JP5585122B2 - Imaging lens, twin stereo camera and distance measuring device - Google Patents

Description

  The present invention relates to an imaging lens / twin stereo camera and a distance measuring device.

  A distance measuring device that performs distance measurement by triangulation using two cameras is known. Such a distance measuring device is intended to be implemented as a vehicle-mounted distance measuring device.

  “Two cameras” used in such a distance measuring device is called “stereo camera”, but when used for in-vehicle use, distance measurement from a short distance to a long distance and a field of view in the measurement range are possible. Is required to be wide.

In order to improve “distance detection accuracy at a long distance” with a stereo camera, it is necessary to increase the base length between two cameras or increase the focal length of the imaging lens. There is a problem that the distance measuring device itself is increased in size, and there is a problem that if the focal length of the imaging lens is increased, the angle of view becomes narrow and the measurement field of view becomes narrow.
As a distance measuring apparatus that solves this problem, a distance measuring apparatus that uses a camera apparatus (hereinafter referred to as “twin stereo camera”) that combines “two stereo cameras having different focal lengths” is known.
In the conventionally intended “distance measuring device using a twin stereo camera”, each set of stereo cameras constitutes one camera by “a combination of an imaging lens and an imaging device”, and constitutes one stereo camera. Since two cameras to be combined have different “focal lengths of the imaging lenses” and each camera requires an imaging device, as a whole, two pairs of imaging lenses having different focal lengths and four imaging devices are used. There is a problem that it is difficult to reduce the cost of the distance measuring device because it requires four and the most expensive image sensors.

  In order to deal with this problem, it has been proposed that each of the two cameras of the stereo camera “uses an imaging device in common for an imaging lens having a short focal length and an imaging lens having a long focal length”.

  That is, the imaging light flux of the imaging lens with a short focal length and the imaging light flux of the imaging lens with a long focal length are synthesized by an “optical path synthesis prism”, guided to the same light receiving element, and connected to this light receiving element. The image light flux is switched according to the length of the focal length.

  In this method, as the long-distance imaging lens, the back focus of the long-distance imaging lens is lengthened, and the optical path synthesis is performed by the optical path synthesis prism by the difference from the back focus of the short-distance imaging lens. . The long-distance imaging lens used in this method is required to be a bright lens with a large aperture while having a long back focus.

As an imaging lens that is structurally close to the imaging lens of the present invention, the one described in Patent Document 1 is known.
The imaging lens described in Patent Document 1 uses a small CCD as an imaging element, but has a small number of lens components, and in order to cut high-frequency components of light, a “crystal plate” is interposed between the imaging lens and the imaging element. The back focus length necessary for inserting a low-pass filter composed of, etc. ”.

  However, according to the embodiment specifically described in Patent Document 1, the back focus length is too short to arrange the “light path synthesis prism”, and FNO. : About 2.8, which is not always sufficient for the brightness required for an imaging lens having a long focal length of a twin stereo camera.

  The present invention has been made in view of the above-described circumstances, has a back focus length that enables use of an optical path combining prism in a twin stereo camera, and has FNO. : An object of the present invention is to realize an imaging lens capable of realizing a brightness of about 2.4 to 2.55.

  As illustrated in FIG. 1, the imaging lens of the present invention includes, in order from the object side, a first lens having a negative refractive power, a second lens having a positive refractive power, a diaphragm, and a third lens having a negative refractive power. The five-lens configuration includes a lens, a fourth lens having a positive refractive power, and a fifth lens having a positive refractive power, and the first lens and the second lens are cemented.

  The imaging lens according to claim 1 satisfies the following conditions.

That is, the focal length of the entire system: f, the back focus length: BF, the distance from the object side surface of the first lens to the image side surface of the lens located closest to the image plane: OL, the object side of the first lens The half-value of the effective optical diameter of the lens: H _L1 , the combined focal length of the first lens and the second lens: the common logarithm of the numerical value representing fL ₁₂ in mm: log | fL ₁₂ |
(1) 0.3 <(H _L1 / OL) · log | fL ₁₂ | <1.0
(2) 0.7 <Bf / f <1.0
(3) 11.30 <BF <15.70
Satisfied.
The condition (1) log in | _{fL 12} | is the combined focal length of the first lens and the second lens: While _{fL 12} is a common logarithm of a number expressed in units of mm, "combined focal length: the _{fL 12} “Numerical value expressed in mm” is a dimensionless numerical value without a unit, and log | fL ₁₂ | is also a dimensionless quantity.

“From the object side, in order from the object side, a first lens having a negative refractive power, a second lens having a positive refractive power, a diaphragm, a third lens having a negative refractive power, a fourth lens having a positive refractive power, and a positive lens The point that the first lens and the second lens are cemented in a five-lens configuration composed of a fifth lens having a refractive power of “is the same as in Example 2 of Patent Document 1.
The conditions (1) and (2) will be described. The condition (1) is a condition for ensuring lens performance, compactness, and brightness as an imaging lens. As will be described later with reference to the imaging lens, in the imaging lens according to the present invention, the composite focal length fL ₁₂ of the first lens and the second lens is allowed to have a “pretty large range” ranging from a positive value to a negative value. Therefore, the power of the cemented lens of the first lens and the second lens on the object side of the diaphragm can be positive or negative, and “log | fL ₁₂ |” in the condition (1) is combined focal length: within allowable range of fL ₁₂ to "slow monotonically change".

The parameter in the condition (1): (H _L1 / OL) is a ratio of the total length of the imaging lens to the effective diameter of the first lens. 1 lens) is “larger than the total lens length”, which leads to an increase in the size of the imaging lens.

In addition, an increase in “log | fL ₁₂ |” means that the combined focal length of the first lens and the second lens increases and the combined power decreases. When the power of the cemented lens is reduced, “the radius of curvature of the lens surfaces of the first lens and the second lens is increased and the effective diameters of the first lens and the second lens are increased”, leading to an increase in the size of the imaging lens.

  Further, if the combined power of the first lens and the second lens is small, it is difficult to obtain a bright lens even if the lens diameter is large.

That is, if the parameter ((H _L1 / OL) · log | fL ₁₂ |) of the condition (1) becomes large and exceeds the upper limit of 1.0, the imaging lens becomes large and sufficient brightness cannot be realized.

Conversely, when the parameter (1) of the condition (1): (H _L1 / OL) · log | fL ₁₂ | There is a tendency that the combined focal length of the lens is reduced, the combined power is increased, the radius of curvature of the lens surfaces of the first lens and the 21st lens is reduced, and spherical aberration is increased.

  If the lower limit of condition (1) is exceeded, it will be difficult to achieve the performance required for the imaging lens.

Condition (2) is a condition for ensuring the back focus length and performance with respect to the focal length required for the imaging lens for long focal length.
When the lower limit of the condition (2) is exceeded, it becomes difficult to install a “prism for optical path synthesis” as the back focus length, and when the upper limit is exceeded, coma aberration increases.

In the imaging lens according to claim 1 , FNo is
2.4 <FNo <2.55
(Claim 2).

  The 1st thru | or 5th lens in the imaging lens of Claim 1 or 2 can be the following shapes (Claim 3).

  That is, the first lens is “a meniscus shape with a convex surface facing the object side”, and the second lens is “a shape where the object side lens surface is convex on the object side and has a stronger curvature than the image side lens surface”, The third lens has a “biconcave shape”, the fourth lens “the image side lens surface has a convex shape on the image side and has a stronger curvature than the object side lens surface”, and the fifth lens has an “object side lens surface , A shape that is convex on the object side and has a stronger curvature than the image side lens surface.

  The 1st thru | or 5th lens in the imaging lens of Claim 1 or 2 can also be the following shapes (Claim 4).

  That is, the first lens is “biconvex”, the second lens is “biconvex”, and the third lens is “the object side lens surface is convex toward the object side, and the image side lens surface is the object side lens surface”. The shape of the fourth lens is “biconvex shape”, the fifth lens is “the shape of the object side lens surface is convex on the object side, and has a stronger curvature than the image side lens surface”. Can be.

  The 1st thru | or 5th lens in the imaging lens of Claim 1 or 2 can also be the following shapes (Claim 5).

  That is, the first lens is “a meniscus shape with a convex surface facing the object side, and the image side lens surface has a stronger curvature than the object side lens surface”, and the second lens is “the object side lens surface is on the object side. Convex shape with a stronger curvature than the image side lens surface ”, the third lens is“ biconvex shape ”, the fourth lens is“ biconvex shape ”, and the fifth lens is“ biconvex shape ”. it can.

  The 1st thru | or 5th lens in the imaging lens of Claim 1 or 2 can also be the following shapes (Claim 6).

  That is, the first lens is “a meniscus shape with a convex surface facing the object side, and the image side lens surface has a stronger curvature than the object side lens surface”, the second lens is “biconvex shape”, and the third lens is “Bi-concave shape”, the fourth lens “the image side lens surface is convex on the image side and has a curvature that is stronger than the object side lens surface”, and the image side lens surface of the fifth lens is “on the image side “A shape that is formed in a convex shape and has a curvature stronger than that of the object-side lens surface”.

  The 1st thru | or 5th lens in the imaging lens of Claim 1 or 2 can be the following shapes (Claim 7).

  That is, the first lens is “a meniscus shape with a convex surface facing the object side, and the image side lens surface has a stronger curvature than the object side lens surface”, and the second lens is “the object side lens surface is on the object side. Convex shape with a curvature that is stronger than the image side lens surface ”, the third lens is“ biconvex shape ”, the fourth lens is“ biconvex shape ”, and the fifth lens is“ object side lens surface is object side A convex shape, and a shape having a stronger curvature than the image side lens surface.

  The 1st thru | or 5th lens in the imaging lens of Claim 1 or 2 can be the following shapes (Claim 8).

  That is, the first lens is “a meniscus shape with a convex surface facing the object side, and the image side lens surface has a stronger curvature than the object side lens surface”, and the second lens is “the object side lens surface is on the object side. Convex shape with a stronger curvature than the image side lens surface ”, third lens“ bi-concave shape ”, fourth lens“ image side lens surface is convex on the image side, than object side lens surface The fifth lens can be “a shape having an object side lens surface that is convex on the object side and having a stronger curvature than the image side lens surface”.

  In the twin stereo camera of the present invention, the imaging light fluxes of the “short focal length imaging lens and long focal length imaging lens” constituting each of the two cameras are guided to the same imaging device by the optical path combining prism. An imaging lens according to any one of claims 1 to 8, wherein the imaging light beam for the light receiving element is switched according to the length of the focal length. Used. ”(Claim 9).

  A distance measuring device of the present invention is a distance measuring device having the twin stereo camera according to claim 9 (claim 10). This distance measuring device can be suitably used for in-vehicle use.

As described above, according to the present invention, a novel imaging lens, a twin stereo camera using the same, and a distance measuring device can be realized.
The imaging lens of the present invention has a back focus length sufficient to adapt to the use of the optical path combining prism in the twin stereo camera, and is bright and has good optical performance, as will be apparent from the embodiments described later.

  Therefore, by using the imaging lens of the present invention as a lens having a long focal length of a twin stereo camera, it is possible to satisfactorily measure the distance to a distant place.

It is a figure for demonstrating Example 1 of an imaging lens. FIG. 6 is an aberration diagram of Example 1 of the imaging lens. FIG. 6 is an aberration diagram of Example 1 of the imaging lens. It is a figure for demonstrating Example 2 of an imaging lens. It is an aberration diagram of Example 2 of the imaging lens. It is an aberration diagram of Example 2 of the imaging lens. It is a figure for demonstrating Example 3 of an imaging lens. It is an aberration diagram of Example 3 of the imaging lens. It is an aberration diagram of Example 3 of the imaging lens. It is a figure for demonstrating Example 4 of an imaging lens. It is an aberration diagram of Example 4 of the imaging lens. It is an aberration diagram of Example 4 of the imaging lens. It is a figure for demonstrating Example 5 of an imaging lens. It is an aberration diagram of Example 5 of the imaging lens. It is an aberration diagram of Example 5 of the imaging lens. It is a figure for demonstrating Example 6 of an imaging lens. FIG. 10 is an aberration diagram for Example 6 of the imaging lens. FIG. 10 is an aberration diagram for Example 6 of the imaging lens. It is a figure for demonstrating Example 7 of an imaging lens. It is an aberration diagram of Example 7 of the imaging lens. It is an aberration diagram of Example 7 of the imaging lens. It is a figure for demonstrating a twin stereo camera.

Hereinafter, embodiments will be described.
1 to 7 show seven examples of imaging lens embodiments.
The embodiments shown in these drawings show examples of an imaging lens described later. In order to avoid complications, a common reference numeral is used for these FIGS.

  That is, in (a) of FIG. 1 to FIG. 7 showing the lens configuration of the imaging lens, the left side of the drawing is the object side, the right side is the image side, and the first lens to the fifth lens are represented by reference numerals L1 to L5. A symbol S represents an “aperture”, and a symbol IS represents an “image plane”, that is, a light receiving surface of an image sensor.

  In each of the embodiments whose lens configurations are shown in FIGS. 1A to 7A, the first lens L1 having a negative refractive power and the positive refraction in order from the object side (left side in the figure). The first lens includes a second lens L2 having a power, a diaphragm S, a third lens L3 having a negative refractive power, a fourth lens L4 having a positive refractive power, and a fifth lens L5 having a positive refractive power. L1 and the second lens L2 are cemented.

Further, as shown in the embodiments described later, these imaging lenses are all lenses that are located closest to the image plane from the object side surface of the first lens, with the focal length of the entire system: f, the back focus length: BF, and the like. The distance to the image side surface of the lens is OL, the half of the effective optical diameter on the object side of the first lens is HL1, and the combined focal length of the first lens and the second lens is a dimensionless numerical value in which fL12 is expressed in mm. Common logarithm: log | fL12 |
(1) 0.3 <(HL1 / OL) · log | fL12 | <1.0
(2) 0.7 <Bf / f <1.0
(3) 11.30 <BF <15.70
Satisfied.

These imaging lenses are all FNO. But
2.4 <FNO. <2.55
It is in the range.

  In the imaging lens shown in FIG. 1A, the first lens L1 has a “meniscus shape with a convex surface facing the object side (negative meniscus shape)”, and the second lens L2 has a “object side lens surface convex on the object side. The shape is a shape having a curvature stronger than the image side lens surface (positive meniscus shape) ”, the third lens L3 is“ biconcave ”, and the fourth lens L4 is“ the image side lens surface is on the image side ” The fifth lens L5 has a convex shape and a curvature having a stronger curvature than the object side lens surface (biconvex shape). The fifth lens L5 has a "object side lens surface convex toward the object side and stronger than the image side lens surface. “Shape with curvature (biconvex shape)”.

  In the imaging lens shown in FIG. 2A, the first lens L1 has a “biconvex shape”, the second lens L2 has a “biconvex shape”, and the third lens L3 has an “object side lens surface facing the object side”. Convex shape, image side lens surface having a stronger curvature than object side lens surface (negative meniscus shape), fourth lens L4 is “biconvex shape”, and fifth lens L5 is “object side lens surface is A shape that is convex on the object side and has a stronger curvature than the image side lens surface (positive meniscus shape) ”.

  In the imaging lens shown in FIG. 3A, the first lens L1 is “a meniscus shape having a convex surface facing the object side, and the image side lens surface has a stronger curvature than the object side lens surface (negative meniscus shape)”. The second lens L2 is “a shape in which the object side lens surface has a convex shape on the object side and has a stronger curvature than the image side lens surface (positive meniscus shape)”, and the third lens L3 has a “biconcave shape”. The fourth lens L4 has a “biconvex shape”, and the fifth lens L5 has a “biconvex shape”.

  In the imaging lens shown in FIG. 4A, the first lens L1 is “a meniscus shape having a convex surface facing the object side, and the image side lens surface has a stronger curvature than the object side lens surface (negative meniscus shape)”. The second lens L2 is “biconvex shape”, the third lens L3 is “biconcave shape”, and the fourth lens L4 is “the image side lens surface is convex toward the image side, and has a stronger curvature than the object side lens surface. The fifth lens L5 is “a shape in which the image side lens surface is convex to the image side and has a curvature that is stronger than the object side lens surface (positive meniscus shape)”. It is.

  In the imaging lens shown in FIG. 5A, the first lens L1 is “a meniscus shape having a convex surface directed toward the object side, and the image side lens surface has a stronger curvature than the object side lens surface (negative meniscus shape)”. The second lens L2 is “a shape in which the object side lens surface has a convex shape on the object side and has a stronger curvature than the image side lens surface (positive meniscus shape)”, and the third lens L3 has a “biconcave shape”. The fourth lens L4 has a “biconvex shape”, and the fifth lens L5 has a “shape in which the object-side lens surface is convex on the object side and has a stronger curvature than the image-side lens surface (biconvex shape)”.

  In the imaging lens shown in FIG. 6A, the first lens L1 is “a meniscus shape having a convex surface facing the object side, and the image side lens surface has a curvature stronger than the object side lens surface (negative meniscus shape)”. The second lens L2 is “a shape in which the object side lens surface is convex toward the object side and has a curvature that is stronger than the image side lens surface (biconvex shape)”, and the third lens L3 is “biconcave shape”. The fourth lens L4 is “a shape on which the image side lens surface is convex on the image side and has a curvature that is stronger than the object side lens surface (positive meniscus shape)”, and the fifth lens L5 is “the object side lens surface is on the object side The shape is a convex shape and has a stronger curvature than the image side lens surface (positive meniscus shape).

  In the imaging lens shown in FIG. 7A, the first lens L1 has a “biconvex shape”, the second lens L2 has a “biconvex shape”, and the third lens L3 has an “object side lens surface convex to the object side”. The shape is such that the image side lens surface has a stronger curvature than the object side lens surface (negative meniscus shape) ”, the fourth lens L4 is“ biconvex shape ”, and the fifth lens L5 is“ object side lens surface is A shape that is convex on the object side and has a stronger curvature than the image side lens surface (positive meniscus shape) ”.

  The lens shown in FIG. 7A is the same type as that shown in FIG.

  FIG. 8 is a diagram for explaining a twin stereo camera. FIG. 8A shows a state in which distance measurement is performed by well-known triangulation using two cameras 8-1 and 8-2. .

  FIG. 8B is a diagram for explaining the configuration of the camera 8-1.

  The camera has a short focal length lens LS as a short distance lens and a long focal length lens LL as a long distance lens. The lenses LS and L1 are arranged as close as possible to each other with the optical axes parallel.

  The upper side of FIG. 8B is the object side. On the image side of the lenses LS and LL, a prism PR for “optical path synthesis” is provided close to the lenses LS and LL.

The prism PR has a reflection film RS and a polarization reflection film PRS.
When a short-distance imaging light beam incident on the short focal length lens LS along the optical axis direction (shown by a solid line) is incident on the polarization reflection film PRS, only the P-polarized component in the imaging light beam is the polarization reflection film PRS. Transparent.

  A long-distance imaging light beam incident on the lens LL having a long focal length along the optical axis direction (shown by a broken line) is reflected by the reflection film RS and enters the polarization reflection film PRS. Only the component is reflected by the polarization reflection film PRS.

  Therefore, the P-polarized component of the short-distance imaging light beam and the S component of the long-distance imaging light beam are combined in the optical path and enter the analyzer PS. By aligning the polarization direction of the analyzer PS with the “P-polarized component of the short-distance imaging light beam”, only the short-distance imaging light beam can be imaged on the image sensor AS.

  In addition, by switching the polarization direction of the analyzer PS by 90 degrees to match the S polarization component of the long-distance imaging light beam, only the long-distance imaging light beam can be imaged on the image sensor AS. it can.

  Therefore, a long-distance target object can be imaged using the long-distance lens LL, and a short-distance target object can be imaged using the short-distance lens LS, and “distance measurement by triangulation” is performed for both long-distance and short-distance. It can be performed well.

  However, the image-side optical path on the image side of the long-distance lens LL is longer than the image-form optical path on the image side of the short-distance lens LS by the distance between the reflective film RS and the polarizing reflective film PRS of the prism PR. Therefore, the back focus length of the lens LL needs to be sufficiently long.

  Hereinafter, seven specific examples of the imaging lens will be described.

  In each embodiment, the focal length is represented by “f”, the F number is represented by “FNo”, the half angle of view is represented by “A”, and the back focus is represented by “BF”. The unit of the quantity having the length dimension is “mm”.

In each table showing the specifications, “No” is a surface counted from the object side and includes the surface of the diaphragm. “R” is the radius of curvature, “D” is the surface separation, “Nd” is the refractive index of the lens material with respect to the d-line, “Vd” is the Abbe number, and “Sd” is “half the optical effective diameter of the lens”. Sd on the object side surface of the first lens is “H _L1 ”.

"Example 1"
Example 1 has the lens configuration shown in FIG.
f = 16.01 FNo = 2.4 2A = 15.7 ° Bf = 11.36
The specifications of Example 1 are shown in Table 1.

The parameter values of the conditional expression are as follows.
Condition (1) H _L1 / OL·log | fL ₁₂ | = 0.328
Condition (2) Bf / f = 0.7096
A “lateral aberration diagram” relating to Example 1 is shown in FIG. 1B, and a “longitudinal aberration diagram” is shown in FIG.
In addition, about the numerical value of condition (3), and the value of FNo, it describes in the table | surface which shows a specification. The same applies to the following embodiments.

  In these aberration diagrams, the aberration curve “A1” is for light with a wavelength of 587.5618 nm, and the aberration curve “A2” is for light with a wavelength: 435.8343 nm. The same applies to the aberration diagrams of other examples described below.

  Example 1 is an example closest to the lower limits of the conditions (1) and (2) among all examples.

"Example 2"
Example 2 has the lens configuration shown in FIG.
f = 16.01 FNo = 2.4 2A = 16.6 ° Bf = 13.93
The specifications of Example 2 are shown in Table 2.

The parameter values of the conditional expression are as follows.
Condition (1) H _L1 / OL·log | fL ₁₂ | = 0.744
Condition (2) Bf / f = 0.8702
A “lateral aberration diagram” relating to Example 2 is shown in FIG. 2B, and a “longitudinal aberration diagram” is shown in FIG.

"Example 3"
Example 3 has the lens configuration shown in FIG.
F = 16.11 Fno = 2.4 2A = 18.5 ° Bf = 12.08
The specifications of Example 3 are shown in Table 3.

The parameter values of the conditional expression are as follows.
Condition (1) H _L1 / OL·log | fL ₁₂ | = 0.444
Condition (2) Bf / f = 0.7496
The “lateral aberration diagram” regarding Example 3 is shown in FIG. 3B, and the “longitudinal aberration diagram” is shown in FIG.

Example 4
Example 4 has the lens configuration shown in FIG.
f = 16.00 FNo = 2.55 2A = 16.5 ° Bf = 12.54
The specifications of Example 4 are shown in Table 4.

The parameter values of the conditional expression are as follows.
Condition (1) H _L1 / OL·log | fL ₁₂ | = 0.380
Condition (2) Bf / f = 0.7840
A “lateral aberration diagram” regarding Example 4 is shown in FIG. 4B, and a “longitudinal aberration diagram” is shown in FIG. 4C.

"Example 5"
Example 5 has the lens configuration shown in FIG.
f = 16.01 FNo = 2.5 2A = 14.9 ° Bf = 12.05
The specifications of Example 5 are shown in Table 5.

The parameter values of the conditional expression are as follows.
Condition (1) H _L1 / OL·log | fL ₁₂ | = 0.411
Condition (2) Bf / f = 0.7525
A “lateral aberration diagram” regarding Example 5 is shown in FIG. 5B, and a “longitudinal aberration diagram” is shown in FIG. 5C.

"Example 6"
Example 6 has the lens configuration shown in FIG.
f = 16.01 FNo = 2.4 2A = 15.0 ° Bf = 12.06
The specifications of Example 6 are shown in Table 6.

The parameter values of the conditional expression are as follows.
Condition (1) H _L1 / OL·log | fL ₁₂ | = 0.346
Condition (2) Bf / f = 0.7530
A “lateral aberration diagram” regarding Example 6 is shown in FIG. 6B, and a “longitudinal aberration diagram” is shown in FIG. 6C.

"Example 7"
Example 7 has the lens configuration shown in FIG.
f = 16.01 FNo = 2.4 2A = 15.9 ° Bf = 15.68
The specifications of Example 7 are shown in Table 7.

  The parameter values of the conditional expression are as follows.

Condition (1) H _L1 / OL·log | fL ₁₂ | = 0.9053
Condition (2) Bf / f = 0.7996
A “lateral aberration diagram” regarding Example 7 is shown in FIG. 7B, and a “longitudinal aberration diagram” is shown in FIG. 7C.

  Example 7 is an example closest to the upper limits of the conditions (1) and (2) among all the examples.

Each of Examples 1 to 7 has good performance as shown in the aberration diagrams, and realizes a back focus length sufficient to arrange the optical path combining prism PR shown in FIG.
Further, as shown in the ray diagrams of the respective examples, each of the examples shows very good “telecentricity” on the image side.
Incidentally, the values of “H _L1 / OL” and “fL ₁₂ ” in the parameters of the condition (1) are as follows for each example.
A = H _L1 / OL, B = fL ₁₂

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7
A 0.3351 0.2955 0.3689 0.3748 0.3190 0.3370 0.3191
B 9.55 329.20 15.99 10.34 19.35 10.64 -687.14

L1 first lens
L2 second lens
S Aperture
L3 3rd lens
L4 4th lens
L5 5th lens

Japanese Patent No. 4239248

Claims (10)

In order from the object side, a first lens having negative refractive power, a second lens having positive refractive power, a diaphragm, a third lens having negative refractive power, a fourth lens having positive refractive power, and positive refraction A fifth lens having power,
The first lens and the second lens are cemented,
Focal length of the entire system: f, back focus length: BF, distance from the object side surface of the first lens to the image side surface of the lens located closest to the image plane: OL, optics on the object side of the first lens Half-value of effective diameter: H _L1 , combined focal length of first lens and second lens: common dimension logarithm of non-dimensional numerical value in which fL ₁₂ is expressed in mm: log | fL ₁₂ |
(1) 0.3 <(H _L1 / OL) · log | fL ₁₂ | <1.0
(2) 0.7 <Bf / f <1.0
(3) 11.30 <BF <15.70
An imaging lens characterized by satisfying The imaging lens according to claim 1,
FNo. But,
2.4 <FNo. <2.55
An imaging lens characterized by being in the range. The imaging lens according to claim 1 or 2,
The first lens has a meniscus shape with a convex surface facing the object side,
The second lens has a shape in which the object side lens surface is convex on the object side and has a stronger curvature than the image side lens surface,
The third lens is a biconcave shape,
The fourth lens has a shape in which the image side lens surface is convex on the image side and has a stronger curvature than the object side lens surface,
An imaging lens, wherein the fifth lens has an object side lens surface that is convex toward the object side and has a stronger curvature than the image side lens surface. The imaging lens according to claim 1 or 2,
The first lens is a biconcave shape,
The second lens is biconvex,
The third lens has a shape in which the object side lens surface has a convex shape on the object side, and the image side lens surface has a stronger curvature than the object side lens surface,
The fourth lens is a biconvex shape,
An imaging lens, wherein the fifth lens has an object side lens surface that is convex toward the object side and has a stronger curvature than the image side lens surface. The imaging lens according to claim 1 or 2,
The first lens has a meniscus shape with a convex surface facing the object side, and the image side lens surface has a stronger curvature than the object side lens surface,
The second lens has a shape in which the object side lens surface is convex on the object side and has a stronger curvature than the image side lens surface,
The third lens is a biconcave shape,
The fourth lens is a biconvex shape,
An imaging lens, wherein the fifth lens has a biconvex shape. The imaging lens according to claim 1 or 2,
The first lens has a meniscus shape with a convex surface facing the object side, and the image side lens surface has a stronger curvature than the object side lens surface,
The second lens is biconvex,
The third lens is a biconcave shape,
The fourth lens has a shape in which the image side lens surface is convex on the image side and has a stronger curvature than the object side lens surface,
The fifth lens has an image-side lens surface formed in a convex shape on the image side and a shape having a stronger curvature than the object-side lens surface. The imaging lens according to claim 1 or 2,
The first lens has a meniscus shape with a convex surface facing the object side, and the image side lens surface has a stronger curvature than the object side lens surface,
The second lens has a shape in which the object side lens surface is convex on the object side and has a stronger curvature than the image side lens surface,
The third lens is a biconcave shape,
The fourth lens is a biconvex shape,
An imaging lens, wherein the fifth lens has an object side lens surface that is convex toward the object side and has a stronger curvature than the image side lens surface. The imaging lens according to claim 1 or 2,
The first lens has a meniscus shape with a convex surface facing the object side, and the image side lens surface has a stronger curvature than the object side lens surface,
The second lens has a shape in which the object side lens surface is convex on the object side and has a stronger curvature than the image side lens surface,
The third lens is a biconcave shape,
The fourth lens has a shape in which the image side lens surface is convex on the image side and has a stronger curvature than the object side lens surface,
An imaging lens, wherein the fifth lens has an object side lens surface that is convex toward the object side and has a stronger curvature than the image side lens surface. In the two cameras constituting the stereo camera, the imaging light flux of the short focal length imaging lens and the long focal length imaging lens is guided to the same imaging device by the optical path combining prism, and the imaging light flux for the light receiving device In a twin stereo camera that is switched according to the length of the focal length,
A twin stereo camera, wherein the imaging lens according to any one of claims 1 to 8 is used as an imaging lens having a long focal length.   A distance measuring device having the twin stereo camera according to claim 9.

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