JPH0678100A - Original size detector - Google Patents

Abstract

PURPOSE:To enable to accurately detect the size of an original by inexpensive constitution and to prevent the image transfer of the color of an original cover by using a white original cover. CONSTITUTION:An original image covered with a white original pressure plate is read out by a line image sensor 9 and the effective area of the original image is detected by a size detecting circuit 16. A CPU 17a previously stores regular sizes of respective originals with B5, A4, B4 sizes, etc., compares the effective range of the original image with respective regular sizes and judges the smallest regular size among regular sizes larger than the effective range of the original image as the size of the original.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document size detecting device for automatically detecting the size of a document in an image forming apparatus such as a digital copying machine or a facsimile machine by reading a document image with a line image sensor such as a CCD. .

[0002]

2. Description of the Related Art An original size detecting device of this type cuts light reflected from an original cover previously colored in a specific color other than white by an optical filter, as disclosed in Japanese Patent Laid-Open No. 63-280569. The size of the document is detected based on the difference between the background area of the document that has passed through the optical filter and the amount of light received by the document cover.

[0003]

However, in the above-mentioned conventional document size detecting apparatus, since the background area of the document is extracted by the optical filter, it becomes expensive and there is a possibility that the document cover may be erroneously detected depending on the color of the document cover. There's a problem. In addition, when the original is displaced and placed on the original table, the color area of the original cover is transferred.

In view of the above-mentioned conventional problems, the present invention provides a document size detecting device which can detect the size of a document accurately with an inexpensive structure and can prevent the document cover from being transferred. The purpose is to provide.

[0005]

In order to achieve the above object, the first means is to perform photoelectric conversion by detecting an illuminating means for illuminating a document surface and reflected light from an illuminated surface illuminated by the illuminating means. The photoelectric conversion means, the detection means for reading the original image covered by the original cover by the photoelectric conversion means and detecting the effective range of the original image, the storage means for pre-storing each standard size of the original, and the detection means. The effective range of the detected image is compared with each of the standard sizes stored by the storage means, and the determining means determines the smallest standard size among the standard sizes larger than the effective range of the image as the size of the document. It is configured.

The second means is further provided with a selecting means for automatically selecting the size of the recording paper according to the size of the original discriminated by the discriminating means of the first means.

In addition to the first means, the third means further comprises a control means for detecting the size of the original document by prescanning, and performing the prescanning only during facsimile transmission and not during copying operation. It is configured.

[0008]

According to the first means, the smallest fixed size among the fixed sizes larger than the effective range of the original image is discriminated as the size of the original by the above-mentioned construction, so that the optical filter can be omitted and therefore the cost is low. With such a configuration, the size of the document can be detected accurately. Further, even if the color of the document cover is white, the size can be surely detected, and the document cover can be prevented from being transferred.

In the second means, since the selecting means automatically selects the size of the recording paper according to the size of the original, it is possible to prevent the selection mistake of the recording paper.

In the third means, the control means controls so as not to detect the size of the original by the prescan during the copy operation, so that the operation delay during the copy can be avoided.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a block diagram showing an electric system of an embodiment of a document size detecting apparatus according to the present invention, FIG. 2 is a block diagram showing a document reading apparatus using the document size detecting apparatus of FIG.
3 is a perspective view showing the document reading device of FIG. 2, FIG. 4 is a plan view for explaining a document placing method in the document reading device of FIGS. 2 and 3, and FIG. 5 is a timing chart showing read data. 6 is a block diagram showing a detailed configuration of the size detection circuit of FIG. 1, and FIG. 7 is a configuration diagram showing a laser printer in which the document size detection device of FIG. 1 is used.

First, a document reading device using the document size detecting device of this embodiment will be described with reference to FIGS. In FIG. 2, a document (not shown) is placed on the transparent contact glass 1 and illuminated by the light sources 2a and 2b. The reflected light of the original is sequentially reflected by the mirrors 3, 4, 5, 6, 7 and is imaged by the lens 8 on the light receiving surface of the line image sensor 9 such as a CCD (charge coupled device). It is read by the line image sensor 9. In this embodiment, when detecting the size of the document, as shown in FIGS. 3 and 4,
The image of the document 42 and the white area of the document pressure plate 39 are pre-scanned, and in this case, the image output period signal FGATE (described later) is not output to the printer or the like.

As shown in FIG. 3, the contact glass 1 is covered with a manuscript pressure plate 39 which can be opened and closed in order to press the manuscript 42 on the contact glass 1.
The pressing surface of is composed of white. A scale 40 is formed on one end of the contact glass 1 along the main scanning direction X, that is, the direction of the line image sensor 9. An operation panel 41 and the like are provided on the front side of the upper surface of the document reading apparatus. As shown in FIG.
2 is positioned in the sub-scanning direction Y with reference to the scale 40, and is positioned in the main scanning direction X with reference to the front end of the contact glass 1. Therefore, the intersection of the scale 40 and the front end of the contact glass 1 is the reference point A. Become.

The document placement reference is not limited to this embodiment, and the document placement may be performed by centering the document or by reading only the document image no matter how the document is placed. Good. As a method of placing the originals, instead of pressing the originals 42 by the original pressing plate 39, a plurality of originals 42 may be sequentially fed onto the contact glass 1 by using an automatic original feeder (ADF). In this case as well, the pressing surface is white.

Next, the configuration of the document size detecting apparatus of this embodiment will be described with reference to FIG. Line image sensor 9
Is driven by the sensor driver 12 to read the image of the entire area on the contact glass 1, that is, the image of the original 42 and the white area of the original pressure plate 39. Line image sensor 9
The signal read by is amplified by the amplifier 13 and is, for example, 6 bits (64 gradations) by the A / D conversion circuit 14.
Signal, and then the shading correction circuit 1
5, the unevenness of the illuminance of the light sources 2a and 2b and the variation of the sensitivity of the line image sensor 9 are corrected.

When the image of the original 42 is recorded by scanning again after the pre-scan, the blurring due to the light sources 2a and 2b is corrected by the MTF correction circuit 18, and then the binarization processing circuit 19 is finally used. It is converted into binary information of white or black and output through the output circuit 20. It should be noted that this image data is shown in FIG.
It is output to the laser printer as shown in. Further, in the case of facsimile transmission, necessary processing such as compression processing is performed, modulated by a modem, and transmitted to a facsimile apparatus on the other side via a communication line.

When detecting the size of the original, the signals obtained by prescanning the image of the original 42 and the white area of the original pressure plate 39 are the image sensor 9, the amplifier 13, and the signal A mentioned above.
It is output to the size detection circuit 16 via the / D conversion circuit 14 and the shading correction circuit 15, and the size detection circuit 16
Thus, the length X in the main scanning direction and the length Y in the sub scanning direction of the image effective range of the original 42 are detected, and then the size data X and Y are converted into serial data by the parallel-serial conversion circuit 17. . CPU 17a is B5, A
Each standard size of the original such as 4 and B4 size is stored in advance, the effective range (X, Y) of the image is compared with each standard size, and the smallest standard size among the standard sizes larger than the effective range of the image is stored. Is determined as the size of the original, and this size data is output to a printer or a facsimile machine on the other side.

Next, the operation of detecting the effective ranges X and Y of the image of the original 42 will be described in detail. First, in this embodiment,
Since the pre-scan time is an extra time before reading the original, the sub-scanning speed, that is, the speed of the carriage 10 shown in FIG. 2 is twice as high as that at the time of reading the original. In addition,
The reading pitch in the sub-scanning direction is, for example, 2 mm, as in normal reading. In addition, the image sensor 9
The gain of the output signal is determined for each scan in consideration of a change in the light amount due to the temperature of the tube wall of the light sources 2a and 2b such as a fluorescent lamp and deterioration over time. Specifically, a reference white plate is provided between the home position of the carriage 10 and the original reading start position, and the gain of the amplifier 13 is adjusted so that the level when the image sensor 9 reads the reference white plate becomes the reference level. It is determined.

Then, in order to correct variations in the orientation distribution of the light sources 2a and 2b in the main scanning direction and the sensitivity of each element of the line image sensor 9, the level (digital data) when the reference white plate is read is shaded. It is written in the memory of the correction circuit 15. In this example,
2 lines in main scanning direction (2 rasters) for gain setting
Minutes, about 32 lines (32 rasters) are used as shading data, and the largest (white) value is written.

Here, in the case of digital copy interlocking with a laser printer, when the print button is turned on when reading an original, the printer starts feeding the recording sheet, and when the recording sheet reaches the registration roller, the recording sheet stops. Then, the light sources 2a and 2b are turned on and the carriage 10 starts moving. Then, when the time required for the speed of the carriage 10 and the light amounts of the light sources 2a and 2b to stabilize becomes longer, the reference white plate is read and the image data after the original reading start position is output to the printer. In the printer, a toner image is formed on the photoconductor by the image data, the waiting recording sheet is fed, and copying is performed by transfer and fixing.

During the prescan for detecting the size of the original, the printer does not operate, and only the reading device shown in FIG. 1 operates. First, since the moving speed of the carriage 10 is high, in order to stabilize the light amount of the light sources 2a and 2b, the light source 2
After the lights a and 2b are turned on and the amount of light is stabilized, the carriage 10
Starts moving, reads the reference white plate, and then scans the entire area of the contact glass 1.

In this case, the size detection circuit 16 first uses the image data corrected by the shading correction circuit 15 to divide it into a background area of the document and an image area of the document.
Since this image data DATA is raster scanning, it is input as one-dimensional data in the main scanning (X) direction, and as shown in FIG. 5, one raster worth of data is synchronized with the pixel clock signal VCLK at the cycle of the horizontal synchronization signal HSYNC. It is read and extracted by the image effective signal MVALID indicating the effective image range of the contact glass 1 in the main scanning direction.

In this embodiment, one raster corresponds to about 480
It is composed of 0 pixels (64 gradations / 1 pixel), the whitest level is “0”, and the blackest level is “63”.
Then, a threshold value is set between the density in the image valid signal MVALID and the density regarded as the background area of the document, and the density data is binarized by this threshold value to extract the image area of the document in the main scanning direction. . That is, data that is equal to or greater than this threshold is used as the image of the original, and data that is less than the threshold is used as the white area of the original or the white area of the original pressure plate 39.

Next, referring to FIG. 6, the size detection circuit 16
The detailed configuration of will be described. First, the case of obtaining the maximum value of the document in the X direction will be described. The comparator 47 compares the densities of the image data DATA and the threshold value THR, and outputs a high level signal when the image data DATA> the threshold value THR. Further, an X-direction address counter (shown as X-cou)
nt) 48 sets the pixel clock signal VCLK to the value “0” while the image valid signal MVALID in the main scanning direction is at the high level.
Then, the value is counted up, and this value is output to the D flip-flop (DF-F / F) circuit 49. The D-F / F circuit 49 outputs the count value at the time when the read data exceeds the threshold value THR while the image valid signal MVALID is at the high level to the D-F / F circuit 50 at the next stage.

Then, the D-F / F circuit 50 outputs this count value to the selector 51a and the comparator 51b each time the high-level image valid signal MVALID ends. The count value of this time is D- in the comparator 51b.
When it is larger than the maximum count value held by the FF circuit 52 up to the previous time, the selector 51a controls to select the current count value and output it to the D-FF circuit 52. Therefore, by performing this operation for each raster, the maximum value in the X direction of the document is held by the D-FF circuit 52.

Next, the case of obtaining the maximum value in the Y direction of the original will be described. The JK flip-flop circuit 53 is cleared (Q = L) when the image valid signal MVALID is low level in each raster, and the image valid signal is also valid. M
It is set when the read data exceeds the threshold value THR even once while VALID is at the high level (Q
= H). Then, the Q output signal of the JK-FF circuit 53 is taken out to the D-FF circuit 54 in the subsequent stage every time the image valid signal MVALID becomes low level.

Then, a Y-direction address counter (Y in the figure)
-Count) 55 counts the image valid signal MVALID in the main scanning direction from "0" while the signal FGATE indicating the image valid period in the sub-scanning direction is at high level, and D-F
When the inverted Q output signal of the F circuit 54 changes from the low level to the high level, that is, when the raster where the end portion of the image of the document exists changes to the raster which does not exist, the count value of the Y direction address counter 55 is the D-FF circuit. It is taken out at 56. If the inverted Q output signal of the D-FF circuit 54 changes from low level to high level a plurality of times, it is updated and taken out to the D-FF circuit 56 to obtain the maximum value in the Y direction of the original.

The maximum values in the X and Y directions of this original document are sent to the CPU 17 via the parallel-serial converter 17 shown in FIG.
The standard size which is captured by a and is compared with each standard size is determined to be the smallest standard size among the standard sizes larger than the effective range of the image. The size of the original is used to automatically select the size of the recording paper of the laser printer and the copy magnification, or is transmitted by facsimile. The maximum value data in the X and Y directions are
For example, it is composed of 8 bits, and therefore the CPU 17a
Captures a total of 16 bits of data with a read pulse.

Next, the structure of the laser printer will be described with reference to FIG. The image data read by the document reading device as described above is scanned by the laser output unit 21, the imaging lens 22, and the mirror 23 to form an electrostatic latent image on the photoconductor 24. The surface of the photoconductor 24 is charged in advance by the charging charger 25, the outside of the image area is discharged by the eraser 26, and an electrostatic latent image is formed by irradiation of the laser beam. Then, this electrostatic latent image is visualized with toner by the developing unit 27, and this toner image is transferred onto the recording paper by the transfer charger 28.

The recording papers 32a and 32b are preset in the paper feed cassettes 33a and 33b for each size, and the paper feed rollers 37a and 37b are set in accordance with the size of the above-mentioned document.
Are selectively taken in by. The recording sheets 32a, 3
A sensor for detecting the size of 2b is used as the paper feed cassette 33a,
You may provide in 33b. The recording papers 32a and 32b selectively taken in by the paper feed rollers 37a and 37b are temporarily stopped upstream of the registration rollers 38, and then conveyed so as to match the toner images on the photoconductor 24, and the toner images are transferred to the transfer charger. After being transferred to the recording paper by 28, it is separated from the photoconductor 24 by the separation charger 29 and the separation claw 30. Then, the toner image is transported by the transport belt 34, fixed by the fixing roller 35, and discharged onto the paper discharge tray 36. The residual toner on the photoconductor 24 is removed by the cleaning unit 31.

Here, if the document size detection operation by the prescan is performed only during facsimile transmission and not during copy operation, delay of copy operation can be prevented.

[0032]

As described above, according to the first aspect of the present invention, the photoelectric conversion device for illuminating the document surface and the photoelectric conversion for detecting the reflected light from the illuminated surface illuminated by the illuminating device and performing photoelectric conversion. Means, a detection means for reading the original image covered by the original cover by the photoelectric conversion means, and detecting the effective range of the original image, a storage means for pre-storing each standard size of the original, and the detection means. Since the effective range of the image and each standard size stored by the storage means are compared, and the smallest standard size among the standard sizes larger than the effective range of the image is discriminated as the size of the original document, The filter can be omitted, and thus the size of the original can be accurately detected with an inexpensive configuration. Further, since the original area is not detected by the color difference of the original, it is possible to make the original cover white, thereby preventing transfer of the original cover.

According to the second aspect of the invention, the selecting means automatically selects the size of the recording paper according to the size of the original document discriminated by the discriminating means according to the first aspect. be able to.

According to the third aspect of the present invention, the size of the original is detected by the pre-scan, and the control means controls the pre-scan only during the facsimile transmission and not during the copy operation. Therefore, the delay of the copy operation can be avoided.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electric system of an embodiment of a document size detecting apparatus according to the present invention.

FIG. 2 is a block diagram showing a document reading device using the document size detecting device of FIG.

FIG. 3 is a perspective view showing the document reading apparatus of FIG.

FIG. 4 is a plan view for explaining a method of placing a document in the document reading device of FIGS. 2 and 3.

FIG. 5 is a timing chart showing read data.

6 is a block diagram showing a detailed configuration of the size detection circuit of FIG.

7 is a configuration diagram showing a laser printer in which the document size detecting device of FIG. 1 is used.

[Explanation of symbols]

 9 line image sensor 16 size detection circuit 17a CPU (central processing unit) 39 document pressure plate 42 document

Claims (3)

[Claims] 1. An illuminating means for illuminating a document surface, a photoelectric converting means for detecting reflected light from an illuminated surface illuminated by the illuminating means and photoelectrically converting the reflected light, and a photoelectric conversion for an original image covered by an original cover. Detecting means for detecting the effective range of the original image read by the means, storage means for pre-storing each fixed size of the original, effective range of the image detected by the detecting means and each fixed shape stored by the storage means A document size detection apparatus comprising: a determination unit that compares sizes and determines the smallest standard size among the standard sizes larger than the effective range of an image as the document size. 2. The document size detecting apparatus according to claim 1, further comprising a selection unit that automatically selects the size of the recording paper according to the size of the document discriminated by the discrimination unit. 3. The size of the original is detected by prescanning, and this prescanning is performed only during facsimile transmission,
2. The document size detecting apparatus according to claim 1, further comprising control means for controlling not to perform the copying operation.