JPS59133771A - Picture reading device - Google Patents

Abstract

PURPOSE:To improve the S/N ratio of a reproduced picture by providing an optical shutter standing in line a single liquid crystal, array on an image forming line in the main scan direction and arranging a single long-size photoelectric transducer at the opposite side to a ''Selfoc'' lens respectively. CONSTITUTION:An original 1 which is carried in the subscanning direction A at a fixed speed is irradiated by the light of an exposure lamp 3 which is condensed by a mirror 2. Then an extremely narrow linear part B of an original picture which is orthogonal to the direction A is successively formed into an image on a prescribed line via a ''Selfoc'' lens 4. This image is scanned from an end to the other end of the part B, and the bright and dark images of the original are converted into series electric signals. Then liquid crystal cells 8 constituting an optical shutter 7 are successively driven from an end through another end of the cell 8 within a period of time corresponding to the subscanning speed of the original 1. The bright and dark images on the main scanning line B on the original surface are successively transmitted every minute part and then formed into images on a photoelectric transducer 6.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image reading device, and more particularly to a device that optically scans a document used for facsimile or the like and converts it into an image signal using a photoelectric conversion element.

For example, as shown in FIG. 1, the most commonly used image reading device using photoelectric conversion conveys a document 1 at a constant speed (this conveyance is referred to as sub-scanning) and uses a condensing mirror 2. The light from the exposure lamp 3 collected in is irradiated onto the image surface of the original 1, and the reflected light is sent to a photoelectric conversion element array 5 such as a photodiode through a collective optical system 4 such as an optical fiber play or a selfoc lens. At the same time as the image is formed, each element arranged in a straight line in the photoelectric conversion element array 5 is scan-driven in time series (this is called main scanning), and the brightness and darkness on the main scanning scale of the original image is extracted as a serial signal. Ta.

However, in order to improve the resolution of the image reading device as described above, it is necessary to increase the element density of the photoelectric conversion element array 5, but in this way, the voltage applied to each element can be increased. This has the disadvantage that the sensitivity is reduced.

Furthermore, since a drive circuit is required to read the output of each element as an electric signal in time series, it also has the drawback that noise generated during switching mixes into the image signal and reduces the S/N ratio of the reproduced image. It was something.

The present invention has been made in order to eliminate the defects of the conventional photoelectric conversion image reading device as described above, and is directed to an image forming system that is arranged at minute intervals along the main scanning line on the main scanning direction imaging line of the original exposure scanning optical system. It is an object of the present invention to provide an image reading device in which optical shutters that are arranged and can be opened and closed in chronological order are arranged, and a long single photoelectric conversion element is provided at a position that receives light from the optical shutters.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 2 is a configuration diagram showing an embodiment of an image reading device according to the present invention.

That is, a document 1 being conveyed at a foot speed in the sub-scanning direction (arrow A) is irradiated with light from an exposure lamp 3 collected by a condensing mirror 2 to form an extremely narrow line of the document image perpendicular to the sub-scanning direction. The shaped portion B is sequentially imaged onto a predetermined line through the SELFOC lens 4, and this is scanned (main scanning) from one end of the linear portion 9B to the other end to convert the brightness and darkness images of the document into serial electrical signals. It is similar to the traditional method.

However, when performing the above-mentioned photoelectric conversion, it is extremely difficult to improve the resolution and the S/N ratio of the reproduced image by using a so-called photoelectric conversion element array in which a large number of microphotoelectric conversion elements are closely arranged like a giant ship. It's uri.

In order to solve this problem, in the present invention, an optical shack 7 in which a single liquid crystal display is arranged on the main scanning direction imaging line of the imaging optical system is provided, and a single elongated photoelectric conversion element 6 is provided. is placed on the opposite side from the Selfox lens (trade name) 4.

The single elongated photoelectric conversion element 6 has selenium on a conductive substrate.
T+ may be a material to which a photoconductive semiconductor such as cadmium oxide or polyvinyl carbazole is attached, or a photoconductive material such as cadmium oxide or polyvinyl carbazole may be used.
It is also possible to configure it with a transistor or a photo-diode. Further, as shown in FIG. 3, the optical shutter 7 is equipped with a switching circuit 9 that aligns fine liquid crystal cells 8 in the main scanning direction and drives each of them sequentially in time series.

In the image reading apparatus of the present invention configured as described above, each liquid crystal cell 8, 8j, . is sequentially driven toward the main scanning line B on the document surface.
Since the above bright and dark image is transmitted sequentially in minute parts ω and is imaged on the photoelectric conversion element 6, the noise accompanying the switching of the optical shutter T does not have a direct effect on the image signal, and the reproduced image is The S/N ratio can be greatly improved, and since the photoelectric conversion element is a single element, there is no problem even if a high voltage is applied, and the photoelectric conversion element exhibits a remarkable effect in improving its sensitivity.

Furthermore, by interposing an appropriate filter between the optical shack I and the single photoelectric conversion element, original image information having the same color as that of the filter can be cut. This also has the advantage that there is no risk of damage due to heat from light mixing or a decrease in light intensity.

Note that the present invention is not limited to the above-described embodiments; for example, the optical system may be an imaging optical system using an energized lens without a path length using a collective optical system such as a SELFOC lens or an optical fiber array. It is obvious that there is no problem.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the general configuration of a conventional image reading device, FIG. 2 is a configuration diagram showing an embodiment of the image reading device of the present invention, and FIG. 3 is a diagram showing the configuration of an image reading device of the present invention. FIG. 3 is a perspective view showing the structure of the optical shutter used. 1... Document, 2, 3 and 4... Exposure scanning optical system, 6... Photoelectric conversion element having a long single light receiving surface.
7. --- Light shutter. Figure 1 Figure 3

Claims (1)

[Claims] A light shutter is provided on the exposure scanning optical system connection of the original, arranged at minute intervals, and sequentially opened and closed in chronological order to sequentially transmit minute portions of the optical image of the original, and receives the light passing through the light shack. 1. An image reading device comprising: a photoelectric conversion element having a single elongated light-receiving surface; brightness and darkness of the optical image of the original document is extracted as a signal synchronized with opening and closing of the optical shutter;