JP2003072144A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute stable forming of an image by a method wherein a temperature and a humidity are monitored by an environment sensor, a drum voltage and a development property with respect to a quantity of an exposing light are predicted, and then the quantity of the exposing light is varied. SOLUTION: An SLED driving signal generator is equipped with a PWM circuit which can vary a duty of a light exposing signal ϕI based on a value of the environment sensor. The PWM circuit has a means for predicting variation of the drum voltage and the development property of a photosensitive drum and can vary the duty of the light exposing signal ϕI based on the result of the prediction.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an image forming apparatus using an SLED head in an LED array (SLED) used as a recording light emitting element for forming a permanent visible image on a recording medium by an electrophotographic recording method. The present invention relates to exposure drive control of the SLED head.

[0002]

2. Description of the Related Art Conventionally, SLEDs (self-scanning type LED arrays: hereinafter referred to as SLEDs) are disclosed in Japanese Patent Application Laid-Open Nos. 1-238962, 2-208067 and 2-21.
No. 2170, No. 3-20457, No. 3-194978, No. 4-5872, No. 4-2.
3367, JP-A-4-296579, JP-A-5-
84971 Publication and Japan Hard Copy '91 (A
-17) Proposal of a light emitting element array for optical printers integrated with a driving circuit, IEICE ('90 .3.5) PNP
Self-scanning light emitting device (SLE) using N thyristor structure
Introduced in the proposal of D) and the like, it is attracting attention as a light emitting element for recording. An example of this SLED is shown in FIG. 1 and its operation will be described.

FIG. 2 shows a conventional control signal and timing for controlling this SLED, which is an example of the case where all the elements are turned on. The VGA of FIG. 1 corresponds to the ground of the SLED and is connected to the diode connected in cascade to φS via the resistor of FIG. 1 as shown in FIG. As shown in FIG. 2, the SLED is composed of transfer thyristors arranged in an array and light-emitting thyristors arranged in an array. The gate signals of the thyristors are connected to each other, and the first thyristor is φS. Connected to the signal input section of. The gate of the second thyristor is φ
It is connected to the cathode of the diode connected to the S terminal, and the third is connected to the cathode of the next diode.

Transfer and light emission will be described with reference to the timing chart of FIG. The transfer is started by changing φS from 0V to 5V. Since φS becomes 5V, Va = 5V, Vb = 3.6V (the forward voltage drop of the diode is 1.4V), Vc = 2.2.
V, Vd = 0.8V, 0V after Ve, and 5V each from the gate signal 0V of the transfer thyristors 1'and 2 '.
It changes to V and 3.6V.

In this state, by changing φ1 from 5V to 0V, the potential of the 1'transfer thyristor becomes anode: 5V, cathode: 0V, gate: 3.6V, respectively, and the thyristor is turned on, so that the transfer is performed. Even if φS is changed to 0V in that state in which the thyristor 1 ′ is turned on, Va≈5V because the thyristor 1 ′ is turned on (reason:
A pulse is applied to φS via a resistor. When the thyristor is turned on, the potential between the anode and the gate becomes almost equal).

Therefore, even if φS is set to 0V, the ON condition of the first thyristor is held and the first shift operation is completed. In this state, the φI signal for the light emitting thyristor is 5V.
From 0V to 0V, the conditions are the same as when the transfer thyristor is turned on, so that the light emitting thyristor 1 is turned on and the first LED is turned on. When the first LED returns φI to 5V, the potential difference between the anode and the cathode of the light emitting thyristor disappears and the minimum holding current of the thyristor cannot flow, so the light emitting thyristor 1 is turned off.

Next, the transfer of the ON condition of the thyristor from 1'to 2'will be explained.
Since φ1 remains 0V even if F is applied, the transfer thyristor is in the ON state. Even at this time, the gate voltage Va of the transfer thyristor 1'is approximately 5V, and Vb = 3.6V.
Is.

In this state, by changing φ2 from 5V to 0V, the potential of the transfer thyristor 2'is set to the anode:
The transfer thyristor 2 ′ is turned on because the voltage is 5V, the cathode is 0V, and the gate is 3.6V. By changing φ1 from 0V to 5V after the transfer thyristor 2 ′ is turned on, the transfer thyristor 1 ′ is turned off in the same manner as the light emitting thyristor 1 is turned off. In this way, the ON state of the transfer thyristor shifts from 1'to 2 '. And φI is 5V
From 0V to 0V, the light emitting thyristor 2 is turned on and emits light.

Next, the reason why only the light emitting thyristor whose transfer thyristor is ON can emit light (ON) will be described.

In the SLED, the gates of the light emitting thyristors forming a pair with the transfer thyristors are connected to each other, and when a certain transfer thyristor is turned on, the gate potential of the light emitting thyristors forming a pair also becomes 5V. . As a result, the light emitting thyristor paired with the place where the transfer thyristor is turned on can be turned on. The light emitting thyristor of SLED has a cathode potential difference of 1.4 with respect to the gate potential.
It can be turned on for the first time when V or more occurs, but when turned on, the cathode potential of the thyristor maintains the difference of 1.4 V from the gate potential, and the cathode potential does not drop any more.

That is, when a certain light emitting thyristor is turned on, φI cannot drop below 3.6V. The gate potential of the transfer and light emitting thyristors next to the transfer thyristor in the ON state is 3.6V, but φI is 3.6V.
Since it does not drop below, a potential difference of 1.4V between the gate potential of 3.6V and the cathode potential cannot be generated, and the adjacent light emitting thyristor cannot be turned on.

The SLED head in which the SLED chips having the above-described circuit structure are arranged in an array outputs the amount of light necessary for exposing the photoconductor of the electrophotographic image forming apparatus by the light emission of the light emitting thyristor.

[0013]

In the conventional printer using the SLED head, the toner potential is changed in the latent image due to the change in the drum potential with respect to the exposure amount due to environmental changes such as temperature and humidity, and the drum potential formed on the photosensitive drum. There is a problem in that the characteristics of the developing to be applied change and the image density depends on the environment even with the same exposure amount. Also S
In a conventional printer using an LED head, it is used as an exposure unit of a binary printer that turns a light emitting thyristor on or off with a constant light amount. However, the binary printer has a limit in expressing an image, and the image has a granular feeling. There was also the problem of being conspicuous.

Therefore, it is necessary to change the exposure amount so that one pixel can be expressed in multiple gradations. However, since the density change with the exposure amount is not constant depending on the environment, there is a problem that the image is not stable, and multi-value driving is performed. Was difficult to realize.

The reason why binary exposure is performed in the conventional printer is that the driver IC is configured to drive the SLED. If the driver IC is switched to the multivalue exposure IC with the current driving method, the IC is changed. More images are being input to
At the same time, it is necessary to increase the image memory area in the driver IC, and a PWM circuit of each chip and a light emission current control circuit for multivalue driving are required. As a result, the driver IC, which is a semiconductor, becomes larger, and not only does it have a problem of cost, but since the image data supplied to the driver IC is increased, the number of signal lines to the head and the speed UP of the image transfer clock are also required. Driver IC
However, it was difficult to incorporate the head into the head due to the strict construction.

An object of the present invention is to perform stable image formation by monitoring temperature and humidity by an environmental sensor, predicting drum potential and developing property with respect to exposure amount, and varying exposure amount accordingly.

[0017]

At least one transfer thyristor is arranged in an array, and at least one light emitting thyristor paired in parallel with the transfer thyristor is also arranged in an array. A gate between the transfer thyristor and the light emitting thyristor is connected to each other, and a self-scanning LED array (hereinafter referred to as SLED)
SLED for photoconductor exposure with chips arranged in a straight line in an array
The light emitting thyristor having a head is sequentially turned on from the head transfer thyristor of each SLED chip, the transfer thyristors of each chip are sequentially turned on, and thereby the light emitting thyristors selected as sequentially operable are converted into image data. Each SLED chip drive I has at least one SLED chip drive IC for driving in accordance with
In an image forming apparatus having a controller for sending an SLED chip drive signal and exposure data to C and controlling the entire printer, and having an environmental sensor in the printer body,
Depending on the value of the environmental sensor, the light emission D of the light emitting thyristor
An image forming apparatus having a variable UTY.

Further, the SLE of the image forming apparatus having the above structure
In the D chip driving IC, the SLED chip driving I
The image forming apparatus is characterized in that the image data transmitted to C is a binary signal of ON or OFF of a light emitting thyristor which is selected by the transfer thyristor of each SLED chip and is capable of emitting light.

Further, in one SLED chip of the image forming apparatus having the above structure, one light emitting thyristor capable of emitting light selected by the ON state of one transfer thyristor is provided in at least two ON sections of one transfer thyristor. An image forming apparatus characterized in that it emits light more than once and the respective light emitting times are different.

Further, in the SLED head printer having the above structure, it is possible to make the light emitting thyristor, which is selected and emitted depending on the ON state of the transfer thyristor, emit light at least twice in one ON section of the transfer thyristor, and each time. An image forming device in which the light emission time can be changed depending on the value of the environment sensor.

Further, in the SLED head printer having the above structure, the latent image for one pixel on the photoconductor formed by one light emitting thyristor can be formed by performing the exposure operation for at least one line. Image forming apparatus.

Further, in the SLED head printer having the above structure, a latent image for one pixel on the photoconductor formed by one light emitting thyristor can be formed by performing an exposure operation for at least one line, An image forming apparatus characterized in that each light emitting thyristor for forming one pixel has different exposure times for a plurality of times, and each exposure time can be changed by a value of an environmental sensor.

When one light emitting thyristor forms a latent image on the photoconductor, the light emitting thyristor emits light at least twice or more, and one of them is used as offset exposure. An image forming apparatus, wherein the light emitting thyristor does not emit light once when a latent image is not formed on the photoconductor.

Further, when one light emitting thyristor forms a latent image on the photoconductor, the light emitting thyristor emits light at least twice or more, and one of them is used as an offset exposure. An image forming apparatus, wherein the light emitting thyristor does not emit light once when a latent image is not formed on the photoconductor.

Further, the image forming apparatus is capable of changing the exposure time of the offset exposure according to the value of the environment sensor.

The environment sensor is capable of measuring both temperature and humidity.

Further, in the image forming apparatus having the above structure, means for predicting the drum potential with respect to the exposure amount due to environmental changes, and developing DC for the drum potential with environmental changes
It has a means to predict the voltage and the value of the environmental sensor
By the relationship between the drum potential with respect to the exposure amount and the developing DC voltage with respect to the drum potential,
An image forming apparatus in which the duty of a light emitting thyristor can be changed.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 shows the overall schematic structure of a color image forming apparatus. First, the structure of a color reader section will be described.

Reference numeral 101 is a CCD, 311 is a substrate on which the CCD 101 is mounted, 312 is a printer processing unit, 301 is a platen glass, 302 is a document feeding device (note that
There is also a configuration in which a mirror pressure plate or a white pressure plate (not shown) is mounted instead of the document feeding device 302), 303 and 3
Reference numeral 04 is a light source of a halogen lamp or a fluorescent lamp for illuminating the original, 305 and 306 are reflectors for collecting the light from the light sources 303 and 304 on the original, 307 to 309 are mirrors, 310
Is a lens for condensing reflected light or projected light from the original on the CCD 101, 314 is a carriage that houses the halogen lamps 303 and 304, reflectors 305 and 306, and the mirror 307, 315 is a carriage that houses the mirrors 308 and 309, 313 is an interface (I
/ F) part. The carriage 314 is at a speed V
The carriage 315 mechanically moves at a speed of V / 2 in a direction perpendicular to the electrical scanning (main scanning) direction of the CCD 101 to scan (sub-scan) the entire surface of the document.

Next, the configuration of the printer section in FIG. 3 will be described. Reference numeral 317 is a magenta (M) image forming unit, 318 is a cyan (C) image forming unit, 319 is a yellow (Y) image forming unit, and 320 is a black (K) image forming unit. The unit 317 will be described in detail, and the description of the other image forming units will be omitted.

In the M image forming section 317, 342 is a photosensitive drum on which a latent image is formed by the light from the LED array 210. A primary charger 321 charges the surface of the photosensitive drum 342 to a predetermined potential to prepare for latent image formation. A developing device 322 develops the latent image on the photosensitive drum 342 to form a toner image. The developing device 322 includes a sleeve 345 for applying a developing bias and developing.

A transfer charger 323 is a transfer material conveying belt 3.
The toner image on the photosensitive drum 342 is transferred to the recording paper or the like on the transfer material conveying belt 333 by discharging from the back surface of 33. In the present embodiment, since the transfer efficiency is good, the cleaner section is not arranged, but it goes without saying that there is no problem even if the cleaner section is attached.

Next, a procedure for transferring a toner image onto a transfer material such as recording paper will be described. Transfer materials such as recording paper stored in the cassettes 340 and 341 are picked up by the pickup roller 33.
The sheet is supplied to the transfer material conveying belt 333 by the sheet feeding rollers 336 and 337 one by one by 9.338. The supplied recording paper is charged by the adsorption charger 346. A transfer material conveyance belt roller 348 drives the transfer material conveyance belt 333 and charges the recording paper or the like in combination with the adsorption charger 346 to adsorb the recording paper or the like to the transfer material conveyance belt 333. The transfer material transport belt roller 348 may be a drive roller for driving the transfer material transport belt 333, and a drive roller for driving the transfer material transport belt 333 may be arranged on the opposite side.

A paper tip sensor 347 detects the tip of recording paper or the like on the transfer material conveying belt 333. The detection signal of the paper leading edge sensor 347 is sent from the printer unit to the color reader unit, and is used as a sub-scanning synchronization signal when sending a video signal from the color reader unit to the printer unit.

Thereafter, the recording paper or the like is transferred onto the transfer material conveying belt 3
The toner image is formed on the surface of the image forming units 317 to 320 in the order of M, C, Y, and K. The transfer material such as the recording paper that has passed through the K image forming unit 320 is separated from the transfer material conveying belt 333 after being discharged by the discharging charger 349 in order to facilitate separation from the transfer material conveying belt 333. Reference numeral 350 denotes a peeling charger, which prevents image disturbance due to peeling discharge when the recording paper or the like is separated from the transfer material conveying belt 333. The separated recording paper or the like is charged by the pre-fixing chargers 351 and 352 in order to supplement the toner suction force and prevent image disturbance, and then the toner image is thermally fixed by the fixing device 334 and then 33
The paper is discharged to the discharge tray of No. 5.

Reference numeral 353 denotes an environment sensor having the configuration of the present invention, which measures temperature and humidity, predicts the drum potential with respect to the exposure amount, and predicts the developing characteristic, which is the toner sticking ratio with respect to the drum potential, SLE by them
This is for controlling the light emission DUTY of the D light emitting thyristor.

FIG. 4 shows S in the color image forming apparatus.
It represents the exposure control circuit by the LED head,
FIG. 5 shows a timing waveform when an image is output in the exposure control circuit of FIG. In addition, in the SLED drive signal of FIG. 5, S-RST (reset) and S-CLK other than those in the figure are used.
(Clock) is omitted.

As an explanation of the present embodiment, first, an example in which one pixel is configured as a printer capable of expressing 8 gradations (image data of 3 bit width) will be shown.

When the printer controller CPU for controlling the entire printer receives the print start signal, it first generates an image output start signal to the image processing means,
The image processing means receives the image output start signal and sends a READ enable for acquiring image data to the image data output means. Thereby, the image processing means reads the image data from the image data output means. In the image processing means, color correction and color conversion (RGB image Y
(Converted to MCK) and converted to image data having a gradation of 3 bits per pixel.

When the image processing is completed by the image processing means,
The image processing means transmits image data to an image memory provided for each station. At that time, the image processing means sends a write clock and a write enable for writing the image data to the image memory of each station together with the image data to write the image to the image memory. The image memory has an area for 4 bits per pixel and has 3 bits.
Image data of 3 bits is written in the memory area of
In the memory area of the 4th bit, 3bit of 3 image data
If the sum of t is 0 or more, 1 is written, and if 0, 0 is written.
Write.

Next, the printer controller CPU sends enable signals (M_ENB, C_ENB, Y_ENB, K_ENB) for each station according to the printer speed.
Are output in the order of M, C, Y, K.

Upon receiving the image formation start signal, the SLED head drive signal generator generates φS, φ1, φ2, φI, S-RST, necessary for driving the SLED head.
An S-CLK SLED drive signal is generated.

The SLED drive signal generating circuit has a P of φI.
There is a WM circuit, which receives a predetermined PWM setting value from the printer controller, and sequentially changes φI according to the order of each bit of the image data to be exposed. Also, the minimum amount of light required to be exposed is taken as the offset exposure amount, and this is taken as the exposure time of the 4th bit image data (turned on if at least one of the 3 bit image data is 1). A preset PWM setting value is received from the printer controller and generated by the PWM circuit.

A signal from an environment sensor is connected to the PWM circuit, and the environment sensor detects the temperature and humidity in the printer body. Based on this temperature and humidity, the PWM circuit changes the drum potential of the photosensitive drum with respect to the exposure amount and the DC component voltage (developing DC voltage) of the developing device with respect to the electrostatic latent image (drum potential) formed on the photosensitive drum. )
Both of the changes are predicted, and the DUTY of the light emitting thyristor of the SLED is changed based on the result. The change in the drum potential with respect to the exposure amount due to the environmental change is represented as shown in FIG.

Further, the development characteristic change represented as the development DC voltage with respect to the drum potential due to the environmental change is represented as shown in FIG.

The SLED drive signal is simultaneously transmitted to the SLED head controller section of each color, and after receiving the ENB, the SLED head controller of each color outputs the read clock and the read enable for receiving the image data from the image memory and outputs from the image memory. Image data is received and read in synchronization with the SLED drive signal, and S for each color is read.
The drive signal and the image data are transmitted to the LED head. 7, 8 and 9 show S mounted in the SLED head shown in FIG. 6 from the SLED head controller shown in FIG.
7 is a timing waveform of a drive signal output sent to the LED chip drive IC.

FIG. 6 shows an SLED drive driver IC for driving the individual SLED chips mounted in the SLED head. In the embodiment, one driver IC can drive 14 SLEDs, and the SLEDs A maximum of four drive driver ICs can be arranged and used (that is, 56 SLED chips can be driven).

FIG. 7 relates to the exposure signal of the magenta SLED in the exposure control circuits of FIGS. 4 and 5.
S-RST and S, which are described in more detail and are omitted in particular in FIG.
It also shows the timing waveform of the image output for -CLK.

FIG. 8 is a more detailed representation of FIG. 7, which is a timing waveform of image output that best represents the present invention, and what is particularly noteworthy is the exposure signal φI of the light emitting thyristor. One transfer thyristor is ON
In this example, it is turned on twice during the period in which the DUTY is different, and each DUTY is different, and each DUTY can be changed by the value of the environmental sensor.

FIG. 9 shows an image signal in the case of expressing one pixel by using several lines of sub-scanning.

Here, two lines (odd and even lines) are used, and the number of times φI is emitted during the period in which one transfer thyristor is turned on is two times as an example.
In this case, image data having a gradation of 3 bits is used, and if at least one of the 3 bits has 1 (if the data of 3 bits is not 0), the data of the 4th bit is set to 1 and the 4th bit is set to offset exposure. It is configured to emit light.

In FIG. 10, the image data for one pixel is 3
FIG. 3 is a block diagram showing a configuration in a controller of a main body having PWM control for changing image data transmission and SLED exposure time in the case of bit.

When the image forming signal is received from the printer controller, the drive signal generating counter for generating each signal for driving the SLED operates. This counter is SLE by the counter based on the CLK of the printer.
Each drive signal of D is generated. ΦS, which is one of the SLED drive signals, is also input to the line counter. The line counter counts only the lines necessary for exposure based on the paper selection information received from the printer controller, and when the paper set value counter becomes full, SL
Stops generation of ED drive signal. The φI output from the drive signal generation counter enters the PWM circuit. P
The WM circuit receives a predetermined PWM setting value from the printer controller. At the same time, the value from the environmental sensor is also obtained. The PWM circuit calculates the PWM setting value and the exposure correction amount obtained from the environment sensor based on φI output from the drive signal generation counter, and based on the result, sequentially changes φI according to the image data to be exposed.

The drive signal generated by the SLED drive signal generator is sent to the SLED head controller for each station. When receiving the ENB from the printer controller, the exposure signal control unit in the SLED head controller receives the drive signal and generates a signal for reading the image data in the image memory.
The read image data (here, 3-bit image data) is stored in each memory area for each bit via the FIFO memory.

At the same time, the 3-bit data is also supplied to one OR circuit, and the output of the OR circuit is stored in the memory area as the 4th bit data. This 3 bit
The exposure data of the 4th bit created by the OR circuit of
This is data for offset exposure which is also a feature of this specification. The saved data for each bit is the DU of φI.
Corresponding to TY, it is output to the SLED head together with the SLED drive signal while being selected.

FIG. 11 shows generation of φI DUTY for each bit of image data in the PWM circuit shown in FIG. Here, in order to make it easier to understand the difference in the exposure amount by changing φI, the PW from the printer is used.
In this example, the M set value for exposure of 0 bit of the image data of 3 bits is set to 5 clocks of the printer clock, and the first bit is doubled and the second bit is quadrupled. However, depending on the value of the environmental sensor, the DUTY of the light emitting thyristor for each image data
The width can be increased or decreased with respect to the PWM setting value.

[0057]

According to the present invention, changes in the drum potential with respect to the exposure amount due to environmental changes such as temperature and humidity, and changes in the developing characteristics for attaching toner to a latent image due to the drum potential formed on the photosensitive drum can be expected. Thus, the image density with respect to the exposure amount due to environmental changes can be predicted, and a clearer image can be formed by changing the light emission DUTY of the light emitting thyristor. As a result, it is possible to suppress the density change with respect to the exposure amount due to the environment, which has been a problem when multi-valued driving the SLED head in the past, and the multi-valued driving reduces the graininess and stabilizes the image expression with richer gradation. You will be able to do so.

In addition, since the driver IC for driving the SLED in this specification has a structure capable of multi-valued with a structure of binary driving as it is, the driver IC which is conventionally driven by binary is used. Not only can it be used, but multi-valued driving can be easily realized without increasing the image data supplied to the driver IC or increasing the speed UP of the image transfer clock.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a basic configuration of an SLED.

FIG. 2 shows prior art control signals and timing for controlling an SLED.

FIG. 3 is an example of a configuration diagram of a color image forming apparatus that constitutes the present invention.

4 is a configuration diagram of an exposure control circuit in the color image forming apparatus of FIG. 3 according to the present invention.

FIG. 5 is a diagram showing an image forming timing in FIG.

FIG. 6 is a diagram showing an internal configuration of an SLED chip drive IC according to the present invention.

FIG. 7 is a diagram showing timing waveforms related to SLED head drive in magenta (M) of the SLED controller of FIG.

FIG. 8 is a diagram showing the timing waveform of FIG. 7 in more detail only for the SLED head drive waveform, in particular showing that the DUTY of φI that is the exposure signal can be changed by the environment sensor.

FIG. 9 is a diagram showing a timing waveform of driving an SLED head in magenta (M) for exposing and forming image data of 3 bft with two lines.

10 is a configuration diagram best representing the present invention, and FIG.
SLED drive signal generator and SLED that generate the drive waveform
Diagram showing the configuration of the head controller

11 is a PW in the SLED drive signal generator of FIG.
The figure which shows the simple example of the formation method of exposure signal (phi) I in M circuit, and a timing waveform.

FIG. 12 is a diagram showing changes in the drum potential with respect to the exposure amount due to environmental changes

FIG. 13 is a diagram showing a relationship between a drum potential and a developing DC voltage in an environmental change.

[Explanation of symbols]

101 CCD 311 substrate 312 Printer processing unit 301 Platen glass 302 Document feeder 303, 304 light source 305,306 Reflective umbrella 307,308,309 Mirror 310 lens 314 carriage 315 carriage 313 Interface (I / F) part

Claims (11)

[Claims] 1. At least one transfer thyristor is arranged in an array, and at least one light-emitting thyristor paired in parallel with the transfer thyristor is also arranged in an array, and the transfer thyristor and The gate between the light emitting thyristors has an SLED head for exposing a photoconductor, in which self-scanning LED array (hereinafter referred to as SLED) chips connected to each other are linearly arranged in an array, and the transfer thyristor at the head of each SLED chip is provided. ON sequentially from
State and turn on the transfer thyristors of each chip sequentially
S to drive the light-emitting thyristors that are selected to be sequentially operable according to the image data.
At least one LED chip drive IC is provided in the SLED head, and a controller for sending the SLED chip drive signal and exposure data to each SLED chip drive IC and controlling the entire printer is provided. In the image forming apparatus having a light emitting device, the light emission D of the light emitting thyristor is changed according to the value of the environment sensor.
An image forming apparatus having a variable UTY. 2. An S of the image forming apparatus having the structure of claim 1.
In the LED chip driving IC, the image data transmitted to the SLED chip driving IC is a binary signal of ON or OFF of the light emitting thyristor which is selected by the transfer thyristor of each SLED chip and can emit light. Image forming apparatus. 3. In one SLED chip of an image forming apparatus having the structure of claim 1 or 2, one light emitting thyristor capable of emitting light selected by an ON state of one of the transfer thyristors is transferred once. O
An image forming apparatus characterized in that N sections are made to emit light at least twice and the respective emission times are different. 4. The SLED head printer having the structure of claim 3, wherein the light emitting thyristor capable of emitting light selected depending on an ON state of the transfer thyristor can emit light at least twice in an ON section of one transfer thyristor. The image forming apparatus is characterized in that the light emission time of each time can be changed by the value of the environment sensor. 5. The SLED head printer having the structure of claim 4, wherein a latent image for one pixel on a photoconductor formed by one light emitting thyristor is formed by performing an exposure operation for at least one line. An image forming apparatus capable of performing the above. 6. The SLED head printer having the structure of claim 5, wherein a latent image for one pixel on a photoconductor formed by one light emitting thyristor is formed by performing an exposure operation for at least one line. The image forming apparatus is characterized in that one light emitting thyristor for forming one pixel has different exposure times for a plurality of times, and each exposure time can be changed by the value of the environmental sensor. 7. The S having the structure according to claim 3 or 6.
In the LED head printer, when one light emitting thyristor forms a latent image on a photoconductor, the light emitting thyristor emits light at least twice or more,
An image forming apparatus characterized in that it is used once as an exposure for offsetting, and does not emit light once when the light emitting thyristor does not form a latent image on a photoconductor. 8. An S having the structure according to claim 3 or claim 6.
In the LED head printer, when one light emitting thyristor forms a latent image on a photoconductor, the light emitting thyristor emits light at least twice or more,
An image forming apparatus characterized in that it is used once as an exposure for offsetting, and does not emit light once when the light emitting thyristor does not form a latent image on a photoconductor. 9. The image forming apparatus according to claim 8, wherein the exposure time of the offset exposure is variable by the value of the environment sensor. 10. The SLED head printer having the structure of claim 1, wherein the environment sensor is capable of measuring both temperature and humidity. 11. The SLED head printer having the structure of claim 1, comprising means for predicting a drum potential with respect to an exposure amount due to environmental changes, and means for predicting a developing DC voltage with respect to a drum potential due to environmental changes, and an environmental sensor. The image forming apparatus is characterized in that the DUTY of the light emitting thyristor can be changed by the relationship between the drum potential with respect to the exposure amount and the developing DC voltage with respect to the drum potential.