JPS63276366A - Original reading device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Technical field] The present invention relates to a document reading device.

[Prior Art] For example, in a document reading device used in a data processing device such as a facsimile machine that inputs image information, the image surface of the document is illuminated and the reflected light is guided to a line image sensor. The document is moved relative to the line image sensor in the sub-scanning direction in synchronization with the line reading operation.

In such a document reading device, when changing the reading line density of an image, the read image signal is thinned out line by line based on the ratio between the basic line density and the changed line density.

FIG. 6 shows a conventional example of a document reading device that can change the image reading linear density in this manner. Note that this document reading device is capable of reading halftones of images.

In the figure, a line image sensor 1 is used to read a document image line by line, and starts reading with a line synchronization signal LS output from a sensor drive unit 2, and synchronizes with a pixel clock signal PC. An image signal AV corresponding to the density of each pixel for one line is output. Note that this line image sensor 1 is a CCD (charge coupled device)
It is of type.

The image signal AV is DC-regenerated by the video amplifier 3 and amplified by a predetermined amplification degree, and then converted into a corresponding digital image signal DV by the analog/digital converter 4 and applied to the binarization circuit 5.

The dither generator 6 is, for example, a 4×4 dither generator as shown in FIG.
Each element of the dither matrix MD is sequentially generated in synchronization with the line synchronization signal LS and the pixel clock signal pc, and the output signal is applied to the binarization circuit 5 as a threshold for binarization.

As a result, the binarization circuit 5 outputs a binarization signal G that displays the read image as a pseudo halftone image.

is output. The binarized image signal GD is input to a line memory 7 having a storage capacity for a plurality of lines.

The line memory 7 receives the input binary signal G on the condition that the enable signal ME is applied from the control unit 8.
D is stored line by line, and when the binarized signal GD is stored to the full storage capacity and is in a full state, a memory full signal FM is output to the control section 8.

The binary image signal GO stored in the line memory 7 is
It is read out via the interface 9 by a host device (for example, a facsimile machine; not shown).

The motor drive unit 10 drives a step motor 11 that moves the read document relative to the line image sensor 1 in the sub-scanning direction.

A linear density setting signal SD specifying the reading linear density is manually input to the control unit 8 from the host device.

The linear density can be arbitrarily set to a value below the maximum linear density (hereinafter referred to as the reference linear density) specific to this document reading device.

The control section 8 performs the processing shown in FIG. 8 every time the sensor drive section 2 outputs the line synchronization signal S.

That is, first, the memory full signal F is sent from the line memory 7.
It is checked whether or not M is output (decision 101), and if the result of determination 101 is NO, the read line is a thinning line based on the counted value of the number of read lines and the value of the linear density setting signal SD. It is determined whether or not (determination 102).

If the result of the judgment 102 is YES, the output of the enable signal ME is prohibited in order to prevent the halftone signal GD of that line from being stored in the line memory 7 (103), and if the result of the judgment 102 is No, the process 103) Processing 104) to output the enable signal, the motor drive unit 1 moves the reading position by one line in order to read the next line.
Outputs the drive signal to 0.

In this way, the halftone signal GD obtained by binarizing the image signal AV read by the line image sensor 1 using the dither matrix MD is applied to the line image on the condition that the line memory 7 has an empty area. The data are sequentially stored in the memory 7 and the read line is updated. Further, when the line memory 7 is full, the read line is not updated.

In addition, when the read line density is set to a value smaller than the reference line density, the lines of the halftone signal GD of the read line are thinned out in accordance with the ratio of the set line density and the reference line density. Storage in the memory 7 is prohibited, and the image signal of that line is thinned out.

However, such conventional devices have the following disadvantages.

That is, since one control unit 8 performs the image signal thinning process and the step motor 11 driving process,
This has caused an inconvenience in that the control processing of the control section 8 becomes complicated.

[Objective] The present invention has been made in order to eliminate the disadvantages of the prior art, and it is an object of the present invention to provide a document reading device that can simplify the control processing executed by the control means.

[Configuration] In order to achieve this object, the present invention counts the number of lines read by the line image sensor on the condition that the line memory is not full, and the counted value matches the number of thinned lines corresponding to the read line density. A thinning control means for prohibiting the accumulation of image signals in the line memory at a time, and a sub-scanning reading control means for moving the read line in the sub-scanning direction on the condition that the line memory is not full. This simplifies the control process.

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

FIG. 1 shows a document reading device according to an embodiment of the present invention. In this figure, the same parts and corresponding parts as in FIG. 6 are given the same reference numerals, and the explanation thereof will be omitted.

In the figure, a control section 20 outputs a linear density count value CD corresponding to a linear density signal SD to a thinning control section 21. This linear density count value CD is set by the ratio between the reference linear density and the linear density specified by the linear density signal SD.

The thinning control unit 21 converts the line synchronization signal LS output from the sensor drive unit 2 into a linear density count value C on the condition that the memory full signal FM is not output from the line memory 7.
Count D as the initial value. Then, when the count value reaches a predetermined value and when the memory full signal FM is being output, output of the memory enable signal ME is prohibited.

The line memory 7 stores the halftone signal GD output at that time on the condition that the memory enable signal ME is applied. That is, when the line for thinning out the image signal and the line memory 7 are full, storage of the halftone signal GD in the line memory 7 is prohibited. Note that reading of the accumulated halftone signal GD is not prohibited.

The motor control unit 22 synchronizes with the input timing of the line synchronization signal LS on the condition that the memory full signal FM is not output from the line memory 7 and the motor enable signal ED is output from the control unit 20. The motor drive section 10 drives the step motor 11 one step.

With the above configuration, when starting to read a document image, the host device specifies the reading linear density at that time to the control unit 20 using the linear density signal SD, and also instructs the control unit 20 to start the reading operation. do.

Thereby, the control section 20 forms a linear density count value CD corresponding to the linear density signal SD being input at that time, and adds it to the thinning control section 21.

A motor enable signal ED is output to the motor control section 22.

At the same time, the operation of the sensor driving section 2 is started, and image reading by the line image sensor 1 is started.

Furthermore, in this case, since the memory enable signal ME is output from the thinning control section 21, the halftone signal GD is in a state where it can be stored in the line memory 7.

When the line synchronization signal LS is output from the sensor drive section 2, the thinning control section 21 performs a counting operation, and the motor control section 22 drives the step motor 11 by one step. Therefore, the reading line of the line image sensor 1 moves by one line.

The image signal AV for one line outputted from the line image sensor 1 is converted into a corresponding digital image signal DV by the analog/digital converter 4, converted into a halftone signal GD by the binarization circuit 5, and then It is stored in the memory 7. Further, the halftone signal GD thus accumulated in the line memory 7 is taken out to the host device via the interface 9 at an appropriate timing.

In this way, the read lines are updated in synchronization with the reading operation of the line image sensor 1, and the halftone signal GD corresponding to each line is stored in the line memory 7.
The halftone signals GO are sequentially accumulated in the host device, and the halftone signals GO are appropriately taken out to the host device in the order of accumulation.

The speed at which the halftone signal GD is accumulated in the line memory 7 is
If the speed at which the halftone signal GD is read out from the line memory 7 is higher than the speed at which the host device reads it, the number of lines stored in the line memory 7 increases, and the halftone signal GD is stored to the full storage capacity of the line memory 7. .

As a result, when the memory full signal FM is output from the line memory 7, the thinning control unit 21 stops outputting the memory enable signal MH and prohibits the line memory 7 from accumulating the halftone signal GO. At the same time, driving of the step motor 11 by the motor control section 22 is stopped.

Therefore, when the memory full signal FM is output from the line memory 7, the line image sensor 1 reads the image signal of the same read line, and also stores the halftone signal GD corresponding to the image signal in the line memory 7. is prohibited.

Then, when the host device takes out one or more lines of halftone signals GD from the line memory 7 and one or more lines of empty space is created in the line memory 7, the line memory 7 stops outputting the memory full signal F, and The read operation is resumed.

Furthermore, when the count value of the thinning control section 21 reaches a predetermined value, the thinning control section 21 stops outputting the memory enable signal ME.

As a result, in the same way as described above, the line memory 7 does not store the halftone signal GD input at that time.

Also, at this time, since the motor control section 22 drives the step motor 11 one step, the image signal of the line input at that time is thinned out.

In this way, thinning control corresponding to the linear density set at that time is performed.

On the other hand, the control section 20 performs the processing shown in FIG. 2 every time the sensor drive section 2 outputs the line synchronization signal LS.

That is, it is checked whether the contents of the line density signal SD inputted from the host device at that time have changed from when the line synchronization signal LS was output immediately before (determination 20).
1). When the result of determination 201 is YES, the linear density count value CD is changed to a value corresponding to the linear density signal SD input at that time (process 202).

In this way, the processing content executed by the control unit 20 becomes extremely simple.

Furthermore, since the control unit 20 monitors changes in the line density every time the line synchronization signal LS is applied, if the host device changes the contents of the line density signal S[) at an appropriate timing, immediately after the change At the timing when the line synchronization signal LS is generated, the control unit 20 changes the value of the line density count value CD to a value corresponding to the new line density signal SD.

Therefore, for example, as shown in FIG.
It is possible to read images at different linear densities.

An example of the thinning control section 21 is shown in FIG.

In the figure, the latch circuit $21a is for storing the linear density count value CD output from the control section 20,
The stored data is applied to the preset input terminal of counter 21b.

Memory full signal F old output from line memory 7.
It is applied to one input terminal of the NOR circuit 21c, and is also applied to one input terminal of the AND circuit 21e via the inverter 21d.

A line synchronization signal LS output from the sensor drive section 2 is applied to the other input terminal of the AND circuit 21e. The output of this AND circuit 21e is applied to the clock input terminal of the counter 21b.

Furthermore, all digits of the count output of the counter 21e are input to an AND circuit 21f, and the output of this AND circuit 21f is input to the other input terminal of the NOR circuit 21c and the counter 21b.
A load has been added to the input end. The output of the NOR circuit 21c is sent to the line memory 7 as a memory enable signal ME.
is added to the write enable input terminal.

With the above configuration, when the memory full signal FM output from the line memory 7 is at the logic L level (i.e., non-output state), the AND circuit 2Le becomes operable, and thereby the line synchronization signal LS is AND circuit 2
1e to the clock input terminal of the counter 21b, and the counter 21b performs a counting operation in synchronization with the line synchronization signal LS.

At this time, if the count value of the counter 21b has not reached the maximum value, the output of the AND circuit 21f is at the logic L level, and thereby the memory enable signal ME output from the NOR circuit 21c is at the logic H level. As a result, the line memory 7 stores the halftone signal GD.

When the count value of the counter 21e reaches the maximum value corresponding to the number of bits, the output of the AND circuit 21f rises to the logic H level for one period of the in-sync signal LS.

As a result, the counter 21b loads the linear density count value CD applied to the preset input terminal at that time, presets the count value to the same value as the linear density count value CD, and then outputs the next line synchronization signal LS. Resume counting operation from.

Also, at this time, the output of the NOR circuit 21c goes to the logic L level for one period of the line synchronization signal LS, and the memory enable signal ME goes to the logic L level, so the line memory 7 stores the 1 added at that time. The halftone signal GD for the line is not accumulated.

As a result, the image signal for one line at that time is thinned out.

Further, when the line memory 7 is in a full state and the memory full signal FM is at a logic H level (that is, an output state), the memory enable signal ME output from the NOR circuit 21c falls to a logic L level. Therefore, the line memory 7 prohibits storage of the halftone signal GD.

In this way, when the line memory 7 is in the full state, the accumulation operation of the line memory 7 is prohibited, so that the halftone of the same line that is repeatedly added while the line memory 7 continues to be in the full state is Signal GD is not stored in line memory 7. Thereby, the stored contents of the line memory 7 are protected.

An example of the motor control section 22 is shown in FIG. In this case, the motor drive unit 10 drives the step motor 11 with 1-2 phase excitation.

In the figure, a motor enable signal outputted from the control section 20 and a line synchronization signal LS outputted from the sensor drive section 2 are respectively applied to the input terminal of an AND circuit 22a, and a memory full signal outputted from the line memory 7. FMt is applied to the other input terminal of the AND circuit 22a via the inverter 22b.

The output of the AND circuit 22a is applied to the clock input terminal of an octal counter 22c.

The output of the counter 22c is applied to the motor drive section 10 and the AND circuit 22d. The output of the AND circuit 22d is applied to the reset input terminal of the counter 22c.

With the above configuration, when the motor enable signal ED is at the logic H level (ie, output state) and the memory full signal FM is at the logic L level, the AND circuit 22a becomes operable.

Therefore, the line synchronization signal LS is applied to the clock input terminal of the counter 22c via the AND circuit 22a, thereby causing the counter 22c to perform a counting operation.

Here, the motor drive unit 10 is a
, A, B, and B phases are switched to eight different patterns to drive the step motor 11. Then, the motor drive section 10 selects the pattern based on the count value of the counter 22c.

That is, the motor drive section 10 sequentially switches the excitation state of the step motor 11 every time the count value of the counter 22c increments, thereby driving the step motor 11 in one direction.

As a result, each time the line synchronization signal LS is output,
The reading position of the line image sensor l moves by one line.

Further, when the count value of the counter 22c reaches "7", the output of the AND circuit 22d rises to the logic H level, and thereby the counter 22c resets the count value to "0".

As a result, the count value of the counter 22c changes from r04 to "7".
” changes cyclically.

Further, when the line memory 7 becomes full and the memory full signal FM becomes a logic H level, the AND circuit 22a becomes inactive, so the counter 22c does not perform a counting operation at that time.

Thereby, when the line memory 7 is in a full state, the reading position of the line image sensor 1 does not move.

In the embodiments described above, the image is read in halftones, but the present invention can also be applied to cases where the image is not read in halftones.

[Effects] As explained above, according to the present invention, the number of lines read by the line image sensor is counted on the condition that the in-memory is not full, and the counted value becomes the number of thinned lines corresponding to the read line density. It is equipped with thinning control means that prohibits the accumulation of image signals in the line memory every time there is a match, and sub-scanning reading control means that moves the read line in the sub-scanning direction on the condition that the line memory is not full.
The effect is that the control processing executed by the two control means can be simplified.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a document reading device according to an embodiment of the present invention, FIG. 2 is a flowchart showing an example of processing executed by the control section, and FIG. 3 is an example of changing the linear density when reading a document. 4 is a block diagram showing an example of a thinning control section, FIG. 5 is a block diagram showing an example of a motor drive section, and FIG. 6 is a block diagram showing a conventional example of a document reading device.
Figure 7 is a schematic diagram showing an example of a dither matrix;
The figure is a flowchart showing an example of processing executed by a control unit in a conventional device. 2...Sensor drive unit, 20...Control unit, 21...
Thinning control section, 22... motor control section. \・, Agent Patent Attorney Crest 1) Makoto ,'+-1. -' Figure 2 Figure 3 Figure 4 Figure 5 Figure 7 Figure 8

Claims (1)

[Claims] In a document reading device that outputs image signals output from a line image sensor via a line memory that stores multiple lines of image signals, the number of lines read by the line image sensor is counted and the counted value is calculated on the condition that the line memory is not full. thinning control means for prohibiting the accumulation of image signals in the line memory each time the number of thinning lines corresponds to the read line density, and moving the read line in the sub-scanning direction on the condition that the line memory is not full. What is claimed is: 1. A document reading device comprising a sub-scanning reading control means.