JPH05276336A - Control board for image forming device - Google Patents

Abstract

PURPOSE:To provide the control board of the image forming device in which no missing pulse takes place in an index signal. CONSTITUTION:The control board is provided with a timing means 23 obtaining a control timing pulse signal (b) based on an initial pulse (a) used to start a semiconductor pulse and an index pulse signal IDX obtained by detecting a scanning light and with a light quantity control means 21 implementing light quantity control making an emitted light quantity (m) of the semiconductor laser coincident with a reference light quantity (r) synchronously with a control start pulse signal obtained through frequency division of the control timing pulse signal (b) and rising at the falling of the control timing pulse signal (b), and 2-stage control of rough control for a first control period and then of fine control for a succeeding control period is adopted for the light quantity control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control board of an image forming apparatus for controlling the timing of controlling the amount of light emitted from a semiconductor laser for forming a color image.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing a schematic structure of a general image forming apparatus.

In an image forming apparatus, a drum-shaped photosensitive member (hereinafter simply referred to as "photosensitive member") 1 as an image forming member is uniformly charged by a scorotron charger 2 and then binarized spot light is used as a scanning optical system. 8 to 12 form an imagewise exposure on the photoreceptor 1 to form a dot-shaped electrostatic latent image, which is reversely developed by the developing devices 4 to 6 to form a dot-shaped toner image. The steps are repeated to form a color toner image on the photoconductor 1, and the color toner image is transferred onto the paper surface and fixed to obtain a color image.

As shown in FIG. 4, the image forming apparatus includes a photoconductor 1, a scorotron charger 2, developing devices 4 to 6, a semiconductor laser 7, scanning optical systems 8 to 12, a photodiode 13,
Control board 20, reference clock generation circuit 30,
It consists of drivers 40 and 50.

The photodiode 13 includes scanning optical systems 8 to.
The scanning light obtained by scanning the emitted light of the semiconductor laser 7 is detected by 12 and the index pulse signal IDX is output. The control board 20 outputs a drive signal L for the semiconductor laser 7, inputs the index pulse signal IDX, and outputs the same signal IDX to other circuits.

The reference clock generation circuit 30 outputs a pulse signal having the same repetition period as the pixel clock to the reference clock CK.
The reference clock CK is output to the control board 20 and the drivers 40 and 50. As a result, the rotation speed of the photoconductor 1 and the scanning of the scanning optical systems 8 to 12 are synchronized.

The photoconductor 1 has a motor M1 mounted on its drive shaft. The motor M1 is rotated by the driver 40 to rotate the photoconductor 1 at a predetermined speed.

Further, the polygon mirror 10 has a drive shaft of a motor M2 attached to the center of rotation thereof. Motor M2
Are rotated at a predetermined speed by the driver 50.

By inputting the reference clock CK from the reference clock generation circuit 30 to the drivers 40 and 50,
The rotation phases of the photoconductor 1 and the polygon mirror 10 are synchronized.

Further, the semiconductor laser 7 is oscillated according to the value of the image data D, and the polygon mirror 10 which rotates the laser light (emitted light) from the semiconductor laser 7 at a predetermined speed.
Then, the fθ lens 11 and the cylindrical lenses 9 and 12 are used to scan the surface of the uniformly charged photoreceptor 1 with a minute spot. The semiconductor laser 7 is a coherent light source, a collimator lens 8 is provided as a light emission optical system, a polygon mirror 10 and an fθ lens 11 are provided as deflection optical systems, and the polygon mirror 1 is provided.
Cylindrical lenses 9 and 12 are provided as a surface tilt correction optical system based on 0.

FIG. 5 shows a conventional example of a control board for such an image forming apparatus.

In FIG. 5, the APC circuit 21 divides the input reference clock CK (FIG. 6A) to generate an APC start signal (control start pulse signal) as shown in FIG. 6B. To occur. The cycle of this APC start signal is a cycle of one page, and control of the amount of light emitted from the semiconductor laser 7 is started by the rise of the APC start signal.

In this control, the reference light amount r set in the APC circuit 21 is compared with the emission light amount m of the laser 7 detected by the photodiode incorporated in the semiconductor laser 7, and the emission light amount m of the laser 7 is determined as described above. The output signal value R is changed so as to match the reference light amount r. Laser drive circuit 2
The level of the laser drive signal L output from 2 corresponds to the output signal value R, and therefore the amount of light emitted from the laser 7 becomes a value corresponding to the signal value R.

The emitted light quantity m of the semiconductor laser 7 is as shown in FIG.
As shown in (c), the reference light amount r is obtained in a period of about half a line. The control of the emitted light amount m is a two-step control including an initial low precision control (coarse control) and a subsequent high precision control (fine control). For example, as shown in FIG. 6C, T1 =
Low precision control is performed during the period of 2 lines, and high precision control is performed during the period of T2 = 0.7 line. Then, the control is stopped when the emitted light amount m of the laser 7 becomes about 98% of the reference light amount r.

After the control of the amount of emitted light is stopped, the output signal value R is fixed to the final value RR during the control period. The amount of light emitted from the semiconductor laser 7 thereafter in the period of one page is a binary light amount value or zero light amount value according to the fixed output signal value RR. Which value will be determined by the image data D input to the laser drive circuit 22.

[0016]

However, in the above-mentioned conventional control board, as shown in FIG. 6 (c), a constant value r from the rising edge of the APC start signal.
It takes a period of about 3 lines to settle in, the amount of light emitted from the semiconductor laser 7 is small immediately after the rise of the APC start signal, and the index pulse signal IDX is not output from the photodiode 13 (the amount of light emitted from the laser 7 is (Approximately 50% of the reference light amount r when one line has passed from the rise of the APC start signal).

Therefore, the index pulse signal IDX
As shown in FIG. 6 (d), the pulse signal train is such that two pulses are omitted in the period of one page. Therefore, control may be unstable in other circuits that require the index pulse signal IDX.

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a control board for an image forming apparatus in which no pulse omission occurs in the index pulse signal.

[0019]

In order to solve the above-mentioned problems, the present invention discloses that a scanning light obtained by scanning emitted light of a semiconductor laser by a scanning optical system is exposed on a photosensitive member to form a latent electrostatic image. In the control board of the image forming apparatus, a timing means for obtaining a control timing pulse signal from an initial pulse for starting the semiconductor laser and an index pulse signal obtained by detecting the scanning light, and the control timing pulse A light quantity control means for performing light quantity control for synchronizing the emitted light quantity of the semiconductor laser with a reference light quantity in synchronization with a control start pulse signal obtained by frequency-dividing the signal and rising at the trailing edge of the control timing pulse signal. The light amount control is a two-step control in which coarse control is performed in the first control period and fine control is performed in the next control period. And wherein the Rukoto.

[0020]

In the control board of the image forming apparatus according to the present invention, as shown in FIG.
The initial pulse generation circuit 24 of No. 3 generates an initial pulse a (FIG. 2A) for starting the semiconductor laser. The initial pulse a is input to the APC circuit 21 via the OR circuit 25, and an APC start signal (FIG. 2B) as a control start pulse signal which rises at the trailing edge of the initial pulse a is generated in this circuit 21. ..

After the APC start signal is generated, the emitted light quantity (FIG. 2C) of the semiconductor laser 7 (FIG. 4) is the reference light quantity r.
Is controlled so that Emitted light intensity m of the semiconductor laser 7
Control is a two-step control of low precision control and high precision control. In low precision control, the laser
The amount m of emitted light of is made close to the reference light amount r, and is matched with the reference light amount r in the next high-precision control.

When the emitted light amount m matches the reference light amount r, the control of the emitted light amount is stopped, and the emitted light amount is determined by the fixed output signal value RR by the image data D input to the laser drive circuit 22 or It is controlled to a binary value of zero light intensity.

After the semiconductor laser 7 is activated in this manner, the light emitted from the semiconductor laser 7 is emitted by the photodiode 13.
(FIG. 4), the index pulse signal IDX (FIG.
(D)) is input to the APC control circuit 23.

When the index pulse signal IDX input to the APC control circuit 23 is input to the APC circuit 21 via the OR circuit 25 and the APC start signal rises at the trailing edge of the signal IDX, the amount of light emitted from the semiconductor laser 7 m
Is controlled to be the reference light amount r. When the emitted light amount m matches the reference light amount r, the control of the emitted light amount is stopped as described above.

Output signal b of the OR circuit 25 (FIG. 2 (e))
Is a control timing pulse signal as a logical sum signal of the initial pulse a and the index pulse signal IDX,
The APC start signal is obtained by dividing the control timing pulse signal b, and rises when the signal b falls.

As described above, the APC start signal is the control timing pulse signal b, that is, the index pulse signal I.
Since the pulse rises at the fall of DX, the pulse of the index pulse signal IDX does not exist immediately after the rise of the APC start signal, and the emitted light amount m of the semiconductor laser 7 is 2
Since the reference light amount r is rapidly approached by the step control, APC
Immediately after the start signal rises, the amount of light emitted from the semiconductor laser is greatly reduced, so that the problem that the pulse disappears does not occur.

[0027]

Next, an embodiment of a control board of an image forming apparatus according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, and differs from FIG. 5 in that an APC control circuit (timing means) 23 is added.

The index pulse signal IDX output from the photodiode 13 (FIG. 4) is input to the APC control circuit 23. In addition, the initial pulse generation circuit 24
Is the semiconductor laser 7 (FIG. 4) as shown in FIG.
In order to activate the above, one initial pulse a synchronized with the rotating operation of the polygon mirror 10 is generated.

Initial pulse a and index pulse signal I
DX is input to the OR circuit 25 and becomes a logical sum signal (control timing pulse signal) b (FIG. 2 (e)). The pulse P1 of the control timing pulse signal b is a pulse corresponding to the initial pulse a, and the other pulses are pulses corresponding to the pulse of the index pulse signal IDX.

First, the initial pulse a is input to the APC circuit (light quantity control means) 21 via the OR circuit 25, and this A
In the PC circuit 21, an APC start signal as a control start pulse signal rising at the trailing edge of the initial pulse a (see FIG. 2).
(B)) occurs.

This APC start signal is shown in FIG.
As indicated by the dotted lines in (c) and (e), control is performed so that the pulse P1 of the control timing pulse signal b corresponding to the initial pulse a rises and rises and the emitted light amount m of the semiconductor laser 7 becomes the reference light amount r. To be done. As shown in FIG. 2C, the emitted light amount m of the laser 7 approaches the reference light amount r in the period of one line. The control of the emitted light amount m will be described later. The emitted light amount of the laser 7 is controlled by changing the output signal value R of the APC circuit 21, but when the emitted light amount m of the laser 7 matches the reference light amount r, the output signal value R is the value at the time of the match. (Final value) Fixed to RR.

When the emitted light amount m matches the reference light amount r, the control of the emitted light amount is stopped, and the emitted light amount is determined by the fixed output signal value RR by the image data D input to the laser drive circuit 22 or It is controlled to be a binary value of zero light amount (FIG. 2 (c) shows only the emitted light amount determined by the output signal value RR).

In this way, after the semiconductor laser 7 is activated, the light output from the scanning optical systems 8 to 12 (FIG. 4) in which the emitted light of the semiconductor laser 7 is the scanning light is converted into one line by the photodiode 13. Each time, the index signal IDX, which is a pulse train with an interval of one line, is obtained (see FIG. 2).
(D)). The index pulse signal IDX is input to the APC control circuit 23 via the terminal T1, and further, as the control timing pulse signal b via the OR circuit 25.
It is input to the PC circuit 21 and generates an APC start signal.

As can be seen from FIGS. 2 (b) and 2 (e), A
The PC start signal is a signal that divides the control timing pulse signal b and rises when the control timing pulse signal b falls. The frequency division is such that the number of pulses of the control timing pulse signal b becomes 1, for example, 3600.

The APC start signal of the APC circuit 21 is
As indicated by the dotted lines in FIGS. 2B, 2C, and 2E, the pulse P2 of the index pulse signal IDX rises when the pulse P2 falls, and the emitted light amount m of the semiconductor laser 7 is changed to the reference light amount r.
When the emitted light amount m matches the reference light amount r, the control of the emitted light amount is stopped as described above. The interval between the pulses P1 and P2 is one page period.

In this way, the APC start signal rises due to the trailing edge of the pulse of the index pulse signal IDX, so the pulse of the index pulse signal IDX is A
It does not exist immediately after the rise of the PC start signal, and the problem that the pulse disappears due to a large decrease in the emitted light amount of the semiconductor laser immediately after the APC start signal does not occur.

Next, the control of the emitted light amount of the semiconductor laser 7 in FIG. 2 will be described with reference to FIG.

In the control shown in FIG. 3, low precision control (coarse control) with a large level difference of one step is performed in the first control period (for example, one line period) t1, and the next control period (for example, one line period). In the period t2, high precision control (fine control) with a small level difference of one step is performed. With this two-step control, the emitted light quantity m of the semiconductor laser 7 can be quickly brought close to the reference light quantity r to prevent the index pulse signal IDX from disappearing.
If the reference light amount r is approached to a certain extent, the level difference of one step can be reduced to improve the control accuracy of the emitted light amount m.

[0040]

As described above, the control board of the image forming apparatus according to the present invention controls the emitted light amount of the semiconductor laser by the control start pulse signal which rises at the fall of the control timing pulse signal, that is, the fall of the index pulse signal. With the start of, two-step control is performed, in which coarse control is first performed and then fine control is performed.
Immediately after the rise of the control start pulse signal, there is no index pulse signal at the time when the emitted light amount of the semiconductor laser significantly decreases, and the emitted light amount of the semiconductor laser itself can be rapidly increased. It has the effect of not occurring.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a control board of an image forming apparatus according to the present invention.

FIG. 2 is a time chart for explaining the operation of the circuit of FIG.

FIG. 3 is a time chart showing another example of control of the emitted light amount of the semiconductor laser.

FIG. 4 is a configuration diagram showing a general image forming apparatus.

FIG. 5 is a block diagram showing a conventional control board of the image forming apparatus.

FIG. 6 is a time chart for explaining the operation of the circuit of FIG.

[Explanation of symbols]

 21 APC circuit (light quantity control means) 22 Laser drive circuit 23 APC control circuit (timing means) 24 Initial pulse generation circuit 25 OR circuit

Front page continuation (72) Inventor Kenji Taki 2970 Ishikawa-cho, Hachioji, Tokyo Konica stock company (72) Inventor Masaji Akamatsu 2970 Ishikawa-cho, Hachioji, Tokyo Konica stock company (72) Inventor Kurohata Takao 2970 Ishikawa-cho, Hachioji City, Tokyo Konica Stock Company

Claims (1)

[Claims] 1. A control board of an image forming apparatus for obtaining a latent electrostatic image by exposing scanning light obtained by scanning emitted light of a semiconductor laser with a scanning optical system onto a photoconductor to activate the semiconductor laser. Timing means for obtaining a control timing pulse signal from an initial pulse for detecting the scanning light and an index pulse signal obtained by detecting the scanning light; and a rising edge of the control timing pulse signal obtained by dividing the control timing pulse signal. In synchronization with the control start pulse signal that rises in the downward direction, and a light amount control means for performing a light amount control to match the emitted light amount of the semiconductor laser with a reference light amount, and the light amount control is roughly controlled in the first control period, A control board for an image forming apparatus, which is a two-step control in which fine control is performed in the next control period.