JP6604144B2 - Imaging lens system, imaging device, and inspection device - Google Patents

Description

  The present invention relates to an imaging lens system, an imaging apparatus, and an inspection apparatus.

  2. Description of the Related Art Conventionally, various types of imaging lens systems having a two-lens group structure known as a so-called “single focus lens” are known, including a retrofocus type (Patent Documents 1 to 3, etc.).

In the retrofocus type imaging lens system, the power of the first lens group disposed on the object side is negative, and the power of the second lens group disposed on the image side is positive.
An imaging lens system having a two-lens group configuration in which the power of the second lens group is positive and the power of the first lens group is also well known is well known.

  The present invention is a two-lens group configuration including a first lens group on the object side and a second lens group on the image side. The power of the second lens group is positive and the power of the first lens group is positive or An object is to realize a novel imaging lens system that can be negative.

The imaging lens according to the present invention includes a first lens group and a positive power second lens group in order from the object side to the image side, and the first lens group extends from the object side to the image side. A negative power 1a lens group and a positive power 1b lens group are arranged in order, and the second lens group sequentially has a positive power second a from the object side to the image side. A lens group, a stop, and a 2b lens group having a positive power are arranged, and the 1a lens group is constituted by arranging a negative lens L11 and a negative lens L12 in order from the object side to the image side. The 1b lens group includes a positive lens L13, and the lens surface interval in the first lens group is the maximum between the negative lens L12 and the positive lens L13, and the 2a lens group. Are positive lenses in order from the object side to the image side. 21 and a negative lens L22, and the second lens group moves to the object side during focusing from an infinitely distant object to a close object, and the focal length of the first lens group: f1, The focal length of the entire system in a state in which focusing is performed on an object at infinity: f is a condition:
(1A) -0.1 <f / f1 <0.1
Satisfied.

  According to the present invention, in the two-lens group configuration including the first lens group on the object side and the second lens group on the image side, the power of the second lens group is positive and the power of the first lens group is A novel imaging lens system that can be positive or negative can be realized.

FIG. 2 is a diagram illustrating a cross section of the imaging lens system of Example 1. FIG. 6 is a diagram showing a cross section of an imaging lens system of Example 2. 6 is a diagram showing a cross section of an imaging lens system of Example 3. FIG. 6 is a diagram illustrating a cross section of an imaging lens system of Example 4. FIG. FIG. 6 is an aberration diagram for the imaging lens system of Example 1 when focused on an object at infinity. FIG. 6 is an aberration diagram in a state in which the imaging lens system of Example 1 is focused on an object with a magnification of −0.05. FIG. 6 is an aberration diagram in a state in which the imaging lens system of Example 1 is focused on an object with a magnification of −0.1. FIG. 10 is an aberration diagram for the imaging lens system of Example 2 when focused on an object at infinity. FIG. 10 is an aberration diagram in a state in which the imaging lens system of Example 2 is focused on an object with a magnification of −0.05. FIG. 10 is an aberration diagram in a state where the imaging lens system of Example 2 is focused on an object with a magnification of −0.1. FIG. 10 is an aberration diagram for the imaging lens system of Example 3 when focusing on an object at infinity. FIG. 10 is an aberration diagram in a state where the imaging lens system of Example 3 is focused on an object with a magnification of −0.05. FIG. 12 is an aberration diagram in a state where the imaging lens system of Example 3 is focused on an object with a magnification of −0.1. FIG. 10 is an aberration diagram for the imaging lens system of Example 4 when focusing on an object at infinity. FIG. 12 is an aberration diagram in a state in which the imaging lens system of Example 4 is focused on an object with a magnification of −0.05. FIG. 12 is an aberration diagram in a state where the imaging lens system of Example 4 is focused on an object with a magnification of −0.1. It is a figure which shows the external appearance of one Embodiment of an imaging device, (A) is a perspective view of the front side, (B) is a perspective view of the back side. It is a block diagram which shows the system configuration example of the imaging device of FIG. It is a figure for demonstrating one Embodiment of an inspection apparatus.

Hereinafter, embodiments will be described.
1 to 4 show four embodiments of the imaging lens system.
These four embodiments correspond to Examples 1 to 4 of the imaging lens system described later in the order shown. In order to avoid complication, the reference numerals are shared in FIGS.
1 to 4, the left side is the “object side” and the right side is the “image side”. In these embodiments, it is assumed that an image of an object by the imaging lens system is picked up by a solid-state image sensor, and in the drawing, symbol Im indicates an image plane (matches the light-receiving surface of the solid-state image sensor). . The symbol G on the object side of the image plane Im indicates the cover glass and various filters of the solid-state imaging device as transparent parallel plates equivalent to these.

Referring to FIG. 1 as a representative, the imaging lens system is configured by arranging a first lens group G1 and a second lens group G2 in order from the object side to the image side.
The first lens group G1 has “positive or negative power”, and the second lens group G2 has “positive power”.
The first lens group G1 includes a 1a lens group G1a and a 1b lens group G1b in order from the object side to the image side.
The first a lens group G1a is configured by arranging a negative lens L11 and a negative lens L12 in order from the object side to the image side, and the first b lens group G1b is configured by a positive lens L13.
Accordingly, the first-a lens group G1a has “negative power”, and the first-b lens group G1b has “positive power”. That is, the power of the first lens group G1 can be either positive or negative depending on the relative magnitude of the negative power of the 1a lens group G1a and the positive power of the 1b lens group G1b.

The “lens surface interval” in the first lens group G1 is the maximum between the negative lens L12 and the positive lens L13.
The second lens group G2 includes a positive power second-a lens group G2a, a diaphragm S, and a positive power second-b lens group G2b in order from the object side to the image side.
The second-a lens group G2a is configured by arranging a positive lens L21 and a negative lens L22 in order from the object side to the image side. In the embodiment shown in FIGS. 1 to 4, the positive lens L21 and the negative lens L22 are cemented, and the cemented surface is concave on the object side.
Of course, the positive lens L21 and the negative lens L22 are not limited to those shown in FIGS. 1 to 4, and a configuration in which they are not joined is also possible.

In the second lens group G2, the second lens group G2b on the image side of the stop S is a negative lens having a concave surface on the object side in order from the object side to the image side in the embodiment shown in FIGS. L23, a positive lens L24, a negative lens L25, a positive lens L26, and a positive lens L27 are arranged.
The configuration (number of lenses, lens shape) of the second b lens group G2b is not limited to that shown in FIGS. That is, under the condition that a positive power is realized, the 2b lens group can be composed of “less than 5 lenses” or “consisting of 6 or more lenses”. The positive / negative of the power can be set as appropriate.
In the example shown in FIGS. 1 to 4, the negative lens L23 and the positive lens L24 of the second b lens group G2b are cemented, but a configuration in which these are not cemented is also possible.

The imaging lens system of the present invention is capable of focusing from an infinite object to a close object according to the object distance of the object to be photographed. During “focusing from an infinitely distant object to a close object”, the second lens group G2 moves to the object side.
In the imaging lens system of the present invention, the focal length: f1 of the first lens group G1 and the focal length: f of the entire system in a state of focusing on an infinite object are:
(1A) -0.1 <f / f1 <0.1
Or
(1) -0.15 <f / f1 <0.15
Satisfied.
When the condition (1) is satisfied, the focal length: f2a of the second a lens group G2a and the focal length: f2b of the second b lens group G2b are:
(4) 1.0 <f2a / f2b <1.8
To be satisfied at the same time.
Condition (4) can be satisfied simultaneously with condition (1A).

As described above, the lens surface interval (the interval between the image side surface of the negative lens L12 and the object side surface of the positive lens L13) of the 1a lens group G1a and the 1b lens group G1b constituting the first lens group G1 is the first lens group. It is the largest in G1.
By arranging “the largest lens surface distance in the first lens group” between the negative power 1a lens group G1a and the positive power 1b lens group G1b, aberrations generated in the 1a lens group G1a Can be sufficiently corrected by the first-b lens group G1b.
Further, the negative lens L11 and L12 can share the negative power that the first-a lens group G1a should have by configuring the first-a lens group G1a with the negative lens L11 and the negative lens L12.

  By assigning the negative power of the first-a lens group G1a to the negative lens L11 and the negative lens L12, it is possible to suppress aberrations that occur on the lens surfaces of these negative lenses. Then, by ensuring a large distance between the negative lens L12 and the positive lens L13, the aberration generated in the first a lens group G1a is favorably corrected by the first b lens group G1b including one positive lens L13. It is possible.

By configuring the “second a lens group G2a on the object side of the stop S” of the second lens group G2 with the positive lens L21 and the negative lens L22, the chromatic aberration can be sufficiently corrected and the second b lens group G2b can be corrected. “Aberration exchange” can be prevented from becoming excessive.
The condition (1A) is a condition that can effectively reduce the “change in curvature of field” due to a change in the object distance accompanying focusing while securing the performance of the imaging lens system.
When the parameter of condition (1A) : f / f1 increases, it means that the “positive or negative power” of the first lens group G1 with respect to the power of the entire system becomes relatively strong.
When the upper limit of the condition (1A) is exceeded, the positive power of the first lens group G1 becomes excessive, and it is difficult to sufficiently correct coma and the like. When the lower limit of the condition (1A) is exceeded, the negative power of the first lens group G1 becomes excessive, and “the field curvature is likely to change greatly” with a change in the object distance.
By satisfying the condition (1A) , it is possible to effectively suppress “changes in field curvature accompanying changes in object distance” during focusing while satisfactorily correcting various aberrations such as coma.
In place of the condition (1A), the condition (1) and the condition (4) can be satisfied simultaneously as described above.

Since the focal length f of the entire system is positive, the conditions (1) and (1A) may also be expressed as follows.
(1) | f / f1 | <0.15
(1A) | f / f1 | <0.1.

  As described above, when focusing from an infinitely distant object to a close object, the second lens group G2 moves to the object side. At this time, the configuration may be such that “the first lens group G1 also moves”, but the first lens group G1 may be “fixed”. That is, focusing can be performed without changing the positional relationship between the first lens group G1 and the image plane Im. In this way, the lens group moving mechanism for focusing can be simplified.

The imaging lens system of the present invention preferably satisfies any one or more of the following conditions (2) to (5) and (7) in addition to the above condition (1A) .
(2) 0.05 <D_foc / f <0.15
(3) 0.2 <D12 / f <0.4
(4) 1.0 <f2a / f2b <1.8
(5) 0.3 <D1ab / D1 <0.5
(7) 0.2 <D2ab / D2 <0.4.
When the conditions (1) and (4) are satisfied, any one or more of the conditions (2), (3), (5), and (7) should be satisfied together.

The meanings of symbols in the parameters in these conditions (2) to (5) and (7) are as follows.
“D_foc” is the amount of change in the distance between the first lens group G1 and the second lens group G2 during focusing from an object at infinity to a “short distance object with a magnification of −0.1”.
“D12” is the distance between the first lens group G1 and the second lens group G2 in the state of focusing on an object at infinity (on the optical axis between the image side lens surface of the positive lens L13 and the object side lens surface of the positive lens L21). Distance).
“F2a” is the focal length of the second-a lens group G2a.
“F2b” is the focal length of the second b lens group G2b.

“D1ab” is the distance between the 1a lens group G1a and the 1b lens group G1b (distance on the optical axis between the image side lens surface of the negative lens L12 and the object side lens surface of the positive lens L13).
“D1” is “group thickness (distance on the optical axis from the most object-side lens surface to the most image-side lens surface of the first lens group G1)” of the first lens group G1.
“D2ab” is the distance between the 2a lens group G2a and the 2b lens group G2b (the optical axis from the most image side lens surface of the 2a lens group G2a to the most object side lens surface of the 2b lens group G2b). Above distance) ”.
“D2” is “group thickness (distance on the optical axis from the most object-side lens surface to the most image-side lens surface of the second lens group G2)” of the second lens group G2.

As described above, the positive lens L21 and the negative lens L22 constituting the 2a lens group G2a can be “junction lenses”. At this time, the joint surface is concave on the object side.
In this case, together with the condition (1A) , or the condition (1A) and “any one or more of the conditions (2) to (5) and (7)” , or the condition (1) and the condition (4) or the condition ( It is preferable that the following condition (6) is satisfied together with 1), (4) and “any one or more of conditions (2), (3), (5), (7)” .
(6) -1.5 <Ra / f <-0.5
“Ra” in the parameter of the condition (6) is a radius of curvature (<0) of the cemented surface between the positive lens L21 and the negative lens L22.

Hereinafter, conditions (2) to (7) will be described.
Condition (2) is an effective condition for suppressing curvature of field.
Condition (2) is that the amount of change in the “distance between the first lens group G1 and the second lens group G2” when focusing from an object at infinity to “a short distance object with a magnification of −0.1 times” is This is a condition that defines the range of parameters normalized by the focal length f of the entire system in a state of focusing on an object at infinity.

As described above, the distance between the first lens group G1 and the second lens group G2 in the state of focusing on an object at infinity is “D12”. For convenience, this is referred to as “D12 (∞)”, and the distance in the state of focusing on “a short-distance object with a magnification of −0.1” is referred to as “D12 (−0.1)” for convenience.
“D_foc” is | D12 (∞) −D12 (−0.1) |.
When focusing from an infinitely distant object to a close object, the second lens group moves to the object side. In Examples 1 to 4 to be described later corresponding to FIGS. 1 to 4, since the first lens group G1 is fixed, when focusing from an infinite object to a short-distance object, the first lens group G1 The distance from the second lens group G2 decreases. In this case,
D_foc = D12 (∞) −D12 (−0.1)
It is.

Condition (2) parameter: D_foc / f becomes larger (smaller) because the amount of change in the “interval between the first lens group G1 and the second lens group G2” accompanying focusing from an object at infinity to a near object Means larger (smaller).
If the upper limit of the condition (2) is exceeded, “positive curvature of field” is likely to occur in a state of focusing on a short distance object, and if the lower limit is exceeded, “negative curvature of field” is likely to occur in the state of focusing on a short distance object. It is easy to generate.
The curvature of field that occurs outside the range of condition (2) is not always easily corrected by the design parameters of the imaging lens system.
In the range of condition (2), it is possible to effectively reduce the curvature of field when focusing from an infinitely distant object to a close object.

The imaging lens system of the present invention is often used so as to “form an image of an object on a light receiving surface of a solid-state imaging device and read” as in the embodiments shown in FIGS. When a large curvature of field occurs in such a usage pattern, the image plane and the light receiving surface deviate according to the curvature of field, and the resolution of an image to be read is reduced at the deviated portion.
In this case, it is important that the curvature of field is small regardless of the “position of the object to be focused” in such a case, but by satisfying the condition (2), the variation in curvature of field due to focusing is reduced. It can be effectively suppressed.

Condition (3) is a parameter range in which “the distance between the first lens group G1 and the second lens group G2: D12” in the state of focusing on an object at infinity is normalized by the focal length f of the entire system. It is a condition to regulate.
Increasing (decreasing) the parameter in the condition (3) corresponds to increasing (decreasing) the “interval between the first lens group G1 and the second lens group G2 when focusing on an object at infinity”. .
When the upper limit of the condition (3) is exceeded, the “interval between the first lens group G1 and the second lens group G2” becomes excessive in the state of focusing on an object at infinity, and the off-axis ray passing through the first lens group G1 becomes high. As a result, the imaging lens system is enlarged, and it is difficult to correct various aberrations.
When the lower limit of the condition (3) is exceeded, the “interval between the first lens group G1 and the second lens group G2” becomes small in the state of focusing on an object at infinity, and the second lens necessary for focusing on a short-distance object. The displacement area of the group is limited to be small, and it is difficult to “achieve focusing on the short distance side while suppressing curvature of field”.

Condition (4) is that the positive power of the second lens group G2b on the image side of the aperture S and the positive power of the second lens group G2a on the image side of the aperture S of the second lens group G2. This is a condition to “balance appropriately”.
When the parameter of condition (4): f2a / f2b becomes larger (smaller), the positive power of the second-a lens group G2a becomes smaller (larger) than the positive power of the second-b lens group G2b.
If the upper limit of the condition (4) is exceeded, the power of the second b lens group G2b becomes excessive, and it is difficult to correct aberrations occurring in the second b lens group G2b in the second b lens group G2b.
When the lower limit of the condition (4) is exceeded, the power of the second lens group G2a becomes excessive, and it is difficult to correct aberrations occurring in the second lens group G2a in the second lens group G2a.
Within the range of condition (4), each of the second-a lens group G2a and the second-b lens group G2b can “correct to some extent” the aberration within the group.

Condition (5) regulates the parameter range in which the distance between the first lens group G1a and the first b lens group G1b: D1ab in the first lens group G1 is normalized by the group thickness: D1 of the first lens group G1. It is a condition to do.
In the imaging lens system of the present invention, in the first lens group G1, the distance between the first a lens group G1a and the second b lens group G2b is the maximum surface distance: D1ab.
In a range where the condition (5) is satisfied, it is easy to correct the aberration generated in the first lens group G1a with the first lens group G1b.
When the upper limit of the condition (5) is exceeded, the distance between the 1a lens group G1a and the 1b lens group G1b becomes excessive, and the thickness of the 1a lens group G1a and the 1b lens group G1b decreases.

For this reason, it is difficult to correct the aberration generated in the first lens group G1a with the first lens group G1b.
If the lower limit of the condition (5) is exceeded, the distance between the 1a lens group G1a and the 1b lens group G1b becomes too small, and it is difficult to correct the aberration generated in the 1a lens group G1a with the 1b lens group G1b. .

Condition (6) is a condition that prescribes a range of the curvature radius Ra of the cemented surface when the positive lens L21 and the negative lens L22 of the second-a lens group G2a are cemented to “a cemented surface concave on the object side”. .
By satisfying the condition (6), the “chromatic aberration correction function” of the 2a lens group G2a is satisfactorily exhibited, and it is possible to sufficiently correct the chromatic aberration while correcting the monochromatic aberration.

  Condition (7) regulates the parameter range in which the distance between the second lens group G2a and the second b lens group G2b in the second lens group G2: D2ab is normalized by the group thickness of the second lens group G2: D2. It is a condition to do.

When the upper limit of the condition (7) is exceeded, the distance between the second a lens group G2a and the second b lens group G2b becomes excessive, and the “group thickness” of the second a lens group G2a and the second b lens group G2b becomes thin. It tends to be difficult to “correct to some extent” aberrations occurring within a group within the same group.
If the lower limit of the condition (7) is exceeded, the distance between the 2a lens group G2a and the 2b lens group G2b becomes too small, and it becomes difficult to correct the aberration generated in the 2a lens group G2a with the 2b lens group G2b. easy.

  Of the two lenses L21 and L22 constituting the 2a lens group G2a in the imaging lens system of the present invention, the negative lens L22 is made of a glass material that satisfies the following conditions (8) to (10). preferable.

_{(8) 1.78 <n d <} 2.00
(9) 20.0 <ν _d <32.0
(10) 0.005 <P _{g, F} − (− 0.001802ν _d +0.6483) <0.009
“N _d , ν _d and P _{g, F} ” in the conditions (8) to (10) are “refractive power with respect to the d line, Abbe number, and partial dispersion ratio”, respectively.

Partial dispersion ratio: P _{g, F} is expressed by the following formula using refractive indexes: n _g , n _F , n _C for g-line, F-line, and C-line:
_{P g, F = (n g} -n F) / (n F -n C)
Defined by

  By forming the negative lens L22 with a high refractive index that satisfies the conditions (8) to (10) and having “high dispersion and anomalous dispersion”, the monochromatic aberration of the imaging lens system is sufficiently corrected. However, it becomes easy to sufficiently correct chromatic aberration.

  As described above, of the first lens group and the second lens group constituting the imaging lens system of the present invention, the configuration (number of lenses, lens shape) of the second b lens group G2b is a condition that a positive power is realized. Can be set as appropriate.

  In the embodiment shown in FIG. 1 to FIG. 4, “the negative lens L23 having a concave surface on the object side, the positive lens L24, the negative lens L25, the positive lens in order from the object side to the image side” exemplified as the 2b lens group G2b. The “configuration including the lens L26 and the positive lens L27” is an example of a preferable configuration of the second b lens group G2b.

  As shown in Examples 1 to 4 to be described later, such a configuration of the second b lens group G2b makes it possible to reduce the incident angle on the image plane Im and to sufficiently correct various aberrations.

  Further, the imaging lens system of the present invention can be configured by “spherical lens only” as shown in the first to fourth embodiments. Of course, an aspherical lens may be used, but an imaging lens system composed of only a spherical lens is advantageous in terms of manufacturing cost.

In addition, in this specification, “L11 to L13, L21 to L27” are “a part of the name of each lens” as described in the claims.
That is, for example, “negative lens L11” is “a negative lens named negative lens L11”.

In FIGS. 1 to 4, L11 to L13 and L21 to L27 forming “a part of the name” of this lens are also used as “a symbol representing the corresponding lens”.
As described above, “L11 to L13, L21 to L27” are part of the name of the lens. Therefore, the lens forms and materials described in the claims are described as the embodiments and examples. Needless to say, it is not limited to the above.

  Prior to the description of specific embodiments, an “imaging device (hereinafter also referred to as“ camera device ”)” and an “inspection device” using the imaging lens system of the present invention will be described.

  As shown in FIG. 18, the system configuration of the camera apparatus shown in FIG. 17 includes a photographic lens 1 as a photographic optical system and a light receiving element 13 that is a “solid-state imaging device”. An image of the object is captured by the light receiving element 13.

The output from the light receiving element 13 is processed by the signal processing device 14 under the control of the central processing unit 11 and converted into digital information.
The image converted into digital information is displayed on the liquid crystal monitor 7 and stored in the semiconductor memory 15 or used for communication to the outside by the communication card 16. As a simpler configuration of the “imaging device”, a configuration including “a portion excluding a communication function” can be cited.
As the photographing lens 1, the imaging lens system according to any one of claims 1 to 10 is used, and specifically, "imaging lens system" of Examples 1 to 4 described later can be used. .

The “monitored image” can be displayed on the liquid crystal monitor 7 or an image recorded in the semiconductor memory 15 can be displayed.
When the camera lens is carried with the camera device, it is in the “collapsed state” as shown in FIG. 17A. When the power is turned on by operating the power switch 6 (FIG. It is paid out. When the lens barrel is extended, the taking lens system 1 is in a state of “focusing on an object at infinity”.

Focusing is performed by “half-pressing” the shutter button 4.
Focusing is performed by moving the second lens group. When the shutter button 4 is further pressed, shooting is performed, and thereafter the above processing is performed.
When an image recorded in the semiconductor memory 15 is displayed on the liquid crystal monitor 7 or transmitted to the outside using the communication card 16 or the like, the operation button 8 is operated. The semiconductor memory 15 and the communication card 16 are inserted into dedicated or general-purpose slots 9 for use.
When the photographing lens 1 is in the “collapsed state”, the lens groups of the imaging lens system do not necessarily have to be arranged on the optical axis. For example, if the second lens group is retracted from the optical axis to be “stored in parallel with the first lens group”, the camera device can be made thinner.
In this case, since the second lens group G2 has a larger “group thickness” than the first lens group G1, retracting the second lens group from the optical axis greatly contributes to “thinning of the retracted state”. be able to.

  In the camera apparatus shown in FIGS. 17 and 18, as described above, the part excluding the communication function constitutes an “imaging apparatus”, and this imaging apparatus is an “imaging function unit” of the camera apparatus.

  17 and 18 includes a solid-state imaging element that captures an image by an imaging lens system that is an imaging optical system.

  Since the imaging apparatus has the “communication function” as described above, it also has a function as a so-called “portable information terminal apparatus”.

Hereinafter, an embodiment of the “inspection apparatus” will be described with reference to FIG.
The inspection apparatus described below is an inspection apparatus for performing so-called “product inspection”.
There may be various inspections and inspection items in the product inspection, but for the sake of simplicity, an example will be described in which “inspection for presence / absence” of a product manufactured by a large number is manufactured.
In FIG. 19A, reference numeral 20 indicates an “imaging unit”, reference numeral 23 indicates an “inspection process execution unit”, and reference numeral 24 indicates a “display unit”. Reference numeral “W” indicates “product”, and reference numeral 26 indicates “product conveyance belt”.
The imaging unit 20 includes an imaging optical system 21 and an image processing unit 22.

The products W to be inspected are placed on the product transport belt 26 at equal intervals, and are transported at a constant speed by the transport belt 26 in the direction of the arrow (to the right in the figure).
The imaging optical system 21 forms an image of the product W that is an imaging target, and the imaging lens system of the present invention is used. Specifically, any of the imaging lens systems of Examples 1 to 4 described later can be used.
The product inspection is performed over each of the “preparation process”, “inspection process”, and “result display process” shown in FIG. Among these processes, the “inspection process and result display process” is the “inspection process”.

In the “preparation process”, inspection conditions are set.
That is, depending on the size and shape of the product W transported by the transport belt 26, the site to be inspected for the presence or absence of scratches, and the like, the imaging position and imaging position of the imaging lens system 21 (the direction of the imaging lens and the imaging target) Distance, that is, object distance).
Then, the imaging lens system 21 is focused according to the position and size of the “scratch” whose presence or absence is to be detected. Since the imaging lens system of the present invention has a “focusing function”, focusing can be performed in accordance with an appropriately set object distance in accordance with an inspection item (in the example being described, the presence or absence of a flaw).

On the other hand, a “model product that has been confirmed to be free of scratches” is placed at the inspection position on the conveyor belt, and this is photographed by the imaging lens system 21.
Shooting is performed by imaging with a solid-state imaging device disposed in the image processing unit 22, and an image captured by the solid-state imaging device 22 is set as “image information”, and image processing to convert it into digital data is performed.

The image-processed digital data is sent to the inspection process execution unit 23, and the inspection process execution unit 23 stores the digital data as “model data”.
In the “inspection process”, the product W is placed in the “same state as the model product” on the transport belt 26 and is sequentially transported by the transport belt 26. When each conveyed product W passes through the “inspection position”, photographing is performed by the imaging lens system 21, converted into digital data by the image processing unit 22, and sent to the inspection process execution unit 23. .
The inspection process execution unit 23 is configured as a “computer or CPU”, controls the image processing unit 22, and controls imaging and focusing of the imaging lens system 21 via the image processing unit 22.
Upon receipt of “image data of product W” converted into digital data by the image processing unit 22, the inspection process execution unit 23 matches the image data with the stored model data.

If the photographed product W has “scratches”, the image data and the model data do not match, and in this case, the product is determined to be “defective”.
If the product W is not damaged, the image data of the product and the model data match, and in this case, it is determined that the product is “good”.

  The “result display step” is a step of displaying the determination result of “good product, defective product” of each product by the inspection process execution unit 23 on the display unit 24.

  In the configuration of the apparatus, the inspection process execution unit 23 and the display unit 24 constitute “inspection process execution means”.

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

  In all the examples, the “maximum image height is 8.0 mm”.

Examples 1 to 4 correspond to the imaging lens system depicted in FIGS. 1 to 4 in this order, and an image of an object by the imaging lens system is picked up by a solid-state imaging device.
As described above, the symbol G on the object side of the image plane Im matched with the light receiving surface of the solid-state imaging device is equivalent to the cover glass of the solid-state imaging device and various filters (such as an optical low-pass filter and an infrared cut filter). It is shown as a transparent parallel plate.

The meanings of the symbols in the examples are as follows.
f: Focal length of the entire system in a state of focusing on an object at infinity
F: F number
ω: Half angle of view (degrees)
R: radius of curvature
D: Surface spacing
N: Refractive index for d-line
ν: Abbe number
φ: Effective beam diameter
The unit of “amount having a dimension of length” is “mm” unless otherwise specified.

"Example 1"
Focal length f: 16.00mm, F number: F1.80, angle of view 2ω: 53.2 degrees
The data of Example 1 is shown in Table 1. The leftmost column of Table 1 is a surface number (surface number) counted from the object side and includes “aperture surface”.

"Variable interval"
The “variable distance” is a surface distance between the first lens group and the second lens group, and changes with focusing. In the first embodiment, the variable interval is an interval D6 (shown as “A”) between the surface numbers 6 and 7.

  The variable intervals of Example 1 are shown in Table 2. “Inf” in the upper row indicates a state in which an object at infinity is in focus, “× 0.05” indicates a state in which an object with an imaging magnification of −0.05 times, and “× 0.10” indicates a result. Image magnification: This is a state in which an object of -0.10 times is focused. The same applies to the following embodiments.

"Condition Parameter Values"
Table 3 shows the values of the parameters according to the conditions (1) , (1A) to (10).

  Since the parameter of condition (1): f / f1 is positive, the power of the first lens group G1 in the imaging lens system of Example 1 is “positive”.

"Example 2"
Focal length f: 16.00mm, F number: F1.80, angle of view 2ω: 53.2 degrees
The data of Example 2 is shown in Table 4.

"Variable interval"
Table 5 shows the variable intervals of Example 2.

"Condition Parameter Values"
Table 6 shows the values of the parameters according to the conditions (1) , (1A) to (10).

  Since the parameter (1): f / f1 is positive, the power of the first lens group G1 in the imaging lens system of Example 2 is “positive”.

"Example 3"
Focal length f: 16.00mm, F number: F1.80, angle of view 2ω: 53.2 degrees
The data of Example 3 is shown in Table 7.

"Variable interval"
Table 8 shows the variable intervals of Example 3.

"Condition Parameter Values"
Table 9 shows the values of the parameters according to the conditions (1) , (1A) to (10).

  Since the parameter (1): f / f1 is negative, the power of the first lens group G1 in the imaging lens system of Example 3 is “negative”.

Example 4
Focal length f: 16.00mm, F number: F1.80, angle of view 2ω: 53.2 degrees
The data of Example 4 is shown in Table 10.

"Variable interval"
Table 11 shows the variable intervals of Example 4.

"Condition Parameter Values"
Table 12 shows the values of the parameters according to the conditions (1) , (1A) to (10).

  Since the parameter of condition (1): f / f1 is negative, the power of the first lens group G1 in the imaging lens system of Example 4 is “negative”.

  FIG. 5 to FIG. 16 show aberration diagrams of Examples 1 to 4. FIG.

  FIG. 5 is an aberration diagram of the imaging lens system of Example 1 in a state where focusing is performed on an object at infinity. FIG. 6 is an aberration diagram in a state where the imaging lens system of Example 1 is focused on an object with a magnification of −0.05. FIG. 7 is an aberration diagram in a state in which the imaging lens system of Example 1 is focused on an object with a magnification of −0.1.

  The broken line in the spherical aberration diagram indicates “sine condition”, the solid line in the astigmatism diagram indicates “sagittal”, and the broken line indicates “meridional”. The “thin line” is an aberration curve with respect to the d line and the “thick line” is an aberration curve with respect to the g line. The same applies to the aberration diagrams of the other examples.

  FIG. 8 is an aberration diagram of the imaging lens system of Example 2 in a state where focusing is performed on an object at infinity. FIG. 9 is an aberration diagram of the imaging lens system of Example 2 in a state where focusing is performed on an object with a magnification of −0.05. FIG. 10 is an aberration diagram of the imaging lens system of Example 2 in a state where focusing is performed on an object with a magnification of −0.1.

  FIG. 11 is an aberration diagram of the imaging lens system of Example 3 in a state where focusing is performed on an object at infinity. FIG. 12 is an aberration diagram of the imaging lens system of Example 3 in a state where focusing is performed on an object with a magnification of −0.05. FIG. 13 is an aberration diagram of the imaging lens system of Example 3 in a state where focusing is performed on an object with a magnification of −0.1.

  FIG. 14 is an aberration diagram of the imaging lens system of Example 4 in a state where focusing is performed on an object at infinity. FIG. 15 is an aberration diagram of the imaging lens system of Example 4 in a state where focusing is performed on an object with a magnification of −0.05. FIG. 16 is an aberration diagram of the imaging lens system of Example 4 in a state where focusing is performed on an object with a magnification of −0.1.

  As shown in these aberration diagrams, in Examples 1 to 4, each aberration is corrected at a high level, and the spherical aberration and the longitudinal chromatic aberration are so small that they do not cause a problem. Astigmatism, curvature of field, and lateral chromatic aberration are sufficiently small, and coma and disturbance of the color difference are well suppressed to the outermost periphery.

  The distortion aberration is 1.0% or less in absolute value at a magnification of −0.05 times.

  In other words, the imaging lens systems of Examples 1 to 4 ensure a very good image performance even though the half angle of view is as wide as 53 degrees and the F number is as large as 1.8.

  In each embodiment, the number of constituent lenses is as small as 10 and is small. The imaging lens system of these embodiments has a resolution corresponding to an imaging device having 6 to 10 million pixels when used with a solid-state imaging device as in the embodiments.

  In addition, it is possible to draw straight lines without distortion from the full aperture to the high contrast and the peripheral part of the angle of view without distortion, and it has high performance from infinity to close objects.

  As described above, according to the present invention, the following novel imaging lens system, imaging device, and inspection device can be realized.

[1]
In order from the object side to the image side, a first lens group (G1) and a second lens group (G2) having a positive power are arranged, and the first lens group (G1) moves from the object side to the image side. A negative power 1a lens group (G1a) and a positive power 1b lens group (G1b) are arranged in order, and the second lens group (G2) is directed from the object side to the image side. A positive power second a lens group (2Ga), a diaphragm (S), and a positive power second b lens group (2Gb) are arranged in order, and the first a lens group (G1a) is an image from the object side. In order toward the side, a negative lens L11 and a negative lens L12 are arranged in order, the 1b lens group (G1b) is configured by a positive lens L13, and the lens surface interval in the first lens group is negative. It is the largest between the lens L12 and the positive lens L13, and the second a lens The group (G2a) is configured by arranging a positive lens L21 and a negative lens L22 in order from the object side to the image side, and the second lens group (G2) during focusing from an infinite object to a short-distance object. ) Moves toward the object side, the focal length of the first lens group (G1) is f1, and the focal length of the entire system in a state of focusing on an object at infinity: f is the condition:
(1A) -0.1 <f / f1 <0.1
Imaging lens system satisfying the above (Examples 1 to 4).
[2]
The imaging lens system according to [1], wherein the focal length: f2a of the second a lens group and the focal length: f2b of the second b lens group are:
(4) 1.0 <f2a / f2b <1.8
Imaging lens system satisfying the above (Examples 1 to 4).
[3]
In order from the object side to the image side, a first lens group (G1) and a second lens group (G2) having a positive power are arranged, and the first lens group (G1) moves from the object side to the image side. A negative power 1a lens group (G1a) and a positive power 1b lens group (G1b) are arranged in order, and the second lens group (G2) is directed from the object side to the image side. A positive power second a lens group (2Ga), a diaphragm (S), and a positive power second b lens group (2Gb) are arranged in order, and the first a lens group (G1a) is an image from the object side. In order toward the side, a negative lens L11 and a negative lens L12 are arranged in order, the 1b lens group (G1b) is configured by a positive lens L13, and the lens surface interval in the first lens group is negative. It is the largest between the lens L12 and the positive lens L13, and the second a lens The group (G2a) is configured by arranging a positive lens L21 and a negative lens L22 in order from the object side to the image side, and the second lens group (G2) during focusing from an infinite object to a short-distance object. ) Moves toward the object side, the focal length of the first lens group (G1) is f1, the focal length of the entire system in a state of focusing on an infinite object: f, the focal length of the second a lens group (G2a): f2a, The focal length: f2b of the second b lens group (G2b) is:
(1) -0.15 <f / f1 <0.15
(4) 1.0 <f2a / f2b <1.8
Imaging lens system satisfying the above (Examples 1 to 4).

[4]
The imaging lens system according to any one of [1] to [3] , wherein the first lens group (G1) is fixed when focusing from an object at infinity to an object at a short distance. (Examples 1 to 4).
[5]
The imaging lens system according to any one of [1] to [4] , wherein the first lens group (G1) is used for focusing from an object at infinity to an object at a short distance with a magnification of −0.1. Change amount of the distance between the second lens group (G2): D_foc, and the focal length of the entire system: f are the conditions:
(2) 0.05 <D_foc / f <0.15
Imaging lens system satisfying the above (Examples 1 to 4).

[6]
The imaging lens system according to any one of [1] to [5], wherein the distance between the first lens group (G1) and the second lens group (G2) in a state of focusing on an object at infinity: D12 The focal length of the entire system: f is the condition:
(3) 0.2 <D12 / f <0.4
Imaging lens system satisfying the above (Examples 1 to 4).

[7]
The imaging lens system according to any one of [1] to [6] , wherein a distance between the first-a lens group (G1a) and the first-b lens group (G1b): D1ab, the first lens group (G1) Group thickness: D1 is the condition:
(5) 0.3 <D1ab / D1 <0.5
Imaging lens system satisfying the above (Examples 1 to 4).

[8]
The imaging lens system according to any one of [1] to [7] , wherein the positive lens L21 and the negative lens L22 of the second-a lens group (G2a) are cemented, and the cemented surface is concave on the object side. Yes, Ra is the radius of curvature of the joint surface: Ra, the focal length of the entire system: f, the condition:
(6) -1.5 <Ra / f <-0.5
Imaging lens system satisfying the above (Examples 1 to 4).

[9]
The imaging lens system according to any one of [1] to [8] , wherein a distance between the second a lens group (G2a) and the second b lens group (G2b): D2ab, a group thickness of the second lens group : D2 is the condition:
(7) 0.2 <D2ab / D2 <0.4
Imaging lens system satisfying the above (Examples 1 to 4).

[10]
The imaging lens system according to any one of [1] to [9] , wherein a refractive index: n _d , an Abbe number: ν _d , and a partial dispersion ratio: P _{g, F} are:
_{(8) 1.78 <n d <} 2.00
(9) 20.0 <ν _d <32.0
(10) 0.005 <P _{g, F} − (− 0.001802ν _d +0.6483) <0.009
An imaging lens system in which a negative lens L22 is formed of a glass material satisfying the above (Examples 1 to 4).

[11]
The imaging lens system according to any one of [1] to [10] , wherein the second lens group (2Gb) is a negative lens L23 having a concave surface on the object side in order from the object side to the image side. An imaging lens system (Examples 1 to 4) configured by arranging a positive lens L24, a negative lens L25, a positive lens L26, and a positive lens L27.

[12]
An imaging apparatus having the imaging lens system according to any one of [1] to [11] as a photographing optical system (FIGS. 17 and 18).

[13]
[12] The imaging apparatus according to [12], wherein the imaging apparatus includes a solid-state imaging device (13) that captures an image by an imaging optical system.

[14]
An imaging lens system (21) that forms an image of the inspection object (W), a solid-state imaging device that images an image of the inspection object (W) imaged by the imaging lens system, and the solid-state imaging element Inspection process execution means (23) for executing an inspection process for the inspection object (W) based on the output image information
. 24), and an inspection apparatus using the imaging lens system according to any one of [1] to [11] as the imaging lens system (21) (FIG. 19).

The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the specific embodiments described above, and the invention described in the claims unless otherwise specified in the above description. Various modifications and changes are possible within the scope of the above.
The effects described in the embodiments of the present invention are merely a list of suitable effects resulting from the invention, and the effects of the present invention are not limited to those described in the embodiments.

G1 first lens group
G1a 1a lens group
G1b 1b lens group
G2 second lens group
G2a 2a lens group
G2b 2b lens group
S Aperture
Im image plane

JP 2009-198855 A Japanese Laid-Open Patent Publication No. 9-113798 JP-A-63-61213

Claims (14)

In order from the object side to the image side, a first lens group and a second lens group having a positive power are arranged.
The first lens group includes, in order from the object side to the image side, a negative power 1a lens group and a positive power 1b lens group, and the second lens group extends from the object side. In order toward the image side, a positive power 2a lens group, a stop, and a positive power 2b lens group are arranged,
The 1a lens group includes a negative lens L11 and a negative lens L12 in order from the object side to the image side.
The 1b lens group includes a positive lens L13,
The distance between the lens surfaces in the first lens group is the maximum between the negative lens L12 and the positive lens L13.
The second a lens group is configured by arranging a positive lens L21 and a negative lens L22 in order from the object side to the image side,
During focusing from an object at infinity to a near object, the second lens group moves toward the object side, the focal length of the first lens group is f1, and the focus of the entire system in the state of focusing on the object at infinity Distance: f, condition:
(1A) -0.1 <f / f1 <0.1
An imaging lens system that satisfies The imaging lens system according to claim 1,
The focal length: f2a of the 2a lens group and the focal length: f2b of the 2b lens group are:
(4) 1.0 <f2a / f2b <1.8
An imaging lens system that satisfies In order from the object side to the image side, a first lens group and a second lens group having a positive power are arranged.
The first lens group includes, in order from the object side to the image side, a negative power 1a lens group and a positive power 1b lens group, and the second lens group extends from the object side. In order toward the image side, a positive power 2a lens group, a stop, and a positive power 2b lens group are arranged,
The 1a lens group includes a negative lens L11 and a negative lens L12 in order from the object side to the image side.
The 1b lens group includes a positive lens L13,
The distance between the lens surfaces in the first lens group is the maximum between the negative lens L12 and the positive lens L13.
The second a lens group is configured by arranging a positive lens L21 and a negative lens L22 in order from the object side to the image side,
During focusing from an object at infinity to a near object, the second lens group moves toward the object side, the focal length of the first lens group is f1, and the focus of the entire system in the state of focusing on the object at infinity Distance: f, focal length of the 2a lens group: f2a, focal length of the 2b lens group: f2b
(1) -0.15 <f / f1 <0.15
(4) 1.0 <f2a / f2b <1.8
An imaging lens system that satisfies The imaging lens system according to any one of claims 1 to 3,
An imaging lens system in which the first lens group is fixed when focusing from the object at infinity to the object at a short distance. The imaging lens system according to any one of claims 1 to 4,
The amount of change in the distance between the first lens group and the second lens group during focusing from the object at infinity to a near object with a magnification of −0.1 ×: D_foc, focal length of the entire system: f But the condition:
(2) 0.05 <D_foc / f <0.15
An imaging lens system that satisfies An imaging lens system according to any one of claims 1 to 5,
The distance between the first lens group and the second lens group in the state of focusing on the object at infinity: D12, and the focal length f of the entire system are the conditions:
(3) 0.2 <D12 / f <0.4
An imaging lens system that satisfies The imaging lens system according to any one of claims 1 to 6,
The distance between the 1a lens group and the 1b lens group: D1ab, and the group thickness of the first lens group: D1 are as follows:
(5) 0.3 <D1ab / D1 <0.5
An imaging lens system that satisfies An imaging lens system according to any one of claims 1 to 7,
The positive lens L21 and the negative lens L22 of the second-a lens group are cemented, the cemented surface is concave on the object side, the radius of curvature of the cemented surface is Ra, and the focal length of the entire system is f:
(6) -1.5 <Ra / f <-0.5
An imaging lens system that satisfies An imaging lens system according to any one of claims 1 to 8,
The distance between the second a lens group and the second b lens group: D2ab, and the group thickness of the second lens group: D2 are:
(7) 0.2 <D2ab / D2 <0.4
An imaging lens system that satisfies An imaging lens system according to any one of claims 1 to 9,
Refractive index: n _d , Abbe number: ν _d Partial dispersion ratio: P _{g, F} But the condition:
  (8) 1.78 <n _d <2.00
(9) 20.0 <ν _d <32.0
(10) 0.005 <P _{g, F} − (− 0.001802ν _d +0.6483) <0.009
An imaging lens system in which the negative lens L22 is formed of a glass material satisfying the above. An imaging lens system according to any one of claims 1 to 10,
The second b lens group is formed by arranging, in order from the object side to the image side, a negative lens L23, a positive lens L24, a negative lens L25, a positive lens L26, and a positive lens L27 that are concave on the object side. Lens system. An imaging apparatus comprising the imaging lens system according to any one of claims 1 to 11 as a photographing optical system. 13. The imaging apparatus according to claim 12, further comprising a solid-state imaging element that captures an image by the imaging optical system. Based on an imaging lens system that forms an image of an inspection object, a solid-state image sensor that images the image of the inspection object imaged by the imaging lens system, and image information output by the solid-state image sensor, An inspection process execution means for executing an inspection process for an inspection object;
An inspection apparatus using the imaging lens system according to claim 1 as the imaging lens system.

Images