JP7267115B2 - Optical lens system and imaging device - Google Patents

Description

The present invention relates to an optical lens system and an imaging device.

In recent years, the application of wide-angle lenses installed in cars has changed from viewing to sensing. Sensing requires the resolution necessary for image analysis, so high-resolution images that support megapixels are in demand. A wide angle of view is also required.

In this way, in-vehicle imaging devices are required to capture images of distant objects in the traveling direction with high resolution and images of nearby objects at a wide angle. Furthermore, a bright optical system is required. Compactness is also required particularly in imaging lens systems for vehicle-mounted cameras.

For example, in Patent Document 1, a wide-angle optical system and a telephoto optical system arranged so that the optical axes are orthogonal to each other are switched by a mirror, and an optical image by either optical system is formed on a common imaging device. An imaging device is described.

JP 2009-122379 A

However, the imaging apparatus of Patent Document 1 uses two types of lenses, a telephoto optical system for long-distance imaging and a wide-angle optical system for short-distance imaging, which increases the size of the unit and increases the cost. .

As described above, in the conventional optical lens system, there is a problem that it is impossible to realize an optical lens system and an imaging device having both the characteristics of a telephoto lens and a wide-angle lens and having a small diameter of the first lens.

The optical lens system of one embodiment includes, in order from the object side to the image side, a first lens having negative power, a convex surface on the object side and a concave surface on the image side, and a concave surface on the object side. a second lens, an aperture, a third lens having positive power and having convex surfaces on the object side and the image side, a fourth lens having negative power and having a concave surface on the image side, and a fifth lens having a convex surface;
At least the object-side surface shape of the first lens is a curved surface shape having an inflection point,
The focal length of the entire optical lens system is F, the focal length of the first lens is FL1, and the distance from the intersection of the object-side surface of the first lens with the optical axis to the position of the stop on the optical axis is When L1-STOP, the following formulas (1) and (2) are satisfied.
0.3<F/(L1-STOP)<0.6 (1)
-2.0<FL1/F<-1.5 (2)

Preferably, in the optical lens system of one embodiment, the second lens may have a concave surface on the object side and a convex surface on the image side.

Preferably, the optical lens system of one embodiment may satisfy the following formula (3), where Φ1 is the surface diameter of the first lens and L is the optical total length of the optical lens system.
Φ1/L<0.5 (3)

An imaging apparatus according to one embodiment includes any one of the optical lens systems described above, and an imaging device arranged at a focal position of the optical lens system.

ADVANTAGE OF THE INVENTION According to this invention, the optical lens system and imaging device which have the characteristic of a telephoto lens and a wide-angle lens and whose diameter of a 1st lens is small can be provided.

1 is a cross-sectional view of an optical lens system according to Example 1; FIG. It is a figure explaining the surface diameter of a 1st lens. FIG. 4 is a spherical aberration diagram (longitudinal aberration diagram), a field curvature diagram, and a distortion aberration diagram in the optical lens system of Example 1. FIG. FIG. 8 is a cross-sectional view of an optical lens system according to Example 2; FIG. 10 is a spherical aberration diagram (longitudinal aberration diagram), a field curvature diagram, and a distortion aberration diagram in the optical lens system of Example 2; FIG. 11 is a cross-sectional view of an optical lens system according to Example 3; FIG. 10 is a spherical aberration diagram (longitudinal aberration diagram), a field curvature diagram, and a distortion aberration diagram in the optical lens system of Example 3. FIG. FIG. 11 is a cross-sectional view of an optical lens system according to Example 4; FIG. 10 is a spherical aberration diagram (longitudinal aberration diagram), a field curvature diagram, and a distortion aberration diagram in the optical lens system of Example 4. FIG. 10 is a cross-sectional view of an imaging device according to Embodiment 2; FIG.

Embodiment 1
BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First Embodiment: Optical Lens System FIG. 1 is a cross-sectional view of an optical lens system 11 according to a first embodiment. In FIG. 1, the optical lens system 11 includes, in order from the object side to the image side, a first lens L1 having negative power, a convex surface on the object side and a concave surface on the image side, and a concave surface on the object side. a second lens L2 having a stop STOP, a third lens L3 having positive power and having convex surfaces on the object side and the image side, and a fourth lens having negative power and having a concave surface on the image side L4 and a fifth lens L5 having a convex surface on the object side. Further, the optical lens system 11 may include a wavelength filter glass and a cover glass (not shown) between the image-side lens surface S11 of the fifth lens L5 and the imaging plane IMG.

The first lens L1 is a lens with negative power. The object-side lens surface S1 of the first lens L1 has a convex aspherical surface that protrudes toward the object side. Moreover, at least the object-side lens surface S1 of the first lens L1 preferably has a curved surface shape having an inflection point. The image-side lens surface S2 of the first lens L1 has a concave aspherical surface that is recessed toward the object side. Further, the image-side lens surface S2 of the first lens L1 may also have a curved shape having an inflection point. Here, the curved surface shape having an inflection point means a curved surface shape having a portion (inflection point) where the inclination of the tangent line contacting the lens surface switches from increasing to decreasing .

The second lens L2 is a lens with positive power. The object-side lens surface S3 of the second lens L2 has a concave curved surface portion that is depressed toward the image side. The image-side lens surface S4 of the second lens L2 has a convex curved surface portion that protrudes toward the image side. Note that the object-side lens surface S3 and the image-side lens surface S4 of the second lens L2 may be curved surfaces having an inflection point.

Aperture STOP adjusts the amount of light passing through. For example, the diaphragm STOP is preferably plate-shaped with holes.

The third lens L3 is a lens with positive power. The object-side lens surface S6 of the third lens L3 has a convex aspherical surface that protrudes toward the object side. The image-side lens surface S7 of the third lens L3 has a convex aspherical surface that protrudes toward the image side. Note that the object-side lens surface S6 and the image-side lens surface S7 of the third lens L3 may be curved surfaces having an inflection point.

The fourth lens L4 is a lens with negative power. The object-side lens surface S8 of the fourth lens L4 has a convex shape that protrudes toward the object side or a concave shape that is recessed toward the image side. The image-side lens surface S9 of the fourth lens L4 has a concave curved surface shape that is depressed toward the object side. Note that the object-side lens surface S8 and the image-side lens surface S9 of the fourth lens L4 may be curved surfaces having an inflection point.

The fifth lens L5 is a lens with positive power. The object-side lens surface S10 of the fifth lens L5 has a convex aspherical surface protruding toward the object side. The image-side lens surface S11 of the fifth lens L5 has a concave aspherical surface recessed toward the object side or a convex aspherical surface protruding toward the image side. Note that the object-side lens surface S10 and the image-side lens surface S11 of the fifth lens L5 may be curved surfaces having an inflection point.

Further, the focal length of the entire optical lens system 11 is F, and the focal length of the first lens L1 is FL1. is L1-STOP (mm), the optical lens system 11 satisfies the following formulas (1) and (2).
0.3<F/(L1-STOP)<0.6 (1)
-2.0<FL1/F<-1.5 (2)

When the optical lens system 11 satisfies the above formulas (1) and (2), the diameter of the first lens L1 can be made relatively small while widening the angle of view of the optical lens system 11 . Specifically, when the value of F/(L1-STOP) is 0.3 or less, the diameter of the first lens L1 becomes large. On the other hand, when the value of F/(L1-STOP) is 0.6 or more, sufficient resolution performance of the optical lens system 11 cannot be obtained. Further, when the value of FL1/F is −2.0 or less, the diameter of the first lens L1 becomes large. On the other hand, when the value of FL1/F is -1.5 or more, sufficient resolution performance of the optical lens system 11 cannot be obtained.

Further, since at least the object-side lens surface S1 of the first lens L1 has a curved surface shape having an inflection point, the imaging magnification of the central portion (low image height position) and the peripheral portion (high image height position) can be easily controlled to change the distance, and it becomes easy to achieve both a sensing function such as a long-distance distance measurement function and a short-distance wide-range imaging function.

Further, the second lens L2 has a concave surface on the object side, so that a light beam spread at a wide angle can be incident on the stop STOP at an angle close to parallel. As a result, the distance (L1-STOP) from the intersection of the object-side surface S1 of the first lens L1 with the optical axis to the position of the stop STOP on the optical axis is shortened, that is, the diameter of the first lens L1 is decreased. while maintaining a wide angle of view.

Further, when the surface diameter of the first lens L1 is Φ1 and the optical total length of the optical lens system 11 is L, the optical lens system 11 preferably satisfies the following formula (3).
Φ1/L<0.5 (3)
Here, the surface diameter means the width on the object-side lens surface S1 of a light beam (a light beam) that can pass through the first lens L1, and the range in which the lens surface S1 is subjected to a predetermined processing such as antireflection treatment. means the diameter of Specifically, the surface diameter corresponds to Φ1 shown in FIG. In FIG. 2, the range of light beams that can pass through the first lens L1 is indicated by a chain double-dashed line.
Further, the angle of view of the optical lens system 11 means the angle at which extended lines of rays passing through the outermost diameter side of the bundle of rays incident on the object-side lens surface S1 of the first lens L1 intersect with each other. Specifically, the angle of view of the optical lens system 11 corresponds to the "angle of view" shown in FIG. The angle of view of the optical lens system 11 according to Embodiment 1 is preferably 110° or more.

Since the optical lens system 11 satisfies the above formula (3), the diameter of the first lens L1 can be made smaller while keeping the angle of view of the optical lens system 11 wide.

Next, an example corresponding to the optical lens system 11 of Embodiment 1 will be described with reference to the drawings.
(Example 1: Optical lens system)
The optical lens system 11 according to Example 1 has the configuration shown in FIG. Also, the first lens L1 to the fifth lens L5 are composed of glass lenses or plastic lenses. Characteristic data of the optical lens system 11 according to Example 1 will be described below.
First, Table 1 shows lens data of each lens surface of the optical lens system 11 according to the first embodiment. Table 1 presents, as lens data, the radius of curvature (mm) of each surface, the spacing between surfaces (mm), the refractive index at the d-line, and the Abbe number at the d-line. Here, the half angle of view of the optical lens system 11 is 67.5° and the F number is 1.6. Also, the refractive index at the d-line and the Abbe number at the d-line shown in Table 1 are values when the environmental temperature t (° C.), which is the temperature around the optical lens system 11, is 25 (° C.). Also, in Table 1, the surfaces marked with "*" are aspheric surfaces.

Further, the aspherical shapes adopted for the lens surfaces of the first lens L1, the third lens L3, and the fifth lens L5 are such that Y (h) is the amount of sag in the optical axis direction, c is the reciprocal of the radius of curvature, and c is the reciprocal of the radius of curvature. The height from the optical axis in the direction perpendicular to the axis is h, the conic coefficient is K, the 4th, 6th, 8th, 10th, 12th, 14th and 16th aspheric coefficients are A4, A6, respectively. A8, A10, A12, A14, and A16 are represented by the following formula (4). It should be noted that the meaning of each symbol and the formula expressing the aspheric surface shape are the same in the examples described later.

Table 2 shows the aspherical coefficients for defining the aspherical shapes of the lens surfaces of the first lens L1, the third lens L3, and the fifth lens L5 in the optical lens system 11 of Example 1. In Table 2, for example, "-7.3915E-01" means "-7.3915×10 ^-1 ".

Table 3 shows the F-number (Fno), the angle of view (Fov (°)), the optical length L (mm), and the object-side surface S1 of the first lens L1 of the optical lens system 11 according to Example 1. distance L1-STOP (mm) from the intersection with the optical axis to the position on the optical axis of the stop STOP, the focal length F (mm) of the entire optical lens system 11, the first lens L1 to the fifth lens L5 Focal lengths F1 to F5 (mm), surface diameter Φ1 (mm) of the first lens L1, values of F1/F, F2/F, F3/F, F4/F and F5/F, F/(L1-STOP) and the value of Φ1/L. The values shown in Table 3 are values when the wavelength of light is 555 nm and the environmental temperature t (°C) is 25 (°C).

3 shows a spherical aberration diagram (longitudinal aberration diagram), a field curvature diagram, and a distortion aberration diagram in the optical lens system 11 of Example 1. FIG. As shown in FIG. 3, the optical lens system 11 of Example 1 has a half angle of view of 67.5° and an F number of 1.6. Also, the curvature of field diagrams and the distortion diagrams of FIGS. 3B and 3C show simulation results with light rays having a wavelength of 555 nm. FIG. 3 shows a spherical aberration diagram (longitudinal aberration diagram), a field curvature diagram, and a distortion aberration diagram when the environmental temperature t (° C.) is 25 (° C.).

In the longitudinal aberration diagram of FIG. 3A, the horizontal axis indicates the position where the light beam intersects the optical axis, and the vertical axis indicates the height at the pupil diameter. As shown in the longitudinal aberration diagram of FIG. 3A, according to the optical lens system 11 of this embodiment, longitudinal aberrations at wavelengths of 486 nm, 587 nm, and 656 nm are well corrected. Therefore, the optical lens system 11 has a high resolution.

In the field curvature diagram of FIG. 3B, the horizontal axis indicates the distance in the optical axis direction, and the vertical axis indicates the image height (angle of view). In the curvature of field diagram of FIG. 3B, Sag indicates the curvature of field on the sagittal plane, and Tan indicates the curvature of field on the tangential plane. As shown in the curvature of field diagram of FIG. 3B, according to the optical lens system 11 of this embodiment, the curvature of field is well corrected. Therefore, the optical lens system 11 has a high resolution.

In the distortion diagram of FIG. 3C, the horizontal axis indicates the distortion amount (%) of the image, and the vertical axis indicates the image height (angle of view). As shown in the distortion diagram of FIG. 3C, according to the optical lens system 11 of this embodiment, the distortion is well corrected. Therefore, the optical lens system 11 has a high resolution.

As shown in Table 3, in Example 1, the value of F/(L1-STOP) is 0.524, and the optical lens system 11 of Example 1 satisfies the above formula (1). Further, as shown in Table 3, in Example 1, the value of F1/F is −1.743, and the optical lens system 11 of Example 1 satisfies the above formula (2). Therefore, as shown in Table 3, in Example 1, the lens diameter Φ1 of the first lens L1 is 10.504 mm, the optical total length L is 27.196 mm, and Φ1/L in Equation (3) is 0.386. , the ratio to the overall length is smaller than that of a normal wide-angle lens system mounted on an in-vehicle camera or the like. Further, in Example 1, since the lens surfaces of the first lens L1, the third lens L3, and the fifth lens L5 are aspherical, as shown in FIG. , 587 nm, and 656 nm longitudinal aberration, curvature of field, and distortion are well corrected. In other words, in the optical lens system 11 according to Example 1, high resolution is achieved at positions with high image heights (peripheral portions of the captured image).

(Example 2: Optical lens system)
FIG. 4 is a cross-sectional view of the optical lens system 11 according to the second embodiment. In FIG. 4, the same components as in FIG. 1 are denoted by the same reference numerals, and descriptions thereof are omitted. In FIG. 4, the optical lens system 11 according to Example 2 has, in order from the object side to the image side, a convex aspherical surface having a negative power and an inflection point on the object side. A first lens L1 having a concave aspherical surface on the side, a second lens L2 having positive power, a concave surface on the object side, and a convex surface on the image side, an aperture STOP, and a positive power. a third lens L3 having a convex aspheric surface on the object side and a convex aspheric surface on the image side; and a third lens L3 having negative power, a convex surface on the object side and a concave surface on the image side. and a fifth lens L5 having positive power, a convex aspherical surface on the object side, and a concave aspherical surface on the image side.
Also, the first lens L1 to the fifth lens L5 are composed of glass lenses or plastic lenses.

Characteristic data of the optical lens system 11 according to Example 2 will be described below.
First, Table 4 shows lens data of each lens surface of the optical lens system 11 according to the second embodiment. Since the items shown in Table 4 are the same as the items shown in Table 1, the description thereof is omitted.

Also, the aspherical shapes adopted for the lens surfaces of the first lens L1, the third lens L3, and the fifth lens L5 are represented by the above equation (4).
Table 5 shows the aspherical coefficients for defining the aspherical shapes of the lens surfaces of the first lens L1, the third lens L3, and the fifth lens L5 in the optical lens system 11 of Example 2.

Table 6 shows characteristic data of the optical lens system 11 according to Example 2. Since the items shown in Table 6 are the same as the items shown in Table 3, the description thereof is omitted.

5 shows a spherical aberration diagram (longitudinal aberration diagram), a field curvature diagram, and a distortion aberration diagram in the optical lens system 11 of Example 2. FIG. Description of each aberration diagram shown in FIG. 5 is omitted because it is the same as the description of FIG.

As shown in the longitudinal aberration diagram of FIG. 5A, according to the optical lens system 11 of this embodiment, longitudinal aberrations at wavelengths of 486 nm, 587 nm, and 656 nm are well corrected. Therefore, the optical lens system 11 has a high resolution.

As shown in the curvature of field diagram of FIG. 5B, according to the optical lens system 11 of this embodiment, the curvature of field is well corrected. Therefore, the optical lens system 11 has a high resolution.

As shown in the distortion aberration diagram of FIG. 5C, according to the optical lens system 11 of this embodiment, the distortion aberration is corrected satisfactorily. Therefore, the optical lens system 11 has a high resolution.

As shown in Table 6, in Example 2, the value of F/(L1-STOP) is 0.456, and the optical lens system 11 of Example 2 satisfies the above formula (1). Further, as shown in Table 6, in Example 2, the value of F1/F is -1.706, and the optical lens system 11 of Example 2 satisfies the above formula (2). Therefore, as shown in Table 6, in Example 2, the lens diameter Φ1 of the first lens L1 is 11.848 mm, the optical total length L is 28.087 mm, and Φ1/L in Equation (3) is 0.422. , the ratio to the overall length is smaller than that of a normal wide-angle lens system mounted on an in-vehicle camera or the like. Further, in Example 2, since the lens surfaces of the first lens L1, the third lens L3, and the fifth lens L5 are aspherical, as shown in FIG. , 587 nm, and 656 nm longitudinal aberration, curvature of field, and distortion are well corrected. In other words, in the optical lens system 11 according to Example 2, high resolution is achieved at positions with high image heights (peripheral portions of the captured image).

(Example 3: Optical lens system)
FIG. 6 is a cross-sectional view of the optical lens system 11 according to Example 3. As shown in FIG. In FIG. 6, the same components as in FIGS. 1 and 4 are denoted by the same reference numerals, and descriptions thereof are omitted.
Also, the first lens L1 to the fifth lens L5 are composed of glass lenses or plastic lenses.

Characteristic data of the optical lens system 11 according to Example 3 will be described below.
First, Table 7 shows lens data of each lens surface of the optical lens system 11 according to the third embodiment. Since the items shown in Table 7 are the same as the items shown in Table 1, the description thereof is omitted.

Also, the aspherical shapes adopted for the lens surfaces of the first lens L1, the third lens L3, and the fifth lens L5 are represented by the above equation (4).
Table 8 shows the aspherical coefficients for defining the aspherical shapes of the lens surfaces of the first lens L1, the third lens L3, and the fifth lens L5 in the optical lens system 11 of Example 3.

Table 9 shows characteristic data of the optical lens system 11 according to Example 3. Since the items shown in Table 9 are the same as the items shown in Table 3, the description thereof is omitted.

7 shows a spherical aberration diagram (longitudinal aberration diagram), a field curvature diagram, and a distortion aberration diagram in the optical lens system 11 of Example 3. FIG. Description of each aberration diagram shown in FIG. 7 is omitted because it is the same as the description of FIG.

As shown in the longitudinal aberration diagram of FIG. 7A, according to the optical lens system 11 of this embodiment, longitudinal aberrations at wavelengths of 486 nm, 587 nm, and 656 nm are well corrected. Therefore, the optical lens system 11 has a high resolution.

As shown in the curvature of field diagram of FIG. 7B, the optical lens system 11 of this embodiment satisfactorily corrects the curvature of field. Therefore, the optical lens system 11 has a high resolution.

As shown in the distortion diagram of FIG. 7C, according to the optical lens system 11 of this embodiment, the distortion is well corrected. Therefore, the optical lens system 11 has a high resolution.

As shown in Table 9, in Example 3, the value of F/(L1-STOP) is 0.379, and the optical lens system 11 of Example 3 satisfies the above formula (1). Further, as shown in Table 9, in Example 3, the value of F1/F is -1.990, and the optical lens system 11 of Example 3 satisfies the above formula (2). Therefore, as shown in Table 9, in Example 3, the lens diameter Φ1 of the first lens L1 is 12.112 mm, the optical total length L is 28.398 mm, and Φ1/L in Equation (3) is 0.427. , the ratio to the overall length is smaller than that of a normal wide-angle lens system mounted on an in-vehicle camera or the like. In addition, in Example 3, since the lens surfaces of the first lens L1, the third lens L3, and the fifth lens L5 are aspherical, as shown in FIG. , 587 nm, and 656 nm longitudinal aberration, curvature of field, and distortion are well corrected. In other words, in the optical lens system 11 according to Example 3, high resolution is achieved at positions with high image heights (peripheral portions of the captured image).

(Example 4: Optical lens system)
FIG. 8 is a cross-sectional view of an optical lens system 11 according to Example 4. FIG. As shown in FIG. 8, in the optical lens system 11 according to Example 4, the object-side lens surface S8 of the fourth lens L4 has a concave surface recessed toward the image side, and the image-side lens surface S11 of the fifth lens L5 has a concave surface. It differs from the optical lens system 11 according to Examples 1 to 3 in that it has an aspherical surface that protrudes toward the image side. Therefore, in the optical lens system 11 according to Example 4, the same components as in Examples 1 to 3 are denoted by the same reference numerals, and descriptions thereof are omitted.
Also, the first lens L1 to the fifth lens L5 are composed of glass lenses or plastic lenses.

Characteristic data of the optical lens system 11 according to Example 4 will be described below.
First, Table 10 shows lens data of each lens surface of the optical lens system 11 according to the fourth embodiment. Since the items shown in Table 10 are the same as the items shown in Table 1, the description thereof is omitted.

Also, the aspherical shapes adopted for the lens surfaces of the first lens L1, the third lens L3, and the fifth lens L5 are represented by the above equation (4).
Table 11 shows the aspherical coefficients for defining the aspherical shapes of the lens surfaces of the first lens L1, the third lens L3, and the fifth lens L5 in the optical lens system 11 of Example 4.

Table 12 shows characteristic data of the optical lens system 11 according to Example 4. Since the items shown in Table 9 are the same as the items shown in Table 3, the description thereof is omitted.

Also, FIG. 9 shows a spherical aberration diagram (longitudinal aberration diagram), a field curvature diagram, and a distortion aberration diagram in the optical lens system 11 of the fourth embodiment. Description of each aberration diagram shown in FIG. 9 is omitted because it is the same as the description of FIG.

As shown in the longitudinal aberration diagram of FIG. 9A, according to the optical lens system 11 of this embodiment, longitudinal aberrations at wavelengths of 486 nm, 587 nm, and 656 nm are well corrected. Therefore, the optical lens system 11 has a high resolution.

As shown in the curvature of field diagram of FIG. 9B, according to the optical lens system 11 of this embodiment, the curvature of field is well corrected. Therefore, the optical lens system 11 has a high resolution.

As shown in the distortion diagram of FIG. 9C, according to the optical lens system 11 of this embodiment, the distortion is well corrected. Therefore, the optical lens system 11 has a high resolution.

As shown in Table 12, in Example 4, the value of F/(L1-STOP) is 0.397, and the optical lens system 11 of Example 4 satisfies the above formula (1). Further, as shown in Table 12, in Example 4, the value of F1/F is -1.890, and the optical lens system 11 of Example 4 satisfies the above formula (2). Therefore, as shown in Table 12, in Example 4, the lens diameter Φ1 of the first lens L1 is 11.842 mm, the optical total length L is 27.975 mm, and Φ1/L in Equation (3) is 0.423. , the ratio to the overall length is smaller than that of a normal wide-angle lens system mounted on an in-vehicle camera or the like. In addition, in Example 4, the lens surfaces of the first lens L1, the third lens L3, and the fifth lens L5 are aspherical. , 587 nm, and 656 nm longitudinal aberration, curvature of field, and distortion are well corrected. In other words, in the optical lens system 11 according to Example 4, high resolution is achieved at positions with high image heights (peripheral portions of the captured image).

In the optical lens system 11 according to Embodiment 1 described above, the optical lens system 11 satisfies the above formulas (1) and (2), thereby widening the angle of view of the optical lens system 11 and The diameter of one lens L1 can be made relatively small. Specifically, when the value of F/(L1-STOP) is 0.3 or less, the diameter of the first lens L1 becomes large. Specifically, when the power F of the optical lens system 11 is the same, the longer the distance L1-STOP from the first lens L1 to the stop, the smaller the angle formed by the light beam entering the first lens L1 and the optical axis. In order to widen the angle of view of the optical lens system 11, it is necessary to increase the diameter of the first lens L1. On the other hand, when the value of F/(L1-STOP) is 0.6 or more, sufficient resolution performance of the optical lens system 11 cannot be obtained. Specifically, when the power F of the optical lens system 11 is the same, if the distance L1-STOP from the first lens L1 to the stop is short, the angle of view of the optical lens system 11 is can be widened, but the resolution performance deteriorates because the aberration cannot be sufficiently corrected.
Further, when the value of FL1/F is −2.0 or less, the diameter of the first lens L1 becomes large. Specifically, when the power F of the optical lens system 11 is the same, the smaller the power FL1 of the first lens L1 (larger the absolute value), the smaller the angle formed by the light beam emitted from the first lens L1 and the optical axis. Therefore, in order to widen the angle of view of the optical lens system 11, it is necessary to increase the diameter of the first lens L1. On the other hand, when the value of FL1/F is -1.5 or more, sufficient resolution performance of the optical lens system 11 cannot be obtained. Specifically, when the power F of the optical lens system 11 is the same, if the power FL1 of the first lens L1 is large (the absolute value is small), the image of the optical lens system 11 can be obtained without increasing the diameter of the first lens L1. Although the angle can be widened, the resolution performance deteriorates because the aberration cannot be sufficiently corrected.
Since the diameter of the first lens L1 can be made relatively small, even if the optical lens system 11 is mounted on an in-vehicle camera, the probability that the first lens L1 will be hit by a flying stone can be reduced. Also, the size of the optical lens system 11 can be reduced. As a result, the size of the camera in which the optical lens system 11 is mounted can be reduced, and restrictions on the installation location and design of the camera can be reduced. In addition, since the angle of view of the optical lens system 11 can be widened, a bright optical lens system with an F number of 1.6 can be realized.

Further, since at least the object-side lens surface S1 of the first lens L1 has a curved surface shape having an inflection point, the imaging magnification of the central portion (low image height position) and the peripheral portion (high image height position) can be easily controlled to change the distance, and it becomes easy to achieve both a sensing function such as a long-distance distance measurement function and a short-distance wide-range imaging function. As a result, the optical lens system 11 that is compact and has high performance can be realized.

Thus, according to the optical lens system 11 according to Embodiment 1, it is possible to provide the optical lens system 11 having both the characteristics of a telephoto lens and a wide-angle lens and having a small diameter of the first lens.

Further, the second lens L2 has a concave surface on the object side, so that a light beam spread at a wide angle can be incident on the stop STOP at an angle close to parallel. As a result, the distance (L1-STOP) from the intersection of the object-side surface S1 of the first lens L1 with the optical axis to the position of the stop STOP on the optical axis is shortened, that is, the diameter of the first lens L1 is decreased. while maintaining a wide angle of view.

Further, by satisfying the above formula (3), the optical lens system 11 can keep the angle of view of the optical lens system 11 wide while making the diameter of the first lens L1 smaller.

Further, since the image-side lens surface S11 of the fifth lens L5 has a curved surface shape having an inflection point, the curvature of field of the optical lens system 11 can be satisfactorily corrected, and high resolution can be realized. .

The image-side lens surface S7 of the third lens L3 has a convex shape protruding toward the image side, and the image-side lens surface S9 of the fourth lens L4 has a concave shape recessed toward the object side. chromatic aberration correction can be performed.

Second Embodiment Application Example to Imaging Apparatus FIG. 10 is a cross-sectional view of an imaging apparatus 20 according to a second embodiment. The imaging device 20 includes an optical lens system 11 and an imaging device 21 . The optical lens system 11 and the imaging element 21 are housed in a housing (not shown). The optical lens system 11 is the optical lens system 11 described in the first embodiment above.

The imaging element 21 is an element that converts received light into an electric signal, and for example, a CCD image sensor or a CMOS image sensor is used. The imaging element 21 is arranged at the image forming position of the optical lens system 11 . In this specification, unless otherwise specified, the term "angle of view" refers to a diagonal angle of view.

It should be noted that the present invention is not limited to the above embodiments, and can be modified as appropriate without departing from the scope of the invention. For example, the application of the optical lens system of the present invention is not limited to vehicle-mounted cameras and surveillance cameras, but can also be used for other applications such as being mounted on small electronic devices such as mobile phones.

11 Optical lens system 20 Imaging device 21 Imaging elements L1, L2, L3, L4, L5 Lens STOP Aperture

Claims (4)

In order from the object side to the image side, a first lens having negative power, a convex surface on the object side and a concave surface on the image side, a second lens having a concave surface on the object side, an aperture stop, and a positive lens. a third lens having a convex surface on the object side and the image side, a fourth lens having a negative power and a concave surface on the image side, and a convex surface on the object side and a concave surface on the image side. and a fifth lens having
At least the object-side surface shape of the first lens is a curved surface shape having an inflection point,
The inflection point is a point at which the slope of the tangent line in contact with the lens surface switches from increasing to decreasing,
The focal length of the entire optical lens system is F, the focal length of the first lens is FL1, and the distance from the intersection of the object-side surface of the first lens with the optical axis to the position of the stop on the optical axis is An optical lens system that satisfies the following formulas (1) and (2) when L1-STOP.
0.3<F/(L1-STOP)<0.6 (1)
-2.0<FL1/F<-1.5 (2) The optical lens system according to claim 1, wherein the second lens has a concave surface on the object side and a convex surface on the image side. 3. The optical lens system according to claim 1, which satisfies the following formula (3), where Φ1 is the surface diameter of the first lens and L is the optical total length of the optical lens system.
Φ1/L<0.5 (3) an optical lens system according to any one of claims 1 to 3;
and an imaging device arranged at a focal position of the optical lens system.

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