JPH11275310A - Picture reader, picture reading method and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constantly and stably reproduce high gradation and to attain reproducibility even if the output level of an image sensor fluctuates owing to changes in service environment and to secular deteriorations. SOLUTION: A control part is constituted so that a reference white base is read for respective light sources 3, 4 and 5 before read operation of an original, it is checked whether or not the maximum value of picture data outputted from an A/D converter 16 at that time is within a prescribed range, and the light quantity of a light source, if out of the prescribed range, is adjusted again. Thus, the maximum value of A/D conversion output is always within the prescribed range by correcting the level whenever the original is read or at any time, and the picture of high gradation and reproducibility can stably be read.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image reading apparatus, an image reading method, and a recording medium, and more particularly to R, G, B (red, green,
The present invention relates to a lighting control technique for each light source in a facsimile apparatus having an image reading unit that has a light source of three colors (blue) and switches the emission color of the light source to enable color reading.

[0002]

2. Description of the Related Art Conventionally, in an image reading section such as a facsimile apparatus, an output of an image sensor represented by a CCD or the like is converted into digital data by an A / D converter, transferred to an image processing section, and appropriately processed. The image is read by this. Here, there has been proposed an image reading unit configured to perform color reading by switching between three color light sources of R, G, and B to emit light.

In such a color reading unit, there is a difference in the light amounts of the three color light sources, and there is a variation in the individual sensitivities of the image sensors. , A difference occurs in the image signal level output from the image sensor even for the same lighting time. In this case, the voltage output of the image sensor may exceed the range in which the A / D converter can convert.

Therefore, in order to effectively use the dynamic range of the A / D converter, one of the image sensors is set so that the maximum value of the output of the image sensor when reading the reference white background is within a predetermined range. A device for controlling the lighting time of each light source during the accumulation period has been devised.

[0005]

However, in the above-mentioned conventional example, the lighting time of each light source is determined in the production process of the image reading unit, or is determined by operation of a service person such as a maker or a store. You. Then, once set, the reading operation is always performed during the lighting time.

However, the light amount of the light source and the sensitivity of the image sensor have temperature characteristics, and when the reading operation is performed in an environment that is significantly different from the setting of the lighting time, the output level of the image sensor is reduced. There is a difference. If the output level shifts to the lower side, the dynamic range of the A / D converter cannot be used effectively, and the gradation characteristics will be reduced. On the other hand, if the output level shifts to the higher one, the A / D converter overflows, and there is a problem that the image flies white.

Also, when the light source is deteriorated and the amount of light is reduced, similarly, there is a problem that the output level of the image sensor is reduced and the gradation is deteriorated.

The present invention has been made to solve such a problem. Even if the output level of the image sensor fluctuates due to a change in the use environment of the apparatus or deterioration over time, the present invention has been made.
It is a first object of the present invention to provide an image reading unit which can always realize high gradation and reproducibility stably. It is a second object of the present invention to provide an image reading unit that can always realize high gradation and reproducibility stably even when reading in a color mode. A third object of the present invention is to make it possible to adjust the light amount of each light source by a simple method. It is a fourth object of the present invention to adjust the light amount of each light source while averaging the density of each reading line. A fifth object of the present invention is to provide an image reading unit which can always realize high gradation and reproducibility stably even when reading in a monochrome mode. A sixth object of the present invention is to cope with a case where a sufficient output of the image sensor cannot be obtained within the adjustment range of the light amount due to deterioration or abnormality of the light source or the image sensor. A seventh object of the present invention is to realize a smooth reading operation without taking extra time for the inspection of the light quantity. Further, an eighth object of the present invention is to avoid erroneous light amount adjustment.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides, for example, reading a reference white background before starting reading of an original at each original reading operation, and performing A / D conversion at that time. Check whether the maximum value of the subsequent image data is within a predetermined range.If the maximum value is within the predetermined range, the light source emits light with the same amount of light to read the original, and if it is out of the predetermined range, The configuration is such that the light amount is set again. With this configuration, even if the output of the image sensor fluctuates due to a change in the use environment of the apparatus or a change over time, it can be corrected as needed for each reading operation.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration example of a reading control unit of a facsimile apparatus implementing an image reading apparatus according to the present invention.

In FIG. 1, reference numeral 1 denotes a control unit for controlling the entire facsimile apparatus, which controls the entire facsimile apparatus according to a program written in a ROM (not shown). 2 is an oscillator for generating a reference clock for operating the control unit 1, 3 is a red (R) LED, 4 is a green (G) LED, 5 is a blue (B) LED, and 6, 7, and 8 are respectively Transistors for driving (lighting) the LEDs 3, 4, and 5 of each color, and 9, 10, and 11 are limiting resistors for the LEDs 3, 4, and 5 of each color.

Reference numeral 12 denotes a motor driver, 13 denotes a motor for conveying a document to be read, 14 denotes an image sensor represented by a CCD or the like, 15 denotes an amplifier, 16 denotes an A / D converter, 17 denotes a transfer clock for one pixel, 18 is a line synchronization signal determined by the accumulation time of the image sensor 14,
Reference numeral 19 denotes an image signal output from the image sensor 14, and reference numeral 20 denotes an image signal converted into digital data by the A / D converter 16.

First, the operation at the time of color reading and the method of determining the lighting time of the light source of each color will be described. here,
When the ports P0, P1 and P2 of the control unit 1 become high level, the transistors 6, 6 connected to the respective ports
Conduction between the collector and the emitter of 7, 8
Electric current flows through 4, 5 to light up.

Each LED 3 for color reading
FIG. 2 shows the timings of turning on the lights 4 and 5. When performing color reading, it is necessary to obtain image signals 19 of R, G, and B components for one reading line. Therefore, the control unit 1 controls the line synchronization (SH) signal 1
8 are switched (each port P0, P1, P2 is sequentially set to a high level in synchronization with the SH signal 18) at each output timing of the LED 8.
An image signal 19 when the lights 4 and 5 are turned on is obtained.

When the lighting of three colors is completed for one line (when reading of the original in three colors is completed), the control unit 1
A trigger is issued to the motor driver 12 to advance the document by one scanning line density. By repeating this, one page of color original is read.

The image signal 19 output from the image sensor 14 is amplified by the amplifier 15 and then converted into a digital signal by the A / D converter 16 by sampling and holding at the timing of the transfer clock 17. In the present embodiment, since an 8-bit A / D converter is used, one pixel becomes 8-bit digital data. Also, since it is 8 bits, 256 levels of gradation expression can be performed.

The image data 20 converted to a digital signal and input to the control unit 1 is subjected to shading correction,
Image processing such as γ conversion is performed, and data processing according to the purpose is performed. At this time, if the level of the image signal input to the A / D converter 16 is too high, the A / D converter 16
Overflows and correct data cannot be obtained. Conversely, if the image signal is too small, the dynamic range of the A / D converter 16 will not be used effectively, and the gradation will be reduced.

The output from the image sensor 14 is L
It is determined by the light intensity of the ED light source and the sensitivity of the sensor, and varies depending on each device. Therefore, in order to absorb the variation and obtain a constant output with respect to a certain standard, it is necessary to appropriately adjust the light amount of the LED light source. Therefore, in the present embodiment, the light amount is adjusted by controlling the lighting time of each of the R, G, and B light sources.

A method of setting the lighting time of each of the R, G, and B light sources will be described below. FIG. 3 shows a platen and a light source (LED3,
4, 5) and the relationship between the image sensor 14 and the image sensor 14. In FIG. 3, reference numeral 31 denotes a document table through which a document to be read passes, and 32 denotes a reference white background.

When determining the lighting time of each light source, first, the range of the maximum value of the output of the A / D converter 16 when the reference white background 32 is read is determined in advance. deep. This range is determined by an experiment or the like so that the A / D converter 16 does not overflow when any original is read and the gradation of the image is not impaired.

Next, taking the RLED 3 as an example, in a state where there is no document, the port P0 is set to the high level at the timing when the control unit 1 issues the SH signal 18, and the lighting of the RLED 3 is started. R for an appropriate time in the cycle
The LED 3 is turned on. That is, the output (image signal) of the image sensor 14 when red light is applied to the reference white background 32.
To get

The A / D converted image data 20
If the maximum value of the data exceeds the predetermined range, the lighting time is reduced and the reference white background 32 is read again. This is repeated until the maximum value of the data after A / D conversion falls within a predetermined range. Conversely, if the maximum value of the data after the A / D conversion is below the predetermined range, the lighting time is increased and the reference white background 32 is re-established.
Is repeated until the data after A / D conversion falls within a predetermined range.

By such an operation, a lighting time is determined such that the maximum value of the output of the A / D converter 16 when the reference white background 32 is read falls within the above-mentioned predetermined range. In the example of FIG. 2, the lighting time of the RLED ₃ is indicated by TR.

The lighting time is obtained by appropriately dividing the reference clock 17 generated by the oscillator 2 of the control unit 1 (hereinafter referred to as a lighting clock) by a counter (not shown) included in the control unit 1. Calculate by counting. Then, a count value such that the maximum value of the output of the A / D converter 16 falls within the above-mentioned predetermined range when the reference white background 32 is read is stored in a RAM (not shown).
Further, the read data of the reference white background 32 at this time is stored in the RAM as red shading correction data.

When actually reading a document under red light emission, the port P0 is set to a high level simultaneously with the issuance of the SH signal 18 from the control unit 1, and the lighting clock is counted by the counter. When the count value matches the count value stored in the RAM, the port P0 is returned to the low level.

The seek GLED4 and lighting time by performing the same operation for BLED5 (each in the example of FIG. 2 indicated by T _G and T _B), and stored in RAM. At the same time, the read data of the reference white background 32 at this time is stored in the RAM as green and blue shading correction data.

When actually reading a document under green or blue light emission, the port P1 or P2 is set to a high level upon issuing of the SH signal 18 from the control unit 1, and
The lighting clock is counted by the counter. When the count value matches the green or blue count value stored in the RAM, the port P1 or P2 is returned to a low level.

FIG. 4 is a flowchart showing an example of a process for determining the lighting time of each of the LEDs 3, 4, and 5. The method of determining the lighting time will be described again with reference to FIG. First, in step S101, the maximum value of the count value of the lighting clock that can be set is set in the RAM. After setting the maximum value, the SH signal 18 is set in step S102.
Is issued, and the process proceeds to step S103 at the issuance timing of the SH signal 18 to turn on the LED.

In the next step S104, the counter of the lighting clock is monitored, and when the count value becomes equal to the count value set in the RAM, the process proceeds to step S105 to turn off the LED. Further, in step S106, the next SH signal 18
Is issued, and if issued, step S107
Proceed to. In step S107, the above step S103
A to S105 output from the image sensor 14
The image data converted into digital data by the D converter 16 and sequentially output is read.

Then, in step S108, the read image data is stored in a predetermined area of the RAM. In the next step S109, the RAM in the above step S108
It is determined whether or not the maximum value of the image data stored in the RAM falls within a predetermined range. If the maximum value does not fall within the predetermined range, the flow advances to step S111 to decrement the count value set in the RAM by one. And set it in RAM,
The process returns to step S102.

On the other hand, if it is determined in step S109 that the maximum value of the image data is within the predetermined range, it is determined that the count value at that time is an optimum value, and in step S110, the count value is stored in the RAM. Hereafter, it is assumed that the LED lighting time during color reading. Finally, step S
The image data stored in the RAM at 108 becomes shading correction data at the light source. The above process is common to the R, G, and B light sources.

Next, the operation when reading a document will be described. When a document is set on the reading document table 31 shown in FIG. 3 and a reading operation is performed, the reference white background 32 is read for each of the R, G, and B light sources before the document is conveyed to the reading position. A / D at that time
It is checked whether the maximum value of the converted image data is within a predetermined range.

If the maximum value of the image data when the reference white background 32 is read is within a predetermined range for each light source, the image data is stored again in the RAM as shading correction data (the previous time). Update shading correction data at the time of reading). Thereafter, the reading motor 13 is driven to convey the document to the reading position,
The image is read with the lighting time set in advance.

On the other hand, if the maximum value of the image data when the reference white background 32 is read out of the predetermined range with any one of the light sources, the appropriate lighting time is again determined for the deviated light source by the above-described method. Ask for. When the lighting time is determined, the lighting time and the reference white background 3 at that time are determined.
2 as the shading correction data R
Store in AM. For a light source in which the maximum value of the image data when the reference white background 32 is read falls within a predetermined range, only the shading correction data is updated. Thereafter, the reading motor 13 is driven to convey the document to the reading position, and reading of an image is started according to the newly set lighting time.

If the maximum value of the image data when the reference white background 32 is read does not fall within the predetermined range even if the adjustment is made within the settable range of the lighting time of the light source, the failure of the image sensor 14 Then, the user is notified using a display unit or a recording unit (not shown) of the apparatus, or a display unit of the personal computer when the apparatus is a peripheral device of the personal computer.

If the original has already arrived at the reading position when the reading start operation is performed, if the above-described lighting time correction operation is performed, the original is read instead of the reference white background 32. Since the correction operation is performed, it is needless to say that a correct lighting time cannot be obtained. In order to avoid this, if the original has already arrived at the reading position when the reading start operation is performed, the above lighting time correction operation is not performed, and the lighting time data already stored in the RAM is not used. The original is read using the shading correction data.

FIGS. 5 and 6 show flowcharts of the above-described document reading operation. Hereinafter, the operation at the time of starting document reading will be described again with reference to FIGS. First, in step S201 of FIG.
It is monitored whether or not an original is set on the original platen 31 by the operator and an operation of starting reading is performed. When the reading start operation is performed, step S20 is performed.
The process proceeds to step 2 to check whether the original has already come to the reading position.

If the document has not already arrived at the reading position, the process proceeds to step S203, where the RLED 3 is turned on for the time stored in the RAM to read the reference white background 32. Then, in step S204, the image data obtained at that time is stored in a predetermined area of the RAM as shading correction data for reading red. Next, in step S205, the image data stored in the RAM in step S204 is checked to determine whether the maximum value is within a predetermined range.

Here, if the maximum value of the image data does not fall within the predetermined range, the process proceeds to step S206, and FIG.
The lighting time of the RLED 3 is reset by the method shown in the flowchart of FIG. Then, in step S207, the RLED
If it is determined that the resetting of the lighting time of the LED 3 has been completed, the process proceeds to step S208, and the GLE is performed similarly to the case of the RLED3.
At D4, the reference white background 32 is read. If it is determined in step S205 that the maximum value of the image data is within the predetermined range, the process proceeds to step S208 without resetting the lighting time, and the GLED 4 reads the reference white background 32.

Thereafter, as in the case of the RLED 3, in step S209, the image data obtained when the reference white background 32 is read by the GLED 4 is stored in a predetermined area of the RAM as shading correction data for reading the green color. Next, in step S210, the above step S209
To check the image data stored in the RAM, and check whether the maximum value is within a predetermined range.

Here, if the maximum value of the image data does not fall within the predetermined range, the process proceeds to step S211 and FIG.
The lighting time of the GLED 4 is reset by the method shown in the flowchart of FIG. Then, in step S212, the GLED
If it is determined that the reset of the lighting time of No. 4 has been completed, the process proceeds to step S213, and the BLED 5 reads the reference white background 32. If it is determined in step S210 that the maximum value of the image data is within the predetermined range, the process proceeds to step S213 without resetting the lighting time.
The BLED 5 reads the reference white background 32.

In step S214, the image data obtained when the reference white background 32 is read in step S213 is stored in a predetermined area of the RAM as shading correction data for reading blue. Next, in step S215 in FIG. 6, the image data stored in the RAM in step S214 is checked to determine whether the maximum value is within a predetermined range.

Here, if the maximum value of the image data does not fall within the predetermined range, the process proceeds to step S216, and FIG.
The lighting time of the BLED 5 is reset by the method shown in the flowchart of FIG. Then, in step S217, the BLED
If it is determined that the resetting of the lighting time of No. 5 has been completed, or if it is determined in step S215 that the maximum value of the image data is within a predetermined range, preparation for reading the document has been completed. Then, the reading motor 13 is driven to convey the document to the reading position. Further, the process proceeds to step S219 to start reading the document.

If the original has already arrived at the reading position in step S202 in FIG. 5, the lighting time inspection and resetting and the updating of the shading correction data as described above are not performed. Step S21
Jumping to step 9 starts reading the document immediately.

Further, in steps S207 and S212 in FIG. 5 and in step S217 in FIG. 6, even if the adjustment is made within the variable range of the lighting time of each light source, the image data obtained when the reference white background 32 is read is obtained. If the maximum value does not fall within the predetermined range, it is considered that there is an abnormality in each of the LED light sources 3, 4, 5 and the image sensor 14, so the process proceeds to step S220 and an error is displayed on the display unit of the apparatus. .

Next, a reading operation in a monochrome mode such as when facsimile transmission is described. R, G,
When reading is performed in the monochrome mode in the reading system having the three color light sources B, in this embodiment, as shown in FIG. 7, the lighting time of each light source in the color mode obtained by the above-described method is reduced by 1 /. The light source for each color of R, G, and B is sequentially switched on within one accumulation period of the image sensor 14 (for one cycle of the SH signal 18).

In this case, similarly to the reading in the color mode, the reference white background 32 is read by the lighting method in the monochrome mode before the reading of the original is started.
It is checked whether or not the maximum value of the image data after the / D conversion is within a predetermined range. If the maximum value of the image data is within the predetermined range, the image data is stored in the RAM as shading correction data again (the shading correction data at the previous reading is updated). Thereafter, the document is transported to the reading position, and reading of an image is started with the lighting time set in advance.

On the other hand, when the maximum value of the image data is out of the predetermined range, an appropriate lighting time is calculated again for each of the R, G, and B light sources. This operation is the same as the method for determining the lighting time of each light source in the color mode. Then, the lighting time of each light source obtained here is reduced to 1/3, the reference white background 32 is read again in the monochrome mode, and the shading correction data is updated with the image data. Thereafter, the document is transported to the reading position, and reading of an image is started with a new lighting time.

In the monochrome mode, as in the color mode, even if the lighting time of the light source is adjusted within the settable range, the maximum value of the image data when the reference white background 32 is read is within the predetermined range. If not, it is determined that the image sensor 14 is faulty or the like, and the user uses the display unit or recording unit (not shown) of the apparatus or the display unit of the personal computer when the apparatus is a peripheral device of the personal computer. To that effect.

If the original has already arrived at the reading position when the reading start operation is performed, the lighting time correction operation as described above is not performed, and the R
The original is read using the lighting time data and the shading correction data stored in the AM.

FIG. 8 is a flowchart showing the operation of reading an original in the monochrome mode described above.
Hereinafter, the operation at the time of starting document reading will be described again with reference to FIG. First, in step S301, it is monitored whether an original is set on the reading original platen 31 by an operator and an operation of starting reading is performed. When the reading start operation is performed, the process advances to step S302 to check whether or not the document has already come to the reading position.

If the document has not already arrived at the reading position, the flow advances to step S303, and the LEDs 3, 4, and 5 are sequentially turned on by １ ／ of the time stored in the RAM by the lighting method in the monochrome mode shown in FIG. Then, the reference white background 32 is read. In step S304, the image data obtained at that time is stored in a predetermined area of the RAM as shading correction data at the time of reading in the monochrome mode. Next, in step S305, the image data stored in the RAM in step S304 is checked to determine whether the maximum value is within a predetermined range.

Here, if the maximum value of the image data does not fall within the predetermined range, the process proceeds to step S306, and FIG.
R, G, B LEDs by the method shown in the flowchart of
The lighting times of 3, 4, and 5 are reset. If it is determined in step S307 that the reset of the lighting time has been completed, the process proceeds to step S308, where the reference white background 32 is read again by the monochrome mode lighting method. Step S
In step 309, the read image data is stored in a predetermined area of the RAM as shading correction data for monochrome reading.

Next, in step S310, the reading motor 13 is driven to convey the document to the reading position. If it is determined in step S305 that the maximum value of the image data is within the predetermined range, each LE
The process jumps to step S310 without resetting the lighting times of D3, D4, D5, and conveys the document to the reading position. Then, the process proceeds to step S311 to start reading the document.

If the document has already arrived at the reading position in step S302, the inspection and resetting of the lighting time and the updating of the shading correction data are not performed, and the process jumps to step S311 to read the document. Start immediately. Also, the above step S307
When the maximum value of the image data when the reference white background 32 is read does not fall within the predetermined range even when the adjustment is performed within the variable range of the lighting time of each light source,
Since there is a possibility of an abnormality of the image sensor 4 or 5 or an abnormality of the image sensor 14, the process advances to step S312 to display an error on a display unit or the like of the apparatus.

With the above-described configuration, even if the output of the image sensor 14 fluctuates due to a change in the use environment of the apparatus or a change over time, it is possible to make a correction every time a document is read, and to maintain a stable state. Thus, high gradation and reproducibility can be realized. In addition, each LED light source 3,
Since the light amounts of the light sources 4 and 5 are adjusted by controlling the lighting time, the adjustment of the light amount of each light source can be realized by a simple method.

In the present embodiment, even when reading in the monochrome mode, the output level of the image sensor is corrected at any time in accordance with the lighting method of the monochrome mode. A reading unit having high gradation and reproducibility can be realized. Further, if the lighting time cannot be corrected within the variable range of the lighting time due to deterioration or abnormality of the light source or the image sensor, a message to that effect is displayed to notify the user of the abnormality of the light source or the image sensor. Can be notified.

In the process of updating the shading correction data, the inspection of the light quantity, that is, the inspection of the output level of the image sensor is performed, and the inspection of the lighting time is also used as the process of updating the shading correction data. Therefore, if it is not necessary to reset the lighting time, it is possible to realize a smooth reading operation without giving the user a sense of incongruity without extra time for the inspection of the amount of light until the start of reading the document. it can.

Further, if the original is already at the reading position when the reading of the original is started, the correction of the lighting time can be avoided by not correcting the lighting time.

In the above-described embodiment, the light amount is adjusted by controlling the lighting time of the light source. However, the brightness of the light source itself is adjusted by varying the value of the current flowing through the light source. You may. With such a configuration, the light source is always lit during one accumulation period of the image sensor 14, so that the density of one reading line can be averaged.

In the above-described embodiment, the lighting time is corrected at the time of starting the reading of the document (immediately before the reading of the document is started). The lighting time may be corrected at regular intervals, or the lighting time may be corrected at a predetermined time. With this configuration, even if the output of the image sensor 14 fluctuates, the correction of the light amount is completed at the time of reading the original, so that the original can be read smoothly.

Although the present invention has been described with respect to the reading unit capable of reading in color, the same effect can be obtained by the same control in the reading unit which performs only monochrome reading using a single color light source.

(Other Embodiments of the Present Invention) The present invention can be applied to a system constituted by a plurality of devices (for example, a host computer, an interface device, a reader, a printer, a scanner, a facsimile device, etc.), and one device can be used. (For example, a copier, a scanner, and a facsimile machine).

The present invention also provides the apparatus connected to the various devices or the computer in the system to operate the various devices so as to realize the functions of the above-described embodiments. A program code of software for realizing the system is supplied, and a computer (CPU or MP) of the system or apparatus is supplied.
The invention implemented by operating the various devices according to the program stored in U) is also included in the scope of the present invention.

In this case, the program code of the software implements the functions of the above-described embodiment, and the program code itself and means for supplying the program code to the computer are provided.
For example, a storage medium storing such a program code constitutes the present invention. As a storage medium for storing such a program code, for example, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM,
A magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

When the computer executes the supplied program code, not only the functions of the above-described embodiment are realized, but also the OS (Operating System) or other operating system running on the computer. Needless to say, even when the functions of the above-described embodiments are realized in cooperation with application software or the like, such program codes are included in the embodiments of the present invention.

Further, after the supplied program code is stored in a memory provided in a function expansion board of the computer or a function expansion unit connected to the computer, the function expansion board or the function expansion unit is specified based on the instruction of the program code. It is needless to say that the present invention also includes a case where the CPU or the like provided in the first embodiment performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

[0068]

As described above in detail, according to the first aspect of the present invention, the reference white background is set before the start of the original reading operation when the original reading operation is performed or at a predetermined timing. The reading is performed, and it is checked whether the maximum value of the image data after the A / D conversion is within a predetermined range. If the maximum value is within the predetermined range, the original is read with the same light amount, If the value is out of the range, the light amount of the light source is adjusted again, so even if the output level of the image sensor fluctuates due to changes in the use environment of the device or aging deterioration, it is corrected as needed every time the document is read. Thus, an image having high gradation and reproducibility can always be read stably.

According to the second aspect of the present invention, in the configuration in which color image data is obtained by performing multiple readings with the image sensor while changing the emission color of the light source, the above-described inspection and resetting of the light amount Since it was done for each light source,
Even when reading in the color mode, it is possible to always read stably with high gradation and reproducibility.

According to the third aspect of the present invention, the light amount of the light source is adjusted by controlling the lighting time of the light source, so that the light amount can be adjusted with a simple configuration.

According to the fourth aspect of the present invention, the light amount of the light source is adjusted by controlling the value of the current supplied to the light source. Therefore, the light amount of each light source can be adjusted while averaging the density of each reading line. It can be carried out.

According to the fifth aspect, when reading in the monochrome mode, the reference white background is read by the lighting method in the monochrome mode, and the light amount of each light source is corrected based on the result to correct the output level of the image sensor. Since resetting is performed, reading with high gradation and reproducibility can be always performed stably even when reading in the monochrome mode.

According to the sixth aspect of the present invention, even when the light amount of the light source is set again, the maximum value of the output of the A / D converter when reading the reference white background falls within the predetermined range. If not, the user is notified that the reading unit is abnormal, so if the output of the image sensor cannot be obtained sufficiently within the adjustment range of the light amount, the display unit or the recording unit of the device or the present device may be used. When a peripheral device of a personal computer is used, the user can be notified of an abnormality in the reading unit by using a display unit or the like of the personal computer.

According to the seventh aspect, the inspection and resetting of the light amount of the light source and the updating of the shading correction data are performed at the same time, so that extra time is required for the inspection of the light amount. And a smooth reading operation can be realized.

According to the eighth aspect, if the original is already at the reading position at the start of the original reading operation, the light amount is not reset, so that the original which is not the reference white background is read and the light amount is reset. This makes it possible to prevent the inconvenience of performing the adjustment, and to avoid erroneous correction of the light amount.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of a reading control unit of a facsimile apparatus implementing an image reading apparatus according to the present invention.

FIG. 2 shows each L when reading an original in the color mode.
5 is a timing chart showing the lighting timing of the ED light source.

FIG. 3 is a diagram simply illustrating a relationship between a document table, a light source, and an image sensor.

FIG. 4 is a flowchart illustrating an example of a process for determining a lighting time of each LED light source.

FIG. 5 is a flowchart showing a lighting time correction operation at the start of reading of a document in a color mode.

FIG. 6 is a flowchart showing a lighting time correction operation at the start of reading a document in a color mode.

FIG. 7 is a timing chart showing the lighting timing of each LED light source when reading a document in the monochrome mode.

FIG. 8 is a flowchart showing a lighting time correction operation at the start of reading of a document in a monochrome mode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Control part 2 Oscillator 3 Red (R) LED 4 Green (G) LED 5 Blue (B) LED 6,7,8 Switching transistor 9,10,11 Limiting resistance of each LED 12 Motor driver 13 Motor 14 Image sensor Reference Signs List 15 amplifier 16 A / D converter 17 1-pixel transfer clock 18 line synchronization signal 19 image signal 20 image signal converted into digital data 31 platen 32 reference white background

Claims (18)

[Claims] 1. An image reading apparatus capable of obtaining image data by reading a document with an image sensor by emitting light from a light source, wherein an output of the image sensor when a reference white background is read is represented by A And a light amount control unit for controlling the light amount of the light source so that the maximum value of the data converted into a digital signal by the / D converter falls within a predetermined range. At the set timing, the reference white background is read, and if the maximum value of the output of the A / D converter at that time is out of a predetermined range, the light amount of the light source is set again. An image reading apparatus, comprising: 2. An image sensor according to claim 1, wherein said image sensor reads the image a plurality of times while changing the emission color of said light source, and obtains color image data. When a white background is read, and the maximum value of the output of the A / D converter at that time is out of a predetermined range,
2. The image reading apparatus according to claim 1, wherein the light amount is reset for the deviated light source. 3. The image reading apparatus according to claim 1, wherein the light amount control unit controls the light amount by controlling a lighting time of the light source. 4. The image reading apparatus according to claim 1, wherein the light amount control unit controls the light amount by controlling a current value flowing through the light source. 5. Within one accumulation period of the image sensor,
An image reading apparatus in which monochrome mode reading is performed by sequentially switching and lighting each light source for a time shorter than the lighting time in the color mode at the same ratio as the lighting time of each light source in the color mode. The light amount control means, when reading in the monochrome mode, reads the reference white background according to the lighting method in the monochrome mode before starting the reading operation of the document or at a predetermined timing. 4. The image according to claim 3, wherein when the maximum value of the output of the A / D converter is out of a predetermined range, the setting of the lighting time is performed again for each light source. Reader. 6. The maximum value of the output of the A / D converter when the reference white background is read even if the light amount of the light source is reset by the light amount control means. The image reading apparatus according to claim 1, further comprising a notification unit configured to notify a user of an abnormality in the reading unit when the reading unit does not exist. 7. The image according to claim 1, wherein the inspection and resetting of the light amount of the light source by the light amount control unit and the updating of the shading correction data are performed simultaneously. Reader. 8. The method according to claim 1, wherein when the document reading operation is started, if the document is already at the reading position, the light amount control means does not reset the light amount. The image reading device according to claim 1. 9. An image reading method for obtaining color image data by performing a plurality of readings with an image sensor while changing a light emission color of a light source, wherein each of the plurality of readings is performed before starting a reading operation of a document or at a predetermined timing. A reference white background is read for each light source, and it is checked whether the maximum value of the A / D conversion output of the image sensor at that time falls within a predetermined range. An image reading method for resetting the light amount of the deviated light source so as to fall within the predetermined range. 10. The image reading method according to claim 9, wherein the control of the light amount of each light source is performed by controlling a lighting time of each light source. 11. The image reading method according to claim 9, wherein the control of the light amount of each light source is performed by controlling a current value flowing through each light source. 12. Within one accumulation period of the image sensor, each light source is sequentially switched and lit for a time shorter than the lit time in the color mode at the same ratio as the lit time of each light source in the color mode. An image reading method for reading in a monochrome mode, wherein when reading in the monochrome mode, before starting the document reading operation or at a predetermined timing, the image reading method according to the lighting method in the monochrome mode is used. A reference white background is read, and when the maximum value of the A / D conversion output at that time is out of a predetermined range, the lighting time is set again for each light source. The image reading method according to claim 10. 13. The A / D converter when the reference white background is read even if the light amount of each light source is reset.
13. The apparatus according to claim 9, wherein when a maximum value of the converted output does not fall within a predetermined range, the user is notified of the abnormality of the reading unit.
The image reading method according to the item. 14. The image reading method according to claim 9, wherein inspection and resetting of the light amount of each light source and updating of shading correction data are performed simultaneously. 15. At the start of the document reading operation,
15. The image reading method according to claim 9, wherein when the document is already at the reading position, the light amount of each light source is not reset. 16. An image reading apparatus capable of obtaining color image data by performing a plurality of readings with an image sensor while changing a light emitting color of a light source, wherein the reading operation is performed before a document reading operation is started or at a predetermined time. At the timing, a reference white background is read for each light source, and it is checked whether the maximum value of the A / D conversion output of the image sensor at that time falls within a predetermined range. A computer having recorded thereon a program for causing a computer to function as light amount control means for resetting the light amount of the out-of-light source so as to fall within the predetermined range when the light amount falls outside the predetermined range. A readable recording medium. 17. The computer-readable recording medium according to claim 16, wherein the control of the light amount by said light amount control means is performed by controlling a lighting time of each light source. 18. Within one accumulation period of the image sensor, each light source is sequentially switched and lit for a time shorter than the lit time in the color mode at the same ratio as the lit time of each light source in the color mode. In the image reading apparatus configured to perform reading in the monochrome mode, when performing the reading in the monochrome mode, before starting the reading operation of the original or at a predetermined timing, the reference white background is determined according to the lighting method in the monochrome mode. When the maximum value of the A / D conversion output at that time is out of the predetermined range, the light amount correcting means is operated so that the lighting time of each light source is set again. 18. The computer-readable recording medium according to claim 17, wherein said program is recorded.