JP2000292693A - Method of manufacturing anamorphic lens - Google Patents

Abstract

(57) [Problem] To provide a method of manufacturing an anamorphic lens which can easily obtain good imaging performance. A method of manufacturing an anamorphic lens using a mold to mold an anamorphic lens having at least one surface having a rotationally asymmetric shape with respect to an optical axis, wherein the edge of the anamorphic lens has the largest width in the optical axis direction, or Molding by injecting an injection material from a gate provided in the vicinity thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an anamorphic lens, and more particularly, to reading an anamorphic lens manufactured by injection molding into an imaging lens when image information is read by a line sequential reading method using an image pickup device such as a CCD. It is suitable for an apparatus such as an image scanner, a digital copying machine, and a facsimile, which can perform high-precision image reading by being introduced into the apparatus.

[0002]

2. Description of the Related Art FIG. 8 is a schematic view of a main part when a conventional imaging lens for image reading is used in a flatbed image scanner.

In FIG. 1, a light beam radiated from an illumination light source 701 is directly or through a reflection shade 709 to an original 708.
And illuminates the reflected light flux from the original 708 with the first, second,
Third and fourth reflecting mirrors 703a, 703b, 703c,
The optical path of the light beam is bent inside the carriage 706 via the 703d, and the CCD (Cha) is formed by the imaging lens 704.
An image is formed on a surface of a linear image sensor 705 (hereinafter, referred to as a “CCD”) such as an Rge Coupled Device. The carriage 706 is moved by a sub-scanning motor 707 in the direction of arrow A (sub-scanning direction) shown in FIG.
, The image information of the original 708 is read. The CCD 705 shown in the figure has a configuration in which a plurality of light receiving elements are arranged in a one-dimensional direction (main scanning direction).

In order to reduce the size of the image scanner in the above configuration, it is necessary to reduce the size of the carriage 706.
In order to reduce the size of the carriage 706, for example, there is a method of increasing the number of reflection mirrors, or ensuring the optical path length by reflecting a plurality of times with one reflection mirror.

[0005]

However, these methods have a problem in that the structure inside the carriage 706 becomes complicated, so that the assembling accuracy is severe and the cost is greatly increased. Further, there is also a problem that the imaging performance is deteriorated in proportion to the surface accuracy of the reflection mirror and the number of reflections, which also affects the read image.

On the other hand, it is conceivable to widen the angle of view of the imaging lens (imaging system) 704 to reduce the distance between object images. Various types of imaging lenses with a wide angle of view realized with a realistic number of lenses and a spherical shape have been conventionally proposed. However, they all have a half angle of view of 2
The upper limit is about 5 degrees, and if the angle of view is made wider than that, there is a problem that field curvature and astigmatism increase, and sufficient optical performance cannot be exhibited.

Therefore, the present applicant has proposed the previously proposed Japanese Patent Application No. Hei 10-2.
In the image reading apparatus disclosed in Japanese Patent No. 76053, the above problem is solved by introducing an anamorphic lens having at least one surface which is rotationally asymmetrical with respect to the optical axis in the imaging lens.

In general, it is very costly to manufacture a lens having an anamorphic surface by grinding and polishing with a glass material. Further, in the case of manufacturing by molding using a plastic material, there are currently many problems to be solved, such as non-uniformity of the refractive index inside the lens and prevention of birefringence.

According to the present invention, when an anamorphic lens used in an imaging lens (imaging system) of an image reading apparatus is molded using a mold, the edge of the anamorphic lens having the largest width in the optical axis direction, or the edge portion thereof is used. By injecting and molding the injection material from the gate provided near,
It is an object of the present invention to provide a method for manufacturing an anamorphic lens which can suppress non-uniformity of the refractive index of the material of the lens, and can obtain simple and good imaging performance.

[0010]

According to a first aspect of the present invention, there is provided a method of manufacturing an anamorphic lens, wherein at least one surface of the anamorphic lens has a shape which is rotationally asymmetric with respect to the optical axis using a mold. Wherein the anamorphic lens is formed by injecting an injection material from an edge portion having the largest width in the optical axis direction or a gate provided near the edge portion.

According to a second aspect of the present invention, there is provided an image forming lens for image reading for forming image information of an original on a reading means, wherein at least one surface of the image forming lens is rotated with respect to an optical axis. An anamorphic lens having an asymmetrical shape, and the anamorphic lens is formed by injecting an injection material from a gate provided at the edge portion having the largest width in the optical axis direction or a gate provided near the edge using a mold. It is characterized by.

According to a third aspect of the present invention, there is provided an image reading apparatus, comprising: light source means for illuminating a document; an image forming lens for forming image information of the document illuminated by the light source means; The image forming lens has an anamorphic lens having at least one surface having a rotationally asymmetric shape with respect to the optical axis, and the anamorphic lens has a width in the optical axis direction using a mold. It is characterized by being formed by injecting an injection material from the thickest edge portion or a gate provided in the vicinity thereof.

[0013]

1 and 4 are sectional views of numerical examples 1 and 2 of an image forming lens according to the present invention, respectively. FIGS. 2 and 5 are numerical examples 1 and 2 of the present invention, respectively. And 2 are aberration diagrams. The imaging lens in FIGS. 1 and 4 includes a positive first lens 11, a negative second lens 12, an aperture, a positive third lens 13, a negative fourth lens 14, and a negative lens in order from the object (original surface) side. The fifth lens 15 is composed of a telephoto type having five lenses.

In the present invention, the negative fifth lens 15 is constituted by an anamorphic lens having at least one surface (the lens surface on the object side) having a rotationally asymmetric shape with respect to the optical axis. This anamorphic lens 15 is formed by using a mold, and has the edge portion having the largest width in the optical axis direction (the outer peripheral surface of the lens: edge surface);
Alternatively, it is formed by injecting an injection material (for example, a plastic made into a fluid by high heat or pressure) from a gate provided in the vicinity thereof. Note that a surface that is rotationally asymmetric with respect to the optical axis is also referred to as an “anamorphic surface” below.

Here, in Numerical Embodiment 1, the shape of the anamorphic surface 21 on the object side of the anamorphic lens 15 (generating line shape X and sagittal line shape S) will be described later (1),
It is represented by equation (2). In Numerical Embodiment 2, the shape of the anamorphic surface 22 on the object side of the anamorphic lens 15 (generating line shape X and sagittal line shape S) is expressed by the following equations (1) and (3).

(Numerical Embodiment 1) In Numerical Embodiment 1, the radius of curvature R of the generatrix of the anamorphic surface 21 and the radius of curvature r of the sagittal wire are made coincident with each other on the optical axis. The curvature radius r in the direction is changed to a value different from the curvature radius R in the generatrix direction. By adopting such a surface shape, the sagittal image plane and the meridional image plane can be set independently, and astigmatism can be eliminated for all angles of view.

As shown in FIG. 2, the various aberrations in Numerical Embodiment 1 are generated such that the sagittal image plane is joined to the meridional image plane, thereby eliminating astigmatism. Further, the amounts of various aberrations other than the field curvature and astigmatism can be suppressed to a practically sufficient range.

In the imaging lens of Numerical Example 1, the effective ray diameter on the R10 surface side of the anamorphic lens 15 is approximately φ15. Therefore, R of the anamorphic lens 15
The ten surfaces are manufactured as φ16 circles. At this time, according to equations (1) and (2) described later, when y = 8, X = −3.
5, and S = −3.2. Since the R11 surface is a spherical surface, it can be understood that the thickness of the edge in the plane including the optical axis and the generatrix is 0.3 thicker than the thickness of the edge in the plane including the optical axis and the sagittal line.

In the present invention, the anamorphic lens 1
5 is manufactured by injection molding a lens material using a mold. When a lens is manufactured by injection molding, the fluidity of the material inside the mold is an important factor in suppressing non-uniformity of the refractive index of the lens material (local fluctuation and occurrence of birefringence). . At the time of injecting the material from the molding machine into the mold, attaching the gate to the edge portion is a surface that contributes to imaging (R10,
This is preferable because the lens outer diameter does not need to be increased unnecessarily than when the lens is attached to R11).

In the case of a conventionally used rotationally symmetric aspherical lens, when the lens is finished in a circular shape around the optical axis, the thickness of the edge is constant. It is optional to attach to the position.

However, in the anamorphic lens shown in the present invention, when the outer shape is finished in a circular shape centered on the optical axis, the thickness of the edge portion is not uniform. Therefore, in order to ensure that the molded lens has stable optical characteristics, a new problem arises in which position in the edge portion having a different thickness the gate is preferably mounted.

The inventor of the present invention compared and considered the optical characteristics of the prototype, and found that the anamorphic lens 1 described above.
In No. 5, it was found that it is desirable to mount the gate in a plane including the optical axis and the generatrix with a relatively thick edge portion. As a result, the molding pressure can be set relatively high, the fluidity of the material inside the mold can be suitably secured, and the above-mentioned non-uniformity of the refractive index can be prevented. Further, it is preferable because the filling property of the material inside the mold can be maintained uniformly. Since the thickness of the injection port for injection injection of the molding machine is fixed according to the molding conditions and is considered to be a constant thickness, according to the molding method described above, the edge of the edge in the direction in which the gate is not attached is formed. The thickness can be made relatively thin. Accordingly, a relatively thin lens can be manufactured, and from the viewpoint of design, the degree of freedom is increased, which is preferable. Further, the molding time can be shortened and the cost can be reduced.

FIGS. 3A and 3B are sectional views of a main part of a molding machine (mold) when molding the anamorphic lens 15 according to the present invention. FIG. 3A is a cross-sectional view of a main part of the anamorphic lens 15 in a plane (xy plane) including the optical axis and the generating line, and FIG. 3B is a plane (xz) including the optical axis of the anamorphic lens 15 and the sagittal line. FIG. In Numerical Example 1, as shown in FIG. 3A, a gate 101 indicated by a broken line is set in the edge portion 102, and molding is performed by injecting an injection material therefrom.

As described above, in Numerical Embodiment 1, when the anamorphic lens 15 having at least one surface introduced into the imaging lens and having a shape rotationally asymmetrical with respect to the optical axis is formed using a mold, By injecting and molding the injection material from the edge portion where the width of the anamorphic lens 15 in the optical axis direction is the thickest, or from the gate provided in the vicinity thereof, the above-described non-uniformity of the refractive index can be prevented. And good imaging performance is obtained.

In Numerical Example 1, the radius of curvature R of the generatrix of the anamorphic surface 21 on the optical axis coincides with the radius of curvature r of the sagittal wire, but this is not always necessary.

(Numerical Embodiment 2) The anamorphic surface 22 in Numerical Embodiment 2 differs from the anamorphic surface 21 shown in Numerical Embodiment 1 in that the radius of curvature R of the generating line and the radius of curvature r of the sagittal line are different. It is formed so as not to depend on the distance from the axis.

In Numerical Embodiment 2, since the radius of curvature R of the generating line and the radius of curvature r of the sagittal line of the anamorphic surface 22 on the optical axis are set to be different, astigmatism on the optical axis is slightly reduced. Although it occurs, it is of such a degree that there is no practical problem. On the other hand, astigmatism at an image height with a large angle of view is well corrected.

In Numerical Example 2, as shown in FIG. 5, since the occurrence of spherical aberration is small, the imaging performance is well balanced at all angles of view, and favorable optical characteristics of the imaging lens can be obtained.

In Numerical Embodiment 2, similarly to Numerical Embodiment 1 described above, the effective ray diameter on the R10 surface side of the anamorphic lens 15 is approximately φ15. Accordingly, the R10 surface of the anamorphic lens 15 is manufactured as a φ16 circle. At this time, according to equations (1) and (3) described later, on the R10 surface, X = −4.5 at y = 8 and S = −2.8.
It is. Since the R11 surface is a spherical surface, it can be understood that the thickness of the edge in the plane including the optical axis and the generatrix is 1.7 thicker than the thickness of the edge in the plane including the optical axis and the sagittal line.

Therefore, when molding the anamorphic lens 15 in Numerical Embodiment 2, when the material is injected into the mold from the molding machine, as in Numerical Embodiment 1 described above, the optical axis and the busbar having a relatively thick edge portion are used. It is desirable to set the gate in a plane including Thereby, the fluidity of the material inside the mold is suitably secured, and the above-mentioned non-uniformity of the refractive index can be prevented.

FIGS. 6A and 6B are sectional views of a main part of a molding machine (mold) when molding the anamorphic lens 15 according to the present invention. FIG. 3A is a cross-sectional view of a main part of the anamorphic lens 15 in a plane (xy plane) including the optical axis and the generating line, and FIG. 3B is a plane (xz) including the optical axis of the anamorphic lens 15 and the sagittal line. FIG. In Numerical Example 2, as shown in FIG. 2A, a gate 101 shown by a broken line is set in the edge portion 102, and molding is performed by injecting an injection material therefrom.

The shape of the anamorphic surface is such that the intersection point between the lens surface of the imaging lens and the optical axis is the origin, the optical axis direction is the x-axis,
When the axis orthogonal to the optical axis in the main scanning section is the y-axis and the axis orthogonal to the optical axis in the sub-scanning section is the z-axis, the generatrix shape X corresponding to the main scanning direction is

[0033]

(Equation 1)

[0034] Here, R is the radius of curvature k _y, B _4, B ₆ is represented by the aspheric coefficients becomes equation.

The sagittal shape S corresponding to the sub-scanning direction is

[0036]

(Equation 2)

Here, r '= r ₀ (1 + D ₂ y ² + D ₄ y ⁴ + D ₆ y ⁶ ) where r ₀ is a radius of curvature D ₂ , D ₄ and D ₆ on the optical axis.

[0038]

(Equation 3)

Here, r is a sagittal radius of curvature k _z , D ₄ , D ₆ are expressed by an equation representing an aspheric coefficient.

In the present invention, the generatrix is a cut surface between the xy plane and the curved surface of the relative coordinate system of the surface, and the sagittal line is a cut surface between the plane perpendicular to the xy plane and the curved surface.

FIG. 7 is a schematic view of a main part when the imaging lens of the present invention is applied to an image reading apparatus such as an image scanner or a copying machine.

In FIG. 1, reference numeral 2 denotes a platen glass on which a document 8 is placed. Reference numeral 6 denotes a carriage, which integrally houses an illumination light source, a reflection shade, a plurality of reflection mirrors, an imaging lens, and a reading unit, which will be described later.
Scanning is performed in the sub-scanning direction (the direction of arrow A in FIG. 7) by a driving device such as a sub-scanning motor, and the image information of the original 8 is read. An illumination light source 1 is composed of, for example, a fluorescent lamp or a halogen lamp. Reference numeral 9 denotes a reflection shade, which reflects the light beam from the illumination light source 1 and illuminates the original 8 efficiently. Reference numerals 3a, 3b, 3c, and 3d denote first, second, third, and fourth reflection mirrors, respectively, which bend the optical path of the light beam from the original 8 inside the carriage 6. Reference numeral 4 denotes an image forming lens according to the present invention, which has the above-described lens configuration, includes an anamorphic lens formed by the above-described manufacturing method, and forms a light beam based on image information of the original 8 on the reading means 5 surface. Let me. Reference numeral 5 denotes a linear image sensor (CCD) as reading means.

In this embodiment, the light beam emitted from the illumination light source 1 illuminates the original 8 directly or via the reflection shade 9, and the reflected light beam from the original 8 is converted into first, second, third and fourth light beams.
The light path of the light flux is bent inside the carriage 6 via the reflection mirrors 3a, 3b, 3c and 3d to form an image on the surface of the CCD 5 by the imaging lens 4. The image information of the original 8 is read by moving the carriage 6 in the direction of arrow A (sub-scanning direction) by the sub-scanning motor 7.

In the present invention, the method of manufacturing an anamorphic lens has been described as described above. However, the present invention is not limited to this. For example, a lens having at least one surface having a rotationally asymmetric shape with respect to the optical axis (for example, a cylindrical lens) Etc.) can be applied to all.

Next, numerical embodiments 1 and 2 of the present invention will be described. In Numerical Examples 1 and 2, Ri is the radius of curvature of the i-th lens surface in order from the object side, Di is the i-th lens thickness and air gap from the object side, and Ni and νi are the i-th lenses in order from the object side. Are the refractive index and Abbe number of the glass of the lens.
The anamorphic surface indicates the coefficient of the anamorphic surface.

Numerical Example 1 fe = 30.59 mm FNO = 1: 5.0 2 ω = 60.0 ° m = -0.189 R 1 = 16.201 D 1 = 1.87 N 1 = 1.772 ν 1 = 49.6 R 2 = 35.993 D 2 = 1.26 R 3 = -46.836 D 3 = 2.30 N 2 = 1.640 ν 2 = 34.5 R 4 = 22.827 D 4 = 3.14 R 5 = (Aperture) D 5 = 0 R 6 = 18.418 D 6 = 6.27 N 3 = 1.772 ν 3 = 49.6 R 7 = -19.587 D 7 = 0.35 R 8 = -13.708 D 8 = 5.74 N 4 = 1.847 ν 4 = 23.8 R 9 = -18.096 D 9 = 7.31 R10 = -11.562 D10 = 1.00 N 5 = 1.699 ν 5 = 30.1 R11 = -26.668 Anamorphic surface coefficient R10 = -11.562 ky = 3.680 × 10 ^-1 B4 = -4.154 × 10 ^-6 B6 = 5.351 × 10 ^-8 D2 = -2.630 × 10 ^-3 D4 = 2.820 × 10 ^-5 D6 = -2.267 × 10 ^-7 Numerical example 2 fe = 30.60mm (meridional), 30.71mm (sagittal) FNO = 1: 5.0 2 ω = 60.0 ° m = -0.189 R 1 = 15.247 D 1 = 1.89 N 1 = 1.772 ν 1 = 49.6 R 2 = 31.433 D 2 = 0.866 R 3 = -51.163 D 3 = 3.00 N 2 = 1.640 ν 2 = 34.5 R 4 = 19.643 D 4 = 1.33 R 5 = (Aperture) D 5 = 0 R 6 = 16.826 D 6 = 6.27 N 3 = 1.772 ν 3 = 49.6 R 7 = -19.058 D 7 = 0.39 R 8 = -12.332 D 8 = 6.00 N 4 = 1.847 ν 4 = 23.8 R 9 = -15.738 D 9 = 7.51 R10 = -9.264 D10 = 1.00 N 5 = 1.699 ν 5 = 30.1 R11 = -19.041 * R1 0 is the coefficient of the meridional shape Anamorphic surface R10 = -9.264 ky = -4.234 × 10 ^-2 B4 = -3.465 × 10 ^-6 B6 = 8.394 × 10 ^-8 r10 = -9.227 kz = -7.526 × 10 ^-1 D4 =- 4.447 × 10 ^-5 D6 = 4.110 × 10 ^-6

[0047]

According to the present invention, when the anamorphic lens used in the imaging lens (imaging system) of the image reading apparatus is molded by using a mold as described above, the width of the anamorphic lens in the optical axis direction is reduced. By injecting and molding an injection material from the thickest edge portion or a gate provided in the vicinity thereof, non-uniformity of the refractive index of the material of the lens can be suppressed, and simple and good imaging performance can be obtained. An anamorphic lens manufacturing method can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lens according to a numerical example 1 of the present invention.

FIG. 2 is a diagram showing various aberrations of Numerical Embodiment 1 of the present invention.

FIG. 3 is a sectional view of a main part of an anamorphic lens according to Numerical Example 1 of the present invention;

FIG. 4 is a sectional view of a lens according to a numerical example 2 of the present invention.

FIG. 5 is a diagram showing various aberrations of Numerical Example 2 of the present invention.

FIG. 6 is a sectional view of a main part of an anamorphic lens according to Numerical Example 2 of the present invention;

FIG. 7 is a schematic diagram of a main part when the imaging lens of the present invention is applied to an image reading device.

FIG. 8 is a schematic view of a main part of a conventional image reading apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Illumination light source 2 Platen glass 3a, 3b, 3c, 3d Reflection mirror 4 Imaging lens 5 Reading means (CCD) 6 Carriage 7 Sub-scanning motor 8 Document 9 Reflection shade 11 First lens 12 Second lens 13 Third lens 14 Fourth lens 15 Fifth lens (anamorphic lens) 101 Edge 102 Gate

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H04N 1/107 F term (Reference) 2H087 KA08 LA02 LA28 PA04 PA17 PB04 QA02 QA07 QA12 QA22 QA25 QA37 QA42 QA45 RA05 RA13 5B047 BA02 BB02 BC05 BC11 5C051 AA01 BA03 DB22 DC07 DD00 FA01 5C072 AA01 BA02 DA02 EA05 XA01

Claims (3)

[Claims] 1. A method of manufacturing an anamorphic lens using a mold to mold an anamorphic lens having at least one surface having a rotationally asymmetric shape with respect to an optical axis, wherein the anamorphic lens has a thickest edge in the optical axis direction. Alternatively, a method of manufacturing an anamorphic lens, characterized by molding by injecting an injection material from a gate provided in the vicinity thereof. 2. An image forming lens for image reading for forming image information of a document on a reading means, said image forming lens having an anamorphic lens having at least one surface having a rotationally asymmetric shape with respect to an optical axis. An imaging lens characterized in that the anamorphic lens is formed by injecting an injection material from a gate portion having the largest width in the optical axis direction or a gate provided near the edge portion using a mold. 3. An image reading apparatus comprising: light source means for illuminating a document; an image forming lens for forming image information of the document illuminated by the light source means; and reading means arranged at an image forming position of the image forming lens. In the imaging lens, at least one surface has an anamorphic lens having a shape that is rotationally asymmetric with respect to the optical axis, and the anamorphic lens is formed by using a mold at or near the edge portion having the largest width in the optical axis direction. An image reading device formed by injecting an injection material from a gate provided.