Image inputting apparatus and image forming apparatus using four-line CCD sensor

Abstract

A four-line CCD sensor is structured by line sensors R, G, B in which color filters are respectively disposed on surfaces of light receiving elements, and a line sensor BK at which no color filter is disposed. Amplitudes of signals which are outputted from the line sensors R, G, B at a time of reading a color document, and an amplitude of a signal which is outputted from the line sensor BK at a time of reading a monochrome document are adjusted so as to be substantially equal to one another. In a case in which a color document is read, outputs of the line sensors R, G, B are selectively provided, and in a case in which a monochrome document is read, output of the line sensor BK is selectively provided.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates to an image inputting apparatus such as a scanner or the like which reads image information by scanning a document, and to an image forming apparatus such as a digital copier or the like which uses the image inputting apparatus.[0002]Conventionally, there are generally two types of CCD line sensors which are used in a reduction optical system: a CCD line sensor which is structured by only a one-line line sensor, and a CCD line sensor which is structured by a three-line line sensor in which color filters of red (hereinafter denoted as R), green (hereinafter denoted as G), and blue (hereinafter denoted as B) are disposed on the surfaces of the respective line sensors.[0003]The aforementioned one-line CCD line sensor is basically used for reading monochrome (white / black) documents. When a color document is read by using this CCD line sensor, a method is adopted in which, by successively turning on three light sources having...

AI Technical Summary

Benefits of technology

[0010]The object of the present invention is to provide an image inputting apparatus and an image forming apparatus which can read color information of a document, and can provide image data in which positional offset and false colors do not arise in a case in which a monochrome document is read.

[0018]The photoelectric converting efficiency (sensitivity) of the line sensor at which no color filter is disposed is high as compared with those of the three line sensors at which the color filters of R, G, B are respectively disposed. Thus, the line sensor can be driven at high speed. Further, because the photoelectric converting efficiency of the line sensor at which no color filter is disposed is high, the output signal of the line sensor is divided into an even signal and an odd signal which are outputted as parallel signals of two systems, and the light accumulating time is shortened. Moreover, the even signal and the odd signal may be divided into two, and may be outputted as parallel signals of four systems.

Problems solved by technology

Thus, there are disadvantages in that the control of the light source relationships is complicated, and costs accompanying such control increase.

However, the green color information and the white information on the document cannot be distinguished from one another, and as a result, information of green characters or images or the like cannot be read.

In the same way, in a case in which the line sensor having sensitivity of R is used, a drawback arises in that the red information cannot be read, and in a case in which the line sensor having sensitivity of B is used, a drawback arises in that the blue information cannot be read.

However, because the one-line reading range in the subscanning direction varies in accordance with the reading magnification, there is the problem that the above-described proportional relationship is not established, and the alignment of color information by the line buffers is poor.

Moreover, in a case in which an image is rapidly changed from white to black or from black to white such as a monochrome characters, the drawback that false colors such as red or blue are generated at the changing points arises.

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