JPH0275268A - Picture reduction method - Google Patents

Abstract

PURPOSE:To prevent the deterioration in the picture quality of a reduced picture by obtaining a picture signal of nearly the same content as that of a picture signal obtained through the arithmetic processing in the unit of picture elements at the same main scanning position from picture signals on an interleaved line and its adjacent lines as a picture signal outputted from a line image sensor. CONSTITUTION:A picture of a read original 1 is read in the unit of lines by synchronizing the reading of a line image sensor 8 with the carrying of the read original by carrier roller pairs 3, 4. Then the read position is set to an intermediate position between the interleaved line and its adjacent lines. Thus, a picture signal of nearly the same content as that of a picture signal obtained through the arithmetic processing to picture signals on the interleaved line and its adjacent lines in the unit of picture elements of the same main scanning position is obtained. Thus, the deterioration in the picture quality of a reduced picture is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image reduction method for a document reading device. There is a method in which the position of a line image sensor that reads an original image line by line is fixed, and the read original is moved in the sub-scanning direction with respect to the reading position of the line image sensor.

In such a reading mechanism, it is necessary to move the document to be read in the sub-scanning direction in synchronization with the reading operation of the line image sensor, and for this reason, a step motor is widely used as the power source for the sub-scanning mechanism. .

Now, when such an original reading device forms an image signal corresponding to a reduced image, the reduction in the main scanning direction is performed by thinning out pixels depending on the reduction ratio, or by thinning out pixels between thinned pixels and their adjacent pixels. Executes predetermined arithmetic processing to convert two pixels into one
Methods such as converting into one pixel are used.

In addition, in the sub-scanning direction, lines corresponding to the reduction ratio are thinned out, or the image signals of the thinned-out line and the line adjacent to the thinned-out line are OR-processed between pixels at the same main scanning position, and the two lines are A method such as forming one line of image signal from an image signal is used.

[Problems to be Solved by the Invention] However, such conventional image reduction methods in the sub-scanning direction have the following disadvantages.

That is, in the former method, all the content of the image signal of the thinned out line is lost, resulting in the disadvantage that the image quality of the reduced image is significantly degraded.

The latter method requires a special arithmetic processing circuit for thinning out, resulting in an expensive device.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an image reduction method that is inexpensive and capable of preventing deterioration in image quality of reduced images by solving the problems of the conventional methods.

[Means for Solving the Problems] The present invention uses a sub-scanning mechanism that can step the read document in the sub-scanning direction in intervals shorter than the interval between the reading lines, and the reading position of the line image sensor is adjusted to the reduction ratio. When the corresponding line to be thinned out is reached, the step timing of the sub-scanning mechanism is adjusted to move the reading position of the line image sensor to an intermediate position between the thinned out line and the line adjacent to it, and the image is read at that position. The line image sensor is moved to the next line reading position.

[Operation] Therefore, since the reading position is set to the intermediate position between the thinning line and its adjacent line, the image signal of the thinning line and its adjacent line (identical to number i) is output as an image signal from the line image sensor at that time. Since it is possible to obtain an image signal with almost the same content as the image signal obtained by arithmetic processing pixel by pixel at the main scanning position, deterioration in the image quality of the reduced image can be prevented.Also, since no special arithmetic circuit is required, It is also possible to reduce the cost of the device.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a reading system of a document reading device according to an embodiment of the present invention.

In the figure, the original to be read 1 is transported in the sub-scanning direction by a pair of transport rollers 3.4, which are arranged in the front-rear direction in the sub-scanning direction, with the image surface facing down. transported to.

A light source 5 that illuminates the document surface at the image reading position is arranged below the contact glass 2. The document image at the reading position is reflected by a mirror 6, reduced by a lens 7, and sent to a line image sensor 8. is imaged.

By synchronizing the reading operation of the line image sensor 8 with the conveyance operation of the document to be read by the pair of conveyor rollers 3 and 4, the image of the document to be read 1 is read line by line.

FIG. 2 shows a control system of a document reading device according to an embodiment of the present invention.

In the figure, an image signal reading unit 10 operates a line image sensor 8 at regular main scanning time intervals to output an analog image signal AV for one line, and also performs a predetermined image correction on the analog image signal AV. Along with applying processing operations, the binarized signal is converted into a binary signal, which is temporarily stored in an internal line buffer (not shown), and upon request from the control unit 11, the accumulated data of the line buffer is is output to the control section 1 as a digital image signal DV.

Further, the image signal reading section 10 outputs a main scanning synchronization signal LS that determines the timing of starting the operation of the line image sensor 8 to the control section 1.

The control unit 11 is for controlling the operation of this document reading device, and forms an output enable signal OEN that instructs the capture of the analog image signal AV output from the line image sensor 8 line by line. Reading section] 0
At the same time, a step pulse signal sp is generated and output to the motor drive circuit 12 to instruct the document 1 to be advanced by one step. Further, while the document is being read, a lighting signal To is output to the light source drive circuit 13.

Further, the control section 1 exchanges various information with an external device that uses this document reading device, and outputs a digital image signal DV to the external device.

The motor immediate action circuit 12 drives the step motor 14 that immediately moves the pair of conveyance rollers 3 and 4, and is connected to the control unit 11.
Each time a step pulse signal SP is input from the step motor 13, the step motor 13 is driven one step.

Further, in this case, when the step motor 14 operates one step, the document 1 to be read is moved in the sub-scanning direction by w! of the reading line interval of 172. , move away. In this case, the two-step operation of the step motor 14 causes the document 1 to be read to
moves one line in the sub-scanning direction.

The light source drive circuit 13 turns on the light source 5 when the lighting signal TO is applied.

With the above configuration, when the external device issues a command to read a document at the same magnification, the control unit 11 sends a lighting signal TO to the light source drive circuit 13.
At the same time, the control section 11 instructs the image signal reading section]0 to start image reading.

As a result, the image signal reading unit]0 starts the reading operation of the line image sensor 8, and outputs the main scanning synchronization signal LS to the control unit 11 in synchronization with the reading timing.

The control unit 11 generates the step pulse signal SP at the timing when the main scanning synchronizing signal LS is input, and at the timing when 172 of the main scanning time interval has elapsed after inputting the main scanning synchronizing signal LS. and outputs it to the motor drive circuit 12.

Each time the step pulse signal SP is input, the step motor 14 operates, thereby moving the leading edge of the document 1 to be read toward the reading position.

Then, the document sensor (
(not shown) detects the leading edge of the JMs, it counts the number of outputs of the step pulse signal SP from the detection timing, and when the counted value reaches a value corresponding to the distance from the document sensor to the reading position, the control unit 11 , initiates a read operation such as:

That is, the control unit 11 receives the main scanning synchronization signal! , S no Tachi”
The output enable signal OEN is output from the second timing until the real analog image signal AV is output from the line image sensor 8, and the output is output from the line image sensor 8 in the read operation started by the main scanning synchronization signal LS. The input and signal processing of the analog image signal AV is effectively performed, and the obtained digital image signal DV is thereby stored in the image signal reading section 10.

Then, the digital image signal DV stored in the image signal reading section 10 is read out and inputted between the rising -1-v timing of the next main scanning synchronization signal LS and the next output of the output enable signal OEN. Then, the input digital image signal OV is transferred to the external device in synchronization with the request timing from the external device.

In this manner, the control unit 11 reads the image of the original to be read 1 line by line, and sequentially transfers the digital image signal DV obtained by the reading to an external device.

Then, when the count value of the step pulse signal SP after the document sensor detects the trailing edge of the document reaches a value corresponding to the distance from the document sensor to the reading position, the control unit 11 terminates the two consecutive reading operations. and notifies the external device that image reading has ended.

Furthermore, when the count value of the step pulse signal Sll reaches a value corresponding to the distance from the document sensor to the pair of transport rollers 4 on the paper ejection side, the operation of the image signal reading section 10 is terminated, and the lighting signal To is turned off. and turn off the light source 5. Also, as a result of this, the output of the main scanning synchronization No. 4g LS of the image signal reading section], OhI, etc. is finished, so the output of the step pulse signal SP is also finished, and thereby the driving of the step motor 14 is finished and the reading is started. Conveyance of document 1 is completed.

In this way, when the same-size reading is specified, the line image sensor 8 is driven at a predetermined main scanning time interval, and during the main scanning time interval, the step motor 1
4 is driven twice, the original to be read 1 moves a distance of one line, and thereby the original image of the original to be read 1 is read.

In addition, the digital image signal DV obtained by reading the image
are sequentially transferred to the external device that has issued the command to read the image.

Now, when reduced reading is commanded from an external device, the control section 11 first moves the original to be read 1 to the reading position in the same manner as described above, and then performs image reading in the following manner.

That is, the reduction rate (length) commanded at this time is (k
-1)/, in this case, the image reduction in the sub-scanning direction will be reduced by one line every k lines, and the image reduction in the main scanning direction will be reduced by one pixel from k consecutive pixels. This is done by subtracting .

At this time, in this embodiment, (k-
1) After reading a line of image, next, one line of reading operation is performed with the reading position advanced by 1.5 lines in the sub-scanning direction, thereby reading the image of one line as a reduction unit. Then, change the reading position by 1 in the sub-scanning direction.
．． Advance 5 lines and start reading the image for the next line.

In this way, by subtracting the number of read lines for k lines, the image is reduced to (k-1)/fold in the sub-scanning direction.

That is, in this embodiment, reading is performed before and after the m-th (=ak) line, which is an integral multiple of k, as shown in FIGS. 3(a) to 3(e).

On the line (m-1,) one line before that, when the main scanning synchronization signal 1.3 is output at time T□, the control unit ]1
While reading the digital image signal DV of line (m-2), the step pulse signal SP is output to move the step motor 14 one step, thereby moving the original document 1 to be read a distance of 172 at intervals of one line. .

Furthermore, when the input of the digital image signal DV is finished, the output enable signal OEN is output, and the image signal reading unit]O is prepared to receive the analog image signal AV output from the line image sensor 8 on the line (m-1). make them do

Then, at time T2 when 172 of the main scanning time interval has elapsed since time T], the step pulse signal SP is output, the step motor 14 is moved one step, and the read original is moved 1. /2 distance.

-1]- In this way, when the original to be read 1 moves a distance of one line interval from time T1 and the reading position reaches line m (see Fig. 4), the next main scanning synchronization signal is sent at time T3. LS is output.

Thereby, the control unit 11 reads the digital image signal DV of line (m-1,), outputs the step pulse signal SP, drives the step motor 4 by one step, and thereby changes the original document 1 to be read. 17 with 1 line spacing
Move 2 distances.

Also, at this time, the output enable signal OEN is not output because it is the reading timing for line m which is an integral multiple of line k, and at the same time, at the time when 172 of the main scanning time interval has elapsed from time T, the step pulse signal SP is output. No output.

Next, at time T,1 when the main scanning time has elapsed from time T3, when the main scanning synchronization signal LS is output, at this point,
The reading position is located on line m', which is an intermediate position between line m and the next line (m+1), and therefore, at this ejection timing, the line image sensor 8 has line m and line (m+1). An intermediate image between both images IZ- (m+1) is formed.

Therefore, at this timing, the line image sensor 8 has an image that can obtain an image signal equivalent to the result of ORing the image signals of line m and line (m+1) pixel by pixel at the same main scanning position. In this embodiment, the image of this line m' is input.

That is, when the main scanning synchronization signal LS is output at time T4, the control section 11 outputs the step pulse signal SP to drive the step motor 14 by one step without reading the digital image signal DV of line m. As a result, the original to be read 1 is moved a distance of ]/2 of one line interval.

Then, it outputs an output enable signal OEN to make the image signal reading section ] 0 ready to capture the analog image signal AV output from the line image sensor 8 on line m''.

Also, at this time, 1 of the main scanning time interval from time T.
At the time after 72, the step pulse signal SP is not output.

When the main scanning synchronizing signal LS is output at time T when the main scanning time interval has elapsed from time T4, the control section 11 reads the digital image signal DV of line m' and outputs the step pulse signal SP. , step motor 14
The step moves, thereby moving document 1 a distance of ]/2 of the line spacing.

Also, the reading position at time T5 is on a line (+n+1) that is 172 distances away from line m', which is an interval of one line.
, and the line (m+1
．． ), the output enable signal OEN is not output because the image is not read.

Then, at time T6 when 172 of the main scanning time interval has elapsed from time T, the step pulse signal SP is output, the step motor 4 is moved by 1 step, and the original to be read is scanned at 1 line interval. move the distance.

Therefore, at time T7, when the main scanning time interval has elapsed since time T5, the reading position is located at the line (m+2), which is an integral multiple of the line plus 2, and this is the start of the cycle of the next line. Therefore, when the main scanning synchronization signal LS is output, the control section 11 controls the line (Ill+])-+1'1
- The step pulse signal SP is output without reading the digital image signal DV, and the step motor 14 is moved by one step.
Move 2 distances.

Then, it outputs an output enable signal OEN to make the image signal reading section]0 ready to capture the analog image signal AV output from the line image sensor 8 on line (m+2).

Next, at time T, when ]/2 of the main scanning time interval has elapsed from time T7, the step pulse signal SP is output, and the original to be read 1 is further moved a distance of 172 at intervals of one line.

After this, the same reading operation as for line (m-1) is repeated until the next line (a+1)k is reached.

In Figure 4, which shows the relationship between the reading position and image signal reading, the circles shown with solid lines indicate pixels on the line where image signals are read, and the circles shown with broken lines indicate pixels on lines where image signals are not read. Hail line pixels.

FIG. 5 shows an example of reduction processing in the sub-scanning direction executed by the control unit 11.

As described above, when the leading edge of the original to be read 11 reaches the reading position, the control unit 11 first clears the line counter n for storing the number of lines to be read to O, and enters a state in which it does not output the step pulse signal SP. A flag FSK for storing the state of the read line and a flag FDR for detecting the state of the read line are respectively reset (process 101).

Then, the value of line counter n becomes an integer multiple of k,
Determine whether the line is a thinning line (
Judgment 102).

When the result of the judgment 102 is NO, it is not a thinned line, so the line counter n is incremented (103), the output enable signal OEN is output, and the digital image signal DV is input from both signal reading sections 10. Process 104) to set the flag FRD for storage, and wait for the sub-scanning interrupt to be input or for the main-scanning synchronization signal LS to be input and the main-scanning interrupt to be input (No in judgments 105 and 106) loop).

Here, the sub-scanning interrupt is a timer interrupt that is generated within the control unit 11 when 172 of the main-scanning time interval has elapsed when the main-scanning synchronization signal LS is input.

When a sub-scanning interrupt occurs and the result of judgment 105 becomes YES, the state of flag FSK is checked (judgment 107), and if flag FSK has been reset (judgment 107).
If the result of step pulse signal sp is output (No), the step pulse signal sp is processed 108), and if the flag FSK is set to Sera 1 or higher (the result of judgment 107 is YES), a judgment is made to wait for the next main scanning interrupt to occur. ] Return to 05.

When a main scanning interrupt occurs and the result of step 06 is YES, process 109 to output the step pulse signal SP.
), it is checked whether the flag FRD is set (decision 110).

When the result of judgment 110 is YES, processing 111) is performed to input one line of digital image signal Dv from both signal reading sections 10, and when the result of judgment 110 is NO, processing 111 is not executed.

Then, it is checked whether or not image reading of the original document 1 to be read has been completed (determination 112), and when the result of determination 112 is NOL, the process returns to determination 102 and the next line is processed. Further, when the result of determination 112 is '/ES, this process is ended.

Further, when the value of the line counter n matches an integral multiple of k and the result of judgment 102 becomes YES, first check whether the flag FSK is in the reset 1 state (judgment 1
13) When the result of judgment 113 is YES, it is checked whether the flag F is in the reset state (judgment 114).

When the result of judgment 114 is YES, the flag FS
K and flag F are both reset 1-, and this is the state immediately after the time T3 described above, so both flag FSK and flag F are set.15), No loop of judgment 105 and judgment 106 to move to.

Therefore, in this case, line counter n is not updated, output enable signal OEN is not output, flag FRD remains at reset 1-, and flag FSK and flag F are both set, so time T3 When a sub-scanning interrupt occurs after 172 of the main-scanning time interval has elapsed, the step pulse signal SP is not output, and when a main-scanning interrupt occurs at time T4, the step pulse signal SP is output. However, one line of digital image signal DV is not read.

Judgment], when the result of 1.3 is NO, flag F
Check whether RD is in the reset state (decision 116).
), when the result of decision 116 is NO, flag F
Both SK and flag F have been set to cellar 1, and this is the state immediately after the above-mentioned time T4, so flag FRI is
Reset I (processing 117), output the output enable signal 01EN and set the flag FRD (processing 1]8),
Go to loop.

Therefore, in this case, the line counter n is not updated, the output enable signal OEN is outputted to prepare for reading line m', and the flag FRD
is set, flag FSK is set to Sera 1~, flag F
Since the leaf has been reset from 1 to 1, when a sub-scanning interrupt occurs when 172 of the main-scanning time interval has elapsed from time T4, the step pulse signal SP is not output.
Furthermore, when a main scanning interrupt occurs at time T5, the step pulse signal SP is output, and one line of digital image signal DV is read.

When the result of decision 116 is YES, the flag FS
K has been set and the flag FRD has been reset to 1-, and this is the state immediately after the above-mentioned time T5, so the flag FSK is reset to 1 and the flag FRD is set (step 119), and the No of decisions 105 and 106 is made. Go to loop.

Therefore, in this case, the line counter n is not updated, the output enable signal OEN is not output, the flag FRD remains at reset 1, the flag FSK is reset to 1, and the flag FDR is set to cell 1. Therefore, when a sub-scanning interrupt occurs at time T6, when 172 of the main-scanning time interval has elapsed from time T, the step pulse signal SP is output, and when a main-scanning interrupt occurs at time T7, the step pulse signal SP is output. Pulse signal S
P is output, but one line of digital image signal DV is not read.

When the result of decision 114 is N'O, flag FS
K has been reset to 1 and the flag FRD has been set, and the state is immediately after two consecutive times T7, so the flag FRD is reset to 1 (processing 120) and the line counter n is incremented (processing 121). ), the output enable signal OEN is output, and the flag FRD is set (step 122), and the process moves to a No loop of determinations 1.05 and 1.06.

Therefore, in this case, the output enable signal OEN is output, the flag FRD is set to zero, and the flag FSK and the flag FAIR are reset, so at time T8 when 172 of the main scanning time interval has elapsed from time T7. When a sub-scanning interrupt occurs, a step pulse signal SP is output, and at the next main-scanning interrupt generation timing, a step pulse signal SP is output and one line of digital image signal Dν is read. .

Also, at this time, the value of the line counter n is an integral multiple of k plus 1, so the result of judgment 102 is No.
Thus, two consecutive processes are performed.

In the following manner, the image in the sub-scanning direction is reduced in such a manner that one line of image signal is subtracted from the k line.

By the way, - in the above-mentioned embodiment, the main scanning time is lost twice in order to advance the reading position between the thinned out line and the next line, but such time loss can be solved as follows. It can be resolved by

That is, the sub-scanning mechanism is configured so that the original to be read is moved the same distance as in the above-described embodiment per pulse, and the step motor can be driven many times during the main-scanning time interval, and when the thinning line is reached, The step motor is rotated three times until the next main scanning synchronization signal is generated, and the reading position is moved by 1.5 lines.

As a result, the reading position can be advanced by 1.5 lines in one main scanning time, and the reading time during reduction can be shortened.

In the above description, descriptions of parts that are not directly related to the present invention, such as a method of image reduction in the main scanning direction, are omitted because they are the same as those of the conventional apparatus.

[Effects of the Invention] As explained above, according to the present invention, the reading position of the line image sensor is adjusted by using a sub-scanning mechanism that can move the read original in the sub-scanning direction in intervals shorter than the reading line interval. When the line reaches the thinning line corresponding to the reduction ratio, the step timing of the sub-scanning mechanism is adjusted to move the reading position of the line image sensor to an intermediate position between the thinning line and the adjacent line, and the image is scanned at that position. When the line image sensor is read, the line image sensor is moved to the reading position of the next line, so the reading position is set to the middle position between the thinning line and its adjacent line, so the line image sensor outputs at that time. As an image signal, it is possible to obtain an image signal with almost the same content as the image signal obtained by processing both the thinned-out line and its adjacent line signals pixel by pixel at the same main scanning position, and as a result, the reduced image Image quality deterioration can be prevented. Further, since no special arithmetic circuit is required, the loss 1- of the device can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a reading system of a document reading device according to an embodiment of the present invention, FIG. 2 is a schematic configuration diagram showing a control system of a document reading device according to an embodiment of the present invention, and FIG. 4 is a schematic diagram for explaining the thinning operation, and FIG. 5 is a flowchart showing an example of processing at the time of reading. 10... Image signal reading section, 11... Control section.

Claims (1)

[Claims] The image is scanned in the sub-scanning direction by a document reading device that advances the scanned document in the sub-scanning direction using a sub-scanning mechanism using a step motor in synchronization with the reading operation of a line image sensor that reads the original image line by line. In the image reduction method, the sub-scanning mechanism advances the read document in intervals shorter than the interval between the reading lines, and when the reading position reaches a line to be thinned out in accordance with the reduction ratio, the sub-scanning mechanism advances the scanned document in units of intervals shorter than the interval between the reading lines, and when the reading position reaches a thinning line corresponding to the reduction ratio, the thinning line and the adjacent line are scanned. An image reduction method characterized in that the reading position of a line image sensor is moved to an intermediate position of a line to be read, and when an image is read at that position, the line image sensor is moved to a reading position of the next line.