JPH01224606A - Document size detecting device - Google Patents

Abstract

PURPOSE:To shorten the time of a 1st copy by using a member which is processed so that a specific light beam is not reflected and deciding a document area according to the output of a photodetection part based upon light which is projected by a projecting device and reflected by a conveyed document. CONSTITUTION:The document is set on the platen 101 of an automatic document feeder ADF and sent by paper feed rollers 102. When the light projected by the lighting 104 of an exposure device strikes on the document, its reflected light reaches a photodetector 105. When there is no document, the light is reflected except its infrared light by an infrared-light absorbing filter 111 which is provided between the rollers 102 and a conveyor belt 108 on the side of the reverse surface of the document and absorbs the infrared light and does not reflect them, so that the light reaches the photodetector 105. The quantity of the reflected light from the photodetector 105 is compared by a document area deciding circuit with a constant threshold value to decide the document area.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention is a document size detection device used in copying machines, facsimile machines, etc. The present invention relates to a device that detects by reading the amount of light reflected from a member that has been exposed.

This type of detection device is provided on the inner surface of the platen cover 1, as shown in FIG.

A colored member 2 colored in a predetermined color, a light projecting device 3 that illuminates the colored member 2, and a light projecting device 3 that are arranged in parallel on the lower surface side of the document table 5, and after the light projecting device 3 illuminates the colored member 2, a light receiving section 4 consisting of a color sensor that receives illumination light;
A part or all of the illumination light irradiated from the light projecting device 3 to the light receiving section 4 is blocked by the original 6 placed on the original platen 5, and the size of the original 6 is detected. It is known (Japanese Patent Publication No. 56-22424).

The problem to be solved by the invention is that in the case of the above-mentioned detection device, there is a problem that a pre-scan for size detection is required, and the first copy takes time. There was a problem in that the original 6 having the same color as 2 could not be detected.

Therefore, the present invention solves the problems of the conventional detection devices, and provides a document size detection device that does not require pre-scanning, can shorten the time for first copying, and can detect the size of documents of any color. The purpose is to provide

In order to achieve the above-mentioned object, this invention is installed on the back side of a document between the document table of an automatic document feeder and the document feed port, and processed to prevent a predetermined light beam from being reflected. The applied parts and
a light projecting device that irradiates the predetermined light beam onto the member; a light receiving unit that receives the reflected light after being irradiated onto the member by the light projector; and the predetermined light beam is conveyed by an automatic document feeder. The present invention is characterized by comprising a determining means for determining the document area based on the output of the light receiving section of the reflected light reflected by the document.

When a predetermined light beam emitted from the light projecting device hits the conveyed document, it is reflected by the document and reaches the light receiving section. On the other hand, if there is no document to be transported, the predetermined light rays are directed toward the member treated to prevent the predetermined light rays from being reflected, but are not reflected and do not reach the light receiving section. As a result, the determining means determines the document area based on the outputs of the light receiving sections having different amounts of reflected light, and the document size is detected.

Husband's L spots An embodiment of the invention will be described with reference to the drawings.

In FIG. 1, 100 is a document image reading device, and 200 is an image recording device. The image reading device 100 digitally reads the original image using a light receiving section made of a photoelectric conversion element such as a COD, and transmits the data to the image recording device 200 for recording and reproduction. At this time, the reading section detects the document size. Select the paper and perform editing such as automatic scaling and cornering.

101 is a document table of an automatic document feeder (ADF); 102
1 is an original feeding roller, and 103 to 105 are exposure devices, which are composed of a light collecting plate 103, an illumination 104, and a light receiving element 105 consisting of a CCD line sensor.

Further, 106 is a reference white board for shading correction;
7 is a contact glass, 108 is a document conveyance belt colored white or a color similar to white, 109 is a platen cover, and 110 is a document discharge table.

Between the document table 101 of the ADF and the document feed slot,
In the figure, an infrared absorbing filter 111 is installed on the back side of the document between the feeding roller 102 and the conveying belt 108 and is treated to absorb infrared rays emitted from the illumination 104 and not reflect them.

The illumination 104 emits visible light and infrared light, and when the document size is detected (the carriage 10 is at the home position in FIG.
3 to 105), a filter 112 that transmits infrared rays is inserted between the illumination 104 and the infrared absorption filter 1110, and the filter 112 is retracted so that it does not exist in the optical path during document reading and shading correction. There is. Note that such a filter 112 may be omitted and the illumination 104 may be configured to emit only infrared rays when detecting the document size, and emit a light beam having spectral sensitivity over the entire visible light range when reading the document and during shading correction.

Reference numeral 113 denotes an infrared cut filter, which is not present in the optical path when the original size is detected, but is inserted into the optical path so as to cover the light receiving element 105 during original reading and shading correction.

FIG. 3 shows a block diagram of a processing circuit that detects the original size and creates image data from the output of the light receiving element 105. The image density data of the original 115 is photoelectrically converted into an electrical signal by the light receiving element 105, and the analog data is converted into digital data by the A/D converter 116. This digital data is subjected to image processing such as γ conversion and filter processing in an image processing circuit 117, and at the same time, an area determination circuit 11
8 and is compared with the threshold from the I10 boat 120 to determine the document area, and the result is input to the I10 port 120.
10 is output to port 120. The data image-processed by the image processing circuit 117 is edited by the image editing circuit 121, and is inputted to the laser driver 123 as multivalued or binary data via the gradation processing circuit 122, thereby starting the laser 125. Ru. RAMI27, RAMI
27 is a memory for storing programs and data used when the CPU 130 performs arithmetic processing, and 131 is an address data control bus, which is a bus circuit for transferring data between the elements. Synchronous control for sequentially processing data in the circuit is performed by a main scanning readout signal and a subscanning readout signal from a synchronization control circuit 132. If the CPU 130 determines that the above operation is effective only when the document size is detected, the correct document size will be detected.

Figure 4 shows a specific circuit for determining the document area.
In this area determination circuit 118, the interrupt signal and m-document main scanning size are input to the I10 port 120, and the CPU 130
The document position data is calculated in .

On the other hand, in the image recording apparatus 200, a polygon mirror 201 is a device that reflects output light from a laser diode installed vertically in the drawing and distributes it during main scanning. 202 consists of a toroidal lens and an fθ lens.

Correction system for correcting angle error of laser beam, 20
3 is a mirror, 204 is a photoreceptor, 205 is a charger, 206 is a developing section, 207 and 208 are paper feed cassettes, 2
09, 210 is a paper feed roller, 211 is a conveyance guide, 21
2 is a registration roller, 213 is a transfer charger, 214
215 is a separation claw, 216 is a cleaning section, 217 is a static eliminator, 218 is a transport guide, 219
220 is a conveyance belt, 220 is a conveyance guide, 221 is a fixing roller, 222 is a paper discharge roller, and 223 is a paper discharge table.

The operation of the above embodiment will be explained next.

When the original 115 is set on the original platen 101 of the ADF and the start key of the operation unit (not shown) is turned on, the feeding roller 102 is driven and the feeding of the original 115 begins.
The conveyor belt 10g is also driven, and the document sent by the feed roller 102 is conveyed to a predetermined position on the contact glass 107.

During this document conveyance, the light rays emitted from the illumination 104 of the exposure device pass through the filter 112 and hit the conveyed document 115, whereupon it is reflected by the document and reaches the light receiving element 105.

On the other hand, if there is no document being transported, if the infrared rays directly hit the filter 111, only the infrared rays will be absorbed by the filter and the light receiving element 1
It reaches 05. When the amount of reflected light is below a certain threshold, an interrupt signal is applied by the area determination circuit 118, and if there is no next interrupt signal even after a certain period of time (2 line scanning time) from both interrupt signals, sub-scanning ends. It is determined that the document has passed (end of document passage), and the time from the start of sub-scanning (the first interrupt signal after document feeding) is measured. Then, y during sub-scanning of the original 115 is determined from the product of this time and the original transport speed (FIG. 5). In the figure, the marks indicate reference positions for document setting on the document table 101.

At the same time, during main scanning of the original 115, X is still the light receiving element 105.
From the output, it is determined at what pixel from the reference edge (print) the document area becomes, and at what pixel it falls outside the document area again.
As a result, the coordinates of the starting point and ending point of the document area in the main scanning direction are determined. The coordinates determined for each line (the number of columns in the main scanning direction and the number of lines in the sub-scanning direction) are then compared with the coordinate values of the points that have been determined to be document areas up to that point. The larger value is selected and this operation is performed over the entire scan area.

Then, the difference between the minimum value at the start point and the maximum value at the end point is taken to determine the main scanning rll x.

The document size is detected from X during main scanning and y during sub-scanning of the document 115.

When the original 115 is inserted obliquely by the ADF as shown in FIG.
It is required as. Therefore, editing processing such as automatic paper selection and cornering is performed using x′×y′ detected as described above.
This is done according to the size of the original. Further, in this case, since the conveyor belt 108 is colored white or the like, an extra image is not created in the periphery of the document such as the shaded area in FIG. 6 during copying.

After the original 115 is conveyed to a predetermined position, image reading is started. The exposure devices 103 to 105 move together as a carriage, first read the reference white board 106, perform shading correction, and begin reading the image area. Then, it sequentially moves in the sub-scanning direction, and after reading y' of the document 115 during the sub-scanning, it returns to the home position shown in FIG. 5 and prepares for the next reading. The home position is the position of the carriage shown in FIG. 1, and is the position where the light receiving element 105 reads the reflected light from the infrared absorption filter 111. The image recording device 200 is driven in synchronization with these image readings, and sequentially records the image data sent from the reading section.

This invention is as described above, and the reading of reflected light is A.
Since the DF does not transport the document, pre-scanning for size detection is not required, and the time for first copying can be shortened. Further, the present invention has excellent effects in that it is possible to detect the size of documents of any color, has a simple structure, can be easily attached to existing documents, and is economical.

[Brief explanation of the drawing]

FIG. 1 is a schematic front view showing an embodiment of the present invention, FIG. 2 is an enlarged front view of the same essential parts, FIG. 3 is a block diagram of the 1± processing circuit, and FIG. 4 is a circuit for determining the document area. 5 and 6 are action explanatory diagrams, and FIG. 7 is a perspective view showing a conventional example. 100... Image recording device 101... Original platen 1
02... Feeding roller 105... Light receiving element 1
11... Infrared absorption filter 112... Infrared transmission filter 113... Infrared cut filter 115... Document 200... Image recording device FIG.

Claims (1)

[Claims] 1. A document size detection device for a document reading device having an automatic document feeder, which is installed on the back side of the document between the document table of the automatic document feeder and the document feed slot, and is processed to prevent reflection of a predetermined light beam. a light projecting device that irradiates the predetermined light beam onto the member; a light receiving section that receives the reflected light after being irradiated onto the member by the light projecting device; 1. A document size detection device comprising: determination means for determining a document area based on the output of the light receiving section of reflected light reflected by a document conveyed by an automatic conveyance device.