WO2016021016A1 - Imaging optical system - Google Patents

Imaging optical system Download PDF

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Publication number
WO2016021016A1
WO2016021016A1 PCT/JP2014/070859 JP2014070859W WO2016021016A1 WO 2016021016 A1 WO2016021016 A1 WO 2016021016A1 JP 2014070859 W JP2014070859 W JP 2014070859W WO 2016021016 A1 WO2016021016 A1 WO 2016021016A1
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Prior art keywords
lens
optical system
imaging optical
bandpass filter
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PCT/JP2014/070859
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French (fr)
Japanese (ja)
Inventor
典久 坂上
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ナルックス株式会社
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Priority to PCT/JP2014/070859 priority Critical patent/WO2016021016A1/en
Priority to JP2015137655A priority patent/JP5884113B1/en
Publication of WO2016021016A1 publication Critical patent/WO2016021016A1/en
Priority to US15/204,728 priority patent/US10365539B2/en

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/20—Filters
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00—Optical objectives specially designed for the purposes specified below
    • G02B13/04—Reversed telephoto objectives
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B11/00—Filters or other obturators specially adapted for photographic purposes

Definitions

  • the present invention relates to an imaging optical system including a bandpass filter.
  • the sun Background noise such as light can be reduced.
  • the full width at half maximum of the bandpass filter is, for example, ⁇ 100 nanometers or less.
  • the bandpass filter has been disposed between the optical system and the image plane for reasons such as ease of assembly (for example, FIG. 1 of Patent Document 1).
  • the F number is defined as the reciprocal of the sine of the angle formed by the principal ray and the peripheral ray at the intersection of the optical axis and the image plane, with the line connecting all the optical centers of the lenses of the imaging optical system as the optical axis. . Therefore, in an imaging optical system having a small F number of 1.1 or less, the angle formed between the principal ray and the peripheral ray at the intersection of the optical axis and the image plane is large.
  • the angle formed by the principal ray and the peripheral ray also increases at the incident surface of the bandpass filter arranged near the image plane, the incident angle of the peripheral ray to the bandpass filter increases, and the transmittance is increased.
  • the problem of decreasing was inevitable.
  • an imaging optical system that includes a bandpass filter having a small F number of 1.1 or less and a half-width of a band of ⁇ 100 nanometers or less and that does not reduce the transmittance of the bandpass filter. .
  • An imaging optical system includes a first lens that is a negative lens from the object side to the image side, a second lens that is a meniscus lens having a convex surface directed to the image side, a diaphragm, the diaphragm and the image Two or more lenses including at least one positive lens between the surface and a half width of the band of ⁇ 100 on the object side or the image side of the stop adjacent to the stop.
  • a band pass filter having a nanometer or less is provided, and an F number is 1.1 or less.
  • the first lens which is a negative lens
  • the second lens which is a meniscus lens having a convex surface facing the image side
  • the stop are arranged in this order from the object side to the image side.
  • a band pass filter is disposed adjacent to the stop on the object side or the image side of the stop.
  • the imaging optical system according to the first embodiment of the present invention includes a third lens that is a glass positive lens, a fourth lens that is an aspheric lens, and a positive lens between the stop and the image plane. And a fifth lens which is a lens.
  • the imaging optical system according to the second embodiment of the present invention is the imaging optical system according to the first embodiment, and the third lens is a spherical lens.
  • the cost of the lens can be reduced by making the third glass lens a spherical lens.
  • the imaging optical system according to the third embodiment of the present invention is the imaging optical system according to the first or second embodiment, and the fourth lens is a negative lens.
  • spherical aberration can be reduced by making the fourth lens a negative lens.
  • the imaging optical system according to the fourth embodiment of the present invention is the imaging optical system according to the third embodiment, wherein the overall focal length is f and the focal length of the fourth lens is f4. f4 / f ⁇ -4 Meet.
  • spherical aberration can be reduced by relatively increasing the focal length of the fourth lens.
  • the focal length of the fourth lens relatively long, the sensitivity of manufacturing error can be reduced, the manufacturing yield can be improved, and the cost can be reduced.
  • the imaging optical system according to the fifth embodiment of the present invention is the imaging optical system according to the first embodiment, and a third lens that is a positive aspheric lens between the stop and the image plane, And a positive fourth lens.
  • spherical aberration can be reduced by making the third lens a positive aspheric lens.
  • the incident angle of the principal ray on the image plane can be reduced by giving the fourth lens positive power.
  • the imaging optical system according to the sixth embodiment of the present invention is the imaging optical system according to any one of the first to fifth embodiments, and has a diaphragm radius larger than the image height.
  • the incident angle of the principal ray on the image plane can be reduced by making the aperture radius larger than the image height.
  • the imaging optical system according to the seventh embodiment of the present invention is the imaging optical system according to any one of the first to sixth embodiments, and the half angle of view is 55 degrees or less.
  • the half angle of view by setting the half angle of view to 55 degrees or less, it is possible to limit the incident angle of the light beam to the bandpass filter.
  • the imaging optical system according to the eighth embodiment of the present invention is the imaging optical system according to any one of the first to seventh embodiments, where the center thickness of the first lens is t1, and the total focal length is f. , t1 / f> 1.2 Meet.
  • the influence of stray light reflected on the image plane side of the first lens can be reduced by relatively increasing the center thickness of the first lens.
  • the image pickup optical system according to the ninth embodiment of the present invention is the image pickup optical system according to any one of the first to eighth embodiments, and the center thickness of the second lens is t2, and the total focal length is f. , t2 / f> 1.2 Meet.
  • the imaging optical system according to the tenth embodiment of the present invention is the imaging optical system according to any one of the first to ninth embodiments, and the object side of the first lens is a convex surface.
  • the image pickup optical system according to the eleventh embodiment of the present invention is the image pickup optical system according to any one of the first to tenth embodiments, and the incident angle of light rays on the bandpass filter is 25 degrees or less. It is configured.
  • the transmittance of the bandpass filter can be maintained at a predetermined value or more by setting the incident angle of the light beam to the bandpass filter to 25 degrees or less.
  • FIG. 1 is a diagram illustrating a configuration of an imaging optical system according to Example 1.
  • FIG. FIG. 6 is a diagram illustrating a configuration of an imaging optical system according to a second embodiment.
  • FIG. 6 is a diagram illustrating a configuration of an imaging optical system of Example 3.
  • FIG. 1 is a diagram illustrating a configuration of an imaging optical system 100 according to an embodiment (Example 1 described later) of the present invention.
  • the imaging optical system includes a first lens 101 that is a negative lens from the object side to the image side, a second lens 102 that is a meniscus lens having a convex surface directed to the image side, a bandpass filter 103, and a diaphragm 104. And a third lens 105 that is a positive lens, a fourth lens 106 that is a negative lens, and a fifth lens 108 that is a positive lens.
  • a negative lens means a lens having a negative power with respect to a paraxial ray
  • a positive lens means a lens having a positive power with respect to a paraxial ray. Means.
  • the imaging optical system of the present invention is used together with a light projecting system including a light source that emits signal light in a specific wavelength range.
  • a band-pass filter that matches a specific wavelength region of signal light, it is possible to reduce background noise such as sunlight without reducing the signal light.
  • the band width of the bandpass filter is ⁇ 100 nanometers or less.
  • the bandpass filter of an imaging optical system for a near-infrared camera has a bandwidth of 700 to 900 nanometers.
  • the F number of the imaging optical system of the present invention is 1.1 or less.
  • the F number is defined as the reciprocal of the sine of the angle between the principal ray and the peripheral ray at the intersection of the optical axis and the image plane. . Therefore, in an imaging optical system having a small F number of 1.1 or less, the angle formed between the principal ray and the peripheral ray at the intersection of the optical axis and the image plane is large.
  • the principal ray is indicated by a one-dot chain line
  • the peripheral ray is indicated by a dotted line.
  • the bandpass filter is disposed between the optical system and the image plane for reasons such as ease of assembly.
  • the imaging optical system having the above-described arrangement having a small F-number of 1.1 or less the angle formed by the principal ray and the peripheral ray is large even on the incident surface of the bandpass filter arranged near the image plane. Therefore, the incident angle of the peripheral ray to the bandpass filter increases, and the transmittance decreases.
  • the maximum value of the incident angle of the light beam on the bandpass filter arranged near the image plane is, for example, an example described later. Similarly, when the F number was 0.9, it was 34 degrees or more.
  • a first lens that is a negative lens, a second lens that is a meniscus lens having a convex surface facing the image side, a bandpass filter, and an aperture are arranged from the object side to the image side. , Arranged in the above order.
  • the first lens negative the incident angle of the chief ray to the bandpass filter can be reduced.
  • the second lens a meniscus lens having a convex surface directed to the image side, the incident angle of the peripheral ray to the bandpass filter can be reduced.
  • each optical element of the imaging optical system is as follows. An x-axis and a y-axis orthogonal to each other are defined in a plane perpendicular to the optical axis with a line connecting all optical centers of the lenses of the imaging optical system as an optical axis.
  • the coordinate Z is determined with the direction from the intersection of the optical axis and the surface of each optical element toward the image side along the optical axis being positive.
  • h is the distance from the optical axis
  • R is the radius of curvature
  • c is the curvature.
  • k represents a conic constant
  • A represents an aspherical coefficient.
  • i and m are integers.
  • FIG. 1 is a diagram illustrating a configuration of the imaging optical system 100 according to the first embodiment.
  • the imaging optical system 100 includes a first lens 101 that is a negative lens from the object side to the image side, a second lens 102 that is a meniscus lens having a convex surface directed to the image side, a band-pass filter 103, a diaphragm 104, a third lens 105 that is a positive lens, a fourth lens 106 that is a negative lens, a wavelength filter 107, a sixth lens 108 that is a positive lens, and a cover glass 109.
  • the image plane is indicated at 110.
  • the material of the third lens 105 is glass, and the other lens material is cycloolefin polymer (COP).
  • the material of the band pass filter 103 is glass, and the material of the wavelength filter 107 is polycarbonate.
  • the diaphragm 104 is plate-shaped, has a circular opening and a surrounding light blocking portion, and is arranged in a plane perpendicular to the optical axis such that the circular center coincides with the optical axis.
  • the band of the band pass filter 103 is 700 nanometers to 900 nanometers.
  • the wavelength filter 107 is used as an auxiliary to the band-pass filter 103 and blocks light in the visible light region so that no problem occurs even if the transmittance of the band-pass filter 103 in the visible light region is slightly increased.
  • the third lens 105 that is a positive lens, the fourth lens 106 that is a negative lens, and the fifth lens 108 that is a positive lens are configured to have an F number of 1.1 or less. .
  • Table 1 is a table showing the optical arrangement of the imaging optical system 100 of the first embodiment.
  • Surface number 1 indicates the object side surface of the first lens 101
  • surface number 2 indicates the image side surface of the first lens 101.
  • the surface interval corresponding to the surface number 1 indicates the center thickness of the first lens 101
  • the surface interval corresponding to the surface number 2 is the object side surface of the second lens 102 adjacent to the image side surface of the first lens 101. The center distance between is shown.
  • Table 2 is a table showing coefficients of the surface definition formulas of the surfaces of the first lens 101, the second lens 102, and the third lens 105.
  • Table 3 is a table showing the coefficients of the surface definition formulas of the surfaces of the fourth lens 106 and the fifth lens 108.
  • Numerical values representing the main optical performance of the imaging optical system of Example 1 are as follows. Overall focal length: 2.64mm F number: 0.9 Half angle of view: 48 degrees Incident angle to the bandpass filter: 22 degrees or less Incident angle of the chief ray to the image plane: 3 degrees or less
  • the incident angle to the bandpass filter is the incident angle of all rays including the principal ray and peripheral rays is there.
  • FIG. 2 is a diagram illustrating a configuration of the imaging optical system 200 according to the second embodiment.
  • the imaging optical system 200 includes a first lens 201 that is a negative lens from the object side to the image side, a second lens 202 that is a meniscus lens having a convex surface directed to the image side, a bandpass filter 203, a diaphragm 204, a third lens 205 that is a positive lens, a wavelength filter 206, a fourth lens 207 that is a positive lens, and a cover glass 208.
  • the image plane is indicated at 209.
  • the material of the third lens 205 is glass, and the other lens material is cycloolefin polymer (COP).
  • the material of the band pass filter 203 is glass, and the material of the wavelength filter 206 is polycarbonate.
  • the diaphragm 204 is plate-shaped, has a circular opening and a surrounding light blocking portion, and is arranged in a plane perpendicular to the optical axis so that the center of the circle coincides with the optical axis.
  • the band of the band pass filter 203 is 700 nanometers to 900 nanometers.
  • the wavelength filter 206 is used as an auxiliary to the bandpass filter 203 and blocks light in the visible light region so that no problem occurs even if the transmittance of the bandpass filter 203 in the visible light region is slightly increased.
  • the third lens 205 which is a positive lens
  • the fourth lens 207 which is a positive lens, are configured so that the F number is 1.1 or less.
  • Table 4 is a table showing an optical arrangement of the imaging optical system 200 according to the second embodiment.
  • Surface number 1 indicates the object side surface of the first lens 201
  • surface number 2 indicates the image side surface of the first lens 201.
  • the surface interval corresponding to surface number 1 indicates the center thickness of the first lens 201
  • the surface interval corresponding to surface number 2 is the object side surface of the second lens 202 adjacent to the image side surface of the first lens 201. The center distance between is shown.
  • Table 5 is a table showing the coefficients of the surface definition formulas of the surfaces of the first lens 201, the second lens 202, and the third lens 205.
  • Table 6 is a table showing the coefficients of the surface definition formula of each surface of the fourth lens 207.
  • Numerical values representing main optical performance of the imaging optical system of Example 2 are as follows. Overall focal length: 2.56mm F number: 0.9 Half angle of view: 47 degrees Incident angle to bandpass filter: 22 degrees or less Principal ray incident angle to image plane: 5 degrees or less
  • FIG. 3 is a diagram illustrating a configuration of the imaging optical system 300 according to the third embodiment.
  • the imaging optical system 300 includes a first lens 301 that is a negative lens from the object side to the image side, a second lens 302 that is a meniscus lens having a convex surface directed to the image side, a bandpass filter 303, a diaphragm 304, a third lens 305 that is a positive lens, a wavelength filter 306, a second lens 307 that is a positive lens, and a cover glass 308.
  • the image plane is indicated at 309.
  • the material of the third lens 305 is glass, and the other lens material is cycloolefin polymer (COP).
  • the material of the band pass filter 303 is glass, and the material of the wavelength filter 306 is polycarbonate.
  • the diaphragm 304 is plate-shaped, has a circular opening and a surrounding light blocking portion, and is arranged in a plane perpendicular to the optical axis such that the circular center coincides with the optical axis.
  • the band of the band pass filter 303 is 700 nanometers to 900 nanometers.
  • the wavelength filter 306 is used as an auxiliary to the bandpass filter 303 and blocks light in the visible light region so that no problem occurs even if the transmittance of the bandpass filter 303 in the visible light region is slightly increased.
  • the third lens 305 which is a positive lens
  • the fourth lens 307 which is a positive lens, are configured so that the F number is 1.1 or less.
  • Table 7 is a table showing the optical arrangement of the imaging optical system 300 of the third embodiment.
  • Surface number 1 indicates the object side surface of the first lens 301
  • surface number 2 indicates the image side surface of the first lens 301.
  • the surface interval corresponding to the surface number 1 indicates the center thickness of the first lens 301
  • the surface interval corresponding to the surface number 2 is the object side surface of the second lens 302 adjacent to the image side surface of the first lens 301. The center distance between is shown.
  • Table 8 is a table showing the coefficients of the surface definition equations for the surfaces of the first lens 301, the second lens 302, and the third lens 305.
  • Table 9 is a table showing the coefficients of the surface definition formula of each surface of the fourth lens 307.
  • Table 10 is a table showing the focal length of the entire imaging optical system and each lens in Examples 1 to 3. The unit of the focal length is millimeter.
  • Table 11 is a table showing the relationship between the center thickness of the lens and the focal length.
  • F indicates the overall focal length
  • f4 indicates the focal length of the fourth lens
  • t1 and t2 indicate center thicknesses of the first lens and the second lens, respectively.
  • Table 12 is a table showing numerical values representing main optical performances of the imaging optical systems of Examples 1 to 3.
  • the unit of length in Table 12 is millimeter.
  • the image height is a vertical distance from the intersection of the optical axis and the image plane with the optical axis as the horizontal direction.
  • y tan ⁇ It is.
  • the aperture radius is the radius of a circle that forms the aperture of the aperture.
  • the maximum value of the incident angle of all the light rays including the principal ray and the peripheral rays to the bandpass filter is 22 degrees.
  • the maximum value of the incident angle of the light beam on the bandpass filter of the conventional imaging optical system is about 24 degrees.
  • the number is 0.9, it is 34 degrees or more.
  • the imaging optical system of the present invention even when the F number is 0.9, the incident angle of the light beam to the bandpass filter does not increase, and the incident angle of the light beam to the bandpass filter decreases. There is nothing. Therefore, according to the imaging optical system of the present invention, even when the F number is 0.9, the same optical performance as when the F number is larger can be obtained.

Abstract

The purpose of the present invention is to provide an imaging optical system that has a small F number less than or equal to 1.1, is equipped with a bandpass filter having a half bandwidth less than or equal to ±100 nanometers, and is capable of preventing a decrease in the transmittance of the bandpass filter. The imaging optical system according to the present invention comprises, in order from the object side toward the image side: a first lens which is a negative lens; a second lens which is a meniscus lens with a convex surface facing the image side; a diaphragm; two or more lenses between the diaphragm and the image surface, including at least one positive lens. The imaging optical system further comprises a bandpass filter having a half bandwidth less than or equal to ±100 nanometers, provided adjacent to the diaphragm on the object side or the image side. The F number thereof is less than or equal to 1.1.

Description

撮像光学系Imaging optical system
　本発明は、バンドパスフィルタを備えた撮像光学系に関する。 The present invention relates to an imaging optical system including a bandpass filter.
　特定の波長域の信号光を発する光源を含む投光系と、信号光の特定の波長域に合わせたバンドパスフィルタを含む撮像光学系を使用することで、信号光を減少させることなく、太陽光などの背景雑音を低減することが可能となる。バンドパスフィルタの帯域の半値幅は、たとえば、±１００ナノメータ以下である。 By using a projection system that includes a light source that emits signal light in a specific wavelength range and an imaging optical system that includes a band-pass filter that matches the specific wavelength range of the signal light, without reducing the signal light, the sun Background noise such as light can be reduced. The full width at half maximum of the bandpass filter is, for example, ± 100 nanometers or less.
　従来、このような撮像光学系において、組み立ての容易さなどの理由により、バンドパスフィルタは、光学系と像面との間に配置されていた（たとえば、特許文献１の図１）。 Conventionally, in such an imaging optical system, the bandpass filter has been disposed between the optical system and the image plane for reasons such as ease of assembly (for example, FIG. 1 of Patent Document 1).
　他方、このような撮像光学系を赤外域で使用する場合などに、撮像光学系のＦナンバーを小さくする必要がある。Ｆナンバーは、撮像光学系のレンズの全ての光学中心を結んだ線を光軸として、光軸と像面との交点における、主光線と周辺光線とのなす角度の正弦の逆数として定義される。したがって、１．１以下の小さなＦナンバーを有する撮像光学系においては、光軸と像面との交点における、主光線と周辺光線とのなす角度が大きくなる。その結果、像面の近くに配置されたバンドパスフィルタの入射面においても、主光線と周辺光線とのなす角度が大きくなり、周辺光線のバンドパスフィルタへの入射角度が増加し、透過率が減少してしまうという問題が避けられなかった。 On the other hand, when such an imaging optical system is used in the infrared region, it is necessary to reduce the F-number of the imaging optical system. The F number is defined as the reciprocal of the sine of the angle formed by the principal ray and the peripheral ray at the intersection of the optical axis and the image plane, with the line connecting all the optical centers of the lenses of the imaging optical system as the optical axis. . Therefore, in an imaging optical system having a small F number of 1.1 or less, the angle formed between the principal ray and the peripheral ray at the intersection of the optical axis and the image plane is large. As a result, the angle formed by the principal ray and the peripheral ray also increases at the incident surface of the bandpass filter arranged near the image plane, the incident angle of the peripheral ray to the bandpass filter increases, and the transmittance is increased. The problem of decreasing was inevitable.
WO2010/103595A1WO2010 / 103595A1
　したがって、１．１以下の小さなＦナンバーを有し、帯域の半値幅が±１００ナノメータ以下であるバンドパスフィルタを備え、バンドパスフィルタの透過率を減少させることのない撮像光学系に対するニーズがある。 Therefore, there is a need for an imaging optical system that includes a bandpass filter having a small F number of 1.1 or less and a half-width of a band of ± 100 nanometers or less and that does not reduce the transmittance of the bandpass filter. .
　本発明による撮像光学系は、物体側から像側に、負のレンズである第一のレンズと、像側に凸面を向けたメニスカスレンズである第二のレンズと、絞りと、該絞りと像面との間に、少なくとも一つの正のレンズを含む２個以上のレンズと、を備え、さらに、該絞りの物体側または像側に、該絞りに隣接して、帯域の半値幅が±１００ナノメータ以下であるバンドパスフィルタを備え、Ｆナンバーが１．１以下である。 An imaging optical system according to the present invention includes a first lens that is a negative lens from the object side to the image side, a second lens that is a meniscus lens having a convex surface directed to the image side, a diaphragm, the diaphragm and the image Two or more lenses including at least one positive lens between the surface and a half width of the band of ± 100 on the object side or the image side of the stop adjacent to the stop. A band pass filter having a nanometer or less is provided, and an F number is 1.1 or less.
　本発明では、負のレンズである第一のレンズと、像側に凸面を向けたメニスカスレンズである第二のレンズと、絞りと、を、物体側から像側に、上記の順で配置した。さらに、該絞りの物体側または像側に、該絞りに隣接して、バンドパスフィルタを配置した。第一のレンズを負とすることにより、主光線のバンドパスフィルタへの入射角度を低減することができる。また、第二のレンズを、像側に凸面を向けたメニスカスレンズとすることにより、周辺光線のバンドパスフィルタへの入射角度を低減することができる。このように、光線のバンドパスフィルタへの入射角度を低減することにより、バンドパスフィルタの透過率を所定値以上に維持することができる。 In the present invention, the first lens, which is a negative lens, the second lens, which is a meniscus lens having a convex surface facing the image side, and the stop are arranged in this order from the object side to the image side. . Further, a band pass filter is disposed adjacent to the stop on the object side or the image side of the stop. By making the first lens negative, the incident angle of the chief ray to the bandpass filter can be reduced. In addition, by making the second lens a meniscus lens having a convex surface directed to the image side, the incident angle of the peripheral ray to the bandpass filter can be reduced. Thus, by reducing the incident angle of the light beam to the bandpass filter, the transmittance of the bandpass filter can be maintained at a predetermined value or more.
　本発明の第１の実施形態による撮像光学系は、該絞りと像面との間に、ガラスの正のレンズである第三のレンズと、非球面レンズである第四のレンズと、正のレンズである第五のレンズと、を備えている。 The imaging optical system according to the first embodiment of the present invention includes a third lens that is a glass positive lens, a fourth lens that is an aspheric lens, and a positive lens between the stop and the image plane. And a fifth lens which is a lens.
　本実施形態においては、第三のレンズをガラスの正のレンズとすることにより、温度変化による焦点ずれを低減することができる。また、第四レンズを非球面レンズとすることにより球面収差を低減できる。さらに、第五レンズに正パワーを持たせることにより像面への主光線の入射角度を低減することができる。 In the present embodiment, the third lens is a glass positive lens, so that defocus due to temperature change can be reduced. In addition, spherical aberration can be reduced by using an aspheric lens as the fourth lens. Furthermore, the incident angle of the chief ray on the image plane can be reduced by giving the fifth lens positive power.
　本発明の第２の実施形態による撮像光学系は、第１の実施形態による撮像光学系であって、第三のレンズが球面レンズである。 The imaging optical system according to the second embodiment of the present invention is the imaging optical system according to the first embodiment, and the third lens is a spherical lens.
　本実施形態においては、ガラスの第３のレンズを球面レンズとすることによって、レンズのコストを低減することができる。 In the present embodiment, the cost of the lens can be reduced by making the third glass lens a spherical lens.
　本発明の第３の実施形態による撮像光学系は、第１または第２の実施形態による撮像光学系であって、第四のレンズが負のレンズである。 The imaging optical system according to the third embodiment of the present invention is the imaging optical system according to the first or second embodiment, and the fourth lens is a negative lens.
　本実施形態においては、第４のレンズを負のレンズとすることによって球面収差を低減することができる。 In this embodiment, spherical aberration can be reduced by making the fourth lens a negative lens.
　本発明の第４の実施形態による撮像光学系は、第３の実施形態による撮像光学系であって、全体の焦点距離をｆ、第四のレンズの焦点距離をｆ４として、
　　ｆ４／ｆ＜－４
を満たす。 The imaging optical system according to the fourth embodiment of the present invention is the imaging optical system according to the third embodiment, wherein the overall focal length is f and the focal length of the fourth lens is f4.
f4 / f <-4
Meet.
　本実施形態においては、第四のレンズの焦点距離を相対的に長くすることにより、球面収差を低減することができる。また、第四のレンズの焦点距離を相対的に長くすることにより、製造誤差感度が減少し、製造歩留まりが向上し、コストを低減することができる。 In this embodiment, spherical aberration can be reduced by relatively increasing the focal length of the fourth lens. In addition, by making the focal length of the fourth lens relatively long, the sensitivity of manufacturing error can be reduced, the manufacturing yield can be improved, and the cost can be reduced.
　本発明の第５の実施形態による撮像光学系は、第１の実施形態による撮像光学系であって、該絞りと像面との間に、正の非球面レンズである第三のレンズと、正の第四のレンズと、を備えている。 The imaging optical system according to the fifth embodiment of the present invention is the imaging optical system according to the first embodiment, and a third lens that is a positive aspheric lens between the stop and the image plane, And a positive fourth lens.
　レンズが四枚ある構成の光学系において、第三のレンズを正の非球面レンズとすることにより球面収差を低減することができる。レンズが四枚ある構成の光学系において、第四のレンズに正パワーを持たせることにより像面への主光線の入射角度を低減することができる。 In an optical system having four lenses, spherical aberration can be reduced by making the third lens a positive aspheric lens. In an optical system having four lenses, the incident angle of the principal ray on the image plane can be reduced by giving the fourth lens positive power.
　本発明の第６の実施形態による撮像光学系は、第１乃至第５のいずれかの実施形態による撮像光学系であって、絞り半径が像高よりも大きい。 The imaging optical system according to the sixth embodiment of the present invention is the imaging optical system according to any one of the first to fifth embodiments, and has a diaphragm radius larger than the image height.
　本実施形態においては、絞り半径を像高よりも大きくすることにより、主光線の像面への入射角度を低減することができる。 In the present embodiment, the incident angle of the principal ray on the image plane can be reduced by making the aperture radius larger than the image height.
　本発明の第７の実施形態による撮像光学系は、第１乃至第６のいずれかの実施形態による撮像光学系であって、半画角が５５度以下である。 The imaging optical system according to the seventh embodiment of the present invention is the imaging optical system according to any one of the first to sixth embodiments, and the half angle of view is 55 degrees or less.
　本実施形態においては、半画角を５５度以下とすることにより、光線のバンドパスフィルタへの入射角度を制限することができる。 In the present embodiment, by setting the half angle of view to 55 degrees or less, it is possible to limit the incident angle of the light beam to the bandpass filter.
　本発明の第８の実施形態による撮像光学系は、第１乃至第７のいずれかの実施形態による撮像光学系であって、第一のレンズの中心厚をｔ１、全体の焦点距離をｆとして、
　　ｔ１／ｆ＞１．２
を満たす。 The imaging optical system according to the eighth embodiment of the present invention is the imaging optical system according to any one of the first to seventh embodiments, where the center thickness of the first lens is t1, and the total focal length is f. ,
t1 / f> 1.2
Meet.
　本実施形態においては、第一のレンズの中心厚を相対的に大きくすることにより、第１のレンズの像面側で反射した迷光の影響を小さくすることができる。 In the present embodiment, the influence of stray light reflected on the image plane side of the first lens can be reduced by relatively increasing the center thickness of the first lens.
　本発明の第９の実施形態による撮像光学系は、第１乃至第８のいずれかの実施形態による撮像光学系であって、第二のレンズの中心厚をｔ２、全体の焦点距離をｆとして、
　　ｔ２／ｆ＞１．２
を満たす。 The image pickup optical system according to the ninth embodiment of the present invention is the image pickup optical system according to any one of the first to eighth embodiments, and the center thickness of the second lens is t2, and the total focal length is f. ,
t2 / f> 1.2
Meet.
　本実施形態においては、第二のレンズの中心厚を相対的に大きくすることにより、周辺光線のバンドパスフィルタへの入射角度を低減することができる。 In the present embodiment, by making the center thickness of the second lens relatively large, the incident angle of the peripheral rays to the bandpass filter can be reduced.
　本発明の第１０の実施形態による撮像光学系は、第１乃至第９のいずれかの実施形態による撮像光学系であって、第一のレンズの物体側が凸面である。 The imaging optical system according to the tenth embodiment of the present invention is the imaging optical system according to any one of the first to ninth embodiments, and the object side of the first lens is a convex surface.
　本発明の第１１の実施形態による撮像光学系は、第１乃至第１０のいずれかの実施形態による撮像光学系であって、該バンドパスフィルタへの光線の入射角度が２５度以下であるように構成されている。 The image pickup optical system according to the eleventh embodiment of the present invention is the image pickup optical system according to any one of the first to tenth embodiments, and the incident angle of light rays on the bandpass filter is 25 degrees or less. It is configured.
　本実施形態においては、バンドパスフィルタへの光線の入射角度を２５度以下とすることにより、バンドパスフィルタの透過率を所定値以上に維持することができる。 In this embodiment, the transmittance of the bandpass filter can be maintained at a predetermined value or more by setting the incident angle of the light beam to the bandpass filter to 25 degrees or less.
実施例１の撮像光学系の構成を示す図である。1 is a diagram illustrating a configuration of an imaging optical system according to Example 1. FIG. 実施例２の撮像光学系の構成を示す図である。FIG. 6 is a diagram illustrating a configuration of an imaging optical system according to a second embodiment. 実施例３の撮像光学系の構成を示す図である。FIG. 6 is a diagram illustrating a configuration of an imaging optical system of Example 3.
　図１は、本発明の一実施形態（後で説明する実施例１）の撮像光学系１００の構成を示す図である。撮像光学系は、物体側から像側に、負のレンズである第一のレンズ１０１と、像側に凸面を向けたメニスカスレンズである第二のレンズ１０２と、バンドパスフィルタ１０３と、絞り１０４と、正のレンズである第三のレンズ１０５と、負のレンズである第四のレンズ１０６と、正のレンズである第五のレンズ１０８と、を備えている。本明細書及び特許請求の範囲において、負のレンズとは、近軸光線に対して負のパワーを有するレンズを意味し、正のレンズとは、近軸光線に対して正のパワーを有するレンズを意味する。 FIG. 1 is a diagram illustrating a configuration of an imaging optical system 100 according to an embodiment (Example 1 described later) of the present invention. The imaging optical system includes a first lens 101 that is a negative lens from the object side to the image side, a second lens 102 that is a meniscus lens having a convex surface directed to the image side, a bandpass filter 103, and a diaphragm 104. And a third lens 105 that is a positive lens, a fourth lens 106 that is a negative lens, and a fifth lens 108 that is a positive lens. In the present specification and claims, a negative lens means a lens having a negative power with respect to a paraxial ray, and a positive lens means a lens having a positive power with respect to a paraxial ray. Means.
　本発明の撮像光学系は、特定の波長域の信号光を発する光源を含む投光系とともに使用される。信号光の特定の波長域に合わせたバンドパスフィルタを使用することで、信号光を減少させることなく、太陽光などの背景雑音を低減することが可能となる。信号光の波長域を考慮して、バンドパスフィルタの帯域の半値幅は、±１００ナノメータ以下である。一例として、近赤外線カメラ用の撮像光学系のバンドパスフィルタの帯域は、７００ナノメータから９００ナノメータである。 The imaging optical system of the present invention is used together with a light projecting system including a light source that emits signal light in a specific wavelength range. By using a band-pass filter that matches a specific wavelength region of signal light, it is possible to reduce background noise such as sunlight without reducing the signal light. Considering the wavelength range of the signal light, the band width of the bandpass filter is ± 100 nanometers or less. As an example, the bandpass filter of an imaging optical system for a near-infrared camera has a bandwidth of 700 to 900 nanometers.
　また、本発明の撮像光学系のＦナンバーは１．１以下である。撮像光学系のレンズの全ての光学中心を結んだ線を光軸として、Ｆナンバーは、光軸と像面との交点における、主光線と周辺光線とのなす角度の正弦の逆数として定義される。したがって、１．１以下の小さなＦナンバーを有する撮像光学系においては、光軸と像面との交点における、主光線と周辺光線とのなす角度が大きくなる。 Further, the F number of the imaging optical system of the present invention is 1.1 or less. With the line connecting all optical centers of the lenses of the imaging optical system as the optical axis, the F number is defined as the reciprocal of the sine of the angle between the principal ray and the peripheral ray at the intersection of the optical axis and the image plane. . Therefore, in an imaging optical system having a small F number of 1.1 or less, the angle formed between the principal ray and the peripheral ray at the intersection of the optical axis and the image plane is large.
　図１乃至図３において、主光線を一点鎖線で示し、周辺光線を点線で示す。 1 to 3, the principal ray is indicated by a one-dot chain line, and the peripheral ray is indicated by a dotted line.
　従来の撮像光学系において、組み立ての容易さなどの理由により、バンドパスフィルタは、光学系と像面との間に配置されていた。１．１以下の小さなＦナンバーを有する、上記の配置の撮像光学系において、像面の近くに配置されたバンドパスフィルタの入射面においても、主光線と周辺光線とのなす角度が大きくなる。したがって、周辺光線のバンドパスフィルタへの入射角度が増加し、透過率が減少してしまう。１．１以下の小さなＦナンバーを有する、上記の配置の従来の撮像光学系において、像面の近くに配置されたバンドパスフィルタへの光線の入射角度の最大値は、たとえば、後述の実施例と同様に、Ｆナンバーが０．９の場合には、３４度以上であった。 In a conventional imaging optical system, the bandpass filter is disposed between the optical system and the image plane for reasons such as ease of assembly. In the imaging optical system having the above-described arrangement having a small F-number of 1.1 or less, the angle formed by the principal ray and the peripheral ray is large even on the incident surface of the bandpass filter arranged near the image plane. Therefore, the incident angle of the peripheral ray to the bandpass filter increases, and the transmittance decreases. In the conventional imaging optical system having the above-described arrangement having a small F-number of 1.1 or less, the maximum value of the incident angle of the light beam on the bandpass filter arranged near the image plane is, for example, an example described later. Similarly, when the F number was 0.9, it was 34 degrees or more.
　そこで、本発明では、負のレンズである第一のレンズと、像側に凸面を向けたメニスカスレンズである第二のレンズと、バンドパスフィルタと、絞りと、を、物体側から像側に、上記の順で配置した。第一のレンズを負とすることにより、主光線のバンドパスフィルタへの入射角度を低減することができる。また、第二のレンズを、像側に凸面を向けたメニスカスレンズとすることにより、周辺光線のバンドパスフィルタへの入射角度を低減することができる。 Therefore, in the present invention, a first lens that is a negative lens, a second lens that is a meniscus lens having a convex surface facing the image side, a bandpass filter, and an aperture are arranged from the object side to the image side. , Arranged in the above order. By making the first lens negative, the incident angle of the chief ray to the bandpass filter can be reduced. In addition, by making the second lens a meniscus lens having a convex surface directed to the image side, the incident angle of the peripheral ray to the bandpass filter can be reduced.
　本発明の実施例について以下に説明する。 Examples of the present invention will be described below.
　撮像光学系の各光学素子の面定義式は、以下のとおりである。
Figure JPOXMLDOC01-appb-M000001
 撮像光学系のレンズの全ての光学中心を結んだ線を光軸として、光軸に垂直な面内に互いに直交するｘ軸及びｙ軸を定める。光軸と各光学素子の面との交点から、光軸に沿って像側に向かう方向を正として、座標Ｚを定める。ｈは光軸からの距離、Ｒは曲率半径、ｃは曲率を示す。ｋはコーニック定数、Ａは非球面係数を示す。ｉ及びｍは整数を示す。 The surface definition formula of each optical element of the imaging optical system is as follows.
Figure JPOXMLDOC01-appb-M000001
 An x-axis and a y-axis orthogonal to each other are defined in a plane perpendicular to the optical axis with a line connecting all optical centers of the lenses of the imaging optical system as an optical axis. The coordinate Z is determined with the direction from the intersection of the optical axis and the surface of each optical element toward the image side along the optical axis being positive. h is the distance from the optical axis, R is the radius of curvature, and c is the curvature. k represents a conic constant, and A represents an aspherical coefficient. i and m are integers.
実施例１
　図１は、実施例１の撮像光学系１００の構成を示す図である。撮像光学系１００は、物体側から像側に、負のレンズである第一のレンズ１０１と、像側に凸面を向けたメニスカスレンズである第二のレンズ１０２と、バンドパスフィルタ１０３と、絞り１０４と、正のレンズである第三のレンズ１０５と、負のレンズである第四のレンズ１０６と、波長フィルタ１０７と、正のレンズである第六のレンズ１０８と、カバーガラス１０９と、を備えている。像面は、１１０で示される。 Example 1
FIG. 1 is a diagram illustrating a configuration of the imaging optical system 100 according to the first embodiment. The imaging optical system 100 includes a first lens 101 that is a negative lens from the object side to the image side, a second lens 102 that is a meniscus lens having a convex surface directed to the image side, a band-pass filter 103, a diaphragm 104, a third lens 105 that is a positive lens, a fourth lens 106 that is a negative lens, a wavelength filter 107, a sixth lens 108 that is a positive lens, and a cover glass 109. I have. The image plane is indicated at 110.
　第三のレンズ１０５の材料はガラスであり、その他のレンズの材料は、シクロオレフィンポリマー(COP)である。バンドパスフィルタ１０３の材料は、ガラスであり、波長フィルタ１０７の材料は、ポリカーボネートである。絞り１０４は、板状で、円形の開口部とその周囲の光遮断部とを有し、光軸に垂直な面内に円形の中心が光軸と一致するように配置される。 The material of the third lens 105 is glass, and the other lens material is cycloolefin polymer (COP). The material of the band pass filter 103 is glass, and the material of the wavelength filter 107 is polycarbonate. The diaphragm 104 is plate-shaped, has a circular opening and a surrounding light blocking portion, and is arranged in a plane perpendicular to the optical axis such that the circular center coincides with the optical axis.
　バンドパスフィルタ１０３の帯域は、７００ナノメータから９００ナノメータである。波長フィルタ１０７は、バンドパスフィルタ１０３の補助として使用され、バンドパスフィルタ１０３の可視光域の透過率が若干上昇しても問題を生じないように、可視光域の光を阻止する。 The band of the band pass filter 103 is 700 nanometers to 900 nanometers. The wavelength filter 107 is used as an auxiliary to the band-pass filter 103 and blocks light in the visible light region so that no problem occurs even if the transmittance of the band-pass filter 103 in the visible light region is slightly increased.
　正のレンズである第三のレンズ１０５、負のレンズである第四のレンズ１０６、及び正のレンズである第五のレンズ１０８は、Ｆナンバーが１．１以下となるように構成されている。 The third lens 105 that is a positive lens, the fourth lens 106 that is a negative lens, and the fifth lens 108 that is a positive lens are configured to have an F number of 1.1 or less. .
　表１は、実施例１の撮像光学系１００の光学配置を示す表である。面番号１は、第一のレンズ１０１の物体側面を示し、面番号２は第一のレンズ１０１の像側面を示す。面番号１に対応する面間隔は、第一のレンズ１０１の中心厚を示し、面番号２に対応する面間隔は、第一のレンズ１０１の像側面と隣接する第二のレンズ１０２の物体側面との間の中心間隔を示す。
Figure JPOXMLDOC01-appb-T000002
 Table 1 is a table showing the optical arrangement of the imaging optical system 100 of the first embodiment. Surface number 1 indicates the object side surface of the first lens 101, and surface number 2 indicates the image side surface of the first lens 101. The surface interval corresponding to the surface number 1 indicates the center thickness of the first lens 101, and the surface interval corresponding to the surface number 2 is the object side surface of the second lens 102 adjacent to the image side surface of the first lens 101. The center distance between is shown.
Figure JPOXMLDOC01-appb-T000002
　表２は、第一のレンズ１０１、第二のレンズ１０２、及び第三のレンズ１０５の各面の面定義式の係数を示す表である。
Figure JPOXMLDOC01-appb-T000003
 Table 2 is a table showing coefficients of the surface definition formulas of the surfaces of the first lens 101, the second lens 102, and the third lens 105.
Figure JPOXMLDOC01-appb-T000003
　表３は、第四のレンズ１０６、及び第五のレンズ１０８の各面の面定義式の係数を示す表である。
Figure JPOXMLDOC01-appb-T000004
 Table 3 is a table showing the coefficients of the surface definition formulas of the surfaces of the fourth lens 106 and the fifth lens 108.
Figure JPOXMLDOC01-appb-T000004
　実施例１の撮像光学系の主要な光学性能を表す数値は以下のとおりである。
　全体の焦点距離：2.64mm 
　Ｆナンバー：0.9 
　半画角：48度 
　バンドパスフィルタへの入射角度：22度以下
　像面への主光線入射角度：3度以下
ここで、バンドパスフィルタへの入射角度とは、主光線及び周辺光線を含むすべての光線の入射角度である。 Numerical values representing the main optical performance of the imaging optical system of Example 1 are as follows.
Overall focal length: 2.64mm
F number: 0.9
Half angle of view: 48 degrees
Incident angle to the bandpass filter: 22 degrees or less Incident angle of the chief ray to the image plane: 3 degrees or less Here, the incident angle to the bandpass filter is the incident angle of all rays including the principal ray and peripheral rays is there.
実施例２
　図２は、実施例２の撮像光学系２００の構成を示す図である。撮像光学系２００は、物体側から像側に、負のレンズである第一のレンズ２０１と、像側に凸面を向けたメニスカスレンズである第二のレンズ２０２と、バンドパスフィルタ２０３と、絞り２０４と、正のレンズである第三のレンズ２０５と、波長フィルタ２０６と、正のレンズである第四のレンズ２０７と、カバーガラス２０８と、を備えている。像面は、２０９で示される。 Example 2
FIG. 2 is a diagram illustrating a configuration of the imaging optical system 200 according to the second embodiment. The imaging optical system 200 includes a first lens 201 that is a negative lens from the object side to the image side, a second lens 202 that is a meniscus lens having a convex surface directed to the image side, a bandpass filter 203, a diaphragm 204, a third lens 205 that is a positive lens, a wavelength filter 206, a fourth lens 207 that is a positive lens, and a cover glass 208. The image plane is indicated at 209.
　第三のレンズ２０５の材料はガラスであり、その他のレンズの材料は、シクロオレフィンポリマー(COP)である。バンドパスフィルタ２０３の材料は、ガラスであり、波長フィルタ２０６の材料は、ポリカーボネートである。絞り２０４は、板状で、円形の開口部とその周囲の光遮断部とを有し、光軸に垂直な面内に円形の中心が光軸と一致するように配置される。 The material of the third lens 205 is glass, and the other lens material is cycloolefin polymer (COP). The material of the band pass filter 203 is glass, and the material of the wavelength filter 206 is polycarbonate. The diaphragm 204 is plate-shaped, has a circular opening and a surrounding light blocking portion, and is arranged in a plane perpendicular to the optical axis so that the center of the circle coincides with the optical axis.
　バンドパスフィルタ２０３の帯域は、７００ナノメータから９００ナノメータである。波長フィルタ２０６は、バンドパスフィルタ２０３の補助として使用され、バンドパスフィルタ２０３の可視光域の透過率が若干上昇しても問題を生じないように、可視光域の光を阻止する。 The band of the band pass filter 203 is 700 nanometers to 900 nanometers. The wavelength filter 206 is used as an auxiliary to the bandpass filter 203 and blocks light in the visible light region so that no problem occurs even if the transmittance of the bandpass filter 203 in the visible light region is slightly increased.
　正のレンズである第三のレンズ２０５、及び正のレンズである第四のレンズ２０７は、Ｆナンバーが１．１以下となるように構成されている。 The third lens 205, which is a positive lens, and the fourth lens 207, which is a positive lens, are configured so that the F number is 1.1 or less.
　表４は、実施例２の撮像光学系２００の光学配置を示す表である。面番号１は、第一のレンズ２０１の物体側面を示し、面番号２は第一のレンズ２０１の像側面を示す。面番号１に対応する面間隔は、第一のレンズ２０１の中心厚を示し、面番号２に対応する面間隔は、第一のレンズ２０１の像側面と隣接する第二のレンズ２０２の物体側面との間の中心間隔を示す。
Figure JPOXMLDOC01-appb-T000005
 Table 4 is a table showing an optical arrangement of the imaging optical system 200 according to the second embodiment. Surface number 1 indicates the object side surface of the first lens 201, and surface number 2 indicates the image side surface of the first lens 201. The surface interval corresponding to surface number 1 indicates the center thickness of the first lens 201, and the surface interval corresponding to surface number 2 is the object side surface of the second lens 202 adjacent to the image side surface of the first lens 201. The center distance between is shown.
Figure JPOXMLDOC01-appb-T000005
　表５は、第一のレンズ２０１、第二のレンズ２０２、及び第三のレンズ２０５の各面の面定義式の係数を示す表である。
Figure JPOXMLDOC01-appb-T000006
Table 5 is a table showing the coefficients of the surface definition formulas of the surfaces of the first lens 201, the second lens 202, and the third lens 205.
Figure JPOXMLDOC01-appb-T000006
　表６は、第四のレンズ２０７の各面の面定義式の係数を示す表である。
Figure JPOXMLDOC01-appb-T000007
 Table 6 is a table showing the coefficients of the surface definition formula of each surface of the fourth lens 207.
Figure JPOXMLDOC01-appb-T000007
　実施例２の撮像光学系の主要な光学性能を表す数値は以下のとおりである。
　全体の焦点距離：2.56mm
　Ｆナンバー：0.9 
　半画角：47度 
　バンドパスフィルタへの入射角度：22度以下
　像面への主光線入射角度：5度以下 Numerical values representing main optical performance of the imaging optical system of Example 2 are as follows.
Overall focal length: 2.56mm
F number: 0.9
Half angle of view: 47 degrees
Incident angle to bandpass filter: 22 degrees or less Principal ray incident angle to image plane: 5 degrees or less
実施例３
　図３は、実施例３の撮像光学系３００の構成を示す図である。撮像光学系３００は、物体側から像側に、負のレンズである第一のレンズ３０１と、像側に凸面を向けたメニスカスレンズである第二のレンズ３０２と、バンドパスフィルタ３０３と、絞り３０４と、正のレンズである第三のレンズ３０５と、波長フィルタ３０６と、正のレンズである第二のレンズ３０７と、カバーガラス３０８と、を備えている。像面は、３０９で示される。 Example 3
FIG. 3 is a diagram illustrating a configuration of the imaging optical system 300 according to the third embodiment. The imaging optical system 300 includes a first lens 301 that is a negative lens from the object side to the image side, a second lens 302 that is a meniscus lens having a convex surface directed to the image side, a bandpass filter 303, a diaphragm 304, a third lens 305 that is a positive lens, a wavelength filter 306, a second lens 307 that is a positive lens, and a cover glass 308. The image plane is indicated at 309.
　第三のレンズ３０５の材料はガラスであり、その他のレンズの材料は、シクロオレフィンポリマー(COP)である。バンドパスフィルタ３０３の材料は、ガラスであり、波長フィルタ３０６の材料は、ポリカーボネートである。絞り３０４は、板状で、円形の開口部とその周囲の光遮断部とを有し、光軸に垂直な面内に円形の中心が光軸と一致するように配置される。 The material of the third lens 305 is glass, and the other lens material is cycloolefin polymer (COP). The material of the band pass filter 303 is glass, and the material of the wavelength filter 306 is polycarbonate. The diaphragm 304 is plate-shaped, has a circular opening and a surrounding light blocking portion, and is arranged in a plane perpendicular to the optical axis such that the circular center coincides with the optical axis.
　バンドパスフィルタ３０３の帯域は、７００ナノメータから９００ナノメータである。波長フィルタ３０６は、バンドパスフィルタ３０３の補助として使用され、バンドパスフィルタ３０３の可視光域の透過率が若干上昇しても問題を生じないように、可視光域の光を阻止する。 The band of the band pass filter 303 is 700 nanometers to 900 nanometers. The wavelength filter 306 is used as an auxiliary to the bandpass filter 303 and blocks light in the visible light region so that no problem occurs even if the transmittance of the bandpass filter 303 in the visible light region is slightly increased.
　正のレンズである第三のレンズ３０５、及び正のレンズである第四のレンズ３０７は、Ｆナンバーが１．１以下となるように構成されている。 The third lens 305, which is a positive lens, and the fourth lens 307, which is a positive lens, are configured so that the F number is 1.1 or less.
　表７は、実施例３の撮像光学系３００の光学配置を示す表である。面番号１は、第一のレンズ３０１の物体側面を示し、面番号２は第一のレンズ３０１の像側面を示す。面番号１に対応する面間隔は、第一のレンズ３０１の中心厚を示し、面番号２に対応する面間隔は、第一のレンズ３０１の像側面と隣接する第二のレンズ３０２の物体側面との間の中心間隔を示す。
Figure JPOXMLDOC01-appb-T000008
 Table 7 is a table showing the optical arrangement of the imaging optical system 300 of the third embodiment. Surface number 1 indicates the object side surface of the first lens 301, and surface number 2 indicates the image side surface of the first lens 301. The surface interval corresponding to the surface number 1 indicates the center thickness of the first lens 301, and the surface interval corresponding to the surface number 2 is the object side surface of the second lens 302 adjacent to the image side surface of the first lens 301. The center distance between is shown.
Figure JPOXMLDOC01-appb-T000008
　表８は、第一のレンズ３０１、第二のレンズ３０２、及び第三のレンズ３０５の各面の面定義式の係数を示す表である。
Figure JPOXMLDOC01-appb-T000009
 Table 8 is a table showing the coefficients of the surface definition equations for the surfaces of the first lens 301, the second lens 302, and the third lens 305.
Figure JPOXMLDOC01-appb-T000009
　表９は、第四のレンズ３０７の各面の面定義式の係数を示す表である。
Figure JPOXMLDOC01-appb-T000010
 Table 9 is a table showing the coefficients of the surface definition formula of each surface of the fourth lens 307.
Figure JPOXMLDOC01-appb-T000010
　実施例３の撮像光学系の主要な光学性能を表す数値は以下のとおりである。
　全体の焦点距離：2.56mm
　Ｆナンバー：0.9 
　半画角：47度 
　バンドパスフィルタへの入射角度：22度以下
　像面への主光線入射角度：5度以下 Numerical values representing the main optical performance of the imaging optical system of Example 3 are as follows.
Overall focal length: 2.56mm
F number: 0.9
Half angle of view: 47 degrees
Incident angle to bandpass filter: 22 degrees or less Principal ray incident angle to image plane: 5 degrees or less
　表１０は、実施例１乃至３の、撮像光学系全体及び各レンズの焦点距離を示す表である。焦点距離の単位はミリメータである。
Figure JPOXMLDOC01-appb-T000011
 Table 10 is a table showing the focal length of the entire imaging optical system and each lens in Examples 1 to 3. The unit of the focal length is millimeter.
Figure JPOXMLDOC01-appb-T000011
　表１１は、レンズの中心厚と焦点距離との関係を示す表である。
Figure JPOXMLDOC01-appb-T000012
 Table 11 is a table showing the relationship between the center thickness of the lens and the focal length.
Figure JPOXMLDOC01-appb-T000012
　ｆは、全体の焦点距離を示し、ｆ４は第四のレンズの焦点距離を示す。ｔ１及びｔ２は、それぞれ、第一のレンズ及び第二のレンズの中心厚を示す。 F indicates the overall focal length, and f4 indicates the focal length of the fourth lens. t1 and t2 indicate center thicknesses of the first lens and the second lens, respectively.
　表１２は、実施例１乃至実施例３の撮像光学系の主要な光学性能を表す数値を示す表である。表１２における長さの単位はミリメータである。
Figure JPOXMLDOC01-appb-T000013
 Table 12 is a table showing numerical values representing main optical performances of the imaging optical systems of Examples 1 to 3. The unit of length in Table 12 is millimeter.
Figure JPOXMLDOC01-appb-T000013
　像高とは、光軸と像面との交点から、光軸を水平方向として鉛直方向の距離である。像高をｙ、半画角をθで表すと、
　ｙ＝ｔａｎθ
である。絞り半径とは、絞りの開口部を形成する円の半径である。 The image height is a vertical distance from the intersection of the optical axis and the image plane with the optical axis as the horizontal direction. When the image height is represented by y and the half angle of view is represented by θ,
y = tan θ
It is. The aperture radius is the radius of a circle that forms the aperture of the aperture.
　表１２に示すように、実施例１乃至実施例３の撮像光学系において、主光線及び周辺光線を含むすべての光線の、バンドパスフィルタへの入射角度の最大値は２２度である。従来の撮像光学系のバンドパスフィルタへの光線の入射角度の最大値は、たとえば、Ｆナンバーが１．２の場合には、約２４度であるが、実施例１乃至３と同様に、Ｆナンバーが０．９の場合には、３４度以上である。このように、従来の撮像光学系においては、Ｆナンバーを小さくする（明るくする）と、バンドパスフィルタへの光線の入射角度が増加し、バンドパスフィルタの透過率が低下する。しかし、本発明の撮像光学系によれば、Ｆナンバーが０．９の場合でも、バンドパスフィルタへの光線の入射角度が増加することはなく、バンドパスフィルタへの光線の入射角度が低下することもない。したがって、本発明の撮像光学系によれば、Ｆナンバーが０．９の場合でも、Ｆナンバーがより大きな場合と同等の光学性能が得られる。 As shown in Table 12, in the imaging optical systems of Examples 1 to 3, the maximum value of the incident angle of all the light rays including the principal ray and the peripheral rays to the bandpass filter is 22 degrees. For example, when the F number is 1.2, the maximum value of the incident angle of the light beam on the bandpass filter of the conventional imaging optical system is about 24 degrees. When the number is 0.9, it is 34 degrees or more. As described above, in the conventional imaging optical system, when the F number is decreased (lightened), the incident angle of the light beam to the bandpass filter increases and the transmittance of the bandpass filter decreases. However, according to the imaging optical system of the present invention, even when the F number is 0.9, the incident angle of the light beam to the bandpass filter does not increase, and the incident angle of the light beam to the bandpass filter decreases. There is nothing. Therefore, according to the imaging optical system of the present invention, even when the F number is 0.9, the same optical performance as when the F number is larger can be obtained.

Claims (12)

  1. 　物体側から像側に、負のレンズである第一のレンズと、像側に凸面を向けたメニスカスレンズである第二のレンズと、絞りと、該絞りと像面との間に、少なくとも一つの正のレンズを含む２個以上のレンズと、を備え、さらに、該絞りの物体側または像側に、該絞りに隣接して、帯域の半値幅が±１００ナノメータ以下であるバンドパスフィルタを備えた、Ｆナンバーが１．１以下である撮像光学系。 At least one of a first lens that is a negative lens from the object side to the image side, a second lens that is a meniscus lens having a convex surface facing the image side, a stop, and the stop and the image surface. Two or more lenses including two positive lenses, and further, on the object side or the image side of the diaphragm, adjacent to the diaphragm, a bandpass filter having a band half-value width of ± 100 nanometers or less An imaging optical system having an F number of 1.1 or less.
  2. 　該絞りと像面との間に、ガラスの正のレンズである第三のレンズと、非球面レンズである第四のレンズと、正のレンズである第五のレンズと、を備えた請求項１に記載の撮像光学系。 A third lens that is a glass positive lens, a fourth lens that is an aspherical lens, and a fifth lens that is a positive lens are provided between the stop and the image plane. The imaging optical system according to 1.
  3. 　第三のレンズが球面レンズである請求項２に記載の撮像光学系。 The imaging optical system according to claim 2, wherein the third lens is a spherical lens.
  4. 　第四のレンズが負のレンズである請求項２または３に記載の撮像光学系。 The imaging optical system according to claim 2 or 3, wherein the fourth lens is a negative lens.
  5. 　全体の焦点距離をｆ、第四のレンズの焦点距離をｆ４として、
    　　ｆ４／ｆ＜－４
    を満たす請求項４に記載の撮像光学系。     Assuming that the overall focal length is f and the focal length of the fourth lens is f4,
    f4 / f <-4
    The imaging optical system according to claim 4, wherein:
  6. 　該絞りと像面との間に、正の非球面レンズである第三のレンズと、正の第四のレンズと、を備えた請求項１に記載の撮像光学系。 The imaging optical system according to claim 1, further comprising a third lens that is a positive aspherical lens and a positive fourth lens between the stop and the image plane.
  7. 　絞り半径が像高よりも大きい請求項１から６のいずれかに記載の撮像光学系。 The imaging optical system according to any one of claims 1 to 6, wherein the aperture radius is larger than the image height.
  8. 　半画角が５５度以下である請求項１から７のいずれかに記載の撮像光学系。 The imaging optical system according to any one of claims 1 to 7, wherein the half angle of view is 55 degrees or less.
  9. 　第一のレンズの中心厚をｔ１、全体の焦点距離をｆとして、
    　　ｔ１／ｆ＞１．２
    を満たす請求項１から８のいずれかに記載の撮像光学系。     The center thickness of the first lens is t1, and the overall focal length is f.
    t1 / f> 1.2
    The imaging optical system according to claim 1, wherein:
  10. 　第二のレンズの中心厚をｔ２、全体の焦点距離をｆとして、
    　　ｔ２／ｆ＞１．２
    を満たす請求項１から９のいずれかに記載の撮像光学系。     The center thickness of the second lens is t2, and the overall focal length is f.
    t2 / f> 1.2
    The imaging optical system according to claim 1, wherein:
  11. 　第一のレンズの物体側が凸面である請求項１から１０のいずれかに記載の撮像光学系。 The imaging optical system according to claim 1, wherein the object side of the first lens is a convex surface.
  12. 　該バンドパスフィルタへの光線の入射角度が２５度以下であるように構成された請求項１から１１のいずれかに記載の撮像光学系。 The imaging optical system according to any one of claims 1 to 11, wherein an incident angle of a light beam to the band pass filter is 25 degrees or less.
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