JPS6173482A - Picture processing system - Google Patents

Abstract

PURPOSE:To execute the binary coding processing of necessary and effective picture information in an original area by recognizing the prescribed level of reading data and executing a binary coding processing on the basis of a generating frequency. CONSTITUTION:While moving an original, the original is recognized and the stopped original is read out by a moving scanning system. A CPU 211 inputs a black peak value and a white peak value from the original area in each main scanning line, counts up the contents of 2-byte area corresponding to detected data BPi, WPi in a 64X2-byte black peak histogram area and a 64X2-byte white peak histogram area which are prepared in a RAM one by one and sets up and stores a slice level in a ROM 212. When the same original is to be continuously read out plural times and copied, a slice level ROM pattern is held and then cancelled after a fixed period from the end of copying of prescribed sheets.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an image processing method, and particularly to a processing method for document read image data.

2. Description of the Prior Art As a method for binarizing image signals, a method is known in which a document is preliminarily scanned to determine a slice level for binarization, and a read image signal is binarized based on the slice level. This conventional method cannot necessarily perform optimal binarization because the slice level is determined based on unnecessary information other than the document area on the document table.

Furthermore, since the slice level was determined based on the average value of the original level or the background level, binarization was not necessarily optimal.

Purpose In view of the above-mentioned points, an object of the present invention is to provide an image processing method for performing binarization processing based on necessary and effective image information in a document area.

Another object of the present invention is to provide an image processing method that recognizes a predetermined error in read data and performs one line of binarization processing based on the frequency of occurrence of the error.

Another object of the present invention is to provide an image processing method that can shorten the preliminary time required for reading.

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

FIG. 1 is a schematic diagram of a document reading device to which the present invention can be applied. Pressed by the document cover 110, Ig, document table 10
1) In order to read the image information of the original 102 placed on C.
Line image sensors 1 and 03 such as OD are used, and a light source 10
The illumination light from 4 is reflected on the surface of the original 102, and is imaged on the image sensor 103 by the lens 108 via the mirrors 105.degree.1, 06, and 107. Light source 104. Mirror 105 and mirrors 106 and 107 are configured to move at a relative speed of 2:1. This optical unit moves from left to right at a constant speed while being subjected to PLL control by a DC servo motor 109. The moving speed varies from 90 mm/sec to 360 mva/sec depending on the magnification on the outward journey.
sec, and always 630 mm/sec on the return trip.
sec. The main scanning line perpendicular to the sub-scanning direction A in which this optical unit moves is detected by the image sensor.
While reading with a resolution of pel/mm, the optical unit is moved forward from the left end to the right end, and then moved back to the left end to complete one scan. Note that it is also possible to read the original while moving it, thereby reducing the total time required for reading.

FIG. 2 shows a schematic block diagram of a circuit that processes an image signal from the image sensor 103. The image signal Vo read by the image sensor 103 is converted into a 6-bit digital signal by an A/D converter 201. The latch 203 . Comparators 204 and 207. latches 205-208.

The comparator 204 compares the 6-bit image signal sent from the latch 202 with the 6-bit image signal sent from the launch 203 one clock ago.
02 If the new image signal sent is smaller,
A comparison output is output to the AND gate 206. AND gate 206 sends the comparison output from comparator 204 to latch 205 in synchronization with sampling clock SCL.

The comparator 207 compares the 6-bit image signal sent from the latch 202 with the 6-bit image signal sent from the latch 203 before l clock, and if
If the strength of the new image signal sent from 02 is greater, it outputs a comparator output to the AND gate 209, and the AND gate 209 outputs the hump rate output from the comparator 207 to launch 2 in synchronization with the pulling clock SCL.
Send to 08.

When the launches 20' 5 and 208 receive the comparator output, they send both signals sent from the launch 202 to the CPU 2.
Send to 11.

Further, in addition to the comparator output and the sampling clock SCL, the AND gates 206 and 209 receive an enable signal EN indicating the effective period of the image signal from the image sensor 103, and perform the comparison of the image signal in a predetermined period for each main scanning line. The results are sent to the CPU 211 from the latches 205 and 208. The CPU 211 receives the main scanning line synchronization signal M
By taking in image signals from the RA and CH 205 and 208 in synchronization with S, the lowest density level (hereinafter referred to as white peak) and highest density level (hereinafter referred to as black peak) of each main scanning line can be detected. .

The CPU 211 determines a slice level based on the white peak and black peak detected for each line using an algorithm described later, and sends it to the comparator 210.

In the comparator 210, the image signal from the latch 203 and the C
The slice levels from the PU211 are compared and the binarized signal V
Generate IDEO. In addition, instead of the comparator 210, 2
It is also possible to provide a digitized output data ROM, select a pattern in the ROM based on recognition by the CPU 211, address the pattern with data from the launch 203, and output the corresponding binary data. In this case, it is possible to reproduce halftones in two values using a ROM that stores dither patterns.

FIG. 3 shows a state in which a document is placed on the document table 101 of the document reading device (FIG. 1). In this case, the coordinates of four points (X+, Y+), (X2
, Y2 ), (X3 , Y3).

(X4.Y4) is detected by pre-scanning the optical system.

The document cover 1.10 (FIG. 1) is mirror-finished so that image data outside the area where the document is placed is always black data. The pre-scanning includes main scanning and sub-scanning to cover the entire glass surface.

The circuit diagram of FIG. 4 shows the logic for detecting the coordinates. The image data VIDEO binarized by the previous scan is shifted and
The data is input to the register 301 in units of 8 bits. When the 8-bit input is completed, the gate circuit 302 checks whether all of the 8-bit data is a white image, and if YES, outputs 1 to the signal line 3. After starting scanning the original, the F/F 304 is set when the first 8-bit white appears. This F/F is reset in advance by VSYNC (image leading edge signal). After that, it is left set until the next VSYNG comes. When the F/F 304 is set, the main scanning counter 351 at that time is stored in the latch F/F 305.
The value of is loaded. The value of the sub-scanning counter 350 at that time is loaded into the latch 306, which becomes the x1 coordinate value. This will be the Y1 coordinate value. Therefore P+ (X
+, Y+) can be found.

Also, each time the signal 303 is outputted as 1, the input signal from the main scanning is loaded into the launch 307. This input is immediately stored in latch 308 until the next eight pins enter shift register 301. When the value from the main scan when the first 8-bit white appears is loaded into latch 308, latch 31
A comparator 309 compares the data with the data of 0 (which is set to O° at the time of VSYNC). If the data in launch 308 is greater, the data in latch 308, that is, the data in latch 307, is loaded into latch 310. Also, at this time, the value of the sub-scanning counter is launch 311.
loaded into. This operation is processed until the next 8 vias enter the shift register 301. Latch 3 like this
If the data in 08 and latch 310 are applied to the entire image area, the maximum value in the X direction of the document area remains in 310, and the coordinate in the Y direction at this time remains in latch 311. This is the P2 (X2, Y2) coordinate.

F/F 312 is an F/F that sends a cent when 8-bit white appears for the first time in each main scanning line, and the water synchronization signal HSY
NC: is reset and the first 8 bits are set to white and held until the next HSYNC. At the time when the F/F 312 is set, the value of the main scanning counter is set in the register 313 and is loaded into the latch 314 until the first HSYNC. Then, the latch 315 and the comparator 316 compare the magnitude.

The latch 315 is
Ilax I direct has been reset. Moshi Lunch 315
If the data in the launch 314 is greater than the data in the launch 314, the signal 317 becomes active and the data in the launch 314, that is, the data in the tick 313 is loaded into the launch 315. This operation is performed between )[5YNC-HSYNC:. The above comparison operation is performed for the entire image area.
5 remains the minimum value of the document coordinates in the X direction. This is x3. Also, when the signal line 317 outputs,
The value from the sub-scan is loaded into latch 318. This will be Y3.

In chips 319 and 320, each time 8-bit white appears in the entire image area, the main scanning counter value and sub-scanning counter value at that time are overloaded. Therefore, when the document pre-scanning is completed, the count value at the time when 8-bit white appears last remains on the counter. This is (X, 1.Y
,? ).

The above eight latches (6, 11, 20, 18°5.1.
The data lines 0, 15, 19) are connected to the pass line BUS of the CPU shown in FIG. 2, and the CPU reads this data at the end of the previous scan.

FIG. 5 is a flowchart of the document reading resequence, and the program is stored in the ROM and executed by the CPU in FIG.

First, in step 501, the optical system performs forward scanning from the left end to the right end in FIG. 1 to detect the coordinates of the document on the document table as described in FIG. 4.

Next, in step 502, the area for sampling the peak value for determining the slice level for binarization is
Y3 is calculated from the coordinate data detected in step 501. For example, from the coordinates detected for a document such as the shaded area in FIG.
, Y2 and a rectangular area surrounded by X r and X a. This is because the original is normally placed as parallel to the original table as possible, and even if the original is placed tilted in the R direction as shown in FIG. 3, there is no possibility of reading unnecessary information from outside the original. It is also possible to determine the sampling area using other methods. FIG. 6 shows the scanning system path. When the document coordinate detection is completed, the optical system is at the point in the sub-scanning direction Ymax, and the peak value sampling start point Y2 and end point Y3 are known, so step 504
505 and 506 can be scheduled. That is, when the backward motion is started in step 503, the CPU 211 counts the main scanning line synchronization signals for the distance (Y+5ax-Y2), starts detecting the white peak value/black peak value described above, and further calculates the distance from that point. After counting the main scanning line synchronizing signals for an amount equivalent to gi (Y2-Y3), detection of the peak value is finished, and after counting the main scanning line synchronizing signals for an amount equivalent to the distance glE Y 3, the backward movement is stopped.

Also, in step 504, the peak value detection start poem includes:
The enable signal EN mentioned above is set corresponding to the detected coordinates XI, X, as shown in FIG.

With the above operations, the white peak and black peak of the image density can be detected for each main scanning line in the document located at any position on the document table.

Next, an algorithm for determining slice levels for binarization will be explained.

Using the above-described means, the CPU 211 takes in the black peak value and white peak value for each main scanning line from within the document area.

Now, assuming that the black peak on the i-th main scanning line is BPi and the white peak is WPi, the image data is a 6-bit value and takes one of the following values: h 00 (HEX) Color 3 F (HEX) t And BPi≧WPi.

The CPU stores the detected data BP in a 64 x 2 byte black peak histogram area and a 64 x 2 byte white peak histogram area prepared in the RAM.
i,! = Counts up the contents of the 2-byte areas corresponding to WPi one by one, waits for the next main scanning line synchronization signal MS, and calculates the data from the 1st ÷ 1st line BPi + 1.
and W P i÷1, count up the I5 area of the histogram again, and proceed to step 505.
Continue until the sample ends.

However, at this time, the detected BPi and WPi are not necessarily used as histogram data.

For example, if there is a band of uniform density in the main scanning line direction,
Even if it is pure white or pure black, the sample values BPi and WPi from it will be almost the same even if it is a different density, and as information for binarization, which requires data to distinguish the background from the information. unbecoming,
For that reason.

The CPU is BPi when BPi-WPi≦α.

WPi is not used as histogram data and is discarded, and BPi+1 and WPi+1 are waited for.

This α is a constant set empirically, and for example, 4 is 3. Furthermore, it is a matter of course that the entire histogram area 64×2×2 bytes be cleared to 0 before sampling is started in step 504.

As a result, when the sample is completed in step 505, a histogram as shown in FIG. 7, for example, has been created for each of the black peaks and white peaks. After completing the sample, the optical system returns to the starting point and completes the backward motion in step 506. Next, in step 507, the slice level is set.

First, the density level showing the peak frequency of each histogram is considered to be the respective representative value.

According to the example shown in FIG. 7, the density of the document information part is 36H, the density of the background part of the document is OAH, and for example, the center and value are 20H and 5 slice levels.

Note that the slice level can also be determined based on another predetermined level of fineness of the read data. In addition to the slice level, it is also possible to select and determine dither patterns and output patterns stored in the ROM.

After that, the document is read and scanned in step 508, and the operation ends.

The slice level ROM pattern obtained as described above is retained when the same document is read and copied multiple times in succession, and is canceled after a certain period of time after a predetermined number of copies have been completed. Also, slice level only when reading a new document.

The ROM pattern is canceled, and then a preliminary scan is performed.The preliminary scan can be selected as necessary, and it is also possible to increase the copy speed without the preliminary scan.

In FIG. 8, a document 601 is transferred to a glass 101 by a belt 600.
It is automatically set in the holder and ejected after reading is completed. In this case, with the scanning unit 200 set in advance at point A, the original 601 is moved with a belt for setting, and the original can be read while the scanning unit 200 is stopped. The width and length of the document are recognized from the read data at that time. Then, the scanning movement section is moved backward from point A to determine the level of the document. When the document is sent to the left end, forward movement is started and binarization is performed based on level recognition of the necessary and effective document area.

In the case of Fig. 8, if binarization based on recognition is not required, the scanned data of the document moving with the scanning unit stopped at point A can be converted into binarized data and output as it is, thereby making it easier to read. The time required can be shortened.

Effects The present invention enables appropriate binarization processing of read image data.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the document reading device, Figure 2 is a block diagram of the image signal processing circuit, Figure 3 is a diagram showing the relationship between the document placed on the document table and the position coordinates, and Figure 4 is the position coordinates. Detection circuit diagram, Figure 5 is a flow diagram of the image reading sequence, Figure 6 is a diagram showing the relationship between document position and sequence, Figure 7 is a diagram showing an example of a black peak histogram and a white peak histogram, and Figure 8 (Δ 1 is another schematic diagram of the document reading device. In the figure, 104 is a lamp, 103 is an image sensor, and 101 is a document table.

Claims (1)

[Claims] In a method of reading a document and outputting it as image data, the document is recognized while moving, the stopped document is read by a moving scanning system, and the read data is processed based on the previously recognized data. Processing method.