JP3048613B2 - Image reading device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus for reading an image of a subject.

[Conventional technology]

Conventionally, an image reading device, for example, an image scanner,
In order to detect the image reading start reference position in the main scanning direction, the white reference plate and the photoelectric element (CCD) are mechanically aligned, and the home position of the scanning optical system in the sub-scanning direction is determined by a photointerrupter or the like. It was detected by a sensor.

[Problems to be solved by the invention]

However, in the above-described conventional example, there are two types of alignment between the photoelectric element (CCD) and the white reference plate, namely, adjustment for aligning the read start position and adjustment for keeping the CCD and the white reference plate parallel. Such an adjustment requires considerable precision, and it has not been easy to accurately detect the image reading start position in the main scanning direction.

In addition, when using a sensor for detecting the home position, since the position of the home position had to be adjusted from the image that was actually read and output, the cost of the sensor was increased, and adjustment at the time of assembly was performed. It was necessary and it was not easy to accurately detect the home position.

An object of the present invention is to provide an image reading device that solves the above problems.

[Means for solving the problem]

In order to achieve such an object, the present invention provides a reading unit that reads light from a document and outputs an image signal, a shading correction unit that performs shading correction on the image signal, and a reference density used for the shading correction. A member, a marker provided on the reference density member, and detection means for detecting a change point of an image signal level obtained by reading the marker by the reading means in a main scanning direction and a sub-scanning direction of the reading means. Determining means for determining a reading start position in the main scanning direction and sub-scanning direction of the reading means based on the change point detected by the detecting means; and the reading means based on the reading start position determined by the determining means. Control means for controlling to start reading in the main scanning direction and the sub-scanning direction. To.

〔Example〕

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

FIG. 1 shows the internal configuration of a document image reading apparatus according to one embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a document image reading device that reads a document image. Reference numeral 2 denotes a scanning optical system, which includes a document illumination unit 15, a reflection mirror 16, a lens 14, a CCD 12, and a CCD driver 13.

The illumination unit 15 has a fluorescent lamp FL, and is movable in the direction A in the figure. The reflection mirror 16 regulates the optical path L of the reflected light from the document screen. lens
Numeral 14 converges the reflected light. The CCD 12 is arranged in an array corresponding to one line in the main scanning direction of the document, and photoelectrically converts the reflected light converged by the lens 14. The CCD driver 13 drives the CCD 12.

Reference numeral 11 denotes a control unit for controlling each unit, and reference numeral 17 denotes a platen glass for regulating a document screen for reading flat. Reference numeral 18 denotes an original placed on the platen glass 17, and reference numeral 19 denotes a platen cover. Reference numeral 20 denotes a stepping motor, which constitutes a moving means together with a stepping motor drive circuit (not shown). The stepping motor drive circuit drives the stepping motor according to the excitation signal from the CPU 208 in FIG.

FIG. 2 shows the CCD driver 13 and the control unit 11 shown in FIG.
1 shows a circuit configuration.

(CCD driver 13) 201 is an amplifier (AMP) for amplifying the output of the CCD 12. Two
An A / D converter (A / D) 02 converts an analog signal from the amplifier 201 into a 6-bit digital signal. Reference numeral 203 denotes a CCD drive circuit that drives the CCD 12 according to a timing signal supplied from the control unit 11 to regulate the read timing.

(Control unit 11) 204 is a shading RAM (random access memory) in which the light distribution characteristics of the illumination lamp are stored. 205
Denotes a shading control unit, which includes a shading ROM (read only memory) storing a shading correction coefficient and a circuit for controlling the shading RAM 204, and performs A / D based on the light distribution data of the fluorescent lamp FL stored in the shading RAM 204. The shading correction is performed on the image signal from the converter 202.

Reference numeral 210 denotes a peak value detection circuit for detecting the maximum value (black peak value) of a specified section in one line with respect to the image signal subjected to shading correction by the shading control unit 205. Reference numeral 206 denotes a binarizing circuit for binarizing the image signal subjected to shading correction by the shading control unit 205. An interface circuit 207 receives a control signal and outputs an image signal with an external device 250 which is a host device such as a personal computer.

Reference numeral 208 denotes a microcomputer-type CPU (central processing unit) which has a ROM 208A storing a control program and a working RAM 208B, and controls each unit according to the control program stored in the RAM 208A. 209 is a timing signal generation circuit, and a crystal oscillator according to the setting of the CPU 208.
The output of 211 is frequency-divided to generate various timing signals serving as operation references.

FIG. 3 is a view of the platen glass of FIG. 1 as viewed from the back side.

In this figure, Q is a white reference plate used for shading correction, and R is a white plate printed in white. P is a marker printed in black for detecting the home position, and is provided at a reference point at the corner of the back surface of the platen glass 17, that is, at a reference position for starting image reading in the main scanning and sub-scanning directions.

Next, the procedure for determining the actual read start reference position in the main scanning direction and the procedure for determining the home position in the sub-scanning direction will be described with reference to FIGS.

FIG. 4 shows the timing regarding the interrupt processing by the CPU 208.

In the figure, HSYNC is a main scanning synchronization signal, and this signal causes an HSYNC interrupt. PMCK is CPU208
Is a motor drive signal for driving the pulse motor, output from the controller, one pulse corresponds to one step of the pulse motor, and one line is driven by four pulses. ENDI
NT is an internal interrupt signal generated by counting the signal PMCK, and the CPU 208 has a predetermined number of pulses (for example, 4 pulses).
Is written into the register ECNT of the CPU 208 to start outputting pulses, and an internal interrupt signal ENDINT is generated when only four pulses have been output (ie, one line has been moved).

The peak value output is a multi-level signal output from the peak value detection circuit 210, and is updated each time the main scanning synchronization signal HSYNC is generated.

FIG. 5 is a flowchart showing a control procedure by the CPU 208.

When the reading instruction command is received, the fluorescent lamp FL is turned on in step S1, and a peak detection area signal is output to the peak value detection circuit 210 in step S2 according to the width of the third illustrated white plate R.

Next, the actual black peak value obtained via the shading control unit 205 read from the CCD 12 in step S3 is read into an accumulator A inside the CPU 208,
In step S4, it is determined whether the black peak value is larger than a predetermined threshold value, for example, “32”. If the result of the determination is large, it is determined that the optical system shown in FIG. 1 is located at the home position. And
In step S5, a flag CW is set so that the optical system advances in the direction opposite to the home position in the rotation direction of the pulse motor.

On the other hand, if it is determined in step S4 that it is not larger than 32, it is determined that the optical system is not located at the home position, and in step S6, the optical system advances the rotation direction of the pulse motor toward the home position. The flag CCW as shown.

Thereafter, the flag PMENB is set in step S7, and the process waits until the flag PMENB is reset in step S8. When the flag PMENB is reset, it is determined that the optical system has reached the edge of the marker, and the step
Proceed to S9. In step S9, it is determined whether or not the flag CCW is set.If the determination result indicates that the flag is set, the optical system reaches the edge portion of the marker while traveling in the home position direction and is located at the home position. And the process proceeds to step S10. On the other hand, if it is not set, it is the edge when leaving the home position, and the process returns to step S6.

Then, in step S10, the shading unit 2
The shading data from 05 is read, the data is stored in the RAM 208 in the CPU 208, and in step S11, the data read in step S10 is sequentially read from the first pixel, and within a predetermined range indicated by S in FIG. It is checked whether there is a transition point from black level to white level. As a result of the examination, if the change point is not found, it is regarded as an error and the process proceeds to step S12, where the error processing, that is, the reading operation is interrupted and the processing is skipped.

On the other hand, if a change point is found as a result of the check in step S11, the process proceeds to step S13. At this point, the image reading start position in the main scanning direction can be determined.

Next, in step S14, the rotation direction of the pulse
In step S15, the number of pulses corresponding to the image reading reference position in the sub-scanning direction from the home position, for example, “40” is set in the register ECNT. Next, in step S16, the pulse motor is started.

When the pulse motor moves by 40 pulses and the flag PMEND is set by the interruption of the internal interruption signal ENDINT, it is determined in step S17 that the optical system has reached the image reading reference position in the sub-scanning direction. S1
At 8, transfer of image data to the external device 250 through the interface circuit 209 is started.

If it is determined in step S19 that the predetermined number of data has been transferred, the pulse motor is stopped in step S20, the fluorescent lamp FL is turned off in step S21, and the rotation direction of the pulse motor is changed to CCW in step S22. And the flag PMENB is set in step S23. Thereafter, if it is determined in step S24 that the flag PMENB has been reset, it is determined that the optical system has reached the home position, and the reading sequence is terminated.

FIG. 6 is a flowchart showing an interrupt operation procedure by the main scanning synchronization signal HSYNC.

If it is determined in step S30 that the flag PMENB has been set, the process proceeds to step S31 to detect the home position. If the flag PMENB has not been set, the interrupt process ends.

Then, in step S31, the above-mentioned black peak value is read into accumulator A, and in step S32, it is determined whether flag CW or flag CCW is set. If the result of the determination is that the flag CW has been set, the flow proceeds to step S33, and in step S33, it is determined whether the black peak value is smaller than “32”. If the result of the determination is not small, the process proceeds to step S35, and in step S35, the number of pulses for one line, that is, "4"
Is set in the flag ECNT, the pulse motor is started in step S306, and the interrupt processing is terminated. On the other hand,
As a result of the determination in step S33, the black peak value A is "32"
If smaller than this, it is determined that the edge has been reached, and the process proceeds to step S37. In step S37, the flag PMENB is reset and the interrupt process is terminated.

On the other hand, if the result of the determination in step S32 is that the flag CCW has been set, the flow proceeds to step S34,
At 34, it is determined whether the black peak value A is greater than "32". If it is not greater than 32,
Proceed to step S35, and if larger than "32", proceed to step S37.

In step S12 shown in FIG. 5, when the light source has reached a certain light amount and no change point is found,
Since it is considered that the light distribution of the light source is significantly reduced, a lamp error prompting replacement of the light source may be notified.

Further, in the present embodiment, an example in which the home position is detected each time scanning is performed has been described. However, since the pulse motor is used to drive the optical system, the home position detection position when the power is turned on can be determined. Then, since the position can be managed by the number of pulses thereafter, the detection of the home position may be changed to be performed only when the power is turned on.

Furthermore, an example has been described in which the read start position in the main scanning direction is also detected each time a read scan is performed.
If the read start address is stored in the memory, it is not necessary to detect the read start address every time scanning is performed. Therefore, the read start position may be detected only when the power is turned on.

〔The invention's effect〕

As described above, according to the present invention, as described above, reading can be started from an accurate reading start position of the reading unit in the main scanning direction and the sub-scanning direction.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the structure of one embodiment of the present invention, FIG. 2 is a block diagram showing the structure of one embodiment, and FIG. 3 shows a marker provided on the back surface of the platen glass 17 in FIG. FIG. 4 is a timing chart for explaining interrupt processing of the CPU 208 shown in FIG. 2, FIG. 5 is a flowchart showing a control procedure by the CPU 208, and FIG. 6 is an interrupt operation procedure by the main scanning synchronization signal HSYNC. It is a flowchart shown. 1 Document reader, 11 Control unit, 12 CCD, 17 Platen glass, 208 CPU, 209 Timing generation circuit, 210 Peak value detection circuit, P Marker.

Claims (1)

(57) [Claims] A reading unit that reads light from a document and outputs an image signal; a shading correction unit that performs shading correction on the image signal; a reference density member used for the shading correction; A detecting means for detecting a change point of an image signal level obtained by reading the marker by the reading means in a main scanning direction and a sub-scanning direction of the reading means; and Determining means for determining a reading start position in the main scanning direction and the sub-scanning direction of the reading means based on a change point; and the reading means in the main scanning direction and the sub-scanning direction from the reading start position determined by the determining means. An image reading apparatus, comprising: control means for controlling to start reading.