JP6094857B2 - Reading lens and spectrometer - Google Patents

Description

  The present invention relates to a reading lens, and more particularly to a reading lens that is substantially telecentric on the image side, and a spectroscopic measurement apparatus having the reading lens.

The present applicant has previously proposed a spectroscopic measurement apparatus as described in Patent Document 1 (Japanese Patent Laid-Open No. 2011-99718).
The spectroscopic measurement device described in Patent Document 1 includes a light irradiation unit that irradiates light to an image bearing medium, and a plurality of openings arranged in one dimension to transmit part of diffused light from the image bearing medium. A hole array provided with a section, an imaging optical system for forming an image on the hole array, a diffraction element for diffracting the light beam for imaging, and light dispersed by the diffraction element A light receiving unit having a plurality of pixels arranged in a one-dimensional array for receiving light. In the light receiving unit, a plurality of spectral sensor units are formed for each predetermined number of pixels. The light that has passed through one opening of the hole array is split by the diffraction element and is incident on each pixel in the corresponding one of the spectral sensor units in the light receiving unit, so that the spectral characteristics of the light in the diffused light. The structure of the diffractive element is formed so as to change in accordance with the image height of the image formed by the imaging optical system.
The reading lens of the imaging optical system used in such a spectroscopic measurement apparatus has telecentricity on the image side in order to form an image diffracted by the diffraction element on a line sensor which is a one-dimensional light receiving unit. It is necessary to correct chromatic aberration well over the entire visible range.

Examples of lenses that are telecentric on the image side include the inventions described in Patent Document 2 (Japanese Patent No. 4867356) and Patent Document 3 (Japanese Patent Laid-Open No. 2002-162562).
Moreover, as an example of the telecentric lens of 4 groups 6 elements, the wide angle optical system described in patent document 4 (Unexamined-Japanese-Patent No. 2010-186011) and the wide-angle optical system described in patent document 5 (Unexamined-Japanese-Patent No. 2012-37640) are mentioned. There are systems.
However, the telecentric objective lens described in Patent Document 2 has a large number of nine lenses. When this objective lens is used, there is a problem that the measuring apparatus is enlarged and the cost is increased. .
In addition, the lens described in Patent Document 3 has a relatively small number of lenses, which is six, but uses two or three aspheric surfaces, and the entire lens system has a focal length. Therefore, there is a problem that the total length of the lens is large, and the measuring device is similarly enlarged and the cost is increased.
In addition, the lens described in Patent Document 4 and the wide-angle optical system described in Patent Document 5 have a relatively small number of lenses of 6 elements in 4 groups, but use two or three aspheric surfaces in the optical system. Therefore, there are problems that the cost is increased and the distortion is very large.

  The present invention has been made in view of the above-described circumstances, and the invention according to claim 1 has telecentricity on the image side while the number of lenses is six, and further includes c-line ( In the wide range from 656.27 nm to g-line (435.83 nm), the objective is to provide a reading lens that is excellent in correcting axial chromatic aberration and that is small in size and low in cost.

In order to achieve the above-described object, a reading lens according to claim 1 is provided.
A first lens group including a first lens of a positive meniscus lens, which is arranged with a convex surface directed toward the object side in order from the object side to the image side, and a positive second lens and a negative third lens are cemented together. A second lens group having a negative refractive power as a whole, a third lens group having a negative refractive power as a whole by joining a negative fourth lens and a positive fifth lens, and a positive sixth lens. In a four-group six-lens configuration composed of four lens groups, an aperture stop is provided between the second lens group and the third lens group,
The second lens is a biconvex lens, the third lens is a biconcave lens, the fourth lens is a negative meniscus lens having a concave surface facing the object side, and the fifth lens is disposed with a concave surface facing the object side. A positive meniscus lens, and the sixth lens is a biconvex lens,
here,
f6: focal length of e-line of the sixth lens f: total focal length of e-line of the entire system n convex: average of refractive indices of d-line of the positive lens (the first lens, the second lens, the fifth Lens, the sixth lens)
n-concave: average of refractive index of d-line of negative lens (the third lens, the fourth lens)
ν convex: average Abbe number of positive lenses (the first lens, the second lens, the fifth lens, the sixth lens)
ν concave: average of Abbe number of negative lens (the third lens, the fourth lens)
α: The principal ray of the incident light beam from the c-line to the g-line is the angle formed by the optical axis when exiting the final surface of the fourth lens group, and the sign of α is measured from the optical axis to counterclockwise. When the clockwise direction is negative ,
Conditional expressions (1), (2), (3) and (4) below:
0.5 <f6 / f <0.85 (1)
−0.01 <n convex−n concave <0.07 (2)
11.0 <ν convex−ν concave <16.5 (3)
| Α | <1 (4)
It is characterized by satisfying.
In order to achieve the above-described object, a reading lens according to claim 2 is provided.
A first lens group including a first lens of a positive meniscus lens, which is arranged with a convex surface directed toward the object side in order from the object side to the image side, and a positive second lens and a negative third lens are cemented together. A second lens group having a negative refractive power as a whole, a third lens group having a negative refractive power as a whole by joining a negative fourth lens and a positive fifth lens, and a positive sixth lens. In a four-group six-lens configuration composed of four lens groups, an aperture stop is provided between the second lens group and the third lens group,
The second lens is a biconvex lens, a third lens is a biconcave lens, the fourth lens is biconcave lens, the fifth lens is a biconvex lens, the sixth lens is biconvex lens,
here,
f6: focal length of e-line of the sixth lens f: total focal length of e-line of the entire system n convex: average of refractive indices of d-line of the positive lens (the first lens, the second lens, the fifth Lens, the sixth lens)
n-concave: average of refractive index of d-line of negative lens (the third lens, the fourth lens)
ν convex: average Abbe number of positive lenses (the first lens, the second lens, the fifth lens, the sixth lens)
ν concave: average of Abbe number of negative lens (the third lens, the fourth lens)
α: The angle α formed by the principal ray of the incident light beam from the c-line to the g-line with the optical axis when exiting the final surface of the fourth lens group, and the sign of the angle is measured from the optical axis to counterclockwise When the clockwise direction is negative ,
Conditional expressions (1), (2), (3) and (4) below:
0.5 <f6 / f <0.85 (1)
−0.01 <n convex−n concave <0.07 (2)
11.0 <ν convex−ν concave <16.5 (3)
| Α | <1 (4)
It is characterized by satisfying.

According to the invention of claim 1,
A first lens group including a first lens of a positive meniscus lens, which is arranged with a convex surface directed toward the object side in order from the object side to the image side, and a positive second lens and a negative third lens are cemented together. A second lens group having a negative refractive power as a whole, a third lens group having a negative refractive power as a whole by joining a negative fourth lens and a positive fifth lens, and a positive sixth lens. In a four-group six-lens configuration composed of four lens groups, an aperture stop is provided between the second lens group and the third lens group,
The second lens is a biconvex lens, the third lens is a biconcave lens, the fourth lens is a negative meniscus lens having a concave surface facing the object side, and the fifth lens is disposed with a concave surface facing the object side. A positive meniscus lens, and the sixth lens is a biconvex lens,
here,
f6: focal length of e-line of the sixth lens f: total focal length of e-line of the entire system n convex: average of refractive indices of d-line of the positive lens (the first lens, the second lens, the fifth Lens, the sixth lens)
n-concave: average of refractive index of d-line of negative lens (the third lens, the fourth lens)
ν convex: average Abbe number of positive lenses (the first lens, the second lens, the fifth lens, the sixth lens)
ν concave: average of Abbe number of negative lens (the third lens, the fourth lens)
α: The principal ray of the incident light beam from the c-line to the g-line is the angle formed by the optical axis when exiting the final surface of the fourth lens group, and the sign of α is measured from the optical axis to counterclockwise. When the clockwise direction is negative ,
Conditional expressions (1), (2), (3) and (4) below:
0.5 <f6 / f <0.85 (1)
−0.01 <n convex−n concave <0.07 (2)
11.0 <ν convex−ν concave <16.5 (3)
| Α | <1 (4)
By satisfying, the telecentricity on the image side can have a very good telecentricity and the range of ± 1 °, a wider range of c line (655.27nm) g-ray and (435.83 nm) in, axial chromatic aberration is satisfactorily corrected, it is and aberrations also satisfactorily corrected and, moreover, Ru can provide low-cost reading lens compact.
According to invention of Claim 2,
A first lens group including a first lens of a positive meniscus lens, which is arranged with a convex surface directed toward the object side in order from the object side to the image side, and a positive second lens and a negative third lens are cemented together. A second lens group having a negative refractive power as a whole, a third lens group having a negative refractive power as a whole by joining a negative fourth lens and a positive fifth lens, and a positive sixth lens. In a four-group six-lens configuration composed of four lens groups, an aperture stop is provided between the second lens group and the third lens group,
The second lens is a biconvex lens, the third lens is a biconcave lens, the fourth lens is a biconcave lens, the fifth lens is a biconvex lens, and the sixth lens is a biconvex lens;
here,
f6: focal length of e-line of the sixth lens f: total focal length of e-line of the entire system n convex: average of refractive indices of d-line of the positive lens (the first lens, the second lens, the fifth Lens, the sixth lens)
n-concave: average of refractive index of d-line of negative lens (the third lens, the fourth lens)
ν convex: average Abbe number of positive lenses (the first lens, the second lens, the fifth lens, the sixth lens)
ν concave: average of Abbe number of negative lens (the third lens, the fourth lens)
α: The principal ray of the incident light beam from the c-line to the g-line is the angle formed by the optical axis when exiting the final surface of the fourth lens group, and the sign of α is measured from the optical axis to counterclockwise. When the clockwise direction is negative ,
Conditional expressions (1), (2), (3) and (4) below:
0.5 <f6 / f <0.85 (1)
−0.01 <n convex−n concave <0.07 (2)
11.0 <ν convex−ν concave <16.5 (3)
| Α | <1 (4)
By satisfying, the telecentricity on the image side can have a very good telecentricity and the range of ± 1 °, a wider range of c line (655.27nm) g-ray and (435.83 nm) Thus, the axial chromatic aberration is corrected well, the various aberrations are also corrected, and a small and low-cost reading lens can be provided.

It is sectional drawing along the optical axis for demonstrating the concept of the reading lens of this invention. 1 is a cross-sectional view along an optical axis showing a configuration and an optical path of a reading lens according to a first embodiment of the present invention and Example 1. FIG. FIG. 3 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration of the reading lens according to Example 1 shown in FIG. 2. FIG. 6 is a cross-sectional view along the optical axis showing the configuration and optical path of a reading lens according to a second embodiment of the present invention and Example 2. FIG. 5 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration of the reading lens according to Example 2 shown in FIG. 4. FIG. 6 is a cross-sectional view along the optical axis showing the configuration and optical path of a reading lens according to Example 3 of the third embodiment of the present invention. FIG. 7 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration of the reading lens according to Example 3 shown in FIG. 6. It is a top view of the spectrometer which concerns on the 4th Embodiment of this invention. It is a side view of the spectrometer shown in FIG.

Hereinafter, a reading lens according to the present invention and a spectroscopic measurement apparatus employing the reading lens as an imaging optical system will be described with reference to the drawings.
Before describing specific examples, a conceptual (principal) embodiment of the present invention will be described first.
The reading lenses according to the first to third embodiments of the present invention are:
A first lens group including a first lens of a positive meniscus lens, which is arranged with a convex surface directed toward the object side in order from the object side to the image side, and a positive second lens and a negative third lens are cemented together. A second lens group having a negative refractive power as a whole, a third lens group having a negative refractive power as a whole by joining a negative fourth lens and a positive fifth lens, and a positive sixth lens. This is a reading lens composed of 4 groups and 6 elements in 4 groups, and has the following features.
And configured to have a aperture stop between the second lens group and the third lens group.
In order to satisfactorily correct the image side telecentricity and axial chromatic aberration, the above-described lens configuration is required.

Further, according to the present invention, in the reading lens configured as described above, the focal length of the e-line of the sixth lens is f6, the combined focal length of the entire e-line is f, and the positive lens (the first lens, The average of the refractive index of the d-line of the second lens, the fifth lens, and the sixth lens is n-convex, and the average of the refractive index of the d-line of the negative lens (the third lens and the fourth lens) is calculated. n-concave, average of Abbe number of the positive lens (the first lens, the second lens, the fifth lens, the sixth lens) is ν-convex, the negative lens (the third lens, the fourth lens) The average Abbe number is ν-concave , the chief ray of the incident light beam from the c-line to the g-line is α and the angle formed by the optical axis when exiting the final surface of the fourth lens group is α. The following conditions (1), (2), (3) when the counterclockwise direction measured from the axis is positive and the clockwise direction is negative: , (4) :
(1) 0.5 <f6 / f <0.85
(2) −0.01 <n convex−n concave <0.07
(3) 11.0 <ν convex−ν concave <16.5
| Α | <1 (4)
It is desirable to satisfy
Conditional expression (1) determines the power of the sixth lens. If the upper limit is exceeded, the power of the sixth lens becomes too weak, making it difficult to ensure telecentricity and increasing the lens cost. Cause up. Below the lower limit, the power of the sixth lens becomes too strong, making it difficult to correct various aberrations satisfactorily.

Conditional expression (2) defines the range of the refractive index of the convex lens and the concave lens constituting the reading lens in the first to third embodiments of the present invention. If the upper limit is exceeded, the Petzval sum Becomes too small, and the image plane falls to the positive side, and the curvature of field increases. On the contrary, if the value falls below the lower limit, the Petzval sum becomes too large, the image surface falls to the negative side, and the astigmatic difference becomes large.Under these conditions, good imaging performance can be obtained over the entire screen. Disappear.
Conditional expression (3) is a condition for satisfactorily correcting axial chromatic aberration. If the upper limit is exceeded, the axial chromatic aberration will be overcorrected, and the axial chromatic aberration will become larger on the positive side at shorter wavelengths than the dominant wavelength. On the other hand, if the lower limit is not reached, the axial chromatic aberration is insufficiently corrected, and the axial chromatic aberration becomes larger on the negative side on the shorter wavelength side than the dominant wavelength.
In the reading lens according to the present invention, after satisfying the conditional expressions (1), (2), (3) and (4) , the second lens is a biconvex lens, the third lens is a biconcave lens, The fourth lens is a negative meniscus lens having a concave surface facing the object side, the fifth lens is a positive meniscus lens having a concave surface facing the object side, and the sixth lens is a biconvex lens. not desirable.
It is possible to satisfactorily correct various aberrations including chromatic aberration without forming an aspherical surface in the optical system, and to reduce costs.
In the reading lens described above, the angle between the principal ray of the incident light beam from the c line to the g line and the optical axis when exiting the final surface of the fourth lens group is α, and the sign of α is measured from the optical axis. Where counterclockwise is positive and clockwise is negative, the following conditional expression (4):
| Α | <1 (4)
Is preferably satisfied (corresponding to claim 1 ).
When the number of lenses is 6 in 4 groups and the telecentricity on the image side is within a range of ± 1 °, very good telecentricity can be obtained. In addition, the axial chromatic aberration is corrected well in the wide range from the c-line (656.27 nm) to the g-line (435.83 nm), and the leading aberration is also corrected, and good performance can be obtained.

Various aberrations can be favorably corrected while keeping the lens system compact in a state where the conditional expressions (1), (2), (3) , and (4) are satisfied.
In addition, after satisfying the conditional expressions (1), (2), (3) and (4) , the second lens is a biconvex lens, the third lens is a biconcave lens, the fourth lens is a biconcave lens, The fifth lens may be a biconvex lens, and the sixth lens may be a biconvex lens (corresponding to claim 2).
Even with such a lens configuration, various aberrations can be corrected satisfactorily while keeping the lens system compact while satisfying the conditional expressions (1), (2), (3) , and (4). Can do.
In the reading lens configured as described above, it is desirable that all six lenses are glass lenses, and that the glass material does not contain harmful substances such as lead and arsenic (corresponding to claim 3).
In this way, all lenses are made of optical glass that is chemically stable and does not contain harmful substances such as lead and arsenic, so that materials can be recycled, and there is no water pollution due to waste liquid during processing, saving energy. It is possible to reduce CO2 and the like generated at the time of resource recycling and processing, and to obtain a reading lens that is small and low cost in consideration of the global environment.

In the reading lens described above, it is desirable that all the six lenses are composed of only spherical lenses (corresponding to claim 4).
It is possible to satisfactorily correct various aberrations including chromatic aberration without forming an aspherical surface in the optical system, and to reduce costs .

A light irradiating unit configured to irradiate the image bearing medium with light; a hole array provided with a plurality of openings arranged in one dimension to transmit part of diffused light from the image bearing medium; An image forming optical system for forming an image on the hole array, a diffraction element for diffracting the light beam for the image formation, and a plurality of one-dimensionally arranged light receiving light dispersed by the diffraction element A light receiving portion having pixels, wherein the light receiving portion has a plurality of spectral sensor portions formed for each predetermined number of pixels, and the light passing through one opening of the hole array is diffracted In the spectroscopic measurement device that obtains the spectral characteristics of the light in the diffused light by being split by the element and entering each pixel in the corresponding one of the spectral sensor units in the light receiving unit, It is desirable to have as Kiyuizo optical system (corresponding to claim 5).
The imaging optical system used in the spectroscopic measurement apparatus needs to have telecentricity on the image side in order to form an image diffracted by the diffraction element on a line sensor which is a one-dimensional light receiving unit, and the entire visible range. Therefore, the reading lens according to the present invention is exactly suitable for a spectroscopic measurement apparatus because it is necessary that the lens has a chromatic aberration corrected satisfactorily.
Embodiments and specific examples (numerical examples) of the reading optical system of the present invention are shown below.

In addition, the meaning of the symbol in Example 1- Example 3 is as follows.
Examples of the present invention are shown below. The meanings of symbols in each embodiment are as follows.
f: Composite focal length of e-line of the entire system FNo: F number m: Reduction ratio ω: Half angle of view (degrees)
Y: object height ri (i = 1 to 11): radius of curvature of the i-th lens surface counted from the object side di (i = 1 to 10): i-th surface interval counted from the object side nj (j = 1) ˜6): Refractive index of the material of the jth lens counted from the object side νj (j = 1 to 6): Abbe number of the material of the jth lens counted from the object side rc1: Curvature of the dummy glass on the object side Radius rc2: Radius of curvature on the image side of the dummy glass dc1: Thickness of the dummy glass nc1: Refractive index of the dummy glass νc1: Abbe number of the dummy glass nd: Refractive index of the d line ne: Refractive index of the e line f6: Sixth Focal length of lens e-line n convex: average of nd of lenses having positive refractive power n concave: average of nd of lenses having negative refractive power ν convex: average of nd of lenses having positive refractive power ν Concave: Average nd of lenses having negative refractive power FIG. Together is a conceptual diagram of a reading lens, is a cross-sectional view showing a configuration of an optical system of the reading lens.

The reading lens shown in FIG. 1 includes a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power in order from the object side to the image side along the optical axis. The third lens group G3 having negative refractive power and the fourth lens group G4 having positive refractive power are disposed, and the aperture stop AD is disposed between the second lens group G2 and the third lens group G3. doing.
The first lens group G1 includes a single first lens L1.
The second lens group G2 includes a second lens L2 and a third lens L3. The third lens group G3 includes a fourth lens group L4 and a fifth lens group L5. The fourth lens group G4 includes a single sixth lens L6.
The two lenses, the second lens L2 and the third lens L3, and the fourth lens L4 and the fifth lens L5, are intimately bonded to each other and joined together to form a cemented lens composed of two lenses. doing.
The first lens group G1 to the fourth lens group G4 are each supported by an appropriate support frame for each group.
FIG. 1 also shows surface numbers r1 to r11, rc1, rc2, surface intervals d1 to d10, dc, refractive indexes n1 to n6, nc, and Abbe numbers ν1 to ν6, νc of each optical surface.
The sectional view shown in FIG. 1 is the same as the sectional view of the first embodiment of the present invention shown in FIG. 2, and detailed description will be made with reference to FIG.

FIG. 2 is an optical path diagram showing a refraction state of a light beam transmitted through the lens, together with a sectional view showing a sectional configuration of the reading lens according to the first embodiment of the present invention and Example (Numerical Example) 1. Represents.
In FIG. 2, the reading lens 1 according to the first embodiment includes a first lens group G1 having a positive refractive power and negative refraction in order from the object side to the image side along the optical axis. A second lens group G2 having power, a third lens group G3 having negative refracting power, and a fourth lens group G4 having positive refracting power are arranged, and the second lens group G2 and the third lens group G3 are arranged. An aperture stop AD is disposed between the two.
The first lens group G1 includes a single first lens L1, the second lens group G2 includes a second lens L2 and a third lens L3, and the third lens group G3 includes a fourth lens L4. The fourth lens group G4 includes a fifth lens L5 and a single sixth lens L6.
Each of the two lenses, the second lens L2 and the third lens L3, and the fourth lens L4 and the fifth lens L5, are closely bonded to each other and joined together to form a cemented lens formed by joining the two lenses. Forming.

The first lens group G1 to the fourth lens group G4 are supported by each group or by a common support frame (not shown). The surface number of each optical is also shown. Note that each reference symbol in FIG. 2 is used independently for each embodiment in order to avoid complication of explanation due to an increase in the number of digits of the reference symbol, and therefore, a reference common to the drawings according to the other embodiments. Even if the reference numerals are given, they are not necessarily in common with the other embodiments.
An aperture stop AD is fixedly disposed between the second lens group G2 and the third lens group G3.
The reading lens 1 according to the first embodiment has a configuration of six elements in four groups of positive / negative / negative / positive.
In the first lens group G1, a first lens (positive lens) composed of a positive meniscus lens having a convex surface directed toward the object side is sequentially arranged from the object side toward the image side. The second lens group G2 includes, in order from the object side to the image side, a second lens L2 (positive lens) composed of a biconvex lens having a convex surface with a larger curvature than the image side surface toward the object side, and the image side. A third lens L3 (negative lens) composed of a biconcave lens having a concave surface having a larger curvature than the object side surface is disposed, and the two lenses of the second lens L2 and the third lens L3 are in close contact with each other. And bonded together to form a cemented lens consisting of two lenses.

The third lens group G3 includes, in order from the object side, a fourth lens L4 (negative lens) composed of a negative meniscus lens having a concave surface facing the object side and a fifth lens L5 (negative lens) composed of a positive meniscus lens having a convex surface directed to the image side. A positive lens), and the four lenses, the fourth lens L4 and the fifth lens L5, are closely bonded to each other to be joined together to form a cemented lens composed of two lenses. Yes.
In the fourth lens group G4, a sixth lens (positive lens) L6 including a biconvex lens having a convex surface with a larger curvature than the image side surface is disposed on the object side.
In the first embodiment, the parallel flat plate FG disposed on the image plane side of the fourth lens group G4 includes various filters such as an optical low-pass filter and an infrared cut filter, and light receiving elements such as a CMOS and a CCD sensor. A cover glass (or seal glass) is assumed.
The optical materials from the first lens L1 of the first lens group G1 to the sixth lens L6 of the fourth lens group G4 are all composed of optical lenses, and from the first surface r1 to the eleventh surface of the reading lens 1. It is also characterized in that no aspherical surface is formed on any lens surface.
The optical characteristics of each optical element in Example 1 are as shown in Table 1 below.

The values corresponding to the conditional expressions (1) to (3) in the first embodiment are as follows:
Conditional expression (1): f6 / f = 0.810
Conditional expression (2): n convex-n concave = 0.064055
Conditional expression (3): ν convex−ν concave = 11.10
And satisfy conditional expressions (1) to (3), respectively.
Further, the value corresponding to the conditional expression (4) in the first embodiment, that is, the incident angle α of the principal ray to the image plane is
-0.502 ° at 0.25y
-0.748 ° at 0.5y
-0.430 ° when 0.75y
0.208 ° at 0.9y
0.901 ° at 1.0y
And conditional expression (4) is satisfied.
Therefore, in the reading lens 1 of Example 1, the angle formed by the optical axis when the principal ray of the incident light beam from the c-line to the g-line exits the final surface of the fourth lens group (incident angle of the principal ray with respect to the image plane) It is clear that α has a very good telecentricity of 0.901.

FIG. 3 shows aberration diagrams of spherical aberration, astigmatism, distortion, and coma aberration (lateral aberration) in Example 1. In these drawings, a broken line in spherical aberration represents a sine condition, a solid line in astigmatism represents sagittal, and a broken line represents meridional. Further, c, e, F, and g in the respective aberration diagrams of spherical aberration, astigmatism, and coma aberration (lateral aberration) represent the c-line, e-line, F-line, and g-line, respectively. The same applies to the aberration diagrams of the other examples.
As can be seen from these aberration diagrams, the axial chromatic aberration in a wide range is corrected well, and various aberrations are also corrected.

FIG. 4 is an optical path diagram showing a refraction state of a light beam transmitted through the lens, together with a sectional view showing a sectional configuration of a reading lens according to Example 2 (Numerical Example) 2 according to the second embodiment of the present invention. Represents.
In FIG. 4, the reading lens 2 according to the second embodiment includes a first lens group G1 having a positive refractive power and negative refraction in order from the object side to the image side along the optical axis. A second lens group G2 having power, a third lens group G3 having negative refracting power, and a fourth lens group G4 having positive refracting power are arranged, and the second lens group G2 and the third lens group G3 are arranged. An aperture stop AD is disposed between the two.
The first lens group G1 includes a single first lens L1, the second lens group G2 includes a second lens L2 and a third lens L3, and the third lens group G3 includes a fourth lens L4. The fourth lens group G4 includes a fifth lens L5 and a single sixth lens L6.
The first lens group G1 to the fourth lens group G4 are supported by each group or by a common support frame (not shown). FIG. 4 also shows the surface numbers of the respective optics. In addition, in order to avoid complication of explanation due to an increase in the number of digits of the reference code, each reference code in FIG. 4 is used independently for each embodiment, and therefore, the same reference as the drawings according to other embodiments. Even if the reference numerals are given, they are not necessarily in common with the other embodiments.

The reading lens 2 according to the second embodiment also has six groups of four groups of positive / negative / negative / positive.
In the first lens group G1, a first lens (positive lens) composed of a positive meniscus lens having a convex surface directed toward the object side is sequentially arranged from the object side toward the image side. The second lens group G2 includes, in order from the object side to the image side, a second lens L2 (positive lens) composed of a biconvex lens having a convex surface with a larger curvature than the image side surface toward the object side, and the image side. A third lens L3 (negative lens) composed of a biconcave lens having a concave surface having a larger curvature than the object side surface is disposed, and the two lenses of the second lens L2 and the third lens L3 are in close contact with each other. And bonded together to form a cemented lens consisting of two lenses.
The third lens group G3 includes, in order from the object side, a fourth lens L4 (negative lens) composed of a biconcave lens having a concave surface with a larger curvature than the object side surface on the image side, and a positive meniscus lens having a convex surface on the object side. The fifth lens L5 (positive lens) is arranged, and the fourth lens L4 and the two lenses of the fifth lens L5 are closely bonded to each other and integrally joined to each other. A cemented lens is formed.
In the fourth lens group G4, a sixth lens (positive lens) L6 including a biconvex lens having a convex surface with a larger curvature than the image side surface is disposed on the object side.

In the second embodiment, the parallel flat plate FG disposed on the image plane side of the fourth lens group G4 includes various filters such as an optical low-pass filter and an infrared cut filter, and light receiving elements such as a CMOS and a CCD sensor. It is a dummy glass that assumes a cover glass (or seal glass).
The optical materials from the first lens L1 of the first lens group G1 to the sixth lens L6 of the fourth lens group G4 are all composed of glass lenses, and from the first surface r1 to the eleventh surface of the reading lens 1. It is also characterized in that no aspherical surface is formed on any lens surface. Glass materials that do not contain harmful substances such as lead and arsenic are used.
The optical characteristics of each optical element in Example 2 are as shown in Table 2 below.

The values corresponding to the conditional expressions (1) to (3) in the second embodiment are as follows:
Conditional expression (1): f6 / f = 0.666
Conditional expression (2): n convex-n concave = -0.00978
Conditional expression (3): ν convex−ν concave = 15.71
And satisfy conditional expressions (1) to (3), respectively.

Further, the value corresponding to the conditional expression (4) in the above-described second embodiment, that is, the incident angle α of the principal ray to the image plane is
-0.367 ° at 0.25y
-0.557 ° at 0.5y
-0.781 ° at 0.75y
-0.730 ° at 0.9y
-0.623 ° at 1.0y
And conditional expression (4) is satisfied.
Therefore, in the reading lens 2 of Example 2, the angle formed by the optical axis when the principal ray of the incident light beam from the c-line to the g-line exits the final surface of the fourth lens group (incident angle of the principal ray with respect to the image plane) It is clear that α has a very good telecentricity of −0.623 (when 1.0y).

FIG. 5 shows aberration diagrams of spherical aberration, astigmatism, distortion, and coma aberration (lateral aberration) in Example 2. In these drawings, a broken line in spherical aberration represents a sine condition, a solid line in astigmatism represents sagittal, and a broken line represents meridional. Further, c, e, F, and g in the respective aberration diagrams of spherical aberration, astigmatism, and coma aberration (lateral aberration) represent the c-line, e-line, F-line, and g-line, respectively. The same applies to the aberration diagrams of the other examples.
As can be seen from these aberration diagrams, the axial chromatic aberration in a wide range is corrected well, and various aberrations are also corrected.

FIG. 6 is an optical path diagram showing a refraction state of light rays passing through the lens, along with a sectional view showing a sectional configuration of a reading lens according to Example 3 (Numerical Example) 3 according to the third embodiment of the present invention. Represents.
In FIG. 6, the reading lens 3 according to the third embodiment includes a first lens group G <b> 1 having a positive refractive power and negative refraction in order from the object side to the image side along the optical axis. A second lens group G2 having power, a third lens group G3 having negative refracting power, and a fourth lens group G4 having positive refracting power are arranged, and the second lens group G2 and the third lens group G3 are arranged. An aperture stop AD is disposed between the two.
The first lens group G1 includes a single first lens L1, the second lens group G2 includes a second lens L2 and a third lens L3, and the third lens group G3 includes a fourth lens L4. The fourth lens group G4 includes a fifth lens L5 and a single sixth lens L6.
The first lens group G1 to the fourth lens group G4 are supported by each group or by a common support frame (not shown). The surface number of each optical is also shown. In addition, in order to avoid complication of explanation due to an increase in the number of digits of the reference code, each reference code in FIG. 6 is used independently for each embodiment, and therefore, is a reference common to the drawings according to other embodiments. Even if the reference numerals are given, they are not necessarily in common with the other embodiments.

The reading lens 3 according to the third embodiment has a configuration of six elements in four groups of positive / negative / negative / positive.
In the first lens group G1, a first lens (positive lens) composed of a positive meniscus lens having a convex surface directed toward the object side is sequentially arranged from the object side toward the image side. The second lens group G2 includes, in order from the object side to the image side, a second lens L2 (positive lens) composed of a biconvex lens having a convex surface with a larger curvature than the image side surface toward the object side, and the image side. A third lens L3 (negative lens) composed of a biconcave lens having a concave surface having a larger curvature than the object side surface is disposed, and the two lenses of the second lens L2 and the third lens L3 are in close contact with each other. And bonded together to form a cemented lens consisting of two lenses.
The third lens group G3 includes, in order from the object side, a fourth lens L4 (negative lens) composed of a biconcave lens with a concave surface having a larger curvature than the object side surface facing the image side, and a larger curvature than the image side surface toward the object side. A fifth lens L5 (positive lens) composed of a biconvex lens with its convex surface facing is disposed, and the fourth lens L4 and the two lenses of the fifth lens L5 are closely bonded to each other and integrated. A cemented lens composed of two lenses is joined.
In the fourth lens group G4, a sixth lens (positive lens) L6 including a biconvex lens having a convex surface with a larger curvature than the object-side surface is disposed on the image side.

In the third embodiment, the parallel flat plate FG disposed on the image plane side of the fourth lens group G4 includes various filters such as an optical low-pass filter and an infrared cut filter, and light receiving elements such as a CMOS and a CCD sensor. It is a dummy glass that assumes a cover glass (or seal glass).
The optical materials from the first lens L1 of the first lens group G1 to the sixth lens L6 of the fourth lens group G4 are all composed of glass lenses, and from the first surface r1 to the eleventh surface of the reading lens 3. It is also characterized in that no aspherical surface is formed on any lens surface. Further, the glass materials of the six lenses do not contain harmful substances such as lead and arsenic.
The optical characteristics of the optical elements in Example 3 are as shown in Table 3 below.

The values corresponding to the conditional expressions (1) to (3) in Example 3 described above are
Conditional expression (1): f6 / f = 0.530
Conditional expression (2): n convex-n concave = -0.00978
Conditional expression (3): ν convex−ν concave = 15.71
And satisfy conditional expressions (1) to (3), respectively.

Further, the value corresponding to the conditional expression (4) in the above-described third embodiment, that is, the incident angle α of the principal ray to the image plane is
-0.302 ° at 0.25y
-0.562 ° at 0.5y
-0.737 ° at 0.75y
-0.777 ° at 0.9y
-0.769 ° at 1.0y
And conditional expression (4) is satisfied.
Therefore, in the reading lens 3 of Example 3, the angle formed by the optical axis when the principal ray of the incident light beam from the c-line to the g-line exits the final surface of the fourth lens group (incident angle of the principal ray with respect to the image plane) It is clear that α has a very good telecentricity of −0.769 (when 1.0y).

FIG. 7 shows aberration diagrams of spherical aberration, astigmatism, distortion, and coma aberration (lateral aberration) in Example 3. In these drawings, a broken line in spherical aberration represents a sine condition, a solid line in astigmatism represents sagittal, and a broken line represents meridional. Further, c, e, F, and g in the respective aberration diagrams of spherical aberration, astigmatism, and coma aberration (lateral aberration) represent the c-line, e-line, F-line, and g-line, respectively. The same applies to the aberration diagrams of the other examples.
As can be seen from these aberration diagrams, the axial chromatic aberration in a wide range is corrected well, and various aberrations are also corrected.
Regarding conditional expressions (1) to (3),
The values of conditional expressions (1) to (3) in Examples 1 to 3 are summarized in Table 4 below.

  Moreover, about conditional expression (4), the value of conditional expression (4) in Examples 1 to 3 is shown in Table 5 below for each image height and summarized in Table 5.

[Fourth Embodiment]
Next, the reading lenses 1 to 3 according to the first to third embodiments of the present invention described above are employed as the imaging optical system of the spectroscopic measurement apparatus, and the fourth aspect of the present invention is configured. A spectroscopic measurement apparatus according to this embodiment will be described with reference to FIGS.
In FIG. 8 and FIG. 9, the spectroscopic measuring device displays a line illumination light source 12 that irradiates light on the image bearing medium 11, a light irradiating unit including a lens 13, and an image formed on the image bearing medium 11 on a hole array 15. A hole array 15 provided with a plurality of openings arranged in one dimension to transmit a part of diffused light from the image bearing medium 11, and a hole array 15. An imaging optical system 16 for forming an image on the upper side, a diffraction element 17 that diffracts a light beam for image formation, and a plurality of pixels arranged in a one-dimensional array that receive light dispersed by the diffraction element 17 A plurality of spectral sensor units are formed for each predetermined number of pixels, and the light passing through one opening of the hole array 15 is a diffraction element. By 17 The spectral characteristics of the diffused light can be obtained by being incident on each pixel in one corresponding spectral sensor section in the light receiving section 18, and the structure of the diffraction element 17 is an imaging optical system. 16 is formed so as to change in accordance with the image height of the image formed by 16.

The image height of the image formed by the imaging optical system 16 is the center of the optical axis of the imaging optical system 16 in the image formed on the line sensor (light receiving unit) 18 by the imaging optical system 16. The position in the X-axis direction when the origin is used, that is, the position in the arrangement direction of the pixels 21 in the line sensor 18 is meant.
In the spectroscopic measurement apparatus having the above configuration, when light is incident on the diffraction element 17 with an angle, the diffraction angle changes for each light having a different angle.
Then, it can be controlled that the width and angle of the diffraction image incident on the subsequent line sensor (for example, CCD) changes depending on the image height and the focal position changes.
Also, the optical layout is one-to-one correspondence between pinholes and microlenses, and the optical axes are aligned in a straight line, so it is necessary to enter the pinholes straight and reach the microlens as it is. Like the invention, the angle α formed when the final surface of the fourth lens group G4 is emitted is less than 1 ° (−0.623 ° in Example 2, 0.901 ° in Example 1), which is extremely low. Good telecentricity is a very important factor.

G1 First lens group G2 Second lens group G3 Third lens group G4 Fourth lens group L1 to L6 First lens to sixth lens ri (i = 1 to 11) Curvature of i-th lens surface counted from the object side Radius di (i = 1 to 10) i-th surface interval counted from the object side nj (j = 1 to 6) Refractive index of the material of the j-th lens counted from the object side νj (j = 1 to 6) Object Abbe number of material of the j-th lens from the side rc1 Radius of curvature of dummy glass on the object side rc2 Radius of curvature of dummy glass on the image side dc1 Thickness of dummy glass

JP 2011-99718 A Japanese Patent No. 4867356 JP 2002-162562 A JP 2010-186011 A JP 2012-37640 A

Claims (5)

A first lens group including a first lens of a positive meniscus lens, which is arranged with a convex surface directed toward the object side in order from the object side to the image side, and a positive second lens and a negative third lens are cemented together. A second lens group having a negative refractive power as a whole, a third lens group having a negative refractive power as a whole by joining a negative fourth lens and a positive fifth lens, and a positive sixth lens. In a four-group six-lens configuration composed of four lens groups, an aperture stop is provided between the second lens group and the third lens group,
The second lens is a biconvex lens, the third lens is a biconcave lens, the fourth lens is a negative meniscus lens having a concave surface facing the object side, and the fifth lens is disposed with a concave surface facing the object side. A positive meniscus lens, and the sixth lens is a biconvex lens,
A reading lens satisfying the following conditional expressions (1), (2), (3) , and (4) .
0.5 <f6 / f <0.85 (1)
−0.01 <n convex−n concave <0.07 (2)
11.0 <ν convex−ν concave <16.5 (3)
| Α | <1 (4)
However,
f6: focal length of e-line of the sixth lens f: total focal length of e-line of the entire system n convex: average of refractive indices of d-line of the positive lens (the first lens, the second lens, the fifth Lens, the sixth lens)
n-concave: average of refractive index of d-line of negative lens (the third lens, the fourth lens)
ν convex: average Abbe number of positive lenses (the first lens, the second lens, the fifth lens, the sixth lens)
ν concave: average of Abbe number of negative lens (the third lens, the fourth lens)
α: The principal ray of the incident light beam from the c-line to the g-line is the angle formed by the optical axis when exiting the final surface of the fourth lens group, and the sign of α is measured from the optical axis to counterclockwise. , Clockwise is negative. A first lens group including a first lens of a positive meniscus lens, which is arranged with a convex surface directed toward the object side in order from the object side to the image side, and a positive second lens and a negative third lens are cemented together. A second lens group having a negative refractive power as a whole, a third lens group having a negative refractive power as a whole by joining a negative fourth lens and a positive fifth lens, and a positive sixth lens. In a four-group six-lens configuration composed of four lens groups, an aperture stop is provided between the second lens group and the third lens group,
The second lens is a biconvex lens, the third lens is a biconcave lens, the fourth lens is a biconcave lens, the fifth lens is a biconvex lens, and the sixth lens is a biconvex lens,
A reading lens satisfying the following conditional expressions (1), (2), (3) , and (4) .
0.5 <f6 / f <0.85 (1)
−0.01 <n convex−n concave <0.07 (2)
11.0 <ν convex−ν concave <16.5 (3)
| Α | <1 (4)
However,
f6: focal length of e-line of the sixth lens f: total focal length of e-line of the entire system n convex: average of refractive indices of d-line of the positive lens (the first lens, the second lens, the fifth Lens, the sixth lens)
n-concave: average of refractive index of d-line of negative lens (the third lens, the fourth lens)
ν convex: average Abbe number of positive lenses (the first lens, the second lens, the fifth lens, the sixth lens)
ν concave: average of Abbe number of negative lens (the third lens, the fourth lens)
α: The principal ray of the incident light beam from the c-line to the g-line is the angle formed by the optical axis when exiting the final surface of the fourth lens group, and the sign of α is measured from the optical axis to counterclockwise. , Clockwise is negative.   3. The reading lens according to claim 1, wherein all of the six lenses are glass lenses, and the glass material does not contain harmful substances such as lead and arsenic.   The reading lens according to any one of claims 1 to 3, wherein all of the six lenses are composed of only spherical lenses. A light irradiating section for irradiating light to the image bearing medium; a hole array provided with a plurality of openings arranged in one dimension to transmit part of diffused light from the image bearing medium; and the hole array An imaging optical system for forming an image on the top, a diffractive element that diffracts the light beam for the image formation, and a plurality of pixels arranged in a one-dimensional array that receive the light dispersed by the diffractive element A plurality of spectroscopic sensor portions are formed for each predetermined number of pixels, and the light passing through one opening of the hole array is transmitted by the diffraction element. In the spectroscopic measurement apparatus which obtains the spectral characteristics of the light in the diffused light by being split and entering each pixel in the corresponding one of the spectral sensor sections in the light receiving section, according to any one of claims 1 to 4. Reading of description A spectroscopic measurement apparatus using a lens as the imaging optical system.

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