JP2000214305A - Compact lens array for erect real image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a lens array for an erect real image having simple constitution, made excellent in mass-productivity, made compact, making the distance between object images short and having excellent performance. SOLUTION: Equal fine projecting condensing curved surfaces are respectively arranged at equal intervals in a state where they are connected through a thin base layer on a line on the front surface and the back surface of a plane parallel transparent base plate, and the light condensing curved surfaces on the front and the back surfaces hold an optical axis in common. The 1st image of an object is reduced and formed at a distance being nearly 1/2 thickness of the base plate by the projecting condensing curved surface on the object side, and the image is enlarged and reformed by the projecting condensing curved surface on an image side so as to obtain an erect real image. By setting relation between the thickness of the base plate and curvature, the erect image is obtained. A metallic mold is formed by pressing a punch on one projecting condensing curved surface to a metallic plane at equal intervals. Ultraviolet curing resin is dripped on the metallic mold and a transparent base plate is placed thereon, and ultraviolet rays are radiated from a base plate side. The material of the projecting condensing curved surface layer on the object side is equal to that of the base plate and the layer and the base plate are integrally molded by an injection molding method when the material is plastic, and by a press molding method when the material is glass.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an erect real image compact lens array suitable for reading an original such as a copier, a facsimile, and an image scanner.

[0002]

2. Description of the Related Art As a lens array for obtaining an erect real image, a gradient index rod lens array is used, but there is a difficulty in removing chromatic aberration, and it is not possible to cope with a sufficient color. Also, a method of combining a micro-imaging lens and a roof mirror to obtain an erect real image (Japanese Patent Laid-Open No.
308121) and a method of inserting a roof prism between lenses (Japanese Patent Application Laid-Open No. 6-273692).
The flatness of the mirror and the tolerance of the prism apex angle must be tight, which is complicated and increases the number of parts. JP-A-55-909
The rod-shaped lens described in JP-A-07-07207 re-images the first image formed by the rod-shaped lens on the object side by a rod-shaped lens on the image side which is symmetrically opposed to the first image. The convex surface close to and facing one image acts as a condenser and is advantageous for holding the peripheral light amount. However, the biconvex surface near the focal point is difficult to prevent dust and scratches and is conspicuous, and the number of lenses is large. The accuracy of alignment also becomes severe.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide an erect real image lens array having a simple structure, excellent mass productivity, a small size, a short distance between object images, and excellent performance.

[0004]

According to the present invention, as shown in FIG. 1, fine convex condensing curved surfaces which are equal to a straight line on one (object side) surface of a parallel flat transparent substrate are connected by thin base layers. In the same state, fine convex light-condensing curved surfaces equivalent to this are also arranged at equal intervals on a straight line on the opposite (image side) surface, with the thin base layers connected to each other. In a lens array in which the minute convex converging curved surfaces share the same optical axis, the divergent light from the object is reduced to approximately 1 / th of the substrate thickness by the minute convex converging curved surface on the object side in order to obtain an erect real-size real image.
In a configuration in which the image is reduced and formed at a distance of 2 and the image is enlarged and re-imaged by a minute convex condensing curved surface convex to the image side arranged symmetrically to the object side, in order from the object side as shown in FIG. r _i : radius of curvature of spherical surface or apex of aspheric surface _di : thickness on the optical axis or air space _ni : refractive index of material r ₃ : radius of curvature of object-side convex condensing curved surface or apex of aspheric surface Curvature radius d ₃ : On-axis thickness of object-side convex condensing curved surface layer n ₂ : Refractive index of material of object-side convex condensing curved surface layer d ₄ : 1/2 thickness of substrate n ₃ : Refractive index of substrate material , and satisfies the _{1.14 <{(d 3 n 3} + d 4 n 2) · (n 2 -1)} / r 3 n 2 n 3 <1.55 ...... (1) the condition Things. In order to create minute convex condensing curved surfaces at equal intervals, press a punch of a convex curved surface formed in a predetermined shape on a relatively soft metal plane at equal intervals, and then harden the surface to obtain an accurate mold. I knew it could be done. An ultraviolet curable resin is dropped on this mold, a transparent substrate is placed thereon, and irradiation with ultraviolet rays is performed from the substrate side, so that a fine convex converging curved surface array with high accuracy can be obtained. On the opposite side, use the same mold or a mold with the same pitch even if the data is slightly different, and use a jig with the optical axis of the fine convex condensing curved surface on the front and back to fix the ultraviolet curing resin on the mold Is dropped, a completed transparent substrate on one side is placed, and ultraviolet rays are irradiated from the substrate side, whereby a lens array of an erect real image can be formed.

In addition, when the refractive index n ₂ of the material of the object side convex condensing curved surface layer is equal to the refractive index n ₃ of the material of the substrate and the material is plastic, injection molding is used. It is a major feature of the present invention that it can be integrally molded by a molding method.

Next, conditional expression (1) will be described. Conditional expression (1) is the relationship between the radius of curvature of the convex condensing curved surface on the object side or the apex radius of curvature of the aspheric surface, the axial thickness of the convex condensing curved surface layer, the refractive index of the material, the thickness of the substrate, and its refractive index. With respect to, the range of the imaging magnification m ₁ of the first image on the object side is defined, the magnification is reduced to m ₁ by the convex condensing curved surface on the object side, and the magnification m by the symmetrically arranged convex condensing curved surface on the image side. _{When the} image is enlarged and re-imaged by ₂ = 1 / m _1, a real image at the same magnification of the erect image is obtained. If the corresponding value on the image side is slightly different, the re-imaging magnification m ₂ on the image side
However, the total magnification M (= m ₁ × m ₂ ) does not become 1, but has little influence on aberration.

Therefore, determining the range of the imaging magnification m ₁ on the object side is an important point in the configuration of the present invention.
Conditional expression (1) is {r ₃ / (n ₂ -1)} · (1-m ₁ ) = (d ₃ / n
₂ ) In (d ₄ / n ₃ ), the distance is set within the range of 0.14 <−m ₁ <0.55. If the lower limit is exceeded, the distance between object images becomes large. A certain miniaturization becomes impossible, and the effective aperture of the convex condensing curved surface on the object side is limited, the effective F number EF _NO becomes large, and the image surface illuminance at the time of re-imaging decreases. When the value exceeds the upper limit, the image plane illuminance increases, but the peripheral light amount decreases because there is no condenser.

[0008] In the second aspect, the spherical aberration, astigmatism, and field curvature are improved when an aspherical surface having a smaller curvature is employed as the convex light-converging curved surface facing the object side and the image side goes to the periphery. Therefore, the performance is improved, and the object field and the image field can be widened, so that the pitch between the lenses can be increased. In the third aspect, when a thin flat base layer other than the convex condensing curved surface portion is used as a sanding surface, it is effective in preventing stray light, and it is more effective to make this surface a matte black. In addition, it is of course possible to cover portions other than the lens portion with a light shielding plate. In claim 4, the radius of curvature of the convex condensing curved surface on the re-imaging side or the apex radius of curvature of the aspheric surface is determined to be within 5% of the radius of curvature of the convex condensing curved surface on the object side or the apex radius of curvature of the aspheric surface. This is because, if this condition is deviated, the total imaging magnification deviates as much as 15% or more for the purpose of erecting the same magnification. A fifth aspect of the present invention is to make the stray light prevention according to the third aspect more effective, and as shown in FIG. 3A, a comb whose width becomes narrower toward the object than the gap of the lens gap on the object side. When one or both of the tooth-shaped light-shielding wall and the comb-teeth-shaped light-shielding wall whose width becomes narrower toward the image than the gap between the lenses on the image side is provided, stray light prevention is perfect.

According to an eighth aspect of the present invention, the width of the light-shielding wall according to the fifth aspect is constant from the gap between the lenses toward the object and the image, and as shown in FIG. By making it three times or less, it is easy to manufacture and has an effect of preventing stray light.

[0010] Claim 6, when the imaging magnification -m ₁ by convex condensing curved surface of the object side is small, less reduction in large very peripheral light amount of the object height, the convex condensing curved surface in one row of the array take larger array pitch but with an increase of the object height when -m ₁ increases, a decrease in the peripheral light amount occurs. In this case, when the array is increased to two rows as shown in FIG. 4 and the pitch is shifted by １ ／, there is an effect of compensating for the insufficient light quantity.

[0011]

Next, Tables 1 to 10 show Embodiments 1 to 10 of an erect real image compact lens array according to the present invention. FIG. 2 shows a lens array 1 in which a document as an object is in close contact with a document holding plate having a thickness of d ₁ , and a convex condensing curved surface layer is bonded to the object side and the image side of the transparent substrate with an air gap therebetween. The first image of the object formed by the object-side convex condensing curved surface layer is reduced and formed at a position of approximately の of the thickness of the substrate with a magnification m ₁ , and the image is formed. To form an enlarged image at a magnification of m ₂ . The total magnification M = m ₁ × m ₂ . In order from the object side, the radius of curvature of a plane or a sphere or the radius of curvature of the apex of an aspheric surface is r _i , the thickness or air interval on the axis is d _i , the refractive index of the material with respect to the e-line is n _i , and the Abbe number is v _i . The formula for the shape of the aspheric surface is as follows: X: distance from a tangent plane at the vertex of the lens surface to a point on the aspheric surface h: height from the optical axis C: curvature of the aspherical vertex (C = 1 / r) K: cone Constant A _2i : aspherical surface coefficient

[0012]

(Equation 1) It is represented by In each embodiment, the focal length of the entire system is represented by f, the effective F number is represented by EF _NO , the object height is represented by y, the image height of re-imaging is represented by y ', and the distance between the object and the image is also described.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

[Table 3]

[0016]

[Table 4]

[0017]

[Table 5]

[0018]

[Table 6]

[0019]

[Table 7]

[0020]

[Table 8]

[0021]

[Table 9]

[0022]

[Table 10] FIGS. 5 to 14 show aberration curves and MTF curves of each embodiment of the erect real image compact lens array of the present invention. As can be seen from this curve, spherical aberration, astigmatism, and coma are well corrected, and the chromatic aberration of magnification is zero. The white light MTF also has a wide depth and a high MTF value at a high frequency of 600 DPI when the aspherical surface is employed, and at a frequency of 400 DPI when the aspherical surface is not used. It is also an advantage of the present invention that it can sufficiently handle color documents.

[0023]

As described above, according to the present invention, in the manufacture of a mold, a punch having a convex curved surface formed in a predetermined shape is formed and pressed at a regular interval onto a relatively soft metal plane. As a result, a fine convex light-condensing curved surface having a uniform and high accuracy can be obtained, and transfer to a transparent substrate can be performed in one step while being connected by a thin base layer. If an image is transferred to the opposite surface using a jig in which the optical axes of the minute convex condensing curved surfaces on the front surface and the rear surface match, a lens array of an erect real image can be accurately formed. Moreover, equal refractive index n ₃ of the material of refractive index n ₂ and the substrate material of the object side convex condensing curved surface layer, by injection molding if the material is a plastic, if the material is a glass by press molding The ability to be integrally molded is also a major feature of the present invention. Since the first image, which is a reduced image of the object, is formed at the position and inside of the transparent substrate at a thickness of approximately １ ／, the erect real image of re-imaging has an advantage that no dust is formed at all. It is possible to provide a low-cost lens array that has a simple configuration, is excellent in mass productivity, is small, has a short distance between object images, can handle color documents, and has high performance even at a high frequency of 600 DPI.

[Brief description of the drawings]

FIG. 1 is a side sectional view and a plan view of an erect real image compact lens array according to the present invention.

FIG. 2 is a diagram showing an optical system of the present invention.

FIG. 3 is an explanatory view of a stray light preventing light-shielding wall according to the present invention.

FIG. 4 is a plan view showing the array of the present invention in two columns.

FIG. 5 is an aberration curve and an MTF / DEF curve of Example 1.

FIG. 6 shows an aberration curve and an MTF / DEF curve of Example 2.

FIG. 7 is an aberration curve and an MTF / DEF curve of Example 3.

FIG. 8 shows an aberration curve and an MTF / DEF curve of Example 4.

9 is an aberration curve and an MTF / DEF curve of Example 5. FIG.

FIG. 10 shows an aberration curve and an MTF / DEF curve of Example 6.

11 shows an aberration curve and an MTF / DEF curve of Example 7. FIG.

FIG. 12 shows an aberration curve and an MTF / DEF curve of Example 8.

13 shows an aberration curve and an MTF / DEF curve of Example 9. FIG.

FIG. 14 shows aberration curves and MTF / DEF of Example 10.
It is a curve.

Claims (8)

[Claims] 1. A micro-convex condensing curved surface equal to a straight line on one surface of a transparent substrate in a parallel plane is arranged at equal intervals while being connected by a thin base layer, and also on a straight line on an opposite surface. Equivalent microconvex condensing curved surfaces are arranged at equal intervals in a state where they are connected by a thin base layer, and the microconvex condensing curved surfaces on the front and back of the transparent substrate are erect equal magnification in a lens array each sharing an optical axis. In order to obtain a real image, the divergent light from the object is reduced and combined to a distance of about 1/2 of the substrate thickness by the minute convex condensing curved surface on the object side, and the image becomes convex on the image side arranged symmetrically with the object side fine convex condensing curved surface r in order from the object side in the structure to expand reimaging by _i: radius of curvature or aspheric vertex curvature radius d _i of the spherical: thickness or air space along the optical axis n _i: the refractive index of the material , r _3: the object-side convex condensing curved surface of curvature radius or aspherical Vertex curvature radius d _3: axial thickness of the object side convex condensing curved surface layer n _2: refractive index of the material of the object side convex condensing curved surface layer d _4: 1/2 the thickness of the substrate n _3: refraction of the material of the substrate in _{rate, 1.14 <{(d 3 n} 3 + d 4 n 2) · (n 2 -1)} / r 3 n 2 n 3 satisfies the <1.55 ... (1) the condition A small lens array of an upright real image. 2. The small lens array according to claim 1, wherein the minute convex light condensing curved surface is an aspheric surface whose curvature decreases as it goes to a spherical surface or a peripheral edge. 3. A small lens array of an upright real image, wherein the thin flat base layer other than the minute convex condensing curved surface portion according to claim 1 or 2 is a sandblast surface. 4. The lens array according to claim 1, wherein the absolute value of the radius of curvature of the minute convex condensing curved surface on the image side or the absolute value of the apex curvature radius of the aspheric surface is determined by the radius of curvature of the minute convex condensing curved surface on the object side. Alternatively, an erect real image compact lens array characterized by being allowed within 5% of the apex radius of curvature of the aspherical surface. 5. The lens array according to claim 1, wherein a comb-shaped light-shielding wall having a width narrower toward the object than a gap between the object-side lenses and an image from the gap between the image-side lenses. An erect real image miniature lens array comprising one or both of a comb-shaped light-shielding wall having a width narrowing toward the end. 6. The small erect real image according to claim 1, wherein the linear rows of the minute convex condensing curved surfaces on the object side and the image side of the transparent substrate can be two rows. Lens array. 7. The refractive index n ₂ of the material of the object-side convex light-condensing curved layer and the refractive index n of the material of the substrate in the configuration according to claim 1.
_3. An erect real image compact lens array characterized by being able to be integrally molded by an injection molding method when the material is plastic and by a press molding method when the material is glass. 8. The erecting wall according to claim 5, wherein the width toward the object and the image from the gap between the lenses is constant, and the length is three times or less the outer diameter of the lens. Small lens array of real images.