JP2008252320A - Image reading device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to execute fine light-emitting control of a light source while suppressing processing load of a CPU in an image reading device. <P>SOLUTION: The image reading device makes a plurality of light sources whose emitting colors are different, irradiate the light to an original, and create image data of the original by carrying out photoelectric conversion of a reflection light of the lights by an image sensor. The image reading device is characterized to be provided with an indication means which indicates to discharge, stored charges obtained by the photoelectric conversion to the image sensor, a counter to count a number of times in which the indication is performed by the indication means, a memory which memorizes light emitting information which shows that the plurality of light sources emit light when the counter value reaches how many, and a control circuit which controls light emitting of the plurality of respective light sources. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image reading apparatus that photoelectrically converts reflected light from a document to generate image data.

  An image reading apparatus generally includes a plurality of color LEDs as a light source. Then, the light source is controlled to irradiate light on the document to be read, and the reflected light from the document is photoelectrically converted by a plurality of storage type line image sensors, thereby accumulating charges as an image signal. The accumulated charges are sequentially output to the A / D converter and converted into digital data, and image data of the original is generated.

  As a light source of the image reading device, for example, LEDs of three colors of red (Red), green (Green), and blue (Blue) are used. The image reading apparatus reads the document by sequentially switching the colors of the LEDs to emit light and irradiating the document. Details of the reading operation by the image reading apparatus will be described below.

  The image reading device first causes the Red LED to emit light for an appropriate period to read the Red image for one line in the main scanning direction, and then causes the Green LED to emit light to similarly emit the Green image for one line. Read. Finally, the Blue LED is turned on to read one line of Blue image. The image reading apparatus A / D converts the electric signal of the read image, and finally obtains image data for one line in the main scanning direction.

  As a method for controlling the light emission of each color LED in the reading operation by the image reading device (controlling lighting and extinguishing), a method of controlling based on a line synchronization signal for defining the charge accumulation time in the image sensor is known. ing.

For example, in Patent Document 1, when the main CPU provided in the image reading apparatus receives a line synchronization signal for accumulating charges, the main CPU enters an interrupt process. Within the interrupt processing routine, the main CPU performs selection of the LED color for reading starting from the next line synchronization signal, and register setting for light emission control of the selected LED, so that the light sources of multiple colors The light emission control is performed.
JP 11-298673 A

  In general, in order to obtain image data that satisfactorily reproduces an image of a document, it is important that the amount of light of each color LED is constant and an appropriate amount (light amount). Here, as an example, consider a case where the image reading apparatus reads an image of a document with high resolution to generate a large amount of image data, and transfers the image data to a host PC (personal computer) connected to the image reading apparatus. . In this case, in order to secure the transfer time of the image data to the host PC, the image reading apparatus generates image data for one line in the main scanning direction of the document by the above-described reading operation, and then reads the image for a certain period. It is necessary to interrupt and wait.

  FIG. 5 is a timing chart showing the relationship between the lighting period of each color LED and the line synchronization signal in the above-described reading operation. In the example of FIG. 5, the image reading apparatus turns on the LED of the next color (Red) after the period (periods 503 and 507) for reading an image using a blue LED. For this reason, the LED of a specific color (Red) is lit even during a period in which the image reading apparatus transfers image data to the host PC (periods 504 and 508), that is, a period in which image reading is not performed. LED lights up at the time of). In this case, since the LED of Red lights up for a longer time than other LEDs (Green and Blue LEDs), when the reading operation is repeated, there is a possibility that the deterioration proceeds faster than the other LEDs. As a result, the amount of light of the Red LED varies with characteristics different from those of other LEDs, and the amount of light of each color LED is not constant, and the image quality of the generated image data may deteriorate.

  In order to suppress the deterioration of the LED and the accompanying deterioration of the image quality, the image reading apparatus needs to perform fine light emission control such as turning off the LED during a period when the image is not read. Here, in Patent Document 1, the image reading apparatus performs the light emission control of the LED in the reading period starting from the next line synchronization signal when the main CPU accepts the interruption by the line synchronization signal.

  However, if the interrupt response time of the main CPU is long, there is a possibility that the register setting for LED light emission control in the next reading period may not be in time after the main CPU receives the interrupt signal. Even if the LED light emission control by the interrupt process is in time, the main CPU must perform register setting for the LED light emission control every time the interrupt is performed by the line synchronization signal, and the processing load is heavy. Accordingly, it is necessary to mount a CPU with high processing capability in the image reading apparatus, and various problems such as an increase in the price of the image reading apparatus, an increase in heat generation, or an increase in size may occur.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a technique capable of executing fine light emission control of a light source while suppressing a processing load of a CPU of an image reading apparatus.

  In order to solve the above problems, according to the present invention, a plurality of light sources having different emission colors are emitted to irradiate light on a document, and the reflected image of the light is photoelectrically converted by an image sensor, thereby image of the document. An image reading apparatus for generating data, the instruction means for instructing the image sensor to sweep out the accumulated charge obtained by photoelectric conversion, the counter for counting the number of times the instruction is performed by the instruction means, For each of the plurality of light sources, a memory for storing light emission information indicating when the counter value is emitted, and the light emission of each of the plurality of light sources is controlled based on the counter value and the light emission information. And an image reading apparatus including the control circuit.

  Other features of the present invention will become more apparent from the accompanying drawings and the following description of the best mode for carrying out the invention.

  With the above configuration, according to the present invention, it is possible to execute fine light emission control of the light source while suppressing the processing load on the CPU of the image reading apparatus.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. The individual embodiments described below will help to understand various concepts from the superordinate concept to the subordinate concept of the present invention.

  The technical scope of the present invention is determined by the claims, and is not limited by the following individual embodiments. In addition, all combinations of features described in the embodiments are not necessarily essential to the present invention.

[First Embodiment]
FIG. 1 is a block diagram illustrating a configuration example of an image reading apparatus 101 such as a scanner to which the present invention is applied. The image reading apparatus 101 includes a ROM 106, a light source current control unit 111, an A / D conversion unit 112, a motor 113, a RAM 114, a light source 115, an image sensor 116, and a system control unit 117.

  The system control unit 117 includes a CPU 103, a USB I / F 104, a ROM control unit 105, a reading control unit 107, a motor control unit 108, an image processing unit 109, and a RAM control unit 110.

  The CPU 103 controls the entire image reading apparatus 101 by reading and executing a control program stored in the ROM 106 via the ROM control unit 105. The RAM 114 is used as a work area for the CPU 103, and is also used as an area for temporarily storing image data generated by reading a document. Data is read from and written to the RAM 114 via the RAM control unit 110.

  The light source 115 includes a plurality of LEDs having different emission colors, specifically, three types of LEDs of red (red), green (green), and blue (blue) (that is, the light source 115 has different emission colors. Including multiple light sources). The light source 115 irradiates light on a document (not shown) to be read. The image sensor 116 is an accumulation type (charge accumulation type) image sensor, and photoelectrically converts light reflected from the original by the light source 115 and accumulates charges as image signals.

  A motor control unit 108 controls a motor 113 provided in the image reading apparatus 101. A reading control unit 107 controls an image reading operation from a document. The reading control unit 107 transmits a control signal for performing light emission control (lighting on / off control) of the light source 115 to the light source current control unit 111.

  Based on the control signal received from the reading control unit 107, the light source current control unit 111 supplies an appropriate amount of current to the LED to be lit included in the light source 115 to light (emit) the light.

  The reading control unit 107 also transmits a line synchronization signal to the image sensor 116 to instruct the image sensor 116 to sweep out (output) the accumulated charge obtained by photoelectric conversion. The image sensor 116 sequentially outputs accumulated charges as an image signal based on the line synchronization signal.

  The analog image signal output from the image sensor 116 is converted into digital data as image data by the A / D converter 112 and sequentially transmitted to the reading controller 107. The read control unit 107 stores the received image data in the RAM 114. Thereafter, the image processing unit 109 reads the image data from the RAM 114, performs image processing such as shading correction, and transfers the image data to the external device (host PC 102) via the USB I / F 104.

  FIG. 2 is a block diagram illustrating a detailed configuration of the reading control unit 107. The reading control unit 107 includes an input data processing unit 201, a timing generator 202, a light source control unit 203, a line synchronization signal generation unit 204, and registers 205 to 208.

  Based on the value set in the register 207, the light source control unit 203 transmits to the timing generator 202 an instruction signal that instructs to turn on or off each LED of each color included in the light source 115. Details of the light source control unit 203 and the register 207 will be described later with reference to FIG.

  The line synchronization signal generation unit 204 generates a line synchronization signal at a time interval indicated by the value set in the register 208 and supplies the line synchronization signal to the timing generator 202 and the light source control unit 203.

  The timing generator 202 generates timing for controlling the image sensor 116 and the light source current control unit 111. The timing generator 202 sends a control signal for performing light emission control of the light source 115 to the light source current control unit 111 based on the logical product of the value of the instruction signal received from the light source control unit 203 and the value set in the register 206. Send. In addition, the line synchronization signal supplied from the line synchronization signal generation unit 204 is output to the image sensor 116.

  The image sensor 116 accumulates charges as an image signal obtained by photoelectric conversion in synchronization with the line synchronization signal supplied from the timing generator 202, and outputs it to the A / D converter 112. The A / D conversion unit 112 converts the image signal received from the image sensor 116 into digital data as image data, and supplies the digital data to the input data processing unit 201.

  The input data processing unit 201 sequentially processes the image data based on the value set in the register 205 and stores it in the RAM 114 via the internal system bus 209. Here, in the register 205, for example, a value for instructing the input data processing unit 201 whether or not to convert the resolution is set.

  The CPU 103 writes appropriate values to the registers 205 to 208 via the internal system bus 209 according to the control program in the ROM 106.

  Next, details of the operation of the light source control unit 203 will be described with reference to FIGS. 3 and 4. FIG. 3 is a block diagram showing a detailed configuration of the light source control unit 203 and the register 207. FIG. 4 is a timing chart showing the relationship between the lighting period of each color LED and the line synchronization signal in the image reading operation according to the first embodiment.

  The light source control unit 203 includes selectors 301 to 303 and a line synchronization signal counter 307. The register 207 includes a red register 309, a green register 310, and a blue register 311.

  The line synchronization signal counter 307 counts the number of times the line synchronization signal is supplied from the line synchronization signal generation unit 204. The value of the line synchronization signal counter 307 is supplied to the selectors 301 to 303. The line synchronization signal counter 307 may be configured to be reset (for example, reset to 0) when the value of the counter reaches a predetermined value (for example, 4).

  The Red register 309 holds information indicating how many values of the line synchronization signal counter 307 the Red LED emits light. Similarly, the Green register 310 holds information indicating when the value of the line synchronization signal counter 307 emits light for the Green LED, and the Blue register 311 holds for the Blue LED. That is, the register 207 is a memory that stores light emission information indicating how many times the value of the line synchronization signal counter 307 emits light for each color LED.

  The format of the light emission information is arbitrary, but as an example, the light emission information is represented by information having a bit number of 4 bits. Each bit is associated with a different value of the line synchronization signal counter 307, respectively. For example, the value of the line synchronization signal counter 307, 0, 1, 2, 3 is associated with the upper bits one by one in order from the least significant bit of the light emission information. In this case, if the light emission information is “0b0001” (“0b” indicates that the following number is a binary number), it indicates that the LED emits light when the value of the line synchronization signal counter 307 is 0. Alternatively, the light emission information may be defined so that “0” indicates light emission and “1” indicates no light emission.

  When the value of the line synchronization signal counter 307 is not reset, the light emission information “0b0001” indicates that the LED emits light when the value obtained by dividing the value of the line synchronization signal counter 307 by 4 is zero. Light emission information may be defined in

  The selector 301 transmits to the timing generator 202 an instruction signal instructing to turn on or turn off the Red LED based on the value of the line synchronization signal counter 307 and the value of the Red register 309. Similarly, the selector 302 transmits an instruction signal for instructing to turn on or off the green LED to the timing generator 202 based on the value of the line synchronization signal counter 307 and the value of the green register 310. Further, the selector 303 transmits an instruction signal for instructing to turn on or off the blue LED to the timing generator 202 based on the value of the line synchronization signal counter 307 and the value of the blue register 311. That is, the selectors 301 to 303 function as a control circuit that controls the light emission of each of the plurality of light sources. In one embodiment, the selectors 301 to 303 select the bit associated with the value of the line synchronization signal counter 307 in the light emission information for the corresponding color light source. The selectors 301 to 303 generate an instruction signal so that the light source emits light when the selected bit is a predetermined value (for example, 1).

  Here, a section from a certain line synchronization signal to the next line synchronization signal is referred to as a sh (sample hold) section (see FIG. 4). The line synchronization signal generation unit 204 outputs an interrupt signal (referred to as “int_shdiv interrupt signal”) to the CPU 103 every time a predetermined number of line synchronization signals are generated based on the value set in the register 208. A section from the int_shdiv interrupt signal to the next int_shdiv interrupt signal is referred to as a shdiv section (see FIG. 4).

  In the present embodiment, the LED of the line synchronization signal counter 307 emits red LED in the sh section, the green LED in the sh section of “1”, and the blue LED in the sh section of “2”. In the sh section, all LEDs are turned off. In this case, the CPU 103 sets the Red register 309 to “0b0001”, the Green register 310 to “0b0010”, and the Blue register 311 to “0b0100” in advance. In the sh period where the value of the line synchronization signal counter 307 is “3”, the image reading apparatus 101 transfers image data to the host PC 102 instead of reading an image. The value of the line synchronization signal counter 307 is reset every time the line synchronization signal is counted four times.

  According to this configuration, as shown in the timing chart of FIG. 5, the light source control unit 203 repeats the same light emission control unless the value set in the register 207 is changed. In addition, since none of the LEDs is lit during the transfer of the image data, it is possible to suppress the usage frequency of a specific LED from being significantly different from the usage frequency of other LEDs. Furthermore, since it is not necessary to change the value set in the register 207 unless the setting of the section in which the LED emits light is changed, the processing load on the CPU 103 is reduced.

  As described above, according to the present embodiment, the reading control unit 107 of the image reading apparatus 101 includes the light source control unit 203 and the register 207. The light source control unit 203 includes selectors 301 to 303 and a line synchronization signal counter 307, and the register 207 includes a red register 309, a green register 310, and a blue register 311. The selectors 301 to 303 control the light emission of the LEDs of the respective colors of the light source 115 based on the value of the line synchronization signal counter 307 and the value of each register in the register 207.

  Thereby, it is possible to execute fine light emission control of the light source while suppressing the processing load on the CPU of the image reading apparatus. Furthermore, if the register 207 is set so that none of the LEDs emit light during the period when the image reading apparatus does not read an image, the occurrence of a situation where a specific LED emits light more frequently than other LEDs is suppressed. Is done.

<Modification>
In the above description, the image reading apparatus 101 transfers image data to the host PC 102 in each shdiv section. However, for example, when the storage capacity of the RAM 114 is large, or when the data size of image data obtained from a document is small, the image reading apparatus 101 collects a certain amount of image data after being stored in the RAM 114. You may transfer to host PC102. Thereby, the reading speed of the image by the image reading apparatus 101 is increased.

  In this case, for example, the line synchronization signal generation unit 204 generates an int_shdiv interrupt signal every time the line synchronization signal is generated three times. The line synchronization signal counter 307 is reset to 0 when the value reaches 3. The CPU 103 determines whether or not image transfer is necessary every time it receives an int_shdiv interrupt signal.

  If it is determined that image transfer is necessary, the CPU 103 instructs the line synchronization signal counter 307 to reset to 0 when the value reaches 4 in the next shdiv section. In addition, the line synchronization signal generation unit 204 is instructed to generate the int_shdiv interrupt signal after generating the line synchronization signal four times.

  The int_shidiv interrupt occurs every time a line synchronization signal is generated, not every time it is generated (every time). Therefore, even if the CPU determines whether or not processing is necessary every time the int_shdiv signal is received, an increase in the CPU interrupt processing load is suppressed.

It is a block diagram which shows the structural example of image reading apparatuses, such as a scanner, to which this invention is applied. It is a block diagram which shows the detailed structure of a reading control part. It is a block diagram which shows the detailed structure of the register which a light source control part and a light source control part use. 4 is a timing chart showing a relationship between a lighting period of each color LED and a line synchronization signal in the image reading operation according to the first embodiment. It is a timing chart which shows the relationship between the lighting period of LED of each color in the conventional image reading operation | movement, and a line synchronizing signal.

Claims (5)

An image reading apparatus that emits light from a plurality of light sources having different emission colors to irradiate light on a document and photoelectrically converts reflected light of the light by an image sensor, thereby generating image data of the document.
Instruction means for instructing the image sensor to sweep out the accumulated charge obtained by photoelectric conversion;
A counter that counts the number of times the instruction is performed by the instruction means;
For each of the plurality of light sources, a memory that stores light emission information indicating when the value of the counter emits light,
A control circuit for controlling the light emission of each of the plurality of light sources based on the value of the counter and the light emission information;
An image reading apparatus comprising: The counter is configured to be reset when a value of the counter reaches a predetermined first value;
The light emission information is information of a predetermined number of bits for each of the plurality of light sources, and each bit has information associated with a different value of the counter,
The image reading apparatus according to claim 1, wherein the control circuit causes each of the plurality of light sources to emit light according to a value of a bit associated with a value of the counter in the light emission information. The plurality of light sources includes light sources of three kinds of emission colors,
The counter is configured to be reset every time the instruction is performed four times.
The light emission information is information of at least 4 bits for each of the plurality of light sources, and each bit has information associated with a different value of the counter,
The control circuit includes a selector that selects a bit associated with a value of the counter in the light emission information for each of the plurality of light sources, and causes the light source to emit light according to the value of the selected bit. The image reading apparatus described in 1.   The image reading apparatus according to claim 3, wherein the light sources of the three kinds of emission colors are red, green, and blue light sources. Conversion means for converting an analog value representing the amount of accumulated charge into digital data by A / D conversion;
Transfer means for transferring the digital data to an external device while the value of the counter is a predetermined second value;
Setting means for setting the light emission information in the memory;
Further comprising
The setting means sets the light emission information so that none of the plurality of light sources emits light when the value of the counter is the second predetermined value. The image reading apparatus according to any one of the above.

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