JP2692835B2 - Image reading device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading device, and more particularly to an image reading device having variable image density and reading magnification when reading a document.

[Prior Art] Conventionally, there is known an image reading apparatus that specifies a reading density from the outside of the reading apparatus and transmits a read image to the outside according to the instructed reading pixel density. Similar devices are also known for reading magnification.

[Problems to be Solved by the Invention] However, in the conventional image reading apparatus, the reading magnification and the reading pixel density are not associated with each other, and the reading magnification is within a predetermined magnification range regardless of the designated pixel density. It was configured to be able to specify only. That is, when a certain reading magnification is designated from the outside and the magnification is outside the above range, the reading is not performed.

[Means for Solving Problems] The present invention has been made in view of the above points, and in an image reading apparatus configured to scan a document image and transmit it as an image signal to the outside, a reference read pixel density. A second designating means for designating a reading magnification with respect to the reference read pixel density designated by the first designating means, and a reference read pixel density designated by the first designating means. A setting unit that sets an actual read pixel density and a read magnification according to the read magnification designated by the second designation unit, and the second designation according to the read image density designated by the first designation unit. An image reading apparatus having different magnification ranges that can be specified by means.

[Examples] The present invention will be described below based on preferred examples.

FIG. 1 is an external perspective view of an embodiment of an image reading apparatus to which the present invention is applied, and FIG. 2 is an explanatory diagram of its internal configuration. still,
The image density of the image reading apparatus of this embodiment is 75,150,300 PPI (P
ixel Per Inch) and the scaling factor is 50 to 200%.

In FIG. 1, 1 is a document image reading device (hereinafter referred to as a reader), 2 is a reader body, and 3 is an automatic document feeding device for feeding a document to a reading position. In FIG. 2, the original is placed on the platen glass 27 with the image surface to be read facing downward, and the halogen lamp 24a in the original illuminating unit 24 is used.
Is illuminated by. The reflected light from the original is imaged by a lens 26 on a CCD (charge coupled device) 22 having a plurality of light receiving elements arranged in a line. Reference numeral 23 is a CCD driver that drives the CCD 22, and reference numeral 25 is a reflecting mirror that guides the reflected light from the document to the lens 26. Reference numeral 21 is a control unit that controls the operation of the reader. The document illumination unit 24 and the mirror 25 are reciprocated in the direction of the arrow shown by a stepping motor.

FIG. 3 shows a block diagram for electrical control of the image reading apparatus shown in FIG. According to this figure,
22 is a CCD sensor that reads an image, 203 is a C that drives the CCD 22
A CD drive circuit, 201 is an amplifier that amplifies an image analog signal from the CCD 22, and 202 is an A / D converter that digitizes the analog signal from the amplifier 201 into a predetermined bit for each pixel.

209 is a timing generation circuit for timing operation of the CCD 22 and other circuits, and 213 and 214 are rate multiplier circuits for thinning the clock from the timing signal generation circuit 209 according to the signal from the micro processor 208. , And a control circuit for converting the pixel density in the main scanning direction and the image magnification, respectively.

212 is a binarization circuit for binarizing the image signal,
The configuration is such that binarization using a dither matrix and binarization using a fixed threshold value are performed. 205 is a binarization circuit 212
A packing circuit having a serial-to-parallel converter function for converting the binarized image signal into an 8-bit parallel signal by 206 is a buffer memory of the 8-bit parallel binarized image signal, Used to match the output of the image signal to the speed of the external device receiving the image information.

These image signals are once passed through the I / F circuit 207 to an external device.
Sent to 250. 249 is an external device to the image reading device
This is a control signal line for giving an instruction from 250, and information including the image signal from the image reading device to the external device 250 is also transmitted through this signal line 249. That is, this signal line 249 is bidirectional and external device 250 (host)
The direction is determined according to the instructions from. Also,
Reference numerals 215 and 216 are circuits for controlling data read / write to the buffer memory 206. The external device 250 is provided with a pixel density and scaling ratio setting unit 251 including a keyboard and the like.

Microprocessor 208 has memory ROM208A, memory R
AM208B is attached and controls the sequence inside the reader.

A stepping motor 230, for example, is for controlling the position of the document illumination unit 24 and the mirror 25 in the sub-scanning direction when reading a document image. Reference numeral 211 is a circuit for generating a motor drive signal for driving the stepping motor 230, which operates according to a drive clock generated by an internal timer (not shown) of the CPU 208.

FIG. 4 shows an operation example of the density control circuit 213 in the main scanning direction. The main scanning direction density control circuit 213 is composed of, for example, a rate multiplier for thinning out an input clock at a rate according to an external instruction and outputting the thinned clock. In FIG. 4, (1) is the output clock of the control circuit 213 at 300 PPI, and the base clock input to the main scanning direction density control circuit 213 is output as it is. (2) is the bass clock divided by 1/2, which is the clock at 150 PPI. Also, (3) is the output clock at 75 PPI. These density switching is performed by the density instruction signal from the CPU 208.

FIG. 5 shows an operation example of the main scanning direction magnification control circuit 214. The main scanning direction magnification control circuit 214 is composed of, for example, a rate multiplier based on a decimal counter, and the input clock of the rate multiplier is given by the main scanning direction density control circuit 213.

FIGS. 5 (1), (2), (3) and (4) all show the state of the output clock of the main scanning direction magnification control circuit 214 at 300 PPI. In this figure,
(1) at 200%, (2) at 150%, (3) at 100%
And (4) shows the situation at 50%. These are CPU2
It is done according to the 08 order.

The output clock generated by the main scanning direction magnification control circuit 214 is applied to the packing circuit 205 and the write control circuit 215. In the binary mode, the packing circuit 205 outputs packing data when eight clocks are counted. The write control circuit 215 generates address information and write information to be given to the buffer memory 206 based on the clock given from the main scanning direction magnification control circuit 214, and these address information and write information are binary like the packing circuit 205. In the case of the mode, the effective information is output when the eight clocks are calculated.

The read control circuit 216 controls the transmission of the image information stored in the buffer memory 206 to the external device 250 via the interface circuit 207. That is, the read control circuit 216 sequentially outputs the address information and the read information based on the preset transfer speed.
The data is output to the memory 206 and the image data is sequentially read out.

FIG. 6 shows an optical system in the sub-scanning direction (original illumination unit 2
4, the state of the input clock given to the motor drive signal generation circuit 211 for moving the mirror 25) is shown. In this figure, the HSYNC signal of (1) is 1
The periodic signal of the line is shown. (2) is an example of clock at the time of reading of 50 to 100%, and in this example, 4 pulses are given to drive one line. (2) is an example of a clock at the time of reading from 101 to 200%, which is obtained by dividing (1) in half. These clocks are generated by the internal timer of CPU 208.

FIG. 7 shows an operation example in which the writing permission signal is controlled and the image signal is thinned out in a line unit when the image data is written in the buffer memory 206. (2) shows the output state of the write enable signal when performing thinning to 1/2, (3) thinning to 1/3, and (4) thinning to 1/4.

Pixel density control and reading magnification control in the sub-scanning direction are performed by a combination of the operations shown in FIGS. 6 and 7. That is, the pixel density and the reading magnification are controlled by controlling both the moving speed control of the optical system in the sub-scanning direction and the thinning ratio of the image signal in line units.

Under each of the hardware described above, how the read magnification and the read pixel density are related will be described.

FIGS. 8A and 8B show an example of the procedure for determining the read variable magnification range of image reading according to the present embodiment.
First, the external device 250 specifies a pixel density, a read magnification, and some other parameters. These data are expanded into the work area of the RAM 208B, for example, in step S1.

In step S2, the range of the scaling factor is calculated according to the pixel density designated by the external device 250. A detailed description of this step S2 will be given with reference to FIG.

First, in step S21, it is checked whether the pixel density designated by the external device 250 is 300 PPI. If it is 300 PPI, step S22 is processed. In step S22, the maximum scaling factor is calculated first. That is, in this embodiment, the maximum pixel density is 300 PPI and the maximum magnification is 200%. Therefore, as shown in the calculation formula, the maximum magnification at the time of reading 300 PPI is 200%.
In step S23, the minimum scaling factor is calculated. In step S23, the minimum scaling factor is calculated. In the case of this embodiment, the minimum pixel density is 75 PPI and the minimum scaling factor is 50%.
It is. Therefore, as shown in the equation, the minimum scaling factor is 12.5% when reading 300 PPI. When performing the magnification change of 12.5%, the CPU 208 issues an instruction of 75 PPI to the main scanning direction density control circuit 213, and the main scanning direction magnification control circuit 214
To give 50% instructions. The meaning of the expression is as described above. When 300 PPI is instructed in this way, the image reading apparatus can obtain a magnification change from 12.5% to 200%.

Similarly, the magnification range when 1500 PPI and 75 PPI are designated is calculated in steps S24 to S29. These results are RAM208B
It is used for the transmission to the external device (step S4). The specified pixel density is 300,150,75
If it is neither PPI, an error signal is generated at step S30.

By the above procedure, after the external device 250 is notified of the variable magnification specified range corresponding to the specified pixel density, the external device 25
At 0, the reader is instructed to start reading together with the required magnification (step S3).

A procedure for the reader to determine the actual internal resolution and the actual internal scaling factor ISR from the scaling factor designated by the external device 250 will be described with reference to FIGS. 9A to 9D.
In this figure, SMAX and SMIN are steps S2 in FIG. 8 (A).
It is the maximum value and the minimum value of the variable range obtained in. RSF is an abbreviation for Requested Scaling Factor,
This is a parameter of the scaling instruction transmitted from the external device. Further, RR is an abbreviation for Requested Resolution, and is a parameter of a pixel density instruction transmitted from an external device.

First, the contents of RR are checked in steps S501 and S601,
According to each value, the process branches to each processing routine of steps S502, S602, and S701. If the designated resolving power represented by RR is 300 PPI, it is carried out from step S502, and in step S503, the designated scaling factor represented by RSF is within the variable magnification range determined according to the designated resolving power. I can investigate. In case of more than 200% exceeding SMAX,
In step S504, an error is notified to the external device 250, and the process ends. When RSF is 50% to 200%, RSF is used without changing ISR, that is, the internal scaling factor. When the RSF is 50% or less, first, in step S506, the internal reading resolution is changed to 75 PPI. After that, in step S507, the value of X shown in the equation is obtained. Then, in step S508, X is determined as the internal scaling factor ISF. For example, when RSF is 40%, X is 160% and 16
0% is decided as ISF.

Since each process when S150 and PPIH is designated subsequent to S602 and S701 is almost the same as the case of 300 PPI, a brief description will be given below.

That is, in steps S603 and S702, it is checked whether or not the designated scaling ratio RSF represented by RSF is a variable magnification range determined according to each designated resolution, and if out of the range, step S604, External device 250 as an error in S703
Will be notified. On the other hand, if it is within the range, steps S605, S70
In step 4, the specified scaling factor RSF is classified, and in accordance with the classification, in steps S606 to 612 and S705 to 711, the internal resolution is changed and the internal scaling factor IRF is determined if necessary.

As described above, the variable magnification range is determined according to the designated resolution from the external device, and the internal resolution and the internal scaling factor are determined according to the designated magnification from the external device. Then, by setting the decimation rate of the clocks of the control circuits 213 and 214 according to the internal resolution and the internal magnification, the image is read from the external device with the designated resolution and the designated magnification.

In the description of the present embodiment, the image scaling density conversion in the main scanning direction has been described in detail, but it is also described in the sub scanning direction with reference to FIGS. 6 and 7 based on the respective values similarly obtained. This is performed by executing the movement control of the optical system and the thinning control of the image signal line by line.

Although the present invention has been described above with the preferred embodiment configuration, the present invention is not limited to this configuration, for example, the read density may be other than 300, 150, 75 PPI, and the scaling factor may be other than that of the embodiment. It is the same. The pixel signals may be thinned out by changing the packing operation or the input clock to the buffer memory, or may be executed at the time of reading from the buffer memory, for example.

Further, as the output destination of the image signal, not only an external device such as a host computer but also a printer or a display can be used.

[Effects of the Invention] As described above, according to the present invention, in an image reading apparatus which scans a document image and transmits it as an image signal to the outside, a magnification range that can be designated according to a designated reading pixel density. The image reading can be executed by fully utilizing the reading function.

[Brief description of the drawings]

FIG. 1 is an external view of an image reading apparatus according to the present invention, FIG. 2 is a view showing an internal configuration, FIG. 3 is a circuit configuration block diagram of a main portion of FIG. 1, and FIGS. Each signal timing chart in FIG. 3, FIGS. 8 (A) and 8 (B) are flow charts showing the procedure for determining the reading variable range, FIG.
(A) to (D) are flow charts showing the procedure for determining the internal reading resolution and the internal scaling factor from the required scaling factor. 2 Image reader (reader) 21 Control unit 22 CCD 24 Document illumination unit 208 CPU

Claims (1)

(57) [Claims] 1. An image reading apparatus adapted to scan a document image and send it as an image signal to the outside, and a first designating means for designating a reference read pixel density, and a reference designated by the first designating means. Of the read pixel density with respect to the read pixel density, and the actual read pixel density by the reference read pixel density specified by the first specifying means and the read magnification specified by the second specifying means. And an image reading apparatus, and setting means for setting a reading magnification, wherein the magnification range that can be designated by the second designating means is made different according to the read image density designated by the first designating means. .