JPS6243619B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a document reading device used in a copying machine, facsimile machine, printer, etc., which reads a document screen and converts it into an electrical signal.

In general, conventional copying machines, facsimile machines, etc. use a one-dimensional image sensor as a photoelectric conversion element to read a document and convert it into an electrical signal. The dimensional image sensor reads the document while simultaneously feeding the document or moving an optical system such as a mirror in the sub-scanning direction.

However, when using a one-dimensional image sensor,
Since the light amount accumulation time can only be taken for a time equal to the scanning time of one line, there is a risk that the light amount will be insufficient during high-speed reading. Therefore, it is possible to increase the amount of light by using a halogen lamp as the light source, but
It is not preferable to use a halogen lamp as a light source because the compatibility with the spectral sensitivity characteristics of the image sensor or the resolution characteristics deteriorate particularly with respect to infrared light.

Furthermore, since the sub-scanning is continuous movement, there is a possibility that the resolution may deteriorate. Therefore, it is possible to use a step motor, but considering its response characteristics, if a one-dimensional image sensor is used, it will be equivalent to continuous movement, and resolution deterioration cannot be prevented.

In order to solve this problem, the reading line in the main scanning direction (hereinafter simply referred to as "line")
It is conceivable to read the document using a two-dimensional image sensor having multiple rows of images on one chip.
In other words, if you use a two-dimensional image sensor,
There are the following advantages compared to using a one-dimensional image sensor.

(1) The light intensity accumulation time can be multiple times the scanning time of one line, thereby increasing the intensity of the light source,
Directly, the image plane illuminance can be lowered.

(2) In the case of a one-dimensional image sensor, in order to increase light utilization efficiency, it is necessary to illuminate only the area of the document to be read with one line of the image sensor. Measures such as creating an aperture and adding a cylindrical lens were required. However, when a two-dimensional image sensor is used, a relatively wide area of the document is illuminated, so there is no burden on the light source.

(3) Since the image is stopped during photoelectric conversion, there is less deterioration in resolution.

In this way, by reading a document using a two-dimensional image sensor, it is possible to eliminate the problems that occur when a one-dimensional image sensor is used, especially during high-speed reading.

However, due to manufacturing problems, two-dimensional image sensors currently have a maximum number of lines of about 500 lines, and there is no element that can read the entire surface of a document at once. Therefore, when reading the entire surface of a document using an existing two-dimensional image sensor, it is necessary to divide the surface of the document into several parts in the sub-scanning direction and perform the reading multiple times.

Here, if the number of lines required to read the entire document is L and the number of effective lines read by the two-dimensional image sensor at one time is n, then the number of readings N is a value determined by N=L/n.

In this way, when using a two-dimensional image sensor, reading is required N times, and if the image moves continuously at this time, resolution becomes impossible. For this purpose, the image must be moved intermittently, but it is extremely difficult to control the amount of movement for each movement step to be exactly the same. Therefore, the continuity of reproduced images may be impaired due to intermittent forwarding, and there is a risk that, for example, images may be duplicated or missing.

This invention was made in view of the above points,
While the document is intermittently conveyed in the sub-scanning direction, a predetermined range that partially overlaps in the sub-scanning direction of the document is sequentially scanned at each conveyance step of the document using a two-dimensional image sensor having multiple rows of reading lines in the main-scanning direction. A document reading device configured to read and convert image signals as electrical signals, which includes providing a reference mark on the document or a member that moves together with the document for determining the effective reading range of the document, and detecting the reference mark. A signal processing circuit is provided for correcting image seams by passing or blocking the image signal depending on the signal,
By outputting a read image signal for each conveyance step via this signal processing circuit, a document reading device is provided that is capable of high-speed reading with good resolution and does not impair the continuity of reproduced images. It is something to do.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIGS. 1 and 2 are schematic perspective views showing the configurations of different parts of a document reading device according to the present invention, respectively. In FIG. 1, reference numeral 1 is a document, and one side edge of its image surface (the back surface in the figure), that is, an area where no document image is formed, is used as a reference for determining the effective reading range in each conveyance step. Marks 1a are provided at intervals S that are approximately equal to the set movement amount for each step in the sub-scanning direction (direction of arrow A).

Reference numeral 2 denotes a conveyor belt that intermittently conveys the document 1 in the direction of arrow A for sub-scanning, and is regulated by the step rotation of feed rollers 3 and 3' driven by a step motor (not shown). It rotates intermittently in the B direction, and the set movement amount for each step is determined by the image sensor 7 shown in FIG.
The width W of the imaging range P in the sub-scanning direction is made smaller than the width W in the sub-scanning direction.

In FIG. 2, 4 is a contact glass serving as a document table, and 5 is a light source for slit illumination consisting of a fluorescent lamp 5a and a reflecting mirror 5b. Slit lighting. Reference numeral 6 denotes a lens that reduces and forms an image formed by reflected light from the original 1 on the photoelectric conversion surface 7a of the image sensor 7.

The image sensor 7 is a two-dimensional type element having a photoelectric conversion surface 7a consisting of a plurality of reading lines 7b, and reads the screen of the original 1 within a single imaging range P, converts it into an electrical signal, and generates an image signal a. Output.

Reference numeral 8 denotes a signal processing circuit which inputs the image signal a output from the image sensor 7 and outputs the effective image signal b.The structure and operation of this signal processing circuit 8 will be described in detail later.

Next, the operation of the document reading device according to the present invention configured as described above will be explained. The document 1 and the reference mark 1a are intermittently moved on the contact glass 4 by the rotation of the conveyor belt 2. Each time the document 1 stops, the image sensor 7 accumulates light according to the amount of light reflected from the document screen located within the imaging range P at one time, and generates a charge corresponding to the amount of light. This charge is transferred to a shift register by a transfer pulse from the controller, and sequentially read out by a read pulse to output an image signal a. This image signal a is outputted via the signal processing circuit 8 as a binarized effective image signal b. The entire screen of the document 1 can be read by the image sensor 7 performing the above-described reading N times.

By the way, since the amount of movement of the transport belt 2 per step is less than the width W in the sub-scanning direction of the imaging range P at one time, the image of the document 1 that comes to the position of the imaging range P at each transport step is One part overlaps in sequence. Therefore, among the signals of each line constituting the image signal a output from the image sensor 7, the signals of some lines are output in duplicate. Further, since the reference mark 1a is also read at the same time as the original image, the signal of one part of the lines includes the reference mark component. Therefore, if the image signal a output from the image sensor 7 is used as it is as a reproduced image signal, image overlap will occur in the reproduced image, and the component of the reference mark 1a will also be reproduced. Therefore, the signal processing circuit 8 cuts out the signals of the overlapping lines and performs correction to remove the reference mark components from the signals of each line.

FIG. 3 is a block circuit diagram showing the configuration of this signal processing circuit 8. In the figure, 9 is the image sensor 7
A controller 10 is a binary circuit that converts the image signal a of the image sensor 7 into a binary signal.
Reference numeral 11 detects, from the controller 9, a signal of a portion (hereinafter referred to as "mark detection area") that may include a component of the reference mark 1a line by line from the image signal of each line of the image signal a during document reading in each transport step. This is a first gate circuit that outputs a mark detection signal mDT separated by a gate signal GDT. 12 is a detection circuit which samples whether or not the mark detection signal mDT outputted from the first gate circuit 11 includes a component of the reference mark 1a using the strobe signal STB from the controller 9, and indicates the result in a binary level. This is a sampling circuit that outputs the signal DT.

13 is initialized by the reset signal RS from the controller 9 at the beginning of document reading in each transport step, and the sampling circuit 1
This is a counting circuit that outputs a video enable signal VEN indicating at a binary level whether each line within one imaging range P is a valid read line based on the second detection signal DT. 14 is a video enable signal output by the count circuit 13 in response to the detection gate signal GDT from the controller 9;
This is a second gate circuit that makes VEN valid for each line only during a period for reading a portion of that line excluding the mark detection area (hereinafter referred to as "original image reading area"), and outputs it as a valid reading signal V.Val. Reference numeral 15 denotes a third gate circuit that allows or blocks the image signal a' depending on the valid read signal V.Val output from the second gate circuit 14.

The operation of the signal processing circuit configured in this way will be explained with reference to FIGS. 4 to 6.

First, a method for outputting the image signal a from the image sensor 7 will be explained. If the number of lines of the image sensor 7 is M, then one imaging range P is read in M lines from the first line to the Mth line as shown in FIG. Furthermore, since the interval S between the respective reference marks 1a is approximately equal to the set movement amount for each step, two reference marks 1a are included for each step within a single imaging range P having a wider width W. .

Then, when the image sensor 7 from the first line to the Mth line photoelectrically converts the image of the original 1 and the two reference marks 1a, the controller 9 in FIG. 3 outputs a transfer pulse as an image sensor control signal d. The signal is transferred to the shift register in the image sensor 7, and then a read pulse is output to sequentially read out the signal line by line starting from the first line. In this way, the image signal a obtained by reading the image of the original 1 within the imaging range P and the two reference marks 1a is output.

In the following explanation, two reference marks 1a that fall within one imaging range P are used for each transport step.
The earlier one (the one with the smaller line number) is referred to as the reference mark F, and the later one (the one with the later line number) is referred to as the reference mark L.

Next, the operation of the signal processing circuit 8 that aligns the seams of the reproduced image and removes the reference mark component from the signal of each line will be explained with reference to FIGS. 5 and 6. Note that FIG. 6A shows the line number of the reading line 7b of the two-dimensional image sensor 7.

First, the document 1 is conveyed by the conveyor belt 2 and the reference marks 1a (F, L) are moved to the position shown in FIG. When the reference marks F and L are read, the image signal a from the image sensor 7 is input to the signal processing circuit 8. This image signal a is converted into an image signal a' which is sequentially binarized line by line by the binarization circuit 10, and the first and third gate circuits 11, 1
5 respectively. In this case, the image signal a' of each line is in the mark detection area D as shown in FIG.
and a component of the original image reading area, and in the case of a line including a reference mark component, the portion corresponding to the reference marks F and L in the mark detection area D is at a high level "H".

The first gate circuit 11 is outputted from the controller 9 in synchronization with the readout of each line.As shown in FIG. 5B and FIG. Detection gate signal GDT is input. Then, only when this detection gate signal GDT is at a high level "H", the first gate circuit 11 turns on the gate and separates only the component of the mark detection area D from the image signal of that line for each line and generates the mark detection signal mDT. Output. Therefore, in the line including the reference mark component, the reference mark F or L as shown in FIG.
The sampling circuit 12 outputs a mark detection signal mDT in which the portion corresponding to
Enter.

Looking at this for one imaging range P, for example, as shown in Fig. 6C, the mark detection signal mDT as shown in Fig. 5C is generated from the second and third lines and the M-2 and M-1 lines as shown in Fig. 5C. Output.

A strobe signal STB as shown in FIG. 5D, which is output by the controller 9 in synchronization with the reading of each line, is input to the sampling circuit 12, and the mark detection signal mDT is referenced line by line by this strobe signal STB. A detection signal DT is output by sampling whether or not a mark component is included. When the mark detection signal mDT of that line includes a reference mark component (high level "H"), the detection signal DT is at a high level from the time when the strobe signal STB is input, as shown by the line α in FIG. When it becomes "H" and no reference mark component is included (low level "L"), it becomes low level "L" from the time when the strobe signal STB is input, as shown by line β in FIG.

Looking at this for one imaging range P, according to the previous example, the detection signal DT becomes high level "H" from the second line where the reference mark F is detected, as shown in FIG. At the fourth line where F is no longer detected, it becomes low level "L". This low level "L" state is maintained until the M-3 line, and it becomes high level "H" again from the M-2 line where the reference mark L is detected, and becomes low level "L" at the M-th line. .

The count circuit 13 is initialized by the reset signal RS output from the controller 9 at the beginning when reading the imaging range P once, is set by the first fall of the detection signal DT from the sampling circuit 12, and then is initialized by the reset signal RS output from the controller 9. It is reset by the falling edge of the detection signal DT (it may be set by the first rising edge of the detection signal DT and reset by the next rising edge), and outputs the video enable signal VEN.

Looking at this for one imaging range P, the 6th
As shown in Figure E, the falling edge of the detection signal DT when the reference mark F is detected, that is, the fourth edge in the previous example.
t ₁ when line strobe signal STB is input
It goes to high level "H" from t2, and goes to low level "L" from _t2 when the detection signal DT falls when the reference mark L is detected, that is, when the strobe signal STB of the Mth line is input in the previous example. return. In this way, it is detected that the effective reading lines within the current imaging range P are from the fourth line to the M-1th line.

The video enable signal VEN output from the count circuit 13 is input to the second gate circuit 14. The gate circuit 14 generates a detection gate signal as shown in FIG. 6F by the detection gate signal GDT shown in FIG.
It turns off only while GDT is at a high level "H" to cut off the video enable signal VEN, that is, outputs to the third gate circuit 15 a valid read signal V.Val that is valid only during the read period of the original image read area.

The third gate circuit 15 receives the valid read signal V.Val output from the second gate circuit 14 at a high level "H".
The gate is turned on only when , allowing image signal a' to pass. Therefore, in the previous example, the third gate circuit 15
From among the image signals of each line within one imaging range P, an image signal is output from which the signal of the mark detection area D is removed for each line from the 4th line to the M-1th line. In this way, an effective image signal b obtained by reading a predetermined range of the document screen within the imaging range P at one time is output.

Next, when the original 1 is transported, the set movement amount for each step and each reference mark 1a (F, L)
Since the spacing S between the steps S is approximately equal, even if the actual step movement amount varies slightly, the reference mark L at the time of current reading becomes the reference mark F at the time of the next readout, and the next imaging range P is set in the same manner as described above. It is effectively output from the image signal of the next line of the previous reference mark F within. That is, in the previous example, the screen portion of the document 1 corresponding to the Mth line within the current imaging range P becomes the screen portion corresponding to the first effective reading line within the next imaging range P.

Therefore, the seam between the reproduced image read in the current conveyance step and the reproduced image read in the next conveyance step is continuous.

By repeating the above operations N times, the entire screen of the original 1 can be read.

In the above embodiment, when reading the document for the first time, the controller 9 sends a set signal S (FIG. 3) that sets the video enable signal VEN of the count circuit 13 to a high level "H" at the beginning of reading the first line. is output, the image signal a' outputted through the third gate circuit 15 is made valid from the first line by the same operation as described above, and is cut off by the falling edge when the reference mark L is detected. From the second time onward, the document may be read by the same operation as described above. If you do this, the first
When reading the document for the first time, it is sufficient to place one reference mark 1a (L) within the imaging range P for the first time, and when reading the document for the final time, as is clear from the above operation description, the reference mark L If there is no line, the last read line (Mth line) of the image sensor 7 is read out. Therefore, it is not necessary to attach the reference marks 1a to both ends of the document 1 in the moving direction, making it easy to attach the reference marks and eliminating the possibility of leaving both ends of the document unread.

In addition, in the above embodiment, the signal of the part that may include the reference mark part is removed from the signal of each line and output, but it is not necessary to perform such removal on the document reading device side, and it is not necessary to perform such removal on the image reproduction device side. You may go.

Furthermore, the reference mark for determining the effective reading range of the document in each transport step does not necessarily need to be attached to the document, but may be attached to a member that moves together with the document.

For example, as shown in FIG. 7, a reference mark 1a may be attached to one side of a paper holder 20 made of transparent resin, which is larger than the original 1, and can be read by an image sensor at the same time as the original. In addition, in the system in which the original is conveyed by moving the original table as shown in FIG. A reference mark 1a may be provided on the side. In this way, any type of original can be processed by simply inserting the original 1 into the paper holder 20 and transporting it, or placing the original 1 on the contact glass 4', in addition to special originals with reference marks attached. It can also be used.

As described above with respect to the embodiments, according to the present invention, a predetermined range that partially overlaps in the sub-scanning direction of the document is sequentially read along with the reference mark by the two-dimensional image sensor at each conveyance step of the document.
Since the image signal is corrected in the signal processing circuit by removing the image signal of the overlapping line using the reference mark detection signal, it is possible to perform high-speed reading with good resolution. Continuity is not lost.

[Brief explanation of the drawing]

1 and 2 are schematic perspective views showing the configurations of different parts of a document reading device according to an embodiment of the present invention, and FIG. 3 is a block circuit diagram showing a signal processing circuit according to an embodiment of the present invention. Figure 4 is a perspective explanatory diagram showing the relationship between the one-time imaging range by the two-dimensional image sensor and the reference mark, and Figures 5A to 5H are time frames showing signals for one line in each part of the signal processing circuit in Figure 3. Chart diagrams, Figures 6A to 6F are time charts showing the signals of one imaging range in each part of the signal processing circuit in Figure 3, and Figures 7 and 8 are the members that move the reference mark with the document. It is a perspective explanatory view which shows the example attached to. 1... Manuscript, 1a (F, L)... Reference mark,
2... Conveyor belt, 4, 4'... Contact glass, 5... Light source for slit illumination, 6... Lens,
7... Two-dimensional image sensor, 8... Signal processing circuit, 9... Controller, 10... Binarization circuit,
11...First gate circuit, 12...Sampling circuit, 13...Counting circuit, 14...Second gate circuit, 15...Third gate circuit, 20...Vapor holder.

Claims (1)

[Claims] 1 While conveying the document intermittently in the sub-scanning direction,
A two-dimensional image sensor having multiple rows of reading lines in the main scanning direction sequentially reads a predetermined range that partially overlaps in the sub-scanning direction of the document at each transport step of the document and converts it into an image signal as an electric signal. In the document reading device, reference marks are placed on one side of the document or a member that moves together with the document for determining the effective reading range of the document at each transport step in the sub-scanning direction. The two-dimensional image sensor is attached at intervals approximately equal to the set movement amount, and sequentially determines whether the image signal of each line includes the reference mark component from the image signal outputted by the two-dimensional image sensor after reading the document image and the reference mark. A signal processing circuit is provided which detects whether or not the two-dimensional image sensor is in use, turns on the gate when the first reference mark component is detected, and gates off when the reference mark component is detected later, and the two-dimensional image sensor A document reading device characterized in that the image signal outputted by the device is outputted through the signal processing circuit, and the entire screen of the document is read while correcting the seams of the images.