JPH06273692A - Image forming element - Google Patents

Abstract

PURPOSE:To provide the line image forming element which does not require especially difficult know-how and is easy to produce and has less chromatic aberrations. CONSTITUTION:A pair of transparent members 3 and 3 where the reflecting face of the rectangular prism face, where one or more rectangular prisms having edge lines parallel with intersections between faces orthogonal to incidence and exit faces and reflecting faces are arranged is substituted for a Dove prism, are symmetrically arranged so that rectangular prism faces of transparent members are outside, and two convex lenses 1 and 2 having the same focal length are placed on incidence and exit faces of both transparent member respectively, and they are taken as a constitution unit, and plural constitution units are arranged on a line perpendicular to the optical axes of convex lenses, thus constituting this line image forming element. Three or more constitution units at least one of which is not on the same line may be arranged into a plane- shape on a face perpendicular to the optical axes of convex lenses.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming element used in facsimiles, electronic copying machines, LED printers and the like.

[0002]

2. Description of the Related Art In facsimiles, electronic copying machines, LED printers and the like, line-shaped image-forming elements are used to project an object on a line onto a sensor or a photosensitive drum at an equal magnification. An example of such an imaging element is a so-called rod lens array, which is an array of cylindrical transparent bodies whose refractive index continuously changes in the radial direction from the center, and a plate on which an array of spherical lenses is formed (three layers). (For example, Japanese Patent Publication No. Sho 49-8893,
JP-A-57-104923, JP-A-57-664
14), an erecting equal-magnification optical system formed by combining a roof prism and a lens is arranged in an array (for example, JP-A-61-210319 and JP-A-56-1).
17201, JP-A-56-126801,
JP-A-56-140301, JP-A-56-149
002, JP 60-254018, JP 60-254019, and JP 60-25402.
No. 0, JP 61-233714 A, JP 6
2-91902 and JP-A-62-201417).

[0003]

Each of these conventional techniques has the following problems. In the above-mentioned imaging element method, it is necessary to form a refractive index distribution in a cylindrical transparent body and to control it precisely, but this requires special know-how. , It is not an easily realizable technology. Further, since it is particularly difficult to make a rod lens having a large diameter, there is a problem that when it is desired to increase the distance between the lens and the subject, the F value decreases and the optical system becomes dark.

Next, the method has a problem that it is difficult to align the optical axes of the single lenses in each layer of the lens array with sufficient accuracy, and it is difficult to form a particularly long array. In addition, the method has a drawback that chromatic aberration is likely to be large because the integration of refraction angles of light rays is large.

On the other hand, in the method, since the roof prism (or roof prism) is used for reversing the image, the integration of the refraction angles is small and the chromatic aberration is small. However, there is a problem that it is difficult to accurately align the axes of the roof prism (or roof mirror) and the lens. Therefore, it is an object of the present invention to solve the problems of the above-mentioned various conventional techniques, and to provide an imaging element that does not require particularly difficult know-how, is easy to manufacture, and has small chromatic aberration.

Another object of the present invention is to provide an image forming element which can be formed not only in a line shape but also in a plane shape capable of projecting a two-dimensional image.

[0007]

In the imaging element according to the first aspect of the present invention, the reflecting surface of the dove prism (or the trapezoidal prism) is parallel to the straight line intersecting the surface orthogonal to the entrance / exit surface and the reflecting surface. A pair of transparent members, each forming a Dove prism in which at least one right-angled prism having a ridge line is replaced by a right-angled prism surface, are arranged symmetrically in contact with each other so that the right-angled prism surface of the transparent member faces outward. ,
Further, two convex lenses having the same focal length are respectively arranged on the entrance and exit surfaces of both transparent members as a constitutional unit, and a plurality of the constitutional units are arranged on a straight line perpendicular to the optical axis of the convex lens. It

Further, the imaging element according to the second invention of the present application,
Three or more of these constituent units are arranged on a plane perpendicular to the optical axis of the convex lens so that at least one is not on the same straight line. Another imaging element according to the second invention of the present application is
Each of the dove prisms is formed by replacing the reflecting surface of the dove prism with a surface of a right-angle prism having at least one right-angle prism having a ridge line parallel to a straight line intersecting the reflecting surface and the surface orthogonal to the entrance / exit surface. A pair of transparent members are symmetrically arranged so that the right-angled prism surfaces of the transparent members are in contact with each other, and two cylindrical convex lenses with equal focal lengths and parallel generatrices are arranged on each of the entrance and exit surfaces. A plurality of structural units that are arranged on a straight line perpendicular to the generatrix of the cylindrical convex lens, and that have two generatrix lines facing both cylindrical convex lens rows and parallel to the arrangement direction of the structural units. The band-shaped cylindrical convex lens is arranged.

[0009]

In the image forming device using the lens array, it is necessary for each constituent unit to form a continuous line image in which an erect image is formed. According to the above-described image forming element of the present invention, since the image can be erected by using the image inverting action of the Dove prism and the right angle prism, the burden on the lens is reduced and the burden of chromatic aberration and optical axis alignment is reduced. It becomes possible.

In addition, the imaging element according to the present invention can obtain an erecting equal-magnification image in a two-dimensional direction, and therefore a planar imaging element can be formed.

[0011]

1 is a perspective view of an example of a structural unit of an imaging element according to the first invention of the present application, FIG. 2 (a) is a yz plane, and FIG. 2 (b) is a plan view of an xz plane. . In the figure, 1 and 2 are convex lenses, 3 is a transparent member, 4 is a rectangular prism surface, 5 is an adhesive, 6 is an object surface, and 7 is an image surface. Object plane 6, image plane 7
Is located at a position away from each lens by a focal length, the convex lenses 1 and 2 have a common optical axis, and the points where they intersect the object plane 6 and the image plane 7 are the object plane and the origin O of the image plane, respectively.
And As shown in FIG. 2A, an erect image is obtained in the y direction by the action of the right-angle prism surface, and an erect image is obtained in the x direction by the action of the Dove prism 3. This will be described in more detail.

FIG. 3 is a xy plan view of the structural unit of FIG. 1 viewed from the image plane 7 for explaining the function of the right-angled prism. The light emitted from the origin O of the object plane and the point x ₁ on the x-axis is
The convex lens 1 converts the traveling vector into parallel light whose y component is 0, enters the transparent member 3, is reflected by the rectangular prism surface 4, and exits the transparent member 3 to reach the convex lens 2.
Since the ray vector does not generate the y component during this period, it can be seen that these rays reach the same y coordinate as the point O on the image plane.

The transparent member 3 has the same function as a Dove prism (or a trapezoidal prism) in the xz plane. Figure 4
Explains the function of the Dove prism, and is characterized in that the light incident on the incident surface at an angle α with the optical axis is reflected by the reflecting surface and emitted from the emitting surface in the opposite direction at the same angle α. Since the entrance / exit surface forms an acute angle θ with the reflecting surface, it efficiently acts on the light along the optical axis due to refraction.

From this, the action of the above-mentioned structural units in the xz plane can be explained as follows. The light entering the convex lens ₁ from the point x _{1 on the} object plane 6 is first converted into parallel light which forms an angle −tan ⁻¹ (x ₁ / f) with the optical axis (z axis) by the action of the lens 1 (however, f represents the focal length of lenses 1 and 2). Then, due to the above-mentioned action of the transparent member 3 (action of the Dove prism), this light is transmitted through the optical axis at an angle tan.
^The light is converted into parallel light of ⁻¹ (x ₁ / f) and is focused by the action of the lens 2 at the point of coordinate x ₁ on the image plane 7. Thus x
_Since the y-coordinate of ₁ is stored as described above, the light emitted from the point x _{1 on the} object plane is eventually at the same position as seen from the point O on the image plane, that is, the position of the erecting equal-magnification image. It will be focused.

In FIG. 3, light emitted from a point y ₁ on the y-axis of the object plane is converted by the convex lens 1 into parallel light having a traveling vector x component of 0, and enters the transparent member 3 to form a right angle. The light is reflected by the prism surface 4, but at this time, the action of the right-angle prism 4 causes the sign of the y component of the traveling vector to be reversed and the sign to be reversed, and the light exits the transparent member 3 and reaches the convex lens 2. In the operation of FIG. 4, since the vector of the light emitted from the transparent member 3 does not have the x component, the above description of the x coordinate applies to the y coordinate as it is, and this light ray is acted on the image plane 7 by the action of the lens 2. Will be focused on the point of the position coordinate y ₁ of the erecting equal-magnification image of.

The above description can be applied to a point at arbitrary coordinates on the object plane 6, and a perfect erect image of equal magnification can be obtained on the image plane 7. That is, an erecting equal-magnification image in the x direction is obtained by (1) position-angle conversion by the lens 1, (2) angle reversal by the Dove prism and right-angle prism surfaces, and (3) angle-position conversion by the lens 2. . Therefore, by arranging these structural units in the x direction or the y direction, continuous erecting equal-magnification images can be obtained.

This means that the position information between the lens 1 and the lens 2 has no meaning, which leads to the optical stability of the present imaging element. That is, the lens 1 or the lens 2 in FIG.
Even if the position of is slightly shifted in the x and y directions, it appears only in the translation of the image, and the image quality itself is hardly changed. The most important factor in assembling the lens array is that the fluctuations in the pitch between the lenses are integrated in the array direction and cause a non-negligible optical axis shift. It has the characteristic that it is not easily affected by the gap.

FIGS. 7 to 9 schematically show an example of an arrangement method when the above-mentioned constituent units are arranged on a straight line. (A) and (b) in each figure are transparent. An array of members 3 and an array of convex lenses 1 and 2 are shown. 7 and 8 show the rectangular prism surface 4 of each structural unit.
7 are arranged so as to be in contact with each other. In the example shown in FIG. 7, since the arrangement density is increased by using the meshing of the right-angle prisms, the lens 1 is arranged so that the light of the adjacent structural unit is not mixed in the meshing part. , 2, it is necessary to provide a light-shielding portion 1-1 (2-1) and use an array that is discontinuously arranged. In this case, as shown in FIG. 5A, when the side surface of the right-angle prism is not shielded, the lenses 1 and 2 are shielded by the shield portions 1-1 (2
-1) is required, but when using a transparent member in which overlapping portions are shielded by black coating 8 as shown in FIG. 5B, this shielding portion is not necessary.

On the other hand, as shown in FIG. 8, even in the example in which the constituent units are arranged so as not to overlap each other, the light shielding portion is not necessary. Further, although the example shown in FIG. 9 is an example of arranging in a direction perpendicular to this, in this case as well, the light shielding plates 3-1 and 3 are provided between the respective constituent units so that light of adjacent constituent units is not mixed. -1
It is better to put a shield on it. FIG. 6 shows an embodiment in which the constituent units of the imaging device according to the first invention of the present application are arranged as shown in FIG. 8, and FIG. 10 shows an embodiment in which the constituent units are arranged as shown in FIG. In either case, continuous erecting equal-magnification images can be obtained.

As a concrete example, a = 11.2 mm,
b = 2.8 mm, θ = 45 °, 20 mm prisms shown in FIG. 5 (a) made of polymethylmethacrylate in which 6 rows of rectangular prisms with a pitch of 1 mm are engraved on the reflecting surface with a prism height of 6 mm and a radius of curvature. One 8 mm 6 mm x 6 mm square convex lens
The image-forming element of FIG. 6 was assembled by using two lens arrays made of polymethylmethacrylate arranged in a line. It was confirmed that a bright erect equal-magnification image with a conjugate length of 47 mm was obtained by using this imaging element. Also, when the same parts were assembled as shown in FIG. 10, an erecting equal-magnification image was obtained with the same conjugate length.

Further, as can be easily understood, the continuity of the image is maintained even when the present structural unit is not limited to a straight line but arranged two-dimensionally. Therefore, for example, the brightness can be increased by stacking a plurality of columns in the y direction by the arraying method of FIGS.
It is possible to obtain a large area image. The imaging element according to the second invention of the present application realizes this, and for example, FIG.
7 is arranged by the arrangement method. FIG. 18 is a perspective view showing an embodiment of such an imaging element according to the second invention of the present application, and the present imaging element is suitable for obtaining an erecting equal-magnification image of a large area.

With respect to the constituent units of the above-mentioned image forming element, it is preferable that the surfaces facing the two transparent members 3, that is, the surfaces opposite to the reflecting surfaces are rough surfaces and are bonded with the black adhesive 5. As a result, as shown by the dotted line in FIG. 11, it is possible to absorb rays that have not reached the emission surface after being reflected by the reflection surface, and prevent stray light from being generated. Even in this case, stray light as shown in FIG. 12 may be generated, but such stray light is θ ≦ 90 ° -sin ⁻¹ (1 / n).
It does not exist if is satisfied.

FIG. 13 shows a preferable length of the transparent member 3. The condition that a light ray along the optical axis (z axis) propagates without loss is

[0024]

[Equation 1]

In this case, in each constitutional unit, the image around the central axis of the lens is the brightest and the portion with the smallest aberration can be effectively used, which is advantageous. Next, FIG. 14 is a perspective view showing an example of a structural unit of an imaging element and a part of a cylindrical lens according to the third invention of the present application, and FIG.
Is a yz plane and FIG. 15B is a plan view of an xz plane. The functions of the lenses 1 and 2 in the above-described structural unit are replaced by a combination of two cylindrical convex lenses 9 and 11 and cylindrical convex lenses 10 and 12, respectively. Although the number of parts is increased by using the cylindrical convex lens as described above, (1) the cylindrical convex lenses 11 and 12 can be respectively formed into one common band-shaped cylindrical convex lens when arrayed.
As a result, it is unlikely that the image of each structural unit is displaced in the y direction. (2) If necessary, the viewing angle (aperture angle) in the y direction is changed by changing the focal lengths and positions of the belt-shaped cylindrical convex lenses 11 and 12. It has the advantage that it can be enlarged or reduced.

FIG. 16 shows an embodiment of the image forming device according to the third invention of the present application in which the constituent units shown in FIGS. 14 and 15 are arranged. Also in this image forming element, the arrangement as shown in FIG. 9 is possible, and in that case, the two cylindrical transparent members 3 of the respective constituent units are bonded to each other along the z axis while leaving the cylindrical convex lenses 9 to 12 in FIG. It will be rotated 90 ° to the center.

As a concrete example, 20 same prisms as above, two polymethylmethacrylate lens arrays in which 10 cylindrical convex lenses having a radius of curvature of 9 mm and a square of 6 mm × 6 mm are arranged, and a radius of curvature of 8 mm and a width The image forming element of FIG. 16 was assembled using two 6 mm band-shaped cylindrical convex lenses. By using this imaging element,
It was confirmed that a bright erect image with a conjugate length of 50 mm was obtained.

The image forming element shown in FIG. 16 can also be stacked in the y direction to obtain a large area image, but if stacked as shown in FIG. 17, the merit of using a cylindrical lens cannot be realized. This image forming element is basically a one-dimensional array, and if necessary, one-dimensional arrays are stacked to form a two-dimensional array.

[0029]

As described above, in the image forming element according to the present invention, unlike the rod lens array and the three-layer lens array, the image inversion is performed by utilizing reflection to reduce the burden on the lens, so that the chromatic aberration caused by refraction is caused. The aberrations such as are smaller than those of other lens arrays.

Further, the image forming element according to the present invention is composed of a combination of simple optical parts, and it is possible to obtain a practical performance with a relatively simple axial alignment. Furthermore,
According to the imaging element of the present invention, not only the line shape,
It is possible to form a planar object and not only obtain a bright image, but also to project an erecting equal-magnification image of a two-dimensional image, which adds new utility.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a structural unit of an imaging element according to the first invention of the present application.

FIG. 2 is a plan view showing an example of a structural unit of the imaging element according to the first invention of the present application.

FIG. 3 is an explanatory diagram for explaining an operation of a structural unit of the imaging element according to the first invention of the present application.

FIG. 4 is an explanatory diagram illustrating an operation of a Dove prism.

FIG. 5 is a perspective view of a transparent member in the imaging element according to the first invention of the present application.

FIG. 6 is a perspective view showing an embodiment of the imaging element according to the first invention of the present application.

FIG. 7 is an explanatory diagram showing an example of arrangement of constituent elements in the imaging element according to the first invention of the present application.

FIG. 8 is an explanatory diagram showing an arrangement example of components in the imaging element according to the first invention of the present application.

FIG. 9 is an explanatory diagram showing an arrangement example of constituent elements in the imaging element according to the first invention of the present application.

FIG. 10 is a perspective view showing another embodiment of the imaging element according to the first invention of the present application.

FIG. 11 is an explanatory diagram for explaining the operation of the structural units in the imaging element according to the first invention of the present application.

FIG. 12 is an explanatory diagram for explaining the operation of the structural units in the imaging element according to the first invention of the present application.

FIG. 13 is an explanatory diagram for explaining the operation of the structural units in the imaging element according to the first invention of the present application.

FIG. 14 is a perspective view showing an example of a structural unit of an imaging element according to the third invention of the present application.

FIG. 15 is a plan view showing an example of a structural unit of an imaging element according to the third invention of the present application.

FIG. 16 is a perspective view showing an embodiment of an imaging element according to the third invention of the present application.

FIG. 17 is an explanatory diagram showing an example of arrangement of constituent elements in the imaging element according to the second invention of the present application.

FIG. 18 is a perspective view showing an embodiment of an imaging element according to the second invention of the present application.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Convex lens 1-1 ... Light-shielding part 2 ... Convex lens 2-1 ... Light-shielding part 3 ... Transparent member 3-1 ... Light-shielding plate 4 ... Right-angled prism surface 5 ... Adhesive agent 6 ... Object surface 7 ... Image surface 8 ... Black paint 9 ... Cylindrical convex lens 10 ... Cylindrical convex lens 11 ... Band-shaped cylindrical convex lens 12 ... Band-shaped cylindrical convex lens

Claims (3)

[Claims] 1. A dove prism in which the reflecting surface of the dove prism is replaced with at least one right-angle prism having a ridge line parallel to a straight line intersecting the reflecting surface and the surface orthogonal to the entrance / exit surface. A pair of transparent members forming prisms are symmetrically arranged so that the right-angled prism surfaces of the transparent members are in contact with each other, and two convex lenses having the same focal length are arranged on the entrance and exit surfaces, respectively. An imaging element in which a plurality of the constituent units are arranged on a straight line perpendicular to the optical axis of the convex lens. 2. The imaging element according to claim 1, wherein three or more constituent units are arranged on a plane perpendicular to the optical axis of the convex lens, and at least one of them is not on the same straight line. 3. A dove prism in which the reflecting surface of the dove prism is replaced with a right-angle prism surface in which at least one right-angle prism having a ridge line parallel to a straight line intersecting the reflecting surface and the surface orthogonal to the entrance / exit surface is arranged. A pair of transparent members forming each prism are symmetrically arranged so that the right-angled prism surface of the transparent member is on the outer side, and further, the two entrance and exit surfaces have the same focal length and the generatrix is parallel to each other. With a cylindrical convex lens arranged as a structural unit,
A plurality of the constituent units arranged on a straight line perpendicular to the generatrix of the cylindrical convex lens, and a generatrix arranged so as to face each row of the cylindrical convex lenses and parallel to the arrangement direction of the constituent units. With two strip-shaped cylindrical convex lenses having an image forming element.