Abstract:
A picture image signal compensation device for devices such as image scanner, facsimile and etc. comprises a whiteboard provided before manuscript in which an average value of white level signals of said whiteboard with unusually low values eliminated in obtaining the average value or an average value of white level signals of said whiteboard with an average value by the plural scannings is used as a standard datum for each of picture elements for picture image signal compensation.

Description:
BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     This invention relates to devices such as image scanning, facsimile and etc. and particularly to the picture image signal compensation device for eliminating variations among picture elements of said devices. 
     (2) Description of the Prior Art 
     FIG. 3 is a block diagram showing a circuit construction of a conventional picture image signal compensation device. 
     In the drawing, (1) indicates an A/D signal converter which converts analogous picture image signals to digital picture image signals, (2) a latch which holds data temporarily, (3) a memory storage for storing said held data, and (4) a comparison calculator to compensate for picture image data by comparison of manuscript image data with the data from whiteboard stored in the memory storage 3. 
     Next, compensating operation of the conventional picture image signal compensating device as shown in above FIG. 3 is explained. A standard picture image signal (A&#39;) at a level of whiteboard 10 converted by the A/D converter (1) is held at the latch 2 at the time of reference at the level of the whiteboard, stored at each location of tahe memory storage 3 corresponding to each of picture elements and on completion of reference of 1 line of the white level, storing the data into the memory storage finishes also. 
     Next, the original manuscript image signals converted by the A/D convertor are compared proportionally with the signal data B of the picture elements at the white level stored in the memory storage 3, and picture image compensation signals C having been compensated from the original manuscript image signals A are taken out from this comparison calculator 4. 
     Since said conventional picture image signal compensation device is constructed as stated above, there has been a problem that the whiteboard which functions as a white level standard must be kept free from even a little dust and scratches and for this reason is necessary to be cleaned periodically. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to solve such a problem and to provide a picture image signal compensation device which is capable of obtaining stable picture image signals from a whiteboard even with some dust and scratches and which erases the variations among picture elements. The picture image signal compensation device of this invention is provided with a wide whiteboard 10 placed before a manuscript 11 is made to refer plural times to the whiteboard 10 passing before a line image sensor 12 reads the manuscript 11, decide as a standard datum an average value of the white data among each of picture elements referred plural times eliminating the usually low values, and store the average value datum into the memory storage corresponding to each of picture elements. 
     Furthermore, a picture image signal eompensation device of an embodiment of another invention of this invention application is also provided with a wide whiteboard 10 placed before manuscript 11 and is made to refer plural times to the whiteboard passing before a line image sensor 12 reads the manuscript, decide as a standard datum the average value of the white data among each of picture elements referred plural times eliminating the unusually low values, and stores the average value datum into the memory storage corresponding to each of picture elements. 
     In this picture image signal compensation device of this invention, the standard datum of an average value of each of picture elements is processed to be equal to the average value obtained by referring plural times to the whiteboard eliminating the unusually low values from the white data in the plural lines of the whiteboard referred plural times without any influence of a little dust and scratches and in order to obtain good qualitied picture image signals, the average value of the whie data of each picture element obtained from the whiteboard eliminating the unusually low values is decided as a standard datum. 
     Furthermore, in the picture image signal compensation device of an embodiment of another invention of this invention application, the standard datum of an average value of each of picture elements is processed, also, to be equal to an average white datum obtained by referring plural times to the whiteboard eliminating the unusually low values from the white data from the plural lines of the whiteboard referred plural times without any influence of a little dust and scratches, and in order to obtain good quality picture image signals, the average value of the white data of each picture element obtained from the whiteboard is decided as a standard datum. 
    
    
     BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
     FIG. 1A is a block drawing showing a circuit construction of an embodiment of the picture image signal compensation device of this invention. FIG. 1 B is a schematic diagram of the block diagram of FIG. 1. FIG. 1 C is a diagrammatic view showing the method of operation of the apparatus shown in FIG. 1 B. FIG. 2 is a block drawing showing a circuit construction of an embodiment of the picture image signal compensation device of another invention of this invention application. FIG. 3 is a block drawing showing a circuit construction of a conventional picture image signal compensation device. FIG. 4 is a simplified plan view of the scanning apparatus used in the present invention. FIG. 5 is an elevational view of the apparatus shown in FIG. 4. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1 is a block drawing indicating a circuit construction of a picture image signal compensation device of an embodiment according to this invention. The identical or corresponding parts to the parts shown in FIG. 3 are indicated with the same marks and numerals, but the explanation in detail is omitted here. In the drawing, (5) indicates a comparison analyzer to enable to eliminate the unusually low values and (6) an average value calculator constructed of addition and division calculators calculates an average value by processing the data. 
     Next, an explanation on working of the picture image signal compensation device of an embodiment of this invention as shown above in FIG. 1 will be made below. The picture image signal A&#39; of the standard white level obtained from a whiteboard converted by A/D convertor is held by a latch 2 at a time of reference to the white level. In order to eliminate the unusually low values equivalent to the black data caused by dust and scratches, said picture image signal A&#39; being compared with a comparing signal D by a comparison analyzer 5 in terms of largeness or smallness, and the contents of the latch 2 holding the picture image signal A&#39; on condition of largeness being stored to the corresponding picture element in the memory storage 3. 
     Then the white data larger than the data of the comparative signal D over the plural lines are successively stored into each location corresponding to each of picture elements. 
     Reference activities of white level by the whiteboard 10 will be completed this way. During the period before a line image sensor 12 reads a manuscript 11, an average value datum of each of picture elements is obtained from the white data signals E of each of picture elements with the unusual values eliminated in the plural lines and added and divided successively by the average value calculator 6, and said average value data signal F being stored as a standard datum into the corresponding location of each of picture elements in the memory storage 3. Next, manuscript picture image signals A converted by A/D convertor 1 are compared proportionally by a comparison calculator 4, with the standard data signal B (white data signal) of the average value with the unusual values of the corresponding picture elements eliminated and stored in the memory, storage 3 and picture image compensated signals C having the manuscript picture element signals A compensated by the comparison calculator 4 are taken out. FIG. 2 is a block drawing indicating a circuit construction of a picture image signal compensation device of an embodiment of another invention of this invention application. 
     The identical or corresponding parts to the parts shown in FIG. 3 are indicated with the same marks and numerals but the explanation in details is omitted here. 
     In the drawing, (6) indicates an average value calculator constructed of addition and division calculators and calculates an average value by proceeding the data. 
     Next, an explanation on working of the picture image signal compensation of an embodiment of another invention of this invention application as shown above in FIG. 2 will be made below. The picture image signals A&#39; of the standard white level obtained from a whiteboard 10 (not shown) converted by an A/D convertor 1 is held by a latch 2 at a time of reference at the white level and successively stored into the corresponding location of each of picture elements of a first line in the memory storage 3. Next, the picture image signals A&#39; of a second line is stored successively into the corresponding location of each of picture elements of a second line in the memory storage 3, repeating above operation in plural lines, and in this manner the reference to the whiteboard 10 at the white level will be completed. Next, during the period before a line image sensor 12 reads a manuscript 11, an average value datum of each of picture elements is obtained from the white data (comparison signals) D of each picture element of each line by successive adding and dividing operations of an average value calculator 6, and the average value data signal E is stored into each location of the memory storage corresponding to each of picture elements as a standard datum. Next, manuscript picture image signals A converted by A/D convertor is compared proportionally by a comparison calculator 4, with the standard datum signal B of the average value at the white level of the corresponding picture element stored in the memory storage 3 and a picture image compensated signal C having the manuscript picture element signal A compensated by the comparison calculator 4 is taken out. 
     As explained above, this invention is a picture image signal compensation device in which data at the white level is decided at an average value eliminating the unusually low value of whiteboard in the scannings of plural times, or the datum at the white level are decided as an average value in the scannings of plural times of the whiteboard, and consequently even in a case that some dust or scratches on the whiteboard are on, precise and stable picture signals could be taken out, and consequently excellent effects such that low cost device which does not require too severe preciseness in maintaining, installing or manufacturing the whiteboard, are realized.