JPS58161566A - Original reading device - Google Patents

Abstract

PURPOSE:To compensate simply a shading distortion, by reading the data on the shading distortion to a reference plate with an image sensor and controlling the gain of the data output of the original information read by another image sensor on the basis of the data on the shading distortion. CONSTITUTION:An image of a white reference plate 25 is formed on an image sensor 23 through a mirror 7 and a lens 9 and then delivered to a variable amplifier 21 via a signal line 17a after amplification 27 and A/D conversion 17. At the same time, an image of an original 3 is formed on an image sensor 24 through the mirror 7 and a lens 9' and read successively with the same timing as the sensor 23 to be supplied to the amplifier 21 after amplification 26. Here the digital data obtained by the converter 17 is supplied to the amplifier 21. Therefore the gain is always controlled by the amplifier 21 for the signal read by the sensor 24. Thus the shading distortion contained in the original reading information is compensated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a document reading device, and more particularly to a document reading device that corrects shading distortion based on information obtained by reading a reference plate and reads a document.

2. Description of the Related Art Conventionally, a document read by a facsimile machine, a copying machine, or the like is converted into an electric signal as grayscale information by a document reading device, and image processing is performed on the document. In this case, shading distortion (a phenomenon in which shading appears in a portion of the screen) occurs due to distortion of the optical system and variations in the light source. In order to correct this shading distortion, a document reading device equipped with a shading distortion correction device as shown in FIG. 1 has conventionally been used. That is, in FIG. 1, a white reference plate having a uniform reflectance that is irradiated by a light source 5 through a mirror 10a provided on a mounting table 10 is connected to a linear image sensor (for example, CC) through a mirror 7 and a lens 9.
D) is imaged on. This image sensor 11 is controlled by a reading control section that controls drive timing, and information is sequentially read out.The information is amplified by an amplifier 13, converted into 1 by a 1-converter 17, and then read out by a reading control section. According to the address signals outputted from 15, the signals are sequentially stored in the memory 19 as digital signals.

At this time, if there is shading distortion, the output from the amplifier 13 will have a waveform as shown in Figure 2, and when this is Nx-converted, it will have a waveform as shown in Figure A (2). , the outputs from the 1st bit to the final bit are stored at corresponding addresses in the memory 19. That is, this data becomes shading distortion data. Furthermore, when the original 3 is read, the information from the original 3 is similarly read by the image sensor 11 and sent to the amplifier 1.
After being amplified by 3, the signal is input to the variable gain amplifier 21.

At this time, the information from the memory 19 is transferred to the variable gain amplifier 21.
Therefore, the gain of the image reading failure data is changed, and an image output with corrected shading distortion as shown in FIG. 2(B) and FIG. 3 FB+ is obtained.

In this way, in conventional systems, the standard white level is read as initial data before reading the original, and shading distortion is analyzed and stored based on that data.On the other hand, when reading the original, the initial data is read and the shading distortion is corrected based on it. to output the read image.

However, the most commonly used light source today is a fluorescent lamp.
Therefore, since the light amount distribution changes greatly over time, there is a drawback that if shading distortion is corrected using initial data, the shading distortion cannot be sufficiently corrected as time passes.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an apparatus for failing to read a document, which eliminates such conventional drawbacks and eliminates imperfections in shading distortion correction due to changes in the optical system over time.

In order to achieve this object, the present invention provides two image sensors, one for failing to read the reference plate and one for reading the original, and adjusts the output of the image sensor for reading the original based on the output of the image sensor for reading the reference plate. We adopted a configuration that corrects shading distortion and fails to read the original.

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

FIG. 4 shows an embodiment of the present invention, in which the same or similar parts as in FIG. 1 are designated by the same reference numerals, and their explanation will be omitted. In this embodiment, the image of the white reference plate 25 having a uniform reflectance is transferred to the mirror 7 and the lens 9.
The image is formed on the image sensor 23 through
After being amplified via the A/D converter 11, the
The signal is converted and output to the variable gain amplifier 21 via the signal line 17a.

Similarly, the image of the original 3 is formed on the image sensor 24 via the mirror 7 and the lens 9'.
After being read out sequentially at the same read out timing, the signals are input to the variable gain amplifier 21 via the amplifier 26.

In this case, the digital data obtained from the A/D converter 17 is data for correcting shading distortion that occurs when the image sensor 24 fails to read the original, and this data is sent to the variable gain amplifier 21 when reading the original. Since the signal is input, the gain of the signal that has been read and failed by the image sensor 24 is always controlled by the variable gain amplifier 21.
As a result, shading distortion included in the document failure information is corrected.

In the embodiment described above, the shading distortion data is converted to digital data via the A/D converter and then inputted to the variable gain amplifier. If used, it is also possible to directly input the output from the amplifier 27 to a variable gain amplifier to correct shading distortion.

As described above, according to the present invention, two image sensors are used, and one of the image sensors constantly reads and misses shading distortion data through the reference plate, and based on this data, the other image sensor reads the data. Since it uses a configuration that corrects shading distortion included in the information of the failed original, it constantly controls changes in the light intensity distribution due to changes in the optical system, especially the light source, over time, thereby eliminating incomplete shading distortion correction. It became possible to do so. Furthermore, since there is no need to store shading distortion data in the present invention, there is no need for an expensive A/] converter or a memory for storing the data, resulting in an inexpensive document reading device.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a conventional document reading device; FIG. Fig. 4 is a block diagram showing the configuration of the document reading failure device according to the present invention. 3... Original 5... Light source 15... Reading failure control section 17..., A/D converter 21 ...Variable gain amplifier 23.24...Image sensor 25
・・・Basic, quasi-board

Claims (1)

[Claims] In a document reading device that corrects shading distortion and reads a document based on information obtained by reading a reference plate, an image sensor for reading the reference plate and an image sensor for reading the original are provided. A document reading device that corrects the output of a document reading image sensor based on the output to read the document.