WO2020036032A1

WO2020036032A1 - Lens-based optical system and image capture device

Info

Publication number: WO2020036032A1
Application number: PCT/JP2019/027771
Authority: WO
Inventors: 岩澤　嘉人; 慎吾布施
Original assignee: 株式会社タムロン
Priority date: 2018-08-14
Filing date: 2019-07-12
Publication date: 2020-02-20
Also published as: JP7100534B2; JP2020027206A

Abstract

The purpose of the present invention is to provide a lens-based optical system and an image capture device capable of efficiently introducing the reflective light from an object to an image capture element. The present invention provides a lens-based optical lens system to be used only within a wavelength range of N±50 nm, wherein the lens-based optical system has a band-pass filter that allows only wavelengths within the range of N±50 nm to pass therethrough, the lens-based optical system has at least one or more faces that have a negative refractive power, and a prescribed conditional expression is satisfied.

Description

Lens optical system and imaging device

{Circle around (1)} The present invention relates to a lens optical system and an imaging device used for a light beam having a specific wavelength and having high performance for a light beam having a specific wavelength.

In recent years, there has been a demand for advanced sensing technology in order to enhance security and safety. For this reason, a light beam in a specific wavelength range scans a wide area of a region where a person or an object is present. There is a demand for detecting the diffused light of the reflected light or disturbance light by the projection target object with a lens optical system and detecting the target object with high accuracy.

Concerning the above-mentioned demand for a conventional lens optical system using light of a specific wavelength, a lens group composed of three lenses and an interference filter that transmits light in a specific wavelength band in the near infrared region are connected from the object side to the image side. In this order, the lens group includes a first meniscus lens convex to the object side having positive power, and a convex lens convex to the image side having positive power from the object side to the image side. An infrared lens unit provided in order has been proposed (for example, see Patent Document 1).

However, in the conventional lens unit, a wide-angle lens is configured with a small number of lenses of three or less. However, since the Fno is dark and the angle of incidence on the image sensor is large, the amount of light incident on the image sensor is small. There is a problem that it is not enough. In particular, in the present technical field, it is desirable to project light rays of a specific wavelength band and to detect light reflected by an object by an image sensor without receiving any reflected light. Lack is an important issue to be resolved.

JP 2016-80774 A

(Object of the invention)
The present invention has been made in view of the above-described problem, and has as its object to provide a lens optical system and an image pickup apparatus that efficiently input reflected light or scattered light from an object to an image pickup device.

A first invention is a lens optical system used only within a wavelength range of wavelength N ± 50 nm, wherein the lens optical system has a band-pass filter transmitting only within a wavelength range of wavelength N ± 50 nm, A lens optical system characterized in that the system has at least one surface having negative refractive power and satisfies the following conditional expression.
-2.00 <fn / f <-0.45 (1)
0.10 <Y / f <0.60 (2)
However,
fn: focal length at the wavelength Nnm of the surface having the largest negative refractive power among all surfaces of the lens optical system f: focal length Y at the wavelength Nnm of the lens optical system Y: maximum at the wavelength Nnm of the lens optical system The image height.

The second invention is
An image pickup apparatus comprising: the lens optical system according to the first invention; and an image pickup device that converts an optical image formed by the lens optical system into an electric signal.

According to the present invention, it is possible to configure a lens optical system and an imaging device that efficiently input reflected light or scattered light from an object to an imaging device.

FIG. 4 is an explanatory diagram of a term “light incident angle B”. It is explanatory drawing of a term "ray incident angle C". It is explanatory drawing of a term "ray incident angle D". It is explanatory drawing of the term "tangent angle of a lens surface." FIG. 2 is a lens cross-sectional view illustrating a lens configuration of a lens optical system according to a first example of the present invention. FIG. 3 is a longitudinal aberration diagram of the lens optical system according to the first example of the present invention. It is a lens sectional view showing the lens composition of the lens optical system of the 2nd example of the present invention. FIG. 10 is a longitudinal aberration diagram of the lens optical system according to Example 2 of the present invention. It is a lens sectional view showing the lens composition of the lens optical system of the 3rd example of the present invention. It is a longitudinal aberration figure of the lens optical system of the 3rd Example of the present invention. It is a lens sectional view showing the lens composition of the lens optical system of the 4th example of the present invention. It is a longitudinal aberration diagram of the lens optical system of the fourth example of the present invention. FIG. 1 is an explanatory diagram illustrating a configuration of an imaging device according to an embodiment of the present invention.

Hereinafter, embodiments of the lens optical system and the imaging apparatus according to the present invention will be described. However, what is described below is one embodiment of the lens optical system and the imaging device, and the present invention is not limited to the following embodiment.

The lens optical system according to the first embodiment includes:
In a lens optical system used only within a wavelength range of wavelength N ± 50 nm, the lens optical system has a band-pass filter that transmits only within a wavelength range of wavelength N ± 50 nm, and the lens optical system is negative. A lens optical system having at least one surface having a refractive power and satisfying the following conditional expression.
-2.00 <fn / f <-0.45 (1)
0.10 <Y / f <0.60 (2)
However,
fn: focal length at the wavelength Nnm of the surface having the largest negative refractive power among all surfaces of the lens optical system f: focal length Y at the wavelength Nnm of the lens optical system Y: maximum at the wavelength Nnm of the lens optical system The image height.

The lens optical system according to the first embodiment is a lens optical system used only within a wavelength range of wavelength N ± 50 nm, wherein the lens optical system has a band-pass filter that transmits only the wavelength range of wavelength N ± 50 nm. It is characterized by the following. By having the band-pass filter, it is only necessary to correct aberration in a specific wavelength region, and it is possible to configure a lens optical system with a small number of lenses, thereby achieving high performance and low cost.
Incidentally, the band-pass filter is an interference filter formed by forming a multilayer film on the surface of the substrate, and has a function of increasing the transmittance of light in a specific wavelength band and decreasing the transmittance of other wavelength bands.
The position of the bandpass filter in the direction of the optical axis does not matter. However, since the transmission spectrum of the interference filter shifts to the shorter wavelength side as the incident light beam angle departs from 0 °, it is preferable to dispose the bandpass filter at a position where the light incident angle to the bandpass filter is not large. In addition, the curvature of the base of the band-pass filter does not matter. However, it is preferable that the substrate is a parallel plate because the light enters the bandpass filter at various angles and the angle of incidence of the light varies depending on the incident position when the substrate is spherical.

レンズ The lens optical system according to the first embodiment is characterized in that at least one surface having negative refractive power is provided. In the case of an optical system that is used only in a specific narrow wavelength region, there is no need to correct chromatic aberration. it can. However, in order to improve image quality, it is necessary to correct the Petzval sum. Therefore, it is preferable that at least one surface has a negative refractive power.

The lens optical system according to the first embodiment satisfies the following conditional expression.
−2.00 <fn / f <−0.45 (1)
However,
fn: focal length at the wavelength Nnm of the surface having the largest negative refractive power among all surfaces of the lens optical system f: focal length at the wavelength Nnm of the lens optical system

The conditional expression (1) is an expression for defining the focal length of the surface having the negative refractive power.
By satisfying conditional expression (1), the focal length of the surface having the negative refractive power falls within an appropriate range, and the image surface property can be corrected with a lens configuration that does not require a large number of lenses.
If the lower limit of conditional expression (1) is exceeded, the negative refractive power becomes too weak, making it difficult to correct the image surface properties, which is not preferable.
When the value exceeds the upper limit of the conditional expression (1), the negative refractive power becomes too strong and the image surface property is excessively deteriorated, which is not preferable in terms of performance. Further, it is difficult to correct the image plane property with a small number of lenses, which is not preferable in terms of cost reduction.

The lower limit of conditional expression (1) is more preferably -1.80, further preferably -1.60, further preferably -1.50, and still more preferably -1.40, More preferably, it is −1.30, and still more preferably −1.20.
Also, the upper limit of conditional expression (1) is preferably -0.50, more preferably -0.55, further preferably -0.60, further preferably -0.65, and- More preferably, it is 0.70.

The lens optical system according to the first embodiment satisfies the following conditional expression.
0.10 <Y / f <0.60 (2)
However,
Y: maximum image height at the wavelength Nnm of the lens optical system f: focal length at the wavelength Nnm of the lens optical system

The conditional expression (2) is an expression that defines the ratio between the maximum image height of the lens optical system and the focal length.
By satisfying conditional expression (2), the angle of view of the lens optical system falls within an appropriate range, and high performance can be achieved with a lens configuration that does not require a large number of lenses.
If the lower limit of conditional expression (2) is exceeded, the maximum angle of view becomes too narrow, so that it becomes difficult to capture a wide range, which is not preferable.
When the value exceeds the upper limit of conditional expression (2), the maximum angle of view is widened, so that it is difficult to achieve high performance with a small number of lenses, which is not preferable in terms of cost reduction.

The lower limit of conditional expression (2) is more preferably 0.12, further preferably 0.14, further preferably 0.16, and even more preferably 0.20. Further, the upper limit of conditional expression (2) is preferably 0.55, more preferably 0.50, further preferably 0.45, further preferably 0.40, and more preferably 0.35. Is more preferable.

撮像 The imaging optical system of the first embodiment is not limited to this lens configuration. Regardless of the number of lenses and the arrangement of the lenses, these effects can be obtained by applying the present embodiment. In addition, from the viewpoint of cost reduction and miniaturization, it is more preferable to configure the camera with seven or less lenses. Regarding the shape of the lens, it is preferable that the outermost object side surface is a convex surface. The number and shape of the lenses can be appropriately changed according to the required focal length, size, F number, and image height.

The lens optical system according to the second embodiment has at least one resin lens Lp.
By using a resin lens, weight reduction and cost reduction can be achieved.
Preferably, the resin lens Lp has an aspheric surface. By using an aspherical surface for the resin lens Lp, aberrations can be effectively corrected while realizing cost reduction, so that high performance is also achieved. When an aspherical surface is used for the resin lens Lp, it is preferable that the resin lens Lp be an aspherical surface having a shape that reduces paraxial refracting power in order to correct aberration.

The lens optical system according to the third embodiment is characterized in that the resin lens Lp satisfies the following conditional expression.
1.5 <| fLp | / f <2000.0 (3)
However,
fLp: Focal length at the wavelength Nnm of the resin lens Lp f: Focal length at the wavelength Nnm of the lens optical system (if there are a plurality of resin lenses Lp, fLp is the one with the largest refractive power).

The conditional expression (3) is an expression for defining the focal length of the resin lens Lp at the wavelength Nnm. In the case of a resin lens, since the change in optical characteristics with respect to a temperature change is large, it is better that the resin lens Lp does not have a very large refractive power.

By satisfying conditional expression (3), it is possible to improve the optical performance with a small number of lenses while minimizing the change in the optical characteristics with respect to the temperature change.
If the lower limit of conditional expression (3) is exceeded, the refractive power of the resin lens Lp becomes too large, and the change in the optical characteristics with respect to the temperature change becomes undesirably large.
If the value exceeds the upper limit of conditional expression (3), the refractive power of the resin lens Lp is too small, so that the effect of aberration correction is reduced, and it is not possible to configure the lens with a small number of lenses.

The lower limit of conditional expression (3) is more preferably 1.7, still more preferably 1.9, even more preferably 2.1, even more preferably 2.4, and 2.8. It is more preferable that there is. Further, the upper limit of conditional expression (3) is preferably 1000.0, more preferably 500.0, further preferably 200.0, further preferably 100.0, and most preferably 50.0. Is more preferably, 20.0 is more preferable, 10.0 is more preferable, and 8.0 is more preferable.

樹脂 In addition, it is preferable that one positive lens and one negative lens are arranged for the resin lens. By arranging one resin lens having a positive refractive power and one resin lens having a negative refractive power, a change in optical characteristics due to a temperature change of the resin lens cancels out, and the change in optical characteristics can be reduced, which is preferable. .

The lens optical system according to the fourth embodiment is characterized in that the lens optical system has at least one biconvex air lens and satisfies the following conditional expression.
-0.70 <(Crpf + Crpr) / (Crpf-Crpr) <0.70 (4)
However,
Crpf: radius of curvature of the object side surface of the biconvex air lens Crpr: radius of curvature of the image side surface of the biconvex air lens

The above conditional expression (4) is an expression for defining the shape of the biconvex air lens. Here, the air lens is an air space formed by an object-side surface and an image-side surface which are arranged adjacent to each other with an air space therebetween.

By satisfying conditional expression (4), it is possible to configure a large-aperture lens optical system in which the spherical aberration and the image surface property are corrected by a lens configuration that does not require a large number of lenses.
When the value exceeds the range of the conditional expression (4), the shape of the air lens approaches a plano-convex shape, so that it is not preferable from the viewpoint of high performance that spherical aberration and correction of image surface property are not compatible.

The lower limit of conditional expression (4) is more preferably −0.65, further preferably −0.50, further preferably −0.35, and still more preferably −0.15. More preferably, it is -0.05. Further, the upper limit of conditional expression (4) is preferably 0.65, more preferably 0.60, further preferably 0.50, further preferably 0.45, and more preferably 0.40. Is more preferable.

The lens optical system according to the fifth embodiment has a lens Lf having the object-side convex surface closest to the object, and satisfies the following conditional expression.
0.35 <CrLf / f (5)
However,
CrLf: radius of curvature f of the object-side convex surface of the lens Lf: focal length at a wavelength Nnm of the lens optical system

The conditional expression (5) is an expression for defining the radius of curvature of the object-side convex surface of the lens Lf having the object-side convex surface. Since the conditional expression (5) takes a positive value, it defines that the surface closest to the object has a shape convex toward the object.
By satisfying conditional expression (5), the radius of curvature of the object-side convex surface falls within an appropriate range, and distortion can be corrected with a lens configuration that does not require a large number of lenses.
If the lower limit of conditional expression (5) is divided, the radius of curvature of the convex surface on the object side becomes too small, and it becomes difficult to correct distortion, which is not preferable.
The upper limit of the conditional expression (5) is not limited as long as the object side surface has a convex shape.

The lower limit of conditional expression (5) is more preferably 0.25, further preferably 0.35, further preferably 0.50, further preferably 0.65, and 0.80. It is more preferable that there is.
The upper limit of conditional expression (5) is not specified. However, if the radius of curvature is too large, there is a problem that a ghost occurs due to inter-surface reflection between the surface closest to the object and the cover glass, the imaging surface, a band-pass filter of a parallel plate, or the like. Therefore, the upper limit of conditional expression (5) is preferably 5000.00, more preferably 1000.00, further preferably 200.00, further preferably 20.00, and 10.00. Is more preferable, 5.00 is more preferable, 3.0 is more preferable, 1.60 is more preferable, and 1.45 is more preferable.

The lens optical system according to the sixth embodiment satisfies the following conditional expression.
0.50 <1 / tan (| Bmax |) <4.00 (6)
However,
Bmax: the maximum value of the angle between the normal to the lens surface and the incident light beam on all the lens surfaces included in the lens optical system

The conditional expression (6) is an expression that defines the light incident angle B. Here, the light incident angle B is an angle with respect to a normal line B1 of the lens surface in the meridional section of the light beam B2 as shown in FIG. The light incident angle B is represented by an absolute value, and all take positive values. When the lens surface is an aspherical surface, the normal is calculated not from the paraxial curvature but from the aspherical shape.

By satisfying conditional expression (6), the angle of incidence of the light beam with respect to the normal to the lens surface is in an appropriate range, and a lens configuration having a low reflectance and not requiring a large number of lenses is possible.
If the lower limit of conditional expression (6) is exceeded, that is, if the maximum light ray incident angle with respect to the normal to the lens surface becomes large, large aberrations occur, which is not preferable.
If the upper limit of conditional expression (6) is exceeded, that is, if the maximum ray incident angle with respect to the normal to the lens surface is small, the aberration correction effect becomes too small, and it becomes difficult to configure a lens optical system with a small number of lenses. It is not preferable in terms of cost reduction.

The lower limit of conditional expression (6) is more preferably 0.55, further preferably 0.60, further preferably 0.65, and even more preferably 0.70. The upper limit of conditional expression (6) is preferably 3.00, more preferably 2.60, further preferably 2.10, and still more preferably 1.80.

The lens optical system according to the seventh embodiment satisfies the following conditional expression.
1.90 <1 / tan (| Cmax |) <20.00 (7)
However,
Cmax: maximum value of the angle between the band-pass filter and the light beam incident on the band-pass filter

The conditional expression (7) is an expression that specifies the light incident angle C with respect to the normal F1 of the bandpass filter surface F. Here, as shown in FIG. 2A, the light incident angle C is defined in the same manner as the light incident angle B in FIG. 1, and the angle is represented by an absolute value, and all take positive values.

In the interference filter, the transmission spectrum shifts to the short wavelength side as the incident ray angle departs from 0 °. Therefore, by satisfying the conditional expression (7), the light incident angle with respect to the normal to the surface of the bandpass filter falls within an appropriate range, and the wavelength shift of the transmission spectrum can be suppressed.

If the lower limit of conditional expression (7) is divided, that is, if the maximum incident angle of the light beam incident on the band-pass filter increases, the transmission spectrum shifts to the shorter wavelength side, and the transmittance at the used wavelength decreases, which is not preferable.
When the value exceeds the upper limit of the conditional expression (7), that is, the maximum incident angle of the light beam incident on the band-pass filter becomes too small, which means that the principal light beam and the upper and lower light beams are all arranged in a telecentric optical path arrangement. This makes it difficult to configure with the number of sheets, which is not preferable in terms of cost reduction.

In addition, the lower limit of conditional expression (7) is more preferably 2.55, furthermore preferably 2.60, furthermore preferably 2.65, furthermore preferably 2.70, and 2.77. It is more preferable that there is. The upper limit of conditional expression (7) is preferably 15.00, more preferably 12.00, further preferably 8.00, and still more preferably 7.00.
In the case of an optical system having an Fno higher than 1.4, if a band-pass filter is disposed closest to the image plane, the light incident angle C is about 20 degrees. It is preferable not to dispose a bandpass filter closest to the image plane.
In a wide-angle lens having a maximum angle of view exceeding 20 degrees, it is preferable not to dispose a bandpass filter closest to the object side.

The lens optical system according to the eighth embodiment satisfies the following conditional expression.
-0.09 <tan (D) <0.27 (8)
However,
D: Angle on the meridional section formed by the principal ray of the most off-axis ray at a wavelength of N nm emitted from the most image-side surface of the lens optical system and incident on the image plane and a line parallel to the optical axis.

The above conditional expression (8) is an expression that defines the angle at which the most off-axis ray in the lens optical system is incident on the image plane. Here, the principal ray is a ray passing through the center of the stop among the off-axis rays at the wavelength Nnm. The light incident angle on the meridional section formed by the principal ray and a line parallel to the optical axis is positive in the direction shown in FIG. 2B. In FIG. 2B, IMG represents an image plane.

When the value exceeds the upper limit of the conditional expression (8), that is, the angle of the light beam incident on the image plane becomes too large, and the aperture ratio of the on-chip lens of the image pickup device is reduced, and the peripheral light amount is remarkably reduced, which is not preferable.
Also, if the lower limit of conditional expression (8) is divided, that is, the angle of incidence on the image plane becomes small, it becomes difficult to reduce the diameter of the final lens, which is not preferable.

In addition, the lower limit of conditional expression (8) is more preferably −0.05, further preferably −0.02, further preferably −0.01, and still more preferably 0.00. Further, the upper limit of conditional expression (8) is preferably 0.25, more preferably 0.22, further preferably 0.18, further preferably 0.15, and more preferably 0.12. And more preferably 0.08.

レンズ The lens optical system according to the ninth embodiment is characterized in that the wavelength N is longer than 780 nm. Since the wavelength that can be sensed by human eyes is 400 nm to 750 nm, it is preferable to use a wavelength that cannot be sensed by human eyes in order to project a specific wavelength and receive the scattered light.

The wavelength N is more preferably longer than 800 nm, further preferably longer than 830 nm, and further preferably longer than 850 nm.

The lens optical system of the tenth embodiment is characterized by satisfying the following conditional expression.
0.10 <1 / tan (| Amin |) <1.35 (9)
However,
Amin: The minimum value of the angle between the tangent of the lens surface and the optical axis in all the lens surfaces included in the lens optical system.

The conditional expression (9) is an expression that defines a tangent angle to the lens surface. Here, as shown in FIG. 3, the tangent angle A is represented by an absolute value, and all of the tangent angles take positive values. Therefore, the smaller the tangent angle, the stronger the surface inclination.
By satisfying the conditional expression (9), the thickness error of the antireflection coat is reduced and the antireflection coat has an appropriate refractive power, which leads to a reduction in the number of lenses. In addition, when the lens is molded with resin, the moldability of the surface is maintained.

When the lower limit of conditional expression (9) is divided, that is, the inclination of the surface approaches a flat surface, the refractive power is weak, the overall length of the lens is increased, and a large number of lenses are required for aberration correction. It is not preferable because it is difficult to reduce the cost and cost.
When the value exceeds the upper limit of the conditional expression (9), that is, the inclination of the surface is increased, and the thickness of the film is different between the lens central portion and the lens peripheral portion when the antireflection coating is deposited. For this reason, the reflectance characteristics change between the central portion and the peripheral portion of the lens, and it is difficult to increase the transmittance, which is not preferable. Further, in the case of a resin lens, the mold releasability from the mold is deteriorated, so that the moldability of the surface is deteriorated, which is not preferable in achieving high performance.

In addition, the lower limit of conditional expression (9) is more preferably 0.15, further preferably 0.25, further preferably 0.35, and still more preferably 0.50. Further, the upper limit of conditional expression (9) is preferably 1.30, more preferably 1.28, further preferably 1.26, and still more preferably 1.20.

The imaging apparatus according to the eleventh embodiment includes an imaging device that converts an optical image formed by the lens optical system into an electric signal on an image side of the lens optical system. Here, the configuration of the image sensor is not particularly limited, and a solid-state image sensor such as a CCD sensor or a CMOS sensor is exemplified.

It is more preferable that the imaging apparatus of the present invention has an image processing step of electrically processing image data captured by the image sensor to change the shape of the image data. As an example of the image processing performed in the image processing process, for example, image processing in which correction data for correcting distortion of an image shape is held, and the image data is corrected using the correction data, or the like is given. . When miniaturizing an optical system including a lens, distortion of the image shape becomes a problem, but by performing the image processing as described above, it is possible to form a distortion-free image and achieve miniaturization of the lens optical system. Is preferred.

In the image pickup apparatus of the present invention, when distortion is corrected by the image processing process, the negative refractive power of the lens disposed closest to the image can be increased, and miniaturization of the lens closest to the image can be achieved. Is preferred.

In the imaging apparatus of the present invention, it is preferable that the chromatic aberration of magnification is corrected by the image processing process, because the number of correction targets for optical aberration correction is reduced, the number of lenses is reduced, and the size of the lens optical system is reduced.

。 An image sensor for converting an optical image formed by the optical system into an electric signal is provided on the image side of the lens optical system. Here, the imaging device is not particularly limited, and a solid-state imaging device such as a CCD sensor or a CMOS sensor can be used.

(First embodiment)
FIG. 4 is a lens cross-sectional view showing the lens configuration of the lens optical system according to Example 1 of the present invention. The lens optical system according to the first embodiment uses a light beam having a wavelength N of 905 nm, and in order from the object side, a biconvex first lens L1 and an object-side convex meniscus shape having a positive refractive power on both surfaces. A second lens L2 having an aspheric surface, a third meniscus lens L3 having a negative refractive power and convex on the object side, a fourth lens L4 having a positive refractive power and a concave meniscus on the object side, It comprises a fifth meniscus lens L5 having a positive refractive power and convex on the object side, and a sixth lens L6 having a negative refractive power and a concave meniscus on the object side. A band-pass filter BPF is arranged on the object side of the lens L1 closest to the object. The aperture stop S is arranged on the image side of the band pass filter BPF closest to the object.

The band-pass filter BPF has a wavelength range from 884 nm to 936 nm of a transmittance of 1% or more at an incident angle of 0 ° for a light beam having a wavelength N of 905 nm, and a transmittance range of half of the maximum transmittance, that is, a half-value width of 890 nm. 927 nm.
The second lens L2 and the fourth lens L4 are resin lenses.

All lenses have an anti-reflection coating on their lens surfaces. The object side surface of the fifth lens L5 is provided with an antireflection coating in which the wavelength at which the reflectance becomes the smallest in the wavelength range of N ± 100 nm exists in the range of N ± 50 nm.
Further, a layer containing MgF ₂ as a material is provided on the air interface of the antireflection coat on the object side surface of the fifth lens L5, and the total number of layers is five. At the air interface of the antireflection coat of the second lens L2 and the fourth lens L4, which are resin lenses, a layer containing SiO ₂ as a material is provided, and the total number of layers is three.

In the lens optical system of the first embodiment, the band-pass filter BPF is disposed closest to the object side. Instead, the band-pass filter BPF based on a parallel plate is replaced by the fourth lens L4 and the fifth lens L5. , And Cmax in that case is 24.953 degrees.

ＩＭIn FIG. 4, IMG indicates an image plane. The IMG specifically corresponds to an imaging surface of a solid-state imaging device such as a CCD sensor or a CMOS sensor. A parallel flat plate having no substantial refractive power, such as a cover glass CG, is provided on the object side of the imaging plane IMG. These points are the same in each lens cross-sectional view shown in the other examples, and the description thereof will be omitted below.

Next, a numerical example in which specific numerical values of the lens optical system of the first example are applied will be described. Table 1 is a specification table of the lens optical system. The specification table shows the focal length “f”, the F number “Fno.”, The half angle of view “ω”, the image height “Y”, and the total optical length “TL” of the lens optical system at a wavelength of 905 nm.
(Table 1)
f 30.658
Fno 1.095
ω 12.000
Y 6.492
TL 49.917

Table 2 shows the surface data of the lens optical system of the first example. In Table 2, “surface number” is the order of the lens surface counted from the object side, “r” is the radius of curvature of the lens surface, “d” is the distance between the lens surfaces on the optical axis, and “Nd” is the d-line (wavelength λ = 587.6 nm), “νd” indicates Abbe number for d-line, and “H” indicates effective radius. “ASP” displayed in the column next to the surface number indicates that the lens surface is aspheric, and “S” indicates an aperture stop. The units of length in each table are all “mm”, and the units of angle are all “°”. The radius of curvature “0” means a plane. The first and second surfaces in Table 2 are bandpass filters BPF, and the fifteenth and sixteenth surfaces are surface data of the cover glass CG.
(Table 2)
Surface number r d Nd νd H
1 0.0000 1.100 1.50892 64.20 14.153
2 STOP 0.0000 0.200 14.000
3 30.7024 7.000 1.97213 29.13 14.858
4 -808.7238 0.200 14.348
5 ASP 32.5340 5.908 1.63641 20.37 13.770
6 ASP 40.7623 0.880 12.975
7 114.1620 1.700 1.55932 56.04 12.234
8 14.3799 10.423 10.342
9 ASP -11.3293 4.904 1.63641 20.37 10.321
10 ASP -13.0587 0.200 11.932
11 19.0455 7.900 1.92859 32.32 11.916
12 88.7164 2.862 10.357
13 -50.7286 1.600 1.55932 56.04 9.484
14 -400.0008 4.101 8.823
15 0.0000 0.400 1.50892 64.17 6.838
16 0.0000 0.539 6.720

Table 3 shows the aspheric coefficient of each aspheric surface. The aspheric coefficient is a value when each aspheric shape is defined by the following equation.
X (Y) = CY ² / [1+ {1− (1 + Κ) · C ² Y ² ｝ ^1/2 ] + A4 · Y ⁴ + A6 · Y ⁶ + A8 · Y ⁸ + A10 · Y ¹⁰ + A12 · Y ¹²
However, in Table 3, “ ^Ea ” indicates “× 10 ^−a ”. In the above equation, “X” is the displacement amount from the reference plane in the optical axis direction, “C” is the curvature at the surface vertex, “Y” is the height from the optical axis in a direction perpendicular to the optical axis, “ “Κ” is a conic coefficient, and “An” is an nth-order aspherical coefficient.
Matters relating to these tables are the same in each table shown in the other embodiments, and therefore description thereof is omitted below.
(Table 3)
5 6 9 10
Κ 1.2351 -6.2405 -1.9119 -0.8763
A4 -3.5693E-05 -5.4180E-05 -1.1207E-04 -7.0156E-06
A6 -1.8233E-07 -2.5994E-07 4.0654E-07 1.0549E-07
A8 7.7233E-10 2.2271E-09 -6.2718E-09 -2.4940E-09
A10 -3.4714E-12 -8.1079E-12 8.5243E-11 2.5602E-11
A12 7.3369E-15 1.3452E-14 -4.4259E-13 -9.6409E-14

Table 4 shows the focal length of each lens at a wavelength of 905 nm.
(Table 4)
Lens surface number Focal length
L1 3-4 30.553
L2 5-6 197.965
L3 7-8 -29.595
L4 9-1 1307.890
L5 11-12 24.765
L6 13-14 -104.040

FIG. 5 shows a longitudinal aberration diagram of the lens optical system of the first example. The longitudinal aberration diagrams shown in each figure are spherical aberration (mm), astigmatism (mm), and distortion (%) in order from the left side in the drawings.
In the figure showing the spherical aberration, the vertical axis indicates the ratio to the open F value, and the horizontal axis indicates defocus, and indicates the spherical aberration at a wavelength λ = 905 nm.
In the figure showing astigmatism, the vertical axis is image height, the horizontal axis is defocused, the solid line is a sagittal image plane (ds) at a wavelength λ = 905 nm, and the dotted line is a meridional image plane (dm) at a wavelength λ = 905 nm. Show.
In the figure showing distortion, the vertical axis represents image height and the horizontal axis represents%, and represents distortion at a wavelength λ = 905 nm. The matters relating to these longitudinal aberration diagrams are the same in the longitudinal aberration diagrams shown in the other examples, and therefore description thereof is omitted below.

The back focus “fb” at the wavelength λ = 905 nm of the lens optical system according to the first example is as follows. However, the following values do not include the cover glass (Nd = 1.50892), and the same applies to the back focus shown in other examples.
fb = 4.9904 (mm)

Table 17 shows values of the conditional expressions (1) to (9) of the lens optical system of the first example.

(Second embodiment)
FIG. 6 is a lens cross-sectional view illustrating a lens configuration of a lens optical system according to Example 2. The lens optical system of the second example includes, in order from the object side, a biconvex first lens L1 and a second lens L2 having a positive refractive power and an object-side convex meniscus and having aspheric surfaces on both surfaces. A third lens L3 having a negative refractive power and an object-side convex meniscus shape, a fourth lens L4 having a negative refractive power and an object-side concave meniscus, and a biconvex fifth lens L5. It is composed of A band-pass filter BPF is arranged on the object side of the lens L1 closest to the object. The aperture stop S is arranged on the image side of the band pass filter BPF closest to the object.

The bandpass filter BPF has a wavelength range of transmittance of 1% or more at an incident angle of 0 ° for light having a wavelength N of 905 nm from 884 nm to 936 nm, and a transmittance range that is half of the maximum transmittance, that is, a half width from 890 nm. 927 nm.
The second lens L2 and the fourth lens L4 are resin lenses.

All lenses have an anti-reflection coating on their lens surfaces. The object side surface of the fifth lens L5 is provided with an antireflection coating in which the wavelength at which the reflectance becomes the smallest in the wavelength range of N ± 100 nm exists in the range of N ± 50 nm.
A layer containing MgF ₂ as a material is provided on the air interface of the antireflection coat on the object side surface of the fifth lens L5, and the total number of layers is five. A layer containing SiO ₂ as a material is provided on the air interface of the antireflection coat of the second lens L2 and the fourth lens L4, which are resin lenses, and the total number of layers is three.

Further, in the lens optical system of the second embodiment, a band-pass filter BPF is disposed closest to the object side. Instead, a band whose parallel plate is a base between the fourth lens L4 and the fifth lens L5 is used. A pass filter BPF may be provided, in which case Cmax is 23.412 degrees.

Next, a numerical example in which specific numerical values of the lens optical system of the second example are applied will be described. Table 5 is a table of specifications of the lens optical system of the second example.
(Table 5)
f 30.869
Fno 1.200
ω 12.000
Y 6.561
TL 49.441

Table 6 shows surface data of the lens optical system of the second example. The first and second surfaces in Table 6 are bandpass filters BPF, and the thirteenth and fourteenth surfaces are surface data of the cover glass CG.
(Table 6)
Surface number r d Nd νd H
1 0.0000 1.100 1.50892 64.20 13.015
2 STOP 0.0000 0.200 12.862
3 30.4662 6.000 1.97213 29.13 13.584
4 -240.7561 0.100 13.238
5 ASP 38.3859 6.010 1.63641 20.37 12.735
6 ASP 95.0197 1.000 11.974
7 -73.0253 1.770 1.50892 64.20 11.588
8 12.3119 8.922 9.600
9 ASP -12.2585 4.550 1.63641 20.37 9.645
10 ASP -15.6370 0.200 11.678
11 33.2385 6.300 1.97213 29.13 13.585
12 -63.7223 12.207 13.384
13 0.0000 0.500 1.50892 64.17 6.962
14 0.0000 0.582 6.815

Table 7 shows the aspheric coefficient of each aspheric surface.
(Table 7)
5 6 9 10
Κ 6.4527 55.5248 -1.2127 -0.6032
A4 -4.1920E-05 -7.1713E-05 -5.7922E-05 -1.3478E-05
A6 -2.2301E-07 -1.3274E-07 9.9430E-07 1.1139E-06
A8 7.1955E-10 1.2655E-09 1.7388E-09 -1.1537E-08
A10 -2.2983E-12 -7.2254E-12 -2.3641E-10 4.6508E-11
A12 -1.0660E-14 1.6334E-15 1.2423E-12 -8.8969E-14

Table 8 shows the focal length of each lens at a wavelength of 905 nm.
(Table 8)
Lens surface number Focal length
L1 3-4 28.126
L2 5-6 97.187
L3 7-8 -20.558
L4 9-10 -187.190
L5 11-12 23.214

FIG. 7 shows a longitudinal aberration diagram of the lens optical system of the second example.
The back focus “fb” of the lens optical system at the wavelength λ = 905 nm is as follows.
fb = 13.1201 (mm)

Table 17 shows values of the conditional expressions (1) to (9) of the second embodiment.

(Third embodiment)
FIG. 8 is a lens cross-sectional view illustrating a lens configuration of a lens optical system according to Example 3. The lens optical system of the third example includes, in order from the object side, a biconvex first lens L1 and a second lens L2 having a positive refractive power and an object-side convex meniscus shape and having aspheric surfaces on both surfaces. A third lens L3 having a negative refractive power and an object-side convex meniscus shape, a fourth lens L4 having a negative refractive power and an object-side concave meniscus, and a biconvex fifth lens L5. It is composed of A band-pass filter BPF is arranged on the object side of the lens L1 closest to the object. The aperture stop S is arranged on the image side of the band pass filter BPF closest to the object.

The lens surfaces of all the lenses are provided with an anti-reflection coating, and the object side surface of the fifth lens L5 is such that the wavelength at which the reflectance becomes the smallest in the wavelength range of N ± 100 nm is in the range of N ± 50 nm. An anti-reflection coating is present.
Further, a layer containing MgF ₂ as a material is provided on the air interface of the antireflection coat on the object side surface of the fifth lens L5, and the total number of layers is five. A layer containing SiO ₂ as a material is provided at the air interface of the antireflection coat of the second lens L2 and the fourth lens L4, which are resin lenses, and the total number of layers is three.

Further, the band-pass filter BPF is disposed closest to the object, but instead, a band-pass filter BPF based on a parallel plate may be disposed between the fourth lens L4 and the fifth lens L5. Cmax in that case is 22.434 degrees.

Next, a numerical example in which specific numerical values of the lens optical system of the third example are applied will be described.
Table 9 is a table of specifications of the lens optical system of the third example.
(Table 9)
f 30.117
Fno 1.205
ω 12.000
Y 6.402
TL 49.634

Table 10 shows the surface data of the lens optical system. The first and second surfaces in Table 10 are bandpass filters BPF, and the thirteenth and fourteenth surfaces are surface data of the cover glass CG.
(Table 10)
Surface number r d Nd νd H
1 0.0000 1.100 1.50892 64.20 12.653
2 STOP 0.0000 0.200 12.500
3 32.9134 6.000 1.97213 29.13 13.123
4 -251.5358 0.010 12.794
5 ASP 42.4007 6.010 1.63641 20.37 12.484
6 ASP 72.4349 1.000 11.761
7 -83.8728 1.770 1.50892 64.20 11.408
8 18.9014 9.359 10.153
9 ASP -8.9611 4.550 1.63641 20.37 10.108
10 ASP -12.2658 0.200 11.264
11 27.2871 6.300 1.97213 29.13 12.772
12 -136.7202 12.207 12.363
13 0.0000 0.500 1.50892 64.17 6.726
14 0.0000 0.429 6.587

Table 11 shows the aspheric coefficient of each aspheric surface.
(Table 11)
5 6 9 10
Κ 8.9071 29.6816 -0.8880 -0.1389
A4 -4.7241E-05 -9.2351E-05 -7.0871E-05 4.0736E-05
A6 -1.5948E-07 -1.6631E-07 6.0194E-07 7.0414E-07
A8 2.8786E-10 1.3382E-09 1.4888E-08 1.6059E-09
A10 -2.9428E-12 -7.7403E-12 -3.0849E-11 2.2175E-11
A12 -3.4823E-15 3.1449E-14 -3.0183E-13 -8.5723E-14

Table 12 shows the focal length of each lens at a wavelength of 905 nm.
(Table 12)
Lens surface number Focal length
L1 3-4 30.254
L2 5-6 149.080
L3 7-8 -30.135
L4 9-10 -112.507
L5 11-12 23.851

FIG. 9 shows a longitudinal aberration diagram of the lens optical system of the third example.
The back focus “fb” at the wavelength λ = 905 nm of the lens optical system is as follows.
fb = 12.9669 (mm)

Table 17 shows values of the conditional expressions (1) to (9) of the third embodiment.

(Fourth embodiment)
FIG. 10 is a lens cross-sectional view illustrating a lens configuration of a lens optical system according to Example 4. The lens optical system of the second example includes, in order from the object side, a biconvex first lens L1 and a second lens L2 having a positive refractive power and an object-side convex meniscus and having aspheric surfaces on both surfaces. A third lens L3 having a negative refractive power and an object-side convex meniscus shape, a fourth lens L4 having a negative refractive power and an object-side concave meniscus, and a biconvex fifth lens L5. It is composed of A band-pass filter BPF is arranged on the object side of the lens L1 closest to the object. The aperture stop S is arranged on the image side of the band pass filter BPF closest to the object.

All lenses have an anti-reflection coating on the lens surface. The object side surface of the fifth lens L5 is provided with an antireflection coating in which the wavelength at which the reflectance becomes the smallest in the wavelength range of N ± 100 nm exists in the range of N ± 50 nm.
A layer containing MgF ₂ as a material is provided on the air interface of the antireflection coat on the object side surface of the fifth lens L5, and the total number of layers is five. A layer containing SiO ₂ as a material is provided on the air interface of the antireflection coat of the second lens L2 and the fourth lens L4, which are resin lenses, and the total number of layers is three.

Furthermore, in the lens optical system of the fourth embodiment, a band-pass filter BPF is disposed closest to the object side. Instead, a band whose base is a parallel flat plate between the fourth lens L4 and the fifth lens L5 is used. A pass filter BPF may be provided, in which case Cmax is 19.448 degrees.

Next, a numerical example in which specific numerical values of the lens optical system of the fourth example are applied will be described. Table 13 is a table of specifications of the lens optical system of the fourth example.
(Table 13)
f 30.049
Fno 1.200
ω 10.000
Y 5.297
TL 49.654

Table 14 shows the surface data of the lens optical system of the fourth example. The first and second surfaces in Table 14 are bandpass filters BPF, and the thirteenth and fourteenth surfaces are surface data of the cover glass CG.
(Table 14)
Surface number r d Nd νd H
1 0.0000 1.100 1.50892 64.20 12.627
2 STOP 0.0000 0.200 12.500
3 32.7400 6.000 1.97213 29.13 13.011
4 -234.0000 0.149 12.637
5 ASP 41.2130 6.010 1.63641 20.37 12.220
6 ASP 82.1802 1.000 11.434
7 -69.8000 1.770 1.50892 64.20 11.108
8 16.5500 9.126 9.676
9 ASP -8.8021 4.550 1.63641 20.37 9.644
10 ASP -11.4366 0.200 10.780
11 24.8000 6.300 1.97213 29.13 11.675
12 -800.0000 12.207 11.021
13 0.0000 0.500 1.50892 64.17 5.705
14 0.0000 0.542 5.568

Table 15 shows the aspheric coefficient of each aspheric surface.
(Table 15)
5 6 9 10
Κ 8.2203 37.8603 -0.9723 -0.1843
A4 -4.8824E-05 -9.0205E-05 -6.8785E-05 3.7490E-05
A6 -1.5712E-07 -1.3562E-07 5.2603E-07 9.9278E-07
A8 3.8830E-10 1.4792E-09 1.3172E-08 -1.3622E-09
A10 -2.8759E-12 -7.3932E-12 -4.6550E-11 1.0841E-11
A12 -5.8433E-15 2.1091E-14 -3.4978E-14 1.1639E-13

Table 16 shows the focal length of each lens at a wavelength of 905 nm.
(Table 16)
Lens surface number Focal length
L1 3-4 29.876
L2 5-6 122.894
L3 7-8 -26.107
L4 9-10 -182.876
L5 11-12 24.838

FIG. 11 shows a longitudinal aberration diagram of the lens optical system of the fourth example.
The back focus “fb” at the wavelength λ = 905 nm of the lens optical system of the fourth example is as follows.
fb = 13.0803 (mm)

Table 17 shows values of the conditional expressions (1) to (9) of the lens optical system of the fourth example.

Table 17 shows the values of the conditional expressions (1) to (9) of the lens optical system of the fourth embodiment in addition to the first to third embodiments.
(Table 17)
Example 1 Example 2 Example 3 Example 4
Conditional expression (1) fn / f -0.839 -0.784 -0.765 -0.813
Conditional expression (2) Y / f 0.212 0.213 0.213 0.176
Conditional expression (3) | fLp | / f 6.457 3.148 3.736 5.015
Conditional expression (4) (Crpf + Crpr) / (Crpf-Crpr) 0.119 0.002 0.357 0.271
Conditional expression (5): CrLf / f 1.001 0.987 1.093 1.090
Conditional expression (6) 1 / tan (| Bmax |) 0.837 0.730 0.754 0.899
Conditional expression (7) 1 / tan (| Cmax |) 4.706 4.706 4.706 5.674
Conditional expression (8) tan (D) 0.005 -0.003 -0.004 0.001
Conditional expression (9) 1 / tan (| Amin |) 1.139 1.245 0.787 0.727
fn -25.710 -24.192 -23.042 -24.424
f 30.658 30.869 30.117 30.049
Y 6.492 6.561 6.402 5.297
fLp 197.965 97.187 -112.507 150.704
Crpf 14.380 12.312 18.901 16.561
Crpr -11.329 -12.258 -8.961 -9.499
CrLf 30.702 30.466 32.913 32.761
| Bmax | 50.067 53.886 52.970 48.049
| Cmax | 11.996 11.996 11.996 9.996
D 0.309 -0.200 -0.252 0.059
| Amin | 41.272 38.765 51.810 53.986

(Imaging device of embodiment)
As illustrated in FIG. 12, the imaging apparatus 100 according to the embodiment includes a lens optical system 102 according to the present invention and a solid-state imaging device 104 disposed on an imaging plane IMG of the imaging optical system 102. The solid-state imaging device 104 has a cover glass CG. An image formed by the lens optical system 102 is converted into an image signal via the solid-state image sensor 104. The imaging signal is sent to a liquid crystal monitor (not shown) and displayed as an image.

BPF Bandpass filter IMG Image plane CG Cover glass S Aperture stop L1 First lens L2 Second lens L3 Third lens L4 Fourth lens L5 Fifth lens L6 Sixth lens 102 Lens optical system 104 Solid-state image sensor

Claims

In a lens optical system used only within a wavelength range of wavelength N ± 50 nm, the lens optical system has a band-pass filter that transmits only within a wavelength range of wavelength N ± 50 nm, and the lens optical system is negative. A lens optical system having at least one surface having a refractive power and satisfying the following conditional expression.
-2.00 <fn / f <-0.45 (1)
0.10 <Y / f <0.60 (2)
However,
fn: focal length at the wavelength Nnm of the surface having the largest negative refractive power among all surfaces of the lens optical system f: focal length Y at the wavelength Nnm of the lens optical system Y: maximum at the wavelength Nnm of the lens optical system Image height
The lens optical system according to claim 1, wherein the lens optical system has at least one resin lens Lp.
The lens optical system according to claim 2, wherein the resin lens Lp satisfies the following conditional expression.
1.5 <| fLp | / f <2000.0 (3)
However,
fLp: focal length at wavelength Nnm of the resin lens Lp having the largest refractive power
4. The lens optical system according to claim 1, wherein the lens optical system has at least one biconvex air lens, and satisfies the following conditional expression. 5.
-0.70 <(Crpf + Crpr) / (Crpf-Crpr) <0.70 (4)
However,
Crpf: radius of curvature of the object side surface of the biconvex air lens Crpr: radius of curvature of the image side surface of the biconvex air lens
The lens optical system according to any one of claims 1 to 4, wherein the lens optical system has a lens Lf having an object-side convex surface closest to the object side, and satisfies the following conditional expression. .
0.35 <CrLf / f (5)
However,
CrLf: radius of curvature of the object-side convex surface of the lens Lf
The lens optical system according to any one of claims 1 to 5, wherein the following conditional expression is satisfied.
0.50 <1 / tan (| Bmax |) <4.00 (6)
However,
Bmax: the maximum value of the angle between the normal to the lens surface and the incident light beam on all the lens surfaces included in the lens optical system
The lens optical system according to any one of claims 1 to 6, wherein the following conditional expression is satisfied.
1.90 <1 / tan (| Cmax |) <20.00 (7)
However,
Cmax: maximum value of the angle between the band-pass filter and the light beam incident on the band-pass filter
The lens optical system according to any one of claims 1 to 7, wherein the following conditional expression is satisfied.
-0.09 <tan (D) <0.27 (8)
However,
D: Angle on the meridional section formed by the principal ray of the most off-axis ray at a wavelength of N nm emitted from the most image-side surface of the lens optical system and incident on the image plane and a line parallel to the optical axis.
The lens optical system according to any one of claims 1 to 8, wherein the wavelength N is longer than 780 nm.
The lens optical system according to any one of claims 1 to 9, wherein the following conditional expression is satisfied.
0.10 <1 / tan (| Amin |) <1.35 (9)
However,
Amin: The minimum value of the angle between the tangent of the lens surface and the optical axis in all the lens surfaces included in the lens optical system.
An image pickup device for converting an optical image formed by the lens optical system into an electric signal is provided on an image side of the lens optical system according to any one of claims 1 to 10. Imaging device.