JPS6033778A - Method for detecting original - Google Patents

Abstract

PURPOSE:To detect accurately a position of an original by painting the rear side of an original retaining cover monochromaticly and detecting the original based on the periodicity of a picture signal. CONSTITUTION:The rear side of the original retaining cover is painted in monochrome 2a such as yellow and the original P is placed. A digital picture signal S1 is obtained by scanning the color and the result is stored in a serial input/ parallel output shift register. A coincidence circuit 9 makes a data from a register storing a data of a platen cover coincident with an output of a shift register 7. When coincident, a coincidence signal S3 is inputted to a one-shot pulse generator 10, which is triggered. A flip-flop 11 is set by a horizontal synchronizing signal S2 and reset by an output S4 of the one-shot pulse generator 10. Thus, where the original P is placed to the original retaining cover is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for detecting a current document in a digital image recording system, and basically relates to a method for detecting the document size and placement position.

(b) Prior art Recently, an image reader using an image sensor (a photoelectric conversion element such as a solid-state image sensor) reads the image information of a document placed on a document table in batches, and the obtained image signals are
A digital image recording system has been developed in which an image is recorded based on a digital signal that is converted into a value and stored in a memory, and then read out from the memory. In such an image recording system, it is possible not only to normally record each original document, but also to record a single image by combining a plurality of original documents. When recording a composite image, the image data of each original is stored in memory sequentially, but knowing the original size at this time determines the storage capacity required for each original, so data can be stored in memory without wasting data. Capacity can be used effectively. A file management method is also being considered in which the image information of the document read by an image sensor is stored in memory for each document and read out and used whenever necessary, but even in this case, it is possible to store it if the document size is known. It is convenient for management because it allows you to know the amount of information and make effective use of memory. Furthermore, since the recording paper to be fed is automatically determined when the document size is known, there is no need to perform a paper feed selection operation, and memory capacity can be allocated according to the document size. This is also the case with ordinary copying machines that do not digitize the image information of the original, but once the original size is known, the paper feed size is determined, and the paper feed size is determined based on the selected paper feed size and the paper placed on the document table. When the original size is different, the reduction ratio or enlargement ratio of the original image can be automatically determined from the JJX 86 size and the paper feed size.

On the other hand, in order to record a composite image in a digital image recording system, it is necessary to know the position of the document on the document table.

This is also the case with ordinary copying machines, but once the original position is known, the paper feeding timing can be controlled and adjusted to match the original position no matter where the original is placed on the original table. There is no need to worry about matching.

In this way, in an image recording system, knowing the document size and document position has the above-mentioned advantages, so several methods for detecting the document size and document position have been proposed.

As an example of a detection method in a digital image recording system, the back side of a document holding cover (hereinafter referred to as "platen cover-1") is painted in a single color (for example, silver with high reflectance), and document image information is detected by an image sensor (for example, a CCD). There is a known method of detecting the document size by utilizing the fact that the output level of the image sensor is higher than the output level of the document image information due to the large amount of light reflected from the back surface of the platen cover during reading.

However, with this method, as both images are recorded for a long time, the back surface of the platen gradually becomes dirty, and the output level of the image sensor gradually decreases. If this happens, there is a possibility that the document size and document position cannot be detected.

Object and structure of the invention The present invention has been made in view of the above-mentioned points. The purpose of this method is to ensure that the document and the document position can be detected even if the back surface of the platen cover is dirty, and for this purpose, the back surface of the document holding cover is painted in a single color and the image signal is This digital image recording system is configured to detect a document based on the periodicity of a binary image signal obtained by dithering the image.

(→Example The present invention will be explained below based on the drawings.

FIG. 1 is a block diagram of an embodiment of a digital image recording system to which the document size detection method according to the present invention is applied. In this example.

A systematic dithering method is used to binarize the original image information, in other words, the pixel level of the original image information optically read by the image sensor is compared with a predetermined threshold, and the binary value is determined based on the magnitude relationship. (0 or I) is converted to represent a pseudo halftone, and the document size and document position are detected. In the figure, l is an image sensor that optically reads the image information of a document placed on the document table 2a of the image reader 2 shown in FIG. 2, and 3 is a pixel of the image information of the document read by the image sensor I. This is a binarization processing circuit using a systematic dither method that performs binarization using a threshold value that changes periodically in a pattern determined by a predetermined dither matrix.

Reference numeral 4 temporarily stores the binary image signal outputted from the binary processing circuit 3 in the memory 5, and then records the image in the image printer 6 based on this image signal, and also detects the document size and position, which will be described later. This is an image controller that performs.

Now, open the platen cover 2b painted in a single color (second
(see figure), the original P is placed on the original table 2a as shown in FIG. When the original image and the back surface of the platen cover 2b are scanned once in the horizontal direction (main scanning direction), the density level of the area AC (corresponding to the shaded area in FIG. 3) on the back surface of the platen cover remains constant as shown in FIG. a, and when this is binarized based on a periodically changing threshold level b (indicated by a chain line) using the dither method, a binary luck signal in which a predetermined pattern is repeated is obtained. On the other hand, image area B (
The density level of the image (corresponding to the white portion in FIG. 3) is indicated by C, for example, depending on the image information.

FIG. 5 shows a document size detection circuit according to the present invention.
8 is a serial input/parallel output type shift register that stores the digital image signal S□ of the image information of the back side of the platen cover and the original outputted from the image reader 2 (see Figure 1), and 8 is a shift register of red, yellow, etc. as described above. This is a register in which pattern data D, in which information on the back side of the platen cover painted in a single color is binarized, is stored in advance.

9 is a matching circuit that determines whether or not the data sent out from the shift register 8 matches the pattern data D of the register 8, and outputs a matching signal S3 when they match; 10 is a matching circuit that outputs a matching signal S3; The time is set to be slightly longer than the pattern period corresponding to the matrix size of the retriggerable single pulse which outputs the open signal S4 for a predetermined period of time based on the pattern period. Therefore, if the signal S3 is input at each pattern period during the image effective period (corresponding to the ox in Fig. 6), which is the maximum area in which an image can be recorded, the signal S3 is continuously input as shown by the signal s5 in Fig. 6. It will maintain the H level. 11 is an R-S flip-flop, and its set terminal S is connected to the area A (
(corresponding to the shaded area) and the horizontal synchronization signal S2 that is output every time the image area B of the document P is scanned in the main scanning direction N.
is done manually.

The output of the single pulse generator 10 is input to the reset terminal R. I2 is an OR circuit in which the signal from the single pulse generator 10 and the flip-flop output signal s6 from the flip-flop 11 are manually input, and the document size and document position are detected from the OR signal 37G from the output terminal Q. It has become so.

Next, a method for detecting the document size and document position will be explained based on the time chart of FIG.

The digital image signal Sl from the image reader 2 (see Figure 1) is applied to the back area A of the platen cover and the original image area B.
4a are stored in the shift register 7 as shown in the figure. Thereafter, a match circuit 9 determines whether these digital image signals S□ match the pattern data D in the register 8 or not. As a result, the image signal S1 in the back surface area i of the platen cover changes over time t.
When it is determined that there is a match with the first pattern data D, the match circuit 9 outputs a match signal D, and then a little before the time t, v has elapsed, the pattern data (same as the first pattern data) is output. ), the coincidence signal S3 is outputted again, so the single pulse generator 10 is retriggered at this time, and the S4 signal continues to be at the H level as shown in the figure.

Next, in the document image area B, the document image signal S1
Since " does not match the pattern data 1, the match signal S3 is not outputted from the match circuit 9 during this period, and therefore the signal S4 also goes to L level. Thereafter, after the scanning moves from the original image area B to the platen cover back area A again at time 11JJta, the same signal as the complete pattern data D is sequentially output at time t4, and at time t5. When the image signal S□ and the pattern data match, a match signal S3 is output. ?
1'L (such a coincidence signal S from the pulse generator 10
3, m'F S4 is output. On the other hand, since the horizontal synchronizing signal S2 is output when scanning of the back side of the platen cover and the original image in the main scanning direction starts (after time t), the flip-flop 11 is activated before the back side of the platen cover is scanned. It is in a set state,
During that time, the OR circuit 12 outputs an OR signal S7 based on the flip-flop output signal S7. Now, even if the output signal S6 from the flip-flop ll becomes zero at time te, the signal S4 is output from the single pulse generator lO at this time, so the OR signal J continues to be output, and the output signal S6 continues to be output for the area A on the back surface of the platen cover. It becomes zero at time t2 when the scanning ends.

In this way, the document size in the main scanning direction can also be detected from time t2 to t5, that is, time T1 during which the OR signal S7 is at the L level. Also, the time t when the horizontal synchronizing signal is output. The time from 1 to the time t2 representing the start Nrl of the original image area B.

46. Can detect the original position. The document size in the vertical direction (sub-scanning direction)/M (see Figure 3) is output from the time when the portion corresponding to 'r1 of the signal brightness shown in Figure 6 begins to occur until the end of the page. horizontal synchronous signal; 3-
It can be detected by counting 82 numbers. In other words, the size in the sub-travel direction can be detected by counting the number of signal activations during the image valid period 1-2 (see signal gS5 in Figure 6).

Here, as can be seen from Fig. 6, the time for detecting the end of the original image area B (original size) is actually delayed from t3 by one pattern and one data, or at most two patterns and one data. Although not shown in , the time t when moving from the platen cover back area A to the original image area B
2 is actually delayed by a time corresponding to the maximum l pattern data, but since the time of this pattern data corresponds to the dither matrix size and is very short in terms of length, such a time delay results in a delay of the original image area B. The detection error of the boundary can be ignored.

Now, in the above detection circuit, the pattern data D corresponding to the back surface of the platen cover, which is stored in advance in the register 8, is collected every 1 or 2 months (or depending on the number of recording times) depending on the degree of dirt on the back surface of the platen cover. ) If it is replaced automatically or manually, the back side of the platen cover will get dirty and the binary image signal corresponding to the back side of the platen cover will change, but the pattern data given to the register to be compared will also change. Therefore, the document size and document position can be detected using the same operating principle regardless of the degree of dirt.

The present invention is applicable not only to a system in which an original is fixed and an image is recorded, but also to an image recording system equipped with an ADFr automatic document feeding mechanism (ADFr automatic document feeding mechanism) in which the original is automatically fed to the original table.

(E) Detailed Description of the Invention As described above, the present invention is capable of printing a document based on an image signal obtained by reading light ↑1'j information from the document placed on the document table and the back surface of the document holding cover. In the detection method, the back side of the document holding cover is painted in a single color, and the document is detected based on the periodicity of the binary image signal obtained by dithering the image signal, so that both images can be recorded for a long time. Even if the pattern of the binary image signal corresponding to the back side of the platen cover changes as the back side of the platen cover becomes more dirty while cleaning, the pattern data stored will also change, so regardless of the degree of dirt, the original size and It is possible to detect the document position. Furthermore, detection accuracy can be improved by making the dither matrix thinner in the binarization process using the dither method. It goes without saying that the image reading signal can also be used as is for detecting the document size in the same manner as in the past.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of a digital image recording system to which the document size detection method according to the present invention is applied. FIG. 5 is a diagram showing density levels and threshold levels according to the dither method, FIG. 5 is a document size detection circuit according to the present invention, and FIG. 6 is a time chart for explaining the operation of the detection circuit shown in FIG. 5. . l...Image sensor 2...Image reader 3.
...Binarization processing circuit 4...Image controller 5...
-Memory 6...Image printer 7...Shift register 8...Register 919. Matching circuit 1()・
...Single pulse generator 11...-R-S flip-flop 12...OR circuit Patent applicant Roku Konishi Photo Industry Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] In a method for detecting a document based on an image signal obtained by reading optical information from a document placed on a document table and the back surface of a document flap cover, the back surface of the document flap cover is painted in a single color, and the image A document detection method characterized by detecting a document based on the periodicity of a binary image signal obtained by dithering a signal.