TWI621873B - Projecting lens - Google Patents

Abstract

The invention provides a projection lens which sequentially includes, from the object end to the imaging surface along the optical axis direction thereof, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a positive refractive power. a third lens group, and a prism; the first lens group includes at least three lenses and at least two of the image side surfaces of the lens are aspherical; the second lens group is from the object end along the optical axis thereof The imaging surface includes at least one lens and one aperture; the third lens group includes at least five lenses and at least one of the lenses is a cemented lens; the projection lens satisfies the following conditional formula: 18<TT/f<22 and 0.9< BFL/f, where TT is the total length of the projection lens, f is the focal length of the projection lens, and BFL is the focal length of the projection lens, that is, the distance from the last lens of the third lens group to the imaging surface.

Description

Projection lens

The present invention relates to the field of optical lenses, and more particularly to a projection lens.

The focal length of the projection lens is an important parameter that affects the performance of the projection lens. If the focal length is not short enough, a projection picture having a sufficiently large size cannot be projected in a limited size. How to ensure high resolution of the projected picture is also an urgent problem to be solved by those skilled in the art.

In view of this, it is necessary to provide a projection lens while satisfying conditions such as high resolution and short focal length.

A projection lens sequentially includes, from an object end to an imaging surface along an optical axis direction thereof, a first lens group having a negative power, a second lens group having a positive power, and a third having a positive power. a lens group, and a prism; the first lens group includes at least three lenses and an image side surface of at least two of the lenses is aspherical; the second lens group is from an object end to an imaging surface along an optical axis direction thereof Included at least one lens and one aperture; the third lens group includes at least five lenses and at least one of the lenses is a cemented lens; the projection lens satisfies the following conditional formula: 18<TT/f<22 and 0.9<BFL/f Where TT is the total length of the projection lens, f is the focal length of the projection lens, and BFL is the focal length of the projection lens, that is, the distance from the last lens of the third lens group to the imaging surface.

The projection lens that satisfies the above conditions has high resolution, short focal length and the like.

1 is a schematic structural view of a projection lens according to a preferred embodiment of the present invention.

2 is a field curvature diagram of a projection lens according to an embodiment of the present invention.

3 is a distortion diagram of a projection lens according to an embodiment of the present invention.

4 is a spherical aberration diagram of a projection lens according to an embodiment of the present invention.

The invention will be further described in detail below with reference to the accompanying drawings.

Referring to FIG. 1 , a projection lens 100 according to an embodiment of the present invention includes, in an optical axis direction thereof, from an object end to an imaging surface 61: a first lens group 10 having a negative refractive power and a positive optical lens. The second lens group 20, a third lens group 30 having positive power, a prism 40, and a protective cover 50. When projecting, the light passes through the first lens group 10, the second lens group 20, the third lens group 30, the prism 40, and the protective cover 50, and is imaged on the imaging surface 61. .

The first lens group 10 includes at least three lenses, and the image end surfaces of at least two lenses of the first lens group 10 are aspherical. In the present embodiment, the first lens group 10 includes the first lens 11, the second lens 12, and the third lens 13 in order from the object end to the imaging surface in the optical axis direction thereof. The first lens 11 includes a first object end surface S111 and a first image end surface S112. The second lens 12 includes a second object end surface S121 and a second image end surface S122. The third lens 13 includes a third object end surface S131 and a third image end surface S132. The first object end surface S111, the first image end surface S112, the third object end surface S131, and the third image end surface S132 are aspherical surfaces. The second object end surface S121 and the second image end surface S122 are spherical surfaces. The first object end surface S111 and the second object end surface S121 are convex surfaces. The first image end surface S112, the second image end surface S122, the third object end surface S131, and the third object end surface S132 are concave surfaces.

The second lens group 20 sequentially includes at least one lens and an aperture from the object end to the imaging surface along the optical axis direction thereof. In the present embodiment, the second lens group 20 includes the fourth lens 21, the fifth lens 22, and the aperture 23 in order from the object end to the imaging surface in the optical axis direction thereof. The fourth lens 21 includes a fourth object end surface S211 and a fourth image end surface S212. The fifth lens 22 includes a fifth object end surface S221 and a fifth image end surface S222. The fourth object end surface S211, the fourth image end surface S212, the fifth object end surface S221, and the fifth image end surface S222 are all spherical surfaces. The fourth object end surface S211, the fourth image end surface S212, the fifth object end surface S221, and the fifth image end surface S222 are all convex surfaces.

The third lens group 30 includes at least five lenses and at least one of the lenses is a cemented lens. In the present embodiment, the third lens group 30 sequentially includes a sixth lens 31, a seventh lens 32, an eighth lens 33, a ninth lens 34, and a tenth lens 35 from the object end to the imaging surface in the optical axis direction thereof. . The sixth lens 31 includes a sixth object end surface S311 and a sixth image end surface S312. The seventh lens 32 includes a seventh object end surface S321 and a seventh image end surface S322. The eighth lens 33 is a cemented lens and includes an eighth object end surface S331, a cementing surface S332, and an eighth image end surface S333. The ninth lens 34 includes a ninth object end surface S341 and a ninth image end surface S342. The tenth lens 35 includes a tenth object end surface S351 and a tenth image end surface S352. The sixth object end surface S311 and the sixth image end surface S312 are aspherical surfaces. a seventh object end surface S321, a seventh image end surface S322, an eighth object end surface S331, a cemented surface S332, an eighth image end surface S333, a ninth object end surface S341, a ninth image end surface S342, and a tenth object end The surface S351 and the tenth image end surface S352 are spherical surfaces. The sixth object end surface S311, the seventh object end surface S321, the eighth object end surface S331, and the tenth object end surface S351 are concave surfaces. The sixth image end surface S312, the seventh image end surface S322, the eighth image end surface S333, the ninth object end surface S341, the ninth image end surface S342, and the tenth image end surface S352 are convex surfaces.

The function of the prism 40 is to turn the light in the optomechanical system. The protective cover 50 is made of glass to protect the above-described first lens group 10, second lens group 20, third lens group 30, prism 40 and the like.

The present invention employs a far focus structure such that the lens can have a larger viewing angle and a longer back focus. In addition to using the negative positive power with the effective balance aberration, the aperture 23 is placed between the second lens group 20 and the third lens group 30, so that the overall lens structure is symmetrical with respect to the aperture 23, which can effectively balance the coma and distortion. Aberration. In addition, the first lens group 10 and the third lens group 30 use an aspherical lens, which can effectively improve the lens resolution quality and improve the distortion degree, and can also reduce the cost.

The projection lens 100 satisfies the following conditional expression:

(1) 18<TT/f<22

(2) 0.9<BFL/f

Where TT is the total length of the lens, f is the focal length of the lens; BFL is the focal length of the lens, that is, the distance from the last lens of the third lens group 30 to the imaging surface 61.

Conditional formula (1) limits the overall length of the projection lens 100, and ensures a balance between the total length of the lens and the aberration under the combination of positive and positive power; conditional expression (2) ensures that the optical system has Sufficient space can be placed between the third lens group 30 and the imaging surface 61.

Further, the projection lens 100 further satisfies the following conditional formula:

(3) -0.2<f1/f3<-0.5

Wherein f1 is a focal length of the first lens group 10, and f3 is a focal length of the third lens group 30.

Conditional formula (3) ensures both the control of the telecentric system and the requirement of a wide viewing angle.

Further, the projection lens 100 further satisfies the following conditional formula:

(4) 0.92<f2/f3<1.25

Where f2 is the focal length of the second lens group 20.

The conditional expression (4) ensures that the projection lens maintains a negative positive power distribution, and the aberrations generated by the second lens group 20 and the third lens group 30 can be balanced with each other.

By substituting the data of Table 1-2 (see below) into the above-described arithmetic expression, the shape of each lens surface in the projection lens 100 according to the first embodiment of the present invention can be obtained.

The following table lists the optical surfaces sequentially arranged from the object end to the image end, wherein R is the radius of curvature of the optical surface of each lens, and D is the on-axis distance from the corresponding optical surface to the latter optical surface ( The two optical surfaces cut the length of the optical axis), Nd is the refractive index of the corresponding lens group for d light (wavelength is 587 nm), and Vd is the Abbe number of the d-light at the corresponding lens.

Each optical element of the projection lens 100 according to an embodiment of the present invention satisfies the conditions of Table 1-2.

Table 1

Table 2

The field curvature, distortion, and spherical aberration of the projection lens 100 of the present embodiment are as shown in FIGS. 2 to 4, respectively. In Fig. 2, the curves T and S are the tangential field curvature characteristic curve and the sagittal field curvature characteristic curve, respectively. It can be seen that the meridional field curvature value and the sagittal field curvature value of the projection lens 100 of the present embodiment are controlled within the range of (-0.03 mm, 0.01 mm).

In Fig. 3, the curve is a distortion characteristic curve. As can be seen from the figure, the distortion of the projection lens 100 of the present embodiment is controlled within the range of (-1.2%, 0.4%).

In FIG. 4, the projection lens 100 is an aberration value curve observed for an F line (wavelength of 486.1 nanometers (nm)), a d line (wavelength of 587.6 nm), and a C line (wavelength of 656.3 nm). In general, the projection lens 100 of the present embodiment controls the aberration value generated for visible light (wavelength range between 400 nm and 700 nm) in the range of (-0.004 mm, 0.014 mm).

According to the projection lens of the present invention, the projection lens has the characteristics of high resolution, short focal length and the like by the limitation of the above four formulas, thereby improving the imaging quality of the projection lens.

In summary, the present invention has indeed met the requirements of the invention patent, and has filed a patent application according to law. However, the above description is only a preferred embodiment of the present invention, and it is not possible to limit the scope of the patent application of the present invention. Equivalent modifications or variations made by persons skilled in the art in light of the spirit of the invention are intended to be included within the scope of the following claims.

100‧‧‧Projection lens

10‧‧‧First lens group

11‧‧‧First lens

12‧‧‧second lens

13‧‧‧ third lens

S111‧‧‧First object surface

S112‧‧‧First image end surface

S121‧‧‧Second object surface

S122‧‧‧Second image end surface

S131‧‧‧ Third end surface

S132‧‧‧ Third image end surface

20‧‧‧second lens group

21‧‧‧Fourth lens

22‧‧‧ fifth lens

23‧‧‧ aperture

S211‧‧‧fourth end surface

S212‧‧‧Four image end surface

S221‧‧‧ fifth end surface

S222‧‧‧Fifth image surface

30‧‧‧third lens group

31‧‧‧ sixth lens

32‧‧‧ seventh lens

33‧‧‧ eighth lens

34‧‧‧ ninth lens

35‧‧‧Eleventh lens

S311‧‧‧ Sixth end surface

S312‧‧‧ sixth image end surface

S321‧‧‧ seventh end surface

S322‧‧‧ seventh image end surface

S331‧‧‧ eighth end surface

S332‧‧‧ glued surface

S333‧‧‧ eighth image end surface

S341‧‧‧ ninth end surface

S342‧‧‧ ninth image end surface

S351‧‧‧ Tenth end surface

S352‧‧‧10th image surface

40‧‧‧Ling Mirror

50‧‧‧ protective cover

61‧‧‧ imaging surface

no

Claims (7)

A projection lens sequentially includes, from an object end to an imaging surface along an optical axis direction thereof, a first lens group having a negative power, a second lens group having a positive power, and a third having a positive power. a lens group, and a prism; the first lens group includes at least three lenses and an image side surface of at least two of the lenses is aspherical; the second lens group is from an object end to an imaging surface along an optical axis direction thereof Included at least one lens and one aperture; the third lens group includes at least five lenses and at least one of the lenses is a cemented lens; the projection lens satisfies the following conditional formula: 18<TT/f<22 and 0.9<BFL/f Where TT is the total length of the projection lens, f is the focal length of the projection lens, and BFL is the focal length of the projection lens, that is, the distance from the last lens of the third lens group to the imaging surface. The projection lens of claim 1, wherein the projection lens further satisfies the following conditional expression: -0.2 < f1/f3 < -0.5, wherein f1 is a focal length of the first lens group, and f3 is the The focal length of the third lens group. The projection lens of claim 1, wherein the projection lens further satisfies the following conditional formula: 0.92 < f2 / f3 < 1.25, wherein f2 is a focal length of the second lens group, and f3 is the third The focal length of the lens group. The projection lens of claim 1, wherein the projection lens further comprises a protective cover, the protective cover being located between the third lens group and the imaging surface. The projection lens of claim 1, wherein the first lens group sequentially includes a first lens, a second lens, and a third lens from an object end to an imaging surface along an optical axis direction thereof; the first lens includes a first object end surface and a first image end surface; the second lens includes a second object end surface and a second image end surface; the third lens includes a third object end surface and a third The first object end surface, the first image end surface, the third object end surface, and the third image end surface are aspherical; the second object end surface and the second image end surface are spherical . The projection lens of claim 1, wherein the second lens group sequentially includes at least a fourth lens, a fifth lens, and the aperture from an object end to an imaging surface in an optical axis direction thereof, the fourth lens a fourth object end surface and a fourth image end surface, the fifth lens includes a fifth object end surface and a fifth image end surface; wherein the fourth object end surface and the fourth image end surface The fifth object end surface and the fifth image end surface are spherical surfaces. The projection lens of claim 1, wherein the third lens group sequentially includes a sixth lens, a seventh lens, an eighth lens, a ninth lens, and a tenth in the optical axis direction from the object end to the imaging surface. a lens, the sixth lens includes a sixth object end surface and a sixth image end surface, the seventh lens includes a seventh object end surface and a seventh image end surface, and the eighth lens is The cemented lens includes an eighth object end surface, a cemented surface and an eighth image end surface, the ninth lens includes a ninth object end surface and a ninth image end surface, and the tenth lens includes a first a tenth end surface and a tenth image end surface; wherein the sixth object end surface and the sixth image end surface are aspherical; the seventh object end surface, the seventh image end surface, and the eighth object end surface The glued surface, the eighth image end surface, the ninth object end surface, the ninth image end surface, the tenth object end surface, and the tenth image end surface are spherical surfaces.