JP2010008496A - Wide angle lens, illumination optical system and surface light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wide angle lens which is reduced in distortion aberration, and bright and telecentric. <P>SOLUTION: The wide angle lens for an imaging optical system having a plurality of lens elements and a diaphragm includes, in order from a long conjugate distance side, a first lens group having negative refractive power and a second lens group having positive refractive power. The longest air interval of all the lens intervals exists between the first lens group and the second lens group. The first lens group includes at least one aspherical surface and the second lens group is constituted only of a positive lens element. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wide-angle lens, an illumination optical system, and a surface light emitting device, and more specifically, a wide-angle lens that can be used as a relay optical system that relays light emitted from a light source unit and guides it to an illuminated area of an object, In addition, the present invention relates to an illumination optical system and a surface light emitting device using the wide-angle lens.

  In recent years, liquid crystal displays have been widely used as display devices for televisions and computers. However, since the liquid crystal itself does not emit light, the liquid crystal display includes a surface light emitting device (backlight) for illuminating the display surface.

A light source used in a surface light emitting device has non-uniform light distribution characteristics. Therefore, in order to make the brightness of the illuminated area uniform, the light from the light source is once incident on a uniformizing optical system such as a rod integrator, and the light emitted from the rod integrator is relayed by a relay optical system to be illuminated area. The structure leading to is known.
JP 2002-207167 A

  The relay optical system used in such an illumination optical system is required to have the following characteristics.

  First, the relay optical system is required to be a telecentric optical system in order to effectively capture the light emitted from the integrator. Second, in order to obtain uniform illumination light, it is necessary to emit light having the same intensity from the central part to the peripheral part of the optical system, and it is necessary to provide an optical system that does not squeeze the light beam in the peripheral part. Third, it is required that the distortion is small. When there is distortion, the magnification changes between the peripheral part and the central part of the optical system, so that the brightness changes. Further, when there is distortion, it is necessary to enlarge the illumination area by the amount of distortion, and the illumination efficiency is reduced.

  Further, while the screen size of the display is increased, there is a demand for thinning the device size. Therefore, even when the illumination area of the illumination optical system is large, it is required that the entire optical system can be made compact. In order to make the entire optical system compact, it is desirable that the uniformizing optical system such as the light emitting unit and the rod integrator is small. Therefore, it is necessary to increase the illumination area by increasing the magnification of the relay optical system. Become. However, if the magnification of the relay optical system is increased, the total length of the relay optical system becomes longer. Therefore, it is necessary to shorten the total length by increasing the angle of view, that is, by widening the relay optical system.

  However, when it is attempted to construct a wide-angle optical system that satisfies the above characteristics required for the relay optical system, that is, telecentric, bright, and less distorted on the reduction side, the relay optical system Since the number of lens elements constituting the lens increases, there arises a problem that the cost increases. Therefore, it is desirable that the number of lens elements required for the relay optical system is small.

  Therefore, one of the objects of the present invention is to provide a bright and telecentric wide-angle lens with little distortion.

  Another object of the present invention is to provide a compact illumination optical system and surface light emitting device that can illuminate a large illumination area brightly and uniformly.

  In order to achieve the above object, a wide-angle lens according to the present invention is a wide-angle lens for an imaging optical system having a plurality of lens elements and a stop, and has a negative refractive power in order from the side having the long conjugate distance. And a second lens group having a positive refractive power. The space between the first lens group and the second lens group is the longest air interval among all the lens intervals. The first lens group includes at least one aspheric surface, and the second lens group includes only positive lens elements.

  The inventor of the present invention has realized that the constituent lens elements of each lens group can be minimized by arranging the negative first lens group and the positive second lens group apart from each other. According to such a configuration, it is possible to realize a bright wide angle lens with a large angle of view with a small number of lens elements. In addition, since the first lens group is provided with an aspheric surface, it is possible to suppress distortion that is a problem with wide-angle lenses.

  The first lens group is preferably composed only of negative lens elements.

  With this configuration, a wide-angle lens that is bright to the periphery can be realized with a small number of lens elements.

  It is preferable that the first lens group includes a first negative lens element having an aspherical surface and a second negative lens element in order from the side having the long conjugate distance.

  If comprised in this way, a wide-angle lens with few distortions and bright to the periphery is realizable.

  The aperture is preferably provided only at one location.

  With this configuration, since the aperture restriction at the periphery due to the stop is relaxed, a wide-angle lens that is bright to the periphery can be realized.

  The second lens group is preferably composed of three positive lens elements, and the diaphragm is preferably provided in the second lens group.

  With this configuration, a bright wide-angle lens can be realized with a small number of components.

  The second lens group includes at least two positive lens elements, and the stop is provided in or near the positive lens element disposed on the long conjugate distance side in the second lens group. May be.

  With this configuration, a bright wide-angle lens can be realized with a small number of components.

The above wide-angle lens preferably satisfies the following conditions.
10 <T ₁₂ / f <20 (1)
here,
T ₁₂ : Air distance between the first lens group and the second lens group f: The focal length of the entire system.

  With this configuration, the power of each lens group can be reduced, and a bright wide-angle lens can be realized with a small number of components.

  Moreover, it is preferable that the effective F number of a wide-angle lens is 1.7 or less.

  In order to achieve the above object, an illumination optical system according to the present invention is an illumination optical system that guides light emitted from a light source to illuminate an illuminated area of an object, and emits light emitted from the light source. There is provided a homogenizing optical system that emits light having a uniform intensity distribution and a wide-angle lens that relays the light emitted from the homogenizing optical system and guides it to an illuminated area.

  If comprised in this way, since said wide angle lens is used as a relay optical system, a big illumination area can be illuminated brightly and uniformly. In addition, since the distance between the object images of the relay optical system can be reduced by using the above wide-angle lens, the illumination optical system can be formed compactly.

  In this case, it is preferable that the magnification of the wide-angle lens is 170 times or more.

  If comprised in this way, a big to-be-illuminated area can be illuminated with a small light source.

  Moreover, you may further provide the Fresnel lens arrange | positioned in the focal position vicinity of the side with a long conjugate distance.

  With this configuration, telecentricity can be imparted also to the side having a long conjugate distance, so that a telecentric relay optical system can be realized on both sides.

  All lens elements constituting the wide-angle lens may be cylindrical lenses.

  If comprised in this way, the illumination optical system which can illuminate a large to-be-illuminated area uniformly can be implement | achieved.

  In order to achieve the above object, a surface light emitting device according to the present invention includes a light emitting panel that emits light incident from an incident surface from an emission surface, a light source unit that emits light having a uniform intensity distribution, and A wide-angle lens that relays the light emitted from the light source unit and guides the light to the incident surface.

  If comprised in this way, since said wide angle lens is used as a relay optical system, a large illumination area can be illuminated brightly and uniformly, and a compact surface-emitting device can be implement | achieved.

  According to the present invention, a wide-angle lens that is well corrected for distortion, bright to the periphery, and telecentric can be configured with a small number of lens elements. In addition, by using such a wide-angle lens, it is possible to realize a compact illumination optical system and a surface emitting device that can illuminate a large illumination region brightly and uniformly.

  1, 3, 5, and 7 are configuration diagrams of the wide-angle lens according to Embodiments 1, 2, 3, and 4. FIG. In each figure, an asterisk “*” attached to a specific surface indicates that the surface is aspheric. In each figure, “A” represents a diaphragm, “P” represents a glass block such as a prism, and “S” represents an image plane. The image plane S corresponds to a film or a CCD in the imaging apparatus, corresponds to an LCD that is a spatial modulation element in the projection apparatus, and corresponds to an exit end face of the rod integrator in the illumination apparatus.

  The wide-angle lenses according to Embodiments 1 to 4 include a first lens group G1 having a negative refractive power and a second lens group G2 having a positive refractive power in order from the side having the long conjugate distance. The first lens group G1 includes at least one aspheric surface. The second lens group G2 includes only positive lens elements.

  The detailed configuration of the wide-angle lens according to each embodiment will be described below.

(Embodiment 1)
In the first embodiment, the first lens group G1 includes a biconcave first lens element L1 and a negative meniscus second lens element L2 with a convex surface facing the object surface in order from the side having the long conjugate distance. It consists of. The second lens group G2 includes, in order from the long conjugate distance side, a biconvex third lens element L3, a biconvex fourth lens element L4, and a planoconvex second lens having a convex surface facing the object surface. 5 lens elements L5.

(Embodiment 2)
In the second embodiment, the first lens group G1 includes a biconcave first lens element L1 and a biconcave second lens element L2 in order from the side having the long conjugate distance. The second lens group G2 includes, in order from the longer conjugate distance side, a plano-convex third lens element L3 having a convex surface facing the object surface side, and a plano-convex fourth lens element having a convex surface facing the image surface side. L4 and a plano-convex fifth lens element L5 having a convex surface facing the object surface. The third lens element L3 and the fourth lens element L4 are integrated with each other through a stop to constitute one positive lens element.

(Embodiment 3)
In Embodiment 3, the first lens group G1 includes a biconcave first lens element L1 and a negative meniscus second lens element L2 with a convex surface facing the object surface in order from the side with the long conjugate distance. It consists of. The second lens group G2 includes, in order from the long conjugate distance side, a biconvex third lens element L3, a biconvex fourth lens element L4, and a planoconvex second lens having a convex surface facing the object surface. 5 lens elements L5.

(Embodiment 4)
In the fourth embodiment, the first lens group G1 includes a biconcave first lens element L1 and a biconcave second lens element L2 in order from the side having the long conjugate distance. The second lens group G2 includes, in order from the long conjugate distance side, a biconvex third lens element L3, a biconvex fourth lens element L4, and a planoconvex second lens having a convex surface facing the object surface. 5 lens elements L5.

  In the above first to fourth embodiments, both surfaces of the first lens element L1 are aspheric.

  The wide-angle lens according to the present invention has a so-called retrofocus type configuration including a negative lens group and a positive lens group. Retrofocus is suitable for wide-angle lenses and is easy to obtain telecentricity. However, distortion tends to occur and the number of lens elements tends to increase.

  On the other hand, in each of the above-described embodiments, the stop is provided in the second lens group G2. In this case, since the position through which the principal ray passes becomes higher in the first lens group G1, distortion can be effectively corrected by arranging an aspheric lens in the first lens group G1. The first lens group is configured so that the incident angle does not increase with respect to the lens surface so that the light beam having a large incident angle passes therethrough so that the light beam passing through the first lens unit is not totally reflected. Therefore, the positive lens element for correcting distortion aberration is not arranged, and the first lens group G1 is composed of only the negative lens element.

  Further, the first lens group G1 generates excessively corrected spherical aberration. If a spherical aberration that cancels this overcorrected spherical aberration is generated in the second lens group G2, the spherical aberration can be corrected in the entire lens system. In addition, by generating spherical aberration by sharing a plurality of positive lenses, the number of components of the second lens group can be reduced.

  Note that the number of positive lens elements constituting the second lens group G2 may be two or more. In order to give the wide-angle lens telecentricity, it is necessary to adjust the power with a positive lens element arranged on the short conjugate distance side in the second lens group G2. Therefore, at least two positive lens elements are required for the second lens group G2.

  As described above, in each of the above embodiments, the first lens group including at least one aspherical surface and having a negative refractive index, and the second lens having only a positive lens element and having a positive refractive index. A bright wide-angle lens is realized by the group. The wide-angle lens targeted by the present invention can be achieved only by these requirements, but it is preferable that the following conditions are further satisfied in order to improve the optical performance.

  The diaphragm for limiting the light beam is preferably provided only at one location.

  With this configuration, the amount of light at the peripheral portion is not further limited, and the opening state of the central portion and the peripheral portion is substantially the same. In addition, since the distortion is corrected by the aspherical surface of the first lens group G1, it is possible to realize a wide-angle lens bright to the periphery.

  In addition, it is preferable that the second lens group G2 includes three positive lens elements, and a diaphragm is provided in the second lens group G2 (Embodiments 1, 3, and 4). Alternatively, the second lens group G2 includes two positive lens elements, and in the positive lens element arranged on the long conjugate distance side or in the vicinity of the positive lens element arranged on the long conjugate distance side. A diaphragm is preferably provided (Embodiment 2).

  With this configuration, a small F number can be realized, and telecentricity can be ensured on the side with a short conjugate distance.

The wide-angle lens according to the present invention preferably satisfies the following condition (1).
10 <T ₁₂ / f <20 (1)
here,
T ₁₂ : air distance between the first lens group G 1 and the second lens group G 2 f: the focal length of the entire system.

  Condition (1) defines the ratio of the air spacing between the first lens group G1 and the second lens group G2 with respect to the focal length. If the lower limit of the condition (1) is not reached, it is necessary to increase the negative power of the first lens group G1 and the positive power of the second lens group G2 in order to ensure a necessary angle of view. The aberration generated in the lens group G1 cannot be corrected by the second lens group G2. In addition, since light having a large angle of view cannot pass, the brightness at the peripheral portion decreases. On the contrary, if the upper limit of the condition (1) is exceeded, the total length of the lens becomes large and a compact wide-angle lens cannot be configured.

(Embodiment 5)
FIG. 9 is a schematic configuration diagram of an illumination optical system according to Embodiment 5 of the present invention.

  The illumination optical system 10 according to the fifth embodiment includes a homogenizing optical system 2 that receives light emitted from the light emitting element 3 serving as a light source, and a light emitted from the homogenizing optical system 2 as an illuminated area of the object. And a wide-angle lens 1 led to 5.

  The light emitting element 3 is, for example, a laser element, an LED, or a cold cathode tube, and has nonuniform light distribution characteristics. The homogenizing optical system 2 equalizes the intensity of light emitted from the light emitting element 3 and emits light having a uniform intensity distribution from the emission end face. Therefore, a uniform secondary light source surface without light source unevenness is formed on the exit end face of the uniformizing optical system 2. For the homogenizing optical system 2, for example, a rod integrator can be used.

  In the present embodiment, the light source unit 4 that emits light having a uniform intensity distribution is configured by combining the light emitting element 3 and the uniformizing optical system 2. However, the light source unit 4 may have another configuration as long as it has uniform light distribution characteristics.

  The wide-angle lens 1 is a wide-angle lens having the above-described configuration, and functions as a relay optical system that relays light emitted from the light source unit 4 and guides it to the incident surface. The wide-angle lens 1 enlarges and projects the secondary light source surface formed on the exit end face of the uniformizing optical system 2 onto the illuminated area 5.

  Since the illumination optical system 10 according to the present embodiment includes the wide-angle lens 1 having the above-described configuration, it is possible to uniformly illuminate a wide illuminated area. Moreover, since the distance between the object images of the relay optical system can be reduced by using the wide-angle lens 1, the illumination optical system can be made compact. Furthermore, since the illumination optical system 10 can be configured with a small number of lens elements, the cost can be reduced.

  In the present embodiment, the illumination optical system 10 including the wide-angle lens 1 and the uniformizing optical system 2 has been described. However, the light incident from the light source unit 4 and the wide-angle lens 1 and the incident surface is surface-emitted from the output surface. You may comprise a surface emitting device by combining with the surface emitting panel to be made. The surface light emitting panel corresponds to a light guide plate or a diffusing plate, and is arranged so that its incident surface is located in the illuminated area 5 of FIG. The wide angle lens 1 relays the light emitted from the light source unit 4 to illuminate the incident surface of the surface light emitting panel.

  Also in the surface light emitting device configured as described above, the above wide angle lens is used as a relay optical system, so that a surface light emitting device having a large and bright illumination area can be realized in a compact manner.

  In the wide-angle lens, the illumination optical system, and the surface light emitting device according to each of the above embodiments, a Fresnel lens may be disposed in the vicinity of the focal position on the side having a long conjugate distance. With this configuration, telecentricity can be imparted even on the side with a long conjugate distance, so that it is possible to configure a telecentric relay optical system on both sides using the wide-angle lens according to the present invention. .

  In the wide-angle lens, illumination optical system, and surface light emitting device according to each of the above embodiments, all lens elements constituting the wide-angle lens may be cylindrical lenses. If comprised in this way, the wide angle lens which can illuminate a wide to-be-illuminated area with uniform brightness is realizable.

  Furthermore, in the wide-angle lens, illumination optical system, and surface emitting device according to each of the above-described embodiments, it is preferable that the F-number of the wide-angle lens is 1.7 or less. By using the wide-angle lens configured as described above, an illumination optical system with high light use efficiency can be realized.

  Furthermore, in the illumination optical system and the surface emitting device described in the fifth embodiment, the magnification of the wide-angle lens constituting the relay optical system may be 170 times or more. If comprised in this way, it will become possible to illuminate a big area using a small light source part.

  Hereinafter, numerical examples in which the wide-angle lenses according to Embodiments 1 to 4 are specifically implemented will be described. Numerical Examples 1 to 4 correspond to Embodiments 1 to 4, respectively.

ただし、数式中の各符号の意味は以下の通りである。
Ｘ：光軸からの高さがｈの非球面上の点から、非球面頂点の接平面までの距離
ｈ：光軸からの高さ
Ｃｊ：第ｊ面の非球面頂点の曲率（Ｃｊ＝１／Ｒｊ）
Ｋｊ：第ｊ面の円錐定数
Ａｊ，ｎ：第ｊ面のｎ次の非球面係数 In each numerical example, the unit of length in the table is “mm”, and the unit of angle of view is “°”. In the surface data of each numerical example, r is a radius of curvature, d is a surface interval or thickness, nd is a refractive index with respect to the d line, and vd is an Abbe number with respect to the d line. In each numerical example, the surface marked with * is an aspheric surface, and the aspheric shape is defined by the following equation.

However, the meaning of each symbol in the mathematical formula is as follows.
X: distance from a point on the aspherical surface having a height from the optical axis to the tangent plane of the aspherical vertex h: height from the optical axis Cj: curvature of the aspherical vertex of the jth surface (Cj = 1) / Rj)
Kj: conic constant of the jth surface Aj, n: nth-order aspheric coefficient of the jth surface

  In various data of each numerical example, the total lens length represents the distance between the first surface and the image surface. The entrance pupil position represents the distance from the first surface, and the exit pupil position represents the distance from the final surface. The front principal point position and the rear principal point position represent distances from the first surface.

  2, 4, 6, and 8 are longitudinal aberration diagrams of the wide-angle lenses according to Numerical Examples 1, 2, 3, and 4, respectively. Each longitudinal aberration diagram shows spherical aberration (SA (mm)), astigmatism (AST (mm)), and distortion (DIS (%)) in order from the left side. In the spherical aberration diagram, the vertical axis represents the F number (indicated by F in the figure), the solid line is the d line (d-line), the short broken line is the F line (F-line), and the long broken line is the C line (C- line). In the astigmatism graph, the vertical axis represents the image height (indicated by H in the figure), the solid line represents the sagittal plane (indicated by s), and the broken line represents the meridional plane (indicated by m in the figure). To express. In the distortion diagram, the vertical axis represents the image height (indicated by H in the figure).

(Numerical example 1)
The wide-angle lens of Numerical Example 1 corresponds to Embodiment 1 shown in FIG. Table 1 shows surface data of the zoom lens system of Numerical Example 1, Table 2 shows aspheric data, and Table 3 shows various data.

Table 1 (Surface data)

Surface number rd nd vd
Object ∞ 376.79300
1 ∞ 0.00000
2 * -61.13800 1.95700 1.50967 56.4
3 * 6.88300 6.37900
4 154.38500 0.60500 1.69680 55.5
5 8.84000 30.54900
6 61.25400 3.00000 1.84666 23.8
7 -32.56200 5.20900
8 (Aperture) ∞ 8.13400
9 15.19300 2.56900 1.51680 64.2
10 -46.85500 8.78600
11 13.79700 1.19200 1.62004 36.3
12 ∞ 2.49000
13 ∞ 1.06700 1.48749 70.4
14 ∞ 0.85706
Image plane ∞ 0.00000

Table 2 (Aspherical data)

Second side
K = 1.24166E + 01, A4 = 3.40235E-04, A6 = -7.39399E-07, A8 = -1.03089E-10
A10 = -3.08828E-13
Third side
K = -6.77641E-01, A4 = -3.09837E-06, A6 = 1.79300E-05, A8 = -1.95344E-07
A10 = 1.26479E-08

Table 3 (various data)

Focal length 2.0109
F number 1.33187
Half angle of view 44.8448
Statue height 2.0000
Total lens length 72.7941
BF 0.85706
Entrance pupil position 8.1804
Exit pupil position 322.5752
Front principal point position 10.2039
Rear principal point position 70.7726

(Numerical example 2)
The wide-angle lens of Numerical Example 2 corresponds to Embodiment 2 shown in FIG. Table 4 shows surface data of the zoom lens system of Numerical Example 2, Table 5 shows aspheric data, and Table 6 shows various data.

Table 4 (Surface data)

Surface number rd nd vd
Object ∞ 376.79300
1 ∞ 0.00000
2 * -63.07400 1.95700 1.50967 56.4
3 * 9.59400 6.37900
4 -106.27900 0.60500 1.69680 55.5
5 10.32800 38.99600
6 33.77200 12.00000 1.58913 61.3
7 (Aperture) ∞ 8.00000 1.58913 61.3
8 -24.22800 12.60300
9 11.76800 3.00000 1.58913 61.3
10 ∞ 9.00000
11 ∞ 1.06700 1.48749 70.4
12 ∞ 1.16173
Image plane ∞ 0.00000

Table 5 (Aspherical data)

Second side
K = 1.24166E + 01, A4 = 2.76286E-04, A6 = -4.77446E-07, A8 = 3.82483E-09
A10 = -1.50840E-11
Third side
K = -1.32375E + 00, A4 = 8.37798E-05, A6 = 1.34917E-05, A8 = -2.75970E-07
A10 = 7.55115E-09

Table 6 (various data)

Focal length 2.0809
F number 1.57007
Half angle of view 43.8625
Statue height 2.0000
Total lens length 94.7687
BF 1.16173
Entrance pupil position 9.4984
Exit pupil position -235.5468
Front principal point position 11.5610
Rear principal point position 92.6766

(Numerical Example 3)
The wide-angle lens of Numerical Example 3 corresponds to Embodiment 3 shown in FIG. Table 7 shows surface data of the zoom lens system of Numerical Example 3, Table 8 shows aspheric data, and Table 9 shows various data.

Table 7 (Surface data)

Surface number rd nd vd
Object ∞ 376.79300
1 ∞ 0.00000
2 * -52.90500 1.95700 1.50967 56.4
3 * 5.21100 6.37900
4 41.91400 0.60500 1.69680 55.5
5 7.62800 23.48300
6 205.49600 3.00000 1.84666 23.8
7 -20.72800 5.20900
8 (Aperture) ∞ 8.13400
9 13.85800 2.56900 1.51680 64.2
10 -59.08000 8.53200
11 13.68700 1.19200 1.62004 36.3
12 ∞ 2.49000
13 ∞ 1.06700 1.48749 70.4
14 ∞ 0.85956
Image plane ∞ 0.00000

Table 8 (Aspherical data)

Second side
K = 1.24166E + 01, A4 = 6.34236E-04, A6 = -2.97623E-06, A8 = -1.30481E-10
A10 = 3.25482E-11
Third side
K = -3.41973E-01, A4 = -2.21666E-05, A6 = 4.03078E-05, A8 = -7.14390E-09
A10 = 6.05173E-08

Table 9 (various data)

Focal length 2.0122
F number 1.54954
Half angle of view 44.8267
Statue height 2.0000
Total lens length 65.4766
BF 0.85956
Entrance pupil position 7.0633
Exit pupil position 323.1483
Front principal point position 9.0881
Rear principal point position 63.4538

(Numerical example 4)
The wide-angle lens of Numerical Example 4 corresponds to Embodiment 4 shown in FIG. Table 10 shows surface data of the zoom lens system of Numerical Example 4, Table 11 shows aspheric data, and Table 12 shows various data.

Table 10 (Surface data)

Surface number rd nd vd
Object ∞ 376.79300
1 ∞ 0.00000
2 * -64.10300 1.95700 1.49178 57.2
3 * 7.83900 6.37900
4 -306.32900 0.60500 1.69680 55.5
5 9.69800 33.47800
6 63.86200 3.00000 1.84666 23.8
7 -38.54800 5.20900
8 (Aperture) ∞ 8.13400
9 15.18500 2.56900 1.51680 64.2
10 -47.01200 8.78400
11 13.79700 1.19200 1.62004 36.3
12 ∞ 2.49000
13 ∞ 1.06700 1.48749 70.4
14 ∞ 1.49383
Image plane ∞ 0.00000

Table 11 (Aspherical data)

Second side
K = 1.24166E + 01, A4 = 3.29483E-04, A6 = -7.41173E-07, A8 = 1.01313E-09
A10 = -2.41953E-12
Third side
K = -6.48722E-01, A4 = 3.66992E-05, A6 = 1.56073E-05, A8 = -1.95867E-07
A10 = 8.20004E-09

Table 12 (various data)

Focal length 2.0122
F number 1.55822
Half angle of view 44.8261
Statue height 2.0000
Total lens length 76.3578
BF 1.49383
Entrance pupil position 8.8714
Exit pupil position 323.9473
Front principal point position 10.8962
Rear principal point position 74.3351

  Table 13 below shows corresponding values of the condition (1) in the wide-angle lens according to each numerical example.

Table 13 (corresponding values of conditions)

Numerical example T ₁₂ / f
1 15.2
2 18.7
3 11.7
4 16.6

  The wide-angle lens according to the present invention can be used as, for example, a relay optical system used in a surface light emitting device.

Configuration diagram of wide-angle lens according to Embodiment 1 (Example 1) Longitudinal aberration diagram of the wide-angle lens according to Example 1 Configuration diagram of wide-angle lens according to Embodiment 2 (Example 2) Longitudinal aberration diagram of the wide-angle lens according to Example 1 Configuration diagram of wide-angle lens according to Embodiment 3 (Example 3) Longitudinal aberration diagram of the wide-angle lens according to Example 1 Configuration diagram of wide-angle lens according to Embodiment 4 (Example 4) Longitudinal aberration diagram of the wide-angle lens according to Example 1 Schematic configuration diagram of illumination optical system according to Embodiment 5

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wide angle lens 2 Uniformization optical system 3 Light emitting element 4 Light source part 5 Illuminated area 10 Illumination optical system

Claims (14)

A wide-angle lens for an imaging optical system having a plurality of lens elements and a diaphragm,
From the longest conjugate distance,
A first lens group having negative refractive power;
A second lens group having a positive refractive power,
Between the first lens group and the second lens group is the longest air interval among all lens intervals,
The first lens group includes at least one aspheric surface;
The second lens group is a wide-angle lens composed of only positive lens elements.   The wide-angle lens according to claim 1, wherein the first lens group includes only a negative lens element. The first lens group includes:
From the longest conjugate distance,
A first negative lens element having an aspheric surface;
The wide-angle lens according to claim 1, comprising a second negative lens element.   The wide-angle lens according to claim 1, wherein the diaphragm is provided only at one location. The second lens group is composed of three positive lens elements,
The wide-angle lens according to claim 1, wherein the diaphragm is provided in the second lens group. The second lens group includes at least two positive lens elements,
2. The wide-angle lens according to claim 1, wherein the stop is provided in a positive lens element disposed on a side having a long conjugate distance in the second lens group or in the vicinity of the positive lens element. The wide-angle lens according to claim 1, wherein the following condition is satisfied:
10 <T ₁₂ / f <20 (1)
here,
T ₁₂ : Air distance between the first lens group and the second lens group f: The focal length of the entire system.   The wide-angle lens according to claim 1, wherein an effective F number is 1.7 or less. An illumination optical system that guides light emitted from a light source to illuminate an illuminated area of an object,
Uniformizing light emitted from the light source and emitting light having a uniform intensity distribution; and
An illumination optical system comprising: the wide-angle lens according to claim 1, which relays light emitted from the uniformizing optical system and guides the light to the illuminated area.   The illumination optical system according to claim 9, wherein a magnification of the wide-angle lens is 170 times or more.   The illumination optical system according to claim 9, further comprising a Fresnel lens disposed in the vicinity of the focal position on the longer conjugate distance side.   The illumination optical system according to claim 9, wherein all the lens elements constituting the wide-angle lens are cylindrical lenses. A surface emitting device,
A surface emitting panel for emitting light incident from the incident surface from the exit surface;
A light source unit that emits light having a uniform intensity distribution;
A surface light emitting device comprising: the wide-angle lens according to claim 1, wherein the light emitted from the light source unit is relayed and guided to the incident surface. A wide-angle lens for an imaging optical system having a plurality of lens elements and a diaphragm,
From the longest conjugate distance,
A first lens group having negative refractive power;
A second lens group having a positive refractive power,
Between the first lens group and the second lens group is the longest air interval among all lens intervals,
The first lens group includes at least one aspheric surface;
The second lens group is a wide-angle lens composed of only positive lens elements (however, the half angle of view W is 40 ° or more).

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