JPH06208083A - Line image forming element - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] To provide a line imaging element that enables performance and cost equal to or higher than that of a rod lens array and does not require special know-how. A line imaging element according to the present invention comprises three cylindrical lenses 3, 4 and 5 arranged coaxially with a predetermined distance so that the generatrix lines are parallel to each other. A plurality of cylindrical lenses 1 and 2 are arranged in the direction, and the cylindrical lenses 1 and 2 are arranged so as to face the outside of these cylindrical lens rows and the generatrix lines of which are parallel to each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line 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 image forming elements are used to project an object on a line onto a sensor or a photosensitive drum at an equal magnification. As such an image-forming element, an array of cylindrical transparent bodies whose refractive index continuously changes from the center to the radial direction,
A so-called rod lens array, a plate in which an array of spherical lenses is formed is laminated in multiple layers (often three layers) (for example, JP-B-49-8893 and JP-A-57-104923) JP-A-57-66414), an erecting equal-magnification optical system formed by combining a roof prism and a lens in an array (for example, JP-A-61-210319 and JP-A-56-1172).
01, JP-A-56-126801, JP-A-56-140301, and JP-A-56-149002.
JP, JP-A-60-254018, JP, JP-A-60
No. 254019, No. 60-254020, No. 61-233714, and No. 62-9.
1902 and JP-A-62-201417).

[0003]

The above-mentioned rod lens array is most widely used at present, and the commercialized product leads the other system in terms of quality and price. In the rod lens array, the technical point is to form the refractive index distribution in a cylindrical transparent body and to control it precisely, but this requires special know-how, It is not easy for a third party who does not have one to make. Further, since it is particularly difficult to make a rod lens having a particularly large diameter, there is a problem that the F value increases when a large distance between the lens and the subject is desired, resulting in a dark optical system.

Therefore, there is a demand for an image-forming element which does not use a rod lens and which can be easily manufactured. However, in the known method, the optical axis of the optical unit composed of the lenses of each layer lens array is aligned with sufficient accuracy. It is difficult to perform work such as providing a light-shielding means between adjacent optical units, and it is quite difficult to form a particularly long array, and it is also disadvantageous in terms of cost.

Further, this is also common to the rod lens, but if the F-number is lowered by increasing the aperture of the lens or shortening the working distance in order to increase the brightness of the image, in particular, The integration of the refraction angles of the light passing through the peripheral portion of the lens becomes large, and the chromatic aberration becomes large, which is not preferable. Therefore, it is difficult to make a bright optical system by the above methods except for a special case where a monochromatic light is used as a light source.

The method (1) uses a roof prism (or roof mirror) for reversing the image, which is advantageous in terms of aberrations, but requires a reflecting means for changing the optical path other than the lens and the prism. The distance between the lens and the object or image needs to be several times or more the lens aperture in order to ensure a curved optical path, and there is a problem that it is difficult to obtain brightness because the F value cannot be made too small. Further, there is a problem that the reflection surface of the prism and the reflection coating (generally metal plating) on the reflection means increase the manufacturing cost.

After all, it is understood that it is difficult for the conventional method to realize the performance and cost equal to or higher than those of the rod lens array without requiring a special technique of controlling the refractive index distribution. The problem to be solved by the present invention is to provide an imaging element that can realize performance and cost equal to or higher than those of a rod lens array and does not require special know-how.

[0008]

The line imaging element according to the first aspect of the present invention comprises three cylindrical lenses arranged coaxially with a predetermined distance therebetween so that the generatrix lines are parallel to each other. A plurality of cylindrical lenses are arranged in a direction perpendicular to the generatrix, and the cylindrical lenses are arranged so as to face the outside of the cylindrical lens array and the generatrix of which is parallel to the generatrix.

Further, in the line imaging element according to the second aspect of the present invention, one of the cylindrical surfaces is a transparent member, and the other surface is a surface formed by arranging a plurality of the cylindrical surfaces having a plane perpendicular to the cylindrical surface. Two surfaces are arranged in parallel with the surface in which a plurality of surfaces are arranged inside, and a plurality of cylindrical lenses whose generatrices are parallel to each other at the same pitch as the cylindrical surface row are arranged between both transparent members. Each of the cylindrical lens rows disposed between them corresponds to each other, and the two cylindrical surfaces and the cylindrical lenses corresponding to each other are arranged to be coaxial.

It should be noted that the cylindrical lens and the cylindrical surface referred to here do not indicate only so-called a part of a cylinder or a cylindrical surface, but the shape of the bottom surface is expressed by a quadratic curve or other curves with less aberration as a lens. It also includes a lens having a cylindrical surface and a cylindrical surface.

[0011]

In the image forming device using the lens array, it is necessary for each constituent unit to form an erecting equal-magnification image in order to obtain a continuous image. However, if this erecting condition is satisfied only in the arrangement direction of the lens array, the continuity of the image is maintained, so there is no problem even if the image is inverted in the direction perpendicular thereto.

In the line imaging element of the present invention, an erecting equal-magnification image is formed by three cylindrical lenses or lens surfaces in the arrangement direction of the lens array, and an upright image is formed by two cylindrical lenses or lens surfaces in the vertical direction. An image obtained by reversing only one direction by connecting the images is obtained.By using a cylindrical lens or a lens surface, the need for axial alignment is limited to only the longitudinal direction, and the light shielding means may be in the same direction. It is easier to manufacture than the conventional three-layer lens array. Further, since the width of the cylindrical lens array or the lens surface in the generatrix direction can be set arbitrarily, the brightness of the image can be easily obtained by widening the width.

[0013]

1 is a perspective view showing the construction of an embodiment of a line imaging element according to the present invention, and FIG. 2 is a plan view thereof. The object plane 7 and the image plane 8 on which an erecting equal-magnification image can be obtained by the three-layer cylindrical lens arrays 3, 4, and 5 are located at positions away from the cylindrical lenses 1 and 2 by focal lengths, respectively, and 2 (a), an inverted image is obtained by the cylindrical lenses 1 and 2, and an erect image is obtained in the x direction by the action of the cylindrical lens arrays 3, 4, 5 as shown in FIG. 2 (b). .

The functions of the cylindrical lens arrays 3, 4, and 5 in the xz plane are the same as those of the conventional three-layer lens array of the above-mentioned system, and as shown in FIG. The image is formed at the position of the lens 4 by the lens 3, and the inverted image is enlarged and inverted by the lens 5 so that an erect image of the original size is obtained on the image plane 8. Here, the lens 4 is a field lens and has a function of efficiently transmitting light from the object plane.

As described above, according to the projection of the erect image by the three lenses, the aberrations of the individual lenses are integrated to form the total aberration, and it is a problem to suppress it.
Actually, aberrations other than chromatic aberration can be considerably reduced by optimizing the shapes of the cylindrical lenses 3 and 5, but using an achromatic lens for the cylindrical lenses 3 and 5 is not practical in terms of cost. It's not easy to hold back. In this respect, the smaller the individual width T of the cylindrical lens arrays 3, 4, 5 is, the more advantageous it is.

On the other hand, since the inverted image is projected by the two cylindrical lenses in the y direction, the problem of aberration including chromatic aberration is not as severe as in the x direction. Therefore, the width W of the cylindrical lenses 1 and 2 can be set wider than T, and thus brightness can be increased. 1 and 2, the cylindrical lens array 3,
As the components 4 and 5, integrally molded components are used, and a light shielding means 6 is placed between adjacent optical cells to prevent generation of stray light. According to a typical three-layer lens array design method, a cylindrical lens having a shorter focal length than the cylindrical lenses 3 and 5 is used for the cylindrical lens 4, and the distance between the cylindrical lenses 3 and 4 and the cylindrical lenses 4 and 5 is used. And the focal length of the cylindrical lens 4 is twice, the light reaching the cylindrical lens 4 from the cylindrical lens 3 in the same cell is all acted on by the cylindrical lens 4 to belong to the cylindrical lens 5 belonging to the same cell. Since they are collected, the light shielding means 6 between the cylindrical lenses 4 and 5 can be omitted as shown in FIG. Alternatively, as can be easily understood from a simple reasoning, on the contrary, the light shielding means 6 may be provided between the cylindrical lenses 4 and 5 and the light shielding means 6 between the cylindrical lenses 3 and 4 may be omitted.

The method of manufacturing the line imaging element according to the first aspect of the present invention is not limited to the method of using the integrally molded cylindrical lens array as described above. For example, three cylindrical lenses and the light shielding means may be used. Alternatively, a method of arranging the integrally assembled ones and adding the cylindrical lenses 1 and 2 thereto may be used. FIG. 7 is a perspective view showing the configuration of an embodiment of the line imaging element according to the second invention of the present case, and FIG. 8 is a plan view thereof. In this embodiment, the cylindrical lens arrays 3, 5 of the first embodiment of the present invention are replaced by the cylindrical lenses 9,
It is replaced with the cylindrical surfaces 11 and 12 formed on the inner side of 10, and the operation is the same as in the case of the above-mentioned embodiment. However, since the number of parts through which the light passes is reduced by two, the reflection loss of the light beam generated when the light crosses the boundary surface is reduced by four faces, and as a result, the brightness of the image is increased.

FIG. 4 is a use example of the embodiment of the line imaging element according to the first invention of the present case, and FIG. 9 is a use example of the embodiment of the second invention of the present case. Inverted in the y direction, a continuous image is obtained in the x direction. Inverting the image in the y direction does not cause any inconvenience in applications such as linear image sensors, liquid crystal printers, and LED printers. On the other hand, in the use of a copying machine, it is inconvenient to invert the image, but if it is inverted by a mirror to make the image erect, it can be used for the copying machine.

[0019]

As described above, the imaging element of the present invention obtains continuous images on a line by using a three-layer cylindrical lens array and two cylindrical lenses. The imaging element does not require special know-how such as control of the refractive index distribution of the rod lens in manufacturing, is easier to manufacture than the conventional three-layer lens array, and can obtain a brighter image. It is possible.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of an embodiment of a line imaging element according to the first invention of the present application.

FIG. 2 is a plan view of an embodiment of the line imaging element according to the present invention.

FIG. 3 is an explanatory diagram for explaining the operation of each optical unit by three cylindrical lens arrays.

FIG. 4 is a perspective view showing a usage example of an embodiment of the line imaging element according to the first invention of the present application.

FIG. 5 is a plan view showing a modification of the embodiment of the line imaging element according to the first invention of the present application.

FIG. 6 is a perspective view showing another embodiment of an optical unit formed by three cylindrical lenses in the line imaging element according to the first aspect of the present invention.

FIG. 7 is a perspective view showing a configuration of an example of a line imaging element according to the second invention of the present application.

FIG. 8 is a plan view of an embodiment of the line imaging element according to the second invention of the present application.

FIG. 9 is a perspective view showing a usage example of an embodiment of the line imaging element according to the second invention of the present application.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cylindrical lens 2 ... Cylindrical lens 3 ... Cylindrical lens array 4 ... Cylindrical lens array 5 ... Cylindrical lens array 6 ... Shading means 7 ... Object surface 8 ... Image surface 9 ... Transparent member 10 ... Transparent member 11 ... Cylindrical surface 12 ... Cylindrical surface

Claims (2)

[Claims] 1. A cylindrical lens array in which a plurality of three cylindrical lenses arranged coaxially at a predetermined distance such that their generatrix lines are parallel to each other are arranged in a direction perpendicular to the axis and the generatrices. A line imaging element having a pair of outer cylindrical lenses facing the outside of the cylindrical lens array and having cylindrical lenses whose generatrix is parallel to the array direction arranged so as to face each other. 2. A transparent member having one surface as a first cylindrical surface and the other surface as a second cylindrical surface having a shape in which a plurality of cylindrical surfaces whose generating lines are orthogonal to the first cylindrical surface are arranged. And a pair of transparent members arranged in parallel with the second cylindrical surface in which the plurality of cylindrical surfaces are arranged inward, and between the pair of transparent members is equal to the cylindrical surface row of the second cylindrical surfaces. And a plurality of cylindrical lens rows arranged so that the generatrix is in parallel with each other, and each cylindrical surface of the second cylindrical surface of the pair of transparent members and each cylindrical lens of the cylindrical lens row Individually, the corresponding cylindrical surface and the cylindrical lens exist coaxially. Imaging element.