JPS62216587A - Image reader - Google Patents

Abstract

PURPOSE:To correct the sensitivity of one-dimensional image sensor with a simple constitution by extending the counting capacity of a main scanning picture element counter and the main scanning direction memory capacity of a binarization threshold memory circuit up to one main scanning line length and storing the binarization threshold information multiplying with the sensitivity coefficient of the one-dimensional image sensor into a memory circuit. CONSTITUTION:By a main scanning picture element counter 2 and a scanning line counter 3, main scanning position information 13 in one main scanning line and subscanning position information 14 in a dither matrix are given to a binarization threshold memory circuit 4. In the memory circuit 4, as the data of respective addresses equivalent to the scanning position information, the value to multiply a dither threshold level corresponding to a scanning position with a sensitivity coefficient at the main scanning position equivalent to one-dimensional image sensor 1 measured beforehand is stored. An analog digital converter 5 converts an analog output signal 16 of the one-dimensional image sensor 1 to a digital picture signal 17, a digital comparator 6 compares a binarization threshold information signal 15 outputted from the memory circuit 4 with the digital picture signal 17, to output the deciding result as a binary picture signal 18.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image reading apparatus, and more particularly to an image reading apparatus used in a facsimile machine having a pseudo halftone reproduction function using a dither method.

[Conventional technology]

Main scanning is used in image reading devices for facsimile machines that perform halftone reproduction using the dither method.

The threshold level generated for each pixel in synchronization with sub-scanning is changed between the white level and the black level with a period corresponding to the spatial dimension of the dither matrix, and the gray level information of the document is transferred to the one-dimensional image sensor. The analog output signal obtained by scanning is compared with this threshold 1st level and binarized, and the shading information of the original is dithered). expressing.

However, the photoelectric conversion output of the image sensor used for document scanning is based on Lv due to sensitivity non-uniformity of each photoelectric conversion element, shading characteristics of the optical system, etc.
Since the sensitivity distribution does not necessarily have a uniform rate over the main scanning line, the above-mentioned simple binarization process is performed using this simple image sensor, and F image reproduction is performed on the resulting image signal. and l, which corresponds to the area where the sensitivity of the image sensor is low.
In the ll1i image, the original edge is also reproduced in black, and as a result, stripes appear in the sub-scanning direction at positions corresponding to the low-sensitivity areas of the image sensor across one screen, resulting in poor image quality. . In order to avoid such problems, conventional image reading devices either correct the drive voltage of the image sensor for each pixel to equalize the sensitivity, or read and record the image sensor output signal in advance. The sensitivity of the F-image sensor has been corrected using methods such as removing and correcting the output signal of a white image original.

[Problem that the invention seeks to solve]

However, in conventional image reading devices that use this complicated sensitivity correction method, image sensor drive voltage correction,
Alternatively, a circuit for dividing the image 7/s output signal by the reference white number can be added to the existing image 1#! The image reading device +t of the present invention has the drawback that the overall circuit scale increases because it needs to be added to the reading tack. a main scanning pixel counting means having a counter fi1' for the number of pixels in the line; - a scanning counting means having a counting capacity for the number of main scanning pixels included in the buzzer matrix; and at least - a number of pixels for the main scanning line. - dithering) It has a storage capacity of nine values or more multiplied by the main scanning line contained in the IJ box, and has an F address specified by the counted value by the main scanning pixel counting means and the counted value by the scanning line counting means. , 211 stored in advance as a value multiplied by the sensitivity coefficient of the image 77 for the corresponding scanning position.
Binarization 1m111 storage means for outputting f conversion threshold 1 direct information as a digital 1st signal; analog-to-digital conversion means for converting an analog output signal from an image sensor into an analog-to-digital signal and outputting a gain signal; Comparing means compares the magnitude of the output value of the valuation threshold storage means and the output value of the analog-digital conversion means and outputs a determination binary signal as an image signal.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

The image reading device includes a one-dimensional image unit 1, a main scanning pixel counter 2, a scanning line counter 3, and a binarization threshold storage circuit 4.
, an analog-to-digital converter 5 , and a digital comparator 6 .

In FIG. 1, the main scanning pixel counter 2 counts up the number of pixels corresponding to the raw scanning length 11, and after counting the number of pixels corresponding to the raw scanning length, the sub-scanning synchronization pulse 12 is cleared by L.
Then, pixel counting t″8 degrees is started for the primary main running f-line.

Scanning line counter 3μ, sub-scanning synchronization pulse 12, increases the number of scans included in the nl-dither matrix, finishes counting, automatically clears the count of the number of scan lines for the n-th dither matrix. Start. For example, in an image reading device where the main scanning line is 1728 pixels and the dither matrix size is 4 x 4, the main scanning pixel counter 2 is cleared every 1728 counts, and the scanning line counter 3 is cleared every 4 counts. It is a vessel.

Main scanning pixel counter output 13% and scanning line counter output 14
is connected to the address input of the binarization 1 sea bream value storage circuit 4 n1
The former provides main scanning position Ii\ information within the main scanning line, and the latter provides sub-scanning position information within the dither matrix to the binarization threshold storage circuit 4, respectively. The binarization threshold storage circuit 4 stores the dithering threshold level corresponding to the scanning position and the corresponding main scanning data of the dimensional image sensor 1 as data at each address corresponding to the above-mentioned scanning position information. The value multiplied by the sensitivity coefficient at the position is stored. The analog e-digital converter 5 receives the analog output 1i! of the one-dimensional image sensor 1! No. 16 as digital image signal 1
7, the digital comparator 6 compares the 211σ threshold information signal 15 outputted from the binarization threshold storage circuit 4 with the digital image 16 and 17 to determine the size, and converts the determination result into two. Value Ii! Output as 1i16 No. 18.

Such an image and the configuration of the t-taking device are such that the counting capacity of the main scanning pixel counter 2 and the main scanning direction memory 8'lk of the binarization threshold value storage circuit 4 are used for lifetime scanning from the width of the dither matrix in the main scanning direction. Image sensor sensitivity correction is possible except that the data stored in the binarization threshold storage circuit 4 is multiplied by the sensitivity coefficient of the one-dimensional image sensor 1. The basic wt range is exactly the same as that of a conventional image reading device with a dithering function.
However, if the sensitivity coefficient of the one-dimensional image 7/the l is included in the binarization threshold information number 15 output from the binarization threshold storage circuit 4, the sensitivity of the -dimensional image sensor 1 is For low main scanning positions, the 211 threshold is given at the same ratio as for main scanning positions with high sensitivity, and as a result, it is possible to obtain the same effect as the sensitivity correction for image sensor output 1. In order to expand the counter capacity of the scanning image cumulative counter 2 and the storage capacity in the main scanning direction of the binarization threshold storage circuit 4 to the -main scanning line length, a small amount of circuitry may be added, or 16 circuit elements with high integration density may be added. Instead, F can be easily realized. Also, for storing the binarization threshold information multiplied by the image sensor sensitivity coefficient in the binarization threshold storage circuit 4.

This can be realized by using an appropriate external device without any modification to the present image reading device.

〔Effect of the invention〕

As described above, the image reading device of the present invention expands the storage capacity in the main scanning direction of the counter t1 of the main scanning pixel counter and the binarization threshold storage circuit to -main scanning line length, and The system stores the binarization threshold information multiplied by the sensitivity coefficient of the one-dimensional image sensor in the memory circuit, reads out the binarization amount from the binarization amount memory circuit according to the scanning position, compares it with the image sensor output, and binarizes it. , the effect of being able to correct the sensitivity of a one-dimensional image sensor with a simple configuration is 0.

[Brief explanation of drawings]

In Figure 0, an embodiment of the invention is shown in a block diagram.
...Main scanning pixel counter, 3...Scanning line counter, 4...Memory circuit, 5...Analog...
Digital converter, 6...Digital comparator.

Claims (1)

[Claims] - a main scanning pixel counting means having a counting capacity for the number of pixels of the main scanning line; - a scanning line counting means having a counting capacity for the number of main scanning lines included in the dither matrix; at least -
It has a storage capacity greater than the value obtained by multiplying the number of pixels of a main scanning line by -the main scanning line included in the dither matrix, and the address is determined by the count value by the main scanning pixel counting means and the count value by the scanning line counting means. a binarization threshold storage means for outputting, as a digital signal, binarization threshold information stored in advance with a value obtained by multiplying the specified scanning position by a sensitivity coefficient of the image sensor; and an analog output from the image sensor. an analog-to-digital conversion means for converting a signal from analog to digital and outputting a digital signal;
An image reading device characterized by comprising: comparison means for comparing the output value of the binarization threshold storage means and the output value of the analog-to-digital conversion means and outputting a judgment binary signal as an image signal. .