JP5893997B2 - Imaging lens and imaging apparatus - Google Patents
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本発明は、監視用カメラや車載用カメラ等、固体撮像素子を備えた撮像装置に用いられる単焦点の広角撮像レンズおよびそれを用いた撮像装置に関するものである。 The present invention relates to a single-focus wide-angle imaging lens used in an imaging apparatus equipped with a solid-state imaging device, such as a monitoring camera and an in-vehicle camera, and an imaging apparatus using the same.
監視用カメラや車載用カメラ等に用いられる撮像レンズには、広画角を確保しながら画面全域で結像性能が良いことが要求される。また、搭載スペースが限られることが多いことなどから小型で軽量であることも併せて要求される。 Imaging lenses used for surveillance cameras, in-vehicle cameras, and the like are required to have good imaging performance over the entire screen while ensuring a wide angle of view. In addition, since the mounting space is often limited, it is also required to be small and lightweight.
これらの要望に対応し得る可能性がある単焦点の広角撮像レンズとして、下記の特許文献１、２、３が提案されている。しかしながら、この特許文献１、３に記載される単焦点レンズは温度が変動すると焦点距離が変化してしまい、像面位置で高い光学性能面を満足することが出来なかった。また、この問題を克服した特許文献２に記載される単焦点レンズでは、温度変動による焦点距離の変化を小さくすることは可能となったが、温度変動によって画角が変化してしまうという問題が発生する。 The following Patent Documents 1, 2, and 3 have been proposed as single-focus wide-angle imaging lenses that may be able to meet these demands. However, the focal lengths of the single focus lenses described in Patent Documents 1 and 3 change when the temperature fluctuates, and a high optical performance surface cannot be satisfied at the image plane position. In addition, in the single focus lens described in Patent Document 2 that overcomes this problem, it is possible to reduce the change in focal length due to temperature fluctuation, but the problem is that the angle of view changes due to temperature fluctuation. Occur.
本発明は、小型、軽量且つ安価でありながら、高い光学性能を持ち、且つ温度変動による焦点距離及び画角の変動を小さくした広角撮像レンズを提供する。 The present invention provides a wide-angle imaging lens that is small, light, and inexpensive, has high optical performance, and has reduced focal length and angle of view variation due to temperature variation.
上記課題を解決するため、第１の発明のレンズは、物体側から順に、負の屈折力を 有する第１レンズと、負の屈折力を有する第２レンズと、正の屈折力を有する第３レ ンズと開口絞りと、正の屈折力を有する第４レンズとの４枚のレンズが配置され、下 記条件式（１）〜（６）を満足することを特徴とする。
｜α２｜ ≧ ５０×１０-6 ・・・（１）
｜α３｜ ≧ ５０×１０-6 ・・・（２）
｜α４｜ ≦ １５×１０-6 ・・・（３）
ｆ２／ｆ１ ＜ ０．５ ・・・（４）
−１．１ ＜ ｆ２／ｆ３ ＜ −０．７ ・・・（５）
１．０ ＜ ｆ４／ｆ３ ・・・（６）
ただし、
α２：第２レンズの熱線膨張係数
α３：第３レンズの熱線膨張係数
α４：第４レンズの熱線膨張係数
ｆ１：第１レンズの焦点距離
ｆ２：第２レンズの焦点距離
ｆ３：第３レンズの焦点距離
ｆ４：第４レンズの焦点距離
上記課題を解決するため、本発明の撮像装置は、上述のいずれかの撮像光学系と、 その撮像光学系により形成される光学像を電気信号に変換する撮像素子とを備えたこ とを特徴とする。
In order to solve the above-described problem, the lens of the first invention is, in order from the object side, a first lens having negative refractive power, a second lens having negative refractive power, and a third lens having positive refractive power. Four lenses, which are a lens, an aperture stop, and a fourth lens having a positive refractive power, are arranged, and satisfy the following conditional expressions (1) to ( 6 ).
| Α2 | ≧ 50 × 10 −6 (1)
| Α3 | ≧ 50 × 10 −6 (2)
| Α4 | ≦ 15 × 10 −6 (3)
f2 / f1 <0.5 (4)
−1.1 <f2 / f3 <−0.7 (5)
1.0 <f4 / f3 (6)
However,
[alpha] 2: coefficient of linear thermal expansion of the second lens .alpha.3: linear thermal expansion coefficient of the third lens alpha 4: linear thermal expansion coefficient of the fourth lens
f1 : Focal length of the first lens f2: Focal length of the second lens f3: Focal length of the third lens f4: Focal length of the fourth lens In order to solve the above problem, the imaging apparatus of the present invention is And an image pickup device that converts an optical image formed by the image pickup optical system into an electric signal.
本発明によれば、小型、軽量且つ安価でありながら諸収差が良好に補正され、且つ温度変動による焦点距離及び画角の変動を小さくした広角撮像レンズを提供することができる。その結果、監視カメラや車載用カメラに搭載可能なコンパクトな広角撮像装置を実現することができる。 According to the present invention, it is possible to provide a wide-angle imaging lens in which various aberrations are favorably corrected while being small, light, and inexpensive, and in which the variation in focal length and field angle due to temperature variation is reduced. As a result, a compact wide-angle imaging device that can be mounted on a surveillance camera or a vehicle-mounted camera can be realized.
以下、図面を参照しながら、本発明の実施形態を詳細に説明する。図１に実施の形態のレンズ構成をそれぞれ光学断面で示す。これらの実施形態は物体側から順に、第１レンズ１１０、第２レンズ１２０、第３レンズ１３０、開口絞り１４０、第４レンズ１５０、カバーガラス１６０、ＣＣＤ(Charge Coupled Device)やＣＭＯＳ(Complementary Mental-Oxide Semiconductor device)等の撮像素子の受光面となる結像面１７０が配置される４枚構成の単焦点レンズ１００である。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows the lens configuration of the embodiment in an optical section. In these embodiments, in order from the object side, the first lens 110, the second lens 120, the third lens 130, the aperture stop 140, the fourth lens 150, the cover glass 160, a CCD (Charge Coupled Device) and a CMOS (Complementary Mental- This is a single-focus lens 100 having a four-lens configuration in which an imaging surface 170 serving as a light receiving surface of an imaging device such as an Oxide Semiconductor device is disposed.
本発明を実施した撮像レンズで４枚のレンズは、物体側から順に、負の屈折力を有する第１レンズ１１０と、負の屈折力を有する第２レンズ１２０と、正の屈折力を有する第３レンズ１３０と、開口絞り１４０と、正の屈折力を有する第４レンズ１５０のように配列されている。広角レンズでは、広い画角を得るために焦点距離を短くする必要があるが、機構的な制約からバックフォーカスは焦点距離に比べて長くしなくてはならない。そこで、前方に負の屈折力を有するレンズを配置し、入射した光を一度発散した後、後方の正の屈折力を有するレンズで集光することにより、レンズ系の主点をレンズ後方に飛出させ焦点距離に比べて長いバックフォーカスを確保することが可能となる。具体的には負の第１レンズと第２レンズで光を発散させ、正の第３レンズと第４レンズで集光する。最も物体側に負レンズを配置することで、主点を後方に置くのに十分な負の屈折力を得ることができ、開口絞り前に正の屈折力をもつレンズを配置することにより、倍率の色収差を良好に補正し、開口絞り後に正の屈折力をもつレンズを配置することにより、像面への入射角度を小さくし、かつ収差を良好に補正する。 In the imaging lens embodying the present invention, four lenses are, in order from the object side, a first lens 110 having a negative refractive power, a second lens 120 having a negative refractive power, and a first lens having a positive refractive power. The third lens 130, the aperture stop 140, and the fourth lens 150 having positive refractive power are arranged. With a wide-angle lens, it is necessary to shorten the focal length in order to obtain a wide angle of view, but the back focus must be longer than the focal length due to mechanical limitations. Therefore, a lens having a negative refractive power is arranged in the front, once incident light is diverged, and then condensed by a lens having a positive rear refractive power, so that the principal point of the lens system is moved backward. It is possible to ensure a long back focus compared to the focal length. Specifically, light is diverged by the negative first lens and the second lens, and condensed by the positive third lens and the fourth lens. By placing the negative lens closest to the object side, it is possible to obtain a negative refractive power sufficient to place the principal point behind, and by placing a lens with a positive refractive power in front of the aperture stop, The chromatic aberration is favorably corrected, and a lens having a positive refractive power is disposed after the aperture stop, thereby reducing the incident angle on the image plane and favorably correcting the aberration.
撮像レンズ１００において、物体側ＯＢＪＳ より入射した光は、第１レンズ１１０の物体側Ｒ１面１、像面側Ｒ２面２、第２レンズ１２０の物体側Ｒ３面３、像面側Ｒ４面４、第３レンズ１３０の物体側Ｒ５面５、像面側Ｒ６面６、開口絞り部１４０の面７、第４レンズ１５０の物体側Ｒ７面８、像面側Ｒ８面９、カバーガラス１６０の物体側Ｒ９面１０、像面側Ｒ１０面１１、を順次通過し結像面１７０へと集光される。 In the imaging lens 100, the light incident from the object side OBJS is the object side R1 surface 1, the image surface side R2 surface 2 of the first lens 110, the object side R3 surface 3, the image surface side R4 surface 4 of the second lens 120, The object side R5 surface 5, the image surface side R6 surface 6 of the third lens 130, the surface 7 of the aperture stop 140, the object side R7 surface 8, the image surface side R8 surface 9 of the fourth lens 150, and the object side of the cover glass 160 The light passes through the R9 surface 10 and the image surface side R10 surface 11 in order, and is focused on the image forming surface 170.
本発明を実施した撮像レンズは、α２を第２レンズの熱線膨張係数、α３を第３レンズの熱線膨張係数、α４を第４レンズの熱線膨張係数とすると、条件式（１）〜（３）を満足するように構成される。
｜α２｜ ≧ ５０×１０-6 ・・・（１）
｜α３｜ ≧ ５０×１０-6 ・・・（２）
｜α４｜ ≦ １５×１０-6 ・・・（３）
全てのレンズの熱膨張及び熱収縮が小さければ、温度変化による焦点距離と画角の変化が小さく保たれるのは自明であるが、小型、軽量且つ安価に撮像レンズを構成するためには、樹脂などガラスに比べ熱線膨張係数の大きな材料を使用する必要がある。
The imaging lens embodying the present invention has conditional expressions (1) to (3) where α2 is the thermal linear expansion coefficient of the second lens, α3 is the thermal linear expansion coefficient of the third lens, and α4 is the thermal linear expansion coefficient of the fourth lens. It is configured to satisfy
| Α2 | ≧ 50 × 10 −6 (1)
| Α3 | ≧ 50 × 10 −6 (2)
| Α4 | ≦ 15 × 10 −6 (3)
If the thermal expansion and contraction of all the lenses are small, it is obvious that the change in focal length and angle of view due to temperature change can be kept small, but in order to configure an imaging lens in a small size, light weight and low cost, It is necessary to use a material having a larger coefficient of thermal expansion than glass such as resin.
従来の４枚構成の広角レンズでは、強い負の屈折力を持つ第２レンズと強い正の屈折力を持つ第３レンズ及び第４レンズに熱線膨張係数の大きな材料を使用していたが、温度が変動すると焦点距離が変化してしまい、光学性能が劣化していた。この問題に対し、強い負の屈折力を持つ第２レンズと、開口絞りよりも像側に配置され強い正の屈折力を持つ第４レンズに熱線膨張係数の大きな材料を使用することで、温度変動による焦点距離の変化を小さくすることは可能となるが、温度変動によって画角が変化してしまう。 In a conventional four-lens wide-angle lens, a second lens having a strong negative refractive power, a third lens having a strong positive refractive power, and a material having a large thermal expansion coefficient are used for the fourth lens. When the value fluctuates, the focal length changes and the optical performance deteriorates. By using a material having a large coefficient of thermal linear expansion for the second lens having a strong negative refractive power and the fourth lens having a strong positive refractive power disposed on the image side of the aperture stop, Although it is possible to reduce the change in focal length due to fluctuations, the angle of view changes due to temperature fluctuations.
そこで、この熱線膨張係数の大きな材料を、熱による光学的な変化を互いに打ち消しあうように配置することで、全系として温度変化による焦点距離と画角の変化を小さくすることが本発明の狙いである。そのためには第２レンズと第３レンズに熱線膨張係数の大きな材料を用い、第４レンズには熱線膨張係数の小さな材料を用いることが望ましい。（１）式の下限値を下回ると、第３レンズの正の屈折力の変化のみが大きくなり、その結果、焦点距離は高温で長く、低温で短くなる。また画角は高温で狭く、低温で広くなる。（２）式の下限値を下回ると、第２レンズの負の屈折力の変化のみが大きくなり、その結果、焦点距離は高温で短く、低温で長くなる。また画角は高温で広く、低温で狭くなる。（３）式の上限値を上回ると、第４レンズの正の屈折力の変化が大きくなり、第２レンズと第３レンズでとれているバランスがくずれるため、正の屈折力変化が大きくなる。その結果、焦点距離は高温で長く、低温で短くなる。また、開口絞りよりも像側で、正の屈折力変化が大きくなるので画角は高温で広く、低温で狭くなる。 Therefore, the aim of the present invention is to reduce the change in the focal length and the angle of view due to the temperature change as a whole system by arranging the material having a large coefficient of thermal linear expansion so as to cancel the optical changes due to heat. It is. For this purpose, it is desirable to use a material having a large coefficient of thermal expansion for the second lens and the third lens, and to use a material having a small coefficient of thermal linear expansion for the fourth lens. Below the lower limit of the expression (1), only the change in the positive refractive power of the third lens increases, and as a result, the focal length becomes longer at high temperatures and shorter at low temperatures. The angle of view is narrow at high temperatures and wide at low temperatures. Below the lower limit of the expression (2), only the change in the negative refractive power of the second lens becomes large, and as a result, the focal length is short at high temperatures and long at low temperatures. The angle of view is wide at high temperatures and narrow at low temperatures. If the upper limit value of the expression (3) is exceeded, the change in the positive refractive power of the fourth lens becomes large, and the balance between the second lens and the third lens is lost, so the positive refractive power change becomes large. As a result, the focal length is long at high temperatures and short at low temperatures. Further, since the positive refractive power change is larger on the image side than the aperture stop, the angle of view is wide at high temperatures and narrow at low temperatures.
本発明を実施した撮像レンズで好ましくは、ｆ１を第１レンズの焦点距離、ｆ２を第２レンズの焦点距離、ｆ３を第３レンズの焦点距離、ｆ４を第４レンズの焦点距離とすると、条件式（４）〜（６）を満足するように構成される。
ｆ２／ｆ１ ＜ ０．５ ・・・（４）
−１．１ ＜ ｆ２／ｆ３ ＜ −０．７ ・・・（５）
１．０ ＜ ｆ４／ｆ３ ・・・（６）
前述のように、熱による光学的な変化を互いに打ち消しあうように各レンズを配置する必要があるが、材料の選択と合わせて各レンズの屈折力も適切に調節されるべきである。通常は主な負の屈折力を第２レンズが担うが、（４）式の上限を超えると、第１レンズの負の屈折力が大きくなりすぎて、熱変化を打ち消せなくなり易い。第２レンズと第３レンズは互いに変化を打ち消すように配置するが、（５）式の範囲を超えると、屈折力の差が大きくなりすぎてうまく打ち消すことが出来なくなり易い。（６）式の下限値を下回ると、第４レンズの屈折力が大きくなりすぎるため、熱変化を打ち消せなくなり易い。
In the imaging lens embodying the present invention, preferably, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, and f4 is the focal length of the fourth lens. It is comprised so that Formula (4)-(6) may be satisfied.
f2 / f1 <0.5 (4)
−1.1 <f2 / f3 <−0.7 (5)
1.0 <f4 / f3 (6)
As described above, it is necessary to arrange each lens so that optical changes caused by heat cancel each other, but the refractive power of each lens should be adjusted appropriately in accordance with the selection of materials. Normally, the second lens bears the main negative refractive power. However, if the upper limit of the expression (4) is exceeded, the negative refractive power of the first lens becomes too large and it is difficult to cancel the thermal change. The second lens and the third lens are arranged so as to cancel each other's change. However, if the range exceeds the range of the expression (5), the difference in refractive power becomes too large to easily cancel. If the lower limit of the expression (6) is not reached, the refractive power of the fourth lens becomes too large, so that it is difficult to cancel the thermal change.
以下に、撮像レンズの具体的な数値による実施例１〜４を示す。１〜４の数値実施例において、焦点距離、Fナンバー、画角、像高、レンズ全長、バックフォーカス（Bf）は次の表１に記載の通りである。また、同じく１〜４の数値実施例において、条件式（１）〜（６）の数値データは、次の表２に記載の値になる。 Examples 1-4 according to specific numerical values of the imaging lens are shown below. In the numerical examples 1 to 4, the focal length, F number, field angle, image height, total lens length, and back focus (Bf) are as shown in Table 1 below. Similarly, in the numerical examples of 1 to 4, the numerical data of the conditional expressions (1) to (6) are the values described in Table 2 below.
なお、以下の数値実施例の中で記載されるレンズの非球面の形状は、物体側から像面側へ向かう方向を正とし、ｋを円錐係数、Ａは４次の非球面係数を、Ｂは６次の非球面係数を、Ｃは８次の非球面係数を、Ｄは１０次の非球面係数としたとき次式で表される。ｈは光線の高さ、ｃは中心曲率半径の逆数を、Ｚは面頂点に対する接平面からの深さを、をそれぞれ表している。 The aspherical shape of the lens described in the following numerical examples is positive in the direction from the object side to the image plane side, k is a conical coefficient, A is a fourth-order aspheric coefficient, B Is a 6th-order aspheric coefficient, C is an 8th-order aspheric coefficient, and D is a 10th-order aspheric coefficient. h represents the height of the light beam, c represents the reciprocal of the central radius of curvature, and Z represents the depth from the tangent plane with respect to the surface vertex.
実施の形態１におけるレンズ系の基本構成は図２に示され、各数値データ（設定値）は表３、表４に、球面収差、および非点収差を示す収差図は図３にそれぞれ示される。 The basic configuration of the lens system in Embodiment 1 is shown in FIG. 2, each numerical data (setting value) is shown in Tables 3 and 4, and aberration diagrams showing spherical aberration and astigmatism are shown in FIG. .
図２に示すように、第１レンズ１１０は物体側に凸面を向けたメニスカス形状、第２レンズ１２０は物体側に凸面を向けたメニスカス形状、第３レンズ１３０は両凸形状、開口絞り１４０の像側に配置される第４レンズ１５０は両凸形状を有する。第２レンズ、第３レンズと第４レンズは両面に、それぞれ非球面を有する。 As shown in FIG. 2, the first lens 110 has a meniscus shape with a convex surface facing the object side, the second lens 120 has a meniscus shape with a convex surface facing the object side, the third lens 130 has a biconvex shape, and the aperture stop 140 The fourth lens 150 disposed on the image side has a biconvex shape. The second lens, the third lens, and the fourth lens have aspheric surfaces on both sides.
また、図２に示すように第１レンズの厚さとなる面１と面２間の距離をＤ１、第１レンズの面２と第２レンズの面３までの距離をＤ２、第２レンズの厚さとなる面３と面４間の距離をＤ３、第２レンズの面４と第３レンズの面５までの距離をＤ４、第３レンズの厚さとなる面５と面６間の距離をＤ５、第３レンズの面６絞り部の面７までの距離をＤ６、絞り部の面７と第４レンズの面８間の距離をＤ７、第４レンズの厚さとなる面８と面９間の距離をＤ８、第４レンズの面９とカバーガラスの面１０までの距離をＤ９、カバーガラスの厚さとなる面１０と面１１間の距離をＤ１０、カバーガラスの面１１と結像面１７０までの距離をＤ１１とする。 Further, as shown in FIG. 2, the distance between the surface 1 and the surface 2 that is the thickness of the first lens is D1, the distance between the surface 2 of the first lens and the surface 3 of the second lens is D2, and the thickness of the second lens The distance between the surface 3 and the surface 4 is D3, the distance between the surface 4 of the second lens and the surface 5 of the third lens is D4, the distance between the surface 5 and the surface 6 that is the thickness of the third lens is D5, The distance from the surface 6 of the third lens to the surface 7 of the diaphragm portion is D6, the distance between the surface 7 of the diaphragm portion and the surface 8 of the fourth lens is D7, and the distance between the surface 8 and the surface 9 which is the thickness of the fourth lens. D8, the distance between the surface 9 of the fourth lens and the surface 10 of the cover glass is D9, the distance between the surface 10 and the surface 11 that is the thickness of the cover glass is D10, and the distance between the surface 11 of the cover glass and the imaging surface 170 is The distance is D11.
表３は、実施例１における撮像レンズの各面番号に対応した絞り、各レンズの曲率半径Ｒ、間隔Ｄ、屈折率Ｎd、および分散値νdを示している。表中の記号*は非球面の面を表している（以下の実施例においても同様）。表４は、所定面の非球面係数を示している。
＜数値実施例１＞
Table 3 shows the stop corresponding to each surface number of the imaging lens in Example 1, the radius of curvature R, the interval D, the refractive index Nd, and the dispersion value νd of each lens. The symbol * in the table represents an aspheric surface (the same applies to the following examples). Table 4 shows the aspheric coefficient of the predetermined surface.
<Numerical Example 1>
図３は、実施例１において、図３（Ａ）が球面収差を、図３（Ｂ）が非点収差をそれぞれ示している。図３（Ｂ）の縦軸は結像面での像高を表し、図３（Ｂ）中、実線Ｓはサジタル像面の値、破線Tはタンジェンシャル像面の値をそれぞれ示している。図３からわかるように、実施例１によれば、球面、非点の諸収差が良好に補正され、結像性能に優れた撮像レンズが得られる。 3A and 3B show spherical aberration and FIG. 3B shows astigmatism in Example 1, respectively. The vertical axis in FIG. 3B represents the image height on the imaging plane. In FIG. 3B, the solid line S represents the value of the sagittal image plane, and the broken line T represents the value of the tangential image plane. As can be seen from FIG. 3, according to the first embodiment, spherical and astigmatism aberrations are satisfactorily corrected, and an imaging lens having excellent imaging performance can be obtained.
実施の形態２におけるレンズ系の基本構成は図４に示され、各数値データ（設定値）は表５、表６に、球面収差、および非点収差を示す収差図は図５にそれぞれ示される。 The basic configuration of the lens system according to Embodiment 2 is shown in FIG. 4, numerical data (setting values) are shown in Tables 5 and 6, and aberration diagrams showing spherical aberration and astigmatism are shown in FIG. .
図４に示すように、第１レンズ１１０は物体側に凸面を向けたメニスカス形状、第２レンズ１２０は物体側に凸面を向けたメニスカス形状、第３レンズ１３０は両凸形状、開口絞り１４０の像側に配置される第４レンズ１５０は両凸形状を有する。第２レンズと第３レンズは両面に、第４レンズは物体側面に、それぞれ非球面を有する。 As shown in FIG. 4, the first lens 110 has a meniscus shape with a convex surface facing the object side, the second lens 120 has a meniscus shape with a convex surface facing the object side, the third lens 130 has a biconvex shape, and the aperture stop 140 The fourth lens 150 disposed on the image side has a biconvex shape. The second lens and the third lens have aspheric surfaces on both sides, and the fourth lens has an aspheric surface on the object side surface.
表５は、実施例２における撮像レンズの各面番号に対応した絞り、各レンズの曲率半径Ｒ、間隔Ｄ、屈折率Ｎd、および分散値νdを示している。表６は、所定面の非球面係数を示している。
＜数値実施例２＞
Table 5 shows the diaphragm corresponding to each surface number of the imaging lens in Example 2, the radius of curvature R, the interval D, the refractive index Nd, and the dispersion value νd of each lens. Table 6 shows the aspheric coefficient of the predetermined surface.
<Numerical Example 2>
図５は、実施例２において、図５（Ａ）が球面収差を、図５（Ｂ）が非点収差をそれぞれ示している。図５（Ｂ）の縦軸は結像面での像高を表している。図５からわかるように、実施例２によれば、球面、非点の諸収差が良好に補正され、結像性能に優れた撮像レンズが得られる。 5A and 5B, in Example 2, FIG. 5A shows spherical aberration, and FIG. 5B shows astigmatism, respectively. The vertical axis in FIG. 5B represents the image height on the imaging plane. As can be seen from FIG. 5, according to the second embodiment, spherical and astigmatism aberrations are satisfactorily corrected, and an imaging lens having excellent imaging performance can be obtained.
実施の形態３におけるレンズ系の基本構成は図６に示され、各数値データ（設定値）は表７、表８に、球面収差、および非点収差を示す収差図は図７にそれぞれ示される。 The basic configuration of the lens system according to Embodiment 3 is shown in FIG. 6, the numerical data (setting values) are shown in Tables 7 and 8, and the aberration diagrams showing spherical aberration and astigmatism are shown in FIG. .
図６に示すように、第１レンズ１１０は物体側に凸面を向けたメニスカス形状、第２レンズ１２０は両凹形状、第３レンズ１３０は物体側に凸面を向けた平凸形状、開口絞り１４０の像側に配置される第４レンズ１５０は両凸形状を有する。第２レンズと第３レンズは両面に、第４レンズは像側面に、それぞれ非球面を有する。 As shown in FIG. 6, the first lens 110 has a meniscus shape with a convex surface facing the object side, the second lens 120 has a biconcave shape, the third lens 130 has a plano-convex shape with a convex surface facing the object side, and an aperture stop 140. The fourth lens 150 arranged on the image side has a biconvex shape. The second lens and the third lens have aspheric surfaces on both sides, and the fourth lens has an aspheric surface on the image side surface.
表７は、実施例３における撮像レンズの各面番号に対応した絞り、各レンズの曲率半径Ｒ、間隔Ｄ、屈折率Ｎd、および分散値νdを示している。表８は、所定面の非球面係数を示している。
＜数値実施例３＞
Table 7 shows the stop corresponding to each surface number of the imaging lens in Example 3, the radius of curvature R, the interval D, the refractive index Nd, and the dispersion value νd of each lens. Table 8 shows the aspheric coefficient of the predetermined surface.
<Numerical Example 3>
実施の形態４におけるレンズ系の基本構成は図８に示され、各数値データ（設定値）は表９、表１０に、球面収差、および非点収差を示す収差図は図９にそれぞれ示される。 The basic configuration of the lens system according to Embodiment 4 is shown in FIG. 8, numerical data (setting values) are shown in Tables 9 and 10, and aberration diagrams showing spherical aberration and astigmatism are shown in FIG. .
図８に示すように、第１レンズ１１０は物体側に凸面を向けたメニスカス形状、第２レンズ１２０は像側に凹面を向けた平凹形状、第３レンズ１３０は両凸形状、開口絞り１４０の像側に配置される第４レンズ１５０は両凸形状を有する。第２レンズは像側面に、第３レンズと第４レンズは両面に、それぞれ非球面を有する。 As shown in FIG. 8, the first lens 110 has a meniscus shape with a convex surface facing the object side, the second lens 120 has a plano-concave shape with a concave surface facing the image side, the third lens 130 has a biconvex shape, and an aperture stop 140. The fourth lens 150 arranged on the image side has a biconvex shape. The second lens has an aspheric surface on the image side surface, and the third lens and the fourth lens have an aspheric surface on both surfaces.
表９は、実施例３における撮像レンズの各面番号に対応した絞り、各レンズの曲率半径Ｒ、間隔Ｄ、屈折率Ｎd、および分散値νdを示している。表１０は、所定面の非球面係数を示している。
＜数値実施例４＞
Table 9 shows the stop corresponding to each surface number of the imaging lens in Example 3, the radius of curvature R, the interval D, the refractive index Nd, and the dispersion value νd of each lens. Table 10 shows the aspheric coefficient of the predetermined surface.
<Numerical Example 4>
図９は、実施例４において、図９（Ａ）が球面収差を、図９（Ｂ）が非点収差をそれぞれ示している。図９（Ｂ）の縦軸は結像面での像高を表している。図９からわかるように、実施例３によれば、球面、非点の諸収差が良好に補正され、結像性能に優れた撮像レンズが得られる。 9A and 9B, in Example 4, FIG. 9A shows spherical aberration, and FIG. 9B shows astigmatism. The vertical axis in FIG. 9B represents the image height on the imaging plane. As can be seen from FIG. 9, according to the third embodiment, various spherical and astigmatism aberrations are favorably corrected, and an imaging lens having excellent imaging performance can be obtained.
図１０は、実施例１から実施例４における温度と焦点距離の関係を示している。横軸は温度を、縦軸は焦点距離を２０度での値で正規化したもの示している。また、図１１は、実施例１から実施例４における温度と画角の関係を示している。横軸は温度を、縦軸は画角を２０度での値で正規化したもの示している。図１０及び図１１からわかるように、実施例１から実施例４によれば、諸収差が良好に補正され、温度変化による焦点距離と画角の変化が少ない結像性能に優れた撮像レンズが得られる。 FIG. 10 shows the relationship between the temperature and the focal length in the first to fourth embodiments. The horizontal axis indicates temperature, and the vertical axis indicates the focal length normalized by a value at 20 degrees. FIG. 11 shows the relationship between the temperature and the angle of view in the first to fourth embodiments. The horizontal axis represents temperature, and the vertical axis represents the angle of view normalized by a value at 20 degrees. As can be seen from FIGS. 10 and 11, according to Examples 1 to 4, an imaging lens excellent in imaging performance in which various aberrations are favorably corrected and the focal length and the angle of view are less changed due to a temperature change. can get.
以上、本実施形態の広角光学系および撮像モジュールについて説明したが、本発明はこれらの実施例に限定されるものではなく、発明の要旨を逸脱しない範囲で種種の変形が可能である。例えば、上記実施例において、カバーガラス１６０に赤外線除去フィルターを設ける構成にしたり、赤外カットコートをカバーガラス１６０の面に施しても良い。また、他のレンズ面やローパスフィルター等のフィルターに赤外コートを施しても良い。 The wide-angle optical system and the imaging module of the present embodiment have been described above, but the present invention is not limited to these examples, and various modifications can be made without departing from the scope of the invention. For example, in the above embodiment, the cover glass 160 may be provided with an infrared filter, or an infrared cut coat may be applied to the surface of the cover glass 160. Further, infrared coating may be applied to other lens surfaces and filters such as a low-pass filter.
本実施形態の広角光学系によれば、撮像素子を用いた撮像系、特に監視用カメラや車載カメラ等に好適であり、小型、薄型で高い光学性能の広角光学系、及び、前記広角光学系を備えた撮像モジュールが実現できる。 According to the wide-angle optical system of the present embodiment, it is suitable for an imaging system using an imaging device, particularly a surveillance camera, a vehicle-mounted camera, and the like, and is a small-sized, thin, high-optical performance wide-angle optical system, and the wide-angle optical system. An imaging module having the above can be realized.
図１２に本発明による撮像レンズ１００を用いた撮像装置の実施形態の断面図を示す。撮像レンズ１００およびＣＣＤ(Charge Coupled Device)やＣＭＯＳ(Complementary Mental-Oxide Semiconductor device)等の撮像素子２１０は筐体２２０によって位置関係を規定、保持される。このとき撮像レンズ１００の結像面１７０は撮像素子２１０の受光面に一致するように配置されている。 FIG. 12 shows a cross-sectional view of an embodiment of an imaging apparatus using the imaging lens 100 according to the present invention. The imaging lens 100 and the imaging element 210 such as a CCD (Charge Coupled Device) or a CMOS (Complementary Mental-Oxide Semiconductor device) are defined and held by a housing 220. At this time, the imaging surface 170 of the imaging lens 100 is disposed so as to coincide with the light receiving surface of the imaging element 210.
撮像レンズ１００によって取り込まれ、撮像素子２１０の受光面に結像した被写体像は、撮像素子２１０の光電変換機能によって電気信号に変換されて、画像信号として撮像装置２００から出力される。 The subject image captured by the imaging lens 100 and formed on the light receiving surface of the imaging element 210 is converted into an electrical signal by the photoelectric conversion function of the imaging element 210 and output from the imaging apparatus 200 as an image signal.
上述のような撮像レンズ１００は、構成枚数が少なく、小型、軽量であるため、搭載スペースがコンパクトにできるため、様々な用途の撮像装置に適している。また広角撮像レンズでありながら、歪曲収差の発生を低減し、高い光学性能を持つ被写体像を撮像素子２１０の受光面上に結像でき、視認性に優れた画像信号を出力できるため、特に監視用カメラや車載用カメラ等において優位性の高い撮像装置の実現が可能である。 Since the imaging lens 100 as described above has a small number of components, is small and lightweight, and can be compact in mounting space, it is suitable for imaging apparatuses for various applications. In addition, although it is a wide-angle imaging lens, it can reduce the occurrence of distortion and can form a subject image with high optical performance on the light-receiving surface of the imaging device 210, which can output an image signal with excellent visibility. Therefore, it is possible to realize an imaging device having a superiority in a camera for cameras, a vehicle-mounted camera, and the like.
１００，１００Ａ〜１００Ｄ・・・撮像レンズ、撮像光学系
１１０ ・・・第１レンズ
１２０ ・・・第２レンズ
１３０ ・・・第３レンズ
１４０ ・・・開口絞り部
１５０ ・・・第４レンズ
１６０ ・・・カバーガラス
１７０ ・・・結像面
２００ ・・・撮像装置
２１０ ・・・撮像素子
２２０ ・・・筐体
100, 100A to 100D: Imaging lens, imaging optical system 110: First lens
120 ... second lens 130 ... third lens 140 ... aperture stop
150: Fourth lens 160: Cover glass 170: Imaging surface
200: Imaging device 210: Imaging element 220: Housing
Claims (2)
｜α２｜ ≧ ５０×１０-6 ・・・（１）
｜α３｜ ≧ ５０×１０-6 ・・・（２）
｜α４｜ ≦ １５×１０-6 ・・・（３）
ｆ２／ｆ１ ＜ ０．５ ・・・（４）
−１．１ ＜ ｆ２／ｆ３ ＜ −０．７ ・・・（５）
１．０ ＜ ｆ４／ｆ３ ・・・（６）
ただし、
α２：第２レンズの熱線膨張係数
α３：第３レンズの熱線膨張係数
α４：第４レンズの熱線膨張係数
ｆ１：第１レンズの焦点距離
ｆ２：第２レンズの焦点距離
ｆ３：第３レンズの焦点距離
ｆ４：第４レンズの焦点距離 In order from the object side, a first lens having a negative refractive power, a second lens having a negative refractive power, a third lens having a positive refractive power, an aperture stop, and a fourth lens having a positive refractive power. The imaging lens is characterized in that the following four conditional expressions (1) to ( 6 ) are satisfied.
| Α2 | ≧ 50 × 10 −6 (1)
| Α3 | ≧ 50 × 10 −6 (2)
| Α4 | ≦ 15 × 10 −6 (3)
f2 / f1 <0.5 (4)
−1.1 <f2 / f3 <−0.7 (5)
1.0 <f4 / f3 (6)
However,
α2: Thermal linear expansion coefficient of the second lens α3: Thermal linear expansion coefficient of the third lens α4: Thermal linear expansion coefficient of the fourth lens
f1: Focal length of the first lens
f2: focal length of the second lens
f3: focal length of the third lens
f4: focal length of the fourth lens
Wherein the imaging lens according to the first, the imaging device characterized by comprising an imaging device that converts an optical image formed by the imaging lens into an electric signal.
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