JP2002036622A - Image forming device - Google Patents

Abstract

(57) [Problem] To solve the problem, when the lighting cycle of an LED array is long, luminous efficiency is reduced due to the heat generation amount, and the luminous amount is reduced.
An object of the present invention is to solve the problem that it is difficult to perform light quantity correction in real time as in a semiconductor laser. SOLUTION: The present invention has light emission data processing means 23 to 25 for generating light emission data of an LED array. The light emission data processing means converts the image data into the number of bits matching the LED array, and The image data is converted to generate light emission data in order to correct the light amount characteristic of the light emission.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, etc., which writes data on an image carrier by using a one-dimensional LED (light emitting diode) array.

[0002]

2. Description of the Related Art Some image forming apparatuses, such as copying machines, printers, and facsimile machines, write data on an image carrier using a one-dimensional LED array. Japanese Patent Application Laid-Open No. 8-58156 discloses a reference voltage generation source, compression means for compressing a light quantity control signal for controlling the light quantity of the LED of the LED printer head, and outputting a compression control signal, and generating the reference voltage generation source. Subtraction means for subtracting the compression signal from the reference voltage signal to be applied, and a final control signal as a result of the subtraction to the LED drive device; and a compression means for compressing the compression means based on the magnitude of the value of the final control signal. A driving circuit for an LED print head is described, which includes a compression ratio changing unit for changing a compression ratio.

JP-A-9-309223 discloses a one-dimensional LED in which a plurality of LED elements are arranged in the main scanning direction.
An array, light emission luminance detecting means for detecting each light emission luminance of the plurality of LED elements, and a light emission luminance of each of the plurality of LED elements based on the light emission luminance detected by the light emission luminance detection means. An LED writing device including a light emission luminance control means for controlling the light emission luminance is described.

Japanese Patent No. 2535970 discloses a first setting means for setting a light amount value of an LED array in an electrophotographic apparatus having an LED array as a light source for exposure;
And a light amount setting unit having a second setting unit provided at a position operable by a user and capable of finely adjusting a light amount value set by the first setting unit; and a light amount from the light amount setting unit. An electrophotographic apparatus includes a control circuit that receives a setting signal and outputs a lighting control signal, and a light amount control unit that receives a lighting control signal from the control circuit and outputs a lighting signal. .

[0005]

In the image forming apparatus in which writing is performed on the image carrier by the one-dimensional LED array, the LED array generates a large amount of heat. And the light emission amount decreases. Further, it is difficult to perform light quantity correction in real time like a semiconductor laser.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of correcting a light emission characteristic of an LED array and obtaining a light amount corresponding to input data.

[0007]

According to a first aspect of the present invention, there is provided an image forming apparatus for writing an image on an image carrier using a one-dimensional LED array in which a plurality of LED elements are arranged in a main scanning direction. A light emitting data processing means for generating light emitting data of the LED array, wherein the light emitting data processing means
While converting the number of bits to match the array,
The image data is converted to correct the light amount characteristics of the D array, and light emission data is generated.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the light emission data processing means approximates the light quantity characteristic of the LED array with a broken line and reverses the broken line. The light amount is corrected by generating the light emission data by converting the image data so that

The invention according to claim 3 is the invention according to claim 1 or 2
The image forming apparatus according to claim 1, further comprising a temperature sensor for detecting a temperature, and an environment determining unit for determining an environment based on a detection signal of the temperature sensor, wherein the light emission data processing unit is configured to perform light amount characteristics of the LED array under different environments. A plurality of types of light emission data conversion values stored in advance based on a plurality of types of light emission data conversion values stored in the light emission data conversion value storage means based on detection values of the temperature sensor. A light emission data conversion value suitable for the temperature detected by the temperature sensor is selected from the light emission data conversion values to generate light emission data.

According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, it is possible to output a pattern image used for correcting the light amount of the LED array, and store a light emission data conversion value to store the light emission data conversion value. A light emission data conversion value storage means capable of rewriting a value is provided in the light emission data processing means so that the light emission data conversion value stored in the light emission data conversion value storage means can be rewritten when the pattern image is output. It is.

[0011] The invention according to claim 5 is the invention according to claim 3 or 4.
In the image forming apparatus described above, the light emission data processing means uses a conversion step width when generating a data conversion value,
The conversion step width is stored in the light emission data conversion value storage means, and the conversion step width used when the light emission data processing means generates the data conversion value and the conversion step width stored in the light emission data conversion value storage means are The light amount at the broken point of the broken line obtained when the light amount characteristic of the LED array is approximated by a broken line, the input data, and the maximum light amount.

According to a sixth aspect of the present invention, in an image forming apparatus in which a one-dimensional LED array in which a plurality of LED elements are arranged in a main scanning direction writes on an image carrier, the light emission duty of the LED array is controlled. It has a drive control means, and controls the light emission duty of the LED array by the drive control means to control the light amount characteristics of the LED array.

According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect, the drive control means includes the LED.
The light emission duty of the LED array is controlled so that the light quantity characteristic of the array is approximated by a broken line and the broken line is corrected in reverse.

The invention according to claim 8 is the invention according to claim 6 or 7.
In the image forming apparatus described above, a temperature sensor for detecting a temperature, environment determining means for determining an environment based on a detection signal of the temperature sensor, and a plurality of types of light emission duty correction based on light amount characteristics of the LED array under different environments Light emission duty correction coefficient storage means in which a coefficient is stored in advance,
Based on the detection value of the temperature sensor, the environment determining means selects a light emission duty correction coefficient suitable for the temperature detected by the temperature sensor among a plurality of light emission duty correction coefficients stored in the light emission duty correction coefficient storage means. Thus, the light emission duty of the LED array is controlled.

According to a ninth aspect of the present invention, in the image forming apparatus of the eighth aspect, it is possible to output a pattern image used for correcting the light amount of the LED array, and store a light emission duty correction coefficient to store the light emission duty correction coefficient. A memory capable of rewriting coefficients is provided so that the light emission duty correction coefficient stored in the memory can be rewritten when the pattern image is output.

According to a tenth aspect of the present invention, in the image forming apparatus according to any one of the sixth to ninth aspects, there are provided a plurality of image forming means arranged to face the moving surface of the intermediate transfer member. The image forming means includes one image carrier and one image carrier.
Writing means, at least two developing means for developing the electrostatic latent image formed on the image carrier by the writing means, and switching means for selectively selecting and driving the at least two developing means. Wherein the writing means individually controls the light emission duty by using the LED array.

According to an eleventh aspect of the present invention, in the image forming apparatus according to the eighth or ninth aspect, the drive control means uses a light emission duty correction coefficient when controlling the timing clock, and the drive control means controls the timing clock. The light emission duty correction coefficient used for control and the light emission duty correction coefficient stored in the light emission duty correction coefficient storage means are a broken point of a broken line obtained when the light amount characteristic of the LED array is approximated by a broken line, and a slope before and after the broken line. Is determined from the ratio of

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention is an embodiment of the invention according to claims 1 and 2, and comprises a plurality of LEDs.
This is an embodiment of an image forming apparatus in which a one-dimensional LED array in which elements are arranged in a main scanning direction writes data on an image carrier, and FIG. 8 schematically shows an example thereof. In this image forming apparatus, image forming stations 2 and 3 are provided below the intermediate transfer belt 1 as two image forming units.
Are arranged at predetermined intervals in the moving direction opposite to the lower moving surface. The image forming station 2 includes a photoreceptor 4 as an image carrier, a charger 5, a writing device 6 as an exposure unit, and two developing units 7 and 8 for developing magenta and cyan colors, respectively. No cleaning device. The image forming station 3 includes a photoreceptor 9 as an image carrier, a charger 10, a writing device 11 as an exposure unit, and two developing units 12 and 13 for developing black and yellow, respectively. No cleaning device. Although the photoconductor drums are used as the photoconductors 4 and 9, an image carrier such as a photoconductor belt may be used. The switching means (not shown) selectively drives the developing devices 7 and 8 and drives the developing devices 12 and 13 alternatively.

When a full-color image is formed, the photosensitive drums 4 and 9 are rotationally driven by a drive unit (not shown) in synchronization with the rotation of the intermediate transfer belt 1 and the peripheral speed of the intermediate transfer belt 1 is adjusted. Match the speed. Normally, the photosensitive drums 4 and 9 are slightly separated from the intermediate transfer belt 1, and when the toner images on the photosensitive drums 4 and 9 are transferred to the intermediate transfer belt 1, the intermediate transfer belt 1 is Contact

A mark 14 serving as an image formation start reference is provided in an image non-formation area on one end side in the width direction orthogonal to the rotation direction on the upper surface of the intermediate transfer belt 1, and this mark 14 is used for optically detecting a fixed position. Detected by means 15.

When the mark 14 is detected by the optical detecting means 15 from the intermediate transfer belt 1 whose traveling is stable, the image forming station 2 starts the image forming operation of the first sheet. In the image forming station 2, the photosensitive drum 4 is uniformly charged by the charger 5 and then exposed by the writing device 6 to write the first magenta image information to form an electrostatic latent image. This photosensitive drum 4
The upper electrostatic latent image is developed by the developing device 7 to become a magenta toner image. The magenta toner image on the photosensitive drum 4 is transferred to an image forming area on the intermediate transfer belt 1 by a transfer unit, and the photosensitive drum 4 is cleaned by a cleaning device.

The writing (exposure) operation of the image forming operation for forming a magenta toner image on the photosensitive drum 4 is completed.
The mark 14 from the intermediate transfer belt 1 is
, The image forming station 2 starts a new image forming operation. In the image forming station 2, the photosensitive drum 4 is uniformly charged by the charger 5 and then exposed by the writing device 6 to write the second magenta image information to form an electrostatic latent image. The electrostatic latent image on the photosensitive drum 4 is
To form a magenta toner image. The magenta toner image on the photosensitive drum 4 is transferred to an image forming area on the intermediate transfer belt 1 by a transfer unit, and the photosensitive drum 4 is cleaned by a cleaning device.

On the other hand, in the image forming station 3, the photosensitive drum 9 is uniformly charged by the charger 10 while the first magenta toner image on the intermediate transfer belt 1 approaches as the intermediate transfer belt 1 travels. The electrostatic latent image is formed by being charged and exposed by the writing device 11 to write the first yellow image information, and the electrostatic latent image on the photosensitive drum 9 is developed by the developing device 13 to form a yellow image. It becomes a toner image. The yellow toner image on the photosensitive drum 9 is transferred onto the intermediate transfer belt 1 by the transfer means so as to be superimposed on the first magenta toner image, and the photosensitive drum 9 is cleaned by the cleaning device.

In the image forming station 3, the formation of the first yellow toner image is completed, and the second magenta toner image on the intermediate transfer belt 1 approaches as the intermediate transfer belt 1 travels. The photosensitive drum 9 is a charging device 10
Is charged uniformly, and is exposed by the writing device 11 to write the second yellow image information to form an electrostatic latent image. The electrostatic latent image on the photosensitive drum 9 is developed by the developing device 13. Developed to form a yellow toner image.
The yellow toner image on the photosensitive drum 9 is transferred onto the intermediate transfer belt 1 by the transfer means so as to be superimposed on the second magenta toner image, and the photosensitive drum 9 is cleaned by the cleaning device.

When the formation of the second yellow toner image is completed and the mark 14 on the intermediate transfer belt 1 is detected again by the optical detecting means 15, the image forming station 2
Starts the image forming operation. In the image forming station 2, the photosensitive drum 4 is uniformly charged by the charger 5 and is then exposed by the writing device 6 to write the first sheet of cyan image information to form an electrostatic latent image. The electrostatic latent image on the photosensitive drum 4 is developed by the developing device 8 to become a cyan toner image. This photosensitive drum 4
The upper cyan toner image is transferred to the intermediate transfer belt 1 by the transfer means.
The magenta toner image and the yellow toner image are transferred on top of it, and the photosensitive drum 4 is cleaned by the cleaning device.

When the writing (exposure) operation of the image forming operation for forming the first sheet of cyan toner image is completed and the mark 14 on the intermediate transfer belt 1 is detected by the optical detecting means 15, the image forming station 2 Starts a new image forming operation. In the image forming station 2, the photosensitive drum 4 is uniformly charged by the charger 5 and then exposed by the writing device 6 to write the second cyan image information to form an electrostatic latent image. The electrostatic latent image on the photosensitive drum 4 is developed by the developing device 8 to become a cyan toner image. The cyan toner image on the photosensitive drum 4 is transferred onto the intermediate transfer belt 1 by the transfer means so as to overlap the magenta toner image and the yellow toner image, and the photosensitive drum 4 is cleaned by the cleaning device.

On the other hand, in the image forming station 3, while the first toner image on the intermediate transfer belt 1 approaches as the intermediate transfer belt 1 travels, the photosensitive drum 9 is charged by the charger 1.
0 is uniformly charged, and is exposed by the writing device 11 to write the first black image information to form an electrostatic latent image. The electrostatic latent image on the photosensitive drum 9 is developed by the developing device 12. To form a black toner image. The black toner image on the photosensitive drum 9 is transferred onto the intermediate transfer belt 1 by the transfer means so as to be superimposed on the first magenta toner image, the yellow toner image, and the cyan toner image. The photosensitive drum 9 is formed and is cleaned by the cleaning device.

In the image forming station 3, the formation of the first black toner image is completed, and the second toner image on the intermediate transfer belt 1 approaches as the intermediate transfer belt 1 travels. The photosensitive drum 9 is uniformly charged by the charger 10 and is exposed by the writing device 11 to write the second black image information to form an electrostatic latent image. Electrostatic latent image is developing unit 1
2 to form a black toner image. The black toner image on the photoreceptor drum 9 is transferred onto the intermediate transfer belt 1 by the transfer means so as to be superimposed on the second magenta toner image, yellow toner image, and cyan toner image.
The second full-color image is formed, and the photosensitive drum 9 is cleaned by the cleaning device.

Each full-color toner image on the intermediate transfer belt 1 is transferred by a transfer means using a transfer roller 16 onto a recording medium such as paper fed from a recording medium supply device.
The toner image is fixed on the recording medium by a fixing device (not shown), and the recording medium is discharged out of the device. Also, the intermediate transfer belt 1
Means that the optical detection means 15
The cleaning is performed further downstream by a cleaning device (not shown).

The patch patterns are similarly formed on the photosensitive drums 4 and 9 by the image forming stations 2 and 3 and transferred to the intermediate transfer belt 1 by the transfer means. In addition,
The writing units 6 and 11 are provided with developing units 7, 8 and 1 respectively.
Instead of 2 and 13, a full-color image may be formed using three or four developing units for developing different colors.

FIG. 2 shows the configuration of the LED array head 17 used in the writing devices 6 and 11 in the first embodiment. The LED array head 17 includes a plurality of LEDs.
One-dimensional LED array 1 in which elements are arranged in the main scanning direction
8, shift registers 19 and 20, and latch / drivers 21 and 22. In the LED array head 17,
A transfer clock dCLK, a timing clock TCLK, a data set signal dSET, an enable signal LEDen, and input data are supplied.

The LED array head 17 has an even data Ev
a shift register 19 in which enD1... EvenD4 is stored;
It has a shift register in which odd data OddD1... OddD4 are stored, and the width of each pixel is determined by 4-bit data. Each LED element of the LED array 18 has 4
The lighting cycle duty is controlled by the width determined by the bit data. The image data is divided into even-numbered data and odd-numbered data by a light emission data processing unit, converted from 8 bits to 4 bits, and supplied to the LED array head 17.

FIG. 1 shows the structure of the light emission data processing means. The light emission data processing means includes an odd / even number (Odd / Eve).
n) It comprises a dividing unit 23 and bit converting units 24 and 25.
Image data of 8 bits / pixel for each color from a personal computer or the like is first divided by an odd / even dividing unit 23 into odd data and even data. The divided 8-bit odd-numbered data and even-numbered data are converted into bit numbers matching the LED array head 17 by the bit converters 24 and 25.

Since the LED array head 17 has a 4-bit input, the bit converters 24 and 25 are odd / even (Odd).
/ Even) The 8-bit odd data and even data from the division unit 23 are reduced to 4 bits. LED array head 17
Is linear, the bit conversion units 24 and 25 simply delete the lower 4 bits of the 8-bit odd data and even data from the odd / even (Odd / Even) division unit 23 to obtain 4 bits. Luminescence data is generated.

FIG. 3 shows the timing of the LED element drive signal. The 4-bit odd data and even data from the bit conversion units 24 and 25 are transferred to the shift registers 19 and 20 in the LED array head 17 by the transfer clock dCLK. The number of transfer clocks dCLK is the total LE of the LED array 18.
Requires half the number of D elements. Shift register 19, 2
When the data transfer to 0 is completed, the data set signal dSET
, Data from the shift registers 19 and 20 are latched by the latch / drivers 21 and 22, and the LED array 18
Are turned on in synchronization with the timing clock TCLK in accordance with the 4-bit data from the latch / drivers 21 and 22 while the enable signal LEDen is valid.

The lighting period of each LED element is defined by the timing clock TCLK, and is a period corresponding to 4-bit data. Since the timing clock TCLK that defines the lighting period of the LED element has a constant period t, the lighting period of the LED element monotonically increases and decreases according to 4-bit input data. The lighting period of the LED element is t when the input data is data1, 2t when the input data is data2, and 15t when the input data is dataF. Where data (data1
~ DataF) indicates 4-bit data, data1 is 0001, da
ta2 is 0010,... dataE is 1110, and dataF is 1111.

FIG. 4 shows a case where the LED array 18 is turned on using light emission data obtained by equally converting the 256-valued image data into 16-valued 4-bit image data by the above-mentioned light emission data processing means. 6 shows light amount characteristics. While the input data is small, that is, while the light emitting period of the LED element is short, LE
The light emission amount of the D element increases linearly according to the input data, but the slope of the light amount characteristic becomes gentle from data8,
The light emission amount of the LED element has decreased. Here, the straight line in FIG. 4 is inserted in order to make it easy to understand the decrease in the light emission amount of the LED element.

The light quantity characteristic can be approximated by a polygonal line as shown by a solid line in FIG. The light emitting amount P of the LED element in Data 8 was approximately ／ of the maximum light amount Pmax. Next, the bit conversion unit 2 of the light emission data processing unit in the present embodiment
The bit conversion performed in steps 4 and 25 will be described.

In this embodiment, the bit conversion units 24 and 25
Changes the conversion step width of image data (the width between image data conversion points) with data8 as a boundary in order to correct the light amount characteristic to a straight line. In other words, the bit conversion units 24 and 25 intentionally perform bit conversion at the time of bit conversion so that the light amount characteristic is a polygonal line opposite to the polygonal line as shown in FIG. The image data is converted by changing the step width (width between the image data conversion points) for each broken line, and as a result, the light emission amount of the LED element changes linearly according to the image data. That is, the bit conversion units 24 and 25 decrease the conversion step width until the input data becomes data8, and increase the conversion step width when the input data becomes data8 or later. In this case, the bit conversion units 24 and 25 convert the light emission amount of the LED element into data corresponding to each light emission amount such that the light emission amount of the LED element is divided into approximately 16 as shown in FIG.

Here, half of the maximum light quantity of the LED element (P
/ 2) is obtained by data6 (0110). Light intensity characteristics are LED
It is a straight line until the light emission amount of the element becomes approximately 5P / 8. In this approximately 5P / 8, the conversion data is data8. Light intensity 5P
Input image data required to obtain / 8 is 256 * 5/8
= 160, and the converted data at this time is 8, so the converted data (light emission data) is incremented by 1 every 20 steps of the input data until the input data becomes 160.

That is, when the input data is 0 to 19, the bit conversion units 24 and 25 output the light emission data data0 (000
0) When the input data is 20 to 39, the emission data is data1 (000
1) ・ ・ ・ Input data: When 140-159, the emission data is data
7 (0111).

Since the light emission amount characteristics are substantially the same from the light amount of 5P / 8 to the maximum light amount P, the bit conversion unit 24
25 also converts the image data equally in this section. Since (255−160) / 8 = 12, the bit conversion units 24 and 25 convert the image data every 12 steps.
Therefore, when the input data: 160 to 171, the bit conversion units 24 and 25 output the light emission data of data8 (100
0) When the input data is 172 to 183, the emission data is data9 (100
1) ・ ・ ・ When the input data is 244 to 255, the emission data is dataF (111
1)

If the bit conversion formulas of the bit conversion units 24 and 25 are summarized, if the input data of 1.8 bits is less than 160, +1 is added to the conversion data every 20 steps of the input data. If the 2.8-bit input data is 160 or more, the conversion data is incremented by 1 every 12 steps of the input data. FIG. 6 shows the bit conversion characteristics of the bit conversion units 24 and 25. In this way, by approximating the light quantity characteristic with a polygonal line, data conversion that can correct a decrease in light quantity (changes the light quantity linearly) can be simplified.

According to the first embodiment, an odd / even number (Odd / Eve) for generating the light emission data of the LED array 18 is provided.
n) Emission data processing means comprising a division unit 23 and bit conversion units 24 and 25;
25 convert the image data to the number of bits that match the LED array 18 and generate the light emission data by converting the image data to correct the light amount characteristic of the LED array 18. By performing the correction, the light amount corresponding to the input data can be obtained.

Further, according to the first embodiment, the light emission data processing means 23 to 25 approximate the light amount characteristics of the LED array 18 to a polygonal line so as to obtain a data conversion characteristic in which the polygonal line is reversed. Since the light amount is corrected by converting the image data to generate the light emission data, the light emission characteristics of the LED array can be corrected to obtain the light amount corresponding to the input data.

FIG. 7 shows a part of the second embodiment of the present invention. The second embodiment is an embodiment of the invention according to claim 3, and differs from the first embodiment in the following points. The light amount characteristics when the input image data are equally converted into bits are obtained in advance in different environments (low temperature, room temperature, high temperature, etc.), and a plurality of types of data conversion steps for correcting these are obtained as described above. The data conversion step for the environment is stored in a nonvolatile memory 27 provided in the light emission data conversion means 26.

In the second embodiment, a temperature sensor 28 is provided, and the temperature sensor 28 detects an environmental state (temperature) at the time of image formation. The environment determining means 29 compares the detection result of the temperature sensor 28 with each environmental condition stored in the memory 27, and
The data conversion step of the environment closest to the detection result is selected from the memory 27 and output to the light emission data conversion means 26. The light emission data conversion means 26 generates light emission data from input image data in accordance with a data conversion step input from the memory 27 (converts the input image data into light emission data), and outputs the light emission data to the LED array head 17.
The LED elements 18a of the array 18 emit light.

According to the second embodiment, the temperature sensor 28 for detecting the temperature and the environment judging means 29 for judging the environment based on the detection signal of the temperature sensor 28 are provided. There is a memory 27 as a light emission data conversion value storage means in which a plurality of types of light emission data conversion values (data conversion steps for generating light emission data) based on the light amount characteristics of the LED array 18 below are stored in advance. Based on the detected value of the temperature sensor 28, the environment determining means 29 determines the light emission suitable for the detected temperature of the temperature sensor 28 among a plurality of types of light emission data conversion values stored in the light emission data conversion value storage means 27. Since the light emission data is generated by selecting the data conversion value, the light amount characteristics of the LED array can be appropriately corrected even when the environmental temperature changes.

Next, a third embodiment of the present invention will be described. The third embodiment is an embodiment of the invention according to claim 4, and differs from the second embodiment in the following points. In the third embodiment, the LED array head 17
It has a light amount correction mode for correcting the light amount of
A gradation pattern image can be output in a timely manner.

In the light amount correction mode, a gradation pattern image is formed on the photosensitive drums 4 and 9 by the image forming stations 2 and 3 and is transferred to the intermediate transfer belt 1 by the transfer means. The tone pattern image is transferred to a recording medium such as paper by a transfer unit, and the recording medium is discharged via a fixing device. Here, the LED array head 17 can output 16 gradations, and an image having a pattern of 16 gradations is formed and output on a recording medium. When the operator checks the output image and the desired gradation is not obtained, the conversion step width of the image data can be variably adjusted.

The light emission data processing means is provided with a rewritable memory, in which the currently effective conversion step width is corrected and stored. When the conversion step width up to the break point of the light amount characteristic is w1, the conversion step width after the break point of the light amount characteristic is w2, and these ratios are w1 / w2, the light emission data processing means operates the operating unit in the light amount correction mode. When the density on the high density side is low, w1 / w2 is lowered, and when the density on the high density side is high, w1 / w2 is raised based on the density adjustment instruction signal from the CPU. This modified w1 /
At w2 (at w1 and w2 in the memory), the conversion step width is corrected by the light emission data processing means, and an image having a pattern of 16 gradations is output again, and the operator checks the density. If the density still needs to be corrected, the above operation is repeated. If the density does not need to be corrected, w1 / w2
Is stored in the memory. When the light amount correction mode is canceled by the operation unit by the operator, the mode shifts to the normal image forming mode.

According to the third embodiment, in the second embodiment, it is possible to output a pattern image used for correcting the light amount of the LED array 18 and to convert the light emission data converted value (for generating the light emission data). (A conversion step width as a value) is stored in the light emission data processing means as a light emission data conversion value storage means capable of rewriting the light emission data conversion value, and is stored in the memory when the pattern image is output. Since the light emission data conversion value can be rewritten, the operator can perform light quantity correction as needed.

Next, a fourth embodiment of the present invention will be described. The fourth embodiment is an embodiment of the invention according to claim 5, and differs from the second and third embodiments in the following points. In the fourth embodiment, the light emission data processing means includes an LED array 18 as shown in FIG.
Is approximated by a polygonal line, and the input data value d serving as a break point, the light amount P of the LED element for this input data d, and the maximum light amount Pmax of the LED element are extracted as parameters for obtaining the conversion step width, The conversion step width up to the break point d is (256 × P / Pmax) / d (1), and the conversion step width after the break point d is 256 × (1−P / Pmax) / (16−d) ... (1)

According to the fourth embodiment, in the second and third embodiments, the odd / even (Odd /
Even) When the light emission data processing means having the division unit 23 and the bit conversion units 24 and 25 generates a data conversion value (light emission data), the conversion step width is used, and the light emission data processing means converts the light emission data into a memory as the light emission data conversion value storage means. Store the step width,
The conversion step width used when the light emission data processing means generates a data conversion value and the conversion step width stored in the light emission data conversion value storage means are polygonal lines obtained when the light amount characteristics of the LED array 18 are approximated by polygonal lines. Since it is obtained from the light quantity at the break point and the input data and the maximum light quantity,
It is possible to easily generate light emission data for which light amount correction is possible.

In the first to fourth embodiments, the light amount characteristics of the LED array 18 are approximated by a single broken line, but it is not necessary to limit the broken line approximation to this. Although the circuit scale is complicated, the light amount characteristics of the LED array 18 are approximated by a polygonal line close to a curve, and the conversion step width is finely determined, thereby generating light emission data capable of obtaining more ideal light amount characteristics. Can be. In addition, by converting the image data into light emission data having a light amount correction effect according to the light amount characteristics of the LED array 18 as described above, a light amount corresponding to the image data can be obtained, and a desired gradation expression can be achieved. Become.

Next, a fifth embodiment of the present invention will be described. The fifth embodiment is an embodiment of the invention according to claims 6, 7, and 10, and differs from the first embodiment in the points described below. In the fifth embodiment, a data converter is used instead of the light emission data converter, and the data converter divides the image data into odd data and even data and supplies the divided data to the LED array head 17. The odd data and the even data from the data converter are transferred to the shift registers 19 and 20 in the LED array head 17 by the transfer clock dCLK. The width of each pixel is determined by 4-bit data, and each L of the LED array 18 is
The duty of the lighting period of the ED element is controlled according to 4-bit data.

The above signal (a fixed period timing clock)
FIG. 4 shows the light amount characteristics (conventional light amount characteristics) of the LED array 18 when TCLK (including TCLK) is used, and this light amount characteristic can be approximated by a broken line as shown by a solid line in FIG. Assuming that the slope up to data8 is s1 and the slope after data8 is s2, s1 / s2> 1, and specifically, s1 / s2 = 1.7.

In the fifth embodiment, a drive control means for controlling the light emission duty of the LED array 18 is provided. In order to correct the light quantity characteristic to a straight line, the drive control means controls the cycle of the timing clock TCLK with respect to data8. Change. In this case, the drive control means intentionally adjusts the timing clock TCLK so that the emission amount characteristic becomes a broken line (a broken line whose emission amount characteristic is opposite) as shown by a solid line in FIG. Is changed, resulting in LE
The light emission amount of the D element changes linearly according to the image data.

The timing clock TCLK is an enable signal
Since 16 cycles are required for the effective period of LEDen, the drive control means sets the period of the fixed-period timing clock TCLK to t, the period of the timing clock TCLK until data8 after the change to t0, and the period of the timing clock TCLK after data8. Is set to t1, and 16 × t = 8 × t0 + 8 × t1 = 8 × t0 + 8 × t0 × s1 / s2 (3) is satisfied.

From equation (3), t0 = 0.74t and t1 = 1.26t. At this time, the drive control signal (LE
FIG. 10 shows only the portion where the light emission duty of the D array 18 is generated. Further, the light quantity characteristics when the LED array 18 is turned on by the timing clock TCLK whose cycle is changed by the drive control means are shown by the solid line in FIG. Thus L
By approximating the light amount characteristic of the ED array 18 with a polygonal line,
It is possible to correct a decrease in the light amount (change the light amount linearly) by simply changing the light emission duty.

According to the fifth embodiment, a plurality of LEs
In an image forming apparatus in which a one-dimensional LED array 18 in which D elements are arranged in the main scanning direction writes data on photoconductors 4 and 9 as image carriers, a driving control unit for controlling the light emission duty of the LED array 18 is provided. Having the LE
Since the light emission duty of the LED array 18 is controlled by the drive control means in order to control the light amount characteristic of the D array 18, the light emission characteristic of the LED array can be corrected to obtain the light amount according to the input data.

In addition, according to the fifth embodiment, the drive control means adjusts the light amount characteristics of the LED array 18 in such a manner that the light amount characteristics of the LED array 18 are approximated by broken lines and the broken lines are corrected in reverse. , The light emission characteristics of the LED array can be easily corrected.

Further, according to the fifth embodiment, there is provided a plurality of image forming means 2, 3 arranged opposite to the moving surface of the intermediate transfer belt 1 as an intermediate transfer body. Reference numerals 3 and 3 denote photoconductors 4 and 9 as one image carrier, respectively.
, One writing means 6, 11 and the image carrier 4,
9, at least two developing means 7, 8, 12, for developing the electrostatic latent image formed by the writing means 6, 11;
13 and at least two developing means 7, 8, 12,
Switching means for selectively selecting and driving the LED array 13, and the writing means 6 and 11 individually control the light emission duty by using the LED array 18. The heat radiation fins can be reduced, and a smaller full-color image forming apparatus can be constructed.

Next, a sixth embodiment of the present invention will be described. The sixth embodiment is an embodiment of the invention according to claim 8, and differs from the fifth embodiment in the following points. In the sixth embodiment, as shown in FIG.
The light quantity characteristics of the LED array 18 when the cycle of the timing clock TCLK is a constant cycle t are obtained in advance in different environments (low temperature, room temperature, high temperature, etc.), and the light emission duty correction coefficient is corrected as described above in order to correct these. Asked,
The non-volatile memory 30 as the light emission duty correction coefficient storage means stores the light emission duty correction coefficient for each environment.
To be stored.

In the sixth embodiment, a temperature sensor 31 is provided, and the temperature sensor 28 detects an environmental state (temperature) during execution of image formation. The environment judging means 32 compares the detection result of the temperature sensor 31 with each environmental condition stored in the memory 30,
Is selected from the memory 30 and output to the drive control means 33. The drive control means 33 generates a timing clock TCLK having a cycle corresponding to the light emission duty correction coefficient in accordance with the light emission duty correction coefficient input from the memory 30, and
By outputting to the D array head 17, the LED array 18
LED element 18a is turned on.

According to the sixth embodiment, in the fifth embodiment, a temperature sensor 31 for detecting a temperature,
An environment determining means 32 for determining an environment based on a detection signal of the temperature sensor 31 and the LED array 1 under different environments.
And a memory 30 as a light emission duty correction coefficient storage means in which a plurality of kinds of light emission duty correction coefficients based on the light amount characteristics of the light emission characteristics are stored in advance. The light emitting duty correction coefficient suitable for the temperature detected by the temperature sensor 31 is selected from a plurality of kinds of light emission duty correction coefficients stored in the storage means 30, and the LED is selected.
Since the light emission duty of the array 18 is controlled, it is possible to perform appropriate LED array light emission duty correction even when the environmental temperature changes.

Next, a seventh embodiment of the present invention will be described. The seventh embodiment is an embodiment of the present invention according to claim 9, and differs from the sixth embodiment in the following points. The seventh embodiment is an LED array head 1
7 has a light amount correction mode for correcting the light amount, and the operator sets the light amount correction mode at an appropriate time on the operation unit, so that a gradation pattern image can be output at an appropriate time.

In the light amount correction mode, a gradation pattern image is formed on the photosensitive drums 4 and 9 by the image forming stations 2 and 3 and is transferred to the intermediate transfer belt 1 by the transfer means. The tone pattern image is transferred to a recording medium such as paper by a transfer unit, and the recording medium is discharged via a fixing device. Here, the LED array head 17 can output 16 gradations, and an image having a pattern of 16 gradations is formed and output on a recording medium. When the operator checks the output image and the desired gradation is not obtained, the light emission duty correction coefficient of the LED array 18 can be variably adjusted.

In the seventh embodiment, a rewritable memory is provided, and this memory corrects and stores the currently valid light emission duty correction coefficient (timing clock TCLK cycle ratio = t0 / t1). I do. In the light amount correction mode, the drive control means lowers the light emission duty correction coefficient when the density on the high density side is low, and when the density on the high density side is high, based on the density adjustment instruction signal from the operation unit. Increase the light emission duty correction coefficient. With the corrected light emission duty correction coefficient (with the light emission duty correction coefficient in the memory),
The light emission duty is corrected by correcting the cycle of TCLK, and an image having a pattern of 16 gradations is output again,
The operator checks the density. If the density still needs to be corrected, the above operation is repeated. If the density does not need to be corrected, the light emission duty correction coefficient is stored and held in the memory. When the light amount correction mode is canceled by the operation unit by the operator, the mode shifts to the normal image forming mode.

According to the seventh embodiment, in the sixth embodiment, it is possible to output a pattern image used for correcting the light amount of the LED array 18 and store a light emission duty correction coefficient to store the light emission duty correction coefficient. A memory capable of rewriting the correction coefficient is provided so that the light emission duty correction coefficient stored in the memory can be rewritten when the pattern image is output.
Light amount correction of the ED array can be performed.

Next, an eighth embodiment of the present invention will be described. The eighth embodiment is an embodiment of the invention according to claim 11, and differs from the sixth and seventh embodiments in the following points. In the eighth embodiment,
As shown in FIG. 9, the drive control means approximates the light amount characteristic of the LED array 18 with a polygonal line, sets the input data value as a change point (break point) to c, sets the slope of the light amount characteristic before the break point to s1, and sets the light amount characteristic to Ratio s1 / s2 when the slope after the break point is s2
Is extracted as a parameter for obtaining a light emission duty correction coefficient.

The timing clock TCLK is an enable signal
Since there are 16 clocks within the effective period of LEDen, using the above parameters, from the equation (3), 16 × t = c × t0 + (16−c) × t1 = c × t0 + (16−c) × t0 × s1 / s2... (4) is obtained. The drive control means obtains a slope s1 before the break point and a slope s2 after the break point of the light amount characteristic from equation (4).

According to the eighth embodiment, in the sixth and seventh embodiments, the drive control means uses the light emission duty correction coefficient when controlling the timing clock, and the drive control means The light emission duty correction coefficient used for controlling the clock and the light emission duty correction coefficient stored in the memory as the light emission duty correction coefficient storage means are broken points and broken lines obtained when the light amount characteristics of the LED array 18 are approximated by broken lines. Therefore, a control signal for light quantity correction can be generated by a simple method.

In the fifth to eighth embodiments, the light quantity characteristics of the LED array 18 are approximated by a single broken line, but it is not necessary to limit the broken line approximation to this.
Although the circuit scale becomes complicated, the light-emitting duty correction coefficient is obtained while the light amount characteristic of the LED
By controlling the light emission duty of the array 18, more ideal light quantity characteristics can be obtained. Further, as described above, by generating a drive signal for correcting the light amount of the LED array 18 according to the light amount characteristics of the LED array 18 and controlling the light emission data, a light amount corresponding to the input image data is obtained. Desired gradation expression is possible.

[0075]

As described above, according to the first and second aspects of the present invention, it is possible to obtain the amount of light according to the input data by correcting the light emission characteristics of the LED array. According to the third aspect of the invention, the light amount characteristics of the LED array can be appropriately corrected even when the environmental temperature changes. According to the invention according to claim 4, the operator can perform light quantity correction as needed.

According to the fifth aspect of the invention, it is possible to easily generate light emission data capable of correcting the light amount. According to the invention according to claim 6, it is possible to obtain the light amount according to the input data by correcting the light emission characteristics of the LED array. According to the invention according to claim 7, the light amount characteristics of the LED array can be easily corrected.

According to the eighth aspect of the present invention, appropriate LED array light emission duty correction can be performed even when the environmental temperature changes. According to the ninth aspect, the operator can freely correct the light amount of the LED array. According to the tenth aspect, the radiation fins of the LED array head can be reduced by the light emission duty control,
A smaller full-color image forming apparatus can be constructed. According to the eleventh aspect, a control signal for light quantity correction can be generated by a simple method.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a light emission data processing unit according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a configuration of an LED array head according to the first embodiment.

FIG. 3 is a timing chart showing the timing of an LED element drive signal in the first embodiment.

FIG. 4 is a characteristic diagram showing a light amount characteristic of a conventional LED array.

FIG. 5 is a characteristic diagram showing an approximation of the light amount characteristic by a broken line.

FIG. 6 is a characteristic diagram showing bit conversion characteristics of a bit conversion unit according to the first embodiment.

FIG. 7 is a block diagram showing a part of a second embodiment of the present invention.

FIG. 8 is a diagram schematically showing the first embodiment.

FIG. 9 is a characteristic diagram showing a broken line approximation of the light amount characteristic of the LED array and its inverse characteristic.

FIG. 10 is a timing chart showing an LED array drive control signal according to a fifth embodiment of the present invention.

FIG. 11 is a characteristic diagram showing light quantity characteristics of an LED array before and after correction in the fifth embodiment.

FIG. 12 is a block diagram showing a part of a sixth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Intermediate transfer bell 2, 3 Image forming means 4, 9 Photoreceptor 5, 11 Writing means 7, 8, 12, 13 Developing means 18 LED array 23 Odd / even division part 24.25 and bit conversion part 28 Temperature sensor 29 Environment Judging means 27 Memory 31 Temperature sensor 32 Environment judging means 30 Memory 33 Drive control means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/04 21/14 F term (Reference) 2C162 AF21 AF27 AF72 AF86 FA04 FA17 2H027 DA11 DE07 EA02 ED06 EE06 HA13 ZA07 2H030 AA05 AB02 AD16 BB02 BB13 BB21 BB41 2H076 AB42 AB54 AB76 DA10 DA17 EA01

Claims (11)

[Claims] 1. An image forming apparatus for writing data on an image carrier using a one-dimensional LED array in which a plurality of LED elements are arranged in a main scanning direction, comprising an emission data processing means for generating emission data of the LED array. The light emission data processing means converts the image data into the number of bits corresponding to the LED array, and converts the image data to correct the light amount characteristic of the LED array to generate light emission data. Image forming device. 2. An image forming apparatus according to claim 1, wherein said light emission data processing means has a data conversion characteristic in which the light quantity characteristic of said LED array is approximated by a broken line and said broken line is reversed. An image forming apparatus, wherein the light amount is corrected by generating light emission data by converting image data. 3. An image forming apparatus according to claim 1, further comprising a temperature sensor for detecting a temperature, and an environment judging means for judging an environment based on a detection signal of said temperature sensor, wherein said light emission data processing means is different. A light-emission data conversion value storing means for preliminarily storing a plurality of kinds of light-emission data conversion values based on the light amount characteristics of the LED array under an environment; An image forming apparatus, wherein a light emission data conversion value suitable for a temperature detected by the temperature sensor is selected from a plurality of types of light emission data conversion values stored in a storage unit to generate light emission data. 4. The image forming apparatus according to claim 3, wherein a pattern image used for correcting the light amount of said LED array can be output, and a converted luminescence data value can be stored and rewritten. Image forming, wherein a light emission data conversion value storage means is provided in the light emission data processing means, and the light emission data conversion value stored in the light emission data conversion value storage means can be rewritten at the time of outputting the pattern image. apparatus. 5. An image forming apparatus according to claim 3, wherein said light emission data processing means uses a conversion step width when generating a data conversion value, and said light emission data conversion value storage means stores said conversion step width. The conversion step width stored and stored in the light emission data conversion value storage means is used when the light emission data processing means generates a data conversion value. An image forming apparatus characterized in that the light amount at the break point of the obtained polygonal line and the input data and the maximum light amount are obtained. 6. An image forming apparatus for performing writing on an image carrier by means of a one-dimensional LED array in which a plurality of LED elements are arranged in a main scanning direction, comprising a drive control means for controlling a light emission duty of said LED array. An image forming apparatus, wherein the light emission duty of the LED array is controlled by the drive control means so as to control a light amount characteristic of the LED array. 7. The image forming apparatus according to claim 6, wherein the drive control means approximates the light quantity characteristic of the LED array with a broken line and obtains a light quantity characteristic in a form in which the broken line is corrected in reverse. An image forming apparatus for controlling a light emission duty of the image forming apparatus. 8. An image forming apparatus according to claim 6, wherein a temperature sensor for detecting a temperature, environment judgment means for judging an environment based on a detection signal of said temperature sensor, and said LED array in a different environment. A light emission duty correction coefficient storing means for storing a plurality of kinds of light emission duty correction coefficients based on light amount characteristics in advance, wherein the environment judgment means is stored in the light emission duty correction coefficient storage means based on a detection value of the temperature sensor. An image forming apparatus, wherein a light emission duty correction coefficient suitable for a temperature detected by the temperature sensor is selected from among various light emission duty correction coefficients to control a light emission duty of the LED array. 9. An image forming apparatus according to claim 8, wherein a pattern image used for correcting the light quantity of said LED array can be output, and a light emission duty correction coefficient is stored, and said light emission duty correction coefficient can be rewritten. An image forming apparatus, comprising: a memory, wherein a light emission duty correction coefficient stored in the memory can be rewritten when the pattern image is output. 10. An image forming apparatus according to claim 6, further comprising: a plurality of image forming means arranged to face a moving surface of the intermediate transfer member, wherein said image forming means is provided. One image carrier, one writing unit, at least two developing units for developing the electrostatic latent image formed on the image carrier by the writing unit, and one of the at least two developing units. Switching means for selectively selecting and driving, and wherein the writing means controls the light emission duty individually by using the LED array. 11. An image forming apparatus according to claim 8, wherein said drive control means uses a light emission duty correction coefficient when controlling a timing clock, and said drive control means uses a light emission duty correction coefficient when controlling said timing clock. The duty correction coefficient and the light emission duty correction coefficient stored in the light emission duty correction coefficient storage means are the LED.
An image forming apparatus characterized in that it is obtained from a broken point of a broken line obtained when the light amount characteristic of the array is approximated by a broken line, and a ratio of inclination before and after the broken line.