JPS63133763A - Image reader - Google Patents

Abstract

PURPOSE:To delete an unrequired part where no light flux passes and to make a device thin and miniaturize it, by forming an imageforming lens to image-form an image on a reading element in a main scanning direction in a shape longer than that in a sub scanning direction. CONSTITUTION:An original 1 positioned with a guide 13 placed on an original platen 12 is sent to a read position by an automatic traveling mechanism 2 and a paper supplying roller 3. And an original image is illuminated by a fluorescent lamp 5, and passes a first, a second, and a third mirrors 6, 7, and 8, and after passing a reduction lens 9, it is read in a line shape by a charge coupled device 10. In this case, the reduction lens 9 is formed in a noncylindrical shape in which an upper and a lower parts in an axial direction are notched with respective flat plane, In other words, the reduction lens 9 is formed in the shape in the main scanning direction longer than that in the sub scanning direction of the image of the original 1. In such way, it is possible to make the device thin and to miniaturize it.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image reading device, such as a facsimile machine, which reads an image of a document illuminated by a light source in a line shape with a reading element.

(Prior Art) Conventionally, as this type of image reading device, there is one shown in FIG. 3, for example. In such a conventional example, a light source 101 illuminates an image of a document, and this image is displayed in the first . Second. Third
The light is reflected by reflective mirrors 102, 103, and 104, and read in a line by a photoelectric conversion element 106 via a reduction lens 105.

By the way, as the photoelectric conversion element lO6, for example, a charge-coupled device (COD) is used, and one cell (one pixel) of the charge-coupled device is, for example, 14JLmX l4IL.
The document resolution required for the device is approximately 8 mm/am and 16 mm/cm. That is, if a charge-coupled device is used at the same magnification, this corresponds to 71 trees/square, so as described above, the image is reduced by a reduction imaging lens and projected onto the charge-coupled device. In addition, in recent years, contact type sensors have also been equipped with a 1-magnification imaging lens. These lenses usually have a cylindrical shape.

(Problem to be Solved by the Invention) However, in the case of such a conventional example, since the imaging lens 105 has a cylindrical shape with a wide diameter in the main scanning direction, the vertical direction in FIG. In the narrow portion corresponding to the sub-scanning direction, the lens 105 had a wasted area through which the light beam does not pass. As a result, as shown in FIG. 3, the vertical dimensions of the device are restricted, resulting in an increase in the size of the device and, in turn, an increase in cost. Furthermore, in the conventional example, the reduction lens 105 has a cylindrical shape and is long in the sub-scanning direction, which is a nuisance.

It is impossible to arrange the reduction lens 105 close to the optical path from the second mirror 103 to the third mirror 104 while maintaining a predetermined optical path length. Therefore, in order to maintain a predetermined optical path length without increasing the thickness of the device, the reduction lens 105 is installed as a second lens.
It is unavoidable to place it in a position deeper than the mirror 103.
Therefore, there was a problem in that the width also became wider.

Therefore, the present invention was made to solve the above-mentioned problems of the conventional example, and its purpose is to make it possible to make the device thinner in the vertical and lateral directions.

Further, it is an object of the present invention to provide an image reading device that is miniaturized.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an image reading device that uses a reading element to read an image of a document illuminated by a light source in a line. The image forming apparatus is provided with an imaging lens that forms an image, and the imaging lens is formed in a shape that is longer in the main scanning direction than in the sub-scanning direction of the image.

(Function) In the present invention having the above configuration, the imaging lens for forming an image on the reading element is formed in a shape that is longer in the main scanning direction than in the sub-scanning direction of the image. This is the result of removing unnecessary parts through which the light beam does not pass.

(Example) The present invention will be explained below based on the illustrated example. 1st
The figure shows an embodiment in which the image reading device according to the present invention is applied to a facsimile machine. 4 is a paper ejection roller for discharging the original 1 after it has been read, 5 is a fluorescent lamp as a light source for illuminating the image of the original 1, 6, 7.8 is a first . 2nd and 3rd mirrors, 9 a non-cylindrical reduction lens as an imaging lens, 10 a charge-coupled single element (CCD) as a reading element;
), 11 is a system control board, 12 is an original table on which the original 1 is placed, and 13 is a guide for positioning the original 1 in the width direction.

In the above configuration, the guide 13 is placed on the document table 12.
The original l positioned by the first . Second. The light passes through a third mirror 6.7.8, passes through a reduction lens 9, and is read out in a line by a charge-coupled device IO.

By the way, as shown in FIG. 2, the reduction lens 9 is formed into a non-cylindrical shape with parallel surfaces cut out at the top and bottom in the axial direction. That is, the reduction lens 9 is formed to have a longer shape in the main scanning direction than in the sub-scanning direction of the image of the original 1.

On the other hand, in FIGS. 1 and 2, H indicates the front principal point of the reduction lens 9, H' indicates the rear principal point, F indicates the entrance pupil, and R indicates the exit pupil, and the dashed line indicates the reading position of the original 1. As shown in FIG. While reading in the sub-scanning direction through the axis, i.e. 3.85 trees/rats, 7.7 trees/ra
The reading line width of 260 pm, 130 ILm, and 65 gm, which corresponds to the resolution in the sub-scanning direction of 15.4 mm and 15.4 mm/ram, corresponds to the light flux incident on the light receiving part of the charge coupled device 10 having a width of about 14 IL'm or 7 gm in the charge coupled device IO. Indicates the outermost edge.

However, as shown in Fig. 2, the conventional cylindrical lens (
(shown with a broken line) is cylindrical with a wide diameter in the main scanning direction, so the light beam does not pass through the part corresponding to the sub-scanning direction, which has a narrow vertical width in the figure, and the wasted area is saved. However, in this embodiment, since the reduction lens 9 has a non-cylindrical shape with parallel planes cut out on the upper and lower surfaces, unnecessary parts are eliminated. Further, according to this embodiment, in the three-mirror folding optical system, the second mirror 7 to the third mirror 8
Since the vertical thickness of the reduction lens 9 is reduced in the optical path, it becomes possible to arrange the reduction lens 9 close to the third mirror 8, and the optical path from the first mirror 6 to the second mirror 7 and the third mirror The vertical distance between the optical path between the charge coupled device 8 and the charge coupled device 10 can be reduced.

In the above embodiment, an optical system using three mirrors has been described as an example, but the same effect can be obtained using one or a plurality of mirrors other than three.

Furthermore, in the above embodiments, the reduction lens serving as the imaging lens may have a shape other than that shown in FIG. .

(Effects of the Invention) The image reading device according to the present invention has the above-described configuration and operation, and since the imaging lens is formed in a shape longer in the main scanning direction than in the sub-scanning direction of the image, the device can be made thinner. The device can also be made smaller and, as a result, can be provided at a lower cost.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of an image reading device according to the present invention applied to a facsimile machine, FIG. 2 is a perspective view of the main parts of the same embodiment, and FIG. 3 is an example of a conventional image reading device. FIG. Explanation of symbols 1... Original 5... Fluorescent lamp (light source) 6
...First mirror 7...Second mirror 8...
3rd mirror

Claims (2)

[Claims] (1) An image reading device that reads an image of a document illuminated by a light source in a line with a reading element, comprising an imaging lens that forms an image on the reading element;
An image reading device characterized in that the imaging lens is formed in a shape that is longer in the main scanning direction than the sub-scanning direction of the image. (2) The image reading device according to claim 1, wherein the imaging lens has a non-cylindrical shape having upper and lower parallel surfaces in its axial direction.