JP2003143372A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extend the service life of an LED being a color light source for a contact image sensor and to prevent the LED from being destroyed. SOLUTION: The image reader includes an image read section 13 provided with a color light source section comprising the LED, an optical sensor 132 for detecting a reflected light in an original image of an original 200 receiving each color light emitted from the color light source section and an LED drive signal generating circuit 21 for generating an LED drive signal and an image read control means 18 for controlling the image read section. The image read section 13 is provided with a lighting duty comparator circuit 22 that compares a maximum lighting duty value of a drive signal of each color LED with an actual lighting duty value of the drive signal of each color LED, and a lighting duty abnormity notice circuit 23 that informs the image read control means 18 about the lighting duty abnormity of the LED when the lighting duty comparator circuit detects that the actual lighting duty value exceeds the lighting duty maximum value as to any of the color LEDs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus such as a color facsimile apparatus, a color image scanner, a color copying machine, a composite machine of these, which is equipped with an image reading sensor including a light emitting element such as an LED as a color light source. More specifically, the present invention relates to an image reading apparatus capable of preventing the life of the light emitting element from being shortened and preventing the light emitting element from being damaged by promptly turning off the power supply of the light emitting element when the lighting duty abnormality occurs in the light emitting element.

[0002]

2. Description of the Related Art Some image reading apparatuses such as color facsimile machines, color image scanners, color copying machines, and multifunctional machines of these machines use a contact image sensor as a reading device. In recent years, LEDs have been widely used as color light sources in contact image sensors. LE
In the type that uses D, red (R), green (G),
The LED of three colors of blue (B) is mounted, and the color of the original image is read by the line-sequential reading method. "Line-sequential reading method" means three colors of red (R), green (G), and blue (B)
This is a method of reading by alternately lighting at a storage time interval, and usually the LED lighting duty for each color is controlled to 33% or less at the maximum. FIG. 4A shows the lighting operation of each LED when the duty is normal, and FIG. 4B shows the lighting operation of each LED when the duty is abnormal. In FIGS. 4A and 4B, the light from each color LED is detected by the sensor at every read clock S, and the video signal V is output from the predetermined video circuit. Each color L
FIG. 3 shows the relationship between the lighting duty and the maximum forward current rating for the ED. In FIG. 3, line R indicates a red LED, line G indicates a green LED, and line B indicates a blue LED. For example, with a red LED, the set current is about 30 mA.
In such a case, if the lighting duty exceeds 60%, the life of the LED is shortened or, in the worst case, it is destroyed.

If the LED lighting control is normally performed as shown in FIG. 4A, that is, for example, forward current setting 3
If the red LED, the green LED, and the blue LED are line-sequentially lit at 0 mA and a lighting duty of 33%, the instantaneous value of each conduction current exceeds the rated value during continuous lighting (that is, at a lighting duty of 100%). However, these three colors of LE
D does not have a shortened life and does not break. On the other hand, for example, the LED lighting control software malfunctions due to some cause (for example, thermal runaway),
As shown in FIG. 4 (B), red L with forward current setting of 30 mA
It is assumed that the ED is driven at a lighting duty of 100%. In this case, the red LED exceeds the maximum forward current rating of 25 mA at a lighting duty of 100%. Therefore, green LED and blue L
Even if the ED is driven at a forward current setting of 30 mA and a lighting duty of 33%, the life of the red LED is shortened or destroyed as described above, and the reading function of the image reading device is lost.

According to the present invention, the lighting duty of each color light emitting element of the image sensor is monitored, the abnormality of the lighting duty is detected, and the power supply of the light emitting element is turned off. It is an object of the present invention to provide an image reading device capable of performing the above.

[0005]

An image reading apparatus according to the present invention comprises a color light source section composed of a plurality of light emitting elements for generating different color light, and an optical system for irradiating an original image with each color light from the color light source section. An optical sensor for detecting the reflected light of each color light from the color light source unit irradiated on the document image, and a light emitting element drive signal generation circuit for generating a drive signal for each light emitting element of the color light source unit. And an image reading control means for controlling the image reading unit, wherein the image reading unit is
Further, a lighting duty comparison circuit for comparing the maximum lighting duty value of the drive signal of each color light emitting element and the actual lighting duty value of the drive signal of each color light emitting element generated by the light emitting element drive signal generation circuit, and the lighting duty When the comparison circuit detects that the lighting duty actual value exceeds the lighting duty maximum value for any of the light emitting elements of each color, the lighting duty for notifying the image reading control means of the lighting duty abnormality of the drive signal And an abnormality notification circuit.

In the above-mentioned image reading apparatus, when the lighting duty abnormality notification circuit notifies the lighting duty abnormality, the lighting duty comparison circuit at least turns off the power source of the light emitting element having the lighting duty abnormality. can do.

The image reading apparatus of the present invention includes a color light source section including a plurality of light emitting elements for generating different color lights, an optical system for irradiating each color light from the color light source section to an original image, and irradiating the original image. An optical sensor for detecting reflected light from the original image of each color of light from the colored light source section,
An image reading unit including a light emitting element drive signal generating circuit that generates a drive signal for each light emitting element of the color light source unit, and an image reading control unit that controls the image reading unit. The section further includes a lighting duty comparison circuit that compares the maximum lighting duty value of the drive signal of each color light emitting element and the actual lighting duty value of the drive signal of each color light emitting element generated by the light emitting element drive signal generation circuit, When the lighting duty comparison circuit detects that the actual lighting duty value exceeds the maximum lighting duty value for any of the light emitting elements of each color, at least the light emitting element having the lighting abnormality is turned off. An element power-off circuit is also provided.

In the image reading apparatus of the present invention, the image reading control means includes a storage device that stores a table showing the relationship between the lighting duty and the maximum forward current rating for each color light emitting element, and each light emitting element. Can be determined based on the table, and the maximum lighting duty can be set in the lighting duty comparison circuit.

Further, in the image reading apparatus of the present invention, the lighting duty comparison circuit includes a storage device that stores a table showing a relationship between the lighting duty and the maximum forward current rating for each color light emitting element. The maximum lighting duty value for the light emitting element can be determined based on the table. Each light emitting element used in the image reading apparatus of the present invention is typically an LED, but other light emitting elements such as a laser diode may be used.

[0010]

1A is a system configuration diagram showing an embodiment in which an image reading apparatus of the present invention is applied to a facsimile apparatus. In FIG. 1A, the facsimile device 1 includes a control unit 11, a memory 12, a document image reading unit (scanner unit) 13, and a recording unit (printing unit) 14.
An operation unit 15, a communication control unit 16, and a compression / decompression unit 17
And are interconnected via the system bus 100. The control unit 11 controls the entire apparatus and can drive a scanner driver, a print driver, and the like. The control unit 11 will be described later with reference to FIG.
In the embodiment of (A), as the function of the scanner driver, when the lighting duty of the LED exceeds the set value, L
The power of the ED can be turned off. Although not shown, the memory 12 is composed of a system memory (ROM and RAM) and an image information memory. The ROM of the system memory stores the above-mentioned various drivers and the like, and the RAM stores user information and the like. Further, the image information memory stores image data received via the communication control unit 16 or image data read by the document image reading unit 13.

The reading unit 13 can read a document image in color and convert it into image data. Recording unit 14
Can print out the received image and print out the image read by the document image reading unit 13. The operation unit 15 is a user interface and has a key switch, a display unit, and the like. The communication control unit 16 is connected to a telephone line and a LAN and can send and receive image data. The compression / decompression unit 17 can decompress the image data received via the communication control unit 16 or compress the image data read by the document image reading unit 13. FIG. 1B is the same as FIG.
It is a figure which shows the mechanical part of the image reading part 13 of (A).
Documents 200 set on a paper feed tray (not shown) or the like
Are conveyed one by one by the paper feed roller 131, and the front end of the document is detected by the document front / rear edge detection sensor 132 to confirm the position of the document. After that, the original is sequentially read on the reading line L of the contact image sensor 133, and the paper is discharged by the paper discharge roller 134. Contact image sensor 13
The white pressure plate 135 installed above the third plate 3 is used as a white reference plate when the shading correction data is taken in by the image processing unit (not shown).

FIG. 2 is a block diagram showing a circuit configuration of the original image reading section 13 of the system configuration shown in FIG. In FIG. 2, the document image reading unit 13 includes a contact image sensor 133 (the same as that shown in FIG. 1B) and a drive circuit unit 136. The drive circuit unit 136 includes a drive control circuit 1361, an LED drive circuit 1362, and an LE.
D power supply 1363. Contact image sensor 1
33 is a color light source unit 1331, an optical system 1332,
Shown as sensor board 1333. Although not shown in FIG. 2, the optical system 1332 has a longitudinal shape in the main scanning direction, and the color light source unit 1331 is arranged at one end thereof. Red, green, and blue LEDs (LED-R, LED-G, LED-B) in the color light source unit 1331
Is based on the LED drive control signal LED_D from. It is driven by the color LED drive circuit 1362. Each color L
The ED is connected to the contact image sensor 133.
The sensor substrate 1333 is driven by a drive signal from the drive control circuit 1361. The drive circuit unit 136 is connected to the image reading control unit 18. In the present embodiment, the image reading control unit 18 is realized by the control unit 11 shown in FIG. 1A and a program stored in a ROM (not shown) that constitutes the memory 12.

FIG. 5A is a block diagram showing a drive control circuit 1361 having means (lighting duty abnormality notifying circuit) for notifying the image reading control means 18 of the abnormal lighting duty. The drive control circuit 1361 in FIG.
It includes an LED drive signal generation circuit 21, a lighting duty comparison circuit 22, and a lighting duty abnormality notification circuit 23. A signal C as to whether or not to drive the LED is exchanged between the image reading control means 18 and the LED drive signal generation circuit 21, and the LED drive control signal LED_D from the LED drive signal generation circuit 21 causes the color light source section 21 to be controlled. Each LED (R, G, B) is controlled. Further, the image reading control means 18 can set the LED forward current set value Iset and the lighting duty DTY in the LED drive signal generation circuit 21, and the maximum duty value DTYmax in the duty comparison circuit 22.

This LED drive control signal LED_D is also sent to a lighting duty comparison circuit 22 which compares (monitors) the lighting duty of each LED, and this circuit 22 outputs each L.
When the ED lighting duty is compared with the set lighting duty (set duty DTY) and an abnormal duty is detected, the abnormal lighting duty detection signal duty_S is transmitted to the image reading control means 18. Then, the image reading control means 18 sends L to the LED drive signal generation circuit 21.
A power off signal for the ED is transmitted. The image reading control means 18 uses the lighting duty / current maximum rating table 181.
Is included. The lighting duty / current maximum rating table 181 is stored in the ROM of the memory 2 shown in FIG.

FIG. 5B is a circuit for forcibly turning off the LED when the abnormal lighting duty occurs (power-off circuit 2).
It is a block diagram which shows the drive control circuit 1361 provided with 4). 5A is different from FIG. 5A in that when the lighting duty comparison circuit 22 detects an abnormal lighting duty, the circuit 22 outputs a forced light-off signal E for instructing the power-off circuit 24 to turn off the LED power (light source off). This is the point of transmission.

The operation of the facsimile machine 1 will be described below. Here, the lighting duty of each LED is set to 25%, and the forward current rating of each color LED is 3%.
It shall be set to 0 mA. Referring to FIG. 3, when the forward current rating is 30 mA, the maximum lighting duty is about 55% for LED-R (red LED), LED-G (green LED), LED-B (blue LE).
D) About 70% for each. Therefore,
As long as the color light source unit 1331 is driven at the normal lighting duty shown in FIG. 4A, the forward current of each LED does not exceed the maximum forward current at the lighting duty. That is, the LEDs are line-sequentially turned on within one storage time, and as a result, the video signals from the contact image sensor 133 are output in the order of red (R), green (G), and blue (B), Based on this, color image processing is performed in the reading unit 13 to obtain a color image.

On the other hand, for example, the LED lighting control software malfunctions for some reason (for example, thermal runaway), and as shown in FIG. 4B, the red LED with the forward current setting of 30 mA is driven with the lighting duty of 100%. Let's say that. In this case, the red LED is
The forward current maximum rating of 25 mA at a lighting duty of 100% is exceeded (see FIG. 3). In the present embodiment, when such a situation occurs, the LED power supply is promptly turned off as shown below.

FIG. 6 is a flowchart showing the operation of the circuit shown in FIG. 5A. First, when the power of the facsimile apparatus 1 of the present invention is turned on, and a series of color reading operations is started in step S101. , L in step 102
ED forward current set value Iset and lighting duty DT
While determining Y, the maximum duty value DTYma is determined by referring to the lighting duty / current maximum rating table 181.
Determine x. Then, in step S103, the LED forward current setting value Iset and the lighting duty DTY are set to LE.
The D drive signal generation circuit 21 is set, and the maximum duty value DTYmax is set in the duty comparison circuit 22. Then, when the LEDs of each color are lit, the lighting duty comparison circuit 22 monitors the lighting duty of each of the lit LEDs of the color in step S104, and detects in step S105 whether or not the maximum lighting duty DTYmax is exceeded. If it exceeds, step S10
At 6, the lighting duty abnormality notification circuit 23 transmits the abnormal duty detection signal duty_S to the image reading control means 18. In step S107, the image reading control unit 18 determines that the lighting duty is abnormal.
Upon receiving S, the LED drive signal generation circuit 21 transmits a power-off signal to the LED drive signal generation circuit 21, and the LED drive signal generation circuit 21 powers off the LED (light source is turned off) in step S108. The power is turned off.

FIG. 6 is a flow chart showing the operation of the circuit shown in FIG. 5B. Steps S201 to S205 are the same as steps S101 to S105 of FIG. 7 is different from FIG. 6 in the case where the maximum lighting duty detected in step S206 is exceeded, the power-off circuit 24 is informed of the abnormal lighting duty in step S206, and the power-off circuit 24 notifies the power-off circuit 24 of the abnormal lighting duty. LE to the LED drive signal generation circuit 21
This is the point at which the signal for powering off D (light source off) is transmitted. In FIG. 7, as in the case of FIG. 6, step S208
Then, the light source is turned off, and the power of the contact image sensor 133 is turned off. In the facsimile apparatus 1 equipped with the document image reading unit 13 having the circuit shown in FIG. 5B, the LED of the image reading control unit 18 can be LED by hardware even if the software of the image reading control unit 18 runs away for some reason.
Since the abnormal driving of can be canceled, the power off can be surely controlled even if the lighting duty is abnormal.

In the above embodiment, the case where the lighting duty / current maximum rating table 181 is stored in the ROM of the memory 2 shown in FIG. 1A is provided, but it is provided in the document image reading section 13. The maximum duty value is determined on the side of the original image reading unit 13 and the duty comparison circuit 22
It may be set to. Further, in the above embodiment, the lighting duty of each LED is set to the same (25%), but the lighting duty can be set to be different for each LED. In this case, the duty can be set so that the lighting periods of the LEDs overlap. Further, although the forward current set value of each LED is set to be the same (30 mA), the forward current set value can be set to be different for each LED. Further, in the above-described embodiment, the lighting duty and forward current of each LED are set at the time of reading the original image. However, each of them is stored in advance in the nonvolatile register of the LED drive circuit to read the original image. You can choose not to make each setting.

Further, in the above embodiment, the contact image sensor 133 is used as the document image reading section 13, but the present invention is not limited to this, and other reading methods such as a sensor array type image sensor are adopted. It is also possible to use a sensor. Further, in the above embodiment, the LED is exemplified as the light emitting element, but the present invention is also applied to an image sensor using another light emitting element such as an LD.

[0022]

As described above, according to the image reading apparatus of the present invention, the following effects can be obtained. (1) The system can instantly recognize the abnormal lighting duty of each of the R, G, and B light emitting elements, and can immediately respond. (2) When the system recognizes an abnormal lighting duty,
By turning off the power of the light emitting elements, it is possible to extend the life of each light emitting element, prevent destruction of each light emitting element, and perform stable image reading for a long period of time. . (3) If the drive signal generating circuit of the light emitting element is provided with the function of recognizing the abnormal lighting duty and the light emitting element is powered off in this circuit, runaway occurs in the software of the image reading control means. In addition, not only the effect of (2) above can be obtained in this circuit section,
The fail-safe function can be retained. (4) By prolonging the life of each light emitting element and preventing destruction by providing not only the drive signal generating circuit of the light emitting element but also the image reading control means with the function of recognizing the abnormal lighting duty and the function of turning off the power of the light emitting element. Can be performed more stably, and a more excellent fail-safe function can be provided.

[Brief description of drawings]

FIG. 1A is a diagram showing a system configuration example of a facsimile apparatus according to an embodiment of an image reading apparatus of the present invention;
FIG. 3B is a diagram showing the mechanism of the image reading unit of the facsimile apparatus.

FIG. 2 is a diagram showing a circuit of an image reading unit shown in FIG.

FIG. 3 is a diagram showing a relationship between a lighting duty of an LED and a maximum forward current rating.

FIG. 4A is a diagram showing an example of normal LED lighting control during image reading, and FIG. 4B is a diagram showing an example of abnormal LED lighting control during image reading.

FIG. 5A is a diagram showing an example of functional blocks in the image reading device, and FIG. 5B is a diagram showing another example of functional blocks in the image reading device.

FIG. 6 is a flowchart showing an operation of a functional block shown in FIG.

FIG. 7 is a flowchart showing an operation of a functional block shown in FIG. 5 (B).

[Explanation of symbols]

1 Facsimile machine 11 Control unit 12 memories 13 Document image image reading section 14 Recording section 15 Operation part 16 Communication control unit 17 Compression / expansion section 18 Image reading control means 21 LED drive signal generation circuit 22 Lighting duty comparison circuit 23 Lighting duty abnormality notification circuit 24 Power-off circuit 100 system bus 131 paper feed roller 132 Document front / rear edge detection sensor 133 Contact image sensor 134 Ejection roller 135 White plate 181 Lighting Duty / Current Maximum Rating Table 200 manuscripts 1331 color light source 1332 Optical system 1333 Sensor board 1361 Drive control circuit 1362 LED drive circuit 1363 LED power supply

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5B047 AA01 AB04 BA01 BB02 BC11                       CB04 DA04 DC06                 5C072 AA01 BA13 CA05 CA12 EA05                       QA12 UA02 UA11 XA01                 5C079 HB01 JA27 MA11 MA20 NA18                       NA21 PA01 PA02

Claims (6)

[Claims] 1. A color light source section comprising a plurality of light emitting elements for generating different color light, an optical system for irradiating each color light from the color light source section onto a document image, and a color light source section irradiated onto the document image. An image reading section including an optical sensor for detecting reflected light of each color light from the original image, and a light emitting element drive signal generating circuit for generating a drive signal for each light emitting element of the color light source section; and the image. In an image reading apparatus having image reading control means for controlling a reading unit, the image reading unit further includes a maximum lighting duty value of a driving signal of each color light emitting element and each color generated by the light emitting element drive signal generating circuit. A lighting duty comparison circuit for comparing a lighting duty actual value of a drive signal of the light emitting element, and the lighting duty comparison circuit for any one of the color light emitting elements When it is detected that the actual value of the lighting duty exceeds the maximum value of the lighting duty, the image reading control means is provided with a lighting duty abnormality notification circuit that notifies the lighting duty abnormality of the drive signal. Image reader. 2. The lighting duty comparison circuit turns off at least the light emitting element having the lighting duty abnormality when the lighting duty abnormality notification circuit notifies the lighting duty abnormality. The image reading device according to claim 1. 3. A color light source section comprising a plurality of light emitting elements for generating different color light, an optical system for irradiating the original image with each color light from the color light source section, and a color light source section for irradiating the original image. An image reading section including an optical sensor for detecting reflected light of each color light from the original image, and a light emitting element drive signal generating circuit for generating a drive signal for each light emitting element of the color light source section; and the image. In an image reading apparatus having image reading control means for controlling a reading unit, the image reading unit further includes a maximum lighting duty value of a driving signal of each color light emitting element and each color generated by the light emitting element drive signal generating circuit. A lighting duty comparison circuit for comparing the actual lighting duty value of the drive signal of the light emitting element, and the lighting duty comparison circuit for any one of the color light emitting elements, The light-emitting element power-off circuit turns off at least the light-emitting element that has a lighting abnormality when it is detected that the actual lighting duty value exceeds the maximum lighting duty value. Image reader. 4. The image reading control means includes a storage device that stores a table showing a relationship between the lighting duty of each color light emitting element and the maximum forward current rating, and the maximum lighting duty of each light emitting element. The value,
The image reading apparatus according to claim 1, wherein the image reading apparatus determines the maximum lighting duty based on the table and sets the maximum lighting duty in the lighting duty comparison circuit. 5. The lighting duty comparison circuit includes a storage device that stores a table showing a relationship between the lighting duty and the maximum forward current rating for each color light emitting element, and the maximum lighting duty for each light emitting element. The image reading apparatus according to any one of claims 1 to 4, wherein the value is determined based on the table. 6. The image reading device according to claim 1, wherein each of the light emitting elements is an LED.