. a kind of tight shot, which is characterized in that from Zoom Side to reduced side, include sequentially：

One first lens；

One second lens；

One the third lens；

One the 4th lens；

One the 5th lens；

One the 6th lens；And

One the 7th lens；

Wherein, a wherein lens for first lens, second lens and the third lens are non-spherical lens；

A wherein lens for 4th lens, the 5th lens, the 6th lens and the 7th lens are aspherical Lens；

4th lens, the 5th lens, wherein two lens of the 6th lens and the 7th lens are mutually glued；

BFL is the back of the body focal length degree of the tight shot, and BFL≤11 of the tight shot, TTL are the light path of the tight shot Overall length, TTL≤150mm.

3. such as claim 1-2 any one of them tight shots, which is characterized in that first lens, second lens And in the third lens include at least have a glass spherical lens；4th lens, the 5th lens, the described 6th are thoroughly Being included at least in mirror and the 7th lens has a glass spherical lens.

4. such as claim 1-2 any one of them tight shots, which is characterized in that first lens, second lens And the diopter of the non-spherical lens in the third lens, with the 4th lens, the 5th lens, the described 6th The diopter of lens and the non-spherical lens in the 7th lens is opposite.

5. tight shot as claimed in claim 1 or 2, which is characterized in that EFL is the effective focal length of the tight shot, BFL/EFL≧1.45。

6. such as claim 1-2 any one of them tight shots, which is characterized in that first lens and second lens Diopter summation be negative, the diopters of the third lens is just.

7. such as claim 1-2 any one of them tight shots, which is characterized in that first lens, second lens And the diopter summation of the third lens is just.

8. such as claim 1-2 any one of them tight shots, which is characterized in that the tight shot further includes having one the 8th Lens are set between the third lens and the reduced side.

9. tight shot as claimed in claim 8, which is characterized in that the 4th lens, the 5th lens, the described 6th Wherein three pieces of lens glues of lens, the 7th lens and the 8th lens are combined into one piece of three balsaming lens.

10. tight shot as claimed in claim 2, which is characterized in that the tight shot further includes having an aperture, is set to Between the third lens and the 4th lens.

11. such as claim 1-2 any one of them tight shots, which is characterized in that by the Zoom Side to the reduced side Sequential, including：

It is negative that first lens, which are diopter,；

It is negative that second lens, which are diopter,；

The third lens are that diopter is just；

It is just that 4th lens, which are diopter,；

It is negative that 5th lens, which are diopter,；

It is just that 6th lens, which are diopter,；

It is negative that one the 8th lens, which are diopter,；And

It is just that 7th lens, which are diopter,；

Wherein, the 5th lens, the 6th lens and described 8th lens forming, one piece of diopter are that three negative gluings are saturating The summation of mirror, the diopter of first lens, second lens and the third lens is that just, TTL is the fixed-focus mirror The light path overall length of head, TTL≤150mm, BFL are the back of the body focal length degree of the tight shot, BFL≤11 of the tight shot, institute The effective focal length that EFL is the tight shot is stated, the tight shot meets the condition of BFL/EFL≤1.3, the tight shot Lens numbers be less than 10 pieces, the f-number of the tight shot is less than 2, and the field angle of the tight shot is less than 100 degree.