JPH01137883A - Picture reader - Google Patents

Abstract

PURPOSE:To make the input of a picture faster, to realize the faithful reading of a halftone original, and to prevent a resolution in a sub-scanning direction from being reduced by correcting the after-image characteristics of an image sensor. CONSTITUTION:An analog picture signal outputted from an image sensor 1 is amplified by an amplifier 2, A/D-converted by an A/D converting circuit 3, and an A/D-converted digital picture data are stored in a line memory 5, and inputted to a ROM 4. By using the picture data of a preceding line read from the line memory 5 and the output data of the circuit 3, the ROM 4 corrects the picture data during reading, the picture data, in which the after-image characteristics of the image sensor are corrected by the ROM 4, are shading- corrected by a shading correcting circuit 6, inputted to a processing circuit 7, and a binarizing processing, etc., are carried out. Thus, the input of the picture is made faster, the faithful reading of the halftone original is realized, and the resolution in the sub-scanning direction can be prevented from being reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image scanner, a digital copying machine, an indentation file device, and an image reading device for reading a document used in a facsimile.

2. Description of the Related Art In recent years, there has been a demand for faster image input and faithful reading of halftone originals. In an image reading device that uses a light intensity-integrating image sensor (solid-state image sensor), several percent to several tens of percent of the image information read one line before is superimposed on the output of the image sensor (the image sensor's afterimage characteristics )
is normal. There is a tendency that as the main scanning speed of the image sensor increases, the proportion of the afterimage component in the output of the image sensor increases. However, conventional image reading devices either do not perform processing to correct the afterimage characteristics of the image sensor, or read images at a main scanning speed that does not affect the quality of the image read by the afterimage characteristics of the image sensor.

An example of the conventional image reading device described above will be described below with reference to the drawings.

FIG. 2 is a block diagram of an image signal processing section of a conventional image reading device. 21 is a one-dimensional image sensor, 22 is an amplifier, 23 is an AD converter, 24 is a shading correction circuit, and 25 is a processing circuit that processes an image signal.

The operation of the conventional image reading device shown in FIG. 2 will be described below.

The analog image signal output from the image sensor 21 is amplified by an amplifier 22, AD converted by 23, and subjected to shading correction by 24 to become multivalued digital data. The digital image signal outputted from 24 is input to an image signal processing circuit 25, where it undergoes processing such as binarization.

(For example, Nikkei Electronics 1984.9.10 commentary) Problems to be solved by the invention Conventional image reading devices do not perform processing to correct the afterimage characteristics of the image sensor, or the afterimage characteristics of the image sensor may cause the read image to deteriorate. Since images were read at a main scanning speed that did not affect the quality of the image, there were problems such as increased image input speed, difficulty in faithfully reading halftone originals, and a decrease in resolution in the sub-scanning direction.

In view of the above-mentioned problems, the present invention provides an image reading device that performs processing to correct the afterimage characteristics of an image sensor to realize faster image input and faithful reading of halftone originals.

Means for Solving the Problems In order to solve the above problems, the image reading device of the present invention includes:
a document table; an illumination means for illuminating the document; an image sensor; an optical system for focusing light reflected or transmitted from the document onto the image sensor; a line memory for delaying image data by one line; The image sensor is characterized by comprising a memory that stores data for correcting afterimage characteristics of the image sensor using previous image data.

Effect of the Invention With the above-described configuration, the present invention performs processing to correct the afterimage characteristics of the image sensor, realizes high-speed manual image processing and faithful reading of halftone originals, and prevents a decrease in resolution in the sub-scanning direction.

Embodiment Hereinafter, an image reading apparatus according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 3 is a schematic diagram of an embodiment of the image reading device of the present invention.

31 is a document, 32 is a document table, 33 is a fluorescent light, 34 is a loft lens array, 35 is an image sensor, 36 is a fluorescent light 33, a rod lens array 34, and an image sensor 35
37 is a solid body, and 38 is a document holder. Light from the fluorescent lamp 33 is reflected by the original 31 and focused onto the image sensor 35 by the rod lens array 34 . The sub-scanning unit 36 moves parallel to the document table 32 in the direction of the arrow in the figure to sub-scan the document.

FIG. 1 is a block diagram of an embodiment of an image reading device of the present invention.

1 is an image sensor, 2 is an amplifier, 3 is an AD conversion circuit,
4 is a ROM that stores data for correcting afterimages of the image sensor, 5 is a line memory, 6 is a shading correction circuit, and 7 is a processing circuit that performs processing such as binarization.

The analog image signal output from image sensor 1 is 2
The signal is amplified by the amplifier 3 and AD converted by the amplifier 3.

The AD converted digital image data is stored in the line memory 5.
The data is stored in the ROM 4 and input into the ROM 4. ROM4
Then, the image data being read out from the line memory 5 and using the image data of the previous line and the output data of the AD conversion circuit 3 are corrected. The image data whose afterimage characteristics of the image sensor have been corrected in the ROM 4 undergoes shading correction in a shading correction circuit 6, and is input to a processing circuit 7 where it is subjected to processing such as binarization.

The operation of afterimage correction will be explained in more detail.

FIG. 4 is a wiring diagram of the ROM in the present invention.

41 is AD-converted 8-bit digital image data, 42 is 8-bit image data delayed by one line, 4 is ROM, and 43 is ROM output data. A
The D-converted 8-bit digital image data 41 is R
Connect to address AO-A7 of OM4. The 8-bit image data delayed by one line is stored at address A8 in ROM4.
~ Connect to A15. FIGS. 6 and 7 show graphs of image data in the sub-scanning direction when a document with black lines as shown in FIG. 5 is read with the sub-scanning direction indicated as S in the figure. 7th
The figure shows ideal image data. FIG. 6 shows data when the image sensor has an afterimage in the sub-scanning direction.

8-focus image data 4 with the value of AD-converted 8-bit digital image data 4I delayed by X,..., 1 line
The value of 2 is xn-+. If the image data after afterimage correction is X', then X' can be determined by the following formula.

X' = CLIP (X11+ INT((a+b l
Xl, X7-+ 1) (X, 14.-, )) However, when l xn-Xn-1l≧C, x'=xn,
However, when I Xn x, -, l < C, INT(
) is an integerization function, and CLIP() is a function that clips to 0 to 255. a and b are correction coefficients of O to 1, and C is a parameter that determines the correction dead zone. Parameter C prevents afterimage correction from being applied to noise components of image data. By setting the coefficients a and b appropriately, the image data including the image sensor's afterimage characteristics as shown in FIG. 6 can be made closer to the ideal image data shown in FIG. 7. The data calculated in step 2 above is stored in the ROM 4 and the afterimage of the image sensor is corrected.

Effects of the Invention As described above, the image reading device of the present invention performs processing to correct the afterimage characteristics of the image sensor, realizes faster image input, faithful reading of halftone originals, and reduces resolution in the sub-scanning direction. can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the image reading device of the present invention, FIG. 2 is a block diagram of a conventional image reading device, and FIG. 3 is a schematic configuration diagram of an embodiment of the image reading device of the present invention. Fig. 4 is a wiring diagram of the ROM in the present invention, Fig. 5 is an explanatory diagram showing an example of a document, Fig. 6 is a graph of image data when there is an afterimage on the image sensor, and Fig. 7 is a graph of ideal image data. It is a graph. 1, 21.35・old image sensor, 2.22・・
...Amplifier, 3, 23..."AD conversion circuit, 6, 24...Shading correction circuit, 7,
25...Processing circuit, 4...ROM, 5
... Line memory, 31 ... Manuscript, 3
2...Original table, 33...Fluorescent light, 34
...Rod lens array, 36...Sub-scanning unit, 38...Document holder, 41...
...Image data, 42...Image data delayed by one line. Name of agent Patent attorney Toshio Nakao Hakaichimeika 1 Figure 2 Figure 3

Claims (2)

[Claims] (1) A document table, an illumination unit that illuminates the document, an image sensor, an optical system that focuses light reflected or transmitted from the document onto the image sensor, and a line memory that delays image data by one line. , and a memory that stores data for correcting afterimage characteristics of an image sensor using image data of one line before. (2) The data in the memory that stores data for correcting the afterimage characteristics of the image sensor is data that does not perform afterimage correction on image data when the difference between the image data of one line before and the image data to be corrected is less than a predetermined value. An image reading device according to claim (1), characterized in that: