JPS6066577A - Picture signal binary-coding circuit of facsimile equipment - Google Patents

Abstract

PURPOSE:To obtain a fixed output for variation of depth of an original by determining a threshold level and binary-coding according to the relation to the average density around a read picture element. CONSTITUTION:In an average density circuit 3, a picture signal 6 and a 2-line delayed picture signal 8 are added and inputted to an ROM13 as an address signal together with a 1-line delayed picture signal 7. Data of the ROM13 is written beforehand to become a 3-line average density 16. An adder 14 adds above-mentioned average density for 32 picture elements and outputs to an ROM15 as an address signal, and the average density of an area shown in the figure is outputted from the ROM15 as an average density signal 9. A delay circuit 4 delays the signal 7 in the horizontal direction to become the center 17 of the average density area and outputs a delayed picture signal 10 thus obtained. A threshold circuit 5 is made up of an ROM that converts the signals 9 and 10 to addresses, sets the output to become white or black in a fixed leve, and outputs a binary coding signal 11.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image signal λ value conversion circuit, and more particularly to λ value conversion processing of an image signal read from a facsimile machine.

In conventional facsimile machines, when converting the image signal obtained by reading a transmitted document into white and black slice values, it is necessary to immediately convert the image signal being read into lambda values using a predetermined and fixed slice level. , or by using a 70-ting slice level that changes according to changes in the image signal.
Valuation was being carried out. In this case, since both read signals are converted into λ values on the spot, it is impossible to follow the 0-darkness of the yX draft in the case of a fixed slice, and the slice level is changed depending on the image signal. Even in this case, it was possible to make the IB follow only from the relationship with the data being scanned immediately before.

This invention 8A was made to eliminate the above-mentioned shortcomings inherent in the conventional technology, and the purpose of this invention is to convert the analog image (,'; For the i81!liI pixel, the threshold level is determined based on the relationship with the average density of the surrounding area of that pixel, and by converting it into a λ value, the output is always constant regardless of changes in the background light of the original. The object of the present invention is to provide a novel λ value converting circuit for Llc image signals so that 71J can be obtained.

In order to achieve the above object, the image signal λ value converting circuit of the facsimile apparatus according to the present invention includes a document reading circuit that converts an analog image signal read from a transmitted document into N-pit digital pixels, and a document reading circuit a line memory circuit that stores several lines of digital pixels sent from the document reading circuit; and an average density circuit that outputs the average density of an arbitrary area for digital pixels from the digital pixels from the document reading circuit and the output of the line memory circuit. , a delay circuit that delays each digital pixel so that the digital pixel to be converted into a λ value is at the center of the area of average density, and a threshold using the average density output and the digital pixel delayed so that it is at the center of the area. It is configured to include a threshold circuit that determines the level and converts the digital pixels into m.

Hereinafter, a preferred embodiment of the present invention will be specifically explained with reference to the drawings.

Figure @1 is a block configuration diagram showing an embodiment of the present invention. In the figure, the reference number / indicates nine original reading circuits,
The original reading circuit/transmission original f: reading image signal 6
For example, a /7 bit digital signal is output. Line memory times IP's, 2 tJ: /line can be stored one line at a time. The average density circuit 3 outputs the image signal A and the /line delayed image signal 7.22.
In-delay image signal 1? is input and the average a degree number 9 is output\.

The first figure is the average concentration circuit, ? FIG.

The image signal B and the co-line continuous image signal are added by an adder/co, and are added together with the l-line delayed image signal - RC zA.
/3 is input as an address signal. Here, i(
The OM/3 data is 3 lines with an average density of 16 or 1/! This is then output to the adder/y. Add↓1蓉1÷//1. Now add the 3-line average density circuit fraction 194 and output this as an address signal to the ROM 15, and output the average density of the area shown in FIG. do.

The delay circuit inputs the 1-line delayed image signal 7 and outputs a delayed image signal 10 which is delayed by 76 bits in the horizontal direction so as to be at the center /l of the average density area in FIG.

The threshold circuit S has an average density signal 9 and a delayed image signal I.
From the ROM whose address is O, the output of this (2) is set to be white or natural depending on a certain threshold level, and is output as an a-valued signal /l.

Figure 2 shows an example of actual setting of the threshold level.

In other words, if the image signal level is higher than the threshold level /l in the figure with respect to the average density, it is determined to be black, and if it is lower, it is determined to be white.

As described above, the present invention can convert an original read image signal into a λ value based on the relationship between the image signal level and the average density of an arbitrary area with respect to the image signal.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram showing an embodiment of the present invention, FIG. 1 is a detailed block configuration diagram of the average degree circuit shown in FIG. 1, and FIG. FIG. 9 is a diagram showing an example of actual setting of the threshold level. l... Original reading circuit, Co... 2-in memory circuit. 3... Average density circuit, q... Delay circuit, S... Threshold circuit, 6... Image signal, 7.../line delayed image signal, t... λ line delayed image signal, ...average density signal, io...delayed image signal, /c...λ-valued signal, /u...adder, /3...ROM, /4'...
・Adder, /S...ROM, /A...3 line average density, /7...center, 1g...threshold level Patent applicant NEC Corporation Representative Patent attorney Yutabe Kumagai 13 14 15 2nd figure 41 prong 1

Claims (1)

[Claims] A document reading circuit that converts an analog image signal into N-bit digital pixels, a line memory circuit that stores several lines of digital pixels output from the document reading circuit, and an average of an arbitrary area for digital pixels. An average density circuit that outputs the density, and a delay circuit that delays each digital pixel so that the digital pixel to be converted into a λ value comes to the center of the average density area, the output of the average density circuit and the output of the delay circuit. digital pixel using λ
1. An image signal lambda value converting circuit for a facsimile machine, comprising: a threshold circuit for converting the image signal into a value.