JPH10193684A - LED writing device - Google Patents

Abstract

(57) [Summary] [Object] To compensate for variations in light emission due to aging of an LED element. SOLUTION: When a power supply is turned on and a fixing heater warms up, a first dot of an LED array 523 is turned on, and the light amount is changed to a photodiode 7 of a sensor unit.
04, the signal is input as a light quantity detection signal. The read value is compared with a reference value, and a correction signal for correcting the difference is stored in the RAM. Next, the second dot is turned on by shifting the position of the sensor, and the same operation is performed. In this way, the light amounts of all the LED elements from 1 to 14336 dots are measured, and a correction signal is generated. When the difference between the read value and the reference value is equal to or greater than a predetermined value,
Since the correction cannot be completed even if the light amount of the LED is increased, an abnormal signal is generated to notify the time of replacement of the LED head.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LED for writing a latent image by selectively lighting each element of an LED array in which light emitting diode (LED) elements are arranged in a line and irradiating the light on a photosensitive member. It relates to a writing device.

[0002]

2. Description of the Related Art Generally, an LED printer selectively illuminates each element of an LED array and irradiates light onto a photoreceptor. Therefore, the LED printer has no moving parts such as a polygon mirror of a laser printer and has high reliability. Also, in the case of a wide printer that requires a large-format print output, a laser printer is substituted because a large optical space for scanning light in the main scanning direction is not required and the size can be reduced.

In a laser printer, the output is 10
While one light source (laser diode) of about mW is turned on and its beam is scanned through a polygon mirror, an f-θ lens, and the like, an LED printer emits one beam per pixel.
LED elements are arranged in a row in the main scanning direction,
A drive current of about 10 mA is applied to the ED element to emit light. Therefore, when the invention is applied to a printer whose main purpose is character output and has a relatively low image density or a plotter that outputs only a line drawing such as a figure, the power consumption does not matter so much, and the image density is at most 5%. Only a design assumed to be about 程度 8% has been made. Naturally LE
The same applies to the DC power supply that supplies power to the D head,
It was not possible to provide a sufficient capacity assuming an image density of 100% in terms of shape and cost.

On the other hand, as a method for correcting the variation in the light emission of the LED elements, for example, as shown in Japanese Patent Application Laid-Open No. 62-200966, correction data corresponding to the variation in the light emission of each LED element of the LED head is previously stored in a ROM. Then, a method has been proposed in which the drive current of each LED element is corrected based on the correction data, thereby reducing the variation in light emission of each LED element and making the light amount distribution uniform.

[0005]

By the way, only the on / off control (binary control) of selectively turning on or off each LED element does not cause a problem in light emission variation of each LED element. When the present invention is applied to a copier, for example, an original having a large amount of solid black such as a poster original or an original having a large number of halftones (halftone) such as a photograph may be copied. Increase rapidly. In some cases, the heat generated by the LED head itself increases, or heat is generated in the DC power supply that supplies power to the LED head.

Moreover, in the case of an apparatus equipped with an image memory, the original is read only once and then read out any number of times, and the speed of the image forming engine is increased to increase the copy productivity. In addition, the paper feed interval is set to be as small as possible to increase the productivity. However, if the productivity is increased in this manner, the burden on the power supply side is further increased, and the frequency of occurrence of the above-described problem is also reduced. More.

On the other hand, in the above-mentioned known method, correction data according to the light emission variation at the time of manufacturing an LED element is stored in a ROM in advance.
The correction can be made if the variation during manufacturing does not change, but L
If the light emission variation of the ED element occurs, it cannot be corrected. Also, it is not possible to cope with a case where the load on the power supply side increases and the power consumption sharply increases.

The present invention has been made in view of such a situation of the prior art, and a first object of the present invention is to provide an LE capable of correcting even if there is a variation in the amount of light emitted from an LED element.
D writing device is provided.

A second object is to control the amount of light emitted from the LED element when the variation cannot be corrected.
An object of the present invention is to provide an LED writing device which can notify the result and can cope with the result.

[0010]

In order to achieve the first object, a first means comprises: a one-dimensional LED array in which a plurality of LED elements are arranged in a main scanning direction;
Detecting means for detecting the amount of light emitted from each of the D elements; supplying means for supplying power to the plurality of LED elements;
Driving means for causing the ED element to emit light, and control means for transferring data for driving to the driving means based on the amount of emitted light detected by the detecting means and controlling each emitted light amount of the plurality of LED elements. It is characterized in that it is an LED writing device.

[0011] To achieve the first object, the second means is the first means, wherein the control means changes a duty ratio of a drive signal for lighting the plurality of LED elements to change the plurality of LED elements. It is characterized in that each light emission amount of the LED element is controlled.

A third means for achieving the second object is that, in the first or second means, an abnormality is notified when the amount of emitted light detected by the detecting means is equal to or less than a correctable value. It is characterized by.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an LED according to the present invention.
1 is a block diagram showing a copying machine to which an embodiment of the writing device is applied, FIG. 2 is a configuration diagram showing the document reading device of FIG. 1, FIG. 3 is a configuration diagram showing the copying machine of FIG. 1, and FIG. FIG. 5 is a block diagram showing the LED write control circuit of FIG. 1 in detail, and FIG. 6 is a block diagram showing the LED driver circuit and the LED head of FIG. 1 in detail.

Referring to FIG. 1, the copying machine includes a document reading device 100 for reading a document, a copying device 200 for copying a document image read by the document reading device 100 onto a sheet, and an operation device 400. Having. The copying apparatus 200 includes an image information storage device 300 having an image memory 301 and a system control device 302, and a copying circuit 500. An operation device 400 is operated through an operation panel 420 as shown in FIG. Output the operation information to the system controller 302,
Operation panel 4 based on the control of system controller 302
20 has an operation control circuit 410 for performing display control.

In the document reading apparatus 100, as shown in FIG. 2, when an operator inserts a document into the insertion opening of the roller 1, the document is conveyed on the contact glass 2 by the roller 1, and the document being conveyed is a fluorescent lamp. 4, and the reflected light is reflected by a lens 5 to an image pickup device (CCD) 6.
Is formed on the light-receiving surface of the original, and photoelectrically converted by the CCD 6 to read an original image. The analog image signal photoelectrically converted by the CCD 6 is controlled by the reading control circuit 106 as shown in FIG.
The signal is output to the image amplification circuit 101 in synchronization with the clock from No. 5 and amplified, and then converted into a multi-value digital image signal for each pixel by the A / D conversion circuit 102.

The following shading correction circuit 103 detects uneven light quantity of the fluorescent lamp 4, stains on the contact glass 2,
Is corrected for unevenness in sensitivity of each element. The image signal corrected by the shading correction circuit 103 is stored in the image page memory unit 301 after being converted into digital recording image information by the image processing circuit 104. This image information is read out as appropriate, output to the copying circuit 500, and applied to the LED head 503 shown in FIG. 6 through the LED write control circuit 501 and the LED driver circuit 502 shown in FIG. It is converted into infrared light modulated according to the image information.

The configuration of the copying apparatus 200 will be described with reference to FIG. The surface of the photosensitive drum 25 is uniformly charged to, for example, −850 V by the charging device 26, and the LED head 50 is charged.
A latent image is formed by the infrared light of No. 3. Here, the LED head 503 is configured so that a large number of LEDs are arranged in an array, and each of the infrared lights is irradiated on the photosensitive drum 25 via the SELFOC lens array. And
In a portion where the document density is low (a binary signal is a non-recording level), L
The ED element is not turned on, and the LED element is turned on in a portion where the document density is high (a binary signal is a recording level).
V, the irradiation section has a potential of about -100 V, and as a result,
An electrostatic latent image corresponding to the density of the image is formed on the photosensitive drum 25.

The latent image on the photosensitive drum 25 is developed by the developing unit 27. Here, the developing unit 27
The toner inside is agitated and negatively charged, and a bias of −600 V is applied, and the toner adheres only to the portion of the photosensitive drum 25 irradiated with the infrared light, whereby the latent image is developed with the toner. The toner image on the photoconductor drum 25 is transferred to the paper by the transfer charger 23, then the paper is separated from the photoconductor drum 25 by the separation charger 28, and the remaining toner on the photoconductor drum 25 is removed by the cleaning unit 29. You.

The paper is set in advance in the form of roll papers 11a, 11b, 11c having different widths on the three paper feed tables 9a, 9b, 9c. Roll paper 11a to 11c
Is a feed roller 12a corresponding to the size of the image.
12a to 13c and selectively supplied to the cutters 13a to 13c.
c, and then conveyed by the rollers 14a to 14c, then conveyed by the registration roller 24 so as to match the toner image on the photosensitive drum 25, and the toner image is transferred by the transfer charger 23. Next, the sheet separated from the photosensitive drum 25 is conveyed by a conveying belt 31, the toner is fixed by a fixing unit 30, and is discharged onto a discharge tray 32. Such a copying apparatus 200 is driven by the printer driving device 505 under the control of the printer driving control circuit 504 shown in FIG.

As shown in FIG. 4, the operation panel 420
Keys for specifying various functions include, for example, a paper size key, paper type specification key, paper source designation key, numeric keypad, start key, mode clear key, stop key, density adjustment key, image quality adjustment key, zoom key, etc. Further, a display unit such as a copy number display unit, a magnification display unit, a document insertable display unit, and the like are provided as display units.

Next, the LED write control circuit 501 shown in FIG. 5 will be described in detail. The image input from the reading apparatus 100 to the copying apparatus 200 is temporarily stored in an image memory 301 inside the copying apparatus 200 and is synchronized with a synchronization signal and an image clock as it is or after data editing or data processing is performed. LED write control circuit 50
1 is input. Two lines (n lines, n + 1 lines) are input to the image input unit 511 of the LED write control circuit 501.
The simultaneously input image data is stored in a shift register 51.
2 and 513 are respectively divided into ODD and EVEN, and the first half and the second half are temporarily stored in separate line memory groups 514. In the division processing, since the internal structure of the LED head is created for the purpose of shortening the processing time, the stored image data is first read out by the selector 515 in the n-th line, and then the data in the (n + 1) -th line is read out in a time-division manner. It is. In the n-th line, four divided data of “ODD / first half”, “EVEN / first half”, “ODD / second half”, and “EVEN / half half” are simultaneously read out, and a synchronization signal and a pixel transfer clock signal are output. , Light emission amount (Duty) signal, LE
A D light quantity correction signal is added, and the L
The data is transferred to the ED head 503. The same processing is performed on the (n + 1) th line. This series of processing is performed within the time when the (n + 2) and (n + 3) th lines are input and stored in the same line memory, and thereafter, this operation is repeated.

Reference numeral 516 denotes L from the timer of the printer control unit.
A generation unit 517 that generates each timing of the LED control unit in response to the ED write CLK is an image data transfer clock generation unit that generates a transfer clock in the LED head based on a signal from the generation unit 516, and 519 is a unit for each LED of one dot. A light emission amount correction control unit 520 that measures the light amount of the light and corrects the variation is a control unit that controls the light emission amount of the LED based on the variation in the sensitivity of the photosensitive drum.

The operation of the LED write control circuit 501 composed of such elements is as follows.

Each morning, when the power of the machine is turned on and the fixing heater warms up, the first dot of the LED array 523 is turned on, the light amount is read by the photodiode 704 of the sensor unit 605, and the signal is input as a light amount detection signal. Is done. The read value is compared with a reference value, and a correction signal for correcting the difference is stored in a RAM (not shown). Next, the second dot is turned on by shifting the position of the sensor, and the same operation is performed. In this way 1-1
The light amounts of all the LED elements up to 4336 dots are measured to generate a correction signal. When the difference between the read value and the reference value is equal to or larger than a predetermined value, the correction is not completed even if the light amount of the LED is increased, so that an abnormal signal indicating the replacement time of the LED head 503 is output.

The image data transferred to the LED head 503 is transmitted to the shift register 5 via the LED driver 502.
22-1 to 22-4 sequentially transfer to the corresponding elements 1 to 14336 dot positions of the LED array 523, and pulse-light the light emission amount (Duty) signal and the time corresponding to the correction of both signals, and the latent light is laid on the surface of the photosensitive drum 25. Form an image. 50
Reference numeral 4 denotes an LED for supplying a power supply Vcc for lighting to the LED head.
Power supply for lighting.

FIG. 6 is a perspective view of a main part of the LED head.
In the same figure, reference numeral 601 denotes a heat sink, which is made of an extruded aluminum material having a large surface area in order to release heat generated by lighting of the LED into the air.
The structure also serves as a structure to which the ceramic substrate 602 and the SLA (Selfoc lens array) 604 are attached. 602
Is the LED array 523 and the driver IC 502 of the LE
On a ceramic substrate. Reference numeral 604 denotes a convergence SLA that is attached by adjusting the position so that the light of the LED element is focused on the surface of the photoconductor. Reference numeral 605 denotes a sensor unit for detecting the amount of light, which scans the surface of the SLA 604 once a day, every morning, from one end of the LED head 503 to the other to measure the amount of light emitted from each LED element. 6
A helical screw shaft 06 for scanning the sensor unit is rotated by a stepping motor.

As shown in the sectional view of FIG. 7, the sensor unit 605 has a cleaner 701 composed of a sponge pad for wiping the surface of the SLA 604, a dustproof glass 702 for preventing the sensor unit from being stained, and an LED element (52).
The mirror 701 directs the light from 3) to the photosensitive drum 25 to the photodiode 704 of the sensor. The mirror 701 is cleaned as described above, and the light emission amount of each LED element is measured by the photodiode 704.

[0028]

As described above, according to the first aspect of the present invention, the amount of light emitted from each of the plurality of LED elements is detected, and the driving data is transferred to the driving means based on the detected amount of emitted light. In addition, since the light emission amounts of the plurality of LED elements are controlled, it is possible to correct even if the light emission of the LED elements varies, thereby providing a high-quality image.

According to the second aspect of the present invention, a plurality of LEs
Since the light emission amount of each of the plurality of LED elements is controlled by changing the duty ratio of the drive signal for turning on the D element, even if there is a variation in the light emission of the LED elements, it is possible to correct more accurately.

According to the third aspect of the present invention, when the detected light emission amount is equal to or less than the correctable value, the abnormality is notified. If the correction is impossible, for example, the replacement of the LED is urged. Can be dealt with promptly.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a copying machine to which an embodiment of an LED writing device according to the present invention is applied.

FIG. 2 is a configuration diagram illustrating the document reading apparatus of FIG. 1;

FIG. 3 is a configuration diagram illustrating the copying machine of FIG. 1;

FIG. 4 is an explanatory diagram showing an operation panel of FIG. 1;

FIG. 5 is a block diagram showing the LED write control circuit of FIG. 1 in detail.

FIG. 6 is a perspective view showing a main part of the LED head of FIG. 1 in detail.

FIG. 7 is a cross-sectional view illustrating an internal structure of a sensor unit that detects a light amount of an LED.

[Explanation of symbols]

 501 LED write control circuit 502 LED driver 503 LED head 504 LED lighting power supply 511 Image input section 512, 513 Shift register 514 Line memory group 515 Selector 516 Timing generation section 517 Image data transfer clock generation section 518 Image output section 519 Light emission amount ( (Duty) control unit 520 emission light amount correction control unit 522-1 to 4 shift register 523 LED array 604 SLA 605 light amount sensor unit

Claims (3)

[Claims] 1. An LED writing device for supplying an electric power to an arbitrary LED of a one-dimensional LED array in which a plurality of LED elements are arranged in a main scanning direction by a driving unit and causing the supplied LED to emit light to write an image. Detecting means for detecting the amount of emitted light of each of the plurality of LED elements; and transferring drive data to the driving means based on the amount of emitted light detected by the detecting means;
Control means for controlling each light emission amount of the element.
D writing device. 2. The apparatus according to claim 1, wherein the control unit controls the light emission amount of each of the plurality of LED elements by changing a duty ratio of a drive signal for lighting the plurality of LED elements. LED writing device. 3. The LED writing device according to claim 1, wherein an abnormality is notified when the amount of emitted light detected by said detection means is equal to or less than a correctable value.