JPH0831941B2 - Document reader - Google Patents

Description

The present invention relates to an image reading device used in a copying machine or the like.

[Conventional technology]

A function to position image information in the center of the recording medium for a document placed at any position on the platen, a function to automatically determine the image scaling factor from the size of the document and the size of the recording medium, etc. In order to support multifunctional image processing,
A document reading device having a function of detecting the position and size of a document placed on the document table is required.

In such a function, it is necessary to prevent malfunction of document recognition due to dirt on the platen or dust on the platen.
There are the ideas shown in FIG. 3 and FIG. 4 as a concept for preventing the malfunction of the document recognition due to this dust. In FIG. 3, S is a document table,
It is assumed that M is a document and N is a stain on the platen, for example. Further, X is the scanning direction of the laser (hereinafter referred to as the main scanning direction) in a laser copying machine, and Y is the moving direction of the optical system (hereinafter referred to as the sub-scanning direction). When recognizing a manuscript as shown in Fig. 3, consider the small square 1 in the figure as one unit area for manuscript recognition, and a reading element such as a CCD line sensor scans an area in which all pixels in that area are white. Only when the original is recognized in this area, the original shown in FIG. 4 is recognized when the original shown in FIG. 3 is read. That is, according to this method, the stain of N in FIG. 3 can be ignored.

And K1 (X in the minimum Y coordinate in FIG. 4)
The point with the smallest coordinate), K2 (X with the largest Y coordinate)
The point with the largest coordinate), K3 (Y with the smallest X coordinate)
The point with the maximum coordinate), K4 (Y with the maximum X coordinate)
The position and size of the document can be detected by determining and selecting four points (points having the smallest coordinates).

That is, considering 3 × 3 9 pixels as one unit area for document recognition, when each pixel reads black and white by CCD as shown in FIG. 5, document recognition is performed as shown in FIG. If the number of pixels in this unit area is increased, the recognition accuracy will decrease, but large stains can be removed, and if the number of pixels is reduced, the recognition accuracy will increase, but the risk of recognizing even small stains as an original There is. The number of pixels in such a unit area must be appropriately selected depending on the usage of this device and the performance of the line sensor such as CCD.

[Problems that the invention is trying to solve]

However, the above detection method has the following drawbacks. It is generally realized by changing the scanning speed of the optical system at the time of enlargement / reduction, especially in the sub-scanning direction, and changing the moving speed of the reading position of the line sensor, and when the scanning speed in the sub-scanning direction changes. , For example, since the speed becomes low at the time of enlargement, if 3 × 3 9 pixels are set as 1 unit area at the same magnification, if the scan speed becomes 2/3, 3 × 2 6 pixels become 1 unit area. Become. That is, at the time of enlargement, stains on the document table are spread in the sub-scanning direction, and there is a risk that stains cannot be read out. For example, if there is a stain such as A in FIG. 7 on the platen, and if it is divided into areas as shown in FIG. 7 at the same magnification, the stain will be skipped at the same magnification, but the optical system will be 2/3 when enlarged. As shown in FIG. 8, the area is shortened in the sub-scanning direction Y in the figure, and as a result, the stain is recognized as a document.

However, such a drawback can be solved by scanning the optical system separately for document recognition and document image reading, for example, at the time of document recognition, the scanning speed is kept constant regardless of enlargement or reduction. However, it takes a dedicated time for document recognition. Further, when it is necessary to simultaneously perform document recognition and image reading, for example, when masking an area outside the document with white, particularly when the document is placed at an angle, it is necessary to perform scanning once. This is because it is necessary to recognize the original area at the same time when one main scanning line is read, and to output the area outside the original as white based on the original area information of the previous one line when writing the next one line.
Further, when the main scanning is performed in real time for each main scanning without the page memory, it is necessary to recognize the original area and scan the image by scanning once.

[Means for solving problems]

The present invention has been made in view of the above points, and an object thereof is to make it possible to perform excellent document position detection even when the moving speed of the document reading position changes according to the scaling factor. A reading unit that reads the image information of the document placed on the table line by line, a moving unit that moves the document reading position by the reading unit at a speed according to the magnification change ratio, and image information output from the reading unit. A determination unit that determines whether or not all image information included in the unit area on the document is white and a detection unit that detects the position of the document on the document table by integrating a plurality of determination results of the determination unit. And a target to be judged by the judgment means by causing the judgment means to perform a judgment operation every time the document reading position moved by the moving means at a speed according to the scaling ratio moves by a predetermined amount. Unit area on the manuscript The size, there is provided a document reading apparatus constant regardless magnification.

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 2 is a simplified block diagram of a document reading apparatus to which the present invention can be applied.

Place a document placed on the platen 59 with the reading side facing down with a fluorescent lamp.
Illuminated by 52, through reflective mirrors 53, 55, and optical lens 56
An original image is formed on the CCD sensor 1. The dotted line in the figure indicates the optical path of the reflected light from the document. Fluorescent lamp 52, reflecting mirrors 53, 55
The optical unit consisting of (1) is moved along a guide rail 58 by a DC motor (not shown) to scan the original on the original table 59. The CCD sensor 1 reads the original image by converting the intensity of the reflected light from the original into an electric signal of a predetermined pixel unit for each line.

At the time of enlargement, the optical unit moves at a lower speed than at the same size, and at the time of reduction, the optical unit moves at a higher speed than at the same size. This makes it possible to read an image at a desired magnification in the sub-scanning direction.

FIG. 1 is a circuit block diagram for processing an image read signal.

The image information on the document is read by the CCD sensor 8-1 (corresponding to CCD sensor 1 in Fig. 2) and photoelectrically converted, and then the line
It is sent to the shift register 8-2 through S8-1. The shift register 8-2 sends information for four consecutive pixels which are synchronized by the video clock S8-2 corresponding to the pixels to the NOR circuit 8-3. If the image information is "0" for white and "1" for black, the output of the NOR circuit 8-3 is "1" if the information of all four consecutive pixels is white, and vice versa. Even if a pixel contains black information, it will be “0”.

Considering the case where the output of the OR circuit 8-9 is 1,
When the information of four consecutive pixels is white, the gate 8-4 opens and 1 is written in the RAM 8-5 at the address corresponding to the main scanning address sent from the main scanning address counter 8-6. In this way, the image information for one main scanning line is written in the RAM 8-5. Next, the same thing is repeated for the next main scanning one line, but in this case, the same information of the main scanning address of the previous one line is output from the Dout of the RAM8-5 and the OR circuit 8-9. Through gate 8-4. That is,
Information input to the RAM 8-5 is "1" when the main scanning 4 pixels are white and the sub scanning 2 pixels are white.

When such an operation is repeated four times, information as to whether or not the main and sub 4 × 4 pixels are all white is written. At this point, "1" is output from the RAM output gate 8-8 through the line S8-7 for one main scanning line, and the RAM 8-5 is refreshed. The timing of this refresh determines the size of the unit area in the sub-scanning direction.

That is, since the number of encoder pulses of the DC motor 8-18 for moving the optical unit is proportional to the speed of the optical system, the RAM 8-5 is refreshed based on the encoder pulse of the DC motor 8-18. By doing so, even when the speed of the optical system changes during zooming, the size of the unit area on the document does not change, and document recognition can be performed without malfunction. The DC motor 8-18 is controlled by the motor driver 8-16, the CPU 8-17 reads the encoder pulse of the DC motor 8-18, and the motor driver 8-16 feeds the feedback. Also, the relationship between the number of encoder pulses and the movement distance of the optical system is about 0.05 mm per pulse at equal magnification, so 20 pulses per 1 mm, so an image can be read at 16 pels and a 4 × 4 unit area can be considered. For example, the encoder pulse may be synchronized with the video clock of line S8-2 and divided by 1/4 to be used as the refresh signal of RAM8-5. This frequency dividing operation is performed by the frequency dividing circuit 8-19.

In this way, a unit area of a fixed size can be used as the document presence / absence detection area regardless of the moving speed of the optical unit. Therefore, even in the case of enlargement or reduction, it is possible to eliminate the malfunction of the document detection due to the stain on the document table. In addition, the RAM output gate 8-8 opens for each unit area, and if it is all white through the line S8-8, the clock is output, and the main scan and sub scan at that time are output to the latches 8-10 and 8-11. Address is latched.

It should be noted that 8-12 to 8-15 are coordinate determining units, and finally, the coordinates K1, K2, K3, K4 near the four corners of the original document in FIG.
When the original detection and the image reading are performed separately, the information is used when reading the image. The CPU 8-17 is the optical unit motor driver 8-1.
6 can be controlled to access the document detection information. The main scanning address counter 8-6 is initialized by the video enable signal on the line S8-4 and counts the main scanning address in synchronization with the video clock on the line S8-3.
The sub-scanning address counter 8-7 is initialized by the document start signal on the line S8-5 and counts the sub-scanning address in synchronization with the video enable signal on the line S8-4.

In the present embodiment, the unit area in the sub-scanning direction is fixed, but the size of the unit area in the sub-scanning direction can be arbitrarily selected by, for example, the operator selecting an arbitrary value, and the main scanning can be performed. The operator can also arbitrarily select the unit area of the direction. Further, by simple modification, it can be judged that there is no original when, for example, 2 pixels out of 16 pixels are black.

In this way, for example, the operator can select the accuracy of the original detection, and the accuracy of the original detection suitable for the apparatus can be realized.

In addition to moving the optical unit, the original is passed through a fixed reading position at a speed that matches the reading magnification,
It is also applicable to a configuration in which the reading position is moved.

〔The invention's effect〕

As described above, according to the present invention, it is determined whether or not all the image information included in the unit area on the document is white, and a plurality of the determination results are combined to detect the position of the document on the document table. In the configuration, the determination operation is performed each time the document reading position moved at a speed corresponding to the scaling ratio moves by a predetermined amount, so that the unit area of the document on which the determination is made whether all the image information is white is performed. Since the size is constant regardless of the scaling factor, even if the moving speed of the document reading position changes according to the scaling factor, the accuracy of document detection is affected by the change of the moving speed of the document reading position. Therefore, it is possible to always perform good document position detection regardless of the scaling factor.

[Brief description of drawings]

FIG. 1 is a block diagram of an image processing circuit to which the present invention is applied. FIG. 2 is a configuration diagram of an image reading apparatus, FIG. 3 is a diagram of a document for detecting a document and a stain on a document table, and FIG. 4 is a diagram of FIG. FIG. 5 is a view showing the result of document detection, FIG. 5 is a supplementary view of FIG. 3, FIG. 6 is a diagram showing the result of document detection of FIG. 5, and FIGS. 7 and 8 are unit areas in the sub-scanning direction. FIG. 7 is a diagram showing that stains are detected as a document by expanding the image. In the figure, 8-1 is a line sensor, 8-2 is a shift register, 8-17
Is a CPU, 8-19 is a frequency dividing circuit, 8-6 is a main scanning address counter, and 8-7 is a sub-scanning address counter.

Claims (1)

[Claims] 1. A reading unit for reading, for each line, image information of a document placed on a document table, a moving unit for moving a document reading position by the reading unit at a speed according to a scaling ratio, and the reading unit. By inputting the image information to be output and determining whether or not all the image information included in the unit area on the document is white, and a plurality of the determination results of the determining unit are combined, A determination unit that detects a position, and causes the determination unit to perform a determination operation each time the document reading position moved by the moving unit at a speed according to the scaling ratio moves by a predetermined amount, thereby performing the determination. An original reading apparatus, wherein the size of a unit area on an original which is a determination target of the means is constant regardless of the scaling factor.