JPH07294810A - Color picture reading lens - Google Patents

Abstract

PURPOSE:To reduce a number of lenses. to make a half viewing angle a wide angle of 20 deg., to excellently compensate chromatic aberration in a wide wavelength region and to increase MTF for a high special frequency by composing the lens of three-group four-lenses. CONSTITUTION:A first lens 11 arranged on the object side is bi-convex lens, a second lens 12 on the image side is bi-concave lens, a third and a fourth lenses 13, 14 arranged on the image side of the second lens 12 and mutually joined are bi-convex and bi-concave lenses, respectively, and the surface of the first lens 11 on the object side is an aspherical surface. By representing the composite focal distance of the whole system for (e) line by (f), the focal distances of the first and the second groups for (e) line by f1, f2 the refractive index and the Abbe number of the material of the jth lens for (d) line by nj, nuj (J=1-4), respectively, the conditions: 0.4f<f1< 0.5f, -0.3<f2<-0.4f, 0.1<{(n1+n3)-(n2+n4)}/2<0.2, 9.0<{(nu1+nu3)-(nu2+nu4)}/2<10.5 are satisfied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image reading lens, that is, a reading lens suitable for reading a color original.

[0002]

2. Description of the Related Art In a color image reading using a 3-line 1-chip CCD as an image sensor, a color image reading lens for forming a reduced image of a color original on the image sensor is a position for forming an image of each color for color separation. In order to make the values coincide with each other, it is necessary that the chromatic aberration of the lens is properly corrected in a wide wavelength range.

Further, in order to reduce the size of the reading device,
The color image reading lens desirably has a wide angle of view, and preferably has a large aperture and is bright so that high-speed reading can be realized. Further, in view of downsizing of the reading device and cost, it is required that the number of constituent lenses is as small as possible.

As an image reading lens having a small number of lens elements, a tesser type element having a three-group, four-element configuration disclosed in JP-A-63-25611 and JP-A-3-100612 has been known. Has been.

However, although the lens disclosed in Japanese Patent Laid-Open No. 63-25611 has its chromatic aberration corrected, its correction area is as narrow as the d to F lines, and therefore, when used for reading a color image, The difference in the imaging performance of each color light after the decomposition becomes large.

Further, the lens disclosed in Japanese Patent Laid-Open No. 3-100612 has a wide wavelength range in which chromatic aberration is corrected,
When the aperture is increased to about /No=4.15, coma aberration becomes large as is apparent from the aberration diagram of Example 2 of the same publication, and it is difficult to read even a fine image with high spatial frequency. is there.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has a three-group, four-lens configuration and a small number of lens components, has a wide half angle of view of about 20 degrees, and covers a wide wavelength range. An object of the present invention is to provide a color image reading lens in which chromatic aberration is well corrected and which has a high MTF for high spatial frequencies (claims 1 to 18).

[0008]

The color image reading lens of the present invention comprises first to third groups arranged from the object side, that is, the original glass side, toward the image side, that is, the image sensor side. The first group is a first lens which is a positive lens, the second group is a second lens which is a negative lens, and the third group is a third lens which is a positive lens and is cemented to the image side of this third lens. It is composed of a fourth lens which is a negative lens. Therefore, the overall configuration is a three-group, four-element configuration. Further, among the lens surfaces of the first to fourth lenses, one or more lens surfaces are aspherical.

Further, through all the color image reading lenses of the present invention, the combined focal length of the entire system is f with respect to the e-line, and the focal lengths of the first and second groups with respect to the e-line are f ₁ , respectively.
f ₂ and the refractive index and Abbe number of the material of the j-th lens with respect to the d-line are d _j and ν _j (j = 1 to 4), respectively.

The color image reading lens described in claim 1 is
As shown in FIG. 38, the first lens 11 arranged on the object side (left side in the figure) is a “biconvex lens”, the second lens 12 on the image side is a “biconcave lens”, and the image side of the second lens 12 is And are joined to each other to form a third group,
The lens 13 and the fourth lens 14 are “biconvex lens” and “biconcave lens”, respectively, and the object side surface of the first lens 11 is aspherical.

The above f, f ₁ , f ₂ , d _j , ν _j (j = 1 to 1)
4) the _{condition: (1-1) 0.4f <f 1} <0.5f (1-2) -0.3f <f 2 <-0.4f (1-3) 0.1 <{(n ₁ + n ₃ )-(n ₂ +
n ₄ )} / 2 <0.2 (1-4) 9.0 <{(ν ₁ + ν ₃ ) − (ν ₂ +
ν ₄ )} / 2 <10.5 is satisfied.

In FIG. 38, reference numeral 10 is the original glass, reference numeral 15 is the cover glass of the 3-line 1-chip CCD, and reference numeral S is the diaphragm. Hereinafter, claim 2
39 to 43 referred to the description of the color image reading lens described in Nos. 18 to 18, in order to avoid complication, the original glass is denoted by reference numeral 10, the cover glass is denoted by reference numeral 15, and the first to the fourth.
The lenses are represented by reference numerals 11 to 14, and the diaphragm is represented by reference numeral S.

In any of the color image reading lenses described in claims 2 to 8, as shown in FIG. 39, the first lens is "a convex meniscus lens with its convex surface facing the object side" and the second lens 12 is "both. A “concave lens”, a third lens 13 is a “biconvex lens”, a fourth lens 14 is a “concave meniscus lens cemented to the image side of the third lens 13 with its concave surface facing the object side”, and the first to fourth lenses Any one of the lens surfaces of is an aspherical surface.

The color image reading lens described in claim 2 is
In the configuration of FIG. 39, the f, f ₁ , f ₂ , d _j ,
ν _{j (j} = 1~4) the _{condition: (2-1) 0.5f <f 1} <1.5f (2-2) -0.45f <f 2 <-0.25f (2-3) 0.1 <{((n ₁ + n ₃ )-(n ₂ +
n ₄ )} / 2 <0.2 (2-4) -0.5 <{((ν ₁ + ν ₃ )-(ν ₂ +)
ν ₄ )} / 2 <15.0 is satisfied.

The color image reading lens described in claim 3 is
In the configuration of FIG. 39, the object side surface of the first lens 11 is an aspherical surface, and f, f ₁ , f ₂ , d _j , ν _j (j = 1
To 4), the _{conditions: (3-1) 0.5f <f 1} <1.1f (3-2) -0.4f <f 2 <-0.25f (3-3) 0.1 <{( _{n 1 + n 3) - (} n 2 +
n ₄ )} / 2 <0.16 (3-4) -0.5 <{(ν ₁ + ν ₃ )-(ν ₂ +
ν ₄ )} / 2 <15.0 is satisfied.

The color image reading lens described in claim 4 is
In the configuration of FIG. 39, the image side surface of the first lens 11 is an aspherical surface, and the f, f ₁ , f ₂ , d _j , ν _j (j = 1 to 1)
4) the _{condition: (4-1) 0.7f <f 1} <1.1f (4-2) -0.4f <f 2 <-0.25f (4-3) 0.1 <{(n ₁ + n ₃ )-(n ₂ +
n ₄ )} / 2 <0.2 (4-4) -0.5 <{(ν ₁ + ν ₃ )-(ν ₂ +
ν ₄ )} / 2 <15.0 is satisfied.

The color image reading lens described in claim 5 is
39, the object side surface of the second lens 12 is an aspherical surface, and the f, f ₁ , f ₂ , d _j , ν _j (j = 1)
To 4), the _{conditions: (5-1) 0.7f <f 1} <1.0f (5-2) -0.37f <f 2 <-0.25f (5-3) 0.12 <{( _{n 1 + n 3) - (} n 2 +
n ₄ )} / 2 <0.2 (5-4) -0.5 <{(ν ₁ + ν ₃ )-(ν ₂ +
ν ₄ )} / 2 <12.0 is satisfied.

The color image reading lens described in claim 6 is
In the configuration of FIG. 39, the image side surface of the second lens 12 is an aspherical surface, and the f, f ₁ , f ₂ , d _j , ν _j (j = 1 to
4) the _{condition: (6-1) 0.75f <f 1} <1.0f (6-2) -0.35f <f 2 <-0.25f (6-3) 0.13 <{(n ₁ + n ₃ )-(n ₂ +
n ₄ )} / 2 <0.17 (6-4) -0.5 <{(ν ₁ + ν ₃ )-(ν ₂ +
ν ₄ )} / 2 <1.0 is satisfied.

The color image reading lens described in claim 7 is
39, the object side surface of the third lens 13 is an aspherical surface, and the f, f ₁ , f ₂ , d _j , ν _j (j = 1)
To 4), the _{conditions: (7-1) 0.8f <f 1} <1.5f (7-2) -0.45f <f 2 <-0.25f (7-3) 0.1 <{( _{n 1 + n 3) - (} n 2 +
n ₄ )} / 2 <0.2 (7-4) -0.5 <{(ν ₁ + ν ₃ )-(ν ₂ +
ν ₄ )} / 2 <15.0 is satisfied.

A color image reading lens according to claim 8 is:
39, the image side surface of the fourth lens 14 is an aspherical surface, and the f, f ₁ , f ₂ , d _j , ν _j (j = 1 to
4) the _{condition: (8-1) 0.7f <f 1} <0.9f (8-2) -0.4f <f 2 <-0.25f (8-3) 0.13 <{(n ₁ + n ₃ )-(n ₂ +
n ₄ )} / 2 <0.2 (8-4) -0.5 <{(ν ₁ + ν ₃ )-(ν ₂ +
ν ₄ )} / 2 <12.0 is satisfied.

As shown in FIGS. 40 and 41, in the color image reading lens according to the ninth to thirteenth aspects, the first lens 11 is a “positive lens”, the second lens 12 is a “biconcave lens”, and the third lens. The lens 13 is a “biconvex lens”, and the fourth lens 1
Reference numeral 4 denotes a “biconcave lens”, and any two surfaces of the first to fourth lenses are aspherical surfaces.

The color image reading lens described in claim 9 is
In such a configuration, the above f, f ₁ , f ₂ , d _j , ν _j
(J = 1 to 4) is a _{condition: (9-1) 0.35f <f 1} <0.9f (9-2) -0.25f <f 2 <-0.5f (9-3) 0. 12 <{(n ₁ + n ₃ )-(n ₂ +
n ₄ )} / 2 <0.16 (9-4) 9.0 <{(ν ₁ + ν ₃ ) − (ν ₂ +
ν ₄ )} / 2 <13.5 is satisfied.

In the color image reading lens of claim 10, as shown in FIG. 40, the first lens 11 is "a convex meniscus lens having a convex surface facing the object side", the second lens 12 is a "biconcave lens", and The third lens 13 is a “biconvex lens”, the fourth lens 14 is a “biconcave lens”, and the object side surface of the first lens 11 and the object side surface of the third lens 13 are aspherical surfaces, and the f, f ₁ , f _{2, d j, ν j (} j = 1~4) are _{conditions: (10-1) 0.5f <f 1} <0.9f (10-2) -0.3f <f 2 <-0.5f (10-3) 0.12 <{(n 1 + n 3) - (n 2 +
n ₄ )} / 2 <0.14 (10-4) 9.5 <{(ν ₁ + ν ₃ ) − (ν ₂ +
ν ₄ )} / 2 <13.5 is satisfied.

41, the first lens 11 is a "biconvex lens", the second lens 12 is a "biconcave lens", and the third lens 1 is
3 is a “biconvex lens”, and 4th lens 14 is a “biconcave lens”
Then, the object side surface of the first lens 11 and the object side surface of the third lens 13 are aspherical surfaces, and the f, f ₁ , f ₂ , d _j , and ν _{j are}
(J = 1 to 4), the _{conditions: (11-1) 0.4f <f 1} <0.5f (11-2) -0.3f <f 2 <-0.4f (11-3) 0. 13 <{(n ₁ + n ₃ )-(n ₂ +
n ₄ )} / 2 <0.16 (11-4) 10.0 <{(ν ₁ + ν ₃ ) − (ν ₂ +
ν ₄ )} / 2 <12.0 is satisfied.

In the color image reading lens according to claim 12, as shown in FIG. 41, the first lens 11 is a "biconvex lens", the second lens 12 is a "biconcave lens", and the third lens 1 is used.
3 is a “biconvex lens”, and 4th lens 14 is a “biconcave lens”
Then, the object side surface of the first lens 11 and the image side surface of the fourth lens 14 are aspherical surfaces, and f, f ₁ , f ₂ , d _j , ν
_{j (j} = _1~4) are _{conditions: (12-1) 0.35f <f 1} <0.5f (12-2) -0.25f <f 2 <-0.4f (12-3) 0 .13 <{(n ₁ + n ₃ ) − (n ₂ +
n ₄ )} / 2 <0.16 (12-4) 9.0 <{(ν ₁ + ν ₃ ) − (ν ₂ +
ν ₄ )} / 2 <11.0 is satisfied. The color image reading lens according to any one of claims 13 to 18, as shown in FIGS.
"Convex meniscus lens with convex surface facing the object side", No. 2
The lens 12 is a “concave meniscus lens having a convex surface facing the object side”, the third lens 13 is a “positive lens”, and the fourth lens 14
Is a “negative lens”, and at least the object side surface of the first lens 11 is an aspherical surface.

According to a thirteenth aspect of the present invention, in the above-mentioned configuration, the color image reading lens has the above-mentioned f, f ₁ , f ₂ , d _j and ν.
_{j (j} = _1~4) are _{conditions: (13-1) 0.35f <f 1} <0.55f (13-2) -0.35f <f 2 <-0.55f (13-3) 0 .1 <{(n ₁ + n ₃ ) − (n ₂ +
n ₄ )} / 2 <0.17 (13-4) 9.0 <{(ν ₁ + ν ₃ ) − (ν ₂ +
ν ₄ )} / 2 <12.0 is satisfied.

As shown in FIG. 42, in the color image reading lens according to claim 14, in the lens structure according to claim 13, the third lens 13 which is a positive lens has a “convex meniscus lens with a concave surface facing the object side”. , The fourth lens 14 which is a negative lens is arranged such that “the third lens 13 has the concave surface facing the object side.
Of the concave meniscus lens cemented to the image side of the first lens 11, the object side surface of the first lens 11 is an aspherical surface, and f, f ₁ , f ₂ ,
d _j , ν _j (j = 1 to 4) have the following conditions: (14-1) 0.35f <f ₁ <0.55f (14-2) -0.35f <f ₂ <-0.55f (14 -3) 0.1 <{(n ₁ + n ₃ )-(n ₂ +
n ₄ )} / 2 <0.17 (14-4) 9.0 <{((ν ₁ + ν ₃ ) − (ν ₂ +)
ν ₄ )} / 2 <12.0 is satisfied.

In the color image reading lens according to the fifteenth aspect, like the color image reading lens according to the thirteenth aspect, the first lens 11 is a “convex meniscus lens with its convex surface facing the object side”, and the second lens 12 is “Concave meniscus lens with convex surface facing the object side”, third lens 13 is “positive lens”, fourth lens 14 is “negative lens”, object side surface of first lens 11 and one other lens surface There are non-spherical, the _{f, f 1, f 2,} d j, ν j is (j = 1 to 4), _{condition: (15-1) 0.35f <f 1} <0.47f (15-2 _{) -0.35f <f 2 <-0.41f (} 15-3) 0.1 <{(n 1 + n 3) - (n 2 +
n ₄ )} / 2 <0.14 (15-4) 9.0 <{(ν ₁ + ν ₃ ) − (ν ₂ +
ν ₄ )} / 2 <11.5 is satisfied.

As shown in FIG. 42, in the color image reading lens according to claim 16, in the lens structure of the color image reading lens according to claim 14, the third lens 13, which is a positive lens, has a concave surface on the object side. Is a “concave meniscus lens”, and the fourth lens 14 that is a negative lens is a “concave meniscus lens in which the concave surface faces the object side and is cemented to the image side of the third lens 13”. , Third
The object side surface of the lens 13 is an aspherical surface, and the f, f ₁ ,
f ₂ , d _j , ν _j (j = 1 to 4) satisfy the condition: (16-1) 0.35f <f ₁ <0.45f (16-2) -0.37f <f ₂ <-0. 39f (16-3) 0.11 <{(n ₁ + n ₃ )-(n ₂ +
n ₄ )} / 2 <0.14 (16-4) 9.0 <{(ν ₁ + ν ₃ ) − (ν ₂ +
ν ₄ )} / 2 <11.0 is satisfied.

As shown in FIG. 42, in the color image reading lens according to claim 17, in the lens structure of the color image reading lens according to claim 14, the third lens 13 which is a positive lens has “a concave surface on the object side. Is a “concave meniscus lens”, and the fourth lens 14 that is a negative lens is a “concave meniscus lens in which the concave surface faces the object side and is cemented to the image side of the third lens 13”. , 4th
The image side surface of the lens 14 is an aspherical surface, and the f, f ₁ ,
f ₂ , d _j , ν _j (j = 1 to 4) satisfy the condition: (17-1) 0.37f <f ₁ <0.46f (17-2) -0.38f <f ₂ <-0. 41f (17-3) 0.1 <{( n 1 + n 3) - (n 2 +
n ₄ )} / 2 <0.14 (17-4) 9.5 <{(ν ₁ + ν ₃ ) − (ν ₂ +
ν ₄ )} / 2 <11.5 is satisfied.

As shown in FIG. 43, in the color image reading lens according to claim 18, in the lens structure of the color image reading lens according to claim 14, the third lens 13 which is a positive lens is a “biconvex lens”, The fourth negative lens
The lens 14 is a “biconcave lens”, and the object side surface of the first lens 11 and the object side surface of the second lens 12 are aspherical surfaces, and f, f ₁ , f ₂ , d _j , ν _j (j = 1 to 1) 4) _{conditions: (18-1) 0.36f <f 1} <0.47f (18-2) -0.35f <f 2 <-0.39f (18-3) 0.11 <{(n ₁ + n ₃ )-(n ₂ +
n ₄ )} / 2 <0.13 (18-4) 9.5 <{(ν ₁ + ν ₃ ) − (ν ₂ +
satisfies ν ₄ )} / 2 <10.5

[0032]

According to the color image reading lens of the present invention, the first lens is a positive lens, the second lens is a negative lens, the third lens is a positive lens, and the fourth lens is a negative lens. -Positive / negative configuration, which is formed by cementing the third lens and the fourth lens, and has an aspherical surface on one or more lens surfaces. Then, four conditions are set in order to realize a compact lens system and good performance.

The conditions (1-1) to (18-1) for controlling the lens power of the first lens are conditions for realizing the color image reading lens in a compact and low cost and with good performance. If the upper limit of the condition is exceeded,
The power of the first lens becomes too weak, the lens diameter becomes large, which causes an increase in cost, which is disadvantageous for compactness. On the other hand, if the value goes below the lower limit, it is advantageous for size reduction, but since coma flare becomes large, the MTF characteristic with respect to a high spatial frequency deteriorates.

The conditions (1-2) to (18-2) for controlling the lens power of the second lens are conditions for improving the performance of the color image reading lens. When “” becomes negative and becomes larger than the lower limit, spherical aberration becomes positive and becomes large, and coma flare also increases. Then, outside the range of these conditions, the balance of on-axis and off-axis aberrations is greatly lost.

Conditions (1-3) to (18) for defining the range of "difference between average refractive index of positive lens and average refractive index of negative lens"
-3) is a condition for obtaining good imaging performance. If the upper limit is exceeded, the Petzval sum becomes too small, and the image surface falls to the positive side and the "field curvature" increases, and the lower limit can be reached. On the contrary, the Petzval sum becomes too large and the image surface falls to the negative side, and the "astigmatism difference" becomes large. Outside of these conditions, it is difficult to obtain good imaging performance over the entire screen.

Conditions (1-4) to defining the range of "difference between average Abbe number of positive lens and average Abbe number of negative lens"
(18-4) is a condition for satisfactorily correcting chromatic aberration. When the upper limit is exceeded, the axial chromatic aberration is overcorrected, the axial chromatic aberration on the shorter wavelength side of the main wavelength becomes positive and large, and the lower limit is reached. On the contrary, on the contrary, the axial chromatic aberration on the longer wavelength side than the main wavelength becomes negative and becomes large.

In the present invention, in addition to the above four conditions, by using an aspherical surface for one or more lens surfaces, the occurrence of high-order aberrations is suppressed to a low level, and a high-contrast image is formed over the entire image surface. Achieve performance.

[0038]

EXAMPLES Specific examples will be given below. Throughout all of the embodiments, as shown in FIG. 1, the radius of curvature of the original side surface and the image side surface of the original glass 10 are rc ₁ and rc ₂ , respectively.
The thickness, the refractive index and the Abbe number of the original glass 10 are dc ₁ , nc ₁ and νc ₁ , respectively, and the curvature radii of the object side surface and the image side surface of the cover glass 15 of the image sensor are rc ₃ and rc ₄ , respectively. The thickness, the refractive index and the Abbe number of the cover glass 15 are respectively dc ₂ and nc ₂
And ν c ₂ .

Regarding the color image reading lens, counting from the object side, the radius of curvature of the i-th surface (including the surface of the diaphragm S) is r _i (i = 1 to 8), counting from the object side, The optical axis upper surface distance between the i-th surface and the (i + 1) th surface is defined as d _i (i
= 1 to 7), and the refractive index and the Abbe number of the j-th lens counted from the object side are n _j and ν _j (j = 1 to 4), respectively.
It is represented by.

As is well known, an aspherical surface has a radius of curvature on the optical axis R, a height from the optical axis H, coordinates X in the optical axis direction corresponding to H, a cone constant of quaternary, When the 6th, 8th, and 10th aspherical coefficients are A, B, C, and D, respectively, X = [(H ² / R) / {1 + √ (Y)}] + A · H ⁴ + B
-H ⁶ + C-H ⁸ + D-H ¹⁰ , Y = 1- (1 + K)-(H ² / R ² ) A curved surface obtained by rotating the curve around the optical axis Constant: K and high-order aspheric coefficient: A,
The shape can be specified by giving B, C, and D. In each embodiment, the lens surface adopted is "ASP".
Is added, the conical constant: K and the aspherical surface coefficient: A4, A
6, A8 and A10 are given. Aspherical coefficients A4, A6, A
8 and A10 correspond to the high-order aspherical surface coefficients: A, B, C, and D in the above equation, respectively. Note that the [E-number] in the display of the high-order aspherical coefficient represents a power. For example, [E-
10] means [1/10 ¹⁰ ] and this number is multiplied by the number that precedes it.

Note that f is the combined focal length of the entire system, F / No
Is brightness, m is an imaging magnification, and ω is a half angle of view.

The data relating to Examples 1 to 37 are sequentially shown as a chart in FIGS. 1 to 37.

Embodiments 1 and 2 are embodiments of the invention described in claim 1. Examples 3 to 20 are examples of the invention described in claim 2, Examples 3 to 6 are examples of the invention described in claim 3, and Examples 7 to 9 are examples of the invention described in claim 4. 10 to 12 are the embodiment and the embodiment 1 of the invention according to claim 5.
3, 14 are the embodiment of the invention described in claim 6 and the embodiment 15-
Reference numeral 17 is an embodiment of the invention according to claim 7, and Examples 18 to 20.
Is an embodiment of the invention described in claim 8.

Further, Examples 21 to 26 are Examples of the invention described in claim 9 and Examples 21 and 22 are Claims 1
The embodiment of the invention described in No. 0, Embodiments 23 and 24 are claims 11.
The embodiment of the invention described and the embodiments 25 and 26 are embodiments of the invention described in claim 12.

The twenty-seventh to thirty-seventh embodiments are embodiments of the invention described in the thirteenth aspect, and the twenty-seventh to twenty-ninth aspects are the fourteenth aspect.
Embodiments of the invention described, Examples 30 to 37 are embodiments of the invention described in claim 15, Examples 30 to 32 are embodiments of the invention described in claim 16, and Examples 33 to 35 are described in claim 17. The embodiments of the invention and Embodiments 36 to 38 are embodiments of the invention described in claim 17.

44 to 80, the above Examples 1 to 3 are sequentially performed.
The aberration diagram regarding 7 is shown. In these aberration diagrams, the broken line in the “spherical aberration” diagram indicates the “sine condition”, the solid line in the “astigmatism” diagram indicates the “sagittal ray”, and the broken line indicates the “meridional ray”. Further, are e-line (546.07 nm) and C-line (656.27), respectively.
nm) and g-line (435.83 nm).

In each of the examples, as shown in the above aberration charts,
Chromatic aberration is satisfactorily corrected in a wide wavelength range of C to g lines, and on-axis and off-axis aberrations are well balanced, and even though the aperture efficiency is almost 100%, the coma flare is small and up to a high spatial frequency. It has a high MTF.

[0048]

As described above, according to the present invention, a novel color image reading lens can be provided. Since the color image reading lens of the present invention is configured as described above, it has a bright F / No: 4.5, a half angle of view of 19.4 degrees and a wide angle of view, and various aberrations such as chromatic aberration. It is well corrected and has good performance, has a high MTF characteristic between high spatial frequencies, and can be realized at low cost and compactly.

Needless to say, the color image reading lens of the present invention can be suitably used for reading ordinary monochrome images.

[Brief description of drawings]

FIG. 1 is a chart showing data of Example 1.

FIG. 2 is a chart showing data of Example 2.

FIG. 3 is a chart showing data of Example 3.

FIG. 4 is a chart showing data of Example 4.

5 is a chart showing data of Example 5. FIG.

FIG. 6 is a chart showing data of Example 6.

FIG. 7 is a chart showing data of Example 7.

FIG. 8 is a chart showing data of Example 8.

9 is a chart showing data of Example 9. FIG.

FIG. 10 is a chart showing data of Example 10.

11 is a chart showing data of Example 11. FIG.

FIG. 12 is a chart showing data of Example 12.

FIG. 13 is a chart showing the data of Example 13.

FIG. 14 is a chart showing data of Example 14.

FIG. 15 is a chart showing data of Example 15.

16 is a chart showing the data of Example 16. FIG.

FIG. 17 is a chart showing data of Example 17.

FIG. 18 is a chart showing data of Example 18.

FIG. 19 is a chart showing the data of Example 19;

FIG. 20 is a chart showing the data of Example 20.

21 is a chart showing the data of Example 21. FIG.

22 is a chart showing data of Example 22. FIG.

FIG. 23 is a chart showing the data of Example 23.

FIG. 24 is a chart showing the data of Example 24.

FIG. 25 is a chart showing the data of Example 25.

FIG. 26 is a chart showing data of Example 26.

FIG. 27 is a chart showing the data of Example 27.

FIG. 28 is a chart showing data of Example 28.

FIG. 29 is a chart showing the data of Example 29.

FIG. 30 is a chart showing the data of Example 30.

FIG. 31 is a chart showing the data of Example 31.

FIG. 32 is a chart showing the data of Example 32.

FIG. 33 is a chart showing the data of Example 33.

FIG. 34 is a chart showing data of Example 34.

FIG. 35 is a chart showing the data of Example 35.

FIG. 36 is a chart showing data of Example 36.

FIG. 37 is a chart showing data of Example 37.

FIG. 38 is a diagram showing a lens configuration of a color image reading lens according to claim 1;

FIG. 39 is a diagram showing a lens configuration of a color image reading lens according to claims 2-8.

FIG. 40 is a diagram showing a lens configuration of a color image reading lens according to claims 9 and 10;

FIG. 41 is a diagram showing a lens configuration of a color image reading lens according to claims 9, 11 and 12;

FIG. 42 is a diagram showing a lens configuration of a color image reading lens according to claims 13 to 17;

FIG. 43 is a diagram showing a lens configuration of a color image reading lens according to claims 13, 15 and 18;

FIG. 44 is an aberration diagram for Example 1.

FIG. 45 is an aberration diagram for Example 2.

FIG. 46 is an aberration diagram for Example 3.

FIG. 47 is an aberration diagram for Example 4.

FIG. 48 is an aberration diagram for Example 5.

FIG. 49 is an aberration diagram for Example 6.

FIG. 50 is an aberration diagram for Example 7.

FIG. 51 is an aberration diagram for Example 8.

52 is an aberration diagram for Example 9. FIG.

FIG. 53 is an aberration diagram for Example 10.

54 is an aberration diagram for Example 11. FIG.

55 is an aberration diagram for Example 12. FIG.

FIG. 56 is an aberration diagram of Example 13;

FIG. 57 is an aberration diagram for Example 14.

FIG. 58 is an aberration diagram for Example 15.

59 is an aberration diagram for Example 16. FIG.

FIG. 60 is an aberration diagram for Example 17;

FIG. 61 is an aberration diagram for Example 18.

62 is an aberration diagram for Example 19. FIG.

63 is an aberration diagram for Example 20. FIG.

64 is an aberration diagram for Example 21. FIG.

65 is an aberration diagram for Example 22. FIG.

66 is an aberration diagram for Example 23. FIG.

67 is an aberration diagram for Example 24. FIG.

68 is an aberration diagram for Example 25. FIG.

69 is an aberration diagram for Example 26. FIG.

70 is an aberration diagram for Example 27. FIG.

71 is an aberration diagram for Example 28. FIG.

72 is an aberration diagram for Example 29. FIG.

73 is an aberration diagram for Example 30. FIG.

74 is an aberration diagram for Example 31. FIG.

75 is an aberration diagram for Example 32. FIG.

76 is an aberration diagram for Example 33. FIG.

77 is an aberration diagram for Example 34. FIG.

78 is an aberration diagram for Example 35. FIG.

79 is an aberration diagram for Example 36. FIG.

80 is an aberration diagram for Example 37. FIG.

[Explanation of symbols]

 11 1st lens 12 2nd lens 13 3rd lens 14 4th lens

Claims (18)

[Claims] 1. A first to a third lens group, which are sequentially arranged from the object side, wherein the first lens group is a biconvex lens, and the second lens group is a biconcave lens. The group consists of a third lens, which is a biconvex lens, and a fourth lens, which is a biconcave lens cemented to the image side of the third lens. It is a spherical surface, and the combined focal length of the entire system is f with respect to the e-line, and the focal lengths of the first and second groups with respect to the e-line are f ₁ , f ₂ , and j-th, respectively.
Refractive index for the material of the d line of the lens and the Abbe number, respectively, when the _{d j, ν j (j =} 1~4), these are _{conditions: (1-1) 0.4f <f 1} <0.5f _{(1-2) -0.3f <f 2 <} -0.4f (1-3) 0.1 <{(n 1 + n 3) - (n 2 +
n ₄ )} / 2 <0.2 (1-4) 9.0 <{(ν ₁ + ν ₃ ) − (ν ₂ +
A color image reading lens characterized by satisfying ν ₄ )} / 2 <10.5. 2. A first lens, which is a convex meniscus lens having a convex surface directed toward the object side, and a second group, which is a biconcave lens. And the third lens group is composed of a third lens which is a biconvex lens and a fourth lens which is a concave meniscus lens cemented to the image side of the third lens with its concave surface facing the object side. In the three-group, four-lens configuration, any one of the lens surfaces of the first to fourth lenses is an aspherical surface, the combined focal length of the entire system is f with respect to the e-line, and the first and second groups are The focal lengths for the e-line are f ₁ , f ₂ , and j-th, respectively.
Refractive index for the material of the d line of the lens and the Abbe number, respectively, when the _{d j, ν j (j =} 1~4), these are _{conditions: (2-1) 0.5f <f 1} <1.5f _{(2-2) -0.45f <f 2 <} -0.25f (2-3) 0.1 <{(n 1 + n 3) - (n 2 +
n ₄ )} / 2 <0.2 (2-4) -0.5 <{((ν ₁ + ν ₃ )-(ν ₂ +)
A color image reading lens characterized by satisfying ν ₄ )} / 2 <15.0. 3. A first lens group, which is a convex meniscus lens having a convex surface facing the object side, and a second lens group is a biconcave lens. And the third lens group is composed of a third lens which is a biconvex lens and a fourth lens which is a concave meniscus lens cemented to the image side of the third lens with its concave surface facing the object side. In the three-group, four-lens configuration, the object side surface of the first lens is an aspherical surface, the combined focal length of the entire system is f with respect to the e-line, and the focal lengths of the first and second groups with respect to the e-line are respectively f ₁ , f ₂ , the j th
Refractive index for the material of the d line of the lens and the Abbe number, respectively, when the _{d j, ν j (j =} 1~4), these are _{conditions: (3-1) 0.5f <f 1} <1.1f _{(3-2) -0.4f <f 2 <} -0.25f (3-3) 0.1 <{(n 1 + n 3) - (n 2 +
n ₄ )} / 2 <0.16 (3-4) -0.5 <{(ν ₁ + ν ₃ )-(ν ₂ +
A color image reading lens characterized by satisfying ν ₄ )} / 2 <15.0. 4. A first lens which is a convex meniscus lens having a convex surface directed toward the object side, and a second group is a biconcave lens. And the third lens group is composed of a third lens which is a biconvex lens and a fourth lens which is a concave meniscus lens cemented to the image side of the third lens with its concave surface facing the object side. In the three-group, four-lens configuration, the image side surface of the first lens is aspherical, the combined focal length of the entire system is f with respect to the e-line, and the focal lengths of the first and second groups with respect to the e-line are respectively f ₁ , f ₂ , the j th
Refractive index for the material of the d line of the lens and the Abbe number, respectively, when the _{d j, ν j (j =} 1~4), these are _{conditions: (4-1) 0.7f <f 1} <1.1f _{(4-2) -0.4f <f 2 <} -0.25f (4-3) 0.1 <{(n 1 + n 3) - (n 2 +
n ₄ )} / 2 <0.2 (4-4) -0.5 <{(ν ₁ + ν ₃ )-(ν ₂ +
A color image reading lens characterized by satisfying ν ₄ )} / 2 <15.0. 5. A first lens group, which is a convex meniscus lens having a convex surface facing the object side, and a second lens group is a biconcave lens. And the third lens group is composed of a third lens which is a biconvex lens and a fourth lens which is a concave meniscus lens cemented to the image side of the third lens with its concave surface facing the object side. In the three-group, four-lens configuration, the object side surface of the second lens is aspherical, the combined focal length of the entire system is f with respect to the e-line, and the focal lengths of the first and second groups with respect to the e-line are respectively f ₁ , f ₂ , the j th
Refractive index for the material of the d line of the lens and the Abbe number, respectively, when the _{d j, ν j (j =} 1~4), these are _{conditions: (5-1) 0.7f <f 1} <1.0f _{(5-2) -0.37f <f 2 <} -0.25f (5-3) 0.12 <{(n 1 + n 3) - (n 2 +
n ₄ )} / 2 <0.2 (5-4) -0.5 <{(ν ₁ + ν ₃ )-(ν ₂ +
A color image reading lens characterized by satisfying ν ₄ )} / 2 <12.0. 6. A first lens group, which is a convex meniscus lens having a convex surface facing the object side, and a second lens group is a biconcave lens. And the third lens group is composed of a third lens which is a biconvex lens and a fourth lens which is a concave meniscus lens cemented to the image side of the third lens with its concave surface facing the object side. In the three-group, four-lens configuration, the image side surface of the second lens is aspherical, the combined focal length of the entire system is f with respect to the e-line, and the focal lengths of the first and second groups with respect to the e-line are respectively f ₁ , f ₂ , the j th
Refractive index for the material of the d line of the lens and the Abbe number, respectively, when the _{d j, ν j (j =} 1~4), these are _{conditions: (6-1) 0.75f <f 1} <1.0f _{(6-2) -0.35f <f 2 <} -0.25f (6-3) 0.13 <{(n 1 + n 3) - (n 2 +
n ₄ )} / 2 <0.17 (6-4) -0.5 <{(ν ₁ + ν ₃ )-(ν ₂ +
A color image reading lens characterized by satisfying ν ₄ )} / 2 <1.0. 7. A first lens group, which is a convex meniscus lens having a convex surface directed toward the object side, and a second lens group is a biconcave lens. And the third lens group is composed of a third lens which is a biconvex lens and a fourth lens which is a concave meniscus lens cemented to the image side of the third lens with its concave surface facing the object side. In the three-group, four-lens configuration, the object side surface of the third lens is an aspherical surface, the combined focal length of the entire system is f with respect to the e-line, and the focal lengths of the first and second groups with respect to the e-line are respectively f ₁ , f ₂ , the j th
Refractive index for the material of the d line of the lens and the Abbe number, respectively, when the _{d j, ν j (j =} 1~4), these are _{conditions: (7-1) 0.8f <f 1} <1.5f _{(7-2) -0.45f <f 2 <} -0.25f (7-3) 0.1 <{(n 1 + n 3) - (n 2 +
n ₄ )} / 2 <0.2 (7-4) -0.5 <{(ν ₁ + ν ₃ )-(ν ₂ +
A color image reading lens characterized by satisfying ν ₄ )} / 2 <15.0. 8. A first lens group, which is a convex meniscus lens having a convex surface directed toward the object side, and a second lens group is a biconcave lens. And the third lens group is composed of a third lens which is a biconvex lens and a fourth lens which is a concave meniscus lens cemented to the image side of the third lens with its concave surface facing the object side. In the third lens group consisting of four lenses, the image side surface of the fourth lens is aspherical, the combined focal length of the entire system is f with respect to the e-line, and the focal lengths of the first and second groups with respect to the e line are respectively f ₁ , f ₂ , the j th
Refractive index for the material of the d line of the lens and the Abbe number, respectively, when the _{d j, ν j (j =} 1~4), these are _{conditions: (8-1) 0.7f <f 1} <0.9f _{(8-2) -0.4f <f 2 <} -0.25f (8-3) 0.13 <{(n 1 + n 3) - (n 2 +
n ₄ )} / 2 <0.2 (8-4) -0.5 <{(ν ₁ + ν ₃ )-(ν ₂ +
A color image reading lens characterized by satisfying ν ₄ )} / 2 <12.0. 9. The first to third groups are sequentially arranged from the object side, the first group is a first lens which is a positive lens, the second group is a second lens which is a biconcave lens, and a third lens. The group consists of a third lens, which is a biconvex lens, and a fourth lens, which is a biconcave lens cemented to the image side of the third lens. Any two of the surfaces are aspherical surfaces, the combined focal length of the entire system is f with respect to the e-line, and the focal lengths of the first and second groups with respect to the e-line are f ₁ , f ₂ , and j-th, respectively.
Refractive index for the material of the d line of the lens and the Abbe number, respectively, when the _{d j, ν j (j =} 1~4), these are _{conditions: (9-1) 0.35f <f 1} <0.9f _{(9-2) -0.25f <f 2 <} -0.5f (9-3) 0.12 <{(n 1 + n 3) - (n 2 +
n ₄ )} / 2 <0.16 (9-4) 9.0 <{(ν ₁ + ν ₃ ) − (ν ₂ +
A color image reading lens characterized by satisfying ν ₄ )} / 2 <13.5. 10. A first lens unit, which is a convex meniscus lens having a convex surface facing the object side, and a second lens unit is a biconcave lens. The second lens and the third lens group each have a third lens group consisting of a third lens element which is a biconvex lens element and a fourth lens element which is a biconcave lens element which is cemented to the image side of the third lens element. The object side surface of the first lens and the object side surface of the third lens are aspherical surfaces, the combined focal length of the entire system is f with respect to the e-line, and the focal lengths of the first and second groups with respect to the e line are respectively f ₁ , f ₂ , the j th
Refractive index for the material of the d line of the lens and the Abbe number, respectively, when the _{d j, ν j (j =} 1~4), these are _{conditions: (10-1) 0.5f <f 1} <0.9f _{(10-2) -0.3f <f 2 <} -0.5f (10-3) 0.12 <{(n 1 + n 3) - (n 2 +
n ₄ )} / 2 <0.14 (10-4) 9.5 <{(ν ₁ + ν ₃ ) − (ν ₂ +
A color image reading lens characterized by satisfying ν ₄ )} / 2 <13.5. 11. A first lens unit, which is a biconvex lens, a first lens unit, a second lens unit, which is a biconcave lens unit, and a third lens unit. The group consists of a third lens, which is a biconvex lens, and a fourth group, which is a biconcave lens cemented to the image side of the third lens. The object side surface of the third lens is aspherical, the combined focal length of the entire system is f with respect to the e-line, and the focal lengths of the first and second groups with respect to the e-line are f ₁ , f ₂ , and j-th, respectively.
Refractive index for the material of the d line of the lens and the Abbe number, respectively, when the _{d j, ν j (j =} 1~4), these are _{conditions: (11-1) 0.4f <f 1} <0.5f _{(11-2) -0.3f <f 2 <} -0.4f (11-3) 0.13 <{(n 1 + n 3) - (n 2 +
n ₄ )} / 2 <0.16 (11-4) 10.0 <{(ν ₁ + ν ₃ ) − (ν ₂ +
A color image reading lens characterized by satisfying ν ₄ )} / 2 <12.0. 12. A first lens unit, which is a biconvex lens, a first lens unit, a second lens unit, which is a biconcave lens unit, and a third lens unit. The group consists of a third lens, which is a biconvex lens, and a fourth group, which is a biconcave lens cemented to the image side of the third lens. The image side surface of the fourth lens is an aspherical surface, the combined focal length of the entire system is f with respect to the e-line, and the focal lengths of the first and second groups with respect to the e-line are f ₁ , f ₂ , and j
Refractive index for the material of the d line of the lens and the Abbe number, respectively, when the _{d j, ν j (j =} 1~4), these are _{conditions: (12-1) 0.35f <f 1} <0.5f _{(12-2) -0.25f <f 2 <} -0.4f (12-3) 0.13 <{(n 1 + n 3) - (n 2 +
n ₄ )} / 2 <0.16 (12-4) 9.0 <{(ν ₁ + ν ₃ ) − (ν ₂ +
A color image reading lens characterized by satisfying ν ₄ )} / 2 <11.0. 13. A first lens group, which is a convex meniscus lens having a convex surface facing the object side, and a second lens group having a convex surface. The second lens, which is a concave meniscus lens facing the object side, and the third group are composed of a third lens, which is a positive lens, and a fourth lens, which is a negative lens cemented to the image side of the third lens. In the three-group, four-lens configuration, at least the object side surface of the first lens is aspherical, the combined focal length of the entire system is f with respect to the e-line, and the focal lengths of the first and second groups with respect to the e-line are: F ₁ , f ₂ and jth respectively
Refractive index for the material of the d line of the lens and the Abbe number, respectively, when the _{d j, ν j (j =} 1~4), these are _{conditions: (13-1) 0.35f <f 1} <0.55f _{(13-2) -0.35f <f 2 <} -0.55f (13-3) 0.1 <{(n 1 + n 3) - (n 2 +
n ₄ )} / 2 <0.17 (13-4) 9.0 <{(ν ₁ + ν ₃ ) − (ν ₂ +
A color image reading lens characterized by satisfying ν ₄ )} / 2 <12.0. 14. A first lens group, which is a convex meniscus lens having a convex surface facing the object side, and a second lens group having a convex surface. The second lens, which is a concave meniscus lens facing the object side, and the third lens group, which is a convex meniscus lens with the concave surface facing the object side, and the image side of the third lens with the concave surface facing the object side In the three-group four-lens configuration including the fourth lens, which is a concave meniscus lens cemented to, the object side surface of the first lens is an aspherical surface, and the combined focal length of the entire system is f with respect to the e-line, The focal lengths of the first and second groups with respect to the e-line are f ₁ , f ₂ , and j-th, respectively.
Refractive index for the material of the d line of the lens and the Abbe number, respectively, when the _{d j, ν j (j =} 1~4), these are _{conditions: (14-1) 0.35f <f 1} <0.55f _{(14-2) -0.35f <f 2 <} -0.55f (14-3) 0.1 <{(n 1 + n 3) - (n 2 +
n ₄ )} / 2 <0.17 (14-4) 9.0 <{((ν ₁ + ν ₃ ) − (ν ₂ +)
A color image reading lens characterized by satisfying ν ₄ )} / 2 <12.0. 15. A first lens group, which is a convex meniscus lens having a convex surface facing the object side, and a second lens group having a convex surface. The second lens, which is a concave meniscus lens facing the object side, and the third group are composed of a third lens, which is a positive lens, and a fourth lens, which is a negative lens cemented to the image side of the third lens. In the three-group, four-lens configuration, the object side surface of the first lens and the other one lens surface are aspherical surfaces, the combined focal length of the entire system is f with respect to the e-line, and the first and second lens groups are The focal lengths for the e-line are f ₁ , f ₂ , and j-th, respectively.
Refractive index for the material of the d line of the lens and the Abbe number, respectively, when the _{d j, ν j (j =} 1~4), these are _{conditions: (15-1) 0.35f <f 1} <0.47f _{(15-2) -0.35f <f 2 <} -0.41f (15-3) 0.1 <{(n 1 + n 3) - (n 2 +
n ₄ )} / 2 <0.14 (15-4) 9.0 <{(ν ₁ + ν ₃ ) − (ν ₂ +
A color image reading lens characterized by satisfying ν ₄ )} / 2 <11.5. 16. A first lens group, which is a convex meniscus lens having a convex surface facing the object side, and a second lens group having a convex surface. The second lens, which is a concave meniscus lens facing the object side, and the third lens group, which is a convex meniscus lens with the concave surface facing the object side, and the image side of the third lens with the concave surface facing the object side The third lens group is composed of a fourth lens, which is a concave meniscus lens cemented to, and the object side surface of the first lens and the object side surface of the third lens are aspherical surfaces. With respect to the e-line, and the focal lengths of the first and second groups with respect to the e-line are f ₁ , f ₂ , and j-th, respectively.
Refractive index for the material of the d line of the lens and the Abbe number, respectively, when the _{d j, ν j (j =} 1~4), these are _{conditions: (16-1) 0.35f <f 1} <0.45f _{(16-2) -0.37f <f 2 <} -0.39f (16-3) 0.11 <{(n 1 + n 3) - (n 2 +
n ₄ )} / 2 <0.14 (16-4) 9.0 <{(ν ₁ + ν ₃ ) − (ν ₂ +
A color image reading lens characterized by satisfying ν ₄ )} / 2 <11.0. 17. A first lens group, which is a convex meniscus lens having a convex surface facing the object side, and a second lens group having a convex surface. The second lens, which is a concave meniscus lens facing the object side, and the third lens group, which is a convex meniscus lens with the concave surface facing the object side, and the image side of the third lens with the concave surface facing the object side The fourth lens is a concave meniscus lens cemented to the third lens group, and the object side surface of the first lens and the image side surface of the fourth lens are aspherical surfaces, and the combined focal length of the entire system. With respect to the e-line, and the focal lengths of the first and second groups with respect to the e-line are f ₁ , f ₂ , and j-th, respectively.
Refractive index for the material of the d line of the lens and the Abbe number, respectively, when the _{d j, ν j (j =} 1~4), these are _{conditions: (17-1) 0.37f <f 1} <0.46f _{(17-2) -0.38f <f 2 <} -0.41f (17-3) 0.1 <{(n 1 + n 3) - (n 2 +
n ₄ )} / 2 <0.14 (17-4) 9.5 <{(ν ₁ + ν ₃ ) − (ν ₂ +
A color image reading lens characterized by satisfying ν ₄ )} / 2 <11.5. 18. A first lens group, which is a convex meniscus lens having a convex surface facing the object side, and a second lens group having a convex surface. The second lens, which is a concave meniscus lens facing the object side, and the third group are composed of a third lens, which is a biconvex lens, and a fourth lens, which is a biconcave lens cemented to the image side of the third lens. In the three-group, four-lens configuration, the object side surface of the first lens and the object side surface of the second lens are aspherical surfaces, the combined focal length of the entire system is f with respect to the e-line, and The focal lengths for the e-line are f ₁ , f ₂ , and j-th, respectively.
Refractive index for the material of the d line of the lens and the Abbe number, respectively, when the _{d j, ν j (j =} 1~4), these are _{conditions: (18-1) 0.36f <f 1} <0.47f _{(18-2) -0.35f <f 2 <} -0.39f (18-3) 0.11 <{(n 1 + n 3) - (n 2 +
n ₄ )} / 2 <0.13 (18-4) 9.5 <{(ν ₁ + ν ₃ ) − (ν ₂ +
A color image reading lens characterized by satisfying ν ₄ )} / 2 <10.5.