JPH11286135A - Laser driver and driving method, imaging method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve service life without sacrifice of the response of a laser emitting means in a system where a pulse current is applied appropriately to the laser emitting means being applied constantly with a bias current. SOLUTION: A decision is made whether a beam is emitted from a laser emitting means 34 or not based on Nth and (N+1)th control data. It a decision is made that a beam is not emitted for both data, a bias current is fed at the timing of laser beam emission control corresponding to Nth control data but it is not fed if a decision is made that a beam is emitted for any one data. The bias current is not fed when a laser beam is not emitted continuously but since it is fed immediately before emitting a laser beam, service life can enhanced without sacrifice of response.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser driving method and apparatus which emits a laser beam controlled according to a control signal to a laser emitting means, and a laser driving apparatus which emits a laser beam by the laser driving method. The present invention relates to an electrophotographic image forming apparatus used.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus such as a laser printer has a laser driving device, and the laser driving device emits a laser beam corresponding to image data. Such a laser drive device, for example,
A semiconductor laser is provided as a laser emitting unit, and a pulse current is supplied to the semiconductor laser to emit a laser beam of a corresponding light amount.

At this time, a laser beam emitted from a semiconductor laser is controlled in accordance with image data, and the laser beam is deflected and scanned in a main scanning direction by a rotating polygon mirror or the like. At the same time, the photosensitive drum as the latent image holding means is rotated to move the peripheral surface at the exposure position in the sub-scanning direction, and the peripheral surface of the photosensitive drum moving in the sub-scanning is charged by the charger.

The charged, rotating photosensitive drum rotating in the sub-scanning direction is exposed and scanned with a laser beam deflected and scanned to form an electrostatic latent image, and the electrostatic latent image is formed by a latent image developing means. The toner is developed with a certain developing device. The toner on the peripheral surface of the photosensitive drum developed in this way is transferred to a recording medium by a transfer charger as a toner transfer unit, and the toner transferred to the recording medium is fixed by a fixing device as a toner fixing unit.

[0005] However, a semiconductor laser generally used as a laser light source in such an image forming apparatus is shown in FIG.
As shown in (1), there is a delay until the laser beam is emitted even when the driving current is supplied. This is because the semiconductor laser is L
After emitting ED (Light Emitting Diode), LD (L
(Aser Diode) light emission, and during the delay time, the drive current is consumed for LED light emission and carrier accumulation.

Therefore, in order to improve the response of such a semiconductor laser, an image forming apparatus in which a bias current is constantly supplied to the semiconductor laser, and a pulse current controlled corresponding to image data is supplied thereto as appropriate. There are, for example,
It is disclosed in Japanese Patent Publication No. 7-64089 and Japanese Patent Application Laid-Open No. 9-83050.

FIG. 6 shows a conventional example of such an image forming apparatus.
This will be described below with reference to FIG. FIG. 6 is a schematic block diagram showing a main part of the image forming apparatus, and FIG. 7 is a plan view showing an optical system of the image forming apparatus.

First, this conventional image forming apparatus 1
The laser device 2 is provided with a semiconductor laser 3 serving as a laser emitting unit and a photodiode 4 serving as a laser monitoring unit. The semiconductor laser 3 emits a laser beam corresponding to the current supply, and the photodiode 4 monitors the laser beam emitted by the semiconductor laser 3 and outputs a current signal corresponding to the light amount.

A laser power source 5 and a laser driver 6 are connected to the laser device 2. The laser driver 6 includes a bias current source 7 as bias supply means and a pulse current source 8 corresponding to pulse supply means. And an APC (Automatic Power Control) circuit 9 which is a current adjusting means.

The two current sources 7, 8 are connected in parallel to one semiconductor laser 3, and the bias current source 7 is directly connected to the semiconductor laser 3, while the pulse current source 8 is CMOS (Complementary Metal Oxide Se)
The semiconductor laser 3 is connected via a high-speed analog switch 10 such as a semiconductor.

A bias current source 7 constantly generates a bias current and supplies the bias current to the semiconductor laser 3, and a pulse current source 8
Analog switch 1 corresponding to externally input control signal
A pulse current controlled by turning on and off 0 is supplied to the semiconductor laser 3 as appropriate.

The APC circuit 9 is connected to the photodiode 4 and the bias current source 7, and adjusts the bias current of the bias current source 7 according to the detection result of the photodiode 4. More specifically, the APC circuit 9 includes a current-to-voltage converter 11, a sample-and-hold circuit 12, a constant voltage power supply 13, a comparator 14, and the like, and converts a current signal output from the photodiode 4 into a current-to-voltage converter 11 Into a voltage signal.

The sample and hold circuit 12 samples and holds the voltage signal of the current / voltage converter 11 at a predetermined timing.
Is compared with the reference voltage of the constant voltage power supply 13 to increase or decrease the bias current generated by the bias current source 7.

An analog switch 10 connected to the pulse current source 8 has an image processing circuit 1 corresponding to signal input means.
The system controller 16 is connected to the image processing circuit 15. Image processing circuit 1
5 turns on and off the analog switch 10 using image data sequentially input from an external device as a control signal, and the system controller 16 integrally controls each unit such as the image processing circuit 15.

On the optical axis of the semiconductor laser 3 of the laser device 2, as shown in FIG. 7, a reflecting surface of a polygon mirror 21 corresponding to a beam deflecting means is positioned via a collimator lens 20, and The peripheral surface of the photosensitive drum 23 serving as a latent image holding unit is located in the reflection optical path of the mirror 21 via a correction optical system 82 such as an fθ lens.

The polygon mirror 21 is rotatably supported by a scanner motor (not shown) and deflects and scans the laser beam emitted from the semiconductor laser 3 in the main scanning direction. The photosensitive drum 23 is rotatably supported by a drum driving mechanism (not shown) that is a sub-scanning unit.
The peripheral surface exposed and scanned by the laser beam relatively moves in the sub-scanning direction.

At a position in the scanning range of the polygon mirror 21 which precedes the photosensitive drum 23 in the main scanning direction, a BD (Beam Detect) sensor 24 serving as a beam detecting means is disposed. The BD sensor 24 is a polygon mirror. The laser beam deflected and scanned by 21 is detected immediately before the photosensitive drum 23 is irradiated.

The BD sensor 24 is also connected to the system controller 16 via an amplifier (not shown) or the like.
4 controls the operation of the image processing circuit 15, the APC circuit 9, and the like in accordance with the timing at which the laser beam is detected.

Although not shown and described because it has a general structure, on the peripheral surface of the photosensitive drum 23, in addition to the above-described laser scanning mechanism, a charging charger as carrying charging means, and a developing means as latent image developing means. Various devices such as a transfer device and a transfer charger serving as a toner transfer unit are also arranged to face each other. In a gap between the transfer charger and the photosensitive drum 23, a conveyance path for a printing paper as a recording medium is also formed.

The image forming apparatus 1 having the above-described structure can form an image by electrophotography. In this case, a pulse current supplied from the main body power supply 5 and the laser driver 6 to the semiconductor laser 3 of the laser device 2 is controlled by the image processing circuit 15 in accordance with image data sequentially input from a host computer or the like.

That is, in a state where the bias current is always supplied from the bias current source 7 to the semiconductor laser 3, the image processing circuit 15 controls on / off of the analog switch 10 of the pulse current source 8 in accordance with the image data. Thus, the semiconductor laser 3 emits a laser beam controlled according to the image data.

The image data is sequentially input as a large number of continuous pixel data, and each of the large number of pixel data is composed of binary data indicating the presence or absence of a dot and multi-value data indicating the diameter of the dot. When the pixel data of the image data is binary, the on / off of the analog switch 10 is controlled, and when the pixel data is multi-valued, the on time of the analog switch 10 is controlled.

The laser beam emitted by the semiconductor laser 3 in accordance with the image data is deflected in the main scanning direction by the rotating polygon mirror 21 and irradiates the peripheral surface of the photosensitive drum 23 rotating in the sub-scanning direction. Therefore, an electrostatic latent image of the main scanning line is formed here as a large number of dots continuous in the main scanning direction.

At this time, the laser beam that has been deflected and scanned immediately before the laser beam is irradiated on the polygon mirror 21.
The laser beam corresponding to the image data is emitted a predetermined time after the detection of the beam by the BD sensor 24, so that the start positions of a number of main scanning lines continuous in the sub-scanning direction are matched.

Since the laser beam needs to be detected by the BD sensor 24 prior to the image scanning, the system controller 16 and the image processing circuit need to detect the timing at which the deflection-scanned laser beam is applied to the BD sensor 24. 15 drives the semiconductor laser 3 continuously.

The semiconductor laser 3 is continuously driven for the APC operation immediately before the laser beam is detected by the BD sensor 24, and the emitted light amount is detected by the photodiode 4 and the APC circuit 9 of the laser driver 6. The bias current of the bias current source 7 is adjusted.

In the image forming apparatus 1 described above, a pulse current controlled in accordance with image data is appropriately supplied to the semiconductor laser 3 while a bias current is constantly supplied. An image can be formed at a high speed by driving with a high response.

In order to improve the response of the semiconductor laser 3 satisfactorily, the bias current must
It is preferable to set a current value close to the threshold value of D light emission.
For example, in the semiconductor laser 3 as described above, if the rated current is 5.0 (mW), the output is 3.0 (mW), the operating current is 35 (mA), and the threshold current is 20 (mA), the bias current is 15 (mA). ) Is appropriate.

[0029]

In the above-described image forming apparatus 1, the responsiveness of the semiconductor laser 3 is controlled by appropriately supplying a pulse current controlled in accordance with image data to the semiconductor laser 3 which constantly supplies a bias current. To speed up image formation.

The responsiveness of the semiconductor laser 3 is improved as the bias current is closer to the threshold of LD (Laser Diode) emission. However, when the bias current is closer to the threshold of LD emission, the semiconductor laser 3 always emits LED. .

In this case, since the semiconductor laser emits a very small amount of light until a dot is not formed in the image due to the bias current, black or gray stripes or blur occur in an originally white portion of the image, and Quality may degrade. Further, fatigue of the photosensitive drum 23 and the semiconductor laser 3 progresses, so that the durability of these components is reduced.

For example, as described above, a bias current of 15 (mA) is applied to the semiconductor laser 3 having a threshold current of 20 (mA) and an operating current of 35 (mA).
(mA), the ratio of the bias current to the operating current is 43 (%). Here, when the component life of the semiconductor laser 3 when the bias current is set variously is converted into the number of printable sheets of the image forming apparatus 1, the following table 1 is obtained.

[0033]

[Table 1] In Table 1 above, various conditions are set using the bias current of the semiconductor laser 3 and the ratio of the black region in the printed image as parameters, and the number of sheets that can be output when the bias current is 0 (mA) is set.
The output possible number under various conditions is calculated as 1.0.
Here, the laser life consumed in the APC adjustment is ignored.

When forming a character-centered binary image,
The ratio of the black region is generally 5 to 10 (%), and when a gradation image such as a photograph is formed, the ratio of the black region is 20%.
~ 25 (%) is common. Therefore, referring to Table 1 above, when the black ratio is 5%, the component life of the semiconductor laser 3 when the bias current is 15 (mA) is about sufficient compared to when the bias current is 0 (mA). It is one of

An image forming apparatus for solving the above-mentioned problems is disclosed in Japanese Patent Publication No. 7-64089 or Japanese Patent Laid-Open No. 9-8305.
No. 0 has been proposed. For example, 7-6
In the image forming apparatus disclosed in Japanese Patent No. 4089, the bias current of the semiconductor laser is stopped when the photosensitive drum is stopped.

However, even if the bias current of the semiconductor laser is stopped only when the photosensitive drum is stopped, the time for stopping the bias current is not sufficient, and it is difficult to extend the life of the semiconductor laser satisfactorily.

In the image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 9-83050, the drive signal of the semiconductor laser is delayed by a predetermined time, and the bias current is applied to the semiconductor laser by the sum of the drive signal and the delay signal. By supplying
A bias current is supplied to the semiconductor laser only for a delay time immediately before beam emission.

However, current image forming apparatuses are required to form a high-density image at a high speed, and may form a gradation image in dot units. In such a case, since it is necessary to perform high-speed data processing on a large amount of image data, it is actually difficult to accurately manage and execute the above-described signal delay processing and logical operation.

The present invention has been made in view of the above-described problems, and a single laser monitor means accurately detects the emission light amounts of a plurality of laser emission means to which a pulse current and a bias current are supplied. It is an object of the present invention to provide a laser driving method and apparatus that can perform correction, and an image forming apparatus that can form an image with high quality.

[0040]

According to a first aspect of the present invention, there is provided a laser driving method, wherein a bias current supplied to a laser emitting means is constantly generated, and a pulse current controlled in response to a sequentially input control signal is provided. And a laser driving method for supplying the pulse current to the laser emitting means to which the bias current is supplied to emit a laser beam, wherein the laser emitting means responds to a sequentially input control signal. The presence or absence of beam emission is determined, and if it is determined that there is no beam emission, the supply of the bias current to the laser emitting means is stopped at the corresponding timing.

Therefore, according to the laser driving method of the present invention, basically, a pulse current is appropriately supplied to a laser emitting means to which a bias current is constantly supplied in accordance with a control signal to emit a laser beam. However, the presence / absence of beam emission of the laser emitting means is determined in response to the sequentially input control signal, and if it is determined that no beam is emitted, the supply of the bias current to the laser emitting means is stopped at the corresponding timing. Therefore, at the timing when the laser beam is not emitted, no bias current is supplied to the laser emitting means.

According to a second aspect of the present invention, there is provided a laser driving device comprising:
Signal input means for sequentially inputting control signals, pulse supply means for appropriately generating a pulse current controlled in response to the control signals sequentially input to the signal input means, and bias supply means for constantly generating a bias current A laser emitting unit for emitting a laser beam corresponding to a pulse current and a bias current supplied from the pulse supplying unit and the bias supplying unit; and a laser emitting unit corresponding to a control signal sequentially input to the signal input unit. An emission determining means for determining the presence or absence of beam emission by the laser emitting means; and stopping supply of a bias current from the bias supply means to the laser emitting means at a corresponding timing when the emission determining means determines no emission. Current control means.

Therefore, in the laser driving apparatus of the present invention, the pulse supply means appropriately generates a pulse current controlled in response to the control signal sequentially input to the signal input means, and the bias supply means constantly generates the bias current. Therefore, the laser emitting means emits a laser beam corresponding to the pulse current and the bias current. However, the presence / absence of beam emission of the laser emitting means is determined by the emission determining means in response to the control signal sequentially input to the signal input means, and if no emission is determined by this, the bias is determined by the current control means at the corresponding timing. Since the supply of the bias current from the supply unit to the laser emitting unit is stopped, the bias current is not supplied to the laser emitting unit at a timing when the laser beam is not emitted.

According to a third aspect of the present invention, there is provided the laser driving device according to the second aspect, wherein the signal input means includes a plurality of continuous light sources each having at least the presence or absence of beam emission by the laser emission means. A control signal is sequentially input as control data, and the emission determination unit determines the presence or absence of beam emission of the laser emission unit based on the Nth control data of the control signal from the Nth control data, and the current control unit includes: When the emission determination means determines that there is no emission in the N-th control data, supply of a bias current from the bias supply means to the laser emission means at a laser beam emission control timing corresponding to the N-th control data. To stop.

Therefore, when a control signal is sequentially input to the signal input means as a large number of continuous control data in which at least the presence or absence of beam emission by the laser emission means is individually set, the control signal is determined by the Nth control data. The presence / absence of beam emission by the laser emitting means is determined by the emission determining means from the Nth control data. If it is determined that there is no emission in the N-th control data, the current control means
Since the supply of the bias current from the bias supply unit to the laser emission unit is stopped at the timing of the emission control of the laser beam corresponding to the control data, the laser emission unit does not emit the laser beam at the timing of the N-th control data that does not emit the laser beam. Is not supplied with bias current.

According to a fourth aspect of the present invention, in the laser driving apparatus according to the third aspect, the emission determination means determines whether or not the laser emission means emits a beam based on the Nth control data of the control signal. When judging from the control data of
Whether the beam is emitted by the (N + 1) th control data
Judging from the (N + 1) th control data, the current control means determines that there is emission in the (N + 1) th control data even if the emission determination means determines no emission in the Nth control data. Then, the supply of the bias current from the bias supply unit to the laser emission unit is not stopped even at the emission control timing of the laser beam corresponding to the N-th control data.

Accordingly, when the presence / absence of beam emission of the laser emitting means based on the Nth control data of the control signal is determined from the Nth control data by the emission determining means, (N +
1) The presence / absence of beam emission by the control data is also (N +
It is determined from the 1) th control data. Even if it is determined that there is no emission in the Nth control data, if it is determined that there is emission in the (N + 1) th control data, the current control means controls the emission of the laser beam corresponding to the Nth control data. At this timing, the supply of the bias current from the bias supply unit to the laser emission unit is not stopped. That is, when the laser beam is not emitted at the (N + 1) -th timing but emitted at the (N + 1) -th timing of the control data, the bias current is supplied from the N-th timing preceding the (N + 1) -th timing. Even if the response of the supply unit or the laser emission unit is not good
The (N + 1) -th laser beam is emitted satisfactorily.

According to a fifth aspect of the present invention, in the laser driving apparatus according to the third aspect, the emission determining means determines whether or not the laser emission means emits a beam based on the Nth control data of the control signal. When judging from the control data of
Whether the beam is emitted by the (N + a) th control data
Judging from the (N + a) th control data, the current control means determines that there is emission in the (N + a) th control data even if the emission determination means determines no emission in the Nth control data. Then, the supply of the bias current from the bias supply unit to the laser emission unit is not stopped at the laser beam emission control timing corresponding to the Nth to (N + a) th control data.

Accordingly, when the presence / absence of beam emission of the laser emitting means based on the Nth control data of the control signal is determined from the Nth control data by the emission determining means, (N +
The presence / absence of beam emission by the (a) th control data is also (N +
It is determined from the a) th control data. Thus, even if it is determined that there is no emission in the Nth control data, if it is determined that there is emission in the (N + a) th control data, the current control means starts the timing corresponding to the Nth control data.
Until the timing corresponding to the (N + a) th control data,
The supply of the bias current from the bias supply unit to the laser emission unit is not stopped. That is, when the laser beam is not emitted at the (N + a) -th timing but emitted at the (N + a) -th timing of the control data, the bias current is continuously supplied from the N-th timing preceding the (N + a) -th timing. Therefore, even when the responsiveness of the bias supply unit or the laser emission unit is not good, the laser beam at the (N + a) -th timing is successfully emitted.

According to a sixth aspect of the present invention, there is provided an image forming method, wherein image data is sequentially supplied to a laser driving device having a laser emitting means to emit a laser beam, and the laser beam is deflected and scanned in the main scanning direction. The latent image holding unit relatively moving in the sub-scanning direction is exposed and scanned, and the electrostatic latent image formed on the latent image holding unit is developed with toner by the exposure scanning, and the developed toner is transferred to a recording medium. An image forming method in which a bias current supplied to a laser emitting unit is constantly generated, and a pulse current controlled in accordance with image data sequentially supplied to the laser driving device is appropriately adjusted. In the image forming method of generating the laser beam and supplying the pulse current to a laser emitting unit to which a bias current is supplied to emit a laser beam, the laser driving device is sequentially driven. In accordance with the supplied image data, the presence / absence of beam emission of the laser emitting means is determined, and when the absence of emission is determined, the supply of the bias current to the laser emitting means is stopped at the corresponding timing. did.

Therefore, in the laser driving method of the present invention used in the image forming method of the present invention, since the bias current is applied to the laser emitting means, the laser beam controlled in accordance with the image data is good. It is emitted with an appropriate response. However, the presence or absence of the beam emission is determined from the image data, and the bias current is not supplied to the laser emission unit at the timing when the laser beam is not emitted.

According to a seventh aspect of the present invention, there is provided an image forming apparatus, comprising: the laser driving device according to the second aspect; data supplying means for supplying image data as a control signal to a signal input means of the laser driving device; Beam deflecting means for deflecting and scanning a plurality of laser beams emitted by the laser driving device in the main scanning direction in response to a control signal supplied by the means, and exposing with the plurality of laser beams deflected and scanned by the beam deflecting means A latent image holding unit to be scanned, a sub-scanning unit that relatively moves the latent image holding unit in the sub-scanning direction with respect to the beam deflecting unit, and develops the latent image formed on the latent image holding unit with toner Latent image developing means, toner transfer means for transferring the toner of the latent image carrying means developed by the latent image developing means to a recording medium, and transfer to the recording medium by the toner transferring means. And comprising a toner fixing unit configured to fix the toner that is, the.

Therefore, in the image forming apparatus of the present invention, since the image data is supplied as a control signal to the signal input means of the laser driving apparatus of the present invention by the data supplying means, the laser emitting means of the laser driving apparatus is provided with the image data. And emits a laser beam controlled correspondingly. This laser beam is deflected and scanned in the main scanning direction by beam deflection means,
The latent image carrying means is exposed and scanned by the deflection-scanned laser beam, and the latent image carrying means thus exposed and scanned is relatively moved by the sub-scanning means in the sub-scanning direction with respect to the beam deflecting means. Thus, the latent image formed on the latent image carrying means is developed with the toner by the latent image developing means, and the developed toner of the latent image carrying means is transferred to the recording medium by the toner transferring means. Since the toner transferred to the recording medium is fixed by the toner fixing means, an image corresponding to the image data is formed on the recording medium by the electrophotography using the toner. In the laser driving apparatus of the present invention used in the image forming apparatus of the present invention, since a bias current is applied to the laser emitting means, a laser beam controlled according to image data is emitted with good responsiveness. Is done. However, the presence or absence of the beam emission is determined from the image data, and the bias current is not supplied to the laser emission unit at the timing when the laser beam is not emitted.

According to an eighth aspect of the present invention, in the image forming apparatus according to the seventh aspect, the data supply means supplies a large number of continuous pixel data as image data to the laser driving device, and The emission determination unit of the device determines whether or not the laser emission unit emits a beam based on the Nth pixel data of the image data from the Nth pixel data,
The current control means of the laser driving device, when the emission determination means determines that there is no emission at the N-th pixel data, at the timing of emission control of the laser beam corresponding to the N-th pixel data, from the bias supply means. The supply of the bias current to the laser emitting means is stopped.

Therefore, when a large number of continuous pixel data are supplied as image data to the laser driving device by the data supply means, the presence / absence of beam emission of the laser emission means by the Nth pixel data of the image data is determined by the emission determination means. From the N-th pixel data. When it is determined that there is no emission in the Nth pixel data, the bias control unit supplies the bias current from the bias supply unit to the laser emission unit at the timing of the emission control of the laser beam corresponding to the Nth pixel data. Since the laser beam is stopped, no bias current is supplied to the laser emitting unit at the timing of the N-th pixel data at which no laser beam is emitted.

According to a ninth aspect of the present invention, in the image forming apparatus according to the eighth aspect, the emission determining means of the laser driving device determines whether or not the laser emission means emits a beam based on the Nth pixel data of the image data. When the presence / absence is determined from the Nth pixel data, the presence / absence of beam emission by the (N + 1) th pixel data is also determined from the (N + 1) th pixel data,
The current control means of the laser driving device is configured such that, even if the emission determination means determines that there is no emission at the Nth pixel data, if it is determined that there is emission at the (N + 1) th pixel data, the Nth pixel data The supply of the bias current from the bias supply unit to the laser emission unit is not stopped even at the laser beam emission control timing corresponding to the above.

Accordingly, when the presence / absence of beam emission of the laser emitting means based on the Nth pixel data of the image data is determined from the Nth pixel data by the emission determining means, (N
The presence or absence of beam emission based on the (+1) th pixel data is also (N +
It is determined from the 1) th pixel data. Even if it is determined that there is no emission in the Nth pixel data, if it is determined that there is emission in the (N + 1) th pixel data, the emission control of the laser beam corresponding to the Nth pixel data is performed by the current control means. At this timing, the supply of the bias current from the bias supply unit to the laser emission unit is not stopped. That is, when the laser beam is not emitted at the (N + 1) -th timing but emitted at the (N + 1) -th timing of the pixel data, the bias current is supplied from the N-th timing preceding the (N + 1) -th timing. Even if the response of the supply unit or the laser emission unit is not good
The (N + 1) -th laser beam is emitted satisfactorily.

According to a tenth aspect of the present invention, in the image forming apparatus according to the eighth aspect, the emission determining means of the laser driving device determines whether or not the laser emission means emits a beam based on the Nth pixel data of the image data. When the presence / absence is determined from the Nth pixel data, the presence / absence of the beam emission based on the (N + a) th pixel data is also determined from the (N + a) th pixel data. Even if it is determined that there is no emission in the Nth pixel data, the emission control of the laser beam corresponding to the Nth to (N + a) th pixel data is determined if it is determined that there is emission in the (N + a) th pixel data. At this timing, the supply of the bias current from the bias supply unit to the laser emission unit is not stopped.

Accordingly, when the presence / absence of beam emission of the laser emitting means based on the Nth pixel data of the image data is determined from the Nth pixel data by the emission determining means, (N
The presence or absence of beam emission based on the (+ a) th pixel data is also (N +
The determination is made from the a) -th pixel data. Thus, even if it is determined that there is no emission in the N-th pixel data, if it is determined that there is emission in the (N + a) -th pixel data, the current control means starts the timing corresponding to the N-th pixel data.
Until the timing corresponding to the (N + a) th pixel data,
The supply of the bias current from the bias supply unit to the laser emission unit is not stopped. That is, when the laser beam is not emitted at the Nth timing of the pixel data but emitted at the (N + a) th timing, the bias current is continuously supplied from the Nth timing preceding the (N + a) th timing. Therefore, even when the responsiveness of the bias supply unit or the laser emission unit is not good, the laser beam at the (N + a) -th timing is successfully emitted.

The various means referred to in the present invention only need to be formed so as to realize their functions. For example, dedicated hardware, a computer provided with a proper function by a program, a computer with a proper program , The functions realized inside, and the combination thereof are allowed.

[0061]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. In the present embodiment, the same parts as those in the above-described conventional example are denoted by the same names, and detailed description is omitted.

FIG. 1 is a block diagram showing a laser driving apparatus according to the present embodiment, FIG. 2 is a schematic vertical sectional side view showing a laser printer which is an image forming apparatus according to the present embodiment, and FIG. FIG. 4 is a circuit diagram showing a current control circuit serving as current control means, and FIG. 4 is a time chart showing a relative relationship between various signals.

In this embodiment, as shown in FIG. 2, a laser driving device 30 is provided as a part of a laser printer 31 which is an image forming device. The laser printer 31 includes a scanner motor 32, and the scanner motor 32 rotatably supports the polygon mirror 33 in the main scanning direction.

The polygon mirror 33 is arranged on the optical axis of the semiconductor laser 34 of the laser driving device 30, and the laser beam emitted from the semiconductor laser 34 is subjected to main scanning by the polygon mirror 33 which is rotationally driven by the scanner motor 32. Since the beam is deflected in the scanning direction, a beam deflecting unit is formed here.

The fθ lens 35 and the reflection mirror 36 are sequentially arranged on the scanning optical path of the laser beam deflected and scanned as described above, and the reflection optical path of the reflection mirror 36 includes a latent image holding means. Of the photosensitive drum 37 are opposed to each other. The photosensitive drum 37 is rotatably supported by a drum driving mechanism (not shown) serving as a sub-scanning means. The photosensitive drum 37 is driven to rotate by the drum driving mechanism, and the peripheral surface moves in the sub-scanning direction. I do.

On the peripheral surface of the photosensitive drum 37, a charging charger 38, a developing device 39 serving as a latent image developing means, a transfer roller 40 serving as a toner transferring means, and the like are arranged in this order in opposition. It faces the peripheral surface of the photosensitive drum 37 from the gap between the charging charger 38 and the developing device 39.

The charging charger 38 charges the peripheral surface of the photosensitive drum 37 rotating in the sub-scanning direction by corona discharge.
Exposure and scanning are performed by the main scanning light reflected at 6 to form an electrostatic latent image. The developing device 39 develops the electrostatic latent image formed on the photosensitive drum 37 with toner, and the transfer roller 40 applies the toner on the photosensitive drum 37 developed by the developing device 39 to a printing paper P as a recording medium by a potential difference. Transcribe.

In the laser printer 31 of the present embodiment, a transport path 41 for the printing paper P is formed inside, and a paper feed tray 42 and a paper discharge tray 43 are arranged at both ends of the transport path 41. Printing paper P continuous from the paper feed tray 42
Is passed through a gap between the photosensitive drum 37 and the transfer roller 40, and a fixing device 44 serving as a toner fixing unit.
, And communicates with the paper discharge tray 43. The printing paper P is sequentially fed along a transport path 41 from a paper feeding tray 42 to a paper discharging tray 43, and the fixing device 44 transfers the toner transferred from the photosensitive drum 37 to the printing paper P by the transfer roller 40 as described above. Heat and press to fix.

The laser printer 31 according to the present embodiment
Has a communication interface 45, and the printer controller 46 connected to the communication interface 45 controls the laser driving device 30 and the scanner motor 32.
And so on. The communication interface 45
A personal computer, a word processor, and the like are detachably connected by a connection connector (not shown), and image data is supplied from these. Printer controller 46
Controls the operation of the laser driving device 30 according to the image data, and synchronizes this operation with the rotation of the scanner motor 32.

The laser driving device 30 which is a part of the laser printer 31 having the above-described structure, as shown in FIG.
The laser device 50 is provided with a semiconductor laser 34 as a laser emitting unit and a photodiode 51 as a laser monitoring unit.

A laser power source 52 and a laser driver 53 are connected to the laser device 50. The laser driver 53 includes a pulse driver 54 corresponding to pulse supply means and a bias current source 55 as bias supply means.
And an APC circuit 56 as current adjusting means.

The pulse driver 54 and the bias current source 55 are connected in parallel to one semiconductor laser 34 in the same manner as in the case of the laser driver 1 described above as a conventional example. In contrast, both the pulse driver 54 and the bias current source 55
They are connected to the semiconductor laser 34 via high-speed analog switches 57 and 58 such as MOSs, respectively.

The pulse driver 54 is composed of a pulse current source and a serial / parallel converter, converts image data externally input in parallel to serial by a serial / parallel converter, and converts the analog data into an analog switch 5 corresponding to the image data.
At 7, the connection between the pulse current source and the semiconductor laser 34 is turned on / off.

The APC circuit 56 includes a photodiode 51
And a pulse driver 54, and APC adjusts the pulse current of the pulse driver 54 according to the detection result of the photodiode 51.

Analog switch 5 of pulse driver 54
A current control circuit 59 is connected to 7, 58, and the current control circuit 59 functions as various units such as a data supply unit, a signal input unit, an emission determination unit, and a current control unit.

That is, the current control circuit 59 sequentially converts the image data composed of a large number of continuous pixel data as control signals composed of a large number of continuous control data in which the presence / absence of beam emission by the semiconductor laser 34 is individually set. Since they are input, they function as data supply means and signal input means from this viewpoint.

More specifically, in the laser driving device 30 of the present embodiment, since image data is input in parallel to the current control circuit 59 every four bits, as shown in FIG. It has four data input terminals 61 to 64 and one clock input terminal 65 as supply means and signal input means.

The four data input terminals 61 to 64 are individually connected to four data output terminals 74 to 77 via two D-type FF (Flip Flop) circuits 66 to 73, respectively. The data output terminals 74 to 77 are connected to the pulse driver 54 described above.

Further, the data output terminals of the FF circuits 66 to 73 are commonly connected to eight data input terminals of one OR gate 78 corresponding to emission determination means and current control means. Output terminal 7
9 is connected to the analog switch 58 described above.

For this reason, in the laser driving device 30 of the present embodiment, whether the semiconductor laser 34 emits a beam based on the Nth and (N + 1) th pixel data of the image data depends on the Nth and (N + 1) th pixel data. It is determined by the OR gate 78 from the data.

Only when the beam emission of the semiconductor laser 34 is not set for both the Nth and (N + 1) th pixel data, the timing at which the semiconductor laser 34 emits the beam corresponding to the Nth pixel data , The analog switch 58 is turned off. Otherwise, the analog switch 58 is turned on at the timing when the semiconductor laser 34 emits a beam corresponding to the Nth pixel data.

That is, when the semiconductor laser 34 does not emit a laser beam in both the Nth and (N + 1) th pixel data, the semiconductor laser 34 emits a beam corresponding to the Nth pixel data. A bias current is supplied. At this time, the presence or absence of the supply of the bias current at the (N + 1) -th timing also depends on the setting of the (N + 2) -th pixel data at the next stage. A bias current is supplied to the semiconductor laser 34 even at a timing corresponding to the pixel data.

In the above-described configuration, the laser printer 31 of the present embodiment uses the laser beam emitted from the semiconductor
An electrostatic latent image is formed on the printing paper P, and the image is formed by developing the electrostatic latent image with toner and transferring it to the printing paper P.

More specifically, in the laser printer 31 of this embodiment, an electronic device such as a personal computer is connected to the communication interface 45, and image data externally input here is transferred to the printer controller 46. Since the printer controller 46 controls the operation of the laser driving device 30 according to the image data, the laser beam emitted from the semiconductor laser 34 by the laser driving device 30 is modulated according to the image data.

At the same time, the printer controller 46 controls the rotational driving of the polygon mirror 33 by the scanner motor 32, so that the laser beam emitted from the semiconductor laser 34 by the laser driving device 30 is deflected by the polygon mirror 33 in the main scanning direction. Is done. The laser beam that has been deflected and scanned is optically corrected by the fθ lens 35, is reflected by the reflection mirror 36, and is irradiated on the peripheral surface of the rotating photosensitive drum 37 that moves in the sub-scanning direction.

Since the peripheral surface of the photosensitive drum 37 is charged in advance by corona discharge of the charging charger 38, the photosensitive drum 37 is exposed and scanned by a laser beam to form an electrostatic latent image. The electrostatic latent image formed on the peripheral surface of the photosensitive drum 37 is developed with the toner supplied from the developing device 39, and is transferred onto the printing paper P fed from the paper feed tray 42 through the transport path 41 by the transfer roller 40. Transcribed.

The printing paper P on which the toner has been transferred is fed to the fixing device 44 through the transport path 41, where it is heated and pressed to fix the toner. The printing paper P on which the toner has been fixed in this way is fed through the transport path 41 and discharged to the paper discharge tray 43. Thus, the image formation by the laser printer 31 is completed.

The laser driving device 30 according to the present embodiment generates a pulse current supplied from the main body power supply 52 and the laser driver 53 to the semiconductor laser 34 of the laser device 50 when forming an image by electrophotography as described above. Is controlled in accordance with image data sequentially input from a host computer or the like.

That is, when the bias current is supplied from the bias current source 55 to the semiconductor laser 34, the pulse driver 54
7, the semiconductor laser 34 emits a laser beam controlled according to the image data.

However, the laser driving device 3 of the present embodiment
At 0, the bias current is not always supplied to the semiconductor laser 34, and the presence or absence of the supply is controlled in accordance with the sequentially input image data. However, unlike the control of the pulse current, the control of the bias current also corresponds to the immediately preceding one pixel data. Therefore, when the semiconductor laser 34 emits a laser beam, the bias current is supplied in advance. The pulse current is supplied in the state.

For example, as shown in FIG. 4, when (N−2) th to (N + 1) th pixel data DV are sequentially input as image data, “DV (N−2) = DV (N− 1)
= DV (N + 1) = 0H, DV (N) = XXH ", and N
It is assumed that the beam emission for the XX time is set only for the pixel data of the th.

In this case, the pixel data DV as described above
Are input in parallel to the current control circuit 59 by four bits and sequentially latched by the two-stage FF circuits 66 to 73, and the pixel data DV thus latched every two clocks is sequentially input to the OR gate 78. For example, OR gate 78
DV (N−2) and DV (N−1) are input from time t0 to t1. Since both of them are 0H, time t0 to t1
The output B of the OR gate 78 is also "0". This is D
At this timing, the analog switch 58 is turned off and the bias current Ib is not supplied to the semiconductor laser 34 because it is synchronized with the timing at which the beam emission of the semiconductor laser 34 is controlled in accordance with V (N−2).

However, at time t1 to t2, DV (N-1)
And DV (N) are input to the OR gate 78, and since the DV (N) is not 0H, the output B of the OR gate 78 is also "1" between times t1 and t2. Since this is synchronized with the timing at which the beam emission of the semiconductor laser 34 is controlled in accordance with DV (N-1), the semiconductor laser 34 does not emit a laser beam in accordance with DV (N-1) at this timing. However, the analog switch 58 is turned on and the bias current I
b is supplied.

At time t2, DV (N) and DV (N)
(N + 1) is input to the OR gate 78, and DV (N) becomes 0
Since it is not H, the output B of the OR gate 78 is "1" even at the time t2. This is synchronized with the timing at which the beam emission of the semiconductor laser 34 is controlled in accordance with DV (N). At this timing, the semiconductor laser 34 supplies the pulse currents Id and DV ( The laser beam is emitted by the bias current Ib continuously supplied from the timing of N-1).

The laser printer 31 of the present embodiment
Since the image is expressed in gradation by modulating the emission time of the laser beam in dot units by the 4-bit pixel data, the parallel pixel data DV (N) is used in the above-mentioned times t2 to t6.
Is converted to serial to control the supply time of the pulse current Id.

In the laser driving device 30 of the present embodiment,
As described above, at the timing when the semiconductor laser 34 does not emit a laser beam, no bias current is supplied to the semiconductor laser 34, so that LED emission due to the bias current of the semiconductor laser 34 can be prevented, and the life of components can be improved. It is also possible to prevent a decrease in image quality in which black or gray stripes or blur occur in a white portion of the image.

Even when the semiconductor laser 34 does not emit a laser beam, if a laser beam is emitted immediately thereafter, a bias current is supplied to the semiconductor laser 34, so that the responsiveness of the semiconductor laser 34 deteriorates. Therefore, a high-density image can be formed at high speed.

When the threshold current is 20 (mA) and the operating current is 35 (m
The component life when the bias current and the ratio of the black region in the printed image are variously set as parameters for the semiconductor laser 34 of FIG. Become like

[0099]

[Table 2] Referring to Table 2 above, when the black ratio is 5%, the bias current is 15 (m) compared to when the bias current is 0 (mA).
In the case (A), the component life of the semiconductor laser 34 is seven tenths. Since this is about one tenth, which is about 6.4 times that of the related art, in the laser driving device 30 of the present embodiment, the component life of the semiconductor laser 34 is improved to several times that of the related art.

The life of components of the semiconductor laser 34 in the laser printer 31 of the present embodiment is compared with that of the conventional example under various conditions with reference to Tables 1 and 2 described above. 31 indicates that the lower the ratio of the black region of the formed image, the longer the component life of the semiconductor laser 34 can be improved. That is, the laser printer 31 of the present embodiment is suitable for forming a binary image in which the ratio of the black region of the formed image is low.

The laser printer 31 according to the present embodiment
In this case, as described above, the bias current is supplied to the semiconductor laser 34 immediately before the beam is emitted.
It can be assumed that image quality is degraded by ED emission.

However, since the supply of the bias current is executed only immediately before the beam emission, it is absorbed by the responsiveness of the semiconductor laser 3, and no LED light emission occurs, so that the image quality does not deteriorate. Even if LED light emission occurs, the minute black spots formed by this will continue to the black image formed thereafter, and as a result, the deterioration of image quality will be reduced.

The present invention is not limited to the above-described embodiment, but allows various modifications without departing from the gist of the present invention. For example, in the above-described embodiment, the laser printer 31 forms a black-and-white image in which gradation is performed in dot units using 4-bit pixel data. However, it is also possible to use a binary black-and-white image as a color image. It is also possible to use

In the above embodiment, a 4-bit parallel-serial conversion is exemplified as a method of processing image data.
This is converted to an 8-bit PWM (Pulse Width Modulatio).
n) Modulation or the like is also possible. Further, in the above-described embodiment, the laser printer 31 is exemplified as the image forming apparatus. However, the image forming apparatus may be used as a printer unit of a digital copying machine or a facsimile machine.

In the above embodiment, the bias current at the beam emission timing corresponding to the N-th pixel data is set to N
The control is performed in accordance with the (N + a) th and (N + 1) th pixel data.
It is also possible to perform control in accordance with the pixel data of the th.

In this case, even if it is determined that there is no emission in the N-th pixel data, if it is determined that there is emission in the (N + a) -th pixel data, the timing corresponding to the N-th pixel data is (N + a). It is preferable to continuously supply the bias current until the timing corresponding to the pixel data.

Further, in the above embodiment, the laser driving device 30
It is illustrated that the various units are formed as dedicated hardware. However, for example, various units of the laser driving device 30 can be realized by installing and operating appropriate software on a computer. Yes,
It is also possible to realize a part by software and to form a part as hardware.

[0108]

Since the present invention is configured as described above, it has the following effects.

The laser driving method according to the first aspect of the present invention
By judging the presence or absence of beam emission of the laser emitting means in response to the sequentially input control signal, by stopping the supply of the bias current to the laser emitting means at a corresponding timing when it is determined that no emission is performed by this. At the timing when the laser beam is not emitted, no bias current is supplied to the laser emitting means, so that the component life of the laser emitting means can be improved satisfactorily.

The laser driving device according to the second aspect of the present invention
Signal input means for sequentially inputting control signals, pulse supply means for appropriately generating a pulse current controlled in response to the control signals sequentially input to the signal input means, and bias supply means for constantly generating a bias current A laser emitting unit for emitting a laser beam corresponding to a pulse current and a bias current supplied from the pulse supplying unit and the bias supplying unit; and a laser emitting unit corresponding to a control signal sequentially input to the signal input unit. An emission determining means for determining the presence or absence of beam emission by the laser emitting means; and stopping supply of a bias current from the bias supply means to the laser emitting means at a corresponding timing when the emission determining means determines no emission. And the current control means, the laser emission means at the timing when the laser beam is not emitted. Since the bias current is not supplied,
The component life of the laser emitting means can be improved satisfactorily.

According to a third aspect of the present invention, there is provided the laser driving apparatus according to the second aspect, wherein the signal input means includes a plurality of continuous light sources each of which is individually set as to whether or not a beam is emitted by the laser emitting means. A control signal is sequentially input as control data, and the emission determination unit determines the presence or absence of beam emission of the laser emission unit based on the Nth control data of the control signal from the Nth control data, and the current control unit includes: When the emission determination means determines that there is no emission in the N-th control data, supply of a bias current from the bias supply means to the laser emission means at a laser beam emission control timing corresponding to the N-th control data. When the laser beam is not emitted, no bias current is supplied to the laser emitting means. Part life of the emitting means can be satisfactorily improved.

According to a fourth aspect of the present invention, in the laser driving apparatus according to the third aspect, the emission determining means determines whether or not the laser emission means emits a beam based on the Nth control data of the control signal. When judging from the control data of
Whether the beam is emitted by the (N + 1) th control data
Judging from the (N + 1) th control data, the current control means determines that there is emission in the (N + 1) th control data even if the emission determination means determines no emission in the Nth control data. Then, by not stopping the supply of the bias current from the bias supply unit to the laser emission unit even at the emission control timing of the laser beam corresponding to the N-th control data, the laser emission unit is not emitted at the timing when the laser beam is not emitted. Since the bias current is not supplied, the component life of the laser emitting means can be improved satisfactorily, but the bias current is supplied to the laser emitting means immediately before the beam emission, so that the responsiveness of the laser emitting means decreases. In addition, it is possible to maintain the responsiveness of the laser emitting means and to improve the life of the laser emitting means.

According to a fifth aspect of the present invention, in the laser driving apparatus according to the third aspect, the emission determining means determines whether or not the laser emission means emits a beam based on the Nth control data of the control signal. When judging from the control data of
Whether the beam is emitted by the (N + a) th control data
Judging from the (N + a) th control data, the current control means determines that there is emission in the (N + a) th control data even if the emission determination means determines no emission in the Nth control data. Then, at the laser beam emission control timing corresponding to the Nth to (N + a) th control data, the supply of the bias current from the bias supply unit to the laser emission unit is not stopped, so that the laser beam is emitted. Since the bias current is not supplied to the laser emitting means at the timing when the laser emission is not performed, the life of the components of the laser emitting means can be improved satisfactorily. However, the bias current is supplied to the laser emitting means immediately before the beam is emitted. Without reducing the responsiveness of the means, it is possible to maintain both the responsiveness of the laser emitting means and improve the life. That.

According to the image forming method of the present invention, the presence or absence of the beam emission of the laser emitting means is determined in accordance with the image data sequentially supplied to the laser driving device. By stopping the supply of the bias current to the laser emitting means at the corresponding timing, the bias current is not supplied to the laser emitting means at the timing when the laser beam is not emitted, so that the component life of the laser emitting means can be improved. Can be improved.

According to a seventh aspect of the present invention, there is provided an image forming apparatus, comprising: the laser driving device according to the second aspect; data supply means for supplying image data as a control signal to a signal input means of the laser driving device; Beam deflecting means for deflecting and scanning a plurality of laser beams emitted by the laser driving device in the main scanning direction in response to a control signal supplied by the means, and exposing with the plurality of laser beams deflected and scanned by the beam deflecting means A latent image holding unit to be scanned, a sub-scanning unit that relatively moves the latent image holding unit in the sub-scanning direction with respect to the beam deflecting unit, and develops the latent image formed on the latent image holding unit with toner Latent image developing means, toner transfer means for transferring the toner of the latent image carrying means developed by the latent image developing means to a recording medium, and transfer to the recording medium by the toner transferring means. And a toner fixing means for fixing the toner thus obtained, since the bias current is not supplied to the laser emitting means at a timing when the laser beam is not emitted, it is possible to satisfactorily improve the component life of the laser emitting means. it can.

According to an eighth aspect of the present invention, in the image forming apparatus according to the seventh aspect, the data supply means supplies a large number of continuous pixel data as image data to the laser driving device, and The emission determination unit of the device determines whether or not the laser emission unit emits a beam based on the Nth pixel data of the image data from the Nth pixel data,
The current control means of the laser driving device, when the emission determination means determines that there is no emission at the N-th pixel data, at the timing of emission control of the laser beam corresponding to the N-th pixel data, from the bias supply means. By stopping the supply of the bias current to the laser emitting means, the bias current is not supplied to the laser emitting means at the timing when the laser beam is not emitted, so that the component life of the laser emitting means can be improved satisfactorily.

According to a ninth aspect of the present invention, in the image forming apparatus of the eighth aspect, the emission determining means of the laser driving device determines whether or not the laser emission means emits a beam based on the Nth pixel data of the image data. When the presence / absence is determined from the Nth pixel data, the presence / absence of beam emission by the (N + 1) th pixel data is also determined from the (N + 1) th pixel data,
The current control means of the laser driving device is configured such that, even if the emission determination means determines that there is no emission at the Nth pixel data, if it is determined that there is emission at the (N + 1) th pixel data, the Nth pixel data By not stopping the supply of the bias current from the bias supply unit to the laser emission unit at the timing of the emission control of the laser beam corresponding to the, since the bias current is not supplied to the laser emission unit at the timing when the laser beam is not emitted, The component life of the laser emitting means can be improved satisfactorily, but the bias current is supplied to the laser emitting means immediately before beam emission, so that the responsiveness of the laser emitting means does not decrease and the laser emitting means does not deteriorate. Responsiveness and improved life.

According to a tenth aspect of the present invention, in the image forming apparatus according to the eighth aspect, the emission determining means of the laser driving device determines whether or not the laser emission means emits a beam based on the Nth pixel data of the image data. When the presence / absence is determined from the Nth pixel data, the presence / absence of the beam emission based on the (N + a) th pixel data is also determined from the (N + a) th pixel data. Even if it is determined that there is no emission in the Nth pixel data, the emission control of the laser beam corresponding to the Nth to (N + a) th pixel data is determined if it is determined that there is emission in the (N + a) th pixel data. By not stopping the supply of the bias current from the bias supply unit to the laser emitting unit at the timing of Since the bias current is not supplied to the laser emitting means, the component life of the laser emitting means can be improved satisfactorily, but the bias current is supplied to the laser emitting means immediately before the beam is emitted. It is possible to maintain the responsiveness of the laser emitting means and improve the life of the laser emitting means without lowering the responsiveness.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a laser driving device according to an embodiment of the present invention.

FIG. 2 is a schematic vertical sectional side view showing a laser printer as an embodiment of the image forming apparatus of the present invention.

FIG. 3 is a circuit diagram showing a current control circuit serving as emission determination means and current control means.

FIG. 4 is a time chart showing a relative relationship between various signals.

FIG. 5 is a characteristic diagram showing a time relationship between a driving current of a semiconductor laser and beam emission.

FIG. 6 is a schematic block diagram illustrating a main part of the image forming apparatus.

FIG. 7 is a plan view illustrating an optical system of the image forming apparatus.

[Explanation of symbols]

 Reference Signs List 30 laser printer as image forming apparatus 31 laser driving device 34 polygon mirror forming beam deflecting means 37 photosensitive drum as latent image holding means 39 developing device as latent image developing means 40 transfer roller as toner transferring means 44 toner fixing Fixing unit 54, a pulse driver corresponding to a pulse supply unit 55 bias current source, a bias supply unit 59 current control circuit functioning as various units

Claims (10)

[Claims] 1. A bias current supplied to a laser emitting means is constantly generated, and a pulse current controlled in accordance with a sequentially input control signal is appropriately generated, and the pulse current is supplied as a bias current. A laser driving method for supplying a laser beam to a laser emitting unit and emitting a laser beam, wherein it is determined whether or not the laser emitting unit emits a beam in response to a sequentially input control signal, and it is determined that no beam is emitted. Stopping the supply of the bias current to the laser emitting means at a timing corresponding to the above. 2. A signal input means to which a control signal is sequentially input; a pulse supply means for appropriately generating a pulse current controlled in response to the control signal sequentially input to the signal input means; Bias supply means for generating; laser emission means for emitting a laser beam corresponding to the pulse current and the bias current supplied from the pulse supply means and the bias supply means; and a control signal sequentially input to the signal input means. Emission determination means for determining the presence or absence of beam emission of the laser emission means in response to a bias current from the bias supply means to the laser emission means at a corresponding timing when the emission determination means determines no emission. And a current control means for stopping supply of the laser. 3. A control signal is sequentially input to the signal input unit as a large number of continuous control data in which at least the presence or absence of beam emission by the laser emitting unit is individually set. The presence / absence of beam emission of the laser emitting means based on the N-th control data is determined from the N-th control data, and the current control means determines that there is no emission in the N-th control data by the emission determining means. 3. The laser driving device according to claim 2, wherein the supply of the bias current from the bias supply unit to the laser emission unit is stopped at a timing of the emission control of the laser beam corresponding to the Nth control data. 4. The emission determining means (N + 1) when determining the presence or absence of beam emission of the laser emitting means based on the N-th control data of the control signal from the N-th control data.
The presence / absence of beam emission based on the Nth control data is also determined from the (N + 1) th control data, and the current control means determines whether or not there is no emission in the Nth control data by the emission determination means. 4. The supply of the bias current from the bias supply unit to the laser emission unit is not stopped at the laser beam emission control timing corresponding to the N-th control data when it is determined that the emission is performed in the control data. Laser drive device. 5. The emission determining means determines whether or not a beam is emitted from the laser emitting means based on the Nth control data of the control signal from the Nth control data.
a: a is an integer of 2 or more). The presence or absence of beam emission based on the (n) th control data is also determined from the (N + a) th control data, and the current control means does not emit the Nth control data by the emission determination means. Is determined, if it is determined that there is emission at the (N + a) th control data, the Nth to (N)
4. The laser driving device according to claim 3, wherein the supply of the bias current from the bias supply unit to the laser emission unit is not stopped at the timing of the emission control of the laser beam corresponding to the + a) th control data. 6. A latent image carrier which sequentially supplies image data to a laser driving device having a laser emitting means to emit a laser beam, deflects and scans the laser beam in a main scanning direction, and relatively moves in a sub-scanning direction. An image forming method in which an electrostatic latent image formed on the latent image holding means is developed with toner by this exposure scanning, and the developed toner is transferred to a recording medium and then fixed. Wherein a bias current supplied to the laser emitting means is constantly generated, and a pulse current controlled in accordance with image data sequentially supplied to the laser driving device is appropriately generated. In an image forming method for supplying a laser beam to a supplied laser emitting unit and emitting a laser beam, the image forming method may be configured to correspond to image data sequentially supplied to the laser driving device. Determines the presence of the beam emission of the laser emitting unit, this image forming method so as to stop the supply of the bias current with no emission is determined to the laser emitting means at the corresponding timing. 7. A laser driver according to claim 2, data supply means for supplying image data as a control signal to a signal input means of said laser drive, and a control signal supplied by said data supply means. Beam deflecting means for deflecting and scanning a plurality of laser beams emitted by the laser driving device in the main scanning direction; latent image carrying means for exposure and scanning with the plurality of laser beams deflected and scanned by the beam deflecting means; Sub-scanning means for relatively moving the latent image carrying means in the sub-scanning direction with respect to the beam deflecting means; latent image developing means for developing a latent image formed on the latent image carrying means with toner; Toner transfer means for transferring the toner of the latent image holding means developed by the means to a recording medium, and toner for fixing the toner transferred to the recording medium by the toner transfer means Comprising a fixing unit, the in which the image forming apparatus. 8. The data supply means supplies a large number of continuous pixel data as image data to the laser drive device, and the emission determination means of the laser drive device outputs the laser based on Nth pixel data of the image data. The presence / absence of beam emission of the emission unit is determined from the N-th pixel data. The current control unit of the laser driving device determines that the emission determination unit determines that the emission is not performed with the N-th pixel data. 8. The supply of a bias current from said bias supply means to said laser emission means at the timing of laser beam emission control corresponding to data.
The image forming apparatus as described in the above. 9. An emission determination unit of the laser driving device,
When judging the presence or absence of the beam emission of the laser emitting means by the Nth pixel data of the image data from the Nth pixel data, the presence or absence of the beam emission by the (N + 1) th pixel data is also determined from the (N + 1) th pixel data. The current control means of the laser drive device determines that the emission determination means determines that there is no emission in the (N + 1) th pixel data even if the emission determination means determines that there is no emission in the (N + 1) th pixel data. 9. The image forming apparatus according to claim 8, wherein the supply of the bias current from the bias supply unit to the laser emission unit is not stopped even at the timing of the emission control of the laser beam corresponding to the pixel data. 10. The (N + a) -th pixel when determining from the N-th pixel data whether or not the laser-emitting unit emits a beam based on the N-th pixel data of the image data. The presence / absence of beam emission based on the data is also determined from the (N + a) -th pixel data, and the current control means of the laser driving device determines that the emission determination means determines no emission at the N-th pixel data (N + a). When it is determined that there is emission in the pixel data of the N-th to (N + a) -th pixel data, the timing of the emission control of the laser beam corresponding to the N-th to (N + a) -th pixel data is set to 9. The image forming apparatus according to claim 8, wherein the supply is not stopped.