JPH0720194B2 - Image reader - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading device for reading an image, a text original, or the like.

2. Description of the Related Art Image reading apparatuses include a so-called camera type in which a document is projected by a reading lens and a projected image is scanned, and a so-called flying spot type in which an image is projected on a sensor through a minute hole. The camera type can set the reading area and reading pitch relatively easily by adjusting the projection magnification, while the flying spot type has the feature that the reading magnification is set only by the scanning mechanism.

FIG. 4 shows the structure of a document reading apparatus according to the conventional method. The drum 301 on which the original is attached is rotated in the direction of arrow A by the motor 302, and the original pixel point is read by the reading lens 30.
Document data is read by sensor 305 through 4. The subscanning motor 306 moves the document reading point in the Y direction.
The motor controller 307 is controlled by a control unit 308 composed of a microcomputer, etc.
Controls movement in the direction. A stepping motor is used as the sub-scanning motor 306 for obtaining the normal movement accuracy. The position of the original by the movement in the X direction is obtained by the pulse generated by the rotary encoder 303 mechanically connected to the drum shaft. The circumferential pulse generated by the rotary encoder 303 is converted into a finer pulse by the frequency multiplier 311 and further converted into a read pulse corresponding to the necessary read pitch by the frequency divider 312. The zero point pulse of the rotary encoder is connected to the other input of the frequency divider 312 to adjust the frequency division phase. The read pulse output from the frequency divider 312 is output as a conversion pulse from the A / D converter 310. On the other hand, the output from the sensor 305 is used as the conversion input of the A / D converter 310 after the output level is adjusted by the amplifier 309, and image data can be obtained at the designated pitch by the conversion pulse.

However, in the configuration described above, when reading a desired reading area (l: length) with a certain number of pixels (N: integer), the pitch P
Must be set to l / N. On the other hand, since the settable pitch, which is limited to the minimum feed pitch of the sub-scanning pulse motor and the number of rotations generated by the rotary encoder, can take only discrete values, the necessary reading pitch P cannot be set accurately in many cases. Therefore, the image is read by setting the closest settable pitch P ', or the necessary reading area is read by adjusting the number of pixels.

FIG. 5 shows how the reading area changes when the reading pitch is corrected to a settable pitch and the number of pixels is left unchanged.

In FIG. 5, l = P × N (however, P ... reading pitch, N ... number of pixels, l ... reading area) and l ′ = P ′ × N l ″ = P ″ × N (however, P ′, P ″ ... Set pitch, l ′, l ″ ... Actual reading size).

When the reading pitch P cannot be set, when the reading area ABCD is read at the smaller reading pitch P'that can be set, the difference in reading length (P-P ') from the actual reading area (AB'C'D'). ×
N occurs, and conversely, when the reading is performed at the larger reading pitch P ″, a difference in reading length from the actual reading area (AB ″ C ″ D ″) (P ″ −P) × N occurs. For example, when the pitch setting accuracy is 5 μm and the number of read pixels is 2000 pixels, the uncertainty of the read area is ± 55 mm at maximum, and the error is large especially when reading a small document.

The present invention solves the above-mentioned problems of the prior art, and an object of the present invention is to minimize the error in the reading area that occurs when a certain area is read with a certain number of pixels and the settable reading pitch cannot be set as a continuous value. It is what

Means for Solving the Problems The present invention uses two pitches that can be set above and below the calculated pitch as the pitch at the time of reading a pixel, and switches between the two pitches at the time of reading. The above problem is solved by switching according to the information.

Effect of the Invention With the above-described configuration, when the image reading position exceeds the target position, the next reading pitch is set to the smaller one for reading, and the image reading position does not reach the target position. At this time, the reading position can be adjusted by setting the next reading pitch to the larger one. Further, since the difference between the two reading pitches can be set to the minimum unit amount of the set reading pitch, the error of the total reading area can be kept within the minimum unit amount.

Embodiment 1 FIG. 1 is a block diagram of an image reading apparatus in an embodiment of the present invention.

In FIG. 1, 101 is a document mounting drum, and 102 is a drum.
A motor for rotating 101, a rotary encoder 103 for converting the rotation state of the motor 102 into a pulse signal, 104
Is a reading lens for optically reading the information of the original attached to the drum 101, 105 is its optical sensor, 106 is a stepping motor for moving the sensor 105 in the Y-axis direction, 107 is its stepping motor driver, 108 is a control CPU, 109 is an amplifier that amplifies the read information signal of the sensor 105, and 110 is an A / D converter that A / D converts the input signal.
D converter, 111 is a pulse multiplier that multiplies the output of the rotary encoder 103, 112 is a variable frequency divider for generating read pulses, 113 is an address counter, 114 is a memory for storing a pitch switching table, and 115 is a read pitch switch. Is a register for.

The operation of the above configuration will be described below. Ten
The operations 1 to 110 have the same functions as 301∧310 in FIG.
The circumferential pulse of the rotary encoder is multiplied by a multiplier 111 as necessary to generate a division signal in the X direction of the circumference of the original drum 101. The period of this pulse becomes the minimum set pitch unit in the X direction. Subsequently, the multiplied circumferential pulse is divided by the dividing ratio set by the variable divider 112, and A / D
Get the converted pulse. On the other hand, the reading pitch setting register 115
Stores two settable pitches above and below the actual reading pitch calculated by the CPU 108, and switches the set pitch according to the contents of the reading pitch switching table memory 114. The variable frequency divider 112 divides the switched pitch data based on the pitch data. The output of the variable frequency divider 112 is an A / D converter
In addition to using as the conversion pulse of 110, the address counter 113 is incremented, the output of the memory 114 of the pitch switching table is updated, and the register 115 of the read pitch setting is used.
Select one of the registers in and output it to the variable frequency divider 112. Switching of the moving pitch in the Y direction is realized by the CPU 108 calculating the image data in the X direction and sending the required moving pitch number to the step motor driver 107. The data in the memory 114 for the pitch switching table is calculated by the CPU 108 before image reading and is written in the table as binary data of 0 or 1 (1 bit).

FIG. 2 is a timing chart of reading pitch switching.
201 is the output of the pulse multiplier 111, 202 is the output of the variable frequency divider 112, 203 is the output of the pitch switching table memory 114, 20
4 indicates the output of the address counter 113. In FIG. 2, the variable frequency divider 112 is operated by switching the pitch between 4 and 3. The counter of the variable frequency divider 112 counts down using the output of the pulse multiplier 111 as an input clock, and when the counter value becomes 0, the output of the variable frequency divider 112 (Fig. 2 (b)) changes to high. To do.
Next, when the clock is input, the variable frequency divider 1 according to the value of the output (FIG. 2 (c)) of the memory 114 for the pitch switching table.
Twelve internal states are set to one pitch value, and frequency division is performed from that value according to the clock input. Variable frequency divider 11
At the same time as the initial setting of 2, the pitch switching table memory 1
The address counter 14 is changed to the next address as shown in FIG. 2 (d) and used for setting the next pitch.

FIG. 3 shows the relationship between sample pixel point numbers and reading point coordinates when it is desired to read an image at a certain pitch P according to the present invention. In this case, the pitch P is 8.5 which is the minimum reading interval.
Although an example of reading at a double pitch is shown, it shows that reading can be performed while adjusting the pitch as shown by the broken line in the figure by reading the reading pitch in a distributed manner between 8 and 9.

In the present embodiment, the description has been given of the case where the hardware pitch changer is used only in the X direction of the drum type image reading device and the Y direction is changed by software.
It goes without saying that the direction can be the same as the X direction. Further, the present invention is not limited to the drum type image reading device, and can be used for adjusting the reading pitch of an image reading device using a line sensor or an image reading device using a surface sensor, for example.

EFFECTS OF THE INVENTION As described above, according to the present invention, by switching and using two reading pitches that can physically set the reading pitch of the image reading apparatus, the accuracy is less than the minimum pixel division pitch held by the apparatus. The whole area can be read with high accuracy, and the effect is great.

[Brief description of drawings]

FIG. 1 is a block connection diagram of an image reading apparatus according to an embodiment of the present invention, FIG. 2 is a timing diagram showing a pitch switching operation of the apparatus, and FIG. 3 is reading point coordinates by reading pitch switching by the apparatus. FIG. 4 is a diagram showing the coordinates of a calculation reading point, FIG. 4 is a block connection diagram of an image reading apparatus having a conventional single pitch setting mechanism, and FIG. 5 is a reading dimension error when a pitch is set by a conventional method. FIG. 101 ... Drum, 103 ... Rotary encoder, 104 ...
… Reading lens, 105 …… Optical sensor, 106 …… Stepping motor, 108 …… CPU, 111 …… Pulse multiplier, 112…
… Variable divider, 113 …… Address counter, 114 …… Memory, 115 …… Register.

Claims (3)

[Claims] 1. A document scanning unit for electronically or mechanically scanning a document in the vertical and horizontal directions, a photoelectric conversion unit for reading the document, and a preset scanning pitch for reading the document.
A pitch switching unit for switching to a type, a register for storing two types of scanning pitches calculated so as to minimize a reading area error of an original, and a memory for storing the switching information of the two types of scanning pitches calculated in advance. And an image reading apparatus including a control unit that switches the two types of scanning pitches by the pitch switching unit according to the switching information during document scanning, and moves the reading position by the value of the scanning pitch. 2. The image reading apparatus according to claim 1, wherein the switching information is binary data of 0 or 1. 3. A method according to claim 2, wherein one pitch switching requiring high speed is performed by hardware by a memory and the other pitch switching not requiring high speed is performed by software. Image reading device.