JPH06227037A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain an image forming device capable of preventing deterioration of an image with the same writing width in a main scanning direction on a photosensitive surface by modulating LDs by separate video clock signals corresponding to the respective LDs. CONSTITUTION:In an image forming device, a plurality of laser beams emitted from a semiconductor laser array 1 (LD array) consisting of a plurality of semiconductor lasers 1a, 1b (LDs) are scanned by the same polygon mirror to be emitted on the surface of a photosensitive body through a lens optical system, whereby a latent image of a plurality of lines is simultaneously formed on the surface of the photosensitive body. This image forming device is provided with LD modulation means 12a, 12b for modulating the LDs by independently transmitting video clock signals BK1, BK2 to the respective LDs 1a, 1b of the LD array 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming an image on a surface of a photoconductor by scanning a laser beam with an optical system using an LD array in the fields of copying machines, FAX and the like.

[0002]

2. Description of the Related Art As a conventional image forming apparatus, a laser scanning apparatus will be described as an example with reference to FIG. A semiconductor laser array (LD array) 1 is composed of two semiconductor lasers 1a and 1b (LD). The laser beams a and b emitted from the individual LDs 1a and 1b are collimated by the collimator lens 2, and the collimated light linearly enters the polygon mirror 4 through the cylindrical lens 3 and is deflected. This polygon mirror 4
Is rotated by the motor 5. Then, the deflected laser beams a and b pass through the fθ lens 6 and are reflected by the mirrors 7 and 8 and the photoconductor 1 through the dustproof glass 9.
The surface 0 is scanned in the X direction (main scanning direction). The photoconductor 10 rotates in the Y direction (sub scanning direction). In addition,
The dustproof glass 9 is provided for dust such as toner to enter the optical system.

In such an optical system, in order to prevent the deviation of each line in the main scanning direction when the light is deflected by the polygon mirror 4 and written on the surface of the photoconductor 10, the synchronous detector 1
1 detects a part of the laser beams a and b to obtain a synchronization detection signal (DETP signal). By using the DETP signal as a reference, the phases of the video clock signals for modulating the LDs 1a and 1b are matched, whereby the polygon mirror 4
It is possible to write from substantially the same position of the photoconductor 10 in the main scanning direction X with respect to the deflection.

[0004]

In the conventional device as described above, the writing position on the surface of the photoconductor 10 is controlled by using the DETP signal, but the LDs 1a and 1b are controlled.
Are both modulated and driven by the same video clock signal (same frequency). By modulating with the same video clock signal in this way, the following problems occur. That is, each LD 1a, 1 of the LD array 1
The wavelengths of the laser beams a and b emitted from b are not completely the same but different from each other. When the wavelengths of the emitted laser beams a and b are different, the refractive index of the lens is different. In the scanning optical system of FIG. 11, when the wavelengths of the laser beams a and b are different, the laser beams a and b after being reflected by the polygon mirror 4 at the same angle are the photosensitive members 1.
The irradiation position on the 0 plane differs in the main scanning direction X due to the difference in the refractive index. This allows these two LD1s
The writing width in the main scanning direction on the surface of the photoconductor 10 is different between a and 1b, and the dot formation position by the beam is displaced in the main scanning direction on the end end side in the main scanning direction.
There is a problem of deteriorating the image formed on the surface.

[0005]

According to a first aspect of the invention, a plurality of laser beams emitted from a semiconductor laser array (LD array) including a plurality of semiconductor lasers (LD) are scanned by the same polygon mirror. Then, by irradiating the surface of the photoconductor with the plurality of laser beams through the lens optical system, in an image forming apparatus configured to simultaneously form latent images of a plurality of lines on the surface of the photoconductor, LD modulation means for independently sending a video clock signal to the individual LDs of the LD array to perform modulation is provided.

According to a second aspect of the invention, in the first aspect of the invention, there is provided video clock frequency varying means for varying the frequency of at least one video clock signal of the video clock signals of the LD modulating means for modulating the LD. Provided.

According to a third aspect of the invention, in the invention according to the first aspect, at least one L of the LD arrays is L.
A phase detection means is provided for D to synchronize with the rotation of the polygon mirror, and a phase synchronization means for generating an independent synchronization clock signal for all LDs based on the synchronization detection signal from this synchronization detection mechanism. Was set up.

According to a fourth aspect of the present invention, in the first and second aspects of the present invention, a synchronization detection mechanism for synchronizing the rotation of the polygon mirror with at least one LD in the LD array is provided. Phase synchronization means for generating an independent synchronization clock signal for all LDs based on the synchronization detection signal issued from the synchronization detection mechanism is provided, and the timing for generating the synchronization detection signal and the synchronization clock signal is variable. The possible synchronization timing variable means is provided.

According to the invention of claim 5, claims 1, 2,
In the inventions of 3 and 4, the beam power magnification adjusting means for uniformly setting the beam power of the laser beam emitted from each LD of the LD array onto the surface of the photoconductor is provided.

[0010]

According to the first aspect of the present invention, since the LD modulation means is provided, each LD is modulated by an independent video clock signal. Therefore, the laser beam of each LD causes the main scanning direction on the surface of the photosensitive member. The writing width can be made equal.

According to the second aspect of the present invention, by providing the video clock frequency changing means, the video clock signal for modulating each LD is changed so that the writing widths in the main scanning direction on the photoconductor surface are all made equal. Is possible.

According to the third aspect of the present invention, since the phase synchronization means is provided, even if a separate video clock signal is used for each LD, the timing is set by the synchronization clock signal based on the synchronization detection signal. It is possible to form an image in which the writing positions in the main scanning direction are always aligned on the body surface.

According to the fourth aspect of the present invention, by providing the synchronization timing varying means, even if the magnification is changed by adjusting the video clock frequency of each LD, the writing in the main scanning direction on the photoconductor surface is started. It is possible to finely adjust the position.

According to the fifth aspect of the present invention, since the beam power magnification adjusting means is provided, the video clock frequency of each LD becomes different, and the beam power on the photoconductor surface is different even if the light energy amount per dot is different. It is possible to suppress density unevenness because all of the above are aligned.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the invention described in claim 1 will be described with reference to FIGS. Since the entire configuration of the image forming apparatus has been described in the related art (see FIG. 10), the description of the same parts will be omitted and the same reference numerals will be used for the same parts.

In this embodiment, in the image forming apparatus as shown in FIG. 2, the individual LDs 1 constituting the LD array 1 are
LD modulation circuits 12a and 12b as LD modulation means for independently sending video clock signals to a and 1b for modulation.
Is provided. FIG. 1 shows a connection state in the internal circuit thereof. The LD modulation circuit 12a is a first crystal oscillator 13a, and the LD modulation circuit 12b is a second crystal oscillator 1a.
3b, respectively. Further, the LD modulation circuits 12a and 12b are connected to the image processing unit 14 and image data is input.

The operation of modulating the LDs 1a and 1b of the LD array 1 in such a configuration will be described. The LD modulating circuit 12a, a video clock signal BK ₁ frequency f ₁ is input from the first crystal oscillator 13a. As a result, the LD 1a operates according to the image data from the image processing unit 14 and outputs the frequency f
Modulated by ₁ . On the other hand, the LD modulation circuit 12b has a second
Video clock signal BK ₂ of frequency f ₂ is input from a crystal oscillator 13b. As a result, the LD 1b receives the LD modulation circuit 1 according to the image data from the image processing unit 14.
2b is modulated with a frequency f ₂ . In this case, the frequency f _1, f ₂ of each video clock signal BK _1, BK ₂ is, LD
It corresponds to the wavelengths of the laser beams 1a and 1b. Thus each LD1a, by 1b is to be modulated with independent video clock signal BK _1, BK _2, the value of the main scanning direction write width on the surface of the photoreceptor 10 to a predetermined object (magnification) And the deviation of the dot formation position at the end in the main scanning direction can be suppressed. Therefore, from the above, the photoconductor 1
It is possible to prevent the deterioration of the image on the 0-th surface and form an image in which the writing positions in the main scanning direction are uniform.

Next, an embodiment of the invention described in claim 2 will be described with reference to FIG. The description of the same parts as those in the first aspect of the present invention will be omitted, and the same reference numerals will be used for the same parts.

In this embodiment, as shown in FIG.
Video as a video clock frequency varying means for varying the frequency of at least one of the video clock signals BK ₁ , BK ₂ of the LD modulation circuits 12a, 12b for modulating a, 1b, that is, here, the frequency of the video clock signal BK _2. A clock frequency variable circuit 15 is provided. The variable video clock frequency circuit 15 is connected between the crystal oscillator 16 for generating the video clock signal BK ₁ having the frequency f ₃ and the LD modulation circuit 12b. The video clock frequency variable circuit 15 is provided in the phase comparator 1
7, LPF 18 (low-pass filter), VCO 19
It is configured by a (voltage-controlled oscillator), a frequency divider 20, and a PLL circuit including a frequency division ratio setting circuit 21.

The operation for modulating each of the LDs 1a and 1b of the LD array 1 in such a configuration will be described. Image data is input from the image processing unit 14 and the video clock signal BK ₁ of frequency f ₃ is input from the crystal oscillator 16 to the LD modulation circuit 12a. As a result, the LD 1a is modulated at the frequency f ₃ by the LD modulation circuit 12a according to the image data from the image processing unit 14. On the other hand, the frequency f ₃ from the crystal oscillator 16 is sent to the video clock frequency variable circuit 15 (PLL circuit) to be frequency-divided into the LD modulation circuit 12b, which is input as the video clock signal BK ₂ having the frequency f _4. It The frequency divider 20 can change the frequency division ratio according to the data value of the frequency division ratio setting circuit 21, and can change the frequency f ₄ of the video clock signal BK ₂ input to the LD modulation circuit 12b. As a result, the LD 1b is controlled by the LD modulation circuit 12b according to the image data from the image processing unit 14.
Is modulated by frequency ₄ . And in this case, LD
The writing width in the main scanning direction when 1b is modulated with the frequency f ₄ is
The value of the frequency f ₄ is adjusted so as to be equal to the writing width in the main scanning direction when the LD 1a is modulated with the frequency f ₃ . In this way, by using the video clock frequency variable circuit 15,
By changing the video clock signal BK ₂ that modulates the LD 1b, it is possible to make all the writing widths in the main scanning direction on the surface of the photoconductor 10 equal, and to suppress the deviation of the dot formation position at the end in the main scanning direction. be able to. Therefore,
For this reason, it is possible to prevent deterioration of the image on the surface of the photoconductor 10 and form an image in which the writing position in the main scanning direction is uniform.

Next, an example in which the invention according to claim 1 and the invention according to claim 2 are compared will be described with reference to FIGS. 4 and 5. According to the first aspect of the invention, in order to suppress the positional deviation of the end end in the main scanning direction, the LD1a and 1b are formed so that the writing widths formed by the LDs 1a and 1b are equal to desired values. Video clock signal B
K ₁ and BK ₂ are set. On the other hand, according to the second aspect of the invention, the video clock frequency variable circuit 15 is used so that the writing width in the main scanning direction formed by the LD 1b becomes equal to the writing width in the main scanning direction formed by the LD 1a. Therefore, only the video clock signal BK ₂ on the LD 1b side is changed. Therefore, in the invention described in claim 1, the writing width in the main scanning direction is adjusted toward a constant value by changing each of the two frequencies, whereas in the invention described in claim 2, only one frequency is adjusted. By changing one of the writing widths in the main scanning direction to the writing width in the other main scanning direction, both of which can suppress the dot formation position deviation at the end end in the main scanning direction. Are the same. In the inventions described in claims 1 and 2, the number of LDs on the LD array 1 is two, but the invention can be applied to a case where the number of LDs is three or more, and the dot formation position shift can be suppressed. You can

Here, a concrete comparative example of the invention according to claims 1 and 2 and the conventional example will be described with reference to FIGS. 4 and 5. Figure 4 (a) ~ (c) is DETP signal (synchronization detection signals) in the invention of claim 1, wherein the video clock signal BK ₁ of LD1a, LD1b video clock signal B
Shows the K _2, FIG. 4 (d) (e) is indicative DETP signal in the conventional apparatus shown in FIG. 11, LD1a, a video clock signal 1b. Further, FIG. 5A shows an output image 2 when the video clock signals BK ₁ and BK _{2 according} to the present invention (the invention according to claims 1 and 2) are used.
2 and FIG. 5B shows an output image 23 in the conventional case (see FIG. 11).

As a result, the conventional method shown in FIG.
Since L is adjusted with one video clock signal,
Whereas if the wavelengths of D1a and LD1b are different, the image becomes a picture with a different magnification for each line, whereas in FIG. 5 (a) according to the method of the present invention, even if the wavelengths of LD1a and LD1b are different, the respective video clocks are different. Since the frequencies of the signals BK ₁ and BK ₂ are changed and adjusted, it is possible to form a picture image in which the magnification of each line is the same.

Next, an embodiment of the invention described in claim 3 will be described with reference to FIGS. 6 and 7. The description of the same parts as those in the first and second aspects of the present invention is omitted, and the same parts are designated by the same reference numerals.

When the video clock signals BK ₁ and BK ₂ having different phases and frequencies are used for the LDs 1a and 1b of the LD array 1 as in the inventions described in claims 1 and 2, the LDs 1a and LD1b are used. Are the respective video clock signals B at the write start position where a specific line is written.
Since the phase relationship of K ₁ and BK ₂ is not constant, a phase difference of up to about 2 clocks is generated, which deteriorates the image, which may make it difficult to describe fine characters or fine lines, resulting in poor resolution. is there.

Therefore, in this embodiment, as shown in FIG. 6, a synchronization detection mechanism (not shown) for synchronizing the rotation of the polygon mirror 4 with at least one LD in the LD array 1 is provided. DET from the synchronization detection mechanism
All LDs 1a, 1 based on the P signal (synchronization detection signal)
Phase synchronization circuits 24a, 24 as phase synchronization means for generating the synchronization clock signals DK ₁ , DK ₂ independent of b
b is provided.

The operation of the LDs 1a and 1b of the LD array 1 for modulation in such a configuration will be described with a focus on the phase-locked circuits 24a and 24b. Phase synchronization circuit 24
a and 24b both trigger the DETP signal, and the frequency f
A _first synchronized clock signal DK _1, it generates the synchronization clock signal DK ₂ frequency f _2. At this time, as shown in FIG. 7, the synchronous clock signals DK ₁ and DK ₂ are different from the DETP signal in the generation timing of the first pulse by t ₁ and t ₂ . Therefore, the reason why the generation timing is changed by t ₁ and t ₂ will now be described. The deflection of the scanning light by the polygon mirror 4 does not mean that the screen can be written with 100% of each surface, and the writing is performed on the photoconductor 10 only at a constant deflection angle as shown in FIG. As a result, the photoconductor 10
It is divided into an effective image area that can be written to and a non-image area other than that. Further, when separate video clock signals BK ₁ and BK ₂ are used as in the configuration shown in FIG. 1, due to the positional relationship between the LD array 1 and the optical system (including the fθ lens 6 and the mirrors 7 and 8), The magnification and the effective image area (the time widths of the LD1a and LD1b are different because the clock frequencies are different) are determined to have a fixed relationship. Considering such a point, t ₁ and t ₂ are determined so that the start positions of the effective image areas of the LD 1 a and LD 1 b match on the surface of the photoconductor 10. As a result, it is possible to obtain a high-quality picture (equivalent to that shown in FIG. 5A) in which the image positions are aligned on the surface of the photoconductor 10. Therefore, even if the respective video clock signals BK ₁ and BK ₂ are used for the LDs 1a and 1b, the phase synchronization circuits 24a and 24b use the DETP signals to synchronize the timings with the synchronization clock signals DK ₁ and DK ₂ . It is possible to prevent deterioration of the image on the surface of the photoconductor 10 and always form an image in which writing positions are aligned in the main scanning direction.

Next, an embodiment of the invention described in claim 4 will be described with reference to FIGS. 8 and 9. In addition, claims 1, 2,
The description of the same parts as those in the invention described in 3 is omitted, and the same reference numerals are used for the same parts.

The present embodiment is constructed for the same purpose as the invention described in claim 3 described above. That is, as shown in FIG. 8, the DETP signal and the synchronous clock signal DK
_1. Variable delay circuits 25a and 25b as synchronization timing variable means capable of varying the timings generated by ₁ and DK _2.
Was set up. In addition, in addition to the circuit configuration of FIG. 6 described above, a synchronization detection mechanism (not shown) for synchronizing the rotation of the polygon mirror 4 and the synchronization clock signal DK ₁ ,
Phase lock circuits 24a and 24b for generating DK ₂ , and a video clock frequency variable circuit 15 are provided.

The operation of modulating the LDs 1a and 1b of the LD array 1 having such a configuration will be described with a focus on the variable delay circuits 25a and 25b. Generation timing t _{1 of} the synchronous clock signals DK ₁ and DK ₂ as shown in FIG.
The relationship of t ₂ is changed by varying the video clock signal BK ₂ by the video clock frequency varying circuit 15 and adjusting the magnification. In this case, the delay signals DL ₁ and D ₁ are changed from the DETP signal by using the variable delay circuits 25a and 25b.
By generating L ₂ and inputting these delay signals DL ₁ and DL ₂ to the phase synchronization circuits 24a and 24b, the generation timing of the synchronous clock signals DK ₁ and DK ₂ is from t ₁ and t _{2 in} FIG. 9 can be changed to t ₁ ′ and t ₂ ′. Therefore, even if the frequency of the video clock signal BK ₂ is adjusted by the video clock frequency variable circuit 15 and the magnification is changed, the photosensitive drum 1 is adjusted by using the variable delay circuits 25a and 25b.
It becomes possible to finely adjust the writing start position in the main scanning direction on the 0th surface, thereby preventing deterioration of the image on the surface of the photoconductor 10 and always forming an image in which the writing position in the main scanning direction is aligned. Can be formed.

Next, an embodiment of the invention described in claim 5 will be described with reference to FIG. The description of the same parts as those in the first to fourth aspects of the present invention is omitted, and the same parts are designated by the same reference numerals.

In the invention described in claims 1 to 4, the magnification error on the surface of the photoconductor 10 is absorbed by changing the clock cycle of the LD array 1. However, if the clock cycle of each LD 1a, 1b is changed, the amount of light output energy per dot changes, and when writing with the same power, an image with a density difference is generated due to the difference in power for each line and color In some cases, unevenness occurs, and in multi-gradation expression, since the power of each LD in each gradation is different, the gradation may not be clear, resulting in a defective gradation. In order to deal with this, in the past,
As shown in FIG. 10B, one APC 26 (auto power control) is used for two LDs 1a and 1b, and this is connected to the switch 27 to switch the control. It cannot be said that it is a simple control.

Therefore, in this embodiment, the beam power magnification adjusting means 28 for uniformly setting the beam power of the laser beams a and b emitted from the LDs 1a and 1b of the LD array 1 onto the surface of the photoconductor 10 is provided. It is a thing. The beam power magnification adjusting means 28 is composed of APCs 29a and 29b that are independently connected to the LDs 1a and 1b, and the voltages Vref ₁ and V are applied to these APCs 29a and 29b.
ref ₂ is applied. Therefore, by providing the beam power magnification adjusting means 28 in this way and by making the video clock frequencies of the LDs 1a and 1b separate, the beam power on the surface of the photoconductor 10 is different even if the light energy amount per dot is different. Can be made uniform, so that density unevenness can be suppressed and gradation deterioration can be prevented.

[0034]

According to the first aspect of the present invention, a plurality of laser beams emitted from a semiconductor laser array (LD array) including a plurality of semiconductor lasers (LD) are scanned by the same polygon mirror to form a lens optical system. In the image forming apparatus, the latent image of a plurality of lines is simultaneously formed on the surface of the photoconductor by irradiating the surface of the photoconductor with the plurality of laser beams through a system. Since the LD modulation means for independently sending the video clock signal to the individual LDs for modulation is provided, each LD is modulated by the independent video clock signal, and each LD is modulated.
The width of writing in the main scanning direction on the surface of the photoconductor by the laser beam of D can be made equal, whereby the deviation of the dot formation position at the end in the main scanning direction on the surface of the photoconductor is suppressed and the deterioration of the image is prevented. It is possible to form an image in which writing positions are aligned in the main scanning direction.

According to a second aspect of the invention, in the first aspect of the invention, there is provided video clock frequency varying means for varying the frequency of at least one video clock signal of the video clock signals of the LD modulating means for modulating the LD. Since it is provided, the video clock signal that modulates each LD can be changed to make all the writing widths on the photoconductor surface in the main scanning direction equal, and thereby the dots at the end ends in the main scanning direction on the photoconductor surface. It is possible to suppress the deviation of the formation position and prevent the deterioration of the image, and to form the image in which the writing positions in the main scanning direction are aligned.

According to a third aspect of the invention, in the invention according to the first aspect, at least one LD in the LD array is used.
A synchronization detection mechanism for synchronizing with the rotation of the polygon mirror is provided for the phase synchronization means for generating an independent synchronization clock signal for all LDs based on the synchronization detection signal from the synchronization detection mechanism. Since the LDs are provided, even if different video clock signals are used for the LDs, the main scanning direction writing position can be always aligned on the photoconductor surface because the timing is synchronized with the sync clock signal based on the sync detection signal. Thus, it is possible to suppress the deviation of the dot formation position at the end of the main scanning direction on the surface of the photoconductor and prevent the deterioration of the image, and to form the image in which the writing positions in the main scanning direction are aligned.

According to a fourth aspect of the present invention, in the first and second aspects of the present invention, a synchronization detection mechanism for synchronizing the rotation of the polygon mirror with at least one LD in the LD array is provided. Phase synchronization means for generating an independent synchronization clock signal for all LDs based on the synchronization detection signal issued from the synchronization detection mechanism is provided, and the timing for generating the synchronization detection signal and the synchronization clock signal is variable. Since the possible synchronization timing changing means is provided, the writing start position in the main scanning direction on the photoconductor surface can be finely adjusted even if the video clock frequency of each LD is adjusted to change the magnification. It is possible to form an image in which the writing position in the main scanning direction is uniform by suppressing the deviation of the dot forming position at the end end in the main scanning direction above and preventing image deterioration. A.

The invention according to claim 5 is the same as claim 1, 2 or 3.
In the inventions of 3 and 4, since the beam power magnification adjusting means for uniformly setting the beam power of the laser beam emitted from each LD of the LD array onto the surface of the photoconductor is provided, the video clock frequency of each LD is Even if the amount of light energy per dot is different, the beam powers can be made uniform on the surface of the photoconductor, and uneven density can be suppressed and gradation deterioration can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a control system of an image forming apparatus which is an embodiment of the invention described in claim 1.

FIG. 2 is a perspective view showing a configuration of a scanning optical system of the image forming apparatus.

FIG. 3 is a block diagram showing a configuration of a control system of the image forming apparatus according to the second embodiment of the invention.

4 (a) to (c) are timing charts of the present invention, and (d) to (e) are conventional timing charts.

FIG. 5A is a schematic diagram showing an output image of the present invention,
(B) is a schematic diagram which shows the conventional output image.

FIG. 6 is a block diagram showing a configuration of a control system of the image forming apparatus according to the third embodiment of the invention.

FIG. 7 is a timing chart of the invention according to claim 3;

FIG. 8 is a block diagram showing a configuration of a control system of the image forming apparatus which is an embodiment of the invention described in claim 4.

FIG. 9 is a timing chart of the invention according to claim 4;

FIG. 10A is a block diagram showing a configuration of a control system of the image forming apparatus according to an embodiment of the present invention;
(B) is a block diagram showing a configuration of a control system of a conventional image forming apparatus.

FIG. 11 is a perspective view showing a configuration of a scanning optical system of the image forming apparatus.

[Explanation of symbols]

1 LD Array 1a, 1b LD 4 Polygon Mirror 10 Photoreceptors 12a, 12b LD Modulating Means 15 Video Clock Frequency Changing Means 25a, 25b Synchronizing Timing Changing Means 28 Beam Power Magnification Adjusting Means a, b Laser Beams BK ₁ , BK ₂ Video Clocks Signal DK ₁ , DK ₂ Sync clock signal DETP Sync detection signal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiki Yoshida 1-3-6 Nakamagome, Ota-ku, Tokyo Stock company Ricoh Company (72) Hideo Nakagawa 1-3-6 Nakamagome, Ota-ku, Tokyo Share Company Ricoh

Claims (5)

[Claims] 1. A plurality of laser beams emitted from a semiconductor laser array (LD array) including a plurality of semiconductor lasers (LD) are scanned by the same polygon mirror, and the plurality of laser beams are scanned through a lens optical system. In an image forming apparatus in which a latent image of a plurality of lines is simultaneously formed on the surface of the photoconductor by irradiating the surface of the photoconductor with a laser beam, the individual LDs of the LD array are independently provided. An image forming apparatus comprising an LD modulation means for transmitting a video clock signal to perform modulation. 2. An image forming apparatus according to claim 1, further comprising video clock frequency varying means for varying the frequency of at least one video clock signal of the video clock signals of the LD modulating means for modulating the LD. apparatus. 3. At least one L of the LD array
A phase detection means is provided for D to synchronize with the rotation of the polygon mirror, and a phase synchronization means for generating an independent synchronization clock signal for all LDs based on the synchronization detection signal from this synchronization detection mechanism. The image forming apparatus according to claim 1, further comprising: 4. At least one L of the LD array
A phase for generating a synchronous clock signal for all LDs based on the synchronous detection signal issued from this synchronous detection mechanism by providing a synchronous detection mechanism for synchronizing the rotation of the polygon mirror with D 3. The image forming apparatus according to claim 1, further comprising a synchronization means, and a synchronization timing varying means capable of varying a timing of generating the synchronization detection signal and the synchronization clock signal. 5. A beam power magnification adjusting means for uniformly setting the beam power of the laser beam emitted from each LD of the LD array onto the surface of the photoconductor is provided. Alternatively, the image forming apparatus according to item 4.