JPS6244741B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a document reading method used in copying machines, facsimile machines, printers, 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. That is, the use of a two-dimensional image sensor has the following advantages over the case of 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, and if the light source is a fluorescent lamp, an aperture should be provided on a part of the fluorescent screen. This required measures such as adding a cylindrical lens. 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 light intensity 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. This is a document reading device that converts the reading into an image signal as an electric signal, and a reference mark is placed on a portion of a conveyor belt that intermittently conveys the document that can be read at the same time as the document to determine the effective reading range of the document. At the same time, a signal processing circuit is provided that corrects the seam of the image by passing or blocking the image signal according to the detection signal of the reference mark, and outputs the image signal read at each conveyance step via this signal processing circuit. An object of the present invention is to provide a document reading device which is capable of high-speed reading with good resolution and which does not impair the continuity of reproduced images.

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

Reference marks 2a for determining the effective reading range of the original 1 at each transport step are placed on the transport belt 2 at intervals S that are approximately equal to the set movement amount for each step in the sub-scanning direction. One side edge that can be read at the same time as the screen of 1, that is, the image sensor 7 shown in FIG.
It is attached within an area having a width D in the main scanning direction of a single imaging range P according to the method.

In FIG. 2, reference numeral 4 indicates a contact glass serving as a document table, and reference numeral 5 indicates a slit illumination light source consisting of a fluorescent lamp 5a and a reflector 5b. illuminate. Reference numeral 6 denotes a lens that reduces and forms an image formed by reflected light from the document 1 and the conveyor belt 2 on 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 simultaneously reads the screen of the original 1 and the reference mark 2a within a single imaging range P and converts it into an electrical signal. It converts and outputs the image signal a.

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 2a are intermittently moved on the contact glass 4 by the rotation of the conveyor belt 2. Every time the original 1 and the reference mark 2a stop, the image sensor 7 accumulates light according to the amount of light reflected from each part of the original screen and the reference mark located within one imaging range P, and generates a charge according to the amount of light. Then, the charges are transferred to a shift register by a transfer pulse from a controller in a signal processing circuit 8, which will be described later, 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 2a is also read at the same time as the original screen, the signal of one part of the lines includes a 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 2a 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. As shown in FIG. In the figure, 9 is the image sensor 7
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 contain a component of the reference mark 2a for each line from the image signal of each line of the image signal a during document reading in the plate conveyance step. This is a first gate circuit that outputs a mark detection signal mDT separated by a gate signal GDT. 12 samples whether or not the mark detection signal mDT output from the first gate circuit 11 includes a component of the reference mark 2a using the strobe signal STB from the controller 9;
This is a sampling circuit that outputs a detection signal DT that indicates the result at a binary level.

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 the period of reading a portion of that line excluding the mark detection area (hereinafter referred to as "document 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 as described above 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 2a is approximately equal to the set movement amount for each step, two reference marks 2 are set for each step within a single imaging range P having a width W wider than that.
a enters.

Then, when the image sensor 7 from the first line to the Mth line photoelectrically converts the screen of the original 1 and the two reference marks 2a, 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, an image signal a that successively captures the screen of the document 1 within the imaging range P and the two reference marks 2a is output.

In the following explanation, two reference marks 2a 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 2a (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 1
1 and 15, respectively. In this case, the image signal a' of each line is a signal consisting of a component of the mark detection area D and a component of the document reading area I, as shown in FIG. The portions corresponding to the reference marks F and L in the mark detection area D become 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 part 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-3rd line, becomes high level "H" again from the M-2nd line where the reference mark L is detected, and becomes low level "L" at the Mth 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.
GDT is turned off only while the GDT is at high level “H” to cut off the video enable signal VEN, and outputs a valid reading signal V.Val valid only during the reading period of the document reading area I to the third gate circuit 15. .

The third gate circuit 15 turns on the gate only when the valid read signal V.Val output from the second gate circuit 14 is at a high level "H" and allows the image signal a' to pass through.
Therefore, in the previous example, the third gate circuit 15 outputs the mark detection area D for each line from the 4th line to the M-1th line among the image signals of each line within the one imaging range P. Outputs the image signal from which the signal is removed. 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 document 1 is transported, the set movement amount for each step and each reference mark 2a (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.

Note that in this embodiment, the signal of the part that may contain the reference mark component was removed from the signal of each line and outputted, but it is not necessarily necessary to perform such removal on the document reading device side, and it can be performed on the image reproducing device side. It's okay to get old.

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. The image signal is corrected in the signal processing circuit by using the reference mark detection signal to cut out the image signal of the overlapping line, which enables high-speed reading with good resolution.Moreover, intermittent feeding of the original allows for the reproduction of the reproduced image. 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 invention, and FIG. 3 is a block circuit diagram showing a signal processing circuit according to an embodiment of the invention, and FIG. 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. The charts and FIGS. 6A to 6F are time charts showing signals of one imaging range in each part of the signal processing circuit of FIG. 3. 1...Document, 2...Transport belt, 2a (F,
L)... Reference mark, 4... Contact glass (original table), 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.

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 original reading device, a conveyor belt that intermittently conveys the original in the sub-scanning direction has a conveyor belt that has a side portion that can be read simultaneously with the original by the two-dimensional image sensor, at each conveyance step in the sub-scanning direction. Reference marks for determining the effective reading range of the original are attached at intervals approximately equal to the set movement amount for each step, and the two-dimensional image sensor reads the original and the reference marks and outputs an image signal. A signal that sequentially detects for each line whether or not the image signal of that line includes the reference mark component, turns on the gate when the first reference mark component is detected, and gates off when the next reference mark component is detected. A processing circuit is provided, and the image signal outputted by the two-dimensional image sensor is outputted via the signal processing circuit for each conveyance step of the document, so that the entire screen of the document is read while correcting image seams. A document reading device characterized by: